Force and Torque Model of Magnetically Levitated System with 2D Halbach Array and Printed Circuit Board Coils.

Precision machining fields often require worktables with different stroke sizes. To address the need for scalability and facilitate manufacturing, this study proposes a novel infinite expansion magnetically levitated planar motor (MLPM) based on PCB stator coils. Different from existing magnetic levitation systems that use PCB coils, the design presented in this paper utilizes smaller coil units, with each coil being independent of one another. The coils are structured in a spiral pattern on a 16-layer PCB, comprising 15 layers of coils, while the last layer is dedicated to wiring and other circuits. Magnetic field modeling is conducted for both the stator coil and the 2D Halbach array structure employed in the system. A simple table lookup method is employed to accurately account for the prevalent end effects observed during system motion. Additionally, the decoupling effect of magnetic force and torque is evaluated by solving for the current vector at different points along a specific trajectory. To verify the accuracy of the proposed system's modeling, a prototype is developed and tested. Experimental results demonstrate that compared to traditional harmonic model methods, the proposed approach improves the calculation accuracy of magnetic force by 50.31% and torque by 70.65%. This study presents a new MLPM system with vast potential applications in precision manufacturing and robotics. The innovative design and improved performance characteristics make it a promising technology for enhancing the capabilities of worktables in precision machining fields.

Spectral properties of B40 enhanced by small molecule adsorption.

The luminescence characteristics of small molecule excited B40 have not been studied yet, and it may have a potential application value in quantum dot luminescence. Herein, the adsorption and fluorescence emission spectra of small molecules (pyridine, pyrazine and benzene) adsorbed on B40 are studied using first-principles. The results show that the absorption of pyridine and pyrazine on B40 can form stable chemisorption structures pyridine-B40 and pyrazine-B40, while benzene adsorption can form physisorption structure benzene-B40. Moreover, the adsorbed pyridine can enhance the intensity of emission spectra of B40. And the pyrazine adsorbed can obviously enhance the intensity of absorption and emission spectra of B40 and cause the spectra to redshift to the visible light range. And the adsorption of benzene has almost no enhancement effect on absorption and emission spectra of B40. In addition, the influence of different computational basis sets on spectra characteristics has also been discussed and the results show that the main peaks of absorption and emission spectra calculated by the diffuse function augmented basis sets are redshifted relatively. This finding provides a strategy for quantum dot luminescence and a theoretical reference for experimental research.

Iterative neural network adaptive robust control of a maglev planar motor with uncertainty compensation ability.

In this paper, an iterative neural network adaptive robust control (INNARC) strategy is proposed for the maglev planar motor (MLPM) to achieve good tracking performance and uncertainty compensation. The INNARC scheme consists of adaptive robust control (ARC) term and iterative neural network (INN) compensator in a parallel structure. The ARC term founded on the system model realizes the parametric adaptation and promises the closed-loop stability. The INN compensator based on the radial basis function (RBF) neural network is employed to handle the uncertainties resulted from the unmodeled non-linear dynamics in the MLPM. Additionally, the iterative learning update laws are introduced to tune the network parameters and weights of the INN compensator simultaneously, so the approximation accuracy is improved along the system repetition. The stability of the INNARC method is proved via the Lyapunov theory, and the experiments are conducted on an home-made MLPM. The results consistently demonstrate that the INNARC strategy possesses the satisfactory tracking performance and uncertainty compensation, and the proposed INNARC is an effective and systematic intelligent control method for MLPM.

Tuning the Red-to-Green-Upconversion Luminescence Intensity Ratio of Na3ScF6: 20% Yb3+, 2% Er3+ Particles by Changes in Size.

Na3ScF6: 20% Yb3+, 2% Er3+ samples were synthesized with different reaction times and reaction temperatures using the solvothermal method. We carried out a series of tests on Na3ScF6 crystals. The XRD patterns showed that the monoclinic phases of the Na3ScF6 samples could be synthesized under different reaction conditions, and doping with Yb3+ ions and Er3+ ions did not change the crystal structures. The SEM images showed that the sizes of the samples gradually increased with reaction time and reaction temperature. The fluorescence spectra showed that the emission peaks of the prepared samples under 980 nm near-infrared (NIR) excitation were centered at 520 nm/543 nm and 654 nm, corresponding to the 2H11/2/4S3/2→4I15/2 and 4F9/2→4I15/2 transitions, respectively. With the increasing size of the samples, the emission intensities at 654 nm increased and the luminescence colors changed from green to red; at the same time, the red-to-green luminescence intensity ratios (IR/IG ratios) increased from 0.435 to 15.106-by as much as ~34.7 times. Therefore, this paper provides a scheme for tuning the IR/IG ratios of Na3ScF6: 20% Yb3+, 2% Er3+ samples by changing their sizes, making it possible to enhance the intensity of red upconversion, which has great potential for the study of color displays and lighting.

