Search

Todays large-scale parallel workflows are often processed on heterogeneous distributed computing platforms. From an economic perspective, computing resource providers should minimize the cost while offering high service quality. It has become well-organized that energy consumption accounts for a large part of a computing systems total cost, and timeliness and reliability are two important service indicators. This article studies the problem of scheduling a parallel workflow that minimizes the system energy consumption under the constraints of response time and reliability. We first mathematically formulate this problem as a Non-linear Mixed Integer Programming problem. Since this problem is hard to solve directly, we present some highly-efficient heuristic solutions. Specifically, we first develop an algorithm that minimizes the schedule length while meeting reliability requirement, on top of which we propose a processor-merging algorithm and a slack time reclamation algorithm using a dynamic voltage frequency scaling (DVFS) technique to reduce energy consumption. The processor-merging algorithm tries to turn off some energy-inefficient processors such that energy consumption can be minimized. The DVFS technique is applied to scale down the processor frequency at both processor and task levels to reduce energy consumption. Experimental results on two real-life workflows and extensive synthetic parallel workflows demonstrate their effectiveness.

This paper demonstrates the analysis of a long-distance high-power microwave wireless power transmission (MWPT) system based on asymmetrical resonant magnetron and cyclotron-wave rectifier. In the system, the novel magnetron with the asymmetrical resonant cavity, the straps, and the output loop coupling circuit can effectively promote the beam–wave interaction, suppress the mode competition, and enhance the output coupling, which results in a 400 kW output microwave power with a conversion efficiency of 45%. The transceiver Cassegrain antenna system with its simple structure, high conversion efficiency, and high power capacity can attain an integral power transmission efficiency of 2.6% at 10 km distance. The cyclotron-wave rectifier with high efficiency and single-tube high power capacity can achieve 85% microwave to DC conversion efficiency. Finally, the long-distance high-power MWPT system can achieve 8.5 kW DC power with about 1% DC–DC transmission efficiency at the operating 2.45 GHz frequency and for the 10 km distance. Such a system is likely a potential and attracting solution to remotely power the fuel-free aerial vehicle from the ground, can also provide electrical power to an isolated mountain top or an island, and even an alternative to transmit the power from space solar power satellite in geostationary orbit to the ground.

This article presents a generalized theory and new design methodology for reverse-load-modulated dual-branch (RMDB) power amplifiers (PAs), which uses a current-biased transistor in the main branch to realize optimal load modulation without using the impedance transformers at the output of the PAs. Consequently, this topology offers a proper load modulation mechanism over a wider frequency bandwidth. Besides, smaller output matching network (OMN) footprint and lower loss are suitable features for monolithic microwave integrated circuit (MMIC) designs. The proposed theory can be applied for symmetrical and asymmetrical designs to realize different output power back-off (OPBO) ranges. The theory and design methodology were used to design the first MMIC RMDB PA. The broad bandwidth of this design (2.6–3.8 GHz) allows it to cover multiple bands in 4th-generation (4G) Long Term Evolution (LTE) and 5th-generation (5G) New Radio (NR) standards. Under continuous wave (CW) excitation, the experimental results show a drain efficiency (DE) higher than 58% at peak output power (POP) and 37% at 9 dB OPBO, over the whole frequency band.

This research develops an analytical approach to explore the wave propagation problem of piezoelectric sandwich nanoplates. The core of the sandwich nanoplates is a nanocomposite layer reinforced with graphene platelets, which is integrated by two piezoelectric layers exposed to electric field. The material properties of nanocomposite layer are obtained by the Halpin–Tsai model and the rule of mixtures. The Euler–Lagrange equations of nanoplates are derived from Hamilton’s principle. By using the nonlocal strain gradient theory, the nonlocal governing equations are presented. Finally, numerical studies are conducted to demonstrate the influences of propagation angle, small-scale and external loads on wave frequency. The results reveal that the frequency changes periodically with the propagation angle and can be reduced by increasing voltage, temperature and the thickness of graphene platelets.

This article presents a framework that extends a rapidly exploring random tree (RRT) algorithm to plan the motion for a wheeled robot under kinodynamic constraints. Unlike previous RRT-based path planning algorithms that apply complex steer functions during a path sampling phase, this framework uses a straight line to connect a pair of sampled waypoints such that an obstacle-free path can be quickly found. This path is further pruned by the short-cutting algorithm. Under the kinodynamic constraints, we propose a motion-control law that is guided by a pose-based steer function for the robot to reach its destination in a short time. A path deformation strategy is presented that shifts the waypoint away from the collision point such that the trajectory can be generated without any collision. Simulation results demonstrate that the proposed framework needs less computation to generate a smoother trajectory with shorter length than its peers, and experimental results show that simulated trajectories of our controller are very close to real ones and the performance is better than that of a prior pose-based controller.

