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Full-Text Articles in Computer Engineering
Volumeviewer: An Interactive Tool For Fitting Surfaces To Volume Data, Ross Sowell, Lu Liu, Tao Ju, Cindy Grimm, Christopher Abraham, Garima Gokhroo, D Low
Volumeviewer: An Interactive Tool For Fitting Surfaces To Volume Data, Ross Sowell, Lu Liu, Tao Ju, Cindy Grimm, Christopher Abraham, Garima Gokhroo, D Low
All Computer Science and Engineering Research
Recent advances in surface reconstruction algorithms allow surfaces to be built from contours lying on non-parallel planes. Such algorithms allow users to construct surfaces of similar quality more efficiently by using a small set of oblique contours, rather than many parallel contours. However, current medical imaging systems do not provide tools for sketching contours on oblique planes. In this paper, we take the first steps towards bridging the gap between the new surface reconstruction technologies and putting those methods to use in practice. We develop a novel interface for modeling surfaces from volume data by allowing the user to sketch …
Scheduling Design With Unknown Execution Time Distributions Or Modes, Robert Glaubius, Terry Tidwell, Christopher Gill, William D. Smart
Scheduling Design With Unknown Execution Time Distributions Or Modes, Robert Glaubius, Terry Tidwell, Christopher Gill, William D. Smart
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Open soft real-time systems, such as mobile robots, experience unpredictable interactions with their environments and yet must respond both adaptively and with reasonable temporal predictability. Because of the uncertainty inherent in such interactions, many of the assumptions of the real-time scheduling techniques traditionally used to ensure predictable timing of system actions do not hold in those environments. In previous work we have developed novel techniques for scheduling policy design where up-front knowledge of execution time distributions can be used to produce both compact representations of resource utilization state spaces and efficient optimal scheduling policies over those state spaces. This paper …
On Unusual Pixel Shapes And Image Motion, Nathan Jacobs, Stephen Schuh, Robert Pless
On Unusual Pixel Shapes And Image Motion, Nathan Jacobs, Stephen Schuh, Robert Pless
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We introduce the integral-pixel camera model, where measurements integrate over large and potentially overlapping parts of the visual field. This models a wide variety of novel camera designs, including omnidirectional cameras, compressive sensing cameras, and novel programmable-pixel imaging chips. We explore the relationship of integral-pixel measurements with image motion and find (a) that direct motion estimation using integral-pixels is possible and in some cases quite good, (b) standard compressive-sensing reconstructions are not good for estimating motion, and (c) when we design image reconstruction algorithms that explicitly reason about image motion, they outperform standard compressive-sensing video reconstruction. We show experimental results …
Feedback Thermal Control For Real-Time Systems, Yong Fu, Nicholas Kottenstette, Yingming Chen, Chenyang Lu, Xenofon D. Koutsoukos, Hongan Wang
Feedback Thermal Control For Real-Time Systems, Yong Fu, Nicholas Kottenstette, Yingming Chen, Chenyang Lu, Xenofon D. Koutsoukos, Hongan Wang
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Thermal control is crucial to real-time systems as excessive processor temperature can cause system failure or unacceptable performance degradation due to hardware throttling. Real-time systems face significant challenges in thermal management as they must avoid processor overheating while still delivering desired real-time performance. Furthermore, many real-time systems must handle a broad range of uncertainties in system and environmental conditions. To address these challenges, this paper presents Thermal Control under Utilization Bound (TCUB), a novel thermal control algorithm specifically designed for real-time systems. TCUB employs a feedback control loop that dynamically controls both processor temperature and CPU utilization through task rate …
The Design And Performance Of Cyber-Physical Middleware For Real-Time Hybrid Structural Testing, Huang-Ming Huang, Xiuyu Gao, Terry Tidewell, Christopher Gill
The Design And Performance Of Cyber-Physical Middleware For Real-Time Hybrid Structural Testing, Huang-Ming Huang, Xiuyu Gao, Terry Tidewell, Christopher Gill
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Real-time hybrid testing of civil structures, in which computational models and physical components must be integrated with high fidelity at run-time represents a grand challenge in the emerging area of cyber-physical systems. Actuator dynamics, complex interactions among computers and physical components, and computation and communication delays all must be managed carefully to achieve accurate tests. To address these challenges, we have developed a novel middleware for integrating cyber and physical components flexibly and with suitable timing behavior within a Cyber-physical Instrument for Real-time hybrid Structural Testing (CIRST). This paper makes three main contributions to the state of the art in …
Augmented Lagrangian Algorithms Under Constraint Partitioning, You Xu, Yixin Chen
Augmented Lagrangian Algorithms Under Constraint Partitioning, You Xu, Yixin Chen
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We present a novel constraint-partitioning approach for solving continuous nonlinear optimization based on augmented Lagrange method. In contrast to previous work, our approach is based on a new constraint partitioning theory and can handle global constraints. We employ a hyper-graph partitioning method to recognize the problem structure. We prove global convergence under assumptions that are much more relaxed than previous work and solve problems as large as 40,000 variables that other solvers such as IPOPT [11] cannot solve.
