Designing a Protection Scheme in Micro-Grid Systems with DG Using Central Protection Unite and Multiple Setting Group Protection Relays

Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this continuous changes in generation condition, the fault current level in network will be affected, this changes in fault current level will affect in the coordination between protection relays and to keep the coordination at right way, an adaptive protection system is required that can adaptive its setting according to generation changes, the fault current level in each case is evaluated using ETAP software, and the required relay setting in each case is also evaluated using Grey Wolf Optimizer (GWO) algorithm, and to select suitable setting which required in each condition, to select the active setting group of protection relay according to generation capacity, central protection unite can be used, and to improve protection stability and minimizing relays tripping time, a proposed method for selecting suitable backup relay is used, which leads to decrease relays tripping time and increase system stability, output settings for relays in all cases achieved our constrains.

Optimization Design of High-speed Interior Permanent Magnet Motor with High Torque Performance Based on Multiple Surrogate Models

In order to obtain better torque performance of high-speed interior permanent magnet motor(HSIPMM) and solve the problem that electromagnetic optimization design is seriously limited by its mechanical strength, a complete optimization design method is proposed in this paper. The object of optimization design is a 15 kW、20000 r/min HSIPMM whose permanent magnets in rotor is segmented. Eight structural dimensions are selected as its optimization variables. After design of experiment(DOE), multiple surrogate models are fitted, a set of surrogate models with minimum error is selected by using error evaluation indexes to optimize, the NSGA-II algorithm is used to get the optimal solution. The optimal solution is verified by load test on a 15 kW, 20000 r/min HSIPMM prototype. This paper can be used as a reference for the optimization design of HSIPMM.

Longitudinal train dynamics of electric multiple units under rescue

Once operating trains are disabled on the railway lines,an efficient manner is to utilize the train for train rescue.Owning to the different train and coupler types,it is difficult to formulate uniform regulations for train to train rescue.In this paper,the longitudinal train dynamics of electric multiple units under rescue were analyzed by field and laboratory tests.The angling behavior of the brakinginduced coupler under compressed in-train forces was analyzed.A dynamic model for the train and draft gear system was developed considering accurate boundary limitations and braking characteristics.The safety indices and their limits for the coupled rescue train were defined.Thedynamic evaluations of different train to train rescue scenarios were analyzed.It is indicated that the coupler vertical rotation occurs during the emergency braking applied by the assisting train.The vertical force components of intrain forces lead to the carbody pitch behavior and even cause local destructions to the coupler system.The carbody pitch motion can arise the inference of in-train devices.Based on the safety evaluation of train and coupler system,the regulations for typical train to train rescue scenarios were formulated.

Influence of hypocalcemia on the prognosis of patients with multiple trauma

BACKGROUND Hypocalcemia is highly common in hospitalized patients,especially in those with trauma,On the other hand,abnormal calcium metabolism is an important metabolic challenge;however,it is often neglected and untreated,and certain factors may induce serious neurological and cardiovascular complications.AIM To retrospectively analyze the impact of hypocalcemia on the prognosis of patients with multiple traumas.METHODS The study was conducted from January 2020 to December 2021.Ninety-nine patients with multiple injuries were treated at the critical care medicine department of Fuyang People’s Hospital.The selected indicators included sex,age,and blood calcium and hematocrit levels.Many indicators were observed,including within 24 h of hospitalization,and the prognosis was collected after 28 d.Based on the blood calcium levels,the patients were divided into the following two groups:Normocalcemia and hypocalcemia.Of the 99 patients included,81 had normocalcemia,and 18 had hypocalcemia.Separate experiments were conducted for these two groups.RESULTS There was an association between serum calcium levels and the prognosis of patients with polytrauma.CONCLUSION Clinically,the prognosis of patients with multiple traumas can be preliminarily evaluated based on serum calcium levels.

Thermal Model of High-Speed Spindle Units

For the purpose to facilitate development of high-speed Spindle Units (SUs) running on rolling bearings, we have developed a beam element model, algorithms, and software for computer analysis of thermal characteristics of SUs. The thermal model incorporates a model of heat generation in rolling bearings, a model of heat transfer from bearings, and models for estimation of temperature and temperature deformations of SU elements. We have carried out experimental test and made quantitative evaluation of the effect of operation conditions on friction and thermal characteristics of the SUs of grinding and turning machines of typical structures. It is found that the operation conditions make stronger effect on SU temperatures when rpm increases. A comparison between the results of analysis and experiment proves their good mutual correspondence and allows us to recommend application of the models and software developed for design and research of high-speed SUs running on rolling bearings.

Noisy Chaotic Neural Network for Resource Allocation in High-Speed Train OFDMA System

High-speed train communication system is a typical high-mobility wireless communication network. Resource allocation problem has a great impact on the system performance. However, conventional resource allocation approaches in cellular network cannot be directly applied to this kind of special communication environment. A multidomain resource allocation strategy was proposed in the orthogonal frequency-division multiple access(OFDMA) of high-speed. By analyzing the effect of Doppler shift, sub-channels, antennas, time slots and power were jointly considered to maximize the energy efficiency under the constraint of total transmission power. For the purpose of reducing the computational complexity, noisy chaotic neural network algorithm was used to solve the above optimization problem. Simulation results showed that the proposed resource allocation method had a better performance than the traditional strategy.

