AIM: To compare the outcomes of hand-sewn(HS) and linearly stapled(LS) esophagogastric anastomosis for esophageal cancer.METHODS: Before beginning this study, a rigorous protocol was established according to the recom...AIM: To compare the outcomes of hand-sewn(HS) and linearly stapled(LS) esophagogastric anastomosis for esophageal cancer.METHODS: Before beginning this study, a rigorous protocol was established according to the recommendations of the Cochrane Collaboration. Databases and references were searched for all randomizedcontrolled trials and comparative clinical studies that compared LS with HS esophagogastric anastomosis for esophageal cancer. The primary outcomes compared were anastomotic leak and stricture. Subgroup analyses were performed according to site of anastomosis.RESULTS: Fifteen studies were used, comprising 3203 patients(n = 2027 LS and 1176 HS). Primary outcome analysis revealed a significant decrease in anastomotic leakage(RR = 0.51, 95%CI: 0.41-0.65; P < 0.00001) a s s o c i a t e d w i t h L S a n a s t o m o s i s. A s i g n i f i c a n t l y reduced rate of anastomotic stricture associated with LS was also found(RR = 0.56, 95%CI: 0.49-0.64; P < 0.00001). A subgroup analysis according to the site of anastomosis revealed a significantly reduced rate of anastomotic stricture(P < 0.00001). Although there was no significant difference in the decrease in thoracic anastomotic leakage, there was a significant decrease in cervical anastomotic leakage associated with LS(P < 0.00001).CONCLUSION: This meta-analysis indicates that the LS technique contributes to a reduced rate of leakage and stricture compared with the HS method.展开更多
The plane structure of bars jointed to a rigid-body is a complex and universal structure.Some other structure of bars can be considered as its special cases. Many material have different stress-strain relation in tens...The plane structure of bars jointed to a rigid-body is a complex and universal structure.Some other structure of bars can be considered as its special cases. Many material have different stress-strain relation in tension and compression, generally the relation is nonlinear. In this paper,we use the constitutive model of linearly elastic and power hardening of strength difference to analyze plane structure of bars. The displacement method is used to derive the universal expression of calculating stress and strain. The nonlinear equations for computing displacements of the rigid-body has been given and general computing program has been worked out. This problem has been solved satisfactorily.展开更多
Active set method and gradient projection method are curre nt ly the main approaches for linearly constrained convex programming. Interior-po int method is one of the most effective choices for linear programming. In ...Active set method and gradient projection method are curre nt ly the main approaches for linearly constrained convex programming. Interior-po int method is one of the most effective choices for linear programming. In the p aper a predictor-corrector interior-point algorithm for linearly constrained c onvex programming under the predictor-corrector motivation was proposed. In eac h iteration, the algorithm first performs a predictor-step to reduce the dualit y gap and then a corrector-step to keep the points close to the central traject ory. Computations in the algorithm only require that the initial iterate be nonn egative while feasibility or strict feasibility is not required. It is proved th at the algorithm is equivalent to a level-1 perturbed composite Newton method. Numerical experiments on twenty-six standard test problems are made. The result s show that the proposed algorithm is stable and robust.展开更多
We investigate the ellipticity of the high-order harmonic generation from the oriented H_(2)^(+)exposed to a linearly polarized laser field by numerically solving the two-dimensional time-dependent Schrodinger equatio...We investigate the ellipticity of the high-order harmonic generation from the oriented H_(2)^(+)exposed to a linearly polarized laser field by numerically solving the two-dimensional time-dependent Schrodinger equation(2 D TDSE).Numerical simulations show that the harmonic ellipticity is remarkably sensitive to the alignment angle.The harmonic spectrum is highly elliptically polarized at a specific alignment angleθ=30°,which is insensitive to the variation of the laser parameters.The position of the harmonic intensity minima indicates the high ellipticity,which can be attributed to the two-center interference effect.The high ellipticity can be explained by the phase difference of the harmonics.This result facilitates the synthesis of a highly elliptical isolated attosecond pulse with duration down to 65 as,which can be served as a powerful tool to explore the ultrafast dynamics of molecules and study chiral light-matter interaction.展开更多
