The Ti-doped waveguide-type periodically poled LiNbO3 (PPLN) were fabricated and the dependence of domain wall velocity on an external field applied for domain inversion was investigated. The whole polarization revers...The Ti-doped waveguide-type periodically poled LiNbO3 (PPLN) were fabricated and the dependence of domain wall velocity on an external field applied for domain inversion was investigated. The whole polarization reversal process was computer-controlled to regulate domain wall expansion at a feedback time shorter than 5 μs. The coercive voltage and several values of excess voltage were applied on 500 μm-thick wafers serially connected to a 1-MOhm external resistor which had an effect of the poling current reduction, i.e. the deceleration of domain wall expansion. The domain wall velocity is sensitive to the poling voltage, precisely speaking, to the excess voltage. The domain wall velocities were 28.70, 16.02 and 5.75 μm·s-1 under poling field of 23.5, 22.0 and 21.0 kV·mm-1, respectively. Moreover, average duty cycle of PPLN is about 49.93%.展开更多
Films were prepared from mixtures of copolymers of 4-nitro-4’- [N- methylacryloyloxyethyl,N’-ethyl] amino azobenzene with glycidyl methacrylate (chromophore content: 6 mol%) andcopolymers containing anhydride units,...Films were prepared from mixtures of copolymers of 4-nitro-4’- [N- methylacryloyloxyethyl,N’-ethyl] amino azobenzene with glycidyl methacrylate (chromophore content: 6 mol%) andcopolymers containing anhydride units, which was obtained by the reaction of 4-nitro-4’-[N-hydroxyethyl, N’-ethyl] amino azobenzene with polymethacryloyl chloride (chromophorecontent: 25 mol %). During thermal poling process the anhydride reacts with the epoxygroup and the resulting crosslinked network structure will stabilize the second harmonicgeneration in the poled film. The second harmonic generation of the poled film shows amaximum with the variation of composition, this is presumed to be due to the effects of theincreasing of concentration, orientation order as well as orientation stability of chromophoregroups during crosslinking.展开更多
The experiment on quasi-phase-matched second harmonic generation (SHG) in a channel waveguide was reported. The waveguide was made by annealed proton exchange in the periodically poled lithium niobate (PPLN) with the ...The experiment on quasi-phase-matched second harmonic generation (SHG) in a channel waveguide was reported. The waveguide was made by annealed proton exchange in the periodically poled lithium niobate (PPLN) with the period of PPLN of 14.9 μm, which was designed for cascading wavelength conversion in dense wavelength division multiplexer optical communications. The measurement results of SHG conversion efficiency as a function of fundamental wavelength at room temperature fit well to sinc^2 shape. The peak of SHG conversion efficiency was 75%·W~ -1 ·cm~ -2 as well as reported. The relationship between the center fundamental wavelength and temperature shows that SHG can be effectively tuned by the temperature in PPLN waveguide.展开更多
The investigation of electrochromic effect of corona-poled nonlinear optical polymer films is an effective method for the estimation of poling level and the selection of poling conditions. The poling electric field E&...The investigation of electrochromic effect of corona-poled nonlinear optical polymer films is an effective method for the estimation of poling level and the selection of poling conditions. The poling electric field E<sub>p</sub> and orientational order parameter Φ, which are the important parameters to predict d<sub>33</sub> of poled films, can be calculated by a simple operation from the number of red shift of charge transfer absorption band. The calculated results are in good agreement with the experimental data.展开更多
RELAXOR ferroelectric ceramics with complex perovskite structure is considered as the first material chosen for multilayer capacitors (MLC) in technology and economy, because of their high permittivity, lower sinterin...RELAXOR ferroelectric ceramics with complex perovskite structure is considered as the first material chosen for multilayer capacitors (MLC) in technology and economy, because of their high permittivity, lower sintering temperature and lower capacitors changing rate with temperature (temperature coefficient) for diffuse phase transition (DPT). Thus, preparations and properties about the materials received more attention. There are many reports about their dielectric properties but there are few about their poled dielectric behavior. In the展开更多
The nonlinear Talbot effect is a near-field nonlinear diffraction phenomenon in which the self-imaging of periodic objects is formed by the second harmonics of the incident laser beam. We demonstrate the first, to the...The nonlinear Talbot effect is a near-field nonlinear diffraction phenomenon in which the self-imaging of periodic objects is formed by the second harmonics of the incident laser beam. We demonstrate the first, to the best of our knowledge, example of nonlinear Talbot self-healing, i.e., the capability of creating defect-free images from faulty nonlinear optical structures. In particular, we employ the tightly focused femtosecond infrared optical pulses to fabricate LiNbO_(3) nonlinear photonic crystals and show that the defects in the form of the missing points of two-dimensional square and hexagonal periodic structures are restored in the second harmonic images at the first nonlinear Talbot plane. The observed nonlinear Talbot self-healing opens up new possibilities for defect-tolerant optical lithography and printing.展开更多
