• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.114.1-114.1
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• 2012

To measure the magnetic field strength in the solar corona, we examined 10 fast (>1000 km/s) limb coronal mass ejections (CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and magnetic field strength in the height range 3-15 solar radii (Rs). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock strength is in the range 1.49-3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47-1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the magnetic field strength is in the range 6-105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of two, the Alfven speeds and the magnetic field strengths are consistent in both methods; and (5) the magnetic field strengths derived from the shock parameters are similar to those of empirical models and previous estimates.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.170-175
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• 2003

A control algorithm is developed for highly efficient operation of auxiliary power unit (APU) that consists of a diesel engine and a directly coupled induction generator in series hybrid electric Bus (SHEB). In a series hybrid configuration the APU supplies the electric power needed for maintaining the state of charge (SOC) of the battery unit in various conditions of vehicle operation. As the rotational speed of generator does not depend on the vehicle speed, an optimized operation of engine-generator unit based on the efficiency map of each component can be achieved. The output torque of diesel engine can be controlled by the amount of fuel injection, and the power converted from mechanical to electrical energy can be adjusted by generate control unit (GCU) using the decoupling vector control of torque and flux. As for the given reference of the generating power, the multiply of speed and torque, many combinations of operating speed and torque are possible. The algorithm decides the new operating point based on the engine efficiency map and generator characteristic curve. During the transition of operating points, the speed controller saturation is avoided using variable limit and filtering of generator torque reference. A test rig and SHEB consist of a 1.5L diesel engine and a 30kw induction generator are constructed by Hyundai Motor Company.

• IE interfaces
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• v.18 no.2
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• pp.205-220
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• 2005

This study presents a web log analysis model for e-CRM, which combines the on-line customer's purchasing pattern data and transaction data between companies in B2B environment of make-to-order company. With this study, the customer evaluation and the customer subdivision are available. We can forecast the estimate demands with periodical products sales records. Also, the purchasing rate per each product, the purchasing intention rate, and the purchasing rate per companies can be used as the basic data for the strategy for receiving the orders in future. These measures are used to evaluate the business strategy, the quality ability on products, the customer's demands, the benefits of customer and the customer's loyalty. And it is used to evaluate the customer's purchasing patterns, the response analysis, the customer's secession rate, the earning rate, and the customer's needs. With this, we can satisfy various customers' demands, therefore, we can multiply the company's benefits. And we presents case of the 'H' company, which has the make-to-order manufacture environment, in order to verify the effect of the proposal system.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.425-427
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• 1996

New fabrication technique was developed to make three dimensional silicon microstructure with five fold vertical steps through entire wafer thickness. Each step is pre-defined on multiply stacked thermal oxide and silicon nitride (O/N) layers by photolithographies. Multi-stepped silicon microstructure is formed by anisotropic etch in aqueous KOH solution with the patterned nitride film as masking layer. Fabricated microstructure consists of four $16{\mu}m$ thick flexural spring beams, $290{\mu}m$ thick proof mass, mesas for overrange stop with $10{\mu}m$ height from the surface of the proof mass, and the other mesas and V grooves used for assembling this structure to the packaging frame of pendulous servo accelerometer. Using the numerical finite element method (FEM) simulator: ABAQUS, mechanical characteristics of the fabricated microstructure by the developed technique was compared with those of the same structure processed by one step silicon bulk etch followed by oxidation and patterning the etched region.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.10
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• pp.1454-1460
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• 1993

The scattering pattern, due to an E-Polarized wave incident on M circular parallel dielectric cylinders, is computed. The multiply-scattered fields between the cylinders are considered. Modeling of infinite cylindrical scatterer of arbitrary cross sections by a number of circular cylinders is executed. By enforcing the boundary conditions on the surface of each cylinder, an infinite set of equations is obtained. The first order of scattering results from the excitation of each cylinder by only the incident wave. The second order results from the excitation of each cylinder by the first order of scattering from the remaining cylinders, and so no to an infinite order of scattering. Although the resulting equation is of infinite size, proper truncation yields very accurate numerical results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.2
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• pp.19-26
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• 2015

