• Journal of the Korean Institute of Gas
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• v.15 no.3
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• pp.67-73
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• 2011

One of the important topics to prepare the up-coming era of so-called ‘hydrogen economy’ is hydrogen transmission. Pipeline is conceivably the most economic way to consistently and safely transport a large amount of hydrogen over a long distance, which may be strongly requested in hydrogen economy era. As a good starting point for the purpose, one might wonder whether conventional API pipeline steels as designed for natural gas transmission can be used as the hydrogen pipeline materials or not. To answer the question, here we performed a series of micro-/nano-indentations together with tensile tests on the hydrogen-charged API X65, X70 and X100 steels having different strength level. In this paper, from the results of tensile tests, the hydrogen effects on the mechanical behavior in the API steels are systematically evaluated.

• Korean Journal of Metals and Materials
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• v.48 no.10
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• pp.875-883
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• 2010

This study assessed the Charpy impact properties of the heat-affected zones (HAZs) of API X80 linepipe steels containing complex oxides. Three types of steel were fabricated by adding Mg and $O_2$ to form complex oxides and their microstructures and Charpy impact properties were investigated. The number of complex oxides increased with the amount of excess Mg and $O_2$ that was included in the steels. Simulated HAZs containing a number of oxides showed a high volume fraction of acicular ferrite (AF) because the oxides acted as nucleation sites for AF, thereby leading to an improvement in the Charpy impact properties. According to a correlation study between the heat input, the volume fraction of the AF, and the Charpy impact properties, ductile fractures occurred predominantly when the fraction of the AF was 20% or higher; moreover, the Charpy absorbed energy was excellent at more than 100 J. These findings suggest that the improvement of the Charpy impact properties of the HAZs was associated with the active nucleation of AF in the oxide-containing steel HAZs.

• Geomechanics and Engineering
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• v.28 no.1
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• pp.11-23
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• 2022

The response of pile foundations under lateral loads are usually analyzed using beam-on-nonlinear-Winkler-foundation (BNWF) model framework employing various forms of empirically derived p-y curves and p-multipliers. In practice, the p-y curve presented by the American Petroleum Institute (API) is most often utilized for piles in granular soils, although its shortcomings are recognized. The objective of this study is to evaluate the performance of the BNWF model and to quantify the error in the estimated pile response compared to a rigorous numerical model. BNWF analyses are performed using three sets of p-y curves to evaluate reliability of the procedure. The BNWF model outputs are compared with results of 3D nonlinear finite element (FE) analysis, which are validated via field load test measurements. The BNWF model using API p-y curve produces higher load-displacement curve and peak bending moment compared with the results of the FE model, because empirical p-y curve overestimates the stiffness and underestimates ultimate resistance up to a depth equivalent to four times the pile diameter. The BNWF model overestimates the peak bending moment by approximately 20-30% using both the API and Reese curves. The p-multipliers are revealed to be sensitive on the p-y curve used as input. These results highlight a need to develop updated p-y curves and p-multipliers for improved prediction of the pile response under lateral loading.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.118-118
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• 2022

지속적인 학문의 발전을 위해서는 선행연구에 대한 재현성이 무엇보다도 중요하다고 할 수 있다. 하지만 컴퓨터와 소프트웨어의 급속한 발달로 인한 컴퓨터 환경의 다양화, 분석 소프트웨어의 지속적 최신화로 인해서 최근 구축된 모델도 짧게는 몇 달, 길게는 1~2년후면 다양한 에러로 인하여 재현성이 불가능해지고 있다. 이러한 재현성의 극복을 위해서 온라인을 통한 데이터와 소스코드의 공유의 필요성이 제시되고 있으나, 실제로는 개인마다 컴퓨터 환경, 버전, 소프트웨어 설치에 필요한 라이브러리의 버전 또는 디렉토리 등이 달라 단순히 온라인을 통한 데이터와 소스코드의 공유만으로 재현성을 개선하기는 힘든 것이 현실이다. 따라서 이러한 컴퓨터 모델링 환경의 공유는 과거의 형태와 같이 데이터, 소스코드와 매뉴얼의 공유만으로 불가능하다고 할 수 있다. 따라서 본 연구에서는 수자원 모델링의 재현성 개선을 위해 1) 온라인 저장소, 2) 클라우드기반 JupyterHub 모델링 환경과 3) 모델 APIs 3개의 핵심 구성요소를 제시하고, 최근 미국에서 개발된SUMMA(Structure for Unifying Multiple Modeling Alternative) 수자원 모델에 적용하여 재현성 달성을 위한 3개의 핵심 구성요소의 필요성과 용이성을 검증하였다. 첫 번째, 데이터와 모델의 온라인 공유는 FAIR(Findable, Accessible, Interoperable, Reusable) 원칙으로 개발된 수자원분야의 대표적인 온라인 저장소인 HydroShare를 활용하여 모델입력자료를 메타데이터와 함께 공유하였다. 두 번째, HydroShare에서 Web App의 형태로 제공되는 클라우드기반 JupyterHub환경인 CUAHSI JupyterHub(CJH)와 일루노이대학에서 제공하는 CyberGIS-Jupyter for water JupyterHub(CJW)환경에 수자원모델링 환경을 컨테이너(Docker) 환경을 통해 구축·공유하였다. 마지막으로, 클라우드에서 수자원모델의 효율적 이용을 위해 Python기반의SUMMA모델 API인 pySUMMA를 개발·공유하였다. 이와같이 구축된 3개의 핵심 구성요소를 이용하여 2015년 Water Resources Research에 게재된 SUMMA 논문의 9개 Test Cases 중에서 5개를 누구나 쉽게 재현할 수 있음을 증명하였다. 재현성의 중요성에 대한 인식의 증가로 Open과 Transparent Hydrology에 대한 요구가 증대되고 있으며, 이를 위해서 클라우드 기반의 모델링 환경구축 및 제공이 확대되고 있다. 본 연구에서 제시한 HydroShare와 같은 온라인 저장소, CJH와 CJW와 같은 클라우드기반 모델링환경, 모델의 효율적 이용을 위한 모델 APIs는 급속도로 발달하고 있는 컴퓨터 및 소프트웨어 환경에서 핵심구성요소이며, 연구의 재현성 개선을 통해 수자원공학 발전에 기여할 것으로 기대된다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10b
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• pp.388-390
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• 2004

