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The increase in repetitive strain injuries to the hand underscores the need for assessing and preventing musculoskeletal overuse associated with hand-intensive tasks. This study investigates the risk of overload injuries in soft tissue structures of the hand by analyzing the pressure distribution and location of peak pressure in the hand during snap-fit connection assembly in the automotive industry. The influence of the surface geometry of automotive trim components the pressure distribution and force imparted during strikes with the palm and the fist are investigated in a cohort of 30 subjects with extensive experience installing trim parts with snap-fit connections. Using the palm or fist (ulnar hand side) of the dominant hand, the subjects struck a simulation device with a flat, rounded, or edged surface geometry. The average peak force applied was 600 N (±122 N), nearly 3 times the force required to overcome the technical resistance of the snap-fit connector (220 N). Fist strikes exerted a 40% higher mean peak pressure and 18% higher mean pressure than did palm strikes. The pressure distribution in the region of the thenar eminence and soft tissue of the ulnar side of the hand did not differ between fist strikes on flat and edged surfaces. Considering the delicate anatomy of the hand, especially the hypothenar muscles on the ulnar side, assembling connection claps using the fist instead of the palm may prevent repetitive blunt trauma to the sensitive blood vessels and nerves in the palm. [ABSTRACT FROM AUTHOR]

Introduction: The assessment of seal pressure or leak pressure in supraglottic devices has commonly been used to confirm device functionality and for research purposes regarding laryngeal mask airways (LMAs). When used for controlled ventilation, the LMA Protector provides a better oropharyngeal seal pressure. Materials and Methods: In this cross-over study, thirty-five patients of either sex, aged 18 to 70 years, American Society of Anaesthesiology (ASA) class I and II, with a weight range of 50-70 kg, scheduled for elective surgery under general anaesthesia where a supraglottic airway device was indicated, were enrolled. In all 35 patients, the position of the patient's head and neck was changed from neutral to flexion, extension, and right and left lateral rotation. The primary objective of the study was to compare the differences in oropharyngeal leak pressure (OLP) with changes in head and neck positions using the LMA Protector airway device. Results: The mean age of the participants was 42.26 years, and the average weight was 63.34 kg. The LMA Protector was placed in 18 females and 17 males. A Mallampati grade of I was noted in 16 patients, while a grade of II was observed in 19 patients. The OLP achieved in this study was higher, providing adequate ventilation and oxygenation in all positions. The OLP and tidal volume in flexion were higher compared to the seal pressure in the neutral position (31.89 cm H2O, SD 5.080 cm H2O vs. 34.49 cm H2O, SD 4.804 cm H2O, p<0.05). No significant difference in OLP was observed when changing to different head positions, i.e., in extension, right lateral, and left lateral positions. Conclusion: The LMA Protector is an effective device in terms of achieving high oropharyngeal seal pressure. It produced better oropharyngeal seal pressure in the flexion position compared to the neutral position. [ABSTRACT FROM AUTHOR]

This study foresees the behavior of a 'Z' shaped in plan tall building under transient wind storms using unsteady Reynolds-averaged Navier Stokes (URANS) Computational Fluid Dynamics (CFD) technique. Numerical simulations are carried out using ANSYS - CFX, adopting length and velocity scales of 1:300 and 1:5, respectively. Surface streamlines are presented in the article to depict the wind flow characteristics and envisage the regions and nature of flow separations and vortex generations. The flow features also facilitate visualizing the wind pressure contours on building facets. The peak pressure coefficients concerning wind angles of 0° and 90° are presented to enable the cladding design of the building. Moreover, normalized wind pressure power spectra at three different sections along the altitude are offered for 0° to 150° wind at an interval of 30°. It is observed that towards the bottom portion of the building, the peak of the power spectra usually occurs in the low-frequency values. In contrast, at the top and main body of the building, the vortex shedding energy exaggerates at comparatively high reduced frequencies.. [ABSTRACT FROM AUTHOR]

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Current study provides comprehensive insights into the estimation of blast wave parameters within three distinct anisotropic media, namely transversely isotropic (Cadmium Sulphide CdS), monoclinic (Lithium Tantalate LiTaO3), and orthotropic (Ammonium Dihydrogen Phosphate ADP). Within the domain of blast modeling, there remains a significant gap in understanding the impact of surrounding media anisotropy—a crucial aspect often disregarded by numerous researchers. Acknowledging anisotropy holds paramount importance in studying the blast characteristics, the present work explores the velocity profiles of seismic quasi waves within the aforementioned anisotropic media, laying the groundwork for subsequent analyses estimating Scaled Peak Particle Displacement (SPPD) and Peak Pressure (PP). These parameters are evaluated using the Smith and Hetherington's model, and relying on experimental Peak Particle Velocity (PPV). Furthermore, the study investigates the influence of various sand types, ranging from very dense to loosen, on PP and SPPD within the context of the aforementioned anisotropic media. Additionally, the research entails the estimation and numerical simulation of underground blast parameters, along with the Reflection and Transmission (RT) coefficients relevant to scattering at the interface between two dissimilar media. The findings bear significant relevance in the field of geotechnical engineering, ground shock estimation, mining, particularly in predicting how various sand types respond under diverse loading conditions and external stresses. [ABSTRACT FROM AUTHOR]

Background: Hallux valgus (HV) morphological alterations impact forefoot kinetics. Surgery aims to restore both the morphology and function. Plantar pressure (PP) distribution systems represent an innovative additional tool to evaluate the hallux functional outcome after surgery in order to assess the hallux dorsiflexion, coupled with plantar flexion of the first ray. However, the literature reports limited evidence regarding the rebalancing of the plantar pressure distribution following surgery. The purpose of the present study was to examine the PP distribution in HV patients before and after a distal metatarsal osteotomy using a novel anatomically based protocol for in-shoe plantar load analysis during gait. Methods: A consecutive series of 18 patients with mild-to-moderate symptomatic HV who underwent a distal metatarsal osteotomy (S.E.R.I. technique) were prospectively evaluated using clinical scores (AOFAS and NRS), radiographic parameters (hallux valgus angle, intermetatarsal angle), and PP measurements via W-INSHOE© (Medicapteurs, Balma, France). Data were collected preoperatively and 12 months after surgery. Results: At 12 months follow-up, 3 patients were lost to follow-up, leaving 15 patients (24 HV) for examination. Both clinical and radiographical outcomes showed significant improvements from the pre- to postoperative periods. The PP distribution pattern revealed a significant increase in the peak pressure under the first metatarsal head associated with a significant increase in the peak pressure under the central metatarsals area between the pre- and postoperative periods. Conclusions: PP measurement systems hold promise as an additional clinical tool, yet current findings remain inconclusive. Further long-term follow-up studies that incorporate additional parameters are warranted. [ABSTRACT FROM AUTHOR]

