• Structural Engineering and Mechanics
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• 제77권4호
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• pp.473-479
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• 2021

The propagation of plane waves in a linear, homogeneous and isotropic nonlocal generalized thermoelastic solid medium is considered in the framework of Lord and Shulman generalization. The governing field equations are formulated and specialized in a plane. Plane wave solutions of governing equations show that there exists three plane waves, namely, P, thermal and SV waves which propagate with distinct speeds. Reflection of P and SV waves from thermally insulated or isothermal boundary of a half-space is considered. The relevant boundary conditions are applied at stress free boundary and a non-homogeneous system of three equations in reflection coefficients is obtained. For incidence of both P and SV waves, the expressions for energy ratios of reflected P, thermal and SV waves are also obtained. The speeds and energy ratios of reflected waves are computed for relevant physical constants of a thermoelastic material. The speeds of plane waves are plotted against nonlocal parameter and frequency. The energy ratios of reflected waves are also plotted against the angle of incidence of P wave at a thermally insulated stress-free surface. The effect of nonlocal parameter is shown graphically on the speeds and energy ratios of reflected waves.

• Steel and Composite Structures
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• 제46권4호
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• pp.553-563
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• 2023

In the current research, the nonlinear free vibrations of curved pipes made of functionally graded (FG) carbon nanotube reinforced composite (CNTRC) materials are investigated. It is assumed that the FG-CNTRC curved pipe is supported on a three-parameter nonlinear elastic foundation and is subjected to a uniform temperature rise. Properties of the curved nanocomposite pipe are distributed across the radius of the pipe and are given by means of a refined rule of mixtures approach. It is also assumed that all thermomechanical properties of the nanocomposite pipe are temperature-dependent. The governing equations of the curved pipe are obtained using a higher order shear deformation theory, where the traction free boundary conditions are satisfied on the top and bottom surfaces of the pipe. The von Kármán type of geometrical non-linearity is included into the formulation to consider the large deflection in the curved nanocomposite pipe. For the case of nanocomposite curved pipes which are simply supported in flexure and axially immovable, the motion equations are solved using the two-step perturbation technique. The closed-form expressions are provided to obtain the small- and large-amplitude frequencies of FG-CNTRC curved pipes rested on a nonlinear elastic foundation in thermal environment. Numerical results are given to explore the effects of CNT distribution pattern, the CNT volume fraction, thermal environment, nonlinear foundation stiffness, and geometrical parameters on the fundamental linear and nonlinear frequencies of the curved nanocomposite pipe.

• Steel and Composite Structures
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• 제47권5호
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• pp.569-585
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• 2023

This paper proposes an efficient approach for the structural topology optimization of bi-directional functionally graded structures by incorporating popular radial basis functions (RBFs) into an implicit level set (ILS) method. Compared to traditional element density-based methods, a level set (LS) description of material boundaries produces a smoother boundary description of the design. The paper develops RBF implicit modeling with multiquadric (MQ) splines, thin-plate spline (TPS), exponential spline (ES), and Gaussians (GS) to define the ILS function with high accuracy and smoothness. The optimization problem is formulated by considering RBF-based nodal densities as design variables and minimizing the compliance objective function. A LS-RBF optimization method is proposed to transform a Hamilton-Jacobi partial differential equation (PDE) into a system of coupled non-linear ordinary differential equations (ODEs) over the entire design domain using a collocation formulation of the method of lines design variables. The paper presents detailed mathematical expressions for BiDFG beams topology optimization with two different material models: continuum functionally graded (CFG) and mechanical functionally graded (MFG). Several numerical examples are presented to verify the method's efficiency, reliability, and success in accuracy, convergence speed, and insensitivity to initial designs in the topology optimization of two-dimensional (2D) structures. Overall, the paper presents a novel and efficient approach to topology optimization that can handle bi-directional functionally graded structures with complex geometries.

• 복식
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• 제12권
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• pp.9-23
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• 1988

