• 전기전자학회논문지
• /
• 제18권4호
• /
• pp.593-602
• /
• 2014

인공신경망회로 목표 중의 하나는 최소한의 회로구성으로 구현가능함수를 가능한 많게 하는데 있다. 본 논문은 인공신경망회로의 가장 기본이 되는 하나의 입력노드와 하나의 출력노드, 그리고 입출력에 다단(multi-level)값을 갖는 단층(입출력 2 layer) 다단 코어넷(CoreNet)을 제안하고 그 처리 용량을 구하였고, 무게값 공간에서 구현 가능한 함수와 각 무게값 좌표(${\omega}$,${\theta}$)를 계산으로 구하여 한 함수의 구현 가능 여부를 알 수 있게 하였다. 또 입력 단계(level)값 설정 방법으로 cot(${\sqrt{x}}$)을 제안하였다. 제안된 p단 입력과 q단 출력을 갖는 코어넷의 처리용량(구현 가능한 함수의 수)은 $a_{p,q}={\frac{1}{2}}p(p-1)q^2-{\frac{1}{2}}(p-2)(3p-1)q+(p-1)(p-2)$임을 유도 증명하였다. 시뮬레이션으로 5단(level) 입력 값과, 6단 출력 값을 갖는 1(5)-1(6) 모델을 분석한 결과, cot(${\sqrt{x}}$) 입력 레벨링법에서 총 246가지의 함수가 구현가능 함을 보였다. 이 모델의 시뮬레이션 결과에서는 최대 219개의 함수가 수렴(구현 가능)하였고, 구현가능 함수 중에서 나머지 수렴되지 않은 27개의 함수는 무게값 공간에서 무게값 좌표를 계산하여 구현 가능함을 보였다. 이는 앞에서 제시된 코어넷 처리용량 $a_{5,6}(=246)$에 의한 계산 값과 일치하였다. 무게값 공간에서, 구현 가능한 함수가 차지하는 영역의 함수번호 매김 방법도 제시하여 구현 가능함수의 번호도 알 수 있도록 하였다.

• Steel and Composite Structures
• /
• 제27권2호
• /
• pp.201-216
• /
• 2018

In this paper, three-dimensional (3D) elasticity theory in conjunction with nonlocal strain gradient theory (NSGT) is developed for mechanical analysis of anisotropic nanoparticles. The present model incorporates two scale coefficients to examine the mechanical characteristics much accurately. All the elastic constants are considered and assumed to be the functions of (r, ${\theta}$, ${\varphi}$), so all kind of anisotropic structures can be modeled. Moreover, all types of functionally graded spherical structures can be investigated. To justify our model, our results for the radial vibration of spherical nanoparticles are compared with experimental results available in the literature and great agreement is achieved. Next, several examples of the radial vibration and wave propagation in spherical nanoparticles including nonlocal strain gradient parameters are presented for more than 10 different anisotropic nanoparticles. From the best knowledge of authors, it is the first time that 3D elasticity theory and NSGT are used together with no approximation to derive the governing equations in the spherical coordinate. Moreover, up to now, the NSGT has not been used for spherical anisotropic nanoparticles. It is also the first time that all the 36 elastic constants as functions of (r, ${\theta}$, ${\varphi}$) are considered for anisotropic and functionally graded nanostructures including size effects. According to the lack of any common approximations in the displacement field or in elastic constant, present theory can be assumed as a benchmark for future works.

• 천문학회지
• /
• 제50권3호
• /
• pp.61-70
• /
• 2017

We study the angular correlation function of bright ($K_s{\leq}19.5$) Extremely Red Objects (EROs) selected in the Subaru GTO 2$deg^2$ field. By applying the color selection criteria of $R-K_s$ > 5.0, 5.5, and 6.0, we identify 9055, 4270, and 1777 EROs, respectively. The number density is consistent with similar studies on the optical - NIR color selected red galaxies. The angular correlation functions are derived for EROs with different limiting magnitude and different $R-K_s$ color cut. When we assume that the angular correlation function $w({\theta})$ follows a form of a power-law (i.e., $w({\theta})=A{\theta}^{-{\delta}}$), the value of the amplitude A was larger for brighter EROs compared to the fainter EROs. The result suggests that the brighter, thus more massive high-redshift galaxies, are clustered more strongly compared to the less massive galaxies. Assuming that EROs have redshift distribution centered at ~ 1.1 with ${\sigma}_z=0.15$, the spatial correlation length $r_0$ of the EROs estimated from the observed angular correlation function ranges ${\sim}6-10h^{-1}Mpc$. A comparison with the clustering of dark matter halos in numerical simulation suggests that the EROs are located in most massive dark matter halos and could be progenitors of $L_{\ast}$ elliptical galaxies.

