Effect of surface blowing on aerodynamic characteristics of tubercled straight wing

Recent research proves that wings with leading-edge tubercles have the ability to perform efficiently in post-stall region over the conventional straight wing. Moreover, the conventional straight wing outperforms the tubercled wing at a pre-stall region which is quintessential. Even though tubercled wing offers great performance enhancement, because of the complexity of the flow, the trough region of the tubercled wing is more prone to flow separation. Henceforth, the present paper aims at surface blowing – an active flow control technique over the tubercled wing to enhance the aerodynamic efficiency by positively influencing its lift characteristics without causing any additional drag penalty. Flow parameters like blowing velocity ratios and the location of blowing were chosen to find the optimised configuration keeping the amplitude and frequency of the leading-edge tubercles constant as 0.12 c and 0.25 c respectively. Numerical investigations were carried out over the baseline tubercled wing and tubercled wing with surface blowing at various blowing jet velocity ratios 0.5, 1 and 2 over four different chordwise locations ranging from 0.3 c to 0.8 c.The results confirm that blowing at various x/c with different blowing velocity ratios performs better than the conventional tubercled wing. Comparatively, blowing velocity ratio 2 at 0.3 c shows peak performance of about 28% enhancement in the lift characteristics relative to the baseline model. Particularly, in the pre-stall region, 25–50% increase in aerodynamic efficiency is evident over the tubercled wing with surface blowing compared with the baseline case. Additionally,attempts were made to delineate the physical significance of the flow separation mechanism due to blowing by visualizing the streamline pattern.     

S5 0716+714: GeV variability study

The GeV observations by Fermi-LAT give us the opportunity to characterize the high-energy emission (100 MeV–300 GeV) variability properties of the BL Lac object S5 0716+714. In this study, we performed flux and spectral analysis of more than 3 year long (August 2008 to April 2012) Fermi-LAT data of the source. During this period, the source exhibits two different modes of flux variability with characteristic timescales of ∼75 and ∼140 days, respectively. We also notice that the flux variations are characterized by a weak spectral hardening. The GeV spectrum of the source shows a clear deviation from a simple power law, and is better explained by a broken power law. Similar to other bright Fermi blazars, the break energy does not vary with the source flux during the different activity states. We discuss several possible scenarios to explain the observed spectral break.     

ANALYSIS OF COUPLING SENSITIVITY OF UN－CONVENTIONAL RESPONSES FOR DIRECTFORCE CONTROL AIRCRAFT

ＡＮＡＬＹＳＩＳＯＦＣＯＵＰＬＩＮＧＳＥＮＳＩＴＩＶＩＴＹＯＦＵＮ－ＣＯＮＶＥＮＴＩＯＮＡＬＲＥＳＰＯＮＳＥＳＦＯＲＤＩＲＥＣＴＦＯＲＣＥＣＯＮＴＲＯＬＡＩＲＣＲＡＦＴＸｕＲｕｉｊｕａｎ（Ｆａｃｕｌｔｙ５０３，ＮｏｒｔｈｗｅｓｔｅｒｎＰｏｌｙｔｅｃｈ...     

基于广义既约梯度法的航空发动机性能寻优控制

提出了一种基于航空发动机约束物理意义的寻优方法，并将其应用于性能寻优控制之中。该方法根据航空发动机约束的物理特性完全已知的特点，利用起作用集法和既约梯度法将发动机非线性约束寻优问题转化为低维的无约束寻优问题，提高了计算速度。应用该方法对全包线内的工作点，对最大推力、最低油耗、最低涡轮进口温度和加力最大推力等模式进行了寻优，给出了寻优结果。     

房地产调控的政策导向及其市场走势

2006年是我国房地产宏观调控政策出台最多和调控力度最大的一年，文章就调控后的房地产业的政策环境、市场情况、价格走势和消费心态等进行了深入的研究并对我国2007年房地产走势进行了相关分析，认为随着国家对土地资源的严格控制，土地出让制度的逐步规范，房地产市场供需矛盾出现两极分化态势；房地产宏观调控也会对自住者、投资者、中介、银行和开发商产生不同的影响，中国房产市场将在调控中稳定、持续、健康发展。     

高阶系统的降阶控制研究

本文根据线性随机系统的最优控制理论较详细地给出了利用优化技术对高阶系统进行降阶控制的理论分析,并对提高整个控制系统的稳定性提出了一种改进方法.最后对飞机机翼的最简模型——自由-自由梁的振动抑制进行了具体的计算,取得了较为满意的结果。     

论“健壮设计”—产品设计的新观念

“健壮设计”（田口方法）的理论和方法，已受到工业先进国家的高度重视，并取得显著成果和效益，本文概略而系统地介绍了健壮设计之由来，基本概念、原理及其优性，提出质量损失函数概念及其表示方法；新产品开发过程中的三次设计思想，即系统设计，参数设计和容差设计，说明信噪比参数的新应用及其在望目特性、望大特性、望小特性、动态特性情况下的表达式，分析健壮设计对影响产品质量损失函数的三种干扰因素之作用，提出在航空部     

氢钟开发技术和展望

由氢脉泽原理对原子频率标准目前的发展进行了分析。对主动和被动氢脉泽限制频率稳定度的基本不稳定因素进行了分析。描述确保主动和被动氢脉泽高短期和长期频率稳定的设计方法。现在,主动氢脉泽指标可达到1.10-13/s和3.5.10-16/d,被动氢脉泽指标可达到4.10-13/s和2.5.10-15/d。还讨论了氢脉泽指标的进一步改善。     

机载固态有源阵指数约束二维可分离的多阶振幅量化

提出了一种用于机载有源相控阵具有指数约束的二维可分离多阶振幅量化低副瓣口径设计技术,它能有效地降低水平面和非主平面的峰值副瓣电平并能减少Ｔ／Ｒ组件的品种数。采用二维可分离的设计思想,在工程应用中可大大地减少到馈网络的品种数。计算机仿真计算结果证明了理论分析。     

基于自抗扰技术的挠性航天器高精度指向控制

针对存在外部干扰和模型不确定性的挠性航天器,提出了一类新颖的基于自抗扰技术的控制方案,实现无姿态角速度反馈的航天器对目标高精度姿态指向控制。对目标相对姿态指向控制系统进行建模,引入一光滑连续秦函数,构造三阶扩张观测器,观测系统姿态角速度和总扰动,并利用其实现动态补偿线性化及扰动抑制。针对单框架控制力矩陀螺群作为执行机构常存在的奇异,引入零空间空转指令设计了一类奇异避免操纵律。将控制系统方案用于某挠性航天器模型,仿真结果验证了方案的有效性、合理性。