Microscopic three-body forces and kaon condensation in cold neutrino-trapped matter

We investigate the composition and the equation of state of the kaon condensed phase in neutrino-free and neutrino-trapped star matter within the framework of the Brueckner-Hartree-Fock approach with three-body forces. We find that neutrino trapping shifts the onset density of kaon condensation to a larger baryon density, and reduces considerably the kaon abundance. As a consequence, when kaons are allowed, the equation of state of neutrino-trapped star matter becomes stiffer than the one of neutrino free matter. The effects of different three-body forces are compared and discussed. Neutrino trapping turns out to weaken the role played by the symmetry energy in determining the composition of stellar matter, and thus reduces the difference between the results obtained by using different three-body forces.

Theoretical investigation on excitation, ionization and capture in H(1s, 2s)+H(1s, 2s) collisions

Cross sections of electron- loss in H( 1s)+ H( 1s) collisions and total collisional destruction of H( 2s) in H( 1s) + H( 2s) collisions are calculated by four- body classical- trajectory Monte Carlo ( CTMC) method and compared with previous theoretical and experimental data over the energy range of 4 - 100 keV. For the former a good agreement is obtained within di. erent four- body CTMC calculations, and for the incident energy Ep > 10 keV, comparison with the experimental data shows a better agreement than the results calculated by the impact parameter approximation. For the latter, our theory predicts the correct experimental behaviour, and the discrepancies between our results and experimental ones are less than 30%. Based on the successive comparison with experiments, the cross sections for excitation to H( 2p), single- and double- ionization and H- formation in H( 2s)+ H( 2s) collisions are calculated in the energy range of 4 - 100 keV for the. rst time, and compared with those in H( 1s)+ H( 1s) and H( 1s)+ H( 2s) collisions.

