• Journal of Microbiology and Biotechnology
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• 제25권12호
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• pp.2116-2124
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• 2015

To understand the effects of physicochemical factors on nitrite transformation by microalgae, a lipid-rich Chlorella with high nitrite tolerance was cultured with 8 mmol/l sodium nitrite as sole nitrogen source under different conditions. The results showed that nitrite transformation was mainly dependent on the metabolic activities of algal cells rather than oxidation of nitrite by dissolved oxygen. Light intensity, temperature, pH, NaHCO₃ concentrations, and initial cell densities had significant effects on the rate of nitrite transformation. Single-factor experiments revealed that the optimum conditions for nitrite transformation were light intensity: 300 μmol/m²/s; temperature: 30℃ pH: 7-8; NaHCO₃ concentration: 2.0 g/l; and initial cell density: 0.15 g/l; and the highest nitrite transformation rate of 1.36 mmol/l/d was achieved. There was a positive correlation between nitrite transformation rate and the growth of Chlorella. The relationship between nitrite transformation rate (mg/l/d) and biomass productivity (g/l/d) could be described by the regression equation y = 61.3x (R² = 0.9665), meaning that 61.3 mg N element was assimilated by 1.0 g dry biomass on average, which indicated that the nitrite transformation is a process of consuming nitrite as nitrogen source by Chlorella. The results demonstrated that the Chlorella suspension was able to assimilate nitrite efficiently, which implied the feasibility of using flue gas for mass production of Chlorella without preliminary removal of NO_X.

• 한국건설관리학회논문집
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• 제14권1호
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• pp.63-70
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• 2013

주택재개발사업에서 수익성 예측은 성공적인 사업의 수행을 위한 중요한 요소이기 때문에 수익성 예측을 소홀히 할 경우 많은 그에 따른 리스크가 커지게 된다. 그러나 현행 주택재개발사업은 사업이 많이 진행된 시점에서 수익성을 분석하기 때문에, 수익성이 없는 것으로 판단될 경우 그에 따른 큰 손실을 감수해야 한다. 이로 인해 현재 사업이 중단되거나 지연됨에 따라 경제적인 손실을 보는 사업장이 늘어나고 있으며, 그에 따른 이해관계자간 갈등이 심화되고 있다. 주택재개발사업 시 이러한 사회적 갈등과 경제적 손실을 줄이기 위해서는 사업추진여부를 결정하기 위한 적절한 수익성 예측 방법의 개발이 필요하며, 더불어 적절한 시기에 적용할 수 있는 프로세스의 제시가 요구된다. 본 연구는 사업 초기단계인 기획단계에서 수익성을 예측할 수 있는 방법을 제시하여, 합리적이고 타당한 의사결정의 지원을 위한 것으로 본 연구모델의 적용 시 사업 초기단계에 사업 수행 여부의 결정이 가능하도록 하여, 부적절한 사업의 무리한 진행으로 인한 경제적인 손실과 그에 따른 이해관계자간의 갈등을 줄일 수 있을 것으로 판단된다.

• 센서학회지
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• 제26권4호
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• pp.235-238
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• 2017

In this study, the design of a tri-axis micromachined gyroscope is proposed and the vibration characteristic of the structure is analyzed. Tri-axis vibratory gyroscopes that utilize Coriolis effect are the most commonly used micromachined inertial sensors because of their advantages, such as low cost, small packaging size, and low power consumption. The proposed design is a single structure with four proof masses, which are coupled to their adjacent ones. The coupling springs of the proof masses orthogonally transfer the driving vibrational motion. The resonant frequencies of the gyroscope are analyzed by finite element method (FEM) simulation. The suspension beam spring design of proof masses limits the resonance frequencies of four modes, viz., drive mode, pitch, roll and yaw sensing mode in the range of 110 Hz near 21 kHz, 21173 Hz, 21239 Hz, 21244 Hz, and 21280 Hz, respectively. The unwanted modes are separated from the drive and sense modes by more than 700 Hz. Thereafter the drive and the sense mode vibrations are calculated and simulated to confirm the driving feasibility and estimate the sensitivity of the gyroscope. The cross-axis sensitivities caused by driving motion are 1.5 deg/s for both x- and y-axis, and 0.2 deg/s for z-axis.

