Arginine (2-amino-5-guanidino pentanoic acid) was shown in 1895 by Hedin to be present in the proteins of horn. Metabolic nitrogen balance studies, conducted in 1957 by Rose in human adults and in 1959 by Snyderman an...Arginine (2-amino-5-guanidino pentanoic acid) was shown in 1895 by Hedin to be present in the proteins of horn. Metabolic nitrogen balance studies, conducted in 1957 by Rose in human adults and in 1959 by Snyderman and coworkers in young infants, revealed that a dietary source of this amino acid was not an obligatory requirement for growth and maintenance of nitrogen homeostasis in healthy individuals. Hence, It was initially classified as a non-essential (dispensable) amino acid and, perhaps, for reasons of this classification arginine did not receivc the earlier atteniion it now deserves, in relation to an understanding of the nutritional biochemistry and physiology of its metabolism in humans subjects. However, there is currently a considerable interest in the cellular and tissue functions, as well as clinical, therapeutic significance, of arginine. In this paper we review the multiple functions of arginlne, including its role in the L-arginine-nitric oxide pathway,cellular regeneration, immune function, protein synthesis and protein breakdown. We then consider some in vivo aspects of the physiology of arginine metabolism, which varies greatly among eukaryotes, with particular reference to humans. Against this background, studies of arginine in the nutrition of humans under various pathophysiological conditions are reviewed briefly. Finally, a new, updated concept for the metabolic basis for the 'conditional essentiality' of arginine is proposed展开更多
Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom,were considered.This problem of diffraction by th...Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom,were considered.This problem of diffraction by these two cylinders,which were considered as idealization of a buoy and a circular plate,can be considered as a wave energy device.The wave energy that is created and transferred by this device can be appropriately used in many applications in lieu of conventional energy.Method of separation of variables was used to obtain the analytical expressions for the diffracted potentials in four clearly identified regions.By applying the appropriate matching conditions along the three virtual boundaries between the regions,a system of linear equations was obtained,which was solved for the unknown coefficients.The potentials allowed us to obtain the exciting forces acting on both cylinders.Sets of exciting forces were obtained for different radii of the cylinders and for different gaps between the cylinders.It was observed that changes in radius and the gap had significant effect on the forces.It was found that mostly the exciting forces were significant only at lower frequencies.The exciting forces almost vanished at higher frequencies.The problem was also investigated for the base case of no plate arrangement,i.e.,the case having only the floating cylinder tethered to the sea-bed.Comparison of forces for both arrangements was carried out.In order to take care of the radiation of the cylinders due to surge motion,the corresponding added mass and the damping coefficients for both cylinders were also computed.All the results were depicted graphically and compared with available results.展开更多
A hydraulic exciting system with a wave exciter has been constructed in order to study the hydraulic vibra- tion law. The system consists of an oil source, wave-exciter and oil cylinder, and is controlled by a wave-ex...A hydraulic exciting system with a wave exciter has been constructed in order to study the hydraulic vibra- tion law. The system consists of an oil source, wave-exciter and oil cylinder, and is controlled by a wave-exciter. The working principle of the hydraulic exciting system and wave exciter has been analyzed, and its excitation process has been illustrated. The law of every pipe＇s pressure fluctuation of the system is obtained by experiment. The theo- retical analysis and experimental data prove that the pipeline pressure periodically changes and the pipeline pressure fluctuation frequency is independently controlled by the excitation frequency of the wave-exciter. Every pipelinc＇s pressure wave is produced by system flow fluctuation and water hammer coupling. The pressure fluctuation rules of the system provide a theoretical basis for the study of the associated liberation system.展开更多
In this paper, the homology of four radio bursts occuring on August 28, 1989 are discussed in time domain, in frequency domain and in their exciting functions.From the discussions, it may be possible that if two radio...In this paper, the homology of four radio bursts occuring on August 28, 1989 are discussed in time domain, in frequency domain and in their exciting functions.From the discussions, it may be possible that if two radio bursts are homologus, then their ratios of the duration time for rising phases, decaying phases and total bursts are similar in time domain, so do their exciting functions. Therefore they resemble each other in their Fourier apectra.展开更多
Ground-borne vibrations caused by vibration sources such as road traffic and construction exhibit complicated properties during propagation from the vibration source to the inside of a building. In the present paper, ...Ground-borne vibrations caused by vibration sources such as road traffic and construction exhibit complicated properties during propagation from the vibration source to the inside of a building. In the present paper, a numerical analysis technique for the system of vibration source and propagation path of ground vibration is developed in order to systematically determine the propagation properties of the vibration as part of developing a predictive technique for exposure evaluations by vibrations in three directions at receiving points of vibration in the human body. First, the exciting forces in three directions for input into the numerical computation are inversely-estimated by using the measured acceleration rec- ords of the measurement points, which are near the vibration source. The thin-layered element method is used for numerical computation of the ground vibration. Then, the calculation results for the ground vibration obtained by using the estimated exciting force are compared with the measured results, and the influence of the stratified structure of the ground on the exciting force and the propagation properties of the ground vibration are studied. From these results, in a prediction of the ground vibration in three directions, it is emphasized that it is necessary to consider the influence of horizontal exciting force, although attention has been paid to only the vertical exciting force for simulating ground vibration.展开更多
One Wednesday morning 1 eleven o'clock, Tom was walking down Main Street. 2 he heard the sound of gun (手枪), he 3 the sound must come from the bank. He ran to the bank and 4 a man coming out of the bank.
