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141.
Leschkies KS Divakar R Basu J Enache-Pommer E Boercker JE Carter CB Kortshagen UR Norris DJ Aydil ES 《Nano letters》2007,7(6):1793-1798
We combine CdSe semiconductor nanocrystals (or quantum dots) and single-crystal ZnO nanowires to demonstrate a new type of quantum-dot-sensitized solar cell. An array of ZnO nanowires was grown vertically from a fluorine-doped tin oxide conducting substrate. CdSe quantum dots, capped with mercaptopropionic acid, were attached to the surface of the nanowires. When illuminated with visible light, the excited CdSe quantum dots injected electrons across the quantum dot-nanowire interface. The morphology of the nanowires then provided the photoinjected electrons with a direct electrical pathway to the photoanode. With a liquid electrolyte as the hole transport medium, quantum-dot-sensitized nanowire solar cells exhibited short-circuit currents ranging from 1 to 2 mA/cm2 and open-circuit voltages of 0.5-0.6 V when illuminated with 100 mW/cm2 simulated AM1.5 spectrum. Internal quantum efficiencies as high as 50-60% were also obtained. 相似文献
142.
A parallel multithreaded program that is ostensibly deterministic may nevertheless behave nondeterministically due to bugs
in the code. These bugs are called determinacy races, and they result when one thread updates a location in shared memory while another thread is concurrently accessing the location.
We have implemented a provably efficient determinacy-race detector for Cilk, an algorithmic multithreaded programming language.
If a Cilk program is run on a given input data set, our debugging tool, which we call the ``Nondeterminator,' either determines
at least one location in the program that is subject to a determinacy race, or else it certifies that the program is race
free when run on the data set.
The core of the Nondeterminator is an asymptotically efficient serial algorithm (inspired by Tarjan's nearly linear-time
least-common-ancestors algorithm) for detecting determinacy races in series-parallel directed acyclic graphs. For a Cilk program
that runs in T time on one processor and uses v shared-memory locations, the Nondeterminator runs in O(T α(v,v)) time, where α is Tarjan's functional inverse of Ackermann's function, a very slowly growing function which, for all practical purposes,
is bounded above by 4 . The Nondeterminator uses at most a constant factor more space than does the original program. On a variety of Cilk program
benchmarks, the Nondeterminator exhibits a slowdown of less than 12 compared with the serial execution time of the original optimized code, which we contend is an acceptable slowdown for debugging
purposes.
Received November 11, 1997, and in final form September 21, 1998. 相似文献
143.
144.
Abstract To demonstrate the Pancharatnam phase as a geometric (Berry's) phase, each polarization state must be obtained by projecting the previous state on it. We describe a simple interferometric arrangement for such a demonstration which only uses a single rotation linear analyser to introduce a continuously variable phase difference between the two beams. 相似文献
145.
R. S. Ramachandran C. Kleinstreuer T.-Y. Wang 《Numerical Heat Transfer, Part A: Applications》2013,63(4):471-487
A basic understanding of the highly nonlinear interaction effects of closely spaced spheres on fluid mechanics and heat transfer parameters is important for improving the design of a variety of thermal fluid-particle systems. Fluid flow patterns, isotherms, as well as Nusselt number distributions and extended correlations are presented for steady laminar axisym-metric flow past a linear array of three spheres. A finite-element method is used to solve the complete Navier-Stokes and heat transfer equations for the system parameter ranges 1 Red 200 (Reynolds number) 2 dij10 ( particle spacings)and 0. 1 prRed 2000 (Piclet number). The verified computer simulation results indicate that convection heat transfer parameters of interacting spherical particles deviate significantly from solitary spheres for all Reynolds and Piclet numbers. 相似文献
146.
Chen E. Ramachandran Hongwei Du Yoo Joong Kim Mayfair C. Kung Randall Q. Snurr Linda J. Broadbelt 《Journal of Catalysis》2008,253(1):148-158
The epoxidation of 1-hexene with titanium silicalite-1 (TS-1) catalyst was investigated to gain insight into the effect of the solvent on the observed reactivity. Three different solvents were examined: methanol, acetonitrile, and acetone. Kinetic data were obtained from batch reaction experiments, with an emphasis placed on gathering more accurate initial rates than those reported in the literature. The dependencies of the rates on the concentrations of 1-hexene, water, and hydrogen peroxide were determined. The adsorption behavior of 1-hexene in TS-1 in the three different solvents was determined independently by batch sorption experiments. Results showed that the solvent has a significant effect on the adsorption of 1-hexene, and hence on the reaction kinetics. Kinetic modeling incorporating experimental and simulated quaternary adsorption isotherms to describe quasi-equilibrated steps revealed that the differences in the observed reaction kinetics may be attributed mostly, but not entirely, to differences of the partitioning of 1-hexene between the bulk and intraporous phases among the three different solvents. 相似文献
147.
