Padma was 17 when the democratic reform was introduced in Xizang in 1959.Before the reform,the region had been ruled by feudal serfdom under a theocracy for centuries.Nearly one million serfs were subjected to estate-...Padma was 17 when the democratic reform was introduced in Xizang in 1959.Before the reform,the region had been ruled by feudal serfdom under a theocracy for centuries.Nearly one million serfs were subjected to estate-holders'cruel exploitation and oppression.Padma was one of them.展开更多
“civil discourse”amongst multiple individuals with diverse viewpoints is necessary to move toward truth,to maintain democratic buoyancy,and to get the most accurate read on how best to move forward toward our collec...“civil discourse”amongst multiple individuals with diverse viewpoints is necessary to move toward truth,to maintain democratic buoyancy,and to get the most accurate read on how best to move forward toward our collective good,civil discourse is nonetheless under catastrophic threat by contemporary forces that include the sloppy use of the term“hate speech”;the“libelling by labeling”(aka“cancelling”)in the public square of social media;technologically powered disinformation campaigns;and the growth of“safetyism”in academia.In light of these threats,the goal must be to convince educators,particularly philosophical educators,of the need to adopt a whole new focus in education,namely one that puts a spotlight on the fact that the utilization of the freedom of speech to destroy the freedom of speech of others utterly undermines the positive value of freedom of speech.In order to motivate individuals to turn their back on the dopamine rush of shutting someone down,educators must also spend a great deal of time showcasing the merits of“civil discourse”by providing young people with extensive experience in engaging in facilitated“civil discourse”(aka Communities of Philosophical Inquiry)so that its value can be woven into a personal commitment.展开更多
Objective:This study aimed to explore the effect of aromatherapy combined with emotional release technology on recurrence fear and sleep quality of lung cancer survivors.Methods:114 cases of lung cancer survivors were...Objective:This study aimed to explore the effect of aromatherapy combined with emotional release technology on recurrence fear and sleep quality of lung cancer survivors.Methods:114 cases of lung cancer survivors were divided into routine nursing group,emotional release technology group and aromatherapy combined with emotional release technology group.Routine nursing group received routine nursing;Emotional release technology group implemented emotional release technology for one month on the basis of routine nursing group;Aromatherapy combined with emotional release technology group used lavender aromatherapy on the basis of emotional release technology group.Results:After one month of intervention,there were statistically significant differences in the scores of fear of disease progression and sleep quality among the three groups.Conclusion:Aromatherapy combined with emotional release technology can improve the sleep quality of lung cancer survivors and reduce the economic toxicity of cancer to some extent.展开更多
The dynamic behavior of high-speed craft navigating through variable sea states plays a pivotal role in ensuring maritime safety.However,many existing simulation approaches rely on linear or overly simplified represen...The dynamic behavior of high-speed craft navigating through variable sea states plays a pivotal role in ensuring maritime safety.However,many existing simulation approaches rely on linear or overly simplified representations of the marine environment,thereby limiting the fidelity of motion predictions.This study explores the motion characteristics of a 4.5-t high-speed vessel by conducting fully coupled numerical simulations using the STAR-CCM+software.The analysis considers both calm and varying sea conditions,incorporating fluctuations in wave height,wavelength,and wind speed to reflect more realistic operating scenarios.Simulation results reveal that the vessel’s hydrodynamic response is highly sensitive to changes in sea state.As conditions deteriorate,the free surface becomes increasingly complex,with higher wave amplitudes and more pronounced interactions between the waves generated by the vessel and those imposed by the external environment.These effects lead to significant increases in roll,pitch,heave,and sway motions,thereby imposing greater demands on the vessel’s dynamic stability and operational safety.Furthermore,both hydrodynamic resistance and propulsive thrust exhibit notable dependence on sea state and vessel speed.Total resistance generally increases with rougher sea conditions,while thrust tends to rise with increasing forward speed.Under calm or mildly disturbed waters,a Froude number(Fr)of 0.5 appears to offer an optimal balance for initiating and controlling primary motions such as roll,pitch,heave,and sway.Conversely,in more challenging conditions-such as those represented by a Sea State 3-effective motion control is better achieved at a higher Froude number of approximately 1.0.展开更多