链式可变形机器人的构形与运动研究

本文的研究内容围绕中国科学院创新基金和GUCAS-BHPB基金资助的项目“可变形机器人的研究”展开，其目的是研制具有较强环境适应能力和高机动性能的可变形移动机器人系统，为我国在灾难救援和特种作业等应用领域提供技术储备。论文首先对可变形机器人的研究现状进行了概述，接下来展开了三个方面的研究工作：平台方面，提出了一种新型可变形链式结构，并进行了结构设计和实验验证；构形方面，提出了基于相似理论的构形研究方法，对链式可变形机器人的构形设计和构形转化方法进行了研究；运动性能方面，通过理论和实验分析了链式可变形履带模块机器人不同构形的转向性能、越障性能和倾翻稳定性能等。各种用于非结构环境的移动机器人机构中，模仿生物蛇原型的链式机构由于具有多于确定空间位置和姿态所需的自由度，能够有效、迅速、可靠地响应许多复杂的作业任务，但是该类系统具有转向半径大和侧向稳定性差等缺点。在非结构环境中，机器人需要通过“以变应变”才能够应对复杂多变的任务和环境。因此，论文基于偏置关节的思想，提出了一种形态和结构均能够变化的新型链式结构。机器人的单个标准模块由模块本体、连接臂和偏置关节等组成。偏置关节避免了模块间的运动干涉，扩大了机器人模块间的相对运动空间。机器人模块的数量可以根据实际需要选择，机器人通过变形可以产生多种构形，同时每种构形又具有多种步态以适应作业任务的需要。根据变形机理，研制了链式可变形机器人样机，并对样机进行了相应的原理验证实验。链式可变形机器人构形的复杂性随着模块数量和构形数量的增加呈指数增长，增加了构形设计和构形控制的难度。针对构形设计和构形转化问题，本文基于相似理论，提出了构形研究的一般分析方法，并将其归纳成为：表达(Expression)、计数(Enumeration)、评价(Evaluation)和有效性(Efficiency)等四个方面的问题(简称“Four-E Problem”)。在构形设计方面，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有效的描述；提出了基于组合计数原理的递归算法用于多模块可变形机器人非同构构形的计数、枚举，并根据构形矩阵所表征的拓扑信息对构形进行评价；最后根据仿真结果，给出了可变形机器人的构形设计示例。在构形转化方面，论文利用图论中的基本思想和原理对机器人的构形和构形网络进行了建模，对构形转化的路径进行了计算，对构形转化的最佳路径和中心构形的选择进行了分析；以三模块可变形机器人的构形网络为例，证实了该方法的可行性。履带式移动机器人的运动能力涉及的问题很多，包括接地比压、驱动能力、地面阻力、启动特性、转向能力、越障能力、平顺性和倾翻稳定性等。本文主要研究链式可变形履带模块机器人不同构形的平面转向特性、系统越障性能和倾翻稳定性能等。论文首先对链式可变形履带模块机器人单模块(单履带)的接地比压分布进行了研究，并对接地比压的核心区域进行了分析。在复杂的环境中，机器人运动的路径多由弯曲的道路组成，转向性能是其改变运动方向的一种重要能力。转向形式通常有滑移转向和铰接转向两种，分别适用不同的构形。论文参照杨红旗模型和Kitano模型分别对链式可变形双模块机器人和链式可变形三模块机器人不同构形下的滑移转向和铰接转向进行了理论和实验分析。移动机器人的越障性能是机器人本体和环境相互作用时所产生的一种综合特性。论文分析了链式可变形机器人系统的斜坡爬行性能、沟壑爬行性能、楼梯爬行性能和倾翻稳定性能。考虑到城市环境中，楼梯是最为典型的障碍物之一，论文重点对履带式移动机器人在踢面爬升、踢面翻越和坡度线爬行等阶段的运动条件、运动性能和影响因素进行了分析。在非结构环境中，大多数情况是坎坷不平的地面和复杂的三维地形，机器人的倾翻稳定性(或者说是抗倾翻能力)非常重要。根据Iagnemma和Papadopoulos提出的稳定性分析方法，定义机器人的倾翻稳定锥，对履带式可变形机器人变形过程中的倾翻稳定性进行了综合判定，同时通过仿真比较了机器人三种对称构形在仰俯、倾斜和偏转等组合干扰下的倾翻稳定性。稳定锥方法，为可变形机器人的倾翻问题提供了有效的理论分析手段，同时稳定锥方法还可以适用于其它轮式或腿式移动机器人的稳定性分析。理论分析和实验表明，本文研制的履带驱动链式可变形机器人平台，具有多种构形和步态以适应不同的环境和任务，具有废墟、砾石、草地、沙地、楼梯、坡度和管道等城市或野外环境的通过能力。可变形机器人机构灵巧、结构紧凑、便于携带，它不仅能够用于救援、消防、公安和环保等领域，在星球探测、国防安全等方面也有着潜在的应用前景。

Distribution, feeding and body condition of four small fish species in the near-shore and central areas of Liangzi Lake, China

Small fish abundance is usually high in heavily vegetated habitats in Yangtze lakes, China. Visual and swimming barriers created by dense macrophytes beds could reduce feeding efficiency and growth of small fishes. We tested the hypothesis that small fishes in habitats with dense macrophytes would show decreased feeding efficiency and reduced growth rates by comparing feeding efficiency (measured as the relative weight of fore-gut contents), total length, and condition factor of four small young-of-the-year fishes collected in the near-shore (heavily vegetated) and central (less vegetated) areas of Liangzi Lake. Feeding efficiency, total length, or condition factor were each significantly reduced in the near-shore area compared with the central area for Ctenogobius giurinus, Pseudorasbora parva and Carassius auratus auratus. This supports our hypothesis that vegetation abundance may mediate feeding efficiency and growth of small fishes. Although Hypseleotris swinhonis did not show significant decreases in feeding efficiency or growth in the near-shore area, there was not any reversed tendency, i.e. increased feeding rate or growth in the near-shore area compared to the central area.

