The study of phase transition processes in liquid crystals(LCs)remains challenging.Most thermotropic LCs exhibit a narrow temperature range and a rapid phase transition from the isotropic(ISO)to the nematic(N)phase,wh...The study of phase transition processes in liquid crystals(LCs)remains challenging.Most thermotropic LCs exhibit a narrow temperature range and a rapid phase transition from the isotropic(ISO)to the nematic(N)phase,which make it difficult to capture and manipulate the phase transition process.In this study,we observed the evolution of small droplets during the ISO–N phase transition in ferroelectric nematic(NF)LC RM734.After doping with metal nanoparticles(NPs),the temperature range of the phase transition broadened,and the droplets formed during the phase transition remained stable,with their diameter increasing linearly with temperature.In addition,droplets doped with NPs can be well controlled by an external electric field.This discovery not only aids in understanding the fundamental mechanisms of LC phase transitions but also provides a simple alternative method for preparing droplets,which is potentially valuable for applications in optoelectronic devices and sensors.展开更多
Buckybowl structures as non-uniform electrostatic potential distributions of poly-cyclic aromatic materials show a unique photoelectric performance.In this work,OTC was utilized for dynamic modulation of triplet excit...Buckybowl structures as non-uniform electrostatic potential distributions of poly-cyclic aromatic materials show a unique photoelectric performance.In this work,OTC was utilized for dynamic modulation of triplet exciton transition processes.Five host molecules with different functional units were selected,thus providing dif-ferent intermolecular interactions in the host/guest systems.Therefore,the delayed emissions were regulated from 536 to 624 nm via the tuning of the triplet exciton transition processes of OTC in different hosts.Experimental data and theoretical calculations revealed that the varied triplet transition behaviors resulted from the competition between the intersystem crossing(ISC)process of OTC-monomer and the reverse intersystem crossing(RISC)process of OTC-aggregates.This work proves the superior structure of buckybowl-based luminophore for controlling triplet exciton transition processes and supplies a new perspective for persistent afterglow luminophore design.展开更多
The operation methods of channel and the speed of gate regulation have great influence on the transformation of flow in water conveyance channels. Based on characteristics method, a 1-D unsteady flow numerical model f...The operation methods of channel and the speed of gate regulation have great influence on the transformation of flow in water conveyance channels. Based on characteristics method, a 1-D unsteady flow numerical model for gate regulation was established in this study. The process of water flow was simulated under different boundary conditions. The influence of gate regulation speed and channel operation methods on flow transition process was analyzed. The numerical results show that under the same conditions, with increasing regulation speed of the gate, the change rates of discharge and water level increase, while the response time of channel becomes shorter, and ultimately the discharge and water level will transit to the same equilibrium states. Moreover, the flow is easier to reach stable state, if the water level in front of the sluice is kept constant, instead of,behind the sluice. This study will be important to the scheme design of automatic operation control in water conveyance channels.展开更多
In order to analyze the response of a hydraulic turbine to a variation in the operating conditions,different laws of variation in time of the massflow rate have been considered.After validating the overall numerical fr...In order to analyze the response of a hydraulic turbine to a variation in the operating conditions,different laws of variation in time of the massflow rate have been considered.After validating the overall numerical framework through comparison with relevant experiments,the performances of the considered turbine have been analyzed from afluid-dynamic point of view.The results show that different time profiles of the massflow rate(in this work,for simplicity,referred to as“transition functions”)have a varying influence on the transient behavior of the turbine.When a quadratic function is considered for the case of largeflow,the transient head and torque increase gradually with time,thefluctuation amplitude of the transient hydraulic efficiency at the main frequency is the largest,and thefluctuation amplitude of the radial force is the smallest.For the smallflow case,the time profile with exponential nature leads to the best results.The transient head and torque decrease gradually with time,the pulsation amplitude of the transient hydraulic efficiency is the largest at the main frequency,and the pulsation amplitude of the radial force is the smallest.展开更多
The fast phase-transitional process of ploy（N-isopropylacrylamide） （PNIPAM） in deuterated solution was studied by laser induced temperature jump technique combined with time-resolved mid-infrared absorbance differ...The fast phase-transitional process of ploy（N-isopropylacrylamide） （PNIPAM） in deuterated solution was studied by laser induced temperature jump technique combined with time-resolved mid-infrared absorbance difference spectroscopy on nanosecond level. The multi-peaks of amide I＇band of PNIPAM among the energy range of 1565-1700 cm^-1 was experimentally resolved to three groups （i, ii, iii） for the first time, while the distinct threestage procedure in the phase transitional process of long-chain PNIPAM was observed firstly too. Furthermore, proper assignments were also made for the three group peaks in amide I＇band and the three steps in the kinetics process of long-chain PNIPAM.展开更多
