• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.331-332
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• 2015

본 논문은 3상 T-type 3-레벨 인버터에 적용할 수 있는 예측제어 방법에 관한 논문이다. 최근 인버터의 효율 향상 등의 장점으로 멀티레벨 인버터가 주목받고 있다. 그중 T-type 방식은 저전압, 중전압에서 강점이 있는 토폴로지이며, 예측제어 방식은 직관적이고 쉽게 이해가능한 스위치 제어방법이다. 3-레벨 인버터에서는 전압벡터의 개수가 많아 예측제어기법을 적용하기에는 계산시간이 오래걸리는 단점이 있다. 본 논문에서는 CB PWM 방식에 예측값으로 offset을 주는 방식으로 DC단 중성점 전압제어와 출력전압제어를 하였다.

• The Journal of the Convergence on Culture Technology
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• v.3 no.3
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• pp.27-30
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• 2017

IoT could be applied to various areas because of the important role of sensor. The existing sensor communication method is to quickly transmit data by using clock and two data pins based on the I2C serial communication method. As the objects used are gradually light-weighted and the amount of data transmission is decreased, the simplification of hardware is more emphasized as an essential design element than the speed of transmission. This paper designed a circuit to send/receive data in series, and also realized arduino, by analyzing the existing communication method and then using a single pin for light-weight. The single pin serial communication could reduce power consumption, which is suitable for the sensor area using digital communication of IoT area.

• The Korean Journal of Rheology
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• v.3 no.2
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• pp.135-147
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• 1991

압출공정 중에 화학반응이 수반되는 경우에 화확반응은 온도와 체류시간분포 (Residence Time Distribution (RTD))에 의해 결정되므로 압출기의 설계 및 공정조건의 확 립에 있어서 RTD를 정확히 측정하거나 예측하는 것은 매우 중요하다. RTD를 예측하기 위 해 제안된 종래의 방법은 압출기내에서의 유동을 2차원으로 단순화하여 RTD와 체류시간분 포함수 f(T)와 누적 체류시간 분포함수 F(T)를 해석적으로 구하였다. 그러나 이러한 종래의 RTD에 관한 해석방법은 실제압출기 내부에서 일어나는 3차원적 순환유동(Circulatory Flow)을 정확하게 고려하지 못하는 문제점을 갖고 있다. 본논문에서는 RTD를 정확하게 예 측하기 위하여 3차원 순환유동을 고려한 RTD를 구하는 방식을 제시하고 f(T)에 관한 새로 운 공식을 유도하였다. 새로운 방식을 적용하기 위해서 유사 3차원(Quasi-3-Dimensional) 유한요소 해석법을 이용하여 속도분포를 구한 후에 순환유동을 고려한 RTD 및 f(T), F(T) 를 계산하였다. 순환유동이 고려안된 종래의 방법에 따른 계산 결과와 비교한 결과로서 종 래의 방식은 순환유동이 고려안되었기 때문에 RTD를 과소평가하는 경향이 있음을 알수 있 었다.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.412-417
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• 1998

This paper suggests the drive characteristics of a Switched Reluctance Motor(SRM) by 2-phase excitation method. T This scheme excites 2 phases simultaneously, which is similar to 2-phase excitation method of a step motor. In this s scheme. the torque is produced by mutual inductances as well as self inductances. The abrupt change of a phase e excitation produces mechanical stresses and it results in vibration and noise. The acoustic noise is reduced remarkably t through the sequential phase excitation in the 2-phase excitation. Operational principle and characteristic comp없1son t to that of the conventional SRM show that this excitation scheme has some advantages including torque ripple and n noise reduction.

• Korean Journal of Soil Science and Fertilizer
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• v.29 no.4
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• pp.403-410
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• 1996

Variations of temperature and physicochemical environment during composting of a mixtures(2:1, v/v) of cattle manure and rice hulls(CMR) in two different composting methods, static windrow(SW) and aerated static pile system(ASPS), were monitored for evaluating the efficient composting system in greenhouse. The pH of composting materials increased to around 8.9 initially, then decreased and stabilized slowly to the neutral value. Composting materials in ASPS showed a rapid stabilization in pH value from the 4th week comparing to the speed in SW. Thermophilic stage for ASPS Lasted at 3 week whereas 6 weeks for WS. Required time to get thermophilic zone in compost was shorter in ASPS than in WS. Reduction rate in total carbon(T-C) was higher in ASPS than in WS. Organic matter was reduced more rapidly in ASPS than in SW showing 9 percent difference after the 6th week. Total nitrogen(T-N) increased while composting process, showing 9 percent after 6th week in WS and 1.8 percent after 7th week in ASPS. C/N ratio was stabilized after 6th week showing 17 and 21 level in WS and ASPS each. Quantity of ash and mineral content increased during composting in both system, showing higher content in ASPS. Composting process by intermittent, aerated static pile system in greenhouse had a significant effect on the reduction of required period for composting.

