虚拟空间会议系统中视频合成技术的研究与实现

虚拟空间会议系统能够把所有与会者合成同一个虚拟会场中,从而构造一个能提供无缝的会场环境,眼神接触、凝视感知等普通多媒体会议系统不具备的虚拟协同工作环境。VST系统是我们刚刚完成的一个虚拟空间会议系统。视频合成技术是其实现的关键技术之一。本文介绍了VST系统中视频合成技术的研究与实现。     

Querying and creating visualizations by analogy

While there have been advances in visualization systems, particularly in multi-view visualizations and visual exploration, the process of building visualizations remains a major bottleneck in data exploration. We show that provenance metadata collected during the creation of pipelines can be reused to suggest similar content in related visualizations and guide semi-automated changes. We introduce the idea of query-by-example in the context of an ensemble of visualizations, and the use of analogies as first-class operations in a system to guide scalable interactions. We describe an implementation of these techniques in VisTrails, a publicly-available, open-source system.     

Algorithms for the Homogeneous Set Sandwich Problem

A homogeneous set is a non-trivial module of a graph, i.e. a non-empty, non-unitary, proper subset of a graph's vertices such that all its elements present exactly the same outer neighborhood. Given two graphs the Homogeneous Set Sandwich Problem (HSSP) asks whether there exists a sandwich graph which has a homogeneous set. In 2001 Tang et al. published an all-fast algorithm which was recently proven wrong, so that the HSSP's known upper bound would have been reset thereafter at the former determined by Cerioli et al. in 1998. We present, notwithstanding, new deterministic algorithms which have it established at We give as well two even faster randomized algorithms, whose simplicity might lend them didactic usefulness. We believe that, besides providing efficient easy-to-implement procedures to solve it, the study of these new approaches allows a fairly thorough understanding of the problem.     

Coordination components for collaborative virtual environments

This paper deals with the behavior of virtual environments from the collaboration point-of-view, in which actors (human or virtual beings) interact and collaborate by means of interdependent tasks. In this sense, actors may realize tasks that are dependent on tasks performed by other actors, while the interdependencies between tasks (through resource management and temporal relations) delineate the overall behavior of a virtual environment. Our main goal is to propose an approach for the coordination of those behaviors. Initially a generic study of possible interdependencies between collaborative tasks is presented, followed by the formal modeling (using Petri Nets) of coordination mechanisms for those dependencies. In order to implement such mechanisms, an architecture of reusable and pluggable coordination components is also introduced. These components are used in an implementation of a multi-user videogame. The presented approach is a concrete step to create virtual societies of actors that collaborate to reach common goals without the risk of getting involved in conflicting or repetitive tasks.     

Portugal's contribution to navigation and discovery of the New World

Even before the birth of Prince Henry the Navigator (1394) Portugal had displayed a maritime calling due to its 500-mile shore line and numerous natural bays. Inspired by the riches of India he saw during the Portuguese exploration along the coast of West Africa, Prince Henry set out methodically to collect information by bringing together Jews and Moors with geographical knowledge to found his School of Navigation. From 1415 until his death in 1460 he attracted to his school the foremost contemporary scholars in mathematics, astronomy, and cartography along with experts in knowledge of the compass, astrolabe, water currents, and the winds. This concentration of talent yielded the invention of the caravel, the most important navigational advancement of the time, crucial for long voyages across the high seas. Although the rest of Europe busied itself in political and religious wars, for 70 years (1415-1492) Portugal alone pursued the discovery of the Atlantic. "No nation in the 15th century exhibited so great a spirit of maritime enterprise as the Portuguese."     

