• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.796-803
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• 1997

The PVT and $^2H$-NMR characteristic of main-chain dimer liquid crystals having structures such as ${\alpha}$, ${\omega}$-bis[4,4'-cyanobiphenyl) oxy] alkane(CBA-10) were studied. In this work, V-T curves obtained from isobaris measurements on various pressures, volume changes were observed at the nematic-isotropic and nematic-crystal phase transition. The volume changes at the transition exhibit slight odd-even effect with respect to the number of methylene unit n. The values of the$({\Delta}S_{tr})_V$ obtained at the NI transition for CBA-10 was $12.6J/mol{\cdot}K$. The values of $({\Delta}S_{CN})_V$ for the CN transition was estimated on the basis of DSC data : $65.3J/mol{\cdot}K$. For both transition, it was found that the correction about the volume change is significant, ranging from 40 to 60% of the total transition entropy observed under constant pressure. The RIS analysis of the spectra was performed so as to elucidate the conformational characteristics of the spacer in the nematic phase. The conformational entropy changes at both CN and NI interphases were estimated on the basis of the nematic conformations taken from the conformation map as well as those derived from the simulation. The estimated conformational entropy change values were then compared with the corresponding constant-volume entropies obtained from PVT measurements. The correspondence between both entropy values was found to be quite good in consideration of the uncertainties involved in both experiment and calculations.

• Archives of design research
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• v.20 no.3 s.71
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• pp.119-128
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• 2007

With the development of digital technologies, CAID became an essential part in the industrial design process. Creating photo-realistic images from a virtual scene with 3D models is one of the specialized task for CAID users. This task requires a complex interface of setting the positions and the parameters of camera and lights for optimal rendering results. However, the user interface of existing CAID tools are not simple for designers because the task is mostly accomplished in a parameter setting dialogue window. This research address this interface issues, in particular the issues related to lighting, by developing and evaluating TLS(Tangible Lighting Studio) that uses Augmented Reality and Tangible User Interface. The interface of positioning objects and setting parameters become tangible and distributed in the workspace to support more intuitive rendering task. TLS consists of markers, and physical controller, and a see-through HMD(Head Mounted Display). The user can directly control the lighting parameters in the AR workspace. In the evaluation experiment, TLS provide higher effectiveness, efficiency and user satisfaction compared to existing GUI(Graphic User Interface) method. It is expected that the application of TLS can be expanded to photography education and architecture simulation.

• Journal of the Korean Institute of Landscape Architecture
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• v.30 no.4
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• pp.37-46
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• 2002

The main purpose of this research is to discuss the urban heat island which will be caused by urbanization, especially by the construction of new town on a wide green zone. Over the last ten years, five new towns have been developed around the Seoul metropolitan area. However these new towns become bedroom communities and create traffic problems between Seoul and its surrounding areas because of an increase in population and a lack of roads and other infrastructures. The construction of another such new town is under consideration in the Pan-gyo area. But it is important that Pan-gyo remains a wide green zone. Many studies show that green space can play an important role in improving urban eco-meteorological, ameliorative capability and air hygiene. The objective of this study is to analyze the urban heat islands of Bund-Dang Si which was constructed in 1996 and of the Pan-Gyo area planned as new town. To investigate the local thermal environment and its negative effects caused by change of the land use type and urbanization we used LANDSAT TM images for extraction of urban surface temperature according to change of land use over 15 years. These data were analyzed together with digital land use and topographic data. As a study result, we found that the thermal island of this area from 1985 to 1999 rapidly increased with a difference of mean temperature of more than 12'E. Before construction of Bun-Dang Si the temperature of this area was the same as the forest, but during the new town construction in 1991, an urban heat island developed. The temperature of forest with a size of over 50% of the investigation area was lowest, which leads us to conclude that the forest cools the urban and its surroundings. The mean temperature of the residential and commercial area is more than +4.5$^{\circ}C$ higher then forest, so this method of land use is the main factor increasing the urban heat island. Urban heat islands and green space play an important role in urban wind systems, i.e. Thermal Induced Air Exchange and Structural Wind Circulation, because of their special properties with regard to energy balance between constructed urban and land. The skill to allocate land use types in urban areas is a very important planning device to reduce air pollution and induce the fresh cold air from green space. An urban climatic experiment featuring a numerical wind simulation study to show the air corridor will be published in a following research paper.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.3
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• pp.180-201
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• 2020

