• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.11
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• pp.1686-1696
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• 2022

The impedance matching circuit design technique based on the phasor plot introduced in this paper is based on the impedance triangle of electric circuit. It is a technique that designs through the construction of a phasor figure using the values given to the matching circuit design. The design pattern is based on L-type, inverted L-type, T-type, and 𝜋-type, and unknown reactance elements are determined through phasor shapes. In this paper, using a design by phasor plot, we design several cases, such as the case where the input and output ports are pure resistance and have reactance. It was confirmed that the design value was verified by serial-parallel equivalent conversion to achieve matching. This design technique can immediately grasp the phase or size of input/output power, so it is expected to be applied mainly in a low frequency band due to rapid design change and application.

• Proceedings of the Korea Information Processing Society Conference
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• 2024.05a
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• pp.323-326
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• 2024

본 연구에서는 커널 퍼저인 Syzkaller 를 사용하여 리눅스 커널의 네트워크 서브시스템을 퍼징하고 그 결과를 분석하여, 높은 커버리지를 달성하기가 왜 어려운지 분석하고 이를 개선하기 위한 방법들을 제안한다. 첫 번째 실험에서는 TCP 및 IPv4 소켓과 관련된 시스템 콜 및 매개변수만 허용하여 리눅스 커널 네트워크 퍼징을 진행하고, 두 번째 실험에서는 Syzkaller 가 지원하는 모든 시스템 콜을 포함하도록 범위를 확장한다. 첫 번째 실험 결과, 퍼징 시작 약 55 시간만에 TCP 연결 수립에 성공하였다. 두 번째 실험 결과, 첫 번째 실험보다 전반적인 커버리지와 라우팅 서브시스템의 커버리지는 개선되었으나 TCP 연결 수립에는 실패하였다. TCP 연결 수립을 위해서는 서버의 IP 주소 및 포트번호를 클라이언트가 무작위 입력 생성을 통해 맞혀야 하는데, 이 과정에서 시간이 오래 걸리기 때문에 연결 수립이 쉽게 이루어지지 않는 것으로 분석된다. 추가적으로, 본 연구에서는 TCP 연결 수립을 쉽게 하기 위한 하이브리드 퍼징, IP 패킷 포워딩 허용, 패킷 description 없이 퍼징 등 Syzkaller 를 이용하여 리눅스 커널 네트워크 서브시스템을 더 효율적으로 퍼징할 수 있는 방법들을 제안한다.

• Journal of the Institute of Convergence Signal Processing
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• v.17 no.2
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• pp.53-60
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• 2016

In this paper, we introduce the implementation and test results of a new method of correlated result storage to achieve the full performance of the Daejeon hardware correlator. Recently, the observation of 8 Gbps speed, which is the maximum observational standard of KVN(Korean VLBI Network), has been performed. The correlation processing using the Daejeon hardware correlator is also required. Therefore, a new correlation result storage introduction has become necessary. The maximum correlation result output speed of the Daejeon hardware correlator is 1.4 GB/sec per 25.6 ms integration time. The conventional correlation result storage system can not cope with the maximum correlation output speed of the Daejeon hardware correlator, and the output speed is limited to 1/4. That is, among the four input ports of the Daejeon hardware correlator, the three inputs are limited to correspond to the observation rate of 1 Gbps. This new storage system uses the Gluster file system among many of the latest technologies used in storage systems. In tests that meet the maximum output rate of 1.4 GB/sec for the Daejeon hardware correlator, 350 MB/sec for each of the four optical outputs, resulting in 1.4 GB/sec in total.

