• Journal of electromagnetic engineering and science
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• v.16 no.2
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• pp.134-142
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• 2016

This paper proposes a technique for improving the conventional conical horn antenna for the X-band frequency using metamaterial on a wire medium structure. The main idea of this research is the application of the wire medium metamaterial to the conical horn's aperture for the enhancement of the horn's gain; this is done without changing the antenna's dimensions. The results show that the wire medium structure can increase the gain of a conventional conical horn antenna from approximately 17.7 dB to 20.9 dB (an increase of approximately 3.2 dB). A prototype antenna was fabricated, and its fundamental parameters including its reflection coefficient ($S_{11}$), radiation patterns, and directive gain were measured. The simulated and measured results were very good. The wire medium structure of the proposed antenna improved the radiation pattern, enhanced the directivity, increased the gain, and reduced the side lobe level using a simple integrated wire medium structure.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.67-73
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• 1994

The simulation code was developed to analyze the amplification properties of the regenerative amplifier, such as gain narrowing, nonlinear effect, and energy saturation. To reduce gain narrowing in the regenerative amplifier, the input pulse with a symmetrical shape and the same center wavelength of the active medium should be amplified in the active medium with a broad fluorescence linewidth. In this respect, Ti:Sapphire with a low nonlinear refractive index, a high saturation fluence, and a broad fluorescence linewidth is the most appropriate medium for the regenerative amplifier. The knowledge and the important parameters were acquired for the optimum design of the regenerative amplifier.

• Applied Science and Convergence Technology
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• v.23 no.6
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• pp.371-375
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• 2014

Diffusion coefficient of Fe in polycrystalline host ZnSe as a mid-IR gain medium has been measured in the annealing temperature ranges of 850 to $950^{\circ}C$. The synthesis of the samples was carried out in quartz ampoule in which the Fe thin film deposited by physical vapor evaporation method on the ZnSe. One can realize that the diffusion coefficient strongly depends on the surface active surfactants through the cleaning process and the substrate temperature during the thin film deposition leading to $2.04{\times}10^{-9}cm^2/s$ for $Fe^{2+}:ZnSe$. The Annealing temperature dependence of the Fe ions diffusion in ZnSe was used to evaluate the activation energy, $E_a$=1.39 eV for diffusion and the pre-exponential factor $D_0$ of $13.5cm^2/s$.

• ETRI Journal
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• v.29 no.6
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• pp.779-784
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• 2007

In this paper, we report the experimental results of a hybrid wideband fiber amplifier. The amplifying medium is a concatenated hybrid fiber consisting of Er-doped fiber (EDF) and dispersion compensating fiber (DCF). The gain mechanisms are based on stimulated emission in the EDF and stimulated Raman scattering (SRS) in the DCF. Since we simultaneously use optical amplification by the two processes, the gain bandwidth is easily expanded over 105 nm by a two-tone pumping scheme. Using an experimental setup constructed with a hybrid structure of EDF-DCF-EDF, we analyzed the spectral behavior of amplified spontaneous emission for pumping powers. We achieved an optical gain of over 20 dB in the wavelength range from 1,500 to 1,600 nm under optimized pumping conditions to make the spectral gain shape flat.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.5
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• pp.665-671
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• 2003

