• 대한의용생체공학회:의공학회지
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• 제19권5호
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• pp.495-502
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• 1998

Y.C. Fung[1]에 의한 연조직의 점탄성에 관한 수학적 모델이론 (Fung's Quasi-linear vlscoelastic theory)을 이용하여 인간의 인두조직의 점탄성(vlscoelatlcity)특성을 측정하기 위하여 반복성하중(cyclic load) ,응력완화 (tensile stress relaxation), incremental load, 그리고 일축성인장 (uniaxial tensile) 시험 등을 실시하였다. 실험적으로 측정한 인두조직의 점탄성특성이 이미 조사된 다른 조직의 점탄성특성과 정량적으로 비교되었다. 인두조직의 점탄성특성의 정량화를 위하여 Y.C.Fung의 수학적 모델이 적용되었는데 응력완화(tensile stress relaxation) 시험 측정결과로부터 도출된 표준화된 응력완화(reduced stress relaxation)함수 G(t)와 일축성인장(uniaxial tensile)시험에서 도출된 탄성반응(elastic response)함수 5(t)를 이용하여 시간에 따른 응력의 궤적을 산출하여 이를 반복성 하중(cyclic load)실험에서 측정된 결과와 비교, 분석하였다. 이러한 인두조직의 점탄성특성에 관한 연구결과는 향후 유한요소를 이용한 인두의 생체역학적 모델의 기본 데이터로 이용될 수 있다.

• 한국광학회지
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• 제27권6호
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• pp.223-228
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• 2016

액정과 같은 단축 이방성 분자들의 정렬 정도에 따라 달라지는 복굴절으로부터 상대 복굴절 ${\Delta}n_{rel}$를 구하고 ${\Delta}n_{rel}$과 방향질서변수(orientational order parameter) S의 관계를 탐색하였다. 무질서한 분포를 하고 있는 경우를 포함하여 액정의 정렬정도를 달리 표현할 수 있는 분포함수를 도입하고 이 분포함수를 사용하여 질서변수 S가 0부터 1까지 변하도록 액정분자들의 정렬정도를 달리하며 ${\Delta}n_{rel}$과 S를 수치계산 하였다. 이 계산 결과로부터 s와 ${\Delta}n_{rel}$는 $S=(1+a){\Delta}n_{rel}-a{\Delta}n^2_{rel}$와 같이 준선형적인 관계를 만족하며 a는 $n_o{\frac{{\Delta}n}{4}}$으로 근사할 수 있음을 확인하였다. 또한 복굴절으로부터 Vuks의 방법에 따라 구한 분자분극의 이방성과 Neugebauer의 방법에 따라 구한 분자분극의 이방성이 각각 질서변수 S와 또 다른 준선형 관계식들을 따름을 보였다.

• 한국통신학회논문지
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• 제27권3C호
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• pp.234-240
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• 2002

AlGaAs/InGaAs/GaAs HBT를 이용하여 준밀리미터파 광대역 무선망(BWLL) 시스템의 가입자용 장치에 사용 가능한 전력증폭기를 개발하였다. 베이스 접지 HBT 소자의 비선형 등가 회로를 추출하여 선형 및 비선형 회로 시뮬레이션을 통하여 출력 전력 정합 회로를 갖는 증폭기를 설계하였으며, 이를 기초로 하여 세라믹 기판 위의 스텁을 이용하여 하이브리드 형태로 증폭기를 구현하였다. 제작된 전력증폭기는 24.4 GHz에서 최대 포화 출력 25.5 dBm, 35%의 전력 부가 효율을 얻었으며, 24.8 GHz에서는 7.5 dB의 최대 선형 이득을 얻었다. 또한, 24.25 GHz∼24.75 GHz의 주파수 대역에서 22 dBm 이상의 포화 출력 전력과 25% 이상의 전력 부가 효율을 얻었다.

• 충청수학회지
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• 제24권1호
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• pp.19-34
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• 2011

A bounded linear operator T on a complex Banach space X is said to have property (I) provided that T has Bishop's property (${\beta}$) and there exists an integer p > 0 such that for a closed subset F of ${\mathbb{C}}$ ${X_T}(F)={E_T}(F)=\bigcap_{{\lambda}{\in}{\mathbb{C}}{\backslash}F}(T-{\lambda})^PX$ for all closed sets $F{\subseteq}{\mathbb{C}}$, where $X_T$(F) denote the analytic spectral subspace and $E_T$(F) denote the algebraic spectral subspace of T. Easy examples are provided by normal operators and hyponormal operators in Hilbert spaces, and more generally, generalized scalar operators and subscalar operators in Banach spaces. In this paper, we prove that if T has property (I), then the quasi-nilpotent part $H_0$(T) of T is given by $$KerT^P=\{x{\in}X:r_T(x)=0\}={\bigcap_{{\lambda}{\neq}0}(T-{\lambda})^PX$$ for all sufficiently large integers p, where ${r_T(x)}=lim\;sup_{n{\rightarrow}{\infty}}{\parallel}T^nx{\parallel}^{\frac{1}{n}}$. We also prove that if T has property (I) and the spectrum ${\sigma}$(T) is finite, then T is algebraic. Finally, we prove that if $T{\in}L$(X) has property (I) and has decomposition property (${\delta}$) then T has a non-trivial invariant closed linear subspace.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1998년도 The Third Asian Fuzzy Systems Symposium
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• pp.118-121
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• 1998

