Two-Dimensional Mathematical Model of Tidal Current and Sediment for Oujiang Estuary and Wenzhou Bay

A 2-D mathematical model of tidal current and sediment has been developed for the Oujiang Estuary and the Wenzhou Bay. This model accomodates complicated features including multiple islands, existence of turbidity, and significant differ-ence in size distribution of bed material. The governing equations for non-uniform suspended load and bed load transport are presented in a boundary-fitted orthogonal curvilinear coordinate system. The numerical solution procedures along with their initial conditions, boundary conditions, and movable boundary technique are presented. Strategies for computation of the critical condition of deposition or erosion, sediment transport capacity, non-uniform bed load discharge, etc. are suggested. The model verification computation shows that, the tidal levels computed from the model are in good agreement with the field data at the 18 tidal gauge stations. The computed velocities and flow directions also agree well with the values measured along the totally 52 synchronously observed verticals distributed over 8 cross sections. The coraputed tidal water throughputs through the Huangda'ao cross section are close to the measured data. And the computed values of bed deformation from Yangfushan to the estuary outfall and in the outer-sea area are in good agreement with the data observed from 1986 to 1992. The changes of tidal volumes through the estuary, velocities in different channels and the bed form due to the influence of the reclamation project on the Wenzhou shoal are predicted by means of this model.

A 2D Mathematical Model for Sediment Transport by Waves and Tidal Currents

In this study, the combined actions of waves and tidal currents in estuarine and coastal areas are considered and a 2D mathematical model for sediment transport by waves and tidal currents has been established in orthogonal curvilinear coordinates. Non-equilibrium transport equations of suspended load and bed load are used in the model. The concept of background concentration is introduced, and the formula of sediment transport capacity of tidal currents for the Oujiang River estuary is obtained. The Dou Guoren formula is employed for the sediment transport capacity of waves. Sediment transport capacity in the form of mud and the intensity of back silting are calculated by use of Luo Zaosen＇ s formula. The calculated tidal stages are in good agreement with the field data, and the calculated velocities and flow directions of 46 vertical lines for 8 cross sections are also in good agreement with the measured data. On such a basis, simulations of back silting after excavation of the waterway with a sand bar under complicated boundary conditions in the navigation channel induced by suspended load, bed load and mud by waves and tidal currents are discussed.

ESTABLISHMENT AND VERIFICATION OF MATHEMATICAL MODEL FOR CURRENT LEAKAGE IN BIPOLAR MULTI－COMPARTMENT CELL

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Computation of Wave, Tide and Wind Current for the South China Sea Under Tropical Cyclones

Based on the third-generation oceanic wave prediction model (WAVEWATCH (.) III) the third-generation nearshore wave calculation model (SWAN) and the mathematical tide, tidal current and cyclone current model, which have been improved, interconnected and expanded, a coupled model of offshore wave, tide and sea current under tropical cyclone surges in the South China Sea has been established. The coupled model is driven by the tropical cyclone field containing the background wind field. In order to test the hindcasting effect of the mathematical model, a comparison has been made between the calculated results and the observational results of waves of 15 cyclone cases, water levels and current velocities of the of 7 cyclones. The results of verification indicate that the calculated and observed results are basically identical.

MATHEMATICAL MODEL FOR CONTINUOUS DETECTION OF CURRENT EFFICIENCY IN ALUMINUM PRODUCTION

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CALCULATION OF TWO-DIMENSIONAL TIDAL CURRENT AND ANALYSES OF EROSION AND SILTATION IN BEILUN HARBOR

ADI method is adopted to establish a two-dimensional tidal current numerical model for Beilun Harbor based on the hydrologic data and sediment data. The current conditions of the site where the second stage project is going to be carried out are described. The analysis and calculations for the deposition and erosion in the harbor basin are performed, which provides references for the construction of the harbor. The effect of the pile group on the current is simulated by increasing the sea bed roughness which can be determined with empirical equations of artificial roughness. The method is considered to be applicable after verification with field data. The test has provided experiences for future mathematical modelling to simulate the open type hydraulic structures.

