航电系统的升级改装

<正>零部件短缺及空中交通管理系统的持续改进,使航空公司不得不开始对其现有机型的驾驶舱进行升级改装。随着新一代空中交通管理系统逐渐成为未来全球的发展趋势,传统系统零备件淘汰的问题日趋严重,航空公司正在考虑采用现代航空电子设备替换旧的机电/电子飞行仪表系统,对老龄机队的驾驶舱进行升级改造。ICF SHE咨询公司预计,2013年全球航电系统升级改装的维修市值为5.7亿美元,到2023年将达到10亿美     

数字力传感器

本文叙述一种数字力传感器装置,更准确地定义为间接数字装置。该装置保持模拟力传感器的大部分优点,并具有数字系统的稳定性和与计算机的相容性。数字力传感器可处理700克以内的力,用普遍采用的敏感元件,二进制8位,分辨率4克。询问率为7仟赫,可识别频率大大超过1仟赫的力。线性度优于±0.1％±二进制最低位的1/2,重复率优于满量程的±0.25％。所述的装置在三年内几乎每天使用,经考核是十分可靠的。此传感器用作全数字张力测试仪的总体部分,其性能超过测试系统的需要。与联结大批生产的模一数硬件的模拟传感器相比,此传感器在设计和制造上是经济的。     

Iron meteorites can support the growth of acidophilic chemolithoautotrophic microorganisms

Chemolithoautotrophy based on reduced inorganic minerals is considered a primitive energy transduction system. Evidence that a high number of meteorites crashed into the planet during the early period of Earth history led us to test the ability of iron-oxidizing bacteria to grow using iron meteorites as their source of energy. Here we report the growth of two acidophilic iron-oxidizing bacteria, Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans, on a piece of the Toluca meteorite as the only source of energy. The alteration of the surface of the exposed piece of meteorite, the solubilization of its oxidized metal constituents, mainly ferric iron, and the formation of goethite precipitates all clearly indicate that iron-meteorite-based chemolithotrophic metabolism is viable.     

Quantification of spatial structure of human proximal tibial bone biopsies using 3D measures of complexity

Changes in trabecular bone composition during development of osteoporosis are used as a model for bone loss in microgravity conditions during a space flight. Symbolic dynamics and measures of complexity are proposed and applied to assess quantitatively the structural composition of bone tissue from 3D data sets of human tibia bone biopsies acquired by a micro-CT scanner. In order to justify the newly proposed approach, the measures of complexity of the bone architecture were compared with the results of traditional 2D bone histomorphometry. The proposed technique is able to quantify the structural loss of the bone tissue and may help to diagnose and to monitor changes in bone structure of patients on Earth as well as of the space-flying personnel.     

Induction of vascular endothelial phenotype and cellular proliferation from human cord blood stem cells cultured in simulated microgravity

Recent studies have demonstrated that stem cells derived from adult hematopoietic tissues are capable of trans-differentiation into non-hematopoietic cells, and that the culture in microgravity (microg) may modulate the proliferation and differentiation. We investigated the application of microg to human umbilical cord blood stem cells (CBSC) in the induction of vascular endothelial phenotype expression and cellular proliferation. CD34+ mononuclear cells were isolated from waste human umbilical cord blood samples and cultured in simulated microg for 14 days. The cells were seeded in rotary wall vessels (RWV) with or without microcarrier beads (MCB) and vascular endothelial growth factor was added during culture. Controls consisted of culture in 1 G. The cell cultures in RWV were examined by inverted microscopy. Cell counts, endothelial cell and leukocyte markers performed by flow cytometry and FACS scan were assayed at days 1, 4, 7 and at the termination of the experiments. Culture in RWV revealed significantly increased cellular proliferation with three-dimensional (3D) tissue-like aggregates. At day 4, CD34+ cells cultured in RWV bioreactor without MCB developed vascular tubular assemblies and exhibited endothelial phenotypic markers. These data suggest that CD34+ human umbilical cord blood progenitors are capable of trans-differentiation into vascular endothelial cell phenotype and assemble into 3D tissue structures. Culture of CBSC in simulated microg may be potentially beneficial in the fields of stem cell biology and somatic cell therapy.     

苏联防空系统现状

苏联防空雷达的特征为:尽管雷达防空网异常庞大,但其部件的质量和可靠性大成问题;设计、维护、气候条件和操作手的能力等综合起来看,防空雷达具有一定的性能优点(能探测低空目标).但同时也有某些可靠性方面的问题.研究表明.雷达操作手的50%～70%的工作差错都是由人机学设计配合不佳所引起的;     

凯夫拉49复合材料缠绕孔眼的特性

用试验方法研究了凯夫拉49复合材料“缠绕孔眼”的强度。由于制作部件时绕在可拆卸销钉上的纤维是连续的,故这样形成的孔眼的强度显著超过钻削孔眼的强度。己研制成功一种模拟纤维缠绕孔眼的纤维缠绕环形试样,并用它来研究绕孔的强度。对厚度为0.04至0.25英寸和销钉直径为0.300至0.480英寸的试样均进行了试验。试验结果表明:试样极限强度明显受销钉形状、尺寸的影响。用有头销钉作试验,其承载极限应力达90000磅/英寸~2以上。基于这些试验结果的设计数据已被确认,并与采用缠绕孔眼作结构连接的小直径(2.7英寸和6.9英寸)纤维缠绕火箭发动机壳体的孔眼强度试验进行了比较。其相关程度是发动机壳体直径的函数,直径较小,则一致程度较高。     

用扭摆法测定预浸胶的固化度

引言用复合材料制造尺寸越来越大的复杂构件时,必然会遇到大量的纤维——树脂预浸渍工艺问题。由于预浸渍工艺要满足日趋严格的技术要求,所以必需有精确的测定方法。然而,目前在测定方法(如预浸渍材料批量验收和储存期间用的测定方法)和审定模压周期(如审定某种新型材料和改变某种原有材料的模压周期)上均还存在着问题。     

湍流边界层中脉动压力和脉动速度之间的相关测量

1.前言 最早的压力-速度相关测量是Kawamura和Serafini做的。随后,发表了许多壁面压力脉动与速度脉动相关和功率谱的研究结果,其中壁面压力脉动和速度脉动之间相关的详细结果是Willmarth和Wooldrige所提供的。 Bradshaw研究了急剧减速的边界层中壁面压力脉动和速度脉动的关系,他在逆压梯度边界层中发现了较低的对流速度。他还应用Townsend关于“非活动”(inactive)运动的重要概念来解释在逆压梯度中湍流壁面层相似性的明显破坏。