• Current Optics and Photonics
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• v.3 no.3
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• pp.236-242
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• 2019

An Nd:YAG slab structure was designed for a high-power zigzag slab laser amplifier based on computational simulation of the wavefront distortion. For the simulation, the temperature distribution in the slab was calculated at first by thermal analysis. Then, the optical path length (OPL) was obtained by a ray tracing method for the corresponding refractive index variation inside the slab. After that, the OPL distribution of the double-pass amplified beam was calculated by summing the results obtained for the first and second passes. The amount of wavefront distortion was finally obtained as the peak-to-valley value of the OPL distribution. As a result of this study, the length and position of the gain medium were optimized by minimizing the transverse wavefront distortion. Under the optimized conditions, the transverse wavefront distortion of the double-pass amplified beam was less than $0.2{\mu}m$ for pump power of 14 kW.

• Current Optics and Photonics
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• v.4 no.6
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• pp.551-557
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• 2020

A mirror-in-slab waveguide is fabricated on a slab waveguide by using the refractive-index contrast between two materials, with the reflection performance depending on the slab waveguide's design. In this research, a slab waveguide design consisting of silicon (Si) as the core and SiO2 as the substrate was designed and developed to determine the coupling, waveguide, and mirror losses. Based on experimental results, coupling loss is dominant and is affected by the design of the slab waveguide. Furthermore, the mirror loss is affected by the design of the mirror, such as the curvature radius and the size of the mirror. TE and TM polarizations of light are used in the measurements. The experimental results show that mirror losses due to reflection by mirrors are 0.011 dB/mirror and 0.007 dB/mirror for TE and TM polarizations respectively. A simulation was performed to confirm whether the size of mirror is sufficient to reflect the input light, and to check the quality of the surfaces of fabricated mirrors.

• Journal of Bio-Environment Control
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• v.26 no.2
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• pp.100-107
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• 2017

This experiment was carried out to analyze the effects of substrate reuse on the growth and yield of summer paprika in cyclic hydroponics. The test group was divided into a new coco slab, one year reused coco slab two year reused coco slab based on 30% nutrient solution reuse, and was performed from April 18 to November 31, 2016 for 30 weeks. As a result, plant height of early growth was that the 2 year reused slab was longer than the new slab but the final growth period was 56.58 cm shorter. First group flower position was that reused slab was shorter by 2.92 cm than the new slab and the second group flower position was 0.31 cm long. The relative internode length of early growth, when the reused slab was used, the imbalance in the late growth stage was increased compared with the use of the new slab. The number of growth nodes in the 1 and 2 year reused slab was the smallest with 27.4 nodes. However, the number of harvested nodes did not show the difference in the test group, and the ratio of harvested that the 2 year reused slab was the highest at 26.8%. The ratio of unmarketable fruit tended to increase as the growth progressed. Fresh weight was 227.7g for new slab, 219.2g for 2 year reused slab and 21.2g for 1 year reused slab. The dry weight of the new slab increased with the reuse of the slab. It was 17.13g for new slab, 18.26g for 1 year reused, and 19.28g for 2 year reused. The average water content of the entire growth period was smaller as the slab was reused, and the 1 year reused slab was about 20g less than the 2 year reused slab. This trend was steadily occurring throughout the entire growing season. Especially, the reused slab for 1 year was less than 60g after 3 groups compared to other test groups. In conclusion, If will control seriously occurrence of unmarketable fruits by weakening after medium growth in summer-cultivated paprika in EC-based recycling hydroponic cultivation with reused cocopeat substrate, It is not what I have to worry that decrease of the yield and deterioration of the quality due to the change of physical and chemical properties of the slab and the pathogenic bacteria infection.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.111-116
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• 2003

The Permanent Way consisting of rails and sleeper laid on ballast is a technically and economically viable solution. After two decades of targeted research and development activities Slab Track turned out to be a reasonable option on special fields. Slab Track proves that especially under extreme condition and loads - they reliably help stability and a long service life of track. Technical and experimental solution of slab track are particularly underlined. This paper presents a few Results of the experiments of SFRC slab tracks under fatigue load.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.87-90
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• 2000

In this paper. we present a method for a systematic design of a dielectric slab polarizer in the circular waveguide. This structure is realized using a tapered dielectric slab inside a circular waveguide. Commercial software is used to obtain the equivalent dielectric constant of the circular waveguide partially filled with a dielectric slab. The length of the tapered region is determined so that the reflection from the dielectric slab is sufficiently low. A polarizer operating at 10 GHz band is designed, fabricated and tested.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.50-59
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• 2014

