Yong-Kab Kim

An Enhanced Broadcasting Algorithm in Wireless Ad-hoc Networks

In a multi-hop wireless ad hoc network, broadcasting is an elementary operation to support many applications. Broadcasting by flooding may cause serious redundancy, contention, and collision in the network, which is referred to as the broadcast storm problem. Many broadcasting schemes are proposed to give better performance than simple flooding in wireless ad hoc network. How to decide whether rebroadcast or not also poses a dilemma between reachability and efficiency under different host densities. In this paper, we propose enhanced broadcasting schemes, which can reduce rebroadcast packets without loss of reachability. Simulation results show that proposed schemes can offer better reachability as well as efficiency as compared to other previous schemes.

Thermal Characteristics of Designed Heat Sink for 13.5W COB LED Down Light

The high power COB(Chip on Board) LED, densely arranged chips on a board, are increasing to resolve heat problems in LED that has luminous semiconductor chips as main materials. In case of high-power COB LED, protection against heat is necessary due to the power consumption is high. Also if the temperature of device increases, the optical emission becomes less efficient and the life rapidly reduces due to thermal stress. This study packaged 13.5W COB LED and heat sink with difference form and produced 13.5W COB LED down-light heat sink by analyzing the thermal modes with Solidworks Flow Simulation. And finally it analyzed and evaluated the thermal modes using contacting and non-contacting thermometers. 키워드 Heat Sink Design, COB LED, Thermal Characteristics, Down Light, Temperature Measurement. 방열판 형상 설계, 온도 측정, 방열 특성, 다운라이트 * 원광대학교 정보통신공학과(kojman@wonkwang.ac.krl) ** 교신저자(corresponding author) : 원광대학교 반도체·디스플레이학부(gchoang@wonkwang.ac.kr) 접수일자 : 2014. 03. 10 심사(수정)일자 : 2014. 04. 21 게재확정일자 : 2014. 05. 15 I. 서 론 LED(Light emitting diode)는 차세대 조명 소자로 주목받고 있다. LED는 조명을 비롯해 의료, 농업등 여러 분야에 응용되고 있다. 국가적 절전을 위해 현재 공공기관을 중심으로 실내 백열등과 형광등, 주차장 조명등이 LED로 교체되고 있다[1-3]. 하지만 고출력 을 요구하는 사회적 욕구로 인해 반도체 소자의 단일 http://dx.doi.org/10.13067/JKIECS.2014.9.5.561 JKIECS, vol. 9, no. 5, 561-566, 2014 562 용량이 커지면서 발열에 의한 문제로 소자의 수명 저 하 및 광 출력에 직접적인 영향을 미친다[4-5]. LED 접합부의 온도 상승에 따른 열적 문제를 해결하기 위 해 SMD (Surface mount device)패키징 기술이 개발 되었다. 하지만 고출력 조명등의 사용으로 인해 다량 의 칩을 배열 하는 구조를 사용하여 글레어 현상과 쉐도우 현상의 문제점이 발생되어 발광되는 빛의 품 질이 저하되어 SMD패키지의 복잡한 공정의 해결과 열전달 경로의 최소화가 필요하게 되었다. 이러한 문 제를 해결하기 위해 COB 패키징 기술이 개발되었고, COB LED 모듈은 기판위에 직접 Chip을 실장하기 때문에 공정의 단순화가 가능하다. 현재 고출력 고집 적 LED모듈은 COB형태의 패키지가 주종을 이루고 있으며 열전달 면에서 경로를 최소화하는 발열구조로 연결되어 있어 열 특성을 20% 이상 개선이 가능하며 방열판을 통한 열 응집현상 해소가 가능하다[4]. 하지 만 SMD타입 패키지에 방열판을 적용한 연구는 진행 중이나, COB타입의 패키지에 적용된 방열판에 관한 연구는 미비한 실정이다. COB LED 광원용 패키지에 높은 열 전도성과 경량성을 가진 실장기판용으로 알 루미늄 기판이 적합하다[6-7]. 따라서 본 논문에서는 주거용 13.5W급 COB LED 패키지에 적합한 방열판을 설계하고자 COB LED 패 키지 이미지와 형상이 각기 다른 4가지 알루미늄 방 열판을 3D 형상 설계 프로그램인 Solidworks를 사용 하여 설계하고, 설계된 두 소자를, 13.5W급 COB LED 패키지 이미지와 방열판, 결합 하여 열 유동 시 뮬레이션인 Flow Simulation을 통해 온도를 측정하였 다. 그중 가장 특성이 좋은 방열판을 선정하여 실물 제작을 하고, 13.5W급 COB LED 실물과 결합하여 1 m의 공간 속에서, Omega社의 접촉식 온도계 (Thermo Couple)를 사용한 접촉식 열 특성과 Fluke 社의 열화상 카메라를 사용하여 비접촉식 열 특성을 분석하고 두 경우를 비교 평가하였다. II. COB LED 및 방열판 성능 분석 2.1. 13.5W COB LED의 3D 형상 설계 그림 1(a)은 실물 13.5W급 COB LED 패키지이다. COB 패키지는 동부 LED社의 36~38V, 360mA를 사 용하는 13.5W급 COB LED 패키지로써 다수의 LED 칩이 직 병렬로 배열되어 있는 구조이다. 이 COB는 가로 2mm, 세로 2mm, 높이 1.4mm에 다량의 칩이 집적화 되어있어 열을 해소 할 수 있는 2차 방열판이 필요하 다. 2차 방열판 제작에 앞서 열 유동 시뮬레이션을 통 해 대류 현상과 온도를 측정하기위해 그림 2-1 (b)와 같은, 제품과 동일 크기의, 3D형상을 설계하였다. (a) 13.5W COB LED 제품 (b) 3D 형상 그림 1. 13.5W COB LED 제품(a)과 3D 형상(b) Fig. 1 (a) 13.5W COB LED product and (b) 3D design 2.2. 방열판 형상 설계에 따른 해석 방열판 형상 설계에 앞서 Flow 시뮬레이션으로 대 류 열과 온도를 측정하고 실제 실험과 동일한 조건을 위해 표 1과 같이 설계사양을 설정하였다.

