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Soam, A.,Kwon, Jugmi,Maheswar, G.,Tamura, Motohide,Lee, Chang Won IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.803 No.2
<P>LDN 328 is cited as an example of a fairly isolated clump contracting to form multiple sub-cores, possibly through gravitational fragmentation. In one of these sub-cores, a proto-brown dwarf (L328-IRS) candidate is in the process of formation through the self-gravitating contraction, similar to the formation scenario of a low-mass star. We present results of our optical and near-infrared polarization observations of regions toward LDN 328. This is the first observational attempt to map the magnetic field geometry of a cloud harboring a proto-brown dwarf candidate associated with a sub-parsec-scale molecular outflow. On a parsec scale, the magnetic field is found to follow the curved structure of the cloud showing a head-tail morphology. The magnetic field is found to be well ordered over a 0.02-0.2 pc scale around L328-IRS. Taking into account the uncertainties in the determination of position angles, the projected angular offset between the magnetic field direction and the outflow axis is found to be in the range of 0 degrees-70 degrees. Considering outflow to be the proxy for the rotation axis, the result obtained in this study implies that the rotation axis in L328 is preferably parallel to the local magnetic field. The magnetic field strength estimated in the close vicinity of L328-IRS is similar to 20 mu G. Results from the present study suggest that the magnetic field may be playing a vital role even in the cores that are forming sub-stellar sources.</P>
A-Rong Kim,Hyo-Ryong Seo,Gyeong-Hun Kim,Minwon Park,In-Keun Yu,Otsuki, Yusuke,Tamura, Junji,Seok-Ho Kim,Kideok Sim,Ki-Chul Seong IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3
<P>This paper analyses operating characteristic of high temperature superconducting magnetic energy storage (HTS SMES) for frequency stabilization of dispersed power generation system. The wind power generation system (WPGS) fluctuates due to wind speed variation and affects the frequency and voltage fluctuations of the utility. SMES is probably a key technology to overcome these fluctuations. To stabilize power system frequency, a large-scale HTS SMES is connected to the terminal of the WPGS. The authors analysed the load side frequencies using two different configurations of SMES, one consisting of a single magnet and the other of a dual magnet. From the simulation results, it can be concluded that the SMES is a useful device for stabilizing the power system frequency fluctuations, and a dual magnet type SMES is more effective for frequency stabilizing but exhibits more AC loss due to the increased operating current than a single magnet type.</P>
Ku, C.J.,Tamura, Y.,Yoshida, A.,Miyake, K.,Chou, L.S. Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.16 No.2
Output-only modal parameter identification is based on the assumption that external forces on a linear structure are white noise. However, harmonic excitations are also often present in real structural vibrations. In particular, it has been realized that the use of forced acceleration responses without knowledge of external forces can pose a problem in the modal parameter identification, because an external force is imparted to its impulse acceleration response function. This paper provides a three-stage identification procedure as a solution to the problem of harmonic and white noise excitations in the acceleration responses of a linear dynamic system. This procedure combines the uses of the mode indicator function, the complex mode indication function, the enhanced frequency response function, an iterative rational fraction polynomial method and mode shape inspection for the correlation-related functions of the force-embedded acceleration responses. The procedure is verified via numerical simulation of a five-floor shear building and a two-dimensional frame and also applied to ambient vibration data of a large-span roof structure. Results show that the modal parameters of these dynamic systems can be satisfactorily identified under the requirement of wide separation between vibration modes and harmonic excitations.
C.J. Ku,Y. Tamura,A. Yoshida,K. Miyake,L.S. Chou 한국풍공학회 2013 Wind and Structures, An International Journal (WAS Vol.16 No.2
Output-only modal parameter identification is based on the assumption that external forces on a linear structure are white noise. However, harmonic excitations are also often present in real structural vibrations. In particular, it has been realized that the use of forced acceleration responses without knowledge of external forces can pose a problem in the modal parameter identification, because an external force is imparted to its impulse acceleration response function. This paper provides a three-stage identification procedure as a solution to the problem of harmonic and white noise excitations in the acceleration responses of a linear dynamic system. This procedure combines the uses of the mode indicator function, the complex mode indication function, the enhanced frequency response function, an iterative rational fraction polynomial method and mode shape inspection for the correlation-related functions of the force-embedded acceleration responses. The procedure is verified via numerical simulation of a five-floor shear building and a two-dimensional frame and also applied to ambient vibration data of a large-span roof structure. Results show that the modal parameters of these dynamic systems can be satisfactorily identified under the requirement of wide separation between vibration modes and harmonic excitations.
