Rotation alignment in neutron-rich Cr isotopes: A probe of deformed single-particle levels across N=40

Recent experiments have reached the neutron-rich Cr isotope with N = 40 and confirmed enhanced collectivity near this subshell. The current data focus on low-spin spectroscopy only, with little information on the states where high-j particles align their spins with the system rotation. By applying the projected shell model, we show that rotation alignment occurs in neutron-rich even-even Cr nuclei as early as spin 8 (h) over bar h and, owing to shell filling, the aligning particles differ in different isotopes. It is suggested that observation of irregularities in moments of inertia is a direct probe of the deformed single-particle scheme in this exotic mass region.

Emergy Assessment of a Wheat-Maize Rotation System with Different Water Assignments in the North China Plain

Sustainable water use is seriously compromised in the North China Plain (NCP) due to the huge water requirements of agriculture, the largest use of water resources. An integrated approach which combines the ecosystem model with emergy analysis is presented to determine the optimum quantity of irrigation for sustainable development in irrigated cropping systems. Since the traditional emergy method pays little attention to the dynamic interaction among components of the ecological system and dynamic emergy accounting is in its infancy, it is hard to evaluate the cropping system in hypothetical situations or in response to specific changes. In order to solve this problem, an ecosystem model (Vegetation Interface Processes (VIP) model) is introduced for emergy analysis to describe the production processes. Some raw data, collected by investigating or observing in conventional emergy analysis, may be calculated by the VIP model in the new approach. To demonstrate the advantage of this new approach, we use it to assess the wheat-maize rotation cropping system at different irrigation levels and derive the optimum quantity of irrigation according to the index of ecosystem sustainable development in NCP. The results show, the optimum quantity of irrigation in this region should be 240-330 mm per year in the wheat system and no irrigation in the maize system, because with this quantity of irrigation the rotation crop system reveals: best efficiency in energy transformation (transformity = 6.05E + 4 sej/J); highest sustainability (renewability = 25%); lowest environmental impact (environmental loading ratio = 3.5) and the greatest sustainability index (Emergy Sustainability Index = 0.47) compared with the system in other irrigation amounts. This study demonstrates that application of the new approach is broader than the conventional emergy analysis and the new approach is helpful in optimizing resources allocation, resource-savings and maintaining agricultural sustainability.

The electrochemical behavior of a system with a limited number of molecules

In this paper, based on Einstein relationship between diffusion and random walk, the electrochemical behavior of a system with a limited number of molecules was simulated and explored theoretically. The transition of the current vs time responses from discrete to continuous was clearly obtained as the number of redox molecules increased from 10 to 10(6).

What has brought on the effects of number-average molecular weight on the spinodals in polymer mixtures?

On the basis of the thermodynamics of Gibbs, the spinodal for the quasibinary system was derived in the framework of the Sanchez-Lacombe lattice fluid theory. All of the spinodals were calculated based on a model polydisperse polymer mixture, where each polymer contains three different molecular weight subcomponents. According to our calculations, the spinodal depends on both weight-average ((M) over bar (w)) and number-average ((M) over bar (n)) molecular weights, whereas that of the z-average molecular weight is invisible. Moreover, the extreme of the spinodal decreases when the polydispersity index (eta = (M) over bar (w)/(M) over bar (n)) of the polymer increases. The effect of polydispersity on the spinodal decreases when the molecular weight gets larger and can be negligible at a certain large molecular weight. It is well-known that the influence of polydispersity on the phase equilibrium (coexisting curve, cloud point curves) is much more pronounced than on the spinodal. The effect of M, on the spinodal is discussed as it results from the infuluence of composition temperatures, molecular weight, and the latter's distribution on free volume. An approximate expression, which is in the assumptions of v* v(1)* = v(2)* and 1/r --> 0 for both of the polymers, was also derived for simplification. It can be used in high molecular weight, although it failed to make visible the effect of number-average molecular weight on the spinodal.

A novel electrochemical method for simultaneously measuring diffusion coefficient and ion transference number

This paper introduces a new method to estimate the diffusion coefficient and transference number of a salt or an electroactive ion in a solution with little or no supporting electrolyte. The above two parameters can be obtained from a single potential step experiment without previous knowledge of either one. It would appear that the method could also be used in the study of ion transport in a high viscosity solvent or a solid electrolyte. (C) 1998 Elsevier Science S.A.

Influence of the earth rotation on the interfacial wave solutions and wave-induced tangential stress in a two-layer fluid system

Interfacial waves and wave-induced tangential stress are studied for geostrophic small amplitude waves of two-layer fluid with a top free surface and a flat bottom. The solutions were deduced from the general form of linear fluid dynamic equations of two-layer fluid under the f-plane approximation, and wave-induced tangential stress were estimated based on the solutions obtained. As expected; the solutions derived from the present work include as special cases those obtained by Sun et al. (2004. Science in China, Set. D, 47(12): 1147-1154) for geostrophic small amplitude surface wave solutions and wave-induced tangential stress if tire density of the upper layer is much smaller than that of the lower layer. The results show that the interface and the surface will oscillate synchronously, and the influence of the earth's rotation both on the surface wave solutions and the interfacial wave solutions should be considered.

Outer wave number spectrum and statistical distribution of apparent wave number vector

Based on the ray theory and Longuet-Higgins's linear,model of sea waves, the joint distribution of wave envelope and apparent wave number vector is established. From the joint distribution, we define a new concept, namely the outer wave number spectrum, to describe the outer characteristics of ocean waves. The analytical form of the outer wave number spectrum, the probability distributions of the apparent wave number vector and its components are then derived. The outer wave number spectrum is compared with the inner wave number spectrum for the average status of wind-wave development corresponding to a peakness factor P = 3. Discussions on the similarity and difference between the outer wave number spectrum and inner one are also presented in the paper. (C) 2002 Elsevier Science Ltd. All rights reserved.