The dynamic characteristic of complex network failure and recovery is one of the main research topics in complex networks. Real world systems such as traffic jams and Internet recovery could be described by the comple...The dynamic characteristic of complex network failure and recovery is one of the main research topics in complex networks. Real world systems such as traffic jams and Internet recovery could be described by the complex network theory. We propose a model to study the recovery process in complex networks. Two different recovery mechanisms are considered in three kinds of networks： external recovery and internal recovery. By simulating the process of the nodes recovery in networks, it is found that the system exhibits the feature of first-order phase transition only when the external recovery is considered. Internal recovery cannot induce such a kind of transitions. As external recovery and internal recovery coexist on networks, the systems will retain the most efficient part of external recovery and internal recovery. Meanwhile, a hysteresis could be observed when increasing or decreasing the failure probability. Finally, a largest degree node protection strategy is proposed for improving the robustness of networks.展开更多
An objective method for discriminating the process of extratropical transition （ET） in tropical cyclones is introduced. With this method, the gridpoint output data of NWP are used to calculate three parameters： sto...An objective method for discriminating the process of extratropical transition （ET） in tropical cyclones is introduced. With this method, the gridpoint output data of NWP are used to calculate three parameters： storm-relative thickness symmetry （B）, low-level （-VL^L ） and upper-level thermal wind （-VT^U ）. This objective method is easy to calculate and convenient for operational use. To verify the method, this paper uses the NCEP reanalysis data to identify the evolution of ET for ＂Haima＂, a tropical storm （0421） that affected the eastern part of China in 2004. The result shows that the three parameters defined with the objective method are good indicators of the ET process.展开更多
In this paper, an emotional mathematical model and affective state probability description space of a humanoid robot are set up on the basis of psycho-dynamics＇ psychological energy and affective energy conservation ...In this paper, an emotional mathematical model and affective state probability description space of a humanoid robot are set up on the basis of psycho-dynamics＇ psychological energy and affective energy conservation law. The emotional state transferring process and hidden Markov chain algorithm of stimulating transition process are then studied. The simulation results show that the mathematical model is applicable to the authentic affective state change rule of human beings. Finally, the gait generation experiment results of control signal and electric current tracking wave-form are presented to demonstrate the validity of the proposed mathematical model.展开更多
There exists inlet-engine match conflict between high and low speeds for a non-adjustable bump inlet.A scheme of using a bistable bump surface at the throat region of the inlet is proposed to adjust the throat area.Th...There exists inlet-engine match conflict between high and low speeds for a non-adjustable bump inlet.A scheme of using a bistable bump surface at the throat region of the inlet is proposed to adjust the throat area.The FEM model of the bistable surface is established with hinged constraint,and the bistability condition and structural transition process are investigated in detail.Moreover,the effects of loading method,loading position and structural parameters on critical driving force,input energy and structural strain are studied.Finally,the influences of an elastic boundary condition on the structural bistability are discussed.The results show that the bistability of the adjustable bump surface requires a certain boundary constraint and geometric parameter combination,and that there are local and overall snap-through phenomena during transition which are related to the loading position and structural parameters.Therefore,suitable loading position and structural material could reduce input energy and meet the demand of structural strain.展开更多
Background: In the developed part of the world, coronary heart disease is the major cause of death and is one of the leading causes of disease burden. In Sweden, more than 30,000 people per year are affected by myocar...Background: In the developed part of the world, coronary heart disease is the major cause of death and is one of the leading causes of disease burden. In Sweden, more than 30,000 people per year are affected by myocardial infarction and out of these approximately 40% are women. Nearly 70% of the women survive and after a myocardial infarction a recovery process follows. Today’s health care focuses more on treatment, symptoms and risk factors than on the individuals’ perceptions of the recovery process. Aim: To explore cardiac rehabilitation nurses’ experiences of factors influencing female patients’ recovery after their first myocardial infarction. Methods: Twenty cardiac rehabilitation nurses were interviewed. The study was conducted using qualitative content analysis. Results: The cardiac rehabilitation nurses experienced that women’s recovery after a first myocardial infarction was influenced whether they had a supportive context, their ability to cope with the stresses of life, if they wanted to be involved in their own personal care and how they related to themselves. Conclusions: Women’s recovery after a myocardial infarction was influenced by factors related to surroundings as well as own individual factors. The underlying meaning of women’s recovery can be described as the transition process of a recovery to health. Our findings suggest that a focus on person-centered nursing would be beneficial in order to promote the every woman’s personal and unique recovery after a myocardial infarction. Finally, the cardiac rehabilitation nurses’ experiences of factors influencing male patients’ recovery after their first myocardial infarction should be important to investigate.展开更多
