• Title/Summary/Keyword: 펄스열

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A Research on Low-power FFT(Fast Fourier Transform) Design for Multiband OFDM UWB(Ultra Wide Band) Communication System (Multiband OFDM UWB(Ultra Wide Band) 통신시스템을 위한 저전력 FFT(Fast Fourier-Transform) 설계에 관한 연구)

  • Ha, Jong-Ik;Kim, In-Soo;Min, Hyoung-Bok
    • Proceedings of the KIEE Conference
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    • 2009.07a
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    • pp.2119.1_2120.1
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    • 2009
  • UWB(Ultra Wide Band)는 차세대 무선통신 기술로 무선 디지털펄스라고도 한다. GHz대의 주파수를 사용하면서도 초당 수천~수백만 회의 저출력 펄스로 이루어진 것이 큰 특징이다[1]. 기존 무선통신 기술의 양대 축인 IEEE 802.11과 블루투스 등에 비해 속도와 전력소모 등에서 월등히 앞서고 있으며, SoC(System on a Chip)의 저전력 구현에 대한 연구가 활발히 진행되고 있다. OFDM은 크게 FFT(Fast Fourier Transform) 블록, Interpolation /decimation 필터 블록, 비터비 블록, 변복조 블록, 등화기 블록 등으로 구성된다. 고속 시스템에서는 대역효율성이 우수한 OFDM(Orthogonal Frequency Division Multiplexing) 방식을 사용하고 있으며, OFDM 전송방식은 직렬로 입력되는 데이터 열을 병렬 데이터 열로 변환한 후에 부반송파에 실어 전송하는 방식이다. 이와 같은 병렬화와 부반송파를 곱하는 동작은 IFFT와 FFT로 구현이 가능한데, FFT 블록의 구현 비용과 전력소모를 줄이는 것이 핵심사항이라고 할 수 있다. 기존논문에서는 OFDM용 FFT 구조로 단일버터플라이연산자 구조, 파이프라인 구조, 병렬구조 등의 여러 구조가 제안되었다[2]. 본 논문에서는 Radix-8 FFT 알고리즘 기반의 New partial Arithmetic 저전력 FFT 구조를 제안하였다. 제안한 New partial Arithmetic 저전력 FFT구조는 곱셈기 대신 병렬 가산기를 이용 하여 지금까지 사용되는 FFT 구조보다 전력소모를 줄일 수 있음을 보였다.

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Modeling of high energy laser heating and ignition of high explosives (고출력 레이저에 의한 가열과 폭약의 점화 모델링)

  • Lee, Kyung-Cheol;Kim, Ki-Hong;Yoh, Jai-Ick
    • Journal of the Korean Society of Propulsion Engineers
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    • v.12 no.3
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    • pp.1-8
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    • 2008
  • We present a model for simulating high energy laser heating of metal for ignition of energetic materials. The model considers effect of ablation of steel plate with long laser pulses and continuous lasers of several kilowatts and the thermal response of well-characterized high explosives for ignition. Since there is enough time for the thermal wave to propagate into the target and to create a region of hot spot in the high explosives, electron thermal diffusion of ultra-short (femto- and pico-second) lasing is ignored; instead, heat diffusion of absorbed laser energy in the solid target is modeled with thermal decomposition kinetic models of high explosives. Numerically simulated pulsed-laser heating of solid target and thermal explosion of RDX, TATB, and HMX are compared to experimental results. The experimental and numerical results are in good agreement.

A Numerical Study on the Transmission of Thermo-Acoustic Wave Induced by Step Pulsed Heating in an Enclosure (제한공간내 펄스가열에 기인한 열음향파의 전달특성에 관한 수치적 연구)

  • 황인주;김윤제
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.11
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    • pp.914-922
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    • 2002
  • Thermo-acoustic waves can be thermally generated in a compressible flow field by rapid heating and cooling, and chemical reaction near the boundary walls. This mechanism is very important in the space environment in which natural convection does not exist. Also this may be a significant factor for heat transfer when the fluids are close to the thermodynamic critical point. In this study, the generation and transmission characteristics of thermo-acoustic waves in an air-filled confined domain with two-step pulsed heating are studied numerically. The governing equations are discretized using control volume method, and are solved using PISO algorithm and second-order upwind scheme. For the purpose of stable solution, time step was set to the order of 1×109s,andgridsare50×2000. Results show that temperature and pressure distributions of fluid near the boundary wall subjected to a rapid heating are increased abruptly, and the induced thermo-acoustic wave propagates through the fluid until it decays due to viscous and heat dissipation. Pressure waves have sharp front shape and decay with a long tail in the case of step heating, but these waves have sharp pin shape in the case of pulsed heating.

