A hybrid model of the Akamai adaptive streaming control system

Video streaming is the application generating the largest fraction of the Internet traffic. Adaptive video streaming adds to classic video streaming the possibility of dynamically adapting the video bitrate to track the time-varying network available bandwidth, avoid playback interruptions and ensure the delivery of the best video quality. This work focuses on the adaptive video streaming control system employed by Akamai, a major Content Delivery Network operator whose video delivery system is used by several video streaming platforms, including Livestream. Differently from the typical client-side control, Akamai employs an interesting and unique hybrid client/server control architecture. In this paper we propose and experimentally validate a closed loop mathematical model of the control system in the form of a hybrid automaton. The model is analyzed to derive key properties which can be used to properly tune the controller parameters.     

End-to-end QoS issues of MPEG-4 FGS video streaming traffic delivery in an IP/DVB/UMTS network

The paper addresses the end-to-end QoS problem of MPEG-4 FGS video streaming traffic delivery over a heterogeneous IP/DVB/UMTS network. It proposes and validates an architecture that explores the joint use of packet prioritization and scalable video coding together with the appropriate mapping of UMTS traffic classes to the DiffServ traffic classes. A set of experimental scenarios, involving eight different video sequences, demonstrates the quality gains of both scalable video coding and prioritized packetization.     

A robust P2P streaming architecture and its application to a high quality live-video service

This paper explores the design of a P2P architecture that sends real-time video over the Internet. The aim is to provide good quality levels in a highly dynamic P2P topology, where the frequent connections/disconnections of the nodes makes it difficult to offer the Quality-of-Experience (QoE) needed by the client.We study a multi-source streaming approach where the stream is decomposed into several flows sent by different peers to each client including some level of redundancy, in order to cope with the fluctuations in network connectivity. We employ the recently proposed PSQA technology for evaluating automatically the perceived quality at the client side. We introduce a mathematical programming model to maximize the global expected QoE of the network (evaluated using PSQA), selecting a P2P connection scheme which enhances topology robustness. In addition, we provide an approximated algorithm to solve the proposed model, and we apply it to solve a case study based on real life data.     

Mobile WiMAX MAC and PHY layer optimization for IPTV

WiMAX (Worldwide Interoperability for Microwave Access) embodies the IEEE 802.16 family of standards that provision wireless broadband access. With the IEEE 802.16e?2005 mobility amendment, WiMAX promises to address the ever-increasing demand for mobile high speed wireless data in fourth-generation (4G) networks. WiMAX market studies continue to project increased subscriber growth rates and planned carrier trials worldwide. Coupled with these increasing growth rates and higher WiMAX throughput rates, bandwidth intensive video on demand (VoD), Internet Protocol TV (IPTV), and mobile TV services are emerging in the forefront of the mobile arena.In this paper, we explore and derive optimum system level WiMAX parameters by quantifying network performance using such video-rich services. The video traffic will sufficiently load and stress the network to exploit the potential bandwidth, delay, and mobility limitations. We use the OPNET Modeler to engineer simulation sequences and explore the impact of channel bandwidth, time division duplex (TDD) frame size, advanced antenna systems support, and retransmission schemes using four objective performance metrics while streaming a feature-length movie to a Mobile WiMAX subscriber. The objective of this paper is to provide greater insight into Mobile WiMAX system performance using emerging, load intensive and delay sensitive media streaming services.     

Buffer storage for continuous delivery of video data

The video communication requires considerable large bandwidth – a scarce resource and thus it needs be used efficiently. It can be traded for buffer storage, i.e. for maintaining more buffer storage the data downloading rate (bandwidth) can be reduced. In order to transmitting the videos, they are divided into segments and the bandwidth of the physical channel is divided into logical channels. A logical channel transmits only one segment of each video. When there is switching of the segments, some time delay, called jitter delay, occurs. The jitter delay, being independent, memoryless, and positive, can be modeled as exponentially distributed random variable. In this paper, we propose a stochastic model incorporating jitter delay for estimating the storage space required in the user’s system in order to maintain continuous delivery of the video data to the users.     

