Search

High-temperature superconducting (HTS) power equipment and tests at present require operating temperatures higher than the liquid nitrogen (LN2). LN2 is an important cryogenic refrigerant and liquid insulation material, which is widely used in HTS equipment. Although pressurized LN2 can achieve temperatures higher than 77 K, it requires the use of sealed pressure vessels. Thus, a liquid cryogen that can offer temperatures higher than LN2 at atmospheric pressure, excellent electrical insulation performance, and high thermal conductivity has to be explored. Tetrafluoromethane (CF4) is another cryogenic refrigerant and electrical insulation material. The mixture of LN2 and liquid CF4 has excellent thermal properties. When mixed in appropriate proportions, it has a melting point of 50 K and a boiling point of 145 K. The LN2/CF4 mixture is used in the insulating layer of the superconducting energy pipeline to provide a low-temperature environment (85–100 K) for the HTS dc cable. However, the insulation characteristics of the LN2/CF4 mixture at cryogenic temperatures have not been studied, quantitatively. In this article, a test platform is developed to measure the breakdown voltage of the liquid mixture. The dc breakdown voltages of LN2/CF4 liquid mixture under varying mixing proportions are obtained at cryogenic temperature. The insulation failure probability is estimated using a two-parameter Weibull statistical method. The results reveal that the breakdown strength of the LN2/CF4 mixture is lower than that of pure LN2. As the proportion of CF4 increases, the breakdown field strength of liquid mixture first decreases and then increases. When the mole fraction of CF4 is 60%, the average breakdown strength decreases to the lowest value (14.07 kV/mm), about half of that of pure LN2 (28.26 kV/mm). The results of this article can provide a reference for the applications of LN2/CF4 liquid mixture in HTS power equipment and a scheme to expand the working temperature range of superconducting applications.

Metamaterials with local resonance show promising application prospects in low-frequency vibration attenuation. However, with the drawback of narrow band gap, such potential is greatly limited. In order to broaden the local resonant band gap, a semi-active graded magnetorheological elastomer (MRE) metamaterial sandwich beam (GMREMSB) with real-time tunable graded stiffness was proposed and investigated in this study. For theoretical calculation, a mass-spring model was established for the GMREMSB. Then the calculated band gap and transmissibility using Timoshenko beam theory and spectral element method were compared. An experimental test was also conducted for verification. The results show that the bandwidth of the proposed GMREMSB can be widened by the graded stiffness arranged in ascending order. The experimental band gap of the GMREMSB under the graded current of 0.0–0.5–1.0 A is 6.4 Hz wider than the band gap of the periodic structure with the single current of 0.0 A and is 5.0 Hz wider than that of 1.0 A. The growth rate reaches 15.06% and 11.39%, respectively.

Incremental sheet metal forming characterized as increased flexibility and local plastic deformation is well suitable for low-production-run manufacturing and a new sample trial production of complex shapes. Thickness thinning is still an obstacle to the application of incremental forming. In this study, a novel mathematical algorithm based on a non-uniform rational B-spline (NURBS) surface was proposed and implemented which focuses on predicting and calculating the final thickness for arbitrary parts in incremental forming. In order to evaluate the validity of the proposed model, the finite element simulation and forming experiments of three kinds of parts, such as truncated cones, truncated pyramids and ellipsoid parts, were conducted. The thickness of theoretical prediction was compared with that of finite element simulation and experiment, and good agreements were obtained. The results show that the proposed model and the method are effective and robust for predicting the thickness of the formed parts in incremental sheet metal forming.

Graph summarization has a wide range of applications that involve many large-scale graph data processing problems. However, most of existing approaches for graph summarization neglect attributes and relationships residing in nodes and edges in graphs. In this paper, an aggregation-based attributed graph summarization approach is proposed by fully taking attributes and relationships into account during graph summarization. We present a new approach to quantitatively calculate node merge error, and a heuristic measure to dynamically determine the threshold of node merge error per iteration. We implemented our aggregation-based attributed graph summarization approach. Extensive experiments were made for illustrating effectiveness and efficiency of our approach in comparison with the state-of-the-art approach based on graph topology.

