Inductance and Current Distribution Analysis of a Prototype HTS Cable

Cooling of the long HTS power transmission lines performs by pumping of subcooled liquid nitrogen (LN2) along the cable. The temperature of LN2 along the cable increases due to the heat losses of the cryostat and heat generation in the HTS cable. The experiment using test cable line in Ishikari shows that flow rate of 35 L/min retains increasing of LN2 temperature by 1 K per 1 km of length. The technology when the back flow of LN2 cools the radiation shield surrounding the cable pipe is also applied in Ishikari-2 project. In this case the ambient heat flow into cable pipe is 50 times less than that without radiation shield. Back flow of LN2 removes almost all heat coming from the environment. When transport current is close to the critical value the Joule heat of HTS cable is significant. This heat additionally increases the temperature of LN2 flowing along the HTS cable. Near the outlet the temperature of HTS cable is maximal and the local critical current is minimal. The current matching critical current criterion of average electrical field of E0 = 10−4 V/m provides the voltage drop and significant Joule heat at the hot end of the cable. It can lead the damage of the cable. The present work contains analysis of temperature distribution along the cable and the way to achieve the fail-safe operation of long HTS cable cooled by subcooled LN2. We also performed extrapolation of obtained results for several times longer cable lines by decreasing the LN2 flow rate.

Development of HTS power cable using YBCO coated conductor

Current redistribution in carpet-stack cables made from 2nd generation HTS tapes is investigated. In the carpet stack geometry tapes are stacked with their broad faces parallel to each other to build up a cable. Current redistribution in HTS cables is complex because the built-in insulation layer in each tape prevents effective current transfer between tapes. A method of shunting the tapes using periodically distributed superconducting bridges is investigated to improve current transfer, avoiding the need to solder the cable together. We calculate the mutual inductance between different tapes in a cable, and the effective resistance/transconductance for representative cable configurations. The effective time constants for current transfer and current redistribution are then calculated under different assumptions. We show that periodic shunting of the tapes using distributed superconducting bridges is an attractive method to achieve uniform current distribution in a HTS cable. The solution is flexible, and the performance of the system can be optimized by changing the width of shunt and/or the distance between shunts.

In the calibration process of industrial robots, selecting the optimal measurement position configuration can improve calibration accuracy. However, existing research on the optimal measurement configurations selection mainly focuses on open-loop measurement methods using laser trackers. The exploration of the optimal measurement configuration selection for closed-loop measurement methods has not been developed to a large extent. This research introduces a measurement configurations selection observability index based on the position difference error equation, as well as an optimization method based on this index. Initially, we establish an error model for the kinematic parameters of industrial robots, which is based on the position difference of measurement configurations. Subsequently, by minimizing the relative error of the measurement, we proposed an observability index, denoted as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{O}_{\boldsymbol{e}}$</tex-math></inline-formula>. Using this index, construct a fitness function and use particle swarm optimization (PSO) algorithm to optimize the selection of robot measurement configuration set. The effectiveness of the proposed optimization method has been demonstrated through experiments conducted on CRP RA07 and JAKA Zu seven robots. The experimental results show that using the observability index <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{O}_{\boldsymbol{e}}$</tex-math></inline-formula> to select the optimal configuration set can improve the calibration accuracy of the robot by 25.8% and 37.0%, respectively. The verification experiment using a laser tracker confirms that our optimal configuration set selection method can effectively improve calibration accuracy. This research fills the gap in the selection of optimal measurement configurations for constrained measurement. It is of great significance for field calibration research of robots.

In optimal design of a permanent magnet (PM) motor, many design variables are required to consider some device properties. These variables are, for example, the shape of core and magnet, the tooth length, the number of turns, and the winding radius. Moreover, many restrictions must be considered in practical PM motor design. These restrictions are, for example, the slot space factor and the cogging torque. However, the optimization problem, which has many design variables by the finite element method (FEM), has not been reported. In this paper, the efficiency of PM motor under the considerations given above is optimized by using FEM and optimization algorithm. In this problem, an objective function has many local minima and it is difficult to calculate its gradient. For these reasons, the genetic algorithm (GA) and simulated annealing method (SA), which are stochastic methods, are used for optimization method, because of the possibility of global range search and because gradient calculation is not required. Adding to both optimization methods, in this paper, SA combined with GA is used for one of the optimization methods. It is found that the solutions optimized by these methods are reasonable from an engineering point of view. © 2001 Scripta Technica, Electr Eng Jpn, 138(3): 72–79, 2002

