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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 956-960 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We propose a spectrally agile far-infrared detector based on an InSb n-i-p-i superlattice. We show that the spectral response of the detector can be tuned with an applied electrical bias that modulates the tunneling-assisted interband absorption coefficient by changing the internal electric fields. Calculations for several possible superlattice designs are presented and the limitation on the design parameters imposed by the tunneling current is discussed. It is shown that the detector can distinguish between blackbodies with temperatures in the range of 200–400 K independent of the distance between the object and the detector. We also present a simple discussion of the response time that can be expected from such a detector and of the noise sources that will limit its performance.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Decision sciences 17 (1986), S. 0 
    ISSN: 1540-5915
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Wirtschaftswissenschaften
    Notizen: Product-concept testing is a popular activity in marketing research. Often the number of new product/service concepts under study far exceeds the time available for any single respondent. Respondents therefore may receive only a subset of the concepts comprising the total design. Researchers are interested in making plausible imputations for the missing evaluations of any given respondent.This paper proposes a model and an iterative estimation procedure to impute missing entries for each evaluator. The model and the procedure incorporate (1) the internal structure of the response matrix and (2) an ancillary matrix of (nonmissing) respondent background data; they also (3) allow for individual differences in respondents' uses of the numerical rating scale. The model is applied to both real and synthetic data. Suggestions also are given on how the data imputations may be used in market segmentation and product-line decisions.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 40 (1985), S. 0 
    ISSN: 1365-2044
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Anaesthetic equipment was studied to determine whether the accuracy was improved and failure rate decreased by routine maintenance and calibration by a biomedical technician. Each piece was evaluated, and then repaired and rechecked at intervals by the same technician. Equipment failures were divided into three types: first, equipment that was completely nonfunctional; second, equipment that was functional but inaccurate; and third, equipment that was functional and accurate but needed minor repairs. The percentage of equipment failures in each group was compared on initial evaluation and after 6 months. Of the 311 pieces of equipment, 40% needed repair at the time of the initial survey; 8% was nonfunctional, and 18% was functional but inaccurate. After six months on a maintenance schedule, only 15% of the equipment needed repair, 3% was nonfunctional, and 6% was functional but inaccurate. The difference between the total percentage of equipment failure initially and after six months was statistically significant. After a regular maintenance, calibration, and checkout schedule by a biomedical technician was instituted, there was a significant improvement in the accuracy of the equipment and a reduction in the percentage of equipment needing repair.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 138 (1936), S. 349-352 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] THE expedition of the Joint Permanent Eclipse A Committee of the Royal and Royal Astronomical Societies, and the University of Aberdeen, which was stationed at Omsk, had the good fortune to observe the total solar eclipse of June 19, 1936, under excellent conditions. The expedition consisted of ...
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of classification 2 (1985), S. 173-192 
    ISSN: 1432-1343
    Schlagwort(e): Ultrametric trees ; Mathematical programming ; Variable importance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract This paper presents the development of a new methodology which simultaneously estimates in a least-squares fashion both an ultrametric tree and respective variable weightings for profile data that have been converted into (weighted) Euclidean distances. We first review the relevant classification literature on this topic. The new methodology is presented including the alternating least-squares algorithm used to estimate the parameters. The method is applied to a synthetic data set with known structure as a test of its operation. An application of this new methodology to ethnic group rating data is also discussed. Finally, extensions of the procedure to model additive, multiple, and three-way trees are mentioned.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-1343
    Schlagwort(e): Hierarchical clustering ; Path length trees ; Mathematical programming ; Constrained classification methods
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract A mathematical programming algorithm is developed for fitting ultrametric or additive trees to proximity data where external constraints are imposed on the topology of the tree. The two procedures minimize a least squares loss function. The method is illustrated on both synthetic and real data. A constrained ultrametric tree analysis was performed on similarities between 32 subjects based on preferences for ten odors, while a constrained additive tree analysis was carried out on some proximity data between kinship terms. Finally, some extensions of the methodology to other tree fitting procedures are mentioned.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of classification 6 (1989), S. 105-119 
    ISSN: 1432-1343
    Schlagwort(e): Individual differences ; Multidimensional scaling ; Rational starting configuration ; INDSCAL
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Five different methods for obtaining a rational initial estimate of the stimulus space in the INDSCAL model were compared using the SINDSCAL program for fitting INDSCAL. The effect of the number of stimuli, the number of subjects, the dimensionality, and the amount of error on the quality and efficiency of the final SINDSCAL solution were investigated in a Monte Carlo study. We found that the quality of the final solution was not affected by the choice of the initialization method, suggesting that SINDSCAL finds a global optimum regardless of the initialization method used. The most efficient procedures were the methods proposed by by de Leeuw and Pruzansky (1978) and by Flury and Gautschi (1986) for the simultaneous diagonalization of several positive definite symmetric matrices, and a method based on linearly constraining the stimulus space using the CANDELINC approach developed by Carroll, Pruzansky, and Kruskal (1980).