Mathematical Analysis of caching policies and cooperation in YouTube-like services

Currently, most video on-demand services offered over the Internet do not exploit the idle resources available from end-users. We discuss the benefits of user-assistance in video on-demand systems, where users are both clients and servers, helping with the task of video distribution. The mathematical machinery for the systematic analysis of video on-demand services is not mature yet. In this paper we develop a deterministic fluid model to determine the expected evolution of user-assisted on-demand video streaming services. We theoretically prove that cooperative systems always outperform non-cooperative solutions. A combinatorial optimization problem is proposed, where the goal is to distribute a set of video items into repositories trying to offer the minimum waiting times to end-users. This combinatorial problem is proved to be in the class of NP-Complete computational problem, and is heuristically solved with a GRASP methodology. Predictions inspired in YouTube scenarios suggest the introduction of cooperation is both robust and extremely attractive from an economical viewpoint as well.     

Approximate reasoning and finite state machines to the detection of actions in video sequences

In this paper a novel approach for recognizing actions in video sequences is presented, where the information obtained from the segmentation and tracking algorithms is used as input data. First of all, the fuzzification of input data is done and this process allows to successfully manage the uncertainty inherent to the information obtained from low-level and medium-level vision tasks, to unify the information obtained from different vision algorithms into a homogeneous representation and to aggregate the characteristics of the analyzed scenario and the objects in motion. Another contribution is the novelty of representing actions by means of an automaton and the generation of input symbols for the finite automaton depending on the comparison process between objects and actions, i.e., the main reasoning process is based on the operation of automata with capability to manage fuzzy representations of all video data. The experiments on several real traffic video sequences demonstrate encouraging results, especially when no training algorithms to obtain predefined actions to be identified are required.     

儿童额叶癫痫临床和长程视频脑电图特征

目的通过对46例儿童额叶癫痫患儿的临床表现、长程视频脑电图（VEEG）特点进行分析,提高对儿童额叶癫痫的认识。方法收集2008年12月至2014年8月儿科门诊及住院确诊的46例儿童额叶癫痫病例的资料,回顾性分析其临床表现、VEEG及神经影像学等特征。结果本组患儿发病年龄最小11个月,最大15岁。46例患儿共监测到临床发作258次,明确临床发作34例,14.7%仅于清醒期发作,61.8%仅在睡眠期发作,23.5%在清醒、睡眠中均有发作;临床发作形式包括额叶失神、局部阵挛发作、偏转性强直、姿势性强直、过度运动性自动症、口咽自动症、发声、发笑发作、临床下放电和自主神经性发作等。73.9%患儿记录到发作间期额叶为主的癫痫样放电,63.0%患儿记录到发作期额叶为主的癫痫样放电。结论儿童额叶癫痫临床发作频繁、短暂,以睡眠期发作为主,临床表现复杂多样,易漏诊;长程VEEG可监测到儿童额叶癫痫发作期临床及异常脑电图表现,可提供明确诊断率。     

A discrete wavelet transform and singular value decomposition-based digital video watermark method

Digital video watermark is widely used to protect copyright and content authentication. DWT-SVD based method, i.e., discrete wavelet transform (DWT) and singular value decomposition (SVD) based method, is one of the most popular state-of-the-art methods. There are two main criteria to evaluate it, i.e., imperceptibility and robustness. The former is measured via the peak signal to noise ratio (PSNR) and structural similarity (SSIM). They should be as high as possible after the watermark is embedded. Robustness measures how easy to restore the embedded watermark by the owner even if the watermarked video is damaged by an outside attacker. Current studies randomly choose embedded positions for watermark, which hardly achieves its highest imperceptibility and robustness. In this paper, we propose a more imperceptible and robust digital video watermarking method than the existing one. First, we introduce a method to measure video frame distortion in a wavelet transform domain. Second, we model the problem to achieve the minimum video frame distortion as an optimization problem, i.e., choose embedded positions that can maximize peak signal to noise ratio. Finally, we evaluate and compare our method with the state-of-the-art approaches by using real experiments and show its advantages in both imperceptibility and robustness.     

