• 상하수도학회지
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• 제25권5호
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• pp.635-642
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• 2011

Hydraulic efficiency was a vital component in evaluating the disinfection capability of clearwell. Current practice evaluates these system based on the tracer test only. In this paper, CFD(Computational Fluid Dynamics) was applied on the clearwell for alternating or supplementing the tracer test. The baffle factor derived from the CFD modeling closely matched the values obtained from full scale tracer testing. And, for suggesting proper numerical model in clearwell; the turbulence model, discretization scheme, convergence criteria were investigated through separate simulation runs. The model validation was conducted by comparing the simulated data with experimental data. In the turbulence model, the realizable ${\kappa}-{\varepsilon}$ model and the standard ${\kappa}-{\varepsilon}$ model were found to be more appropriate than RNG ${\kappa}-{\varepsilon}$ model. The residuals of convergence criteria should be used as not $10^{-3}$ but $10^{-4}$ or $10^{-5}$. In discretization scheme, the difference of simulated values in 1st, 2nd, 3rd upwind scheme was found to be insignificant. Moreover, the result of this study suggest that CFD modeling can be a reliable alternative to tracer testing for evaluating the hydraulic efficiency.

• 상하수도학회지
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• 제31권4호
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• pp.297-301
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• 2017

Wastewater treatment using ferrate (VI) solution is becoming a promising technology for several years, because it is high efficient and harmless technology. In this study, the ferrate (VI) solution was tested to treatment of desulfurization wastewater. The effluent from desulfurization wastewater treatment process of power plant was used as raw water, and the COD and T-N removal efficiency of ferrate(VI) solution were investigated. In the test, as the injection rate increased from 0.1 to 1.0%, the removal efficiency of COD also slightly increased, about 80% of COD were removed in 1.0% of injection rate. In the case of T-N, about 50% of T-N was removed in the condition of 1.0% of injection rate. The removal efficiency of COD and T-N also affected by reaction time, maximum removal efficiency was shown in 30 min of treatment. From these results, the wastewater treatment with ferrate(VI) solution can be great solutions for treatment of non-biodegradable pollutants in wastewater, especially for the 3rd treatment of wastewater.

• 한국IT서비스학회지
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• 제14권2호
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• pp.129-142
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• 2015

The purpose of this study is to suggest an effective regression testing method in order to minimize the scope of test resulting from the modification of software and to prevent mismatch of test case and test objects. As a way to improve the efficiency of regression testing which uses a change-centric testing technique, the method flow is analyzed and grasped through a static analysis based on source code in order to identify modified parts. After the order of priority is set according to the results of user action log-based dynamic analysis on identified regression testing objects, test effect can be raised by adjusting the order of priority using code complexity. Quality assurance coverage can be checked using the user action log suggested in this study, and the progress of test and whether or not each function has been verified can be checked, too. In addition, by minimizing test parts and adjusting the order of test, costs and time can be saved, making it possible to conduct regression testing effectively.

• 한국항행학회논문지
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• 제14권1호
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• pp.119-126
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• 2010

지난 30여년간 개발소프트웨어의 잔여결함, 결함률 및 신뢰도와 같은 신뢰도 척도를 분석하기 위해 소프트웨어의 신뢰도 성장 모델이 개발되어 왔다. 이들 대부분은 개발중 검출되는 소프트웨어의 오류가 완벽하게 수정되는 것으로 가정하였다. 즉, 이들은 테스트중에 검출되는 오류가 완벽하게 제거되는 것을 가정하여 그들의 연구를 진행해왔던 것이다. 그러나 오류를 검출하는 것이 어려울 뿐만 아니라 그 과정에서 새로운 오류가 도입되기도 하기 때문에 오류를 완벽하게 제거하기는 대단히 어렵다. 따라서 본 논문에서는 그동안 가장 보편 타당한 것으로 평가되어 왔던 웨이불형과 비교하여 로지스틱 테스트 노력함수를 적용한 불왼전한 소프트웨어의 테스트 노력을 제안하여 연구 검토한다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권1호
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• pp.147-155
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• 2017

A new endurance test-pattern generation on NAND-flash memory is proposed to improve test cost. We mainly focus on the correlation between the data-pattern and the device error-rate during endurance testing. The novelty is the development of testing method using quasi-random pattern based on device architectures in order to increase the test efficiency during time-consuming endurance testing. It has been proven by the experiments using the commercial 32 nm NAND flash-memory. Using the proposed method, the error-rate increases up to 18.6% compared to that of the conventional method which uses pseudo-random pattern. Endurance testing time using the proposed quasi-random pattern is faster than that of using the conventional pseudo-random pattern since it is possible to reach the target error rate quickly using the proposed one. Accordingly, the proposed method provides more low-cost testing solutions compared to the previous pseudo-random testing patterns.