The Cu–Mg–Zn system is one of the important ternary sub-systems in multicomponent light alloys. This ternary system was reassessed in the framework of the CALPHAD method in view of the drawbacks of previous thermodynamic assessments. A critical review of the literature data on phase equilibria and thermodynamic properties has been performed. An updated thermodynamic description for the ternary system is obtained by considering the available literature data. Isothermal and vertical sections, as well as the liquidus surface and the related invariant reactions, are calculated and compared with the corresponding experimental ones. The reaction scheme for the whole ternary system is also presented. The solidification microstructures of several Cu–Mg–Zn alloys along the Mg–Cu0.5Zn0.5 and Mg–Cu0.385Zn0.615 sections were simulated under equilibrium and non-equilibrium conditions. The calculated solidification microstructures do not contradict the experimental ones presented in the literature. This indicates the reliability of the thermodynamic parameters.

This paper presents a 12-bit 100-MS/s asynchronous successive approximation register (SAR) analog-to-digital converter (ADC) for low-power wireless and imaging systems. A split-capacitor digital-to-analog converter (CDAC) structure is adopted for reducing the core area and improving the sampling speed. The linearity of the CDAC is calibrated by programming the least-significant-bits (LSBs) dummy capacitor. The unit capacitor in the CDAC array is customized for higher symmetry and reducing their mismatch. Our SAR ADC is based on asynchronous logic, and its timing is controlled by a delaying block in the critical path. The prototype is fabricated in a 65-nm CMOS process with a 1.2 V supply and occupies an active area of 0.029 mm2. With a 100-MS/s sampling rate, the measured ENOB scores 10.17 bits for 1.5 MHz input with a figure-of-merit (FoM) of 6.94 fJ/conversion-step. It can achieve 8.83 bits for Nyquist input signal.

Resource consumption cost minimization is important in embedded systems due to their limited resource and high computation load. Previous approaches apply either meta-heuristic algorithms such as genetic algorithm or simple heuristics to minimize the resource consumption cost, which, however, are computationally expensive and sometimes ineffective. In this article, we propose how to schedule a directed acyclic graph application with reliability requirement in a heterogeneous embedded system. The scheduling aim is to minimize system resource consumption cost. We start by finding a quasi-optimal solution that minimizes the resource consumption cost in ignorance of reliability. Then, we introduce an indicator that price the tradeoff between reliability and resource consumption cost, based on which we build a scheme that progressively tunes this schedule toward improving its reliability. We also explore an approach that updates this indicator in a lightweight way. Compared to several state-of-the-art approaches such as MRCRG, experimental results demonstrate that our approach constantly outperforms them, and its superiority becomes more significant with the enhancement of reliability requirement.

The influence of interphase on the level and distribution of thermal residual stress (TRS) in SiCp/6061Al composites was studied by using a three-dimensional (3D) interface-phase model. The thermal...

Chemical vapor synthesis was used to prepare Nb nanopowders with NbCl5 vapor as a raw material and Na vapor as a reductant. Thermodynamic analysis indicated that Na had a strong ability to reduce NbCl5. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with energy dispersive spectrometry (EDS), and transmission electron microscopy (TEM) were used to analyze and characterize the product powders. These powders contained two phases: Nb and NaCl. Pure-phase Nb powders were synthesized by vacuum evaporation. The spherical Nb particles had an average size of 30 to 120 nm. In addition, the effects of operating conditions, such as the evaporation temperature, the reaction temperature, and the argon flow rate, on the Nb particle size were investigated.

This study examined the influence of particle sizes and adsorption equilibrium time (AET) on pore structure characterization using low pressure N2 adsorption (LPGA-N2) method. The results demonstrate that pore structures change with progressive crushing. The increase in pore volume in the minipore and mesopore with decreasing coal particle sizes was caused by creating additional large pores during the crushing. The tendency of decreasing at first and then increasing was observed for both the specific surface area (SSA) and micropore volume, demonstrating that the micropore structure was primarily damaged and then followed by additional micropores being created when the sample was broken down smaller than 80 mesh. It is difficult to choose a suitable coal particle size for LPGA-N2 measurement to yield pore structure parameters closest to the “real” values due to the difficulty in evaluating the compound effect of crushing on pore structures. To make testing results closer to the coal structure under in situ conditions, we propose 1∼3 mm as the preferred coal particle size. Additionally, many replicate experiments were performed by adjusting the AET to ensure LPGA-N2 isotherms in equilibrium states. The results indicate that a decrease in particle size did not reduce the time for reaching N2 adsorption equilibrium. Comparison of pore size distributions under different AETs shows that the AETs' increase has a little influence on the measurement of minipore and mesopore but has a positive correlation with micropore, revealing that N2 adsorption equilibrium is mainly influenced by the micropore whose volume is underestimated at small AETs. The optimal AET for LPGA-N2 measurement was 8 min and its yielded data can more accurately characterize the pore structure parameters.