Measuring interaction quality in mathematics instruction: How differences in operationalizations matter methodologically

Quality of interaction can enhance or constrain students’ mathematical learning opportunities. However, quantitative video studies have measured the quality of interaction with very heterogeneous conceptualizations and operationalizations. This project sought to disentangle typical methodological choices to assess interaction quality in six quality dimensions, each of them in task-based, move-based, and practice-based operationalizations. The empirical part of the study compared different conceptualizations with their corresponding operationalizations and used them to code video data from middle school students (n = 210) organized into 49 small groups who worked on the same curriculum materials. The analysis revealed that different conceptualizations and operationalizations led to substantially different findings, so their distinction turned out to be of high methodological relevance. These results highlight the importance of making methodological choices explicit and call for a stronger academic discourse on how to conceptualize and operationalize interaction quality in video studies.     

Steady streaming around a spherical drop displaced from the velocity antinode in an acoustic levitation field

The steady (acoustic) streaming associated with a sphericaldrop displaced from the velocity antinode of a standing waveis studied. The ratio of the particle size to the acoustic wavelengthis treated as small but non-zero, and the solution is developedin the form of a two-term expansion in terms of the correspondingsmallness parameter. The drop viscosity is assumed to be muchhigher than that of the surrounding fluid, which is the casefor a drop in a gas medium. There are essentially three distinctregions where the steady streaming flow is analysed: insidethe drop (internal circulation), in the Stokes shear-wave layerat the surface on the gas side, and the gas outside the Stokeslayer (the outer streaming region). Solutions for the internalcirculation and the outer streaming are obtained in the limitof small Reynolds number. Despite the gas-to-liquid viscosity ratio being small, the outerstreaming may be dramatically affected by the fact that thesphere is liquid as opposed to solid. The parameter that measuresthe effect of liquidity is essentially the viscosity ratio dividedby the relative (to the particle size) thickness of the Stokeslayer. The case of a solid sphere is recovered by letting thisparameter go to zero.     

Playing with Representations: How Do Kids Make Use of Quantitative Representations in Video Games?

This paper describes the use of quantities in video games by young people as part of a broader effort to understand thinking and learning across naturally occurring contexts of activity. Our approach to investigating the use of quantities in game play is ethnographic; we have followed eight children over a six-month period as they play their own games at home. The data set is composed of video recordings and artifact-based interviews. The concept of disciplined perception is used to understand how quantities are coordinated during game play. The current study shows young people using quantities in games to make predictions and organize their actions based on those predictions. Some ideas based on the study’s findings for using video games in school are discussed.

Belief Scheduler based on model failure detection in the TBM framework. Application to human activity recognition

A tool called Belief Scheduler is proposed for state sequence recognition in the Transferable Belief Model (TBM) framework. This tool makes noisy temporal belief functions smoother using a Temporal Evidential Filter (TEF). The Belief Scheduler makes belief on states smoother, separates the states (assumed to be true or false) and synchronizes them in order to infer the sequence. A criterion is also provided to assess the appropriateness between observed belief functions and a given sequence model. This criterion is based on the conflict information appearing explicitly in the TBM when combining observed belief functions with predictions. The Belief Scheduler is part of a generic architecture developed for on-line and automatic human action and activity recognition in videos of athletics taken with a moving camera. In experiments, the system is assessed on a database composed of 69 real athletics video sequences. The goal is to automatically recognize running, jumping, falling and standing-up actions as well as high jump, pole vault, triple jump and long jump activities of an athlete. A comparison with Hidden Markov Models for video classification is also provided.     

