Results 1 - 10
of
182
Computational visual attention systems and their cognitive foundations: A survey
- ACM Trans. on Applied Perception
"... Based on concepts of the human visual system, computational visual attention systems aim to detect regions of interest in images. Psychologists, neurobiologists, and computer scientists have investigated visual attention thoroughly during the last decades and profited considerably from each other. H ..."
Abstract
-
Cited by 67 (4 self)
- Add to MetaCart
Based on concepts of the human visual system, computational visual attention systems aim to detect regions of interest in images. Psychologists, neurobiologists, and computer scientists have investigated visual attention thoroughly during the last decades and profited considerably from each other. However, the interdisciplinarity of the topic holds not only benefits but also difficulties: concepts of other fields are usually hard to access due to differences in vocabulary and lack of knowledge of the relevant literature. This paper aims to bridge this gap and bring together concepts and ideas from the different research areas. It provides an extensive survey of the grounding psychological and biological research on visual attention as well as the current state of the art of computational systems. Furthermore, it presents a broad range of applications of computational attention systems in fields like computer vision, cognitive systems and mobile robotics. We conclude with a discussion on the limitations and open questions in the field.
Continuity analysis of programs
- SIGPLAN Not
"... We present an analysis to automatically determine if a program represents a continuous function, or equivalently, if infinitesimal changes to its inputs can only cause infinitesimal changes to its outputs. The analysis can be used to verify the robustness of programs whose inputs can have small amou ..."
Abstract
-
Cited by 40 (12 self)
- Add to MetaCart
(Show Context)
We present an analysis to automatically determine if a program represents a continuous function, or equivalently, if infinitesimal changes to its inputs can only cause infinitesimal changes to its outputs. The analysis can be used to verify the robustness of programs whose inputs can have small amounts of error and uncertainty— e.g., embedded controllers processing slightly unreliable sensor data, or handheld devices using slightly stale satellite data. Continuity is a fundamental notion in mathematics. However, it is difficult to apply continuity proofs from real analysis to functions that are coded as imperative programs, especially when they use diverse data types and features such as assignments, branches, and loops. We associate data types with metric spaces as opposed to just sets of values, and continuity of typed programs is phrased in terms of these spaces. Our analysis reduces questions about continuity
Proving Programs Robust ∗
"... We present a program analysis for verifying quantitative robustness properties of programs, stated generally as: “If the inputs of a program are perturbed by an arbitrary amount ɛ, then its outputs change at most by Kɛ, where K can depend on the size of the input but not its value. ” Robustness prop ..."
Abstract
-
Cited by 38 (6 self)
- Add to MetaCart
(Show Context)
We present a program analysis for verifying quantitative robustness properties of programs, stated generally as: “If the inputs of a program are perturbed by an arbitrary amount ɛ, then its outputs change at most by Kɛ, where K can depend on the size of the input but not its value. ” Robustness properties generalize the analytic notion of continuity—e.g., while the function e x is continuous, it is not robust. Our problem is to verify the robustness of a function P that is coded as an imperative program, and can use diverse data types and features such as branches and loops. Our approach to the problem soundly decomposes it into two subproblems: (a) verifying that the smallest possible perturbations to the inputs of P do not change the corresponding outputs significantly, even if control now flows
Secure control against replay attacks
- Proceedings of the 47th annual Allerton conference on Communication, control, and computing
, 2009
"... This paper analyzes the effect of replay attacks on a control system. We assume an attacker wishes to disrupt the operation of a control system in steady state. In order to inject an exogenous control input without being detected the attacker will hijack the sensors, observe and record their reading ..."
