3,532 research outputs found

    Book Review: Angkor the Magnificent: Wonder City of Ancient Cambodia by Helen Churchill Candee

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    Mid-infrared photodetectors operating over an extended wavelength range up to 90 K

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    We report a wavelength threshold extension, from the designed value of 3.1 to 8.9 μm, in a -type heterostructure photodetector. This is associated with the use of a graded barrier and barrier offset, and arises from hole–hole interactions in the detector absorber. Experiments show that using long-pass filters to tune the energies of incident photons gives rise to changes in the intensity of the response. This demonstrates an alternative approach to achieving tuning of the photodetector response without the need to adjust the characteristic energy that is determined by the band structure

    Semantic analysis of field sports video using a petri-net of audio-visual concepts

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    The most common approach to automatic summarisation and highlight detection in sports video is to train an automatic classifier to detect semantic highlights based on occurrences of low-level features such as action replays, excited commentators or changes in a scoreboard. We propose an alternative approach based on the detection of perception concepts (PCs) and the construction of Petri-Nets which can be used for both semantic description and event detection within sports videos. Low-level algorithms for the detection of perception concepts using visual, aural and motion characteristics are proposed, and a series of Petri-Nets composed of perception concepts is formally defined to describe video content. We call this a Perception Concept Network-Petri Net (PCN-PN) model. Using PCN-PNs, personalized high-level semantic descriptions of video highlights can be facilitated and queries on high-level semantics can be achieved. A particular strength of this framework is that we can easily build semantic detectors based on PCN-PNs to search within sports videos and locate interesting events. Experimental results based on recorded sports video data across three types of sports games (soccer, basketball and rugby), and each from multiple broadcasters, are used to illustrate the potential of this framework

    Heritage Language Maintenance and Use among 1.5 Generation Khmer College Students

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    Most studies of heritage language maintenance have reported a steep attrition in heritage language use among the 1.5 and 2nd generation children of immigrants, in particular among East Asian groups. However, not much is known about the role of heritage languages and the patterns of language maintenance within refugee communities. This study focuses on heritage language use and maintenance among 1.5 generation Khmer college students. The findings show that Khmer students report a high frequency of heritage language use within the home with their parents as well as outside of the home with their co-ethnic peers. The data reveal that oral proficiency in Khmer is significantly more developed than literacy skills and is a necessity for bridging communication with parents and participating in co-ethnic peer social networks. The results of the study also indicate that these students development of English oral and literacy skills were significantly higher than their heritage language skills suggesting a similar trajectory of language loss similar to other immigrant groups, but perhaps at a slower rate

    Collision Avoidance Method for Self-Organizing Unmanned Aerial Vehicle Flights

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    This work was supported in part by the National Natural Science Foundation of China, China, under Grant 71601181, in part by the Young Talents Lifting Project, China, under Grant 17JCJQQT048, in part by the Huxiang Young Talents, China, under Grant 2018RS3079, and in part by the Complex Situational Cognitive Technology under Grant 315050202.Autonomous unmanned aerial vehicle (UAV) swarm flights have been investigated widely. In the presence of a high airspace density and increasingly complex flight conditions, collision avoidance between UAV swarms is very important; however, this problem has not been fully addressed, particularly among self-organizing flight clusters. In this paper, we developed a method for avoiding collisions between different types of self-organized UAV clusters in various flight situations. The Reynolds rules were applied to self-organized flights of UAVs and a parameter optimization framework was used to optimize their organization, before developing a collision avoidance solution for UAV swarms. The proposed method can self-organize the flight of each UAV swarm during the overall process and the UAV swarm can continue to fly according to the self-organizing rules in the collision avoidance process. The UAVs in the airspace all make decisions according to their individual type. The UAVs in different UAV swarms can merge in the same space while avoiding collisions, where the UAV's self-organized flight process and collision avoidance process are very closely linked, and the trajectory is smooth to satisfy the actual operational needs. The numerical and experimental tests were conducted to demonstrate the effectiveness of the proposed algorithm. The results confirmed the effectiveness of this approach where self-organized flight cluster collision avoidance was successfully achieved by the UAV swarms

    Discharge coefficient of high viscosity liquids through nozzles

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    Experimental investigation on discharge coefficient, Cd, for high viscosity fluid through nozzles was carried out. The viscosity of the fluid used for the test ranged from 350 to 1500 mPa s. The length-to-diameter ratio of the nozzle, l/d and the ratio of nozzle diameter to pipe diameter ratios β were used to investigate the influence of geometry on Cd. Results show a significant dependence of Cd on Re, l/d and β ratio. An empirical correlation on the discharge coefficient was developed based on the data from this study which was also compared with data from other published studies. This correlation, with an R-squared value of 0.9541, was valid for nozzle sizes 10–20 mm and for Re between 1 and 200. Cd values obtained from experimental data, and those from the empirical correlation were compared, and a mean standard deviation of 0.0231 was obtained

    Comparison of chemical profiles and effectiveness between Erxian decoction and mixtures of decoctions of its individual herbs : a novel approach for identification of the standard chemicals

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    Acknowledgements This study was partially supported by grants from the Seed Funding Programme for Basic Research (Project Number 201211159146 and 201411159213), the University of Hong Kong. We thank Mr Keith Wong and Ms Cindy Lee for their technical assistances.Peer reviewedPublisher PD
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