• Journal of Advanced Navigation Technology
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• v.7 no.1
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• pp.38-50
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• 2003

In this paper, a new high resolution reflectometry scheme, time-frequency domain reflectometry (TFDR), is proposed to detect and locate fault in wiring. Traditional reflectometry methods have been achieved in either the time domain or frequency domain only. However, time-frequency domain reflectometry utilizes time and frequency information of a transient signal to detect and locate the fault. The time-frequency domain reflectometry approach described in this paper is characterized by time-frequency reference signal design and post-processing of the reference and reflected signals to detect and locate the fault. Design of the reference signal in time-frequency domain reflectometry is based on the determination of the frequency bandwidth of the physical properties of cable under test. The detection and estimation of the fault on the time-frequency domain reflectometry relies on the time-frequency domain reflectometry is compared with commercial time domain reflectomtery (TDR) instrument. In these experiments provided in this paper, TFDR locates the fault with smaller error than TDR. Knowledge of time and frequency localized information for the reference and reflected signal gained via time-frequency analysis, allows one to detect the fault and estimate the location accurately.

• Journal of KIISE:Software and Applications
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• v.26 no.11
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• pp.1359-1371
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• 1999

대규모 네트워크 상에서 동작하는 분산 시스템의 구현을 위해 제시된 방법 중의 하나인 이동 코드 개념은 네트워크 공유 자원에 접근할 수 있는 효과적인 방법을 제시하였고 이 개념을 지원하는 많은 언어들의 개발을 가져왔다. 개발된 언어들이 가지고 있는 이동 코드를 지원하기 위한 언어 구문과 적용하려는 문제 영역의 특성을 반영한 언어 구문은 네트워크 프로그래밍을 하는데 있어서 효율과 문제 중심의 프로그램의 두 가지를 모두 가능하게 하고 있다. 본 논문에서는 현재 분산 컴퓨팅 환경에서 가장 많이 사용되고 있는 클라이언트-서버 모델을 확장하여 서버의 자원에 접근할 수 있는 또 다른 방법을 가진 모델을 제시하고, 이 모델을 표현할 수 있는 언어를 설계하였다. 설계된 언어는 이동 코드의 개념을 지원함으로써 대규모 네트워크에서 수행되는 프로그램의 작성을 가능하게 하고, 분산 범위 규칙을 채택함으로써 이동 코드의 기술을 일반 함수를 기술하듯 명확한 관점에서 할 수 있도록 하였다. 또한 네트워크 관련 자원들을 언어 구문으로 채택하여 네트워크 프로그래밍을 언어 수준에서 할 수 있도록 하였다. 언어의 이론적인 설계에 그치지 않고 설계된 언어를 수행할 수 있는 실행 시간 지원 시스템을 구현하였다. 실행 시간 지원 시스템은 언어를 해석하고 실행하는 코드 해석기와 이동 코드를 지원하는 네트워크 감독으로 구성되며 설계된 언어를 사용하여 실제로 네트워크 응용 프로그램을 작성하고 테스트 해 볼 수 있다.Abstract Some studies bring up a concept of code mobility as an innovative way to access network resources in order to develop distributed systems working on a large scale network. After that, many languages are suggested to support this concept. In these languages, language constructors for their particular application domains and mobile codes provide both problem-oriented views to the programmer and reasonable performance to the system. In this thesis, we extend the client-server model that is the most popular model in developing distributed systems these days. We propose a model to have another method to access server's resources and extend the C language to implement the proposed model for the large scale network. The new language has capability to build a software working on a large scale network by supporting mobile code and gives a consistent network programming view to the programmer by adapting distributed semantics. The language also makes network programming easy by providing network primitives at the language level. We implement a prototype of run-time system to support this language. The run-time system is composed of two major parts: code-interpreter that interprets and executes the language and network-daemon that supports mobile codes.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.10
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• pp.357-364
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• 2014

The first mission for the IoT based hyper-connectivity communication is developing a device-to-device communication technique in infra-less low-power and lossy networks. In a low-power and lossy wireless network, IoT devices and routers cannot keep the original path toward the destination since they have the limited memory. Different from the previous light-weight routing protocols focusing on the reduction of the control messages, the proposed scheme provides the light-weight IPv6 address auto-configuration, IPv6 neighbor discovery and routing protocol in a IoT capable infra-less wireless networks with the bloom filer and enhanced rank concepts. And for the first time we evaluate our proposed scheme based on the modeling of various probability distributions in the IoT environments with the lossy wireless link. Specifically, the proposed enhanced RPL based light-weight routing protocol improves the robustness with the multi-paths locally established based on the enhanced rank concepts even though lossy wireless links are existed. We showed the improvements of the proposed scheme up to 40% than the RPL based protocol.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.4
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• pp.724-729
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• 2008

