• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.179.1-179.1
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• 2014

Si nanowires have exhibited unique optical characteristics, including nano-antenna effects due to the guided mode resonance, significant optical absorption enhancement in wide wavelength and incident angle range due to resonant optical modes, graded refractive index, and scattering. Since Si poor optical absorption coefficient due to indirect bandgap, all such properties have stimulated proposal of new optoelectronic devices whose performance can surpass that of conventional planar devices. We have carried out finite-difference time-domain simulation studies to design optimal Si nanowire array for solar cell applications. Optical reflectance, transmission, and absorption can be calculated for nanowire arrays with various diameter, length, and period. From the absorption, maximum achievable photocurrent can be estimated. In real devices, serious recombination loss occurring at the surface states is known to limit the photovoltaic performance of the nanowire-based solar cells. In order to address such issue, we will discuss how the geometric parameters of the array can influence the spatial distribution of the optical field (resulting optical generation rate) in the nanowires.

• Journal of Information Processing Systems
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• v.12 no.4
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• pp.765-778
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• 2016

In watermarking schemes, the discrete wavelet transform (DWT) is broadly used because its frequency component separation is very useful. Moreover, LU decomposition has little influence on the visual quality of the watermark. Hence, in this paper, a novel blind watermark algorithm is presented based on LU transform and DWT for the copyright protection of digital images. In this algorithm, the color host image is first performed with DWT. Then, the horizontal and vertical diagonal high frequency components are extracted from the wavelet domain, and the sub-images are divided into $4{\times}4$ non-overlapping image blocks. Next, each sub-block is performed with LU decomposition. Finally, the color image watermark is transformed by Arnold permutation, and then it is inserted into the upper triangular matrix. The experimental results imply that this algorithm has good features of invisibility and it is robust against different attacks to a certain degree, such as contrast adjustment, JPEG compression, salt and pepper noise, cropping, and Gaussian noise.

• Atmosphere
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• v.18 no.4
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• pp.485-492
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• 2008

This study confirms that a decadal variation of the SST (Sea Surface Temperature) in the WNP (Western North Pacific) has an influence on the genesis and passage ofa Tropical Cyclone. The decadal mode was obtained by calculating the SST anomaly on the domain $150^{\circ}E-190^{\circ}E$, and $5^{\circ}S-5^{\circ}N$. Such decadal variation was subsequently analyzed to confirm that it is a dominant mode in central Pacific region. Next, after classifying the years into relatively positive years and relatively negative years, the characteristics of Tropical Cyclone in each year, such as a genesis and passage frequency, were investigated. Compared to the relatively negative years, during the relatively positive years, the location of Tropical Cyclone genesis was biased toward South-Eastern region, while the characteristics of the cyclone were more distinct during late season of the year trom September to December than in mid season from June to August. Examining the movement passage through the observation of passage fiequency, there was a significant difference between positive year and negative year in their passages at a 90% confidence level. Moreover, the number of Tropical Cyclone, maximum wind, and life time also showed higher values in positive years than in negative years. These features were confirmed by examining the 850hPa cyclonic flow field, vorticity field, and vertical wind shear field, all of which contribute to the genesis of a Tropical Cyclone.

• Asian Journal of Atmospheric Environment
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• v.8 no.2
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• pp.108-114
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• 2014

In the companion paper (Lee et al., 2012), it was showed that CMAQ simulation using a lateral boundary conditions (LBCs) derived from RAQMS-CMAQ linkage, compared to the CMAQ results with the default CMAQ LBCs, improved ozone simulations in the conterminous US domain. In the present paper, the study is extended to investigate the influence of LBCs on PM2.5 simulation. MM5-SMOKE-CMAQ modeling system was used for meteorological field generation, emissions preparation and air quality simulations, respectively. Realtime Air Quality Modeling System (RAQMS) model assimilated with satellite observations were used to generate the CMAQ-ready LBCs. CMAQ PM2.5 simulations with RAQMS LBCs and predefined LBCs were compared with U.S. EPA Air Quality System (AQS) measurements. Mean PM2.5 lateral boundary conditions taken from RAQMS outputs showed strong variations both in the horizontal grid and vertical layers in the northern and western boundaries and affected the results of CMAQ PM2.5 predictions. CMAQ with RAQMS LBCs could improve CMAQ PM2.5 predictions resulting in the improvement of index of agreement from 0.38 to 0.63.

• Journal of the Korean Regional Science Association
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• v.6 no.1
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• pp.1-10
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• 1990

Regionalism has become a liability in Korea, hampering national harmony and political stability. The regionalism finds its roots in several centuries back in history. The traditional regionalism was based on the provincial differences in cultural and social characteristics, and behavioral mannerism. Therefore, the traditional regionalism should be regarded as benign and common as in many other countries in the world. The modern version of Korean regionalism seems to be founded on the "discriminatory" treatments of Honam provinces in economic policy and the resultant regional economic disparity during the last three decades. Many believe that such "discriminatory" policy had been enforced during the period of the "third" and "fourth" republics under the influence of the key government officials and presidents form the Southeastern provinces. Since the early 80s, many public investment projects have found its home in the Honam region with the consideration of regional balance and more equitable distribution. This paper attempts to elucidate on various causes of regional disparity amplified during the period of industrialization, and also presents the economic indices which demonstrate the impacts of the policy in narrowing the economic disparity among the regions in recent years. The paper also clarifies the limits of regional economic policy in achieving regional. balance and consequently social integrity. The last part of the paper attempts to clarify the effective domain of regional policy and the new direction of regionalism.cy and the new direction of regionalism.