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Journal of classification 6 (1989), S. 247-270 
    ISSN: 1432-1343
    Schlagwort(e): Multivariate data analysis ; Ordinal network representation ; NETSCAL ; Proximities
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract We present an algorithm for fitting general graphs to proximity data. The algorithm utilizes a mathematical programming procedure based on a penalty function approach to impose additivity constraints upon parameters. For a user-specified number of links, the algorithm seeks to provide the connected network that gives the least-squares approximation to the proximity data with the specified number of links, allowing for linear transformations of the data. The network distance is the minimum-path-length metric for connected graphs. As a limiting case, the algorithm provides a tree where each node corresponds to an object, if the number of links is set equal to the number of objects minus one. A Monte Carlo investigation indicates that the resulting networks tend to fall within one percentage point of the least-squares solution in terms of the variance accounted for, but do not always attain this global optimum. The network model is discussed in relation to ordinal network representations (Klauer 1989) and NETSCAL (Hutchinson 1989), and applied to several well-known data sets.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Optical and quantum electronics 18 (1986), S. 355-363 
    ISSN: 1572-817X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract A detailed description of a multiport detection experiment operating close to the quantum noise limit is presented. Simultaneous phase and amplitude measurements were made on signals of only five photons energy with a signal-to-noise ratio that was accountable to within 2 dB of the quantum limit. Statistical examination of the noise showed excellent agreement with the gaussian distribution predicted by both the semiclassical and fully quantum theories.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 53 (1989), S. 111-116 
    ISSN: 1570-7458
    Schlagwort(e): Tick repellent ; larvicide ; Commiphora erythraea Burseraceae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé Un extrait à l'hexane de la gomme de la plante africaine, C. erythraea Engler (Burseraceae) a des effets larvicides et répulsifs contre les tiques, Amblyomma americanum L. et Dermacentor variabilis Say; les adultes de Ixodes dammini Spielman, Clifford, Piesman & Corwin, ont été aussi éloignés par l'extrait. Une concentration de 0,02 mg/cm2 de l'extrait imprégnant du papier filtre a tué 96,15% (±3,56) larves de A. americanum exposées pendant 24 h. Une concentration de 0,16 mg/cm2 a été nécessaire pour tuer 80,3% des larves de D. variabilis. L'extrait a été moins efficace que la perméthrine comme larvicide contre A. americanum et D. variabilis. Moins de 15,5% des larves et des adultes de A. americanum et des adultes de D. variabilis et de I. dammini pénétrèrent et séjournèrent 2 à 3 minutes dans des morceaux de tissu traités avec l'extrait à raison de 0,2 mg/cm2, contre 73,3 et 83,3% qui pénétrèrent et restèrent lors de traitement avec de l'hexane. Contre A. americanum, la perméthrine est un répulsif d'un ordre de grandeur une à deux fois supérieur à l'extrait de C. erythraea.
    Notizen: Abstract A hexane extract of the gum of an African plant, Commiphora erythraea Engler (Burseraceae), has larvicidal and repellent activity against the lone star tick, Amblyomma americanum (L.) and the American dog tick, Dermacentor variabilis (Say). Adult deer ticks, Ixodes dammini Spielman, Clifford, Piesman and Corwin, were also repelled by the extract. Concentrations of 0.02 mg/cm2 of the extract impregnated onto filter paper killed 96.15 (±3.56)% of A. americanum larvae exposed to it for 24h. A concentration of 0.16 mg/cm2 was needed to kill 80.3% of D. variabilis larvae. The extract was less effective as a larvicide against A. americanum and D. variabilis than permethrin. Less than 15.5% of A. americanum larvae and adults and D. variabilis and I. dammini adults entered and remained for 2 or 3 min on areas of cloth strips treated with the extract at the rate of 0.2 mg/cm2. However, 73.3 to 83.3% of the ticks tested entered and remained in areas treated with hexane. Permethrin was about 1 or 2 orders of magnitude more effective against A. americanum larvae as a repellent than the extract.
    Materialart: Digitale Medien
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