Effort has been made to investigate the concentration of titanium white waste acid (TWWA) by direct contact membrane distillation (DCMD) and the focus is the influence of polyacrylamide (PAM) on membrane wetting and fouling. It was found that the presence of PAM in feed reduced membrane flux and retarded wetting development, even though its level in feed of H2SO4 solution was only 0.0002 wt%. The difference between the tests using pure water and neat PAM aqueous solution, respectively, as feed also indicated the above effect registered with PAM. AFM results showed that the addition of PAM in feed solution changed the membrane shell surface morphology. However, conclusive proof of the PAM existence in membrane cross-section and inner surface was not obtained, probably due to its low concentration in feed solution. Two approaches were tried to recover membrane flux. In comparison with operation w/o any treatment, HCl solution rinsing did not lead to obvious improvement in membrane flux recovery, while rinsing combined with gas purge has clearly delayed the degradation in acid concentration factor. Nevertheless, even the latter could not ensure long term stability. High tortuosity and low hydrophobicity of the membranes used were suggested as underlying causes and should be addressed in the future.

To realize multiband mode conversion in the high-power microwave (HPM) application system, a novel compact dual-band mode converter based on a universal method is proposed in this article. The proposed converter has a hybrid circular-embedded coaxial structure, and it integrates the conventional plate-inserted coaxial TEM-TE11 converter and serpentine circular TM01-TE11 converter simultaneously. Its outer and inner waveguides have the same curvature distributions along a longitudinal direction. Both the numerically calculated results and simulations exhibit that its maximum conversion efficiencies at two central frequencies are over 99% with a structure length of 240 mm. Simulated results indicate that the bandwidths reach 390 MHz (at ${X}$ -band) and 4.2 GHz (at Ka-band), respectively, when the conversion efficiencies are over 95%. A prototype is fabricated and measured. The far-field results demonstrate that coaxial TE11 and circular TE11 modes with high purity are detected at the output port of converter, and the S-parameter measurements illustrate that high conversion efficiencies at 8.4 and 30.5 GHz are obtained. The measurement results have a good agreement with the theoretical predictions and simulations.

Three full-scale exterior beam–column joints with anti-seismic steel reinforcement were tested under quasi-static cyclic loading and column axial compressive loading. The test variables were column axial load ratio and joint core hoop reinforcement ratio. Experimental results, including failure mode, hysteretic curve, ductility, energy dissipation, stiffness degradation, and decoupling of deformations, were presented and analyzed. The tests revealed that the anti-seismic rebar resulted in good joint seismic performance and that column axial load ratio and joint core hoop reinforcement ratio impose limited influence of joint performance when the joint failed in beam flexural failure. The calibrated finite element models developed based on OpenSees were then used to simulate the behavior of joint specimens. Parametric studies via finite element modeling were performed to study the influence of various parameters on the performance of beam–column joints.

Phase equilibria in the Ni-Si-Zr ternary system have been investigated experimentally by means of x-ray diffraction and electron probe micro-analyzer on equilibrated ternary alloys. Four ternary phases were detected at 1023 and 1173 K. The Ni16Si7Zr6 phase tends to present in two different contrasts and has a wide homogeneity range. The reported Ni2Si9Zr14 phase is not detected in this work. It is proposed that the Ni2Si9Zr14 phase is unstable at these temperatures. As for the binary phases, Ni5Zr and Ni7Zr2 dissolve appreciable amounts of Si and γNi31Si12, βNi3Si, δNi2Si, NiSi2 exhibit a considerable solubility of Zr.

The thermodynamic assessment of the Mg–Ni–Si system has been developed in the framework of the CALPHAD method. The critical review of the literature data has been provided. A set of selfconsistent thermodynamic parameters for the phases in this ternary system is obtained using the phase diagram data available in the literature. The excess Gibbs energy term of solution phases is described using the Redlich–Kister polynomial. The sublattice model is used to describe the MgNi2 intermetallic phase having homogeneity range in the ternary system. Ternary intermetallic compounds are modelled as line compounds. Isothermal sections and liquidus surface, as well as the coordinates of the invariant reactions, are calculated. The calculated results are in satisfactory agreement with the experimental data. The calculated liquidus surface is extremely complex and contains 38 invariant reactions including 8 degenerated reactions and 10 invariant maxima. Most of the presented invariant reactions must be considered as approximate. The τ3 and τ5 phases melt congruently at 1544 and 1487 K, respectively. The τ4 forms via the peritectoid τ5 + NiSi + βNi2Si ↔ τ4 reaction at a temperature of 1193 K. According to our calculations, τ1 and τ8 melt at 1359 K (the L + τ5 ↔ τ1 reaction) and 1267 K (the L + τ1 ↔ τ8 reaction). The τ2 and τ6 are formed via the peritectic reactions at 1317 K (the L + τ3 + MgNi2 ↔ τ2 reaction) and at 1229 K (the L + τ5 + Mg2Si ↔ τ6 reaction), and the τ7 is formed via peritectoid Mg2Si + τ1 + τ5 ↔ τ7 reaction at 1279 K.