The present theoretical assessment deals with the peristaltic-ciliary transport of a developing embryo within a fallopian tubal fluid in the human fallopian tube.A mathematical model of peristalsis-cilia induced flow ...The present theoretical assessment deals with the peristaltic-ciliary transport of a developing embryo within a fallopian tubal fluid in the human fallopian tube.A mathematical model of peristalsis-cilia induced flow of a linearly viscous fluid within a fallopian tubal fluid in a finite two-dimensional narrow tube is developed. The lubrication approximation theory is used to solve the resulting partial differential equation. The expressions for axial and radial velocities, pressure gradient, stream function, volume flow rate, and time mean volume flow rate are derived. Numerical integration is performed for the appropriate residue time over the wavelength and the pressure difference over the wavelength. Moreover, the plots of axial velocity, the appropriate residue time over wavelength, the vector, the pressure difference over wavelength, and the streamlines are displayed and discussed for emerging parameters and constants. Salient features of the pumping characteristics and the trapping phenomenon are discussed in detail. Furthermore, a comparison between the peristaltic flow and the peristaltic-ciliary flow is made as the special case. Relevance of the current results to the transport of a developing embryo within a fallopian tubal fluid from ampulla to the intramural in the fallopian tube is also explored. It reveals the fact that cilia along with peristalsis helps to complete the required mitotic divisions while transporting the developing embryo within a fallopian tubal fluid in the human fallopian tube.展开更多
The characteristics of coherent radiation produced by a cylindrical electron beam passing through a rectangular waveguide and linearly polarized wiggler are studied. The instability analysis is based on the linearized...The characteristics of coherent radiation produced by a cylindrical electron beam passing through a rectangular waveguide and linearly polarized wiggler are studied. The instability analysis is based on the linearized Vlasov-Maxwell equations for the perturbations about a self-consistent beam equilibrium. The dispersion equation of TMmn mode is deduced and by making use of numerical calculation the radiation frequency and growth rate as a function of electron beam energy and radius, axial magnetic field, wiggler field and wave length are presented and discussed.展开更多
A technique for measuring the linearity of a linearly frequency-modulated continuous wave (LFM-CW) signal is presented. It uses a delay-line and a mixer to sense the slope of the output of a sweep oscillator, so that ...A technique for measuring the linearity of a linearly frequency-modulated continuous wave (LFM-CW) signal is presented. It uses a delay-line and a mixer to sense the slope of the output of a sweep oscillator, so that the original form of frequency function deviated from idealized linear slope is retrieved by means of spectrum analysis. Consequently,the linearity of the LFM signal is determined. The formulation is performed based on the principle that an angle-modulated signal can be approximated by an amplitude-modulated signal if the modulation coefficient is sufficiently small. To examine the validity of the procedure and to study the effect of each parameter on the accuracy of measurement, a number of computer simulations has been made. The results of simulation show that the error of the measurement is less than 2%.展开更多
The focusing phenomena of SAW excited by an IDT with sinusoidal wavefront and linearly chirped periodic distribution has been explored.Some experimental results are compared with theoretical one and agree with it fair...The focusing phenomena of SAW excited by an IDT with sinusoidal wavefront and linearly chirped periodic distribution has been explored.Some experimental results are compared with theoretical one and agree with it fairly well.展开更多
We demonstrated the~2.8-μm and~3.5-μm linearly polarized continuous wave(CW)laser outputs from a polarization-maintaining(PM)Er^(3+)-doped fluoride fiber laser.By introducing a film polarizer into the cavity to sele...We demonstrated the~2.8-μm and~3.5-μm linearly polarized continuous wave(CW)laser outputs from a polarization-maintaining(PM)Er^(3+)-doped fluoride fiber laser.By introducing a film polarizer into the cavity to select the laser polarization orientation,the~2.8-μm linearly polarized CW laser with a high polarization extinction ratio(PER)of~23 dB and maximum output power of 2.37 W was achieved under double-end pumping at 976 nm.By adding another 1981-nm pump source simultaneously,the~3.5-μm linearly polarized CW laser was also obtained,giving higher PER of~27 dB and maximum output power of 307 mW which is only limited by the available power of 1981-nm pump.To the best of our knowledge,this is the first report on a mid-infrared linearly polarized CW PM fiber laser in the>2.5-μm mid-infrared region.This work not only opens up opportunities for some new mid-infrared applications,but also provides a promising platform for developing high-stability and versatile mid-infrared laser sources.展开更多
In this paper, analysis of post-treatment of wire coating is presented. Coating material satisfies power law fluid model. Exact solutions for the velocity field, volume flow rate and average velocity are obtained. Mor...In this paper, analysis of post-treatment of wire coating is presented. Coating material satisfies power law fluid model. Exact solutions for the velocity field, volume flow rate and average velocity are obtained. Moreover, the heat transfer results are presented for different cases of linearly varying on the boundaries. The variations of velocity, volume flow rate, radius of coated wire, shear rate and the force on the total wire are presented graphically and discussed.展开更多
