The decay dynamic of an excited quantum emitter(QE)is one of the most important contents in quantum optics.It has been widely applied in the field of quantum computing and quantum state manipulation.When the electroma...The decay dynamic of an excited quantum emitter(QE)is one of the most important contents in quantum optics.It has been widely applied in the field of quantum computing and quantum state manipulation.When the electromagnetic environment is described by several pseudomodes,the effective Hamiltonian method based on the multi-mode Jaynes-Cummings model provides a clear physical picture and a simple and convenient way to solve the decay dynamics.However,in previous studies,only the resonant modes are taken into account,while the non-resonant contributions are ignored.In this work,we study the applicability and accuracy of the effective Hamiltonian method for the decay dynamics.We consider different coupling strengths between a two-level QE and a gold nanosphere.The results for dynamics by the resolvent operator technique are used as a reference.Numerical results show that the effective Hamiltonian method provides accurate results when the two-level QE is resonant with the plasmon.However,when the detuning is large,the effective Hamiltonian method is not accurate.In addition,the effective Hamiltonian method cannot be applied when there is a bound state between the QE and the plasmon.These results are of great significance to the study of the decay dynamics in micro-nano structures described by quasi-normal modes.展开更多
Representative volume element （RVE） method and asymptotic homogenization （AH） method are two widely used methods in predicting effective properties of pe- riodic materials. This paper develops a novel implementa- ...Representative volume element （RVE） method and asymptotic homogenization （AH） method are two widely used methods in predicting effective properties of pe- riodic materials. This paper develops a novel implementa- tion of the AH method, which has rigorous mathematical foundation of the AH method, and also simplicity as the RVE method. This implementation can be easily realized using commercial software as a black box, and can use all kinds of elements available in commercial software to model unit cells with rather complicated microstructures, so the model may remain a fairly small scale. Several examples were car- fled out to demonstrate the simplicity and effectiveness of the new implementation.展开更多
Dear Editor,I am Dr.Jia X from the Department of Ophthalmology,Second Xiangya Hospital,Central South University,Changsha,China.I write to present a rare case report of 9p deletion syndrome with congenital infantile gl...Dear Editor,I am Dr.Jia X from the Department of Ophthalmology,Second Xiangya Hospital,Central South University,Changsha,China.I write to present a rare case report of 9p deletion syndrome with congenital infantile glaucoma in an infant,accompanying with an effective method of both diagnosis and treatment.展开更多
BACKGROUND Severe skeletal class II malocclusion is the indication for combined orthodontic and orthognathic treatment.CASE SUMMARY A woman with a chief complaint of a protruding chin and an inability to close her lip...BACKGROUND Severe skeletal class II malocclusion is the indication for combined orthodontic and orthognathic treatment.CASE SUMMARY A woman with a chief complaint of a protruding chin and an inability to close her lips requested orthodontic camouflage.The treatment plan consisted of extracting the right upper third molar,right lower third molar,left lower second molar,and left upper third molar and moving the maxillary dentition distally using a convenient method involving microimplant nail anchors,push springs,long arm traction hooks,and elastic traction chains.After 52 months of treatment,her overbite and overjet were normal,and her facial profile was favorable.CONCLUSION This method can be used for distal movement of the maxillary dentition and to correct severe skeletal class II malocclusion in adults.展开更多
Matrix effect primarily impacts the accuracy and precision of zircon LA-ICP-MS U-Pb data.This paper describes three types of matrix effect in zircon LA-ICPMS U-Pb dating,i.e.,the element matrix effect,high Ddpa or ura...Matrix effect primarily impacts the accuracy and precision of zircon LA-ICP-MS U-Pb data.This paper describes three types of matrix effect in zircon LA-ICPMS U-Pb dating,i.e.,the element matrix effect,high Ddpa or uranium matrix effect and alpha dose matrix effect,and illustrates the correction of these three effects.In addition,we point out the limitation and possible problems of the existing correction methods.展开更多
A reconstruction method is proposed for the polyurethane foam and then a complete numerical method is developed to predict the effective thermal conductivity of the polyurethane foam. The finite volume method is appli...A reconstruction method is proposed for the polyurethane foam and then a complete numerical method is developed to predict the effective thermal conductivity of the polyurethane foam. The finite volume method is applied to solve the 2D heterogeneous pure conduction. The lattice Boltzmann method is adopted to solve the 1D homogenous radiative transfer equation rather than Rosseland approximation equation. The lattice Boltzmann method is then adopted to solve 1D homogeneous conduction-radiation energy transport equation considering the combined effect of conduction and radiation. To validate the accuracy of the present method, the hot disk method is adopted to measure the effective thermal conductivity of the polyurethane foams at different temperature. The numerical results agree well with the experimental data. Then, the influences of temperature, porosity and cell size on the effective thermal conductivity of the polyurethane foam are investigated. The results show that the effective thermal conductivity of the polyurethane foams increases with temperature; and the effective thermal conductivity of the polyurethane foams decreases with increasing porosity while increases with the cell size.展开更多