One Wednesday morning 1 eleven o'clock, Tom was walking down Main Street. 2 he heard the sound of gun (手枪), he 3 the sound must come from the bank.He ran to the bank and 4 a man coming out of the bank. The man w...One Wednesday morning 1 eleven o'clock, Tom was walking down Main Street. 2 he heard the sound of gun (手枪), he 3 the sound must come from the bank.He ran to the bank and 4 a man coming out of the bank. The man was 5 and fat 6 red hair.What's more,he carried a bag and a gun in his hand. Before Tom could do _7_,he had run into the street and disappeared(消失)among people.展开更多
The vibration response formulas of the mechanical system under the affect of thevari-frequency exciting force are deduced. It is proved by the theoretical analysis and experimentalresults that the vibration response a...The vibration response formulas of the mechanical system under the affect of thevari-frequency exciting force are deduced. It is proved by the theoretical analysis and experimentalresults that the vibration response amplitude of the mechanical system under the affect of thevari-frequency exciting force is far smaller than that under the affect of the constant frequency exciting force on condition that the exciting force amplitudes are just the same;while the vari-fre-quency rate a increases to 5 Hz per second the vibration amplitude will decrease to 10% only as lowas that under the affect of the constant frequency exciting force. All these conclusions will be of significance for revealing the mechanism of suppressing chatter in van-speed cutting and analyzing theexperimental results of sine-wave scanning exciting test.展开更多
Chaoyang Theatre is famous for presenting acrobatic shows in Beijing. For Sichuan Suining Acrobatic Troupe, the performance here in the theatre is as usually-fully seated and most audiences are tourists from abroad. H...Chaoyang Theatre is famous for presenting acrobatic shows in Beijing. For Sichuan Suining Acrobatic Troupe, the performance here in the theatre is as usually-fully seated and most audiences are tourists from abroad. However,展开更多
"Teacher, what are we going to do next class?" This is an exciting question which I often hear from my students. As an English conversation teacher, I can make the learning of English either a dull and borin..."Teacher, what are we going to do next class?" This is an exciting question which I often hear from my students. As an English conversation teacher, I can make the learning of English either a dull and boring duty, or an exciting adventure. It is very important that I make my students hate missing my class, and keep them guessing just what will happen the next time! Let us consider some important ways that any teacher can help his other students want to do展开更多
Vibration cementing is a new technique that can significantly improve the bond strength of cementing interface.To popularize this technique,it is necessary to solve the key problem of how to make cementing string gene...Vibration cementing is a new technique that can significantly improve the bond strength of cementing interface.To popularize this technique,it is necessary to solve the key problem of how to make cementing string generate downhole radial vibration in the WOC stage.For this purpose,an electric vibrator was developed.With this vibrator,electric energy is converted into mechanical energy by means of a high-temperature motor vibration unit.The motor vibration unit rotates the eccentric block through an output shaft to generate an exciting source,which produces an axial-rotating exciting force at the bottom of the casing string.Then,the vibration characteristics of vertical well casing string under the exciting force were analyzed by using the principal coordinate analysis method,and the response model of casing string to an electric vibrator was developed.Finally,the effects of casing string length,exciting force and vibration frequency on the vibration amplitude at the lowermost of the casing string were analyzed based on a certain casing program.It is indicated that the casing string length and the square of vibration frequency are inversely proportional to the vibration amplitude at the lowermost of the casing string,and the exciting force is proportional to the vibration amplitude at the lowermost of the casing string.These research results provide a theoretical support for the application of vibration cementing technology to the cementing sites with different requirements on well depth and amplitude.展开更多
