排序方式： 共有69条查询结果，搜索用时 15 毫秒
1.
研制了 30 0双向自调导叶透平试验机组 ,安装在 10 0 0活塞式往复流透平试验台上 ,对两种叶轮方案和 6种不同喷咀、扩压器进行了不同活塞行程、不同周期和不同恒定输出电压下性能试验。试验结果表明在喷咀出口角α1=2 1 5°、扩压器入口角α2 =6 5 5°和α1=2 4°、α2 =6 3°组合最佳 ,最高效率达 5 3 3% ,而且在宽广流量系数范围内 ,特别是大流量系数范围内都有较高效率。大大优于常用对称翼透平。将上下游导叶固定 ,变成双向固定导叶透平。用No 1叶轮和 6种导叶出口角组合进行试验。表明最佳导叶出口角为 2 4°～ 30°,最高效率仍达 38 5 % ,比对称翼透平仍高许多 相似文献
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广州航空邮件处理中心位于岩溶发育地区,场区内存在大量土洞、溶洞等不良地质现象。该建筑物拟采用静压桩基础。为保证建筑物及场道安全,须对场区土洞进行处理。结合场地具体情况和施工工期要求,首先对大体积土洞进行泵注细石砼骨料充填处理,以消除地面大面积塌陷的危险,消灭压桩机械施工安全隐患,然后开始进行静压桩基础施工,同时在场地允许区域对中小体积土洞、桩端软土层等分别进行泵注砂浆骨料和袖阀注浆处理．以确保洞体密实和保证桩基承载力。通过对处理工艺、处理范围的比较筛选和对质量控制要点、施工技术要点的分析提炼．达到了施工简便、造价合理、安全高效的目的,并采用骨料取芯检测、土体标贯试验和压缩试验、洞体物探等多种检测手段,完全达到了设计要求,取得了良好的工程效果和经济效益。 相似文献
3.
K. W. Keatings I. Hawkes J. A. Holmes R. J. Flower M. J. Leng R. H. Abu-Zied A. R. Lord 《Journal of Paleolimnology》2007,38(2):261-283
The utility of ostracod-based palaeoenvironmental reconstruction was evaluated using instrumental data for Lake Qarun, Egypt.
The euryhaline ostracod Cyprideis torosa was the only species found in the lake’s recent sediment record. This species is known to tolerate salinity levels and water
solute compositions that may prevent colonisation by other species. Oxygen and carbon isotope ratios of ostracod carbonate
from lake sediments covary with changes in instrumental values for lake level and salinity for the period 1890–1974. δ13C-values correlate negatively with lake water salinity (r
2 = 0.87) and δ18O-values correlate negatively with measured lake level changes (r
2 = 0.41). Other ostracod proxy data provide qualitative information on lake level trends. Fossil assemblage data (juvenile/adult
and valve/carapace ratios and valve preservation) provide information on wave energy. Ecophenotypic variation of C. torosa valves provided some useful palaeolimnological information. Sr/Ca and Mg/Ca ratios in ostracods were not found to reflect
water composition, due to the uncoupling of these ratios with salinity in Lake Qarun. Overall, our results highlight the need
to calibrate ostracod proxy data in modern systems prior to their use for palaeoenvironmental reconstruction. 相似文献
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某钢筋混凝土箱形铁路桥发生不均匀沉降,经方案优化对比,采用了沉井射水掏土纠偏和塑料袖阀管注浆加固进行综合治理。介绍了其施工工艺和治理效果。 相似文献
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水源供水井，在封井止水下艺中，始终存在封井质量、水泥固结质量及井内钻具事故等风险，为此在对准格尔旗施工的10口水源供水井施工中，制作了单向逆止阀水泥封隔器，并与Ф340套、筛管用吊卡按一定顺序下入井内。该装置的使用，有效地提高了封井止水的质量。 相似文献
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The species of Epithemia ocellata (Ehr.) Kütz. from Northeastern China were observed by scanning electron microscopy (SEM). The studies on silica valve formation in different stages were made. At the early stage, a Y-shaped raphe sternum was found. Areolae were made from virgae and vimines. In immature valves, the canal formation before the raphe fissure is visible. The raphe system, virgae and vimines (areolae) might be the early siliceous elements of the valve during morphogenesis. The formations of virgae and vimines are similar to that of Gephyria media W. Arnott. Rows of silica papillae formed gradually on the face of the valve. After the areolae were covered with silica and form rows of papillae, the outer valve surface could become mature. Details of the internal costae were observed in mature valves. 相似文献
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埕岛油田位于渤海西南部极浅一浅海地区，是一个大型潜山披覆构造油田。随着埕岛油田开采力度加强，地层亏空十分严重，作业过程中的地层漏失是困绕埕岛油田油层保护的一大难题。据此介绍了胜利油田海上埕岛油田油层保护的一项新技术——井下双向流动阀防漏失技术的应用情况，阐述了井下双向流动阀的结构、原理以及应用后对油层保护所起到的作用。 相似文献
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基于壳板和齿舌形态对中国沿岸几种常见多板纲软体动物的分类研究 总被引：1，自引：1，他引：0
多板纲软体动物统称石鳖,是软体动物门较为低等的一个类群,在软体动物的系统进化中占有重要的地位。但有关我国沿海多板纲软体动物的调查研究十分欠缺,而且对中国沿海多板纲的分布状况和区系特点尚不明确,并存在着一些鉴定错误和分类混乱现象。本研究利用10%Na OH溶液处理齿舌部获取齿舌带和壳板的方法,通过扫描电镜和显微镜观察拍照,对我国沿岸常见多板纲软体动物中5科7属13种的齿舌和壳板形态结构进行了描述,并进行了比较研究。 相似文献
10.
An ion chromatographic method with a valve switching facility was developed to determine trace nitrate concentrations in seawater using two pumps, two different suppressors, and two columns. A carbohydrate membrane desalter was used to reduce the high concentrations of sodium salts in samples. In this method, trace nitrate was eluted from the concentrator column to the analytical columns, while the matrix flowed to waste. Neither chemical pre-treatment nor sample dilution was required. In the optimized separation conditions, the method showed good linearity （R〉0,99） in the 0.05 and 50 mg/L concentration range, and satisfactory repeatability （RSD〈5%, n=6）. The limit of detection for nitrate was 0.02 mg/L. Results showed that the valve switching system was suitable and practical for the determination of trace nitrate in seawater. 相似文献