The purpose of the paper is to demonstrate the effectiveness of using project method in teaching professional English in non-linguistic colleges. The main principles of project teaching, the technology of its adoption...The purpose of the paper is to demonstrate the effectiveness of using project method in teaching professional English in non-linguistic colleges. The main principles of project teaching, the technology of its adoption in teaching process, and some kinds of projects used in studying are reviewed. During the research the following methods were used： theoretical analysis, empirical, and statistical. While studying the course ＂Professional foreign language＂, the monitoring of effectiveness of project method use in teaching a foreign language was made. Monitoring was conducted under the following criteria： percent of progress, percent of quality of knowledge, and the level of motivation in studying English. The experience showed that in the process of project work learners＇ general educational abilities, special abilities, and communication abilities are developed.展开更多
A repeatable and simple thermal splicing method for low loss splice between fluoride and silica fibers is presented. The minimum splicing loss of 0.58 dB is achieved experimentally with this approach, Meanwhile, the p...A repeatable and simple thermal splicing method for low loss splice between fluoride and silica fibers is presented. The minimum splicing loss of 0.58 dB is achieved experimentally with this approach, Meanwhile, the power capacity of this splicing joint is also tested with a high power fiber laser. The maximum input power is up to 15 W, only limited by the available power of the laser source. To the best of our knowledge, this is the first report on thermal splicing between fluoride and silica fibers operating in a high power regime without any complicated ion-assisted deposition process.展开更多
This work aims to establish comparisons between two models used for the performance of heat exchangers. The chosen system, in this case, consists of a heat exchanger used in automotive radiators flat finned tube type....This work aims to establish comparisons between two models used for the performance of heat exchangers. The chosen system, in this case, consists of a heat exchanger used in automotive radiators flat finned tube type. Water and ethylene glycol compound as base fluid and volume fractions of iron oxide nanoparticles (Fe<sub>3</sub>O<sub>4</sub>) are used as a refrigerant. The quantities determined in this work are the nanofluid exit temperature, the air exit temperature, the absolute error between the models for heat transfer rate, and Effectiveness. The quantities that constitute parameters, independent variables, are the airflow, represented by the Reynolds number, and the iron oxide volume fraction. Ethylene Glycol 50% compound has slightly better thermal performance than pure water and reduces the reactive effect of water on the environment, increasing the average life of the equipment. The absolute relative error between the models is less than 20% and presents maximum values with the increase of the nanoparticle volume fraction and growth in the Reynolds number for the air.展开更多
Effective Hamiltonians in periodically driven systems have received widespread attention for realization of novel quantum phases, non-equilibrium phase transition, and Majorana mode. Recently, the study of effective H...Effective Hamiltonians in periodically driven systems have received widespread attention for realization of novel quantum phases, non-equilibrium phase transition, and Majorana mode. Recently, the study of effective Hamiltonian using various methods has gained great interest. We consider a vector differential equation of motion to derive the effective Hamiltonian for any periodically driven two-level system, and the dynamics of the spin vector are an evolution under the Bloch sphere. Here, we investigate the properties of this equation and show that a sudden change of the effective Hamiltonian is expected. Furthermore, we present several exact relations, whose expressions are independent of the different starting points. Moreover, we deduce the effective Hamiltonian from the high-frequency limit, which approximately equals the results in previous studies. Our results show that the vector differential equation of motion is not affected by a convergence problem, and thus, can be used to numerically investigate the effective models in any periodic modulating system. Finally, we anticipate that the proposed method can be applied to experimental platforms that require time-periodic modulation, such as ultracold atoms and optical lattices.展开更多
In wall-bounded turbulent flow calculations, the past focus has been directed to the modelling of the Reynolds-stress gradients. Not much attention has been paid to the effects of the numerical methods used to calcula...In wall-bounded turbulent flow calculations, the past focus has been directed to the modelling of the Reynolds-stress gradients. Not much attention has been paid to the effects of the numerical methods used to calculate these terms and the modelled equations. Discrepancies between model calculations and measurements are quite often attributed to incorrect modelling, while the suitability and accuracy of the numerical methods used are seldom scrutinized. Instead, alternate near-wall and Reynolds-stress models are proposed to remedy the incorrect turbulent flow calculations. On the other hand, if care is not taken in the numerical treatment of the Reynolds-stress gradient terms, physically unrealistic results and solution instability could occur. Previous studies by the author and his collaborators on the effects of numerical methods have shown that some of the more commonly used numerical methods could enhance numerical stability in the solution procedure but would introduce considerable inaccuracy to the results. The flow cases chosen to demonstrate these inaccuracies are a backstep flow and flow in a square duct, where flow complexities are present. The current investigation attempts to show that the above-mentioned effects of numerical methods could also occur in the calculation of a developing plane channel flow, where flow complexities are absent. In addition, this study shows that the results thus obtained lead to a predicted skin friction coefficient that is influenced more by the numerical method used than by the turbulence model invoked. Together, these results show that numerical treatment of the Reynolds-stress gradients in the equations play an important role, even for a developing plane channel flow.展开更多
