Management and Performance of APPLE Battery in High Temperature Environment

India's first experimental communication satellite, APPLE, carried a 12 AH Ni-Cd battery for supplying power during eclipse. Failure to deploy one of the two solar panels resulted in the battery operating in a high temperature environment, around 40 C. This also resulted in the battery being used in diurnal cycles rather than just half yearly eclipse seasons. The management and performance of the battery during its life of two years are described. An attempt to identify the probable degradation mechanisms is also made

Mass flux similarity for slotted transonic-wind-tunnel walls

A discussion of the flow field measurements obtained in the vertical plane at several stations along the centerline of slots in two different longitudinally slotted wind tunnel walls is presented. The longitudinal and transverse components of the data are then transformed using the concept of flow similarity to demonstrate the applicability of the technique to the development of the viscous shear flow along and through a slotted wall of an airfoil tunnel. Results are presented showing the performance of the similarity transformations with variations in tunnel station, Mach number, and airfoil induced curvature of the tunnel free stream

Dimensional Issues in Stereolithography

New stereolithography photopolymers have recently been introduced that provide a wider range of functional properties similar to those of high-density polyethylene. One of the important criteria for these materials is the dimensional accuracy and stability in end-use applications as mold masters or the actual functional parts. This work investigates the dimensional stability of one of these new materials with varying amounts of exposure during build. The effect of aging on the part dimensions is reported. The result of environmental humidity extremes at ambient temperature on part dimensions is investigated and compared for parts made from two different families of stereolithography resins, namely DuPont Somos® 7100 and Somos® 8100.Mechanical Engineerin

Theoretical methods and design studies for NLF and HLFC swept wings at subsonic and supersonic speeds

Laminarization of the boundary layer on the surface of aircraft wings can be accomplished by the use of concepts such as Natural Laminar Flow (NLF), Laminar-Flow Control (LFC), and Hybrid Laminar-Flow Control (HLFC). Several integral boundary-layer methods were developed for the prediction of laminar, transition, and separating turbulent boundary layers. These methods were developed for use at either subsonic or supersonic speeds, have small computer execution times, and are simple to use. The theoretical equations and assumptions which form the basis of the boundary-layer method, are briefly outlined and the results of several correlation cases with exciting experimental data are presented

On the one-loop correction of "phi^4" theory in higher dimensions

We have considered phi^4 theory in higher dimensions. Using functional diagrammatic approach, we computed the one-loop correction to effective potential of the scalar field in five dimensions. It is shown that phi^4 theory can be regularised in five dimensions. Temperature dependent one-loop correction and critical temperature T_c are computed and T_c depends on the fundamental scale M of the theory. A brief discussion of symmetry restoration is also presented. The nature of phase transitions is examined and is of second orderComment: 8 pages, 5 figures. To appear in IJMP

Reduction of derived Hochschild functors over commutative algebras and schemes

We study functors underlying derived Hochschild cohomology, also called Shukla cohomology, of a commutative algebra S essentially of finite type and of finite flat dimension over a commutative noetherian ring K. We construct a complex of S-modules D, and natural reduction isomorphisms Ext^*_{S\otimes^L_{K}S}(S|K;M\otimes^L_{K}N) ~ Ext^*_S(RHom_S(M,D),N) for all complexes of S-modules N and all complexes M of finite flat dimension over K whose homology H(M) is finitely generated over S; such isomorphisms determine D up to derived isomorphism. Using Grothendieck duality theory we establish analogous isomorphisms for any essentially finite type flat maps f: X->Y of noetherian schemes, with f^!(O_Y) in place of D.Comment: 32 pages. Minor changes from previous version. To appear in the Advances in Mathematic

Thermodynamic properties of Pb determined from pressure-dependent critical-field measurements

We have carried out extensive low-temperature (1.5 to 10 K) measurements of the critical field, $H_c$, for the element Pb up to a pressure of $P=1.2$ GPa. From this data the electronic entropy, specific heat, thermal expansion coefficient and compressibility is calculated as a function of temperature, pressure and magnetic field. The zero-field data is consistent with direct thermodynamic measurements and the $P$-dependence of $T_c$ and specific heat coefficient, $\gamma(T,P)$ allows the determination of the $P$-dependence of the pairing interaction.Comment: 5 pages, 6 figures, in press Phys. Rev.

Rectangular Layouts and Contact Graphs

Contact graphs of isothetic rectangles unify many concepts from applications including VLSI and architectural design, computational geometry, and GIS. Minimizing the area of their corresponding {\em rectangular layouts} is a key problem. We study the area-optimization problem and show that it is NP-hard to find a minimum-area rectangular layout of a given contact graph. We present O(n)-time algorithms that construct $O(n^2)$-area rectangular layouts for general contact graphs and $O(n\log n)$-area rectangular layouts for trees. (For trees, this is an $O(\log n)$-approximation algorithm.) We also present an infinite family of graphs (rsp., trees) that require $\Omega(n^2)$ (rsp., $\Omega(n\log n)$) area. We derive these results by presenting a new characterization of graphs that admit rectangular layouts using the related concept of {\em rectangular duals}. A corollary to our results relates the class of graphs that admit rectangular layouts to {\em rectangle of influence drawings}.Comment: 28 pages, 13 figures, 55 references, 1 appendi