BACKGROUND: Middle ear effusion (MEE) and tympanic membrane perforation (TMP) are difficult to distinguish using existing immittance techniques, necessitating the use of a separate test battery. Wideband absorbance (WBA) tympanometry is a new enhanced technique, and studies have shown a reliable WBA pattern to identify middle ear disorders. Thus, the study was performed to determine the WBA across the frequencies in ears with MEE, TMP, and compared with normal hearing individuals. METHODS: A total of 109 ears with TMP and 122 ears with MEE in the age range of 22-50 years were compared with 150 normal hearing ears. Otoscopic examination, middle ear fluid monitor, pure tone audiometry, and immittance measurements were performed to categorize the subject ears into groups. The absorbance levels at peak and ambient pressure across one-third octave frequencies in each group were statistically evaluated at α=0.05. RESULTS: Wideband absorbance for the normal ear group was lowest at low (<800 Hz) and high frequencies (>3000 Hz) and highest at midfrequency regions (800-3000 Hz). The MEE group had significantly lower WBA at all frequencies, and TMP group showed reduced WBA at low and mid-frequencies (<2500 Hz). Wideband absorbance at peak pressure was slightly higher than ambient pressure in all the groups. Receiver operating characteristic analysis demonstrated a high diagnostic value in the mid-frequency region for both the TMP and MEE groups. CONCLUSION: Wideband absorbance provides high reliability in discriminating between MEE and TMP and has a unique WBA pattern. Thus, WBA can be a useful diagnostic tool for the identification of middle ear disorders. [ABSTRACT FROM AUTHOR]

In this study, microemulsion synthesized from chemically extracted Salvinia molesta oil with diesel was evaluated as fuel in stationary unmodified diesel engine. The microemulsions from S. molesta oil was prepared using the best combinations of 67% S. molesta oil, 15% ethanol, 13% water and 5% surfactant (span 80) and its properties were compared with that of diesel. The engine test conducted with M10, M20 and M30 blends and reported a brake thermal efficiency of 29.76% and brake specific fuel consumption of 0.3239 kg/kWh with M20. The emissions like NO and smoke reduced by 18.07% and 7.37%, respectively, with marginal increase in CO, CO2 and unburned hydrocarbon by 3.8%, 3.4% and 16.66% respectively, with M20 compared to diesel at maximum engine load of 3.73 kW. At lower engine loads with M10, M20 and M30 slightly lower CO2 emission than diesel. A drop in peak pressure and heat release rate was found to be 1.73% and 8.40%, correspondingly with M20, as that of diesel. Even though a slight reduction in brake thermal efficiency observed with M20 as compared to M10 and diesel by considering the lowest emissions of NO and smoke, it is feasible to use as promising fuel for unmodified diesel engines.

The present study was conducted to study the benefit of high frequency tympanometry (HFT) in detecting middle ear pathologies in infants. This study also aims to find the effect of middle ear diseases on absent otoacoustic emissions (OAE). Our study was a prospective study which included 123 healthy neonates below 1 month of age. The babies were referred for the new born hearing screening programme. They were subjected to DPOAE followed by tympanometry with a 1000z probe tone (HFT). The study was approved by the institutions ethical committee. "Present" OAE result was obtained for 202 ears, while "absent" OAE result was obtained for 44 ears. High frequency tympanometry was also performed on all the participants, where a normal tympanogram was obtained in 170 ears and 76 ears showed an abnormal tympanogram. The following parameters were studied: peak pressure, ear canal volume and compliance. Descriptive statistics were obtained for the same. Association of OAE with HFT was studied. Out of the 44 ears with refer OAE, 34 ears had an abnormal tympanogram and among 202 ears with a present OAE, 160 ears had a normal tympanometric peak indicating a sensitivity and specificity of 77.3% and 79.2% respectively. High frequency tympanometry not only helps in early detection of middle ear pathologies but also to find the effect of middle ear diseases on absent otoacoustic emissions. [ABSTRACT FROM AUTHOR]

To address the problem of the insufficient regeneration of dust filter cartridges, a Venturi nozzle is introduced to improve the cleaning performance. The jet distance, cone height, and compressed air pressure effects on the pulsed-jet pressure distribution were experimentally investigated. Changes in the filtration pressure drop, fallen dust mass, and dust emission were also studied. As the jet distance increased, the pulsed-jet pressure and the total pulsed-jet intensity first increased and then decreased for both cases of common and Venturi nozzles, but the pulsed-jet uniformity increased. In the Venturi nozzle case, the pulsed-jet pressure in the lower section of the cartridge was effectively increased due to the larger induced airflow. As the cone height increased, the pulsed-jet pressure in the lower section of the cartridge decreased and that in the upper section increased for both nozzle cases. The dust filtration-cleaning experiment showed that the Venturi nozzle improved the operation performance of the dust collector. [Display omitted] [ABSTRACT FROM AUTHOR]

There are many influencing factors of bubble curtain clipping technology. In order to obtain the optimal combination of bubble curtain in engineering applications, AUTODYN software was used to design a three factor and three level orthogonal test. The average reduction rate of shock wave peak pressure was used as an evaluation index to study the influence and sensitivity of the number of bubble curtain layers, the burst distance of the bubble curtain and the charge depth on the bubble curtain clipping effect. The results indicate that the clipping ability of the bubble curtain has a great value, and there will be a negative effect if the number of bubble curtain layers continues to increase. The number of bubble curtain layers has the greatest effect on the clipping ability, followed by the charge depth, and the effect of bubble curtain explosion center distance is the smallest. The smaller the burst center distance and the greater the depth of the packet, the better the bubble curtain chipping effect. When the number of bubble curtain layers is 2, the bubble curtain burst distance is 1 m, and the charge depth is 10.5 m, the clipping effect is the best. [ABSTRACT FROM AUTHOR]

Increased ulcer risk diminishes the quality of life in diabetes. This study assessed abnormalities in foot plantar pressure distribution in adolescents with T1D to detect early signs of ulcer risk. A total of 102 T1D patients, without diabetic neuropathy, were included (mean age 17.8 years, mean diabetes duration 7.4 year). Pedography was captured using Novel emed. Data from the study group were compared with reference data. The study revealed a statistically significant reduced foot contact area in both feet in the entire foot and under the head of the fifth metatarsal bone and the second toe. In both feet, the peak pressure was increased under the entire foot, hindfoot, midfoot, first metatarsal head, big toe, and second toe. There was no statistically significant difference in peak pressure. The mean plantar pressure rating was statistically significantly increased in both feet across the entire sole, in the hindfoot, midfoot, and first metatarsal head. T1D patients of age near adulthood without neuropathy have increased values in mean pressure and reduced contact area, pointing to the need of monitoring and preventive measures. These results point to the need of further research and analysis which should include various risk factor such as foot anatomy, body posture, or certain metabolic factors. [ABSTRACT FROM AUTHOR]

