• 대한전자공학회논문지SP
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• 제37권5호
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• pp.105-114
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• 2000

본 논문에서는 영상 변환 기반 자동 립리딩 알고리즘에서 처리하는 데이터 수를 효과적으로 감소시키는데 중점을 두었다 화자의 입술에 대한 압축된 정보를 갖는 영상 변환 방식이 입술 윤곽선 기반 방식보다 우수한 립리딩 성능을 보이지만 이 방식은 입술 특정 파라미터를 다수 갖게 되므로 데이터 처리량이 많아지고 인식시간이 길어지게 된다 계산되는 데이터를 줄이기 위해 우리는 엽술의 대칭성에 기반하여 입술영상을 수직으로 접는 간단한 방법을 제안한다 추가적으로 주성분 분석(PCA) 알고리즘을 사용하여 빠른 알고리즘을 고려하였고, HMM을 이용한 단어 인식실험 결과를 보인다 제안된 방법에서 접어진 입술영상을 이용한 결과, 일반적으로 $16{\times}16$ 입술영상을 사용하는 방법에 비해 특정파라미터 수가 $22{\sim}47%$ 감소하였고, HMM(hidden Markov model) 인식 알고리즘을 이용한 단어 인식률에서도 $2{\sim}3%$ 개선된 결과를 얻었다.

• Geomechanics and Engineering
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• 제14권5호
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• pp.479-489
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• 2018

In this paper, a comparative study of the effects of soil modelling on the interaction between tunnelling in soft soil and adjacent piled structure is presented. Several three-dimensional finite element analyses are performed to study the deformation of pile caps and piles as well as tunnel internal forces during the construction of an underground tunnel. The soil is modelled by two material models: the simple, yet approximate Mohr Coulomb (MC) yield criterion; and the complex, but reasonable hardening soil (HS) model with hyperbolic relation between stress and strain. For the former model, two different values of the soil stiffness modulus ($E_{50}$ or $E_{ur}$) as well as two profiles of stiffness variation with depth (constant and linearly increasing) were used in attempts to improve its prediction. As these four attempts did not succeed, a hybrid representation in which the hardening soil is used for soil located at the highly-strained zones while the Mohr Coulomb model is utilized elsewhere was investigated. This hybrid representation, which is a compromise between rigorous and simple solutions yielded results that compare well with those of the hardening soil model. The compared results include pile cap movements, pile deformation, and tunnel internal forces. Problem symmetry is utilized and, therefore, one symmetric half of the soil medium, the tunnel boring machine, the face pressure, the final tunnel lining, the pile caps, and the piles are modelled in several construction phases.

• ETRI Journal
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• 제41권6호
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• pp.838-849
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• 2019

We present a permanent magnet-based spherical wheel motor that can be used in omnidirectional mobility applications. The proposed motor consists of a ball-shaped rotor with a magnetic dipole and a hemispherical shell with circumferential air-core coils attached to the outer surface acting as a stator. Based on the rotational symmetry of the rotor poles and stator coils, we are able to model the rotor poles and stator coils as dipoles. A simple physical model constructed based on a torque model enables fast numerical simulations of motor dynamics. Based on these numerical simulations, we test various control schemes that enable constant-speed rotation along arbitrary axes with small rotational attitude error. Torque analysis reveals that the back electromotive force induced in the coils can be used to construct a control scheme that achieves the desired results. Numerical simulations of trajectories confirm that even without explicit methods for correcting the rotational attitude error, it is possible to drive the motor with a low attitude error (<5°) using the proposed control scheme.

• Journal of the Korean Data and Information Science Society
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• 제20권3호
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• pp.475-483
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• 2009

본 연구에서는 한국종합주가지수 데이터를 이용하여 다양한 비선형 시계열 모형들을 소개하였다. 조건부 평균의 선형 모형으로는 상수항 모형, 자기회귀 모형을 살펴보았으며, 비선형 모형으로는 분계점 자기회귀 모형, 지수적 자기회귀 모형을 살펴보았다. 조건부 분산 모형으로는 일반 자기회귀 이분산 모형과 지수적 일반 자기회귀 이분산 모형, Glosten 등 (1993)의 모형 그리고 일반화 이항멱변환 분계점 일반 자기회귀 이분산 모형을 살펴보았다. 한편, 일반화 이항멱변환 분계점 일반 자기회귀 이분산 모형은 대표적 비대칭성 이분산성 모형인 Zakoian (1993) 모형과 Li와 Li (1996) 모형을 효과적으로 통합할 수 있는 변형된 모형이다. 본 연구에서는, 한국종합주가지수 데이터를 분석하여 새로운 모형의 효율성을 증명하였다.

