열복사 감쇠 성능에 대한 미분무 노즐 설치 조건의 영향 검토

박지호,강준석,이치영 한국화재소방학회 2022 한국화재소방학회논문지 Vol.36 No.5

In this experimental study, the effect of installation conditions of a water mist nozzle on thermal radiation attenuationperformance was investigated. Two types of nozzles (Small_nozzle and Large_nozzle) were used. Experiments wereconducted under conditions in which the nozzle was installed near the heater and heat flux sensor (Position_NH andPosition_NS, respectively), and water mist was discharged from one and two nozzles (Case_ID and Case_SD, respectively). To characterize the water mist spray, the water supply pressure and droplet size were measured, and visualization of thesprayed water mist was performed. The thermal radiation attenuation performance improved with an increase in the waterflow rate, and Small_nozzle showed higher thermal radiation attenuation performance than Large_nozzle. Moreover,Case_SD showed lower thermal radiation attenuation performance than Case_ID_Sum (that is, the Sum of Case_ID &Position_NS and Case_ID & Position_NH) and the difference in thermal radiation attenuation performance betweenCase_SD and Case_ID_Sum at a higher water flow rate was more significant than that at a lower water flow rate. Thesemight be attributed to the wide overlapping area of water mist discharged from two nozzles in Case_SD and at a higherwater flow rate, narrowing the overall width of the water mist. 본 연구에서는 열복사 감쇠 성능에 대한 미분무 노즐 설치 조건의 영향을 실험적으로 검토하였다. Small_nozzle과Large_nozzle을 이용하였고, 노즐이 히터와 열유속계 근처에 설치된 조건(각각 Position_NH와 Position_NS)과 1개와2개의 노즐에서 미분무가 분사되는 조건(각각 Case_ID와 Case_SD)에서 실험을 수행하였다. 미분무 분사 특성을 파악하기 위해 노즐의 물 공급 압력과 액적 크기를 측정하였고, 분사되는 미분무를 가시화하였다. 열복사 감쇠 성능은물 공급 유량이 증가할수록 향상되었고 Small_nozzle이 Large_nozzle보다 높은 것으로 나타났다. 한편, Case_SD 조건은 Case_ID_Sum 조건(즉, Case_ID & Position_NS와 Case_ID & Position_NH 조건에서의 합)에 비해 열복사 감쇠 성능이 낮고, Case_SD와 Case_ID_Sum 조건의 열복사 감쇠 성능 간 차이는 물 공급 유량이 많은 경우가 적은 경우에 비해더 큰 것으로 관찰되었다. 이는 Case_SD 조건과 물 공급 유량이 많은 조건에서 미분무의 중첩 영역이 넓어져서 전체적인 분무폭이 좁아지는 효과가 나타나기 때문으로 판단된다.

홀센서가 장착된 보행보조기 스마트 핸들 설계 연구

박지호,김수언,이원구 제어로봇시스템학회 2018 제어로봇시스템학회 국내학술대회 논문집 Vol.2018 No.5

공진모델을 이용한 3상 능동전력필터의 강인한 내부모델제어

박지호,김영빈,노인배,우정인 동아대학교 생산기술연구소 2002 生産技術硏究所硏究論文集 Vol.7 No.1

A new simple control method for active power filter, which can realize the complete compensation of harmonics is proposed. In the proposed scheme, a model-based digital current control strategy is presented. The Proposed control system is designed and implemented in a form referred to as Internal Model Control structure. In the proposed control algorithm, overshoots and oscillations due to the computation time delay is prevented by explicit incorporating of the delay in the controller transfer function. In addition, a new compensating current reference generator employing resonance model implemented by a DSP(Digital Signal Processor) is introduced. Resonance Model has an infinite gain at resonant frequency, and it exhibits a band-pass filter. Consequently, the difference between the instantaneous load current and the output of this model is the current reference signal for the harmonic compensation.

