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Piezoelectric-actuator-driven nanopositioning stages, with large stroke and low crosstalk, are quite appealing for fulfilling the through-silicon via lithography etching task. The motivation of this paper is to combine the ability to enable the nanopositioning stage running in a manner of millimeter scale workspace and nanometer scale positioning accuracy. Two pairs of flexure-guided kinematic modules with high displacement amplification ratio are adopted to construct a 4-PP (P is prismatic) XY nanopositioning stage. A new decoupling design is implemented to realize the decoupling behavior between the input actuators and output compliant limbs, respectively. Kinematics modeling including output compliance, input stiffness, displacement amplification ratio modeling, and workspace determination are carried out. After a series of mechanism dimension optimizations via particle swarm optimization algorithm, the performance of the optimized mechanism is analyzed and assessed by using the ANSYS workbench. Then, a repetitive-compensated PID controller and a single-input and single-output closed-loop control strategy are designed. Finally, a series of experimental tests in terms of crosstalk test, frequency characteristic analysis, damping property analysis, dynamic hysteresis nonlinearity characterization, signal trajectory tracking, workspace determination, and Bode diagram plotting are carried out in details. It indicates that the workspace of fabricated prototype has reached to 1.035 mm $\times$ 1.035 mm, the crosstalk ratio is kept within 0.5%, and the closed-loop positioning accuracy is determined as 400 nm. [ABSTRACT FROM PUBLISHER]

Recent smartphones increasingly employ a metal frame for a sophisticated design. However, the metal frame becomes a good coupling path for electromagnetic (EM) noise within smartphones and increases noise coupling to radio-frequency antennas located at the top and bottom sides of the smartphones. This paper proposes two novel metal frame structures with ferrite absorbing sheets or electromagnetic band gap patterns to reduce the coupling of EM noise to the antenna. Using a fabricated test board, the effects of the proposed metal frames on noise coupling suppression are experimentally validated. [ABSTRACT FROM PUBLISHER]

Using a configuration-space approach, the paper develops a 2nd-order mobility theory for rigid bodies in contact. A major component of this theory is a coordinate invariant 2nd-order mobility index for a body, B, in frictionless contact with finger bodies A/sub 1/,...A/sub k/. The index is an integer that captures the inherent mobility of B in an equilibrium grasp due to second order, or surface curvature, effects. It differentiates between grasps which are deemed equivalent by classical 1st-order theories, but are physically different. We further show that 2nd-order effects can be used to lower the effective mobility of a grasped object, and discuss implications of this result for achieving new lower bounds on the number of contacting finger bodies needed to immobilize an object. Physical interpretation and stability analysis of 2nd-order effects are taken up in the companion paper. [ABSTRACT FROM PUBLISHER]

Fasteners are widely used in automobile, electronic and other fields, and the demand for high performance fastener materials is increasingly urgent. 10B21 mild steel has the advantages of good plasticity, obvious heat treatment effect and so on. It is used to produce fasteners below grade 9.8. In this paper, the domestic 10B21 boron steel as the research object, through quenching, tempering and other heat treatment, change its structure from ferrite to tempered martensite, in order to improve the strength and hardness. [ABSTRACT FROM AUTHOR]

Vibration damping fastener is an important means for vibration and noise reduction in urban rail transit. At present, a common type of double-layer nonlinear vibration damping fastener has such problems as large consumables and high installation height. In this paper, a design scheme for a double-layer nonlinear vibration damping fastener is provided by means of structural design, simulation analysis and indoor test, which can effectively overcome the defects existing in a certain type of fastener. After indoor drop hammer test, the vibration reduction effect reaches 8. 9 dB. The Fatigue test indicates that the vertical stiffness of the system is 17 kN/mm, which meets the requirements of medium vibration damping stiffness. The traffic safety analysis shows that the derailment coefficient is low and meets the safety requirements. It is thus ensured that the fastener satisfies the requirements of medium vibration reduction fasteners and can be used for medium vibration reduction tracks of urban rail transit. [ABSTRACT FROM AUTHOR]

Automated fastener hole drilling is a key technology for low-cost and high-quality assembly of aircrafts. In this paper, a new circumferential drilling machine for fuselage assembly of large aircrafts is introduced. In order to meet the required position accuracy of drilled holes, this paper focuses on the kinematic calibration of the machine in order to improve its positioning accuracy. A modeling strategy, which combines the Denavit-Hartenberg (D-H) method and a modified version of the Hayati-Mirmirani (H-M) method, is proposed to deal with the special kinematic structure of the arc-base drilling unit of the machine. Main issues in kinematic parameter identification such as definition of objective function, calibration data selection, acquisition of initial values, and setting of convergence criteria are also discussed. Experiments of repeatability testing and kinematic calibration have been performed, and the results show that the positioning accuracy of the arc-base drilling unit is comparable to its repeatability after calibration. This suggests that the proposed kinematic calibration method is effective. Actual drilling tests have been performed on a simulated aircraft fuselage after implementing the identified kinematic model in the machine's control software. Position errors of drilled holes are within ±0.5 mm, which meets the requirement for fastener hole drilling in the fuselage assembly of large aircrafts. [ABSTRACT FROM AUTHOR]

