반추위 미생물의 질산염 환원 조절물질에 관한 연구

손용석,홍성호,이성호 한국영양사료학회 1999 韓國營養飼料學會誌 Vol.23 No.5

반추위내 미생물들의 질산염(NO₃^-) 환원능력에 관여할 수 있는 물질로 잠재성이 있다고 판단되는 Yeast culture(YC), L-cysteine(CSH) 및 Sodium tungstate(W)의 첨가효과를 관찰하고자, in vivo 및 in vitro 실험을 실시하였다. In vitro 실험에서는 미생물 공여축으로 반추위 누관이 장착된 55㎏ 숫면양에 체중 ㎏당 400 ㎎의 NaNO₃를 2주간 급여 적응시킨 후, 반추위액을 채취하여 첨가물질(YC, CSH. W)들과 함께 배양하면서 pH, 질산염, 아질산염 및 암모니아의 농도변화를 시간별로 관찰하였다. 배양액 내 NO₃^-농도는 대조구에 비해 CSH구와 W구에서는 높게, 그리고 YC구에서는 낮게 나타났다(P<0.05). 배양액 내 NO₂^- 농도는 대조구에 비해 YC, CSH, W구에서 유의적으로 감소하였고(P<0.05), 암모니아 농도는 CSH구에서 가장 낮게 나타났다(P<0.05). In vivo 시험에서는 질산염 중독반응에 대한 Yeast culture의 첨가효과를 관찰하기 위하여, 1차 시험에서는 숫면양 4두를 Switch-over design으로 배치하여 2%의 YC를 2주간 첨가급여하였다. 2차 시험에서는 L-cysteine (CSH)의 첨가효과를 관찰하고자 3두의 숫면양을 3×3 Latin Square 방법으로 배치하여 2주간 NaNO₃(0.5g NO₃^-/BW ㎏^(0.75))와 L-cysteine(0.115g S/W ㎏^(0.75))을 누관을 통해 주입한 후 혈중 NO₂^-와 MHb의 농도 변화를 시간별로 관찰하였다. 혈액 내 NO₂^- 농도는 NaNO₃ 투여 후 2시간때에 대조구에 비해 YC 첨가구에서 유의적으로 낮게 나타났으며, 혈액 내 MHb 농도는 NaNO₃ 투여 후 3시간과 4시간때에 YC 첨가구에서 유의적으로(P<0.05) 감소하였다. 또한, L-Cysteine의 경우에도 NaNO₃에서 유래한 혈중 NO₂^- 농도를 유의적으로(P<0.05) 감소시켰으며, NaNO₃ 투여 후 6시간 때에 혈중 MHb 형성을 유의적으로(P<0.05) 억제시켰다. 따라서, 본 시험에 공시한 3가지 물질들은 모두가 반추위 내 질산염 대사 속도를 조절함으로써 대사산물에서 유래하는 독성을 예방 또는 억제하는데 기여할 수 있음이 확인되었다. This study was conducted to examine the activities of some materials which could affect nitrate and nitrite reduction in the rumen and eventually their toxicity in ruminant animals. Rumen fluid (RF) taken from a fistulated ram was used as inoculum for an in vitro study, where 400 ㎎ NO₃^- ㎏^(-1) BW was added to RF donor rams for 14 days for adaptation. RF was incubated with 20 mM NaNO₃ in the presence of 0.25% Yeast culture (YC), 10 mM L-cysteine (CSH) or 1 mM sodium tungstate (W) for 24 hrs, and time changes of NO₃^-, NO₂^- and NH₃ concentrations in the medium were observed. NO₃^- concentration showed higher values in the medium with CSH and W group than that without addition (P<0.05). As compared with control, significantly lower NO₂^- concentrations were observed in the medium incubated with YC, CSH and W (P<0.05). The addition of CSH caused lower NH₃ concentration than control (P<0.05). Prophylactic effects of yeast culture and L-cysteine on the intensity of nitrate poisoning were also observed in vivo. Four rams were assigned to two group (Control, 2% YC) in a Switch-over design, and three rams were allotted to three treatments (CSH, NO₃^-, CSH + NO₃^- supplement) in a 3 × 3 Latin square design. The sheep fed Yeast culture had lower NO₂^- and MHb concentrations of blood than those fed without Yeast culture (P<0.05). A supplementation of L-cysteine to the diet decreased the level of blood NO₂^- as well as concentration of MHb (P<0.05) caused by NaNO₃ feeding. Consequently, continuous feeding either Yeast culture or L-cysteine could help prevent nitrate toxicity.

In 과 Sb 의 첨가가 Tin Oxide 가스센서에서 Resistivity 와 Sensitivity 에 미치는 영향

한상도,손영목,김종원,심규성 한국센서학회 1992 센서학회지 Vol.1 No.1

To determine the effect of additions of trivalent and pentavalent ions on the electrical conductivity and sensing behaviour, indium and antimony were incorporated in tin oxide by the coprecipitation method. Antimony may be considered to enter the cassiterite structure as pentavalent ions, thermal energy could excite electrons from these ions into the conduction band. Similarly the indium ions would enter the lattice as In^(3+) but could accept electrons from the valence band, thereby becoming monovalent or divalent. These phenomena, however, how the potential barrier existing SnO₂ by addition of two kinds of ions could influence on the sensing behaviour in comparison with their influence on the resistivity were observed.

