• Water for future
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• v.21 no.3
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• pp.299-307
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• 1988

A model is developed to predict the long-term beach evolution near the long groin considering the combined effects of variation of sea level, wave refraction and diffraction. A numerical solution for this problem is solved by considering the equation as a system subject to the boundary condition for longshore transport rate. One possible method is the centered Crank-Nicolson type implicit scheme. The results which ard obtained by applying this numerical model at Songdo beach, Pohang are as follows. Owing to the approximation used in the calculation of the refraction and diffraction coefficients, the discrepancy between the predicted and actual shoreline occurs to the interior of long groin. However, the shape of shoreline at the exterier of long groins agrees well.

• Journal of the Korean Society of Clothing and Textiles
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• v.9 no.2
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• pp.75-84
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• 1985

In order to improve dyeing and finishing technology of thin cloth of microfiber(super-fine fiber), the degrees of deep dyeing method, the light fastness, and the washing fastness were investiagted. 1. The thin cloth made of microfiber, $0.15^d\~0.2^d$, was conjugated type and the dyeing degree was lower at 5 to $10\%$ than that of cloth made of common fiber. The cloth of excellent dyeing fastness, light fastness, was developed by increasing the concentration of dye of high quality up to $5\~10\%$. 2. Because refractory rate of microfiber of $0.2^d$ was lower than that of $0.01^d$, the surface refractory rate of $0.2^d$ was lower than that of $0.01^d$ fiber. Therefore the surface of micro-fiber, $0.2^d$, was more rougher than that of $0.01^d$ and it belongs to separate type. 3. The higher degree of dyeing was increased by using dye of microparticle. Also the degree of textile printing was increased by adding urea solution ($20\%$) and glycerine diethylene glycol. 4. Light fastness was very excellent, marked 5 grade. However, washing fastness was 2$\~$3 grade. After dyeing, we could improve to 4 grade, through hot water washing including some organic chlorine solvent. 5. Super microfiber of $0.01^d$ will not be dyed by present dye and dyeing equipment, because right reflection light rate(white light) of fiber surface was too high and the more refraction rate higher the more surface refraction rate will be increased.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.7
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• pp.455-461
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• 2015

The paper deals with the accuracy comparison between two kinds of ultrasonic paths for flow rate measurement. In the Z-path, two transducers are installed on the opposite sides of each other on a pipe, and the ultrasonic waves generated at one transducer propagate to arrive at the other one only by refraction. In the V-path, two transducers are installed on one side of a pipe, and the ultrasonic waves reflected at the inner wall of the pipe are received. Transit times were confirmed to identify the propagation paths by comparing the theoretically calculated results and measured ones. The flow rate measurements with two kinds of ultrasonic paths appeared very similar. It would be possible to select either of the paths by considering the advantages and disadvantages.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.329-330
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• 2008

GPS which measured user's location information outdoors should be of poor sensitivity because of interference and jamming of different electromagnetic waves. Specially, it has a defect of low received rate in high-rise urban where reflection and refraction of satellite signal go well. In this paper, I propose user location information sharing modeling of both vehicle and mobile phone using bluetooth in urban.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.736-738
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• 2014

The paper deals with the accuracy comparison between two kinds of ultrasonic paths for flow rate measurement. In the Z-path, two transducers are installed on the opposite side of each other on a pipe, and the ultrasonic waves generated of one transducer propagate and arrive at the other one only through refraction. In the V-path, two transducers are installed on one side of a pipe, and the ultrasonic waves reflected at the inner wall of the pipe are received. The backgrounds were established to select one path to fit the usage by considering the advantages and disadvantages.

• The Journal of Pediatrics of Korean Medicine
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• v.29 no.4
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• pp.12-22
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• 2015

Objectives Myopia has a higher prevalence rate in eastern countries, which also have a higher rate of educational fever compared to western countries. Considering this, social costs paid for myopia will increase rapidly in Korea. Although the development of myopia treatment is necessary, there has been a lack of relevant studies. Thus, this study aims to produce data to prevent unnecessary treatments and medical expenses. Methods The objective is to evaluate the effect of periocular acupressure exerted by a medical massager for myopia. This is an open-label, prospective, single-arm, and pre and post superiority study. The subjects are 7~12-year-old myopia patients with under 5 D (diopter) of spherical equivalent. A total of 56 subjects were enrolled. The selected subjects will wear the massager for 15 minutes twice a day for 24 weeks. The primary endpoint is the refraction change. The secondary endpoint is the axial length change. Statistical analysis was performed at a significant level of 0.05, using a two-tailed test. The criterion for significantly improved refraction was $-0.17{\pm}0.50$ D/6 months and that of axial length change was 0.126 mm. Results and Conclusions This study did not include a control group because children represent a vulnerable group. This objective study will bring some impact on Korean medical myopia treatment. A long-term confirmatory clinical study may be necessary in future.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.311-318
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• 2015

