• 대한치과교정학회지
• /
• 제47권4호
• /
• pp.229-237
• /
• 2017

Objective: The aim of this study was to compare the initial stability as insertion and removal torque and the clinical applicability of novel orthodontic zirconia micro-implants made using a powder injection molding (PIM) technique with those parameters in conventional titanium micro-implants. Methods: Sixty zirconia and 60 titanium micro-implants of similar design (diameter, 1.6 mm; length, 8.0 mm) were inserted perpendicularly in solid polyurethane foam with varying densities of 20 pounds per cubic foot (pcf), 30 pcf, and 40 pcf. Primary stability was measured as maximum insertion torque (MIT) and maximum removal torque (MRT). To investigate clinical applicability, compressive and tensile forces were recorded at 0.01, 0.02, and 0.03 mm displacement of the implants at angles of $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$, and $40^{\circ}$. The biocompatibility of zirconia micro-implants was assessed via an experimental animal study. Results: There were no statistically significant differences between zirconia micro-implants and titanium alloy implants with regard to MIT, MRT, or the amount of movement in the angulated lateral displacement test. As angulation increased, the mean compressive and tensile forces required to displace both types of micro-implants increased substantially at all distances. The average bone-to-implant contact ratio of prototype zirconia micro-implants was $56.88{\pm}6.72%$. Conclusions: Zirconia micro-implants showed initial stability and clinical applicability for diverse orthodontic treatments comparable to that of titanium micro-implants under compressive and tensile forces.

• 구강회복응용과학지
• /
• 제19권4호
• /
• pp.291-296
• /
• 2003

The use of resonance frequency analysis (RFA) provides a possibility to clinically measure implant stability and osseointegration. The implant stability quotient (ISQ) value of RFA is well known that influenced by effective abutment length and stiffness of the implant in the surrounding tissues. Among these factors stiffness is not accurately defined histologically yet. And the purpose of this study was to find the histolgical relationship of RFA. 17 implants in 3 beagle dogs were used for this study. Among these implants 10 were survived for 7 months, 4 were survived for 3 months and 3 were immediate status after placement. Resonance frequency analyses were conducted and the dogs were sacrificed. Percentage of the bone to implant contact (BIC) in the interface, percentage of the mineralized bone (bone area) within the threads of the implant, and marginal bone level were measured under light microscopy. The correlation between resonance frequency and histomorphometric measurements were analysed and following results were obtained. 1. There was statistically significant correlation between ISQ value and BIC on healed implants. But ISQ value and BIC of all implants were not significantly correlated. (P<0.01) 2. Significant correlation between ISQ value and bone area was not found in this study. 3. There was statistically significant correlation between ISQ value and marginal bone level on all implants as well as on healed implants. (P<0.01).

• 대한치과기공학회지
• /
• 제42권2호
• /
• pp.99-105
• /
• 2020

Purpose: A study analysed the stress distribution of abutment screw and supporting bone of fixture by the tightening torque force of the abutment screw within clinical treatment situation for the stability of the dental implant prosthesis. Methods: The finite element analysis was targeted to the mandibular molar crown model, and the implant was internal type 4.0 mm diameter, 10.0 mm length fixture and abutment screw and supporting bone. The occlusal surface was modeled in 4 cusps and loaded 100 N to the buccal cusps. The connection between the abutment and the fixture was achieved by combining three abutment tightening torque forces of 20, 25, and 30 Ncm. Results: The results showed that the maximum stress value of the supporting bone was found in the buccal cortical bone region of the fixture in all models. The von Mises stress value of each model showed 184.5 MPa at the 20 Ncm model, 195.3 MPa in the 25 Ncm model, and 216.5 MPa in the 30 Ncm model. The contact stress between the abutment and the abutment screw showed the stress value in the 20 Ncm model was 201.2 MPa, and the 245.5 MPa in the 25 Ncm model and 314.0 MPa in the 30 Ncm model. Conclusion: The increase of tightening force within the clinical range of the abutment screw of the implant dental prosthesis was found to have no problem with the stability of the supporting bone and the abutment screw.

