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[IEEE 2019 11th International Conference on Information Technology and Electrical Engineering (ICITEE) - Pattaya, Thailand (2019.10.10-2019.10.11)] 2019 11th International Conference on Information Technology and Electrical Engineering (ICITEE) - Activated Carbon as the Counter Electrode on Perovskite Solar Cells
摘要： An open-winding permanent-magnet synchronous generator (PMSG) system with the integration of fully controlled and uncontrolled converter is investigated in this paper, in which half the amount of controllable power switches are needed compared with the conventional open winding system fed by two voltage source converters. The voltage space vector of open winding PMSG is modulated by controlled converter, which will be integrated with the voltage vector by uncontrolled converter to implement the operation of open winding PMSG. In order to analyze and compare the operation capability on the different dc voltage ratios, the available modulation range of the open winding PMSG is analyzed in detail. Moreover, unity power factor control is proposed as the optimized control method to achieve the maximum modulation index. Finally, a 1-kW experimental setup is built to validate the theoretical investigation on the open winding PMSG system.
关键词： integration of fully controlled and uncontrolled converter,unity power factor control,open winding permanent-magnet synchronous generator (PMSG),DC voltage ratio,linear modulation range
更新于2025-09-23 15:19:57
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Widely triple Brillouin frequency shift multiwavelength Brillouin erbium fiber laser
摘要： We experimentally propose simple and widely tunable multiwavelength Brillouin erbium fiber laser with triple Brillouin frequency spacing. Only two dispersion compensation fiber spools with total length of 12 km, as a Brillouin gain media and erbium-doped fiber amplifier section with maximum pump power of 220 mW are utilized. In the developed structure, we achieved six triple Stokes lines with high peak power and large optical signal to noise ratio of more than 45 dB. Wide tuning range of 50 nm (1530–1580 nm) in the absence of self lasing cavity modes is recorded using both of high Brillouin pump and extracting the residual pump power outside the cavity.
关键词： Tuning range,SBS,MBEFL,Triple Brillouin frequency spacing
更新于2025-09-23 15:19:57
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Formation of Quantum Vortices at the Ionization of an Atom by an Ultrashort Laser Pulse: Two- and Three-Dimensional Cases
摘要： Quantum vortices formed at the barrier-suppression ionization of an atom by an ultrashort laser pulse have been studied theoretically and numerically. The ionization of a hydrogen atom is considered in the two-dimensional space and the ionization of an atom in the zero-range potential approximation is considered in the three-dimensional space. The resulting analytical expressions imply that the localization of quantum vortices in the three-dimensional space can be predicted by analyzing the two-dimensional model.
关键词： hydrogen atom,zero-range potential approximation,ultrashort laser pulse,Quantum vortices,barrier-suppression ionization
更新于2025-09-23 15:19:57
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Tunability of the Freea??Spectral Range by Microwave Injection into a Mida??Infrared Quantum Cascade Laser
摘要： The free-spectral range (FSR) of quantum cascade lasers (QCLs) emitting at 4.7 μm can be tuned through direct microwave modulation. The intrinsic short carrier lifetime of inter-subband transitions, along with impedance matched electrical packaging, allows a high-speed modulation up to more than 30 GHz. A signi?cant broadening and ?attening of the lasing spectrum is observed under radio frequency (RF) injection with frequencies close to the round-trip cavity. An accurate analysis of the high resolution spectra of the laser shows a comb-like regime for both free-running and RF modulated QCLs, if the modulation frequency is within the locking-range of the device. One of the main advantages of collecting high-resolution mid-infrared spectra, over the plain investigation of the beatnote in the microwave region, is the access to all the longitudinal modes and thus the accurate measure of the FSR over the whole optical spectrum. The use of high-resolution spectroscopy provides an in-depth and comprehensive analysis of lasing spectra under microwave modulations.