Implementation of brillouin-active fiber based neural network in smart structures

We propose a novel application of SBS in embedded optical fibers as a building block for the implementation of optical neural net in smart structures. By employing well established technology in fiber embedding in structures, and exploiting the ability of SBS as a highly versatile ambient sensor, and its nonlinear optical property of energy addition and subtraction to perform optical arithmetic, we predict the possible integration of sensing and actuation for smart structures. In this paper, the fiber based SBS neuron is explained. Optical arithmetic schemes are shown to demonstrate the simplicity of operation of these neurons. Typical implementation schemes are illustrated.

Identification and characterization of flowering repressor-related genes in Chinese cabbage

In this study, we used a five-step process to identify those genes most likely involved in flowering repression in the Chinese cabbage (Brassica rapa). We tested 6,275 candidate genes with 300K microarrays, which included specific gene expression profiles of FLOWERING LOCUS C (FLC) mutants and normal cultivars during five cold vernalization stages. From that, we identified 289 transcription factor genes and 59 pathway network genes associated with floweringrelated metabolism. Then we compared the 348 genes to 1,287 genes from Gene Ontology and Clusters of Orthologous Groups analyses, which use similar orthologs to categorize conserved genes. Those analyses revealed 10 hypothetical genes for B. rapa, which we verified by reverse transcription-polymerase chain reaction. The final selected genes most likely play regulatory roles in either B. rapa flowering time control or flowering repression during vernalization. While these final genes require further characterization and validation, our study illustrates the usefulness of a multi-layered screening method after initially identifying genes from microarrays.

A Study on Realization of Visible Light Communication System for Power Line Communication Using 8-bit Microcontroller

The purpose of this study is to solve the problems of radio frequency bandwidth frequency depletion, confusion possibilities, and security that are in current wireless communications systems, and to confirm the possibility of applying those solutions for the next generation network. To solve the problems of the current wireless communications system, a visible light communications system for power line communication (PLC) via 8-bit microcontroller is created and the capacity is analyzed. The exclusive PLC chip APLC-485MA, an 8-bit ATmega16 microcontroller, high brightness 5pi light emitting diodes (LEDs), and the LLS08-A1 visible light-receiving sensor were used for the transmitter and receiver. The performance was analyzed using a designed program and an oscilloscope. The voltage change was measured as a function of distance from 10-50 cm. Blue LEDs showed the best performance among the measured LED types, with 0.47 V of voltage loss, but for a distance over 50 cm, precise data was not easy to obtain due to the weak light. To overcome these types of problems, specific values such as the changing conditions and efficiency value relevant to the light emitting parts and the visible light-receiving sensor should be calculated, and continuous study and improvements should also be realized for better communication conditions. pISSN: 1229-7607 eISSN: 2092-7592

Whole-Genome Resequencing and Transcriptomic Analysis to Identify Genes Involved in Leaf-Color Diversity in Ornamental Rice Plants

