- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Characteristics of multi-pass narrow-gap laser welding of D406A ultra-high strength steel
摘要： A universal and applicable method to predict bonding quality in narrow-gap laser beam filler wire welding of D406A ultra-high strength steel was presented. Defect-free joint could be achieved under the predicted optimal welding condition, while the production efficiency of narrow-gap laser beam filler wire welding under optimized welding condition was about 3.75 times that of traditional tungsten arc welding currently used in practical industry. Compared with the tungsten arc welding joint, microstructure in the fusion zone of laser welded joint was more uniform, which brought out a less fluctuation in the microhardness of fusion zone along the thickness direction. The tensile strength of as-welded laser welding joint was slightly higher than that of as-welded tungsten arc welding joint while the elongation of the former increased by 15.9% over that of the latter. A binocular stereo three-dimensional scanning method was adopted to compare the residual distortion of D406A joints between laser welding and tungsten arc welding. Notably, the distortion of laser welded joint was about 21% of that of the tungsten arc welding joint. Narrow-gap laser filler wire welding is a feasible substitute for conventional tungsten arc welding in the fabrication of welded construction of D406A steel.
关键词： ultra-high strength steel,welding distortion,filler wire,narrow-gap laser beam welding,microstructure
更新于2025-11-28 14:24:20
-
Laser welding process evaluation on stake-welded T-joints
摘要： Ship structural steel EH36 sheets with thickness of 3 mm were stake-welded with T-joints by using ?ber laser beam welding (LBW). Optical microscope (OM) observation, angular distortion measurement and tensile test were conducted to investigate the in?uence of defocusing distance, welding speed and line energy on the joint properties. The experiment results showed that laser stake-welded T-joints with high quality could be obtained at 1.8 m min?1 speed high, ?5 mm defocusing distance and 5 kW power. The loss of liquid metal in the misalignment condition led to severe under?ll. In addition, laser line energy and misalignment contributed signi?cantly to welding angular distortion. The welding width between face panel and web panel exerted an important in?uence on the tensile properties. Moreover, the thermal distortion process induced by ?ber laser welding has been schematically illustrated and systematically revealed.
关键词： laser welding,angular distortion,tensile property,T-joint,misalignment
更新于2025-11-28 14:24:20
-
Investigations of VO2+ doped SrZn2(PO4)2 nanophosphors by solution combustion synthesis
摘要： VO2+ doped SrZn2(PO4)2 nanophosphor is prepared using solution combustion synthesis. The prepared nanophosphor is studied by structural and spectral characterizations XRD, SEM with EDS, TEM, FT-IR, Optical absorption, EPR, and PL. XRD analyses the monoclinic phase of the prepared sample and the crystallite size determined to be in the order below 60 nm. SEM and TEM micrographs show the agglomerated stone-like structures for VO2+ doped SrZn2(PO4)2 nanophosphors. FT-IR spectrum exhibits various vibrational modes for PO4 3- anionic groups and other related groups. Optical absorption spectrum exhibited characteristic VO2+ bands in visible region and the crystal field and tetragonal field parameters are evaluated as Dq = 1461, Ds = -3035 and Dt = 602 cm-1. EPR spectrum shows well resolved hyperfine octet structure for VO2+ doped nanophosphor. The spin Hamiltonian parameters (g), hyperfine coupling constants (A) are calculated and are satisfying the condition g║<g┴<ge and A║ > A┴. From Optical and EPR data, VO2+ ions with the host ligands are identified as tetragonal distortion in octahedral site symmetry. PL spectrum illustrates, emission peaks in blue and green regions and its CIE and CCT parameters are evaluated, which are useful in LEDs and lightening devices.
关键词： Electron paramagnetic resonance,SrZn2(PO4)2 nanophosphor,Photoluminescence,tetragonal distortion,solution combustion
更新于2025-11-21 11:18:25
-
Enhanced piezoelectric properties and temperature stability of Bi4Ti3O12-based Aurivillius ceramics via W/Nb substitution
摘要： This work provides an effective method of inducing structure distortion, relieving the tetragonal strain of the TiO6 octahedron and decreasing the concentration of oxygen vacancies to improve the piezoelectricity and temperature stability of BIT ceramics. Bi4Ti2.98W0.01Nb0.01O12 possesses an optimum piezoelectric coefficient (d33) of 32 pC/N, a high Tc of 655 °C and a large resistivity of 3 × 106 Ω·cm at 500 °C. The maximum d33 reported here is approximately quadruple than that of pure BIT (~7 pC/N). Moreover, the d33 of W/Nb co-doped BIT and the in-situ temperature stability of the compression-mode sensor present a highly stable characteristic in the range of 25–600 °C. These results imply that W/Nb-modified BIT ceramics is a promising candidate for application at high temperatures of up to 600 °C.
关键词： Bi4Ti3O12,Structure distortion,Piezoelectric properties,Oxygen vacancy,Temperature stability
更新于2025-09-23 15:23:52
-
Ultra-low-distortion optical system design based on tolerance sensitivity optimization
摘要： This study theoretically analyzed the relationship between the primary aberrations and tolerances to meet the distortion requirements of an ultra-low-distortion optical system. Theoretical analysis shows that the distortion sensitivities of the optical system are related to the primary aberrations of the optical surfaces. Consequently, a method of optimizing the primary aberrations on the surface of the optical system to reduce the distortion sensitivities of sensitive tolerances is proposed. A distortion sensitivity analysis of manufacturing and assembly tolerance was carried out for the designed ultra-low-distortion and telecentric optical system. The distortion sensitivities of the sensitive tolerances were reduced by optimizing the primary aberrations on the surface of the optical system. A Monte Carlo analysis of the optimized ultra-low-distortion optical system showed that the proposed method has a remarkable effect on the distortion sensitivity optimization of the tolerances.
