分布式计算中BC复合客户端的设计与实现

在网络环境下,客户端指三层构架（表示层、业务层和数据层）中的表示层,它可分别用Browser或Client两种方式提供。本文论述了当前广为流行的MVC客户端设计模式,然后介绍实现客户端所涉及的功能性及非功能性需求,将Browser和Client两种客户端模式进行比较,提出在一些应用场合二者融合的必然性,并将二者的融合应用到一个实际的系统中,结果表明所提出的融合模式是有效而实用的。     

Render2MPEG: A Perception-based Framework Towards Integrating Rendering and Video Compression

Currently 3D animation rendering and video compression are completely independent processes even if rendered frames are streamed on‐the‐fly within a client‐server platform. In such scenario, which may involve time‐varying transmission bandwidths and different display characteristics at the client side, dynamic adjustment of the rendering quality to such requirements can lead to a better use of server resources. In this work, we present a framework where the renderer and MPEG codec are coupled through a straightforward interface that provides precise motion vectors from the rendering side to the codec and perceptual error thresholds for each pixel in the opposite direction. The perceptual error thresholds take into account bandwidth‐dependent quantization errors resulting from the lossy com‐pression as well as image content‐dependent luminance and spatial contrast masking. The availability of the discrete cosine transform (DCT) coefficients at the codec side enables to use advanced models of the human visual system (HVS) in the perceptual error threshold derivation without incurring any significant cost. Those error thresholds are then used to control the rendering quality and make it well aligned with the compressed stream quality. In our prototype system we use the lightcuts technique developed by Walter et al., which we enhance to handle dynamic image sequences, and an MPEG‐2 implementation. Our results clearly demonstrate many advantages of coupling the rendering with video compression in terms of faster rendering. Furthermore, temporally coherent rendering leads to a reduction of temporal artifacts.     

Multimedia presentation organization and playout management using intelligent agents

This paper presents a model for organization, computation and management of automated multimedia presentations based on active multimedia segments retrieved from a multimedia information system as well as the Web. Existing multimedia presentation system is extended in such a way that its content selection component spans from local data resources to the entire Web by use of intelligent agents which associates related multimedia segments. We describe a multimedia presentation authoring environment in which a new heuristic method is introduced based on the multimedia resources selected and organization operators to apply. This method is used for the construction of a presentation graph representing an organized presentation. Once the presentation graph is constructed, we show how to obtain an event-point representation of the presentation graph. Based on event-point representation, three methods are given for playing out the constructed presentations at the presentation terminal. Presentation environments of the end-users are modeled as (i) without any constraint, (ii) with a single constraint, and (iii) with multiple constraints (one constraint for each type of multimedia segments in the organized presentation). In accordance with these limitations (i.e., without violating any of the end-user specified constraints), three methods play out any organized presentation.     

Internet-Based Robotic System Using CORBA as Communication Architecture

In this paper, we propose the Internet-based robotic system that uses Common Object Request Broker Architecture (CORBA) to implement networking connections between a client and a remote robotic system. The client can transparently invoke a method on a server across the network without any need to know where the application servers are located, or what programming language and operating system are used. This lets the system overcome the shortcomings of the other typical Internet robotic system. To cope with time delays on the communication path, we have implemented the robot control server, which allows the user to control the telerobotic system at a task-level. We have also implemented the live image feedback server, which provides live image feedback for a remote user. The proposed system gives the users the ability to operate the remote robotic system to retrieve and manipulate the desired tableware or other things to support the aged and disabled over the Internet by using the intuitive user interface.     

A scalable architecture for 3D map navigation on mobile devices

Mobile devices such as smart phones or tablets are rapidly increasing their graphics and networking capabilities. However, real-time visualization of 3D maps is still a challenging task to accomplish on such limited devices. In this paper, we describe the principles involved in the design and development of a scalable client–server architecture for delivering 3D maps over wireless networks to mobile devices. We have developed a hybrid adaptive streaming and rendering method that distributes the 3D map rendering task between the mobile clients and a remote server. This architecture provides support for efficient delivery of 3D contents to mobile clients according to their capabilities. As a proof of concept, we have implemented a prototype and carried out exhaustive experiments considering different scenarios and hundreds of concurrent connected clients. The analysis of the server workload and the mobile clients performance show that our architecture achieves a great scalability and performance even when using low-end hardware.     

ICOME: An Immersive Collaborative 3D Object Modelling Environment

In most existing immersive virtual environments, 3D geometry is imported from external packages. Within ICOME (an Immersive Collaborative 3D Object Modelling Environment) we focus on the immersive construction of 3D geometrical objects within the environment itself. Moreover, the framework allows multiple people to simultaneously undertake 3D modelling tasks in a collaborative way. This article describes the overall architecture, which conceptually follows a client/server approach. The various types of clients, which are implemented, are described in detail. Some illustrative 3D object modelling examples are given. Extensions to the system with regard to 3D audio are also mentioned.     

