计算机网络风险防范模式研究

网络风险管理的目的是为确保通过合理步骤,以防止所有对网络安全构成威胁的事件发生.计算机网络风险防范模式包括风险防范策略、风险防范措施和实施风险防范.网络风险防范策略主要有:①当存在系统漏洞时,实现保证技术来降低弱点被攻击的可能性;②当系统漏洞被恶意攻击时,运用层次化保护、结构化设计以及管理控制将风险最小化或防止这种情形的发生;③当攻击者的成本比攻击得到更多收益时,运用保护措施,通过提高攻击者成本来降低攻击者的攻击动机;④当损失巨大时,运用设计原则、结构化设计以及技术或非技术类保护措施来限制攻击的程度,从而降低可能的损失.风险防范措施包括风险假设、风险规避、风险限制、风险计划、研究和了解、风险转移.在实施风险防范的过程中包括对行动进行优先级排序、评价建议的安全控制类别、成本-收益分析、选择风险防范控制、分配责任、制定安全措施实现计划、实现被选择的安全控制及残余风险分析.最后以某市政府官方门户网络应用系统为例进行了实证.     

一株耐铜细菌的鉴定及富集特性的研究

从铜矿污染区的土壤中分离纯化得到一株耐铜菌株USTB-E,最高耐受浓度为560 mg/L,通过形态观察,生理生化鉴定及16S rDNA序列分析技术鉴定出此菌株为假单胞菌。该菌的最适生长温度为35℃,pH为6.0,渗透压为0.3%。为了研究该菌耐铜机理,实验对铜离子富集机理进行了动力学研究,研究结果表明,USTB-E菌对...     

兰坪铅锌尾矿区土壤与自然发生的5种植物的研究

对兰坪铅锌尾矿区的土壤和自然发生植物的调查分析发现:该尾矿区土壤污染以Cd最为严重,是云南土壤背景值的350倍,其次是以Pb、Zn为主.尾矿区重金属含量随堆积时间而减少,尾矿边缘重金属含量明显低于中心.尾矿区自然发生多种植物类群,绝大多数植物类群零星发生,仅有5种植物为优势类群.5种优势植物对铅锌富集和耐性研究表明,这...     

乌苏-奎屯-独山子地区生态系统服务功能变化研究

在3S技术的支持下,以1990年和2005年的TM图像解译数据为基础,采用谢高地的评价方法分析了乌苏-奎屯-独山子地区景观类型与生态系统服务功能的变化特征,为研究该地区水土开发与生态环境演变提供了依据。结果表明,1990-2005年,乌苏-奎屯-独山子地区农田、灌木林地、城镇及工业用地、盐碱地、水域和未利用地面积增加,其他乔木林地、草地、冰川和沼泽面积均减少;区域生态系统服务功能从1990年的9 182.84×106元减少到2005年的8 627.96×106元,减少量为554.87×106元,减少率为6.04%。保护区域生态环境,恢复和提高区域生态系统服务功能是该区域生态环境建设的重要任务。     

湖北丹江口水库库区降雨侵蚀力特征

降雨侵蚀力(R)指数是估算土壤侵蚀量的一个基本因子,但如何利用气象站常规降雨统计资料估算R值具有重要的实践意义。利用湖北丹江口水库库区4个观测站(丹江口、十堰、郧县、郧西)的多年逐日降雨资料,通过比较分析多个经验模型对该地区的降雨侵蚀力的计算结果,优选出了表现最佳的估算模型,并用其计算结果分析了库区年降雨侵蚀力的空间分布和时间变化特征。结果表明,湖北丹江口库区丹江、郧西、十堰、郧县的年均降雨侵蚀力分别为3 331.94、3 272.40、3 501.21、3 187.94 MJ·mm/hm²·h·a,4个测站的均值为3 323.37 MJ·mm/hm2·h·a,空间分布比较均匀,与多年平均降雨量分布类似;降雨侵蚀力主要集中于5～9月份,占全年的88.60%以上;库区4个测站年降雨侵蚀力值波动较大,以郧西和十堰为甚,其最大单次降雨侵蚀力分别占其研究时段内总降雨侵蚀力的6.94%和4.87%。离差系数Cv(0.45～0.58)和趋势系数r(绝对值0.05～0.08)计算结果表明研究年限内年均降雨侵蚀力整体趋势保持平稳。
     

A/O和A2/O工艺对膜生物反应器处理焦化废水影响的研究

为提高膜生物反应器对焦化废水的处理效果,采用A/O和A2/O两种工艺的膜生物反应器处理焦化废水,通过对比处理效果、分析膜污染情况,寻求膜生物反应处理焦化废水的最优工艺。实验结果表明：A2/O工艺系统对酚、NH3-N、COD的去除率分别为99%、90%和95%;A/O工艺系统对酚、NH3-N和COD的去除率分别为97%、75%和93%。A2/O膜生物反应器系统对焦化废水中NH3-N的去除效果明显优于A/O膜生物反应器系统,其反硝化率为50%-70%。对膜污染分析表明不同工艺对膜污染的影响不显著,A2/O工艺膜通量衰减59%,A/O工艺膜通量衰减56%。研究表明在膜生物反应器中,A2/O工艺对焦化废水的去除效果要优于A/O工艺。     

