Numerical investigation of freak wave effects on offshore structures

The freak wave is extremely dangerous to offshore structures due to its unexpected high wave height and strong nonlinearity. Although increasingly more attention is paid to the investigations of freak wave, the principle of its generation mechanism and the factors that contribute to its occurrence remain unclear. Also, few efforts were exerted to investigate the interactions between offshore structures and a freak wave such as wave run-up and slamming force. In this present work, both the two dimensional (2D) and three dimensional (3D) numerical wave tanks are established based on Navier-Stokes equations for viscous, incompressible fluid by CFD commercial software FLUENT.;At first, the regular waves are generated numerically. Two different wave generation methods, paddle wave making method and the source function wave making method, are introduced. The paddle wave-making method is a physical wave generation technology which is to imitate the wave makers in the laboratory. The source function wave-making method is discussed later and the empirical formulas of the source size and source intensity are introduced. The numerical wave elevations are compared with the linear analytical results.;Second, the freak waves are generated numerically. According to Longuet-Higgins wave model theory, the wave free surface can be represented by the linear sum of the individual wave components with different frequencies and random phases. Improving this wave model, the wave components have their phase adjusted, so that a large amount of energy is located at the focus position at a given time. Then two more efficient and realistic freak wave models are presented, combining wave models and phase modulation wave models, respectively. Finally, the numerical results of the shift of freak wave train focusing position and focusing time are analysed, and the time history of wave elevations are compared with the analytical results.;Third, a 3-D numerical wave tank is established to perform the interactions between a freak wave train and a single cylinder or a pair of two cylinders. How the focused wave parameters, including wave steepness, frequency bandwidth, focused position and the distance between the two cylinders, affect the freak wave run-up and total slamming forces on the cylinders are investigated.;Finally, the hydrodynamic behaviour of a rectangular body in roll motions under both freak wave excitation and internal flow sloshing is investigated in a CFD numerical wave tank. In this study, three different freak wave conditions are considered, and two different water levels are investigated.;The comparisons of numerical regular wave elevations and first order analytical results show that the current CFD numerical wave tank based on computational fluid dynamic commercial software FLUENT has a good capacity in sea water waves simulation. The focused wave parameters, such as frequency bandwidth and input wave steepness, have an obvious effect on the nonlinear behaviour of a focused wave group.;This nonlinear behaviour will not only downstream shift the focused position and focused time, but also change the wave elevation at the focused position largely. The increased nonlinear behaviour of a focused wave group will increase the wave run-up along a fixed vertical cylinder at the incident wave facing direction largely. The bigger nonlinear behaviour of a focused wave group can result in larger rolling motion amplitude for a floating rectangular body, however the anti-rolling behaviour is obvious for the low filling case.The freak wave is extremely dangerous to offshore structures due to its unexpected high wave height and strong nonlinearity. Although increasingly more attention is paid to the investigations of freak wave, the principle of its generation mechanism and the factors that contribute to its occurrence remain unclear. Also, few efforts were exerted to investigate the interactions between offshore structures and a freak wave such as wave run-up and slamming force. In this present work, both the two dimensional (2D) and three dimensional (3D) numerical wave tanks are established based on Navier-Stokes equations for viscous, incompressible fluid by CFD commercial software FLUENT.;At first, the regular waves are generated numerically. Two different wave generation methods, paddle wave making method and the source function wave making method, are introduced. The paddle wave-making method is a physical wave generation technology which is to imitate the wave makers in the laboratory. The source function wave-making method is discussed later and the empirical formulas of the source size and source intensity are introduced. The numerical wave elevations are compared with the linear analytical results.;Second, the freak waves are generated numerically. According to Longuet-Higgins wave model theory, the wave free surface can be represented by the linear sum of the individual wave components with different frequencies and random phases. Improving this wave model, the wave components have their phase adjusted, so that a large amount of energy is located at the focus position at a given time. Then two more efficient and realistic freak wave models are presented, combining wave models and phase modulation wave models, respectively. Finally, the numerical results of the shift of freak wave train focusing position and focusing time are analysed, and the time history of wave elevations are compared with the analytical results.;Third, a 3-D numerical wave tank is established to perform the interactions between a freak wave train and a single cylinder or a pair of two cylinders. How the focused wave parameters, including wave steepness, frequency bandwidth, focused position and the distance between the two cylinders, affect the freak wave run-up and total slamming forces on the cylinders are investigated.;Finally, the hydrodynamic behaviour of a rectangular body in roll motions under both freak wave excitation and internal flow sloshing is investigated in a CFD numerical wave tank. In this study, three different freak wave conditions are considered, and two different water levels are investigated.;The comparisons of numerical regular wave elevations and first order analytical results show that the current CFD numerical wave tank based on computational fluid dynamic commercial software FLUENT has a good capacity in sea water waves simulation. The focused wave parameters, such as frequency bandwidth and input wave steepness, have an obvious effect on the nonlinear behaviour of a focused wave group.;This nonlinear behaviour will not only downstream shift the focused position and focused time, but also change the wave elevation at the focused position largely. The increased nonlinear behaviour of a focused wave group will increase the wave run-up along a fixed vertical cylinder at the incident wave facing direction largely. The bigger nonlinear behaviour of a focused wave group can result in larger rolling motion amplitude for a floating rectangular body, however the anti-rolling behaviour is obvious for the low filling case