This paper designs and optimizes a new structure hybrid material B‐pillar assembly. Establish a finite element analysis model for the side impact test of an electric vehicle to verify the model's accuracy. Construct a finite element model of the hybrid material B‐pillar assembly. Combined with the static performance analysis of the B‐pillar, the laminate design of the carbon fiber composite B‐pillar reinforcement plate and optimization. For the outer and inner panels of the B‐pillar, the surrogate model method and the multiobjective optimization method are combined to set 11 design variables and 13 responses. The optimal Latin hypercube design method was used to randomly sample each design variable and fit the radial basis function (RBF) approximate model. The modified second‐generation non‐dominated sorting genetic algorithm (MNSGA‐II) was used to carry out multiobjective optimization of the mixed material B‐pillar assembly, and the multicriteria decision‐making method was used to obtain the optimal solution for the Pareto solution set. A drop weight impact test was performed on the hybrid material B‐pillar assembly. The results showed that the peak collision force of the hybrid material B‐pillar was reduced by 43.7% compared with the original steel B‐pillar, the specific energy absorption was increased by 17.5%, and the side impact safety performance was better. After optimization, the weight of the mixed material B‐column was reduced by 26.44%. The improvement rates of the intrusion amount at P2 and the intrusion speed at P1 were 23.99% and 0.63%, respectively, and the lightweight effect and side impact safety were significantly improved.Highlights The finite element analysis parameters of carbon fiber composite materials were constructed through experiments, and the basis for simulation analysis under various working conditions of the B‐pillar based on performance‐driven optimization was established. A hybrid material B‐pillar design method is proposed, which consists of a variable‐thickness high‐strength steel B‐pillar outer plate, a variable‐thickness high‐strength steel B‐pillar inner plate, and a carbon fiber composite B‐pillar reinforcement plate. The super layer of the carbon fiber composite B‐pillar reinforcement plate was optimized and the laying plan of the carbon fiber composite B‐pillar reinforcement plate was determined. Performance‐driven optimization is adopted to realize the collaboration of multilevel design and optimization methods such as B‐pillar conceptual design, detailed design, and multiobjective optimization. A modified NSGA‐II algorithm was proposed and combined with the multicriteria decision‐making method and the entropy‐weighted gray relation analysis method to determine the Pareto optimal solution and the optimal design scheme for the mixed material B‐pillar.

The paper discusses optimization methods that are based on processes occurring in nature. Suchmethods have become increasingly used to solve complex problems. However, such methods have somedrawbacks, which stimulates the development of new and more advanced optimization methods. SolvingNP complete problems requires optimal methods that will meet all design requirements, so there is aneed to develop new and more advanced methods for solving this class of problems. As such a method,the authors propose an optimization method based on a model of the behavior of stem cells in the naturalenvironment. The conducted studies of the proposed method provide solutions that can overcomemany of the shortcomings of standard optimization approaches, such as getting into the local optimumor low convergence rate of the algorithm based on the method under consideration. The purpose of thiswork is to develop an optimization method and an algorithm based on it for solving a complex objectivefunction. The scientific novelty lies in the development of an optimization method based on the stem cellbehavior model for solving NP complete problems. The aim of the work is to create conditions for theoptimal search for a solution to complex functions by applying the search method and, based on it, analgorithm for the behavior of stem cells. The practical value of the work lies in the development of a newmetaheuristic optimization method for the efficient solution of NP complete problems. Also in the work,a comparative analysis with well-known competitors was carried out. The main difference of the proposedmethod from other known methods is the use of a new approach of bioinspired search based onthe behavior of stem cells, which, as shown by practical comparison, has an advantage over knownanalogues. The results of a practical comparison of methods and algorithms based on them showed theadvantages of the approach proposed in the work on known test functions. After analyzing the problemof creating methods, algorithms and software for solving NP complete problems, we can conclude thatthe development of such approaches is currently an urgent task.

Construction and optimization methods of spherical hexagonal–pentagonal geodesic grids are investigated. The objective is to compare grid structures on common ground. The distinction between two types of hexagonal–pentagonal grids is made. Three conventional grid optimization methods are summarized. In addition, three new optimization methods are proposed. Six desirable conditions for an ideal grid are described, and the grid optimization methods are organized in view of such conditions. Interval uniformity, area uniformity, isotropy, and bisection of cell faces are systematically investigated for optimized grids. There are compensations of preferable grid features in each optimization method, and an optimal method cannot be decided based only on the research of grid features. It is suggested that grid optimization methods should be selected based on research of numerical schemes.

The limited availability of the recorded rainfall-runoff data for many watersheds restricts the development and management of different activities of water resources. To overcome this limitation, the Natural Resources Conservation Service (NRCS) for estimating storm excess rainfall and momentum and optimization methods were combined in a mathematical model to estimate the optimal parameters of Nash Instantaneous unit hydrograph (IUH) and resulting direct runoff hydrograph (DRH), using a developed computer program in MATLAB. The available recorded data of 14 storms (out of 18) of four watersheds in northern Iraq have been applied in the calibration stage. An empirical relationship was developed between the average of each IUH optimal parameter (obtained by optimization as an optimal method according to the applied tests) and the effective watershed topographical characteristics. The developed empirical relations were used in the verification stage to estimate the IUH parameters and DRH for the verification storms and compare with that resulted from Haan’s empirical relations and optimization method. The statistical tests showed that the developed empirical relations efficiency was better than that of Haan’s method and close to that of the recorded storm by optimization method, where the average value of the Nash-Sutcliffe Efficiency for the four watersheds resulted from applying the optimization method, Haan’s method and the developed empirical relations were 0.925, 0.587, 0.883 respectively. The results indicated the developed model’s ability to estimate the IUH and direct runoff hydrograph for ungauged watersheds in northern Iraq.

