Spatio-temporal variation and propagation direction of coal fire in Jharia Coalfield,India by satellite-based multi-temporal night-time land surface temperature imaging

In this paper,the spatio-temporal variation and propagation direction of coal fire were studied in the Jharia Coalfield(JCF),India during 2006–2015 through satellite-based night-time land surface temperature(LST)imaging.The LST was retrieved from Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER)night-time thermal-infrared data by a robust split-window algorithm based on scene-specific regression coefficients,band-specific hybrid emissivity,and night-time atmospheric transmittance.The LST-profile-based coal fire detection algorithm was formulated through statistical analysis of the LST values along multiple transects across diverse coal fire locations in the JCF in order to compute date-specific threshold temperatures for separating thermally-anomalous and background pixels.This algorithm efficiently separates surface fire,subsurface fire,and thermally-anomalous transitional pixels.During the observation period,it was noticed that the coal fire area increased significantly,which resulted from new coal fire at many places owing to extensive opencast-mining operations.It was observed that the fire propagation occurred primarily along the dip direction of the coal seams.At places,lateral-propagation of limited spatial extent was also observed along the strike direction possibly due to spatial continuity of the coal seams along strike.Moreover,the opencast-mining activities carried out during 2009–2015 and the structurally weak planes facilitated the fire propagation.

Directional Filter for SAR Images Based on Nonsubsampled Contourlet Transform and Immune Clonal Selection

A directional filter algorithm for intensity synthetic aperture radar （SAR） image based on nonsubsampled contourlet transform （NSCT） and immune clonal selection （ICS） is presented. The proposed filter mainly focuses on exploiting different features of edges and noises by NSCT. Furthermore, ICS strategy is introduced to optimize threshold parameter and amplify parameter adaptively. Numerical experiments on real SAR images show that there are improvements in both visual effects and objective indexes.

Image Filter for Removal of Impulse Noise Based on Directional Derivatives

One of the most common image processing tasks involves the removal of noise from images. Noise can be introduced during image capture, during transmission, or during storage. For design purposes, noise sources are frequently approximated by random variables with a known probability distribution. One common noise model corrupts a signal by introducing impulses. And the surface of the image disturbed by impulse noise displays many peaks or vales. According to the characteristic of impulse noise, a novel algorithm is proposed to the detection of impulse noise point from images based on directional derivatives. First, the theory of calculus on directional derivatives is introduced in detail. Then it is applied to the field of image to removing noise with the discrete form derived from its continuous mathematical model. And a number of contrasting simulations illustrate that our algorithm not only can preserve the structure information while removing impulse noise but also can mostly save the gray value of the pixels undisturbed by noise. In addition, the comparisons of the filtering performance for removing impulse noise are analyzed in detail in the case of different noise densities, and also show that the algorithm suggested outperforms the conventional filter algorithms such as mean filter, median filter and so on in speed and impulse noise reduction, especially in random-valued impulse noise reduction. So it is a very good alternative to the existing schemes.

Directional Filtering Due to Mesospheric Wind Shear on the Propagation of Acoustic-gravity Waves

Gravity waves with periods close to the Brunt-V(a|¨)is(a|¨)l(a|¨) period of the upper troposphere are often observed at mesopause altitudes as short period,quasi-monochromatic waves.The assumption that these short period waves originate in the troposphere may be problematic because their upward propagation to the mesosphere and lower thermosphere region could be significantly impeded due to an extended region of strong evanescence above the stratopause.To reconcile this apparent paradox,an alternative explanation is proposed in this paper.The inclusion of mean winds and their vertical shears is sufficient to allow certain short period waves to remain internal above the stratopause and to propagate efficiently to higher altitudes.A time-dependent numerical model is used to demonstrate the feasibility of this and to determine the circumstances under which the mesospheric wind shears play a role in the removal and directional filtering of short period gravity waves. Finally this paper concludes that the combination of the height-dependent mean winds and the mean temperature structure probably explains the existence of short period,quasi-monochromatic structures observed in airglow images of mesopause region.

