• Microbiology and Biotechnology Letters
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• v.39 no.3
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• pp.218-223
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• 2011

To obtain eicosapentaenoic acid (EPA)-producing bacteria, some 600 strains of bacteria were isolated from Antarctic sediment and marine organisms during the summer expedition of 1999-2000 and 7 EPA-producing bacteria were obtained through screening with TLC and GC. A strain designated as L93 showed the highest EPA production, which was gram-negative, rod-shaped bacterium. L93 strain was identified as Shewanella sp., from the sequence analysis of 16S rDNA. Optimal conditions temperature and pH for the growth and EPA production were about $4^{\circ}C$ and pH 7. In addition, its production was optimized by 50%(w/v) sea salt. We establish the optimal production system to produce about 320 mg per liter by using this optimal EPA production conditions. EPA-methyl ester was purified from cultured L93 strain to a purity of higher than 97% and typical purification yield is greater than 72% of the input amount via urea complexation and HPLC.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.10
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• pp.52-56
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• 2009

In this paper, we investigate the performance of the ARQ-aided downlink Time Switched Transmit Diversity (TSTD) in the WCDMA LCR-TDD system, when power ramping is applied. The proposed power ramping scheme ramps up the transmission power and then retransmits the data, when the receiver sends the response signal (ACK or NACK signal) to the transmitter and the response signal is NACK signal. Simulation results demonstrate that the proposed scheme yields about 0.7dB performance gain in terms of average Eb/N0, compared with the conventional ARQ-aided TSTD when a mobile speed is 3km/h and an frame error rate (FER) is 1%, respectively. In addition, 2.5% of throughput gain is shown when average Eb/N0 is equal to 0dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.61-68
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• 2010

In this paper, we investigate the performance of ARQ-aided Time Switched Transmit Diversity (ARQ-TSTD) applying the multi-level control signaling in the WCDMA LCR-TDD system. Proposed ARQ-TSTD system applies the multi-level control signaling scheme in which the receiver sends the response signal (ACK or NACK signal) to the transmitter and defines NACK2 signal for multi-level control. Transmitter utilize the NACK2 control signal to the postponement of transmission and multi-user scheduling scheme proposed by this paper. Simulation results demonstrate that the proposed postponement of transmission and multi-user scheduling scheme yield about 1.3dB, 1.4dB performance gain respectively, compared with the conventional ARQ-TSTD with antenna switching scheme in tenn of the frame error rate (FER) for mobile speed of 3km/h and FER value of 10%. In addition, 14% and 11.5% of throughput gain respectively is shown when Eb/N0=-3dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.7 s.361
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• pp.47-52
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• 2007

This paper analyzes the output signal-to-interference-plus-noise ratio (SINR) for a multiple-input-multiple-output (MIMO) multicarrier code division multiple access (MC-CDMA) system with minium mean square error receivers in multi-cell environments. A previous work in single cell environments is extended into analysis in multi-cell environments. The use of Haar unitary code matrix for asymptotic analysis causes other cell interferences expressed with a diagonal matrix haying different diagonal values. This paper shows that other cell interferences converge to an identity matrix whose gain is expressed by only other cell interference power in mean square sense and finds asymptotic deterministic SINRs for a given other cell interference. Under the assumption that the sum of lognormal fading components is distributed by other lognormal function, we show the comparison between theoretical performances and simulations from the view point of bit error rate and present average throughput performance according to the cell radius.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.18-25
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• 2014

To increase wireless capacity, the concurrent use of multiple wireless interfaces on different frequency bands, called aggregation, can be considered. In this paper, we focus on aggregation of multiple Wi-Fi interfaces with packet-level traffic spreading between the interfaces. Two aggregation schemes, link bonding and multipath TCP (MPTCP), are tested and compared in a dualband Wi-Fi radio system with their Linux implementation. Various test conditions such as traffic types, network delay, locations, interface failures and configuration parameters are considered. Experimental results show that aggregation increases throughput performance significantly over the use of a single interface. Link bonding achieves lower throughput than MPTCP due to duplicate TCP acknowledgements (ACKs) resulting from packet reordering and filtering such duplicate ACKs out is considered as a possible solution. However, link bonding is fast responsive to links' status changes such as a link failure. It is shown that different combinations of interface weights for packet spread in link bonding result in different throughput performance, envisioning a spatio-temporal adaptation of the weights. We also develop a mathematical model of power consumption and compare the power efficiency of the schemes applying different power consumption profiles.