• 대한수학회보
• /
• 제48권3호
• /
• pp.655-672
• /
• 2011

Let $C^r$[0,t] be the function space of the vector-valued continuous paths x : [0,t] ${\rightarrow}$ $R^r$ and define $X_t$ : $C^r$[0,t] ${\rightarrow}$ $R^{(n+1)r}$ and $Y_t$ : $C^r$[0,t] ${\rightarrow}$ $R^{nr}$ by $X_t(x)$ = (x($t_0$), x($t_1$), ..., x($t_{n-1}$), x($t_n$)) and $Y_t$(x) = (x($t_0$), x($t_1$), ..., x($t_{n-1}$)), respectively, where 0 = $t_0$ < $t_1$ < ... < $t_n$ = t. In the present paper, with the conditioning functions $X_t$ and $Y_t$, we introduce two simple formulas for the conditional expectations over $C^r$[0,t], an analogue of the r-dimensional Wiener space. We establish evaluation formulas for the analogues of the analytic Wiener and Feynman integrals for the function $G(x)=\exp{{\int}_0^t{\theta}(s,x(s))d{\eta}(s)}{\psi}(x(t))$, where ${\theta}(s,{\cdot})$ and are the Fourier-Stieltjes transforms of the complex Borel measures on ${\mathbb{R}}^r$. Using the simple formulas, we evaluate the analogues of the conditional analytic Wiener and Feynman integrals of the functional G.

• Kyungpook Mathematical Journal
• /
• 제52권4호
• /
• pp.413-431
• /
• 2012

Let $C^r[0,t]$ be the function space of the vector-valued continuous paths $x:[0,t]{\rightarrow}\mathbb{R}^r$ and define $X_t:C^r[0,t]{\rightarrow}\mathbb{R}^{(n+1)r}$ and $Y_t:C^r[0,t]{\rightarrow}\mathbb{R}^{nr}$ by $X_t(x)=(x(t_0),\;x(t_1),\;{\cdots},\;x(t_{n-1}),\;x(t_n))$ and $Y_t(x)=(x(t_0),\;x(t_1),\;{\cdots},\;x(t_{n-1}))$, respectively, where $0=t_0$ < $t_1$ < ${\cdots}$ < $t_n=t$. In the present paper, using two simple formulas for the conditional expectations over $C^r[0,t]$ with the conditioning functions $X_t$ and $Y_t$, we establish evaluation formulas for the analogue of the conditional analytic Fourier-Feynman transform for the function of the form $${\exp}\{{\int_o}^t{\theta}(s,\;x(s))\;d{\eta}(s)\}{\psi}(x(t)),\;x{\in}C^r[0,t]$$ where ${\eta}$ is a complex Borel measure on [0, t] and both ${\theta}(s,{\cdot})$ and ${\psi}$ are the Fourier-Stieltjes transforms of the complex Borel measures on $\mathbb{R}^r$.

• 대한방사선기술학회지:방사선기술과학
• /
• 제39권2호
• /
• pp.163-170
• /
• 2016

강내 근접치료(intracavitary brachytherapy)에서 다른 고선량률 $^{192}Ir$ 선원의 기하학적 특성으로 인한 선량분포의 차이를 비교 및 분석하였다. 본 연구에서는 Nucletron사에서 제작된 microSelectron-v1 (classic) 선원이 2014년 이후로 판매가 종료되면서 새로운 microSelectron-v2 (new) 선원과의 선량분포 차이를 치료계획시스템을 이용하여 비교 및 분석하였다. 두 선원에서 획득된 선량분포를 비교하기 위하여 point A, point B, ICRU 방광 및 직장의 기준점을 분석인자로 사용하였다. 선원과 가까운 거리에서는 microSelectron-v2 선원의 반경선량함수(radial dose function)가 microSelectron-v1 선원 보다 최대 2.6% 높았다. 선원으로부터 거리가 1, 3, 그리고 5 cm의 비등방성함수(anisotropy function)는 $20^{\circ}$ <${\theta}$ < $165^{\circ}$에서 두 선원 간에 2% 이내에서 잘 일치하였다. 다만, 거리가 0.25 cm에서 ${\theta}$ < $20^{\circ}$ 구간에서는 두 선원 간 최대 27%의 차이를 보였으며, 거리가 1, 3, 그리고 5 cm에서 ${\theta}$ > $170^{\circ}$ 구간에서는 두 선원 간 각각 13%, 10%, 그리고 7% 차이를 보였다. 두 선원을 이용한 치료계획에서는 point A, point B, 방광에 들어가는 선량의 차이는 없었으며, ICRU에서 권고하는 직장에 들어가는 선량 지점은 microSelectron-v2 선원이 microSelectron-v1선원보다 평균 0.65%, 최대 약 1%까지 높게 평가되었다. 두 선원 간의 선량분포 차이는 주로 선원의 기하학적 차이와 선원을 감싸고 있는 스테인리스 스틸(stainless steel) 캡슐의 두께 차이로 발생되지만 두 선원에서의 선량분포 차이는 1% 이내이므로 새로운 모델의 선원으로 교체하여 사용하더라도 근접치료에서의 선량분포는 임상적으로 크지 않을 것으로 판단된다.

