• 한국광학회지
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• 제16권2호
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• pp.133-137
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• 2005

본 논문에서는 테이퍼된 구조를 갖는 광섬유 브래그 격자를 이용한 광학적 RF 실시간 지연 소자를 제안하고 구현하였다. 광섬유격자 표면에는 금속 박막의 히팅용 전극이 코팅되어 있다. 전극에 인가되는 전압에 의해 유발되는 열광학 효과를 통하여 광섬유 격자로부터 반사되는 광신호의 반사 위치를 변화시킴으로써 광신호에 변조용 신호로 실려서 전달되는 RF 신호의 시간 지연을 조절할 수 있다. 따라서 이 제안된 소자는 기존의 소자들과는 달리 기계적 변형이나 움직임 없이 전압에 의하여 연속적으로 정밀하게 시간지연 값을 제어할 수 있는 특징을 갖는다. 측정된 최대 시간 지연은 소비 전력이 $250{\cal}mW$일 때 약 120 ps였다.

• Journal of Mechanical Science and Technology
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• 제19권11호
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• pp.1975-1987
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• 2005

An input time delay always exists in practical systems. Analysis of the delay phenomenon in a continuous-time domain is sophisticated. It is appropriate to obtain its corresponding discrete-time model for implementation via digital computers. In this paper a new scheme for the discretization of nonlinear systems using Taylor series expansion and the zero-order hold assumption is proposed. The mathematical structure of the new discretization method is analyzed. On the basis of this structure the sampled-data representation of nonlinear systems with time-delayed multi-input is presented. The delayed multi-input general equation has been derived. In particular, the effect of the time-discretization method on key properties of nonlinear control systems, such as equilibrium properties and asymptotic stability, is examined. Additionally, hybrid discretization schemes that result from a combination of the scaling and squaring technique (SST) with the Taylor series expansion are also proposed, especially under conditions of very low sampling rates. Practical issues associated with the selection of the method's parameters to meet CPU time and accuracy requirements, are examined as well. A performance of the proposed method is evaluated using a nonlinear system with time delay maneuvering an automobile.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.922-924
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• 1995

The modeling of accurate timing in storage elements of ASIC cell library was studied. The propagation delay time of clock signal affects the critical time and this can cause malfunction in the chip designed in synchronous. In this paper, an analysis on the effect of input slope of clock signal in timing modeling were carried out. For the first time, in ASIC design, the design guides that can be used in both $0.6{\mu}M$ and $0.8{\mu}m$ design rule were offered, reducing the run time of SPICE and the time of cell library development.

• 대한기계학회논문집B
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• 제27권3호
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• pp.326-333
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• 2003

In the measurement using DMA and CPC in series, there is some time delay for particles classified in DMA to detect in CPC. During this time, the DMA time-response changes due to the velocity profile of sampling tube and the diffusion of particles in the volume that exists between the DMA exit and the detector of ultra-fine CPC. This is called mixing effect. In the accelerated measurement methods like the TSI -SMPS, the size distribution is obtained from the correlation between the time-varying electrical potential of the DMA and the corresponding particle concentrations sampled in DMA. If the DMA time -response changes during this delay time, this can cause the error of a size distribution measured by this accelerated technique. The kernel function considering this mixing effect using the residence time distribution is proposed by Russell et al. In this study, we obtained a size distribution using this kernel to compare to the result obtained by the commercial accelerated measurement system, TSI -SMPS for verification and considered the errors that result from the mixing effect with the geometric mean diameters of originally sampled particles, using virtually calculated responses obtained with this kernel as input data.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.121-124
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• 1999

In a packet-switched wireless cellular network, a packet destined to a mobile station is queued at a base station and then broadcast over the base station's cell. When an active mobile station leaves a cell, there re-main packets which are destined to the mobile and not yet delivered to it at the cell's base station. For application which are sensitive to packet losses, such back- logged packets must be forwarded to the new base station. Otherwise, an end-to-end retransmission may be required. However, an increase in packet delay is incurred by employing the packet forward scheme, since a packet may be forwarded many times before it is delivered to the destined mobile station. For an enhanced quality-of-service level, it is preferred to reduce tile packet delay time. In this paper, we develop an analytical approximation method for deriving mean packet delay times. Using the approximation and simulation methods, we investigate the effect of network parameters on the packet delay time.

• 한국안전학회지
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• 제1권1호
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• pp.33-40
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• 1986

The results from a study on the combustion of the ferrosilicon-miniun delay powder which was examined under the various conditions are as follows. 1. It has been found that in case of these delay powders, decomposition of oxidiging agents occurs first and then reducing agents are oxidized by the gases evolved from the oxidizing agents and by the oxygen in air. Therefore, the main reactions are heterogenous reaction and especially He gas phase plays an important role in combustion reactions of delay Powders. 2. In case the loading pressure is below 100kg per a detonator, the dispresion of burning time is large. 3. Little or no increase in humidity was observed on daily measurement during six month preservation tests. 4. The amperage of electric current for igniting the fuse head has no effect on the burning time of delay conposition itself changed in the detonator.