The detection of fastener defects is an important task in railway inspection systems, and it is frequently performed to ensure the safety of train traffic. Traditional inspection is usually operated by trained workers who walk along railway lines to search for potential risks. However, the manual inspection is very slow, costly, and dangerous. This paper proposes an automatic visual inspection system for detecting partially worn and completely missing fasteners using probabilistic topic model. Specifically, our method is able to simultaneously model diverse types of fasteners with different orientations and illumination conditions using unlabeled data. To assess the damages, the test fasteners are compared with the trained models and automatically ranked into three levels based on the likelihood probability. The experimental results demonstrate the effectiveness of this method. [ABSTRACT FROM PUBLISHER]

In order to characterize the mechanical behavior of fragile resonant microelectromechanical systems (MEMS)/nanoelectromechanical systems (NEMS), nondestructive measurements are required. In this paper, a cartography of local stiffness variations on a suspended micromembrane is established for the first time, by a tuning-fork-based dynamic force sensor inside a scanning electron microscope (SEM). Experiments are conducted individually on a batch of InP membranes 200  nm thin, using a 9-degree-of-freedom (dof) nanomanipulation system, complemented with virtual reality and automation tools. Results provide stiffness values in the range of a few newton per meter, with variations in a single sample depending on the membrane models. [ABSTRACT FROM PUBLISHER]

Commonly used fastener positioning methods include pixel statistics (PS) method and template matching (TM) method. For the PS method, it is difficult to judge the image segmentation threshold due to the complex background of the track. For the TM method, the search in both directions of the global is easily affected by complex background, as a result, the locating accuracy of fasteners is low. To solve the above problems, this paper combines the PS method with the TM method and proposes a new fastener positioning method called local unidirectional template matching (LUTM). First, the rail positioning is achieved by the PS method based on the gray-scale vertical projection. Then, based on the prior knowledge, the image of the rail and the surrounding area of the rail is obtained which is referred to as the 1-shaped rail image; then, the 1-shaped rail image and the produced offline symmetrical fastener template is pre-processed. Finally, the symmetrical fastener template image is searched from top to bottom along the rail and the correlation is calculated to realize the fastener positioning. Experiments have proved that the method in this paper can effectively realize the accurate locating of the fastener for ballastless track and ballasted track at the same time. [ABSTRACT FROM AUTHOR]

This paper considers the problem of servicing a set of locations by a fleet of robots so as to minimize overall makespan. Although motivated by a specific real-world, multi-robot drilling and fastening application, the problem also arises in a range of other multi-robot domains where service start times are subject to precedence constraints and robots must be routed in space and time to avoid collisions. We formalize this general problem and analyze its complexity. We develop a heuristic local search procedure for solving it and analyze its performance on a set of synthetically generated problem instances, some of which capture the specific structure of the motivating drilling and fastening application, and others that generalize to other application settings. We provide a differential analysis of our local search procedure and a comparison to other approaches to demonstrate the efficacy of the proposed heuristic. [ABSTRACT FROM AUTHOR]

A review is made of the growth dynamics of metal radioactive waste on a world scale. The most commonly applied technologies (hydro- and pyrometallurgical) for deactivation of this waste are presented. The implementation of the blocks obtained by remelting for the manufacture of fasteners of nuclear reactors is demonstrated. Based on the conducted experiments and drawn conclusions, the inference is made that the pyrometallurgical methods of processing have greater advantages. The paper exhibits a convincing motivation for the essential necessity of investigation of the metal radioactive waste processing, following the system D&D (deconstruction + deactivation), using effective and environmentally friendly technology. [ABSTRACT FROM AUTHOR]

Due to the variety of materials used for flat belts of belt conveyors and the further development of material engineering in relation to these belts, the methods of their connection become an increasingly problematic issue. The belts can be connected mainly in three ways: vulcanized (weldable or heat-weldable), glued or mechanically. The latter method is one of the simplest and most universal in terms of the material variety of belts; however, there are many design variations of mechanical fasteners, and each of them has a certain advantage in a narrow group of properties, e.g., the thickness spectrum of a conveyor belt, the minimum diameter of a drive roller or the range of transferable longitudinal loads. The objective of this paper is to analyze the design solutions of commercial mechanical fasteners used mainly for flat rubber-fabric, composite or plastic belts. To fulfill this goal, a preliminary analysis of the stress distribution for an exemplary solid mechanical fastener was carried out in two cases: during ramp-up and during circulating around the roll, followed by a detailed review of commercial solutions available on the market. In addition to determining the current state of knowledge and technology and determining the state of ignorance, special algorithm and design maps have been created, thanks to which the process of selecting the right mechanical fastening will be easier. The overview includes several tables with detailed information on individual connection properties. Additionally, several design aspects were derived, within which individual mechanical connections may differ. This is to enable the generation of customized solutions in the future by proposing an appropriate mathematical model, on the basis of which it will be possible to generate optimal design properties for a given application. [ABSTRACT FROM AUTHOR]

