检索结果-南通市图书馆

Chinese Optics Letters 2013年第5期11卷 28-32页

作者： Y.K.Lam w.C.Situ p.w.m.tsang Department of Electronic Engineering City University of Hong Kong

A method for fast and low bit-rate compression of digital holograms based on a new vector quantization （VQ） method known as the skip-dimension VQ （SDVQ） is proposed. Briefly, a complex hologram is converted into a real off-axis hologram, and partitioned into a set of image vectors. The image vectors are passed into a graphic processing unit （GpU）, and compressed through SDVQ into a set of code indices considerably smaller in data size than the source hologram. Experimental evaluation reveals that our scheme is capable of compressing a digital hologram to a compression ratio of over 500 times, in approximately 20-22 ms.

关键词： GpU Fast compression of computer-generated holographic images based on a GpU-accelerated skip-dimension vector quantization method VQ

Enhancement on the generation of sampled phase-only holograms

在线全文

学校读者我要写书评

暂无评论

Chinese Optics Letters 2015年第6期13卷 27-30页

作者： p.w.m.tsang Y.T.Chow T.-C.poon Department of Electronic Engineering City University of Hong Kong Hong KongSpecial Administrative Region (SAR) Bradley Department of Electrical and Computer Engineering

past research has demonstrated that if the intensity image of an object is uniformly down-sampled and converted into a Fresnel hologram, the phase component alone will be sufficient to reconstruct the source image. However, due to down-sampling, the edge and line patterns are degraded heavily. In this Letter, we propose an enhance- ment on the parent method by incorporating an adaptive down-sampling lattice. A hologram generated with our proposed method, which is referred to as the edge-enhanced sampled phase-only hologram, preserves favorable visual quality on both the shaded regions as well as the edge patterns of the object image.

关键词： Lithography Signal sampling

Review of fast methods for point-based computer-generated holography [Invited]

在线全文

学校读者我要写书评

暂无评论

photonics Research 2018年第9期6卷 837-846页

作者： p.w.m.tsang T.-C.pOON Y.m.wU Department of Electronic Engineering City University of Hong Kong Bradley Department of Electrical and Computer Engineering Virginia Tech

Computer-generated holography(CGH) is a technique for converting a three-dimensional(3D) object scene into a two-dimensional(2D), complex-valued hologram. One of the major bottlenecks of CGH is the intensive computation that is involved in the hologram generation process. To overcome this problem, numerous research works have been conducted with the aim of reducing arithmetic operations involved in CGH. In this paper,we shall review a number of fast CGH methods that have been developed in the past decade. These methods,which are commonly referred to as point-based CGH, are applied to compute digital Fresnel holograms for an object space that is represented in a point cloud model. while each method has its own strength and weakness,trading off conflicting issues, such as computation efficiency and memory requirement, they also exhibit potential grounds of synergy. we hope that this paper will bring out the essence of each method and provide some insight on how different methods may crossover into better ones.

关键词：全息术计算机技术发展现状三维技术

Fast reconstruction of digital holograms for extended depths of field

在线全文

学校读者我要写书评

暂无评论

Chinese Optics Letters 2016年第7期14卷 34-37页

作者： p.w.m.tsang T.-C.poon T.Kim Y.S.Kim Department of Electronic Engineering City University of Hong Kong Bradley Department of Electrical and Computer Engineering Virginia Tech Dept of Optical Engineering Sejong University

past research has demonstrated that a static, three-dimensional （3D） object scene can be directly recorded as a complex digital hologram. However, numerical reconstruction of the object scene, which may comprise multiple sections located at unknown distances from the hologram, is a complicated and computation-intensive process. To the best of our knowledge, we propose, for the first time, a low complexity method that is capable of recon- structing a complex hologram, such that sections at different depths in the 3D object scene can be automatically reconstructed at the correct focal distances and merged into a single image for an extended depth of field. we demonstrate an order of magnitude increase of the depth of field for binary objects. with the use of a graphical processing unit, the reconstruction of a 512 × 512 complex hologram can be accomplished in about 100 ms, equivalent to around 10 frames per second.