In this article, an artificial neural network (ANN)-based large-signal model (LSM) of AlGaN/GaN high electron mobility transistors (HEMTs) with accurate buffer-related trapping effects characterization and modeling is proposed. A hybrid small-signal parameter-extraction method for AlGaN/GaN HEMTs is used to acquire the parasitic parameters. To simplify the modeling procedure of the drain–source current $I_{\mathrm{ ds}}$ , an ANN-based model associated with the empirical equations taking into account the trapping effects, self-heating effects, and breakdown issue is developed. The low-frequency dispersions related to the buffer-related trapping effects have been well modeled by using a new empirical equation, which has been verified by small-signal S-parameters. Also, a new thermal factor $K_{T}$ and an improved Shockley diode equation are given in the proposed model as well. The developed LSM has been fully verified by a $2\times 100\,\,\mu \text{m}$ AlGaN/GaN HEMT with the pulsed I–V, small-signal S-parameters, power sweep, and load—pull measurements.

We have theoretically and experimentally studied exciton properties of three normal Nb2O5 polymorphs, including pseudo-hexagonal (TT-), orthorhombic (T-) and monoclinic (H-) phases. The theoretical...

Based on the experimental data available in the literature, the Ag-X (X = B, Fe, Sm, Pu) binary systems were assessed by means of the CALPHAD (CALculation of PHAse Diagrams) approach. Six intermetallic compounds, i.e. αAg2Sm, βAg2Sm, AgSm, Ag51Sm14, Ag51Pu14 and Ag2Pu, were treated as stoichiometric phases. The solution phases including liquid, (Ag, γFe, δPu), (βB), (αFe, δFe, ePu), (αSm, γSm), (βSm), (αPu), (βPu), (γPu) and (δ’Pu) were described by the substitutional solution model with the Redlich–Kister polynomial. A set of self-consistent thermodynamic parameters for each of the binary systems was obtained. The calculated phase diagrams and thermodynamic properties were in agreement with the reported experimental data.

Although energy piles are widely used worldwide as green foundations, currently no approach is available to quantify the design uncertainties in their long-term performance. Based on the cyclic load-transfer curves, this paper presents a probabilistic model for life-cycle analysis of energy piles under seasonal thermal loading. For computational efficiency, the subdomain sampling method is adopted for estimating the failure probability due to excessive settlement, and is compared with Monte Carlo simulation. This probabilistic analysis approach for energy piles is illustrated through a case study. The life-cycle failure probability of energy piles for various mechanical loading and thermal loading scenarios is investigated.

A novel and generalized methodology of mode conversion based on the transmissive metasurfaces is studied in this article. The mathematic formulations, the design criterions, and procedures have been presented in detail. To further demonstrate the proposed methodology, four typical examples are designed. Subsequently, a prototype with the input mode of circular waveguide TM0,1 mode is designed, fabricated, and measured at ${X}$ -band. The simulated and measured results show that the input mode has been converted into the Guassian-like mode, which could verify the correctness of the proposed design methodology. In addition, due to the rich applications of the transmissive metasurfaces, the proposed methodology will start a new page to realize the mode conversion, especially for the high-frequency case.

The dynamic analysis and optimal design of reactive extraction are challenging due to high nonlinearity of model equations and tough decision of judging criteria. In this work, a dynamic rate-based method is developed on gPROMS platform to get easy access to the solutions of reactive extraction with phase splitting. Based on rigorous criteria, dynamic analysis from initial state to final equilibrium (e.g., evolution of phase composition, mass transfer rate and reaction rate) and optimal design of operating conditions (e.g., extractant dosage and feed molar ratio) are achieved. To illustrate the method, the esterification of n-hexyl acetate is taken as an example. The approach proves to be reliable in the analysis and optimization of the exemplified system, which provides instructive reference for further process design and simulation of reactive extraction.

The path planning problem is important and has been well-studied in multi-robot systems. Current approaches have a common assumption that each robot is required to move from a start point to another one, while implicitly ignoring the fact that a robot may be assigned several jobs in a single trip. In this paper, we take this fact into account and propose optimal path planning solutions. The studied problem is modeled as a max-flow problem of a network, and integer linear programming(ILP) solver can be used to find its optimal solution. However, the optimal solver suffers the problem of dimensional disaster and becomes impractical for a large-scale system. We thus propose a heuristic approach to find a sub-optimal solution with an acceptable computation time. Experimental results demonstrate the high effectiveness of our proposed approaches.

This paper presents a new pavement design approach based on the concept of robust design. Robust pavement design is capable of minimizing the influence of various uncertainties (such as uncertain material properties) on the designed pavement rutting life and fatigue life through a rational adjustment of the design parameters. In this new approach, the signal-to-noise ratio is used to quantify the design robustness, and a genetic algorithm is employed to determine the Pareto front. Using a marginal utility function, the knee point on the Pareto front is selected and is recommended as the optimal design that simultaneously best meets the requirements of safety, robustness and cost. A case study is performed to illustrate this new design approach.

