Efficient Expression and Purification of Recombinant Alcohol Oxidase in Pichia pastoris

Yunping Liu,Jianfeng Pan,Peilian Wei,Jianzhong Zhu,Lei Huang,Jin Cai,Zhinan Xu 한국생물공학회 2012 Biotechnology and Bioprocess Engineering Vol.17 No.4

In order to improve the production of alcohol oxidase (AOX), a recombinant Pichia pastoris (P. pastoris)system was constructed by transformation of the plasmid pPIC9K-AOX into P. pastoris GS115. The effects of different expression conditions on alcohol oxidase activity in the culture supernatant were investigated in the shake flask scale. The results showed that the highest extracellular activity (562 U/L) of alcohol oxidase was obtained after 56h induction with 4% methanol at OD600 1.0 in the medium containing 50 g/L maltose, which is about 4.2 folds higher than previously reported. High-purity functional recombinant AOX (>90%) was purified from the culture with the Ni-NTA affinity column and Sephadex G-100 chromatographical methods, with a total recovery rate of 68.9%. Further studies showed that the purified rAOX had similar enzymatic characteristics as the native enzyme, except that the thermal stability and resistance to H2O2 inhibition of rAOX were significantly greater compared to the previous report. The purified rAOX was well tolerant to various water-miscible organic solvents. This efficient expression and purification process will be promising for large-scale production of rAOX as an important diagnostic enzyme for alcohol detection in many areas.

A Method for Mapping Sensor Data to SSN Ontology

Xiaoming Zhang,Yunping Zhao,Wanming Liu 보안공학연구지원센터 2015 International Journal of u- and e- Service, Scienc Vol.8 No.9

Along with the continuous development of the sensor network technology, sensors from all over the world are constantly producing sensor data. However, the sensor data from different source is hard to work together for lack of semantic. Fortunately, SSN ontology provide a way to represent sensor data semantically, but how to transform sensor data into the instance of SSN ontology conveniently is still an issue to be considered. This paper proposed a solution to map sensor data to SSN ontology automatically based on a predefined XML-based document. We design a mapping language SASML (Sensors Annotation and Semantic Mapping Language) which provide a schema to annotate sensors and sources so as to generate a XML document for mapping. Then, an algorithm (namely SDRM) is designed to automatically transform sensor data, which described by SASML, to RDF conforming to SSN ontology, according to the mapping document and the element correspondences between the SASML and SSN ontology. Further, a case study about sensor data from greenhouse is presented to illustrate our method, and a prototype is also developed to demonstrate the feasibility and effectiveness.

Deadbeat Control with a Repetitive Predictor for Three-Level Active Power Filters

He, Yingjie,Liu, Jinjun,Tang, Jian,Wang, Zhaoan,Zou, Yunping The Korean Institute of Power Electronics 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.4

Three-level NPC inverters have been put into practical use for years especially in high voltage high power grids. This paper researches three-level active power filters (APFs). In this paper a mathematical model in the d-q coordinates is presented for 3-phase 3-wire NPC APFs. The deadbeat control scheme is obtained by using state equations. Canceling the delay of one sampling period and providing the predictive value of the harmonic current is a key problem of the deadbeat control. Based on this deadbeat control, the predictive output current value is obtained by the state observer. The delay of one sampling period is remedied in this digital control system by the state observer. The predictive harmonic command current value is obtained by the repetitive predictor synchronously. The repetitive predictor can achieve a better prediction of the harmonic current with the same sampling frequency, thus improving the overall performance of the system. The experiment results indicate that the steady-state accuracy and the dynamic response are both satisfying when the proposed control scheme is implemented.

Nonlinear aerodynamic stability analysis of orthotropic membrane structures with large amplitude

Zhoulian Zheng,Yunping Xu,Changjiang Liu,Xiaoting He,Weiju Song 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.37 No.4

The aerodynamic stability of orthotropic tensioned membrane structures with rectangular plane is theoretically studied under the uniform ideal potential flow. The aerodynamic force acting on the membrane surface is determined by the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics. Then, based on the large amplitude theory and the D'Alembert's principle, the interaction governing equation of wind-structure is established. Under the circumstances of single mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction equation into a system of second order nonlinear differential equation with constant coefficients. Through judging the stability of the system characteristic equation, the critical divergence instability wind velocity is determined. Finally, from different parametric analysis, we can conclude that it has positive significance to consider the characteristics of orthotropic and large amplitude for preventing the instability destruction of structures.

A PI Control Algorithm with Zero Static Misadjustment for Tracking the Harmonic Current of Three-Level APFs

He, Yingjie,Liu, Jinjun,Wang, Zhaoan,Zou, Yunping The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.1

Tracking harmonic current quickly and precisely is one of the keys to designing active power filters (APF). In the past, the current state feedback decoupling PI control was an effective means for three-phase systems in the current control of constant voltage constant frequency inverters and high frequency PWM reversible rectifiers. This paper analyzes in detail the limitation of the conventional PI conditioner in the APF application field and presents a novel PI control method. Canceling the delay of one sampling period and the misadjustment for tracking the harmonic current is the key problem of this PI control. In this PI control, the predictive output current value is obtained by a state observer. The delay of one sampling period is remedied in this digital control system by the state observer. The predictive harmonic command current value is obtained by a repetitive predictor synchronously. The repetitive predictor can achieve better predictions of the harmonic current. By this means, the misadjustment of the conventional PI control for tracking the harmonic current is cancelled. The experiment results with a three-level NPC APF indicate that the steady-state accuracy and dynamic response of this method are satisfying when the proposed control scheme is implemented.