Throughput-Optimal Systolic Arrays From Recurrence Equations, Arpith C. Jacob, Jeremy D. Buhler, Roger D. Chamberlain
Throughput-Optimal Systolic Arrays From Recurrence Equations, Arpith C. Jacob, Jeremy D. Buhler, Roger D. Chamberlain
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Many compute-bound software kernels have seen order-of-magnitude speedups on special-purpose accelerators built on specialized architectures such as field-programmable gate arrays (FPGAs). These architectures are particularly good at implementing dynamic programming algorithms that can be expressed as systems of recurrence equations, which in turn can be realized as systolic array designs. To efficiently find good realizations of an algorithm for a given hardware platform, we pursue software tools that can search the space of possible parallel array designs to optimize various design criteria. Most existing design tools in this area produce a design that is latency-space optimal. However, we instead wish …
Achieving Coordination Through Dynamic Construction Of Open Workflows ** Please See Wucse-2009-14 **, Louis Thomas, Justin Luner, Grui-Catalin Roman, Christopher Gill
Achieving Coordination Through Dynamic Construction Of Open Workflows ** Please See Wucse-2009-14 **, Louis Thomas, Justin Luner, Grui-Catalin Roman, Christopher Gill
All Computer Science and Engineering Research
Workflows, widely used on the Internet today, typically consist of a graph-like structure that defines the orchestration rules for executing a set of tasks, each of which is matched at run-rime to a corresponding service. The graph is static, specialized directories enable the discovery of services, and the wired infrastructure supports routing of results among tasks. In this paper we introduce a radically new paradigm for workflow construction and execution called open workflow. It is motivated by the growing reliance on wireless ad hoc networks in settings such as emergency response, field hospitals, and military operations. Open workflows facilitate goal-directed …
Architectures For The Future Networks And The Next Generation Internet: A Survey, Subharthi Paul, Jianli Pan, Raj Jain
Architectures For The Future Networks And The Next Generation Internet: A Survey, Subharthi Paul, Jianli Pan, Raj Jain
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Networking research funding agencies in the USA, Europe, Japan, and other countries are encouraging research on revolutionary networking architectures that may or may not be bound by the restrictions of the current TCP/IP based Internet. We present a comprehensive survey of such research projects and activities. The topics covered include various testbeds for experimentations for new architectures, new security mechanisms, content delivery mechanisms, management and control frameworks, service architectures, and routing mechanisms. Delay/Disruption tolerant networks, which allow communications even when complete end-to-end path is not available, are also discussed.
