• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.97-97
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• 2000

In this thesis, the metastable state diamond thin films have been deposited on Si substrates from methane-hydrogen and oxygen mixture using Microwave Plasma Enhanced Chemical Vapor deposition (MWPCVD) method. Effects of each experimental parameters of MWPCVD including methane concentrations, oxygen additions, operating pressure, deposition time, etc. on the growth rate and crystallinity were investigated. SEM, XRD, and Raman spectroscopy were employed to analyze the growth rate and morphology, crystallinity and prefered growth direction, and relative amounts of diamond and non-diamond phases respectively. As a methane concentration below 4%, the deposited films having well-defined facets could be obtained. As the methane concentration increases over 4%, the shape of films gradually changed into a amorphos form. The best crystallinity of the film at 3% in the Raman spectroscopy. Addition of oxygen to the methane-hydrogen mixture gave an improved film crystallinity at 50% oxygen concentration due to its more effectiveness in the selective removal of the non-diamond phased compared to the of H atom. on the contrary, the growth rate generally decreased by oxygen to from the more stable CO and CO2 is responsible for such an effect. Upon increasing the operating pressure and time, increased of growth rate and crystallinity were increased simultaneously.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.498-501
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• 2005

Photonic crystals, periodic structure with a high refractive index contrast modulation, have recently become very interesting platform for manipulation of light. The existence of a photonic bandgap, a frequency range in which propagation of light is prevented in all direction, makes photonic crystal very useful in application where spatial localization of light is required for waveguide, beam splitter, and cavity. But fabrication of 3 dimensional photonic crystal is still difficult process. a concept that has recently attracted a lot of attention is a planar photonic crystal based on a dielectric membrane, suspended in the air, and perforated with 2 dimensional lattice of hole. We show that the polymer slabs suspended in air with triangular lattice of air hole can exhibit the in-plane photonic bandgap for TE-like modes. The fabrication of Si master with pillar structure using hot embossing process was investigated for 2 dimensional low-index-contrast photonic crystal waveguide.

• Journal of the Semiconductor & Display Technology
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• v.9 no.2
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• pp.1-6
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• 2010

Star-like ZnO nanostructures were grown on SI(100) substrates with carbon(C) catalyst by employing vapor-solid(VS) mechanism. The morphologies and structure of ZnO nanostructures were investigated by Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Raman spectrum, Photoluminescence spectrum. The results demonstrated that the as-synthesized products consisted of star-like ZnO nanostructure with hexagonal wurtzite phase. Nanostructures grown at 1100 were mainly star-like in structure with diameters of 500 nm. The legs of the star-like nanostructures were preferentially grown up along the [0001] direction. A vapor.solid (VS) growth mechanism was proposed to explain the formation of the star-like structures. Photoluminescence spectrum exhibited a narrow emission band peak around 380 nm and a broad one around 491 nm. Raman spectrum of the ZnO nanostructures showed oxygen defects in ZnO nanostructures due to the existence of Ar gas during the growth process, leading to the dominant green band peak in the PL spectrum.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.24 no.3
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• pp.19-31
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• 2021

The waste landfill that has been used as a park through a stabilization project to provide green space to local residents. Vegetation restoration is necessary for the landfill park project, but it is difficult to restore vegetation due to various disturbances in the landfill. This study analyzed the successional dynamics and ecological characteristics of Robinia pseudoacacia communities from the slopes of Noeul Park by applying the 7-stage successional hypothesis. As a result of the study, there was almost no intermediate successional stage. There are only the early successional stage which Robinia pseudoacacia has an absolute dominance of 100% in the crown and middle layers, and the degeneration successional stage which formed by the introduction of Morus alba. This result showed that the succession of Robinia pseudoacacia communities were not able to proceed to the climax forest due to various disturbances in the waste landfill. Therefore, it was analyzed that it is necessary to induce the succession through intermediate steps such as Morus alba, since it is difficult to transition from Robinia pseudoacacia community to the native Quercus spp. community.

• Journal of Korea Society of Digital Industry and Information Management
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• v.18 no.4
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• pp.23-30
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• 2022

Recently, traffic congestion and environmental pollution have occurred due to population concentration and vehicle increase in large cities. Various studies are being conducted to solve these problems. Most of the traffic congestion in cities is caused by traffic signals at intersections. This paper proposes a dynamic traffic light control (DTLC) scheme to support safe vehicle operation and smooth traffic flow using real-time traffic information based on VANET. DTLC receives instantaneous speed and directional information of each vehicle through road side units (RSUs) to obtain the density and average speed of vehicles for each direction. RSUs deliver this information to traffic light controllers (TLCs), which utilize it to dynamically control traffic lights at intersections. To demonstrate the validity of DTLC, simulations were performed on average driving speed and average waiting time using the ns-2 simulator. Simulation results show that DTLC can provide smooth traffic flow by increasing average driving speed at dense intersections and reducing average waiting time.

