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SUMMARY With the emergence of massive seismic data sets, surface wave methods using deep learning (DL) can effectively obtain shear wave velocity (Vs) structure for non-invasive near-surface investigations. Previous studies on DL inversion for deep geophysical investigation have a reference model to generate the training data set, while near-surface investigations have no model. Therefore, we systematically give a set of training data set generation processes. In the process, we use both prior information and the observed data to constrain the data set so that the DL inversion model can learn the local geological characteristics of the survey area. Because the space of inverted Vs models is constrained and thus narrowed, the inversion non-uniqueness can be reduced. Furthermore, the mean squared error, which is commonly used as loss function, may cause a poor fitting accuracy of phase velocities at high frequencies in near-surface applications. To make the fitting accuracy evenly in all frequency bands, we modify the loss function into a weighted mean squared relative error. We designed a convolutional neural network (CNN) to directly invert fundamental-mode Rayleigh-wave phase velocity for 1-D Vs models. To verify the feasibility and reliability of the proposed algorithm, we tested and compared it with the Levenberg–Marquardt (L-M) inversion and neighbourhood algorithm (NA) using field data from the Lawrence experiment (USA) and the Wuwei experiment (China). In both experiments, the inverted Vs models by CNN are consistent with the borehole information and are similar to that from existing methods after fine tuning of model parameters. The average root mean squares errors (RMSEs) of the CNN, NA and L-M methods are also similar, except in the Lawrence experiment, the RMSE of CNN is 17.33 m s−1 lower than previous studies using the L-M method. Moreover, the comparison of different loss functions for the Wuwei experiment indicates that the modified loss function can achieve higher accuracy than the traditional one. The proposed CNN is therefore ideally suited for rapid, repeated near-surface subsurface imaging and monitoring under similar geological settings.

As a critical element of time-varying mesh stiffness (TVMS), contact stiffness of a gear drive has been defined based on simplified Hertzian contact stiffness or semi-empirical nonlinear Hertzian contact stiffness in previous works. This study proposes a general contact stiffness model for elastic bodies through piecewise linear interpolation of contact pressure. The TVMS of a spur gear drive is determined through potential energy method and proposed contact stiffness model verified by Hertzian contact theory and finite-element method. Then, the influence of applied load on contact stiffness is studied, and the differences among proposed contact stiffness, simplified Hertzian contact stiffness, and nonlinear Hertzian contact stiffness are analyzed. Results show that contact stiffness increases with the applied load, and the TVMS based on the proposed contact stiffness model is the smallest among the three contact stiffness models. Effects of tooth width and input torque on the TVMS are further discussed. The TVMS becomes bigger with increased tooth width and input torque, but the increase rate decreases as tooth width or input torque increases. These findings indicate that reasonable matching of design parameters is beneficial for increasing load capacity and optimizing the dynamic performance of gear systems.

A reversible dual-responsive luminescent material was introduced by our group to show the simultaneous color and lifetime switching in response to external stimuli. Pristine crystalline powder of (...

Chromium (Cr) and the emission of its compounds into the environment have caused long-term environmental contamination. In this study, the modes of occurrence of Cr in low-rank coal and their thermal stability in pyrolysis were investigated by sequential chemical extraction (SCE), single-component samples (SCS) pyrolysis, and thermochemical equilibrium simulation. The results showed that organic matter, aluminosilicate, and carbonate were the dominant modes of occurrence of Cr in low-rank coal. The modes of occurrence and chlorine (Cl) content affected the volatilization of Cr in coal. The characteristic release temperature range of Cr bounded to aluminosilicate was >600 °C and 400–600 °C for Cr bounded to a disulfide. Cr bounded to organic matter almost released completely before 600 °C. Cl enhanced the volatility of Cr and reduced its release temperature in Cr bounded to aluminosilicate. The simulation showed the content of gas products was very low, mainly chlorides. While the content of solid products, sulfides, and oxides, was much higher than gas products, showing their high thermal stability. The sulfides and oxides in chars were closely related to the carbonate and aluminosilicate bound form of Cr. The results of the equilibrium simulation were consistent with the experimental results.

