Search

This article compares the doubly salient permanent magnet machine (DSPMM) having 18/13-pole number combination with 18/17-pole biased flux permanent magnet machine (BFPMM) to verify its improvement in torque characteristics. In such DSPMM, the stator/rotor-pole number combination is 18/13 rather than the conventional one (i.e., 18/12) to achieve balanced three phases, sinusoidal phase flux linkage and back electromotive force (back EMF), small cogging torque, and low torque ripple. On the other hand, an 18/17-pole BFPMM having the similar structure with the 18/13-pole DSPMM is analyzed, which has the best torque performance among such machines with the same stator pole number. To further improve average torque, the inner-type flux focusing (IFC) method is employed in both 18/13-pole DSPMM and 18/17-pole BFPMM. Then, both machines are optimized under the fixed copper loss and envelope size. The comparison shows that both machines have comparably small torque ripple while the 18/13-pole DSPMM with IFC (IFC-DSPMM) exhibits 35% higher torque density and 100% higher ratio of torque to PM volume. An 18/13-pole IFC-DSPMM is manufactured and tested to experimentally validate the predicted results.

In this article, two doubly fed (DF) flux-reversal permanent magnet (FRPM) machines with different PM arrangements are proposed, both of which have an additional set of armature winding in their rotor slots to further enhance the torque performance. Together with their one-set armature winding counterparts, comprehensive analyses and comparison among these four machines are conducted. The operation principles and winding configurations of these four machines are firstly introduced. Then, based on finite-element (FE) method, the electromagnetic performances of four machines after optimization with the purpose of maximum torque are compared in terms of no-load, on-load, and over-load capabilities. The results show that the DF-FRPM machine with consequent-pole structure offers the highest average torque and lowest torque ripple, which make it a promising candidate for low-speed and high-torque applications. A prototype machine has been manufactured and the FE results have been verified.

Three lumped-parameter magnetic circuit (LMC) models of dual-armature flux-switching permanent magnet (DA-FSPM) machines are proposed and compared in this article. First, the characteristics of the magnetic flux fields produced by the PM, stator armature reaction, and rotor armature reaction flux sources are analyzed, with particular attention paid to the air-gap and slot leakage flux paths. Based on the former analyses, three LMC models are developed, which consider the air-gap and slot leakage permeances in different ways. The electromagnetic performances of the DA-FSPM machines are predicted by the three LMC models and validated by the finite-element method, including the flux linkage, average torque, inductance, and power factor. The model accuracy sensitivity to the geometric parameters, copper loss allocation, electric loading, stator pole/rotor tooth number combinations, power level, and conductor distributions are analyzed. It shows that appropriate consideration of slot leakage permeance is important to improve the model accuracy.

A single crystal of (5,10,15,20-tetraphenylporphyrinato)-silver was obtained and its structure reported. Using direct growth on quartz substrates method, a crystal thin film was obtained and the film’s morphology was investigated by atomic force microscopy. The nonlinear absorption properties of the film were studied using open aperture [Formula: see text]-scan technique by picosecond laser pulses at different fluence at wavelength 532 nm, nonlinear saturable absorption behavior was observed. Time-dependent unrestricted Hartree-Fock with the basis set LanL2DZ was used in computing the linear and non-linear optical properties of (5,10,15,20-tetraphenylporphyrinato)-silver.

(5,10,15,20-Tetraphenylporphyrinato)-copper(II) (TPP-Cu) are synthesized, and characterized by X-ray single crystal diffraction. TPP-Cu doped polymethylmethacrylate (PMMA) thin film on quartz substrate were prepared by spin-coating method. The morphology of the film were investigated by scanning electron microscopy. The nonlinear refractive properties of the film were studied using closed aperture Z-scan technique by picosecond (PS) laser pulses at different irradiance at wavelength 1064 nm. The nonlinear refraction coefficient n 2 I value of the film were determined to be 1.28 × 10−12 m2/W, this making them ideally suited to the applications in the field of all-optical switches.

