| 1. |
- Araujo, Carlos Moyses, et al.
(author)
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Disorder-induced Room Temperature Ferromagnetism in Glassy Chromites
- 2014
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4, s. 4686-
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Journal article (peer-reviewed)abstract
- We report an unusual robust ferromagnetic order above room temperature upon amorphization of perovskite [YCrO3] in pulsed laser deposited thin films. This is contrary to the usual expected formation of a spin glass magnetic state in the resulting disordered structure. To understand the underlying physics of this phenomenon, we combine advanced spectroscopic techniques and first-principles calculations. We find that the observed order-disorder transformation is accompanied by an insulator-metal transition arising from a wide distribution of Cr-O-Cr bond angles and the consequent metallization through free carriers. Similar results also found in YbCrO3-films suggest that the observed phenomenon is more general and should, in principle, apply to a wider range of oxide systems. The ability to tailor ferromagnetic order above room temperature in oxide materials opens up many possibilities for novel technological applications of this counter intuitive effect.
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| 2. |
- Nagar, Sandeep, et al.
(author)
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Room Temperature Ferromagnetism and Lack of Ferroelectricity in Thin Films of 'Biferroic?' YbCrO3
- 2009
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In: Novel Materials and Devices for Spintronics. - : Materials Research Society. - 9781605111568 ; , s. 163-168
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Conference paper (peer-reviewed)abstract
- Search for novel multi-functional materials, especially multiferroics, which are ferromagnetic above room temperature and at the same time exhibit a ferroelectric behavior much above room temperature, is an active topic of extensive studies today Ability to address an entity with an external field, laser beam, and also electric potential is a welcome challenge to develop multifunctional devices enabled by nanoscience While most of the studies to date have been on various forms of Bi and Ba based Ferrites, rare earth chromites are a new class of materials which appear to show some promise However m the powder and bulk form these materials are at best canted antiferromagnets with the magnetic transition temperatures much below room temperature In this presentation we show that thin films of YbCrO3 deposited by Pulsed Laser Deposition exhibit robust ferromagnetic properties above room temperature It is indeed a welcome surprise and a challenge to understand the evolution of above room temperature ferromagnetism in such a thin film The thin films are amorphous in contrast to the powder and bulk forms which are crystalline The magnetic properties are those of a soft magnet with low coercivity We present extensive investigations of the magnetic and ferroelectric properties, and spectroscopic studies using XAS techniques to understand the electronic states of the constituent atoms in this novel Chromite While the amorphous films are ferromagnetic much above room temperature, we show that any observation of ferroelectric property in these films is an artifact of a leaky highly resistive material
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| 3. |
- Joshi, Prachi, et al.
(author)
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Approaches for Assigning Offsets to Signals for Improving Frame Packing in CAN-FD
- 2020
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In: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0070 .- 1937-4151. ; 39, s. 1109-1122
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Journal article (peer-reviewed)abstract
- Controller area network (CAN) is a widely used protocol that allows communication among electronic control units (ECUs) in automotive electronics. It was extended to CAN with flexible data-rate (CAN-FD) to meet the increasing demand for bandwidth generated by the growing number of features in modern automobiles. The signal-to-frame packing problem has been studied in the literature for both CAN and CAN-FD. In this paper, we propose and formulate the signal offset assignment problem (SOAP) in CAN-FD to improve the bus utilization during frame packing. We propose two algorithmic themes to solve SOAP and establish their worst case performance guarantees. The first is a general approximation framework (GAF) which can use any approximation algorithm for the makespan minimization problem (MMP) in multiprocessor systems. Its performance guarantee is the product of the performance guarantee of the MMP algorithm and the number of distinct periods in the frame. The second is a 2-D strip packing-based framework (2DSPF) which uses the bottom left fill algorithm for 2-D strip packing. The performance guarantee is 2G , where G is the minimum number of groups into which the set of signals can be partitioned so that the periods of the signals in the same group form a geometric series. The experimental results for GAF and 2DSPF indicate that by carefully assigning offsets for signals in frame packing schemes, one can achieve about 10.83% improvement in bus utilization in CAN-FD systems.