This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(S...This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(SDOF)and the experimentally validated Finite Element(FE)methods(LSDYNA).For this purpose,special atten-tion is given to calculating the response of H-shaped steel columns under blast.The damage amount is determined based on the support rotation criterion,which is expressed as a function of their maximum lateral mid-span dis-placement.To account for uncertainties in input parameters and obtain the failure probability,the Monte Carlo simulation(MCS)method is employed,complemented by the Latin Hypercube Sampling(LHS)method to reduce the number of simulations.A parametric analysis is hence performed to examine the effect of several input pa-rameters(including both deterministic and probabilistic parameters)on the probability of column damage as a function of support rotation.First,the MSDOF method confirms its higher accuracy in estimating the probability of column damage due to blast,compared to the conventional SDOF.The collected results also show that un-certainties of several input parameters have significant effects on the column behavior.In particular,geometric parameters(including cross-sectional characteristics,boundary conditions and column length)have major effect on the corresponding column response,in the same way of input blast load parameters and material properties.展开更多
The essence of academic freedom lies in scholars’autonomy in the pursuit of knowledge,free from external coercion and internal constraints,encompassing various aspects such as freedom of research,teaching,and learnin...The essence of academic freedom lies in scholars’autonomy in the pursuit of knowledge,free from external coercion and internal constraints,encompassing various aspects such as freedom of research,teaching,and learning.Leadership plays a crucial role in safeguarding academic freedom.Drawing on Macfarlane’s conceptualization of intellectual leadership,this article examines faculty-based agency protection,as well as institutional,cultural,and resource-based protections at the university level.展开更多
The interaction between regular waves and an oscillating wave energy converter(WEC)in front of a vertical seawall is investigated using a 2D analytical model.A three-degree of freedom(DOF)WEC and a WEC hinged to the s...The interaction between regular waves and an oscillating wave energy converter(WEC)in front of a vertical seawall is investigated using a 2D analytical model.A three-degree of freedom(DOF)WEC and a WEC hinged to the seawall(constrained to pitch mode)are considered to examine the influence of the DOF of the WEC on the wave energy extraction performance.Results show that the piston-mode water resonance in the gap and the coupled WEC and water column resonant motion significantly influence the wave energy extraction efficiency.At low frequency,the case with a 3-DOF WEC has a broader high-efficiency bandwidth than that with a heaving WEC.However,3-DOF WEC exhibits worse performance at high frequencies.The frequency response of the wave energy capture width ratio(CWR)for the pitching WEC case shows a trimodal trend under the specified conditions.It showcases the best overall wave energy extraction performance in terms of the high-efficiency bandwidth.Furthermore,a parametric study indicates that the gap distance between the WEC and the seawall has tremendous effects on the CWR of both cases.As the position of the hinge point of the pitching WEC changes,the CWR at the low and high frequencies shows opposite trends.展开更多
A floating horizontal-axis tidal current turbine(HATT)is an underwater power generation device where cavitation inevitably occurs on blade surfaces,severely affecting a turbine’s lifespan.Under wave action,these floa...A floating horizontal-axis tidal current turbine(HATT)is an underwater power generation device where cavitation inevitably occurs on blade surfaces,severely affecting a turbine’s lifespan.Under wave action,these floating turbines exhibit six degrees of freedom motion,potentially intensifying the cavitation on the blade surfaces.This study selects three types of oscillatory motions from the six degrees of freedom:roll,yaw,and pitch.Computational fluid dynamics(CFD)methods are used for numerical calculations,and transient simulations of multiphase flow are conducted on the basis of the Reynolds-Averaged Navier-Stokes(RANS)model.Research has revealed strong correlations between flow velocity,the blade tip speed ratio,and cavitation.During oscillatory motion,the motion period and amplitude also significantly impact cavitation.In roll motion,the cavitation rate can increase by up to 59%with decreasing period,whereas in pitch and yaw motions,the increases are 7.57 times and 36%larger,respectively.With an increase in amplitude during roll motion,the cavitation rate can increase by up to 1.08 times,whereas in pitch and yaw motions,the increases are 3.49 times and 45%,respectively.The cavitation rate on the blade surfaces is the highest in pitch motion,followed by roll and yaw motions.展开更多
