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The propeller will generate a lot of harmful vibration and noise underwater. In order to effectively solve the problem of vibration and noise, it is of great significance to accurately obtain the modal parameters of propeller for the design and optimization of the propeller structure. Since it is difficult to measure the load of propeller when it is running underwater, only operational modal analysis (OMA) method can be used to identify the operational modal parameters of propeller. This paper is aimed at solving this problem by taking the metal propeller as the research object, an open-water test platform was built, and the Fiber Bragg Grating (FBG) sensors were used to obtain the underwater strain information of the propeller. Finally, the operational modal parameters of propeller are identified by the Stochastic subspace identification (SSI) method. In addition, the modal simulation analysis of propeller was carried out by using finite element simulation software, and the experimental results were compared with the simulation results. The results show that the stochastic subspace identification method can accurately identify the operational modal parameters of propeller. • In this paper, a contact measurement method based on Fiber Bragg Grating(FBG) Sensing is used to monitor the underwater operation status of the propeller. • Using the Stochastic Subspace Identification method, after removing the harmonic modes by half-power spectral matrix, the operational modal parameters were identified more accurately. • A propeller underwater monitoring system and open-water test platform were designed based on Fiber Bragg Grating sensing network. • The comparison errors are within 15% proves that it is feasible to identify the operational modal parameters of the underwater propeller by Stochastic Subspace Identification method based on the FBG sensing network. [ABSTRACT FROM AUTHOR]

Deformation monitoring of the propeller can help understand its deformation under various operating conditions, provide guidance for the optimization and theoretical design of its structure, and realize the health monitoring of its structure. In this paper, a contact measurement method based on Fiber Bragg Grating Sensor (FBG) is used to monitor the underwater operation status of the propeller. Using the inverse finite element method, the strain information collected by FBG is converted into the deformation information of the propeller to achieve deformation monitoring during the propeller operation. Fluid-structure coupling simulation analysis of the propeller is performed on the platform of ANSYS Workbench under different operating conditions. By comparing the reconstructed and simulated displacements of propellers operating underwater with different velocity coefficients and different rotational speeds, it can be found that relative errors between the reconstructed and simulated displacements of the propeller are within 15%, proving that it is feasible to monitor the operating deformation of the underwater propeller based on the FBG sensing network. • In this paper, a contact measurement method based on Fiber Bragg Grating(FBG) Sensor is used to monitor the underwater operation status of the propeller. • Using the inverse finite element method, the strain information collected by FBG is converted into the deformation information of the propeller to achieve deformation monitoring during the propeller operation. • A propeller underwater deformation monitoring system was designed based on fiber Bragg grating sensor network. • The fluid-solid coupling simulation analysis is carried out on the platform of ANSYS Workbench. Comparison of the reconstructed and simulated displacements of the propeller reveals that the relative error is within 15%, which proves that it is feasible to monitor the operational deformation of the underwater propeller based on the FBG sensing network. [ABSTRACT FROM AUTHOR]

Real-time prediction of the deformed propeller has important implications in engineering applications. While, the traditional contact measurement method cannot satisfy the on-line measurement of propeller deformation, because the weight and arrangement of the strain gage used will make it difficult to measure propeller deformation. In this paper, the FBG sensing technology was applied to detect propeller deformation, which was constructed based on discrete input strain measures in the structure. To avoid the inaccuracy and complexity of contact measurement of propeller deformation, this paper proposed a strain-deformation reconstruction method (inverse finite element method based), where a linear discretization-inverse finite element deformation reconstruction algorithm was developed based on the unique shape and structure of the propeller at the same time. In this paper, a propeller strain-deformation reconstruction experimental system based on the FBG sensor network is constructed, according to which a single propeller blade is loaded and the deformation is reconstructed. Meanwhile, the deformation of the blade is measured with a Hexagon Three-Coordinate Measuring Arm. From the study, the error between the reconstructed deformation and the measured deformation propeller is within 7% under the concentrated load of 50N, 100N and 150N, which clearly verifies the feasibility and accuracy of the strain-deformation reconstruction of the propeller. • We application of the inverse finite element method for real-time monitoring of 3D deformations of the propeller based on FBG sensor network for the first time. • Propeller modelling and strain-deformation simulations were carried out in the software ANSYS. • The feasibility and accuracy of propeller deformation reconstruction based on the FBG sensor network were verified both theoretically and experimentally. [ABSTRACT FROM AUTHOR]

