• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.553-555
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• 1996

This paper concerns with a method to improve the current and power waveforms of the variable speed $3{\Phi}$ AC motor system driven by the single-pulse PWM, and the current waveforms and $3{\Phi}$ power waveforms are analyzed by FFT under various running conditions. By the performance analysis through the experiments, the following results have been obtained. AC source of pseudo sine waveform can be obtained from the modulated alternating square voltage by means of the well designed LC filter. It is confirmed that current waveforms and $3{\Phi}$ power waveforms can be improved by utilizing the high order low pass LC filter than that of lower order. Especially, current waveforms and $3{\Phi}$ power waveforms tan be much improved at low frequency domain. $3{\Phi}$ power waveforms have a smatter ripple and bigger power by utilizing the high order low pass LC filter than that of lower order. Also, the running condition of $3{\Phi}$ AC motor is good at low frequency domain.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.451-454
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• 1998

This paper proposes a new method of Model Predictive Control (MPC) of nonlinear process by us-ing the measured Volterra kernels as the nonlinear model. A nonlinear dynamical process is usually de-scribed as Volterra kernel representation, In the authors' method, a pseudo-random M-sequence is ar plied to the nonlinear process, and its output is measured. Taking the crosscorrelation between the input and output, we obtain the Volterra kernels up to 3rd order which represent the nonlinear characteristics of the process. By using the measured Volterra kernels, we can construct the nonlinear model for MPC. In applying Model Predictive Control to a nonlinear process, the most important thing is, in general, what kind of nonlinear model should be used. The authors used the measured Volterra kernels of up to 3rd order as the process model. The authors have carried out computer simulations and compared the simulation results for the linear model, the nonlinear model up to 2nd Volterra kernel, and the nonlinear model up to 3rd order Vol-terra kernel. The results of computer simulation show that the use of Valterra kernels of up to 3rd order is most effective for Model Predictive Control of nonlinear dynamical processes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6567-6574
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• 2015

In order to estimate the characteristics of the growth and composition of phytoplankton according to the available nutrients, we added nitrate (0, 1, 5, 10, 20, 50, $100{\mu}M$) and phosphate (0, 0.1, 0.5, 1, 2, 5, $10{\mu}M$) to field samples in a eutrophic site (St. 1) and an oligotrophic site (St. 22) in 2010 as well as a eutrophic site (St. 1, 5), a mesotrophic site (St. 19), and an oligotrophic site (St. 22) in 2011 at Jinhae Bay, Korea. The phytoplankton growth in the areas with additional nitrates and phosphates on St. 1 were significantly different from the control (One-way ANOVA:P<0.01). The dominant species at St. 1 in 2010 were Heterocapsa triquetra and Pseudo-nitzchia spp., to which nitrate and phosphate were added, respectively. The dominant species at St. 22 in 2010 differed between treatment conditions as follows: nitrate treatment Chaetoceros spp. (${\leq}10{\mu}M$), Thalassiosira spp. ($20{\mu}M$), and Pseudo-nitzchia spp.(${\geq}50{\mu}M$) for nitrate treatment; Cylindrotheca spp. ($2{\mu}M$) and Pseudo-nitzchia spp. ($5{\mu}M$) for phosphate treatment. Phytoplankton growth in 2011 according to the added nutrient were significantly different with treatment concentrations (One-way ANOVA: P<0.01). Moreover, the beginning of exponential growth in phytoplanktons was different between the eutro-mesotrophic sites (St. 1, 5, and 19) and the oligotrophic sites (St. 22) on day 2 and day 6 respectively. This implies that phytoplankton growth in the low nutrient condition may be retarded. The dominant species at St. 1 were Eucampia spp. and Chaetoceros spp. in the low nutrient treatment compared to Skeletonema spp., and Thalassiosira spp in the high nutrient treatment. The dominant species at St. 5 and St. 19 were mostly Skeletonema spp. and Chaetoceros spp. However, the dominant species at St. 22 was Thalassiosira spp.. The results of this study showed that phytoplankton growth and composition were different in areas with different nutrient characteristics resulting from the additional nutrients. Therefore, the nutrients additional algal assay could be indirectly explained why the biomass and composition of phytoplankton in Jinhae Bay has shown spatial differences.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.12
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• pp.1255-1261
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• 2008