Non-uniform linear array(NULA)configurations are well renowned due to their structural ability for providing increased degrees of freedom(DOF)and wider array aperture than uniform linear arrays(ULAs).These characteris...Non-uniform linear array(NULA)configurations are well renowned due to their structural ability for providing increased degrees of freedom(DOF)and wider array aperture than uniform linear arrays(ULAs).These characteristics play a significant role in improving the direction-of-arrival(DOA)estimation accuracy.However,most of the existing NULA geometries are primarily applicable to circular sources(CSs),while they limitedly improve the DOF and continuous virtual aperture for noncircular sources(NCSs).Toward this purpose,we present a triaddisplaced ULAs(Tdis-ULAs)configuration for NCS.The TdisULAs structure generally consists of three ULAs,which are appropriately placed.The proposed antenna array approach fully exploits the non-circular characteristics of the sources.Given the same number of elements,the Tdis-ULAs design achieves more DOF and larger hole-free co-array aperture than its sparse array competitors.Advantageously,the number of uniform DOF,optimal distribution of elements among the ULAs,and precise element positions are uniquely determined by the closed-form expressions.Moreover,the proposed array also produces a filled resulting co-array.Numerical simulations are conducted to show the performance advantages of the proposed Tdis-ULAs configuration over its counterpart designs.展开更多
The reduced weight and improved efficiency of modern aeronautical structures result in a decreasing separation of frequency ranges of rigid and elastic modes.Particularly,a high-aspect-ratio flexible flying wing is pr...The reduced weight and improved efficiency of modern aeronautical structures result in a decreasing separation of frequency ranges of rigid and elastic modes.Particularly,a high-aspect-ratio flexible flying wing is prone to body freedomflutter(BFF),which is a result of coupling of the rigid body short-periodmodewith 1st wing bendingmode.Accurate prediction of the BFF characteristics is helpful to reflect the attitude changes of the vehicle intuitively and design the active flutter suppression control law.Instead of using the rigid body mode,this work simulates the rigid bodymotion of the model by using the six-degree-of-freedom(6DOF)equation.A dynamicmesh generation strategy particularly suitable for BFF simulation of free flying aircraft is developed.An accurate Computational Fluid Dynamics/Computational Structural Dynamics/six-degree-of-freedom equation(CFD/CSD/6DOF)-based BFF prediction method is proposed.Firstly,the time-domain CFD/CSD method is used to calculate the static equilibrium state of the model.Based on this state,the CFD/CSD/6DOF equation is solved in time domain to evaluate the structural response of themodel.Then combinedwith the variable stiffnessmethod,the critical flutter point of the model is obtained.This method is applied to the BFF calculation of a flyingwing model.The calculation results of the BFF characteristics of the model agree well with those fromthe modalmethod andNastran software.Finally,the method is used to analyze the influence factors of BFF.The analysis results show that the flutter speed can be improved by either releasing plunge constraint or moving the center ofmass forward or increasing the pitch inertia.展开更多
Degree of freedom(DOF)is a key indicator for spatial multiplexing layers of a wireless channel.Traditionally,the channel of a multiple-input multiple-output(MIMO)half-wavelength dipole array has a DOF that equals the ...Degree of freedom(DOF)is a key indicator for spatial multiplexing layers of a wireless channel.Traditionally,the channel of a multiple-input multiple-output(MIMO)half-wavelength dipole array has a DOF that equals the antenna number.However,recent studies suggest that the DOF could be less than the antenna number when strong mutual coupling is considered.We utilize a mutual-coupling-compliant channel model to investigate the DOF of the holographic MIMO(HMIMO)channel and give a upper bound of the DOF with strong mutual coupling.Our numerical simulations demonstrate that a dense array can support more DOF per unit aperture as compared with a half-wavelength MIMO system.展开更多
The thesis analyzes and comments on the two main characters in The Adventure of Huckleberry Finn so as to reveal the truth that to win both physical and psychological freedom in the society, we must learn to stand on ...The thesis analyzes and comments on the two main characters in The Adventure of Huckleberry Finn so as to reveal the truth that to win both physical and psychological freedom in the society, we must learn to stand on ourselves. It begins with a brief introduction to the author, the novel and the paper thesis. Then, the author discloses the freedom-fighting process of the two main characters and the functions of Mississippi River and the raft in The Adventure of Huckleberry Finn: On the hegira,Huck realizes the cruelty, greed, murder, trickery, hypocrisy, racism, and a general lack of morality of the society; Jim, with his in telligence and compassion, wins his freedom; the Mississippi River and the raft are symbols of freedom. Finally, the author reveals that to win both physical and psychological freedom, one must rely on his or her own efforts.展开更多
