• Journal of the Korean Geosynthetics Society
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• v.13 no.2
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• pp.21-29
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• 2014

The use of filling material based on cement paste is inefficient at field construction because it needs a lot of the charging mass. In addition, it has environmental problem according to the large amount of cement use because its strength is also larger than criterion. The excavated soil with stabilizer can be used as the filling materials when the bored pile is constructed. Therefore, this paper describes field application of solidified soil for economical efficiency and environment-friendly. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. As results, the flowability, segregation and bleeding, and bond strength of filling materials was a good performance than that of the existing cement paste. But the skin friction of pile by PDA was slightly decreased than that of the existing cement paste. However, as pile filling materials, and in terms of economics and environment, the applicability of filling material is considered very effective.

• Korean Journal of Remote Sensing
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• v.14 no.4
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• pp.315-324
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• 1998

The total precipitable water fields derived from HIRS(High Resolution Infrared Radiometer Sounder)and MSU(Microwave Sounding Unit) measurements of TOVS and brightness temperature of SSM/I were used to investigate the evolution of moisture fields for the Typhoon WALT(9407) which after landing in Japan it became tropical depression in Korea-Japan Strait, and FAYE(9503) which was the first tropical storm of 1995 to became a typhoon, respectively. The total precipitable water derived from TOVS observations is delineated according to the evolutions of WALT and FAYE movements because total precipitable water fields of TY WALT(9407) and FAYE9\(9503) were largely controlled by horizontal transport of water vapor over the Northwest Pacific Ocean which dominantly plays an important role in maintaining and accelerating their intensities toward Korea and Japan . These fields demonstrated that two major bands, which imply the rain bands, were locally well-organized and similar to the thick convective cloud features over Japan and the Korean peninsula while WALT and FAYE were approaching away and to. But the values of derived TOVS total precipitable water have shown the underestimate of those of SSM/I total comparatively for two typhoons.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.4
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• pp.643-652
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• 2021

Accidents or faults in the transmission and distribution system are never completely avoidable, and short-circuit and earth faults are occurs despite the efforts of the TSO and DSO. Recently, the connection to the transmission and distribution system of large-capacity new and renewable distributed power has increased rapidly and has various effects on the operation of the system. In order to minimize this, connection standards such as FRT (Fault-Ride-Through) have been established to provide wind turbines or solar inverters. In the event of a major faults of the power system, the operation support shall be provided so that the operator can stably operate the system by smoothly performing connection maintenance or rapid system separation. In this paper, in order to appropriately determine whether the FRT condition, which is the grid connection criterion for a representative DERs, is sufficient, a detection system using a PMU (Phasor Measurement Unit) that measures a synchro-phasors was designed and deployment and a system accident due to a generator step-out to analyze and evaluate the proposed system based on the case.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.61-64
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• 2013

가상화는 가상의 자원이 물리적 자원에 접근할 수 있게 해주는 기술이며 VM(가상머신)을 다수 설치하여 VM의 수만큼 운영체제들을 이용할 수 있다. 이러한 가상화는 자원의 낭비를 막고 관리비용을 줄이기 위해 사용한다. 가상화 기술은 CPU, 메모리, I/O 가상화로 구분 지을 수 있으며 이 중 메모리 가상화 기술은 메모리 자원의 효율적인 사용을 가능하게 해준다. 여러 VM들이 실제 머신의 메모리보다 많은 메모리를 할당받아 사용하는 것이 가능한데 이것을 오버커밋 상태라고 한다. 중첩 가상화는 VM에 하드웨어 가상화 기법의 사용을 허용하게 하여 VM 위에 또 다른 VM이 동작할 수 있는 환경을 제공해준다. 이와 같은 (중첩) 가상화 환경에서의 메모리 접근은 일반적으로 하드웨어 지원을 통한 중첩 페이징 기법을 이용하여 메모리의 접근이 이루어진다. 본 논문에서는 오버커밋 발생 시 중첩 VM과 하이퍼바이저 VM의 성능 차이를 실험을 통하여 보여주고자 한다.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.4
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• pp.11-20
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• 2015

