• 디지털산업정보학회논문지
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• 제15권1호
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• pp.21-28
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• 2019

Internet of Things(IoT) is a technology or environment that collects data by attaching sensors to objects and transmits the collected information to each other through wired / wireless communication in real time. It is expected that when the Internet of objects is activated, many objects can identify and recognize each other by themselves and provide various services to facilitate our lives through mutual information exchange. In addition, the internet market for things is growing rapidly each year, and various IT technologies are expected to converge. In the Internet environment of objects, data exchange technology between object devices, that is, message protocol, is classified as one of important technologies. In this paper, we examine various lightweight message protocols suitable for the Internet environment of objects, and compare the reliability of the CoAP protocol structure with the MQTT protocol for a limited environment. Finally, we confirm the reliability of TCP / TLS and WebSockets-based CoAP transmission protocol of IETF's CoRE WG that can use various transport layers other than UDP in Internet environment including cloud infrastructure.

• 디지털산업정보학회논문지
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• 제15권1호
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• pp.53-59
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• 2019

As the number of harmful sites increases, many social problems are occurring. Therefore, in order to solve this problem, the government is carrying out activities to block access to web sites to harmful sites based on the law. However, due to the change from HTTP to HTTPS protocol, it has become difficult to block the harmful sites in the existing method. In the existing HTTP protocol, a method of blocking the site corresponding to the harmful site domain list by utilizing the DNS information was used. However, due to the generalization of HTTPS, it is difficult to block the harmful sites in the existing method. Therefore, the ISP uses the method of blocking the website using the SNI field in the TLS (Transport Layer Security) Handshake protocol used for HTTPS. However, since the method using SNI field raises the concern of monitoring Internet users or exposing information about connected sites, in this paper, we proposed method which can support anonymity to Internet users while blocking harmful sites. The suggested method also can support integrity and source authentication to the transmitted data.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 춘계종합학술대회
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• pp.648-652
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• 2003

제 3세대 이동 통신망인 GPRS(General Packet Radio Service)망에서는 SGSN(Serving GPRS Support Node)과 GGSN(Gateway GPRS Support Node) 사이의 전송계층을 IP-Over-ATM 망을 기반으로 한다. 이는 비연결형(connectionless) IP 트래픽들을 연결지향형(connection-oriented) ATM 전송계층을 통해 전송하는 것을 의미한다. 이때 효율적인 자원관리를 위해 적절한 VC(Virtual Circuit)의 접속과 해제를 수행해야 한다. 본 논문에서는 GPRS망에 인터넷 웹 서비스 트래픽 모델을 다양한 VC holding Cost Pricing Model(LRU, Mean-Variance, Adaptive policy[2])에 적용하였다. 각각의 기법들에서 VC의 이용율(utilization)과 설정율(setup rate)을 분석함으로써 각 기법의 성능을 비교하였다.

• 정보처리학회논문지C
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• 제9C권6호
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• pp.865-874
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• 2002

HTTP(HyperText Transfer Protocol)는 월드 와이드 웹 분산 시스템이 객체를 인출하기 위해 사용하는 전송 프로토콜이다. HTTP는 연결 지향 프로토콜이므로 트랜스포트계층에서 TCP(Transmission control Protocol)를 사용한다. 그러나 HTTP는 TCP와의 상호운용이 좋은 편이 아닌 것으로 알려져 있다. 본 연구에서는 TCP의 성능에 영향을 주는 요인들을 살펴보고, HTTP 접근을 위해 TCP의 slow-start 오버헤드 및 연결에 소요되는 트랜잭션 시간과 TCP의 성능 향상 대안중의 하나인 T-TCP(Transaction TCP)의 트랜잭션 시간을 검토한다. 평균 대기 시간과 평균 반환 시간은 사용자의 서비스 품질을 만족시키기 위한 중요한 파라메터들이다. TCP와 T-TCP 트랜잭션 시간이 주어지는 경우 그러한 파라메터들의 계산 공식이 유도되었다. 실험 및 계산 경험을 통해 제안된 공식이 잘 작동됨을 확인하였고, 대역폭의 확장이 필요한 환경에 적용될 수 있으며 T-TCP의 시간 특성이 TCP 보다 우수함을 확인하였다. 아울러, 평균 대기 시간과 평균 반환 시간을 줄이기 위해 대역폭을 조합하여 서버를 분산하는 방법이 제시되었다.

• Safety and Health at Work
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• 제10권4호
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• pp.452-460
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• 2019

