Search

Estimating penetration rates of Jumbo drills is crucial for optimizing underground mining drilling processes, aiming to reduce costs and time. This study investigates various regression and machine learning methods, including Multilayer Perceptron (MLP), Support Vector Regression (SVR), and Random Forests (RF), to predict the penetration rates (ROP) using multivariate inputs such as operation parameters and rock mass characteristics. The Rock Mass Drillability Index (RDi), incorporating both intact rock properties and structural parameters, was utilized to characterize the rock mass. The dataset was split into 80% for training and 20% for testing. Performance metrics including correlation coefficient (R2), variance accounted for (VAF), mean absolute error (MAE), mean absolute percentage error (MAPE), and root mean square error (RMSE) were calculated for each method to evaluate the accuracy of the predictions. SVR exhibited the best prediction performance for ROP, achieving the highest R2, lowest RMSE, MAE, and MAPE, as well as the largest VAF values of 0.94, 0.15, 0.11, 4.84, and 94.13 during training, and 0.91, 0.19, 0.13, 6.02, and 91.11 during testing, respectively. With this high accuracy, we conclude that the proposed machine learning algorithms are valuable and efficient predictors for estimating jumbo drill penetration rates in underground mining operations. [ABSTRACT FROM AUTHOR]

Predicting the drill penetration rate is a fundamental requirement in mining operations, profoundly impacting both the cost-effectiveness of mining activities and strategic mine planning. Given the intricate web of factors influencing rotary drilling performance, the necessity for advanced modeling techniques becomes evident. To this end, the hybrid extreme gradient boosting (XGBoost) was utilized to gauge the penetration rate of rotary drilling machines, utilizing random search, grid search, Harris Hawk optimization (HHO), and the dragonfly algorithm (DA) as metaheuristic algorithms. Our research draws from extensive data collected in copper mine case studies, encompassing both field and investigational data. This dataset incorporates critical material properties, such as tensile strength (TS), uniaxial compressive strength (UCS), as well as vital rock-mass characteristics including joint direction (JD), joint spacing (JS), and bit diameter (D). Our investigation evaluates the reliability of these prediction methods using various performance indicators, including mean absolute error (MAE), root mean square error (RMSE), average absolute relative error (AARE), and coefficient of determination (R2). The multivariate analysis reveals that the HHO-XGB model stands out, demonstrating superior prediction accuracy (MAE: 0.457; RMSE: 2.19; AARE: 2.29; R2: 0.993) compared to alternative models. Furthermore, our sensitivity analysis emphasizes the substantial impact of uniaxial compressive strength and tensile strength on the drill penetration rate. This underlines the importance of considering these material properties in mining operations. In conclusion, our research offers robust models for forecasting the penetration rate of similar rock formations, providing invaluable insights that can significantly enhance mining operations and planning processes. [ABSTRACT FROM AUTHOR]

The mission of Advanced Ionospheric Probe (AIP) onboard FORMOSAT-5 (F5) satellite is to detect pre-earthquake ionospheric anomalies (PEIAs) and observe ionospheric space weather. F5/AIP plasma quantities in the nighttime of 22:30 LT (local time) and the total electron content (TEC) of the global ionosphere map (GIM) are used to study PEIAs of an M7.3 earthquake in the Iran–Iraq border area on 12 November 2017, as well as signatures of two magnetic storms on 7 and 21–22 November 2017. Statistical analyses of the median base and one sample test are employed to find the characteristics of temporal PEIAs in GIM TEC over the Iran–Iraq area. The anomalous increases of the GIM TEC and F5/AIP ion density over the epicenter area on 3–4 November (day 9–8 before the M7.3 earthquake) agree with the temporal PEIA characteristics that the significant TEC increase frequently appears on day 14–6 before 53 M ≥ 5.5 earthquakes in the area during 1999–2016. The spatial analyses together with odds studies show that the PEIAs frequently appear specifically over the epicenter day 9–8 before the M7.3 earthquake and day 10–9 before a M6.1 earthquake on 1 December, while proponent TEC increases occur at worldwide high latitudes on the two magnetic storm days. The F5/AIP ion velocity uncovers that the PEIAs of the two earthquakes are caused by associated eastward electric fields, and the two positive storm signatures are due to the prompt penetration electric fields. [ABSTRACT FROM AUTHOR]

As the backing plate conditions significantly affect the ballistic performance of ceramic/metal composite armor, we have conducted impact experiments using 12.7 mm API projectiles (brittle-hard) to examine the influence of different material characteristics of metal backing plates on the ballistic impact performance of ceramic/metal composite armor. By weighing multilevel sieved fragments and employing the Rosin-Rammler fragment distribution model, we analyzed the influence of backing plate material parameters on the fragment size distribution patterns of the penetrator and ceramic panel. Further, we utilized numerical simulations to explore the impact of backing plate density, Young's modulus, and yield strength on ceramic fracture and energy absorption during penetration. Overall, a high-density backing plate provides better inertial support. Backing materials with a high Young's modulus can enhance the ballistic performance of the ceramic composite target, but there is a limit to this effect. The yield strength of the backing plate is not necessarily better when higher; instead, there is an optimal value. Either too high or too low yield strength can reduce the energy absorption efficiency of the ceramic. [ABSTRACT FROM AUTHOR]

The Keyhole Plasma Arc Welding (KPAW) process utilizes arc plasma highly constricted by a water-cooled cupper nozzle to produce great arc pressure for opening a keyhole in the weld pool, achieving full penetration to the thick plate. However, advanced control of welding is known to still be difficult due to the complexity of the process mechanism, in which thermal and dynamic interactions among the arc, keyhole, and weld pool are critically important. In KPAW, two large eddies are generally formed in the weld pool behind the keyhole by plasma shear force as the dominant driving force. These govern the heat transport process in the weld pool and have a strong influence on the weld pool formation process. The weld pool flow velocity is much faster than those of other welding processes such as Tungsten Inert Gas (TIG) welding and Gas Metal Arc (GMA) welding, enhancing the heat transport to lower the weld pool surface temperature. Since the strength and direction of this shear force strongly depend on the keyhole shape, it is possible to control the weld pool formation process by changing the keyhole shape by adjusting the torch design and operating parameters. If the lower eddy is relatively stronger, the heat transport to the bottom side increases and the penetration increases. However, burn-through is more likely to occur, and heat transport to the top side decreases, causing undercut. In order to realize further sophistication of KPAW, a deep theoretical understanding of the process mechanism is essential. In this article, the recent progress in studies regarding the interaction mechanism of arc, keyhole, and weld pool in KPAW is reviewed. [ABSTRACT FROM AUTHOR]

The article presents a numerical study of the high-speed impact of a steel projectile on a concrete target. Calculations have been carried out within the framework of a porous elastoplastic medium. The dynamic fracture is considered as the growth and coalescence of microdefects under the action of stresses formed during loading. The projectile interacts with the target at a speed of 600 m/s. As a result of impact loading, through penetration occurs in the concrete target with the formation of a crater on the front side and a back spall. [ABSTRACT FROM AUTHOR]

A novel gas-curtain launch technique is proposed to enhance the interior ballistic performance for underwater guns. The size of the initial gas curtain in front of the projectile is a critical factor in determining the subsequent behavior of the gunpowder gas jet flow field once the projectile leaves the muzzle. Hence, a validated two-dimensional unsteady multiphase model is built for the flow field at the muzzle of an underwater gas-curtain launch. The calculation involves determining the development of the initial gas curtain sizes for a 30 mm underwater gun, specifically focusing on the evolution of the precursor jet and gunpowder gas jet flow field. The results indicate that a double three-wave point structure forms within the bottle-shaped shock wave structure of the precursor jet when the initial gas curtain length equals the barrel. As the initial gas curtain size increases, the "bottle" structure elongates along the axial direction and compresses radially. After the projectile exits the muzzle, the gunpowder gas quickly expands toward the front, causing the collapse of the Mach disk of the precursor jet. The gunpowder gas jet then reforms a new bottle-shaped shock wave structure. A larger initial gas curtain can facilitate the expansion of the gunpowder gas, resulting in an increased size of the bottle, delayed formation, and weakened intensity of the Mach disk. Additionally, increasing the size of the initial gas curtain decreases the resistance experienced by the projectile outside the barrel. The initial gas curtain can also affect the cavitation bubble evolution process on the projectile sidewall, showing a growth-(attenuation)-stability trend. [ABSTRACT FROM AUTHOR]

