• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.12
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• pp.695-702
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• 2009

Dynamic behavior of Libr-water absorption system using low-temperature hot water was investigated numerically. Thermal-hydraulic model of single-effect/double-lift 100 RT chiller was developed by applying transient conservation equations of total mass, Libr mass, energy and momentum to each component. Transient variations of system properties and transport variables were analysed during start-up operation. Numerical analysis were performed to quantify the effects of bulk concentration and part-load operation on the system performance in terms of cooling capacity, coefficient of performance, and time constant of system. For an absorption chiller considered in the present study, optimum bulk concentration was found to exist, which resulted in the minimum time constant with stable cooling capacity. COP and time constant increased as the load decreased down to 40%, below which the time constant increased abruptly and COP decreased as the load decreased further.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1465-1478
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• 2015

The effect of cutting off fibers on transient load in a polymeric matrix composite lamina was studied in this paper. The behavior of fibers was considered to be linear elastic and the matrix behavior was considered to be linear viscoelastic. To model the viscoelastic behavior of matrix, a three parameter solid model was employed. To conduct this research, finite difference method was used. The governing equations were obtained using Shear-lag theory and were solved using boundary and initial conditions before and after the development of break. Using finite difference method, the governing integro-differential equations were developed and normal stress in the fibers is obtained. Particular attention is paid the dynamic overshoot resulting when the fibers are suddenly broken. Results show that considering viscoelastic properties of matrix causes a decrease in dynamic load concentration factor and an increase in static load concentration factor. Also with increases the number of broken fibers, trend of increasing load concentration factor decreases gradually. Furthermore, the overshoot of load in fibers adjacent to the break in a polymeric matrix with high transient time is lower than a matrix with lower transient time, but the load concentration factor in the matrix with high transient time is lower.

• Journal of ILASS-Korea
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• v.26 no.4
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• pp.212-218
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• 2021

The present study aims to develop the Surface Plasmon Resonance (SPR) imaging system facilitating the real-time measurement of the concentration of evaporating binary mixture droplet (BMD). We introduce the theoretical background of the SPR imaging technique and its methodology for concentration measurement. The SPR imaging system established in the present study consists of a LED light source, a polarizer, a lens, and a band pass filter for the collimated light of a 589 nm wavelength, and a CCD camera. Based on the Fresnel multiple-layer reflection theory, SPR imaging can capture the change of refractive index of evaporating BMD. For example, the present study exhibits the visualization process of ethylene glycol (EG)-water (W) BMD and measures real-time concentration change. Since the water component is more volatile than the ethylene glycol component, the refractive index of EG-W BMD varies with its mixture composition during BMD evaporation. We successfully measured the ethylene glycol concentration within the evaporating BMD by using SPR imaging.

• The Korean Journal of Physiology
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• v.9 no.2
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• pp.33-39
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• 1975

Changes of urinary aldosterone excretion, concurrent sodium and potassium excretion following furosemide administration were studied in normotensive young Korean with high sodium intake, moderate sodium restriction and marked sodium depletion. After intravenous injection of furosemd 40mg, plasma and urine samples were collected at every thirty minutes for two hours. Plasma-and urinary aldosterone, electrolyte concentration and urine flow rate were measured by means of radioimmunoassay or flamephotometry. Relations of urinary aldosterone to concurrent sodium or potassium/sodium ratio, and of urinary aldosterone to concurrent plasma aldosterone activity were studied. Following were the results: 1. Furosemide administration resulted in a increased urinary aldosterone concentration and unchanged or somewhat decreased sodium concentration in course of time after the injection. 2. Urinary potassium concentration showed initial decrease and subsequent increase in course of time after furosemide administration and it resulted in a gradual increase in urinary potassium/sodium ratio. 3. Studying the relations between urinary aldosterone excretion and potassium/sodium excretion ratio, or sodium excretion were meaningless because of the urinary flow rate after the injection was decreased with time course. 4. Furosemide administration showed a good relationship of urinary aldosterone concentration to concurrent potassium/sodium ratio rather than concurrent sodium concentration in subjects with sodium restriction, but no meaningful relationship was detected in subjects with high sodium intake because increasing rate of the ratio was not so wide. 5. Furosemide also resulted a reasonable relation of plasma aldosterone concentration to concurrent urinary aldosterone concentration especially during low sodium intake. 6. Above results suggested that relation of urinary aldosterone concentration to K/Na ratio following furosemide administration during sodium restriction is significant and has a benefit to reduce the variation induced by kalemic change showing in the diragram for daily aldosterone to sodium excretion.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.1
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• pp.3-5
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• 2023

Objective: This study introduces exposure concentrations of time-weighted average standard (TWA) evaluation and short-time exposure standard (STEL) evaluation for trichloroethylene in the cleaning process. Methods: Trichloroethylene measurement was conducted according to the KOSHA Guide (A-24-2019) method. It was carried out twice. Results: As a result of the first measurement, TWA concentration exceeded 4 times the exposure standard and STEL concentration exceeded 16 times, but the inaccuracy and breakthrough of the collection time could not be considered, so the second measurement was conducted. The second measurement result was lower than the first measurement result, but exceeded the exposure standards (TWA, STEL). Conclusions: We were able to confirm that the exposure level of workers in the cleaning process using trichloroethylene exceeded the exposure standard. And it is also considered necessary to grasp the approximate concentration using a detector tube in the preliminary survey.