Due to the dynamical character of electromagnetic exciter and the coupling between structure and exciter(s),the actual output force acting on the structure is usually not equal to the exact value that is supposed to b...Due to the dynamical character of electromagnetic exciter and the coupling between structure and exciter(s),the actual output force acting on the structure is usually not equal to the exact value that is supposed to be,especially when multi-exciters are used as actuators to precisely actuate large flexible structure.It is necessary to consider these effects to ensure the force generated by each exciter is the same as required.In this paper,a robust control method is proposed for the multi-input and multi-output(MIMO)structural vibration control system to trace the target actuating force of each exciter.A special signal is designed and put into the coupled mul-ti-exciter-structure system,and the input and output signals of the system are used to build a dynamic model involving both the dynamical characters of the exciters and the structure using the subspace identification method.Considering the uncertainty factors of the multi-exciter/structure system,an H-infinity robust controller is designed to decouple the coupling between structure and exciters based on the identified system model.A MIMO vibration control system combined with a flexible plate and three electromagnetic exciters is adopted to demonstrate the proposed method,both numerical simulation and model experiments showing that the output force of each exciter can trace its target force accurately within the requested frequency band.展开更多
The fluorescence imaging (FLI) in the second near-infrared window (NIR-II, 1000–1700nm) has attracted considerable attention in the past decade. In contrast to conventional NIR-I window excitation (808nm/980nm), FLI ...The fluorescence imaging (FLI) in the second near-infrared window (NIR-II, 1000–1700nm) has attracted considerable attention in the past decade. In contrast to conventional NIR-I window excitation (808nm/980nm), FLI with NIR-II window excitation (1064nm/other wavelength beyond 1000nm) can afford deeper tissue penetration depth with high clarity due to the merits of suppressed photon scattering and diminished autofluorescence. In this review, we have summarized NIR-II window excitable/emissive organic/polymeric fluorophores recently developed. The characteristics of these fluorophores such as chemical structures and photophysical properties have also been critically discussed. Furthermore, the latest development of noninvasive in vivo FLI with NIR-II excitation was highlighted. The ideal imaging results emphasized the importance of NIR-II excitation of these fluorophores in enabling deep tissue penetration and high-resolution imaging. Finally, a perspective on the challenges and prospects of NIR-II excitable/emissive organic/polymeric fluorophores was also discussed. We expected this review will be served as a source of inspiration for researchers, stimulating the creation of novel NIR-II excitable fluorophores and fostering the development of bioimaging applications.展开更多
The dissolved organic matter(DOM)with high mobility and reactivity plays a crucial role in soil.In this study,the characteristics and phytotoxicity ofDOMreleased fromthe hydrochars prepared from different feedstocks(c...The dissolved organic matter(DOM)with high mobility and reactivity plays a crucial role in soil.In this study,the characteristics and phytotoxicity ofDOMreleased fromthe hydrochars prepared from different feedstocks(cowmanure,corn stalk and Myriophyllum aquaticum)under three hydrothermal carbonization(HTC)temperatures(180,200 and 220°C)were evaluated.The results showed that the hydrochars had high dissolved organic carbon content(20.15 to 37.65 mg/g)and its content showed a gradual reduction as HTC temperature increased.Three fluorescent components including mixed substance of fulvic acid-like and humic acid-like substances(C1,30.92%-58.32%),UVA humic acid-like substance(C2,25.27%-29.94%)and protein-like substance(C3,11.74%-41.92%)were identified in hydrochar DOM by excitation emission matrix spectra coupled with parallel factor analysis.High HTC temperature increased the relative proportion of aromatic substances(C1+C2)and humification degree of hydrochar DOM from cow manure,while it presented adverse effects on the hydrochar DOM from corn stalk and Myriophyllum.aquaticum.The principal component analysis suggested that feedstock type and HTC temperature posed significant effects on the characteristics of hydrochar DOM.Additionally,seed germination test of all hydrochar DOM demonstrated that the root length was reduced by 8.88%-26.43%in contrast with control,and the germination index values were 73.57%-91.12%.These findings provided new insights into the potential environmental effects for hydrochar application in soil.展开更多