Two-Dimensional Lithium-Ion Battery Modeling with Electrolyte and Cathode Extensions

A two-dimensional model for transport and the coupled electric field is applied to simulate a charging lithium-ion cell and investigate the effects of lithium concentration gradients within electrodes on cell performance. The lithium concentration gradients within electrodes are affected by the cell geometry. Two different geometries are investigated: extending the length of the electrolyte past the edges of the electrodes and extending the length of the cathode past the edge of the anode. It is found that the electrolyte extension has little impact on the behavior of the electrodes, although it does increase the effective conductivity of the electrolyte in the edge region. However, the extension of the cathode past the edge of the anode, and the possibility for electrochemical reactions on the flooded electrode edges, are both found to impact the concentration gradients of lithium in electrodes and the current distribution within the electrolyte during charging. It is found that concentration gradients of lithium within electrodes may have stronger impacts on electrolytic current distributions, depending on the level of completeness of cell charge. This is because very different gradients of electric potential are expected from similar electrode gradients of lithium concentrations at different levels of cell charge, especially for the LixC6 cathode investigated in this study. This leads to the prediction of significant electric potential gradients along the electrolyte length during early cell charging, and a reduced risk of lithium deposition on the cathode edge during later cell charging, as seen experimentally by others.

Experimental and Numerical Study of Wave-Induced Long-Shore Currents on A Mild Slope Beach

The long-shore current distribution on a mild slope beach is studied by combining the numerical model and the physical experiment. The experiments of long-shore currents under the action of regular and irregular waves are conducted on mild beaches with different slopes in a wave basin. A numerical model is established, which includes a wave propagation model, a wave breaking model and a long-shore current model. The validity of the numerical model is proved by the comparison of its results with the results of the experimental model. It is concluded that the wave-ioduced long-shore current is influenced significantly by the incident wave height, the wave angle and the beach slope. Its application to the Bohai Bay indicates that the wave-induced currents have the same order of magnitude as the tide currents in the near-shore zone of mill slope beach. In the design of wastewater ouffall locations on a mild-slope beach with shallow water of the Bohai Bay, the position of the outfall should be 10 km away from the shoreline, which is outside of the surf-zone.

Three-dimensional tidal current numerical model of the Oujiang Estuary

The characteristics of three-dimensional （3-D） tidal current in the Oujiang Estuary are investigated according to in situ observations. The Oujiang Estuary has features of irregular coastline, complex topography, many islands, moveable boundary, and submerged dyke, therefore, σ 3-D numerical model oil an unstructured triangular grid has been degeloped. The σ coordinate transforination, the moveable boundary and submerged dyke treatment techniques were employed in the model so it is suitable for the tidal simulations in the Oujing Estuary with submerged dyke and moveable boundary problems. The model is evaluated with the in situ data, and the results show that the calculated water elevations at 19 stations and currents at 19 profiler stations are in good agreement with measured data both in magnitude and phase. This numerical model is applied to the 3-D tidal circulation simulations of experiments in stopping flow transport through the South Branch of the Oujiang Estuary, and the feasibility to cutoff the flow in the South Branch of the Oujiang Estuary is demonstrated by numerical simulation experiments. The developed numerical model simulated the 3-D tidal current circulations in complicated coastal and estuarine waters very well.

