Development and characterization analysis of a radar polarimeter

The interaction of electromagnetic waves with natural earth surface was of interest for many years. A particular area of interest in controlled remote sensing experiments is the phenomena of depolarization. The development stages of the radar system are documented. Also included are the laboratory procedures which provides some information about the specifications of the system. The radar system developed is termed the Radar Polarimeter System. A better insight of the operation of the RPS in terms of the newly developed technique--synthetic aperture radar system is provided. System performance in tems of radar cross section, in terms of power, and in terms of signal to noise ratio are also provided. In summary, an overview of the RPS in terms of its operation and design as well as how it will perform in the field is provided

Unexpected contraction of a zeolite framework upon isomorphous substitution of Si by Al

Isomorphous substitution of Si by Al in the framework of sodalites synthesized in ethylene glycol causes an unexpected contraction of the zeolite framework

Debunking myths in CAQDAS use and coding in qualitative data analysis: experiences with and reflections on grounded theory methodology

'The author deliberates firstly the primacy of grounded theory as a methodology and secondly the primacy of grounded theory coding as a method in deciding on CAQDAS use in his research. In the first section of this paper, the author weighs the extent to which his research draws and departs from the principles and practices of grounded theory methodology (GTM). In examining the impact of cultures and religions on women's human rights in Malaysia the author has used for example hypothesis-guided criteria for sampling. This is strictly speaking not in the original sense a grounded theory approach. In the paper, the author makes transparent the extent to which GTM has informed his work in enhancing the qualitative research and in highlighting the uses and limits of GTM, the author poses the question to what extent has the author demystified its paradigmatic status in CAQDAS and its homogenising effects. In the second section, the author discusses the dominance of coding in qualitative data analysis and the author argues that the pitfall of reifying coding as analyses can be avoided through a researcher's reflexivity and agency (self-determination) combined with a pragmatic view and the use of codes as a means and not as an end, essentially, grounded theory coding. The author discusses whether CAQDAS use as a tool facilitates the rigour of GTM and the transparency of grounded theory coding as method as manifested in one's audit trail, and whether this in turn constitute research that is more accountable, innovative and effective.' (author's abstract)

Dynamics of the molecular orientation field coupled to ions in two-dimensional ferroelectric liquid crystals

Molecular orientation fluctuations in ferroelectric smectic liquid crystals produce space charges, due to the divergence of the spontaneous polarization. These space charges interact with mobile ions, so that one must consider the coupled dynamics of the orientation and ionic degrees of freedom. Previous theory and light scattering experiments on thin free-standing films of ferroelectric liquid crystals have not included this coupling, possibly invalidating their quantitative conclusions. We consider the most important case of very slow ionic dynamics, compared to rapid orientational fluctuations, and focus on the use of a short electric field pulse to quench orientational fluctuations. We find that the resulting change in scattered light intensity must include a term due to the quasistatic ionic configuration, which has previously been ignored. In addition to developing the general theory, we present a simple model to demonstrate the role of this added term

Microscale Fluid Behavior during Cryo-EM Sample Blotting

Blotting has been the standard technique for preparing aqueous samples for single-particle electron cryo-microscopy for over three decades. This technique removes the excess solution from a transmission electron microscope grid by pressing absorbent filter paper against the specimen before vitrification. However, this standard technique produces vitreous ice with inconsistent thickness from specimen to specimen and from region to region within the same specimen, the reasons for which are not understood. Here, high-speed interference contrast microscopy is used to demonstrate that the irregular pattern of fibers in the filter paper imposes tortuous, highly variable boundaries during the removal of excess liquid from a flat, hydrophilic surface. As a result, aqueous films of nonuniform thickness are formed while the filter paper is pressed against the substrate. This pattern of nonuniform liquid thickness changes again after the filter paper is pulled away, but the thickness still does not become completely uniform. We suggest that similar topographical features of the liquid film are produced during the standard technique used to blot EM grids and that these manifest in nonuniform ice after vitrification. These observations suggest that alternative thinning techniques, which do not rely on direct contact between the filter paper and the grid, may result in more repeatable and uniform sample thicknesses

Role of electrostatics in the texture of islands in free standing ferroelectric liquid crystal films

Curved textures of ferroelectric smectic C* liquid crystals produce space charge when they involve divergence of the spontaneous polarization field. Impurity ions can partially screen this space charge, reducing long range interactions to local ones. Through studies of the textures of islands on very thin free-standing smectic films, we see evidence of this effect, in which materials with a large spontaneous polarization have static structures described by a large effective bend elastic constant. To address this issue, we calculated the electrostatic free energy of a free standing film of ferroelectric liquid crystal, showing how the screened coulomb interaction contributes a term to the effective bend elastic constant, in the static long wavelength limit. We report experiments which support the main features of this model

Radar cross calibration investigation TAMU radar polarimeter calibration measurements

A short pulse, 20 MHz bandwidth, three frequency radar polarimeter system (RPS) operates at center frequencies of 10.003 GHz, 4.75 GHz, and 1.6 GHz and utilizes dual polarized transmit and receive antennas for each frequency. The basic lay-out of the RPS is different from other truck mounted systems in that it uses a pulse compression IF section common to all three RF heads. Separate transmit and receive antennas are used to improve the cross-polarization isolation at each particular frequency. The receive is a digitally controlled gain modulated subsystem and is interfaced directly with a microprocesser computer for control and data manipulation. Antenna focusing distance, focusing each antenna pair, rf head stability, and polarization characteristics of RPS antennas are discussed. Platform and data acquisition procedures are described

Do Firms Adjust Their Timely Loss Recognition in Response to Changes in the Banking Industry?

This paper investigates the impact of changes in the banking sector on firms’ timely recognition of economic losses. In particular, we focus on the entry of foreign banks into India during the 1990s, which likely causes an exogenous increase in lender demand for timely loss recognition. Analyzing variation in both the timing and the location of the new foreign banks’ entries, we find that foreign bank entry is associated with more timely loss recognition and this increase is positively related to a firm\u27s subsequent debt levels. The change appears driven by a shift in firms’ incentives to supply additional information to lenders and lenders seem to value this information. The increase in timely loss recognition is also concentrated among firms more dependent on external financing: private firms, smaller firms, and nongroup firms. Overall, our evidence suggests that a firm\u27s accounting choices respond to changes in the banking industry