This study is on the costumes for Korean traditional play, Nong-ak(farm music), and intends to analyze their aesthetic features, laying emphasis on Pilbong Nong-ak, Im sil, Chollanam-do. About its origin there are many kinds of theories; for example, the theory of hoping stability, the theory of it being related with Buddhism, the theory of martial music, etc. Shamanic, Buddhist, and martical fators that support these theories are expressed through flags, bells, drums, Deograe (half-coats), Cheonrips (sang-mo, felf hats), go-kkals(peaked hats), colored lines called 'ga-sa', which are used in Nong-ak. The characteristic of the costumes used in Pilbong Nong-ak is that it keeps its conservativeness and the costumes of its members are various and splendid. For example, leader groups' black half coats, Changbu's and Hwa-dong's red and bule over coats are remarkable. Particpants wear gok-kal or cheonrip, trousers and half coats which are the basic costumes of Korean Hanbok, and wear blak half coats or blue vests and put blue, red, and yellow lines around them. The colors and knotting methods of those lines in this region are the same with those of chollawoo-do and Kyongi province, but different form those of Kongwon and Kyong-sang province using green, red, and yellow colors. This comparison of colors shows each region's preference of peculiar colors and those colors coincide with colors used in flags. The research on the aesthetic characteristics of Nong-ak clothes through each region's clothes tells us that these can be linear clothes which have expressiveness as stage clothes used in Madangori, the play which is performed in the field, and modern spatial formativeness. Those characteristics are as follows; 1. The expressions of a rhythmical and daring round line by turning a long line of sang-mo. 2. Various rhythms according to the attaching methods. 3. The expressions of thick, simple, and daring color lines. 4. Natural beauty of materials. 5. The popular simplicity and non-technicality 6. The beauty of five-direction colors, Oriental ideal colors Consequently in this study our national consciousness of beauty are examined through clothes. It is suggested that the aesthetic characteristics of Nong-ak clothes and ornaments should be effectively expressed, for this purpose. interests in participants' clothes should be increased in order to prevent the confusion of each region's features. Also it is necessary to improve color lines, their length, width, and knotting methods, and beautify instrument. Finally this study intends to bring the reappraisal about the art of Nong-ak clothes and its re-establishment in view of modern aesthetic consciousness.

• 디자인학연구
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• 제17권1호
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• pp.319-328
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• 2004

디지털 기술에 의한 커뮤니케이션 환경은 시간과 공간을 초월한 가상의 공간에서 다양한 사람과 빠르고 쉽게 정보교환과 의사전달을 가능하게 하였다. 그리고 이러한 가상의 공간에 익숙해진 Net 세대들은 선형적인 텍스트 중심의 문자언어에 만족하지 못하고 자기구별과 드러내기 욕구를 표출하기 위하여 컴퓨터를 도구로 한 기호를 만들어 사용하기 시작했다. 그 중에서도 이모티콘은 젊은 세대를 중심으로 대중문화와 디지털 커뮤니케이션 환경이 접목되어 만들어진 새로운 형태의 시각기호인 동시에 메시지에 포함되어 있는 발신자의 감정을 전달할 수 있는 감성기호로서 의미작용과 역할을 하고 있다. 본 연구는 미디어의 발달 및 커뮤니케이션 환경의 변화와 대중문화 현상에 대한 문헌조사를 통해 사회현상과 이모티콘에 대한 상호 연관성 및 생성배경을 알아보고, 기존 활용되고 있는 이모티콘에 대한 조사 및 분석을 통해 기호학적 측면에서 이모티콘의 기호로서 의미작용과 역할 등을 비교 분석하여 새로운 감성기호로서 이모티콘에 대한 활용 가능성을 파악하였다. 연구 결과 Net세대들의 언어로서 이모티콘은 일반적인 기호의 역할처럼 의미작용을 통해 상호교류가 이루어지는 비언어적 기호로서 역할을 가능하게 하는 기호로 활용할 될 수 있음을 알 수 있었고, 가상의 공간에서뿐만 아니라 광고, 포스터, 잡지 및 기업이미지를 전달하는 CI 등 각종 다양한 매체에서 감성을 전달하는 기호로서 효과적으로 메시지 전달할 수 있는 기호로서 폭넓게 활용될 수 있음을 알 수 있었다. 다만 아직까지 이모티콘은 다른 문자기호나 시각기호에 비하여 감성표현의 측면에서 강하지만, 보편적이고 대중적인 기호로 자리 잡기 위해서는 감정표현의 명확성, 메시지 이해의 편차, 메시지 내용전달의 효율성 등 보완점이 필요하다.

• 감성과학
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• 제20권2호
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• pp.161-170
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• 2017

감정은 학습능력, 행동, 판단력 등 삶의 많은 부분에 영향을 끼치므로 인간의 본질을 이해하는 데 중요한 역할을 한다. 그러나 감정은 개인이 느끼는 강도가 다르며, 시각 영상 자극을 통해 감정을 유도하는 경우 감정이 지속적으로 유지되지 않는다. 이러한 문제점을 극복하기 위하여 총 4가지 감정자극(행복, 슬픔, 공포, 보통) 시 생체신호(뇌전도, 맥파, 피부전도도, 피부 온도)를 획득하고, 이로부터 특징을 추출하여 분류기의 입력으로 사용하였다. 감정 패턴을 확률적으로 해석하여 다른 공간으로 매핑시켜주는 역할을 하는 Restricted Boltzmann Machine (RBM)과 Multilayer Neural Network (MNN)의 은닉층 노드를 이용하여 비선형적인 성질의 감정을 구별하는 Deep Belief Network (DBN) 감정 패턴 분류기를 설계하였다. 그 결과, DBN의 정확도(약 94%)는 오류 역전파 알고리즘의 정확도(약 40%)보다 높은 정확도를 가지며 감정 패턴 분류기로서 우수성을 가짐을 확인하였다. 이는 향후 인지과학 및 HCI 분야 등에서 활용 가능할 것으로 사료된다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.577-582
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• 2007

