To obtain a longer natural period in single degree of freedom(SDF) conservative vibration isolation systems, many scholars have proposed different methods. This paper uncovers a clockwise energy cycle existing in a ma...To obtain a longer natural period in single degree of freedom(SDF) conservative vibration isolation systems, many scholars have proposed different methods. This paper uncovers a clockwise energy cycle existing in a mass-spring system, in which the potential energy and kinetic energy convert with each other, and the natural period is determined by the magnitude of the energy cycle. Compared to water flow inside a pipe, the previous methods can be consolidated into two methods to make the energy cycle narrower;one is to optimize the parameters directly, the other is to indirectly add an anticlockwise energy cycle to the original one. The anticlockwise energy cycle has the characteristic of gravitational potential energy or elastic potential energy that reduces with displacement. The highly abstract method can provide a better optimization tool to design a practice system.展开更多
This paper is devoted to develop an expert system to manage the fault isolation and maintenance knowledge of the engine indication and crew alerting system (EICAS). The object oriented programming (OOP) technique and...This paper is devoted to develop an expert system to manage the fault isolation and maintenance knowledge of the engine indication and crew alerting system (EICAS). The object oriented programming (OOP) technique and the microsoft foundation class (MFC) are applied to set up a frame decision tree (FDT) which incorporates the expert system′s knowledge base, inference engine and user interface. Once a fault symptom indicated by the EICAS is input, by inferring step by step, the expert system can locate it in the engine and provide some homologous constructive maintenance advice.展开更多
Motivated by the need for improving the isolation performance, many research studies have been performed on isolators with nonlinear characteristics. Based on the shape of their phase portrait, such devices can be con...Motivated by the need for improving the isolation performance, many research studies have been performed on isolators with nonlinear characteristics. Based on the shape of their phase portrait, such devices can be configured as either a mono-or bi-stable isolator. This paper focuses on investigating the relative performance of these two classes under the same excitations. Force transmissibility is used to measure the isolation performance, which is defined in terms of the RMS of the ratio of the transmitted force to the excitation force. When the system is subjected to harmonic excitation, it is found that the maximum reduction of the force transmissibility in the isolation range using Quasi-Zero stiffness is achieved. When the system is subjected to random excitation, it has the same effect of Quasi-Zero stiffness. Further, optimum damping can be changed with stiffness and has minimum value.展开更多
This paper addresses the gas path component and sensor fault diagnosis and isolation(FDI) for the auxiliary power unit(APU). A nonlinear dynamic model and a distributed state estimator are combined for the distributed...This paper addresses the gas path component and sensor fault diagnosis and isolation(FDI) for the auxiliary power unit(APU). A nonlinear dynamic model and a distributed state estimator are combined for the distributed control system. The distributed extended Kalman filter(DEKF)is served as a state estimator,which is utilized to estimate the gas path components’ flow capacity. The DEKF includes one main filter and five sub-filter groups related to five sensors of APU and each sub-filter yields local state flow capacity. The main filter collects and fuses the local state information,and then the state estimations are feedback to the sub-filters. The packet loss model is introduced in the DEKF algorithm in the APU distributed control architecture. FDI strategy with a performance index named weight sum of squared residuals(WSSR) is designed and used to identify the APU sensor fault by removing one sub-filter each time. The very sensor fault occurs as its performance index WSSR is different from the remaining sub-filter combinations. And the estimated value of the soft redundancy replaces the fault sensor measurement to isolate the fault measurement. It is worth noting that the proposed approach serves for not only the sensor failure but also the hybrid fault issue of APU gas path components and sensors. The simulation and comparison are systematically carried out by using the APU test data,and the superiority of the proposed methodology is verified.展开更多
As a flexible auxiliary heating method,the electron cyclotron resonance heating（ECRH） has been widely used in many tokamaks and also will be applied for the J-TEXT tokamak.To meet requirements of protection and faul...As a flexible auxiliary heating method,the electron cyclotron resonance heating（ECRH） has been widely used in many tokamaks and also will be applied for the J-TEXT tokamak.To meet requirements of protection and fault analysis for the ECRH system on J-TEXT,signals of gyrotrons such as the cathode voltage and current,the anode voltage and current,etc should be transmitted to the control and data acquisition system.Considering the high voltage environment of gyrotrons,isolation transmission module based on FPGA and optical fiber communication has been designed and tested.The test results indicate that the designed module has strong anti-noise ability,low error rate and high transmission speed.The delay of the module is no more than 5 μs which can fulfill the requirements.展开更多
