• Transactions of the KSME C: Technology and Education
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• v.1 no.2
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• pp.153-165
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• 2013

The established gait analysis studies have regarded leg as one single spring. If we can design a knee-ankle actuating mechanism as a primary actuator for supporting knee extension, it might be possible to revolutionary store or release elastic strain energy, which is consumed during the gait cycle, and as a result leg stiffness is expected to increase. An ankle joint actuating mechanism that stores and releases the energy in ankle joint is expected to support and solve excessive artificial leg stiffness caused by the knee actuator (primary actuator) to a reasonable extent. If unnecessary kinematic energy is released with the artificial speed reduction control designed to prevent increase in gait speed caused by increase in time passed, it naturally brings question to the effectiveness of the actuator. As opposed to the already established studies, the authors are currently developing knee-ankle two actuator system under the concept of increasing lower limb stiffness by controlling the speed of gait in relative angular velocity of the two segments. Therefore, the author is convinced that compensatory mechanism caused by knee actuating must exist only in ankle joint. Ankle joint compensatory mechanism can be solved by reverse-examining the change in metatarso-phalangeal joint (MTPJ) tilt angle (${\theta}_1=0^{\circ}$, ${\theta}_2=17^{\circ}$, ${\theta}_3=30^{\circ}$) and the effect of change in gait speed on knee activity.

• The Journal of Dong Guk Oriental Medicine
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• v.9
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• pp.179-191
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• 2000

Anti-bone resorption properties of the Korean herbal medicine, CEDR, which is comprised 5 herbs of [Drynariae Rhizoma, Loranthi Ramus, Cibotii Rhizoma, Amydae carapax, Psoraleae semen], were investigated. Mouse calvarial osteoblast cells were isolated and cultured. Mouse osteoblasts, which were stimulated by PTH, $1,25(OH)_2D_3$, $TNF-\alpha$ and IL-1 as bone resorption agents, showed increased collagenolysis by producing the active gelatinase. IL-1 in stimulating bone resorption was examined using fetal mouse long bone organ culture. IL-1 stimulated bone resorption and produced marked resorption when present simultaneously. The results of in vitro cytotoxicities showed that CEDR extracts have no any cytotoxicities in concentrations of $1-60{\mu}g/ml$ and furthermore there is no any cytotoxicity even in concentration of $120{\mu}g/ml$ on mouse calvarial bone cells. CEDR extracts had protective activity against PTH (5 units/ml, or $IL-1{\alpha}$ (1 ng/ml) or $TNF-\alpha$ or $1,25(OH)_2D_3$ (20 ng/ml), $IL-1{\alpha}$ and $IL-1{\beta}-induced$ collagenolysis in the mouse calvarial cells. Pretreatment of the CEDR extracts for 1 h, which by itself had little effect on cell survival, did not enhance the collagenolysis, nor significantly reduced the collagenolysis by pretreatment. Furthermore, the medicinal extracts were shown to have the protective effects against collagenolysis induced by $IL-1{\alpha}$ and $IL-1{\beta}$. Pretreatment of the extracts for 1 h significantly reduced the collagenolysis. Interestingly, the CEDR extracts were shown to have the inhibiting effects against gelatinase enzyme and processing activity induced by the bone resorption agents of PTH, $1,25(OH)_2D_3$, $TNF-\alpha$, $IL-1{\beta}$ and $IL-1{\alpha}$ with strong protective effect in pretreatment with the extracts. CEDR extracts were shown to have the inhibiting effects against $IL-1{\alpha}-$ and $IL-1{\beta}-stimulated$ bone resorption and the effect of the pretreatment with a various concentrations of the medicinal extracts were significant. These results indicated that the CEDR extracts are highly stable and applicable to clinical uses in osteoporosis.

