• Applied Microscopy
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• v.50
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• pp.21.1-21.3
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• 2020

Sample preparation is significantly important to the high-resolution transmission electron microscopy (HRTEM) characterization of nanomaterials. However, many general organic solvents can dissolve the necessary organic polymer support layer in TEM grid, which causes it difficult to obtain high-quality samples of oil-soluble nanomaterials. In this study, a new sample preparation method for oil-soluble nanomaterials has been developed by using the sublimable material as a transition layer. Experiments also show that there is no damage to TEM grids and high-quality HRTEM images can be obtained via this method. This approach paves the way to applicable HRTEM sample preparation of oil-soluble nanomaterials.

• Applied Microscopy
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• v.45 no.4
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• pp.203-207
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• 2015

Sample preparation is very important for crystal structure analysis of novel nanostructured materials in electron microscopy. Generally, a grid dispersion method has been used as transmission electron microscope (TEM) sampling method of nano-powder samples. However, it is difficult to obtain the cross-sectional information for the tabular-structured materials. In order to solve this problem, we have attempted a new sample preparation method using focused ion beam. Base on this approach, it was possible to successfully obtain the electron diffraction patterns and high-resolution TEM images of the cross-section of tabular structure. Finally, we were able to obtain three-dimensional crystallographic information of novel zeolite nano-crystal of the tabular morphology by applying the new sample preparation technique.

• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.368-378
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• 2020

In the paper, corrosion behavior of T91 steel in different concentrations of NaHSO₃ solution was studied in combination with scanning electron microscope (SEM) and electrochemical measurements. The results showed that the steel exhibited active anodic dissolution characteristics in the solution, and NaHSO₃ concentration affected both cathodic and anodic behaviors. The steel surface was covered by intact corrosion products in the solutions, but the compactness and mechanical properties of the corrosion products degraded with the increase of NaHSO₃ concentration. In low-concentration NaHSO₃ solution the steel tended to undergo uniform corrosion with slight corrosion pits, but its corrosion mode gradually transited to localized corrosion as the NaHSO₃ concentration increased. The mechanical property degradation of the corrosion products caused by sulfur compounds and the pH decrease of the solution are the important factors to accelerating its corrosion process.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.2
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• pp.67-72
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• 2015

Power grid techniques are distributed over general power systems ranging from power stations to power transmission, power distribution, and users. To monitor and control the elements and performance of a power system in real time in the extensive area of power generation, power transmission, wide-area monitoring (WAM) and control techniques are required (Sattinger et al. 2007). Also, to efficiently operate a power grid, integrated techniques of information and communication technology are required for the application of communication network and relevant equipment, computing, and system control software. WAM should make a precise power grid measurement of more than once per cycle by time synchronization using GPS. By collecting the measurement values of a power grid from substations located at faraway regions through remote communication, the current status of the entire power grid system can be examined. However, for GPS that is used in general national industries, unexpected dangerous situations have occurred due to its deterioration and jamming. Currently, the power grid is based on a synchronization system using GPS. Thus, interruption of the time synchronization system of the power system due to the failure or abnormal condition of GPS would have enormous effects on each field such as economy, security, and the lives of the public due to the destruction of the synchronization system of the national power grid. Developed countries have an emergency substitute system in preparation for this abnormal situation of GPS. Therefore, in Korea, a system that is used to prepare for the interruption of GPS reception should also be established on a long-term basis; but prior to this, it is required that an evaluation technique for the time synchronization performance of a GPS receiver using an atomic clock within the power grid. In this study, a monitoring system of time synchronization based on GPS at a power grid was implemented, and the results were presented.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.6
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• pp.1375-1391
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• 2012

Smart grid is a next-generation intelligent power grid that applying ICT to power grid to maximize the energy efficiency ratio. Recently, technologies and standards for smart grid are being developed around the world. Information security which is an essential part of smart grid development has to be managed continuously. Information security management system certification for organizational risk management has been implemented in Korea. Although preparation for information security management system certification which is applicable to smart grid is considered, there are no specific methods. This paper is to propose core and added evaluation criteria for Korean smart grid based on K-ISMS through comparative analysis between ISMS operated in Korea and smart grid information security management system developed in the United States. Added evaluation criteria enable smart grid related business that certified existing ISMS to minimize redundant and unnecessary certification assessment work.

• Applied Microscopy
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• v.44 no.4
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• pp.133-137
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• 2014

We suggest a facile transmission electron microscopy (TEM) specimen preparation method for the direct (polymer-free) transfer of layer-area graphene from Cu substrates to a TEM grid. The standard (polymer-based) method and direct transfer method were by TEM, high-resolution TEM, and energy dispersive X-ray spectroscopy (EDS). The folds and crystalline particles were formed in a graphene specimen by the standard method, while the graphene specimen by the direct method with a new etchant solution exhibited clean and full coverage of the graphene surface, which reduced several wet chemical steps and accompanying mechanical stresses and avoided formation of the oxide metal.

