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Keywords = transient-grating effect

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17 pages, 4067 KiB  
Article
Numerical Simulation and Intelligent Prediction of Effects of Primary Air Proportion and Moisture Content on MSW Incineration
by Shanping Chen, Fang Xu, Yong Chen and Lijie Yin
Processes 2025, 13(5), 1479; https://doi.org/10.3390/pr13051479 - 12 May 2025
Viewed by 522
Abstract
As the core process of the thermal treatment of municipal solid waste (MSW), incineration process optimization has become a frontier topic in the field of environmental engineering. This study took a 500 t/d incinerator for engineering application as the research object. Based on [...] Read more.
As the core process of the thermal treatment of municipal solid waste (MSW), incineration process optimization has become a frontier topic in the field of environmental engineering. This study took a 500 t/d incinerator for engineering application as the research object. Based on a two-fluid model, a three-dimensional transient model of a proportional incinerator was established. The effects of primary air proportion and moisture content on the combustion state in the incinerator were verified and discussed using field test data, and the dynamic changes in flue gas temperature were predicted by a BPNN (Backpropagation Neural Network). The results show that the increase in air volume in the drying section promotes water evaporation but inhibits the devolatilization and combustion of fixed carbon. The position where complete devolatilization and fixed carbon combustion begins was delayed by 1.5 m~3 m. The moisture content (M) is negatively correlated with the devolatilization and combustion of fixed carbon. From M = 25% to M = 40%, the flue gas outlet temperature decreased by 140 K. In addition, a dynamic combustion BP neural network model with the movement of the grate under rated conditions was constructed, with the MSE (Mean Squared Error) being 1.629%. The model can learn data characteristics well and has a good prediction effect. This study provides a scientific basis for optimizing the operating parameters of municipal solid waste incinerators, helps to optimize the incineration process, and is of great significance to the thermal treatment of MSW. Full article
(This article belongs to the Section Chemical Processes and Systems)
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15 pages, 2251 KiB  
Article
Reliable Determination of Pulses and Pulse-Shape Instability in Ultrashort Laser Pulse Trains Using Polarization-Gating and Transient-Grating Frequency-Resolved Optical Gating Using the RANA Approach
by Rana Jafari, Elizabeth Grace and Rick Trebino
Appl. Sci. 2025, 15(5), 2617; https://doi.org/10.3390/app15052617 - 28 Feb 2025
Viewed by 950
Abstract
Devices that measure the presence of instability in the pulse shapes in trains of ultrashort laser pulses do not exist, so this task necessarily falls to pulse-measurement devices, like Frequency-Resolved Optical Gating (FROG) and its variations, which have proven to be a highly [...] Read more.
Devices that measure the presence of instability in the pulse shapes in trains of ultrashort laser pulses do not exist, so this task necessarily falls to pulse-measurement devices, like Frequency-Resolved Optical Gating (FROG) and its variations, which have proven to be a highly reliable class of techniques for measuring stable trains of ultrashort laser pulses. Fortunately, multi-shot versions of FROG have also been shown to sensitively distinguish trains of stable from those of unstable pulse shapes by displaying readily visible systematic discrepancies between the measured and retrieved traces in the presence of unstable pulse trains. However, the effects of pulse-shape instability and algorithm stagnation can be indistinguishable, so a never-stagnating algorithm—even when instability is present—is required and is generally important. In previous work, we demonstrated that our recently introduced Retrieved-Amplitude N-grid Algorithmic (RANA) approach produces highly reliable (100%) pulse-retrieval in the second-harmonic-generation (SHG) version of FROG for thousands of sample trains of pulses with stable pulse shapes. Further, it does so even for trains of unstable pulse shapes and thus both reliably distinguishes between the two cases and provides a rough measure of the degree of instability as well as a reasonable estimate of most typical pulse parameters. Here, we perform the analogous study for the polarization-gating (PG) and transient-grating (TG) versions of FROG, which are often used for higher-energy pulse trains. We conclude that PG and TG FROG, coupled with the RANA approach, also provide reliable indicators of pulse-shape instability. In addition, for PG and TG FROG, the RANA approach provides an even better estimate of a typical pulse in an unstable pulse train than SHG FROG does, even in cases of significant pulse-shape instability. Full article
(This article belongs to the Special Issue Recent Advances in Ultrafast Laser Pulses)
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26 pages, 5841 KiB  
Article
Sensitization and Habituation of Hyper-Excitation to Constant Presentation of Pattern-Glare Stimuli
by Thomas Jefferis, Cihan Dogan, Claire E. Miller, Maria Karathanou, Austyn Tempesta, Andrew J. Schofield and Howard Bowman
Neurol. Int. 2024, 16(6), 1585-1610; https://doi.org/10.3390/neurolint16060116 - 21 Nov 2024
Cited by 2 | Viewed by 1862
Abstract
Background/Objectives: Pattern glare, associated with cortical hyperexcitability, induces visual distortions and discomfort, particularly in individuals susceptible to migraines or epilepsy. While previous research has primarily focused on transient EEG responses to patterned stimuli, this study aims to investigate how continuous presentation of pattern-glare [...] Read more.
