• Macromolecular Research
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• v.17 no.3
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• pp.163-167
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• 2009

This study presents a microfluidic method for the production of monodisperse poly(ethylene glycol) (PEG) microspheres using continuous droplet formation and in situ photopolymerization in microfluidic devices. We investigated the flow patterns for the stable formation of droplets using capillary number and the flow rate of the hexade-cane phase. Under the stable region, the resulting microspheres showed narrow size distribution having a coefficient of variation (CV) of below 1.8%. The size of microspheres ($45{\sim}95{\mu}m$) could be easily controlled by changing the interfacial tension between the two immiscible phases and the flow rates of the dispersed or continuous phase.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1999.03a
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• pp.243-248
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• 1999

There is substantial evidence that anatomical connections and functional interactions exist between vestibular and autonomic systems. Heart rate variability (HRV) including mean, standard deviation, coefficient of variation (CV), power spectrum was analyzed for evaluation of the physiological role of the vestibular system on control of heart rate in rabbits. In anesthetized rabbits, electrical stimulation of the vagus nerve decreased heart rate and decreased LF/HF by increasing HF. On the cervical sympathetic nerve increased heart rate and increased LF/HF by increasing LF. Atropine, cholinergic blocker, increased heart rate and increased LF/HF by reducing HF, and propranolol, ${\beta}$-adrenergic blocker, decreased heart rate and decreased LF/HF by reducing LF> In unanesthetized rabbits, stimulation of the vestibular system induced by rotation or caloric increased heart rate and increased LF/HF by increasing LF> Also electrical stimulation of the vestibular nerve produced the same of effects as rotation or caloric in anesthetized rabbits. These results suggest that Stimulation of the vestibular system increased heart rate not by inhibiting the parasympathetic nerve but by activating the sympathetic nerve.

• Environmental Analysis Health and Toxicology
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• v.15 no.1_2
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• pp.45-51
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• 2000

Analytical method of 4-nitrotoluene (4-NT) in water was developed by 9as chromatography/mass selective detector/selected ion monitoring (GC/MSD/SIM). 4-NT was extracted with diethyl ether. Organic layer was washed with 5 % sodium chloride solution. The influence of solvent and evaporation condition on extraction of 4-NT were examined. The retention time of 4-NT peak was 7.72 min. Coefficient of variation (CV) of 4-NT (ng) within day and day-to-day was ranged from 7.0 to 14.6% and from 7.7 to 20.8%, respectively. Recovery of 4-NT was ranged from 84 to 109%, and detection limit of 4-H was lese than 1 ng/㎖.

• Journal of the Korean Wood Science and Technology
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• v.43 no.5
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• pp.539-547
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• 2015

To investigate dimensional responses of wood under dynamic temperature condition, poplar (populous euramericana Cv.) specimens, 20 mm in radial (R) and tangential (T) directions with two thicknesses of 4 and 10 mm along the grain, were exposed to cyclic temperature changes in square wave between $25^{\circ}C$ and $40^{\circ}C$ at 60% relative humidity (RH) for three different cycling periods of 6 h, 12 h and 24 h. R and T dimensional changes measured during the cycling gave the following results: 1) Transverse dimensional changes of the specimens were generally square but at an opposite phase and lagged behind the imposed temperature changes. The phase lag was inversely correlated with cycling period, but positively related to specimen thickness, while the response amplitude was directly proportional to cycling period, but in a negative correlation with specimen thickness. 2) The specimens showed swelling hysteresis behavior. The heat shrinkage coefficient (HSC) became greater as cycling period increased or specimen thickness decreased. 3) Dimensional changes of the specimens produced deformation accumulation during repeated adsorption and desorption. The deformation accumulating ratio decreased with an increase in cycling period and specimen thickness. 4) Wood suffered 1.5 times as many dimensional changes per unit temperature variation as per unit humidity variation, and this deformation behaved even more seriously under static condition.

• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.329-338
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• 2014

The purpose of this study was to analyze of the rider postural alignments according to the fitting of stirrups lengths during walk of high level riders. Participants selected as subject were consisted of horse riders of high level (age: $47.66{\pm}3.51yrs$, height: $168.40{\pm}4.84cm$, body weight: $73.36{\pm}15.58kg$, low extremity length: $94.76{\pm}3.98cm$, career: $23.33{\pm}5.77yrs$) and walk with 3 types of stirrup lengths(ratio of low extremity 68.04%, 73.25%, 78.48%). The variables analyzed were consisted of the displacement of Y axis (center of mass, head, thigh, shank and foot), FR angle, LR angle, dynamic postural stability index (DPSI), coefficient of variation (CV%), and distance (X axis) of low extremity limb between right and left. The displacement of Y axis in COM, thigh, shank, foot limbs were not statistically significant, but movements of head showed greater distance of B type and C type than that of A type during 1 stride of walk. The FR and LR angle in trunk of horse rider, dynamic postural stability index and, coefficient of variation didn't show significant difference statistically according to the fitting of stirrup lengths. Also the distance (X axis) of low extremity in thigh and shank didn't show significant difference statistically in between right and left, but right and left foot showed greater distance in C type than that of B and A types during walk in horse back riding. The hip and ankle joint angle not statistically significant according to stirrups lengths, But knee joint angle showed more extended according to the increase of stirrups lengths during stance and swing phase in walk.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.1
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• pp.39-49
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• 2002

In this study, limits of detection (LOD), accuracy and precision of four sampling/ analytical methods were evaluated and compared for the determination of airborne hexavalent chromium, Cr (VI). The methods include : (1) a combination of the National Institute for Occupational Safety and Health (NIOSH) Method 7600/U. S. Environmental Protection Agency (EPA) Method 218.6 (NIOSH/EPA Method) proposed by Shin and Paik, 2) two impinger methods using 2% NaOH/3% Na$_2$CO$_3$. (3) same as (2) but with 0.02 N NaHCO$_3$absorbing solution, and (4) the Occupational Safety and Health (OSHA) Method ID-215. An ion chromatograph/visible absorbance detector was used for the analysis of Cr (VI) in sample solution. Limit of detection (LOD) , analytical accuracy, and precision were also tested using Cr (VI) spike samples. Recoveries (as index of accuracy) and coefficient of variation (CV) (as a index of precision) were determined. Two-way ANOVA and Turkey's test were performed to test the significance in differences among recoveries and CVs of the methods. In all the methods, the peaks of Cr (VI) were separated sharply on chromatograms and exhibited a strong linearity with Cr (VI) concentrations in solution. The correlation coefficients of calibration curves typically ranged from 0.9997 to 0.9999, and the analytical LODs from 0.025 to 0.1$\mu\textrm{g}$/sample. All the method had good sensitivities and linearities between Cr (VI) levels and peak areas. The accuracies (% mean recoveries) of the methods ranged from 80.1 to 104.2%, while the precisions (pooled coefficient of variation) ranged from 3.16 to 4.43%. The impinger methods showed higher recoveries ( > 95%) than those of the PVC filter methods (the OSHA Method and the NIOSH/EPA Method). It was assumed that Cr (VI) on PVC filter was exposed to air and reduced to trivalent chromium, Cr (III), whereas it was stabilized in alkali solution contained in impinger. Thus, a special treatment of Cr (VI) samples collected on PVC filters may be required.

• Korean Journal of Community Nutrition
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• v.19 no.5
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• pp.415-424
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• 2014

Objectives: Vegetables are the most left over side dishes in school lunch programs. This study intended to analyze the differences in preference for vegetables among the students of different age groups in order to determine potential ways of increasing vegetable consumption in this study group. Methods: A total of 308 primary to university students in Gyeongbuk area were recruited and a questionnaire-based survey was conducted. The preference score (7-Likert scale: very much dislike (1)~so-so (4)~like very much (7)) and intake frequency (5-Likert scale) of 48 kinds of vegetables in 4 vegetable groups, such as vegetable (fruit-, root-, leaf-, and stalk-vegetable), seaweeds, mushrooms, and kimchi were investigated, and data were analyzed by SPSS WIN (ver 12.0). Results: The preference scores of vegetables except for seaweeds were significantly different among school groups, university was the highest, followed by high school. Primary and middle school students showed the lowest preference score, especially for leaf- and stalk- vegetables. The preference score for seaweeds was the highest of 5.28, followed by kimchi of 4.99. With regard to kimchis, the preference score was the highest in university', followed by high school, middle school, and primary school' was the lowest. The number of vegetables with < 4.0 preference score was the highest in primary school of 16, 15 in middle school, 11 in high school, and 7, the lowest in university. The vegetable with preference score of < 4.0 in all 4 school groups were mallow, chard, bud, radish leaf, mugwort, butterbur and sweet potato stalk. With regard to the intake frequency of vegetables, kimchis, an indispensable part of the Korean diet, was the highest of 2 times/day, followed by cooked vegetables of 1.5 times/day. The correlation coefficients between preference scores and intake frequencies were statistically significant in all groups of vegetables. As for the coefficient of variation (CV) of preference score, primary school' was the highest and university' was the lowest. The number of vegetables with high CV and high inexperience were highest in primary school students. Conclusions: Providing more opportunities for consuming a variety of vegetables, such as leaf- and stalk-vegetable, it may be possible to increase vegetable consumption, especially for the primary school students.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.561-574
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• 2018

