• Journal of Korean Society of Disaster and Security
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• v.9 no.2
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• pp.63-75
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• 2016

For safe water supply, residual chlorine has to be maintained in tap-water above a certain level from drinking water treatment plants to the final tap-water end-point. However, according to the current literature, approximately 30-60% of residual chlorine is being lost during the whole water supply pathways. The losses of residual chlorine may have been attributed to the current tendency for water supply managers to reduce chlorine dosage in drinking water treatment plants, aqueous phase decomposition of residual chlorine in supply pipes, accelerated chlorine decomposition at a high temperature during summer, leakage or losses of residual chlorine from old water supply pipes, and disappearances of residual chlorine in water storage tanks. Because of these, it is difficult to rule out the possibility that residual chlorine concentrations become lower than a regulatory level. In addition, it is concerned that the regulatory satisfaction of residual chlorine in water storage tanks can not always be guaranteed by using the current design method in which only storage capacity and/or hydraulic retention time are simply used as design factors, without considering other physico-chemical processes involved in chlorine disappearances in water storage tank. To circumvent the limitations of the current design method, mathematical models for aqueous chlorine decomposition, sorption of chlorine into wall surface, and mass-transfer into air-phase via evaporation were selected from literature, and residual chlorine reduction behavior in water storage tanks was numerically simulated. The model simulation revealed that the major factors influencing residual chlorine disappearances in water storage tanks are the water quality (organic pollutant concentration) of tap-water entering into a storage tank, the hydraulic dispersion developed by inflow of tap-water into a water storage tank, and sorption capacity onto the wall of a water storage tank. The findings from his work provide useful information in developing novel design and technology for minimizing residual chlorine disappearances in water storage tanks.

• 한국지구물리탐사학회:학술대회논문집
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• 2010.10a
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• pp.87-91
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• 2010

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.16 no.3
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• pp.197-207
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• 2016

It is very important to maintain a constant chlorine concentration in the post chlorination process, which is the final step in the water treatment process (hereafter WTP) before servicing water to citizens. Even though a flow meter between the filtration basin and clear well must be installed for the post chlorination process, it is not easy to install owing to poor installation conditions. In such a case, a raw water flow meter has been used as an alternative and has led to dosage errors due to detention time. Therefore, the inlet flow to the clear well is estimated by a time series neural network for the plant without a measurement value, a new residual chlorine meter is installed in the inlet of the clear well to decrease the control period, and the proposed modeling and controller to analyze the chlorine concentration change in the well is a neuro fuzzy algorithm and cascade method. The proposed algorithm led to post chlorination and chlorination improvements of 1.75 times and 1.96 times respectively when it was applied to an operating WTP. As a result, a hygienically safer drinking water is supplied with preemptive response for the time delay and inherent characteristics of the disinfection process.

• Geophysics and Geophysical Exploration
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• v.12 no.3
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• pp.233-238
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• 2009

An inversion method regulated by the error in the measurement of the first arrival time was developed, and we conducted a feasibility study by applying the method to a real cross-well seismic data. The inversion is a two-step regulation process; 1) derive the measurement error bound based on the resolution of the velocity image want to derive, and exclude the records whose picking error is larger than the error bound, 2) set the travel time residual to zero if the residual is less than the measurement error. This process prevents the trivial residuals are accumulated and contribute to the velocity-model update. Comparison of two velocity images, one by using all records and another by using the regulate inversion method, shows that the later velocity image exhibits less numerical artefacts, and it also indicates that, according to the Fermat's principle, the latter image is a more feasible velocity model.

• Journal of the Korea Society of Computer and Information
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• v.20 no.2
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• pp.131-136
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• 2015

The chemical tank loading problem has been classified as nondeterministic polynomial time (NP)-complete problem because of the polynomial-time algorithm to find the solution has been unknown yet. Gu$\acute{e}$ret et al. tries to obtain the optimal solution using linear programming package with $O(m^4)$ time complexity for chemical tank loading problem a kind of bin packing problem. On the other hand, this paper suggests the rule of loading chemical into minimum margin tank algorithm with O(m) time complexity. The proposed algorithm stores the chemical in the tank that has partial residual of the same kind chemical firstly. Then, we load the remaining chemical to the minimum marginal tanks. As a result of experiments, this algorithm reduces the $O(m^4)$ of linear programming to O(m) time complexity for NP-complete chemical tank loading problem.