The paper presents numerical findings of reinforced concrete interior beam-column joints under monotonic antisymmetrical load. The finite element models considered compression and tension damage were calibrated by test results in terms of the load-displacement, failure modes, and strains of longitudinal steel. The emphasis was put on studying the effects of hoop reinforcement ratio in joint core and the axial compression ratio on the responses of the joints. The results show that, in addition to the truss and strut-and-tie mechanisms, the confinement mechanism also existed in the joint core. A certain amount of stirrup is not only able to enhance the confinement in joint core, undertake a part of shear force and thus to increase the shear capacity, prevent the outward buckling of steel bars in column, improve the stress distribution in joint core, delay cracking and restrain the propagation of cracks, but also to increase the yield load, decrease the yield displacement of beam and improve the joint ductility. However, excessive horizontal stirrups contribute little to the joint performance. In a certain range, larger axial compression ratio is beneficial for the joint mechanical behavior, while it is negative when axial compression ratio is too large.

This article presents a Bayesian approach for simultaneously calibrating models and soil parameters using field data on wall deflections and ground surface settlement from braced excavations. This ...

This study examined the influences of crushing on the microporous and ultramicroporous structures of coal by low-pressure CO2 adsorption (LPGA-CO2). Many replicate experiments were carried out by a...

The mode converter is a key component in a gyrotron traveling-wave tube (gyro-TWT) application system, which can transform the output circular TE $_{0n}$ modes (in a gyro-TWT loaded with lossy ceramic dielectric or photonic bandgap interaction structure, the output mode is normally a TE $_{0n}$ mode) into a mode conducive to transmission and emission (linearly polarized Gaussian-like HE11 mode). In particular, the bandwidth of the TE01–TE11 mode converter is the most important challenge in the conversion sequence. In this paper, based on the deformation of the transverse cross section and the modified multi-frequency iteration synthesis technique along the longitudinal propagation axis, a novel method for synthesis of a broad bandwidth mode converter is proposed. Then, an application of the method to a wideband serpentine TE01–TE11 mode converter with an elliptical section is given. This novel mode converter including transitional waveguides achieves a 19.18% relative bandwidth (conversion efficiency over 95%) at center frequency 30.5 GHz, which increases nearly 195% compared with the conventional circular design, and its structure length is 1151.65 mm. Overall, this method offers a novel solution to the requirement of broad bandwidth in the high-power microwave transmission system.

The safe operation of marine turbine generators is a crucial concern in industries and academics. It is always important to monitor the health status of marine turbine generators. The lubricant oil...

In the present study, the microstructure evolution of 35Cr45NiNb+MA ethylene cracking furnace tubes during service and its effect on the properties were investigated. According to the results, in t...

On the basis of Ag/Ag–Mg and Ag/Ag–Mn semi-infinite diffusion couples together with electron probe microanalysis technique, the interdiffusion coefficients in fcc phases of Ag–Mg and Ag–Mn alloys were measured between 873 and 1173 K via the Sauer-Freise method. A statistic method was applied to evaluate the errors of the identified interdiffusivities in terms of the propagation of errors. Based on available thermodynamic information and the experimental interdiffusion coefficients, the atomic mobilities for the fcc Ag–Mg and Ag–Mn systems are obtained by using the DICTRA software package. The quality of the assessed atomic mobilities was confirmed by the comprehensive comparisons between calculated concentration profiles and the experimental data.

Using hydrated manganese sulfate and general type graphene (GR) as raw materials, Mn3O4/GR composite has been successfully prepared by the liquid phase chemical co-precipitation method at room temperature. X-ray diffraction (XRD) was used to investigate the phase structure of Mn3O4powder and Mn3O4/GR composite; The electrochemical performances of the samples were elucidated by cyclic voltammetry and galvanostatic charge-discharge test in 0.5 mol/L Na2SO4electrolyte. The results show that the Mn3O4/GR composite possesses graphene phase and good reversibility; the composite also displays a specific capacitance of 318.8 F/g at a current density of 1 A/g.

Gesture recognition is important in human–machine interaction. Current methods for solving gesture recognition have several disadvantages such as low recognition rate, slow speed and poor performance on recognizing multiple targets or long-distance targets in complex environments. In view of the above problems, we propose a gesture recognition approach that can recognize gestures quickly and accurately from complex background. This approach works on a deep convolutional network, which consists of a basic network module for extracting feature information, a squeeze-and-excitation networks for increasing feature channel affinity and a feature pyramid attention module for fusing context information with different scales. To test the proposed approach, we make a data set that contains 3289 images from difference complex scenes. Generally gestures in those images can be generally classified into 16 types. We have uploaded this data set for researchers use. Experimental results demonstrate that the recognition accuracy and speed of the proposed method can achieve 83.45% and 32.2 frames per second respectively, which has better comprehensive performance compared with other state-of-the-art recognition algorithms.