Scalable Scheduling Policy Design For Open Soft Real-Time Systems, Robert Glaubius, Terry Tidewell, Braden Sidoti, David Pilla, Justin Meden, Christopher Gill, William D. Smart
Scalable Scheduling Policy Design For Open Soft Real-Time Systems, Robert Glaubius, Terry Tidewell, Braden Sidoti, David Pilla, Justin Meden, Christopher Gill, William D. Smart
All Computer Science and Engineering Research
Open soft real-time systems, such as mobile robots, must respond adaptively to varying operating conditions, while balancing the need to perform multiple mission specific tasks against the requirement that those tasks complete in a timely manner. Setting and enforcing a utilization target for shared resources is a key mechanism for achieving this behavior. However, because of the uncertainty and non-preemptability of some tasks, key assumptions of classical scheduling approaches do not hold. In previous work we presented foundational methods for generating task scheduling policies to enforce proportional resource utilization for open soft real-time systems with these properties. However, these methods …
Design Of An Extensible Network Testbed With Heterogeneous Components, Charlie Wisemen, Jyoti Parwatikar, Ken Wong, John Dehart, Jonathan Turner
Design Of An Extensible Network Testbed With Heterogeneous Components, Charlie Wisemen, Jyoti Parwatikar, Ken Wong, John Dehart, Jonathan Turner
All Computer Science and Engineering Research
Virtualized network infrastructures are currently deployed in both research and commercial contexts. The complexity of the virtualization layer varies greatly in different deployments, ranging from cloud computing environments, to carrier Ethernet applications using stacked VLANs, to networking testbeds. In all of these cases, there are many users sharing the resources of one provider, where each user expects their resources to be isolated from all other users. Our work in this area is focused on network testbeds. In particular, we present the design of the latest version of the Open Network Laboratory (ONL) testbed. This redesign generalizes the underlying infrastructure to …
Open Workflows: Context-Dependent Construction And Execution In Mobile Wireless Settings, Louis Thomas, Justin Wilson, Grui-Catalin Roman, Christopher Gill
Open Workflows: Context-Dependent Construction And Execution In Mobile Wireless Settings, Louis Thomas, Justin Wilson, Grui-Catalin Roman, Christopher Gill
All Computer Science and Engineering Research
Existing workflow middleware executes tasks orchestrated by rules defined in a carefully handcrafted static graph. Workflow management systems have proved effective for service-oriented business automation in stable, wired infrastructures. We introduce a radically new paradigm for workflow construction and execution called open workflow to support goal-directed coordination among physically mobile people and devices that form a transient community over an ad hoc wireless network. The quintessential feature of the open workflow paradigm is dynamic construction and execution of custom, context-specific workflows in response to unpredictable and evolving circumstances by exploiting the knowledge and services available within a given spatiotemporal context. …
Design And Evaluation Of A Practical, High Performance Crossbar Scheduler, Jonathan Turner
Design And Evaluation Of A Practical, High Performance Crossbar Scheduler, Jonathan Turner
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The Least Occupied Output First (LOOFA) scheduler is one of several unbuffered crossbar schedulers that provides strong performance guarantees when operated with a speedup of 2 or more. Because LOOFA requires the computation of a maximal matching, it has been considered too slow for use in systems with link rates of 10 Gb/s or more. This paper studies an approximate variant of LOOFA described briefly in [16]. We introduce a general family of schedulers that allows for partial sorting and that includes the LOOFA scheduler as a special case. We show that all schedulers in this class are work-conserving and …
Adaptive Service Provisioning For Wireless Sensor Networks, Chien-Liang Fok, Gruia-Catalin Roman, Chenyang Lu
Adaptive Service Provisioning For Wireless Sensor Networks, Chien-Liang Fok, Gruia-Catalin Roman, Chenyang Lu
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Service provisioning has gained significant attention as a promising programming model for heterogeneous wireless sensor networks. Its key idea is to exploit the decoupling of service providers and consumers to enable platform-independent applications that are dynamically bound to platform-specific services. We explore novel adaptive service binding strategies that are able to cope with network dynamics and to promote energy conservation. To achieve this goal, we developed policies and algorithms that automatically switch providers in response to network topology changes and adapt application behavior when opportunities for energy savings surface. The latter is accomplished by providing limited information about the energy …
