A deeper understanding of the biological events occurring when bioprocess parameters changed will be of great value in improving the monoclonal antibodies (mAbs) production. Design of experiment (DoE) was applied to i...A deeper understanding of the biological events occurring when bioprocess parameters changed will be of great value in improving the monoclonal antibodies (mAbs) production. Design of experiment (DoE) was applied to investigate the effect of process parameters (pH, temperature shift and dissolve oxygen (DO)) on protein titer. The key metabolites connecting the critical process parameters (CPPs) with monoclonal antibody production were identified by different chemometrics tools. Finally, the biological events of marker metabolites relating with titer improvement were concluded. pH and temperature shift were identified as CPPs that affect the target protein titer. A series of metabolites influenced by the altered CPPs and correlated with protein titer were screened by principal component analysis (PCA) and Pearson' correlation test. The marker metabolites and their pathways linking CPPs to target protein titer in different culture phases were summarized. Metabolomics and chemometrics are promising data-driven tools to shine light into the biological black box between the bioprocess parameters and process performance.展开更多
Recasting the BCS theory in the larger framework of the Bethe-Salpeter equation, a new equation is derived for the temperature-dependent critical current density jc(T) of an elemental superconductor (SC) directly in t...Recasting the BCS theory in the larger framework of the Bethe-Salpeter equation, a new equation is derived for the temperature-dependent critical current density jc(T) of an elemental superconductor (SC) directly in terms of the basic parameters of the theory, namely the dimensionless coupling constant [N(0)V], the Debye temperature θD and, additionally, the Fermi energy EF—unlike earlier such equations based on diverse, indirect criteria. Our approach provides an ab initio theoretical justification for one of the latter, text book equations invoked at T = 0 which involves Fermi momentum;additionally, it relates jc with the relevant parameters of the problem at T ≠ 0. Noting that the numerical value of EF of a high-Tc SC is a necessary input for the construction of its Fermi surface—which sheds light on its gap-structure, we also briefly discuss extension of our approach for such SCs.展开更多
Based on the important role in mine safety played by parameters of the first gas outburst, we propose a method of combining historic data, theoretical analysis and experimental research for the purpose of critical val...Based on the important role in mine safety played by parameters of the first gas outburst, we propose a method of combining historic data, theoretical analysis and experimental research for the purpose of critical values of gas parameters of the first gas outburst in a coal seam of the Xieqiao Mine. According to a characteristic analysis and a summary of the rules of coal and gas outbursts in the No.8 coal seam of a Huainan mine, we have investigated their effect on coal and gas outbursts in terms such as ground stress, gas, and coal structure. We have selected gas parameters and determined the critical values of each of the following indices: gas content as 7.7 m 3 /t, tectonic coal as 0.8 m thick, the absolute gas emission as 2 m 3 /min, the rate of change as 0.7 m 3 /min, the gas desorption index of a drilling chip K 1 as 0.26 mL/(g min 1/2 ) and the values of desorption indexes 4h 2 as 200 Pa. From a verification of the production, the results indicate that application of each index and their critical values significantly improve the level of safety in the production process, relieve the burden upon the mine, save much labor and bring clear economic benefits.展开更多
TraPPE force field combined with grand-canonical transition-matrix Monte Carlo simulation were used to investigate the vapor-liquid coexistence curve and critical properties of methane,ethane,propane,and n-butane in s...TraPPE force field combined with grand-canonical transition-matrix Monte Carlo simulation were used to investigate the vapor-liquid coexistence curve and critical properties of methane,ethane,propane,and n-butane in slit pores ranging from 6?to 40?.Long range correction for intermolecular potential in slit pore model was developed,and the fact indicating that its influence on various thermodynamic properties is not negligible was found.The simulation results show that the thermodynamic properties of nano-confined alkanes shift tremendously from the bulk state.The critical temperature under confinement experiences a roughly linear decrease with an inverse in the slit width,while the critical pressure and the critical density have a relative increment related with carbon number on both the large slit width region and the small slit width region.Further analysis on z-density profiles of alkanes revealed that the complex behaviors of shift in critical parameters are the results of interplay between fluid-fluid and fluid-wall interaction.展开更多
The La5/8Ca3/8Mn0.9750Pd0.025O3 compound was studied using DC magnetization measurements. The data were analyzed in the paramagnetic-ferromagnetic phase transition region by the Arrott plot method. The results show th...The La5/8Ca3/8Mn0.9750Pd0.025O3 compound was studied using DC magnetization measurements. The data were analyzed in the paramagnetic-ferromagnetic phase transition region by the Arrott plot method. The results show the Curie temperature TC ~ 247.8 K and the critical exponents of b = 0.48633, g = 1.18623 and d = 3.431682. The values of the critical exponents are between the mean- field theory and 3D Ising model. The magnetocaloric value is ~5 J/kgK, extracted from the M(H) curves.展开更多
