• 터널과지하공간
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• 제31권6호
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• pp.480-493
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• 2021

일반화된 Hoek-Brown(GHB) 파괴기준식은 GSI 값을 이용하여 현장 암반조건이 반영된 강도정수 값을 효과적으로 결정할 수 있기 때문에 암반공학 분야에서 표준 파괴기준식의 하나로 인식되고 있다. 그러나 GHB 파괴기준식의 비선형적 형태는 이 식의 수학적 취급을 어렵게 하고 이 식의 적용 범위를 제약하는 요인이 되고 있다. GHB 파괴기준식의 이러한 단점을 극복하기 위한 노력의 하나로 Taylor 다항함수 근사원리를 적용하여 파괴 최대주응력에 대응하는 최소주응력을 근사적으로 계산할 수 있는 명시적, 해석적 수식을 유도하였다. 근사식으로 구한 최소주응력과 수치해석적으로 계산한 정해를 비교하여 이 연구에서 유도한 최소주응력 근사식의 정확성을 검증하였다. 연구결과의 응용사례를 제시하기 위해 근사 최소주응력 계산식을 활용하여 GHB 암반에 굴착된 원형터널 주변에 예상되는 소성영역의 등가 마찰각과 등가 점착력을 계산하였다. 소성영역의 등가 Mohr-Coulomb 강도정수를 정밀하기 산정하기 위해서는 mi, GSI, 초기지압의 크기를 동시에 고려하는 것이 중요한 것으로 나타났다.

• 대한기계학회논문집
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• 제10권1호
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• pp.102-109
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• 1986

본 연구에서는 앞의 여러 연구자들이 시도한 3차원 연쇄기구의 운동해석법을 비교 검토하고, 이중 기호방정식을 이용하여 3차원 연쇄기구의 운동해석을 일반화 하고져 한다. 또 품질향상, 대량생산(mass production) 및 생산가 절하를 위해 만족시키기 위해, 기본해석모델인2차원 연쇄기구에서 3차원연쇄기구로 정밀화 하면서, 가능한 모든 3차원 연쇄기구의 복잡화 되고 있는 현대 기계의 운동요구를 만족시키기 위해, 기본해석모델인 2차원 연쇄기구에서 3차원연쇄기구로 정밀화 하면서, 가능한 모든 3차원 연쇄기구의 운동을 해석 하기 위한 일반해석법을 개발하므로써 해석을 일반화 시키고, 그것을 컴퓨터로 시뮬레이션하여 운동해석을 신빙성있고 신속하게 수행토록 하며, 컴퓨터 결과를 실제모형 즉 구면 4-R 연쇄기구, R-S-S-R 기구 및 3C-R 기구등을 제작하여,실제결과와 비교 검토하므로써 개발된 일반운동해석법의 타당성을 실험적으로 입증 비교 검토하므로써 일반운동해석법의 타당성을 실험적으로 입증하려 한다.

• 한국통신학회논문지
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• 제25권7A호
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• pp.967-977
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• 2000

본 논문은 도립전자 시스템을 LFR(Linear Fractional Representation)로 표현하여 얻어진 일반화 제어대상에 대하여 혼합 ${H_2}/H_{\infty}$ 제어기법을 적용한다. 먼저, 일반화 제어대상을 얻기 위하여, LFR로 표현한 도립진자의 선형 모델을 유도한다. LFR에서 고려한 구체적인 불확실성은 3개의 비선형 성분과 1개의 진자질량 불확실성이다. 유도된 선형모델에 하중함수를 더하여 LFR 모델을 확대함으로써 일반화된 제어대상을 얻는다. 다음으로, 이 일반화 제어대상에 대하여 혼합 ${H_2}/H_{\infty}$ 제어기를 설계한다. 혼합 ${H_2}/H_{\infty}$ 제어기 설계를 위해서 LMI(Linear Matrix Inequalities) 기법을 이요한다. 설계된 혼합 ${H_2}/H_{\infty}$ 제어기의 제어성능과 강건 안정성을 평가하기 위해서 모의실험과 실물실험을 통하여 $H_{\infty}$ 제어기와 비교한다. 실험결과, $H_{\infty}$ 제어때 보다 적은 피드백 정보만으로도 혼합 ${H_2}/H_{\infty}$ 제어기는 도립진자의 진자각도 측면에서 $H_{\infty}$ 제어기보다 나은 강건 안정성과 제어 성능을 보인다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.792-795
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• 2004

Despite is product that ship, vehicles, development equipment and Metal Bearing for plant equipment that is mass-produced by present domestic companies Cast White Metal Lining Bearing that is Bimetal Bearing standing 2 generation is accomplishing master and servant and this is foreseen to be used widely on industry whole in hereafter but Cast White Metal Bearing need minuteness processing, while price competitive power is depending on income from superior another thing area than itself manufacture already in advanced nation to lowdown that the technique is generalized widely, when take into account technology change aspect of industrial technology developing country, Go added value creation by deepening of price competition is judged to be difficult hereafter. Because domestic production and supply are wholly lacking almost in Metal Bearing Cladding that take advantage of these technology, Data-base about connection technology is weak with technique and Know-How for product. This research unites Back Steel and Aluminium Alloy different kind metal and make the Clad river studying technology about union of Gogangseong Dacheung metal bearing hereupon.