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| 4. |
- Joshi, Prachi, et al.
(author)
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Offset Assignment to Signals for Improving Frame Packing in CAN-FD
- 2017
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In: 2017 IEEE REAL-TIME SYSTEMS SYMPOSIUM (RTSS). - : IEEE. - 9781538614143 ; , s. 167-177
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Conference paper (peer-reviewed)abstract
- Controller Area Network (CAN) is a widely used protocol that allows communication among Electronic Control Units (ECUs) in automotive electronics. It was extended to CAN-FD (CAN with Flexible Data-rate) to meet the increasing demand for bandwidth utilization caused by the growing number of features in modern automobiles. The signal-to-frame packing problem has been studied in literature for both CAN and CAN-FD. In this work, we propose and formulate, for the first time, the signal offset assignment problem (SOAP) in a frame in order to improve the bus bandwidth utilization. We prove that SOAP is NP-complete. We propose a general approximation framework (GAF) for SOAP which can use any approximation algorithm for the makespan minimization problem (MMP) in multiprocessor systems. We derive the performance guarantee provided by GAF as a function of the performance guarantee of the approximation algorithm for MMP and the number of signal periods in the frame. We demonstrate the efficacy of our approach through experiments using three different algorithms (two approximation algorithms and an integer linear programming formulation) for MMP in GAF. Our results indicate that by using offsets for signals in frame packing schemes, one can achieve about 10.54% improvement in bandwidth utilization (on a single bus) in CAN-FD systems.
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| 5. |
- Joshi, Prachi, et al.
(author)
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The Multi-Domain Frame Packing Problem for CAN-FD
- 2017
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In: 29th Euromicro Conference on Real-Time Systems (ECRTS 2017). - : Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik. - 9783959770378
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Conference paper (peer-reviewed)abstract
- The Controller Area Network with Flexible Data-Rate (CAN-FD) is a new communication protocol to meet the bandwidth requirements for the constantly growing volume of data exchanged in modern vehicles. The problem of frame packing for CAN-FD, as studied in the literature, assumes a single sub-system where one CAN-FD bus serves as the communication medium among several Electronic Control Units (ECUs). Modern automotive electronic systems, on the other hand, consist of several sub-systems, each facilitating a certain functional domain such as powertrain, chassis and suspension. A substantial fraction of all signals is exchanged across sub-systems. In this work, we study the frame packing problem for CAN-FD with multiple sub-systems, and propose a two-stage optimization framework. In the first stage, we pack the signals into frames with the objective of minimizing the bandwidth utilization. In the second stage, we extend Audsley's algorithm to assign priorities/identifiers to the frames. In case the resulting solution is not schedulable, our framework provides a potential repacking method. We propose two solution approaches: (a) an Integer Linear Programming (ILP) formulation that provides an optimal solution but is computationally expensive for industrial-size problems; and (b) a greedy heuristic that scales well and provides solutions that are comparable to optimal solutions. Experimental results show the efficiency of our optimization framework in achieving feasible solutions with low bandwidth utilization. The results also show a significant improvement over the case when there is no cross-domain consideration (as in prior work).
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| 6. |
- Mathaikutty, Deepak A., et al.
(author)
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SML-Sys : a functional framework with multiple models of computation for modeling heterogeneous system
- 2008
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In: Design automation for embedded systems. - : Springer Science and Business Media LLC. - 0929-5585 .- 1572-8080. ; 12:1-2, s. 1-30
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Journal article (peer-reviewed)abstract
- System-on-Chip and other complex distributed hardware/software systems contain heterogeneous components. High-level modeling of such systems require frameworks that provide designers with the ability to express concepts of models of computation (MoC)s as modeling constructs. Many system-level modeling frameworks and corresponding modeling notations such as Ptolemy II and SystemC-H facilitate multi-MoC modeling but are based on imperative programming languages (C++, Java, etc). In such frameworks, the computation and communication aspects between the components of models get intertwined thereby hindering its amenability to formal analysis. In this work, we illustrate function-based semantic definitions of MoCs, which are formulated in a functional framework called SML-Sys. We illustrate through a number of examples how to create system models using this functional programming paradigm.