• Hip & pelvis
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• 제35권3호
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• pp.206-215
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• 2023

Purpose: Delay in performance of hip fracture surgery can be caused by medical and/or administrative reasons. Although early surgery is recommended, it is unclear what constitutes a delayed surgery and whether the impact of delayed surgery can differ depending on the reason for the delay. Materials and Methods: A total of 269 consecutive hip fracture patients over 50 years of age who underwent surgery were prospectively enrolled. They were divided into two groups: early and delayed (time from reaching the hospital to surgery less than or more than 48 hours). Patients were also categorized as fit or unfit based on anesthetic fitness. One-year mortality was recorded, and regression analyses were performed to assess the impact of delay on mortality. Results: A total of 153 patients (56.9%) had delayed surgery with a mean time to surgery of 87±70 hours. A total of 115 patients (42.8%) were considered medically fit to undergo surgery. No difference in one-year mortality was observed between patients with early surgery and those with delayed surgery (P=0.854). However, when assessment of the time to surgery was performed in a continuous manner, mortality increased with prolonged time to surgery, particularly in unfit patients, and higher mortality was observed when the delay exceeded six days (fit: P=0.117; unfit: P=0.035). Conclusion: The effect of delay on mortality was predominantly observed in patients who were not considered medically fit, suggesting that surgical delays might have a greater impact on patients with medical reasons for delay.

• 방송공학회논문지
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• 제12권1호
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• pp.28-40
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• 2007

본 논문에서는 기존에 제안된 잔향 알고리즘 구조에서 문제점으로 대두된 잔향특성을 개선한 새로운 알고리즘 구조를 제안하였다. 제안된 알고리즘 구조는 초기 잔향을 위하여 탭 지연라인을 사용하여 초기반사음을 충분히 구현하였고, 후기 반사음과 잔향을 위해 nested allpass delay line을 이용하여 잔향 밀도를 높이도록 제안하였다. 실내음향의 파라메터를 추출하여 각 지연 라인의 지연 시간을 설정 및 조절하여 가장 좋은 잔향 효과를 갖도록 계수 값들을 설정하였으며, 제안한 알고리즘을 일반 범용 신호처리기를 이용하여 구현 및 실험 고찰을 통해 기존에 제시된 모델에서의 임펄스성음에 대한 비선형적인 거친 응답과 급격한 음색변화가 감소하여, 고르고 평탄한 잔향 밀도가 향상되어 잔향특성이 개선됨을 관찰하였다.

• 대한기계학회논문집B
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• 제32권9호
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• pp.720-727
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• 2008

Time delay effects on near-wall turbulent structures are investigated by performing a large-eddy simulation of a transient turbulent flow in a pipe. To elucidate the time delay effects on the near-wall turbulence, we selected the dimensionless acceleration parameter which was used in the previous study. Various turbulent statistics revealed the distinctive features of the delay. It was shown that the dynamic Smagorinsky model is valid to capture the alterations of the turbulence physics well. A dimensionless time for the responses of the flow quantities was introduced to give the detailed information on the delay of the nearwall turbulence. The conditionally-averaged flow fields associated with Reynolds shear stress producing events show that sweep and ejections are closely related to the delays of the turbulence production and the turbulence propagation toward the pipe center. The present study suggested that the enhanced anisotropy of the turbulence in the initial and transient stages would be a challenging problem to standard turbulence models.

• 감성과학
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• 제11권2호
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• pp.227-234
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• 2008

시각과 청각으로 표현된 디지털 콘텐츠가 감각표현을 확장하려는 연구가 활발하다. 최근에는 촉각 표현이 가능한 다양한 촉각 표현 시스템이 개발하여 촉감을 표현하는 디지털 콘텐츠 개발하고 있다. 하드웨어에 의한 촉감각 표현시 다른 감각과의 동기화가 중요한 표현 요소로 대두되고 있다. 본 연구는 햅틱(haptic)표현이 다른 감각에 비해 표현 지연 발생할 경우 실감도에 미치는 영향에 관한 것이다. 시각 및 햅틱 지연 시간을 0.5, 1.0, 2.0, 4.0(초)로 설정하여 각 지연에 대한 실감도 평가를 실시하여 선형 회귀 분석하였다. 촉각 지연 보다 시각 지연에서 실감도와 상관성을 보였으며 지연 시간이 길어질수록 실감도가 떨어지는 것을 볼 수 있었다. 그러므로 사용자는 촉감 표현에 대한 지연이 시각 지연 보다 관대한 것으로 사료된다.