• Journal of Magnetics
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• 제19권3호
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• pp.295-299
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• 2014

Recently, module-integrated converter (MIC) research has shown interest in small-scale photovoltaic (PV) generation. The converter is capable of efficient power generation. In this system, the high frequency transformer should be made compact, and demonstrate high efficiency characteristics. This paper presents a core structure optimization procedure to improve the efficiency of a high frequency transformer of compact size. The converter circuit is considered in the finite element analysis (FEA) model, in order to obtain an accurate FEA result. The results are verified by the testing of prototypes.

• International Journal of Reliability and Applications
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• 제4권2호
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• pp.57-69
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• 2003

A non-parametric test based on U-statistic for testing exponentiality against the new better than used renewal failure rate (NBURFR) alternatives is introduced and the percentiles of this test statistic are tabulated for sample size 5(1)50. Its properties are also discussed including the Pitman asymptotic efficiency relative to the tests of the new better than used and new better than used failure rate (Ahmed (1994) and Hendi (2000)). The powers of this test are also calculated for some used life distributions. An example from blood cancer patients demonstrates a practical application of our test in the medical sciences is presented. Finally the problem when right-censored data is available is handled.

• 한국융합학회논문지
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• 제7권6호
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• pp.35-41
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• 2016

소프트웨어의 중요성이 높아지면서 소프트웨어 품질평가에 대한 관심이 높아지고 있다. 본 연구에서는 소프트웨어 품질 평가를 위한 국제 표준 문서를 비교 분석하고 테스트 데이터 분석을 통한 평가 방안을 제시한다. 국제표준 ISO/IEC 9126-2의 평가 모델과 ISO/IEC 25023의 평가 모델에 대한 차이점을 비교했다. ISO/IEC 25023의 평가모델인 8가지 품질 특성, 즉 기능성, 신뢰성, 사용성, 유지보수성, 이식성, 효율성, 상호운영성, 보안성적인 측면에서 평가 메트릭을 제시했다. 실제 테스트를 통해 얻어진 331개 자료를 분석해서 테스트 데이터의 발견된 오류 특징을 파악했다. 또한 결함 자료를 분석하고 차이점을 파악했다. 테스트데이터가 남녀에 따라서 시험 일수나 발견하는 품질 특성별 오류의 수에는 차이가 있음을 증명하고 시험일수를 기능성, 사용성, 성별을 가지고 예측했으며, 제품의 종류에 따라서도 오류수에 차이가 있음을 증명했다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.3339-3352
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• 2016

In ciphertext-policy attribute-based encryption (CP-ABE) scheme, a user's secret key is associated with a set of attributes, and the ciphertext is associated with an access policy. The user can decrypt the ciphertext if and only if the attribute set of his secret key satisfies the access policy specified in the ciphertext. In the present schemes, access policy is sent to the decryptor along with the ciphertext, which means that the privacy of the encryptor is revealed. In order to solve such problem, we propose a CP-ABE scheme with hidden access policy, which is able to preserve the privacy of the encryptor and decryptor. And what's more in the present schemes, the users need to do excessive calculation for decryption to check whether their attributes match the access policy specified in the ciphertext or not, which makes the users do useless computation if the attributes don't match the hidden access policy. In order to solve efficiency issue, our scheme adds a testing phase to avoid the unnecessary operation above before decryption. The computation cost for the testing phase is much less than the decryption computation so that the efficiency in our scheme is improved. Meanwhile, our new scheme is proved to be selectively secure against chosen-plaintext attack under DDH assumption.

• International Journal of Fluid Machinery and Systems
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• 제8권4호
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• pp.294-303
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• 2015

The present study is conducted to identify a better design and optimal number of Francis runner blades for sediment laden high head micro hydropower site, Tara Khola in the Baglung district of Nepal. The runner is designed with in-house code and Computational Fluid Dynamics (CFD) analysis is performed to evaluate the performance with three configurations; 11, 13 and 17 numbers of runner blades. The three sets of runners were also investigated for the sediment erosion tendency. The runner with 13 blades shows better performance at design as well as in variable discharge conditions. 96.2% efficiency is obtained from the runner with 13 blades at the design point, and the runners with 17 and 11 blades have 88.25% and 76.63% efficiencies respectively. Further, the runner with 13 blades has better manufacturability than the runner with 17 blades as it has long and highly curved blade with small gaps between the blades, but it comes with 65% more erosion tendency than in the runner with 17 blades.