A Study on the Operating Characteristics of SMES for the Dispersed Power Generation System
Hee-Yeol Jung,A-Rong Kim,Jae-Ho Kim,Minwon Park,In-Keun Yu,Seok-Ho Kim,Kideok Sim,Hae-Jong Kim,Ki-Chul Seong,Asao, T.,Tamura, J. IEEE 2009 IEEE transactions on applied superconductivity Vol.19 No.3
<P>WPGS (Wind Power Generation System) output fluctuates due to wind speed variations and PV power generation output is changed by sudden cloudy weather conditions. Hence, if a large number of wind and PV power generators are connected to power system, their output can cause a serious influence on the power system operation, that is, frequency and voltage fluctuations. In order to solve these problems, the control of generator output fluctuations is very important. With these points as background, Superconducting Magnetic Energy Storage (SMES) is probably a key technology to overcome these fluctuations. For stabilization of power, the SMES is connected to the terminal of the WPGS. The authors compared the load side frequencies under the 1 MJ and 2.5 MJ of SMES connection, respectively. From the simulation results, it can be concluded that the SMES is a very effective device for stabilization of power system and minimization of frequency fluctuations.</P>
Wind-induced responses of super-tall buildings with various atypical building shapes
Kim, Y.C.,Tamura, Y.,Tanaka, H.,Ohtake, K.,Bandi, E.K.,Yoshida, A. Elsevier Scientific Pub. Co 2014 Journal of wind engineering and industrial aerodyn Vol.133 No.-
A wind tunnel tests were conducted on 13 super-tall building models with atypical building shapes under an urban area flow. The primary purpose of the present study was to directly compare the wind load effects on atypical super-tall buildings. Time history analyses were conducted using a frame model by inputting local wind forces at the center of each floor. The results show that the peak normal stresses on a square model are the largest among all the models tested, the setback model shows the smallest peak normal stresses of the single modification models tested, and CC+TP+360Hel shows the smallest peak normal stresses of the multiple modification models tested. The contributions of bending moments are about 20% of the total, and most of the peak normal stresses resulted from axial force. The increase in bending moment in the across-wind direction becomes significant as the damping ratio decreases, and the sensitivity of the peak normal stresses for the helical and multiple modification models to damping ratio is smaller than those of the other models. From the analyses for the various loading conditions, it was found that the contribution of bending moment in the along-wind direction is the largest and that of torsional moment is almost negligible.
Plasticity of indium nanostructures as revealed by synchrotron X-ray microdiffraction
Budiman, A.S.,Lee, G.,Burek, M.J.,Jang, D.,Han, S.M.J.,Tamura, N.,Kunz, M.,Greer, J.R.,Tsui, T.Y. Elsevier Sequoia 2012 Materials science & engineering. properties, micro Vol.538 No.-
Indium columnar structures with diameters near 1μm were deformed by uniaxial compression at strain rates of approximately 0.01 and 0.001s<SUP>-1</SUP>. Defect density evolution in the nanopillars was evaluated by applying synchrotron Laue X-ray microdiffraction (μSLXRD) on the same specimens before and after deformation. Results of the μSLXRD measurements indicate that the dislocation density increases as a result of mechanical deformation and is a strong function of strain rate. These results suggest that the rate of defect generation during the compression tests exceeds the rate of defect annihilation, implying that plasticity in these indium nanostructures commences via dislocation multiplication rather than nucleation processes. This is in contrast with the behaviors of other materials at the nanoscale, such as, gold, tin, molybdenum, and bismuth. A hypothesis based on the dislocation mean-free-path prior to the multiplication process is proposed to explain this variance.
운동자세 및 의복압이 최대의 산소섭취량(VO₂Pmax)에 미치는 영향
정명희,田村熙子,서미아 漢陽大學校 韓國生活科學硏究所 2001 韓國 生活 科學 硏究 Vol.- No.19
This study focuses on the influence of body pressure for posture and clothing pressure on physiological responses of the human body from the viewpoint of clothing physiology. Physiological responses for different exercise postures and different levels of clothing pressure were examined. Six untrained female subjects performed leg exercises, using a bicycle ergometer in the supine and sitting postures. Clothing used in the experiment consisted of two kinds of sportswear -non-pressure suits and pressure suits-both of which were made in the same shape of short sleeves and short pants and were made of the same material of 90% nylon/10% polyurethane. Environmental conditions were at 30±1℃ air temperature, 50±10% relative humidity and 0.2m/sec air velocity. Clothing pressure on the 10 sites of the human body surface and maximal of oxygen intake(V˙O2Pmax) were measured. As a result, body pressure for posture was significantly higher(45 ~55gf/cm3) than the clothing pressure(3~ 25gf/cm2). V˙O2Pmax during exercise was affected both by the posture and clothing pressure. V˙O2Pmax in the sitting posture was 9∼20% higher than that for the supine posture, and V˙O2Pmax in the pressure suits was 2∼12% higher than that in the non-pressure suits.