A generalized machine learning-based model for the detection of DDoS attacks

As time is progressing, the number and the complexity of methods adopted for launching distributed denial of service (DDoS) attacks are changing. Therefore, we propose a methodology for the development of a generalized machine learning (ML)-based model for the detection of DDoS attacks. After exploring various attributes of the dataset chosen for this study, we propose an integrated feature selection (IFS) method which consists of three stages and integration of two different methods, that is, filter and embedded methods to select features which highly contribute to the detection of various types of DDoS attacks. We use light gradient boosting machine (LGBM) algorithm for training of the model for classification of benign and malicious flows. For ensuring satisfactory performance and generalized behavior of the developed model, we test it by passing records of unseen DDoS attack types. Several performance metrics are employed for the evaluation of the model. By comparing the performance of developed model against state-of-the-art models, we state an improvement of around 20% for almost all the reported metrics. We also show that the performance of the model improves if feature space is reduced by 77%. Furthermore, the generalized behavior of the developed model is justified by demonstrating a trade-off between high variance and high bias ML models.     

A generalized two-threshold detection procedure

A modified sequential procedure for testing binary hypotheses with different means, proposed by C.C. Lee and J.B. Thomas (ibid., vol.IT-30, no.1, p.16-23, Jan. 1984), is generalized for application to the case of multiple hypotheses with different means/variances of the Gaussian distribution. The method constitutes a two-threshold test for fixed-size packages of samples with a sequential procedure of discarding the package for which no decision is reached and subsequently testing a new package. The objective is to find an optimum package size N₀ which leads to the minimum overall average sample number (ASN) for a given overall error probability. An optimization algorithm is developed to extend the application of the Lee-Thomas procedure to the M-ary case. Performance characteristics of the generalized two-threshold (GTT) test procedure are compared with those of conventional sequential as well as fixed-sample-size (FSS) methods. It is shown for the M-ary different means/variances cases that for low error rates the number of samples required by the GTT test is, on the average, approximately half that needed by a FSS test. However, it is somewhat more than the ASN obtained with a conventional sequential test. With decreasing error probabilities the GTT test performance approaches that of conventional sequential methods     

A generalized Gaussian image model for edge-preserving MAPestimation

The authors present a Markov random field model which allows realistic edge modeling while providing stable maximum a posterior (MAP) solutions. The model, referred to as a generalized Gaussian Markov random field (GGMRF), is named for its similarity to the generalized Gaussian distribution used in robust detection and estimation. The model satisfies several desirable analytical and computational properties for map estimation, including continuous dependence of the estimate on the data, invariance of the character of solutions to scaling of data, and a solution which lies at the unique global minimum of the a posteriori log-likelihood function. The GGMRF is demonstrated to be useful for image reconstruction in low-dosage transmission tomography.     

广义空间调制系统的低复杂度检测算法

针对广义空间调制( GSM)系统接收端最大似然( ML)检测算法计算复杂度极高的缺点,提出了一种基于压缩感知( CS)信号重构理论的低复杂度信号检测算法。首先,在多输入多输出( MI-MO)信道模型下,通过改进正交匹配追踪( OMP)算法,得到一个激活天线索引备选集;然后,利用ML算法在该备选集中进行遍历搜索,检测出激活天线索引和星座调制符号。仿真结果表明所提算法的检测性能接近于ML算法,且复杂度约为ML算法的2%。因此,所提算法在保证检测性能的同时也大大降低了计算复杂度,实现了检测性能与复杂度之间的平衡。     

广义空间调制系统的正则化OMP检测算法

在广义空间调制（GSM）系统中,最大似然（ML）检测可以取得最优的检测性能,然而其计算复杂度随激活天线数的增加急剧增长。针对这一问题,提出了一种基于稀疏重构理论的低复杂度检测算法——正则化正交匹配追踪（ROMP）算法。该算法首先根据信道矩阵和当前残差的内积选取多个候选激活天线索引,接着对候选天线索引按正则化标准进行可靠性验证,剔除错误索引,缩小信号的搜索空间,最后通过求解最小二乘问题估计信号。仿真结果表明,与经典的正交匹配追踪（OMP）算法相比,所提算法以少许复杂度的增加为代价极大提升了检测性能,能够在检测性能与复杂度之间取得更好的折中。     

列车车轮踏面擦伤动态检测系统研究

列车车轮踏面擦伤在列车行进中带来额外的冲击荷载,严重影响列车与轨道设施的安全与使用寿命。在综合分析了国内外常用车轮踏面擦伤动态检测系统原理的基础上,介绍了基于激光器-PSD位置传感器方式的光学式踏面擦伤检测方法,并设计了相关的检测系统,同时利用Matlab对实验相关数据进行低通滤波、荷载值转换、阈值比较等处理,得到了车轮擦伤的情况。     

