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Times-Series Photometry & Spectroscopy of the Bright Blue Supergiant Rigel: Probing the Atmosphere and Interior of a SN II Progenitor
- Edward F. Guinan, J. A. Eaton, R. Wasatonic, H. Stewart, S. G. Engle, G. P. McCook
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- Journal:
- Proceedings of the International Astronomical Union / Volume 5 / Issue H15 / November 2009
- Published online by Cambridge University Press:
- 21 October 2010, p. 359
- Print publication:
- November 2009
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As the 7th brightest star and the most luminous star in the solar neighborhood, Rigel (β Orionis) is a very intriguing object. This blue supergiant (B8 Iab; V-mag = +0.05–0.18-mag; B–V = -0.03), at a distance (from Hipparcos) of ~240±35 pc has a 〈MV〉 = -6.7 mag. The following physical properties were determined via spectroscopic, photometric, and interferometric studies: L/L⊙ ≈ 66,000 K; Teff ≈ 12,000 K; M/M⊙ ≈ 17±3; R/R⊙ ≈ 70; τ ≈ 3–10 Myr. Interestingly Rigel has similar physical properties with the 12th mag blue supergiant progenitor of SN 1987A: Sanduleak -69° 202a. Thus Rigel (along with its co-asterism Betelgeuse) are likely to be the nearest progenitors of a Type II supernova. Such a nearby explosion would be V ≈ -11th mag (similar to a quarter moon).
10 - Seasonal Integration and Cointegration
- Clive W. J. Granger
- Edited by Eric Ghysels, University of North Carolina, Chapel Hill, Norman R. Swanson, Rutgers University, New Jersey, Mark W. Watson, Princeton University, New Jersey
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- Book:
- Essays in Econometrics
- Published online:
- 06 July 2010
- Print publication:
- 23 July 2001, pp 189-211
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Summary
This paper develops tests for roots in linear time series which have a modulus of one but which correspond to seasonal frequencies. Critical values for the tests are generated by Monte Carlo methods or are shown to be available from Dickey–Fuller or Dickey–Hasza–Fuller critical values. Representations for multivariate processes with combinations of seasonal and zero-frequency unit roots are developed leading to a variety of autoregressive and error-correction representations. The techniques are used to examine cointegration at different frequencies between consumption and income in the U.K.
INTRODUCTION
The rapidly developing time-series analysis of models with unit roots has had a major impact on econometric practice and on our understanding of the response of economic systems to shocks. Univariate tests for unit roots were first proposed by Fuller (1976) and Dickey and Fuller (1979) and were applied to a range of macroeconomic data by Nelson and Plosser (1982). Granger (1981) proposed the concept of cointegration which recognized that even though several series all had unit roots, a linear combination could exist which would not. Engle and Granger (1987) present a theorem giving several representations of cointegrated series and tests and estimation procedures. The testing is a direct generalization of Dickey and Fuller to the hypothesized linear combination.
All of this work assumes that the root of interest not only has a modulus of one, but is precisely one.
26 - Short-Run Forecasts of Electricity Loads and Peaks
- Clive W. J. Granger
- Edited by Eric Ghysels, University of North Carolina, Chapel Hill, Norman R. Swanson, Texas A & M University, Mark W. Watson, Princeton University, New Jersey
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- Book:
- Essays in Econometrics
- Published online:
- 06 July 2010
- Print publication:
- 23 July 2001, pp 497-516
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Abstract
This paper reports on the design and implementation of a short-run forecasting model of hourly system loads and an evaluation of the forecast performance. The model was applied to historical data for the Puget Sound Power and Light Company, who did a comparative evaluation of various approaches to forecasting hourly loads, for two years in a row. The results of that evaluation are also presented here. The approach is a multiple regression model, one for each hour of the day (with weekends modelled separately), with a dynamic error structure as well as adaptive adjustments to correct for forecast errors of previous hours. The results show that it has performed extremely well in tightly controlled experiments against a wide range of alternative models. Even when the participants were allowed to revise their models after the first year, many of their models were still unable to equal the performance of the authors' models. © 1997 Elsevier Science B.V.
