Current optimization-based control of dual three-phase PMSM for low-frequency temperature swing reduction

In this paper,a control scheme based on current optimization is proposed for dual three-phase permanent-magnet synchronous motor(DTP-PMSM)drive to reduce the low-frequency temperature swing.The reduction of temperature swing can be equivalent to reducing maximum instantaneous phase copper loss in this paper.First,a two-level optimization aiming at minimizing maximum instantaneous phase copper loss at each electrical angle is proposed.Then,the optimization is transformed to a singlelevel optimization by introducing the auxiliary variable for easy solving.Considering that singleobjective optimization trades a great total copper loss for a small reduction of maximum phase copper loss,the optimization considering both instantaneous total copper loss and maximum phase copper loss is proposed,which has the same performance of temperature swing reduction but with lower total loss.In this way,the proposed control scheme can reduce maximum junction temperature by 11%.Both simulation and experimental results are presented to prove the effectiveness and superiority of the proposed control scheme for low-frequency temperature swing reduction.

基于FIA*-APF算法的蟹塘投饵船动态路径规划

为了提高无人投饵船在含障碍物河蟹养殖池塘自主巡航的作业效率和安全性,该研究提出基于改进A*算法与人工势场法相融合(fusion of improved A*and artificial potential field,FIA*-APF)的蟹塘投饵船动态路径规划算法。首先引入动态加权因子优化A*算法评价函数;其次加入转折惩罚函数并删除冗余点,接着利用B样条曲线对全局路径进行平滑处理;最后将改进A*算法得到的全局路径作为改进人工势场法中的引力路径,生成投饵船自主巡航高效路径。根据养殖池塘创建静态和动态2种仿真环境,分别对传统人工势场法(traditional artificial potential field,TAPF)、基于A*和人工势场法的融合算法(the A*and artificial potential field,TA*-APF)和FIA*-APF算法的性能进行20次测试。仿真试验结果表明:2种环境下,FIA*-APF算法的平均规划时间是TAPF算法的17.23%,是TA*-APF算法的51.96%,平均指令节点数量比TAPF算法减少50.64%,比TA*-APF算法减少65.03%,平均路径长度比TA*-APF算法减少2.82%。蟹塘试验结果表明:FIA*-APF算法的规划时间为TAPF算法的38.16%,为TA*-APF的62.42%,路径长度比TAPF算法减少29.13%,比TA*-APF减少10.15%;另外,TAPF和TA*-APF算法规划路径上大于60°的转角分别是FIA*-APF算法的3.28和2.62倍,大于100°的转角分别是FIA*-APF算法的3.73和1.67倍,该研究算法规划的路径更高效平滑。研究结果可为无人投饵船自主导航提供参考。

Deciphering engineering principle of three-phase interface for advanced gas-involved electrochemical reactions

As an alternative to conventional energy conversion and storage reactions,gas-involved electrochemical reactions,including the carbon dioxide reduction reaction(CO_(2)RR),nitrogen reduction reaction(NRR)and hydrogen evolution reaction(HER),have become an emerging research direction and have gained increasing attention due to their advantages of environmental friendliness and sustainability.Various studies have been designed to accelerate sluggish kinetics but with limited results.Most of them promote the reaction by modulating the intrinsic properties of the catalyst,ignoring the synergistic effect of the reaction as a whole.Due to the introduction of gas,traditional liquid-solid two-phase reactions are no longer applicable to future research.Since gas-involved electrochemical reactions mostly occur at the junctions of gaseous reactants,liquid electrolytes and solid catalysts,the focus of future research on reaction kinetics should gradually shift to three-phase reaction interfaces.In this review,we briefly introduce the formation and constraints of the three-phase interface and propose three criteria to judge its merit,namely,the active site,mass diffusion and electron mass transfer.Subsequently,a series of modulation methods and relevant works are discussed in detail from the three improvement directions of‘exposing more active sites,promoting mass diffusion and accelerating electron transfer’.Definitively,we provide farsighted insights into the understanding and research of three-phase interfaces in the future and point out the possible development direction of future regulatory methods,hoping that this review can broaden the future applications of the three-phase interface,including but not limited to gas-involved electrochemical reactions.