• The KIPS Transactions:PartB
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• v.9B no.1
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• pp.1-6
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• 2002

Many customers consult the Internet before making purchase goods and using contents. The systems in the Internet could store a lot of data and classify the data into information to get relationship between a company and customers. To do that, let's consider a knowledge-assisted hybrid system that utilizes individually a customer's preference to make an optimal solution in the his/her decision making. The knowledge made by using the preference is employed to select an domain set appropriate to him/her business, and the process of selecting definitely provides the customer some benefits: elimination of discomfort from unknown information and reduction of costs and search time for forming an suitable domain set. To effectively adopt individual customer's preference and actively adapt change of business situation, this study propose an architecture of the system which includes rule presentations and an inference engine, and integrates a knowledge-based component into a quadratic programming component. In the experimental results, it is found that a knowledge-assisted hybrid system implemented by this idea is more flexible than existing systems in extension of knowledge about an customer's preference and goes beyond the traditional models.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.10 s.352
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• pp.34-44
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• 2006

A system-on-a-chip (SoC) design uses pre-verified IP hardware blocks in order to reduce design time. We need interface circuits to connect IPs with different protocols. In SoC design we should design interface circuits frequently and these tasks are somewhat time-consuming and error-prone. So it is necessary to generate the interface circuits automatically. Several studies have been made on generating interface circuits only from the communication protocols of IPs. With existing approaches, it is not easy to generate interface circuits connecting two IPs only from communication protocols: connection between IP with address and W without address, connection between IP with only one port to transfer address/data and IP with different ports for address and data connection between IP that transfer address and data together and IP that transfer only one address with a number of data in a burst. No consideration of various characteristics of IPs and no changed algorithm are responsible for it. In order to solve this problem, the proposed approach categorizes communication protocols of IPs, and takes characteristics matching of IPs into account during the interface synthesis. In experiments, we show that we could correctly generate and verify interface circuits for IPs with different characteristics.

• Journal of IKEEE
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• v.9 no.1 s.16
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• pp.19-30
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• 2005

Packet classification is defined as the action to match the packet with a set of predefined rules. One of classification is to use Ternary Content Addressable Memory hardware search engine that has faster than other algorithmic methods. However, TCAM has some limitations. One of them is that TCAM can not perform range matching efficiently. A range has to be expanded into prefixes to fit the boundary. In general, the number of expansion could be up to 2w-2, where w is the width of the field. For example, if two range fields with 16 bits are used, there could be up to $30\;{\times}\;30\;=\;900$ expansions for a single rule. In this paper, we describe the novel algorithm for converting range matching rules into TCAM entry efficiently. The number of maximum entry is 2w-4 when using the algorithm. Furthermore, it has also benefit about the negation range. In the result of experimentation, the new scheme practically reduces 14 percent in case that searched fields are source port and destination port number.

• Journal of Intelligence and Information Systems
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• v.25 no.2
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• pp.39-55
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• 2019

