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81.
水文统计中的月径流资料是非常重要的。月径流系列是一随机过程,由于水文现象的复杂性,难以用准确的分布函数来描述。但作出某些合理手假设后,可将其变为符合各态历经定理的平稳随机过程。用Mapkob自回归模型可以生成人工月径流系列,以满足规划、设计等方面的要求。本文以三屯河为例,用Mapkob模型模拟了该河的月径流系列。  相似文献   
82.
塔里木河干流区地方性氟病区水化学成分的多元分析   总被引:2,自引:0,他引:2  
本文运用相关分析、回归分析及R-型系统聚类分析等方法,研究了里木河干流地区的地方性氟中毒病区内,氟斑牙患病率与饮用水中氟元素及其它化学成分的定量关系,并建立了生活饮用水中氟元素与其它化学成分的回归计算模型,提示了区域内氟斑牙治病的主导因素以及水体中各化学成分和化学性质指标间的相互关系,为探求饮用水型地方性氟中毒的病因提供了科学依据。  相似文献   
83.
The mucosal upheaval (MU), where the mucosal wave starts and propagates upward, appears only when the vocal fold vibrates. The location of the MU histologically and the effect of changes in mean air flow rate (MFR) and vocal fold length on occurrence of the MU were studied in twelve excised canine larynges. The lower surface of the vocal fold was marked to serve as a landmark for subsequent study. Cricothyroid approximation was performed to lengthen the vocal fold. After taking high-speed pictures or recording stroboscopic images from the tracheal side, a small cut wound was made at the mark. This wound served to compare the position of the MU with the histologically identified location of the mark. The larynx was then sectioned in the frontal plane. Before lengthening the vocal fold, the MU occurred on the area where the lamina propria became thinner and where the muscular layer neared the epithelial layer. After lengthening the vocal fold, the MU actually shifted medially compared with its original position. The subglottic area surrounded by the bilateral MUs became longer and thinner. Whether or not complete glottal closure during a vibratory cycle was achieved did not alter these findings. In contrast, with a fixed vocal fold length the MU appeared more laterally as MFR increased, but, based on the relation with the mark, its location on the vocal fold did not change from its original position before increase of MFR.  相似文献   
84.
尚也淳  张义门  张玉明 《物理学报》2001,50(7):1350-1354
提出了一种SiC反型层表面粗糙散射的指数模型,并对6H-SiC反型层迁移率进行了单电子的Monte Carlo模拟,模拟中考虑了沟道区的量子化效应.模拟结果表明,采用表面粗糙散射的指数模型能够使SiC反型层迁移率的模拟结果和实验值符合得更好.模拟结果还反映出有效横向电场较高时表面粗糙散射的作用会变得更显著,电子的屏蔽效应降低了粗糙散射对沟道迁移率的影响,温度升高会引起沟道迁移率降低. 关键词: 6H-SiC 反型层迁移率 表面粗糙散射 指数模型  相似文献   
85.
研究了基于NZ30K合金开发的新型Mg-3Nd-0.2Zn-0.4Zr-0.2Mn镁合金耐腐蚀性、体外降解行为特性及浸提液细胞生物毒性. 采用金相显微镜得到新型镁合金金相显微图, 采用扫描电镜(Scanning Electron Microscope, SEM)获取SEM图; 采用武汉科思特电化学工作站进行电化学测试, 并绘制动电位极化曲线, 以磷酸盐缓冲液(Phosphate Buffer Solution, PBS)模拟体液环境, 记录氢气析出体积并计算腐蚀速率; 利用细胞完全培养基测定pH值、重量变化曲线; 获取大鼠骨髓间充质干细胞(Bone Mesenchymal Stem Cells, BMSCs), 并利用完全细胞培养基制作新型镁合金浸提液, 检测细胞生物活性, 以ZA75镁合金为基础添加0.3%Mn元素制成合金作为对照组, 比较腐蚀电位、体外降解情况以及细胞活性. 结果表明: 新型Mg-3Nd-0.2Zn-0.4Zr-0.2Mn镁合金横截面等轴晶体组织细小均匀性较好, 纵截面呈长条状组织均匀性稍差; 自腐蚀电位较高, 为-1.3912V; 自腐蚀电流密度较低, 为7.37×10-7 A?cm-2; 体外析氢量低, 失重量、pH值变化幅度相对较小; 降解速率下降后呈现小范围上升后趋于平缓; 具有良好的细胞相容性, 可以促进BMSCs细胞增殖分化.  相似文献   
86.