Electrical characteristics of new three-phase traction power supply system for rail transit

A novel three-phase traction power supply system is proposed to eliminate the adverse effects caused by electric phase separation in catenary and accomplish a unifying manner of traction power supply for rail transit.With the application of two-stage three-phase continuous power supply structure,the electrical characteristics exhibit new features differing from the existing traction system.In this work,the principle for voltage levels determining two-stage network is dissected in accordance with the requirements of traction network and electric locomotive.The equivalent model of three-phase traction system is built for deducing the formula of current distribution and voltage losses.Based on the chain network model of the traction network,a simulation model is established to analyze the electrical characteristics such as traction current distribution,voltage losses,system equivalent impedance,voltage distribution,voltage unbalance and regenerative energy utilization.In a few words,quite a lot traction current of about 99%is undertaken by long-section cable network.The proportion of system voltage losses is small attributed to the two-stage three-phase power supply structure,and the voltage unbal-ance caused by impedance asymmetry of traction network is less than 1‰.In addition,the utilization rate of regenerative energy for locomotive achieves a significant promotion of over 97%.

Speed Regulation Method Using Genetic Algorithm for Dual Three-phase Permanent Magnet Synchronous Motors

Dual three-phase Permanent Magnet Synchronous Motor(DTP-PMSM)is a nonlinear,strongly coupled,high-order multivariable system.In today’s application scenarios,it is difficult for traditional PI controllers to meet the requirements of fast response,high accuracy and good robustness.In order to improve the performance of DTP-PMSM speed regulation system,a control strategy of PI controller based on genetic algorithm is proposed.Firstly,the basic mathematical model of DTP-PMSM is established,and the PI parameters of DTP-PMSM speed regulation system are optimized by genetic algorithm,and the modeling and simulation experiments of DTP-PMSM control system are carried out by MATLAB/SIMULINK.The simulation results show that,compared with the traditional PI control,the proposed algorithm significantly improves the performance of the control system,and the speed output overshoot of the GA-PI speed control system is smaller.The anti-interference ability is stronger,and the torque and double three-phase current output fluctuations are smaller.

Optimization of Control Loops and Operating Parameters for Three-Phase Separators Used in Oilfield Central Processing Facilities

In this study,the Stokes formula is used to analyze the separation effect of three-phase separators used in a Oilfield Central Processing Facility.The considered main influencing factors include(but are not limited to)the typical size of oil and water droplets,the residence time and temperature of fluid and the dosage of demulsifier.Using the“Specification for Oil and Gas Separators”as a basis,the control loops and operating parameters of each separator are optimized Considering the Halfaya Oilfield as a testbed,it is shown that the proposed approach can lead to good results in the production stage.

Purification of Moringa oleifera Leaves Protease by Three-Phase Partitioning and Investigation of Its Potential Antibacterial Activity

One of plant-based products for dental care is plant-based proteolytic enzymes which are principally proteases. In order not to damage the protein and bioactive content, an efficient method should be employed for their purifications. As such, three-phase partitioning (TPP) was used to purify protease from moringa (Moringa oleifera). TPP is an emerging, promising, non-chromatographic and economical technology which is simple, quick, efficient and often one-step process for the separation and purification of bioactive molecules from natural sources. It involves the addition of salt (ammonium sulphate) to the crude extract followed by the addition of an organic solvent (butanol). The protein appears as an interfacial precipitate between upper organic solvent and lower aqueous phases. The various conditions such as ammonium sulphate, ratio of crude extract to t-butanol and pH which are required for attaining efficient purification of the protease fractions were optimized. Under optimized conditions, it was seen that, 35% of ammonium sulphate saturation with 1:0.75 ratio of crude extract to t-butanol at pH 7 gave 4.94-fold purification with 96.20% activity yield of protease in the middle phase of the TPP system. The purified enzyme from Moringa oleifera has no antimicrobial effect on the pathogenic bacteria tested. However, this purified enzyme, can be considered as a promising agent, cheap, and safe source which is suitable for using in various industries.

Vibration characteristics of sandwich plates with an auxetic honeycomb core and laminated three-phase skin layers under blast load

In this article,vibration characteristics of sandwich plates with an auxetic honeycomb core and laminated three-phase skin layers subjected to blast load are studied.Higher-order ES-MITC3 element based on higher-order shear deformation theory(HSDT)to achieve the governing equations.The sandwich plates with the ultra-light feature of the auxetic honeycomb core layer(negative Poisson’s ratio)and reinforced by two laminated three-phase skin layers.The obtained results in our work are compared with other previously published to confirm accuracy and reliability.In addition,the effects of parameters such as geometrical and material parameters on the vibration characteristics of sandwich plates with an auxetic honeycomb core and laminated three-phase skin layers are fully investigated.