A factorial experiment was conducted to assess nutrient utilization by growing lambs maintained on three levels each of digestible energy (high: HE, medium: ME, low: LE) and protein (high: HP, medium: MP, low: LP) in nine combinations (HEHP, HEMP, HELP, MEHP, MEMP, MELP, LEHP, LEMP, LELP). The experiment was conducted during the hot season in a semiarid location. Daily dry matter intake (DMI) was similar in all the groups in terms of unit body weight or metabolic body size. Digestibility of DM and nitrogen free extract increased (p<0.01) from low to medium and high energy regimen while the CF digestibility followed a reverse trend. The digestibility of crude protein (CP) decreased from high to medium and low protein regimens while it was similar in terms of energy variation. Nitrogen intake was higher in high followed by medium and low protein regime while fecal and urinary nitrogen loss were similar in all the treatment groups. Lambs in all the three levels of protein were in positive N balance and percent N retention was higher (p<0.01) in high followed by medium and low protein levels whereas it was similar in terms of energy variation. Initial body weight was similar in all the groups while final weight, total gain in the experiment and average daily gain (ADG) were higher in high than medium and low energy regimens. It is concluded that crossbred lambs required 75.1 g DM, 9.6 g CP, 6.3 g DCP and 711 KJ DE/kg W $^{0.75}$or 11.0 g CP/MJ DE or 7.2 g DCP/MJ DE for 93 g average daily gain in a hot semiarid environment.

• ETRI Journal
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• v.29 no.5
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• pp.673-675
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• 2007

We present the design and fabrication of a 60 GHz medium power amplifier monolithic microwave integrated circuit with excellent gain-flatness for a 60 GHz radio-over-fiber system. The circuit has a 4-stage structure using microstrip coupled lines instead of metal-insulator-metal capacitors for unconditional stability of the amplifier and yield enhancement. The gains of each stage of the amplifier are modified to provide broadband characteristics of input/output matching for the first and fourth stages and to achieve higher gains for the second and third stages to improve the gain-flatness of the amplifier for wideband.

• Current Optics and Photonics
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• v.6 no.5
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• pp.479-488
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• 2022

To account for the internal thermal effects of solid-state lasers, a method using a back propagation (BP) neural network integrated with a particle swarm optimization (PSO) algorithm is developed, which is a new wavefront distortion correction technique. In particular, by using a slab laser model, a series of fiber pumped sources are employed to form a controlled array to pump the gain medium, allowing the internal temperature field of the gain medium to be designed by altering the power of each pump source. Furthermore, the BP artificial neural network is employed to construct a nonlinear mapping relationship between the power matrix of the pump array and the thermally induced wavefront aberration. Lastly, the suppression of thermally induced wavefront distortion can be achieved by changing the power matrix of the pump array and obtaining the optimal pump light intensity distribution combined using the PSO algorithm. The minimal beam quality β can be obtained by optimally distributing the pumping light. Compared with the method of designing uniform pumping light into the gain medium, the theoretically computed single pass beam quality β value is optimized from 5.34 to 1.28. In this numerical analysis, experiments are conducted to validate the relationship between the thermally generated wavefront and certain pumping light distributions.

• Journal of the Korean Professional Engineers Association
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• v.29 no.1
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• pp.29-35
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• 1996

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.282-283
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• 2002

• Journal of Animal Environmental Science
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• v.6 no.3
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• pp.201-209
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• 2000

Optimal conditions to utilize egg type male chicks from hatchery for cultivating yeast(Saccharomyces cerevisiae) and the effects of the yeast culture on growth of broiler chicks were investigated. The protein concentration of the spent cockerel extracts was the highest when extracted for 72 hours. Optimal water volume added to the spent cockerel chicks for the extraction was 1.5 times to the cockerel chicks weight (v/w ratio). Lipid in the extracts from the spent cockerel chicks did not affect on the yeast growth. The number of yeast cultured in the SCELP2 medium containing spent cockerel extracts and 4 % sugarcane molasses was higher by 26 % than that in the YEPD medium containing 1 % yeast extract, 2 % bacto pepton and 2 % glucose. Also the number of yeast cultured in the SBYW2 medium containing SCEP2 medium containing SCELP2 and 4 % brewer's yeast waste was increased by 8 %, compared to that in the SCELP2 medium. Body weight gain of chicks fed 4 % yeast culture supplementations cultivated in the SBYW2 medium was increased at 5 weeks by 9 %, relative to no supplementation(P<0.05). The results from this study suggest that the spent cockerel chicks can be utilized as nitrogen sources to produce yeast culture for animal feed.