• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.5
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• pp.419-428
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• 2015

Multipath routing technique is recognized as one of the effective approaches to improve the reliability of data forwarding. However, the traditional multipath routing focuses only on how many paths are needed to ensure a desired reliability. For this purpose, the protocols construct additional paths and thus cause significant energy consumption. These problems have motivated the study for the energy-efficient and reliable data forwarding. Thus, this paper proposes an energy-efficient cooperative multipath routing protocol with a small number of paths based on an inter path communication. The inter path communication (namely, cooperative multipath routing) in the proposed protocol helps to reinforce the multipath reliability and reduce the use of network resources. In addition, the proposed protocol provides a reliable end-to-end transmission time by using a transmission recovery method based on the local decision for the path or transmission failures.

• Clean Technology
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• v.21 no.1
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• pp.62-67
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• 2015

We have developed a versatile method for the preparation of chemically linked graphene/multi-walled carbon nanotubes (MWNTs) hybrid materials via simple acid-catalyzed dehydration reaction between graphene oxide (GO) and amine-functionalized MWNTs (af-MWNTs). In this condition, ketone (-C=O) groups in GO and primary amine (-NH₂) moieties in af-MWNTs readily react to form imine (-C=N-) linkage. The chemical structures of graphene/MWNTs hybrid materials have been investigated using various microscopic and spectroscopic measurements. As a result of the synergetic effects of hybrid materials such as improved surface area and the superior structural restoration of graphitic networks, the hybrid materials demonstrate improved capacitance with excellent long-term stability. Furthermore, controlled experiments were conducted to optimize the weight ratio of graphene/MWNTs in hybrid materials. The highest capacitance of 132.4 F/g was obtained from the GM7.5 material, in which the weight ratio between graphene and MWNTs was adjusted to 7.5/1, in 1M KOH electrolyte at a scan rate of 100 mV/s.

• The Journal of the Acoustical Society of Korea
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• v.22 no.5
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• pp.408-417
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• 2003

In this paper, we have studied the enhancement of the acoustic image by combining bases of support for SFR (Spatial Frequency Response) taken at multi-frequencies. The scanning acoustic microscope system have been constructed using the quadrature detector that is able to measure the amplitude and phase of the reflected signal simultaneously. Both real and quadrature components of reflected signal have been acquired at 4.4 ㎒ to 5.6 ㎒ reliably and accurately. In this experimental result, better depth resolution can be obtained by numerically combining images taken at several different frequencies. Image intensity have been better about 3.4 times at multi-frequency than one at a single frequency.

• Electric Engineers Magazine
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• s.273
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• pp.32-36
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• 2005

최근 일부 선진국을 중심으로 대용량 전력제어용 반도체 소자와 제어기술의 발달로 인해 전력전자 반도체 소자인 IGBT(Insulated Gate Bi-polar Transistors) 등을 사용한 승강압형 컨버터 방식으로 동기발전기 계자전류를 제어하는 특이한 모델이 발전기 출력전압을 보다 속응성있게 제어함은 물론, 신뢰성 있고 안정적으로 제어 할 수 있는 방법으로 등장함에 따라 이에 대한 기술적 연구가 진행되고 있다. 이에 따라 본 고에서는 발전기 제어시스템의 개요, 국내외 기술개발 동향과 개발시스템의 구성, 주요기능 그리고 발전소 현장 적용 전에 시스템의 신뢰도 확보를 위해 전동발전기(M-G Set)를 이용한 시스템의 모의시험 결과와 향후 발전기 제어시스템의 발전 전망 등을 그회에 걸쳐 기술한다.

• ETRI Journal
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• v.7 no.2
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• pp.18-25
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• 1985

현재의 TDX-1 에서 사용되는 푸쉬버튼 수신기는 애널로그형으로 TDM방식의 디지틀 교환기인 TDX-1 에는 적합치 못하며 애널로그방식의 푸쉬버튼 수신기는 채널당 한 회로가 필요하게 되어 32채널 수용시 경제성 및 회로 팩 부피에서 불리한 입장이다. 따라서 본고에서는 디지틀화 추세에 따라 디지틀 필터 방식에 의한 디지틀 푸쉬버튼 수신기를 구성하여 채널을 다중화할 수 있으며, 이에 따라 애널로그 방식보다 경제성 및 집적도가 향상되며 안정도가 높은 디지틀 푸쉬버튼 수신기를 구성하는 방법을 제시하였다.

