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Drop-In Tests of R-404A Alternative Refrigerants R-455A and R-454C in a Small Ice Maker
이병무,NAE-HYUN KIM 대한설비공학회 2019 International Journal Of Air-Conditioning and Refr Vol.27 No.2
R-404A, which had long been used as the refrigerant of a unitary ice maker, has to be replaced due to global warming. In the present study, drop-in tests were conducted for long-term alternative refrigerants R-455A and R-454C on the ice maker of 100 kg/day capacity. Five samples were made having different combinations of refrigerant, condenser and compressor. Tests were conducted changing the outdoor and the supply water temperature. At the standard outdoor condition (21∘C, 65 RH and 10∘C water temperature), change of refrigerant from R-404A to R-455A for the same ice maker extended the ice ball formation time by 13% and reduced the amount of ice production per day by 6%. Larger vapor density and smaller temperature glide of R-404A may have resulted in a better performance. Furthermore, adoption of a larger (from 1/3 HP to 3/8 HP) compressor reduced the ice ball formation time by 12% and increased the amount of ice production per day by 8%. In addition, change of the fin-tube condenser to the microchannel condenser reduced the ice ball formation time by 9% and increased the amount of ice production per day by 4%. The refrigerant charge was also significantly reduced from 440 g to 316 g. Thermal performance of R-454C was poorer than that of R-455A. Replacement to R-454C increased the ice ball formation time by 14% and decreased the amount of ice production per day by 8%. The reason may be attributed to a larger pressure lift, which leads to smaller refrigerant mass flow rate. Ice production was possible even at the harsh environment (35∘C, 65 RH and 21∘C water temperature), although the production amount decreased.
이병무 한국작물학회 2007 Journal of crop science and biotechnology Vol.10 No.2
Antibiotics used for suppressing Agrobacterium in plant transformation might have negative effects on plant tissues and regeneration. The effects of antibiotics on growth suppression of Agrobacterium and plant regeneration were investigated for enhancing Agrobacterium-mediated transformation using wheat mature embryos. All the antibiotics tested, except for carbenicillin, prevented embryos from becoming coated with a layer of Agrobacterium cells in callus induction medium. Agrobacterium growth was suppressed at 50 mg/l of timentin, while cefotaxime and clavamox completely suppressed growth at a concentration of 250 mg/l. In the carbenicillin treatment, initiation of growth suppression of Agrobacterium occurred at 750 mg/l of concentration because Agrobacterium KYRT1 carries a carbenicillin-resistant gene. In Agrobacterium inoculation, effects of antibiotics were significantly different on the rate of callus induction and shoot formation. Almost all embryos produced calli at 50 mg/l of timentin whereas callus induction rate was achieved above 90% at 100 and 250 mg/l of cefotaxime and clavamox, respectively. Shoot formation rate was higher in the treatment with timentin than with cefotaxime and clavamox at 500 mg/l of concentration. Timentin can be used as an effective antibiotic in Agrobacterium-mediated wheat transformation. Antibiotics used for suppressing Agrobacterium in plant transformation might have negative effects on plant tissues and regeneration. The effects of antibiotics on growth suppression of Agrobacterium and plant regeneration were investigated for enhancing Agrobacterium-mediated transformation using wheat mature embryos. All the antibiotics tested, except for carbenicillin, prevented embryos from becoming coated with a layer of Agrobacterium cells in callus induction medium. Agrobacterium growth was suppressed at 50 mg/l of timentin, while cefotaxime and clavamox completely suppressed growth at a concentration of 250 mg/l. In the carbenicillin treatment, initiation of growth suppression of Agrobacterium occurred at 750 mg/l of concentration because Agrobacterium KYRT1 carries a carbenicillin-resistant gene. In Agrobacterium inoculation, effects of antibiotics were significantly different on the rate of callus induction and shoot formation. Almost all embryos produced calli at 50 mg/l of timentin whereas callus induction rate was achieved above 90% at 100 and 250 mg/l of cefotaxime and clavamox, respectively. Shoot formation rate was higher in the treatment with timentin than with cefotaxime and clavamox at 500 mg/l of concentration. Timentin can be used as an effective antibiotic in Agrobacterium-mediated wheat transformation.
원형 도파관을 이용한 초고출력용 TM<sub>01</sub>-TE<sub>11</sub> 직접 모드 변환기
이병무,이상흔,윤영중,양기주,Lee Byoung-Moo,Lee Sang-Heun,Yoon Young-Joong,Yang Gi-Joo 한국전자파학회 2006 한국전자파학회논문지 Vol.17 No.4
본 논문에서는 초고출력용 X-band 협대역 안테나 시스템으로부터 초고출력 에너지를 최대 지향성으로 방사할 수 있도록 확장된 원형 도파관의 입력 $TM_{01}$ 모드를 출력 $TE_{11}$ 모드로 직접 변환하는 장치를 설계하고 그특성을 고찰하였다. 제안된 모드 변환기는 1차 미분 커플링 방정식으로부터 $TM_{01}$와 $TE_{11}$ 모드 사이에 최대 커플링 효과를 갖도록 non-constant serpentine 형태의 비선형 함수에 대한 근사 설계법을 제안하고, X-band 10 GHz의 동작 주파수에서 200 mm의 전체 길이와 95% 이상의 변환 효율 특성을 갖도록 구현되었으며, 기존의 $TM_{01}-TE_{11}$ 직접 모드 변환기와 비교, 분석을 통해 소형, 고효율의 특성을 확인하였다. In this paper, a direct $TM_{01}-TE_{11}$ mode converter of circular waveguide which is used the approximated design method of mode conversion between $TM_{01}$ and $TE_{11}$ modes is designed for radiation with the maximum directivity of high power energy into air (rom high power microwave antenna system. The proposed direct $TM_{01}-TE_{11}$ mode converter is calculated and designed with an approximated method for non-linear function about an extended non-constant serpentine type of circular waveguide. Then, the designed mode converter is optimized by length of 200 mm and efficiency above 95% by FIM simulation and achieved short length and high efficiency of the antenna by results of fabricated and measured characteristics.
재순환 영역이 있는 축대칭 난류 확산화염의 구조 (II)
이병무,신현동 대한기계학회 1986 대한기계학회논문집 Vol.10 No.1
본 논문에서는 재순환 영역이 존재하는 축대칭 난류 확산화염 구조예측의 전 단계로서, 이미 발표된 바있는 필자의 실험 데이터를 바탕으로 하여 등온유동에 서의 난류모델을 검토한다. 유선의 곡률이 큰 유동에 2방정식 모델을 적용함은 큰 결점을 보완한 수정-2방정식모델을 채택하여 실험결과와 비교, 검토하여 모델의 타당성을 조사하였다. Turbulent mixing field with recirculating flow which is formed by injecting gaseous fuel on the main air stream is solved numerically by a finite difference method. The turbulence model for obtaining transport properties was k-.epsilon. model, which was obtained from turbulent kinetic energy and its dissipation rate. Considering the effects of streamline curvature, modified k-.epsilon model was used. Generally, Modified k-.epsilon. model makes better predictions than standard model, and from this result, it is recognized that standard model has deficiency when applied to turbulent recirculating flows, and that modified k-.epsilon. model takes into account of streamline curvature effects properly. Meanwhile, A more study will be necessary to find the reason why large differences between predicted and experimental turbulent kinetic energy exist.