"New Curriculum Standards" points out that preview is an independent exploration activity of learning individuals. Preview is actually improve a student's self-study ability, let them to an unknown or ne..."New Curriculum Standards" points out that preview is an independent exploration activity of learning individuals. Preview is actually improve a student's self-study ability, let them to an unknown or new knowledge, through their effective learning method to master knowledge, when cultivating the self-learning ability, the students met before he don't understand the knowledge, or is in the process of preparation of encountered obstacles, can prepare to cultivate the ability to solve. Preview is to let students have an understanding of the knowledge they will learn in advance, so that they have a good idea of the follow-up study, so that they can get twice the result with half the effort and smoothly link up the classroom learning.展开更多
Objective: to test the clinical nursing method and effect of using IOE tube in patients with dysphagia after stroke. Methods: 62 patients with dysphagia caused by cerebral apoplexy were selected as test subjects, and ...Objective: to test the clinical nursing method and effect of using IOE tube in patients with dysphagia after stroke. Methods: 62 patients with dysphagia caused by cerebral apoplexy were selected as test subjects, and the treatment time in our hospital was from January 2021 to January 2022. According to the method of touching the ball, 62 test subjects were divided into 2 groups, with 31 test subjects in each group. Routine nursing intervention and IOE management nursing intervention were implemented respectively. The scores of dysphagia, nursing satisfaction and quality of life of the two groups were observed. Results: after nursing intervention, the swallowing disorder scores of the two groups were compared. The nursing intervention group was lower than the routine group (P 0.05);The quality of life and nursing satisfaction in the nursing intervention group were higher than those in the routine group (P 0.05). Conclusion: the clinical nursing effect of using IOE tube for patients with dysphagia is more ideal and can be widely used in clinic.展开更多
Introduction Frequency-dependent dielectric response is one of the important properties of ferroelectrics,reflecting the polarization response to high-frequency electric fields.Polarizations are closely related to fer...Introduction Frequency-dependent dielectric response is one of the important properties of ferroelectrics,reflecting the polarization response to high-frequency electric fields.Polarizations are closely related to ferroelectric domain structures,such as single domain,which represents the region with homogeneous polarizations direction.Ferroelectrics usually possess complex domain structures with domain walls(DWs)separating adjacent homogeneously polarized domains.DWs have attracted much attention during the past two decades due to their properties and potential for device designing.The related issues include DW motion,nonvolatile memory,topological defects,enhanced susceptibility,enhanced quality factor,low dielectric loss,and others.(Ba0.8,Sr0.2)TiO3(BST0.8)is a ferroelectric usually with multi-domain structures.Previous work identified two typical types of domain walls(DWs),i.e.,90°DWs and 180°DWs.The enhancement of dielectric response in systems with 90°DWs is now well understood,and the behavior of dielectric response in multi-domain systems with 180°DWs remains unclear.Therefore,gaining insights into how 180°DWs affect the dielectric response can clarify the effects in multidomain systems.Methods We performed molecular dynamics simulations using the ALFE-H code with the first-principles-based effective Hamiltonian method to study the BST0.8 system.All the calculations were performed in the NPT ensemble using the Evans-Hoover thermostat,and periodic boundary condition(PBC)along all three directions.To simulate the substrate,a uniform biaxial strain was fixed to the 1.55%in-plane strain.To analyze the multi-domain with different DWs,the simulations started with a self-constructed initial multi-domain polarization configuration.Subsequent 50 ps MD simulation was performed under chosen strains for structural relaxation.In the initial configuration,the magnitude of non-zero components of soft mode on each site was set to 0.1Å,atomic occupations(alloying)were randomized,and unless otherwise specified,all other mode variables were set to zero.The trajectory of local mode averaged over the supercell during MD simulations was extracted to calculate the dielectric response.The 8 ns MD simulations were performed to obtain an autocorrelation function for any time t ranging from 0 to 1 ns by one step of 10 fs.The fast Fourier transformation(FFT)was performed to calculate the dielectric response.Then two uncoupled damped harmonic oscillators(DHOs)were used to fit the data of dielectric response.Results and discussion The dielectric response of single domain at 300 K with the different electric fields along[110]from 0 to 2 MV/cm was computed.The computational results can be well fitted with the model of two uncoupled DHOs.The real and imaginary parts of the predicted dielectric response at each chosen electric field both exhibit two peaks.As the electric field increases,the low-frequency mode with 300 GHz at zero field in the system gradually disappears,and a high-frequency mode of larger than 8 THz appears when electric field is larger than 1 MV/cm.The high frequencies modes of 3 THz at zero filed and 8 THz under 1 MV/cm shift towards higher frequencies as the electric field increases.In other words,the present simulations reveal that it is possible