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排序方式: 共有273条查询结果,搜索用时 15 毫秒
81.
Wiebel A Garth C Scheuermann G 《IEEE transactions on visualization and computer graphics》2007,13(4):641-651
We present, extend, and apply a method to extract the contribution of a sub-region of a data set to the global flow. To isolate this contribution, we decompose the flow in the subregion into a potential flow that is induced by the original flow on the boundary and a localized flow. The localized flow is obtained by subtracting the potential flow from the original flow. Since the potential flow is free of both divergence and rotation, the localized flow retains the original features and captures the region-specific flow that contains the local contribution of the considered subdomain to the global flow. In the remainder of the paper, we describe an implementation on unstructured grids in both two and three dimensions for steady and unsteady flow fields. We discuss the application of some widely used feature extraction methods on the localized flow and describe applications like reverse-flow detection using the potential flow. Finally, we show that our algorithm is robust and scalable by applying it to various flow data sets and giving performance figures. 相似文献
82.
Jüllig M Hickey AJ Middleditch MJ Crossman DJ Lee SC Cooper GJ 《Proteomics. Clinical applications》2007,1(6):565-576
Diabetes now affects more than 5% of the world's population and heart failure is the most common cause of death amongst diabetic patients. Accumulating evidence supports a view that myocardial mitochondrial structural and functional changes are central to the onset of diabetic heart failure, but the exact nature of these changes at the proteomic level remains unclear.Here we report on proteomic changes in diabetic rat heart mitochondria following 120 days of streptozotocin‐diabetes using the recently developed iTRAQ? labeling method, which permits quantification of proteins directly from complex mixtures, bypassing the limitations associated with gel‐based methods such as 2‐DE. Of 252 unique proteins identified, 144 were represented in at least three of six individual paired experiments. Relative amounts of 65 proteins differed significantly between the groups, confirming that the cardiac mitochondrial proteome is indeed impacted by diabetes. The most significant changes were increased protein levels of enzymes involved in mitochondrial oxidation of long‐chain fatty acids, which was also confirmed by enzyme assays, and decreased levels of multiple enzymes involved in oxidative phosphorylation and catabolism of short‐chain fatty acids and branched‐chain amino acids. We also found significant changes in levels of several enzymes linked to oxidative stress. 相似文献
83.
Streamline integration using MPI-hybrid parallelism on a large multicore architecture 总被引:1,自引:0,他引:1
Camp D Garth C Childs H Pugmire D Joy KI 《IEEE transactions on visualization and computer graphics》2011,17(11):1702-1713
Streamline computation in a very large vector field data set represents a significant challenge due to the nonlocal and data-dependent nature of streamline integration. In this paper, we conduct a study of the performance characteristics of hybrid parallel programming and execution as applied to streamline integration on a large, multicore platform. With multicore processors now prevalent in clusters and supercomputers, there is a need to understand the impact of these hybrid systems in order to make the best implementation choice. We use two MPI-based distribution approaches based on established parallelization paradigms, parallelize over seeds and parallelize over blocks, and present a novel MPI-hybrid algorithm for each approach to compute streamlines. Our findings indicate that the work sharing between cores in the proposed MPI-hybrid parallel implementation results in much improved performance and consumes less communication and I/O bandwidth than a traditional, nonhybrid distributed implementation. 相似文献
84.
Warlow OM Johnson GR 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2012,226(7):521-528
Biomechanical models of the fingers are used to gain a greater understanding of internal loading. This can help guide the treatment of injuries and pathologies. However, to be valid these models require accurate measurement of body kinematics, external reaction forces and soft tissue architecture. This study aimed to quantify the sensitivity of one such model, to errors in these inputs. Experimental data was collected from a single subject carrying out a simple gripping activity and the experimental data altered to introduce artificial errors. We found that the correlations between errors in measurement of body kinematics and the model outputs could be used to express errors in motion capture data in terms of internal loading. However, these correlations were specific to grip type, therefore, if the grip changed significantly a new analysis would be required. Sensitivity analysis of the muscle and tendon locations indicated which parameters were most important to measure accurately; outputs were most sensitive to changes in the most highly loaded muscle-tendon units, these results were applicable across different hand orientations. 相似文献
85.
The solid state morphology of recently developed sulfonated polyisobutylene (PIB) telechelic ionomers with narrow molecular weight distribution (MWD) (M¯w/M¯n ≈ 1.15) was investigated. A small angle X-ray scattering (SAXS) peak often associated with the aggregation of the ionic species in the bulk, as well as a secondary peak, have been observed in the narrow distribution sulfonated PIB telechelic ionomers for the first time. Ionomers of difunctional and tri-arm architecture at several number average molecular weights (M¯n) with one of several counterions were investigated and the preparation method was also considered in terms of observed SAXS behavior. Compression-molded films made from these narrow MWD telechelics were examined in detail using SAXS. Primary and secondary peaks were observed in the slit-smeared SAXS profiles up to an M¯n of 27 kg/mol. The ratio of the interdomain spacings derived from these peaks (ca. 2 : 1) suggests cylindrical or lamellar ordering in the morphology in both difunctional and tri-arm ionomers. Pinhole SAXS images showed no azimuthal dependence in the scattering pattern and thus, this ordering is on a local scale. It was found that the counterion has an inconsistent effect on the smeared interdomain spacing associated with the SAXS peak. The smeared interdomain spacings were systematic with respect to architecture and M¯n for solution cast Cs+ ionomers. The difunctional telechelics exhibited higher smeared interdomain spacings than tri-arms of comparable M¯n and unlike the compression-molded films, the smeared interdomain spacings of the solution cast Cs+ telechelic ionomers increased systematically with increasing M¯n. Even a broad MWD (M¯n/M¯n ≈ 1.8) tri-arm telechelic ionomer M¯n of 20.6 kg/mol exhibited a diffuse primary peak in SAXS when solution-cast. However, it exhibited no peak when compression-molded. © 1997 John Wiley & Sons, Inc. 相似文献
86.
