Parallel methods for visibility and shortest-path problems in simple polygons

In this paper we give efficient parallel algorithms for solving a number of visibility and shortest-path problems for simple polygons. Our algorithms all run inO(logn) time and are based on the use of a new data structure for implicitly representing all shortest paths in a simple polygonP, which we call thestratified decomposition tree. We use this approach to derive efficient parallel methods for computing the visibility ofP from an edge, constructing the visibility graph of the vertices ofP (using an output-sensitive number of processors), constructing the shortest-path tree from a vertex ofP, and determining all-farthest neighbors for the vertices inP. The computational model we use is the CREW PRAM.     

Studies on the influence of lanthanum oxide on the sinterability of chromium(III) oxide

The mechanism of sintering in chromium(III) oxide in the presence of varying amounts of lanthanum oxide under firing conditions which simulate a controlled reducing atmosphere, has been investigated. The investigation is based on isothermal shrinkage measurements at different temperatures. The data suggest that the vapour-phase transport mechanism becomes predominant with evidence of a grain-boundary diffusion process.     

Reaction chemistry and subsolidus phase equilibria in lead-based relaxor systems: Part I Formation and stability of the perovskite and pyrochlore compounds in the system PbO-MgO-Nb2O5

The reaction chemistry involved in the synthesis of perovskite Pb(Mg_1/3Nb_2/3)O₃ [Pb₃MgNb₂O₉] was studied by the solid state reaction technique using precursor oxides as reactants. At the initial stage of the reaction process, a large fraction of PbO present in the mixtures combined with Nb₂O₅ and a small amount of MgO to form an oxygen-deficient pyrochlore phase with a composition Pb_1.714(Mg_0.286Nb_1.714)O_6.286 [Pb₆MgNb₆O₂₂]. The pyrochlore phase thus formed further reacted with the remaining PbO and MgO to yield the perovskite Pb(Mg_1/3Nb_2/3)O₃. The pyrochlore Pb_1.714(Mg_0.286Nb_1.714)O_6.286 accomodates a small amount of PbO into its lattice and forms a narrow homogeneity range which extends from the composition Pb_1.714(Mg_0.286Nb_1.714)O_6.286 [Pb₆MgNb₆O₂₂] to a composition Pb₂(Mg_0.286Nb_1.714)O_6.571 [Pb₇MgNb₆O₂₃] with a corresponding increase in the lattice constant value from a = 10.586 to 10.601 Å. The pyrochlore phase melts incongruently at a temperature near 1230°C to yield Mg₄Nb₂O₉ and a liquid. Below this temperature, the perovskite Pb(Mg_1/3Nb_2/3)O₃ coexists with the pyrochlore solid solutions. However, the compound Pb(Mg_1/3Nb_2/3)O₃ is not compatible with Nb₂O₅ and these two phases react with one another to form the pyrochlore Pb_1.714(Mg_0.286Nb_1.714)O_6.286 and MgO.     

Mechanical and surface properties of corona-treated titanium dioxide-embedded opaque white low-density/Linear low-density polyethylene film

This study encompasses the characterization of corona-treated milky white co-extruded polyethylene films. The surface energies developed at various applied voltages were investigated by standard wetting (dyne) solutions of binary liquid mixtures. A maximum treatment of 40 dynes/cm was achieved at 3.0 kW of the applied load. Maximum heat seal joint strength of 1.05 kN/m was achieved only when an untreated/untreated surface combination was sealed, while a treated/treated surface combination exhibited the minimum heat seal joint strength of 0.98 kN/m. Standard Scotch tape method was employed for testing peel adhesion. An applied load of more than 3.0 kW shows a decreasing trend in surface energy. The coefficient of friction on the treated surface was also investigated. Aging under different environmental conditions had hardly any impact on the treatment levels within the time period under study. A sufficiently opaque (Opacity—99%) white film at Titanium dioxide (TiO₂) loading of 7.5% resulted in a very good barrier film.     

