• Geomechanics and Engineering
• /
• 제16권2호
• /
• pp.195-204
• /
• 2018

Based on theories of rock mechanics, rock fragmentation, mechanics of elasto-plasticity, and energy dissipation etc., a method is presented for evaluating the rock fragmentation efficiency by using plastic energy dissipation ratio as an index. Using the presented method, the fragmentation efficiency of rocks with different strengths (corresponding to soft, intermediately hard and hard ones) under indentation is analyzed and compared. The theoretical and numerical simulation analyses are then combined with experimental results to systematically reveal the fragmentation mechanism of rocks under indentation of indenter. The results indicate that the fragmentation efficiency of rocks is higher when the plastic energy dissipation ratio is lower, and hence the drilling efficiency is higher. For the rocks with higher hardness and brittleness, the plastic energy dissipation ratio of the rocks at crush is lower. For rocks with lower hardness and brittleness (such as sandstone), most of the work done by the indenter to the rocks is transferred to the elastic and plastic energy of the rocks. However, most of such work is transferred to the elastic energy when the hardness and the brittleness of the rocks are higher. The plastic deformation is small and little energy is dissipated for brittle crush, and the elastic energy is mainly transferred to the kinetic energy of the rock fragment. The plastic energy ratio is proved to produce more accurate assessment on the fragmentation efficiency of rocks, and the presented method can provide a theoretical basis for the optimization of drill bit and selection of well drilling as well as for the selection of the rock fragmentation ways.

• 대한기계학회논문집A
• /
• 제39권6호
• /
• pp.625-629
• /
• 2015

본 연구에서는 수냉식 발전기 고정자 권선의 건전성 예지 방법에 대해 연구하였다. 권선의 데이터를 흡습 데이터와 정상 데이터로 분류 하였으며 각각의 데이터 군을 다른 방법으로 예측 하였다. 흡습 데이터를 예측하기 위해 픽의 제 2 법칙(Fick's second law)를 이용하여 건전성 감소 모델링을 하였고 픽의 제 2법칙의 해를 이용하여 흡습 모델식을 만들었다. 정상 데이터는 데이터의 분포가 정규분포를 따른다는 가설을 세운 후 카이제곱 검정을 통해 이를 입증하였다. 예측된 흡습 데이터와 정상 데이터를 이용하여 건전성 인자인 방향성 마할라노비스 거리(Directional mahalanobis distance; DMD)의 예측값을 산출하였고 흡습 권선의 고장 예상시점을 계산했다.

• Nutrition Research and Practice
• /
• 제8권1호
• /
• pp.94-102
• /
• 2014

Diet attrition and failure of long term treatment are very frequent in obese patients. This study aimed to identify pre-treatment variables determining dropout and to customise the characteristics of those most likely to abandon the program before treatment, thus making it possible to modify the therapy to increase compliance. A total of 146 outpatients were consecutively enrolled; 73 patients followed a prescriptive diet while 73 followed a novel brief group Cognitive Behavioural Treatment (CBT) in addition to prescriptive diet. The two interventions lasted for six months. Anthropometric, demographic, psychological parameters and feeding behaviour were assessed, the last two with the Italian instrument VCAO Ansisa; than, a semi-structured interview was performed on motivation to lose weight. To identify the baseline dropout risk factors among these parameters, univariate and multivariate logistic models were used. Comparison of the results in the two different treatments showed a higher attrition rate in CBT group, despite no statistically significant difference between the two treatment arms (P = 0.127). Dropout patients did not differ significantly from those who did not dropout with regards to sex, age, Body Mass Index (BMI), history of cycling, education, work and marriage. Regardless of weight loss, the most important factor that determines the dropout appears to be a high level of stress revealed by General Health Questionnaire-28 items (GHQ-28) score within VCAO test. The identification of hindering factors during the assessment is fundamental to reduce the dropout risk. For subjects at risk, it would be useful to dedicate a stress management program before beginning a dietary restriction.

