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Measurements on Effects of Locations of Obstacles in an Explosion Chamber

  • Han, Jae-Beom;Lee, Young-Soon;Park, Dal-Jae
    • Journal of the Korean Institute of Gas
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    • v.12 no.3
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    • pp.68-74
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    • 2008
  • Measurements were performed to investigate the effects on flame and pressure development by varying locations of multiple obstacles in a top-venting explosion chamber. The chamber dimension was 1000 mm in height with a $700\;{\times}\;700\;mm^2$ cross-section and a rectangular vent area of $700\;{\times}\;700\;mm^2$. Three different multiple obstacles with blockage ratio of 30% were used by changing from 200 mm, 500 mm to 800 mm in heights within the chamber. Temporally resolved flame front images were recorded by a high speed camera to investigate the interaction between the propagating flame and the obstacles. The results showed that the triangular bar caused the fastest flame developments at given times whereas the lowest was obtained with the cylindrical bar. It was also found that local flame displacement speeds of different obstacles were sensitive to the locations of obstacles. The local speed becomes larger in going from 200 mm, to 500 mm and to 800 mm in heights. The obstacles in height of 800 mm yielded the highest overpressure whereas the lowest was in height of 200 mm.

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A Development and Performance Experiment on In-rack Sprinkler Head for Rack Type Warehouse (적층식 대형창고 스프링클러헤드 개발 및 성능실험)

  • Kim, Woon-Hyung;Lee, Jun;Hong, Seong-Ho;Kim, Jong-Hoon;Yang, So-Jin
    • Journal of the Society of Disaster Information
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    • v.15 no.2
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    • pp.214-222
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    • 2019
  • Purpose: The purpose of this study is to develop a sprinkler head that can be controlled and initial suppressed by installing it in a rack-type warehouse. Method: Considering the spray radius and spray pattern, various deflectors were designed, and the spray angle, discharge characteristics and protection performance test was conducted, and these results were compared and analyzed. Results: An optimal sprinkler head was developed to protect full load, front side of a commodity with minimum water volume 115L/min. Conclusion: The developed head of K-115 and 1Bar pressure was tested with one tier storage confirming that the fire control is carried out without burning all the loadings. In addition, the vertical distance from the top of the load to the deflector shall be separated by 450mm and installed to allow sufficient discharge to the outer part of the commodity.

The Relationship between Disturbances of Hydromorphological Structures and Naturalized Plants Ratio in Small and Mid-sized Streams (중·소하천에서 물리적 구조의 교란과 하안식생 귀화율의 관계)

  • Chun, Yeajun;Choi, Yun Eui;Hong, Sun Hee;Chon, Jinhyung
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.16 no.1
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    • pp.207-225
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    • 2013
  • Current ecological stream restoration is focusing on recovery of physical characteristic and ecological functions of individual stream. For effective stream restoration, the relationship between stream environment and riparian flora should be investigated. The purpose of this study is to analyze the relationship between disturbance of hydromorphological structures and naturalized plants ratio in small to mid-sized streams. For the study sites, Gwanpyeong stream, Dongdal stream, and Yongchoo streams were chosen as 'reference stream' while, Gunnam stream, Anchang stream, and Hwa stream were chosen as 'damaged stream'. The hydromorphological structures of streams were evaluated with LAWA and flora of the streams were completely enumerated to calculate naturalized plants ratio. The result showed that there was a significant correlation between the outcome of LAWA and naturalized plants ratio(r=0.675, p<0.01). The result of factor analysis of LAWA identified three factors, 'River front and land use', 'River bed materials and structures', and 'Crossing structure and bar'. Among the factors of hydromorphological structures given by the result of factor analysis, 'river front and land use' and 'bed materials and structures' have statistically significant relationship with naturalized plants ratio($R^2$=0.470, p<0.01). Given this results, quantitative analysis on the relationship between disturbance of hydromorphological structures of streams and naturalized plants ratio could provide some essential information for stream restoration. Also, as this study figured out major factors of hydromorphological structures that affect naturalized plants ratio, it might help monitor ecological states and current problems of small and mid-sized streams.