Thermodynamic modeling of the Al–X (X = S, Se, Te) binary systems was performed by means of the CALPHAD method. The solution phases, i.e., (Al), (αS), (βS), (Se), and (Te), were described using a substitutional solution model, and the intermetallic compounds, i.e., αAl2S3, γAl2S3, AlS, Al2Se3, AlTe, αAl2Te3, βAl2Te3, and Al2Te5, as stoichiometric compounds due to the narrow homogeneity ranges. A set of thermodynamic parameters describing the Al–X (X = S, Se, Te) binary systems was obtained. The calculated results for the phase equilibria and thermodynamic properties agree well with literature data.

Energy piles are sustainable green foundations. Although several geotechnical design methods have been proposed, no methods have yet been developed to quantify the uncertainty propagation in thermo-mechanical pile-soil interactions. The probabilistic model proposed in this paper, which is based on load-transfer curves, considers the effects of spatial variability for energy pile design. The developed random finite difference method is used to address the effects of vertical spatial variability on the ultimate limit state design and serviceability limit state design. This study points to the necessity of modeling the soil spatial variability in the thermo-mechanical pile-soil interactions in energy piles.

This paper presents an experimental study on shear behavior of full-scale rectangular reinforced concrete (RC) beams under shear-strengthening of carbon fiber-reinforced polymer (CFRP) U-strips. The test involved five RC beams with transverse reinforcement, including one control beam, one shear-strengthened by externally bonded (EB) CFRP U-strips only, and the remaining three strengthened in shear by a hybrid bonded (HB) CFRP system under different normal pressures applied on the CFRP U-strips. The transverse reinforcing steel bars and CFRP U-strips were extensively instrumented with strain gauges, which enabled the accurate quantitative assessment of shear strength contributions from CFRP (Vf), stirrups (Vs) and concrete (Vc) during the whole loading process of a shear test. Further, by comparing Vs and Vc for beams with and without CFRP strengthening, the interactions can be evaluated and clarified. In addition, key features of shear behaviors, e.g. failure mode, load-deflection curves, shear capacity and ductility, shear crack angle, and strain development and distribution of stirrups as well as CFRP strips, are presented, compared and analyzed.

Scene flow is an essential part of a stereo-based perception system for autonomous driving and mobile robotics. As in most of these platforms, the computing resource is limited but the computing requirement is high, embedded and parallelized algorithms are of vital importance for real-time tasks. This paper develops a cross-platform embedded scene flow algorithm by using an OpenCL (Open Computing Language) programming. Meanwhile, we propose a method to achieve a good performance by using a novel coarse-grained software pipeline for the embedded stream application. Experimental results show that the proposed algorithm can boost the average processing speed to 50 fps for different commercial off-the-shelf (COTS) hardware, including desktop graphics processing units (GPUs), field-programmable gate arrays (FPGAs), and mobile phone platforms. For certain GPUs, the peak frame rates can also reach 1000 fps. By comparing the efficiency among the serial platform, we illustrate that with the help of OpenCL programming, COTS platforms can provide enough computing resources for the stereo-based perception algorithm.

Based on the thermodynamic descriptions of constitutive binary systems as well as the experimental phase equilibria data available in the literature, the Ti-W-M (M = Zr, Mo, Nb) ternary systems have been thermodynamically evaluated by the CALPHAD (CALculation of PHAse Diagram) approach. The solution phases, i.e. liquid and bcc, are described by the substitutional solution model. The binary phase W2Zr with the solubilities of Ti is modeled using the sublattice model. A set of self-consistent thermodynamic parameters is finally obtained for each of these ternary systems. Some representative isothermal and vertical sections are calculated. Comparisons between the calculated and measured phase diagrams show that the most of experimental data are satisfactorily reproduced by the present thermodynamic descriptions.

The labyrinth screw pump is a new type of low-flow rotor pump with a simple structure and good sealing performance. It is suitable for the transport of high-viscosity, high-gas-content, and particle-containing media. In this study, a rectangular labyrinth screw pump was used as the research object. The effect of the medium viscosity on the performance of the labyrinth pump was studied through numerical simulations, and the correctness of the simulation method was verified using existing test data. The efficiency and head of the labyrinth screw pump were selected as the optimization objectives, and the pump structural parameters were selected as the optimization parameters. A structural optimization model of the labyrinth screw pump based on response surface theory was established. The structural parameters of the labyrinth pump were reasonably simplified through size correlations, and then parameter sensitivity analysis was performed to determine the important structural parameters that needed to be optimized. The OSFD (optimized space-filling design) was used to combine the optimized parameters and generate the sample space. The response surface theory was combined with a neural network prediction model and a multi-objective genetic algorithm to perform optimization calculations. The results showed that there was an interactive influence between the structural parameters of the stator and rotor of the labyrinth screw pump. Compared with the original model, the optimized model pump had an efficiency increase of 13.55% and a lift increase of 19.53% when conveying a medium with a viscosity of 133 cp.

