• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.321-326
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• 2021

This paper presents a technique to minimize damaged wafers during loading. A thin wafer used in solar cells and semiconductors can be damaged easily. This makes it difficult to separate the wafer due to surface tension between the loaded wafers. A technique for minimizing damaged wafers is to supply compressed air to the wafer and simultaneously apply a small horizontal movement mechanism. The main experimental factors used in this study were the supply speed of wafers, the nozzle pressure of the compressed air, and the suction time of a vacuum head. A higher supply speed of the wafer under the same nozzle pressure and lower nozzle pressure under the same supply speed resulted in a higher failure rate. Furthermore, the damage rate, according to the wafer supply speed, was unaffected by the suction time to grip a wafer. The optimal experiment conditions within the experimental range of this study are the wafer supply speed of 600 ea/hr, nozzle air pressure of 0.55 MPa, and suction time of 0.9 sec at the vacuum head. In addition, the technology improved by the repeatability performance tests can minimize the damaged wafer rate.

• The Transactions of the Korea Information Processing Society
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• v.7 no.8
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• pp.2528-2535
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• 2000

Technology mapping is a part of VLSI CAD system, where circuits in logical level are mapped into circuits in physical level. The performance of technology mapping system is evaluatecJ by the delay and area of the resulting circuits. In the sequential circuits, the delay of the circuit is decided by the maximal delay between registers. In this work, we introduce an FPGA mapping algorithm improved by retiming technique used in constructive level and iterative level, and by fuzzy logic technique. Initial circuit is mapped into an FPGA circuit by constructive manner and improved by iterative retiming. Criteria given to the initial circuit are structured hierarchically by decision-making functions of fuzzy logic. The proposed system shows better results than previous systems by the experiments with MCNC benchmarkers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.872-877
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• 2011

In this paper, the new decoding algorithm of Block Turbo Codes using Channel State Information(CSI), which is estimated to compensate for the distorted signal caused by multi-path fading, is proposed in order to improve error correction capacity during decoding procedure in OFDM system. The performance of the new decoding algorithm is compared to that of the conventional decoding algorithm without using channel state information under the Rayleigh fading channel. Experimental results showed that in case of only one iteration coding gains of up to 5.0dB~9.0dB can be obtained by applying the channel state information to the conventional decoding algorithm according to the modulation methods. In addition to that, the new decoding algorithm using channel state information at only one iteration shows a performance improvement of 3.5dB to 5.0dB when compared to the conventional decoding algorithm after four iterations. This leads to reduce the considerable amount of computation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1596-1602
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• 2021

Battery-operated IoT devices in IoT systems require low power consumption. In general, IoT devices enter a sleep state synchronously to reduce power consumption. A problem arises when an IoT device has to handle asynchronous user requests, as the duty cycle must be reduced to enhance response time. In this paper, we propose a new low-power-consumption scheme, called Repetitive Wake-up scheme for IoT systems of asynchronous environments such as indoor lights control. The proposed scheme can reduce power consumption by sending wake-up signals from the smartphone repetitively and by retaining the IoT device in sleep state to the smallest possible duty cycle. In the various environments with IoT devices at home or office space, we showed that the proposed scheme can reduce power consumption by up to five times compared to the existing synchronous interlocking technique.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.6 s.336
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• pp.9-16
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• 2005

It is well blown about the fact that turbo code has better the BER performance as the number of decoding iterations increases in the AWGN channel environment. However, as the number of decoding iterations is increased under the several channel environments, any further iteration results in very little improvement, and it requires much delay and computation in proportion to the number of decoding iterations. In this paper, it proposes the efficient iterative decoding stop criterion algorithm which can largely reduce the computation and the average number of decoding iterations of turbo code. Through simulations, it is verifying that the proposed algorithm can efficiently stop the iterative decoding by using the variance value of LLR and can largely reduce the computation and the average number of decoding iterations without BER performance degradation. As a result of simulation, the computation for the proposed algerian is reduced by about $40\%$ compared to conventional CE algorithm. The average number of decoding iterations for the proposed algorithm is reduced by about $9.94\%$ and $8.32\%$ compared to conventional HDA and SCR algorithm respectively, and by about $2.16\%{\~}7.84\%$ compared to conventional CE algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1387-1394
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• 2004

Turbo code, a kind of error correction coding technique, has been used in the field of digital mobile communication systems. And it is well known about the fact that turbo code has better the BER performance as the number of decoding iterations increases in the AWGN channel environment. However, as the number of decoding iterations is increased under the several channel environments, any further iteration results in very little improvement, and it requires much delay, computation and power consumption in proportion to the number of decoding iterations. In this paper, it proposes the efficient iterative decoding stop criterion algorithm which can largely reduce the average number of decoding iterations of turbo code. Through simulations, it is verifying that the proposed algorithm can efficiently stop the iterative decoding by using the variance value of error probability for the soft output value, and can largely reduce the average number of decoding iterations without BER performance degradation. As a result of simulation, the average number of decoding iterations for the proposed algorithm is reduced by about 2.25% ~14.31％ and 3.79％ ~14.38% respectively compared to conventional schemes, and power consumption is saved in proportion to the number of decoding iterations.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.162.2-162.2
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• 2015