With the development of Information Technology, question answering approaches have been applied in assisted decision, which can assist custom service staffs to automatically answer some basic questions and therefore can greatly reduce the cost of system operation. In this paper, we propose a question answering based approach for electric power fault diagnosis. First, the question answer data is analyzed and preprocessed from the conversation of manually answering the possible causes of given power equipment faults for making sure that one question corresponds to multiple answers. Then, the question and answers at word-level are matched based on a general “compare-aggregate” framework. Based on the matching measure, we can further rank the answers and select the answer with the highest correlation as the most likely fault cause for assisted decision. The relevant experimental results show that the model achieves good results and finds the best answer to the question.

In this paper, the isothermal vapour-liquid equilibrium (VLE) data for pure difluoromethane (R32) and trifluoroiodomethane (R13I1) and their binary mixtures have been measured based on a vapour – phase single recirculation method. The data were collected for five temperatures from 253.150 K to 293.150 K. The experimental VLE data were regressed by PR-MHV2-NRTL model and PR-vdW model. The deviation curves of pressures and vapour compositions for the binary system between experimental and calculated values were given. The results indicated that the maximum mean absolute relative deviation of pressure (MARDp) for PR-MHV2-NRTL is 0.54%, which shows a better fit than PR-vdW with a maximum MARDp of 2.73%. The maximum mean absolute deviation of vapour phase mole fraction (MADy) for PR-MHV2-NRTL and PR-vdW are 0.013 and 0.010, respectively. The azeotropic behaviours were found at T = (253.150, 263.150, 273.150) K, while the zeotropic behaviours were found at 283.150 K and 293.150 K.

This paper investigates the effect of network throughput on the stability of a collection of cyber-physical systems (CPSs) which transmit their measurement information via a single communication channel. The slotted ALOHA access protocol is used for scheduling all CPSs, where time is divided into time slots and only one plant can access the channel at any time slot. By formulating the collection of cyber-physical systems into a switch system, we derive the relationship between the throughput and the attenuation rate using the average dwell time technique. Finally, a co-design algorithm is given to compute the controller gains. A numerical example illustrates the effectiveness of the proposed co-design procedure.

The matching filtering method based on the inertial measurement unit has become the development trend of ship deformation measurement. In the matching filtering method, the Kalman filter used to estimate the deformation angle requires certain dynamic deformation model parameters. Traditionally, these dynamic deformation parameters are empirically set according to previous experience or determined from previously collected experimental data, and all the parameters in the filter are certain. However, the actual deformation model parameters are changing and uncertain, and the Kalman filter will perform poorly when the current application environment is different from that utilized in the filter design. To overcome this difficulty, an inertial deformation measurement method under the condition of uncertain model parameters is proposed in this paper. Specifically, the interactive multi-model(IMM) Kalman filter method is introduced to solve the uncertainty problem of model parameters. According to our simulation results, the proposed method can estimate the ship deformation angle with a fast convergence and a high degree of accuracy, To be specific, the accuracy of the IMM-based method is improved by 5%∼10% in comparison with traditional single model KF method. Besides, a further advantage of the proposed method is that it enhances the adaptability of the deformation measurement system to the external environment changes.

Based on particle swarm optimization (PSO) algorithm and its power system reactive power optimization method to in-depth study and research proposed a new hybrid particle swarm optimization algorithm (HPSO). Algorithm combines the differential evolution algorithm and simulated annealing algorithm and particle swarm optimization algorithm, in particle searching optimal except for tracking individual and global, and tracks produced by particle information difference of the three value. At the same time, when the particle search space of one dimension speed lower than the setting value will be re initialized the dimensional particle velocity and the particle of differential evolution mutation. For the crossover and mutation operations, new solution may be worse than the original solution to, the introduction of simulated annealing algorithm, the metropolis rule in a certain extent accept bad solutions, allows the target function in a certain degree of deterioration, practical calculation is not according to the probability to choose the poor solution, but rather the judgment target function difference is less than allows the target function deterioration range. Hybrid particle swarm optimization algorithm combines the advantages of particle swarm optimization algorithm, differential evolution algorithm and simulated annealing algorithm, to maintain the diversity of particles, has very strong practicability.

