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BackgroundDue to the imaging mechanism of neutron radiography and the limitation of neutron source, neutron radiography images are prone to lack of contrast, and it is a common method to improve image quality by contrast enhancement algorithm.PurposeThis study aims to solve the problems related to low contrast and loss of details in neutron imaging.MethodsAn adaptive contrast enhancement (ACE) algorithm based on the particle swarm optimization (PSO) was proposed. First of all, the gain factor coefficient was treated as a particle and initializes a particle swarm. Then, the optimal gain factor coefficient with the PSO algorithm was calculated, and the contrast of the high frequency part of neutron images was improved through implementing this optimal gain factor coefficient in ACE algorithm. Finally, several neutron images were processed by this PSO algorithm and compared with the results of traditional optimization algorithm.ResultsThe new algorithm has obvious contrast enhancement effect for different neutron images, and the parameters such as entropy value, gray average gradient value and contrast value of the optimized image are improved compared with the traditional optimization algorithm.ConclusionsThis algorithm can enhance the contrast of image stably, which has practical significance for the wide application of neutron radiography.

Storage and transportation are one of the primary restrictions on the approach involving hydrogen energy. The traditional hydrogen storage methods, including high-pressure gas cylinder and cryogenic liquid tank show unfavorable economy, thus hindering their further industrial application and development. Metal hydrides can reversibly react with hydrogen and accomplish the hydriding/dehydriding process under mild operation conditions, which feature advantages such as large hydrogen storage amount, low operation pressure and energy consumption. This process is expected to replace the conventional hydrogen storage and transportation. Meanwhile, considering the strong endothermal/exothermic effect during hydrogenation/dehydrogenation, the prompt heat removal/support inside the metal hydride reactor is a key parameter for H2 absorption/desorption rate and H2 storage efficiency. To improve the heat transfer and absorption/desorption rates of metal hydride reactor, comprehensive analysis and evaluation were conducted. Based on the heat and mass transfer intensification, a new elliptical spiral mini-tube bundle reactor (ESMBR) with high efficiency was designed and proposed; the reactor possesses numerous features, such as high heat transfer speed, compact structure, high reaction rate, and convenient operation. All the hydrogen storage reactor models were established, and both the model accuracy and effectiveness were experimentally validated. Numerical simulations of ESMBR, spiral mini-tube bundle reactor, and mini-tube bundle reactor were calculated and compared by COMSOL. ESMBR was proven to exhibit favorable heat and mass transfer performance during the H2 storage. Results of further analysis indicate that the sensitivity order of elliptical spiral structure parameters as follows: Dc > A > B > Pt > α. A multi-element valued model was used to evaluate the reactor schemes systematically, and the calculation results show the integrated superiority of ESMBR could achieve a value of 0.845. The comparison results indicate that the ESMBR presents an outstanding performance compared with other reactors and features a broad application prospect in the field of hydrogen energy.

The acoustic emission signals of fatigue crack propagation in Q345R,which is the typical representative of common steel for pressure vessels,were investigated in detail to construct a relationship between fatigue and acoustic emission. The results show that there are three distinct stages of acoustic emission during fatigue crack propagation in Q345R. Cumulative count and cumulative energy can characterize the whole fatigue crack propagation well. The transition from the 2nd stage to the 3rd stage of acoustic emission advances that of linear elastic fracture mechanics,indicating that acoustic emission is more sensitive to the unstable fracture stage of fatigue crack propagation. The relations of count rate and energy rate to fatigue crack propagation rate of Q345R are established respectively for predicting the remaining life of Q345R.

The aim of the present study was to investigate the differences of the pathological changes and cognitive function after bilateral common carotid artery occlusion (BCCAO) between Sprague-Dawley (SD) and Wistar rats. Male SD and Wistar rats were randomly divided into 2 groups, respectively: sham operated (S-sham and W-sham) and operated (S-BCCAO and W-BCCAO) groups. The survival rate and the rate of loss of pupillary light reflex (PLR) were observed on day 1, 3, 7, 14 and 28 after the operation, and the light-dark box, Y-maze and odor recognition tests were performed to detect cognitive function on day 28 after the operation. HE and Luxol fast blue staining were used to observe the pathological changes of gray matter (hippocampus), white matter (optical tract), optic nerve, and retina. The results showed that the survival rate of the W-BCCAO group was 62.5%, and PLR loss rate was 100%; whereas the survival rate of the S-BCCAO group was 100%, and PLR loss rate was 58.3%. In the W-BCCAO group, percentages of time spent and distance traveled in the light box were more than those in the W-sham group, but there was no statistical significance between the S-BCCAO and S-sham groups. In the S-BCCAO group, the percentages of time spent and distance traveled in the III arm (labyrinth arm) of the Y-maze were less than those in the S-sham group, but no statistical significance was found between the W-BCCAO group and W-sham group. In the S-BCCAO group, the discrimination ratio of the odor recognition task was less than that in the S-sham group, but no statistical significance could be seen between the W-BCCAO and W-sham groups. Ischemic injury was observed in the CA1 area of the hippocampus in the S-BCCAO group, but no readily visible damage was observed in the W-BCCAO group. Ischemic injury of the visual beam and optic nerve was observed in both the S-BCCAO and W-BCCAO groups. Compared with the corresponding sham groups, the S-BCCAO and W-BCCAO groups showed serious retinal damage with significant thinner retina. The ganglion cell layer (GCL), inner plexiform layer (IPL), and outer plexiform layer (OPL) were thinner in the S-BCCAO group, but no statistical significances were shown in the other layers. All the layers, except the outer nuclear layer (ONL), were significantly thinner in the W-BCCAO group. The results indicate that there are differences of the pathological changes in the hippocampus and visual conduction pathway after BCCAO between SD and Wistar rats, and the degree of learning and memory injury was also different, which suggests that the vascular dementia model of different rat strains should be selected according to research purpose.