Background/Objectives: Pattern glare, associated with cortical hyperexcitability, induces visual distortions and discomfort, particularly in individuals susceptible to migraines or epilepsy. While previous research has primarily focused on transient EEG responses to patterned stimuli, this study aims to investigate how continuous presentation of pattern-glare stimuli affects neural adaptation over both fine (seconds) and coarse (entire experiment) temporal scales. Methods: EEG recordings were obtained from 40 healthy participants exposed to horizontal square-wave gratings at three spatial frequencies presented continuously for three seconds each across multiple trials. Participants’ susceptibility to visual stress, headaches, and discomfort was assessed using questionnaires before and during the experiment. The experiment employed a two-by-two design to evaluate habituation (exponentially decreasing response) and sensitisation (exponentially increasing response) effects at two different time granularities. Mass univariate analysis with cluster-based permutation tests was conducted to identify significant brain response changes during the period of constant stimulation, which we call the DC-shift period. Results: Significant effects were observed during the DC-shift period, indicating sustained hyper-excitation to the medium-pattern glare stimulus. In particular, the mean/intercept analysis revealed a consistent positive-going response to the medium stimulus throughout the DC-shift period, suggesting continued neural engagement. Participants reporting higher discomfort exhibited sensitisation at fine temporal granularity and habituation at coarser temporal granularity. These effects were predominantly localised to the right posterior scalp regions. Conclusions: The study demonstrates that individuals sensitive to pattern-glare stimuli exhibit dynamic neural adaptation characterised by short-term sensitisation and long-term habituation. These findings enhance the understanding of cortical hyperexcitability mechanisms and may inform future interventions for visual-stress-related conditions, such as migraines and epilepsy. Further research is needed to explore the underlying neural processes and validate these effects in clinical populations. Full article
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16 pages, 4462 KiB  
Article
Wafer Level Vacuum Packaging of MEMS-Based Uncooled Infrared Sensors
by Gulsah Demirhan Aydin, Orhan Sevket Akar and Tayfun Akin
Micromachines 2024, 15(8), 935; https://doi.org/10.3390/mi15080935 - 23 Jul 2024
Cited by 3 | Viewed by 2704
Abstract
This paper introduces a cost-effective, high-performance approach to achieving wafer level vacuum packaging (WLVP) for MEMS-based uncooled infrared sensors. Reliable and hermetic packages for MEMS devices are achieved using a cap wafer that is formed using two silicon wafers, where one wafer has [...] Read more.
