• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.9
• /
• pp.1037-1041
• /
• 2014

Slurry used for polishing semiconductors processed by exchange, pressurization, and multi-step feeding has been studied to investigate the effect of the size and shape of slurry particles on the oxide CMP removal rate. First, spherical silica sol was prepared by the ion exchange method. The spherical silica particle was used as a seed to grow non-spherical silica sol in accordance with the multi-step feeding of silicic acid by the ion exchange and pressurization methods. The oxide removal rate of both non-spherical silica sol and commercially available slurry were compared with increasing average particle size in the oxide CMP. The more alkaline the pH level of the non-spherical silica sol, the higher was the removal rate and non-uniformity.

• Proceeding of Spring/Autumn Annual Conference of KHA
• /
• 2008.11a
• /
• pp.140-143
• /
• 2008

As the number of family living alone is expected to soar due to a change in socio-demographics like divorce, more middle-aged women returning to work, homes become smaller and so on. In addition to in 2020 these people will be increase so that 85 percent of the Koreans compose elderly living alone who is over 65. This study aims at developing a sharing-typed elderly people-centered rental model which is accessible in the community integration dimension as an alternative and finding out theirconscious, their need about residence. and we need to check about their major requirements on improvement step by step. so that we suggest the desirable way on the existing multi house. The model provides benefits in the social, economical and pragmatic dimensions as the families living alone get together and living with others, Particularly, as a residence model which reduces a psychological loneliness and at the same time enables the elderly to continue to live a life in the community while they live together with other people, this model could be a strategy which supports the "Aging in Place." This study is in progress via small group workshop which debate gradually about special subject with similar group member. So we can find the residence's preference on living environment in various condition and the member can imagine freely on their future living arrangement by giving the various informations which can be proceed in future. The workshop proceed three times. at the first workshop, we're check their living environment and satisfaction level. and second time we give the knowledge about shared-type rental house then discuss about the model. and last time we're listen to the residence's opinion.

• Journal of Advanced Navigation Technology
• /
• v.16 no.5
• /
• pp.794-800
• /
• 2012

In this paper, we propose a scheme for improving not only the utilization of frequency bands in the guard channel scheme but also the dropping rate of cognitive radio user in the wireless cognitive radio-based cellular network. The proposed scheme enables cognitive radio users to utilize the guard channel for servicing only handoff calls in normal times, but cognitive radio users must vacate the frequency channel when handoff call appearing. At this time our scheme ensures their seamless services for cognitive radio users, by predicting handoff call's appearance by MMOSPRED (Multi-Media One Step Prediction) method and then reserving the demanded channels for spectrum handoff calls. Our simulations show that our scheme performs better than other schemes; GCS(Guard Channel Scheme) and a scheme without prediction in terms of cognitive users call's dropping rate and resource utilization efficiency.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.27 no.4
• /
• pp.437-444
• /
• 2009

A bi-directional, multi-step numerical integrator is developed to determine the GPS (Global Positioning System) orbit based on a dynamic approach, which shows micrometer-level accuracy at GPS altitude. The acceleration due to the planets other than the Moon and the Sun is so small that it is replaced by the empirical forces in the Solar Radiation Pressure (SRP) model. The satellite orbit parameters are estimated with the least-squares adjustment method using both the integrated orbit and the published IGS (International GNSS Service) precise orbit. For this estimation procedure, the integration should be applied to the partial derivatives of the acceleration with respect to the unknown parameters as well as the acceleration itself. The accuracy of the satellite orbit is evaluated by the RMS (Root Mean Squares error) of the residuals calculated from the estimated orbit parameters. The overall RMS of orbit error during March 2009 was 5.2 mm, and there are no specific patterns in the absolute orbit error depending on the satellite types and the directions of coordinate frame. The SRP model used in this study includes only the direct and once-per-revolution terms. Therefore there is errant behavior regarding twice-per-revolution, which needs further investigation.

• Composites Research
• /
• v.34 no.5
• /
• pp.269-276
• /
• 2021

PCM (Prepreg Compression Molding) process is a high-speed molding technology that can manufacture high-quality CFRP (Carbon Fiber Reinforced Plastic) parts. Compared to the autoclave process, it generates less waste and can significantly reduce cycle time, so various studies are being conducted in the aerospace and automobile industries. In this study, in order to improve the quality of the PCM process, a molding method was developed to increase the compression pressure of the press step by step according to the curing behavior of the prepreg. It was confirmed that this multi-stage compression molding technology is a good means to produce high-quality CFRP products and shorten cycle times. And, the laminated prepreg at room temperature was immediately put into the mold and preheated and molded at the same time, so that it could be molded without a separate preheating process. In addition, as a result of applying the same process conditions optimized for flat plate molding to three-dimensional shapes, a product similar to a flat plate in appearance could be made without the process of establishing process conditions.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.50 no.3
• /
• pp.91-104
• /
• 2008

