• 한국어업기술학회:학술대회논문집
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• 한국어업기술학회 2003년도 춘계 수산관련학회 공동학술대회발표요지집
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• pp.203-204
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• 2003

Ammonia in aquaculture system may lead to suppression of fish growth, sublethal histopathological changes, and even death thus ammonia is considered toxic to fish. Tricking filter and submerged filter have many advantages include: low construction cost, easy management and maintenance, and well adaptation to different water and waste loading rates. (omitted)

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.727-733
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• 1999

In general ,wastes of livestock are covered 1% in the total wastes in Korea. But, actual pollutant loading rates by an organic material are 18% which will be serious problem in fresh water lake. An aim of this study is analyzing water quality in Bo-Ryeoung fresh water lake which are arounded by a lot of small livestock area, so that look for how to manage water quality of fresh waterlake.

• 한국수산과학회지
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• 제29권2호
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• pp.230-237
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• 1996

본 연구는 살수여상공법을 양어장 순환수 처리 장치로 설치하여 유기물질 제거 효율, 암모니아 제거효율, 동력학적 상수, 슬러지 생산량과 산소소요량 등의 최적 운전방법을 도출하였다. 유기물질 부하율이 $0.500\~0.082kg\;COD/m^3/day$에서 $66.4\~81.2\%$의 SCOD 제거 효율과 $74.5\~84.0\%$의 SBOD 제거 효율을 보였다. 암모니아 부하율이 $0.271\~0.044kg\;NH_4^+-N/M^3/day$에서 $43.7\~61.8\%$ 의 암모니아성 질소 제거 효율을 보였으며 암모니아 제거량은 $27.2\~119.5mg\;NH_4^+-N/L/day$로 나타났다. Eckenfelder 식에 의해 구한 K, n값은 각각 $0.168\;min^{-1}$과, 0.132로 나타났으며 총 생성된 슬러지 생산량은 0.233g VSS/day로 kg BOD 제거량당 생성되는 슬러지 생산량은 0.572 kg VSS/kg $BOD_{rem}$로 나타났다. 산소소요량은 3.89mg $O_2/L/hr$로 수리학적부하가 $6.712\~40.341\;m^3/m^2/day$에서 $1.33\~7.22\;mg\;O_2/L/hr$로 수리학적 부하가 증가할수록 산소소요량이 증가하였으며 미생물당 산소소모율은 1.08kg $O_2/kg$ VSS로 나타났다.

• 한국가축번식학회지
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• 제15권1호
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• pp.49-57
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• 1991

생쥐 수정란의 동결보존법을 개선하고자 유리화 동결과정에서 제1보존액에서의 평형시간, 제2보존액에서의 전냉각 여부 및 straw loading 방법에 따른 동결보존 후 수정란의 생존율을 조사하고, 또한 유리화 동결보존 과정에서 수정란의 부분적인 손상 여부를 확인하기 위하여 동결보존 후 배양하여 수정란의 할구수를 Hoechst 33342로 염색하여 조사하였던 바 그 결과는 다음과 같다. 1. 동결융해 후 생존율은 Medium-1에서 10분간 평형시간을 준 경우(81.0%)는 5분간(40.0%) 및 15분간(74.1%)의 평형시간을 준 경우보다 유의적(P<0.05)으로 높았다. 2. Double Medium-2 column방법으로 얻은 생존율(81.0%)은 single Medium-2 column방법으로 얻은 생존율(62.8%)보다 유의적(P<0.01)으로 높았다. 그리고 Double Medium-2 column방법에서는 유리화 용액이 희석액에 오염되지 않아 순수하게 투명한 유리화를 이룰 수 있었다. 3. 전냉각을 않은 경우에 비하여 전냉각한 Medium-2로 동결한 수정란은 생존율에 있어서 다소 높은 성적을 보였으나 유의적인 효과는 없었다. 4. 상실배기의 수정란을 24~28시간동안 배양하여 얻은 후기 배반포를 Hoechst 33342로 염색하여 할구수를 조사하였던 바 신선란(53.3${\pm}$1.6)보다 동결란(41.4${\pm}$1.5)에서 유의적(P<0.05)으로할구수가 적었다. 이는 동결융해 과정에서의 부분적인 손상에 의하였던 것으로 사료된다.

• 동력기계공학회지
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• 제7권4호
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• pp.55-60
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• 2003

This paper is to investigate the fatigue crack growth of plasma-sprayed coating steels according to heat treatments. The experimental materials are carbon steels(substrate: S45C) with plasma-sprayed coating layers of Ni-4.5%Al and $TiO_2$. The fatigue test is conducted on compact tension specimen by a servo-hydraulic fatigue testing machine. The specimens are heat-treated at $400^{\circ}C\;and\;800^{\circ}C$, respectively. Loading condition is a constant amplitude sinusoidal wave with a frequency of 10Hz and a load ratio of 0.1. The fatigue crack growth length is automatically measured by a compliance method. In the case of non-heat treated specimens, the fatigue crack growth rates of both substrate and coating specimen are almost same. The crack growth rates of substrates and coating steels by heat treatment are larger than those of the non-heat treated one, because the ductile property increase by heat treatment. In ${\Delta}K<18MPa{\cdot}m^{1/2}$, the crack growth rates of the heat-treated specimens are slightly taster than non-heat treated one. But the both heated and non-heated one are almost same in ${\Delta}K>18MPa{\cdot}m^{1/2}$.