Model of Rotation Accuracy of High-Speed Spindles on Ball Bearings

For the purpose to improve a design quality of high-speed spindle units, we have developed mathematical models and software to simulate a rotation accuracy of spindles running on ball bearings. In order to better understand the mechanics of ball bearings, the dynamic interaction of ball bearings and spindle unit, and the influence of the bearing imperfections on the spindle rotation accuracy, we have carried out computer aided analysis and experimental studies. When doing this, we have found that the spindle rotation accuracy can vary drastically with rotational speed. The influence of bearing preload has a secondary importance. Comparison of the results of these studies has demonstrated adequacy of the models developed to the real spindle units.

High-Speed EMU TCMS Design and LCC Technology Research

This paper introduces the high-speed electrical multiple unit （EMO） life cycle, including the design, manufacturing, testing, and maintenance stages. It also presents the train control and monitoring system （TCMS） software development platform, the TCMS testing and verification bench, the EMU driving simulation platform, and the EMU remote data transmittal and maintenance platform. All these platforms and benches combined together make up the EMU life cycle cost （LCC） system. Each platform facilitates EMU LCC management and is an important part of the system.

BOUNDEDNESS FROM BELOW OF MULTIPLICATION OPERATORS BETWEEN α-BLOCH SPACES ON THE UNIT BALL

In this article, we characterize the boundedness from below of multiplication operators between α-Bloch spaces on the unit ball.

A passive optical network based on optical code division multiplexing and time division multiple access technology

A passive optical network （PON） scheme based on optical code division multiplexing （OCDM） for the downstream traffics is proposed and analyzed in detail. In the PON, the downstream traffics are broadcasted by OCDM technology to guarantee the security, while the upstream traffics pass through the same optical fiber by the common time division multiple access （TDMA） technology to decrease the cost. This schemes are denoted as OCDM/TDMA-PON, which can be applied to an optical access network （OAN） with full services on demand, such as Internet protocol, video on demand, tele-presence and high quality audio. The proposed OCDM/TDMA-PON scheme combines advantages of PON, TDMA, and OCDM technology. Simulation results indicate that the designed scheme improves the OAN performance, and enhances flexibility and scalability of the system.

Models for Ordering Multiple Products Subject to Multiple Constraints, Quantity and Freight Discounts

One of the most important responsibilities of a supply chain manager is to decide “how much” (or “many”) of inventory items to order and how to transport them. This paper presents four mixed-integer linear programming models to help supply chain managers make these decisions for multiple products subject to multiple constraints when suppliers offer quantity discounts and shippers offer freight discounts. Each model deals with one of the possible combinations of all-units, incremental quantity discounts, all-weight and incremental freight discounts. The models are based on a piecewise linear approximation of the number of orders function. They allow any number of linear constraints and determine if independent or common (fixed) cycle ordering has a lower total cost. Results of computational experiments on an example problem are also presented.

Investigations on lubrication characteristics of high-speed electric multiple unit gearbox by oil volume adjusting device

In this paper,a numerical simulation model of the flow field in a gearbox with an oil volume adjusting device is established for the first time to study its influence on the lubrication characteristics of a high-speed electric multiple unit(EMU)gearbox.The moving particle semi-implicit(MPS)method is used to numerically simulate the internal flow field of the gearbox of the high-speed EMU under working conditions.The effects of the velocity of the high-speed EMU,the immersion depth,and the oil sump temperature on the power loss of the gears and the lubricant quantity of each bearing are studied and provide an effective tool for the quantitative evaluation of the lubrication characteristics of the gearbox.The lubrication characteristics of the gearbox under different working conditions are studied when the oil volume adjusting device is closed and opened.The results show that the oil volume adjusting device mainly changes the amount of lubricant stirred by the output gear by changing the flow rate of lubricant from the cavity pinion(Cavity P)to the cavity gear(Cavity G),and thus affects the power loss of gears and the lubricant quantity of each bearing.

电力动车组变刚度转臂节点的半主动控制

为抑制电力动车组运行中由异常轮轨匹配产生的车体晃动,提出一种采用半主动转臂节点代替被动式转臂节点的解决方法。设计了具有两级刚度特性的半主动转臂节点并建立其力学模型,推导了具有可变惯性通道的半主动转臂节点复刚度表达式,并通过台架试验验证了力学模型的准确性。基于半主动转臂节点控制策略,建立了半主动转臂节点与车辆动力学的联合仿真模型,分析了不同轮轨匹配状态下半主动转臂节点对车辆动力学性能的影响。结果表明:在低等效锥度轮轨匹配状态下,半主动转臂节点能有效衰减一次蛇行对应速度区间内车体大幅值、低频的横向振动,显著减小车体横向加速度主频处的幅值;正常轮轨匹配状态下,与搭载传统被动转臂节点的车辆相比,搭载半主动转臂节点的车辆有更优的曲线通过能力和更高的临界速度。