In this paper, effect of thermal gradient on vibration of trapezoidal plate of varying thickness is studied. Thermal effect and thickness variation is taken as linearly in x-direction. Rayleigh Ritz technique is used ...In this paper, effect of thermal gradient on vibration of trapezoidal plate of varying thickness is studied. Thermal effect and thickness variation is taken as linearly in x-direction. Rayleigh Ritz technique is used to calculate the fundamental frequencies. The frequencies corresponding to the first two modes of vibrations are obtained for a trapezoidal plate for different values of taper constant, thermal gradient and aspect ratio. Results are presented in graphical form.展开更多
In this paper, the effect of thermal gradient on the vibration of parallelogram plate with linearly varying thickness in both direction having clamped boundary conditions on all the four edges is analyzed. Thermal eff...In this paper, the effect of thermal gradient on the vibration of parallelogram plate with linearly varying thickness in both direction having clamped boundary conditions on all the four edges is analyzed. Thermal effect on vibration of such plate has been taken as one-dimensional distribution in linear form only. An approximate but quiet convenient frequency equation is derived using Rayleigh-Ritz technique with a two-term deflection function. The frequencies corresponding to the first two modes of vibration of a clamped parallelogram plate have been computed for different values of aspect ratio, thermal gradient, taper constants and skew angle. The results have been presented in tabular forms. The results obtained in this study are reduced to that of unheated parallelogram plates of uniform thickness and have generally been compared with the published one.展开更多
<div style="text-align:justify;"> A photonics approach to generate a linearly chirped waveform with increased TBWP is proposed and investigated. The time bandwidth product (TBWP) of the linearly chirpe...<div style="text-align:justify;"> A photonics approach to generate a linearly chirped waveform with increased TBWP is proposed and investigated. The time bandwidth product (TBWP) of the linearly chirped waveform is improved based on optical microwave frequency multiplying combined with temporal synthesis. An integrated dual-polarization modulator and an optical filter are utilized to perform frequency doubling operation by generating an orthogonally polarized optical signal, which consists of an optical carrier in one polarization direction and a second-order chirped optical sideband in another. Then the orthogonally polarized optical signal puts into a polarization modulator (PolM) to perform phase coding process. By driving a Pseudorandom (PN) sequence to the PolM, the time duration of the generated bandwidth doubled linearly chirped waveform can be synthesized to arbitrary length. The approach is verified by simulation. A linearly chirped waveform with central frequency of 8.25 GHz, bandwidth of 500 MHz, time duration of 6.4 ns is used to generate a synthesized waveform with central frequency of 16.5 GHz, bandwidth of 1 GHz, time duration of 819.2 ns. The TBWP of the linearly chirped signal is improved from 3.2 to 819.2. The proposed method features arbitrary large TBWP, and it can be used in a radar system to improve its resolution. </div>展开更多
A common current source, generally used to bias cross-coupled differential amplifiers in a transconductor, controls third harmonic distortion (HD3) poorly. Separate current sources are shown to provide better control ...A common current source, generally used to bias cross-coupled differential amplifiers in a transconductor, controls third harmonic distortion (HD3) poorly. Separate current sources are shown to provide better control on HD3) . In this paper, a detailed design and analysis is presented for a transconductor made using this biasing technique. The transconductor, in addition, is made to offer high Gm, low power dissipation and is designed for linearly tunable Gm with current mode load as one of the applications. The circuit exhibits HD3) of less than –43.7 dB, high current efficiency of 1.18 V-1 and Gm of 390 μS at 1 VGp-p @ 50 MHz. UMC 0.18 μm CMOS process technology is used for simulation at supply voltage of 1.8 V.展开更多
In this paper, we propose a three-layered chiral metamaterial (CMM) that exhibits an asymmetric transmission effect for linearly polarized waves along forwardly and backwardly propagating in the microwave region, whic...In this paper, we propose a three-layered chiral metamaterial (CMM) that exhibits an asymmetric transmission effect for linearly polarized waves along forwardly and backwardly propagating in the microwave region, which not only realizes the asymmetric transmission effect of multi-frequency points for linearly polarized wave in microwave band, but also breaks through the limitation of single transformation from linear polarization to linear polarization. Numerical simulation results indicate that incident wave for linearly polarized waves will be converted and transmitted as a circularly polarized wave along the forward direction at 8.31 GHz. Moreover, the asymmetric transmission (AT) parameter Δ achieves 0.8 around 12 GHz, proving the existence of strong polarization conversion and diode-like function. The proposed CMM shows great potential applications in high performance linear polarization convertor and isolator in microwave frequency.展开更多
