Weak Zone Related Seismic Cycles in Progressive Failure Leading to Collapse in Brittle Crust

Until quite recently our understanding of the basic mechanical process responsible for earthquakes and faulting was not well known. It can be argued that this was partly a consequence of the complex nature of fracture in crust and in part because evidence of brittle phenomena in the natural laboratory of the earth is often obliterated or obscured by other geological processes. While it is well understood that the spatial and temporal complexity of earthquakes and the fault structures emerge from geometrical and material built-in heterogeneities, one important open question is how the shearing becomes localized into a band of intense fractures. Here the authors address these questions through a numerical approach of a tectonic plate by considering rockmass heterogeneity both in microscopic scale and in mesoscopic scale. Numerical simulations of the progressive failure leading to collapse under long-range slow driving forces in the far-field show earthquake-like rupture behavior. $En Echelon$ crack-arrays are reproduced in the numerical simulation. It is demonstrated that the underlying fracturing induced acoustic emissions (or seismic events) display self-organized criticality------from disorder to order. The seismic cycles and the geometric structures of the fracture faces, which are found greatly depending on the material heterogeneity (especially on the macroscopic scale), agree with that observed experimentally in real brittle materials. It is concluded that in order to predict a main shock, one must have extremely detailed knowledge on very minor features of the earth's crust far from the place where the earthquake originated. If correct, the model proposed here seemingly provides an explanation as to why earthquakes to date are not predicted so successfully. The reason is not that the authors do not understand earthquake mechanisms very well but that they still know little about our earth's crust.

Heteroclinic cycles in lattice dynamical systems

A criterion of spatial chaos occurring in lattice dynamical systems-heteroclinic cycle-is discussed. It is proved that if the system has asymptotically stable heteroclinic cycle, then it has asymptotically stable homoclinic point which implies spatial chaos.

锡林河流域温带草地植物VOC释放及其对草地生态系统碳循环的贡献

植物源挥发性有机碳化合物（Volitale organic compounds, VOC）是大气VOC的主要来源，与对流层大气质量、大气化学密切相关。鉴于温带草地的分布范围很广，草地植物VOC释放潜力某种程度上影响植物源VOC的总释放量。另外，植物源VOC也是光合作用固定碳素的损失方式之一，可能在特定区域或生态系统中具有重要意义。基于上述想法，本文设计了四个方面的实验作为研究内容：1） 温带草地物种水平VOC释放潜力、及其与植物功能群的关系？2) 沙地植物物种水平VOC释放潜力、及其与植物功能群的关系？3) 沙地植物-草地植物VOC释放潜力存在显著性差异吗？4) 温带典型草地和退化草地的VOC释放速率如何？在生态系统水平，植物源VOC对温带草地碳循环的贡献多大？ 在所测定的175种温带草地植物中，不同植物间异戊二烯和单萜释放潜力差异很大;除少数物种外，大多数植物的异戊二烯和单萜释放潜力都较低，尤其是典型草地的优势物种。在此基础上，作者探讨了分类学赋值方法对温带草地植被的可行性，并初步建立了锡林河流域温带草地植物的VOC释放目录（共277种植物）。另外，温带草地植物的异戊二烯和单萜释放潜力与植物功能群（植物生活型和水分功能群）具有一定的联系，尤其是植物生活型。总的来说，温带草原的优势生活型（物种），即多年生根茎禾草（或多年生丛生禾草），具有较低的异戊二烯和单萜释放潜力。各水分功能群间差异不显著，但中旱生植物、旱中生植物 (温带草原的优势功能群)，具有较低的异戊二烯、单萜释放潜力。因此，温带草原退化过程中，那些具有较高VOC释放潜力的植物，重要性将会增加。 沙地植物种类组成非常丰富，不同物种间的异戊二烯和单萜释放潜力变异也很大。另外，沙地植物的异戊二烯和单萜释放潜力与其功能群间关系较密切，不同植物生活型间差异显著;其中也以多年生根茎禾草、多年生从生禾草的释放潜力最低，而乔木的释放潜力相对最高;该结论基本与草地的研究结论一致。然而，沙地植物的异戊二烯和单萜释放潜力与其水分功能群的关系比较模糊，中生植物具有更高的释放潜力，湿生植物的释放潜力较小。 通过对比沙地植物和草地植物的释放潜力，发现沙地植物的异戊二烯和单萜释放潜力比草地植物高，且这种差异整体上显著。另外，这种显著性差异，在不同植物生活型、水分功能群间也同样存在。沙地植物比对应的草地植物具有更高的异戊二烯和单萜释放潜力，最可能的原因：沙地正午的温度明显比草地温度高，前者实测温度可超过 45 ℃,这种经常性、周期性高温，促使沙地植物采用与草地植物不同的适应策略，即沙地植物通过释放更多的异戊二烯或单萜来减少其可能遭的热胁迫或热伤害，这种长期适应策略，使沙地植物具有更高的萜类化合物释放潜力。 本文还调查了温带典型草地生态系统和退化草地生态系统的异戊二烯和单萜释放速率，结果表明典型草地的标准异戊二烯和单萜释放速率分别为0.50 μgC g-1 h-1和0.69 μgC g-1 h-1;退化草地的标准异戊二烯和单萜释放潜力分别为0.32 μgC g-1 h-1和1.59 μgC g-1 h-1。总的来说，温带草地的异戊二烯和单萜释放速率都比较低，尤其是典型草地。整个生长季，典型草地释放的异戊二烯和单萜分别为31.6 mgC•m-2　和 70.4 mgC•m-2;退化草地的异戊二烯和单萜释放量分别为20.8 mgC•m-2 和 168.8 mgC•m-2。退化草地萜类化合物总释放速率远高于典型草地，尤其是单萜释放能力。过度放牧引起的草地退化，通过改变植被种类组成，对温带草地的异戊二烯和单萜释放速率产生显著影响;总体而言，温带草地退化将会使草地释放更多萜类化合物。 在温带草地生态系统中，Clost as VOC相对其NPP而言很小，在环境PAR和温度高时,它的贡献率相对较大;Clost as VOC约占典型草地生态系统NEP的5.32 %，退化草地生态系统NEP的0.23 %。植物源VOC释放所损失的碳素相对草地生态系统NPP而言几乎可以忽略不计;但是，相对其NEP，Clost as VOC还是具有一定的相关性。虽然，草地生态系统Clost as VOC对NPP或NEP的贡献率较小，但考虑到全球尺度植物源VOC的巨大释放速率，它在碳循环中的贡献率仍然不容忽视;在某些特殊的生态系统中，仍可能扮演重要角色。