The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local loading process forming limit is restricted by...The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local loading process forming limit is restricted by forming defects in the transitional region.In this work,the feasibility of controlling forming defects and improving the process forming limit by adjusting die parameters is explored through finite element（FE） simulation.It is found that the common cavum and folding defects in the transitional region are significantly influenced by the fillet radii of left rib and middle rib,respectively.The cavum and folding defects can be effectively controlled by increasing the fillet radii of left rib and middle rib,respectively.The process forming limits considering forming defects in the transitional region are determined by the stepwise searching method under various die parameters.Moreover,the relationship between the process forming limit and die parameters is developed through the response surface methodology（RSM）.The developed RSM models suggest that increasing the fillet radii of left and middle ribs is effective to improve the process forming limit during local loading forming of rib-web components.The results will provide technical basis for the design of die parameters and the reduction amount,which is of great importance to control forming defects and improve the process forming limit in local loading forming of Ti-alloy large-scale rib-web components.展开更多
Automatic process control (APC) based on design of experiment (DOE) is a cost-efficient approach for variation reduction. The process changes both in mean and variance owing to online parameter adjustment make it hard...Automatic process control (APC) based on design of experiment (DOE) is a cost-efficient approach for variation reduction. The process changes both in mean and variance owing to online parameter adjustment make it hard to apply traditional SPC charts in such DOE-based APC applied process. An adaptive SPC scheme is developed, which can better track the process transitions and achieve the possible SPC run cost reduction when the process is stable. The control law of SPC parameters is designed by fully utilizing the estimation properties of the process model instead of traditionally using the data collected from the production line. An example is provided to illustrate the proposed adaptive SPC design approach.展开更多
The oscillation of multi-time scales and the process of transition between cold and warm periods over most parts of China and its 6 regions (the Northeast,North China,Changjiang River Valley,South China,the Southwest,...The oscillation of multi-time scales and the process of transition between cold and warm periods over most parts of China and its 6 regions (the Northeast,North China,Changjiang River Valley,South China,the Southwest,the Northwest) were analyzed with wavelet transformation and by computing the variances of the wavelet components for the temperature grade series during January 191I to February 2001,The prediction model for cold and warm periods has been developed and the trend of cold and warm change in the coming 10 years is predicted.The results show that the oscillation with periods of around 30-40 years was the strongest in the last 100 years and the 3-year oscillation in both winter and summer was also stronger,especially in winter. The transition time of cold and warm periods in terms of winter mean did not coincide with that of annual mean,but the difference between summer mean and annual mean is less.The processes of transition of 6 regions are somewhat different,their main characteristics are that the beginning year of significant warming for 1980s to 1990s was very different for the southern and the northern part of China.It is found that the stronger oscillation with 3-year period causes cooling in Northeast China in recent several winters.The experimental predictions show that the models used in the paper can project the major transition between high and low temperature periods.展开更多
To research the correlation between vibrational energy transition rates and acoustic relaxation processes in excitable gases, the vibrational relaxation theory provided by Tanczos [J. Chem. Phy3. 25, 439 （1956）] is ...To research the correlation between vibrational energy transition rates and acoustic relaxation processes in excitable gases, the vibrational relaxation theory provided by Tanczos [J. Chem. Phy3. 25, 439 （1956）] is applied to calculate the energy transition rates of Vibrational- Vibrational （V-V） and Vibrational-Translational （V-T） energy transfer in gas mixtures. The results of calculation for the multi-relaxation processes in various gas mixtures, consisting of carbon dioxide, methane, chlorine, nitrogen, and oxygen at room temperature, demonstrate that the acoustic energy stagnated in every vibrational mode is coupled with each other through V-V energy exchanges. The vibrational excitation energy will relax through the V-T de-excitation path of the lowest mode because of its fastest V-T transition rate, resulting in that only one absorption peak can be measured for most of excitable gas mixtures. Thus, an effective model is provided to analyze how the vibrational energy transition rates affect the characteristics of acoustic relaxation processes and acoustic propagation in excitable gas mixtures.展开更多
