基于视觉感知增强的最大密度投影算法

提出一种基于视觉感知增强的最大密度投影算法,无需调节复杂的传输函数,就可以有效增强体数据内部最大密度特征的深度感知和形状感知.在传统的最大密度投影算法的基础上,利用梯度模属性精确查找特征或相似特征的边界,以确定最佳法向特征;利用最佳法向特征的深度信息自适应地修改局部光照系数,进而对最大密度特征进行光照处理,以获得视觉感知增强的可视化结果;采用基于密度值和三维空间距离的双阈值区域增长策略,动态区分感兴趣区域和背景区域,交互地实现特征突出显示.实验结果表明,该算法在传统算法的基础上进一步增强了最大密度特征的视觉感知,并提供了丰富的形状信息和背景补偿信息,具有较强的实用性.     

Weight functions for the determination of stress intensity factor and T‐stress for semi‐elliptical cracks in finite thickness plate

This paper presents the application of weight function method for the calculation of stress intensity factors (K) and T‐stress for surface semi‐elliptical crack in finite thickness plates subjected to arbitrary two‐dimensional stress fields. New general mathematical forms of point load weight functions for K and T have been formulated by taking advantage of the knowledge of a few specific weight functions for two‐dimensional planar cracks available in the literature and certain properties of weight function in general. The existence of the generalised forms of the weight functions simplifies the determination of specific weight functions for specific crack configurations. The determination of a specific weight function is reduced to the determination of the parameters of the generalised weight function expression. These unknown parameters can be determined from reference stress intensity factor and T‐stress solutions. This method is used to derive the weight functions for both K and T for semi‐elliptical surface cracks in finite thickness plates, covering a wide range of crack aspect ratio (a/c) and relative depth (a/t) at any point along the crack front. The derived weight functions are then validated against stress intensity factor and T‐stress solutions for several linear and nonlinear two‐dimensional stress distributions. These derived weight functions are particularly useful for the development of two‐parameter fracture and fatigue models for surface cracks subjected to fluctuating nonlinear stress fields, such as these resulting from surface treatment (shot peening), stress concentration or welding (residual stress).     

A sectoral decomposition analysis of Turkish CO2 emissions over 1990–2007

At a time of increased international concern and negotiations for greenhouse gas emission reduction, country studies on the underlying effects of greenhouse gas emission growth gain importance. The case of Turkey is particularly interesting due to rapidly growing emissions, accompanied by a political will and actions to reduce the quick growth. The refined Laspeyres method is used in this study to identify factors that accelerate or reduce the increase in Turkish CO₂ emissions. A year-by-year decomposition over 1990-2007 is carried out at sectoral level based on disaggregated data that is consistent over time and consistent with international standards. Various interesting results on the underlying effects of sectoral emission growth are found. Valuable insights are gained into CO₂ impacts of sectoral policies including energy and emission intensities, fuel switching and activity changes. The results yield important hints for the planning of energy and climate policy.     

Room Airflow Studies Using Sonic Anemometry

Abstract To ensure prompt response by real-time air monitors to an accidental release of toxic aerosols in a workplace, safety professionals should understand airflow patterns. This understanding can be achieved with validated computational fluid dynamics (CFD) computer simulations, or with experimental techniques, such as measurements with smoke, neutrally buoyant markers, trace gases, or trace aerosol particles. As a supplementary technique to quantify airflows, the use of a state-of-the art, three-dimensional sonic anemometer was explored. This instrument allows for the precise measurements of the air-velocity vector components in the range of a few centimeters per second, which is common in many indoor work environments. Measurements of air velocities and directions at selected locations were made for the purpose of providing data for characterizing fundamental aspects of indoor air movement in two ventilated rooms and for comparison to CFD model predictions. One room was a mockup of a plutonium workroom, and the other was an actual functioning plutonium workroom. In the mockup room, air-velocity vector components were measured at 19 locations at three heights (60, 120 and 180 cm) with average velocities varying from 1.4 cm s^?1 to 9.7 cm s^?1. There were complex flow patterns observed with turbulence intensities from 39% up to 108%. In the plutonium workroom, measurements were made at the breathing-zone height, recording average velocities ranging from 9.9 cm s^?1 to 35.5 cm s^?1 with turbulence intensities from 33% to 108%.     

高能超声处理对原位Al3Ti/A356复合材料显微组织和力学性能的影响

采用熔体直接反应法,以工业钛剂和A356合金为反应物,利用高能超声原位合成了Al3Ti/A356复合材料。利用X射线衍射与扫描电镜对该复合材料的微观组织和物相组成进行分析,并通过拉伸实验对该复合材料的力学性能进行测试。结果表明,经过高能超声处理后,复合材料中的Al3Ti颗粒尺寸较高能超声处理前明显变小,分布也更均匀。当超声功率为1.2kW/cm2,超声作用时间为360s时,颗粒尺寸最小,为0.5～2μm。复合材料的抗拉强度、屈服强度和伸长率分别达到281.83、226.72MPa和5.6%,较未施加高能超声的复合材料分别提高了16.2%、10.3%和33.3%。     

Approximate Closed from Weight Function for an Elliptical Crack in an Infinite Body

It have been reported that in literature there exists some number of approximate closed form weight functions for elliptical crack in an infinite body. The general procedure for refining them by Rice's integral formula is suggested. A tentative formula obtained in this way has been numerically verified by a carefully elaborated procedure. For uniform loading the accuracy of suggested formula lies within 6 percent of the strict solution. The practical usage of the formula in the point weight function method for semi-elliptical crack is demonstrated. This revised version was published online in July 2006 with corrections to the Cover Date.     

电捕焦油器中焦油雾滴预团聚过程的研究

为了提高电捕焦油器对超细焦油雾滴的捕集效率,提出声波法和荷电法两种焦油雾滴的预团聚方法,并对采用这两种方法的雾滴预团聚过程进行了数值模拟,研究了声波频率和电场强度对雾滴预团聚效率的影响.     

钢纤维混凝土断裂过程测试与力学性能

为了研究钢纤维混凝土的断裂过程和承载力的估算方法，通过加载试验机分别对四种不同尺寸的钢纤维混凝土试件进行楔入式劈裂断裂实验，并对其中两个试件粘贴应变片进行跟踪电测。实验得到了一系列载荷–位移关系曲线，由数据计算获得各个试件的载荷与张开位移关系曲线，以及断裂损伤区变形随载荷变化曲线。结合黏聚裂纹应力强度因子与双 断裂准则，对各组试件的承载力进行估计，并将其计算值与实验结果的平均值作比较，两者较吻合；表明用断裂力学原理分析该类材料结构的初期失效，和估计中小尺寸构件的承载能力是可行的。