• Environmental Engineering Research
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• 제13권3호
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• pp.141-146
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• 2008

Transport of Escherichia coli ATCC 11105 through porous media was investigated in this study using two sets of column experiments to quantify the attachment-related parameters (sticking efficiency, attachment rate coefficient and filter factor). The first set of experiments was performed in quartz sand under different ionic strength conditions (1, 20, 100, 200 mM) while the second experiments were carried out in quartz sand mixed with metal oxyhydroxide-coated sand (0, 5, 10, 25%). The breakthrough curves of bacteria were obtained by monitoring effluent, and then bacterial mass recovery and attachment-related parameters were quantified from these curves. The first experiments showed that the mass recoveries were in the range of 13.3 to 64.7%, decreasing with increasing ionic strength. In the second experiments, the mass recoveries were in the range of 15.0 to 43.4%, decreasing with increasing coated sand content. The analysis indicated that the sticking efficiency, attachment rate coefficient and filter factor increased with increasing ionic strength and coated sand content. The value of filter factor in the first experiments ranged from 1.45 e-2 to 6.72 e-2 1/cm while in the second experiments it ranged from 2.78 e-2 to 6.32 e-2 1/cm. Our filter factor values are one order of magnitude lower than those from other studies. This discrepancy can be attributed to the size of sand used in the experiment. The analysis demonstrated that the travel distance of bacteria estimated using the filter factor can be varied greatly depending on the solution chemistry and charge heterogeneity of porous media.

• 한국물환경학회지
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• 제37권1호
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• pp.10-19
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• 2021

In the flotation process to remove microplastic (MP) particles, the attachment and separation efficiency is determined by the basic physicochemical characteristics of MP particles as well as bubbles. To evaluate the flotation characteristics of MP particles, we carried out a series of simulations using the population balance (PB) model. The initial attachment coefficient (αo) of MP particles was in the range of 0.2-0.275, and it was slightly lower than that of typical particles, such as clay, debris and algae particles, which exist in water bodies, αo, 0.3-0.4. The relative bubble number (RBN) attached to the surface of the typical number of bubbles was 0.30 and 0.32 for MP 30 ㎛ and MP 58 ㎛, respectively. In comparison, the RBN of larger MP particles (138 ㎛) was as high as 0.53. Furthermore, smaller microbubbles were required to separate properly or additional treatment needed to be applied to enhance collision and attachment efficiency since the flotation of MP particles was found to be difficult to treat as high-rate. As a result of comparing the removal rate (experimental value) of MP particles obtained from the batch-type flotation apparatus and the flotation removal rate (predicted value) of MP obtained through the PB model, the final particles by the particle size of MP overall except for the initial separation time area. With respect to the removal efficiency, the observed and predicted values were similar, and it was confirmed that the floating separation characteristics and evaluation of the MP particles through the PB model could be possible.

• 한국해양학회지:바다
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• 제3권4호
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• pp.271-275
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• 1998

해수에 잠긴 인공기질 표면에 부착한 박테리아가 규조류의 후속부착에 미치는 영향에 대해 상반된 견해가 있다. 그러나 자연조건의 해수에서 인공기질 표면에 먼저 부착한 해산 박테리아가 규조류의 후속부착에 어떤 영향을 주는지에 대해서는 아직 알려져 있지 않다. 따라서 본 연구에서는 해산 박테리아를 일정 시간별로 미리 부착시킨 여러 재질을 이용하여 실험하였다. 첫번째 실험에서는 유리 슬라이드에 미리 해산 박테리아를 0~133 시간별로 부착시키고 해수에 일정기간 노출시킨 후 규조류의 부착수도를 조사하였다. 규조류의 부착은 먼저 부착된 박테리아의 수도와 관련이 없었으며(p>0.05), 무처리 슬라이드에 가장 많은 수의 규조류가, 가장 높은 수도의 박테리아가 부착된 표면에는 가장 적은 수의 규조류가 부착하였다. 두번째 실험에서는 유리와 아크릴 슬라이드를 이용하여 해산 박테리아를 6 일 동안 먼저 부착시킨 것과 한천(agar)을 입힌 슬라이드 그리고 대조구로서 무처리 슬라이드를 해수 중에 함께 노출시켰다. 박테리아가 가장 높은 수도($5.4{\pm}0.02{\times}10^5\;cells\;cm^{-2}$)로 부착된 아크릴 슬라이드에서는 무처리 슬라이드보다 적은 수의 규조류가 부착하였으나, 박테리아가 $2.5{\pm}1.0{\times}10^5\;cells\;cm^{-2}$로 부착된 유리 슬라이드에서는 무처리 슬라이드와 차이가 없었다. 반면 점액질을 모사한 표면에 부착한 규조류의 수도와 이입계수는 다른 표면들에 비해 평균 2 배 이상 높게 나타났다. 따라서 해산 박테리아의 부착이 규조류 후속부착의 선결요건이 아닌 것으로 판단된다.