Keywords: comparative methods; energy forecasting; forecasting competitions; regression methods; exponential smoothing.
INTRODUCTION
Electric utilities have always forecast the hourly system loads as well as peak loads to schedule generator maintenance and to choose an optimal mix of on-line capacity. As some facilities are less efficient than others, it is natural to bring them into service only during hours when the load is predicted to be high. Nowadays however, the need for accurate hourly load forecasts is even greater.
10 - Semiparametric Estimates of the Relation Between Weather and Electricity Sales
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- By R. F. Engle, J. Rice, A. Weiss
- Clive W. J. Granger
- Edited by Eric Ghysels, University of North Carolina, Chapel Hill, Norman R. Swanson, Texas A & M University, Mark W. Watson, Princeton University, New Jersey
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- Book:
- Essays in Econometrics
- Published online:
- 06 July 2010
- Print publication:
- 23 July 2001, pp 247-270
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Summary
A nonlinear relationship between electricity sales and temperature is estimated using a semiparametric regression procedure that easily allows linear transformations of the data. This accommodates introduction of covariates, timing adjustments due to the actual billing schedules, and serial correlation. The procedure is an extension of smoothing splines with the smoothness parameter estimated from minimization of the generalized cross-validation criterion introduced by Craven and Wahba (1979). Estimates are presented for residential sales for four electric utilities and are compared with models that represent the weather using only heating and cooling degree days or with piecewise linear splines.
INTRODUCTION
The relationship between temperature and electricity usage is highly nonlinear, because electricity consumption increases at both high and low temperatures. Estimating this relationship, however, is complicated by the need to control for many other factors such as income, price, and overall levels of economic activity and for other seasonal effects such as vacation periods and holidays. A second complicating factor is the form in which the data on sales are collected: Meter readers do not record all households on the same day and for the same period. A third factor is the possibility of unobserved changes in behavior or other causal variables that will introduce serial correlation into the disturbances.
This article introduces a combined parametric and nonparametric regression procedure that easily accommodates linear transformations of the data and therefore provides a convenient framework for analysis of this problem.
Looking Backward, Looking Forward: MLA Members Speak
- April Alliston, Elizabeth Ammons, Jean Arnold, Nina Baym, Sandra L. Beckett, Peter G. Beidler, Roger A. Berger, Sandra Bermann, J.J. Wilson, Troy Boone, Alison Booth, Wayne C. Booth, James Phelan, Marie Borroff, Ihab Hassan, Ulrich Weisstein, Zack Bowen, Jill Campbell, Dan Campion, Jay Caplan, Maurice Charney, Beverly Lyon Clark, Robert A. Colby, Thomas C. Coleman III, Nicole Cooley, Richard Dellamora, Morris Dickstein, Terrell Dixon, Emory Elliott, Caryl Emerson, Ann W. Engar, Lars Engle, Kai Hammermeister, N. N. Feltes, Mary Anne Ferguson, Annie Finch, Shelley Fisher Fishkin, Jerry