Visibility Evaluation for Agricultural Tractor Operators According to ISO 5006 and 5721-1 Standards

  • Kabir, Md. Shaha Nur;Song, Mingzhang;Chung, Sun-Ok;Kim, Yong-Joo;Kim, Su-Chul;Ha, Jong-Kyou
    • Journal of Biosystems Engineering
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    • v.40 no.1
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    • pp.19-27
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    • 2015
  • Purpose: A system to measure the visibility of agricultural tractor operators was designed and evaluated according to ISO standards, and a blind area diagram around the tested tractor was created based on the manual method recommended by the National Institute for Occupational Safety and Health (NIOSH). Methods: A visibility measurement system was designed and evaluated based on the ISO 5006 and ISO 5721-1 standards. Two bulbs used to simulate the operator's eyes were mounted on a bar with a supporting frame. A wooden frame was used to determine the seat index point position. The 12-m visibility test circle was divided into six sectors of vision, and the test tractor was placed at the center of the circle. Artificial light was supplied in the darkened environment, and shadow or masking effects were measured manually around the 12-m circle. Results: When the bulbs were placed at the operator's eye level, front visibility was good; no masking was found in the "A" vision sector, but larger masking widths were found in the "B" and "C" vision sectors. Since the masking width exceeded 700 mm, additional tests, such as movement of the light sources to both sides of the operator's eye level, were performed. Less than six masking effects were found in the semi-circle of vision to the front, and more than one masking was found in the "B" and "C" visual fields. The minimum distance between the centers of two masking effects exceeded 2500 mm when measured as a chord on the semi-circle of vision. A blind area diagram was created to define the exact nature of the blind spots and mirror visibility. Conclusions: Visibility evaluation is an effective way to enable proper and safe operation for agricultural tractor operators. Inclusion of this visibility evaluation test in the general testing process might aid tractor manufacturers.

The Effects of Eye Lateralization on Transient Evoked Otoacoustic Emissions of Auditory Function (측방 눈 주시가 유발이음향방사 청각기능에 미치는 영향)

  • Joo, Seokhee
    • Journal of The Korean Society of Integrative Medicine
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    • v.7 no.4
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    • pp.131-140
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    • 2019
  • Purpose : The purpose of this study was to investigate the interrelationship between eye movement and auditory function through the effects of eye lateralization on transient evoked otoacoustic emissions of auditory function. Methods : 25 subjects with complete set of ears were used in this study, which composed of 12 males and 13 females with pure tone threshold of below 25 dB without otolaryngology were evaluated. Each of the patient has a visual acuity of greater than 1.0 after correction, and has no problems with eye disease, eye movement, and human parallel system. In a dark silent room, the subjects sat on a chair with their heads fixed on a headrest. The tests were performed by asking the patients to look at a fixed red light dot on a light bar in front of them. This light was directed to the front, right and left sides of the subject at an angle of 40 ° In the presence of the stimulus sound in the ipsilateral ear, the transient evoked otoacoustic emissions of the ipsilateral ear was measured at the straight, right and left fixation. In order to evaluate the transient evoked otoacoustic emissions through the efferent auditory pathway, the transient evoked otoacoustic emission values of the contralateral ear were measured at the straight, right and left fixation. These measurements were taken at frequencies of 1 kHz, 1.4 kHz, 2.0 kHz, 2.8 kHz and 4 kHz, respectively. Results : Transient evoked otoacoustic emissions caused by lateral movement of the eye showed significant changes at 1.4 KHz and 2 KHz of the afferent pathway of the ipsilateral ear. Also, significant changes were observed at 1.4 KHz and 4 KHz of the efferent pathway of the contralateral ear. Conclusion : These results indicated that there is a close relationship between eye movement and auditory cochlea. In the future, further studies considering more diverse subjects and age groups will be needed.

A Dynamic Set-up Technique for High Accuracy set-up of Continuous Hot Strip Finishing Mill (열간 마무리압연 설정의 정도향상을 위한 동적 설정법)

  • 문영훈;이준정
    • Transactions of Materials Processing
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    • v.5 no.3
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    • pp.232-238
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    • 1996
  • A dynamic mill set-up technique was developed to achieva a more precise roll gap set-up of the finishing mill stands for steel strip rolling. In the conventional mill set-up model the set-up values such as roll gap and roll speed are determined before the sheet bar reached the entry side of the finishing mill train and maintained constant until the strip top end passes through the last stand. In the way however a dynamic set-up logic that gives a way to adjust the roll gap value of the final mill stand for the strip ingoing from the ahead of the front stand was developed and attached to the existing set-up model. The roll gap modification is based on the analysis of the observation in the third stand of the finishing mill train. The dynamic set-up model was proved very effective for the more precise mill set-up and for operational stability in the hot strip finishing mill train.

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Development of a Computer Model for the Turning Maneuver Analysis of a Heavy Truck (대형 트럭의 선회 주행특성 해석을 위한 컴퓨터 모델의 개발)

  • 문일동;권혁조;오재윤
    • Transactions of the Korean Society of Automotive Engineers
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    • v.8 no.4
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    • pp.121-129
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    • 2000
  • this paper develops a computational model for the turning maneuver analysis of a cabover type heavy truck. The model having 42 degree-of-freedom is developed using ADAMS. Leaf springs used in the front and rear suspension systems are modeled by dividing it three links and joining them with joints. Force and displacement relationship showing nonlinear hysteric characteristics of the leaf spring is measured and modeled with an exponential function. A velocity and force relationship of a shock absorber is measured and modeled with a spline function. And a stabilizer bar is modeled using ADAMS beam element to consider a twisting and bending effect. To verify the developed model an actual vehicle test is performed in the double lane change course with 50kph and 60kph vehicle velocity. In the actual vehicle test lateral acceleration roll angle and yaw rate are measured, The tendency and peak-to-peak values of the actual vehicle test and simultion results are compared each other.

