• Water Engineering Research
• /
• v.4 no.2
• /
• pp.59-68
• /
• 2003

The applicabilities and validities of two methodologies fur the prediction of THM (trihalomethane) formation in a water pipeline system were proposed and discussed. One is the multiple regression technique and the other is an artificial neural network technique. There are many factors which influence water quality, especially THMs formations in water pipeline systems. In this study, the prediction models of THM formation in water pipeline systems are developed based on the independent variables proposed by American Water Works Association(AWWA). Multiple linear/nonlinear regression models are estimated and three layer feed-forward artificial neural networks have been used to predict the THM formation in a water pipeline system. Input parameters of the models consist of organic compounds measured in water pipeline systems such as TOC, DOC and UV254. Also, the reaction time to each measuring site along pipeline is used as input parameter calculated by a hydraulic analysis. Using these variables as model parameters, four models are developed. And the predicted results from the four developed models are compared statistically to the measured THMs data set. It is shown that the artificial neural network approaches are much superior to the conventional regression approaches and that the developed models by neural network can be used more efficiently and reproduce more accurately the THMs formation in water pipeline systems, than the conventional regression methods proposed by AWWA.

• Journal of the Korean Society of Safety
• /
• v.14 no.4
• /
• pp.114-119
• /
• 1999

When NaOCl was generated and put into sea-water cooling machine in order to overcome the biological hindrances against sea-water cooling machine, it was converted into metallic ion, particularly Ca and Mg, as a hydrate in sea-water and is to stick to electrolyte as a side reaction. This phenomena make the distance between the electrolytes narrow to decrease the flow rate, which induces the local vortex flow which erodes the pole plate. Moreover, this increases the resistance of the electrolyte as well as voltage to decrease the electrolytic efficiency, which has curtailed a chlorine yield and caused a pole plate cut. We are able to overcome these problems by chemical cleaning and intend to extend the life-time of electrolyte and to increase output of the sea-water electrolysis facilities by studying optimal policy regarding chemical cleaning of electrolytic cell. Cleaning time of electrolytic facilities is determined when both increase in electrolytic efficiency and decrease in pole-plate voltage are 10%. At this time as operating current of electrolytic facilities is high, operating time is diminished. Whereas, parameter of end point determination according to cleaning is Mg ionic concentration in solution. When we use Cleaner as a 7wt% HCl, cleaning time is about 80min proper. We are able to maintain pole plate performance by protecting against pole plate cut by means of electrolytic by-product, improve operating rate of facilities, and cut down on maintenance expenditure after acidic cleaning.

• Environmental Engineering Research
• /
• v.13 no.4
• /
• pp.210-215
• /
• 2008

The present study investigates the effect of oxidation-reduction potential (ORP) and organic compounds on specific anaerobic ammonium oxidation activity (SAA) using batch experiments. The batch tests were based on the measurement of nitrogen gas production. The relationship between ORP and dissolved oxygen (DO) concentration was found to be ORP (mV) = 160.38 + 68 log [$O_2$], where [$O_2$] is the DO concentration in mg/L. The linear relationship obtained between ORP and SAA ($R^2$ = 0.99) clearly demonstrated that ORP can be employed as an operational parameter in the Anammox process. At ORP value of -110 mV, the SAA was $0.272{\pm}0.03\;g\;N_2-N\;(g\;VSS)^{-1}\;d^{-1}$. The investigation also revealed inhibitory effect of glucose on the SAA while acetate concentration up to 640 mg COD/L (corresponding to 10 mM) had stimulating effect on the SAA. However, acetate concentration beyond 640 mg COD/L had inhibitory effect on the Anammox activity. The results indicated that nitrogen rich wastewaters containing low level organic matter could be better treated by Anammox microorganisms in real-world conditions after some acidification process.

• 한국연소학회:학술대회논문집
• /
• 2000.05a
• /
• pp.122-132
• /
• 2000

Computational fluid dynamic simulation is performed for the floating turbulent premixed flames stabilized in stagnation flows of Cho et al. [1] and Cheng and Shepherd [2]. They are both in the wrinkled flamelet regime far from the extinction limit with $u'/S^{0}_{L}$ less than unity. The turbulent flux is given in the first moment closure as a sum of the classical gradient flux due to turbulent motions and the countergradient flux due to thermal expansion. The parameter $N_{B}'s$ are greater than unity with the countergradient flux dominant over the gradient flux. The countergradient flux is assumed to be zero in $\bar{c}<0.05$. The flame surface density is modeled as a symmetric parabolic function with respect to $\bar{c}$. The product of the maximum flame surface density and the mean stretch factor is considered as a tuning constant to match the flame location. Good agreement is achieved with the measured $\tilde{w}$ and $\bar{c}$ profiles along the axis in both flames.

• Journal of Microbiology and Biotechnology
• /
• v.8 no.1
• /
• pp.81-88
• /
• 1998

The determination of appropriate parameters and parameter conditions is very important for the optimization of production of target materials. Taguchi's method has been used widely as the basis for development trials and optimization during industrial process design. Reaction variables which influence product yield are easily determined and their effects are revealed by just a few reactions, negating the need for extensive experimental investigation. There are usually some factors that are responsible for variations in process characteristics, so called noise factors. Controlling noise factors is very costly and difficult or impossible. Taguchi's experimental design method was examined to determine the control factor's level that is less sensitive to the changes in environmental conditions and other noise factors without control of noise factors. In this study, optimization of lipase-catalyzed production of lysophosphatidic acid (LPA) which has various physiological functions was performed by Taguchi's method. We obtained LPA yields ($66.5\%$) with low variance (5.32) at 400 RPM, molar ratio of 40 : 3 (mol) (fatty acid: G-3-P), 48 h, and $50^{\circ}C$. Thus, bioactive LPA with a desired fatty acid moiety could be produced with high yields and low variance despite various environmental noise factors.

