红壤丘陵区土地利用变化对土壤质量影响

以鄂南红壤丘陵典型区的三个村为代表 ,应用地理信息系统对 1981和 1998年两个时期的土地利用变化和土壤质量进行对比研究 ,分析了土地利用变化对土壤质量的影响。结果表明 :研究区土地利用结构总体上具有农业型特点 ,17a间水田减少了 2 1% ;其余的利用方式则有不同幅度的增加 ,居民地、水域、林地、园地和旱地增加了 4 2 .2 %、99.6 %、8%、5 6 .8%和 8%。土壤质量有从优劣两端向中等靠拢的趋势 ,17a后 、 、 和 等地面积分别减少 18.6 %、12 .2 %、2 9.6 %和 2 5 % ; 等地增幅达 5 1.9%。土地利用方式及管理措施是影响土壤质量演变方向和强度的关键因子 ,园地和林地的土壤质量大多得到明显改善 ,水田的Δ SQI多数呈下降的趋势 ,旱地的土壤质量变化比较复杂 ,与土地利用结构相关。依此 ,本文探讨了定向培育土壤质量的途径     

Sensitivity of Ozone Production to the Nmhc Composition, Aerosol Back-Scattering and High Chimney Emission

In this paper, three sensitivity studies are designed to analyze the effect of the NMHC (Non-Methane HydroCarbon) composition, the aerosol back-scattering and the high chimney NO_x emission to the photochemical prodution of ozone by using a one-dimensional photochemistry-diffusion model under a favourable meteorological condition. Measurements of the NMHC composition in Taipei indicated that the percentage of iso-butene, cis-2-butene, trans-2-butene and benzene in a unit volume was much higher than of those observed in other major cities. the high ratio of benzene was directly linked to its high percentage in gasoline. As to the unusually high amount of iso-butene, cis-2-butene and trans-2-butene, more researches are needed to identify their source. Concerns are raised as to how productive is NMHC composition is to the photochemical production of the surface ozone. A rough estimate shows that the total reactivity of the Taipei NMHC composition is about 1.21 × 10^-9 cm³ s^-1 which is 1.6 times that of the Los Angeles (LA) NMHC composition, while the simulated noon peak will be different by 28 ppbv, i.e. 18% more than that simulated with a LA composition.

Meanwhile, high aerosol loading is a serious problem in Taipei. the attenuation of the UV radiation by aerosols cannot be ignored. A numerical simulation shows that the noon ozone level will decrease from 178 to 141ppbv, i. e. about 21% reduction, with deterioration of the visual range from 85 to 5 km.

In the southern Taiwan, industry parks are mixed with the populated Kaohsiung city, hence the large emission of NO_x from high chimneys cannot be ignored. in this study, NO_x is assumed to be emitted in the layer between 235-460 m high with an emission rate of 0.05 or 0.145 ppbv/sec. the results show that the NO_x emitted from the elevated stack lead to a considerable reduction of surface ozone. Such conclusion is obtained due to the fact that a one-dimensional model is used in this paper. Whereas, if a three-dimensional regional model was used, then a higher productivity of ozone downstream would be simulated.     

公路运输化学事故应急救援体系研究

以动态源的定义为基础 ,结合危化品公路运输特殊性 ,阐述了危化品在公路运输过程中发生化学事故后应急救援的原则、工作特点与基本要求 ;提出化学事故应急救援中的基本任务是控制危险源 ,抢救受害人员 ,指导并组织群众疏散、自救和做好事故现场清理洗消工作 ,消除危害后果 ;提出公路运输化学事故应急救援预案系统建设的总体目标是 ,在应用ITS智能交通系统对动态源精确定位的基础上 ,建立公路运输化学事故应急救援预案动态库及应急救援组织保障系统和应急救援技术支持系统 ,一旦事故发生 ,能够做到尽快有效处理 ,最大限度地减小或消除事故损失。     

基于证书权威(CA)中心的时间戳服务系统的实现

介绍了数字签名不具有抗抵赖的问题 ,以及数据抗抵赖在信息安全中的重要性。在对原有的时间戳协议缺乏可靠的身份认证和可信性分析后 ,提出了一种新的基于证书权威 (CA)中心的时间戳服务协议。利用CA中心的信任原理和数字证书的身份认证作用 ,使提供时间戳服务的服务方具备了可靠的身份鉴别和可信性。并利用XML标记对时间戳的数据内容进行描述 ,形成简单、直观的时间戳 ,且无需复杂的编解码过程。通过正确和可信的时间戳可以判定用户数据产生的时间 ,防止用户事后的抵赖行为 ,为网络应用提供更为安全的数据。     