A new fuzzy-decision based load balancing system for distributed object computing

Distributed object computing systems are widely envisioned to be the desired distributed software development paradigm due to the higher modularity and the capability of handling machine and operating system heterogeneity. Indeed, enabled by the tremendous advancements in processor and networking technologies, complex operations such as object serialization and data marshaling have become very efficient, and thus, distributed object systems are being built for many different applications. However, as the system scales up (e.g., with larger number of server and client objects, and more machines), a judicious load balancing system is required to efficiently distribute the workload (e.g., the queries, messages/objects passing) among the different servers in the system. Unfortunately, in existing distributed object middleware systems, such a load balancing facility does not exist. In this paper, we present the design and implementation of a new dynamic fuzzy-decision-based load balancing system incorporated in a distributed object computing environment. Our proposed approach works by using a fuzzy logic controller which informs a client object to use the most appropriate service such that load balancing among servers is achieved. We have chosen Jini to build our experimental middleware platform, on which our proposed approach as well as other related techniques are implemented and compared. Extensive experiments are conducted to investigate the effectiveness of our fuzzy-decision-based algorithm, which is found to be consistently better than other approaches.     

Building a geodatabase for mapping hydrogeological features and 3D modeling of groundwater systems: Application to the Saguenay-Lac-St.-Jean region, Canada

Understanding and managing groundwater resources require the integration of a large amount of high-quality data from a variety of sources. Due to the limitations in accessing information related to groundwater and subsurface conditions, the gathering of available existing information is of crucial importance when conducting a successful hydrogeological study. Here, we present an approach for the development of an exhaustive and comprehensive groundwater database through (1) the gathering of relevant sources of information relating to groundwater, and (2) the application of a quality control process in order to screen the data for accuracy and quality. This hydrogeological database is then implemented within a GIS (geographic information system) framework coupled to a Relational Database Management System (RDBMS) as a personal geodatabase (ESRI format) GIS technology. Once established, the spatial database allows a user to request the relevant data required for a specific hydrogeological study. In addition, stratigraphic data stored within the spatial database may be utilized for constructing 3D subsurface hydrostructural models. In order to achieve this objective, the software Arc Hydro Groundwater combined with the ArcGIS spatial database is shown to be appropriate for the 3D structural representation of aquifers (groundwater reservoirs). The innovative contribution of this approach in building 3D hydrostructural subsurface models from a spatial database resides in simplifying the required step-by-step processes by considering a unified compatible combination of “RDBMS-ArcGIS-Arc Hydro Groundwater” technologies. The proposed methodology is illustrated using data from an ongoing project aimed at developing an inventory of the groundwater resources of the Saguenay-Lac-Saint-Jean region, Quebec (Canada).     

MOVIE model for open-systems-based high-performance distributed computing

MOVIE (Multitasking Object-oriented Visual Interactive Environment) is a new software system for high-performance distributed computing (HPDC), currently in the advanced design and implementation stage at Northeast Parallel Architectures Center (NPAC), Syracuse University. The MOVIE system is structured as a multiserver network of interpreters of the high-level object-oriented programming language MovieScript. MovieScript derives from PostScript and extends it in the C⁺⁺ syntax-based object-oriented interpreted style towards 3D graphics, high-performance computing and general-purpose high-level communication protocol for distributed and MIMD-parallel computing. The paper describes the overall open systems-based MOVIE design and itemizes currently implemented, developed and planned components of the system.     

ICOME: An Immersive Collaborative 3D Object Modelling Environment

In most existing immersive virtual environments, 3D geometry is imported from external packages. Within ICOME (an immersive Collaborative 3D Object Modelling Environment) we focus on the immersive construction of 3D geometrical objects within the environment itself. Moreover, the framework allows multiple people to simultaneously undertake 3D modelling tasks in a collaborative way. This article describes the overall architecture, which conceptually follows a client/server approach. The various types of clients, which are implemented, are described in detail. Some illustrative 3D object modelling examples are given. Extensions to the system with regard to 3D audio are also mentioned.This paper is a republished version of Virtual Reality 1999; 4: 129–138 with corrections     

Omni-directional Relief Impostors

Relief impostors have been proposed as a compact and high-quality representation for high-frequency detail in 3D models. In this paper we propose an algorithm to represent a complex object through the combination of a reduced set of relief maps. These relief maps can be rendered with very few artifacts and no apparent deformation from any view direction. We present an efficient algorithm to optimize the set of viewing planes supporting the relief maps, and an image-space metric to select a sufficient subset of relief maps for each view direction. Selected maps (typically three) are rendered based on the well-known ray-height-field intersection algorithm implemented on the GPU. We discuss several strategies to merge overlapping relief maps while minimizing sampling artifacts and to reduce extra texture requirements. We show that our representation can maintain the geometry and the silhouette of a large class of complex shapes with no limit in the viewing direction. Since the rendering cost is output sensitive, our representation can be used to build a hierarchical model of a 3D scene.     