• Proceedings of the KWS Conference
• /
• 2002.10a
• /
• pp.545-550
• /
• 2002

In order to ensure the signal could be transported cocrrectly, the microwave devices made of Aluminmn alloys must be assembled and brazed flaw-freely. In this paper, a new approach of using contact reactive brazing (CRB) process to realize the compact brazing of Aluminum alloys was put forward. The reason for this is that CRB, which realizes bonding depending on the liquid alloy produced by metallurgy reaction between the materials to be joined, overcomes the limitation of traditional brazing that the macroscopically disorganized filling flow of liquid filler metal would result in defects in brazed seam. Joint ofLF21 (AA3003) with the compactness of over 95% was brazed by the method of CRB using Si powder as an interlayer. At last, the influence of the physical parameter related to the Si powder interlayer on the compactness of the joints was investigated in detail.

• Journal of the Korean Vacuum Society
• /
• v.8 no.4B
• /
• pp.541-547
• /
• 1999

Reactive ion etching process for InP using BCl3/O2/Ar high density inductively coupled plasma was investigated. The experimental design method proposed by the Taguchi was utilized to cover the whole parameter range while maintaining reasonable number of actual experiments. Results showed that the ICP power and the chamber pressure were the two dominant parameters affectsing etch results. It was also observed that the etch rate decreased and the surface roughness improved as the ICP power and the bias voltage increased and as the chamber pressure decreased. The Addition of oxygen to the gas mixture drastically improved surface roughness by suppressing the formation of the surface reaction product. The optimum condition was ICP power 600W, bias voltage -100V, 10% $O_2$, 6mTorr, and $180^{\circ}C$, resulting in about 0.15$\mu\textrm{m}$ etch rate with smooth surfaces and vertical mesa sidewalls Also, the maximum etch rate of abut 4.5 $\mu\textrm{m}$/min was obtained at the condition of ICP power 800W, bias voltage -150V, 15% $O_2$, 8mTorr and $160^{\circ}C$.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.12
• /
• pp.2279-2282
• /
• 2007

Highly crystalline, uniform Fe nanoparticles were successfully synthesized and encapsulated in zirconia shell using sol-gel process. Two different approaches have been employed for the coating of Fe nanoparticle with zirconia. The thickness of zirconia shell can be readily controlled by altering molar ratio of Fe nanoparticle core to zirconia precursor in the first case where as reaction time was found to be most effective parameter to controlled the shell thickness in the second method. The structure and magnetic properties of the ZrO2-coated Fe nanoparticles were studied. TEM and HRTEM images show a typical core/shell structure in which spherical α-iron crystal sized of ~25 nm is surrounded by amorphous ZrO2 coating layer. TGA study showed an evidence of weight loss of less than 2% over the temperature range of 50-500 °C. The nanoparticles are basically in ferromagnetic state and their magnetic properties depend strongly on annealing temperature. The thermal treatment carried out in as-prepared sample resulted in reduction of coercivity and an increase in saturation magnetization. X-ray diffraction experiments on the samples after annealing at 400-600 °C indicate that the size of the Fe@ZrO2 particles is increased slightly with increasing annealing temperature, indicating the ZrO2 coating layer is effective to interrupt growing of iron particle according to heat treatment.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.28 no.7
• /
• pp.275-282
• /
• 2016

MILD (Moderate and Intense Low-oxygen Dilution) combustion using oxygen as an oxidizer is considered as one of the most promising combustion technologies for high energy efficiency and for reducing nitrogen oxide and carbon dioxide emissions. In order to investigate the effects of nozzle angle and oxygen velocity conditions on the formation of oxygen-MILD combustion, numerical and experimental approaches were performed in this study. The numerical results showed that the recirculation ratio ($K_V$), which is an important parameter for performing MILD combustion, was increased in the main reaction zone when the nozzle angle was changed from 0 degrees to 15 degrees. Also, it was observed that a low and uniform temperature distribution was achieved at an oxygen velocity of 400 m/s. The perfectly invisible oxy-MILD flame was observed experimentally under the condition of a nozzle angle of $10^{\circ}$ and an oxygen velocity of 400 m/s. Moreover, the NOx emission limit was satisfied with NOx regulation of less than 80 ppm.

• Carbon letters
• /
• v.14 no.4
• /
• pp.210-217
• /
• 2013

The synthesis of carbon nanomaterials (CNMs) by a chemical vapor deposition method using three different plant oils as precursors is presented. Because there are four parameters involved in the synthesis of CNM (i.e., the precursor, reaction temperature of the furnace, catalysts, and the carrier gas), each having three variables, it was decided to use the Taguchi optimization method with the 'the larger the better' concept. The best parameter regarding the yield of carbon varied for each type of precursor oil. It was a temperature of $900^{\circ}C$ + Ni as a catalyst for neem oil; $700^{\circ}C$ + Co for karanja oil and $500^{\circ}C$ + Zn as a catalyst for castor oil. The morphology of the nanocarbon produced was also impacted by different parameters. Neem oil and castor oil produced carbon nanotube (CNT) at $900^{\circ}C$; at lower temperatures, sphere-like structures developed. In contrast, karanja oil produced CNTs at all the assessed temperatures. X-ray diffraction and Raman diffraction analyses confirmed that the nanocarbon (both carbon nano beads and CNTs) produced were graphitic in nature.