22,374 research outputs found
Spatial Chow-Lin Methods for Data Completion in Econometric Flow Models
No full textFlow 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
No full textCompleting 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
Chow Theorem and structure of Carnot-Caratheodory balls
No full textopenThis 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
Mme Chan et M. Chow à Singapour
No full text M. Chow, oppressé par l’atmosphère étouffante et les commérages de Hong-Kong, est parti pour Singapour, laissant Mme Chan seule à Hong-Kong. Cette séquence dévoile progressivement une visite de Mme Chan à Singapour dans l’appartement de M. Chow, sans que celui-ci ne le sache. S’il s’agit d’une tentative de retrouvailles en dehors de l’étouffante Hong-Kong, Singapour se révèle tout aussi exiguë et impropre à leur amour et cette dernière tentative d’union se solde par le constat de l’impossi..
Chow forms of congruences
No full textFor X PN an n-dimensional variety the set of linear spaces of dimension N − n − 1 meeting X defines a hypersurface, H, in the Grassmann variety G(N − n,N + 1).
The homogeneous form in the Pl¨ucker coordinates defining H or H itself is called the Chow form of X. This notion was defined by Cayley [A. Cayley, “On a new analytical representation of curves in space”, Q. J. Pure Appl. Math. 3, 225-236 (1860), and 5, 81-86 (1862); for a modern treatment see M. Green and I. Morrison, Duke Math. J.
53, 733-747 (1986; Zbl 0621.14028)].
In the present paper the authors study Chow forms of integral surfaces in G(2, 4) following the approach of M. Green and I. Morrison. Let V be a fixed 4-dimensional space and F P3 סP3, the flag variety parametrizing all chains V1 V3, where Vi is a subspace of V with dim Vi = i. F parametrizes the lines of G and to each integral surface Y in G there corresponds, in a natural way, an integral hypersurface X in F. The main result in this paper is a characterization of integral hypersurfaces X in F that are Chow forms of integral surfaces in G, in terms of some differential equations.Depto. de Álgebra, Geometría y TopologíaFac. de Ciencias MatemáticasTRUEpu
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]
The (almost) integral Chow ring of M~37
No full textThis paper is the third in a series of four papers aiming to describe the (almost integral) Chow ring of M¯3, the moduli stack of stable curves of genus 3. In this paper, we compute the Chow ring of M~37 with Z[1/6]-coefficients.</p
Biometric and plasma parameters (mean ± SEM) of sedentary (SED), control (CON) and treadmill-trained (TML: 12 m/min; TMH: 17 m/min) female rats fed a standard chow diet (ST) or a cafeteria (CAF) + standard chow diet.
No full textBiometric and plasma parameters (mean ± SEM) of sedentary (SED), control (CON) and treadmill-trained (TML: 12 m/min; TMH: 17 m/min) female rats fed a standard chow diet (ST) or a cafeteria (CAF) + standard chow diet.</p
Misja salezjańska Chiu Chow w Chinach
No full textThis article tells the story of Shiu Chow\u27s Salesian Mission in China (1918–1951), became Apostolic Vicariate (1920) and then diocese (1948). The Mission had lived a enormous development under the three Salesian bishops: Msgr. Versiglia (1918–1930), first Vicar Apostolic and Salesian protomartyr, Monk. Canazei (1930–1946), the Inspector in China and then Vicar Apostolic of Shiu Chow, Msgr. Arduino (1948–1951), director of the Salesian schools in Shanghai and first bishop of the diocese of Shiu Chow. Thriving mission activity and development closes the expulsion of the Salesian missionaries, the FMA nuns and Msgr. Arduino (December 2, 1951) from China from the Communists. The last part is dedicated to the Polish Salesian missionaries working in Shiu Chow Mission: coad. J. Urban, Ps. W. Spinek, sac. T. Szeliga, priest W. Wieczorek. The material for the article I found in the books of don. M. Rassiga, missionary and chronicler of Shiu Chow mission, I kindly offers to the author himself.Ten artykuł opowiada historię misji salezjańskiej Shiu Chow w Chinach (1918–1951), został wikariatem apostolskim (1920), a następnie diecezją (1948). Misja żyła a ogromny rozwój pod rządami trzech biskupów salezjańskich: ks. Versiglia (1918-1930), pierwszy wikariusz Pierwszy męczennik apostolski i salezjański, ks. Canazei (1930–1946), inspektor w Chinach, a następnie wikariusz Apostolski Shiu Chow, ks. Arduino (1948-1951), dyrektor szkół salezjańskich w Szanghaju i pierwszy biskup diecezji Shiu Chow. Prężnie rozwijająca się działalność i rozwój misji dobiegają końca wypędzenie salezjanów misjonarzy, sióstr CMW i ks. Arduino (2 grudnia 1951) od Chiny od komunistów. Ostatnia część poświęcona jest polskim misjonarzom salezjańskim pracującym w Polsce Misja Shiu Chow: dowódca. J. Urban, Ps. W. Spinek, sac. T. Szeligi, ks W. Wieczorek. The materiał do artykułu znalazłem w księgach dona. M. Rassiga, misjonarz i kronikarz Misję Shiu Chow, uprzejmie ofiarowuję samemu autorowi
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