• Geomechanics and Engineering
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• 제11권2호
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• pp.253-267
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• 2016

The stability of surrounding rock will be poor when the tunnel is excavated through nearly horizontal stratum. In this paper, the instability mechanism of local nearly horizontal stratum in super-large section and deep buried tunnel is revealed by the analysis of the macro failure and micro fracture. A structural model is proposed to explain the mechanics of surrounding rock collapse under the action of stress redistribution and shed light on the macroscopic analytical approach of the stability of surrounding rock. Then, some highly effective formulas applied in the tunnel engineering are developed according to the theory of mixed-mode micro fracture. And well-documented field case is made to demonstrate the effectiveness and accuracy of the proposed analytical methods of mixed-mode fracture. Meanwhile, in order to make the more accurate judgment about yield failure of rock mass, a series of comprehensive failure criteria are formed. In addition, the relationship between the nonlinear failure criterion and $K_I$ and $K_{II}$ of micro fracture is established to make the surrounding rock failure criterion more comprehensive and accurate. Further, the influence of the parameters related to the tension-shear mixed-mode fracture and compression-shear mixed-mode fracture on the propagation of rock crack is analyzed. Results show that ${\sigma}_3$ changes linearly with the change of ${\sigma}_1$. And the change rate is related to ${\beta}$, angle between the cracks and ${\sigma}_1$. The proposed simple analytical approach is economical and efficient, and suitable for the analysis of local nearly horizontal stratum in super-large section and deep buried tunnel.

• 대한기계학회논문집A
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• 제38권10호
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• pp.1179-1184
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• 2014

일반적으로 신뢰도 배분은 시스템 개발 초기단계에 시스템의 신뢰도 목표 값을 하위 모듈에 배분하기 위해 사용된다. 본 연구에서는 KTX 승강문 시스템의 목표 신뢰도를 하위 모듈에 배분하기 위해 Comprehensive 배분방법을 제시한다. Comprehensive 배분방법은 시스템의 신뢰도를 배분하기 위해 각 모듈에 대한 고장의 중요도, 작동시간 비율, 위험도, 복잡도, 고장률, 수리/정비성, 개발완성도, 사용환경 가혹도, 신뢰도 달성비용의 평가항목을 고려한다. 승강문 시스템의 목표 신뢰도를 만족하기 위해서 시스템을 구성하는 4 가지 모듈의 $B_{10}$ 수명을 제시한다.

• 콘크리트학회지
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• 제8권3호
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• pp.209-218
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• 1996

프리캐스트 프리스트레스트 콘크리트 구조물의 정착부에 프리스트레스트 힘이 도입되면, 과다한 국부 집중 하중으로 인하여 균열이 발생할 수 있으며, 최근 이러한 구조물 건설시 텐던을 따라가며 심각한 균열이 발생한 경우가 있다. 본 논문은 프리캐스트 프리스트레스트 콘크리트 구조물의 정착부에 발생하는 국부집중응력의 분포 특성을 규명하고, 정착부 보강 형태에 따른 국부응력 효과를 규명하여 합리적인 정착부 설계 개념을 제시함에 목적이 있다. 이를 위하여 정착부 형태에 따른 역학적 거동 실험 및 해석연구가 수행되었다. 위의 연구 결과 나선형 보강철근이 극한 및 균열하중에 대한 저항능력이 가장 우수함이 집중응력 분포 특성을 고찰함으로서 나타났으며, 정착부의 파괴기구, 정착부 보강설계를 위한 기본 개념 및 그 방법이 제시되었다.

