A PDES/STEP-based model and system for concurrent integrated design and assembly planning

Product data exchange and interfacing between different CAD/CAM systems are of great importance to the development of concurrent integrated design environments and computer integrated manufacturing systems. This paper presents a STEP-based method and system for concurrent integrated design and assembly planning. An integrated object model for mechanical systems and assemblies is first defined by a hierarchy of structure, geometry and feature. The structure is represented as a component-connector or joint multi-level graph with both hierarchical functional and assembly relations. These hierarchical relation models are then used for uniformly describing their causal relations both for assembly level and feature based single part level. The generic product assembly model is organized according to STEP, using mostly the entities of integrated resources and partly self-defined entities, which are necessary for design and assembly planning. Based on the generic product assembly model, STEP-based strategies and agent concepts are used for agent-based concurrent integration of design and assembly planning. A prototype system, consisting of a CAD system, a product modeling system, an assembly planning system, and an assembly evaluation system is developed, in which product data can be exchanged between these subsystems. Details about the implementation of the system are addressed. The integrated design and assembly planning system can support the introduction of a new product. The results of assembly planning are feedback to the stage of assembly design to improve on the design. A case study is carried out for assembly-oriented design of a gearbox, to illustrate the proposed approach and to validate the developed system.     

面向需求面向服务(上)——深圳广播电影电视集团网络化建设实践

本文从深圳广播电影电视集团网络化建设实践出发,针对电视台全台网系统的建设、维护两大阶段的相关问题,提出了面向需求的网络系统架构模式和面向服务的网络系统运维管理模式,对广电媒体行业的网络系统架构和运维管理的模式和方法进行了初步的探讨.     

Quantitative detection of change in grass cover from multi-temporal TM satellite data

In this paper, change in grassland cover near Lake Qinghai, west China was quantitatively detected from satellite remote-sensing data. Two Thematic Mapper images recorded in 1987 and 2000 were radiometrically corrected and used to derive the Normalized Difference Vegetation Index (NDVI). The NDVI image in 2000, after standardization via in situ measured spectra, was converted to a map of grass cover with the aid of in situ grass-cover samples. Another map was produced from the 1987 image after it was radiometrically benchmarked to the 2000 image using the calibration to like-values method. Comparison of these two maps revealed that a total of 36.28 km² of grassland had a higher cover, versus 44.72 km² that experienced grassland degradation in the study area. The absolute cover changed by a net value of??1.27%. The magnitude of change is related inversely to the value of the cover. The large majority of the area (82.6%), however, had a small change that was within ±20%. With this proposed method, it is possible to quantify changes in grassland cover from multi-temporal satellite data if one set of ground samples are concurrently collected with one of the satellite images.     

Remote sensing of phycocyanin pigment in highly turbid inland waters in Lake Taihu,China

Cyanobacterial blooms are an environmental issue that can cause health hazards by toxins and malodorous compounds. The pigment phycocyanin is indicative of cyanobacterial presence. In eutrophic inland waters in which nitrogen is not a limiting nutrient, the phycocyanin concentration (PC) is closely related to cyanobacterial biomass. This study proposes a simple semi-analytical four-band algorithm for PC estimation to overcome the deficiency of existing algorithms. This algorithm was calibrated using a data set collected from Lake Taihu in 2007. Optimal reference wavelengths for the algorithm were located through model tuning and accuracy optimization. The algorithm was evaluated for its accuracy against an independent data set collected in 2008. The performance of the algorithm was also compared with that of the nested band-ratio algorithm, which was developed for PC estimation in turbid waters.

Although both algorithms enabled the establishment of a linear relationship between measured and predicted PC, the nested band-ratio algorithm did not have a satisfactory performance with either data set, having a high level of uncertainty. Its mean relative error stands at 51.07% and 51% for the 2007 and 2008 data sets, respectively. It accounted for 68% and 74% of the variation in PC in the 2007 and 2008 data sets, respectively. The four-band algorithm worked well in PC estimation. It accounted for 87% of the variation in PC for the 2007 data set and 86% of the variation in the 2008 data set. Furthermore, it decreased estimation uncertainty, compared with the nested band-ratio algorithm, by more than 20%. The values of mean relative error for the correspondence data sets are 29.1% and 30%. Therefore, the proposed four-band algorithm holds great potential in estimating PC in highly turbid waters.     

