Research of NO_(2) vertical profiles with look-up table method based on MAX-DOAS

Obtaining the vertical distribution profile of trace gas is of great significance for studying the diffusion procedure of air pollution.In this article,a look-up table method based on multi-axis differential optical absorption spectroscopy(MAX-DOAS)technology is established for retrieving the tropospheric NO_(2) vertical distribution profiles.This method retrieves the aerosol extinction profiles with minimum cost function.Then,the aerosol extinction profiles and the atmospheric radiation transfer model(RTM)are employed to establish the look-up table for retrieving the NO_(2) vertical column densities(VCDs)and profiles.The measured NO_(2) differential slant column densities(DSCDs)are compared with the NO_(2) DSCDs simulated by the atmospheric RTM,and the NO_(2) VCDs,the weight factor of NO_(2) in the boundary layer,and the boundary layer height are obtained by the minimization process.The look-up table is established to retrieve NO_(2) VCDs based on MAX-DOAS measurements in Huaibei area,and the results are compared with the data from Copernicus Atmospheric Monitoring Service(CAMS)model.It is found that there are nearly consistent and the correlation coefficient R2 is more than 0.86.The results show that this technology provides a more convenient and accurate retrieval method for the stereoscopic monitoring of atmospheric environment.

A general purpose exact Rayleigh scattering look-up table for ocean color remote sensing

The current exact Rayleigh scattering calculation of ocean color remote sensing uses the look-up table （LUT）, which is usually created for a special remote sensor and cannot be applied to other sensors. For practical application, a general purpose Rayleigh scattering LUT which can be applied to all ocean color remote sensors is generated. An adding-doubling method to solve the vector radiative transfer equation in the plane-parallel atmosphere is deduced in detail. Compared with the exact Rayleigh scattering radiance derived from the MODIS exact Rayleigh scattering LUT, it is proved that the relative error of Rayleigh scattering calculation with the adding-doubling method is less than 0.25%, which meets the required accuracy of the atmospheric correction of ocean color remote sensing. Therefore, the adding-doubling method can be used to generate the exact Rayleigh scattering LUT for the ocean color remote sensors. Finally, the general purpose exact Rayleigh scattering LUT is generated using the adding-doubling method. On the basis of the general purpose LUT, the calculated Rayleigh scattering radiance is tested by comparing with the LUTs ofMODIS, SeaWiFS and the other ocean color sensors, showing that the relative errors are all less than 0.5%, and this general purpose LUT can be applied to all ocean color remote sensors.

AES加密算法的一种优化的FPGA实现方法

介绍AES算法的原理并阐述了明文分组和密钥长度都是128 b的情况下基于FPGA的设计和实现。结合算法和FPGA的特点,采用查表法优化处理了字节代换运算、列混合运算和密钥扩展运算。同时,为了提高系统工作速度,在设计中应用了流水线技术,但由于流水线结构不能用于反馈模式,因此,实现时使用的是电码本模式(ECB)的工作方式。利用QuartusⅡ开发工具给出仿真结果,时钟频率达70.34 MHz。最后做了应用分析。

基于FPGA的AES加密算法的高速实现

介绍AES算法的原理以及基于FPGA的高速实现。结合算法和FPGA的特点,采用查表法优化处理了字节代换运算、列混合运算。同时,为了提高系统工作速度,在设计中应用了内外结合的流水线技术,并应用Altera公司的开发工具及芯片进行实际开发。

针对AES查表法最后一轮加密的L3缓存攻击

文中对Cache最新的攻击方法进行了研究,在配置Intel i5-4590四核心、3.3 GHz CPU处理器的机器上,对Linux系统虚拟环境下Bouncy Castle JDK1.0库中的AES快速加密法—AESFastEngine.java进行flush+flush计时攻击。在加密进程持续执行时,使用flush+flush方法遍历共享主存地址来检测活动地址集(S盒地址),然后找到S盒偏移位,对S盒偏移位中的表项进行监控,从密文数据中筛选对应flush+flush时间较短的密文值,再利用S盒中的表项值恢复最后一轮密钥值,即通过确定监测S盒中固定范围的表项的使用情况来恢复最后一轮加密使用的密钥值,这种方法需要大量的已知密文,并且能够精确地计算出S盒的偏移和最后一轮的密钥值。