This paper introduces a cost-effective, high-performance approach to achieving wafer level vacuum packaging (WLVP) for MEMS-based uncooled infrared sensors. Reliable and hermetic packages for MEMS devices are achieved using a cap wafer that is formed using two silicon wafers, where one wafer has precise grating/moth-eye structures on both sides of a double-sided polished wafer for improved transmission of over 80% in the long-wave infrared (LWIR) wavelength region without the need for an AR coating, while the other wafer is used to form a cavity. The two wafers are bonded using Au-In transient liquid phase (TLP) bonding at low temperature to form the cap wafer, which is then bondelectrical and Electronics d to the sensor wafer using glass frit bonding at high temperature to activate the getter inside the cavity region. The bond quality is assessed using three methods, including He-leak tests, cap deflection, and Pirani vacuum gauges. Hermeticity is confirmed through He-leak tests according to MIL-STD 883, yielding values as low as 0.1 × 10−9 atm·cc/s. The average shear strength is measured as 23.38 MPa. The package pressure varies from 133–533 Pa without the getter usage to as low as 0.13 Pa with the getter usage. Full article
(This article belongs to the Special Issue MEMS Nano/Microfabrication)
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15 pages, 8793 KiB  
Article
Optical Design of a Hyperspectral Remote-Sensing System Based on an Image-Slicer Integral Field Unit in the Short-Wave Infrared Band
by Yi Ding, Chunyu Liu, Guoxiu Zhang, Pengfei Hao, Shuai Liu, Yingming Zhao, Yuxin Zhang and Hongxin Liu
Sensors 2024, 24(12), 4004; https://doi.org/10.3390/s24124004 - 20 Jun 2024
Viewed by 2047
Abstract
Grating-type spectral imaging systems are frequently employed in scenes for high-resolution remote-sensing observations of the Earth. However, the entrance of the grating-type spectral imaging system is a slit or a pinhole. This structure relies on the push broom method, which presents a challenge [...] Read more.
Grating-type spectral imaging systems are frequently employed in scenes for high-resolution remote-sensing observations of the Earth. However, the entrance of the grating-type spectral imaging system is a slit or a pinhole. This structure relies on the push broom method, which presents a challenge in capturing spectral information of transiently changing targets. To address this issue, the IFU is used to slice the focal plane of the telescope system, thereby expanding the instantaneous field of view (IFOV) of the grating-type spectral imaging system. The aberrations introduced by the expansion of the single-slice field of view (FOV) of the IFU are corrected, and the conversion of the IFU’s FOV from arcseconds to degrees is achieved. The design of a spectral imaging system based on an image-slicer IFU for remote sensing is finally completed. The system has a wavelength range of 1400 nm to 2000 nm, and a spectral resolution of better than 3 nm. Compared with the traditional grating-type spectral imaging system, its IFOV is expanded by a factor of four. And it allows for the capture of complete spectral information of transiently changing targets through a single exposure. The simulation results demonstrate that the system has good performance at each sub-slit, thereby validating the effectiveness and advantages of the proposed system for dynamic target capture in remote sensing. Full article
(This article belongs to the Section Remote Sensors)
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13 pages, 2934 KiB  
Article
Transient Interference Excision and Spectrum Reconstruction with Partial Samples Using Modified Alternating Direction Method of Multipliers-Net for the Over-the-Horizon Radar
by Zhang Man, Quan Huang and Jia Duan
Sensors 2024, 24(9), 2770; https://doi.org/10.3390/s24092770 - 26 Apr 2024
Viewed by 1091
Abstract
Transient interference often submerges the actual targets when employing over-the-horizon radar (OTHR) to detect targets. In addition, modern OTHR needs to carry out multi-target detection from sea to air, resulting in the sparse sampling of echo data. The sparse OTHR signal will raise [...] Read more.
Transient interference often submerges the actual targets when employing over-the-horizon radar (OTHR) to detect targets. In addition, modern OTHR needs to carry out multi-target detection from sea to air, resulting in the sparse sampling of echo data. The sparse OTHR signal will raise serious grating lobes using conventional methods and thus degrade target detection performance. This article proposes a modified Alternating Direction Method of Multipliers (ADMM)-Net to reconstruct the target and clutter spectrum of sparse OTHR signals so that target detection can be performed normally. Firstly, transient interferences are identified based on the sparse basis representation and then excised. Therefore, the processed signal can be seen as a sparse OTHR signal. By solving the Doppler sparsity-constrained optimization with the trained network, the complete Doppler spectrum is reconstructed effectively for target detection. Compared with traditional sparse solution methods, the presented approach can balance the efficiency and accuracy of OTHR signal spectrum reconstruction. Both simulation and real-measured OTHR data proved the proposed approach’s performance. Full article
(This article belongs to the Special Issue Signal Processing in Radar Systems)
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9 pages, 3035 KiB  
Communication
Study on a Plasmonic Tilted Fiber Grating-Based Biosensor for Calmodulin Detection
by Xiaoyong Chen, Jie Jiang, Nan Zhang, Wenwei Lin, Pin Xu and Jinghua Sun
Biosensors 2021, 11(6), 195; https://doi.org/10.3390/bios11060195 - 14 Jun 2021
Cited by 17 | Viewed by 4285
Abstract
Tilted fiber Bragg grating, which has the advantages of both fiber Bragg grating and long-period fiber grating, has been widely studied for sensing in many fields, especially in the field of biochemistry. Calmodulin, which has a wide distribution in eukaryotes, can regulate several [...] Read more.