• Journal of the Society of Disaster Information
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• v.17 no.1
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• pp.25-38
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• 2021

Purpose: To reduce the damage caused by continuously occurring typhoons, we proposed a standardized grid so that it could be actively utilized in the prevention and preparation stage of typhoon response. We established grid-based convergence information on the typhoon risk area so that we showed the effectiveness of information used in disaster response. Method: To generate convergent information on typhoon hazard areas that can be useful in responding to typhoon situation, we used various types of data such as vector and raster to establish typhoon hazard area small grid-based information. A standardized grid model was applied for compatibility with already produced information and for compatibility of grid information generated by each local government. Result: By applying the grid system of National branch license plates, a grid of typhoon risk areas in Seoul was constructed that can be usefully used when responding to typhoon situations. The grid system of National branch license plates defines the grid size of a multi-dimensional hierarchical structure. And a grid of typhoon risk areas in Seoul was constructed using grids of 100m and 1,000m. Conclusion: Using real-time 5km resolution grid based weather information provided by Korea Meteorological Administration, in the future, it is possible to derive near-future typhoon hazard areas according to typhoon travel route prediction. In addition, the national branch number grid system can be expanded to global grid systems for global response to various disasters.

• The Journal of Advanced Prosthodontics
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• v.15 no.3
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• pp.145-154
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• 2023

PURPOSE. The objective of this study was to investigate how internal structures influence the overall and marginal accuracy of full arch preparations fabricated through additive manufacturing in different printing systems. MATERIALS AND METHODS. A full-arch preparation digital model was set up with three internal designs, including solid, hollow, and grid. These were printed using three different resin printers with nine models in each group. After scanning, each data was imported into the 3D data processing software together with the master cast, aligned and trimmed, and then put into the 3D data analysis software again to compare the overall and marginal deviation whose results are expressed using root mean square values and color maps. To evaluate the trueness of the resin model, the test data and reference data were compared, and the precision was evaluated by comparing the test data sets. Color maps were observed for qualitative analysis. Data were statistically analyzed by one-way analysis of variance and Bonferroni method was used for post hoc comparison (α = .05). RESULTS. The influence of different internal structures on the accuracy of 3D printed resin models varied significantly (P < .05). Solid and grid models showed better accuracy, while the hollow model exhibited poor accuracy. The color maps show that the resin models have a tendency to shrink inwards. CONCLUSION. The internal structure design influences the accuracy of the 3D printing model, and the effect varies in different printing systems. Irrespective of the kind of printing system, the printing accuracy of hollow model was observed to be worse than those of solid and grid models.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.116-116
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• 2012

국내 섬유산업의 경쟁력을 향상시키고 채산성을 확보하기 위해 고부가가치 섬유 제품의 개발이 요구된다. 심미성을 발현하는 대표적인 후가공 기술인 카렌더 가공은 국내뿐만 아니라 국외 후진국에서도 보편화된 기술로 대량 생산으로 인한 가공비 저하, 물량 확보 등에 많은 어려움을 격고 있어 고부가가치의 신기술을 요구한다. 최근 이태리, 일본 등의 선진국에서 후가공 기술인 EMBO 롤러를 이용한 무아레 가공 원단이 고가로 거래되고 있다. 무아레(Moire)는 프랑스어로 "물결 모양의 무늬"라는 뜻으로 직물에 파형(波形)또는 나뭇결 무늬를 나타나게 하는 가공 기술로, 국내에서도 EMBO 롤러를 이용하여 무아레 가공을 하거나 두 겹의 원단을 이용한 무아레 가공이 시도되고 있으나, 전자의 경우 사용되는 롤러가 일반 롤러에 비해 훨씬 고가이고 한 종류의 롤러로 제한된 패턴 밖에 표현할 수 없고 적용 소재가 한정되는 등 많은 단점을 지니고 있고, 후자의 경우 세탁내구성이 나빠 상품화조차 되지 못하고 있어 현재 국내 섬유가공 기술로는 고내구성을 가지고 다양한 효과를 발현하는 무아레 가공이 불가능한 실정이다. 직물의 경 위사 밀도차이를 이용하여 무아레를 형성할 수 있다는 점에 착안하여, 경 위사 조직을 갖는 이형(離型)원단에 PU 수지를 코팅하여 격자무늬(grid) 필름을 제조하고 제조된 Grid 필름과 Base원단을 라미네이팅하여 경 위사 밀도차에 의해 무아레 무늬를 형성할 수 있었다. 이형원단과 Base원단의 경 위사의 밀도에 따라 다양한 패턴의 3차원 무아레 무늬를 발현시킬 수 있으며 합성섬유 및 천염섬유 등의 원단 소재에 제약 없이 영구 내구성의 무아레 제품을 생산할 수 있을 것으로 판단된다. 본 연구에서는 Grid 필름을 이용한 무아레 가공을 위하여 이형원단 제조 조건을 확립하였고, grid 필름 캐스팅 조건, 라미네이팅 조건을 달리하여 이형성 및 무아레 형상을 비교하여 고찰함으로써 제품화에 필요한 요소 기술의 기초를 마련하고자 한다.

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.788-792
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• 2013

A shortcoming of using transmission electron microscopy (TEM) for structural analysis via electron diffraction is the relatively large error of the measurements as compared to X-ray diffraction. To reduce these errors, various internal standard methods from earlier studies have been widely used. We developed a new device to facilitate the application of internal standard methods in preparation of TEM grids used for nanopowder analysis. Through the application of a partial mask on the TEM grid, both the internal standards and the research materials can be loaded on the same grid. Through this process, we conducted a TEM analysis that compared synthetic hydroxyapatite (HAp) nanopowder to bone apatite from a bovine femur. We determined that the accuracy of the d-spacing measurements of the HAp and bone powders could be improved to better than 1% after statistical treatments of the experimental data. By applying a quarter mask, we loaded four different nanoparticles on a single TEM grid, with one section designated for the internal standard.