An {\alpha}-Matte Boundary Defocus Model Based Cascaded Network for Multi-focus Image Fusion

Capturing an all-in-focus image with a single camera is difficult since the depth of field of the camera is usually limited. An alternative method to obtain the all-in-focus image is to fuse several images focusing at different depths. However, existing multi-focus image fusion methods cannot obtain clear results for areas near the focused/defocused boundary (FDB). In this paper, a novel {\alpha}-matte boundary defocus model is proposed to generate realistic training data with the defocus spread effect precisely modeled, especially for areas near the FDB. Based on this {\alpha}-matte defocus model and the generated data, a cascaded boundary aware convolutional network termed MMF-Net is proposed and trained, aiming to achieve clearer fusion results around the FDB. More specifically, the MMF-Net consists of two cascaded sub-nets for initial fusion and boundary fusion, respectively; these two sub-nets are designed to first obtain a guidance map of FDB and then refine the fusion near the FDB. Experiments demonstrate that with the help of the new {\alpha}-matte boundary defocus model, the proposed MMF-Net outperforms the state-of-the-art methods both qualitatively and quantitatively.Comment: 10 pages, 8 figures, journal Unfortunately, I cannot spell one of the authors' name coorectl

Real-MFF: A Large Realistic Multi-focus Image Dataset with Ground Truth

Multi-focus image fusion, a technique to generate an all-in-focus image from two or more partially-focused source images, can benefit many computer vision tasks. However, currently there is no large and realistic dataset to perform convincing evaluation and comparison of algorithms in multi-focus image fusion. Moreover, it is difficult to train a deep neural network for multi-focus image fusion without a suitable dataset. In this letter, we introduce a large and realistic multi-focus dataset called Real-MFF, which contains 710 pairs of source images with corresponding ground truth images. The dataset is generated by light field images, and both the source images and the ground truth images are realistic. To serve as both a well-established benchmark for existing multi-focus image fusion algorithms and an appropriate training dataset for future development of deep-learning-based methods, the dataset contains a variety of scenes, including buildings, plants, humans, shopping malls, squares and so on. We also evaluate 10 typical multi-focus algorithms on this dataset for the purpose of illustration

基于雷电物理的风机叶片动态击距与 电气几何模型

The damage of wind turbine blades suffered lightning strikes has been a key factor of the safe and reliable operation of wind farms. The electric geometrical model of wind turbine blades (EGMTB) was presented based on the traditional electric geometrical method and the physical process of lightning leader. The concept of dynamic striking distance was introduced and clarified the physical meaning of striking distance. And the calculation method of blade lightning protection system (LPS) efficiency was deduced. Finally, the effectiveness of EGMTB was validated by the long gap breakdown experiment of blades. The EGMTB was used to analyze the influence factors of blade LPS efficiency. It is indicated that the efficiency of blade LPS reduces with the decrease of lightning current and the angle between the blade and horizontal, and the efficiency of blade LPS can be improved by increasing the side lightning receptors. The EGMTB is intended to provide a theory for lightning protection design and evaluation of wind turbine blades

Experimental study on lightning attachment manner to rotation wind turbine blade

Lightning strike is one of the most serious damages to the wind turbine blade. The blade is in rotation when lightning strike happens. The influence of the rotation to the lightning attachment manner of wind turbine blade is not fully studied. Experimental work has been done in this paper. A 1:30 scale 3MW wind turbine is built. There are 3 side receptors on each blade according to the real wind turbine blade. A rod electrode is used as the high voltage electrode to simulate the downward leader. Both negative and positive 250/25000μs standard switching impulses are applied. Different blade tip linear speeds, equal to the real wind turbine, are used to study the influence of the blade rotation to attachment process. The results show that the influence of the rotation can be classified into two types, one is the impact on the location of the striking attachment point, the other is the impact on the discharge channel close to the blade. The influence depends on the polarity of the discharge. Positive discharge is more dangerous to wind turbine blade in rotation

Experimental study on interception failure of lightning protection system of wind turbine blade

