Tech Science Press
Not a member yet
3972 research outputs found
Sort by
Pose Estimation of Space Targets Based on Model Matching for Large-Aperture Ground-Based Telescopes
Get PDFWith the development of adaptive optics and post restore processing techniques, large aperture ground-based telescopes can obtain high-resolution images (HRIs) of targets. The pose of the space target can be estimated from HRIs by several methods. As the target features obtained from the image are unstable, it is difficult to use existing methods for pose estimation. In this paper a method based on real-time target model matching to estimate the pose of space targets is proposed. First, the physically-constrained iterative deconvolution algorithm is used to obtain HRIs of the space target. Second, according to the 3D model, the ephemeris data, the observation time of the target, and the optical parameters of the telescope, the simulated observation image of the target in orbit is rendered by a scene simulation program. Finally, the target model searches through yaw, pitch, and roll until the correlation between the simulated observation image and the actual observation image shows an optimal match. The simulation results show that the proposed pose estimation method can converge to the local optimal value with an estimation error of about 1.6349°
Machine Learning Based Resource Allocation of Cloud Computing in Auction
Get PDFResource allocation in auctions is a challenging problem for cloud computing. However, the resource allocation problem is NP-hard and cannot be solved in polynomial time. The existing studies mainly use approximate algorithms such as PTAS or heuristic algorithms to determine a feasible solution; however, these algorithms have the disadvantages of low computational efficiency or low allocate accuracy. In this paper, we use the classification of machine learning to model and analyze the multi-dimensional cloud resource allocation problem and propose two resource allocation prediction algorithms based on linear and logistic regressions. By learning a small-scale training set, the prediction model can guarantee that the social welfare, allocation accuracy, and resource utilization in the feasible solution are very close to those of the optimal allocation solution. The experimental results show that the proposed scheme has good effect on resource allocation in cloud computing
Tunable Light Emission from P-Acetylbiphenyl-Cl-DPQ Organic Phosphor: For Blue and Near UV-OLED Applications
Get PDFA novel 2-([1, 1’-biphenyl]-4-yl)-6-chloro-4-phenylquinoline (P-Acetylbiphenyl-Cl-DPQ) phosphor was synthesized by Friedlander condensation reaction at 1400C. To check its suitability for fabricating near UV – organic light emitting diodes (UV-OLEDs) by vacuum vapor deposition, the synthesized organic phosphor is assessed by various characterization techniques such as Fourier Transform Infrared (FTIR) spectroscopy, H-NMR, C-NMR, Thermo gravimetric/ Differential Thermal Analysis (TGA/DTA), optical absorption spectra and photoluminescence (PL) spectra in solid state. The synthesized phosphor is molecularly doped in Polystyrene matrix different wt% to explore its compatibility with polymers. FTIR and NMR confirm the structural formation of the desired complex. TGA and DTA reveal appreciable thermal stability and melting point. Absorption spectra were employed to study optical transitions in the synthesized phosphor at 10-3 M concentration in various organic solvents. The energy band gap of the synthesized organic phosphor was found to be 3.37, 3.40, 3.02, and 3.03 eV in chloroform, dichloromethane, acetic acid and formic acid, respectively. PL spectra of the phosphor in solid state, various organic solvents and in polystyrene reveal emission in the range of 383-495 nm, under excitation wavelength ranging between 360-419 nm. Stokes shift of about 63-66 nm was observed. CIE coordinates reflect that the synthesized organic phosphor can be used as a tunable emissive material in the range of blue to near UV emission in the fabrication of blue and near UV -OLEDs
Absorption Less All-Optical Memory Cell Based on Active Micro Ring Optical Integrators
Get PDFThe three-level nano particles are doped in dual micro ring resonators of the proposed all-optical memory unit cell as the active gain segment in which the optical power loss is compensated due to the effect of lasing without inversion in doped quantum dots. The effect of parameters such as pumping rate and density of doped QDs are investigated. The optical integrator generates an optical step function to save input data. Also, the effect of electromagnetically induced transparency in three-level quantum dots is investigated as an on/off phase shifter for data reading at requested time. Both input data into the memory and output read pulse are return -to-zero Gaussian signals, but the output data has narrower pulse width. This is because of that the light in the integrator is mostly erased during the rising edge of the phase shift pulse. The proposed integrated memory cell can operate in high speed situations
A Coupled Friction-Poroelasticity Model of Chimneying Shows that Confined Cells Can Mechanically Migrate Without Adhesions
