The path loss analysis model based on 5 rays in vacancy indoor environment is proposed. The relationship between multipath overlapping and the path loss is analyzed mathematically. Time-domain technique is introduced ...The path loss analysis model based on 5 rays in vacancy indoor environment is proposed. The relationship between multipath overlapping and the path loss is analyzed mathematically. Time-domain technique is introduced to compute reflection coefficient in a very short time interval. A 5 rays path loss calculation method, which is satisfactory accurate, is developed. 5 typical environments are involved to analyze and generalize the common path loss characteristics in vacancy indoor environment. The simulation result shows that the path loss can be characterized as 3 zones with different path loss exponent as distance between transmitter and receiver increasing.展开更多
The multi-dimensional time-domain computational fluid dynamics(CFD) approach is extended to calculate the acoustic attenuation performance of water-filled piping silencers. Transmission loss predictions from the time-...The multi-dimensional time-domain computational fluid dynamics(CFD) approach is extended to calculate the acoustic attenuation performance of water-filled piping silencers. Transmission loss predictions from the time-domain CFD approach and the frequency-domain finite element method(FEM) agree well with each other for the dual expansion chamber silencer, straight-through and cross-flow perforated tube silencers without flow. Then, the time-domain CFD approach is used to investigate the effect of flow on the acoustic attenuation characteristics of perforated tube silencers. The numerical predictions demonstrate that the mean flow increases the transmission loss, especially at higher frequencies, and shifts the transmission loss curve to lower frequencies.展开更多
Metallic ring-shaped nanotube arrays are proposed and its optical transmission properties are studied by using finite-difference time-domain （FDTD） method. Compared with the transmission spectra of conventional circ...Metallic ring-shaped nanotube arrays are proposed and its optical transmission properties are studied by using finite-difference time-domain （FDTD） method. Compared with the transmission spectra of conventional circular nanotube arrays, two photonic band gaps are emerged in the transmission spectra offing-shaped nanotube arrays, the two band gaps and transmission spectra are adjusted by the length, inner radius, intertube spacing and the dielectric constants of the core and embedding medium, and magnitude modification, redshift and blueshift of the resonance modes are observed. A metallic ring-shaped nanotube arrays for subwavelength band-stop filter in the range of visible light can be achieved. To understand its physical origin, field-interference mechanism was suggested by the field distributions. The proposed nanostructures and results may have great potential applications in subwavelength near-field optics.展开更多
针对南海单点系泊浮式生产储卸油装置(floating production storage and offloading,FPSO),利用水动力分析软件ANSYS AQWA,基于三维势流理论建立其时域耦合分析模型,计算FPSO在正常作业和极端海况下的运动响应及系泊缆张力,分析其在不...针对南海单点系泊浮式生产储卸油装置(floating production storage and offloading,FPSO),利用水动力分析软件ANSYS AQWA,基于三维势流理论建立其时域耦合分析模型,计算FPSO在正常作业和极端海况下的运动响应及系泊缆张力,分析其在不同单缆和双缆组合失效条件下系统的刚度大小、船体运动响应和系泊缆张力,并对系泊系统的安全性能进行量化评估。结果表明:双缆失效对系泊系统纵荡和横荡刚度的降低更加显著,其中船艉同组双缆失效导致系泊纵荡刚度降至最小,舷侧同组双缆系泊失效则使横荡刚度降至最小,两种工况下船体纵荡与横荡更加剧烈,正常作业工况最大纵荡与横荡距离可达25 m和40 m;在十年一遇风浪条件下,单缆断裂后剩余缆绳张力仍可满足安全要求,但同组双缆断裂后,剩余系泊缆张力接近缆绳破断张力,失效风险显著增加;在百年一遇风浪条件下,单缆断裂时满足瞬态破损工况的安全标准,而双缆失效会引发剩余缆绳发生连续破断,最终导致FPSO完全失控。展开更多
基金This project was supported by the key programof the Nationed Natural Science Foundation of China (60432040)
文摘The path loss analysis model based on 5 rays in vacancy indoor environment is proposed. The relationship between multipath overlapping and the path loss is analyzed mathematically. Time-domain technique is introduced to compute reflection coefficient in a very short time interval. A 5 rays path loss calculation method, which is satisfactory accurate, is developed. 5 typical environments are involved to analyze and generalize the common path loss characteristics in vacancy indoor environment. The simulation result shows that the path loss can be characterized as 3 zones with different path loss exponent as distance between transmitter and receiver increasing.
基金Project(11174065)supported by the National Natural Science Foundation of China
文摘The multi-dimensional time-domain computational fluid dynamics(CFD) approach is extended to calculate the acoustic attenuation performance of water-filled piping silencers. Transmission loss predictions from the time-domain CFD approach and the frequency-domain finite element method(FEM) agree well with each other for the dual expansion chamber silencer, straight-through and cross-flow perforated tube silencers without flow. Then, the time-domain CFD approach is used to investigate the effect of flow on the acoustic attenuation characteristics of perforated tube silencers. The numerical predictions demonstrate that the mean flow increases the transmission loss, especially at higher frequencies, and shifts the transmission loss curve to lower frequencies.
基金Projects(11164007,61275174)supported by the National Natural Science Foundation of ChinaProject(20100162110068)supported by the Doctoral Program of Higher Education of China+1 种基金Project(20132BAB212007)supported by the Natural Science Foundation of Jiangxi Province,ChinaProject(GJJ11107)supported by Scientific Foundation of Jiangxi Education Department,China
文摘Metallic ring-shaped nanotube arrays are proposed and its optical transmission properties are studied by using finite-difference time-domain （FDTD） method. Compared with the transmission spectra of conventional circular nanotube arrays, two photonic band gaps are emerged in the transmission spectra offing-shaped nanotube arrays, the two band gaps and transmission spectra are adjusted by the length, inner radius, intertube spacing and the dielectric constants of the core and embedding medium, and magnitude modification, redshift and blueshift of the resonance modes are observed. A metallic ring-shaped nanotube arrays for subwavelength band-stop filter in the range of visible light can be achieved. To understand its physical origin, field-interference mechanism was suggested by the field distributions. The proposed nanostructures and results may have great potential applications in subwavelength near-field optics.
基金Project supported by China Postdoctoral Science Foundation （20100481488）, Key Fund Project of Advanced Research of the Weapon Equipment （9140A33040512JB3401）.
文摘针对南海单点系泊浮式生产储卸油装置(floating production storage and offloading,FPSO),利用水动力分析软件ANSYS AQWA,基于三维势流理论建立其时域耦合分析模型,计算FPSO在正常作业和极端海况下的运动响应及系泊缆张力,分析其在不同单缆和双缆组合失效条件下系统的刚度大小、船体运动响应和系泊缆张力,并对系泊系统的安全性能进行量化评估。结果表明:双缆失效对系泊系统纵荡和横荡刚度的降低更加显著,其中船艉同组双缆失效导致系泊纵荡刚度降至最小,舷侧同组双缆系泊失效则使横荡刚度降至最小,两种工况下船体纵荡与横荡更加剧烈,正常作业工况最大纵荡与横荡距离可达25 m和40 m;在十年一遇风浪条件下,单缆断裂后剩余缆绳张力仍可满足安全要求,但同组双缆断裂后,剩余系泊缆张力接近缆绳破断张力,失效风险显著增加;在百年一遇风浪条件下,单缆断裂时满足瞬态破损工况的安全标准,而双缆失效会引发剩余缆绳发生连续破断,最终导致FPSO完全失控。
