82 research outputs found
Dan gen na mi xian de zhu xiang ju yu de guang xue xing zhi
No full textZhuang, Junping = 單根納米線的軸向局域的光學性質 / 庄俊平.Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.Includes bibliographical references.Abstracts in English and Chinese.Zhuang, Junping = Dan gen na mi xian de zhu xiang ju yu de guang xue xing zhi / Zhuang Junping.Acknowledgement --- p.IAbstract --- p.II摘要 --- p.IVContents --- p.iList of Figures --- p.ivList of Tables --- p.viiiAbbreviations --- p.ixChapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Background --- p.1Chapter 1.2 --- ZnSe Semiconductor Nanowires --- p.2Chapter 1.3 --- Carrier Dynamics in Semiconductor Nanowires --- p.3Chapter 1.3.1 --- Carrier Relaxation --- p.3Chapter 1.3.2 --- Surface Effects on Carrier Recombination --- p.7Chapter 1.4 --- Principle ofTCSPC Technique --- p.9Chapter 1.5 --- Motivations and Works --- p.10References --- p.12Chapter Chapter 2 --- Experiments --- p.17Chapter 2.1 --- Growth of ZnSe Nanowires --- p.17Chapter 2.2 --- Measurements with Electron Microscopes --- p.17Chapter 2.3 --- Measurements by a Laser Scanning Microscope --- p.18Chapter 2.3.1 --- Experimental Setup --- p.18Chapter 2.3.2 --- Settings of Measurements --- p.23References --- p.25Chapter Chapter 3 --- Methods of Analysis --- p.26Chapter 3.1 --- Luminescence Intensity --- p.26Chapter 3.1.1 --- Intensity Detected by PMT --- p.27Chapter 3.1.2 --- Intensity Detected by SPAD --- p.28Chapter 3.2 --- Lifetime Histogram --- p.29Chapter 3.2.1 --- Pixel Binning --- p.29Chapter 3.2.2 --- Lifetime Fitting --- p.32References --- p.33Chapter Chapter 4 --- Results and Discussion --- p.34Chapter 4.1 --- "Morphology, Structure and Composition of As-Grown Nanowires" --- p.34Chapter 4.2 --- Cathodoluminescence of Individual ZnSe Nanowires --- p.36Chapter 4.3 --- Photoluminescence of ZnSe Nanowires --- p.36Chapter 4.4 --- Luminescence of Individual Nanowires --- p.39Chapter 4.4.1 --- Luminescence of As-Grown Nanowires --- p.39Chapter 4.4.2 --- Nonlinear Optical Properties --- p.42Chapter 4.5 --- Luminescence Lifetimes of Individual Nanowires --- p.47Chapter 4.5.1 --- Power Dependence --- p.48Chapter 4.5.2 --- Chemical Environments --- p.53Chapter 4.5.3 --- Concentration of Ammonium Sulfide Solution --- p.56Chapter 4.6 --- Axially Resolved Luminescence Lifetimes --- p.60Chapter 4.6.1 --- Axially Resolved 2D Decay Diagrams --- p.60Chapter 4.6.2 --- Axially Resolved Luminescence Lifetimes --- p.62Chapter 4.6.3 --- (TNBE) and T1 of DL Emission --- p.69References --- p.72Chapter Chapter 5 --- Conclusions --- p.76Appendix A --- p.79Chapter A.1 --- Laser Beam Diameter and Spatial Resolution --- p.79Chapter A.2 --- Instrument Response Function of TCSPC module --- p.81Chapter A.3 --- Photo-Injection --- p.82Chapter A.3.1 --- Two-Photon Excitation by Pulse Laser --- p.82Chapter A.3.2 --- One-Photon Excitation by CW UV Laser --- p.84Chapter A.4 --- Lifetime Distributions --- p.85References --- p.86Appendix B Supporting Data --- p.8
A GaAs-based hybrid integration of a tunneling diode and a 1060-nm semiconductor laser
No full textWe report on a hybrid integrated tunneling diode, with a simple structure, and a quantum well laser diode, lasing at ~1060 nm, on GaAs substrate. The low-frequency operation of the integrated circuit was measured and obvious negative differential resistance regions were shown in the electrical and optical output. The electrical and optical bistability were measured, and the peak and valley voltage were 2.03 and 2.17 V, respectively. A 140-mV-wide hysteresis loop and an optical on/off ratio of 21 dB were obtained. The device has potential applications in biomedicine and optical interconnects
Selective Area Growth of GaAs in V-Grooved Trenches on Si(001) Substrates by Aspect-Ratio
No full text
A hybrid single-mode laser based on slotted silicon waveguides
No full textAn InGaAsP-Si hybrid single-mode laser based on etched slots in silicon waveguides was demonstrated operating at 1543 nm. The InGaAsP gain structure was bonded onto a patterned silicon-on-insulator wafer by selective area metal bonding method. The mode-selection mechanism based on a slotted silicon waveguide was applied, in which the parameters were designed using the simulation tool cavity modeling framework. The III-V lasers employed buried ridge stripe structure. The whole fabrication process only needs standard photolithography and inductively coupled plasma etching technology, which reduces cost for ease in technology transfer. At room temperature, a single mode of 1543-nm wavelength at a threshold current of 21 mA with a maximum output power of 1.9 mW in continuous-wave regime was obtained. The side mode suppression ratio was larger than 35 dB. The simplicity and flexibility of the fabrication process and a low cost make the slotted hybrid laser a promising light source
A directional-emission 1060-nm GaAs/InGaAs microcylinder laser
No full textA GaAs/InGaAs microcylinder laser in diameter of 15 μm connected with a 2-μm wide output waveguide is fabricated using standard photolithography and inductively coupled plasma etching technique. With the output waveguide, we realize the directional emission with the pulsed lasing operation wavelength of 1060 nm at room temperature. The maximum output power is ~6 μW and the minimum threshold current is 2 mA, which is comparatively low compared with previous reported GaAs material microlasers. A single mode operation is achieved near threshold current at the wavelength of 1060 nm. Mode characteristics are calculated and analyzed by 2-D finite-difference time-domain simulation. The small volume, low threshold current, and low energy consumption make the GaAs/InGaAs microcylinder laser we presented a promising light source for optical interconnection on chip
