• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.282-283
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• 2007

본 논문에서는 저전압에서 구동 할 수 있는 압전구동 방식의 RF MEMS 스위치를 설계하였다. 설계는 유한요소기법(FEM)을 지원하는 시뮬레이터 (ConventorWare)를 사용하여 수행하였고, 이를 바탕으로 deflection, contact force, stress 등 기계적인 해석을 함으로써 최적화된 설계를 할 수 있었다. 이번 설계에서는 적절한 contact force를 유지하면서 hinge에서 받는 stress를 최소화하기 위하여 구동기를 2개 사용한 듀얼형식의 모델을 제안하였고, hinge의 모양은 'ㄷ'로 하여 deflection을 향상시켰다. 이 듀얼형식의 최적화된 모델은 signal line과 contact pad 간의 gap이 3.4${\mu}m$일 때, 최초 2.8V에서 contact이 이루어졌으며, 5V에서 12.4${\mu}N$의 contact force와 116MPa의 stress를 얻었고, 차후, SP4T나 SP6T 등의 설계시 공간 효율이 높은 다양한 형태의 구조를 설계할 수 있다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.9
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• pp.834-843
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• 2016

In this paper, the design of a PIN diode S-band transfer-type SP4T including its driver circuit is presented. Each path of the SP4T is composed of the cascade connection of series-shunt PIN diodes to improve the isolation performance. The SP4T is implemented using chip type PIN diodes and a 20 mil AIN substrate fabricated using thin film technology. The driver circuit for the SP4T is designed using a multiplexer and four NMOS-PMOS push-pull pair. From on-wafer measurement, the fabriacted SP4T shows a maximum insertion loss of 1.1 dB and a minimum isolation of 41 dB. The time performance of the driver circuit is evaluated using the packaged PIN diodes with the identical PIN diode chip, and the transition time for on-off and off-on are below 100 nsec. For an input power level of 150 W, the measured insertion loss and isolation are close to those of the on-wafer measurement taking into consideration of the coaxial package mismatch and insertion loss.

• Journal of the Korean Society for Railway
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• v.12 no.3
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• pp.348-356
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• 2009

The objective of this paper is to estimate the DMT utility function for the transportation mode choice using SP survey. With the freight OD data the estimated utility function can be used as a basic data for forecasting DMT market. 3 alternatives of transportation mode are considered in SP survey; railway, road and DMT. The utility functions are developed according to the freight items, which are container, steel and chemical product. In this study the attribute variable are chosen as time, cost and reliability. The number of level for attribute variables are 3. The high valve is determined as +10% above the standard and the low value -20% below the standard.

• Journal of IKEEE
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• v.23 no.2
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• pp.622-627
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• 2019

This paper propose an initial rotor position detection method for sensorless operation of a single-phase permanent magnet synchronous motor(SP-PMSM) with asymmetric air-gap. In general, the sensorless control based on back-emf estimation is difficult to estimate the back-emf at the zero and low speed regions. For this reason, an open loop start-up technique is indispensable, and it is also necessary to detect the initial position of the rotor in order to rotate in a certain direction. In this paper, we propose a method to detect rotor polarity by adding offset voltage to high frequency voltage signal based on the magnetic characteristics of SP-PMSM. The validity and usefulness of the proposed algorithm are verified through several experimental results.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.985-990
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• 2005

The success of road transportation, in dominating the surface movement of freight, is now threatened by increased traffic congestion, falling average motorway speed and rising in logistics costs, oil price. Due to the necessity for an effective transport system, we need to improve domestic transport infrastructure to reduce logistics cost by shifting to rail system. To analysis the demand characteristics in advance against these hypothetical circumstances, Stated Preference, which is called SP, approaches have been adopted to analysis the shipper's mode choice behaviors as RP(Revealed Preference) approaches are not appropriate. The results also indicate that the most effective policy to divert the freight volume from road to railway is to reduce freight rates for the railway with improved reliability.

• The Korean Journal of Mycology
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• v.25 no.3 s.82
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• pp.202-208
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• 1997

In this study, we evaluated the use of RAPD method to discriminate among strains of Fusarium species including F. oxysporum and f. sp. of F. oxysporum. As a result of the amplication, fifteen primers showed total 180 bands ranging from 0.2 to 3 Kb. Among those 180 bands, 126 polymorphic bands were used for bionominal matrix code (0, 1), and UPGMA dendrogram analysis. Fusarium oxysporum isolate 355 showed high similarity with F. oxysporum isolate 358 at 0.9603. Fusarium roseum isolate 87 and F. oxysporum isolate 358, F. o. f. sp. lycopersici isolate 69 and F. o. f. sp. melongena 68 showed low similarity of 0.3809. Fusarium oxysporum isolate 361 and F. o. f. sp. raphani isolate 218 showed similarity of 0.8730, F. oxysoprum isolate 354 and unidentified Fusarium sp. isolate 228 showed similarity matrix of 0.7936, and F. roseum isolate 87 and F. o. f. sp. raphani isolate 57 showed similarity matrix of 0.5873.

