• Journal of electromagnetic engineering and science
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• 제16권2호
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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.

• 한국광학회지
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• 제5권1호
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• pp.67-73
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• 1994

재생증폭기에서의 gain narrowing 현상, 비선형형상, 에너지 포화상태 등의 증폭특성 해석 및 최적 설계를 위한 시뮬레이션 코드를 개발하였다. 재생증폭기에서 gain narrowing 현상을 줄이기 위해서는 증폭매질의 중심파장에 일치하는 대칭인 펄스를 이득대역폭이 넓은 매질에 입사시켜야 한다. 재생증폭기의 특성을 최대한 활용할 수 있는 증폭매질로는 이득대역폭이 넓고, 비선형굴절율이 작으며, 고에너지를 얻을 수 있는 Ti-Sapphire가 최적매질로 평가되었고, 재생증폭기 설계시 중요한 파라미터에 대하여 해석하였다.

• Applied Science and Convergence Technology
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• 제23권6호
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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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• 제29권6호
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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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• 제16권5호
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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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• 제29권5호
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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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• 제6권5호
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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.

• 기술사
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• 제29권1호
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• pp.29-35
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• 1996

• 한국광학회:학술대회논문집
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• 한국광학회 2002년도 제13회 정기총회 및 2002년도 동계학술발표회
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• pp.282-283
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• 2002

• 한국축산시설환경학회지
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• 제6권3호
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• pp.201-209
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• 2000

수평아리 사체를 이용한 효모의 최적 배양 조건과 효모배양물이 육계의 성장에 미치는 영향을 조사하였다. 수평아리 추출물의 단백질 농도는 72시간 동안 추출되었을 때 가장 높았으며, 수평아리 사체에서 추출물을 얻기 위한 물의 첨가 비율은 수평아리 사체의 무게에 1.5배(v/w ratio)가 적당하였다. 수평아리 사체의 추출물에서 지방은 효모의 성장에 영향을 미치지 못하였다. 수평아리 사체의 추출물과 4% sugarcane molasses로 구성된 SCELP2 배지는 1% yeast extract, 2% bacto pepton 그리고 2% glucose로 구성된 YEPD 배지보다 효모수가 26% 더 증가하였다. 또한 SCELP2 배지에 4% 폐이스트를 첨가한 SBYW2 배지는 SCELP2 배지보다 효모수가 8% 증가하였다. SBYW2 배지에서 배양된 효모배양물을 5주 동안 육계에 급여한 결과 종체량은 4% 첨가구가 대조구보다 9% 증가하였다. 따라서 본 연구 결과 부화부산물로 발생되는 수평아리 사체는 사료용 효모배양물을 생산하기 위한 효모배양 배지의 질소원으로서 이용될 수 있음을 의미한다.