• 한국해양학회지:바다
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• 제3권4호
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• pp.249-260
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• 1998

해수에 잠긴 인공기질 표면에서 미세조류의 부착과 후속적으로 나타나는 성장과정을 이해하기 위해 규조류의 부착과 주변수의 종 급원(species pool)과의 관계를 조사하였다. 1995년 7월부터 1997년 2월까지 인천항 내에서 아크릴 슬라이드를 이용하여 규조류의 부착에 관해 연구하였고, 주변 해수를 조사하였다. 또한 생물막 초기형성 과정에서 노출시간의 증가에 따라 나타나는 부착미세조류 군집의 종조성과 수도의 변화를 유리, 아크릴, 티타늄, 구리 및 생물오손방지 페인트로 도포된 슬라이드 등 다양한 인공기질 표면을 이용하여 조사하였다. 아크릴 슬라이드에서 규조류의 이입률은 주변수의 저서규조류의 수도변화와 유의성 있는 상관관계를 나타냈으며 ($r^2$=0.78, p<0.01, n=42), 이는 주변수의 저서규조류의 수도에 의해 영향을 받는 것을 지시한다. 아크릴 슬라이드에서 봄철에 단배선 형태 규조류의 부착능력(이입계수)이 복배선 형태에 비해 5 배 높게 나타났다. 그러나 부착점유율은 단배선 형태가 복배선 형태에 비해 3 배 낮게 나타났다. 겨울철에는 중심형 규조류의 부착능력이 다른 형태들에 비해 높게 나타났고 부착점유율도 높게 나타났다. 이는 규조류의 부착이 주변해수에 출현한 저서 규조류의 수도 및 부착능력에 의한 결과임을 지시한다. 우상형 규조류가 연구기간동안 모든 인공기질 표면에 대부분 부착 출현하였고, 겨울철에는 중심형 규조류가 모든 인공기질 표면에 우정 부착하였다. 생물오손방지 페인트로 처리된 표면에서는 독성에 대한 내성이 강한 것으로 판단되는 Hantzschia virgata, Licmophora abbreviata, Melosira nummuloides가 우점하여 부착하였다. 노출시간이 증가함에 따라 부착규조류의 수도는 유리, 티타늄, 아크릴 슬라이드에서 지수적으로 증가하였고, 최대수도는 유리 ${\geq}$ 아크릴 > 티타늄 > 구리 ${\geq}$ 페인트처리 슬라이드의 순으로 높게 나타났다. 모든 인공기질 표면에서 부착규조류의 성장률은 $2{\sim}3^{\circ}C$에서 보다 $24{\sim}25^{\circ}C$의 수온에서 높게 나타났고, 유리 슬라이드에서 다른 표면에 비해 전반적으로 높은 값을 보였다. 해수 중에서 노출시간의 증가에 따라 관찰된 우점종은 납작한 형태인 Amphora coffeaeformis, 부채꼴 형태인 Synedra tabulata, stalk 형태인 Licmophora paradoxa 그리고 사슬형태인 M. nummuloides로 나타났고, 부착미세조류 군집에서 미소천이(micro-succession)가 관찰되었다. 이러한 우점종 조성은 미세조류 생물막이 발달하여 서식공간이 제한됨에 따라 나타난 종 적응의 결과로 보인다.

