• 한국축산식품학회지
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• 제36권2호
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• pp.262-266
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• 2016

This study evaluated the growth kinetics of Salmonella spp. in processed meat products formulated with low sodium nitrite (NaNO₂). A 5-strain mixture of Salmonella spp. was inoculated on 25-g samples of sausages formulated with sodium chloride (NaCl) (1.0%, 1.25%, and 1.5%) and NaNO₂ (0 and 10 ppm) followed by aerobic or vacuum storage at 10℃ and 15℃ for up to 816 h or 408 h, respectively. The bacterial cell counts were enumerated on xylose lysine deoxycholate agar, and the modified Gompertz model was fitted to the Salmonella cell counts to calculate the kinetic parameters as a function of NaCl concentration on the growth rate (GR; Log CFU/g/h) and lag phase duration (LPD; h). A linear equation was then fitted to the parameters to evaluate the effect of NaCl concentration on the kinetic parameters. The GR values of Salmonella on sausages were higher (p<0.05) with 10 ppm NaNO₂ concentration than with 0 ppm NaNO₂. The GR values of Salmonella decreased (p<0.05) as NaCl concentration increased, especially at 10℃. This result indicates that 10 ppm NaNO₂ may increase Salmonella growth at low NaCl concentrations, and that NaCl plays an important role in inhibiting Salmonella growth in sausages with low NaNO₂.

• 한국축산식품학회지
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• 제34권6호
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• pp.736-741
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• 2014

This study developed probabilistic models to determine the initiation time of growth of Pseudomonas spp. in combinations with $NaNO_2$ and NaCl concentrations during storage at different temperatures. The combination of 8 NaCl concentrations (0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, and 1.75%) and 9 $NaNO_2$ concentrations (0, 15, 30, 45, 60, 75, 90, 105, and 120 ppm) were prepared in a nutrient broth. The medium was placed in the wells of 96-well microtiter plates, followed by inoculation of a five-strain mixture of Pseudomonas in each well. All microtiter plates were incubated at 4, 7, 10, 12, and $15^{\circ}C$ for 528, 504, 504, 360 and 144 h, respectively. Growth (growth initiation; GI) or no growth was then determined by turbidity every 24 h. These growth response data were analyzed by a logistic regression to produce growth/no growth interface of Pseudomonas spp. and to calculate GI time. NaCl and $NaNO_2$ were significantly effective (p<0.05) on inhibiting Pseudomonas spp. growth when stored at $4-12^{\circ}C$. The developed model showed that at lower NaCl concentration, higher $NaNO_2$ level was required to inhibit Pseudomonas growth at $4-12^{\circ}C$. However, at $15^{\circ}C$, there was no significant effect of NaCl and $NaNO_2$. The model overestimated GI times by $58.2{\pm}17.5$ to $79.4{\pm}11%$. These results indicate that the probabilistic models developed in this study should be useful in calculating the GI times of Pseudomonas spp. in combination with NaCl and $NaNO_2$ concentrations, considering the over-prediction percentage.

• 문화기술의 융합
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• 제9권6호
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• pp.581-587
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• 2023

본 연구의 목적은 초등학교 1~4학년의 자아존중감 변화궤적 및 잠재계층유형을 분석하는 것이다. 이를 위해 한국아동패널 8~11차년도 자료를 사용하여 잠재성장모형과 잠재계층성장분석을 실시했다. 먼저 잠재성장모형을 통해 분석한 결과, 가장 적합한 모형으로 선형변화모형이 채택되었으며 변화궤적은 학년이 높아짐에 따라 미세하게 증가하는 것으로 나타났다. 다음으로 잠재계층성장분석을 통해 총 4개의 잠재계층 집단('고수준-유지', '저수준-증가', '고수준-감소', '저수준-유지')이 도출됐다. 집단별 분포를 살펴보면, 대부분의 아동은 '고수준-유지' 집단이었고, 다음으로 '고수준-감소', '저수준-증가', '저수준-유지' 집단의 순으로 나타났다. 이에 연구자들은 교육현장에서 초등학교 아동의 자아존중감이 상이한 잠재계층유형을 통해 변화할 수 있음을 인식할 필요가 있으며, 나아가 각 유형에 적합한 개별화된 지원을 제공하는 것이 요구됨을 제안한다.

