• Journal of Korean Society of Water and Wastewater
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• v.26 no.1
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• pp.21-27
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• 2012

This study evaluated the performance of a thermophilic two-phase anaerobic digestion (TTPAD) coupled with membrane process treating garbage leachate. The pilot-scale treatment system is consisted of thermophilic acidogenic reactor (TAR) and thermophilic methanogenic reactor (TMR) coupled with an ultrafiltration (UF) membrane unit. The hydraulic retention time of TAR and TMR were 4 and 20 days, respectively. Effluent TCOD and SCOD of the TTPAD were $25\;{\pm}\;6\;and\;12\;{\pm}\;3$ g/L, respectively, and the corresponding TCOD and SCOD removal efficiencies were 77% and 81%, respectively. Propionate was major acids as 75% in the effluent. Scum formation was not observed in TTPAD, which might be resulted from complete lipid degradation. However, TTPAD was appeared to be sensitive to free ammonia toxicity. The UF membrane was operated with constant pressure filtration at average TMP 1.3 atm. Permeate flux had a range of 15-30 $L/m^2/hr$. With UF membrane, TCOD removal increased from 77% to 93%, and this SS free effluent would be beneficial to subsequent processes such as ammonia stripping.

• Nuclear Engineering and Technology
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• v.31 no.1
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• pp.29-48
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• 1999

Local two-phase flow parameters of subcooled flow boiling in inclined annulus were measured to investigate the effect of inclination on the internal flow structure. Two-conductivity probe technique was applied to measure local gas phasic parameters, including void fraction, vapor bubble frequency, chord length, vapor bubble velocity and interfacial area concentration. Local liquid velocity was measured by Pilot tube. Experiments were conducted for three angles of inclination; 0$^{\circ}$(vertical), 30$^{\circ}$, 60$^{\circ}$. The system pressure was maintained at atmospheric pressure. The range of average void fraction was up to 10% and the average liquid superficial velocities were less than 1.3 m/sec. The results of experiments showed that the distributions of two-phase How parameters were influenced by the angle of channel inclination. Especially, the void fraction and chord length distributions were strongly affected by the increase of inclination angle, and flow pattern transition to slug flow was observed depending on the How conditions. The profiles of vapor velocity, liquid velocity and interfacial area concentration were found to be affected by the non-symmetric bubble size distribution in inclined channel. Using the measured distributions of local phasic parameters, an analysis for predicting average void fraction was performed based on the drift flux model and flowing volumetric concentration. And it was demonstrated that the average void fraction can be more appropriately presented in terms of flowing volumetric concentration.

• Food Science of Animal Resources
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• v.35 no.6
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• pp.800-806
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• 2015

We investigated the effects of a pulsed electric field (PEF) treatment on microbial inactivation and the physical properties of low-fat milk. Milk inoculated with Escherichia coli, Saccharomyces cerevisiae, or Lactobacillus brevis was supplied to a pilot-scale PEF treatment system at a flow rate of 30 L/h. Pulses with an electric field strength of 10 kV/cm and a pulse width of 30 µs were applied to the milk with total pulse energies of 50-250 kJ/L achieved by varying the pulse frequency. The inactivation curves of the test microorganisms were biphasic with an initial lag phase (or shoulder) followed by a phase of rapid inactivation. PEF treatments with a total pulse energy of 200 kJ/L resulted in a 4.5-log reduction in E. coli, a 4.4-log reduction in L. brevis, and a 6.0-log reduction in S. cerevisiae. Total pulse energies of 200 and 250 kJ/L resulted in greater than 5-log reductions in microbial counts in stored PEF-treated milk, and the growth of surviving microorganisms was slow during storage for 15 d at 4℃. PEF treatment did not change milk physical properties such as pH, color, or particle-size distribution (p<0.05). These results indicate that a relatively low electric-field strength of 10 kV/cm can be used to pasteurize low-fat milk.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.6 s.348
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• pp.1-8
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• 2006

In the asynchrous OFCDM(Orthogonal Frequency and Code Division Multiplexing) system, a three-step cell search algorithm is performed for the initial synchronization in the following three steps: OFCDM symbol timing, i.e., Fast Fourier Transform(FFT) window timing is estimated employing guard interval (GI) correlation in the first step, then the frame timing and CSSC (Cell Specific Scrambling Code) group is detected by taking the correlation of the CPICH(Common Pilot Channel) based on the property yeilded by shifting the CSSC phase in the frequency domain. Finally, the CSSC phase within the group is identified in the third step. This paper proposes a modification code(PCSSCG:Patial Cell Specific Scrambling Code Group) of the conventional CPICH based cell search algorithm in the second step which offers MS(Mobile Station) complexity reductions with the nearly same performance. The proposed method is to be compared and verified through the computer simulation.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.523-533
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• 2000