In The Portrait of a Lady, Isabel Archer values her liberty higher than a sense of security that might be guaranteed by possessing great fortune. But there are some paradoxes in Isabel Archer's view of freedom, wh...In The Portrait of a Lady, Isabel Archer values her liberty higher than a sense of security that might be guaranteed by possessing great fortune. But there are some paradoxes in Isabel Archer's view of freedom, which have caused her failure in the fulfillment of her view of freedom.展开更多
Any understanding of America must come to terms with its central value and ideal.Freedom is such an influential val ue as well as one of the core values of American culture.It remains the sole basis for American socie...Any understanding of America must come to terms with its central value and ideal.Freedom is such an influential val ue as well as one of the core values of American culture.It remains the sole basis for American society as we know.Without free dom the great nation of America would never have been founded.This paper tries to explore freedom as a value and its manifesta tion in USA from four aspects:politics,religion,speech and academics.展开更多
This essay aims at an analysis of Murphy's failure of his quest for freedom from the aspect of narrative temporality whichwill focus on order, duration and frequency. From the perspective of temporal order, the es...This essay aims at an analysis of Murphy's failure of his quest for freedom from the aspect of narrative temporality whichwill focus on order, duration and frequency. From the perspective of temporal order, the essay will endeavor to probe into the pro-lepsis in the novel to analyse predetermined narrative and its function. Considering with temporal duration, this essay will penetratethe deceleration of narrative—scene and pause in Murphy to explore its thematic meaning. To investigate the temporal frequency,iterative narrative within text will be exemplified to discuss closed systems in the novel. Based on the analysis of the narrativity tem-porality in Murphy, the essay will focuses on that how its narrative strategy well embodies its theme—the predetermined failure ofMurphy's quest for freedom in closed systems.展开更多
1. Often blacks were not allowed intohotels, schools or libraries at all. (Page 28)【考点】allow的用法【归纳】allow 意为"允许, 准许"。用法有:allow sth. doing sth.allow sb. to do sth.allow sb. sth.allow for +...1. Often blacks were not allowed intohotels, schools or libraries at all. (Page 28)【考点】allow的用法【归纳】allow 意为"允许, 准许"。用法有:allow sth. doing sth.allow sb. to do sth.allow sb. sth.allow for +n. (考虑, 顾及) / doing / obj.+展开更多
Increasing degrees of freedom(DOFs)is a useful way to raise the power capture efficiency of oscillating wave energy converters.Thus,this study proposes a buoy with three DOFs,which are surge,heave,and pitch.The hydrod...Increasing degrees of freedom(DOFs)is a useful way to raise the power capture efficiency of oscillating wave energy converters.Thus,this study proposes a buoy with three DOFs,which are surge,heave,and pitch.The hydrodynamic performance and power capture efficiency of the buoy is physically modeled.Amplitudes of unidirectional and coupled motions are compared to analyze the interaction effect between freedoms under conditions with and without power take-off damping.The capture width ratio and corresponding growth rates are also calculated.Results show that the buoy makes a periodic sinusoidal(or approximate)movement in every DOF.Coupling effect can cause an increase in the amplitude in one DOF and a decrease in the amplitudes of the others.This phenomenon shows that the kinematic energy of the buoy redistributes to all DOFs compared with the unidirectional conditions.Adding DOFs can improve the power absorption of the buoy in most cases,but the number of DOFs is not the more the better.展开更多
A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced...A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced to design the internal model controller,and a desired closed-loop transfer function is designed to eliminate the unrealizable factors of the derived controller. In addition,set-point tracking and load-disturbance rejection of each process are separately controlled by two controllers. The simulation results show that in addition to high decoupling performance and robustness,the proposed control method also effectively improves loaddisturbance rejection and simultaneously optimizes the input tracking performance and disturbance rejection performance by selecting the parameters of controllers. Furthermore,the higher tolerance of model mismatch is achieved in this paper.展开更多
文摘Padma was 17 when the democratic reform was introduced in Xizang in 1959.Before the reform,the region had been ruled by feudal serfdom under a theocracy for centuries.Nearly one million serfs were subjected to estate-holders'cruel exploitation and oppression.Padma was one of them.