In this paper, Reinforced concrete (R/C) and R/C+steel plate concrete slab was carried out by SAP2000 software program in order to compare the stability of the multi-functional fishway, that is Bonggok fishway, built at Bonggok river recently in Gumi city, when the size of underground passage is $1m{\times}0.2m$, $1m{\times}0.4m$, $1m{\times}0.6m$ and the velocity is 0.8m/s, 1.2m/s, 1.6m/s respectively for the S2 (R/C+S/C). The analysis shows the maximum stress of S2 decreases less 26~50% than that of Bonggok, bending moment of sidewall decreases less 28~54%, maximum stress of side wall decreases less 17~31%, bending moment of upper slab decreases less 24~47%, maximum stress of upper slab decreases less 4~20%, and bending moment decreases less 10~27% than that of Bonggok. The complementation is required as much as the following percent; 27% and 25% for the maximum stress and bending moment of underground passage, 15% and 24% for the side wall maximum stress and bending moment, and 10% and 14% for the upper slab maximum stress and bending moment, respectively. This result shows that the S2 is greatly superior to that of the Bonggok fishway, and underground passage size of $1m{\times}0.4m$ is superior to that of $1m{\times}0.2m$ or $1m{\times}0.6m$, and R/C+S/C slab is superior to that of R/C slab. This result is expected to be the basic data for the construction and design of the multi-functional fishway.

• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.60-65
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• 2015

This study is to explore floor impact sound and sound insulation of reinforced concrete structure with void-deck slab system which combines polystyrene void foam and T-shaped steel deck plate. A void-deck slab system can effectively reduce the amount of concrete used and hence the mass of a reinforced concrete slab. Also void slab system has dynamically favorable for bending. Three-bay 2-story building was constructed as a mock up test specimen using void-deck slab system and floor impact sound was measured to valuate sound insulation performance. Light weight floor impact and heavy weight floor impact were investigated. Light weight floor impact pressure levels were 32dB, 28dB, and 29db at representative locations which are $1^{st}$ level in the floor impact sound insulation performance grading system. The heavy-weight floor impact pressure levels were 44dB, 45dB, and 43dB at representative locations which are $2^{nd}$ level in the floor impact sound insulation performance grading system. Therefore void-deck slab system can be used in public housing apartment building in terms of not only effectively reduced construction materials but also floor impact sound insulation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.527-532
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• 2008

In this study, numerical analysis is performed to investigate the sound radiation characteristics of an apartment house according to the type of the slab system. In order to satisfy the boundary condition of the apartment house, the whole floor is modelled with FEM model for three different structural system: wall, RC, flat slab system. From the analytical results, it Is shown that heavy weight floor impact noise of wail type slab is larger than that of the other slab systems and the noise radiated from the wall have great effect on the sound pressure level. The results also show that the vibration energy of RC or flat slab system is widely distributed over the whole slab, which is main reason that the noise induced by the slab systems is reduced in comparison with wail slab system.

• Journal of the Korea Institute of Building Construction
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• v.5 no.2 s.16
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• pp.161-166
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• 2005

This study is to evaluate on the increased cost of construction according to the depth change of concrete slabs in apartment building. When we increased the depth of concrete slab from 150mm to 180, 210mm, the qualitative and cost of construction were calculated by the high-rise type, the unit-size type. As a result of this study, in 32 Pyong type, increment of construction cost rate appeared by $5.1\%$ in case of increase from slab 150mm to 180mm, and $10.0\%$ in case of increase from slab 150mm to 210mm. In 45 Pyong type, Increment of construction cost rate appeared by $5.7\%$ in case of increase from slab 150mm to 180mm, and $10.2\%$ in case of increase from slab 150mm to 210mm. In 55 Pyong type, Increment of construction cost rate appeared by $2.4\%$ in case of increase from slab 150mm to 180mm, and $8.9\%$ in case of increase from slab 150mm to 210mm.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.161-169
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• 2017

Flat slab systems are vastly used in multi-story buildings because of their savings in story height and construction time, as well as for their flexibility in architectural remodeling. However, they frequently suffer brittle punching-shear failure around columns, especially when subjected to lateral loads. Therefore, seismic codes labeled flat slabs as non-ductile systems. This research goal is investigating some construction alternatives to enhance flat slab ductility and deformability. The alternatives are: adding different types of punching-shear reinforcement, using discreet fibers in concrete mixes, and increasing thickness of slab around columns. The experimental study included preparation and testing of seven half-scale interior slab-column connections up to failure. The first specimen is considered a reference, the second two specimens made of concrete mixes with different volumetric ratios of polymer fibers. Another three specimens reinforced with different types of punching-shear reinforcement, and the last specimen constructed with drop panel of inverted pyramidal shape. It is found that using the inverted pyramid-shape drop panel of specimen, increases the punching-shear capacity, and the initial and the post-cracking stiffnesses. The initial elastic stiffnesses are different for all specimens especially for the slab with closed stirrups where it is experienced the highest initial stiffness compared to the reference slab.