Summer diet of two sympatric species of raptors Upland Buzzard (Buteo hemilasius) and Eurasian Eagle Owl (Bubo bubo) in alpine meadow: problem of coexistence

Summer diets of two sympatric raptors Upland Buzzards (Buteo hemilasius Temminck et Schlegel) and Eurasian Eagle Owls (Bubo bubo L. subsp. Hemachalana Hume) were studied in an alpine meadow (3250 m a.s.l.) on Qinghai-Tibet Plateau, China. Root voles Microtus oeconomus Pallas, plateau pikas Ochotona curzoniae Hodgson, Gansu pikas O. cansus Lyon and plateau zokors Myospalax baileyi Thomas were the main diet components of Upland Buzzards as identified through the pellets analysis with the frequency of 57, 20, 19 and 4%, respectively. The four rodent species also were the main diet components of Eurasian Eagle Owls basing on the pellets and prey leftovers analysis with the frequency of 53, 26, 13 and 5%, respectively. The food niche breadth indexes of Upland Buzzards and Eurasian Eagle Owls were 1.60 and 1.77 respectively (higher value of the index means the food niche of the raptor is broader), and the diet overlap index of the two raptors was larger (C-ue = 0.90) (the index range from 0 - no overlap - to I - complete overlap). It means that the diets of Upland Buzzards and Eurasian Eagle Owls were similar (Two Related Samples Test, Z = -0.752, P = 0.452). The classical resource partitioning theory can not explain the coexistence of Upland Buzzards and Eurasian Eagle Owls in alpine meadows of Qinghai-Tibet Plateau. However, differences in body size, predation mode and activity rhythm between Upland Buzzards and Eurasian Eagle Owls may explain the coexistence of these two sympatric raptors.

Complex potentials and singular integral equation for curve crack problem in antiplane elasticity

Four types of the fundamental complex potential in antiplane elasticity are introduced: (a) a point dislocation, (b) a concentrated force, (c) a dislocation doublet and (d) a concentrated force doublet. It is proven that if the axis of the concentrated force doublet is perpendicular to the direction of the dislocation doublet, the relevant complex potentials are equivalent. Using the obtained complex potentials, a singular integral equation for the curve crack problem is introduced. Some particular features of the obtained singular integral equation are discussed, and numerical solutions and examples are given.

Three-dimensional crack problem analysis using boundary element method with finite-part integrals

A set of hypersingular integral equations of a three-dimensional finite elastic solid with an embedded planar crack subjected to arbitrary loads is derived. Then a new numerical method for these equations is proposed by using the boundary element method combined with the finite-part integral method. According to the analytical theory of the hypersingular integral equations of planar crack problems, the square root models of the displacement discontinuities in elements near the crack front are applied, and thus the stress intensity factors can be directly calculated from these. Finally, the stress intensity factor solutions to several typical planar crack problems in a finite body are evaluated.

On the non-linear stability theory of spinning solid bodies with liquid-filled cavities and its application to the columbus problem

In this paper, we first present a system of differential-integral equations for the largedisturbance to the general case that any arbitrarily shaped solid body with a cavity contain-ing viscous liquid rotates uniformly around the principal axis of inertia, and then develop aweakly non-linear stability theory by the Lyapunov direct approach. Applying this theoryto the Columbus problem, we have proved the consistency between the theory and Kelvin'sexperiments.

