We propose using dimensionality reduction techniques for analyzing House-Keeping (HK) data of satellites for condition inspection of faults. HK data are high-dimensional data and recorded for a long time, which makes it difficult for analyzers, especially when the persons are not specialists of the satellite. Utilizing hidden data structures and power of computers, dimensionality reduction techniques can be used for visualizing and classification of high-dimensional HK data and that provides useful information. In this paper we treated image degradation problem occurring in an ultra-small satellite XI-V, which is under operation in space. We showed that dimensionality reduction techniques are actually effective in the real spacecraft problem.
In the present paper, viscoplastic property of epoxy resin reinforced by carbon nanotube (CNT) is investigated by numerical approach based on finite element method (FEM) and homogenization theory. Homogenization theory is employed to estimate the homogenized elastic moduli of the composite material which consists of matrix resin and carbon nanotubes. Viscoplastic constitutive equation of epoxy resin have been estimated by uni-axial tensile tests under several strain rates. The parameter of approximation equation of the constitutive equation for epoxy resin was identified based on J2 flow theory. The stress-strain relation under constant strain rate can be identified by the viscoplastic property of epoxy resin and elastic moduli of CNT, where finite element method and homogenization theory were applied. The effect of strain rate, volume fraction of fiber for the viscoplastic property of epoxy resin reinforced with CNT was clarified by some numerical demonstration using the present approach.
Numerical simulations using an Euler solver are done to clarify the influence of direction of rotor rotation on aerodynamic characteristics and flowfields of a rotor hovering near a structure in a crosswind. Parameters for numerical simulations are direction of rotor rotation and crosswind speed to the rotor and structure. The crosswind blows parallel to the rotor and structure. In this condition, the position of structure is on retreating side of the rotor disk when the rotor rotates CW (Clockwise), and is on advancing side when the rotor rotates CCW (Counterclockwise). After discussing the validity of numerical method by comparing numerical results with experimental data, comparisons concerning the rotor torque coefficient, the amplitude and phase angle of blade flapping motion, flowfields around the rotor and inflow distributions on the rotor disk are made between CW and CCW. As a result, it is shown that the rotation direction of main rotor hovering near the structure has a great influence on the blade flapping motion, inflow distributions and wake skew angle when the crosswind blows weakly.
For common understanding between satellite and disaster communities, concept of total evaluation method by using ``Serviceability Function'' is proposed. This function consists of probability to observe damaged area and qualitative coefficient of information interpretability through satellite images. To accomplish ``detection and/or recognition of damaged area within 24 hours'' as the top priority mission, some examples of evaluation are also introduced. By this evaluation concept, promotion of communication and consistency between satellite and disaster communities is expected.
In this study we carried out transient numerical computations to scrutinize the behavior of magnetothermal convection created in a circular pipe located inside the bore space of a superconducting magnet in a nongravitational field. The numerical analysis model considered uses two coaxial circular pipes with open ends. The outer pipe corresponds to the bore space, and the inner one was installed inside the bore space. The inner pipe was initially filled with hotter air or colder air compared to that in the outer pipe. We first examined the behavior of the magnetothermal convections created in a gravitational field to clarify the effects of both the magnetic and the gravitational buoyant forces. Next, we investigated the behavior of the magnetothermal convections created in a nongravitational field to clarify the effect of the magnetic force alone. The magnetothermal convection was created by the magnetic force alone with interaction by the temperature difference between the air in the inner and outer pipes.
A new image-extraction method of a debris cloud for hypervelocity impact is proposed. The method can capture the accurate shape of the debris cloud from the image shot by a high-speed camera. The measurement method for the shape of the debris cloud in the image has not been founded so far. It is important to establish a method to obtain the cloud shape considering the major influence that the cloud exerts on the pressure wall. We apply the classification error rate for extracting the debris cloud from the image shot by a high-speed camera. Specifically, the normalized histogram of a background is assumed to be gamma distribution in order to fit the histogram with the reality. Our method excels conventional methods in a measurement accuracy of the shape of the debris cloud.
We visualized two-dimensional wing buffet using fast-framing focusing schlieren method. A supercritical airfoil of NASA SC(2)-0518 was used in this study. Mach number of the freestream was 0.7, and Reynolds number based on the wing code (c) was 5×106. Angle of attack without corrections (α) was changed from 4° to 6°. The present focusing schlieren system had ±18mm depth of field, which was narrow than spanwise region where the two-dimensionality of the flow field was maintained. 8,345 successive images were captured by high speed CMOS camera with 7,000 frames per second with 20μs exposure time. The present imaging system well captured the shock wave motion on the airfoil. At α = 4°, the shock wave was positioned at x/c∼0.45. The shock wave was slightly fluctuated with a frequency of 585.5Hz. Above α = 5°, the wing buffet occurred. The buffet frequency increased as increasing α. The focusing schlieren movies revealed that the shock wave was bifurcated on the wing surface, as the shock traveling upstream. The boundary layer largely separated from the leading oblique foot of the bifurcated shock wave, whereas, the bifurcated shock wave changed into a normal shock and the flow separation disappeared, as the shock traveling downstream. For both cases, many pressure waves propagated from the downstream of the shock wave to the upstream. These waves merged with the shock wave, and seem to drive the shock oscillation.