Enhancing ammonia production rates from electrochemical nitrogen reduction by engineering three-phase boundary with phosphorus-activated Cu catalysts

Electrochemical N_(2) reduction reaction(eNRR) over Cu-based catalysts suffers from an intrinsically low activity of Cu for activation of stable N_(2) molecules and the limited supply of N_(2) to the catalyst due to its low solubility in aqueous electrolytes.Herein,we propose phosphorus-activated Cu electrocatalysts to generate electron-deficient Cu sites on the catalyst surface to promote the adsorption of N_(2) molecules.The eNRR system is further modified using a gas diffusion electrode(GDE) coated with polytetrafluoroethylene(PTFE) to form an effective three-phase boundary of liquid water-gas N_(2)-solid catalyst to facilitate easy access of N_(2) to the catalytic sites.As a result,the new catalyst in the flow-type cell records a Faradaic efficiency of 13.15% and an NH_(3) production rate of 7.69 μg h^(-1) cm^(-2) at-0.2 V_(RHE),which represent 3.56 and 59.2 times increases from those obtained with a pristine Cu electrode in a typical electrolytic cell.This work represents a successful demonstration of dual modification strategies;catalyst modification and N_(2) supplying system engineering,and the results would provide a useful platform for further developments of electrocatalysts and reaction systems.

Automatic measurement of three-phase contact angles in pore throats based on digital images

With the help of digital image processing technology, an automatic measurement method for the three-phase contact angles in the pore throats of the microfluidic model was established using the microfluidic water flooding experiment videos as the data source. The results of the new method were verified through comparing with the manual measurement data.On this basis, the dynamic changes of the three-phase contact angles under flow conditions were clarified by the contact angles probability density curve and mean value change curve. The results show that, for water-wetting rocks, the mean value of the contact angles is acute angle during the early stage of the water flooding process, and it increases with the displacement time and becomes obtuse angle in the middle-late stage of displacement as the dominant force of oil phase gradually changes from viscous force to capillary force. The droplet flow in the remaining oil occurs in the central part of the pore throats, without three-phase contact angle. The contact angles for the porous flow and the columnar flow change slightly during the displacement and present as obtuse angles in view of mean values, which makes the remaining oil poorly movable and thus hard to be recovered. The mean value of the contact angle for the cluster flow tends to increase in the flooding process, which makes the remaining oil more difficult to be recovered. The contact angles for the membrane flow are mainly obtuse angles and reach the highest mean value in the late stage of displacement, which makes the remaining oil most difficult to be recovered. After displacement, the remaining oils under different flow regimes are just subjected to capillary force, with obtuse contact angles, and the wettability of the pore throat walls in the microfluidic model tends to be oil-wet under the action of crude oil.

基于APF的局部路径规划算法研究

针对传统人工势场法(artificial potential field,APF)规划的路径存在易陷入局部最优与路径不平滑问题,提出一种“触碰引导”策略为先导的控制方法。该方法在无人机运动过程中,引入合适的阶段性子目标点引导无人机飞行,从而降低规划结果陷入局部极值点的概率,并利用贝塞尔曲线法处理控制点以解决路径平滑问题。仿真实验结果表明,改进后的算法能够有效解决易陷入局部极小值点和路径不平滑问题,相较于传统算法效率更高。

Application of CD34 expression combined with three-phase dynamic contrast-enhanced computed tomography scanning in preoperative staging of gastric cancer