CuBr 반도체 양자구슬에서의 Hole Burning 현상

박지호,박성욱,김일곤,유동선 昌原大學校 基礎科學硏究所 2002 基礎科學硏究所論文集 Vol.14 No.-

PSHB spectrum was measured by the pump-probe method. After the absorption band of the nanocrystals sample was excited by the spectrally narrow band light, the spectral hole was produced at the position of the exciting light. The depth of spectral holes(main hole and side hole) was decreased with the temporal change. The energy difference between the zero phonon line and side hole depends on the radius of nanocrystals.

Engineering Biological Systems to Improve Nanomedicine

박지호 한국고분자학회 2015 한국고분자학회 학술대회 연구논문 초록집 Vol.2015 No.4

통계로 본 한국농업의 어제와 오늘

박지호 한국종자연구회 2013 종자과학과 산업 Vol.10 No.3

Effect of Ultrasonic Energy on Self-Weight Consolidation of Clay Minerals

박지호,천영우,Hoang Tien Trung,김영욱 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.4

Consolidation is the densification of soft saturated soils occurring when water is extruded from the soil. Because water flows slowly through porous media, consolidation is time intensive. We investigated the effect of ultrasonic energy on the self- weight consolidation of clay minerals, with a series of laboratory tests in which a sonic bath directly generated ultrasonic waves at the clay slurry. The test conditions included the power and duration of the sonic energy, the initial water content, and the soil type. The results showed a significant reduction in consolidation time when ultrasound is applied. The time required for the same amount of settlement is shorter for the sonicated specimens, and the sonicated clay slurry had a much-increased final settlement. The degree of enhancement varied with the test conditions. A scanning electron microscope was used to monitor possible changes in the soil structure during the tests. The ultrasound did not significantly affect the soil structure, but density the layers of particles. Using the test results, we discuss the potential development of a new method that can reduce the construction period.

와이브로기반의 서비스영역 확대와 핸드오프 보장에 관한 연구

박지호,오영환 대한전자공학회 2006 電子工學會論文誌-TC (Telecommunications) Vol.43 No.5

This thesis deals with solutions such as coverage area extension, reduction of the shadow region and performance enhancement of handover caused by structural modification of WiBro network.The More far the distance of RAS(Radio Access Station) and SS(Subscriber Station) is in micro cell, the more bad the quality of channel environment becomes owing to radio interference. Consequently, it causes the deterioration of the throughput and also the deterioration of communication quality in many sides. In fact, most users of WiBro are located in the region, the QPSK region which is bad in point of channel quality. It brings the service complaint by user. We select RS(relay station) to solve the matter caused by channel environment in this cell, and extend coverage and improve the performance of handover call blocking. 이 논문은 휴대인터넷 통신 네트워크 구조 변경으로 커버리지 확대 및 음영지역 해소, 그리고 핸드오버 성능 향상에 관한 논문이다. 마이크로 셀 내의 RAS(Radio Access Station)를 중심으로 SS(Subscriber Station)와의 거리가 멀어질수록 전파감쇄로 인하여 통신환경의 질이 64QAM, 16QAM 그리고 QPSK로 떨어지게 된다. 그 결과 Throughput의 저하는 물론이고, 여러 면에서 통신 품질의 질도 떨어지게 된다. 실제로 휴대인터넷의 대부분의 지역은 환경이 좋지 않은 QPSK 지역으로 사용자 대부분은 이러한 지역에서 휴대인터넷을 사용하게 된다. 그 결과 사용자들은 많은 불만을 가지게 될 것이다. 이런 셀 내의 통신 환경으로 인한 문제점을 해결하기 위하여 RS(Relay Station)를 적용하여 셀의 커버리지 확대는 물론이고, 통신환경을 향상시켜 핸드오버 호 블록킹 성능 향상을 시키는데 그 목적이 있다.

