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71.
高温冻结砂土温度界限试验研究 总被引：1，自引：1，他引：0
由于高温冻土力学特性与融土相近,对其研究越来越多,然而迄今并没有一个广为接受的基于力学指标的明确定义。以冻结饱和标准砂为研究对象,利用三轴剪切试验和侧限压缩试验获得黏聚力、割线变形模量和压缩指数等力学指标,通过分析这些指标随温度变化的规律,试图从力学特性的角度对于高温冻结砂土给出一个明确的温度界限。研究发现,冻结砂土在-1.0℃到-0.5℃之间,黏聚力、割线变形模量和压缩指数等力学指标发生突变,因此,将-1.0℃定义为高温冻结砂土的温度界限,对涉及高温冻土的工程建设和维护具有重要的意义。 相似文献
72.
Vortex-induced motion is based on the complex characteristics of the flow around the tension leg platform (TLP) hull. By considering the flow field of the South China Sea and the configuration of the platform, three typical flow velocities and three flow directions are chosen to study the numerical simulation of the flow field characteristics around the TLP hull. Reynolds-averaged Navier–Stokes equations combined with the detached eddy simulation turbulence model are employed in the numerical study. The hydrodynamic coefficients of columns and pontoons, the total drag and lift coefficients of the TLP, the formation and development of the wake, and the vorticity iso-surfaces for different inlet velocities and current directions are discussed in this paper. The average value of the drag coefficient of the upstream columns is considerably larger than that of the downstream columns in the inlet direction of 0°. Although the time history of the lift coefficient demonstrates a “beating” behavior, the plot shows regularity in general. The Strouhal number decreases as the inlet velocity increases from the power spectral density plot at different flow velocities. The mean root values of the lift and drag coefficients of the front column decrease as the current direction increases. Under the symmetrical configuration of 45°, the streamwise force on C4 is the smallest, whereas the transverse force is the largest. The broken vortex conditions in current directions of 22.5° and 45° are more serious than that in the current direction of 0°. In addition, turbulence at the bottom of the TLP becomes stronger when the current direction changes from 0° to 45°. However, a high inlet velocity indicates a large region influenced by the broken vortex and shows the emergence of the wake behind the TLP under the same current angle. 相似文献
73.
Reference materials (RM) are essential to achieve traceability of measurements. Specific uses of RM in analytical laboratories are the validation of methods, the calibration of instruments, the quality control and the demonstration of proficiency. This paper describes the certification of a new geochemical reference material, named BRP-1 (Basalt Ribeirão Preto), and acts as the certificate of analysis for this RM. The rock sample was crushed and pulverised at the USGS (Denver, USA), homogenised and split into 1920 bottles, with 55 g each. BRP-1 was transported back to Brazil and the homogeneity between and within bottles was assessed to demonstrate sufficient homogeneity for certification. The chemical characterisation was performed by twenty-five laboratories. Each laboratory received two bottles of BRP-1 and one of BCR-2 (Basalt Columbia River) used for quality control (QC). Reference values and uncertainties were calculated for forty-four constituents of BRP-1, following ISO Guide 35 recommendations and the IAG Protocol. The calculation of each reference value included data of proven traceability from at least ten laboratories using two or more analytical techniques and the uncertainties combines the characterisation and between bottle homogeneity contributions. 相似文献
74.
ISO90 0 0系列标准是国际上通用的外部质量管理和质量保证的国际标准 ,具有很高的公证性和权威性。获得该体系认证的企业和产品都具有良好的信誉 ,因而在激烈的市场竞争中占有更大的优势。随着入世的临近 ,我国企业应抓紧时间 ,取得认证 ,为企业将来参与国际竞争打下基础。 相似文献
75.
The ISOCAM detector is subjected to transient effects induced bycosmic rays, the so-called glitches. This paper is focused onthe ISOCAM long wave detector. The predicted glitch rates havebeen re-evaluated by taking into account secondary particlesproduction in the materials surrounding the LW detector. We showin this preliminary study that the difference between thepreviously predicted glitch rate and the observed rate may beexplained by secondary particles. 相似文献
76.
One of the main limitations to the sensitivity of observations carried out withthe ISOCAM infrared camera comes from the responsivity variations and glitchescaused by impacts of charged particles. After more than 28 months of successfuloperations, the predicted glitch rate has been re-evaluated and compared toin-flight measurements. Glitch properties have been studied in orderto improve the removal algorithms, and thus the ultimate sensitivity of ISOCAM.All informations about the glitch phenomenon are very useful in order toprepare next space experiments. 相似文献
77.
A. Abergel M. A. Miville-Deschênes F. X. Désert M. Pérault H. Aussel M. Sauvage 《Experimental Astronomy》2000,10(2-3):353-368
The detector of the long wavelength channel of the ISOCAMcamera on-board the Infrared Space Observatory is a Galliumdoped Silicon photo-conductor hybridized by Indium bump. Itpresents systematic memory effects of the response which canbias the photometry by a factor of typically 40%. The main features of the response after flux variations are discussed. A simple empirical model actually used to correct systematically the data with a photometric accuracy of 5–10% is detailed. 相似文献
78.
亚洲两个季风区大气季节内振荡的比较分析 总被引：1，自引：0，他引：1
本文利用ECMWF逐日再分析资料(1961～2000年),主要从结构和水平传播包括经向传播和纬向传播方面对南海和南亚两个季风区的30～60天振荡进行了比较分析.研究结果发现,两个季风区的大气季节内振荡都存在明显的年际变化,但并没有出现同相或反相的变化关系.两个季风区ISO在结构上既有相似的地方也有不同点,在垂直结构上都... 相似文献
79.
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