Two-Color Ultrafast Yb:Fiber Chirped Pulse Amplifier for Mid-Infrared Generation and Sensitive Mid-Infrared Detector Based on Extreme Non-Degenerate Two Photon Absorption in GaAs

This thesis outlines the development and optimization of a two-color three-stage ultrafast Yb:fiber chirped pulse amplifier for the generation of mid-infrared (MIR) radiation and a novel sensitive mid-infrared detector by using extreme non-degenerate two photon absorption (END-TPA) technique in GaAs. The two amplified colors used to generate MIR by difference frequency generation are centered at 1038nm and 1103nm respectively. The two colors are generated by continuum generation in a photonic crystal fiber pumped by a mode-locked Yb:fiber laser. One of the main goals of this thesis is to improve the power of the two colors to improve the MIR generation efficiency, because the difference frequency nonlinear mixing is proportional to the product of the power of the input colors. Towards this goal, we developed a three-stage Yb:fiber chirped pulse amplifier system that can generate more powerful MIR radiation compared with our previous two-stage system. In this thesis, approximately 65nm of wavelength separation between the two colors centered at 1038nm and 1103nm is accomplished through our pre-amplifier and two main amplifiers. The maximum combined average power is 2.65W after the last amplifier. A three-grating compressor is then used to compress the two colors to around 600fs and 1ps pulse durations and the average power of two colors is reduced to 1.86W after the compressor. By applying difference frequency generation in a 1-mm-thick GaSe crystal, 1.7mW average power, short-pulse MIR radiation is achieved. In this research, another important goal is to develop a sensitive MIR radiation detector based on END-TPA. It is well known that when the total photon energies of two photons exceed the energy band-gap of a semiconductor, the two photons will be absorbed simultaneously. More recently, it has been shown that if there is an extremely large difference between the frequencies of the two incident photons there can be a large increase in the two-photon absorption coefficient. Our goal is to demonstrate END-TPA in GaAs with the generated 17.6µm MIR radiation pulses and 920nm pulses that are generated in the continuum produced in the photonic crystal fiber. The two pulses are temporally and spatially overlapped onto a GaAs detector. This END-TPA detector could then be used to measure the pulse duration of the ultra-short MIR pulse based by cross-correlation of the MIR and 920nm pulses

D&D: Learning Human Dynamics from Dynamic Camera

3D human pose estimation from a monocular video has recently seen significant improvements. However, most state-of-the-art methods are kinematics-based, which are prone to physically implausible motions with pronounced artifacts. Current dynamics-based methods can predict physically plausible motion but are restricted to simple scenarios with static camera view. In this work, we present D&D (Learning Human Dynamics from Dynamic Camera), which leverages the laws of physics to reconstruct 3D human motion from the in-the-wild videos with a moving camera. D&D introduces inertial force control (IFC) to explain the 3D human motion in the non-inertial local frame by considering the inertial forces of the dynamic camera. To learn the ground contact with limited annotations, we develop probabilistic contact torque (PCT), which is computed by differentiable sampling from contact probabilities and used to generate motions. The contact state can be weakly supervised by encouraging the model to generate correct motions. Furthermore, we propose an attentive PD controller that adjusts target pose states using temporal information to obtain smooth and accurate pose control. Our approach is entirely neural-based and runs without offline optimization or simulation in physics engines. Experiments on large-scale 3D human motion benchmarks demonstrate the effectiveness of D&D, where we exhibit superior performance against both state-of-the-art kinematics-based and dynamics-based methods. Code is available at https://github.com/Jeffsjtu/DnDComment: ECCV 2022 (Oral

Aperture-scanning Fourier ptychography for 3D refocusing and super-resolution macroscopic imaging