The Quasi-phase-matching periodically poled flux-grown KTP by high electrical field method is researched. A 8×5×1mm3,∧=9.0μm PPKTP wafer is successfully fabricated for the first order QPM SHG. The interact...The Quasi-phase-matching periodically poled flux-grown KTP by high electrical field method is researched. A 8×5×1mm3,∧=9.0μm PPKTP wafer is successfully fabricated for the first order QPM SHG. The interactive length of the sample is about 3mm. The SHG scheme of Nd: YAG at 1064nm tested that the output power of cw 532nm green light is 0.2mw at room temperature with fundamental power of 1.2w. The normalized conversion efficiency is about 0.09% (W·cm)-1.展开更多
The molecules formed in a structure of A-π-D possess large hyperpolarizability β, in which A is an acceptor, D is a donor, and π is an electronic bridge connecting A and D. From such molecules one can make poled po...The molecules formed in a structure of A-π-D possess large hyperpolarizability β, in which A is an acceptor, D is a donor, and π is an electronic bridge connecting A and D. From such molecules one can make poled polymer films of large second-order展开更多
A logarithmic expression is proposed to describe relaxation of the polar order in side chain polymers,together with a new way of plotting temperature dependent relaxation data.This results in a straight line extending...A logarithmic expression is proposed to describe relaxation of the polar order in side chain polymers,together with a new way of plotting temperature dependent relaxation data.This results in a straight line extending even below the glass transition temperature in the case of poled nonlinear optics (NLO) side chain polymers.A simple procedure to determine the rotational diffusion constant Dr is given and Dr values of several polymer systems have been evaluated and compared with each other.It appears that,starting from the conventional and well known poled polymer system currently applied,a further lowering of Dr by about 3 orders of magnitude is necessary in order to reach an acceptable orientational stability or lifetime of poled polymers for practical applications.Attempts have been made to introduce electron push-pull substituents into high thermostable molecular frameworks and results of preliminary measurements are reported.展开更多
The determination of nonlinearities near the band edge of organic and polymeric electro-optic(EO)materials is important from the viewpoint of molecular nonlinear optics(NLO)and photonic device applications.Based on tr...The determination of nonlinearities near the band edge of organic and polymeric electro-optic(EO)materials is important from the viewpoint of molecular nonlinear optics(NLO)and photonic device applications.Based on transmission-mode Stark effect electromodulation(EM)spectroscopy,we study the electric-field-induced changes in optical absorption and refraction of newly developed EO polymers from the visible to near-infrared(NIR)wavelengths and report record-high near-band-edge complex EO effects from poled thin films.Values ofΔn andΔk up to 10^(-3) and 10^(-2) are found at an applied electric field of 2.0×10^(5)-3.0×10^(5)V/cm.The study of linear optical properties of poled films by spectroscopic ellipsometry shows large polinginduced birefringence and a nearly two-fold increase in the extinction coefficients at the extraordinary polarization.Through the Kramers-Kronig analysis,we obtained the real and imaginary second-order nonlinear coefficients up to~3,500 and~5,600 pm/V,respectively,which are believed to be the highest NLO coefficients of poled polymers through the resonance enhancement.Our approach goes beyond the previous works,applicable only to several discrete wavelengths,to a full-spectral analysis with independent verification of slab waveguide measurements.By considering both the electroabsorption and electrorefraction effects,our study overcomes the limitation of the classic qualitative two-level model and provides a quantitative understanding of near-resonance optical nonlinearities of organic EO materials.It can inspire the exploration of high-speed,absorptive,or phase-shifting light-modulators using EO polymers for on-chip applications.展开更多
In this paper, we report a passively mode-locked Nd∶Y3Sc2Al3O12(Nd:YSAG) laser using a periodically poled Li Nb O3(PPLN)superlattice. Nonlinear mirror mode locking based on PPLN intracavity frequency doubling was the...In this paper, we report a passively mode-locked Nd∶Y3Sc2Al3O12(Nd:YSAG) laser using a periodically poled Li Nb O3(PPLN)superlattice. Nonlinear mirror mode locking based on PPLN intracavity frequency doubling was theoretically analyzed. The modulation depth of nonlinear reflectivity of the nonlinear mirror is approximately 8.8%. Optical performances of the modelocked laser including output power, radio frequency spectrum, and optical spectrum were experimentally investigated. An average output power of 710 m W with a slope efficiency of 14.6% was obtained at the pump power of 6.5 W. The repetition rate is 101.7 MHz, and the signal-to-noise ratio of the mode-locked pulse is 45 d B. The mode-locked pulse width was approximately 9 ps.展开更多