Conical pick cutters are by far the most common type of rock cutting tools used on variety of excavation equipment in mining and civil applications. Prediction of the forces acting on pick cutters when cutting rock can be an important input towards cutterhead design and performance estimation for such equipment. The cutting forces are a function of the rock strength and pick tip geometry, which is impacted by the bit wear. To develop a prediction model, a database of mean cutting force (MCF) measured in full-scale testing has been compiled and subsequently analyzed using regression methods to find the empirical equations linking MCF to the bit, cutting geometry and rock properties. Full-scale cutting tests are known to offer precise measurement of the cutting forces for a given bit geometry, cutting geometry (spacing between the cuts and depth of penetration), and combined rock mechanic characteristics of the sample; consequently, the information can be used to develop models of prediction of cutting forces. Linear and log-linear regression and tree-based machine learning models (random forest, decision tree, and extreme gradient boost) were used for the analysis of the experimental data. The results demonstrated that while using input parameters including uniaxial compressive strength (UCS), spacing, Brazilian tensile strength (BTS), penetration, and pick cutter's tip radius and tip angle, models can offer a reasonable prediction of the cutting forces. Among the models that have been examined, regression tree models, especially extreme gradient boost shows the highest coefficient of determination (R2), and the lowest mean absolute error (MAE). Highlights: The key input parameters that affect MCF are recognized, and their influence on MCF is thoroughly examined. The most important parameters for predicting cutting forces are UCS, tip angle, penetration, and BTS. Tree-based machine learning models demonstrate superior performance in predicting MCF. [ABSTRACT FROM AUTHOR]

Summary: Due to the energy crisis and environmental concerns, wind power has seen a considerable increase in use over the past 10 years as a source of renewable energy. Since wind is intermittent and variable, it is obvious that as penetration levels rise, the influence of wind power generation on the electric power system must be considered. Wind power forecasting is essential because large‐scale wind power integration will make it more difficult to plan, operate, and control the power system. An accurate forecast is an efficient way to deal with the operational problems brought on by wind variability. To better utilize wind energy resources, it is essential to increase prediction accuracy. Frequently, the noise in the dataset causes the ramp events to be misclassified or overestimated. The main emphasis of this study is the pre‐processing of wind power data that produces precise time‐series data while reducing noise or artifact content and maintaining the swing feature of the original data. For this task, the data augmentation approach is proposed, where the augmented data (synthetic data) will be added up with the training data, in such a way as to make the strategy useful for real‐time applications. As the next step, the significant features, such as higher‐order statistical features and lower‐order statistical features are extracted. The extracted features act as the input to the recurrent neural network (RNN) classifier, the weights of which are tuned using the proposed honey badger crow (HBCro) optimization algorithm. The proposed HBCro optimization algorithm acts as the major contribution of the proposed model, and it is modeled with the integration of the concepts of the crow search optimization (CSO) algorithm and the honey badger optimization algorithm (HBA). The proposed system is simulated in MATLAB and the effectiveness of the proposed method is validated by comparison with other conventional methods in terms of Error measures. Furthermore, the developed HBCro‐based RNN obtained efficient performance in terms of MSE, MAE, RMSE, RMPSE, MAPE, MARE, MSRE, and RMSRE of 0.1578, 0.0442, 0.2102, 123.238, 124.72, 0.9944, 1.1799, and 1.0732, respectively. [ABSTRACT FROM AUTHOR]

In estimated 10–15% of neurosurgical interventions employing a conventional three-pin head fixation device (HFD) the patient's head loses position due to slippage. At present no scientifically based stability criterion exists to potentially prevent the intraoperative loss of head position or skull fractures. Here, data on the skull penetration depth both on the single and two-pin side of a three-pin HFD are presented, providing scientific evidence for a stability criterion for the invasive three-pin head fixation. Eight fresh, chemically untreated human cadaveric heads were sequentially pinned 90 times in total in a noncommercially calibrated clamp screw applying a predefined force of 270 N (approximately 60 lbf) throughout. Three head positions were pinned each in standardized manner for the following approaches: prone, middle fossa, pterional. Titanium-aluminum alloy pins were used, varying the pin-cone angle on the single-pin side from 36° to 55° and on the two-pin side from 25° to 36°. The bone-penetration depths were directly measured by a dial gauge on neurocranium. The penetration depths on the single-pin side ranged from 0.00 mm (i.e., no penetration) to 6.17 mm. The penetration depths on the two-pin side ranged from 0.00 mm (no penetration) to 4.48 mm. We measured a significantly higher penetration depth for the anterior pin in comparison to the posterior pin on the two-pin side in prone position. One pin configuration (50°/25°) resulted in a quasi-homogenous pin depth distribution between the single- and the two-pin side. Emanating from the physical principle that pin depths behave proportionate to pin pressure distribution, a quasi-homogenous pin penetration depth may result in higher resilience against external shear forces or torque, thus reducing potential complications such as slippage and depressed skull fractures. The authors propose that the pin configuration of 50°/25° may be superior to the currently used uniform pin-cone angle distribution in common clinical practice (36°/36°). However, future research may identify additional influencing factors to improve head fixation stability. [ABSTRACT FROM AUTHOR]

The vibration of tunnel boring machine (TBM) is very difficult to monitor on sites, and related research on prediction methods is rare. Based on the field tunnelling test of a TBM in the Xinjiang Ehe project, the vibration information of the main beam of the TBM under different surrounding rock conditions is collected. The relationships among the tunnelling parameters, surrounding rock parameters and vibration parameters were studied. The results show that the penetration, cutter head speed, torque and thrust are important parameters affecting TBM vibration. In addition, the field penetration index and cutter head driving power index are significantly related to the root mean square of acceleration. Based on this, a multiple regression prediction model of TBM vibration is established. The model was verified and analysed via field projects, and the relative prediction error was less than 12%. This method can be used to predict the vibration of a TBM in real time through characteristic parameters without the use of a traditional monitoring system. This approach is highly important for determining the status of TBM equipment in real time. [ABSTRACT FROM AUTHOR]

A general geometric model of the elliptical cross-section double-ogive-nose projectile (ECDP) was established, and the expression of penetration resistance was obtained. Based on the special shape and penetration process characteristics of the ECDP, a three-stage penetration model was constructed, and closed-form penetration equations were derived. Three ECDPs with the major-minor axis ratio of 1.5 were launched by a 130 mm gas-gun to impact the plain concrete targets with the oblique angle of 10° at a nominal striking velocity of 650 m/s, the experimental data such as the penetration depth of the ECDPs and the failure characteristic parameter of the targets was obtained. The initial posture of the ECDP had little effect on the penetration depth and trajectory deflection under the condition of the target with 10° oblique angle, but it had obvious influence on the structural response. The theoretical model was verified by experimental data, the calculated result of the penetration depth was in good agreement with the experimental data, the deviation was within the range of -13.5% ~ -8.5%. [ABSTRACT FROM AUTHOR]

Steady pressure grouting exhibits the problems of low efficiency and uneven penetration. Therefore, this paper proposes a novel high-frequency pulsating grouting method to improve these problems. Through extensive experimentation and numerical simulations, the impact of pulsating parameters (grouting frequency, pressure amplitude), soil parameters (porosity, particle size), grouting pressure, water–cement ratio, and slurry rheological parameters on slurry penetration is investigated. The results indicate that the stone body grouted by the pulsating pressure is significantly more uniform and has longer penetration distances. During steady pressure grouting, as the grouting pressure or the water–cement ratio increases, the slurry is more prone to flow upward along the interface between the grouting pipe and the soil, which makes the grouted body uneven. When high-frequency pulsating grouting is employed, the slurry tends to flow into the soil, resulting in a more uniform grouted body. In the operating conditions described in this paper, the optimal pulsating frequency is around 3–4 Hz, and the optimal pulse amplitude is approximately 60% of the constant pressure. The results also show that the pulsating grouting method can increase the width by up to 68%. With the increase in porosity and particle size, the percentage of distance increase first increases and then decreases. The percentage of distance increase increases with the increase in viscosity and decreases with the increase in the Bingham rheological parameters ( μ p and τ 0 ). This implies that the pulsating grouting needs certain resistance conditions to achieve optimal penetration performance. The mechanism of pulsating grouting is also analyzed. Pulsating pressure can clear blocked particles and lead to more uniform penetration of the slurry. This study can provide reference for the development of new grouting methods and equipment. [ABSTRACT FROM AUTHOR]

