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111.
To better understand the operation of a new fuel cell design, we used magnetic resonance imaging (MRI) to measure the water content distribution in a polymer electrolyte membrane under fuel cell operation with and without a supply of liquid water. The supply of liquid water to the membrane improved the cell performance by increasing the water content in the membrane and thus reducing the electrical resistance of the membrane. The study also showed that MRI is a promising method to investigate the distribution of water in the membrane of a fuel cell under operating conditions.  相似文献   
112.
We report here "strain glass," a new glassy phenomenon in ferroelastic-martensitic system of Ni-rich intermetallic Ti(50-x)Ni(50+x) (x > 1), where local strain is frozen in disordered configuration below a critical temperature Tg. The ac elastic modulus shows a minimum at Tg, which exhibits logarithmic frequency dependence following Vogel-Fulcher relationship, and the corresponding internal friction shows a frequency-dependent peak located at a lower temperature. In situ high-resolution transmission electron microscopy observations reveal uncorrelated nanoclusters of martensiticlike phase, randomly frozen in the otherwise untransformed parentlike matrix. Being parallel to spin glass and relaxor, strain glass may shed new light on the fundamental physics of glass and lead to the discovery of novel properties.  相似文献   
113.
The purpose of this project was to assess the reliability of the cerebral mean transit time (MTT) obtained using perfusion-weighted MR imaging by comparing it with the MTT obtained when performing positron emission tomography (PET). Ten patients with chronic occlusive cerebrovascular disease were investigated. They had either unilateral internal carotid artery occlusion or middle cerebral artery occlusion. The regions-of-interest were placed in non-infarcted areas within the territory of the middle cerebral artery on the affected side. Control regions-of-interest were placed in mirrored regions of the contralateral side. Linear regression analyses were performed using the parameters of the MTT obtained with perfusion-weighted MR imaging and the MTT, cerebral blood flow, vascular reactivity, and oxygen extraction fraction obtained with PET. The respective MTTs of the affected and non-affected sides obtained with perfusion-weighted MR imaging versus those with PET were 7.3 +/- 2.2 s and 6.0 +/- 1.2 s versus 8.2 +/- 3.0 s and 6.4 +/- 1.7 s. The MTT obtained using perfusion-weighted MR imaging and PET demonstrated statistically significant correlation (r = 0.87, p < 0.0001). The MTT obtained with perfusion-weighted MR imaging correlated statistically with cerebral blood flow (r = -0.74, p < 0.001), vascular reactivity (r = -0.73, p < 0.001) and oxygen extraction fraction (r = 0.61, p < 0.01). Similarly, the MTT obtained using PET statistically correlated with cerebral blood flow (r = -0.78, p < 0.0001), vascular reactivity (r = -0.51, p < 0.05) and oxygen extraction fraction (r = 0.68, p < 0.01). The reliability of the MTT obtained using perfusion-weighted MR imaging appears to be approximately equal to that obtained with positron emission tomography.  相似文献   
114.
In this paper, we study boundedness of integral operators on generalized Morrey spaces and its application to estimates in Morrey spaces for the Schrödinger operator with nonnegative (reverse Hölder class) and small perturbed potentials .

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115.
Let be a locally -connected compact metric space. Then, the canonical homomorphism from the singular homology group to the Cech homology group is surjective. Consequently, if a compact metric space is locally connected, then the canonical homomorphism from to is surjective.

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116.
Methyl mercaptoacetate (MA) on Cu(1 1 1) surface was investigated using synchrotron radiation-based X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. MA adsorbs on the surface via thiolate formation and weak interaction of the carbonyl group with the surface. Two different adsorption states previously reported for methanethiolate and ethanethiolate were confirmed, besides atomic sulfur. NEXAFS measurements support gauche-type conformation of MA whose skeleton lies on the surface.  相似文献   
117.
A new noise-removal technique is applied to scanning laser microscopic (SLM) images to remove clustered spike noise in the images and to recover the shapes of diamond abrasive grains degraded by the noise. For achievement of this purpose, noise points in the SLM image are accurately detected by taking advantage of their properties in the space and spatial-frequency regions. The noise points are removed by a method of smoothing that is based on linear interpolation; that is, their pixel values are replaced by the interpolated values of their non-noise neighboring points. Noise-point information in the space region is acquired from image segmentation based on pixel classification, while noise-point information in the frequency region is derived from redundant wavelet decomposition for the SLM image. Fisher's linear discriminant method is used to yield the two noise-point images. The degraded grain shapes in the SLM images at different noise levels are satisfactorily recovered with a single iteration of smoothing without losses in sharp edges although a single smoothing needed four interpolations. Thus, the present noise-removal technique is shown to be effective for recovering the original shapes of the grains in every SLM image.  相似文献   
118.
119.
The influence of high-temperature annealing on the electrical properties and microstructure of tin-doped indium oxide (ITO) thin films was investigated as a function of oxygen gas flow ratio to argon gas during the sputtering deposition. The ITO thin films were annealed at 500 °C in air after the deposition. It was found that the ITO thin films, which were deposited in relatively low oxygen gas flow ratio, exhibited high Hall mobility and low-resistivity after the annealing. Furthermore, the X-ray reflectivity and diffraction measurement revealed that the ITO thin film with low-resistivity after annealing exhibited high packing density, smooth surface and low crystallization degree. It can be considered that the carrier electron scattering was suppressed with increasing in the packing density of the ITO thin film; as a result, the Hall mobility and resistivity were improved.  相似文献   
120.
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