• Journal of Korean Port Research
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• v.14 no.4
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• pp.451-461
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• 2000

The design and maintenance of navigation channel and water facilities of an harbor which is located at the mouth of river or at the estuary area are difficult due to the complexity of estuarial water and sediment circulation. Effects of deepening navigable waterways, of changing coastline configurations, or of discharging dredged material to the open sea are necessary to be investigated and predicted in terms of water quality and possible physical changes to the coastal environment. A borad analysis of the transport mechanism in the estuary area was made in terms of sediment property, falling velocity, concentration and flow characteristics. In order to simulate the transport processes, a two-dimensional finite element model is developed, which includes erosion, transport and deposition mechanism of suspended sediments. Galerkin’s weighted residual method is used to solve the transient convection-diffusion equation. The fluid domain is subdivided into a series of triangular elements in which a quadratic approximation is made for suspended sediment concentration. Model could deal with a continuous aggregation by stipulating the settling velocity of the flocs in each element. The model provides suspended sediment concentration, bed shear stress, erosion versus deposition rate and bed profile at the given time step.

• Journal of Radiation Industry
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• v.4 no.1
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• pp.13-17
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• 2010

The radioisotope labelling study was carried out for the sediment transport investigation. The fate of suspended solid materials is deeply related to the harbour siltation and the shoreline deformation that take place as a result of the artificial development of coastal area. In the experiment, $^{99m}TcO_4{^-}$ was chemically reduced and labelled in such a way that the labelled particles have the similar settling characteristics with the natural sediment. The radioisotope labelling techniques can be widely used for the natural resource exploration where the hydraulic dynamics of underground water and surface water are of importance.

• International Journal of Computer Science & Network Security
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• v.24 no.2
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• pp.169-177
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• 2024

Interacting Spherical tank has maximum storage capacity is broadly utilized in industries because of its high storage capacity. This two tank level system has the nonlinear characteristics due to its varying surface area of cross section of tank. The challenging tasks in industries is to manage the flow rate of liquid. This proposed work plays a major role in controlling the liquid level in avoidance of time delay and error. Several researchers studied and investigated about reducing the nonlinearity problem and their approaches do not provide better result. Different types of controllers with various techniques are implemented by the proposed system. Intelligent Adaptive Neuro Fuzzy Inference System (ANFIS) based Sliding Mode Controller (SMC) with Fractional order PID controller is a novel technique which is developed for a liquid level control in a interacting spherical tank system to avoid the external disturbances perform better result in terms of rise time, settling time and overshoot reduction. The performance of the proposed system is obtained by analyzing the simulation result obtained from the controller. The simulation results are obtained with the help of FOMCON toolbox with MATLAB 2018. Finally, the performance of the conventional controller (FOPID, PID-SMC) and proposed ANFIS based SMC-FOPID controllers are compared and analyzed the performance indices.

• Applied Biological Chemistry
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• v.17 no.1
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• pp.42-48
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• 1974

Hot air thin layer drying method was studied for red pepper, Capsicum annum var. longum as the whole and cut pod states, at various temperature and air velocities. Drying curve of whole pod showed a settling down period followed by the first and second falling rate periods. By lowering the drying temperature, the first falling rate period approached to a constant rate one. Cut drying curve had simple falling rate period and also cut drying method could effectively shorten the drying time. Drying rate constant, k, was varied with time for both the drying methods and the plots of k vs. time in two methods sugested the different drying mechanisms. When an average k was taken as a constant value, the following equations; $M-M_e/M_o-M_e=e^{-0.118t}$ and $M-M_e/M_o-M_e=e(-0.342t^{0.128})$ were applicable for whole and cut drying, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.3
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• pp.117-127
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• 1983

An experimental research was performed employing the two stage anaerobic digestion of the mixture of the nightsoil and septic tank sludge to determine the effects of various hydraulic retention time of the digestion on chemical characteristics and treatment effeciency, thus determining the proper retention time. Results of the research are as follows, 1. Volatile-acid decreased as HRT increased. 2. Alklinity and ammonia-N tended to increase as HRT increased as did pH values, however, were observed to be constant at higher HRT values than 15 days. 3. The removal efficiencies of TBOD, TCOD and VS increased as HRT increased. 4. The removal efficiency of volatile solid decreased as VS loading increased. 5. It was observed that the rates of gas production were: 0.33 with HRT of 5 days, 0.58 with HRT of 15 days and $0.57m^3/kg$ VS fed/day with HRT of 25 days respectively. It is believed that the highest rate of gas production was at HRT of 15 days. 6. The sludge settling experiment showed that the minimum settling time required to ensure the desired underflow concentraton was estimated to be 8.6 days.