• Environmental Analysis Health and Toxicology
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• v.11 no.3_4
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• pp.17-22
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• 1996

To elucidate the fatal blood concentration of paraquat (Gramoxone), a contact herbicide, we investigated blood concentration of paraquat in 91 cases of paraquat intoxication. The blood paraquat concentration of 91 cases due to ingestion of paraquat was 0.9 $\mu$g/ml-1023.5$\mu$g/ml and has been subdivided according to survival time. 48 of 91 cases were identified survival time. In 34 of 48 cases died within a day after ingestion of paraquat, blood paraquat concentration was ranged from 2.3-636.61$\mu$g/ml, and in 12 of 48 cases died 1-4 days after ingestion of paraquat, blood paraquat concentration was ranged from 0.9- 25.1 $\mu$g/ml.

• Journal of Korean Society for Atmospheric Environment
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• v.10 no.2
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• pp.130-136
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• 1994

Concentration of volatile particulate nitrate(NH$_4$NO$_3$) in TSP in ambient air was determined from Feb. to Oct 1993. Sampling was carried out using a two-stage Andersen air sampler at the top of a five-story building located at Kon- Kuk University in Seoul Concentration of NH$_4$NO$_3$ in TSP was measured by Pyrolysis of sample filters at 16$0^{\circ}C$ for 1hr. Concentration of NH$_4$NO$_3$ was higher in winter time compared with that in summer time. Also, concentration of NH$_4$NO$_3$ was higher in fine particles compared with that in coarse particle. The range of NH$_4$NO$_3$concentration was between 2.99 and 9.86 $\mu\textrm{g}$/㎥. Weight fraction of NH$_4$NO$_3$ in total particulate nitrate was 31.1~59.5%, and weight fraction of NH$_4$NO$_3$ in YSP was 2.1~11.2%.

• Korean Journal of Food Science and Technology
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• v.22 no.1
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• pp.99-104
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• 1990

The effects of concentrations of sulfur dioxide (0.16-0.20%) and steeping times (25-50hr) at $52^{\circ}C$ on the changes in pH of steep water and weight and volume of corn and starch properties were investigated. The pH of steep water increased and remained constant after steeping time of 20 hours. The degree of weight or volume gain decreased as the concentration of sulfur dioxide increased. The protein content of starch increased as the concentration of sulfur dioxide increased. Water·binding capacity of starch showed the highest value at the steeping time of 35 hours. Swell ins power and solubility decreased as cocentration of sulfur dioxide and steeping time increased. The initial pasting temperature and peak viscosity were increased and decreased, respectively, as the concentration of sulfur dioxide increased. At the same concentration of sulfur dioxide, the peak viscosity was increased and then decreased. Viscosity of starch in sodium hydroxide solution tended to decrease as the concentration of sulfur dioxide and sleeping time increased. The gel volume of starch in 3M KSCN solution was not affected by concentration of sulfur dioxide and steeping time.

• Journal of Fashion Business
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• v.15 no.2
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• pp.120-130
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• 2011

This study is a fundamental research on the natural Polygoum tinctoria dyeing to quantify scientifically and satisfy the reproducibility of the procedure. By dyeing the silk fabrics, the establishment of accurate dyeing method was sought. At the same time, we tried to modify the traditional dyeing methods, broaden the methods, and apply the dyeing variously. The dyeability and color changes were compared and reviewed according to the changes in the reducing temperature, reducing time, concentration of the reducing agent, dyeing temperature, dyeing time, concentration of NaOH, and the number of repetition of dyeing. The optimum conditions in the dyeing procedure are as follows: Added concentration of the reducing agent is 3g/${\ell}$. Reducing temperature is $60^{\circ}C$. Reducing time is 40minutes. Dyeing temperature is $30^{\circ}C$. Added concentration of NaOH is 1g/${\ell}$. Dyeing time is 30minutes.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.3
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• pp.521-526
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• 2023

Due to the recent pandemic, most educational systems are being conducted through online classes. Unlike face-to-face classes, it is even more difficult for learners to maintain concentration, and evaluating the learners' attitude toward the class is also challenging. In this paper, we proposed a real-time concentration-based review support system for learners in real-time video lectures that can be used in online classes. This system measured the learner's face, pupils, and user activity in real-time using the equipment used in the existing video system, and delivers real-time concentration measurement values to the instructor in various forms. At the same time, if the concentration measurement value falls below a certain level, the system alerted the learner and records the timestamp of the lecture. By using this system, instructors can evaluate the learners' participation in the class in real-time and help to improve their class abilities.