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31.
Michael Fellows Jörg Flum Danny Hermelin Moritz Müller Frances Rosamond 《Theory of Computing Systems》2010,46(2):311-339
The classes of the W-hierarchy are the most important classes of intractable problems in parameterized complexity. These classes
were originally defined via the weighted satisfiability problem for Boolean circuits. Here, besides the Boolean connectives
we consider connectives such as majority, not-all-equal, and unique. For example, a gate labelled by the majority connective outputs true if more than half of its inputs are true. For any finite set
C\mathcal{C}
of connectives we construct the corresponding W(
C\mathcal{C}
)-hierarchy. We derive some general conditions which guarantee that the W-hierarchy and the W(
C\mathcal{C}
)-hierarchy coincide levelwise. If
C\mathcal{C}
only contains the majority connective then the first levels of the hierarchies coincide. We use this to show that a variant
of the parameterized vertex cover problem, the majority vertex cover problem, is W[1]-complete. 相似文献
32.
33.
Vehicles with electric drive trains are currently the subject of intense discussion by society. The cost trends of the individual components in the electric drive train are a central aspect of the future market success of the different vehicle drive systems. 相似文献
34.
35.
Danny Bradbury Author Vitae 《Computer Fraud & Security》2010,2010(10):10-13
36.
Tamir Heyman Danny Geist Orna Grumberg Assaf Schuster 《Formal Methods in System Design》2002,21(3):317-338
This paper presents a scalable method for parallelizing symbolic reachability analysis on a distributed-memory environment of workstations. We have developed an adaptive partitioning algorithm that significantly reduces space requirements. The memory balance is maintained by dynamically repartitioning the state space throughout the computation. A compact BDD representation allows coordination by shipping BDDs from one machine to another. This representation allows for different variable orders in the sending and receiving processes. The algorithm uses a distributed termination protocol, with none of the memory modules preserving a complete image of the set of reachable states. No external storage is used on the disk. Rather, we make use of the network, which is much faster.We implemented our method on a standard, loosely-connected environment of workstations, using a high-performance model checker. Initial performance evaluation of several large circuits shows that our method can handle models too large to fit in the memory of a single node. The partitioning algorithm achieves reduction in space, which is linear in the number of workstations employed. A corresponding decrease in space requirements is measured throughout the reachability analysis. Our results show that the relatively slow network does not become a bottleneck, and that computation time is kept reasonably small. 相似文献
37.
Danny E Akin Luanne L Rigsby Wayne W Hanna Roger N Gates 《Journal of the science of food and agriculture》1991,56(4):523-538
The tissues in leaf blades, midribs, sheaths and stems of normal (N), 5848, and two brown midrib (bmr) mutants, 5753 and 5778, of pearl millet (Pennisetum glaucum (L) R Br) were examined for structural characteristics related to digestibility. The anatomies of the various plant parts were not substantially different between N and bmr plants. The more rigid, lignified tissues such as vascular bundles in all plant parts and the rind of stems were not digested after incubation for 7 days in N or bmr plants, indicating that modifications in these tissues were not sufficient to affect biodegradation. Modifications in the digestible tissues resulted in faster and more extensive degradation in bmr plants, and these changes appear to be the most significant in relation to biodegradation. The parenchyma of midveins and stems, which occupies c 70 and 60% of the cross-sectional area of these respective parts, were the sites where modification in phenolics resulted in the greatest improvement in digestibility. 相似文献
38.
de Boer AR Letzel T van Elswijk DA Lingeman H Niessen WM Irth H 《Analytical chemistry》2004,76(11):3155-3161
Liquid chromatography (LC) was coupled on-line to a continuous-flow enzymatic assay using electrospray ionization mass spectrometry (ESI-MS) as readout for the screening of enzyme inhibitors in complex samples. Inhibitors were detected by changes in the concentration of the enzymatic reaction products, indicating the inhibition of enzymatic activity. The molecular masses of the inhibitors were determined with high certainty by using retention time matching and peak shape comparison. Due to the high matching accuracy, baseline separation of coeluting analytes was not necessary in order to identify the correct masses of the bioactive compounds. The continuous-flow system was successfully applied for the screening of complex samples, such as natural extracts. For a red clover extract, detection limits of 0.3-0.8 micromol/L were obtained. System validation was performed by determining the IC(50) values of four inhibitors in the flow-injection mode. The IC(50) values were in the 0.11-5.6 micromol/L range and correspond closely to data obtained by microtiter plate assays. Detection limits were in the range of 0.018-0.35 micromol/L in the flow-injection mode, and 0.075-0.75 micromol/L in the LC mode. These values are well below the typical compound concentrations (1-10 micromol/L) used in high-throughput screening. Together with an interday precision of 12.6%, these results demonstrate the applicability of the system for bioactivity screening of complex mixtures, generating both chemical and biological information on bioactive compounds in a single run. 相似文献
39.
When complex flow structures are designed, such as in DNA computing, it is essential to be able to predict the flow pattern of the solutions in the fluidic network. A model based on the resistance of the channels and flow velocities of the inlets can eliminated re-iterative design steps. We have constructed a symbolic model using Mathematica ® to determine the desired flow pattern based on the equations of Ohm and Kirchoff. The values from this simulation were used in a flow simulation program and then tested in a microflow network. Results show that the simulation and calculation match very well, while the experiments in the fluidic network show a flow pattern as predicted by the model. 相似文献
40.
The best linear unbiased estimator of the parameter of the Rayleigh distribution using order statistics in a Type II censored sample from a potential sample of size N is considered. The coefficients for this estimator are tabled to five decimal places for N = 2(1)15 and censoring values of r1, (the number of observations censored from the left) and r2 (the number of observations censored from the right) such that r1 + r2 ? N - 2 for N = 2(1)10, r1 + r2 ? N - 3 for N = 11(1)15. 相似文献