• 한국임상약학회지
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• 제24권2호
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• pp.115-125
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• 2014

Purpose: The purpose of the present study was to assess the incidence of the potentially inappropriate medication (PIM) use in Korean elderly patients with heart failure, and to evaluate factors that influence PIM use. Method: Korean National Health Insurance claims database between January 2009 and December 2009 was used. Using 2012 updated Beers criteria, PIM use in heart failure patients aged 65 years or older was examined. Result: The incidence of PIM use in elderly heart failure patients was higher than in overall elderly patients. Among the 12,759 elderly patients with heart failure, 46.2% of study subjects were prescribed PIM(s) at least once. The number of PIM per 10 medications that patients received per patient was 1.53. The most commonly used PIMs in elderly heart failure patients were benzodiazepines (30.9%), non-steroidal anti-inflammatory drugs (NSAIDs) including COX-2 inhibitors (16.3%), digoxin (9.9%), and spironolactone (9.0%). Women (odds ratio, 1.20; 95% CI, 1.17-1.24), medical aid (odds ratio, 1.11; 95% CI, 1.08-1.13), and long-term facilities (odds ratio, 2.69; 95% CI, 2.44-2.96) were revealed to be important factors associated with PIM use. In addition, patient's age also seems to influence PIM use. Conclusion: Elderly heart failure patients are at a greater risk for adverse drug events attributed by inappropriate medication use. Efforts to increase awareness of PIM use in elderly heart failure patients are needed. In addition, various comprehensive strategies and policies to identify and prevent PIM use should be established nationwide.

• Geomechanics and Engineering
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• 제15권1호
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• pp.621-630
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• 2018

In the note a comprehensive and optimal passive-active mode for describing the limit failure of circular shallow tunnel with settlement is put forward to predict the catastrophic stability during the geotechnical construction. Since the surrounding soil mass around tunnel roof is not homogeneous, with tools of variation calculus, several different curve functions which depict several failure shapes in different soil layers are obtained using virtual work formulae. By making reference to the simple-form of Power-law failure criteria based on numerous experiments, a numerical procedure with consideration of combination of upper bound theorem and stochastic medium theory is applied to the optimal analysis of shallow-buried tunnel failure. With help of functional catastrophe theory, this work presented a more accurate and optimal failure profile compared with previous work. Lastly the note discusses different effects of parameters in new yield rule and soil mechanical coefficients on failure mechanisms. The scope of failure block becomes smaller with increase of the parameter A and the range of failure soil mass tends to decrease with decrease of unit weight of the soil and tunnel radius, which verifies the geomechanics and practical case in engineering.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제23권6호
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• pp.501-510
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• 2020

Purpose: To develop a probability-based differential diagnosis for pediatric acute liver failure (PALF) based on age and socioeconomic status of the country of origin. Methods: Comprehensive literature search using PubMed, EMBASE, and SCOPUS databases was performed. Children 0-22 years of age who met PALF registry criteria were included. Articles included >10 children, and could not be a case report, review article, or editorial. No language filter was utilized, but an English abstract was required. Etiology of PALF, age of child, and country of origin was extracted from included articles. Results: 32 full text articles were reviewed in detail; 2,982 children were included. The top diagnosis of PALF in developed countries was acetaminophen toxicity (9.24%; 95% CredI 7.99-10.6), whereas in developing countries it was Hepatitis A (28.9%; 95% CredI 26.3-31.7). In developed countries, the leading diagnosis of PALF in children aged <1 year was metabolic disorder (17.2%; 95% CredI 10.3-25.5), whereas in developing countries it was unspecified infection (39.3%; CredI 27.6-51.8). In developed countries, the leading diagnosis in children aged >1 year was Non-A-B-C Hepatitis (8.18%; CredI 5.28-11.7), whereas in developing countries it was Hepatitis A (32.4%; CredI 28.6-36.3). Conclusion: The leading causes of PALF in children aged 0-22 years differ depending on the age and developmental status of their country of origin, suggesting that these factors must be considered in the evaluation of children with PALF.

• Journal of Welding and Joining
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• 제32권1호
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• pp.79-86
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• 2014

The purpose of this study is to determine the proper fillet weld size for the stiffeners on hull bottom plate of crude oil tanker. To achieve it, the effective notch stress and hot spot stress of the fillet weld with leg length specified in the rule were evaluated by using comprehensive FE analyses. Based on the results, the fatigue damages at each location of weld were calculated. Meanwhile the transitional behavior of initial welding distortion in the hull bottom plate under the design conditions was investigated by using a non-linear FEA. Welding distortion and residual stress introduced during fabrication process were considered as initial imperfections. According to FE analysis results, if the fillet leg length satisfies the design criteria of the classification society, the concern on the root failure at the fillet welds in the bottom hull plate during the design life can be negligible. In addition, considering the transitional behavior of the distortion during the service life, the fillet leg length should be minimized.

