Development of a Cell Size Relaxed Scheme for the Direct Simulation Monte Carlo Method

The conventional direct simulation Monte Carlo (DSMC) method has a strong restriction on the cell size because simulated particles are selected randomly within the cell for collisions. Cells with size larger than the molecular mean free path are generally not allowed in correct DSMC simulations. However, the cell-size induced numerical error can be controlled if the gradients of flow properties are properly involved during collisions. In this study, a large cell DSMC scheme is proposed to relax the cell size restriction. The scheme is applied to simulate several test problems and promising results are obtained even when the cell size is greater than 10 mean free paths of gas molecules. However, it is still necessary, of course, that the cell size be small with respect to the flow field structures that must be resolved.

Interface cracking and particulate size effect in particle-reinforced metal-matrix composites

The mechanical behaviors of the ceramic particle-reinforced metal matrix composites are modeled based on the conventional theory of mechanism-based strain gradient plasticity presented by Huang et al. Two cases of interface features with and without the effects of interface cracking will be analyzed, respectively. Through comparing the result based on the interface cracking model with experimental result, the effectiveness of the present model can be evaluated. Simultaneously, the length parameters included in the strain gradient plasticity theory can be obtained.

Dislocations and twins in nanocrystalline Ni after severe plastic deformation: the effects of grain size

Deformation microstructures have been investigated in nanocrystalline (nc) Ni with grain sizes in the 50-100 nm range. It was found that deformation twinning started to occur in grains of similar to 90 nm, and its propensity increased with decreasing grain size. In most of the nc grains dislocations were observed as well, in the form of individual dislocations and dipoles. It is concluded that dislocation-mediated plasticity dominates for grain sizes in the upper half, i.e. 50-100 nm, of the nanocrystalline regime. (C) 2007 Published by Elsevier B.V.

Bag and size limit analyses for red drum in Northern and Southern Regions of the U.S. Atlantic

Assessments of the Atlantic red drum for the northern (North Carolina and north) and southern (South Carolina through east coast of Florida) regions along the U. S. Atlantic coast were recently completed. The joint Red Drum Technical Committee (SAFMC/ASMFC) selected the most appropriate catch matrix (incorporating an assumption on size of recreationally-released fish), selectivity of age 3 relative to age 2, and virtual population analysis (FADAPT). Given gear- and age-specific estimates of fishing mortality (F) for the 1992-1998 period, analyses were made of potential gains in escapement through age 4 and static spawning potential ratio (SPR) from further reductions in fishing mortality due to changes in slot and bag limits. Savings from bag limits were calculated given a particular slot size for the recreational fishery, with no savings for the commercial fisheries in the northern region due to their being managed primarily through a quota. Relative changes in catch-at-age estimates were used to adjust age-specific F and hence calculated escapement through age 4 and static SPR. Adjustment was made with the recreational savings to account for release mortality (10%, as in the stock assessment). Alternate runs for the northern region commercial fishery considered 25% release mortality for lengths outside the slot (instead of 0% for the base run), and 0% vs. 10% gain or loss across legal sizes in F. These results are summarized for ranges of bag limits with increasing minimum size limit (for fixed maximum size), and with decreasing maximum size limit (for fixed minimum size limit). For the southern region, a bag limit of one-fish per angler trip would be required to attain the stated target of 40% static SPR if the current slot limit were not changed. However, for the northern region, a bag limit of one-fish per angler trip appears to be insufficient to attain the stated target of 40% static SPR while maintaining the current slot limit. (PDF contains 41 pages)

Size-dependent elastic properties of Ni nanofilms by molecular dynamics simulation

Size-dependent elastic properties of Ni nanofilms are investigated by molecular dynamics ( MD) simulations with embedded atom method (EAM). The surface effects are considered by calculating the surface relaxation, surface energy, and surface stress. The Young's modulus and yield stress are obtained as functions of thickness and crystallographic orientation. It is shown that the surface relaxation has important effects on the the elastic properties at nanoscale. When the surface relaxation is outward, the Young's modulus decreases with the film thickness decreasing, and vice versa. The results also show that the yield stresses of the films increase with the films becoming thinner. With the thickness of the nanofilms decreasing, the surface effects on the elastic properties become dominant.