Designing Laser Pulses for Manipulating the Interior Structure of Solids (고체 내부의 구조적 변화를 위한 Laser Pulse의 설계)

  • Kim, Young Sik
    • Journal of the Korean Chemical Society
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    • v.39 no.1
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    • pp.14-22
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    • 1995
  • This paper is concerned with the design of optimal surface heating patterns that result in focusing acoustic energy inside a subsurface target volume at a specified target time. The surface of the solid is heated by an incident laser beam which gives rise to shear and compressional waves propagating into the solid. The optimal heating design process aims to achieve the desired energy focusing at the target with minimal laser power densities and minimal system disturbance away from the target. The optimality conditions are secured via the conjugated gradient method and by the finite element method along with using the half-space Green's function matrix. Good quality energy focusing is achived with the optimal designs reflecting the high directivity of the photothermally generated shear wave patterns.

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Changes in Physicochemical Properties of Paprika by Intense Pulsed Light Treatment (광펄스 처리에 의한 파프리카의 이화학적 변화)

  • Hong, Hee Joung;Kim, Ae-Jin;Park, Hee Ran;Shin, Jung-Kue
    • Korean Journal of Food Science and Technology
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    • v.45 no.3
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    • pp.339-344
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    • 2013
  • Application of intense pulsed light (IPL) treatment is an emerging technology with interesting prospects in food preservation. However, information concerning the factors affecting the inactivation of microorganisms and their impact on the quality of fresh-cut food is scarce. In this study, the effects of IPL treatment on the microbial inactivation and physicochemical change in paprika were determined. The viability of bacteria in paprika treated with IPL decreased slightly with the treatment time. In addition, water content was slightly decreased after IPL treatment regardless of the color of paprika. However, except in red paprika, sugar content increased after IPL treatment. The pH of paprika increased in all samples, and the polyphenol content decreased with treatment time, but these differences were very small. After IPL treatment of paprika, vitamin C content increased in yellow and red samples. Hunter color values-lightness (L), redness (a), and yellowness (b)-increased in red paprika, but all values decreased in orange paprika.

Ablation Effects of Er:YAG Laser at Various Energy Levels, Different Repetition Rates and Irradiation Time on Enamel (Er:YAG 레이저를 법랑질에 조사 시 에너지수준, 조사반복율 및 조사시간에 따른 삭제효과)

  • Lee, Sae-Yong;Kim, Ki-Suk
    • Journal of Oral Medicine and Pain
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    • v.26 no.4
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    • pp.395-406
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    • 2001
  • 지난 수십년동안, 다양한 레이저기기를 이용하여 치아 경조직에 대한 응용 실험을 수행되었다. 그러나, 발생한 주요한 문제는 열발생과 플라즈마 형성과 같은 부작용이 지속된다는 점이었다. 실망스러운 실험결과에 따라 치아 삭제에 대한 레이저의 응용에 대한 연구가 거의 진행되지 못하였다. 본 연구의 목적은 국내에서 처음으로 개발된 얼비움레이저기기를 사용하여 다양한 에너지 수준과 다양한 펄스빈도에서 법랑질의 삭제율을 비교하고자 하였다. 본 연구에 사용된 레이저기기는 국내에서 최초로 개발된 2.94μm 펄스를 250μs 방출하는 얼비움야그레이저 기기이다. 기기의 에너지는 20 mJ에서 350 mJ까지 다양하게 방출하며, 최대 출력은 3.5 W이다. 22개의 치아를 에폭시 레진에 포매하고 경화하였다. 치아의 법랑질을 회전 다이아몬드 칼을 흐르는 물과 함께 사용하여 협측 또는 설측으로 평탄하게 삭제하였다. 제작된 법랑질표면은 6개의 구획으로 구분하여 에너지 수준과 펄스빈도에 따라 조사하였다. 본 연구에서 사용된 표본 수는 132개이며, 삭제율을 조사하기 위한 모든 표본은 22개의 실험 군으로 분류하였다. 실험결과는 다음과 같다. 1. 에너지 수준간에는 유의한 삭제율의 차이가 있었다. 2. 40 및 80 mJ로 조사한 경우에는 펄스빈도 간에 차이가 없었지만, 120 mJ의 출력으로 동일한 에너지를 조사한 경우에는 20 Hz가 40 또는 80 mJ로 조사한 경우 보다 가장 삭제효과가 높았다. 3. 연속조사 한 경우 조사시간 경과에 따라 법랑질의 삭제율은 증가되지 않았다. 결론적으로 효과적으로 법랑질을 삭제하기 위해서는 적절한 에너지와 펄스의 레이저를 사용해야 하며, 또한 항상 정확한 초점거리를 유지해야 할 것으로 사료된다.

