Determination of the Initiating Capability of Detonators Containing TKX‐50, MAD‐X1, PETNC,DAAF, RDX,HMX or PETN as a Base Charge,by Underwater Explosion Test

A comprehensive investigation to determine the initiation power of detonators containing as a base charge the novel explosives: dihydroxylammonium 5,5′‐bis(tetrazolate‐1N‐oxide) – TKX‐50, dihydroxylammonium 5,5′‐bis(3‐nitro‐1,2,4‐triazolate‐1N‐oxide) – MAD‐X1, pentaerythritol tetranitrocarbamate – PETNC and 3,3′‐diamino‐4,4′‐azoxyfurazan – DAAF in comparison with RDX, HMX and PETN was undertaken. In order to estimate the initiation power of the detonators, the underwater initiating capability test was used. The total energy as a sum of the primary shock wave energy and the bubble gas energy was determined for each of these explosives, by measuring the overpressure of the shock waves generated in water. Moreover, the complete synthesis for novel explosives is presented. The thermal behavior of the explosives was investigated using DSC (differential scanning calorimetry). The gas phase absolute molar enthalpies at 298 K and 10⁵ Pa were calculated theoretically using the modified complete basis set method (CBS‐4M; M referring to the use of minimal population localization) with the Gaussian 09 software. Gas phase standard molar enthalpies of formation (ΔH_f°_(g)) at 298 K were computed using the atomization energy method. Standard molar enthalpies of formation (▵H_(s)°) were calculated using ΔH_f°_(g) and the standard molar enthalpies of sublimation by applying Trouton’s rule. The Chapman‐Jouguet (CJ) characteristics based on calculated ▵H_(s)° values were computed using the EXPLO5 V6.01 thermochemical computer code. For the calculations the theoretical maximum densities and densities obtained during the experiments presented in this work were used.     

基于多传感器的微弱磁异常信号提取方法研究

针对磁异常探测(magnetic anomaly detection, MAD)问题,许多学者提出了相应的检测方法。检测只能判断目标存在与否,而为了实现目标定位和识别需要获取异常信号本身。通过建立机载磁异常信号提取模型,基于卷积盲源分离(convolution blind source separation, CBSS)理论,提出频域相关提取算法实现异常信号提取。仿真实验结果验证了该方法的可行性和有效性。     

Improved macroblock level rate control for the spatially scalable extension of H.264/AVC

An improved rate control algorithm, designed for scalable video coders incorporating interlayer prediction, is proposed. Firstly, a Rate Distortion (RD) model for interlayer prediction involving the spatial enhancement layers is devised. An optimised Mean Absolute Difference (MAD) prediction model for the spatial enhancement layers that considers both the MAD from the spatial base layer in the same frame and the MAD from the corresponding macroblock in previous frames is also proposed. Simulation results show that the resulting algorithm produces accurate rate control with an average bit rate error of less than 0.26%. Compared with the JVT-W043 default rate control algorithm of the JSVM, the proposed algorithm improves the average PSNR by up to 0.53 dB or reduces the bit rate by an average of 10.95%. Furthermore, the proposed algorithm can be combined with the existing rate control scheme for H.264/AVC, resulting in further improvements.     

基于H.264码率控制算法的优化

在给定的比特流的条件下,编解码器采用码率控制可以获得高质量和高平滑的视频。因此码率控制广泛应用在视频压缩与传输过程中,起着重要作用。本文基于最新的视频编码标准H.264提出一种改进的码率控制算法--关于MAD(mean absolute differences)在计算QP(量化参数)上的改进.MAD在二次失真模型中用于计算QP,取得了很好的信噪比、压缩比和码流的稳定性。本文在像素差值计算后加入Hadamard计算即SATD(sum absolute of transform differences),采用SATD来代替MAD在二次失真模型中计算量化参数。实验结果表明:与JM18.0原算法比较,视频输出序列的亮度峰值信噪比(PSNR)提高了0.2 dB左右,取得更好的码率控制效果,便于接收端获得更加稳定的压缩视频流。     

基于正交基分解算法的航空磁探方法

航空磁探中,将潜艇目标以磁偶极子模型代替。针对目标信号信噪比较低的情况,利用正交基分解检测算法,大幅提高了水中磁性目标信号的信噪比,有效地检测到磁性目标。采用双L型航空磁探方法,确定磁性目标的运动位置、航向和航速。仿真试验表明,该方法具有一定的工程应用价值。     