In this study, The effects of three different biological activated carbon (BAC) materials (each coal, coconut and wood based activated carbons), empty bed contact time (EBCT) and water temperature on the removal of haloacetic acid (HAA) 5 species in BAC filters were investigated. Experiments were conducted at three water temperatures (5, 10 and 20$^{\circ}C$) and four EBCTs (5, 10, 15 and 20 min). The results indicated that coal based BAC retained more attached bacterial biomass on the surface of the activated carbon than the other BAC, increasing EBCT or increasing water temperature increased the HAA 5 species removal in BAC columns. To achieve an HAA removal efficiency 50% or higher in a BAC filter, the authors suggest 10 min EBCT or longer for 5$^{\circ}C$ waters and 5 min EBCT for waters at 10$^{\circ}C$ or higher. The kinetic analysis suggested a first-order reaction model for HAA 5 species removal at various water temperatures (5, 10 and 20$^{\circ}C$). The pseudo-first-order reaction rate constants and half-lives were also calculated for HAA removal at 5, 10 and 20$^{\circ}C$. The pseudo-first-order reaction rate constants and half-lives were also calculated for HAA 5 species removal at 5$\sim$ 20$^{\circ}C$. The half-lives of HAA 5 species ranging from 0.75 to 18.58 min could be used to assist water utilities in designing and operating BAC filters for HAA removal.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.158-160
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• 2005

This paper presents a new approach to the problem of designing a cascaded three-parameters controller for a given linear time invariant (LTD plant in unity feedback system. We consider a proportional-integral-derivative (PID) and a first-order controller with specified overshoot and settling time. This problem is difficult to solve because there may be no analytical solution due to the use of low-order controller and furthermore. the zeros of controller just appear in the zeros of feedback system. The key idea of our method is to impose a constraint on the controller parameters so that the zeros of resulting controller are distant from the dominant pole of closed-loop system to the left as far as the given interval. Two methods realizing the idea are suggested. We have employed the characteristic ratio assignment (CRA) in order to deal with the time response specifications. It is noted that the proposed methods are accomplished only in parameter space. Several illustrative examples are given.

• Journal of Environmental Science International
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• v.21 no.4
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• pp.411-419
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• 2012

In this study, Ibuprofen (IBP) degradation by the photo catalytic process was investigated under various parameters, such as UV intensity, optimum dosage of $TiO_2$, alkalinity, temperature and pH of bulk solution. The pseudo-first order degradation rate constants were in the order of $10^{-1}$ to $10^{-4}min^{-1}$ depending on each condition. The Photocatalytic IBP degradation rate increased with an increase in the applied UV power. At high UV intensity a high rate of tri-iodide ($I_3{^-}$) ion formation was also observed. Moreover, in order to avoid the use of an excess catalyst, the optimum dosage of catalyst under the various UV intensities (30 and 40 W/L) was examined and ranged from approximately 0.1 $gL^{-1}$. The photo catalytic IBP degradation rate was changed depending on the alkalinity and temperature and pH in the aqueous solution. This study demonstrated the potential of photo catalytic IBP degradation under different conditions.

• Journal of the Korean Chemical Society
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• v.22 no.5
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• pp.281-288
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• 1978

Pseudo-first order rate constants $k_{obs}$ were determined for the reactions of naphthalenesulfonyl chlorides (1-NSC and 2-NSC) and anilines. The second order rate constant $k_2$ and third order catalytic $k_3$ were then determined from $k_{obs}$. For 1-NSC peri-hydrogen effect was observed. The large Brønsted ${\beta}$ and large negative slopes ${\rho}$ for the Hammett plots were obtained. These results with the unsually low values of activation parameters were consistent with the $S_AN$-elimination mechanism, but these can be equally well interpreted with the associative $S_N2$mechanism.