Author(s): Cheng, Feng; Xia, Jianghai; Zhang, Kai; Zhou, Changjiang; Ajo-Franklin, Jonathan B | Abstract: SUMMARY Surface wave retrieval from ambient noise records using seismic interferometry techniques has been widely used for multiscale shear wave velocity (Vs) imaging. One key step during Vs imaging is the generation of dispersion spectra and the extraction of a reliable dispersion curve from the retrieved surface waves. However, the sparse array geometry usually affects the ability for high-frequency (g1 Hz) seismic signals’ acquisition. Dispersion measurements are degraded by array response due to sparse sampling and often present smeared dispersion spectra with sidelobe artefacts. Previous studies usually focus on interferograms’ domain (e.g. cross-correlation function) and attempt to enhance coherent signals before dispersion measurement. We propose an alternative technique to explicitly deblur dispersion spectra through use of a phase-weighted slant-stacking algorithm. Numerical examples demonstrate the strength of the proposed technique to attenuate array responses as well as incoherent noise. Three different field examples prove the flexibility and superiority of the proposed technique: the first data set consists of ambient noise records acquired using a nodal seismometer array; the second data set utilizes distributed acoustic sensing (DAS) and a marine fibre-optic cable to acquire a similar ambient noise data set; the last data set is a vibrator-based active-source surface wave data. The enhanced dispersion measurements provide cleaner and higher-resolution spectra without distortions which will assist both human interpreters as well as ML algorithms in efficiently picking curves for subsequent Vs inversion.

The development of hydrogen sensors is of paramount importance for timely leak detection and remains a crucial unmet need. Palladium-based materials, well known as hydrogen sensors, still suffer from poisoning and deactivation. Here, a hybrid hydrogen sensor consisting of a Pd nanocluster (NC) film, a metal-organic framework (MOF), and a polymer, are proposed. The polymer coating, as a protection layer, endows the sensor with excellent H

Named entity recognition is a traditional task in natural language processing. In particular, nested entity recognition receives extensive attention for the widespread existence of the nesting scenario. The latest research migrates the well-established paradigm of set prediction in object detection to cope with entity nesting. However, the manual creation of query vectors, which fail to adapt to the rich semantic information in the context, limits these approaches. An end-to-end entity detection approach with proposer and regressor is presented in this paper to tackle the issues. First, the proposer utilizes the feature pyramid network to generate high-quality entity proposals. Then, the regressor refines the proposals for generating the final prediction. The model adopts encoder-only architecture and thus obtains the advantages of the richness of query semantics, high precision of entity localization, and easiness of model training. Moreover, we introduce the novel spatially modulated attention and progressive refinement for further improvement. Extensive experiments demonstrate that our model achieves advanced performance in flat and nested NER, achieving a new state-of-the-art F1 score of 80.74 on the GENIA dataset and 72.38 on the WeiboNER dataset., Comment: Accepted to the Neural Processing Letters (2023)

