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排序方式: 共有1394条查询结果,搜索用时 484 毫秒
161.
Robert D. Schmidt Eldon D. Case Zayra Lobo Travis R. Thompson Jeffrey S. Sakamoto Xiao-Yuan Zhou Ctirad Uher 《Journal of Materials Science》2014,49(20):7192-7212
The thermoelectric skutterudite Ba0.3Co4Sb12 is a promising candidate for waste heat recovery applications. Recently, it was demonstrated that the addition of silver nanoparticles (AgNP) to Ba0.3Co4Sb12 increases both the thermoelectric figure of merit and electrical conductivity. This study is the first to examine the effect of AgNP addition on the material’s mechanical properties. This study also found that the Young’s modulus, E, shear modulus, G, and bulk modulus, B, decreased linearly with increasing volume fraction porosity, P. Resonant ultrasound spectroscopy was employed to measure the elastic moduli, and Vickers indentation was used to determine the hardness, H, and fracture toughness, K C. Trends in the mechanical properties as a function of grain size, porosity, and the AgNP are discussed in terms of the pertinent literature. While K C was independent of AgNP addition, porosity, and grain size, both E and H decreased linearly with increasing porosity. In addition, this study is the first to identify (i) the Ag3Sb phase formed and (ii) the enhanced densification that occurs when the AgNP is sintered with Ba0.3Co4Sb12 powders, where both effects are consistent with the eutectic and peritectic reactions observed in the binary phase diagram Ag–Sb. These eutectic/peritectic reactions may also be linked to the enhancement of electrical conductivity previously observed when Ag is added to Ba0.3Co4Sb12. Also, similar beneficial eutectic/peritectic reactions may be available for other systems where conductive particles are added to other antimonides or other thermoelectric systems. 相似文献
162.
John J. Boyle Maiko Kume Matthew A. Wyczalkowski Larry A. Taber Robert B. Pless Younan Xia Guy M. Genin Stavros Thomopoulos 《Journal of the Royal Society Interface》2014,11(100)
When mechanical factors underlie growth, development, disease or healing, they often function through local regions of tissue where deformation is highly concentrated. Current optical techniques to estimate deformation can lack precision and accuracy in such regions due to challenges in distinguishing a region of concentrated deformation from an error in displacement tracking. Here, we present a simple and general technique for improving the accuracy and precision of strain estimation and an associated technique for distinguishing a concentrated deformation from a tracking error. The strain estimation technique improves accuracy relative to other state-of-the-art algorithms by directly estimating strain fields without first estimating displacements, resulting in a very simple method and low computational cost. The technique for identifying local elevation of strain enables for the first time the successful identification of the onset and consequences of local strain concentrating features such as cracks and tears in a highly strained tissue. We apply these new techniques to demonstrate a novel hypothesis in prenatal wound healing. More generally, the analytical methods we have developed provide a simple tool for quantifying the appearance and magnitude of localized deformation from a series of digital images across a broad range of disciplines. 相似文献
163.
A prototype Stirling cycle refrigerator employing helium as a working fluid was investigated to determine whether a freon‐free machine was a viable alternative for the current household refrigerator. A displacer‐type or β‐type Stirling cycle machine of 100‐W capacity was designed and tested using varying design parameters such as dead volume ratio, working fluids, the ratio of the compression volume to the expansion volume, and the phase difference between a power piston and displacer. The detrimental effect of the dead space on the refrigeration capacity was confirmed. The refrigeration produced by nitrogen in an expansion space was 28% less than that produced by helium. The optimum volume ratio and the phase difference for maximum refrigeration was determined under the design operation conditions. Moreover, the refrigeration correlation formula as a function of these parameters was obtained. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(5): 344–361, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10033 相似文献
164.
Printed Electronics: Room‐Temperature Printing of Organic Thin‐Film Transistors with π‐Junction Gold Nanoparticles (Adv. Funct. Mater. 31/2014) 下载免费PDF全文
165.
Sorimachi A Sakamoto K Sakai M Ishihara H Fukuyama T Utiyama M Liu H Wang W Tang D Dong X Quan H 《Environmental science & technology》2004,38(12):3396-3404
Laboratory and field measurements were conducted to examine dry deposition of SO2 onto Chinese loess surfaces using native soil sampled in the loess plateau, China. The field tests were employed in Beijing and Lanzhou, China, by directly measuring the dry deposition of SO2 on soil, which uses soil put on a collector as an SO2 passive sampling medium. In the laboratory, a high rate of uptake to SO2 deposition for Chinese soil surfaces due to the highly alkalinity was found. The uptake of SO2 deposition was dependent on the pH soil and relative humidity. Furthermore, we evaluated some factors that affect the measurement precision: response of SO2 uptake, repeatability, recovery factor, and variability associated with the weight and the surface coverage on the collectors. As a result, it was shown that the measurement precision was primarily related to the ratio of the SO2 deposition amount relative to the sulfur content of the original soil. This result was consistent with the field observations. The laboratory and field results indicated an excellent agreement on the SO2 uptake inherent in the results from the soil surfaces in different regions. 相似文献
166.
Sakamoto K. Kasahara Y. Kimura I. 《Geoscience and Remote Sensing, IEEE Transactions on》1995,33(3):528-534
A straightforward method for determination of k-vector (wave normal) direction of a whistler mode signal observed onboard spacecraft consists in measuring three components of the wave magnetic field with their instantaneous amplitudes and phases. In that method, one needs to send by telemetry a total wave form of a signal, which requires much larger bandwidth than for sending amplitudes only. The present study develops another method of determination of the wave normal direction based only on the amplitude data; the method is checked using Omega signal observations by the Akebono satellite. It should, however, be noted that the sense of k-vector is not determined by this proposed method 相似文献
167.