The surface- and size-dependent elastic moduli of nanostructures

A theoretical model is presented to investigate the size-dependent elastic moduli of nanostructures with the effects of the surface relaxation surface energy taken into consideration. At nanoscale, due to the large ratios of the surface-to-volume, the surface effects, which include surface relaxation surface energy, etc., can play important roles. Thus, the elastic moduli of nanostructures become surface- and size-dependent. In the research, the three-dimensional continuum model of the nanofilm with the surface effects is investigated. The analytical expressions of five nonzero elastic moduli of the nanofilm are derived, and then the dependence of the elastic moduli is discussed on the surface effects and the characteristic dimensions of nanofilms.

Fixed Points of Closed and Compact Composite Sequences of Operators and Projectors in a Class of Banach Spaces

Some results on fixed points related to the contractive compositions of bounded operators in a class of complete metric spaces which can be also considered as Banach's spaces are discussed through the paper. The class of composite operators under study can include, in particular, sequences of projection operators under, in general, oblique projective operators. In this paper we are concerned with composite operators which include sequences of pairs of contractive operators involving, in general, oblique projection operators. The results are generalized to sequences of, in general, nonconstant bounded closed operators which can have bounded, closed, and compact limit operators, such that the relevant composite sequences are also compact operators. It is proven that in both cases, Banach contraction principle guarantees the existence of unique fixed points under contractive conditions.

M/V ELPIS Coral Reef Restoration Monitoring Report Monitoring Events 2004-2007 Florida Keys National Marine Sanctuary, Monroe County, Florida

This document presents the results of the first three monitoring events to track the recovery of a repaired coral reef injured by the M/V Elpis vessel grounding incident of November 11, 1989. This grounding occurred within the boundaries of what at the time was designated the Key Largo National Marine Sanctuary (NMS), now designated the Key Largo NMS Existing Management Area within the Florida Keys National Marine Sanctuary (FKNMS). Pursuant to the National Marine Sanctuaries Act (NMSA) 16 U.S.C. 1431 et seq., and the Florida Keys National Marine Sanctuary and Protection Act (FKNMSPA) of 1990, NOAA is the federal trustee for the natural and cultural resources of the FKNMS. Under Section 312 of the NMSA, NOAA has the authority to recover monetary damages for injury, destruction, or loss of Sanctuary resources, and to use the recovered monies to restore injured or lost sanctuary resources within the FKNMS. The restoration monitoring program tracks patterns of biological recovery, determines the success of restoration measures, and assesses the resiliency to environmental and anthropogenic disturbances of the site over time. To evaluate restoration success, reference habitats adjacent to the restoration site are concurrently monitored to compare the condition of restored reef areas with natural coral reef areas unimpacted by the vessel grounding. Restoration of the site was completed September 1995, and thus far three monitoring events have occurred; one in the summer of 2004, one in the summer of 2005, and the latest in the summer of 2007. The monitoring in 2004 was in the nature of a “pilot project,” or proof of concept. Only the quantitative results of the 2005 and 2007 monitoring are presented and discussed. Monitoring has consisted of assessment of the structural stability of limestone boulders used in the restoration and comparison of the coral communities on the boulders and reference areas. Corals are divided into Gorgonians, Milleporans, and Scleractinians. Coral densities at the Restored and Reference areas for the 2005 and 2007 events are compared, and it is shown that the densities of all taxa in the Restored area are greater by 2007, though not significantly so. For the Scleractinians, number and percentage of colonies by species, as well as several common biodiversity indices are provided. The greater biodiversity of the Restored area is evidenced. Also, size-class frequency distributions for Agaricia spp. (Scleractinia) are presented. These demonstrate the approaching convergence of the Restored and Reference areas in this regard. An inter-annual comparison of densities, within both areas, for all three Orders, is presented. The most noteworthy finding was the relative consistency across time for all taxa in each area. Finally, certain anomalies regarding species settlement patterns are presented. (PDF contains 48 pages.)

