2,590 research outputs found
Tuan liu re dui liu zhong su du chang jie gou han shu he liu dong xun huan de shi yan yan jiu
No full textQi, Pengfei = 湍流熱對流中速度場結構函數和流動循環的實驗研究 / 齊鵬飛.Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.Includes bibliographical references (p. 65-69).Abstracts in English and Chinese.Qi, Pengfei = Tuan liu re dui liu zhong su du chang jie gou han shu he liu dong xun huan de shi yan yan jiu / Qi Pengfei.Abstract --- p.i摘要 --- p.iiAcknowledgements --- p.iiiContents --- p.ivList of Figures --- p.viList of Tables --- p.XChapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- What is turbulence? --- p.1Chapter 1.2 --- Why study turbulence and experimentally? --- p.2Chapter 1.3 --- Turbulent Rayleigh-Benard convection --- p.4Chapter 1.4 --- Basic equations and characteristic parameters --- p.SChapter 1.4.1 --- Continuity equation --- p.5Chapter 1.4.2 --- Momentum equation (Navier-Stokes equation) --- p.5Chapter 1.4.3 --- Energy equation --- p.7Chapter 1.4.4 --- Averaged equations --- p.9Chapter 1.4.5 --- Characteristic parameters --- p.10Chapter 1.5 --- Statistical properties in small-scale turbulence --- p.13Chapter 1.5.1 --- Phenomenological description and Kolmogorov hypotheses --- p.14Chapter 1.5.2 --- Local structure of the velocity fluctuations --- p.15Chapter 1.6 --- Large-scale circulation --- p.17Chapter 1.7 --- Motivation and Organizations of this thesis --- p.19Chapter 1.7.1 --- B059 scaling --- p.19Chapter 1.7.2 --- Large-scale circulation --- p.19Chapter 1.7.3 --- Organization of the thesis --- p.20Chapter 1.8 --- Some words to my experiment and further expectation --- p.21Chapter Chapter 2 --- Experimental apparatus and techniques --- p.27Chapter 2.1 --- Rectangle cell --- p.27Chapter 2.2 --- The power supply and cooler --- p.28Chapter 2.3 --- Thermistor and multimeter --- p.29Chapter 2.4 --- Particle image velocimetry (PIV) technology --- p.30Chapter 2.4.1 --- Seeding particles --- p.31Chapter 2.4.2 --- Light source and light-sheet optics --- p.33Chapter 2.4.3 --- Imaging system --- p.34Chapter 2.4.4 --- Control system --- p.34Chapter 2.4.5 --- Analysis method --- p.35Chapter Chapter 3 --- Small-scale properties in rectangular cell --- p.37Chapter 3.1 --- Introduction --- p.37Chapter 3.2 --- Experimental condition --- p.37Chapter 3.3 --- Homogeneity --- p.39Chapter 3.4 --- Isotropy --- p.40Chapter 3.5 --- Scaling of structure function --- p.42Chapter Chapter 4 --- Large-scale circulation --- p.51Chapter 4.1 --- Introduction --- p.51Chapter 4.2 --- Experimental condition and limitation --- p.54Chapter 4.3 --- Statistical properties of large-scale circulation period --- p.56Chapter 4.4 --- Scaling of the Reynolds number --- p.59Chapter 4.5 --- Oscillation period --- p.60Chapter Chapter 5 --- Conclusion --- p.63Chapter 5.1 --- Small-scale properties in rectangular cell --- p.63Chapter 5.2 --- Large-scale circulation --- p.63Reference --- p.6
Xianggang he Beijing de bi jiao yan jiu
No full text刁鵬飛.論文(哲學博士)--香港中文大學, 2007.參考文獻(p. 174-182).Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Abstracts in Chinese and English.Lun wen (zhe xue bo shi)--Xianggang Zhong wen da xue, 2007.Can kao wen xian (p. 174-182).Diao Pengfei
Author Correction: REST regulates the cell cycle for cardiac development and regeneration
No full textThe original version of this Article contained an error in the spelling of the author Jianyun Yan, which was incorrectly given as Jiangyun Yan. This has now been corrected in both the PDF and HTML versions of the Article.</jats:p
Suppressed Drell-Yan process by an external magnetic field
No full textThe strongest electromagnetic fields in nature are created in high energy nuclear collisions and expected to change the dynamic scattering processes in the early stage. The magnetic field effect on the Drell-Yan process is investigated in this work. The single photon decay into quark pairs and lepton pairs in an external magnetic field leads to a significant Drell-Yan suppression in low and intermediate invariant mass region. The calculation up to the Landau level n−1 is complete in the energy region s<2/3n(eB), and the enlarged phase space at higher landau levels may enhance the dilepton spectrum in the high mass region
Surface-emitting lasers for communications: novel metal-cavity microlasers and high-contrast-grating tunable VCSELs