Computation of flow over a rotating body on unstructured Chimera mesh

Flow around moving boundary is ubiquitous in engineering applications. To increse the efficienly of the algorithm to handle moving boundaries is still a major challenge in Computational Fluid Dynamics (CFD). The Chimera grid method is one type of method to handle moving boundaries. A concept of domain de-composition has been proposed in this paper. In this method, sub-domains are meshed independently and governing equations are also solved separately on them. The Chimera grid method was originally used only on structured (curvilinear) meshes. However, in a problem which involves both moving boundary and complex geometry, the number of sub-domains required in a traditional (structured) Chimera method becomes fairly large. Thus the time required in the interior boundary locating, link-building and data exchanging also increases. The use of unstructured Chimera grid can reduce the time consumption significantly by the reduction of domain(block) number. Generally speaking, unstructured Chimera grid method has not been developed. In this paper, a well-known pressure correction scheme - SIMPLEC is modified and implemented on unstructured Chimera mesh. A new interpolation scheme regarding the pressure correction is proposed to prevent the possible decoupling of pressure. A moving-mesh finite volume approach is implemented in an inertial reference frame. This approach is then used to compute incompressible flow around a rotating circular and elliptic cylinder. These numerical examples demonstrate the capability of the proposed scheme in handling moving boundaries. The numerical results are in good agreement with other experimental and computational data in literature. The method proposed in this paper can be efficiently applied to more challenge cases such as free-falling objects or heavy particles in fluid.

Cytogenetics, morphology and evolution of four subspecies of the Giant Sheep argali (Ovis ammon) of Asia

Dalai-lamae (Ovis ammon dalai-lamae), Gobi (O. a. darwini), Kara Tau (O. a. nigrimontana) and Tibetan (O. a. hodgsoni) argali share a 2n = 56 diploid chromosome number and a karyotype consisting of 2 pairs of biarmed and 25 pairs of acrocentric autosomes, a large acrocentric X and a minute Y chromosome. The Giemsa-banding patterns of the largest pair of biarmed chromosomes were identical to those of the largest biarmed chromosomes in all wild sheep and domestic sheep of the genus Ovis. The banding patterns of the second pair of biarmed chromosomes (metacentric) were identical to the third pair of biarmed chromosomes in Ovis with 2n = 54 and to the third largest pair of chromosomes in the 2n = 52 karyotype of Siberian snow sheep (O. nivicola). The G-banded karyotypes of dalai-lamae, darwini, hodgsoni and nigrimontana are consistent with all subspecies of argali (O. ammon), except that the Y chromosome is acrocentric instead of metacentric as typical of the argaliform wild sheep and Ovis. The Dalai-lamae and Tibetan argali specimens exhibit the light-colored, long-haired ruffs and body coloration typical of argalis from the Tibetan Plateau. The Gobi argali, from the extreme western Gobi, is similar to the dark phase argali.

Effect of body size on growth and energy budget of Nile tilapia, Oreochromis niloticus

A growth trial was conducted at 30 degrees C to investigate the effect of body size on growth and energy budget of Nile tilapia. The average initial body weights of the four size groups tested were 9.3, 34.1, 80.3 and 172.4 g, respectively. Fish were fed to satiation twice a day with a diet containing 35.6% crude protein. Food consumption (C-max: kJ/day) increased with body size (W: g) according to the relationship: Ln C-max = 1.45 + 0.42 LnW. The final body contents of dry matter, crude protein and ash per unit body weight increased with increasing body size while contents of fat and energy were independent of body size. Specific growth rates of wet weight, dry weight, protein and energy decreased as the fish increased in size. Feed efficiencies in wet weigh, dry weight and crude protein decreased with increasing body size, while that of energy remained unchanged. The proportions of energy intake allocated to the various components (faecal energy, excretory energy, heat production and recovered energy) of the energy budget were not significantly affected by body size, and the average budget was: 100IE-18.5(+/- 1.33)FE + 5.9 (+/- 3.09)(ZE + UE) + 49.3(+/- 3.77)HE + 26.3(+/- 6.23)RE, where IE, FE, (ZE + UE), HE and RE represent gross energy intake, faecal energy, excretory (non-faecal) energy loss, heat production and recovered energy (growth), respectively. It is suggested that the decrease in growth rate in larger fish is mainly due to the decrease in relative food intake. (C) 1997 Elsevier Science B.V.