具有自适应能力管道机器人的设计与运动分析

提出并研制一种基于自适应移动机构的管内探查机器人。通过对机器人传动机构的设计,实现了在不增加驱动电动机数量的前提下,机器人具有适应不同管道直径的能力。机器人的传动机构能够在管道直径改变时,自动地改变行走部件的输出形式以克服障碍,完成越障任务。在没有应用链式多节构型的情况下,机器人配备一个驱动电动机就能够完成越障任务,改善了传统螺旋驱动式机器人越障能力不高的问题,同时也提高了对驱动电动机的使用效率。为了分析试验中发现的机器人保持架自转现象,对机器人进行运动分析,并由分析结果对相关部分进行改进。试验结果表明,该机器人能够在内径为190 mm和180 mm的管道中行进,并能够顺利通过两节管道间形成的同心台阶障碍,验证了自适应移动机构的行走能力。

模块化变形机器人非同构构形表达与计数

提出一种新型链式可重构模块机器人平台,该机器人平台具有手动可重构和自动变形的特点,介绍一种三模块变形机器人样机。组成机器人的单个模块可以简化为由模块本体、连接臂和偏置关节组成。模块的数量可以根据实际工作的需要进行选择,模块间的连接具有规则连接和非规则连接两种方式;同时,由连接模块的偏置关节的运动,模块间的相对位置可以改变。由于模块连接方式的不同和模块间相对位置的变化,变形机器人具有多种非同构构形;为此,根据模块的物理结构和邻接关系提出了用构形矩阵来表达机器人结构的拓扑信息,并在仿真环境下进行等效描述;提出基于组合计数原理的递归算法,用于多模块变形机器人的非同构构形的计数,并根据构形矩阵的拓扑信息对构形进行评价。最后根据仿真结果给出了一种三模块变形机器人样机对称构形的设计示例,验证了算法的可行性。

大型反倾岩体变形破坏机制及稳定性分析———以金沙江宽谷坝址龙蟠边坡为例

A large number of catastrophic accidents were aroused by the instability and destruction of anti-dip rock masses in the worldwide engineering projects, such as hydropower station, mine, railways and so on. Problems in relation to deformation and failure about anti-dip rock slopes are significant for engineering geology research. This dissertation takes the Longpan slope in the Jinsha River as a case to study the deformation mechanism of large-scale anti-dip rock masses and the slope stability analysis method. The primary conclusions are as follows. The Dale Reach of Jinsha River, from Longpan to the debouchment of Chongjiang tributary, is located in the southeastern margin of the Qinghai-Tibet Plateau. Longpan slope is the right embankment of Dale dam, it is only 26 km to the Shigu and 18 km to Tiger Leaping Gorge. The areal geology tectonic structures here area are complicated and blurry. Base on the information of geophysical exploration (CSAMT and seismology) and engineering geological investigation, the perdue tectonic pattern of Dale Reach is put forward for the first time in this paper. Due to the reverse slip of Longpan fault and normal left-rotation of Baihanchang fault, the old faulted valley came into being. The thick riverbed sediments have layered characters of different components and corresponding causes, which attribute to the sedimentary environments according with the new tectonic movements such as periodic mountain uplifting in middle Pleistocene. Longpan slope consists of anti-dip alternate sandstone and slate stratums, and the deformable volume is 6.5×107m3 approximately. It was taken for an ancient landslide or toppling failure in the past so that Dale dam became a vexed question. Through the latest field surveying, displacement monitoring and rock masses deforming characters analyses, the geological mechanism is actually a deep-seated gravitational bending deformation. And then the discrete element method is used to simulate the deforming evolution process, the conclusion accords very well with the geo-mechanical patterns analyses. In addition strength reduction method based on DEM is introduced to evaluate the factor of safety of anti-dip rock slope, and in accordance with the expansion way of the shear yielding zones, the progressive shear failure mechanism of large-scale anti-dip rock masses is proposed for the first time. As an embankment or a close reservoir bank to the lower dam, the stability of Longpan slope especially whether or not resulting in sliding with high velocity and activating water waves is a key question for engineering design. In fact it is difficult to decide the unified slip surface of anti-dip rock slope for traditional methods. The author takes the shear yielding zones acquired form the discrete element strength reduction calculation as the potential sliding surface and then evaluates the change of excess pore pressure and factor of stability of the slope generated by rapid drawdown of ponded water. At the same time the dynamic response of the slope under seismic loading is simulated through DEM numerical modeling, the following results are obtained. Firstly the effective effect of seismic inertia force is resulting in accumulation of shear stresses. Secondly the discontinuous structures are crucial to wave transmission. Thirdly the ultimate dynamic response of slope system takes place at the initial period of seismic loading. Lastly but essentially the effect of earthquake load to bringing on deformation and failure of rock slope is the coupling effect of shear stresses and excess pore water pressure accumulation. In view of limitations in searching the critical slip surface of rock slope of the existing domestic and international software for limit equilibrium slope stability analyses, this article proposes a new method named GA-Sarma Algorithm for rock slope stability analyses. Just as its name implies, GA-Sarma Algorithm bases on Genetic Algorithm and Sarma method. GA-Sarma Algorithm assumes the morphology of slip surface to be a broken line with traceability to extend along the discontinuous surface structures, and the slice boundaries is consistent with rock mass discontinuities such as rock layers, faults, cracks, and so on. GA-Sarma Algorithm is revolutionary method that is suitable for global optimization of the critical slip surface for rock slopes. The topics and contents including in this dissertation are closely related to the difficulties in practice, the main conclusions have been authorized by the engineering design institute. The research work is very meaningful and useful for the engineering construction of Longpan hydropower station.