CRDS Study of Tropospheric Ozone Production Kinetics : Isoprene Oxidation by Hydroxyl Radical

박지호 한국환경보건학회 2009 한국환경보건학회지 Vol.35 No.6

The tropospheric ozone production mechanism for the gas phase additive oxidation reaction of hydroxyl radical (OH) with isoprene (2-methyl-1,3-butadiene) has been studied using cavity ring-down spectroscopy (CRDS) at total pressure of 50 Torr and 298 K. The applicability of CRDS was confirmed by monitoring the shorter (~4%) ringdown time in the presence of hydroxyl radical than the ring-down time without the photolysis of hydrogen peroxide. The reaction rate constant, (9.8±0.1)×10−11 molecule−1cm3s−1, for the addition of OH to isoprene is in good agreement with previous studies. In the presence of O2 and NO, hydroxyl radical cycling has been monitored and the simulation using the recommended elementary reaction rate constants as the basis to OH cycling curve gives reasonable fit to the data.

특징벡터의 상관관계에 의한 한글 단모음 음성인식에 관한 연구

박지호,김중규 成均館大學校 科學技術硏究所 1994 論文集 Vol.45 No.2

본 논문에서는 통계적 처리에 의한 한글 단모음 인식 판별법을 제시하려고 한다. 본 논문에서 제시하는 새로운 음성 판별 방법은 기존의 알고리즘에서 요구되는 긴 학습시간과 많은 수행단계, 그리고 인식시의 대용량 메로리에 비해 짧은 수행 시간과 함께 높은 인식률을 동시에 보장할 수 있다. 본 연구에서는 음성 파형과 그 음성의 특징 파라미터를 음성과 화자의 특징을 포함하는 Random Process로 가정하고, 단모음의 경우 각 프레임에서 음성 파형 및 LPC계수, LPC계수 Spectrum과 같은 특징 파라미터들이 거의 일정하다는 것에 착안하여, 각 음성 파형에서 나오는 평균 LPC log spectrum을 모음별로 구분하여 그 평균들로 기준 패턴을 만든다. 또, 각 음성파형의 특징파라미터를 Ramdom Process로 가정하여 그 평균들로 기준 패턴을 만든다. 또, 각 음성파형의 특징파라미터를 Ramdom Process로 가정하고 입력파형의 평균 LPC log spectrum과 기준 패턴 Set의 Vector 들간의 Ramdom Correlation Coefficient를 각각 구한 후 그중 가장 큰 Correlation Coefficient값을 갖는 기준 Vector에 의한 음성을 입력신호의 음성으로 인식한다. 이러한 판별법은 성도모델이 정확히 나타나고 빠른 추출이 가능한 LPC Parameter를 기반으로 하고 또한 Distance measure, 즉 Correlation Coefficient를 계산하는데 걸리는 시간이 매우 짧기 때문에 기존의 방법에 비해 전체적인 Processing Time을 훨씬 더 줄일 수 있을 것이다. 본 실험에서는 새로운 알고리즘을 검증하기 위하여 9명의 화자가 3번식 발음한 단모음 8개의 Data를 사용하였으며 화자독립 음성인식의 경우 96.30%, 화자종속 음성인식의 경우 100%의 인식률을 보였다. In this paper, we propose a statistical recognition algorithm for isolated words and applied it to Korean vowels. The proposed scheme requires relatively short processing time with reasonably high performance, compared to existing conventional algorithms which need rather longer period of training as well as much larger capacity of memory. In this research, we assume that the speech waveform and associated feature parameters are random processes, and we form the reference pattern of each speech with the mean LPC log spectrum averaged over the frames. This is feasible since the speech waveform of Korean vowels can be considered stationary over the duration of signals. Then, we compute the correlation coefficient between the feature parameters (i.e. the LPC log spectrum) of the input speech and those of reference vectors, and choose the speech signal among reference patterns which renders the highest correlation with the input as the recognized vowel. Since this method is based on the LPC parameters which provide an accurate model of vocal tract and can be extracted very quickly from the speech waveform, and since the computation time required for the distance measure (i.e. the correlation coefficient) is fractional, the overall processing time for recognition could be very much shortened. We tested the proposed algorithm with eight Korean vowels spoken by nine male speakers three times each, and showed 96.3% recognition rate for speaker independent case and 100% for speaker dependent case respectively.