排序方式: 共有67条查询结果,搜索用时 15 毫秒
31.
32.
针对二年制高职教育的特点和机械制造业的发展,对二年制高职机械制造类专业课程体系的改革的具体内容进行了深入的探讨研究,提出了课程体系改革的原则以及优化和整合现设课程;构建基础素质和专业素质两大模块,建立和加强改革的保障体系等方法,是机制专业培养复合型社会急需人才的有效途径。 相似文献
33.
本文评述了惯性器件用高性能铍材的发展,讨论了微屈服强度与应变指数和屈服强度之间存在的关系,最后得出结论;应同时使用MYS和n值反映材料的尺寸稳定性,以及可以用屈服强度取代微屈服强度。 相似文献
34.
35.
In 1996 the NASA Advisory Council asked for a comprehensive look at future launch projections out to the year 2030 and beyond. In response to this request NASA sponsored a study at The Aerospace Corporation to develop long-range space transportation models for future commercial and government applications, and to analyze the design considerations and desired characteristics for future space transportation systems. Follow-ons to present space missions as well as a wide array of potential new space applications are considered in the study. This paper summarizes the space transportation system characteristics required to enable various classes of future missions. High reliability and the ability to achieve high flight rates per vehicle are shown to be key attributes for achieving more economical launch systems. Technical, economic and policy implications are also discussed. 相似文献
36.
针对测控与数据传输信道一体化的需求,采用AOS(Advanced Orbiting System,高级在轨系统)空间链路层的等时业务,设计了一种测控数传信道一体化方案,可在上下行信道采用非相干信息帧同时传输测量信息及高速载荷数据.该方案设计了2种工作模式,模式一在上下行信道同时使用AOS传输帧,双向数据传输速率最高3 Mbit/s,测距精度优于2 m;模式二上行信道使用遥控扩频帧,可进行多站测距,抗多址干扰能力不低于15 dB,抗单频干扰能力不低于23 dB,下行信道使用AOS传输帧,最高数据传输速率3 Mbit/s,测距精度优于1 m. 相似文献
37.
38.
Petri网以其简洁、直观、潜在模拟能力强等特点被广泛用于离散事件系统的模拟和分析中。随着业务流程建模、工作流概念的出现以及Petri网技术的发展,Petri网也被用于工作流模型的建立。在介绍工作流和Petri网概念的基础上,通过实例研究如何使用Petri网建立模型,并进一步做了可达性分析。 相似文献
39.
M. Stasiak D. Gidzinski M. Jordan M. Dixon 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
As part of an ESA MELiSSA investigation into advanced life support (ALS) candidate crop cultivar selection and growth requirements, the University of Guelph’s Controlled Environment Systems Research Facility (CESRF) conducted a case study on growth and development of four durum wheat cultivars (Triticum turgidum var durum) grown hydroponically under controlled conditions in a sealed environment. Cultivars tested were Canadian developed Avonlea, Commander, Eurostar and Strongfield. There were few fundamental differences in durum quality parameters between hydroponically and field grown wheat, however yields of Eurostar and Strongfield exceeded those of field trials by 41% and 87% respectively. 相似文献
40.
为探索与预浸料先进拉挤成型技术相适应的工艺方案,采用DSC研究了碳纤维/环氧预浸料USN12500的固化放热过程,对USN 12500的典型固化工艺进行改进,以此为基础设计了不同压力和加压时机下的试验方案,采用实验室现有设备模拟先进拉挤过程制备了试样,以制品的孔隙率作为考察指标优选了的拉挤成型固化的工艺参数.结果表明:制品在110℃下处理20 min,热压阶段130℃下处理15 min同时保持0.4MPa的工艺压力,后固化150℃下处理1.5h为工艺试验的优化方案,并且能够制得孔隙率<1.1%的制品. 相似文献