Cavitation noise around propellers has many adverse effects.It is still very limited nowadays to inhibit propeller cavitation noise in engineering.In this study,the cavitation noise around a PPTC propeller is simulate...Cavitation noise around propellers has many adverse effects.It is still very limited nowadays to inhibit propeller cavitation noise in engineering.In this study,the cavitation noise around a PPTC propeller is simulated using the large eddy simulation(LES)coupled with the porous Ffowcs Williams-Hawkings(PFW-H)equation.The investigation aims to find a strategy to suppress cavitation noise and analyze the noise suppression mechanism.The predicted hydrodynamic results agree well with the experimental data and are utilized in the hydroacoustic analysis.The hydroacoustic results indicate that the pseudo-thickness noise dominates the dominant frequency component of the total cavitation noise due to the effect of cavity evolution,which is one of the reasons why the pseudo-thickness noise dominates the total cavitation noise.A method is found to weaken the cavitation noise through ventilation at the generation location of the sheet cavity(SC).It is worth noting that ventilation inhibits the generation and development of SC by changing the pressure distribution on the suction surface of the blade and pushing away the cavities around the ventilation holes.Moreover,cavity evolution noise dominates the fluid volume evolution noise under the ventilated cavitating condition.Ventilation significantly attenuates the vapor volume pulsation and thus the cavity evolution noise,which leads to a reduction in pseudo-thickness noise and total cavitation noise.The ventilation mainly reduces noises at the dominant frequency of the pseudo-thickness noise and the total cavitation noise.展开更多
Colorectal cancer(CRC)is a common malignant tumor that affects people worldwide.Metagenomic analyses have shown an enrichment of Fusobacterium nucleatum(F.nucleatum)in colorectal carcinoma tissue;many studies have ind...Colorectal cancer(CRC)is a common malignant tumor that affects people worldwide.Metagenomic analyses have shown an enrichment of Fusobacterium nucleatum(F.nucleatum)in colorectal carcinoma tissue;many studies have indicated that F.nucleatum is closely related to the colorectal carcinogenesis.In this review,we provide the latest information to reveal the related molecular mechanisms.The known virulence factors of F.nucleatum promote adhesion to intestinal epithelial cells via FadA and Fap2.Besides,Fap2 also binds to immune cells causing immunosuppression.Furthermore,F.nucleatum recruits tumor-infiltrating immune cells,thus yielding a pro-inflammatory microenvironment,which promotes colorectal neoplasia progression.F.nucleatum was also found to potentiate CRC development through toll-like receptor 2(TLR2)/toll-like receptor 4(TLR4)signaling and microRNA(miRNA)-21 expression.In addition,F.nucleatum increases CRC recurrence along with chemoresistance by mediating a molecular network of miRNA-18a*,miRNA-4802,and autophagy components.Moreover,viable F.nucleatum was detected in mouse xenografts of human primary colorectal adenocarcinomas through successive passages.These findings indicated that an increased number o f F.nucleatum in the tissues is a biomarker for the diagnosis and prognosis of CRC,and the underlying molecular mechanism can probably provide a potential intervention treatment strategy for patients with F.nucleatum-associaied CRC.展开更多
The acoustic propagation characteristics of the cavitating flow are essential for the noise suppression, but were not well studied. In the current paper, a new technique concerning the propagation path of the monopole...The acoustic propagation characteristics of the cavitating flow are essential for the noise suppression, but were not well studied. In the current paper, a new technique concerning the propagation path of the monopole acoustic energy is presented and two typical thermodynamic cavitation modes (the inertial and thermal modes) are selected to investigate the effect of the cavity shedding dynamics on the acoustic propagation path. In the inertial mode, the temporal variation and the spatial distributions of the monopole acoustic energy as well as the divergence of the monopole acoustic pressure are both more powerful and concentrated than that in the thermal mode. The acoustic propagation path in the thermal mode strictly satisfies the feature of the convective amplification, while there exists another propagation direction close to the normal direction of the foil surface in the inertial mode. Furthermore, the occurrence of the normal direction propagation will make the path deviate from the convective direction.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFB3303501),the National Natural Science Foundation of China(Grant No.52176041)supported by the National Key Laboratory of Ship Vibration and Noise,China Ship Development and Design Center(Grant No.JCKY2021207CI01).
