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•Increasing global offshore pollution as a worldwide problem.•Coastal geological disasters due to global offshore pollution.•Complex offshore sedimentary dynamics through long-term ...accumulating pollutants.•The stable succession and development trend of marine ecosystems was significantly interrupted.
Populations and metropolitan centers are accumulated in coastal areas around the world. In view of the fact that they are geographically adjacent to coasts and intense anthropogenic activities, increasing global offshore pollution has been an important worldwide concern over the past several decades and has become a very serious problem that needs to be addressed urgently. Due to offshore pollution, various geological disasters occur in high frequency, including intensified erosion and salinization of coastal soils, frequent geological collapses and landslides and increasing seismic activities. Moreover, offshore pollution shows increasingly serious impacts on the topography and geomorphology of offshore and coastal areas, including coastal degradation, retreating coastlines and estuary delta erosion. Offshore sedimentation processes are strongly influenced by the pH changes of terrestrial discharges, and sedimentary dynamics have become extremely acute and complex due to offshore pollution. The seabed topography and hydrodynamic environment determine the fate and transport of pollutants entering offshore regions. Coastal estuaries, port basins and lagoons that have relatively moderate ocean currents and winds are more likely to accumulate pollutants. Offshore regions and undersea canyons can be used as conduits for transporting pollutants from the continent to the seabed. It is particularly noteworthy that the spatial/temporal distribution of species, community structures, and ecological functions in offshore areas have undergone unprecedented changes in recent decades. Due to increasing offshore pollution, the stable succession and development trend of marine ecosystems has been broken. It is thus important to identify and regulate the quantity, composition and transportation of pollutants in offshore regions and their behavior in marine ecosystems. In particular, crucial actions for stabilizing marine ecosystems, including increasing species and biodiversity, should be implemented to enhance their anti-interference capabilities. This review provides an overview of the current situation of offshore pollution, as well as major trends of pollutant fate and transportation from continent to marine ecosystems, transformation of pollutants in sediments, and their bioaccumulation and diffusion. This study retrospectively reviews the long-term geological evolution of offshore pollution from the perspective of marine geology, and analyses their long-term potential impacts on marine ecosystems. Due to ecological risks associated with pollutants released from offshore sediments, more research on the influence of global offshore pollution based on marine geology is undoubtedly needed.
•High intensity ultrasound propagation generates high order harmonics.•NCG expansion and compression spread regularly and symmetrically beneath sonotrode.•Gaseous cavitation distributes ...asymmetrically beneath sonotrode while symmetrically far away.•Cavitation zones grow and coalescence beneath sonotrode and break away periodically.
In a sono-reactor, complex ultrasound pressure wave signal can be detected, containing multiple information related to acoustic cavitation. In this present study, acoustic cavitation in a cylinder is investigated numerically. Via Fast Fourier Transfer (FFT), the sound pressure signals from sonotrode emitting surface are separated into harmonics, sub/ultra-harmonics and cavitation white noise: (1) the appearance of harmonics proved the non-linear propagation of ultrasound, (2) at the vibratory amplitude from 5∼20μm, only harmonics exists in the frequency spectra, corresponding to expansion and compression of non-condensable gas (NCG), (3) at the vibratory amplitude range of 30∼50μm, the occurrence of sub/ultra-harmonics demonstrated gaseous cavitation occurred, and (4) at the vibratory amplitude higher than 55μm, cavitation white noise arose, pointing out the initiation of vaporous cavitation. Based on the combination of frequency spectra and cavitation zones distribution, the acoustic cavitation state in water liquid is determined.
With the rapid development of cloud computing, there are more and more large-scale data centers, which makes the energy management of data centers more complex. In order to achieve better ...energy-saving effect, it is necessary to solve the problems of concurrent management and interdependence of IT, refrigeration, storage, and network equipment. Reinforcement learning learns by interacting with the environment, which is a good way to realize the independent management of the data center. In this paper, a overall energy consumption method for data center based on deep reinforcement learning is proposed to achieve collaborative energy saving of data center task scheduling and refrigeration equipment. A new multi-agent architecture is proposed to separate the training process from the execution process, simplify the interaction process during system operation and improve the operation effect. In the deep learning stage, a hybrid deep Q network algorithm is proposed to optimize the joint action value function of the data center and obtain the optimal strategy. Experiments show that compared with other reinforcement learning methods, our method can not only reduce the energy consumption of the data center, but also reduce the frequency of hot spots.
