• Safety and Health at Work
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• v.10 no.4
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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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.871-878
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• 2017

As the interest of things to the Internet increases, the market of IoT grows larger and devices and protocols related with IoT are evolving.As these IoT devices and protocols evolve, There was a problem with interoperability. As a result, market and standard of IoT are confused, and communication between objects and objects is being hindered by different platforms. Currently, various IoT platforms are being developed and interoperability with heterogeneous platforms is under study, but the protocols used on each platform are limited and designed to have no generalized structure. Therefore, in this paper, we analyze services of HTTP, CoAP, and MQTT protocols, which are typical in the Internet market, and design services that enable selective protocol communication. We also design resources that apply the RESTful API to generalize platform usage. and We implemented the platform through database modeling for quick processing and safety of the collected data. Through this process, devices communicating with different protocols can be interworked on one platform and We propose a "generalized selective protocol based Internet object data collecting platform" that can be applied to various protocols.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.852-854
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• 2016

oneM2M 표준은 다양한 플랫폼을 지원하기 위해 다양한 통신 프로토콜과의 바인딩을 지원한다. 이 통신 프로토콜들은 HTTP, MQTT, COAP, WebSocket 등 경량화 혹은 단일 대상에 적합한 통신 프로토콜이며, 데이터 형식이 고정되어 있다. 본 논문에서는 자유로운 데이터 형식을 지원하며, 대규모/실시간 통신에 적합한 DDS를 oneM2M 표준에 따르는 OCEAN 플랫폼에 적용하는 방법을 제안한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.10
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• pp.1943-1949
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• 2017

In recent years, the maker culture has realized the concept of 'making' itself through the latest technology of high technology. It is rapidly spreading as a maker's movement by sharing the production methods and information of individuals through the Internet. Countries that are leading the makers' movement expect the maker's movement to be the driving force for new value creation and economic growth from the point of view of things and the Internet. We are developing various types of open IoT platforms that can register various Internet devices and services manufactured and developed through DIY and realize interoperable services. Typical open IoT platforms require specialized API analysis capabilities and difficult access to general users due to difficult platform registration conditions and procedures. In this paper, we try to construct an open IoT platform that can be operated as a real service by creating a simple Internet application device and service application from a general manufacturer's point of view.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.3
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• pp.661-666
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• 2016

The Internet of Things (IoT) is an infrastructure of physical objects that could be connected to the Internet. Most of these are low performance to ensure a reasonable cost for the smart physical objects. Thus, these devices usually use a lightweight messaging protocol: message queue telemetry transport with SSL/TLS. Cipher suites in device are fixed by default and selected based on preference in SSL/TLS. However, the selected cipher suite provides high security level more than expected. This limitation causes energy waste and overhead of devices. In order to counter this problem, we proposed fuzzy logic based cipher suite decision method to improve energy efficiency. Our proposed method saved 36.03% energy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1895-1902
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• 2016

People and goods through the recent smart device, IoT to things and things are connected, it has emerged as the driving force of a new economic growth in the future. While conducting research of this international standardization organization in the IoT-based protocol, to the institutions and companies that belong to the standards bodies interests are different from each other, protocols have been developed also, different order, heterogeneous device interoperability has emerged is a problem that the lowering of. Therefore, in this paper, to investigate the structure of the MQTT and CoAP that are commonly used and trying to figure out the trend of low power consumption, a lightweight protocol that is suitable for IoT environment, process and standardization trends of evolution, features, analysis and on, to derive the advantages and disadvantages, and comparative analysis, it presented a development scheme for each protocol.

• Journal of Digital Convergence
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• v.17 no.12
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• pp.235-241
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• 2019

The structure of the IoT can be divided into devices, gateways, and servers. First, the gateway collects data from the device, and the gateway sends data to the server through HTTP protocol, Websocket protocol, and MQTT protocol. The processing server then processes, analyzes, and transforms the data, and the database makes it easy to store and use this data. These IoT services are basically centralized structures with servers, so attacks on the entire platform are concentrated only on the central server, which makes hacking more successful than distributed structures. One way to solve this problem is to develop IoT that combines blockchain. Therefore, the proposed research suggests that the blockchain is a distributed structure, in which blocks containing small data are connected in a chain form, so that each node agrees and verifies the data with each other, thereby increasing reliability and lowering the probability of data forgery.

• KEPCO Journal on Electric Power and Energy
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• v.4 no.2
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• pp.67-73
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• 2018

There are many types of power facilities such as transformers, switches, and energy storage devices in the micro grid environment. However, with the development of IoT technology, opportunities to acquire sensor information such as temperature, pressure, and humidity are provided. In the existing micro grid environment, the communication protocols such as MMS transport protocol in IEC 61850 standard is applied in accordance with the integrated operation between the power facilities and the platform. Therefore, to accommodate IoT data, a gateway technology that can link IoT data to a data collection device (FEP) based on IEC 61850 is required. In this paper, we propose IEC 61850 based IoT gateway platform prototype for microgrid operating system linkage. The gateway platform consists of an IoT protocol interface module (MQTT, CoAP, AMQP) and database, IEC 61850 server. For databases, We used open source based NoSQL databases, Hbase and MongoDB, to store JSON data. We verified the interoperability between the IoT protocol and the IEC 61850 protocol using Sisco's MMS EASY Lite.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.2
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• pp.229-236
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• 2019

IOT middleware is required to play a pivotal role in interpreting, managing, and controlling data information of Internet devices (sensors, etc.). In particular, the root industry has different process flows for different industries, and there are various data processing requirements for each company. Therefore, a general purpose IOT middleware is needed to accommodate this. The IOT middleware structure proposed by this paper is a plug-in that can be used as an engine part for middleware basic processes such as communication, data collection, processing and service linkage, We propose a flexible and effective smart process for root industry. In addition, we propose a method to strengthen prevention and security against tampering, deodorization, etc. through encryption of network data between middleware plug - in and related service layer. We propose a system that will be developed as an IOT middleware platform that is specialized in the root industry so that it can be extended in various network protocols such as MQTT, COAP, XAMP.

• Journal of IKEEE
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• v.25 no.2
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• pp.291-301
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• 2021

OPC UA at the control and field level does not provide enough performance to replace the field bus. The OPC Foundation aims for a real-time and connection-less mechanism, and has added the OPC UA publish-subscribe model, a new specification that supports broker functions such as MQTT and AMQP, as the OPC UA Part 14 standard. This paper is about a gateway for interoperability between OPC UA publisher with the addition of OPC UA Part14 standard and DDS subscribers. Raspberry Pi 4 is used for the gateway proposed in this paper, and OpenDDS, an open source, is used for DDS. OPC UA publish-subscribe module used A-Open62541 publish-subscribe module, which additionally implements functions not provided by the corresponding source based on Open62541 publish-subscribe open source.