A variational formulation for plane elasticity problems is derived based on an isogeometric approach. The isogeometric analysis is an emerging methodology such that the basis functions in analysis domain arc generated directly from NURBS (Non-Uniform Rational B-Splines) geometry. Thus. the solution space can be represented in terms of the same functions to represent the geometry. The coefficients of basis functions or the control variables play the role of degrees-of-freedom. Furthermore, due to h-. p-, and k-refinement schemes, the high order geometric features can be described exactly and easily without tedious re-meshing process. The isogeometric sensitivity analysis method enables us to analyze arbitrarily shaped structures without re-meshing. Also, it provides a precise construction method of finite element model to exactly represent geometry using B-spline base functions in CAD geometric modeling. To obtain precise shape sensitivity, the normal and curvature of boundary should be taken into account in the shape sensitivity expressions. However, in conventional finite element methods, the normal information is inaccurate and the curvature is generally missing due to the use of linear interpolation functions. A continuum-based adjoint sensitivity analysis method using the isogeometric approach is derived for the plane elasticity problems. The conventional shape optimization using the finite element method has some difficulties in the parameterization of boundary. In isogeometric analysis, however, the geometric properties arc already embedded in the B-spline shape functions and control points. The perturbation of control points in isogeometric analysis automatically results in shape changes. Using the conventional finite clement method, the inter-element continuity of the design space is not guaranteed so that the normal vector and curvature arc not accurate enough. On tile other hand, in isogeometric analysis, these values arc continuous over the whole design space so that accurate shape sensitivity can be obtained. Through numerical examples, the developed isogeometric sensitivity analysis method is verified to show excellent agreement with finite difference sensitivity.

• Structural Engineering and Mechanics
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• 제69권3호
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• pp.257-268
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• 2019

Infills are as important members in structural design as beams, columns and braces. They have significant effect on structural behavior. Because of lots of variables in infills like material non-linear behavior, the interaction between frames and infill, etc., the infills performance during an earthquake is complicated, so have led designers do not consider the effect of infills in designing the structure. However, the experimental studies revealed that the infills have the remarkable effect on structure behavior. As if these effects ignored, it might occur soft-story phenomena, torsion or short-column effects on the structures. One simple and appropriate method for considering the infills effects in analyzing, is replacing the infills with diagonal compression strut with the same performance of real infill, instead of designing the whole infill. Because of too many uncertainties, codes and researchers gave many expressions that were not as the same as the others. The major intent of this paper is calculation the width of this diagonal strut, which has the most characteristics of infill. This paper by comprehensive on different parameters like the modulus of young or moment of inertia of columns presents a new formula for achieving the equivalent strut width. In fact, this new formula is extracted from about 60 FEM analyses models. It can be said that this formula is very efficient and accurate in estimating the equivalent strut width, considering the large number of effective parameters relative to similar relationships provided by other researchers. In most cases, the results are so close to the values obtained by the FEM. In this formula, the effect of out of plane buckling is neglected and this formula is used just in steel structures. Also, the thickness of infill panel, and the lateral force applied to frame are constant. In addition, this new formula is just for modeling the lateral stiffness. Obtaining the nearest response in analyzing is important to the designers, so this new formula can help them to reach more accurate response among a lot of experimental equations proposed by researchers.

• Journal of applied mathematics & informatics
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• 제41권1호
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• pp.51-70
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• 2023

The flow of an incompressible Ellis fluid in an inclined asymmetric channel, driven by peristaltic waves was studied under low Reynolds number and long wavelength assumptions. The wave on each side of the channel are assumed to be an infinite train of sinusoidal waves, both having the same constant wave speed and wavelength however, they vary in wave amplitude, channel half width and phase angle. We derived expressions for the axial and transverse velocities, volume flow rate, pressure rise per unit wavelength and streamlines. The effects of varying the wave amplitudes, the phase angle, the channel width, the angle of inclination of the channel as well as the fluid parameters on the flow were analyzed. Trapping conditions were determined and the presence of reflux highlighted using the streamlines for the necessary channel and fluid conditions. By varying the fluid parameters, changes in the fluid that deviated from the Newtonian case resulted in a reduction in the axial velocity in the neighborhood of the center of the channel and a simultaneous increase in the velocity at the periphery of the channel. A nonlinear relation was observed with the pressure rise and the volume flow rate. This nonlinear relation is more pronounced with an increase in the absolute value of the volume flow rate. For Newtonian fluids a linear relation exists between these two variables. The fluid parameters had little effects on the streamlines. However, variations of the wave amplitudes, volume flow, channel width and phase angle had greater effects on the streamlines and hence the trapped region.