• The Journal of the Acoustical Society of Korea
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• v.39 no.4
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• pp.270-278
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• 2020

In this paper, sound transmission of Micro-Perforated Plates (MPPs) installed in an impedance tube with a circular cross-section is described using an analytic method. Vibration of the plates is expressed in terms of an infinite series of modal functions, where modal function in the radial direction is given by the Bessel function. Under the plane wave assumption, a low frequency approximation is derived, and a formula for the sound transmission coefficient of multi-layered MPPs is presented using the transfer matrix method. The Sound Transmission Losses (STLs) of single and double MPPs are computed using the proposed method and compared with those done by the Finite Element Method (FEM), which shows an excellent agreement. As the perforation increases, the STL is degraded, since the STL becomes dominated by the perforation ratio rather than by vibration of the plate. The STL shows dips at natural frequencies as well as at the mass-spring-mass resonance frequency. The proposed model for the STL prediction in this study can be applied to an arbitrary number of MPPs, where each MPP may or may not have a perforation.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.75-81
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• 2008

Purpose: To develop a solar concentrator having the reflecting surface with the 2m class diameter. Methods: In order to make the reflecting surface for the solar concentrator, the shape of the reflecting surface sector is required. So, first, we induced the formula that can produce this shape. After that, using Delphi 6.0 language, we developed a program which uses this formula and produces the shape and the numerical data of the reflecting surface sector with the input variables such as the external diameter of the reflecting mirror, the reflecting mirror's radius of curvature at the paraxial range, the number of reflecting mirror sector, the size of the center hole of the reflecting mirror, and the interval of the output data. Results: This program, which was developed to produce the shape and the numerical data of the reflecting surface sector, enables us to see the shape of sector on the monitor and to save the numerical data files for the shape of sector. As a result, the user of this program can easily access the numerical data of the reflecting surface sector. Conclusions: Developing the program which produce the reflecting surface sector used to make the reflecting surface of the solar concentrator, we could succeed in making the prototype products by applying it to the development of the real solar concentrator with the diameter of the 2m class.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.4
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• pp.273-281
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• 2005

The weight of spectacles fined on is resolved into its components along the nose's slide plane and the normal to the nose plane where the nosepad is located. The equation and its numerical solution to determine the component force was derived as a function of splay angle ${\Psi}$, $sin{\Psi}$, $cos{\Psi}$, and $cot{\Psi}$, incorporated with ${\theta}$ and ${\Phi}$, the angles viewed from side and front of the face, respectively. Values of inclination angle ${\theta}$ and ${\Phi}$ could be obtained to fulfill the condition where the frictional force between the nose and pad is either greater than the normal pressure exerted by the spectacles on the nose. With the value of ${\theta}$ fixed the normal pressure increases as ${\Phi}$ increases. With ${\Phi}$ fixed, the effect of ${\theta}$ is the same.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.2
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• pp.9-15
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• 2004

We present a new unified analytical front surface potential model, which can accurately describe the transitions between the partially-depleted (PD) and the fully-depleted (FD) regimes with an analytical expression for the critical voltage V$_{c}$ delineating the PD and the FD region. It is valid in all regions of operation (from the sub -threshold to the strong inversion) and has the shorter calculation time than the iterative procedure approach. A charge sheet model based on the above explicit surface potential formulation is used to derive a single formula for the drain current valid in all regions of operation. Most of the secondary effects can be easily included in the charge sheet model and the model accurately reproduces various numerical and experimental results. No discontinuity in the derivative of the surface potential is found even though three types of smoothing functions are used. More importantly, the newly introduced parameters used in the smoothing functions do not strongly depend on the process parameter.

• Journal of Korea Water Resources Association
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• v.33 no.6
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• pp.711-723
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• 2000

Existing equations of bed load transport have large variations in their forms and adopt different variables so that it is very difficult to understand the characteristics of each equation. Different sets of measurement data have been employed for the development of various equations, and the comparison between them is completely dependent on the choice of the data for the verification. Several equations seem to have some defects in their basic assumptions. Various non-dimensional physical numbers directly associated with the mechanism of bed load transport are related with each other, and one of them is chosen for the unification of the form. Good ideas introduced in a certain equation are employed for the refinement of other equations. Then optimum values of empirical parameters have been determined by using the data collected by Brownlie(1981) and a new bed load equation has been developed, which is considered widely valid and relatively very accurate.curate.

• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.785-794
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• 2004

This paper describes a new refined truss modeling technique derived based on the well-known relationship of V=dM/dx=zdT/dx+Tdz/dx in a reinforced concrete beam subjected to combined shear and moment loads. The core of the model is that a new perspective on the shear behavior can be gained by considering the variation of the internal arm length along the span, so that the shear resistance mechanism can be expressed by the sum of two base components; arch action and beam action. The sharing ratio of these two actions is determined by accounting for the compatibility of deformation associated to the two actions. Modified Compression Field Theory and the tension-stiffening effect formula in CEB/FIP MC-90 are employed in calculating the deformations. Then the base equation of V=dM/dx has been numerically duplicated to form a new refined truss model.

