Energy modeling with an objective function targeting the entire power supply system can determine a power supply mix for a high share of variable renewable energy (VRE) electricity in the power supply. However, actual power supply systems are developed by the partial optimization of the various components of the entire system, such as the power transmission and distribution (PTD) company. This study aims to determine the effective electricity price conditions for the optimal utilization of geographically distributed VRE power by the PTD company. The analysis method used is an optimization model with an objective function targeting the PTD company cost. The optimization model minimizes the PTD company cost, which includes the costs of electricity purchase and installation of battery storage and transmission systems. The methodology is applied to the power supply system of Hokkaido as a case study. The results show that the amount of VRE electricity utilized by the PTD company depends on the electricity prices from thermal and VRE power generation companies. Increasing the VRE share of the power supply requires higher electricity prices from thermal power. The higher shares of VRE require increases in battery storage and power transmission capacities to minimize the VRE power output fluctuations. Further, the results show that the price difference between thermal and VRE electricity prices is a key factor to determine the VRE utilization by the PTD company. A larger price difference is necessary for the PTD company to increase the VRE share and install battery storage and transmission systems. High prices of thermal power increase the revenues of power generation companies and the cost to the PTD company. To reduce the PTD company costs, additional measures such as a carbon tax, cheaper VRE electricity prices, and subsidies may be effective to incentivize battery storage and transmission costs.
This paper presents a vibration analysis using the substructure elimination method for vibration systems governed by a one-dimensional wave equation. The utilization of a one-dimensional continuous body serves as a suitable approach for understanding the fundamental aspects of physical phenomena. Consequently, the significance of one-dimensional computer-aided engineering has witnessed a noticeable upsurge in recent years. The vibration analysis of continuous bodies through modal analysis is effective for reducing the degrees of freedom (DOFs). In addition, modal analysis of continuous bodies using the substructure elimination method can reduce the DOFs further, compared with modal analysis using the substructure synthesis method. However, the substructure elimination method was reported only briefly by the first author, and several problems remained. Focusing on continuous bodies governed by one-dimensional wave equations, this study aimed to address the aforementioned problems by devising solutions and establishing criteria for the effective utilization of the substructure elimination method. As a versatile method for setting arbitrary boundary conditions, a new formulation method based on constraint conditions was proposed. In addition, appropriate material properties of the elimination regions and highest order of the eigenmode were determined through a simulation-based investigation. The effectiveness of the substructure elimination method was verified by comparing the simulation results obtained using the substructure elimination method and exact solutions obtained using the boundary conditions. To investigate the advantage of low DOFs, the simulation results obtained using the substructure elimination method were also compared with those obtained using the substructure synthesis method. As an example, in a simulation of a 0.85 m one-dimensional acoustic field with a non-reflective boundary, highly precise results were obtained below 1200 Hz using 15 DOFs and the substructure elimination method.
This study proposes a method to improve the computational accuracy of modal analysis by considering higher-order residual terms in addition to the residual stiffness. Conventionally, the effect of the residual stiffness of higher-order eigenmodes has been considered using the Hansteen and Bell method. However, it is insufficient to consider only the effect of the residual stiffness in the frequency range near the natural frequencies of the omitted eigenmodes. The proposed method improves computational accuracy by considering lower-order residual terms in addition to the residual mass when low-order eigenmodes are omitted rather than high-order eigenmodes. Furthermore, assuming that a continuous body is analyzed, we also present an approach to evaluate the residual stiffness of the eigenmodes of the degrees of freedom (DOF) excluded from the equations of motion by using the exact solution of the static displacement. The concept and essence of the proposed method were theoretically described using a 1-DOF vibration system. Then, higher-order and lower-order residual terms were theoretically formulated in a multi-DOF vibration system. Furthermore, we also describe the approach used to evaluate the residual stiffness of the degrees of freedom excluded from the equations of motion by using static displacement. The effectiveness of the proposed method was verified by comparing the exact solution with the simulation results of modal analysis using the proposed method.
The previous research of speech separation has significantly improved separation performance based on the time-domain method: encoder, separator, and decoder. Most research has focused on revising the architecture of the separator. In contrast, a single 1-D convolution layer and 1-D transposed convolution layer have been used as encoder and decoder, respectively. This study proposes deep encoder and decoder architectures, consisting of stacked 1-D convolution layers, 1-D transposed convolution layers, or residual blocks, for the time-domain speech separation. The intentions of revising them are to improve separation performance and overcome the tradeoff between separation performance and computational cost due to their stride by enhancing their mapping ability. We applied them to Conv-TasNet, the typical model in the time-domain speech separation. Our results indicate that the better separation performance is archived as the number of their layers increases and that changing the number of their layers from 1 to 12 results in more than 1 dB improvement of SI-SDR on WSJ0-2mix. Additionally, it is suggested that the encoder and decoder should be deeper, corresponding to their stride since their task may be more difficult as the stride becomes larger. This study represents the importance of improving these architectures as well as separators.
