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Articles 30511 - 30540 of 41023

Full-Text Articles in Engineering

Complex Electronic States In Double-Layered Ruthenates (Sr1−Xcax)3ru2o7, Zhe Qu, Jin Peng, David Fobes, Leonard Spinu, Zhiqiang Mao Jan 2009

Complex Electronic States In Double-Layered Ruthenates (Sr1−Xcax)3ru2o7, Zhe Qu, Jin Peng, David Fobes, Leonard Spinu, Zhiqiang Mao

Physics Faculty Publications

The magnetic ground state of (Sr1−xCax)3Ru2O7 (0≤x≤1) is complex, ranging from an itinerant metamagnetic state (0≤x<0.08) to an unusual heavy-mass nearly ferromagnetic (FM) state (0.08<x<0.4), and finally to an antiferromagnetic (AFM) state (0.4≤x≤1). In this report we elucidate the electronic properties for these magnetic states, and show that the electronic and magnetic properties are strongly coupled in this system. The electronic ground state evolves from an AFM quasi-two-dimensional metal for x=1.0 to an Anderson localized state for 0.4≤x<1.0 (the AFM region). When the magnetic state undergoes a transition from the AFM to the nearly FM state, the electronic ground state switches to a weakly localized state induced by magnetic scattering for 0.25≤x<0.4, and then to a magnetic metallic state with the in-plane resistivity ρab∝Tα (α>2) for 0.08<x<0.25. The system eventually transforms into a Fermi-liquid ground state when the magnetic ground state enters the itinerant metamagnetic state for x<0.08. When x approaches the critical composition (x∼0.08), …

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Volumeviewer: An Interactive Tool For Fitting Surfaces To Volume Data, Ross Sowell, Lu Liu, Tao Ju, Cindy Grimm, Christopher Abraham, Garima Gokhroo, D Low Jan 2009

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 …

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Achieving Coordination Through Dynamic Construction Of Open Workflows, Louis Thomas, Justin Wilson, Grui-Catalin Roman, Christopher Gill Jan 2009

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 …

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On Unusual Pixel Shapes And Image Motion, Nathan Jacobs, Stephen Schuh, Robert Pless Jan 2009

On Unusual Pixel Shapes And Image Motion, Nathan Jacobs, Stephen Schuh, Robert Pless

All Computer Science and Engineering Research

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 …

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Radio Mapping For Indoor Environments, Octav Chipara, Gregory Hackmann, Chenyang Lu, William D. Smart Jan 2009

Radio Mapping For Indoor Environments, Octav Chipara, Gregory Hackmann, Chenyang Lu, William D. Smart

All Computer Science and Engineering Research

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 …

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Submodular Utility Optimization In Sensor Networks For Capacity Constraints, You Xu, Yixin Chen, Chenyang Lu, Sangeeta Bhattacharya, Abu Saifullah Jan 2009

Submodular Utility Optimization In Sensor Networks For Capacity Constraints, You Xu, Yixin Chen, Chenyang Lu, Sangeeta Bhattacharya, Abu Saifullah

All Computer Science and Engineering Research

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 …

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Achieving Coordination Through Dynamic Construction Of Open Workflows ** Please See Wucse-2009-14 **, Louis Thomas, Justin Luner, Grui-Catalin Roman, Christopher Gill Jan 2009

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 …

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A Simple Algorithm For Triconnectivity Of A Multigraph, Abusayeed Saifullah, Alper Ungor Jan 2009

A Simple Algorithm For Triconnectivity Of A Multigraph, Abusayeed Saifullah, Alper Ungor

All Computer Science and Engineering Research

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 …

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Partial Order Based Reduction In Planning: A Unifying Theory And New Algorithms, You Xi, Yixin Chen Jan 2009

Partial Order Based Reduction In Planning: A Unifying Theory And New Algorithms, You Xi, Yixin Chen

All Computer Science and Engineering Research

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 …

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Online Bayesian Analysis, Ruibin Xi, Yongjin Kim, Nan Lin, Yixin Chen, Gruia-Catalin Roman Jan 2009

Online Bayesian Analysis, Ruibin Xi, Yongjin Kim, Nan Lin, Yixin Chen, Gruia-Catalin Roman

All Computer Science and Engineering Research

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 …

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Non-Programmers Identifying Functionality In Unfamiliar Code: Strategies And Barriers, Paul Gross, Caitlin Kelleher Jan 2009

Non-Programmers Identifying Functionality In Unfamiliar Code: Strategies And Barriers, Paul Gross, Caitlin Kelleher

All Computer Science and Engineering Research

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 …

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Augmented Lagrangian Algorithms Under Constraint Partitioning, You Xu, Yixin Chen Jan 2009

Augmented Lagrangian Algorithms Under Constraint Partitioning, You Xu, Yixin Chen

All Computer Science and Engineering Research

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.