Solving the coastal eutrophication problem by large scale seaweed cultivation

Eutrophication is becoming a serious problem in coastal waters in many parts of the world. It induces the phytoplankton blooms including 'Red Tides', followed by heavy economic losses to extensive aquaculture area. Some cultivated seaweeds have very high productivity and could absorb large quantities of N, P, CO2, produce large amount of O-2 and have excellent effect on decreasing eutrophication. The author believes that seaweed cultivation in large scale should be a good solution to the eutrophication problem in coastal waters. To put this idea into practice, four conditions should be fulfilled: (a) Large-scale cultivation could be conducted within the region experiencing eutrophication. (b) Fundamental scientific and technological problems for cultivation should have been solved. (c) Cultivation should not impose any harmful ecological effects. (d) Cultivation must be economically feasible and profitable. In northern China, large-scale cultivation of Laminaria japonica Aresch. has been encouraged for years to balance the negative effects from scallop cultivation. Preliminary research in recent years has shown that Gracilaria lemaneiformis (Bory) Daws. and Porphyra haitanensis Chang et Zheng are the two best candidates for this purpose along the Chinese southeast to southern coast from Fujian to Guangdong, Guangxi and Hong Kong. Gracilaria tenuistipitata var. liui Chang et Xia is promising for use in pond culture condition with shrimps and fish.

Evaluation of a combined wavelet and a combined principal component analysis classification system for BCG diagnostic problem

Heart disease is one of the main factor causing death in the developed countries. Over several decades, variety of electronic and computer technology have been developed to assist clinical practices for cardiac performance monitoring and heart disease diagnosis. Among these methods, Ballistocardiography (BCG) has an interesting feature that no electrodes are needed to be attached to the body during the measurement. Thus, it is provides a potential application to asses the patients heart condition in the home. In this paper, a comparison is made for two neural networks based BCG signal classification models. One system uses a principal component analysis (PCA) method, and the other a discrete wavelet transform, to reduce the input dimensionality. It is indicated that the combined wavelet transform and neural network has a more reliable performance than the combined PCA and neural network system. Moreover, the wavelet transform requires no prior knowledge of the statistical distribution of data samples and the computation complexity and training time are reduced.

Chromosome segregation in fertilized eggs from triploid Pacific oysters, Crassostrea gigas (Thunberg), following inhibition of polar body 1

Chromosome segregation in fertilized eggs from triploid Pacific oysters, following inhibition of the first polar body (PB1), was studied with acetic orcein staining techniques. To block the release of PB1, fertilized eggs were treated with 0.5 mg/l of cytochalasin B (CB). Four types of segregation were observed, namely, ''tripolar segregation'' (54.5%), ''united bipolar segregation'' (12%), ''separated bipolar segregation'' (2.5%), and ''incomplete united bipolar segregation'' (4%). The remaining 23% could not be classified because of chromosome disorganization, but appeared to be variants of the above. It seemed clear that the predominant pattern that gave rise to tetraploids was united bipolar segregation, although certain separated bipolar segregations might also lead to the formation of tetraploids. The sequential events of meioses observed in CB-treated eggs are described. The asynchrony of meiotic events and possible mechanisms for the various types of chromosome segregation are discussed.

一种基于旋转体的摄像机定位方法

基于旋转体的摄像机定位是单目合作目标定位领域中的涉及较少并且较为困难的一个问题,传统的基于点基元、直线基元及曲线基元的定位方法在用于旋转体定位过程中都存在相应的问题.文中设计了一种由4个相切椭圆构成的几何模型,该模型环绕于圆柱体表面,利用二次曲线的投影仍然是二次曲线的特性和椭圆的相应性质能够得到唯一确定模型位置的3个坐标点,从而将旋转体定位问题转化为P3P问题.在对P3P的解模式区域进行分析后,推导了根据模型上可视曲线的弯曲情况来确定P3P问题解模式的判别方法,并给出证明过程.仿真实验表明了这种模型定位方法的有效性.最后利用这个模型引导机械手完成目标定位的实验.