Conflict management between and within teams for trusting relationships and performance in China

Trusting relationships are increasingly considered vital for making teams productive. We propose that cooperative management of conflict can help team members to be convinced that their teammates are trustworthy. Results from 102 organizations in China support the theorizing that how teams to manage conflict with each other affects within‐team conflict management. Specifically, cooperative conflict between teams helps teams to manage their internal conflicts cooperatively that strengthens trust that in turn facilitates team performance. Results provide support for managing conflict cooperatively as a foundation for trusting, productive relationships in China as well as in the West. Copyright © 2008 John Wiley & Sons, Ltd.     

The effect of excess Zn on mineral nutrition and antioxidative response in rapeseed seedlings

Zinc (Zn) is a necessary element for plants, but excess Zn can be detrimental. To investigate Zn toxicity, rapeseed (Brassica napus) seedlings were treated with 0.07–1.12 mM Zn for 7 d. Inhibition of plant growth along with root damage, chlorosis and decreased chlorophyll (a and b) content in newly expanded leaves (the second and third leaves formed following cotyledons) were found under Zn stress. The Zn content increased in plants under external Zn stress, while concentrations of phosphorus, copper, iron, manganese and magnesium reduced significantly, especially in roots. Meanwhile, increased lipid peroxidation was detected biochemically and histochemically. Compared with controls, NADH oxidase and peroxidase (POD) activity increased in leaves and roots of plants under high Zn, but superoxide dismutase (SOD), catalase and ascorbate peroxidase activities decreased. The changes in glutathione S-transferase activity and in ascorbic acid, dehydroascorbate, non-protein thiols and glutathione contents were also measured under Zn stress. Isoforms of SOD and POD were separated using non-denaturing polyacrylamide gel electrophoresis and their activities were analyzed. Our results suggested that excess Zn exerts its toxicity partially through disturbing nutrient balance and inducing oxidative stress in plants. These data will be helpful for better understanding of toxicity of Zn and the adaptive mechanism in Zn non-hyperaccumulator plants.     

斜生栅藻的无菌化培养及其在原油降解中的应用研究

选用组合抗生素结合溶菌酶/SDS预处理方法对斜生栅藻进行无菌化培养,对不同抗生素组合的除菌效果进行了比较。青霉素+庆大霉素对斜生栅藻和附生菌都有强烈的抑制性能,而青霉素+利福平和青霉素+四环素组合除菌不彻底。青霉素+卡那霉素组合能彻底除去附生菌并且对藻的抑制作用最小,可得到无菌斜生栅藻。将斜生栅藻与石油组分降解菌构建菌藻共生体系,未除菌藻的附生菌与石油组分菌之间不能很好地相互适应,使得原油降解效果反而降低。纯栅藻则对石油降解菌表现出非常良好的促进作用,利用除菌后的斜生栅藻与石油组分降解菌构建了一个高效降解原油的菌藻共生体系,充分肯定了微藻无菌化培养的积极意义。     

Analysis of the soil water balance for large-scale reforestation with <Emphasis Type="Italic">Eucommia ulmoides</Emphasis> in the hilly red soil region of southern China

Returning farmland to forests is important for the protection of ecological values. Eucommia ulmoides is considered to be a suitable species for reforestation in the hilly red soil region of southern China. The objective of this study was to investigate the relationship between the water supply and demand of an E. ulmoides plantation to provide insights into the feasibility of large-scale planting for ecological restoration and forest management activities in the hilly red soil region of southern China. With the measured precipitation, surface runoff and interflow and actual evapotranspiration (ET_c) estimated by the modified P–M model, soil water storage (SWS) was estimated based on the water balance equation. Monthly variations of SWS were then compared with in situ measured SWS. The results showed that the estimated mean monthly water losses (the sum of the surface runoff, interflow and ET_c) were 139.8 mm in a wet year and 120.0 mm in a dry year, while the measured mean monthly water input values (net precipitation) were 131.2 mm in a wet year and 70.8 mm in a dry year. Net soil water storage (ΔSWS) was negative in each month of the growing season in a dry year, but the soil water deficit was replenished during the following season. The model performance showed that the modified P–M model can be adapted to estimate the soil water storage in other forest catchments where no adequate in situ data are available. As a result of estimating the water balance and observing soil water storage in two different hydrological years, E. ulmoides is recommended as a suitable forest rehabilitation species in the study area, and a suitable plant region has been defined by the GIS technique based on the water balance model.