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41.
H. Hou J. C. Holste
B. E. Gammon
K. N. Marsh 《International Journal of Refrigeration》1992,15(6):365-371This paper reports densities of compressed R134a (1,1,1,2-tetrafluoroethane) determined by using a contiuously weighed pycnometer at 20 K intervals between 180 and 380 K at pressures from slightly greater than the vapour pressure to 70 MPa. The results are accurate to within ±0.1%. Saturated liquid densities derived by extrapolation from the experimental values agree with other reported values to within ±0.3%. 相似文献
42.
The use of the analytically decoupled near-tip displacement solutions as an alternative approach, is presented in this paper for the efficient finite element evaluation of the decoupled weight functions for an orthotropic 2-D crack. This alternative approach has been validated by directly comparing the prior weight function results with a symmetric mesh approach in the crack-tip neighborhood, and indirectly by comparing the calculated stress intensity factors (KI(II)) values using the computed weight functions with available KI(II) solutions of the 2-D mixed mode orthotropic cracks. In addition, this approach with analytically decoupled near-tip displacement solutions for calculating weight functions at all locations, can facilitate further extension of weight function evaluations to a more general 2-D anisotropic crack. 相似文献
43.
介绍燕山石化公司为扩大1Mt/a中压加氢改质装置的原料来源,改用大庆减二线油和重油催化裂化柴油组成的混合料开工投产的经验以及装置初期的运行条件。中压加氢改质技术可以生产优质柴油和蒸汽裂解制乙烯的原料,还可增产喷气燃料。 相似文献
44.
L. K. Seah
J. Rhodes
B. S. Lim
《Thin》1993,16(1-4):145-177Turning the free edge of an unstiffened flange inwards or outwards to form a ‘lip’, can substantially improve the local buckling resistance of a member. The lip is the most common type of edge stiffener used in cold-rolled, thin-walled sections. In this paper the behaviour of plate elements of thin-walled sections stiffened by compound lips (i.e. lips which are folded twice to form ‘lips on the lips’) is examined both theoretically and experimentally. An outline of a series of tests on compound edge-stiffened thin-walled sections of various geometries is given and some load-end compression displacement paths are compared with the theoretical predictions. Reasonably good agreement is obtained between the experimental and theoretical results. Comparisons of the theoretical predictions with experimental results of other researchers are also presented in this paper. 相似文献
45.
Xanthomonas campestris 《Food microbiology》1996,13(6):441-446
By adding acetic, pentanoic and octanoic acids to batch cultures ofXanthomonas campestrisa close correlation between the acid concentration and the length of the lag phase and the value of the specific growth rate was obtained. The specific growth rate was largely affected by acid toxicity. As the amount of acetic acid was increased the specific growth rate dropped to 0.08 h−1at 5 m
and 0.07 h−1at 9.99 m
. Pentanoic acid produced a decrease of the specific growth rate to 0.06 h−1at 3.92 m
. Octanoic acid produced a greater effect on the specific growth rate. At 0.69 m
the specific growth rate was reduced to 0.09 h−1and then it dropped to 0.06 h−1at 1.39 m
. The lag phase length was increased as the result of the activation of the tolerance mechanism. The octanoic acid produced a 40 h lag in the culture containing 1.39 m
total acid concentration. The cells in contact with 0.69 m
octanoic acid had a lag phase of 5 h, twice that obtained in the acid-free cultures. Acetic and pentanoic acids at 9.99 and 3.92 m
, increased the lag phases to 30 and 6 h, respectively. 相似文献
46.
The subject of fatigue which comprises crack nucleation, crack propagation and final failure or fracture has, over the years, been the subject of numerous theoretical and experimental studies. These studies have highlighted the extrinsic influence of mixed-mode loading in governing the fatigue behavior of a wide spectrum of engineering materials and structures. In this paper we review the basic criteria and models that have been proposed and used to predict crack behavior and response for structures containing large cracks and subject to mixed-mode loading. Since the aspect of crack growth is the focus of this review, the effects or contributions from intrinsic microstructural effects are largely excluded. Specific criteria discussed are the maximum tangential stress, minimum strain-energy density and the maximum energy-release rate criteria. The use of these criteria to predict the behavior of structures is examined based on results published in the open literature. The characteristics and implications of each criterion are examined and discussed with particular relevance to threshold conditions on crack growth, direction of crack growth and crack-growth rate. The limitations of each criterion are highlighted. 相似文献
47.
A new mathematical model for study of an interface crack between two dissimilar elastic half planes is proposed. A process zone is formed along the interface between the physical crack and the continuous part. Both the crack opening (and sliding) displacement with a smooth shape and the finite magnitude of stress concentration appear in this zone. The analytical model is expressed by closed elastic solutions using complex variables, but with no oscillations at the crack tip. 相似文献
48.
49.
钻井技术水平的不断提高和PDC钻头的广泛使用给现场录井作业带来了新问题。与传统的三牙轮钻头相比,PDC钻头突出的特点是产生的岩屑稀少、细小甚至失真,给地质录井的岩屑采集、鉴定、识别以及油气层级别的判定、解释、评价带来了一系列困难。为此,结合PDC钻头在新疆塔河、松辽盆地、鄂尔多斯等地油田的使用及录井经验,从PDC钻头条件下岩屑特征和岩性特征的分析入手,阐述使用PDC钻头对气测录井、荧光录井的影响,总结了在PDC钻头条件下搞好录井作业的应对措施,并列举了提高录井技术水平的可行途径。 相似文献
50.