Evaluation of growth mode and optimization of growth parameters for GaAs epitaxy in V-shaped
No full textTwo‐order superconvergence for a weak Galerkin method on rectangular and cuboid grids
No full textThis is the peer reviewed version of the following article: Wang, J., Wang, X., Ye, X., Zhang, S., Zhu, P., Two-order superconvergence for a weak Galerkin method on rectangular and cuboid grids, Numer. Methods Partial Differ. Eq.. (2022), 1– 15. https://doi.org/10.1002/num.22918, which has been published in final form at https://doi.org/10.1002/num.22918. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited. This article will be embargoed until 09/22/2023.This article introduces a particular weak Galerkin (WG) element on rectangular/cuboid partitions that uses k th order polynomial for weak finite element functions and ( k + 1 ) th order polynomials for weak derivatives. This WG element is highly accurate with convergence two orders higher than the optimal order in an energy norm and the L 2 norm. The superconvergence is verified analytically and numerically. Furthermore, the usual stabilizer in the standard weak Galerkin formulation is no longer needed for this element.The research of Junping Wang was supported by the NSF IR/D program, while working at National Science Foundation. However, any opinion, finding, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. This research was supported in part by National Science Foundation Grant DMS-1620016, Zhejiang Provincial Natural Science Foundation of China (LY19A010008), and National Natural Science Foundation of China (12071184)
A Looseness Detection Method for Railway Catenary Fasteners based on Reinforcement Learning Refined Localization
No full textBrace sleeve (BS) fasteners, i.e., nut and bolt, are small components but play essential roles in fixing BS and cantilever in railway catenary system. They are commonly inspected by onboard cameras using computer vision to ensure the safety of railway operation. However, most BS fasteners cannot be directly localized because they are too small in the inspection images. Instead, the BS is first localized for detecting the BS fastener. This leads to a new problem that the localized BS boxes may not contain the complete BS fasteners due to low localization accuracy, making it infeasible to further diagnose the fastener conditions. To tackle this problem, this article proposes a novel pipeline for BS fastener looseness diagnosis. First, the competitive deep learning model Faster RCNN ResNet101 is used to coarsely localize BSs. Second, an action-driven reinforcement learning agent is adopted to refine the coarse-localized boxes through a dynamic position searching process. Then, BS fasteners are extracted from the refined localized BS image by the deep segmentation model YOLACT++, which is fast and interpretable. Finally, a looseness diagnosis criterion based on segmented information are proposed. We evaluate the performance of submodels independently and the overall performance of the whole model on a real-life catenary image dataset collected from a high-speed line in China. The test results show that the proposed method is effective for BS looseness detection in railway catenary.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Railway Engineerin
Ruscogenin Alleviates Myocardial Ischemia-Induced Ferroptosis through the Activation of BCAT1/BCAT2
No full textRuscogenin (RUS), a natural steroidal sapogenin, exerts various biological activities. However, its effectiveness for preventing myocardial ischemia (MI) and its molecular mechanisms need further clarification. The model of MI mice and oxygen-glucose deprivation-induced cardiomyocytes injury was performed. RUS significantly alleviated MI, as evidenced by decreased infarct size, ameliorated biochemical indicators and cardiac pathological features, and markedly inhibited ferroptosis by means of the up-regulation of GPX4 and down-regulation of ACSL4 and FLC. Simultaneously, RUS notably mitigated cell injury and oxidative stress, and ameliorated ferroptosis in vitro. Subsequently, HPLC-Q-TOF/MS-based metabolomics identified BCAT1/BCAT2 as possible regulatory enzymes responsible for the cardioprotection of RUS. Importantly, RUS treatment significantly increased the expression of BCAT1 and BCAT2 in MI. Furthermore, we found that BCAT1 or BCAT2 siRNA significantly decreased cell viability, promoted ferroptosis, and increased Keap1 expression, and induced Nrf2 and HO-1 degradation in cardiomyocytes. Conversely, cardiac overexpression of BCAT1 or BCAT2 in MI mice activated the Keap1/Nrf2/HO-1 pathway. Moreover, RUS significantly activated the Keap1/Nrf2/HO-1 pathway in MI, whereas BCAT1 or BCAT2 siRNA partially weakened the protective effects of RUS, suggesting that RUS might suppress myocardial injury through BCAT1 and BCAT2. Overall, this study demonstrated that BCAT1/BCAT2 could alleviate MI-induced ferroptosis through the activation of the Keap1/Nrf2/HO-1 pathway and RUS exerted cardioprotective effects via BCAT1/BCAT2
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