Dicyandiamide was used as a toughening agent to modify the brittleness of the phenolic foam. The effects of dicyandiamide on mechanical and flame-retardant properties of phenolic foam were studied by compressive strength, tensile strength, scanning electron microscopy (SEM), UL-94, limited oxygen index (LOI), TG, and cone calorimeter (CONE). The apparent density and SEM results showed that the addition of dicyandiamide can decrease the apparent density of phenolic foam. The compressive, impact test results showed that the incorporation of dicyandiamide into PF dramatically improved the compressive strength, impact strength, indicating the excellent toughening effect of dicyandiamide. The LOI of dicyandiamide-modified phenolic foams remained a high value, and the UL-94 results showed all samples can pass V-0 rating. The modified PF has the slightly lower degradation temperatures but a higher char yield. CONE data indicated that the rate of heat release, total heat release, mass loss rate of the modified PF are decreased compared with that of pure PF, indicating that the modified foams had better flame-retardant performance.

This paper proposes a novel full kinematic incremental forming process, called three opposite point incremental forming (TOPIF), in which one pair of main opposite forming tools and two pairs of auxiliary opposite tools as the supporting dynamic die are utilized to perform the components along a predefined path. Compared to the conventional kinematic incremental sheet forming (KISF) and SPIF, the process can effectively control the local deformation, improve geometric accuracy and increase the ability to form complex curved surface. The deformation analysis on TOPIF is the key to control the local deformation. A deformation analysis and the strain distributions are proposed based on a plane strain deformation mode. The results by the deformation analysis of a truncated conical shape are in accord with experimental values for 1 mm Al5052.

Effective allocation of shared resources limited is a key problem for chip multiprocessors. As the processor core growth in the scale, multi thread for the shared resource limited system competition will become more intense, the performance of the system will also be more significant. In order to alleviate this problem, a fair and effective multi thread shared resources allocation scheduling algorithm is important. In all kinds of shared resources, the largest effect on the system performance is the shared cache and DRAM system. There are essential differences between the last level cache and a cache. The goal of a cache design is to provide fast data processor which requires high access speed. However, the object of the last level cache is to save data in the chip as much as possible, and the access speed requirements are not too high, it is more subject to the plate number of available transistors. Management level cache LRU strategy and its approximate algorithm are not applicable to the large capacity last level cache for traditional. It may cause destructive interference between threads, cache thrashing of stream media program lead, which will lead to a decline in the performance of processor. This paper focuses on the analysis of some hot problems of the last level cache management in the process of the large capacity of multi-core platform sharing, and puts forward the corresponding costs less.

A novel and sensitive gas sensor was developed for the determination of benzene based on its cataluminescence (CTL) by oxidation in air on the surface of hollow magnesium silicate spheres. Luminescence characteristics and optimum conditions were investigated. Results indicated that the as-prepared magnesium silicate hollow spheres exhibited outstanding CTL properties such as stable intensity, high signal/noise values, and short response and recovery times. Under optimized conditions, benzene exhibited a broad linear range of 1–4500 ppm, with a correlation coefficient of 0.9946 and a limit of detection (signal-to-noise ratio (S/N) = 3) of 0.6 ppm, which was below the standard permitted concentration. The relative standard deviation (RSD) for 100 ppm benzene was 4.3% (n = 6). Furthermore, the gas sensor system showed outstanding selectivity for benzene compared with nine other common volatile organic compounds (VOCs). The proposed gas sensor showed good characteristics of high selectivity, fast response time and long lifetime, which suggested the promising application of magnesium silicate hollow spheres as a novel highly efficient CTL sensing material. The mechanism for the improved performance was also discussed based on the experimental results. Copyright © 2014 John Wiley & Sons, Ltd.

A battery-operated, low-cost and portable embedded gas detection device consisting of a cataluminescence (CTL)-based sensor array was developed for the determination and identification of drug precursor gas. A total of 16 nanomaterials, including nano-sized metal oxides, decorated nanoparticles, and carbonates have been carefully selected as sensing elements of 4 × 4 sensor array. Dynamic and static analysis methods were utilized to characterize the performance of the portable gas detection device to 6 kinds of drug precursor gas. Each compound gave its unique CTL pattern after interaction with the sensor array, which can be employed for the detection and identification of drug precursor gas. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used to analyze the CTL patterns. The PCA plots showed that the groups of 6 types of drug precursor gas were well classified. In addition, the patterns obtained at different working temperature and the quantitative determination of the portable device was investigated. The results showed that the linear ranges and detection limits of the portable device for the analytes were excellent. Illegal drug detection is of great importance for public security, our study demonstrated the portable gas detection device shows promising perspective for the recognition and discrimination of drug precursor gas.