• 대한전자공학회논문지SP
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• 제46권3호
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• pp.125-137
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• 2009

음향방출 기법은 작동중인 상태에서 기계 설비를 비파괴 검사할 수 있는 기법이며, 균열성장 같은 장애의 신뢰성 있는 감시를 위해서 순간적인 균열신호뿐만 아니라 동특성을 이용하는 것이 중요하다. 균열성장을 검출하기 위해 널리 사용되는 물리적 파괴 3단계는 음향방출 현상이 시간에 따라 서로 겹치는 문제점이 있어 정확한 균열성장 시간을 추정하기 어렵다. 제안한 패턴인식 기법은 오경보와 미탐지를 최소화하기 위해서 음향방출 동특성을 입력으로 사용하고, 균열성장 시간을 정확히 추정하기 위해 시간에 따른 클러스터링 기법을 사용한다. 실험결과는 제안한 패턴인식 기법이 압력의 변화에 의한 음향방출의 변화의 강인함 때문에 실용화에 효율적임을 보여준다.

• Korean Chemical Engineering Research
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• 제43권5호
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• pp.595-602
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• 2005

파라디옥사논에 포함된 주요한 불순물인 디에틸렌글리콜을 제거하기 위해, 파라디옥사논과 디에틸렌글리콜과의 이성분계 고액 상평형 및 혼합물의 밀도를 측정하였으며, 종(seed)을 이용한 경막 용융결정화 실험을 하였다. 얻어진 2성분계 고액 상평형 결과는 단순 공융계를 형성하였는데, 공용점은 파라디옥사논의 0.08 몰농도에서 246 K였다. 또한, 혼합물의 밀도 데이터는 ${\rho}_l=k_1+k_2x+k_3T+k_4xT$ 식과 잘 연관되었으며, 각 파라메타인 $k_1$, $k_2$, $k_3$ 및 $k_4$의 값은 0.405, 1.361, 0.002, -0.004이었다. 용융결정화 실험에서 결정 성장속도(G)는 냉각속도가 감소하거나 파라디옥사논의 초기농도가 증가할수록 감소하는 경향을 나타내었으며, 결정 성장속도식은 과냉각 온도의 1.5승에 비례하였다. 또한, 불순물의 제거 정도를 나타내는 유효 분배계수($K_{eff}$)는 냉각속도 및 PDX 초기농도가 증가할수록 증가하는 경향을 나타내었으며, 유효분배계수는 Wintermantel 모델에 의해 $K_{eef}=-0.0604+6.392{\times}Z$ 관계로 표현되었다. 최종적으로 얻어진 PDX 순도는 결정화 조작변수를 최적화하여 99% 이상으로 조절할 수 있음을 알 수 있었다.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 1998년도 가을 학술발표회 프로그램
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• pp.2-4
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• 1998