BACKGROUND Accurate preoperative staging of gastric cancer(GC),a common malignant tumor worldwide,is critical for appropriate treatment plans and prognosis.Dynamic three-phase enhanced computed tomography(CT)scanning for preoperative staging of GC has limitations in evaluating tumor angiogenesis.CD34,a marker on vascular endothelial cell surfaces,is promising in evaluating tumor angiogenesis.We explored the value of their combination for preoperative staging of GC to improve the efficacy and prognosis of patients with GC.Medical records of 106 patients with GC treated at the First People's Hospital of Lianyungang between February 2021 and January 2023 were retrospectively studied.All patients underwent three-phase dynamic contrast-enhanced CT scanning before surgery,and CD34 was detected in gastroscopic biopsy specimens.Using surgical and pathological results as the gold standard,the diagnostic results of three-phase dynamic contrast-enhanced CT scanning at different T and N stages were analyzed,and the expression of CD34-marked microvessel density(MVD)at different T and N stages was determined.The specificity and sensitivity of three-phase dynamic contrast-enhanced CT and CD34 in T and N staging were calculated;those of the combined diagnosis of the two were evaluated in parallel.Independent factors affecting lymph node metastasis were analyzed using multiple logistic regression.RESULTS The accuracy of three-phase dynamic contrast-enhanced CT scanning in diagnosing stages T1,T2,T3 and T4 were 68.00%,75.00%,79.41%,and 73.68%,respectively,and for diagnosing stages N0,N1,N2,and N3 were 75.68%,74.07%,85.00%,and 77.27%,respectively.CD34-marked MVD expression increased with increasing T and N stages.Specificity and sensitivity of three-phase dynamic contrast-enhanced CT in T staging were 86.79%and 88.68%;for N staging,89.06%and 92.86%;for CD34 in T staging,64.15%and 88.68%;and for CD34 in N staging,84.38%and 78.57%,respectively.Specificity and sensitivity of joint diagnosis in T staging were 55.68%and 98.72%,and N staging were 75.15%and 98.47%,respectively,with the area under the curve for diagnosis improving accordingly.According to multivariate analysis,a longer tumor diameter,higher pathological T stage,lower differ-entiation degree,and higher expression of CD34-marked MVD were independent risk factors for lymph node metastasis in patients with GC.CONCLUSION With high accuracy in preoperatively determining the invasion depth and lymph node metastasis of GC,CD34 expression and three-phase dynamic contrast-enhanced CT can provide a reliable basis for surgical resection.

关于变频多联机APF能效试验中针对低温制冷实测时准确性的检讨和建议

目前我国多联机变频空调机组均采用全年性能系数(APF)替代IPLV作为评价指标。基于现有多联变频空调器的调节范围广的特点,指出了现有APF中对于选择性试验即低温制冷工况实测时,会出现不符合实际的情况,利用实测数据和理论分析产生的原因,水平展开,并给出了针对实测的改进建议。

矿井救援机器人的B样条-APF-BRRT路径规划方法

针对矿井非结构化、形状狭长的地形结构以及传统BRRT算法规划路径曲折、转折点较多等路径质量较差问题,提出一种基于B样条-APF-BRRT算法的矿井救援机器人路径规划方法。首先根据BRRT路径中产生的目标点和矿井环境中障碍物信息,引入APF目标引力的思想,构建人工势场;然后利用Douglas-Peuker算法进行分线段处理,重新提取关键节点;最后使用B样条函数进行光滑拟合获得路径,减少了APF-BRRT算法所得路径的转折点和长度。对B样条-APF-BRRT算法进行实验,结果表明改进算法所获路径转折点和长度都明显优于BRRT算法,在矿井狭窄巷道中,相对于BRRT算法,B样条-APF-BRRT方法产生的路径更加平滑,转折次数减少到9次,路径长度减少了7.73%。

基于改进麻雀算法的多APF协调控制研究

有源电力滤波器(APF)因其具有快速追踪和消除谐波的功能而广泛应用于配电网中。其中,LCL型APF对高频谐波有更好的抑制能力。随着APF并网数目的日益增多,各APF间的交互影响问题变得不可忽视。针对多APF间的交互影响,首先基于诺顿定理推导了多APF并网等效模型,其次利用广义动态相对增益矩阵(GDRGA)对交互影响进行定量分析,最后将抑制交互影响转化为多目标优化问题。针对传统麻雀算法在搜索后期存在全局寻优能力差、易陷入局部最优的缺陷,引入tent混沌和动态随机柯西变异进行改进,并采用改进麻雀算法对APF各控制参数进行协调优化。结果表明,改进麻雀算法能得到分布更加良好的pareto解集,求解性能更优,多目标优化后能有效抑制APF间的交互影响,验证本文所提方法的有效性。

POMDP-APF:一种基于POMDP模型的APF无人机路径规划策略

针对无人机在路径规划过程中会遇到静态或者动态的障碍物,从而导致路径规划失败的问题,提出一种基于部分可观测马尔可夫决策过程(partially observable Markov decision process,POMDP)模型的人工势场(artificial potential field,APF)无人机路径规划策略(POMDP-APF)。首先使用传感器获得的障碍物信息结合POMDP模型预测障碍物的未来位置,为无人机的路径规划做准备;其次,提出一种新的基于障碍物的正方体外接球的模型,保障无人机在路径规划过程中的安全性;最后,结合改进的APF算法实现无人机的路径规划。仿真结果表明,POMDP-APF策略在无人机实时路径规划中具有良好的可行性和有效性,使无人机能够有效避开障碍物,同时路径长度以及耗费时间更短。