Background and Aims Diabetes is associated with dysfunction and damage in various organs due to abnormal pressure on ten plantar regions. This study aims to compare the effect of offloading plantar pressure on peak pressure of ten plantar regions and gait speed in men with diabetes and active diabetic foot ulcers, and healthy men.Methods This is a causal-comparative study. Participants were 30 healthy men, 30 diabetic men and 30 men with active diabetic foot ulcers who needed no leg amputation according to their physicians. Sampling was done using random and convenience methods. Diabetic foot ulcers were classified based on the Meggitt-Wagner classification criteria, according to which grade 1 indicates grade 1 indicates a superficial ulcer and was used as a criterion for selecting people with diabetic foot ulcers. Plantar pressure variables were recorded using RSscan software (RSscan International, Belgium; 0.5×0.5×0.02 m, 4363 sensors) at a sampling frequency of 300 Hz and the gait speed was measured using a digital stopwatch. Correct walking considered as the full impact of the foot on the middle of the foot scan machine. Data were analyzed using independent t-test in SPSS software, version 24.Results The peak pressure in the metatarsal 3 (P

Air-inflated fabric arch structure has obvious advantage of being light-weight, able to accommodate large spans, low cost, easy mobilization and reusable. It has been widely applied to military and aerospace structures. However, there are few studies on its dynamic deployment behavior and self-erection feasibility during the construction phase, which restricts the breakthrough of its span and its development in civil buildings. In this study, the effects of considering heat exchange with the environment and the traditional adiabatic assumption of Control Volume method (CV Method)on deployment pressure were analysed and compared. Comparing the simulation with the experimental data, the feasibility of the ABAQUS fluid cavity in simulating the dynamic deployment behavior of Air-inflated fabric arch structure was verified. The traditional Control Volume Method were modified by including a heat exchange, and the feasibility of this method was verified. Next, the modified Control Volume method was employed to evaluate the factors influencing the deployment pressure of air-inflated fabric arch structure. Research was conducted on influence of deployment time, span to height ratio, and arch length to diameter. The reasonable design parameters for span to height ratio and arch length to diameter ratio of air-inflated fabric arch structure are given. A fully connected neural network with two layers was constructed to predict the peak pressure. The accuracy of this method was verified by the results. Thus, this study serves as a reference for deployment behavior in engineering applications.

Laser shock peening (LSP) is mainly used for machining complex structural parts in aviation and so it is of significance to investigate how the machining parameters influence the fatigue life of the complex aerostructure. Herein we describe how we carried out fatigue tests on 2024-T351 alloy aircraft wing panel structures, which adopted different laser power density peening strategies. Simulation of the stress at the edge of the hole is also carried out. It is found that in Strategy A there are cracks on the inner wall of the hole and the fatigue life decreases, while in Strategy B there are corner cracks and the fatigue life increases. The main reason is that the pressure wave peak has a large effect on the residual stress distribution in the structure. In Strategy A the laser power density is too large, the structure appears to demonstrate that residual tensile stresses lead to structural life reduction. [ABSTRACT FROM AUTHOR]

This study introduces an approach for constructing groups of filled cracks in the surrounding rock to achieve anti-blasting and wave elimination protection for underground caverns. To verify the attenuation effect of the explosion wave by the filled cracks, two models, a no-crack model, and a filled-crack model, were constructed using a certain proportion of analogue materials based on the similarity theory. With the implementation of small equivalent explosion conditions, the peak pressure of the surrounding rock of the cavern and the vibration acceleration of the cavern wall under different explosion conditions were measured. To accurately judge the attenuation efficiency of the filled cracks, the peak pressure attenuation percentages between different measuring points were calculated. Furthermore, the corresponding numerical simulation analysis process was performed according to the test conditions. The results show that not only the peak pressure attenuation percentages, but also the value of vibration acceleration, were significantly reduced due to the existence of filled cracks in the model. This indicates that filled cracks in the surrounding rock of the cavern can effectively attenuate the peak pressure and vibration acceleration caused by the explosion wave, thereby achieving the protection engineering goal of anti-explosion and wave elimination. [ABSTRACT FROM AUTHOR]

Foot pressure has an essential impact on the entire musculoskeletal chain. So far, the direct influence of foot pressure onto the spinal posture and vice versa is still unclear. The aim of this study was to determine the relationship between foot pressure and spinal posture in healthy adults under static and dynamic conditions. Systematic research was conducted using PubMed to demonstrate the relationship between foot pressure and spinal posture. The search strategy was based on the PICOS selection criteria. The risk of bias within the studies was assessed using SIGN rankings. Based on the search strategy, 719 articles were identified by screening title and abstract. 11 studies with moderate methodological quality partially showed a relationship between foot pressure and spinal posture (SIGN:2-1- and B-D). Apart from the foot pressure, the included studies analyzed parameters of muscle thickness (sonography), trunk displacement, head position, posterior tilt angle, trunk tilt, pelvic rotation, spinal range of motion, or spinal motion. Strength training and increased muscle thickness in the lumbar spine ensure decreased foot pressure. The head position partly induces a change of foot pressure under static conditions. No correlation was identified between spinal posture and foot pressure during forward and backward walking without manipulation. The static and dynamic measurements only show statistical correlations between foot and back muscles. Foot pressure and spinal posture seem to be interrelated under static and dynamic conditions. Static and dynamic measurements are necessary for body posture analysis, as the conditions do not always show consistent results. Due to the small number of studies and low sample sizes, further investigations are necessary to gain more precise perception of the interplay of the spine and foot pressure. For better comparison, more homogeneous studies investigating similar spine parameters are needed. • A systematic review of the relationship between foot pressure and spinal posture. • Database search revealed 11 studies about the relationship of spine posture and foot pressure. • Muscular strength in the lumbar spine seems to influence foot pressure. • Similarities in the results of static and dynamic measurements are evident. • Further studies with a higher sample size are necessary to attain specific results. [ABSTRACT FROM AUTHOR]

In order to research the impact of baffle location on the shockwave propagation characteristics in a fork road of closed roadway, using ANSYS to simulate the two-dimensional explosion flow field, then comparing the baffle in the different situations and positions, we monitor and draw the overpressure change curves of each point in tunnel and the velocity vector diagrams at baffle, which can be used to analyze the propagation law of explosion shock wave. The result shows that when the single baffle is placed on the direction of shock wave, the influence on overpressure at the bottom of tunnel has little change compared with the same tunnel without baffle, but having the best effect on reducing overpressure at the center of closed tunnel, on the other hand it has a certain stability effect on pressure fluctuation. When double baffles are set on the direction of shock wave, the overpressure has the greatest reduction in the center of closed tunnel. On the contrary, when the double baffles are placed on the opposite side and the inlet baffle at the entrance is on the side of shock wave, the overpressure weakening effect on the inner surface of the roadway is the best.