A novel metal-organic complex: bis(imidazole)-bis(isothiocyanato)-copper(II) ((C3H4N2)2Cu(NCS)2) has been synthesized, its crystal structure has been determined by means of X-ray single crystal diffraction. The copper(II) ion is four coordinated with the four nitrogen atoms in a square planar environment, short contacts of C-H⋯C and S‾⋯Cu2+ leading to the formation of a two-dimensional (2D) supramolecular plane structure parallel ab plane. Its crystal thin film were prepared using in-situ crystallization methods on quartz substrates. The surface morphology of the thin film were studied by atomic force microscopy (AFM). The nonlinear optical (NLO) properties of the thin film were investigated by using closed aperture Z-scan technique with 20 picosecond (ps) pulses at wavelength 532 nm. Time-dependent density-functional theory (TDDFT) with the basis set LanL2DZ were used in theoretically computing the frontier molecular orbitals (FMO) and molecule’s second hyperpolarizability γ value.

A cobalt complex constructed by the ligand(L): 4-hydroxy-3-methoxybenzaldehyde [Co(C8H7O3)2(H2O)2] has been synthesized and characterized by X-ray single crystal diffraction. The cobalt(II) atom is...

Cobalt and zinc tetraphenylporphyrins have been obtained and characterized by X-ray single crystal diffraction. Their crystal thin films were prepared using direct growth on quartz substrates. The surface morphology of the thin films were studied by atomic force microscopy. The nonlinear optical refraction properties of the thin films were investigated by using closed aperture Z-scan technique with 20 ps (ps) pulses at wavelength 1064 nm. Time-dependent unrestricted Hartree-Fock (TDUHF) with the basis set LanL2DZ were used in computing the linear and non-linear optical properties.

A series of trace Fe3+-doped KH2PO4 single crystals were grown using the conventional temperature cooling method. The Fe3+ ion content in the as-grown crystals and the corresponding transmission spectrum were measured, respectively. With an increase of Fe3+ ion concentration, the transmittance of the crystal gradually decreases within the wavelength range of 200 nm to 370 nm. Under picosecond pulse laser irradiation, third-order nonlinear optical characteristics were systematically measured at λ = 532 nm. The existence of nonlinear absorption and nonlinear refraction was demonstrated. The results show that the nonlinear refractive index n2 is positive, indicating the presence of a self-focusing effect for the as-grown crystals. Specially, nonlinear absorption and refraction have a heavy dependence on the Fe3+ ion content and crystal directions (II and z). With increasing Fe3+ ion concentration, a significant variation has been observed with respect to the nonlinear absorption coefficient β, nonlinear refractive index n2 and third-order nonlinear susceptibility χ(3). A similar pattern for II < z has been presented for nonlinear absorption and refraction. The investigations suggest that nonlinear absorption and refraction caused by distortion of the electron cloud might be associated with the H2PO4− and (FeO4)2− groups.

The nonlinear refractive index n2 is an important parameter for the nonlinear optical properties of a medium. This study primarily targets to measure the third-order nonlinear optical properties of potassium dihydrogen phosphate (KDP) and deuterated potassium dihydrogen phosphate (DKDP) with 70% deuteration content at λ = 532 nm using the Z-scan technique. The relationship between nonlinear refraction and direction has been studied in detail. Nonlinear refractive index n2, γ and third-order nonlinear susceptibilities xk3 (esu) were calculated through normalized transmittance curves and theoretical formulas. The results indicate that the nonlinear refractive indexes of KDP and DKDP are positive and possess obvious self-focusing effects in high-power laser systems.

Three dmit 2− complexes, [(C 4 H 9 ) 4 N] 2 [Mn(dmit) 2 ], [(C 4 H 9 ) 4 N] 2 [Cu(dmit) 2 ] and [(C 3 H 7 ) 4 N] [Ni(dmit) 2 ], abbreviated as BuMn, BuCu and PrNi, were synthesized. Their third-order nonlinear optical properties in acetonitrile were investigated using the laser Z -scan technique with 20 ps pulses at 1064 nm. The Z -scan spectra revealed that BuMn exhibited self-focusing effect and negligible nonlinear absorption, BuCu exhibited self-defocusing effect and two-photon absorption, PrNi exhibited self-focusing effect and a stronger saturable absorption. The reason for the difference was analyzed. The nonlinear refractive index n 2 , the third-order nonlinear susceptibility □ (3) , the molecular second-order hyperpolarizability □ of these complexes were with the magnitude of 10 −18 m 2 /W, 10 −13 esu and 10 −31 esu, respectively. All these results suggest that these materials are candidates for application in the different nonlinear optical fields at infrared band.

