A survey on freehand sketch recognition and retrieval

With the development of digital devices and pressure sensing equipment, research into freehand sketches from touch-screen interfaces has increased significantly in recent years. As such, we provide the first comprehensive survey of recognition tasks based on sketch generation, freehand sketch classification, sketch-based image retrieval (SBIR), fine-grained sketch-based image retrieval (FG-SBIR), and sketch-based 3D shape image retrieval. Specifically, SBIR and FG-SBIR were the main focus of the survey. Primary technologies and benchmark datasets related to all sketch-based recognition topics are also discussed, along with future trends for this promising technology.     

结合细粒度特征与深度卷积网络的手绘图检索

目的 传统的手绘图像检索方法主要集中在检索相同类别的图像，忽略了手绘图像的细粒度特征。对此，提出了一种新的结合细粒度特征与深度卷积网络的手绘图像检索方法，既注重通过深度跨域实现整体匹配，也实现细粒度细节匹配。方法 首先构建多通道混合卷积神经网络，对手绘图像和自然图像分别进行不同的处理；其次通过在网络中加入注意力模型来获取细粒度特征；最后将粗细特征融合，进行相似性度量，得到检索结果。结果 在不同的数据库上进行实验，与传统的尺度不变特征（SIFT）、方向梯度直方图（HOG）和深度手绘模型Deep SaN（sketch-a-net）、Deep 3DS（sketch）、Deep TSN（triplet sketch net）等5种基准方法进行比较，选取了Top-1和Top-10，在鞋子数据集上，本文方法Top-1正确率提升了12%，在椅子数据集上，本文方法Top-1正确率提升了11%，Top-10提升了3%，与传统的手绘检索方法相比，本文方法得到了更高的准确率。在实验中，本文方法通过手绘图像能在第1幅检索出绝大多数的目标图像，达到了实例级别手绘检索的目的。结论 提出了一种新的手绘图像检索方法，为手绘图像和自然图像的跨域检索提供了一种新思路，进行实例级别的手绘检索，与原有的方法相比，检索精度得到明显提升，证明了本文方法的可行性。     

基于可变形卷积的手绘图像检索

手绘图像仅包含简单线条轮廓, 与色彩、细节信息丰富的自然图像有着截然不同的特点. 然而目前的神经网络大多针对自然图像设计, 不能适应手绘图像稀疏性的特性. 针对此问题, 本文提出一种基于可变形卷积的手绘检索方法. 首先通过Berkerly边缘检测算法将自然图转化为边缘图, 消除域差异. 然后将卷积神经网络中的部分标准卷积替换为可变形卷积, 使网络能够充分关注手绘图轮廓信息. 最后分别将手绘图与边缘图输入网络并提取全连接层特征作为特征描述子进行检索. 在基准数据集Flickr15k上的实验结果表明, 本文方法与现有方法相比能够有效提高手绘图像检索精度.     

QoSPlan: A Measurement Based Quality of Service aware Network Planning Framework

In this article we present QoSPlan—a measurement based framework for preparing information relevant to Quality of Service (QoS)-aware IP network planning, which aims at reducing a core operational expenditure for the network operator. QoSPlan is designed to reduce the cost of deployment and maintenance of network monitoring systems. The process involves analysis of pre-existing accounting data to estimate a network-wide traffic matrix. Part of this estimation process relates to the generalization of QoS-related effective bandwidth coefficients taken from traffic analyzed on the network. We offer recommendations on how to appropriately realize QoSPlan to maximize its accuracy and effectiveness when applied to different network traffic scenarios. This is achieved through a thorough sensitivity analysis of the methods proposed using real traffic scenarios and indicative network topologies. We also provide an economic analysis of the deployment and maintenance costs associated with QoSPlan in comparison to a direct measurement approach, demonstrating cost savings of up to 60 % given different topology sizes.     

Sketch-based mesh cutting: A comparative study

In this paper we present the first comprehensive study and analysis on different sketch-based mesh cutting approaches. To compare a representative number of state-of-the-art sketch-based mesh cutting methods, we conduct a large scale user study which was carried out via extensive user experiments. To address the objective assessment of the performances of different algorithms, a complete framework with various intuitive sketch-based interfaces was developed to enable interactive mesh cutting by simply drawing sketches on mesh surface. To address the subjective assessment of user’s experience, we presented the analysis of the user’s responses, where the analytic hierarchy process was employed to quantify the performance of algorithms in terms of multiple criteria. Our results suggest that human in general agree on the evaluation of the performance of algorithms, and some sketch-based mesh cutting methods are consistently more favorable than others. The importance of our work lies in studying users’ experience on operating various sketch-based mesh cutting tools, to motivate more practical interactive systems in the future.     

