Interaction of Pseudostellaria heterophylla with Quorum Sensing and Quorum Quenching Bacteria Mediated by Root Exudates in a Consecutive Monoculture System^s

( Liaoyuan Zhang ),( Zewang Guo ),( Huifang Gao ),( Xiaoqian Peng ),( Yongyu Li ),( Shujing Sun ),( Jung-kul Lee ),( Wenxiong Lin ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.12

Many plant-pathogenic bacteria are dependent on quorum sensing (QS) to evoke disease. In this study, the population of QS and quorum quenching (QQ) bacteria was analyzed in a consecutive monoculture system of Pseudostellaria heterophylla. The isolated QS strains were identified as Serratia marcescens with SwrIR-type QS system and exhibited a significant increase over the years of monoculture. Only one QQ strain was isolated from newly planted soil sample and was identified as Bacillus thuringiensis, which secreted lactonase to degrade QS signal molecules. Inoculation of S. marcescens to P. heterophylla root could rapidly cause wilt disease, which was alleviated by B. thuringiensis. Furthermore, the expression of lactonase encoded by the aiiA gene in S. marcescens resulted in reduction of its pathogenicity, implying that the toxic effect of S. marcescens on the seedlings was QS-regulated. Meanwhile, excess lactonase in S. marcescens led to reduction in antibacterial substances, exoenzymes, and swarming motility, which might contribute to pathogensis on the seedlings. Root exudates and root tuber extracts of P. heterophylla significantly promoted the growth of S. marcescens, whereas a slight increase of B. thuringiensis was observed in both samples. These results demonstrated that QS-regulated behaviors in S. marcescens mediated by root exudates played an important role in replanting diseases of P. heterophylla.

An Enhanced Power Sharing Strategy for Islanded Microgrids Considering Impedance Matching for Both Real and Reactive Power

Liaoyuan Lin,Qian Guo,Zhihong Bai,Hao Ma 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

There exists a strong coupling between real and reactive power owing to the complex impedances in droop based islanded microgrids (MGs). The existing virtual impedance methods consider improvements of the impedance matching for sharing of the voltage controlled power (VCP) (reactive power for Q-V droop, and real power for P-V droop), which yields a 1-DOF (degree of freedom) tunable virtual impedance. However, a weak impedance matching for sharing of the frequency controlled power (FCP) (real power for P-ω droop, and reactive power for Q-ω droop) may result in FCP overshoots and even oscillations during load transients. This in turn results in VCP oscillations due to the strong coupling. In this paper, a 2-DOF tunable adaptive virtual impedance method considering impedance matching for both real and reactive power (IM-PQ) is proposed to improve the power sharing performance of MGs. The dynamic response is promoted by suppressing the coupled power oscillations and power overshoots while realizing accurate power sharing. In addition, the proposed power sharing controller has a better parametric adaptability. The stability and dynamic performances are analyzed with a small-signal state-space model. Simulation and experimental results are presented to investigate the validity of the proposed scheme.

Optimal Power Allocation for Wireless Uplink Transmissions Using Successive Interference Cancellation

( Liaoyuan Wu ),( Yamei Wang ),( Jianghong Han ),( Wenqiang Chen ),( Lusheng Wang ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.5

Successive interference cancellation (SIC) is considered to be a promising technique to mitigate multi-user interference and achieve concurrent uplink transmissions, but the optimal power allocation (PA) issue for SIC users is not well addressed. In this article, we focus on the optimization of the PA ratio of users on an SIC channel and analytically obtain the optimal PA ratio with regard to the signal-to-interference-plus-noise ratio (SINR) threshold for successful demodulation and the sustainable demodulation error rate. Then, we design an efficient resource allocation (RA) scheme using the obtained optimal PA ratio. Finally, we compare the proposal with the near-optimum RA obtained by a simulated annealing search and the RA scheme with random PA. Simulation results show that our proposal achieves a performance close to the near-optimum and much higher performance than the random scheme in terms of total utility and Jain`s fairness index. To demonstrate the applicability of our proposal, we also simulate the proposal in various network paradigms, including wireless local area network, body area network, and vehicular ad hoc network.