Locust and grasshopper plagues pose a serious threat to crop production in many areas worldwide.However,there is a lack of effective,quick-acting methods to control such outbreaks.Methods exploiting the phototactic re...Locust and grasshopper plagues pose a serious threat to crop production in many areas worldwide.However,there is a lack of effective,quick-acting methods to control such outbreaks.Methods exploiting the phototactic response of these insects are receiving increasing attention.The current study investigated the effect of linearly polarized and unpolarized light on locust phototactic and polarotactic responses,in particular the function of their dorsal rim area(DRA)and non-DRA visual fields.The results showed that the polarotactic function weight of DRA vision was stimulated by linearly polarized ultraviolet(UV)and violet light,the phototactic function weight was induced by blue,green,and orange light,and under linearly polarized light,the functional effect of DRA vision was strongest in response to linearly polarized violet light.Moreover,the locust visual response effect was related to spectral light attributes,with the linear polarization effect intensifying in response to the short-range vision sensitivity of non-DRA visual fields,whereas DRA vision regulated the short-range sensitivity of compound eye vision.When illumination increased,the synergistic enhancement effects of linearly polarized ultraviolet and violet light were significant,whereas the visual sensitivity was restricted significantly by linearly polarized blue,green,or orange light.Thus,non-DRA vision determined,while DRA vision enhanced,the phototactic response sensitivity,whereas,in linearly polarized UV or violet light,non-DRA vision determined,while DRA vision enhanced,the visual trend and polarotaxic aggregation sensitivity,with opposite effects in linearly polarized blue,green,or orange light.When illumination increased,there was a driving effect caused by linearly polarized violet light on non-DRA vision,whereas at short-wave lengths,the control effect induced by linearly polarized orange light was optimal;however,the photo-induced effect of linearly polarized violet light and the visual distance control effect of linearly polarized orange light were optimal.These results provide theoretical support for the photo-induced mechanism of the locust visual response effect and for the development of linearly polarized light sources for the environmentally friendly prevention and control of locust populations.展开更多
In this paper, we propose and experimentally investigate a linearly polarized narrow-linewidth random fiber laser(RFL) operating at 1080 nm and boost the output power to kilowatt level with near-diffraction-limited be...In this paper, we propose and experimentally investigate a linearly polarized narrow-linewidth random fiber laser(RFL) operating at 1080 nm and boost the output power to kilowatt level with near-diffraction-limited beam quality using a master oscillation power amplifier. The RFL based on a half-opened cavity, which is composed of a linearly polarized narrow-linewidth fiber Bragg grating and a 500 m piece of polarization-maintained Ge-doped fiber, generates a 0.71 W seed laser with an 88 pm full width at half-maximum(FWHM) linewidth and a 22.5 dB polarization extinction ratio(PER) for power scaling. A two-stage fiber amplifier enhances the seed laser to the maximal 1.01 k W with a PER value of 17 dB and a beam quality of M_x^2=1.15 and M_y^2=1.13. No stimulated Brillouin scattering effect is observed at the ultimate power level, and the FWHM linewidth of the amplified random laser broadens linearly as a function of the output power with a coefficient of about 0.1237 pm∕W.To the best of our knowledge, this is the first demonstration of a linearly polarized narrow-linewidth RFL with even kilowatt-level near-diffraction-limited output, and further performance scaling is ongoing.展开更多
We report on the high-power amplification of a 1064 nm linearly polarized laser in an all-fiber polarizationmaintained master oscillator power amplifier,which can operate at an output power level of 1.3 kW.The beam qu...We report on the high-power amplification of a 1064 nm linearly polarized laser in an all-fiber polarizationmaintained master oscillator power amplifier,which can operate at an output power level of 1.3 kW.The beam quality(M^2) was measured to be <1.2 at full power operation.The polarization extinction rate of the fiber amplifier was measured to be above 94% before mode instabilities(MIs) set in,which reduced to about 90% after the onset of MI.The power scaling capability of strategies for suppressing MI is analyzed based on a semianalytical model,the theoretical results of which agree with the experimental results.It shows that mitigating MI by coiling the gain fiber is an effective and practical method in standard double-cladding large mode area fiber,and,by tight coiling of the gain fiber to the radius of 5.5 cm,the MI threshold can be increased to three times higher than that without coiling or loose coiling.Experimental studies have been carried out to verify the idea,which has proved that MI was suppressed successfully in the amplifier by proper coiling.展开更多
In this manuscript, we demonstrate high-power, narrow-linewidth linearly polarized fiber laser with excellent beam quality through compact one-stage amplification scheme. By employing a single-mode–multimode–single-...In this manuscript, we demonstrate high-power, narrow-linewidth linearly polarized fiber laser with excellent beam quality through compact one-stage amplification scheme. By employing a single-mode–multimode–single-mode structure seed laser, a linearly polarized Yb-doped fiber laser with narrow linewidth and high output power is achieved.This laser, when used as a master oscillator, can be capable of suppressing the ASE in the process of power amplification.Thus, only one-stage amplification structure is used to scale up the laser power, and linearly polarized output with a polarization extinction ration of 14 d B, a narrow linewidth of 0.3 nm and an output power of 1018 W are achieved.Moreover, due to the good beam quality of seed laser and the well-designed amplifier stage, the beam quality of the output laser is near-diffraction-limited with M_x^2 ~1.18 and M_y^2 ~ 1.24 at the maximum power, and without mode instability occurring.展开更多
