1,798,409 research outputs found
Spatial Chow-Lin Methods for Data Completion in Econometric Flow Models
Get PDFFlow data across regions can be modeled by spatial econometric models, see LeSage and Pace (2009). Recently, regional studies became interested in the aggregation and disaggregation of flow models, because trade data cannot be obtained at a disaggregated level but data are published on an aggregate level. Furthermore, missing data in disaggregated flow models occur quite often since detailed measurements are often not possible at all observation points in time and space. In this paper we develop classical and Bayesian methods to complete flow data. The Chow and Lin (1971) method was developed for completing disaggregated incomplete time series data. We will extend this method in a general framework to spatially correlated flow data using the cross-sectional Chow-Lin method of Polasek et al. (2009). The missing disaggregated data can be obtained either by feasible GLS prediction or by a Bayesian (posterior) predictive density.Missing values in spatial econometrics, MCMC, non-spatial Chow-Lin (CL) and spatial Chow-Lin (SCL) methods, spatial internal flow (SIF) models, origin and destination (OD) data
SPATIAL CHOW-LIN METHODS: BAYESIAN AND ML FORECAST COMPARISONS
Get PDFCompleting data that are collected in disaggregated and heterogeneous spatial units is a quite frequent problem in spatial analyses of regional data. Chow and Lin (1971) (CL) were the rst to develop a uni ed framework for the three problems (interpolation, extrapolation and distribution) of predicting disaggregated times series by so-called indicator series. This paper develops a spatial CL procedure for disaggregating cross-sectional spatial data and compares the Maximum Likelihood and Bayesian spatial CL forecasts with the naive pro rata error distribution. We outline the error covariance structure in a spatial context, derive the BLUE for the ML estimator and the Bayesian estimation procedure by MCMC. Finally we
apply the procedure to European regional GDP data and discuss the disaggregation assumptions. For the evaluation of the spatial Chow-Lin procedure we assume that only NUTS 1 GDP is known and predict it at NUTS 2 by using employment and spatial information available at NUTS 2. The spatial neighborhood is de ned by the inverse travel time by car in minutes. Finally, we present the forecast accuracy criteria comparing the predicted values with the actual observations.
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Evaluation by simulation of interpolation and acceleration algorithms for Stepper Motors
No full textStepper motors are used to control CNC machines for many applications. As well as following the required path precisely, it is also important that the motion be smooth and that the surface speed be controllable. Improved interpolation algorithms for individual straight lines and circular arcs have been developed using distance as a parameter [Chow et al, 2002], [Chow, 2003]. The algorithms control the motor by means of pulses and the generation of the pulse timings is based on the geometry of the shape. For high speeds it is necessary to allow smooth acceleration at the beginning and similar smooth deceleration at the end. Thus, appropriate acceleration and deceleration algorithms have been developed for use with the new interpolation algorithms. This paper describes how simulation has been used to evaluate the new algorithms and compare them with previous algorithms. The algorithms are described for the 2D case but the principle can be extended to 3D
An interview with Rey Chow
No full textAn interview with Rey Chow was carried out for this special themed issue of Social Semiotics, which is concerned with asking Rey Chow about her past, present and future work. It is organized by questions related to her ongoing work in postcolonialism, cultural studies, cultural theory and comparative literature, as well as her work's connections to history, philosophy and cultural politics
Chow Theorem and structure of Carnot-Caratheodory balls
Get PDFopenThis thesis is meant to be a study on the role of the C-C metrics in the Chow theorem and on the structure of C-C balls.
It opens with a section in which we give the definitions of vector field and bracket and we state the properties of the latter.
Then we give the definition of the most important object of this work: the Carnot-Caratheodory metrics and we state some basic propositions on its behavior, hinting also to some metrics which are equivalent to it.
We now proceed giving preliminary notions about exponential maps on a compact set of R^n, we state the Campbell-Hausdorff formula for two smooth vector fields and we introduce an object defined as a composition of exponentials E(J,t).
We finally state the Chow theorem for m smooth vector fields in R^n satisfying the Chow-Hoermander condition. We prove it using the Campbell-Hausdorff formula and defining through E(J,t) n approximated exponential maps whose composition provides us with a local diffeomorphism.
This theorem is particularly important because it tells us that under Chow-Hoermander condition we can regain directions that would be otherwise prohibited.
We introduce the doubling metric spaces and in particular we state a theorem on the structure of C-C balls: the Nagel-Stein-Wainger theorem, which provides us with the size of the C-C balls and tells us they are represented as the image of rectangles under the exponential map.
At last, we close this work with a variant of the structure theorem.This thesis is meant to be a study on the role of the C-C metrics in the Chow theorem and on the structure of C-C balls.
It opens with a section in which we give the definitions of vector field and bracket and we state the properties of the latter.
Then we give the definition of the most important object of this work: the Carnot-Caratheodory metrics and we state some basic propositions on its behavior, hinting also to some metrics which are equivalent to it.
We now proceed giving preliminary notions about exponential maps on a compact set of R^n, we state the Campbell-Hausdorff formula for two smooth vector fields and we introduce an object defined as a composition of exponentials E(J,t).
We finally state the Chow theorem for m smooth vector fields in R^n satisfying the Chow-Hoermander condition. We prove it using the Campbell-Hausdorff formula and defining through E(J,t) n approximated exponential maps whose composition provides us with a local diffeomorphism.
This theorem is particularly important because it tells us that under Chow-Hoermander condition we can regain directions that would be otherwise prohibited.
We introduce the doubling metric spaces and in particular we state a theorem on the structure of C-C balls: the Nagel-Stein-Wainger theorem, which provides us with the size of the C-C balls and tells us they are represented as the image of rectangles under the exponential map.
At last, we close this work with a variant of the structure theorem
Urban heat island research in Phoenix, Arizona: Theoretical contributions and policy applications
No full textabstract: This review investigates the possible reasons and motivations underpinning the large body of work, as well as summarizing specific themes, approaches, and theoretical contributions arising from such study.Corresponding Author:
Winston T. L. Chow
Arizona State University
[email protected]
Interview with Dr. Rosemary Tung Chow and Granddaughter
No full textInterview with Dr. Rosemary Tung Chow, 2000 South Carolina Mother of the Year.https://digitalcommons.winthrop.edu/scmotheroftheyear/1008/thumbnail.jp
Chow Chow
No full textPhoto of a Chow Chow dog in a yard. The photo was taken for Mrs. Underwood's account
The Rey Chow Reader
No full textRey Chow is arguably one of the most prominent intellectuals working in the humanities today. Characteristically confronting both entrenched and emergent issues in the interlocking fields of literature, film and visual studies, sexuality and gender, postcolonialism, ethnicity, and cross-cultural politics, her works produce surprising connections among divergent topics at the same time as they compel us to think through the ethical and political ramifications of our academic, epistemic, and cultural practices. This anthology - the first to collect key moments in Chow's engaging thought - provides readers with an ideal introduction to some of her most forceful theoretical explorations. Organized into two sections, each of which begins with a brief statement designed to establish linkages among various discursive fields through Chow's writings, the anthology also contains an extensive Editor's Introduction, which situates Chow's work in the context of contemporary critical debates. For all those pursuing transnational cultural theory and cultural studies, this book is an essential resource
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