Temporal filtering of successive MODIS data in monitoring a locust outbreak

The emergence of high temporal resolution satellite data such as MODIS enables timely monitoring of locust outbreaks from space. This monitoring is hampered by the effect of random atmospheric variations on satellite imagery, which may be suppressed through temporal filtering. This paper aims to evaluate the utility of temporally filtering successive MODIS data in monitoring an outbreak in East China. Of the eight vegetation indices examined, the commonly used NDVI was the most indicative of varying vegetation conditions caused by locust infestation inside the study area. The averaging of three successive days of satellite data improves the R ² value of NDVI regression models by 0.227 over single‐day data. It also outperforms the data averaged from two successive days (a broader window size was not attempted due to the short span of the study period). Temporally, NDVI changed at varying rates daily during the outbreak. Early in the outbreak it increased at a reduced pace until 7.5 days. Afterwards it started to decrease at an accelerated rate. If temporally filtered with a proper window size, successive MODIS data allow the outbreak to be monitored accurately (R ² = 0.696).     

浅谈建筑外窗热工的计算方法

进入21世纪后节约能源已经是全世界共同关注的问题，我们国家针对我国的国情，对建筑外窗的节能指标也提出了更高的要求。以北京为例，《北京市标准住宅建筑门窗应用技术规范》要求建筑外窗的传热系数不能大于2．8W／（m^2·K），如何才能达到这个指标？又如何计算外窗的传热系数呢？本文将以一个标准的外窗为例，介绍一种外窗传热系数的计算方法。     

Cyclic voltammograms obtained from the optical signals: Study of the successive electro-oxidations of rutin

This paper describes a novel method of obtaining cyclic voltammograms (CVs) from optical signals. The obtained CVs correspond to the various specific species involved in the electrode process, which give more detailed information on the system under investigation than the common CV. For this purpose cyclic voltabsorptometry was used to investigate the successive oxidation processes of rutin on a graphite-wax electrode by using a long optical-path thin-layer electrochemical cell. The dynamic UV spectra of rutin showed the information on the structures of the oxidation products at different potentials. Cyclic voltabsorptiograms (CVAs) were measured in three potential ranges at the characteristic absorption wavelengths of rutin, 346, 254 and 296 nm, respectively. The CVs of three species in solution (rutin and its two products) were obtained from the derivative cyclic voltabsorptiograms (DCVAs). Based on this the redox mechanisms of rutin in different CV peaks were discussed.     

城市轨道交通无缝线路施工技术探讨

文章探讨了城市轨道交通无缝线路铺设新工艺,经期能科学有效地提高无缝线路施工进度及焊接和铺设质量。     

科马格街区空间改造

与其他历史悠久的城市一样，丹麦首都哥本哈根市是有序和随意的规划设计共同作用的结果，它不仅继承了城市的人文建筑遗产，还体现了城市有机发展的过程。本项目位于哥本哈根市中心，紧挨着斯特罗里耶步行街。我们的设计力求在历史与现代、本地化与国际化以及动态与静止之间寻找平衡。黑白相间的石材铺装，营造出视觉上的美学连贯性。     

东营凹陷沙三段泥岩盖层超压演化及其对油气成藏的影响

泥岩盖层封闭性随超压演化呈阶段性变化,在超压释放期封闭性降至最低点,随着泥岩的愈合,超压逐渐增大,封闭性也逐渐增强,直至超压再一次释放.经计算,东营凹陷沙三段泥岩超压在埋深904～1 713m开始形成,在埋深2 200～2 800m开始第1次释放.据此评价了沙三段泥岩盖层的封闭能力及其对油气成藏的影响.研究结果表明:①东营凹陷沙三段泥岩超压形成于沙一段-东营组沉积早期,而深部烃源岩的大量排烃期为馆陶期,超压形成期比排烃期早,因此超压泥岩能够有效地封闭烃源岩生成大量的油气;②沙三段泥岩超压在馆陶组沉积末期发生第1次释放,而后泥岩愈合,超压再次增加,目前正处于第2次超压演化过程中;③现今沙三段泥岩超压值约为8MPa,具有较强的超压封闭能力,是深层油气成藏的重要条件之一.