• Environmental Engineering Research
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• v.14 no.4
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• pp.244-249
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• 2009

Designing an ozone contactor is complicated because the residual ozone, log C. parvum inactivation, and bromate formation should be optimized with fluctuating water quality. OCM software was developed to assist a plant designer or an operator to fulfill the sophisticated optimization required in the design or operation of a new or an existing plant. In this article, numerical simulations were carried out using the OCM software for the design of a new ozone contactor under diverse design factors (i.e., three pHs, three temperatures, low and high dispersion numbers, and four and ten cells with complete mixing) with kinetic parameters obtained from the sand-filter effluent of a water treatment plant treating water from the Paldang impoundment. The results of the simulation suggested that a high residual ozone concentration at low pH and low temperature would be challenging, and PFR-like hydrodynamics could lower the residual ozone concentration. The inactivation of C. parvum oocysts increased at a lower pH. A lower dispersion number and more cell division increased the inactivation efficiency. Bromate was instantaneously formed during the initial ozonation stage. The effluent concentration was much lower than the regulatory levels imposed by the USEPA because of the low bromide level in raw water.

• International Journal of Ocean System Engineering
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• v.1 no.2
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• pp.95-101
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• 2011

Perforated plates with cutouts (or holes) are widely used in structural members. These cutouts provide stress concentration in plates. Extensive studies have been carried out on stress concentration in perforated plates, which consider cutout shapes, boundary conditions, bluntness of cutouts, and more. This study presents stress concentration analyses of perforated plates with not only various cutouts and bluntness but also different cutout orientations. Especially, the effect of cutout orientation on stress concentration is emphasized since structural members have become more complicated recently. To obtain stress concentration patterns, a finite element program, ANSYS, is used. For the designated goal, three parameters are considered as follows: the shapes of polygonal cutouts (circle, triangle, and square), bluntness (a counter measure of radius ratio, r/R), and rotation of cutouts (${\theta}$). From the analyses, it is shown that, in general, as bluntness increases, the stress concentration increases, regardless of the shape and rotation. A more important finding is that the stress concentration increases as the cutouts become more oriented from the baseline, which is the positive horizontal axis (+x). This fact demonstrates that the orientation is also a relatively significant design factor to reduce stress concentration. In detail, in the case of the triangle cutout, orienting one side of the triangle cutout to be perpendicular to the applied tensile forces is preferable. Similarly, in the case of the square cutout, it is more advantageous to orient two sides of square cutout to be perpendicular to the applied tensile force. Therefore, at the design stage, determining the direction of a major tensile force is required. Then, by aligning those polygon cutouts properly, we can reduce stress concentration.

• Korean Institute of Interior Design Journal
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• no.17
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• pp.60-64
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• 1998

The results of simulation on greenery ratio using CG are as follows: arrangement type of optimal condition and greenery ratio were summarized as below as dispersion type and 5% ratio greenery for 20 pairs of assessment items and these assessment items were classified into 5 factors as a result of factor analysis,. These factors were Harmony Animation Atmosphere texture Peculiarity. Verification results of factors differences according to each condition can be. there was no apparent difference among factors in accordance with gender, In case of arrangement type dispersion type was higher than concentration type in all factors. Based on the above results dispersion type was assessed higher than concentration type the most suitable condition of Harmony Factor was 5% dispersion type Animation Factor was 5% dispersion type Animation Factor was 7% dispersion type Atmosphere Factor was 10% dispersion type Texture Factor was 5% concentration type and $\ulcorner$Peculiarity Factor$\lrcorner$was 7% concentration type.

• Toxicological Research
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• v.25 no.4
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• pp.237-242
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• 2009

This study was carried out to investigate the irritation of the prodigiosin isolated from Zooshikella rubidus on the skin and eyes in New Zealand white rabbits. The tests were performed on the basis of Korea Food and Drug Administration (KFDA) guidelines. Prodigiosin induced severe eye irritation at high concentration (0.5 g/site/ml) but there was no eye irritation at low concentration (0.3 mg/sitel ml). The primary irritation index was calculated from higher concentration (0.5 g/site/ml) to lower concentration (0.3 mg/site/ml). There were found non-irritation or induced mild irritation at lower concentration of prodigiosin application. On the basis of this study, it could be concluded that the prodigiosin may be non-irritant to mild irritant of usual application at lower concentration (0.3 mg/site) resulting it is safe and useful in dyeing technology of fabrics.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.1
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• pp.88-94
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• 2012

An axle drive shaft with double joint shaft, cross kit and yoke has an important role by transferring power and changing steering angle between axle and wheel in power train system. It has been used widely in the heavy machinery requiring a high reliability in the power train system. At fatigue failures of the axle drive shaft with the long span, a relatively high stress concentration at a snap ring groove on the drive shaft brings to significant fatigue damages under repeated loading condition. As Peterson's suggestions on this study, a relief groove in the vicinity of the snap ring groove is applied by decreasing the stress concentration and improving the fatigue life of axle drive shaft. By using FEM analysis, the decreasing effect of the stress concentration and extended fatigue life are due to the change of design parameters related with size and location of the relief groove. The relief groove with the design parameters such as d/b=2.0 and r/h=1.2 enables to decrease the stress concentration of 22.3% and increase the fatigue life more than 3 times by comparing with no relief groove application.