플렉서블 디스플레이에 사용되는 투명전극은 벤딩에 의한 인장(tensile) 및 압축(compressive) 스트레스 하에서도 전극의 특성이 지속적으로 유지되어야 한다. 기존 OLED소자의 투명전극으로 사용되던 인듐산화물(ITO, Indium Tin Oxide)는 인듐(Indium)의 희소성 문제뿐만 아니라 벤딩에 대한 복원력이 나쁜 것으로 알려져 플렉서블 디스플레이에는 적합하지 않은 것으로 알려져 있다. 벤딩에 강하고 복원력이 우수한 투명전극 재료가 필요하게 되었다. 본 연구에서는 PEN (Polyethylene Naphthalate) 유연기판 상에 그래핀(Graphene)전극을 구현하여 벤딩에 대한 저항특성을 관찰하였고 일반적으로 많이 사용하는 Aluminum 전극과의 비교를 통해 광효율을 지속적으로 유지할 수 있는 플렉서블 OLED용 전극구현 가능성을 연구하였다. 일반적으로 Al금속은 인장 스트레스를 받음에 따라 저항이 증가하고 다시 복원되면 저항이 감소하는 특성을 갖고 있는데 인장 스트레스에 따라 저항과 늘어난 길이와의 관계는 다음과 같다. $R/R0=(L/L0)^2$ ----------------------------------------- (1) 그러나 반복된 스트레스가 가해질 경우 Al 금속 전극은 복원력을 잃고 저항이 원래대로 돌아가지 않는 문제가 발생하는데 반해 그래핀은 벌집모양의 구조를 갖고 있어 벤딩에 대한 강도가 셀 뿐만 아니라 고탄력으로 인해 복원력이 우수하여 여러 싸이클(cycle)의 벤딩 실험에 의해서도 복원력이 지속적으로 유지되었다. Al 금속 전극의 경우 벤딩 각도 또는 정도에 따라 복원력이 유지되는 구간이 있으나 반복적인 벤딩 싸이클에 의해 복원력이 감소하여 인장 스트레스에 의한 저항 증가 후 스트레스 제거 시 저항 감소가 되지 않는데 24시간 동안 전기 저항 변화를 관찰하면 수시간 후에나 저항이 어느 수준까지만 복원되는 것을 확인할 수 있었으나 복원에 오랜 시간이 소요된다는 점에서 그래핀과 비교가 된다. SEM(Scanning electron microscopy) 분석을 통해 인장 스트레스 인가/제거를 반복함에 따라 Al 금속표면이 표면에 열화되는 것을 확인하였으나 그래핀에서는 나타나지 않았다. 본 연구에서는 높은 투과도와 우수한 전기적 특성을 가지는 그래핀 투명 전도성 전극이 다양한벤딩 조건에서도 뛰어난 복원 특성을 보이는 것을 밝혀내어 차세대 투명 전극 물질로 개발하고자 하였다.

• Journal of the Korea Society of Computer and Information
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• v.9 no.4 s.32
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• pp.117-125
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• 2004

The berth and crane scheduling problem in a container terminal encompasses the whole process of assigning berth to each ship. determining the duration of berthing, assigning container cranes to each ship, and determining the specific start and end time of each crane service, for all the ships scheduled to be arriving at the terminal during a certain scheduling horizon. This problem is basically a constraint satisfaction problem in which all the constraints should be satisfied. However, it is also an optimization problem because the requested arrival and departure time should be met for as many of the scheduled ships as possible. while the operation cost of the terminal should be minimized. In this paper. I present an effective approach to solving this problem, which combines both constraint satisfaction search and iterative improvement search. I test this method on a real world container terminal problem and the results show that the method can produce better results than any other existing method.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.11
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• pp.195-205
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• 2013

The analysis of electroencephalographic signal associated with the attention is essential for the understanding of human cognition. In this paper, the characteristic differences between the attention and inattention status in the brain were inspected by nonlinear analysis. The recurrence quantification analysis was applied to the relatively small number of samples of evoked potential having time varying characteristics, where the recurrence plot (RP), the color recurrence plot (CRP), and mean and time-sequential trend parameters were extracted. The dimension and the time delay in phase transformation can be determined by the paired set of extracted parameters. It is observed from RP, CRP, and parameters that the brain dynamics in attention is more complex than that in the inattention, as well as the synchronized brain response is stable in the mean sense but locally time varying. It is feasible that the non-linear analysis method can be useful for the analysis of complex brain dynamics associated during visual attentional task.

• The KIPS Transactions:PartD
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• v.11D no.3
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• pp.495-508
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• 2004

Recently, in content-based music information retrieval systems, to enhance the response time of retrieving music data from large music database, some researches have adopted the indexing mechanism that extracts and indexes the representative melodies. The representative melody of music data must stand for the music itself and have strong possibility to use as users' input queries. However, since the previous researches have not considered the musical composition forms, they are not able to correctly catch the contrast, repetition and variation of motif in musical forms. In this paper, we use an index automatically constructed from representative melodies such like first melody, climax melodies and similarly repeated theme melodies. At first, we expand the clustering algorithm in order to extract similarly repeated theme melodies based on the musical composition forms. If the first melody and climax melodies are not included into the representative melodies of music by the clustering algorithm, we add them into representative melodies. We implemented a prototype system and did experiments on comparison the representative melody index with other melody indexes. Since, we are able to construct the representative melody index with the lower storage by 34％ than whole melody index, the response time can be decreased. Also, since we include first melody and climax melody which have the strong possibility to use as users' input query into representative melodies, we are able to get the more correct results against the various users' input queries than theme melody index with the cost of storage overhead of 20％.