The challenges pertaining to low rock-breaking efficiency and high drilling cost in deep hard formation and hot dry rock (HDR) are highly pronounced. A novel drilling technology, the combined thermomechanical drilling technology, has demonstrated its potential to enhance the rate of penetration. However, the rock-breaking mechanism for thermal spalling-assisted rock breaking by the drilling bit remains inadequately understood. This paper establishes a model of thermal spalling-assisted rock cutting (TSARC) by polycrystalline diamond compact (PDC) cutter to investigate the influence of different heating and cutting parameters on the rock-breaking efficiency. The outcomes indicate that the brittleness of heterogeneous rock decreases while its plasticity increases after undergoing high-temperature heating. Consequently, this reduces the cutting force and mechanical specific energy (MSE) of the PDC cutter. In the TSARC process, an increase in heating power corresponds to an increase in rock-breaking efficiency. However, once a certain temperature threshold is reached, the rock surface suffers complete destruction due to the high temperature, while the MSE remains unchanged. When considering the same heating parameters, the MSE of TSARC and traditional rock cutting (TRC) is directly proportional to the cutting velocity. The larger the cutting depth and rake angle of TRC, the higher is the rock-breaking efficiency. In contrast, the smaller the cutting depth and rake angle of TSARC, the higher is the rock-breaking efficiency, and the cutting force can be reduced by up to 94%. This study also includes an experimental program to examine the effect of thermal source height and velocity on the rock-breaking behavior of TSARC. It was observed that in comparison to TRC, when the thermal source movement speed of TSARC is 7.5 cm/s or the thermal source height is 5 cm, a significant reduction of 47.37% and 54.1% in the average cutting force, respectively, can be achieved. The results are of positive significance for increasing the rock-breaking efficiency and drilling speed in deep hard and HDR formations. Highlights: The numerical simulation model of granite based on geometric heterogeneity and material heterogeneity is established; Based on the thermal mechanical coupling theory, the numerical model of thermal spalling-assisted rock cutting by the PDC cutter is established. The rock-breaking mechanism of assisted rock cutting under different heating power and cutting parameters is investigated. The laboratory experiment of thermal spalling-assisted rock cutting is carried out to verify the numerical experiment, and the rock-breaking characteristics of cutting under different thermal source heights and moving velocities are studied. [ABSTRACT FROM AUTHOR]

Polyurea has gained significant attention in recent years as a functional polymer material, specifically regarding blast and impact protection. The molecular structure of polyurea is characterized by the rapid reaction between isocyanate and the terminal amine component, and forms an elastomeric copolymer that enhances substrate protection against blast impact and fragmentation penetration. At the nanoscale, a phase-separated microstructure emerges, with dispersed hard segment microregions within a continuous matrix of soft segments. This unique microstructure contributes to the remarkable mechanical properties of polyurea. To maximize these properties, it is crucial to analyze the molecular structure and explore methods like formulation optimization and the incorporation of reinforcing materials or fibers. Current research efforts in polyurea applications for protective purposes primarily concentrate on construction, infrastructure, military, transportation and industrial products and facilities. Future research directions should encompass deliberate formulation design and modification, systematic exploration of factors influencing protective performance across various applications and the integration of numerical simulations and experiments to reveal the protective mechanisms of polyurea. This paper provides an extensive literature review that specifically examines the utilization of polyurea for blast and impact protection. It encompasses discussions on material optimization, protective mechanisms and its applications in blast and impact protection. [ABSTRACT FROM AUTHOR]

Recently, worldwide, the attention being paid to hydrogen and its derivatives as alternative carbon-free (or low-carbon) options for the electricity sector, the transport sector, and the industry sector has increased. Several projects in the field of low-emission hydrogen production (particularly electrolysis-based green hydrogen) have either been constructed or analyzed for their feasibility. Despite the great ambitions announced by some nations with respect to becoming hubs for hydrogen production and export, some quantification of the levels at which hydrogen and its derived products are expected to penetrate the global energy system and its various demand sectors would be useful in order to judge the practicality and likelihood of these ambitions and future targets. The current study aims to summarize some of the expectations of the level at which hydrogen and its derivatives could spread into the global economy, under two possible future scenarios. The first future scenario corresponds to a business-as-usual (BAU) pathway, where the world proceeds with the same existing policies and targets related to emissions and low-carbon energy transition. This forms a lower bound for the level of the role of hydrogen and its penetration into the global energy system. The second future scenario corresponds to an emission-conscious pathway, where governments cooperate to implement the changes necessary to decarbonize the economy by 2050 in order to achieve net-zero emissions of carbon dioxide (carbon neutrality), and thus limit the rise in the global mean surface temperature to 1.5 °C by 2100 (compared to pre-industrial periods). This forms an upper bound for the level of the role of hydrogen and its penetration into the global energy system. The study utilizes the latest release of the annual comprehensive report WEO (World Energy Outlook—edition year 2023, the 26th edition) of the IEA (International Energy Agency), as well as the latest release of the annual comprehensive report WETO (World Energy Transitions Outlook—edition year 2023, the third edition) of the IRENA (International Renewable Energy Agency). For the IEA-WEO report, the business-as-usual situation is STEPS (Stated "Energy" Policies Scenario), and the emissions-conscious situation is NZE (Net-Zero Emissions by 2050). For the IRENA-WETO report, the business-as-usual situation is the PES (Planned Energy Scenario), and the emissions-conscious situation is the 1.5°C scenario. Through the results presented here, it becomes possible to infer a realistic range for the production and utilization of hydrogen and its derivatives in 2030 and 2050. In addition, the study enables the divergence between the models used in WEO and WETO to be estimated, by identifying the different predictions for similar variables under similar conditions. The study covers miscellaneous variables related to energy and emissions other than hydrogen, which are helpful in establishing a good view of how the world may look in 2030 and 2050. Some barriers (such as the uncompetitive levelized cost of electrolysis-based green hydrogen) and drivers (such as the German H2Global initiative) for the hydrogen economy are also discussed. The study finds that the large-scale utilization of hydrogen or its derivatives as a source of energy is highly uncertain, and it may be reached slowly, given more than two decades to mature. Despite this, electrolysis-based green hydrogen is expected to dominate the global hydrogen economy, with the annual global production of electrolysis-based green hydrogen expected to increase from 0 million tonnes in 2021 to between 22 million tonnes and 327 million tonnes (with electrolyzer capacity exceeding 5 terawatts) in 2050, depending on the commitment of policymakers toward decarbonization and energy transitions. [ABSTRACT FROM AUTHOR]

Natural protective materials offer unparalleled solutions for impact-resistant material designs that are simultaneously lightweight, strong, and tough. Particularly, the Bouligand structure found in the dactyl club of mantis shrimp and the staggered structure in nacre achieve excellent mechanical strength, toughness, and impact resistance. Previous studies have shown that hybrid designs by combining different bioinspired microstructures can lead to enhanced mechanical strength and energy dissipation. Nevertheless, it remains unknown whether combining Bouligand and staggered structures in nanofibrillar cellulose (NFC) films, forming a discontinuous fibrous Bouligand (DFB) architecture, can achieve enhanced impact resistance against projectile penetration. Additionally, the failure mechanisms under such dynamic loading conditions have been minimally understood. In our study, we systematically investigate the dynamic failure mechanisms and quantify the impact resistance of NFC thin films with DFB architecture by leveraging previously developed coarse-grained models and ballistic impact molecular dynamics simulations. We find that when nanofibrils achieve a critical length and form DFB architecture, the impact resistance of NFC films outperforms the counterpart films with continuous fibrils by comparing their specific ballistic limit velocities and penetration energies. We also find that the underlying mechanisms contributing to this improvement include enhanced fibril sliding, intralayer and interlayer crack bridging, and crack twisting in the thickness direction enabled by the DFB architecture. Our results show that by combining Bouligand and staggered structures in NFC films, their potential for protective applications can be further improved. Our findings can provide practical guidelines for the design of protective films made of nanofibrils. [ABSTRACT FROM AUTHOR]

