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151.
介绍了关于身管寿命研究的国内外发展现状、趋势和差距,论述了身管寿命的定义与评定标准。基于一般身管寿命预测方法,从发射装药、身管材料、身管发射负载、身管内膛表面强化等方面,分析了身管寿命的影响因素,确定了热作用、化学作用、机械作用、膛压作用的影响因素,提出了包括身管内膛镀铬技术在内的身管寿命提升需要解决的问题和关键技术,以及初步技术措施,并详细论述了身管内膛镀铬技术方案与技术途径,提出了达到世界先进水平的身管寿命提升技术发展目标,指出了身管寿命提升技术的发展趋势等,为今后身管寿命提升技术研究提供技术参考。 相似文献
152.
为了研究经柠檬酸铝、混合稀土或亚硒酸钠浸泡处理温石棉对温石棉晶格结构和表面电荷的影响,用不同浓度的柠檬酸铝、混合稀土或亚硒酸钠溶液浸泡温石棉1小时后,通过透射电镜测定其衍射环直径的大小,分析石棉晶格结构的改变,并利用石棉纤维吸附亚甲蓝能力的测定方法,分析温石棉表面电荷。结果显示,用三种化合物处理石棉后,其衍射环直径均增大,而且用三种化合物处理后的石棉对亚甲蓝的吸附能力均明显降低,并且随着化合物剂量的增加其降低愈明显。上述结果表明,用三种化合物处理石棉,均可改变石棉的晶格结构,且可能减少其表面电荷。 相似文献
153.
针对在含硬夹矸高瓦斯低透气性煤层开采时,一方面煤层瓦斯抽采困难,另一方面煤层中的坚硬夹矸难破碎的问题,开展含硬夹矸高瓦斯低透气性煤层多向聚能爆破研究。理论上,分析多向聚能装药对爆破的影响,引入多向聚能影响系数,计算得出了不同方向上裂隙的范围。通过相似模拟试验,验证了多向聚能爆破实际效果;利用LS-DYNA数值模拟软件,对不同装药方式爆破作用下煤与夹矸裂隙的发育特征及应力演化规律进行了数值模拟研究。研究结果表明:多向聚能爆破能够将爆破能量积聚在夹矸弱化和煤层增透的方向上,形成以导向裂隙为主,大量分支裂隙为辅的裂隙网,在夹矸弱化和煤层增透方向上的应力峰值分别为普通爆破的1.21倍和1.16倍。多向聚能爆破能够在提高破碎坚硬夹矸能力的同时提升煤体中裂隙的发育程度,从而大幅优化爆破效果。 相似文献
154.
Soils contain diverse colloidal particles whose properties are pertinent to ecological and human health, whereas few investigations systematically analyze the surface properties of these particles. The objective of this study was to elucidate the surface properties of particles within targeted size ranges (i.e. > 10, 1–10, 0.5–1, 0.2–0.5 and < 0.2 μm) for a purple soil (Entisol) and a yellow soil (Ultisol) using the combined determination method. The mineralogy of corresponding particle-size fractions was determined by X-ray diffraction. We found that up to 80% of the specific surface area and 85% of the surface charge of the entire soil came from colloidal-sized particles (< 1 μm), and almost half of the specific surface area and surface charge came from the smallest particles (< 0.2 μm). Vermiculite, illite, montmorillonite and mica dominated in the colloidal-sized particles, of which the smallest particles had the highest proportion of vermiculite and montmorillonite. For a given size fraction, the purple soil had a larger specific surface area, stronger electrostatic field, and higher surface charge than the yellow soil due to differences in mineralogy. Likewise, the differences in surface properties among the various particle-size fractions can also be ascribed to mineralogy. Our results indicated that soil surface properties were essentially determined by the colloidal-sized particles, and the < 0.2 μm nanoparticles made the largest contribution to soil properties. The composition of clay minerals within the diverse particle-size fractions could fully explain the size distributions of surface properties. 相似文献
155.
Leader–member exchange and job performance: The effects of taking charge and organizational tenure
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We theorized and tested the mechanisms by which leader–member exchange (LMX) quality is associated with job performance. The results obtained using 212 employee–supervisor pairs from eight Chinese companies indicated that LMX quality had an indirect and positive relationship with taking charge via psychological empowerment and had an indirect and positive relationship with job performance via taking charge. In addition, organizational tenure significantly moderated the relationship between taking charge and job performance, such that the positive effect of taking charge on job performance became weaker as organizational tenure increased. Furthermore, organizational tenure significantly moderated the indirect positive relationship between LMX quality and job performance via taking charge; the indirect effect became weaker as organizational tenure increased. These results suggest that organizations should encourage managers to develop high‐quality LMX with their subordinates, which may make them feel more empowered and engage in more taking charge, and result in better job performance. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
156.
157.
Food waste treatment plants (FWTPs) are usually associated with odorous nuisance and health risks, which are partially caused by volatile organic compound (VOC) emissions. This study investigated the VOC emissions from a selected full-scale FWTP in China. The feedstock used in this plant was mainly collected from local restaurants. For a year, the FWTP was closely monitored on specific days in each season. Four major indoor treatment units of the plant, including the storage room, sorting/crushing room, hydrothermal hydrolysis unit, and aerobic fermentation unit, were chosen as the monitoring locations. The highest mean concentration of total VOC emissions was observed in the aerobic fermentation unit at 21,748.2-31,283.3 μg/m3, followed by the hydrothermal hydrolysis unit at 10,798.1-23,144.4 μg/m3. The detected VOC families included biogenic compounds (oxygenated compounds, hydrocarbons, terpenes, and organosulfur compounds) and abiogenic compounds (aromatic hydrocarbons and halocarbons). Oxygenated compounds, particularly alcohols, were the most abundant compounds in all samples. With the use of odor index analysis and principal components analysis, the hydrothermal hydrolysis and aerobic fermentation units were clearly distinguished from the pre-treatment units, as characterized by their higher contributions to odorous nuisance. Methanthiol was the dominant odorant in the hydrothermal hydrolysis unit, whereas aldehyde was the dominant odorant in the aerobic fermentation unit. Terpenes, specifically limonene, had the highest level of propylene equivalent concentration during the monitoring periods. This concentration can contribute to the increase in the atmospheric reactivity and ozone formation potential in the surrounding air. 相似文献
158.
我国废弃电子电器产品的回收体系研究 总被引:1,自引:1,他引:0
分析了废弃电子电器产品的特点,介绍了国内外废弃电丰电器产品的回收处理现状,结合生产者责任延伸制度,从观念、法律、管理、企业、收费等方面对我国废弃电子电器产品回收体系的建设进行了探讨,并提出了建议。 相似文献
159.
160.
无规则排放废气由于无法准确监测和计量,此项排污费的征收尚处于“无规则”状态。采用“环境欠量补偿经验系数法”对其进行探讨,探索出切实可行的征收办法。 相似文献