• 한국철도학회논문집
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• 제8권4호
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• pp.348-353
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• 2005

In designing the structures of railway rolling stocks, deterministic methods associated with the concept of a safety factor have been traditionally used. The deterministic approaches based on the mean values of applied loads and material properties have been used as safety verification for the design of rolling-stock car body structures. The uncertainties in the applied loading for the high speed train and the strength of new materials in the rolling stocks require the application of probabilistic approaches to ensure fatigue safety in the desired system. Pressure loadings acting on the car body when the train passes through tunnels show reflected pressure waves for high-speed trains and they may cause a fatigue failure in vehicle bodies. Use of new material technology as body structures also introduces uncertainties in the material strength. A probabilistic approach is more adaptable in designing reliable structures when the pressure waves from the tunnels pounds and new material technology is adopted. In this paper, it is proposed that a fatigue design and assessment method based on a reliability which deals with the loading variations on a railway vehicle due to the pressure reflected in tunnels and the strength variations of material. Equation for the fatigue reliability index has been formulated to calculate the reliability assessment of a vehicle body under fluctuating pressure loadings in a tunnel. Considered in this formulation are the pressure distribution characteristics, the fatigue strength distribution characteristics, and the concept of stress-transfer functions due to the pressure loading.

• 산경연구논집
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• 제10권3호
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• pp.25-33
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• 2019

Purpose - With the economic development in China, the lifestyle of Chinese customers has changed dramatically. Chinese customers are more likely to have coffee in a shop with the ability to make them happy than those with high quality coffee in a nice physical environment. Happiness becomes a critical driver of customers' intention to purchase a cup of coffee in a specific coffee shop again and again. As a result, happiness becomes an important factor for managers to make strategies for attracting customers. Although managers and scholars pay more attention to emphasize the importance of happiness in customers' consumption, little research has been conducted to investigate the relationship between happiness and coffee shop's continuous usage intention in the Chinese coffee industry. Research design, data, and methodology - A research model is made to explain the impact of happiness on customer's behavior. To understand the influence of happiness better, we consider two dimensions of happiness which are subjective well-being and psychological well-being. In order to confirm the relationships of the variables in the research model, the online survey is constructed in China. Customers who have experienced the services in a coffee shop are asked to do the questionnaire. With 453 reliable questionnaires, structural equation modeling is used to analyze the causal relationships of the coffee quality, physical environment, subjective well-being, psychological well-being, and continuous usage intention. Results - Results indicate that coffee quality and physical environment are not the direct factors that influence customers' continuous usage intention. However, good coffee quality and physical environment are the significant predictors of Chinese customers' happiness associated with subjective well-being and psychological well-being, which in turn affects customers' continuous usage intention. Conclusions - In this study, it is proposed that coffee quality and physical environment may be the key factors influencing customers' happiness. Happiness, including subjective well-being and psychological well-being matters in decision making process. More importantly, happiness increases the continuous usage intention when the coffee shop can serve customers with higher quality coffee at a good atmospheric place. Managers should consider happiness as an important factor in making marketing strategies to compete in this industry.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.3940-3955
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• 2023