Ⅰ. INTRODUCTION By using degenerate four-wave mixing (DFWM) method, the third-order nonlinear optical susceptibility of transparent media can be conventionally measured. Nonlinear properties of media in ground state ...Ⅰ. INTRODUCTION By using degenerate four-wave mixing (DFWM) method, the third-order nonlinear optical susceptibility of transparent media can be conventionally measured. Nonlinear properties of media in ground state are well known, but those in exciting state are less studied. When a medium absorbs incident radiation, a part of population can be excited into high exciting state. In DFWM this resonant enhancement effect can be used to increase the third-展开更多
The living world remains a mystery with many exciting discoveries awaiting scientists. My interest in observing living phenomena dates back to my childhood. I was lucky enough to enter Peking University to study biolo...The living world remains a mystery with many exciting discoveries awaiting scientists. My interest in observing living phenomena dates back to my childhood. I was lucky enough to enter Peking University to study biology and have been on a journey of life science research ever since. Along the way, I have made stops at many scientific journals to report my discoveries. When I was a postgraduate student.展开更多
The ultrafast excitation dynamics of atoms and molecules exposed to circularly polarized two-color(CPTC)laser fields constitute a fascinating topic in attosecond science. Although extensive research has established th...The ultrafast excitation dynamics of atoms and molecules exposed to circularly polarized two-color(CPTC)laser fields constitute a fascinating topic in attosecond science. Although extensive research has established the relationship between the Rydberg state excitation(RSE) yields and the CPTC field parameters, such as field amplitude ratios and helicity of two components, the role of the relative phase(φ) in modulating RSE efficiency remains unclear. In this work, we theoretically investigate the φ dependence of RSE and ionization yields in the co-rotating and counter-rotating circularly polarized two-color(CPTC) few-cycle laser fields by a semiclassical model. We find that, in co-rotating CPTC fields, both RSE and ionization yields display pronounced oscillations as a function of φ and these oscillations are significantly suppressed in the counter-rotating configuration, particularly for ionization yields. Moreover, the ratio of RSE to ionization yields exhibits an out-of-phase oscillatory pattern between low-and high-intensity regimes. These results can be comprehended by the unique feature of φ dependence of CPTC few-cycle fields, based on our semiclassical analysis. Our results demonstrate that phase-controlled CPTC fields offer a versatile tool for steering ultrafast ionization and RSE dynamics of atoms and molecules.展开更多
Background:Acupuncture is widely used in modulating brain excitability and motor function,as a form of complementary and alternative medicine.However,there is no existing meta-analysis evaluating the effectiveness and...Background:Acupuncture is widely used in modulating brain excitability and motor function,as a form of complementary and alternative medicine.However,there is no existing meta-analysis evaluating the effectiveness and safety of acupuncture on corticospinal excitability(CSE),and the credibility of the evidence has yet to be quantified.Objective:This study was designed to assess the efficacy and safety of electroacupuncture(EA)and manual acupuncture(MA)in enhancing brain excitability,specifically focusing on CSE as measured by transcranial magnetic stimulation(TMS).Search strategy:This study followed a systematic approach,searching 9 databases up to August 2024 and examining grey literature,in compliance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.Inclusion criteria:Studies were included if they compared the clinical efficacy of EA or MA with sham acupuncture,no treatment or usual training.Data extraction and analysis:Three investigators independently conducted literature screening,data extraction,and risk of bias assessment.The primary outcome focused on motor-evoked potentials as measured by TMS,with treatment effects quantified using mean differences or standardized mean differences between pre-and post-treatment.Subgroup analyses were conducted using mixed-effects models,while random-effects or fixed-effects models were used to estimate average treatment differences across studies.Results:Based on 34 studies involving 1031 adults,acupuncture techniques significantly enhanced CSE.EA had a greater impact than MA,with effect sizes of 0.53 mV vs 0.43 mV(95%confidence interval[CI]:[0.30,0.76],P<0.00001 vs 95%CI:[0.28,0.59],P<0.00001).The 5 most frequently used acupoints were LI4(Hegu,32 times),ST36(Zusanli,10 times),LI11(Quchi,7 times),TE5(Waiguan,6 times),and GB34(Yanglingquan,5 times).Conclusion:This systematic review indicates that both EA and MA could effectively and safely enhance CSE,bringing the corticospinal pathway closer to the threshold for firing,which may ultimately improve motor function.LI4,ST36,LI11,TE5 and GB34 are the most commonly used acupoints.展开更多
