• International Journal of Reliability and Applications
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• 제3권1호
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• pp.1-16
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• 2002

In reliability engineering, the bathtub-shaped hazard rates play an important role in survival analysis and many other applications as well. For the bathtub-shaped, initially the hazard rate decreases from a relatively high value due to manufacturing defects or infant mortality to a relatively stable middle useful life value and then slowly increases with the onset of old age or wear out. In this paper, we present a new two-parameter lifetime distribution function, called the Loglog distribution, with Vtub-shaped hazard rate function. We illustrate the usefulness of the new Vtub-shaped hazard rate function by evaluating the reliability of several helicopter parts based on the data obtained in the maintenance malfunction information reporting system database collected from October 1995 to September 1999. We develop the S-Plus add-in software tool, called Reliability and Safety Assessment (RSA), to calculate reliability measures include mean time to failure, mean residual function, and confidence Intervals of the two helicopter critical parts. We use the mean squared error to compare relative goodness of fit test of the distribution models include normal, lognormal, and Weibull within the two data sets. This research indicates that the result of the new Vtub-shaped hazard rate function is worth the extra function-complexity for a better relative fit. More application in broader validation of this conclusion is needed using other data sets for reliability modeling in a general industrial setting.

• Steel and Composite Structures
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• 제33권1호
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• pp.143-162
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• 2019

A number of desirable characteristics concerning excellent durability, aesthetics, recyclability, high ductility and fire resistance have made stainless steel a preferred option in engineering practice. However, the relatively high initial cost has greatly restricted the application of stainless steel as a major structural material in general construction. This drawback can be partially overcome by introducing composite stainless steel-concrete structures, which provides a cost-efficient and sustainable solution for future stainless steel construction. This paper presents a preliminary numerical study on stainless steel-concrete composite beam-to-column joints with bolted flush endplates. In order to ensure a consistent corrosion resistance within the whole structural system, all structural steel components were designed with austenitic stainless steel, including beams, columns, endplates, bolts, reinforcing bars and shear connectors. A finite element model was developed using ABAQUS software for composite beam-to-column joints under monotonic and symmetric hogging moments, while validation was performed based on independent test results. A parametric study was subsequently conducted to investigate the effects of several critical factors on the behaviour of composite stainless steel joints. Finally, comparisons were made between the numerical results and the predictions by current design codes regarding the plastic moment capacity and the rotational stiffness of the joints. It was concluded that the present codes of practice generally overestimate the rotational stiffness and underestimate the plastic moment resistance of stainless steel-concrete composite joints.

• Advances in Energy Research
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• 제4권3호
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• pp.213-221
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• 2016

The main purpose of this work is to test the validation of use of a four step reaction mechanism to simulate the laminar speed of hydrogen enriched methane flame. The laminar velocities of hydrogen-methane-air mixtures are very important in designing and predicting the progress of combustion and performance of combustion systems where hydrogen is used as fuel. In this work, laminar flame velocities of different composition of hydrogen-methane-air mixtures (from 0% to 40% hydrogen) have been calculated for variable equivalence ratios (from 0.5 to 1.5) using the flame propagation module (FSC) of the chemical kinetics software Chemkin 4.02. Our results were tested against an extended database of laminar flame speed measurements from the literature and good agreements were obtained especially for fuel lean and stoichiometric mixtures for the whole range of hydrogen blends. However, in the case of fuel rich mixtures, a slight overprediction (about 10%) is observed. Note that this overprediction decreases significantly with increasing hydrogen content. This research demonstrates that reduced chemical kinetics mechanisms can well reproduce the laminar burning velocity of methane-hydrogen-air mixtures at lean and stoichiometric mixture flame for hydrogen content in the fuel up to 40%. The use of such reduced mechanisms in complex combustion device can reduce the available computational resources and cost because the number of species is reduced.

