45 research outputs found
High-Resolution Remotely Sensed Small Target Detection by Imitating Fly Visual Perception Mechanism
The difficulty and limitation of small target detection methods for high-resolution remote sensing data have been a recent research hot spot. Inspired by the information capture and processing theory of fly visual system, this paper endeavors to construct a characterized model of information perception and make use of the advantages of fast and accurate small target detection under complex varied nature environment. The proposed model forms a theoretical basis of small target detection for high-resolution remote sensing data. After the comparison of prevailing simulation mechanism behind fly visual systems, we propose a fly-imitated visual system method of information processing for high-resolution remote sensing data. A small target detector and corresponding detection algorithm are designed by simulating the mechanism of information acquisition, compression, and fusion of fly visual system and the function of pool cell and the character of nonlinear self-adaption. Experiments verify the feasibility and rationality of the proposed small target detection model and fly-imitated visual perception method
Dynamic Control of Particle Separation in Deterministic Lateral Displacement Separator with Viscoelastic Fluids
We proposed an innovative method to achieve dynamic control of particle separation by employing viscoelastic fluids in deterministic lateral displacement (DLD) arrays. The effects of shear-thinning and elasticity of working fluids on the critical separation size in DLD arrays are investigated. It is observed that each effect can lead to the variation of the critical separation size by approximately 40%. Since the elasticity strength of the fluid is related to the shear rate, the dynamic control can for the first time be easily realized through tuning the flow rate in microchannels
Natural Convection of Cu-Gallium Nanofluid in Enclosures
In this work, the natural convection heat transfer of Cu-gallium nanofluid in a differentially heated enclosure is investigated. A single-phase model is employed with constant or temperature-dependent properties of the fluid. The results are shown over a wide range of Grashof numbers, volume fractions of nanoparticles, and aspect ratios. The Nusselt number is demonstrated to be sensitive to the aspect ratio. It is found that the Nusselt number is more sensitive to thermal conductivity than viscosity at a low velocity (especially for a low aspect ratio and a low Grashof number), however, it is more sensitive to the viscosity than the thermal conductivity at a high velocity (high aspect ratio and high Grashof number). In addition, the evolution of velocity vectors, isotherms, and Nusselt number for a small aspect ratio is investigated
Analysis of dynamic splitting tensile failure and energy evolution characteristics of Jinping marble
Splitting tensile failure is one of the main forms of instability failure of tunnel surrounding rock. At present, the mechanisms of rock crack propagation and energy evolution at the corresponding stages under dynamic splitting conditions have been rarely addressed. In this study, the splitting tests were carried out on Jinping marble samples using a split-Hopkinson pressure bar under different striking velocities. The dynamic damage processes of the samples were simulated with the ANSYS/LS-DYNA finite element software. From the perspectives of loboratory tests and numerical calculations, the mechanism of crack propagation and the characteristics of energy evolution during the splitting process of marble were comprehensively analyzed. The results show that the dynamic tensile strength of marble is linearly and positively related to the strain rate in the range of 5 s−1 to 35 s−1. The strain rate sensitivity of the Jinping marble is relatively low compared with the marbles of other regions. With the increase of the striking velocity, both the internal energy and kinetic energy of the system increase. At the moment of sample failure, the internal energy of the system drops to a minimum. Based on the calibrated parameters of Cowper-Symonds constitutive model, the final failure modes of the numerically simulated samples are basically consistent with the observed ones in the experiments. The research results of this study can provide guidance and reference for specific engineering applications
Research on adaptive impedance control technology of upper limb rehabilitation robot based on impedance parameter prediction