to manipulate the frequency of peaks in dielectric response via changing the magnitude of the external electric field.The dielectric responses of multi-domain with 90°DWs and 180°DWs are further analyzed.According to the experimental PFM results,the multi-domain structures are simulated and the dielectric response through MD simulations is calculated.The analysis of the dielectric response of single domain structure and multi-domain structures shows that the single domain structures exhibit high-frequency peaks at>300 GHz,whereas the multi-domain structures exhibit low-frequency peaks at 8 GHz and 120 GHz for 180°DWs system and at 10 GHz for 90°DWs system,revealing that there exists a low-frequency mode related to collective oscillation of DWs in multi-domain structures.In addition,the frequencies of peaks in multi-domain with DWs are in a gigahertz range,whereas the single domain structure exhibits peaks in a terahertz range.The contribution of DWs to the dielectric response primarily arises from the timescale of DWs motion,such as sliding or breathing,which differs significantly from the high-frequency vibrations of optical phonon modes.The vibrational frequency of DWs is much lower,with relaxation times in the order of nanoseconds,resulting in a response frequency in GHz range,which is far below the terahertz range of optical phonon modes.Therefore,DWs oscillations dominate the dielectric response at a low frequency.Moreover,multi-domain structure with 180°DWs exhibits a unique low frequency mode at 120 GHz,which is significantly different from single domain and 90°DWs system.In other words,multi-domain structures with 180°DWs and 90°DWs exhibit different dielectric responses.There exists a common low-frequency mode related to the oscillations of DWs in BST0.8.Conclusions It was possible to manipulate the frequency of peaks in dielectric response of single domain through changing the magnitude of the external electric field.Domain walls oscillations dominated the dielectric response in a low frequency gigahertz range,whereas the single domain structures exhibited resonant peaks in a terahertz range.Moreover,multi-domain structures with different domain walls in BST0.8 had different dielectric responses,but the both have a same low-frequency mode at 10 GHz related to the domain walls oscillations.The results of this study indicated the dielectric response behaviors of ferroelectrics induced in an external electric field and internal multi-domain configurations and provided the potential mechanisms and guidance for optimizing application performance.展开更多
Improved waveguide designs for 9.0μm GaAs-based quantum cascade laser （QCL） structures are presented. Modal losses and confinement factors are calculated for TM modes with the transfer matrix method （TMM） and eff...Improved waveguide designs for 9.0μm GaAs-based quantum cascade laser （QCL） structures are presented. Modal losses and confinement factors are calculated for TM modes with the transfer matrix method （TMM） and effective index method （EIM）. The thicknesses of the cladding layer and waveguide layer, the ridge-width, and the cavity length are all taken into account. Appropriate thicknesses of epilayers are given with lower threshold gain and more economical material growth time.展开更多
The process and mechanism of the ligand volume controlled Pd（PR3）2 （PR3=PH3, PMe3, and PtBu3） oxidative addition with aryl bromide were investigated, using density functional theory method with the conductor-like ...The process and mechanism of the ligand volume controlled Pd（PR3）2 （PR3=PH3, PMe3, and PtBu3） oxidative addition with aryl bromide were investigated, using density functional theory method with the conductor-like screening model. Association pathway and dissocia-tion pathway were investigated by the comparison of several energies. The cleavage energy of Pd（PR3）2 complex was calculated, as well as the oxidative addition reaction barrier energy of Pd（PR3）n （n=1,2） with aryl bromide in N,N-dimethylformamide solvent. This study proved that the ligands volume possessed a great impact on the mechanism of oxidative addition： less bulky ligand palladium associated with aryl bromide via two donor ligands,but larger bulky ligand palladium coordinated via monoligand.展开更多
Experimental evidence is presented relevant to the angular dependences of multiple-bit upset （MBU） rates and patterns in static random access memories （SRAMs） under heavy ion irradiation. The single event upset （...Experimental evidence is presented relevant to the angular dependences of multiple-bit upset （MBU） rates and patterns in static random access memories （SRAMs） under heavy ion irradiation. The single event upset （SEU） cross sections under tilted ion strikes are overestimated by 23.9%-84.6%, compared with under normally incident ion with the equivalent linear energy transfer （LET） value of 41 MeV/（mg/cm2）, which can be partially explained by the fact that the MBU rate for tilted ions of 30° is 8.5%-9.8% higher than for normally incident ions. While at a lower LET of - 9.5 MeV/（mg/cm2）, no clear discrepancy is observed. Moreover, since the ion trajectories at normal and tilted incidences are different, the predominant double-bit upset （DBU） patterns measured are different in both conditions. Those differences depend on the LET values of heavy ions and devices under test. Thus, effective LET method should be used carefully in ground-based testing of single event effects （SEE） sensitivity, especially in MBU-sensitive devices.展开更多