We demonstrate a high power linearly polarized Raman fiber laser(RFL)pumped by an amplified spontaneous emission(ASE)source.Temporal-stable operation of RFL could be ensured owing to the employment of ASE,which mitiga...We demonstrate a high power linearly polarized Raman fiber laser(RFL)pumped by an amplified spontaneous emission(ASE)source.Temporal-stable operation of RFL could be ensured owing to the employment of ASE,which mitigates the inherent intensity noise compared with the classic scheme adopting laser oscillator as pump source.In this experiment,the RFL has up to 119.5W output power,with central wavelength of 1129.2nm,and full width at half maximum(FWHM)linewidth of about 4.18nm.The polarization extinction ratio(PER)of the Raman laser is about 23dB.Moreover,this laser has excellent long-term and short-term stabilities in terms of the output power and time domain.展开更多
文摘AIM: To compare the outcomes of hand-sewn(HS) and linearly stapled(LS) esophagogastric anastomosis for esophageal cancer.METHODS: Before beginning this study, a rigorous protocol was established according to the recommendations of the Cochrane Collaboration. Databases and references were searched for all randomizedcontrolled trials and comparative clinical studies that compared LS with HS esophagogastric anastomosis for esophageal cancer. The primary outcomes compared were anastomotic leak and stricture. Subgroup analyses were performed according to site of anastomosis.RESULTS: Fifteen studies were used, comprising 3203 patients(n = 2027 LS and 1176 HS). Primary outcome analysis revealed a significant decrease in anastomotic leakage(RR = 0.51, 95%CI: 0.41-0.65; P < 0.00001) a s s o c i a t e d w i t h L S a n a s t o m o s i s. A s i g n i f i c a n t l y reduced rate of anastomotic stricture associated with LS was also found(RR = 0.56, 95%CI: 0.49-0.64; P < 0.00001). A subgroup analysis according to the site of anastomosis revealed a significantly reduced rate of anastomotic stricture(P < 0.00001). Although there was no significant difference in the decrease in thoracic anastomotic leakage, there was a significant decrease in cervical anastomotic leakage associated with LS(P < 0.00001).CONCLUSION: This meta-analysis indicates that the LS technique contributes to a reduced rate of leakage and stricture compared with the HS method.
文摘The plane structure of bars jointed to a rigid-body is a complex and universal structure.Some other structure of bars can be considered as its special cases. Many material have different stress-strain relation in tension and compression, generally the relation is nonlinear. In this paper,we use the constitutive model of linearly elastic and power hardening of strength difference to analyze plane structure of bars. The displacement method is used to derive the universal expression of calculating stress and strain. The nonlinear equations for computing displacements of the rigid-body has been given and general computing program has been worked out. This problem has been solved satisfactorily.
文摘Active set method and gradient projection method are curre nt ly the main approaches for linearly constrained convex programming. Interior-po int method is one of the most effective choices for linear programming. In the p aper a predictor-corrector interior-point algorithm for linearly constrained c onvex programming under the predictor-corrector motivation was proposed. In eac h iteration, the algorithm first performs a predictor-step to reduce the dualit y gap and then a corrector-step to keep the points close to the central traject ory. Computations in the algorithm only require that the initial iterate be nonn egative while feasibility or strict feasibility is not required. It is proved th at the algorithm is equivalent to a level-1 perturbed composite Newton method. Numerical experiments on twenty-six standard test problems are made. The result s show that the proposed algorithm is stable and robust.
基金supported by the National Natural Science Foundation of China(Grants Nos.12074142 and 11904122)。
文摘We investigate the ellipticity of the high-order harmonic generation from the oriented H_(2)^(+)exposed to a linearly polarized laser field by numerically solving the two-dimensional time-dependent Schrodinger equation(2 D TDSE).Numerical simulations show that the harmonic ellipticity is remarkably sensitive to the alignment angle.The harmonic spectrum is highly elliptically polarized at a specific alignment angleθ=30°,which is insensitive to the variation of the laser parameters.The position of the harmonic intensity minima indicates the high ellipticity,which can be attributed to the two-center interference effect.The high ellipticity can be explained by the phase difference of the harmonics.This result facilitates the synthesis of a highly elliptical isolated attosecond pulse with duration down to 65 as,which can be served as a powerful tool to explore the ultrafast dynamics of molecules and study chiral light-matter interaction.