• Journal of IKEEE
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• v.23 no.3
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• pp.1020-1026
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• 2019

In this paper, a rotor polarity detection algorithm is proposed to control the single-phase permanent magnet synchronous motors(SP-PMSMs) for high speed sensorless operation. Generally, the sensorless control of a SP-PMSM is switched to the sensorless operation in a specific speed region after the open loop startup. As a result, it is necessary to detect the rotor polarity to maintain a constant rotational direction of the SP-PMSM at the starting process. There, this paper presents a novel rotor polarity detection method using a high frequency voltage signal and offset current which is generated by current regulator. The proposed algorithm verified the effectiveness and usefulness of the rotor polarity detection through several experiments.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.1
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• pp.25-39
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• 2018

NIST(National Institute of Standards and Technology) has recently published SP 800-90B second draft which is the document for evaluating security of entropy source, a key element of a cryptographic random number generator(RNG), and provided a tool implemented on Python code. In SP 800-90B, the security evaluation of the entropy sources is a process of estimating min-entropy by several estimators. The process of estimating min-entropy is divided into IID track and non-IID track. In IID track, the entropy sources are estimated only from MCV estimator. In non-IID Track, the entropy sources are estimated from 10 estimators including MCV estimator. The running time of the NIST's tool in non-IID track is approximately 20 minutes and the memory usage is over 5.5 GB. For evaluation agencies that have to perform repeatedly evaluations on various samples, and developers or researchers who have to perform experiments in various environments, it may be inconvenient to estimate entropy using the tool and depending on the environment, it may be impossible to execute. In this paper, we propose high-speed implementations and an efficient memory usage technique for min-entropy estimation algorithm of SP 800-90B. Our major achievements are the three improved speed and efficient memory usage reduction methods which are the method applying advantages of C++ code for improving speed of MultiMCW estimator, the method effectively reducing the memory and improving speed of MultiMMC by rebuilding the data storage structure, and the method improving the speed of LZ78Y by rebuilding the data structure. The tool applied our proposed methods is 14 times faster and saves 13 times more memory usage than NIST's tool.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.4
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• pp.312-321
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• 2013

In this paper, high efficiency control method for flyback inverter with synchronous rectifier(SR) based on photovoltaic AC modules is proposed. In this control method, the operation of SR is classified according to the voltage spike across main switch SP. When the voltage spike across SP is lower than the rating voltage of SP, the operation of active clamp circuit is interrupted for reducing the switching loss of auxiliary switch. In this time, the SR is operated for soft-switching of SP. When the voltage spike across Sp is higher than the rating voltage of SP, the operation of active circuit is activated for reducing the voltage spike. The SR is operated for reducing the conduction loss of secondary output diode. Thus, a switching loss of the main switch can be reduced in low power region, and weighted-efficiency can be improved. A theoretical analysis and the design principle of the proposed method are provided. And validity is confirmed through simulation and experimental results.

• Applied Biological Chemistry
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• v.38 no.6
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• pp.507-511
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• 1995

In an attempt to improve the productivity of ${\beta}-galactosidase$ from Bacillus sp. A1, which was isolated from soil and has remarkably higher transgalactosylation activity than lactose hydrolysis activity, a chemical mutation procedure using N-methyl-N'-nitro-N-nitrosoguanidine followed by selection was conducted. The final selection, designated as Bacillus sp. A4442, turned out to show a substantially increased enzyme productivity. Catabolite repression by glucose and lactose requirement as an inducer for the enzyme biosynthesis, which were shown in the parent strain, was markedly diminished; instead it was found out that galactose acts as another inducer. Because pH of medium, one of the most important factors for cell growth as well as enzyme production, is closely related with the sugar concentration during culture, it was kept in the optimum range of $6.5{\sim}7.5$; for this the initial glucose concentration was adjusted to be 0.5% which was thereafter maintained by the controlled pumping-in of lactose using the pH-stat technique. By doing so, we were able to increase the productivity of ${\beta}-galactosidase$ with high transgalactosylation activity up to $44\;unit/m{\ell}-broth$.