Due to technical limitations,existing vibration isolation and energy harvesting(VIEH)devices have poor performance at low frequency.This paper proposes a new multilink-spring mechanism(MLSM)that can be used to solve t...Due to technical limitations,existing vibration isolation and energy harvesting(VIEH)devices have poor performance at low frequency.This paper proposes a new multilink-spring mechanism(MLSM)that can be used to solve this problem.The VIEH performance of the MLSM under harmonic excitation and Gaussian white noise was analyzed.It was found that the MLSM has good vibration isolation performance for low-frequency isolation and the frequency band can be widened by adjusting parameters to achieve a higher energy harvesting power.By comparison with two special cases,the results show that the MLSM is basically the same as the other two oscillators in terms of vibration isolation but has better energy harvesting performance under multistable characteristics.The MLSM is expected to reduce the impact of vibration on high-precision sensitive equipment in some special sites such as subways and mines,and at the same time supply power to structural health monitoring devices.展开更多
A modified guanidinium isothiocyanate method was used to extract total RNA from two forest insect species Clostera anastomosis and Saperda populnea. The integrity of RNA was demonstrated by the methods of gel electrop...A modified guanidinium isothiocyanate method was used to extract total RNA from two forest insect species Clostera anastomosis and Saperda populnea. The integrity of RNA was demonstrated by the methods of gel electrophoresis and cDNA analysis. Typical A260/ A280 absorbance ratio of the total RNA was in range of 1.8 to 2.0. The size of double strand cDNAs obtained by RT-PCR was more than 2 kb, which indicated that intact mRNA was obtained. The fragments of β-actin and chitinase gene from the RNA of C. anastomosis were obtained by RT-PCR, which indicated that the RNA could be used for other molecular operation. By this procedure, RNAs could be extracted and analyzed by electrophoresis from at least 8 samples within 4 hours. These results showed that this method was time- and cost-saving and effective.展开更多
A novel friction pendulum system （FPS） with dual rollers is studied based on the multibody dynamics theory. By analyzing kinematic characteristics of the system, it is reduced to a one degree-of-freedom system. Then...A novel friction pendulum system （FPS） with dual rollers is studied based on the multibody dynamics theory. By analyzing kinematic characteristics of the system, it is reduced to a one degree-of-freedom system. Then the equation of motion for the system is analytically derived by applying the theorem of the relative kinetic energy for a system of particles in differential form in the non-inertial reference system described as a nonlinear differential equation. In the case of the small angular displacement, the natural frequency of the corresponding undamped linear system is obtained, which is consistent with the experimental observation. The derived equation is useful for the study of dynamic characteristics of novel FPS, and its solution directly expedites the simulation of the system in a control loop, and further facilitates the semi-active control process including novel FPS.展开更多
The relation of mass, stiffness and rate of damping is obtained by using the mechanical analysis of the obstructive vibration system of two dimensions for the design of the obstructive vibration system of more freedom...The relation of mass, stiffness and rate of damping is obtained by using the mechanical analysis of the obstructive vibration system of two dimensions for the design of the obstructive vibration system of more freedom and the micro vibration test bed. The result of stimulational experiment indicates that the isolation of vibration of this system is satisfactory. The design method of vibration can be used as the reference to ultra precision machine tool, super micro orientation machanism and so on.展开更多
A direct synthesis of methyl levulinate from cellulose alcoholysis in methanol medium under mild condition(180 210 C)catalyzed by extremely low concentration sulfuric acid(0.01 mol/L)and the product isolation were dev...A direct synthesis of methyl levulinate from cellulose alcoholysis in methanol medium under mild condition(180 210 C)catalyzed by extremely low concentration sulfuric acid(0.01 mol/L)and the product isolation were developed in this study.Effects of different process variables towards the catalytic performance were performed as a function of reaction time.The results indicated that sulfuric acid concentration,temperature and initial cellulose concentration had significant effects on the synthesis of methyl levulinate.An optimized yield of around 50%was achieved at 210 C for 120 min with sulfuric acid concentration of 0.01 mol/L and initial cellulose concentration below 100 g/L.The resulting product mixture was isolated by a distillation technique that combines an atmospheric distillation with a vacuum distillation where n-dodecane was added to help distill the heavy fraction.The light fraction including mainly methanol could be reused as the reaction medium without any substantial change in the yield of methyl levulinate.The chemical composition and structural of lower heavy fraction were characterized by GC/MS,FTIR,1H-NMR and13C-NMR techniques.Methyl levulinate was found to be a major ingredient of lower heavy fraction with the content over 96%.This pathway is efficient,environmentally benign and economical for the production of pure levulinate esters from cellulose.展开更多