Tilted fiber Bragg grating, which has the advantages of both fiber Bragg grating and long-period fiber grating, has been widely studied for sensing in many fields, especially in the field of biochemistry. Calmodulin, which has a wide distribution in eukaryotes, can regulate several enzymes such as adenylate cyclase and guanylate cyclase and mediates several cellular processes such as cell proliferation and cyclic nucleotide metabolism. The abnormal levels of calmodulin in the body will result in serious effects from metabolism to nerve growth and memory. Therefore, it is important to measure the calmodulin concentration in the body. In this work, we propose and experimentally demonstrate a plasmonic tilted fiber Bragg grating-based biosensor for calmodulin detection. The biosensor was made using an 18° tilted fiber Bragg grating with a 50 nm-thick gold nanofilm coating the surface of the fiber, and transient receptor potential channels were bonded onto the surface of the gold nanofilm to serve as bio-detectors for calmodulin detection. Experimental results showed that the limit of detection using our biosensor was 0.44 nM. Furthermore, we also demonstrated that the interaction between calmodulin and transient receptor potential channels was quite weak without calcium in the solution, which agrees with the biology. Our proposed biosensor has a simple structure, is easy to manufacture, and is of small size, making it a good choice for real-time, label-free, and microliter-volume biomolecule detection. Full article
(This article belongs to the Special Issue Recent Progress of Optical Fiber Based Biosensors)
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15 pages, 6820 KiB  
Article
Analytical Evaluation and Experiment of the Dynamic Characteristics of Double-Thimble-Type Fiber Bragg Grating Temperature Sensors
by Chuan Luo, Han Wang, Dacheng Zhang, Zhengang Zhao, Yingna Li, Chuan Li and Ke Liang
Micromachines 2021, 12(1), 16; https://doi.org/10.3390/mi12010016 - 26 Dec 2020
Cited by 11 | Viewed by 3125
Abstract
A double-thimble-type fiber Bragg grating (FBG) temperature sensor that isolates the stress strain is developed, and the three materials of air, grease, and copper thimble are employed for encapsulating. To investigate the effect of different encapsulation materials on the time constant of the [...] Read more.
A double-thimble-type fiber Bragg grating (FBG) temperature sensor that isolates the stress strain is developed, and the three materials of air, grease, and copper thimble are employed for encapsulating. To investigate the effect of different encapsulation materials on the time constant of the sensors under dynamic conditions, the transient heat conduction mathematical model is built according to the lumped heat capacity (LHC) system and thermal equilibrium theory, and the time constant is solved by an analytical solution. Then, a proportional three-dimensional sensor simulation model is established and the transient heat transfer process is numerically solved by the finite element analysis method. To verify the models, an experimental system is established to test the response speed of the three-type sensor and the experimental data are compared with the analytical and numerical solution results. The results show that the dynamic response performance depends on the encapsulation material parameters; the response speed is faster than recovery speed; and the response speed of the air packaging sensor is more than 20% faster than that of the grease packaging sensor, and more than 30% faster than that of the copper packaging sensor. The smaller the heat storage capacity and the larger the heat transfer coefficient, the faster the sensor’s response speed. Full article
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10 pages, 2856 KiB  
Article
Spatially Broadband Coupled-Surface Plasmon Wave Assisted Transmission Effect in Azo-Dye-Doped Liquid Crystal Cell
by Guan-Ting Dong, Chun-Ta Wang and Yu-Ju Hung
Nanomaterials 2020, 10(7), 1357; https://doi.org/10.3390/nano10071357 - 11 Jul 2020
Cited by 1 | Viewed by 2808
Abstract
Active tuning on a plasmonic structure is discussed in this report. We examined the transient transmission effects of an azo-dye-doped liquid crystal cell on a metallic surface grating. The transition between isotropic and nematic phases in liquid crystal generated micro-domains was shown to [...] Read more.