Recently banks and large financial institutions have introduced lots of Robo-Advisor products. Robo-Advisor is a Robot to produce the optimal asset allocation portfolio for investors by using the financial engineering algorithms without any human intervention. Since the first introduction in Wall Street in 2008, the market size has grown to 60 billion dollars and is expected to expand to 2,000 billion dollars by 2020. Since Robo-Advisor algorithms suggest asset allocation output to investors, mathematical or statistical asset allocation strategies are applied. Mean variance optimization model developed by Markowitz is the typical asset allocation model. The model is a simple but quite intuitive portfolio strategy. For example, assets are allocated in order to minimize the risk on the portfolio while maximizing the expected return on the portfolio using optimization techniques. Despite its theoretical background, both academics and practitioners find that the standard mean variance optimization portfolio is very sensitive to the expected returns calculated by past price data. Corner solutions are often found to be allocated only to a few assets. The Black-Litterman Optimization model overcomes these problems by choosing a neutral Capital Asset Pricing Model equilibrium point. Implied equilibrium returns of each asset are derived from equilibrium market portfolio through reverse optimization. The Black-Litterman model uses a Bayesian approach to combine the subjective views on the price forecast of one or more assets with implied equilibrium returns, resulting a new estimates of risk and expected returns. These new estimates can produce optimal portfolio by the well-known Markowitz mean-variance optimization algorithm. If the investor does not have any views on his asset classes, the Black-Litterman optimization model produce the same portfolio as the market portfolio. What if the subjective views are incorrect? A survey on reports of stocks performance recommended by securities analysts show very poor results. Therefore the incorrect views combined with implied equilibrium returns may produce very poor portfolio output to the Black-Litterman model users. This paper suggests an objective investor views model based on Support Vector Machines(SVM), which have showed good performance results in stock price forecasting. SVM is a discriminative classifier defined by a separating hyper plane. The linear, radial basis and polynomial kernel functions are used to learn the hyper planes. Input variables for the SVM are returns, standard deviations, Stochastics %K and price parity degree for each asset class. SVM output returns expected stock price movements and their probabilities, which are used as input variables in the intelligent views model. The stock price movements are categorized by three phases; down, neutral and up. The expected stock returns make P matrix and their probability results are used in Q matrix. Implied equilibrium returns vector is combined with the intelligent views matrix, resulting the Black-Litterman optimal portfolio. For comparisons, Markowitz mean-variance optimization model and risk parity model are used. The value weighted market portfolio and equal weighted market portfolio are used as benchmark indexes. We collect the 8 KOSPI 200 sector indexes from January 2008 to December 2018 including 132 monthly index values. Training period is from 2008 to 2015 and testing period is from 2016 to 2018. Our suggested intelligent view model combined with implied equilibrium returns produced the optimal Black-Litterman portfolio. The out of sample period portfolio showed better performance compared with the well-known Markowitz mean-variance optimization portfolio, risk parity portfolio and market portfolio. The total return from 3 year-period Black-Litterman portfolio records 6.4%, which is the highest value. The maximum draw down is -20.8%, which is also the lowest value. Sharpe Ratio shows the highest value, 0.17. It measures the return to risk ratio. Overall, our suggested view model shows the possibility of replacing subjective analysts's views with objective view model for practitioners to apply the Robo-Advisor asset allocation algorithms in the real trading fields.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.15-19
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• 2004

Domestic use, or embody program that transmit NMEA protocol using multi port as software and is using because there is no fee and product that develop NMEA protocol Multiplexer, import mounting for foreign climax present. These method is paid or there is problem that must make out special processing part in each application program. Also, each mountings that display NMEA protocol can cause double resources waste and damage etc. because manufacturing firm and platform are different. Can act separatively as single hardware module of reliable processing method and high efficiency to supplement this in this treatise, and because using design of optimized cue, heighten memory efficiency of module, and proposed NMEA protocol Multiplexer that can keep high trustability of Come on, deviation compass, echo sound, mountings of GPS and so on and real time communication that is main input sensor equipment about embodiment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.5
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• pp.413-420
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• 2009

We propose a novel feed network for a $2{\times}2$ array antenna to form a sectoral conical beam. The proposed feed network, which is a symmetrical structure, consists of four $90^{\circ}$ hybrids, a crossover, and four $90^{\circ}$ delay lines. To verify the performance of the feed network a $2{\times}2$ array antenna and the feed network are fabricated on a microstrip structure, and the radiation patterns are measured at the center frequency of 2.57 GHz. The maximum radiation is measured at the $45^{\circ}$ elevation angle and at the $45^{\circ}$, $135^{\circ}$, $225^{\circ}$, and $315^{\circ}$ azimuth angles depending on the choice of the input port of the feed network.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.11
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• pp.2327-2332
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• 2011

Recently, the increase of loading amount on cargo ships due to the automation of loading process results in much complex ship operation. For this reason, NMEA-0183 based on RS-422,485 and NMEA-2000 based on CAN communication methods have been usually used as a standardized method in the marin electric interfacing equipments. In this paper, a general NMEA-0183 protocol was designed to support 7-channel NMEA-0183 serial communication data, which can receive 3-channel 16 bits ADC and 2-channel pulse using SPI(Serial Peripheral Interface). In particular, this method was designed for ship communication requires 7 important factors. Also in this study, using the minimization of the proposed method and realizing the monitoring system based on PC, the effectiveness of multichannel indicator system was proposed.