• Journal of Korean Society on Water Environment
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• v.18 no.4
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• pp.411-419
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• 2002

In this study, the series of ultrasonic irradiation for removal of refractory aromatic compounds has been selected as a model reaction in the batch reactor system in order to obtain the reaction kinetics. The products obtained from the ultrasonic irradiation were analysed by GC and GC/MSD. The decomposition of benzene produced toluene, phenol, and C1-C4 compounds, while the intermediates during the ultrasonic irradiation of 2,4-Dichlorophenol(DCP) were phenol, HCl, catechol, hydroquinone, and benzoquinone. It was found that more than 80% of benzene, and 2,4-DCP solutions were removed within 2 hours in all reaction conditions. The reaction order in the degradation of these three compounds was verified as pseudo-zero or first order. From the fore-mentioned results, it can be concluded that the refractory organic compounds could be removed by the ultrasonic irradiation with radicals, such as $H{\cdot}$ and $OH{\cdot}$ radical causing the high increase of pressure and temperature. Finally, it appeared that the technology using ultrasonic irradiation can be applied to the treatment of refractory compounds which are difficult to be decomposed by the conventional methods.

• Carbon letters
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• v.15 no.2
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• pp.105-112
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• 2014

Wastewater from textile industries is a major cause of water pollution in most developing countries. In order to address the issues of water pollution and high cost for treatment processes, the use of an inexpensive and environmentally benign adsorbents has been studied. The objective was to find a better alternative to the conventional methods. Lemon grass waste (ash) collected from a lemon grass stream distillation subunit in Bhutan was tested for dye removal from aqueous solutions. The study investigated the removal of methylene blue using the following operational parameters: initial concentration (100-600 mg/L), contact time, adsorbent dose (0.1-0.55 gm/100 mL), and pH (3-10). It was found that the percentage removal of dye increased with a decrease of the initial concentration and increased contact time and dose of adsorbent. The basic pH solution of dye showed better adsorption capacity as compared to the acidic dye solution. Langmuir and Freundlich adsorption isotherms were fitted to the data well. Data fitted better to Lagergren pseudo 2nd order kinetics than a 1st order kinetic model. Surface morphology was also examined via scanning electron microscopy. An elemental analysis was also carried out and the chemical composition and functional groups were analyzed using energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy techniques, respectively. The obtained results indicate that lemon grass ash could be employed as a low cost alternative to commercial activated carbon in wastewater treatment for the removal of dyes.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2269-2273
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• 2012

Pseudo-first-order rate constants $k_{amine}$ have been measured spectrophotometrically for the reactions of benzyl 4-pyridyl carbonate 6 with a series of alicyclic secondary amines in $H_2O$ at $25.0^{\circ}C$. The plots of $k_{amine}$ vs. [amine] curve upward, indicating that the reactions proceed through a stepwise mechanism with two intermediates, a zwitterionic tetrahedral intermediate $T^{\pm}$ and its deprotonated form $T^-$. This contrasts to the report that the corresponding reactions of benzyl 2-pyridyl carbonate 5 proceed through a forced concerted pathway. The $k_{amine}$ values for the reactions of 6 have been dissected into the second-order rate constant $Kk_2$ and the thirdorder rate constant $Kk_3$. The Br${\o}$nsted-type plots are linear with ${\beta}_{nuc}=0.94$ and 1.18 for $Kk_2$ and $Kk_3$, respectively. The $Kk_2$ for the reaction of 6 is smaller than the second-order rate constant $k_N$ for the corresponding reaction of 5, although 4-pyridyloxide in 6 is less basic and a better nucleofuge than 2-pyridyloxide in 5.