•The performance of plain, serrated and perforated fins was research experimentally.•j/f, j/f1/2 and j/f1/3 are used as the performance evaluation criteria.•The effects of heating condition and ...Prandtl number on heat transfer were studied.•A modified Colburn factor j was proposed based on the Prandtl number effects.
An experimental investigation is performed using liquid R113 to study the thermohydraulic characteristics of plate-fin heat exchanger with plain, serrated and perforated fins. Meanwhile, three performance evaluation criteria j/f, j/f1/2 and j/f1/3 are used to qualitative compare their comprehensive performance. Further, to study the effects of heating condition and Prandtl number on heat transfer, a numerical model of serrated fins is carried out. The fin channels with a uniform heat flux at bottom end or at both bottom and upper ends are studied as two types of heating conditions, namely, single-fold and two-fold modes. Besides, using air (Pr = 0.744), R113 (Pr = 9.02) and ethylene glycol (Pr = 51.65) aqueous solution as working media, the Prandtl number effect is discussed. The results reveal that the comprehensive performance of serrated fins is the best. Colburn factor j of single-fold mode is lower than that of two-fold mode. The Colburn factor j decreases as the Prandtl number increases in laminar flow and it is independent of Prandtl number in turbulent flow. A modified Colburn factor j based on the Manglik & Bergles correlation is proposed as functions of (Pr/Prair)−0.04827 in laminar flow. The conclusions provide the guidance on the design of plate fin heat exchanger.
Sphagnum acid, a major phenolic metabolite of Sphagnum mosses, is considered to play a key role in the remarkable accumulation of organic matter in Sphagnum-dominated wetlands. However, while ...previous studies have mainly focused on the antimicrobial property of Sphagnum metabolites, the effects of sphagnum acid on other soil biogeochemical processes related to soil organic carbon (SOC) stabilization are poorly investigated. Here we employ a series of incubation experiments involving sphagnum acid amendment into natural wetland soils and artificial reaction systems to comprehensively evaluate potential pathways driving SOC stabilization by sphagnum acid. We show that sphagnum acid greatly enhances the reductive dissolution of ferric iron Fe(III) (hydr)oxides in both wetland soils and synthetic Fe(III)-organic matter complexes, induces the formation of amorphous and poorly-crystalline Fe(III) and increases Fe-bound organic carbon. Furthermore, sphagnum acid quenches hydroxyl radicals produced by Fenton reactions during redox oscillations and indirectly suppresses the activity of phenol oxidase and β-glucosidase by inhibiting microbial activity, acidification and increasing enzyme sorption to newly formed Fe(III). Hence, sphagnum acid exerts “triple locks” on SOC through (i) Fe protection of organic matter, (ii) radical quenching, and (iii) microbial suppression. These important but under-investigated pathways are all closely related to Fe transformation, highlighting the key role of Sphagnum metabolite–Fe–organic matter interactions in regulating wetland soil carbon sinks. Changing distribution of Sphagnum under climate change and human activity will have cascading effects on soil Fe species, microbial activity and SOC stabilization, which warrants further investigation in the attempt to protect and increase wetland soil carbon stocks.
•Heat transfer, flow resistance and stress distribution of serrated fin are comprehensively studied.•The region of higher stress distribution is located.•The effects of geometric parameters on fin ...surface performance are studied.•Improved structures of serrated fin are proposed.
The comprehensive performance of serrated fin in plate-fin heat exchangers (PFHEs) is numerically studied based on fluid structure interaction (FSI) analysis in this paper. Based on Full 2nd-Order Polynomial response surface (RS) and analysis of variance (ANOVA), the effects and second order interaction effects of the fin height, fin space, fin thickness and fin interrupted length on heat transfer, flow resistance and stress are quantitatively and thoroughly assessed. The results show that the heat transfer is the most sensitive to fin interrupted length, and the flow resistance and the maximum stress are the most sensitive to fin thickness. The interaction effect of the fin space and fin interrupted length is the strongest when the j factor is set as objective function, while the interaction effect of the fin space and fin thickness is the strongest when the f factor or maximum stress is set as objective function. Based on Full 2nd-Order Polynomial RS, Multi-Objective Genetic Algorithm (MOGA) is applied to optimize the fin structure comprehensively, with enhancing heat transfer, decreasing pressure drop and stress set as objectives. To demonstrate the effectiveness of optimized structures, a comprasion between the original design and optimized structures is performed. The results show that the JF factor of optimized structures 2 and 3 increases by 23.0% and 19.7% respectively, and the maximum stress decreases by 5.8% and 15.2% respectively. The MOGA offers theorectical guidance for optimization design of PFHE.