Rail corrugation can reduce riding comfort by vibration and noise, and even cause running accident. In this paper, the vehicle–track coupled dynamic model was developed for a metro's tangential track considering the wear in rail materials. The influences of different track structure parameters and vehicle speed on the generation and development of rail corrugation of the tangential track were analyzed using the developed model by the control variable method. The results show that for different parameters, the friction power in wheel–rail contact patch fluctuates with time, but the overall fluctuation range is relatively uniform. Meantime, an analysis of one-third octave curves of the friction power reveals that the characteristic frequencies of friction power are mainly concentrated in the middle and low frequency bands. At the dominant characteristic frequency, the longitudinal stiffness and damping of fasteners, and lateral and vertical damping of fasteners have less influence on rail corrugation, while the lateral and vertical stiffnesses of fasteners, spacing of fasteners, wheel–rail friction coefficient and vehicle speed have greater effect on rail corrugation. The changes in vertical stiffness and spacing of fasteners will cause the characteristic frequency of friction power to be offset, resulting in a shift from 80 Hz to 100 Hz, which will further lead to rail corrugation of the corresponding wavelength. Thus, it can be concluded that the vertical stiffness and spacing of fasteners have an important impact on the generation and development of rail corrugation at the specific frequency. Besides, the variations of the other variables bring little change to the characteristic frequencies of friction power as well as on rail corrugation. The mechanism of parameters unveiled here provides some guides for the parameter optimization problem on restraining the generation or development of rail corrugation on the tangential track. [ABSTRACT FROM AUTHOR]

Traditional hinge loss function-based large-scale support vector machine (SVM) algorithms tend to perform poorly in the presence of noise, especially when the model is trained incrementally. In this paper, we propose an efficient stochastic quasi-Newton method-based twin parametric SVM using the pinball loss function (termed as SQN-PTWSVM), which is efficient and more robust to the presence of noise when compared to conventional hinge loss SVM for large-scale data scenarios. To establish the theoretical convergence of the method, a modified version of SQN-PTWSVM, termed as SQN-SPTWSVM, has also been proposed. It overcomes the poor convergence issue faced by stochastic gradient twin SVM thus resulting in a faster and reliable model. In SQN-SPTWSVM, the hyperplanes obtained are stable enough to handle noise and resampling issues that occur frequently in stochastic learning scenarios, leading to better generalization ability of the classifier. The proposed method has been extended to nonlinear scenarios as well. Moreover, batch versions of the proposed algorithms have also been introduced which significantly reduce the training time and memory requirement of SQN-PTWSVM and SQN-SPTWSVM. The experimental results on several benchmark datasets and activity recognition applications have shown that the performance of our method is better than the existing classifiers in terms of speed and accuracy. [ABSTRACT FROM AUTHOR]

This paper proposes a two-element multi-input multi-output (MIMO) open-slot antenna implemented on the display ground plane of a laptop computer for eight-band long-term evolution/wireless wide-area network operations. The metal surroundings of the antennas have been well integrated as a part of the radiation structure. In the single-element open-slot antenna, the nearby hinge slot (which is bounded by two ground planes and two hinges) is relatively large as compared with the open slot itself and acts as a good radiator. In the MIMO antenna consisting of two open-slot elements, a T slot is embedded in the display ground plane and is connected to the hinge slot. The T and hinge slots when connected behave as a radiator; whereas, the T slot itself functions as an isolation element. With the isolation element, simulated isolations between the two elements of the MIMO antenna are raised from 8.3–11.2 to 15–17.1 dB in 698–960 MHz and from 12.1–21 to 15.9–26.7 dB in 1710–2690 MHz. Measured isolations with the isolation element in the desired low- and high-frequency ranges are 17.6–18.8 and 15.2–23.5 dB, respectively. Measured and simulated efficiencies for the two-element MIMO antenna with either element excited are both larger than 50% in the desired operating frequency bands. [ABSTRACT FROM AUTHOR]

In the automobile industry, the simple inspection method of detecting the slack of the high-tension bolt in the engine section is desired. Since the permeability of the compression direction inside the steel is decreased when the steel material is compressed, the permeability of the compressed domain in the bolt is decreased when the fastened force of the bolt is increased. Therefore, the evaluation of the slack of the bolt is possible by detecting the difference of the magnetic characteristics near the compressed position in the bolt. However, the detection signal is also influenced by the change of distance (lift-off) between the bolt and an electromagnetic sensor. In this paper, the inspection method for measuring the slack of the bolt taking account of the lift-off is proposed using the 3-D edge-based hexahedral nonlinear finite element method and the experimental verification. [ABSTRACT FROM AUTHOR]

