Survey on performance of vertical slot and nature-like fishways at Angu hydropower station, Southwest China

To restore dam-blocked natural fish migratory passages,a growing number of artificial fishways have been built in water conservancy and hydropower projects in China.The Angu hydropower station involved diverse important fish habitats in the lower reaches of the Daduhe River in Southwest China.Therefore,a vertical slot fishway(VSF)and a nature-like fishway(NLF)were built near the backwater area of the reservoir to connect the upstream and downstream habitats.Hydrodynamic and aquatic ecological surveys were conducted after the completion of the project to estimate the fish passing effect of the two fishways.The results indicated that both fishways were in effective operation and could maintain the desired hydrodynamic conditions and be used by several local fish species.During the survey,149 fish from 15 species and 111 fish from 17 species were captured by the traps in the VSF and NLF,respectively,while 1263 fish from 27 species were found in the downstream area.Some species captured in the VSF were not found in the NLF,and vice versa,which implied the different preferences of fish.Meanwhile,3789 signals including 2099 upward ones and 1690 downward ones were monitored with an ultrasonic fish detector at the inlet of the VSF.These findings revealed the characteristics of fish species observed in and near the fishways and provided valuable insights into the different fish passing capabilities of VSFandNLF.

Stress release mechanism of deep bottom hole rock by ultra-high-pressure water jet slotting

To solve the problems of rock strength increase caused by high in-situ stress,the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed.The stress conditions of bottom hole rock,before and after slotting are analyzed and the stress release mechanism of slotting is clarified.The results show that the stress release by slotting is due to the coupling of three factors:the relief of horizontal stress,the stress concentration zone distancing away from the cutting face,and the increase of pore pressure caused by rock mass expansion;The stress concentration increases the effective stress of rock along the radial distance from O.6R to 1R(R is the radius of the well),and the presence of groove completely releases the stress,it also allows the stress concentration zone to be pushed away from the cutting face,while significantly lowering the value of stresses in the area the drilling bit acting,the maximum stress release efficiency can reach 80%.The effect of slotting characteristics on release efficiency is obvious when the groove location is near the borehole wall.With the increase of groove depth,the stress release efficiency is significantly increased,and the release range of effective stress is enlarged along the axial direction.Therefore,the stress release method and results of simulations in this paper have a guiding significance for best-improving rock-breaking efficiency and further understanding the technique.

Joint Slot Scheduling and Power Allocation in Clustered Underwater Acoustic Sensor Networks

Dear Editor, This letter deals with the joint slot scheduling and power allocation in clustered underwater acoustic sensor networks(UASNs),based on the known clustering and routing information, to maximize the network's energy efficiency(EE). Based on the block coordinated decent(BCD) method, the formulated mixed-integer non-convex problem is alternatively optimized by leveraging the KuhnMunkres algorithm.

Effect of an Inclined Slots on the Power Consumption and Vortices Size in a Rushton Turbine Agitated Tank

Mechanical agitation in baffled vessels with turbines plays a vital role in achieving homogeneous fluid mixing and promoting various transfer operations.Therefore,designing vessels with optimal energy efficiency and flow dynamics is essential to enhance operational performance and eliminate flow perturbations.Hence,the present research focuses on a numerical investigation of the impact of inclined slots with different angles installed at the side-wall of a cylindrical vessel equipped with a Rushton turbine.This study explores power consumption and vortex size while considering various rotation directions of the impeller with different rotation speeds.The numerical simulations are conducted for Reynolds numbers ranging from 104 to 105,using the RANS k-εturbulence model to govern the flow inside the stirred vessel,accounting for mass and momentum balances.The results have shown that the installation of slots reduces power consumption and vortex size compared to conventional vessel configu-rations.Moreover,increasing the slot angle from 0 to 32.5°further reduces energy consumption and vortex size,especially with negative rotation speeds.On the other hand,increasing the Reynolds numbers leads to a decrease in power consumption and an increase in vortex size.The present research therefore proposes a design for con-structing Rushton-turbine stirred vessels offering optimal operation,characterized by reduced energy consumption and minimized vortex size.

Numerical Study on Mechanism of Blast-Induced Damage Considering Guiding Effect of Water Jet Slot

Damage is one of the most important characteristics of rock failure.Studying the damage mechanism of rock blasting under the guiding effect of the water jet slot and revealing the mechanism of controlled blasting with water jet assistance are crucial.In this study,a rock-like material was chosen as the research object for the calibration experiment of the numerical model.The numerical simulation models were then established by ANSYS/LS-DYNA,and the blastinduced damage mechanism under the guiding effect of the water jet slot was analyzed according to the blasting theory.The results indicated that explosive energy accumulates toward the direction of the slot as the guiding effect of the water jet slot,which allows the rock mass in the direction of the slot bear more damage.Meanwhile,the rock mass in the middle of the connection line between two blast-holes bears more damage under the combination of the effect of the explosion stress wave and guiding effect of water the jet slot on the detonation gas during double-slotted borehole blasting,which results in the formation of a gourd-shaped blast-induced damage area.In addition,the influence of the water jet slot on blast-induced damage varies depending on the blasting-process stage.