This article addresses the leader-following output consensus problem of heterogeneous linear multi-agent systems with unknown agent parameters under directed graphs.The dynamics of followers are allowed to be non-mini...This article addresses the leader-following output consensus problem of heterogeneous linear multi-agent systems with unknown agent parameters under directed graphs.The dynamics of followers are allowed to be non-minimum phase with unknown arbitrary individual relative degrees.This is contrary to many existing works on distributed adaptive control schemes where agent dynamics are required to be minimum phase and often of the same relative degree.A distributed adaptive pole placement control scheme is developed,which consists of a distributed observer and an adaptive pole placement control law.It is shown that under the proposed distributed adaptive control scheme,all signals in the closed-loop system are bounded and the outputs of all the followers track the output of the leader asymptotically.The effectiveness of the proposed scheme is demonstrated by one practical example and one numerical example.展开更多
The research aims to study recent Antarctic plate kinematics based on Global Navigation Satellite System(GNSS)data.The research covers 60 continuous GNSS stations located on the Antarctic plate during 1994-2021.We det...The research aims to study recent Antarctic plate kinematics based on Global Navigation Satellite System(GNSS)data.The research covers 60 continuous GNSS stations located on the Antarctic plate during 1994-2021.We determine the components of horizontal displacement vectors of these GNSS stations and construct the schematic map of their distribution.The results indicate that the direction of velocity vectors of horizontal displacements has a rotational nature in clockwise order.The analysis of deformation processes shows that a gradual decrease in the horizontal strain rates,maximum shear strain and area strain is taking place from west to east,in the direction of West Antarctica-the Transantarctic Mountains-East Antarctica.The absolute rotation pole of the Antarctic plate in the ITRF2014/IGS14 reference frame has been determined,and the obtained values are in good agreement with recent plate models.展开更多
Objective:To evaluate the long-term stone-free rate(SFR)of retrograde intrarenal surgery(RIRS)in the treatment of lower pole renal calculi using only basket relocation and identify independent predictors of stone-free...Objective:To evaluate the long-term stone-free rate(SFR)of retrograde intrarenal surgery(RIRS)in the treatment of lower pole renal calculi using only basket relocation and identify independent predictors of stone-free status.Methods:All consecutive patients undergoing RIRS lower pole renal calculi at a single highvolume tertiary center were analyzed retrospectively.Lower pole stones were relocated to the upper pole,where laser lithotripsy was performed.All patients were followed up in the clinic following the surgery and yearly thereafter.The stone-free status was assessed with a combination of an abdominal ultrasound and abdominal X-ray,or an abdominal non-contrast computed tomography if the stones were known to be radiolucent.Results:A total of 480 consecutive patients who underwent RIRS for treatment of lower pole renal calculi,between January 2012 and December 2018,were analyzed from a prospectively maintained database of 3000 ureteroscopies.With a median follow-up time of 18.6 months,the mean SFR was 94.8%.The procedures were unsuccessful in 26(5.4%)patients due to unreachable stones.The median stone size of the unreachable stones was 12 mm(range 10e30 mm).Multivariable logistic regression analysis revealed two predictors of SFR for lower pole stones:a small cumulative stone burden(odds ratio[OR]:0.903,95%confidence interval[CI]:0.867e0.941,p<0.0001)and preoperative ureteral stent insertion(OR:0.515,95%CI:0.318e0.835,pZ0.007).Conclusion:The long-term SFR of RIRS for the treatment of lower pole stones with basket displacement with appropriate patient selection is high.展开更多