• Journal of Power Electronics
• /
• 제14권2호
• /
• pp.351-361
• /
• 2014

The discrete torque generation mechanism and inherently nonlinear magnetic characterization of switched reluctance motors lead to unacceptable torque ripples and limit the application of these motors. In this study, a phase current profiling technique and torque sharing function are proposed in consideration of magnetic saturation effects and by minimizing power loss in the commutation area between the adjacent phases. Constant torque trajectories are considered in incoming and outgoing phase current planes based on nonlinear T-i-theta curves obtained from experimental measurements. Optimum points on constant torque trajectories are selected by improving drive efficiency and minimizing copper loss in each rotor position. A novel analytic invertible function is introduced to express phase torque based on rotor position and its corresponding phase current. The optimization problem is solved by the proposed torque function, and optimum torque sharing functions are derived. A modification method is also introduced to enhance the torque ripple-free region based on simple logic rules. Compared with conventional torque sharing functions, the resultant reference current from the proposed method has less peak and effective values and exhibits lower copper loss. Experimental and simulation results from a four-phase 4 KW 8/6 SRM validate the effectiveness of the proposed method.

• 한국자기학회지
• /
• 제8권2호
• /
• pp.49-56
• /
• 1998

본 연구에서는 비등방성 에너지가 Ksin2$\theta$로 표현되는 일축 비등방성 자성체의 자기행동을 기술하는 닫힌형태 (closed-form)의 양함수들 (explicit functions)을 구하였다. 인가 자기마당, 포화 자기화량, 비등방성 에너지뿐만아니라, 자기화역전 기구에도 의존하는 돌림형, 자기화방향, 자기화갑수율을 나타내는 닫인형태의 양함수들과 결정하였다. 개발된 단힌형태의 양함수들과 실험적으로 측정 가능한 물리량들에 대한 그들의 편미분 함수들은 최소제곱맞춤법에 의한 포화 자기화량 및 비등방성 측정법의 개발, 자성 집합체의 분산된 자기적 특성 측정법의 개발 뿐만 아니라, 자기이론 계산에도 큰 기여를 하리라 사료된다.

• 설비공학논문집
• /
• 제15권10호
• /
• pp.860-869
• /
• 2003

Design optimization of the heat sink with 7${\times}$7 square pin-fins is performed numerically using the Computational Fluid Dynamics (CFD) and the Computer Aided Optimization (CAO). In the pin-fins heat sink, the optimum design variables for fin height (h), fin width (w), and fan-to-heat sink distance (c) can be achieved when the thermal resistance ($\theta$$_{j}$) at the junction and the overall pressure drop ($\Delta$p) are minimized simultaneously. To complete the optimization, the finite volume method for calculating the objective functions, the BFGS method for solving the unconstrained non-linear optimization problem, and the weighting method for predicting the multi-objective problem are used. The results show that the optimum design variable for the weighting coefficient of 0.5 are as follows: w=4.653 mm, h=59.215 mm, and c=2.667 mm. In this case, the objective functions are predicted as 0.56K/W of thermal resistance and 6.91 Pa of pressure drop. The Pareto optimal solutions are also presented.re also presented.d.

• Animal cells and systems
• /
• 제2권1호
• /
• pp.65-69
• /
• 1998

The hippocampus and prefrontal cortex are regarded as the highest-order association cortices. The hippocampus has been proposed to store "cognitive maps" of external environments, and the prefrontal cortex is known to be involved in the planning of behavior, among other functions. Considering the prominent functional roles played by these structures, it is not surprising to find direct monosynaptic projections from the hippocampus to the prefrontal cortex. Rhythmic stimulation of this projection patterned after the hippocampal EEG theta rhythm induced stable long-term potentiation of field potentials in the prefrontal cortex. Comparison of behavioral correlates of hippocampal and prefrontal cortical neurons during an a-arm radial maze, working memory task shows a striking contrast. Hippocampal neurons exhibit clear place-specific firing patterns, whereas prefrontal cortical neurons do not show spatial selectivity, but are correlated to different stages of the behavioral task. These data lead to the hypothesis that the role of hippocampal projection to the prefrontal cortex is not to impose spatial representations upon prefrontal activity, but to provide a mechanism for learning the spatial context in which particular behaviors are appropriate.propriate.