• Journal of the Optical Society of Korea
• /
• 제8권4호
• /
• pp.168-173
• /
• 2004

Brillouin scattering-based fiber optic sensors are useful to measure strain or temperature in a distributed manner. Since the Brillouin frequency of an optical fiber depends on both the strain and temperature, it is very important to know whether the Brillouin frequency shift is caused by the strain change or temperature change. This article presents a temperature compensation technique of a Brillouin scattering-based fiber optic strain sensor. Both the changes of the Brillouin frequency and the Brillouin gain power is observed for the temperature compensation using a BOTDA sensor system. Experimental results showed that the temperature compensated strain values were highly consistent with actual strain values.

• 한국습지학회지
• /
• 제13권3호
• /
• pp.623-631
• /
• 2011

최근 기후변화에 따른 전지구적인 지구온난화는 대형 태풍의 발생, 집중호우의 증가 등 기존의 기후 특성을 변화시키고 있다. 이로 말미암아 자연재해의 강도가 강해지고 있고, 인명과 재산피해가 대규모화되고 있다. 따라서 본 연구에서는 기후변화로 인한 자연재해에 대비하기 위하여 미래 기후변화를 예측하고 도심지에 미치는 영향을 파악하고자 하였으며, 대상지역으로는 배수 관거의 용량 초과로 인해 상습적으로 침수가 발생하는 인천광역시 계양구 일대를 선정하였다. 먼저, 기후변화 시나리오 및 기후모형들을 검토하여 적정 기후시나리오와 기후모형을 선정하고, 수집한 강우자료를 시간단위로 축소한 뒤 미래 기후변화의 영향으로 인해 발생할 수 있는 확률강우량을 구하였다. 미래 증가하는 확률강우량을 XP-SWMM모형에 적용해 도시배수시스템의 홍수유출량을 산정 하였는데, 대상지역에 월류가 발생할 것으로 예상되었다. 따라서 이에 대한 적절한 대책 마련이 필요할 것으로 사료된다.

• 대한토목학회논문집
• /
• 제39권5호
• /
• pp.561-568
• /
• 2019

최근 우리나라는 기후변화 영향으로 극심한 가뭄으로 인한 피해가 발생하고 있다. 따라서 가뭄에 대한 완화대책을 마련하기 위해서는 가뭄 위험도의 변화를 분석할 필요가 있다. 본 연구에서는 관측 강수량 자료와 RCP 4.5 및 8.5 기후변화 시나리오에 따른 미래 강수량 자료를 활용하여 극한가뭄에 대한 수문학적 위험도를 평가하였다. 먼저, 임계수준방법으로 가뭄사상을 정의하고 풀링을 통하여 미소가뭄을 제거하여 도출한 가뭄 지속기간 및 심도를 대상으로 이변량 가뭄빈도분석을 실시하였다. 극한가뭄사상에 대한 수문학적 위험도를 산정한 결과, RCP 4.5 시나리오에서 위험도가 가장 높은 지역은 전라북도이며 과거보다 51 % 증가하였다. 또한, RCP 8.5 시나리오에서 위험도가 가장 높은 지역은 강원도이며 과거보다 47 % 증가하였다.

• 한국환경복원기술학회지
• /
• 제25권6호
• /
• pp.1-11
• /
• 2022

Recently, climate change has been regarded as a major cause of large-scale forest fires worldwide, and there is concern that more frequent and severe forest fires will occur due to the level of greenhouse gas emissions. In this study, the daily Keetch and Byram Drought Index (KBDI) of the Baekdudaegan in Chungcheong region including Sobaeksan, Songnisan, and Woraksan National Parks were calculated to assess effect of climate change on the forest fire potential- severity of annual maximum KBDI and frequency of high KBDI days. The present (2000~2019) and future KBDI(2021~2040, 2041~2060, 2081~2090) were calculated based on the meteorological observation and the ensemble regional climate model of the SSP1-2.6 and SSP5-8.5 scenarios with a spatial resolution of 1-km provided by Korea Meteorological Administration(KMA). Under the SSP5-8.5 scenario, 6.5℃ increase and 14% precipitation increase are expected at the end of the 21st century. The severity of maximum daily KBDI increases by 48% (+50mm), and the frequency of high KBDI days (> 100 KBDI) increases more than 100 days, which means the high potential for serious forest fires. The analysis results showed that Songnisan National Park has the highest potential for forest fire risk and will continue to be high in intensity and frequency in the future. It is expected that the forest vulnerability of the Baekdudaegan in the Chungcheong region will greatly increase and the difficulty in preventing and suppressing forest fires will increase as the abundance of combustible materials increases along with climate changes.