Validation Approach of the Tectonic Lineament Extraction Enhancement Using Sentinel 2A Images and Modified 3 ×3 Bidirectional Prewitt Filters. Case Study: Grombalia, Tunisia

In this study, filters are used to extract directional tectonic lineaments and, thus, to reveal the presence of faults or fractures in the satellite images. The extraction process consists first in eliminating other different types of lineaments (e.g. the lithological limit, ridgelines, hydrographic network, roads, etc.). Besides, a comparative and quantitative approach is applied to show that when the directional Prewitt filter has a zero setting of the opposite of the assumed direction, as is the case of the N-S direction, the East-West direction is also set to zero. This research work, based on a bidirectional filter (N-S;E-W), shows satisfactory results especially concerning the quantitative fluctuation of lineament directions by interval. This fluctuation is in perfect agreement with the lineaments provided by the digitizing of the different tectonic accidents directions extracted in a GIS environment from the geological map of Grombalia. In this research work, a quantitative approach was used to evaluate the result of the lineament extraction methodology based on one direction analysis and by an interval of directions. Indeed, the N45 lineament direction, well documented in the geological study of the region, was more clearly distinguished by applying the Prewitt filter than by using the Sobel filter. The result was validated by comparison with the results obtained by the digitization of the tectonic accidents mapped on the geological map.

Using LMS Adaptive Filter in Direct Wave Cancellation

The way to use the least-mean-square (LMS) arithmetic to cancel the direct wave for a passive radar system is introduced. The model of the direct wave is deduced. By using the LMS adaptive FIR filter, the software solution for FM passive radar system is developed instead of the hardware consumption of the existent experiment system of passive radar. Further more some simulative results are given. The simulative results indicate that using LMS arithmetic to cancel the direct wave is effective.

Direction navigability analysis of geomagnetic field based on Gabor filter

Direction navigability analysis is a supplement to the navigability analysis theory, in which extraction of the direction suitable-matching features(DSMFs) determines the evaluation performance. A method based on the Gabor filter is proposed to estimate the direction navigability of the geomagnetic field. First,the DSMFs are extracted based on the Gabor filter’s responses.Second, in the view of pattern recognition, the classification accuracy in fault diagnosis is introduced as the objective function of the hybrid particle swarm optimization(HPSO) algorithm to optimize the Gabor filter’s parameters. With its guidance, the DSMFs are extracted. Finally, a direction navigability analysis model is established with the support vector machine(SVM), and the performances of the models under different objective functions are discussed. Simulation results show the parameters of the Gabor filter have a significant influence on the DSMFs, which, in turn, affects the analysis results of direction navigability. Moreover, the risk of misclassification can be effectively reduced by using the analysis model with optimal Gabor filter parameters. The proposed method is not restricted in geomagnetic navigation, and it also can be used in other fields such as terrain matching and gravity navigation.

Directions of Arrival Optimization Method for Broadband Antenna Array Based on Filter Bank

This paper proposes an estimation method of the directions of arrival(DOA) for the broadband signals received by a uniform planar antenna array including the mutual coupling effect. The process modeling of antenna array receiving dynamic signal is obtained accurately via building the array system electromagnetic space-time model, and the mutual coupling effect is included in the synthesis procedure automatically. The broadband signal is divided into several sub-bands, and the complex weight of these sub-bands frequencies is figured out using the least mean square iteration programming. In the proposed method, the mutual coupling effect is compensated at the different frequencies. The calculation results show that the method is suitable for the uniform linear and uniform circular array pattern integration, and it is commendably satisfied with the requirement of engineering design.

Model Predictive Direct Torque Control of Permanent Magnet Synchronous Motor (PMSM) with Online Parameter Estimation Based on Extended Kalman Filter

Aiming at the torque and flux ripples in the direct torque control and the time-varying parameters for permanent magnet synchronous motor (PMSM), a model predictive direct torque control with online parameter estimation based on the extended Kalman filter for PMSM is designed. By predicting the errors of torque and flux based on the model and the current states of the system, the optimal voltage vector is selected to minimize the error of torque and flux. The stator resistance and inductance are estimated online via EKF to reduce the effect of model error and the current estimation can reduce the error caused by measurement noise. The stability of the EKF is proved in theory. The simulation experiment results show the method can estimate the motor parameters, reduce the torque, and flux ripples and improve the performance of direct torque control for permanent magnet synchronous motor (PMSM).

Direction-Based Adaptive Switching Filter for Removing High-Density Impulse Noise

A direction-based adaptive switching(DBAS) filter is presented for the removal of high-density impulse noise in images. The extrema detection and 28-directional detection are employed to discriminate the pixels as noisy or noise-free. If a pixel is classified as noisy, it will be replaced by a median or a mean value within an adaptive filter window with respect to different noise densities. Simulation results show that the miss-detection ratio and false-alarm ratio are both very low even at noise level as high as 90%. At the same time, better results are obtained in terms of the qualitative and quantitative measures. The peak signal-to-noise ratios increase by nearly 1 dB compared with other existing algorithms. In addition, the computation time is around 10 s for test images with resolutions of 512×512since the proposed approach has low complexity.