• Journal of Korean Neurosurgical Society
• /
• 제54권2호
• /
• pp.128-131
• /
• 2013

Transforaminal lumbar interbody fusion (TLIF) is commonly used procedure for spinal fusion. However, there are no reports describing anterior cage dislodgement after surgery. This report is a rare case of anterior dislodgement of fusion cage after TLIF for the treatment of isthmic spondylolisthesis with lumbosacral transitional vertebra (LSTV). A 51-year-old man underwent TLIF at L4-5 with posterior instrumentation for the treatment of grade 1 isthmic spondylolisthesis with LSTV. At 7 weeks postoperatively, imaging studies demonstrated that banana-shaped cage migrated anteriorly and anterolisthesis recurred at the index level with pseudoarthrosis. The cage was removed and exchanged by new cage through anterior approach, and screws were replaced with larger size ones and cement augmentation was added. At postoperative 2 days of revision surgery, computed tomography (CT) showed fracture on lateral pedicle and body wall of L5 vertebra. He underwent surgery again for paraspinal decompression at L4-5 and extension of instrumentation to S1 vertebra. His back and leg pains improved significantly after final revision surgery and symptom relief was maintained during follow-up period. At 6 months follow-up, CT images showed solid fusion at L4-5 level. Careful cage selection for TLIF must be done for treatment of spondylolisthesis accompanied with deformed LSTV, especially when reduction will be attempted. Banana-shaped cage should be positioned anteriorly, but anterior dislodgement of cage and reduction failure may occur in case of a highly unstable spine. Revision surgery for the treatment of an anteriorly dislodged cage may be effectively performed using an anterior approach.

• 한국건축시공학회지
• /
• 제17권5호
• /
• pp.403-409
• /
• 2017

본 연구에서는 다공성 블록의 내구성 향상을 위해 압축강도 3MPa 및 공극률 30%를 만족하는 배합설계를 확인하였으며, 선정된 배합에서 GFRP 보강 방법에 따른 보의 내력 및 인성 증가를 평가하였다. 다공성 콘크리트의 목표성능 만족을 위해서는 골재입도 15~20mm에서 물-시멘트 비 및 시멘트-골재 비가 각각 25% 및 15%로 추천될 수 있었다. GFRP로 보강된 다공성 콘크리트 보의 거동은 전단파괴에 의해 지배되었다. 이에 따라 GFRP의 휨 저항 발휘는 매우 적었으며, GFRP 보강근의 장부작용에 의한 전단내력상승은 결과적으로 다공성 콘크리트 보의 하중 저항성과 인성을 향상시켰다. GFRP 보강근을 압축과 인장측에 각각 1본(D9)씩 배근한 경우 내력은 무보강 보에 비해 약 2.1배 증가하였으며, 인성지수 $I_{30}$값은 43.4를 보임으로서 인성지수 값을 측정할 수 없었던 무보강 보에 비해 상당히 향상되었다.

• Composites Research
• /
• 제31권1호
• /
• pp.37-41
• /
• 2018

본 연구에서는 IIHS기준 범퍼 충돌해석을 통하여, 구간 조합 복합 범퍼 빔의 특성 분석하였다. 충돌 시 범퍼 빔의 5개 영역에서 지배적인 하중 유형에 대한 정보를 얻기 위해 Al 범퍼 빔에 대한 IIHS 범퍼 충돌 해석이 진행되었다. 또한, 항공우주 분야에서 빈번히 사용되는 5가지 적층순서 중, 인장 및 압축하중에 가장 효과적인 적층순서가 복합재료 쿠폰 해석을 통해 결정되었다. 이와 더불어, 결정된 두가지 복합재료의 적층순서를 적용한 복합재료 빔에 대해 3점 굽힘 해석이 수행되었다. 마지막으로, IIHS 범퍼 충돌 해석을 진행하여 구간 조합으로 이루어진 복합재료 범퍼 빔을 다른 유형의 복합 범퍼 빔과 비교하였다. 제안된 구간조합 복합재료 범퍼 빔은 단일 적층순서로 이루어진 복합재료 범퍼 빔에 비해 우수한 충돌 특성을 나타내었다.

• 보건행정학회지
• /
• 제30권1호
• /
• pp.37-49
• /
• 2020

Background: Unmet healthcare needs have many advantages for measuring inequalities in healthcare use. However, the existing indicator is difficult to capture the reality of unmet healthcare needs sufficiently and is not quite appropriate in comparing regional inequality. The purpose of this study is to critically analyze the utilization of the unmet healthcare need indicator for regional healthcare inequalities research. Methods: We used the level of healthcare accessibility and healthcare need to categorize the regions that are known to cause differences in healthcare utilization between regions and verified how existing unmet healthcare need indicator is distributed at the regional level. Results: Four types of regions were classified according to the high and low levels of healthcare needs and accessibility. The hypothesis about the regional type expected to have the highest unmet healthcare need was not proved. The hypothesis about the lowest expected regional type was proved, but the difference in the average rate of unmet healthcare needs among regional types was not significant. The standard deviation of the rate of unmet healthcare needs among regions within the same type was also higher than the overall regional variation, which also disproved the whole frame of hypothesis. Conclusion: Failure to prove the hypothesis means the gap between the supposed meaning of the indicator and the reality. In order to understand the current state of healthcare utilization of people in various regions of Korea and to resolve inequality, fundamental research on the in-depth structure and mechanisms of healthcare utilization is needed.