Supervisory control and protection system of the neutral beam injector （NBI） in the HL-2A tokamak is presented. The system is used for a safe coordination of all the main NBI subsystems. Because the system is based ...Supervisory control and protection system of the neutral beam injector （NBI） in the HL-2A tokamak is presented. The system is used for a safe coordination of all the main NBI subsystems. Because the system is based on computer networks with its transmission medium of optical fiber, its advantages in high operational stability, reliability, security and flexible functional expandability are clearly shown during the NBI commissioning and heating experiment in HL-2A.展开更多
A remote-control tether-less isolation tool is a mechanical device that is normally used in pipelines to block the flow at a given position by transforming a blocking module. In this study, the interactions between th...A remote-control tether-less isolation tool is a mechanical device that is normally used in pipelines to block the flow at a given position by transforming a blocking module. In this study, the interactions between the fluid and the plug module of the isolation tool were investigated. Simulations of the plug process and particle image velocimetry measurements were performed to study the flow characteristics. Numerical solutions for the continuity, momentum, and energy equations were obtained by using commercial software based on finite-volume techniques. Box–Behnken design was applied, and response surface methodology（RSM）-based CFD simulation analysis was conducted. The dynamic model in the plug process was built by RSM and used to evaluate the influences of the main mechanical parameters on the pressure during the plug process. The diameter of the isolation tool and the diameter of the plug module have strong influences on the process, and the length of the isolation tool has only a little influence on the plug process.展开更多
Collimating lenses are an important component of laser ranging systems,and high overload environments severely affect the beam shaping effect of such lenses.This study proposes a buffer isolation method on the basis o...Collimating lenses are an important component of laser ranging systems,and high overload environments severely affect the beam shaping effect of such lenses.This study proposes a buffer isolation method on the basis of impact stress wave attenuation theory for collimating lens spacers,ANSYS finite element software was applied to simulate the high load dynamics of collimating lenses,and the buffer isolation performance of different materials and composite structures was compared and analysed.Optical simulation analysis of the collimating lenses under different buffer conditions was performed using ZEMAX software to study the mechanism by which a high overload affects the collimating lenses.High overload and optical shaping experiments based on theoretical analysis were further conducted.Results showed the superiority of butadiene rubber to polytetrafluoroethylene after application of 70000 g impact acceleration.The combination-gasket method was superior to the single-gasket method,and the sandwich combination-gasket method was superior to the double-layer combination-gasket method.展开更多
We used callus of Populus euphratica Olive to isolate protoplasts, and IT fluxes across plasma membrane were investigated. The concentration of enzymes for protoplast isolation, e.g. cellulase, pectolyase, macerozyme,...We used callus of Populus euphratica Olive to isolate protoplasts, and IT fluxes across plasma membrane were investigated. The concentration of enzymes for protoplast isolation, e.g. cellulase, pectolyase, macerozyme, hemicellulase, and sorbitol content, incubation time were systemically studied. High yield and viability of protoplast was achieved after 6-8 hours incubation of P. euphratica callus in enzyme solution containing 1.5% （w：v） cellulase R-10, 0.1% （w：v） pectolyase Y-23, 0.2% （w：v） macerozyme R-10, 0.05% （w：v） hemicellulase and 0.75M）.80 mol·L^-1 sorbitol. Non-invasively ion selective microelectrode technique was used to access proton fluxes in the absence and presence of NaCl （20 mmol.L-1）. Salt-induced transient net IT effiux was observed in the plasma membrane ofP. euphratica cells. The shift of IT flux response to NaC1 shock and the relevance to salt tolerance were discussed.展开更多
Total RNA was isolated from shoots regenerated in vitro of Populus suaveolens by the modified method of CTAB, and two clear bands of rRNA (28S and 18S) were observed in agarose electrophoresis. In addition, the values...Total RNA was isolated from shoots regenerated in vitro of Populus suaveolens by the modified method of CTAB, and two clear bands of rRNA (28S and 18S) were observed in agarose electrophoresis. In addition, the values of OD260/OD280 and OD260/OD230 of extracted RNA were 2.12 and 2.23 respectively. The results show that RNA is little decomposed and the purity of RNA is high. Moreover, RNA isolated by the modified method of CTAB reagent had been successfully used for reverse transcription of P. suaveolens cDNAs and ideal special band was observed.展开更多
