• Journal of Korean Society of Environmental Engineers
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• v.30 no.9
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• pp.948-954
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• 2008

Membrane bioreactor(MBR) processes have been widely applied to wastewater treatment for last decades due to its excellent capability of solid-liquid separation. However, membrane fouling was considered as a limiting factor in wide application of the MBR process. Excess aeration into membrane surface is a common way to control membrane fouling in most MBR. However, the excessively supplied air is easily dissipated in the reactor, which results in consuming energy and thus, it should be modified for effective control of membrane fouling. In this study, cylindrical tube was introduced to MBR in order to use the supplied air effectively. Membrane fibers were immersed into the cylindrical tube. This makes the supplied air non-dissipated in the reactor so that membrane fouling could be controlled economically. Two different air supplying method was employed and compared each other; nozzle and porous diffuser which were located just beneath the membrane module. Transmembrane pressure(TMP) was monitored as a function of airflow rate, flux, and ratio of the tube area and cross-sectioned area of membrane fibers(A$_m$/A$_t$). Flow rate of air and liquid was regulated to obtain slug flow in the cylindrical tube. With the same flow of air supply, nozzle was more effective for controlling membrane fouling than porous diffuser. Accumulation of sludge was observed in the tube with the nozzle, if the air was not suppled sufficiently. Reduction of membrane fouling was dependent upon the ratio, A$_m$/A$_t$. For diffuser, membrane fouling was minimized when A$_m$/A$_t$ was 0.27, but 0.55 for nozzle.

• Korean Journal of Animal Reproduction
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• v.17 no.2
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• pp.149-157
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• 1993

A new technique was established to maximize the numbers of follicular oocytes recovered from the ovaries obtained at the slaughter house. And their further developmental capacity was demonstrated. There recovery techniques were used; aspiration (ASP, control), slicing (SLC) and slicing combining aspiration (ASP+SLC). Recovered oocytes were cultured in TCM 199+15% FCS+gonadotrophins in an atmosphere of 5% CO$_2$ in air at 39$^{\circ}C$ for 24 h. The nuclear maturation was detemined with chromo-some configuration by rapid staining. And cytoplasmic maturation was examined by the formation of female pronuclei with parthenogenetic activation of the matured oocyte after 18 h of co-culture with granulosa cell monolayer. Total 1,641 bovine follicular oocytes recovered from 245 ovaries. The number of oocytcs per ovary was 1.87 in ASP, 11.05 in SLC and 7.88 in ASP+SLC, respectively. SLC would yield 5.9 folds increase, compared with ASP. The rate of maturation were 92.9% in ASP, 79.1% in SLC and 71.7% in ASP+SLC, respectively. Although the maturation rate in ASP was the highest, metaphase II oocytes per ovary in SLC was 5 times higher than that of ASP. The rates of pronuclei formation upon ethanol activation were 75% in ASP, 67% in SLC and 62.5% in ASP+SLC, respectively. The results demonstrate that it should be possible to maximize the number of the follicular oocyte from the ovary for mass production of bovine embryos. Thus the established technique may provide efficient supply of bovine embryos for biochemical and molecular study of early bovine embryos.

• Magazine of the Korean Society of Agricultural Engineers
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• v.14 no.3
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• pp.2741-2748
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• 1972

With 31 existing reservoirs selected in the Yong San River Basin, the sedimentation of the reservoirs has been calulated by comparing the precent capacity with original value, which revealed its reduced reservoir capacity. The reservoirs have a total catchment area of 13,871 ha. with a total capacity of 17.6 million cubic meter, and are short of water supply due to reduction of reservoir capacity. Annual sedimentation in the reservoir ranged from 120 to 3,770 cubic meter per square kilometer with great difference in its distribution, and the average value was 877 cubic meter. This wide disparity is analysed to come principally from the topography, geology, vegetation and hydraulics. The reservoir basin had a large portion of devastated land but has become green more and more in the last 10 years. It can be summarized that in the reservoirs with an average period of sedimentation of 26 years, the reduction rate of reservoir capacity amounts 12.5%, and 0.48% is shown for annual capacity reduction rate.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.475-484
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• 2000