Heat storage properties of phase change materials(PCMs) are essential characteristics that perform a key role in thermal heat energy storage systems.The thermal properties of PCMs can be improved by developing metal f...Heat storage properties of phase change materials(PCMs) are essential characteristics that perform a key role in thermal heat energy storage systems.The thermal properties of PCMs can be improved by developing metal foam/PCM composites.The addition of metal foam in PCMs has a significant effect on the thermal characteristics of PCMs.In this paper,the heat storage properties of two different metal foam/PCM composites were experimentally examined.The behavior of paraffin in metal foam(copper and iron-nickel)/paraffin composites concerning pure paraffin at a constant heat flux of 1000 W/m^(2) in three directions simultaneously(x,y,and z) was studied.Paraffin was infiltrated into copper and iron-nickel foams to develop composite materials which resulted in enhancing the thermal conductivity of the paraffin.A comparative analysis is made on the heat storage properties of paraffin in copper and iron-nickel foams/paraffin composites.Inner temperature distribution during the phase transition process is experimentally evaluated.This comparison indicates that temperature uniformity in copper foam/paraffin composite is better than in iron-nickel foam/paraffin composite and pure paraffin at the same heat flux.Experimental results show that at heat flux of 1000 W/m^(2),the heat storage time for copper foam/paraffin composite is 20.63% of that of iron-nickel foam/paraffin composite.展开更多
In this paper, we study the point process of state transitions in a regular Markov chain.Under a weaker condition, we prove that the point process is a 1-memory self-exciting point process and again obtain four useful...In this paper, we study the point process of state transitions in a regular Markov chain.Under a weaker condition, we prove that the point process is a 1-memory self-exciting point process and again obtain four useful formulas of the transition frequency, the absorbing distribution,the renewal distribution and the entering probability. As an applicstion, using these formulas we derive the LS transform of the busy period for the M/M/∞ queue.展开更多
The stimuli-responsive polymers with upper critical solution temperatures(UCST) are highly attractive for drug delivery applications. However, the phase transition process of UCST polymer is usually characterized by t...The stimuli-responsive polymers with upper critical solution temperatures(UCST) are highly attractive for drug delivery applications. However, the phase transition process of UCST polymer is usually characterized by turbidity measurement and electron microscopy, which are significantly restricted by low sensitivity and static observation. In contrary, the fluorescence technique has significant advantages in terms of high sensitivity, easy operation, and dynamic observation. However, the conventional fluorophores suffer from the drawbacks of aggregation-caused quenching(ACQ) after being encapsulated by UCST polymers, which are not suitable for direct visualization of the phase transition process. To tackle this challenge, we herein developed a series of UCST polymers based on polyacrylamides decorated with bile acid and aggregation-induced emission(AIE)-active tetraphenylethene(TPE) groups, which can be used for direct fluorescence monitoring of the phase transition process. Moreover, the AIE-active UCST polymers can serve as drug carriers, which can not only monitor the drug release process under thermal stimuli, but also verify the drug release by fluorescence recovery after thermal stimuli. It is expected that the AIE-active UCST polymers with self-monitoring ability are promising for biomedical applications.展开更多
The paper discusses the diffusion of new technologies from the perspective of the classical economists and Schumpeter. After a comparison of the pre- and post-technical change long-period positions of the economy, we ...The paper discusses the diffusion of new technologies from the perspective of the classical economists and Schumpeter. After a comparison of the pre- and post-technical change long-period positions of the economy, we illustrate the process of transition between the two in terms of a two-sector model Next, we turn to a system with joint production. The fact that some products may be ＂bads＂ that need to be disposed of leads to a study of systems of production-cure-disposal. Finally, we investigate the selection pressure innovations exert on incumbent firms. An important message is that technical change cannot generally be studied within a partial framework of the analysis.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFA1405000)the Natural Science Foundation of Jiangsu Province(Grant No.BK20211277)+2 种基金the Frontier Leading Technology Basic Research Project of Jiangsu Province(Grant No.BK20212004)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX230971)the Natural Science Foundation of Nanjing University of Posts and Telecommunications(Grant No.NY223087).