The high-temperature superconductor (HTS) machines are more attractive due to the advantages of high power density and efficiency. This paper introduces a new HTS electromagnetic screw (HTS-EMS) that is developed for artificial heart. Two helical-shaped slots are introduced to the translator; the key to the HTS-EMS is that the HTS coils carrying dc currents are placed in the helical-shaped slots. The permanent-magnet array is placed in the rotor. Due to the high current density of the HTS coil, the power density of the HTS-EMS can be improved effectively. The electromagnetic performance of the HTS-EMS is analyzed, including the flux, thrust force, as well as torque. The proposed HTS-EMS is evaluated compared with the existing magnetic screw using time-stepping finite-element method, verifying the advantages of the proposed structure. [ABSTRACT FROM AUTHOR]

Person reidentification (re-id) aims to match a specific person across nonoverlapping cameras, which is an important but challenging task in video surveillance. Conventional methods mainly focus either on feature constructing or metric learning. Recently, some deep learning-based methods have been proposed to learn image features and similarity measures jointly. However, current deep models for person re-id are usually trained with either pairwise loss, where the number of negative pairs greatly outnumbering that of positive pairs may lead the training model to be biased toward negative pairs or constant margin hinge loss, without considering the fact that hard negative samples should be paid more attention in the training stage. In this paper, we propose to learn deep representations with an adaptive margin listwise loss. First, ranking lists instead of image pairs are used as training samples, in this way, the problem of data imbalance is relaxed. Second, by introducing an adaptive margin parameter in the listwise loss function, it can assign larger margins to harder negative samples, which can be interpreted as an implementation of the automatic hard negative mining strategy. To gain robustness against changes in poses and part occlusions, our architecture combines four convolutional neural networks, each of which embeds images from different scales or different body parts. The final combined model performs much better than each single model. The experimental results show that our approach achieves very promising results on the challenging CUHK03, CUHK01, and VIPeR data sets. [ABSTRACT FROM PUBLISHER]

Hybrid excitation synchronous generators are a special class of electrical machines in which the total rotor current linkage is produced by the simultaneous action of two different excitation sources: permanent-magnet (PM) excitation and field winding excitation. In the island operation, there is a need to compensate the armature reaction to keep the generator terminal voltage constant. The permanent magnet excitation is used to create the no-load excitation to the generator and the rotor winding is used as an armature reaction compensating winding. This paper studies the applicability of an armature-reaction-compensated PM synchronous generator to a marine diesel genset. This paper presents an analytical approach for the electromagnetic design of the proposed topology. Finite-element analysis and experimental measurements are performed to verify the results of the analytical approach. [ABSTRACT FROM PUBLISHER]

This paper addresses the modeling, controller design, and stability analysis of an electric parking brake system in which a screw–nut self-locking mechanism is used. The system is modeled as a state-dependent switched system according to the operating mode. A nonlinear proportional (P) clamping force controller using the measured force is proposed to enhance the performance specifications. We show the uniform stability of the state-dependent switched system with the nonlinear P controller using a common Lyapunov theorem and LaSalle's invariance principle. We derive the conditions to assure stable self-locking operation of the system. We also show the existence of the largest invariant set depending on the target braking force. This analysis offers a guideline as to how a nonlinear controller can be designed in view of the self-locking stability and control performance. Through simulation and experimental results, we confirm that the solution is locally uniformly ultimately bounded. Through the experimental results, we show that the nonlinear P controller outperforms a simple on/off controller in terms of the average and deviation of the braking force error. Furthermore, it is experimentally verified that the system is also able to function as a pseudo-antilock braking system. [ABSTRACT FROM AUTHOR]

This paper summarizes the results of the static structural analyses, which were conducted in support of the ITER magnet feeder design with the aim of validating certain components against the structural design criteria. While almost every feeder has unique features, they all share many common constructional elements and the same functional specifications. The analysis approach to assess the load conditions and stresses that have driven the design is equivalent for all feeders, except for particularities that needed to be modeled in each case. The mechanical analysis of the feeders follows the sub-modeling approach: the results of the global mechanical model of a feeder assembly are used as input for the detailed models of the feeder' sub-assemblies or single components. Examples of such approach, including the load conditions, stress assessment criteria and solutions for the most critical components, are discussed. It has been concluded that the feeder system is safe in the referential operation scenarios. [ABSTRACT FROM PUBLISHER]