Unidirectional Sound Signage for Speech Frequency Range Using Multiple-Loudspeaker Reproduction System

Human safety is the most important issue in disaster management. Speech is a sound signal containing information that is easily and quickly understood by humans. Using speech as sound signage in emergency systems can effectively increase human safety in low or poor visibility conditions such as in smoke-filled situations. However, reflections of sound through walls, floor surfaces, and ceilings will affect clarity of speech. Unfortunately, because of the characteristics of sound reproduction systems, a single loudspeaker propagates sound waves omni-directionally at low frequencies. This paper proposes a simple multiple-loudspeaker system for reproducing sound with uni-directional characteristics. The proposed system consists mainly of a primary loudspeaker for introducing sound in the desired beam, a secondary loudspeaker for reducing gain in the undesired direction, and digital filters. An adaptive finite-impulse-response (FIR) filter is used to produce the controlling sound by implementing a filtered-x least-mean-square algorithm, and a delay filter for adjusting the time alignment of sound propagation between primary and secondary sources at the control point. Several operational conditions for illustrating real situations and reflections were considered in an anechoic chamber. Experimental results show the directivity patterns of the proposed multiple-loudspeaker system for the required conditions. In a low frequency range, the system is able to control unidirectional propagation;there is a sound beam in the desired direction and, conversely, reduction of gain in the undesired direction around the control point.

九轴MEMS微型AHRS设计及其在矢量水听器中的应用

为了精确测量矢量水听器的姿态,设计了一种体积为20 mm×20 mm×5 mm、重量为1.8 g的微型航姿参考系统(AHRS)。利用微机电系统(MEMS)陀螺仪测定角速度,用四元数等效旋转矢量算法求解姿态角;采用扩展卡尔曼滤波器对姿态角估计值进行修正,并估计出MEMS陀螺仪的角速度漂移量。测试结果表明,所提AHRS的俯仰、横滚和航向角误差均方根值分别为0.04°、0.04°和0.34°。最后,将AHRS集成到矢量水听器中,并在加窗直方图统计波达方向估计算法中加入姿态修正。海上实验结果表明,对于航速为8 kn的目标船,经AHRS修正后的单矢量水听器方位角误差均方根值约为3.8°,减小了平台运动导致的方位测量误差。

双重响应异常约束的无人机目标跟踪

针对无人机跟踪目标易受视角变化、部分遮挡、背景杂波等因素影响而难以完成对目标的鲁棒跟踪问题,提出一种双重响应异常约束的无人机目标跟踪算法。首先,通过计算局部响应变化向量和全局响应峰值旁瓣比,在线动态更新空间正则化参数,降低边界效应的影响;其次,针对STRCF算法中的时间正则项的参数固定的问题,提出响应异常峰值判断机制,计算次峰响应系数,并将其融合到时间正则化参数上进行实时更新,避免目标模板变异造成跟踪漂移问题;目标函数通过交替方向乘子法迭代求解最优解。在UAV123、UAV20L和DTB70三个无人机数据集上与代表性的目标跟踪算法进行大量实验,结果表明,在UAV123数据集上的精确度达到71.7%,在DTB70数据集上的跟踪平均速度达到48.3帧/s。本文结果与现有相关滤波类无人机目标跟踪算法相比表现较好,具有较高的实时性和鲁棒性。

考虑MAF延时和前馈补偿的高压直流快速锁相环

同步参考坐标系锁相环是高压直流(high voltage direct current,HVDC)同步触发控制系统中广泛应用的一种窄带宽锁相环,在交流系统故障引起相位跳变情况下,其动态响应缓慢。为增大锁相环的带宽,一种滑动平均滤波器(moving average filter,MAF)被前置于锁相环路,然而MAF本身存在响应延迟,制约了锁相环的同步速度。为了缓解响应延迟问题,文中提出一种考虑MAF延时和前馈补偿的HVDC快速锁相环。首先,利用MAF线性暂态特征预测相位变化,并分别针对故障接入和切除引起的相位跳变问题提出不同的补偿策略;接着,利用不变性原理对锁相环路进行前馈补偿,在负反馈控制和前馈补偿共同构成的复合校正控制系统的作用下,锁相环能够在较小PI参数下实现快速响应;最后,将所提快速锁相环在CIGRE HVDC标准模型和三峡—上海直流工程模型中进行仿真验证。结果表明,该快速锁相环能够有效缓解滤波器响应延迟的制约,缩短失锁时间,进而提高高压直流逆变侧抵御换相失败的能力。

基于DirectShow的MPEG4网络视频流处理系统

介绍了一种基于DirectShow的MPEG4网络视频流处理系统。该系统采用Microsoft Di-rectShow框架技术,接收以MPEG4压缩的网络视频流,对视频流进行切帧、实时解码和播放。系统的关键技术是DirectShow Source Filter的设计和实现。