Image-Based Network Rendering of Large Meshes for Cloud Computing

Recent advances in sensing and software technologies enable us to obtain large-scale, yet fine 3D mesh models of cultural assets. However, such large models cannot be displayed interactively on consumer computers because of the performance limitation of the hardware. Cloud computing technology is a solution that can process a very large amount of information without adding to each client user’s processing cost. In this paper, we propose an interactive rendering system for large 3D mesh models, stored on a remote environment through a network of relatively small capacity machines, based on the cloud computing concept. Our system uses both model- and image-based rendering methods for efficient load balance between a server and clients. On the server, the 3D models are rendered by the model-based method using a hierarchical data structure with Level of Detail (LOD). On the client, an arbitrary view is constructed by using a novel image-based method, referred to as the Grid-Lumigraph, which blends colors from sampling images received from the server. The resulting rendering system can efficiently render any image in real time. We implemented the system and evaluated the rendering and data transferring performance.     

Development of a collaborative CAD/CAM system

This paper presents the development of a collaborative CAD/CAM system (COCADCAM). COCADCAM extends an existing single-location CAD/CAM system to a multi-location CAD/CAM application so that two geographically dispersed CAD/CAM users can work together on a three-dimensional CAD-geometry coediting and CAD-related tasks collaboratively and dynamically. COCADCAM dynamically supports CAD data communication that are not available in traditional single-location CAD/CAM. The dynamic data communication is achieved through the development of networking algorithms and CAD/CAM functions in this paper. The networking algorithms based on UNIX Interprocess Communication (IPC), the Network File System (NFS), and a connection-oriented client and server model under the Transmission Control Protocol/Internet Protocol (TCP/IP) suite. The CAD/CAM functions included surface modelling, simulation of a milling toolpath, and post-processing of an NC program following collaborative CAD-geometry coediting, which are directly or indirectly supported by the Application Programming Interface (API) of the CAD/CAM software. The networking algorithms and CAD/CAM functions together can facilitate an environment for CAD-geometry coediting and related tasks such as design, analysis and manufacture. COCADCAM has been successfully implemented through local area network (LAN) and the Internet; a remote machining cell is also linked so that the generated NC program based on a coedited free-form surface can be used for the physical machining operation. The algorithm proposed by COCADCAM can be referenced for the extension of other single-location CAD/CAM systems to multi-location applications.     

基于Android的手机时间管理App的设计与实现

在越来越多的大学生离不开手机,学习效率日益下降的背景下,采用设计实现了一种基于Android系统开发的一个时间管理应用软件,可以用于帮助学生控制使用手机的时间。该系统一共分为两部分,一部分是客户端,即时间管理软件,采用了AChartEngine图表库,作为Android应用实现数据可视化的第三方类库,为用户提供了友好的数据表现形式,采用界面劫持攻击分析实现了对其他app的拦截。另外笔者采用了JSON数据格式实现了服务端和客户端的通信,而针对服务器端,采用了该系统使用Mysql作为数据库,体积小,成本低,并且支撑多线程,能够充分利用CPU资源来编写数据库,实现数据存储用于更新不同用户的提醒语。     

GeoVR: a web-based tool for virtual reality presentation from 2D GIS data

A tool called GeoVR has been designed and developed under a client/server architecture to enable the interactive creation of a 3D scene and virtual reality modeling language (VRML) model from 2D spatial data by integrating Internet geographical information system (GIS) and HTML programming. The client front-end of this tool provides an HTML form to set properties for building 3D scenes, while the server back-end supported by off-the-shelf software: ArcView Internet Map Server and ArcView 3D Analyst through Avenue programming, processes the parameters and generates a 3D scene. This 3D scene is then transformed into a VRML model, which, together with its legend, is sent back to the VRML-enabled WWW browser for display and navigation. It is demonstrated that this tool, not only automates the conversion of the conventional 2D GIS data into VRML, but also adapts the current GIS 3D capabilities to the increasingly popular Web environment. The development of GeoVR offers new opportunities for geoscientists to build applications that benefit from virtual reality presentation based upon the existing GIS spatial databases.     