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.1013-1021
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• 2001

A series of rabbit common extensor tendon specimens of the humeral epicondyle were subjected to tensile tests under two displacement rates (100mm/min and 10mm/min) and different elbow flexion positions 45°, 90°and 135°. Biomechanical properties of ultimate tensile strength, failure strain, energy absorption and stiffness of the bone-tendon specimen were determined. Statistically significant differences were found in ultimate tensile strength, failure strain, energy absorption and stiffness of bone-tendon specimens as a consequence of different elbow flexion angles and displacement rates. The results indicated that the bone-tendon specimens at the 45°elbow flexion had the lowest ultimate tensile strength; this flexion angle also had the highest failure strain and the lowest stiffness compared to other elbow flexion positions. In comparing the data from two displacement rates, bone-tendon specimens had lower ultimate tensile strength at all flexion angles when tested at the 10mm/min displacement rate. These results indicate that creep damage occurred during the slow displacement rate. The major failure mode of bone-tendon specimens during tensile testing changed from 100% of midsubstance failure at the 90°and 135°elbow flexion to 40% of bone-tendon origin failure at 45°. We conclude that failure mechanics of the bone-tendon unit of the lateral epicondyle are substantially affected by loading direction and displacement rate.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.204-209
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• 2008

The interest in the mechanical behavior of materials at high strain rates has increased in recent years, and by now it is well known that mechanical properties can be strongly influenced by the speed of applied load. The split Hopkinson pressure bar (SHPB) has been widely used to determine mechanical properties of materials at high loading rates. However, to ensure test reliability, measurement error source must be accounted for and eliminated. During experiment, the specimens were located between the incident and the transmit bar. The presence of contact frictions between the test bars and specimen may cause errors. In this work, numerical experiments were carried out to investigate the effect of friction on test results. In SHPB test, the measured stress by the transmitted bar is assumed to be flow stress of the test specimen. Through the numerical experiments, however, it is shown that the measured stress by the transmit bar is axial stress components. When, the contact surface is frictionless, the flow stress and the axial stress of the specimen are about the same. When the contact surface is not frictionless, however, the flow stress and the axial stress are not the same anymore. Therefore, the measured stress by the transmitted bar is not flow stress. The effect of friction on the difference between flow stress and axial stress is investigated.

• Journal of the Korean Wood Science and Technology
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• 제36권5호
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• pp.56-65
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• 2008

In this paper experimental results are presented for the rheological behavior of high-solids saccharification of mixed northeast hardwood as a model feedstock. The experimental determination of the viscosity, shear stress, and shear rate relationships of the 10 to 20 percent slurry concentrations with constant enzyme concentrations were performed under variable rotational speed of a viscometer (2.0 to 200 RPM) at combined temperatures (50 to $30^{\circ}C$) for the initial four hours. The viscosities of saccharification slurries observed were in the ranges of 0.024 to 0.028, 0.401 to 0.058, and 0.840 to 0.087 Pa s for shear rates up to 100 reciprocal seconds at 10, 15, and 20 percent initial solids (w/v) respectively. The fluid behavior of the suspensions was modeled using the power-law, the Herschel-Bulkley, the Casson, and the Bingham model. The results showed that broth slurries were pseudoplastic with a yield stress. The model slope increased and the model intercept decreased with increasing fermentation time at shear rates normal for the fermentor. The broth slurries exhibited Newtonian behavior at high and low shear rates during initial saccharification process. The solid particle size ranged from 57.8 to $70.0{\mu}m$ for $40^{\circ}C$ and from 44.0 to 57.5 11m for combined temperatures at 10, 15, and 20 percent initial solids (w/v) respectively.

• 한국안전학회지
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• 제27권6호
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• pp.7-13
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• 2012

A lack of study on the dynamic tensile strengths of Sn-based solder joints at high strain rates was the motivation for the present study. A modified miniature Charpy impact testing machine instrumented with an impact sensor was built to quantitatively evaluate the dynamic impact strength of a solder joint under tensile impact loading. This study evaluated the tensile strength of lead-free solder ball joints at strain rates from $1.8{\times}10^3s^{-1}$ and $8.5{\times}10^3s^{-1}$. The maximum tensile strength of the solder ball joint decreases as the load speed increases in the testing range. This tensile strength represented that of the interface because of the interfacial fracture site. The tensile strengths of solder joints between Sn-3.0Ag-0.5Cu and copper substrate were between 21.7 MPa and 8.6 MPa in the high strain range.

• Nuclear Engineering and Technology
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• 제25권4호
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• pp.561-569
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• 1993

CANDU 6 발전소의 측면 및 하단 차폐 구조에서의 방사선 선량율을 해석하기 위하여 DOT4.2-QAD-CG 접속 방법을 이용한 평가 방법이 시도되었다. 평가 결과에 의하면 주 출입구 및 신연료 장전 구역에서의 평균 방사선 선량율은 설계 목표치인. 약 6 $\mu$Sv/h 정도로 나타났으며, 또한 이러한 평가 결과는 CANDU 6 발전소에서의 실측지와도 잘 일치하고 있음을 확인할 수 있었다. 따라서, 본 논문에서 사용된 평가법은 앞으로 건설 될 CANDU 6 원자로인 월성 2, 3 및 4호기의 방사선 차폐해석에도 이용될 수 있을 것이다.