In this mini-review, the complexity of protein fractionation using ultrafiltration is discussed. The coupling of the system hydrodynamics, boundary Layer transport, membrane permeation, electrostatic and hydrophobic i...In this mini-review, the complexity of protein fractionation using ultrafiltration is discussed. The coupling of the system hydrodynamics, boundary Layer transport, membrane permeation, electrostatic and hydrophobic interactions and its effects on protein transmission and membrane selectivity are analysed. Although ultrafiltration is promising for larger scale protein purification and also with outstanding advantages both technically and economically, much needs to be done to derive the general guidance for membrane selection, process design and system operation. With fine tuning of operational and physiochemical conditions, the process can be greatly improved in terms of process productivity and protein purity. A coupled multi-scale approach might provide a way forward to analyse this complex system and improve the confidence in applying such a promising technology and predictability of the outcome.展开更多
This paper focuses on optimizing an unknown cost function through extremum seeking(ES)control in the presence of a slow nonlinear dynamic sensor responsible for measuring the cost.In contrast to traditional perturbati...This paper focuses on optimizing an unknown cost function through extremum seeking(ES)control in the presence of a slow nonlinear dynamic sensor responsible for measuring the cost.In contrast to traditional perturbation-based ES control,which often suffers from sluggish convergence,the proposed method eliminates the time-scale separation between sensor dynamics and ES control by using the relative degree of the nonlinear sensor system.To improve the convergence rate,the authors incorporate high-frequency dither signals and a differentiator.To enhance the robustness with the existence of rapid disturbances,an off-the-shelf linear high-gain differentiator is applied.The first result demonstrates that,for any desired convergence rate,with properly tuned parameters for the proposed ES algorithm,the input of the cost function can converge to an arbitrarily small neighborhood of the optimal solution,starting from any initial condition within any given compact set.Furthermore,the second result shows the robustness of the proposed ES control in the presence of sufficiently fast,zero-mean periodic disturbances.Simulation results substantiate these theoretical findings.展开更多
Since the dynamical system and control system of the missile are typically nonlinear, an effective acceleration tracking autopilot is designed using the dynamic surface control(DSC)technique in order to make the missi...Since the dynamical system and control system of the missile are typically nonlinear, an effective acceleration tracking autopilot is designed using the dynamic surface control(DSC)technique in order to make the missile control system more robust despite the uncertainty of the dynamical parameters and the presence of disturbances. Firstly, the nonlinear mathematical model of the tail-controlled missile is decomposed into slow acceleration dynamics and fast pitch rate dynamics based on the naturally existing time scale separation. Secondly, the controller based on DSC is designed after obtaining the linear dynamics characteristics of the slow and fast subsystems. An extended state observer is used to detect the uncertainty of the system state variables and aerodynamic parameters to achieve the compensation of the control law. The closed-loop stability of the controller is derived and rigorously analyzed. Finally, the effectiveness and robustness of the design is verified by Monte Carlo simulation considering different initial conditions and parameter uptake. Simulation results illustrate that the missile autopilot based DSC controller achieves better performance and robustness than the other two well-known autopilots.The method proposed in this paper is applied to the design of a missile autopilot, and the results show that the acceleration tracking autopilot based on the DSC controller can ensure accurate tracking of the required commands and has better performance.展开更多
The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbu...The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbulence. The spectra are calculated from direct numerical simulation （DNS） of turbulent channel flows and zero-pressure-gradient boundary layer flows. These two peaks locate in the nearwall and outer regions and are referred to as the inner peak and the outer peak, respectively. This result implies that the streamwise velocity fluctuations can be separated into large and small scales in the spanwise direction even though the friction Reynolds number Rer can be as low as 1000. The properties of the inner and outer peaks in the spanwise spec- tra are analyzed. The locations of the inner peak are invariant over a range of Reynolds numbers. However, the locations of the outer peak are associated with the Reynolds number, which are much higher than those of the outer peak of the pre-multiplied streamwise energy spectra of the streamwise velocity.展开更多
The objective of the present study is to develop a method for large-scale separating and purifying salidroside from rhodiola kirilowii roots and for preparing injectable medicinal ingredient.Crude extract of salidrosi...The objective of the present study is to develop a method for large-scale separating and purifying salidroside from rhodiola kirilowii roots and for preparing injectable medicinal ingredient.Crude extract of salidroside was prepared by water-ethanol system,and purified by column chromatography of macroporous resins.Static adsorption and desorption studies were performed on six kinds of macroporous resins,and SP825 resin was chosen,followed by optimizing process parameters.The optimum sample volume,feed concentration,ratio of diameter to height,and feeding flow rate were 1.5 bed volumes(BV),15 mg/mL,1:10 and 1 BV/h,respectively.Dynamic desorption was performed consecutively with 8 BV of distilled water,3 BV of 5% ethanol and 8 BV of 10% ethanol at a flow rate of 2 BV/h.After three cycles in separating 3.5 tons of rhodiola kirilowii roots,salidroside purity was increased from 3.4% in the crude extract to 93.6% in purified salidroside product.This study provides a novel method to separate salidroside for injectable use.展开更多
文摘In this mini-review, the complexity of protein fractionation using ultrafiltration is discussed. The coupling of the system hydrodynamics, boundary Layer transport, membrane permeation, electrostatic and hydrophobic interactions and its effects on protein transmission and membrane selectivity are analysed. Although ultrafiltration is promising for larger scale protein purification and also with outstanding advantages both technically and economically, much needs to be done to derive the general guidance for membrane selection, process design and system operation. With fine tuning of operational and physiochemical conditions, the process can be greatly improved in terms of process productivity and protein purity. A coupled multi-scale approach might provide a way forward to analyse this complex system and improve the confidence in applying such a promising technology and predictability of the outcome.