One of the pleasantest of Toms dreams had been realized.He had often longed to go off on some adventure with a band of outlaws,and here was his opportunity.The day was perfect,the river was smooth,and the woods along ...One of the pleasantest of Toms dreams had been realized.He had often longed to go off on some adventure with a band of outlaws,and here was his opportunity.The day was perfect,the river was smooth,and the woods along the shore were full of the music of birds.Tom and Joe Harper had planned their escape carefully.They had gathered their provisions and hidden them in a secret place.Now,with their hearts full of excitement,they set off down the river in a small raft they had built.展开更多
文摘Arginine (2-amino-5-guanidino pentanoic acid) was shown in 1895 by Hedin to be present in the proteins of horn. Metabolic nitrogen balance studies, conducted in 1957 by Rose in human adults and in 1959 by Snyderman and coworkers in young infants, revealed that a dietary source of this amino acid was not an obligatory requirement for growth and maintenance of nitrogen homeostasis in healthy individuals. Hence, It was initially classified as a non-essential (dispensable) amino acid and, perhaps, for reasons of this classification arginine did not receivc the earlier atteniion it now deserves, in relation to an understanding of the nutritional biochemistry and physiology of its metabolism in humans subjects. However, there is currently a considerable interest in the cellular and tissue functions, as well as clinical, therapeutic significance, of arginine. In this paper we review the multiple functions of arginlne, including its role in the L-arginine-nitric oxide pathway,cellular regeneration, immune function, protein synthesis and protein breakdown. We then consider some in vivo aspects of the physiology of arginine metabolism, which varies greatly among eukaryotes, with particular reference to humans. Against this background, studies of arginine in the nutrition of humans under various pathophysiological conditions are reviewed briefly. Finally, a new, updated concept for the metabolic basis for the 'conditional essentiality' of arginine is proposed
文摘Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom,were considered.This problem of diffraction by these two cylinders,which were considered as idealization of a buoy and a circular plate,can be considered as a wave energy device.The wave energy that is created and transferred by this device can be appropriately used in many applications in lieu of conventional energy.Method of separation of variables was used to obtain the analytical expressions for the diffracted potentials in four clearly identified regions.By applying the appropriate matching conditions along the three virtual boundaries between the regions,a system of linear equations was obtained,which was solved for the unknown coefficients.The potentials allowed us to obtain the exciting forces acting on both cylinders.Sets of exciting forces were obtained for different radii of the cylinders and for different gaps between the cylinders.It was observed that changes in radius and the gap had significant effect on the forces.It was found that mostly the exciting forces were significant only at lower frequencies.The exciting forces almost vanished at higher frequencies.The problem was also investigated for the base case of no plate arrangement,i.e.,the case having only the floating cylinder tethered to the sea-bed.Comparison of forces for both arrangements was carried out.In order to take care of the radiation of the cylinders due to surge motion,the corresponding added mass and the damping coefficients for both cylinders were also computed.All the results were depicted graphically and compared with available results.
基金supported by National Natural Science Foundation of China under Grant No.50775154Shanxi Province Science Foundation of China under Grant No.2011011026-2
文摘A hydraulic exciting system with a wave exciter has been constructed in order to study the hydraulic vibra- tion law. The system consists of an oil source, wave-exciter and oil cylinder, and is controlled by a wave-exciter. The working principle of the hydraulic exciting system and wave exciter has been analyzed, and its excitation process has been illustrated. The law of every pipe＇s pressure fluctuation of the system is obtained by experiment. The theo- retical analysis and experimental data prove that the pipeline pressure periodically changes and the pipeline pressure fluctuation frequency is independently controlled by the excitation frequency of the wave-exciter. Every pipelinc＇s pressure wave is produced by system flow fluctuation and water hammer coupling. The pressure fluctuation rules of the system provide a theoretical basis for the study of the associated liberation system.