• Structural Engineering and Mechanics
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• 제25권2호
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• pp.181-200
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• 2007

A decoupling technique for simulating near-field wave motions in two-phase media is introduced in this paper. First, an equivalent but direct weighted residual method is presented in this paper to solve boundary value problems more explicitly. We applied the Green's theorem for integration by parts on the equivalent integral statement of the field governing equations and then introduced the Neumann conditions directly. Using this method and considering the precision requirement in wave motion simulation, a lumped-mass FEM for two-phase media with clear physical concepts and convenient implementation is derived. Then, considering the innate attenuation character of the wave in two-phase media, an attenuation parameter is introduced into Liao's Multi-Transmitting Formula (MTF) to simulate the attenuating outgoing wave in two-phase media. At last, two numerical experiments are presented and the numerical results are compared with the analytical ones demonstrating that the lumped-mass FEM and the generalized MTF introduced in this paper have good precision.

• 대한수의학회지
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• 제56권2호
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• pp.121-123
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• 2016

A 7-year-old castrated male domestic short-hair cat presented with anorexia, constipation, depression, and voice alteration. Physical and neurological examinations revealed hyperthermia ($40.5^{\circ}C$), ventroflexion of the neck, reduced responses to external stimuli, generalized muscle weakness, and exercise intolerance. Thoracic radiographs revealed the presence of a cranial mediastinal mass. The history, clinical signs, and other examination results were compatible with acquired myasthenia gravis (MG). Acetylcholine receptor (AChR) antibody titers were determined to confirm MG and the serum AChR antibody concentration was 1.24 nmol/L (reference interval, < 0.3 nmol/L). This is the first diagnosis of acquired MG in a cat in Korea.

• Journal of the Korean Physical Society
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• 제73권10호
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• pp.1410-1419
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• 2018

A skier's motion was analyzed by a simple model consist of point mass m and a single rod connected to a single ski plate. We studied the conditions for the stable ski turn as functions of the linear velocity and the radius of the turn. The solutions for the stable ski turn in our model do not require any extra skier's movement to complete a stable circular turn. The solution may then give the skier the most comfortable skiing method without any active movement to control the ski. The generalized force supporting the point mass from the ski plate was calculated. We obtained the force from the ground (rebound force) without any geometrical structure of the ski plate. Adding an active movement to the direction of the ski plate, the conditions for the stable ski turn were also analyzed. Our result gives some insight for the skier who wants to develop technique.

• Structural Engineering and Mechanics
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• 제7권3호
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• pp.259-276
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• 1999

An analytical solution for the shape functions of a beam segment supported on a generalized two-parameter elastic foundation is derived. The solution is general, and is not restricted to a particular range of magnitudes of the foundation parameters. The exact shape functions can be utilized to derive exact analytic expressions for the coefficients of the element stiffness matrix, work equivalent nodal forces for arbitrary transverse loads and coefficients of the consistent mass and geometrical stiffness matrices. As illustration, each distinct coefficient of the element stiffness matrix is compared with its conventional counterpart for a beam segment supported by no foundation at all for the entire range of foundation parameters.

• Structural Engineering and Mechanics
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• 제25권6호
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• pp.691-716
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• 2007

The purpose of the present work is to establish a method for predicting the location and depth of a crack in a circular cross section beam by only considering the frequencies of the cracked beam. An accurate knowledge of the material properties is not required. The crack location and size is identified by finding the point of intersection of pulsation ratio contour lines of lower vertical and horizontal modes. This process is presented and numerically validated in the case of a simply supported beam with various crack locations and sizes. If the beam has structural symmetry, the identification of crack location is performed by adding an off-center placed mass to the simply supported beam. In order to avoid worse diagnostic, it was demonstrated that a robust identification of crack size and location is possible if two tests are undertaken by adding the mass at the left and then right end of the simply supported beam. Finally, the pulsation ratio contour lines method is generalized in order to be extended to the case of rectangular cross section beams or more complex structures.

• Wind and Structures
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• 제11권2호
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• pp.153-178
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• 2008

Based on the empirical formulas for power spectra of generalized modal forces and local fluctuating wind forces in across-wind and torsional directions, the wind-induced lateral-torsional coupled response analysis of a representative rectangular tall building was conducted by setting various parameters such as eccentricities in centers of mass and/or rigidity and considering different torsional to lateral stiffness ratios. The eccentricity effects on the lateral-torsional coupled responses of the tall building were studied comprehensively by structural dynamic analysis. Extensive computational results indicated that the torsional responses at the geometric center of the building may be significantly affected by the eccentricities in the centers of mass and/or rigidity. Covariance responses were found to be in the same order of magnitude as the along-wind or across-wind responses in many eccentricity cases, suggesting that the lateral-torsional coupled effects on the overall wind-induced responses can not be neglected for such situations. The calculated results also demonstrated that the torsional motion contributed significantly to the total responses of rectangular tall buildings with mass and/or rigidity eccentricities. It was shown through this study that the framework presented in this paper provides a useful tool to evaluate the wind-induced lateral-torsional coupled responses of rectangular buildings, which will enable structural engineers in the preliminary design stages to assess the serviceability of tall buildings, potential structural vibration problems and the need for a detailed wind tunnel test.