• Advances in nano research
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• 제16권3호
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• pp.231-249
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• 2024

When the amplitude of the vibrations is equivalent to that clearance, the vibrations for small amplitudes will really be significantly nonlinear. Nonlinearities will not be significant for amplitudes that are rather modest. Finally, nonlinearities will become crucial once again for big amplitudes. Therefore, the concrete panel system may experience a big amplitude in this work as a result of the high temperature. Based on the 3D modeling of the shell theory, the current work shows the influences of the von Kármán strain-displacement kinematic nonlinearity on the constitutive laws of the structure. The system's governing Equations in the nonlinear form are solved using Kronecker and Hadamard products, the discretization of Equations on the space domain, and Duffing-type Equations. Thermo-elasticity Equations. are used to represent the system's temperature. The harmonic solution technique for the displacement domain and the multiple-scale approach for the time domain are both covered in the section on solution procedures for solving nonlinear Equations. An effective data-driven solution is often utilized to predict how different systems would behave. The number of hidden layers and the learning rate are two hyperparameters for the network that are often chosen manually when required. Additionally, the data-driven method is offered for addressing the nonlinear vibration issue in order to reduce the computing cost of the current study. The conclusions of the present study may be validated by contrasting them with those of data-driven solutions and other published articles. The findings show that certain physical and geometrical characteristics have a significant effect on the existing concrete panel structure's susceptibility to temperature change and GPL weight fraction. For building construction industries, several useful recommendations for improving the thermo-mechanics' behavior of structural concrete panels are presented.

• Structural Engineering and Mechanics
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• 제89권6호
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• pp.557-570
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• 2024

Due to interfacial ageing, chemical action and interfacial damage, the interface debonding may appear in the interfaces of composite laminates. Particularly, the laminates display a side-dependent effect at small scale. In this work, a three-dimensional (3D) and anisotropic thick nanoplate model is proposed to investigate the effects of imperfect interface and nonlocal parameter on the bending deformation, vibrational response and buckling stability of one-dimensional (1D) hexagonal quasicrystal (QC) layered nanoplates. By combining the linear spring model with the transferring matrix method, exact solutions of phonon and phason displacements, phonon and phason stresses of bending deformation, the natural frequencies of vibration and the critical buckling loads of 1D hexagonal QC layered nanoplates are derived with imperfect interfaces and nonlocal effects. Numerical examples are illustrated to demonstrate the effects of the imperfect interface parameter, aspect ratio, thickness, nonlocal parameter, and stacking sequence on the bending deformation, the vibrational response and the critical buckling load of 1D hexagonal QC layered nanoplate. The results indicate that both the interface debonding and nonlocal effect can reduce the stiffness and stability of layered nanoplates. Increasing thickness of QC coatings can enhance the stability of sandwich nanoplates with the perfect interfaces, while it can reduce first and then enhance the stability of sandwich nanoplates with the imperfect interfaces. The biaxial compression easily results in an instability of the QC layered nanoplates compared to uniaxial compression. QC material is suitable for surface layers in layered structures. The mechanical behavior of QC layered nanoplates can be optimized by imposing imperfect interfaces and controlling the stacking sequence artificially. The present solutions are helpful for the various numerical methods, thin nanoplate theories and the optimal design of QC nano-composites in engineering practice with interfacial debonding.

• Advances in nano research
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• 제17권1호
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• pp.33-49
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• 2024

Using the mechanical treatments for mechanical properties improvement was rarely in the development scope before. This research approves through analytical ways that surface impacts can improve the quality of the surface significantly. This fact is approved for deposited titanium on silicone substrate. The new algorithm called minimum resultant error method (MREM) which is a direct combination of nanoindentation, FEM and dimensional analysis through a reverse method is utilized to extract the mechanical characteristics of the coating surface before and after impact. This method is extended to the time dependent behavior of the material to obtain strain rate coefficient. To implement this new approach, a new analysis technic is developed to define the residual stress field caused by surface impact as initial condition for nanoindentation. Analyzing the model in micro and macro scale at the same time was one of the main resolved challenges in this study. The result was obtaining of the constants of Johnson-Cook constitutive equation. Comparing the characteristics of the coating surface before and after impact shows high improvement in yield stress (34%), Elastic modulus (7.75%) and strain hardening coefficient (2.8%). The main achievement is that the strength improvement in titanium thin layer is much higher than bulk titanium. The yield strength shows 41.7% improvement for coated titanium comparing with 24% for bulk material. The rate of enhancement is about 6 times when it comes to the Young's modulus.