文摘In this paper, the homology of four radio bursts occuring on August 28, 1989 are discussed in time domain, in frequency domain and in their exciting functions.From the discussions, it may be possible that if two radio bursts are homologus, then their ratios of the duration time for rising phases, decaying phases and total bursts are similar in time domain, so do their exciting functions. Therefore they resemble each other in their Fourier apectra.
基金supported in part by the Minis-try of the Environment of Japan
文摘Ground-borne vibrations caused by vibration sources such as road traffic and construction exhibit complicated properties during propagation from the vibration source to the inside of a building. In the present paper, a numerical analysis technique for the system of vibration source and propagation path of ground vibration is developed in order to systematically determine the propagation properties of the vibration as part of developing a predictive technique for exposure evaluations by vibrations in three directions at receiving points of vibration in the human body. First, the exciting forces in three directions for input into the numerical computation are inversely-estimated by using the measured acceleration rec- ords of the measurement points, which are near the vibration source. The thin-layered element method is used for numerical computation of the ground vibration. Then, the calculation results for the ground vibration obtained by using the estimated exciting force are compared with the measured results, and the influence of the stratified structure of the ground on the exciting force and the propagation properties of the ground vibration are studied. From these results, in a prediction of the ground vibration in three directions, it is emphasized that it is necessary to consider the influence of horizontal exciting force, although attention has been paid to only the vertical exciting force for simulating ground vibration.
文摘One Wednesday morning 1 eleven o'clock, Tom was walking down Main Street. 2 he heard the sound of gun (手枪), he 3 the sound must come from the bank. He ran to the bank and 4 a man coming out of the bank.
文摘One Wednesday morning 1 eleven o'clock, Tom was walking down Main Street. 2 he heard the sound of gun (手枪), he 3 the sound must come from the bank.He ran to the bank and 4 a man coming out of the bank. The man was 5 and fat 6 red hair.What's more,he carried a bag and a gun in his hand. Before Tom could do _7_,he had run into the street and disappeared(消失)among people.
文摘The vibration response formulas of the mechanical system under the affect of thevari-frequency exciting force are deduced. It is proved by the theoretical analysis and experimentalresults that the vibration response amplitude of the mechanical system under the affect of thevari-frequency exciting force is far smaller than that under the affect of the constant frequency exciting force on condition that the exciting force amplitudes are just the same;while the vari-fre-quency rate a increases to 5 Hz per second the vibration amplitude will decrease to 10% only as lowas that under the affect of the constant frequency exciting force. All these conclusions will be of significance for revealing the mechanism of suppressing chatter in van-speed cutting and analyzing theexperimental results of sine-wave scanning exciting test.
文摘Chaoyang Theatre is famous for presenting acrobatic shows in Beijing. For Sichuan Suining Acrobatic Troupe, the performance here in the theatre is as usually-fully seated and most audiences are tourists from abroad. However,
文摘"Teacher, what are we going to do next class?" This is an exciting question which I often hear from my students. As an English conversation teacher, I can make the learning of English either a dull and boring duty, or an exciting adventure. It is very important that I make my students hate missing my class, and keep them guessing just what will happen the next time! Let us consider some important ways that any teacher can help his other students want to do
文摘Vibration cementing is a new technique that can significantly improve the bond strength of cementing interface.To popularize this technique,it is necessary to solve the key problem of how to make cementing string generate downhole radial vibration in the WOC stage.For this purpose,an electric vibrator was developed.With this vibrator,electric energy is converted into mechanical energy by means of a high-temperature motor vibration unit.The motor vibration unit rotates the eccentric block through an output shaft to generate an exciting source,which produces an axial-rotating exciting force at the bottom of the casing string.Then,the vibration characteristics of vertical well casing string under the exciting force were analyzed by using the principal coordinate analysis method,and the response model of casing string to an electric vibrator was developed.Finally,the effects of casing string length,exciting force and vibration frequency on the vibration amplitude at the lowermost of the casing string were analyzed based on a certain casing program.It is indicated that the casing string length and the square of vibration frequency are inversely proportional to the vibration amplitude at the lowermost of the casing string,and the exciting force is proportional to the vibration amplitude at the lowermost of the casing string.These research results provide a theoretical support for the application of vibration cementing technology to the cementing sites with different requirements on well depth and amplitude.