It is inevitable to cut reinforced concrete (RC) appeared in cross passage of city metro by cutting tools when constructing in densely populated area. The previous cutters employed to cut RC are insufficient and easily damaged, so a new polycrystalline diamond compact (PDC) cutter is used to solve this question. Based on the theoretical analysis of cutting mechanism, both circular and tapered PDC cutters with cutting edge angle of 90° and negative front rack angle of 10° are used to cut RC. The peeling and breaking patterns of cutting concrete are proposed, the nodular and grainy chips are the preferred modes in cutting steel bars. The LS-DYNA is employed to investigate the cutting performance in advance. The simulation results show that the average and peak cutting forces increase with the growth of penetration depth, cutting speed, and roundness, and subsequently the recommended penetration depth less than 1.2 mm is obtained to cut RC due to the existence of steel bars. Moreover, the linear cutting platform is adopted to investigate the force ability and damage state of PDC cutters. It is concluded that the cutting force increases abruptly and fluctuates heavily when cutting the coarse aggregates. The patterns occurred in both numerical and experimental results are generally similar. Notably, the steel bar is pulled out and the PDC cutter is damaged at the penetration depth of 0.8 mm, while a good cut occurs at the penetration depth of 0.3 mm. The tapered PDC cutter with a relatively low cutting force is prone to be broken compared with circular PDC cutter. It is suggested that the circular PDC cutter at the penetration depth of 0.3 mm should be used to cut RC in practical engineering. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study and theoretical analysis on the penetration behavior of a tungsten-alloy long-rod projectile into a concrete target with an impact velocity ranging from 900 to 1,700 m/s. Different penetration regimes are investigated in the experiment in order to have a better understanding of the penetration mechanism of tungsten-alloy projectiles with different impact velocities. The state of the projectiles during penetration and damage parameters of residual projectile and targets are analyzed. Penetration models during abrasion and deforming stages are modified by taking into account of the coupling effects of abrasion, deforming, and shape evolution. Furthermore, the model during the eroding penetration stage is improved to describe the penetration process by considering shape evolution and deforming characteristics of the projectiles. Finally, the improved models are validated against the corresponding experimental results. The results indicate that the crater depth, diameter, and volume of a target are proportional to the impact velocity and impact kinetic energy, separately. The abrasion and deformation of the projectile have a great influence on its penetration process, which cannot be ignored. The calculated depth of penetration (DOP) with different velocities is well-correlated with the experimental results. Residual projectile after erosion penetration still has a greater penetration ability to the concrete target and contributes a larger proportion in the penetration depth. [ABSTRACT FROM AUTHOR]

Electrons in Earth's outer radiation belt are highly dynamic, with fluxes changing by up to orders of magnitude. The penetration of electrons from the outer belt to the inner belt is one such change observed during geomagnetic storms and was previously observed in electrons up to 1 MeV for some strong storms observed by the Van Allen Probes. We analyze pulse height analysis data from the Relativistic Electric and Proton Telescope (REPT) on the Van Allen Probes to produce electron flux measurements with lower minimum energy and significantly improved resolution compared to the standard REPT data and show that electron penetrations into the inner belt (L ≤ 2) extend to at least 1.3 MeV and penetrations into the slot region (2 < L < 2.8) extend to at least 1.5 MeV during certain geomagnetic storms. We also demonstrate that these penetrations are associated with butterfly pitch angle distributions from 1 to 1.3 MeV. Plain Language Summary: Electrons in Earth's outer radiation belt are highly dynamic with the amount and energy of them changing drastically, especially during geomagnetic storms. The penetration of electrons from the outer belt to the inner radiation belt is one such change and was previously observed in electrons with energies ≤1 MeV during some of the strongest storms during the Van Allen Probes mission. Electrons in the radiation belts also have a pitch angle that describes what portion of their motion is along or perpendicular to the direction of the magnetic field. Pitch angle distributions (PAD) are often used to gain information on the dynamics of the electrons, as unstable distributions can be caused by and indicative of wave activity that cannot always be measured directly. PADs with a minimum at 90°, called butterfly PADs, are one such unstable distribution that have previously been observed in penetrating electrons with energies ∼100–900 keV. We use instrument simulation to analyze data from the Van Allen Probes that could not previously be analyzed to show that the maximum energy of these penetrations is higher than previously observed, up to 1.3 MeV, and that these penetrations are associated with butterfly PADs at 1–1.3 MeV. Key Points: REPT PHA data can be used to produce high energy resolution flux spectra of >1 MeV electronsElectron penetrations below L = 2 during strong geomagnetic storms extend in energy up to 1.3 MeVElectron penetrations below L = 2 at energies 1–1.3 MeV are associated with butterfly pitch angle distributions [ABSTRACT FROM AUTHOR]

This study aimed to ascertain the alterations in aging responses of fiber‐reinforced composites, as well as the effects of their natural particle reinforcement, through exposure to acidic and alkaline solutions. Specimens were produced with 0 wt. % (neat), 1 wt. %, 2 wt. % and 3 wt. % particle ratios from acorn and pinecone particles. A particle content of 2 wt. % was determined to yield the best mechanical properties in all mechanical tests conducted for pinecone reinforcement. The highest improvement in strength, observed in 3 wt. % pinecone‐reinforced composites, reached 22.5% at flexural strength. HCl and NaOH diluted in water were chosen as aging solutions. Mechanical tests were repeated at different stages of aging. According to the findings, 1 wt. % particle‐reinforced composites showed better resilience to the mechanical property reduction effect of aging compared to the 2 wt. % and 3 wt. % particle‐reinforced composites. At a particle ratio of 2 wt. %, the acorn‐reinforced specimens exhibit their highest maximum penetration force, which is 5% higher than that of the 0 wt. % composite, consistent with the results of tensile and compressive tests. Highlights: Composite material was manufactured by hand lay‐up and vacuum bagging method.Specimens were aged using acid and base solutions.Tensile, compressive, and bending results were obtained depending on particle type and ratio.Tensile, compressive, and bending strengths of composites were compared according to various aging times. [ABSTRACT FROM AUTHOR]

The social burden of dementia is remarkable since it affects some 57.4 million people all over the world. Impairment of autophagy in age-related diseases, such as dementia, deserves deep investigation for the detection of novel disease-modifying approaches. Several drugs belonging to different classes were suggested to be effective in managing Alzheimer's disease (AD) by means of autophagy induction. Useful autophagy inducers in AD should be endowed with a direct, measurable effect on autophagy, have a safe tolerability profile, and have the capability to cross the blood–brain barrier, at least with poor penetration. According to the PRISMA 2020 recommendations, we propose here a systematic review to appraise the measurable effectiveness of autophagy inducers in the improvement of cognitive decline and neuropsychiatric symptoms in clinical trials and retrospective studies. The systematic search retrieved 3067 records, 10 of which met the eligibility criteria. The outcomes most influenced by the treatment were cognition and executive functioning, pointing at a role for metformin, resveratrol, masitinib and TPI-287, with an overall tolerable safety profile. Differences in sample power, intervention, patients enrolled, assessment, and measure of outcomes prevents generalization of results. Moreover, the domain of behavioral symptoms was found to be less investigated, thus prompting new prospective studies with homogeneous design. PROSPERO registration: CRD42023393456. [ABSTRACT FROM AUTHOR]