A three-dimensional hierarchical CdO nanostructure with a novel bio-inspired morphology is reported. The field emission scanning electronic microscopy, transmission electron microscopy and X-ray diffractometer were employed to characterize the as-prepared samples. In gas-sensing measurements, acetone and diethyl ether were employed as target gases to investigate cataluminescence (CTL) sensing properties of the CdO nanostructure. The results show that the as-fabricated CdO nanostructure exhibited outstanding CTL properties such as stable intensity, high signal/noise values, short response and recovery time. The limit of detection of acetone and diethyl ether was ca. 6.5 ppm and 6.7 ppm, respectively, which was below the standard permitted concentrations. Additionally, a principal components analysis method was used to investigate the recognizable ability of the CTL sensor, and it was found that acetone and diethyl ether can be distinguished clearly. The performance of the bio-inspired CdO nanostructure-based sensor system suggested the promising application of the CdO nanostructure as a novel highly efficient CTL sensing material. Copyright © 2014 John Wiley & Sons, Ltd.

Based on the success in the design of an Emigration Operator and the introduction of other approaches such as the fitness sharing, the clustering method, and the elitism strategy, an Emigration Genetic Algorithm is now proposed for the vector optimizations of electromagnetic devices. Numerical results are reported to demonstrate the effectiveness of the proposed algorithm in solving engineering multiobjective optimal design problems.

To alleviate the difficulties encountered in the generation of meshes for the finite element method for solving thin skin depth problems involving three-dimensional (3-D) eddy-currents, particularly in cases in which the eddy-current region is only a fraction of the entire domain, a new technique based on the combination of finite element and meshless methods is proposed. The use of numerical approach to uphold the mathematical properties of the combined shape functions in terms of consistency and linear independence is also investigated. It is shown that a very coarse mesh is already sufficient to give accurate numerical results with the proposed algorithm. To validate and demonstrate the advantages of the proposed method, typical numerical results on studies of high-frequency 3-D eddy-current problems are reported.

The emigration genetic algorithm, which is a genetic-based algorithm, is proposed to obtain the Pareto optimal solution of vector optimal designs of electromagnetic devices. The proposed algorithm differs from the traditional ones in its design of an emigration operator as well as the inclusion of some useful approaches such as the fitness sharing, clustering, and elitism strategy. Detailed numerical results on three different multiobjective design problems are reported to demonstrate the effectiveness and advantages of the proposed algorithm for solving practical engineering multiobjective optimal design problems.

Several important mechanisms for storm-induced entrainment of estuarine cohesive sediments are analyzed using field measurements collected in a moderately energetic estuary, central Long Island Sound, U.S.A. The sediment concentration and hydrographic data were obtained by an array of sensors mounted at 1 m above the bottom. The bottom sediment in the study site composed mostly of silt and silty sand. The study showed that the bottom shear stress, computed using a wave-current interaction model, increased significantly during the episodic wind events. A large resuspension event was triggered by a frontal passage when strong wind-driven currents augmented the tidal currents. The timing of storm waves with respect to the tidal phase also was a critical factor. Based on the changes of suspended sediment concentration, the bottom appeared to respond to the shear stress in two phases: the tidal resuspension and the storm-induced erosion. During each tidal cycle, entrainment was associated with resuspension of high water content, loosely consolidated material. During episodic events, a thin layer of more consolidated bed below the sediment-water interface was eroded by the enhanced bottom stress.

A three-dimensional hierarchical CdO nanostructure with a novel bio-inspired morphology is reported. The field emission scanning electronic microscopy, transmission electron microscopy and X-ray diffractometer were employed to characterize the as-prepared samples. In gas-sensing measurements, acetone and diethyl ether were employed as target gases to investigate cataluminescence (CTL) sensing properties of the CdO nanostructure. The results show that the as-fabricated CdO nanostructure exhibited outstanding CTL properties such as stable intensity, high signal/noise values, short response and recovery time. The limit of detection of acetone and diethyl ether was ca. 6.5 ppm and 6.7 ppm, respectively, which was below the standard permitted concentrations. Additionally, a principal components analysis method was used to investigate the recognizable ability of the CTL sensor, and it was found that acetone and diethyl ether can be distinguished clearly. The performance of the bio-inspired CdO nanostructure-based sensor system suggested the promising application of the CdO nanostructure as a novel highly efficient CTL sensing material.

