A new algorithm for parallel solution of linear equations

Abstract is not available.

Representation of functional dependencies in relational databases using linear graphs

Functional dependencies in relational databases are investigated. Eight binary relations, viz., (1) dependency relation, (2) equipotence relation, (3) dissidence relation, (4) completion relation, and dual relations of each of them are described. Any one of these eight relations can be used to represent the functional dependencies in a database. Results from linear graph theory are found helpful in obtaining these representations. The dependency relation directly gives the functional dependencies. The equipotence relation specifies the dependencies in terms of attribute sets which functionally determine each other. The dissidence relation specifies the dependencies in terms of saturated sets in a very indirect way. Completion relation represents the functional dependencies as a function, the range of which turns out to be a lattice. Depletion relation which is the dual of the completion relation can also represent functional dependencies and similarly can the duals of dependency, equipotence, and dissidence relations. The class of depleted sets, which is the dual of saturated sets, is defined and used in the study of depletion relations.

Comment: Eigenvalue sensitivity method for optimal stabilisation of linear systems

In a letter RauA proposed a new method for designing statefeedback controllers using eigenvalue sensitivity matrices. However, there appears to be a conceptual mistake in the procedure, or else it is unduly restricted in its applicability. In particular the equation — BR~lBTK = A/.I, in which K is a positive-definite symmetric matrix.

Non-linear dynamic analysis of rotors by finite element method

Non-linear natural vibration characteristics and the dynamic response of hingeless and fully articulated rotors of rectangular cross-section are studied by using the finite element method. In the formulation of response problems, the global variables are augmented with appropriate additional variables, facilitating direct determination of sub-harmonic response. Numerical results are given showing the effect of the geometric non-linearity on the first three natural frequencies. Response analysis of typical rotors indicates a possibility of substantial sub-harmonic response especially in the fully articulated rotors widely adopted in helicopters.

Low-frequency dielectric constant measurements in the critical polar + non-polar binary liquid system: Methanol + n-heptane

The low-frequency (5–100 kHz) dielectric constant ε has been measured in the temperature range 7 × 10−5 < T = (T − Tc)/Tc < 8 × 10−2. Near Tc an exponent ≈0.11 characterizes the power law behaviour of dε/dt consistent with the theoretically predicted t−α singularity. However, over the full range of t an exponent ≈0.35 is obtained.

Estimation of red blood cell lifespan from alveolar carbon monoxide measurements

Measurement of alveolar carbon monoxide (CO) presents a facile technique to estimate the lifespan, L, of red blood cells (RBCs) in vivo. Several recent studies employ this technique and calculate L (in days) using the expression, L = 13.8 (Hb)/P-CO(end), where (Hb) is the concentration (in g/dL) of hemoglobin in blood, and P-CO(end) is the endogenous production of CO (in ppm). Implicit in this calculation is the assumption that the fraction, f, of endogenous CO production due to RBC turnover is a constant equal to 0.7, which yields the expected RBC lifespan, L approximate to 120 days, in normal controls. In anemic patients, however, enhanced RBC turnover may increase f substantially above 0.7. The above expression then overestimates L. Here, we deriv an alternative tive expression, L = 3390[Hb]/322P(CO (end)-110, that accounts explicitly for the dependence of f on the rate of RBC turnover and thereby provides more accurate estimates of L without requiring additional measurements. Using the latter expression, we recalculate L from recent measurements on hepatitis C virus infected patients undergoing treatment with ribavirin. We find that our estimates of L in these patients (39 +/- 13 days) are significantly lower than current estimates (46 +/- 14 days), indicating that ribavirin affects RBC survival more severely than expected from current studies. Our expression for L is simple to employ in a clinical setting and would render the broadly applicable technique of alveolar CO measurement for the estimation of RBC lifespan more accurate.

How Good is the Assumption About Visible Surface Reflectance in MODIS Aerosol Retrieval Over Land? A Comparison With Aircraft Measurements Over an Urban Site in India

In this paper, we discuss the measurements of spectral surface reflectance (rho(s)(lambda)) in the wavelength range 350-2500 nm measured using a spectroradiometer onboard a low-flying aircraft over Bangalore (12.95 degrees N, 77.65 degrees E), an urban site in southern India. The large discrepancies in the retrieval of aerosol propertiesover land by the Moderate-Resolution Imaging Spectroradiometer (MODIS), which could be attributed to the inaccurate estimation of surface reflectance at many sites in India and elsewhere, provided motivation for this paper. The aim of this paper was to verify the surface reflectance relationships assumed by the MODIS aerosol algorithm for the estimation of surface reflectance in the visible channels (470 and 660 nm) from the surface reflectance at 2100 nm for aerosol retrieval over land. The variety of surfaces observed in this paper includes green and dry vegetations, bare land, and urban surfaces. The measuredreflectance data were first corrected for the radiative effects of atmosphere lying between the ground and aircraft using the Second Simulation of Satellite Signal in the Solar Spectrum (6S) radiative transfer code. The corrected surface reflectance in the MODIS's blue (rho(s)(470)), red (rho(s)(660)), and shortwave-infrared (SWIR) channel (rho(s)(2100)) was linearly correlated. We found that the slope of reflectance relationship between 660 and 2100 nm derived from the forward scattering data was 0.53 with an intercept of 0.07, whereas the slope for the relationship between the reflectance at 470 and 660 nm was 0.85. These values are much higher than the slope (similar to 0.49) for either wavelengths assumed by the MODIS aerosol algorithm over this region. The reflectance relationship for the backward scattering data has a slope of 0.39, with an intercept of 0.08 for 660 nm, and 0.65, with an intercept of 0.08 for 470 nm. The large values of the intercept (which is very small in the MODIS reflectance relationships) result in larger values of absolute surface reflectance in the visible channels. The discrepancy between the measured and assumed surface reflectances could lead to error in the aerosol retrieval. The reflectance ratio (rho(s)(660)/rho(s)(2100)) showed a clear dependence on the N D V I-SWIR where the ratio increased from 0.5 to 1 with an increase in N V I-SWIR from 0 to 0.5. The high correlation between the reflectance at SWIR wavelengths (2100, 1640, and 1240 nm) indicated an opportunity to derive the surface reflectance and, possibly, aerosol properties at these wavelengths. We need more experiments to characterize the surface reflectance and associated inhomogeneity of land surfaces, which play a critical role in the remote sensing of aerosols over land.

