• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.5
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• pp.15-21
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• 2008

It is generally known that the PRAT(Plysteer Residual Aligning Torque) is one of indicating a performance factors of a tire for assessing the vehicle pull, also tire pattern shape, which means lateral groove angle, is very important tire design factor in relation to the PRAT. Lateral grooves of tire pattern are widely divided into center and shoulder parts. So, this paper has studied the correlation between the PRAT and their lateral groove angles using FEM. Especially, the steady state rolling analysis among tire rolling analysis methods has been used for the PRAT performance study. Firstly, analysis result data have been compared with the experimental data to validate FE analysis for PRAT. Next, the PRAT due to the lateral groove angle about PCR(Passenger Car Radial) tire and SUV tire has been analyzed. The tendency of the PRAT due to the lateral groove angles can be used as a guide line for the tire design in relation to vehicle pull.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.2
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• pp.89-98
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• 2017

The control moment gyroscope(CMG) can be used for essential balancing control of a one-wheeled mobile robot. A single-gimbal CMG has a simple structure and can supply strong restoring torque against external disturbances. However, the CMG generates unwanted directional torque also besides the restoring torque; the unwanted directional torque causes instability in the one-wheeled robot control system that has high rotational degrees of freedom. This study proposes a control system for a one-wheeled mobile robot by using a CMG scissored pair to eliminate the unwanted directional torque. The well-known LQR control algorithm is designed for robustness against modeling error in the dynamic motion equations of a one-wheeled robot. Computer simulations for 3D nonlinear dynamic equations are carried out to verify the proposed control system with the CMG scissored pair and the LQR control algorithms.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.4
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• pp.300-306
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• 2013

Purpose: This study was to evaluate the accuracy of how to use the Mechanical Torque-Limiting Devices. Materials and methods: Three different implant manufacturers (Dentium, Osstem, Shinhung) were prepared for each two implant torque controllers. Divided into two groups depending on the method used for removal torque was measured. Repeated measures of ANOVA test (${\alpha}=.05$) was used as statistics to evaluate the effect of repeated loading number on the removal torque. Independent t-test was used to evaluate the difference in removal torque of two groups. Results: The removal torque significantly decreased as the number of loading repetition increased (P<.05). There was significant difference between two groups. Conclusion: Loosen the handle part of the implant torque controllers spring resilience to recover one group compared to the group that did not, showed a little more closed to the reference value.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.4
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• pp.173-180
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• 2004

The tread pattern of a tire has an important effect on tire performances such as handling, wear, noise, hydroplaning and so on. However, a finite element analysis of a patterned tire with detailed tread blocks has been limited owing to the complexity of making meshes for tread blocks and the huge computation time. The computation time has been shortened due to the advance in the computer technology. The modeling of tread blocks usually requires creating a solid model using a CAD software. Therefore it is a very complicated and time-consuming job to generate meshes of a patterned tire using a CAD model. A new efficient and convenient method for generating meshes of a patterned tire has been developed. In this method, 3-D meshes of tread pattern are created by mapping 2-D meshes of tread geometry onto 3-D tread surfaces and extruding them through tread depth. Then, the tread pattern meshes are assembled with the tire body meshes by the tie contact constraint. Residual aligning torque and frictional energy are calculated by using a patterned tire model and compared to the experimental results. It is shown that the calculated results of a patterned tire model are in a good agreement with the experimental ones.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.2 s.179
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• pp.104-112
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• 2006

The influence of tire belt angle on the Plysteer Residual Aligning Torque(PRAT) and the cornering stiffness by the FEM has been studied. The PRAT is a performance factor of the tire about vehicle pull, and the cornering stiffness has relation to vehicle steering response of outdoor test. To validate FE model for analysis, simulation data for both the static stiffness(vertical, lateral) and the PRAT have been compared with the experimental data. In addition to the characteristics of the PRAT and the cornering stiffness due to the tire belt angle, rolling and cornering contact characteristics have been studied. The tendency of the PRAT and the cornering stiffness due to the belt angle can be used as a guide line for the tire design in relation to vehicle pull and vehicle steering response.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.6
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• pp.307-317
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• 2002