Highlights: What are the main findings? 819 mm2 of nozzle area leads to the best deashing performance. 0.3 MPa of jet pressure leads to the best deashing uniformity. What is the implication of the main finding? Bigger nozzle area causes bigger on-positive nozzle pressure. 819 mm2, 0.3 MPa and 20 mm were optimized to get the best deashing performance. The difference of deashing performance between the areas of positive-to-blowing holes and that of non-positive-to-blowing holes is an important problem that causes a non-uniform deashing performance to a flat box filter cartridge, which limits the improvement of raising the ash cleaning efficiency to this kind of filter. In order to solve the above problems, the influence of blowing pressure, blowing distance and blowing hole area on cleaning performance was studied. Industrial coating test was also carried out to investigate and verify the actual ash cleaning performance under the optimal conditions obtained from the above investigations. Finally, the design method of the size of the slotted blowing hole was optimized. The results showed that at 0.3 MPa of the pulse pressure, the cleaning performance can meet the cleaning requirements and the best cleaning uniformity can be obtained. With the increase in slot-type nozzle area, the pressure at the areas facing the non-positive nozzles increased significantly, and thus the overall cleaning uniformity increased. The slot-type nozzle area of 273, 546 and 819 mm2 had the best cleaning effects at the jet distances of 40, 20~40 and 20 mm, respectively. The findings of this study are of great significance and can provide theoretical and experimental reference for important parameters selection of the flat cartridges filter in industrial application to improve the efficiency of dust removal. [ABSTRACT FROM AUTHOR]

As part of the environmentally friendly policy of ships, active research is being conducted on energy storage systems (ESS) for ships. This ESS has a major influence on determining the propulsion and operation system of the ship in the future. A separate space must be provided for the ESS, but small and medium-sized ships often require it to be located at the bottom of the ship to make use of the available space. If the ESS is located at the bottom of the ship, the slamming impact load should be considered, and a study of the vibrations generated during the slamming impact is required. Ships are subjected to various environmental effects while sailing. Among them, the risk factor caused by waves is one of the direct risk factors for the operation of the ship. This slamming phenomenon affects not only ships but also offshore structures, and is a risk factor that can cause structural damage as well as damage to human life. Therefore, it is necessary to study the slamming load, and a method is needed to address it with a dynamic load instead of a static load. In order to reflect the slamming load in the design as a dynamic load rather than the equivalent hydrostatic pressure, which is a static load, it is necessary to study the elastic effect of the structure. The plate thickness is calculated by considering the equivalent design pressure based on the measured slamming pressure peak, and several experimental and theoretical studies have been conducted to estimate the exact value of the peak pressure. However, according to recent studies, structural damage is affected not only by the peak pressure but also by the peak width in the time interval of the peak pressure. Research on slamming has been ongoing for a long time, but structural damage due to slamming is still being reported steadily. In order to understand the slamming phenomenon and reflect it in the structural design formula, high-quality experimental results are required. The slamming phenomenon occurs in a very short time. In order to obtain high-quality experimental results for this slamming phenomenon, numerous experimental variables such as experimental equipment setting, appropriate sensor selection, and data measurement and storage capability must be carefully considered. Normally the slamming load can be expressed in terms of peak pressure, peak width, and duration of the pressure, and the maximum pressure and the idealized pressure value (impulse) are applied to the structure. This slamming pressure is affected by the shape and natural period of the structure and shows the largest pressure value when the dead-rise angle is 3° to 10°. In this study, the test was performed by repeatedly dropping into the water using structural bottom angles of 0°, 3°, 10°, and 20° to the free surface of the water. The peak pressure, peak width, impulse, pressure coefficient, and traveling velocity of peak pressure obtained from the repeated tests are estimated with mean and coefficient of variation. [ABSTRACT FROM AUTHOR]

The problem of serious ash accumulation at the lower part of flat box filter cartridges is an important limitation for the improvement of ash cleaning efficiency in this kind of filter. To solve the above-mentioned problem, the type of slotted blowing hole impacting the performance of the ash removing under the same ash cleaning area was studied. In the present work, a total of four types of slotted blowing holes with different length were designed. The influence of blowing distance and blowing pressure on dust removal performance were investigated. Numerical simulation was conducted to demonstrate the mechanism of the dust removal process. An industrial coating test was also carried out to investigate and verify the actual ash cleaning performance under the optimal conditions as obtained from the above investigations. The results showed that: (1) the performance of dust cleaning produced by a three-slit blowhole was better than that by a four-slit blowhole; (2) 0.2 MPa was determined to be the optimal blowing pressure, which meets the requirement of ash cleaning; (3) 20 mm was selected as the optimal blowing distance, as this was the distance at which the surface side wall pressure at the non-positive-to-blow hole area was obviously increased, indicating that the whole performance of ash cleaning could be improved. The results obtained in this study are of great significance for improving the efficiency of dust removal in the use of flat box filters, promoting the development of dust removal technology, protection of environment, and reduction of human health damage. [ABSTRACT FROM AUTHOR]

Laser shock peening (LSP) process parameters have an important influence on the strengthening effect. In this study, theoretical calculations were used to determine a suitable range of stress wave peaks (5.09 GPa–6.36 GPa) for laser shocking, which consider the material properties of alloy steel 40Cr. In addition to theoretical calculations, the finite element numerical simulation of a single-point laser shock was also performed. The residual stresses of specimens under different shock pressure waves were simulated, and then the optimal pulse width was determined as 20 ns and the optimal pulse energy was determined as 10 J. Finally, the influences of different pulse energies on the microhardness, residual stress, microstructure, and shock-affected layer thickness of metallic materials were comprehensively investigated through experiments, and the optimization of the laser shock energy was proved to be 10 J. An optimized combination of parameters of a single-point laser shock for 40Cr was obtained, in which the spot diameter was 3 mm, the pulse width was 20 ns, and the pulse energy was 10 J. The study has implications for the selection of LSP process parameters for alloy steels. [ABSTRACT FROM AUTHOR]