BACKGROUND The standard treatment of transitional cell carcinoma of the upper urinary tract consists of radical nephroureterectomy with bladder cuff removal,which can be performed either in open or laparoscopy or robo...BACKGROUND The standard treatment of transitional cell carcinoma of the upper urinary tract consists of radical nephroureterectomy with bladder cuff removal,which can be performed either in open or laparoscopy or robot-assisted laparoscopy.Treatment of chronic renal insufficiency patients with upper urothelial tumor is in a dilemma.Urologists weigh and consider the balance between tumor control and effective renal function preservation.European Association of Urology guidelines recommend that select patients may benefit from endoscopic treatment,but laparoscopic treatment is rarely reported.CASE SUMMARY In this case report,we describe a case of 79-year-old female diagnosed with urothelial carcinoma of the renal pelvis and adrenal adenoma with chronic renal insufficiency.The patient was treated with retroperitoneal laparoscopic partial resection of the renal pelvis and adrenal adenoma resection simultaneously.CONCLUSION Retroperitoneal laparoscopic partial resection of the renal pelvis is an effective surgical procedure for the treatment of urothelial carcinoma of the renal pelvis.展开更多
基金Project supported by the National Natural Science Foundation of China(11964010,11564013 and 11464014)the Natural Science Foundation of Hunan Province(2020JJ4495)+1 种基金the Scientific Research Fund of Hunan Provincial Education Department(22A0377 and 21A0333)the Jishou University Innovation Foundation for Postgraduate(Jdy20038)。
文摘The decay dynamic of an excited quantum emitter(QE)is one of the most important contents in quantum optics.It has been widely applied in the field of quantum computing and quantum state manipulation.When the electromagnetic environment is described by several pseudomodes,the effective Hamiltonian method based on the multi-mode Jaynes-Cummings model provides a clear physical picture and a simple and convenient way to solve the decay dynamics.However,in previous studies,only the resonant modes are taken into account,while the non-resonant contributions are ignored.In this work,we study the applicability and accuracy of the effective Hamiltonian method for the decay dynamics.We consider different coupling strengths between a two-level QE and a gold nanosphere.The results for dynamics by the resolvent operator technique are used as a reference.Numerical results show that the effective Hamiltonian method provides accurate results when the two-level QE is resonant with the plasmon.However,when the detuning is large,the effective Hamiltonian method is not accurate.In addition,the effective Hamiltonian method cannot be applied when there is a bound state between the QE and the plasmon.These results are of great significance to the study of the decay dynamics in micro-nano structures described by quasi-normal modes.
基金supported by the National Natural Science Foundation of China(91216201)
文摘Representative volume element （RVE） method and asymptotic homogenization （AH） method are two widely used methods in predicting effective properties of pe- riodic materials. This paper develops a novel implementa- tion of the AH method, which has rigorous mathematical foundation of the AH method, and also simplicity as the RVE method. This implementation can be easily realized using commercial software as a black box, and can use all kinds of elements available in commercial software to model unit cells with rather complicated microstructures, so the model may remain a fairly small scale. Several examples were car- fled out to demonstrate the simplicity and effectiveness of the new implementation.
基金Supported by the Natural Science Foundation of China(No.81370913)
文摘Dear Editor,I am Dr.Jia X from the Department of Ophthalmology,Second Xiangya Hospital,Central South University,Changsha,China.I write to present a rare case report of 9p deletion syndrome with congenital infantile glaucoma in an infant,accompanying with an effective method of both diagnosis and treatment.
基金Supported by Medical Science Research Project Plan by Health Commission of the Hebei Province,No.20220063.
文摘BACKGROUND Severe skeletal class II malocclusion is the indication for combined orthodontic and orthognathic treatment.CASE SUMMARY A woman with a chief complaint of a protruding chin and an inability to close her lips requested orthodontic camouflage.The treatment plan consisted of extracting the right upper third molar,right lower third molar,left lower second molar,and left upper third molar and moving the maxillary dentition distally using a convenient method involving microimplant nail anchors,push springs,long arm traction hooks,and elastic traction chains.After 52 months of treatment,her overbite and overjet were normal,and her facial profile was favorable.CONCLUSION This method can be used for distal movement of the maxillary dentition and to correct severe skeletal class II malocclusion in adults.
文摘Matrix effect primarily impacts the accuracy and precision of zircon LA-ICP-MS U-Pb data.This paper describes three types of matrix effect in zircon LA-ICPMS U-Pb dating,i.e.,the element matrix effect,high Ddpa or uranium matrix effect and alpha dose matrix effect,and illustrates the correction of these three effects.In addition,we point out the limitation and possible problems of the existing correction methods.
基金Funded by Key Project of International Joint Research of National Natural Science Foundation of China(No.51320105004)
文摘A reconstruction method is proposed for the polyurethane foam and then a complete numerical method is developed to predict the effective thermal conductivity of the polyurethane foam. The finite volume method is applied to solve the 2D heterogeneous pure conduction. The lattice Boltzmann method is adopted to solve the 1D homogenous radiative transfer equation rather than Rosseland approximation equation. The lattice Boltzmann method is then adopted to solve 1D homogeneous conduction-radiation energy transport equation considering the combined effect of conduction and radiation. To validate the accuracy of the present method, the hot disk method is adopted to measure the effective thermal conductivity of the polyurethane foams at different temperature. The numerical results agree well with the experimental data. Then, the influences of temperature, porosity and cell size on the effective thermal conductivity of the polyurethane foam are investigated. The results show that the effective thermal conductivity of the polyurethane foams increases with temperature; and the effective thermal conductivity of the polyurethane foams decreases with increasing porosity while increases with the cell size.