• The Korean Journal of Physiology and Pharmacology
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• 제15권3호
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• pp.137-142
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• 2011

Extremely low frequency magnetic fields (ELF-MF) have the ability to produce a variety of behavioral and physiological changes in animals. The stomach, as the most sensitive part of the neuroendocrine organ of the gastrointestinal tract, is crucial for the initiation of a full stress response against all harmful stress. Thus, the purpose of this study was to examine whether ELF-MF stimuli induce changes in the activity of neuroendocrine cells, considering their involvement in endocrine or paracrine effect on surrounding cells. The exposure to ELF-MF (durations of 24 h and 1 or 2 weeks, 60 Hz frequency, 0.1 mT intensity) altered the distribution and occurrence of gastrin, ghrelin and somatostatinpositive endocrine cells in the stomach of rats. The change, however, in the secretion of those hormones into blood from endocrine cells did not appear significantly with ELF-MF exposure. Comparing with sham control, ELF-MF exposure for 1 and 2 week induced an increase in $BaSO_4$ suspension propelling ratio of gastrointestinal tract, indicating that ELF-MF affects gastrointestinal motility. Our study revealed that ELF-MF exposure might influence the activity of endocrine cells, an important element of the intrinsic regulatory system in the digestive tract. The pathophysiological character of these changes and the mechanism responsible for neuroendocrine cell are still unclear and require further studies.

• Elastomers and Composites
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• 제47권3호
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• pp.194-200
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• 2012

고무재료는 배합조건에 따라 기계적 거동이 다르기 때문에 피로수명평가를 위해 부품소재에 대한 물성데이터 확보가 선행되어야 한다. 그러나 모든 종류의 배합조건을 고려하여 표준화된 재료물성을 확보하는 것은 현실적으로 불가능하다. 따라서 본 연구에서는 최소한의 제한된 실험으로부터 피로수명평가를 위한 입력물성을 선택하기 위한 방법을 제시하였으며, 피로수명 평가를 위한 최적 피로손상 파라미터를 결정하였다. 이러한 결과를 활용하여 부품의 피로수명 평가결과와 내구시험결과를 비교한 후, 본 연구에서 제안된 피로수명 평가절차의 타당성을 검토하였다.

• Human Ecology Research
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• 제55권4호
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• pp.363-384
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• 2017

The Korean government implemented better support for adolescent single-parent families by expanding the coverage of the Single-parent Family Support Act in 2010. In order to understand the effect, this study verified the moderating effect of the single-parent family policy's support for child rearing in the context of adolescent female single-parent's stress levels and education sustainability. This study utilized part of the National Youth Policy Institute's 'Research on the Actual Condition of the Adolescent Pregnancy, Birth and Rearing Children'. Participants of the study were 248 adolescent single-parents aged 24 and below. The findings and discussion of this study are as follows. First, the stress level of adolescent female single-parent in continuing studies was lower than those for discontinued studies. Students who discontinued their education in the middle of studies showed an increase in life stress level relative to age because they had a low level of education and had discontinued studies before pregnancy. Second, the public nanny service has been verified as an element to increase the continuation of education by controlling the level of stress. It is advisable to fortify and expand the scope of support for childcare services in the form of a study assistant or child education assistant. Last, adolescent single-parent childcare subsidies have been verified as a direct factor that raised the meaningful level of education continuity potential to a meaningful standard that can be seen as a more effective method than general policy support for single-parent families.

• Smart Structures and Systems
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• 제15권3호
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• pp.665-682
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• 2015

Structural identification or St-Id is 'the parametric correlation of structural response characteristics predicted by a mathematical model with analogous characteristics derived from experimental measurements'. This paper describes a St-Id exercise on Humber Bridge that adopted a novel two-stage approach to first calibrate and then validate a mathematical model. This model was then used to predict effects of wind and temperature loads on global static deformation that would be practically impossible to observe. The first stage of the process was an ambient vibration survey in 2008 that used operational modal analysis to estimate a set of modes classified as vertical, torsional or lateral. In the more recent second stage a finite element model (FEM) was developed with an appropriate level of refinement to provide a corresponding set of modal properties. A series of manual adjustments to modal parameters such as cable tension and bearing stiffness resulted in a FEM that produced excellent correspondence for vertical and torsional modes, along with correspondence for the lower frequency lateral modes. In the third stage traffic, wind and temperature data along with deformation measurements from a sparse structural health monitoring system installed in 2011 were compared with equivalent predictions from the partially validated FEM. The match of static response between FEM and SHM data proved good enough for the FEM to be used to predict the un-measurable global deformed shape of the bridge due to vehicle and temperature effects but the FEM had limited capability to reproduce static effects of wind. In addition the FEM was used to show internal forces due to a heavy vehicle to to estimate the worst-case bearing movements under extreme combinations of wind, traffic and temperature loads. The paper shows that in this case, but with limitations, such a two-stage FEM calibration/validation process can be an effective tool for performance prognosis.