This research aimed to examine the radiation shielding properties of unique polymer composites for medical and non-medical applications. For this purpose, polymer composites, based on poly methyl methacrylate (PMMA) as a matrix, were prepared and reinforced with micro- and nanoparticles of ZrO2 fillers at a loading of 15%, 30%, and 45% by weight. Using the high purity germanium (HPGe) detector, the suggested polymer composites' shielding characteristics were assessed for various radioactive sources. The experimental values of the mass attenuation coefficients (MAC) of the produced composites agreed closely with those obtained theoretically from the XCOM database. Different shielding parameters were estimated at a broad range of photon energies, including the linear attenuation coefficient (μ), tenth value layer (TVL), half value layer (HVL), mean free path (MFP), effective electron density (Neff), effective atomic number (Zeff), and equivalent atomic number (Zeq), as well as exposure buildup factor (EBF) and energy absorption buildup factor (EABF) to provide more shielding information about the penetration of γ-rays into the chosen composites. The results showed that increasing the content of micro and nano ZrO2 particles in the PMMA matrix increases μ values and decreases HVL, TVL, and MFP values. P-45nZ sample with 45 wt% of ZrO2 nanoparticles had the highest μ values, which varied between 2.6546 and 0.0991 cm−1 as γ-ray photon energy increased from 0.0595 to 1.408 MeV, respectively. Furthermore, the highest relative increase rate in μ values between nano and micro composites was 17.84%, achieved for the P-45nZ sample at 59.53 keV. These findings demonstrated that ZrO2 nanoparticles shield radiation more effectively than micro ZrO2 even at the same photon energy and filler wt%. Thus, the proposed nano ZrO2/PMMA composites can be used as effective shielding materials to lessen the transmitted radiation dose in radiation facilities. [ABSTRACT FROM AUTHOR]

Microfluidic based sensors are one of the emerging alternatives for bringing solutions studies on paper platforms. Microfluidic paper assisted platform was developed over here through a simple, easy, cost effective and instrument free process. The self‐same method of waxing through crayoning, was estimated thoroughly on different paper platforms. Varied parameter including type of crayoning, way of patterning, color effect, wicking rate and channel optimization was performed on paper milieus. Optimized time of baking for obtaining controlled penetration ranges from 2 min to 8 min depending on the type of paper used. Wax crayoning was preferred over oil pasteling for making hydrophobic barriers uniformly, solid as well fully penetrated within paper inner layers. Fabrication through this easy cost‐effective route allows a formation of hydrophilic reaction or sensing zone of 0.25 cm2 with sufficient reactive area. Further sensing of dopamine on paper platform was carried using paper chip adsorbed with fluorescent modified graphene quantum dots as sensing material. The patterned paper showed advantage as only few microliter (5 μl to 10 μl) range of sample volume was required for testing. Fluorescence quenching with increase of concentration was witnessed where around 25–75 μM dopamine concentration was positively tested through naked eye; which for the first time was demonstrated here via robust wax crayoning method for developing paper based biosensor. [ABSTRACT FROM AUTHOR]

A vast scientific literature has shed light on hydrogen as a promising vector for carbon-free mobility. Within this scope, over the last few decades several efforts were directed towards the characterization of hydrogen spray, given its significant influence on the combustion efficiency. Nevertheless, several aspects underlying the hydrogen spray development are still far from being fully understood. This framework prompted the authors to undertake a robust experimental campaign, performing hydrogen injections over a wide range of injection settings. In this study, the schlieren method was utilized to capture the image of jets performed at injection pressure of 3.6 MPa and exiting an outward-opening injector. Afterwards, the spray images were processed by means of an in-home developed Matlab script. In order to assess the spray characteristics, such as the penetration length, area and volume, the analysis of the results was focused on the combined impact of backpressure, ranging from 0.12 to 1.5 MPa, with current profile determining the pintle dynamic. Besides, a qualitative analysis of the injection setting impact on the shock wave position was carried out. In the light of emerged findings, the research serves as a further baseline for forthcoming research activities dealing with hydrogen spray. • The pintle motion engenders a rarefaction wave, benefiting the hydrogen momentum. • Greater currents, energizing the injector coils, boost the pintle descent, and the jet penetration is faster. • Increasing backpressure and weaker currents curb the spray area and volume developments. • Weaker currents prolong the transient of the shock wave position. • Higher backpressures and lower currents lead the shock wave to arise more closely to the injector. [ABSTRACT FROM AUTHOR]

Introduction/purpose: In recent times, with the tendency to develop new types of armor-piercing ammunition, constant investments in the development of new types of armored obstacles is necessary. Obstacles made of high-alloy steel plates are still the best form of protection against larger caliber ammunition. There are a number of factors to consider when selecting an alloy, including the weight, dimensions, intended use, desired ballistic performance, and costs. According to that, a numerical analysis of penetration of a 30mm armor-piercing fin-stabilized discarding sabot projectile into the steel alloy Weldox 460 plates of different thicknesses at a distance of 1000m with a velocity of 1300m/s is presented in this paper. Methods: The stresses and deformations of the penetration effect were calculated through numerical analysis and finite element modeling. To specify material characteristics, the Johnson-Cook material model and the fracture of materials model have been utilized. In order to define models and carry out numerical calculations, the software packages FEMAP and LS Dyna have been used in this paper. Results: For a numerical analysis of the penetration process of this projectile type against armor obstacle, four different armor plate thicknesses are calculated: 10mm, 50mm, 100mm, and 110mm. For each of them, the results are shown in a form of stress and displacement, so that the interaction phenomena between the sub-projectile and the armor plate can be described. Conclusion: Modeling the impact on armor-piercing obstacles is extremely difficult, time-consuming, and complex, and the resulting models very successfully (or with some deviation) approximate the real problem of projectile penetration. One of the most effective methods for solving problems of this kind and others of a similar nature in recent times is the finite element method analysis. The material and the target dimensions, as well as the ballistic parameters and the material of the projectile have the biggest influence on projectile penetration. The target's resistance to penetration increases when all input parameters are maintained at the same level and its thickness is increased, and vice versa. [ABSTRACT FROM AUTHOR]

The potential improvement in sonication efficiency achieved by tilting the focused ultrasound (FUS) transducer of the transcranial MR-guided FUS system is presented. A total of 56 cases of patient treatment data were used. The relative position of the clinical FUS transducer to the patient's head was reconstructed, and region-specific skull density and porosity were calculated based on the patient's CT volume image. The total transmission coefficient of acoustic waves emitted from each channel was calculated. Then, the total energy penetrating the human skull—which represents the sonication efficiency—was estimated. As a result, improved sonication efficiency was by titling the FUS transducer to a more appropriate angle achieved in all 56 treatment cases. This simulation result suggests the potential improvement in transcranial-focused ultrasound treatment by simply adjusting the transducer angle. [ABSTRACT FROM AUTHOR]

In mechanized tunneling, the ability to accurately predict the performance of the tunnel boring machine (TBM) is critical, because of its impacts on the project schedule and cost. A substantial amount of research has been conducted on predicting the penetration rate of TBMs in rocks but sometimes the actual cutting process of the disc cutter has been ignored, as most of the available models have been developed based on the assumption that the chipping process is the dominant mode of rock breakage. This might be true in many cases, but there are also situations where tensile fractures do not extend long enough to form chips, instead the tracks get deeper, and fines and rock powder are generated instead of chipping. This situation happens when the cutter load is insufficient to form chips, or so called sub-critical loading occurs. Two of the recent tunneling projects where subcritical cutter load has been the dominant mode are the southern extension of Tehran subway Line 6 (SEL6), and the southern lot of Kerman water conveyance tunnel (KrWCT). The issue in SEL6 was insufficient thrust of the machine and in KrWCT the high strength of the rock. Evaluation of the FPIs in SEL6 shows that the FPIs were less than 100 (kN/cutter/mm/rev) and the prediction errors of the existing models are low. However, in KrWCT project in rocks with higher strength and higher FPIs, the prediction errors are considerable. This indicates that the common models cannot offer an accurate estimate of the performance of TBM in subcritical loading in rocks with high strength. This study attempts to use statistical and machine learning methods to develop a new relation for TBM performance prediction in such conditions based on actual machine operating data and rock engineering geological features. New equations are introduced for the estimation of FPI in subcritical loading conditions to achieve more reliable and accurate prediction of TBM penetration rate. Highlights: Issues of hard rock TBM performance predictions in subcritical cutter load conditions. Development of a new performance prediction model for subcritical loading conditions using regression analysis and AI algorithms. Consideration of geological and geotechnical parameters and machine specification in model development. [ABSTRACT FROM AUTHOR]