基金supported by the National Natural Science Foundation of China(Grant Nos.11072198,11102162)111 Project of China(Grant No.B07050)
文摘Due to the dynamical character of electromagnetic exciter and the coupling between structure and exciter(s),the actual output force acting on the structure is usually not equal to the exact value that is supposed to be,especially when multi-exciters are used as actuators to precisely actuate large flexible structure.It is necessary to consider these effects to ensure the force generated by each exciter is the same as required.In this paper,a robust control method is proposed for the multi-input and multi-output(MIMO)structural vibration control system to trace the target actuating force of each exciter.A special signal is designed and put into the coupled mul-ti-exciter-structure system,and the input and output signals of the system are used to build a dynamic model involving both the dynamical characters of the exciters and the structure using the subspace identification method.Considering the uncertainty factors of the multi-exciter/structure system,an H-infinity robust controller is designed to decouple the coupling between structure and exciters based on the identified system model.A MIMO vibration control system combined with a flexible plate and three electromagnetic exciters is adopted to demonstrate the proposed method,both numerical simulation and model experiments showing that the output force of each exciter can trace its target force accurately within the requested frequency band.
基金supported by the National Nature Science Foundation of China(Nos.62075079,62305127,61975200)the Natural Science Foundation of Jilin Province(20230508135RC)the Science and Technology Development Foundation of Changchun City(23GZZ15).
文摘The fluorescence imaging (FLI) in the second near-infrared window (NIR-II, 1000–1700nm) has attracted considerable attention in the past decade. In contrast to conventional NIR-I window excitation (808nm/980nm), FLI with NIR-II window excitation (1064nm/other wavelength beyond 1000nm) can afford deeper tissue penetration depth with high clarity due to the merits of suppressed photon scattering and diminished autofluorescence. In this review, we have summarized NIR-II window excitable/emissive organic/polymeric fluorophores recently developed. The characteristics of these fluorophores such as chemical structures and photophysical properties have also been critically discussed. Furthermore, the latest development of noninvasive in vivo FLI with NIR-II excitation was highlighted. The ideal imaging results emphasized the importance of NIR-II excitation of these fluorophores in enabling deep tissue penetration and high-resolution imaging. Finally, a perspective on the challenges and prospects of NIR-II excitable/emissive organic/polymeric fluorophores was also discussed. We expected this review will be served as a source of inspiration for researchers, stimulating the creation of novel NIR-II excitable fluorophores and fostering the development of bioimaging applications.
基金supported by the Director Fund Project provided by the Institute of Plant Nutrition,Resources and Environment,Beijing Academy of Agriculture and Forestry Sciences(No.YZS202101)the Youth Fund Project provided by Beijing Academy of Agriculture and Forestry Sciences(No.QNJJ202125)China Agriculture Research System of MOF and MARA.
文摘The dissolved organic matter(DOM)with high mobility and reactivity plays a crucial role in soil.In this study,the characteristics and phytotoxicity ofDOMreleased fromthe hydrochars prepared from different feedstocks(cowmanure,corn stalk and Myriophyllum aquaticum)under three hydrothermal carbonization(HTC)temperatures(180,200 and 220°C)were evaluated.The results showed that the hydrochars had high dissolved organic carbon content(20.15 to 37.65 mg/g)and its content showed a gradual reduction as HTC temperature increased.Three fluorescent components including mixed substance of fulvic acid-like and humic acid-like substances(C1,30.92%-58.32%),UVA humic acid-like substance(C2,25.27%-29.94%)and protein-like substance(C3,11.74%-41.92%)were identified in hydrochar DOM by excitation emission matrix spectra coupled with parallel factor analysis.High HTC temperature increased the relative proportion of aromatic substances(C1+C2)and humification degree of hydrochar DOM from cow manure,while it presented adverse effects on the hydrochar DOM from corn stalk and Myriophyllum.aquaticum.The principal component analysis suggested that feedstock type and HTC temperature posed significant effects on the characteristics of hydrochar DOM.Additionally,seed germination test of all hydrochar DOM demonstrated that the root length was reduced by 8.88%-26.43%in contrast with control,and the germination index values were 73.57%-91.12%.These findings provided new insights into the potential environmental effects for hydrochar application in soil.
