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排序方式: 共有91条查询结果,搜索用时 15 毫秒
1.
滨海盐碱地利用变化与优化研究   总被引:4,自引:1,他引:4  
土地利用变化与优化配置的综合研究是土地科学和可持续发展的重要议题,我国滨海盐碱地是重要的后备土地资源,研究其利用变化与优化对于缓解人地矛盾,改善生态环境和促进可持续发展具有战略意义.本文制定了滨海盐碱地盐化程度分级分类标准,提出了依据区域盐碱程度和耕层土壤全盐含量进行土地利用优化的对策和"台田-浅池"优化利用模式.黄骅1986年-2006年间土地利用变化剧烈,耕地增加14.31%,建设用地增长93.95%,未利用地减少23.07%.2006年,黄骅非盐碱耕地、轻度、中度、重度以上盐碱耕地分别占耕地面积的54.67%、27.01%、12.55%和5.77%.盐碱地开垦是黄骅耕地增长的主要方式.黄骅实施"台田-浅池"模式后,耕地面积降为28.7%.沼泽湿地和盐碱草地增加,可收到生态安全与生产高效的效果.研究成果可为滨海盐碱地资源的持续利用管理提供科学依据.  相似文献   
2.
该从立党为公,坚持实现广大人民的根本利益是无产阶级政党的根本立足点;实践宗旨,始终代表广大人民根本利益是党的理论、路线、方针、政策和工作的出发点;执政为民,努力实现、维护、发展广大人民根本利益是一切工作的落脚点立论,论述实现人民根本利益是实现“三个代表”重要思想的出发点和归宿。  相似文献   
3.
吉林油田浅气层区块较多,井控风险高,井喷失控后造成的危害较大。文章对该油田浅气层特点、分布及形成原因、存在的危害进行简要分析,提出加强井控防范意识、严格落实一次井控措施、早期发现早期处理、提高班组应对突发险情的防喷处置能力、发现溢流及时关井、关井后节流循环、压井恢复井筒内压力平衡等应对措施,对浅气层钻井施工井控安全工作有一定的指导作用。  相似文献   
4.
王哲  王哲  王志达 《科技通报》2012,28(9):97-102
修建人行地下通道是缓解城市交通拥挤、保障行人交通安全、提高城市运行效率的一项有效措施。人行地道施工不可避免对周边环境造成不利的影响,严重者可能影响地面建构筑物和地下管线的正常使用。本文通过对浅埋暗挖法修建杭州清泰街过街地道的有限元模拟,模拟CRD工法开挖方式通过考虑地道上方道路刚度与否两种模型的对比得出道路刚度对浅埋暗挖人行地道的地表沉降及地层变形的影响规律,并与实测数据进行了对比分析,得出较为一致的结果。研究对此类地道的施工与设计有一定的指导意义。  相似文献   
5.
Who are We?     
This article scrutinises the usage of the words “we”, “us” and “our” by BBC radio journalists when reporting and discussing news and current affairs. By analysing reports and discussions on the “flagship” Radio 4 Today, a daily news programme whose centrality to political and public debate is widely recognised, the article raises substantive questions about clarity, accuracy and impartiality in senior broadcast journalists’ choice of language. In exploring the assumptions which may underlie the invocation, via such language choices, of an implied community, and against the backdrop of the BBC's commitment to impartiality in its Editorial Guidelines, the article identifies numerous recent examples where the choice of words and identifiers can be seen as undermining the BBC's impartiality and which show several of its senior journalists adopting the first-person plural “we” when reporting on matters of public policy. The findings therefore indicate a general need to codify norms which are seen to integrate the need for accuracy as well as impartiality, and for these norms to take into account issues which might at first glance seem to be inconsequential, micro-level features of the journalists’ language. The evidence suggests that more fine-grained guidelines on permissible circumstances for BBC journalists’ usage of “we” and “our” need revising and disseminating in the light of these findings.  相似文献   
6.
根据薄壳非线性动力学理论和拟壳法的思想,给出了扁球面网壳在动、静荷载协同作用下的非线性动力学控制方程.然后利用扁球面网壳的非线性动力学变分方程和协调方程,在夹紧固定的边界条件下,通过Galerkin作用得到一个含二次和三次的非线性动力学微分方程.用Floquet指数方法研究了系统的分岔问题,讨论了平衡点(奇点)邻域的稳定性问题.指出了系统在纯动态作用和在动静荷载协同作用下其平衡位置的变化情况.  相似文献   
7.
以“主客二分法”的哲学理论为依据的传统法学理论将动物定位为客体,曾对人们改造世界起到过积极的作用。但近来有学者提出,它忽视了动物自身作为一种生命形式而客观存在的价值,导致了人类对动物权利的漠视,加剧了地球物种的灭绝,违背了人与自然和谐共处的核心理念。笔者认为,从环境生态学的角度来看,动物作为生命物质的表现形式之一,也有其生存、发展的权利。要加强对动物的法律保护,有必要突破传统的法律思维定式,进而确立动物法律主体地位。  相似文献   
8.
In past terrorist attacks, vehicle borne improvised explosive devices (VBIED) have been the primary manner of attacking buildings and infrastructures. Preventing unauthorized vehicles from approaching a protected area with anti-ram systems would maintain an established standoff distance against moving and stationary vehicles and consequently reduce blast and debris threats. This strategy has been considered the first line of defence against terrorists. Several types of anti-ram devices have been developed in accordance with U. S. Department of State K-rating criteria, for example, wedge barriers, rising beams, sliding/swing gates, and drop arms. However, these devices typically need a deep foundation for installation and can't be implemented into many locations where a depth of excavation is limited in order to protect utility lines of buildings and infrastructures. This paper presents a recent development of a series of shallow footing anti-ram bollard systems (SFABS) that can satisfy K-12 rating with only five-inch thick footing. A high-fidelity physics based finite element technique with a vehicle crash model is used for predicting anti-ram capacity and determining design parameters of the SFABS. Full-scale vehicle crash tests of the developed SFABS systems have been carried out to validate the design and analysis.  相似文献   
9.
The study of solitary waves has been a subject highly popular and full of interest sinec Russell[1]first observed the solitary waves in a channel and the research on the internal solitary waves in stratified fluids is one of the branches of this subject.There are extensively internal solitary waves in the atmosphere,oceans.fjords and lakes.To study them is of academic and practical significance[2].Numerous investigators have made contributions since the theoretical work on internal solitary waves was initiated by Keulegan[3].Nevertheless,some problems remain still to be discussed,for example,the higher-order theories for one-dimensional internal solitary waves in stratified fluids of small depth,the two-dimensional internal solitary waves,the explanation of the experimental and the practical phenomena by means of theoretical analysis.In this thesis,we hope to gain an insight into the above three items by combining of theoretical analysis and symbolic computation.The following work has been completed.  相似文献   
10.
结合长春火车站南北广场地下通道工程实例,建立了二维有限元模型模拟隧道施工过程,按施加常规地面拟静力列车荷载的方法,获得了极浅埋隧道施工时地面最大沉降值及其分布规律,为施工决策提供科学依据,以确保列车运营的绝时安全和隧道施工安全.  相似文献   
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