• 대한전자공학회논문지SD
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• 제43권10호
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• pp.90-96
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• 2006

본 논문에서는 capacitance scaling 구조를 이용하여 짧은 locking 시간과 작은 fractional spur를 가지는 ${\Sigma}{\Delta}$ fractional-N PLL을 설계하였다. 루프필터의 실효 커패시턴스를 변화시키기 위하여 여러 개의 전하펌프를 이용해 서로 다른 경로로 커패시터에 전류를 공급하였다. 필터의 실효 커패시턴스는 동작상태에 따라 크기가 변하며 커패시터들은 하나의 PLL 칩에 집적화 할 수 있을 정도로 작은 크기를 가진다. 또한 PLL이 lock 되면 전하펌프 전류의 크기도 작아져 fractional spur의 크기도 작아진다. 제안된 구조는 HSPICE CMOS $0.35{\mu}m$ 공정으로 시뮬레이션 하였으며 $8{\mu}s$ 이하의 locking 시간을 가진다. PLL의 루프필터는 200pF, 17pF의 작은 커패시터와 $2.8k{\Omega}$의 저항으로 설계되었다.

• 한국인터넷방송통신학회논문지
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• 제12권5호
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• pp.1-9
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• 2012

본 논문은 레이더 시스템에 적용되는 고성능 PLL 주파수 합성기를 설계하고, 그 성능을 분석하였다. 소형화제작을 위해 PLL 간접합성방식을 적용하였으며, 광대역특성에서 우수한 위상잡음과 고속의 주파수합성시간을 갖기 위해 offset 방식의 PLL에 DDS를 기준신호로 설계 하였다. 또한, offset PLL에서 고속의 주파수 변환을 위해 DAC를 이용하여 coarse tune을 적용하였다. 이러한 구조에서의 성능 예측을 위해 각각의 잡음원에 대해 모델링을 적용하여 출력위상잡음을 예측하였으며, 제작결과와 비교 분석하였다. 그 결과 simulation과 측정결과가 일치함을 확인하였으며, 100KHz 옵셋 주파수에서 -126dBc/Hz의 우수한 위상잡음 특성과 10usec 이내의 고속의 주파수변환시간을 갖는 항공기용 레이더 주파수합성기를 설계하였다.

• 한국의류학회지
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• 제30권4호
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• pp.507-518
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• 2006

This study aims to prove that traditional patchwork wrapping cloth can be a creative motive for modem fashion, and the application of it can be a way of expressing not only the pride in our cultural heritage but also the originality of fashion design. The analysis of the plasticity of 108 patchwork wrapping clothes has come up with the following findings: Firstly, the plane structure consists of 41 basic forms and 67 applied ones. Secondly, 61 contrast color harmony and 47 similarity color harmony. Thirdly, the fabric consists of 88 silk clothes, 19 ramie clothes, and 1 silk and ramie cloth. Fourthly, 47 unlined clothes and 61 lined ones. The study also expresses the analyzed plasticity of patchwork wrapping cloth for fashion with the following findings: Firstly, basic plane structures, contrast color harmony, silk cloth and the press flower coating technique become one piece dress to express splendid and elegant image. Secondly, application plane structures, similarity color harmony of natural dyeing method using persimmon, ramie cloth and the press flower coating and over lock technique become a jacket and a blouse to express calm and dynamic image. Thirdly, the needling and over lock technique used to patch clothes has become a desirable way to express fabric with unique surface effects. Fourthly, the press flower coating which modernizes embroidery in patchwork wrapping. cloth has become a new technique which can create high values with its extended the visual effects of the material. Fifthly, Patchwork wrapping cloth in Chosun Dynasty has now become a motive for modem fashion design to express tradition and creation.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 춘계학술대회
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• pp.241-243
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• 2016

과거, 자동차 보안은 'Door Lock'과 같은 물리적인 접근을 방지하는 것이었다. 그러나 시대가 발달함에 따라, 자동차 보안의 트렌드는 이러한 물리적인 보안에서 굉장히 지능적으로 바뀌었다. 이러한 변화는 해커들로 하여금 차량 통신 시스템을 공격할 계기를 만들게 되었고 현재 차량 통신 시스템은 몇 가지 취약점이 존재하는 CAN Protocol을 사용하고 있다. 첫 째로 ID 스푸핑, 둘 째로 서비스 분산 공격, 셋 째로 안드로이드 좀비 어플리케이션이다. 현재 자동차들은 엔진 제어나, 도어 락 제어, 그리고 핸들의 제어를 위해 수많은 ECU들을 사용하고 있다. 그리고 CAN Protocol은 신호를 Broad - Cast 방식으로 제공하기 때문에 해커들은 굉장히 쉽게 그 신호에 접근 가능하다. 그리고 차량 통신 시스템을 공격하기 위해 Android나 IOS와 같은 범용성이 높은 어플리케이션을 자주 이용한다. 차량의 소유주가 블루투스 동글을 통해 신호를 넓게 퍼뜨리게 되면 해커는 이 신호에 쉽게 접근하게 되고, 해당 데이터를 수집해 분석하고 그들은 차량의 ECU를 공격하기 위해 특정한 데이터를 만들고 ECU에 전송해 ECU를 제어하게 된다. 그래서 본인은 인증 시스템과 안드로이드의 말단에서 이러한 공격을 막을 방법을 제시한다.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제29권5호
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• pp.429-438
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• 2007