In this study, regional variations and factors associated with prevalence of metabolic syndrome were grasped using GWR (geographically weighted regression) and methodologies for the efficient management of metabolic syndrome were then set up to resolve health inequalities. Based on the National Health Screening Statistical Yearbook published by the National Health Insurance Service (NHIS), community health survey (KCDC) and other governmental institutions, indicators of social structural and mediation factors related to the regional prevalence of metabolic syndrome were collected. First, the existence of indicators to measure variations in metabolic syndrome were confirmed with the collected data by calculating the EQ (extremal quotient) and CV (coefficient of variations). The GWR, which is able to take spatial variations into consideration, was then adopted to analyze the factors of regional variations in metabolic syndrome. The GWR analysis revealed that severity and management of the main causes need to be prioritized in accordance with the prevalence of metabolic syndrome. Consequently, the order of priority in management of regional prevalence of metabolic syndrome was established, and plans that can increase the effectiveness of management of metabolic syndrome were confirmed to be feasible.

• Analytical Science and Technology
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• v.16 no.2
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• pp.95-101
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• 2003

In this study, water content in the mixture of methanol and ethanol was nondestructively measured by near infrared (NIR) spectroscopy. Two types of NIR instruments, portable NIR system with a photo-diode array and scanning type NIR spectrometer were used and the calibration results were compared. Partial least squares regression (PLSR) was applied for the calibration and validation for the quantitative analysis. The calibration results from both instruments showed good correlation with actual values. The calibration with the use of PLS model predicted water concentration with a standard error of prediction (SEP) of 0.10% and 0.12% for photo diode array and scanning type, respectively. During 6 days, routine analyses for 3%, 5% and 7% water in ethanol solution with 2% methanol were performed to validate the robustness of the developed calibration model. The routine analyses showed good results with coefficient of variation (CV) of within 3% for both types of NIR spectrometers. This study showed that the rapid determination of water in the mixture of methanol and ethanol was successfully performed by NIR spectroscopy and the performance of the portable NIR system with a photo diode array detector was comparable to that of the scanning type NIR spectrometer.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.3
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• pp.488-495
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• 1997

The effects of ammonia on survival and growth of the flounder larva, Paralichthys olivaceus, were examined by a static renewal bioassay method. The $96\;hr-LC_{50}$ with the developmental stages during the period from 1day to 23 day-old larvae ranged 0.273 to 1.023 mg $NH_3/\ell$. Tolerance of the larvae to ammonia toxicity was much sensitive at the early larval stage, and increased with the growth of the larvae. Threshold $96hr-LC_{50}$ in 1, 3 and S day-old larvae after hatching were 0.293, 0.248 and 0.379 mg $NH_3/\ell$, respectively. Survival rate and growth in body weight and body weight of the larva were reduced with increase of ammonia concentration in the range of 0.055 and 0.341 mg $NH_3/\ell$. The no-observable-effect concentration (NOEC) and lowest-observable- effect concentration (LOEC) of the flounder larve were 0.102 and 0.174 mg $NH_3/\ell$ for body length, and 0.151 and 0.198 mg $NH_3/\ell$ for body weight, respectively. Chronic value (ChV), which is the geometric mean of the NOEC and $NH_3/\ell$ to body length of the larvae were 0.124 mg $NH_3/\ell$. The coefficient of variation (CV) for body length was higher at high concentration than at low concentration.