A Simple Algorithm For Triconnectivity Of A Multigraph, Abusayeed Saifullah, Alper Ungor
A Simple Algorithm For Triconnectivity Of A Multigraph, Abusayeed Saifullah, Alper Ungor
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Vertex-connectivity and edge-connectivity represent the extent to which a graph is connected. Study of these key properties of graphs plays an important role in varieties of computer science applications. Recent years have witnessed a number of linear time 3-edge-connectivity algorithms - with increasing simplicity. In contrast, the state-of-the-art algorithm for 3-vertex-connectivity due to Hopcroft and Tarjan lacks the simplicity in the sense of ease of implementation as well as the number of passes over the graph although its time and space complexity is theoretically linear. In this paper, we propose a linear time reduction from 3-vertex-connectivity to 3-edge- connectivity of …
Non-Programmers Identifying Functionality In Unfamiliar Code: Strategies And Barriers, Paul Gross, Caitlin Kelleher
Non-Programmers Identifying Functionality In Unfamiliar Code: Strategies And Barriers, Paul Gross, Caitlin Kelleher
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Source code on the web is a widely available and potentially rich learning resource for non-programmers. However, unfamiliar code can be daunting to end-users without programming experience. This paper describes the results of an exploratory study in which we asked non-programmers to find and modify the code responsible for specific functionality within unfamiliar programs. We present two interacting models of how non-programmers approach this problem: the Task Process Model and the Landmark-Mapping model. Using these models, we describe code search strategies non-programmers employed and the difficulties they encountered. Finally, we propose guidelines for future programming environments that support non-programmers in …
The Virtual Network Scheduling Problem For Heterogeneous Network Emulation Testbeds, Charlie Wisemen, Jonathan Turner
The Virtual Network Scheduling Problem For Heterogeneous Network Emulation Testbeds, Charlie Wisemen, Jonathan Turner
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Network testbeds such as Emulab and the Open Network Laboratory use virtualization to enable users to define end user virtual networks within a shared substrate. This involves mapping users' virtual network nodes onto distinct substrate components and mapping virtual network links onto substrate paths. The mappings guarantee that different users' activities can not interfere with one another. The problem of mapping virtual networks onto a shared substrate is a variant of the general graph embedding problem, long known to be NP-hard. In this paper, we focus on a more general version of the problem that supports advance scheduling of virtual …
Globally Clocked Magnetic Logic Circuits, Michael Hall, Albrecht Jander, Roger D. Chamberlain, Pallavi Dhagat
Globally Clocked Magnetic Logic Circuits, Michael Hall, Albrecht Jander, Roger D. Chamberlain, Pallavi Dhagat
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Magnetic spin valve devices enable the design of logic and memory elements that are suitable for use when constructing digital systems. A master-slave flip-flop design is proposed that can be clocked using an externally applied global magnetic field. With an external global clock, the digital system no longer needs to deliver the clock on-chip, thereby eliminating the need for a clock distribution network. We assess the power, area, and speed implications associated with the ability to eliminate the clock distribution network on a hybrid CMOS-magnetologic digital system.
Defending Against Distributed Denial-Of-Service Attacks With Weight-Fair Router Throttling, Abusayeed Saifullah
Defending Against Distributed Denial-Of-Service Attacks With Weight-Fair Router Throttling, Abusayeed Saifullah
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A high profile internet server is always a target of denial-of-service attacks. In this paper, we propose a novel technique for protecting an internet server from distributed denial-of-service attacks. The defense mechanism is based on a distributed algorithm that performs weight-fair throttling at the upstream routers. The throttling is weight-fair because the traffics destined for the server are controlled increased or decreased ) by the leaky-buckets at the routers based on the number of users connected, directly or through other routers, to each router. To the best of our knowledge, this is the first weight-fair technique for saving an internet …
Self-Stabilizing Computation Of 3-Edge-Connected Components, Abusayeed Saifullah, Yung Tsin
Self-Stabilizing Computation Of 3-Edge-Connected Components, Abusayeed Saifullah, Yung Tsin
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No abstract provided.
