On-Board Experimental Study Of Bubble Thermocapillary Migration In A Recoverable Satellite

An on-board space experiment of bubble thermocapillary migration was performed in the Chinese 22nd recoverable satellite in 2005. Silicone oil of nominal viscosity 5cSt was used as the continuous phase in the experiment. Air bubbles were injected into the liquid in the same direction as the constant temperature gradient in the liquid. The velocities of bubbles were obtained by recording the paths of the bubbles. The results indicate that the scaled velocity of bubbles decreases with an increase of the Marangoni number extended to 9288, which agrees with the results of previous space experiments and numerical simulation. In addition, the interaction between two bubbles was also observed in the space experiment. The trajectories and the velocities of the bubbles were obtained. The two-bubble experiment results are also consistent with the theoretical analysis.

The scientific project of the small satellite of china

The efforts involved in developing a small satellite for scientific purposes in China in recent years are introduced in the present paper. The project is arranged on a case to case principle depending upon requirements and financial support. The space technology of a satellite and rockets, which have been developed over a relatively longer period in China, have been transferred to the scientific research of small satellites for improvement of the quality requirements. The surplus payloads of the rocket and satellite are used as the payloads of the small satellite and scientific experiments at a low cost. As an example, the project of balloon satellites for atmospheric research was successfully completed in 1991. The experience of the project management is of great benefit for further organization and arrangement of other projects. Opportunities exist for surplus payloads to be used in the future, and a small satellite for magnetospheric research will be launched in 1993.

Two Bubbles Thermocapillary Migration Experimental System

An experimental investigation will be performed on the thermocapillary motion of two bubbles in Chinese return-satellite. The experiment will study the migration process of bubble caused by thermocapillary effect in microgravity environment, and their interaction between two bubbles. The bubble is driven by the thermocapillary stress on the surface on account on the variation of the surface tension with temperature. The interaction between two bubbles becomes significant as the separation distance between them is reduced drastically so that the bubble interaction has to be considered. Recently, the problem has been discussed on the method of successive reflections, and accurate migration velocities of two arbitrarily oriented bubbles were derived for the limit of small Marangoni and Reynolds numbers. Numerical results for the migration of the two bubbles show that the interaction between two bubbles has significant influence on their thermocapillary migration velocities with a bubble approaching another. However, there is a lack of experimental validate for the theoretic results. Now the experimental facility is designed for experimenting time after time. A cone-shaped top cover is used to expel bubble from the cell after experiment. But, the cone-shaped top cover can cause temperature uniformity on horizontal plane in whole cell. Therefore, a metal board with multi-holes is fixed under the top cover. The board is able to let the temperature distribution on the board uniform because of their high heat conductivity, and the bubble can pass through it. In the system two bubbles are injected into the test cell respectively by two sets of cylinder. And the bubbles sizes are controlled by two sets of step-by-step motor. It is very important problem that bubble can be divorced from the injecting mouth in microgravity environment. Thus, other two sets of device for injecting mother liquid were used to push bubble. The working principle of injecting mother liquid is to utilize pressure difference directly between test cell and reservoir

Migration routes and stopover sites of Black-necked Cranes determined by satellite tracking

Because their breeding and wintering areas are in remote locations, little is known about the biology of Black-necked Cranes (Grus nigricollis), including their migratory behavior. Using satellite telemetry, we monitored the migration of Black-necked Cran

Suckers (Fish, Catostomidae) from the Eocene of China account for the family's current disjunct distributions

Unequivocal Eocene suckers from China are for the first time reported here. This discovery demonstrates that catostomids of the Eocene Epoch (some 55-35 Ma ago) are scattered widely on mainland Asia as well as western North America. The present day disjunct distribution pattern of catostomids, with 68 extant species widespread in North America and the northern part of Middle America and only two in the restricted areas of Asia, is the result of their post-Eocene decline in Asia due to the competitive pressure from cyprinids, their Late Cenozoic radiation in North America, and the vicariant and dispersal events triggered by the changed biogeographic landscape. All of these prove to be a historical product of the geological, biological, and climatic changes throughout the Cenozoic.

X-ray diffraction analysis on gallium-indium interdiffusion in quantum dot superlattices

Thermal-induced interdiffusion in InAs/GaAs quantum dot superlattices is studied by high-resolution x-ray diffraction rocking curve and photoluminescence techniques. With increasing annealing temperatures, up to 300 meV a blueshift of the emission peak position and down to 16.6 meV a narrowing of the line width are found in the photoluminescence spectra, and respective intensity of the higher-order satellite peaks to lower-order ones in the x-ray rocking curves decreases. Dynamical theory is employed to simulate the measured x-ray diffraction data. Excellent agreement between the experimental curves and the simulations is achieved when the composition, thickness and stress variations caused by interdiffusion are taken into account. It is found that the significant In-Ga intermixing occurs even in the as-grown InAs/GaAs quantum dots. The estimated diffusion coefficient is 1.8 x 10(-17) cm(2) (.) s(-1) at 650 degreesC, 3.2 x 10(-17) cm(2 .) s(-1) at 750 degreesC, and 1.2 x 10(-14) cm(2 .) s(-1) at 850 degreesC.

Satellite Constellation Design for Complex Coverage

Most traditional satellite constellation design methods are associated with a simple zonal or global, continuous or discontinuous coverage connected with a visibility of points on the Earth's surface. A new geometric approach for more complex coverage of a geographic region is proposed. Full and partial coverage of regions is considered. It implies that, at any time, the region is completely or partially within the instantaneous access area of a satellite of the constellation. The key idea of the method is a two-dimensional space application for maps of the satellite constellation and coverage requirements. The space dimensions are right ascension of ascending node and argument of latitude. Visibility requirements of each region can be presented as a polygon and satellite constellation as a uniform moving grid. At any time, at least one grid vertex must belong to the polygon. The optimal configuration of the satellite constellation corresponds to the maximum sparse grid. The method is suitable for continuous and discontinuous coverage. In the last case, a vertex belonging to the polygon should be examined with a revisit time. Examples of continuous coverage for a space communication network and of the United States are considered. Examples of discontinuous coverage are also presented.