• 제어로봇시스템학회논문지
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• 제2권2호
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• pp.102-107
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• 1996

It is difficult to analyze the high speed rolling missile with the generally used missile body fixed coordinates. In this study, we formulate the dynamic equations of the high speed rolling missile with the principal axis of inertia, and make the analytical model of one axis steering missile using pitch/yaw symmetry and complex summation method. With this model we analyze the control characteristics and propose the design considerations of high speed rolling missile with one axis control fin using PNG law in conjuntion with a seeker signal.

• Journal of Advanced Marine Engineering and Technology
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• 제32권1호
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• pp.137-146
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• 2008

Nd:YAG pulse laser welding of stainless steel plate was simulated to find welding condition by using commercial finite element code MARC. Due to geometric symmetry, a half model of AISI 304 stainless steel plate was considered and user subroutines were applied to boundary condition for the heat transfer. Material properties such as conductivity, specific heat, mass density and latent heat were given as a function of temperature. As results, Three dimensional heat source model for pulse laser beam conditions of butt welding has been designed by the comparison between the finite element analysis results and experimental data on AISI 304 stainless steel plate. Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 추계 학술대회논문집
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• pp.71-76
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• 1999

The base flow regions of a three-body sounding rocket containing multiple exhaust plumes were numerically investigated in three dimensions for a free stream Mach number of 2.7 at flight altitude 18.5 km. The flowfields were calculated using the full compressible Navier-Stokes equations with an one-equation turbulence model of Baldwin-Earth. The present calculations were executed based upon a chemically frozen, single perfect gas model assumption. Due to the symmetry of the three-body rocket of each single nozzle, only one fourth of the computational domain was considered for the analysis. The results indicate that a babe heating effect is not considerable due to the small expansion of the plumes. In the base, however, a low speed recirculating flow dominates the region.

• 대한기계학회논문집B
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• 제27권3호
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• pp.311-318
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• 2003

The present work evaluates the effects of mixing vane shape on the flow structure and heat transfer downstream of mixing vane in a subchannel of fuel assembly. by obtaining velocity and pressure fields. turbulent intensity. flow-mixing factors. heat transfer coefficient and friction factor using three-dimensional RANS analysis. Four different shapes of mixing vane. which were designed by the authors were tested to evaluate the performances in enhancing the heat transfer. Standard k-$\varepsilon$ model is used as a turbulence closure model. and. periodic and symmetry conditions are set as boundary conditions. The flow blockage ratio is kept constant. but the twist angle of mixing vane is changed. The results with three turbulence models were compared with experimental data.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.641-645
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• 2002

In case of aluminum-cased battery, The ratio of height and base of square is generally above the ten times, square-shaped and problem of non-axis symmetry. It is typical model to set up the analysis method of finite element. The reliable analysis of finite element method is suggested, which is used to investigate the possibility that multi-stage deep drawing and ironing used currently is replaced by backward impact extrusion favorable in the respect of cost production and productivity. The influence of parameter was analyzed and compared, which was considered to analyze the process of large deformation plasticity such as extrusion. Die and billet was made as the same shape of finite element model. The results of experiment show good forming without the rupture and wrinkles with the optimum velocity 100mm/sec obtained by analysis.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2002년도 춘계 학술대회논문집
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• pp.79-87
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• 2002

The present work analyzed the effect of mixing vane shape on the flow structure and heat transfer downstream of mixing vane in a subchannel of fuel assembly, by obtaining velocity and pressure fields, turbulent intensity, flow-mixing factors, heat transfer coefficient and friction factor using three-dimensional RANS analysis. NJl5, NJ25, NJ35, NJ45, which were designed by the authors, were tested to evaluate the performances in enhancing the heat transfer. Standard $\kappa-\epsilon$ model is used as a turbulence closure model, and, periodic and symmetry conditions are set as boundary conditions. The flow blockage ratio is kept constant, but the twist angle of mixing vane is changed. The results with three turbulence models( $\kappa-\epsilon$, $\kappa-\omega$, RSM) were compared with experimental data.