A new method of numerical simulating prediction and decontamination effect evaluation for abrasive jet decontamination to radioactively contaminated metal is proposed. Based on the Computational Fluid Dynamics and Discrete Element Model (CFD-DEM) coupled simulation model, the motion patterns and distribution of abrasives can be predicted, and the decontamination effect can be evaluated by image processing and recognition technology. The impact of three key parameters (impact distance, inlet pressure, abrasive mass flow rate) on the decontamination effect is revealed. Moreover, here are experiments of reliability verification to decontamination effect and numerical simulation methods that has been conducted. The results show that: ⁶⁰Co and other homogeneous solid solution radioactive pollutants can be removed by abrasive jet, and the average removal rate of Co exceeds 80%. It is reliable for the proposed numerical simulation and evaluation method because of the well goodness of fit between predicted value and actual values: The predicted values and actual values of the abrasive distribution diameter are Ф57 and Ф55; the total coverage rate is 26.42% and 23.50%; the average impact velocity is 81.73 m/s and 78.00 m/s. Further analysis shows that the impact distance has a significant impact on the distribution of abrasive particles on the target surface, the coverage rate of the core area increases at first, and then decreases with the increase of the impact distance of the nozzle, which reach a maximum of 14.44% at 300 mm. It is recommended to set the impact distance around 300 mm, because at this time the core area coverage of the abrasive is the largest and the impact velocity is stable at the highest speed of 81.94 m/s. The impact of the nozzle inlet pressure on the decontamination effect mainly affects the impact kinetic energy of the abrasive and has little impact on the distribution. The greater the inlet pressure, the greater the impact kinetic energy, and the stronger the decontamination ability of the abrasive. But in return, the energy consumption is higher, too. For the decontamination of radioactively contaminated metals, it is recommended to set the inlet pressure of the nozzle at around 0.6 MPa. Because most of the Co elements can be removed under this pressure. Increasing the mass and flow of abrasives appropriately can enhance the decontamination effectiveness. The total mass of abrasives per unit decontamination area is suggested to be 50 g because the core area coverage rate of the abrasive is relatively large under this condition; and the nozzle wear extent is acceptable.

• Geomechanics and Engineering
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• 제13권4호
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• pp.621-640
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• 2017

The double-row long-short composite anti-sliding piles system is an effective way to control the landslides with high thrust. In this study, The double-row long-short composite anti-sliding piles with different load segment length (cantilever length) and different pile row spacing were studied by a series of physical tests, by which the influences of load segment length of rear-row piles as well as pile row spacing on the mechanical response of double-row long-short composite anti-sliding pile system were investigated. Based on the earth pressures in front of and behind the piles obtained during tests, then the maximum bending moments of the fore-row and the rear-row piles were calculated. By ensuring a equal maximum moments in the fore-row and the rear-row piles, the optimum lengths of the rear-row piles of double-row long-short composite system under different piles spacing were proposed. To investigate the validity of the reduced scale tests, the full-scale numerical models of the landside were finally conducted. By the comparisons between the numerical and the physical test results, it could be seen that the reduced scale tests conducted in this study are reliable. The results showed that the double-row long-short composite anti-sliding piles system is effective in the distribution of the landslide thrust to the rear-row and the fore-row piles.

• The Korean Journal of Pain
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• 제31권4호
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• pp.268-276
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• 2018

Background: Although a variety of instruments implement body maps for the precise identification of pain symptoms, no instrument has been validated for use in people with obesity. This study reports the adaptation and validation of body maps for musculoskeletal pain location in people with obesity. Methods: Nine key anatomical regions were highlighted based on the original images of the Nordic Musculoskeletal Questionnaire body maps. Adult silhouettes were generated from photographs of men and women with obesity. The body dimensions were adjusted to take into account the different body fat distribution patterns of people with obesity. The validity of the images was assessed by 12 experts. Subsequently, a data collection stage was performed with 58 patients with severe obesity from both sexes. The reproducibility of the images was tested by comparison with the original images. Results: The results of the validation pilot study indicated that the adapted images facilitated the location of musculoskeletal pain in men and women with obesity. The reproducibility of the original and adapted versions of the body maps indicated good agreement for pain over the last 12 months and 7 days (80% vs. 79.7%). Pain scores in the last 12 months indicated good and high sensitivity and specificity for all body areas (60.9% vs. 89.1%). Considering pain in the last 7 days, high sensitivity and specificity for all areas of the body (85.1% vs. 70.1%). Conclusions: The body maps developed in this study are reliable and valid to identify the location of pain in people with obesity.

