Optimal PV system dimensioning with obstructed solar radiation

This paper describes an analytical methodology for the optimised design of stand-alone photovoltaic (PV) systems installed at locations where the solar radiation is considerably shortened by obstacles, i.e. at the bottom of a gorge. A method for the computation of the real available solar energy incident on the PV panel is proposed, based on easily conducted measurements. The optimum tilt of the PV array, under such conditions, is obtained and a dimensioning procedure provides the optimal size of the PV-array/storage. The resulting system is tested by a verification routine. A case study, employing the complete algorithm proposed, is illustrated.     

The role of N,N-dimethylaniline in the formation of titania gel monolith by sol-gel method

19950405 Our investigation on the rheological aspects such as gelling time, specific density, fluidity, viscosity and surface tension of the sol derived from titanium-tetra-isopropoxide (TTIP), water and isopropanol (i-PrOH) has been reviewed in the presence of n,n-dimethylaniline (DMA) as a drying control chemical agent (DCCA). Dry gels derived from DMA stabilized sol were found to be crack free with a larger surface area. The titania gel monolith obtained in the presence of DMA could be processed into rutile at much lower temperatures.     

Alignment of fluorescent molecules vapour-deposited on to highly oriented PTFE substrates

The alignment of six fluorescent materials (p-terphenyl, p-quaterphenyl, p-quinquephenyl, diphenylstilbene, 1,4-bis(2-methylstyryl)benzene, and 1,4-bis-2-(5-phenyloxazolyl)benzene) grown from the vapour phase on to friction-deposited, highly oriented poly(tetrafluoroethylene) (PTFE) films was studied. The dichroic ratio of the fluorescent films produced was determined by polarized spectroscopic fluorescence measurements, and the crystallographic orientation of these materials was determined by transmission electron microscopy. The measured dichroic ratios ranged from 1.7 for diphenylstilbene to 5.0 for the p-quaterphenyl film. Electron diffraction patterns revealed that five of the fluorescent materials grew epitaxially on the single crystal-like PTFE films, the fluorescent crystals adopting particular orientations with respect to the crystallographic planes of PTFE. On the other hand, crystals of 1,4-bis-2-(5-phenyloxazolyl) benzene aligned in a fibre pattern, apparently by a grapho-epitaxial mechanism.     

A broadband power meter calibration system in the frequency rangefrom 10 MHz to 40 GHz using a coaxial calorimeter

A broadband power meter calibration system based on a newly constructed coaxial calorimeter has been developed in the frequency region 10 MHz-40 GHz. The RF power is measured as the difference of DC power supplied to the calorimeter built-in heater in the RF load, when RF is turned off and on, holding an isothermal control between the RF load and a temperature reference. To minimize the error due to the adiabatic coaxial waveguide, we devised a new method utilizing its output port as a test port. The evaluations showed a calibration uncertainty of (0.28-2.2)% expressed by one standard deviation at the 1 mW level in the full band     

Generalized model of the quantization error-a unified approach

The effective resolution of AD converters is a crucial quantization quality parameter in modern instrumentation. A usual theoretical assumption about the quantized (training) signal is that it is a pure sine wave with a “zero” offset. This means that either the average value of the sine wave is equal to one of the threshold levels (quantizer without dead zone) or that it lies exactly in the middle of them (rounding quantizer). In the measurement technique this assumption is hardly fulfilled, and that is why we meet something intermediate between the above-mentioned hypothetical situations. Here we generalize the known results for “zero” offset to the case of unknown offset. A general problem of an arbitrary random offset distribution is considered first. Two important practical cases are then analyzed. The first one is an unknown and nonrandom offset (one-point distribution). The second one is a case of a uniform distribution of the offset (effect of dithering on quantizer input). In particular, the expected values and variances are derived and analyzed versus the offset and the number of quantizing levels. The results obtained are applied to the effective resolution measurement     

ERD facility for analysis of hydrogen and deuterium in solids

Hydrogen is the lightest element in nature, and so, its detection and quantitative analysis is difficult by the conventional methods utilized for other elements. In the recent years the technique of elastic recoil detection analysis (ERD) using 1–2 MeV He⁺ beam has been developed to quantitatively and simultaneously analyze hydrogen and its isotopes in solids. Such a facility has been set up using the 2 MeV Van-de-Graaff accelerator at IIT Kanpur. It facilitates H and D analysis in a material up to a depth of ∼ 1μm with a detection sensitivity of 0·1 at.% and depth resolution of about 300 ?. The application potential of this setup is illustrated by presenting the results of measurements performed on Al:H:D systems prepared by plasma source ion implantation and highT _c YBCO pellets exposed to humid atmosphere.     

Analysis of adhesive bonded composite lap joints with transverse stitching

The effect of transverse stitching on the stresses in the adhesive is investigated using an adhesive sandwich model with nonlinear adhesive properties and a transverse stitching model for adhesive bonded composite single-lap and double-lap joints. Numerical results indicate that, among all stitching parameters, thread pretension and stitch density have significant effect on the peel stresses in the adhesive; increase in the thread pretension and the stitch density leads to a decrease in peel stress in the adhesive, while an increase in other parameters generally results in a negligible reduction in peel stress. The effect of stitching was found to be negligible on the shear stresses in the adhesive. Thus it is concluded that stitching is effective for the joints where peel stresses are critical and ineffective for those where shear stresses are critical.     

Discussion of “an interpretation of the carbon redistribution process during aging of high-carbon martensite”

Y. OHMORI and I. TAMURA:Metall. Trans. A, 1992, vol. 23A,