• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.05a
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• pp.445-455
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• 2003

Relatively high carbon-14 emissions, which occurred at PHWR Plant during 1998 and 1999, made the site staff to implement several operational improvements: 1) the frequency and volume of the moderator cover gas purging were reduced through increased $O_2$ additions to the cover gas, 2) the 'old' resin columns were not used during re-start of the reactor from outage, 3) efforts were made to minimize air ingress, 4) the maximum service time of moderator ion-exchange columns were restricted to about 80 days. Through the improvements, the carbon-14 emission from each PHWR reactor returned to the normal levels during the remainder of 1999 and during 2000. We carried out a special surveillance at W-1 and W-3 from September 2001 to August 2002 to properly evaluate ways to optimize the use of moderator ion exchange resins from a C-14 perspective. The surveillance showed that only data that provided an operational marker for deciding when to remove the IX-resin column is an observed increase in the C-14 stack emissions themselves. Also, it is shown that any increase over the rate of 0.4 Ci $month^{-1}$ for two consecutive weeks may be the indication for an ion-exchange resin column change, especially if the IX-resin column has been in service for more than 80 days.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.47-48
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• 2016

Recently over the world, many studies on the methods for using some binding materials which replace cement, such as FA, etc., for reducing CO₂. However, it has sometimes been reported that some cement products without passing through the refining process at some of FA refineries in Korea are released for sales for some reasons of shortening the production time and the cost reduction, etc., so it exerts a bad effect on the quality of many construction structures. Therefore, in this study, it was intended to conduct an experimental review on the effects of using an extreme quality of FA which is distributable domestically on the engineering characteristics of high-strength mortar. As a result, it was judged that it is beneficial for the engineering characteristics of concrete, such as, flow property, air volume and strength, etc, to use some refined FA.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2791-2796
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• 2010

In the present study, we constructed a membrane inlet assembly for selective permeation of volatile airborne organic compounds for subsequent analysis by time-of-flight mass spectrometry. The time-dependent diffusion of analytes through a $75\;{\mu}m$ thick polydimethylsiloxane membrane was measured by monitoring the ion signal after a step change in the sample concentration. The results fit well to a non-steady-state permeation equation. The diffusion coefficient, response time, and sensitivity were determined experimentally for a range of polar (halogenated) and nonpolar (aromatic) compounds. We found that the response times for several volatile organic compounds were greatly influenced by the alkyl chain length as well as the size of the substituted halogen atoms. The detection limits for benzene, ethylbenzene, and 2-propanol were 0.2 ppm, 0.1 ppm, and 3.0 ppm by volume, respectively, with a linear dynamic range greater than three orders of magnitude. These results indicate that the membrane inlet/time-of-flight mass spectrometry technique will be useful for a wide range of applications, particularly for in situ environmental monitoring.

• Journal of computational fluids engineering
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• v.14 no.2
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• pp.32-38
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• 2009

In the present study, a numerical simulation for the diffusion of hydrogen jet in a enclosure was performed to aid the leakage test of the hydrogen for the safety of the hydrogen vehicle. The temporal and spatial distributions of the hydrogen concentration in the test chamber are predicted from the present numerical analyses. Flammable region of 4-74% and explosive region of 18-59% hydrogen by volume was identified from the present results. Factors influencing the diffusion of the hydrogen jet were examined to evaluate the effectiveness of forced ventilation for relieving the accumulation of the leaked hydrogen gas in the chamber, which include location of open windows, size of leakage nozzle, and leakage rate among others. The distribution of the concentration of the leaked hydrogen for various cases can be used as a database in various applications for the hydrogen safety.

• Journal of Korean Elementary Science Education
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• v.31 no.1
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• pp.13-24
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• 2012

This purpose of this study was to analyze the characteristics of elementary students' argumentation in science problem solving process. For this study, the two argumentation topics were developed on the basis of Williams and Colomb's argumentation model. The topics of argumentation were the weight of the air and the change of volume according to state of water. The participants of this study were 6th grade students (n=51). Data were analyzed by Williams and Colomb's argumentation model and Kienpointner's argumentation style. The results of this study were as follows: In the argumentation model, most of students had the factors of claim, reason, evidence/data in their statements. But low-achievement students had difficulty in warrant and acknowledge & response. In argumentation style, the frequency of the cause-effect and explanation of example style were higher than other argumentation styles. Some implications were suggested, such as understanding the characteristics of elementary students' argumentation activities and need of educational programs including scientific argumentation.