Theoretical Analysis and Control of DC Neutral-point Voltage Balance of Three-level Inverters in Active Power Filters

He, Yingjie,Liu, Jinjun,Tang, Jian,Wang, Zhaoan,Zou, Yunping The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.2

In recent years, multilevel technology has become an effective and practical solution in the field of moderate and high voltage applications. This paper discusses an APF with a three-level NPC inverter. Obviously, the application of such converter to APFs is hindered by the problem of the voltage unbalance of DC capacitors, which leads to system instability. This paper comprehensively analyzes the theoretical limitations of the neutral-point voltage balancing problem for tracking different harmonic currents utilizing current switching functions from the space vector PWM (SVPWM) point of view. The fluctuation of the neutral point caused by the load currents of certain order harmonic frequency is reported and quantified. Furthermore, this paper presents a close-loop digital control algorithm of the DC voltage for this APF. A PI controller regulates the DC voltage in the outer-loop controller. In the current-loop controller, this paper proposes a simple neutral-point voltage control method. The neutral-point voltage imbalance is restrained by selecting small vectors that will move the neutral-point voltage in the direction opposite the direction of the unbalance. The experiment results illustrate that the performance of the proposed approach is satisfactory.

Theoretical Analysis and Control of DC Neutral-point Voltage Balance of Three-level Inverters in Active Power Filters

Yingjie He,Jinjun Liu,Jian Tang,Zhaoan Wang,Yunping Zou 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.2

In recent years, multilevel technology has become an effective and practical solution in the field of moderate and high voltage applications. This paper discusses an APF with a three-level NPC inverter. Obviously, the application of such converter to APFs is hindered by the problem of the voltage unbalance of DC capacitors, which leads to system instability. This paper comprehensively analyzes the theoretical limitations of the neutral-point voltage balancing problem for tracking different harmonic currents utilizing current switching functions from the space vector PWM(SVPWM)point of view. The fluctuation of the neutral point caused by the load currents of certain order harmonic frequency is reported and quantified. Furthermore, this paper presents a close-loop digital control algorithm of the DC voltage for this APF. A PI controller regulates the DC voltage in the outer-loop controller. In the current-loop controller, this paper proposes a simple neutral-point voltage control method. The neutral-point voltage imbalance is restrained by selecting small vectors that will move the neutral-point voltage in the direction opposite the direction of the unbalance. The experiment results illustrate that the performance of the proposed approach is satisfactory.

A PI Control Algorithm with Zero Static Misadjustment for Tracking the Harmonic Current of Three-Level APFs

Yingjie He,Jinjun Liu,Zhaoan Wang,Yunping Zou 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.1

Tracking harmonic current quickly and precisely is one of the keys to designing active power filters (APF). In the past, the current state feedback decoupling PI control was an effective means for three-phase systems in the current control of constant voltage constant frequency inverters and high frequency PWM reversible rectifiers. This paper analyzes in detail the limitation of the conventional PI conditioner in the APF application field and presents a novel PI control method. Canceling the delay of one sampling period and the misadjustment for tracking the harmonic current is the key problem of this PI control. In this PI control, the predictive output current value is obtained by a state observer. The delay of one sampling period is remedied in this digital control system by the state observer. The predictive harmonic command current value is obtained by a repetitive predictor synchronously. The repetitive predictor can achieve better predictions of the harmonic current. By this means, the misadjustment of the conventional PI control for tracking the harmonic current is cancelled. The experiment results with a three-level NPC APF indicate that the steady-state accuracy and dynamic response of this method are satisfying when the proposed control scheme is implemented.

Deadbeat Control with a Repetitive Predictor for Three-Level Active Power Filters

Yingjie He,Jinjun Liu,Jian Tang,Zhaoan Wang,Yunping Zou 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.4

Three-level NPC inverters have been put into practical use for years especially in high voltage high power grids. This paper researches three-level active power filters (APFs). In this paper a mathematical model in the d-q coordinates is presented for 3-phase 3-wire NPC APFs. The deadbeat control scheme is obtained by using state equations. Canceling the delay of one sampling period and providing the predictive value of the harmonic current is a key problem of the deadbeat control. Based on this deadbeat control, the predictive output current value is obtained by the state observer. The delay of one sampling period is remedied in this digital control system by the state observer. The predictive harmonic command current value is obtained by the repetitive predictor synchronously. The repetitive predictor can achieve a better prediction of the harmonic current with the same sampling frequency, thus improving the overall performance of the system. The experiment results indicate that the steady-state accuracy and the dynamic response are both satisfying when the proposed control scheme is implemented.

Nonlinear aerodynamic stability analysis of orthotropic membrane structures with large amplitude

Zheng, Zhoulian,Xu, Yunping,Liu, Changjiang,He, Xiaoting,Song, Weiju Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.37 No.4

The aerodynamic stability of orthotropic tensioned membrane structures with rectangular plane is theoretically studied under the uniform ideal potential flow. The aerodynamic force acting on the membrane surface is determined by the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics. Then, based on the large amplitude theory and the D'Alembert's principle, the interaction governing equation of wind-structure is established. Under the circumstances of single mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction equation into a system of second order nonlinear differential equation with constant coefficients. Through judging the stability of the system characteristic equation, the critical divergence instability wind velocity is determined. Finally, from different parametric analysis, we can conclude that it has positive significance to consider the characteristics of orthotropic and large amplitude for preventing the instability destruction of structures.