Active tuning on a plasmonic structure is discussed in this report. We examined the transient transmission effects of an azo-dye-doped liquid crystal cell on a metallic surface grating. The transition between isotropic and nematic phases in liquid crystal generated micro-domains was shown to induce the dynamic scattering of light from a He-Ne laser, thereby allowing transmission through a non-transparent aluminum film overlaying a dielectric grating. Various grating pitches were tested in terms of transmission effects. The patterned gratings include stripe ones and circular forms. Our results indicate that surface plasmon polariton waves are involved in the transmission process. We also demonstrated how momentum diagrams of gratings and Surface Plasmon Polariton (SPP) modes combined with Mie scattering effects could explain the broadband coupling phenomenon. This noteworthy transition process could be applied to the development of spatially broadband surface plasmon polariton coupling devices. Full article
(This article belongs to the Section Nanophotonics Materials and Devices)
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16 pages, 2244 KiB  
Article
Evaluation of Effective Elastic Properties of Nitride NWs/Polymer Composite Materials Using Laser-Generated Surface Acoustic Waves
by Evgeny Glushkov, Natalia Glushkova, Bernard Bonello, Lu Lu, Eric Charron, Noëlle Gogneau, François Julien, Maria Tchernycheva and Olga Boyko
Appl. Sci. 2018, 8(11), 2319; https://doi.org/10.3390/app8112319 - 21 Nov 2018
Cited by 10 | Viewed by 3900
Abstract
In this paper we demonstrate a high potential of transient grating method to study the behavior of surface acoustic waves in nanowires-based composite structures. The investigation of dispersion curves is done by adjusting the calculated dispersion curves to the experimental results. The wave [...] Read more.
In this paper we demonstrate a high potential of transient grating method to study the behavior of surface acoustic waves in nanowires-based composite structures. The investigation of dispersion curves is done by adjusting the calculated dispersion curves to the experimental results. The wave propagation is simulated using the explicit integral and asymptotic representations for laser-generated surface acoustic waves in layered anisotropic waveguides. The analysis of the behavior permits to determine all elastic constants and effective elastic moduli of constituent materials, which is important both for technological applications of these materials and for basic scientific studies of their physical properties. Full article
(This article belongs to the Special Issue Laser Ultrasonics)
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22 pages, 8803 KiB  
Review
Self-Referenced Spectral Interferometry for Femtosecond Pulse Characterization
by Xiong Shen, Peng Wang, Jun Liu, Takayoshi Kobayashi and Ruxin Li
Appl. Sci. 2017, 7(4), 407; https://doi.org/10.3390/app7040407 - 18 Apr 2017
Cited by 9 | Viewed by 8107
Abstract
Since its introduction in 2010, self-referenced spectral interferometry (SRSI) has turned out to be an analytical, sensitive, accurate, and fast method for characterizing the temporal profile of femtosecond pulses. We review the underlying principle and the recent progress in the field of SRSI. [...] Read more.
Since its introduction in 2010, self-referenced spectral interferometry (SRSI) has turned out to be an analytical, sensitive, accurate, and fast method for characterizing the temporal profile of femtosecond pulses. We review the underlying principle and the recent progress in the field of SRSI. We present our experimental work on this method, including the development of self-diffraction (SD) effect-based SRSI (SD-SRSI) and transient-grating (TG) effect-based SRSI (TG-SRSI). Three experiments based on TG-SRSI were performed: (1) We built a simple TG-SRSI device and used it to characterize a sub-10 fs pulse with a center wavelength of 1.8 μm. (2) On the basis of the TG effect, we successfully combined SRSI and frequency-resolved optical gating (FROG) into a single device. The device has a broad range of application, because it has the advantages of both SRSI and FROG methods. (3) Weak sub-nanojoule pulses from an oscillator were successfully characterized using the TG-SRSI device, the optical setup of which is smaller than the palm of a hand, making it convenient for use in many applications, including sensor monitoring the pulse profile of laser systems. In addition, the SRSI method was extended for single-shot characterization of the temporal contrast of ultraintense and ultrashort laser pulses. Full article
(This article belongs to the Special Issue Ultrashort Optical Pulses)
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