• Journal of the Korean Geographical Society
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• v.33 no.spc
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• pp.677-684
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• 1998

There are certain polemics regarding what kind of approach is most appropriate in the study of urban cluture. The tension seems to come from the misunderstanding of each other. A major source of the misunderstanding is different usage of the term 'culture' The lerm 'culture' may be interpreted either as way of life (fig. 1), system of meaning (fig. 2), the fourth structural condition (fig. 3), sophisticated taste (fig. 4), a superstructure of intellect and arts (fig. 5), biological supporting system (fig. 6), or all encompassing conditions (fig. 7). Whatever definition is taken for the term 'culture', there is a parallel definition of 'environment' for each stance (figures 1 - 7) What kind of definition is adopted matters because each of them is deeply rooted in different perspectives and focuses. It however, seems impossible to completely deny or disprove the utility of any of the slances. This, we may have to accept the diversity of definitions and consider urban cultural geography as a basket in which diverse concepts and perspectives are collected and nurtured.

• The Journal of the Korean dental association
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• v.56 no.9
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• pp.462-478
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• 2018

The presence of implant-prosthesis misfits can cause various complications. It is very important to detect misfits to prevent such complications. There are various evaluation methods for misfit assessment including clinical methods and laboratory in vitro methods. The clinical misfit evaluation includes radiographic analysis, visual observation, probing, Sheffield test, evaluation with disclosing materials, and screw resistance test. The laboratory in vitro evaluation method includes indirect modelling evaluation and direct metrological visualization. Of the indirect modelling methods, photoelastic stress analysis, finite element analysis, strain gauge analysis, and microbial colonization analysis were reviewed. Of the direct metrological visualization, microscopic analysis, 3-D photogrammetric analysis, coordinate measuring analysis, and radiographic analysis were reviewed. In this review, the characteristics, advantages and disadvantages of each method were evaluated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.201-201
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• 2008

박형초음파모터의 구조는 그림 1(a) 와 같이 크로스형태의 앓은 스테이터에 윗면과 아랫면에 각각 8 개의 압전세라믹이 부착된 형태이다. 압전세라믹의 분극방향은 로터와 접촉하는 스테이터의 A, B, C, D 네 개의 타점에서 순차적인 타원변위가 생성되도록 결정된다. 유한요소해석프로그램인 ATILA 5.2.4를 사용하여 최적설계를 한 결과 폭 3[mm], 길이 18[mm], 두께 1.8[mm], Brass 재질, Mid surface clamp 조건에서 입력전압 18[Vrms] 일 때 0.3[${\mu}m$]의 변위를 보였다. 최적설계된 모델을 제작하였고, 정확한 실험결과를 얻기 위해서 푸쉬풀게이지, x-y스테이지, rpm 메타, 토크게이지를 이용하여 실험테이블을 구성하였다. 그림 1(b) 는 마이크로컨트롤러를 이용한 구동 드라이버를 보여준다. 한 주기에서 1/4분주의 순차적인 네 개의 구형파를 생성하고, 이를 push-pull회로를 동하여 90도의 위상차가 나는 정현파를 생성하여 초음파 모터의 구동전원으로 사용한다. 엔코더와 AD 컨버터를 이용하여 정속도 운전을 위한 피드백 제어가 된다. 제안된 구동드라이버를 이용하여 측정한 결과, 구동 주파수 88.6[kHz], 입력전압 [40Vrms], preload 0.2 [N]에서 130 [rmp] 의 속도와 25 [gfcm] 의 토크특성을 보였다. 압력전압을 증가시킬수록 속도는 선형적인 증가를 보였고, 토크는 이와 반대로 감소하는 특성을 보였다. 피드백 제어회로가 없는 경우에는 preload 변화에 따른 극심한 속도 변화를 보였고, 피드백 제어를 하였을 경우에는 0.2~0.4[N]의 범위에서 정속도 운전이 가능함을 확인하였다. 기존의 주파수발생기와 파워 엠프를 이용한 구동장비와의 특성비교에서도 큰 차이를 보이지 않았으며, 장시간의 운전에도 안정적인 구동이 가능함을 확인하였다.

