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3D-CAD Data Structure Based on Shape Feature for Massive Machinery Models
Masakatsu Kinjo,Tomoaki Takano,Hidekazu Matsuna (사)한국CDE학회 2013 한국CAD/CAM학회 국제학술발표 논문집 Vol.2010 No.8
In recent years, three-dimensional design with 3D-CAD (three-dimensional computer aided design) systems is being increasingly used in areas such as production facility design and machine tools engineering. In these fields, a machine model with a massive number of parts sometimes needs to be processed in order to design or verify the full assembly of an entire production line. However, most modern 3D-CAD systems face difficulties in handling such machinery models with a very large number of parts. Therefore, the designers are forced to design the machine using partial models or specific units. To solve this problem, we have focused on the surface shape of parts constituting the machinery models and clarified that most surfaces have simple shapes. We take advantage of this feature to propose a new data structure that applies simple data structures to simple-shape surfaces rather than a data structure applied to all kinds of surfaces including freeform surfaces. Based on the new data structure, we devise ways and means to speed up the display process. This paper describes these processes. We are able to handle the data of very massive models such as production facilities or machine tools using our new data structure. Our proposed data structure can provide a design environment that reduces the stress on designers through its high-speed display response.
Surface Terms in the Action of the Gravitational Theory
Masakatsu Kenmoku,Kazuyasu Shigemoto 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.1
We evaluate the Hilbert action with the surface term by using the Schwarzschild-De Sitter type solution in (2+1)-dimensions to investigate whether the action takes a stationary value for the solutions in dierent frames. We obtained the following results: i) The nite value of the action is obtained . ii) The Hilbert action takes the same value, but the surface term does not for the solutions in the static frame and that in the cosmological frame. iii) The mass contribution appears even in closed space.
Chiba, Masakatsu,Murase, Ryo,Nambu, Yohsuke,Komatsu, Keiji The Society for Aerospace System Engineering 2015 International Journal of Aerospace System Engineer Vol.2 No.2
Experimental studies were conducted on the liquid sloshing characteristics in a spherical tank covered with a flexible membrane. A spherical acrylic tank with 145.2 mm in radius was used as a test tank, and it was half-filled with water. Silicon membranes with 0.2 mm thickness were used as a test membrane with plane or hemispherical types. The test tank was harmonically excited in a vertical direction by an electro-dynamic exciter. In this case, a parametric instability vibration comes up when the excitation frequency is twice the natural frequency. Parametric instability regions of natural modes were measured for three cases, i.e. liquid surface is free, covered with plane membrane and hemi-spherical membrane.
Bargmann-Wigner formulation and superradiance problem of bosons and fermions in Kerr space-time
Kenmoku, Masakatsu,Cho, Y. M. World Scientific Publishing Company 2015 International Journal of Modern Physics A Vol.30 No.11
<P>The superradiance phenomena of massive bosons and fermions in the Kerr space-time are studied in the Bargmann-Wigner formulation. In case of bi-spinor, the four independent components spinors correspond to the four bosonic freedom: one scalar and three vectors uniquely. The consistent description of the Bargmann-Wigner equations between fermions and bosons shows that the superradiance of the type with positive energy (0 < ω) and negative momentum near horizon (p<SUB>H</SUB> < 0) is shown not to occur. On the other hand, the superradiance of the type with negative energy (ω < 0) and positive momentum near horizon (0 < p<SUB>H</SUB>) is still possible for both scalar bosons and spinor fermions.</P>
Influence of torsional rigidity of flexible appendages on the dynamics of spacecrafts
Chiba, Masakatsu,Magata, Hidetake Techno-Press 2019 Coupled systems mechanics Vol.8 No.1
The influence of torsional rigidity of hinged flexible appendage on the linear dynamics of flexible spacecrafts with liquid on board was analyzed by considering the spacecraft's main body as a rigid tank, its flexible appendages as two elastically supported elastic beams, and the onboard liquid as an ideal liquid. The meniscus of the liquid free surface due to surface tension was considered. Using the Lagrangian of the spacecraft's main body (rigid tank), onboard liquid, and two beams (flexible appendages) in addition to assuming the system moved symmetrically, the coupled system frequency equations were obtained by applying the Rayleigh-Ritz method. The influence of the torsional rigidity of the flexible appendages on the spacecraft's coupled vibration characteristics was primary focus of investigation. It was found that coupled vibration modes especially that of appendage considerably changed with torsion spring parameter ${\kappa}_t$ of the flexible appendage. In addition, variation of the main body displacement with system parameters was investigated.
Chiba, Masakatsu,Chiba, Shinya,Takemura, Kousuke Techno-Press 2013 Coupled systems mechanics Vol.2 No.4
The coupled free vibration of flexible structures and on-board liquid in zero gravity space was analyzed, considering the spacecraft main body as a rigid mass, the flexible appendages as two elastic beams, and the on-board liquid as a "spring-mass" system. Using the Lagrangians of a rigid mass (spacecraft main body), "spring-mass" (liquid), and two beams (flexible appendages), as well as assuming symmetric motion of the system, we obtained the frequency equations of the coupled system by applying Rayleigh-Ritz method. Solving these frequency equations, which are governed by three system parameters, as an eigenvalue problem, we obtained the coupled natural frequencies and vibration modes. We define the parameter for evaluating the magnitudes of coupled motions of the added mass (liquid) and beam (appendages). It was found that when varying one system parameter, the frequency curves veer, vibration modes exchange, and the significant coupling occurs not in the region closest to the two frequency curves but in the two regions separate from that region.