Wind turbine (WT) blades are equipped with lightning protection system (LPS) consisting of receptors and down conductor in order to intercept lightning strikes. However, severe damages caused by lightning strikes still happen frequently, which costs huge losses. In this paper, experiments were conducted to study the lightning interception failure of WT blade LPS, and the results can be useful to improve the optimal design of LPS. Experiments using 5m blade specimen with tip receptor from 1.5MW wind turbine under 3m air gap are conducted to investigate the lightning interception failure of LPS in different orientations and lateral distances (LDs). Factors such as the polarity of lightning strikes, the blade orientation of wind turbine and lateral distance between wind turbine and lightning downward leader were investigated. The lateral distance between downward leader (DL) and wind turbine blade is a key factor which influences the interception efficiency. Three patterns of receptor interception failure are discovered. The protection area shows asymmetry under different lateral distance. Multi-upward leaders (UL) from WT blade have been observed in the experiment

Experimental study on lightning attachment manner to wind turbine blades with lightning protection system

Different types of lightning protection systems (LPSs) have been developed for wind turbines to protect the blades from lightning strikes. However, severe damages caused by lightning strikes still happen frequently, which creates huge costs. Experiments using a 5-m blade specimen with tip receptors from 1.5-MW wind turbine blades under 3-m air gap were conducted to investigate the lightning attachment manner to the wind turbine blade with LPS in different situations. Factors including the polarity of the lightning strikes, the orientation of the blade, and the lateral distances (LDs) between the wind turbine blade and the lightning downward leader were taken into account. It was found that the types of discharge paths under positive and negative lightning strikes are quite different, and the positive discharges are much more dangerous to wind turbine blade than the negative ones. The LD between the downward leader and the wind turbine blade is a key factor that influences the interception efficiency. Three types of receptor interception failures were discovered. Multiple upward leaders may incept from the blade body as to intercept the downward leader. However, the protection range of the tip receptor is quite limited, and the connection of the tip receptor and the blade body is the most vulnerable position hit by the lightning strikes. The results present the useful reference to the optimal design of the wind turbine blade LPS

Experimental study on interception efficiency of receptor on wind turbine blade with brine adhesion

Lightning creates a huge threat to offshore wind turbine due to its height and the marine environment. The blade surface will be polluted by brine after long operation in highsalinity and high-humidity environment. In order to study the efficiency of the receptor under the influence of brine covered on blade surface, a group controlled test is conducted in this paper. Statistical analysis is applied according to the test results. The results show that, the adhesion of brine on the blade surface reduces the interception efficiency of receptor greatly, which makes the blade exposed to a huge threat of lightning damage. Only water or salt has limited impact compared with brine. The influence of the brine area is more obvious if the area is close to the receptor. It can expand the severe area of strike and reduce the interception efficiency of the receptor. The brine area far from the receptor has a limited effect on attracting downward leader

Arylpyrrole and fipronil analogues that inhibit the motility and/or development of Haemonchus contortus in vitro

Due to widespread drug resistance in parasitic nematodes, there is a need to develop new anthelmintics. Given the cost and time involved in developing a new drug, the repurposing of known chemicals can be a promising, alternative approach. In this context, we tested a library (n = 600) of natural product-inspired pesticide analogues against exsheathed third stage-larvae (xL3s) of Haemonchus contortus (barber's pole worm) using a whole-organism, phenotypic screening technique that measures the inhibition of motility and development in treated larvae. In the primary screen, we identified 32 active analogues derived from chemical scaffolds of arylpyrrole or fipronil. The seven most promising compounds, selected based on their anthelmintic activity and/or limited cytotoxicity, are arylpyrroles that reduced the motility of fourth-stage larvae (L4s) with significant potency (IC50 values ranged from 0.04 ± 0.01 μM to 4.25 ± 0.82 μM, and selectivity indices ranged from 10.6 to 412.5). Since the parent structures of the active compounds are uncouplers of oxidative phosphorylation, we tested the effect of selected analogues on oxygen consumption in xL3s using the Seahorse XF24 flux analyser. Larvae treated with the test compounds showed a significant increase in oxygen consumption compared with the untreated control, demonstrating their uncoupling activity. Overall, the results of the present study have identified natural product-derived molecules that are worth considering for chemical optimisation as anthelmintic drug leads. Keywords: Arylpyrrole, Fipronil, Haemonchus contortus, Anthelmintic, Drug discover