Proliferation of Nocardia amarae cells in activated sludge has often been associated with the generation of nuisance foams. Despite intense research activities in recent years to examine the causes and control of Nocardia foaming in activated sludge, the foaming continued to persist throughout the activated sludge treatment plants in United States. In addition to causing various operational problems to treatment processes, the presence of Nocardia may have secondary effects on the fate of heavy metals that are not well known. For example, for treatment plants facing more stringent metal removal requirements, potential metal removal by Nocardia cells in foaming activated sludge would be a welcome secondary effect. In contrast, with new viosolid disposal regulations in place (Code o( Federal Regulation No. 503), higher concentration of metals in biosolids from foaming activated sludge could create management problems. The goal of this research was to investigate the metal sorption property of Nocardia amarae cells grown in batch reactors and in chemostat reactors. Specific surface area and metal sorption characteristics of N. amarae cells harvested at various growth stages were compared. Three metals examined in this study were copper, cadmium and nickel. Nocardia amarae strain (SRWTP isolate) used in this study was obtained from the University of California at Berkeley. The pure culture was grown in 4L batch reactor containing mineral salt medium with sodium acetate as the sole carbon source. In order to quantify the sorption of heavy metal ions to N amarae cell surfaces, cells from the batch reactor were harvested, washed, and suspended in 30mL centrifuge tubes. Metal sorption studies were conducted at pH 7.0 and ionlc strength of 10-2M. The sorption Isotherm showed that the cells harvested from the stationary and endogenous growth phase exhibited significantly higher metal sorption capacity than the cells from the exponential phase. The sequence of preferential uptake of metals by N. amarae cells was Cu>Cd>Ni. The specific surFace area of Nocardia cells was determined by a dye adsorption method. N.amarae cells growing at ewponential phase had significantly less specific surface area than that of stationary phase, indicating that the lower metal sorption capacity of Nocardia cells growing at exponential phase may be due to the lower specific surface area. The growth conditions of Nocardia cells in continuous culture affect their cell surface properties, thereby governing the adsorption capacity of heavy metal. The comparison of dye sorption isotherms for Nocardia cells growing at various growth rates revealed that the cell surface area increased with increasing sludge age, indicating that the cell surface area is highly dependent on the steady-state growth rate. The highest specific surface area of 199m21g was obtained from N.amarae cell harvested at 0.33 day-1 of growth rate. This result suggests that growth condition not only alters the structure of Nocardia cell wall but also affects the surface area, thus yielding more binding sites of metal removal. After reaching the steady-state condition at dilution rate, metal adsorption isotherms were used to determine the equilibrium distributions of metals between aqueous and Nocardia cell surfaces. The metal sorption capacity of Nocardia biomass harvested from 0.33 day-1 of growth rate was significantly higher than that of cells harvested from 0.5- and 1-day-1 operation, indicatng that N.amarae cells with a lower growth rate have higher sorpion capacity. This result was in close agreement with the trend observed from the batch study. To evaluate the effect of Nocardia cells on the metal binding capacity of activated sludge, specific surface area and metal sorption capacity of the mixture of Nocardia pure cultures and activated sludge biomass were determined by a series of batch experiments. The higher levels of Nocardia cells in the Nocardia-activated sludge samples resulted in the higher specific surface area, explaining the higher metal sorption sites by the mixed luquor samples containing greater amounts on Nocardia cells. The effect of Nocardia cells on the metal sorption capacity of activated sludge was evaluated by spiking an activated sludge sample with various amounts of pre culture Nocardia cells. The results of the Langmuir isotherm model fitted to the metal sorption by various mixtures of Nocardia and activated sludge indicated that the mixture containing higher Nocardia levels had higher metal adsorption capacity than the mixture containing lower Nocardia levels. At Nocardia levels above 100mg/g VSS, the metal sorption capacity of activate sludge increased proportionally with the amount of Noeardia cells present in the mixed liquor, indicating that the presence of Nocardia may increase the viosorption capacity of activated sludge.

• Journal of Microbiology and Biotechnology
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• 제10권3호
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• pp.399-404
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• 2000

The adjuvant effect of a muramyl dipeptide (MDP) derivative, MDP-Lys(L18), on enhancing of antitumor immunity induced by X-irradiated tumor cells against highly metastatic B16-BL6 melanoma cells was examined in mice. Mice immunized intradermally (i.d.) with a mixture of X-irradiated B16-BL6 cells and MDP-Lys (L18) [Vac+MDP-Lys (L18)] followed by an intravenous (i.v.)inoculation of $10^4$ viable tumor cells 7 days after immunization, showed a significant inhibition of experimental lung metastasis of B16-BL6 melanoma cells. The most effective immunization for the prophylactic inhibition of tumor metastasis was obtained from the mixture of $100{\;}\mu\textrm{g}$ of MDP-Lys (L18) and $10^4$ X-irradiatied tumor vaccine. Furthermore, immunization of mice with Vac+MDP-Lys(L18), 3 days after tumor challenge, resulted in a significant inhibition of lung metastasis of B16-BL6 melanoma cells in an experimental lung metastasis model. Similarly, the administration of Vac+MDP-Lys(L18), 1 or 7 days after tumor removal, markedly inhibited tumor metastasis of B16-BL6 in a spontaneous lung metastasis model. When Vac+MDP-Lys (L18) was i.d. administered 3 days after subcutaneous (s.c.) inoculation of tumor cells ($5{\times}10^5/site$) on the back, mice treated with Vac+MDP-Lys(L18) showed inhibition of significantly tumor growth on day 20. These results suggest that MDP-Lys (L18) is able to enhance antitumor activity induced by X-irradiated tumor vaccine to reduce lung metastasis of tumor cells, and is a potent immunomodulating agent which may be applied prophylactically as well as therapeutically to treatment of cancer metastasis.