A novel,carbon nanotubefield effect transistor(CNTFET)based fully differentialfirst order all passfilter(FDFAPF)circuit configuration is presented.The FDFAPF uses CNTFET based negative transconductors(NTs)and positive...A novel,carbon nanotubefield effect transistor(CNTFET)based fully differentialfirst order all passfilter(FDFAPF)circuit configuration is presented.The FDFAPF uses CNTFET based negative transconductors(NTs)and positive transconductors(PTs)in its realization.The proposed circuit topology employs two PTs,two NTs,two resistors and one capacitor.All the passive components of the realized topology are grounded.Active only fully differentialfirst order all passfilter(AO-FDFAPF)topology is also derived from the proposed FDFAPF.The electronic tunability of the AO-FDFAPF is obtained by controlling the employed CNTFET based varactor.A tunabilty of pole frequency in the range of 10.5 to 26 GHz is obtained.Both the circuits are potential candidates for high frequency fully differential analog signal processing applications.As compared to prior state-of-the-art works,both the realized topologies have achieved highest pole frequency and lowest power dissipation.Moreover,they utilize compact circuit structures and suitable for low voltage applications.Moreover,both topologies work equally well in the deep submicron.The proposedfilters are analyzed and verified through HPSPICE simulations by utilizing Stanford CNTFET model at 16 nm technology node.It is observed that the proposed circuit simulation outcomes verify the theory.展开更多
Soft magnetic composite(SMC)material is an ideal soft magnetic material employed for developing 3D magnetic flux electromagnetic equipment,due to its advantages of 3D magnetic isotropy characteristic,low eddy current ...Soft magnetic composite(SMC)material is an ideal soft magnetic material employed for developing 3D magnetic flux electromagnetic equipment,due to its advantages of 3D magnetic isotropy characteristic,low eddy current loss,and simple manufacturing process.The permanent magnet claw pole machine(PMCPM)with SMC cores is a good case that the SMC to be adopted for developing 3D flux electrical machines.In this paper,a novel axial-radial flux permanent magnet claw pole machine(ARPMCPM)with SMC cores and ferrite magnets is proposed.Compared with the traditional PMCPM,the proposed ARPMCPM is designed with only one spoke PM rotor and its whole structure is quite compact.For the performance prediction,the 3D finite element method(FEM)is used.Meanwhile,for the performance evaluation,a previously developed axial flux claw pole permanent magnet machine(AFCPM)is employed as the benchmark machine and all these machines are optimized by using the combined multilevel robust Taguchi method.It can be seen that the proposed ARPMCPM is with higher torque/weight density and operation efficiency.展开更多
Permanent magnet claw pole machine(PMCPM) is a special kind of transverse flux permanent magnet machine. Compared with other electrical machines, it has the advantages of high torque density and high efficiency for hi...Permanent magnet claw pole machine(PMCPM) is a special kind of transverse flux permanent magnet machine. Compared with other electrical machines, it has the advantages of high torque density and high efficiency for high speed operation. However, because of its complex irregular structure, the manufacturing process using silicon sheets is complicated. Soft magnetic composite material(SMC) is manufactured by powder metallurgy technology, which can produce various shapes of stator core structures, so it is easier to produce various irregular shapes of the stator core. However, the raw SMC material is relatively expensive, and the mechanical strength of SMC is weak. In this paper, a PMCPM with hybrid cores is proposed. With the adoption of hybrid silicon sheet-SMC cores and amorphous alloy-SMC cores, the torque ability of PMCPM can be improved greatly and it can have higher efficiency for more wide operation frequency. Meanwhile, its mechanical strength has been improved and it can be designed for high torque direct drive applications as it is a modular machine. Furthermore, three methods are proposed to reduce the additional eddy current loss which resulted from the employment of hybrid cores in PMCPM.展开更多
Background and Objectives: Pyelo-Ureteral Junction Syndrome (PUJS) is the most common obstructive malformation of the upper urinary tract in children and adults. The standard treatment is open pyeloplasty using the Ku...Background and Objectives: Pyelo-Ureteral Junction Syndrome (PUJS) is the most common obstructive malformation of the upper urinary tract in children and adults. The standard treatment is open pyeloplasty using the Kuss-Anderson technique. Because of the minimally invasive nature of the laparoscopic approach, it has become the approach of choice for the management of this pathology. We present the results of laparoscopic transperitoneal pyeloplasty used in the management of PUJS. Materials and Methods: This was a retrospective study from 2015 to 2020, including 26 patients who underwent laparoscopic transperitoneal pyeloplasty for PUJS. Results: Twenty-six patients, including 18 (69.2%) men and 6 (30.8%) women, with a mean age of 35.42 ± 13.62 years, were treated. Renal colic was the primary symptom in the majority of the cases (22, 84.6%)). The diagnosis was confirmed in all patients through an abdominal CT scan, which revealed that all 26 patients had hydronephrosis. Half of the patients (50.0%) were classified as Valayer-Cendron Type II, and eight (30.8%) patients had associated stones. Seventeen (65.4%) patients had pathologies on the left side, and all patients were treated using the Kuss-Anderson technique with a median operating time of 108.5 (90.0 - 136.0) minutes. The uncrossing of lower pole vessels was performed in 10 patients. The average duration of hospitalisation was 2.23 ± 0.82 days. No conversion was observed, and after an average follow-up of 53.69 days, the success rate was 92.3%. Conclusion: Laparoscopic pyeloplasty is a minimally invasive technique of choice for the treatment of pyelo-ureteral junction obstruction. It is dependable, repeatable, and produces good functional outcomes that are equal to those of traditional surgery.展开更多
