236 research outputs found
Ji tai 23Na 87Rb fen zi de ji xing chao leng qi ti
No full textPh.D.This thesis describes the creation and collisional investigations of a high density sample of ultracold ground-state dipolar ²³Na⁸⁷Rb molecules. These molecules are produced by transferring weakly-bound Feshbach molecules to the ground state through a two-photon Raman process. To this end, an ultrastable and narrow linewidth Raman laser system is constructed by locking two diode lasers to a dual-wavelength coated high-finesse optical cavity. After identifying the two-photon pathway, a Stimulated Raman adiabatic passage with efficiency up to 93% is achieved, which allows us to produce a sample of absolute ground-state ²³Na⁸⁷Rb molecules with density as high as 6×10¹¹ cm⁻³. An effective electric dipole moment over 1 Debye, the largest ever achieved in ultracold molecules, is also demonstrated by applying a static electric field.Although the absolute ground-state ²³Na⁸⁷Rb molecules are chemically stable, an unexpected fast two-body loss is observed. Thus, collisions of the molecules prepared to different internal states, which is achieved by combining the high-resolution two-photon Raman process with extra microwave pulses, are investigated. Loss rates of the ground-state molecules with different dipolar interaction strength are also measured. These results pave the way toward the investigations of ultracold gases with strong dipolar interactions本論文介紹了高密度基態超冷極性鈉銣分子的製備以及對其碰撞性質的研究。為了把分子從弱束縛費什巴赫態轉移到基態，我們搭建了一套超穩且具備超窄線寬的激光系統。通過合適的雙光子拉曼過程，我們實現了93%的轉移效率，成功製備了密度高達6×10¹¹ cm⁻³的基態超冷鈉銣分子。通過外加靜電場，我們成功誘導基態分子達到1 Debye的等效電偶極矩，這是目前在超冷分子里實現的最大等效電偶極矩。儘管基態鈉銣分子是化學穩定的，我們依然在實驗上觀測到了分子的嚴重損耗。通過對分子內態的超精密操控，我們研究了分子在有化學反應和沒有化學反應發生情況下的損耗行為，並且觀測到了非常相似的動力學過程。此外，我們還研究了在不同偶極相互作用強度下的分子損耗，在超冷溫度下同時觀測到了s分波和d分波的貢獻。雖然這些結果還不足以確定基態分子的損耗機制，我們的成果對極性超冷氣體的研究具有重要意義。Guo, Mingyang = 基態23Na 87Rb分子的極性超冷氣體 / 郭鳴阳."December 2017."23, 87 in title are superscript.Thesis Ph.D. Chinese University of Hong Kong 2018.Includes bibliographical references (leaves 129-156).Abstracts also in Chinese.Title from PDF title page (viewed on 20, April, 2021).Guo, Mingyang = Ji tai 23Na 87Rb fen zi de ji xing chao leng qi ti / Guo Mingyang
Data from: A study on the Influence of submergence ratio on the transportation of suspended sediment in a partially vegetated channel flow
No full textRiparian or aquatic vegetation thrives with seasons. The understanding of canopies' Submergence-Ratio SR (stems' height to water depth) influence on suspended sediments' transportation is still limited. Thus, Large Eddy Simulations (LES) coupled with the Discrete Phase Method (DPM) are used to investigate the particles' 3-dimensional distribution in a partially vegetated straight channel. The spanwise distribution of particles is quantified by the Probability Density Function (PDF), showing a non-uniformity of particles in time as quantified by the PDF variance. The findings and conclusions: (Ⅰ) With SR rising, the particles' depletion effects exerted by the vegetation-side mixing layer are improved along the interface between vegetated and vegetation-side bare channel region. However, the SR has little effect on the variance of the particles' PDF in the spanwise direction when the mixing layer is fully developed. (Ⅱ) During the developing stage of the over-canopy mixing layer, submerged vegetation with higher SR gain a stronger upwards (vertical) entrainment capability. The case (SR=60%) has a higher sediment concentration than other cases in the fully developed vertical mixing layer region above canopy. (III) The vertical suspension of particles in the vegetation-side bare channel region is analysed. Particles migrating from the vegetated region are entrained into the vegetation-side bare channel region by turbulent structures. Nevertheless, the vertical concentration profile is more uniform in the vegetated region than in the vegetation-side bare channel at the same streamwise location. The cases SR=40% and 60% still have higher sediment concentrations than other cases in the vegetation-side bare channel's upper region.The corresponding author is Dr. Eldad Avital. Mingyang Wang is the first author. Funding provided by: Engineering and Physical Sciences Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000266Award Number:The datasets are produced mainly based on the numerical simulations, some exprimental data is collected from published literatures
Battery charging and discharging research based on the interactive technology of smart grid and electric vehicle
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A study of the dynamics and rheology of passive and active suspensions of particles with various geometries