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Supercharged Planetlab Platform Architecture, Jonathan Turner, Patrick Crowley, John Dehart, Mart Haitjema, Fred Kuhns Kuhns, Ritun Patney, Michael Wilson, Charlie Wiseman, David Zar Jan 2009

Supercharged Planetlab Platform Architecture, Jonathan Turner, Patrick Crowley, John Dehart, Mart Haitjema, Fred Kuhns Kuhns, Ritun Patney, Michael Wilson, Charlie Wiseman, David Zar

All Computer Science and Engineering Research

This report describes the Supercharged Planetlab Platform (SPP), a system designed as a prototype of an internet-scale overlay hosting platform. Overlay networks have become an important vehicle for delivering Internet applications. Overlay network nodes are typically implemented using general purpose servers or clusters. The SPP offers a more integrated architecture, combining general-purpose servers with high performance Network Processor (NP) subsystems. SPP nodes have recently been deployed as part of the Global Environment for Network Innovation (GENI) and are available for use by research users.

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Self-Stabilizing Computation Of 3-Edge-Connected Components, Abusayeed Saifullah, Yung Tsin Jan 2009

Self-Stabilizing Computation Of 3-Edge-Connected Components, Abusayeed Saifullah, Yung Tsin

All Computer Science and Engineering Research

No abstract provided.

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Design And Evaluation Of A Practical, High Performance Crossbar Scheduler, Jonathan Turner Jan 2009

Design And Evaluation Of A Practical, High Performance Crossbar Scheduler, Jonathan Turner

All Computer Science and Engineering Research

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 …

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Performance-Engineered Network Overlays For High Quality Interaction In Virtual Worlds, Mart Haitjema, Ritun Patney, Jon Turner, Charlie Wiseman, John Dehart Jan 2009

Performance-Engineered Network Overlays For High Quality Interaction In Virtual Worlds, Mart Haitjema, Ritun Patney, Jon Turner, Charlie Wiseman, John Dehart

All Computer Science and Engineering Research

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 …

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Geodesic Grassfire For Computing Mixed-Dimensional Skeletons, Lu Liu, Tao Ju Jan 2009

Geodesic Grassfire For Computing Mixed-Dimensional Skeletons, Lu Liu, Tao Ju

All Computer Science and Engineering Research

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 …

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Enhanced Coordination In Sensor Networks Through Flexible Service Provisioning, Chien-Liang Fok, Gruia-Catalin Roman, Chenyang Lu Jan 2009

Enhanced Coordination In Sensor Networks Through Flexible Service Provisioning, Chien-Liang Fok, Gruia-Catalin Roman, Chenyang Lu

All Computer Science and Engineering Research

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 …

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Throughput-Optimal Systolic Arrays From Recurrence Equations, Arpith C. Jacob, Jeremy D. Buhler, Roger D. Chamberlain Jan 2009

Throughput-Optimal Systolic Arrays From Recurrence Equations, Arpith C. Jacob, Jeremy D. Buhler, Roger D. Chamberlain

All Computer Science and Engineering Research

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 …

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The Virtual Network Scheduling Problem For Heterogeneous Network Emulation Testbeds, Charlie Wisemen, Jonathan Turner Jan 2009

The Virtual Network Scheduling Problem For Heterogeneous Network Emulation Testbeds, Charlie Wisemen, Jonathan Turner

All Computer Science and Engineering Research

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 …

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Architectures For The Future Networks And The Next Generation Internet: A Survey, Subharthi Paul, Jianli Pan, Raj Jain Jan 2009

Architectures For The Future Networks And The Next Generation Internet: A Survey, Subharthi Paul, Jianli Pan, Raj Jain

All Computer Science and Engineering Research

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.

