测井技术的成像化和组合化发展使得井下仪器上传的数据量越来越大,需要开发高效率的通信系统以解决数控测井中的通信瓶颈。提出了一种基于正交频分复用OFDM(Orthogonal Frequency Division Multiplexing)的单芯测井电缆调制解调系统方案...测井技术的成像化和组合化发展使得井下仪器上传的数据量越来越大,需要开发高效率的通信系统以解决数控测井中的通信瓶颈。提出了一种基于正交频分复用OFDM(Orthogonal Frequency Division Multiplexing)的单芯测井电缆调制解调系统方案,并完成了实现此方案的软硬件系统设计。此外,在MATLAB中进行了系统级仿真,模拟了调制解调系统的实现过程和所需的数字信号处理方法,仿真结果表明设计正确、可行。设计中采用了调制解调技术OFDM,使单芯电缆测井系统的数传速率从原来多用的22.8 kbit/s提高到102.4 kbit/s,满足了成像测井及组合测井对单芯电缆测井系统的数据传速率要求。展开更多
This paper investigates the wave attenuation properties of the double trapezoidal submerged breakwaters on the flat-bed by conducting physical experiments subjected to linear and cnoidal incident waves.The method of G...This paper investigates the wave attenuation properties of the double trapezoidal submerged breakwaters on the flat-bed by conducting physical experiments subjected to linear and cnoidal incident waves.The method of Goda's two points is used to separate the heights of incident,reflected and transmitted waves based on the experimental data.The possible factors affecting the wave attenuation properties of the double trapezoidal submerged breakwaters(i.e.,the relative submerged water depth,relative breakwater spacing,wave steepness and relative wave height) are investigated with respect to the reflection and transmission coefficients.The results show that there is a range,within which the breakwater spacing has little impact on the reflection coefficient,and the transmission coefficient tends to be a constant.The influence of the wave steepness is reduced while the breakwater spacing is too large or too small.Within the range of the relative wave height tested in this study,the reflection and transmission coefficients increase and decrease with the relative wave height,respectively.The double trapezoidal submerged breakwaters model indicates a good attenuation effect for larger wave steepness,big relative wave height and within the range of the relative breakwater spacing between 12.5 and 14 according to linear and cnoidal waves.The changes of wave energy spectra between the double submerged breakwaters on the flat-bed are investigated by the fast Fourier transform(FFT) method,showing that wave energy dissipation can be reached more effectively when the relative breakwater spacing is 12.5.展开更多
基金Supported by the General Program of National Natural Science Foundation of China(No.50979066 and No.50979008)Ph.D.Programs Foundation of Ministry of Education of China(No.20094316110002)Scientific Research Fund of Department of Education, Hunan Province(No.10A006)
文摘This paper investigates the wave attenuation properties of the double trapezoidal submerged breakwaters on the flat-bed by conducting physical experiments subjected to linear and cnoidal incident waves.The method of Goda's two points is used to separate the heights of incident,reflected and transmitted waves based on the experimental data.The possible factors affecting the wave attenuation properties of the double trapezoidal submerged breakwaters(i.e.,the relative submerged water depth,relative breakwater spacing,wave steepness and relative wave height) are investigated with respect to the reflection and transmission coefficients.The results show that there is a range,within which the breakwater spacing has little impact on the reflection coefficient,and the transmission coefficient tends to be a constant.The influence of the wave steepness is reduced while the breakwater spacing is too large or too small.Within the range of the relative wave height tested in this study,the reflection and transmission coefficients increase and decrease with the relative wave height,respectively.The double trapezoidal submerged breakwaters model indicates a good attenuation effect for larger wave steepness,big relative wave height and within the range of the relative breakwater spacing between 12.5 and 14 according to linear and cnoidal waves.The changes of wave energy spectra between the double submerged breakwaters on the flat-bed are investigated by the fast Fourier transform(FFT) method,showing that wave energy dissipation can be reached more effectively when the relative breakwater spacing is 12.5.