High pressure Raman study of LiClO4.

Lithium perchlorate (LiClO4), as one of the new high-energy oxidizers, is chosen for high pressure Raman research to gain a better understanding of the structure and stability, which is very important for the performance of an explosive. Raman spectra of LiClO4 crystal have been measured from ambient to 25.07 GPa with diamond anvil cells (DACs) at room temperature to investigate the structural stability of this system. Raman vibrational modes of LiClO4 crystal at ambient pressure were resolved comprehensively on the basis of our experimental and calculated results. Upon increase of pressure on LiClO4 crystal sample to 1.96 GPa, it was found that the LiClO4 crystal exhibited a pressure-induced first-order phase transformation behavior. The occurrence of a second phase transformation of LiClO4 crystal induced by pressure was observed at about 5.09 GPa. Both phase transformations were demonstrated based on the detailed spectroscopic analysis of the variations in the number of lattice modes, splitting of Raman bands and frequency jumps of the Raman vibrational modes of LiClO4 crystal.

Fatigue Fracture Analysis on 2524 Aluminum Alloy with the Influence of Creep-Aging Forming Processes.

The different creep-aging forming processes of 2524 aluminum alloy were taken as the research object, and the effects of creep-aging temperature and creep stress on the fatigue-crack propagation properties of the alloy were studied. The research results showed the following under the same sintering time of 9 h, at creep-aging temperatures of 100 °C, 130 °C, 160 °C, and 180 °C, respectively, with an increase in creep-aging temperature: the fatigue-crack propagation rate was promoted, the spacing of fatigue striations increased, and the sizes of dimples decreased while the number was enlarged; this proves that the fatigue property of the alloy was weakened. Compared with the specimens with creep deformation radii of 1000 mm and 1500 mm, the creep deformation stress was the smallest when the forming radius was 1800 mm, with a higher threshold value of fatigue-crack growth in the near-threshold region of fatigue-crack propagation (ΔK ≤ 8 MPa·m1/2). Under the same fatigue cycle, the specimens under the action of larger creep stress endured a longer fatigue stable-propagation time and a faster fracture speed. Comparing the effect of creep-aging temperature and creep stress, the creep-aging temperature plays a dominant role in the fatigue-crack propagation of creep-aged 2524 aluminum alloy.

Raman spectroscopy study of acetonitrile at low temperature.

We report the low-temperature studies of liquid CH3CN by Raman spectral measurements at ambient pressure with decreasing the temperature from 20 to -196 °C. Detailed internal modes especially the lattice modes analysis revealed that the structural phase transitions of acetonitrile from liquid to solid phase ß and solid phase ß to solid phase α were occurring at -50 and -60 °C, respectively. Further, the Fermi resonance parameters between the fundamental ν2 and combination (ν3 + ν4) of CH3CN at different temperatures were calculated based on the Bertran's equations. It is found that the Fermi resonance parameters as a function of temperature become discontinued at -50 and -60 °C, which coincides with discontinuities observed in the Raman shifts of CH3CN at -50 and -60 °C. The results suggest that the Fermi resonance parameters could be used as an indicator to assess the structural phase transition for CH3CN under low temperature.

Tunable Ionic Liquid-Water Separation Enabled by Bioinspired Superwetting Porous Gel Membranes.

Selectively wettable porous membranes have been demonstrated to be outstanding energy-efficient materials for use in continuous liquid separation (including separating industrial oils or common organic solvents), in environmental protection, and in the chemical industry. The continuous separation of ionic liquids (ILs), which is important for chemical synthesis and chemical engineering, has been less explored. Herein, we report an on-demand liquid-passed-through strategy for the efficient and continuous separation of ILs from their aqueous solutions via the utilization of bioinspired liquid-infused porous gel membranes. We show how a porous gel film can be used to design functional membranes for reliable separation that is independent of the surface energies of the separated liquids. This tunable IL-water separation strategy can further enable highly efficient and continuous purification and recycling of ILs for use in IL-related chemical processes and is promising for scalable processes.