文摘The present theoretical assessment deals with the peristaltic-ciliary transport of a developing embryo within a fallopian tubal fluid in the human fallopian tube.A mathematical model of peristalsis-cilia induced flow of a linearly viscous fluid within a fallopian tubal fluid in a finite two-dimensional narrow tube is developed. The lubrication approximation theory is used to solve the resulting partial differential equation. The expressions for axial and radial velocities, pressure gradient, stream function, volume flow rate, and time mean volume flow rate are derived. Numerical integration is performed for the appropriate residue time over the wavelength and the pressure difference over the wavelength. Moreover, the plots of axial velocity, the appropriate residue time over wavelength, the vector, the pressure difference over wavelength, and the streamlines are displayed and discussed for emerging parameters and constants. Salient features of the pumping characteristics and the trapping phenomenon are discussed in detail. Furthermore, a comparison between the peristaltic flow and the peristaltic-ciliary flow is made as the special case. Relevance of the current results to the transport of a developing embryo within a fallopian tubal fluid from ampulla to the intramural in the fallopian tube is also explored. It reveals the fact that cilia along with peristalsis helps to complete the required mitotic divisions while transporting the developing embryo within a fallopian tubal fluid in the human fallopian tube.
基金Supported by the National Natural Science Foundation of China
文摘The characteristics of coherent radiation produced by a cylindrical electron beam passing through a rectangular waveguide and linearly polarized wiggler are studied. The instability analysis is based on the linearized Vlasov-Maxwell equations for the perturbations about a self-consistent beam equilibrium. The dispersion equation of TMmn mode is deduced and by making use of numerical calculation the radiation frequency and growth rate as a function of electron beam energy and radius, axial magnetic field, wiggler field and wave length are presented and discussed.
文摘A technique for measuring the linearity of a linearly frequency-modulated continuous wave (LFM-CW) signal is presented. It uses a delay-line and a mixer to sense the slope of the output of a sweep oscillator, so that the original form of frequency function deviated from idealized linear slope is retrieved by means of spectrum analysis. Consequently,the linearity of the LFM signal is determined. The formulation is performed based on the principle that an angle-modulated signal can be approximated by an amplitude-modulated signal if the modulation coefficient is sufficiently small. To examine the validity of the procedure and to study the effect of each parameter on the accuracy of measurement, a number of computer simulations has been made. The results of simulation show that the error of the measurement is less than 2%.
文摘The focusing phenomena of SAW excited by an IDT with sinusoidal wavefront and linearly chirped periodic distribution has been explored.Some experimental results are compared with theoretical one and agree with it fairly well.
基金supported by the National Natural Science Foundation of China under Grant No.62005040the Fundamental Research Funds for the Central Universities under Grant No.ZYGX2020KYQD003the Science and Technology Project of Sichuan Province under Grant No.2021YJ0368.
文摘We demonstrated the~2.8-μm and~3.5-μm linearly polarized continuous wave(CW)laser outputs from a polarization-maintaining(PM)Er^(3+)-doped fluoride fiber laser.By introducing a film polarizer into the cavity to select the laser polarization orientation,the~2.8-μm linearly polarized CW laser with a high polarization extinction ratio(PER)of~23 dB and maximum output power of 2.37 W was achieved under double-end pumping at 976 nm.By adding another 1981-nm pump source simultaneously,the~3.5-μm linearly polarized CW laser was also obtained,giving higher PER of~27 dB and maximum output power of 307 mW which is only limited by the available power of 1981-nm pump.To the best of our knowledge,this is the first report on a mid-infrared linearly polarized CW PM fiber laser in the>2.5-μm mid-infrared region.This work not only opens up opportunities for some new mid-infrared applications,but also provides a promising platform for developing high-stability and versatile mid-infrared laser sources.
文摘In this paper, analysis of post-treatment of wire coating is presented. Coating material satisfies power law fluid model. Exact solutions for the velocity field, volume flow rate and average velocity are obtained. Moreover, the heat transfer results are presented for different cases of linearly varying on the boundaries. The variations of velocity, volume flow rate, radius of coated wire, shear rate and the force on the total wire are presented graphically and discussed.
文摘In this paper, effect of thermal gradient on vibration of trapezoidal plate of varying thickness is studied. Thermal effect and thickness variation is taken as linearly in x-direction. Rayleigh Ritz technique is used to calculate the fundamental frequencies. The frequencies corresponding to the first two modes of vibrations are obtained for a trapezoidal plate for different values of taper constant, thermal gradient and aspect ratio. Results are presented in graphical form.
