A High-Precision Time-Frequency Entropy Based on Synchrosqueezing Generalized S-Transform Applied in Reservoir Detection

According to the fact that high frequency will be abnormally attenuated when seismic signals travel across reservoirs, a new method, which is named high-precision time-frequency entropy based on synchrosqueezing generalized S-transform, is proposed for hydrocarbon reservoir detection in this paper. First, the proposed method obtains the time-frequency spectra by synchrosqueezing generalized S-transform (SSGST), which are concentrated around the real instantaneous frequency of the signals. Then, considering the characteristics and effects of noises, we give a frequency constraint condition to calculate the entropy based on time-frequency spectra. The synthetic example verifies that the entropy will be abnormally high when seismic signals have an abnormal attenuation. Besides, comparing with the GST time-frequency entropy and the original SSGST time-frequency entropy in field data, the results of the proposed method show higher precision. Moreover, the proposed method can not only accurately detect and locate hydrocarbon reservoirs, but also effectively suppress the impact of random noises

Wettability Improvement in Oil–Water Separation by Nano-Pillar ZnO Texturing

The nanostructure-based surface texturing can be used to improve the materials wettability. Regarding oil–water separation, designing a surface with special wettability is as an important approach to improve the separation efficiency. Herein, a ZnO nanostructure was prepared by a two-step process for sol–gel process and crystal growth from the liquid phase to achieve both a superhydrophobicity in oil and a superoleophobic property in water. It is found that the filter material with nanostructures presented an excellent wettability. ZnO-coated stainless-steel metal fiber felt had a static underwater oil contact angle of 151.4° ± 0.8° and an underoil water contact angle of 152.7° ± 0.6°. Furthermore, to achieve water/oil separation, the emulsified impurities in both water-in-oil and oil-in-water emulsion were effectively intercepted. Our filter materials with a small pore (~5 μm diameter) could separate diverse water-in-oil and oil-in-water emulsions with a high efficiency (>98%). Finally, the efficacy of filtering quantity on separation performance was also investigated. Our preliminary results showed that the filtration flux decreased with the collection of emulsified impurities. However, the filtration flux could restore after cleaning and drying, suggesting the recyclable nature of our method. Our nanostructured filter material is a promising candidate for both water-in-oil and oil-in-water separation in industry

Nanostructure-Based Oil–Water Separation: Mechanism and Status

Flexible and effective methods for oil–water separation are crucial for reducing pollutant emissions and safeguarding water and fuel resources. In recent years, there has been growing interest in fundamental research and engineering applications related to water and fuel purification, especially oil–water separation. To date, filter materials with special wetting characteristics have been widely used in oil–water separation. Nanostructured materials are one of the most attractive candidates for next-generation oil–water separation. This review systematically summarizes the mechanisms and current status of oil–water separation using nanostructured materials. Basically, this can be achieved by using nanostructured materials with specific wettability and nanostructures. Here, we provide a detailed discussion of two general approaches and their filtration mechanisms: (1) the selective filtration technique, based on specific surface wettability, which allows only oil or water to penetrate while blocking impurities; (2) the absorption technique, employing porous sponges, fibers, or aerogels, which selectively absorbs impure oil or water droplets. Furthermore, the main failure modes are discussed in this review. The purposes of this article are: (1) to summarize the methods of oil–water separation by nanotechnology; (2) to raise the level of environmental protection consciousness of water pollution by using nanotechnology; (3) to tease out the features of different approaches and provide a pivotal theoretical basis to optimize the performance of filtering materials. Several approaches for oil and water separation are compared. Furthermore, the principle and application scope of each method are introduced

Semantic segmentation for plastic-covered greenhouses and plastic-mulched farmlands from VHR imagery

ABSTRACTDue to their important role in maintaining temperature and soil moisture, agricultural plastic covers have been widely utilized around the globe for improving crop-growing conditions, which include both plastic-covered greenhouses (PCGs) and plastic-mulched farmlands (PMFs). However, it is a challenging and long-neglected issue to separate PCGs from PMFs due to their spectral similarity. The objective of this study is to propose a deep semantic segmentation model for accurate PCG and PMF mapping based on very high-resolution satellite images and to improve the model’s spatial generalization capability using a transfer learning strategy. Specifically, the proposed semantic segmentation model has an encoder-decoder structure, where the encoder is composed of a new convolutional neural network for discriminative spatial feature learning, while the decoder utilizes a multi-task strategy to improve the predictions on the boundaries. Meanwhile, a transfer learning framework is adopted to increase mapping performance and generalization ability under limited samples. Experimental results in several typical regions across the Eurasian continent show that the proposed model could separate PCGs from PMFs accurately with a mean overall accuracy of 94.49% and an average mIoU of 0.8377. Ablation studies verify the role of encoder-decoder and transfer learning strategy in improving classification performance

Overview of pulsed power researches at CAEP

Pulsed power researches for military and civil applications have been conducted at China Academy of Engineering Physics (CAEP) for more than fifty years. The pulsed power research activities include development of pulsed power components such as different kinds of high voltage switches, series of pulsed power sources and pulsed X-ray machines, high current accelerators for Z-pinch and flash X-ray radiography as well as medical application, electro-magnetic launch and so on. The most recent progress of pulsed power researches at CAEP will be presented