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Vibration parameters optimum of 316L steel laser welding under high frequency micro-vibration condition
摘要： High frequency micro vibration combined with laser was applied in the laser welding process parameters were chosen by comparison of weld geometry. In detail, laser power(P) is 2.5kW, welding speed(V) is 1.2m / min, defocusing amount(DA) is -5mm. Three parameters including frequency(F), vibration acceleration(A) and angle(θ) were changed according to the orthogonal test scheme. The microstructure and the tensile properties of the welded joint were compared and analyzed. The morphology of weld tail was analyzed to describe hole stability. It was found that micro-structure and mechanical of joint was significantly influenced by A and F. In the case of vibration resonance, the higher the F, the better the ultimate tensile strength(UTS), and the higher the hardness. When F was 1360 Hz, UTS was 602 MPa. When A was increased from 10 to 60 m/s2, the UTS was improved by 10 MPa. HW and HL were even disappeared in a higher resonance state. Response surface analysis results showed that factors of F and A have significant effects on the width of weld. Width was increased by higher resonance state. It was obtained that optimum process parameters were F=1360 Hz, A= 60 m/s2 and θ = 90°. UTS was 602MPa, hardness was 214.5 Hv, and elongation was 40%. This is mainly due to the grain refinement strengthening.
关键词： Laser welding,Mechanical property,Parameter,Response surface,Vibration
更新于2025-11-28 14:24:20
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Extrinsic Fabry Perot interferometer fiber sensor for simultaneous measurement of hydrazine vapor and temperature
摘要： A novel optical fiber sensor of hydrazine (N2H4) vapor and temperature is proposed and demonstrated. The perylene diimide derivative (TClPDI) is deposited on the enlarged optical fiber end face as sensitive film, and an extrinsic Fabry Perot resonator is formed with fiber bragg grating (FBG) and fiber end face. The film device exhibits high sensitivity and reproducibility to hydrazine vapor with liner concentration dependent characteristic, which owes to the change of refractive index under hydrazine vapor. The enhancement sensitivity and temperature monitoring could be obtained due to the FBG. The results show that a hydrazine vapor sensitivity of 0.01 dB m/ppm, a temperature sensitivity of 9.8 pm/?C could be achieved. In addition, the effect of enlarged fiber end face on the form of TClPDI film was investigated, the sensing mechanism of the film device to hydrazine vapor was studied. The sensor has the advantages of all optical system, tiny, high repeatability, high reliability and two parameters sensing, showing high potential for practical application.
关键词： Tautomerism,Simultaneous measurement,The change of RI,FBG-FP,Two-parameter
更新于2025-11-28 14:23:57
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Electric and dielectric characteristics of Al/ZrO2/IL/n-Si MOS capacitors using three-frequency correction method
摘要： In this study, MOS capacitors of Al/ZrO2/IL/n-Si (IL: interface layer) have been fabricated. Bias scan and frequency scan data of measured parallel capacitance (Cm) and parallel resistance (Rm) have been taken in the frequency of ～1 kHz to 2 MHz. To correct external frequency dispersion of parasitic parameters, we have used five-element model (including MOS capacitance C, parallel resistance Rp, IL capacitance Ci, IL resistance Ri, and series resistance Rs) and three-frequency correction method. Extracted capacitance C by the three-frequency correction method has negligible frequency dependence from 0.38 nF to 0.34 nF in the average frequency of ～3.7 kHz to 1.54 MHz. The frequency dispersion of Rp, Ci, Ri, and Rs are explained by some physical mechanisms. Small relative errors ΔC/C, ΔRp/Rp, ΔCi/Ci, ΔRi/Ri and ΔRs/Rs are less than 0.2%, 2%, 3%, 1.2% and 0.4% respectively. We have also used two existing double-frequency methods of three- and four-element models for comparison, and the extracted capacitances show abnormal frequency dependence. Above results indicate the three-frequency method of five-element model is necessary, effective and convenient in providing sufficient list data for bias voltage dependence or frequency dependence. The dielectric parameters, such as relative dielectric constant, conductivity, imaginary part of complex dielectric constant, and dielectric loss tangent have been calculated. The mechanisms of frequency dispersion for the dielectric parameters have been analyzed.