文摘The Ti-doped waveguide-type periodically poled LiNbO3 (PPLN) were fabricated and the dependence of domain wall velocity on an external field applied for domain inversion was investigated. The whole polarization reversal process was computer-controlled to regulate domain wall expansion at a feedback time shorter than 5 μs. The coercive voltage and several values of excess voltage were applied on 500 μm-thick wafers serially connected to a 1-MOhm external resistor which had an effect of the poling current reduction, i.e. the deceleration of domain wall expansion. The domain wall velocity is sensitive to the poling voltage, precisely speaking, to the excess voltage. The domain wall velocities were 28.70, 16.02 and 5.75 μm·s-1 under poling field of 23.5, 22.0 and 21.0 kV·mm-1, respectively. Moreover, average duty cycle of PPLN is about 49.93%.
文摘Films were prepared from mixtures of copolymers of 4-nitro-4’- [N- methylacryloyloxyethyl,N’-ethyl] amino azobenzene with glycidyl methacrylate (chromophore content: 6 mol%) andcopolymers containing anhydride units, which was obtained by the reaction of 4-nitro-4’-[N-hydroxyethyl, N’-ethyl] amino azobenzene with polymethacryloyl chloride (chromophorecontent: 25 mol %). During thermal poling process the anhydride reacts with the epoxygroup and the resulting crosslinked network structure will stabilize the second harmonicgeneration in the poled film. The second harmonic generation of the poled film shows amaximum with the variation of composition, this is presumed to be due to the effects of theincreasing of concentration, orientation order as well as orientation stability of chromophoregroups during crosslinking.
基金The National Natural Science Foundation ofChina (No 60477016)Shanghai MunicipalEducation Commission"Shu Guang"Project
文摘The experiment on quasi-phase-matched second harmonic generation (SHG) in a channel waveguide was reported. The waveguide was made by annealed proton exchange in the periodically poled lithium niobate (PPLN) with the period of PPLN of 14.9 μm, which was designed for cascading wavelength conversion in dense wavelength division multiplexer optical communications. The measurement results of SHG conversion efficiency as a function of fundamental wavelength at room temperature fit well to sinc^2 shape. The peak of SHG conversion efficiency was 75%·W~ -1 ·cm~ -2 as well as reported. The relationship between the center fundamental wavelength and temperature shows that SHG can be effectively tuned by the temperature in PPLN waveguide.
文摘The investigation of electrochromic effect of corona-poled nonlinear optical polymer films is an effective method for the estimation of poling level and the selection of poling conditions. The poling electric field E<sub>p</sub> and orientational order parameter Φ, which are the important parameters to predict d<sub>33</sub> of poled films, can be calculated by a simple operation from the number of red shift of charge transfer absorption band. The calculated results are in good agreement with the experimental data.
文摘RELAXOR ferroelectric ceramics with complex perovskite structure is considered as the first material chosen for multilayer capacitors (MLC) in technology and economy, because of their high permittivity, lower sintering temperature and lower capacitors changing rate with temperature (temperature coefficient) for diffuse phase transition (DPT). Thus, preparations and properties about the materials received more attention. There are many reports about their dielectric properties but there are few about their poled dielectric behavior. In the
基金supported by the National Natural Science Foundation of China(Nos.61905124,11974196,and 61905125)the Australian Research Council(No.DP19010774)+2 种基金the Qatar National Research Fund(No.NPRP 12S-0205190047)the Yongjiang Scholar Foundation of Ningbothe K.C.Wong Magna Fund of Ningbo University。
文摘The nonlinear Talbot effect is a near-field nonlinear diffraction phenomenon in which the self-imaging of periodic objects is formed by the second harmonics of the incident laser beam. We demonstrate the first, to the best of our knowledge, example of nonlinear Talbot self-healing, i.e., the capability of creating defect-free images from faulty nonlinear optical structures. In particular, we employ the tightly focused femtosecond infrared optical pulses to fabricate LiNbO_(3) nonlinear photonic crystals and show that the defects in the form of the missing points of two-dimensional square and hexagonal periodic structures are restored in the second harmonic images at the first nonlinear Talbot plane. The observed nonlinear Talbot self-healing opens up new possibilities for defect-tolerant optical lithography and printing.