This study developed the WSM (weighted scenario method)-AHP method that can optimize the weighting value for multi-criteria to make GIS grid-based potential surface. The potential surface has been used to simulate urban expansion using distributed cellular automata model and to generate land-use planning as basic data. This study formulated the WSM-AHP method in mathematically and applied to test region, Suwon city, which located on south area from Seoul. WSM-AHP method generates potential map for each pair of weighting value for all criteria, which one criterion is weighted with high weighting value and the others use low weighting value, considering that the summation for all criteria weighting values should be "1". The potential change rate to the step of weighted scenario for weighting value of criteria is standardized like AHP intensity matrix in this study. From the standard potential change rate, WSM-AHP intensity matrix is completed, and then the optimal weighting value is calculated from the maximum eigenvector of the WSM-AHP matrix, according to the new WSM-AHP method developed in this study. The applied results of new method showed that the optimal weighting value from WSM-AHP is more resonable than the general AHP specialists' evaluation for weighting value. The another new finding of this study is to suggest the deterministic approach to optimize the weighting value for the distributed CA model, which is used to find new city area and to generate rational land-use planning.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.18 no.3
• /
• pp.535-544
• /
• 2023

In this paper, we study the effect of gradient vector calculation method(analytical method, central finite difference method) on adaptive beamforming to control weight distribution during iterated calculation when LMS algorithm (repeating method) is used to realize desired beam pattern. To this end, a quasi-ideal beam having an arbitrarily set beam width, a rotating beam, and a multi-beam were reviewed as examples. Numerical experiments applied the step parameters of the appropriate values to the adaptive beamforming system through trial and error equally to the two calculations, and compared the convergence characteristics of objective functions that evaluate adaptability and error using two methods for calculating gradient vectors.

• Journal of the Korean association of regional geographers
• /
• v.8 no.4
• /
• pp.480-491
• /
• 2002

The purpose of this study is to construct interregional input-output table for multi-regions using non-survey methods. Despite of wide use of interregional input-output table, there have been continuing debates with respect to it's accuracy mostly when it is constructed by non-survey method. The best ideal one is to construct through real survey, while we must pay much time and cost. With regard to this concern, Hulu and Hewings developed a step by step method for the estimation of interregional input coefficients for the Indonesian economy which might be a challenge for the limitation of location quotient method, for which Round pointed out earlier. A five regions interregional input-output table for Korea is developed in this study by expanding Location Quotient method. Some development was made, however, according to the degree of collection of data and the assumption in treating the interregional flows. Finally, a comparison was made for the accuracy of input coefficients between the real surveyed and derived ones.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.221.2-221.2
• /
• 2015

Graphene is very interesting 2 dimensional material providing unique properties. Especially, graphene has been investigated as a stretchable and transparent conductor due to its high mobility, high optical transmittance, and outstanding mechanical properties. On the contrary, high sheet resistance of extremely thin monolayer graphene limits its application. Artificially stacked multilayer graphene is used to decrease its sheet resistance and has shown improved results. However, stacked multilayer graphene requires repetitive and unnecessary transfer processes. Recently, growth of multilayer graphene has been investigated using a chemical vapor deposition (CVD) method but the layer controlled synthesis of multilayer graphene has shown challenges. In this paper, we demonstrate controlled growth of multilayer graphene using a two-step process with multi heating zone low pressure CVD. The produced graphene samples are characterized by optical microscope (OM) and scanning electron microscopy (SEM). Raman spectroscopy is used to distinguish a number of layers in the multilayer graphene. Its optical and electrical properties are also analyzed by UV-Vis spectrophotometer and probe station, respectively. Atomic resolution images of graphene layers are observed by high resolution transmission electron microscopy (HRTEM).

• The Journal of Information Systems
• /
• v.5
• /
• pp.21-41
• /
• 1996

Linear programming has become an important tool in decision-making of modern business management. This remarkable growth can be traced to the pioneering efforts of many individuals and research organizations. The popular using of personal computers make it very easy to process those complicated linear programming models. Furthermore advanced linear programming software packages assist us to solve L.P. models without any difficult process. Even though the advanced L.P. professional packages, the needs of more detailed deterministic elements for business decisions have forced us to apply dynamic approaches for more resonable solutions. For the purpose of these problems applying to the "Mathematica" packages which is composed of mathematic tools, the simplex processes show us the flexible and dynamic decision elements included to any other professional linear programming tools. Especially we need proper dynamic variables to analyze the shadow prices step by step. And applying SAS(Statistical Analysis System) packages to the L.P. problems, it is also one of the best way to get good solution. On the way trying to the other L.P. packages which are prepared for Spreadsheets i.e., MS-Excel, Lotus-123, Quatro etc. can be applied to linear programming models. But they are not so much useful for the problems. Calculating simplex tableau is an important method to interpret L.P. format for the optimal solution. In this paper we find out that the more detailed and efficient techniques to interpret useful software of mathematica and SAS for business decision making of linear programming. So it needs to apply more dynamic technique of using of Mathematica and SAS multiple software to get more efficient deterministic factors for the sophiscated L.P. solutions.