Adaptive Time Slot Resource Allocation in SWIPT IoT Networks

The rapid advancement of Internet of Things(IoT)technology has brought convenience to people’s lives;however further development of IoT faces serious challenges,such as limited energy and shortage of network spectrum resources.To address the above challenges,this study proposes a simultaneous wireless information and power transfer IoT adaptive time slot resource allocation(SIATS)algorithm.First,an adaptive time slot consisting of periods for sensing,information transmission,and energy harvesting is designed to ensure that the minimum energy harvesting requirement ismet while the maximumuplink and downlink throughputs are obtained.Second,the optimal transmit power and channel assignment of the system are obtained using the Lagrangian dual and gradient descent methods,and the optimal time slot assignment is determined for each IoT device such that the sum of the throughput of all devices is maximized.Simulation results show that the SIATS algorithm performs satisfactorily and provides an increase in the throughput by up to 14.4%compared with that of the fixed time slot allocation(FTS)algorithm.In the case of a large noise variance,the SIATS algorithm has good noise immunity,and the total throughput of the IoT devices obtained using the SIATS algorithm can be improved by up to 34.7%compared with that obtained using the FTS algorithm.

Loss Analysis of Magnetic Gear with Slotted in Magnetic Modulation Ring

In order to improve the operation efficiency of coaxial magnetic gear(CMG),in this paper,a CMG model with slotted in magnetic modulation ring is proposed.In this model,the permanent magnets(PMs)of internal and external rotors are distributed in Halbach array,the inner rotor PMs are equally divided into 3 small pieces,and the outer rotor PMs are equally divided into 2 small pieces.At the same time,the static magnetic modulation ring iron blocks are slotted,each iron block has 3 slots,the width of the slot is 0.4°,and the depth of the single side slot is 1mm.Finally,a two-dimensional model is established,and the eddy current loss and iron loss of the model are optimized,compared with the conventional CMG model,it is found that the changed pattern can increase the internal and external output torque by 4%and 4.12%,respectively.The eddy current loss is reduced by 66.57%,and the iron loss is reduced by 8.9%,which significantly improve the operation efficiency of the CMG.

Compact 5G Vivaldi Tapered Slot Filtering Antenna with Enhanced Bandwidth

Compact fifth-generation(5G)low-frequency band filtering antennas(filtennas)with stable directive radiation patterns,improved bandwidth(BW),and gain are designed,fabricated,and tested in this research.The proposed filtennas are achieved by combining the predesigned compact 5G(5.975–7.125 GHz)third-order uniform and non-uniform transmission line hairpin bandpass filters(UTL and NTL HPBFs)with the compact ultrawide band Vivaldi tapered slot antenna(UWB VTSA)in one module.The objective of this integration is to enhance the performance of 5.975–7.125GHz filtennas which will be suitable for modern mobile communication applications by exploiting the benefits of UWB VTSA.Based on NTL HPBF,more space is provided to add the direct current(DC)biassing circuits in cognitive radio networks(CRNs)for frequency reconfigurable applications.To overcome the mismatch between HPBFs and VTSA,detailed parametric studies are presented.Computer simulation technology(CST)software is used for the simulation in this study.Good measured S11 appeared to be<−13 and<−10.54 dB at 5.48–7.73 and 5.9–7.98GHz with peak realized gains of 6.37 and 6.27 dBi,for VTSA with UTL and NTL HPBFs,respectively which outperforms the predesigned filters.Validation is carried out by comparing the measured and simulated results.

联合多意图识别与语义槽填充的双向交互模型

意图识别与语义槽填充是口语理解的两个主要任务,两者具有高度相关性,通常进行联合训练。随着口语理解任务的深入,研究发现用户在现实场景中的话语往往含有多个意图。但部分联合模型只能识别用户话语中的单个意图,未能充分建模多个意图和语义槽之间的关联性。考虑到话语中多个意图的信息可以引导语义槽填充,语义槽信息也可以帮助意图更好的识别,模型采用图注意力网络建立意图和语义槽之间的双向交互。具体的,将两个任务双向关联以便模型能够挖掘多个意图与语义槽之间的关系,同时引入两个任务的标签信息使模型能够学习到话语上下文和标签的关系,从而提高意图识别与语义槽填充的准确率,优化口语理解的整体性能。实验表明,模型在MixATIS和MixSNIPS两个多意图数据集上对比其他模型性能得到了显著提升。