文摘The purpose of the paper is to demonstrate the effectiveness of using project method in teaching professional English in non-linguistic colleges. The main principles of project teaching, the technology of its adoption in teaching process, and some kinds of projects used in studying are reviewed. During the research the following methods were used： theoretical analysis, empirical, and statistical. While studying the course ＂Professional foreign language＂, the monitoring of effectiveness of project method use in teaching a foreign language was made. Monitoring was conducted under the following criteria： percent of progress, percent of quality of knowledge, and the level of motivation in studying English. The experience showed that in the process of project work learners＇ general educational abilities, special abilities, and communication abilities are developed.
基金Supported by the National Natural Science Foundation of China under Grant No 61275144the Innovative Research and Development Project of Nanshan District under Grant No KC2013JSCX0013A+1 种基金the Shenzhen Science and Technology Innovation Projects under Grant No JCYJ20150324140036862the Funding from Shenzhen University under Grant No 00008355
文摘A repeatable and simple thermal splicing method for low loss splice between fluoride and silica fibers is presented. The minimum splicing loss of 0.58 dB is achieved experimentally with this approach, Meanwhile, the power capacity of this splicing joint is also tested with a high power fiber laser. The maximum input power is up to 15 W, only limited by the available power of the laser source. To the best of our knowledge, this is the first report on thermal splicing between fluoride and silica fibers operating in a high power regime without any complicated ion-assisted deposition process.
文摘This work aims to establish comparisons between two models used for the performance of heat exchangers. The chosen system, in this case, consists of a heat exchanger used in automotive radiators flat finned tube type. Water and ethylene glycol compound as base fluid and volume fractions of iron oxide nanoparticles (Fe<sub>3</sub>O<sub>4</sub>) are used as a refrigerant. The quantities determined in this work are the nanofluid exit temperature, the air exit temperature, the absolute error between the models for heat transfer rate, and Effectiveness. The quantities that constitute parameters, independent variables, are the airflow, represented by the Reynolds number, and the iron oxide volume fraction. Ethylene Glycol 50% compound has slightly better thermal performance than pure water and reduces the reactive effect of water on the environment, increasing the average life of the equipment. The absolute relative error between the models is less than 20% and presents maximum values with the increase of the nanoparticle volume fraction and growth in the Reynolds number for the air.
基金supported by the National Natural Science Foundation of China (Grant No. 11774328)。
文摘Effective Hamiltonians in periodically driven systems have received widespread attention for realization of novel quantum phases, non-equilibrium phase transition, and Majorana mode. Recently, the study of effective Hamiltonian using various methods has gained great interest. We consider a vector differential equation of motion to derive the effective Hamiltonian for any periodically driven two-level system, and the dynamics of the spin vector are an evolution under the Bloch sphere. Here, we investigate the properties of this equation and show that a sudden change of the effective Hamiltonian is expected. Furthermore, we present several exact relations, whose expressions are independent of the different starting points. Moreover, we deduce the effective Hamiltonian from the high-frequency limit, which approximately equals the results in previous studies. Our results show that the vector differential equation of motion is not affected by a convergence problem, and thus, can be used to numerically investigate the effective models in any periodic modulating system. Finally, we anticipate that the proposed method can be applied to experimental platforms that require time-periodic modulation, such as ultracold atoms and optical lattices.
文摘In wall-bounded turbulent flow calculations, the past focus has been directed to the modelling of the Reynolds-stress gradients. Not much attention has been paid to the effects of the numerical methods used to calculate these terms and the modelled equations. Discrepancies between model calculations and measurements are quite often attributed to incorrect modelling, while the suitability and accuracy of the numerical methods used are seldom scrutinized. Instead, alternate near-wall and Reynolds-stress models are proposed to remedy the incorrect turbulent flow calculations. On the other hand, if care is not taken in the numerical treatment of the Reynolds-stress gradient terms, physically unrealistic results and solution instability could occur. Previous studies by the author and his collaborators on the effects of numerical methods have shown that some of the more commonly used numerical methods could enhance numerical stability in the solution procedure but would introduce considerable inaccuracy to the results. The flow cases chosen to demonstrate these inaccuracies are a backstep flow and flow in a square duct, where flow complexities are present. The current investigation attempts to show that the above-mentioned effects of numerical methods could also occur in the calculation of a developing plane channel flow, where flow complexities are absent. In addition, this study shows that the results thus obtained lead to a predicted skin friction coefficient that is influenced more by the numerical method used than by the turbulence model invoked. Together, these results show that numerical treatment of the Reynolds-stress gradients in the equations play an important role, even for a developing plane channel flow.
