Multistep temperature prediction for proactive thermal management on chip multiprocessors

The Journal of Supercomputing - In chip multiprocessors, the thermal hot spot prediction is vital to take proactive thermal management decisions for mitigating its impact on the performance of the...     

Performance of an activated carbon made from waste palm shell in simultaneous adsorption of SO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> and NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> of flue gas at low temperature

This study examined the individual and simultaneous adsorption of SO{in{itx}} (SO{in{it2}}) and NO{in{itx}} (NO-NO{in{it2}}) on activated carbon prepared from waste palm shell. The adsorption process was examined in a fixed bed reactor at low temperatures (100\2-300\dgC). For individual adsorption without any catalytic activation, SO{in{itx}} showed good adsorption whereas NO{in{itx}} was very much poor. In the simultaneous adsorption of SO{in{itx}} and NO{in{itx}}, SO{in{itx}} showed greater adsorption affinity than NO{itx}. For palm shell activated carbon (PSAC) impregnated with metal catalyst (Ni and Ce) the concentration adsorbed profile showed that the amount of SO{in{itx}} adsorbed decreased regularly, while the amount of the adsorbed NO{in{itx}} increased irregularly. The properties of the pure and impregnated PSAC were analyzed by BET, SEM and EDX. These investigations indicated that PSAC impregnated with metal catalyst is the determining factor in the adsorption of SO{in{itx}} and NO{in{itx}} simultaneously. Supported financially by Yayasan FELDA, Malaysia (Grant No. 6050075)     

Estimation of sharma constant and thermoacoustic properties of fatty acids

From the volume expansivity α, a number of thermoacoustic parameters, including the Sharma constant,S ₀, are estimated for four fatty acids as a function of temperature. The Sharma constant, which was established to be a constant with the characteristic value 1.11 ± 0.01 over a number of systems investigated by earlier investigators, is also found to be a constant with the same value for all fatty acids under investigation. Further, the Sharma constant,S ₀, is independent of temperature and dependent only on α. All other parameters estimated are discussed and compared with the values reported in the literature by earlier workers for different systems.     

Dual solutions in a double-diffusive convection near stagnation point region over a stretching vertical surface

The development of double-diffusive convection near stagnation point region over a stretching vertical surface with constant wall temperature has been investigated. The external flow and the stretching velocities are assumed to vary with $\sqrt{x}\text{,}$ where x is the distance from the slot where the stretching surface is issued. Using the local similarity method, it has been shown that a set of suitable similarity transformations reduces the non-linear coupled partial differential equations governing the flow, thermal and concentration fields into a set of non-linear coupled ordinary differential equations. The non-linear self-similar equations along with the boundary conditions form a two point boundary value problem and are solved using Shooting method, by converting into an initial value problem. In this method, the system of equations is converted into the set of first order system which is solved by fourth-order Runge–Kutta method. Flows with both assisting and opposing buoyancy forces are considered in the present investigation. The study reveals that the dual solutions of velocity, temperature and concentration exist for certain values of suction/injection and buoyancy parameters. Prandtl and Schmidt numbers strongly affect the thermal and concentration boundary layer thicknesses, respectively. The effects of various parameters on the velocity, temperature and concentration profiles are also presented here.     

Copper-doped flower-like molybdenum disulfide/bismuth sulfide photocatalysts for enhanced solar water splitting

A facile synthesis approach to fabricate Cu-doped MoS₂/Bi₂S₃ (Cu-MoS₂/Bi₂S₃) photocatalysts is reported. The photocatalyst samples with varying amounts of Cu are applied in the photocatalytic splitting of water to produce H₂ under the irradiation of simulated solar light. The Cu-MoS₂/Bi₂S₃ photocatalysts with an optimum Cu loading of 20 mol% exhibited high photocatalytic performance, achieving a total H₂ yield of 32.4 μmol/h after 6 h of reaction. The photoactivity of the Cu-doped sample was shown to have risen more than 40% than that of pure MoS₂/Bi₂S₃. The improved performance is attributed to the impurity states generated within Cu-doped MoS₂, which serve as trapping sites for photogenerated electrons. The effective charge transfer mechanism achieved was evidenced by photoelectrochemical measurements. Based on the experimental results obtained, a plausible mechanism for the photocatalytic process associated with Cu-MoS₂/Bi₂S₃ was proposed.     