YASA轴向磁通永磁电机定子槽漏感计算

定子槽漏感是定子无轭模块化(yokeless and segmented,YASA)轴向磁通永磁电机电感的主要分量,会降低电机的功率因数和最大输出转矩。该文提出定子槽内微小单元磁场能量法计算YASA电机的定子槽漏感,通过建立计及铁心饱和影响的二维等效磁网络模型准确计算槽内微小单元储存的磁场能量,进而计算定子槽漏感。基于所提出的方法,进一步研究定子结构参数以及极槽配合对YASA电机定子槽漏感的影响规律。有限元仿真和实验结果表明,该文所提出的YASA电机定子槽漏感计算方法的可行性和准确性。

齿调制作用下转子开槽对永磁电机电磁振动影响

为了研究齿调制作用下转子表面开槽对永磁同步电机电磁振动的影响,以小功率分数槽集中绕组(FSCW)内置永磁同步电机(IPMSM)为研究对象,通过麦克斯韦应力张量法推导径向电磁力波的频率及空间阶数特征。分析齿调制作用在FSCW-IPMSM中将空间高阶电磁力波调制为低阶电磁力波的过程,并给出转子表面开槽在齿调制作用影响下与电磁振动间的联系。研究表明,转子表面开槽结构的改变会使各次谐波磁场发生变化,进而改变以极数阶电磁力波为代表的高阶电磁力波的幅值。在齿调制作用下,这些高阶电磁力波会被调制为幅值较高的低阶电磁力波,并引起不同幅度的低阶振动。然后建立C型、V型两种不同转子表面开槽结构的10极12槽FSCW-IPMSM电磁及结构有限元分析模型并进行仿真分析。结果表明,极数阶即10阶电磁力波会被调制为2阶并引起2阶振动,且两种不同开槽结构间的电磁振动存在着高达22.1%的差异。最后,在一台10极12槽样机上进行振动实验,验证理论与仿真分析结果。

基于特征蒸馏的变分编码器交通流预测模型

针对交通流数据高维非线性和时空依赖性复杂,本文构建了基于特征蒸馏的变分贝叶斯编码器交通流预测模型.对每段时间序列对应的时间窗口特征,构建了基于多模态时间槽和空间槽的交通流特征提取模型.以时空槽特征提取模型作为特征知识蒸馏架构的输入.通过知识蒸馏结构提取的时空特征结晶体,利用教师模型指导学生模型的学习过程,从而提高学生模型的泛化能力.变分贝叶斯编码器对交通流时空特征结晶编码获取交通流数据的隐变量,根据隐变量的生成采样,利用解码器将其解码重构成新的预测值.实验结果表明,本文提出的模型预测性能显著提升,且中长期预测中鲁棒性更优.

基于石墨烯片的频率可调太赫兹天线

本文设计了一种基于石墨烯片的频率可调太赫兹天线,采用了折叠缝隙结构并使用共面波导馈电方式,以更好地实现阻抗匹配.通过调控在缝隙之间添加的4个石墨烯片的电导率,改变缝隙天线的等效长度,使天线在两种不同工作模式下的谐振频率分别为230.5 GHz和270.5 GHz.除此之外,在天线下方加载了方形封闭谐振环(Closed-Ring Resonator,CRR)构成的超表面,并使其谐振频率与天线的谐振频率匹配,将z轴负方向的辐射进行反射,使天线在两种工作模式下的增益提高至5.41 dBi和7.63 dBi,与无反射结构时相比分别增长2.48 dBi和3.55 dBi.

无等待与时隙映射复用结合的时间触发流调度方法

工业控制系统中众多应用的正常运行依赖于确定性低时延的网络传输,这一需求推动了时间敏感网络的发展。为保证工业控制系统中流量传输的确定性,提出了无等待与时隙映射复用结合的时间触发流调度方法。首先,对工业控制系统时间敏感网络的通信要素进行建模,通过分析时间触发流的特性,简化了链路、流传输、流隔离和帧隔离等约束条件;其次,使用基础周期作为调度循环时间,实时流采取无等待调度,循环流采取时隙映射复用,从而缩短了门控列表长度;然后,提出了基于数据帧传输区间中点的冲突判别方法,降低了时隙冲突判断的时间复杂度;最后,设计了时间触发流调度优化函数,并基于改进的多目标遗传算法进行求解。实验验证了该方法的正确性与可行性,平均门控列表长度缩短了59.7%。

