• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1084-1087
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• 2017

When a liquid rocket engine is started the oxidizer and fuel must be flowed into combustion chamber and gas generator with time differences. The wrong time difference between propellants or malfunction of ignition device can occur the explosion of combustion chamber due to detonation by energized premixed-propellants. Therefore it is important to observe the transient characteristic of propellants or to measure the inflow time of propellants into combustion chamber and gas generator. The measurement of static pressure is not enough to observe the propellants inflow time into combustion chamber and gas generator. By measuring dynamic pressure of main flow passage of propellants the accurate propellants inflow time could be investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.10
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• pp.864-869
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• 2009

The measurement of contact wire uplift in electric railways is one of the most important test parameters to accepting the maximum permitted speed of new electric vehicles and pantographs. The contact wire uplift can be measured over short periods when the pantograph passes monitoring stations. In this paper, a high-speed image measurement system and its image processing method are being developed to evaluate dynamic uplift of overhead contact wires caused by pantograph contact forces of Korea Tilting Train eXpress (TTX) and Korea Train eXpress (KTX). The image measurement system was implemented utilizing a high-speed CMOS (Complementary Metal Oxide Semiconductor) camera and gigabit ethernet LAN. Unlike previous systems, the uplift measurement system using high speed camera is installed on the side of the rail, making maintenance convenient. On-field verification of the uplift measurement system for overhead contact wire using high speed camera was conducted by measuring uplift of the TTX followed by operation speeds at the Honam conventional line and high-speed railway line. The proposed high-speed image measurement system to evaluate dynamic uplift of overhead contact wires shows promising on-field applications for high speed trains such as KTX and TTX.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.12
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• pp.104-109
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• 2001

With the increase of storage density and data transfer rates in optical disk drive, mechanical issues, mainly noise and vibration, become critical. Rubber materials are extensively used in various machine design application, mainly for vibration/shock/noise control devices. However, there are still a lot of difficulties in the use of designing the rubber components with complex shape and under pre-deformed state. It was demonstrated in that the variation of rubber component stiffness with the pre-deformed state were calculated by the finite element method and the reliability of numerical results were checked by compared with the measuring the deflection values. This paper presents a efficient design method of rubber mounts for anti-vibration of an optical disk thrive. With an empirical equation to estimate elastic modulus from hardness, and dynamic characteristics of rubber material of a cylindrical shape, this method is capable of predicting the dynamic characteristics of rubber components at design stage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.375-382
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• 2010

This paper presents the extraction of natural frequencies and mode shapes of a cable-stayed bridge using data acquired from GNSS. The response signals of 6 GNSS measuring points installed at the Seohae cable-stayed bridge are used for analysis of dynamic characteristics. Using normalization process and a third order Butterworth filter for the measured signals, the related pass band's signals have been isolated. Then, the acceleration data by double differentiation for these signals are obtained. Total five natural frequencies have been extracted by the fast Fourier transform and compared to the results of different studies. For the acceleration obtained from GNSS signals, the mode shapes of the bridge have been successfully extracted by TDD technique.

• The Journal of the Korea Contents Association
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• v.19 no.4
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• pp.368-380
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• 2019

This study proposes a method to evaluate the performance of a detector by analyzing the dynamic step wedge and histogram according to the change of the tube voltage and sensitivity when using the Automatic Exposure Control (AEC). The performance of a detector was evaluated by measuring X-ray quality, Entrance Surface Dose (ESD), tube current, dynamic range corresponding to detector sensitivities of S200, S400, S800, S1000 per tube voltage of 60, 70, 81, 90 kVp. As a results, all of the qualities satisfied the acceptance criteria, and the Entrance Surface Dose and tube current were decreased stage by stage as sensitivity was set higher. In the dynamic step wedge, the observable dynamic range has also increased as tube voltage became higher. The histogram showed the quantization separation phenomena as the tube voltage was set higher. The higher the sensitivity, the more the underflow and overflow occurred in which the amount of information on both ends of the histogram was lost. In conclusion, the deterioration in the performance of the detector was found to be insufficient to realize the change of the tube voltage and sensitivity when using the Automatic Exposure Control, and it is useful to use dynamic step wedge and histogram in evaluating detector performance evaluation.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1320-1322
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• 1994

Photoisomerization characteristics of 4-octyl-4'-(5-carboxy-pentamethyleneoxy) azobenzene molecules (8A5H) were attained by measurement of absorbtion spectra. 8A5H in chroloform($6.0{\times}10^{-5}[M/l]$) shows trans to cis and cis to trans isomerization by irradiation of lights of 360[nm] and 450[nm] wavelength. From LB monolayer films of 8A5H, also the cis/trans photoisomerization was obtained and it has reversibility and memory characteristics. We are now trying to detect these properties of 8A5H electrically. On this paper, we investigated the structural changes of monolayer on the water surface by measuring the displacement current as a preliminary experiment. The measuring system was constructed at home-made Kuhn type LB(Langmuir-Blodgett) deposition apparatus. 8A5H solution was spreaded at the air-water interface and the currents induced by the dynamic behavior of molecules were measured when the molecules were pressed by barrier. The reversibility of displacement currents by compression and expansion was obtained from 8A5H molecules, which shows the compressed molecules have a tendency to disperse after the compression. From this experiment, we conclude that the behavior of molecules on water surface can be monitored electrically by using this current measuring method, and this method can also be applied to detect the photoisomerization of monolayers on water surface.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.713-722
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• 2000