• Nuclear Engineering and Technology
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• 제39권4호
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• pp.327-336
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• 2007

The influence of density differences on the mixing of the primary loop inventory and the Emergency Core Cooling (ECC) water in the downcomer of a Pressurised Water Reactor (PWR) was analyzed at the ROssendorf COolant Mixing (ROCOM) test facility. ROCOM is a 1:5 scaled model of a German PWR, and has been designed for coolant mixing studies. It is equipped with advanced instrumentation, which delivers high-resolution information for temperature or boron concentration fields. This paper presents a ROCOM experiment in which water with higher density was injected into a cold leg of the reactor model. Wire-mesh sensors measuring the tracer concentration were installed in the cold leg and upper and lower part of the downcomer. The experiment was run with 5% of the design flow rate in one loop and 10% density difference between the ECC and loop water especially for the validation of the Computational Fluid Dynamics (CFD) software ANSYS CFX. A mesh with two million control volumes was used for the calculations. The effects of turbulence on the mean flow were modelled with a Reynolds stress turbulence model. The results of the experiment and of the numerical calculations show that mixing is dominated by buoyancy effects: At higher mass flow rates (close to nominal conditions) the injected slug propagates in the circumferential direction around the core barrel. Buoyancy effects reduce this circumferential propagation. Therefore, density effects play an important role during natural convection with ECC injection in PWRs. ANSYS CFX was able to predict the observed flow patterns and mixing phenomena quite well.

• Journal of Hospice and Palliative Care
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• 제23권4호
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• pp.228-240
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• 2020

Purpose: The purpose of this study was to test the validity of the Korean version of the Nurses' Involvement in Dying Patients and Family Care (NIDPFC) instrument. Methods: Data were collected from 410 registered nurses at a university hospital, general hospitals, and a convalescent hospital. Data were collected from June 23 to July 17, 2020. Internal consistency reliability, construct validity, and criterion validity were examined using the SPSS and AMOS software. Results: Of the 35 preliminary items of the instrument, 24 items were finally selected after evaluating the content validity, analyzing the items, and assessing construct validity. The following four factors were derived: "burden" (seven items), "deep involvement" (eight items), "resilience" (five items), and "empathy" (four items), with a cumulative explanatory variance of 55.2%. For criterion validity, a significant positive relationship was found between the NIDPFC and attitudes toward caring for the dying. For internal consistency reliability, the Cronbach's α was 0.82. Conclusion: The validity and reliability of the NIDPFC were verified. Therefore, the NIDPFC is an effective instrument to use in further studies.

• 한국전자통신학회논문지
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• 제17권5호
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• pp.809-814
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• 2022

주의력결핍장애는 산만함, 과잉행동을 보여주는 질환으로 소아청소년기에 진단 시 성인까지 증상이 지속되기 때문에 조기에 진단 및 치료를 시작하는 것이 중요하다. 그러나 소아는 정신적으로 미성숙하기 때문에 자가진단법 또는 측정 장비를 이용할 때 올바른 진단 데이터를 획득하기 어려운 문제가 있다. 이 논문에서는 ADHD 진단의 객관성과 정확도를 높이기 위하여 게임 콘텐츠를 이용하여 측정된 뇌전도 데이터에 대하여 CNN 모델링을 기반으로 분류하는 기법을 제시하고 실험하였다. 실험을 위하여 3D 네트워크 모델을 구성하였으며 평균적으로 97%의 정확도를 보여주었다.

• International Journal of Computer Science & Network Security
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• 제23권1호
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• pp.53-63
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• 2023

Many researchers are trying hard to minimize the incidence of cancers, mainly Gastric Cancer (GC). For GC, the five-year survival rate is generally 5-25%, but for Early Gastric Cancer (EGC), it is almost 90%. Predicting the onset of stomach cancer based on risk factors will allow for an early diagnosis and more effective treatment. Although there are several models for predicting stomach cancer, most of these models are based on unbalanced datasets, which favours the majority class. However, it is imperative to correctly identify cancer patients who are in the minority class. This research aims to apply three class-balancing approaches to the NHS dataset before developing supervised learning strategies: Oversampling (Synthetic Minority Oversampling Technique or SMOTE), Undersampling (SpreadSubsample), and Hybrid System (SMOTE + SpreadSubsample). This study uses Naive Bayes, Bayesian Network, Random Forest, and Decision Tree (C4.5) methods. We measured these classifiers' efficacy using their Receiver Operating Characteristics (ROC) curves, sensitivity, and specificity. The validation data was used to test several ways of balancing the classifiers. The final prediction model was built on the one that did the best overall.