基于抽真空系统的继电器线圈BMC热固性塑料模具结构设计

对于原有BMC继电器线圈模具的外观较差、线圈断线丝、生产效率及合格率较低等问题,设计了一种1模16腔布局的上、下双顶出系统的压注模具,通过抽真空系统结构的设计将注塑压力从原充填压力19~42 MPa降低至22~25 MPa,成型件采用电加热及电阻测温方法,上模镶件的温度控制在148~151℃之间,下模镶件的温度控制在148~151℃之间,通过实际生产验证抽真空系统的效果。该改进方案使不合格品率从0.08%降低至0.015%,生产效率提高了20%。结果表明,该模具通过抽真空系统的应用提高了模具的可靠性及稳定性,满足自动化数字化生产线的要求,并且,提高了生产效率与产品的合格率。

脉冲宽度对高功率微波阵列天线辐射特性的影响

为了研究馈入脉冲波形的脉冲宽度(脉冲半高宽)对高功率微波阵列天线辐射特性的影响,以L波段(1.575 GHz)高功率微波波导缝隙阵列天线为例,首先从理论分析、数值仿真方面研究不同馈入脉冲波形脉宽对阵列天线辐射增益和辐射脉冲脉宽的影响,然后根据仿真模型加工制作了一款由4根波导组成的宽边纵缝阵列天线,并将波导缝隙阵列天线结合功分网络与吉瓦级微波源(高功率微波磁控管)连试,开展了高功率微波辐射实验。数值仿真结果表明,当馈入的L波段微波脉冲脉宽约为10 ns时,阵列天线辐射增益比连续波馈入时的增益减小2.2 dB,脉宽展宽2.6 ns;当馈入脉冲波形脉宽约为15 ns时,阵列天线时域增益比连续波馈入时的时域增益减小1.5 dB,脉宽展宽1.9 ns。高功率微波实验结果表明,与辐射场脉宽为9.6 ns的高功率微波相比,辐射场脉冲脉宽为15.65 ns的高功率微波功率密度提升了3.1 dB。

竖缝式双池室鱼道与传统VSF水力特性对比

鱼道是为保障鱼类的生存繁衍,保护洄游性水生生物通过水坝、水闸等障碍物的重要通道。采用RNG k-ε模型对竖缝式双池室鱼道和传统竖缝式鱼道(VSF)进行数值模拟计算,对比分析各项水力特性。结果表明:与传统VSF相比,竖缝式双池室鱼道流场的主流区数量更多、回流区更稳定;鱼道具有丰富的流速信息,且各竖缝处的最大流速和平均流速均小于传统VSF的50%;鱼道3条主流区位置分布均匀,流速综合衰减率较传统VSF高3%左右。竖缝式双池室鱼道作为一种新型VSF,其水力特性达到了传统VSF结构优化设计的目的,相关成果可为鱼道工程建设提供参考。

基于空闲时隙探测机制的分组帧时隙标签防碰撞算法

多标签碰撞是射频识别系统中无法避免的问题,大量的标签碰撞会增加系统的能量消耗和时间开销,严重影响系统的识别效率。为此提出一种新型的标签防碰撞算法,该算法结合了传统帧时隙算法简单易实施的优点,同时引入了分组和空闲时隙探测机制,以极小的探测时隙开销,消除了识别过程中的空闲时隙,同时减低了标签冲突概率。仿真结果显示,相对于FuzzyQ算法和帧时隙ALOHA算法,本算法平均吞吐率提高了22.64%和61.74%,系统通信传输量平均节省了16.73%和30.41%。

不同槽配比下绕线式无刷双馈电机性能对比研究

无刷双馈电机由于结构简单、可靠性高、变频器容量小等优点在恒频变速发电领域受到广泛关注,其定转子的槽数配比对电机性能与振动具有一定程度的影响。为探究这一问题,该文以绕线式无刷双馈电机定转子磁势分析为基础,推导不同槽配合的电磁力波对比以及槽配合对电机性能的影响,给出3种符合要求的槽配比方案,计算出各方案转子绕组谐波,并进行对比分析;利用有限元法对48/36槽、42/36槽与36/30槽3种方案在相同要求下的负载性能进行研究,导出定子齿部电磁力,对电机进行振动响应分析对比;最后,通过样机试验,验证有限元仿真的正确性,同时试验结果也证明所选槽配合下电机具有振动形变量小、转子电流小、系统输出电压和效率高、饱和程度低等优点。

宽频小型化U形槽微带天线

针对微带贴片天线宽带化和小型化的设计需求,提出并设计了一种工作在S/C波段的改进的U形槽微带贴片天线。通过在辐射贴片中心开曲折U形槽,使缝隙和馈电探针偏离贴片中心,形成非对称曲折U形槽的层叠介质微带贴片天线。通过共面容性耦合馈电进一步提高天线的阻抗带宽。实测结果表明:该天线在3.11~5.40 GHz频率范围内回波损耗小于-10 dB,相对带宽可达53.8%,与仿真结果吻合,可为微带天线的小型化、宽带化设计提供参考。