陈徐宗 《物理》2006,35(3):207-212
2005年的诺贝尔物理学奖授予了现代光学领域的科学家,其中诺贝尔奖的一半授予了哈佛大学的Roy J.Glauber教授,以表彰他在光的量子相干性理论方面的突出贡献,诺贝尔奖的另外一半授予了美国科罗拉多大学与美国国家标准技术研究院联合实验(JILA)的John L.Hall教授和德国慕尼黑大学教授、马克斯普朗克-量子光学研究所所长TheodorW.Hansch教授,以表彰他们在光的超高精密测量方面的突出贡献,文章介绍了三位诺贝奖得主的贡献及其意义.  相似文献   
87.
Raman spectroscopy has been effectively applied to clinically differentiate normal and cancerous mucosal tissues. Micro‐Raman spectroscopy provides a tool to better understand the molecular basis for the Raman clinical signal. The objective of the current study was to utilize micro‐Raman spectroscopy to define the molecular/spectral differences between normal and abnormal squamous cell carcinoma (SCC) in oral mucosa (in vitro). Understanding this may help in identifying unique spectra or may be useful for in vivo application of this technology. Micro‐Raman (confocal) spectroscopy was used to obtain molecular images of normal and SCC cells of human oral mucosa. Four fresh flashed‐frozen tumor and four matched normal tongue specimens were studied. The spectra covered a wavenumber range from 300 to 4000 cm−1 with a spectral resolution of 8 cm−1 and a spatial resolution of 1.0 µm. The cells were located within thin sections of tongue mucosa biopsies. The excitation wavelength of 515 nm was used. We were able to obtain Raman images with rich information about the spectroscopic and structural features within the cytoplasm, cell membrane, and cell nuclei. Significant spectral differences were observed between the Raman images of normal and malignant squamous cells. The heterogeneity of tumor cells within the abnormal tissue was also demonstrated. Spectral differences demonstrated between both tissue types have provided important information regarding the origins of specific signals within the cells of each tissue type. In our search for specific spectral biomarkers, we believe that a cell surface protein, greatly upregulated in SCC cells, was discovered at 1583 cm−1. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
88.
Advances in the field of Femtosecond Stimulated Raman Spectroscopy (FSRS), a new time‐resolved structural technique that provides complete vibrational spectra on the ultrafast timescale, are reviewed. When coupled with a femtosecond optical trigger, the time evolution of a reacting species can be monitored with unprecedented <25 femtosecond temporal and 5 cm‐1 spectral resolution. New technological and theoretical advances including the development of tunable FSRS and a background‐free FSRS format are discussed. The most recent experimental studies focus on ultrafast reaction dynamics in electronically excited states: isomerization in cyanobacterial phytochrome, ultrafast spin flipping in a solar cell sensitizer, and excited state proton transfer in green fluorescent protein. The use of FSRS to directly map multidimensional reactive potential energy surfaces and to probe the mechanism of reactive internal conversion is prospectively discussed.  相似文献   
89.
A new energy source originating from extra dimensions   总被引:1,自引:0,他引:1       下载免费PDF全文
陶必修  吉世印  李芳琼 《中国物理》2004,13(11):1830-1834
In this work the Einstein gravitational field equations and the Lichnerowicz boundary formalism in the extra dimensions are used to build up our black hole model from 6-dimensional space-time. From the internal stress-energy tensor the solutions with energy levels and semiclassical space-quantization are obtained, which combines with only one metric condition outside the defect. We show a new type of energy source, which originates from extra dimensions. A part of the energy source of quasi-stellar object (QSO) maybe come from extra dimensions in that way. The theoretical arithmetic upper limit is identical to that of the output energy of QSO.  相似文献   
90.
孙宗扬 《大学物理》2005,24(12):18-20
给出了电磁学中通用的国际单位制及相当流行的实用单位制之间的简单并且便于记忆及使用的转换方式。  相似文献   
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