This paper presents structure thermal mechanics analysis of spindle disk assembly used in spinning magnetic data storage hard disk drives (HDDs). With the view toward understanding the underlying physics and to minimize the corresponding repeatable run-out (RRO) of track following position error signal (PES) in high track per inch (TPI) magnetic disk drives, analytical representation of thermal expansion mismatch between disk and spindle hub structure formulated in form of operators and finite element analyses (FEA) are employed in this paper. Parameter studies with analyses taken at different operational temperatures suggest that RRO can be minimized significantly when location of spindle notch, which is can be the internal feature used to position bearings to the hub structure, is properly located. RRO harmonics resulted from the thermal expansion mismatch and structure misalignments having ramping characteristics from disk outer diameter to inner diameter are studied and concluded with simple algebraic expression related to number of fasteners used in disk-spindle assembly. [ABSTRACT FROM AUTHOR]

This paper presents a review of the design provisions for screw-fastened cold-formed steel connections in the United States, including criteria for testing and evaluating the strength of screw fasteners. In addition, the paper examines the relationship between the connected elements/components computed connection strength and the strength of the connector (screws). Fastener strength test data from three independent manufacturers is presented and it is shown that as the thickness or yield strength of the connected elements/components is increased, the ratio of the fastener strength to the bearing/tilting strength decreases to values less than one-half in some cases. Analysis of the test data showed that even when the 2001 North American Specification (NASPEC) for the Design of Cold-Formed Steel Structural Members statistical requirements for distribution of the test data are met, the computed safety and resistance factors can exceed the recommended limits in Section E4 of the 2001 NASPEC. On this basis, it is recommended that the current language in the 2001 NASPEC be revised to specify, if necessary, limits on manufacturer computed safety and resistance factors. Finally, it is recommended that fastener tilt during screw shear strength tests be eliminated to facilitate an accurate evaluation of the shear strength of a fastener. [ABSTRACT FROM AUTHOR]

The paper derives the optimal second-order coding rate for the continuous-time Poisson channel. We also obtain bounds on the third-order coding rate. This is the first instance of a second-order result for a continuous-time channel. The converse proof hinges on a novel construction of an output distribution induced by Wyner’s discretized channel and the construction of an appropriate $\epsilon $ -net of the input probability simplex. While the achievability proof follows the general program to prove the third-order term for non-singular discrete memoryless channels put forth by Polyanskiy, several non-standard techniques—such as new definitions and bounds on the probabilities of typical sets using logarithmic Sobolev inequalities—are employed to handle the continuous nature of the channel. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate the influence of vertical fastener stiffness on the sound power characteristics of rail rolling noise. The rail mobility is obtained by using the Timoshenko-beam track model and the spectral element method. The decay rate is obtained by using the periodic track model and the spectral transfer matrix method. Then, the simulation results of the rail mobility and the decay rate are used to calculate the sound power level of the rail subjected to a harmonic point excitation. Furthermore, the influence of vertical fastener stiffness on the rail sound power level is investigated. Finally, field measurements of the rail accelerance and the decay rate are performed to verify the accuracy of models and calculation methods. The results show that the sound power level of the rail subjected to a harmonic point excitation increases with the increase of the frequency and peaks at the center frequency of 800 Hz. When the vertical fastener stiffness decreases from 50 kN/mm, the rail sound power level below the center frequency of 200 Hz gets increased. The increase of the sound power level is most significant at the center frequency which is close to the decreased vertical rail resonance frequency, because in the corresponding one-third octave band the rail mobility amplitude increases significantly while the decay rate decreases considerably. The simulations of the rail accelerance and the decay rate both coincide well with the measurements. [ABSTRACT FROM AUTHOR]

This paper presents a study on strategies of searching for the worst case configuration of a multi-configuration implantable system under magnetic resonance imaging, which induces the highest radio frequency energy exposure among all possible configurations. The strategies are usually based on parameter search to avoid brutal study of a huge number of possible configurations. Comparison studies of four different searching strategies, i.e., single sequential search, sequential search with the second worst case validations, hotspots-based sequential search, and multi-iteration sequential search, are evaluated. It is found that the initial configuration and sequence of parameter search can significantly affect the searched worst case configuration. For the multi-configuration system considered in this investigation, the simple sequential search strategy leads to a high probability of search failure, which means that the worst case configuration may be easily missed. Single sequential search with the second worst case validations and multi-iteration sequential search can significantly reduce the probability of search failure. [ABSTRACT FROM AUTHOR]

As regular inspection for the bolt connection in inaccessible areas is difficult and costly, computer vision technology provides a suitable noncontact approach for real-time bolt looseness detection as an alternative to inspection approaches. However, computer vision still suffers from various impracticalities. In this paper, a new vision-based bolt looseness detection method is designed and implemented with the bolt images acquired by a camera at arbitrary positions around the bolts. The new method includes the perspective transformation of original images acquired, identification of bolt positioning with the convolutional neural network digit recognition, detection of bolt rotation angles using Hough transform line detection, and density-based spatial clustering of applications with noise. To demonstrate the effectiveness of the new method, an experiment with bolted connections is setup. The experimental results demonstrate that the new method can accurately detect the looseness of the bolts in the bolted connection. [ABSTRACT FROM AUTHOR]

The article comments on the paper “Effective Flange Width Definition for Steel— Composite Bridge Girder” by Methee Chiewanichakorn and Amjad J. Aref, Stuart S. Chen and II-Sang Ahn. A prominent role is played by the degree of interaction between steel and concrete in the theoretical determination of effective widths. The authors express dissatisfaction with the computational results obtained for bridge girders.