Genomic dissection of genetic effects on desirable traits and the subsequent use of genomic selection hold great promise for accelerating the rate of genetic improvement of forest tree species. In this study, a total of 661 offspring trees from 66 open-pollinated families of Japanese larch (Larix kaempferi (Lam.) Carrière) were sampled at a test site. The contributions of additive and non-additive effects (dominance, imprinting and epistasis) were evaluated for nine valuable traits related to growth, wood physical and chemical properties, and competitive ability using three pedigree-based and four Genomics-based Best Linear Unbiased Predictions (GBLUP) models and used to determine the genetic model. The predictive ability (PA) of two genomic prediction methods, GBLUP and Reproducing Kernel Hilbert Spaces (RKHS), was compared. The traits could be classified into two types based on different quantitative genetic architectures: for type I, including wood chemical properties and Pilodyn penetration, additive effect is the main source of variation (38.20-67.46%); for type II, including growth, competitive ability and acoustic velocity, epistasis plays a significant role (50.76-91.26%). Dominance and imprinting showed low to moderate contributions (< 36.26%). GBLUP was more suitable for traits of type I (PAs = 0.37–0.39 vs. 0.14–0.25), and RKHS was more suitable for traits of type II (PAs = 0.23–0.37 vs. 0.07–0.23). Non-additive effects make no meaningful contribution to the enhancement of PA of GBLUP method for all traits. These findings enhance our current understanding of the architecture of quantitative traits and lay the foundation for the development of genomic selection strategies in Japanese larch. [ABSTRACT FROM AUTHOR]

Microstructure evolution and physical property differences in tungsten inert gas (TIG) welding and laser beam welding (LBW) with a Nd:YAG laser of Q235 steel and 304 stainless steel in qualified welded joints were obtained through single factor experimental design. The results showed that the microstructure of the weld zone (WZ) is composed of lath martensite, and carbon migration occurred at the interface in the Q235 steel. Under the condition of full penetration of the welded joint, the tensile specimens fractured on the side of Q235 steel, indicating that the strength of the welded joint is higher than that of the Q235 base material (BM). These fracture morphologies presented the characteristics of ductile fracture. The distribution of microhardness in each region of welded joint in terms of heat affected zone (HAZ), BM and WZ was WZ > 304 side HAZ > 304 BM > Q235 side HAZ > Q235 BM. [ABSTRACT FROM AUTHOR]

Porous tantalum (Ta) implants have important clinical application prospects due to their appropriate elastic modulus, and their excellent bone growth and bone conduction ability. However, porous Ta microstructure designs generally mimic titanium (Ti) implants commonly used in the clinic, and there is a lack of research on the influence of the microstructure on the mechanical properties and penetration characteristics, which will greatly affect bone integration performance. This study explored the effects of different microstructure parameters, including the fillet radius of the middle plane and top planes, on the mechanics and permeability properties of porous Ta diamond cells through simulation, and put forward an optimization design with a 0.5 mm midplane fillet radius and 0.3 mm top-plane fillet radius in order to significantly decrease the stress concentration effect and improve permeability. On this basis, the porous Ta structures were prepared by Laser Powder Bed Fusion (LPBF) technology and evaluated before and after microstructural optimization. The elastic modulus and the yield strength were increased by 2.31% and 10.39%, respectively. At the same time, the permeability of the optimized structure was also increased by 8.25%. The optimized microstructure design of porous Ta has important medical application value. [ABSTRACT FROM AUTHOR]

This paper proposes a method for estimating the speed and position of unsampled vehicles using sampled data from connected automated vehicles (CAVs). The determination of vehicle speed and position on the road is a challenging and crucial task, as they can effectively reflect traffic flow characteristics and contribute to traffic state estimation and intersection signal timing optimization. Connected automated vehicles have the capability to upload their own trajectory data while also capturing trajectory data of surrounding vehicles through onboard sensors. Therefore, this paper proposes a novel approach to estimate the speed and position of unsampled vehicles. Firstly, using real vehicle trajectory data, the correlation between the velocity of following vehicles and the velocity of leading vehicles under different densities is analyzed, leading to the development of a velocity estimation model incorporating a speed correction factor. Secondly, the correlation between time headway, the rate of change of following vehicle acceleration, and traffic density is examined. To address the issue of heterogeneous behavior in vehicle following described by the Intelligent Driver Model (IDM), a real-time optimization model for estimating vehicle position by optimizing IDM parameters is proposed. The velocity estimation model and the position estimation model are summarized as two nonlinear optimization problems. Finally, the proposed method is validated using actual vehicle trajectory data. Experimental results demonstrate that when the number of connected automated vehicles (CAVs) is 2, the proposed method reduces the average absolute error by 30.73% and the standard deviation of the average absolute error by 42.8% compared to a linear model-based speed estimation method under different density conditions. Compared to a method that estimates vehicle position by calibrating desired gaps, the proposed method reduces the average absolute error by 38.2% and the standard deviation of the average absolute error by 41.7% under different density conditions. Furthermore, the proposed method exhibits good practicality under different CAV penetration rates. [ABSTRACT FROM AUTHOR]

To support the structural optimization design of metal-ceramic armor against penetration protection performance, this paper optimizes the armor in terms of protection material, armor structure, and bullet resistance mechanism, and envisages a new metal-constrained ceramic composite armor, which overcomes the disadvantages of ceramic material fragility. A coupled finite element-smooth particle hydrodynamics (FEM-SPH) algorithm is used to simulate the penetration process, and the influence of ceramic unit shape and size on the armor protection performance is investigated by quantitatively comparing the bullet energy loss, velocity change, penetration depth, and other indicators that reflect the ballistic protection mechanism. The results show that metal-confined ceramic armor has repairable performance, and filling ceramic units can reduce armor failure area, save armor repair time, and extend armor service life. When the velocity of the projectile is less than 500 m/s, the damaged area of the armor filled with small-sized unit ceramics (1/4 bullet caliber) is small and easy to repair; when the velocity of the projectile is greater than 500 m/s, the armor filled with large-sized unit ceramics (2 times the bullet caliber) can effectively increase the bullet residence time and improve the armor's resistance to elasticity. The results of this paper can provide a reference for the optimal design of the armor structure. [ABSTRACT FROM AUTHOR]

Poor fuel–air mixing of the diesel spray in low ambient temperature and pressure or thin air leads to intricate fuel breakup mechanism near the nozzle, which still remains worth of study. In this study, a pressure-based modified multiphase lattice Boltzmann flux solver (MLBFS) is proposed to accommodate the fuel spray breakup characteristics of multiphase, multicomponent, and large density ratio, in which the source terms of governing equation are modified emphatically for high injection pressure. Therefore, the characteristics of microscopic diesel spray breakup induced by Rayleigh–Taylor instability are investigated, including spray penetration, spray area, and spray arc length. It is revealed that the spray penetration is increased exponentially with the fuel–air density ratio Rρ. Influenced by air resistance and circulation interference, the roll-up vortex, droplet size, and spray area increase with the decreasing of Rρ (corresponding to high ambient pressure). Affected by entrainment and Rayleigh–Taylor instability, the development of the spray arc length experienced three stages: rapid growth, peak, and violent fluctuation, in which the lower Rρ facilitates development. It is concluded that Rayleigh–Taylor instability is favorable for stimulating the spray internal circulation of spray to enhance entrainment with surrounding air, while improving roll-up and breakup in the spray tail region. Such investigation is conductive to better understanding the micro-breakup mechanisms of fuel spray in the spray-induced internal combustion engine. [ABSTRACT FROM AUTHOR]

