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91.
在大型水利水电施工中,经常遇到岩质高边坡稳定问题,天荒坪抽水蓄能电站500kV开关站所处的地形地质条件非常复杂,本文着重介绍在边坡开挖和支护过程中,根据不同的地形地质情况所采取的控制爆破和支护措施。 相似文献
92.
BACKGROUND: Cigarette smoke may promote atherogenesis by producing oxygen-derived free radicals that damage lipids. However, evidence in support of this hypothesis is inconsistent because most studies did not control for aspects of diet (antioxidants and lipid substrate) that may confound the association between smoking and measures of lipid peroxidation. METHODS AND RESULTS: The relationships between cigarette smoking and two measures of lipid peroxidation, breath ethane (an in vivo assay) and thiobarbituric acid-reactive substances (TBARS, an in vitro assay), were examined in 123 adults (11% of whom were smokers) participating in a controlled feeding study. After 3 weeks of controlled feeding on a common diet (36% total fat, 14% saturated fats, 6% polyunsaturated fats, and 12% monounsaturated fats), breath and fasting serum samples were collected for measurement of ethane and TBARS, respectively. Baseline characteristics of smokers and nonsmokers were similar, including several indices related to diet and nutritional status (albumin, cholesterol, body mass index, and oxygen radical-absorbing capacity). Cigarette smokers had significantly higher breath ethane (8.88 versus 1.71 pmol/L; P<.0001) and TBARS (24.0 versus 20.7 micromol/mL; P=.008) than nonsmokers. The interval between breath collection and the time the last cigarette was smoked was significantly and inversely correlated with breath ethane. Neither measure of lipid peroxidation was associated with measures of serum cholesterol or albumin, body mass index, or serum oxygen radical-absorbing capacity. CONCLUSIONS: Cigarette smokers have higher rates of in vivo and in vitro lipid peroxidation. These results support the hypothesis that the atherogenic effects of smoking are mediated in part by free radical damage to lipids. 相似文献
93.
姜让荣 《核电子学与探测技术》1994,14(1):26-33
本文针对Beck公式的局限性,对土壤的含水量和^222Rn析出引起的γ辐射剂量率变化进行了修正。通过浙江省576组测量数据的实验拟合,给出了剂量率计算的修正公式。该公式应用到浙江省自身的测量数据上,使计算的总体均值与实测均值仅相差0.8%;每一点位的计算值与实测值相比,平均仅相差3.4%,其比值离散性与实验误差相一致。而Beck公式的计算结果与实测剂量率相比较,以上两项分别偏离+10%和15.2% 相似文献
95.
96.
本文对ATM(异步转移模式)网络中话音、数据和图像业务的漏桶流量控制特性进行了研究。计算机模拟结果表明,由于各种业务内在的相关性不同,相应的漏桶流量控制特性有较大的差异。漏桶参数的选择对于各种业务具有不同的公平性,因而应根据业务的特性来设计漏桶参数。 相似文献
97.
本文详细系统地介绍了我国有线是视发展历史和现状,及其经营和管理方法。重点介绍了北美的CATV技术发展动向。最后,指出我国CATV事业发展中的应用重视的问题。 相似文献
98.
本文用X射线研究了Cu-20Zn-6Al(wt%)合金中贝氏体结构的有序性,并与马氏体结构进行了比较,实验表明,从高温B2母相和低温L21母相生成的贝氏体中(115)和(205)衍射峰或(1210)和(2010)衍射峰是重叠的,对生成的贝氏体进行一段时间的保温或缓慢冷却处理,其衍射峰的特征并不改变,这与马氏体(115)和(205)衍射峰或(1210)和(2010)衍射峰的分离特性不相符合。说明贝氏体结构有序度与马氏体明显不同,它的形成不可能继承母相的有序度。 相似文献
99.
J. Jiang M. D. Olson 《International journal for numerical methods in engineering》1993,36(13):2203-2217
A numerical model for non-linear static and dynamic analysis of stiffened box structures is presented. The model is based on a new super element formulation which provides complete C1 continuity for both plate and beam elements. Geometric and material non-linearities are included and the temporal equations are solved by the implicit Newmark-β method with Newton-Raphson subiteration. The new formulation has been applied to the static, vibration and transient analysis of various structures such as flat plates, folded plates and rectangular boxes. Both isotropic and beam stiffened structures are considered and the results obtained are compared with other available solutions. It is observed that the new super element formulation can provide reasonable solutions to both linear and non-linear problems of stiffened box structures. The mathematical formulation of the model is presented in this paper, while the numerical verifications are given in the companion paper.1 相似文献
100.
Bo Jiang Jeffrey L. Brown Jane Sheraton Nathalie Fortin Howard Bussey 《Yeast (Chichester, England)》1994,10(3):341-353
We have identified three yeast genes, KES1, HES1 and OSH1, whose products show homology to the human oxysterol binding protein (OSBP). Mutations in these genes resulted in pleiotropic sterol-related phenotypes. These include tryptophan-transport defects and nystatin resistance, shown by double and triple mutants. In addition, mutant combinations showed small but apparently cumulative reductions in membrane ergosterol levels. The three yeast genes are also functionally related as overexpression of HES1 or KES1 alleviated the tryptophan-transport defect in kes1Δ or osh1Δ mutants, respectively. Our study implicates this new yeast gene family in ergosterol synthesis and provides comparative evidence of a role for human OSBP in cholesterol synthesis. 相似文献