• 한국수산과학회지
• /
• 제20권3호
• /
• pp.177-184
• /
• 1987

통발과 자망 등에 어획되는 게류의 측면적인 보행운동은 매우 특이하여 어획 메카니즘을 밝히는데 매우 중요한 요소가 된다. 여기서는 해운대 동백섬의 조간대에서 채집한 풀게를 사용하여 망지위에서의 직선적인 운동과 회전 운동 등을 관찰하고 다리의 보행위치와 시간적인 변화를 분석하였다. 그 결과 망지위에서의 보행운동은 착지위치에 따라 그물코 사이로 다리가 빠지게 되는 불규칙적인 움직임이 대부분이므로 여러가지 보행 요인들의 편차가 게의 크기에 관계 없이 크게 나타났다. 풀게의 망지위에서의 보폭, 보행속도, 다리간의 위상차 등은 평면에서 보다 훨씬 작았으나, 보행주기, 다리마디간의 각도 등은 평면에서 보다 양간 증가하였다. 따라서 게가 자망에 걸리는 현상은 게의 크기에 따른 다리의 보행운동과 망지의 망목크기 등을 고려하여 세밀하게 조사되어야 할 것이다.

• 한국주조공학회지
• /
• 제26권5호
• /
• pp.222-226
• /
• 2006

Steel making slag has gained a considerable attraction as one candidate of eco-materials in research fields for recycling resources. Thus, many researches have been performed but were limited to development of substitute for cement being used in the construction field. A little research work also has been done on development of higher value-added materials, including heat resistant and sound absorbing materials. For this reason, the present study were focused on macrostructure characterization of fabricated slag fibers which are applicable to heat resistant materials. The slag fibers were fabricated through a modified melt extraction method. The processing variables employed were the wheel speed and molten slag temperature. The synthesized fibers were characterized by optical microscope and scanning electron microscopy. It was found that the wheel speed of 1400 rpm generated better quality of mineral fibers in terms of the relative amount of shot, diameter and length. This was attributed to the relative extent of contact width between the flowing melt and the rotating wheel. The thickness of the slag fibers also were decreased with increasing the slag melt temperature due mainly to significant decrease in the viscosity of the slag melt. In addition, the lower melt temperature caused an increase in number of shots plus the mineral fibers.

• 척추신경추나의학회지
• /
• 제2권1호
• /
• pp.99-114
• /
• 2007

Objectives : The purpose of this study was to introduce the Chuna Manual Therapy (CMT) using Bong (a type of stick which is called 'bong') as a part of Oriental Medicine. Methods : We searched several traditional methods of CMT using Bong, either individual contact to specialist of CMT using Bong or referred to publications, and summarized briefly for introduction. Authors also made a comparative study between existing CMT and CMT using the bong. Results & Conclusions : The indications of Bong CMT are regarded as acute or chronic pain syndrome, whiplash associated disorders, facet syndrome, vertebral misalignment, chronic fatigue syndrome, obesity and also lower extremity length difference caused by malalignment of vertebrae and pelvic bone. The Meridian Muscle Therapy by pressing down using the Bong can be carried out on the imbalances of the muscle by shortening and lengthening contraction. CMT with Bong is considered more effective than other existing CMT in terms of effectiveness. In the case of pelvic correction which needs a tremendous amount of force, it can reduce the force required effectively. This fact can be inferred by the theory of composition and decomposition of force during the transmission of power. We can perform Bong CMT feeling less fatigued subsequently than general CMT. Pressing down with flexed fingers to grip bong acts on the contraction of flexor digiti and extensor digiti muscle, this protects the $doctor^{\circ}{\emptyset}s$ wrist joints from injury. The bong which acts as a tool between the doctor and the patient, while being given treatment, absorbs and spreads out the direct impact from the patient to the doctor. CMT with Bong is able to apply to both existing massage therapies with the hand. The bong appliance can be used in all applications, particularly, but not limited to; Orthopedic and Manual Correction Therapy, Meridian Muscle Pressing, Exercise Therapy, and Meridian Point Manual Pressing Therapy. CMT with Bong belongs to the category of oriental rehabilitation and Chuna manual medicine.