Rice field art is a large-scale art form in which people design rice fields using various kinds of ornamental rice plants with different leaf colors. Leaf color-related genes play an important role in the study of chlorophyll biosynthesis, chloroplast structure and function, and anthocyanin biosynthesis. Despite the role of different metabolites in the traditional relationship between leaf and color, comprehensive color-specific metabolite studies of ornamental rice have been limited. We performed whole-genome resequencing and transcriptomic analysis of regulatory patterns and genetic diversity among different rice cultivars to discover new genetic mechanisms that promote enhanced levels of various leaf colors. We resequenced the genomes of 10 rice leaf-color accessions to an average of 40× reads depth and >95% coverage and performed 30 RNA-seq experiments using the 10 rice accessions sampled at three developmental stages. The sequencing results yielded a total of 1,814 × 106 reads and identified an average of 713,114 SNPs per rice accession. Based on our analysis of the DNA variation and gene expression, we selected 47 candidate genes. We used an integrated analysis of the whole-genome resequencing data and the RNA-seq data to divide the candidate genes into two groups: genes related to macronutrient (i.e., magnesium and sulfur) transport and genes related to flavonoid pathways, including anthocyanidin biosynthesis. We verified the candidate genes with quantitative real-time PCR using transgenic T-DNA insertion mutants. Our study demonstrates the potential of integrated screening methods combined with genetic-variation and transcriptomic data to isolate genes involved in complex biosynthetic networks and pathways.

A Study on the Thermal Characteristics of COB LED using Thermoelectric Element

This paper was designed to analyze thermal properties using thermoelectric element for air-cooling heat dissipation of 13.2W-class COB LED. For comparative analysis with generally used air cooling methods, the heat sink was designed and produced, and this experiment was conducted to measure the temperature distribution using a contact thermometer while the COB LED was operating for 100 minutes. One result was about 75℃ for the general cooling method, and the other was 57℃ while the thermoelectric element was operating with applying the current of 0.8A to the thermoelectric element. This results confirmed that the method of applying thermoelectric element was much better in the dissipation of thermal condense on the COB LED than that of the general air cooling one. The temperature on the contact points of COB LED using thermoelectric element was decreased about 31% compared with the air cooling method from 75℃ to 57℃.

Design of Optimized Pattern Recognizer by Means of Fuzzy Neural Networks Based on Individual Input Space

In this paper, we introduce the fuzzy neural network based on the individual input space to design the pattern recognizer. The proposed networks configure the network by individually dividing each input space. The premise part of the networks is independently composed of the fuzzy partition of individual input spaces and the consequence part of the networks is represented by polynomial functions. The learning of fuzzy neural networks is realized by adjusting connection weights of the neurons in the consequent part of the fuzzy rules and it follows a back-propagation algorithm. In addition, in order to optimize the parameters of the proposed network, we use real-coded genetic algorithms. Finally, we design the optimized pattern recognizer using the experimental data for pattern recognition.

Multi-Layered Screening Method Identification of Flavonoid-Specific Genes, using Transgenic Rice

ABSTRACT We used microarray analysis to identify 6 730 genes potentially related to flavonoid biosynthesis by comparing their expression between high- and low-flavonoid cultivars at three stages of seed development. The genes included 167 transcription factors, 104 pathway-network genes, and 1 207 potential orthologs with flavonoid-related functions. We compared the transcription factors, pathway genes, and orthologs and identified seven conserved hypothetical genes that are involved in flavonoid biosynthesis. We then verified the seven genes experimentally by reverse transcription-polymerase chain reaction. These conserved genes most likely play regulatory roles either in rice-flavonoid production or flavonoid signaling during seed development. Our study illustrates the effectiveness of microarray analysis followed by multi-layered screening for the identification of flavonoid-related genes in rice.

LRCA: enhanced energy-aware routing protocol in MANETs

Mobile Ad hoc Networks (MANETs) is power constrained since mobile nodes operate with limited battery energy. So battery life is also important research issue in the routing protocol design. During packet transmission over multi-hop nodes, if a node failed, it should be caused link failure and source node will perform route recovery. It results that increases time of route recovery and packet loss rate. The objective of this study is to reduce route failure caused by dead nodes which consume all the battery life. We propose a new routing protocol based on AODV which provides an ability of changing routes to neighbor nodes before some of intermediate nodes be shutting down. From extensive simulations, results show that possibility of cut-offs and time-delay caused by packet-loss have been decreased and also improve overall performance by comparison with original AODV.