Abstract
-
Cited by 23 (1 self)
- Add to MetaCart
(Show Context)
This paper analyzes the effect of replay attacks on a control system. We assume an attacker wishes to disrupt the operation of a control system in steady state. In order to inject an exogenous control input without being detected the attacker will hijack the sensors, observe and record their readings for a certain amount of time and repeat them afterwards while carrying out his attack. This is a very common and natural attack (we have seen numerous times intruders recording and replaying security videos while performing their attack undisturbed) for an attacker who does not know the dynamics of the system but is aware of the fact that the system itself is expected to be in steady state for the duration of the attack. We assume the control system to be a discrete time linear time invariant gaussian system applying an infinite horizon Linear Quadratic Gaussian (LQG) controller. We also assume that the system is equipped with a χ 2 failure detector. The main contributions of the paper, beyond the novelty of the problem formulation, consist in 1) providing conditions on the feasibility of the replay attack on the aforementioned system and 2) proposing a countermeasure that guarantees a desired probability of detection (with a fixed false alarm rate) by trading off either detection delay or LQG performance, either by decreasing control accuracy or increasing control effort. 1.
A pret microarchitecture implementation with repeatable timing and competitive performance
- In To appear in Proceedings of International Conference on Computer Design (ICCD
, 2012
"... Abstract—We contend that repeatability of execution times is crucial to the validity of testing of real-time systems. However, computer architecture designs fail to deliver repeatable timing, a consequence of aggressive techniques that improve averagecase performance. This paper introduces the Preci ..."
Abstract
-
Cited by 22 (10 self)
- Add to MetaCart
(Show Context)
Abstract—We contend that repeatability of execution times is crucial to the validity of testing of real-time systems. However, computer architecture designs fail to deliver repeatable timing, a consequence of aggressive techniques that improve averagecase performance. This paper introduces the Precision-Timed ARM (PTARM), a precision-timed (PRET) microarchitecture implementation that exhibits repeatable execution times without sacrificing performance. The PTARM employs a repeatable thread-interleaved pipeline with an exposed memory hierarchy, including a repeatable DRAM controller. Our benchmarks show an improved throughput compared to a single-threaded in-order five-stage pipeline, given sufficient parallelism in the software. I.
Taming Dr. Frankenstein: Contract-Based Design for Cyber-Physical Systems
- European Journal of Control
, 2012
"... Abstract—Cyber-physical systems combine a cyber side (com-puting and networking) with a physical side (mechanical, electri-cal, and chemical processes). In many cases, the cyber component controls the physical side using sensors and actuators that observe the physical system and actuate the controls ..."
Abstract
-
Cited by 21 (5 self)
- Add to MetaCart
(Show Context)
Abstract—Cyber-physical systems combine a cyber side (com-puting and networking) with a physical side (mechanical, electri-cal, and chemical processes). In many cases, the cyber component controls the physical side using sensors and actuators that observe the physical system and actuate the controls. Such systems present the biggest challenges as well as the biggest opportunities in several large industries, including electronics, energy, automotive, defense and aerospace, telecommunications, instrumentation, industrial automation. Engineers today do successfully design cyber-physical systems in a variety of industries. Unfortunately, the development of systems is costly, and development schedules are difficult to stick to. The complexity of cyber-physical systems, and particularly the increased performance that is offered from interconnecting what in the past have been separate systems, increases the design and verification challenges. As the complexity of these systems in-creases, our inability to rigorously model the interactions between the physical and the cyber sides creates serious vulnerabilities. Systems become unsafe, with disastrous inexplicable failures that could not have been predicted. Distributed control of multi-scale complex systems is largely an unsolved problem. A common view that is emerging in research programs in Europe and the US is “enabling contract-based design (CBD),” which formulates a broad and aggressive scope to address urgent needs in the systems industry. We present a design methodology and a few examples in controller design whereby contract-based design can be merged with platform-based design to formulate the design process as a meet-in-the-middle approach, where design requirements are implemented in a subsequent refinement process using as much as possible elements from a library of available components. Contracts are formalizations of the conditions for correctness of element integration (horizontal contracts), for lower level of abstraction to be consistent with the higher ones, and for abstractions of available components to be faithful representations of the actual parts (vertical contracts).