文摘“civil discourse”amongst multiple individuals with diverse viewpoints is necessary to move toward truth,to maintain democratic buoyancy,and to get the most accurate read on how best to move forward toward our collective good,civil discourse is nonetheless under catastrophic threat by contemporary forces that include the sloppy use of the term“hate speech”;the“libelling by labeling”(aka“cancelling”)in the public square of social media;technologically powered disinformation campaigns;and the growth of“safetyism”in academia.In light of these threats,the goal must be to convince educators,particularly philosophical educators,of the need to adopt a whole new focus in education,namely one that puts a spotlight on the fact that the utilization of the freedom of speech to destroy the freedom of speech of others utterly undermines the positive value of freedom of speech.In order to motivate individuals to turn their back on the dopamine rush of shutting someone down,educators must also spend a great deal of time showcasing the merits of“civil discourse”by providing young people with extensive experience in engaging in facilitated“civil discourse”(aka Communities of Philosophical Inquiry)so that its value can be woven into a personal commitment.
基金Guiding Science and Technology Program Project of Yichang City in 2024(Project No.:B24-2-002)。
文摘Objective:This study aimed to explore the effect of aromatherapy combined with emotional release technology on recurrence fear and sleep quality of lung cancer survivors.Methods:114 cases of lung cancer survivors were divided into routine nursing group,emotional release technology group and aromatherapy combined with emotional release technology group.Routine nursing group received routine nursing;Emotional release technology group implemented emotional release technology for one month on the basis of routine nursing group;Aromatherapy combined with emotional release technology group used lavender aromatherapy on the basis of emotional release technology group.Results:After one month of intervention,there were statistically significant differences in the scores of fear of disease progression and sleep quality among the three groups.Conclusion:Aromatherapy combined with emotional release technology can improve the sleep quality of lung cancer survivors and reduce the economic toxicity of cancer to some extent.
基金funded by the National College Students Innovation and Entrepreneurship Training Program(202411646031)the Zhejiang Xinmiao Talents Program(2024R405A052)the SRIP Research Program of Ningbo University(2025SRIP1707).
文摘The dynamic behavior of high-speed craft navigating through variable sea states plays a pivotal role in ensuring maritime safety.However,many existing simulation approaches rely on linear or overly simplified representations of the marine environment,thereby limiting the fidelity of motion predictions.This study explores the motion characteristics of a 4.5-t high-speed vessel by conducting fully coupled numerical simulations using the STAR-CCM+software.The analysis considers both calm and varying sea conditions,incorporating fluctuations in wave height,wavelength,and wind speed to reflect more realistic operating scenarios.Simulation results reveal that the vessel’s hydrodynamic response is highly sensitive to changes in sea state.As conditions deteriorate,the free surface becomes increasingly complex,with higher wave amplitudes and more pronounced interactions between the waves generated by the vessel and those imposed by the external environment.These effects lead to significant increases in roll,pitch,heave,and sway motions,thereby imposing greater demands on the vessel’s dynamic stability and operational safety.Furthermore,both hydrodynamic resistance and propulsive thrust exhibit notable dependence on sea state and vessel speed.Total resistance generally increases with rougher sea conditions,while thrust tends to rise with increasing forward speed.Under calm or mildly disturbed waters,a Froude number(Fr)of 0.5 appears to offer an optimal balance for initiating and controlling primary motions such as roll,pitch,heave,and sway.Conversely,in more challenging conditions-such as those represented by a Sea State 3-effective motion control is better achieved at a higher Froude number of approximately 1.0.
