• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.6
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• pp.408-413
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• 2015

Road lighting has emerged in importance as an essential system to secure safety and visibility for drivers and pedestrians. According to the Road Lighting Standards (KS A 3701), the luminance uniformity (U0) should be 0.4, the luminance uniformity for lanes (UI) should be 0.5, and a threshold increment (TI) of 10% should be satisfied. In this study, we conducted simulations using the Relux program in which the secondary optical lens was applied to a 21 W engine. Ten LED engines were installed on a two-way four-lane road, and the simulation result satisfied the requirements with U0 0.47, UI 0.63 and TI 8%. The U0, UI, and TI were compared with the angle of the LED streetlight varied in the range of $9^{\circ}{\sim}15^{\circ}$ with $0.5^{\circ}$ intervals. The range was selected as ${\pm}25%$ of the standard inclination angle of $12^{\circ}$ according to the Road Lighting Standard. The U0 was high and the UI and TI were low when the tilting angle was in the range of $9.5^{\circ}{\sim}10.5^{\circ}$. Consequently, an optimum-design of lighting distribution was obtained for the concrete two-way four-lane road when the inclination angle was $9^{\circ}$.

• Journal of the Korean Geosynthetics Society
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• v.21 no.4
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• pp.93-100
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• 2022

This study describes the evaluation results on the effect of soil particle surfaces coated with various hydrophobic conditions on spectral information according to water content. Wettability test and spectral information evaluation test were performed on the hydrophobic coated standard sand. When the standard sand was coated with 1%, 3%, and 5% hydrophobic, the contact angles of sand-water interface were 130°~143°, 129°~144°, and 131°~144°, respectively. This means that the contact angle increased as the degree of hydrophobic coating increased at the same drying time, but the range of the contact angle had the same wettability. This means that the contact angle increases as the hydrophobic coating degree increases at the same drying time, whereas the contact angle range has the same wettability. As a result of spectral information evaluation, the maximum spectral reflectance of the dried sand with hydrophobic condition decreased compared to that of the hydrophilic sand, as the degree of hydrophobic increased. However, the maximum spectral reflectance was increased by increasing the degree of hydrophobic under the same water content conditions.

• Journal of computational fluids engineering
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• v.10 no.1
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• pp.107-112
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• 2005

A cross-flow fan is generally used on the region within the low static pressure difference and the high flow rate. It relatively makes high dynamic pressure at low rotating speed because a working fluid passes through an impeller blade twice and blades have a forward curved shape. At off-design points, there are a rapid pressure head reduction, a noise increase and an unsteady flow. Those phenomena are remarkably influenced by the setting angle of a stabilizer. Therefore, it should be considered how the setting angle of a stabilizer affects on the performance and the flow fields of a cross-flow fan. It is also required to investigate the effect of the volumetric flow rate before occurring stall. Two-dimensional, unsteady governing equations are solved using a commercial code, STAR-CD, which uses FVM. PISO algorithm, sliding grid system and standard k - ε turbulence model are also adopted. Pressure and velocity profiles with various setting angles are graphically depicted. Furthermore, the meridional velocity profiles around the impeller are plotted with different flow rates for a given rotating speed.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.8 no.1
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• pp.68-74
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• 2008

In this paper, a novel neural fuzzy control method is proposed to control nonlinear systems. A standard PD-like fuzzy controller is designed and used as a main controller for the system. Then a neural network controller is added to the reference trajectories to form a neural-fuzzy control structure and used to compensate for nonlinear effects. Two neural-fuzzy control schemes based on two well-known neural network control schemes, the feedback error learning scheme and the reference compensation technique scheme as well as the standard PD-like fuzzy control are studied. Those schemes are tested to control the angle and the position of the inverted pendulum and their performances are compared.

• Proceedings of the KIEE Conference
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• 2008.09a
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• pp.61-63
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• 2008

We established a system to evaluate the ratio error and phase angle error of electronic voltage transformer using high voltage capacitance bridge and standard capacitors. The uncertainty of evaluation system is about 0.005% in ratio error and 1.5 min in phase angel error.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.96-103
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• 2006

To establish of standard technique of nano-length measurement in 2D plane, new AFM system has been designed. In the long range (about several tens of ${\mu}m$), measurement uncertainty is dominantly affected by the Abbe error of XY scanning stage. No linear stage is perfectly straight; in other words, every scanning stage is subject to tilting, pitch and yaw motion. In this paper, an AFM system with minimum offset of XY sensing is designed. And XY scanning stage is designed to minimize rotation angle because Abbe errors occur through the multiply of offset and rotation angle. To minimize the rotation angle optimal design has performed by maximizing the stiffness ratio of motion direction to the parasitic motion direction of each stage. This paper describes the design scheme of full AFM system, especially about XY stage. Full range of fabricated XY scanner is $100{\mu}m\times100{\mu}m$. And tilting, pitch and yaw motion are measured by autocollimator to evaluate the performance of XY stage. As a result, XY scanner can have good performance. Using this AFM system, 3um pitch specimen was measured. The uncertainty of total system has been evaluated. X and Y direction performance is different. X-direction measuring performance is better. So to evaluate only ID pitch length, X-direction scanning is preferable. Its expanded uncertainty(k=2) is $\sqrt{(3.96)^2+(4.10\times10^{-5}{\times}p)^2}$ measured length in nm.