It has been widely known that the effect of diffracted waves at the tip of composite breakwater with finite length causes the change of standing wave height along the length of breakwater, the spatial change of wave pressure on caisson, and the occurrence of meandering damage on the different sliding distance in sequence. It is hard to deal with the spatial change of wave force on trunk of breakwater through the two-dimensional experiment and/or numerical analysis. In this study, two and three-dimensional numerical techniques with olaFlow model are used to approach the spatial change of wave force including the impulsive breaking wave pressure applied to trunk of breakwater, the effect of rear region, and the occurrence of diffracted waves at the tip of caisson located on the high crested rubble mound. In addition, it is thoroughly studied the mean wave height, mean horizontal velocity, and mean turbulent kinetic energy through the numerical analysis. In conclusion, it is confirmed that the larger wave pressure occurs at the front wall of caisson around the still water level than the original design conditions when it generates the shock-crushing wave pressure checked by not two-dimensional analysis, but three-dimensional analysis through the change of wave pressure applied to the caisson along the length of breakwater.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.4
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• pp.314-321
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• 2000

A gap between a $Al_2O_3/Fe$ thermite and lower head vessel is formed in the lower-plenum arrested vessel attack(LAVA) experiment which is the 1st phase study of simulation of naturally arrested vessel attack in vessel(SONATA-IV). The gap measurement using a conventional ultrasonic method would be lack of a reliability due to the structure complexity and the metallurgical grain size change of the lower head HAZ occurred by a thermite $Al_2O_3/Fe$ melt or a $Al_2O_3$ melt at $2300^{\circ}C$. The grain echoes having false signals and lower S/N ratio signals are detected due to a multiple scattering, a mode conversion and an attenuation of a ultrasonic resulted from at the interface of increased grain size zone. In this test, the signals pattern was classified to understand the behavior of the ultrasonic in a multi-layer specimen of solid-liquid-solid of assuming that the thermite and the lower head vessel is immersed. The polarity threshold algorithm of frequency diversity gives us the enhancement about 6dB of the ratio S/N.

• Korean Journal of Remote Sensing
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• v.30 no.6
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• pp.777-786
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• 2014

Mt. Ontake is the second highest volcano in Japan. On 02:52 Universal Time Coordinated(UTC), 27th September 2014, Ontake volcano began on the large eruption without notice. Due to the recent eruption, 55 people were killed and around 70 people injured. Therefore, This paper performed numerical experiment to analyse damage effect of volcanic ash corresponding to Ontake volcano erupt. The forecast is based on the outputs of the HYSPLIT Model for volcanic ash. This model, which is based on the UM numerical weather prediction data. Also, a quantitative analysis of the ash dispersion area, it has been detected using satellite images from optical Communication, Ocean and Meterological Satellite-Geostationary Ocean Color Imager (COMS-GOCI) images. Then, the GOCI detected area and simulated ash dispersion area were compared and verified. As the result, the similarity showed the satisfactory result between the detected and simulated area. The concordance ratio between the numerical simulation results and the GOCI images was 38.72 % and 13.57 %, Also, the concordance ratio between the JMA results and the GOCI images was 9.05 % and 11.81 %. When the volcano eruptions, volcanic ash range of damages are wide more than other volcanic materials. Therefore, predicting ash dispersion studies are one of main way to reduce damages.

• Journal of the Korean Wood Science and Technology
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• v.45 no.3
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• pp.343-359
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• 2017