Objective. To investigate the value of transabdominal combined transvaginal color Doppler ultrasonography in the diagnosis of uterine adenomyoma. Methods. A total of 80 patients with suspected uterine adenomyoma in our hospital from January 2019 to December 2021 were selected as the study subjects. All of them were examined by transabdominal color Doppler ultrasound (TA-CDUS) and transvaginal color Doppler ultrasound (TV-CDUS), and the postoperative pathological examination results were taken as the gold standard to analyze the diagnostic efficacy of different examination methods for uterine adenomyoma. Results. By postoperative pathological biopsy, 46 cases (57.50%) were diagnosed as positive and 34 cases (42.50%) were diagnosed as negative, including 29 cases of uterine adenomyoma and 5 other cases. The sensitivity, accuracy, and negative predictive value of TA-CDUS combined with TV-CDUS in the diagnosis of adenomyoma were higher than those of TA-CDUS ( P < 0.05 ), and the Kappa value between TA-CDUS and pathological diagnosis was 0.923, which was higher than the 0.615 between TV-CDUS and pathological diagnosis. TA-CDUS combined with TV-CDUS showed that there were significant differences in the distribution of Adier blood flow grades between patients with uterine adenomyoma and uterine fibroids ( P < 0.05 ), and the Adier blood flow grades of patients with uterine adenomyoma were mainly grade 0 and grade I; and the resistance index (RI), peak systolic velocity (Vs), and pulsatile index (PI) in patients with uterine adenomyoma were higher than those in patients with uterine fibroids ( P < 0.05 ). Conclusion. Compared with TA-CDUS, TA-CDUS combined with TV-CDUS is more sensitive and accurate in the diagnosis of uterine adenomyoma and has a good consistency with pathological diagnosis results. Attention should be paid to the blood flow parameter values in the differential diagnosis of uterine fibroids.

In the context of high-quality development of education, vigorously promoting the construction of new agricultural science is the need to serve the national strategy and rural revitalization, and is an inevitable choice for the development of agriculture-related colleges and universities. Exploring a new path of agricultural science construction that is in line with both national policies and local socio-economic development, and cultivating high-quality agricultural talents is a realistic problem that needs to be solved at present. This paper adopts inductive method through interviews with experts from agriculture-related colleges and universities, research institutes, industry enterprises and government authorities, and expert discussion sessions, and proposes that the construction of new agricultural science in Xinjiang needs to adopt such paths as innovative talent cultivation system, innovative talent practice platform, innovative curriculum system, innovative teacher team construction, innovative research platform for rural revitalization, and support for the construction of Xinjiang New Agricultural Science Education Union to achieve high-quality talent cultivation and enhance the ability to serve rural revitalization. This study tries to propose a new construction path for the construction of Xinjiang agricultural science, explore a new track for agriculture-related colleges and universities to serve the needs of rural strategy and shape a new development momentum.

Revealing the photoluminescence (PL) origin and mechanism is a most vital but challenging topic of carbon dots. Herein, confined-domain crosslink-enhanced emission (CEE) effect was first studied by a well-designed model system of carbonized polymer dots (CPDs), serving as an important supplement to CEE in the aspect of spatial interactions. The “addition-condensation polymerization” strategy was adopted to construct CPDs with substituents exerting different degrees of steric hindrance. The effect of confined-domain CEE on the structure and luminescence properties of CPDs have been systematically investigated by combining characterizations and theoretical calculations. Such tunable spatial interactions dominated the coupling strength of the luminophores in one particle, and eventually resulted in the modulated PL properties of CPDs. These findings provide insights into the structural advantages and the PL mechanism of CPDs, which are of general significance to the further development of CPDs with tailored properties.

Endoscopic image has complex backgrounds and spatially different noise, bringing mainstream denoising methods to the problem of incomplete noise removal and the loss of image detail. Thus, an endoscopic image denoising algorithm based on spatial attention UNet network is proposed in this paper. UNet based on residual learning is utilized as the backbone network. Spatial attention modules based on noise intensity estimation and edge feature extraction modules are used to remove noise better while preserving the image details and improving generalization ability. We take endoscopic images of real scenes using gastroscopy and compare our method with mainstream methods. Experimental results show that our approach improves PSNR by 3.51 or 2.93 and SSIM by 0.03 or 0.015 compared with CBDNet or EDCNN, respectively. Our method can effectively improve the impact of noise on the image quality of endoscopic images, thus better assisting doctors in diagnosis and treatment.

