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A Design Strategy for the LCR Filter and Carrier Frequency in a Series Voltage Compensator
Nakata, Atsushi,Torii, Akihiro,Ueda, Akiteru The Korean Institute of Electrical Engineers 2013 The Journal of International Council on Electrical Vol.3 No.2
In this paper, we propose the LCR filter design method and the carrier frequency decision method in the series voltage compensator. In this proposed design method, the filter $L_f$ is calculated from the peak value of the ripple current, and the filter $C_f$ is calculated from the ripple voltage component. The damping resistance is calculated from the percentage of the elimination of the carrier frequency component and the settling time. We verify a model equipment in the experiment, and the experimental results agree well with the calculated design values.
Acceleration of computation speed for elastic wave simulation using a Graphic Processing Unit
Nakata, Norimitsu,Tsuji, Takeshi,Matsuoka, Toshifumi Korean Society of Earth and Exploration Geophysici 2011 지구물리와 물리탐사 Vol.14 No.1
Numerical simulation in exploration geophysics provides important insights into subsurface wave propagation phenomena. Although elastic wave simulations take longer to compute than acoustic simulations, an elastic simulator can construct more realistic wavefields including shear components. Therefore, it is suitable for exploration of the responses of elastic bodies. To overcome the long duration of the calculations, we use a Graphic Processing Unit (GPU) to accelerate the elastic wave simulation. Because a GPU has many processors and a wide memory bandwidth, we can use it in a parallelised computing architecture. The GPU board used in this study is an NVIDIA Tesla C1060, which has 240 processors and a 102 GB/s memory bandwidth. Despite the availability of a parallel computing architecture (CUDA), developed by NVIDIA, we must optimise the usage of the different types of memory on the GPU device, and the sequence of calculations, to obtain a significant speedup of the computation. In this study, we simulate two- (2D) and threedimensional (3D) elastic wave propagation using the Finite-Difference Time-Domain (FDTD) method on GPUs. In the wave propagation simulation, we adopt the staggered-grid method, which is one of the conventional FD schemes, since this method can achieve sufficient accuracy for use in numerical modelling in geophysics. Our simulator optimises the usage of memory on the GPU device to reduce data access times, and uses faster memory as much as possible. This is a key factor in GPU computing. By using one GPU device and optimising its memory usage, we improved the computation time by more than 14 times in the 2D simulation, and over six times in the 3D simulation, compared with one CPU. Furthermore, by using three GPUs, we succeeded in accelerating the 3D simulation 10 times.
Nakata Chisa,Itaya Akemi 대한공간정보학회 2021 Spatial Information Research Vol.29 No.4
The rapid increase of woody biomass power plants has given rise to concerns about the balance of supply and demand. The purpose of this study was to explore forests vulnerable to over-logging and show them visually in Mie Prefecture, central Japan when supplying woody biomass to power plants based on transportation distance and the time using a non-commercial road network. The destinations were the three biomass power plants and the origins were artificial forests divided by watersheds. Transportation distances and time between destinations and origins were estimated using the routesearch function in Google Maps. Forests vulnerable to over-logging were explored based on two thresholds: a one-way distance of 50 km and a travel time of 2.5 h. Our results show that many of the artificial forests in Mie Prefecture might be subject to high harvesting competition. In all, 55.07% of the forest plantations in Mie Prefecture were within 50 km of two or three biomass power plants and 87.11% were within 2.5 h one-way. It might be necessary to supply woody biomass from southern Mie Prefecture. The stakeholder should share logging plans and monitor over-logging while planning for the efficient use of woody biomass in the southern part of Mie Prefecture.
Compensation techniques for experimental errors in real-time hybrid simulation using shake tables
Nakata, Narutoshi,Stehman, Matthew Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.6
Substructure shake table testing is a class of real-time hybrid simulation (RTHS). It combines shake table tests of substructures with real-time computational simulation of the remaining part of the structure to assess dynamic response of the entire structure. Unlike in the conventional hybrid simulation, substructure shake table testing imposes acceleration compatibilities at substructure boundaries. However, acceleration tracking of shake tables is extremely challenging, and it is not possible to produce perfect acceleration tracking without time delay. If responses of the experimental substructure have high correlation with ground accelerations, response errors are inevitably induced by the erroneous input acceleration. Feeding the erroneous responses into the RTHS procedure will deteriorate the simulation results. This study presents a set of techniques to enable reliable substructure shake table testing. The developed techniques include compensation techniques for errors induced by imperfect input acceleration of shake tables, model-based actuator delay compensation with state observer, and force correction to eliminate process and measurement noises. These techniques are experimentally investigated through RTHS using a uni-axial shake table and three-story steel frame structure at the Johns Hopkins University. The simulation results showed that substructure shake table testing with the developed compensation techniques provides an accurate and reliable means to simulate the dynamic responses of the entire structure under earthquake excitations.
Nakata, Kazue,Taniguchi, Yoshie,Yoshioka, Noriko,Yoshida, Aya,Inagawa, Hiroyuki,Nakamoto, Takeru,Yoshimura, Hiroshi,Miyake, Shin-Ichiro,Kohchi, Chie,Kuroki, Masahide,Soma, Gen-Ichiro The Korean Nutrition Society 2011 Nutrition Research and Practice Vol. No.
At present, lifestyle-related diseases are one of the most critical health issues worldwide. It has been reported that lipopolysaccharide derived from a Gram-negative bacteria (IP-PA1) symbiotic with wheat exhibited several advantageous biological effects, such as the reduction of plasma glucose levels in NOD mice and low-density lipoprotein (LDL) levels in WHHL rabbits. In this study, the beneficial effects on plasma glucose and lipids of a tea (SI tea) consisting of IP-PA1 and Salacia (which contains an inhibitor of ${\alpha}$-glucosidase) were investigated in the KK-Ay/TaJcl type 2 diabetic model mice and in human subjects with premetabolic syndrome in a double-blind, randomized study. S1 tea significantly decreased plasma glucose levels in KK-Ay/TaJcl mice. A clinical trial of SI tea was performed with 41 subjects between the ages of 40 and 69, who belonged either to a high plasma glucose group (HG: FPG 100-125 mg/dl) or to a hyperlipidemia group (HL: TG ${\geq}$ 150 mg/dl, or LDL ${\geq}$ 120 mg/dl, or HDL <40 mg/dl). These subjects ingested either Salacia without IP-PA1 (the control) or SI tea. Blood samples were collected at 0, 30, and 60 days after initiating SI tea treatment, and were measured for FPG, HbA1c, TG, LDL, and HDL. These results showed that SI tea reduced FPG and HbA1c more rapidly than the control in the HL group, and also significantly improved LDL and HDL levels in the HG group. Thus, SI tea may be helpful in preventing lifestyle-related diseases.