A generalized dynamical model for three-phase switch-mode converter circuits

Advances in power electronics and high-performance electrical technology are driving a move toward switch-mode circuits for AC-DC conversion. The efficient control of these circuits is an ongoing research challenge, and to date has focussed on the more popular voltage-driven converter. This paper presents a model applicable to the study and control of generic three-phase switch-mode converters (voltage and current-driven), under the widest possible range of switching scenarios. The model permits a generalization of the "space vector" framework, and makes possible a three-tiered approach to control in which AC-side, DC-side and low-level switching control tasks are decoupled from one another.     

A generalized analytical model for the quantum well injectiontransit time diode

A generalized small-signal model of the quantum well injection transit time (QWITT) diode derived from the authors' previous large-signal model (see. ibid., vol.35, p.2315-2322, Dec. 1987), which includes not only the carrier space-charge effects but also the velocity transient effects and the carrier diffusion effects is presented. Simple closed forms for the device impedance have been obtained for efficient computation, where only one-dimensional integrations are required. It can be applied to any fashion of time dependence of the velocity transient and diffusivity transient, adopting a Gaussian form for the spatial profile of injected carriers. Using the formulas, the small-signal behavior and the design criteria for the QWITT diode are analyzed. Large-signal impedance of the device can also be estimated by the formulas     

基于FPGA与DSP的车轮踏面擦伤系统的研究

为了实时监测高速列车的安全性,介绍了基于FPGA和DSP的多通道数据采集系统,该系统利用安装在钢轨上的加速度传感器采集列车在行进过程中踏面与钢轨产生的振动信号,并利用Xilinx公司FPGA芯片SP3xc3s1000和TI公司的TMS320C6713的DSP芯片作为核心控制模块,实现对振动的信号采集和传输,并对现场采集到的数据进行处理和分析。经过现场实验的结果表明,本系统能够准确检测出有擦伤的车轮,有效地保障了列车的安全运行。     

A fuzzy model for path delay fault detection

A fuzzy model is proposed to analyze the effectiveness of test pairs targeting path delay faults. This model is accurate enough to rank nonrobust tests by accounting for conditions not considered in existing models. It remains fully consistent with the traditional test robustness analysis. Finally, it also provides a coverage metric to be used to rank whole test sets. The proposed model has been implemented in a logic level path delay fault simulator. Its accuracy has been validated, for a set of combinational benchmarks, by means of a Monte Carlo logic-level event-driven path delay fault simulator.     

A generalized model for Kalman filtering of motion information in video compression

In this paper, we tackle the problem of motion estimation in video compression. Since Full Search Algorithms (FSA) present the disadvantage of adding a high computational burden to the encoder, fast search techniques have been used in conjunction with predictive filtering, in such a way to guarantee an acceptable quality with an affordable complexity. The aim of this work is to propose a novel framework for Kalman filtering of motion information in compressed video sequences. The merits of our new framework are twofold: First, using an appropriate formulation of the system equations, several shortcomings inherent with former models in the literature are greatly counteracted. Secondly, it is constructed using a generalized structure in such a way to enclose a large variety of prediction models. Therefore, it can adapt to different types of motion activities in video sequences, without the need for a different formulation in each prediction model, as was the case in previous studies. Furthermore, we propose an adaptive motion compensation technique that permits an additional improvement to the decoded video quality. Our framework permits a considerable gain in the average performance compared to previous models and even to the FSA technique.     

A generalized model for coupled lines and its applications totwo-layer planar circuits

A generalized network model for asymmetrical and inhomogeneous coupled lines has been derived based on normal mode parameters. This model is useful for synthesis of single and multilayer coupled-line circuits, such as planar baluns and directional couplers. The synthesis procedures are described and have been verified by comparing with analysis results     

An algorithm for the design of generalized quantizers for detection

A procedure based on the generalized Lloyd algorithm approach using a sequence of independent noise samples to design M-region generalized quantizers for signal detection is presented. Included in this case are the conventional M-interval quantizer detectors. The quantizer parameters for S.A. Kassam's (1985) four-region generalized quantizer detector are computed using various sample sizes for the known sequence of independent noise samples. Two families of densities which cover a wide spectrum of possible nonGaussian densities are considered: the generalized Gaussian densities and the Johnson S_u family of densities. The performance of the quantizer detector is compared to that of the locally optimum detector, and the results are presented as the asymptotic relative efficiencies of the respective detectors. The case when the noise density is not known before analysis is considered, and the detection performance is examined using an estimate of the density. A mean-squared-error distortion criterion is used in the proposed algorithm to obtain quantizers that yield maximum efficacy. It is shown through numerical examples that the design procedure is simple, fast, and applicable to a wide range of nonGaussian distributions     