We report an imaging scheme, termed aperture-scanning Fourier ptychography, for 3D refocusing and super-resolution macroscopic imaging. The reported scheme scans an aperture at the Fourier plane of an optical system and acquires the corresponding intensity images of the object. The acquired images are then synthesized in the frequency domain to recover a high-resolution complex sample wavefront; no phase information is needed in the recovery process. We demonstrate two applications of the reported scheme. In the first example, we use an aperture-scanning Fourier ptychography platform to recover the complex hologram of extended objects. The recovered hologram is then digitally propagated into different planes along the optical axis to examine the 3D structure of the object. We also demonstrate a reconstruction resolution better than the detector pixel limit (i.e., pixel super-resolution). In the second example, we develop a camera-scanning Fourier ptychography platform for super-resolution macroscopic imaging. By simply scanning the camera over different positions, we bypass the diffraction limit of the photographic lens and recover a super-resolution image of an object placed at the far field. This platform’s maximum achievable resolution is ultimately determined by the camera’s traveling range, not the aperture size of the lens. The FP scheme reported in this work may find applications in 3D object tracking, synthetic aperture imaging, remote sensing, and optical/electron/X-ray microscopy

Visualización del proceso de enseñanza-aprendizaje, apoyado de una interfaz gráfica

186 páginas. Doctorado en DiseñoEn esta tesis se presenta un conjunto de requerimientos obtenidos a partir de un análisis metodológico, con el objetivo de conformar un sistema educativo, haciendo énfasis en el diseño de una interfaz gráfica, en lo sucesivo IG que permita el proceso de enseñanza- aprendizaje de la matemática, en el dominio de las ecuaciones de primer grado con una incógnita. Para tal propósito fue necesario que se abordarán distintos enfoques metodológicos pertenecientes al campo de: 1) Los modelos para el diseño de una interfaz gráfica, 2) Los modelos instruccionales, tomando en consideración las inteligencias múltiples de Gardner, 3) Las metodologías de desarrollo de software educativ

Research on Vibration Control of Power Transmission Lines-TMDI Based on Colliding Bodies Optimization

To investigate the vibration control capability of a tuned mass damper inerter (TMDI) on a transmission line, the motion equations of the transmission line with TMDI under harmonic excitation were derived. Thus, the closed-form solutions of the displacement response spectrum were obtained by Fourier transform. Based on the colliding bodies optimization (CBO), one of the metaheuristic algorithms, the TMDI parameters, was optimized to minimize the displacement of the transmission line-TMDI system. The research results show that the response of the transmission line was reduced by at least half for different mass ratio and frequency ratio conditions, which indicates that the TMDI can effectively control the displacement response of the transmission line. In addition, the TMDI parameters were optimized by CBO, and the vibration control efficiency was significantly improved. The results of the study show that the data converge quickly with fewer iterations in collision body optimization. On the one hand, CBO avoids getting into local optimization compared to other metaheuristic algorithms. On the other hand, it is cheaper in terms of the cost of its calculations compared to the methods of mathematical derivation. It plays an active role in the optimization of complex structures. The vibration suppression performance of the TMDI after optimization reaches 56–96%

Toxicological effects and transcriptome mechanisms of rice (Oryza sativa L.) under stress of quinclorac and polystyrene nanoplastics

The absorption and accumulation of nanoplastics (NPs) by plants is currently attracting considerable attention. NPs also tend to adsorb surrounding organic pollutants, such as pesticides, which can damage plants. However, molecular mechanisms underlying the phytotoxicity of NPs are not sufficiently researched. Therefore, we analyzed the toxicological effects of 50 mg/L polystyrene NPs (PS 50 nm) and 5 mg/L the herbicide quinolinic (QNC) on rice (Oryza sativa L.) using 7-day hydroponic experiments, explaining the corresponding mechanisms by transcriptome analysis. The main conclusion is that all treatments inhibit rice growth and activate the antioxidant level. Compared with CK, the inhibition rates of PS, QNC, and PS+QNC on rice shoot length were 3.95%, 6.68%, and 11.43%, respectively. The gene ontology (GO) term photosynthesis was significantly enriched by QNC, and the combination PS+QNC significantly enriched the GO terms of amino sugar and nucleotide sugar metabolisms. The chemicals QNC and PS+QNC significantly affected the Kyoto Encyclopedia of Genes and Genomes (KEGG) of the MAPK signaling pathway, plant hormone signal transduction, and plant-pathogen interaction. Our findings provide a new understanding of the phytotoxic mechanisms and environmental impacts of the interactions between NPs and pesticides. It also provides insights into the impact of NPs and pesticides on plants in the agricultural system