The purpose of this study was to develop model for estimating biodegrability of organic sludge (sewage and papermill) in various environmental conditions. to assume degradable degree with operating time of SRB reactor. and evaluate duratior of organic sludge as carbon source. Average TCOD was 28.7~63.2mg/L in effluent. organic sludge did not much supply carbon source for experimental period. But in point of durability. it seemed that organic sludge was efficient because it was not consumed by degradation of much organic matter within short period. With increasing $SO_4{^{2-}}$ reduction rate. Pb and Fe was removed 77~82% and 33~59%. respectively. Because Al was precipitated as a hydroxide. its removal rate wa,. about $54{\pm}2%$ in R-l~R-3 maintaining low pH but about 78% in R-4 maintaining high pH. Because Mn was large in solubility. it showed to be much lower than other heavy metals. Considering supportable capacity or durability of orgainc matter for initial SRB mixing ratio of sewage/papermill 0.5 was regarded as appropriate substituting material and at this time. it estimated that carbon source continued about 3.08 year but safety factor must apply to be thought over. because various factors had an effect on degradation of organic sludge.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.137-147
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• 2013

In this paper, an 1.2V 8b 1GS/s A/D Converter(ADC) based on a folding architecture with a resistive interpolation technique is described. In order to overcome the asymmetrical boundary-condition error of conventional folding ADCs, a novel scheme with an odd number of folding blocks and a fractional folding rate are proposed. Further, a new digital encoding technique with an arithmetic adder is described to implement the proposed fractional folding technique. The proposed ADC employs an iterating offset self-calibration technique and a digital error correction circuit to minimize device mismatch and external noise The chip has been fabricated with a 1.2V 0.13um 1-poly 6-metal CMOS technology. The effective chip area is $2.1mm^2$ (ADC core : $1.4mm^2$, calibration engine : $0.7mm^2$) and the power dissipation is about 350mW including calibration engine at 1.2V power supply. The measured result of SNDR is 46.22dB, when Fin = 10MHz at Fs = 1GHz. Both the INL and DNL are within 1LSB with the self-calibration circuit.

• Clean Technology
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• v.26 no.1
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• pp.72-78
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• 2020

The use of fossil fuel and biogas production causes air pollution and climate change problems. Research endeavors continue to focus on converting methane and carbon dioxide, which are the major causes of climate change, into quality energy sources. In this study, a novel plasma-carbon converter was proposed to convert biogas into high quality gas, which is linked to photovoltaic and wind power and which poses a problem on generating electric power continuously. The characteristics of conversion and gas production were investigated to find a possibility for biogas conversion, involving parametric tests according to the change in the main influence variables, such as O₂/C ratio, total gas feed rate, and CO₂/CH₄ ratio. A higher O₂/C ratio gave higher conversions of methane and carbon dioxide. Total gas feed rate showed maximum conversion at a certain specified value. When CO₂/CH₄ feed ratio was decreased, both conversions increased. As a result, the production of solar fuel by plasma oxidation destruction-carbon material gasification conversion, which was newly suggested in this study, could be known as a possibly useful technology. When O₂/C ratio was 0.8 and CO₂/CH₄ was 0.67 while the total gas supply was at 40 L min^-1 (VHSV = 1.37), the maximum conversions of carbon dioxide and methane were achieved. The results gave the highest production for hydrogen and carbon dioxide which were high-quality fuel.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1015-1020
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• 2012

