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排序方式: 共有1491条查询结果,搜索用时 15 毫秒
81.
Cong Tam Nguyen Nicolas Galanis Guillaume Polidori Stéphane Fohanno Catalin V. Popa Arnaud Le Bechec 《International Journal of Thermal Sciences》2009,48(2):401-411
An experimental investigation was performed to study the heat transfer performance of a 36 nm-Al2O3-particle–water nanofluid in a confined and submerged impinging jet on a flat, horizontal and circular heated surface. The tests were realized for the following ranges of the governing parameters: the nozzle diameter is 3 mm and the distance nozzle-to-heated-surface was set to 2, 5 and 10 mm; the flow Reynolds number varies from 3800 to 88 000, the Prandtl number from 5 to 10, and the particle volume fraction is ranging from 0 to 6%. Experimental data, obtained for both laminar and turbulent flow regimes, have clearly shown that, depending upon the combination of nozzle-to-heated surface distance and particle volume fraction, the use of a nanofluid can provide a heat transfer enhancement in some cases; conversely, for other combinations, an adverse effect on the convective heat transfer coefficient may occur. Within the experimental parameters used, it has been observed that highest surface heat transfer coefficients can be achieved using an intermediate nozzle-to-surface distance of 5 mm and a 2.8% particle volume fraction nanofluid. Nanofluids with high particle volume fractions, say 6% or higher, have been found not appropriate for the heat transfer enhancement purpose under the confined impinging jet configuration. On the other hand, for a very small and a large distance of nozzle-to-heated-surface, it has been observed that the nanofluid use does not provide a perceptible heat transfer enhancement and has, for some particular cases, produced a clear decrease of the convective heat transfer coefficient while compared to that obtained using distilled water. 相似文献
82.
Numerical simulations have been carried out for spontaneous ignition in the sudden release of pressurized hydrogen into air. A mixture-averaged multi-component approach was used for accurate calculation of molecular transport. Spontaneous ignition and combustion chemistry were accounted for using a 21-step kinetic scheme. To reduce false numerical diffusion, extremely fine meshes were used along with the arbitrary Lagrangian–Eulerian (ALE) method in which convective terms are solved separately from the other terms. 相似文献
83.
Heald R. Aingaran K. Amir C. Ang M. Boland M. Dixit P. Gouldsberry G. Greenley D. Grinberg J. Hart J. Horel T. Wen-Jay Hsu Kaku J. Chin Kim Song Kim Klass F. Kwan H. Lauterbach G. Lo R. McIntyre H. Mehta A. Murata D. Nguyen S. Yet-Ping Pai Patel S. Shin K. Tam K. Vishwanthaiah S. Wu J. Yee G. You E. 《Solid-State Circuits, IEEE Journal of》2000,35(11):1526-1538
This quad-issue processor achieves 1-GHz operation through improved dynamic circuit techniques in critical paths and a more extensive on-chip memory system which scales in both bandwidth and latency. Critical logic paths use domino, delayed clocked domino, and logic embedded in dynamic flip-flops for minimum delay. A 64-KB sum-addressed memory data cache combines the address offset add with the cache decode, allowing the average memory latency to scale by more than the clock ratio. Memory bandwidth is improved by using wave pipelined SRAM designs for on-chip caches and a write cache for store traffic. Memory power is controlled without increased latency by use of delayed-reset logic decoders. The chip operates at 1000 MHz and dissipates less than 80 W from a 1.6-V supply. It contains 23 million transistors (12 million in RAM cells) on a 244 mm2 die 相似文献
84.
Honorine Angue Mintsa Gilles Roy Cong Tam Nguyen Dominique Doucet 《International Journal of Thermal Sciences》2009,48(2):363-371
This paper presents effective thermal conductivity measurements of alumina/water and copper oxide/water nanofluids. The effects of particle volume fraction, temperature and particle size were investigated. Readings at ambient temperature as well as over a relatively large temperature range were made for various particle volume fractions up to 9%. Results clearly show the predicted overall effect of an increase in the effective thermal conductivity with an increase in particle volume fraction and with a decrease in particle size. Furthermore, the relative increase in thermal conductivity was found to be more important at higher temperatures. Obtained results compare favorably with certain data sets and theoretical models found in current literature. 相似文献
85.
