• 한국전산구조공학회논문집
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• 제16권1호
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• pp.1-8
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• 2003

위상최적설계는 개념설계에 적합하며, 제품의 설계에서 사용되어지고 있다. 전통적인 위상최적화는 균질화법과 최적조건법을 사용해 왔다. 균질화법은 구멍으로 구성된 구조물과 강성행렬사이의 관계를 연결해주는데 사용되며, 최적조건법은 부피분율을 유지하며 설계변수의 개선에 사용되어진다. 전통적인 위상최적설계는 수렴성이 좋은 장점은 있지만 수렴시간이 많이 걸린다는 단점이 있었다. 이 문제를 해결하는 하나의 방법으로 평균 응력량을 기준으로 요소를 제거하는 요소제거법을 제시하였다. 예제에서 수렴속도가 향상됨을 알 수 있었다.

• 디지털융복합연구
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• 제11권9호
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• pp.319-324
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• 2013

노인은 그 어느 연령층보다 다양한 특성을 지니고 있다. 다양한 환경과 경험에 따라 다른 성향을 지니고 있기 때문이다. 따라서 모든 노인들에게 획일적인 미술치료프로그램의 진행은 불가능하며 스스로가 치료의 필요성을 느낄 때 참여하여야만 효과적이라고 본다. 미술치료는 미술매체를 통해 내면의 감정을 표출하기 때문에 노인들의 심상에 간직된 감정을 자연스럽게 드러내는 것을 돕고, 감정의 위기를 완화시키는 역할을 한다. 미술치료에서의 치료수단은 비언어적 수단이므로 통제를 적게 받아 자기방어가 감소된다. 또한 미술매체는 감각을 사용할 기회 자체가 줄어드는 노인들의 본연의 감각을 자극하므로 매우 유용한 교육프로그램으로 평가되어진다.

• 문화기술의 융합
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• 제4권1호
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• pp.237-240
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• 2018

최근 군수품의 발달과 더불어 군복과 전투화 등 많은 부분이 기능성으로 바뀌였으나 전투화의 경우 밑창의 갈라짐, 전투화 불량같은 기능성임에도 불구하고 여러 가지 애로사항을 통해 개선되고 있다는 점에서 연구동기가 되어 연구를 하게 되었다. 군 전투화의 만족도에 대한 연구는 전무한 실정이며 연구내용들도 전투화 압력, 전투화 끈에 대한 자살자 연구 등 본인이 관심을 가지고 연구하는 분야가 없어서 더욱 더 관심을 가지게 되고 연구를 진행하게 되었다.

• Journal of information and communication convergence engineering
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• 제11권1호
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• pp.1-6
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• 2013

Suppressing or mitigating signal distortion due to group velocity dispersion and optical Kerr effects is necessary in ultra-high speed and long-haul wavelength division multiplexing (WDM) transmission systems. Dispersion management (DM), optical phase conjugation (OPC), and the combination of these two are promising techniques to compensate for signal distortion. In this paper, to implement a flexible optical WDM network, a new optical link configuration with a randomly distributed single-mode fiber (SMF) length and fixed residual dispersion per span in the combination of DM and OPC is proposed and investigated. The simulation results show that the best net residual dispersion (NRD) in the proposed optical links is +10 ps/nm, which is independent of pre- and postcompensation. The effective launch power of the WDM channel is increased more in the optical links with NRD = +10 ps/nm controlled by only precompensation. Furthermore, the system performance difference between the proposed optical link configuration with the best NRD and the conventional optical link with uniform distribution of the SMF length had little significance. Consequently, it is confirmed that the proposed optical link configuration with the best NRD is effective and useful for implementing a reconfigurable long-haul WDM network.

• Advances in aircraft and spacecraft science
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• 제5권3호
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• pp.295-318
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• 2018

This research studies thermo-elastic behavior of rotating micro discs that are employed in various micro devices such as micro gas turbines. It is assumed that material is functionally graded with a variable profile thickness, density, shear modulus and thermal expansion in terms of radius of micro disc and as a power law function. Boundary condition is considered fixed-free with uniform thermal loading and elastic field is symmetric. Using incompressible material's constitutive equation, we extract governing differential equation of four orders; to solution this equation, we utilize general differential quadrature (GDQ) method and the results are schematically pictured. The obtained result in a particular case is compared with another work and coincidence of results is shown. We will find out that surface effect tends to split micro disc's area to compressive and tensile while nonlocal parameter tries to converge different behaviors with each other; this convergence feature make FGIMs capable to resist in high temperature and so in terms of thermo-elastic behavior we can suggest, using FGIMs in micro devices such as micro turbines (under glass transition temperature).