• Nuclear Engineering and Technology
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• v.50 no.3
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• pp.439-445
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• 2018

Experimental measurements of the response of $BF_3$ detector to a 3 Ci Am-Be neutron source for three different reflecting materials, i.e., aluminum, wood, and Perspex of varying thicknesses have been carried out. The varying contribution of wall effect to the response due to change in active volume of the detector has also been determined experimentally. Then, a Monte Carlo code has been developed for the calculation of the neutron response function of the $BF_3$ detector using source biasing and importance sampling. This code simulates the $BF_3$ detector response exposed to the neutron field in a three-dimensional source, detector, and reflecting medium configurations. The results of simulation have been compared with the corresponding experimental measurements and are found to be in good agreement. The experimental neutron albedo measurements for various values of Perspex thickness show saturating behavior, and results agree very well with the data obtained by Monte Carlo simulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.6
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• pp.53-61
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• 2022

The estimation method of combustion efficiency has been introduced by using closed bomb test(CBT). The Noble-Abel equation of state was applied to consider the real gas effects to take account of high operation pressure about a couple of 100 atm. of CBT. The heat loss through the CBT wall was considered. The volume change of grain was calculated by applying form functions, which estimated combustion efficiency of 8 different gain shapes. The combustion estimation method proposed in this study was fairly validated by the comparision with the pressure-time history data of the CBT experiments. The effects of both grain shape and propellant loading density were analyzed.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.17 no.1
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• pp.43-48
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• 2006

Background and Objectives: Countertenors who can produce higher vocal pitch like female classical singer's voice and use both modal and falsetto register. This study was conducted to study phonatory characteristics between modal and falsetto register of the countertenor. Materials and Methods: A male countertenor who had 8 years of experience was examined using a videostroboscopy and his voice was analyzed using aerodynamic measures; fundamental frequency(F0), Mean air flow rate(MFR), intensity(SLP), subglottal air pressure(Psub) with phonatory function analyzer(Nagashima) and acoustic measures; jitter, shimmer, HNR, closed quotient(CQ) using a Electro-glottography(EGG) of Lx. Speech Studio(Laryngoscope, Ltd, UK) and voice range profile of CSL(Kay elemetrics). Results: In the stroboscopy finding, the longitudinal length of vocal folds was increased at the falsetto register and the upper margin of vocal folds vibrated with incomplete closure of true vocal folds. In aerodynamic analysis, intensity was same at the modal and falsetto register. However, MFR, Psub, MPT were higher at the falsetto register. In the electroglottographic analysis, closed quotient(CQ) at the modal register was high and also much higher at the high-pitch falsetto than at the loud falsetto. In the VRP, intensity was similar though F0 was different between modal and falsetto register. Conclusion: It implied that countertenor could produce powerful voice quality by increasing of respiratory pressure and respiratory volume though glottal closure was incomplete. In addition, no change of EGG waveform, similar voice range with alto was observed.

• The Journal of the Korean dental association
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• v.49 no.4
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• pp.219-226
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• 2011

Snoring and obstructive sleep apnea (OSA) are common sleep disordered breathing conditions. Habitual snoring is caused by a vibration of soft tissue of upper airway while breath in sleeping, and obstructive sleep apnea is caused by the repeated obstructions of airflow for a sleeping, specially airflow of pharynx. Researchers have shown that snoring is the most important symptom connected with the obstructive sleep apnea syndrome The treatment is directed toward improving the air flow by various surgical and nonsurgical methods. The current surgical procedures used are uvulopalatopharyngoplasty(UPPP), orthognathic surgery, nasal cavity surgery. Among the nonsurgical methods there are nasal continuous positive air pressure(CPAP), pharmacologic therapy. weight loss in obese patient, oral appliance(sleep splint). Sleep splint brings the mandible forward in order to increase upper airway volume and prevents total upper airway collapse during sleep. However, the precise mechanism of action is not yet completely understood, especially aerodynamic factor. The aim of this study evaluated the effect of conservative treatment of snoring and OSAS by sleep splint through measured aerodynamic change by an aerophone II. We measured a airflow, sound pressure level, duration, mean power from overall airflow by aerophone II mask. The results indicated that on a positive correlation between a decrease in maximum airflow rate and a decrease in maximum sound pressure level, on a negative correlation between a decrease in maximum airflow rate and a increase in duration.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1090-1097
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• 1998

Lidocaine compounds have widely been used as local anesthetics. Regarding the molecular mechanism for anesthesia by lidocaine, it is proposed that lidocaine molecules penetrate to the hydrophobic region of cell membrane and expand the membrane volume, producing a change in protein conformation that blocks sodium permeability or lidocaine molecules directly adsorb into lidocaine receptor in the protein channel without expanding the cell membrane. But these proposals have never been proven experimentally. In this study, the expansion of cell membrane by lidocaine compounds was investigated by employing lipid monolayer at the air/water interface as the mimetic system of cell membrane. It was found that oil-soluble lidocaine contracted the area/molecule of lipid in the monolayer of phosphatidyl choline, sphingomyelin, DS-PL95E and lipoid, but expanded the monolayer of phosphatidyl ethanolamine only in a certain range of mixing ratios. On the contrary, water-soluble lidocaine-HCl salt expanded the monolayers of all lipids used in this study.