基于自适应多类中心和半异构网络的三维模型草图检索

草图具有易于构建且不受语言、专业、年龄限制等优势,基于手绘草图的三维模型检索受到越来越多的关注.然而在三维模型草图检索任务中,三维模型具有复杂性,草图具有类内多样性,同时三维模型与草图之间又具有巨大的域间差异性,这些特点的相互作用严重影响检索的准确性.针对以上问题,提出了一种基于自适应多类中心和半异构网络的三维模型草图...     

Network traffic classification for data fusion: A survey

Traffic classification groups similar or related traffic data, which is one main stream technique of data fusion in the field of network management and security. With the rapid growth of network users and the emergence of new networking services, network traffic classification has attracted increasing attention. Many new traffic classification techniques have been developed and widely applied. However, the existing literature lacks a thorough survey to summarize, compare and analyze the recent advances of network traffic classification in order to deliver a holistic perspective. This paper carefully reviews existing network traffic classification methods from a new and comprehensive perspective by classifying them into five categories based on representative classification features, i.e., statistics-based classification, correlation-based classification, behavior-based classification, payload-based classification, and port-based classification. A series of criteria are proposed for the purpose of evaluating the performance of existing traffic classification methods. For each specified category, we analyze and discuss the details, advantages and disadvantages of its existing methods, and also present the traffic features commonly used. Summaries of investigation are offered for providing a holistic and specialized view on the state-of-art. For convenience, we also cover a discussion on the mostly used datasets and the traffic features adopted for traffic classification in the review. At the end, we identify a list of open issues and future directions in this research field.     

Context-aware garment modeling from sketches

Modeling of realistic garments is essential for creating believable virtual environments. Sketch-based modeling of garments presents an appealing, easy to use alternative to the established modeling approaches which are time consuming and require significant tailoring expertise. Unfortunately, the results created using existing sketch-based methods lack realism. Driven by human perception of garment sketches, we propose a context-aware garment sketch interpretation based on a set of observations about key factors that affect the shape of garments. Based on this analysis we develop a geometric method for sketch-based modeling of garments which obtains more realistic results than previous techniques. We demonstrate the effectiveness of our method on a variety of inputs and validate our approach via a user study where viewers were asked to compare the believability of our outputs versus previous ones.     

流量矩阵估算的研究

流量矩阵是许多网络规划和流量工程任务的关键输入,精确的流量矩阵至关重要,但直接监控非常具有挑战性.因此,如何根据对有限链路的测量数据和路由信息等先验信息,通过合理建模来推断流量矩阵,成为重要的研究课题.首先给出了流量矩阵的基本概念和估算原理;然后对近年来提出的20多种不同的解决流量矩阵估算问题的方法进行分类剖析,总结了目前流量矩阵估算方法的最新研究进展,并讨论了部分方法的性能和估算误差;最后讨论了未来流量矩阵估算的研究趋势和应用前景.     

Uncovering Global Icebergs in Distributed Streams: Results and Implications

Discovering icebergs in distributed streams of data is an important problem for a number of applications in networking and databases. While previous work has concentrated on measuring these icebergs in the non-distributed streaming case or in the non-streaming distributed case, we present a general framework that allows for distributed processing across multiple streams of data. We compare several of the state-of-the-art streaming algorithms for estimating local elephants in the individual streams. However, since an iceberg may be hidden by being distributed across many different streams, we add a sampling component to handle such cases. We provide a novel taxonomy of current sketches and perform a thorough analysis of the strengths and weaknesses of each scheme under various QoS metrics, using both real and synthetic Internet trace data. We summarize their performance and discuss the implications for the future design of sketches.     