In real systems,the unpredictable jump changes of the random environment can induce the critical transitions(CTs)between two non-adjacent states,which are more catastrophic.Taking an asymmetric Lévy-noise-induced...In real systems,the unpredictable jump changes of the random environment can induce the critical transitions(CTs)between two non-adjacent states,which are more catastrophic.Taking an asymmetric Lévy-noise-induced tri-stable model with desirable,sub-desirable,and undesirable states as a prototype class of real systems,a prediction of the noise-induced CTs from the desirable state directly to the undesirable one is carried out.We first calculate the region that the current state of the given model is absorbed into the undesirable state based on the escape probability,which is named as the absorbed region.Then,a new concept of the parameter dependent basin of the unsafe regime(PDBUR)under the asymmetric Lévy noise is introduced.It is an efficient tool for approximately quantifying the ranges of the parameters,where the noise-induced CTs from the desirable state directly to the undesirable one may occur.More importantly,it may provide theoretical guidance for us to adopt some measures to avert a noise-induced catastrophic CT.展开更多
Some electrical parameters of the SIS-type hysteretic underdamped Josephson junction(JJ)can be measured by its current-voltage characteristics(IVCs).Currents and voltages at JJ are commensurate with the intrinsic nois...Some electrical parameters of the SIS-type hysteretic underdamped Josephson junction(JJ)can be measured by its current-voltage characteristics(IVCs).Currents and voltages at JJ are commensurate with the intrinsic noise level of measuring instruments.This leads to the need for multiple measurements with subsequent statistical processing.In this paper,the digital algorithms are proposed for the automatic measurement of the JJ parameters by IVC.These algorithms make it possible to implement multiple measurements and check these JJ parameters in an automatic mode with the required accuracy.The complete sufficient statistics are used to minimize the root-mean-square error of parameter measurement.A sequence of current pulses with slow rising and falling edges is used to drive JJ,and synchronous current and voltage readings at JJ are used to realize measurement algorithms.The algorithm performance is estimated through computer simulations.The significant advantage of the proposed algorithms is the independence from current source noise and intrinsic noise of current and voltage meters,as well as the simple implementation in automatic digital measuring systems.The proposed algorithms can be used to control JJ parameters during mass production of superconducting integrated circuits,which will improve the production efficiency and product quality.展开更多
Based on the assumption of gas-liquid stratified flow pattern in inclined gas wells,considering the influence of wettability and surface tension on the circumferential distribution of liquid film along the wellbore wa...Based on the assumption of gas-liquid stratified flow pattern in inclined gas wells,considering the influence of wettability and surface tension on the circumferential distribution of liquid film along the wellbore wall,the influence of the change of the gas-liquid interface configuration on the potential energy,kinetic energy and surface free energy of the two-phase system per unit length of the tube is investigated,and a new model for calculating the gas-liquid distribution at critical conditions is developed by using the principle of minimum energy.Considering the influence of the inclination angle,the calculation model of interfacial friction factor is established,and finally closed the governing equations.The interface shape is more vulnerable to wettability and surface tension at a low liquid holdup,resulting in a curved interface configuration.The interface is more curved when the smaller is the pipe diameter,or the smaller the liquid holdup,or the smaller the deviation angle,or the greater gas velocity,or the greater the gas density.The critical liquid-carrying velocity increases nonlinearly and then decreases with the increase of inclination angle.The inclination corresponding to the maximum critical liquid-carrying velocity increases with the increase of the diameter of the wellbore,and it is also affected by the fluid properties of the gas phase and liquid phase.The mean relative errors for critical liquid-carrying velocity and critical pressure gradient are 1.19%and 3.02%,respectively,and the misclassification rate is 2.38%in the field trial,implying the new model can provide a valid judgement on the liquid loading in inclined gas wells.展开更多
The influences of steady aerodynamic loads on hunting stability of high-speed railway vehicles were investigated in this study.A mechanism is suggested to explain the change of hunting behavior due to actions of aerod...The influences of steady aerodynamic loads on hunting stability of high-speed railway vehicles were investigated in this study.A mechanism is suggested to explain the change of hunting behavior due to actions of aerodynamic loads:the aerodynamic loads can change the position of vehicle system(consequently the contact relations),the wheel/rail normal contact forces,the gravitational restoring forces/moments and the creep forces/moments.A mathematical model for hunting stability incorporating such influences was developed.A computer program capable of incorporating the effects of aerodynamic loads based on the model was written,and the critical speeds were calculated using this program.The dependences of linear and nonlinear critical speeds on suspension parameters considering aerodynamic loads were analyzed by using the orthogonal test method,the results were also compared with the situations without aerodynamic loads.It is shown that the most dominant factors a ff ecting linear and nonlinear critical speeds are different whether the aerodynamic loads considered or not.The damping of yaw damper is the most dominant influencing factor for linear critical speeds,while the damping of lateral damper is most dominant for nonlinear ones.When the influences of aerodynamic loads are considered,the linear critical speeds decrease with the rise of cross wind velocity,whereas it is not the case for the nonlinear critical speeds.The variation trends of critical speeds with suspension parameters can be significantly changed by aerodynamic loads.Combined actions of aerodynamic loads and suspension parameters also a ff ect the critical speeds.The effects of such joint action are more obvious for nonlinear critical speeds.展开更多
