• Journal of the Korean institute of surface engineering
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• v.50 no.5
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• pp.315-321
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• 2017

Antireflective pyramid arrays can be readily obtained via anisotropic etching in alkaline solution (KOH, NaOH), which is widely used in crystalline-Si (c-Si) solar cells. The periodic inverted pyramid arrays show even lower light reflectivity because of their superior light-trapping characteristics. Since this inverted pyramidal structures are mostly achieved using very complex techniques such as photolithograpy and laser processes requiring extra costs, here, we demonstrate the Cu-nanoparticle assisted chemical etching processes to make the inverted pyramidal arrays without the need of photolithography. We have mainly controlled the concentration of $Cu(NO_3)_2$, HF, $H_2O_2$ and temperature as well as time factors that affecting the reaction. Optimal inverted pyramid structure was obtained through reaction parameters control. The reflectance of inverted pyramid arrays showed < 10% over 400 to 1100 nm wavelength range while showing 15~20% in random pyramid arrays.

• The Korean Journal of Food & Health Convergence
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• v.8 no.2
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• pp.7-13
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• 2022

The purpose of this study was to compare the nutrient intake of elderly according to their cohabitation status and determine its effects on the prevalence of anemia. Data from the KNHANES were used for this study, including raw data on socioeconomic characteristics, nutrient intake, health status, and clinical laboratory findings. Study subjects aged 60 to 80 years were retrieved and analyzed. As a result, the prevalence of anemia was 12.0% (men, 11.6%; women, 12.3%). The prevalence rate increased with age, and odds ratio [OR] of anemia among those aged 75 to 80 years was 4.16 times higher in men (OR=4.16, 95% confidence interval [CI]=2.48-6.97) and 2.77 times higher in women (OR=2.77, 95% CI=1.86-4.14) compared to 60~64 years old. Socioeconomic factors (area of residence, education level, household income), including cohabitation Status (living alone VS living with other family members), and health behaviors (high-risk drinking, smoking, aerobic exercise) did not significantly effect on anemia. In addition, other than protein intake for men, nutrient intake did not have a significant effect on the prevalence rate of anemia. Hypertension, diabetes, and cancer significantly increased the risk of anemia. In Korea, the influencing factors of elderly anemia change over time, so periodic follow-up studies are needed.

• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.4
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• pp.27-36
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• 2015

This study analyzed the characteristics of the entries at the design competition for the Hoehyeon section of Namsan from a perspective of the Historic Urban Landscape and made suggestions from them. Hoehyeon, located at the foot of Namsan, is the most changing site in the park and Seoul City Wall. Recent excavation of the old city walls of the Joseon Era has uncovered evidence of the Japanese occupation period, making it a site where park facilities in modern and contemporary history coexist. The frame analysis has been made by the concept of the Historic Urban Landscape, the methods of approach, specialists' discussion and the guidelines of the competition. The entries were analyzed by classification of the understanding of the spatiality and cultural diversity, the recognition of the periodic layers of time, and the design implementation, the preservation, the park plan, and the future management plan. From a perspective of an Historic Urban Landscape, this study has found that each entry placed priority on the objects for preservation and suggested creative involvement and comprehensive designs for the preservation and the park plan through the understanding of the spatiality and cultural diversity and the reflection of the periodic layers of time in the designs. This study provided two implications. Firstly, there was a possibility for new recognition and the methods of approach for preservation and development. Secondly, the basic plan for the Historic Landscape should be established through research and mapping for the preservation and management of objects in Seoul having valuable historic variability. Further study for resident participation and the process by network from public to private should be taken. This study looks forward to the consideration of the direction for the design plans of places with historic and cultural value.

• Journal of KIISE
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• v.44 no.1
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• pp.84-94
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• 2017

Recently, the importance of velocity, one of the characteristics of big data (5V: Volume, Variety, Velocity, Veracity, and Value), has been emphasized in the data processing, which has led to several studies on the real-time stream processing, a technology for quick and accurate processing and analyses of big data. In this paper, we propose a Squall framework using Time-triggered Message-triggered Object (TMO) technology, a model that is widely used for processing real-time big data. Moreover, we provide a description of Squall framework and its operations under a single node. TMO is an object model that supports the non-regular real-time processing method for certain conditions as well as regular periodic processing for certain amount of time. A Squall framework can support the real-time event stream of big data and micro-batch processing with outstanding performances, as compared to Apache storm and Spark Streaming. However, additional development for processing real-time stream under multiple nodes that is common under most frameworks is needed. In conclusion, the advantages of a TMO model can overcome the drawbacks of Apache storm or Spark Streaming in the processing of real-time big data. The TMO model has potential as a useful model in real-time big data processing.

• Journal of Korea Water Resources Association
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• v.54 no.spc1
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• pp.1083-1093
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• 2021

It is an essential to predict water usage for establishing an optimal supply operation plan and reducing power consumption. However, the water usage by consumer has a non-linear characteristics due to various factors such as user type, usage pattern, and weather condition. Therefore, in order to predict the water consumption, we proposed the methodology linking various techniques that can consider non-linear characteristics of water use and we called it as KWD framework. Say, K-means (K) cluster analysis was performed to classify similar patterns according to usage of each individual consumer; then Wavelet (W) transform was applied to derive main periodic pattern of the usage by removing noise components; also, Deep (D) learning algorithm was used for trying to do learning of non-linear characteristics of water usage. The performance of a proposed framework or model was analyzed by comparing with the ARMA model, which is a linear time series model. As a result, the proposed model showed the correlation of 92% and ARMA model showed about 39%. Therefore, we had known that the performance of the proposed model was better than a linear time series model and KWD framework could be used for other nonlinear time series which has similar pattern with water usage. Therefore, if the KWD framework is used, it will be possible to accurately predict water usage and establish an optimal supply plan every the various event.