Background: Monitoring and control of PM_2.5 are being recognized as key to address health issues attributed to PM_2.5. Availability of low-cost PM_2.5 sensors made it possible to introduce a number of portable PM_2.5 monitors based on light scattering to the consumer market at an affordable price. Accuracy of light scatteringe-based PM_2.5 monitors significantly depends on the method of calibration. Static calibration curve is used as the most popular calibration method for low-cost PM_2.5 sensors particularly because of ease of application. Drawback in this approach is, however, the lack of accuracy. Methods: This study discussed the calibration of a low-cost PM_2.5-monitoring device (PMD) to improve the accuracy and reliability for practical use. The proposed method is based on construction of the PM_2.5 sensor network using Message Queuing Telemetry Transport (MQTT) protocol and web query of reference measurement data available at government-authorized PM monitoring station (GAMS) in the republic of Korea. Four machine learning (ML) algorithms such as support vector machine, k-nearest neighbors, random forest, and extreme gradient boosting were used as regression models to calibrate the PMD measurements of PM_2.5. Performance of each ML algorithm was evaluated using stratified K-fold cross-validation, and a linear regression model was used as a reference. Results: Based on the performance of ML algorithms used, regression of the output of the PMD to PM_2.5 concentrations data available from the GAMS through web query was effective. The extreme gradient boosting algorithm showed the best performance with a mean coefficient of determination (R²) of 0.78 and standard error of 5.0 ㎍/㎥, corresponding to 8% increase in R² and 12% decrease in root mean square error in comparison with the linear regression model. Minimum 100 hours of calibration period was found required to calibrate the PMD to its full capacity. Calibration method proposed poses a limitation on the location of the PMD being in the vicinity of the GAMS. As the number of the PMD participating in the sensor network increases, however, calibrated PMDs can be used as reference devices to nearby PMDs that require calibration, forming a calibration chain through MQTT protocol. Conclusions: Calibration of a low-cost PMD, which is based on construction of PM_2.5 sensor network using MQTT protocol and web query of reference measurement data available at a GAMS, significantly improves the accuracy and reliability of a PMD, thereby making practical use of the low-cost PMD possible.

• 한국ITS학회:학술대회논문집
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• 한국ITS학회 2008년도 제7회 추계학술대회 및 정기총회
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• pp.463-466
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• 2008

기존의 교통상황판운영에 사용하는 지도는 2D를 기본으로 하는 전자지도를 중심으로 표준노드링크의 속성을 반영하는 형태이다. 2D형태의 교통전자지도는 그래픽형식에 운영자에게 실시간으로 교통상황을 직관적으로 판단하는데 도움을 제공 하였으나 2D형식이라는 한계가 존재할 수밖에 없었다. 점차적으로 IT기술의 고도화, 하드웨어, 통신기술의 발달 등으로 과거에 다룰 수 없었던 대용량데이터처리가 원활해지고, 다양한 도로이용자의 고급화된 교통수요에 대응하기 위해서는 점차적으로 교통관리자나 운영자들이 교통정보관련 장비들이나 운영시나리오에 대해 다각적으로 분석을 할 수 있는 방안이 강구되어야 한다. 이에 위도, 경도, 고도를 제공하는 3D형식의 전자지도에 실시간적으로 교통정보를 제공하는 4D형식의 교통상황판이 운영될 수 있도록 하는 방안을 제공할 수 있는 기술적 내용과 교통시나리오를 제공하고자 한다.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2007년도 춘계학술발표회 논문집
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• pp.323-328
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• 2007

Geotechnical Information Database Project was began by Ministry of Construction Transport at the 1999, because many people need a sharing and reusing the geotechnical report in construction process. In the beginning, target was report of national highway construction. the whole of country has been target on since the 2005. Today, the 60,581 number of geotechnical data(counted by boring number) is maintained. In this study, Geotechnical Information Distribute System(GIDS) was developed, in order to improve practical use and to be connected to National Geographic Information Center(NGIC). and program to be applicable to construction was suggested. We expect that GIDS make a effect to improve geotechnical data application and to be use in all part of construction process.

• International Journal of Concrete Structures and Materials
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• 제2권2호
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• pp.115-122
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• 2008

Ductility is important in the design of reinforced concrete structures. In seismic design of reinforced concrete members, it is necessary to allow for relatively large ductility so that the seismic energy is absorbed to avoid shear failure or significant degradation of strength even after yielding of reinforcing steels in the concrete member occurs. Therefore, prediction of the ductility should be as accurate as possible. The principal aim of this paper is to present the basic data for the ductility evaluation of reinforced high-strength concrete beams. Accordingly, 23 flexural tests were conducted on full-scale structural concrete beam specimens having concrete compressive strength of 40, 60, and 70MPa. The test results were then reviewed in terms of flexural capacity and ductility. The effect of concrete compressive strength, web reinforcement ratio, tension steel ratio, and shear span to beam depth ratio on ductility were investigated experimentally.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 2003년도 춘계공동학술대회
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• pp.704-707
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• 2003

The Purpose of carrier tracking and tracing is to achieve more information over shipments via carrying in mobile business .At multimodes, especially consignor wants to be aware of the exact situation and position of goods. As an innovate business model, we present CGPS(Carrier Global Positioning System) scheme usiug LEO(Low Earth Orbital) satellite. The LEO collects the data periodically and sends to the web server, and eventually customer's PC or PDA. This provides shipping company or freight forwarder with more robust information such as door status, container inside condition, etc.

• Journal of Communications and Networks
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• 제5권1호
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• pp.65-72
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• 2003

Internet roundtrip delay/time (RTT) prediction plays an important role in detecting packet losses in reliable transport protocols for traditional web applications and determining proper transmission rates in many rate-based TCP-friendly protocols for Internet-based real-time applications. The widely adopted autoregressive and moving average (ARMA) model with fixed-parameters is shown to be insufficient for all scenarios due to its intrinsic limitation that it filters out all high-frequency components of RTT dynamics. In this paper, we introduce a novel parameter-varying RTT model for Internet roundtrip time prediction based on the information theory and the maximum entropy principle (MEP). Since the coefficients of the proposed RTT model are updated dynamically, the model is adaptive and it tracks RTT dynamics rapidly. The results of our experiments show that the MEP algorithm works better than the ARMA method in both RTT prediction and RTO estimation.