Based on the framework of critical state soil mechanics,a subloading surface plastic model for sand, being applicable to cyclic loading, was proposed. The model can be used to describe strain softening behaviour of sa...Based on the framework of critical state soil mechanics,a subloading surface plastic model for sand, being applicable to cyclic loading, was proposed. The model can be used to describe strain softening behaviour of sand under monotonic loading when the similarity-ratio equals to unity. The characteristics of the model are as follows: 1) A reverse bullet-shaped yield surface is adopted to ensure accurate prediction of the behavior of sand, instead of bullet-shaped or elliptical yield surface in Cam-Clay model. 2) No unique relationship between void ratio and the mean normal stress for sand prevents the direct coupling of yield surface size to void ratio, so incremental deviatoric strain hardening rule is used. 3) The model combines the concept of state-dependent dilatancy by incorporating state parameter in Rowe's stress dilatancy equation, which accounts for the dependence of dilatancy on the stress state and the material internal state. A single set of model constants, which is calibrated, can simulate stress-strain response under different initial void ratios and different confine pressures. The model is validated true by comparing predicted results with experimental results under monotonic and cyclic loading conditions.展开更多
To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to...To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to frozen silty clay by using RSM-SY5(T) nonmetal supersonic test meter, and the tensile strength and compressive strength of silty clay were measured under various negative temperatures. Test and analysis results indicate that, ultrasonic wave velocity rapidly changes in the temperature range of-1 ℃ to -5 ℃. Ultrasonic wave velocity increased with an increase of water content until the water content reached the critical water content, while decreased with an increase of water content after the water content exceeded the critical water content. This study showed that there was strong positive correlation between the ul- trasonic wave velocity and the frozen soil strength. As ultrasonic wave velocity increased, either tensile strength or com- pressive strength increased. Based on the experimental data, the relationship between ultrasonic wave velocity and frozen silty clay strength was obtained through regression analysis. It was found that the ultrasonic test technique can be used to test frozen soils and lay the foundation for the determination of frozen soil strength.展开更多
A method of estimating the safe storage life (τ), self-accelerating decomposition temperature (TsADT) and critical temperature of thermal explosion (Tb) of double-base propellant using isothermal and non-isothe...A method of estimating the safe storage life (τ), self-accelerating decomposition temperature (TsADT) and critical temperature of thermal explosion (Tb) of double-base propellant using isothermal and non-isothermal decomposition behaviours is presented. For double-base propellant composed of 56±1wt% of nitrocellulose (NC), 27±0.5wt% of nitroglycerine (NG), 8.15±0.15wt% of dinitrotoluene (DNT), 2.5±0.1wt% of methyl centralite, 5.0±0.15wt% of catalyst and 1.0±0.1wt% of other, the values of r of 49.4 years at 40℃, of TSAOT of 151.35℃ and of Tb of 163.01℃ were obtained.展开更多
HoekeBrown failure criterion is one of the widely used rock strength criteria in rock mechanics and mining engineering.Based on the theoretical expression of HoekeBrown parameter m of an intact rock,the parameter m ha...HoekeBrown failure criterion is one of the widely used rock strength criteria in rock mechanics and mining engineering.Based on the theoretical expression of HoekeBrown parameter m of an intact rock,the parameter m has been modified by crack parameters for fractured rocks.In this paper,the theoretical value range and theoretical expression form of the parameter m in HoekeBrown failure criterion were discussed.A critical crack parameter B was defined to describe the influence of the critical crack when the stress was at the peak,while a parameter b was introduced to represent the distribution of the average initial fractures.The parameter m of a fractured rock contained the influences of critical crack(B),confining pressure(s3)and initial fractures(b).Then the triaxial test on naturally fractured limestones was conducted to verify the modification of the parameter m.From the ultrasonic test and loading test results of limestones,the parameter m can be obtained,which indicated that the confining pressure at a high level reduced the differences of m among all the specimens.The confining pressure s3 had an exponential impact on m,while the critical crack parameter B had a negative correlation with m.Then the expression of m for a naturally fractured limestone was also proposed.展开更多
<span style="font-family:Verdana;">The main reason for the early failure of radio-cephalic arteriovenous fistula (RCAVF) is non-maturity, which means that the blood flow rate in the fistula cannot incr...<span style="font-family:Verdana;">The main reason for the early failure of radio-cephalic arteriovenous fistula (RCAVF) is non-maturity, which means that the blood flow rate in the fistula cannot increase to the expected value for dialysis. From a mechanical perspective, the vascular resistance at the artificially designed anastomosis causes an energy loss that affects blood flow rate growth and leads to early failure. This research studied how to maximize the RCAVF maturity and primary patency by controlling the energy loss rate. We theoretically analyzed and derived a model that evaluates the energy loss rate <em>E</em><sub><em>avf</em></sub> in RCAVF as a function of its blood vessel geometric parameters (GPs) for given flow rates. There was an aggregate of five controllable GPs in RCAVF: radial artery diameter (<em>D</em><sub><em>ra</em></sub>), cephalic vein diameter (<em>D</em><sub><em>cv</em></sub>), blood vessel distance between artery and vein (<em>h</em>), anastomotic diameter (<em>D</em><sub><em>a</em></sub>), and anastomotic angle (<em>θ</em>). Through this analysis, it was found that <em>E</em><sub><em>avf</em></sub> was inversely proportional to <em>D</em><sub><em>ra</em></sub>, <em>D</em><sub><em>cv</em></sub>, <em>D</em><sub><em>a</em></sub>, and <em>θ</em>, whereas proportional to <em>h</em>. Therefore, we recommended surgeons choose the vessels with large diameters, close distance, and increase the diameter and angle of the anastomosis to decrease the early failure of RCAVF. Simultaneously, we could explain the results of many clinical empiricisms with our formula. We found that increasing <em>D</em><sub><em>cv</em></sub> and <em>θ</em> was more significant in reducing <em>E</em><sub><em>avf</em></sub> than increasing <em>D</em><sub><em>ra</em></sub> and <em>D</em><sub><em>a</em></sub>. Based on our model, we could define two critical energy loss rates (<em>CEL</em><sub><em>a</em></sub>, <em>CEL</em><sub><em>b</em></sub>) to help surgeons evaluate the blood vessels and choose the ideal range of <em>θ</em>, and help them design the preoperative RCAVF plan for each patient to increase the maturity and the primary patency of RCAVF.</span>展开更多
