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New applications of computational geometry and graph theory to cellular mobile communications
Tamura, Hiroshi,Sengoku, Masakazu,Shinoda, Shoji 대한전자공학회 1996 APCCAS:Asia Pacific Conference on Circuits And Sys Vol.1 No.1
The demand for mobile communication services is rapidly increasing, because the mobile communication service is synonymy of an ideal communication style realizing communication in anytime, anywhere and with anyone. There exist various problems to which computational geometry and graph & network theory is applicable in mobile communication services. For example, it is well-known that Coloring algorithms of graphs are applicable in channel assignment algorithms in cellular systems. In this paper, we show some examples of new applications of computational geometry and graph theory to cellular mobile communications.
Aspects of the dynamic wind-induced response of structures and codification
Tamura, Yukio,Kareem, Ahsan,Solari, Giovanni,Kwok, Kenny C.S.,Holmes, John D.,Melbourne, William H. Techno-Press 2005 Wind and Structures, An International Journal (WAS Vol.8 No.4
This paper describes the work of the International Association for Wind Engineering Working Group E -Dynamic Response, one of the International Codification Working Groups set up at the Tenth International Conference on Wind Engineering in Copenhagen. Comparisons of gust loading factors and wind-induced responses of major codes and standards are first reviewed, and recent new proposals on 3-D gust loading factor techniques are introduced. Then, the combined effects of along-wind, crosswind and torsional wind load components are discussed, as well as the dynamic characteristics of buildings. Finally, the mathematical forms of along-wind velocity spectra for along-wind response calculation and codification of acceleration criteria are discussed.
Wind load combinations and extreme pressure distributions on low-rise buildings
Tamura, Yukio,Kikuchi, Hirotoshi,Hibi, Kazuki Techno-Press 2000 Wind and Structures, An International Journal (WAS Vol.3 No.4
The main purpose of this paper is to demonstrate the necessity of considering wind load combinations even for low-rise buildings. It first discusses the overall quasi-static wind load effects and their combinations to be considered in structural design of low-rise buildings. It was found that the maximum torsional moment closely correlates with the maximum along-wind base shear. It was also found that the instantaneous pressure distribution causing the maximum along-wind base shear was quite similar to that causing the maximum torsional moment, and that this asymmetric pressure pattern simultaneously accompanies considerable across-wind and torsional components. Secondly, the actual wind pressure distributions causing maximum quasi-static internal forces in the structural frames are conditionally sampled and their typical pressure patterns are presented.
Environmental Impact Evaluation for Transportation of Building Materials into Tokyo District
Tamura, Masaki,Watanabe, Kyohei,Nachi, Yoko Sustainable Building Research Center 2011 International journal of sustainable building tech Vol.2 No.1
Building materials such as concrete aggregate used in Tokyo district have recently been transported by ship or truck over a long distance with a long transportation time. Therefore, the evaluation of environmental impact from the total amount of building materials and $CO_2$ emissions due to transport of these materials from outside raw material plants to construction sites in the Tokyo district will become an important issue. In this study, the present conditions of transportation loads from building materials for structural bodies such as concrete, its aggregate and so on in the feasiblility study were investigated in consideration of transportation distance (km), total amount of weight (ton) and total number of transportation times (times) from raw material plants to construction sites in the Tokyo district. The environmental impacts of these transportation loads from building materials such as concrete aggregate conveyed into the Tokyo district were evaluated by the indicators of ton-kilometerage ($t{\cdot}km$) and amount of $CO_2$ emissions (t-$CO_2$), comparing transportation by ship and by truck. Moreover, regarding actual buildings recently built in Tokyo, a comparative analysis was conducted in terms of environmental impacts due to transportation loads from ton-kilometerange ($t{\cdot}km$) and amount of $CO_2$ emissions (t-$CO_2$) in consideration of differences between structural body types of reinforced concrete and structure steel.
Non-elastic responses of tall steel buildings subjected to across-wind forces
Tamura, Yukio,Yasui, Hachinori,Marukawa, Hisao Techno-Press 2001 Wind and Structures, An International Journal (WAS Vol.4 No.2
This paper presents an analytical method which takes into account the non-linearity of individual members, and discusses some case study results. It also discusses the relationship between member non-elastic behavior and excitation duration, and the relationship between member fracture and overall structure behavior. It is clearly demonstrated that the frame already shows almost unstable behavior due to long-columnization just before the occurrence of a column fracture. Then, a column fracture immediately induces a structural collapse mechanism.
Amplitude Dependency of Damping in Buildings and Critical Tip Drift Ratio
Tamura, Yukio Council on Tall Building and Urban Habitat Korea 2012 International journal of high-rise buildings Vol.1 No.1
The importance of appropriate use of damping evaluation techniques and points to note for accurate evaluation of damping are first discussed. Then, the variation of damping ratio with amplitude is discussed, especially in the amplitude range relevant to wind-resistant design of buildings, i.e. within the elastic limit. The general belief is that damping increases with amplitude, but it is emphasized that there is no evidence of increasing damping ratio in the very high amplitude range within the elastic limit of main frames, unless there is damage to secondary members or architectural finishings. The damping ratio rather decreases with amplitude from a certain tip drift ratio defined as "critical tip drift ratio," after all friction surfaces between primary/structural and secondary/non-structural members have been mobilized.