• Journal of the Korean Data and Information Science Society
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• v.27 no.6
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• pp.1443-1452
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• 2016

In this paper, we study a sample design for survey on goodwill in retail properties to provide a protecting policy for small traders and tenants, to use basic data for a dispute case related to goodwill. Since goodwill in retail properties is occurred by individual rent company, we use the census on establishments from the Statistics Korea as population. First of all, we consider preferentially seven metropolitan cities in which there are more than half of population. Total sample size is decided as 8,000. We allocate the sample size for markets as stratum in each city using proportional formula and the sample size for industrial classifications in each market using root proportional formula. Also we compute survey weights and calculate estimators, standard errors and interval of estimators for each characteristic such as type of establishments and market in seven metropolitan cities.

• Korean Journal of Health Education and Promotion
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• v.12 no.2
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• pp.139-145
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• 1995

본 연구의 목적은 알코올 문제의 현황을 파악하고 효과적인 음주교육 방안을 모색하기 위한 것이다. 사회문화적 행위로서의 음주행동의 특징을 파악하고 음주로 인한 위해가 우리에게 미치는 영향을 파악하기 위한 것이다. 음주행동은 한 사람이 속한 사회의 문화와 관습이 허용하는 범위에 따라 그 사회가 공유하는 음주에 대한 태도나 가치의 영향을 받아 학습을 통해 습득하게 된다. 음주는 사망률, 이환율, 유산율, 범죄율 등에 막대한 영향을 끼치고 있으며 이로 인한 사회적 비용과 생명손실은 엄청난 것이다. 매스미디어를 통한 음주교육은 다른법적 제재와 병행될 때 효과적이다. 음주연령이나 세금부과 등을 통해 음주행위를 통제하는 것이 가능하다. 음주교육의 주기능은 법령과 처벌에 대한 두려움(perceived fear)를 높이는 것이다. 음주행위에 관용적인 사회 분위기를 변화시키는 것이 법령이나 처벌보다 더 효과적이다. 과도한 음주행위에 대한 비판적인 사회적 분위기와 같은 비공식적인 사회적인 제재가 음주문제의 예방에 더욱 중요하다. 청소년의 음주행위는 부모와 동료집단과의 관계에 의해 크게 영향을 받기 때문에 부모와 동료집단의 참여하에 객관적인 태도를 통해 자율적인 결정을 할 수 있도록 유도해야 한다. 음주교육에 대해 지식과 경험을 갖춘 교사가 교육을 실시하여야 하며 소그룹 활동을 통해 음주문제에 대한 이해와 바람직한 태도를 습득하게 하고 동료집단의 압력을 거부할 수 있는 능력을 키우는 것이 필요하다. 교사는 편견이 없는 객관적인 태도를 갖추어야 하고 최종적 결정은 지식에 근거하여 청소년이 하도록 하여야 한다. 음주는 가정불화, 좌절감, 실업, 이혼 둥의 부정적 감정과 연관되어 있으며 깊은 인간관계를 통한 상담이 효과적이다. 단주친목과 같은 자발적인 민간단체는 알코올 문제를 가진 사람들이 서로 모여 친목하는 가운데 도움과 치료를 받을 수 있다는 점에서 매우 효과적이다. 이러한 단체의 활용이 더욱 확대되어야 한다. 병원에서의 음주교육은 노조의 참여하에 전문적인 의료인들에 의해 이루어져야 한다. 이전에 알코올중독에서 회복된 사람을 동료교육가(peer educator)로 활용하는 것도 효율적인 교육방법중의 하나이다. 의과대학의 교과과정에 음주교육에 대한 내용을 더욱 확대하여야 한다. 음주교육은 음주라는 행위의 저변에 깔린 문화적 심리적 요인에 대한 깊은 이해를 토대로 계획되고 실시되어야 한다. 음주교육은 지역사회 전체의 참여를 통해 부모, 학생, 정부, 민간단체, 매스미디어의 공동참여를 통한 다각적인 접근이 요구된다.

• Archives of design research
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• v.11 no.2
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• pp.59-68
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• 1998

A work as human's creatures are transformed to bits and multimedia. In the modem society which is governed by simulation, infornlation is symbolized and becoming easily reached to anyone. Thus, collections of image and composition can show a new world beyond the ethical viewpoint. The problem with worries about the differnce between the original and a copy and disappearence of the meaning in postmodern era is the problem of how to set the intellectual properties and copyrights.In this situation, sharing of information according to the theoretical concepts and process of digitalization of photos in the era of information-intensive society was presented. The ethics of intellectual properties and copyrights and in postmordern era were driven. After reviewing the intellectual properties in the era of national information infrastructure of twenty-first century and by identifying the problems, the directions of what we have to do as image makers, and the intellectual properties and copyright.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.154-159
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• 1987

In the previously reported Part I, the behavior of the flank wear for carbide tool was studied as a preceeding step to present a simple method for Quick Tool-Life Testing, and the following general equation was obtained $W_{f}$ =(a+bt) $V^{m}$ . In this study the following step-cutting formula for the constants a, b and m in the above general model is derived by using step-cutting data [a numerical formula] To check the validity of the above formula, the comparison is made between the tool-life equation inferred in this method and that inferred in the conventional tool-life testing method, when the wear criterion is 0.3mm. The equation obtained in the present method is V(T')$^{0.57}$=1763 whereas the equation obtained in the conventional tool-life testing method is V(T)$^{0.56}$=1605 The results of the above two formula are satisfactory and also verify the validity of the present research.earch.