Summary Metal acetyl acetonates of aluminum, zirconium and zinc have been successfully incorporated into poly (tetramethylene oxide) modified TEOS based materials using sol-gel chemistry. Incorporation of these metal acetyl acetonates required modification of the reaction scheme developed earlier to incorporate titanium(IV) isopropoxide. Gelation rates and the physical properties of the subsequent gelled materials varied as a function of the metal acetyl acetonate used. 相似文献
87.
An aminolysis mechanism is proposed to explain the enhanced adhesion between the interface of a bisphenol-A polycarbonate substrate with an alkoxysilane containing sol-gel coating when 3-aminopropyltriethoxysilane (3-APS) is used as a primer. Both a model solution study and surface analyses of polycarbonate substrates exposed to 3-APS indicate that the latter reacts with the carbonate groups in the polycarbonate chain by forming urethane linkages. With 3-APS bonded to the substrate, a sol-gel coating can be chemically bonded to the substrate through hydrolysis of alkoxysilane groups and subsequent silanol condensation. Consequently, enhanced adhesion between the sol-gel coating and the substrate is achieved. 相似文献
88.
Chenghong Li Thomas Glass Garth L. Wilkes 《Journal of Inorganic and Organometallic Polymers》1999,9(2):79-106
Inorganic-organic hybrid materials were prepared by hydrolysis and condensation of triethoxysilylated diethylenetriamine (f-DETA) and tetramethoxysilane (TMOS). The prehydrolysis stage of this f-DETA/TMOS system was monitored by 29Si NMR spectroscopy. The NMR experiments indicated that f-DETA hydrolyzes and condenses nearly as fast as TMOS at pH 0–1, but lags far behind the latter at pH~4.2. Gels derived from f-DETA and TMOS were studied using 13C or 29Si solid state NMR spectroscopy. The concentration of the alkoxy groups and the extent of condensation of the T & Q species in the cured gels were estimated. The contents of the Si–OMe group and Si–OEt group were barely detectable in most water-abundant systems (equivalent ratio of water to alkoxysilane ~4.0). However, a significant amount of Si–O
i
Pr groups was found if the reactant f-DETA was stored at room temperature in solvent 2-propanol for three weeks or longer. The relative composition of each Tz or Qz species was estimated for gels prepared in media of different acidity levels and water concentrations and then cured at 125–130°C for 4 h. As the acidity of the medium increased from pH 0–2 to pH 4–5, the extent of condensation of the T species decreased but that of the Q species increased. The hydrolysis of urea groups in f-DETA during the sol-gel process was also evaluated by 13C solid state NMR spectroscopy. The results indicated that only a very small fraction of urea groups was hydrolyzed during the sol-gel process. 相似文献
89.
Sven Achenbach David Klymyshyn Darcy Haluzan Timo Mappes Garth Wells Jürgen Mohr 《Microsystem Technologies》2007,13(3-4):343-347
Radio frequency micro electro-mechanical systems (RF MEMS) vertical cantilever variable capacitors fabricated using deep X-ray
lithography and electroplating are presented. Polymethylmethacrylate (PMMA) layers of 100 μm and 150 μm have been patterned
and electroplated with 70 μm and 100 μm thick nickel. A 3 μm thick titanium layer was used as plating base as well as etch
time-controlled sacrificial layer for the release of the cantilever beam. The parallel plate layout includes narrow gaps and
cantilever beams with an aspect ratio in nickel of up to 60 for 1 mm long features. Auxiliary structures support the beams
and gaps during the processing. Room temperature electroplating significantly reduces the risk of deformations compared to
the standard process temperature of 52°C. The capacitors operate in the 1–5 GHz range, and demonstrate good RF performance,
with quality factors on the order of 170 at 1 GHz for a 1 pF capacitance. 相似文献
90.
Philip Avery Charbel Farhat Garth Reese 《International journal for numerical methods in engineering》2007,69(13):2848-2875
Problems of the form Z (σ) u (σ)= f (σ), where Z is a given matrix, f is a given vector, and σ is a circular frequency or circular frequency‐related parameter arise in many applications including computational structural and fluid dynamics, and computational acoustics and electromagnetics. The straightforward solution of such problems for fine increments of σ is computationally prohibitive, particularly when Z is a large‐scale matrix. This paper discusses an alternative solution approach based on the efficient computation of u and its successive derivatives with respect to σ at a few sample values of this parameter, and the reconstruction of the solution u (σ) in the frequency band of interest using multi‐point Padé approximants. This computational methodology is illustrated with applications from structural dynamics and underwater acoustic scattering. In each case, it is shown to reduce the CPU time required by the straightforward approach to frequency sweep computations by two orders of magnitude. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献