Transportation of the drilled cuttings to the surface is required to ensure optimum hole cleaning condition that is needed to fasten the drilling process. Transportation of these cuttings is challenging regardless of the well trajectory because of the several parameters controlling the performance of the drilling mud to raise these cuttings, and the severity of the hole cleaning problems is increased for the deviated and horizontal wells due to the increase in the wellbore inclination. All of the currently available parameters considered for evaluating the hole cleaning condition do not include the effect of some of the influential factors affecting the hole cleaning condition. This study evaluates the hole cleaning factor (HCF) which is a new hole cleaning parameter developed by modifying the cutting carrying index. HCF considers the impact of all parameters affecting the hole cleaning conditions, which involve the impact of the drilled hole size and inclination, the size of the drill pipe, the drilling fluid rheology, mud density, and its flowrate, and rate of penetration. The developed HCF is applicable to evaluate the hole cleaning in the vertical and deviated wells on real time while drilling. The HCF model was applied to evaluate the hole cleaning situation in vertical and deviated wells. The results showed an excellent correlation between the conditions predicted with the HCF and the daily drilling reports. The crew members reported an increase in the torque with fluctuation in the drilling parameters followed by stuck pipe condition at the sections identified by the HCF. [ABSTRACT FROM AUTHOR]

This paper presents experimental results on the behavior of a class of glass fiber composites under low velocity impacts, in order to analyze their usage in designing low velocity impact-resistant components in car and marine industries. Also, a finite element model at the meso level (considering yarn as a compact, homogenous and isotropic material) was run with the help of Ansys Explicit Dynamics in order to point out the stages of the failure and the equivalent stress distribution on the main yarns in different layers of the composite. The composites were manufactured at laboratory scale via the laying-up and pressing method, using a quadriaxial glass fiber fabric (0°/+45°/90°/−45°) supplied by Castro Composites (Pontevedra, Spain) and an epoxy resin. The resin was a two-component resin (Biresin® CR82 and hardener CH80-2) supplied by Sika Group (Bludenz, Austria). The mass ratio for the fabric and panel was kept in the range of 0.70–0.77. The variables for this research were as follows: the number of layers of glass fiber fabric, the impact velocity (2–4 m/s, corresponding to an impact energy of 11–45 J, respectively) and the diameter of the hemispherical impactor (Φ10 mm and Φ20 mm) made of hardened steel. The tests were performed on an Instron CEAST 9340 test machine, and at least three tests with close results are presented. We investigated the influence of the test parameters on the maximum force (Fmax) measured during impact, the time to Fmax and the duration of impact, tf, all considered when the force is falling to zero again. Scanning electron microscopy and photography were used for discussing the failure processes at the fiber (micro) and panel (macro) level. At a velocity impact of 2 m/s (corresponding to an impact energy of 11 J), even the thinner panels (with two layers of quadriaxial glass fiber fabric, 1.64 mm thickness and a surface density of 3.51 kg/m2) had only partial penetration (damages on the panel face, without damage on panel back), but at a velocity impact of 4 m/s (corresponding to an impact energy of 45 J), only composite panels with six layers of quadriaxial fabric (5.25 mm thickness and a surface density of 9.89 kg/m2) presented back faces with only micro-exfoliated spots of the matrix for tests with both impactors. These results encourage the continuation of research on actual components for car and naval industries subjected to low velocity impacts. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC) is a cement-based material with excellent impact resistance. Compared with traditional concrete, it possesses ultra-high strength, ultra-high toughness, and ultra-high durability, making it an ideal material for designing structures with impact resistance. The research on the impact resistance performance of UHPC and its composite structures is of great significance for the structural design of protective engineering projects. However, currently, there is still insufficient research on the impact resistance performance of UHPC composite structures. To study the impact resistance performance, experiments were conducted on UHPC targets using high-speed projectiles. The results were compared with impact tests on granite targets. The results indicated that when subjected to projectile impact, the UHPC targets exhibited smaller surface craters compared with the granite targets, while the penetration depth was lower in the granite targets. Afterwards, the process of a projectile impacting the UHPC composite structure was numerically simulated using ANSYS 16.0/LS-DYNA finite element software. The numerical simulation results of penetration depth and crater diameter were in good agreement with the experimental results, which indicates the rationality of the numerical model. Based on this, further analysis was carried out on the influence of impact velocity, impact angle, and reinforcement ratio on the penetration depth of the composite structure. The results show that the larger the incident angle or the smaller the velocity of the projectile is, the easier it is to deflect the projectile. There is a linear relationship between penetration depth and reinforcement ratio; as the reinforcement ratio increases, the penetration depth decreases significantly. This research is of great significance in improving the safety and reliability of key projects and also contributes to the application and development of ultra-high-performance materials in the engineering field. [ABSTRACT FROM AUTHOR]

The impact of corrosion and its inhibition is not new to the scientific world. The present work reports the Copper corrosion inhibition efficiency of Boron Nitride Nanosheets (BNNS) dispersed biopolymer blend of Gum Arabic and Sodium Alginate coded GASA3 in acidic medium. The uniform dispersion of BNNS prepared by liquid phase exfoliation using ultrasonication method with Dimethyl Formamide significantly enhanced the inhibition rate of GASA3 on Copper. UV–visible spectra of bulk BN, BNNS and BNNS dispersed in GASA3 were obtained to confirm the dispersion stability of prepared nanosheets. The inhibition efficiency (IE) on Copper by BNNS dispersed GASA3 blend solution has been investigated by mass loss method, potentiodynamic polarization method, and electrochemical impedance method. The anticorrosion nature of BNNS is attributed to its barrier property, impermeable nature, uniform dispersion and electrical insulating property. The examination of atomic force microscopy images and field emission scanning electron microscope images obtained helped in proving the adsorption of molecules which delayed the penetration of acid molecules onto the Copper surface. The IE% obtained for BNNS dispersed GASA3 solution are 97.2%, 98.7% and 95% from weight loss, potentiodynamic polarization, and electrochemical impedance methods, respectively. [ABSTRACT FROM AUTHOR]

The growing energy demand and the emerging environmental concerns across the globe caused increasing penetration of renewable energy sources (RESs) in distribution systems. One of the major issues faced by modern distribution systems with high RESs penetration is voltage instability. Generally, voltage instability can lead to voltage collapse, which is one of the key drivers for blackout incidents around the world. Under voltage load shedding (UVLS) schemes are usually executed as the final option to prevent a large-scale blackout or voltage collapse. But ever-increasing integration of RESs in distribution systems creates an additional threat to the existing UVLS schemes. Therefore, new UVLS methods are necessary to provide the appropriate corrective scheme for distribution systems, particularly when connected with RESs. This paper reviews and updates the recent UVLS methods emphasizing on distribution network application. In addition, the contributions and limitations of the conventional, adaptive, and computational intelligence techniques of UVLS are highlighted. Moreover, this paper provides an overview of the voltage stability indices applied for UVLS methods. Also, at the end of this review article, the further research directions to improve the safety of modern distribution systems during emergencies using UVLS are drawn as the conclusion. [ABSTRACT FROM AUTHOR]

Electrostatic spraying technology can improve the efficiency of pesticide deposition on the surface of leaves and reduce the environmental pollution caused by pesticide drift, which has an important prospect in agricultural pesticide application. To improve the deposition and penetration of droplets in the crop canopy, we designed and optimized an air-assisted electrostatic nozzle and conducted the spraying performance experiment. Parameters, such as charge-to-mass ratio (CMR) and particle size, were tested and analyzed to obtain the suitable operating parameters of nozzle. The results proved that the improved air-assisted electrostatic nozzle has good atomization and chargeability. There is a good charging effect with a charging voltage of 3,000-5,000 V, the CMR increased 127.8% from 0.86 to 1.97 mC/kg as the charge voltage increases from 1,000 to 4,000 V, at an air pressure of 1.0 bar and liquid flow rate of 200 ml/min. Furthermore, we designed a multi-factor orthogonal experiment, which was conducted using a four-factor, three-level design to investigate the effects of operational parameters and canopy characteristics on droplet deposition and penetration. Analysis of variance (ANOVA) and F-test were performed on the experiment results. The results showed that the factor effect on droplet penetration, in descending order, was as follows: spray distance, leaf area index, air pressure, and air pressure × spray distance. The factor effect on abaxial leaf deposition, in descending order, was as follows: air pressure, spray distance, air pressure × charge voltage, spray distance × charge voltage, and charge voltage. For optimal droplet penetration and abaxial leaf deposition, option A3B1D2 (air pressure 1.5 bar, spray distance 0.2 m, charge voltage 2,500 V) is recommend. The spray nozzle atomization performance and deposition regulation were studied by experimental methods to determine the optimal values of operating parameters to provide a reference for electrostatic spray system development. [ABSTRACT FROM AUTHOR]