Phomopsis longanae Chi-Induced Change in ROS Metabolism and Its Relation to Pericarp Browning and Disease Development of Harvested Longan Fruit

Phomopsis longanae Chi is a major pathogenic fungus that infects harvested longan fruit. This study aimed to investigate the effects of P. longanae on reactive oxygen species (ROS) metabolism and its relation to the pericarp browning and disease development of harvested longan fruit during storage at 28°C and 90% relative humidity. Results showed that compared to the control longans, P. longanae-inoculated longans displayed higher indexes of pericarp browning and fruit disease, higher O2-. generation rate, higher accumulation of malondialdehyde (MDA), lower contents of glutathione (GSH) and ascorbic acid (AsA), lower 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability and reducing power in pericarp. In addition, P. longanae-infected longans exhibited higher activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) in the first 2 days of storage, and lower activities of SOD, CAT, and APX during storage day 2–5 than those in the control longans. These findings indicated that pericarp browning and disease development of P. longanae-infected longan fruit might be the result of the reducing ROS scavenging ability and the increasing O2-. generation rate, which might lead to the peroxidation of membrane lipid, the loss of compartmentalization in longan pericarp cells, and subsequently cause polyphenol oxidase (PPO) and peroxidase (POD) to contact with phenolic substrates which result in enzymatic browning of longan pericarp, as well as cause the decrease of disease resistance to P. longanae and stimulate disease development of harvested longan fruit

A Corrugated Diaphragm-Based Fabry-Perot Ultrasonic Sensor by Two-Photon 3D Printing

peer reviewedA polymer corrugated diaphragm-based fiber-optic Fabry-Perot (FP) interferometer is proposed as an ultrasonic sensor and directly fabricated on an optical fiber tip by direct laser writing via two-photon polymerization. The structure of the corrugated diaphragm is optimized, and the mechanical properties are investigated numerically. The experimental results show that the proposed device has a resonant frequency of 150 kHz and an enhanced mechanical sensitivity of 367.73nm/kPa@100 kHz, and a low noise equivalent level of 1.92 mPa/Hz1/2@100 kHz. The sensitivity is much higher that of FP devices with uniform diaphragm, demonstrating that the designed sensor is capable of detecting weak ultrasonic waves

Identification and classification of the genomes of novel microviruses in poultry slaughterhouse

Microviridae is a family of phages with circular ssDNA genomes and they are widely found in various environments and organisms. In this study, virome techniques were employed to explore potential members of Microviridae in a poultry slaughterhouse, leading to the identification of 98 novel and complete microvirus genomes. Using a similarity clustering network classification approach, these viruses were found to belong to at least 6 new subfamilies within Microviridae and 3 higher-level taxonomic units. Genome size, GC content and genome structure of these new taxa showed evident regularities, validating the rationality of our classification method. Our method can divide microviruses into about 45 additional detailed clusters, which may serve as a new standard for classifying Microviridae members. Furthermore, by addressing the scarcity of host information for microviruses, the current study significantly broadened their host range and discovered over 20 possible new hosts, including important pathogenic bacteria such as Helicobacter pylori and Vibrio cholerae, as well as different taxa demonstrated different host specificities. The findings of this study effectively expand the diversity of the Microviridae family, providing new insights for their classification and identification. Additionally, it offers a novel perspective for monitoring and controlling pathogenic microorganisms in poultry slaughterhouse environments

DeepSearch: A Simple and Effective Blackbox Attack for Deep Neural Networks

Although deep neural networks have been very successful in image-classification tasks, they are prone to adversarial attacks. To generate adversarial inputs, there has emerged a wide variety of techniques, such as black- and whitebox attacks for neural networks. In this paper, we present DeepSearch, a novel fuzzing-based, query-efficient, blackbox attack for image classifiers. Despite its simplicity, DeepSearch is shown to be more effective in finding adversarial inputs than state-of-the-art blackbox approaches. DeepSearch is additionally able to generate the most subtle adversarial inputs in comparison to these approaches

Sex-Specific and State-Dependent Neuromodulation Regulates Male and Female Locomotion and Sexual Behaviors