• Tribology and Lubricants
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• v.38 no.6
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• pp.247-254
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• 2022

Chemical mechanical polishing (CMP) is a hybrid surface-polishing process that utilizes both mechanical and chemical energy. However, the recently emerging semiconductor substrate and thin film materials are challenging to process using the existing CMP. Therefore, previous researchers have conducted studies to increase the material removal rate (MRR) of CMP. Most materials studied to improve MRR have high hardness and chemical stability. Methods for enhancing the material removal efficiency of CMP include additional provision of electric, thermal, light, mechanical, and chemical energies. This study aims to introduce research trends on CMP using ultraviolet (UV) light to these methods to improve the material removal efficiency of CMP. This method, photocatalysis-assisted chemical mechanical polishing (PCMP), utilizes photocatalytic oxidation using UV light. In this study, the target materials of the PCMP application include SiC, GaN, GaAs, and Ru. This study explains the photocatalytic reaction, which is the basic principle of PCMP, and reviews studies on PCMP according to materials. Additionally, the researchers classified the PCMP system used in existing studies and presented the course for further investigation of PCMP. This study aims to aid in understanding PCMP and set the direction of future research. Lastly, since there have not been many studies on the tribology characteristics in PCMP, research on this is expected to be required.

• Journal of the Korean Society of Clothing and Textiles
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• v.47 no.1
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• pp.1-16
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• 2023

The smart fashion industry is showing steady growth worldwide, which will create new value throughout the fashion industry and become an essential element for efficient lifestyles. This study attempted to examine the development trend of smart fashion products from a design perspective and present the direction of design as a fashion item incorporating smart technology from a functional perspective. For this purpose, the category of portable smart fashion and the characteristics of the research object were considered through current status survey and previous research review. Among smart fashion, accessories and clothing/fabric products that have been released thus far that apply portable fashion design principles are selected and its characteristics are analyzed. In addition, function keywords were extracted based on the product description provided by the manufacturer and the function-oriented types were classified to identify each type's design characteristics. Therefore, the area receiving the signal and the sensor size should be considered, as should the fashion accessory type that combines various materials and colors. The clothing/textile type requires a design that mainly focuses on functions related to bio-signal interactions.

• Journal of Environmental Science International
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• v.31 no.12
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• pp.1089-1102
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• 2022

Recently, urbanization has become a serious issue, as there is imbalance between regions and various environmental problems occur intensively in cities. Therefore, cities all over the world are promoting the Green New Deal and trying to realize carbon neutrality. Accordingly, the European Union is leading the creation of carbon-neutral cities by promoting policies aimed at rapidly realizing carbon neutrality. In Korea, projects such as U-City and Smart City have also been promoted continuously for many years, and recently, the projects Smart Green City and Carbon Neutral Green City have been introduced. Therefore, this study aimed to derive directions and implications for future projects based on policies to address climate change by analyzing the guidelines for the Smart Green City project and the project plans of Gimhae-si and Gangjin-gun, which are the leading projects in the Smart Green City business model and are equipped with an extensive budget.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.2
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• pp.153-168
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• 2024

Morphological and skeletal development in the cultured threeline grunt Parapristipoma trilineatum was studied from 1.96 to 61.39 mm notochord length (NL) or standard length (SL) specimens (n=360). After two days post-hatching (dph, 2.13 mm NL), the mouth opened, and melanophores formed in the eyes and egg yolk were absorbed. Oli globules were absorbed at 3 dph (2.71 mm NL). The total number of fin rays reached that of adults at 28 dph (10.58 mm SL). During skeletal development, the premaxillaray, dentary, opercle, preopercle, and cleithrum first began to ossify at 6 dph (3.51 mm NL). Ossification of all skeletal elements was completed at 28 dph (14.57 mm SL). The vertebrae began to ossify at 17 dph (5.63 mm SL) and were completed at 28 dph (8.48 mm SL), progressing from cranium to caudal bone. The centrum ossified from the dorsal to ventral direction. Vertebral fusion and separation were found to be common skeletal abnormalities.

• Journal of Radiation Industry
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• v.17 no.4
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• pp.551-557
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• 2023

In recent years, radiation has become a socially important issue, increasing the need for accurate prediction of radiation levels. In this study, machine learning-based models such as Multiple Linear Regression (MLR), Random Forest (RF), XGBoost, and LightGBM, which predict the dose rate by time(nSv h^-1) by selecting only important variables, were used, and the correlation between temperature, humidity, cumulative precipitation, wind direction, wind speed, local air pressure, sea pressure, solar radiation, and radiation dose rate (nSv h^-1) was analyzed by collecting weather data and radiation dose rate for about 6 months in Jangseong, Jeollanam-do. As a result of the evaluation based on the RMSE (Root Mean Squared Error) and R-Squared (R-Squared coefficient of determination) scores, the RMSE of the XGBoost model was 22.92 and the R-Squared was 0.73, showing the best performance among the models used. As a result of optimizing hyperparameters of all models using the GridSearch method and comparing them by adding variables inside the measuring instrument, it was confirmed that the performance improved to 2.39 for RMSE and 0.99 for R-Squared in both XGBoost and LightGBM.