关于图书馆学经典的研究——南开大学图书馆学前沿研究讨论之一

任何学科中经典著作研究都应该处于该学科最基本的地位,因为它是该学科与其他学科相区别的独立性的体现。在一次专题讨论的基础上,从理论研究到实践操作的层面分析探讨了图书馆学学术经典的概念、图书馆学经典研究的意义、经典著作的标准以及经典研究对图书馆学研究学风的影响等问题,希望可以通过图书馆学经典问题研究提高图书馆学研究的精品意识,促进学科走向成熟。     

主流逆压力梯度下气膜孔流量系数的实验

为研究主流逆压力梯度下气膜孔的几何结构和气动参数对流量系数的影响规律,采用放大模型在低速回流式风洞中进行了实验。在对比研究圆柱孔和双向扩张孔流量系数基础上,重点研究了双向扩张孔的流量系数。结果表明,双向扩张孔的流量系数比圆柱孔的流量系数高。前倾角越大,流量系数越高;径向角越大,流量系数越高。流量系数随动量比的增加而增高,在动量比小于4时增幅尤其明显。主流湍流度增大使流量系数增大,动量比越小,增幅越大。除了在孔轴线与平板的夹角较大情况外,密度比对流量系数的影响较小。     

基于实验设计和响应面模型的风扇转子气动优化设计

针对跨声速风扇动叶中掠、弯结合叶片基于控制点的B样条曲线对积叠线进行参数化,以掠、弯为设计自由度,应用实验设计、三维粘性流场求解、响应面模型及遗传算法对Rotor 67以近尖峰效率工况点为设计点对风扇转子进行了气动优化设计,得到了前掠与弯向旋转方向的复合设计叶片,其总压比有较明显提高。但由于优化是在单一工况点下进行的,其变工况性能不佳。     

Acceleration sensors based modal identification and active vibration control of flexible smart cantilever plate

Some flexible appendages of spacecrafts, such as solar panels, are cantilever plate structures. Thus, vibration problem is unavoidable when there is slewing maneuver or external disturbance excitation. Vibration of such cantilever plate structures includes coupled bending and torsional motion. Furthermore, the low amplitude vibration near the equilibrium point is very difficult to be quickly suppressed due to nonlinear factors of the hardware in the system, which is harmful to stability and attitude control accuracy. To solve these problems, acceleration sensor-based modal identification and active vibration control methods are presented for the first two bending and the first two torsional modes vibration of the cantilever plate. Optimal placements of three acceleration sensors and PZT patches actuators are performed to decouple the bending and torsional vibration of such cantilever plate for sensing and actuating, and identifications are achieved by experiments. A nonlinear control method is presented to suppress both high and low amplitude vibrations of flexible smart cantilever plate significantly. Experimental comparison researches are conducted by using acceleration proportional feedback and the presented nonlinear control algorithms. The experimental results demonstrate that the presented acceleration sensor-based methods can suppress the vibration of cantilever plate effectively.     

Coronal fast wave trains of the decimetric type IV radio event observed during the decay phase of the June 6, 2000 flare

The 22 min long decimetric type IV radio event observed during the decay phase of the June 6, 2000 flare simultaneously by the Brazilian Solar Spectroscope (BSS) and the Ond?ejov radiospectrograph in frequency range 1200–4500 MHz has been analyzed. We have found that the characteristic periods of about 60 s belong to the long-period spectral component of the fast wave trains with a tadpole pattern in their wavelet power spectra. We have detected these trains in the whole frequency range 1200–4500 MHz. The behavior of individual wave trains at lower frequencies is different from that at higher frequencies. These individual wave trains have some common as well as different properties. In this paper, we focus on two examples of wave trains in a loop segment and the main statistical parameters in their wavelet power and global spectra are studied and discussed.     

北斗-罗兰C组合导航的ASF修正计算与研究

介绍讨论了修正ASF的米林顿法和CLC数值积分法,并用MATLAB编程计算;用米林顿法计算的（SF＋ASF）,与军标“长波地波传输信道计算方法”计算结果非常吻合;CLC数值积分法计算的结果与英国Paul Williams的结果也很吻合;而CLC数值积分法计算的（SF＋ASF）与米林顿法有较大差别,但在用以推求陆地路径ASF时,二者差别就很小。试验表明,CLC数值积分法有助于复杂地形路径的ASF修正计算。     

单组元300N发动机低温试验研究

为探究低温环境下单组元300N发动机的工作特性,揭示影响发动机低温性能的主要影响因素,以300N发动机为试验对象,开展了模拟飞行工况的发动机低温试验。给出了低温试验研究方法,分别从温度差异对发动机性能影响、催化剂活性差异对发动机低温启动特性影响和低温对电磁阀响应特性影响等方面获得研究结果。结果表明,低温是影响发动机低温性能的主要影响因素,-48℃条件催化剂无法完成推进剂的催化分解,发动机发生爆炸;-30℃条件下起活时间为80.5～87.5ms,发动机可正常启动,且启动温度与起活时间呈指数关系;催化剂批次差异也对发动机低温工作性能产生一定影响,不同批次催化剂低温起活时间的差异可达91ms;低温试验过程中,电磁阀的关闭受到低温推进剂粘性和背压的影响,产生了明显的迟滞现象,延迟时间约100ms,对发动机在轨的精准控制存在一定影响。     

空间科学任务协同设计论证平台

空间科学任务协同设计论证存在设计方案耦合强,数据一致性差,数据变更难,数据与流程脱节等问题.为了解决上述问题,建立了典型空间科学任务的多层数字化模型;采用图形化方式对论证流程进行建模,并建立流程与数据的映射关系;通过共享数据池的方式为多岗位用户提供多方案数据协同机制;采用消息总线对数据变更进行及时提醒;利用方案依赖关系矩阵来判别方案耦合关系,最终自动合并任务总体设计方案.作为一个分布式平台,空间科学任务协同设计平台采用Eclipse RCP和Spring技术架构,整合了Hibernate、工作流Activiti5等中间件,提供统一门户,支持多岗位、多任务、多方案、多版本的管理能力,提供论证流程监控、数据协同交互等功能.结合某空间科学任务论证验证了该平台的有效性.      

Preliminary study on heat flux measurement data of TT-0 flight test

With the explosive development of aerospace science, the design of the new generation airliner at higher speeds is attracting more attentions. To achieve this goal, it is necessary to achieve accurate prediction of the aerodynamic heating / force loads and successful reduction of drag and heat flux. As a remedy for the existing studies which are based upon the CFD and wind tunnel tests, this study presents a flight test for the drag and heat reduction spike technology. The principal goals of this flight test were to provide reference for verifying the accuracy of the prediction technology on ground and promote the development of the drag and heat reduction technology. By adopting the OS-X rocket, the TT-0 test vehicle designed by Shenyang Aircraft Design & Research Institute reached a maximum Mach number of 5.8 and a maximum altitude of 38 km. Hypersonic and supersonic pressure data by pressure scanning valves and heat fluxes by gauges at different locations were obtained successfully. Also, heat fluxes obtained by in-house CFD code are illustrated in comparison with the flight data. The results indicate that the numerical errors are large in most cases. More technologies, such as more CFD codes and more numerical procedures, should be adopted to conduct studies on this issue in the future.     

United Nations Human Space Technology Initiative (HSTI)

The Human Space Technology Initiative was launched in 2010 within the framework of the United Nations Programme on Space Applications implemented by the Office for Outer Space Affairs of the United Nations. It aims to involve more countries in activities related to human spaceflight and space exploration and to increase the benefits from the outcome of such activities through international cooperation, to make space exploration a truly international effort.