• 한국응용과학기술학회지
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• 제29권2호
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• pp.199-204
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• 2012

유기 박막 트랜지스터 (organic thin-film transistors; OTFTs)는 유기 반도체 그리고 디스플레이와 같은 분야에 그들의 잠재적인 응용 가능성 때문에 많은 주목을 받고 있다. 하지만 급격한 산화 혹은 낮은 전기 이동도와 같은 단점으로 인하여 n-형 물질은 p-형 물질에 비해서 상대적으로 많은 연구가 진행되지 못한 실정이다. 따라서 본 논문에서는 n-형 반도체 물질인 [6,6]-phenyl-C61-butyricacidmethylester (PCBM)과 Poly(4-vinylphenol) (PVP)을 유기 절연막으로 이용하여 o-dichlorobenzene, toluene and chloroform과 같은 다양한 유기 용매를 사용한 플라스틱 기판에 유기트랜지스터를 제작하였고 유기 용매가 ODCB 경우 전계 효과 이동도는 약 0.034 $cm^2/Vs$ 그리고 점멸비(on/off ratio)는 ${\sim}1.3{\times}10^5$ 으로 향상 되었다. 다양한 유기 용매의 휘발성에 따라서 PCBM TFT의 전기적 특성에 미치는 영향을 규명하였다.

• 한국전산구조공학회논문집
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• 제31권4호
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• pp.173-181
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• 2018

최근 복합재료는 향상된 성능, 내구성 및 여러 특정 요구성능에 대한 설계 유연성으로 인해 다양한 분야에서 활발히 활용되고 있다. 컴퓨터 성능이 발달함에 따라, 복합재료의 복잡한 거동에 대한 정확도 높은 모델 역시 함께 연구되고 있으며, 이로 인해 가상시험이 복합재료 거동에 대한 실험을 대체하거나 보충하는데 중요한 역할을 하고 있다. 본 논문에서는 나노수준부터 구조물 단위까지 이르는 다양한 length scale의 homogenization을 통한 멀티스케일 모델링에 대한 문헌을 분석하였다. 또한, 콘크리트 거동 연구에 대한 통합모델의 특징을 다루었으며, 가상 시험기계에 대한 최근 연구동향 및 전망에 대하여 다루었다.

• Advances in nano research
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• 제10권2호
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• pp.115-128
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• 2021

In this article, free vibration behavior of electro-magneto-thermo sandwich Timoshenko beam made of porous core and Graphene Platelet Reinforced Composite (GPLRC) in a thermal environment is investigated. The governing equations of motion are derived by using the modified strain gradient theory for micro structures and Hamilton's principle. The magneto electro are under linear function along the thickness that contains magnetic and electric constant potentials and a cosine function. The effects of material length scale parameters, temperature change, various distributions of porous, different distributions of graphene platelets and thickness ratio on the natural frequency of Timoshenko beam are analyzed. The results show that an increase in aspect ratio, the temperature change, and the thickness of GPL leads to reduce the natural frequency; while vice versa for porous coefficient, volume fractions and length of GPL. Moreover, the effect of different size-dependent theories such as CT, MCST and MSGT on the natural frequency is investigated. It reveals that MSGT and CT have most and lowest values of natural frequency, respectively, because MSGT leads to increase the stiffness of micro Timoshenko sandwich beam by considering three material length scale parameters. It is seen that by increasing porosity coefficient, the natural frequency increases because both stiffness and mass matrices decreases, but the effect of reduction of mass matrix is more than stiffness matrix. Considering the piezo magneto-electric layers lead to enhance the stiffness of a micro beam, thus the natural frequency increases. It can be seen that with increasing of the value of WGPL, the stiffness of microbeam increases. As a result, the value of natural frequency enhances. It is shown that in hc/h = 0.7, the natural frequency for WGPL = 0.05 is 8% and 14% less than its for WGPL = 0.06 and WGPL = 0.07, respectively. The results show that with an increment in the length and width of GPLs, the natural frequency increases because the stiffness of micro structures enhances and vice versa for thickness of GPLs. It can be seen that the natural frequency for aGPL = 25 ㎛ and hc/h = 0.6 is 0.3% and 1% more than the one for aGPL = 5 ㎛ and aGPL = 1 ㎛, respectively.

