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Parametric study of laser cutting of carbon fibre reinforced polymer (CFRP) and the effect of fibre orientation on cutting quality
摘要： Laser cutting of CFRP was performed using 2 kW fibre laser. A detailed analysis of the effect of various laser processing parameters on the cutting of CFRP was carried out. The present work considers mainly laser power (W), scan speed (mm/min), gas pressure (bar) and duty cycle (%) as the process parameters with average kerf width and heat affected zone (HAZ) as the output parameters. Cutting of the fibres at 90o with respect to fibre orientation was performed. The SEM and EDS analysis were also performed to understand the cut quality, matrix melting, fibre pullout and vaporisation phenomena of the matrix in the heat affected zone (HAZ). Laser cutting of CFRP with a minimum kerf width of around 184 μm was observed for 800 W, 600 mm/min, 3 bar and 25% duty cycle while HAZ in this parameter was around 1561 μm. Kerf width and HAZ directly increase with an increase in laser power, gas pressure and duty cycle, but they reduce with increase in scan speed. SEM images confirm that the CFRP cutting process generates relatively burr-free fibre edges. Matrix recession and delamination (fibre pullout) were identified as the major quality defects occurring in the laser cutting process of CFRP.
关键词： fibre delamination,matrix melting,heat affected zone,laser cutting,fibre consolidation,kerf width,CFRP
更新于2025-11-28 14:24:20
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[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou, China (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - Wide-Spectrum Pulsed Fiber Laser based on Picosecond Pulse Generation Supercontinuum
摘要： We demonstrated a wide-spectrum pulsed fiber laser by using supercontinuum (SC) generate from a narrow pulse width fiber laser pump into high nonlinear fiber (HNLF). The pulse width of wide-spectrum pulsed fiber laser is 7.95ps and the repetition frequency is 4GHz with a 20nm bandwidth. It is found that the anomalous dispersion region near the zero dispersion wavelength has a better stability by observing the wide spectrum pulses in different bands.
关键词： different dispersion region,super-continuum,wide-spectrum pulsed fiber laser,narrow pulse width
更新于2025-11-28 14:24:03
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Widely Wavelength-tunable Mode-locked Fiber Laser Based on a 45° Tilted Fiber Grating and Polarization Maintaining Fiber
摘要： We present a passively mode-locked Erbium-doped fiber laser with tunable parameters including central wavelength, 3dB bandwidth and pulse duration. The mode-locking mechanism of the laser is realized by using single-walled carbon nanotubes polyvinyl alcohol (SWCNTs-PVA) composite film as saturable absorber. The tunable operation is implemented via a fiber birefringence filter consisting of a polarization maintaining (PM) fiber and a Brewster fiber grating. The laser achieves a maximum spectral tuning range of 36 nm with 8 cm PM fiber. The maximum spectral width variation of 5.19 nm is acquired when the PM fiber is 12 cm. Simultaneously, the spectral widths of pulses at different central wavelengths are also adjustable. Furthermore, the total cavity length is 8.28 m, which is the shortest cavity length to obtain such wide tuning range in an Erbium-doped fiber laser based on SWCNTs.
关键词： Passively mode-locked fiber laser,spectral width,wavelength-tunable,pulse width,tilted fiber grating
更新于2025-11-28 14:23:57
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Thinning ferroelectric films for high-efficiency photovoltaics based on the Schottky barrier effect
摘要： Achieving high power conversion efficiencies (PCEs) in ferroelectric photovoltaics (PVs) is a longstanding challenge. Although recently ferroelectric thick films, composite films, and bulk crystals have all been demonstrated to exhibit PCEs >1%, these systems still suffer from severe recombination because of the fundamentally low conductivities of ferroelectrics. Further improvement of PCEs may therefore rely on thickness reduction if the reduced recombination could overcompensate for the loss in light absorption. Here, a PCE of up to 2.49% (under 365-nm ultraviolet illumination) was demonstrated in a 12-nm Pb(Zr0.2Ti0.8)O3 (PZT) ultrathin film. The strategy to realize such a high PCE consists of reducing the film thickness to be comparable with the depletion width, which can simultaneously suppress recombination and lower the series resistance. The basis of our strategy lies in the fact that the PV effect originates from the interfacial Schottky barriers, which is revealed by measuring and modeling the thickness-dependent PV characteristics. In addition, the Schottky barrier parameters (particularly the depletion width) are evaluated by investigating the thickness-dependent ferroelectric, dielectric and conduction properties. Our study therefore provides an effective strategy to obtain high-efficiency ferroelectric PVs and demonstrates the great potential of ferroelectrics for use in ultrathin-film PV devices.