Males and females display dimorphic behaviors that often involve sex-specific locomotor patterns. How the sexually dimorphic locomotion is mediated is poorly understood. In this study, we identify a neuropeptide that oppositely regulates locomotion for efficient sexual behaviors in Drosophila males and females. We find that males are less active than females if isolated. However, when sexually aroused through activating homologous but sexually dimorphic pC1 neurons, males exhibit higher activity levels than females. We discover diuretic hormone 44 (DH44) that functions in pC1 neurons in a sex-specific way to inhibit male locomotion and promote female locomotion. Surprisingly, DH44 exerts opposite effects in sexually aroused flies to promote male locomotion and suppress female locomotion, which is crucial for successful male courtship and female receptivity. These findings demonstrate sexually dimorphic and state-dependent control of locomotor activity by pC1 neuronal activity and DH44 modulation

Nanoformulation of a Novel Pyrano[2,3-c] Pyrazole Heterocyclic Compound AMDPC Exhibits Anti-Cancer Activity via Blocking the Cell Cycle through a <i>P53</i>-Independent Pathway

Pyrano[2,3-c]pyrazole derivatives have been reported as exerting various biological activities. One compound with potential anti-tumor activity was screened out by MTT assay from series of dihydropyrazopyrazole derivatives we had synthesized before using a one-pot, four-component reaction, and was named as 6-amino-4-(2-hydroxyphenyl)-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (hereinafter abbreviated as AMDPC). The IC50 of AMDPC against Bcap-37 breast cancer cells was 46.52 &#956;g/mL. Then the hydrophobic AMDPC was encapsulated in PEG-PLGA block copolymers, and then self-assembled as polymeric micelle (mPEG-PLGA/AMDPC) to improve both physiochemical and release profiles. The effect of mPEG-PLGA/AMDPC on BCAP-37 cancer cells showed similar anti-tumor effects as AMDPC. Furthermore, the anti-tumor mechanism of mPEG-PLGA/AMDPC was investigated, which can probably be attributed to stimulating the expression of P21 gene and therefore protein production on BCAP-37 cells, and then blocked the cell cycle through the P53-independent pathway both in S phase and G2 phase. Thus, mPEG-PLGA/AMDPC is a promising therapeutic agent for cancer treatment, and further in vivo studies will be developed

Grouper TRAF4, a Novel, CP-Interacting Protein That Promotes Red-Spotted Grouper Nervous Necrosis Virus Replication

Tumor necrosis factor receptor-associated factors (TRAFs) play important roles in the biological processes of immune regulation, the inflammatory response, and apoptosis. TRAF4 belongs to the TRAF family and plays a major role in many biological processes. Compared with other TRAF proteins, the functions of TRAF4 in teleosts have been largely unknown. In the present study, the TRAF4 homologue (EcTRAF4) of the orange-spotted grouper was characterized. EcTRAF4 consisted of 1413 bp encoding a 471-amino-acid protein, and the predicted molecular mass was 54.27 kDa. EcTRAF4 shares 99.79% of its identity with TRAF4 of the giant grouper (E. lanceolatus). EcTRAF4 transcripts were ubiquitously and differentially expressed in all the examined tissues. EcTRAF4 expression in GS cells was significantly upregulated after stimulation with red-spotted grouper nervous necrosis virus (RGNNV). EcTRAF4 protein was distributed in the cytoplasm of GS cells. Overexpressed EcTRAF4 promoted RGNNV replication during viral infection in vitro. Yeast two-hybrid and coimmunoprecipitation assays showed that EcTRAF4 interacted with the coat protein (CP) of RGNNV. EcTRAF4 inhibited the activation of IFN3, IFN-stimulated response element (ISRE), and nuclear factor-κB (NF-κB). Overexpressed EcTRAF4 also reduced the expression of interferon (IFN)-related molecules and pro-inflammatory factors. Together, these results demonstrate that EcTRAF4 plays crucial roles in RGNNV infection

Phomopsis longanae Chi-Induced Changes in Activities of Cell Wall-Degrading Enzymes and Contents of Cell Wall Components in Pericarp of Harvested Longan Fruit and Its Relation to Disease Development

The main goal of this study was to investigate the influences of Phomopsis longanae Chi infection on activities of cell wall-degrading enzymes (CWDEs), and contents of cell wall components in pericarp of harvested “Fuyan” longan (Dimocarpus longan Lour. cv. Fuyan) fruit and its relation to disease development. The results showed that, compared with the control samples, P. longanae-inoculated longans showed higher fruit disease index, lower content of pericarp cell wall materials (CWMs), as well as lower contents of pericarp cell wall components (chelate-soluble pectin (CSP), sodium carbonate-soluble pectin, hemicelluloses, and cellulose), but higher content of pericarp water-soluble pectin (WSP). In addition, the inoculation treatment with P. longanae significantly promoted the activities of CWDEs including pectinesterase, polygalacturonase, β-galactosidase, and cellulase. The results suggested that the P. longanae stimulated-disease development of harvested longans was due to increase in activities of pericarp CWDEs, which might accelerate the disassembly of pericarp cell wall components. In turn, resulting in the degradation of pericarp cell wall, reduction of pericarp mechanical strength, and subsequently leading to the breakdown of longan pericarp tissues. Eventually resulting in development of disease development and fruit decay in harvested longans during storage at 28°C