Transport distraction osteogenesis has been introduced recently to correct skeletal malformations and discrepancies in the maxillofacial area. To reconstruct 3-dimensitonal mandibular shape, this transport distraction can be considered with the use of reconstruction plate. A 23-years-old male having unilateral mandibular body and angle defects, who had been operated of partial mandibular resection due to unicystic ameloblastoma, was treated by transport distraction procedures with ThreadLock transport $distractor^{(R)}$ (KLS Martin Co., Germany) through the rail of reconstruction plate (Osteomed Co., USA). After being distracted 35 mm defect from mandibular angle to body, and consolidated for 16 weeks, allogenic bone graft on docking site was performed with removal of transgingival pin. For more than 13 weeks follow up period after consolidation period, gradual increase of radiopacity in the radiographic examination was shown, and the curved mandibular continuity according to the reconstruction plate was made firmly. These transport distraction osteogenesis in the mandible was able to be considered as the good and minimally invasive technique for the reconstruction of mandibular discontinuity. Young patient was also very satisfactory for these results.

• 정보과학회 논문지
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• 제43권1호
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• pp.27-33
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• 2016

오늘날 가상화 기술은 가장 유용하게 사용되는 컴퓨팅 기술 중 하나이며 모든 컴퓨팅 환경에서 널리 활용되고 있다. 그러나 가상화 환경의 I/O 계층들은 호스트 머신의 I/O 동작 방식을 인지하지 못하도록 설계되어 있기 때문에 I/O 확장성 문제는 여전히 해결해야 할 문제로 남아 있다. 특히, 다중 큐 SSD가 보조 기억 장치로 사용될 경우, 증가한 잠금 경쟁과 제한된 I/O 병렬화 문제로 가상 머신은 다중 큐 SSD의 공인된 성능을 활용하지 못하는 문제가 발생한다. 이러한 성능 문제를 해결하기 위해 본 논문에서는 가상 CPU마다 전용 큐와 I/O 스레드를 할당하는 새로운 기법을 제안한다. 제안 기법은 성능 저하의 주요한 원인 중 하나인 잠금 경쟁을 효율적으로 분산시키고 또 다른 원인인 Virtio-blk-data-plane의 병렬화 문제를 해소한다. 제안 기법을 평가한 결과 최신 QEMU 보다 IOPS가 최대 155% 향상되는 것을 확인하였다.

• International Journal of Computer Science & Network Security
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• 제21권12호
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• pp.248-256
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• 2021

Now that we're in the big data era, data has taken on a new significance as the storage capacity has exploded from trillion bytes to petabytes at breakneck pace. As the use of cloud computing expands and becomes more commonly accepted, several businesses and institutions are opting to store their requests and data there. Cloud storage's concept of a nearly infinite storage resource pool makes data storage and access scalable and readily available. The majority of them, on the other hand, favour a single cloud because of the simplicity and inexpensive storage costs it offers in the near run. Cloud-based data storage, on the other hand, has concerns such as vendor lock-in, privacy leakage and unavailability. With geographically dispersed cloud storage providers, multicloud storage can alleviate these dangers. One of the key challenges in this storage system is to arrange user data in a cost-effective and high-availability manner. A multicloud storage architecture is given in this study. Next, a multi-objective optimization problem is defined to minimise total costs and maximise data availability at the same time, which can be solved using a technique based on the non-dominated sorting genetic algorithm II (NSGA-II) and obtain a set of non-dominated solutions known as the Pareto-optimal set.. When consumers can't pick from the Pareto-optimal set directly, a method based on Principal Component Analysis (PCA) is presented to find the best answer. To sum it all up, thorough tests based on a variety of real-world cloud storage scenarios have proven that the proposed method performs as expected.