• Journal of Ginseng Research
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• 제47권2호
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• pp.302-310
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• 2023

Background: The most common type of dementia, Alzheimer's disease (AD), is marked by the formation of extracellular amyloid beta (Aβ) plaques. The impairments of axons and synapses appear in the process of Aβ plaques formation, and this damage could cause neurodegeneration. We previously reported that non-saponin fraction with rich polysaccharide (NFP) from Korean Red Ginseng (KRG) showed neuroprotective effects in AD. However, precise molecular mechanism of the therapeutic effects of NFP from KRG in AD still remains elusive. Methods: To investigate the therapeutic mechanisms of NFP from KRG on AD, we conducted proteomic analysis for frontal cortex from vehicle-treated wild-type, vehicle-treated 5XFAD mice, and NFP-treated 5XFAD mice by using nano-LC-ESI-MS/MS. Metabolic network analysis was additionally performed as the effects of NFP appeared to be associated with metabolism according to the proteome analysis. Results: Starting from 5,470 proteins, 2,636 proteins were selected for hierarchical clustering analysis, and finally 111 proteins were further selected for protein-protein interaction network analysis. A series of these analyses revealed that proteins associated with synapse and mitochondria might be linked to the therapeutic mechanism of NFP. Subsequent metabolic network analysis via genome-scale metabolic models that represent the three mouse groups showed that there were significant changes in metabolic fluxes of mitochondrial carnitine shuttle pathway and mitochondrial beta-oxidation of polyunsaturated fatty acids. Conclusion: Our results suggested that the therapeutic effects of NFP on AD were associated with synaptic- and mitochondrial-related pathways, and they provided targets for further rigorous studies on precise understanding of the molecular mechanism of NFP.

• 생명과학회지
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• 제28권3호
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• pp.284-292
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• 2018

멜라닌 농축 호르몬(melanin-concentrating hormone, MCH)은 17개의 아미노산으로 구성된 환형의 시상하부 펩티드로 색소 침착의 조절인자로서 연어에서 처음 분리되었다. 포유동물의 MCH는 19개의 아미노산으로 구성되어 있으며 섭식 및 에너지 항상성을 조절하는데 관여한다. 본 연구에서는 양식넙치의 다양한 조직에서 MCH 유전자의 발현 분포, 멜라닌 함유 세포의 집적, 포유동물 MCH 수용체와 양식넙치 MCH의 상호작용을 조사하였다. Real-time qPCR을 이용하여 뇌, 정소, 난소에서 MCH 유전자의 발현이 나타나는 것을 확인하였고, 수정 후 발달 단계에서도 MCH 유전자의 발현을 확인할 수 있었다. 합성된 연어 sMCH, 포유류 hMCH, 양식넙치 fMCH, dN-fMCH, dC-fMCH를 양식 넙치의 표피에 처리했을 때 다양한 농도에 따라 멜라닌 함유 세포의 집적이 다양하게 나타났다. 연어 sMCH, 포유류 hMCH에 비해 양식넙치 fMCH의 멜라닌 함유세포의 집적도가 36~99.85%로 비역가를 나타났으나 양식넙치 dN-fMCH, dC-fMCH를 처리한 경우 양식넙치 fMCH에 비해 높은 농도에서 집적이 나타나고 짧은 시간에 분산되었다. 또한, 인간 MCH 수용체와 쥐 MCH 수용체가 발현된 포유동물의 세포주에 양식넙치 fMCH를 처리하여 각 수용체와 결합하는 것을 확인하였다. 이러한 결과는 어류에서 발현되는 MCH가 포유동물의 MCH와 유사한 구조를 가지고 있어 MCH 수용체에 대한 새로운 리간드로서 제공될 수 있으며, 향후 어류의 MCH 수용체에 확대 적용할 수 있을 것이다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.93-93
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• 2016