The effect of reinforcement surface modification on the residual stress (RS) in 35vo l%SiCp/6061Al composites was studied, and the experimental conclusions were verified by finite element analysis. The results show that after the SiC particles were modified by pickling, ultrasonic stirring and high-temperature oxidation (1100 ℃/6 h), the composite has the lowest RS, which was only 1.1 MPa. Microstructure and phase composition of 35vo l%SiCp/6061Al composites have been examined by Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD). It was found that the reinforcement surface modification was beneficial to promote the improvement of interface bonding state, and the diffraction peaks of Si element have been significantly enhanced. Additionally, the formed Al-Si-SiC interphase has a higher interface adhesion work, which effectively reduced the concentration degree of RS. An interface-phase model based on the surface morphology of real SiC particles was established. The simulation results show that the RS was mainly concentrated in the sharp corners of reinforcement, and the stress level is relatively high. When the sharp corners were eliminated, the stress level gradually decreases. When the Al-Si-SiC interphase was formed, the stress level in SiCp/6061Al composites decreases significantly. The results of finite element simulation and experimental measurement were relatively consistent.

An important problem in multi-robot system is how to coordinate robot’s motion such that each robot can complete its task without collision. Previous approaches assume that robots’ motion is deterministic once their paths have been planned, which is however not realistic because random interferences such as noise, friction and inaccurate control input in real-life system could disturb the robot motion, leading to a stochastic behavior. In this paper, we take this stochastic behavior into account when planning the path for a heterogeneous multi-robot system. We assume that the motion time of a robot from a location to another can be modeled as a probability distribution. Every robot has its own probability distribution of motion time between any two neighbor locations. We develop a conflict-detection scheme for this model and propose using the conflict-based search algorithm via probability calculation to find the optimal path that minimizes the entire motion time. We also simplify this conflict detection such that our proposed approach is applicable online for a large-scale system. Experimental results demonstrate the high effectiveness of our proposed approaches.

Reinforced concrete (RC) beams that are shear-strengthened by externally bonded (EB) fiber reinforced polymer (FRP) often offer limited structural enhancement. This is due to the inherent weaknesses of EB-FRP strengthening, including the premature debonding of the FRP, its brittle rupture, and inadequate deformation capacity of the strengthening system. In this paper, two techniques of shear strengthening using U-wrapped carbon FRP (CFRP) and effective anchoring devices are proposed and tested with the aim of enhancing both the shear strength and the ductility of retrofitted RC beams. One of the techniques involves a hybrid-bonded (HB) CFRP system with adjustable normal pressure applied to the CFRP U-strips, and the other features the CFRP U-strips fastened by an H-type end anchor (EA). The main test variables of the former and latter shear-strengthening systems are the degree of pressure applied to the CFRP U-strips and the width of the deformation segment (or axial stiffness) of the H-type EA, respectively. The results indicate that both strengthening systems significantly enhanced the shear capacity and ductility of the strengthened RC beams. Compared with the control member, the increments in shear capacity were as high as 54.6 and 68.5% for beams retrofitted with the HB-FRP and the EA FRP systems, respectively, and their deflections at peak shear load increased by 43.9 and 84.1%, respectively. The shear failure modes were found to be related to the parameters used in both the HB-FRP and the EA FRP systems. The critical diagonal crack (CDC) inclination of all specimens was less than 45°, ranging from 38° to 44°. Both positive and negative shear interactions were observed between Vf and Vc plus Vs.

Visual sensors such as optical camera possess fatal shortcomings like vulnerable to the weather condition and light intensity, which may cause catastrophic disasters. Fortunately, the prevalent 3D sensors like Light Detection and Ranging (Lidar) can overcome these drawbacks. Fusing both monocular camera and 3D Lidar data can often achieve a better performance than solely using one of them. In this paper, we propose an object detection approach by fusing monocular camera data and Lidar data in decision level based on Dempster-Shafer evidence theory. First, the 3D point cloud collected from Lidar is projected onto the image plane and the upsampling method is adopted to receive dense depth maps. Then, the RGB images and dense depth maps are separately fed into YOLOv3 detection framework to extract the object features. Next, the final detection attributes, the class confidence and bounding box, are generated by using Dempster’s combination rule and extracting intersection of the associated bounding boxes. Finally, the mean Average Precision (mAP) performance of the proposed method is improved by 0.5% and 3.1% compared with sigle camera method and Lidar method, respectively.

Motion planning with the multi-robot system is complex and challenging in a dynamic environment with unknown obstacles. This paper proposes a two-stage motion planning strategy to guarantee the formation of multi-robot when they pass through some obstacle areas. First, the multi-robot formation is constructed by a leader-follower strategy. Then a two-level algorithmic framework is introduced to optimize both global and local path planning. A Self-adaptive Dynamic Window Algorithm (SDWA) is proposed to dynamically search both global and local optimal path, which aims to balance the speed and safety of the multi-robot system. In SDWA, the weight parameter of the objective function is adaptively controlled based on the distance between the multi-robot system and obstacles. Finally, results of experiments demonstrate convincingly that the SDWA can avoid dynamic obstacles by switching between global path planning and local path planning modes, which makes the trajectory more reasonable in a complex environment, and ensure the smooth path and safety of multirobot formation.

