• 한국전산구조공학회논문집
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• 제16권1호
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• pp.105-111
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• 2003

승용차의 휠은 타이어와 차체 무게를 지지하며, 회전력과 정지력을 노면으로 전달한다. 휠의 경량화는 차량의 연료효율에 효과적이므로, 스틸휠이 무게를 최소화하도록 디스크 홀이 형상을 최적화 하였다. 설계모델은 Pro/ENGINEER를 사용하여 설정하고, 설계모델의 해석은 ANSYS를 이용하였다. 범용 소프트웨어간의 직접적인 자료의 전달이 어려우므로 두 프로그램을 병합 사용하기 위해, 반응표면법을 이용한 근사함수를 구하였다. 5수준의 요인배치법의 실험값을 사용하여 최대응력과 최대 변위를 추출하였다. 초기 모델은 14인치 승용차용 스틸휠을 사용하였고, 디스크 홀의 폭을 설계변수로 선택하였다. 순차이차계획법과 활성화제약조건을 사용하는 PLBA(Pahenichny-Lim-Belegundu-Arora) 알고르즘을 이용하여 최적해를 구하였다.

• The Journal of Advanced Prosthodontics
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• 제11권1호
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• pp.1-6
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• 2019

PURPOSE. The purpose of this in vitro study was to evaluate the effect of surface grinding and polishing procedures using high speed zirconia diamond burs with different grit sizes on the phase transformation and flexural strength of zirconia. MATERIALS AND METHODS. Forty disc shape specimens ($15{\times}1.25mm$) with a cylindrical projection in the center of each disc ($1{\times}3mm$) were fabricated with 3Y-TZP (Prettau, Zirkonzahn, Italy). The specimens were divided into 4 groups (n=10) according to the grinding and polishing procedures: Control group - grinding (coarse-grit diamond bur), Group 1 - grinding (coarse-grit diamond bur) + polishing, Group 2 - grinding (fine-grit diamond bur) + polishing, and Group 3 - grinding (fine grit diamond bur). Each specimen was analyzed by 3D-OM, XRD analysis, and biaxial flexural strength test. RESULTS. Based on the surface morphology by 3D-OM images, polished specimens showed smoother surface and lower roughness value (Ra). In the result of XRD analysis, partial phase transformation from tetragonal to monoclinic zirconia occurred in all groups. Control group, ground with a coarse grit diamond bur, showed more $t{\rightarrow}m$ phase transformation and lower flexural strength than Groups 1 and 2 significantly. CONCLUSION. The flexural strength in all specimens after grinding and polishing showed over 500 MPa, and those were clinically acceptable. However, grinding with a coarse grit diamond bur without polishing induced the phase transformation and low strength. Therefore, surface polishing is required for the occlusal adjustment using a high speed zirconia diamond bur to reduce the phase transformation and to prevent the decrease of flexural strength of zirconia.

• 한국산학기술학회논문지
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• 제22권3호
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• pp.199-207
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• 2021

본 연구는 한국형고속철도(KTX)의 제동장치의 국산화를 통한 성능 개선을 위한 목적으로 수행되었다. 본 연구에서 기존 수입에 의존하고 있는 고속철도용 제동 디스크 허브를 국산화하기 위하여 유한요소 해석을 통해 성능을 분석하고 제동 시험결과와 상관도 분석을 통해 모델의 검증을 수행하였다. 또한, 제동시 발생할 수 있는 기계적인 특성을 검토하기 위하여 마찰열에 의한 열전달-열응력 해석, 고유진동해석 및 강도해석을 수행하였다. 디스크 허브 국산화 신규 모델의 개발을 위해 형상에 따른 설계 인자를 도출하고 파라미터 해석을 수행하여 방열성능을 향상시키고 경량화를 위한 최적 사양을 도출하고자 하였다. 개발 모델을 기존 모델과 비교한 결과 기존 모델 대비 제동시 발생하는 허브의 최고 온도가 낮아졌으며, 냉각 효율이 향상되었음 확인할 수 있었다. 또한, 고유진동수 및 강도 특성 또한 동등 수준 이상의 성능을 확보한 설계임을 확인하였다. 본 연구 결과는 철도차량 및 수송기기 분야의 제동 디스크 시스템 개발에 활용될 수 있을 것으로 기대된다.