Adopting a soft site model built on soft interlayer soil foundation,a shaking table test for soft interlayer soil-isolated structure interaction is conducted to investigate the seismic response of isolated structure o...Adopting a soft site model built on soft interlayer soil foundation,a shaking table test for soft interlayer soil-isolated structure interaction is conducted to investigate the seismic response of isolated structure on soft site,and analyze its isolation effect.Test results show that the test can reflect the earthquake response characteristics of isolated structure on soft site.It is on soft site that the dynamic characteristics of isolated structure,acceleration magnification factor(AMF)of isolated structure and isolation efficiency of the isolation layer differ from those on rigid foundation with an soil-structure interaction(SSI)effect,represented by the reduction in fundamental vibration frequency of isolated structure and the increase of damping ratio with changes of the SSI effect.SSI can either increase or decrease AMF of isolated structure on soft site,depending on the characteristics of earthquake motion input.Furthermore,the isolation efficiency of isolation layer on soft site is decreased with the SSI effect,which is related to the peak ground acceleration(PGA)and the characteristics of earthquake motion input.展开更多
Background Atrial fibrillation(AF)is a generally acknowledged turning-point of the natural history of hypertrophic cardiomyopathy(HCM);however,data from the cryoballoon ablation(CBA)for AF in HCM patients are relative...Background Atrial fibrillation(AF)is a generally acknowledged turning-point of the natural history of hypertrophic cardiomyopathy(HCM);however,data from the cryoballoon ablation(CBA)for AF in HCM patients are relatively scarce.The study aimed to evaluate the efficacy and safety of CBA in HCM patients with AF.Methods We retrospectively analyzed HCM patients among 1253 patients with symptomatic AF who underwent CBA for pulmonary vein isolation in a single center.The study analyzed the AF recurrence and assessed the CBA indexes,including nadir temperature,time-to-isolation,CBA failure,pulmonary vein potentials(PVPs),and redo procedure.Results A total of 108 patients were included(mean age:59.0±6.9 years),27 patients(25%)had HCM,with the median follow-up duration of 25.5 months.The one-year AF-free rates were 79.0%vs.63.0%(non-HCM vs.HCM),while the two-year AF-free rates were 77.8%vs.55.1%[hazard ratio(HR)=2.758,log-rank P=0.024].Patients with persistent AF had poor AF-free rates compared to those with paroxysmal AF(P<0.001).The CBA failure was the most common in the right inferior pulmonary veins,which had the lowest PVPs.Multivariate Cox regression analysis indicated that HCM and persistent AF were risk factors for AF recurrence(HR=2.74,95%CI:1.29–5.79,P=0.008;and HR=3.97,95%CI:1.85–8.54,P<0.001,respectively).Conclusions The CBA can be effectively and safely used to treat HCM patients with symptomatic AF.The freedom from AF for HCM patients after CBA is relatively low compared to that for non-HCM patients.展开更多
During the pipeline plugging process,both the pipeline and the pipe isolation tool(PIT)will be greatly damaged,due to the violent vibration of the flow field.In this study,it was proposed for the first time to reduce ...During the pipeline plugging process,both the pipeline and the pipe isolation tool(PIT)will be greatly damaged,due to the violent vibration of the flow field.In this study,it was proposed for the first time to reduce the vibration of the flow field during the plugging process by optimizing the surface structure of the PIT.Firstly,the central composite design(CCD)was used to obtain the optimization schemes,and the drag coefficient and pressure coefficient were proposed to evaluate the degree of flow field changes.Secondly,a series of computational fluid dynamics(CFD)simulations were performed to obtain the drag coefficient and pressure coefficient during dynamic plugging.And the mathematical model of drag coefficient and pressure coefficient with the surface structure of the PIT were established respectively.Then,a modified particle swarm optimization(PSO)was applied to predict the optimal value of the surface structure of the PIT.Finally,an experimental rig was built to verify the effectiveness of the optimization.The results showed that the improved method could reduce the flow field vibration by 49.56%.This study provides a reference for the design of the PIT surface structure for flow field vibration technology.展开更多
Isolation technique of ground structure is a hot topic in the field of earthquake engineering and structure dynamics.Since soil-isolated structure dynamic interaction study is of great significance to enhance seismic ...Isolation technique of ground structure is a hot topic in the field of earthquake engineering and structure dynamics.Since soil-isolated structure dynamic interaction study is of great significance to enhance seismic performance of isolated structures and revision of relevant isolation specifications,research on dynamic interaction of soil-isolated structure has attracted more and more attention.Based on the basic theory of soil-structure dynamic interaction,we summarize and analyze the research status quo of soil-isolated structure dynamic interaction by means of theoretical analysis,numerical simulation,model test,prototype observation and seismic performance.After reviewing the results of previous research,we reveal that some key issues,which can be used to uncover dynamic interaction mechanism and seismic response characteristics of soil-isolated structures interaction system,should not be neglected.Based on the concept of seismic performance design and the latest research of soil-isolated structure dynamic interaction,we predict the future development of soil-isolated structure dynamic interaction by elastoplastic time history analysis method,seismic performance level and practical analysis method based on energy.展开更多
