• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.1
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• pp.61-66
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• 2005

A theoretical analysis is developed for an annular-injection-type supersonic ejector having a second-throat downstream the ejector under the assumption that the Fabri choking is placed in mixing chamber. Non mixing theory is applied to formulate secondary flow pressure in the region between inlet of the mixing chamber and Fabri choking. To describe the shock standing at the inlet of the mixing chamber, two dimensional oblique shock relations are used and it is assumed that the shock affects only primary flow at Fabri choking plane. Physical constraint, which is that primary flow pressure and secondary flow pressure are same at Fabri choking plane, is added. In conclusion, it agrees well with experiments in case of small contracting angle of mixing chamber, under 4degrees.

• Journal of the Korean Chemical Society
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• v.61 no.6
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• pp.359-368
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• 2017

The purpose of this study was to examine levels of claims and evidence produced by 53 secondary science teachers. Levels of claim and evidence produced by the teachers in this study are various depending on themes. For a problem integrated several science concepts, there were many teachers who produced claims and evidence in a level of 1 or 2. The participant teachers presented claims and evidence in a level of 3 or 4 for a problem related to chemistry concepts presented in chemistry textbooks. Professional development programs should be provided for science teachers to help them develop understanding of argument structure and construct high quality of claims and evidence.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.52-57
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• 2008

Most of the electrons emitted from the filament, are captured by the anode. The portion of the electron current that leaves the gun through the hole in the anode is called the beam current. Electron beam probe is called the focused beam on the specimen. Because of the lenes and aperture, the probe current becomes smaller than the beam current. It generate various signals(backscattered electron, secondary electron) in an interaction with the specimen atoms. Backscattered electron provide an useful signal for composition and local specimen surface inclination. Secondary electron is used far the formation of surface imagination. The steady electron beam probe is very important for the imagination formation and the brightness. In this paper, we show the results of developed elements that create electron beam probe and the measured beam probe in various acceleration voltages by Faraday cup. These data are used to analysis and improve the performance of the system in the development.

• Journal of the Korea Safety Management & Science
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• v.20 no.3
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• pp.21-26
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• 2018

This paper describes result of a study on safety against a fire of charging cable for mobile phone for vehicle. Combustion on the USB cable in the car was happened while driving. Gas coming from the burning USB cable could be a reason which can make a secondary car accident since the driver also can be embarrassed while driving. In order to prevent a secondary car accident connected on the road, to research a reason why USB cable can emit gas and be burned in charging. We did simulation test with abnormal fault condition for the electronic component on the board in the USB cable. So we get the result from abnormal fault condition simulation test, for instance, shorted test for output terminal of 8 pin switch, shorted test for chip resistor after thermal aging in the condition $25^{\circ}C$, 93 % RH during 48 hours. To analysis the result of all test, Combustion on the USB cable was not the 8 pin but other electrical component such as a chip resistor. Therefore we guess that the reason for USB cable combustion in charging in a car was not 8 pin and a LED but another defective component.

• Journal of Korean Biological Nursing Science
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• v.21 no.4
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• pp.275-282
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• 2019

Purpose: This study aimed to identify the differences in blood pressure among adults in the community according to age and time of the blood pressure measurement. Methods: This was a secondary analysis study, using data from a 2015 community health survey, conducted by the Korea Centers for Disease Control and Prevention. The data of three-time-measured blood pressure were collected from 337 subjects, 25, 35, 45, 55, 65, 75 years old, which are median ages by each age group. Results: The primary systolic pressure was significantly higher than the secondary systolic pressure (t= 3.46, p= .001) and the tertiary systolic pressure (t= 4.83, p= .001). The secondary systolic pressure was higher than the tertiary measurement (t= 2.05, p= .041). There was no significant difference between the three-time-measured values for diastolic pressure. There was a significant interaction between measurement times and age in the systoic blood pressure readings (F= 1.95, p= .036). However, there was no significant interaction between measurement times and age in the diastolic blood pressure readings (F= 1.03, p= .418). Conclusion: The findings suggest that attention must be paid to the use of blood pressure values in studies or one-time-measured clinical blood pressure values. In particular, the differences in systolic pressure readings taken at different times in the older age groups were significant. Therefore, it is more important to carefully assess blood pressure in adults over the age of 45 compared to other age groups.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1296-1308
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• 2014