An Enhanced Power Sharing Strategy for Islanded Microgrids Considering Impedance Matching for Both Real and Reactive Power

Lin, Liaoyuan,Guo, Qian,Bai, Zhihong,Ma, Hao The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

There exists a strong coupling between real and reactive power owing to the complex impedances in droop based islanded microgrids (MGs). The existing virtual impedance methods consider improvements of the impedance matching for sharing of the voltage controlled power (VCP) (reactive power for Q-V droop, and real power for P-V droop), which yields a 1-DOF (degree of freedom) tunable virtual impedance. However, a weak impedance matching for sharing of the frequency controlled power (FCP) (real power for $P-{\omega}$ droop, and reactive power for $Q-{\omega}$ droop) may result in FCP overshoots and even oscillations during load transients. This in turn results in VCP oscillations due to the strong coupling. In this paper, a 2-DOF tunable adaptive virtual impedance method considering impedance matching for both real and reactive power (IM-PQ) is proposed to improve the power sharing performance of MGs. The dynamic response is promoted by suppressing the coupled power oscillations and power overshoots while realizing accurate power sharing. In addition, the proposed power sharing controller has a better parametric adaptability. The stability and dynamic performances are analyzed with a small-signal state-space model. Simulation and experimental results are presented to investigate the validity of the proposed scheme.

An artificial synthetic pathway for acetoin, 2,3-butanediol, and 2-butanol production from ethanol using cell free multi-enzyme catalysis

Zhang, Liaoyuan,Singh, Raushan,D, Sivakumar,Guo, Zewang,Li, Jiahuan,Chen, Fanbing,He, Yuanzhi,Guan, Xiong,Kang, Yun Chan,Lee, Jung-Kul unknown 2018 Green Chemistry Vol. No.

<P>Upgrading ethanol to higher order alcohols is desired but difficult using current biotechnological methods. In this study, we designed a completely artificial reaction pathway for upgrading ethanol to acetoin, 2,3-butanediol, and 2-butanol in a cell-free bio-system composed of ethanol dehydrogenase, formolase, 2,3-butanediol dehydrogenase, diol dehydratase, and NADH oxidase. Under optimized conditions, acetoin, 2,3-butanediol, and 2-butanol were produced at 88.78%, 88.28%, and 27.25% of the theoretical yield from 100 mM ethanol, respectively. These results demonstrate that this artificial synthetic pathway is an environmentally-friendly novel approach for upgrading bio-ethanol to acetoin, 2,3-butanediol, and 2-butanol.</P>

Enhanced Acetoin Production by Serratia marcescens H32 Using Statistical Optimization and a Two-stage Agitation Speed Control Strategy

Jianan Sun,Liaoyuan Zhang,Ben Rao,Yunbin Han,Ju Chu,Jiawen Zhu,Yaling Shen,Dong-Zhi Wei 한국생물공학회 2012 Biotechnology and Bioprocess Engineering Vol.17 No.3

Enhanced acetoin production was carried out by Serratia marcescens H32. First, medium compositions were optimized statistically for shake flask fermentations to produce acetoin. Sucrose and corn steep liquor powder (CSLP) were identified as the most significant factors by Plackett–Burman design. The path of steepest ascent and response surface methodology were then employed to determine the optimal concentrations of the two factors. Acetoin yield was up to 41.5 g/L in flask fermentations using the optimized medium. Furthermore, the optimal medium was used to conduct fermentation experiments in a 3.7-L bioreactor. The influences of different agitation speeds on acetoin production were investigated. Based on a process analysis, a two-stage agitation speed control strategy was proposed, in which the agitation speed was controlled at 700 rpm during the first 8 h and then switched to 600 rpm. A relatively high acetoin concentration (44.9 g/L)and high acetoin productivity (1.73 g/L/h) were achieved by applying this strategy. Fed-batch fermentation based on the two-stage agitation speed control strategy was performed,and a maximum acetoin concentration of 60.5 g/L with productivity of 1.44 g/L/h was achieved. Enhanced acetoin production was carried out by Serratia marcescens H32. First, medium compositions were optimized statistically for shake flask fermentations to produce acetoin. Sucrose and corn steep liquor powder (CSLP) were identified as the most significant factors by Plackett–Burman design. The path of steepest ascent and response surface methodology were then employed to determine the optimal concentrations of the two factors. Acetoin yield was up to 41.5 g/L in flask fermentations using the optimized medium. Furthermore, the optimal medium was used to conduct fermentation experiments in a 3.7-L bioreactor. The influences of different agitation speeds on acetoin production were investigated. Based on a process analysis, a two-stage agitation speed control strategy was proposed, in which the agitation speed was controlled at 700 rpm during the first 8 h and then switched to 600 rpm. A relatively high acetoin concentration (44.9 g/L)and high acetoin productivity (1.73 g/L/h) were achieved by applying this strategy. Fed-batch fermentation based on the two-stage agitation speed control strategy was performed,and a maximum acetoin concentration of 60.5 g/L with productivity of 1.44 g/L/h was achieved.