No full textA comprehensive study of the theory and experiments of surface-emitting semiconductor lasers is presented. The design of novel micro and nanolasers using metal cavities for optical confinement is discussed. Theoretical modeling of quantum-well and quantum-dot emission properties, as well as experimental characterization of their coupling with optical cavities, are presented. Lasing behavior of our designed and fabricated devices is demonstrated at room temperature under continuous-wave and pulsed electrical injection with 3-μm and 1-μm cavity diameters, respectively. This work provides the research path toward dense-integrable power-efficient on-chip light sources. Surface-emitting tunable lasers for high-speed, long-haul communication are investigated. Novel laser designs using micro-electro-mechanical system controlled high-contrast gratings as tunable mirrors are presented. Rigorous, accurate, and efficient electromagnetic models for high-contrast gratings are developed. Our model enables us to design high-contrast gratings as one-dimensional or two-dimensional metastructures integrable on surface-emitting lasers. A wide range of optical functionalities such as broadband reflection, high-Q resonance, filtering, beam-steering, focusing, beam-conversion, and generation of photon orbital angular momentum are achieved. Our optical model is integrated with our laser cavity model and the rate equation model to predict the temperature-dependent voltage tunable light output intensity and spectra. Future design and experimental strategies for heterogeneously integrated tunable surface-emitting lasers are discussed.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2017-05-01The student, Pengfei Qiao, accepted the attached license on 2015-04-13 at 17:11.The student, Pengfei Qiao, submitted this Dissertation for approval on 2015-04-13 at 17:33.This Dissertation was approved for publication on 2015-04-14 at 13:35.DSpace SAF Submission Ingestion Package generated from Vireo submission #7840 on 2015-07-22 at 14:24:22Made available in DSpace on 2015-07-22T22:45:14Z (GMT). No. of bitstreams: 2
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Single-cell transcriptomic profiling of goat milk somatic cells highlights immune heterogeneity and epithelial cell-related networks
No full textThe global goat milk market has expanded rapidly, driven by its reputed hypoallergenic properties and associated health benefits. Here we present the first single-cell RNA sequencing (scRNA-seq) atlas of somatic cells in mid-lactation Saanen goat milk, revealing cellular heterogeneity and immune-regulatory mechanisms. Analysis of 7276 high-quality cells from five biological replicates revealed seven populations: myofibroblasts, dendritic cells (DCs), epithelial cells (EPCs), monocytes, bone marrow-derived progenitor cells, neutrophils, and T cells. The proportion of EPCs varied markedly between individuals (23.18 %–94.09 %, p = 0.0295) and was positively correlated with somatic cell count (R = 0.6087, based on five biological replicates), suggesting a moderate association. Pseudotime analysis revealed two differentiation trajectories: high-epithelial samples (HPG; >80 % EPCs) were dominated by immune-cell- dominated, whereas low-epithelial samples (LPG; <60 % EPCs) primarily exhibited epithelial differentiation. Cell-cell communication analyses showed distinct signaling: SELL/CXCL-mediated immune pathways were activated in HPG, while TGF-β/SPP1 signaling—linked to cell migration and immune suppression—was upregulated in LPG. A total of 214 differentially expressed genes (DEGs) were identified. Pro-inflammatory factors, such as SAA and PAEP, were enriched in HPG, whereas anti-inflammatory markers, including SERPIN B3 and C3, were elevated in LPG. Notably, casein genes (CSN1S2, CSN2, CSN3) were markedly upregulated in immune cells of HPG (T cells, monocytes and DCs). In conclusion, this work unveils a key cellular biomarker for milk quality, which is expected to guide the dairy industry towards producing safer and hypoallergenic goat milk products
Tuning piezoelectric properties through epitaxy of La2Ti2O7 and related thin films
No full textAbstractCurrent piezoelectric sensors and actuators are limited to operating temperatures less than ~200 °C due to the low Curie temperature of the piezoelectric material. Strengthening the piezoelectric coupling of high-temperature piezoelectric materials, such as La2Ti2O7 (LTO), would allow sensors to operate across a broad temperature range. The crystalline orientation and piezoelectric coupling direction of LTO thin films can be controlled by epitaxial matching to SrTiO3(001), SrTiO3(110), and rutile TiO2(110) substrates via pulsed laser deposition. The structure and phase purity of the films are investigated by x-ray diffraction and scanning transmission electron microscopy. Piezoresponse force microscopy is used to measure the in-plane and out-of-plane piezoelectric coupling in the films. The strength of the out-of-plane piezoelectric coupling can be increased when the piezoelectric direction is rotated partially out-of-plane via epitaxy. The strongest out-of-plane coupling is observed for LTO/STO(001). Deposition on TiO2(110) results in epitaxial La2/3TiO3, an orthorhombic perovskite of interest as a microwave dielectric material and an ion conductor. La2/3TiO3 can be difficult to stabilize in bulk form, and epitaxial stabilization on TiO2(110) is a promising route to realize La2/3TiO3 for both fundamental studies and device applications. Overall, these results confirm that control of the crystalline orientation of epitaxial LTO-based materials can govern the resulting functional properties.</jats:p