文摘"New Curriculum Standards" points out that preview is an independent exploration activity of learning individuals. Preview is actually improve a student's self-study ability, let them to an unknown or new knowledge, through their effective learning method to master knowledge, when cultivating the self-learning ability, the students met before he don't understand the knowledge, or is in the process of preparation of encountered obstacles, can prepare to cultivate the ability to solve. Preview is to let students have an understanding of the knowledge they will learn in advance, so that they have a good idea of the follow-up study, so that they can get twice the result with half the effort and smoothly link up the classroom learning.
文摘Objective: to test the clinical nursing method and effect of using IOE tube in patients with dysphagia after stroke. Methods: 62 patients with dysphagia caused by cerebral apoplexy were selected as test subjects, and the treatment time in our hospital was from January 2021 to January 2022. According to the method of touching the ball, 62 test subjects were divided into 2 groups, with 31 test subjects in each group. Routine nursing intervention and IOE management nursing intervention were implemented respectively. The scores of dysphagia, nursing satisfaction and quality of life of the two groups were observed. Results: after nursing intervention, the swallowing disorder scores of the two groups were compared. The nursing intervention group was lower than the routine group (P 0.05);The quality of life and nursing satisfaction in the nursing intervention group were higher than those in the routine group (P 0.05). Conclusion: the clinical nursing effect of using IOE tube for patients with dysphagia is more ideal and can be widely used in clinic.
文摘Introduction Frequency-dependent dielectric response is one of the important properties of ferroelectrics,reflecting the polarization response to high-frequency electric fields.Polarizations are closely related to ferroelectric domain structures,such as single domain,which represents the region with homogeneous polarizations direction.Ferroelectrics usually possess complex domain structures with domain walls(DWs)separating adjacent homogeneously polarized domains.DWs have attracted much attention during the past two decades due to their properties and potential for device designing.The related issues include DW motion,nonvolatile memory,topological defects,enhanced susceptibility,enhanced quality factor,low dielectric loss,and others.(Ba0.8,Sr0.2)TiO3(BST0.8)is a ferroelectric usually with multi-domain structures.Previous work identified two typical types of domain walls(DWs),i.e.,90°DWs and 180°DWs.The enhancement of dielectric response in systems with 90°DWs is now well understood,and the behavior of dielectric response in multi-domain systems with 180°DWs remains unclear.Therefore,gaining insights into how 180°DWs affect the dielectric response can clarify the effects in multidomain systems.Methods We performed molecular dynamics simulations using the ALFE-H code with the first-principles-based effective Hamiltonian method to study the BST0.8 system.All the calculations were performed in the NPT ensemble using the Evans-Hoover thermostat,and periodic boundary condition(PBC)along all three directions.To simulate the substrate,a uniform biaxial strain was fixed to the 1.55%in-plane strain.To analyze the multi-domain with different DWs,the simulations started with a self-constructed initial multi-domain polarization configuration.Subsequent 50 ps MD simulation was performed under chosen strains for structural relaxation.In the initial configuration,the magnitude of non-zero components of soft mode on each site was set to 0.1Å,atomic occupations(alloying)were randomized,and unless otherwise specified,all other mode variables were set to zero.The trajectory of local mode averaged over the supercell during MD simulations was extracted to calculate the dielectric response.The 8 ns MD simulations were performed to obtain an autocorrelation function for any time t ranging from 0 to 1 ns by one step of 10 fs.The fast Fourier transformation(FFT)was performed to calculate the dielectric response.Then two uncoupled damped harmonic oscillators(DHOs)were used to fit the data of dielectric response.Results and discussion The dielectric response of single domain at 300 K with the different electric fields along[110]from 0 to 2 MV/cm was computed.The computational results can be well fitted with the model of two uncoupled DHOs.The real and imaginary parts of the predicted dielectric response at each chosen electric field both exhibit two peaks.As the electric field increases,the low-frequency mode with 300 GHz at zero field in the system gradually disappears,and a high-frequency mode of larger than 8 THz appears when electric field is larger than 1 MV/cm.The high frequencies modes of 3 THz at zero filed and 8 THz under 1 MV/cm shift towards higher frequencies as the electric field increases.In other words,the present simulations reveal that it is possible to manipulate the frequency of peaks in dielectric response via changing the magnitude of the external electric field.The dielectric responses of multi-domain with 90°DWs and 180°DWs are further analyzed.According to the experimental PFM results,the multi-domain structures are simulated and the dielectric response through MD simulations is calculated.The analysis of the dielectric response of single domain structure and multi-domain structures shows that the single domain structures exhibit high-frequency peaks at>300 GHz,whereas the multi-domain structures exhibit low-frequency peaks at 8 GHz and 120 GHz for 180°DWs system and at 10 GHz for 90°DWs system,revealing that there exists a low-frequency mode related to collective oscillation of DWs in multi-domain structures.In addition,the frequencies of peaks in multi-domain with DWs are in a gigahertz range,whereas the single domain structure exhibits peaks in a terahertz range.The contribution of DWs to the dielectric response primarily arises from the timescale of DWs motion,such as sliding or breathing,which differs significantly from the high-frequency vibrations of optical phonon modes.The vibrational frequency of DWs is much lower,with relaxation times in the order of nanoseconds,resulting in a response frequency in GHz range,which is far below the terahertz range of optical phonon modes.Therefore,DWs oscillations dominate the dielectric response at a low frequency.Moreover,multi-domain structure with 180°DWs exhibits a unique low frequency mode at 120 GHz,which is significantly different from single domain and 90°DWs system.In other words,multi-domain structures with 180°DWs and 90°DWs exhibit different dielectric responses.There exists a common low-frequency mode related to the oscillations of DWs in BST0.8.Conclusions It was possible to manipulate the frequency of peaks in dielectric response of single domain through changing the magnitude of the external electric field.Domain walls oscillations dominated the dielectric response in a low frequency gigahertz range,whereas the single domain structures exhibited resonant peaks in a terahertz range.Moreover,multi-domain structures with different domain walls in BST0.8 had different dielectric responses,but the both have a same low-frequency mode at 10 GHz related to the domain walls oscillations.The results of this study indicated the dielectric response behaviors of ferroelectrics induced in an external electric field and internal multi-domain configurations and provided the potential mechanisms and guidance for optimizing application performance.