FDTD 방법을 이용한 원통형 유전체 봉 안테나의 해석

이철훈,조영기,손현,이동국 경북대학교 전자기술연구소 2000 電子技術硏究誌 Vol.21 No.1

The finite-difference time-domain (FDTD) method is used toanalyze circular dielectric rod antenna excited by conducting waveguide. Two dimensional cylindrical FDTD algorithm is applied for rotationally symmetric structure. UPML is used for the cylindrical structure. Radiation patterns and reflection coefficients of this structure am obtained and compared with those available in the literature. Antenna characteristics am also determined for different rod length, tapering angle, hole position, and diameter.

회주철의 진동감쇠능과 기계적 성질에 미치는 오스템퍼링처리의 영향

백승한,김정철,손용철,한동운 한국열처리공학회 1999 熱處理工學會誌 Vol.12 No.2

Gray cast iron with a high damping capacity has been used for controlling the vibration and noise in various mechanical structures. Nevertheless, its usage has been often restricted due to its poor tensile strength. Therefore, it is necessary to improve tensile strength at the expense of a loss in damping capacity. This study is aimed at finding the best combination of tensile strength and damping capacity by varying austempering time and temperature range from 320℃ to 380℃ after austenization at 900℃ for 1hr. The effect of austempering condition on hardness and the volume fraction of retained austenite is investigated as well. The results obtained are summarized as follows : (1) With an increase in austempering temperature, both tensile strength and hardness decrease while damping capacity improves. (2) Austempering at 350℃, resulting in a mixture of upper and lower bainite with partially retained austenite, exhibits the optimum combination of tensile strength and damping capacity.

Zn-0.3wt.% Al 합금의 초소성 변형에 따른 미세조직의 변화

이원절,박찬경,하태권,손중락,장영원 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.9

The superplastic deformation of Zn-0.3wt.%Al alloys were investigated at room temperature under various strain rate. These alloys were highly elongated up to 1400% at the initial strain rate of 2×10^(-4)/s, revealing the rate sensitivity parameter of about 0.4. In order to investigate the microstructural change during superplastic deformation, the transmission electron microscopy(TEM) studies were performed on the specimen elongated up to the 100% tensile strain at various strain rate. The microstructure was composed of zinc rich matrix phase, with 1㎛ in grain size, and Al rich second phases precipitated generally at grain boundaries and/or triple point. In region III(5×10^(-2)/s), the high density of dislocations were observed within the grains and deformation twins were also formed within the grains. In region II(2^*10^(-4)/s), however, the dislocations were highly localized along the grain boundaries and deformation twins were not observed. Observation of severe deformation along the grain boundaries and grain boundary migration(GBM) suggest that grain boundary sliding(GBS) is a dominant mechanism of superplastic deformation in this alloy.

Ewald 합 기법을 이용한 구형 도파관의 H-면에 위치한 타원 편파 오프셋 십자 슬롯에 대한 해석

김병문,조영기,윤리호,손현 경북대학교 전자기술연구소 2000 電子技術硏究誌 Vol.21 No.1

This paper presents the analysis of an offset cross slot in the broad wall of a rectangular waveguide. The problem is formulated in teens of integro-differential equation which is solved using the method of moments with triangular Roop-top basis. For the effective numerical intgral evaluation, the Ewald sum technique is applied to the Green's function of the rectangular waveguide, transforming them into the rapidly convergent form. We have shown that a pair of narrow slots crossed at arbitrary angles and located at the proper point in the broad wall of an ordinary rectangular waveguide will radiate a wave very nearly circularly polarized at the desired direction.

고온변형시 Alloy 718 의 동적 및 준동적 재결정 거동

나영상,김인수,박노광,손성만 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.10

Compression tests were carried out on Alloy 718 to investigate the microstructure development following dynamic recrystallization, meta-dynamic recrystallization and grain growth. Tests were performed in the temperature range of 927∼1066℃ and strain rate range of 5∼5×10^(-4)s^_(-1), with true strains up to 0.8. Dynamically recrystallized grain size decreases consistently with increasing Zener-Hollomon parameter (Z=ε exp(Q/RT)) which is function of strain rate and temperature. The extent of recrystallization increases with a decrease in Zener-Hollomon parameter due to an increase in the critical strain (ε_c) corresponding to the initiation of dynamic recrystallization. The fraction of meta-dynamically recrystallized grain, however, increases with increasing the strain rate from 0.01s^(-1) to 1s^(-1). This paper outlines the microstructural evolution of Alloy 718 during the high temperature deformation.

질소이온주입에 따른 생체안전성 티타늄 임플란트의 마모특성

변응선,최종운,손선희,정용수 한국산업안전학회 1999 한국안전학회지 Vol.14 No.4

In this study, plasma source ion implantation was used to improve the wear properties of biocompatible titanium implant. In order to observe the effect of ion energy and dose on wear property of titanium implant, pin-on-disk type wear tests in Hank's solution were carried out. The friction coefficient of ion implanted specimens were increased from 0.47 to 0.65 under high energy and ion dose conditions. As increasing ion energy and ion dose, the amount of wear was reduced.

구선 활인심법에 관한 연구

손인철 한국원불교학회 1999 圓佛敎學 Vol.4 No.-

종동력을 받는 외팔보의 안정성에 관한 이론적 연구

김현수,윤한익,손종동 한국산업안전학회 1998 한국안전학회지 Vol.13 No.1

On the stability of the cantilever beam subjected to a follower force at the free end, the influences of the translational spring and the moment of inertia of a tip mass at the free end have been studied by numerical methods. The centroid of a tip mass is offset from the free end of a Beam and is located along its extended axis to vary the value of moment of inertia of a tip mass. It is proved that as the constants of a spring supporting the free end are augmented, the critical flutter loads of the above system decrease, whereas they increase without a tip mass.