The detection of fastener defects is crucial for ensuring the safety and reliability of high-speed train operations. This paper proposes an intelligent algorithm named YOLO-Fastener for detecting fastener defects in ballastless track systems. The proposed YOLO-Fastener incorporates efficient channel and spatial attention mechanisms, enhancing the extraction of crucial features related to fastener defects. Decision regions of the model in identifying fastener defects are visualized through heatmaps. The model is trained and tested on a limited dataset of high-resolution fastener images collected by a ballastless track detection vehicle equipped with 3-D laser devices. The results show that the precision and recall of the proposed model on the test set are 98.33% and 99.15%, which are 1.63% and 4.81% higher than those of the advanced Faster R-CNN model. In terms of fastener detection efficiency, the proposed model is the fastest with an inference time of 10.4 ms, which is an 18.75% improvement over the result of the advanced YOLOv7 model. • The paper proposes an intelligent algorithm named YOLO-Fastener for detecting fastener defects. • A high-resolution dataset of fastener defects is collected by a ballastless track detection vehicle. • The ECSA module has been developed to extract more crucial fastener defect features. • The GhostConv and RepConv modules are employed to reduce model parameters and increase inference speed. [ABSTRACT FROM AUTHOR]

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Fastener assembly is a tedious and time-consuming work because operators have to check assembly manuals and find right fastener for each hole. Hence, this paper aims to develop a three-dimensional (3-D) projection system that projects assembly instruction onto the work piece surface directly to guide operators to assemble. However, in order to project the instruction accurately, the corresponding part of the computer-aided design model of the physical scanned area needs to be attained through the rapid and accurate registration. In order to achieve this goal, first, a high-accuracy and rapid 3-D measurement system is developed; second, a fast registration method based on local multiscale geometric feature vector is proposed to accelerate the registration speed and improve the registration reliability. Experimental results demonstrate the measurement accuracy of the developed system, and verify the feasibility of the proposed registration method. Hence, the proposed method can lead to improved assembly efficiency and decreased error probability, making great contributions to large-scale structure assembly. [ABSTRACT FROM PUBLISHER]

Energy costs are typically the largest cost element in the life-cycle of a compressed-air system (CAS). Real-time usage information as well as historical data can help identify whether the CAS is functioning properly. To this end, modern variable-speed drives are able to provide this information as well as produce soft-sensor estimates of volume flow rate production and specific energy consumption of a CAS. In this paper, an identification (ID) run sequence for a twin rotary screw compressor-operated system is proposed to identify the total system volume, to improve the estimation accuracy of a volume flow rate soft sensor, and to create a specific energy consumption map for the CAS performance monitoring. Laboratory measurements are carried out to evaluate the feasibility of the proposed ID run and related estimations. Moreover, possible usage applications of the proposed methods are discussed. [ABSTRACT FROM PUBLISHER]

This paper proposes an acceleration-based robust controller for the motion control problem, i.e., position and force control problems, of a novel series elastic actuator (SEA). A variable stiffness SEA is designed by using soft and hard springs in series so as to relax the fundamental performance limitation of conventional SEAs. Although the proposed SEA intrinsically has several superiorities in force control, its motion control problem, especially position control problem, is harder than conventional stiff and SEAs due to its special mechanical structure. It is shown that the performance of the novel SEA is limited when conventional motion control methods are used. The performance of the steady-state response is significantly improved by using disturbance observer (DOb), i.e., improving the robustness; however, it degrades the transient response by increasing the vibration at tip point. The vibration of the novel SEA and external disturbances are suppressed by using resonance ratio control (RRC) and arm DOb, respectively. The proposed method can be used in the motion control problem of conventional SEAs as well. The intrinsically safe mechanical structure and high-performance motion control system provide several benefits in industrial applications, e.g., robots can perform dexterous and versatile industrial tasks alongside people in a factory setting. The experimental results show viability of the proposals. [ABSTRACT FROM PUBLISHER]