• Journal of Korean Living Environment System
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• v.19 no.4
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• pp.479-488
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• 2012

This study investigated the influence of the indoor CO₂concentration level on sleep quality by polysomnography(PSG). One healthy female subject was selected among several subjects based on RI(Risk Indicator) value and BMI(Body Mass Index) value to evaluate judging the risk level of obstructive sleep apnea hypopnea. To get the impact of the indoor carbon dioxide concentration to sleep quality, both CO₂concentration levels were set up using ventilating form with 700~800 ppm and 2000~3000 ppm. Other environments were controlled in the comfortable sleep scope by previous researches. To measure the sleep quality, measurements have carried on polysomnography(PSG). In conclusion, it have shown that high carbon dioxide concentration leads arousal effect about central nervous system and to sustaining dreams and excited condition by bring about REM sleep split phenomenon.

• The Research Journal of the Costume Culture
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• v.30 no.5
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• pp.717-731
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• 2022

The purpose of this study is to suggest effective online pedagogical strategies for a fashion design CAD course to enhance student learning and satisfaction. The study investigated student experience of online learning and compared online learning with a face-to-face learning experience. Student concentration, participation, perceptions of effectiveness of teaching, utilization of learning materials, and satisfaction were analyzed using a 5-point Likert scale. Advantages and disadvantages of online learning as well as advantages of face-to-face learning were also analyzed both quantitatively and qualitatively. Student concentration, participation, and perception of effectiveness of teaching were greater for face-to-face learning with significantly higher concentration on individual practice. Students utilized video recording of synchronous online lectures more actively than PDF lecture notes. The advantages of face-to-face learning were plentiful communication and feedback and easy questioning process as well as high levels of understanding and concentration. Meanwhile, major disadvantages of online learning were the speed of the lecture, lower levels of understanding and concentration, limited peer interaction, and technical problems. Major advantages of online learning were flexibility and convenience, repetitive learning through videos, and instant communication and feedback. Students preferred a blended learning approach for the fashion design CAD course. For effective online learning, it is suggested that instructors frequently question and check student practice through screen share in a private online meeting room and engage activities that are demanding of student interaction. The video recording of synchronous online lectures is also suggested as a supplemental learning material for repetitive learning.

• Current Optics and Photonics
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• v.4 no.1
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• pp.50-56
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• 2020

The design of a concentration system for a solar side-pumped slab laser was investigated. The side size of the slab laser medium is 2 mm × 20 mm. Based on the principle of the edge ray, a secondary concentrating system consisting of a rectangular parabolic mirror (RPM) and a rectangular dielectric-filled compound parabolic concentrator (RDCPC) was demonstrated. The focal length of RPM is 1200 mm and the size is 734 mm × 2000 mm. The outlet size of the RDCPC is 2 mm × 20 mm. The concentration effect was analyzed by using Tracepro optical software. The results showed that the concentration efficiency reached 81.3% and the uniformity of the spot was 91.4% after optimization. This design of concentration system is of great reference value for a solar side-pumped slab laser.

• Korean Journal of Human Ecology
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• v.18 no.6
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• pp.1363-1374
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• 2009

The purpose of this study was to determine the actual state of the indoor air quality in newly built or remodeled kindergartens by TVOC and HCHO concentration and teachers' responses. The field measurements on the levels of TVOC and HCHO were carried out in six classrooms of newly built or remodeled kindergartens before their opening. The interviews with teachers of subject kindergartens were carried out at the end of the first semester. The contents of the interviews were teachers' subjective responses and symptoms of the kindergarten pupils on the Sick New-School Syndrome. The results are as follows; the mean value of TVOC concentration in the classrooms of kindergartens ranged from 0.10ppm to 0.42ppm, which can theoretically exert a harmful influence on residents. The mean value of HCHO concentration ranged from 0.00ppm to 0.03ppm, which does not exceed the standard. The TVOC concentrations of the more ventilated kindergartens were lower than the others. Also, the classrooms with high concentrations of TVOC showed negative responses or symptoms in teachers and kindergarten pupils.

• Current Optics and Photonics
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• v.4 no.5
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• pp.441-445
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• 2020

A novel design for a Fresnel lens for a solar end-pumped laser is demonstrated in this paper. The new hybrid Fresnel lens includes two parts, inner and outer. The inner part is a twice-total-internal-reflection and vertical-transmission lens. The outer part is a once-total-reflection and vertical-transmission lens. The radius of the Fresnel lens is 600 mm, and its focal length is 750 mm. The concentrating performance of the Fresnel lens is examined using TracePro. The results show that the concentration efficiency has been greatly improved. The total concentration efficiency of the hybrid Fresnel lens reaches 73.2% when the radius of the laser rod is 3 mm. This design can simplify the concentration system of a solar end-pumped solid-state laser.