Solenne Taront Audrey Dieudonné Simon Blanchard Pascale Jeannin Philippe Lassalle Yves Delneste Philippe Gosset 《Particle and fibre toxicology》2009,6(1):9
Background
The exposure to pollutants such as diesel exhaust particles (DEP) is associated with an increased incidence of respiratory diseases. However, the mechanisms by which DEP have an effect on human health are not completely understood. In addition to their action on macrophages and airway epithelial cells, DEP also modulate the functions of dendritic cells (DC). These professional antigen-presenting cells are able to discriminate unmodified self from non-self thanks to pattern recognition receptors such as the Toll like Receptors (TLR) and Scavenger Receptors (SR). SR were originally identified by their ability to bind and internalize modified lipoproteins and microorganisms but also particles and TLR agonists. In this study, we assessed the implication of SR in the effects of DEP associated or not with TLR agonists on monocyte-derived DC (MDDC). For this, we studied the regulation of CD36, CXCL16, LOX-1, SR-A1 and SR-B1 expression on MDDC treated with DEP associated or not with TLR2, 3 and 4 ligands. Then, the capacity of SR ligands (dextran sulfate and maleylated-ovalbumin) to block the effects of DEP on the function of lipopolysaccharide (LPS)-activated DC has been evaluated. 相似文献86.
87.
Audrey Dell Hammerich J. Gonzalo Muga Ronnie Kosloff 《Israel journal of chemistry》1989,29(4):461-471
Several novel aspects of scattering resonances are studied. An expression, valid for a finite box, relating the continuum phase shift with the energy shift and unperturbed level separation is proposed and applied to obtain the resonance parameters. The effect of the resonance on propagating a wavepacket in imaginary time is studied. It is observed that the resonance strongly affects the cumulants of the energy distribution. In particular, a local minimum of the first derivative of the energy with respect to time (proportional to the second cumulant) serves to estimate the resonance energy and wavefunction. Once the estimate is known, the autocorrelation function is used to evaluate the resonance width. Alternatively, a new iterative approach is developed that is capable of selectively yielding an arbitrary band of energy eigenvalues and eigenfunctions on a grid. This method is applied to give those energy levels that are of interest for the discrete computation of the resonant phase shift, i.e., those close to resonance. Exact (analytical) and approximate results are in good agreement for a particular separable potential model in one dimension. These methods can be extended to realistic potentials in higher dimensions. 相似文献
88.
Cecil D. Bannon John D. Craske Audrey E. Hilliker 《Journal of the American Oil Chemists' Society》1986,63(1):105-110
Because unsaturated fatty acid methyl esters (FAME) are subject to autoxidation, it is virtually impossible to obtain and
maintain high purity standards. Accordingly, it is not possible to determine flame ionization detector response factors by
the usual technique of analyzing standard mixtures of known composition. In an alternative approach, the response factors
of methyl oleate, methyl linoleate, methyl linolenate, methyl arachidonate and methyl 4,7,10,13,16,19-docosahexaenoate relative
to methyl stearate were estimated by determining the peak areas before and after quantitative hydrogenation in the presence
of an internal standard. The estimates showed excellent agreement in all cases with the theoretical factors predicted by Ackman
and Sipos and thus constitute an independent and unambiguous proof that the theoretical factors are highly accurate for all
olefinic unsaturated FAME. Whereas it is common practice to determine an empirically derived correction factor for each FAME
by analyzing standard mixtures of known composition, the thesis is now proposed that, for both saturated and olefinic unsaturated
FAME, the proper approach to accurate analysis requires that peak areas be corrected using the theoretical response factors
as the only correction factors. If the correct result cannot be obtained when analyzing a primary standard of saturated FAME,
it is an indication of faulty technique or equipment, and the only acceptable resolution of the problem is to locate and correct
the fault(s). 相似文献
89.
A-Ping Zhang Bai-Ou Guan Xiao-Ming Tao Hwa-Yaw Tam 《Photonics Technology Letters, IEEE》2002,14(4):489-491
The spectral characteristics of superstructure fiber Bragg gratings are analyzed numerically based on the coupled mode theory, simultaneously taking into account the counterdirectional guided mode coupling, codirectional and counterdirectional claddings mode coupling. The theoretical results were compared with experimental data and very good agreement was obtained 相似文献
90.