CO2 methanation over Ni and Rh based catalysts: Process optimization at moderate temperature

H₂ was produced from aluminum/water reaction and reacted with CO₂ over Ni and Rh based catalysts to optimize the process conditions for CO₂ methanation at moderate temperature. Monometallic catalysts were prepared by incorporating Ni and Rh using nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) and rhodium(III) chloride trihydrate (RhCl₃·3H₂O)as a precursor chemical. The preliminary study of the catalysts revealed higher activity and CH₄ selectivity for Rh based catalyst compared to that of Ni based catalyst. Further, Rh based catalyst was investigated using response surface methodology (RSM) involving central composite design. The quadratic model was employed to correlate the effects of variable parameters including methanation temperature, %humidity, and catalyst weight with the %CO₂ conversion, %CH₄ selectivity, and CH₄ production capacity. Analysis of variance revealed that methanation temperature and humidity play an important role in CO₂ methanation. Higher response values of CO₂ conversion (54.4%), CH₄ selectivity (73.5%) and CH₄ production capacity (8.4 μmol g^?1 min^?1) were noted at optimum conditions of 206.7°C of methanation temperature, 12.5% humidity and 100 mg of the catalyst. The results demonstrated the ability of Rh catalyst supported on palm shell activated carbon (PSAC) for CO₂ methanation at low temperature and atmospheric pressure.     

Studies on dechlorination of DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) using magnesium/palladium bimetallic system

The aim of our investigation was to compare the rates of dechlorination of DDT using Mg0/Pd4+ system in two different reaction phases, namely, water-acetone and 0.05% biosurfactant in water. Since palladium is expensive and its toxicity effects are not well known we also examined the reuse efficiency of Pd0 immobilized on alumina for dechlorinating DDT. Studies on the dechlorination of DDT in water-acetone (1:1, v/v) and 0.05% biosurfactant phases revealed that the reaction followed second order kinetics and rate of reaction is dependent upon both initial concentrations of the target compound and Mg0/Pd4+. The presence of acid enhanced the rate of reaction by providing protons and preventing passivation of metal that occurs due to deposition of magnesium hydroxide. GC-MS analyses revealed the formation of completely dechlorinated hydrocarbon skeleton of DDT namely, diphenylethane (DPE), as the end product in both reaction phases (water-acetone and 0.05% biosurfactant in water) thereby implying the removal of all five chlorine atoms (three alkyl and two aryl) of DDT. The optimum ratio of water and acetone to facilitate successful dechlorination reaction was found to be 9:1. Results suggested that salt form (K2PdCl6) of palladium had higher potential to dechlorinate DDT as compared to pellet (Pd0-alumina) form (efficiencies of 95 and 36%, respectively, for 100 ppm initial concentration of DDT). We noted that Pd0-alumina pellets could be reused at least four times for successful dechlorination of DDT provided Mg0 granules are present in sufficient quantity. Technical grade DDT (50 ppm) containing significant amounts of DDD was dechlorinated almost completely by the Mg0/Pd4+ (10mg/0.2mg/ml) within 1h in water-biosurfactant phase. Our studies reveal that Mg/Pd system is a promising option due to its high reactivity and its ability to achieve complete dechlorination of DDT. This bimetallic system may be useful for designing indigenous permeable barriers or reactors for the treatment of DDT contaminated water.     