文摘The study of phase transition processes in liquid crystals(LCs)remains challenging.Most thermotropic LCs exhibit a narrow temperature range and a rapid phase transition from the isotropic(ISO)to the nematic(N)phase,which make it difficult to capture and manipulate the phase transition process.In this study,we observed the evolution of small droplets during the ISO–N phase transition in ferroelectric nematic(NF)LC RM734.After doping with metal nanoparticles(NPs),the temperature range of the phase transition broadened,and the droplets formed during the phase transition remained stable,with their diameter increasing linearly with temperature.In addition,droplets doped with NPs can be well controlled by an external electric field.This discovery not only aids in understanding the fundamental mechanisms of LC phase transitions but also provides a simple alternative method for preparing droplets,which is potentially valuable for applications in optoelectronic devices and sensors.
基金National Natural Scientific Foundation of China,Grant/Award Numbers:21975021,21975020,21875019,21871119,22105019,22175023Beijing National Laboratory for Molecular Sciences,Grant/Award Number:BNLMS192007BIT Research and Innovation Promoting Project,Grant/Award Number:2022YCXZ035。
文摘Buckybowl structures as non-uniform electrostatic potential distributions of poly-cyclic aromatic materials show a unique photoelectric performance.In this work,OTC was utilized for dynamic modulation of triplet exciton transition processes.Five host molecules with different functional units were selected,thus providing dif-ferent intermolecular interactions in the host/guest systems.Therefore,the delayed emissions were regulated from 536 to 624 nm via the tuning of the triplet exciton transition processes of OTC in different hosts.Experimental data and theoretical calculations revealed that the varied triplet transition behaviors resulted from the competition between the intersystem crossing(ISC)process of OTC-monomer and the reverse intersystem crossing(RISC)process of OTC-aggregates.This work proves the superior structure of buckybowl-based luminophore for controlling triplet exciton transition processes and supplies a new perspective for persistent afterglow luminophore design.
基金supported by the National Natural SciencFoundation of China (Grant No. 59879016)the National BasiResearch Program of China (973 Program, Grant No2003CB415200)
文摘The operation methods of channel and the speed of gate regulation have great influence on the transformation of flow in water conveyance channels. Based on characteristics method, a 1-D unsteady flow numerical model for gate regulation was established in this study. The process of water flow was simulated under different boundary conditions. The influence of gate regulation speed and channel operation methods on flow transition process was analyzed. The numerical results show that under the same conditions, with increasing regulation speed of the gate, the change rates of discharge and water level increase, while the response time of channel becomes shorter, and ultimately the discharge and water level will transit to the same equilibrium states. Moreover, the flow is easier to reach stable state, if the water level in front of the sluice is kept constant, instead of,behind the sluice. This study will be important to the scheme design of automatic operation control in water conveyance channels.
基金This work is financially supported by Gansu Province Key Research and Development Plan Projects(20YF3GA019)Gansu Province Science and Technology Project(20JR5RA447,20JR10RA174,20JR10RA203)+1 种基金Gansu Province Colleges and Universities Industrial Support Program Projects(2020C-20)Key Laboratory of Fluid and Power Machinery,Ministry of Education,Xihua University(szjj2019-016,LTDL2020-007).
文摘In order to analyze the response of a hydraulic turbine to a variation in the operating conditions,different laws of variation in time of the massflow rate have been considered.After validating the overall numerical framework through comparison with relevant experiments,the performances of the considered turbine have been analyzed from afluid-dynamic point of view.The results show that different time profiles of the massflow rate(in this work,for simplicity,referred to as“transition functions”)have a varying influence on the transient behavior of the turbine.When a quadratic function is considered for the case of largeflow,the transient head and torque increase gradually with time,thefluctuation amplitude of the transient hydraulic efficiency at the main frequency is the largest,and thefluctuation amplitude of the radial force is the smallest.For the smallflow case,the time profile with exponential nature leads to the best results.The transient head and torque decrease gradually with time,the pulsation amplitude of the transient hydraulic efficiency is the largest at the main frequency,and the pulsation amplitude of the radial force is the smallest.
基金This work was supported by the National Natural Science Foundation of China （No.20673107）, the National Key Basic Research Special Foundation of China （No.2007CB815203）, and the Knowledge Innovation Foundation of the Chinese Academy of Science （No.KJCX2-SW-H08）.