This paper presents design, fabrication, and performance evaluation of a high voltage power supply for Carbon Nano Tube-based planar light sources. The proposed power supply employs an LLC resonant half-bridge converter and a sixfold voltage-multiplying rectifier. Steady-state characteristics of the voltage-multiplying rectifier are analyzed and used to derive the input-to-output voltage conversion ratio of the power supply. The input-to-output frequency response characteristics of the LLC tank circuit are analyzed and utilized in designing a proto-type power supply which produces a 15 KV output using a 400 V input source. The high-voltage transformer is fabricated using a sectional bobbin structure with an epoxy impregnation, in order to provide sufficient insulation for high voltage operations. The performance of the proposed power supply is confirmed with stable and reliable operations at the 15 KV output from no load to nominal load conditions. The proposed power supply is well suited as an electric ballast required stable operations of Carbon Nano Tube-based planar light sources.

• Journal of KIISE
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• v.42 no.7
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• pp.868-877
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• 2015

The barcode area extraction from images has been extensively studied, and existing methods exploit frequency characteristics or depend on the Hough transform (HT). However, the slantedness of the images and noise affects the performance of these approaches. Moreover, it is difficult to deal with the case where an image contains multiple barcodes. We therefore propose a barcode detection algorithm that is robust under such unfavorable conditions. The pre-processing step implements a probabilistic Hough transform to determine the areas that contain barcodes with a high probability, regardless of the slantedness, noise, and the number of instances. Then, a frequency component analysis extracts the barcodes. We successfully implemented the proposed system and performed a series of barcode extraction tests.

• Korean Journal of Optics and Photonics
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• v.14 no.6
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• pp.630-635
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• 2003

We propose an encryption method using visual cryptography and virtual phase images. In the encryption process, the original image is shared by virtual images and the decryption key image. We multiply the virtual phase images with each complex image, which has the constant value of its sum after performing the phase modulation of the virtual images and the decryption key. The encryption cards are made by Fourier transforming the multiplied images. It is possible to protect information about the original image because the cards do not have any information from the original image. To reconstruct the original image, all the encryption cards are placed on each path of a Mach-Zehnder interferometer and then the lights passing through them are summed. Since the summed image is inverse Fourier transformed by a Fourier lens, the phase image is multiplied with the decryption key and the output image is obtained in the form of intensity on the CCD plane. Computer simulations show a good performance of the pro-posed optical security system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.195-200
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• 2018

A W-band frequency octupler is implemented on 100-nm GaAs pHEMT process. The fabricated octupler can be used as a local oscillator or a signal source of W-band transceivers. Three common-source doublers are connected in cascade to multiply an input signal of 10.75 GHz to 83 GHz. A common-source amplifier is followed for each doubler to improve the conversion gain and suppress the unwanted harmonics. The fabricated octupler showes high output of more than 6 dBm in the 80 - 84 GHz band and achieved excellent spurious suppression performance over 20 dBc.

• The Mathematical Education
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• v.57 no.4
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• pp.453-475
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• 2018

This study examines how elementary students understand fractions with operations conceptually and how they perform procedures in the division of fractions. We attempted to look into students' understanding about fractions with divisions in regard to mathematical proficiency suggested by National Research Council (2001). Mathematical proficiency is identified as an intertwined and interconnected composition of 5 strands- conceptual understanding, procedural fluency, strategic competence, adaptive reasoning, and productive disposition. We developed an instrument to identify students' understanding of fractions with multiplication and division and conducted the survey in which 149 6th-graders participated. The findings from the data analysis suggested that overall, the 6th-graders seemed not to understand fractions conceptually; in particular, their understanding is limited to a particular model of part-whole fraction. The students showed a tendency to use memorized procedure-invert and multiply in a given problem without connecting the procedure to the concept of the division of fractions. The findings also proposed that on a given problem-solving task that suggested a pathway in order for the students to apply or follow the procedures in a new situation, they performed the computation very fluently when dividing two fractions by multiplying by a reciprocal. In doing so, however, they appeared to unable to connect the procedures with the concepts of fractions with division.