Mathematical model analysis of new-type magnetic integrated CRT considering magnetic leakage

A novel magnetic integrated controllable reactor of transformer type(CRT)has the advantages of simple structure,flexible assembly,convenient maintenance and practicability.To analyze its operation characteristics accurately,we establish corresponding equivalent mathematical model considering magnetic leakage based on magnetic circuit and circuit dualistic transformation method.The distribution of magnetic leakage field of each winding is analyzed qualitatively,and the analytical calculation formulas of magnetizing inductance and leakage inductance of each winding are derived.Based on this,the analytical calculation formulas of short-circuit impedance and winding current of CRT under different working conditions are derived.The field-circuit coupling finite element model of the magnetic integrated CRT is established to simulate the current of each winding under different working conditions.The results show that the analytical calculation results of each winding current have good consistency with the finite element calculation results,indicating the validity of CRT equivalent mathematical model and correctness of the analytical formulas of leakage inductance,short-circuit impedance and winding current of CRT.The working winding current of CRT is increasing gradually with the operation of control winding in turn to realise the transition of CRT compensation capacity from zero to a rated value.

Modeling of Residential Photovoltaic (PV) System Connected to Low Voltage (LV) Network: Application to Public Distribution Network of Burkina Faso

Residential photovoltaic (PV) systems connected to the grid are used for self-consumption. Any surplus production is fed into the grid and contributes to improving the voltage. Several techniques are developed to model their connection. However, studies on methods of injecting energy production into the Low Voltage (LV) network are nowadays a problem. This paper proposes a mathematical model to determine the current to be injected and calculate each node’s voltage. The current equation is a recurrence relation with an initial condition. This initial condition is for the case of a single PV system connected to the LV grid. The equation can also be written in matrix form. Similarly, the voltage solution is a recurrence relation. It also has an initial condition for the first node. Both mathematical formulae with the proposed initial conditions are consistent and can be used for the determination of the current and voltage of the different nodes in the grid.

NUMERICAL SIMULATION OF A MATHEMATICAL MODEL FOR WAVE PROPAGATION ON NON-UNIFORM CURRENT AND DEPTH

A water wave evolution equation is developed from the combinedrefraction-diffraction equation on non-uniform current in water of slowly varying topography byusing the perturbation method. A numerical model is presented with the governing equationdiscretized with an improved Alternating Direction Impicit (ADI) method involving a relaxationfactor which can improve convergent rate. The calculation results show that the model caneffectively reflect the effects of current on wave propagation.

Test Study on Current Force on Mooring Ships

In respect of an offshore berthing pillar, the test study result of current force acting on mooring ships is described in this paper. Empirical and semi-empirical relationships of current force coefficient are given according to the angle between the flow direction and the ship's longitudinal axis, which are coincident with the result of theoretical analysis.

Research on Long Stroke Moving Secondary Permanent Magnet Linear Eddy Current Brake

In this paper,a long stroke moving secondary permanent magnet linear eddy current brake is proposed.Without exciting coils,the permanent magnet eddy current brake possesses the advantage of saving copper and better reliability.The topology and operating principle are presented.The mathematical model was derived with the layer theory.The braking force characteristic was analyzed using the finite element method.The structural parameters of the long stroke moving secondary permanent magnet linear eddy current brake were studied by referring the design progress of the other types of eddy current brakes.Finally,a prototype of long stroke moving secondary permanent magnet linear eddy current brake was built and tested,and the experimental result verifies the correctness of the above analysis.

Current Sharing Technology in Transmission Conductors of Cold Dielectric High Temperature Superconducting Cables Using Second-generation HTS Wires

冷绝缘高温超导电缆的导电层一般设计为多层结构以满足大电流载流特性，但伴随层数的增加，超导体上的集肤效应会引起电缆输电导体各层电流分布不均匀的问题，从而造成电缆损耗增加和传输性能下降。采用基于动态惯性权重因子的粒子群优化算法，提出了电缆导体层电流层间均流优化的设计方法。应用第2代高温超导材料钇钡铜氧涂层导体，通过建立超导电缆的等效电路模型，考虑电场、磁场等约束因素，对一根1km长，110kV／3kA等级的冷绝缘高温超导电缆进行优化设计，获得了电缆本体结构参数及输电导体层和屏蔽层的电流分布。比较优化前后层电流的结果可知，优化后超导电缆各导体层电流与平均电流相比最大不平衡率小于3．5％，各屏蔽层电流达到均布，较好地实现了电缆各导体层电流均匀分布的优化目标。最后，超导模型样缆载流特性实验也验证了优化设计方法的有效性。