Large scale integrated circuits (LSIs) has been improved by the shrinkage of the circuit dimensions. The smaller chip sizes and increase in circuit density require the miniaturization of the line-width and space between metal interconnections. Therefore, an extreme precise control of the critical dimension and pattern profile is necessary to fabricate next generation nano-electronics devices. The pattern profile control of plasma etching with an accuracy of sub-nanometer must be achieved. To realize the etching process which achieves the problem, understanding of the etching mechanism and precise control of the process based on the real-time monitoring of internal plasma parameters such as etching species density, surface temperature of substrate, etc. are very important. For instance, it is known that the etched profiles of organic low dielectric (low-k) films are sensitive to the substrate temperature and density ratio of H and N atoms in the H2/N2 plasma [1]. In this study, we introduced a feedback control of actual substrate temperature and radical density ratio monitored in real time. And then the dependence of etch rates and profiles of organic films have been evaluated based on the substrate temperatures. In this study, organic low-k films were etched by a dual frequency capacitively coupled plasma employing the mixture of H2/N2 gases. A 100-MHz power was supplied to an upper electrode for plasma generation. The Si substrate was electrostatically chucked to a lower electrode biased by supplying a 2-MHz power. To investigate the effects of H and N radical on the etching profile of organic low-k films, absolute H and N atom densities were measured by vacuum ultraviolet absorption spectroscopy [2]. Moreover, using the optical fiber-type low-coherence interferometer [3], substrate temperature has been measured in real time during etching process. From the measurement results, the temperature raised rapidly just after plasma ignition and was gradually saturated. The temporal change of substrate temperature is a crucial issue to control of surface reactions of reactive species. Therefore, by the intervals of on-off of the plasma discharge, the substrate temperature was maintained within ${\pm}1.5^{\circ}C$ from the set value. As a result, the temperatures were kept within $3^{\circ}C$ during the etching process. Then, we etched organic films with line-and-space pattern using this system. The cross-sections of the organic films etched for 50 s with the substrate temperatures at $20^{\circ}C$ and $100^{\circ}C$ were observed by SEM. From the results, they were different in the sidewall profile. It suggests that the reactions on the sidewalls changed according to the substrate temperature. The precise substrate temperature control method with real-time temperature monitoring and intermittent plasma generation was suggested to contribute on realization of fine pattern etching.

• 한국식품과학회지
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• 제41권6호
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• pp.657-661
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• 2009

해조칼슘을 습식분쇄한 초미세액상칼슘을 분무건조하여 부형제 종류에 따른 분말칼슘의 품질특성을 알아보고자 gum arabic, cyclodextrin, Na-caseinate를 첨가하여 품질특성을 비교하였다. 분무건조한 초미세분말칼슘의 수분함량은 2% 내외의 안정한 분말을 얻을 수 있었고, 색도는 원료인 해조칼슘보다 L값은 높았으며, b값은 감소하는 것으로 나타났다. 입자크기는 당류의 부형제 첨가로 초미세 크기로 분쇄되는 것을 확인할 수 있었으며, gum arabic을 첨가하여 제조한 초미세액상칼슘을 분무건조한 분말이 식초와 pH에 대한 용해도에서 가장 우수한 것으로 나타났다. 칼슘함량은 해조칼슘분말이 28%의 칼슘함량을 나타내었고, 부형제를 달리하여 제조한 초미세액상칼슘을 분무건조한 분말은 27% 내외로 비슷한 칼슘함량을 나타내어, 습식분쇄나 분무건조 공정에서 칼슘의 손실은 없는 것으로 나타났다. 흡습에 대한 안정성실험에서는 해조칼슘분말이 흡습에 안정하였으며, gum arabic을 첨가하여 분무건조한 분말이 흡습이 많이 발생하였다. 전자주사 현미경 관찰을 통하여 습식분쇄로 입자크기가 작아지는 것을 확인할 수 있었고, gum arabic을 사용하여 얻은 초미세칼슘분말이 단백질계나 사용하지 않았을 때보다 더 균일한 입자분포를 보였다. 따라서 습식분쇄한 초미세액상칼슘을 분말화하여 용해성등 품질특성이 개선됨을 확인하였으며 습식분쇄기술과 분무건조법을 식품가공기술로 활용할 수 있는 가능성을 확보하였다.