Tetraphenylporphyrin (TPP) and its nickel(II) (NiTPP) complex have been synthesized, their crystal structures have been determined by means of X-ray single crystal diffraction. The TPP possesses good planarity in the porphyrin core, while in the complex the planarity disappeared. The central nickel(II) ion coordinates with four nitrogen atoms, which constructed a distorted square environment. Their third-order nonlinear optical properties have been studied using Z-scan technique at wavelength 532 nm and 1064 nm in picosecond (ps) domain. At 532 nm nonlinear absorption were observed, TPP shows two-photon absorption (TPA) combined with saturable absorption (SA), while NiTPP shows SA. At 1064 nm nonlinear refraction were observed, the molecular second hyperpolarizability γ of the NiTPP was about 1.4 times larger than that of the TPP.

A tin(IV) complex constructed by 1,10-phenanthroline: tetrachloro(1,10-phenanthroline- N , N ′)tin(IV) has been synthesized. Its crystal structure has been determined by means of X-ray single crystal diffraction, the tin(IV) atom is six-coordinate in a distorted octahedral geometry, intermolecular C H···Cl hydrogen bonds lead to the formation of a double chains along [1 0 1]. Its thermal stability was determined by TGA/DSC. Its second hyperpolarizability γ value was determined to be 6.2 × 10 −58 C m 4 /V 3 by Z-scan technique with 20 picosecond (ps) pulses at wavelength 1064 nm. Theoretical calculations of its γ value were performed by MOPAC2012 program and the calculated value is in good agreement with the experimental value.

A new zinc complex bis(benzyltriethylammonium) bis(1,3-dithiole-2-thione-4,5-dithiolato)-zinc(II) has been synthesized, its crystal structure has been determined by means of X-ray single crystal diffraction. The central zinc(II) ion coordinates with two ligands which constructed a distorted tetrahedron environment, cation groups and ligands link each other through weak intermolecular C–H⋯S hydrogen bonds. Its two-photon absorption properties has been studied using open aperture Z-scan technique with 14 ps pulses at wavelength 532 nm, its two-photon absorption cross section σ2 value was determined to be 8.73 × 10−53 (m4·s/photon·molecule). The theoretical mechanism of the two-photon absorption process was analysized by simplied five-energy-band model.

Two new Schiff base, (E)-N-benzylidene-2-methylaniline (CH3C6H4N CHC6H5) (1) and N,N′-methanediylidenedianiline (C6H5N C NC6H5) (2) have been synthesized and characterized by IR and Single crystal X-Ray Diffraction. Their thermal stability was determined by TGA-DSC. Reverse saturable absorption (RSA) nonlinear optical effect has been observed in their methanol solution using open-aperture Z-scan technique with 20 picosecond (ps) pulses at wavelength 1064 nm. Their molecular two-photon absorption cross-section σ2 was determined and the theoretical mechanism was analyzed by simplied five-energy-band model.

A novel organometallic compound, ethyltriphenylphosphonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate (III), abbreviated as TPEPADT, was synthesized. The TPEPADT doped poly(methyl methacrylate) (PMMA) thin film with a mass fraction of 1% (1 wt.%) was prepared by using a spin-coating method. The third-order nonlinear optical properties of TPEPADT in acetonitrile solution and TPEPADT-doped PMMA thin film were investigated by using the laser Z-scan technique at the wavelength 1064 nm with laser duration of 20 ps. The linear refractive index of the polymer thin film was also studied. The Z-scan curves revealed that both TPEPADT in acetonitrile solution and the polymer thin film possessed negative nonlinear refraction, exhibiting a self-defocusing effect and nonlinear absorption was negligible under the experimental conditions used. The nonlinear refractive index was calculated to be −1.9 × 10−18 m2/W for TPEPADT in acetonitrile solution and −8.9 × 10−15 m2/W for the polymer thin film. These results suggest that TPEPADT have potential for the application of all-optical switching devices.

