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Search Results: 1 - 10 of 325202 matches for " P. Li "
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Deployment Optimization Strategy for a Two-Tier Wireless Visual Sensor Network  [PDF]
Hailong Li, Vaibhav Pandit, Dharma P. Agrawal
Wireless Sensor Network (WSN) , 2012, DOI: 10.4236/wsn.2012.44013
Abstract: Wireless visual sensor network (VSN) can be said to be a special class of wireless sensor network (WSN) with smart-cameras. Due to its visual sensing capability, it has become an effective tool for applications such as large area surveillance, environmental monitoring and objects tracking. Different from a conventional WSN, VSN typically includes relatively expensive camera sensors, enhanced flash memory and a powerful CPU. While energy consumption is dominated primarily by data transmission and reception, VSN consumes extra power onimage sensing, processing and storing operations. The well-known energy-hole problem of WSNs has a drastic impact on the lifetime of VSN, because of the additional energy consumption of a VSN. Most prior research on VSN energy issues are primarily focusedon a single device or a given specific scenario. In this paper, we propose a novel optimal two-tier deployment strategy for a large scale VSN. Our two-tier VSN architecture includes tier-1 sensing network with visual sensor nodes (VNs) and tier-2 network having only relay nodes (RNs). While sensing network mainly performs image data collection, relay network only for wards image data packets to the central sink node. We use uniform random distribution of VNs to minimize the cost of VSN and RNs are deployed following two dimensional Gaussian distribution so as to avoid energy-hole problem. Algorithms are also introduced that optimizes deployment parameters and are shown to enhance the lifetime of the VSN in a cost effective manner.
The Energy-Efficient Processing of Fine Materials by the Micropyretic Synthesis Route
H. P. Li
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/727656
Abstract: Energy-efficient processing of TiB compound with nanowhiskers by micropyretic synthesis is investigated in this paper. Micropyretic synthesis not only offers shorter processing time but also excludes the requirement for high-temperature sintering and it is considered as the one of the novel energy-saving processing techniques. Experimental study and numerical simulation are both carried out to investigate the correlation of the processing parameters on the microstructures of the micropyretically synthesized products. The diffusion-controlled reaction mechanism is proposed in this study. It is noted that nanosize TiB whiskers only occurred when the combustion temperature is lower than the melting point of TiB but higher than the extinguished temperature. The results generated in the numerical calculation can be used as a helpful reference to select the proper route of processing nanosize materials. The Arrhenius-type plot of size and temperature is used to calculate the activation energy of TiB reaction. In addition to verifying the accuracy of the experimental measures, the reaction temperature for producing the micropyretically synthesized products with nanofeatures can be predicted.
Zhi Li,P. Govender
South African Journal of Industrial Engineering , 2012,
Abstract: ENGLISH ABSTRACT: This paper presents the design of an intelligent recognition and sorting system. Intelligence is included in the system by using a multilayer feed-forward artificial neural network (ANN) for image recognition. Full duplex Bluetooth communication is used between the intelligent system and a robot-control computer. Image compression and principal component analysis (PCA) reduce the dimensionality of the data, and only the salient feature vectors of an image are used for image recognition. A control signal guides a robot arm to place an object into an allocated space. The system is relatively immune to noise, and can generalise when faced with missing data. AFRIKAANSE OPSOMMING: Hierdie artikel hou die ontwerp van ’n intelligente herkenning- en sorteringsisteem voor. Intelligensie word ingebou in die sisteem deur middel van ’n kunsmatige neurale netwerk vir beeldherkenning. Kommunikasie word bewerkstellig tussen die intelligente sisteem en ’n robot-beheerde rekenaar. Beeldkompressie en hoofkomponentanalise verminder die dimensionaliteit van die data en slegs kritiese kenvektore word aangewend vir beeldherkenning. ’n Beheersein rig die robotarm om die objek op ’n aangewese plek te plaas. Die sisteem is relatief immuun teen geraas en kan veralgemeen wanneer dit gekonfronteer word deur ontbrekende data.
Mercury speciation and mobility in mine wastes from mercury mines in China
Li P.,Feng X.
E3S Web of Conferences , 2013, DOI: 10.1051/e3sconf/20130119002
Abstract: Mine wastes calcines were formed through retorting of cinnabar ores at high temperature, which are considered as significant sources of mercury (Hg) contamination to the local environment. To better understand the role of mine waste in Hg geochemical cycle in Hg mining areas, Hg speciation and mobility were evaluated in mine waste calcines and waste rocks from 9 Hg mines in China. The total mercury (THg) concentrations in the mine wastes ranged from 0.369 to 2620 mg·kg-1 and varied widely in different Hg mines. Cinnabar and Hg0 are dominant forms in the mine wastes. The calcines had significant higher Hg2+ and Hg0 concentrations than the waste rocks, which indicated the retorting process can produce large amounts of secondary by-product Hg compounds. The leaching experiment confirmed mine wastes were important Hg pollution sources to local aquatic system. The mine wastes are also significant Hg sources to the atmosphere.