International audience; This paper introduces the dynamic modelling of a single-link flexible manipulator with two cables. The end-effector is attached at the distal end of the flexible link and tensed cables are used to suppress vibration. The flexible link is considered as E uler-Bernoulli beam and the cable as a massless spring. By applying the Hamilton's principle, a set of nonlinea r equations of motion are derived with two boundary constraints. A calculation method is proposed to determine the natural frequency of the singlelink flexible manipulator with cables. Simulation experiments are performed to validate the effectiveness of the proposed method. Three non-dimensional parameters are introduced to investigate the effect on the natural frequency of the flexible system. An experimental verification is implemented and the actual frequencies are found to be in good agreement with bo th the ones based on the proposed dynamic model and obtained in simulations. The results show that the vibration is greatly suppressed by utili zing cables in the flexible-link manipulator, which demonstrates that a lightweight flexible system with cables has the potential to be employed in the fields of fast lightweight industrial manipulators, robotic arms for remote manipulation in space and bio-inspired engineering.

This study proposes a tribo-dynamic model of a spur gear by coupling an elastic dynamic model and an isothermal elastohydrodynamic lubrication (EHL) model. In this model, the gear shafts are modelled as flexible bodies by the resultant elements of Timoshenko beam and bar elements, and the gyroscopic effect of gear rotors and shafts is also included. The transient and non-Newtonian effects are considered in the EHL model to predict tooth friction forces and moments. Then, an example is provided to analyze the interaction between gear tribology and dynamic behavior. Results indicate that the fluctuations of mesh force and surface tangential velocity caused by gear vibration considerably affect the pressure and thickness of the lubricant film. The gyroscopic effect exerts a significant influence on the dynamic and tribology properties of the gear drive at high speed. The proposed model has important guidance for the design of lubrication systems and dynamic properties in gear drives.

s The start-up motion is the significant process of many mechanical applications especially for high-frequency start-stop equipment; the formation of separating film and the main wear approximately occur in this process. In this paper, the improved mixed algorithm and a new methodology of describing Gaussian rough surface are developed and theoretically validated based on Stribeck curve. Furthermore, the transient film formation of smooth contact and rough contact with the start-up motion is analyzed and validated. Finally, the wear mechanism of different friction pairs is investigated, meanwhile, the applicability of Evans model and Archard model is evaluated. Results show that the contact ratio of smooth contact is considerably large but the transition time is much short in comparison with rough contact because the valleys of rough surface conserve lubricant avoiding solid contact. Combining the Evans equation and this mixed technique, the wear volume and wear rate were successfully calculated. The type of friction pair influences greatly the wear volume and wear rate of contact surfaces. The wear volume and wear rate of TiN–TiN the minimum in the start-up process, and alumina ceramics with satisfactory fracture toughness is a potential coating that can be applied to mechanical elements with a wide range of slide-roll ratio.

Advances in whole-slide images (WSI) technology can promote the pathology environment based on digital imaging and make a very compelling case as part of the clinical workflow. Furthermore, the applications of artificial intelligence (AI) for morphometric image analysis are accelerating the transition of pathology into a more quantitative science. However, several challenges, such as storing, sharing, visualizing, and analyzing large-size WSI files and the acquisition of annotations from pathologists for WSIs still exist in working with WSIs in AI researches. We, therefore, developed a web-based platform PAI-WSIT: Pathologists Annotated and AI-empowered WSI Database for Tumors, which provides storing, sharing, and visualizing services for WSIs with annotations. In addition, PAI-WSIT also supports the management of annotations from different pathologists and integrates an AI service for detecting malignant regions in colorectal WSIs. The platform will provide collaborations between the computer scientists and research pathologists that are of utmost importance for the development of relevant algorithms and computer-aided prognosis. PAI-WSIT is freely accessible from http://www.paiwsit.com .

Thermal deformation caused by temperature rise have an influence on the dynamic performance of a motorized spindle. In turn, the change in the dynamic performance will affect the temperature rise and thermal deformation of the system. However, the latter was rarely focused on in the previous literature. Therefore, a thermal network model of motorized spindle is enhanced by considering the thermal–mechanical coupling effect. Then, an iterative method is presented to solve the coupled equations, and a temperature test rig of the motorized spindle is set up to verify the proposed model. The relative error between the predicted and experimental results at two test points decreases by 9.56% and 3.44% after considering the thermal–mechanical coupling effect. The comparison with the experimental results shows that the proposed model with thermal–mechanical coupling effect can obtain a more accurate temperature field than the previous model.