Automatic measurement of arterial pressure

PURPOSE: To identify patients with lymphoma at risk for tumor lysis after chemotherapy. PATIENTS AND METHODS: The case records of 102 patients receiving combination chemotherapy for non-Hodgkin's lymphoma (intermediate to high-grade histology) were reviewed. Patients were considered to have "laboratory tumor lysis" if two of the following metabolic changes occurred within 4 days of treatment: a 25% increase in the serum phosphate, potassium, uric acid, or urea nitrogen concentrations, or a 25% decline in the serum calcium concentration. "Clinical tumor lysis" was defined as laboratory tumor lysis plus one of the following: a serum potassium level greater than 6 mmol/L, a creatinine level greater than 221 mumol/L, or a calcium level less than 1.5 mmol/L, the development of a life-threatening arrhythmia, or sudden death. RESULTS: Laboratory tumor lysis occurred in 42% of patients and clinical tumor lysis in 6%. There was no statistical difference in the frequency of either tumor lysis syndrome among lymphoma subgroups. Clinical tumor lysis occurred more frequently in patients with pretreatment renal insufficiency (serum creatinine level greater than 132 mumol/L) than in patients with normal renal function (36% versus 2%; p = 0.01). The development of azotemia correlated with high pretreatment serum lactate dehydrogenase concentrations (p < 0.01; r2 = 0.11). CONCLUSION: Clinically significant tumor lysis is a rare occurrence in patients with lymphoma when they are receiving allopurinol. However, tumor lysis can occur in patients with all types of moderate to high-grade non-Hodgkin's lymphoma. Patients with a high serum lactate dehydrogenase level or renal insufficiency are at increased risk for metabolic complications after chemotherapy and should be closely monitored.     

Classical and superposed learning for quantum weightless neural networks

A supervised learning algorithm for quantum neural networks (QNN) based on a novel quantum neuron node implemented as a very simple quantum circuit is proposed and investigated. In contrast to the QNN published in the literature, the proposed model can perform both quantum learning and simulate the classical models. This is partly due to the neural model used elsewhere which has weights and non-linear activations functions. Here a quantum weightless neural network model is proposed as a quantisation of the classical weightless neural networks (WNN). The theoretical and practical results on WNN can be inherited by these quantum weightless neural networks (qWNN). In the quantum learning algorithm proposed here patterns of the training set are presented concurrently in superposition. This superposition-based learning algorithm (SLA) has computational cost polynomial on the number of patterns in the training set.     

Compact yet efficient hardware implementation of artificial neural networks with customized topology

There are several neural network implementations using either software, hardware-based or a hardware/software co-design. This work proposes a hardware architecture to implement an artificial neural network (ANN), whose topology is the multilayer perceptron (MLP). In this paper, we explore the parallelism of neural networks and allow on-the-fly changes of the number of inputs, number of layers and number of neurons per layer of the net. This reconfigurability characteristic permits that any application of ANNs may be implemented using the proposed hardware. In order to reduce the processing time that is spent in arithmetic computation, a real number is represented using a fraction of integers. In this way, the arithmetic is limited to integer operations, performed by fast combinational circuits. A simple state machine is required to control sums and products of fractions. Sigmoid is used as the activation function in the proposed implementation. It is approximated by polynomials, whose underlying computation requires only sums and products. A theorem is introduced and proven so as to cover the arithmetic strategy of the computation of the activation function. Thus, the arithmetic circuitry used to implement the neuron weighted sum is reused for computing the sigmoid. This resource sharing decreased drastically the total area of the system. After modeling and simulation for functionality validation, the proposed architecture synthesized using reconfigurable hardware. The results are promising.     

Preference-based multi-objective evolutionary algorithms for power-aware application mapping on NoC platforms

Network-on-chip (NoC) are considered the next generation of communication infrastructure in embedded systems. In the platform-based design methodology, an application is implemented by a set of collaborative intellectual property (IP) blocks. The selection of the most suited set of IPs as well as their physical mapping onto the NoC infrastructure to implement efficiently the application at hand are two hard combinatorial problems that occur during the synthesis process of Noc-based embedded system implementation. In this paper, we propose an innovative preference-based multi-objective evolutionary methodology to perform the assignment and mapping stages. We use one of the well-known and efficient multi-objective evolutionary algorithms NSGA-II and microGA as a kernel. The optimization processes of assignment and mapping are both driven by the minimization of the required silicon area and imposed execution time of the application, considering that the decision maker’s preference is a pre-specified value of the overall power consumption of the implementation.     

波导耦合机器人控制板的研究

研制了一块微操作机器人控制板，采用USB接口通信和C8051单片机做规划器。介绍了PDIUSBD12和C8051F236的内部结构、性能指标，并给出了波导耦合机器人控制系统软硬件和系统结构设计。该控制板在实际工作中运行良好，性能稳定。