This paper presents a new zero voltage switching (ZVS) converter for medium power and high input voltage applications. Three three-level pulse-width modulation (PWM) circuits with the same power switches are adopted to clamp the voltage stress of MOSFETs at $V_{in}/2$ and to achieve load current sharing. Thus, the current stresses and power ratings of transformers and power semiconductors at the secondary side are reduced. The resonant inductance and resonant capacitance are resonant at the transition interval such that active switches are turned on at ZVS within a wide range of input voltage and load condition. The series-connected transformers are adopted in each three-level circuit. Each transformer can work as an inductor to smooth the output current or a transformer to achieve the electric isolation and power transfer. Thus, no output inductor is needed at the secondary side. Three center-tapped rectifiers connected in parallel are used at the secondary side to achieve load current sharing. Compared with the conventional parallel three-level converters, the proposed converter has less switch counts. Finally, experiments based on a 1.44kW prototype are provided to verify the operation principle of proposed converter.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.490-500
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• 1996

The conventional method to deal with current transformer (CT) Saturation is over dimensioning of the core so that CTs can carry up to 20 times the rated current without exceeding 10% ratio correction. However, this not only reduces the sensitivity of relays as some errors may still be present in the secondary current when a severe fault occurs, but also increases the CT size. This paper presents an algorithm for compensating the distorted secondary current of iron-cored CTs under CT saturation using the magnetization (flux-current : .lambda.-i) curve and its performance is examined for fault currents encountered on a typical 345[kV] Korean transmission system, under a variety of different system and fault conditions. In addition, the results of hardware implementation of the algorithm using a TMS320C10 digital signal processor are also presented. The proposed algorithm can improve the sensitivity of relays to low level internal faults, maximize the stability of relays for external faults, and reduce the required CT core cross-section significantly. (author). refs., figs.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.213-221
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• 2013

We present the first BVRI CCD photometric observations of V345 Cas made on 22 nights during the observing seasons in 2007-2008. Our light curves, resembling those of EB-type binary stars, are analyzed with the 2003 version of the Wilson-Devinney binary code. The photometric study shows that V345 Cas is a typical semi-detached binary system with the primary star being about ${\Delta}T$ = 2400 K hotter, two times more massive, but only 17% larger than the secondary star being filled with it's Roche-lobe. The orbit has a relatively large inclination of about $88^{\circ}$. A cool spot on the secondary component is modeled to explain a small light curve asymmetry. Absolute dimensions and related radiometric parameters of the eclipsing pair are calculated and their evolutionary states are discussed with the HR diagrams of mass-radius and temperature-luminosity. A period analysis of all available times of minima, including our measurements, indicates that the orbital period may vary in a cyclical way, unfortunately the secondary period for the variation can not be uniquely determined because of lack of present timing data.

• Journal of the Korean Magnetic Resonance Society
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• v.21 no.2
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• pp.50-54
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• 2017

Cupin-superfamily proteins represent the most functionally diverse groups of proteins and include a huge number of functionally uncharacterized proteins. Recently, YaiE, a cupin protein from Escherichia coli has been suggested to be involved in a novel activity of pyrimidine/purine nucleoside phosphorylase (PPNP). In the present study, we achieved a complete backbone NMR assignments of YaiE, by a series of heteronuclear multidimensional NMR experiments on its [$^{13}C/^{15}N$]-enriched sample. Subsequently, secondary structure analysis using the assigned chemical shift values identified 10 obvious ${\beta}-strands$ and a tentative $3_{10}-helix$. Taken all together, the results constitute the first structural characterization of a putative PPNP cupin protein.

• International Journal of Highway Engineering
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• v.15 no.1
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• pp.95-102
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• 2013

PURPOSES: The existing method evaluating the existence of the hollows in concrete pavement does not consider the stiffness of pavement. In addition, the method uses unreasonable logic judging the hollow existence by the deflection caused by zero loading. In this study, the deflection of slab corner due to heavy weight deflectometer (HWD) was measured in concrete pavement sections where underground structures are located causing the hollows around them. METHODS: The modulus of subgrade reaction obtained by comparing the actual deflection of slab to the result of finite element analysis was calibrated into the composite modulus of subgrade reaction. The radius of relative stiffness was calculated, and the relationship between the ratio of HWD load to the radius of relative stiffness and the slab deflection was expressed as the curve of secondary degree. RESULTS: The trends of the model coefficients showing width and maximum value of the curve of secondary degree were analyzed by categorizing the pavement sections into three groups : hollows exist, additional investigation is necessary, and hollows do not exist. CONCLUSIONS: The results analyzed by the method developed in this study was compared to the results analyzed by existing method. The model developed in this study will be verified by analyzing the data obtained in other sections with different pavement structure and materials.