• 한국도로학회논문집
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• 제8권1호
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• pp.139-152
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• 2006

Many experimental and numerical approaches have been developed to evaluate paving materials and to predict pavement response and distress. Micromechanical simulation modeling is a technology that can reduce the number of physical tests required in material formulation and design and that can provide more details, e.g., the internal stress and strain state, and energy evolution and dissipation in simulated specimens with realistic microstructural features. A clustered distinct element modeling (DEM) approach was implemented In the two-dimensional particle flow software package (PFC-2D) to study the complex behavior observed in asphalt mixture fracturing. The relationship between continuous and discontinuous material properties was defined based on the potential energy approach. The theoretical relationship was validated with the uniform axial compression and cantilever beam model using two-dimensional plane strain and plane stress models. A bilinear cohesive displacement-softening model was implemented as an intrinsic interface and applied for both homogeneous and heterogeneous fracture modeling in order to simulate behavior in the fracture process zone and to simulate crack propagation. A disk-shaped compact tension test (DC(T)) with heterogeneous microstructure was simulated and compared with the experimental fracture test results to study Mode I fracture. The realistic arbitrary crack propagation including crack deflection, microcracking, crack face sliding, crack branching, and crack tip blunting could be represented in the fracture models. This micromechanical modeling approach represents the early developmental stages towards a 'virtual asphalt laboratory,' where simulations of laboratory tests and eventually field response and distress predictions can be made to enhance our understanding of pavement distress mechanisms, such its thermal fracture, reflective cracking, and fatigue crack growth.

• 한국정보통신학회논문지
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• 제21권2호
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• pp.259-264
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• 2017

신생아의 출생체중은 자궁내발육부전이나 과체중출생아를 진단하는 데 사용되는 등, 의학적으로 여러 가지 중요한 정보를 제공한다. 본 논문에서는 2011년부터 2013년까지 한국에서 태어난 신생아의 출생체중 데이터를 분석하고, 생물학적으로 부자연스러운 체중 분포를 관찰할 수 있음을 보인다. 이러한 비상식적인 체중 분포는 데이터 수집과정 등에서 오류가 존재함을 의미하는데, 특히 임신주수가 28주에서 32주인 신생아들의 체중 데이터에서 현저한 오류 데이터를 관찰할 수 있다. 이를 보정하기 위해, 본 논문은 가우시안 혼합 모델을 사용하여 오류 데이터와 정상 데이터를 예측하고, 오류 데이터로 예측된 자료들을 삭제하는 과정을 제안한다. 제안된 보정 과정을 통하여 보다 자연스럽고 의학적으로 의미 있는 출생체중 백분율을 구할 수 있음을 보인다.

• 한국식품영양학회지
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• 제9권1호
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• pp.29-36
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• 1996

Naengmyon is a Korean buckwheat noodle with chilld broth, and the juice of dongchimi, a Korean radish pickle fermented with wild lactic acid bacteria, has been used as the broth for naengmyon traditionally. The purpose of this study was to demonstrate the inhibitory effect of dongchimi-juice against coliform bacteria in model system of naengmyon-broth. Dongchimi-juice was made from radish juice by the cultivation of lactic acid bacteria which had been isolated from kimchi. Three types of naengmyon-broth, beef-broth type, dongchimi-juice type and the mixed type, were made as model systems, and then the changes in viable cell counts of seven coliform bacteria, Klebsiella planticola Bo2, X. terrigena CO8, K. pneumoniae DOI, K. ozaenae DO4, Enterobacter sp. AO2, Enterobacter sp. CO7, Citrobacter sp. BO7 and Escherichia sp. DO3, which had been added to each type of naengmyon-broth in advance, were investigated during storage at 3$0^{\circ}C$ All coliforms grew rapidly in naengmyon-broth of beef-broth type, while none grew in dongchimi-juice type or in the mixed type. All coliforms died out far more rapidly in dongchimi-juice type than in mixed type. The decreasing slopes of Citrobacter sp. Bo7, K. planticola BO2, X. terrigena CO8 and K. ozaenae DO4 were more steep than those of the rest. It was thought that the preparation method of Korean traditional naengmyon such as dongchimi-naengmyon or Pyongyang style-naengmyon, which uses oxy dongchimi-) juice or the mixture of dongchimi-juice and beef-broth, would be very effective for preventing the growth of coliform bacteria from naengmyon.