The third-order nonlinear optical properties of two Au(dmit)2/PMMA compound thin films, hexadecyltrimethylammonium bis(1,3-dithiole-2-thione-4,5-dithiolato)aurate and tetramethylammonium bis(1,3-dithiole-2-thione-4,5-dithiolato)aurate (abbreviated as MeAu and CtAu, respectively) with a doping concentration of 1 wt.% deposited on quartz-glass substrate were characterized by a single beam Z-scan technique at 1064 nm with 20 ps laser pulse width and 10 Hz repetition rate. The dominant nonlinear refraction and tiny nonlinear absorption of both materials lead to a larger possibility for them to be applied as promising candidates of all-optical switching. The results of two figures of merit, |W|≫1 and |T|≪1, were also calculated; this further validated the excellent properties of the materials for applications of the nonlinear optics.

A copper complex constructed by the ligand: 1,3-dithiole-2-thione-4,5-dithiolato (DMIT) has been synthesized and its crystal structure has been determined by means of X-ray single crystal diffraction. The central copper(II) ion coordinates with two DMIT which constructed a square environment. Intermolecular C–H⋯S hydrogen bonds between cation groups and ligands lead to the formation of a two-dimensional supramolecular network. Its third-order nonlinear optical property has been studied using Z-scan technique at different peak laser irradiance with 20 picosecond (ps) pulses at wavelength 1064 nm. Its molecular second hyperpolarizability γ was determined to be 4.03 × 10−57 m4 C V−3.

A novel chalcone derivative, (2E)-1-(2,4-di- chloro-5-fluorophenyl)-3-[4-dimethylamino)phenyl]prop-2-en-1-one, abbreviated as NNDC, was prepared and characterized by elemental analyses, infrared (IR) and proton nuclear magnetic resonance (1H NMR) spectrum, and thermal analyses. The NNDC-doped poly(methyl methacrylate) (PMMA) thin films with five different doping concentrations by weight were prepared by using a spin-coating method. Their linear optical properties were investigated by using a prism coupling measuring system. The third-order nonlinear optical properties of NNDC in 1,2-dichloroethane (NNDC/1,2-dichloroethane) solution and NNDC-doped PMMA (NNDC/PMMA) films were investigated by using the laser Z-scan technique with 20 ps pulses at 532 nm. A self-focusing effect was observed from the Z-scan curves for solution and thin films and the nonlinear refractive index of the film increases with the increase of the doping concentration. In addition, nonlinear absorption was negligible for all samples. The magnitude of third-order nonlinear refraction index n 2 and the third-order nonlinear susceptibility χ (3) for thin films were 10−15 m2/W and 10−9 esu, respectively, which are about three orders larger than that of NNDC/1,2-dichloroethane solution. Some necessary analyses were presented. The results show that this material is a promising candidate for application in the nonlinear optical devices at 532 nm.

Four novel dmit complexes: [(C2H5)4N][Ni (dmit)2], [(C3H7)4N][Ni(dmit)2], [(C2H5)4N][Au(dmit)2] and [(C3H7)4N][Au(dmit)2], abbreviated as EtNi, PrNi, EtAu, and PrAu, were synthesized. The third-order nonlinear optical properties of them in acetonitrile solutions were investigated by using the Z-scan technique with 20 ps pulses width at 1064 nm. When the on-axis irradiance at focus I 0 was 5.025 GW/cm2, the nonlinear refraction coefficient n 2, the third-order nonlinear susceptibility χ (3), the molecular second-order hyperpolarizability γ of the four types of material were obtained with subject to Z-scan curves, and these indexes were with the magnitudes of 10−18 m2/W, 10−13 esu, and 10−31 esu, respectively. The nonlinear absorption coefficient β of Ni samples had the 10−12 m/W scale. The impact of different metals and cations on the third-order nonlinear optical properties of materials was analyzed. Through the derivation, the result suggests that these dmit complexes are promising candidates for applications to nonlinear optical devices manufacture in the near-infrared waveband.