基金supported by the Australian Research Council Discovery under Grant No.DP200102402.
文摘This paper focuses on optimizing an unknown cost function through extremum seeking(ES)control in the presence of a slow nonlinear dynamic sensor responsible for measuring the cost.In contrast to traditional perturbation-based ES control,which often suffers from sluggish convergence,the proposed method eliminates the time-scale separation between sensor dynamics and ES control by using the relative degree of the nonlinear sensor system.To improve the convergence rate,the authors incorporate high-frequency dither signals and a differentiator.To enhance the robustness with the existence of rapid disturbances,an off-the-shelf linear high-gain differentiator is applied.The first result demonstrates that,for any desired convergence rate,with properly tuned parameters for the proposed ES algorithm,the input of the cost function can converge to an arbitrarily small neighborhood of the optimal solution,starting from any initial condition within any given compact set.Furthermore,the second result shows the robustness of the proposed ES control in the presence of sufficiently fast,zero-mean periodic disturbances.Simulation results substantiate these theoretical findings.
基金supported by Joint Fund of the Ministry of Education f or Equipment Pre-research (6141A20223)。
文摘Since the dynamical system and control system of the missile are typically nonlinear, an effective acceleration tracking autopilot is designed using the dynamic surface control(DSC)technique in order to make the missile control system more robust despite the uncertainty of the dynamical parameters and the presence of disturbances. Firstly, the nonlinear mathematical model of the tail-controlled missile is decomposed into slow acceleration dynamics and fast pitch rate dynamics based on the naturally existing time scale separation. Secondly, the controller based on DSC is designed after obtaining the linear dynamics characteristics of the slow and fast subsystems. An extended state observer is used to detect the uncertainty of the system state variables and aerodynamic parameters to achieve the compensation of the control law. The closed-loop stability of the controller is derived and rigorously analyzed. Finally, the effectiveness and robustness of the design is verified by Monte Carlo simulation considering different initial conditions and parameter uptake. Simulation results illustrate that the missile autopilot based DSC controller achieves better performance and robustness than the other two well-known autopilots.The method proposed in this paper is applied to the design of a missile autopilot, and the results show that the acceleration tracking autopilot based on the DSC controller can ensure accurate tracking of the required commands and has better performance.
基金supported by the National Natural Science Foundation of China (Grants 11302238, 11232011, 11572331, and 11490551)the support from the Strategic Priority Research Program (Grant XDB22040104)+1 种基金the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (Grant QYZDJ-SSW-SYS002)the National Basic Research Program of China (973 Program 2013CB834100 : Nonlinear Science)
文摘The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbulence. The spectra are calculated from direct numerical simulation （DNS） of turbulent channel flows and zero-pressure-gradient boundary layer flows. These two peaks locate in the nearwall and outer regions and are referred to as the inner peak and the outer peak, respectively. This result implies that the streamwise velocity fluctuations can be separated into large and small scales in the spanwise direction even though the friction Reynolds number Rer can be as low as 1000. The properties of the inner and outer peaks in the spanwise spec- tra are analyzed. The locations of the inner peak are invariant over a range of Reynolds numbers. However, the locations of the outer peak are associated with the Reynolds number, which are much higher than those of the outer peak of the pre-multiplied streamwise energy spectra of the streamwise velocity.
基金supported by Puning Kangmei Pharmaceutical Co.,Ltd.in part by Comprehensive Center for Drug Discovery and Development of Peking University
文摘The objective of the present study is to develop a method for large-scale separating and purifying salidroside from rhodiola kirilowii roots and for preparing injectable medicinal ingredient.Crude extract of salidroside was prepared by water-ethanol system,and purified by column chromatography of macroporous resins.Static adsorption and desorption studies were performed on six kinds of macroporous resins,and SP825 resin was chosen,followed by optimizing process parameters.The optimum sample volume,feed concentration,ratio of diameter to height,and feeding flow rate were 1.5 bed volumes(BV),15 mg/mL,1:10 and 1 BV/h,respectively.Dynamic desorption was performed consecutively with 8 BV of distilled water,3 BV of 5% ethanol and 8 BV of 10% ethanol at a flow rate of 2 BV/h.After three cycles in separating 3.5 tons of rhodiola kirilowii roots,salidroside purity was increased from 3.4% in the crude extract to 93.6% in purified salidroside product.This study provides a novel method to separate salidroside for injectable use.