Robust CFO Acquisition in PN-Padded OFDM Systems

Guanghui Liu,Liaoyuan Zeng,Hongliang Li,Linfeng Xu,ZhengningWang 한국전자통신연구원 2013 ETRI Journal Vol.35 No.4

As an alternative to the traditional pilot-aided orthogonal frequency division multiplexing (OFDM), the time-domain pseudonoise (PN)-padded OFDM provides a higher spectral efficiency. However, the carrier frequency offset (CFO) attenuates peaks of the conventional PN correlation output, which limits the CFO estimation range of the OFDM synchronizer. An improved correlation is proposed in this letter to remove the CFO-induced amplitude attenuation of correlation peaks. For a synchronizer adopting the designed correlator, a larger range of CFO acquisition is obtained through using wider correlation windows with a smaller interval between them. The proposed method of CFO acquisition is verified in a digital terrestrial multimedia broadcast receiver, in which the synchronizer is able to acquire CFOs up to ±320 kHz in the DVB-T F1 channel. Furthermore, the acquisition range can be expanded in more favorable channels.

Adaptive Complex Interpolator for Channel Estimation in Pilot-Aided OFDM System

Guanghui Liu,Liaoyuan Zeng,Hongliang Li,Linfeng Xu,ZhengningWang 한국통신학회 2013 Journal of communications and networks Vol.15 No.5

In an orthogonal frequency division multiplexing system,conventional interpolation techniques cannot correctly balanceperformance and overhead when estimating dynamic longdelaychannels in single frequency networks (SFNs). In this study,classical filter analysis and design methods are employed to derivea complex interpolator for maximizing the resistible echo delay in achannel estimator on the basis of the correlation between frequencydomain interpolating and time domain windowing. The coefficientcomputation of the complex interpolator requires a key parameter,i.e., channel length, which is obtained in the frequency domain witha tentative estimation scheme having low implementation complexity. The proposed complex adaptive interpolator is verified in asimulated digital video broadcasting for terrestrial/handheld receiver. The simulation results indicate that the designed channelestimator can not only handle SFN echoes with more than 200 µsdelay but also achieve a bit-error rate performance close to the optimumminimum mean square error method, which significantlyoutperforms conventional channel estimation methods, while preservinga low implementation cost in a short-delay channel.

Adaptive Complex Interpolator for Channel Estimation in Pilot-Aided OFDM System

Liu, Guanghui,Zeng, Liaoyuan,Li, Hongliang,Xu, Linfeng,Wang, Zhengning The Korea Institute of Information and Commucation 2013 Journal of communications and networks Vol.15 No.5

In an orthogonal frequency division multiplexing system, conventional interpolation techniques cannot correctly balance performance and overhead when estimating dynamic long-delay channels in single frequency networks (SFNs). In this study, classical filter analysis and design methods are employed to derive a complex interpolator for maximizing the resistible echo delay in a channel estimator on the basis of the correlation between frequency domain interpolating and time domain windowing. The coefficient computation of the complex interpolator requires a key parameter, i.e., channel length, which is obtained in the frequency domain with a tentative estimation scheme having low implementation complexity. The proposed complex adaptive interpolator is verified in a simulated digital video broadcasting for terrestrial/handheld receiver. The simulation results indicate that the designed channel estimator can not only handle SFN echoes with more than $200{\mu}s$ delay but also achieve a bit-error rate performance close to the optimum minimum mean square error method, which significantly outperforms conventional channel estimation methods, while preserving a low implementation cost in a short-delay channel.

Secondary Voltage Control for Reactive Power Sharing in an Islanded Microgrid

Qian Guo,Hongyan Wu,Liaoyuan Lin,Zhihong Bai,Hao Ma 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

Owing to mismatched feeder impedances in an islanded microgrid, the conventional droop control method typically results in errors in reactive power sharing among distributed generation (DG) units. In this study, an improved droop control strategy based on secondary voltage control is proposed to enhance the reactive power sharing accuracy in an islanded microgrid. In a DG local controller, an integral term is introduced into the voltage droop function, in which the voltage compensation signal from the secondary voltage control is utilized as the common reactive power reference for each DG unit. Therefore, accurate reactive power sharing can be realized without any power information exchange among DG units or between DG units and the central controller. Meanwhile, the voltage deviation in the microgrid common bus is removed. Communication in the proposed strategy is simple to implement because the information of the voltage compensation signal is broadcasted from the central controller to each DG unit. The reactive power sharing accuracy is also not sensitive to time-delay mismatch in the communication channels. Simulation and experimental results are provided to validate the effectiveness of the proposed method.