Synthesis of Small Ce3+-Er3+-Yb3+ Tri-Doped BaLuF5 Active-Core-Active-Shell-Active-Shell Nanoparticles with Strong Down Conversion Luminescence at 1.5 µm.

Small fluoride nanoparticles (NPs) with strong down-conversion (DC) luminescence at 1.5 µm are quite desirable for optical fiber communication systems. Nevertheless, a problem exists regarding how to synthesize small fluoride NPs with strong DC emission at 1.5 µm. Herein, we propose an approach to improve 1.5 µm emission of BaLuF5:Yb3+,Er3+ NPs by way of combining doping Ce3+ ions and coating multiple BaLuF5: Yb3+ active-shells. We prepared the BaLuF5:18%Yb3+,2%Er3+,2%Ce3+ NPs through a high-boiling solvent method. The effect of Ce3+ concentration on the DC luminescence was systematically investigated in the BaLuF5:Yb3+,Er3+ NPs. Under a 980 nm laser excitation, the intensities of 1.53 µm emission of BaLuF5:18%Yb3+,2%Er3+,2%Ce3+ NPs was enhanced by 2.6 times comparing to that of BaLuF5:18%Yb3+,2%Er3+ NPs since the energy transfer between Er3+ and Ce3+ ions: Er3+:4I11/2 (Er3+) + ²F5/2 (Ce3+) → 4I13/2 (Er3+) + ²F7/2 (Ce3+). Then, we synthesized BaLuF5:18%Yb3+,2%Er3+,2%Ce3+@BaLuF5:5%Yb3+@BaLuF5:5%Yb3+ core-active-shell-active-shell NPs via a layer-by-layer strategy. After coating two BaLuF5:Yb3+ active-shell around BaLuF5:Yb3+,Er3+,Ce3+ NPs, the intensities of the 1.53 µm emission was enhanced by 44 times compared to that of BaLuF5:Yb3+,Er3+ core NPs, since the active-shells could be used to not only suppress surface quenching but also to transfer the pump light to the core region efficiently through Yb3+ ions inside the active-shells.

Influences of donor/acceptor ratio on the optical and electrical properties of the D/A alternating model oligomers: A density functional theory study.

We adopted an ingenious method that cut out the DA alternating oligomers from the corresponding DA alternating copolymers. From analyzing the orbital compositions of the HOMOs and LUMOs as well as the reorganization energies, we found the level of charge transfer is increased with the increasing of D/A ratio, but ionization potentials and electron affinities show a contrary trend. Moreover, with the greater ratio, the trend in the nearness of two transitions results in broadening the absorption band in the visible range. That is why experimentally improving the ratio is beneficial for the copolymers used as the p-type materials in the BHJ solar cells. This method is impossible to take the real copolymer system, however, it could provide a strategy to avoid the limitation of the theory level and perform reliable result to study the intrinsic properties of DA alternating copolymers, which can provide a guidance to experimental works.

High-pressure Raman study of Terephthalonitrile.

The in situ high-pressure Raman spectra of Terephthalonitrile (TPN) have been investigated from ambient to 12.6GPa at room temperature. All the fundamental vibrational modes of TPN at ambient were assigned based on the first-principle calculations. A detailed Raman spectroscopy analysis revealed that TPN underwent a phase transition at ~5.3GPa. The frequencies of the TPN Raman peaks increase with increasing the pressure which can be attributed to the reduction in the interatomic distances and the escalation of effective force constants. The intensity of the C-C-C ring-out-plane deformation mode increases gradually as the frequency remains almost constant during the compression which can be explained by the existence of π-π interactions in TPN molecules. Additionally, the pressure-induced structural changes of TPN on the Fermi resonance between the C≡N out-of-plane vibration mode and the C-CN out-of-plane vibration mode have been analyzed.

Theoretical study on a series of iridium complexes with low efficiency roll-off property.