Theoretical Investigation of Some High‐Performance Novel Amine Azide Propellants

Monomethylhydrazine (MMH) is currently the most widely used hypergolic propellant, due to its high performance and low ignition delay. However, its toxicity is a major concern. The present work aims at developing high‐performance hypergolic fuels that are based on tertiary amine azide functionality. A number of potential amine azide candidates have been proposed, and some of their physical and chemical properties have been computed using state‐of‐the‐art molecular modeling techniques. Gas‐phase heats of formation have been calculated using the CBS‐QB3 method, and the first‐principle COSMO‐RS method has been used to compute heats of vaporization and vapor pressures. A density correlation, based on molecular‐volume calculation, has been established to predict the densities of the candidate molecules. Finally, the liquid‐phase heats of formation and densities have been used to predict the specific and density impulses of the proposed candidate molecules. The results show that many of the molecules proposed here have much higher density impulse than that of MMH, and may be considered for experimental studies.     

Dechlorination of chlorophenols using magnesium-palladium bimetallic system

Ninety-four percent removal of 10 mg L(-1) of pentachlorophenol (PCP) was achieved by treatment with 154.5mM Mg(0) and 0.063 mM K(2)PdCl(6) in the presence of 175 mM acetic acid in 1h reaction time. Dechlorination of PCP was found to be sequential and phenol was identified as the end product along with accumulation of trace concentrations of tetra- and trichlorophenols. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) revealed that palladium in its metallic form (Pd(0)) produced by reduction of Pd4+, was spatially separated from magnesium granules when acid was included in the reaction. These colloidal palladium particles generated active reductive species of hydrogen and dechlorinated chlorophenols. In the absence of acid, the efficiency of dechlorination of PCP by Pd/Mg(0) system was very low and chief mechanism of removal of the compound was through sorption onto solid surfaces. Thus, it was important to include acid in the system to: (a) facilitate corrosion of Mg(0) and reduction of Pd4+ to Pd(0), (b) provision of protons to produce H2, (c) retard formation of insoluble oxides and hydroxides that may deposit on the magnesium granules and sorb PCP and its partially dechlorinated products and. Application of 154.5 mM Mg(0)/0.063 mM K(2)PdCl(6) on PCP, 2,4,5-trichlorophenol (TCP) and 2-chlorophenol (MCP) with organic chloride equivalence showed that the rate and extent of removal increased with decrease in number of chlorine atoms on phenol.     

Development of a food frequency questionnaire for Sri Lankan adults

ABSTRACT: BACKGROUND: Food Frequency Questionnaires (FFQs) are commonly used in epidemiologic studies to assess long-term nutritional exposure. Because of wide variations in dietary habits in different countries, a FFQ must be developed to suit the specific population. Sri Lanka is undergoing nutritional transition and diet-related chronic diseases are emerging as an important health problem. Currently, no FFQ has been developed for Sri Lankan adults. In this study, we developed a FFQ to assess the regular dietary intake of Sri Lankan adults. METHODS: A nationally representative sample of 600 adults was selected by a multi-stage random cluster sampling technique and dietary intake was assessed by random 24-h dietary recall. Nutrient analysis of the FFQ required the selection of foods, development of recipes and application of these to cooked foods to develop a nutrient database. We constructed a comprehensive food list with the units of measurement. A stepwise regression method was used to identify foods contributing to a cumulative 90% of variance to total energy and macronutrients. In addition, a series of photographs were included. RESULTS: We obtained dietary data from 482 participants and 312 different food items were recorded. Nutritionists grouped similar food items which resulted in a total of 178 items. After performing step-wise multiple regression, 93 foods explained 90% of the variance for total energy intake, carbohydrates, protein, total fat and dietary fibre. Finally, 90 food items and 12 photographs were selected. CONCLUSION: We developed a FFQ and the related nutrient composition database for Sri Lankan adults. Culturally specific dietary tools are central to capturing the role of diet in risk for chronic disease in Sri Lanka. The next step will involve the verification of FFQ reproducibility and validity.