• 한국정보통신학회논문지
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• 제21권5호
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• pp.893-898
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• 2017

카운터 타입의 시간-디지털 변환기를 공급전압 1.5volts에서 $0.18{\mu}mCMOS$ 공정을 이용하여 설계하였다. 일반적인 시간-디지털 변환기에서는 클록의 주기가 $T_{CK}$일 때, 시작신호와 클록의 시간차에 의해 최대 $T_{CK}$의 변환 에러가 발생한다. 그리고 멈춤신호와 클록의 시간차로 인해 -$T_{CK}$의 에러가 발생한다. 그러나 본 논문에서 제안한 시간-디지털 변환기는 이러한 단점을 보완하기 위해 클록은 시작신호 및 멈춤신호와 동기화하여 회로 내에서 생성되도록 설계하였다. 설계된 시간-디지털 변환기에서 시작신호와 클록의 시간차에 의한 변환에러는 발생하지 않으며, 멈춤신호에 의한 변환에러의 크기는 (1/2)$T_{CK}$로 감소된다.

• 융합신호처리학회논문지
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• 제22권2호
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• pp.64-70
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• 2021

최근 무선 네트워크 기반 실시간 원격제어에 대한 관심이 크게 증가하고 있다. 무선 네트워크를 통하여 실시간 원격 제어를 구현하는데 있어서, 중요한 요소들 중 하나가 실시간 제어메시지의 지연시간 성능이다. 특히, 주기적으로 송신되는 실시간 제어메시지의 안정적인 수신을 위해 지연시간 지터를 줄이는 기술이 필요하다. 본 논문에서는 실시간 제어메시지를 무선 네트워크에서 운용 하는데 있어서 지연시간 지터를 감소시키는 동기화 전송을 제안한다. 제안된 동기화 전송은 송신노드와 무선통신기 간의 동기화를 바탕으로 적절한 전송시점을 제어하여 실시간 제어메시지가 항상 정해진 시간에 무선 네트워크를 통하여 전송 되도록 한다. 군용무인차량 시스템을 이용한 실험 결과에 따르면, 제안된 동기화 전송은 지연시간 지터를 일반 전송 방식의 지연시간 지터의 32% 수준으로 감소시켰다.

• 제어로봇시스템학회논문지
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• 제14권7호
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• pp.624-628
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• 2008

This paper is concerned with multiple motor control using a distributed network control method. Speed and position of multiple motors are synchronized using clock synchronized distributed controllers. CAN (controller area network) is used and a new clock synchronization algorithm is proposed and implemented. To verify the proposed control algorithm, two disks which are attached on two motor shafts are controlled to rotate at the same speed and phase angle with the same time base using network clocks.

• 한국군사과학기술학회지
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• 제14권1호
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• pp.154-159
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• 2011

The effect of the ignition delay time gap is newly studied. The operational characteristics of the linked two pyrotechnic thrusters are affected by the time gap. Although two thrusters are simultaneously ignited, the time at which the pressure starts to rise in each thruster may not be synchronized. The characteristic of the system with the time gap is compared with that of the fully synchronized system without any time gap. Depending upon the magnitude of the time gap, the pressure-time profile and the ballistic performance are different. When two pyrotechnic thrusters have a time gap, the peak pressure of one thruster(in which the pressure is built up earlier) is increased and the other is decreased. As the time gap is increased, the peak pressure is converged into the maximum pressure. This maximum pressure can be obtained when only one thruster is activated. Because the maximum pressure is bounded, it is predicted that there isn't any catastrophic failures in the considered system. When the time gap is relatively small, the impulse of the combined force acting on the moving body is almost maintained. But the ballistic performance of the system with a large time gap should be carefully estimated because the reduction of the ballistic performance should not be easily neglected.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1754-1759
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• 2003

Two-dimensional flow over a pair of circular cylinders in side-by-side arrangements at low Reynolds numbers has been numerically investigated in this study. Numerical simulations are performed, using the immersed boundary method, in the ranges of $40{\leq}Re{\leq}160$ and $g^{\ast}<5$, where Re and $g^{\ast}$ are, respectively, the Reynolds number and the spacing between the two cylinder surfaces divided by the cylinder diameter. Results show that total six kinds of wake patterns are observed over the ranges: antiphase-synchronized, inphase-synchronized, flip-flopping, single bluff-body, deflected, and steady wake patterns. It is found that the characteristics of the flow significantly depends both on the Reynolds number and gap spacing, with the latter much stronger than the former. Instantaneous flow fields, time traces, flow statistics and so on are presented to identify the wake patterns and then to understand the underlying mechanism. It is remarkable that, for the deflected wake pattern, the gap flow is deflected invariably to the cylinder of higher drag coefficient and the deflection way does not change at all. Moreover, the bifurcation phenomena where either of two wake patterns can occur are found at certain flow conditions.