In the present work, a basic study on the in-situ biogenic methane generation from low grade coal bed was conducted. Lignite from Indonesia was used as a sample feedstock. A series of BMP (Biochemical Methane Potential) tests were carried out under the different experimental conditions. Although nutrients and anaerobic digester sludge were added to the coal, the produced amount of methane was limited. Both temperature control and particle size reduction showed little effect on the increase of methane potential. When rice straw was added to lignite as an external carbon source, methane yield of 94.4~110.4 mL/g VS was obtained after 60 days of BMP test. The calorific value of lignite after BMP test decreased (4.5~12.1 %) as increasing the content of rice straw (12.5~50 wt % of lignite), implying that anaerobic digestion of rice straw led to partial degradation of lignite. Therefore, rice straw could be used as an external carbon source for the start-up of in-situ biogas generation from low grade coal bed.

• The Journal of the Korea Contents Association
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• v.7 no.1
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• pp.147-154
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• 2007

In this paper, we propose a new parallel search algorithm to acquire synchronization for UWB(Ultra Wideband) systems that reduces computation of the correlation. The conventional synchronization acquisition algorithms check all the possible signal phases simultaneously using multiple correlators. However it reduces the acquisition time, it makes high power consumption owing to increasing of correlation. The proposed algorithm divides the preamble signal to input the correlator into an m-bit bunch. We check the result of the correlation at first stage of an m-bit bunch data and predict whether it has some synchronization acquisition information or not. Thus, it eliminates the unnecessary operation and save the number of correlation. We evaluate the proposed algorithm under the AWGN and the multi-Path channel model with MATLAB. The proposed parallel search scheme reduces number of the correlation 65% on the AWGN and 20% on the multi-path fading channel.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.122-122
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• 2003

1991년 일본 NEC의 Iijima가 탄소 나노튜브를 발견한 이후, 1995년 Smalley와 De Heer에 의해 탄소 나노튜브의 우수한 전폐방출 특성이 보고되면서 탄소 나노튜브를 새로운 전계방출 물질로 응용하기 위한 연구가 세계적으로 활발히 진행되고 있다. 탄소 나노튜브의 전계방출 연구는 대부분 시장규모가 클 것으로 예상되는 field emission display(FEED)의 cathode에 집중되고 있다. FED cathode는 현재 탄소 나노튜브 페이스트를 스크린 프린팅하여 대면적화를 이루고자 하는 방향과 탄소 나노튜브를 기판 위에 chemical vapor deposition(CVD)로 증착하여 고정세화와 저전압 구동을 이루고자 하는 방향으로 진행되고있다.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1262-1266
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• 1999

More precise operation and control is required to ensure the stability and security of modern large power systems that is a complicated and widely dispersed structure. To ensure the precise operation and control of modern power system, most of all, precise monitoring and measurement of the various state values of power system is required. This paper discusses phasor measurement unit using synchronization signals from the GPS satellite system- Synchronized Phasor Measurement Unit. Considering the power system operation state, the transmitting data format over modems is defined. To provide all available information, PMU process the measurements to generate three phase symmetrical component. This paper proposes the transmitted data format and implements the PMU model using EMTP/Models. The validity of proposed model is confirmed through several contingency on the simple power system.

• Journal of Welding and Joining
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• v.15 no.6
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• pp.85-95
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• 1997

This study is to investigate the optimum conditions of Nd:YAG laser beam welding for Zircaloy-4 end cap closure by optical fiber transmission. Laser welding parameters which affect the penetration depth and bead width were experimentally examined using the various beam radius by the beam quality analyzer, joint geometries of end cap and the laser parameters which mean pulse width, repetition rate and pulse energy. Also, an optimum welding speed and the effect of assistant gas with varying the flow rate of He were investigated. We found that the laser average power for the end cap welding will be 230W and rotation speed must not exceed 8 RPM, the best position of focus using optical fiber with 600.mu.m will be 2 to 3mm below the surface of the material.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.2
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• pp.143-155
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• 2013

A low-complexity dual-user multiplexing scheme is proposed for a pair of mobiles equipped with single antenna operating over frequency-selective fading channels. The proposed scheme employs OFDM transmission scheme with a modified version of a space-frequency code and a low-complexity PIC-SIC group detection is invoked at the corresponding receiver. The BER performances of the proposed scheme are studied using LTE-like parameters through simulations and are compared against those of conventional ZF and ML schemes.