文摘The fast phase-transitional process of ploy（N-isopropylacrylamide） （PNIPAM） in deuterated solution was studied by laser induced temperature jump technique combined with time-resolved mid-infrared absorbance difference spectroscopy on nanosecond level. The multi-peaks of amide I＇band of PNIPAM among the energy range of 1565-1700 cm^-1 was experimentally resolved to three groups （i, ii, iii） for the first time, while the distinct threestage procedure in the phase transitional process of long-chain PNIPAM was observed firstly too. Furthermore, proper assignments were also made for the three group peaks in amide I＇band and the three steps in the kinetics process of long-chain PNIPAM.
基金Supported by the National Natural Science foundation of China under Grant No 11474221
文摘The dynamic characteristic of complex network failure and recovery is one of the main research topics in complex networks. Real world systems such as traffic jams and Internet recovery could be described by the complex network theory. We propose a model to study the recovery process in complex networks. Two different recovery mechanisms are considered in three kinds of networks： external recovery and internal recovery. By simulating the process of the nodes recovery in networks, it is found that the system exhibits the feature of first-order phase transition only when the external recovery is considered. Internal recovery cannot induce such a kind of transitions. As external recovery and internal recovery coexist on networks, the systems will retain the most efficient part of external recovery and internal recovery. Meanwhile, a hysteresis could be observed when increasing or decreasing the failure probability. Finally, a largest degree node protection strategy is proposed for improving the robustness of networks.
基金Integrated Operational Services/Pre-warning System for Tropical Cyclones from China Meteorological AdministrationTyphoon Research Foundation for Shanghai Typhoon Institute
文摘An objective method for discriminating the process of extratropical transition （ET） in tropical cyclones is introduced. With this method, the gridpoint output data of NWP are used to calculate three parameters： storm-relative thickness symmetry （B）, low-level （-VL^L ） and upper-level thermal wind （-VT^U ）. This objective method is easy to calculate and convenient for operational use. To verify the method, this paper uses the NCEP reanalysis data to identify the evolution of ET for ＂Haima＂, a tropical storm （0421） that affected the eastern part of China in 2004. The result shows that the three parameters defined with the objective method are good indicators of the ET process.
基金supported by National High Technology Research and Development Program of China (863 Program)(No.2007AA04Z218)
文摘In this paper, an emotional mathematical model and affective state probability description space of a humanoid robot are set up on the basis of psycho-dynamics＇ psychological energy and affective energy conservation law. The emotional state transferring process and hidden Markov chain algorithm of stimulating transition process are then studied. The simulation results show that the mathematical model is applicable to the authentic affective state change rule of human beings. Finally, the gait generation experiment results of control signal and electric current tracking wave-form are presented to demonstrate the validity of the proposed mathematical model.
基金supported by the National Natural Science Foundation of China(Nos.11172128,51475228)the Specialized Research Fund for the Doctoral Program of Higher Education of China (No.20123218110001)+1 种基金the Research Fund of State Key Laboratory of Mechanics and Control of Mechanics Structures (Nanjing University of Aeronautics and Astronautics)(No.0515G01)the Priority Academic Program Development of Jiangsu Higher Education Institutions and the Funding of Jiangsu Innovation Program for Graduate Education(the Fundamental Research Funds for the Central Universities)(No.CXZZ12_ 0139)
文摘There exists inlet-engine match conflict between high and low speeds for a non-adjustable bump inlet.A scheme of using a bistable bump surface at the throat region of the inlet is proposed to adjust the throat area.The FEM model of the bistable surface is established with hinged constraint,and the bistability condition and structural transition process are investigated in detail.Moreover,the effects of loading method,loading position and structural parameters on critical driving force,input energy and structural strain are studied.Finally,the influences of an elastic boundary condition on the structural bistability are discussed.The results show that the bistability of the adjustable bump surface requires a certain boundary constraint and geometric parameter combination,and that there are local and overall snap-through phenomena during transition which are related to the loading position and structural parameters.Therefore,suitable loading position and structural material could reduce input energy and meet the demand of structural strain.