Computational fluid dynamics has been widely used in the design and analysis of various fluid systems. The proper treatment of boundary conditions is crucial for the accurate simulation of fluid flow. However, in particle methods, such as smoothed particle hydrodynamics method and moving particle semi-implicit method, the treatment of boundary conditions has been a challenging problem. In this paper, starting from the incompressibility condition, we present a new theory for the unified treatment of both rigid bodies and wall boundaries, which allows the strong coupling of rigid bodies and incompressible fluids. Because the boundary models are based on signed distance functions and do not use particles, these models can avoid several problems, such as resolution dependence of particle representations, and unavoidable unevenness of surfaces. We also provide a way to efficiently handle rigid-body boundaries and wall boundaries without particles by finding the fundamental boundary weight function that does not change with time. Several numerical examples are presented to demonstrate the capability of our models and to compare them with theoretical and experimental results.
A method for finding the optimum distribution of the slit density in a shoe upper, such that the contact pressure with the foot approaches an ideal distribution is presented in this paper. In a shoe upper made of warp knitting, slits are made by discontinuously knitting the weft under a uniform arrangement of the warp fiber. In this study, the shoe upper is modeled as an orthotropic hyperelastic body in which the slit density is defined as the design variable for controlling the intermediate density for the maximum and minimum slit densities. Referring to a formulation of a topology optimization problem of the density variation type, an inverse problem for finding the optimum distribution of the slit density is formulated with the objective and constraint cost functions defined by the squared error norm between the actual and ideal contact pressures and the deviation of the rate of the material with the maximum slit density from a limit value, respectively. This problem is solved in the same way as a topology optimization problem. The validity of this method is confirmed by numerical examples using a simple finite element model, which resembles the domain around the big toe.
A general design method for roller paths for multipass conventional spinning has not been established yet. The roller paths in a production site are often decided by experienced spinners by trial and error. In this paper, we propose a roller path solver system, which can automatically generate a roller path for spinning a cylindrical cup and simultaneously realize multiple target values of the spun product and forming process. On the basis of an artificial neural network trained with parameters of the roller paths and property values of the forming results, the path parameters that satisfy the target output are solved by an iterative algorithm using a pseudoinverse Jacobian matrix. In addition, the null space of the Jacobian matrix is used to handle the main and subtasks according to their priority. The experiments show that the target cup height, wall thickness, forming time, and surplus path length can be simultaneously achieved as the main task while moderately controlling the number of passes and the roller feed ratio as the subtask.
Diamagnetic levitation is applied to attain the smallest possible effective spring constant suitable for detection of weak and continuous forces relevant to various phenomena including biological ones. A Nd-Fe-B permanent magnet was suspended under aerial conditions with lifting force from a multi-layered solenoid and stabilized horizontally via repulsive interaction with a diamagnetic substance. The effective spring constant of the suspensions was analyzed via a ringdown measurement of the electromotive force caused by oscillation while changing the magnitude of the DC current in the solenoid. Measured minimum spring constant beyond which the potential energy minima along plumb direction vanishes was 26 mN/m for a ∅1.5 mm x 1.5 mm cylindrical permanent magnet in a Bi cylindrical diamagnetic pore. A variable-sized diamagnetic cavity composed of four mobile graphite slabs adaptable to cubic permanent magnets of arbitrary size was introduced to attain a smaller spring constant. The measured minimum spring constant for a 1 mm cubic permanent magnet levitated in this cavity was approximately 6 mN/m. Although the spring constant for a smaller 0.5 mm cubic magnet was not detectable with the present ringdown setup, its minimum possible value was evaluated from its volume to be below 1 mN/m, which can lead to the detection of a force below 1 nN if combined with an adequate optical displacement detection method. The measured spring constants were compared with the calculated results.
To improve the load characteristics of the transmission error for helical gears, a gear made of laminated materials is proposed. The gear has three layers in which metals with different rigidities are laminated in the tooth width direction. The layers on both sides are made from the same metal, and a different metal is used for the central layer. A theoretical analysis was performed to investigate the effects of arranging high- and low-rigidity layers and changing the width of the central layer. The laminated gear has load characteristics different from the transmission error for a conventional homogeneous material gear. The transmission error can be reduced with the combination of a high-rigidity central layer and a low-rigidity side layers, and a low transmission error can be maintained over a wide load range by adjusting the central layer width appropriately. The principle of the reduction in the transmission error is that, by changing the rigidity along one-pitch meshing progress with laminated materials, the elastic deformation of the teeth can largely cancel out the rotational fluctuations caused by the tooth flank shape over the wide load range. A pair of laminated gears was manufactured, and testing confirmed that the laminated gear has a transmission error lower than that for a gear made from a homogeneous material. The laminated gear has the potential to achieve the lower vibration/noise generation for the wider load range than the homogeneous gear.