• A passive containment cooling system was simulated using Apros software. • Phase change materials are effective in reducing the peak containment pressure after an accident. • The empty tube startup method of the natural circulation shows better heat transfer performance. • Phase change materials can improve the overall heat transfer capability of the system. The passive containment cooling system (PCCS) plays a significant role in ensuring the safety of nuclear power plants. To further reduce peak pressure in the containment during a loss of coolant accident (LOCA), phase change materials (PCMs) are utilized to improve the system's cooling effectiveness. The dynamic simulation model of PCCS has been developed using Apros software. This article focuses on examining the system's dynamic characteristics related to various tube startup methods and comparatively analyzing the impact of different PCM thicknesses on heat transfer capacity. The results indicate that post-accident, PCM significantly suppresses peak pressure in the containment. Under the full tube startup method with 4 mm PCM, the peak pressure decreases to 1.75 MPa, whereas under the empty tube startup method, it is reduced to 1.69 MPa. With natural circulation empty tube startup method, PCM can reduce pressure change intensity in the containment but negatively affects natural circulation heat transfer. Although the full tube startup method underperforms the empty tube startup method on suppressing peak pressure, PCM can positively affect natural circulation heat transfer in the early stages of the accident. Empty tube startup offers the advantages of higher heat transfer capacity and lighter weight, making it the optimal choice for ocean nuclear platforms. Additionally, the higher peak power of PCM heat transfer under the empty tube startup method indicates that system can withstand larger thermal shocks. [ABSTRACT FROM AUTHOR]

Increased ulcer risk diminishes the quality of life in diabetes. This study assessed abnormalities in foot plantar pressure distribution in adolescents with T1D to detect early signs of ulcer risk. A total of 102 T1D patients, without diabetic neuropathy, were included (mean age 17.8 years, mean diabetes duration 7.4 year). Pedography was captured using Novel emed. Data from the study group were compared with reference data. The study revealed a statistically significant reduced foot contact area in both feet in the entire foot and under the head of the fifth metatarsal bone and the second toe. In both feet, the peak pressure was increased under the entire foot, hindfoot, midfoot, first metatarsal head, big toe, and second toe. There was no statistically significant difference in peak pressure. The mean plantar pressure rating was statistically significantly increased in both feet across the entire sole, in the hindfoot, midfoot, and first metatarsal head. T1D patients of age near adulthood without neuropathy have increased values in mean pressure and reduced contact area, pointing to the need of monitoring and preventive measures. These results point to the need of further research and analysis which should include various risk factor such as foot anatomy, body posture, or certain metabolic factors.

The pressurizer is a key equipment to ensure the safe operation of pressurized water reactor by maintaining the reactor coolant system pressure within allowed tolerances. Various pressure control systems (Pressurizer) are adopted in industrial applications to satisfy their characteristics. In accordance with the purpose of using nuclear facilities, steam, gas-steam, and gas pressurizer (PRZ) have been used. In nuclear industry, the dynamic behavior of each PRZ is different. Peak pressure is one of the important parameters in choosing the type of PRZ. This study has been evaluated for the University of Wisconsin High-Pressure Critical Heat Flux (WHPCHF) facility as the base loop. Three PRZs are connected to the WHPCHF loop to evaluate their performance during the in-surge scenario. The Peak pressure of the three PRZs is evaluated during transients. The results showed that the use of the Non-condensable Gas (NCG) increases the peak pressure due to the lack of NCG condensation during transient conditions. The use of gas PRZ makes it possible to change the pressure quickly. Also, the pure gas PRZ has the highest peak pressure but has straightforward control logic. The gas PRZ is the best choice for small reactors and high-pressure test facilities. [ABSTRACT FROM AUTHOR]

Pulse hydraulic fracturing (PHF) is a key technique for reservoir stimulation. PHF can well accelerate the rupture of rock. However, the supercharging mechanism of PHF is not fully understood. The main reason is that the pressure distribution and its variation, especially the peak pressure characteristics, are unclear inside the pipe and fissure. The present research focuses on the sine pulse applied at the inlet of a pipe or fracture to reveal the variation regularity of peak pressure with the pulse frequency, amplitude, pipe length, diameter and wave speed. First, the weakly compressible Navier–Stokes equations were developed to simulate the variation of fluid pressure. The computation codes were developed using the MacCormack method validated by the existing experimental data. Then, the sine pulse effect was studied inside the pipe and fissure. Last, a new frequency model was built to describe the relationship between the optimal pulse frequency, wave speed and pipe length. The results show that there is a family of frequencies at which the peak pressure of the endpoint can be significantly enhanced and that these frequencies are the optimal pulse frequency. It is found that the optimal pulse frequency depends on the pipe or fissure length and wave speed. At the optimal pulse frequency, the peak pressure at the endpoint can be increased by 100% or more, and the cavitation phenomenon occurs. However, the peak pressure decreases when with the decrease in the pipe diameter and fissure departure due to the friction drag effect of the wall. These new landmark findings are very important for the PHF technique. In addition, a new universal frequency model is built to predict the optimal sine pulse frequency. The present research shows the variation regularity of the fluid pressure inside the pipe and develops a sine frequency-controlled method, providing a potential guide for reservoir stimulation. [ABSTRACT FROM AUTHOR]

This study investigated the laminar combustion characteristics of methyl pentanoate (MPe) using the constant volume combustion chamber at the initial pressures and temperatures of 1, 2, and 4 bar and 423, 453, and 483 K, respectively over the equivalence ratios ranging from 0.7 to 1.4. The experimental and simulated peak pressures showed a good trend irrespective of the disparities between both results. The experimental laminar burning velocities agreed well with the simulated laminar burning velocities. Also, laminar burning velocities at the initial temperatures and pressures up to 573 K and 8 bar, respectively were estimated using a deduced empirical formula. Last but not least, the main pathways for the decomposition of MPe were MPe → MPe2J → MPeMJ → MPe3J. [ABSTRACT FROM AUTHOR]

The peak pressures are computed using computational fluid dynamics (CFD) with the synthetic inflow turbulence generator and compared with 1:6 scale Texas Tech University (TTU) wind tunnel measurements. The inflow turbulence is calculated using the Consistent Discrete Random Flow Generation Method (CDRFG) method. The maximum and minimum frequencies from the field or experimental measurements as input to the inflow turbulence generator without considering the largest grid spacing used in the CFD model leads to high pressure error. For one case, more than 100% error in peak pressure results is observed. In addition, spurious pressures are observed at the building location without building. By varying maximum frequencies systematically for each computational mesh size and comparing the velocities and pressures at the inflow and the building location without building, possible causes of the error are explained. From the investigation, it is suggested not to use the maximum frequency in the inflow turbulence generator beyond the frequency that can be transported by the largest grid spacing.