DNA damage repair is a major barrier for chemotherapy efficacy of pancreatic ductal adenocarcinoma (PDAC), including the efficacy of platinum-based and gemcitabine/nab-paclitaxel treatments. N6-methyladenosine modifications (m6A) have recently been reported to play a role in homologous recombination (HR) repair of DNA double strand breaks (DSBs); however, the mechanism of action remains unknown. Our previous work indicated that fisetin may be a promising anti-tumour agent that induces DNA damage. In this study, we reported that fisetin induced DSBs and suppressed HR repair through m6A modification in PDAC cells. The m6A writer ZC3H13 and PHF10, which is a subunit of the PBAF chromatin remodelling complex, were identified as the main molecules affected by fisetin treatment. To our knowledge, it's the first time that PHF10 was found and involved in the DNA damage response. PHF10 loss-of-function resulted in elevated recruitment of γH2AX, RAD51, and 53BP1 to DSB sites and decreased HR repair efficiency. Moreover, ZC3H13 knockdown downregulated the m6A methylation of PHF10 and decreased PHF10 translation in a YTHDF1-dependent manner. In conclusion, our study demonstrates that fisetin enhanced DSBs via ZC3Hl3-mediated m6A modification of PHF10, which may provide insight into novel therapeutic approaches for PDAC. [ABSTRACT FROM AUTHOR]

A high-efficiency flame retardant composed of phosphaphenanthrene, benzothiazole and imidazole groups (PBI) was synthesized and served as flame retardant co-curing agent to reduce the fire hazard of epoxy resin (EP). The chemical structure of PBI was characterized by Fourier transform infrared spectroscopy (FTIR), high-resolution mass spectroscopy (HR-MS), 1H and 31P nuclear magnetic resonance (NMR). The curing behavior, thermal stability and flame retardant properties of the prepared EP systems were investigated. The curing behavior study disclosed that PBI accelerated the crosslinking reaction of EP and was chemically bonded with EP matrix to obtain intrinsic flame retardant thermoset. The resulting EP thermosets showed only slight decrease in glass transition temperature (T g). The thermogravimetric analysis (TGA) results indicated both the catalytic decomposition and catalytic charring effects of PBI demonstrated by decreased thermal stability and enhanced charring capability of EP/DDS/PBI thermosets. The combustion test results showed remarkable improvement in the flame retardant properties of EP/DDS/PBI thermosets. When the phosphorus content was only 0.75 wt%, EP/DDS/PBI-0.75 thermoset achieved a limiting oxygen index (LOI) value of 34.6% and passed UL94 V-0 rating. Moreover, the peak of heat release rate (pk-HRR), average of heat release rate (av-HRR) and total heat release (THR) values were decreased by 48.7%, 31.1% and 28.3%, respectively, in comparison with those of the EP/DDS thermoset. The flame retardant effect of PBI on EP was attributed to the catalytic charring effect to form protective char layer in condensed phase and release of free radicals with quenching effect and nonflammable gases with diluting effect in gaseous phase. • A DOPO based reactive flame retardant (PBI) constructed by multiple heteroaromatic groups was successfully synthesized. • PBI accelerated the crosslinking reaction of EP. • Blowing-out effect was observed for EP/DDS/PBI thermosets. • PBI exhibited bi-phase flame retardant effect on EP. [ABSTRACT FROM AUTHOR]

l Sewer sediment microbiome is of distinct pollution source-characteristic. l Acetoclastic methanogenesis and syntrophism dominate in sanitary sewer sediment. l Hydrogenotrophic methanogenesis is prevailing in both two storm sewer sediments. l Hydrological disconnection drastically decreases CH 4 production. l Turbulent suspension results in stagnation of sediment methanogenesis. Production of methane (CH 4), an essential anthropogenic greenhouse gas, from municipal sewer sediment is a problem deserving intensive attention. Based on long-term laboratory batch tests in conjunction with 16 s rRNA gene sequencing and metagenomics, this study provides the first detailed assessment of the variable sediment CH 4 production in response to different pollution source-associated sewer sediment types and hydrological patterns, while addressing the role of the sediment microbiome. The high CH 4 -production capability of sanitary sewer sediment is shaped by enriched biologically active substrate and dominated by acetoclastic methanogenesis (genus Methanosaeta). Moreover, it involves syntrophic interactions among fermentation bacteria, hydrogen-producing acetogens and methanogens. Distinct source-associated microbial species, denitrifying bacteria and sulfate-reducing bacteria occur in storm sewer and illicit discharge-associated (IDA) storm sewer sediments. This reveals their insufficient microbial function capabilities to support efficient methanogenesis. Hydrogenotrophic methanogenesis (genus Methanobacterium) prevails in both these sediments. In this context, storm sewer sediment has an extremely low CH 4 -production capability, while IDA storm sewer sediment still shows significant carbon emission through a possibly unique mechanism. Hydrological connections promote the sewer sediment biodegradability and CH 4 -production capability. In contrast, hydrological disconnection facilitates the prevalence of acetoclastic methanogenesis, sulfate-reducing enzymes, denitrification enzymes and the sulfur-utilizing chemolithoautotrophic denitrifier, which drastically decreases CH 4 production. Turbulent suspension of sediments results in relative stagnation of methanogenesis. This work bridges the knowledge gap and will help to stimulate and guide the resolution of 'bottom-up' system-scale carbon budgets and GHG sources, as well as the target CH 4 abatement interventions. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In order to meet the requirement in the fields with high flame resistance, the flame retardancy of epoxy resin (EP) must be ameliorated. Herein, a P/N/S-based flame retardant (PAD) was synthesized and used to prepare flame retardant EP. The combustion behavior, thermal property and flame retardant mechanism of the prepared EP thermosets were investigated. PAD induced the decomposition of EP thermoset in advance. Meanwhile, PAD enhanced the flame retardance of EP thermosets and reduced the fire risk of EP matrix. For example, with only 0.5 wt% phosphorus, EP/DDS/PAD-0.5 easily passed UL-94 V-0 rating and achieved a LOI value of 33.6%, together with the declined heat release rate (HRR). Impressively, the glass transition temperature (T g) of EP/DDS/PAD thermosets dropped by only 3–13 °C, compared with that of EP/DDS. During combustion, PAD prompted the formation of an intumescent char layer in condensed phase, and exerted blowing-out effect in gaseous phase. [ABSTRACT FROM AUTHOR]