M/V WELLWOOD Coral Reef Restoration Monitoring Report, Monitoring Events 2004-2006. Florida Keys National Marine Sanctuary Monroe County, Florida

This document presents the results of the first two monitoring events to track the recovery of a repaired coral reef injured by the M/V Wellwood vessel grounding incident of August 4, 1984. This grounding occurred within the boundaries of what at the time was designated the Key Largo National Marine Sanctuary (NMS), now designated the Key Largo NMS Existing Management Area within the Florida Keys National Marine Sanctuary (FKNMS). Pursuant to the National Marine Sanctuaries Act (NMSA) 16 U.S.C. 1431 et seq., and the Florida Keys National Marine Sanctuary and Protection Act (FKNMSPA) of 1990, NOAA is the federal trustee for the natural and cultural resources of the FKNMS. Under Section 312 of the NMSA, NOAA has the authority to recover monetary damages for injury, destruction, or loss of Sanctuary resources, and to use the recovered monies to restore injured or lost sanctuary resources within the FKNMS. The restoration monitoring program tracks patterns of biological recovery, determines the success of restoration measures, and assesses the resiliency to environmental and anthropogenic disturbances of the site over time. To evaluate restoration success, reference habitats adjacent to the restoration site are concurrently monitored to compare the condition of restored reef areas with “natural” coral reef areas unimpacted by the vessel grounding or other injury. Restoration of the site was completed on July 22, 2002, and thus far two monitoring events have occurred; one in the Fall of 2004, and one in the Summer/Fall of 2006. The monitoring has consisted of: assessment of the structural stability of restoration modules and comparison of the coral recruitment conditions of the modules and reference sites. Corals are divided into Gorgonians, Milleporans, and Scleractinians and (except where noted) recruits are defined as follows: Gorgonians—maximum size (height) 150 mm at first monitoring event, 270 mm at second; Milleporans—maximum size (height) 65 mm at first event, 125 mm at second; Scleractinians—maximum size (greatest diameter) 50 mm at second event (only one species was size-classed at first event, at smaller size). Recruit densities at the restored and reference areas for each event are compared, as are size-class frequency distributions. For the Scleractinians, number and percentage of recruits by species, as well as several common biodiversity indices are provided. Finally, a qualitative comparison of recruit substrate settlement preference is indicated. Generally, results indicate that restored areas are converging on reference areas, based on almost all parameters examined, with one noted exception. Further monitoring is planned and the trends are anticipated to continue; close attention will be paid to the indicated anomaly. (PDF contains 63 pages.)

Species and size relationships within schools of yellowfin and skipjack tuna as indicated by catches in the Eastern Tropical Pacific Ocean

ENGLISH: Yellowfin tuna, Neothunnus macropterus, and skipjack tuna, Katsuwonus pelamis, are fished intensively off the west coast of the Americas in an area from about the California-Mexico border in the north to the Peru-Chile border in the south. The historical development of this fishery, and its expansion by the long-range California fleets of bait and purse-seine vessels, are well documented by Godsil (1938), Scofield (1951) and Shimada and Sehaefer (1956). The quarterly distribution of the tuna catches within this area has been reported for some recent years by Alverson (1959). SPANISH: Los atunes aleta amarilla, Neothunnus macropterus, y barrilete, Katsuwonus pelamis, son pescados con intensidad frente a la costa occidental del continente americano, en un área comprendida más o menos entre la frontera California-México en el norte y el límite Perú-Chile en el sur. El desarrollo histórico de esta pesquería y la expansión que le han dado las flotas californianas de largo radio de acción, formadas por los barcos de carnada y rederos, están bien documentados por Godsil (1938), Scofield (1951) y Shimada y Schaefer (1956). La distribución trimestral de las pescas de atún dentro de esta área ha sido tratada por Alverson (1959) con referencia a años recientes.