As one type of latest emitters with simultaneous high efficiency and color-purity, the development of multi-resonance thermally activated delayed fluorescence (MR-TADF) materials represents an important advancement for organic light-emitting diodes (OLEDs). We herein present a new strategy to improve the performance of MR-TADF emitters by fusing sulfur element into the B-N based framework, aiming to utilize the non-metal heavy-atom effect in accelerating the reverse intersystem crossing (RISC) process of the emitter. Two compounds, namely 2PTZBN and 2PXZBN, were developed in this work through rigidifying the DABNA-1 skeleton by sulfur or oxygen atoms. The theoretical calculations and photoluminescence studies revealed that the sulfur-incorporated 2PTZBN enabled considerable rate constant of RISC (kRISC) up to 2.8 × 105 s-1 in toluene due to larger spin-orbital coupling (SOC) values and smaller singlet-triplet energy splitting (ΔEST) compared with 2PXZBN. Consequently, organic light-emitting diodes based on 2PTZBN exhibited highly efficient green emission with maximum external quantum efficiency (EQE) of 25.5%.

A new series of tetrahedral heteroleptic copper(I) complexes exhibiting efficient thermally-activated delayed fluorescence (TADF) in green to orange electromagnetic spectral regions has been developed by using D-A type N^N ligand and P^P ligands. Their structures, electrochemical, photophysical, and electroluminescence properties have been characterized. The complexes exhibit high photoluminescence quantum yields (PLQYs) of up to 0.71 at room temperature in doped film and the lifetimes are in a wide range of 4.3–24.1 μs. Density functional theory (DFT) calculations on the complexes reveal the lowest-lying intraligand charge-transfer excited states that are localized on the N^N ligands. Solution-processed organic light emitting diodes (OLEDs) based on one of the new emitters show a maximum external quantum efficiency (EQE) of 7.96%.

Highly efficient blue thermally activated delayed fluorescence (TADF) materials with high horizontal dipole orientation (Θ//) remain a big challenge due to the concentration quenching effects and serious efficiency roll-offs in their corresponding organic light-emitting diodes (OLEDs). We herein report two novel TADF compounds, namely 2TDBA-SBA and TDBA-SBA, which were facilely synthesized by utilizing a rigid oxygen-bridged cyclized triarylboron-based unit (TDBA) as the acceptor and a spiro acridine (SBA) as the donor. Benefiting from the rigid and planar skeleton of the acceptor and the linear molecular shape, high Θ//s and photoluminescence quantum yields (PLQYs) of ∼ 90% were achieved. Significantly, TDBA-SBA exhibited excellent TADF properties with a short delayed fluorescence lifetime of only 684 ns and narrow full-width at half-maximum (FWHM) of 44 nm in solution state, accompanied by the high PLQYs of over 80% at high doping concentrations, manifesting the alleviated exciton quenching effects. Consequently, OLEDs based on TDBA-SBA achieved a high maximum external quantum efficiency (EQE) of 29.3% and a maximum brightness of 27663 cd cm−2. Importantly, an EQE over 20% was realized even at the high brightness of 10000 cd cm−2, signifying a small efficiency roll-off.

Multi-resonance thermally activated delayed fluorescence (MR-TADF) offered exceptional solution for narrowband organic light emitting diode (OLED) devices in terms of color purity and luminescence efficiency, while the development of new MR skeleton remained an exigent task, especially for long wavelength region. We hereby demonstrate that a simple modification of the B (boron)-N (nitrogen) framework by sp3 -carbon insertion would significant bathochromic shift the short-range chargetransfer emission and improve the device performances. The bis(acridan)phenylenebased skeleton developed in this contribution presented a non-planar conformation and allowed facile introduction of isolating units to prevent triplet-involved quenching, deriving two luminophores with quantum yields approaching 90% and narrow FWMHs below 30 nm in film state. Corresponding green-emissive devices realized superior performances comparing to the planar carbazolyl-based MR-TADF analogues, with a maximum external quantum efficiency (EQEmax) up to 28.2% and small efficiency rolloff without the involvement of any sensitizing host

