Vistas in AstronomyPub Date : 1997-01-01Epub Date: 1999-11-23DOI: 10.1016/S0083-6656(97)00046-9
Charles Taylor
{"title":"Classification and kernel density estimation","authors":"Charles Taylor","doi":"10.1016/S0083-6656(97)00046-9","DOIUrl":"10.1016/S0083-6656(97)00046-9","url":null,"abstract":"<div><p>The method of kernel density estimation can be readily used for the purposes of classification, and an easy-to-use package (<span>alloc</span>80) is now in wide circulation. It is known that this method performs well (at least in relative terms) in the case of bimodal, or heavily skewed distributions.</p><p>In this article we first review the method, and describe the problem of choosing <em>h</em>, an appropriate smoothing parameter. We point out that the usual approach of choosing <em>h</em> to minimize the asymptotic integrated mean squared error is not entirely appropriate, and we propose an alternative estimate of the classification error rate, which is the target of interest. Unfortunately, it seems that analytic results are hard to come by, but simulations indicate that the proposed estimator has smaller mean squared error than the usual cross-validation estimate of error rate.</p><p>A second topic which we briefly explore is that of classification of drifting populations. In this case, we outline two general approaches to updating a classifier based on new observations. One of these approaches is limited to parametric classifiers; the other relies on weighting of observations, and is more generally applicable. We use an example from the credit industry as well as some simulated data to illustrate the methods.</p></div>","PeriodicalId":101275,"journal":{"name":"Vistas in Astronomy","volume":"41 3","pages":"Pages 411-417"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0083-6656(97)00046-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78544936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vistas in AstronomyPub Date : 1997-01-01Epub Date: 1999-11-23DOI: 10.1016/S0083-6656(97)00045-7
Josef Kittler
{"title":"Statistical classification","authors":"Josef Kittler","doi":"10.1016/S0083-6656(97)00045-7","DOIUrl":"https://doi.org/10.1016/S0083-6656(97)00045-7","url":null,"abstract":"<div><p>Statistical pattern classification methodology is overviewed. The recent developments in classifier combination are reviewed.</p></div>","PeriodicalId":101275,"journal":{"name":"Vistas in Astronomy","volume":"41 3","pages":"Pages 405-410"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0083-6656(97)00045-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138216403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vistas in AstronomyPub Date : 1997-01-01Epub Date: 2003-11-20DOI: 10.1016/S0083-6656(97)90112-4
{"title":"List of participants","authors":"","doi":"10.1016/S0083-6656(97)90112-4","DOIUrl":"https://doi.org/10.1016/S0083-6656(97)90112-4","url":null,"abstract":"","PeriodicalId":101275,"journal":{"name":"Vistas in Astronomy","volume":"41 2","pages":"Pages 323-326"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0083-6656(97)90112-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138342069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vistas in AstronomyPub Date : 1997-01-01Epub Date: 1999-11-23DOI: 10.1016/S0083-6656(97)00023-8
W.H. Cannon , D. Baer , G. Feil , B. Feir , P. Newby , A. Novikov , P. Dewdney , B. Carlson , W.T. Petrachenko , J. Popelar , P. Mathieu , R.D. Wietfeldt
{"title":"The S2 VLBI system","authors":"W.H. Cannon , D. Baer , G. Feil , B. Feir , P. Newby , A. Novikov , P. Dewdney , B. Carlson , W.T. Petrachenko , J. Popelar , P. Mathieu , R.D. Wietfeldt","doi":"10.1016/S0083-6656(97)00023-8","DOIUrl":"10.1016/S0083-6656(97)00023-8","url":null,"abstract":"<div><p>The S2 VLBI system is described in some detail, including the S2 data acquisition system, data recorder and playback terminals, and the correlator.</p></div>","PeriodicalId":101275,"journal":{"name":"Vistas in Astronomy","volume":"41 2","pages":"Pages 297-302"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0083-6656(97)00023-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73425359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vistas in AstronomyPub Date : 1997-01-01Epub Date: 1999-11-23DOI: 10.1016/S0083-6656(97)00025-1
H.J. Van Langevelde
{"title":"EVN observations with the MkIV system","authors":"H.J. Van Langevelde","doi":"10.1016/S0083-6656(97)00025-1","DOIUrl":"10.1016/S0083-6656(97)00025-1","url":null,"abstract":"<div><p>Around the EVN telescopes are being upgraded to the MkIV recording system. This enables flexible observing modes and higher recording bandwidth than the existing VLBI recording systems. As of this year (1997) some of these observing modes can be scheduled on the EVN. To make full use of the capabilities, the EVN/JIVE MkIV correlator is being built in Dwingeloo. The capabilities of the full system, as well as the situation during the transition period are discussed.</p></div>","PeriodicalId":101275,"journal":{"name":"Vistas in Astronomy","volume":"41 2","pages":"Pages 307-310"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0083-6656(97)00025-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91470213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vistas in AstronomyPub Date : 1997-01-01Epub Date: 1999-11-23DOI: 10.1016/S0083-6656(97)00017-2