• New & Renewable Energy
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• v.2 no.4 s.8
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• pp.78-85
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• 2006

Selection of flow channel in the separation plate of PEMFC is very important parameter to improve its performance and reduce parasite loss. Flow patterns in the channel have great influence on the transport of hydrogen and air and removal of water generated from electrochemical reaction in diffusion layer. In this study. fluid flow in flow channel with parallel and interdigitated patterns are simulated three dimensionally on full flow domain including anode and cathode channel together. The numerical results show that the fuel cell with interdigitated flow channel represents better performance than that with parallel flow channel due to its strong convective transport across the gas diffusion layer. But the pressure drop in parallel flow channel is much more than that in interdigitated flow channel. And effects of temperature and stoichiometric number on performance can be calculated and analyzed as well. Nomenclature.

• Journal of KSNVE
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• v.5 no.1
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• pp.75-83
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• 1995

The fluctuation of the engine torque appears to be the major source of the torsional vibration of the automotive driveline. The reduction of this torsional vibration has become a significant problem, due to an increase in the fluctuation of the torque of recent light weighted and high powered engines, along with the requirements of higher performance. The torsional vibration of the automotive driveline can be reduced by smoothing the fluctuation by adjusting the torsional characteristics of the clutch-disc. This paper presents an experimental and theoretical research on the clutch-disc torsional characteristics for the reduction of the torsional vibration at driving. The effects of clutch-damper on diminishing the torsional vibration were investigated experimentally. A dynamic model for the automotive driveline was developed, and the engine torque of the model were evaluated with experimental data. By executing a simulation using the model, it has become possible to obtain the clutch-disc torsional characteristics and the clutch-disc torsional characteristics for reducing the torsional vibration has been suggested. The results are as follows: (1) By exceuting simulations using nonlinear model of four degrees of freedom, a design technique to determine the clutch-disc torsional characteristics for reducing the torsional vibration at driving was developed. (2) The influence of barious torsional characteristics of the clutch has been studied in examining design parameters, which indicates that the domain to minimize the torsional vibration at driving depends on the characteristics of the clutch-damper, i. e., spring constant and hysteresis.

• Journal of the Korean Institute of Navigation
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• v.19 no.4
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• pp.1-8
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• 1995

Although ship's draught information onboard is substantial for both the safety of navigation and the estimation of loaded cargoes, its accuracy depends, in conventional surveying method, on the skillfulness of observers and the condition of the sea surface round the vessel. To obtain more accurate information accessibly, measuring instruments with sophisticated sensors such as mechanical, electronic and ultrasonic transducers have been developed. However, they have still limitation in accuracy and in making up a system due to the complexity of processing signal. In this paper, we propose a new technique for analyzing ultrasonic pulse signal, in order to improve the measurement accuracy and simplify a remote sensing system of draught by ultrasonic waves. In this technique, pulse signal is translated into phase curve which is composed of the phase value defined in time domain. Then, the time interval between two signals different in waveform, is waveform, is analytically determined by calculating average time difference on phase curves. Also, analytical procedure can be carried out in real time with the successive five data sampled at T/4, for high speed digital processing with computer and A/D converter. This technique is useful for measuring draught under the influence of sea condition and for interfacing its data briefly to the integrated bridge system.

• Journal for History of Mathematics
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• v.17 no.4
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• pp.87-100
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• 2004

There is great enthusiasm among many mathematics educators to seek to understand how mathematical history can be employed to emphasize the usefulness of mathematics and to make it even more useful. This study focused on reviewing the history of mathematics to provide a 'source of insight.' In this study, the reasons for including the history of mathematics in the mathematics curriculum were divided into three domains: cognitive, affective, and sociocultural. Each domain included the followings: mathematical thinking and understanding; development of a positive attitude and increase motivation; and last, humanistic facets and sociocultural experience. At the same time, we need to develope a pedagogical approach that allows educators to use history properly. Furthermore, we must integrate the historical topics into regular curricula including the syllabus historically-informed grounds.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.5
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• pp.1881-1903
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• 2015

With the fast-developing of mobile terminals, positioning techniques based on fingerprinting method draws attention from many researchers even world famous companies. To conquer some shortcomings of the existing fingerprinting systems and further improve its performance, we propose a radio map building and updating technique, which is able to customize the spatial and temporal dependency of radio maps. The method includes indoor propagation and penetration modeling and the analysis of human traffic. Based on the combination of Ray-Tracing Algorithm, Finite-Different Time-Domain and Rough Set Theory, the approach of indoor propagation modeling accurately represents the spatial dependency of the radio map. In terms of temporal dependency, we specifically study the factor of moving people in the interest area. With measurement and statistics, the factor of human traffic is introduced as the temporal updating component. We improve our existing indoor positioning system with the proposed building and updating method, and compare the localization accuracy. The results show that the enhanced system can conquer the influence caused by moving people, and maintain the confidence probability stable during week, which enhance the actual availability and robustness of fingerprinting-based indoor positioning system.