• Interdisciplinary Bio Central
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• 제4권1호
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• pp.2.1-2.7
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• 2012

Introduction: Histone deacetylases (HDAC) are a class of enzymes that remove acetyl groups from ${\varepsilon}$-N-acetyl lysine amino acids of histone proteins. Their action is opposite to that of histone acetyltransferase that adds acetyl groups to these lysines. Only few HDAC inhibitors are approved and used as anti-cancer therapeutics. Thus, discovery of new and potential HDAC inhibitors are necessary in the effective treatment of cancer. Materials and Methods: This study proposed a method using support vector machine (SVM) to classify HDAC8 inhibitors and non-inhibitors in early-phase virtual compound filtering and screening. The 100 experimentally known HDAC8 inhibitors including 52 inhibitors and 48 non-inhibitors were used in this study. A set of molecular descriptors was calculated for all compounds in the dataset using ADRIANA. Code of Molecular Networks. Different kernel functions available from SVM Tools of free support vector machine software and training and test sets of varying size were used in model generation and validation. Results and Conclusion: The best model obtained using kernel functions has shown 75% of accuracy on test set prediction. The other models have also displayed good prediction over the test set compounds. The results of this study can be used as simple and effective filters in the drug discovery process.

• 한국건설관리학회논문집
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• 제23권2호
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• pp.3-15
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• 2022

본 연구에서는 모듈러 공법 기반 강교 건설공사에 대해 공급사슬 관리를 위한 시뮬레이션 모형을 개발한다. 이를 위해, 우선 강교 건설에 대한 공장 제작/현장 시공 체계 자료를 수집한 후, 이를 바탕으로 공급사슬, 개체, 자원, 공정 등을 정의하였다. 이후, Arena 소프트웨어를 이용하여 데이터, 플로차트, 애니메이션 모듈을 작성함으로써 강교 공급사슬 시뮬레이션 모형을 개발하였다. 마지막으로, 개발된 모형의 논리성 검증과 유효성 확인을 위한 애니메이션 검증, 극한 조건 검증, 평균값 확인, 리틀의 법칙 확인, 사례 실적값 확인 등의 방법론을 이용하여 모형의 타당성을 검토하였다. 검토 결과, 개발된 시뮬레이션 모형은 논리적 오류 없이 강교 공급사슬의 공정과 특성을 적합하게 표현하며, 분석 대상 공급사슬에 대한 정확한 성능평가척도 예측치를 제공하였다. 향후, 본 연구에서 개발된 시뮬레이션 모형은 강교 공급사슬 체계를 최적으로 운영하기 위한 관리기법을 개발함에 있어 성능 평가 플랫폼으로서의 역할을 충실히 수행할 수 있을 것이다.

• 한국융합학회논문지
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• 제6권4호
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• pp.121-126
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• 2015

한국청소년패널(2008)의 중2 패널 5차년도 자료를 가지고 기술통계 분석과 회귀분석을 실시하여 가족의 기능적 결손이라는 위험상황에서 위험요인, 보호요인, 심리적응 간의 관계와 보호요인의 매개효과의 기제를 검증하고, 심리적응 수준이 높은 청소년을 보호해주는 보호요인을 분석하는 데에 그 목적이 있다. 분석방법으로는 대상자의 빈도분석과 개인특성에 따른 차이를 알아보기 위해 PASW(Predictive Analytics Software) 18.0을 이용해 t검증을 실시하였다. 또한 적응에 대한 보호요인의 작용 검증을 위하여 위계적 회귀분석을 실시하여 매개효과를 검증하였다. 연구결과 사회복지실천 현장에서 청소년의 위험요인에 초점을 맞추기보다는 위험요인을 완화시키는 과정이나 보호요인에 초점을 맞춤으로써 위험요인에 노출된 청소년을 바라보는 시각을 전환시킬 수 있으며 이들에 대한 개입도 달라질 것으로 판단된다. 사회복지실천 현장에서 청소년의 위험요인에 초점을 맞추기보다는 위험요인을 완화시키는 과정이나 보호요인에 초점을 맞춤으로써 위험요인에 노출된 청소년을 바라보는 시각을 전환시킬 수 있다. 또한, 가족의 기능적 결손이라는 어려움을 경험하는 청소년을 대상으로 사회복지 실천적 개입 방향을 마련 할 수 있는 기초를 마련한 것으로 판단된다.