• Bulletin of the Korean Chemical Society
• /
• 제33권10호
• /
• pp.3391-3396
• /
• 2012

Two-dimensional infrared (2D-IR) spectroscopy can probe the fast structural evolution of molecules under thermal equilibrium. Vibrational frequency fluctuation caused by structural evolution produced the time-dependent line shape change in 2D-IR spectrum. A variety of methods has been used to connect the evolution of 2D-IR spectrum with Frequency-Frequency Correlation Function (FFCF), which connects the experimental observables to a molecular level description. Here, a new method to extract FFCF from 2D-IR spectra is described. The experimental observable is the time-dependent frequency shift of maximum peak position in the slice spectrum of 2D-IR, which is taken along the excitation frequency axis. The direct relation between the 2D-IR peak shift and FFCF is proved analytically. Observing the 2D-IR peak shift does not need the full 2D-IR spectrum which covers 0-1 and 1-2 bands. Thus data collection time to determine FFCF can be reduced significantly, which helps the detection of transient species.

• Communications for Statistical Applications and Methods
• /
• 제10권2호
• /
• pp.457-469
• /
• 2003

In this paper, we have proposed the efficient algorithm that can segment the video scene change using a various statistical characteristics obtained from by applying the wavelet transformation for each frames. Our method firstly extracts the histogram features from low frequency subband of wavelet-transformed image and then uses these features to detect the abrupt scene change. Second, it extracts the edge information from applying the mesh method to the high frequency subband of transformed image. We quantify the extracted edge information as the values of variance characteristic of each pixel and use these values to detect the gradual scene change. And we have also proposed an algorithm how extract the proper key frame from segmented video scene. Experiment results show that the proposed method is both very efficient algorithm in segmenting video frames and also is to become the appropriate key frame extraction method.

• 한국전자파학회:학술대회논문집
• /
• 한국전자파학회 2002년도 종합학술발표회 논문집 Vol.12 No.1
• /
• pp.241-245
• /
• 2002

Dual-band microstrip antenna is designed for industrial-scientific-medical(ISM) band of 2.4㎓ and 5.8㎓ using finite-difference time-domain method(FDTD). Cross Patch fed by aperture in the ground plane of microstrip line is proposed as radiation element of antenna, which is 2 rectangular Patch is overlapped. To design antenna, change of input impedance by aperture and stub length change is examined. And it is investigated that center frequency and -10 ㏈ bandwidth by Length of radiation element and width change. Experimental result about reflection Loss confirmed that agree well with analysis results of FDTD and IE3D, And -3 ㏈ beam width, front to back ratio and gain in frequency 2.43㎓ and 5.79㎓ is presented by measuring radiation Pattern of antenna.

• 한국정밀공학회지
• /
• 제23권4호
• /
• pp.139-145
• /
• 2006

This paper presents the design and manufacturing of a sensor using SAW and delay line in order to measure temperature. SAW sensors having single and double electrodes are manufactured on the $128^{\circ}YX-LiNbO_3$ substrate, and its process is addressed. Before manufacturing, the device is simulated using a commercial finite element program. The frequency responses of the saw sensor on the temperature change is measured. Since the center frequency on the temperature change from $-30^{\circ}C$ to $80^{\circ}C$ is linearly changed, the saw sensor is applicable to measure the temperature change or strain variation.

• 산업경영시스템학회지
• /
• 제6권8호
• /
• pp.35-40
• /
• 1983

The fusion frequency of flicker (F.F.F.) of 40 pupils were examined every day repeatedly, from Monday to Saturday. (1) The individual Variations of F.F.F. were statistically highly significant, p < 0.01 (2) Day to day Variations of F.F.F. were statistically highly significant, p < 0.01 (3) The interaction between age and weekly change was highly significant, p < 0.01 (4) The interaction between sex difference and weekly change was also significant, p < 0.01 (5) The interaction among age, sex and weekly change was significant at 1% level of significance.

• 한국공작기계학회논문집
• /
• 제10권6호
• /
• pp.8-14
• /
• 2001

We develop a method to analyze dynamic behavior off multi-stage gear train system. The example system consists of three shafts supported by ball bearings at the ends of them and two pairs of spur gear set. For exact analysis, the meshing tooth pair of gear set is modeled as spring and damper having time-dependent meshing stiffness and damping. The bearing is modeled as spring. The result of this analysis is compared to that of other model having mean mesh stiffness. The effect of the excitation force by the unbalance off rotor off motor is also analyzed. Finally, the change ova natural frequency of the whole system due to the change of an angle between three shafts is compared in each case, and from this analysis, the avoiding angle for design is advised.