Estimating the distance distribution of subpopulations and testing observation outlyingness for a large-scale complex survey

Many finite populations targeted by sample surveys comprise a relatively small number of homogeneous subpopulations. In on-going survey operations, it is often of interest to be able to assess whether a new observation belongs to one of those subpopulations or should be flagged as not belonging to any of them. Because the homogeneity of the subpopulations depends on potentially large numbers of survey variables interacting in complex ways, we define a distance measure in the space induced by the survey variables, and consider the distribution of these distances within the subpopulation as a summary of the distributional characteristics of the subpopulation. We also define a measure of the outlyingness of each individual point as the fraction of points with a less extreme distance in the subpopulation. In this thesis, we propose a sample-based estimator for the subpopulation distance distribution functions and measure of outlyingness. We allow for a general distance measure, and consider both multivariate means and medians as centers. We describe the design-based asymptotic properties of the estimator under weak assumptions on the finite population. We investigate several approaches for design-based variance estimation, including a combination of kernel regression and replication variance estimation. The practical properties of the procedures are evaluated in a longitudinal complex survey called the National Resources Inventory.;The theoretical derivations for sample distance distribution can be generalized to a broad class of survey estimators, involving nondifferentiable functions defined at the population level. We extend the theoretical results to two classes nondifferentiable survey estimators, statistics as nondifferentiable functions of estimated parameters and estimators implicitly defined through estimating equations. In both cases, a direct Taylor linearization is not applicable, but we can assume the limiting function is differentiable and do asymptotic expansion on the limits. We offer a design-based perspective of both cases in this thesis and justify the design assumptions under probabilistic mechanism. We also propose a variance estimator using kernel smoothing and show its consistency

NTCIR CLIR Experiments at the University of Maryland

This paper presents results for the Japanese/English cross-language information retrieval task on the NACSIS Test Collection. Two automatic dictionarybased query translation techniques were tried with four variants of the queries. The results indicate that longer queries outperform the required descriptiononly queries and that use of the rst translation in the edict dictionary is comparable with the use of every translation. Japanese term segmentation posed no unusual problems, which contrasts sharply with results previously obtained for cross-language retrieval between Chinese and English.

Analysis of Dynamic Stability of Ejector Expansion Refrigeration System

The stable operation of a system is restricted by the intrinsic characteristics, namely harmonious matching among and between structure parameters and operation parameters. In this paper, we put forward an analysis method of the dynamic stability of the refrigeration system based on the First Approximation Theory of Lyapunov Stability Theorem and the evaluation of stability margin. It is carried out by linearizing the governing equations and analyzing the eigenvalue form of coefficient matrix. And the minimum logarithmic decrement is calculated to represent the stability margin. Analyzing the stability of gas cooler confirms the consistency between the mathematical stability and the actual dynamic one. The proposed method is performed in a transcritical CO2 ejector expansion refrigeration system (EERS) to analyze the system dynamic stability. The present results show that, even each component of the system is in the stable state, it cannot guarantee the dynamic stability of the whole system. Moreover, the effect of state parameter on system dynamic stability is investigated. The work supplies a guiding principle on system control and may be extended in more general thermodynamic cycle

RFID-Based Vehicle Positioning and Its Applications in Connected Vehicles

This paper proposed an RFID-based vehicle positioning approach to facilitate connected vehicles applications. When a vehicle passes over an RFID tag, the vehicle position is given by the accurate position stored in the tag. At locations without RFID coverage, the vehicle position is estimated from the most recent tag location using a kinematics integration algorithm till updates from the next tag. The accuracy of RFID positioning is verified empirically in two independent ways with one using radar and the other a photoelectric switch. The former is designed to verify whether the dynamic position obtained from RFID tags matches the position measured by radar that is regarded as accurate. The latter aims to verify whether the position estimated from the kinematics integration matches the position obtained from RFID tags. Both means supports the accuracy of RFID-based positioning. As a supplement to GPS which suffers from issues such as inaccuracy and loss of signal, RFID positioning is promising in facilitating connected vehicles applications. Two conceptual applications are provided here with one in vehicle operational control and the other in Level IV intersection control