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Defending Against Distributed Denial-Of-Service Attacks With Weight-Fair Router Throttling, Abusayeed Saifullah Jan 2009

Defending Against Distributed Denial-Of-Service Attacks With Weight-Fair Router Throttling, Abusayeed Saifullah

All Computer Science and Engineering Research

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 …

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Open Workflows: Context-Dependent Construction And Execution In Mobile Wireless Settings, Louis Thomas, Justin Wilson, Grui-Catalin Roman, Christopher Gill Jan 2009

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. …

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Globally Clocked Magnetic Logic Circuits, Michael Hall, Albrecht Jander, Roger D. Chamberlain, Pallavi Dhagat Jan 2009

Globally Clocked Magnetic Logic Circuits, Michael Hall, Albrecht Jander, Roger D. Chamberlain, Pallavi Dhagat

All Computer Science and Engineering Research

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.

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Adaptive Service Provisioning For Wireless Sensor Networks, Chien-Liang Fok, Gruia-Catalin Roman, Chenyang Lu Jan 2009

Adaptive Service Provisioning For Wireless Sensor Networks, Chien-Liang Fok, Gruia-Catalin Roman, Chenyang Lu

All Computer Science and Engineering Research

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 …

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A Cryptanalysis Methodology For The Reverse Engineering Of Encrypted Information In Images, Allan Anthony Rwabutaza Jan 2009

A Cryptanalysis Methodology For The Reverse Engineering Of Encrypted Information In Images, Allan Anthony Rwabutaza

Browse all Theses and Dissertations

Security is an important issue related to the storage and communication of data and information. In data and information security, cryptography and steganography are two of the most common security techniques. On one hand, there is cryptography, which is the secret communication between two parties by message scrambling on the sender's side and message unscrambling on the receiver's side so that only the intended receiver gets the secret message. On the other hand, there is steganography, which is the hiding of information in a medium in such a way that no one other than the sender or the intended receiver …

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Radon - Repair And Diagnosis In Ontology Networks, Qiu Ji, Peter Haase, Guilin Qi, Pascal Hitzler, Steffen Stadtmuller Jan 2009

Radon - Repair And Diagnosis In Ontology Networks, Qiu Ji, Peter Haase, Guilin Qi, Pascal Hitzler, Steffen Stadtmuller

Computer Science and Engineering Faculty Publications

One of the major challenges in managing networked and dynamic ontologies is to handle inconsistencies in single ontologies, and inconsistencies introduced by integrating multiple distributed ontologies. Our RaDON system provides functionalities to repair and diagnose ontology networks by extending the capabilities of existing reasoners. The system integrates several new debugging and repairing algorithms, such as a relevance-directed algorithm to meet the various needs of the users.

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Nebraska Summary: S702 Challenger Mt545b, Nebraska Tractor Test Lab Jan 2009

Nebraska Summary: S702 Challenger Mt545b, Nebraska Tractor Test Lab

Nebraska Tractor Tests

ABOUT THE TEST REPORT AND USE OF THE DATA The test data contained in this report are a tabulation of the results of a series of tests. Due to the restricted format of these pages, only a limited amount of data and not all of the tractor specifications are included. The full OECD report contains usually about 30 pages of data and specifications. The test data were obtained for each tractor under similar conditions and therefore, provide a means of comparison of performance based on a limited set of reported data. EXPLANATION OF THE TEST PROCEDURES Purpose The purpose of …

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Nebraska Summary: S701 Challenger Mt535b, Nebraska Tractor Test Lab Jan 2009

Nebraska Summary: S701 Challenger Mt535b, Nebraska Tractor Test Lab

Nebraska Tractor Tests

ABOUT THE TEST REPORT AND USE OF THE DATA The test data contained in this report are a tabulation of the results of a series of tests. Due to the restricted format of these pages, only a limited amount of data and not all of the tractor specifications are included. The full OECD report contains usually about 30 pages of data and specifications. The test data were obtained for each tractor under similar conditions and therefore, provide a means of comparison of performance based on a limited set of reported data. EXPLANATION OF THE TEST PROCEDURES Purpose The purpose of …

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Nebraska Summary: S697 Massey Ferguson 6475, Nebraska Tractor Test Lab Jan 2009

Nebraska Summary: S697 Massey Ferguson 6475, Nebraska Tractor Test Lab

Nebraska Tractor Tests

ABOUT THE TEST REPORT AND USE OF THE DATA The test data contained in this report are a tabulation of the results of a series of tests. Due to the restricted format of these pages, only a limited amount of data and not all of the tractor specifications are included. The full OECD report contains usually about 30 pages of data and specifications. The test data were obtained for each tractor under similar conditions and therefore, provide a means of comparison of performance based on a limited set of reported data. EXPLANATION OF THE TEST PROCEDURES Purpose The purpose of …

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