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991.
基于FLAC3D有限差分软件对开挖深度、侧压力系数、断面形状等多因素影响下的巷道变形参数进行正交试验,根据正交试验分析结果,分别选取同一深度条件下的圆形、马蹄形、直墙拱形、矩形巷道进行模拟试验并以圆形巷道作为典型断面,对不同深度下的巷道变形特征进行模拟试验。研究结果表明:开挖深度对巷道开挖后的应力差变化影响明显,断面形状对巷道围岩内的塑性区深度和具有显著影响;巷道开挖后的塑性区深度和随形状指数增加而呈线性增长趋势,圆形巷道的塑性区深度和最小,矩形最大;应力差随着巷道开挖深度的增加呈线性增加,深部开采应重视巷道内的应力分布情况。 相似文献
992.
The numerous formulated products which are introduced to the market consist of chemical ingredients that may cause various safety and health hazards to the consumers. Therefore, it is extremely important to practice a systematic methodology to formulate products with acceptable safety and health performances. This work presents an index-based methodology to assess the safety and health hazards of the ingredients during the early formulation stage of product design. Hence, new inherent safety and health sub-indexes are introduced to improve the current safety and health hazards that are needed in formulated product design. The inherent safety and health sub-indexes are assigned with scores based on the degree of potential hazards. A higher score indicates a higher safety risk or severe health effect, and vice versa. The proposed methodology will greatly assist the users to identify the adverse safety and health effects caused by the ingredients. Hence, it is pivotal to eliminate or reduce the safety and health impacts from product usage. A case study on common ingredients used in the formulation of paint is presented on this study to describe the proposed method. 相似文献
993.
Simon Holden Sapna Ahuja Amanda Ogilvy-Stuart Helen V. Firth Christoph Lees 《黑龙江环境通报》2007,27(6):566-567
We describe a case of Harlequin Icthyosis where the main 2D and 3D ultrasound findings were digital contractures as opposed to the more commonly described severe facial dysmorphisms. A prenatal finding of distal arthrogryposis can therefore include harlequin icthyosis as a differential diagnosis, where 3D ultrasound may then disclose the facial features more commonly associated with the condition. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
994.
995.
实验证明,亚硒酸钠对水稻外植体(成熟胚、幼穗)、愈伤组织和再生绿芽体细胞的生长都有不同程度的抑制作用,其抑制程度依次为再生绿芽>愈伤组织>外植体,但能促进它们的绿苗分化频率,特别在低硒浓度(1mg/L)处理组,并可改变它们的过氧化物酶同工酶的活性。 相似文献
996.
John E. Kemnitzer Richard A. Gross Stephen P. McCarthy John Liggat David J. Blundell Mike Cox 《Journal of Polymers and the Environment》1995,3(1):37-47
Predominantly syndiotactic poly(-hydroxybutyrate), syn-PHB, of variable syndioregularity (syndyad fractions 0.59, 0.62, 0.64, and 0.71) and molecular weight was prepared by the dibutyltin dimethoxide catalyzed ring opening of racemic-butyrolactone (BL). The crystallization behavior of the syn-PHB polymers was investigated by DSC and X-ray diffraction analyses. DSC of films after melting and annealing showed at least one, and often two distinct melting transitions occuring over a broad (often 40°C) temperature range. These results indicate that syn-PHB chain segments of variable syndioregularity form crystalline regions with very different thermodynamic stabilities. Maximum degrees of crystallinity for melt annealed 0.64- and 0.71-syn-PHB was observed at an annealing temperature (T
c
) of 30°C. AtT
c
values at 45°C and higher, crystallization of relatively lower syndioregular chain segments was apparently excluded to variable degrees dependent onT
c
and sample syndiotactic dyad content. After crystallization of syn-PHB samples at elevated temperatures, ambient temperature annealing resulted in an observed lower temperature melting transition at 50°C. This result showed little to no dependence on syn-PHB syndio-regularity andT
c
. Both solution precipitated 0.62-syn-PHB and 0.71-syn-PHB have WAXS patterns with poorly resolved crystalline reflections superimposed on amorphous haloes indicating low levels of crystallinity (17% and 25%, respectively) and poorly formed crystals. Isothermal crystallization monitored by DSC showed that the syn- and natural origin PHB showed fastest crystallization rates at temperatures between 50°C and 70°C and 60°C and 90°C, respectively. From the dependence of the higher melting transition onT
c
it was determined that the equilibrium melting temperatures for 0.62-syn-PHB (M
n
=83,700 g/mol) and a 0.64-syn-PHB (M
n
=11,900 g/mol) were 157 and 154°C, respectively. An Avrami analysis of syn-PHB yielded results similar to that found for natural origin PHB indicating that crystal growth occurs by a two-dimensional mechanism.Guest Editor: Dr. Graham Swift, Rohm & Haas. 相似文献
997.
本文研究了孔雀绿与磷(砷)酸钼的离子对膜的形成条件。并依此与共存元素分离,进行痕量磷酸根、亚砷酸根和砷酸根的浮膜分光光度法测定。选用硫酸为介质,考察了25种共存离子对测定的影响。拟定了天然水中痕量磷酸根、亚砷酸根和砷酸根的分析方法.操作简便,结果令人满意。 相似文献
998.
999.
Mehlich 1(M1), mehlich 3(M3) and CaCl2 DTPA have been used to predict the available micronutrient in soil. However, the forms of micronutrient extractable by these extractants are not known. In the present study, ten soils, collected from five provinces and the capital of China, representing a wide range of chemical and physical properties, were analyzed by sequential extraction to isolate five forms of cobalt and nickel, they are exchangeable, carbonate bound, Fe Mn oxide bound, organically bound and residual forms. The chemical forms extracted by M1, M3 and CaCl2 DTPA were also investigated. The results show strong correlation between the carbonate bound or organically bound forms of Co or Ni and the amounts of extractable by any of the above three extractants. The main forms extracted by these extractants are carbonate and organically bound forms. The ranking of these three extractants for extraction of Co and Ni are M1>M3=CaCl2 DTPA and M1=M3>CaCl2 DTPA, respectively. 相似文献
1000.
The autoradiographic labelling of different cell types in chorionic villi and decidual tissue was investigated after [3H]-thymidine incorporation in vitro. Although the extent of labelling was found to be lower in decidual than in villus tissue the possibility that direct chromosome preparations may contain maternal metaphases should be considered. The need for careful selection of villi for direct cytogenetic analysis was stressed. 相似文献