• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.64-65
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• 2002

Recently the synthetic antiferromagnetic layer (SAF) has received much attention because it replaces the pinned layer of the conventional spin valve (CSV) sensors and its overall performance [1], The spin valve (SV) with SAF has the from buffer/F/Cu/APl/Ru/AP2/AF, where F is the soft ferromagnetic layer (typically NiFe with CoFe interfacial doping), AP1 and AP2 are two ferromagnetic layers (typically CoFe alloys) antiferromagnetically coupled through a thin Ru layer. (omitted)

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.632-634
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• 2012

In order for the connection to the wireless network from the list of priorities of the wireless AP to AP profile automatic connection by selecting the preferred method to register a profile, which is determined at the time of the change, the user does not respond to the demands of the part. In this study, the frequency of the user's access in accordance with the wireless AP, and by creating a profile, the user needs to meet with regard to network access adaptive research.

• Journal of the Korea Convergence Society
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• v.7 no.4
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• pp.39-44
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• 2016

Due to the dazzling development of IT in this IT-oriented era, information delivering technology among objects, between objects and humans, and among humans has been actively performed. As information delivery technology has been actively performed, IoT became closely related to our daily lives and ubiquitous at any time and place. Therefore, IoT has become a part of our daily lives. CoAp, a web-based protocol, is mostly used in IoT environment. CoAp protocol is mostly used in the network where transmission speed is low along with the huge loss. Therefore, it is mostly used in IoT environment. However, there is a weakness on IoT that it is weak in security. If security issue occurs in IoT environment, there is a possibility for secret information of individuals or companies to be disclosed. If attackers infect the targeted device, and infected device accesses to the wireless frequently used in public areas, the relevant device sends arp spoofing to other devices in the network. Afterward, infected devices receive the packet sent by other devices in the network after occupying the packet flow in the internal network and send them to the designated hacker's server. This study suggests counter-attacks on this issues and a method of coping with them.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.6092-6115
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• 2017

This paper demonstrates a case for an end-to-end pure Application Security Layer for reliable and confidential communications within an Internet of Things (IoT) constrained environment. To provide a secure key exchange and to setup a secure data connection, Transport Layer Security (TLS) is used, which provides native protection against replay attacks. TLS along with digital signature can be used to achieve non-repudiation within app-to-app communications. This paper studies the use of TLS over the JavaScript Object Notation (JSON) via a The Constrained Application Protocol (CoAP) RESTful service to verify the hypothesis that in this way one can provide end-to-end communication flexibility and potentially retain identity information for repudiation. As a proof of concept, a prototype has been developed to simulate an IoT software client with the capability of hosting a CoAP RESTful service. The prototype studies data requests via a network client establishing a TLS over JSON session using a hosted CoAP RESTful service. To prove reputability and integrity of TLS JSON messages, JSON messages was intercepted and verified against simulated MITM attacks. The experimental results confirm that TLS over JSON works as hypothesised.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.05a
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• pp.204-207
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• 2019

DDoS(Distributed Denial of Service) 공격은 네트워크상에서 다수의 시스템 협업으로 하나의 표적 시스템을 공격하여 서비스의 가용성을 침해하는 공격이다. 이는 점차 지능적인 방법으로 진화하고 있으며 특히 IoT를 대상으로 한 DDoS 공격이 증가하고 있다. 이기종의 기기들이 연결된 IoT는 기존 IT디바이스와 비교하여 제한된 자원을 가지고 있어 IoT 네트워크 특성을 고려한 DDoS 보안 기법이 요구된다. 국제 인터넷 표준화 기구 IETF에서 IoT를 지원하기 위해 제정한 CoAP(Constrained Application Protocol)은 기존 IT 네트워크와 호환성을 가진 응용 계층 프로토콜이다. 본 논문은 CoAP의 DDoS 공격 취약점과 대응 방안을 정리하고 새로운 프로토콜을 추가할 시 고려해야 할 사항을 제시한다.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.4
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• pp.21-27
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• 2017

In this paper, in order to control the burning rate and pressure exponent of HTPB/AP/Al based propellant for the improvement of performance, the effect of the size ratio of AP particles and various contents of Butacene as burning catalyst on combustion properties was investigated. In the propellant formulation with both $28{\mu}m$ Al of 23% and Butacene of 3%, the burning rate and pressure exponent were increased with increasing the contents of $9{\mu}m$ AP particles. And the burning rate was increased with increasing the contents of Butacene with showing the relatively low pressure exponent in the propellant containing Butacene. However, the significant variations of pressure exponent by contents of Butacene were not observed.