Effects of rhFSH regimen and time interval on ovarian responses to repeated stimulation cycles in rhesus monkeys during a physiologic breeding season

We studied the effects of repeated stimulation by recombinant human FSH (rhFSH) at various time intervals during a physiologic breeding season in rhesus monkeys. Ovarian recovery and responses were assessed by ultrasonography, serum steroid concentrations

Vertical mixing within the epilimnion modulates UVR-induced photoinhibition in tropical freshwater phytoplankton from southern China

1. The importance of vertical mixing in modulating the impact of UVR on phytoplankton photosynthesis was assessed in a tropical, shallow lake in southern China from late winter to mid-spring of 2005. 2. Daily cycles of fluorescence measurements (i.e. photosynthetic quantum yield, Y) were performed on both 'static' and in situ samples. Static samples were of surface water incubated at the surface of the lake under three radiation treatments - PAB (PAR + UVR, 280-700 nm), PA (PAR + UV-A, 320-700 nm) and P (PAR, 400-700 nm). In situ samples were collected every hour at three different depths - 0, 0.5 and 1 m. 3. The general daily pattern was of a significant decrease in Y from early morning towards noon, with partial recovery in the afternoon. Samples incubated under static conditions always had lower Y than those under in situ conditions at the same time of the day. 4. Under stratified conditions, no overall impact of UVR impact could be detected in situ when compared with the static samples. Further rapid vertical mixing not only counteracted the impact of UVR but also stimulated photosynthetic efficiency. 5. Based on these measurements of fluorescence, the mixing speed of cells moving within the epilimnion was estimated to range between 0.53 and 6.5 cm min(-1). 6. These data show that mixing is very important in modulating the photosynthetic response of phytoplankton exposed to natural radiation and, hence, strongly conditions the overall impact of UVR on aquatic ecosystems.

Compensatory growth and food consumption in gibel carp, Carassius auratus gibelio, and Chinese longsnout catfish, Leiocassis longirostris, experiencing cycles of feed deprivation and re-feeding

The compensatory responses of juvenile gibel carp and Chinese longsnout catfish to four cycles of 1 part of a study designed to determine feeding regimes that would maximise growth rates. Both species showed compensatory growth in the re-feeding periods. The compensation was not sufficient for the deprived fish to match the growth trajectories of controls fed to satiation daily. The compensatory growth response was more clearly defined in the later cycles. The deprived fish showed hyperphagia during the 2-week periods of re-feeding and the hyperphagic response was clearer in the later cycles. The hyperphagia tended to persist for both weeks of the re-feeding period. The gibel carp showed no difference in gross growth efficiency between deprived and control fish. In the catfish, the gross growth efficiency of the deprived fish was marginally higher than that of control fish, but the efficiency varied erratically from week to week. Over the experiment, the deprived fish achieved growth rates 75-80% of those shown by control fish, although fed at a frequency of 66%. There was no evidence of growth over-compensation with the deprivation-re-feeding protocol used in this study. (C) 2004 Elsevier B.V. All rights reserved.