Suo H, "A survey of cyberphysical systems
- International Conference on Wireless Communications and Signal Processing
, 2011
"... Abstract — Cyber-Physical Systems (CPSs) are characterized by integrating computation and physical processes. The theories and applications of CPSs face the enormous challenges. The aim of this work is to provide a better understanding of this emerging multi-disciplinary methodology. First, the feat ..."
Abstract
-
Cited by 20 (4 self)
- Add to MetaCart
(Show Context)
Abstract — Cyber-Physical Systems (CPSs) are characterized by integrating computation and physical processes. The theories and applications of CPSs face the enormous challenges. The aim of this work is to provide a better understanding of this emerging multi-disciplinary methodology. First, the features of CPSs are described, and the research progresses are summarized from different perspectives such as energy control, secure control, transmission and management, control technique, system resource allocation, and model-based software design. Then three classic applications are given to show that the prospects of CPSs are engaging. Finally, the research challenges and some suggestions for future work are in brief outlined. Keywords – cyber-physical systems (CPSs); communications; computation; control I.
Temporal isolation on multiprocessing architectures
- in DAC. ACM
, 2011
"... Multiprocessing architectures provide hardware for executing multiple tasks simultaneously via techniques such as simultaneous multithreading and symmetric multiprocessing. The problem addressed by this paper is that even when tasks that are executing concurrently do not communicate, they may interf ..."
Abstract
-
Cited by 17 (10 self)
- Add to MetaCart
(Show Context)
Multiprocessing architectures provide hardware for executing multiple tasks simultaneously via techniques such as simultaneous multithreading and symmetric multiprocessing. The problem addressed by this paper is that even when tasks that are executing concurrently do not communicate, they may interfere by affecting each other’s timing. For cyberphysical system applications, such interference can nullify many of the advantages offered by parallel hardware. In this paper, we argue for temporal semantics in layers of abstraction in computing. This will enable us to achieve temporal isolation on multiprocessing architectures. We discuss techniques at the microarchitecture level, in the memory hierarchy, in on-chip communication, and in the instruction-set architecture that can provide temporal semantics and control over timing. Categories and Subject Descriptors
A Theory of Synchronous Relational Interfaces
, 2010
"... In a component-based design context, we propose a relational interface theory for synchronous systems. A component is abstracted by its interface, which consists of input and output variables, as well as one or more contracts. A contract is a relation between input and output assignments. In the sta ..."
Abstract
-
Cited by 8 (5 self)
- Add to MetaCart
(Show Context)
In a component-based design context, we propose a relational interface theory for synchronous systems. A component is abstracted by its interface, which consists of input and output variables, as well as one or more contracts. A contract is a relation between input and output assignments. In the stateless case, there is a single contract that holds at every synchronous round. In the general, stateful, case, the contract may depend on the state, modeled as the history of past observations. Interfaces can be composed by connection or feedback. Parallel composition is a special case of connection. Feedback is allowed only for Moore interfaces, where the contract does not depend on the current values of the input variables that are connected (although it may depend on past values of such variables). The theory includes explicit notions of environments, pluggability and substitutability. Environments are themselves interfaces. Pluggability means that the closed-loop system formed by an interface and an environment is well-formed, that is, a state with unsatisfiable contract is unreachable. Substitutability means that an interface can replace another interface in any environment. A refinement relation between interfaces is proposed, that has two main properties: first, it is preserved by composition; second, it is equivalent to substitutability for well-formed interfaces. Shared refinement and abstraction operators, corresponding to greatest lower and least upper bounds with respect to refinement, are also defined. Input-complete interfaces, that impose no restrictions on inputs, and deterministic interfaces, that produce a unique output for any legal input, are discussed as special cases, and an interesting duality between the two classes is exposed. A number of illustrative examples are provided, as well as algorithms to compute compositions, check refinement, and so on, for finite-state interfaces.