• Restorative Dentistry and Endodontics
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• v.29 no.3
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• pp.249-266
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• 2004

The purpose of this study was to determine whether pH and time has any influence on the degradation behavior of composite restoration by analyzing the leached monomers of dental composites qualitatively and quantitatively after storage in acetate buffer solution as a function of time using high performance liquid chromatography (HPLC) / mass spectrometer. Materials and Methods：Three commercial composite restorative resin materials (Z-250, Heliomolar and Aeliteflo) with different matrix structure and filler composition were studied. Thirty specimens (7mm $diameter{\times}2mm$ thick) of each material were prepared. The cured materials were stored in acetate buffer solution at different pH (4, 7) for 1, 7 and 45days. As a reference, samples of unpolymerized composite materials of each product were treated with methanol (10mg/ml). Identification of the various compounds was achieved by comparison of their mass spectra with those of reference compound, with literature data. and by their fragmentation patterns. Data were analysed statistically using ANOVA and Duncan's test. Results：1. Amounts of leached TEGDMA in Aeliteflo were significantly larger than those of UDMA in Z-250 and Heliomolar at experimental conditions of different storage time and pH variation (p<0.001). 2. As to comparison of the amounts of leached monomers per sorage time, amounts of leached TEGDMA in Aeliteflo and UDMA in Z-250 and Heliomolar were increased in the pH 4 solution more significantly than in the pH 7 solution after 1day, 7days and 45days, respectively (p<0.001). 3. In total amounts of all the leached monomers with storage times, the overall amounts of pH 4 extracts were larger than those of pH 7 extracts for all resin groups, but there was no significant difference (p>0.05).

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.8
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• pp.818-822
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• 2009

In this paper, we consider a decentralized observer design problem for fault detection in large-scaled linear time-invariant systems. Since the fault detection residual is desired to be sensitive on the fault, we use the H_ index performance criterion. Sufficient conditions for the existence of such an observer is presented in terms of linear matrix inequalities. Simulation results show the effectiveness of the proposed method.

• 전기의세계
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• v.22 no.2
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• pp.28-32
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• 1973

System modeling is applied in developing a probabilistic linear estimator for the load of an electric power system for the purpose of short term load forecasting. The model assumer that the load in given by the suns of a periodic discrete time serier with a period of 24 hour and a residual term such that the output of a discrete time dynamical linear system driven by a white random process and a deterministic input. And also we have established the main forecasting algorithms, which are essemtally the Kalman filter-predictor equations.

• 전기의세계
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• v.29 no.6
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• pp.401-409
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• 1980

This paper deals with the implementation of forced reclosing the transmission line. Because the ground circuit breaker method decrease the secondary arc current sufficiently, the reclosing time can be reduced. As the secondary arc current is large and its residual time is long in UHV transmission line, this method is more effective in that system. The resistance of ground circuit breaker which minimize the secondary arc current is determined according to the system voltage and the length of transmission line.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1437-1440
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• 2007

Many hydroclimatic time series are marked by interannual and longer quasi-period features that are associated with narrow band oscillatory climate modes. A time series modeling approach that directly considers such structures is developed and presented. The essence of the approach is to first develop a wavelet decomposition of the time series that retains only the statistically significant wavelet components, and to then model each such component and the residual time series as univariate autoregressive processes. The efficacy of this approach is demonstrated through the simulation of observed and paleo reconstructions of climate indices related to ENSO and AMO, tree ring and rainfall time series. Long ensemble simulations that preserve the spectral attributes of the time series in each ensemble member can be generated. The usual low order statistics are preserved by the proposed model, and its long memory performance is superior to the direction application of an autoregressive model.