• Journal of Biosystems Engineering
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• 제27권3호
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• pp.235-240
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• 2002

Performance of the heat pump with attaching an air heat exchanger was investigated in the heating condition when the air heat exchanger was worked in the ambient air temperature of -5 to 11$\^{C}$ and air flow rate of 542 to 747 ㎡/h. Performance tests for heating condition were conducted in an experimental room equipped with heat pump. The performance tests were performed in a ambient temperature of -4 ∼ 11$\^{C}$, and room temperature of 4∼22$\^{C}$ respectively. Measured data(temperature, capacity of heat transfer and consumption of electronic power) were analyzed to the efficiency of HEEVA(Heat Exchanger fur the Evaporator), overall heat transfer coefficient and COP of heat pump. The results of inlet temperature for evaporator increased that the temperature was 2 ∼6$\^{C}$, and inlet temperature for condenser decreased that the temperature was 3 ∼ 8$\^{C}$. The results of comparing efficiency of HEEVA for the ratio of heat exchange between hot air and cold air showed that efficiency were considered to 91% because of the ratio of 83∼98%. The results of comparing of COP for the heat pump increased that improvement COP was approximately 0.3∼7.5 than HEEVA had not been operated.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.74-79
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• 2009

The generation of electric power and plant facilities have been attempting to improve energy efficiency with many efforts as those being basis of our country's economy. In particular, the CHP(Combined Heat Power plant) system, is producing the electricity and process steam, has generally been using for the cogeneration plants. When CHP system operates, the steam has to maintain the high temperature and high pressure in order to have high efficiency of electric power production as much as possible. In addition, the exhausted steam from the turbine has to reform proper temperature to use the needed process. The major purpose of desuperheater is that the superheated steam changes into the saturated steam because it is more efficient and suitable for using the process, furthermore, it is more convenient and stable regarding the process temperature control. The design of the desuperheater obtained through the experiment and preceding analysis. This paper is verified by analysis that water spray nozzle(${\Phi}$=28mm) shows the best ability under the real power plant condition.

• 한국경영과학회지
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• 제40권1호
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• pp.5-19
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• 2015

Literatures on open innovation have two major limitations. First, either on a firm level or on an industry level did they analyze the open innovation issues. The results of a firm's innovation can be diffused through the whole network and the firm can learn back from the network knowledge. Prior literatures did not consider the feedback loop among firms and network in which the firms are involved. Second, most open innovation research had a static perspective on firm's innovation performance. Since the diffusion, spill-over and learning among network members are involved over time, the open innovation is intrinsically dynamic. From the dynamic perspective, we can appreciate the fundamental attributes of the open innovation network which involves diverse firms, research institutes, and universities. In order to overcome the limitations, we suggest a dynamic model for open innovation network. We build an agent-based model which consists of heterogeneous firms. The firms are connected through a scale-free network which is formed by preferential attachment. Through the diverse scenario of simulation, we collect massive data on the firm level and analyze them both on firm and industry level. From the analysis, we found that, on industry level, the overall performance of open innovation increases as the internal research capability, absorptive capacity, and learning curve coefficient increase. Noticeably, as the deprecation rate of knowledge increases, the variability of knowledge increases. From the firm level analysis, we found that the industry-level variables had a significant effect on the firm's innovation performance lasting through all the time, whereas the firm-level variables had only on the early phase of innovation.

• 한국운동역학회지
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• 제27권4호
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• pp.279-285
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• 2017

Objective: The purpose of this study was to perform a muscle function path analysis of muscle function on myofascial meridians. Method: Seven male students (mean age: $22{\pm}3.46years$; mean mass: $72.71{\pm}8.19kg$; mean height: $174{\pm}4.39cm$) without a history of musculoskeletal system symptoms or injuries were recruited for this study. The measurement muscle of the myofascial line was selected along with the muscle presented in "anatomy trains (Thomas W. Myers. 2014)", and the attachment of the surface EMG (Telemyo 2400T G2, USA) pad was determined according to "EMG analysis (Kim Tae Wan et al., 2013)". The subjects underwent maximum volumetric contraction of their fascia line end muscles three times in lying and standing postures and were subjected to the maximum number of contractions of the myofascial line muscle three times in the lying and standing postures. The sampling rate of the EMG signal was set to 1,000 Hz, and the bandwidth was 20 to 350 Hz. The activity of each muscle was quantitated using the Pearson correlation coefficient, and SPSS 22.0 was used for data analysis. Results: In myofascial meridians, a positive correlation in the myofascial connection and a negative correlation in the mechanical connection were observed. Conclusion: Muscles that show significant contract correlations with one another may be expected to be used as an effective clinical marker in muscle strengthening or relaxation therapy, and rehabilitative training. In this study, the correlation of total myofascial meridians may differ without consideration of functional posture. Future studies need to consider these points.