飞艇囊体薄膜材料的双向拉伸试验及结构仿真

飞艇囊体膜材的弹性常数是飞艇外形设计、结构分析、动力学分析的基础。本文根据正交异性平面应力模型假设,应用双向拉伸试验方法获得了飞艇囊体膜材HV130在不同载荷比条件下的经纬向弹性模量和泊松比。对飞艇囊体进行应力分析,得到囊体应力的理论解及环向应力和轴向应力的载荷比。根据飞艇囊体受力情况,选取对应的弹性常数,对飞艇进行不同压差条件下的静力学仿真分析。利用非接触应变测量系统测试不同压差条件下飞艇囊体的变形情况,验证了双向拉伸试验所得的弹性常数的准确性和仿真分析的可靠性。本文能为飞艇的外形设计和结构分析提供参考。      

浮空飞行器压力调节控制系统工程研究

 压力调节控制系统是浮空型飞行器最基本、最重要的组成部分之一,其工程设计直接关系到浮空平台的安全和性能.根据囊体材料应力分析和浮空平台保持形状的要求,推导了以飞艇为代表的浮空型飞行器压力控制的基本控制要求;探讨了浮空型飞行器压力控制系统的构成和主要参数的工程设计方法;从调节速度和调节范围两方面分析了压力控制系统的调节能力及其对飞艇平台性能的影响,并给出设计飞行高度和空气囊占比的关系曲线,从而明确了设计飞行高度对浮空平台体积的要求;介绍了典型的压力系统控制方法,并经中空实验飞艇自主飞行验证,压力控制效果明显.压力控制系统的工程设计研究侧重于实际应用,具有工程实用价值.     

飞艇囊体材料的发展

飞艇的先进性无不和它所用囊体材料的性能息息相关，囊体材料的性能主要包括力学性能、气密性，耐运用性，易成型性，耐候性和低重性，现代工业的发展使飞艇囊体材料在提高其性能方面有了长足进步，相应材料结构形式从不同发民阶段的胶布材料发展到新近的薄膜／织物层压复合材料。评定囊体材料性能的有效试验方法日趋成熟，但现今囊体材料还存在一些不足，本文对上述内容进行了评述。     

层压囊体材料在FK4飞艇上的应用

本文给出了层压囊体材料在FK4飞艇制造和应用中产生的效果,特别是对其中出现的主要问题进行了分析,提出了克服这些问题以求改进的途径并从中引出了飞艇囊体材料值得注意的研究内容。     

无人飞艇气囊体积监测系统设计

三维激光扫描作为一种快速获取立体空间信息的技术手段,通过扫描测量可得到连续、完整、关联的全景点三维坐标,具有点位测量准确度高、空间点采集密度大、速度快、不需建立控制点等特点。由于大型无人飞艇气囊为柔性囊体,形态变化较快,体积难以保持固定不变,因此引入三维激光扫描对无人飞艇气囊体积进行测量。本文主要研究了基于三维激光扫描的无人飞艇气囊体积监测系统,通过激光测距、坐标转换、数据处理、三维重构最终构建气囊的三维几何模型,从而定量计算出气囊的体积。     

高空浮空器发展现状及趋势

高空浮空器是指由充满轻质气体的囊体产生浮力、任务高度处于距离地球表面20～100Km、能执行长期驻留任务的飞行器。高空浮空器包括飞艇和系留气球[1],部分非系留并长期在固定高度工作的气球也被认为是     

浅谈气囊助浮技术在搬运沉箱中的应用

本文介绍了气囊助浮技术的主要原理是利用气囊充气后所具有的浮力、将气囊助浮和传统助浮工具以钢浮筒为例进行了分析比较得出气囊助浮技术的多项优点，简介了搬运沉箱的助浮设计要点和气囊助浮搬运沉箱的工艺流程及其注意事项等内容，并展望了气囊助浮的应用领域前景。     

温度对平流层飞艇蒙皮渗透的影响研究

氦气填充的平流层飞艇在临近空间环境中运行,受到太阳辐照,蒙皮温度变化较大。蒙皮的氦气渗透关系着平流层飞艇运行的时间等问题。从理论分析与实验角度得到温度与蒙皮渗透性的关系,通过数值计算平均渗透率,结合飞艇外形及内部压力范围,估算飞艇的寿命。     

变体飞艇太阳能电池阵列工作特性的影响因素

太阳能电池阵列是近空间变体飞艇的主要能源系统,决定着飞艇的性能。根据变体飞艇的特性,针对变体太阳能飞艇,建立巡航状态下的太阳能电池阵列的几何模型和太阳辐射模型。利用模型,根据太阳辐射和飞艇飞行高度的变化,计算太阳辐射强度和太阳能电池阵列接收功率,绘制太阳能电池阵列接受的有效辐射强度云图。结果表明:正午功效是早晚的3～4倍;当太阳高度较低时,飞艇偏航角对阵列所接受的有效强度分布和功率有一定影响;季节对阵列有效强度分布和正午功率有较大影响;纬度位置影响飞艇功率变化和所产生的总能量;电池布置在艇体顶部获取更多能量。     

变体飞艇太阳能电池阵列工作特性的影响因素EI北大核心CSCD

太阳能电池阵列是近空间变体飞艇的主要能源系统,决定着飞艇的性能。根据变体飞艇的特性,针对变体太阳能飞艇,建立巡航状态下的太阳能电池阵列的几何模型和太阳辐射模型。利用模型,根据太阳辐射和飞艇飞行高度的变化,计算太阳辐射强度和太阳能电池阵列接收功率,绘制太阳能电池阵列接受的有效辐射强度云图。结果表明:正午功效是早晚的3～4倍;当太阳高度较低时,飞艇偏航角对阵列所接受的有效强度分布和功率有一定影响;季节对阵列有效强度分布和正午功率有较大影响;纬度位置影响飞艇功率变化和所产生的总能量;电池布置在艇体顶部获取更多能量。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...