文摘Background: In the developed part of the world, coronary heart disease is the major cause of death and is one of the leading causes of disease burden. In Sweden, more than 30,000 people per year are affected by myocardial infarction and out of these approximately 40% are women. Nearly 70% of the women survive and after a myocardial infarction a recovery process follows. Today’s health care focuses more on treatment, symptoms and risk factors than on the individuals’ perceptions of the recovery process. Aim: To explore cardiac rehabilitation nurses’ experiences of factors influencing female patients’ recovery after their first myocardial infarction. Methods: Twenty cardiac rehabilitation nurses were interviewed. The study was conducted using qualitative content analysis. Results: The cardiac rehabilitation nurses experienced that women’s recovery after a first myocardial infarction was influenced whether they had a supportive context, their ability to cope with the stresses of life, if they wanted to be involved in their own personal care and how they related to themselves. Conclusions: Women’s recovery after a myocardial infarction was influenced by factors related to surroundings as well as own individual factors. The underlying meaning of women’s recovery can be described as the transition process of a recovery to health. Our findings suggest that a focus on person-centered nursing would be beneficial in order to promote the every woman’s personal and unique recovery after a myocardial infarction. Finally, the cardiac rehabilitation nurses’ experiences of factors influencing male patients’ recovery after their first myocardial infarction should be important to investigate.
基金the support of the National Natural Science Foundation of China(Nos.51605388,51675433)111 Project(B08040)+2 种基金the Research Fund of the State Key Laboratory of Solidification Processing(NWPU)in China(Grant No.131-QP-2015)the Fundamental Research Funds for the Central Universitiesthe Open Research Fund of State Key Laboratory of Materials Processing and Die&Mold Technology at Huazhong University of Science and Technology
文摘The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local loading process forming limit is restricted by forming defects in the transitional region.In this work,the feasibility of controlling forming defects and improving the process forming limit by adjusting die parameters is explored through finite element（FE） simulation.It is found that the common cavum and folding defects in the transitional region are significantly influenced by the fillet radii of left rib and middle rib,respectively.The cavum and folding defects can be effectively controlled by increasing the fillet radii of left rib and middle rib,respectively.The process forming limits considering forming defects in the transitional region are determined by the stepwise searching method under various die parameters.Moreover,the relationship between the process forming limit and die parameters is developed through the response surface methodology（RSM）.The developed RSM models suggest that increasing the fillet radii of left and middle ribs is effective to improve the process forming limit during local loading forming of rib-web components.The results will provide technical basis for the design of die parameters and the reduction amount,which is of great importance to control forming defects and improve the process forming limit in local loading forming of Ti-alloy large-scale rib-web components.
基金the National Natural Science Foundation of China (50405016 70671065).
文摘Automatic process control (APC) based on design of experiment (DOE) is a cost-efficient approach for variation reduction. The process changes both in mean and variance owing to online parameter adjustment make it hard to apply traditional SPC charts in such DOE-based APC applied process. An adaptive SPC scheme is developed, which can better track the process transitions and achieve the possible SPC run cost reduction when the process is stable. The control law of SPC parameters is designed by fully utilizing the estimation properties of the process model instead of traditionally using the data collected from the production line. An example is provided to illustrate the proposed adaptive SPC design approach.
文摘The oscillation of multi-time scales and the process of transition between cold and warm periods over most parts of China and its 6 regions (the Northeast,North China,Changjiang River Valley,South China,the Southwest,the Northwest) were analyzed with wavelet transformation and by computing the variances of the wavelet components for the temperature grade series during January 191I to February 2001,The prediction model for cold and warm periods has been developed and the trend of cold and warm change in the coming 10 years is predicted.The results show that the oscillation with periods of around 30-40 years was the strongest in the last 100 years and the 3-year oscillation in both winter and summer was also stronger,especially in winter. The transition time of cold and warm periods in terms of winter mean did not coincide with that of annual mean,but the difference between summer mean and annual mean is less.The processes of transition of 6 regions are somewhat different,their main characteristics are that the beginning year of significant warming for 1980s to 1990s was very different for the southern and the northern part of China.It is found that the stronger oscillation with 3-year period causes cooling in Northeast China in recent several winters.The experimental predictions show that the models used in the paper can project the major transition between high and low temperature periods.