关键词： Three-frequency correction,Parameter extraction,MOS capacitor,Five-element model,Dielectric characteristics,Frequency dispersion
更新于2025-11-14 17:28:48
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Radiative transition probabilities between low-lying electronic states of N <sub/>2</sub>
摘要： This work mainly investigates the transition dipole moments (TDMs) and radiative transition probabilities of dipole-allowed transitions between the b1Σu+, a''1Σg+, 13Σg-, 23Σg-, C'3Σu+, B'3Σu-, W3Δu, 23Σu+ and H3Υu states of N2. Many of these transition properties are previously unknown. For completeness, another 14 electronic states that correlate to four lowest dissociation limits are also calculated. The potential energy curves (PECs) are calculated at the valence internally contracted multireference configuration-interaction (icMRCI) level of theory, along with the Davidson correction, the core-valence (CV) correction and the scalar relativistic correction, as well as the basis-set extrapolation. These corrections, especially the CV correction, greatly improve the accuracy of the PECs, as shown by the excellent agreement of the fitted spectroscopic parameters with the available experimental data. In order to verify the accuracy of transition properties, we calculate the Einstein coefficients of the extensively studied B3Σg- - A3Σu+, C3Σu+ - B3Σg-, W3Δu - B3Σg-, B'3Σu- - B3Σg-, C'3Σu+ - B3Σg-, w1Δu - a1Σg+, a1Σg+ - a'1Σg- and b1Σu+ - X1Σg+ band transition systems and compute the radiative lifetimes of N2 B3Σg-, C3Σu+ and W3Δu states, which are in good agreement with the experimental data. Similar accuracy can be assumed for the previously undetermined 13Σg- - B'3Σu-, 23Σg- - B'3Σu-, 23Σg- - C'3Σu+, 23Σu+ - B3Σg- and b1Σu+ - a''1Σg+ band transition systems. The large Einstein coefficients of these band systems can provide guidelines for observing such newly predicted band transitions in the appropriate spectroscopy experiments.
关键词： radiative lifetime,Spectroscopic parameter,radiative transition probability,transition dipole moment,N2
更新于2025-09-23 15:23:52
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A reliable and efficient small-signal parameter extraction method for GaN HEMTs
摘要： In this paper, a reliable and efficient parameter extraction method for GaN high electron mobility transistor (HEMT) small‐signal models has been proposed. By utilizing parameter scanning method, the initial values of the extrinsic elements are first extracted from the cold pinch‐off and cold unbiased measurement conditions, respectively. An iterative optimization algorithm is employed then to optimize the extrinsic elements. This scanning and iteration combined algorithm based on a direct extraction method of extrinsic elements can reduce the impact of the approximation error, which makes the determined values of the small‐signal parameters more reliable. The extraction flow has been realized in a Matlab program for efficiency. A 16‐element small‐signal equivalent circuit model (SSECM) for GaN HEMTs has been employed, and the new parameter extraction method has been validated by comparing the simulated small‐signal S‐parameters with the measured data from 0.1 GHz to 40 GHz for two different device dimensions.
关键词： small‐signal modeling,parameter extraction,GaN high electron mobility transistor (HEMT)
更新于2025-09-23 15:23:52
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Multi-Parameters Detection Implemented by LC Sensors With Branching Inductors
摘要： Inductor-capacitor (LC) sensors utilize magnetic coupling to transfer signals to the readout coil, realizing a passive wireless working pattern. They are of high use in situations where wired connections are impossible to be established. An increasing number of demands, arising from the emerging applications in the Internet of Things and portable devices, require a simultaneous monitoring in sensors. This paper proposes a branching inductor to implement multiple resonances in a single inductor. Each branch of the inductor forms a secondary inductance, which is connected with a sensitive capacitor to work as an LC sensor. The multiple resonances in the branching inductor work in a multi-mode coupling pattern. The coupling, comprising inductive coupling, and capacitive coupling is analyzed and detected. In experiments, a double branching inductor is fabricated on PET substrate. Two sensitive capacitors for humidity and pressure, respectively, are connected to the inductor, resulting in two resonant peaks to monitor the ambient humidity and pressure level. The experimental results are decoupled to obtain final outcomes: the humidity sensor can respond from 15%RH ~ 90%RH with a sensitivity of -45.3 kHz/%RH; and the pressure sensor can work from 750 mmHg ~ 1000 mmHg with a sensitivity of -811.2 kHz/mmHg.