In this study, the effects of various parameters of the filter bag cleaning system, such as the blow tube size (20A, 40A, 50A), the nozzle diameter (5, 10, 15, 20, 25, 30 mm), the initial tank pressure (0.3, 0.4, 0.5, 0.6, 0.7 MPa), and the pulse duration (50, 100, 150, 200, 250, 300 ms), were evaluated with a view of peak pressure and pressure impulse. This study shows that the peak pressure and pressure impulse are not always in a proportional relationship, since pressure impulse aggregates static pressure and pressure over elapsed time together. For the system investigated, it is found that increasing the blow tube size and pulse duration induce a larger pressure impulse with little change in peak pressure, while higher initial tank pressure enhances both peak pressure and pressure impulse. On the other hand, a larger nozzle diameter was found to increase peak pressure rather than pressure impulse throughout the bag. The experimental results suggest that a higher initial tank pressure is a convenient way to elevate the overall dust-cleaning performance of pulse-jet systems, while other parameters (blow tube size, nozzle diameter, initial tank pressure) can be adopted according to the desired effect for given environment. [ABSTRACT FROM AUTHOR]

On the basis of the existing dust collector structure, this study designed a fan-shaped new structure microporous membrane filter plate (NSMMFP). The pressure distribution law of the NSMMFP can be obtained by measuring the wall surface peak pressure under different injection pressures. The powder attachment experiment was carried out to explore the influence of the dust moisture content on the dust stripping rate (DSR), and a high-speed camera was used to observe the peeling process of the dust. The results show that the peak pressure of each measuring point and the average wall surface peak pressure gradually increase with the injection pressure. The dust stripping quality (DSQ) and rate show an increasing trend as a whole as the injection distance. The DSR of the filter plate shows a downward trend when the dust quality G increases, while DSQ shows the opposite trend. Furthermore, as the dust moisture content increases, the DSQ and DSR gradually decrease. As the dust moisture content increases, the dust attached to the surface of the filter plate is more fragmented and peels from the surface of the filter plate during the dust cleaning process. [ABSTRACT FROM AUTHOR]

Injection molding is a cyclic process of producing plastics products by injecting molten plastic materials. There is much complexity in the process because it is a highly non-linear process; many factors affect the product quality after long-run fabrication processes. In this study, product weight is defined as product quality, and this research aims to minimize the variation in the product weight. In this study, a standard process parameter setup procedure is proposed in order to set the process parameters in a close to optimized value based on the information collected by the sensors so the adaptive process control system can work well. Three polypropylene materials with low to high MI (melting index) values were used to verify the adaptive control system. The study with the information collected through two sensors installed in the machine—the injection nozzle pressure sensor and tie-bar strain gauge. Based on a series of results in the preliminary experiments, the appropriate V/P switchover point and clamping force could be judged from the peak pressure and clamping force peak for materials with different viscosities, respectively. The viscosity index and peak pressure strongly correlated with the weight of the injection molded parts toward the materials of different viscosity. The viscosity index, peak pressure, and clamping force peak are defined in this research as the quality monitoring characteristics used to guide the adjustment and increase the stability of the process in the presented control system. The experiment reveals that a combination of nozzle pressure curve-based adaptive process control incorporated with clamping force peak monitoring can decrease the weight variation of the injection molded parts. With this system, the coefficient of variation of product weight (Cv) of different viscosity materials from low to high can be decreased to 0.031%, 0.020%, and 0.024%, respectively.

Rapid filling in horizontal partially filled pipes with entrapped air may result in extreme pressure transients. This study advanced the current understanding of dynamic behavior of entrapped air above tailwater (the initial water column with a free surface in a partially filled pipe) through rigid-column modeling and sensitivity analysis of system parameters. Water and air were considered as incompressible fluid and ideal gas, respectively, and the continuity and momentum equations for water and a thermodynamic equation for air were solved by using the fourth order Runge-Kutta method. The effects of system parameters were examined in detail, including tailwater depth, entrapped air volume, driving head, pipe friction, and relative length of entrapped air and pipe. The results indicate that the presence of tailwater can mitigate the peak pressure when with identical initial volumes of entrapped air, as it can be considered to reflect a certain amount of loss of the net driving head. However, the peak pressure can increase as much as about 45% for the cases with fixed pipe length, due to the reduction in the initial entrapped air volume. The rise time for the first peak pressure was closely related to pipe friction, whereas the oscillation period (defined as the time duration between the first and second peaks) was virtually irrelevant. The applicability of the rigid-column model was discussed, and a time scale relevant indicator was proposed. When the indicator is larger than 20, the relative difference between the peak pressure estimation and experimental measurements is generally below 5%.

The difference of deashing performance between the areas of positive-to-blowing holes and that of non-positive-to-blowing holes is an important problem that causes a non-uniform deashing performance to a flat box filter cartridge, which limits the improvement of raising the ash cleaning efficiency to this kind of filter. In order to solve the above problems, the influence of blowing pressure, blowing distance and blowing hole area on cleaning performance was studied. Industrial coating test was also carried out to investigate and verify the actual ash cleaning performance under the optimal conditions obtained from the above investigations. Finally, the design method of the size of the slotted blowing hole was optimized. The results showed that at 0.3 MPa of the pulse pressure, the cleaning performance can meet the cleaning requirements and the best cleaning uniformity can be obtained. With the increase in slot-type nozzle area, the pressure at the areas facing the non-positive nozzles increased significantly, and thus the overall cleaning uniformity increased. The slot-type nozzle area of 273, 546 and 819 mm2 had the best cleaning effects at the jet distances of 40, 20~40 and 20 mm, respectively. The findings of this study are of great significance and can provide theoretical and experimental reference for important parameters selection of the flat cartridges filter in industrial application to improve the efficiency of dust removal.

High-voltage pulse discharge in water is a promising technology to enhance the permeability of coal seam and rock mass by generating fractures within them. With the aim of improving the stability and efficiency of this technology, a high voltage electric pulse experiment system was constructed. The discharge electrodes in the experiment was hemispherical. The positive and negative electrodes were arranged on the same axis with adjustable spacing. Five sets of experiments were undertaken with the electrode spacing of 1mm, 2mm, 3mm, 4mm, and 5mm, respectively. In the experiments, an oscilloscope was used to analyze the voltage, current, and pressure wave signals. The experimental results of two typical voltage-current curves indicate that the peak pressure of plasma shock wave follows a parabolic trend with the electrode spacing, and there is an optimal electrode spacing for a given discharge voltage. The peak pressure of plasma shock wave tends to increase linearly with the increase of discharge voltage. The greater the electrode spacing, the greater the sensitivity of shock wave peak pressure to the discharge voltage. The shock wave peak pressure sensitivity of 5 mm discharge spacing is 4.7 times that of 1 mm discharge spacing. The experimental results for the voltages of 9 kV, 12 kV, and 24 kV with the optimal electrode spacing show that a power function is the best fit for the attenuation of the peak pressure of shock wave with its propagation distance.