文摘This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(SDOF)and the experimentally validated Finite Element(FE)methods(LSDYNA).For this purpose,special atten-tion is given to calculating the response of H-shaped steel columns under blast.The damage amount is determined based on the support rotation criterion,which is expressed as a function of their maximum lateral mid-span dis-placement.To account for uncertainties in input parameters and obtain the failure probability,the Monte Carlo simulation(MCS)method is employed,complemented by the Latin Hypercube Sampling(LHS)method to reduce the number of simulations.A parametric analysis is hence performed to examine the effect of several input pa-rameters(including both deterministic and probabilistic parameters)on the probability of column damage as a function of support rotation.First,the MSDOF method confirms its higher accuracy in estimating the probability of column damage due to blast,compared to the conventional SDOF.The collected results also show that un-certainties of several input parameters have significant effects on the column behavior.In particular,geometric parameters(including cross-sectional characteristics,boundary conditions and column length)have major effect on the corresponding column response,in the same way of input blast load parameters and material properties.
文摘The essence of academic freedom lies in scholars’autonomy in the pursuit of knowledge,free from external coercion and internal constraints,encompassing various aspects such as freedom of research,teaching,and learning.Leadership plays a crucial role in safeguarding academic freedom.Drawing on Macfarlane’s conceptualization of intellectual leadership,this article examines faculty-based agency protection,as well as institutional,cultural,and resource-based protections at the university level.
基金supported by the Key R&D Program of Shandong Province,China(No.2021ZLGX04)the National Natural Science Foundation of China(No.52171284)。
文摘The interaction between regular waves and an oscillating wave energy converter(WEC)in front of a vertical seawall is investigated using a 2D analytical model.A three-degree of freedom(DOF)WEC and a WEC hinged to the seawall(constrained to pitch mode)are considered to examine the influence of the DOF of the WEC on the wave energy extraction performance.Results show that the piston-mode water resonance in the gap and the coupled WEC and water column resonant motion significantly influence the wave energy extraction efficiency.At low frequency,the case with a 3-DOF WEC has a broader high-efficiency bandwidth than that with a heaving WEC.However,3-DOF WEC exhibits worse performance at high frequencies.The frequency response of the wave energy capture width ratio(CWR)for the pitching WEC case shows a trimodal trend under the specified conditions.It showcases the best overall wave energy extraction performance in terms of the high-efficiency bandwidth.Furthermore,a parametric study indicates that the gap distance between the WEC and the seawall has tremendous effects on the CWR of both cases.As the position of the hinge point of the pitching WEC changes,the CWR at the low and high frequencies shows opposite trends.
基金supported by the National Natural Science Foundation of China(Grant No.52171261).
文摘A floating horizontal-axis tidal current turbine(HATT)is an underwater power generation device where cavitation inevitably occurs on blade surfaces,severely affecting a turbine’s lifespan.Under wave action,these floating turbines exhibit six degrees of freedom motion,potentially intensifying the cavitation on the blade surfaces.This study selects three types of oscillatory motions from the six degrees of freedom:roll,yaw,and pitch.Computational fluid dynamics(CFD)methods are used for numerical calculations,and transient simulations of multiphase flow are conducted on the basis of the Reynolds-Averaged Navier-Stokes(RANS)model.Research has revealed strong correlations between flow velocity,the blade tip speed ratio,and cavitation.During oscillatory motion,the motion period and amplitude also significantly impact cavitation.In roll motion,the cavitation rate can increase by up to 59%with decreasing period,whereas in pitch and yaw motions,the increases are 7.57 times and 36%larger,respectively.With an increase in amplitude during roll motion,the cavitation rate can increase by up to 1.08 times,whereas in pitch and yaw motions,the increases are 3.49 times and 45%,respectively.The cavitation rate on the blade surfaces is the highest in pitch motion,followed by roll and yaw motions.