文摘Improved waveguide designs for 9.0μm GaAs-based quantum cascade laser （QCL） structures are presented. Modal losses and confinement factors are calculated for TM modes with the transfer matrix method （TMM） and effective index method （EIM）. The thicknesses of the cladding layer and waveguide layer, the ridge-width, and the cavity length are all taken into account. Appropriate thicknesses of epilayers are given with lower threshold gain and more economical material growth time.
基金This work was supported by the National Natural Science Foundation of China （No.20776089） and the New Century Excellent Talents Program of Ministry of Education （No.NCET-05-0783）. The State Key Laboratory of Polymer Materials Engineering in Sichuan University was acknowledged for providing dmol3 modules and Prof. Ying Xue, Xiang-yuan Li, and Quan Zhu were grateful for the useful discussions.
文摘The process and mechanism of the ligand volume controlled Pd（PR3）2 （PR3=PH3, PMe3, and PtBu3） oxidative addition with aryl bromide were investigated, using density functional theory method with the conductor-like screening model. Association pathway and dissocia-tion pathway were investigated by the comparison of several energies. The cleavage energy of Pd（PR3）2 complex was calculated, as well as the oxidative addition reaction barrier energy of Pd（PR3）n （n=1,2） with aryl bromide in N,N-dimethylformamide solvent. This study proved that the ligands volume possessed a great impact on the mechanism of oxidative addition： less bulky ligand palladium associated with aryl bromide via two donor ligands,but larger bulky ligand palladium coordinated via monoligand.
基金supported by the National Natural Science Foundation of China(Grant Nos.11179003,10975164,10805062,and 11005134)
文摘Experimental evidence is presented relevant to the angular dependences of multiple-bit upset （MBU） rates and patterns in static random access memories （SRAMs） under heavy ion irradiation. The single event upset （SEU） cross sections under tilted ion strikes are overestimated by 23.9%-84.6%, compared with under normally incident ion with the equivalent linear energy transfer （LET） value of 41 MeV/（mg/cm2）, which can be partially explained by the fact that the MBU rate for tilted ions of 30° is 8.5%-9.8% higher than for normally incident ions. While at a lower LET of - 9.5 MeV/（mg/cm2）, no clear discrepancy is observed. Moreover, since the ion trajectories at normal and tilted incidences are different, the predominant double-bit upset （DBU） patterns measured are different in both conditions. Those differences depend on the LET values of heavy ions and devices under test. Thus, effective LET method should be used carefully in ground-based testing of single event effects （SEE） sensitivity, especially in MBU-sensitive devices.
文摘BACKGROUND The standard treatment of transitional cell carcinoma of the upper urinary tract consists of radical nephroureterectomy with bladder cuff removal,which can be performed either in open or laparoscopy or robot-assisted laparoscopy.Treatment of chronic renal insufficiency patients with upper urothelial tumor is in a dilemma.Urologists weigh and consider the balance between tumor control and effective renal function preservation.European Association of Urology guidelines recommend that select patients may benefit from endoscopic treatment,but laparoscopic treatment is rarely reported.CASE SUMMARY In this case report,we describe a case of 79-year-old female diagnosed with urothelial carcinoma of the renal pelvis and adrenal adenoma with chronic renal insufficiency.The patient was treated with retroperitoneal laparoscopic partial resection of the renal pelvis and adrenal adenoma resection simultaneously.CONCLUSION Retroperitoneal laparoscopic partial resection of the renal pelvis is an effective surgical procedure for the treatment of urothelial carcinoma of the renal pelvis.