关键词： Lithography

mineral-mediated stability of organic carbon in soil and relevant interaction mechanisms

在线全文

学校读者我要写书评

暂无评论

Eco-Environment & Health 2024年第1期3卷 59-76页

作者： Zibo Xu Daniel C.w.tsang Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyClear Water BayHong KongChina

Soil,the largest terrestrial carbon reservoir,is central to climate change and relevant feedback to environmental *** are the essential components that contribute to over 60%of soil carbon ***,how the interactions between minerals and organic carbon shape the carbon transformation and stability remains poorly ***,we critically review the primary interactions between organic carbon and soil minerals and the relevant mechanisms,including sorption,redox reaction,co-precipitation,dissolution,polymerization,and catalytic *** interactions,highly complex with the combination of multiple processes,greatly affect the stability of organic carbon through the following processes:(1)formation or deconstruction of the mineral–organic carbon association;(2)oxidative transformation of the organic carbon with minerals;(3)catalytic polymerization of organic carbon with minerals;and(4)varying association stability of organic carbon according to the mineral *** pieces of evidence related to the carbon turnover and stability during the interaction with soil minerals in the real eco-environment are then *** also highlight the current research gaps and outline research priorities,which may map future directions for a deeper mechanismsbased understanding of the soil carbon storage capacity considering its interactions with minerals.

关键词： Carbon stability mineral transformation Carbon sequestration Bio-geochemistry Soil carbon management Sustainable waste management

Developing a two-decadal time-record of rice field maps using Landsat-derived multi-index image collections with a random forest classifier:A Google Earth Engine based approach

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Information processing in Agriculture 2024年第2期11卷 260-275页

作者： w.Ashane m.Fernando I.p.Senanayake Department of Nano Science Technology Wayamba University of Sri LankaKuliyapitiya 60200Sri Lanka Dchoolf Engineing CllegeoEngineeringSience and EnionmentThe UniversyewcastleCallaghanW2Austraia

Historic maps showing the temporal distribution of rice fields are important for precision agriculture,irrigation optimisation,forecasting crop yields,land use management and formulating ***,mapping rice felds using traditional ground surveys is impractical when high cost,time and labour requirements are considered,and the availability of such detailed records is *** satellite remote sensing appears to be a viable solution,conventional segmentation and classification methods with spectral bands are often unable to contrast the distinct characteristics between rice fields and other vegetation *** this end,we explored a novel,Google Earth Engine(GEE)based multiindex random forest(RF)classification approach to map rice fields over two *** images from 2000 to 2020 of two Sri Lankan rice cultivation districts were extracted from GEE and a multi-index RF classification algorithm was applied to distinguish the rice *** results showed above 80%accuracy for both training and validation,when compared against high spatial resolution Google Earth *** essence,multi-index sampling and RF together synergised the compelling classifcation accuracy by effectively capturing vegetation,water(ponding)and soil characteristics unique to the rice felds using a single-click *** maps developed in this study were further compared against the mODIS land cover type product(mCD12Q1)and the corresponding superior statistics on rice fields demonstrated the robustness of the proposed *** work seeking effective index combinations is recommended,and this approach can potentially be extended to other crop analyses elsewhere.

关键词： Google Earth Engine(GEE) Image classification Random forest mapping rice fields Time series analysis Vegetation index

Integrated bound-state-in-the-continuum photon-pair source

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

photonics Research 2024年第6期12卷 1322-1327页

作者： FAN YE YUE QIN CHENFEI CUI XIANKAI SUN HON KI tsang Department of Electronic Engineering The Chinese University of Hong KongHong KongChina

Integrated photon-pair sources based on spontaneous parametric down conversion(SpDC)in novel high-χ^((2))materials are used in quantum photonic systems for quantum information processing,quantum metrology,and quantum ***,the need for extensive fabrication process development and optimization of dry-etching processes significantly impedes the rapid exploration of different material platforms for low-loss quantum photonic ***,bound states in the continuum(BICs)have emerged as a promising approach for realizing ultralow-loss integrated photonic circuits without requiring an etching *** realizations of BIC photonic circuits have,however,been limited primarily to the classical ***,we explore the BIC phenomena in the quantum regime and show that the etchless BIC platform is suitable for use in integrated entangled photon-pair sources based on the SpDC process in high-χ^((2))*** lithium niobate as an example,we demonstrate photon-pair generation at telecommunication wavelengths,attaining a maximum internal generation rate of 3.46 mHz,a coincidence-to-accidental ratio of 5773,and an experimental two‐photon interference visibility of 94%.Our results demonstrate that the BIC platform can be used for quantum photonic circuits,and this will enable the rapid exploration of different emergingχ^((2))materials for possible use in integrated quantum photonics in the future.