Facial Expression Classification Using R-CNN Based Methods
No full textWith the rise of artificial intelligence technology and the development of human vision research, most of researchers are gradually putting more and more attention on the machine recognition of face images. In this thesis, we will study facial expression recognition based on deep learning algorithm. Facial expression is the display of one or more movements or states of facial muscles. Facial expression recognition technology is primarily used in human-computer interaction, intelligent control, security, medical, communication and other fields.
In this research, we utilize two deep learning algorithms to implement facial expression recognition system. The first recognition algorithm based on Faster R-CNN, which consists of a fully convolutional network and detector over a region of interest. The second algorithm is Mask R-CNN, which is an extension of Faster R-CNN algorithm that performs image segmentation. Facial expressions are divided into seven categories: anger, contempt, disgust, fear, happy, sadness and surprise. They have been used for object detection and recognition but have not been applied to facial expression classification before. Our experiments show that, compared with the conventional methods, these methods avoided the tedious manual feature extraction, reduced the number of parameters and significantly improved the recognition rate. Moreover, the performance of the trained model in the more realistic settings where the position and angle of the face, lighting, background, etc. are varied are reported in this work
Spatial Data Access Control in Grid Environment
No full textA spatial data access control model in grid environment was proposed base on Globus Security Infrastructure (GSI). Firstly, A spatial datasets sharing framework was built up by Monitor and Discover Service(MDS), and then a common control model was proposed to realize spatial data access control. In this model, every user was mapped to a given role, and every role had a unique digital certificate to distinguish its identification, then every role had the given permission to access the resources. Moreover, a further designed model was proposed to control the role's accessibility of rectangle in given spatial datasets. Two scenarios were put forward to control spatial data access between different organizations. The first was that all of the organizations shared the same roles, and then the organization realized self-control by enduing different roles with different rights. While the second was that every organization had its own users, roles and resource controls, and then the self-control was enhanced. The model was implemented by Globus Toolkits (GT), and experiment results illustrated that the proposed model could control the spatial data access effectively in a grid environment.Computer Science, Information SystemsEngineering, Electrical & ElectronicRemote SensingEICPCI-S(ISTP)
Spatial Data Resource Index in Grid Environment
No full textGrid is a promise technology which could easily share distributed heterogeneous computing resources. It brings together geographically and organizationally dispersed computational resources. This paper presented a framework that aggregated the spatial resources based on grid technology, OGC specification and spatial data index. First, a grid environment for sharing geospatial data resources Was setup by Globus Toolkits(GT); an effective architecture was designed for managing spatial data in a grid environment. Secondly all the geospatial resource was described by geographic markup language (GML), which could describe the metadata of heterogeneous data effectively. And with Monitor and Discovery Service (MDS), a service discovery framework was implemented, with the framework; all the grid services encapsulated with the Web Service Resource Framework (WSRF) could be easily discovered. Then with calling these services, the spatial data could be easily discovered. A spatial data index was also built up by R-tree for access of data more effectively. We implemented the spatial data discovery framework and experiments indicated that spatial data could be easily discovered in the grid environment effectively and reliably.Computer Science, Hardware & ArchitectureEngineering, Electrical & ElectronicEICPCI-S(ISTP)
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