This study analysed error of measurement and reproducibility for particle size analysis by the laser diffraction spectrometer. Laser diffraction spectrometers has become a very important method of particle size analysis. This measuring method has the advantage of simple operation, good reproducibility and rapid analysis. A feeding and dispersing system have been developed, which allows mass throughputs between 0.1~23 g/min in flowing air and 1.4~35% in flowing liquid. It has been used as a feeder unit for wet and dry particle size analysis from diffraction patterns. Relevant parameters, such as particle shape, particle size, dispersion, flow rate, concentration were analysed for measuring error. And system parameters of instruments for measurement of dynamic processes, eg, measuring time, focal plane, injection pressure drop and dispersion effect by the ultrasonic and mixing of preliminary treatment, were also discussed.

• The Journal of Fisheries Business Administration
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• v.46 no.3
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• pp.103-118
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• 2015

The purpose of this paper is to discuss possibilities of applying growth curve models, such as Logistic, Log-Logistic, Log-Normal, Gompertz and Weibull, to three specific technology areas of Fishery Science and Technology in the process of measuring their technology level between Korea and countries with the state-of-the art level. Technology areas of hazard control of organism, environment restoration, and fish cluster detect were selected for this study. Expert panel survey was conducted to construct relevant panel data for years of 2013, 2016, and a future time of approaching the theoretical maximum technology level. The size of data was 70, 70 and 40 respectively. First finding is that estimation of shape and location parameters of each model was statistically significant, and lack-of-fit test using estimated parameters was statistically rejected for each model, meaning all models were good enough to apply for measuring technology levels. Second, three models other than Pearl and Gompertz seemed very appropriate to apply despite the fact that previous case studies have used only Gompertz and Pearl. This study suggests that Weibull model would be a very valid candidate for the purpose. Third, fish cluster detect technology level is relatively higher for both Korea and a country with the state-of-the-art among three areas as of 2013. However, all three areas seem to be approaching their limits(highest technology level point) until 2020 for countries with the state-of-the-art. This implies that Korea might have to speed up her research activities in order to catch up them prior to 2020. Final suggestion is that future study may better apply various and more appropriate models respectively considering each technology characteristics and other factors.

• Progress in Medical Physics
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• v.17 no.2
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• pp.114-122
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• 2006

The two commonly used methods in delivering intensity modulated radiation therapy (IMRT) plan are the dynamic (sliding window) and static (stop and shoot) mode. In this study, the two IMRI delivery techniques are compared by measuring point dose and dose distributions. Using treatment planning system, clinical target volume (CTV) was created as a sphere with various diameter (3 cm, 7 cm, 12 cm). Two IMRT plans were peformed to deliver 200 cGy to the CTV in dynamic and static mode. The two plans were delivered on a phantom and central point dose and dose distributions were measured. The central point dose differences between static and dynamic IMRT delivery were 0.2%, 0.2% and 0.4% when the diameter of CTV was 3 cm, 7 cm, and 12 cm, respectively. The differences In volume receiving 90% of the proscribed dose were 2.7%, 2.2%, and 2.9% for the diameter of CTV was 3 cm, 7 cm, and 12 cm, respectively. For lung cancer patients, the differences in central point dose were 0.2%, 0.2%, and 0.4% when the volume of CTV was 35.5 cc, 296.8 cc, and 903.5 cc, respectively. The differences in volume receiving 90% of the prescribed dose were 2.7%, 4.8%, and 9.1% when the volume of CTV was 35.5 cc, 296.8 cc, and 903.5 cc, respectively. In conclusion, it was possible to deliver IMRT plans using dynamic mode of MLC operation although the loaves are In motion during radiation delivery.

• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.351-362
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• 1999

Damage detection methods which utilize the change in dynamic characteristics are very hard to apply to large civil structures since local damage hardly affects global dynamic characteristics. But, if there is a very important and critical member and we focus only on the local behavior of it, it would be possible to detect damage from the change in local dynamic characteristics, such as natural frequencies and mode shapes .In this study, the cable anchorage part of a cable-stayed bridge under construction is modeled and analyzed by commercial finite element program, ABAQUS. It has both welding and bolting connections with a cable and a stiffening plate, and has a possible high stress concentration portions in it. Several damage scenarios such as crack through the welding or crack through the bolting connection are examined. The result shows that the local natural frequencies of the damaged member decrease up to 16% compared with that of the undamaged member. It is concluded that there is quite a high feasibility that the damage of the cable anchorage can be detected by measuring local dynamic characteristics.