An organometallic complex, bis(tetra-n-propylammonium)bis(2-thioxo-1,3-dithiole-4,5-dithiolato)cuprate(II), [(C3H7)4N]2[Cu(dmit)2] (dmit2−=4,5-dithiolate-1,3-dithiole-2-thione), abbreviated as PrCu, was synthesized. The films of PrCu were prepared using spin coating method. The third-order nonlinear optical properties of PrCu in acetone solution and PMMA films were investigated by Z-scan technique at 1064 nm with laser duration of 20 ps. The Z-scan spectra reveal that the composite films exhibit large negative nonlinear refractive indices of the order of 10−15 m2/W, which are three orders larger than that in acetone solution. The nonlinear absorption coefficients were calculated to be 9.416×10−10 m/W. For the composite films, the figure of merit, W and T, meet the requirement of all-optical switching devices. The experimental results show that the PrCu-doped PMMA films have potential applications for nonlinear optical devices.

An organometallic complex, [(C4H9)4N]2[Cu(C3S5)2], abbreviated as BuCu, was synthesized. Then the BuCu-doped polymethylmethacrylate (PMMA) thin film with a doping concentration 1% by weight (1 wt.%) was fabricated using a spin-coating method and its third-order nonlinear optical properties were characterized using the Z-scan technique with 20 ps pulse duration at 532 and 1064 nm, respectively. The Z-scan curves have revealed that the material exhibits a self-defocusing effect at both wavelengths. Saturable absorption at 532 nm and two-photon absorption at 1064 nm were also found, respectively. Additionally, the calculated results of the material in film were compared with that of acetone solution, which indicated that the values in film were larger than that of acetone solution for about two orders in magnitude. The origins were analyzed of the difference between the two wavelengths. Our results suggest that considerable nonlinear optical properties were confirmed in BuCu-doped PMMA film. The material can easily be doped into PMMA film and forms a waveguide mode. So this material should be considered to be manufactured into devices and applied in all-optical switching, laser locking-mode, optical limiting fields etc.

A series of polymeric thin films with BFDT (BFDT = 4,5-bis(foroylsulfanyl)-1,3-dithiole-2-thione) doped in PMMA (polymethylmethacrylate) were fabricated by means of spin-coating on quartz substrate. The third-order nonlinear optical properties of the films were investigated by Z-scan technique at 532 nm wavelength with 20 ps pulse width. The influences of doping concentration for third-order nonlinearity were also studied. A self-defocusing effect was observed from the Z-scan curves and the nonlinear refractive index of the film increases with the increase in doping concentration. Our results suggest that considerable nonlinear optical properties were found in BFDT. In addition, it was found that the nonlinear coefficient of the BFDT-doped PMMA thin film was about two orders of magnitude larger than that of homologous materials with organic solvents. By analysis, we can conclude that the material is a potential candidate for applications of nonlinear optics and can be considered in the fabrication of all-optical switching devices, etc.

The third-order nonlinear optical properties of two dmit organometallic complexes, [(CH3)4N] [Au(C3S5)2] (MeAu) and [(CH3)4N][Ni(C3S5)2] (Me Ni) in acetone solutions, were characterized using a short pulse Z-scan technique at 1064 nm wavelength. Self-defocusing effects were found in both samples and stronger saturable absorption was observed in MeNi solution comparing with that of MeAu. The origins were analyzed for the differences between the results. Two figures of merit W and T were also calculated to evaluate the suitability of two materials for all-optical integrated devices. The results of W=22.84 and T≈0 of MeAu make it an excellent candidate for the all-optical applications.

A numerical investigation on the flow in a bend channel by coupling the impellerwith the vaneless diffuser in a centrifugal compressor with different r/b ratios (bend radius r to bend channel width b) is presented. The jet-wake effect of the impeller outlet is considered and flow pattern in the bend channel and the performance of the centrifugal compressor stage are investigated. The results indicate that there is an optimal r/b ratio for increasing the stage efficiency to the highest for a specific compressor stage. The change in r/b ratio significantly affects the flow angle of the bend channel outlet. The prime reason for the total pressure loss in the bend channel is the wall friction in the bend channel.

