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51.
随着时间的推移,混凝土的导温系数将发生变化,为了了解参数随时间的变化规律,利用原型观测资料对导温系数进行分段反演,从而拟合出大坝混凝土导温系数随时间的变化规律. 相似文献
52.
Enhancing heat transfer ability of drag reducing surfactant solutions with static mixers and honeycombs 总被引:4,自引:0,他引:4
Yunying Qi Yasuo Kawaguchi Richard N. Christensen Jacques L. Zakin 《International Journal of Heat and Mass Transfer》2003,46(26):5161-5173
Solutions containing drag reducing additives also show reduced heat transfer which limits their use in district heating and cooling recirculation systems where heat exchange is critical. In this study, static mixers A and B and honeycombs were installed at the entrance to a heat exchanger to break the solution microstructure temporarily and thereby enhancing their heat transfer ability when passing through the heat exchanger. The effectiveness of the destructive devices in enhancing the heat transfer ability of drag reducing cationic and mixed zwitterionic/anionic surfactant solutions was investigated together with the microstructure recovery time and pressure drop penalty paid for the heat transfer enhancement. 相似文献
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Jonathan D. Bray Rodolfo B. Sancio Turan Durgunoglu Akin Onalp T. Leslie Youd Jonathan P. Stewart Raymond B. Seed Onder K. Cetin Ertan Bol M. B. Baturay C. Christensen T. Karadayilar 《Canadian Metallurgical Quarterly》2004,130(7):673-685
Ground failure in Adapazari, Turkey during the 1999 Kocaeli earthquake was severe. Hundreds of structures settled, slid, tilted, and collapsed due in part to liquefaction and ground softening. Ground failure was more severe adjacent to and under buildings. The soils that led to severe building damage were generally low plasticity silts. In this paper, the results of a comprehensive investigation of the soils of Adapazari, which included cone penetration test (CPT) profiles followed by borings with standard penetration tests (SPTs) and soil index tests, are presented. The effects of subsurface conditions on the occurrence of ground failure and its resulting effect on building performance are explored through representative case histories. CPT- and SPT-based liquefaction triggering procedures adequately identified soils that liquefied if the clay-size criterion of the Chinese criteria was disregarded. The CPT was able to identify thin seams of loose liquefiable silt, and the SPT (with retrieved samples) allowed for reliable evaluation of the liquefaction susceptibility of fine-grained soils. A well-documented database of in situ and index testing is now available for incorporating in future CPT- and SPT-based liquefaction triggering correlations. 相似文献
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56.
工业现场的温度变化范围大而剧烈,工作在工业现场的传感器大多数都对温度有一定的敏感度,这样就会使传感器的零点发生漂移,导致测量出现附加误差,因此温度补偿问题一直是传感器技术中的关键环节。根据单总线数字式温度传感器DS18820的工作原理、结构,并以电阻应变式传感器为例,提出了具体的补偿方案。 相似文献
57.
BACKGROUND: The matrix metalloproteinases (MMPs) MMP2 and MMP9 play a significant role in epidermal detachment, inflammation and re-epithelialization. We have evaluated their activity in toxic epidermal necrolysis (TEN). DESIGN: The level and pattern of activity of MMP2 and MMP9 were investigated by measuring the degradation of 3H-labelled gelatin and by zymography in blister fluid from six TEN patients and compared the results with three other blistering conditions: bullous pemphigoid (n = 6), second-degree burn (n = 13) or suction blister (n = 3). RESULTS: A higher amount of MMP2 was found in TEN blister fluid with the constant presence of a significantly larger proportion of the activated forms of MMP2, a particular feature of TEN, than the other blistering diseases studied. CONCLUSION: This study emphasizes the potential role of MMP2 in the specific inflammatory reaction and reparation process in TEN skin. 相似文献
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The relative populations and transverse relaxation times of the solid-like hydrogen pool (PB and T2B) and the magnetization transfer (MT) rates between the solid-like and liquid-like hydrogen pools (kappa) have been determined for three different agar gel concentrations (2%, 4%, and 8% by weight) as well as excised fibroglandular breast tissue specimens. PB was determined to be .003(.001), .01(.002), .02(.01), and .06(.01); T2B was determined to be 13.0(.2), 14.0(.1), 14.5(.1) and 15.2(1.3) microseconds; and kappa was determined to be 0.78(.01), 1.15(.02), 2.00(.02), and 3.55(1.5) sec-1 for the 2%, 4%, and 8% agar gels and the fibroglandular tissue, respectively. The image signal intensities of a pulsed MTC-prepared gradient-echo imaging technique are predicted using these MT parameters and are shown to agree well with experimental data obtained from a clinical MR imaging system. This technique is shown to suppress signal intensity of fibroglandular breast tissue by 40%-50% without exceeding SAR limits (< or = 8 W/kg) and is helpful for visualizing lesions and silicone implants. 相似文献
60.
介绍了雷达接收机中STC控制的产生背景、原理及方法,采用MATLAB语言进行仿真,重点介绍了一种基于电控衰减器作为受控部件的数字STC控制曲线的精确设计方法,并提出了雷达STC的设计和使用原则。 相似文献