文摘Cavitation noise around propellers has many adverse effects.It is still very limited nowadays to inhibit propeller cavitation noise in engineering.In this study,the cavitation noise around a PPTC propeller is simulated using the large eddy simulation(LES)coupled with the porous Ffowcs Williams-Hawkings(PFW-H)equation.The investigation aims to find a strategy to suppress cavitation noise and analyze the noise suppression mechanism.The predicted hydrodynamic results agree well with the experimental data and are utilized in the hydroacoustic analysis.The hydroacoustic results indicate that the pseudo-thickness noise dominates the dominant frequency component of the total cavitation noise due to the effect of cavity evolution,which is one of the reasons why the pseudo-thickness noise dominates the total cavitation noise.A method is found to weaken the cavitation noise through ventilation at the generation location of the sheet cavity(SC).It is worth noting that ventilation inhibits the generation and development of SC by changing the pressure distribution on the suction surface of the blade and pushing away the cavities around the ventilation holes.Moreover,cavity evolution noise dominates the fluid volume evolution noise under the ventilated cavitating condition.Ventilation significantly attenuates the vapor volume pulsation and thus the cavity evolution noise,which leads to a reduction in pseudo-thickness noise and total cavitation noise.The ventilation mainly reduces noises at the dominant frequency of the pseudo-thickness noise and the total cavitation noise.
文摘Colorectal cancer(CRC)is a common malignant tumor that affects people worldwide.Metagenomic analyses have shown an enrichment of Fusobacterium nucleatum(F.nucleatum)in colorectal carcinoma tissue;many studies have indicated that F.nucleatum is closely related to the colorectal carcinogenesis.In this review,we provide the latest information to reveal the related molecular mechanisms.The known virulence factors of F.nucleatum promote adhesion to intestinal epithelial cells via FadA and Fap2.Besides,Fap2 also binds to immune cells causing immunosuppression.Furthermore,F.nucleatum recruits tumor-infiltrating immune cells,thus yielding a pro-inflammatory microenvironment,which promotes colorectal neoplasia progression.F.nucleatum was also found to potentiate CRC development through toll-like receptor 2(TLR2)/toll-like receptor 4(TLR4)signaling and microRNA(miRNA)-21 expression.In addition,F.nucleatum increases CRC recurrence along with chemoresistance by mediating a molecular network of miRNA-18a*,miRNA-4802,and autophagy components.Moreover,viable F.nucleatum was detected in mouse xenografts of human primary colorectal adenocarcinomas through successive passages.These findings indicated that an increased number o f F.nucleatum in the tissues is a biomarker for the diagnosis and prognosis of CRC,and the underlying molecular mechanism can probably provide a potential intervention treatment strategy for patients with F.nucleatum-associaied CRC.
基金Projects supported by the National Natural Science Foundation of China(Grant Nos.51822903,11772239)。
文摘The acoustic propagation characteristics of the cavitating flow are essential for the noise suppression, but were not well studied. In the current paper, a new technique concerning the propagation path of the monopole acoustic energy is presented and two typical thermodynamic cavitation modes (the inertial and thermal modes) are selected to investigate the effect of the cavity shedding dynamics on the acoustic propagation path. In the inertial mode, the temporal variation and the spatial distributions of the monopole acoustic energy as well as the divergence of the monopole acoustic pressure are both more powerful and concentrated than that in the thermal mode. The acoustic propagation path in the thermal mode strictly satisfies the feature of the convective amplification, while there exists another propagation direction close to the normal direction of the foil surface in the inertial mode. Furthermore, the occurrence of the normal direction propagation will make the path deviate from the convective direction.
