OKAMURA Hiroyuki

J-GLOBAL         Last updated: Dec 7, 2018 at 03:54
 
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Name
OKAMURA Hiroyuki
E-mail
okamurel.hiroshima-u.ac.jp
Affiliation
Hiroshima University
Degree
Doctor of Engineering(Hiroshima University), Master of Engineering(Hiroshima University)
Research funding number
10311812

Profile

Reliability Engineering, Software Reliability, Stochastic Model

Research Areas

 
 

Academic & Professional Experience

 
Apr 2003
 - 
Mar 2018
Associate Professor, Graduate School of Engineering, Hiroshima University
 
Apr 2007
 - 
Mar 2010
Associate Professor, Graduate School of Engineering, Hiroshima University
 
Apr 2003
 - 
Mar 2007
Assistant Professor, Graduate School of Engineering, Hiroshima University
 
Apr 2001
 - 
Mar 2003
Assistant, Graduate School of Engineering, Hiroshima University
 
Oct 1998
 - 
Mar 2001
Assistant, School of Engineering, Hiroshima University
 

Education

 
Apr 1995
 - 
Mar 1997
Graduate School, Division of Engineering, Hiroshima University
 
Apr 1991
 - 
Mar 1995
Faculty of Engineering, Hiroshima University
 

Awards & Honors

 
Feb 2004
"The IEEE Reliability Society Japan Chapter, Outstanding Young Scientist Award"
 