In the case of 'MAEMI', the Typhoon which formed in September, 2003, the largest-scale damage of tidal wave was caused by the co-occurrence of Typhoon surge and full tide. Until now Korea has been focusing on the calculating the amount of damage and its restoration to cope with these sea and harbor disasters. It is essential to establish some systematic counterplans to diminish such damages of large-scale tidal invasion on coastal lowlands considering the recent weather conditions of growing scale of typhoons. Therefore, the purpose of this research is to make the counterplans for prevention against disasters fulfilled effectively based on the data conducted by comparing and analyzing the accuracy between observation values and the results of estimating the greatest overflow area according to abnormal tidal levels centered on Masan area where there was the severest damage from tidal wave at that time. It's necessary utilize data like high-resolution satellite image and LiDAR(etc.) for correct analysis data considering geographical characteristics of dangerous area from the storm surge. And we must make a solution to minimize the damage by making data of dangerous section of flood into GIS Database using those data (as stated above) and drawing correcter damage function.

• Korean Journal of Remote Sensing
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• v.11 no.3
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• pp.49-60
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• 1995

Features of geological lineaments generally play an important role at the data interpretation concerned geological processes, mineral exploration or natural hazard risk estimation. However, there are intrinsically discordances between lineaments-related features extracted from surficial geological syrvey and those from satellite imagery;nevertheless, any data set contained those information should not be considred as less meaningful within their own task. For the purpose of effective utilization task of extracted lineaments, the mathematical scheme, based on fuzzy set theory, for practical integration of various types of rasterized data sets is studied. As a real application, the geological map named Homyeong sheet(1:50,000) and the Landset TM imageries covering same area were used, and then lineaments-related data sets such as lineaments on the geological map, lineaments extracted from a false-color image composite satellite, and major drainage pattern were utilized. For data fusion process, fuzzy membership functions of pixel values in each data set were experimentally assigned by percentile, and then fuzzy algebraic sum operator was tested. As a result, integrated lineaments by this well-known operator are regarded as newly-generated reasonable ones. Conclusively, it was thought that the implementation within available GISs, or the stand-alone module for general applications of this simple scheme can be utilized as an effective scheme can be utilized as an effective scheme for further studies for spatial integration task for providing decision-supporting information, or as a kind of spatial reasoning scheme.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.377-377
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• 2017

다목적댐은 비어있는 저수지 용량을 활용, 상류에서 유입되는 홍수를 저류하여 하류의 피해를 경감시키고, 저류된 저수량을 활용하여 갈수시 생 공 유지용수 등을 목적에 맞게 하류로의 공급에 주요 목적이 있다. 이를 위해 댐 계획에는 상류에서 유입되는 목표 빈도 계획홍수량을 산정하고, 이에 따른 여수로의 계획방류량 등이 포함된 홍수 조절 방안이 수립된다. 다목적댐은 그 중요도 때문에 많은 사회적 재화(財貨)가 투입되어 하천에서 가장 높은 빈도인 200년 빈도 홍수량에 대비하도록 설계되어 있다. 그러나 대부분의 댐 하류 하천에서는 긴 연장에 따른 투자비용 등의 한계로 상류 댐에 미치지 못하는 100년 빈도 이하로 설정되어있다. 이런 상 하류의 홍수계획간 괴리로 댐의 계획 방류량 수준의 홍수 조절시에는 하류 하천에 재난상황으로 발생할 우려가 있다. 기상예보의 고도화로 단기 예보의 정밀도가 높아져 단기간 댐 운영에는 효과적으로 활용되고 있다. 하지만 5일 이후를 예보하는 중 장기예보는 아직까지도 불확실성이 높은 실정이다. 여기에 기후변화 등 기상의 불확실성을 고려하여 홍수기 초 장마와 태풍 등의 영향에 대비하기 위해 무작정 댐을 저(低)수위로 운영하면 이후 여름 가뭄에 취약해 지고, 반대로 저수량 확보의 고(高)수위 운영을 할 경우 연이은 태풍 등 홍수상황에 취약해 지게 된다. 최근 '14~'15년도 낙동강 수계에 여름가뭄으로 안동 임하댐이 가뭄단계에 돌입하는 등 홍수기초 적정 저수량의 확보는 안정적 수자원시설 운영에 중요성이 커지고 있다. 본 연구에서는 이러한 불확실한 기상상황에 대비하고 댐의 이치수 목적 달성을 위해, 홍수기초 가능한 저수량을 확보하되 계획홍수량이 들어와도 하류피해는 경감시킬 수 있는 저수지 수위를 찾고자하였다. 이를 위해 낙동강 수계 9개 다목적댐(안동, 임하, 성덕, 보현산, 군위, 김천부항, 합천, 남강, 밀양댐)을 대상으로 댐 설계 및 직하류 하천 상황을 고려한 "홍수기초 댐 저수량 확보 수위 검토"를 실시하였다. 댐 직하류 하천의 홍수대비 상황 및 홍수조절시 제약사항 등을 조사해 주요지점(Critical Point)을 선정하고 그 지점의 홍수량을 파악한다. 이어서 저류함수 모형을 활용하여 댐별 저수지 모의 운영을 실시하였다. 대상 댐 저수지에 계획홍수량을 유입시키고 수위를 점차 조정하면서 하류 지점의 홍수량 내의 규모로 방류를 하는 저수지 모의 운영을 실시하였다. 이때 저수지의 계획홍수위를 초과하지 않는 등 안정적 홍수조절이 가능한 특정 수위를 찾아 하류 하천 환경을 고려한 댐 운영 수위로 선정하였다. 최근 홍수기총에는 강수량이 계속 줄어들고 홍수기 이후 더 많은 강수가 내리는 등 기후변화로 댐 운영은 날로 어려워지고 있다. 본 연구의 분석 결과는 홍수기초 가뭄 및 장마 또는 태풍 등에 대비하여 댐 운영의 이 치수 두 가지 목적을 달성하는데 참고가 될 수 있을 것이다.