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A Astudy on Bandwidth Enhancement of a Ultrasonic Transducer with a Taper (Taper형 초음파 진동자의 대역폭 개선에 관한 연구)

  • 정봉규
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.35 no.3
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    • pp.312-322
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    • 1999
  • A ultrasonic transduce with a single acoustic matching layer has been designed as an attempt to increase the bandwidth of underwater transducer. The wideband resonance condition was accomplished by attaching a single matching layer on the front face of a ceramic resonator composed of a piezoelectric bar, a taper part and a head part. A modified Mason's model was used for the performance analysis and the design of transducers, and the constructed transducers were tested experimentally and numerically by changing the impedance and thickness of the matching layer in the water tank.The obtained results are summarized as follows:1. Measured resonant and antiresonant frequencies of the piezoelectric transducer with no matching layer in air were 24.7 kHz and 25.6 kHz, respectively. 2. Two resonant frequencies of the piezoelectric transducer with a single matching layer were 21.7 kHx and 26.9 kHz, respectively, in air and 21.4 kHz and 22.7 kHz, respectively, with a water load.3. Two distinct resonance peaks in the transmitting voltage response(TVR) of the developed transducer were observed at 22.0 kHz and 25.8 kHz, respectively, with center frequency of 24.0 kHz. The values of TVR at these frequencies were 130.1 dB re $1 \muPa$/V at 22.0 kHz and 128.5 dB re $1 \muPa$/V at 25.8 kHz, respectively.Reasonable agreement between the experimental results and the numerical values was achieved.

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A Study on the Effects of Hysteretic Characteristics of Leaf Springs on Handling of a Large-Sized Truck (판스프링의 이력특성이 대형트럭의 조종성능에 미치는 영향에 관한 연구)

  • 문일동;오재윤
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.5
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    • pp.157-164
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    • 2001
  • This paper performs static and dynamic tests of a multi-leaf spring and a tapered leaf spring to investigate their hysteretic characteristics. In the static test, trapezoidal input load is applied with 0.1Hz excitation frequency and with zero initial loading conditions. In the dynamic test, sinusoidal input load is applied with five excitation amplitudes and three excitation frequencies. In these tests, static and dynamic hysteretic characteristics of the multi-leaf spring and the tapered leaf spring are compared, and, the effects of excitation amplitudes and frequencies on dynamic spring rate are also shown. In this paper, actual vehicle tests are performed to study the effects of hysteretic characteristics of the large-sized truck's handling performance. The multi-leaf spring or the tapered leaf spring is used in the front suspension. The actual vehicle test is performed in a double lane change track with three velocities. Lateral acceleration, yaw rate and roll angle are measured using a gyro-meter located at the mass center of the cab. The test results showed that a large-sized truck with a tapered leaf spring needs to have an additional apparatus such as roll stabilizer bar to increase the roll stabilizer due to hysteretic characteristics.

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Estimation of CME 3-D parameters using a full ice-cream cone model

  • Na, Hyeonock;Moon, Yong-Jae
    • The Bulletin of The Korean Astronomical Society
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    • v.42 no.2
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    • pp.62.1-62.1
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    • 2017
  • In space weather forecast, it is important to determine three-dimensional properties of CMEs. Using 29 limb CMEs, we examine which cone type is close to a CME three-dimensional structure. We find that most CMEs have near full ice-cream cone structure which is a symmetrical circular cone combined with a hemisphere. We develop a full ice-cream cone model based on a new methodology that the full ice-cream cone consists of many flat cones with different heights and angular widths. By applying this model to 12 SOHO/LASCO halo CMEs, we find that 3D parameters from our method are similar to those from other stereoscopic methods (i.e., a triangulation method and a Graduated Cylindrical Shell model). In addition, we derive CME mean density (${\bar{\rho}_{CME}}={\frac{M_{total}}{V_{cone}}}$) based on the full ice-cream cone structure. For several limb events, we determine CME mass by applying the Solarsoft procedure (e.g., cme_mass.pro) to SOHO/LASCO C3 images. CME volumes are estimated from the full ice-cream cone structure. For the first time, we derive average CME densities as a function of CME height for several CMEs, which are well fitted to power-law functions. We will compare densities (front and average) of geoeffective CMEs and their corresponding ICME ones.

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