基金supported by the National Natural Science Foundation of China(62031017,61971221)the Fundamental Research Funds for the Central Universities of China(NP2020104)。
文摘Non-uniform linear array(NULA)configurations are well renowned due to their structural ability for providing increased degrees of freedom(DOF)and wider array aperture than uniform linear arrays(ULAs).These characteristics play a significant role in improving the direction-of-arrival(DOA)estimation accuracy.However,most of the existing NULA geometries are primarily applicable to circular sources(CSs),while they limitedly improve the DOF and continuous virtual aperture for noncircular sources(NCSs).Toward this purpose,we present a triaddisplaced ULAs(Tdis-ULAs)configuration for NCS.The TdisULAs structure generally consists of three ULAs,which are appropriately placed.The proposed antenna array approach fully exploits the non-circular characteristics of the sources.Given the same number of elements,the Tdis-ULAs design achieves more DOF and larger hole-free co-array aperture than its sparse array competitors.Advantageously,the number of uniform DOF,optimal distribution of elements among the ULAs,and precise element positions are uniquely determined by the closed-form expressions.Moreover,the proposed array also produces a filled resulting co-array.Numerical simulations are conducted to show the performance advantages of the proposed Tdis-ULAs configuration over its counterpart designs.
基金This work was supported by the National Natural Science Foundation of China(No.11872212)and a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘The reduced weight and improved efficiency of modern aeronautical structures result in a decreasing separation of frequency ranges of rigid and elastic modes.Particularly,a high-aspect-ratio flexible flying wing is prone to body freedomflutter(BFF),which is a result of coupling of the rigid body short-periodmodewith 1st wing bendingmode.Accurate prediction of the BFF characteristics is helpful to reflect the attitude changes of the vehicle intuitively and design the active flutter suppression control law.Instead of using the rigid body mode,this work simulates the rigid bodymotion of the model by using the six-degree-of-freedom(6DOF)equation.A dynamicmesh generation strategy particularly suitable for BFF simulation of free flying aircraft is developed.An accurate Computational Fluid Dynamics/Computational Structural Dynamics/six-degree-of-freedom equation(CFD/CSD/6DOF)-based BFF prediction method is proposed.Firstly,the time-domain CFD/CSD method is used to calculate the static equilibrium state of the model.Based on this state,the CFD/CSD/6DOF equation is solved in time domain to evaluate the structural response of themodel.Then combinedwith the variable stiffnessmethod,the critical flutter point of the model is obtained.This method is applied to the BFF calculation of a flyingwing model.The calculation results of the BFF characteristics of the model agree well with those fromthe modalmethod andNastran software.Finally,the method is used to analyze the influence factors of BFF.The analysis results show that the flutter speed can be improved by either releasing plunge constraint or moving the center ofmass forward or increasing the pitch inertia.
基金supported in part by National Key Research and Develop⁃ment Program of China under Grant No.2020YFB1807600.
文摘Degree of freedom(DOF)is a key indicator for spatial multiplexing layers of a wireless channel.Traditionally,the channel of a multiple-input multiple-output(MIMO)half-wavelength dipole array has a DOF that equals the antenna number.However,recent studies suggest that the DOF could be less than the antenna number when strong mutual coupling is considered.We utilize a mutual-coupling-compliant channel model to investigate the DOF of the holographic MIMO(HMIMO)channel and give a upper bound of the DOF with strong mutual coupling.Our numerical simulations demonstrate that a dense array can support more DOF per unit aperture as compared with a half-wavelength MIMO system.
