Search results for: Masaya Nakahara

Items from 1 to 10 out of 10 results

chapter

Scalable Detection of Frequent Substrings by Grammar-Based Compression

Masaya Nakahara, Shirou Maruyama, Tetsuji Kuboyama, Hiroshi Sakamoto

Lecture Notes in Computer Science > Discovery Science > 236-246

A scalable pattern discovery by compression is proposed. A string is representable by a context-free grammar (CFG) deriving the string deterministically. In this framework of grammar-based compression, the aim of the algorithm is to output as small a CFG as possible. Beyond that, the optimization problem is approximately solvable. In such approximation algorithms, the compressor by Sakamoto et al...

chapter

ESP-Index: A Compressed Index Based on Edit-Sensitive Parsing

Shirou Maruyama, Masaya Nakahara, Naoya Kishiue, Hiroshi Sakamoto

Lecture Notes in Computer Science > String Processing and Information Retrieval > 398-409

We propose a compressed self-index based the edit-sensitive parsing (ESP). Given a string S, its ESP tree is equivalent to a context-free grammar deriving just S, which can be represented as a DAG G. Finding pattern P in S is reduced to embedding P into G. Succinct data structures are adopted and G is then decomposed into two LOUDS bit strings and a single array for permutation, requiring (1 + ε)n...

article

Effect of dilution gas on burning velocity of hydrogen-premixed meso-scale spherical laminar flames

Masaya Nakahara, Fumiaki Abe, Kenichi Tokunaga, Atsushi Ishihara

Proceedings of the Combustion Institute > 2015 > 35 > 1 > 639-646

Aiming to make clear a method for improving combustion of micro/meso-scale flames, effects of dilution gas and characteristic chemical time τ_c on the burning velocity of meso-scale flames were studied experimentally using H₂–O₂–dilution gas mixtures. The meso-scale outwardly propagating spherical laminar flames, in a flame radius r_f range of approximately from 1 to 5mm, were observed by using sequential...

article

Fundamental burning velocities of meso-scale propagating spherical flames with H2, CH4 and C3H8 mixtures

Masaya Nakahara, Fumiaki Abe, Kenichi Tokunaga, Atsushi Ishihara

Proceedings of the Combustion Institute > 2013 > 34 > 1 > 703-710

This study is performed to experimentally examine the fundamental burning velocity characteristics of meso-scale outwardly propagating spherical laminar flames in the range of flame radius r _f approximately from 1 to 5mm for hydrogen, methane and propane mixtures, in order to make clear a method for improving combustion of micro–meso scale flames. Macro-scale laminar flames with r _f ...

article

ESP-index: A compressed index based on edit-sensitive parsing

Shirou Maruyama, Masaya Nakahara, Naoya Kishiue, Hiroshi Sakamoto

Journal of Discrete Algorithms > 2013 > 18 > Complete > 100-112

We propose ESP-index, a self-index based on edit-sensitive parsing. Given a string S, ESP tree is equivalent to a CFG deriving just S, which can be represented as a restricted DAG G. Finding pattern P in S is reduced to embedding the parsing tree of P into G. Adopting several succinct data structures, G is decomposed into two bit strings and a single array, requiring (1+ε)nlogn+4n+o(n) bits of space,...

chapter

An Online Algorithm for Lightweight Grammar-Based Compression

Shirou Maruyama, Masayuki Takeda, Masaya Nakahara, Hiroshi Sakamoto

2011 First International Conference on Data Compression, Communications and Processing > 19 - 28

2011 First International Conference on Data Compression, Communications and Processing (CCP)

Grammar-based compression is a well-studied technique for constructing a small context-free grammar (CFG) uniquely deriving a given text. In this paper, we present an online algorithm for lightweight grammar-based compression. Our algorithm is based on the LCA algorithm [Sakamoto et al. 2004]which guarantees nearly optimum compression ratio and space. LCA, however, is an offline algorithm and requires...

article

Influence of local flame displacement velocity on turbulent burning velocity

Hiroyuki Kido, Masaya Nakahara, Kenshiro Nakashima, Jun Hashimoto

Proceedings of the Combustion Institute > 2002 > 29 > 2 > 1855-1861

In our previous works, the mean local burning velocity turned out to be changed from the originallaminar burning velocity due to the preferential diffusion effect, and it was found to be an important factor dominating the turbulent burning velocity. The present study investigates directly the local flame propagation properties of methane, propane, and hydrogen premixed turbulent flames in the weak...

article

Experimental study on the configuration and propagation characteristics of premixed turbulent flame

Hiroyuki Kido, Kenshiro Nakashima, Masaya Nakahara, Jun Hashimoto

JSAE Review > 2001 > 22 > 2 > 131-138

An attempt is made to examine the configuration and propagation characteristics of premixed turbulent flame in a weak turbulence region. A laser tomography technique is used to obtain the flame shape, and quantitative analysis is performed. It is found that the turbulent flame front can be classified into the active and the inactive part for the flame propagation, where the former is the convex part...

article

Experimental study of the turbulent combustion mechanism of non-stoichiometric mixtures

Hiroyuki Kido, Kimitoshi Tanoue, Masaya Nakahara, Hideki Kido, more

JSAE Review > 1996 > 17 > 4 > 361-367

Recently, in order to establish the lean-burn technique, the structure of non-stoichiometric mixture flames has been studied extensively, as well as that of stoichiometric mixture flames. In those studies, emphasis was placed not only on macroscopic behavior of the turbulent flame but also on microscopic behavior of reactants. The purpose of this paper is to estimate the change in the local burning...

article

Experimental Study of the Turbulent Combustion Mechanism of Non-Stoichiometric Mixtures

Kimitoshi Tanoue, Hiroyuki Kido, Masaya Nakahara, Hideki Kido, more

JSAE Review > 1996 > 17 > 1 > 93

Recently, in order to establish the lean-burn technique, the structure of non-stoichiometric mixture flames have been studied extensively as well as that of stoichiometric mixture flames. In these studies, emphasis is placed not only on macroscopic behavior of the turbulent flame but also on microscopic behavior of reactants. The purpose of this paper is to estimate the change in the local burning...

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