There have been significant advances in the application of critical state,CS,in liquefaction potential assessment.This was done by comparing state parameter,j with estimated characteristic cyclic stress ratio,CSR due ...There have been significant advances in the application of critical state,CS,in liquefaction potential assessment.This was done by comparing state parameter,j with estimated characteristic cyclic stress ratio,CSR due to an earthquake.A cyclic resistance ratio,CRR curve,which can be determined from cyclic liquefaction tests,separates historical liquefied and non-liquefied data points(j,CSR).On the other hand,the concepts of equivalent granular state parameter,j*,which was developed for sands with fines,can be used in lieu j to provide a unifying framework for characterizing the undrained response of sands with non/low plasticity fines,irrespective of fines content(fc).The present work combines these two propositions,and by merely substituting j*for j into the aforementioned CS approach to capture the influence of fc.A series of static and cyclic triaxial tests were conducted,separately and independently of the concept of j*,for sand with up to fc of 30%.The clean sand was collected from Sabarmati river belt at Ahmedabad city in India which was severely affected during the Bhuj earthquake,2001.The experimental data gave a single relation for CRR and j*which was then used to assess liquefaction potential for a SPT based case study,where fc varies along the depth.The prediction matched with the field observation.展开更多
This work represents the extraction of oil with high free fatty acid content from spent bleaching earth using sub-critical water technology as a greener production pathway. The extraction efficiencies under different ...This work represents the extraction of oil with high free fatty acid content from spent bleaching earth using sub-critical water technology as a greener production pathway. The extraction efficiencies under different conditions were investigated. The studied parameters include temperatures in the range of 180 to 270°C, the feed to solventfeed-to-solvent (in this case water) ratio (1:1, 1:2, 1:3, 1:4 and 1:5) and extraction times in the range of 5-60 minutes. The results showed that the optimum temperature, feed to solventfeed-to-solvent ratio, and extraction time were 270°C, 1:3, and 20 minutes, respectively. In another experiment, the extracted free fatty acids were converted into mono-, di-, and triglycerides through esterification with glycerol to increase the value added of the extracted products. The kinetics of the extraction process was found to be corresponding to an irreversible consecutive unimolecular-type first order reaction, consisting of the extraction step followed by the decomposition reaction step. Both reaction rates of extraction and decomposition were estimated using the reaction rate equations utilizing the nonlinear regression method. The apparent activation energy was calculated to be 46.1 kJ·mol-1. This result indicates a diffusion controlled reaction. For more exploration and deep understanding of the extraction mechanism, other thermodynamic parameters were also calculated and analyzed including,ΔH#, ΔS#, and ΔG# of the extraction step.展开更多
The stability and local bifurcation of the lateral parameter-excited resonance of pipes induced by the pulsating fluid velocity and thermal load are studied. A mathematical model for a simply supported pipe is develop...The stability and local bifurcation of the lateral parameter-excited resonance of pipes induced by the pulsating fluid velocity and thermal load are studied. A mathematical model for a simply supported pipe is developed according to Hamilton principle. The Galerkin method is adopted to discretize the partial differential equations to the ordinary differential equations. The method of multiple scales and the singularity theory are utilized to analyze the stability and bifurcation of the trivial and non-trivial solutions. The transition sets and bifurcation diagrams are obtained both in the unfolding parameter space and physical parameter space, which can reveal the relationship between the thermal field parameter and the dynamic behaviors of the pipe. The numerical results demonstrate the accuracy of the single-mode expansion of the solution and verify the stability and local bifurcation analyses. The critical thermal rates are obtained both by the numerical simulation and the local bifurcation analysis. The natural frequency of lateral vibration decreases as the mean fluid velocity or the thermal rate increases according to the numerical results. The present work can provide valuable information for the design of the pipeline and controllers to prevent structural instability.展开更多
基金Supported by the Science and Technology Development Program of Zhejiang Province(2017C03003)
文摘A deeper understanding of the biological events occurring when bioprocess parameters changed will be of great value in improving the monoclonal antibodies (mAbs) production. Design of experiment (DoE) was applied to investigate the effect of process parameters (pH, temperature shift and dissolve oxygen (DO)) on protein titer. The key metabolites connecting the critical process parameters (CPPs) with monoclonal antibody production were identified by different chemometrics tools. Finally, the biological events of marker metabolites relating with titer improvement were concluded. pH and temperature shift were identified as CPPs that affect the target protein titer. A series of metabolites influenced by the altered CPPs and correlated with protein titer were screened by principal component analysis (PCA) and Pearson' correlation test. The marker metabolites and their pathways linking CPPs to target protein titer in different culture phases were summarized. Metabolomics and chemometrics are promising data-driven tools to shine light into the biological black box between the bioprocess parameters and process performance.