모바일 어플리케이션은 플랫폼이 제공하는 API를 통해서 만들어진다. 모바일 어플리케이션을 제작하고 운용하는데 모바일 플랫폼이 차지하는 비중은 아주 높다. 따라서 모바일 어플리케이션의 플랫폼 종속성은 높다고 할 수 있다. 플랫폼 종속적인 모바일 어플리케이션을 테스트하기 위해서는 해당 플랫폼에 대한 정보를 가지고 있어야 한다. 본 논문에서는 플랫폼 종속적인 모바일 어플리케이션을 해당 플랫폼에 대한 종속성을 감소시켜 다양한 플랫폼 환경에서 테스트 할 수 있는 아키텍처를 제시한다. 또한 이를 밑바탕으로 특정 플랫폼에서 수행된 테스트 데이터가 다른 플랫폼에서도 사용될 수 있도록 테스트 데이터의 재사용을 향상시킬 수 있는 테스트 아키텍처를 제시한다

• Journal of Energy Engineering
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• v.18 no.1
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• pp.56-62
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• 2009

With weld metal of X65 steel, hydrogen was charged by electro-chemical method and mechanical behavior such as strength was measured by the small punch test. The weld metal was more sensitive to hydrogen charging than the case of base metal. The small punch (SP) strength was decreased as the hydrogen contents increased. Magnitude of strength decrease was dependent on current density, temperature, charging time. Current density and charging time have significant effect on the mechanical properties but temperature of electrolyte has limited effect. Fractured surfaces of the tested specimens were observed by SEM (scanning electron microscope). In the hydrogen charged specimens cleavage fracture were observed, which is consistent with the SP test results. Since the testing procedure for studying hydrogen embrittlement proposed in this study has shown good reproducibility of test results, the proposed method can be assumed to be a reliable test procedure. Using the electrochemical charging and the small punch test, the change of SP strength for X65 weld metal due to hydrogen embritlement could be evaluated sensitively.

• Journal of Microbiology and Biotechnology
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• v.17 no.7
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• pp.1152-1161
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• 2007

An immunochromatography (ICG) strip test based on a monoclonal antibody for the rapid detection of L. monocytogenes in meat and processed-meat samples was developed in this study. A monoclonal antibody (MAb) specific to L. monocytogenes was produced from cloned hybridoma cells (FKLM-3B12-37) and used to develop an ICG strip test. The antibody showed a stronger binding to L. monocytogenes than other Listeria species, and a weak cross-reaction to S. aureus based on an ELISA. The detection limit of the ICG strip test was $10^5\;cell/ml$. In total, 116 meat and processed-meat samples were collected and analyzed using both the ICG strip test and a PCR. The ICG strip test and PCR indicated L. monocytogenes contamination in 34 and 27 meat samples, respectively. The 7 meat samples not identified as L. monocytogenes positive by the PCR were also tested using an API kit and found to be contaminated by Listeria species. In conclusion, the ICG strip test results agreed well with those obtained using the PCR and API kit. Thus, the developed ICG has potential use as a primary screening tool for L. monocytogenes in various foods and agricultural products, generating results within 20 min without complicated steps.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.291-296
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• 2004

The paper describes a test program on welded K-joints fabricated from circular hollow section brace members and chords made with API 2W 50 grade steel produced by POSCO. The K-joints were tested for three loading conditions at RIST. The specimens were tested in reaction frame that allowed vertical uniform loading to the structure. From the test, the crack initiation and development were observed and the fatigue failure could be predicted. The results were also compared with the provided S-N curves by DnV.

• Advances in nano research
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• v.9 no.1
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• pp.59-67
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• 2020

Filter cake formation during rotary drilling operation is an unavoidable scenario, hence there is need for constant improvement in the approaches used in monitoring the cake thickness growth in order to prevent drill-string sticking. This study proposes an improved model that predicts the growth of mud cake thickness overtime with the consideration of the addition of nanoparticles in the formulated drilling fluid system. Ferric oxide, titanium dioxide and copper oxide nanoparticles were used in varying amounts (2 g, 4 g and 6 g), and filtration data were obtained from the HPHT filtration test. The filter cakes formed were further analyzed with scanning electron microscope to obtain the morphological characteristics. The data obtained was used to validate the new filtrate loss model. This model specifically presents the concept of time variation in filter cake formation as against the previous works of constant and definite time. Regression coefficient which is a statistical measure was used to validate the new model and the predicted results were compared with the API model. The new model showed R² values of 99.9%, and the predictions from the proposed filtration model can be said to be more closely related to the experimental data than that predicted from the API model from the SSE and RMSE results.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.127-132
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• 2002

Shaking table tests are performed on model group piles to investigate the mechanics of dynamic pile-soil interaction, and to evaluate the dynamic group pile effect. Tests are executed on a single pile as well as group piles($3\times3$) by varying a pile spacing from 3D to 8D. A lumped mass is located on top of piles to simulate a superstructure. Dynamic p-y curves of the single pile and the group piles are obtained from the tests and compared with the backbone slopes of API cyclic p-y curves. From the comparisons, dynamic pile group effects are evaluated in terms of a pile spacing, a shaking frequency, and a shaking intensity.