文摘Ⅰ. INTRODUCTION By using degenerate four-wave mixing (DFWM) method, the third-order nonlinear optical susceptibility of transparent media can be conventionally measured. Nonlinear properties of media in ground state are well known, but those in exciting state are less studied. When a medium absorbs incident radiation, a part of population can be excited into high exciting state. In DFWM this resonant enhancement effect can be used to increase the third-
文摘The living world remains a mystery with many exciting discoveries awaiting scientists. My interest in observing living phenomena dates back to my childhood. I was lucky enough to enter Peking University to study biology and have been on a journey of life science research ever since. Along the way, I have made stops at many scientific journals to report my discoveries. When I was a postgraduate student.
基金supported by the National Natural Science Foundation of China (Nos. 12121004, 12274273, and 12450402)the Science and Technology Department of Hubei Province (No. 2020CFA029)+1 种基金CAS Project for Young Scientists in Basic Research (No. YSBR-091)the Youth Innovation Promotion Association CAS (No. 2021328)。
文摘The ultrafast excitation dynamics of atoms and molecules exposed to circularly polarized two-color(CPTC)laser fields constitute a fascinating topic in attosecond science. Although extensive research has established the relationship between the Rydberg state excitation(RSE) yields and the CPTC field parameters, such as field amplitude ratios and helicity of two components, the role of the relative phase(φ) in modulating RSE efficiency remains unclear. In this work, we theoretically investigate the φ dependence of RSE and ionization yields in the co-rotating and counter-rotating circularly polarized two-color(CPTC) few-cycle laser fields by a semiclassical model. We find that, in co-rotating CPTC fields, both RSE and ionization yields display pronounced oscillations as a function of φ and these oscillations are significantly suppressed in the counter-rotating configuration, particularly for ionization yields. Moreover, the ratio of RSE to ionization yields exhibits an out-of-phase oscillatory pattern between low-and high-intensity regimes. These results can be comprehended by the unique feature of φ dependence of CPTC few-cycle fields, based on our semiclassical analysis. Our results demonstrate that phase-controlled CPTC fields offer a versatile tool for steering ultrafast ionization and RSE dynamics of atoms and molecules.
文摘Background:Acupuncture is widely used in modulating brain excitability and motor function,as a form of complementary and alternative medicine.However,there is no existing meta-analysis evaluating the effectiveness and safety of acupuncture on corticospinal excitability(CSE),and the credibility of the evidence has yet to be quantified.Objective:This study was designed to assess the efficacy and safety of electroacupuncture(EA)and manual acupuncture(MA)in enhancing brain excitability,specifically focusing on CSE as measured by transcranial magnetic stimulation(TMS).Search strategy:This study followed a systematic approach,searching 9 databases up to August 2024 and examining grey literature,in compliance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.Inclusion criteria:Studies were included if they compared the clinical efficacy of EA or MA with sham acupuncture,no treatment or usual training.Data extraction and analysis:Three investigators independently conducted literature screening,data extraction,and risk of bias assessment.The primary outcome focused on motor-evoked potentials as measured by TMS,with treatment effects quantified using mean differences or standardized mean differences between pre-and post-treatment.Subgroup analyses were conducted using mixed-effects models,while random-effects or fixed-effects models were used to estimate average treatment differences across studies.Results:Based on 34 studies involving 1031 adults,acupuncture techniques significantly enhanced CSE.EA had a greater impact than MA,with effect sizes of 0.53 mV vs 0.43 mV(95%confidence interval[CI]:[0.30,0.76],P<0.00001 vs 95%CI:[0.28,0.59],P<0.00001).The 5 most frequently used acupoints were LI4(Hegu,32 times),ST36(Zusanli,10 times),LI11(Quchi,7 times),TE5(Waiguan,6 times),and GB34(Yanglingquan,5 times).Conclusion:This systematic review indicates that both EA and MA could effectively and safely enhance CSE,bringing the corticospinal pathway closer to the threshold for firing,which may ultimately improve motor function.LI4,ST36,LI11,TE5 and GB34 are the most commonly used acupoints.
文摘One of the pleasantest of Toms dreams had been realized.He had often longed to go off on some adventure with a band of outlaws,and here was his opportunity.The day was perfect,the river was smooth,and the woods along the shore were full of the music of birds.Tom and Joe Harper had planned their escape carefully.They had gathered their provisions and hidden them in a secret place.Now,with their hearts full of excitement,they set off down the river in a small raft they had built.