基于副本复制和Bloom Filter的P2P概率路由算法

非结构化P2P网络资源定位过程中的查询延迟、查准率和查询成本难以同时被优化,为此,提出一种基于副本复制和Bloom Filter技术的P2P概率路由算法DCBF(data copying and Bloom Filter).DCBF基于有向随机网络,对资源对象进行少量的复制,并将各个副本随机路由给网络中的节点;接收副本的节点,以分布式衰减Bloom Filter向邻近节点传递副本的成员资格信息.理论分析和实验结果均表明,DCBF仅需复制少量的副本,通过以分布式衰减Bloom Filter传递副本的成员资格信息,使得网络中的绝大多数节点能够感知到副本的成员资格信息,从而使得各个节点能够以极低的查询代价,在较低的路由延迟范围内,高概率地将查询路由到目标节点.

基于稀疏约束的低复杂度可变分数时延滤波器

针对基于Farrow结构的可变分数时延(Variable fractional delay,VFD)滤波器需求解大量子滤波器系数这一关键问题,本文将稀疏约束理论引入滤波器的权系数优化中,研究具有稀疏系数的Farrow结构滤波器。在极大极小(Minimax)准则下,通过添加L1正则化约束项改进权系数优化模型,在系数(反)对称性基础上进一步增加系数的稀疏度。然后,采用交替方向乘子法(Alternating direction method of multipliers,ADMM)进行权系数迭代求解。仿真实验表明,本文提出的基于稀疏约束的VFD滤波器在保证高延迟精度的同时,乘法器和加法器分别减少了47.69%和58.60%,极大地降低了系统运算量以及复杂度。

硅基钽酸锂异质晶圆键合工艺研究

5G移动通信的发展对声表面波滤波器提出了高频、小型化、集成化的要求。相较于传统压电体单晶材料,采用硅基压电单晶薄膜材料制备的声表面波滤波器具有高频、低插入损耗、高温稳定性等优势,是高性能声表面波器件发展的核心基础材料。Smart-Cut^(TM)是制备硅基压电单晶薄膜材料的主要方法,键合工艺是其中的核心工序,键合质量决定了硅基压电单晶薄膜晶圆材料的质量,并影响器件性能。本文通过低温直接键合工艺,对等离子活化、兆声清洗、预键合、键合加固四道工序展开优化,最终实现了键合强度高达1.84 J/m^(2)、键合面积超过99.9%的高质量硅基钽酸锂异质晶圆键合。

基于衰落Bloom Filter的P2P网络弱状态路由算法

在P2P网络中,基于衰落Bloom Filter的弱状态路由算法试图将每条查询消息沿着成员资格信息量最强的方向传递,并最终以较低的传输代价和传输时延确保较高的查准率.衰落Bloom Filter在传递过程中存在严重的多径叠加和噪音问题,这直接导致查询消息会以很高的概率沿着错误的方向传播,甚至会退化为泛洪路由算法.为了解决这一挑战性难题,提出了DWalker这种基于衰落Bloom Filter的高效弱状态路由算法.DWalker基于有向随机网络,采用指数衰落Bloom Filter来发布和传播每个节点共享资源的信息,且其最大传播距离小于网络中任意两点之间距离的期望值,从而有效抑制了衰落Bloom Filter在传播过程中的多径叠加问题.DWalker采用多个Bloom Filter而不是单个Bloom Filter来表达一项路由条目,在单个Bloom Filter的错误发生概率达到设计上限时,可按需动态增加新的Bloom Filter,以将更多资源对象信息纳入到当前路由条目中.DWalker仅根据当前节点的各项路由条目中值为1的比特位所占的最大比例,以及查询消息在正确转发方向对应的路由条目中对应比特位中值为1的个数的临界值,就能使进入目标对象传播范围内的查询消息以较高的概率辨认出正确的路由方向.理论分析和实验结果表明,DWalker能够以较低的查询消息代价、较小的路由条目存储开销以及较短的查询时延,使绝大多数查询消息沿正确方向转发,从而获得较高的查准率.

领导-跟随混合阶异质多智能体系统的一致性

混合阶异质多智能体系统由静态领导者和一阶、二阶和三阶积分器型跟随者组成.首先,在无向和有向通讯网络条件下,利用设计线性滤波器的方法提出了一致性协议;其次,基于李雅普诺夫直接法、拉塞尔不变集原理和矩阵理论证明了协议的可行性;最后,通过2个仿真算例验证了所得结论的有效性.