• Journal of Microbiology and Biotechnology
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• v.24 no.7
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• pp.879-887
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• 2014

Bacteria that mediate the anaerobic oxidation of ammonium (anammox) have been detected in natural ecosystems, as well as various wastewater treatment systems. In this study, sludge from a particular landfill leachate anaerobic treatment system was selected as the incubation seed for anammox microorganism enrichment owing to its possible anammox activity. Transmission electron microscopy observation, denaturing gradient gel electrophoresis analysis, and cloning/sequencing techniques were applied to identify the diversity of anammox microorganisms throughout the incubation. During the early stage of operation, the diversity of anammox microorganisms was similar to the original complex microbes in the seed sludge. However, as incubation time increased, the anammox microorganism diversity within the system that was originally dominated by Candidatus (Ca.) Brocadia sp. was replaced by Ca. Anammoxoglobus propionicus. The domination of Ca. Anammoxoglobus propionicus produced a stable removal of ammonia (70 mg-N/l) and nitrite (90 mg-N/l), and the total nitrogen removal efficiency was maintained at nearly 95%. The fluorescence in situ hybridization results showed that Ca. Anammoxoglobus propionicus was successfully enriched from $1.8{\pm}0.6%$ initially to $65{\pm}5%$ after 481 days of operation. Therefore, the present results demonstrated the feasibility of enriching Ca. Anammoxoglobus propionicus from leachate sludge, even though the original cell count was extremely low. Application of this seldom found anammox organism could offer an alternative to current ammonia-nitrogen treatment.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1281-1287
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• 2017

Bone morphogenetic protein-4 (BMP-4) is considered to have therapeutic potential for various diseases, including cancers; however, the high expression of biologically active recombinant human BMP-4 (rhBMP-4) needed for its manufacture for therapeutic purposes has yet to be established. In the current study, we established a recombinant Chinese hamster ovary (rCHO) cell line overexpressing rhBMP-4 as well as a production process using 7.5-l bioreactor (5 L working volume). The expression of the mature rhBMP-4 was significantly enhanced by recombinant furin expression. The combination of a chemically defined medium and a nutrient supplement solution for high expression of rhBMP-4 was selected and used for bioreactor cultures. The 11-day fed-batch cultures of the established rhBMP-4-expressing rCHO cells in the 7.5-L bioreactor produced approximately 32 mg/l of rhBMP-4. The mature rhBMP-4 was purified to homogeneity from the culture supernatant using a two-step chromatographic procedure, resulting in a recovery rate of approximately 55% and a protein purity greater than 95%. The N-terminal amino acid sequences and N-linked glycosylation of the purified rhBMP-4 were confirmed by N-terminal sequencing and de-N-glycosylation analysis, respectively. The mature purified rhBMP-4 has been proved to be functionally active, with an effective dose concentration of $EC_{50}$ of 2.93 ng/ml.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.3
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• pp.27-37
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• 2017

As the global uncertainty of manufacturing has increased and the quality problem has become global, the recall has become a fatal risk that determines the durability of the company. In addition, as the convergence of PSS (product-service system) product becomes common due to the development of IT convergence technology, if the function of any part of hardware or software does not operate normally, there will be a problem in the entire function of PSS product. In order to manage the quality of such PSS products in a stable manner, a new approaches is needed to analyze and manage the hardware and software parts at the same time. However, the Fishbone diagram, FTA, and FMEA, which are widely used to interpret the current quality problem, are not suitable for analyzing the quality problem by considering the hardware and software at the same time. In this paper, a quality risk assessment model combining FTA and FMEA based on defect rate to be assessed daily on site to manage quality and fishbone diagram used in group activity to solve defective problem. The proposed FTA-FMEA based risk assessment model considers the system structure characteristics of the defect factors in terms of the relationship between hardware and software, and further recognizes and manages them as risk. In order to evaluate the proposed model, we applied the functions of ITS (intelligent transportation system). It is expected that the proposed model will be more effective in assessing quality risks of PSS products because it evaluates the structural characteristics of products and causes of defects considering hardware and software together.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.12
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• pp.70-78
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• 2000

A novel capacitance deviation-to-time interval converter based on ramp-integration is presented. It consists of two current mirrors, two schmitt triggers, and control digital circuits by the upper and lower sides, symmetrically. Total circuit has been with discrete components. The results show that the proposed converter has a linearity error of less than 1% at the time interval(pulse width) over a capacitance deviation from 295 pF to 375 pF. A capacitance deviation of 40pF and time interval of 0.2 ms was measured for sensor capacitance of 335 pF. Therefore, the high-resolution can be known by counting the fast and stable clock pulses gated into a counter for time interval. The application of a novel capacitance deviation-to time interval converter to a digital humidity controller is also presented. The presented circuit is insensitive to the capacitance difference in disregard of voltage source or temperature deviation. Besides the accuracy, it features the small MOS device count integrable onto a small chip area. The circuit is thus particularly suitable for the on-chip interface.

