Under the assumption of weak scattering , the acoustical diffraction tomographic imaging of an object can be reconstructed by using the Born (or Rytov) approximation method . When the weak scattering assumption within...Under the assumption of weak scattering , the acoustical diffraction tomographic imaging of an object can be reconstructed by using the Born (or Rytov) approximation method . When the weak scattering assumption within the medium is not satisfied the multiple ultrasound scattering must be taken into account . In this case , the reconstruction results under the first-order Born approximation will be seriously distorted . In this paper we introduce an ' intermediate object function' into the wave equation and take iterative modification in space domain and spatial frequancy domain based on Born approximation . In this way , the distorted image will be improved step by step . In order to examine the method as mentioned above , we have just tried to make computerized simulations . The initial result shows that the quality of the image reconstructed from the object under non-weak scattering may be improved significantly .展开更多
为探究不同加工处理下李光杏脯的理化特性和挥发性成分之间的差异,对传统工艺杏脯(hot air dried apricot,HAD)、复合糖液糖煮杏脯(boiled sugar with apricot,BSW)、弱微波处理杏脯(weak microwave drying of apricot,WMD)进行感官评...为探究不同加工处理下李光杏脯的理化特性和挥发性成分之间的差异,对传统工艺杏脯(hot air dried apricot,HAD)、复合糖液糖煮杏脯(boiled sugar with apricot,BSW)、弱微波处理杏脯(weak microwave drying of apricot,WMD)进行感官评定、褐变度、总糖、可滴定酸等的测定,采用顶空固相微萃取和气相色谱-质谱联用(headspace solid-phase microextraction-gas chromatography-mass spectrometry,HS-SPME-GC-MS)技术进行挥发性成分测定。研究结果表明,HAD的褐变度最高为0.66,BSW的褐变度最低为0.26。WMD处理的总糖含量最低为42.36%,可滴定酸含量为1.03%,WMD可有效降低含糖量,缓解果脯产品口感甜腻的问题。HS-SPME-GC-MS共检测出88种挥发性成分,主要包括醇类19种、醛类20种、酮类13种、酯类9种、萜烯类16种、酸性物质3种以及其他类8种。采用气味活度值结合正交偏最小二乘判别分析确定了3种样品的关键差异香气成分。其中HAD提取的关键香气成分为呋喃、联苯、3-糠醛;BSW的关键香气成分为芳樟醇、己醛、顺式-香叶醇;WMD的关键香气成分为己醛、芳樟醇、3-辛醇。该文通过对3种不同处理工艺的杏脯进行理化指标测定,结合与鲜果挥发性成分对比研究,为进一步阐明不同处理杏脯的理化性质和风味物质差异研究及合理开发相关产品提供科学基础。展开更多
针对数字锁定放大器中稀疏分解算法检测精度受限的缺点,结合非线性方法进行补偿,采用混沌检测联合稀疏分解的算法设计了数字锁定放大器。数字锁定放大器借助稀疏分解算法估计信号参数,根据估计得到的参数设计对应混沌系统;利用混沌系统...针对数字锁定放大器中稀疏分解算法检测精度受限的缺点,结合非线性方法进行补偿,采用混沌检测联合稀疏分解的算法设计了数字锁定放大器。数字锁定放大器借助稀疏分解算法估计信号参数,根据估计得到的参数设计对应混沌系统;利用混沌系统检测信号的过程中产生间歇性混沌状态,并通过测量间歇性混沌状态的周期,精确检测信号。最终,在信号的信噪比低至-20 d B时可以成功检测信号,频率精度达到0.05 Hz,提供了一种非线性微弱信号检测方法。展开更多
文摘Under the assumption of weak scattering , the acoustical diffraction tomographic imaging of an object can be reconstructed by using the Born (or Rytov) approximation method . When the weak scattering assumption within the medium is not satisfied the multiple ultrasound scattering must be taken into account . In this case , the reconstruction results under the first-order Born approximation will be seriously distorted . In this paper we introduce an ' intermediate object function' into the wave equation and take iterative modification in space domain and spatial frequancy domain based on Born approximation . In this way , the distorted image will be improved step by step . In order to examine the method as mentioned above , we have just tried to make computerized simulations . The initial result shows that the quality of the image reconstructed from the object under non-weak scattering may be improved significantly .
文摘为探究不同加工处理下李光杏脯的理化特性和挥发性成分之间的差异,对传统工艺杏脯(hot air dried apricot,HAD)、复合糖液糖煮杏脯(boiled sugar with apricot,BSW)、弱微波处理杏脯(weak microwave drying of apricot,WMD)进行感官评定、褐变度、总糖、可滴定酸等的测定,采用顶空固相微萃取和气相色谱-质谱联用(headspace solid-phase microextraction-gas chromatography-mass spectrometry,HS-SPME-GC-MS)技术进行挥发性成分测定。研究结果表明,HAD的褐变度最高为0.66,BSW的褐变度最低为0.26。WMD处理的总糖含量最低为42.36%,可滴定酸含量为1.03%,WMD可有效降低含糖量,缓解果脯产品口感甜腻的问题。HS-SPME-GC-MS共检测出88种挥发性成分,主要包括醇类19种、醛类20种、酮类13种、酯类9种、萜烯类16种、酸性物质3种以及其他类8种。采用气味活度值结合正交偏最小二乘判别分析确定了3种样品的关键差异香气成分。其中HAD提取的关键香气成分为呋喃、联苯、3-糠醛;BSW的关键香气成分为芳樟醇、己醛、顺式-香叶醇;WMD的关键香气成分为己醛、芳樟醇、3-辛醇。该文通过对3种不同处理工艺的杏脯进行理化指标测定,结合与鲜果挥发性成分对比研究,为进一步阐明不同处理杏脯的理化性质和风味物质差异研究及合理开发相关产品提供科学基础。
文摘针对数字锁定放大器中稀疏分解算法检测精度受限的缺点,结合非线性方法进行补偿,采用混沌检测联合稀疏分解的算法设计了数字锁定放大器。数字锁定放大器借助稀疏分解算法估计信号参数,根据估计得到的参数设计对应混沌系统;利用混沌系统检测信号的过程中产生间歇性混沌状态,并通过测量间歇性混沌状态的周期,精确检测信号。最终,在信号的信噪比低至-20 d B时可以成功检测信号,频率精度达到0.05 Hz,提供了一种非线性微弱信号检测方法。