Published Papers

 
Dohi, T; Okamura, H; Osaki, S
INTERNATIONAL JOURNAL OF PRODUCTION ECONOMICS   74(1-3) 147-155   Dec 2001   [Refereed]
This paper revisits the economic manufacturing quantity (EMQ) model by Cheung and Hausman (Nav. Res. Logist. 44 (1997) 257) from the theoretical point of view, and develops a new stochastic model under somewhat different restrictive assumptions. T...
Okamura, H; Dohi, T; Osaki, S
COMPUTERS & MATHEMATICS WITH APPLICATIONS   46(7) 1103-1110   Oct 2003   [Refereed]
This paper addresses a problem of energy reduction on computer systems, namely the problem of determining the optimal auto-sleep schedule on which the system is changed into a low-power state. For this problem, we provide a stochastic model for a ...
Okamura, H; Dohi, T; Osaki, S
MATHEMATICAL AND COMPUTER MODELLING   38(11-13) 1391-1398   Dec 2003   [Refereed]
This paper addresses the problem of how to determine optimal sleep timing when the computer user should turn the hard disk or the display off in order to save electric power after the computer has not been used. We propose a stochastic model to ob...
Okamura, H; Miyahara, S; Dohi, T
IEICE TRANSACTIONS ON COMMUNICATIONS   E88B(12) 4498-4506   Dec 2005   [Refereed]
Long running software systems are known to experience an aging phenomenon called software aging, one in which the accumulation of errors during the execution of software leads to performance degradation and eventually results in failure. To counte...
Ozaki, T; Dohi, T; Okamura, H; Kaio, N
IEEE TRANSACTIONS ON DEPENDABLE AND SECURE COMPUTING   3(2) 130-140   2006   [Refereed]
In this paper, we consider two kinds of sequential checkpoint placement problems with infinite/finite time horizon. For these problems, we apply approximation methods based on the variational principle and develop computation algorithms to derive ...
Iwamoto, K; Dohi, T; Okamura, H; Kaio, N
COMPUTERS & MATHEMATICS WITH APPLICATIONS   51(2) 335-344   Jan 2006   [Refereed]
Software rejuvenation is a proactive fault management technique that has been extensively studied in the recent literature. In this paper, we focus on an example for a telecommunication billing application considered in [1] and develop the discret...
Ohishi, Koji; Okamura, Hiroyuki; Dohi, Tadashi
JOURNAL OF SYSTEMS AND SOFTWARE   82(3) 535-543   Mar 2009   [Refereed]
Gompertz Curve has been used to estimate the number of residual faults in testing phases of software development, especially by Japanese software development companies. Since the Gompertz curve is a deterministic function, the curve cannot be appl...
Okamura, Hiroyuki; Dohi, Tadashi
IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E92A(7) 1615-1622   Jul 2009   [Refereed]
This paper proposes a dynamic capture-recapture (DCR) model to estimate not only the total number of software faults but also quantitative software reliability from observed data. Compared to conventional static capture-recapture (SCR) model and u...
Okamura, Hiroyuki; Dohi, Tadashi; Trivedi, Kishor S.
IEEE-ACM TRANSACTIONS ON NETWORKING   17(4) 1326-1339   Aug 2009   [Refereed]
This paper addresses a parameter estimation problem of Markovian arrival process (MAP). In network traffic measurement experiments, one often encounters the group data where arrival times for a group are collected as one bin. Although the group da...
Yamaguchi, Y.; Okamura, H.; Dohi, T.
COMMUNICATIONS IN STATISTICS-THEORY AND METHODS   39(13) 2333-2350   2010   [Refereed]
This article proposes a fast algorithm for estimating parameters of a mixture of Erlang (MER) distribution from empirical samples. In particular, we develop a variational approach for approximately computing posterior distributions of parameters o...
Okamura, Hiroyuki; Dohi, Tadashi
JOURNAL OF SYSTEMS AND SOFTWARE   83(9) 1591-1604   Sep 2010   [Refereed]
This paper examines comprehensive evaluation of aperiodic time-based checkpointing and rejuvenation schemes maximizing the steady-state system availability in an operational software system. We consider two kinds of maintenance policies: checkpoin...
Okamura, Hiroyuki; Dohi, Tadashi; Trivedi, Kishor S.
PERFORMANCE EVALUATION   68(10) 938-954   Oct 2011   [Refereed]
This paper proposes an improved computation method of maximum likelihood (ML) estimation for phase-type (PH) distributions with a number of phases. We focus on the EM (expectation-maximization) algorithm proposed by Asmussen et al. [27] and refine...
Software Reliability Prediction Based on Least Squares Estimation
Ishii, Tomotaka; Dohi, Tadashi; Okamura, Hiroyuki
QUALITY TECHNOLOGY AND QUANTITATIVE MANAGEMENT   9(3) 243-264   Sep 2012   [Refereed]
Of the main interest in practical software testing would be the prediction of the number of detected faults in future rather than the estimation of the quantitative reliability function, which is defined as the probability that the software does n...
Zhou, Bo; Okamura, Hiroyuki; Dohi, Tadashi
IEICE TRANSACTIONS ON INFORMATION AND SYSTEMS   E95D(9) 2219-2226   Sep 2012   [Refereed]
This paper proposes the test case prioritization in regression testing. The large size of a test suite to be executed in regression testing often causes large amount of testing cost. It is important to reduce the size of test cases according to pr...
