Monolithic semiconductor antennas for millimeter wave Si and GaAs integrated circuit technologies

It has been reported that the radiation characteristics of semiconductor antennas can be controlled by modulating their conductivity during fabrication and/or operation. This paper describes novel physical layouts integrating these versatile antennas with other components used in the realization of millimeter wave systems. The monolithic integration is discussed for GaAs as well as Si IC technologies.     

A 44 GHz monolithic semiconductor dipole antenna

Monolithic semiconductor antennas integrated with a diode detector have been fabricated using silicon-on-sapphire technology. The performance of these antennas is analyzed on the basis of earlier theoretical work on imperfectly conducting/resistive cylindrical dipoles. The measured radiation patterns of semiconductor antennas are compared with those of the corresponding printed metal dipoles.     

Secretion of cardiac plasminogen activator during hypoxia-induced right ventricular hypertrophy

In the circulation, fibrinolytic activity is determined to a large degree by the relative levels of tissue plasminogen activator (tPA) and its major inhibitor (PAI-1). Vascular beds in different organs secrete tPA and PAI-1 into the circulation, and the total secretory rate of each protein is balanced by its half-life in the bloodstream. We are testing the hypothesis that in the heart, ventricular hypertrophy will alter the rates of formation of tPA and/or PAI-1 and the rates of their release into the cardiac vasculature. In this study, we have examined the effects of continuous hypoxia on PA activity in extracts of rat heart ventricles, on the activity secreted into the cardiac vasculature of perfused hearts, and on the levels of mRNAs for tPA and PAI-1. Rats were subjected to hypobaric hypoxia at 0.5 atm for 1-21 days. The treatment caused polycythemia within 1-3 days, and right ventricular hypertrophy by 3 days. PA activity in extracts of both right and left ventricles was significantly elevated after 3 days of hypoxia, continued to increase for 4 additional days, and remained elevated for 3 weeks. The actions of inhibitors of urokinase and tPA indicated that the PA activity in heart extracts was exclusively tPA. Fibrin zymography confirmed that result. The mRNAs for tPA and for PAI-1 were elevated after 1 day of hypoxia and then returned to near control levels on days 2 and 3. After 7 days, hearts from hypoxic rats secreted more tPA activity into perfusates than did hearts from controls. The difference in secretory rates was proportional to the differences in the levels of tPA in the corresponding heart extracts.     

Dietary protein deficiency induced changes in protein kinase C activity and phospholipid metabolism in rat hepatocytes

Dietary protein deficiency is known to alter the protein kinase C activity in various tissues of rats. Protein kinase C activity is influenced by the metabolism of membrane phosphoinositides and phosphatidyl choline (PC). For metabolic studies, hepatocytes have been the cells of choice of various workers. Therefore, studies on protein kinase C and these phospholipids were conducted in hepatocytes of rats maintained on three different diets viz. casein (20% protein) deficient (4% protein, rice flour as source of protein) and supplemented (deficient diet supplemented with L-lysine and DL-threonine) diet for 28 days. The protein deficiency in diet led to a decline in protein kinase C activity (P < 0.01) without effecting its translocation, an increase in phosphatidyl inositol 4,5-bisphosphate (P < 0.001) and a decrease in phosphatidyl inositol 4-monophosphate and phosphatidyl inositol (P < 0.01) but did not alter the PC contents, as compared to the casein group. Supplementation of deficient diet with L-lysine and DL-threonine could considerably reverse the effect of deficiency of protein in diet. The results suggest that quality of dietary protein is mainly relevant for maintaining phospholipid metabolism and physiology of hepatocytes and thus the signalling mechanism in these cells.     

Decentralized energy planning model for optimum resource allocation with a case study of the domestic sector of rurals in Nepal

The paper is concerned with the development of a simplified linear model which attempts to optimize the cost function of an energy supply system consisting of a mix of energy resources and conversion devices, each of which may have a constraint with respect to availability, efficiency and cost. The model has been applied in three villages, from three different physiographic zones of Nepal, for which detailed data were collected and analysed. The results of the study show that the optimized use of different energy sources in different regions is strongly dependent on demographic and climatic parameters. For hill villages, hydropower could become the cheapest source of energy if technical options were provided, but until then more efficient use of wood is the only viable solution. Commercial sources like kerosene and LPG are not likely to play any significant role in hill and mountain villages. On the other hand, the use of biogas is economically most feasible in Terai village. The availability of kerosene rules out wood or agriculture waste as feasible solutions for cooking energy needs, as this village is closer to the Indian border and has good road access.     

Hyperbolic decline-curve analysis using linear regression

Two rigorous techniques for hyperbolic decline-curve analysis based on the fundamental equations are investigated. The parameter estimation is made more accurate and repeatable than type curve matching if linear regression is used to extract the unknowns D_iq_i and n from the data. Maximizing the regression coefficient is the criterion used to select the correct parameter values. In application to six field examples, it is seen that the two methods do not always give identical results if there is a lot of scatter in the data.     

Sky component grids for glazed vertical windows

Daylight contribution at a point due to sky visible through different areas of a window is a function of the sky luminance, the projected solid angle of these areas at the reference point on the working plane and the transmittance of glass. The transmittance of glass varies considerably with the angle of incidence, which depends upon the relative positions of different parts of a window opening with respect to the reference point. A sky component grid, representing the sky component values from different elemental areas of openings in a window wall, forms one of the simplest ready reckoners in daylighting design. This paper presents the methodology of generating sky component grid for any sky condition. The relevant data on mean altitude of grid elements, the mean angle of incidence for different grid elements, and differential sky factors are included for facilitating the computation of grid values. The sky component grid for Indian clear design sky based on exact equations of sky component for a horizontal plane, with a due allowance for transmittance of 3 mm thick clear glass, is provided for comparing the accuracy of the methodology based on differential sky factors. The values computed from the data and the methodology presented in this paper agree closely with the exact values. The deviation of computed values from exact values is less than ±10%.     

On the sintering kinetics of titania doped ceramic lanthanum chromite

The sintering behaviour of lanthanum chromite with the addition of 1 to 3 wt% TiO₂ was studied. Densification was examined as a function of sintering temperature and TiO₂ concentration. The results showed that pure LaCrO₃ could not be densified to >75% of the theoretical density, while the densities exceeding 90% of the theoretical were achieved with 3 wt% titania addition at 1600° C. Metallographic study reveals a normal grain growth following the rate equationD ²−D ₀ ² =kt. Activation energies both for densification and grain growth have been estimated to be ≈ (80±5) k cal/mole in case of 3 wt% TiO₂ addition.     

Finite element analysis of substation composite insulators

Composite insulators are rapidly replacing their porcelain counterparts in electrical substation applications. These insulators consist of a glass-reinforced polymer (GRP) rod, with two metal end fittings radially crimped onto the ends of the rod during assembly. In this paper, axisymmetric finite element models are developed to evaluate the mechanical performance of composite insulators under externally applied axial compression. The analyses are performed by assuming both a perfectly bonded interface between the composite rod and the end fittings, and an imperfect interface which permits large relative sliding with Coulomb friction. Results indicate that the perfect interface model is unrealistic since it predicts singular stresses at the interface comer and an overall linear structural response. On the other hand, the imperfect interface model is found to simulate accurately the structural non-linearity caused by relative sliding of the GRP rod within the end fittings. The imperfect interface model has therefore been used to evaluate the effects of interface friction, and the extent of crimping, on the maximum load-bearing capacity of substation composite insulators.