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Life Firing Test of 1 N-class Monopropellant Thruster Development Model -Part II: Pulse Mode Performance (1 N급 단일추진제 추력기 개발모델의 장기수명 연소시험 -Part II: 펄스모드 성능 특성)

  • Won, Su-Hee;Kim, Su-Kyum;Jun, Hyoung-Yoll;Lee, Jun-Hui;Park, Su-Hyang;Lee, Jae-Won
    • Journal of the Korean Society of Propulsion Engineers
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    • v.18 no.6
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    • pp.68-74
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    • 2014
  • During the life firing test of 1 N-class thruster development model, pulse mode performance and performance changes were examined. The deviation of pulse mode response time according to thruster feed pressure was relatively small and the resultant ignition delay, response time, tail-off time were 32-35 ms, 86-91 ms, 89-98 ms, respectively. For the stabilized pulse region the impulse bit revealed the outstanding reproducibility of 1.41, 1.32, 2.10% at 3σ. During the life firing test, the impulse bit was decreased with limited amounts, therefore the pulse mode performance could be considered to be maintained. The thrust centroid was also maintained during the life firing test.

Flavor and taste characteristic of black pepper by different nonthermal sterilization methods (비가열 살균 후추의 향미특성)

  • Lee, Gwang Min;Shin, Jung Kue
    • Korean Journal of Food Science and Technology
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    • v.51 no.6
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    • pp.551-557
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    • 2019
  • The purpose of this study was to investigate the changes of flavor and taste characteristics of black pepper treated with three different nonthermal sterilization methods, which are intense pulsed light (IPL), ultraviolet (UV), and cold plasma (CP). Also, the sensorial and instrumental evaluation of black pepper before and after nonthermal treatments were analyzed. As a result of color value, UV and CP treatments did not show chromacity difference (ΔE), but IPL treatment showed a significant difference of 6.58. Piperine contents of sample before nonthermal treatments was 10.7±0.53 mg/g and the piperine contents of all samples decreased after nonthermal treatments. The result of the electronic nose analysis were divided into two groups before and after nonthermal treatments, and divided into three group by principle component analysis. According to the intensity test, after nonthermal treatments, all sample had low flavor and taste, and the intensity was in the order of IPL, CP, and UV. In thirteen sensory attribute languages developed through quantitiative descriptive analysis (QDA), the intensity value of the samples were low after nonthermal treatments.

Sterilization of Rapeseed Sprouts by Intense Pulsed Light Treatment (고강도 광원을 이용한 새싹 채소의 살균)

  • Park, Heeran;Cha, Gyung-Hee;Shin, Jung-Kue
    • Korean Journal of Food Science and Technology
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    • v.48 no.1
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    • pp.36-41
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    • 2016
  • In this study, the effects of intense pulsed light (IPL) treatment on microbial inactivation and quality in rapeseed sprouts were investigated. Untreated rapeseed sprouts exhibit a high level of total aerobic bacteria (TAB) (1.2×107CFU/g), coliform bacteria (coliform) (3.3×106CFU/g), and pathogenic E. coli (PE) (2.1×105CFU/g). The microorganisms found on rapeseed sprouts decreased with exposure to increasing light intensity and treatment time. The greatest reduction in microbial content was observed with a treatment of 1000 V, 5 pps for 10 min, where TAB, coliform, and PE levels decreased to 1.0 log CFU/g, 1.6 log CFU/g, and 1.8 log CFU/g, respectively. In agreement with these data, the microbial inactivation rate increased with the increase in the distance between the light source and the samples during IPL treatment. After IPL treatment of rapeseed sprouts, water content and vitamin C content decreased.