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Material Models for Accurate Simulation of Sheet Metal Forming and Springback
Fusahito YOSHIDA 한국소성가공학회 2010 기타자료 Vol.2010 No.6
For anisotropic sheet metals, modeling of anisotropy and the Bauschinger effect is discussed in the framework of Yoshida-Uemori kinematic hardening model incorporating with anisotropic yield functions. The performances of the models in predicting yield loci, cyclic stress-strain responses on several types of steel and aluminum sheets are demonstrated by comparing the numerical simulation results with the corresponding experimental observations. From some examples of FE simulation of sheet metal forming and springback, it is concluded that modeling of both the anisotropy and the Bauschinger effect is essential for the accurate numerical simulation.
Reduction of Springback of Sheet Metals by Bottoming
Takayuki Ogawa,Atsushi Hirahara,Fusahito Yoshida 한국소성가공학회 2010 기타자료 Vol.2010 No.6
The effect of bottoming on the reduction of springback is investigated by performing V-air-bending experiment on a high strength steel sheet of TS590MPa and the corresponding FE simulation. From the experiment, it was found that the springback is drastically decreased with increasing bottoming force. This is mainly due to the reduction of bending moment by compressive load acting normally to the sheet. At an early stage of bottoming, springback is also influenced by the change of geometrical rigidity of the bent sheet due to the straightening of ridge line warp. Since bottoming is a process of reverse deformation of tension-compression, the Bauschinger effect of materials should be taken into account for its accurate numerical simulation. 3D FE simulation using Yoshida-Uemori kinematic hardening model predicts well the bottoming effect.
Elasto-Plasticity Behavior of Type 5000 and 6000 Aluminum Alloy Sheets and Its Constitutive Modeling
Shohei TAMURA,Satoshi SUMIKAWA,Hiroshi HAMASAKI,Takeshi UEMORI,Fusahito YOSHIDA 한국소성가공학회 2010 기타자료 Vol.2010 No.6
To examine the deformation characteristic of type 5000 and 6000 aluminum alloy sheets, uniaxial tension, biaxial stretching and in-plane cyclic tension-compression experiments were performed, and from these, r-values (r?, r45 and r90), yield loci and cyclic stress-strain responses were obtained. For the accurate description of anisotropies of the materials, high-ordered anisotropic yield functions, such as Gotoh’s biquadratic yield function and Barlat’s Yld2000-2d, are necessary. Furthermore, for the simulation of cyclic behavior, an advanced kinematic hardening model, such as Yoshida-Uemori model (Y-U model), should be employed. The effect of the selection of material models on the accuracy of the springback prediction was discussed by performing hat bending FE simulation using several yield functions and two types of hardening laws (the isotropic hardening model and Y-U model)
Network Effects of Alliances in International Transportation
( Yoshida Shigeru ) 한국해운물류학회(구 한국해운학회) 2003 해운물류연구 Vol.39 No.-
The aim of this study is to analyze the difference of network effects by alliance formation in international liner shipping and airline industries. First of all, the network economy by the alliances is placed in order from the viewpoint of economy of scale. After observing the changes of network service attributes by he alliance formation, the network effects are empirically analyzed on demand and supply sides. We conclude as follows. As it is very difficult for each airline to design freely the route structure to demonstrate the effect of aircraft size, the route of pursuing high frequent service to fulfill customer satisfactions is taken. For liner shipping, as well as for airlines, customers are acquired by increasing the number of service points and frequencies are relatively small.
Yoshida, Yoshiaki,Fujiwara, Koji,Ishihara, Yoshiyuki,Suzuki, Hirokazu The Korean Institute of Electrical Engineers 2013 The Journal of International Council on Electrical Vol.3 No.1
When distributed generators such as photovoltaic (PV) systems spread widely in distribution networks, it is important to detect islanding caused by power system fault for ensuring electrical safety. We developed the nonlinear magnetizing characteristics model of a pole transformer for analyzing islanding-prevention of PV system. Basic experiments of the islanding-detection were conducted by using the RLC resonant circuit for verification of the developed model. Analytical results by the proposed model agreed well with experimental results.
LARGE FORMAT CCD CAMERA FOR THE KISO 105 cm SCHMIDT TELESCOPE
YOSHIDA S.,AOKI T.,SOYANO T.,TARUSAWA K.,HASEGAWA T. The Korean Astronomical Society 1996 Journal of The Korean Astronomical Society Vol.29 No.suppl1
A new CCD camera equipped with a large format chip is now under construction for the Kiso 105-cm Schmidt telescope. We use SITe TK2048E, of which pixel size is 24 ${\mu}m$ and chip size is 48 mm square. TK2048E is thinned back-illuminated so that it has high sensitivity in U-band. The chip is cooled by a refrigerator instead of liquid nitrogen. MESSIA III is used as CCD control system.