Study on Dynamic Characteristics of Hydraulic Pumping Unit on Offshore Platform

A new technology of offshore oil rod pumping production is developed for offshore heavy oil recovery. A new type of miniature hydraulic pumping unit with long-stroke, low pumping speed and compact structure is designed based on the spatial characteristics of offshore platforms. By combining the strengths of sinusoidal velocity curve and trapezoidal velocity curve, a kinematical model of the acceleration, the velocity and displacement of the pumping unit＇s hanging point is established. The results show that the pumping unit has good kinematic characteristics of smooth motion and small dynamic load. The multi-degree-of-freedom dynamic model of the single-well pumping unit is established. The first and second order natural frequencies of the sucker rod string subsystem and the pumping unit subsystem are studied. The results show that the first and the second order natural frequencies among the pumping rod string, pumping unit-platform subsystem and the dynamic excitation have differences over 5 times from each other, indicating that resonance phenomenon will not appear during the operation and the dynamic requirements for field use are met in the system.

High-speed and high-performance polarization-based quantum key distribution system without side channel effects caused by multiple lasers

Side channel effects such as temporal disparity and intensity fluctuation of the photon pulses caused by random bit generation with multiple laser diodes in high-speed polarization-based BB84 quantum key distribution(QKD) systems can be eliminated by increasing the DC bias current condition. However, background photons caused by the spontaneous emission process under high DC bias current degrade the performance of QKD systems. In this study, we investigated the effects of spontaneously emitted photons on the system performance in a high-speed QKD system at a clock rate of 400 MHz. Also, we show further improvements in the system performance without side channel effects by utilizing the temporal filtering technique with real-time fieldprogrammable gate array signal processing.

A Numerical Prediction of Tip Vortices from Tandem Propellers in the Counter-Rotating Type Tidal Stream Power Unit

Ocean energy has a potential of providing a large amount of renewable energy around the world. One of the forms of ocean energy, tidal stream power is widely recognized as the continuous, predictable and eco-friendly ocean energy source. Unique tandem propellers that can counter-rotate have been designed to generate electric power effectively from a tidal stream. This type of power unit has several advantages compare to the conventional unit with a single propeller. At the design of the tidal stream power unit, it is important to investigate the structure of the tip vortex tubes shedding to predict the load of the propeller. In this research, we investigated the tip vortex shedding using the CFD method for the conventional single propeller and counter-rotating type tandem propellers and estimated the performance efficiency using RANS (Reynolds Averaged Navier-Stokes) model and we confirmed the limitation of RANS model on the calculation of the tip vortex stretching.

英国大型阅读推广项目多元协作模式解析

“多元协作”组织实施模式是英国大型阅读推广项目得以成功开展的主要因素之一。政府、社会组织、公共图书馆、企业、公众等多元主体以不同角色和作用结成协作关系及协作网络,形成了特色而有效的协作机制。该模式具有跨界协作、伙伴关系、双核心、专业性、广泛性和适应性等特点及优势,但也存在松散性和不稳定性的潜在问题。我国可从创新和改进政府引导扶持方式、树立公共图书馆多元协作“核心”地位、主动吸纳社会资金并充分利用社会资源、推动跨领域协作、确立规范稳定的协作机制等方面对其经验加以借鉴。

配置吸收式热泵的热电联产机组厂级智能运行优化

为提高配置吸收式热泵的热电联产机组的全厂运行经济性,基于案例电厂的运行历史数据,使用滑动窗口法进行数据预处理并提取稳态工况,建立配置吸收式热泵的热电联产机组煤耗预测数学模型。以全厂热电联产机组总煤耗最小为适应度函数,利用粒子群优化算法求解得出配置吸收式热泵的热电机组最佳背压和各台热电机组最佳抽汽量。基于以上研究设计了供热系统智能优化软件,实现供热系统在线监测与优化调节,对各供热单元分别提出优化指导,使机组运行经济性最佳,进而降低整体煤耗。计算结果表明:实行供热系统智能优化策略可为案例电厂供热系统平均每小时节省标准煤约1.81 t,节能效果显著。

车端侧滚减振装置对高速双层动车组动力学性能的影响分析

双层动车组设置较大的二系横向阻尼来抑制一次蛇行引起的共振,而较大的二系横向阻尼会使车辆的横向平稳性变差。针对某型高速双层动车组横向平稳性差的问题,基于车端侧滚减振装置的工作原理建立了车端侧滚减振装置在车体滚摆和摇头运动状态下的数学模型,并将AMEsim软件中建立的减振器仿真模型与台架试验进行验证。最后通过建立车端侧滚减振装置与被试车辆的联合仿真模型,在不改变车辆现有悬挂参数的基础上对车端侧滚减振装置的关键参数进行优化选取。仿真结果表明,车端侧滚减振装置可以在不影响车辆垂向平稳性、保证曲线运行安全性的前提下有效改善双层动车组的横向平稳性。