A considerable amount of mobility data has been accumulated due to the proliferation of location-based services. Nevertheless, compared with mobility data from transportation systems like the GPS module in taxis, this kind of data is commonly sparse in terms of individual trajectories in the sense that users do not access mobile services and contribute their data all the time. Consequently, the sparsity inevitably weakens the practical value of the data even if it has a high user penetration rate. To solve this problem, we propose a novel attentional neural network-based model, named AttnMove, to densify individual trajectories by recovering unobserved locations at a fine-grained spatial-temporal resolution. To tackle the challenges posed by sparsity, we design various intra- and inter- trajectory attention mechanisms to better model the mobility regularity of users and fully exploit the periodical pattern from long-term history. In addition, to guarantee the robustness of the generated trajectories to avoid harming downstream applications, we also exploit the Bayesian approximate neural network to estimate the uncertainty of each imputation. As a result, locations generated by the model with high uncertainty will be excluded. We evaluate our model on two real-world datasets, and extensive results demonstrate the performance gain compared with the state-of-the-art methods. In-depth analyses of each design of our model have been conducted to understand their contribution. We also show that, by providing high-quality mobility data, our model can benefit a variety of mobility-oriented downstream applications. [ABSTRACT FROM AUTHOR]

To enhance the comprehension of the corrosion mechanism of refractories induced by molten slag, a 2D numerical model was developed in the present work. This model simulates the penetration of CaO–Al2O3–MeO slag into Al2O3–MgO refractory, considering capillary forces, as well as viscous and inertial resistances within the porous matrix acting on the molten slag. Experimental observations and measurements were conducted to validate the accuracy of the model. Through simulation, we visually represented the slag penetration process, highlighting the metamorphic reaction resulting from the diffusion of slag components. Notably, small aggregate particles had minimal impact on slag penetration. Instead, they were entirely enveloped by molten slag, subsequently peeling off from the refractory. The depth of penetration (αslag = 0.05, αslag represents the volume fraction of liquid slag) exceeded three times the corrosion depth (αslag = 0.99). Within the region penetrated by molten slag, a portion of the refractory matrix underwent metamorphosis into the liquidus phase. Significantly, reducing porosity emerged as an effective strategy to control molten slag penetration. A 44.7 pct reduction in corrosion depth was achieved by decreasing porosity from 0.28 to 0.14. This numerical model offers valuable insights into the factors influencing refractory corrosion and presents a quantitative approach for optimizing refractory designs to enhance resistance against slag penetration. [ABSTRACT FROM AUTHOR]

This study focuses on evaluating the influence of the energy accumulation hole diameter on bi-directional cumulative tension blasting. Firstly, the penetration depth of bi-directional cumulative tension blasting is determined, followed by an analysis of the corresponding fracture mechanics behavior. Secondly, the Smooth Particle Hydrodynamics (SPH) method is used for numerical analysis of the bi-directional cumulative tension blasting process, and the Johnson- Holmquist constitutive model is then employed to examine the dynamic process during tensile blasting-induced cracking. This analysis provides insights into damage development, particle distribution, stress distribution, and crack propagation in the rock at different opening diameters. The findings reveal that, except for the 2 mm case, bi-directional cumulative tension blasting effectively produces directional cracks aligned with the energy accumulation direction. For hole diameters between 4-8 mm, linear through cracks form in the energy accumulation direction. However, a 2 mm diameter opening only generates short shear cracks around the blast hole. With energy accumulation hole diameters ranging from 10-14 mm, the crack propagation depth is insufficient for complete penetration, despite the presence of linear cracks in the energy accumulation direction. When diameter exceeds 14 mm, symmetrical airfoil cracks appear in non-concentrated energy directions, with larger diameters resulting in shorter crack propagation lengths. During the directional cracking process for hole diameters of 4-8 mm, explosive particles facilitate crack expansion in width and length through the action of a "gas wedge." Onsite blasting tests confirm the excellent directional pre-splitting effect of bidirectional cumulative tension blasting. [ABSTRACT FROM AUTHOR]

To study the dynamic mechanical properties and failure characteristics of intersecting jointed rock masses with different joint distributions under confining pressure, considering the cross angle α and joint persistence ratio η, a numerical model of the biaxial Hopkinson bar test system was established using the finite element method–discrete-element model coupling method. The validity of the model was verified by comparing and analyzing it in conjunction with laboratory test results. Dynamics-static combined impact tests were conducted on specimens under various conditions to investigate the strength characteristics and patterns of crack initiation and expansion. The study revealed the predominant factors influencing intersecting joints with different angles and penetrations under impact loading. The results show that the peak stress of the specimens decreases first and then increases with the increase of the cross angle. When α < 60°, regardless of the value of η, the dynamic stress of the specimens is controlled by the main joint. When α ≥ 60°, the peak stress borne by the specimens decreases with increasing η. When α < 60°, the initiation and propagation of cracks in the cross-jointed specimens are mainly controlled by the main joint, and the final failure surface of the specimens is composed of the main joint and wing cracks. When α ≥ 60° or η ≥ 0.67, the secondary joint guides the expansion of the wing cracks, and multiple failure surfaces composed of main and secondary joints, wing cracks, and co-planar cracks are formed. Increasing lateral confinement significantly increases the dynamic peak stress able to be borne by the specimens. Under triaxial conditions, the degree of failure of the intersecting jointed specimens is much lower than that under uniaxial and biaxial conditions. [ABSTRACT FROM AUTHOR]

This systematic literature review evaluates reclaimed asphalt pavement (RAP) in concrete construction, targeting reduced natural aggregate use and lower construction carbon footprint. It comprehensively covers RAP in concrete, including mechanical properties, durability, test methods, mix design, performance, influencing factors, RAP content, processing, admixtures, curing, and environmental aspects. RAP concrete matches traditional concrete mechanically while increasing sustainability through waste reduction. Durability parameters, like permeability, freeze-thaw resistance, and chloride penetration, suggest long-term structural enhancement. Reliable testing methods and standards are vital for RAP in concrete assessment. The review explores RAP in mix design, considering content, gradation, and processing. Admixtures and additives optimize RAP concrete. Curing and environmental conditions influence RAP concrete performance. Gaps indicate a need for long-term studies, understanding mechanisms, specific environmental exploration, standardized testing, and economic assessment. The study recommends future research directions to guide sustainable construction practices. [ABSTRACT FROM AUTHOR]

The next generation of low observable (LO) unmanned combat aerial vehicle (UCAV) with highly autonomy to implement a penetration mission requires advanced methods for flyable and safe route planning (i.e., respecting physical capability of vehicle and threat coverage by hostile air defense radars) at a real‐time manner. Currently, the main challenge of real‐time route planning for LO UCAV is to achieve computationally efficiency under dynamic (pop‐up/moving) threats by air defense radars. In this paper, a real‐time planning paradigm in compliance with complex penetration requirements is proposed, and a complete modeling of route planning for LO UCAV's penetration as an optimal control problem is designed. The paper at first devises a direct method to transform the optimal control problem into a nonlinear programming (NLP) problem and then solves the formulated NLP problem under a moving planning horizon. The proposed method can give computationally efficient route planning results for LO UCAV's penetration under multiple kinds of radar threats. Numerical test results based on F‐16 uninhabited platform demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]