Supercritical carbon dioxide as a new working medium for pneumatic launch: A theoretical study

Compared with the conventionally gaseous or liquid working media, the specific internal energy of supercritical carbon dioxide (SCD) is higher at the same temperature and pressure, and the critical temperature of carbon dioxide is close to room temperature, making SCD a potential new working medium for pneumatic launch. To analyze the feasibility of this conception, an analytical model of a pneumatic catapult is established on basis of the conservations of mass and energy. The model consists of a high-pressure chamber and a low-pressure chamber connected by multiple valves, and there is a movable piston in the low-pressure chamber that can push an aircraft to accelerate. The effects of the launch readiness state of SCD in the high-pressure chamber, the initial volume of the low-pressure chamber and the valve control on the movement of the aircraft are analyzed. It is found that there is a restrictive relation between the temperature and pressure of the launch readiness state of SCD, i.e., there is a maximum allowable launch readiness pressure when the launch readiness temperature is fixed. If this restrictive relation is not satisfied, the working medium in the low-pressure chamber will drop to its triple point within a few milliseconds, leading to a launch failure. Owing to this restrictive relation, there is an optimal launch readiness state of SCD with the highest working capacity for any allowable launch readiness temperature. The pressure of the low-pressure chamber will decrease significantly as the initial volume increases, leading to a decreased acceleration of the aircraft. The ac-celeration can be controlled below a critical value by a designed sequential blasting technique of multiple valves. The calculated results show that a 500 kg aircraft can be accelerated from 0 to 58 m/s in 0.9 s with 36 kg of carbon dioxide. This research provides a new technique for the controllable cold launch of an aircraft.     

地下建筑火灾烟气危害及对策探讨

地下建筑发生火灾时,烟气对人员的危害十分巨大。对地下建筑烟气流动规律、人员的安全疏散及其防排烟措施进行了探讨。     

钢管初应力对方钢管混凝土构件性能的影响研究

在14根方钢管混凝土构件试验的基础上,分析了初应力系数、荷载偏心率、混凝土强度、试件长细比等因素对承载力的影响,给出了钢管初应力对方钢管混凝土压弯构件承载力的影响系数,采用ANSYS有限元分析程序进行了非线性全过程分析.     

某塔刹建筑火灾扑救面设计探讨

高大雄伟的塔刹建筑由于其特殊的设计风格,往往会超出消防技术规范的一些要求,火灾预防成为了技术性难题。以长安塔为研究对象,针对长安塔存在消防扑救面不满足规范要求的问题,从防火规范规定高层建筑必须设置消防扑救面的目的出发,分析设置消防扑救面所要达到的消防安全目标,进而定性分析现有防火措施的消防安全性。     

客观辩证地看待当前反腐倡廉建设的形势

客观辩证地看待当前反腐倡廉建设的形势,就是既要看到反腐倡廉工作取得的明显成效,又要看到消极腐败现象仍然比较突出的问题;既要看到反腐败过程中的不利因素,又要看到反腐倡廉建设的有利条件;既要看到反腐败过程中暴露的党内腐败分子,又要看到党员干部队伍的主流是好的;既要认识到反腐败斗争的重要性和紧迫性,又要认识到反腐倡廉建设的长期性、复杂性、艰巨性。     

抗日军政大学华中分校对青年马克思主义者的思想政治教育

抗战时期,新四军创办的抗日军政大学华中分校吸引了大批青年,通过马克思主义理论的学习和实践教学来开展思想政治教育工作。学校采取了灵活多样的思想政治教育形式,培养了大批军政干部,使青年学生提高了马克思主义理论水平,培养了艰苦朴素的作风,坚定了革命意志。其教学方法对当今的思想政治工作仍然具有现实的借鉴意义。     

Unpacking the various meanings of redundancy: from refining the concept to military planning

The authors engage in the debate over waste in military force structure planning by rigorously deconstructing the concept of “redundancy.” First, a typology of redundancy is constructed that provides a common framework for identifying variety among redundant structures. These are labeled “true redundancy,” “expanded capacity,” “portfolio diversification,” and “mission overlap.” Further, a number of mechanisms are identified that produce these types of structures, and show the conditions under which planners may utilize redundant structure in the search for optimization. In sum, the article provides refined concepts for analysts and planners to identify when redundancy is deleterious or beneficial.     

带宽受限下频谱分离对提高RDSS入站容量的影响分析

用户入站容量是RDSS系统设计的一个重要指标,主要受限于入站信号之间的多址干扰.提高扩频码速率可以增加人站容量,但卫星转发器带宽限制了扩频码速率的最大值,从而限制了单个扩频频谱入站信号容量最大值.在卫星转发器带宽受限情况下,提出了采用分离扩频频谱的方法来提高入站容量,并分别对扩频频谱分离为两个和三个的情况进行了详细分析,得出了两种分离扩频频谱方案下扩频码速率的最优值.仿真结果表明,在现有转发器带宽内分离为两个扩频频谱可以提高入站容量29％,分离为三个扩频频谱可以提高人站容量37％.     

折反射全景与遥感图像融合的建筑物高程自动提取方法

为了解决三维城市重建中的建筑物高程提取问题,提出一种折反射全景与遥感图像融合的建筑物高度自动提取方法.该方法分为三步,首先进行折反射全景与遥感图像的配准,然后利用配准结果提取折反射全景图像中建筑物的底部和顶部边界,最后基于边界信息,根据折反射全景成像光路跟踪模型计算建筑物的高度,整个提取过程自动完成.实验结果证明该方法...     

现代居住环境文化研究

消费者对居住环境除了继续要求不断扩大“生活空间”外,更要求高品位的文化环境。提高居住环境的质量、营造自然和人文和谐的生态文化、提升居住文化环境的质量和品位,使人居活动与社会活动、文化活动、生态活动完美地结合在一起,无疑将成为现代居住环境建设的一大亮点。