Online Bayesian Analysis, Ruibin Xi, Yongjin Kim, Nan Lin, Yixin Chen, Gruia-Catalin Roman
Online Bayesian Analysis, Ruibin Xi, Yongjin Kim, Nan Lin, Yixin Chen, Gruia-Catalin Roman
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In the last few years, there has been active research on aggregating advanced statistical measures in multidimensional data cubes from partitioned subsets of data. In this paper, we propose an online compression and aggregation scheme to support Bayesian estimations in data cubes based on the asymptotic properties of Bayesian statistics. In the proposed approach, we compress each data segment by retaining only the model parameters and a small amount of auxiliary measures. We then develop an aggregation formula that allows us to reconstruct the Bayesian estimation from partitioned segments with a small approximation error. We show that the Bayesian estimates …
Geodesic Grassfire For Computing Mixed-Dimensional Skeletons, Lu Liu, Tao Ju
Geodesic Grassfire For Computing Mixed-Dimensional Skeletons, Lu Liu, Tao Ju
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Skeleton descriptors are commonly used to represent, understand and process shapes. While existing methods produce skeletons at a fixed dimension, such as surface or curve skeletons for a 3D object, often times objects are better described using skeleton geometry at a mixture of dimensions. In this paper we present a novel algorithm for computing mixed-dimensional skeletons. Our method is guided by a continuous analogue that extends the classical grassfire erosion. This analogue allows us to identify medial geometry at multiple dimensions, and to formulate a measure that captures how well an object part is described by medial geometry at a …
Submodular Utility Optimization In Sensor Networks For Capacity Constraints, You Xu, Yixin Chen, Chenyang Lu, Sangeeta Bhattacharya, Abu Saifullah
Submodular Utility Optimization In Sensor Networks For Capacity Constraints, You Xu, Yixin Chen, Chenyang Lu, Sangeeta Bhattacharya, Abu Saifullah
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With the fast development of wireless sensor network (WSN) technologies, WSNs have widely shifted from a specialized platform for a single application to an integrated infrastructure supporting multiple applications. It is hence a critical problem to allocate multiple applications to multiple sensors in order to maximize user utility subject to various resource constraints. The resulting constrained optimization problem is difficult since it is discrete, nonlinear, and not in closed-form. In this report, we develop an efficient optimization algorithm with rigorous approximation bounds for submodular monotonic optimization with multiple knapsack constraints. Based on a variance reduction formulation, we prove several important …
Performance-Engineered Network Overlays For High Quality Interaction In Virtual Worlds, Mart Haitjema, Ritun Patney, Jon Turner, Charlie Wiseman, John Dehart
Performance-Engineered Network Overlays For High Quality Interaction In Virtual Worlds, Mart Haitjema, Ritun Patney, Jon Turner, Charlie Wiseman, John Dehart
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Overlay hosting systems such as PlanetLab, and cloud computing environments such as Amazon’s EC2, provide shared infrastructures within which new applications can be developed and deployed on a global scale. This paper ex-plores how systems of this sort can be used to enable ad-vanced network services and sophisticated applications that use those services to enhance performance and provide a high quality user experience. Specifically, we investigate how advanced overlay hosting environments can be used to provide network services that enable scalable virtual world applications and other large-scale distributed applications requiring consistent, real-time performance. We propose a novel network architecture called …
Achieving Coordination Through Dynamic Construction Of Open Workflows, Louis Thomas, Justin Wilson, Grui-Catalin Roman, Christopher Gill
Achieving Coordination Through Dynamic Construction Of Open Workflows, Louis Thomas, Justin Wilson, Grui-Catalin Roman, Christopher Gill
All Computer Science and Engineering Research
Workflow middleware executes tasks orchestrated by rules defined in a carefully handcrafted static graph. Workflow management systems have proved effective for service-oriented business automation in stable, wired infrastructures. We introduce a radically new paradigm for workflow construction and execution called open workflow to support goal-directed coordination among physically mobile people and devices that form a transient community over an ad hoc wireless network. The quintessential feature of the open workflow paradigm is dynamic construction of custom, context-specific workflows in response to unpredictable and evolving circumstances by exploiting the knowledge and services available within a given spatiotemporal context. This paper introduces …