Hydromagnetic instability of two coaxial streaming cylinders with double perturbed interfaces

The magnetohydrodynamic (MHD) stability of a double interface perturbed streaming liquid cylinder coaxial with a streaming fluid mantle acting upon capillary, inertial, pressure gradient and electromagnetic forces has been developed. The problem is formulated, solved and the stability criterion of the model is estabilished. The latter is discussed analytically and the results are confirmed numerically and interpreted physically. Some reported works are recovered as limiting cases. The capillary force is stabilizing or not according to restrictions. The magnetic field has a strong stabilizing influence. The radii (liquid–fluid) ratio plays an important role in increasing the MHD stabilizing domains. The density of liquid–fluid ratio has a little stabilizing effect. The streaming has a destabilizing influence for all kinds of (non-) axisymmetric perturbation modes. However, if the magnetic field strength is so strong such that the Alfvén wave velocity is greater than the streaming velocity, then the destabilizing character due to capillary force or/and streaming is completely suppressed and stability sets in. In the absence of the magnetic field and we neglect the fluid inertial force, the present results are in good agreement with the experimental results of (Kendall J.M. Phys Fluids 1986;29:2086).     

A Lagrangean relaxation and decomposition algorithm for the video placement and routing problem

Video on demand (VoD) is a technology used to provide a number of programs to a number of users on request. In developing a VoD system, a fundamental problem is load balancing, which is further characterized by optimally placing videos to a number of predefined servers and routing the user program requests to available resources. In this paper, an exact solution algorithm is described to solve the video placement and routing problem. The algorithm is based on Lagrangean relaxation and decomposition. The novelty of the approach can be described as the use of integer programs to obtain feasible solutions in the algorithm. Computational experimentation reveals that for randomly generated problems with up to 100 nodes and 250 videos, the use of such integer programs help greatly in obtaining good quality solutions (typically within 5% of the optimal solution), even in the very early iterations of the algorithm.     

Could cell membranes produce acoustic streaming? Making the case for Synechococcus self-propulsion

Sir James Lighthill proposed in 1992 that acoustic streaming (AS) within the mammalian cochlea could play a role in the transmission of acoustic signals to the auditory sensory cells. Microelectromechanical devices for mixing and pumping, based on the acoustic streaming effect were introduced in the mid 1990s. Nature may have preceded this invention by 2.7 Gyr. We believe that acoustic streaming produced by nanometer scale membrane vibrations is widespread in cell biology. Flows generated by acoustic streaming could be produced along the “raphes” (central channels) of silica coated diatoms. Other possible instances are yeast cells and erythrocytes whose membranes generate nanoscale vibrations. We hypothesize that some of the most ancient organisms use acoustic streaming not only for self-propulsion but also to enhance their nutrient uptake. In this paper we focus on a motile strain of Synechococcus, a cyanobacterium whose mechanism for self-propulsion is not known. The calculations presented here show that a traveling surface acoustic wave (SAW) could account for the observed velocities. These SAWs would also produce a non-negligible Stokes layer surrounding the cell, motion within this region being essentially chaotic. Therefore, an AS mechanism would be biologically advantageous, enhancing localized diffusion processes and consequently, chemical reactions. Finally, we discuss possible experiments to support (or rule out) the AS model vs. other contending explanations for Synechococcus locomotion.     

Behavioral event detection and rate estimation for autonomous vehicle evaluation

Autonomous vehicles are continually increasing their presence on public roads. However, before any new autonomous driving software can be approved, it must first undergo a rigorous assessment of driving quality. These quality evaluations typically focus on estimating the frequency of (undesirable) behavioral events. While rate estimation would be straight-forward with complete data, in the autonomous driving setting this estimation is greatly complicated by the fact that detecting these events within large driving logs is a non-trivial task that often involves human reviewers. In this article, we outline a streaming partial tiered event review configuration that ensures both high recall and high precision on the events of interest. In addition, the framework allows for valid streaming estimates at any phase of the data collection process, even when labels are incomplete, for which we develop the maximum likelihood estimate and show it is unbiased. Constructing honest and effective confidence intervals (CI) for these rate estimates, particularly for rare safety-critical events, is a novel and challenging statistical problem due to the complexity of the data likelihood. We develop and compare several CI approximations, including a novel gamma CI method that approximates the exact but intractable distribution with a weighted sum of independent Poisson random variables. There is a clear trade-off between statistical coverage and interval width across the different CI methods, and the extent of this trade-off varies depending on the specific application settings (e.g., rare vs. common events). In particular, we argue that our proposed CI method is the best-suited when estimating the rate of safety-critical events where guaranteed coverage of the true parameter value is a prerequisite to safely launching a new ADS on public roads.     