• Journal of Convergence for Information Technology
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• v.10 no.4
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• pp.18-24
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• 2020

Recently, research on Society 5.0 has been actively carried out in Japan. The Society 5.0 is used in various areas using IoT sensors. This paper proposes a privacy approach model of multiple approaches to IoT users based on Society 5.0. The proposed model used multiple methods of synchronizing important information of IoT devices with one another in the virtual environment. The proposed model improved the efficiency of IoT information by accumulating the weight of IoT information on a probability-based basis. Further, it improves the accuracy of IoT information by segmenting it so that attribute information is linked to IoT information. As a result of the performance evaluation, the efficiency of IoT devices has improved by an average of 5.6 percent, depending on the number of IoT devices and the number of IoT hub devices. Accuracy has improved by an average of 15.9% depending on information collection and processing.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.1
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• pp.46-56
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• 2017

Recently, the spread of IoT technology has been spreading, and it has been applied to all industrial fields such as home / home appliance / medical care. Due to the low specification, low power consumption characteristic and communication data characteristic of IoT, implementation of existing algorithm is difficult thing. From this reason, we have proposed for the first time that encryption and decryption can be proceeded by introducing a kind of variable length bit XOR operation method which changes a variable the bit length value by using carry up and carry down method. We confirmed the practicality of encrypting short message data frequently processed by IoT device / QR code / RFID / NFC without changing the size of data before and after encryption.

• Proceedings of the Korean Society of Computer Information Conference
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• 2012.07a
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• pp.335-338
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• 2012

교통카드는 1996년 충전방식의 선불카드가 처음 사용되었고, 후불방식의 교통카드는 1998년 6월부터 도입되어 함께 사용되었다. 교통카드 사용할 수 있기 위해서는 사용자의 사용여부 및 각종 신상정보의 변경에 따라 결제방식이 변경되는 것에 대해 카드거래 승인시스템에 적절한 반영이 필요하다. 이를 위해 기존 서울교통시스템에서는 메모리 주소를 이용한 카드거래승인시스템을 이용하고 있으며 본 연구에서는 임베디드 교통카드단말기에서 사용 가능한 오프라인 카드거래 승인 알고리즘을 개발하는 것을 목표로 한다. 본 논문에서는 카드 사용정보를 압축 저장하는 방식을 제안하고 있으며, 사용자 할인정보는 한 카드당 2bit의 공간을 차지하도록 설계 했다. 또한 검색알고리즘으로 이진탐색을 사용하여 기존에 비해 검색 속도가 향상 되었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2479-2487
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• 2009

Earlier researches on Sensor Networks preferred symmetric key-based authentication schemes in consideration of limitations in network resources. However, recent advancements in cryptographic algorithms and sensor-node manufacturing techniques have opened suggestion to public key-based solutions such as Merkle tree-based schemes. This paper proposes a new concept of public key-based authentication using Polynomial Secret Sharing that can be effectively applied to sensor networks and a detection of malicious node using the hash function. This scheme is based on exponential distributed data concept, a derivative from Shamir's (t,n) threshold scheme, in which the authentication of neighbouring nodes are done simultaneously while minimising resources of sensor nodes and providing network scalability.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.1
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• pp.98-103
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• 2021

In this study, we propose a group communication technique that guarantees security and expandability by configuring a network consisting of IoT terminals equipped with security functions. As the number of devices participating in the network increases, network resources are proportionally reduced, and adding a security function to the IoT device increases the delay time due to encryption in the IoT device. If the error rate that occurs in the network increases, network resources are quickly consumed due to retransmission. Therefore, IoT terminals are grouped to ensure scalability while supporting security, reducing the consumption of network resources even when the number of participating nodes increases, thus ensuring scalability. For the future implementation, the encryption method used in IoT terminals considered the standard of IEEE802.5.4, and the standardization trend was investigated and classified. The proposed method applies IoT devices that provide security functions of the IEEE802.5.4 standard to the group communication base to ensure reliability and scalability. In the performance evaluation, the effectiveness of the proposed method was confirmed by comparing the delay times when grouping IoT devices with security functions through simulation.