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171.
光纤光栅最佳切趾函数的研究 总被引:6,自引:2,他引:4
采用耦合模理论,给出了用传输矩阵法计算光纤Bragg光栅(FBG)特性的方法,进而得到了在不同切趾函数形式下的FBG反射谱的数值解。通过理论分析,给出了最佳切趾函数反射谱和群时延特性曲线。 相似文献
172.
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175.
通过有限元的方法,分析了T型薄壁管节点受平面内弯矩作用下的疲劳行为,得到了应力最大值的位置和拟合出用于预测T型薄壁管节点受平面内弯矩作用下的应力集中系数的参数公式。 相似文献
176.
Glucosamine, which enters the hexosamine pathway downstream of the rate-limiting step, has been routinely used to mimic the insulin resistance caused by high glucose and insulin. We investigated the effect of glucosamine on insulin-stimulated glucose transport in 3T3-L1 adipocytes. The Delta-insulin (insulin-stimulated minus basal) value for 2-deoxyglucose uptake was dramatically inhibited with increasing concentrations of glucosamine with an ED50 of 1.95 mM. Subcellular fractionation experiments demonstrated that reduction in insulin-stimulated 2-deoxyglucose uptake by glucosamine was due to an inhibition of translocation of both Glut 1 and Glut 4 from the low density microsomes (LDM) to the plasma membrane. Analysis of the insulin signaling cascade revealed that glucosamine impaired insulin receptor autophosphorylation, insulin receptor substrate (IRS-1) phosphorylation, IRS-1-associated PI 3-kinase activity in the LDM, and AKT-1 activation by insulin. Measurement of intracellular ATP demonstrated that the effects of glucosamine were highly correlated with its ability to reduce ATP levels. Reduction of intracellular ATP using azide inhibited Glut 1 and Glut 4 translocation from the LDM to the plasma membrane, insulin receptor autophosphorylation, and IRS-1 tyrosine phosphorylation. Additionally, both the reduction in intracellular ATP and the effects on insulin action caused by glucosamine could be prevented by the addition of inosine, which served as an alternative energy source in the medium. We conclude that direct administration of glucosamine can rapidly lower cellular ATP levels and affect insulin action in fat cells by mechanisms independent of increased intracellular UDP-N-acetylhexosamines and that increased metabolism of glucose via the hexosamine pathway may not represent the mechanism of glucose toxicity in fat cells. 相似文献
177.
Hu Chi Yang Hong-sheng Lu Zhong-zuo 《Journal of Infrared, Millimeter and Terahertz Waves》1995,16(2):401-410
Circular groove guide is a kind of waveguide for millimeter waves with low loss, large dimensions, and low dispersion. In this paper, the dominant mode characteristics of it is analysed. The technique that mode macthing method combines with point matching method is used to derive the Nth-order characteristic equation of the guide. The 1st order, 2nd order and 3rd order approximate curves that the normalized cutoff wavelength of circular groove guide varies with c/a are given. The attenuation curves are given at 1mm, 1.5mm and 3mm wavelength. The numerical results are in well agreement with the experimental results published. 相似文献
178.
BACKGROUND: Although transmission of hepatitis C virus (HCV) through parental exposure is well documented, it is still controversial whether familial clustering of HCV occurs. METHODS: To investigate risk factors for HCV infection, 109 cases and 84 non-infected controls were studied. In addition, 250 family members (104 men, 146 women) of cases and 170 family members of controls (64 men, 106 women) were tested for HCV infection using an anti-HCV antibody, alanine aminotransferase (ALT), and reverse transcribed polymerase chain reaction (RT-PCR). RESULTS: In the case-control analysis, people aged > or =60 were almost three times more likely to be infected by HCV than those aged <40. Risk of HCV infection was most strongly related to a history of blood transfusion (OR = 12.6, 95% CI: 4.3-36.5) followed by a history of jaundice (OR = 4.1, 95% CI: 1.3-12.6). Only one family member of cases and no-one related to the controls had HCV infection. CONCLUSIONS: These results suggest that, in Korea, age and parenteral exposure, such as a blood transfusion, are risk factors for HCV infection and familial clustering of HCV infection, if it occurs, is rare. 相似文献
179.
Mixed variable optimization using Taguchi's orthogonal arrays 总被引:2,自引:0,他引:2
Taguchi's orthogonal arrays for robust design are used in this paper in a nontraditional way to solve a mixed continuous-discrete structural optimization problem. The factors of an orthogonal array correspond to the members of a structure and the levels of each factor correspond to the material choices of each member. Based on the number of factors to be studied and the number of levels of each factor, an appropriate orthogonal array is selected for each specific problem. The number of rows of the orthogonal array correspond to the number of experiments (i.e. continuous sizing optimizations) to be conducted. The response of these experiments, which are the weight of the optimal designs corresponding to different material settings, are then used to calculate the mean effect of each factor level. Some possible optimal material settings can then be determined. Three examples are presented in this paper. Analysis using Taguchi's orthogonal arrays was able to isolate several near optimal or optimal designs. The accuracy and efficiency of the proposed method compared to more traditional solution methodologies are also discussed. 相似文献
180.
Medullary thyroid cancer is a tumor of the thyroid C cells that occurs in sporadic and hereditary clinical settings. Genetic testing of at-risk individuals is available and has been applied to patient management. Plasma calcitonin levels are a sensitive marker for the presence of disease. Surgery offers the best hope for cure and also is an effective modality for managing metastatic and recurrent disease. 相似文献