Three 1,3-dithiole-2-thioxo-4,5-dithiolato compounds, ethyltriphenylphosphonium bis(2-thioxo-1.3-dithiole-4,5-dithiolato)aurate(III) (TPEPADT), benzyltriethylamine bis(2-thioxo-1.3-dithiole-4,5-dithiolato)aurate(III) (BTEAADT) and benzyltriethylamine bis(2-thioxo-1.3-dithiole-4,5-dithiolato)nickel(III) (BTEANDT), were synthesized and the BTEAADT-doped PMMA thin film (BD film) and TPEPADT-doped PMMA thin film (TD film) with mass fraction of 1% were prepared by spin-coating method. The third-order nonlinear optical properties of thin films and three compounds in acetonitrile solutions were investigated by using the laser [Formula: see text]-scan technique with 20 ps pulses at 1064 nm. The [Formula: see text]-scan spectra revealed that TPEPADT and BTEAADT exhibited self-defocusing effect and negligible nonlinear absorption, but BTEANDT exhibited self-focusing effect and stronger saturable absorption. The reason for this difference was analyzed. The magnitudes of third-order nonlinear refractive indices and third-order nonlinear susceptibility were [Formula: see text], 10[Formula: see text] esu for the solution samples and [Formula: see text], [Formula: see text] esu for thin films. All these results suggest that these materials are promising candidates for application in the nonlinear optical area at infrared band.

A series of K(D x H1− x )2PO4 (DKDP; x = 0, 12, 70, and 80%) crystals were grown using the point-seed technique. A positive nonlinear refractive index is exhibited, implying a self-focusing effect. The nonlinear refraction along the z-direction is greater than that along the II-direction, indicating that the distribution of the H2PO4 − and D2PO4 − groups have a critical influence on the nonlinear refraction. The nonlinear refraction effect of "point-seed" crystals is greater than that of traditional growth crystals, demonstrating that the crystalline quality is a major factor. Compared to the pyramid region, the prism region has a larger nonlinear refraction effect. The vital parameters n 2 and have been calculated and the results allow for DKDP applications.

High-quality KDP and DKDP crystals with 12%, 70% and 80%-deuterium content were grown by the conventional temperature cooling method. The nonlinear optical characteristics of K(DxH1-x)2PO4 crystals, including nonlinear absorption and refraction, were systematically investigated through the Z-scan method at λ = 532 nm. The results demonstrate the existence of nonlinear absorption and refraction, and a nonlinear refractive index with a positive sign indicates the generation of self-focusing effect. Moreover, the results indicate that nonlinear absorption and refraction were associated with crystal direction and structure, especially the distribution of H2PO4 - or D2PO4 - groups. For K(DxH1-x)2PO4 crystals, a similar rule of β was z > I > II, while n2 (or χR(3)) was z > II ≈I. These results will evoke more attention to KDP and DKDP applications, especially frequency conversion and electro-optic switch.

This paper studies a nonautonomous predator-prey system with two compete prey predated by one predator and infinite delay. By using differential equation Comparability Theorem and Continuation theorem based on Coincidence degree theory, we obtain the permanent and positive periodic solution existence of the system. Some new results obtained.

An organic material, 4,5-bis(benzoylthio)-1,3-dithiole-2-thione (BBDT), was synthesized. The thin film of BBDT doped into poly(methyl methacrylate) (PMMA) was prepared using spin-coating method. Its linear optical properties were characterized with prism coupler (SPA-4000, Korea). The third-order nonlinear optical (NLO) properties were investigated using Z-scan technique with pulses of picoseconds at 532 nm. The Z-scan spectra reveal a strong nonlinear absorption (reverse saturable absorption) and a positive nonlinear refraction. The nonlinear absorption coefficient is calculated to be 1.302×10−9m/W. The nonlinear refractive index is 2.243×10−9esu. The results show that the film exhibits a great nonlinear optical response.

We investigate the relationship between the hybrid form of center metal-atom and the third order nonlinear optical property in a class of 1,3-dithiole-2-thione-4,5-dithiolato-S, S' bis-chelate transition metal complexes for the first time by z-scan. We find that in bis-chelate complexes when the center metal-atom takes the sp3 hybrid form which construct a tetrahedron construction have better third order nonlinear refraction property than in the form of dsp2 hybrid which construct a plane construction and for nonlinear absorption property the case is quite contrary. Cation group have shielding effect on both nonlinear refraction and nonlinear absorption property for this kind of materials.