中值滤波与各向异性扩散相结合的医学图像滤波方法

医学图像的滤波处理,须保留具有重要诊断意义的边缘细节信息。针对Perona-Malik(PM)各向异性扩散模型遇到强噪声则失效和扩散门限参数K依靠经验选取的不足,提出了一种改进的各向异性扩散算法。将PM算法与中值滤波结合,用经过中值滤波平滑后的梯度模代替原始图像的梯度模,以控制扩散的过程。应用自适应扩散门限(当前邻域内梯度的绝对偏差中值(MAD))和迭代终止准则,提高算法鲁棒性和效率。实验分别对超声心动图、CT图像和Lena图像进行去噪处理,用峰值信噪比(PSNR)和边缘保持能力EPI作为评价标准。实验结果表明,改进算法优于PM算法和Catte-PM方法,在提高信噪比的同时保留了图像的细节信息,可以更好地满足医学图像的使用要求。     

A method for operational calibration of AVHRR reflective time series data

We have developed an automatic method to monitor the AVHRR instrument sensitivity over time in the short-wave reflective channels to ensure that trends in the data series obtained by this instrument are real and not sensor artefacts.Our radiometric calibration method uses the Multivariate Alteration Detection (MAD) algorithm to statistically select invariant features over land areas from multiple image-pairs that are compared to assess changes in the instrument's calibration. This method requires no a priori regional knowledge and is globally applicable. A calibrated time series from Pseudo-Invariant Features located in central Australia are shown to have long-term trends removed. The resulting MAD-based calibration has a root mean squared error of ∼ 5-6% for both channels 1 and 2 and is in alignment with other approaches.     

提问马岩松

文章记录了《时代建筑》对青年建筑师马岩松的一次书面采访。被访者谈及对数字建筑的理解、对红螺湖会所的建造控制、对形式的回应,以及建筑师通过媒体影响社会的潜力等问题。通过若干案例,解析了建筑师和他的MAD事务所对社会问题的敏感回应以及与资本、决策层交流的策略。     

Radiometric correction of multi-temporal Landsat data for characterization of early successional forest patterns in western Oregon

Detecting and characterizing continuous changes in early forest succession using multi-temporal satellite imagery requires atmospheric correction procedures that are both operationally reliable, and that result in comparable units (e.g., surface reflectance). This paper presents a comparison of five atmospheric correction methods (2 relative, 3 absolute) used to correct a nearly continuous 20-year Landsat TM/ETM+ image data set (19-images) covering western Oregon (path/row 46/29). In theory, full absolute correction of individual images in a time-series should effectively minimize atmospheric effects resulting in a series of images that appears more similar in spectral response than the same set of uncorrected images. Contradicting this theory, evidence is presented that demonstrates how absolute correction methods such as Second Simulation of the Satellite Signal in the Solar Spectrum (6 s), Modified Dense Dark Vegetation (MDDV), and Dark Object Subtraction (DOS) actually make images in a time-series somewhat less spectrally similar to one another. Since the development of meaningful spectral reflectance trajectories is more dependant on consistent measurement of surface reflectance rather than on accurate estimation of true surface reflectance, correction using image pairs is also tested. The relative methods tested are variants of an approach referred to as “absolute-normalization”, which matches images in a time-series to an atmospherically corrected reference image using pseudo-invariant features and reduced major axis (RMA) regression. An advantage of “absolute-normalization” is that all images in the time-series are converted to units of surface reflectance while simultaneously being corrected for atmospheric effects. Of the two relative correction methods used for “absolute-normalization”, the first employed an automated ordination algorithm called multivariate alteration detection (MAD) to statistically locate pseudo-invariant pixels between each subject and reference image, while the second used analyst selected pseudo-invariant features (PIF) common to the entire image set. Overall, relative correction employed in the “absolute-normalization” context produced the most consistent temporal reflectance response, with the automated MAD algorithm performing equally as well as the handpicked PIFs. Although both relative methods performed nearly equally in terms of observed errors, several reasons emerged for preferring the MAD algorithm. The paper concludes by demonstrating how “absolute-normalization” improves (i.e., reduces scatter in) spectral reflectance trajectory models used for characterizing patterns of early forest succession.     

H.264码率控制中mad预测的一种改进算法

码率控制是H．264中的一个重要的组成部分。好的码率控制可以有效地提高压缩图像的质量。而目标比特数的来准确估计，对码率控制的工作的好坏，起着不可忽略的作用。该文针对jm模型以及以往研究中，目标比特数的分配和实际比特数存在差值较大的缺点，分析了其不良影响，并提出了对mad预测的改进措施，以此来提高R—Q模型的准确性，从而提高QP预测的精确度，并通过实验结果证明其的合理性。