Introduction: With the aggravation of aging and the growing number of stroke patients suffering from hemiplegia in China, rehabilitation robots have become an integral part of rehabilitation training. However, traditional rehabilitation robots cannot modify the training parameters adaptively to match the upper limbs’ rehabilitation status automatically and apply them in rehabilitation training effectively, which will improve the efficacy of rehabilitation training.Methods: In this study, a two-degree-of-freedom flexible drive joint rehabilitation robot platform was built. The forgetting factor recursive least squares method (FFRLS) was utilized to estimate the impedance parameters of human upper limb end. A reward function was established to select the optimal stiffness parameters of the rehabilitation robot.Results: The results confirmed the effectiveness of the adaptive impedance control strategy. The findings of the adaptive impedance control studies showed that the adaptive impedance control had a significantly greater reward than the constant impedance control, which was in line with the simulation results of the variable impedance control. Moreover, it was observed that the levels of robot assistance could be suitably modified based on the subject’s different participation.Discussion: The results facilitated stroke patients’ upper limb rehabilitation by enabling the rehabilitation robot to adaptively change the impedance parameters according to the functional status of the affected limb. In clinic therapy, the proposed control strategy may help to adjust the reward function for different patients to improve the rehabilitation efficacy eventually
QTL-seq analysis identified the genomic regions of plant height and days to heading in high-latitude rice
Introduction: Rice (Oryza sativa L.) is one of the most extensive crops in the world. China’s Heilongjiang Province is the northernmost rice-growing region in the world. However, rice cultivars suitable for growth in low-latitude regions may not mature normally due to their distinct climate and short frost-free period. It is necessary to precisely determine the frost-free period for each region to make the best use of the rice growth stage so as to ensure the maturity and yield of different rice cultivars in Heilongjiang Province. The time span of the heading stage is a key parameter for evaluating the adaptability of a rice cultivar to a specific rice-growing region. Given the above facts, it is of high importance to study the associated genes and sites controlling days to heading (DH) and plant height (PH) of rice in Heilongjiang Province. Bulked segregant analysis (BSA) combined with high-throughput sequencing can effectively exclude interferences from background genomic differences, making it suitable for analyzing the associated sites of complex agronomic traits in early generations.Methods: In this study, an F3 segregating population was obtained by crossing two main cultivars that are grown under different temperatures and day-light conditions in Heilongjiang. Two pools of extreme phenotypes were built for the DH and PH of the population. For SNP and InDel variants obtained from whole-genome resequencing in the pools, an association analysis was performed using the Euclidean distance (ED) algorithm and the SNP/InDel index algorithm.Results: The intersection of SNP and InDel regions associated with the phenotypes was considered to obtain the final associated sites. After excluding interferences from the cloned genes on chromosomes 2 and 7, a total length of 6.34 Mb on chromosomes 1, 3, and 10 and 3.16 Mb on chromosomes 1 and 10 were left associated with PH and DH, respectively. Then, we performed a gene annotation analysis for candidate genes in the remaining regions using multiple genome annotation databases. Our research provides basic data for subsequent gene mapping and cloning.Discussion: By mining more genetic loci associated with the days to heading and plant height of rice, we may provide abundant genetic resources for refined molecular breeding in Heilongjiang Province
Lattice Boltzmann simulation of alumina-water nanofluid in a square cavity
A lattice Boltzmann model is developed by coupling the density (D2Q9) and the temperature distribution functions with 9-speed to simulate the convection heat transfer utilizing Al2O3-water nanofluids in a square cavity. This model is validated by comparing numerical simulation and experimental results over a wide range of Rayleigh numbers. Numerical results show a satisfactory agreement between them. The effects of Rayleigh number and nanoparticle volume fraction on natural convection heat transfer of nanofluid are investigated in this study. Numerical results indicate that the flow and heat transfer characteristics of Al2O3-water nanofluid in the square cavity are more sensitive to viscosity than to thermal conductivity
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京都大学0048新制・課程博士博士(工学)甲第9564号工博第2150号新制||工||1235(附属図書館)UT51-2002-G322京都大学大学院工学研究科原子核工学専攻(主査)教授 芹澤 昭示, 教授 福山 淳, 教授 小森 悟学位規則第4条第1項該当Doctor of EngineeringKyoto UniversityDA