Large Eddy Simulation of Complex Turbulent Flows: Physical Aspects and Research Trends

In the current paper, we have primarily addressed one powerful simulation tool developed during the last decades-Large Eddy Simulation (LES), which is most suitable for unsteady three-dimensional complex turbulent flows in industry and natural environment. The main point in LES is that the large-scale motion is resolved while the small-scale motion is modeled or, in geophysical terminology, parameterized. With a view to devising a subgrid-scale(SGS) model of high quality, we have highlighted analyzing physical aspects in scale interaction and-energy transfer such as dissipation, backscatter, local and non-local interaction, anisotropy and resolution requirement. They are the factors responsible for where the advantages and disadvantages in existing SGS models come from. A case study on LES of turbulence in vegetative canopy is presented to illustrate that LES model is more based on physical arguments. Then, varieties of challenging complex turbulent flows in both industry and geophysical fields in the near future-are presented. In conclusion; we may say with confidence that new century shall see the flourish in the research of turbulence with the aid of LES combined with other approaches.

A further discussion on basic equations for two-phase flow: On collision stress of solid phase

The following points are argued: (i) there are two independent kinds of interaction on interfaces, i.e. the interaction between phases and the collision interaction, and the jump relations on interfaces can accordingly be resolved; (ii) the stress in a particle can also be divided into background stress and collision stress corresponding to the two kinds of interaction on interfaces respectively; (iii) the collision stress, in fact, has no jump on interface, so the averaged value of its derivative is equal to the derivative of its averaged value; (iv) the stress of solid phase in the basic equations for two\|phase flow should include the collision stress, while the stress in the expression of the inter\|phase force contains the background one only. Based on the arguments, the strict method for deriving the equations for two\|phase flow developed by Drew, Ishii et al. is generalized to the dense two\|phase flow, which involves the effect of collision stress.

Studies on terrestrial interface processes in arid areas, China

In the present paper, we have elucidated the importance of energy and water cycling in arid areas to investigate global climate and local economics. Then, we were concerned with the physical arguments as how to stratify the soil, and the stability of the numerical scheme in the mathematical model for predicting temperature variation and water motion. Furthermore, we discuss the methods to estimate evaporation in arid areas. Numerical simulation of energy and water cycling at the Acsu Observatory, CAS, Xinjiang province and Shapuotou Observatory, CAS, Ningxia Province are conducted as case studies. The results show that the laws of terrestrial processes are rather typical in these arid areas. Planting drought-endurable trees can alleviate unfavourable conditions to a certain extent. (C) 1997 Academic Press Limited.

Phylogenetic study of complete cytochrome b genes in musk deer (genus Moschus) using museum samples

As an endangered animal group, musk deer (genus Moschus) are not only a great concern of wildlife conservation, but also of special interest to evolutionary studies due to long-standing arguments on the taxonomic and phylogenetic associations in this group. Using museum samples, we sequenced complete mitochondrial cytochrome b genes (1140 bp) of all suggested species of musk deer in order to reconstruct their phylogenetic history through molecular information. Our results showed that the cytochrome b gene tree is rather robust and concurred for all the algorithms employed (parsimony, maximum likelihood, and distance methods). Further, the relative rate test indicated a constant sequence substitution rate among all the species, permitting the dating of divergence events by molecular clock. According to the molecular topology, M. moschiferus branched off the earliest from a common ancestor of musk deer (about 700,000 years ago); then followed the bifurcation forming the M. berezouskii lineage and the lineage clustering M. fuscus, M. chrysogaster, and M. leucogaster (around 370,000 years before present), interestingly the most recent speciation event in musk deer happened rather recently (140,000 years ago), which might have resulted from the diversified habitats and geographic barriers in southwest China caused by gigantic movements of the Qinghai-Tibetan Plateau in history. Combining the data of current distributions, fossil records, and molecular data of this study, we suggest that the historical dispersion of musk deer might be from north to south in China. Additionally, in our further analyses involving other pecora species, musk deer was strongly supported as a monophyletic group and a valid family in Artiodactyla, closely related to Cervidae. (C) 1999 Academic Press.