草图交互式地质建模研究

提出一种简单、快捷的草图交互式地质建模方法,旨在帮助地质学家们在地质勘测初期直观、快速地创建无数据地质概念模型.迄今,现存专业地质建模工具依赖成本较高的真实数据创建精细复杂的三维地质模型,且通常具有建模用时长、不易于学习和使用等缺陷.因此,采用直观的“纸-笔”建模隐喻,提供了一套从草图绘制到三维模型创建,再到三维模型编辑的完整建模流程,允许用户在自由定义的绘图平面上绘制描述模型地质特征的三维草图,并对其构成的连通草图网络实时地进行三维模型重建.模型重建使用分治的思想,大致分为3个步骤完成：首先利用三维草图的几何信息,即拐点,根据其拓扑连接搜寻草图网络中近似平面的能量最小圈,然后通过调和函数计算草图网络中每个圈包围区域的目标平均曲率标量及其法线方向,随后以Laplacian方程优化生成曲面片,最后将曲面片拼接成完整的三维模型.褶皱、断层地质现象可以分别通过重绘和切割操作进行建模.此外,利用层级结构树存储地质模型间的层级关系,并通过变形传递的方式对与形变物体接触的地质模型进行形变,从而保持了地质结构中多物质体相互接触的特性.相比现有基于草图的交互式建模工具,该方法融合了地质学知识,且能够更有效地使用少量草图描述地质物体的特征.基于用户体验调查,该方法具有操作简单、建模直观的特点,能够同时满足专业和非专业人士快速创建地质概念模型的需求.     

A multiadaptive sampling technique for cost-effective network measurements

The deployment of efficient measurement solutions to assist network management tasks without interfering with normal network operation assumes a prominent role in today’s high-speed networks attending to the huge amounts of traffic involved. From a myriad of proposals for traffic measurement, sampling techniques are particularly relevant contributing effectively for this purpose as only a subset of the overall traffic volume is handled for processing, preserving ideally the correct estimation of network statistical behavior.     

An accurate estimation algorithm for big data streams

Sketch is a memory-efficient data structure, and is used to store and query the frequency of any item in a given multiset. As it can achieve fast query and update, it has been applied to various fields. Different sketches have different advantages and disadvantages. Sketches are originally proposed for estimation of flow size in network measurement. The key factor of sketches for network measurement is the insertion speed and accuracy. In this paper, we propose a new sketch, which can significantly improve the insertion speed while improving the accuracy. Our key methods include on-chip/off-chip separation and partial update algorithm. Extensive experimental results show that our sketch significantly outperforms the state-of-the-art both in terms of accuracy and speed.     

网络中突发业务自相似建模及其Hurst系数估计

提出了一种基于自回归AR模型的Hurst系数的估计方法，并给出了数学推导过程。采用真实网络突发业务的仿真结果表明，该文所提出的方法比传统的R／S法等估计方法具有更高的估计精度，能更好地反映真实网络业务流量的自相似性。该方法可望用于网络业务流量的管理和网络拥塞控制。     

一种基于分段测量的Internet端到端性能参数估计方法

传统的基于测量的Internet性能参数估计要求测量点是端到端路径的起点和终点,这一方面使得测量和估计带有很大盲目性,增加了网络流量;另一方面会导致测量方法难于实施,估计结果不准确。提出了基于分段测量的思想,对ITU-T定义的延迟、延迟变化、丢包率和错误率4个参数进行测量和估计。由于测量是分段进行的,每次测量值都可应用于多条端到端路径的性能参数估计,因此降低了盲目性并大大减少了网络流量。为验证本方法的性能,基于PlanetLab平台设计和实现了生成器、性能参数测量机和结果收集器。通过在全球的100多个节点上的部署和为期一个月的运行证明了该方法便于实施,并且具有较高的准确性。     

Self-similar cross-traffic analysis as a foundation for choosing among active available bandwidth measurement strategies

Among the many active, available bandwidth estimation tools and methods that have appeared recently in the literature, none has emerged that is accurate and robust enough to function in different networking environments. One of the main reasons for this problem is the highly variable statistical nature of network traffic. We present a novel theoretical method for active measurement strategy analysis through self-similar process sampling analysis. The results obtained show a relationship between the main parameters in the measurement procedure, such as the number of samples, sample length, and sample distance. The study suggests that accurate measurements require the use of many samples and thus long measurement procedures, sometimes on the order of several minutes, depending on the amount of cross traffic. Additionally, through the analysis of several existing Internet packet traces, we recommend that the minimum single sample probe stream length must be longer than the average cross traffic interarrival. Following these findings, we propose a new method for available bandwidth estimation that has shown significant accuracy under different network setups.     