基于体系工程与物流均衡的C2M服务制造物流体系结构模型

C2M服务制造是基于以顾客为中心的C2M(Customer to Manufacture)商业模式,是在服务型制造及生产性服务业为基础上而形成的一种新型产业模式。C2M服务制造要求构建合理的物流体系,而构建物流体系结构已经成为该研究的关键基础。本文基于体系工程和物流均衡理论,通过建立物流体系以解决C(客户)端与M(制造)端的短链式互联问题,在分析C2M服务制造物流体系特征和资源要素的基础上,给出了C2M服务制造物流体系的概念模型和结构模型,并运用价值函数分析体系状态是否优化,从而达到C端与M端快速互联的目标,进而解决了物流体系结构模型在C2M服务制造物流体系构建中的应用问题。     

Multivariable identification and controller design of an integrated flight control system

This paper investigates the multivariable identification and controller design for the longitudinal channel of a Boeing 747 transport. The transfer function matrix of the system is identified using the prediction error (PE) identification method with multivariable ARX model. An ellipsoidal parametric uncertainty set is constructed from the covariance matrix of the identified parameters. It contains the parameters of actual system at a certain probability level. The identified models and the associated uncertainty sets are validated by measuring the worst-case ν-gap and then compared with the maximum value of the generalized stability margin. In automatic flight control system or autopilots, multiple specifications criteria are needed to be satisfied concurrently, such as good holding (small static altitude holding error), fast response, smooth transition (less oscillation, overshoot). The design of a Multiple Simultaneous Specifications (MSS) controller effectively and practically is a very significant and challenging job. Liu and Mills [H.H.T. Liu, J.K. Mills, Multiple specification design in flight control system, in: Proceedings of the American Control Conference, Chicago, Illinois, 2000, pp. 1365–1369] proposed a MSS controller design method using a convex combination approach. In this paper, we apply the method [H.H.T. Liu, J.K. Mills, Multiple specification design in flight control system, in: Proceedings of the American Control Conference, Chicago, Illinois, 2000, pp. 1365–1369; H.H.T. Liu, Design combination in integrated flight control, in: Proceedings of the American Control Conference, Arlington, Virginia, 2001, pp. 494–499; H.H.T. Liu, Multi-objective design for an integrated flight control system: a combination with model reduction approach, in: Proceedings of IEEE International Symposium on Computer Aided Control System Design, Glasgow, 2002, pp. 21–26] to design a MSS controller based on the identified models of the Boeing 747 transport aircraft longitudinal channel. The controllers are also validated by simulation using the true plant transfer functions.     

Parallel Synchronous and Asynchronous Space-Decomposition Algorithms for Large-Scale Minimization Problems

Three parallel space-decomposition minimization (PSDM) algorithms, based on the parallel variable transformation (PVT) and the parallel gradient distribution (PGD) algorithms (O.L. Mangasarian, SIMA Journal on Control and Optimization, vol. 33, no. 6, pp. 1916–1925.), are presented for solving convex or nonconvex unconstrained minimization problems. The PSDM algorithms decompose the variable space into subspaces and distribute these decomposed subproblems among parallel processors. It is shown that if all decomposed subproblems are uncoupled of each other, they can be solved independently. Otherwise, the parallel algorithms presented in this paper can be used. Numerical experiments show that these parallel algorithms can save processor time, particularly for medium and large-scale problems. Up to six parallel processors are connected by Ethernet networks to solve four large-scale minimization problems. The results are compared with those obtained by using sequential algorithms run on a single processor. An application of the PSDM algorithms to the training of multilayer Adaptive Linear Neurons (Madaline) and a new parallel architecture for such parallel training are also presented.