• Journal of IKEEE
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• v.24 no.1
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• pp.319-325
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• 2020

In this paper, a discontinuous-conduction mode (DCM) DC-DC buck converter is presented for mobile device applications. The buck converter consists of compensator for stable operations, pulse-width modulation (PWM) logic, and power switches. In order to achieve small hardware form-factor, the number of off-chip components should be kept to be minimum, which can be realized with simple and efficient frequency compensation and digital soft start-up circuits. Burst-mode operation is included for preventing the efficiency from degrading under very light load condition. The DCM DC-DC buck converter is fabricated with 0.18-um BCDMOS process. Programmable output with external resistors is typically set to be 1.8V for the input voltage between 2.8 and 5.0V. With a switching frequency of 1MHz, measured maximum efficiency is 92.6% for a load current of 100mA.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.117-117
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• 2008

In MIM capacitor, poly-Si bottom electrode is replaced with metal bottom electrode. Noble metals can be used as bottom electrodes of capacitors because they have high work function and remain conductive in highly oxidizing conditions. In addition, they are chemically very stable. Among novel metals, Ru (ruthenium) has been suggested as an alternative bottom electrode due to its excellent electrical performance, including a low leakage of current and compatibility to high dielectric constant materials. Chemical mechanical planarization (CMP) process has been suggested to planarize and isolate the bottom electrode. Even though there is a great need for development of Ru CMP slurry, few studies have been carried out due to noble properties of Ru against chemicals. In the organic chemistry literature, periodate ion ($IO_4^-$) is a well-known oxidant. It has been reported that sodium periodate ($NaIO_4$) can form $RuO_4$ from hydrated ruthenic oxide ($RuO_2{\cdot}nH_2O$). $NaIO_4$ exist as various species in an aqueous solution as a function of pH. Also, the removal mechanism of Ru depends on solution of pH. In this research, the static etch rate, passivation film thickness and wettability were measured as a function of slurry pH. The electrochemical analysis was investigated as a function of pH. To evaluate the effect of pH on polishing behavior, removal rate was investigated as a function of pH by using patterned and unpatterned wafers.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.4
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• pp.220-224
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• 2012

The analysis on the bus bar effect is conducted to develop a cost effective 24kV/2,000A switchgear. The temperature enclosures and bus bars could rise due to several heat sources such as eddy current losses and copper losses. Therefore, a study on the characteristics of the electric field intensity and electromagnetic loss according to the bus bar size in a bus bar compartment is essential to design a electrically reliable high voltage switchgear. It is investigated that the electromagnetic influence to the temperature rising and the dielectric stability according to various bus bar sizes by using finite element method(FEM). The electric field intensity and electromagnetic loss according to various bus bar sizes are calculated to design a reliable and a high voltage switchgear. As results, it is found that the electromagnetic loss and the dielectric stability of bus bar could be determined by a bus bar size. It means that a cost effective 24kV/2,000A high voltage switchgear could be developed by selecting the proper size of a bus bar. Also, it is recognized that the electromagnetic characteristics according to various bus bar sizes in order to design an electrically stable high voltage switchgear when the enclosure size is determined as a fixed value. Futhermore, studies on the various nominal voltage class and bus bar sizes will be conducted to develop a cost effective high voltage switchgear.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.290-294
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• 2014

PID(Proportional, Integral, Derivative) controller is the most popular process controllers in nuclear power plants. The optimized parameter setting of the process controller contributes to the stable operation and the efficiency of the operating nuclear power plants. PID parameter setting is tuned when new process control systems are installed or current process control systems are changed. When the nuclear plant is shut down, a lot of PID tuning methods such as the Trial and Error method, Ultimate Oscillation method operation, Ziegler-Nichols method, frequency method are used to tune the PID values. But inadequate PID parameter setting can be the cause of the unstable process of the operating nuclear power plant. Therefore the results of PID parameter setting should be simulated, optimized and finally verified. This paper introduces the simulation method of PID tuning to optimize the PID parameter setting and confirms them of the actual PID controller in the operating nuclear power plants. The simulation method provides the accurate process modeling and optimized PID parameter setting of the multi-loop control process in particular.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.517-525
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• 2015

A grid connected inverter must be operated as the main electricity source under an isolated condition caused by the grid problem. Conventionally, the dual loop controller is used for the grid inverter, and the controller is used for control under the stand-alone mode. Generally, the PI(Proportional - Integral) controller is highly efficient under a synchronous reference frame, and stable control can be available. However, in this synchronous frame-based control, high-quality DSP is required because many sinusoidal calculations are necessary. When the PI control is conducted under a stationary frame, the controller constructions are made simple so that they work even with a low-price micro controller. However, given the characteristics of the PI controller, it should be designed with the phase of reference voltage considered. Otherwise, the phase delay of the output voltage can occur. Although the current controller also has a higher bandwidth than the voltage controller, distortion of the voltage is difficult to avoid only by the rapid response of the PI controller, as a sudden load change can occur in the nonlinear load. In this study, a new control method that solves the voltage controller bandwidth problem and rapidly copes with it even in the nonlinear load situation is proposed. The validity of the proposed method is proved by simulation and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.550-557
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• 2015

The Jeju Special Self-Governing Province is currently promoting the "Carbon-free Island by 2030" policy, which requires the use of renewable energy instead of fossil fuel so that the island will have no carbon gases generated by 2030. To implement this policy, the island plans to build a wind power plant capacity of 1.09 GW in 2020; this wind power plant is currently ongoing. However, when wind power output is greater than the power demand of the island, the stability of Jeju Island power system must be prepared for it because it can be a problem. Therefore, this study proposes a voltage source-type MMC-HVDC system linked to mainland Korea to expand the wind power penetration limits of Jeju Island under the stable operation of the Jeju Island power system. To verify the effectiveness of the proposed scheme, computer simulations using the PSCAD/EMTDC program are conducted, and the results are demonstrated. The scenarios of the computer simulation consist of two cases. First, the MMC-HVDC system is operated under variable wind power in the Jeju Island power system. Second, it is operated under the predicted Jeju Island power system in 2020.