Quick Response (QR) Code would be easily affected by motion blur. In this study, a new recognition method for blurry QR Code is presented. First, a motion deblurring algorithm based on generative adversarial networks (GAN) is applied to perform the blind motion deblurring on single QR Code image for improving the quality of QR Code pictures. Then a modified local adaptive thresholding algorithm applying integral image technology is utilized in order to acquire binary QR Code pictures. Finally, this algorithm would be compared with some previous methods. Furthermore, for testing this algorithm, a database which contains motion blurry QR Code images from both public database and real scenes is collected. Experimental results show that this proposed algorithm perform well on motion blurry QR Code recognition missions.

In this study, binary interdiffusivities of bcc titanium-scandium (Ti-Sc) alloys in the temperature range of 1273 K to 1473 K were determined by combining the diffusion couple technique and Boltzmann–Matano method. In addition, the composition-dependent Young’s modulus and hardness of bcc Ti-Sc alloys were obtained using the nanoindentation technique. The results reveal that a small amount of Sc additive can be very beneficial to bio-Ti alloys with good properties.

Modern manufacturing systems build on an effective scheduling scheme that makes full use of the system resource to increase the production, in which an important aspect is how to minimize the makespan for a certain production task (i.e., the time that elapses from the start of work to the end) in order to achieve the economic profit. This can be a difficult problem, especially when the production flow is complicated and production tasks may suddenly change. As a consequence, exact approaches are not able to schedule the production in a short time. In this paper, an adaptive scheduling algorithm is proposed to address the makespan minimization in the dynamic job shop scheduling problem. Instead of a linear order, the directed acyclic graph is used to represent the complex precedence constraints among operations in jobs. Inspired by the heterogeneous earliest finish time (HEFT) algorithm, the adaptive scheduling algorithm can make some fast adaptations on the fly to accommodate new jobs which continuously arrive in a manufacturing system. The performance of the proposed adaptive HEFT algorithm is compared with other state-of-the-art algorithms and further heuristic methods for minimizing the makespan. Extensive experimental results demonstrate the high efficiency of the proposed approach.

Power amplifier (PA) models, such as the neural network (NN) models and the multilayer NN models, have problems with high complexity. In this article, we first propose a novel behavior model for wideband PAs, using a real-valued time-delay convolutional NN (RVTDCNN). The input data of the model is sorted and arranged as a graph composed of the in-phase and quadrature ( I/Q ) components and envelope-dependent terms of current and past signals. Then, we created a predesigned filter using the convolutional layer to extract the basis functions required for the PA forward or reverse modeling. Finally, the generated rich basis functions are input into a simple, fully connected layer to build the model. Due to the weight sharing characteristics of the convolutional model's structure, the strong memory effect does not lead to a significant increase in the complexity of the model. Meanwhile, the extraction effect of the predesigned filter also reduces the training complexity of the model. The experimental results show that the performance of the RVTDCNN model is almost the same as the NN models and the multilayer NN models. Meanwhile, compared with the abovementioned models, the coefficient number and computational complexity of the RVTDCNN model are significantly reduced. This advantage is noticeable when the memory effects of the PA are increased by using wider signal bandwidths.

This work investigates locomotion efficiency optimization and adaptive path following of snake-like robots in a complex environment. To optimize the locomotion efficiency, it takes energy consumption and forward velocity into account to investigate the optimal locomotion parameters of snake-like robots controlled by a central pattern generator (CPG) controller. A cuckoo search (CS) algorithm is applied to optimize locomotion parameters of the robot for environments with variable fractions and obstacle distribution. An adaptive path following method is proposed to steer the snake-like robot forward and along a desired path. The efficiency and accuracy of the proposed path following method is researched. In addition, a control framework that includes a CPG network, a locomotion efficiency optimization algorithm, and an adaptive path following method is designed to control snake-like robots move in different environments. Simulation and experimental results are presented to illustrate the performance of the proposed locomotion optimization method and adaptive path following controller for snake-like robots in complexity terrains.

This paper demonstrates a Ku-band medium and long distance microwave wireless energy transmission system based on the rectifier diode. The transmitting compact Cassegrain antenna with an aperture of 1.5m forms a more centralized and uniform 2m x 2m field zone, which has more than 80% transmission efficiency. According to the distribution of receiving field, the multiple ways synthesizers connected to rectangular patch arrays are designed. And the results predict that the receiving efficiency of the antenna is directly related to the performance of the system, which reaches 50%, not including the possible insert loss. Besides, the Ku-band rectifying circuit is optimized and measured, and the comparing results show that the practical rectifier diode can obtain more than 40% conversion efficiency at the operating frequency of 12.75GHz. Finally, the microwave wireless energy transmission system is designed, and it finally obtains 4% DC-DC conversion efficiency at a distance of 60m, which is likely to be used in unmanned aerial vehicle hovering charging system, robot charging while working, isolated island wireless power supplying and wireless charging of various sensors.