复合材料及其结构的力学、设计、应用和评价（第一册）

复合材料结构的力学性能

复合材料及其结构的力学进展（第三册）

岩石介质流变学

第一章 绪论
1.一维情况
2.平衡方程和波动理论基础
第二章 塑性力学和粘塑性力学中的一维本构方程、初值问题和边值问题
1.一维经典塑性力学问题的某些本构方程
2.半线性和拟线性率型本构方程
3.瞬态塑性应变的率型本构方程
4.特征线场，初值问题和边值问题
5.例子
第三章 理论的实验基础
1.静态实验
1.1常规试验
1.2长程试验
1.3短程试验
1.4Portevin-LeChatelier效应
2.杆的动态纵向撞击
3.重复加载试验
3.1静态加载后再动态加载
3.2动态加载后动态重复加载
第四章 用数值方法确定本构方程
1.用于数值例子中的本构方程
2.初始条件与边界条件
3.冲击波
4.数值例子
5.模型之间的比较
6.结论和某些评论
第五章 一维率型本构方程
1.动态重复加载实验对率型本构方程所加的限制条件
2.率型材料的稳态运动
3.关于率型材料的微分方程（5.1.2）的解
4.本构假设Ⅰ和Ⅱ的结论
5.关于动塑性中“平台”存在的评论
第六章 内变量描述的非弹性性状
1.加在带内变量的本构方程上的热力学限制
1.1状态空间，本构方程
1.2加在本构方程上的CLAUSIUS-DUHEM不等式的实质
2.加在本构方程的耗损部分上的热力学限制
3.构架无关原理.材料的同格群
4.对单位自由能限制的意义
5.具有内部状态变量的弹—粘塑性模型
6.具有内变量的一维塑性理论
第七章 具有内变量的材料中的加速度波
1.引言
2.拟线性假设
3.对称加速度波
4.强平衡态.强椭圆率条件
5.实加速度波
6.第二对称假设和强平衡态附近的热流
7.线性理论
8.半线性理论
第八章 经典粘塑性力学中的某些本构方程
1.BINGHAM刚/粘塑性模型
2.弹—粘塑性模型
3.拟线性模型
第九章 岩石的粘塑性本构方程
1.引言
2.标准压缩试验
3.蠕变试验
4.体积压缩性
5.结论
第十章 一维粘塑性本构方程在连续统物理的其他领域中的应用
1.引言
2.拟线性率型本构方程，电线上的实波和对称波
3.线性率型本构方程
4.关于模拟电晕效应的半线性率型本构方程
4.1一般考虑
4.2实验结果的简短描述
4.3本构方程用于数值例子
4.4数值结果与实验结果的比较
4.5关于所讲座的模型的评论和结论
5.电晕效应和波传播的与速率无关的模型
5.1引言
5.2问题的表述
5.3数值例子
5.4结论要点
第十一章 流变学模型在岩体工程中的应用
1.油井周围岩石的里面蠕变、膨胀及压缩
1.1基本方程
1.2线弹性解
1.3线性粘弹性岩石
1.4弹性/粘塑性岩石
1.5井眼周围岩石的膨胀/压缩及损伤
1.6更一般的原始应力状态
2.水平井段周围岩石的蠕变、膨胀及压缩
2.1基本方程
2.2弹性解
2.3线性粘弹性模型下水平井段周围岩石的蠕变
2.4弹性/粘塑性模型的蠕变
2.5水平井段周围岩石的蠕变、膨胀/压缩，损伤破坏
3.开挖后的岩体高边坡流变学性状的分析
3.1简介
3.2岩体流变学模型
3.3有限元分析
3.4数值结果
3.5结论
附录实验数据分析中所使用的数值方法和程序
1.引言
2.问题的表述
3.迭代方法的原理
4.卸载描述
5.边界条件
6.程序方框图
7.关于RI情况的要点
8.其他的特征线方法变量
9.要点
参考文献

力学: 迎接21世纪新的挑战