For the response of the train-track-bridge system under extreme environment, an increasing number of studies employ co-simulation strategies for detailed modeling and calculation of the structure. However, there is a lack of research on the module connectors, which significantly impact simulation accuracy and stability. In this paper, the theoretical differences between weak, moderate, and strong coupling methods in dealing with co-simulation module interface connectors are discussed. An explicit-implicit multi-timestep co-simulation platform is established using MATLAB and OPENSEES software. Taking China's CRTS II slab ballastless track, a simply supported beam bridge, and a train as examples, a three-dimensional train-track-bridge coupling model is created. The three coupling methods are then verified and compared. Finally, two coupling methods are used to model and calculate the train-track-bridge system under earthquake. It is concluded that when calculating the train-track-bridge under earthquake, using the fastener with less damage as the co-simulation partition boundary can avoid complex nonlinear calculation. On this basis, it is feasible to use weak, moderate and strong coupling methods to deal with fastener elements. Different co-simulation software can adopt different coupling methods according to the difficulty of modeling. In the MATLAB-OPENSEES multi-timestep explicit-implicit co-simulation platform, the weak and moderate methods can achieve better calculation accuracy, and can be used to calculate the response of train-track-bridge system under earthquake. • Fasteners aid module partitioning in train-rack-bridge co-simulation under seismic conditions. • In OPENSEES, fixed-spring-damping modifies only diagonal stiffness matrix elements. • Strong, moderate, and weak coupling methods enable diverse simulation strategies. • Moderate/weak coupling ensures consistent train-track-bridge seismic simulation. [ABSTRACT FROM AUTHOR]

The resilient fastener slab track (RFS track) has found extensive application in urban railways, effectively mitigating vibration and noise resulting from train operations. However, the structure elasticity of the RFS track is higher than the normal slab track (NS track), which can affect train running stability and cause abnormal vibration phenomenon. This paper explores the track structure elasticity on vehicle-track interaction and train running stability through experimental tests and numerical simulations. The vibrational properties of the RFS track and the NS track are obtained through field tests. A 3D metro vehicle-track coupled dynamics model is developed and utilized to simulate the dynamic performance of metro vehicles moving on different track structures. The impact of track structure parameters upon the vehicle-track interaction and train running stability are discussed. The findings indicate that the track structure elasticity can reduce train hunting stability and cause abnormal vibration phenomena in metro vehicles under certain conditions. The reasonable matching of the fastener lateral and vertical stiffness can not only accomplish vibration attenuation but also minimize the impact on train running stability. In addition, the rail surface wear and track gauge variation also exert influence on the running stability and dynamic performances of metro vehicles. • Track structure elasticity on vehicle-track interaction and train running stability was investigated. • Train hunting mechanism running on resilient fastener slab (RFS) track was revealed. • Vibrational properties of RFS track and normal slab track were tested on site. • The impact of track structure parameters upon vehicle dynamic performances was evaluated. • The track structure elasticity reduces hunting stability of metro vehicles. [ABSTRACT FROM AUTHOR]

To address the issues of the Real-Time DEtection TRansformer (RT-DETR) object detection model, including poor defect feature extraction in the task of rail fastener defect detection, inefficient use of computational resources, and suboptimal channel attention in the self-attention mechanism, the following improvements were made. Firstly, a Super-Resolution Convolutional Module (SRConv) was designed as a separate component and integrated into the Backbone network, which enhances the image details and clarity while preserving the original image structure and semantic content. This integration improves the model's ability to extract defect features. Secondly, a channel attention mechanism was integrated into the self-attention module of RT-DETR to enhance the focus on feature map channels, addressing the problem of sparse attention maps caused by the lack of channel attention while saving computational resources. Finally, the experimental results show that compared to the original model, the improved RT-DETR-based rail fastener defect detection algorithm, with an additional 0.4 MB of parameters, achieved a higher accuracy, with a 2.8 percentage point increase in the Mean Average Precision (mAP) across IoU thresholds from 0.5 to 0.9 and a 1.7 percentage point increase in the Average Recall (AR) across the same thresholds. [ABSTRACT FROM AUTHOR]

This paper reports on the development of a piezo-actuated nanometric ultra-fast tool servo (NU-FTS) for nanocutting. For motion guidance, a flexure mechanism is especially designed using a novel kind of generalized flexure hinges with the notch profiles described by a rational Bezier curve. Both kinematics and dynamics properties of the mechanism are comprehensively modeled through a novel finite beam modeling method. With this model, the hinge is divided into a set of serially connected beams with constant cross sections. The equivalent stiffness and lumped moving mass of the mechanism are derived based on the Euler-Bernoulli beam theory. Taking advantage of the structure and performance model, the notch shape as well as the dimensions are optimized to achieve the specified criteria for the NU-FTS. Performance of the designed mechanism is verified through both finite-element analysis and practical testing on a prototype. Overall, the NU-FTS is demonstrated to have a stroke of 6 and 1.2 $ \mu $ m for the quasi-static and 10 kHz driving condition, respectively. Through dynamics inversion-based trajectory preshaping, a maximum following error around 25 and 50 nm is obtained for tracking a simple harmonic and a complicated trajectory, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a novel actuator-internal two degree-of-freedom (2-DOF) micro/nano positioning stage actuated by piezoelectric (PZT) actuators, which can be used as a fine actuation part in dual-stage system. To compensate the positioning error of coarse stage and achieve a large motion stroke, a symmetrical structure with an arch-shape bridge-type amplifier based on single notch circular flexure hinges is proposed and utilized in the positioning stage. Due to the compound bridge arm configuration and compact flexure hinge structure, the amplification mechanism can realize high lateral stiffness and compact structure simultaneously, which is of great importance to protect PZT actuators. The amplification mechanism is integrated into the decoupling mechanism to improve compactness, and to produce decoupled motion in X- and Y-axes. An analytical model is established to explore the static and dynamic characteristics, and the geometric parameters are optimized. The performance of the positioning stage is evaluated through finite element analysis and experimental test. The results indicate that the stage can implement 2-DOF decoupled motion with a travel range of 55.4 × 53.2 μm2, and the motion resolution is 8 nm. The stage can be used in probe tip-based micro/nano scratching. [ABSTRACT FROM AUTHOR]

