• Steel and Composite Structures
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• 제50권5호
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• pp.499-513
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• 2024

This paper describes the experimental and numerical investigations of octagonal Concrete-Filled Double Skinned Steel Tube (CFDST) short columns under the influence of various internal sizes of the circular and square steel tubes, with constant cross-sectional dimensions of the external octagonal steel tube under concentric loading. The non-linear finite element analysis of octagonal CFDST columns was executed using the ABAQUS to forecast and compare the axial compression behavior influenced by the various sizes of internal circular and square steel tubes. The study shows that the axial compressive strength and ductility of octagonal CFDST columns were significantly influenced by various internal dimensions of the circular and square steel tubes with the strengths of constituent materials.

• 한국도로학회논문집
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• 제16권2호
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• pp.53-59
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• 2014

PURPOSES : This study estimated an asphalt pavement internal behavior under uphill lanes considering reducing speed of heavy truck on uphill slope. METHODS : Truck performance curve which has been adapted to "Korea Highway Capacity Manual" was analyzed. And asphalt pavement internal behaviors were estimated with Multi-layered elastic analysis using KPRP(Korea Pavement Research Program) dynamic modulus prediction equations. RESULTS : As a result, it is shown that when the standard truck drives 2.0 km at a speed of 80 km/h in 8% climbing slope, it's speed reduced to 25.4 km/h, at same time frequency in asphalt layer decrease to 67.2% and it's dynamic modulus degrades to 30.9%. Based on these results, internal behavior as decreasing vehicle speed on uphill lanes were estimated. CONCLUSIONS : From the results of Multi-layered elastic analysis, internal behavior showed that when the standard truck drives 2.0 km at a speed of 80 km/h in 8% slope on uphill lanes, vertical strain was increased to 44.4% at the bottom of surface course, and lateral tensile strain was increased to 20.5% at the bottom of base course.

• 대한치과보철학회지
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• 제56권2호
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• pp.114-119
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• 2018

목적: 원광대학교 치과대학병원 임플란트 센터에서 임플란트를 식립한 후 1주일 내에 임시보철물을 수복한 다음, 즉시 하중을 가한 환자들을 대상으로 골 흡수량을 측정하고자 하였다. 이러한 후향적 분석을 통하여 임플란트에 대한 즉시 하중의 임상적 근거를 보강하고 주의해야 할 사항 등을 파악하고자 하였다. 대상 및 방법: 2005년 1월 1일부터 2016년 6월 31일 사이에 원광대학교 치과대학병원 임플란트 센터에서 임플란트를 식립한 후 1주일 내에 임시보철물을 수복한 환자들을 대상으로 하여 진료기록부와 방사선 사진을 조사하였다. 총 임플란트의 수는 70개였으며, 임플란트의 제조회사, 길이, 직경, 체결 방식에 따른 변연골의 흡수량을 측정하였다. 변연골의 흡수량을 측정하기 위해 임플란트 식립 직후와 6개월 이후의 치근단 방사선 사진을 비교 분석하였다. 통계 프로그램인 SPSS 22.0을 이용하여 Mann-whitney U test와 Kruskal-wallis test를 시행하였다. 결과: 즉시 하중 임플란트 군에서 임플란트와 지대주의 연결 구조에 따른 변연골 흡수량을 비교한 결과 내부 육각 연결 구조 임플란트에서의 변연골 흡수량은 평균 $1.24{\pm}0.72mm$, 외부 육각 연결 구조 임플란트에서 $1.73{\pm}1.27mm$로 나타났으며 통계적으로 유의한 차이를 보였다. 임플란트 제조회사, 길이, 직경에 따른 변연골 흡수량의 차이는 통계적으로 유의한 차이를 보이지 않았다. 결론: 즉시 하중 임플란트에서 내부 육각 연결 구조 임플란트에서의 변연골 흡수량은 외부 육각 연결 구조 임플란트에서의 변연골 흡수량보다 적게 나타났으며, 임플란트의 다른 조건들에서는 변연골 흡수량에 차이를 보이지 않았다.

• Composites Research
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• 제26권1호
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• pp.1-6
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• 2013

용액 분산법을 이용하여 CNT를 균질하게 분산시켰고, CNT-폴리프로필렌 복합재료 제조를 위해 압출기와 사출기를 사용하였다. CNT 고유의 전도성을 기반으로 CNT-PP 복합재료의 내부 손상을 감지하기 위해 전기저항 측정법을 이용하였다. CNT-PP의 기계적 및 계면 물성을 확인하고 일반 PP와 비교하였다. CNT의 강화 효과로 인하여 CNT를 함유함으로서, PP 기지의 기계적 물성은 더 증가되는 경향을 확인하였다. CNT-PP 복합재료의 내부 손상을 평가하기 위해 파괴 및 굴곡실험을 진행하며, 동시에 발생되는 전기저항 변화도를 감지하여 미세손상을 평가하였다. CNT 강화제의 첨가는 좋은감지능을 보여주었다. 낮은 CNT 함유율임에도 CNT-PP 복합재료의 감지가 가능했으며, 반복 하중 실험 중 최대 임계 응력을 확인하여, 내부에 발생된 미세 파괴를 찾아 낼 수 있었다.