Male-infant-male interactions in Tibetan macaques

Event-sampling and scans were used for collecting data on male-infant-male triadic interactions, and their effects on member spacing respectively in a group of Macaca thibetana at Mt. Emei in 1989. The group was partially provisioned by human visitors in seasons other than winter, and could be observed closely. In addition, a stable linear male-hierarchy among five males existed for two years since the end of 1987, providing a good social condition for this topic. The triadic interactions were specific to the birth season, and recognized as three types being on a continuum functionally changing from passive ''agonistic buffering'' (4.8%) to active spatial cohesion, which resulted in a significant decline of intermale distances. Positive correlations were documented between the triad initiation rate and the number of females in consort with the males in the mating season (MS), and between the triad reception rate and the number of infants in proximity to the males in the MS when maternal care was significantly reduced. Thus the male's mating effort and kin/sexual selection may deeply be involved in the triad of this species. Considering that the two triad-species, M. sylvanus and M. thibetana, had different levels of paternity, but shared similar foraging conditions, and showed similar intensities of male-infant caretaking, the triad was very likely a byproduct of male-infant caretaking, which was probably shaped to compensate heavy maternal investment to young offspring in harsh conditions. Accordingly, the long-term arguments about the triad in M. sylvanus can be united to a model of the way in which ''male-infant caretaking'' hypothesis works ultimately, and ''regulating social relations'' hypothesis does proximately.

Compatibility relationship among reaction equilibria, equivalence principle of reaction approaches, and silicon contamination in semiconductors

This paper discovers some shortcomings in the algorithm for the incorporation of Si into GaAs in the GaAs VPE process. These faults arise from neglecting a link, the compatibility relationship, in chemical thermodynamics. The meaning of said relationship is as follows: In an equilibrium complex system, each species can only contribute one and the same quantity (its equilibrium quantity) to the different equilibria of the various reactions involving it; yet even under this restriction, every equilibrium constant is satisfied, and all the reaction equilibria coexist compatibly in the system. Only by adding the relationship can the equilibrium theory for the complex system be complete. This paper also tells its position in chemical thermodynamics. Such a compatibility concept directly leads to an equivalence principle: In a complex system, a certain species can usually be simultaneously formed by many chemical reactions; when the system has reached equilibrium under fixed environmental conditions, the equilibrium quantity of said species calculated according to each chemical equation of these reactions will be equal and the various reaction approaches will be equivalent, provided that for all the reactants and all the other products of these reactions their equilibrium quantities in the system are respectively taken as corresponding knowns for the calculations, which is extremely useful for seeking a functional relation among the species' equilibrium quantities in a system (Si contamination is one of the examples). Under the guidance of those arguments, the various schools' algorithms for the Si contamination can be uniformized and simplified, and the contamination quantity relation between Si and O, two very important impurities, is found.

纯公钥模型下对NP语言的高效并发零知识证明系统

提出了一种从3轮公开掷币的对任何NP语言的诚实验证者零知识证明系统到纯公钥模型下4轮f轮最优）对同一语言的具有并发合理性的并发零知识证明系统．该转化方法有如下优点：1）它只引起D（1）（常数个）额外的模指数运算，相比DiCrescenzo等人在ICALP05上提出的需要qn）个额外的模指数运算的转化方法孩系统在效率上有着本质上的提高，而所需的困难性假设不变；2）在离散对数假设下，该转化方法产生一个完美零知识证明系统．注意到DiCrescenzo等人提出的系统只具有计算零知识性质．该转化方法依赖于一个特殊的对承诺中的离散对数的3轮诚实验证者零知识的证明系统．构造了两个基于不同承诺方案的只需要常数个模指数运算的系统这种系统可能有着独立价值．

measuring acoustic wave transit time in furnace based on active acoustic source signal

Accurate measurement of transit time for acoustic wave between two sensors installed on two sides of a furnace is a key to implementing the temperature field measurement technique based on acoustical method. A new method for measuring transit time of acoustic wave based on active acoustic source signal is proposed in this paper, which includes the followings: the time when the acoustic source signal arrives at the two sensors is measured first; then, the difference of two arriving time arguments is computed, thereby we get the transit time of the acoustic wave between two sensors installed on the two sides of the furnace. Avoiding the restriction on acoustic source signal and background noise, the new method can get the transit time of acoustic wave with higher precision and stronger ability of resisting noise interference.

Experimental study of the U-238(S-36,3-5n)(269-271)Hs reaction leading to the observation of (270)Hs

The deformed doubly magic nucleus (270)Hs has so far only been observed as the four-neutron (4n) evaporation residue of the reaction Mg-26+Cm-248, where a maximum cross section of 3 pb was measured. Theoretical studies on the formation of (270)Hs in the 4n evaporation channel of fusion reactions with different entrance channel asymmetry in the framework of a two-parameter Smoluchowski equation predict that the reactions Ca-48+Ra-226 and S-36+U-238 result in higher cross sections due to lower reaction Q values, in contrast to simple arguments based on the reaction asymmetry, which predict opposite trends. Calculations using HIVAP predict cross sections for the reaction S-36+U-238 that are similar to those of the Mg-26+Cm-248 reaction. Here, we report on the first measurement of evaporation residues formed in the complete nuclear fusion reaction S-36+U-238 and the observation of (270)Hs, which is produced in the 4n evaporation channel, with a measured cross section of 0.8(-0.7)(+2.6) pb at 51-MeV excitation energy. The one-event cross-section limits (68% confidence level) for the 3n, 4n, and 5n evaporation channels at 39-MeV excitation energy are 2.9 pb, while the cross-section limits of the 3n and 5n channel at 51 MeV are 1.5 pb. This is significantly lower than the 5n cross section of the Mg-26+Cm-248 reaction at similar excitation energy.