Enabling A Low-Delay Internet Service Via Built-In Performance Incentives, Maxim Podlesny, Sergey Gorinsky
Enabling A Low-Delay Internet Service Via Built-In Performance Incentives, Maxim Podlesny, Sergey Gorinsky
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The single best-effort service of the Internet struggles to accommodate divergent needs of different distributed applications. Numerous alternative network architectures have been proposed to offer diversified network services. These innovative solutions failed to gain wide deployment primarily due to economic and legacy issues rather than technical shortcomings. Our paper presents a new simple paradigm for network service differentiation that accounts explicitly for the multiplicity of Internet service providers and users as well as their economic interests in environments with partly deployed new services. Our key idea is to base the service differentiation on performance itself, rather than price. We design …
Partial Program Admission, Michael Wilson, Ron Cytron, Jon Turner
Partial Program Admission, Michael Wilson, Ron Cytron, Jon Turner
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Real-time systems on non-preemptive platforms require a means of bounding the execution time of programs for admission purposes. Worst-Case Execution Time (WCET) is most commonly used to bound program execution time. While bounding a program’s WCET statically is possible, computing its true WCET is difficult.We present a new technique we call partial program admission, a means of statically enforcing an otherwise untrusted assertion of WCET without adding runtime overhead, by means of code duplication. We apply this technique to real programs from the virtual networking arena and present the results.
Partial Order Based Reduction In Planning: A Unifying Theory And New Algorithms, You Xi, Yixin Chen
Partial Order Based Reduction In Planning: A Unifying Theory And New Algorithms, You Xi, Yixin Chen
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Partial order based reduction (POR) has recently attracted research in planning. POR algorithms reduce search space by recognizing interchangable orders between actions and expanding only a subset of all possible orders during the search. POR has been extensively studied in model checking and proved to be an enabling technique for reducing the search space and costs. Recently, two POR algorithms, including the expansion core (EC) and stratified planning (SP) algorithms, have been proposed. Being orthogonal to the development of accurate heuristic functions, these reduction methods show great potential to improve the planning efficiency from a new perspective. However, it is …
Radio Mapping For Indoor Environments, Octav Chipara, Gregory Hackmann, Chenyang Lu, William D. Smart
Radio Mapping For Indoor Environments, Octav Chipara, Gregory Hackmann, Chenyang Lu, William D. Smart
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The efficient deployment and robust operation of many sensor network applications depend on deploying relays to ensure wireless coverage. Radio mapping aims to predict network coverage based on a small number of link measurements from sampled locations. Radio mapping is particularly challenging in complex indoor environments where walls significantly affect radio signal propagation. This paper makes the following key contributions to indoor radio mapping. First, our empirical study in an office building identifies a wall-classification model as the most effective model for indoor environments due to its balance between model complexity and accuracy. Second, we propose a practical algorithm to …
Enhanced Coordination In Sensor Networks Through Flexible Service Provisioning, Chien-Liang Fok, Gruia-Catalin Roman, Chenyang Lu
Enhanced Coordination In Sensor Networks Through Flexible Service Provisioning, Chien-Liang Fok, Gruia-Catalin Roman, Chenyang Lu
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Heterogeneous wireless sensor networks represent a challenging programming environment. Servilla addresses this by offering a new middleware framework that provides service provisioning. Using Servilla, developers can construct platform-independent applications over a dynamic set of devices with diverse computational resources and sensors. A salient feature of Servilla is its support for dynamic discovery and binding to local and remote services, which enables flexible and energy-efficient in-network collaboration among heterogeneous devices. Furthermore, Servilla provides a modular middleware architecture that can be easily tailored for devices with a wide range of resources, allowing resource-constrained devices to provide services while leveraging the capabilities of …