• 한국해양공학회지
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• 제35권6호
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• pp.434-445
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• 2021

This paper proposes an optimal design method for an unmanned underwater vehicle (UUV) platform to overcome strong current. First, to minimize the hydrodynamic drag components in water, the vehicle is designed to have a streamlined disc shape, which help maintaining horizontal motion (zero roll and pitch angles posture) while overcoming external current. To this end, four vertical thrusters are symmetrically mounted outside of the platform to stabilize the vehicle's horizontal motion. In the horizontal plane, four horizontal thrusters are symmetrically mounted outside of the disc, and each of them has the same forward and reverse thrust performances. With these four thrusters, a specific thrust vector control (TVC) method is proposed, and for external current in any direction, four horizontal thrusters are controlled to generate a vectored thrust force to encounter the current while minimizing the vehicle's rotation and maintaining its heading. However, for the numerical simulations, the vehicle's hydrodynamic coefficients related to the horizontal plane are derived based on both theoretical and empirically derived formulas. In addition to the simulation, experimental studies in both the water tank and circulating water channel are performed to verify the vehicle's various final performances, including its ability to overcome strong current.

• 대한치과보철학회지
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• 제61권4호
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• pp.268-274
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• 2023

본 증례는 요양병원에 입원치료 중인 환자에서 치과에 내원하기 힘든 점과 의치 분실이 많은 점을 고려하여 내원 횟수를 감소시키고 재제작이 쉬운 CAD-CAM 총의치를 제작하였다. 환자가 적응한 기존 임시의치의 형태 및 수직고경, 악간관계를 최종의치 제작에 반영하기 위해 기존 임시의치를 스캔하고 프린팅한 개인트레이로 폐구인상을 채득하였다. UTS CAD를 이용하여 디지털 안궁이전하고 CAD 소프트웨어에서 치아배열 후 상하악 총의치를 단일 구조의 디스크로 의치상과 인공치를 한번에 절삭하여 제작하였다.

• 대한치과교정학회지
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• 제24권4호
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• pp.917-932
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• 1994

백서에 있어서 기능적 전방위 장치가 악관절 원판에 미치는 변화 양상을 관찰하기 위하여 생후 4주령 부터 3주간 및 4주간 기능적 전방위 장치를 장착한 후 백서의 악관절 부위를 적출하여 광학 및 전자 현미경으로 관찰한 결과 다음의 소견을 얻었다. 실험 2주군에 있어서 악관절 원판의 전방부 및 후방부 두께는 실험군이 대조군보다 통계적으로 유의성 있는 증가를 나타내었다. 실험 4주군에 있어서 악관절 원판의 두께는 전방부에서 실험군이 대조군보다 통계적으로 유의성 있는 증가를 나타내었다. 광학 현미경 소견에서 2주 및 4주실험군의 전방부에서 대조군에 비하여 섬유아세포의 밀도가 높은 경향을 나타내었다. 전자현미경 소견 2주군에서 내강이 확장된 RER이 대단히 잘 발달하여 collagen등 세포외 물질의 합성이 왕성한 것으로 추측되는 세포, 내강이 확장되지는 않았으나 RER이 발달하고 free ribosome이 발달되어 세포내 세사의 합성이 활발한 것으로 추측되는 세포, 전형적 인 chondroid cell이 관찰되었으며, 실험군 전방부에서는 대조군에 비하여 내강이 확장된 RER이 발달된 섬유 모세포들의 비율이 높았다. 4주 실험군에서 전방부는 대조군에 비하여 전반적으로 세포밀도가 높았으며 RER 및 free ribosome이 발달된 섬유 모세포 비율이 높았다. 이상의 결과를 종합하면, 하악골의 기능적 위치 변화는 관절원판의 부위에 따라 기계적 부하를 변화시키며, 결과적으로 세포수준에서 이에 적응 혹 대응하므로써 형태의 변화가 일어날 수 있다고 사료된다.

• 대한의용생체공학회:의공학회지
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• 제28권3호
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• pp.397-409
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• 2007