基金Supported by the National Science and Technology Major Project of China(2015ZX02104003)the Natural Science Foundation of Hubei Province of China(2018CFC889)
文摘To obtain a longer natural period in single degree of freedom(SDF) conservative vibration isolation systems, many scholars have proposed different methods. This paper uncovers a clockwise energy cycle existing in a mass-spring system, in which the potential energy and kinetic energy convert with each other, and the natural period is determined by the magnitude of the energy cycle. Compared to water flow inside a pipe, the previous methods can be consolidated into two methods to make the energy cycle narrower;one is to optimize the parameters directly, the other is to indirectly add an anticlockwise energy cycle to the original one. The anticlockwise energy cycle has the characteristic of gravitational potential energy or elastic potential energy that reduces with displacement. The highly abstract method can provide a better optimization tool to design a practice system.
文摘This paper is devoted to develop an expert system to manage the fault isolation and maintenance knowledge of the engine indication and crew alerting system (EICAS). The object oriented programming (OOP) technique and the microsoft foundation class (MFC) are applied to set up a frame decision tree (FDT) which incorporates the expert system′s knowledge base, inference engine and user interface. Once a fault symptom indicated by the EICAS is input, by inferring step by step, the expert system can locate it in the engine and provide some homologous constructive maintenance advice.
基金Foundation item： Supported by the National Natural Science Foundation of China （No. 51375103）.
文摘Motivated by the need for improving the isolation performance, many research studies have been performed on isolators with nonlinear characteristics. Based on the shape of their phase portrait, such devices can be configured as either a mono-or bi-stable isolator. This paper focuses on investigating the relative performance of these two classes under the same excitations. Force transmissibility is used to measure the isolation performance, which is defined in terms of the RMS of the ratio of the transmitted force to the excitation force. When the system is subjected to harmonic excitation, it is found that the maximum reduction of the force transmissibility in the isolation range using Quasi-Zero stiffness is achieved. When the system is subjected to random excitation, it has the same effect of Quasi-Zero stiffness. Further, optimum damping can be changed with stiffness and has minimum value.
基金supported by the National Natural Science Foundation of China(No.91960110)the National Science and Technology Major Project(No. 2017-I0006-0007)the Fundamental Research Funds for the Central Universities(NP2022418)。
文摘This paper addresses the gas path component and sensor fault diagnosis and isolation(FDI) for the auxiliary power unit(APU). A nonlinear dynamic model and a distributed state estimator are combined for the distributed control system. The distributed extended Kalman filter(DEKF)is served as a state estimator,which is utilized to estimate the gas path components’ flow capacity. The DEKF includes one main filter and five sub-filter groups related to five sensors of APU and each sub-filter yields local state flow capacity. The main filter collects and fuses the local state information,and then the state estimations are feedback to the sub-filters. The packet loss model is introduced in the DEKF algorithm in the APU distributed control architecture. FDI strategy with a performance index named weight sum of squared residuals(WSSR) is designed and used to identify the APU sensor fault by removing one sub-filter each time. The very sensor fault occurs as its performance index WSSR is different from the remaining sub-filter combinations. And the estimated value of the soft redundancy replaces the fault sensor measurement to isolate the fault measurement. It is worth noting that the proposed approach serves for not only the sensor failure but also the hybrid fault issue of APU gas path components and sensors. The simulation and comparison are systematically carried out by using the APU test data,and the superiority of the proposed methodology is verified.
基金supported by the ITER Special Fund of China(Grant Nos.2013GB106001 and 2013GB106003)
文摘As a flexible auxiliary heating method,the electron cyclotron resonance heating（ECRH） has been widely used in many tokamaks and also will be applied for the J-TEXT tokamak.To meet requirements of protection and fault analysis for the ECRH system on J-TEXT,signals of gyrotrons such as the cathode voltage and current,the anode voltage and current,etc should be transmitted to the control and data acquisition system.Considering the high voltage environment of gyrotrons,isolation transmission module based on FPGA and optical fiber communication has been designed and tested.The test results indicate that the designed module has strong anti-noise ability,low error rate and high transmission speed.The delay of the module is no more than 5 μs which can fulfill the requirements.