• 대한기계학회논문집B
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• 제27권7호
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• pp.909-919
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• 2003

Two-dimensional flow over a pair of circular cylinders in a side-by-side arrangement at low Reynolds numbers has been numerically investigated in this study Numerical simulations are performed, using the immersed boundary method, for the ranges of 40$\leq$Re$\leq$160 and $g^{*}$＜5, where Re and $g^{*}$ are, respectively, the Reynolds number and the spacing between the two cylinder surfaces divided by the cylinder diameter. Results show that a total of six kinds of wake patterns are observed over the ranges: antiphase-synchronized, inphase-synchronized, flip-flopping, single bluff-body, deflected, and steady wake patterns. It is found that the characteristics of the flow significantly depends both on the Reynolds number and gap spacing, with the latter much stronger than the former. Instantaneous flow fields, time traces, flow statistics and so on are presented to identify the wake patterns and then to understand the underlying mechanism. Moreover, the bifurcation phenomenon where either of two wake patterns can occur is found at certain flow conditions.ons.

• 한국전자거래학회:학술대회논문집
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• 한국전자거래학회 2001년도 International Conference CALS/EC KOREA
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• pp.631-635
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• 2001

The Synchronized Multimedia Integration Language (SMIL) is a declarative markup language based on the eXtensible Markup Language (XML) to define a set of markup tags for synchronizing the timing and positioning relationships between multimedia objects. SMIL makes authoring of TV-like multimedia presentations on the Web easier for applications such as electronic commerce. We present the design and implementation of a JAVA-based SMIL player, which processes different types of media objects using multiple threads. Moreover, its cache engine detects the media type and allocates the proper cache memory for the corresponding media object.

• 반도체디스플레이기술학회지
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• 제19권1호
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• pp.11-16
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• 2020

In this paper, system that includes multiple unmanned aerial vehicles (UAVs) are considered. The vehicles are equipped with a mission computer for a specific mission and equipment. The mission equipment operates based on the time of mission computer. Also, data collected by flight computer and mission computer is saved with the time of each operating system. Generally, time offset between multiple computers always exists, though the computers are connected to the Internet. When the data collected by multiple computers is combined, the time offset causes damage on reliability of the combined data. Computers that connected to the Internet are synchronized by network time protocol (NTP). This paper proposes a system that the time of multiple mission computers are synchronized by the same NTP server to minimize the time offset. In the results of the measurement, the system time offset of multiple mission computer is maintained within 10ms from the system time of the server computer.

• Journal of Electrical Engineering and Technology
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• 제1권3호
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• pp.295-301
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• 2006

This paper presents a new two-terminal numerical algorithm for fault location estimation using the synchronized phasor in time-domain. The proposed algorithm is also based on the synchronized voltage and current phasor measured from the PMUs (Phasor Measurement Units) installed at both ends of the transmission lines. In this paper, the algorithm is given without shunt capacitance and with shunt capacitance using II -model and estimated using DFT (Discrete Fourier Transform) and LES (Least Error Squares Method). The algorithm uses a very short data window and classification for real-time transmission line protection. To verify the validity of the proposed algorithm, the Electro-Magnetic Transient Program (EMTP) and MATLAB are used.

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.472-477
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• 2013

An internet-based, real-time GPS synchronized wide-area power system frequency monitoring network(FNET) has been monitoring wide-area power system frequency in continuous time in the United States. This paper analyzes the FNET measurement to the verified disturbances in the US eastern interconnected power system and simulates it using the dynamic system model. By comparing the frequency measurements with its simulation results to the same disturbances in detail, this paper finds that the sequence of monitoring points to detect the frequency fluctuation caused by the disturbances is matched well in the measured data and the simulation results. The similarity comparison index is also proposed to quantify the similarity of the compared cases. The dynamic model based simulation result is expected to compensate for the lack of FNET measurement in its applications.