• The Journal of Advanced Prosthodontics
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• 제14권3호
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• pp.182-202
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• 2022

PURPOSE. The aim of this study is to summarize various biomechanical aspects in evaluating the long-term stability of dental implants based on finite element method (FEM). MATERIALS AND METHODS. A comprehensive search was performed among published studies over the last 20 years in three databases; PubMed, Scopus, and Google Scholar. The studies are arranged in a comparative table based on their publication date. Also, the variety of modeling is shown in the form of graphs and tables. Various aspects of the studies conducted were discussed here. RESULTS. By reviewing the titles and abstracts, 9 main categories were extracted and discussed as follows: implant materials, the focus of the study on bone or implant as well as the interface area, type of loading, element shape, parts of the model, boundary conditions, failure criteria, statistical analysis, and experimental tests performed to validate the results. It was found that most of the studied articles contain a model of the jaw bone (cortical and cancellous bone). The material properties were generally derived from the literature. Approximately 43% of the studies attempted to examine the implant and surrounding bone simultaneously. Almost 42% of the studies performed experimental tests to validate the modeling. CONCLUSION. Based on the results of the studies reviewed, there is no "optimal" design guideline, but more reliable design of implant is possible. This review study can be a starting point for more detailed investigations of dental implant longevity.

• Structural Engineering and Mechanics
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• 제58권5호
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• pp.757-781
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• 2016

The results of diagnostics and analysis of an industrial hall located on the premises of a thermal power plant severely damaged by fire are presented in the paper. The comprehensive failure-related diagnostics, non-destructive and destructive tests of steel and concrete materials, geodetic surveying of selected structural members, numerical modelling, static analysis and reliability assessment were focused on two basic goals: The determination of the current technical condition of the load bearing structure and the assessment of its post fire resistance as well as assessing the degree of damage and subsequent design of reconstruction measures and arrangements which would enable the safe and reliable use of the building. The current mechanical properties of the steel material obtained from the tests and measured geometric characteristics of the structural members with imperfections were employed in finite element models to study the post-fire behaviour of the structure. In order to compare the behaviour of the numerically modelled steel roof truss, subjected to the effects of fire, with the real post-fire response of the damaged structure theoretically obtained resistance, critical temperature and the time at which the structure no longer meets the required reliability criteria under its given loading are compared with real values. A very good agreement between the simulated results and real characteristics of the structure after the fire was observed.

• 수산해양교육연구
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• 제28권4호
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• pp.893-902
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• 2016

The purpose of this study is to investigate the effect of wearing a weightlifting belt, which is an auxiliary equipment used during squat, by measuring and analyzing biomechanical difference in lower limb and proposing safer and to suggest a more effective exercise method for general population. Selected 8 male participants in their 20s who have not performed regular resistance exercise for at least a year, but have experience of performing squat. The comprehensive method of study is as follows: subjects were notified of the purpose of the study and were told to practice warm-up and the squat motion for the experiment for 20 minutes. When the participant believed they were ready to begin, the experiment was started. At controlled points, foot pressure distribution sensor has been installed. Then left and right feet have been placed on the pressure distribution sensor, from which data for successful squat position that does not satisfy the criteria for failure have been collected and computed with Kwon3D XP program and TPScan program. For data processing of this study, SPSS 21.0 was used to calculated mean (M) and standard deviation (SD) of the analyzed values, and paired t-test has been conducted to investigate the difference before and after wearing the weightlifting belt, with p-value of ${\alpha}<.05$. As for time consumed depending on usage of weightlifting belt in squat, statistically significant difference has been found in P2, which is recovery movement. Lower limb angle depending on usage of weightlifting belt in squat has shown statistically significant difference in E1 foot joint(p<. 001). There has been statistically significant difference in E2 knee joint. Foot pressure percentage depending on usage of weightlifting belt in squat were found to be statistically significant (p<. 01) in both regions of anterior and posterior foot.