Mechanical Properties and Microstructure of In Situ TiB_2-7055 Composites

In order to fabricate a kind of high strength particulate reinforced aluminum-matrix composites, the high strength aluminum alloy 7055 was selected as a matrix. Composites reinforced with varying amounts of TiB2 particles were synthesized using the in situ method, and their mechanical properties and microstructure were analyzed. It is found that the in situ TiB2 particles sized from 50 to 400 nm uniformly disperse in the matrix. With the weight fraction of TiB2 particles increasing, the elastic modulus as well as the yield strength and the ultimate tensile strength increase, while the ductility decrease. The improvement of strength could be attributed to good bonding between TiB2 and the matrix, and also the TiB2 particles act as a barrier to dislocation.     

基于51系列单片机平台的64位数据显示

分析了51系列单片机在KeilC开发环境中64位数据的显示问题。51系列单片机为8位，其常用的开发环境KeilC最大支持32的整数，因此无法显示64位的整数。对此作了分析，提出了两种解决办法：计算法和查表法。结合实例，对其原理和实现过程作了详细的分析，并用C语言实现了这两种算法，给出了源程序和流程图．     

防代理技术在校园网中的应用

本文分析了某大学校园网网络现状以及网络存在的问题,针对用户大量代理上网导致网速慢的问题,进行了深入的分析,提出了利用限制用户连接数的方法解决代理问题的方案,介绍了防代理技术的原理和具体实施步骤,并对该方案的落实情况和应用效果进行了比较分析,为网络代理问题的解决提供了一个新的思路。     

浅议高校贫困生资助的途径

目的 探讨完善高校贫困生资助的途径和办法。方法 在分析我国高等教育现阶段采用的多元化资助体系存在问题的基础上，提出解决问题的途径。结果 从政府、高校和贫困生三方面论述了应承担的责任：借鉴了美国多元化混合型大学生资助模式对我们解决问题的启示。结论 建立一套由政府主导，社会各界配合，高校具体实施的资助贫困生的长效机制是解决问题的根本。     

航天电磁继电器可靠性容差分析技术的研究

航天电磁继电器是在航天电子系统中完成信号传递、执行控制、系统配电等功能的主要电子元器件之一，其可靠性直接影响整个航天电子系统的可靠性。航天继电器可靠性设计技术是其产品可靠性工程的关键技术。本文分析了当前各领域可靠性研究现状及航天电磁继电器产品的可靠性现状与问题，提出并建立了基于正交试验表的电磁吸力可靠性容差分析数学模型、基于概率统计方法的机械反力可靠性容差分析数学模型及基于“应力-强度干涉法”的吸反力配合特性可靠性容差分析数学模型。以某型号航天电磁继电器为例，进行了可靠性容差分析与研究，给出了对航天电磁继电器可靠性设计具有指导作用的重要结论。     

应用iGMAS超快速星历的实时精密单点定位研究

中国主导建设的国际GNSS监测评估系统(iGMAS)相比国际上比较成熟的IGS系统在产品精度等方面存在差别,目前实时精密单点定位应用多采用IGS实时、近实时产品.为改变这一现状,针对iGMAS产品特性以及实时精密单点定位对超快速精密星历的需求,对iGMAS超快速星历的精度和稳定性方面进行评估,设计了iGMAS产品实时/...     

Long-term time-varying characteristics of UPD products generated by a global and regional network and their interoperable application in PPP

The quality and availability of Uncalibrated Phase Delay (UPD) solutions are crucial to the Precise Point Positioning (PPP) service, and the long-term temporal variability and its contributing factors should be better understood. In this paper, we comprehensively investigate the long-term time-varying characteristics of each UPD product respectively generated by a global and regional network and their interoperable application in PPP-AR (ambiguity resolution), the sampling of the WL and NL UPDs are daily and 30 s, respectively. Firstly, in terms of our 30 day Wide-Lane (WL) UPD products of 31 satellites, the Standard Deviation (STD) of each satellite WL UPDs ranges from 0.04 to 0.06 cycles, indicating that the long-term prediction accuracy of satellite WL UPD is sufficient for fixing Wide-Lane ambiguities. Secondly, when a satellite in eclipsing the discontinulity may corrupt the determination of Narrow-Lane (NL) UPD in form of offset, as a result of lacking or poor satellite attitude dynamic modeling. When the influence of discontinuity is removed, the STD of our estimated satellite NL UPDs is less than 0.05 cycles. Thirdly, the STD of our estimated receiver WL UPDs is mainly below 0.2 cycles, which implies that its stability is one order poorer that of the satellite. In addition, if they are used for stations in and around the network covered region, the stability of the UPD products from the CMONOC (Crustal Movement Observation Network of China) is better than that from a global network, benefit from the fact that all the CMONOC stations are equipped with the same receiver type. Finally, the PPP-AR results show that a rate of 82.9% for stations with a WL-ambiguity-fixed rate of over 90% while 69.5% for stations with an NL-ambiguity-fixed rate of over 80% can be achieved when using UPD from the global network, which is worse than that of using UPD from the CMONOC (85.7% for stations with a WL-ambiguity-fixed rate of over 90% while 75% for stations with an NL-ambiguity-fixed rate of over 80%). The results of the experiment on the UPD interoperable application in PPP show that the global network UPD products can provide a fast AR at any single station, and the convergence time is well below 25 min. Particularly, when the location of a station is in and around the regional network, our results show that the PPP results obtained using regional UPDs enable the consistent use of global UPDs. When the location of a station is far away from the regional network, using the regional UPDs can not achieve PPP-AR. Finally, the WL UPDs of the previous day is used for forecasting to estimate the NL UPDs, the stability analysis results of NL UPDs solution and positioning results are demonstrate the validity of forecasted UPD products.     

涡轮流量计校准不确定度的评定

根据测量不确定度的原理,详细分析了涡轮流量计的校准不确定度,推导出它的计算公式,并且结合具体的流量校准装置进行了简化和计算举例。     

高职院校商务英语专业学生顶岗实习管理模式实践探索——以长沙航空职业技术学院为例

学生顶岗实习是高职院校高技能型人才培养和实践教学的关键环节。基于长沙航空职业技术学院商务英语专业学生顶岗实习的现状,通过反思顶岗实习中出现的诸多问题,探索和建制了我院该专业的学生顶岗实习管理新模式。     

“做中教”教学法在高职教学中的应用

阐述“教学做合一”教育思想的精髓及其教学观的主要内涵,论述高职教育应以实践教学为中心,教师在教学中应学会在“做中教”,努力达到“教学做合一”。