Purpose: This study was designed to investigate the prevalence rate of refractive error with gender and age presenting visual acuity of primary student in Jeonnam. Methods: Subjective refraction, objective refraction and visual acuity test were examined on 735 primary school children who ages of 8~13 years lived in Jenman. Presenting visual acuity test was using Han's visual acuity chart and objective refraction was carried out using auto-refractometer. Results: The presenting visual acuity was 0.1 worse in the eye of 54(7.3%) students and 49(7.3%) of them wearing the glasses. The rate of the wearing glasses were 79.3% in 0.125~0.25 visual acuity, 64.2% in 0.3~0.5 visual acuity and 61.6% in 0.6~0.8 visual acuity. It was appeared that 269(36.6%) of them were emmetropia, 321(43.7%) of them were myopia and 56(7.6%) of them were hyperopia, and 89(12.1%) of them were astigmatism. The prevalence rate of myopia was the highest and followed by the prevalence rate of astigmatism. The low degree of myopia occupied the most and the medium degree of myopia showed the tendency of increase as the students get olds. The prevalence rate of the hyperopia showed the tendency of decrease as the students get olds. The prevalence rate of with the rule astigmatism were 50.6% students and against the rule astigmatism were 48.3% of students. Conclusions: The present study reveals the considerable prevalence rates, 466(63.4%) of included subjects, of refractive errors among primary students in Jeonnam province. The rate of the wearing glasses were 313(42.6%). The prevalence of myopia increases as the students get older. Therefore students of visual management is considered necessary through the visual acuity test and refractive examination.

• Nuclear Engineering and Technology
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• v.56 no.7
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• pp.2458-2473
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• 2024

The turbulent flow in reactor pressure vessel (RPV) of pressurized water reactor (PWR) is important for the flow rate distribution at core inlet. Thus, it is vital to study the turbulent flow phenomena in RPV. However, the complicated fluid channel consisted of inner structures of RPV will block or refract the laser sheet of particle image velocimetry (PIV). In this work, the matched index of refraction (MIR) of sodium iodide (NaI) solution and acrylic was applied to support optical path for flow field measurements by PIV in the 1/10th scaled-down RPV model. The experimental results show detailed velocity field at different locations inside the scaled-down RPV model. Some interesting phenomena are obtained, including the non-negligible counterflow at the corner of nozzle edge, the high downward flowing stream in downcomer, large vortices above vortex suppression plate in lower plenum. And the intensity of counterflow and the strength of vortices increase as inlet flow rate increasing. Finally, the case of asymmetry flow was also studied. The turbulent flow has different pattern compared with the case of symmetrical inlet flow rate, which may affect the uniformity of flow distribution at the core inlet.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.1036-1041
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• 2004

A newly designed pressure-scanning slit viscometer is developed to combine an optical device without refraction while measuring blood viscosity over a range of shear rates. The capillary tube in a previously designed capillary viscometer was replaced with a transparent slit, which is affordable to mount optical measurement of flowing blood cells. Using a pressure transducer, we measured the change of pressure in a collecting chamber with respect to the time, p(t), from which the viscosity and shear rate were mathematically calculated. For water, standard oil and whole blood, excellent agreement was found between the results from the pressure-scanning slit viscometer and those from a commercially available rotating viscometer. This new viscometer overcomes the drawbacks of the previously designed capillary viscometer in the measuring whole blood viscosity. First, the pressure-scanning slit viscometer can combine an optical instrument such as a microscope. Second, this design is low cost and simple (i.e., ease of operation, no moving parts, and disposable).

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1998.10a
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• pp.137-141
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• 1998

Todays the efficient management of container has not been realized in container terminal, because of the excessive quantity of container transported and manual system. For the efficient and automated management of container in terminal, the automated container identifier recognition system in terminal is a significant problem. However, the identifier recognition rate is decreased owing to the difficulty of image preprocessing caused the refraction of container surface, the change of weather and the damaged identifier characters. Therefore, this paper proposes more accurate system for container identifier recognition as suggestion of Line-Scan Proper Region Detect for stronger preprocessing against external noisy element and Moment Back-Propagation Neural Network to recognize identifier.