Owing to needs of biomechanical comprehension and analysis to obtain various medical treatment designs which are related with the spine in order to cure and diagnose LBP patients, the FE modeling and nonlinear analysis of lumbosacrum including a partial ilium and iliolumbar ligaments, were carried out. First, we investigated whether the geometrical configuration of vertebrae displayed by DICOM slice files is regular and normal condition. After constructing spinal vertebrae including a partial ilium, a sacrum and five lumbars (from L1 to L5)with anatomical shape reconstructed using softwares such as image modeler and CAD modeler, we added iliolumbar ligaments, lumbar ligaments, discs and facet joints, etc.. And also, we assigned material property and discretized the model using proper finite element types, thus it was completely modeled through the above procedure. For the verification of each segment, average sagittal ROM, average coronal ROM and average transversal ROM under various loading conditions(${\pm}10Nm$), average vertical displacement under compression(400N), ALL(Anterior Longitudinal Ligament) and PLL(Posterior Longitudinal Ligament) force at L12 level, strains of seven ligaments on sagittal plane at L45 level and maximal strain of disc fibers according to various loading conditions at L45 level, etc., they were compared with experimental results. For the verification of multilevel-lumbosacrum spine including partial ilium and iliolumbar ligaments, the cases with and without iliolumbar ligaments were compared with ROM of experiment. The results were obtained from analysis of the verified FE model as follows: I) Iliolumbar ligaments played a stabilizing role as mainly posterior iliolumbar ligaments under flexion and as both posterior and anterior iliolumbar ligaments of one side under lateral bending. 2) The iliolumbar ligaments decreased total ROM of 1-8% in total model according to various motion conditions, which changed facet contact forces of L5S level by approximately 0.8-1.4 times and disc forces of L5S level by approximately 0.8-1.5 times more than casewithout ilioligaments, under various loading conditions. 3) The force of lower discs such as L45 and L5S was bigger than upper discs under flexion, left and right bending and left and right twisting, except extension. 4) It was predicted that strains of posterior ligaments among iliolumbar ligaments would produce the maximum 16% under flexion and the maximum 10% under twisting. 5) It's expected that this present model applies to the development and design of artificial disc, since it was comparatively in agreement with the experimental datum.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1547-1552
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• 2008

The tip of these catheter with straight needles is not able to reach in the vicinity of the disc bulging, which are the cause of the low back pain and because the far indirect radio-frequency treatment results in the decompression, the nucleoplasty has the limit. Many incurable diseases has not been solved due to the unexistence of the advanced technique for the MIS human body catheter device. To increase the possibility of nucleoplasty, the needle tip should be located at the closest area of the lesion. For this reason, the best way to increase the success rate of the operation is that the needle tip should access 3-dimensionally to the operating field as soon as possible. To achieve this aim, our studies are restricted as follows: 1) the SMA catheter design to control the 3-dimensional direction, 2) the security of the immediate response by the positive control of the SMA element thermal distribution using Peltier thermoelectric elements, 3) the aquisition of the control data by monitoring the relationship between the temperature of SMA element and the displacement, and 4) the design of the controller to guarantee the accurate location.

• 한국재료학회지
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• 제27권3호
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• pp.132-136
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• 2017

We synthesized potassium hexatitanate, ($K_2Ti_6O_{13}$, PT6), with a non-fibrous shape, by acid leaching and subsequent thermal treatment of potassium tetratitanate ($K_2Ti_4O_9$, PT4), with layered crystal structure. By controlling nucleation and growth of PT4 crystals, we obtained splinter-type crystals of PT6 with increased width and reduced thickness. The optimal holding temperature for the layered PT4 was found to be ${\sim}920^{\circ}C$. The length and width of the PT4 crystals were increased when the nucleation and growth time were increased. After a proton exchange reaction using aqueous 0.3 M HCl solution, and subsequent heat treatment at $850^{\circ}C$, the PT4 crystal transformed into splinter-type PT6 crystals. The frictional characteristics of the friction materials show that as the particle size of PT6 increases, the coefficient of friction (COF) and wear amounts of both the friction materials and counter disc increase.

• 식물분류학회지
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• 제48권3호
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• pp.185-194
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• 2018

A comparative floral morphological study of 19 taxa in Persicaria sect. Cephalophilon with four taxa related to Koenigia was conducted to evaluate the taxonomic implications. The flowers of P. sect. Cephalophilon have (four-)five-lobed tepals; five, six, or eight stamens, and one pistil with two or three styles. The size range of each floral characteristic varies according to the taxa; generally P. humilis, P. glacialis var. glacialis and Koenigia taxa have rather small floral sizes. The connate degrees of the tepal lobes and styles also vary. The tepal epidermis consists of elongated rectangular cells with variation of the anticlinal cell walls (ACWs). Two types of glandular trichomes are found. The peltate glandular trichome (PT) was observed in nearly all of the studied taxa. The PT was consistently distributed on the outer tepal of P. sect. Cephalophilon, while Koenigia taxa and P. glacialis var. glacialis had this type of trichome on both sides of the tepal. P. criopolitana had only long-stalked pilate-glandular trichomes (LT) on the outer tepal. The nectary is distributed on the basal part of the inner tepal, with three possible shapes: dome-like, elongated, and disc-like nectary. The nectaries are always accompanied by elongated or spheroidal papillae. Various combinations of floral characters (e.g., the numbers of stamens and styles, the stigma shape, the nectary shape, ACWs, cuticular striation and the trichome type and distribution) of P. sect. Cephalophilon are useful when attempting to recognize the infrasectional levels of P. sect. Cephalophilon recently proposed. Here, we describe the floral characteristics in detail and discuss the taxonomic significance of the floral characters.