A simple, wide-range, linear thermistor-based temperature indicator

A novel thermistor-based temperature indicator using an RC oscillator and an up/down counter has been developed and described. The indicator provides linear performance over a wide dynamic temperature range of 0-100°C. This indicator is free from the error due to lead resistances of the thermistor and gives a maximum error of ±0 · 1°C in the range 0-100°C. Test results are given to support the theory.

Force Measurements on a Reflex Cambered Delta Wing

AREFLEX spanwise cambered delta wing with a conical camber designed for M= 1.4, using the method of Ref. 1, was tested at the design Mach number as well as off-design Mach number M=0.15 and 2.3, respectively. The test results are compared with those of a plane wing and also with the available theoretical results at the design condition. At subsonic speed, the cambered wing has less lift at a given incidence and higher lift-to-drag ratio at a given lift than the plane wing, while at supersonic speeds, both of these quantities were less on the cambered wing. At supersonic speed, at the design incidence and Mach number, there is good agreement between results from theory and experiment. The center of pressure on the cambered wing is ahead of that on the plane wing at subsonic speed, while the reverse is true at supersonic speeds. Finally, it is found that over a useful range of lift the cambered wing is aerodynamically more efficient at subsonic speeds, and less so at supersonic speeds, than the plane wing.

On a linear steady-state system of equations in microcontinuum fluid mechanics

Galerkin representations and integral representations are obtained for the linearized system of coupled differential equations governing steady incompressible flow of a micropolar fluid. The special case of 2-dimensional Stokes flows is then examined and further representation formulae as well as asymptotic expressions, are generated for both the microrotation and velocity vectors. With the aid of these formulae, the Stokes Paradox for micropolar fluids is established.

A new probe for three-dimensional flow measurements

A new four-hole cylindrical cantilever probe is described which could be used for three-dimensional flow surveys. The probe is more compact than the usual cylindrical type allowing for closer approach to a boundary. The probe is robust and gives good reproducibility. It can be used for a wide range of pitch angle. Review of Scientific Instruments is copyrighted by The American Institute of Physics.

A linear root water uptake model

A model of root water extraction is proposed, in which a linear variation of extraction rate with depth is assumed. Five crops are chosen for simulation studies of the model, and soil moisture depletion under optimal conditions from different layers for each crop is calculated. Similar calculations are also made using the constant extraction rate model. Rooting depth is assumed to vary linearly with potential evapotranspiration for each crop during the vegetative phase. The calculated depletion patterns are compared with measured mean depletion patterns for each crop. It is shown that the constant extraction rate model results in large errors in the prediction of soil moisture depletion, while the proposed linear extraction rate model gives satisfactory results. Hypothetical depletion patterns predicted by the model in combination with a moisture tension-dependent sink term developed elsewhere are indicated.

Biodegradation of gelatin graft copolymers. IV

Gelatin graft copolymers of different compositions were tested for microbial susceptibility in a synthetic medium with pure cultures of Pseudomonas aeruginosa, Bacillus subtilis, and Serratia marcescens. The percent weight losses were recorded over 6 weeks of incubation period in nitrogen-free and nitrogen-rich media. The relationship between [log(rate)] during the first week of the test period and composition of the grafted samples showed a linear behavior. There was no difference in the aggressivity of these bacterial strains. Nitrogen analysis data and pH measurements of the media seem to reinforce our earlier observations. Soil burial tests also indicate degradation of polymer samples under natural weathering conditions. This article also summarizes the salient features of our series of investigations.

Optical and nonlinear absorption properties of Na doped ZnO nanoparticle dispersions

We report linear and nonlinear optical properties of the biologically important Na doped ZnO nanoparticle dispersions. Interesting morphological changes involving a spherical to flowerlike transition have been observed with Na doping. Optical absorption measurements show an exciton absorption around 368 nm. Photoluminescence measurements reveal exciton recombination emission, along with shallow and deep trap emissions. The increased intensity of shallow trap emission with Na doping is attributed to oxygen deficiency and shape changes associated with doping. Nonlinear optical measurements show a predominantly two-photon induced, excited state absorption, when excited with 532 nm, 5 ns laser pulses, indicating potential optical limiting applications.

Heat-Capacity Measurements - Progress In Experimental-Techniques

The heat capacity of a substance is related to the structure and constitution of the material and its measurement is a standard technique of physical investigation. In this review, the classical methods are first analyzed briefly and their recent extensions are summarized. The merits and demerits of these methods are pointed out. The newer techniques such as the a.c. method, the relaxation method, the pulse methods, the laser flash calorimetry and other methods developed to extend the heat capacity measurements to newer classes of materials and to extreme conditions of sample geometry, pressure and temperature are comprehensively reviewed. Examples of recent work and details of the experimental systems are provided for each method. The introduction of automation in control systems for the monitoring of the experiments and for data processing is also discussed. Two hundred and eight references and 18 figures are used to illustrate the various techniques.