Time filter

Source Type

Yokosuka, Japan

National Defense Academy of Japan , abbreviated NDA is the national, four-year university-level military academy aimed to educate and train students who will be serving as officers in the three services of the Japan Self-Defense Forces. It is located in Yokosuka, Kanagawa on the grounds close to the former Imperial Japanese Army Academy. Wikipedia.

Yokoyama N.,Japan National Defense Academy
Journal of Guidance, Control, and Dynamics | Year: 2013

This paper describes a novel algorithm for generating flight paths in real time that avoid turbulent regions detected by an onboard Doppler lidar. Adopting the distance traveled rather than the time as the independent variable in the state equations enables an exact expression to be obtained for the point-mass dynamics and reduces the number of constraints imposed by turbulence avoidance. Moreover, the algorithm estimates the global optimum by applying second-order cone programming relaxation to the original nonconvex problem. Based on this estimate, it then applies convex quadratic programming. This algorithm is well suited for real-time applications since it is guaranteed to converge in polynomial computation time and it is expected to generate practically useful paths. The high computational speed of the algorithm is demonstrated and the physical feasibilities of the calculated paths are analyzed by numerically simulating turbulence avoidance. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source

Ouchi K.,Japan National Defense Academy
Remote Sensing | Year: 2013

The present article is an introductory paper in this special issue on synthetic aperture radar (SAR). A short review is presented on the recent trend and development of SAR and related techniques with selected topics, including the fields of applications, specifications of airborne and spaceborne SARs, and information contents in and interpretations of amplitude data, interferometric SAR (InSAR) data, and polarimetric SAR (PolSAR) data. The review is by no means extensive, and as such only brief summaries of of each selected topics and key references are provided. For further details, the readers are recommended to read the literature given in the references theirin. © 2013 by the author. Source

A single living cell (PC12), cultured on a polystyrene dish and an albumin island immobilized on glass, were successfully imaged utilizing the differential standing approach (d-SA) mode of a scanning ion conductance microscope (SICM). In the d-SA mode, the differential of the output voltage of a tuning fork (rather than its absolute value) is used as the signal for maintaining a constant distance between the probe of a scanning ion conductance microscope (SICM) and the sample. The topography and SICM images were obtained simultaneously, and approach curves, when the tip approached the immobilized albumin or the PC12 cell membrane, were also obtained. The settings for the d-SA mode were carefully determined from the PC12 cell approach curve. Furthermore, differences in the topographies of the immobilized albumin and living PC12 cell images obtained using the standing approach (SA) versus d-SA mode are discussed. It is shown that SICM in d-SA mode is capable of imaging soft samples such as living cells without damaging them. © 2014 Elsevier Ltd. Source

Tada S.,Japan National Defense Academy
Physics in Medicine and Biology | Year: 2010

This study investigates the oxygen mass transport in the region around the human carotid bifurcation, particularly addressing the effects of bifurcation geometry and pulsatile blood flow on the oxygen transport between the blood flow and artery wall tissue, coupled with the metabolic oxygen consumption and oxygen diffusion in the artery wall tissue. The temporal variations and spatial distributions of the oxygen tension are predicted quantitatively using a geometric model of the human carotid bifurcation and realistic blood flow waveforms. Results reveal that the flow separation at the outside wall of the sinus of the internal carotid artery (ICA) can markedly alter the flow pattern, oxygen tension and the oxygen wall flux. Results also clarify that the flow unsteadiness has a secondary effect on the oxygen tension inside the wall. The non-dimensional oxygen flux, the Sherwood number Sh, at the outside wall of the ICA sinus, takes markedly lower values of about 45 than at other sites because the rates of oxygen transport by the convective flow are reduced at the outside wall of the ICA sinus. The transverse distributions of the oxygen tension inside the artery wall show parabolic profiles having minima in the middle of the wall thickness, with the lowest value of 35 mmHg. These predicted distributions of the oxygen tension inside the wall closely resemble those obtained from experiments. The results demonstrate that hypoxic zones appear inside the artery walls at locations where atherosclerotic lesions are prone to develop. © 2010 Institute of Physics and Engineering in Medicine. Source

Kohga M.,Japan National Defense Academy
Propellants, Explosives, Pyrotechnics | Year: 2011

The burning rate of AP/HTPB composite propellant increases with increasing AP content and with decreasing AP size. In addition, the burning rate can be enhanced with the addition of Fe2O3. The burning characteristics and thermal decomposition behavior of AP/HTPB composite propellant using coarse and fine AP particles with and without Fe 2O3 at various AP contents were investigated to obtain an exhaustive set of data. As the AP content decreased, the burning rate decreased and the propellants containing less than a certain AP content self-quenched or did not ignite. The self-quenched combustion began at both lower and higher pressures. The lower limit of AP content to burn the propellant with coarse AP was lower than that with fine AP. The lower limit of AP content to burn was decreased by the addition of Fe2O3. The thermal decomposition behavior of propellants prepared with 20-80 % AP was investigated. The decrease in the peak temperature of the exothermic decomposition suggested an increased burning rate. However, a quantitative relationship between the thermochemical behavior and the burning characteristics, such as the burning rate and the lower limit of AP content to burn, could not be determined. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Discover hidden collaborations