基金Project supported by Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2022A1515010967 and 2023A1515012821)the National Natural Science Foundation of China(Grant Nos.12002272 and 12272293)Opening Project of Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province(Grant No.SZDKF-202101)。
文摘Due to technical limitations,existing vibration isolation and energy harvesting(VIEH)devices have poor performance at low frequency.This paper proposes a new multilink-spring mechanism(MLSM)that can be used to solve this problem.The VIEH performance of the MLSM under harmonic excitation and Gaussian white noise was analyzed.It was found that the MLSM has good vibration isolation performance for low-frequency isolation and the frequency band can be widened by adjusting parameters to achieve a higher energy harvesting power.By comparison with two special cases,the results show that the MLSM is basically the same as the other two oscillators in terms of vibration isolation but has better energy harvesting performance under multistable characteristics.The MLSM is expected to reduce the impact of vibration on high-precision sensitive equipment in some special sites such as subways and mines,and at the same time supply power to structural health monitoring devices.
基金This study was supported by Key Project of Harbin City (2005AA6CN074)
文摘A modified guanidinium isothiocyanate method was used to extract total RNA from two forest insect species Clostera anastomosis and Saperda populnea. The integrity of RNA was demonstrated by the methods of gel electrophoresis and cDNA analysis. Typical A260/ A280 absorbance ratio of the total RNA was in range of 1.8 to 2.0. The size of double strand cDNAs obtained by RT-PCR was more than 2 kb, which indicated that intact mRNA was obtained. The fragments of β-actin and chitinase gene from the RNA of C. anastomosis were obtained by RT-PCR, which indicated that the RNA could be used for other molecular operation. By this procedure, RNAs could be extracted and analyzed by electrophoresis from at least 8 samples within 4 hours. These results showed that this method was time- and cost-saving and effective.
文摘A novel friction pendulum system （FPS） with dual rollers is studied based on the multibody dynamics theory. By analyzing kinematic characteristics of the system, it is reduced to a one degree-of-freedom system. Then the equation of motion for the system is analytically derived by applying the theorem of the relative kinetic energy for a system of particles in differential form in the non-inertial reference system described as a nonlinear differential equation. In the case of the small angular displacement, the natural frequency of the corresponding undamped linear system is obtained, which is consistent with the experimental observation. The derived equation is useful for the study of dynamic characteristics of novel FPS, and its solution directly expedites the simulation of the system in a control loop, and further facilitates the semi-active control process including novel FPS.
文摘The relation of mass, stiffness and rate of damping is obtained by using the mechanical analysis of the obstructive vibration system of two dimensions for the design of the obstructive vibration system of more freedom and the micro vibration test bed. The result of stimulational experiment indicates that the isolation of vibration of this system is satisfactory. The design method of vibration can be used as the reference to ultra precision machine tool, super micro orientation machanism and so on.
基金supported by the National Key Basic Research Program (2010CB732201) from the Ministry of Science and Technology of Chinathe State Key Laboratory Open Foundation of Pulp and Paper Engineering of China (201225)
文摘A direct synthesis of methyl levulinate from cellulose alcoholysis in methanol medium under mild condition(180 210 C)catalyzed by extremely low concentration sulfuric acid(0.01 mol/L)and the product isolation were developed in this study.Effects of different process variables towards the catalytic performance were performed as a function of reaction time.The results indicated that sulfuric acid concentration,temperature and initial cellulose concentration had significant effects on the synthesis of methyl levulinate.An optimized yield of around 50%was achieved at 210 C for 120 min with sulfuric acid concentration of 0.01 mol/L and initial cellulose concentration below 100 g/L.The resulting product mixture was isolated by a distillation technique that combines an atmospheric distillation with a vacuum distillation where n-dodecane was added to help distill the heavy fraction.The light fraction including mainly methanol could be reused as the reaction medium without any substantial change in the yield of methyl levulinate.The chemical composition and structural of lower heavy fraction were characterized by GC/MS,FTIR,1H-NMR and13C-NMR techniques.Methyl levulinate was found to be a major ingredient of lower heavy fraction with the content over 96%.This pathway is efficient,environmentally benign and economical for the production of pure levulinate esters from cellulose.