关键词： Branching inductor,LC sensor,multi-parameter
更新于2025-09-23 15:23:52
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Band gap analysis of periodic structures based on cell experimental frequency response functions (FRFs)
摘要： An approach is proposed to estimate the transfer function of the periodic structure, which is known as an absorber due to its repetitive cells leading to the band gap phenomenon. The band gap is a frequency range in which vibration will be inhibited. A transfer function is usually performed to gain band gap. Previous scholars regard estimation of the transfer function as a forward problem assuming known cell mass and stiffness matrices. However, the estimation of band gap for irregular or complicated cells is hardly accurate because it is difficult to model the cell exactly. Therefore, we treat the estimation as an inverse problem by employing modal identification and curve fitting. A transfer matrix is then established by parameters identified through modal analysis. Both simulations and experiments have been performed. Some interesting conclusions about the relationship between modal parameters and band gap have been achieved.
关键词： Band gap,Periodic structure,Transfer matrix,Parameter identification,Modal analysis
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A Simulation Based Approach to Estimating the Three Dimensional Structure of the Harvard Forest with Multi-Modal Remote Sensing
摘要： Tracking carbon as it enters and exits each stage of the carbon cycle is necessary to help build understanding of the cycle's mechanics and its effect on climate. Satellite and airplane-based remote sensing technologies have shown promising results in aiding in human understanding of our planet, including vegetative areas. The Harvard Forest has been studied in various ways over the course of the last century. In particular, synthetic aperture radar, LiDAR, and passive optical sensors have each been used to study the Harvard Forest. Employing a form of data fusion, we present an approach to estimate a forest stand's mean canopy height and biomass for each component tree species while employing minimal ground measurements. We present an approach where a database of simulated forest stands is generated containing both homogeneous stands and heterogeneous stands with up to four tree species present in a given stand. Each simulated stand is compared to an input stand on a number of criteria and a figure of similarity is calculated. In the case that a simulated stand isn't found with a figure of similarity below a set threshold, an iterative process is employed to modify the most similar stand to improve the factor of similarity by modifying the stand's species composition, tree densities, heights, and biomasses. A simulated stand, either pre-existing or developed dynamically will be considered a reasonable representation of the physical forest stand and the 3-D structure of the simulated stand will be reported as an estimate for that of the physical forest stand. This method relies heavily on our sensor simulators, including our fractal-based tree geometry generator, as well as SAR, IfSAR, LiDAR, and Optical simulators. We have previously investigated the ability of our method to differentiate between coniferous and deciduous trees in the same forest stand. We propose to extend this to a maximum of four different tree species, and to validate our approach in the Harvard Forest, a heavily studied region in central Massachusetts.
关键词： Harvard Forest,Forest Parameter Estimation,IfSAR,Heterogeneous Forests,SAR,LiDAR
更新于2025-09-23 15:23:52
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Photochemical multivariate curve resolution models for the investigation of photochromic systems under continuous irradiation
摘要： We propose a multivariate curve resolution approach for the investigation of photochromic systems using UV-Visible spectroscopy. The incorporation of photochemical hard-models as constraints in multivariate curve resolution alternating least squares (MCR-ALS) allows extracting reaction quantum yields in situations where a complete knowledge of the system is not available. We apply this approach to the study of the photochromism of CMTE (cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene) under continuous monochromatic irradiation. The mechanism, involving 3 species and 2 reversible reactions, is written and translated into a kinetic constraint that can be applied to the concentration profiles within ALS. First, ambiguity of the solution obtained for photochemical model(s) is calculated and discussed for single set analysis. Multiset analysis is then proposed combining data obtained under different irradiation wavelengths to provide more reliable results. Finally, the photochemical reactivity of CMTE is widely unraveled, and some description of the mechanism observed under irradiation at 365 nm is given.
关键词： Multivariate curve resolution,Quantum yield,Hard-soft modelling,Parameter ambiguity,Photochemical reaction
更新于2025-09-23 15:23:52
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Production of a Scalar Boson and a Heavy Fermion Pair in Counterpropagating Е–Е+ Beams
摘要： The process of production of an HSM scalar boson of the Standard Model (H and h bosons of the Minimal Supersymmetric Standard Model) and a heavy fermion pair tt in counterpropagating electron-positron beams e+ e- -> H tt (e+ e- -> h tt) is discussed. Analytical expressions for the energy spectrum of the Higgs boson and the transverse spin asymmetry and the right-left spin asymmetry are obtained, and their dependences on the emission angle and energy of the Higgs boson are investigated.
关键词： left and right coupling constants,heavy fermion pair,Standard Model,Minimal Supersymmetric Standard Model,Weinberg parameter
更新于2025-09-23 15:23:52