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| 7. |
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| 8. |
- Mathaikutty, Deepak Abraham, et al.
(author)
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UMoC++ : A C++-Based Multi-MoC Modeling Environment
- 2006
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In: Advances in Design and Specification Languages for SoCs. - : Springer Publishing Company. ; , s. 115-130
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Conference paper (peer-reviewed)abstract
- System-on-chip (SoC) and other complex distributed hardware/software systemscontain heterogeneous components that necessitate frameworks capable of expressingheterogeneous models of computation (MoCs) for modeling their functionalities.System-level design languages (SLDLs) that facilitate multi-MoCmodeling should have well-defined semantics and should be readily subjectedto formal analysis to handle the design complexity. As a result, we follow themulti-MoC paradigm based on timing abstraction and functional parameterizationsthat have rigorous denotational semantics, which are compliant to functionalidioms as shown in functional frameworks such as ForSyDe and SML-Sys.However, functional frameworks are not widely used in the industry due toissues related to efficiency and interoperability with other widely used SLDLs.This imposes a requirement for an imperative language-based implementationof these generic MoCs that offers all the advantages of the underlying formalsemantics. In this chapter, we formulate the basis for having generic MoCs in animperative language and describe the implementation of an untimed modelingframework called UMoC++.
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| 9. |
- Mathaikutty, Deepak A., et al.
(author)
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UMoC plus plus : A C plus plus -based Multi-MoC modeling environment
- 2006
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In: APPLICATIONS OF SPECIFICATION AND DESIGN LANGUAGES FOR SOCS. - Dordrecht : SPRINGER. ; , s. 115-130
-
Conference paper (peer-reviewed)abstract
- System-on-chip (SoC) and other complex distributed hardware/software systems contain heterogeneous components that necessitate frameworks capable of expressing heterogeneous models of computation (MoCs) for modeling their functionalities. System-level design languages (SLDLs) that facilitate multi-MoC modeling should have well-defined semantics and should be readily subjected to formal analysis to handle the design complexity. As a result, we follow the multi-MoC paradigm based on timing abstraction and functional parameterizations that have rigorous denotational semantics, which are compliant to functional idioms as shown in functional frameworks such as ForSyDe and SML-Sys. However, functional frameworks are not widely used in the industry due to issues related to efficiency and interoperability with other widely used SLDLs. This imposes a requirement for an imperative language-based implementation of these generic MoCs that offers all the advantages of the underlying formal semantics. In this chapter, we formulate the basis for having generic MoCs in an imperative language and describe the implementation of an untimed modeling framework called UMoC++.
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| 10. |
- Mueller, Sven Christian, et al.
(author)
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Interfacing Power System and ICT Simulators : Challenges, State-of-the-Art, and Case Studies
- 2018
-
In: IEEE Transactions on Smart Grid. - : Institute of Electrical and Electronics Engineers (IEEE). - 1949-3053 .- 1949-3061. ; 9:1, s. 14-24
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Journal article (peer-reviewed)abstract
- With the transition toward a smart grid, the power system has become strongly intertwined with the information and communication technology (ICT) infrastructure. The interdependency of both domains requires a combined analysis of physical and ICT processes, but simulating these together is a major challenge due to the fundamentally different modeling and simulation concepts. After outlining these challenges, such as time synchronization and event handling, this paper presents an overview of state-of-the-art solutions to interface power system and ICT simulators. Due to their prominence in recent research, a special focus is set on co-simulation approaches and their challenges and potentials. Further, two case studies analyzing the impact of ICT on applications in power system operation illustrate the necessity of a holistic approach and show the capabilities of state-of-the-art co-simulation platforms.
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