• KSBB Journal
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• v.8 no.2
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• pp.164-171
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• 1993

The production of extracellular polysaccharide by Methylomonas mucosa (NRRL B-5696) was investigated. The microorganism uses methanol as the carbon source for their growth and produces exopolysaccharides. The productivity of exopolysaccharides was investigated under various culture modes: batch, fed-batch and continuous culture. In flask culture the growth of cell mass and the production of polysaccharide were inhibited at above 1% (v/v) methanol. At 1%(v/v) methanol maximum specific growth rate was obtained. As C/N ratio (g methanol/g ammonium sulfate) increased, polysaccharide production increased and cells mass decreased. Magnesium ion was also found to be essential for the polysaccharide production. In batch culture the production of polysaccharides was more affected by the specific growth rate than the cell concentration. In fed-batch culture the concentration of polysaccharide was 4 times higher than that of batch culture, but the yield was lower. The productivity of fed-batch with continuous feeding was higher than that of batch or fed-batch with intermittent feeding. This is due to no methanol limitation or inhibition that used to occur in fed-batch culture with intermittent feeding. In continuous culture pure oxygen was supplied to avoid the oxygen limitation. As the dilution rate in- creased up to 0.21 h-1, the yield and productivity increased. The solution viscosity of the produced polysaccharide obtained from above increased exponentially with the concentration of polysaccharide.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.60-66
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• 2011

LTE (Long Term Evolution) supports QoS (Quality of Service) with several service classes. For each class of traffic, a big difference exists on BER (Bit Error Rate) requirement. This leads to a considerable difference in transmission power for various classes of traffic. In this paper, a novel scheduler is designed and proposed for LTE which supports CoS (Class of Service) with the consideration of priority as well as target BER. By the CQI (Channel Quality Indicator) and QCI (QoS Class Identifier), a minimum transmission power is assigned from the target BER for each class of traffic per each user. Hence, with the other information such as user's used rate in the past and the priority of traffic, the probability of occupying channels is determined. The simulation results of Service Class scheduling are compared with that of Maximum Rate and Proportional Fair. The results show that the service class-aided scheduling can improve the throughput of whole system significantly.

• Journal of Broadcast Engineering
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• v.15 no.3
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• pp.407-413
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• 2010

In DCA (Dynamic Channel Allocation) scheme of uplink cellular system appling a frequency reuse factor of one, when a new call requests a channel, the new call will be blocked if its SINR (Carrier to Noise and Interference Ratio) is less than the required SINR or there is no available channel. The additional channel allocation for the blocked new call can be performed with channel borrowing in the adjacent cells. The channel borrowing causes the CCI (Co-Channel Interference), thus the SINR of the existing calls is deteriorated and the channel reallocation for the existing calls is required. As a result, the channel borrowing leads to a complex calculation so that it is a NP-hard problem. Therefore, to overcome the problem, we propose a novel Group Search-based DCA scheme which decreases the number of the blocked new calls and then reduces the number of the channel reallocation by the channel borrowing for the blocked new calls. The proposed scheme searches the all channels in a group of the adjacent cells and home cell at the same time in order to minimizes the number of the blocked new calls. The simulation results show that proposed Group Search-based DCA scheme provides better new call blocking probability and system throughput than the existing Single Search-based DCA scheme which searches only the channels in home cell.

• 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.

• Clean Technology
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• v.25 no.3
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• pp.223-230
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• 2019

This research was performed to evaluate the characteristics of food waste from 5 areas in Gangwon Province, Korea and to predict the $CH_4$ gas production rate. Food wastes were sampled in July and September, 2017. The amount of methane gas generation was evaluated through the biochemical methane potential (BMP) test and a calculation method using chemical composition. Average bulk density and pH of the food wastes were in the range of $0.758{\sim}0.850g\;cm^{-3}$ and 4.29 ~ 4.75, respectively. By physical composition, vegetables were the highest with 56.43 ~ 72.81% with fruits recording 5.31 ~ 8.95%, cereals 1.60 ~ 18.73%, fish and meat 4.47 ~ 12.11%, and filtrate 1.76 ~ 3.64%. The average water content was 69.30 ~ 75.87%, and VS and ash content were 22.50 ~ 27.98% and 1.63 ~ 2.48%, respectively. In addition, $BOD_5$, $COD_{Cr}$, and $COD_{Mn}$ were in the ranges of $17,690.3{\sim}33,154.9mg\;L^{-1}$, $106,212.3{\sim}128,695.5mg\;L^{-1}$, and $51,266.1{\sim}63,426.3mg\;L^{-1}$, respectively. The NaCl content ranged from 0.81 to 1.17%. The results of elemental analysis showed that the contents of C, H, O, N, and S were 44.87 ~ 48.1%, 7.12 ~ 7.57%, 40.13 ~ 43.78%, 3.22 ~ 4.14%, and 0.00 ~ 0.02%, respectively. In a comparison of the methane production yield per VS mass of food waste, there was no significant difference between the cumulative amount (${0.303{\sim}0.354m_{CH4}}^3\;{kg_{VS}}^{-1}$) by the BMP test and the theoretical amount (${0.294{\sim}0.352m_{CH4}}^3\;{kg_{VS}}^{-1}$) calculated by chemical composition.