• The Journal of the Acoustical Society of Korea
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• v.37 no.3
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• pp.156-162
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• 2018

The LMF (Least Mean Fourth) algorithm is well known for its fast convergence and low steady-state error especially in non-Gaussian noise environments. Recently, there has been increasing interest in the LMS (Least Mean Square) algorithms with self-adjusted step size. It is because the self-adjusted step-size LMS algorithms have shown to outperform the conventional fixed step-size LMS in the various situations. In this paper, a self-adjusted step-size LMF algorithm is proposed, which adopts an averaged gradient based step size as a self-adjusted step size. It is expected that the proposed algorithm also outperforms the conventional fixed step-size LMF. The superiority of the proposed algorithm is confirmed by the simulations in the time invariant and time variant channels.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.353-357
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• 2007

The Apartment resident's make-up of a family and residing preference are diversified by the change of lifestyle through the elevation of economy level and residing level. Accordingly, the remodeling and the early rebuilding for the satisfaction of a life cycle and a life style are increasing, and "Variability" that is the concept of Open Housing was emphasized as a central of residing plan in the apartment. Although apartments which select the space variability to the residing space are increasing gradually, the optimum composition structural system with space variability that satisfies the structure stability, the economical efficiency and the resident usability is not developed. The method of a study was progressed by a comparison and an analysis on each system with estimation elements through analyzing the development process and the special quality of existing composition structural system with space variability in the apartment. This paper offered the improvement direction on the current composition structural system with space variability for the development of modularizing system that is correct in domestic real condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.2
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• pp.245-251
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• 2017

The proposed variable pawer divider in this paper is composed of one equal power 2-way Wilkinson power divider, two variable phase shifters with 90-degree phase variation to be connected two output paths of the 2-way power divider, and one branchline coupler to combine output signals of two variable phase shifter. The proposed variable power divider can theoretically have an arbitrary power division ratio ranging from ${\infty}:1$ to ${\infty}:1$ due to 90-degrees phase variation of two phase shifter. The proposed power divider circuit fabricates on laminated TLX-9(h=20 mil, er=2.5; Taconic) with a center frequency of 1.7 GHz. The power division ratio of the fabricated prototype varies from about 1:100 to 200:1, with an input reflection characteristic(S11) of below -16 dB, an insertion loss of about -1.0 dB, and an isolation characteristic of below -17 dB between two output ports in the range 1.65-1.75 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2066-2070
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• 2009

A voltage controlled attenuator using a PIN diode and two resistors of the $\pi$-type fixed attenuator is described in this paper. The proposed variable attenuator operating for a fixed attenuation range has a good input VSWR and a low intermodulation signal. For the low phase shift, a PIN diode is connected with open stub for the purpose of phase compensation. The stub for phase compensation is calculated by the Deloach method and the related circuit theory. This attenuator is easily fabricated on the microstrip and can be normally used in fine control circuits within small attenuation range. The fabricated attenuator for 2110~2170 MHz frequency band has about 4 dB of an attenuation range, $2^{\circ}$ of phase variance, and -20 dB of S11 according to the input voltage from 0 to 2.7 V.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.280-280
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• 2010

태양전지의 효율을 증가시키는 방법에는 표면 패시베이션, 접촉면적의 가변, back contact의 두께 가변 등이 있다. 특히, back contact 두께의 가변을 통하여 open circuit voltage의 감소를 최소화 할 수 있을 것이라고 전망 되고 있다. open circuit voltage 은 회로가 개방된 상태로, 무한대의 임피던스가 걸린 상태에서 빛을 받았을 때 태양전지의 양단에 전위차가 형성된다. 본 연구에서는 back contact 두께 가변에 따른, open circuit voltage의 변화를 확인하고 분석하는 것에 그 일차적인 초점을 두었다. 또한, open circuit voltage 뿐만 아니라, short circuit current density, fill factor, series resistance 등의 분석을 하였으며, efficiency를 계산하여 back contact 두께의 가변에 따른 소자 특성의 변화 분석을 통하여 최적화된 back contact위 두께를 연구하였다. 접촉면적에 따른 소자의 성능 변화는 후면 $SiN_X$ 70nm가 open circuit voltage를 15mV ~ 20mV 감소시키는 것을 확인 할 수 있었다. 그 이유는 $SiN_X$가 너무 두꺼우면 BSF 덜 형성되기 때문이다. 최종적으로 $SiN_X$ 두께를 얇게하면 open circuit voltage 의 감소를 최소화 할 수 있을 것이라는 판단을 할 수 있다. 이에, back contact인 $SiN_X$ 두께 가변에 따른 open circuit voltage의 변화를 확인하였다. $SiN_X$ 두께가 증가함에 따라, Positive charges 와 Hydrogen 함유량이 증가하며, 이에 BSF 두께 감소하였다. 또한, $SiN_X$ 두께가 감소함에 따라 Doping barrier로서 역할을 못하게 되어 후면에 n+층 형성되어 open circuit voltage가 급격히 하락하였다. 본 연구에서는 back contact인 $SiN_X$ 두께를 10nm, 30nm, 50nm, 80nm 로 가변하며 실험을 진행하였다.