A Study on Synchronous Stability Analysis of Power System with a Large Amount of PVs
Yoshida, Mitsutaka,Tsuji, Takao,Oyama, Tsutomu,Hashiguchi, Takuhei,Goda, Tadahiro,Kihara, Hidemi,Nomiyama, Fumitoshi,Suzuki, Naoto The Korean Institute of Electrical Engineers 2012 The Journal of International Council on Electrical Vol.2 No.2
To solve the energy and environmental issues, it is planned that a large amount of photovoltaics (PVs) are introduced in Japan. However, because the characteristic of PV output is different from that of conventional generators, it is possible that the synchronous stability changes due to a large amount of PVs. Additionally, supposing that some generators are stopped when PV output becomes large, decrease of inertia constant and change of power flow are also important factors for synchronous stability. Hence, in this paper, the synchronous stability of power system with a large amount of PVs is studied considering both the voltage characteristic of PV output and the change of system operation such as unit commitment. Specifically, the stability is evaluated from a viewpoint of critical clearing time (CCT) based on both the accelerating and decelerating energy in P-${\delta}$ curve. IEEJ-WEST10 model system is utilized as a simulation model.
Yoshida, Tomomi,Nishijima, Yoshimi,Hando, Kiyomi,Vilayvong, Soulideth,Arounlangsy, Petsamone,Fukuda, Toshio Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.5
Background: Most developing countries have been unable to implement well-organized health care systems, especially comprehensive Pap smear screening-based programs. One of the reasons for this is regional differences in medical services, and a low-cost portable cervical screening system is necessary. To improve regional discrepancies in cervical screening systems, we investigated the usefulness and acceptability of cervical selfsampling by liquid-based cytology (LBC) for 290 volunteers in the Lao PDR. Materials and Methods: Following health education with comprehensive documents, cervical self-sampling kits by LBC were distributed in three provincial, district, and village areas to a total of 290 volunteers, who were asked to take cytology samples by themselves. Subsequently, the acceptability of self-sampling was evaluated using a questionnaire. Results: The documents were well understood in all three regions. Regarding the acceptability of self-sampling, the selections for subsequent screening were 62% self-sampling, 36% gynecologist-sampling, 1% either method, and 1% other methods. The acceptability rates were higher in the district and the village than in the province. For the relationship between acceptability and pregnancy, the self-sampling selection rate was higher in the pregnancy-experienced group (75%) than in the pregnancy-inexperienced group (60%). For the relationship between selection of self-sampling and experience of screening, the self-sampling selection rate was higher in the screening-inexperienced group (62%) than in the screening-experienced group (52%). Conclusions: Our data show that this new way forward, involving a combination of self-sampling and LBC, is highly acceptable regardless of age, educational background, and residence in rural areas in a developing country.
Field Measurement and Modal Identification of Various Structures for Structural Health Monitoring
Yoshida, Akihiko,Tamura, Yukio Council on Tall Building and Urban Habitat Korea 2015 International journal of high-rise buildings Vol.4 No.1
Field measurements of various structures have been conducted for many purposes. Measurement data obtained by field measurement is very useful to determine vibration characteristics including dynamic characteristics such as the damping ratio, natural frequency, and mode shape of a structure. In addition, results of field measurements and modal identification can be used for modal updating of FEM analysis, for checking the efficiency of damping devices and so on. This paper shows some examples of field measurements and modal identification for structural health monitoring. As the first example, changes of dynamic characteristics of a 15-story office building in four construction stages from the foundation stage to completion are described. The dynamic characteristics of each construction stage were modeled as accurately as possible by FEM, and the stiffness of the main structural frame was evaluated and the FEM results were compared with measurements performed on non-load-bearing elements. Simple FEM modal updating was also applied. As the next example, full-scale measurements were also carried out on a high-rise chimney, and the efficiency of the tuned mass damper was investigated by using two kinds of modal identification techniques. Good correspondence was shown with vibration characteristics obtained by the 2DOF-RD technique and the Frequency Domain Decomposition method. As the last example, the wind-induced response using RTK-GPS and the feasibility of hybrid use of FEM analysis and RTK-GPS for confirming the integrity of structures during strong typhoons were shown. The member stresses obtained by hybrid use of FEM analysis and RTK-GPS were close to the member stresses measured by strain gauges.