• Journal of Korean Society for Atmospheric Environment
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• v.31 no.1
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• pp.72-82
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• 2015

We constructed greenhouse gas (GHG) and air pollution (AP) integrated sink/emission inventories and evaluated the environmental value for the vegetation sector in Seoul during year 2010. The data of vegetation, classified into four sectors of cultivated land, forest land, park and street tree, were obtained from Statistics Korea and Seoul City. Based on the previous studies, only $CO_2$ was chosen as GHG sink by vegetation. $NO_2$ and $SO_2$ were chosen as AP sink by vegetation, while isoprene, monoterpene, other VOC (OVOC) and NH3 were chosen as AP emission from vegetation. Estimation methodology and sink/emission factors were gathered from reports and published literatures. Estimated GHG sink by vegetation during year 2010 was 12,987,173 $tonCO_{2eq}$, of which approximately 1/4 was from pure vegetation and the remaining 3/4 from vegetation soil. AP sink and emission were estimated to be 23,309 tonAP and 2,629,797 tonAP, respectively. The analysis by administrative districts in Seoul revealed that among 25 districts, Seocho-gu, Nowon-gu, Eunpyeong-gu, Gwanak-gu and Gangbuk-gu were the major districts in GHG and AP sink/emission inventories for vegetation sector. Environmental value of vegetation as a function of GHG and AP sink, was estimated as 800 billion won, corresponding to 5% of the total cost of the forest land in Korea evaluated as a public function.

• Journal of KIISE
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• v.44 no.12
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• pp.1296-1306
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• 2017

Recently, as the number of Internet of Things users has increased, IETF (Internet Engineering Task Force) has released the CoAP (Constrained Application Protocol). So Internet of Things have been researched actively. However, existing studies are difficult to adapt to streaming service due to low transmission rate that result from buffer underflow. In other words, one block is transmitted one block to client's one request according to the internet environment of limited resources. The proposed scheme adaptively adjusts the rate of CON(Confirmable) message among all messages for predicting the exact network condition. Based on this, the number of blocks is determined by using buffer occupancy rate and content download rate. Therefore it improves the quality of user experience by mitigating playback interruption. Experimental results show that the proposed scheme solves the buffer underflow problem in Internet of Things streaming environment by controlling transmission rate according to the network condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.5
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• pp.616-622
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• 2020

Recently, as the interest in power saving increases with the development of IoT technology, research on power saving of smart devices, which are being miniaturized, is being actively conducted. In particular, due to the diversification of IoT-based smart devices and the increase in personal penetration rate, the issue of standby power even when not in use is increasing. However, there is a drawback of physically unplugging the outlet or turning off the power in order to substantially reduce standby power. Since Zigbee is used instead of the existing IP, it is necessary to change to the IoT standard protocol based on the Internet network. Therefore, this paper designed and implemented the standby power saving system applying CoAP, the IoT standard protocol, to the existing Zigbee technology. Existing systems and evaluations confirmed that the average standby power of about 8.4Wh was reduced.

• International Journal of Computer Science & Network Security
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• v.21 no.11
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• pp.301-311
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• 2021

The technological advancements of the last two decades directed the era of the Internet of Things (IoT). IoT enables billions of devices to connect through the internet and share their information and resources on a global level. These devices can be anything, from smartphones to embedded sensors. The main purpose of IoT is to make devices capable of achieving the desired goal with minimal to no human intervention. Although it hascome as a social and economic blessing, it still brought forward many security risks. This paper focuses on providing a survey of the most commonly used application layer protocols in the IoT domain, namely, Constrained Application Protocol (CoAP), Message Queuing Telemetry Transport (MQTT), Advanced Message Queuing Protocol (AMQP), and Extensible Messaging and Presence Protocol (XMPP). MQTT, AMQP, and XMPP use TCP for device-to-device communication, while CoAP utilizes UDP to achieve this purpose. MQTT and AMQP are based on a publish/subscribe model, CoAP uses the request/reply model for its structuring. In addition to this, the quality of service provision of MQTT, AMQP, and CoAP is not very high, especially when the deliverance of messages is concerned. The selection of protocols for each application is very a tedious task.This survey discusses the architectures, advantages, disadvantages, and applications of each of these protocols. The main contribution of this work is to describe each of the aforementioned application protocols in detail as well as providing their thorough comparative analysis. This survey will be helpful to the developers in selecting the protocol ideal for their system and/or application.