A two-phase anaerobic reactor with submerged membrane system was developed for increasing acidogen concentration and methane recovery. The membrane used was mixed esters of cellulose of $0.5{\mu}m$ pore size and $0.8m^2$ of effective surface area. The methanogenic reactor comprised of UASB (Upflow Anaerobic Sludge Blanket) and AF (Anaerobic Filter). COD removal efficiency was 70~80% and the methane content in the biogas increased up to 90% for the submerged membrane system in the anaerobic reactor. As the cake resistance of membrane caused a serious problem, stainless steal prefilters (40, 53, $63{\mu}m$) and air backwashing methods were applied to minimize the cake resistance effectively. Among the tested prefilters. the $63{\mu}m$ prefilter showed the best performance for reduction of cake resistance and a successful long-tern operation. By cleaning with alkali first and acidic solution later. the permeate flux decreased by long term operation was recovered to 89% of that with a new membrane.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.4
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• pp.511-517
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• 2015

Korea's modern waterworks began with construction of DDukdo water treatment plant in 1908 and has been growing rapidly along with the country's economic development. As a result, water supply rates have reached 98.5% based on 2013. Despite multilateral efforts for high-quality water supply, such as introduction of advanced water treatment process, expansion of waterworks infrastructure and so on, distrust for drinking tap water has been continuing and domestic consumption rate of tap water is in around 5% level and extremely poor comparing to advanced countries such as the United States(56%), Japan(52%), etc. Recently, the water management has been facing the new phase due to water environmental degradation caused by climate change, aging facilities, etc. Therefore, K-water has converted water management paradigm from the "clean and safe water" to the "healthy water" and been pushing the Smart Water City(SWC) Pilot Project in order to develop and spread new water supply models for consumers to believe and drink tap water through systematic water quality and quantity management combining ICT in the whole water supply process. The SWC pilot projects in Pa-ju city and Go-ryeong county were an opportunity to check the likelihood of the "smart water management" as the answer to future water management. It is needed to examine the necessity of smart water management introduction and nationwide SWC expansion in order to improve water welfare for people and resolve domestic & foreign water problems.

• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.52-59
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• 2021

According to the International Air Transport Association (IATA), 61% of the accidents occurred during the approach and landing phase of the flight, with 16% of the accidents caused by unstable access of the commercial aircraft. It was identified that the pilot's unstable approach and poor manipulation of correction led to accidents by continuing the excessive approach without go-around manuever. The causes of unstable access may vary, including airport approach procedures, pilot error, misplanning, workload, ATC (Air Traffic Contol) congestion, etc. In this study, we use the flight data analysis system to select domestic case airports and aircraft type where unstable approach events occur repeatedly. Through flight data analysis, including main events, airport approach procedures, pilot operations, as well as various environmental factors such as weather and geographical conditions at the airport. It aims to identify and eliminate the tendency of unstable approach events and the causes and risks of them to derive implications for mitigating unstable approach events and for developing navigation safety measures.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.30-37
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• 2011

In this paper, we propose a fast ICI suppression algorithm with adaptive channel estimation for the LTE-Advanced uplink system. In order to effectively remove phase noise and carrier frequency offset at time varying channel, we use the comb type pilot. The purpose is to improve performance by reducing computational complexity than conventional PNFS(Phase Noise & Frequency offset Suppression) algorithm. We reduce computational complexity by decreasing overlapping computation or unnecessary computation at conventional PNFS algorithm. Also, we propose an effective channel estimation method. We estimate and compensate multipath channel through the proposed adaptive channel estimation method. The BER performance of the proposed method is better about 0.5 dB than the conventional method at the Vehicular A channel.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.4
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• pp.683-690
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• 2018

In this paper, a new signal processing technique is proposed for calibrating gain, phase, delay offsets in array antenna based anti-jamming minimum variance distortionless response (MVDR) global-positioning-system (GPS) receivers. The proposed technique estimates gain, phase and delay offsets across the antennas, and compensates for the offsets based on the estimates. A pilot signal with good correlation characteristics is used for accurate estimation of the gain, phase and delay offsets. Based on the cross-correlation, the delay offset is first estimated and then gain/phase offsets are estimated. For fine delay offset estimation and compensation, an interpolation technique is used, and specifically, the discrete Fourier transform (DFT) is employed for the interpolation technique to reduce the computational complexity. The proposed technique is verified through computer simulation using MATLAB. According to the simulation results, the proposed technique can reduce the gain, phaes and delay offset to 0.01 dB, 0.05 degree, and 0.5 ns, respectively.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2020.11a
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• pp.54-55
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• 2020

In 4th Industrial Revolution, technologies such as artificial intelligence, Internet of Things, and Big data are closely related to the maritime industry, which led to the birth of autonomous vessels. Due to the technical characteristics of the current vessel, the speed cannot be suddenly lowered, so complex communication such as the help of a tug boat, boarding of a pilot, and control of the vessel at the onshore control center is required to berth at the port. In this study, clustering analysis was used to resolve how to establish control criteria for vessels to enter port when autonomous vessels are operating. K-Means clustering was used to quantitatively stage the arrival pattern based on the accumulated AIS(Automatic Identification System) data of the incoming vessel, and the arrival phase using SOG(Speed over Ground), COG(Course over Ground), and ROT(Rate of Turn) Was divided into six phase.