Retrieval schedules based on resource availability and flexible presentation specifications

A distributed multimedia document presentation involves retrieval of objects from one or more document servers and their presentation at the client system. The presentation of the multimedia objects has to be carried out in accordance with the specification of temporal relationships between the objects. The retrieval of multimedia objects from the document server(s) is influenced by factors such as temporal specification of objects presentations, throughput offered by the network service provider, and the buffer resources on the client system. Flexibility in the temporal specification of the multimedia document may help in deriving an object retrieval schedule that can handle variations in network throughput and buffer resource availability. In this paper, we develop techniques for deriving a flexible object retrieval schedule for a distributed multimedia document presentation. The schedule is based on flexible temporal specification of the multimedia document using the difference constrai nts approach. We show how the derived retrieval schedule can be validated and modified to ensure that it can work with the offered network throughput and the available buffer resources.     

基于机群操作系统的并行调试器

并行调试工具的设计，是并行计算环境工具研究开发中的一个突出难点。介绍了一个在曙光3000上实现的并行调试器DCDB3．0。该调试器是未来曙光4000机群操作系统的一部分，是曙光3000上的第1个可运行版本，采用典型的客户／服务器模式。客户端的用户界面可将冗繁的调试信息与操作可视化。客户端可以远离提供服务的大型机，其远程通信依赖的是机群操作系统中的DRPC和任务管理，前者提供远程方法调用，后者使得客户端能够在服务器上启动相应的任务。DCDB3．0的服务器端负责处理调试任务和同客户端进行信息交互。DCDB3．0的功能具有可扩放性，使得可以在此平台上研究一些高级并行调试技术的实现。改进了已有的方式，实现了重放技术，并计划进一步添加其他高级并行调试技术。     

Internetworked graphics and the Web

Although the networking and computer graphics fields are considered to be distinct disciplines, they must begin to converge in order to support collaborative exploration and information visualization on the Internet and the World Wide Web. Telecommunication breakthroughs remove bottlenecks and provide new opportunities for interactive 3D graphics across globally interconnected, dissimilar networks. Multicast backbone tools, developed in the networking arena, provide desktop videoconferencing tools for sharing information visualization and virtual reality explorations. The Virtual Reality Modeling Language (VRML), developed in the computer graphics arena, supports the 3D display and fly-through of networked computing resources on the Internet. The computer graphics community considers VRML to be an interactive tool for exploring content on the Web. The telecommunications community calls it an application on the networking infrastructure. The authors define the concept of internetworked graphics to describe the future merger and dependencies of computer graphics applications and the telecommunications networking infrastructure     

Proposed enhanced hybrid framework for efficient 3D-MVC and 3D-HEVC wireless communication

The streaming of Three-Dimensional Video (3DV) over erroneous wireless channels causes Macro-Blocks (MBs) corruptions. Thus, the efficient performance of 3DV communication techniques over wireless channels has become an interesting research topic because of the restricted resources and the existence of severe communication losses. The 3DV consists of various video sequences captured via multiple cameras surrounding an object, and working simultaneously. Therefore, there is a need to achieve high encoding efficiency. Unfortunately, the highly-compressed 3DV content is subject to communication channel corruptions. Thus, in this research, we suggest the utilization of a chaotic randomization technique based on Baker map with convolution coding and equalization for high-quality 3D Multi-view Video Coding (MVC) and High Efficiency Video Coding (HEVC) transmission over an Orthogonal Frequency Division Multiplexing (OFDM) wireless system. Rayleigh fading and Additive White Gaussian Noise (AWGN) are considered in this paper in a real scenario of 3DV transmission. Firstly, the 3DV volume is compressed making use of the intra- and inter-prediction correlations between frames. Then, the compressed 3D-MVC and 3D-HEVC frames are converted into binary data format. After that, the chaotic randomization technique is employed before the modulation stage. It is utilized to minimize the channel corruptions on the streamed encoded 3DV data, and it as well introduces a degree of encryption to the transmitted 3DV frames. To evaluate the efficiency of the suggested hybrid framework; different simulations on several 3D-MVC and 3D-HEVC frames have been executed. The results prove that the delivered 3DV frames with the suggested framework have high Peak Signal-to-Noise Ratios (PSNRs).

     

Software architecture for the UARC Web-based collaboratory

The Upper Atmospheric Research Collaboratory was actively used over a period of six years to study space weather phenomena such as magnetic storms and solar winds. The UARC software was designed as a modular system of independent services that work over a wide area network and support a complex array of data suppliers, transformation modules that provided quality-of-service support, and client tools such as groupware applications. During the last two years of the project, the system provided access to over 30 data sources including ground- and satellite-based instruments and predictive model output from supercomputers during active data collection periods that lasted up to 2 weeks. This article describes the UARC architecture and services. The main UARC servers are a data dissemination substrate specifically designed to support push-based applications using attribute-based routing, and a group management and shared state management server. The servers are scalable, and designed to operate satisfactorily on a wide variety of networking conditions and client resources