• Journal of ILASS-Korea
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• v.28 no.2
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• pp.97-104
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• 2023

A sprinkler is a fire suppression system that extinguishes combustible materials in the early stages of a fire, creating a spray. However, spray formation method of the sprinkler can result in an uneven distribution of water spray on the surface of combustible materials. It is necessary to ensure a consistent water flux density regardless of the spray direction and angle. In this study, the water flux distribution was analyzed for the various types of sprinkler head: circular, flush, pendent, and upright types. All sprinkler heads have a K-factor of 80 LPM/(0.1MPa)^0.5. In this study, water collection cubes were used to examine the water flux distribution. The upright type sprinkler head showed a low standard deviation in total sprayed area, indicating a high level of uniformity. The upright type head showed the lowest standard deviation in the radial direction, and also showed the lowest standard deviation in the azimuthal direction. Upright sprinkler head has no obstructing structure along the path of droplets after they are generated. For this reason, upright sprinkler head showed the most uniform water flux distribution on the floor.

• International Journal of Fluid Machinery and Systems
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• v.3 no.1
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• pp.11-19
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• 2010

The performance of the crossover system of a centrifugal compressor stage consisting of static components of $180^{\circ}$ U-bend, return channel vanes and exit ducting with a $90^{\circ}$ bend is investigated. This study is confined to the assessment of performance of the crossover system by varying the shape of the return channel vanes. For this purpose two different types of Return Channel Vanes (RCV1 and RCV2) were experimentally investigated. The performance of the crossover system is discussed in terms of total pressure loss coefficient, static pressure recovery coefficient and vane surface pressure distribution. The experimentation was carried out on a test setup in which static swirl vanes were used to simulate the flow at the exit of an actual centrifugal compressor impeller with a design flow coefficient of 0.053. The swirl vanes are connected to a mechanism with which the flow angle at the inlet of U-bend could be altered. The measurements were taken at five different operating conditions varying from 70% to 120% of design flow rate. On an overall assessment RCV1 is found to give better performance in comparison to RCV2 for different U-bend inlet flow angles. The performance of RCV2 was verified using numerical studies with the help of a CFD Code. Three dimensional sector models were used for simulating the flow through the crossover system. The turbulence was predicted with standard k-$\varepsilon$, 2-equation model. The iso-Mach contour plots on different planes and development of secondary flows were visualized through this study.

• Physical Therapy Korea
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• v.30 no.3
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• pp.174-183
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• 2023

Background: Office workers experience neck or back pain due to poor posture, such as flexed head and forward head posture, during long-term sedentary work. Posture correction is used to reduce pain caused by poor posture and ensures proper alignment of the body. Several assistive devices have been developed to assist in maintaining an ideal posture; however, there are limitations in practical use due to vast size, unproven long-term effects or inconsistency of maintaining posture alignment. We developed a headphone and necklace posture correction system (HANPCS) for posture correction using an inertial measurement unit (IMU) sensor that provides visual or auditory feedback. Objects: To demonstrate the test-retest reliability and concurrent validity of neck and upper trunk flexion measurements using a HANPCS, compared with a three-dimensional motion analysis system (3DMAS). Methods: Twenty-nine participants were included in this study. The HANPCS was applied to each participant. The angle for each action was measured simultaneously using the HANPCS and 3DMAS. The data were analyzed using the intraclass correlation coefficient (ICC) = [3,3] with 95% confidence intervals (CIs). Results: The angular measurements of the HANPCS for neck and upper trunk flexions showed high intra- (ICC = 0.954-0.971) and inter-day (ICC = 0.865-0.937) values, standard error of measurement (SEM) values (1.05°-2.04°), and minimal detectable change (MDC) values (2.92°-5.65°). Also, the angular measurements between the HANPCS and 3DMAS had excellent ICC values (> 0.90) for all sessions, which indicates high concurrent validity. Conclusion: Our study demonstrates that the HANPCS is as accurate in measuring angle as the gold standard, 3DMAS. Therefore, the HANPCS is reliable and valid because of its angular measurement reliability and validity.

• International Journal of Human Ecology
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• v.3 no.1
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• pp.127-136
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• 2002

According to the Labor Standard Law in Japan which was enacted after World War II in 1947, all work hours for adult men, women, and youth were set at a maximum of eight hours per day and forty-eight hours per week. In other words, a six-day work week, with only one-day off, was set. Now we are in the full five-day and two-day off school system. The five-day school week influences on our home life. Students are highly enthused by the new system, in looking forward to their personal time they now have to play with friends, to relax, or just watch TV. To implement this new five-day school system positively and effectively, we should see the point at issue related to the two-day off system from a different angle, which suggests that we should see far ahead into the future.