Three square plan shaped tall buildings are arranged at the vertices of an equilateral triangle of varying size. The octagonal plan shaped principal building is also positioned randomly such that the position of the principal building is never overlapped with the square plan shaped buildings. The effect of interference of the square buildings on the wind-induced responses of the principal building is thoroughly measured by computational fluid dynamics using large eddy simulation turbulence model. Metamodels for drag and lift coefficients of the principal building in the interfering conditions are established. Interference factors for the pressure coefficients at different faces of the principal building is calculated and cast into efficient mathematical models. Pareto optimality for the maximum interference criterion is obtained. The optimal positions of the principal and interfering buildings for maximum interference are plotted. Selected cases from the Pareto optima are analysed to obtain the transient wind effects for those interference cases. The peak and root-mean-square pressure coefficients of these interfering conditions are compared with that of the isolated condition. The difference between the power spectra of the isolated and interfering conditions are also depicted. [ABSTRACT FROM AUTHOR]

Background: Bat swing and grip type may contribute to hook of hamate fractures in baseball players. Purpose: To compare the effects of swing type and batting grip on the pressure and rate of pressure development over the hook of hamate in collegiate baseball players. Study Design: Descriptive laboratory study. Level of evidence, 3. Methods: This was an experimental quasi-randomized study of bat grip and swing differences in National Collegiate Athletic Association Division I baseball players (N = 14; age, 19.6 ± 1.1 years [mean ± SD]). All participants performed swings under 6 combinations: 3 grip types (all fingers on the bat shaft [AO], one finger off the bat shaft [OF], and choked up [CU]) and 2 swing types (full swing and check swing). Peak pressure and rate of pressure generation over the area of the hamate were assessed using a pressure sensor fitted to the palm of the bare hand over the area of the hamate. Wrist angular velocities and excursions of radial ulnar deviation were obtained using 3-dimensional motion analysis. Results: The OF–check swing combination produced the highest peak pressure over the hamate (3.72 ± 2.64 kg/cm2) versus the AO–full swing (1.36 ± 0.73 kg/cm2), OF–full swing (1.68 ± 1.17 kg/cm2), and CU–full swing (1.18 ± 0.96 kg/cm2; P <.05 for all). There was a significant effect of condition on rate of pressure development across the 6 conditions (P =.023). Maximal wrist angular velocities were 44% lower in all check swing conditions than corresponding full swing conditions (P <.0001). The time to achieve the maximal wrist angular velocity was longest with the AO–full swing and shortest with the CU–check swing (100.1% vs 7.9% of swing cycle; P =.014). Conclusion: The OF–check swing condition produced the highest total pressure reading on the hook of hamate. Check swing conditions also had the steepest rate of pressure development as compared with the full swing conditions. Clinical Relevance: Batters who frequently check their swings and use an OF or AO grip may benefit from bat modifications or grip adjustment to reduce stresses over the hamate. Athletic trainers and team physicians should be aware of these factors to counsel players in the context of previous or ongoing hand injury. [ABSTRACT FROM AUTHOR]

Supplemental Digital Content is Available in the Text. Objective: We hypothesize that athletes who have suffered Jones fractures will apply significantly higher loads at the fifth metatarsal base during athletic activities compared with matched uninjured athletes. Design: Sixteen athletes were recruited to participate. Eight athletes had a history of Jones fracture, and 8 age, gender, and position-matched athletes without a history of foot injury were recruited as controls. Setting: Institutional study at Stanford University. Participants: Sixteen athletes with/without a history of foot injury from Stanford University. Interventions: Athletes performed a standardized series of movements while wearing calibrated, wireless pressure mapping insoles, and then again with their custom corrective insoles. Main Outcome Measures: Peak pressure, mean pressure, maximum force, and force-time integral (ie, impulse) were recorded for each activity. Results: Athletes with a history of Jones fracture showed a significantly increased peak pressure (183 ± 23 vs 138 ± 7 kPA), mean pressure (124 ± 14 vs 95 ± 4 kPA), and maximum force (15 ± 1.2 vs 12 ± 1.2%BW) at the fifth metatarsal base during walking and running compared with uninjured matched controls (all P < 0.05). Conclusions: Athletes with a history of Jones fracture exert significantly increased peak and mean forces at the base of the fifth metatarsal during common athletic activities. Custom orthoses do not seem to offload this region in all cases. Increased loads may contribute to the development of stress injury to the fifth metatarsal during repetitive loading, and ultimately fracture of the bone. [ABSTRACT FROM AUTHOR]

Objective To investigate the protection efficacy of novel polyurea materials concerning their bioprotective effects of lungs and blast mitigation so as to provide the theoretical and material support. Methods A 7kg TNT explosive ball was used to observe the changes in the peak pressure of shock waves in in a human torso model, covered with a series of polyurea materials at 3.8 m and 5.8 m from the explosion center respectively under open field conditions. The first part of experiment was divided into the ultra-high molecular weight polyethylene (UHWPE, PE) and new polyurea series + PE groups. The new polyurea materials were divided into seven types according to the molecular structure transformation method and volume fractions of micron glass particles: PUR1、PUR1G20、PUR1G30、PUR2、PUR2G20、PUR2G30、PUR3. Each type was tested once at 3.6 m and 3.8 m respectively. In the second part, a typical type of polyurea with good blast mitigation was selected in the bioprotective evaluation and a goat chest mold for anti-blast was prepared. Twenty-four experimental goats were randomly divided into the unprotected, PE, polyurea, and polyurea + PE groups. Based on the estimation of peak pressure of 7kg TNT air explosion, the chest wall acceleration, vital signs, and gross injury levels of lungs in explosions as previously described were observed at 3.6 m and 3.8 m from the explosion center. Results At 3.8 m and 5.8 m from the explosion center, the attenuation effects of new polyurea group on shock waves were increased by 23% - 35% and 25% - 50%, respectively, compared with the PE group. At 3.6 m and 3.8 m from the explosion center, the chest wall acceleration in the polyurea + PE group was preferably 55.56% and 65.20% lower than that in the unprotected group, respectively. The lung injury was significantly alleviated compared with the PE group, and the injury was reduced by 2 levels. Conclusion The new polyurea material has ideal protective effects on pulmonary blast injury by attenuating shock waves.