In order to improve the microwave absorption performance of absorbing materials, the composite foam absorbing materials with different multi-walled carbon nanotube (MWCNT) contents were prepared ...using polyurethane foam as the substrate and MWCNTs and flaked carbonyl iron powder as absorbers. The electromagnetic properties of the materials were characterized and analyzed. Then, CST electromagnetic simulation software was used to simulate the electromagnetic shielding effect of absorbing materials on mechatronics products under a strong electromagnetic irradiation environment, and, finally, it was verified by irradiation experiment. The results show that the materials have good microwave absorption properties, in which the composites containing 1.5 wt.% MWCNTs exhibit good microwave absorption properties. The minimum reflectivity reaches −29 dB when the thickness is 3 mm and −15.6 dB when the thickness is 1.5 mm, with a bandwidth of 5.7 GHz for reflectivity less than −10 dB. The good microwave absorption performance of the material is due to the synergistic effect of MWCNTs particles and good impedance matching. The simulation and experimental results show that the mechatronics product with absorbing materials can protect against strong electromagnetic interference and ensure the normal operation of the mechatronics product circuits.
Medical studies have shown that the condition of human retinal vessels may reveal the physiological structure of the relationship between age-related macular degeneration, glaucoma, atherosclerosis, ...cataracts, diabetic retinopathy, and other ophthalmic diseases and systemic diseases, and their abnormal changes often serve as a diagnostic basis for the severity of the condition. In this paper, we design and implement a deep learning-based algorithm for automatic segmentation of retinal vessel (CSP_UNet). It mainly adopts a U-shaped structure composed of an encoder and a decoder and utilizes a cross-stage local connectivity mechanism, attention mechanism, and multi-scale fusion, which can obtain better segmentation results with limited data set capacity. The experimental results show that compared with several existing classical algorithms, the proposed algorithm has the highest blood vessel intersection ratio on the dataset composed of four retinal fundus images, reaching 0.6674. Then, based on the CSP_UNet and introducing hard parameter sharing in multi-task learning, we innovatively propose a combined diagnosis algorithm vessel segmentation and diabetic retinopathy for retinal images (MTNet). The experiments show that the diagnostic accuracy of the MTNet algorithm is higher than that of the single task, with 0.4% higher vessel segmentation IoU and 5.2% higher diagnostic accuracy of diabetic retinopathy classification.
Ovarian cancer (OC), an important cause of cancer-related death in women worldwide, is one of the most malignant cancers and is characterized by a poor prognosis. RNA-binding proteins (RBPs), a class ...of endogenous proteins that can bind to mRNAs and modify (or even determine) the amount of protein they can generate, have attracted great attention in the context of various diseases, especially cancers. Compelling studies have suggested that RBPs are aberrantly expressed in different cancer tissues and cell types, including OC tissues and cells. More specifically, RBPs can regulate proliferation, apoptosis, invasion, metastasis, tumorigenesis and chemosensitivity and serve as potential therapeutic targets in OC. Herein, we summarize what is currently known about the biogenesis, molecular functions and potential roles of human RBPs in OC and their prospects for application in the clinical treatment of OC.
•Long-term drainage induced divergent changes of SOC contents in fen and bog.•Both plant- and microbial-dominated soil fractions increased in drained fen.•Microbial sugars increased at the expense of ...plant sugars in drained bog.•Drainage enhanced soil “microbial carbon pump” both in fen and bog.
Drainage-induced changes in wetland soil organic carbon (SOC) composition and origin are poorly investigated compared to SOC stocks. Here, using soil fractionation and neutral sugars, we find that long-term drainage increased both plant- and microbial-dominated (i.e., light and mineral-associated, respectively) fractions in a fen while microbial residues increased at the expense of plant residues in a drained bog, accompanied by divergent changes of SOC contents. These findings highlight stimulated soil “microbial carbon pump” in drained wetlands, whose efficiency deserves further investigation related to wetland SOC persistence.
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