Colorectal cancer (CRC) is the second leading cause of cancer-related mortality worldwide. In coping with it, histopathology image analysis (HIA) provides key information for clinical diagnosis of CRC. Nowadays, the deep learning methods are widely used in improving cancer classification and localization of tumor-regions in HIA. However, these efforts are both time-consuming and labor-intensive due to the manual annotation of tumor-regions in the whole slide images (WSIs). Furthermore, classical deep learning methods to analyze thousands of patches extracted from WSIs may cause loss of integrated information of image. Herein, a novel method was developed, which used only global labels to achieve WSI classification and localization of carcinoma by combining features from different magnifications of WSIs. The model was trained and tested using 1346 colorectal cancer WSIs from the Cancer Genome Atlas (TCGA). Our method classified colorectal cancer with an accuracy of 94.6 %, which slightly outperforms most of the existing methods. Its cancerous-location probability maps were in good agreement with annotations from three individual expert pathologists. Independent tests on 50 newly-collected colorectal cancer WSIs from hospitals produced 92.0 % accuracy and cancerous-location probability maps were in good agreement with the three pathologists. The results thereby demonstrated that the method sufficiently achieved WSI classification and localization utilizing only global labels. This weakly supervised deep learning method is effective in time and cost, as it delivered a better performance in comparison with the state-of-the-art methods.

Innovative stiffness and damping models for oil films are developed to account for the impacts in both normal and tangential directions. Given that these models are applied to a gear drive in line contact elastohydrodynamic lubrication (EHL), the combined stiffness is derived from the stiffness of both the oil film and gear tooth while the combined damping is established from the damping of these parts. The effects of three fundamental parameters (contact force, rotation speed, and tooth numbers) of the gear drive in line contact EHL on the combined stiffness and damping are then investigated. The results reveal that the small normal and tangential stiffness of the lubricant can alleviate meshing impact and shear vibration, while the impact and friction heat can be reduced by using an oil film with either a large normal damping or small tangential damping. Given that its amplitude and fluctuation are closely related to shear rate, effective viscosity, entrainment velocity, and curvature radii, the improved combined stiffness and damping can be obtained by rationally matching the geometric and operating parameters.

As one type of latest emitters with simultaneous high efficiency and color-purity, the development of multi-resonance thermally activated delayed fluorescence (MR-TADF) materials represents an important advancement for organic light-emitting diodes (OLEDs). We herein present a new strategy to improve the performance of MR-TADF emitters by fusing sulfur element into the B-N based framework, aiming to utilize the non-metal heavy-atom effect in accelerating the reverse intersystem crossing (RISC) process of the emitter. Two compounds, namely 2PTZBN and 2PXZBN, were developed in this work through rigidifying the DABNA-1 skeleton by sulfur or oxygen atoms. The theoretical calculations and photoluminescence studies revealed that the sulfur-incorporated 2PTZBN enabled considerable rate constant of RISC (kRISC) up to 2.8 × 105 s-1 in toluene due to larger spin-orbital coupling (SOC) values and smaller singlet-triplet energy splitting (ΔEST) compared with 2PXZBN. Consequently, organic light-emitting diodes based on 2PTZBN exhibited highly efficient green emission with maximum external quantum efficiency (EQE) of 25.5%.