This paper presents PLDACOL, our parallel implementation on LDACOL model, to effectively cluster large-scale documents. Since phrases contain more semantic information than the sum of its individual word, we use topic model LDACOL for phrase discovery, and use Gibbs sampling for parameter inference. PLDACOL overcomes the high computation time cost in parameter inference by the distributed computing framework based on Hadoop. We show that our PLDACOL can be applied to the clustering of large-scale documents in different size and produces significant improvements on both effectiveness and efficiency compared with other related traditional algorithms.

The online surface defects auto-detecting is important for the ring pieces quality. The proposed method implemented on binarization by iteration threshold. It located the optimized contours using the seed growth and calculated radius and central coordinates of ring pieces through the least square fitting. It measured and recognized the features extracted by masking using pixel-counting area. The PLC control circuit was designed. Experimental results show that the method detects 2038 magnetic rings in half an hour with detection rate 95.92% and false detection 2.06%.

A new method of basic element is proposed to classify distribution network connection modes. Basic element is the smallest connection mode with characters of integrity and independent operation in distribution system. Then a dynamic and comprehensive evaluation criterion of basic element connection mode is raised based on fuzzy membership function, to achieve the dynamic and intelligent selection of connection modes according to different focus of planners. The dynamic and comprehensive evaluation of radial connection mode, "2-1" connection mode and three sub-3 liaison connection mode illustrates that the criterion is of strong feasibility and practicability to the selection of typical connection modes in distribution network planning.

This paper describes a newly developed hardware used in multi-projector displays built with a network of PCs, commodity graphics accelerators, multiple projectors, cameras, and large-scale screens. In order to completely remove the photometric seams or geometric discontinuities on projector boundaries in such a multi-projector display, the frame-buffer content for each projector has to be warped and attenuated properly. So the system must include a high-performance and scalable pixel routing subsystem in order to create seamless imagery. Here we propose to develop a flexible pixel router to solve this problem. Our router is capable of performing an arbitrary mapping of pixels from any input frame to any output frame, and executing typical composition operations at the same time. The main challenge of developing the hardware is to maintain the refresh rate. We analyse hardware pixel routing for multi-projector displays. We demonstrate the construction of large-scale multi-projector display systems using this flexible pixel router that bridges the image generator and the projectors. We also present an initial hardware prototype and some preliminary results in the hardware development. Experimental results show that our approach is both feasible and robust.

Applications of machine vision for automated inspection and sorting of fruits have been widely studied by scientists and engineers. In these applications, edge detection, segmentation, and shape recovery are difficult problem. Previous studies have usually adopted some preprocessing such as noise removal and motion deblurring before using a threshold method to detect shape boundary. In many cases, however, this manner is troubled and not unified and does not work well. This research proposes a novel approach for fruit shape detection in RGB spaces based on a fast level set method and the Chan-Vese model. We called it optimizing Chan-Vese model (OCV). This new algorithm is fast because it needs no re-initialization procedure and thus is suitable for fruit sorting. OCV has three advantages compared to traditional methods. First, it provides a unified framework for detection fruit shape boundary, requiring no preprocessing and even if the raw image is noisy or blurred. Second, it can detect boundaries for images of fruit with multi-colored edges, which traditional methods fail to deal with. Third, it is processed directly in colour space without any transformations that can lose much information. The proposed method has been applied to fruit shape detection with promising results.

Two types of gel were developed, by taking fly ash and foaming cement as aggregate, which is usually used as filling material at the region where top-coal caves above coal entry in the Jinggezhuang coal mine, and adding high molecular polymer and bio-gel as additive. Sweating rates of the two types of gel under various matching ratio and temperature were tested. And then sweating ratio and water retention ratio of the two gels were calculated, based on which, the optimized matching ratios, were determined. Viscosity indexes of the two-type gel under different ratios were tested. The optimized filling ratios of the two types of gel were determined according to the two indexes, water retention rate and the viscosity. The filling experiments were implemented and evaluated in site, the Jinggezhuang coal mine. The results show that the fly ash gel has a good achievement on preventing spontaneous combustion at the Region where Top-Coal Caves above entries. It is promising, economically and environmental friendly, and valuable in popularization in coal mines.