• Journal of the Korean Institute of Educational Facilities
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• v.19 no.6
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• pp.25-36
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• 2012

University campuses have been developed along with the historical development of mankind in association with the characteristics of urban changes. In particular, regarding the master plan reflecting periodic characteristics, now is the time to grope for crucial roles today that we are pursuing international growth of universities. Also, with the development of cities, in terms of the aspects of campus development, various borderline extension strategies are explored due to the physical limitation. And with the program methods through the exchange with the local community, we are concretizing this through the formation of new campuses. Seoul National University, the subject of this paper, is groping for ways of extension through the SNU-Valley Project with its Gwanak campus. Along with this, it is looking for ways of cubic borderline extension by forming Siheung international campus. The conclusion drawn through above contents is as written below: First, universities located in cites have relatively more limitations in the extension of campus space along with the development of urban space changes. To overcome this, various ways like political or physical space extension strategies are being explored. Second, along with the physical strategies visually shown in suggesting university campus master plans, we can recognize the importance of suggesting vision through specialization strategies. Third, it is about the importance of improving relationship with the local community. With the approaches based on human resources and reasonable connection of space, this also plays roles in enhancing the urbanity of the campus. Fourth, we can see the aspects of campus' urban function enhancing. It is needed to connect urban context that a region has with environment and grope for ways to enhance centrality, connection, and accessibility in it.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.1
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• pp.165-172
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• 2017

Machines are physically or chemically degenerated by continuous usage. One of the results of this degeneration is the process mean shift. Under the process mean shift, production cost, failure cost and quality loss function cost are increasing continuously. Therefore a periodic preventive resetting the process is necessary. We suppose that the wear level is observable. In this case, process mean shift problem has similar characteristics to the maintenance policy model. In the previous studies, process mean shift problem has been studied in several fields such as 'Tool wear limit', 'Canning Process' and 'Quality Loss Function' separately or partially integrated form. This paper proposes an integrated cost model which involves production cost by the material, failure cost by the nonconforming items, quality loss function cost by the deviation between the quality characteristics from the target value and resetting the process cost. We expand this process mean shift problem a little more by dealing the process variance as a function, not a constant value. We suggested a multiplier function model to the process variance according to the analysis result with practical data. We adopted two-side specification to our model. The initial process mean is generally set somewhat above the lower specification. The objective function is total integrated costs per unit wear and independent variables are wear limit and initial setting process mean. The optimum is derived from numerical analysis because the integral form of the objective function is not possible. A numerical example is presented.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.127-136
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• 2008

This paper proposes the efficient system for automatic design of FSS(Frequency Selective Surface) with periodic pattern and frequency characteristics specified by operator. The proposed system derives optimal design parameters through tool for analysis of FSS with arbitrary pattern, DB(Data Base) implemented from limited simulation and measurement data of FSS, and GA(Genetic Algorithm) for optimizing design parameters. FSS analysis tool consists of two analysis tools. One is the simulator for analysis of monolayer FSS that using moment method, another is the tool with approximated analysis method of FSS with dielectric layer. Given pattern configuration and characteristics specified by operators, the DB system searches the best matching FSS, and provides initial genes to GA from the searched parameters, which drastically reduces running time of GA for finding the FSS design parameters. In this paper, the proposed design system is verified through simulation and measurement about FSS with various patterns.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.178-178
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• 2023

Drought and flooding have historically coexisted in Korea, occurring at different times and with varying cycles and trends. The drought indicators measured were (PDSI), (SPI), and (SPEI) in order to statistically analyze the annual or periodic drought occurrence and objectively evaluate statistical characteristics such as the periodicity, tendency, and frequency of occurrence of droughts in the Doam watershed. To compute potential evapotranspiration (PET), both Thornthwaite (Thor) and Penman-Monteith (PM) parameterizations were considered, and the differences between the two PET estimators were analyzed. Hence, SPIs 3 and SPIs 6 revealed a tendency to worsen drought in the spring and winter and a tendency to alleviate drought in the summer in the study area. The seasonal variability trend did not occur in the SPIs 12 and PDSI, as it did in the drought index over a short period. As a result of the drought trend study, the drought from winter to spring gets more severe, in addition to the duration of the drought, although the periodicity of the recurrence of the drought ranged from 3 years to 6 years at the longest, indicating that SPIs 3 showed a brief time of around 1 year. SPIs 6 and SPIs 12 had a term of 4 to 6 years, and PDSI had a period of roughly 6 years. Based on the indicators of the PDSI, SPI, and SPEI, the drought severity increases under climate change conditions with the decrease in precipitation and increased water demand as a consequence of the temperature increase. Therefore, our findings show that national and practical measures are needed for both winter and spring droughts, which happen every year, as well as large-scale and extreme droughts, which happen every six years.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.6
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• pp.141-146
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• 2016

Geotechnial engineering projects that requires excavation activity can cause massive ground deformation and this can damage adjacent structures. Depending on the engineering characteristics of ground material and the excavation depth, the ground movement is various. To overcome this issue, the ground deformation is monitored by multiple sensors. Typically, an inclinometer is installed behind the support wall. In this paper, we present an adaptive duty-cycling control mechanism using wireless sensors for monitoring ground deformation in excavations. The proposed mechanism dynamically adjusts the sleep time based on the urgency degree of sensed data from inclinometer. Through analytical evaluation of expected latency time, we confirm our adaptive duty-cycling mechanism has lower latency compared with periodic duty-cycling mechanism under variable conditions.