文摘Supervisory control and protection system of the neutral beam injector （NBI） in the HL-2A tokamak is presented. The system is used for a safe coordination of all the main NBI subsystems. Because the system is based on computer networks with its transmission medium of optical fiber, its advantages in high operational stability, reliability, security and flexible functional expandability are clearly shown during the NBI commissioning and heating experiment in HL-2A.
基金supported by the National Natural Science Foundation of China (Grant No. 51575528)the Scientific Research Foundation of the Education Ministry for Returned Chinese Scholars (China)+1 种基金the State Key Laboratory for Coal Resources and Safe Mining, China University of Mining and Technology (No. SKLCRSM10KFB04)the Science Foundation of China University of Petroleum, Beijing (No. YXQN-2014-02)
文摘A remote-control tether-less isolation tool is a mechanical device that is normally used in pipelines to block the flow at a given position by transforming a blocking module. In this study, the interactions between the fluid and the plug module of the isolation tool were investigated. Simulations of the plug process and particle image velocimetry measurements were performed to study the flow characteristics. Numerical solutions for the continuity, momentum, and energy equations were obtained by using commercial software based on finite-volume techniques. Box–Behnken design was applied, and response surface methodology（RSM）-based CFD simulation analysis was conducted. The dynamic model in the plug process was built by RSM and used to evaluate the influences of the main mechanical parameters on the pressure during the plug process. The diameter of the isolation tool and the diameter of the plug module have strong influences on the process, and the length of the isolation tool has only a little influence on the plug process.
基金National Natural Science Foundation of China(51605227)the Fundamental Research Funds for the Central Universities(NUST30915011303)。
文摘Collimating lenses are an important component of laser ranging systems,and high overload environments severely affect the beam shaping effect of such lenses.This study proposes a buffer isolation method on the basis of impact stress wave attenuation theory for collimating lens spacers,ANSYS finite element software was applied to simulate the high load dynamics of collimating lenses,and the buffer isolation performance of different materials and composite structures was compared and analysed.Optical simulation analysis of the collimating lenses under different buffer conditions was performed using ZEMAX software to study the mechanism by which a high overload affects the collimating lenses.High overload and optical shaping experiments based on theoretical analysis were further conducted.Results showed the superiority of butadiene rubber to polytetrafluoroethylene after application of 70000 g impact acceleration.The combination-gasket method was superior to the single-gasket method,and the sandwich combination-gasket method was superior to the double-layer combination-gasket method.
基金the key project of National Natural Science Foundation of China （30430430） the HI-TECH Research and Development Program of China （863 Program, 2006AA10Z131）+1 种基金 a Foundation for the Author of National Excellent Doctoral Dissertation of PR China （200152） the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institution of MOE, PRC （2002-323）.
文摘We used callus of Populus euphratica Olive to isolate protoplasts, and IT fluxes across plasma membrane were investigated. The concentration of enzymes for protoplast isolation, e.g. cellulase, pectolyase, macerozyme, hemicellulase, and sorbitol content, incubation time were systemically studied. High yield and viability of protoplast was achieved after 6-8 hours incubation of P. euphratica callus in enzyme solution containing 1.5% （w：v） cellulase R-10, 0.1% （w：v） pectolyase Y-23, 0.2% （w：v） macerozyme R-10, 0.05% （w：v） hemicellulase and 0.75M）.80 mol·L^-1 sorbitol. Non-invasively ion selective microelectrode technique was used to access proton fluxes in the absence and presence of NaCl （20 mmol.L-1）. Salt-induced transient net IT effiux was observed in the plasma membrane ofP. euphratica cells. The shift of IT flux response to NaC1 shock and the relevance to salt tolerance were discussed.
基金Supported by the National Natural Science Foundation of China (Grant No. 30271093)
文摘Total RNA was isolated from shoots regenerated in vitro of Populus suaveolens by the modified method of CTAB, and two clear bands of rRNA (28S and 18S) were observed in agarose electrophoresis. In addition, the values of OD260/OD280 and OD260/OD230 of extracted RNA were 2.12 and 2.23 respectively. The results show that RNA is little decomposed and the purity of RNA is high. Moreover, RNA isolated by the modified method of CTAB reagent had been successfully used for reverse transcription of P. suaveolens cDNAs and ideal special band was observed.