• Journal of the Korean Society of Radiology
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• v.13 no.5
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• pp.749-755
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• 2019

In this study, we investigated the effects of tube voltage (kVp) and tube current (mAs) on an exposure index (EI) applied to a digital radiography. There used an inverter type digital X-ray generator and an image receptor (IR) utilized a portable wireless detector without a grid. Radiographic images were acquired using a cone pyramid phantom produced using a 3D printer. The X-ray tube voltage was increased from 40 kVp to 120 kVp with 10 kVp increment, and the tube current was increased from 1 mAs to 128 mAs with the twice increment. As a result, kVp had logarithmic relationship with the EI as high $R^2$ value, and mAs had a very high linear relationship too. Also, there was a high correlation between the area dose and the EI of the IR, with the $R^2$ value being 0.76 or more. In conclusion, it had showed that mAs affected the EI linearly, and that it could be advantageous to adjust the easy-to-predict mAs to maintain proper image qualities.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.294-294
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• 2019

The system for predicting flood of river at Flood Control Office is made up of a rainfall-runoff model and FLDWAV model. This system is mainly operating to predict the excess of the flood watch or warning level at flood forecast points. As the demand for information of the management and operation of riverside, which is being used as a waterfront area such as parks, camping sites, and bike paths, high-level forecasts of watch and warning at certain points are required as well as production of lowland flood forecast information that is used as a waterfront within the river. In this study, a technology to produce flood forecast information in lowland areas of the river used as a waterfront was developed. Based on the results of the 1D hydraulic analysis, a model for performing spatial operations based on high resolution grid was constructed. A model was constructed for Andong district, and the inundation conditions and level were analyzed through a virtual outflow scenarios of Andong and Imha Dam.

• KIPS Transactions on Computer and Communication Systems
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• v.8 no.9
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• pp.217-224
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• 2019

Recently, sensor networks are built and used on many kinds of fields such as home, traffic, medical treatment and power grid. Sensing data manipulation on these fields could be a serious threat on property and safety. Thus, a proper way to block sensing data manipulation is necessary. In this paper, we propose IoT(Internet of Things) sensing data validation mechanism based on data obfuscation and variance analysis to remove manipulated sensing data effectively. IoT sensor device modulates sensing data with obfuscation function and sends it to a user. The user demodulates received data to use it. Fake data which are not modulated with proper obfuscation function show different variance aspect with valid data. Our proposed mechanism thus can detect fake data by analyzing data variance. Finally, we measured data validation time for performance analysis. As a result, block rate for false data was improved by up to 1.45 times compared with the existing technique and false alarm rate was 0.1~2.0%. In addition, the validation time on the low-power, low-performance IoT sensor device was measured. Compared to the RSA encryption method, which increased to 2.5969 seconds according to the increase of the data amount, the proposed method showed high validation efficiency as 0.0003 seconds.

• Journal of the Korea Society of Computer and Information
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• v.25 no.6
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• pp.1-8
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• 2020

Communication between system modules is applied using the Modbus protocol in industrial sites including smart factories, industrial drones, building energy management systems, PLCs, ships, trains, and airplanes. The existing Modbus was used for serial communication, but the recent Modbus protocol is used for TCP/IP communication.The Modbus protocol supports RTU, TCP and ASCII, and implements and uses protocols in embedded systems. However, the transmission I/O devices for RTU, TCP, and ASCII-based protocols may differ. For example, RTU and ASCII communications transmit on a serial-based communication protocol, but in some cases, Ethernet TCP/IP transmission is required. In particular, since the C language (object-oriented) is used in embedded systems, the complexity of source code related to I/O registers increases. In this study, we designed software that can logically separate I/O functions from embedded devices, and designed the execution logic of each instance requiring I/O processing through a delegate class instance with Modbus RTU, TCP, and ASCII protocol generation. We designed and experimented with software that can separate communication I/O processing and logical execution logic for each instance.