• The Journal of Advanced Prosthodontics
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• 제7권1호
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• pp.51-55
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• 2015

PURPOSE. Bone density at implant placement site is a key factor to obtain the primary stability of the fixture, which, in turn, is a prognostic factor for osseointegration and long-term success of an implant supported rehabilitation. Recently, an implant motor with a bone density measurement probe has been introduced. The aim of the present study was to test the objectiveness of the bone densities registered by the implant motor regardless of the operator performing them. MATERIALS AND METHODS. A total of 3704 bone density measurements, performed by means of the implant motor, were registered by 39 operators at different implant sites during routine activity. Bone density measurements were grouped according to their distribution across the jaws. Specifically, four different areas were distinguished: a pre-antral (between teeth from first right maxillary premolar to first left maxillary premolar) and a sub-antral (more distally) zone in the maxilla, and an interforaminal (between and including teeth from first left mandibular premolar to first right mandibular premolar) and a retroforaminal (more distally) zone in the lower one. A statistical comparison was performed to check the inter-operators variability of the collected data. RESULTS. The device produced consistent and operator-independent bone density values at each tooth position, showing a reliable bone-density measurement. CONCLUSION. The implant motor demonstrated to be a helpful tool to properly plan implant placement and loading irrespective of the operator using it.

• 한국지리정보학회지
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• 제3권2호
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• pp.48-60
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• 2000

1:5,000 수치지형도를 GIS로 처리하여 해안단구가 모식적으로 분포하는 경북 경주시 감포읍 일대의 지형면 분포특색을 조사하고, 지형면을 추출하였다. 이 과정에서 해안단구 지형연구에 GIS tool의 유용성과 문제점을 검토하였다. 12 지점에서의 해안단구 종단면에 대하여 종단면분석을 행하여 한국 남부 해안에서는 보고된 바 없는 해발고도 100m 이상인 고고위면을 확인하였다. 또한, 실측으로 얻은 지형면 분포가능범위인 평균경사도 $1{\sim}5^{\circ}$를 해발고도 4~87m에 대입하여, 경사도분석으로 각 단구면의 면적비를 추출하여 해안단구 저위 I 면이 해안단구 연구의 기준면이 될 수 있음을 확인하였다. GIS를 이용함으로서 최소한의 노력으로 해안단구면의 분포가능지역을 탐색해 볼 수 있으나, 상세한 실제측량을 통해 각 지형면의 자료가 제공되어야 정확한 분석이 가능하다. 이 방법은 지형분석결과를 계량화하여 주므로 객관적인 분석의 기초를 제공한다. 또한 현지조사가 어려운 지역에 대한 자료를 획득할 수 있고, 지형면의 기복을 쉽게 파악할 수 있는 효용성이 있으나, 분석의 정확도를 제고하기 위해서는 보다 대축척화된 지형도와 수치지형도가 제공되어야 할 것이다.

• 지질공학
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• 제22권3호
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• pp.275-281
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• 2012

지반 내 열전도 현상은 지구온난화에 따른 지반거동 변화 예측, 극한지 기반시설 건설, 지열 냉난방 시스템의 부하 계산 등 다양한 건설 및 환경 분야에서 중요한 고려사항이다. 열전달 해석에서 가장 중요한 변수인 열전도계수를 산정하는 방법으로 이를 정량적으로 정확하게 예측, 평가할 수 있는 기법의 필요성이 제기되고 있다. 최근 들어서는 세립토를 대상으로 열전도계수에 관한 연구가 활발하게 진행되고 있다. 그러나 기존 연구자들은 세립토의 열전도계수를 정확히 측정하는데 어려움으로 인해 신뢰성 있는 데이터가 부족하다는 문제점들이 제기되고 있다. 본 연구에서는 포화된 카올리나이트와 실리카 혼합점성토를 대상으로 건조밀도 변화에 따른 열전도계수 측정 실내실험을 수행하였다. 표준압밀시험의 단점을 보완한 일정변형율 압밀시험 자동화 장비를 이용하여 건조밀도의 변화에 따른 열전도계수를 연속적으로 측정하고 실내실험 결과의 신뢰성을 분석하였다. 또한, 기존 경험식과의 비교를 통해 최적의 세립토 열전도계수 예측 방법을 제시하고자 한다.