• 대한핵의학회지
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• 제13권1_2호
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• pp.37-43
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• 1979

This is an analysis of 39 patients studied at the Yonsei Medical Center from January, 1976 to March 1979. Of these35 patient were suspected of having hypothalamic insufficiency and subjected to the L-Dopa stimulation test to observe growth hormone sceretory function while four acromegaly patient received the glucose loading test and L-Dopa stimulation test. The results are as follows: 1. The basal level of GH in the various disease was as follows: a. The basal level was lower than the control level but was not statistically significant b. In diabetes the mean value tended to be higher than the control level but was not significant statistically c. In all four acromegaly patients the GH level was significantly higher than the control level 2. Of 13 patients with diabetes, nine had diabetic retinopathy, and of those nine, sir showed increased L-Dopa response. However, of the four non retinopathic DM patients, only one showed increased response to L-Dopa. 3. Two patients out of ten with Sheehan's syndrome responded to L-Dopa stimulation. 4. One Patient of eight with pituitary chromophobe adenoma responded to L-Dopa stimulation. 5. Four acromegaly patients revealed 3 acidophilic adenoma and one chromophobe adenoma histologically. Of patients receiving the L-Dopa stimulation test. Two showed a paradoxical response. Two patients who received the glucose loading test showed supressed response. 6. Of two craniopharyngioma patients, one showed increased GH response after L-Dopa stimulation. Increased response of GH after L-Dopa stimulation was seen in one of two craniopharyngioma patients and also in one of two patients with

• 대한치과보철학회지
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• 제41권4호
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• pp.393-404
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• 2003

Statement of problem. Higher incidence of prosthetic complications such as screw loosening, screw fracture has been reported for posterior single tooth implant. So, there is ongoing research regarding stability of implant-abutment interface. One of those research is increasing the implant diameter and prosthetic table width to improve joint stability. In another part of this research, internal conical type implant-abutment interface was developed and reported joint strength is higher than traditional external hex interface. Purpose. The purpose of this study is to compare stress distribution in single molar implant between external hex butt joint implant and internal conical joint implant when increasing the implant diameter and prosthetic table width : 4mm diameter, 5mm diameter, 5mm diameter/6mm prosthetic table width. Material and method. Non-linear finite element models were created and the 3-dimensional finite element analysis was performed to see the distribution of stress when 300N static loading was applied to model at $0^{\circ},\;15^{\circ},\;30^{\circ}$ off-axis angle. Results. The following results were obtained : 1. Internal conical joint showed lower tensile stress value than that of external hex butt joint. 2. When off-axis loading was applied, internal conical joint showed more effective stress distribution than external hex butt joint. 3. External hex butt joint showed lower tensile stress value when the implant diameter was increased. 4. Internal conical joint showed lower tensile stress value than external hex butt joint when the implant diameter was increased. 5. Both of these joint mechanism showed lower tensile stress value when the prosthetic table width was increased. Conclusion. Internal conical joint showed more effective stress distribution than external hex joint. Increasing implant diameter showed more effective stress distribution than increasing prosthetic table width.

• 한국해안해양공학회지
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• 제7권1호
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• pp.75-90
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• 1995

본 연구에서는 riser 내부의 유체흐름에 의해 발생하는 유체력이 심해저 riser의 동특성에 미치는 영향에 관해 조사하였다. riser의 비선형 동적해석을 위해 riser 내부의 유체흐름을 시스템에 포함하여 수학적 모델을 개발하였으며 유도된 모델에 Galerkin의 유한요소근사법과 시간증분자를 적용함으로써 수치해석을 위한 모델을 개발하였다. 또한 시스템의 자유도를 줄이고 비선형모델의 수치해를 얻기 위해 행해지는 반복계산을 줄이며 정확도를 높이기 위해 riser의 축방향 extensibility 조건을 사용 하였다. 관내부 유체 흐름으로 인한 riser의 동특성에 미치는 영향을 상부 인장력, 조류속도, 파주기 등과 같은 여러 영향요인들을 변화시키면서 조사하였다. 수치해석 결과 내부류체 흐름으로 인한 영향을 줄이기 위해서는 riser의 상부에 인장력을 riser의 허용내력 한도내에서 증가시키는 방법이 있으나 심해저로 갈수록 인장력 증가에 한계가 있기 때문에 riser 주위에 부체를 부착시키는 방법이 제시된다. 이 이외에도 riser의 해석시 대변형으로 인한 비선형성을 고려하게 되면 내부 유체흐름이 riser의 동특성에 미치는 영향을 증가시킴을 알 수 있었다.