文摘Recasting the BCS theory in the larger framework of the Bethe-Salpeter equation, a new equation is derived for the temperature-dependent critical current density jc(T) of an elemental superconductor (SC) directly in terms of the basic parameters of the theory, namely the dimensionless coupling constant [N(0)V], the Debye temperature θD and, additionally, the Fermi energy EF—unlike earlier such equations based on diverse, indirect criteria. Our approach provides an ab initio theoretical justification for one of the latter, text book equations invoked at T = 0 which involves Fermi momentum;additionally, it relates jc with the relevant parameters of the problem at T ≠ 0. Noting that the numerical value of EF of a high-Tc SC is a necessary input for the construction of its Fermi surface—which sheds light on its gap-structure, we also briefly discuss extension of our approach for such SCs.
基金supported by the National Key Basic Research Program of China (No.2005CB 221501)the Innovation Scientists and Technicians Troop Construction Projects of Henan Province (No.084200510002)the Program for New Century Excellent Talents in University (No.NCET-07-0257)
文摘Based on the important role in mine safety played by parameters of the first gas outburst, we propose a method of combining historic data, theoretical analysis and experimental research for the purpose of critical values of gas parameters of the first gas outburst in a coal seam of the Xieqiao Mine. According to a characteristic analysis and a summary of the rules of coal and gas outbursts in the No.8 coal seam of a Huainan mine, we have investigated their effect on coal and gas outbursts in terms such as ground stress, gas, and coal structure. We have selected gas parameters and determined the critical values of each of the following indices: gas content as 7.7 m 3 /t, tectonic coal as 0.8 m thick, the absolute gas emission as 2 m 3 /min, the rate of change as 0.7 m 3 /min, the gas desorption index of a drilling chip K 1 as 0.26 mL/(g min 1/2 ) and the values of desorption indexes 4h 2 as 200 Pa. From a verification of the production, the results indicate that application of each index and their critical values significantly improve the level of safety in the production process, relieve the burden upon the mine, save much labor and bring clear economic benefits.
基金This research was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB10020203)the National Natural Science Foundation of China(U1562215).
文摘TraPPE force field combined with grand-canonical transition-matrix Monte Carlo simulation were used to investigate the vapor-liquid coexistence curve and critical properties of methane,ethane,propane,and n-butane in slit pores ranging from 6?to 40?.Long range correction for intermolecular potential in slit pore model was developed,and the fact indicating that its influence on various thermodynamic properties is not negligible was found.The simulation results show that the thermodynamic properties of nano-confined alkanes shift tremendously from the bulk state.The critical temperature under confinement experiences a roughly linear decrease with an inverse in the slit width,while the critical pressure and the critical density have a relative increment related with carbon number on both the large slit width region and the small slit width region.Further analysis on z-density profiles of alkanes revealed that the complex behaviors of shift in critical parameters are the results of interplay between fluid-fluid and fluid-wall interaction.
文摘The La5/8Ca3/8Mn0.9750Pd0.025O3 compound was studied using DC magnetization measurements. The data were analyzed in the paramagnetic-ferromagnetic phase transition region by the Arrott plot method. The results show the Curie temperature TC ~ 247.8 K and the critical exponents of b = 0.48633, g = 1.18623 and d = 3.431682. The values of the critical exponents are between the mean- field theory and 3D Ising model. The magnetocaloric value is ~5 J/kgK, extracted from the M(H) curves.