In this paper, we propose another paradigm(QNBP) to be capable of overcoming Limitations of the traditional backpropagation(SDBP). QNBPis based on the method of Quasi -Newton(variable metric) with the nomalized direction vectors and computes step size through the linear search. Simulation results showed that QNBP was definitely superior to both the stochasitc SDBP and the deterministic SDBP in terms of accuracy and rate of convergence and might sumount the problem of local minima. and there was no different between DFP+SR1 and BFGS+SR1 combined algrothms in QNBP.

• 대한수학회보
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• 제47권4호
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• pp.777-785
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• 2010

Let X be a linear space and Y be a complete quasi p-norm space. We will show that for each function f : X $\rightarrow$ Y, which satisfies the inequality ${\parallel}{\Delta}_x^nf(y)\;-\;n!f(x){\parallel}\;{\leq}\;\varphi(x,y)$ for suitable control function $\varphi$, there is a unique monomial function M of degree n which is a good approximation for f in such a way that the continuity of $t\;{\mapsto}\;f(tx)$ and $t\;{\mapsto}\;\varphi(tx,\;ty)$ imply the continuity of $t\;{\mapsto}\;M(tx)$.

• Fibers and Polymers
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• 제2권1호
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• pp.140-143
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• 2001

To better understand the formation of necking in drawing processes of fibers, strain distributions during drawing processes have been analyzed. For simplicity, one-dimensional incompressible steady flow at a constant temperature was assumed and quasi-static model was used. To describe mechanical properties of solid polymers, non-linear visco-plastic material properties were assumed using the power law type hardening and rate-sensitive equation. The effects of various parameters on the neck formation were matematically analyzed. As material property parameters, strain-hardening parameter, visco-elastic coefficient and strain-rate sensitivity were considered and, for process parameters, the drawing ratio and the process length were considered. It was found that rate-insensitive materials do not reach a steady flow state and the rate-sensitivity plays a key role to have a steady flow. Also, the neck formation is mainly affected by material properties, especially for the quasi-static model. If the process length changes, the strain distribution was found to be proportionally re-distributed along the process line by the factor of the total length change.

• Journal of applied mathematics & informatics
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• 제27권5_6호
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• pp.1177-1194
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• 2009

In this paper we establish the general solution of the functional equation f(2x+y)+f(x-2y)=2f(x+y)+2f(x-y)+f(-x)+f(-y) and investigate the Hyers-Ulam-Rassias stability of this equation in quasi-Banach spaces. The concept of Hyers-Ulam-Rassias stability originated from Th. M. Rassias' stability theorem that appeared in his paper: On the stability of the linear mapping in Banach spaces, Proc. Amer. Math. Soc. 72 (1978), 297-300.

• 대한수학회보
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• 제45권3호
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• pp.587-600
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• 2008

In this paper we establish the general solution and investigate the Hyers-Ulam-Rassias stability of the following functional equation in quasi-Banach spaces. $${\sum\limits_{{{1{\leq}i<j{\leq}4}\limits_{1{\leq}k<l{\leq}4}}\limits_{k,l{\in}I_{ij}}}\;f(x_i+x_j-x_k-x_l)=2\;\sum\limits_{1{\leq}i<j{\leq}4}}\;f(x_i-x_j)$$ where $I_{ij}$={1, 2, 3, 4}\backslash${i, j} for all $1{\leq}i<j{\leq}4$. The concept of Hyers-Ulam-Rassias stability originated from Th. M. Rassias' stability theorem that appeared in his paper: On the stability of the linear mapping in Banach spaces, Proc. Amer. Math. Soc.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.44.1-44.1
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• 2009

Identification of wave characteristics during current disruption events in the near-Earth geomagnetic tail region (~ 10 RE) is important to understand the substorm onset mechanism. In this paper, linear stability analysis in the ion-cyclotron grequency range, considering temperature anisotropy and cross-field flow is presented. It is found that the ion-cyclotron drift waves propagating in a quasi-perpendicular direction with respect to the ambient magnetic field are characterized by low frequencies ($\omega$ < $0.5{\Omega}ci$), while quasi-parallel waves have frequencies close to the ion-cyclotron frequency ($\omega{\sim}{\Omega}ci$). This finding is consistent with the observation by THEMIS spacecraft of a current disruption event in which a similar high- and low-frequency band structure is also present [A. T. Y. Lui, et al., J. Geophys. Res. 113, A00C06 (2008)]. It is also found that the quasi-perpendicular mode is excited by the ion cross-field flow.