In this paper we propose a new mesh reconstruction scheme that produces a displaced subdivision surface directly from unorganized points. The displaced subdivision surface is a new mesh representation that defines a detailed mesh with a displacement map over a smooth domain surface, but original displaced subdivision surface algorithm needs an explicit polygonal mesh since it is not a mesh reconstruction algorithm but a mesh conversion (remeshing) algorithm. The main idea of our approach is that we sample surface detail from unorganized points without any topological information. For this, we predict a virtual triangular face from unorganized points for each sampling ray from a parameteric domain surface. Direct displaced subdivision surface reconstruction from unorganized points has much importance since the output of this algorithm has several important properties: It has compact mesh representation since most vertices can be represented by only a scalar value. Underlying structure of it is piecewise regular so it ran be easily transformed into a multiresolution mesh. Smoothness after mesh deformation is automatically preserved. We avoid time-consuming global energy optimization by employing the input data dependant mesh smoothing, so we can get a good quality displaced subdivision surface quickly.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.609-617
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• 2014

Even though the variable pitch control of a wind turbine blade is known as an effective component for power control over the rated wind speed, it has limited applicability to small wind turbines because of its relatively high cost on the price of small wind turbine. Instead, stall control is generally applied in the blade design without any additional cost. However, stall delay can frequently be caused by high turbulence around the turbine blade, and it can produce control failures through excessive rotational speed and overpowering the electrical generator. Therefore, a passive pitch control module should be considered, where the pitch moves with the aerodynamic forces of the blade and returns by the elastic restoring force. In this study, a method to calculate the pitch moment, torque, and thrust based on the lift and drag of the rotating blade wing was demonstrated, and several effective wing shapes were reviewed based on these forces. Their characteristics will be estimated with variable wind speed and be utilized as basic data for the design of the passive pitch control module.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1371-1375
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• 2005

The paper has analyzed the influence of tire design variable on the tire Force and Moment (F&M) characteristics, especially by the belt angle, the Plysteer Residual Aligning Torque (PRAT) which is considered as one of the causing factors for the vehicle pull. To validate the tire FE model, the tire stiffness and the PRAT which can be derived from the simulation data have been compared with the experimental data of test machine. In addition to PRAT characteristic, the tire stiffness and cornering characteristics due to the belt angle have been investigated. The effects of drum's curvature on the PRAT have been also investigated using the tire FE model and the usefulness of the current drum type F&M test machine can be confirmed.

• Korean Journal of Optics and Photonics
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• v.30 no.6
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• pp.243-248
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• 2019

The respiratory tract is an essential part of the respiratory system involved in the process of respiration. However, if stenosis occurs, it interferes with breathing and can even lead to death. Asthma is a typical example of a reversible cause of airway narrowing, and the number of patients suffering from acute exacerbation is steadily increasing. Therefore, it is important to detect airway narrowing early and prevent the patient's condition from worsening. Optical coherence tomography (OCT), which has high resolution, is suitable for observing the microstructure of tissues. In this study we developed an endoscopic OCT system. We combined a 1300-nm OCT system with a servo motor, which can rotate at a high speed. A catheter was pulled back using a linear stage while imaging with 360° rotation by the motor. The motor was selected considering various requirements, such as torque, rotational speed, and gear ratio of pulleys. An ex vivo rabbit tracheal model was used as a sample, and the sample and catheter were immobilized by acrylic structures. The OCT images provided information about the structures of the mucosa and submucosa. The difference between normal and stenosed parts in the trachea was confirmed by OCT. Furthermore, through a three-dimensional (3-D) reconstruction process, it was possible to identify and diagnose the stenosis in the 3-D image of the airway, as well as the cross-sectional image. This study would be useful not only for diagnosing airway stenosis, but also for realizing 3-D imaging.