Get PDFCell migration is the cornerstone of many biological phenomena such as cancer metastasis, immune response or organogenesis. Adhesion-based motility is the most renown and examined motility mode, but in an adhesion-free confined environment or simply to achieve a higher migration speed, cells can adopt a very interesting bleb-based migration mode called “chimneying”. This mode rests on the sharp synchronization between the active contraction of the cells uropod and the passive friction force between the cell and the confining surface. In this paper, we propose a one dimensional poroelastic model of chimneying which considers the active strains of the cell, but, as an improvement with respect to our previous works, the synchronization between such strains and the friction forces developed by the cell and necessary to move forward is self-determined. The present work allows to deepen our knowledge on chimneying which is still poorly understood from a mechanical point of view. Furthermore, our results emphasize the key role of poroelasticity in bleb formation and give new insights on the location and the time-synchronization of the friction force. Further development of this exploratory work could provide a major tool to test hypotheses beforehand and thus focus future experiments on mechanically relevant ones
Durability of Reinforced Concrete Structures under Coupling Action of Load and Chlorine Erosion
Get PDFDiffusion behavior of chloride ion in reinforced concrete under bending moment was studied by taking the ratio of bending moment to ultimate flexural capacity as load level indicator. The function relationship between load level and chloride ion diffusion coefficient was established, based on that the limit state equation of the chloride ion critical concentration and chloride ion concentration on surface of the steel bar was established. Then by applying Monte-Carlo method the corrosion probability of reinforcement under different load levels in splash zone was calculated. Calculation results demonstrated that compared with the durability reliability index considering loading effect, the reliability index without considering loading effect could be 100% higher. In consideration of requirement for concrete durability, some revision suggestion was put forward. It was recommended that for beam members with different design life in splash zone, the corresponding minimum cover thickness should be adjusted properly as well as water-cement ratio limit
PHBV Crystallization under Injection Molding Conditions: Influence of Packing Pressure and Mold Temperature
Get PDFPoly(3-hydroxy butyrate)-co-(3-hydroxy valerate) (PHBV) is a biobased and biodegradable polyester. This semicrystalline bioplastic could be a good candidate for the replacement of some commodity plastics derived from oil. However, the control of the conditions of its processing in order to obtain optimal properties of the finished products remains a current research subject. The objective of this work is to better understand the crystallization under injection molding conditions by inline measurements during the process. We focused on the influence of two key processing parameters, namely, mold temperature and packing pressure. The modeling of inline temperature measurements allowed an inverse estimation of the thermodynamic melting temperature of PHBV and of the heat of crystallization's variations with processing parameters
The Effects of Accelerated Photooxidation on Molecular Weight and Thermal and Mechanical Properties of PHBV/Cloisite 30B Bionanocomposites
Get PDFThe effects of accelerated photooxidation on the molecular weight and thermal and mechanical properties of Cast PHBV and PHBV/Cloisite 30B (3 wt%) bionanocomposites are investigated herein. Through size exclusion chromatography (SEC) analysis, a significant decrease in both weight and number average molecular weights was observed for all irradiated samples over time, resulting from the chain scission mechanism. Differential scanning calorimetry (DSC) data indicated a decrease in degree of crystallinity and melting temperature after UV exposure, with the appearance of double melting peaks related to the changes in the crystal structure of PHBV. Thermal stability, tensile and thermo-mechanical properties were also reduced consecutively in photooxidation, being more pronounced for Cast PHBV. This study shows that the incorporation of Cloisite 30B in PHBV provides a better resistance to photooxidation in comparison with the neat polymer
Polyurethanes from Kraft Lignin without Using Isocyanates
Get PDFThe reaction of a desulphurized kraft lignin with hexamethylene diamine and dimethyl carbonate has allowed the development of isocyanate-free polyurethane resins. The present research work is based on previous studies made with hydrolyzable and condensed tannins, but takes advantage of the higher number of hydroxyl groups present in lignin and their different aliphatic and aromatic character. The obtained materials were analyzed by Fourier transform infrared (FTIR) spectroscopy, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and solid-state cross-polarization/magic angle spinning (CP MAS) 13 C nuclear magnetic resonance (NMR), which have revealed the presence of urethane functions. The interpretation of the results has shown a larger number of species than when tannins were used and has indicated the presence of two types of bonds in the new molecules formed: ionic and covalent bonds