关键词： power conversion efficiency,Schottky barrier effect,ferroelectric photovoltaics,PZT ultrathin film,depletion width
更新于2025-11-14 17:28:48
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P-1.1: Anomalous Dependence of Threshold Voltage on Channel Width and Drain Voltage in Back-channel-etched a-IGZO TFTs
摘要： The back-channel-etched (BCE) amorphous InGaZnO thin-film transistors with different channel widths (Ws) are fabricated. The performance of VTH depends on both channel width (W) and drain voltage (VD) in this work. It is shown that neither W nor VD can create influence in VTH when W or VD is relatively small. However, when both W and VD are large enough, there will be an anomalous phenomenon that VTH increases with the increasing W or the increasing VD. The self-heating effect can be used to account for this anomalous dependence of VTH on W and VD.
关键词： self-heating effect,drain voltage,threshold voltage,amorphous InGaZnO TFTs,channel width
更新于2025-09-23 15:23:52
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Distinguishing between closely related species of Allium and of Brassicaceae by narrowband hyperspectral imagery
摘要： Classification of crop species is an actively studied topic in remote sensing using multi-spectral image sensors. Unfortunately, the spectral bands available in the multispectral imagery are broad and limited in number to classify the crop species. In this paper, we propose optimal spectral bands to classify Allium (garlic and onion) and Brassicaceae (Chinese cabbage and radish) by using higher-dimensional data from hyperspectral imagery. A decision-tree classifier was used to determine the optimal method to use the high-dimensional data. The high-dimensional data were analysed for all growth stages and considering bandwidths with different full width at half maximum (FWHM) values at 25, 40, 50 and 80 nm. The spectral bands selected for Allium were differentiated into green, blue, and NIR bands for each growth stage. The results show that Allium can be classified clearly as overall accuracy (OA) 1 and kappa coefficient 1 for all FWHM based on March 22 data. For each April 19 and May 12 data, the decision-tree classifier with each 80 nm FWHM and 50 nm FWHM yielded a better classification accuracy of more than OA 0.921 and kappa coefficient 0.839 than other FWHM. The spectral bands selected for Brassicaceae were found to be similar to blue band for all growth stages. Brassicaceae was classified clearly for all FWHM based on October 27 data. Also, Brassicaceae was classified clearly for 25 nm FWHM based on November 25 data and OA, kappa coefficient for 40 nm FWHM and 50 nm FWHM are high as 0.974, 0.947 respectively.
关键词： Decision-tree classifier,Hyperspectral imagery,Classification,Full width at half maximum,Spectral band
更新于2025-09-23 15:23:52
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PWM as a Low Cost Method for the Analog Control of MEMS Devices
摘要： In this paper, we discuss the use of pulse width modulation (PWM) to control analog MEMS devices. We achieve a precise linear analog control of MEMS by applying PWM signal with a frequency well above the system’s mechanical natural frequency. We first demonstrate this using a parallel plate actuator and comb-drive, and then extend the technique to control a commercial deformable mirror. Such an approach allows the system designer to replace expensive drive electronics such as the high precision DACs and high voltage, linear amplifiers with a simple on-off switch. The advancements in the electronics industry tend to make precise timing cheaper and faster; our approach exploits these long-term trends to create low-cost control circuits. We also show how PWM control can linearize the positional response of the devices, where typically the position would depend quadratically on the applied analog voltage.