基金Project supported by the National Natural Science Foundation of China(No.12072264)the Fundamental Research Funds for the Central Universities+3 种基金the Research Funds for Interdisciplinary Subject of Northwestern Polytechnical Universitythe Shaanxi Project for Distinguished Young Scholarsthe National Key Research and Development Program of China(No.2018AAA0102201)the Shaanxi Provincial Key R&D Program(Nos.2020KW-013 and 2019TD-010)。
文摘In real systems,the unpredictable jump changes of the random environment can induce the critical transitions(CTs)between two non-adjacent states,which are more catastrophic.Taking an asymmetric Lévy-noise-induced tri-stable model with desirable,sub-desirable,and undesirable states as a prototype class of real systems,a prediction of the noise-induced CTs from the desirable state directly to the undesirable one is carried out.We first calculate the region that the current state of the given model is absorbed into the undesirable state based on the escape probability,which is named as the absorbed region.Then,a new concept of the parameter dependent basin of the unsafe regime(PDBUR)under the asymmetric Lévy noise is introduced.It is an efficient tool for approximately quantifying the ranges of the parameters,where the noise-induced CTs from the desirable state directly to the undesirable one may occur.More importantly,it may provide theoretical guidance for us to adopt some measures to avert a noise-induced catastrophic CT.
基金the Ministry of Science and Higher Education of the Russian Federation under Grant No.FSUN-2023-0007.
文摘Some electrical parameters of the SIS-type hysteretic underdamped Josephson junction(JJ)can be measured by its current-voltage characteristics(IVCs).Currents and voltages at JJ are commensurate with the intrinsic noise level of measuring instruments.This leads to the need for multiple measurements with subsequent statistical processing.In this paper,the digital algorithms are proposed for the automatic measurement of the JJ parameters by IVC.These algorithms make it possible to implement multiple measurements and check these JJ parameters in an automatic mode with the required accuracy.The complete sufficient statistics are used to minimize the root-mean-square error of parameter measurement.A sequence of current pulses with slow rising and falling edges is used to drive JJ,and synchronous current and voltage readings at JJ are used to realize measurement algorithms.The algorithm performance is estimated through computer simulations.The significant advantage of the proposed algorithms is the independence from current source noise and intrinsic noise of current and voltage meters,as well as the simple implementation in automatic digital measuring systems.The proposed algorithms can be used to control JJ parameters during mass production of superconducting integrated circuits,which will improve the production efficiency and product quality.
基金Supported by National Natural Science Foundation of China(21978171)。
文摘Based on the assumption of gas-liquid stratified flow pattern in inclined gas wells,considering the influence of wettability and surface tension on the circumferential distribution of liquid film along the wellbore wall,the influence of the change of the gas-liquid interface configuration on the potential energy,kinetic energy and surface free energy of the two-phase system per unit length of the tube is investigated,and a new model for calculating the gas-liquid distribution at critical conditions is developed by using the principle of minimum energy.Considering the influence of the inclination angle,the calculation model of interfacial friction factor is established,and finally closed the governing equations.The interface shape is more vulnerable to wettability and surface tension at a low liquid holdup,resulting in a curved interface configuration.The interface is more curved when the smaller is the pipe diameter,or the smaller the liquid holdup,or the smaller the deviation angle,or the greater gas velocity,or the greater the gas density.The critical liquid-carrying velocity increases nonlinearly and then decreases with the increase of inclination angle.The inclination corresponding to the maximum critical liquid-carrying velocity increases with the increase of the diameter of the wellbore,and it is also affected by the fluid properties of the gas phase and liquid phase.The mean relative errors for critical liquid-carrying velocity and critical pressure gradient are 1.19%and 3.02%,respectively,and the misclassification rate is 2.38%in the field trial,implying the new model can provide a valid judgement on the liquid loading in inclined gas wells.
基金supported by the National Basic Research Program(973 Program)of China(2011CB711100 and 2014CB046801)the National Natural Science Foundation of China(11072246 and51490673)the Knowledge Innovation Program of Chinese Academy of Sciences(KJCX2-EW-L01)
文摘The influences of steady aerodynamic loads on hunting stability of high-speed railway vehicles were investigated in this study.A mechanism is suggested to explain the change of hunting behavior due to actions of aerodynamic loads:the aerodynamic loads can change the position of vehicle system(consequently the contact relations),the wheel/rail normal contact forces,the gravitational restoring forces/moments and the creep forces/moments.A mathematical model for hunting stability incorporating such influences was developed.A computer program capable of incorporating the effects of aerodynamic loads based on the model was written,and the critical speeds were calculated using this program.The dependences of linear and nonlinear critical speeds on suspension parameters considering aerodynamic loads were analyzed by using the orthogonal test method,the results were also compared with the situations without aerodynamic loads.It is shown that the most dominant factors a ff ecting linear and nonlinear critical speeds are different whether the aerodynamic loads considered or not.The damping of yaw damper is the most dominant influencing factor for linear critical speeds,while the damping of lateral damper is most dominant for nonlinear ones.When the influences of aerodynamic loads are considered,the linear critical speeds decrease with the rise of cross wind velocity,whereas it is not the case for the nonlinear critical speeds.The variation trends of critical speeds with suspension parameters can be significantly changed by aerodynamic loads.Combined actions of aerodynamic loads and suspension parameters also a ff ect the critical speeds.The effects of such joint action are more obvious for nonlinear critical speeds.