Microwave Preparation of SiO2-B2O3-Na2O-K2O-CaO-Fe2O3-TiO2 Glass System

This study reports preparation of glass composition （54.50 wt.%） SiO2, （10.80 wt.%） B2O3, （14.20 wt.%） Na2O, （1.20 wt.%） K2O, （6.00 wt.%） CaO, （4.00 wt.%） Fe2O3 and （9.30 wt.%） TiO2 by melt quenching method using direct microwave heating and conventional resistive heating. Study of dielectric loss factor of the glass as function of temperature illustrated increasing loss factor above 370 ℃, 550 ℃, 650 ℃ and 900 ℃, indicating enhanced microwave absorption by the glass at above these temperatures. Chemical analysis results of both the glasses depicted more volatilization loss of volatile ingredients in conventional heating. The study of chemical durability was performed from leachate analysis describing less leaching of Na2O, K2O and other constituents from glass melted in microwave furnace. Glass transition temperatures （Tg） were found to be 576.3 ℃ and 569.5 ℃ for glass melted in conventional and microwave heating route, respectively. Laboratory experiment of glass melting utilizing microwave energy as an alternate heating source demonstrated 70%-75% electrical power saving.     

Models for minimum ignition temperature of organic dust clouds

The minimum ignition temperature of dust clouds is one of the important factors required for the design of preventive measures against dust explosion. The mathematical models available to predict this parameter have been analyzed for thier application to organic dust clouds. A solution of the most general model proposed by Mitsui and Tanaka is presented, together with its comparision with experimental data. It has been found to be quite successful in predicting the minimum ignition temperature for metal dusts but not for organic dusts. Recommendations for the development of a new model to predict the minimum ignition temperature of an organic dust, such as polyethylene, have been given.     

Distribution of IgG subclasses in antimonial unresponsive Indian kala-azar patients

BACKGROUND: Interleukin 10 (IL-10) decreases the severity of experimental acute pancreatitis. The role of endogenous IL-10 in modulating the course of pancreatitis is currently unknown. AIMS: To examine the systemic release of IL-10 and its messenger RNA production in the pancrease, liver, and lungs and analyse the effects of IL-10 neutralisation in caerulein induced acute pancreatitis in mice. METHODS: Acute necrotising pancreatitis was induced by intraperitoneal caerulein. Serum levels of IL-10 and tumour necrosis factor (TNF), and tissue IL-10 and TNF-alpha gene expression were assessed. After injecting control antibody or after blocking the activity of endogenous IL-10 by a specific monoclonal antibody, the severity of acute pancreatitis was assessed in terms of serum enzyme release, histological changes, and systemic and tissue TNF production. RESULTS: In control conditions, serum IL-10 levels increased and correlated with the course of pancreatitis, with a maximal value eight hours after induction. Both IL-10 and TNF-alpha messengers showed a similar course, and were identified in the pancreas, liver, and lungs. Neutralisation of endogenous IL-10 significantly increased the severity of pancreatitis and associated lung injury as well as serum TNF protein levels (+75%) and pancreatic, pulmonary, and hepatic TNF messenger expression (+33%, +29%, +43%, respectively). CONCLUSIONS: In this non-lethal model, systemic release of IL-10 correlates with the course of acute pancreatitis. This anti-inflammatory response parallels the release of TNF and both cytokines are produced multisystemically. Endogenous IL-10 controls TNF-alpha production and plays a protective role in the local and systemic consequences of the disease.     

Analysis and computation of non-equilibrium two-phase flows

Non-equilibrium fluid mechanics and thermodynamics of two-phase vapour-droplet and gas-particle flow are considered. Formation of the droplets as well as their subsequent interaction with the vapour are discussed. A new theory of nucleation in steam turbines is developed that reproduces many aspects of measured droplet size spectra which cannot be explained by any available steady-flow theories. (Steam turbines are responsible for 80% of global electricity production and the presence of moisture significantly reduces turbine efficiency costing 50 million pounds per annum in UK alone.) Fluid dynamic interactions discussed include flow instabilities induced by condensation, condensation wave theory, relaxation gas dynamics for vapour-droplet flow, thermal choking due to non-equilibrium condensation, the structure of shock waves and their development through unsteady processes, and jump conditions and the interpretation of total pressure in two-phase flows.