关键词： quantum devices,mid-infrared region,injection locking,tunability of the free-spectral-range,ultrafast devices
更新于2025-09-23 15:19:57
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Deep learning-based roadway crack classification using laser-scanned range images: A comparative study on hyperparameter selection
摘要： In recent years, deep learning-based crack detection methods have been widely explored and applied due to their high versatility and adaptability. In civil engineering applications, recent research on crack detection through deep convolutional neural network (DCNN) includes road pavement crack detection, bridge inspection, defects detection in shield tunnel lining, etc. Despite the increasing popularity of DCNN on crack detection, many challenges have yet to be properly addressed. For crack detection using three-dimensional (3D) range (i.e., elevation) images, disturbances such as surface variation can negatively affect the detection performance. Besides, some typical non-crack patterns such as grooves can be easily misidentified as cracks, i.e., false positives. Another issue lies in the selection of hyperparameters related with the design of a DCNN architecture. For example, the hyperparameters which are related with network structure (e.g., kernel size, network depth and width) and training (e.g., mini-batch size and learning rate) can impact the network performance to a significant extent. Therefore, they need to be properly determined for optimal performance. However, for deep learning-based roadway crack classification using laser-scanned range images, a comprehensive discussion on the hyperparameter selection/tuning has not been thoroughly performed. This study develops a hyperparameter selection process involving a series of experiments on laser-scanned range images with high diversities, investigating the optimal joint hyperparameter configuration on network structure and training for DCNN-based roadway crack classification. In a comparative study, 36 DCNN architectures with varying layouts are developed for crack classification. These architecture candidates differ in kernel sizes (e.g., 3 × 3, 7 × 7, and 11 × 11), network depths (from 5 to 8 weight layers), and widths (from 16 to 96 kernels in each convolutional layer). The 7-layer DCNN with constant 7 × 7 kernels and increasing network widths yields the highest classification performance among the proposed 36 DCNN classifiers, which may be because it can best reflect the complexity of the acquired laser-scanned roadway range images. Once the optimal architecture layout is determined, further discussion on the selection of min-batch sizes, learning rates, dropout factor and leaky rectified linear unit (LReLU) factor is performed. Experimental results show the optimal architecture with associated training configuration can achieve consistent and accurate performance, under the contamination of surface variations and grooved patterns in laser-scanned range images. Discussion on the hyperparameter selection can provide insights for the development of DCNN in similar applications using laser-scanned range images.
关键词： Roadway crack,Groove,Laser-scanned range image,Hyperparameter selection,Deep convolutional neural network
更新于2025-09-23 15:19:57
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Self-assembled line network in BiFeO3 thin films
摘要： In this work we report on the controlled fabrication of a self-assembled line network in highly epitaxial BiFeO3 thin films on top of LaAlO3 in the kinetically limited grown region by RF sputtering. As previously shown in the case of manganite thin films, the remarkable degree of ordering is achieved using vicinal substrates with well-defined step-terrace morphology. Nanostructured BiFeO3 thin films show mixed-phase morphology. Besides typical formation following (100) and (010) axes, some mixed phase nanodomains are detected also in-between the regular line network. These particular microstructures open a playground for future applications in multiferroic nanomaterials.
关键词： Mixed phase nanodomains,Long-range ordered nanostructures,Multiferroic thin films,Growth kinetic
更新于2025-09-23 15:19:57
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Purple-emissive carbon dots enhance sensitivity of Si photodetectors to ultraviolet range
摘要： In this work, we realized the synthesis of purple-emissive carbon dots (p-CDs) by a facile and highly reproducible route using folic acid as a sole precursor. The emission of the p-CDs is located around 390 nm, and independent of the excitation wavelength with a high photoluminescence quantum yield of 54.6%, thus complementing an emission color palette of brightly emitting carbon dots to a purple. Purple-emissive CDs are highly stable in both the colloidal state and in polymer films. A carbon dot luminescence down-shifting layer is used to sensitize a Si photodetector to UV range. As an example, p-CDs with an excitation maximum at 330 nm were integrated into Si photodetector, resulting in improving the photoresponsivity in a UV range from 0.8 to 2.5 mA/W, with a relative enhancement of 203.8%. This work represents a cheap, scalable and environmentally friendly way to create purple-emissive carbon dots enhancing the photoresponsivity of commercial photodetectors in a UV range thus being applicable in optical power meters, optical wireless communication systems, sunlight sensors, spectrophotometers, or radiation detectors.
关键词： UV range,Si photodetector,carbon dots,purple-emissive,photoluminescence
更新于2025-09-23 15:19:57
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Damage-free patterning of thermally sensitive CIGS thin-film solar cells: Can nanosecond pulses outperform ultrashort laser pulses?