Latent curing epoxy resin (EP) system with satisfactory flame retardancy has attracted rather considerable interest both in academic and industrial communities over the years. Herein, imidazole-blocked bismaleimide compounds were synthesized through the Michael addition reaction of N,N′-bismaleimide-4,4′-diphenylmethane (BDM) with imidazole (IM), 2-methylimidazole (2MI), and 2-ethyl-4-methylimidazole (EMI), respectively, and were simultaneously used as latent curing agent and flame retardant synergist for 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) based EP (DOPO-EP). The storage stability study disclosed that imidazole-blocked bismaleimide compounds kept chemically inert towards epoxy at room temperature, resulting in long pot life over 40 days. When heated, imidazole-blocked bismaleimide compounds underwent retro-Michael addition reaction to regenerate BDM and the corresponding imidazoles. The fast curing ability was thus achieved via chain polymerization of epoxy initiated by thermally generated free imidazoles. Moreover, polybismaleimide component derived from the homopolymerization of thermally generated BDM was incorporated into the cross-linked EP network, resulted in enhanced thermal and charring performance of epoxy matrix. Compared with the contrast samples EP/2MI-BDM and DOPO-EP/2MI thermosets, DOPO-EP/2MI-BDM thermoset exhibited better flame retardancy with remarkably higher limiting oxygen index (LOI) value and UL94 rating as well as lower peak of heat release rate (pk-HRR), average of heat release rate (av-HRR) and total heat release (THR) from cone calorimeter test. The flame-retardant mechanism study revealed the synergistic flame-retardant effect of phosphaphenanthrene and bismaleimide in condensed phase. Image 1 • Imidazole-blocked bismaleimide were used as latent curing agent for DOPO-EP. • Imidazole-blocked bismaleimide underwent retro-Michael addition reaction when heated. • The epoxy systems containing imidazole-blocked bismaleimide exhibited long shelf life and fast curing ability. • DOPO-EP/2MI-BDM thermoset exhibited excellent flame retardancy. [ABSTRACT FROM AUTHOR]

Epoxy resin (EP) is inherently inflammable and most flame retardants used now unavoidably deteriorate other properties of EP. Moreover, the components of EP system tend to be formulated as one-component system for large-scale industrial production instead of being blended just before use. In order to overcome these issues, benzimidazolyl-substituted cyclotriphosphazene (BICP) was synthesized and utilized as latent flame-retardant curing agent for EP. According to the curing and rheological behavior studies, BICP maintained chemically inert towards EP at room temperature and could rapidly cure EP when heated. The combustion test results indicated the outstanding flame retardancy of EP/BICP thermosets. With 10.7 wt% addition of BICP, the limited oxygen index (LOI) of EP/BICP-12 thermoset was as high as 33.5% and UL94 V-0 rating was achieved; the peak of heat release rate (pk-HRR), average of heat release rate (av-HRR), total heat release (THR) and fire growth rate (FIGRA) of EP/BICP-12 thermoset were decreased by 69.8%, 33.2%, 34.7% and 71.8%, respectively, compared with those of the neat EP thermoset. Most attractively, other properties of the EP/BICP thermosets were not impaired despite of the enhancement of flame retardancy. Compared with the neat EP thermoset, the EP/BICP thermosets showed comparable mechanical properties and improved dielectric properties. Especially, the T g values of EP/BICP thermosets (except for EP/BICP-8 sample) were around 190 °C, 34 °C higher than that of the neat EP thermoset. All these results demonstrated that EP/BICP system with remarkable comprehensive performance has the potential to achieve wider application in key fields. [ABSTRACT FROM AUTHOR]