文摘In this paper, the effect of thermal gradient on the vibration of parallelogram plate with linearly varying thickness in both direction having clamped boundary conditions on all the four edges is analyzed. Thermal effect on vibration of such plate has been taken as one-dimensional distribution in linear form only. An approximate but quiet convenient frequency equation is derived using Rayleigh-Ritz technique with a two-term deflection function. The frequencies corresponding to the first two modes of vibration of a clamped parallelogram plate have been computed for different values of aspect ratio, thermal gradient, taper constants and skew angle. The results have been presented in tabular forms. The results obtained in this study are reduced to that of unheated parallelogram plates of uniform thickness and have generally been compared with the published one.
文摘<div style="text-align:justify;"> A photonics approach to generate a linearly chirped waveform with increased TBWP is proposed and investigated. The time bandwidth product (TBWP) of the linearly chirped waveform is improved based on optical microwave frequency multiplying combined with temporal synthesis. An integrated dual-polarization modulator and an optical filter are utilized to perform frequency doubling operation by generating an orthogonally polarized optical signal, which consists of an optical carrier in one polarization direction and a second-order chirped optical sideband in another. Then the orthogonally polarized optical signal puts into a polarization modulator (PolM) to perform phase coding process. By driving a Pseudorandom (PN) sequence to the PolM, the time duration of the generated bandwidth doubled linearly chirped waveform can be synthesized to arbitrary length. The approach is verified by simulation. A linearly chirped waveform with central frequency of 8.25 GHz, bandwidth of 500 MHz, time duration of 6.4 ns is used to generate a synthesized waveform with central frequency of 16.5 GHz, bandwidth of 1 GHz, time duration of 819.2 ns. The TBWP of the linearly chirped signal is improved from 3.2 to 819.2. The proposed method features arbitrary large TBWP, and it can be used in a radar system to improve its resolution. </div>
文摘A common current source, generally used to bias cross-coupled differential amplifiers in a transconductor, controls third harmonic distortion (HD3) poorly. Separate current sources are shown to provide better control on HD3) . In this paper, a detailed design and analysis is presented for a transconductor made using this biasing technique. The transconductor, in addition, is made to offer high Gm, low power dissipation and is designed for linearly tunable Gm with current mode load as one of the applications. The circuit exhibits HD3) of less than –43.7 dB, high current efficiency of 1.18 V-1 and Gm of 390 μS at 1 VGp-p @ 50 MHz. UMC 0.18 μm CMOS process technology is used for simulation at supply voltage of 1.8 V.
文摘In this paper, we propose a three-layered chiral metamaterial (CMM) that exhibits an asymmetric transmission effect for linearly polarized waves along forwardly and backwardly propagating in the microwave region, which not only realizes the asymmetric transmission effect of multi-frequency points for linearly polarized wave in microwave band, but also breaks through the limitation of single transformation from linear polarization to linear polarization. Numerical simulation results indicate that incident wave for linearly polarized waves will be converted and transmitted as a circularly polarized wave along the forward direction at 8.31 GHz. Moreover, the asymmetric transmission (AT) parameter Δ achieves 0.8 around 12 GHz, proving the existence of strong polarization conversion and diode-like function. The proposed CMM shows great potential applications in high performance linear polarization convertor and isolator in microwave frequency.
基金The authors acknowledge that this work was financially supported by the Scientific and Technological Project of Henan Province,China(Grant No.222102210116,212102110229)the special project of Xinxiang Science and Technology of Henan Province,China(Grant No.21ZD003)the National Natural Science Foundation of China(Grant No.31772501).
文摘Locust and grasshopper plagues pose a serious threat to crop production in many areas worldwide.However,there is a lack of effective,quick-acting methods to control such outbreaks.Methods exploiting the phototactic response of these insects are receiving increasing attention.The current study investigated the effect of linearly polarized and unpolarized light on locust phototactic and polarotactic responses,in particular the function of their dorsal rim area(DRA)and non-DRA visual fields.The results showed that the polarotactic function weight of DRA vision was stimulated by linearly polarized ultraviolet(UV)and violet light,the phototactic function weight was induced by blue,green,and orange light,and under linearly polarized light,the functional effect of DRA vision was strongest in response to linearly polarized violet light.Moreover,the locust visual response effect was related to spectral light attributes,with the linear polarization effect intensifying in response to the short-range vision sensitivity of non-DRA visual fields,whereas DRA vision regulated the short-range sensitivity of compound eye vision.When illumination increased,the synergistic enhancement effects of linearly polarized ultraviolet and violet light were significant,whereas the visual sensitivity was restricted significantly by linearly polarized blue,green,or orange light.Thus,non-DRA vision determined,while DRA vision enhanced,the phototactic response sensitivity,whereas,in linearly polarized UV or violet light,non-DRA vision determined,while DRA vision enhanced,the visual trend and polarotaxic aggregation sensitivity,with opposite effects in linearly polarized blue,green,or orange light.When illumination increased,there was a driving effect caused by linearly polarized violet light on non-DRA vision,whereas at short-wave lengths,the control effect induced by linearly polarized orange light was optimal;however,the photo-induced effect of linearly polarized violet light and the visual distance control effect of linearly polarized orange light were optimal.These results provide theoretical support for the photo-induced mechanism of the locust visual response effect and for the development of linearly polarized light sources for the environmentally friendly prevention and control of locust populations.
