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  • 1990-1994  (7)
  • computational learning theory  (4)
  • Physical Chemistry  (3)
  • Molecular Cell Biology
  • 1
    Electronic Resource
    Electronic Resource
    Toward Efficient Agnostic Learning (1994)
    Springer
    Machine learning 17 (1994), S. 115-141 
    Details
    ISSN: 0885-6125
    Keywords: machine learning ; agnostic learning ; PAC learning ; computational learning theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we initiate an investigation of generalizations of the Probably Approximately Correct (PAC) learning model that attempt to significantly weaken the target function assumptions. The ultimate goal in this direction is informally termed agnostic learning, in which we make virtually no assumptions on the target function. The name derives from the fact that as designers of learning algorithms, we give up the belief that Nature (as represented by the target function) has a simple or succinct explanation. We give a number of positive and negative results that provide an initial outline of the possibilities for agnostic learning. Our results include hardness results for the most obvious generalization of the PAC model to an agnostic setting, an efficient and general agnostic learning method based on dynamic programming, relationships between loss functions for agnostic learning, and an algorithm for a learning problem that involves hidden variables.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022615600103
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Learning Probabilistic Read-once Formulas on Product Distributions (1994)
    Springer
    Machine learning 14 (1994), S. 47-81 
    Details
    ISSN: 0885-6125
    Keywords: computational learning theory ; PAC-learning ; learning with noise ; read-once formulas ; product distributions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents a polynomial-time algorithm for inferring a probabilistic generalization of the class of read-once Boolean formulas over the usual basis { AND, OR, NOT }. The algorithm effectively infers a good approximation of the target formula when provided with random examples which are chosen according to any product distribution, i.e., any distribution in which the setting of each input bit is chosen independently of the settings of the other bits. Since the class of formulas considered includes ordinary read-once Boolean formulas, our result shows that such formulas are PAC learnable (in the sense of Valiant) against any product distribution (for instance, against the uniform distribution). Further, this class of probabilistic formulas includes read-once formulas whose behavior has been corrupted by large amounts of random noise. Such noise may affect the formula's output (“misclassification noise”), the input bits ( “attribute noise”), or it may affect the behavior of individual gates of the formula. Thus, in this setting, we show that read-once formula's can be inferred (approximately), despite large amounts of noise affecting the formula's behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022646704993
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Learning probabilistic read-once formulas on product distributions (1994)
    Springer
    Machine learning 14 (1994), S. 47-81 
    Details
    ISSN: 0885-6125
    Keywords: computational learning theory ; PAC-learning ; learning with noise ; read-once formulas ; product distributions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents a polynomial-time algorithm for inferring a probabilistic generalization of the class of read-once Boolean formulas over the usual basis {AND, OR, NOT}. The algorithm effectively infers a good approximation of the target formula when provided with random examples which are chosen according to anyproduct distribution, i.e., any distribution in which the setting of each input bit is chosen independently of the settings of the other bits. Since the class of formulas considered includes ordinary read-once Boolean formulas, our result shows that such formulas are PAC learnable (in the sense of Valiant) against any product distribution (for instance, against the uniform distribution). Further, this class of probabilistic formulas includes read-once formulas whose behavior has been corrupted by large amounts of random noise. Such noise may affect the formula's output (“misclassification noise”), the input bits (“attribute noise”), or it may affect the behavior of individual gates of the formula. Thus, in this setting, we show that read-once formula's can be inferred (approximately), despite large amounts of noise affecting the formula's behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00993162
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Toward efficient agnostic learning (1994)
    Springer
    Machine learning 17 (1994), S. 115-141 
    Details
    ISSN: 0885-6125
    Keywords: machine learning ; agnostic learning ; PAC learning ; computational learning theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we initiate an investigation of generalizations of the Probably Approximately Correct (PAC) learning model that attempt to significantly weaken the target function assumptions. The ultimate goal in this direction is informally termedagnostic learning, in which we make virtually no assumptions on the target function. The name derives from the fact that as designers of learning algorithms, we give up the belief that Nature (as represented by the target function) has a simple or succinct explanation. We give a number of positive and negative results that provide an initial outline of the possibilities for agnostic learning. Our results include hardness results for the most obvious generalization of the PAC model to an agnostic setting, an efficient and general agnostic learning method based on dynamic programming, relationships between loss functions for agnostic learning, and an algorithm for a learning problem that involves hidden variables.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00993468
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    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    A flash photolysis resonance fluorescence investigation of the reactions of Oxygen O(3P) atoms with aliphatic ethers and diethers in the gas phase (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 22 (1990), S. 711-717 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants for the gas phase reCedex 2, Franceactions of O(3P) atoms with a series of symmetric aliphatic ethers have been determined using the flash photolysis resonance fluorescence technique over the temperature range 240-400 K. The Arrhenius parameters derived from these data are (in units of cm3 molecule -1 s-1): \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{rcl} {\rm dimethyl ether,}k &=& (5.39 \pm 1.94) \times 10^{ - 12} {\rm exp[(} - {\rm 1320} \pm 120)/T]; \\ {\rm diethyl ether,}k &=& (1.42 \pm 0.18) \times 10^{ - 11} {\rm exp[(} - {\rm 1070} \pm 40)/T]; \\ {\rm di -}n{\rm - propyle ether,}k &=& (1.41 \pm 0.21) \times 10^{ - 11} {\rm exp[(} - {\rm 960} \pm 50)/T]; \\ {\rm di -}n{\rm - butyl ether,}k &=& (1.37 \pm 0.29) \times 10^{ - 11} {\rm exp[(} - {\rm 880} \pm 70)/T]; \\ {\rm di -}n{\rm - pentyl ether,}k &=& (1.26 \pm 0.84) \times 10^{ - 11} {\rm exp[(} - {\rm 780} \pm 200)/T]; \\ \end{array} $$\end{document}The error limits are two standard deviations derived from the least-squares fit. Rate constants for several other ethers were determined only at 298 K. The values obtained were (in units of 10-14 cm3 molecule-1 s-1): tetrahydrofuran (37.5 ± 1.1); 1,4-dioxane 1(6.81 ± 0.46); diethoxymethane (40.4 ± 1.8); ethyl -t-butyl ether (37.0 ± 1.3); and methyl-t-amylether (57.3 ± 2.3).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550220707
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Rate constants for Hydrogen abstraction reactions of NO3 in aqueous solution (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 22 (1990), S. 505-512 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants have been measured by pulse radiolysis for the reactions of the NO3 radical with five cyclic ethers and a series of alcohols. Rate constants ranged from 3.5 × 104 M×1 s×1 for deuterated methanol to 1.1 × 107 M-1 s-1 for tetrahydrofuran. The rate constants for the reactions of NO3 with the alcohols 1-propanol to 1-heptanol were found to be linearly dependent on the number of CH3 groups with a group reactivity of 6.4 × 105 M-1 s-1.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550220507
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  • 7
    Electronic Resource
    Electronic Resource
    Rate constants for some hydrogen abstraction reactions of the carbonate radical (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 25 (1993), S. 199-203 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants have been measured in aqueous solutions for the reactions of the carbonate radical, CO3·-, with several saturated alcohols and one cyclic ether as a function of temperature. Arrhenius pre-exponential factors ranged from 2×108 to 1×109 l mol-1 s-1 and activation energies ranged from 16 to 29 kJ mol-1. The results suggest that the reactions are not pure hydrogen abstraction, but involve an additional interaction of the radical with the —OH or —O— linkage. © 1993 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550250308
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