Friction is not considered in the calculation of load capacity for spiral bevel gears according to either ISO or AGMA gear standard, and friction effects on the bending, contact and shear of the gears have rarely been discussed. In this regard, the present work establishes analytical solutions to calculate bending and contact strength for spiral bevel gears incorporating friction on the tooth surface, which are verified by ISO gear standard and finite element method (FEM). The bending strength is calculated based on Lewis cantilever beam approximation, utilizing the modified normal force and the friction component. The modified normal force is derived at the highest point of single tooth contact (HPSTC) in the normal equivalent gear. Follow Hertz contact theory, the contact strength is calculated when the modified normal force and the friction component are exerted at the lowest point of single tooth contact (LPSTC) in the normal equivalent gear. The calculated bending and contact stresses agree well with those obtained from the FEM analysis while considering the influence of friction. Both theoretical predictions and FEM analysis have shown that friction has a crucial effect on load capacity of a spiral bevel gear drive, and that it exerts stronger influence on the bending strength (compared with the contact strength). When friction coefficients become larger (with the same input torque), the bending stress considering only the modified normal force decreases at HPSTC, whereas it increases if both the modified normal force and the friction component are included. In comparison, the contact stress will increase at LPSTC under both scenarios. Furthermore, it is illustrated that shear strength check of the tooth is necessary as large friction occurs in the contact zone. This developed analytical solution can be well applied to the determination of load capacity of spiral bevel gears, especially under harsh working conditions or in the demand for higher performance.

A new normal stiffness model of the oil film is established by the viscous-elastic fluid between a spur gear drive being equivalent to a massless spring element, and the tangential stiffness model is proposed according to the hypothesis of equal shear stress on laminar element surfaces. Effects of operating parameters (contact force and rotation speed) and geometry parameters (module, tooth number, pressure angle and modification) on the oil film stiffness from the root to the tip are investigated. The results show that the amplitude and fluctuation of the stiffness are closely related to the shear rate, effective viscosity and curvature radii. It is indicated that the rational parameter match is valid in mesh impact reduction and stationarity enhancement.

Simple and fast detection of chemical warfare agents vapor is necessary and urgent to fight against uncertain terrorist attacks and wars. In this contribution, inspired by the design of the hybrid locally excited and charge transfer (HLCT) excited state, two fast and highly sensitive visualization and fluorescence probes for DCP detection with relative small interstate coupling (J) TPA-2AC and TPA-9AC are reported. Upon exposure to saturated DCP vapor, the TPA-9AC test strips exhibited a rapid fluorescent response in no more than 1 s, accompanied by a change of the color from green to red. The detection limit of the test strips can be estimated as sensitive as 0.15 ppb, which is far superior to the "harmless" level (7 ppb) of human response to acute sarin exposure. More impressively, the fluorescent intensity of the test strips can be quickly restored when exposed to ammonia vapor for cyclic utilization, demonstrating an application prospect in the real-time detection of chemical warfare agents.

This paper proposes a thermal network model to predict the contact temperature of spur gears. A crucial parameter in gear scuffing evaluation is the contact temperature, which comprises the bulk and flash temperatures. Herein, thermal network models of gear bulk temperature and flash temperature are established, by dispersing tooth into multiple temperature elements connected by the thermal resistances of heat conduction and heat convection. The thermal network model of gear bulk temperature is verified by the finite element model and previous work, and the presented model for gear flash temperature is validated by Blok flash temperature formula. Following ISO standard, gear scuffing is evaluated by comparing the contact temperature with scuffing critical temperature. The effects of geometric and operating parameters on the gear temperature are subsequently investigated. Contact temperature is found to decrease with increased tooth width, pressure angle and module, but increases with increased rotational velocity and input torque. These findings indicate that reasonable geometric and operating parameter matching are beneficial for increasing gear-scuffing resistance.

The effects of centring error and angular misalignment on crack initiation life in herringbone gears are investigated in this work. Herringbone gears with centring error or angular misalignment are modelled for contact analysis. A crack initiation life model of standard and error gears is proposed in accordance with tooth stress history and a critical plane method for nonproportional loading. Then, the effects of centring error and angular misalignment on crack initiation life in herringbone gears are investigated. Results show that centring error and angular misalignment sharply reduce crack initiation life, but a moderate tip relief can eliminate stress concentration and extend crack initiation life. Furthermore, angular adjustment balances the load distribution of the left and right teeth in herringbone gears with centring error, improving tooth crack initiation life.