关键词： process quantum continuum

media coverage and price reactions to earnings news

在线全文

学校读者我要写书评

暂无评论

China Journal of Accounting Research 2024年第3期17卷 1-24页

作者： miao Yu Hangsoo Kyung Albert tsang School of Accountancy Shandong University of Finance and EconomicsChina School of Accounting and Finance Hong Kong Polytechnic UniversityChina SUSTech Business School Southern University of Science and TechnologyChina

In this study,we find that relative to firms with less media coverage,stock price sensitivity to positive(negative)earnings surprises in earnings announcements of firms with greater media coverage is stronger(weaker).This asymmetry in the effect of media coverage on stock price sensitivity to positive versus negative earnings surprises suggests that greater media coverage of earnings announcements intensifies stock price reactions to positive earnings surprises but attenuates reactions to negative earnings ***,we find that negative earnings news is less persistent for firms with greater media ***,our findings support the conjecture that greater media coverage increases managers’incentive to avoid future negative news,thereby reducing the persistence of poor financial performance and weakening price reactions to negative earnings news.

关键词： Earnings announcement Asymmetric stock market reactions media coverage Earnings persistence

A three-dimensional feature extraction-based method for coal cleat characterization using X-ray μCT and its application to a Bowen Basin coal specimen

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Rock mechanics and Geotechnical Engineering 2024年第1期16卷 153-166页

作者： Yulai Zhang matthew tsang mark Knackstedt michael Turner Shane Latham Euan macaulay Rhys pitchers ARC Training Centre for m3D Innovation Research School of PhysicsAustralian National UniversityCanberraACT2601Australia Department of materials physics Research School of PhysicsAustralian National UniversityCanberraACT2601Australia Anglo American Steelmaking Coal BrisbaneQLD4000Australia SCT Operations pty Ltd. WollongongNSW2500Australia

Cleats are the dominant micro-fracture network controlling the macro-mechanical behavior of *** understanding of the spatial characteristics of cleat networks is therefore important to the coal mining *** fracture networks(DFNs)are increasingly used in engineering analyses to spatially model fractures at various *** reliability of coal DFNs largely depends on the confidence in the input cleat *** of these parameters can be made from image-based three-dimensional(3D)characterization of coal cleats using X-ray micro-computed tomography(m CT).One key step in this process,after cleat extraction,is the separation of individual cleats,without which the cleats are a connected network and statistics for different cleat sets cannot be *** this paper,a feature extraction-based image processing method is introduced to identify and separate distinct cleat groups from 3D X-ray m CT ***(filters)representing explicit cleat features of coal are built and cleat separation is successfully achieved by convolutional operations on 3D coal *** new method is applied to a coal specimen with 80 mm in diameter and 100 mm in length acquired from an Anglo American Steelmaking Coal mine in the Bowen Basin,Queensland,*** is demonstrated that the new method produces reliable cleat separation capable of defining individual cleats and preserving 3D topology after ***-parallel fractures are also identified and separated,which has his-torically been challenging to delineate and rarely reported.A variety of cleat/fracture statistics is measured which not only can quantitatively characterize the cleat/fracture system but also can be used for DFN ***,variability and heterogeneity with respect to the core axis are *** heterogeneity is observed and suggests that the representative elementary volume(REV)of the cleat groups for engineering purposes may be a complex problem requ

关键词： Cleat separation Cleat statistics Feature extraction Discrete fracture network(DFN)modeling

Selection of digital fabrication technique in the construction industry--A multi-criteria decision-making approach

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2024年第7期18卷 977-997页

作者： m.p.SALAImANImAGUDAm J.JAYApRAKASH Department of Structural and Geotechnical Engineering School of Civil EngineeringVellore Institute of TechnologyVellore 632014India

Digital fabrication techniques,in recent decades,have provided the basis of a sustainable revolution in the construction ***,selecting the digital fabrication method in terms of manufacturability and functionality requirements is a complex *** paper presents alternatives and criteria for selection of digital fabrication techniques by adopting the multi-criteria decision-making *** alternatives considered in the study are concrete three-dimensional(3D)printing,shotcrete,smart dynamic casting,material intrusion,mesh molding,injection concrete 3D printing,and thin forming *** criteria include formwork utilization,reinforcement incorporation,geometrical complexity,material enhancement,assembly complexity,surface finish,and build *** demonstrates different multi-criteria decision-making techniques,with both subjective and objective weighting *** given ranking is based on the current condition of digital fabrication in the construction *** study reveals that in the selection of digital fabrication techniques,the criteria including reinforcement incorporation,build area,and geometrical complexity play a pivotal role,collectively accounting for nearly 70% of the overall *** the evaluated techniques,concrete 3D printing emerged as the best performer,however the shotcrete and mesh molding techniques in the second and third positions.

关键词： digital fabrication multicriteria decision-making concrete 3D printing