关键词： linearize,pulse width modulation,Microelectromechanical systems,electrostatic actuator
更新于2025-09-23 15:22:29
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Backbone Degradable Poly(aryl acetal) Photoresist Polymers: Synthesis, Acid Sensitivity, and Extreme Ultraviolet Lithography Performance
摘要： A new class of acid labile poly(aryl acetal) polymers has been developed that can be used in photoresist formulations for next-generation microlithography techniques including extreme ultraviolet (EUV) or electron beam lithography. Example polymers have been synthesized by an optimized Suzuki polycondensation protocol. They are soluble in common photoresist solvents but are insoluble in water or aqueous bases that are used to develop positive photoresists. The structural design includes further elements that are aimed at improving photoresist resolution, stability, and etch resistance. Upon acid exposure, the acetal linkages are cleaved, and the polymers degrade into phenolic terphenyl fragments, which are readily soluble in a photoresist developer. Polymer degradation has been studied by NMR and LC-MS. Lithographic formulations have been developed and tested in line-and-space patterning experiments using EUV photolithography. Optimized resist formulations achieved 22 nm resolution with line width roughness values of 5.7 nm.
关键词： poly(aryl acetal),resolution,EUV lithography,acid degradation,photoresist,line width roughness,Suzuki polycondensation
更新于2025-09-23 15:22:29
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Stress and Microstructure Study of W/Si X-ray Multilayers with Different Structural Parameters
摘要： X-ray Timing and Polarimetry (XTP) telescope is proposed by using nested focusing optics with a large effective area for studies in the field of high energy physics (energy region of 1–30 keV). High-reflectance and low-stress W/Si multilayers are required for this telescope to improve the spectral response and maintain the figure quality of the mirrors simultaneously. In this paper, we focused on the study of stress and layer structure of W/Si periodic multilayers at different d-spacings (thickness of period), thickness ratios, and bilayer numbers. The results show that the stress of the multilayer increased from ?73.3 to ?465.5 MPa with increase in the d-spacing from 2.7 to 5.5 nm, while the change in the average interface width was negligible, from 0.31 to 0.36 nm. For the multilayers prepared with different thickness ratios of W, from 0.3 to 0.67 (d = 3.7 nm), the lowest stress appeared at the ratio of ～0.46, and the average interface width was unchanged. The number of bilayers (N = 80–160) had negligible effects on both the layer structure and the stress, and the multilayers exhibited a very smooth surface morphology with a root-mean-square roughness of 0.19 nm. To further study the microstructural changes of the multilayer, X-ray diffraction measurements of the samples with different d-spacings and thickness ratios were performed. An increased crystallization along with phase changes were observed in the samples prepared with thicker W layers, which can increase the compressive stress of the multilayer.
关键词： W/Si Multilayer,Stress,X-ray,Crystallization,Interface Width
更新于2025-09-23 15:22:29
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Impact of Multiple Parameters on Energy Performance of PV-DSF Buildings
摘要： Double Skin Fa?ade (DSF) has been widely used in buildings to enhance energy efficiency and bring daylight and aesthetic benefits. Solar photovoltaic (PV) modules can be integrated in DSF to fully or partially meet the electricity demand. Therefore, in this study, the energy performance of a 3-storey PV-DSF building is analyzed for three cities of Iran with distinctive climates namely Tehran, Tabriz and Kish Island considering different orientations, cavity widths and different optical properties for the PV system. The results indicated that the south facing PV-DSF have the maximum electricity generation and the minimum net electricity consumption. With increase in cavity width from 0.4 to 1.2 m, the annual electricity consumption is reduced by 5.88, 5.19 and 7.49 MWh for Tehran, Tabriz and Kish, respectively. The cavity width tends to have negligible impact on electricity generation. The analysis of the outer PV skin showed that the glazing with lower Solar Heat Gain Coefficient (SHGC) offers more energy saving benefits for all the considered cities.
关键词： PV-DSF,cavity width,energy performance,optical properties
更新于2025-09-23 15:22:29