Zhou, Bo; Okamura, Hiroyuki; Dohi, Tadashi
IEEE TRANSACTIONS ON COMPUTERS   62(1) 186-192   Jan 2013   [Refereed]
In this paper, we propose a probabilistic approach to finding failure-causing inputs based on Bayesian estimation. According to our probabilistic insights of software testing, the test case generation algorithms are developed by Markov chain Monte...
Okamura, Hiroyuki; Dohi, Tadashi
PERFORMANCE EVALUATION   70(3) 197-211   Mar 2013   [Refereed]
This paper presents a Markov decision process (MDP) formulation for a transaction-based system with software aging and rejuvenation. In our formulation, the arrival process of transactions is described as a Markovian arrival process (MAP). In addi...
Okamura, Hiroyuki; Dohi, Tadashi; Trivedi, Kishor S.
APPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY   29(2) 141-156   2013   [Refereed]
This paper proposes an improved expectationmaximization (EM) algorithm for phase-type (PH) distributions with grouped and truncated data. Olsson (1996) derived an EM algorithm for PH distributions under censored data, and the similar technique can...
Performance evaluation of workload-based software rejuvenation scheme
IEICE Transactions on Information and Systems   E84D(10) 1368-1375   Oct 2001   [Refereed]
Discrete availability models to rejuvenate a telecommunication billing application
IEICETRANSACTIONSONCOMMUNICATIONS   E86B(10) 2931-2939   Oct 2003   [Refereed]
Fine-Grained Shock Models to Rejuvenate Software Systems
IEICE Transactions on Information and Systems   E86D(10) 2165-2171   Oct 2003   [Refereed]
EMBEDDEDANDUBIQUITOUSCOMPUTING-EUC2005   3824 245-254   Jan 2005   [Refereed]
Cost-effective analysis of software systems with periodic rejuvenation
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences   E85A(12) 2923-2932   Dec 2002   [Refereed]
Dependability Analysis of a Transaction-Based Multi-Server System with Rejuvenation
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences   E86A(8) 2081-2090   Aug 2003   [Refereed]
Okamura, H; Dohi, T; Osaki, S
COMPUTERS & MATHEMATICS WITH APPLICATIONS   39(1-2) 215-227   Jan 2000   [Refereed]
In this paper, we consider two stochastic models for a controlled single-server M/G/1 queueing system under a random vacation circumstance. The relevant expected costs are formulated under two control strategies and approximated by means of a fami...
Performance evaluation of workload-based software rejuvenation scheme
Okamura, H; Miyahara, S; Dohi, T; Osaki, S
IEICE TRANSACTIONS ON INFORMATION AND SYSTEMS   E84D(10) 1368-1375   Oct 2001   [Refereed]
The software rejuvenation is one of the most effective preventive maintenance technique for operational software systems with high assurance requirement. In this paper, we propose the workload-based software rejuvenation scheme for a server type o...
Cost-effective analysis of software systems with periodic rejuvenation
Suzuki, H; Dohi, T; Okamura, H
IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E85A(12) 2923-2932   Dec 2002   [Refereed]
In this paper, we consider the similar software cost models with periodic rejuvenation to Garg, Puliafito, Telek and Trivedi (1995) under the cost effectiveness criteria. First, an alternative model as well as the original one are analyzed by Mark...
Dependability analysis of a transaction-based multi-server system with rejuvenation
Okamura, H; Miyahara, S; Dohi, T
IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E86A(8) 2081-2090   Aug 2003   [Refereed]
This paper considers a transaction-based multiserver system with rejuvenation, and derive the optimal software rejuvenation policies under some system dependability measures; the steady-state availability, the probability of transaction loss and t...
Discrete availability models to rejuvenate a telecommunication billing application
Dohi, T; Iwamoto, K; Okamura, H; Kaio, N
IEICE TRANSACTIONS ON COMMUNICATIONS   E86B(10) 2931-2939   Oct 2003   [Refereed]
Software rejuvenation is a proactive fault management technique that has been extensively studied in the recent literature. In this paper, we focus on an example for a telecommunication billing application considered in Huang et al. (1995) and dev...
Fine-grained shock models to rejuvenate software systems
Fujio, H; Okamura, H; Dohi, T
IEICE TRANSACTIONS ON INFORMATION AND SYSTEMS   E86D(10) 2165-2171   Oct 2003   [Refereed]
The software rejuvenation is a proactive fault management technique for operational software systems which age due to the error conditions that accrue with time and/or load, and is important, for high assurance systems design. In this paper, fine-...
Okamura, H; Dohi, T
EMBEDDED AND UBIQUITOUS COMPUTING - EUC 2005   3824 245-254   2005   [Refereed]
In this paper, we focus on power-aware network devices, and propose a stochastic model to evaluate their performance quantitatively. More precisely, applying the Markovian additive process (MAP) to the arrival stream for network devices, we develo...
Xiao, Xiao; Okamura, Hiroyuki; Dohi, Tadashi
IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E95A(5) 894-902   May 2012   [Refereed]