基金This work is supported by scientific research key project fund of Ministry of Education (02042)
文摘The Quasi-phase-matching periodically poled flux-grown KTP by high electrical field method is researched. A 8×5×1mm3,∧=9.0μm PPKTP wafer is successfully fabricated for the first order QPM SHG. The interactive length of the sample is about 3mm. The SHG scheme of Nd: YAG at 1064nm tested that the output power of cw 532nm green light is 0.2mw at room temperature with fundamental power of 1.2w. The normalized conversion efficiency is about 0.09% (W·cm)-1.
基金Project supported by Guangdong Provincial Science Foundation.
文摘The molecules formed in a structure of A-π-D possess large hyperpolarizability β, in which A is an acceptor, D is a donor, and π is an electronic bridge connecting A and D. From such molecules one can make poled polymer films of large second-order
文摘A logarithmic expression is proposed to describe relaxation of the polar order in side chain polymers,together with a new way of plotting temperature dependent relaxation data.This results in a straight line extending even below the glass transition temperature in the case of poled nonlinear optics (NLO) side chain polymers.A simple procedure to determine the rotational diffusion constant Dr is given and Dr values of several polymer systems have been evaluated and compared with each other.It appears that,starting from the conventional and well known poled polymer system currently applied,a further lowering of Dr by about 3 orders of magnitude is necessary in order to reach an acceptable orientational stability or lifetime of poled polymers for practical applications.Attempts have been made to introduce electron push-pull substituents into high thermostable molecular frameworks and results of preliminary measurements are reported.
基金supported by the Fundamental Research Project Funding from Shenzhen Science & Technology Innovation Committee (JCYJ20180507181718203)the National Natural Science Foundation of China (21975213)+2 种基金the Research Grants Council (RGC) of Hong Kong (11306320, 11303618, 11210218)the City University of Hong Kong (9610389, 9680263, 9610454)the Innovation and Technology Commission of Hong Kong (ITS/461/18)。
文摘The determination of nonlinearities near the band edge of organic and polymeric electro-optic(EO)materials is important from the viewpoint of molecular nonlinear optics(NLO)and photonic device applications.Based on transmission-mode Stark effect electromodulation(EM)spectroscopy,we study the electric-field-induced changes in optical absorption and refraction of newly developed EO polymers from the visible to near-infrared(NIR)wavelengths and report record-high near-band-edge complex EO effects from poled thin films.Values ofΔn andΔk up to 10^(-3) and 10^(-2) are found at an applied electric field of 2.0×10^(5)-3.0×10^(5)V/cm.The study of linear optical properties of poled films by spectroscopic ellipsometry shows large polinginduced birefringence and a nearly two-fold increase in the extinction coefficients at the extraordinary polarization.Through the Kramers-Kronig analysis,we obtained the real and imaginary second-order nonlinear coefficients up to~3,500 and~5,600 pm/V,respectively,which are believed to be the highest NLO coefficients of poled polymers through the resonance enhancement.Our approach goes beyond the previous works,applicable only to several discrete wavelengths,to a full-spectral analysis with independent verification of slab waveguide measurements.By considering both the electroabsorption and electrorefraction effects,our study overcomes the limitation of the classic qualitative two-level model and provides a quantitative understanding of near-resonance optical nonlinearities of organic EO materials.It can inspire the exploration of high-speed,absorptive,or phase-shifting light-modulators using EO polymers for on-chip applications.
基金supported by the National Key Research and Development Project of China (No. 2019YFA0705000)the National Natural Science Foundation of China (Nos. 91950106, 11404196, 11525418, 91750201, and 11974218)+1 种基金the Innovation Group of Jinan (2018GXRC010)the Local Science and Technology Development Project of the Central Government (No. YDZX20203700001766)
文摘In this paper, we report a passively mode-locked Nd∶Y3Sc2Al3O12(Nd:YSAG) laser using a periodically poled Li Nb O3(PPLN)superlattice. Nonlinear mirror mode locking based on PPLN intracavity frequency doubling was theoretically analyzed. The modulation depth of nonlinear reflectivity of the nonlinear mirror is approximately 8.8%. Optical performances of the modelocked laser including output power, radio frequency spectrum, and optical spectrum were experimentally investigated. An average output power of 710 m W with a slope efficiency of 14.6% was obtained at the pump power of 6.5 W. The repetition rate is 101.7 MHz, and the signal-to-noise ratio of the mode-locked pulse is 45 d B. The mode-locked pulse width was approximately 9 ps.