No full textSuspensions of particles in fluids are everywhere in our life, such as paints, pharmacies, food, etc. Suspensions can exhibit properties that common fluids do not possess. For example, the paint needs to flow well when brushing so that it can be smeared on the wall, which is aided by the shear-thinning of the fluid. However, when brushing stops, paint needs to stay still on the wall, which is aided by the yield-stress of the paint. These types of behavior depend on the dynamics and microstructures of the suspensions. Suspensions of particles can serve as precursors of composite materials, for example, a composite can be created by curing a suspension of particles in a monomer solution. In such case, the properties of the composite can be affected by the dynamics of the fluid. Investigating the dynamics of suspensions of particles can be crucial to the manufacture of composite materials. This study covers theoretical, computational, and experimental studies of suspensions of particles in various aspects, such as suspensions of spherical and aspherical particles, suspensions with or without external fields, and suspensions in Newtonian and non-Newtonian fluids. The theoretical and computational study focuses on a fundamental investigation of the dynamics of the suspending particles. Under a magnetic field, magnetic disks can be aligned by a magnetic field. An analytic solution that describes the motion of a single magnetic disk under a rotating field is derived in this study, and it has shown good comparison with experimental data. When multiple particles are present in the fluid, the particles interact with each other hydrodynamically and magnetically if a magnetic field is applied. Under the influence of the magnetic field, the microstructures of the material can be altered. The dynamic behavior depends on hydrodynamic interactions. I discuss the hydrodynamic and magnetic interactions from a fundamental point of view, and I implement a computational method called Stokesian dynamics to simulate such systems. Furthermore, I also discuss a way of simulating aspherical suspensions that is based on the spherical suspensions. The experimental study focuses on the characterization of complex fluids by suspending microparticles as the probes that can measure the local properties of fluids, and the method is called microrheology. The complex fluids that are characterized in this study serve as an inexpensive substitute of the sputum of cystic fibrosis (CF) patients. The goal of this part of the study is to explore an efficient drug-delivery vehicle that can transport through the mucus of CF patients. The formula of the substituting fluids that are proposed by our lab has shown similar rheological properties with the sputum from CF patients in the macroscopic lengthscale. I also characterized the fluids in the microscopic lengthscale and I have seen differences between the macroscopic and microscopic properties. I deduce that the differences arise from the heterogeneity of the fluids, which cannot be well detected in the macroscopic method. Finally, I combine the knowledge that we obtain from the theoretical study with the technique that we utilize in the experimental study to obtain a proof-of-concept study. We have successfully suspended microdisks in a yield-stress fluid so that the microdisks can be aligned while constrained in the elastic cages of the fluid. The yield-stress is characterized by a microrheological technique, and we apply the scalings that we have derived previously to control the parameters to achieve the goal of aligning microdisks while suppressing the translations of microdisks
Study on key technologies of optimization of big data for thermal power plant performance
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Harbin thermal park: transforming an abandoned thermal power plant into green infrastructure
No full textMy research goal was to explore the possibilities of post industrial sites to transform them into green infrastructure by multi-scale approach, making them not only benefit the ecology system in city scale, but also urban environment in local scale, while remaining the industrial beauty of the site
TAN: A Transferable Adversarial Network for DNN-Based UAV SAR Automatic Target Recognition Models
No full textRecently, the unmanned aerial vehicle (UAV) synthetic aperture radar (SAR) has become a highly sought-after topic for its wide applications in target recognition, detection, and tracking. However, SAR automatic target recognition (ATR) models based on deep neural networks (DNN) are suffering from adversarial examples. Generally, non-cooperators rarely disclose any SAR-ATR model information, making adversarial attacks challenging. To tackle this issue, we propose a novel attack method called Transferable Adversarial Network (TAN). It can craft highly transferable adversarial examples in real time and attack SAR-ATR models without any prior knowledge, which is of great significance for real-world black-box attacks. The proposed method improves the transferability via a two-player game, in which we simultaneously train two encoder–decoder models: a generator that crafts malicious samples through a one-step forward mapping from original data, and an attenuator that weakens the effectiveness of malicious samples by capturing the most harmful deformations. Particularly, compared to traditional iterative methods, the encoder–decoder model can one-step map original samples to adversarial examples, thus enabling real-time attacks. Experimental results indicate that our approach achieves state-of-the-art transferability with acceptable adversarial perturbations and minimum time costs compared to existing attack methods, making real-time black-box attacks without any prior knowledge a reality
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