• Journal of Korean Society of Transportation
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• v.17 no.1
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• pp.91-102
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• 1999

The objective of this study is to evaluate traffic management strategies using Variable Message Signs(MCS) on urban freeways. It is well known that real-time information on traffic conditions increases driver's comfort, and reduces the risks of accidents if drivers are aware of the traffic situation in advance, they decide whether to divert from the freeway or continue on the planned route. The experimental data collected on the Olympic highway we have shown the following results : 1. when the information on both the congested freeway and uncontested diversion route is displayed on the variable message sign. an additional 1.7 percent of traffic diverted, which results in a 3.7 percent reduction in total travel time. 2 Compared with one Proposed VMS message of 'reduce the speed', the other Proposed VMS message of 'keep speed 70km/h' is found to be much more effective in reducing mean speed.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.369-369
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• 2017

농업용저수지는 이수 목적으로 비홍수기 농업용수 공급을 위한 용수 확보를 주요 목적으로 하고 있다. 한편, 농업용저수지가 홍수조절능력 또한 지니고 있음이 다수의 연구를 통해 제기되고 있으며, 이에 치수 목적으로 홍수기 홍수피해 저감을 위한 치수 대책 또한 수립할 필요가 있다. 현재 우리나라 농업용저수지의 홍수기 운영은 제한수위 방식을 기준으로 하되 필요에 따라 예비방류를 허용하는 조합 형태를 취하고 있다. 이러한 운영 방식은 홍수기 이후 상시만수위로 복귀하지 못하면 해당 년도 잔여 비홍수기 혹은 다음 년도 영농 시작 시기의 농업용수 공급에 차질이 생길 수 있다는 문제점이 있다. 따라서 홍수기 농업용저수지의 운영은 홍수조절과 함께 상시만수 위로의 복귀를 동시에 고려하여 이루어질 필요가 있다. 가변 홍수기 제한수위 (Variable Restricted Water Level, VRWL) 방식은 홍수 발생빈도와 규모를 고려하여 단위기간별 (일별 혹은 순별) 제한수위를 차등 부여하는 방식으로, 한정된 저수공간의 효율적 재할당에 따라 이수와 치수의 효율을 증대시키는 방안이 될 수 있다. 따라서 본 연구에서는 농업용저수지를 대상으로 저수지 유입량 빈도해석을 수행하고 순별 가변 홍수기 제한수위를 산정한 후 가변 홍수기 제한수위 적용에 따른 홍수조절효과를 평가하고자 한다. 연구대상지는 전국 110개 둑높이기 농업용저수지 중 가능최대홍수량 대상저수지 (유역면적 2,500 ha 이상, 총 저수량 500만 톤 이상) 12개소로 선정하였고, 저수지별 기상자료와 지형자료를 구축하였다. 저수지 유입량 모의를 위하여 장기유출량 산정 모형인 TANK를 이용하였으며, 구축된 저수지 유입량 자료를 토대로 순별 유입량 빈도해석을 수행하고 홍수기 저수지 유입량의 이론적 확률분포형을 선정하였다. 선정된 확률분포형을 토대로 초과확률 10%에 따른 순별 저수지 수위로서 가변 홍수기 제한수위를 산정하였다. 산정된 가변홍수기 제한수위 적용 효과를 분석하기 위하여 홍수조절용량을 산정하였고, 유역비 홍수량을 지표로 하여 홍수조절능력을 평가하였다. 향후 본 연구의 결과는 둑높이기 농업용저수지의 홍수기 제한수위 설정 및 관리, 운영 지침 개선에 있어 기초자료로 활용할 수 있을 것으로 사료된다.

• Journal of Software Engineering Society
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• v.26 no.1
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• pp.1-16
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• 2013

Variable length information message is a communication protocol standard in order for computer network systems to provide efficient delivery of information. The variable length information messages were developed for varying and controlling details of information in accordance with message receiver's required information level or information access level. In the previous studies, data compressing techniques have been in use for information message optimization technologies in order to reduce physical sizes of information messages. In optimization technologies for information messages, accuracy of information is considered as the most important factor; therefore, only non-loss compression techniques are applied to the optimization technologies. However, the non-loss compression based information message optimization methods are not efficient in data compression, and these are limited to efficient delivery of information in wireless network environments that have constraint bandwidth. In this paper, we attempt to optimize information in the variable length information messages at message fields in order to reduce physical sizes of messages more efficiently. To demonstrate the efficiency of our approach, we conduct optimization experiments for variable length information messages.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.117-121
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• 2019

In this study, research and a demonstration for applying DC distribution systems to ships as an environmental and energy conservation solution in domestic and foreign countries were actively carried out. In order to apply a generator to a DC distribution system, a variable speed engine was used. Both engine speed and fuel consumption were reduced. In this paper, a DC generator for DC distribution was constructed using a diesel generator, a generator controller, a governor, and an AVR. A system configuration method for a generator, power quality test, and the power characteristics of a variable speed generator were analyzed. The voltage (250 - 440 VAC) and frequency (34 - 60 Hz) of the variable speed generator were set to 60 - 100 % of the rated value, and the engine was set to operate from 1100 - 1800 rpm. It was confirmed that the voltage, current, and frequency of the generator output fluctuated in a stable manner according to the power amount when changing the engine speed of the generator according to the load variation.

• The Journal of the Acoustical Society of Korea
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• v.40 no.6
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• pp.626-648
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• 2021

Domestically, demands for multi-purpose performance venues which accommodate various performance genres have increased. However, those venues have limited capability and confined to a primary performance. The present work investigated various methods for controlling the acoustics of room for required performance genres by reviewing aurally presented and published materials. The method of varying the acoustics of a space is called Variable Acoustics, and adjusted in either passive and active ways. Passive control encompasses variable absorption, variable volume, coupled volume, and canopy reflectors, where the acoustics of a room is controlled in an architectural way. Active control includes In-line, Regenerative, and Hybrid systems where the acoustics of a room is manipulated electronically. The mechanism and application of each passive control system in existing venues are reviewed and their pros and cons are discussed. Also, the concept of each active systems and product applications are looked at through literature reviews. Lastly, some considerations that need to be taken into in the planning and design stage of a multi-purpose hall using Variable Acoustics are suggested.