基金This work was supported by Research Grants Council of Hong Kong(CityU-11205221).
文摘This article addresses the leader-following output consensus problem of heterogeneous linear multi-agent systems with unknown agent parameters under directed graphs.The dynamics of followers are allowed to be non-minimum phase with unknown arbitrary individual relative degrees.This is contrary to many existing works on distributed adaptive control schemes where agent dynamics are required to be minimum phase and often of the same relative degree.A distributed adaptive pole placement control scheme is developed,which consists of a distributed observer and an adaptive pole placement control law.It is shown that under the proposed distributed adaptive control scheme,all signals in the closed-loop system are bounded and the outputs of all the followers track the output of the leader asymptotically.The effectiveness of the proposed scheme is demonstrated by one practical example and one numerical example.
基金the State Institution National Antarctic Scientific Center of the Ministry of Education and Science of Ukraine of Ukrainian part of the Scientific and Research Programs No.Н/18e2020 andН/22e2021.
文摘The research aims to study recent Antarctic plate kinematics based on Global Navigation Satellite System(GNSS)data.The research covers 60 continuous GNSS stations located on the Antarctic plate during 1994-2021.We determine the components of horizontal displacement vectors of these GNSS stations and construct the schematic map of their distribution.The results indicate that the direction of velocity vectors of horizontal displacements has a rotational nature in clockwise order.The analysis of deformation processes shows that a gradual decrease in the horizontal strain rates,maximum shear strain and area strain is taking place from west to east,in the direction of West Antarctica-the Transantarctic Mountains-East Antarctica.The absolute rotation pole of the Antarctic plate in the ITRF2014/IGS14 reference frame has been determined,and the obtained values are in good agreement with recent plate models.
文摘Objective:To evaluate the long-term stone-free rate(SFR)of retrograde intrarenal surgery(RIRS)in the treatment of lower pole renal calculi using only basket relocation and identify independent predictors of stone-free status.Methods:All consecutive patients undergoing RIRS lower pole renal calculi at a single highvolume tertiary center were analyzed retrospectively.Lower pole stones were relocated to the upper pole,where laser lithotripsy was performed.All patients were followed up in the clinic following the surgery and yearly thereafter.The stone-free status was assessed with a combination of an abdominal ultrasound and abdominal X-ray,or an abdominal non-contrast computed tomography if the stones were known to be radiolucent.Results:A total of 480 consecutive patients who underwent RIRS for treatment of lower pole renal calculi,between January 2012 and December 2018,were analyzed from a prospectively maintained database of 3000 ureteroscopies.With a median follow-up time of 18.6 months,the mean SFR was 94.8%.The procedures were unsuccessful in 26(5.4%)patients due to unreachable stones.The median stone size of the unreachable stones was 12 mm(range 10e30 mm).Multivariable logistic regression analysis revealed two predictors of SFR for lower pole stones:a small cumulative stone burden(odds ratio[OR]:0.903,95%confidence interval[CI]:0.867e0.941,p<0.0001)and preoperative ureteral stent insertion(OR:0.515,95%CI:0.318e0.835,pZ0.007).Conclusion:The long-term SFR of RIRS for the treatment of lower pole stones with basket displacement with appropriate patient selection is high.
基金The authors would like to thank the Deanship of Scientific Research at Umm Al-QuraUniversity for supporting this work by Grant Code: (22UQU4320299DSR01).
文摘A novel,carbon nanotubefield effect transistor(CNTFET)based fully differentialfirst order all passfilter(FDFAPF)circuit configuration is presented.The FDFAPF uses CNTFET based negative transconductors(NTs)and positive transconductors(PTs)in its realization.The proposed circuit topology employs two PTs,two NTs,two resistors and one capacitor.All the passive components of the realized topology are grounded.Active only fully differentialfirst order all passfilter(AO-FDFAPF)topology is also derived from the proposed FDFAPF.The electronic tunability of the AO-FDFAPF is obtained by controlling the employed CNTFET based varactor.A tunabilty of pole frequency in the range of 10.5 to 26 GHz is obtained.Both the circuits are potential candidates for high frequency fully differential analog signal processing applications.As compared to prior state-of-the-art works,both the realized topologies have achieved highest pole frequency and lowest power dissipation.Moreover,they utilize compact circuit structures and suitable for low voltage applications.Moreover,both topologies work equally well in the deep submicron.The proposedfilters are analyzed and verified through HPSPICE simulations by utilizing Stanford CNTFET model at 16 nm technology node.It is observed that the proposed circuit simulation outcomes verify the theory.