基金Project(07JCZDJC09800) supported by Tianjin Natural Science FoundationProject(07FDZDSF01200) supported by Tianjin Science and Technology Innovation Special Funds
文摘Based on the framework of critical state soil mechanics,a subloading surface plastic model for sand, being applicable to cyclic loading, was proposed. The model can be used to describe strain softening behaviour of sand under monotonic loading when the similarity-ratio equals to unity. The characteristics of the model are as follows: 1) A reverse bullet-shaped yield surface is adopted to ensure accurate prediction of the behavior of sand, instead of bullet-shaped or elliptical yield surface in Cam-Clay model. 2) No unique relationship between void ratio and the mean normal stress for sand prevents the direct coupling of yield surface size to void ratio, so incremental deviatoric strain hardening rule is used. 3) The model combines the concept of state-dependent dilatancy by incorporating state parameter in Rowe's stress dilatancy equation, which accounts for the dependence of dilatancy on the stress state and the material internal state. A single set of model constants, which is calibrated, can simulate stress-strain response under different initial void ratios and different confine pressures. The model is validated true by comparing predicted results with experimental results under monotonic and cyclic loading conditions.
基金supported by the National Natural Science Foundation of China (No.41271080 and No.41230630)the Western Project Program of the Chinese Academy of Sciences(KZCX2-XB3-19)the open fund of Qinghai Research and Observation Base, Key Laboratory of Highway Construction and Maintenance Technology in Permafrost Region Ministry of Transport, PRC (2012-12-4)
文摘To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to frozen silty clay by using RSM-SY5(T) nonmetal supersonic test meter, and the tensile strength and compressive strength of silty clay were measured under various negative temperatures. Test and analysis results indicate that, ultrasonic wave velocity rapidly changes in the temperature range of-1 ℃ to -5 ℃. Ultrasonic wave velocity increased with an increase of water content until the water content reached the critical water content, while decreased with an increase of water content after the water content exceeded the critical water content. This study showed that there was strong positive correlation between the ul- trasonic wave velocity and the frozen soil strength. As ultrasonic wave velocity increased, either tensile strength or com- pressive strength increased. Based on the experimental data, the relationship between ultrasonic wave velocity and frozen silty clay strength was obtained through regression analysis. It was found that the ultrasonic test technique can be used to test frozen soils and lay the foundation for the determination of frozen soil strength.
基金We are grateful to the National Natural Science Foundation of China (No. 20573098)
文摘A method of estimating the safe storage life (τ), self-accelerating decomposition temperature (TsADT) and critical temperature of thermal explosion (Tb) of double-base propellant using isothermal and non-isothermal decomposition behaviours is presented. For double-base propellant composed of 56±1wt% of nitrocellulose (NC), 27±0.5wt% of nitroglycerine (NG), 8.15±0.15wt% of dinitrotoluene (DNT), 2.5±0.1wt% of methyl centralite, 5.0±0.15wt% of catalyst and 1.0±0.1wt% of other, the values of r of 49.4 years at 40℃, of TSAOT of 151.35℃ and of Tb of 163.01℃ were obtained.
基金financial support from Beijing Outstanding Young Scientist Program,China(Grant No.BJJWZYJH01201911413037)the National Natural Science Foundation of China(Grant No.41877257)Shaanxi Coal Group Key Project,China(Grant No.2018SMHKJ-A-J-03)。
文摘HoekeBrown failure criterion is one of the widely used rock strength criteria in rock mechanics and mining engineering.Based on the theoretical expression of HoekeBrown parameter m of an intact rock,the parameter m has been modified by crack parameters for fractured rocks.In this paper,the theoretical value range and theoretical expression form of the parameter m in HoekeBrown failure criterion were discussed.A critical crack parameter B was defined to describe the influence of the critical crack when the stress was at the peak,while a parameter b was introduced to represent the distribution of the average initial fractures.The parameter m of a fractured rock contained the influences of critical crack(B),confining pressure(s3)and initial fractures(b).Then the triaxial test on naturally fractured limestones was conducted to verify the modification of the parameter m.From the ultrasonic test and loading test results of limestones,the parameter m can be obtained,which indicated that the confining pressure at a high level reduced the differences of m among all the specimens.The confining pressure s3 had an exponential impact on m,while the critical crack parameter B had a negative correlation with m.Then the expression of m for a naturally fractured limestone was also proposed.