摘要： Nanosecond pulses are usually not considered as a suitable candidate for low-damage processing of heat-sensitive materials due to high thermal effects and significant melt formation. Many studies have shown, that CIGS is thermally sensitive material and ultrashort lasers have been chosen as the primary source for the processing of CIGS cells. However, we report on the P3 scribing of CIGS thin-film solar cells with the ns pulse duration at the wavelength of 2.5 μm – a wavelength close to the mid-infrared region and compare the results with the ps pulses covering traditional wavelengths of 355 nm, 532 nm, 1064 nm, and 1342 nm. In our case, 6 ns pulses at 2.5 μm wavelength outperformed the picosecond laser sources operating at VIS and NIR wavelength range. The minimal P3 scribe conductivity of 4.7 mS/m was achieved for ns laser patterning, corresponding to simulated CIGS module efficiency loss of just 0.01%. We proposed that high absorption in the transparent conductive oxide - TCO efficiently shielded the underlying CIGS with only a fraction of energy reaching the back-contact. Finally, results show that nanosecond pulses can be as competitive as picosecond ones for P3 processing of high-efficiency CIGS devices.
关键词： CIGS,Nanosecond laser,Scribing,Picosecond laser,VIS and NIR wavelength range,Thin-film
更新于2025-09-23 15:19:57
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Origin of short- and medium-range order in supercooled liquid Ge <sub/>3</sub> Sb <sub/>2</sub> Te <sub/>6</sub> using <i>ab initio</i> molecular dynamics simulations
摘要： Phase-change materials such as Ge-Sb-Te compounds have attracted much attention due to the potential value for electrical data storage. In contrast to the amorphous and crystalline phases, supercooled liquid is far from to be deeply understood despite of the inevitable role in both amorphization and crystallization process. To this end, we have studied the dynamics property and structural characteristic of liquid and supercooled liquid Ge3Sb2Te6 during the fast cooling process. As the temperature decreases, chemical bonds become more homogeneous, but coordination numbers of Ge, Sb and Te atoms change very little. Meanwhile, the structural order of short-range configuration is obvious enhanced. Further studies suggest that Ge-centered, Sb-centered and Te-centered configurations change to the more ordered defective octahedrons mainly by adjusting the bond-angle relation and bond length, rather than just changing the coordination environment. It is the more ordered octahedrons that promote the formation of medium-range order. Our findings provide a deep insight on the origin of local structural order in supercooled liquid Ge3Sb2Te6, which are of great importance for the comprehensive understanding of amorphization and crystallization processes.
关键词： molecular dynamics,phase-change material,supercooled liquid,short-range order
更新于2025-09-23 15:19:57
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Impact of external amino acids on fluorescent protein chromophore biosynthesis revealed by molecular dynamics and mutagenesis studies
摘要： The precise positioning of catalytic amino acids against the substrate in an enzyme active site is a crucial factor in biocatalysis. Biosynthesis of the chromophores of fluorescent proteins (FPs) is an autocatalytic process that must conform to these requirements. Here, we show that, in addition to the internal amino acid residues in the proximity of the chromophore, chromophore biosynthesis is influenced by the remote amino acids exposed on the outer surface of the β-barrel structure of the FP. It has been shown earlier that chromophore biosynthesis of the red FP from Zoanthus sp. (zoan2RFP) proceeds via an immature green state. At the same time, the green state is the final stage of chromophore biosynthesis of green FP (zoanGFP), which is highly homologous to zoan2RFP. It was also shown that a single N66D substitution in the chromophore-forming sequence of zoanGFP might trigger the synthesis of the red chromophore. However, in this case, the synthesis of the red chromophore is incomplete and occurs only at elevated temperatures. Here, we tried to uncover additional structural determinants that govern the biosynthesis of the red chromophore. A comparison of zoanGFP and zoan2RFP revealed intrabarrel amino acid differences at five positions. Exhaustive substitutions of these five positions in zoanGFP-N66D gave rise to zoanGFPmut with the same intrabarrel amino acid composition as zoan2RFP. zoanGFPmut showed only partial green-to-red chromophore transformation at elevated temperatures. To elucidate the extra factors that can affect red chromophore biosynthesis, we performed comparative molecular dynamics simulations of zoan2RFP and zoanGFPmut. The simulations revealed several external amino acids that might influence the arrangement and flexibility of the chromophore-surrounding amino acid residues in these proteins. Mutagenesis experiments confirmed the crucial role of these residues in red chromophore biosynthesis. The obtained zoanGFPmut2 exhibited complete green-to-red transformation, suggesting that the mutated amino acids exposed on the surface of the β-barrel contribute to red chromophore biosynthesis.
关键词： autocatalysis,chromophore,protein engineering,fluorescent protein,molecular dynamics simulation,long-range interaction
更新于2025-09-23 15:19:57