Study on high temperature sintering processes of selective laser sintered Al2O3/ZrO2/TiC ceramics
Bai P.,Li Y.
Science of Sintering , 2009, DOI: 10.2298/sos0901035b
Abstract: High temperature sintering processes of selective laser sintered Al2O3/ZrO2/TiC ceramics were studied. The effects of the sintering temperature and the sintering time on the relative density, strength and fracture toughness of Al2O3/ZrO2/TiC ceramics were investigated. The results showed that the sintering temperature and sintering time had a great effect on the relative density and the mechanical properties of Al2O3/ZrO2/TiC ceramics. The mechanical strength increased from 120MPa to 360MPa and KIC increased from 3.7 J/m2 to 6.9 J/m2 when the sintering temperature increased from 1400oC to 1600oC, however, the mechanical strength decreased rapidly from 370MPa to 330MPa and KIC decreased from 6.9 J/m2 to 6.1 J/m2 when the sintering time increased from 30min to 90min. Furthermore, the addition of TiC and ZrO2 in the Al2O3 matrix significantly improved mechanical strength and fracture toughness of the Al2O3 matrix ceramics.
The Influence of Ignition Manner on Micropyretic Synthesis of High Exothermic Reaction with Ti+2B
H.P. Li
Journal of Applied Sciences , 2005,
Abstract: This study investigates the influences of the ignition power on the parameters of the unstable micropyretic synthesis, including the length of pre-heating zone, the propagating velocity and the oscillatory frequency. The results generated in this research can be aided to systematically understand the influence of ignition powers on the unstable micropyretic synthesis.
The Influence of Ignition Manner on Micropyretic Synthesis of Low Exothermic Reaction with Ni+Al
H.P. Li
Journal of Applied Sciences , 2005,
Abstract: The influence of ignition manner on micropyretic synthesis of low exothermic reaction with Ni+Al is numerically investigated in this study. The different ignition powers and ignition regions are chosen to illustrate the influences on the length of pre-heating zone and propagation velocity of the specimens. The numerical results indicate that a lower ignition power or igniting in the center region accelerates the heat loss. Thus, the length of pre-heating zone is increased and the average propagation velocity is correspondingly decreased. In the extreme case, the combustion front may not complete the propagation for the reaction with a lower pre-exponential factor. In addition, it is also shown that a higher ignition power consumes the additional ignition energy to ignite the specimens. Such an increase in the required ignition energy enhances the processing cost, but also probably results in the unstable propagation. The optimal ignition manner for micropyretic synthesis of Ni+Al reaction is generated in this research.
Imaging in Hard X-ray Astronomy
T. P. Li
Physics , 2002,
Abstract: The energy range of hard X-rays is a key waveband to the study of high energy processes in celestial objects, but still remains poorly explored. In contrast to direct imaging methods used in the low energy X-ray and high energy gamma-ray bands, currently imaging in the hard X-ray band is mainly achieved through various modulation techniques. A new inversion technique, the direct demodulation method, has been developed since early 90s. With this technique, wide field and high resolution images can be derived from scanning data of a simple collimated detector. The feasibility of this technique has been confirmed by experiment, balloon-borne observation and analyzing simulated and real astronomical data. Based the development of methodology and instrumentation, a high energy astrophysics mission -- Hard X-ray Modulation Telescope (HXMT) has been proposed and selected in China for a four-year Phase-A study. The main scientific objectives are a full-sky hard X-ray (20-200 keV) imaging survey and high signal-to-noise ratio timing studies of high energy sources.
Timescale Spectra in High Energy Astrophysics
T. P. Li
Physics , 2002,
Abstract: A technique of timescale analysis performed directly in the time domain has been developed recently. We have applied the technique to studying rapid variabilities of hard X-rays from neutron star and black hole binaries, gamma-ray bursts and terrestrial gamma-ray flashes. The results indicate that the time domain method of spectral analysis is a powerful tool in revealing the underlying physics in high-energy processes in objects.
A guided Monte Carlo method for optimization problems
S. P. Li
Physics , 2001, DOI: 10.1142/S0129183102003978
Abstract: We introduce a new Monte Carlo method by incorporating a guided distribution function to the conventional Monte Carlo method. In this way, the efficiency of Monte Carlo methods is drastically improved. To further speed up the algorithm, we include two more ingredients into the algorithm. First, we freeze the sub-patterns that have high probability of appearance during the search for optimal solution, resulting in a reduction of the phase space of the problem. Second, we perform the simulation at a temperature which is within the optimal temperature range of the optimization search in our algorithm. We use this algorithm to search for the optimal path of the traveling salesman problem and the ground state energy of the spin glass model and demonstrate that its performance is comparable with more elaborate and heuristic methods.
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