文摘The thesis analyzes and comments on the two main characters in The Adventure of Huckleberry Finn so as to reveal the truth that to win both physical and psychological freedom in the society, we must learn to stand on ourselves. It begins with a brief introduction to the author, the novel and the paper thesis. Then, the author discloses the freedom-fighting process of the two main characters and the functions of Mississippi River and the raft in The Adventure of Huckleberry Finn: On the hegira,Huck realizes the cruelty, greed, murder, trickery, hypocrisy, racism, and a general lack of morality of the society; Jim, with his in telligence and compassion, wins his freedom; the Mississippi River and the raft are symbols of freedom. Finally, the author reveals that to win both physical and psychological freedom, one must rely on his or her own efforts.
文摘In The Portrait of a Lady, Isabel Archer values her liberty higher than a sense of security that might be guaranteed by possessing great fortune. But there are some paradoxes in Isabel Archer's view of freedom, which have caused her failure in the fulfillment of her view of freedom.
文摘Any understanding of America must come to terms with its central value and ideal.Freedom is such an influential val ue as well as one of the core values of American culture.It remains the sole basis for American society as we know.Without free dom the great nation of America would never have been founded.This paper tries to explore freedom as a value and its manifesta tion in USA from four aspects:politics,religion,speech and academics.
文摘This essay aims at an analysis of Murphy's failure of his quest for freedom from the aspect of narrative temporality whichwill focus on order, duration and frequency. From the perspective of temporal order, the essay will endeavor to probe into the pro-lepsis in the novel to analyse predetermined narrative and its function. Considering with temporal duration, this essay will penetratethe deceleration of narrative—scene and pause in Murphy to explore its thematic meaning. To investigate the temporal frequency,iterative narrative within text will be exemplified to discuss closed systems in the novel. Based on the analysis of the narrativity tem-porality in Murphy, the essay will focuses on that how its narrative strategy well embodies its theme—the predetermined failure ofMurphy's quest for freedom in closed systems.
文摘1. Often blacks were not allowed intohotels, schools or libraries at all. (Page 28)【考点】allow的用法【归纳】allow 意为"允许, 准许"。用法有:allow sth. doing sth.allow sb. to do sth.allow sb. sth.allow for +n. (考虑, 顾及) / doing / obj.+
基金the support of the National Key R&D Program of China (No. 2018YFB1501900)the National Natural Science Fund of China (No. 41706100)+3 种基金the Shandong Provincial Natural Science Key Basic Program (No. ZR2017ZA 0202)the Special Projects for Marine Renewable Energy (No. GHME2016YY02)the Shandong Provincial Key Laboratory of Ocean Engineeringthe Qingdao Municipal Key Laboratory of Ocean Renewable Energy
文摘Increasing degrees of freedom(DOFs)is a useful way to raise the power capture efficiency of oscillating wave energy converters.Thus,this study proposes a buoy with three DOFs,which are surge,heave,and pitch.The hydrodynamic performance and power capture efficiency of the buoy is physically modeled.Amplitudes of unidirectional and coupled motions are compared to analyze the interaction effect between freedoms under conditions with and without power take-off damping.The capture width ratio and corresponding growth rates are also calculated.Results show that the buoy makes a periodic sinusoidal(or approximate)movement in every DOF.Coupling effect can cause an increase in the amplitude in one DOF and a decrease in the amplitudes of the others.This phenomenon shows that the kinematic energy of the buoy redistributes to all DOFs compared with the unidirectional conditions.Adding DOFs can improve the power absorption of the buoy in most cases,but the number of DOFs is not the more the better.
基金Sponsored by the Fundamental Research Funds for the Central Universities(Grant No.N110304008)the National Natural Science Foundation of China(Grant No.61374137)
文摘A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced to design the internal model controller,and a desired closed-loop transfer function is designed to eliminate the unrealizable factors of the derived controller. In addition,set-point tracking and load-disturbance rejection of each process are separately controlled by two controllers. The simulation results show that in addition to high decoupling performance and robustness,the proposed control method also effectively improves loaddisturbance rejection and simultaneously optimizes the input tracking performance and disturbance rejection performance by selecting the parameters of controllers. Furthermore,the higher tolerance of model mismatch is achieved in this paper.