We have developed a measurement method to evaluate the current distributions in several HTS tapes arranged in parallel. In this method, the current distributions are indirectly found from the results of the field distributions measured by a pickup coil located around the upper surface of the sample tapes. To confirm the accuracy and sensitivity of this method, current distributions in a test conductor made of three copper tapes are measured. Numerical and measured current distributions are compared, and it is found that our method is accurate enough to measure the current distributions in HTS tapes. Using this method, we measured the current distributions in Bi-2223 tapes arranged in parallel at room temperature and 77 K. The comparison between the experimental and numerical results shows a good agreement. On the basis of the obtained results, the characteristics of the AC current distributions in the HTS tapes are discussed.

Turnpike Sets in Manufacturing Systems: Some Recent Progress

Micro, Small, and Medium Enterprises (MSMEs) in the food and beverage sector is one of the sectors negatively affected by the COVID-19 outbreak, even though this sector is one of the largest contributors to the Gross Domestic Product of the non-oil and gas industry in Indonesia. This study intends to provide an overview of solutions in the form of case studies on the Mahkota Caman MSME in Bekasi, Indonesia, which experienced a decline in sales during the pandemic, resulting in overstock and damage to non-durable raw materials. As a result, it leads to an increase in inventory costs and even a loss of sales. The solution offered by this study is an optimization of production planning, namely determining what products and how many of these products should be produced in a certain period. The method used is goal programming, both with and without priority, so that Mahkota Caman can meet consumer demands, and minimize production costs, while minimizing the purchase of raw materials. The results of this study indicate that the optimal optimization method used by Mahkota Caman is goal programming with priority because it provides a more efficient solution to production costs and the purchase of raw materials. Based on the results of this study, it is recommended that optimization methods be used by MSMEs in the food and beverage sector during a pandemic, and to avoid using only feeling in production planning.

An optimal calculation method for the mechanical properties of near-space capsule materials was proposed. First, biaxial tensile tests under low tensile ratios were carried out on the envelope materials of a near-space airship. The experimental results showed that the values of the elastic modulus and Poisson’s ratio, which are significantly affected by the warp and weft stresses, were not constant. Second, the elastic modulus and Poisson’s ratio of the near-space airship were obtained by using the traditional calculation method, and the limitations of this method were discussed. Third, an optimal calculation model for the elastic modulus and Poisson’s ratio of airship envelopes was proposed. The strain calculated by the proposed optimization model could be effectively correlated to the strain measured by the experiment. Then, through the user-defined subroutine of the finite element method and the elastic modulus and Poisson’s ratio calculated by the proposed optimization, the strain of the finite element simulation was obtained. The average error between the simulation results and the experimental values was approximately 8.21% (warp) and 8.41% (weft). The proposed method can consider the nonlinear changes of the elastic modulus and Poisson’s ratio of membrane material under different stress ratios and predict the force and deformation of the airship’s capsule more accurately, which is adaptable to engineering applications.

With the development of the magnetic bearing (MB) and its application in industry, the demands of high-speed MB are developing, which bring up new problems and requirement for the design. The motor with a high-speed rigid rotor requires that the axial length of MB is minimized to increase the critical speed, and the diameter of thrust disk is minimized to reduce the air friction loss. Also because of the high speed, the eddy currents induced in the iron cores have a significant influence on the dynamic characteristics of the MB. To design a high-performance MB for a high-speed motor, first an MB structure that has the feature of short axial length and small thrust disk is recommended for the high-speed motor. Next, the dynamic model, which takes into consideration eddy current effects, and leakage effects is developed. Then, an optimal design method with multiobjective of minimum length and air friction loss is presented. Design constraints are imposed, which includes the simultaneous consideration of material properties, load capacity, and power amplifier. Finally, a design example is given and a prototype is manufactured. The experimental results demonstrate that the proposed MB structure and the optimization method are feasible and valid in the application of a high-speed motor.

In order to solve problems of global warming and depletion of energy resource, renewable energy systems such as wind generation is getting attention. This paper describes an optimal operation method to introduce the wind power forecasted data of the wind turbine generators (WTG). Moreover, the wind power forecasted data is considered its forecast error. The optimization purpose is to smooth the output power fluctuation of the wind farm (WF) and to obtain more benefit for electrical power selling. In the optimization of operation planning of WF, tabu search is used as the optimization method.