文摘<span style="font-family:Verdana;">The main reason for the early failure of radio-cephalic arteriovenous fistula (RCAVF) is non-maturity, which means that the blood flow rate in the fistula cannot increase to the expected value for dialysis. From a mechanical perspective, the vascular resistance at the artificially designed anastomosis causes an energy loss that affects blood flow rate growth and leads to early failure. This research studied how to maximize the RCAVF maturity and primary patency by controlling the energy loss rate. We theoretically analyzed and derived a model that evaluates the energy loss rate <em>E</em><sub><em>avf</em></sub> in RCAVF as a function of its blood vessel geometric parameters (GPs) for given flow rates. There was an aggregate of five controllable GPs in RCAVF: radial artery diameter (<em>D</em><sub><em>ra</em></sub>), cephalic vein diameter (<em>D</em><sub><em>cv</em></sub>), blood vessel distance between artery and vein (<em>h</em>), anastomotic diameter (<em>D</em><sub><em>a</em></sub>), and anastomotic angle (<em>θ</em>). Through this analysis, it was found that <em>E</em><sub><em>avf</em></sub> was inversely proportional to <em>D</em><sub><em>ra</em></sub>, <em>D</em><sub><em>cv</em></sub>, <em>D</em><sub><em>a</em></sub>, and <em>θ</em>, whereas proportional to <em>h</em>. Therefore, we recommended surgeons choose the vessels with large diameters, close distance, and increase the diameter and angle of the anastomosis to decrease the early failure of RCAVF. Simultaneously, we could explain the results of many clinical empiricisms with our formula. We found that increasing <em>D</em><sub><em>cv</em></sub> and <em>θ</em> was more significant in reducing <em>E</em><sub><em>avf</em></sub> than increasing <em>D</em><sub><em>ra</em></sub> and <em>D</em><sub><em>a</em></sub>. Based on our model, we could define two critical energy loss rates (<em>CEL</em><sub><em>a</em></sub>, <em>CEL</em><sub><em>b</em></sub>) to help surgeons evaluate the blood vessels and choose the ideal range of <em>θ</em>, and help them design the preoperative RCAVF plan for each patient to increase the maturity and the primary patency of RCAVF.</span>
基金financial support for Australian Academy of Science Early Career Fellowship(RI 18.6) in 2012-2013 from the Australia-India Strategic Research Fund (AISRF) to visit Department of Civil Engineering,Indian Institute of Science,Bangalore,India to work for the background studies of this paper
文摘There have been significant advances in the application of critical state,CS,in liquefaction potential assessment.This was done by comparing state parameter,j with estimated characteristic cyclic stress ratio,CSR due to an earthquake.A cyclic resistance ratio,CRR curve,which can be determined from cyclic liquefaction tests,separates historical liquefied and non-liquefied data points(j,CSR).On the other hand,the concepts of equivalent granular state parameter,j*,which was developed for sands with fines,can be used in lieu j to provide a unifying framework for characterizing the undrained response of sands with non/low plasticity fines,irrespective of fines content(fc).The present work combines these two propositions,and by merely substituting j*for j into the aforementioned CS approach to capture the influence of fc.A series of static and cyclic triaxial tests were conducted,separately and independently of the concept of j*,for sand with up to fc of 30%.The clean sand was collected from Sabarmati river belt at Ahmedabad city in India which was severely affected during the Bhuj earthquake,2001.The experimental data gave a single relation for CRR and j*which was then used to assess liquefaction potential for a SPT based case study,where fc varies along the depth.The prediction matched with the field observation.
文摘This work represents the extraction of oil with high free fatty acid content from spent bleaching earth using sub-critical water technology as a greener production pathway. The extraction efficiencies under different conditions were investigated. The studied parameters include temperatures in the range of 180 to 270°C, the feed to solventfeed-to-solvent (in this case water) ratio (1:1, 1:2, 1:3, 1:4 and 1:5) and extraction times in the range of 5-60 minutes. The results showed that the optimum temperature, feed to solventfeed-to-solvent ratio, and extraction time were 270°C, 1:3, and 20 minutes, respectively. In another experiment, the extracted free fatty acids were converted into mono-, di-, and triglycerides through esterification with glycerol to increase the value added of the extracted products. The kinetics of the extraction process was found to be corresponding to an irreversible consecutive unimolecular-type first order reaction, consisting of the extraction step followed by the decomposition reaction step. Both reaction rates of extraction and decomposition were estimated using the reaction rate equations utilizing the nonlinear regression method. The apparent activation energy was calculated to be 46.1 kJ·mol-1. This result indicates a diffusion controlled reaction. For more exploration and deep understanding of the extraction mechanism, other thermodynamic parameters were also calculated and analyzed including,ΔH#, ΔS#, and ΔG# of the extraction step.
基金Supported by the Natural Science Foundation of Shandong Province of China(No.ZR2013AL017)the Fundamental Research Funds for the Central Universities of China(No.11CX04049A,No.12CX04071A)
文摘The stability and local bifurcation of the lateral parameter-excited resonance of pipes induced by the pulsating fluid velocity and thermal load are studied. A mathematical model for a simply supported pipe is developed according to Hamilton principle. The Galerkin method is adopted to discretize the partial differential equations to the ordinary differential equations. The method of multiple scales and the singularity theory are utilized to analyze the stability and bifurcation of the trivial and non-trivial solutions. The transition sets and bifurcation diagrams are obtained both in the unfolding parameter space and physical parameter space, which can reveal the relationship between the thermal field parameter and the dynamic behaviors of the pipe. The numerical results demonstrate the accuracy of the single-mode expansion of the solution and verify the stability and local bifurcation analyses. The critical thermal rates are obtained both by the numerical simulation and the local bifurcation analysis. The natural frequency of lateral vibration decreases as the mean fluid velocity or the thermal rate increases according to the numerical results. The present work can provide valuable information for the design of the pipeline and controllers to prevent structural instability.