Sequential Estimation of Dynamic Discrete Games

This paper studies the estimation of dynamic discrete games of incomplete information. Two main econometric issues appear in the estimation of these models: the indeterminacy problem associated with the existence of multiple equilibria and the computational burden in the solution of the game. We propose a class of pseudo maximum likelihood (PML) estimators that deals with these problems, and we study the asymptotic and finite sample properties of several estimators in this class. We first focus on two‐step PML estimators, which, although they are attractive for their computational simplicity, have some important limitations: they are seriously biased in small samples; they require consistent nonparametric estimators of players' choice probabilities in the first step, which are not always available; and they are asymptotically inefficient. Second, we show that a recursive extension of the two‐step PML, which we call nested pseudo likelihood (NPL), addresses those drawbacks at a relatively small additional computational cost. The NPL estimator is particularly useful in applications where consistent nonparametric estimates of choice probabilities either are not available or are very imprecise, e.g., models with permanent unobserved heterogeneity. Finally, we illustrate these methods in Monte Carlo experiments and in an empirical application to a model of firm entry and exit in oligopoly markets using Chilean data from several retail industries.     

Identification in Differentiated Products Markets Using Market Level Data

We present new identification results for nonparametric models of differentiated products markets, using only market level observables. We specify a nonparametric random utility discrete choice model of demand allowing rich preference heterogeneity, product/market unobservables, and endogenous prices. Our supply model posits nonparametric cost functions, allows latent cost shocks, and nests a range of standard oligopoly models. We consider identification of demand, identification of changes in aggregate consumer welfare, identification of marginal costs, identification of firms' marginal cost functions, and discrimination between alternative models of firm conduct. We explore two complementary approaches. The first demonstrates identification under the same nonparametric instrumental variables conditions required for identification of regression models. The second treats demand and supply in a system of nonparametric simultaneous equations, leading to constructive proofs exploiting exogenous variation in demand shifters and cost shifters. We also derive testable restrictions that provide the first general formalization of Bresnahan's (1982) intuition for empirically distinguishing between alternative models of oligopoly competition. From a practical perspective, our results clarify the types of instrumental variables needed with market level data, including tradeoffs between functional form and exclusion restrictions.     

相对论速调管中调制腔的三维设计

根据二维模拟中电子束在调制腔中所需要的微波场,采用三维电磁场模拟软件进行调制腔的三维设计。在相对论速调管放大器中输入微波的馈入调制腔内,其作用场为TM01模;由于调制腔需要从外部馈入微波,通常为一种较复杂的三维结构。通过三维带电子束的电磁场模拟,验证了三维设计调制腔在给定输入功率条件下对电子束的调制效率及其三维设计。     

易开盖在线定点剔除技术

设计2种对高速生产线上在线视觉检测不合格易开盖的定点剔除方法。第1种是根据PC采集处理的盖子图片数与PLC计数对比,进行定点剔除;第2种是依靠运动控制卡,利用编码器对传送带位置编码数据,通过位置比较进行定点剔除。在易开盖注胶生产线的实际运行表明,2种方法均能可靠稳定运行。通过使用在线视觉检测和剔除技术,不仅减少了工人的劳动强度,而且保证了产品的质量。     

一种新型的光学时分复用系统的设计及实验

提出一种采用单个皮秒(ps)光源分路后,由具有增益的半导体激光放大器作为南速调制开关的光学时分复用(OTDM)系统方案,并进行了两个信过的2Gbit/s 光学时分复用发射系统模拟实验.     

基于总体方差最小消去DCT的方块效应

提出基于总体方差最小消去离散余弦变换DCT的方块效应,推导出水平集方程,用最小/最大曲率流替代水平集中的平均曲率流。该方法在平滑噪声和消去方块效应的同时,能保留图像的主要结构特征。后续分割实验结果表明,该方法比均值滤波后的图像有更好的视觉和分割效果。     

Doherty高效率放大器的特性分析与仿真实现

在无线通信系统设计中,功率放大器的效率和线性度影响整个系统的性能。该文针对放大器效率问题,研究了Doherty放大器的自身结构特点及其相对于其他的提高效率指标方法的优势。通过对其原理的推导,得到Doherty放大器的效率特性曲线。并结合仿真结果,对比一般的AB类放大器效率曲线,验证了Doherty放大器的高效率性。     

共轭对称数据DFT,FFT的研究及应用

本文研究了共轭对称输入序列的离散付里叶变换DFT的特点,推导出高效的共轭对称数据FFT算法,并将其应用于机构学中对称连杆曲线的综合,取得了令人满意的结果.     

双调谐回路负阻放大器的最大平坦特性

在微波放大器的谐振腔中引入双调谐腔回路是实现宽带微波及毫米波负阻放大器的有效方法。在推导出了该电路的稳态工作方程之后,着重讨论了实现最大平坦增益特性的条件,指出两谐振腔负载Q值的比值是实现最大平坦增益的决定因素,导出了获得最大平坦增益时,电路参数的解析表达式,从而为最大平坦增益设计提供了理论依据,研究的理论得到了以往文献中实验结果的验证。     

A Test for Independence of Competing Risks with Discrete Failure Times

The identifiability problem in Competing Risks is well known. In particular, it implies that independent action or otherwise of the risks cannot be inferred from data alone. However, Crowder (1996) showed that, in the case of purely discrete failure times, an inference can be made. An algebraic criterion was derived which bears essentially on the independence in question. The condition was presented in a theoretical setting but it was pointed out that the quantities involved can be estimated from data and that, therefore, there is the potential to develop practical tests for the hypothesis of independence. It is the purpose of this paper to construct such a test. This revised version was published online in July 2006 with corrections to the Cover Date.