K Ishii S Sakamoto M Sasaki H Kitagaki S Yamaji M Hashimoto T Imamura T Shimomura N Hirono E Mori 《Canadian Metallurgical Quarterly》1998,39(11):1875-1878
Frontotemporal dementia (FTD) is a dementia syndrome characterized by peculiar behavioral changes arising from frontotemporal involvement and distinct from Alzheimer's disease (AD). The purpose of this study was to elucidate the specific patterns in cerebral glucose metabolism in patients with FTD and to compare them with the patterns in patients with AD and normal elderly subjects using fluorodeoxyglucose (FDG) and PET. METHODS: Twenty-one patients with a clinical diagnosis of FTD [mean age 67.0 +/- 7.0 yr, Mini Mental State Examination (MMSE) score 18.7 +/- 5.7], 21 age-, sex- and dementia-severity-matched patients with probable AD (mean age 66.9 +/- 7.1 yr, MMSE score 20.2 +/- 5.5) and 21 age- and sex-matched normal control subjects (mean age 66.8 +/- 5.7 yr) were studied. The cerebral metabolic rate for glucose (CMRglc) was measured with FDG and PET. Absolute measures of regional CMRglc were compared among the three groups. One-way ANOVA and the posthoc Tukey HSD test were used for statistical analyses. RESULTS: In the FTD group, CMRglc was preserved only in the left cerebellum, right sensorimotor area and occipital lobes. The CMRglc was significantly lower in the FTD group as opposed to the AD group in the hippocampi, orbital gyri, anterior temporal lobes, anterior cingulate gyri, basal ganglia, thalami, middle and superior frontal gyri and left inferior frontal gyrus. CONCLUSION: Although metabolic abnormality in FTD is predominant in the frontal and anterior temporal lobes and the subcortical structures, it is more widespread than has been previously stressed. These findings document an FTD-specific cerebral involvement and facilitate differential diagnosis of degenerative dementias. 相似文献
168.
Seven zinc-finger transcription factors are expressed sequentially during the development of anthers in petunia 总被引:1,自引:0,他引:1
A Kobayashi A Sakamoto K Kubo Z Rybka Y Kanno H Takatsuji 《Canadian Metallurgical Quarterly》1998,13(4):571-576
BACKGROUND: Little is known about the value of heart rate variability in patients with symptomatic coronary artery disease with a preserved left ventricular function. We hypothesized that in these patients heart rate variability might be a helpful adjunct to conventional parameters to predict clinical events. METHODS: In a prospective 2-year follow-up study ambulatory electrocardiographic recordings were performed in 263 consecutive male patients (mean age 56+/-8 years) with stable angina pectoris and a mean left ventricular ejection fraction of 71%+/-12%. Clinical events consisted mainly of coronary events such as percutaneous transluminal angioplasty or coronary artery bypass graft operation. RESULTS: Low measures of standard deviation of normal R-R intervals, standard deviation of the mean R-R intervals of 5 minutes, and two spectral components of heart rate variability were found in patients who had had an event compared with patients with no event. Adjusted for severity of angina, the presence of a previous myocardial infarction, and the use of beta-blockers in a logistic regression model this relation remained statistically significant for SDNN. Healthy volunteers appeared to have the highest measures of heart rate variability. CONCLUSION: In patients with ischemic heart disease and normal or near normal ventricular function decreased heart rate variability is associated with adverse clinical events. 相似文献
169.
Genetically engineered rice (Oryza sativa L.) with the ability to synthesize glycinebetaine was established by introducing the codA gene for choline oxidase from the soil bacterium Arthrobacter globiformis. Levels of glycinebetaine were as high as 1 and 5 micromol per gram fresh weight of leaves in two types of transgenic plant in which choline oxidase was targeted to the chloroplasts (ChlCOD plants) and to the cytosol (CytCOD plants), respectively. Although treatment with 0.15 M NaCl [corrected] inhibited the growth of both wild-type and transgenic plants, the transgenic plants began to grow again at the normal rate after a significantly less time than the wild-type plants after elimination of the salt stress. Inactivation of photosynthesis, used as a measure of cellular damage, indicated that ChlCOD plants were more tolerant than CytCOD plants to photoinhibition under salt stress and low-temperature stress. These results indicated that the subcellular compartmentalization of the biosynthesis of glycinebetaine was a critical element in the efficient enhancement of tolerance to stress in the engineered plants. 相似文献
170.
Repetitive electrical stimulation of the midbrain peri-aqueductal grey (PAG) terminates quiet breathing and initiates inspiration that precedes vocalization. To understand the neuronal mechanisms underlying this phenomenon, activities of expiratory neurones (n = 39) of the B?tzinger complex (BOT) were examined in decerebrate cats. Most augmenting expiratory (E-aug) neurones (20/22) of the BOT, including 15 bulbospinal neurones, decreased their activities (9/20) or ceased to discharge (11/20) after the onset of stimulation of the PAG. This suggests that suppression of E-aug neurones of the BOT, which project to phrenic motoneurones, results in disinhibition of these neurones, and, in turn, terminates expiration and initiates inspiration preceding vocalization. 相似文献