一种基于MIMO-FSO的最大似然盲检测算法

在多天线自由空间无线光通信(MIMO-FSO)系统中,提出一种基于通用最大似然的序列(MLSD)盲检测算法,使用等增益合并(EGC)获得MIMO空间分集,研究了大气湍流衰落信道不同强度条件下算法的性能。此外,针对MLSD在较长序列长度下的高复杂度,提出一种次优的快速搜寻算法。蒙特卡洛仿真结果显示,所提出的接收机模型在MIMO-FSO系统中,能够获得空间分集,在不同信道条件、中等序列长度条件下,得到接近最优检测的性能。     

一种改进的火灾颜色模型检测算法

从火焰的颜色特征出发,综合考虑已有颜色模型的优缺点,提出一种改进的基于颜色模型的火灾检测方法.首先结合HSI颜色模型和YCbCr颜色模型对火灾图像进行预处理提取出可能火焰区域,然后在HSI空间上采用颜色空间距离法去除噪声.实验结果表明,该方法提高了火灾图像识别的准确度,并能在一定程度上消除干扰,具有较好的适用性.     

A generalized logarithmic image processing model based on the gigavision sensor model

The logarithmic image processing (LIP) model is a mathematical theory providing generalized linear operations for image processing. The gigavision sensor (GVS) is a new imaging device that can be described by a statistical model. In this paper, by studying these two seemingly unrelated models, we develop a generalized LIP (GLIP) model. With the LIP model being its special case, the GLIP model not only provides new insights into the LIP model but also defines new image representations and operations for solving general image processing problems that are not necessarily related to the GVS. A new parametric LIP model is also developed. To illustrate the application of the new scalar multiplication operation, we propose an energy-preserving algorithm for tone mapping, which is a necessary step in image dehazing. By comparing with results using two state-of-the-art algorithms, we show that the new scalar multiplication operation is an effective tool for tone mapping.     

A new model of generalized invertor and its applications

A new model of generalized invertor is presented, The model is generalized from the conventional K-, J-invertor. So it is easy to be applied directly to design microwave circuits such as impedance transformers, filters, and couplers of any complex discontinuities, when the symmetrical and asymmetrical networks are involved. The theory based on the new model is developed to enrich the microwave theory on network synthesis. Examples are given to show the effectiveness and convenience in application     

A generalized ionic model of the neuronal membrane electricalactivity

A new ionic model of the neuronal-membrane electrical activity has been developed. The proposed model generalizes those usually quoted in the literature, taking into account the significant ionic currents, the temperature dependence of the electrical parameters, and the stochastic synaptic inputs. The model allows the authors to simulate both the membrane firing activity, as a function of the temperature, and the membrane resistance behavior, as a function of temperature and of intracellular calcium concentration. The I-V nonlinear characteristic, together with histograms and correlograms of the time intervals between spikes, have been numerically reproduced. Various comparisons the authors have carried out with available experimental data show a good theoretical-experimental agreement     

A generalized surveillance model with applications to systems safety

This paper presents a generalized surveillance model for predicting the performance of complex systems consisting of many subsystems (units). These subsystems are frequently inspected to keep the entire system operating satisfactorily. Systems of this type are encountered in many areas, including nuclear power plant, national defense system, transportation stations, medical monitoring control rooms, etc. The particular application that motivated a development of this model is an FAA project, where we were asked to develop a surveillance model to better understand both the inspection process and the repair station itself and to provide information that can be used to assist inspectors in scheduling and prioritizing their visits to the stations. A distinguishing feature of this surveillance model is that it combines two mutually dependent stochastic processes. One is a two-stage stochastic process for the occurrence of unfavorable condition in an individual subsystem and the other is a nonhomogeneous Poisson process for the frequency of surveillance.     

采用相位判决的低复杂度广义空间调制检测算法

针对广义空间调制(GSM)系统中信号检测复杂度过高的问题,提出了一种基于相位判决的低复杂度检测算法.首先根据一种排序准则对天线组合进行排序,然后将排序后的天线组合中的符号向量依次通过基于相位判决的迫零(ZF)均衡器进行检测,最终得到星座调制符号和激活天线组合.分析和仿真结果表明,该检测算法可以有效缩小接收端的搜索范围,在提供与最大似然(ML)检测算法相近的误比特率(BER)性能的同时,计算复杂度降低了98％.