基金supported by the Jiangsu Natural Science Foundation of China(Grant No.BK2012477)the Science Research Foundation of Nanjing Institute of Technology(CKJA201505,JCYJ201618)
文摘Adopting a soft site model built on soft interlayer soil foundation,a shaking table test for soft interlayer soil-isolated structure interaction is conducted to investigate the seismic response of isolated structure on soft site,and analyze its isolation effect.Test results show that the test can reflect the earthquake response characteristics of isolated structure on soft site.It is on soft site that the dynamic characteristics of isolated structure,acceleration magnification factor(AMF)of isolated structure and isolation efficiency of the isolation layer differ from those on rigid foundation with an soil-structure interaction(SSI)effect,represented by the reduction in fundamental vibration frequency of isolated structure and the increase of damping ratio with changes of the SSI effect.SSI can either increase or decrease AMF of isolated structure on soft site,depending on the characteristics of earthquake motion input.Furthermore,the isolation efficiency of isolation layer on soft site is decreased with the SSI effect,which is related to the peak ground acceleration(PGA)and the characteristics of earthquake motion input.
基金supported by the National Natural Science Foundation of China(No.81670309)。
文摘Background Atrial fibrillation(AF)is a generally acknowledged turning-point of the natural history of hypertrophic cardiomyopathy(HCM);however,data from the cryoballoon ablation(CBA)for AF in HCM patients are relatively scarce.The study aimed to evaluate the efficacy and safety of CBA in HCM patients with AF.Methods We retrospectively analyzed HCM patients among 1253 patients with symptomatic AF who underwent CBA for pulmonary vein isolation in a single center.The study analyzed the AF recurrence and assessed the CBA indexes,including nadir temperature,time-to-isolation,CBA failure,pulmonary vein potentials(PVPs),and redo procedure.Results A total of 108 patients were included(mean age:59.0±6.9 years),27 patients(25%)had HCM,with the median follow-up duration of 25.5 months.The one-year AF-free rates were 79.0%vs.63.0%(non-HCM vs.HCM),while the two-year AF-free rates were 77.8%vs.55.1%[hazard ratio(HR)=2.758,log-rank P=0.024].Patients with persistent AF had poor AF-free rates compared to those with paroxysmal AF(P<0.001).The CBA failure was the most common in the right inferior pulmonary veins,which had the lowest PVPs.Multivariate Cox regression analysis indicated that HCM and persistent AF were risk factors for AF recurrence(HR=2.74,95%CI:1.29–5.79,P=0.008;and HR=3.97,95%CI:1.85–8.54,P<0.001,respectively).Conclusions The CBA can be effectively and safely used to treat HCM patients with symptomatic AF.The freedom from AF for HCM patients after CBA is relatively low compared to that for non-HCM patients.
基金financially supported by the National Natural Science Foundation of China(Grant No.51575528)。
文摘During the pipeline plugging process,both the pipeline and the pipe isolation tool(PIT)will be greatly damaged,due to the violent vibration of the flow field.In this study,it was proposed for the first time to reduce the vibration of the flow field during the plugging process by optimizing the surface structure of the PIT.Firstly,the central composite design(CCD)was used to obtain the optimization schemes,and the drag coefficient and pressure coefficient were proposed to evaluate the degree of flow field changes.Secondly,a series of computational fluid dynamics(CFD)simulations were performed to obtain the drag coefficient and pressure coefficient during dynamic plugging.And the mathematical model of drag coefficient and pressure coefficient with the surface structure of the PIT were established respectively.Then,a modified particle swarm optimization(PSO)was applied to predict the optimal value of the surface structure of the PIT.Finally,an experimental rig was built to verify the effectiveness of the optimization.The results showed that the improved method could reduce the flow field vibration by 49.56%.This study provides a reference for the design of the PIT surface structure for flow field vibration technology.
基金This work was supported by the National Natural Science Foundation of China(No.51778282).
文摘Isolation technique of ground structure is a hot topic in the field of earthquake engineering and structure dynamics.Since soil-isolated structure dynamic interaction study is of great significance to enhance seismic performance of isolated structures and revision of relevant isolation specifications,research on dynamic interaction of soil-isolated structure has attracted more and more attention.Based on the basic theory of soil-structure dynamic interaction,we summarize and analyze the research status quo of soil-isolated structure dynamic interaction by means of theoretical analysis,numerical simulation,model test,prototype observation and seismic performance.After reviewing the results of previous research,we reveal that some key issues,which can be used to uncover dynamic interaction mechanism and seismic response characteristics of soil-isolated structures interaction system,should not be neglected.Based on the concept of seismic performance design and the latest research of soil-isolated structure dynamic interaction,we predict the future development of soil-isolated structure dynamic interaction by elastoplastic time history analysis method,seismic performance level and practical analysis method based on energy.