K. P. Somashekhar Jose Mathew N. Ramachandran 《The International Journal of Advanced Manufacturing Technology》2012,61(9-12):1241-1246
A fundamental study of microelectric discharge machining (μ-EDM) based on the physics of single spark and electrothermal theory has been carried out. The machining phenomena in the μ-EDM process are investigated through simulations using finite element method. By creating the single-discharge crater, the topography is measured using an atomic force microscope and the simulation results compared with the experimental result. A temperature distribution along the radius and depth of the workpiece is thus reported. For verification purpose, single-discharge experiments with RC pulse circuit are performed with tungsten carbide as the electrode and stainless steel as the workpiece. The diameter-to-depth ratios of the crater obtained by the simulation and the experiments are 2.92 and 2.67, respectively. The simulation results are found to be in close agreement with experimental results. 相似文献
148.
Ramachandran C Quirin KW Resek A Melnick SJ 《International journal of cosmetic science》2012,34(2):155-160
Coenzyme Q10 (CoQ10) is a major ingredient in skin care products because of its anti‐wrinkle effects, although it has some side effects especially at higher amounts. In this study, we compare the anti‐wrinkle related properties of CoQ10 and a proprietary Commiphora mukul gum resin (guggul) and triheptanoin preparation (GU‐TC7). GU‐TC7 is prepared with a supercritical CO2‐co‐solvent extraction with ethanol, standardized to 2% guggulsterones and triheptanoin, a triglyceride composed of three 7‐carbon fatty acids. Treatment of CCL‐110 skin fibroblasts with GU‐TC7 demonstrates a mild proliferative effect compared to CoQ10 and increased type I collagen synthesis. Additionally, GU‐TC7 inhibited matrix metalloproteinase‐1 (MMP‐1) expression in a dose‐dependent manner at 20–100 μg mL?1 and inhibited human elastase expression by more than 50% as compared to no elastase inhibition with CoQ10 treatment. These results suggest that GU‐TC7 possesses properties that are applicable to the treatment of wrinkles and may be considered for its further evaluation in skin care products. 相似文献
149.
Thazhakot V Sankar Alappat Ramachandran 《Journal of the science of food and agriculture》2005,85(4):563-568
The characteristics and stability of natural actomyosin (NAM) from rohu (Labeo rohita), catla (Catla catla) and mrigal (Cirrhinus mrigala) were investigated. The total extractable actomyosin (AM) was higher (7.60 mg ml?1) in the case of rohu compared with that from catla and mrigal (5 mg ml?1). Although the specific AM ATPase activity was similar (0.43–0.5 µmol P min?1 mg P?1) among the three species, the total ATPase activity was lower in mrigal (25 µmol g?1 meat) compared with the other species (37 µmol g?1 meat). The inactivation rate constants (kd) of AM Ca ATPase activity showed differences in the stabilities of actomyosin among these fish, the actomyosin from catla being least stable. The NAM from these species was stable up to 20 °C at pH 7.0. Catla AM became unstable at 30 °C, while rohu and mrigal AM could withstand up to 45 °C. The thermal denaturation with respect to solubility, turbidity, ATPase activity, sulphhydryl group and surface hydrophobicity showed noticeable changes at around these temperatures. Copyright © 2004 Society of Chemical Industry 相似文献
150.
M. Ramachandran D. Mantha C. Williams R. G. Reddy 《Metallurgical and Materials Transactions A》2011,42(1):202-210
The oxidation resistance of Ti-Al intermetallics is superior to many of their counterparts at high temperatures. High-temperature
stability of these intermetallics appears to improve with a ternary alloying addition such as Mo, Nb, etc. A detailed analysis of oxidation of the Ti3Al intermetallics, Ti3Al-2.9 at. pct Mo and Ti3Al-1.1 at. pct Nb, in pure oxygen using crystallographic and microscopic techniques is presented here. The alloy containing
1.1 at. pct Nb did not show an improvement in oxidation resistance over the base alloy but that containing 2.9 at. pct Mo
showed marked resistance to oxidation. Activation energies of oxidation for both the alloys were comparable with those reported
in the literature for similar compositions. TiO2 and Al2O3 were the major phases present in the oxide scales of the oxidized alloys. The crystal orientations from the X-ray diffraction
(XRD) patterns and the morphologies from scanning electron microscopy (SEM) were in good agreement and were helpful in further
analysis of the oxidation process. The effective diffusion of oxygen in the oxide layers was calculated using the mole fraction
of individual oxide and the diffusivity of oxygen in pure oxide. The activation energy for the effective diffusion of oxygen
through the oxide layers was determined to be ~24 kJ/mol. The activation energy for the oxidation process was higher than
that of the diffusion of oxygen. Hence, it can be concluded that the oxidation process in both the alloys studied is not diffusion
controlled. 相似文献