混合气体爆炸性MFC图形分析

判断混合气体爆炸性常用 3种方法 ,即科瓦德爆炸三角形法、美国矿业局采用的爆炸三角形计算法和最小助燃氧浓度法 ,然而如何准确、快速、形象地得到分析结果在防灾救灾中是十分关键的。笔者的重点是提供一个图形分析方法解决上述问题。VC ++是方法的基本理论依据 ,用一个实例来验证方法的有效性。总之 ,研究表明 :图形分析法可提高安全管理效率。     

Radiation Effects on Blends of Poly(ε-Caprolactone) and Diatomites

Poly(-caprolactone) (PCL) was blended with diatomaceous earth (diatomite) and irradiated with -rays to introduce cross-linking between PCL molecules or both components. The unwashed diatomite containing a little of a volatile component showed high efficiency of introduction of cross-linking, whereas that with no volatile component showed low efficiency of introduction of cross-linking. Elongational viscosity, melt viscosity, and modulus of PCL/diatomite blend irradiated at various doses were significantly improved. Enzymatic degradation of the PCL/diatomite blend became faster than that of the PCL, though that of the blend irradiated became slower.     

THERMAL GRADIENTS IN RIVERS AND RESERVOIRS DUE TO HEATED PLANT EFFLUENTS1

ABSTRACT The direction of heated effluents from large thermal power plants into streams and lakes has been a matter of public concern for some time, and the collection of prototype data related to the hydraulic aspects has taken on massive proportions. Unfortunately, most of the data are proprietary and not available for public analysis. The authors have endeavored to collect such data as are available to them for the initiation of steps toward generalization and the discussion of some of the more evident hydraulic considerations. The study is primarily concerned with rivers, including estuaries, with some interest in cooling ponds.     

Effects of Poly(Ethylene Glycol) on the Production of Poly(β-Hydroxybutyrate) by Azotobacter vinelandii UWD

Azotobacter vinelandii UWD, ATCC 53799, an engineered strain derived from Azotobacter vinelandii UW was used in the poly(ethylene glycol) (PEG)-modulated synthesis of poly(-hydroxybutyrate) (PHB). To the best of our knowledge, this is the first report on modulating the production of PHB by amending the fermentation broth with PEG using A. vinelandii UWD. It was determined that A. vinelandii UWD is prone to back-mutation to the parent strain; hence fermentation experiments require the use of the antibiotic rifampicin. Diethylene glycol (DEG) and PEGs with molecular weights of 400, 2000, and 3400 Da and pentaerythritol ethoxylate (PEE) were used in the modulated fermentation experiments in a concentration of 2% (w/v). The molecular weight of the resulting polymers was reduced by up to 78%. No impact on the productivity of the strain was observed. Spectroscopic evidence showed that PEG-modulated synthesis resulted in the covalent attachment of the ethylene glycol moiety only when a small molecule, DEG, was used. PEGs had the same effects on the polymer formation in terms of molecular weight reduction as DEG, but no spectroscopic evidence was found for the formation of a covalent linkage between PHB and higher molecular weight PEGs.     

Bioremediation of Chromate by Sulfate-Reducing Bacteria, Cytochromes c3 and hydrogenases

The treatment of soils and ground waters polluted by heavy metals is of economical and environmental interest. Reduction of Cr(VI) to the less toxic Cr(III) associated to its precipitation is a potentially useful process for bioremediation. In order to develop ecological processes using micro-organisms, we have compared various sulfate-reducing bacteria for enzymatic reduction of chromate. The best Cr(VI) reductase activity was obtained with Desulfomicrobium norvegicum. Despite morphological changes induced by the presence of chromate, this strain can grow in the presence of up to 500 M Cr(VI) and can decontaminate waters polluted by Cr(VI) when seeded in bioreactors. We have demonstrated the ability of several metalloenzymes (cytochromes c ₃ and hydrogenases) to reduce chromate. Biophysical investigations of the chromate/protein interaction in order to get further informations on the mechanism of metal reduction by cytochromes c ₃ are under the way.     

Emergency seed aid in Kenya: some case study insights on lessons learned during the 1990s

This article reviews the effectiveness of seed-aid distributions in Kenya during the 1990s. It analyses the internal process and effects, i.e. the performance of the aid itself as well as the external process and effects, i.e. how seed-aid intervention affected farmers' broader agricultural management strategies. During the drought emergency of 1997, Kenyan farmers favourably judged many of the immediate seed-aid features such as crop and variety appropriateness and seed quality--even through the overarching goals of the seed assistance were muddled, ranging from assistance to the poor, to generalised gift-giving to stimulating progressive farming practice. However, the longer term analyses, drawn from recollections of a decade of relief activity, showed no concrete evidence that seed aid, per se, had strengthened their farming systems, nor that those who have received it once were less likely to receive it again. Thus, while seed aid has been promoted to lessen the effects of an 'acute' stress, drought, Kenyan farmers, in practice, have been experiencing much wider, 'chronic' seed system problems. This article ends by exploring this distinction between acute and chronic seed system stress and suggests a range of interventions appropriate to each.