• 전력전자학회논문지
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• 제26권3호
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• pp.192-198
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• 2021

The battery's State of Health (SOH) is a critical parameter in the process of battery use, as it represents the Remaining Useful Life (RUL) of the battery. Electrochemical Impedance Spectroscopy (EIS) is a widely used technique in observing the state of the battery. The measured impedance at certain frequencies can be used to evaluate the state of the battery, as it is intimately tied to the underlying chemical reactions. In this work, a low-cost portable EIS instrument is developed on the basis of the ARM Cortex-M4 Microcontroller Unit (MCU) for measuring the impedance spectrum of Li-ion battery packs. The MCU uses a built-in DAC module to generate the sinusoidal sweep perturbation signal. Moreover, it performs the dual-channel acquisition of voltage and current signals, calculates impedance using a Digital Lock-in Amplifier (DLA), and transmits the result to a PC. By using LabVIEW, an interface was developed with the real-time display of the EIS information. The developed instrument was suitable for measuring the impedance spectrum of the battery pack up to 1000 V. The measurement frequency range of the instrument was from 1 hz to 1 Khz. Then, to prove the performance of the developed system, the impedance of a Samsung SM3 battery pack and a Bexel pouch module were measured and compared with those obtained by the commercial instrument.

• Asia pacific journal of information systems
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• 제20권1호
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• pp.127-140
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• 2010

The benefit that a consumer derives from the use of a good often depends on the number of other consumers purchasing the same goods or other compatible items. This property, which is known as network externality, is significant in many IT related industries. Over the past few decades, network externalities have been recognized in the context of physical networks such as the telephone and railroad industries. Today, as many products are provided as a form of system that consists of compatible components, the appreciation of network externality is becoming increasingly important. Network externalities have been extensively studied among economists who have been seeking to explain new phenomena resulting from rapid advancements in ICT (Information and Communication Technology). As a result of these efforts, a new body of theories for 'New Economy' has been proposed. The theoretical bottom-line argument of such theories is that technologies subject to network effects exhibit multiple equilibriums and will finally lock into a monopoly with one standard cornering the entire market. They emphasize that such "tippiness" is a typical characteristic in such networked markets, describing that multiple incompatible technologies rarely coexist and that the switch to a single, leading standard occurs suddenly. Moreover, it is argued that this standardization process is path dependent, and the ultimate outcome is unpredictable. With incomplete information about other actors' preferences, there can be excess inertia, as consumers only moderately favor the change, and hence are themselves insufficiently motivated to start the bandwagon rolling, but would get on it once it did start to roll. This startup problem can prevent the adoption of any standard at all, even if it is preferred by everyone. Conversely, excess momentum is another possible outcome, for example, if a sponsoring firm uses low prices during early periods of diffusion. The aim of this paper is to analyze the dynamics of the adoption process in markets exhibiting network effects by focusing on two factors; switching and agent heterogeneity. Switching is an important factor that should be considered in analyzing the adoption process. An agent's switching invokes switching by other adopters, which brings about a positive feedback process that can significantly complicate the adoption process. Agent heterogeneity also plays a important role in shaping the early development of the adoption process, which has a significant impact on the later development of the process. The effects of these two factors are analyzed by developing an agent-based simulation model. ABM is a computer-based simulation methodology that can offer many advantages over traditional analytical approaches. The model is designed such that agents have diverse preferences regarding technology and are allowed to switch their previous choice. The simulation results showed that the adoption processes in a market exhibiting networks effects are significantly affected by the distribution of agents and the occurrence of switching. In particular, it is found that both weak heterogeneity and strong network effects cause agents to start to switch early and this plays a role of expediting the emergence of 'lock-in.' When network effects are strong, agents are easily affected by changes in early market shares. This causes agents to switch earlier and in turn speeds up the market's tipping. The same effect is found in the case of highly homogeneous agents. When agents are highly homogeneous, the market starts to tip toward one technology rapidly, and its choice is not always consistent with the populations' initial inclination. Increased volatility and faster lock-in increase the possibility that the market will reach an unexpected outcome. The primary contribution of this study is the elucidation of the role of parameters characterizing the market in the development of the lock-in process, and identification of conditions where such unexpected outcomes happen.

• 한국소음진동공학회논문집
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• 제23권10호
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• pp.902-908
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• 2013

The input torque ripple induced by combustion engines is a significant source of NVH(noise, vibration and harshness) problem in automotive transmissions. Because this torque fluctuation is primarily transmitted to the input shaft of automotive powertrains(e.g., automatic transmissions) when the lock-up clutches are closed, a torsional damper with helical springs is generally inserted between engine and transmissions to isolate the input vibratory energy, which is essential for the passenger comfort. The torsional vibration isolator exhibits frequency ranges in which there is low vibration transmissibility. However, the isolation performance is currently evaluated through the static torsional spring characteristics. In this study, the transmissibility of torsional spring dampers, essential dynamic performance index for vibration isolator, is first experimentally evaluated.