电子直线加速器磁控管频率稳定的自适应线性神经元方法

 电子直线加速器电子束能量的稳定与否取决于功率源工作频率的稳定性,磁控管在短时间内的散谱和轻微跳谱造成稳频系统的控制精度下降,最后电子束的扫描均匀度下降。引入自适应线性神经元方法(ADALINE)和噪声对消技术以消除对工作频率长期稳定性的影响,从而保证了电子束的扫描均匀度。     

How to compute least infeasible flows

It is well-known how to use maximum flow to decide when a flow problem with demands, lower bounds, and upper bounds is infeasible. Less well-known is how to compute a flow that is least infeasible. This paper considers many possible ways to define “least infeasible” and shows how to compute optimal flows for each definition. For each definition it also gives a dual characterization in terms of cuts, a polynomial routine for recognizing that type of least infeasible flow, and relates that definition to dual cut canceling min-cost flow network algorithms. This research was partially supported by an NSERC Operating Grant, an NSERC Grant for Research Abroad, and a UBC Killam Faculty Study Leave Fellowship. Parts of this research were done while the author was visiting Laboratoire ARTEMIS IMAG at Université Joseph Fourier de Grenoble, France.     

ST摘帽如何影响公司价值和股价

以2004~2015年的ST公司为研究样本,利用事件研究法和双重差分模型,研究了ST摘帽对公司价值和股价的影响效应。实证结果表明,摘帽公告可以引起显著为正的累计超额收益率。而且,摘帽的部分信息含量可以被市场提前预期到,并立即反应到股价上。因此,仅从摘帽信息的股价反应速度看,我国的股票市场是半强式有效市场。此外,双重差分的实证结果显示,ST摘帽对公司价值没有显著的影响。但是,具体而言,摘帽事件可以同时显著地提高公司的市值和账面价值。这些结果都基本符合ST制度的政策预期。为了缓解内生性问题,在考虑控制变量的影响和倾向值匹配后,双重差分的实证结果是稳健的。     

拖船噪声抵消与左右舷分辨联合处理方法的研究

利用拖曳双线阵声纳基阵结构的左右舷分辨能力,并结合拖船相对于拖曳线列阵的空间位置关系,本文提出一种拖船噪声抵消与左右舷分辨联合处理的方法,在波束域分别形成左右波束并将映像波束相减,在检测目标并进行左右分辨的同时,可以显著抵消拖船噪声。海试结果验证了该方法的有效性,拖船噪声被抑制掉约14dB,同时正确分辨出目标的左右舷方位。     

Measurement of properties of a smooth-walled spline-profile feed horn around 840 GHz

For astrophysical applications at submillimeter wavelengths, efficient coupling of the feed horn pattern in the focal plane to the radiation pattern of the telescope is paramount. To date, at 840 GHz with high band width, corrugated feed horns have been used with very good results. The goal of developing instruments for KOSMA above 1 THz where state-of-the-art heterodyne systems are still governed by receiver noise rather than by radiative background, requires fabrication of corrugated structures of the order of λ/3 or less. This is non-trivial, and here we present the performance of a smooth-walled spline-profile feed horn, which is considerably easier to manufacture compared to a corrugated feed horn. The performance is assessed via radiation patterns in H, E and 45° D-Plane in co- and cross-polarization.     

A polynomial cycle canceling algorithm for submodular flows

Submodular flow problems, introduced by Edmonds and Giles [2], generalize network flow problems. Many algorithms for solving network flow problems have been generalized to submodular flow problems (cf. references in Fujishige [4]), e.g. the cycle canceling method of Klein [9]. For network flow problems, the choice of minimum-mean cycles in Goldberg and Tarjan [6], and the choice of minimum-ratio cycles in Wallacher [12] lead to polynomial cycle canceling methods. For submodular flow problems, Cui and Fujishige [1] show finiteness for the minimum-mean cycle method while Zimmermann [16] develops a pseudo-polynomial minimum ratio cycle method. Here, we prove pseudo-polynomiality of a larger class of the minimum-ratio variants and, by combining both methods, we develop a polynomial cycle canceling algorithm for submodular flow problems. Received July 22, 1994 / Revised version received July 18, 1997? Published online May 28, 1999     

逆波束形成的旁瓣抑制

为了降低普通逆波束形成旁瓣,提出了一种新的旁瓣抵消技术。该技术利用指向性函数中的旁瓣部分去估计声场的响应,然后从基阵估计的声场减去这部分指向性函数旁瓣估计的声场,从而得到最终的声场估计。由于较多的旁瓣响应被估计的声场扣除,最终估计的声场中的旁瓣大大降低。利用该技术可有效地抑制干扰,同时又可保持普通逆波束形成的方位高分辨力。湖试结果显示了该技术的有效性和可行性。