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Good parameter settings are crucial to achieve high performance in many areas of artificial intelligence (AI), such as propositional satisfiability solving, AI planning, scheduling, and machine learning (in particular deep learnin...
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Good parameter settings are crucial to achieve high performance in many areas of artificial intelligence (AI), such as propositional satisfiability solving, AI planning, scheduling, and machine learning (in particular deep learning). Automated algorithm con figuration methods have recently received much attention in the AI community since they replace tedious, irreproducible and error-prone manual parameter tuning and can lead to new state-of-the-art performance. However, practical applications of algorithm configuration are prone to several (often subtle) pitfalls in the experimental design that can render the procedure ineffective. We identify several common issues and propose best practices for avoiding them. As one possibility for automatically handling as many of these as possible, we also propose a tool called GenericWrapper4AC
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The NADH: ubiquinone oxidoreductase, respiratory complex I, couples electron transfer from NADH to ubiquinone with the translocation of protons across the membrane. The complex consists of a peripheral arm catalyzing the redox rea...
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The NADH: ubiquinone oxidoreductase, respiratory complex I, couples electron transfer from NADH to ubiquinone with the translocation of protons across the membrane. The complex consists of a peripheral arm catalyzing the redox reaction and a membrane arm catalyzing proton translocation. The membrane arm is almost completely aligned by a 110 angstrom unique horizontal helix that is discussed to transmit conformational changes induced by the redox reaction in a piston-like movement to the membrane arm driving proton translocation. Here, we analyzed such a proposed movement by cysteine-scanning of the helix of the Escherichia coli complex I. The accessibility of engineered cysteine residues and the flexibility of individual positions were determined by labeling the preparations with a fluorescent marker and a spin-probe, respectively, in the oxidized and reduced states. The differences in fluorescence labeling and the rotational flexibility of the spin probe between both redox states indicate only slight conformational changes at distinct positions of the helix but not a large movement.
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Partial autoionization rates of doubly excited one-dimensional helium in the collinear Zee and eZe configuration are obtained by means of the complex rotation method. The approach presented here relies on a projection of back-rota...
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Partial autoionization rates of doubly excited one-dimensional helium in the collinear Zee and eZe configuration are obtained by means of the complex rotation method. The approach presented here relies on a projection of back-rotated resonance wave functions onto singly ionized He+ channel wave functions and the computation of the corresponding particle fluxes. In spite of the long-range nature of the Coulomb potential between the electrons and the nucleus, an asymptotic region where the fluxes are stationary is clearly observed. Low-lying doubly excited states are found to decay predomintantly into the nearest single-ionization continuum. This approach paves the way for a systematic analysis of the decay rates observed in higher-dimensional models, and of the role of electronic correlations and atomic structure in recent photoionization experiments.
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As a rapidly expanding market, carsharing presents a possible remedy for traffic congestion in urban centers. Especially free-floating carsharing, which allows customers to leave their car anywhere within the operator's business a...
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As a rapidly expanding market, carsharing presents a possible remedy for traffic congestion in urban centers. Especially free-floating carsharing, which allows customers to leave their car anywhere within the operator's business area, provides users with flexibility, and complements public transportation. We present a novel method that provides strategic and operational decision support to companies maneuvering this competitive and constantly changing market environment. Using an extensive set of customer data in a zero-inflated regression model, we explain spatial variation in carsharing activity through the proximity of particular points of interests, such as movie theaters and airports. As an application case, as well as a validation of the model, we use the resulting indicators to predict the number of rentals before an expansion of the business area and compare it to the actual demand postexpansion. We find that our approach correctly identifies areas with a high carsharing activity and can be easily adapted to other cities. (c) 2015 Elsevier Ltd. All rights reserved.
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We study a basic buffer management problem that arises in network switches. Consider m input ports, each of which is equipped with a buffer ( queue) of limited capacity. Data packets arrive online and can be stored in the buffers ...
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We study a basic buffer management problem that arises in network switches. Consider m input ports, each of which is equipped with a buffer ( queue) of limited capacity. Data packets arrive online and can be stored in the buffers if space permits; otherwise packet loss occurs. In each time step the switch can transmit one packet from one of the buffers to the output port. The goal is to maximize the number of transmitted packets. Simple arguments show that any work-conserving algorithm, which serves any nonempty buffer, is 2-competitive. Azar and Richter recently presented a randomized online algorithm and gave lower bounds for deterministic and randomized strategies. In practice, greedy algorithms are very important because they are fast, use little extra memory, and reduce packet loss by always serving a longest queue. In this paper we first settle the competitive performance of the entire family of greedy strategies. We prove that greedy algorithms are not better than 2-competitive no matter how ties are broken. Our lower bound proof uses a new recursive construction for building adversarial buffer configurations that may be of independent interest. We also give improved lower bounds for deterministic and randomized online algorithms. In this paper we present the first deterministic online algorithm that is better than 2-competitive. We develop a modified greedy algorithm, called semigreedy, and prove that it achieves a competitive ratio of 17/9 approximate to 1.89. The new algorithm is simple, fast, and uses little extra memory. Only when the risk of packet loss is low does it not serve the longest queue. Additionally we study scenarios when an online algorithm is granted additional resources. We consider resource augmentation with respect to memory and speed; i.e., an online algorithm may be given larger buffers or higher transmission rates. We analyze greedy and other online strategies.