变频空调器APF快速计算的显式表达式

国家标准中给出的空调器能效指标APF的确定方法,包含一系列的判断与嵌套计算,过程复杂。本文旨在将新版空调器能效标准GB 21455—2019中给出的APF系列计算公式转化为显式计算式,从而满足APF计算便捷的要求。首先采用将自变量直接代入的方法对国标定义的APF的4个中间变量进行化简;然后通过数值拟合的办法对化简计算式中需要判定计算区间与分段计算的过程进行简化;最后将4个中间变量的显式表达式代入APF定义式中,得到APF显式表达式。开发的APF显式表达式适用于所有额定制冷量范围的变频空调器并有良好的精度,其中5测试工况点、7测试工况点的APF显式表达式相比于空调器能效标准中APF的定义式计算误差分别为0.73%、1.17%。

Stability analysis of unsaturated soil slope during rainfall infiltration using coupled liquid-gas-solid three-phase model

Generally, most soil slope failures are induced by rainfall infiltration, a process that involves interactions between the liquid phase, gas phase,and solid skeleton in an unsaturated soil slope. In this study, a loosely coupled liquid-gas-solid three-phase model, linking two numerical codes,TOUGH2/EOS3, which is used for water-air two-phase flow analysis, and FLAC^(3D), which is used for mechanical analysis, was established. The model was validated through a documented water drainage experiment over a sandy column and a comparison of the results with measured data and simulated results from other researchers. The proposed model was used to investigate the features of water-air two-phase flow and stress fields in an unsaturated soil slope during rainfall infiltration. The slope stability analysis was then performed based on the simulated water-air two-phase seepage and stress fields on a given slip surface. The results show that the safety factor for the given slip surface decreases first, then increases, and later decreases until the rainfall stops. Subsequently, a sudden rise occurs. After that, the safety factor decreases continually and reaches its lowest value, and then increases slowly to a steady value. The lowest value does not occur when the rainfall stops, indicating a delayed effect of the safety factor. The variations of the safety factor for the given slip surface are therefore caused by a combination of pore-air pressure, matric suction, normal stress, and net normal stress.

Modeling and Analysis of Airlift System Operating in Three-Phase Flow

Based on the momentum theorem, the fluid governing equation in a lifting pipe is proposed by use of the method combining theoretical analysis with empirical correlations related to the previous research, and the performance of an airlift pump can be clearly characterized by the triangular relationship among the volumetric flux of air, water and solid particles, which are obtained respectively by using numerical calculation. The meso-scale river sand is used as tested particles to examine the theoretical model. Results of the model are compared with the data in three-phase flow obtained prior to the development of the present model, by an independent experimental team that used the physical conditions of the present approach. The analytical error can be controlled within 12% for predicting the volumetric flux of water and is smaller than that （±16%） of transporting solid particles in three-phase flow. The experimental results and computations are in good agreement for air-water two-phase flow within a margin of ±8%. Reasonable agreement justifies the use of the present model for engineering design purposes.

Three-Phase Heterojunction NiMo-Based Nano-Needle for Water Splitting at Industrial Alkaline Condition

Constructing heterojunction is an effective strategy to develop high-performance non-preciousmetal-based catalysts for electrochemical water splitting(WS).Herein,we design and prepare an N-doped-carbon-encapsulated Ni/MoO_(2) nano-needle with three-phase heterojunction(Ni/MoO_(2)@CN)for accelerating the WS under industrial alkaline condition.Density functional theory calculations reveal that the electrons are redistributed at the three-phase heterojunction interface,which optimizes the adsorption energy of H-and O-containing intermediates to obtain the best ΔG_(H*) for hydrogen evolution reaction(HER)and decrease the ΔG value of ratedetermining step for oxygen evolution reaction(OER),thus enhancing the HER/OER catalytic activity.Electrochemical results confirm that Ni/MoO_(2)@CN exhibits good activity for HER(ƞ_(-10)=33 mV,ƞ_(-1000)=267 mV)and OER(ƞ_(10)=250 mV,ƞ_(1000)=420 mV).It shows a low potential of 1.86 V at 1000 mA cm^(−2) for WS in 6.0 M KOH solution at 60℃ and can steadily operate for 330 h.This good HER/OER performance can be attributed to the three-phase heterojunction with high intrinsic activity and the self-supporting nano-needle with more active sites,faster mass diffusion,and bubbles release.This work provides a unique idea for designing high efficiency catalytic materials for WS.