• Journal of Chest Surgery
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• v.32 no.10
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• pp.874-882
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• 1999

배경: 체외순환 후의 부종현상 및 이에 따른 여러 장치의 기능 저하를 방지하기 위하여, 최근에 체외 순환 이탈 후 환자의 혈액을 짧은 시간에 관류하여 여과해 주는 변형 초여과법의 사용이 늘고 있다. 이에 대한 긍정적인 임상결과들의 보고도 있으나, 다른 한편 체외 순환 후 염증반응을 포함한 폐손상의 기전에 혈구 성분의 영향이 보고되고 있는 바, 변형 초여과법의 효과, 특히 폐 조직에 대한 영향을 밝혀 보고자 하였다. 대상 및 방법: 몸무게 15에서 22 Kg(평균 16.5$\pm$0.5)의 16 쌍의 잡견을 이용한 정소성 심장이식, 실험에서, 통상적인 인공심폐기 작동군과 인공심폐기 작동 후 변형 초여과 관류를 시행한 군으로 무작위 구분하였다. 변형초여과법은 체외순환 정지 후에 대동맥관에서 나온 혈류를 Roller pump를 거쳐 Amicon Diafilter 초여과 관에 150 mL/m 정도의 속도로 10~15 분 정도 관류시켜 정맥관을 통하여 우심방에 직접 주입하였다. 혈액 채취 및 폐생검은 심폐기 시작 전과 정지 직후, 그리고 변형초여과 시행 군은 초여과 완료 직후에, 대조군은 심폐기 정지 10~15분 후에 각각 시행하였다. 혈류역학 측정요소는 동맥압, 우심방압, 좌심방압 등이었으며, 혈액 검사 항목은 동맥혈 가스분석, 혈색소 농도, 헤마토크릿, 백혈구 수, 혈소판 수, 혈중 단백 성분, 알부민 성분 등이었다. 폐 생검 조직으로는 냉동 건조법을 이용한 수분 함유량을 측정하였고, 광학 및 전자현미경으로 관찰을 하였다. 결과: 변형 초여과 군에서 혈중 혈색소 농도는 수술전 10.3$\pm$1.7 mg/dL, 심폐기 정지 직후 6.3$\pm$1.7 mg/dL, 초여과 직후는 8.3$\pm$2.8 mg/dL의 변화를(p=0.0078, 0.0117), 혈중 총 단백질의 농도 변화는 4.3$\pm$0.9, 3.1$\pm$1.5, 4.1$\pm$1.6 mg/dL, 혈중 알부민의 농도는 1.9$\pm$0.5, 1.4$\pm$0.7, 1.8$\pm$0.8 mg/dL로서, 각각 초여과법의 시행 전후에 유의한 증가를 가져왔고(p=0.0280, 0.0277), 폐조직의 수분 함유량의 변화는 수술전 75.1$\pm$8.6%, 심폐기 정지 직후 82.8$\pm$6.0%, 초여과 직후 77.88%를 보인 반면, 대조군에서는 각각 74.7$\pm$4.9, 82.1$\pm$5.9, 82.3$\pm$5.1%의 변화를 보였다. 미세 구조의 관찰에서, 폐포의 내포세피의 융합 기저막층과 미토콘드리아에서의 부종은 변형 초여과 후에 급격히 감소하였으나, 미토콘드리아내 크리스티의 파괴성 변화와 막성 파괴 성향이 초여과 후에 심화되게 관찰되었고, 세포질 내 소체의 팽창과 공포화 현상도 심폐기 가동 후 발생하여 초여과 후에 더 심화되게 관찰되었다. 세포질 내 소체의 팽창과 공포화 현상도 심폐기 가동 후 발생하여 초여과 후에 더 심화되게 관찰되었다. 폐조직 내의 백혈구는 심폐기 작동 후에 그 수에 있어서 증가하였으며 백혈구의 괴변, 탈과립 정도도 심폐기 작동 후 및 초여과 후에 증가한 소견을 보였다. 결론: 변형 초여과법은 인공 심폐기 후의 혈색소 농도 및 혈중 단백질 농도의 복원에 효과가 있었으며 변형 초여과 관류후 폐의 미세 조직내에서 부종의 급격한 감소 등을 관찰할 수 있었다.