• 한국기계가공학회지
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• 제20권6호
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• pp.114-120
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• 2021

This study is focused on the root mean square and peak-to-valley based on the injection conditions of the f-theta lens, one of the main components of laser printers and laser scanning systems. The f-theta lens of an aspherical plastic lens requires ultra-preaction. Injection molding is typically used for the mass production of aspherical plastic lenses. In the injection-molding method, the resin in the lens shape is filled with the resin after melting the plastic pellets at a constant temperature and then cooled. It is necessary to maintain a uniform injection molding system to produce high-quality lenses. These injection-molding systems are influenced by different factors, such as pressure, speed, temperature, mold, and cooling. It is possible to obtain a lens that exhibits the optical characteristics required to achieve harmony. We investigated the root mean square and peak-to-valley caused by variations in temperature, a critical parameter in the melting and cooling of plastic resins generated inside and outside the injection mold.

• Journal of Electrochemical Science and Technology
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• 제10권1호
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• pp.89-97
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• 2019

As a promising candidate for anode materials in lithium ion battery (LIB), tungsten trioxide ($WO_3$) and tungsten disulfide ($WS_2$) nanocrystals were synthesized, and their electrochemical properties were comprehensibly studied using a half cell. One-dimensional $WO_3$ nanowires with uniform diameter of 10 nm were synthesized by hydrothermal method, and two-dimensional (2D) $WS_2$ nanosheets by unique gas phase sulfurization of $WO_3$ using $H_2S$. $WS_2$ nanosheets exhibits uniformly 10 nm thickness. The $WO_3$ nanowires and $WS_2$ nanosheets showed maximum capacities of 552 and $633mA\;h\;g^{-1}$, respectively, after 100 cycles. Especially, the capacity of $WS_2$ is significantly larger than the theoretical capacity ($433mA\;h\;g^{-1}$). We also examined the cycling performance using a larger size $WO_3$ and $WS_2$ nanocrystals, showing that the smaller size plays an important role in enhancing the capacity of LIBs. The larger capacity of $WS_2$ nanosheets than the theoretical value is ascribed to the lower charge transfer resistance of 2D nanostructures.

• Steel and Composite Structures
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• 제31권5호
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• pp.529-539
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• 2019

Current paper deals with thermoelastic static and free vibrational behaviors of axisymmetric thick cylinders reinforced with functionally graded (FG) randomly oriented graphene subjected to internal pressure and thermal gradient loads. The heat transfer and mechanical analyses of randomly oriented graphene-reinforced nanocomposite (GRNC) cylinders are facilitated by developing a weak form mesh-free method based on moving least squares (MLS) shape functions. Furthermore, in order to estimate the material properties of GRNC with temperature dependent components, a modified Halpin-Tsai model incorporated with two efficiency parameters is utilized. It is assumed that the distributions of graphene nano-sheets are uniform and FG along the radial direction of nanocomposite cylinders. By comparing with the exact result, the accuracy of the developed method is verified. Also, the convergence of the method is successfully confirmed. Then we investigated the effects of graphene distribution and volume fraction as well as thermo-mechanical boundary conditions on the temperature distribution, static response and natural frequency of the considered FG-GRNC thick cylinders. The results disclosed that graphene distribution has significant effects on the temperature and hoop stress distributions of FG-GRNC cylinders. However, the volume fraction of graphene has stronger effect on the natural frequencies of the considered thick cylinders than its distribution.

• 한국인터넷방송통신학회논문지
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• 제19권1호
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• pp.211-218
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• 2019

디스플레이 기술의 발달로 모든 디스플레이 장치들이 대형화, 고화질, 고정밀도가 요구된다. 디스플레이 장치의 대형화에 따라 BLU가 대형화 되고 밝아져야 한다. 이 BLU 상판 Glass는 형상과 두께가 균일해야 균일한 휘도분포를 갖는다. 이런 요인들의 불량으로 인한 디스플레이 성능이 저하된다. 따라서 BLU의 형상 및 두께를 측정하는 고품질 측정 장치들의 요구가 필연적이다. 본 논문에서는 BLU의 형상의 높이 및 두께 측정을 위한 고속이며 고정밀 시스템 구현을 제안하고자 한다. 측정 오차를 최소화하기 위해서 측정 구간을 둘로 나누고 다른 이동 속도로 측정하여 원하는 결과를 도출할 수 있었다.

• 한국기계가공학회지
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• 제20권9호
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• pp.20-27
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• 2021

The effective surface of lens was studied for injection molding process and to enable mass production of f-theta lens, which is the primary component of laser printers and laser scanning systems. Injection molding is an optimal method if f-theta lens is frequently used for the mass production of plastic lenses as an aspherical lens that requires ultra-precision. A uniform injection molding system should be maintained to produce high quality lenses. Additionally, to maintain these injection molding systems, various factors such as pressure, speed, temperature, mold and cooling should be considered. However, a lens with the optical characteristics of an f-theta lens can be obtained. The effects of melting and cooling of plastic resin on the effective surface of f-theta lenses and the numerous factors that affect the injection molding process were studied.