真实感图形渲染算法的研究与实现

真实感图形是一种计算机图形生成技术,其关键技术主要包括光照模型、渲染算法、纹理映射、材质设置、颜色量化等方面。本文主要就我们开发的交互式真实感图形渲染系统中采用的各种渲染算法(深度缓冲算法、光线跟踪和辐射度算法)作详细介绍。     

空间元数据系统的研究与设计

本文介绍了空间元数据的基本概念，分析了空间元数据标准和空间元数据系统研究的现状和面临的困难，提出了一种有效的空间元数据系统模型，用于采集、管理、维护和发布空间元数据，并实现空间元数据的快速查询和准确定位。     

平行工程与海洋石油平台的设计和建造

鉴于国外现代舰船设计、建造发展的新趋势,主张在海洋石油平台设计、建造中引入“平行工程”这一新概念,即从项目一开始就让建造者与用户参与项目顶层建造策略的制定。     

Identification of the Sex Pheromone of the Currant Shoot Borer Lampronia capitella

Under an artificial light:dark cycle, females of Lampronia capitella were observed calling, with extended terminal abdominal segments, during the first 2 hr of the photoperiod. Extracts of terminal abdominal segments from females elicited large electroantennographic responses from male antennae. Gas chromatography with electroantennographic detection revealed three active peaks. Based on comparison of retention times and mass spectra of synthetic standards, these compounds were identified as (Z,Z)-9,11-tetradecadienol and the corresponding acetate and aldehyde. The electroantennographic activity of the four geometric isomers of all three compounds was investigated, and the respective (Z,Z)-isomer was found to be the most active in all cases. Aldehydes generally elicited larger antennal responses than alcohols, whereas acetates were the least active compounds. A subtractive trapping assay in the field, based on a 13:26:100 micrograms mixture of (Z,Z)-9,11-tetradecadienal, (Z,Z)-9,11-tetradecadienyl acetate, and (Z,Z)-9,11-tetradecadienol confirmed that all three compounds are pheromone components. Subtraction of (Z,Z)-9,11-tetradecadienol from the blend completely eliminated its attractiveness, whereas the other two-component blends showed reduced activity. This is the first pheromone identification from the monotrysian superfamily Incurvarioidea, confirming that the common pheromones among ditrysian moths (long-chain fatty acid derivatives comprising alcohols, acetates, and aldehydes with one or more double bonds) is not an autapomorphy of Ditrysia, but a synapomorphy of the more advanced heteroneuran lineages.     

A Refinement Strategy for Circus

We present a refinement strategy for Circus, which is the combination of Z, CSP, and the refinement calculus in the setting of Hoare and Hes unifying theories of programming. The strategy unifies the theories of refinement for processes and their constituent actions, and provides a coherent technique for the stepwise refinement of concurrent and distributed programs involving rich data structures. This kind of development is carried out using Circuss refinement calculus, and we describe some of its laws for the simultaneous refinement of state and control behaviour, including the splitting of a process into parallel subcomponents. We illustrate the strategy and the laws using a case study that shows the complete development of a small distributed program.     

vBSP的算法设计与应用

BSP数据结构已经在大规模的游戏引擎产品中取得了突破性的成功,但是在现实应用中还有许多需要实际改进后才能应用。为此,改进BSP开发出一种简单、灵活的解决方案,即虚拟BSP(vBSP)来解决应用实际应用。通过研究并改进原始的BSP树,意在使BSP树简单化、实用化,并可以减少算法的复杂度,降低其它改进算法的负面影响。基于"空间换时间"的思想,通过开辟引用存储空间而不是直接分割BSP树的方法,最终达到提高算法的实用性。     

答疑系统问题的Z语言规约

分析了目前答疑系统存在的不足之一,即缺少标准框架,从而很难实现答疑系统之间资源的共享.因此提出了使用形式化方法来构建统一的答疑系统,利用形式化语言Z对答疑系统的主要模块进行需求规格说明.同时用Z语言描述了答疑系统的主要操作模式,包括关键词的提取、问题的检索和知识库的更新等操作.     

Failure behavior of Zircaloy-4 cladding after oxidation and water quench

Simulated LOCA (loss of coolant accident) tests and subsequent mechanical tests on Zircaloy-4 cladding were carried out to evaluate the failure behavior of the cladding. Zircaloy-4 claddings were oxidized in a steam environment from 900 to 1250 °C for a given time period followed by a flooding of cool water to simulate LOCA tests. After the simulated LOCA test, the ductility of the oxidized cladding was evaluated by mechanical tests such as ring compression test and 3-point bend test. Evaluation of the absorbed contents such as hydrogen and oxygen were also carried out. The results showed that Zircaloy-4 cladding failed during thermal shock when the ECR (equivalent cladding reacted) value exceeded 20%. Lower boundary of brittle failure at thermal shock corresponds to 20% of ECR line calculated by the Baker-Just equation regardless of test temperature. On the other hand, boundary of ductile failure by the mechanical test did not followed after the ECR line. It rapidly decreased above 1000 °C to show that all Zircaloy-4 claddings behaved brittle fracture above 1150 °C when it oxidized at 300 s. Microstructural analysis revealed that boundary of ductile failure by the mechanical test fitted well when the absorbed oxygen content inside the prior-β layer was below 0.5 wt%.     

Characterization of hot deformation behavior of Zr-1Nb-1Sn alloy

The hot deformation behavior of β-quenched Zr-1Nb-1Sn was studied in the temperature range 650-1050 °C and strain rate range 0.001-100 s⁻¹ using processing maps. These maps revealed three different domains: a domain of dynamic recovery at temperatures <700 °C and at strain rates <3 × 10⁻³ s⁻¹, a domain of dynamic recrystallization in the temperature range 750-950 °C and at strain rates <10⁻² s⁻¹ with a peak at 910 °C and 10⁻³ s⁻¹ (in α + β phase field), and a domain of large-grain superplasticity in the β phase field at strain rates <10⁻² s⁻¹. In order to identify the rate controlling mechanisms involved in these domains, kinetic analysis was carried out to determine the various activation parameters. In addition, the processing maps showed a regime of flow instability spanning both α + β and β phase fields. The hot deformation behavior of Zr-1Nb-1Sn was compared with that of Zr, Zr-2.5Nb and Zircaloy-2 to bring out the effects of alloy additions.     

LFMCW雷达运动目标高精度检测方法

LFMCW雷达检测运动目标，可以采用对称三角LFMCW信号，通过频域配对实现动目标距离、速度的去耦合。但是在实现时，如果只采用传统的FFT作为核心算法就会引起较大的测距、测速误差。本文采用FFT-CZT两级处理方法，从而在运算量增加不多的情况下，显著提高LFMCW雷达的动目标测距、测速精度。仿真结果表明，本方法适用于各种带宽的LFMCW雷达，具有通用性。