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1.
Implementation of a coupled plastic damage distinct lattice spring model for dynamic crack propagation in geomaterials
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This paper studies dynamic crack propagation by employing the distinct lattice spring model (DLSM) and 3‐dimensional (3D) printing technique. A damage‐plasticity model was developed and implemented in a 2D DLSM. Applicability of the damage‐plasticity DLSM was verified against analytical elastic solutions and experimental results for crack propagation. As a physical analogy, dynamic fracturing tests were conducted on 3D printed specimens using the split Hopkinson pressure bar. The dynamic stress intensity factors were recorded, and crack paths were captured by a high‐speed camera. A parametric study was conducted to find the influences of the parameters on cracking behaviors, including initial and peak fracture toughness, crack speed, and crack patterns. Finally, selection of parameters for the damage‐plasticity model was determined through the comparison of numerical predictions and the experimentally observed cracking features. 相似文献
2.
本文回顾了自然和自然贡献情景模型发展的背景、历史和内容,概括总结了自然和自然贡献情景模型的发展进程以及联合国生物多样性与生态系统服务政府间科学—政策平台(IPBES)情景模型的概念框架,讨论了自然和自然贡献情景模型存在的问题和发展方向。为了在全球层面解决现有综合集成模型存在的问题,根据地球表层建模基本定理和生态环境曲面建模基本定理,提出了具有中国原创特点的自然与自然贡献情景模型概念框架。 相似文献
3.
高速滑坡问题是当前工程地质和环境地质学界极为关注的问题。本文对诸如滑体高速滑动所对应的时空界限、滑体滑动过程所产生的热效应以及空气浮托力等高速滑坡产生机制问题进行了初步探讨。 相似文献
4.
In late October and early November 2003, a series of space weather hazard events erupted in solar-terrestrial space. Aiming
at two intense storm (shock) events on 28 and 29 October, this paper presents a Two-Step method, which combines synoptic analysis
of space weather–`observing’ and quantitative prediction – ‘palpating’, and uses it to test predictions. In the first step,
‘observing’, on the basis of observations of the source surface magnetic field, interplanetary scintillation (IPS) and ACE
spacecraft, we find that the propagation of the shock waves is asymmetric and northward relative to the normal direction of
their solar sources due to the large-scale configuration of the coronal magnetic fields, and the Earth is located near the
direction of the fastest speed and greatest energy of the shocks. Being two fast ejection shock events, the fast explosion
of extremely high temperature and strong magnetic field, and background solar wind velocity as high as 600 and 1000 km s−1, are also helpful to their rapid propagation. According to the synoptic analysis, the shock travel times can be estimated
as 21 and 20 h, which are close to the observational results of 19.97 and 19.63 h, respectively. In the second step, ‘palpating’,
we adopt a new membership function of the fast shock events for the ISF method. The predicted results here show that for the
onset time of the geomagnetic disturbance, the relative errors between the observational and the predicted results are 1.8
and 6.7%, which are consistent with the estimated results of the first step; and for the magnetic disturbance magnitude, the
relative errors between the observational and the predicted results are 4.1 and 3.1%, respectively. Furthermore, the comparison
among the predicted results of our Two-Step method with those of five other prevailing methods shows that the Two-Step method
is advantageous in predicting such strong shock event. It can predict not only shock arrival time, but also the magnitude
of magnetic disturbance. The results of the present paper tell us that understanding the physical features of shock propagation
thoroughly is of great importance in improving the prediction efficiency. 相似文献
5.
The dunes in estuary of Tumen River in China lie to the area between the Jiushaping and Fangchuan in the left bank of Tumen River (Fig.1). The dis-tance is about 15~20 km between the dunes and the coast. It ranges from China to D. P. R. Korea and Russia. The range of the height of dunes is about 15~20 m and the width is 100~200 m. By the re-connaissance, we protracted 9 section planes of the dunes and collected 40 sand samples of the dunes, and identified the sedimentary environment … 相似文献
6.
刘峰 《成都信息工程学院学报》2003,18(4):376-380
分组密码是数据通讯中最常用的数据加密方式,以DES为例分析现有分组加密算法的安全隐患,并提出了可变密钥加密和变长密文输出两个新思路,可应用于所有现有分组加密算法以提高安全性,并就该方法的安全性、效率、具体应用做出了分析。 相似文献
7.
着重讨论了网络用户经济效益的内涵以及用户的投入量和产出量,并提出了评价网络用户经济效益的指标体系,包括成本降低率,成本利润增长率、产品开发时间约率、市场占有增长率等系列指标。 相似文献
8.
9.
网络经济是相对于大工业经济而言的,其网络企业经济效益的评价,可以从网络企业成本及收益两个方面讨论,然后以投入产出比等五个方面来建立其评价指标体系。 相似文献
10.
1INTRODUCTION Since the first use in human genetic research in1966,allozyme has become the most popular genetic marker for population genetics studies for almost all groups of animals and plants(Lewontin and Hubby,1966;Murphy et al.,1996).In the past seve… 相似文献