• Journal of Chest Surgery
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• 제32권5호
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• pp.442-447
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• 1999

서론: 성장기에서 기관의 성장양상에 관한 이해는 수많은 기관질병의 관리나 선천성 기관협착증에서 기관 성형술 등에서 매우 중요한 지표가 된다. 그러나 이에 관한 국내의 연구례가 거의없는 실정이다. 본 연구는 한국인 소아에서 기관의 내경과 단면적을 후향적으로 분석하여 기관질환의 치료에 기초자료를 제공하고자 한다. 대상 및 방법: 1996년 5월부터 1998년 8월까지 흉부전산화 단층촬영을 시행한 0세부터 20세까지 106명의 환자를 대상으로 하였는데 기관의 내경이나 단면적에 영향을 줄 수 있는 기관질환, 과거에 개흉술을 받은 경우, 종격동 종양, 폐쇄성 폐질환이 있는 경우는 본 연구에서 제외시켰다. 남자가 69명, 여자가 37명이었으며 기관의 종단내경과 횡단내경은 흉부유입부와 대동맥궁 부위에서 각각 측정하였다. 기관의 형태는 각 부위의 단면에서 원형, 타원형, 말발굽형으로 구분하였으며 단면적은 A = 1/4$\pi$ab (A: 단면적, $\pi$: 3.14, a: 종단내경, b: 횡단내경)의 공식으로 계산하여 각 부위의 내경과 연령 및 성별에 따른 단면적을 비교 분석하였다. 통계처리에서 p값이 0.05이하일 때 통계적 의미가 있는 것으로 간주하였다. 결과: 5세이하에서는 level I과 II 모두에서 기관의 형태가 원형을 이루고 있었으며 두 부위간의 단면적의 차이는 없었다. 성장함에 따라 level I의 형태는 타원형으로 변해가는 반면 level II에서는 그대로 원형을 유지하고 있었으며 level I의 단면적이 level II 보다 크다(p=0.020). 기관의 내경과 단면적은 성장함에 따라 직선관계로 증가한다는 것이 확인되었고(r>0.9), 5세이하의 소아에서는 여자가 남자보다 기관의 단면적이 크고 (p=0.020) 15세가 넘으면 반대로 남자가 더 크다 (p=0.002). 결론: 이상의 결과에서 흉부전산화 단층촬영은 기관의 내경과 단면적을 측정하는데 있어 안전하고 확실한 방법이며 성장기의 한국인에서 기관의 내경과 단면적에 대한 지표가 되고자 한다.

• 지질공학
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• 제32권2호
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• pp.221-239
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• 2022

플랜트, 토목 및 건축 사업에서 말뚝 설계 시 어려움을 겪는 주된 요인은 지반 특성의 불확실성이다. 특히 표준관입시험을 통해 구한 N치가 설계 시 주요 입력값이나 짧은 입찰기간과 광범위한 구역에서 다수의 현장시험을 실시하는 것은 실제적으로 어려운 상황이다. 본 연구에서는 인공지능(AI)을 가지고 회귀분석을 적용하여 N치를 예측하는 연구를 수행하였으며, 최소한의 시추자료를 학습시킨 후 표준관입시험을 실시하지 못한 곳에서 N치를 예측하는데 그 목적이 있다. AI의 학습 성능을 높이기 위해서는 빅 데이터가 중요하며, 금회 연구 시 부족한 시추자료를 빅 데이터화 하는데 '원형증강법'을 적용하여 시추반경 2 m까지 가상 N치를 생성시키는 작업을 선행하였다. AI 모델 중 인공신경망, 의사결정 나무, 오토 머신러닝을 각각 적용하였으며 이 중 최적의 모델을 선택하였다. 최적의 모델을 선택하는 방법은 세 가지의 예측된 AI 모델 중 최소 오차값을 가지는 것이다. 이를 위해 폴란드, 인도네시아, 말레이시아에서 수행한 6개 프로젝트를 대상으로 표준관입시험의 실측N치와 AI의 예측N치를 비교하여 타당성 여부를 연구하였고, 연구 결과 AI 예측값에 대한 신뢰도가 높은 것으로 분석되었다. AI 예측값을 가지고 미시추 구간에서 지반특성을 파악 할 수 있었으며 3차원 N치 분포도를 사용하면 최적의 구조물 배치가 가능함을 확인하였다.