The problem of serious ash accumulation at the lower part of flat box filter cartridges is an important limitation for the improvement of ash cleaning efficiency in this kind of filter. To solve the above-mentioned problem, the type of slotted blowing hole impacting the performance of the ash removing under the same ash cleaning area was studied. In the present work, a total of four types of slotted blowing holes with different length were designed. The influence of blowing distance and blowing pressure on dust removal performance were investigated. Numerical simulation was conducted to demonstrate the mechanism of the dust removal process. An industrial coating test was also carried out to investigate and verify the actual ash cleaning performance under the optimal conditions as obtained from the above investigations. The results showed that: (1) the performance of dust cleaning produced by a three-slit blowhole was better than that by a four-slit blowhole; (2) 0.2 MPa was determined to be the optimal blowing pressure, which meets the requirement of ash cleaning; (3) 20 mm was selected as the optimal blowing distance, as this was the distance at which the surface side wall pressure at the non-positive-to-blow hole area was obviously increased, indicating that the whole performance of ash cleaning could be improved. The results obtained in this study are of great significance for improving the efficiency of dust removal in the use of flat box filters, promoting the development of dust removal technology, protection of environment, and reduction of human health damage.

As part of the environmentally friendly policy of ships, active research is being conducted on energy storage systems (ESS) for ships. This ESS has a major influence on determining the propulsion and operation system of the ship in the future. A separate space must be provided for the ESS, but small and medium-sized ships often require it to be located at the bottom of the ship to make use of the available space. If the ESS is located at the bottom of the ship, the slamming impact load should be considered, and a study of the vibrations generated during the slamming impact is required. Ships are subjected to various environmental effects while sailing. Among them, the risk factor caused by waves is one of the direct risk factors for the operation of the ship. This slamming phenomenon affects not only ships but also offshore structures, and is a risk factor that can cause structural damage as well as damage to human life. Therefore, it is necessary to study the slamming load, and a method is needed to address it with a dynamic load instead of a static load. In order to reflect the slamming load in the design as a dynamic load rather than the equivalent hydrostatic pressure, which is a static load, it is necessary to study the elastic effect of the structure. The plate thickness is calculated by considering the equivalent design pressure based on the measured slamming pressure peak, and several experimental and theoretical studies have been conducted to estimate the exact value of the peak pressure. However, according to recent studies, structural damage is affected not only by the peak pressure but also by the peak width in the time interval of the peak pressure. Research on slamming has been ongoing for a long time, but structural damage due to slamming is still being reported steadily. In order to understand the slamming phenomenon and reflect it in the structural design formula, high-quality experimental results are required. The slamming phenomenon occurs in a very short time. In order to obtain high-quality experimental results for this slamming phenomenon, numerous experimental variables such as experimental equipment setting, appropriate sensor selection, and data measurement and storage capability must be carefully considered. Normally the slamming load can be expressed in terms of peak pressure, peak width, and duration of the pressure, and the maximum pressure and the idealized pressure value (impulse) are applied to the structure. This slamming pressure is affected by the shape and natural period of the structure and shows the largest pressure value when the dead-rise angle is 3° to 10°. In this study, the test was performed by repeatedly dropping into the water using structural bottom angles of 0°, 3°, 10°, and 20° to the free surface of the water. The peak pressure, peak width, impulse, pressure coefficient, and traveling velocity of peak pressure obtained from the repeated tests are estimated with mean and coefficient of variation.

In this study, microemulsion synthesized from chemically extracted Salvinia molesta oil with diesel was evaluated as fuel in stationary unmodified diesel engine. The microemulsions from S. molesta oil was prepared using the best combinations of 67% S. molesta oil, 15% ethanol, 13% water and 5% surfactant (span 80) and its properties were compared with that of diesel. The engine test conducted with M10, M20 and M30 blends and reported a brake thermal efficiency of 29.76% and brake specific fuel consumption of 0.3239 kg/kWh with M20. The emissions like NO and smoke reduced by 18.07% and 7.37%, respectively, with marginal increase in CO, CO 2 and unburned hydrocarbon by 3.8%, 3.4% and 16.66% respectively, with M20 compared to diesel at maximum engine load of 3.73 kW. At lower engine loads with M10, M20 and M30 slightly lower CO 2 emission than diesel. A drop in peak pressure and heat release rate was found to be 1.73% and 8.40%, correspondingly with M20, as that of diesel. Even though a slight reduction in brake thermal efficiency observed with M20 as compared to M10 and diesel by considering the lowest emissions of NO and smoke, it is feasible to use as promising fuel for unmodified diesel engines., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Wind tunnel tests in an open terrain were carried out to study interference effects on peak pressure coefficients of one low-rise flat-roof building due to one high-rise building and similar low-rise buildings. The results demonstrate that amplification interference effects are significant on the minimum pressures at the edge of the low-rise building roof adjacent to the high-rise building and on the maximum pressures in the roof area away from the high-rise building, where the minimum pressure means the algebraic minimum with negative suction. Magnitudes of the envelope peak pressure coefficients on the low-rise building increase when the high-rise building height increases. The envelope minimum peak pressure coefficients in the roof middle area parallel to the high-rise building experience amplification effects at large building height and small spacing ratios, but other roof areas experience shielding effects at small spacing ratios, and interference factors of the envelope minimum peak pressure coefficients increase with the increase of the height and spacing ratios. When the spacing ratio is less than two, cases with large height ratios display amplification effects on the envelope maximum peak pressure coefficients, and amplification effects increase with the increase of the height ratio or the decrease of spacing ratio. [ABSTRACT FROM AUTHOR]

Pulse hydraulic fracturing (PHF) is a key technique for reservoir stimulation. PHF can well accelerate the rupture of rock. However, the supercharging mechanism of PHF is not fully understood. The main reason is that the pressure distribution and its variation, especially the peak pressure characteristics, are unclear inside the pipe and fissure. The present research focuses on the sine pulse applied at the inlet of a pipe or fracture to reveal the variation regularity of peak pressure with the pulse frequency, amplitude, pipe length, diameter and wave speed. First, the weakly compressible Navier–Stokes equations were developed to simulate the variation of fluid pressure. The computation codes were developed using the MacCormack method validated by the existing experimental data. Then, the sine pulse effect was studied inside the pipe and fissure. Last, a new frequency model was built to describe the relationship between the optimal pulse frequency, wave speed and pipe length. The results show that there is a family of frequencies at which the peak pressure of the endpoint can be significantly enhanced and that these frequencies are the optimal pulse frequency. It is found that the optimal pulse frequency depends on the pipe or fissure length and wave speed. At the optimal pulse frequency, the peak pressure at the endpoint can be increased by 100% or more, and the cavitation phenomenon occurs. However, the peak pressure decreases when with the decrease in the pipe diameter and fissure departure due to the friction drag effect of the wall. These new landmark findings are very important for the PHF technique. In addition, a new universal frequency model is built to predict the optimal sine pulse frequency. The present research shows the variation regularity of the fluid pressure inside the pipe and develops a sine frequency-controlled method, providing a potential guide for reservoir stimulation.