• Journal of Digital Contents Society
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• v.9 no.4
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• pp.771-778
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• 2008

A Device performance analyzing method for appropriate level in hybrid rendering model is suggested. In recent research, we proposed a hybrid rendering model which is applying a proper shading method to each of polygons consisting of an object. The number of polygon for Gouraud shading and that for flat shading should be considered according to a current device performance and system environments. Therefore, this paper suggests the method to calculate automatically a proper resolution of a mesh of object and a proper level of mixture between Gouraud and a flat shading, considering a current device performance and a preference of end-user. The rendering model is so simple that it can be an efficient replacement to reduce a real-time rendering time since it provides automatically multi-level of rendering resolution to an executing environments. Moreover, it can be adopted in real-time adaptive service for 3D graphic contents like a graphic game under various device environments.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.3
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• pp.248-257
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• 2011

In the present study, we proposed a new numerical wave tank model to analyze the vertical tension-leg circular floating bodies, using a 2-D Navier-Stokes solver. An IBM(Immersed Boundary Method) capable of handling interactions between waves and moving structures with complex geometry on a standard regular Cartesian grid system is coupled to the VOF(Volume of Fluid) method for tracking the free surface. Present numerical results for the motions of the floating body were compared with existing experimental data as well as numerical results based on FAVOR(Fractional Area Volume Obstacle Representation) algorithm. For detailed examinations of the present model, the additional hydraulic experiments for floating motions and free surface transformations were conducted. Further, the versatility of the proposed numerical model was verified via the numerical and physical experiments for the general rectangular floating bodies. Numerical results were compared with experiments and good agreement was archived.

• Journal of Aerospace System Engineering
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• v.15 no.3
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• pp.65-70
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• 2021

This study presents a method to efficiently advance the Republic of Korea's Unmanned Systems through the analysis of the development of the U.S. Unmanned System Policy. After the occurrence of the September 11 attacks, the U.S. developed Unmanned Systems as a part of RMA and became the leader in this area. The system went through numerous trials and errors during the development and acquisition. From these experiences, the U.S. had embodied Unmanned Systems acquisition methods by establishing Unmanned Systems Development Guidance and DoD Autonomy Community of Interest in 2012. In addition, as diverse unmanned programs started to proceed, it promoted Core Technology development sharing and simplification of functions of the Unmanned Systems to exclude budget-wasting elements such as duplication of programs. The Republic of Korea must politically build a collaborative system between industry/academia/research institute/military and apply evolutionary development strategies from the first step of the development of the Unmanned Systems the future Game Changer. In operations, concepts of the Manned/Unmanned Systems complex operation should be established and intelligent S/W, Open System, and Cyber Security technologies to materialize them developed.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.12
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• pp.169-174
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• 2016

In this study, we evaluated the virtual reality model for dental implant surgery and discussed about the method to make the surgical environment for virtual reality with practical patient data. The anatomical model for patient face was fabricated by facial and oral scan data based on CT data. The simulation scenario was composed step by step fashion with Unity3D. From incision and sinus bone graft procedure which is needed to this patient model to implant installation and bone graft was included in this scenario. We used the HMD and leap motion for immersiveness and feeling of real operation. Twenty training doctor was attended this simulation study, and surveyed their satisfactory results by questionnaire. Implant surgery education program was showed the possibilities of educational tool for dental students and training doctors. Virtual reality for surgical education with HMD and leap motion had advantages, in terms of cheap prcie, easy access.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1B
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• pp.35-45
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• 2009

In this study, a laboratory experiment has been performed on a S-curved channel with two curved sections. In the experiments, effects of 3-D velocity structures on mixing characteristics of tracer material were investigated. As a result, it was clearly noticed that the primary flow travels taking the shortest course of the meandering channel and has a very ununiform distribution at the bends. The secondary cell which was developing at the first bend disappears at the crossover, and then, at the next bend, secondary cell is re-developing in the opposite direction. The experimental results show that mixing of tracer is significantly affected by the combined action of ununiform primary flow and secondary cell. The ununiform primary flow separates the tracer cloud in the longitudinal direction, and the secondary cell further separates the retarding tracer cloud mainly in the transverse direction. As a result, these complex flow structures cause separation and spreading of tracer cloud both in the longitudinal and in the transverse directions. The measured dimensionless transverse dispersion coefficients calculated using 2-D routing procedure ranges 0.012-0.875, and is generally proportional to width to depth ratio (W/h). The predicted values calculated by the theoretical equation overestimate slightly the measured transverse dispersion coefficients.