基金supported by the National Natural Science Foundation of China(61461008,61371139,61571201,61540051)the China Scholarship Council Project(201708525058)+1 种基金the National Science Foundation of Guizhou Province,China(Qian Ke He J Zi[2015]2065),Qian Ke He LH Zi[2014]7361)the Recruitment Program of Guizhou Institute of Technology(XJGC20140601,XJGC20150107)
文摘To research the correlation between vibrational energy transition rates and acoustic relaxation processes in excitable gases, the vibrational relaxation theory provided by Tanczos [J. Chem. Phy3. 25, 439 （1956）] is applied to calculate the energy transition rates of Vibrational- Vibrational （V-V） and Vibrational-Translational （V-T） energy transfer in gas mixtures. The results of calculation for the multi-relaxation processes in various gas mixtures, consisting of carbon dioxide, methane, chlorine, nitrogen, and oxygen at room temperature, demonstrate that the acoustic energy stagnated in every vibrational mode is coupled with each other through V-V energy exchanges. The vibrational excitation energy will relax through the V-T de-excitation path of the lowest mode because of its fastest V-T transition rate, resulting in that only one absorption peak can be measured for most of excitable gas mixtures. Thus, an effective model is provided to analyze how the vibrational energy transition rates affect the characteristics of acoustic relaxation processes and acoustic propagation in excitable gas mixtures.
文摘Heat storage properties of phase change materials(PCMs) are essential characteristics that perform a key role in thermal heat energy storage systems.The thermal properties of PCMs can be improved by developing metal foam/PCM composites.The addition of metal foam in PCMs has a significant effect on the thermal characteristics of PCMs.In this paper,the heat storage properties of two different metal foam/PCM composites were experimentally examined.The behavior of paraffin in metal foam(copper and iron-nickel)/paraffin composites concerning pure paraffin at a constant heat flux of 1000 W/m^(2) in three directions simultaneously(x,y,and z) was studied.Paraffin was infiltrated into copper and iron-nickel foams to develop composite materials which resulted in enhancing the thermal conductivity of the paraffin.A comparative analysis is made on the heat storage properties of paraffin in copper and iron-nickel foams/paraffin composites.Inner temperature distribution during the phase transition process is experimentally evaluated.This comparison indicates that temperature uniformity in copper foam/paraffin composite is better than in iron-nickel foam/paraffin composite and pure paraffin at the same heat flux.Experimental results show that at heat flux of 1000 W/m^(2),the heat storage time for copper foam/paraffin composite is 20.63% of that of iron-nickel foam/paraffin composite.
文摘In this paper, we study the point process of state transitions in a regular Markov chain.Under a weaker condition, we prove that the point process is a 1-memory self-exciting point process and again obtain four useful formulas of the transition frequency, the absorbing distribution,the renewal distribution and the entering probability. As an applicstion, using these formulas we derive the LS transform of the busy period for the M/M/∞ queue.
基金supported by the National Natural Science Foundation of China(21704026,21788102,51620105009,21877040,U1801252,21602063,22075087)the Natural Science Foundation of Guangdong Province,China(2019A1515011129)+4 种基金the Science and Technology Program of Guangzhou(201804020060,202007020002,201704030069,202002030229)Pearl River S&T Nova Program of Guangzhou(201806010152)Fundamental Research Funds for the Central Universities(2018JQ01)Foundation for Xinghua Scholar of South China University of TechnologyNational Key R&D Program of China(2017YFC1103400,2017YFC1105004,2018YFC0311103)。
文摘The stimuli-responsive polymers with upper critical solution temperatures(UCST) are highly attractive for drug delivery applications. However, the phase transition process of UCST polymer is usually characterized by turbidity measurement and electron microscopy, which are significantly restricted by low sensitivity and static observation. In contrary, the fluorescence technique has significant advantages in terms of high sensitivity, easy operation, and dynamic observation. However, the conventional fluorophores suffer from the drawbacks of aggregation-caused quenching(ACQ) after being encapsulated by UCST polymers, which are not suitable for direct visualization of the phase transition process. To tackle this challenge, we herein developed a series of UCST polymers based on polyacrylamides decorated with bile acid and aggregation-induced emission(AIE)-active tetraphenylethene(TPE) groups, which can be used for direct fluorescence monitoring of the phase transition process. Moreover, the AIE-active UCST polymers can serve as drug carriers, which can not only monitor the drug release process under thermal stimuli, but also verify the drug release by fluorescence recovery after thermal stimuli. It is expected that the AIE-active UCST polymers with self-monitoring ability are promising for biomedical applications.
文摘The paper discusses the diffusion of new technologies from the perspective of the classical economists and Schumpeter. After a comparison of the pre- and post-technical change long-period positions of the economy, we illustrate the process of transition between the two in terms of a two-sector model Next, we turn to a system with joint production. The fact that some products may be ＂bads＂ that need to be disposed of leads to a study of systems of production-cure-disposal. Finally, we investigate the selection pressure innovations exert on incumbent firms. An important message is that technical change cannot generally be studied within a partial framework of the analysis.