• 지질공학
• /
• 제17권3호
• /
• pp.339-350
• /
• 2007

암반에 발달하고 있는 단층이나 절리와 같은 불연속면뿐만 아니라 점토의 함량비, 팽창성 점토물질의 협재, 배수특성(drainage) 등은 암반의 붕괴여부를 결정하는 중요한 인자들이다. 특히 점토광물의 성분은 강우에 의한 암반붕괴를 예측할 수 있는 중요한 지표가 될 수 있다. 최근 사면이나 터널의 설계에서도 그 중요성이 점차 증가하는 추세이다. 본 연구는 니질천매암과 사질천매암이 호층을 이루고 있는 OO 터널의 선진시추코어(horizontal boring core)를 이용하여 단층발달에 따른 광물성분의 변화 및 이들이 불연속면의 역학성에 미치는 영향을 파악하고, 암석 구성물질과 파생된 점토광물을 비교하여 암반의 불안정성을 추정하기 위해 수행되었다. 연구방법은 시추코어 중에서 단층의 영향을 받은 구간과 비교적 신선한 구간에서 시료를 채취하여 박편을 제작하여 관찰하였고, 점토광물의 성분 및 함량을 분석하였다. 그리고 야외조사와 실내 시험으로 단층물질의 강도정수를 구하였다.

• 한국지반공학회논문집
• /
• 제18권3호
• /
• pp.95-104
• /
• 2002

본 연구에서는 앵커 널말뚝의 설계값 결정과정에 신뢰성이론을 적용한 설계방법을 제안하였다. 본 설계과정에서 먼저 말뚝의 근입깊이는 공학적으로 널리 사용되는 확률론적 수치계산방법에 따라 근입된 지반조건의 불확실성의 정도에 따라 결정되도록 하였다. 여기서 적용되는 확률론적 수치계산방법은 복잡한 계산과정이 필요하다거나 정확한 계산을 위해서는 지반강도 정수들에 대한 광범위한 통계적 분석이 별도로 필요하다든가 하는 번거로움없이 설계자가 간편하게 사용할 수 있다. 본 연구에서 제안된 설계법의 결과들은 일반적으로 널리 이용되는 다른 결정론적 설재법에 의한 결과들과 호응하는 것으로 나타났다. 본 연구에서는 아울러 널말뚝의 주요 설계입력변수들의 불확실성에 따른 설계결과의 영향을 분석하기 위한 민감도 조사가 실시되었다.

• Clinics in Shoulder and Elbow
• /
• 제23권2호
• /
• pp.62-70
• /
• 2020

Background: Recent studies have reported high rates of recurrence of shoulder instability in patients with glenoid bone defects greater than 20% after capsulolabral reconstruction. The purpose of the present study was to evaluate the failure rate of arthroscopic capsulolabral reconstruction for the treatment of anterior instability in the presence of glenoid bone deficits >20%. Methods: Retrospective analyses were conducted among cases with anterior shoulder instability and glenoid bone defects of >20% that were treated by arthroscopic capsulolabral reconstruction with a minimum 2-year follow-up (30 cases). We included the following variables: age, bone defect size, instability severity index score (ISIS), on-/off-track assessment, incidence recurrent instability, and return to sports. Results: The mean glenoid bone defect size was 25.8%±4.2% (range, 20.4%-37.2%), and 18 cases (60%) had defects of >25%. Bony Bankart lesions were identified in 11 cases (36.7%). Eleven cases (36.7%) had ISIS scores >6 points and 21 cases (70%) had off-track lesions. No cases of recurrent instability were identified over a mean follow-up of 39.9 months (range, 24-86 months), but a sense of subluxation was reported by three patients. Return to sports at the preinjury level was possible in 24 cases (80%), and the average satisfaction rating was 92%. Conclusions: Arthroscopic soft tissue reconstruction was successful for treating anterior shoulder instability among patients with glenoid bone defects >20%, even enabling return to sports. Future studies should focus on determining the range of bone defect sizes that can be successfully managed by soft tissue repair.