Effect of cycles of feed deprivation on growth and food consumption of immature three-spined sticklebacks and European minnows

Individual juvenile three-spined sticklebacks Gasterosteus aculeatus and European minnow Phoxinus phoxinus, from sympatric populations, were subjected to four cycles of I week of food deprivation and 2 weeks of ad libitum feeding. Mean specific growth rate during the weeks of deprivation was negative and did not differ between species. The three-spined stickleback showed sufficient growth compensation to recover to the growth trajectory shown by control fish daily fed ad libitum. The compensation was generated by hyperphagia during the re-feeding periods, and in the last two periods of re-feeding, the gross growth efficiencies of deprived three-spined sticklebacks were greater than in control fish. The expression of the compensatory changes in growth and food consumption became clearer over the successive periods of re-feeding. The European minnow developed only a weak compensatory growth response and the mass trajectory of the deprived fish deviated more and more from the control trajectory During re-feeding periods, there were no significant differences in food consumption or gross growth efficiency between control and deprived European minnows. The differences between the two species are discussed in terms of the possible costs of compensatory growth, the control of growth and differences in feeding biology (C) 2003 The Fisheries Society of the British Isles.

基于PAR的高可信装备保障算法推演

算法被誉为计算的“灵魂”（spirit of computing），算法程序的可靠性和正确性对软件系统的可信度起着至关重要的作用。动态规划、贪心、分支限界等传统的算法设计策略缺乏有效的选择标准，一些算法形式化开发方法和工具的应用水平和范围也很有限，因此算法的可靠性已成为高可信软件系统的一个主要瓶颈。 作为军事运筹学的一个重要分支，装备保障计算主要研究军事活动中装备领域的决策优化问题，保障计算软件特别是算法的可靠性在很大程度上决定了装备保障的效率乃至军事行动的成败。利用形式化软件工程的研究成果、特别是引入算法程序的形式化开发方法，对我军通用装备保障领域中的大量算法类问题进行有效求解，有利于优化保障结构、统筹保障资源、整合保障力量、提高保障时效，促进装备整体战斗力水平的提升。 本文以高可信软件开发方法PAR为基础，面向装备保障计算的领域需求，提出了一类离散最优化问题（discrete optimization problem, DOP）的结构模型和算法推演技术，并成功推演了一系列典型的装备保障算法。本论文的主要创新性贡献如下： （1）定义了DOP的结构模型，提出了基于单点结构（Singleton）的问题分划递推策略，进而通过PAR算法推演生成问题的高效求解算法，涵盖了多种传统算法设计策略，显著提高了算法程序设计的机械化水平。 （2）提出了描述DOP分划递推过程的问题简约图（problem reduction graph, PRG）模型，并针对典型DOP结构推演得到了一组PRG构造算法模式，其中每个算法模式都涵盖了满足特定代数结构性质的一大类具体问题。 （3）阐述了PAR算法推演的范畴模型，为算法设计和重用提供了抽象而有效的方法指导。 （4）对我军通用装备保障领域具有代表性的48个问题进行了形式化的算法推演，构建了领域算法库。 （5）在PAR平台的基础上设计了装备保障算法开发平台的原型COPALM，支持DOP算法推演和重用，进而提高了相关应用软件的开发效率。

基于PAR的算法形式化开发

形式化方法是构建可信软件的重要途径.基于对算法问题的分析,针对形式化方法PAR开发算法的特征,刻划了问题分划、递推关系构造方面的规律.从一类问题的形式化功能规约出发,可机械地完成问题的分划及规约的变换,自然地揭示出求解问题的算法思想,在相关工具的支持下自动生成算法程序.研究结果将算法设计中尽可能多的创造性劳动转化为非创造性劳动,降低了形式化求解算法问题的难度,提高了算法程序的可靠性和形式化开发效率.

PAR方法和循环不变式的范畴语义

范畴论对理解程序规约及程序设计和正确性证明十分有用.PAR方法则是建立在严格的数学基础之上的一种统一的算法程序设计方法.循环不变式在循环算法程序的设计中至关重要.使用格理论和范畴论作为工具对PAR方法建立一个理论框架,并对其用范畴论的概念加以解释,从而使得PAR有更强的理论基础.在此基础上引入不动点原理深入刻划循环不变式的含义,循环不变式可以表示为谓词泛函的最小不动点,并从范畴论的角度解释该过程.

CFD analysis of thermodynamic cycles in a pulse tube refrigerator

The objectives of this paper are to study the thermodynamic cycles in an inertance tube pulse tube refrigerator (ITPTR) by means of CFD method The simulation results show that gas parcels working in different parts of ITPTR undergo different thermodynamic cycles The net effects of those thermodynamic cycles are pumping heat from the low temperature part to the high temperature part of the system The simulation results also show that under different frequencies of piston movement the gas parcels working in the same part of the system will undergo the same type of thermodynamic cycles The simulated thermal cycles are compared with those thermodynamic analysis results from a reference Comparisons show that both CFD simulations and theoretical analysis predict the same type of thermal cycles at the same location However only CFD simulation can give the quantitative results while the thermodynamic analysis is still remaining in quality (C) 2010 Elsevier Ltd All rights reserved

Episodic gullying and paleomonsoon cycles on the Chinese Loess Plateau

IEECAS SKLLQG