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Sakamoto H.,Japan International Center for the Study of East Asia Development
Studies in Regional Science

This paper discusses population distributions in a region that needs to solve regional income disparity problems. The targeted region was the Jiangsu Province in China where the intra regional income disparity city level and prefecture level (shows expansion with recent economic growth. First, the population population distribution) necessary for regional income disparity to completely disappear under very simple assumptions was estimated. The 'desirable' population was named the "convergence population". Differences in the real estimated population and the convergence population were compared, and the degree of the solution for income disparity was verified. Consequentially, population cannot be absorbed sufficiently in rich regions, and income disparity is far from being solved. On the other hand, it is possible to think of a population movement plan for the future by estimating the convergence population. The population and accompanying income disparity were estimated in several projections by combining the registered population with the convergence population. In this estimation, a larger adjustment rate produced a greater decrease in income disparity. © JSRSAI 2012. Source

Simanjorang R.,Japan National Institute of Advanced Industrial Science and Technology | Yamaguchi H.,Japan National Institute of Advanced Industrial Science and Technology | Ohashi H.,Japan National Institute of Advanced Industrial Science and Technology | Nakao K.,Nagasaki University | And 3 more authors.
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC

This paper presents the power density developments of high-power isolated dc-dc converter to be utilized in a higher voltage direct-current (HVDC) power-supply system of a data center. This technique results in a prototype of dc-dc converter unit which is smaller by factor of ten when compared with the conventional one, and the area of power-supply system becomes much smaller than before. Consequently, the cooling power for this power-supply system is saved and both the energy and the space saving are available. In order to realize a prototype of the high-power isolated dc-dc converter, the switching power devices composed of a hybrid pair of Si-CoolMOS and SiC-SBD are utilized and operated in a driving pattern of hard switching with a frequency of 200kHz. As a result, an isolated dc-dc converter with the input/output voltage of 400V/400V, a rating power of 5kW, and a high power density of 10W/cm3 has been fabricated. The experimental confirmation was reported and the surge problems due to diode recovery difficulties mentioned before was solved. © 2011 IEEE. Source

Yamamoto T.,Kyushu Institute of Technology | Rikitake J.,Kyushu Institute of Technology | Matsumoto S.,Kyushu Institute of Technology | Ninomiya T.,Nagasaki University | Abe S.,Japan International Center for the Study of East Asia Development
Proceedings of the International Conference on Power Electronics and Drive Systems

In recent years, a power supply on chip (SoC) has been attracted attentions of many researchers because it can realize ultimate minimization of the power supply. This realizes higher electric power density and lower manufacturing cost. However, it is necessary to connect parallel at heavy loading conditions because this can handle smaller power per chip. In addition, switching frequency of more than 10 MHz is required for reducing the volume of the power supply. In such a scheme, the traditional analog based PWM will face the problems and a new control strategy is required. This paper proposes a new control strategy of the power-SoC based on parallel connections of dc-dc converters by digital control. We also report the simulation and experimental results of the proposed strategy. The results show that the proposed strategy works well and improves the efficiency over the wide range. © 2013 IEEE. Source

Yang S.,Kyushu University | Abe S.,Japan International Center for the Study of East Asia Development | Shoyama M.,Kyushu University
2010 International Power Electronics Conference - ECCE Asia -, IPEC 2010

Low-profile, high efficiency power supply is today's industry trend for Plasma Display Panel (PDP) application system. Transformer is the major challenge and bottleneck for achieving low-profile, high power density converter. Generally, it is necessary for low-profile converter to operate it at high switching frequency. However, it is very difficult to design converter using flat magnetic component because flat transformer temperature becomes high at high switching frequency. In this paper, the design and analysis of flat transformer in LLC resonant converter for the PDP TV is proposed to reduce temperature of the transformer. In this proposed converter, flat transformer is integrated into advanced power conversion application systems. Low-profile power module of profile of about 14mm is achieved. Temperature inside of transformer repressed to 71°C and an overall efficiency of about 96.6% was obtained. © 2010 IEEE. Source

Sakamoto H.,Japan International Center for the Study of East Asia Development
Studies in Regional Science

This study investigated by a comparison analysis of the intra-provincial disparity between Guangxi and Yunnan using statistical data.These two provinces(autonomous region) belong to the southwest region of China, and are comparatively poor.First, this study showed the two provinces do not reach the national average in many economic indicators.Next, the intra-provincial disparity of the two provinces was verified by the prefectural data.Information on the city was deleted beforehand, and the analysis assumed to be an analysis of data from the rural area.Then, the comparison of the structure of the intra-provincial disparity in the rural area between the two provinces was statistically analyzed. A part of the factors for disparity are generally seen in the advancement of industrial structure and urbanization.Especially, data analysis at the prefectural level shows disparity, even when disparity is not found in the rural area itself.Disparity arises from the difference in the situations in the stages for developing from a rural area.Moreover, when a comparison of the kernel density function was done by using a statistical index, it was clear that the economic structure in the rural area is different between Guangxi and Yunnan. Since economic structure shows a difference, a common economic policy to both prefectures is not suitable for Guangxi and Yunnan.Obviously, each province has a separate government, so the possibility of developing a common policy is low, but it is certain that a policy suitable for the actual conditions of each province is desired.This is a future subject for more detailed analysis. Source

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