• 대한치과의사협회지
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• 제53권11호
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• pp.804-816
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• 2015

PURPOSE: The aim of this study was to evaluate the influence of the oxide layer removal process in the Co-Cr-Mo (CCM) abutment after casting procedure on the prosthesis settlement and screw stability. MATERIALS AND METHODS: CCM abutments of four different interface conditions (CCM-M; machined, CCM-O; oxide layer formed, CCM-B; blasted, CCM-P; polished after blasted) and gold abutment (Gold-C; Cast with type III Gold alloy) were used. The initial settling values of abutments were evaluated according to the difference of implant-abutment length when the tightening torques were applied at 5 Ncm and 30 Ncm, and the settling values of abutments caused by loading were evaluated according to the difference of implant-abutment length before and after loading with 250 N, 100000 cycle. The loss ratios of removal torque for abutment screws were evaluated according to the difference in value of removal torques under 30 Ncm tightening torque applied before and after cyclic loading. RESULTS: The CCM-P and CCM-B group showed a higher initial settling value compared with the Gold-C group (P<.05), while the Gold-C group showed the highest settling values caused by loading (P<.05) and no significant differences were observed for between CCM groups (P>.05). The loss ratio of removal torque values for the CCM-B, CCM-P groups did not differ significantly from that of the Gold-C group (P>.05). CONCLUSION: Even though the oxide layer was removed by different methods, CCM abutment with internal conical connection structure showed lower abutment settling and similar screw loosening after cyclic loading compared with gold abutment.

• 한국산학기술학회논문지
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• 제19권9호
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• pp.62-68
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• 2018

본 연구는 군 포병 전력의 핵심 장비인 자주포의 급속장전장치에 장착된 밀대 시스템 개선을 통해 탄의 장전 안정성향상을 목표로 하는 것이다. 종래의 자주포에는 수동 장전장치가 적용되어 있었다. 군에서 운용하는 장비의 현대화와 연속사격 속도 향상을 위해 급속 장전장치를 설치하였으며, 이러한 급속 장전장치를 통해 탄이 장전되는 과정에서 약실 내부와 간섭되는 현상을 줄이고, 비행시간을 감소하도록 설계되었다. 그러나 기본적으로 밀대를 통해 탄의 급속장전이 이루어지는 슈팅 방식의 장전시스템에서는 탄 흐름(fall-back) 현상이 간헐적으로 발생할 수 있다고 보고되고 있다. 그래서 이러한 문제를 해결하기 위해서 장전 과정의 실제 조건을 반영한 전산모사(C.A.E.)를 통해 탄이 장전되는 과정에서 비행 거리를 감소시키면 탄 흐름 현상을 방지할 수 있는 것을 이론적으로 확인 하였고, 탄의 비행거리를 줄이는 최적의 설계 방안을 도출하였다. 최종적으로 이러한 결과를 바탕으로 야전에 배치된 자주포에 장착하여 시험한 결과 개선효과가 있음을 확인하였다.

• The Journal of Advanced Prosthodontics
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• 제6권1호
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• pp.46-52
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• 2014

PURPOSE. The aim of this study was to evaluate the interface accuracy of computer-assisted designed and manufactured (CAD/CAM) titanium abutments and implant fixture compared to gold-cast UCLA abutments. MATERIALS AND METHODS. An external connection implant system (Mark III, n=10) and an internal connection implant system (Replace Select, n=10) were used, 5 of each group were connected to milled titanium abutment and the rest were connected to the gold-cast UCLA abutments. The implant fixture and abutment were tightened to torque of 35 Ncm using a digital torque gauge, and initial detorque values were measured 10 minutes after tightening. To mimic the mastication, a cyclic loading was applied at 14 Hz for one million cycles, with the stress amplitude range being within 0 N to 100 N. After the cyclic loading, detorque values were measured again. The fixture-abutment gaps were measured under a microscope and recorded with an accuracy of ${\pm}0.1{\mu}m$ at 50 points. RESULTS. Initial detorque values of milled abutment were significantly higher than those of cast abutment (P<.05). Detorque values after one million dynamic cyclic loadings were not significantly different (P>.05). After cyclic loading, detorque values of cast abutment increased, but those of milled abutment decreased (P<.05). There was no significant difference of gap dimension between the milled abutment group and the cast abutment group after cyclic loading. CONCLUSION. In conclusion, CAD/CAM milled titanium abutment can be fabricated with sufficient accuracy to permit screw joint stability between abutment and fixture comparable to that of the traditional gold cast UCLA abutment.