Aline Flieger, Norman Friedman, Rosemarie Garland-Thomson, Sandra M. Gilbert, Laurie Grobman, George Guida, Liselotte Gumpel, R. K. Gupta, Florence Howe, Cathy L. Jrade, Richard A. Kaye, Calhoun Winton, Murray Krieger, Robert Langbaum, Richard A. Lanham, Marilee Lindemann, Paul Michael Lützeler, Thomas J. Lynn, Juliet Flower MacCannell, Michelle A. Massé, Irving Massey, Georges May, Christian W. Hallstein, Gita May, Lucy McDiarmid, Ellen Messer-Davidow, Koritha Mitchell, Robin Smiles, Kenyatta Albeny, George Monteiro, Joel Myerson, Alan Nadel, Ashton Nichols, Jeffrey Nishimura, Neal Oxenhandler, David Palumbo-Liu, Vincent P. Pecora, David Porter, Nancy Potter, Ronald C. Rosbottom, Elias L. Rivers, Gerhard F. Strasser, J. L. Styan, Marianna De Marco Torgovnick, Gary Totten, David van Leer, Asha Varadharajan, Orrin N. C. Wang, Sharon Willis, Louise E. Wright, Donald A. Yates, Takayuki Yokota-Murakami, Richard E. Zeikowitz, Angelika Bammer, Dale Bauer, Karl Beckson, Betsy A. Bowen, Stacey Donohue, Sheila Emerson, Gwendolyn Audrey Foster, Jay L. Halio, Karl Kroeber, Terence Hawkes, William B. Hunter, Mary Jambus, Willard F. King, Nancy K. Miller, Jody Norton, Ann Pellegrini, S. P. Rosenbaum, Lorie Roth, Robert Scholes, Joanne Shattock, Rosemary T. VanArsdel, Alfred Bendixen, Alarma Kathleen Brown, Michael J. Kiskis, Debra A. Castillo, Rey Chow, John F. Crossen, Robert F. Fleissner, Regenia Gagnier, Nicholas Howe, M. Thomas Inge, Frank Mehring, Hyungji Park, Jahan Ramazani, Kenneth M. Roemer, Deborah D. Rogers, A. LaVonne Brown Ruoff, Regina M. Schwartz, John T. Shawcross, Brenda R. Silver, Andrew von Hendy, Virginia Wright Wexman, Britta Zangen, A. Owen Aldridge, Paula R. Backscheider, Roland Bartel, E. M. Forster, Milton Birnbaum, Jonathan Bishop, Crystal Downing, Frank H. Ellis, Roberto Forns-Broggi, James R. Giles, Mary E. Giles, Susan Blair Green, Madelyn Gutwirth, Constance B. Hieatt, Titi Adepitan, Edgar C. Knowlton, Jr., Emanuel Mussman, Sally Todd Nelson, Robert O. Preyer, David Diego Rodriguez, Guy Stern, James Thorpe, Robert J. Wilson, Rebecca S. Beal, Joyce Simutis, Betsy Bowden, Sara Cooper, Wheeler Winston Dixon, Tarek el Ariss, Richard Jewell, John W. Kronik, Wendy Martin, Stuart Y. McDougal, Hugo Méndez-Ramírez, Ivy Schweitzer, Armand E. Singer, G. Thomas Tanselle, Tom Bishop, Mary Ann Caws, Marcel Gutwirth, Christophe Ippolito, Lawrence D. Kritzman, James Longenbach, Tim McCracken, Wolfe S. Molitor, Diane Quantic, Gregory Rabassa, Ellen M. Tsagaris, Anthony C. Yu, Betty Jean Craige, Wendell V. Harris, J. Hillis Miller, Jesse G. Swan, Helene Zimmer-Loew, Peter Berek, James Chandler, Hanna K. Charney, Philip Cohen, Judith Fetterley, Herbert Lindenberger, Julia Reinhard Lupton, Maximillian E. Novak, Richard Ohmann, Marjorie Perloff, Mark Reynolds, James Sledd, Harriet Turner, Marie Umeh, Flavia Aloya, Regina Barreca, Konrad Bieber, Ellis Hanson, William J. Hyde, Holly A. Laird, David Leverenz, Allen Michie, J. Wesley Miller, Marvin Rosenberg, Daniel R. Schwarz, Elizabeth Welt Trahan, Jean Fagan Yellin
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- Journal:
- PMLA / Publications of the Modern Language Association of America / Volume 115 / Issue 7 / December 2000
- Published online by Cambridge University Press:
- 23 October 2020, pp. 1986-2078
- Print publication:
- December 2000
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