Lignite of low rank coal and petroleum coke of high sulfur content can be high potential energy sources for coal gasification process because of their plentiful supply. The steam gasification of lignite, anthracite, and pet coke has been carried out in both an atmospheric thermobalance reactor and a lab-scale fludized bed reactor (0.02 m i.d. ${\times}$ 0.6 m height). The effects of gasification temperature ($600{\sim}900^{\circ}C$) and partial pressure of steam (0.15~0.95 atm) on the gasification rate and on the heating value of product gas have been investigated. The modified volumetric reaction model was applied to the experimental data to describe the behavior of carbon conversion, and to evaluate kinetic parameters of char gasification. The results shows that higher temperature bring more hydrogen in the product syngas, and thus increased gas heating value. The feed rate of steam is needed to be optimized because an excess steam input would lower the gasification temperature which results in a degradation of fuel quality. The rank of calorific value of the product gas was anthracite > lignite > pet coke. Their obtained calorific value at $900^{\circ}C$ with 95% steam feed were 10.0 > 6.9 > 5.7 $MJ/m^3$. This study indicates that lignite and pet coke has a potential in fuel gas production.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.184-193
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• 2012

In this paper, a 5-bit 2-GS/s 2-way time interleaved pipeline ADC for high-speed serial link receiver is demonstrated. Implemented as a current-mode amplifier, the stage ADC simultaneously processes the tracking and residue amplification to achieve higher sampling rate. In addition, each stage incorporates a built-in 1-tap FIR equalizer, reducing inter-symbol-interference (ISI）without an extra digital post-processing. The ADC is designed in a 110nm CMOS technology. It comsumes 91mW from a 1.2-V supply. The area excluding the memory block is $0.58{\times}0.42mm^2$. Simulation results show that when equalizer is enabled, the ADC achieves SNDR of 25.2dB and ENOB of 3.9bits at 2.0GS/s sample rate for a Nyquist input signal. When the equalizer is disengaged, SNDR is 26.0dB for 20MHz-1.0GHz input signal, and the ENOB of 4.0bits.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.278-284
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• 1998

This paper describes a l0b CMOS A/D converter (ADC) for HDTV applications. The proposed ADC adopts a typical multi-step pipelined architecture. The proposed circuit design techniques are as fo1lows: A selective channel-length adjustment technique for a bias circuit minimizes the mismatch of the bias current due to the short channel effect by supply voltage variations. A power reduction technique for a high-speed two-stage operational amplifier decreases the power consumption of amplifiers with wide bandwidths by turning on and off bias currents in the suggested sequence. A typical capacitor scaling technique optimizes the chip area and power dissipation of the ADC. The proposed ADC is designed and fabricated in s 0.8 um double-poly double-metal n-well CMOS technology. The measured differential and integral nonlinearities of the prototype ADC show less than ${\pm}0.6LSB\;and\;{\pm}2.0LSB$, respectively. The typical ADC power consumption is 119 mW at 3 V with a 40 MHz sampling rate, and 320 mW at 5 V with a 50 MHz sampling rate.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.3
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• pp.61-71
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• 2014

As the occupancy rate of the flash memory increases in the storage media market for the embedded system and the semi-conductor industry grows, the demand and supply of flash memory is increasing by a big margin. They are especially used in large quantity in the smart phones, tablets, PC, SSD and Soc(System on Chip) etc. The flash memory is divided into the NOR type and NAND type according to the cell arrangement structure and the NAND type is divided into the SLC(Single Level Cell) and MLC(Multi Level Cell) according to the number of bits that can be stored in each cell. Many tests have been performed on NOR type such as BIST(Bulit-In Self Test) and BIRA(Bulit-In Redundancy Analysis) etc, but there is little study on the NAND type. For the case of the existing BIST, the test can be proceeded using external equipments like ATE of high price. However, this paper is an attempt for the improvement of credibility and harvest rate of the system by proposing the BIST for the MLC NAND type flash memory of Finite State Machine structure on which the pattern test can be performed without external equipment since the necessary patterns are embedded in the interior and which uses the MLC NAND March(x) algorithm and pattern which had been proposed for the MLC NAND type flash memory.