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Kenji Ishihara Yoshimichi Tsukamoto 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2004,80(9):443
The simplified method of analysis to assess liquefaction potential of a given sand deposit is briefly introduced in the first part of this paper. Then, recent advances in the laboratory testing for evaluating liquefaction resistance are described with a particular emphasis on the sand partly saturated with water. As a means to identify the degree of saturation which is applicable for both field deposits and laboratory samples, the use of the longitudinal wave (P-wave) is proposed based on a suite of data obtained from the triaxial tests in the laboratory. It is recommended that the non-destructive P-wave measurements be carried out first to determine the degree of saturation, and then the cyclic triaxial tests involving large destructive strains should be performed to determine the cyclic strength on the same sample of the sand. In order to demonstrate usefulness of the proposed approach, two sets of undisturbed samples were secured from two sites; one is located in Sakai-minato city which has suffered severe liquefaction at the time of the 2000 Tottoriken-Seibu earthquake and the other site is located in Koshigaya city, Saitama, where likelihood of liquefaction to occur in a future earthquake is of major concern. Penetration tests and in-situ velocity logging were also conducted at these two sites. By adjusting the P-wave velocity of the undisturbed samples in the laboratory so as to have the same velocity in the field, the in-situ state of saturation was reproduced in the laboratory samples. Then, the cyclic loading tests were conducted to determine the cyclic strength of intact samples. The results of the laboratory tests as above were incorporated into the simple method of liquefaction analysis described in the first section of this paper. The analysis seems to yield results which are in reasonably good agreement with what was observed at the time of the earthquake. 相似文献
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Kahraman S 《Ultrasonics》2007,46(4):341-348
Sometimes engineers need to estimate the wet-rock P-wave velocity from the dry-rock P-wave velocity. An estimation equation embracing all rock classes will be useful for the rock engineers. To investigate the predictability of wet-rock P-wave velocity from the dry-rock P-wave velocity, P-wave velocity measurements were performed on 41 different rock types, 11 of which were igneous, 15 of which were sedimentary and 15 of which was metamorphic. In addition to the dry- and wet-rock P-wave velocity measurements, the P-wave velocity changing as a function of saturation degree was studied. Moreover, dry-rock S-wave velocity measurements were conducted. The test results were modeled using Gassmann’s and Wood’s theory and it was seen that the measured data did not fit the theories. The unconformity is due to the fact that the theories are valid for high-porosity unconsolidated sediments at low frequencies. Gassmann’s equation was modified for the rocks except high-porosity unconsolidated sediments.
The dry- and wet-rock P-wave velocity values were evaluated using regression analysis. A strong linear correlation between the dry- and wet-rock P-wave velocities was found. Regression analyses were repeated for the rock classes and it was shown that correlation coefficients were increased. Concluding remark is that the derived equations can be used for the prediction of wet-rock P-wave velocity from the dry-rock P-wave velocity. 相似文献
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针对低压天然气特点,设计了3套天然气闭式膨胀液化流程,选择PR(Peng-Robinson)方程进行混合物的相平衡计算,采用化工模拟软件PRO/Ⅱ进行了模拟计算;分析比较了不同液化流程的关键热力学参数,并进行了关键设备的可行性分析。结果表明:丙烷预冷双级天然气膨胀液化流程的比功耗比无预冷单级天然气膨胀液化流程、无预冷双级天然气膨胀液化流程低,液化率高,而且设备均可实现。综合分析结果,选用了丙烷预冷双级天然气膨胀液化流程。并指出天然气节流前温度越低,其液化率越高,比功耗越小。天然气膨胀比越高,液化率越高。 相似文献
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To summarize some of the most important findings in the field of ultrasonic (US) testing of early age hydration and formation of structure of different cement based materials (CBMs), a review of literature with focus on US P-wave transmission and S-wave reflection methods is presented in this paper. The review shows a great ability of both US techniques to observe setting phenomena and to determine different milestones during the early age formation of CBM’s microstructure. Clear physical basis, high accuracy, and non-destructive nature of the method indicate that US methods could become standardized in the near future. 相似文献
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氢能是一种新型清洁无污染的二次能源,是我国能源结构调整中不可缺少的组成部分。在氢能的应用中,液氢具有较高的体积与质量存储密度,适合大规模运输及应用,能够显著降低市场化应用的成本。着重分析了氢液化技术的研究进展以及国际上的液氢研究项目:日本WE-NET (World Energy Network)及欧洲IDEALHY (Integrated Design for Efficient Advanced Liquefaction of Hydrogen)。从压缩能耗、液化能耗、运输能耗、总能耗四个方面进行高压氢与液氢的能耗对比,分析结果表明,对于液氢的运输能耗随里程增加缓慢,高压气氢的运输能耗随里程增加成直线上升;运输里程在约500 km时,液氢的总能耗将低于高压气氢,液化能耗在总能耗中占的比例减少。总结了目前氢液化过程相关技术的研究热点跟难点,并对未来液氢的大规模应用进行展望。 相似文献
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The Raman spectra of nine monohydroxy alcohols have been obtained by confocal Raman spectrometer at room temperature. Based on the Raman spectra, the density functional theory was used to analyze the characteristic Raman bands of monohydric alcohols. Through the discussion of the characteristic Raman bands and their corresponding assignment, four major Raman bands were selected to identify nine monohydric alcohols using principal component analysis and Euclidean distance. Finally, nine saturated monohydroxy alcohols can be distinguished exactly, and the recognition rate is 100%. 相似文献
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N. S. ?eng?r Y. ?ak?r C. Güzeli? F. Pekergin ?. Morgül 《ARI - An International Journal for Physical and Engineering Sciences》1999,51(4):268-276