Many researches and policies have been carried out for saving energy in buildings. However, there are a few studies of thermal characteristics of wood-based materials that have been widely used as structural materials and finishing materials in buildings. In this study, thermal bridging areas were found to investigate thermal performance of residential building using non wood-based materials and wood-based materials. And heat transfer analysis of 16 case studies according to composition of structural materials and finishing materials was conducted. Also in this experiment, Physibel Trisco was used as the heat transfer analysis simulation tool, which conforms to the calculation method of ISO 10211. Analytical modeling was also carried out according to the ISO 10211, and the boundary temperature conditions were set at room temperature $20^{\circ}C$ and outdoor temperature $-11.3^{\circ}C$ (Seoul standard) according to the energy saving design standard in South Korea. Applied structures are classified according to the cases of concrete structure with non wood-based finishing materials, concrete structure with wood-based finishing materials and wood structure. Analyzed building elements were divided into a wall, a roof, an interlayer floor and a bottom floor. As a result, it can be confirmed that the thermal bridge of the concrete structure and wood structure were caused by the geometrical and material causes. In addition, the structural thermal bridge was caused in the discontinuity of the insulation in the concrete structure. Also it was confirmed that the linear heat transfer coefficient of the wall decreases when the wood-based materials are applied to the concrete structure.

• Journal of the Korean Vacuum Society
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• v.10 no.4
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• pp.431-439
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• 2001

In this paper, the a-Diamond films were synthesized using filtered vacuum arc source (FVAS), FVAS was composed of a torus structure with bending angle of 60 degree. The radius of torus was 266 mm, the radius of plasma duct was 80 mm and the total length was 600 mm. The magnet parts were composed of one permanent magnet and five solenoid magnets. The plasma duct was electrically isolated from the ground so that a bias voltage could be applied. The baffles inside plasma duct were installed in order to prevent the recoil effect of macro-particles. Cathode was made of graphite with 80 mm in diameter. The effects of solenoid magnet on plasma extraction were investigated by computer simulation and experiment using Taguchi's methode. The source and extraction magnet affected the arc stabilization. The extraction beam current was maximized with low value of the source magnet current and high value of the filtering magnet current. The beam current density was 3.2 mA/$\textrm{cm}^2$ and average deposition rate was 5 $\AA$/sec when the currents of arc discharge, source, extraction, bending, deflection and outlet magnet were 30 A, 1 A, 3 A, 5 A, 5 A, and 5 A, respectively. The beam current density and the efficiency of beam transportation were increased with the positive bias voltage of the plasma duct.

• The KIPS Transactions:PartC
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• v.14C no.3 s.113
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• pp.277-284
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• 2007

The routing algorithm many used in the wireless sensor network features the clustering method to reduce the amount of data transmission from the energy efficiency perspective. However, the clustering method results in high energy consumption at the cluster head node. Dynamic clustering is a method used to resolve such a problem by distributing energy consumption through the re-selection of the cluster head node. Still, dynamic clustering modifies the cluster structure every time the cluster head node is re-selected, which causes energy consumption. In other words, the dynamic clustering approaches examined in previous studies involve the repetitive processes of cluster head node selection. This consumes a high amount of energy during the set-up process of cluster generation. In order to resolve the energy consumption problem associated with the repetitive set-up, this paper proposes the Round-Robin Cluster Header (RRCH) method that fixes the cluster and selects the head node in a round-robin method The RRCH approach is an energy-efficient method that realizes consistent and balanced energy consumption in each node of a generated cluster to prevent repetitious set-up processes as in the LEACH method. The propriety of the proposed method is substantiated with a simulation experiment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.160-168
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• 2003

In Korea, a large portion of aerial power-transmission cables is installed in the mountains. In the case of a fire in the mountains, steel wires coated with zinc and aluminum wires of those power cables exposed to the fire or near around will be deteriorated by the blaze and the high temperature. Deterioration proceeds by interactions of a variety of factors like quality, manufacturing process, the condition of installation and exposure environment of a wire, and so on. Generally, the characteristic of a conductor affect by a forest fire can not be analyzed without the effect through simulating a forest fire. However, there are little research accomplishments of that kind of simulation about it, and there's been no analysis of a sample exposed to an actual forest fire. This thesis shows the experimental results that apply to a new wire by an artificial flame-maker because it's difficult to directly analyze the characteristic of deterioration by a forest fire. Those results include the intensity of extension and wrench for a conductor. In addition, there's been an experiment and analysis about the mechanical characteristics of the wire of ACSR 480[$\textrm{mm}^2$] which was removed from Pohang area by a forest fire. Then, the database will be made to predict the state of deteriorated wires by a forest fire using those two data, and data necessary to diagnose the life state of an ACSR wire affected by a forest fire will be given.