EFFECT OF FUTURE SEA LEVEL RISE ON DISASTROUS FLOODS IN THE TAIHU LAKE LOWER REACH DEPRESSIONS AND COUNTERMEASURES

Use of numerical simulation of the tidal flow of the Changjiang River Estuary and the HuangpuRiver to forecast flood in the Taihu Lake lower reach drainage system for the case of future sea level riseof 0.4 m and 0.8 m,and floods preventing and reducing methods are discussed in this paper.

Study on Factors Effecting Weld Pool Geometry of Pulsed Current Micro Plasma Arc Welded AISI 304L Austenitic Stainless Steel Sheets Using Statistical Approach

Pulsed current Micro Plasma Arc Welding is used to joint thin sheets of AISI 304L sheets, which are used in manufacturing of metallic bellows and diaphragms. In this article the effects of pulsing current parameters on weld pool geometry namely front width, back width, front height and back height of pulsed current micro plasma arc welded AISI 304L stainless steel sheets was analyzed. Four factors, five levels, central composite design was used to develop mathematical models, incorporating pulsed current parameters and weld pool geometry. The mathematical models have been developed by Response Surface Method. The adequacy of the models was checked by ANOVA technique. Variation of output responses with input process variables are discussed. By using the developed mathematical models, weld pool geometry parameters can be predicted.

The Application of the Fault Current Limiters in Power Distribution System

In this paper, an application of fault current limiter-thyristor controller series reactor （FCL-TCSR） in the distribution network is presented in order to minimize the peak value of current during the fault condition. This application considers a single fault current limiting action but can also be applied for a three phase system. The maximum contribution of FCL-TCSR quickly clears the abnormal current in the power distribution system when a fault condition occurs. Using a mathematical model of FCL-TCSR, the impact of series impedance used to adjust the amplitude of the fault current action is demonstrated. The performance of the load with the impedance and load in series is also analyzed.

岱山—洋山跨海通道水沙环境影响数值模拟研究

杭州湾是世界闻名的强潮河口,具有不规则的岸线边界、独特的地形地貌特征和复杂的水动力泥沙环境。岱山—洋山跨海通道位于杭州湾湾口水域,将岱山与洋山近35km连通,实现了上海—洋山—岱山—舟山—宁波跨海通道的全线贯通,其建设具有非常重要的意义。基于考虑波浪作用的潮流泥沙数值模型,讨论了岱山—洋山跨海通道几种工况对杭州湾大范围海域水沙环境的影响。研究结果表明:跨海通道实施后潮位变化在大桥轴线附近较为敏感,远离则基本没有影响,高低潮位变化幅度大多在2 cm以内。杭州湾涨落潮量减小小于0.6%。水流流态和水下地形仅在大桥附近水域存在明显变化。从对杭州湾水沙环境影响角度考虑,岱山—洋山跨海通道几种工况均可行,建议关注桥墩和人工岛附近的局部冲刷问题。

基于参数扰动估计的双三相永磁同步电机鲁棒模型预测控制

双三相永磁同步电机因其损耗小、效率高、容错能力强等特点,广泛应用于航空航天技术、电动汽车等领域。为优化双三相永磁同步电机控制性能,采用双d-q坐标变换对双三相永磁同步电机进行数学建模,为减小电流纹波,在传统模型预测电流控制策略基础上,增加延时补偿;考虑电机参数扰动的影响,提出一种能够对参数进行在线估计的滑模观测器,以提高控制系统鲁棒性,最后在MATLAB/Simulink中进行系统抗负载扰动与鲁棒性能仿真分析。仿真结果表明,改进后的控制策略提高了电机的响应速度,超调减小,系统对电机参数扰动的敏感性减弱,系统抗负载能力和鲁棒性增强。