I.A.G. Snellen , R.T. Schilizzi , A.G. De Bruyn , G.K. Miley , H.J. Van Langevelde
{"title":"Multi-frequency VLBI observations of faint GPS sources from wenss","authors":"I.A.G. Snellen , R.T. Schilizzi , A.G. De Bruyn , G.K. Miley , H.J. Van Langevelde","doi":"10.1016/S0083-6656(97)00017-2","DOIUrl":"10.1016/S0083-6656(97)00017-2","url":null,"abstract":"<div><p>The Westerbork Northern Sky Survey (WENSS) has been used to select a population of Gigahertz Peaked Spectrum (GPS) sources with flux densities one or two orders of magnitude lower than previous samples. We present preliminary VLBI observations of this new GPS sample.</p></div>","PeriodicalId":101275,"journal":{"name":"Vistas in Astronomy","volume":"41 2","pages":"Pages 265-269"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0083-6656(97)00017-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80670148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vistas in AstronomyPub Date : 1997-01-01Epub Date: 1998-05-20DOI: 10.1016/S0083-6656(96)00057-8
T. Canosa , R.P. Fender , G.G. Pooley
{"title":"The decay phase of radio flares from GRS1915+105","authors":"T. Canosa , R.P. Fender , G.G. Pooley","doi":"10.1016/S0083-6656(96)00057-8","DOIUrl":"10.1016/S0083-6656(96)00057-8","url":null,"abstract":"<div><p>Decays of radio flares from the superluminal galactic source GRS1915+105 are analysed and both exponential and power law decays are fitted to the data. It is found that the exponential law is a marginally better approximation, whereas an expanding plasmon model actually predicts a power law type decay. The reason for this is due to relativistic aberration, time dilation and the Doppler effect, in going from the rest frame of the ejecta to the observer's frame. This effect is relevant for telescopes in which the beamwidth encompasses both approaching and receding plasmons, e.g. the radio monitoring programs at GBI and the Ryle Telescope.</p></div>","PeriodicalId":101275,"journal":{"name":"Vistas in Astronomy","volume":"41 1","pages":"Pages 21-26"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0083-6656(96)00057-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86817904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vistas in AstronomyPub Date : 1997-01-01Epub Date: 1998-05-20DOI: 10.1016/S0083-6656(06)00051-1
Alfred Gautschy
{"title":"The development of the theory of stellar pulsations","authors":"Alfred Gautschy","doi":"10.1016/S0083-6656(06)00051-1","DOIUrl":"10.1016/S0083-6656(06)00051-1","url":null,"abstract":"<div><p>A short account is presented of the struggle to understand and provide a theory for stellar pulsations. The observational and theoretical developments from the discovery of δ Cephei in 1784 up to Baker and Kippenhahn's key paper of 1962 are described and their significance discussed.</p></div>","PeriodicalId":101275,"journal":{"name":"Vistas in Astronomy","volume":"41 1","pages":"Pages 95-115"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0083-6656(06)00051-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79526747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vistas in AstronomyPub Date : 1997-01-01Epub Date: 1998-05-20DOI: 10.1016/S0083-6656(96)00065-7
W. Steffen
{"title":"Signatures of helical jets","authors":"W. Steffen","doi":"10.1016/S0083-6656(96)00065-7","DOIUrl":"10.1016/S0083-6656(96)00065-7","url":null,"abstract":"<div><p>Observational signatures of helical jets can be found in some X-ray binaries (XRB), planetary nebulae, Herbig-Haro objects and in jets of active galactic nuclei (AGN). For example, in the XRB SS433 a kinematic model of precessing jets has been applied very successfully and yielded a determination of its distance which is independent of conventional methods. In galactic jets precession appears to be the predominant mechanism for the production of observed helical signatures. In extra-galactic jets other mechanisms seem to be similarly frequent. As a result of their strong dependence on the direction of motion with respect to the observer, special relativistic effects can be pronounced in helical jets. These have to be taken into account in AGN-jets and the newly discovered galactic sources which show apparent superluminal motion. Since the galactic superluminal jets are located in a binary system, jet precession is very likely in these sources. In this paper I review the main structural and kinematic signatures of helical jets and briefly mention the physical mechanisms behind them. I will present kinematic simulations of relativistic jets which are helically bent or have an internal helical flow field.</p></div>","PeriodicalId":101275,"journal":{"name":"Vistas in Astronomy","volume":"41 1","pages":"Pages 71-78"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0083-6656(96)00065-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79700620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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