智能科学与智能技术

当今智能科学与智能技术是科技界的一个热点。在这方面有很多争议。有些学者怀疑智能技术前景，将现有“智能系统”与人相比，根本上否定有什么智能，认为只不过是一套专用软件。有的则过份乐观，我们认为过份悲观或过份乐观都是错误的，这里首先要区分智能科学与智能技术。前者是研究人所具有的自然现象，后者是开发一种技术去替代人的某些脑力劳动。其次，应正确认识现有智能技术方法的局限性。

大学生现实自我与理想自我差异的特点、产生机制和效应

The arguments on self discrepancy can be traced back to the old ages, but the systematic investigations were started by Higgins et al. at 1985.Compared to the large number of foreign studies, only a few ones have been conducted in our own country. Numerous characteristics of undergruaduate’s actual-ideal discrepancy and a great many determinative factors have been found as well as many of its negative effects—especially the greater the actual-ideal discrepancy, the more negative on the mind and behavior. Nevertheless, there are still many issues to be solved, such as the extend of the undergruaduate’s actual-ideal discrepancy level in own country. On the other hand, although there are a great many internal and external determinative factors of actual-ideal discrepancy, how they overally influence the discrepancy of the same individual is still unknown; to what extent does actual-ideal discrepancy influence the human mind and behavior and whether the influence is positive or negtive? This research collected a sample consisting of 4 undergraduate grades and 5 majors from a middle-ranked university. We adopted questionnaires in the study, and analyzed the data using correlation analysis, regression analysis, variances analysis, and path analysis. Our aim focused on the general characteristics of the undergruaduate’s actual-ideal discrepancy in own country, the overall working mechanism of the determinative factors including environmental and personal factors on the actual-ideal discrepancy of the same individual, and the effects of the actual-ideal discrepancy on psychological adaption, motivation, and behavior. The main results are as following: (1)The improved measurement instrument possesses good validity and reliability, and can be used in future research. (2) The actual-ideal discrepancy level among undergraduates is slightly bellow medium. The proportion of undergraduates who have a higher actual-ideal discrepancy level is small. There is significant gender difference in actual-ideal discrepancy level, but no significant difference across different majors and grades. (3)This research probed the overall working mechanism of the parenting style(environmental factors) and the personality factors(personal factors) including stability, flexibility, cleverness, and esteem on the undergruaduate’s actual-ideal discrepancy. The results shows that the parenting style of warmth and understanding, stability, flexibility, and esteem influence the actual-ideal discrepancy. Esteem entirely moderate the relationship between the parenting style of warmth and understanding and actual-ideal discrepancy, partially moderate the relationship between the flexibility, stability and actual-ideal discrepancy. Furthermore, the above factors can be order as stability, flexibility, and parenting style of warmth and understanding in terms of decreasing impact on the actual-ideal discrepancy. No significant effect of cleverness and other parenting style was found. The parenting style of warmth and understanding, stability, and flexibility interactively influence the actual-ideal discrepancy in the following manner: the stability and flexibility, both of which have independent influence on the actual-ideal discrepancy, entirely moderate the relationship between the parenting style of warmth and understanding and actual-ideal discrepancy. (4) Actual-ideal discrepancy plays a negative role in adaption indices, including self-efficacy, self-identity, self-actualization. Actual-ideal discrepancy also has negative effects on the 9 symptoms measured by SCL-90, vitality, approach motivation, avoidance motivation, and performance goals. No significant influence on mastering goals was found. Actual-ideal discrepancy uniquely correlates with depression symptom. The above results contribute from the point of self-discrepancy to the understanding of self-identity of undergraduates, and they enrich the knowledge of the development of self and contribute to the understanding of the development of human personality.This research advances on the two key problems of the developmental mechanism of actual-ideal discrepancy and that promotes the knowledge of the developmental mechanism of actual-ideal discrepancy. The research probed the relationship between the actual-ideal discrepancy and motivation which is an important phenomenon and this enlarges the domain of the actual-ideal discrepancy research. The results make sure that actual-ideal discrepancy is one of the important factors influencing undergruaduate’s mind and behavior. The conclusions can provide reference and guidance in the diagnosis and intervension strategies for mental health education and counseling practice in university.