A MapReduce Algorithm for Minimum Vertex Cover Problems and Its Randomization

MapReduce is a programming paradigm for large-scale distributed information processing. This paper proposes a MapReduce algorithm for the minimum vertex cover problem, which is known to be NP-hard. The MapReduce algorithm can efficiently obtain a minimal vertex cover in a small number of rounds. We show the effectiveness of the algorithm, through experimental evaluation and comparison with exact and approximate algorithms that it demonstrates high quality in a small number of MapReduce rounds. We also confirm from experimentation that the algorithm has good scalability, allowing high-quality solutions under restricted computation times due to increased graph size. Moreover, we extend our algorithm to randomized one to obtain good expected approximate ratio

Petri Net Modeling for Ising Model Formulation in Quantum Annealing

Quantum annealing is an emerging new platform for combinatorial optimization, requiring an Ising model formulation for optimization problems. The formulation can be an essential obstacle to the permeation of this innovation into broad areas of everyday life. Our research is aimed at the proposal of a Petri net modeling approach for an Ising model formulation. Although the proposed method requires users to model their optimization problems with Petri nets, this process can be carried out in a relatively straightforward manner if we know the target problem and the simple Petri net modeling rules. With our method, the constraints and objective functions in the target optimization problems are represented as fundamental characteristics of Petri net models, extracted systematically from Petri net models, and then converted into binary quadratic nets, equivalent to Ising models. The proposed method can drastically reduce the difficulty of the Ising model formulation

Hepatic Branch Vagotomy Can Suppress Liver Regeneration in Partially Hepatectomized Rats

The role of the vagus nerve in liver regeneration after partial hepatectomy was studied by comparing the effects of hepatic branch vagotomy with those of hepatic branch sympathectomy in rats. The liver weight as a percentage of body weight decreased significantly 7 days after vagotomy compared with the controls and this was associated with a reduction in food intake. There was no difference in the liver weights between the control rats and the pair-fed vagotomized rats. Hepatic sympathectomy had no significant effect on the liver weight. The serum scores indicating hepatic function showed no difference between the control and the vagotomized rats except alkaline phosphatase. The concentration of insulin was unchanged. The number of mitotic hepatocytes remained high at 7 days after vagotomy: These observations led us to conclude that the vagus nerve stimulates liver regeneration, and its effect depends on vagal factors directly and specifically

Electron Spin Resonance Study on Irradiated Styrene in Crystalline and Glassy States

Styrene was irradiated at-196°C to give a five-line spectrum with a coupling constant of about 16 gauss. This is attributed to the free radical When a mixture of styrene and 2-methyltetrahydrofuran was irradiated, a broad singlet spectrum (total width 33 gauss) was superposed on the seven-line spectrum due to the methyltetrahydrofuran radical and no sharp singlet spectrum due to trapped electrons was observed. This broad singlet spectrum is thought to be due to styrene anion radicals. This spectrum was bleached by visible light and saturated appreciably with increasing microwave power. Similar phenomena were observed for a styrene-3-methylpentane mixture

Effects of Isotopically Controlled Boron Addition on Microstructure of Nickel Irradiated at the Below Core Canister of FFTF

Nickel specimens doped with several levels of ^B were irradiated in the Fast Flux Test Facility(FFTF) for the purpose of examining the applicability of boron addition to the study of helium production effects. It was found that the boron has its chemical and transmutative effetcs, the former suppressing and the latter enhancing void nucleation. It seems that reliable estimation of helium effects is possible by well designed experiments seprating some side effects of boron from its transmutation effects

水田灌漑卓越流域の水循環モデル開発に関する研究

学位の種別:論文博士University of Tokyo(東京大学