Design of the Virtual Instrument of Frequency/Amplitude Sweep

In this paper the inevitable trend of constructing open ecosystem in modern settlement environment was discussed through the history of the settlement environment and the characters of modern settlement environment.The ecological crisis,change of the modern life and the citizens' needs and the ecological system character show,that it is important for sustainable development of the settlement environment to construct open ecosystem.The construction of modern habitation and the city room embodies the concept of open ecosystem.Then,in construction and research of modern settlement,the ecological viewpoint and method should be applied.     

直墙拱形巷道围岩应力场分析

为得出直墙拱形巷道围岩应力分布规律,应用复变函数弹性理论推导了直墙拱形巷道围岩应力分布的解析表达式。对直墙拱形巷道边界的围岩应力和巷道水平线方向的围岩应力分布规律进行分析,并考虑直墙拱形巷道断面高宽比和侧压系数对其影响规律。研究表明：在不同巷道断面高宽比、侧压系数下,直墙拱形巷道围岩应力集中区域主要集中在直墙底部底角处、拱形顶板中点附近和底板中部3个位置。不同巷道断面高宽比下,直墙拱形巷道沿水平线的应力分布规律基本相同。侧压系数大于1时,采用巷道断面高宽比小于1较有利于巷道稳定;侧压系数小于等于1时,采用巷道断面高宽比大于1较有利于巷道稳定。     

Relationship of Conservation of Historic Buildings and Urban Construction

The conservation of historic buildings and their environment is an unavoidable problem in urban construction. In this paper, the authors give a few new thoughts about the problem. First, the historic buildings are important part of the core power in city competition.Second,the conservation work should be combined with their development. Third, a classified and multilevel system of protection and reuse of old buildings should be set up.     

水库建设与生态系统和谐

水库建设和运行对流域内上下游的生物群落和生态系统产生诸多负面影响,诸如改变流域水文气候,导致水温分层、泥沙淤积、水质恶化,切断河流廊道,阻隔鱼类洄游通道等;此外,传统的水库调度方式仅体现水库的工程效益、经济效益和社会效益,忽视了其生态效益。通过详细探讨这些问题,据此提出生态水库的概念,并从规划、设计、施工及生态调度等方面探讨了生态水库的理论体系,即水库建设需与生态系统达到高度的和谐与统一。     

蔬菜的硝酸盐污染及防控措施

由于不合理的种植手段,造成了蔬菜的硝酸盐污染,影响蔬菜的品质,威胁人类的身体健康和生命安全。通过重视施用有机肥、合理施用氮肥、注意施肥时期和施肥种类、在不同季节使用正确栽培设施、使用硝化抑制剂(氮肥增效剂)等技术手段,可以明显减少硝酸盐在蔬菜中的残留,对发展绿色无公害蔬菜生产和提高人民生活水平有着十分重要的意义。     

A Framework for Valuing Ecological Services of Irrigation Water – A Case of an Irrigation-Wetland System in Sri Lanka

In many countries, irrigation water is usedfor several purposes other than irrigatingfield crops. In Sri Lanka, irrigationwater from canals, wells, and reservoirs isused for domestic purposes, industry,livestock, and fisheries, and it alsocontributes to sustain the environment. However, policy makers and water managersin irrigation systems only take intoaccount water used for irrigating the fieldcrops and sometimes water used for domesticpurposes. Owing to the failure torecognize the different uses and users ofwater, the water in irrigation systems hasbeen undervalued. This paper presents theenvironmental impact of irrigation and aframework for valuing water for itsmultiple and often competing uses,especially focusing on water uses forecological services, in this case wetlands.The south coastal area of Sri Lanka wasselected as a site for a case study, including2,610 ha of irrigated area and adownstream wetland area of 2,250 ha whichhas five lagoons. This wetland areacombines coastal, marine and freshwaterecosystems in a tropical environment inwhich distinct plant and animal speciescoexist in a delicate balance. All users ofwater and other resources, and theirenvironmental problems were identified. Thispaper discusses the policy and managementimplications of valuing water for competinguses.     

海河流域水生态环境破坏的经济损失估算

利用多种方法估算海河流域水生态环境破坏造成的经济损失，并综合已有相关研究，认为1999年的经济损失相当于流域GDP的0．63%-16．6％。利用影子价格法估算的经济损失相当于流域GDP的7．3％。海河流域现状水生态环境恶化造成的相对经济损失值处在历史高峰期。未来在实施南水北调工程及按照规划开展大规模节水挖潜举措的前提下，经济损失的相对量将大为减少，但是绝对经济损失量可能还会有所增大。向流域节水挖潜领域的项目投资，会给全社会带来较高的经济收益。     

农田生态系统中氮循环模型研究进展

农田生态系统中的氮循环是影响农业生产力的主要因素之一,同时也会对环境产生影响。在农田生态系统氮循环的研究中模型已成为重要的工具而受到人们关注。在介绍国际上发表的模型基础上,阐述了目前一些比较成功的模型的研究进展,并指出了今后模型发展的趋势。     

酵母细胞壁多糖与铝硅酸盐复合物对猪生长性能、免疫指标及养分消化率的影响

本研究旨在探讨酵母细胞壁多糖(yeast polysaccharide,YP)与铝硅酸盐复合物(alumi-nosilicate complex,AC)对猪的生长性能、免疫指标及养分消化率的影响。试验选用平均体重为(66.18±1.26)kg的"杜×长×大"三元杂交猪140头,随机分成5组,每组4个重复,每个重复7头猪。各组分别饲喂添加不同剂量复合物的试验饲粮,A组为对照组,不添加复合物;B组添加0.1%YP;C组添加0.1%YP和0.9%AC;D组添加0.1%YP和1.9%AC;E组添加0.1%YP和2.9%AC。试验期51 d。结果表明:1)D、E组平均日增重显著低于对照组(P<0.05),各组平均日采食量和料重比差异不显著(P>0.05);2)与对照组相比,D组血清谷胱甘肽过氧化物酶(GSH-Px)活性及补体3(C3)、免疫球蛋白M(IgM)、免疫球蛋白A(IgA)、免疫球蛋白G(IgG)水平显著提高(P<0.05),血清超氧化物歧化酶(SOD)活性和补体4(C4)水平无显著差异(P>0.05);3)各组养分消化率无显著差异(P>0.05)。由此可见,YP和AC复合使用降低了育肥猪的生长性能,0.1%YP和1.9%AC同时添加可增强生长猪的免疫功能。