A series of heteroleptic cyclometalated Ir (III) complexes for OLEDs application have been investigated theoretically to explore their electronic structures and spectroscopic properties. The geometries, electronic structures, and the lowest-lying singlet absorptions and triplet emissions of (piq)2Ir(acac) (labeled 1) and theoretically designed models (piq)2Ir(dpis) (labeled 2), (4Fpiq)2Ir(dpis) (labeled 3), (4F5M-piq)2Ir(dpis) (labeled 4), (4,5-2F-piq)2Ir(dpis) (labeled 5) and (5-F-piq)2Ir(dpis) (labeled 6) were investigated with density functional theory (DFT)-based approaches, where, piq=1-phenylisoquinolato, acac=acetylacetonate and dpis=diphenylimidodisilicate. Their structures in the ground and excited states have been optimized at the DFT/B3LYP/LANL2DZ and TDDFT/B3LYP/LANL2DZ levels, and the lowest absorptions and emissions were evaluated at B3LYP and M062X level of theory, respectively. Furthermore, the energy-transfer mechanism of these complexes also be analyzed here, and the result shown that the complexes 1-6 are having the low efficiency roll-off property. Except that, the oscillator strength analyze shown that the complexes 2-6, which were designed by theory, are suitable for OLED since their high oscillator strength property.

Production and evaluation of recombinant granule antigen protein GRA7 for serodiagnosis of Toxoplasma gondii infection in cattle.

The precise detection of Toxoplasma gondii infection in cattle has important public health significance. In the present study, recombinant granule antigen protein GRA7 was evaluated as a potential diagnostic marker for T. gondii infection in cattle by an indirect enzyme-linked immunosorbent assay (ELISA) using the reference serum samples determined by immunofluorescence assay and Western blotting, showing that GRA7-ELISA has a sensitivity of 96.4%, and a specificity of 98.6%. The detection results by GRA7- and Toxoplasma lysate antigen-based ELISAs were compared, indicating that no significant difference (p>0.05) and perfect agreement (κ=0.74) was observed between the two tests. Receiver operating characteristic analysis showed a relative sensitivity and specificity of 100% and 97.3% at the cut-off value of 0.3 for GRA7-ELISA. These data demonstrate that GRA7 is a promising serodiagnostic marker for T. gondii infection in cattle.

CASSCF/CASPT2 calculation of the low-lying electronic states of the CH3Se neutral radical and its cation.

Electronic states of the CH(3)Se and its cation CH(3)Se(+) have been studied using the complete active space self-consistent field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) methods in conjunction with the ANO-RCC(TZP) basis set. To investigate the Jahn-Teller effect on the CH(3)Se radical, C(s) symmetry was used for CH(3)Se in calculations. The results show that the Jahn-Teller effect is very small (69 cm(-1)) and the 1(2)A' state is slightly more stable than the 1(2)A'' state (8 cm(-1)). The CH(3)Se has been found to have a 1(2)A' ground state with a C-Se bond distance of 1.975 A. The computed C-Se stretching nu(6)(a') frequency is 554.1 cm(-1), which is in good agreement with the experimental values of 600 +/- 60 cm(-1). The calculations for CH(3)Se at 3.621 and 5.307 eV are attributed to 1(2)A' --> 2(2)A'(1(2)A(1)) and 1(2)A' --> 2(2)A'', respectively. The vertical and adiabatic ionization energies were obtained to compare with the PES data.

A theoretical study of the low-lying electronic states of the AlCCH radical and its ions.

The AlCCH radical is a photolysis product of the aluminum-acetylene adducts and has been considered as a molecule with potential interest in astrophysics. In this study, the low-lying electronic states of the AlCCH radical, cation, and anion have been studied by using complete active space self-consistent field and multiconfigurational second-order perturbation theory. The geometrical parameters, electron configurations, excitation energies, oscillator strengths, and harmonic vibrational frequencies are calculated in C(S) symmetry. For the X(1)Sigma(+) state of AlCCH, the calculated C-C and C-Al stretching modes are in good agreement with experimental reports. Moreover, the vertical excitation energy (T(v)) of 1(1)Pi is 3.68 eV, which is close to the experimental value of 3.57 eV. The electron transitions of AlCCH(+), X(2)Sigma(+) --> 1(2)Pi, X(2)Sigma(+) --> 2(2)Sigma(+), and X(2)Sigma(+) --> 1(2)Sigma(-), are predicted at 2.57, 4.51, and 4.61 eV, respectively. For AlCCH(-), the transition X(2)Pi --> 1(2)Sigma(-) occurs at 3.02 eV. The ionization potentials of AlCCH are computed in order to provide a theoretical guidance to the photoelectron spectrum of the AlCCH radical.