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We study integrated prefetching and caching in single and parallel disk systems. In the first part of the paper, we investigate approximation algorithms for the single disk problem. There exist two very popular approximation algor...
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We study integrated prefetching and caching in single and parallel disk systems. In the first part of the paper, we investigate approximation algorithms for the single disk problem. There exist two very popular approximation algorithms called Aggressive and Conservative for minimizing the total elapsed time. We give a refined analysis of the Aggressive algorithm, improving the original analysis by Cao et al. We prove that our new bound is tight. Additionally, we present a new family of prefetching and caching strategies and give algorithms that perform better than Aggressive and Conservative. In the second part of the paper, we investigate the problem of minimizing stall time in parallel disk systems. We present a polynomial time algorithm for computing a prefetching/caching schedule whose stall time is bounded by that of an optimal solution. The schedule uses at most 2(D - 1) extra memory locations in cache. This is the first polynomial time algorithm that, using a small amount of extra resources, computes schedules whose stall times are bounded by that of optimal schedules not using extra resources. Our algorithm is based on the linear programming approach of [Journal of the ACM 47 (2000) 969]. However, in order to achieve minimum stall times, we introduce the new concept of synchronized schedules in which fetches on the D disks are performed completely in parallel. (c) 2005 Elsevier Inc. All rights reserved.
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The Drosophila cell adhesion molecule Rst plays key roles during the development of the embryonic musculature, spacing of ommatidia in the compound eye and of sensory organs on the antenna, as well as in the neuronal wiring of the...
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The Drosophila cell adhesion molecule Rst plays key roles during the development of the embryonic musculature, spacing of ommatidia in the compound eye and of sensory organs on the antenna, as well as in the neuronal wiring of the optic lobe. In (CT)(rst) mutants lacking the cytoplasmic domain of the Rst protein, cell sorting and apoptosis in the eye are affected, suggesting a requirement of this domain for Rst function. To identify potential interacting proteins, yeast two-hybrid screens were performed using the cytoplasmic domains of Rst and its paralogue Kirre as baits. Among several putative interactors, two paralogous Drosophila PDZ motif proteins related to X11/Mint were identified. X11/Mint family members in C. elegans (LFN-10) and vertebrates are believed to function as adaptor proteins and to regulate the assembly of multi-subunit complexes at the synapse, thereby linking the vesicle cycle to cell adhesion. Using genetic, cell biological, and biochemical approaches, we show that the interaction of Rst with X11L alpha is of biological significance. The proteins interact, for example, in the context of cell sorting in the pupal retina. (c) 2005 Elsevier Inc. All rights reserved.
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In the classical two-dimensional bin packing problem one is asked to pack a set of rectangular items, without overlap and without any rotation, into the minimum number of identical square bins. We give an approximation algorithm w...
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In the classical two-dimensional bin packing problem one is asked to pack a set of rectangular items, without overlap and without any rotation, into the minimum number of identical square bins. We give an approximation algorithm with absolute worst-case ratio of 3. (C) 2004 Elsevier B.V. All rights reserved.
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We report on the realization of a chip- based multipole ion trap manufactured using microelectromechanical systems technology, requiring minimal manual alignment of the electrodes. It provides ion confinement in an almost field- f...
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We report on the realization of a chip- based multipole ion trap manufactured using microelectromechanical systems technology, requiring minimal manual alignment of the electrodes. It provides ion confinement in an almost field- free volume between two planes of radiofrequency electrodes, deposited on glass substrates, which allows for optical access to the trap. An analytical model of the effective trapping potential is presented and compared with numerical calculations. Stable trapping of argon ions is achieved, and a lifetime of 16 s is measured. Electrostatic charging of the chip surfaces is studied and found to agree with a numerical estimate.
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We report on the realization of a chip- based multipole ion trap manufactured using microelectromechanical systems technology, requiring minimal manual alignment of the electrodes. It provides ion confinement in an almost field- f...
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We report on the realization of a chip- based multipole ion trap manufactured using microelectromechanical systems technology, requiring minimal manual alignment of the electrodes. It provides ion confinement in an almost field- free volume between two planes of radiofrequency electrodes, deposited on glass substrates, which allows for optical access to the trap. An analytical model of the effective trapping potential is presented and compared with numerical calculations. Stable trapping of argon ions is achieved, and a lifetime of 16 s is measured. Electrostatic charging of the chip surfaces is studied and found to agree with a numerical estimate.
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