Two triggered information transmission algorithms for distributed moving horizon state estimation

In this work, we consider the reduction of information transmission frequency of distributed moving horizon estimation (DMHE) for a class of nonlinear systems in which interacting subsystems exchange information with each other through a shared communication network. Specifically, algorithms based on two event-triggered methods are proposed to reduce the number of information transmissions between the subsystems in a DMHE scheme. In the first algorithm, a subsystem sends out its current information when a triggering condition based on the difference between the current state estimate and a previously transmitted one is satisfied; in the second algorithm, the transmission of information from a subsystem to other subsystems is triggered by the difference between the current measurement of the output and its derivatives and a previously transmitted measurement. In order to ensure the convergence and ultimate boundedness of the estimation error, we also propose to redesign the local moving horizon estimator of a subsystem to account for the possible lack of state updates from other subsystems explicitly. A chemical process is utilized to demonstrate the applicability and performance of the proposed approaches.     

On the Accuracy of Packet Delay Estimation in Distributed Service Networks

Packet delay (either one-way time or round-trip time) is a very important metric for measuring the performance of networks in a highly dynamic environment such as the Internet. Many network applications are also sensitive to packet delay or delay variation for ensuring an acceptable level of quality in providing network-based services such as VoIP, multimedia streaming, etc. A very important property of packet delay is that it is very dynamic and therefore should be measured frequently with measurement results being updated on a timely basis. Measurement of packet delay has thus generated a great deal of interest in the past years and a lot of research has been performed in the development of measurement architecture as well as specific measurement techniques. However, how to reduce network overhead resulting from measurement while achieving a reasonable level of accuracy still remains a challenge. In this paper, we propose to use delay estimation as an alternative to delay measurement for reducing measurement overhead and, in particular, examine the level of accuracy that delay estimation can achieve. With delay estimation, measurement nodes can be dynamically selected and activated and other nodes can share measurement results by performing delay estimation, thus reducing measurement overhead while supporting the dynamic requirement for delay measurement. Consequently, while measurement overhead can be reduced by activating only a subset of network nodes to perform actual measurement, desired accuracy can be achieved by exploring the correlation between delays as well as by sharing measurement results to do delay estimation based on such a correlation. We illustrate how packet delays of network nodes can correlate to each other based on topological properties and show how delays can be estimated based on such a correlation to meet accuracy requirements, which would make delay measurement in the Internet highly dynamic and adaptable to the accuracy requirements and measurement results highly reliable. We also show how delay estimation can be applied by presenting three application scenarios as well as an example to demonstrate the usefulness and effectiveness of delay estimation in the measurement of packet delays.     

Sketch-based warping of RGBN images

While current image deformation methods are careful in making the new geometry seem right, little attention has been given to the photometric aspects. We introduce a deformation method that results in coherently illuminated objects. For this task, we use RGBN images to support a relighting step integrated in a sketch-based deformation method. We warp not only colors but also normals. Normal warping requires smooth warping fields. We use sketches to specify sparse warping samples and impose additional constraints for region of interest control. To satisfy these new constraints, we present a novel image warping method based on Hermite–Birkhoff interpolation with radial basis functions that results in a smooth warping field. We also use sketches to help the system identify both lighting conditions and material from single images. We present results with RGBN images from different sources, including photometric stereo, synthetic images, and photographs.     

Real-time available-bandwidth estimation using filtering and change detection

This paper presents a filter-based method BART (Bandwidth Available in Real-Time) for real-time estimation of end-to-end available bandwidth in packet-switched communication networks. BART relies on self-induced congestion, and repeatedly samples the available bandwidth of the network path with sequences of probe-packet pairs. The method is light-weight with respect to computation and memory requirements, and performs well when only a small amount of probe traffic is injected. BART uses Kalman filtering, which enables real-time estimation. It maintains a current estimate, which is incrementally improved with each new measurement of the inter-packet time separation in a sequence of probe-packet pairs. It is possible to tune BART according to specific needs. The estimation performance can be significantly enhanced by employing a change-detection technique. An implementation of BART has been evaluated in a physical test network with carefully controlled cross traffic. In addition, experiments have been performed over the Internet as well as over a mobile broadband connection.