• Clean Technology
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• v.18 no.4
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• pp.398-403
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• 2012

Selective nitrification and granulation have been carried out in a pilot scale air-lift sequencing batch reactor (SBR) for stable and economical nitrogen removal from wastewater. The SBR showed about 100% nitrification efficiency up to 1.0 kg ${NH_4}^+-N/m^3{\cdot}d$, about 90% efficiency at 1.0-2.0 kg ${NH_4}^+-N/m^3{\cdot}d$, and it was less than 90% when the load was higher than 2.0 kg ${NH_4}^+-N/m^3{\cdot}d$. Nitrite accumulation was induced by selective inhibition of nitrite oxidizing bacteria by free ammonia inhibition and dissolved oxygen limitation. For the purpose, high nitrite ratio (> 0.95) was obtained by keeping the pH higher than 8.0 and dissolved oxygen lower than 1.5 mg/L. In addition, sludge granulation was achieved by keeping reactor settling time to 5 minutes to wash out poor settling sludge and to promote the growth of granulation sludge. The operation accelerated sludge granulation and the sludge volume index (SVI) decreased and stably maintained to less than 75 in 60 days.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6247-6253
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• 2015

This paper presents the transient-response improved LDO regulator based on parallel error amplifiers. The proposed LDO regulator consists of an error amplifier (E/A1) which has a high gain and narrow bandwidth and a second amplifier (E/A2) which has low gain and wide bandwidth. These amplifiers are in parallel structure. Also, to improve the transient-response properties and slew-rate, some circuit block is added. Using pole-splitting technique, an external capacitor is reduced in a small on-chip size which is suitable for mobile devices. The proposed LDO has been designed and simulated using a Megna/Hynix $0.18{\mu}m$ CMOS parameters. Chip layout size is $500{\mu}m{\times}150{\mu}m$. Simulation results show 2.5 V output voltage and 100 mA load current in an input condition of 2.7 V ~ 3.3 V. Regulation Characteristic presents voltage variation of 26.1 mV and settling time of 510 ns from 100mA to 0 mA. Also, the proposed circuit has been shown voltage variation of 42.8 mV and settling time of 408 ns from 0 mA to 100 mA.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3336-3344
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• 2014

The purpose of this study is small scale coagulation module is developed and demonstrated through a lab-scale test. Recent as a sewage treatment rate increases, have heightened the interest in the necessity on the nonpoint source and developing a small processing unit has been increased. Coagulation sedimentation module in this study is additional growth of floc through swirling in the outside zone, reduction of microstructure floc number and the internal settling zone through vertical/level flow complex sedimentation method after the coagulation process precipitation method as an effective high separation efficiency can be divided was also assessed. Coagulation sedimentation module can increase the load factor was 4.4 times compared to conventional clarifier base on the same volume and surface area through vertical/level flow. In this study, this process was selected formation and maintenance of swirling and uniform flow distribution in the internal settling zone as an important design factor, to derive its FLUENT was used to characteristics of the flow model. Through the simulation of swirling, influent velocity, dimensions of external basin, hopper depth of bottom cone was determined and through analysis of velocity distribution, flow distribution detailed specifications are derived like as diameter and number of effluent hole. Lab-scale($120{\ell}/hr$) test results, influent of 300~800 NTU to less than 10 NTU without polymer feeding was able to operate in the 20minutes retention time(surface loading rate $37.3m^3/m^2$-day), and through analysis FLUENT the possibility of using design parameters were derived.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.53-59
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• 2003

Phosphogypsum is a by-product resulting from the phosphoric acid process for manufacturing fertilizers. It consists mainly of $CaSO_4{\cdot}2H_2O$ and contains some impurities such as $P_2O_5$, $F^-$, and organic substances. Recycling research of phosphogypsum is very limited to a field of study, especially, civil engineering. This study describes an application of phosphogypsum as dredged materials. For this purpose, experiments are performed to evaluate the physicochemical properties and environmental characteristics of dredged clay with phosphogypsum ; sedimentation test, pH, and leaching test. The result of this study are as follows : the settling velocity is increased due to the activity of phosphogypsum. And leaching and radioactive test results are far below than those of regulatory requirement of Waste Management Act in Korea. Therefore phosphogypsum can be used as dredged materials in reclamation.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.1
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• pp.131-140
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• 2008

The application of magnetic ion exchange resin($MIEX^{(R)}$) is effective for natural organic matter(NOM) removal and for control of the formation of disinfection byproducts(DBPs). NOM removal is also enhanced by adding $MIEX^{(R)}$ with coagulant such as polyaluminium chloride(PACl) in conventional drinking water treatment systems. In the application of $MIEX^{(R)}$, it is important to understand changes of NOM characteristics such as hydrophobicity and molecular weight distributions with $MIEX^{(R)}$ or $MIEX^{(R)}$+coagulant treatment.To observe characteristics of NOM by treatment with $MIEX^{(R)}$ or $MIEX^{(R)}$+coagulant, four major drinking water sources were employed. Results showed that the addition of $MIEX^{(R)}$ to coagulation significantly reduced the amount of coagulant required for the optimum removal of dissolved organic matter(DOC) and turbidity in the all four waters. The DOC removal was also increased approximately 20%, compared to coagulant treatment alone. The process with $MIEX^{(R)}$ and coagulant showed that complementary removal of hydrophobic and hydrophilic fraction of DOC. The combined processes preferentially removed the fractions of intermediate (3,000-10,000 Da) and low (< 500 Da) molecular weight. The microfiltration test showed that membrane cake resistance was decreased for waters with flocs from $MIEX^{(R)}$+coagulant. A porous layer was formed to $MIEX^{(R)}$ on the membrane surface and the layer consequently inhibited settling of coagulant flocs, which could act on a foulant.