Different atmospheric effects in remote sensing of uniform and nonuniform surfaces

The atmospheric effect on the radiance of sunlight scattered from the Earth-atmosphere system is greatly dependent on the surface reflectance pattern, the contrast between adjacent fields, and the optical properties of the atmosphere. In addition, the atmospheric effect is described by the range and magnitude of the adjacency effects, the atmospheric modulation transfer function, and the apparent spatial resolution of remotely sensed imagery. This paper discusses the atmospheric effect on classification of surface features and shows that surface nonuniformity can be used for developing procedures to remove the atmospheric effect from the satellite imagery.     

Chromosomal changes in cultured human epithelial cells transformed by low- and high-LET radiation.

For a better assessment of radiation risk in space, an understanding of the responses of human cells, especially the epithelial cells, to low- and high-LET radiation is essential. In our laboratory, we have successfully developed techniques to study the neoplastic transformation of two human epithelial cell systems by ionizing radiation. These cell systems are human mammary epithelial cells (H184B5) and human epidermal keratinocytes (HEK). Both cell lines are immortal, anchorage dependent for growth, and nontumorigenic in athymic nude mice. Neoplastic transformation was achieved by irradiating cells successively. Our results showed that radiogenic cell transformation is a multistep process and that a single exposure of ionizing radiation can cause only one step of transformation. It requires, therefore, multihits to make human epithelial cells fully tumorigenic. Using a simple karyotyping method, we did chromosome analysis with cells cloned at various stages of transformation. We found no consistent large terminal deletion of chromosomes in radiation-induced transformants. Some changes of total number of chromosomes, however, were observed in the transformed cells. These transformants provide an unique opportunity for further genetic studies at a molecular level.     

Strong magnetic field effect on the dissolution process of tetragonal lysozyme crystals.

Either a homogeneous or inhomogeneous magnetic field has been known to dampen the protein crystal growth. To date the mechanism is not clear. However, it was generally proposed that the magnetic field may dampen the convection in the solution, resulting in a reduced crystal growth rate and possibly a good crystal quality, similar to the case of protein crystal growth in space. To understand the mechanism of the magnetic field effect on protein crystal growth, further explorations on the magnetic field effect on protein solution, on the processes of crystal growth and dissolution, and on different crystallization (solution) systems, should be valuable. In this paper we present our recent efforts to study magnetic field effects on the dissolution processes of tetragonal lysozyme crystals under a strong magnetic field. A layer of oriented tetragonal lysozyme crystals was prepared under a temperature gradient and magnetic field, after that the crystals were dissolved by increasing the temperature of the solution. The lysozyme molecules will diffuse upwards due to the steep concentration gradient at the lower side of the cell caused by the dissolution. The evolution of the concentration in the solution was measured in-situ using a Mach-Zehnder interferometer. The results confirmed that the dissolution process of the crystals was slowed by the magnetic field. Judging from the concentration evolution versus time at different positions in the solution, we concluded that the apparent diffusion coefficient of lysozyme molecules was decreased by the magnetic field. The results were discussed using a suspended crystal model in the initial dissolution stage.     

Application of frequency correlation function to radar target detection

Analysis of high-resolution 35 GHz synthetic aperture radar (SAR) imagery of terrain reveals that when point targets, such as vehicles, are viewed at angles close to grazing incidence, they are often difficult to distinguish from tree trunks because the radar cross section (RCS) intensities of the vehicles are comparable to the upper end of the RCS exhibited by tree trunks. To resolve the point target/tree trunk ambiguity problem, a detailed study was conducted to evaluate the use of new detection features based on the complex frequency correlation function (FCF). This paper presents an analytical examination of FCF and its physical meaning, the results of a numerical simulation study conducted to evaluate the performance of a detection algorithm that uses FCF, and the corroboration of theory with experimental observations conducted at 35 and 95 GHz. The FCF-based detection algorithm was found to correctly identify tree trunks as such in over 90% of the cases, while exhibiting a false alarm rate of only 3%.     

Optimization of the Energy-Storage Inductors for DC-to-DC Converters

Three sets of design graphs and equations are developed to facilitate design of the energy-storage inductors for dc-to-dc converters. Using the design graphs, a quick estimate of the inductor minimum weight, the transistor peak current, and the inductor power loss can be obtained. Tradeoff studies can be conveniently conducted using these graphs. The effects of duty cycle controllers, constant frequency and constant tON, on the optimal selection of the energystorage inductors are assessed.     

Absorbed dose measurements on external surface of Kosmos-satellites with glass thermoluminescent detectors.

In this paper we present absorbed dose measurements with glass thermoluminescent detectors on external surface of satellites of Kosmos-serie flying in 1983-87. Experiments were performed with thermoluminescent aluminophosphate glasses of thicknesses 0.1, 0.3, 0.4, 0.5, and 1 mm. They were exposed in sets of total thickness between 5 and 20 mm, which were protected against sunlight with thin aluminized foils. In all missions, extremely high absorbed dose values were observed in the first layers of detectors, up to the thickness of 0.2 to 0.5 gcm-2. These experimental results confirm that, during flights at 250 to 400 km, doses on the surface of the satellites are very high, due to the low energy component of the proton and electron radiation.     

SSRT: First results of millisecond spike observations

We present the results of the first observations of spike-like phenomena with the Siberian Solar Radio Telescope (SSRT) in the one-dimensional mode at the frequency of 5.7 GHz with high spatial and temporal resolutions.     

An adaptive controller for current-fed induction motor

A model reference speed adaptive controller for a current-fed induction motor drive is proposed. It uses a proportional-plus-integral (PI) adaptation to satisfy the hyperstability condition for taking care of the load and machine parameter changes of the drive. The available information on the states and output of the reference model as well as the plant output are all that are required for the control; no explicit parameter identification is needed. The controller can be designed by using a reduced reference model to simplify the design without much degradation of the performance, so that it is relatively easy to implement practically     

Digital control algorithms for multi-degree-of-freedom microgravity isolation systems

Two general methodologies have been developed to design digital controllers for multi-degree-of-freedom microgravity isolation systems such that the desired transmissibility matrix is achieved. The absolute accelerations and relative displacements are used as feedback signals. Absolute acceleration signals are used to provide proportional damping in the system whereas relative displacement signals are used to achieve the desired transmissibility. In the first method, the closed-form expression of the controller transfer function metrix for the relative displacement feedback is obtained directly in the Z-domain. The controller transfer function matrix is first obtained in the S-domain and then discretized in the second method. The discrete-time controller transfer function matrices and numerical results are presented for a three-degree-of-freedom system with attractive electromagnetic actuators.