基金National Natural Science Foundation of China(NSFC)(61322505,61635005)
文摘In this paper, we propose and experimentally investigate a linearly polarized narrow-linewidth random fiber laser(RFL) operating at 1080 nm and boost the output power to kilowatt level with near-diffraction-limited beam quality using a master oscillation power amplifier. The RFL based on a half-opened cavity, which is composed of a linearly polarized narrow-linewidth fiber Bragg grating and a 500 m piece of polarization-maintained Ge-doped fiber, generates a 0.71 W seed laser with an 88 pm full width at half-maximum(FWHM) linewidth and a 22.5 dB polarization extinction ratio(PER) for power scaling. A two-stage fiber amplifier enhances the seed laser to the maximal 1.01 k W with a PER value of 17 dB and a beam quality of M_x^2=1.15 and M_y^2=1.13. No stimulated Brillouin scattering effect is observed at the ultimate power level, and the FWHM linewidth of the amplified random laser broadens linearly as a function of the output power with a coefficient of about 0.1237 pm∕W.To the best of our knowledge, this is the first demonstration of a linearly polarized narrow-linewidth RFL with even kilowatt-level near-diffraction-limited output, and further performance scaling is ongoing.
基金funding from the program for the National Science Foundation of China under Grant No.61322505the program for New Century Excellent Talents in University+1 种基金the Innovation Foundation for Excellent Graduates in National University of Defense Technology under Grant No.B120704the Hunan Provincial Innovation Foundation for Postgraduate under Grant No.CX2012B035
文摘We report on the high-power amplification of a 1064 nm linearly polarized laser in an all-fiber polarizationmaintained master oscillator power amplifier,which can operate at an output power level of 1.3 kW.The beam quality(M^2) was measured to be <1.2 at full power operation.The polarization extinction rate of the fiber amplifier was measured to be above 94% before mode instabilities(MIs) set in,which reduced to about 90% after the onset of MI.The power scaling capability of strategies for suppressing MI is analyzed based on a semianalytical model,the theoretical results of which agree with the experimental results.It shows that mitigating MI by coiling the gain fiber is an effective and practical method in standard double-cladding large mode area fiber,and,by tight coiling of the gain fiber to the radius of 5.5 cm,the MI threshold can be increased to three times higher than that without coiling or loose coiling.Experimental studies have been carried out to verify the idea,which has proved that MI was suppressed successfully in the amplifier by proper coiling.
基金supported by Huo Ying Dong Education Foundation of China(No.151062)the Foundation for the author of National Excellent Doctoral Dissertation of China(No.201329)
文摘In this manuscript, we demonstrate high-power, narrow-linewidth linearly polarized fiber laser with excellent beam quality through compact one-stage amplification scheme. By employing a single-mode–multimode–single-mode structure seed laser, a linearly polarized Yb-doped fiber laser with narrow linewidth and high output power is achieved.This laser, when used as a master oscillator, can be capable of suppressing the ASE in the process of power amplification.Thus, only one-stage amplification structure is used to scale up the laser power, and linearly polarized output with a polarization extinction ration of 14 d B, a narrow linewidth of 0.3 nm and an output power of 1018 W are achieved.Moreover, due to the good beam quality of seed laser and the well-designed amplifier stage, the beam quality of the output laser is near-diffraction-limited with M_x^2 ~1.18 and M_y^2 ~ 1.24 at the maximum power, and without mode instability occurring.
文摘We demonstrate a high power linearly polarized Raman fiber laser(RFL)pumped by an amplified spontaneous emission(ASE)source.Temporal-stable operation of RFL could be ensured owing to the employment of ASE,which mitigates the inherent intensity noise compared with the classic scheme adopting laser oscillator as pump source.In this experiment,the RFL has up to 119.5W output power,with central wavelength of 1129.2nm,and full width at half maximum(FWHM)linewidth of about 4.18nm.The polarization extinction ratio(PER)of the Raman laser is about 23dB.Moreover,this laser has excellent long-term and short-term stabilities in terms of the output power and time domain.