• 대한기계학회논문집A
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• 제39권11호
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• pp.1105-1111
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• 2015

배기계는 엔진 및 현가계와 함께 차량의 주요 가진원 중의 하나이다. 배기계는 엔진과 직접적으로 연결된 시스템으로서 차체와의 연결 마운트를 통하여 엔진 구동 시의 진동을 차체로 전달한다. 따라서 배기계로부터 전달되는 진동을 저감하기 위해서는 배기계 진동특성을 예측해야 하고, 배기계의 주요부품인 벨로우즈의 정확한 특성을 묘사해야 한다. 그러나 벨로우즈는 복잡한 형상으로 인하여 특성을 예측하는 데에 어려움이 있었다. 설계 단계에서 벨로우즈에 대한 등가 변환 이론이 적용되었지만, 구간에 따라 주름의 크기가 달라지는 차량용 벨로우즈에 적용하기에는 부족함이 있다. 본 연구에서는 유한요소 해석기법을 이용하여 차량용 벨로우즈의 모델링 기법을 제시하고, 그 정확성을 실험결과와 비교하여 입증하였다.

• 농업과학연구
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• 제46권1호
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• pp.113-124
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• 2019

Insect-resistant transgenic (Bt-9) rice was generated by inserting mCry1Ac1, a modified gene from the soil bacterium Bacillus thuringiensis, into the genome of a conventional variety of rice (Ilmi). With regard to potential problems such as safety, an evaluation of non-target organisms is necessary as an essential element of an environmental risk assessment of genetically modified (GM) crops. We studied the effects of the Bt-9 rice on the survival of cantor Daphnia magna, a commonly used model organism in ecotoxicological studies. D. magna fed on the Bt-transgenic rice (Bt-9) and its near non-GM counterparts (Ilmi) grown in the same environment (a 100% ground rice suspension). The Bt-9 rice was confirmed to have the inserted T-DNA and protein expression evident by the PCR and ELISA analyses. The feeding study showed a similar cumulative immobility and abnormal response of the Daphnia magna between the Bt-9 rice and Ilmi. Additionally, the 48 h-EC50 values of the Bt-9 and Ilmi rice were 4,400 mg/L (95% confidence limits: 3861.01 - 5015.01 mg/L) and 5,564 mg/L (95% confidence limits: 4780.03 - 6476.93 mg/L), respectively. The rice NOEC (No observed effect concentration) value for D. magna was suggested to be 1,620 mg/L. We conclude that the tested Bt-9 and Ilmi have a similar cumulative immobility for D. magna, a widely used model organism, and the growth of Bt-9 did not affect non-target insects.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.705-713
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• 2018

자동차용 볼 조인트는 현가계와 조향계를 연결하는 부품으로 두 요소 사이에서 조향을 위해 회전 운동 및 직선운동이 가능하도록 돕는 기계 부품이다. 본 연구의 대상은 중대형 픽업 트럭에 사용되는 볼 조인트이다. 각 단품으로는 스터드(Stud), 소켓(Socekt), 시트(Bearing), 플러그(Plug)로 구성되어 있다. 볼 조인트의 주요 구조적 성능으로는 풀-아웃 강도 및 푸시-아웃 강도를 고려해야 한다. 이 구조적 성능들은 정해진 기준을 만족해야 하며 이를 만족시키지 못하면 보다 큰 사고를 유발할 수 있다. 볼 조인트의 설계 요구조건 만족 여부를 확인하기 위한 방법으로는 실험과 시뮬레이션 방법이 있으나 실험은 많은 시간과 비용이 소요된다. 본 연구에서는 볼조인트의 구조적 성능 예측을 위하여 모델링 소프트웨어로서 솔리드웍스(Solid Works)를, 유한요소해석 소프트웨어로서 아바쿠스(Abaqus)를 사용하였다. 유한요소해석은 2D 축대칭 모델의 정적 해석을 이용하여 요구되는 구조적 성능을 구하였다. 볼 조인트의 제작 시 발생되는 불확실한 요소를 제작 공차로 가정하였으며, 이에 따라 구조적 성능에 영향을 미치는 치수 설계 변수를 사례 연구를 수행해 파악하였다. 그리고 제작 공차를 수준 별로 정의 한 후, 사례연구를 이용해 구한 유한요소해석 결과값과 실험값을 비교하였다.