基金supported by the National Natural Science Foundation of China under project 52007047in part by the Outstanding Youth Innovation Project funded by State Key Laboratory of Reliability and Intelligence of Electrical Equipment EERI_OY2021005,and EERI_KF2021014。
文摘Soft magnetic composite(SMC)material is an ideal soft magnetic material employed for developing 3D magnetic flux electromagnetic equipment,due to its advantages of 3D magnetic isotropy characteristic,low eddy current loss,and simple manufacturing process.The permanent magnet claw pole machine(PMCPM)with SMC cores is a good case that the SMC to be adopted for developing 3D flux electrical machines.In this paper,a novel axial-radial flux permanent magnet claw pole machine(ARPMCPM)with SMC cores and ferrite magnets is proposed.Compared with the traditional PMCPM,the proposed ARPMCPM is designed with only one spoke PM rotor and its whole structure is quite compact.For the performance prediction,the 3D finite element method(FEM)is used.Meanwhile,for the performance evaluation,a previously developed axial flux claw pole permanent magnet machine(AFCPM)is employed as the benchmark machine and all these machines are optimized by using the combined multilevel robust Taguchi method.It can be seen that the proposed ARPMCPM is with higher torque/weight density and operation efficiency.
基金supported by the National Natural Science Foundation of China under project 52007047the Outstanding Youth Innovation Project funded by State Key Laboratory of Reliability and Intelligence of Electrical Equipment EERI_OY2021005。
文摘Permanent magnet claw pole machine(PMCPM) is a special kind of transverse flux permanent magnet machine. Compared with other electrical machines, it has the advantages of high torque density and high efficiency for high speed operation. However, because of its complex irregular structure, the manufacturing process using silicon sheets is complicated. Soft magnetic composite material(SMC) is manufactured by powder metallurgy technology, which can produce various shapes of stator core structures, so it is easier to produce various irregular shapes of the stator core. However, the raw SMC material is relatively expensive, and the mechanical strength of SMC is weak. In this paper, a PMCPM with hybrid cores is proposed. With the adoption of hybrid silicon sheet-SMC cores and amorphous alloy-SMC cores, the torque ability of PMCPM can be improved greatly and it can have higher efficiency for more wide operation frequency. Meanwhile, its mechanical strength has been improved and it can be designed for high torque direct drive applications as it is a modular machine. Furthermore, three methods are proposed to reduce the additional eddy current loss which resulted from the employment of hybrid cores in PMCPM.
文摘Background and Objectives: Pyelo-Ureteral Junction Syndrome (PUJS) is the most common obstructive malformation of the upper urinary tract in children and adults. The standard treatment is open pyeloplasty using the Kuss-Anderson technique. Because of the minimally invasive nature of the laparoscopic approach, it has become the approach of choice for the management of this pathology. We present the results of laparoscopic transperitoneal pyeloplasty used in the management of PUJS. Materials and Methods: This was a retrospective study from 2015 to 2020, including 26 patients who underwent laparoscopic transperitoneal pyeloplasty for PUJS. Results: Twenty-six patients, including 18 (69.2%) men and 6 (30.8%) women, with a mean age of 35.42 ± 13.62 years, were treated. Renal colic was the primary symptom in the majority of the cases (22, 84.6%)). The diagnosis was confirmed in all patients through an abdominal CT scan, which revealed that all 26 patients had hydronephrosis. Half of the patients (50.0%) were classified as Valayer-Cendron Type II, and eight (30.8%) patients had associated stones. Seventeen (65.4%) patients had pathologies on the left side, and all patients were treated using the Kuss-Anderson technique with a median operating time of 108.5 (90.0 - 136.0) minutes. The uncrossing of lower pole vessels was performed in 10 patients. The average duration of hospitalisation was 2.23 ± 0.82 days. No conversion was observed, and after an average follow-up of 53.69 days, the success rate was 92.3%. Conclusion: Laparoscopic pyeloplasty is a minimally invasive technique of choice for the treatment of pyelo-ureteral junction obstruction. It is dependable, repeatable, and produces good functional outcomes that are equal to those of traditional surgery.