关键词： primary aberration,ultra-low distortion,optimization,tolerance sensitivity,optical design
更新于2025-09-23 15:23:52
-
Characterization of beam splitters in the calibration of a six-channel Stokes polarimeter
摘要： Polarization distortion in a beam splitter is a phenomenon where the polarization state of output light deviates from the theoretical expectation, which is inevitable and will result in significant errors in the optical systems. A theoretical analysis method based on Mueller matrix ellipsometry is proposed for characterizing the beam splitters and the application in the calibration of a six-channel Stokes polarimeter (SP) is shown. In this study, polarization distortions in the beam splitters including depolarization, linear birefringence, circular birefringence, linear dichroism, and circular dichroism have been considered. With the proposed method, the beam splitters are characterized by the polarization distortions and the effective optical parameters extracted. In our experiment, the Mueller matrices of two different commonly used beam splitters measured by a commercial Mueller matrix ellipsometer (MME) are consistently fitted by the proposed method and the residual errors have shown improvement compared to the conventional methods. A practical application of the proposed method is exhibited by calibrating a SP system containing two non-polarization beam splitters and three polarization beam splitters. With the proposed method introduced, the general error of the measured Stokes vector can be reduced from 3% to 1%, and the errors of the thickness measurement of standard SiO2 thin film samples are within 1 nm compared with the results reported by a commercial MME.
关键词： beam splitter,characterization,calibration,Stokes polarimeter,polarization distortion
更新于2025-09-23 15:23:52
-
[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Signal Distortion Decreasing in Envelope Tracking Power Amplifiers
摘要： When amplifying signals with a high peak to average power ratio, the efficiency of linear radio frequency (RF) power amplifiers (PA) is reduced to about 30%. This flaw can be noticeably corrected by using envelope tracking technology. However, using switched mode PAs of envelope signal (ES) is accompanied by the emergence of nonlinear distortions, which can appear as undesirable components in the RF PA signal spectrum. One of the ways to reduce the negative influence of the switched mode is to use ES PA of multicell structure. The paper covers the issues of the ES PA number of cells influence on its efficiency and output signal distortion, as well as its influence on the efficiency and output signal distortion of the RF PA. It is shown that rational choice of the number of cells allows to increase the efficiency of ES PA from 94 through 98% and to reduce the level of intermodulation components in the envelope signal spectrum by 20 ... 25 dB.
关键词： envelope tracking,power amplifier,harmonic distortion,efficiency,multicell
更新于2025-09-23 15:23:52
-
Blind Quality Metric for Contrast-Distorted Images Based on Eigendecomposition of Color Histograms
摘要： Although contrast is a major issue in overall quality assessment of an image, existing contrast evaluators with a reasonable performance are currently scarce. Here, we propose a learning-based blind/no-reference (NR) image quality assessment (IQA) model, dubbed Histogram Eigen-Feature based Contrast Score (HEFCS) for evaluating image contrast. This research seeks for the inter-relationship between contrast degradation and relevant image histogram features. We introduce "eigen-histograms", which are the eigenvectors of the set of image patches' histograms. We found that the randomness of image eigen-histograms and the amplitude of corresponding eigenvalues can reliably reflect the changes in image contrast. Employing these characteristics leads to contrast-aware Histogram Eigen-Feature (HEF) vectors, which are used to compute the contrast score through a prediction model trained using support vector regression (SVR). Extensive analysis and cross validation are performed with five contrast relevant image databases, and the HEFCS performance results are compared with a collection of full-reference (FR), reduced-reference (RR) and no-reference measures. Despite its simplicity and low computational complexity, the HEFCS performs better than all competing NR-IQA models, and also stands among the three best-performers of FR and RR models.
关键词： no-reference/blind,image quality assessment (IQA),Contrast distortion,eigen-histogram
更新于2025-09-23 15:23:52
-
Adaptive Nonlinear Equalization of a Tunable Bandpass Filter
摘要： The mitigation of third-order intermodulation distortion produced by a nonlinear tunable bandpass filter (BPF) in a digital receiver channel is demonstrated. An iterative solution is proposed, in the use of the least-mean-square algorithm, as an effective way to allow the correction coefficients to adapt to the changes in the system characteristics when the center frequency is changed. Results are shown using a two-pole, varactor-loaded BPF, and an Analog Devices AD9371 transceiver.
关键词： Adaptive signal processing,nonlinear distortion and intermodulation distortion (IMD),nonlinear filters,least mean square
更新于2025-09-23 15:22:29
-
[IEEE 2017 9th IEEE-GCC Conference and Exhibition (GCCCE) - Manama, Bahrain (2017.5.8-2017.5.11)] 2017 9th IEEE-GCC Conference and Exhibition (GCCCE) - OFDM Based Robust Digital Image Watermarking Resistant to Multipath Spatial Shifts
摘要： A digital watermark is a visible or invisible pattern embedded in a digital image which can be used for copyright protection, authentication, broadcast monitoring, telemedicine and many more. This paper describes how an efficient CDMA based spread spectrum technique can be combined with the most prominent spectrum efficient OFDM technology to formulate a robust watermarking algorithm which is suitable for image distortions due to time delays and spatial shift that may occur during the transmission of watermarked images. A detailed simulation of embedding and decoding algorithm was performed. Simulation results reveal that the algorithm is computationally efficient, robust and is well suited for wireless multipath fading channel. The algorithm was tested against a number of the possible noises in the wireless channels and various geometric and signal processing operations. The proposed algorithm is proved to be robust enough to extract a good quality watermark compared to well-known techniques.
关键词： Watermarking,OFDM,multipath,robust,distortion
更新于2025-09-23 15:22:29