Non-homogeneous Poisson processes (NHPPs) have gained much popularity in actual software testing phases to estimate the software reliability, the number of remaining faults in software and the software release timing. In this paper, we propose a n...
Okamura, Hiroyuki; Dohi, Tadashi; Osaki, Shunji
RELIABILITY ENGINEERING & SYSTEM SAFETY   116 135-141   Aug 2013   [Refereed]
This paper proposes software reliability growth models (SRGM) where the software failure time follows a normal distribution. The proposed model is mathematically tractable and has sufficient ability of fitting to the software failure data. In part...
Okamura, Hiroyuki; Dohi, Tadashi
IEICE TRANSACTIONS ON INFORMATION AND SYSTEMS   E96D(9) 1933-1940   Sep 2013   [Refereed]
This paper presents the opportunity-based software rejuvenation policy and the optimization problem of software rejuvenation trigger time maximizing the system performance index. Our model is based on a basic semi-Markov software rejuvenation mode...
Okamura, Hiroyuki; Kishikawa, Hidenari; Dohi, Tadashi
TELECOMMUNICATION SYSTEMS   54(1) 79-90   Sep 2013   [Refereed]
This paper proposes a variant of EM (expectation-maximization) algorithm for Markovian arrival process (MAP) and phase-type distribution (PH) parameter estimation. Especially, we derive the deterministic annealing EM (DAEM) algorithm for MAP/PH pa...
A Fast EM Algorithm for Fitting Marked Markovian Arrival Processes with a New Special Structure
G. Horv?th, H. Okamura
Proceedings of 10th European Workshop on Performance Engineering (EPEW 2013)   (8168) 119-133   2013
Aperiodic checkpoint placement algorithms -- survey and comparison --
S. Hiroyama, T. Dohi and H. Okamura
Journal of Software Engineering and Applications   6(4A) 41-53   2013
Estimating response time distribution of server application in software aging phenomenon,
H. Okamura, C. Luo and T. Dohi
Proceedings of IEEE 5th International Workshop on Software Aging and Rejuvenation (WoSAR-2013)   4   2013
S. Ikemoto, T. Dohi and H. Okamura
Proceedings of 2013 Joint Conference of the 23rd International Workshop on Software Measurement (IWSM-2013) and the 8th International Conference on Software Process and Product Measurement (MENSURA-2013)   219-224   2013
D. Kuwa and T. Dohi
Proceedings of The 19th IEEE Pacific Rim International Symposium on Dependable Computing (PRDC 2013),   328-337   2013
C. Luo, H. Okamura and T. Dohi
Proceedings of The 37th Annual International Computer Software and Applications Conference (COMPSAC 2013)   53-58   2013
NHPP-based software reliability model with mixed gamma distribution,
H. Okamura, T. Hirata and T. Dohi
Advanced Science and Technology Letters   19 240-243   2013
S. Ikemoto, T. Dohi and H. Okamura
Proceedings of The 24th International Symposium on Software Reliability Engineering (ISSRE 2013)   108-117   2013
Quantitative security evaluation for software system from vulnerability database
H. Okamura, M. Tokuzane and T. Dohi
Journal of Software Engineering and Applications   6(4A) 15-23   2013
Semi-parametric approach for software reliability evaluation using mixed gamma distributions
H. Okamura, T. Hirata and T. Dohi
International Journal of Software Engineering and Its Applications   7(4) 401-414   2013
Sensitivity analysis of reliability function for virtualized system,
J. Zheng, H. Okamura and T. Dohi
Proceedings of the 8th International Conference on Mathematical Methods in Reliability, --Theory, Methods and Applications -- (MMR-2013)   229-232   2013
H. Okamura and T. Dohi
Proceedings of The 24th International Symposium on Software Reliability Engineering (ISSRE 2013),   100-117   2013
Okamura, H.; Watanabe, R.; Dohi, T.
COMMUNICATIONS IN STATISTICS-SIMULATION AND COMPUTATION   43(8) 2031-2044   Sep 2014   [Refereed]
This article develops an algorithm for estimating parameters of general phase-type (PH) distribution based on Bayes estimation. The idea of Bayes estimation is to regard parameters as random variables, and the posterior distribution of parameters ...
Transient Analysis of Software Rejuvenation Policies in Virtualized System: Phase-Type Expansion Approach
Okamura, H.; Yamamoto, K.; Dohi, T.
QUALITY TECHNOLOGY AND QUANTITATIVE MANAGEMENT   11(3) 335-351   Sep 2014   [Refereed]
This paper presents a transient analysis of software rejuvenation with virtualization. In particular, we apply the phase-type expansion to analyze the pointwise availability of virtual-machine (VM) based software rejuvenation with two policies; co...
Luo, C.; Okamura, H.; Dohi, T.
JOURNAL OF SUPERCOMPUTING   70(3) 1156-1179   Dec 2014   [Refereed]
Database systems are widely used in many fields. As the scale of database systems increases, more firms decide to deploy the database system in a distributed environment for the sake of data integrity fault tolerance. For guaranteeing the consiste...
Okamura, H; Dohi, T
Proceedings of The 15th IEEE International Symposium on High Assurance Systems Engineering (HASE 2014)   97-104   Jan 2014   [Refereed]

Books etc

 
Principles of Performance and Reliability Modeling and Evaluation
H. Okamura and T. Dohi (Part:Joint Work, Chapter 3)
Springer   Apr 2016   
Advances in Reliability and System Engineering
Z. Yi, T. Dohi and H. Okamura (Part:Joint Work)
Springer   Dec 2016