Shadow Hunter: Low-Illumination Object-Detection Algorithm

Recently, object detection, which is focused on images with normal illumination levels, has achieved great success. However, the accuracy of object detection is reduced in suboptimal environments due to the images plagued by noise and low contrast. For boosting the performance of object-detection tasks under low-illumination conditions, we propose three modules for improvement: (1) the low-level feature attention (LFA) module learns to focus on the regional feature information of the object in the low-illumination environment, highlighting important features and filtering noisy information; (2) the feature fusion neck (FFN) obtains enriched feature information by fusing the feature information of the feature map after backbone; (3) the context-spatial decoupling head (CSDH) enables the classification head to focus on contextual semantic information so that the localization head obtains richer spatial details. Extensive experiments show that our algorithm realizing end-to-end detection shows good performance in low-illumination images

Fretting Wear Damage Mechanism of Uranium under Various Atmosphere and Vacuum Conditions

A fretting wear experiment with uranium has been performed on a linear reciprocating tribometer with ball-on-disk contact. This study focused on the fretting behavior of the uranium under different atmospheres (Ar, Air (21% O2 + 78% N2), and O2) and vacuum conditions (1.05 and 1 × 10−4 Pa). Evolution of friction was assessed by coefficient of friction (COF) and friction-dissipated energy. The oxide of the wear surface was evaluated by Raman spectroscopy. The result shows that fretting wear behavior presents strong atmosphere and vacuum condition dependence. With increasing oxygen content, the COF decreases due to abrasive wear and formation of oxide film. The COF in the oxygen condition is at least 0.335, and it has a maximum wear volume of about 1.48 × 107 μm3. However, the COF in a high vacuum condition is maximum about 1.104, and the wear volume is 1.64 × 106 μm3. The COF in the low vacuum condition is very different: it firstly increased and then decreased rapidly to a steady value. It is caused by slight abrasive wear and the formation of tribofilm after thousands of cycles

Experimental study on shock wave control in high-enthalpy hypersonic flow by using SparkJet actuator

SparkJet (SPJ) actuator was used to control shock and shock-on-shock interaction in high-enthalpy hypersonic flow with a total temperature of 4490 K and Mach number 6.9 for the first time. Aiming at the characteristics of rarefied gas in hypersonic flight environment, the control authority of SPJ actuator was improved by air supply method. The process of SPJ interacting with high-enthalpy hypersonic crossflow near a ramp was obtained by using high-speed schlieren camera. When pressurized cavity pressure was 133 kPa, ramp distance was 22 mm and ramp angle was 50, SPJ can eliminate 68.3 % of the whole ramp shock. Results of different experiment cases showed that, within a certain range, the control effect of SPJ on ramp shock improves with the increase of pressurized cavity pressure, ramp distance and the -12rease of ramp angle. The elimination of shock by SPJ can be explained by the upward motion of the sonic line in the boundary layer due to the formation of SPJ shock, the thickening of boundary layer and the heating of local flow field. Except for the elimination of shock, the shock intersection point moves upstream and downstream corresponding to the strength changes of SPJ and SPJ shock. Accordingly, local high heat flow around the shock intersection point can be -12reased. The control effect of SPJ on shock-on-shock interaction can be improved by properly increasing discharge energy

Assessing the intestinal bacterial community of farmed Nile tilapia (Oreochromis niloticus) by high-throughput absolute abundance quantification

Intestinal microbiota studies based on high-throughput sequencing have attracted increasing attention due to its vital impact on host health. However, the taxonomical profile in relative proportion does not reflect the quantity of the intestinal bacteria and the inter-sample differences among taxa. In this study, we applied a high-throughput absolute abundance quantification method that used an internal standard strain to simultaneously obtain both the relative and absolute abundances in the intestinal bacterial community of farmed Nile tilapia (Oreochromis niloticus). The results showed that the structure, relative and absolute abundances, and function of the intestinal indigenous microbiota didn't change significantly after adding a low concentration of internal standard strain, and a comprehensive quantitative intestinal bacterial ecology was obtained. We first found that the total absolute abundance of the intestinal indigenous bacteria in farmed Nile tilapia was 2.95 x 10(8) cells g(-1), and most genera concentrations were in the range of 10(3) to 10(5) cells g(-1). The intestinal bacterial community was dominated by Cetobacterium with a concentration of 10(8) cells g(-1), followed by Plesiomonas, Romboutsia, and Escherichia-Shigella with concentrations of over 10(7) cells g(-1). The potential intestinal pathogens Aeromonas and Streptococcus reached 10(5) cells g(-1) in the tilapia intestines, while the potential probiotics such as Lactobacillus and Enterococcus with a high concentration of over 10(6) cells g(-1) were detected. Furthermore, PICRUSt analysis revealed that functional genes involved in membrane transport, carbohydrate metabolism, and amino acid metabolism were enriched in the intestinal microbiota of tilapia. This study characterized the intestinal quantitative bacterial ecology of farmed Nile tilapia, providing foundational support for an in-depth understanding of the intestinal microbiota and its interaction mechanism with the host