Several formulations and methods used in solving an NP-hard discrete optimization problem, maximum clique, are considered in a dynamical system perspective proposing continuous methods to the problem. A compact form for a saturated linear dynamical network, recently developed for obtaining approximations to maximum clique, is given so its relation to the classical gradient projection method of constrained optimization becomes more visible. Using this form, gradient-like dynamical systems as continuous methods for finding the maximum clique are discussed. To show the one to one correspondence between the stable equilibria of the saturated linear dynamical network and the minima of objective function related to the optimization problem, La Salle's invariance principle has been extended to the systems with a discontinuous right-hand side. In order to show the efficiency of the continuous methods simulation results are given comparing saturated the linear dynamical network, the continuous Hopfield network, the cellular neural networks and relaxation labelling networks. It is concluded that the quadratic programming formulation of the maximum clique problem provides a framework suitable to be incorporated with the continuous relaxation of binary optimization variables and hence allowing the use of gradient-like continuous systems which have been observed to be quite efficient for minimizing quadratic costs. 相似文献
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Equivalent dose distribution analysis of Holocene eolian and fluvial quartz sands from Central Oklahoma 总被引:5,自引:0,他引:5
Kenneth Lepper Niels Agersnap Larsen Stephen W. S. McKeever 《Radiation measurements》2000,32(5-6):603-608
Holocene quartz sands were collected from fluvial terrace deposits and eolian dune deposits adjacent to the North Canadian and Cimarron Rivers and their tributaries in Central Oklahoma. Single aliquot regenerative dose optically stimulated luminescence techniques were employed to generate equivalent dose (ED) distribution histograms for each sample. We hypothesize that the ED distributions are convolutions of the distribution arising from natural sedimentary processes, influenced primarily by the degree of solar resetting experienced by individual grains, and a distribution due to experimental error. An estimation of the experimental error distribution for each sample was made and this was then deconvolved from the experimentally measured ED distribution to reveal the ‘sedimentary process’ ED distribution. Objective methods for determining EDs, uncertainties, and confidence parameters from the deconvolved distributions are presented. 相似文献
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A three-dimensional (3D) numerical model basing on the thin layer element method and the flexible volume method was established for the computation of dynamic impedances and free-field vibrations of rigidly-capped pile groups embedded in saturated ground. The piles were considered as beams and the saturated ground was represented by Biot?s three-dimensional elastodynamic theory. By recourse to the thin layer element method, Green function of the three dimensional saturated ground was obtained and then verified. The dynamic interaction of the piles and the saturated ground was solved by using the flexible volume method, in which the piles were discretized into three dimensional Euler−Bernoulli beam elements and the dynamic stiffness matrix of saturated ground was formed at the pile−soil interaction nodes by using the Green function. Impedances of the 2×2 pile group and free-field displacement and pore pressure responses caused by harmonic vertical, lateral and rocking forces (moments) applied at the cap center were presented, respectively, for different soil permeability and excitation frequencies. It is found that the soil permeability and the excitation frequency have significant influence on the impedances and the free-field vibration responses. 相似文献
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在用532 nm连续激光辐照TCD-1200D型线阵CCD的过程中,发现了光斑的全饱和单侧拖尾现象。为了分析这种现象的特性,实验测量了拖尾长度随激光功率、CCD积分时间和CCD驱动频率的关系,发现拖尾长度随着激光功率和积分时间的增加而增加,但在一定范围内与CCD驱动频率无关。通过理论计算和实验数据分析拟合发现,拖尾长度和激光功率密度和积分时间的乘积有关,并根据激光辐照下CCD器件光生电荷量的产生过程,推导出了拖尾长度与CCD势阱光生电荷量的关系,得到了拖尾长度随光生电荷量的变化曲线,为全饱和单侧拖尾现象机理分析提供了数据支持。 相似文献
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Prediction of concrete strength using ultrasonic pulse velocity and artificial neural networks 总被引:1,自引:0,他引:1
Ultrasonic pulse velocity technique is one of the most popular non-destructive techniques used in the assessment of concrete properties. However, it is very difficult to accurately evaluate the concrete compressive strength with this method since the ultrasonic pulse velocity values are affected by a number of factors, which do not necessarily influence the concrete compressive strength in the same way or to the same extent. This paper deals with the analysis of such factors on the velocity-strength relationship. The relationship between ultrasonic pulse velocity, static and dynamic Young’s modulus and shear modulus was also analyzed. The influence of aggregate, initial concrete temperature, type of cement, environmental temperature, and w/c ratio was determined by our own experiments. Based on the experimental results, a numerical model was established within the Matlab programming environment. The multi-layer feed-forward neural network was used for this purpose. The paper demonstrates that artificial neural networks can be successfully used in modelling the velocity-strength relationship. This model enables us to easily and reliably estimate the compressive strength of concrete by using only the ultrasonic pulse velocity value and some mix parameters of concrete. 相似文献
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基于中国绝大多数天然气田储量不大,而且分布较分散,离天然气管道较远,因此小型撬装式天然气装置在中国具有广阔的应用前景。小型撬装式天然气装置要求设备少、结构紧凑、操作简单、可靠性高、适应性强、操作弹性大。这对于净化与液化流程提出了更高的要求。采用化工流程软件HYSYS,对单阶混合制冷剂流程,氮气膨胀流程和带丙烷预冷氮气膨胀流程三种工艺流程进行了模拟分析,并以单位能耗为指标对上述三种流程进行了优化。结果发现带丙烷预冷氮气膨胀流程换热平均温差较小,而且能耗较低、流程简单、启动快、操作与维护方便,是比较适合于小型撬装式液化天然气装置的流程。 相似文献