It is of scientific and engineering significance to extract surface wave signals from urban ambient noise for fine-scale three-dimensional velocity structure imaging of underground medium. A series of issues such as ambient noise characteristics in urban environment, observation system design and resolution of small-scale imaging, have put forward a lot of new requirements and challenges to traditional methods and technologies. We utilized the dense array with its aperture extend below hundred meters in Hangzhou urban area, to carry out the ambient noise data acquisition experiments within one day. Based on the time-frequency analysis of noise cross-correlations, we conducted surface wave travel time tomography. Finally, the phase velocity slices were inverted to build a three-dimensional S-wave velocity structure, and the profiles were compared with the drilling data for validations. We concluded that these geometry and processing parameters adopted in the urban environment are feasible for near-surface tomography and can meet the demands of three-dimensional geological survey in cities efficiently.

This study proposes an innovative and comprehensive method for the design and analysis of a high-speed cam mechanism. In the proposed method, the displacement function of the cam follower is described using Fourier series. The coefficients of the series are obtained by constraint equations during the cam rise period and the minimum principle of displacement error function (where, error function refers to the variance between actual displacement and ideal displacement of the cam follower during the dwell). The validity of the proposed design method is verified through a case study with focus on high-speed cam mechanism design. In the design case, kinematic characteristic analysis of this cam follower shows that the order of continuous derivative of displacement transfer function is higher, the characteristic value of its dynamic torque is smaller, and its jerk at the impact point is smaller than some common disc cam mechanisms. The results indicate that the proposed method can reduce the vibration of the cam mechanisms and its impact velocity is smaller than the existing design methods.

This paper carries out the experimental and numerical investigations on the root stress of a light-load spur gear drive. An improved gear test rig is developed to enable the dynamic root stress of a light-load spur gear drive to be wirelessly measured, and the signals of root strain, rotational speeds and torques of input/output gear shafts are sent or received wirelessly. After the random electrical noise is eliminated by multi-point average method, the key parameters of dynamic contact analysis on the root stress (rotational speeds and torque) are obtained, and the root strain signal is converted into root stress. Based on the curve of the measured root stress, the impact of meshing teeth and the alternative variation in the single and double pair gear meshing can be attained quantitatively. The geometric model of gear is developed by the generative machining principle and the coordinate transformation method. Then, the dynamic contact analysis is performed by the display centre difference metho...

This paper presents a continuous elastic–plastic asperity contact model with or without the consideration of friction to investigate the micro-contact properties of gear tooth profiles. The model for normal or side contact analysis is established according to Hertz contact theory and the asperity morphology feature, which yields to similar results as obtained from the model proposed by Chang W.R., Etsion I., and Bogy D.B. (CEB model) and the model proposed by Kogut L. and Etsion I. (KE model). More importantly, this model avoids the constant average contact stress as predicted by the CEB model, and the noncontinuous contact stress and deformation within the ultimate strength as given by the KE model. As a application of the present theoretical model in micro-contact analysis of rough tooth profiles, a finite element model (FE model) for elastic–plastic asperity in normal or side contact is established according to the measured surface parameters of a spur gear pair. It is shown that the extreme point of Von Mise stress of the asperities along the normal vector is ascertained by FE model, and that the extreme point is relative to the initial occurrence of the asperities plastic deformation. Compared with the present theoretical model, the similar normal contact stress along the contact radius is attained by FE model. Though the contact stress isogram in the specific plane in normal or side contact of the asperities is a circle or ellipse respectively when the plastic deformation is expanded from the inside of the asperities to their surfaces, it is in line with the distribution of elastic and plastic region of the theoretical model. Compared with CEB model, KE model, and FE model, the consistent results are attained by the present theoretical model in elastic–plastic asperity contact analysis. The results indicate that the theoretical model is applicable to the elastic–plastic asperity contact analysis on the rough surface of a spur gear drive.