• The korean journal of orthodontics
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• v.27 no.1
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• pp.21-33
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• 1997

The purpose of this study was to investigate the factors affecting the postsurgical mandibular stability for both one- and two jaw surgery. 18 for one-jaw surgerys and 24 for two-jaw surgerys among skeletal class III malocclusion patients who experienced orthodontic treatment and orthognathic surgery at Pusan National University Hospital were selected. Lateral cephalograms taken at the first visit, after presurgical orthodontic treatment, immediately after surgery and follow-up over 6 months, were traced. Based ANOVA, multiple linear regression analysis was completed for one-jaw surgery with postsurgical stability as the criterion and the magnitude of mandibular setback, the change of mandibular incisor height during surgery, the changes of mandibular plane angle and mandibular incisor angle during presurgical orthodontic treatment as affecting factors. Same analysis was completed for two-jaw surgery with postsurgical stability as the criterion and the magnitude of mandibular setback as affecting factor. The results were as follows : 1. In the one-jaw surgery cases, the magnitude of mandibular setback, the change of mandibular incisor height during surgery, the changes of mandibular plane angle and mandibular incisor angle during presurgical orthodontic treatment explained the variability in postsurgical stability with a significant $R^2$ value of 0.84. 2. In the two-jaw surgery cases, the magnitude of mandibular setback explained the variability in postsurgical stability with a significant $R^2$ value of 0,28.

• Tunnel and Underground Space
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• v.24 no.4
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• pp.297-307
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• 2014

Cavern Thermal Energy Storage system stores thermal energy in caverns to recover industrial waste heat or avoid the sporadic characteristics of renewable-energy resources, and its advantages include high injection-and-extraction powers and the flexibility in selecting a storage medium. In the present study, the structural stability of rock mass pillar between these silo-type storage caverns was assessed using a coupled thermal-mechanical model in $FLAC^{3D}$. The results of numerical simulations showed that thermal stresses due to long-term storage depended on pillar width and had significant effect on the pillar stability. A sensitivity analysis of main factors indicated that the influence on the pillar stability increased in the order cavern depth < pillar width < in situ condition. It was suggested that two identical caverns should be separated by at least one diameter of the cavern and small-diameter shaft neighboring the cavern should be separated by more than half of the cavern diameter. Meanwhile, when the line of centers of two caverns was parallel to the direction of maximum horizontal principal stress, the shielding effect of the caverns could minimize an adverse effect caused by a large horizontal stress.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1C
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• pp.90-95
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• 2002

Though the FTP(File Transfer Protocol) has been used widely and stable, It has the structural weakness that can't support current file transmissions so that we have to wait the completion of previous file transmission when try to transmit another file. If try to transmit multiple files concurrently using this FTP, It has to forking multiple FTP servers and clients in each user's PC and ISP's host machine it would result in the waist of memory, resource of network and the high workload of system. In order to solving previous problem, in this paper I have designed the new model of FTP which based on multi-thread and created NFTP(Next-Generation FTP)protocol so that may reduce the workload of system and support current file transmission effectively. I have implemented NFTP and also applied to real service, as a result It have provided reliable service by reducing the workload of system and saved the waiting time which would happened.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.2
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• pp.68-75
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• 2017

In this paper, we propose an energy entropy based multipath routing protocol using dynamic forwarding range in mobile ad-hoc wireless sensor networks. The main features and contributions of the proposed routing protocol are as follows. First, can select stable routing routes by using the calculated route entropy based on energy information of sensor nodes. Second, using dynamic forwarding range based on the route stability of route entropy can reduce energy, control overhead, delay for route establishment, finally improve data transmission efficiency. The performance evaluation using OPNET shows that the proposed routing protocol can efficiently support PDR.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.2
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• pp.156-165
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• 2009

Threat due to malfunction of space launch vehicles is significant since it is bigger and flights longer range than military missiles or scientific rockets. It is necessary to implement a flight safety system to minimize the possible hazard. Design objective of the tracking filter for the flight safety system is different from conventional tracking filters since estimation reliability is more emphasized than estimation accuracy. In this paper, a fusion tracking filter was implemented for processing multi-sensor data from a space launch vehicle. The filter performance is evaluated by analyzing the error of the estimated position and instantaneous impact point. Also a fault detection algorithm is implemented to guarantee fusion filter's reliability under any sensor failure and verified to maintain stability successfully.