• 비파괴검사학회지
• /
• 제28권2호
• /
• pp.137-143
• /
• 2008

안경용 구면 렌즈는 굴절력에 따라 (+)디옵터와 (-)디옵터 렌즈로 구분할 수 있다. 렌즈에 가해지는 외부 열원에 의해서 생기는 열변형은 디옵터의 종류에 따라 다르게 나타난다. 본 논문에서는 빛의 가간섭성을 이용하여 물체의 변형을 비접촉으로 정확하게 측정할 수 있는 전자처리 스페클법을 이용하여 렌즈에 발생되는 열변형을 정량적으로 측정하였다. 외부 열원에 의한 온도 분포의 측정은 실시간 비접촉으로 온도를 측정할 수 있는 적외선 열화상 카메라를 사용하였다. 실험은 총 14종의 플라스틱 상용 안경 렌즈를 대상으로 수행하였다. 동일한 온도차에서 (+)디옵터 렌즈의 경우에는 디옵터의 증가에 따라서 열변형량이 증가하였다. 반면에 (-)디옵터 렌즈는 디옵터의 증가와 관계없이 열변형량이 거의 선형적이었다. 또한 동일한 디옵터에서 (+)디옵터 렌즈의 열변형량이 (-)디옵터 렌즈의 열변형량 보다 작았다. 따라서 본 논문에서는 렌즈에 열이 가해지는 경우 렌즈의 열변형량을 정량적으로 측정할 수 있음을 확인하였다.

• 한국정밀공학회지
• /
• 제29권2호
• /
• pp.178-184
• /
• 2012

This paper presents a transformable track mechanism for wall climbing robots. The proposed mechanism allows a wall climbing robot to go over obstacles by transforming the track shape, and also increases contact area between track and wall surface for safe attachment. The track mechanism is realized using a timing belt track with one driving actuator. The inner frame of the track consists of serially connected 5R-joints and 1P-joint, and all joints of the inner frame are passively operated by springs, so the mechanism does not require any actuators and complex control algorithms to change its shape. Static analysis is carried out to determine design parameters which enable $90^{\circ}$ wall-to-wall transition and driving over projected obstacles on wall surfaces. A Prototype is manufactured using the transformable track on which polymer magnets are installed for adhesion force. The size of the prototype is $628mm{\times}200mm{\times}150mm$ ($Length{\times}Width{\times}Height$) and weight is 4kgf. Experiments are performed to verify its climbing capability focusing on $90^{\circ}$ wall to wall transition and driving over projected obstacle.

• 비파괴검사학회지
• /
• 제28권1호
• /
• pp.1-8
• /
• 2008

본 연구는 내압과 압축이 동시에 작용하는 오링의 변형 거동을 측정하기 위한 시험 기법을 개발하기 위함이다. 오링변형측정치구는 고압에서도 변형되지 않으며 오링변형측정치구 내의 두 곳에 홈을 파서 각각의 홈 안에 오링을 장착하도록 설계하였고 내압에 의한 오링의 압출 길이를 측정하기 위해 1 mm 및 0.1 mm의 압출 틈을 제작하였다. 오링의 변형 형상을 정확히 측정하기 위하여 선속경화현상 보정, 히스토그램 분석 및 불감대 영역 보정을 실시하였으며, 계면반응함수와 선확산함수를 이용하여 오링의 변형 길이를 측정하였다. 전산화 단층촬영은 22.3%의 압착상태에서 0, 1.378, 4.902, 9.804, 15.692 MPa의 압력을 가하여 실시하였으며, 각각의 압력에서 오링의 확장 지름, 접촉 길이 및 압출 길이를 측정하였다. 전산화 단층촬영의 측정 결과를 검증하기 위하여 유한요소법으로 오링의 변형 형상을 해석하였고, 수치해석법으로 실제 오링의 면적과 전산화 단층촬영에서 얻은 오링의 면적을 상호 비교하였다.

• 한국강구조학회 논문집
• /
• 제14권1호
• /
• pp.95-104
• /
• 2002

본 연구에서는 타이어의 접지폭을 고려한 새로운 3차원 차량모델을 개발하여 차량의 동적하중에 대하여 연구하였다. 3차원 차량모델에는 타이어의 접지폭과 텐덤 스프링 차륜축의 피칭을 고려하여 대형차량인 2축 차량과 3축 차량을 각각 7-자유도와 8-자유도로 모델링 하였다. 차량의 운동방정식은 Lagrange 방정식을 사용하여 유도하였으며 IMSL에 내장되어 있는 5차 Runge-Kutter 방법을 사용하여 해를 계산하였다. 본 3차원 차량모델을 이용하여 수치해석한 결과와 Whittemore 등이 실시한 실험값을 비교 검토하여 그 타당성을 입증하였다. 수치해석으로 구한 결과는 실험값과 매우 잘 일치하였다. 차량의 동적 해석에서는 2축 차량인 8톤 덤프트럭과 3축 차량인 15톤 덤프트럭이 스탭 범프를 통과할 때와 여러 가지 종류의 도로를 1.0 km 주행하는 동안 발생하는 타이어력의 최대 충격계수를 구하였다.