Fasteners in assemblies are often subjected to multi-axial loading; however, the role of load angle and the assembly design/geometry on the failure of fasteners are not well understood. Existing experimental data often convolutes multiple sources of uncertainty. Thus, numerical modeling is needed to make accurate conclusions about the failure mechanisms of fasteners. This paper investigates the mechanics that controls the loading angle effects on the mechanical response of fasteners by using a simple finite element bolt model without threads. The material model of this model is calibrated against tensile testing data, which minimizes the contribution of the fixture to the bolt's response. The calibrated material model is then used to investigate the loading fixture effects (including the fixture gap, compliance, and double shear loading configuration) on the mechanical response of the fasteners. After identifying the fixture parameters that the fastener's response is most sensitive to, a model of a simplified fixture is validated against experimental results. This investigation reveals that the loading angle effects and most of the loading fixture effects on fasteners' mechanical response are attributed to the change of stress concentrations at the contact tips. The primary contributions of this paper are novel insights into the failure mechanisms of fasteners, and that a reduced model of a fastener can be used to predict its constitutive behavior accurately. • A simplified fastener-test fixture model is developed to investigate failure mechanisms under mixed shear and tensile loading • The model is validated against multiple sources of experimental data from the literature • The model is used to investigate the fixture's effects on the measured constitutive properties of a fastener • This work highlights the need to account for the test fixture design in extracting properties from fastener testing [ABSTRACT FROM AUTHOR]

Mechanical fastening is widely used in joining metals, particularly in automotive, aerospace, building and construction industries. However, the main concern on mechanical fastening is the issue of corrosion. An effective way to prolong the service life of steel fasteners is to apply protective coatings onto these components. This paper reviews and compares a few common coating deposition techniques, i.e., electroplating, hot-dip galvanizing, ion vapour deposition and mechanical plating, in terms of their characteristics. Compositional and microstructural properties including morphology and porosity, corrosion resistance performance and frictional performance of the coatings formed by each process are discussed in details. Hydrogen embrittlement, a premature failure often occurred on high strength steel fasteners, is also reviewed. The key results of recent studies of various metallic coatings on fasteners are presented to provide a fundamental understanding of the evolving topics, and the research gaps have been identified for further investigation. [ABSTRACT FROM AUTHOR]

The clamping bolts and bolt-holes can be employed to stack the steel laminations in permanent magnet machines. Their influence on the electromagnetic performance is analyzed in this paper, including the electromagnetic torque, open-circuit torque, phase back-EMFs, and circulating current loss. A restraining method of dummy bolt-hole is proposed to achieve both balanced phase back-EMFs and zero circulating currents in bolts. The ratio of bolt-hole edge thickness to bolt-hole radius is optimized to compensate the reduction of stator yoke caused by bolt-holes. Besides, a method of open bolt-hole edge is proposed to restrain the circulating currents. Furthermore, structure analyses are conducted to prove the reliability of the electromagnetic design. The proposed method is verified by experiments on a prototype machine. [ABSTRACT FROM AUTHOR]

Split pins (SPs) play an important role in fixing joint components on catenary support devices (CSDs) of high-speed railway. The occurrence of loose and missing defects of SPs could make the structure of CSDs unstable. In this paper, we present a three-stage automatic defect inspection system for SPs mainly based on an improved deep convolutional neural network (CNN), which is called PVANET++. First, SPs are localized by PVANET++ and the Hough transform & Chan–Vese model, and then, three proposed criteria are applied to detect defects of SPs. In PVANET++, a new anchor mechanism is applied to produce suitable candidate boxes for objects, and multiple hidden layer features are combined to construct discriminative hyperfeatures. The performance of PVANET++ and several recent state-of-the-art deep CNNs is compared in a data set that is collected from a 60-km rail line. The results show that our model is superior to others in accuracy, and has a considerable speed. [ABSTRACT FROM AUTHOR]