16178058
Dataflow Java: implicitly parallel Java
Dataflow computation models enable simpler and more efficient management of the memory hierarchy-a key barrier to the performance of many parallel programs. This paper describes a dataflow language based on Java. Use of the dataflow model enables a programmer to generate parallel programs without explicit directions for message passing, work allocation and synchronisation. A small handful of additional syntactic constructs are required. A pre-processor is used to convert Dataflow Java programs to standard portable Java. The underlying run-time system was easy to implement using Java's object modelling and communications primitives. Although raw performance lags behind an equivalent C-based system, we were able to demonstrate useful speedups in a heterogeneous environment, thus amply illustrating the potential power of the Dataflow Java approach to use all machines-of whatever type-that might be available on a network when Java JIT compiler technology matures.
35763376
Setting a Framework for Trusted Component Trading
Software engineers constructing systems from third-party components need to be able to assess the quality of those components in order to have any confidence in the final system. We argue that the most effective and economic way to do this is for developers to supply test specifications along with the components that they offer to the market. We describe a simple, portable test specification based on XML documents. When a test specification is packaged with a purchased component, system builders are efficiently able to not only verify a component developer’s claim for quality but also use the test specification to elucidate fine details of a component’s capabilities that may be missing or not manifest in a natural language specification. A system builder selecting a component for integration into a new system needs to consider more than its ability to perform the required functions: the degree of testing can be an important indication of its reliability. Thus we propose an index, describing the degree of testing that a component has undergone, which can be used to rate components and aid selection decisions. Combined with a test specification, a purchaser can efficiently determine whether a component meets claims for its quality.
41920402
Real-Time Three Dimensional Vision
Active systems for collision avoidance in ‘noisy’ environments such as traffic which contain large numbers of moving objects will be subject to considerable interference when the majority of the moving objects are equipped with common avoidance systems. Thus passive systems, which require only input from the environment, are the best candidates for this task. In this paper, we investigate the feasibility of real-time stereo vision for collision avoidance systems. Software simulations have determined that sum-of-absolute-difference correlation techniques match well but hardware accelerators are necessary to generate depth maps at camera frame rates. Regular structures, linear data flow and abundant parallelism make correlation algorithms good candidates for reconfigurable hardware. The SAD cost function requires only adders and comparators for which modern FPGAs provide good support. However accurate depth maps require large disparity ranges and high resolution images and fitting a full correlator on a single FPGA becomes a challenge. We implemented SAD algorithms in VHDL and synthesized them to determine resource requirements and performance. Altering the shape of the correlation window to reduce its height compared to its width reduces storage requirements with negligible effects on matching accuracy. Models which used the internal block memory provided by modern FPGAs to store the ‘inactive’ portions of scan lines were compared with simpler models which used the logic cell flip-flops. From these results, we have developed a simple predictor which enables one to rapidly determine whether a target appliction is feasible.
2650464
Web-service-based, Dynamic and Collaborative E-learning
This paper describes an on-going effort to investigate problems and approaches for achieving Web-service-based, dynamic and collaborative e-learning. In this work, a Learning Content Definition Model is used to model distributed and sharable learning resources as content objects. Distributed and sharable software systems/components for supporting e-learning are modeled as software objects. Both types of objects are uniformly published as Web-services in a constraint-based Web-service registry and made sharable and reusable. An extended Web-service infrastructure provides a standard framework for the modeling, registration, discovery, binding and invocation of these objects. In this work, we also introduce a Learning Process Definition Model and a Learning Process Execution Engine for specifying and executing learning process models, which represent instructional modules in the forms of activity trees. An Event-Trigger-Rule Server is integrated with the Learning Process Execution Engine to make learning process models active, flexible, customizable and adaptable. It is also used to facilitate the interaction and coordination among learners, administrators, authors, and other personnel involved in collaborative elearning.
44418882
A Decomposition Approach for Balancing Large-Scale Acyclic Data Flow Graphs
An efficient decomposition technique that provides a more systematic approach in solving the optimal buffer assignment problem of an acyclic data-flow graph (ADFG) with a large number of computational nodes is presented. The buffer assignment problem is formulated as an integer linear optimization problem that can be solved in pseudopolynomial time. However, if the size of an ADFG increases, then integer linear constraint equations may grow exponentially, making the optimization problem more intractable. The decomposition approach utilizes the critical path concept to decompose a directed ADFG into a set of connected subgraphs, and the integer linear optimization technique can be used to solve the buffer assignment problem in each subgraph. Thus, a large-scale integer linear optimization problem is divided into a number of smaller-scale subproblems, each of which can be easily solved in pseudopolynomial time. Examples are given to illustrate the proposed decomposition technique. >
2435549
Learning Object and Dynamic E-Learning Service Technologies for Simulation-Based Medical Instruction
Simulations are increasingly used for instruction and training purposes in many application areas such as commercial and military aviation, battlefield management, building construction, product manufacturing, medical education and others. However, most simulation systems are monolithic, ad hoc and non-reusable. In this work, we apply learning object and e-learning service technologies to modularize an existing Web-based simulation system called the Virtual Anesthesia Machine (VAM). Instructional materials associated with the components of the simulation system are encapsulated as reusable Atomic Learning Objects, each of which consists of content items, practice items, assessment items, meta-information and constraints. Instructional materials associated with the entire simulation system is modeled as a Composite Learning Object having a structure of activities, which is used by a Learning Process Execution Engine to enact the process of delivering contents, instructing learners to use the simulation system for practice on what they learn, and performing assessment to evaluate the performances of learners in learning the functions and operations of the simulation system and its components. An event-trigger-rule server is used in an event-driven, rule-based execution of a learning process to make the learning process active, adaptive, customizable and flexible.
8422740
Characterizations of solution sets of convex vector minimization problems
Complete dual characterizations of the weak and proper optimal solution sets of an infinite dimensional convex vector minimization problem are given. The results are expressed in terms of subgradients, Lagrange multipliers and epigraphs of conjugate functions. A dual condition characterizing the containment of a closed convex set, defined by a cone-convex inequality, in a reverse-convex set, plays a key role in deriving the results. Simple Lagrange multiplier characterizations of the solution sets are also derived under a regularity condition. Numerical examples are given to illustrate the significance of the results.
16229648
Enhancement of a WLAN-based internet service in Korea
A wireless LAN (WLAN)-based Internet service, called NESPOT, of Korea Telecom (KT), the biggest telecommunication and Internet service company in Korea, has been operational since early 2002. As the numbers of subscribers and deployed access points (APs) increase, KT has been endeavoring to improve its service quality as well as the network management. In this paper, we introduce a joint effort between Seoul National University (SNU) and KT to achieve it. We have been addressing two major issues as part of the joint project thus far: (1) a unified WLAN management tool; and (2) real-time traffic support enhancement. We present our on-going efforts as well as some preliminary results. Some issues, which need further attention for the future NESPOT service enhancement, are also introduced.