| 1. |
- Lindeberg, Tony, 1964-
(författare)
-
On the behaviour in scale-space of local extrema and blobs
- 1991
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Ingår i: Theory and Applications of Image Analysis. - : World Scientific. ; , s. 38-47, s. 8-17
-
Bokkapitel (refereegranskat)abstract
- We apply elementary techniques from real analysis and singularity theory to derive analytical results for the behaviour in scale-space of critical points and related entities. The main results of the treatment comprise: a description of the general nature of trajectories of critical points in scale-space. an estimation of the drift velocity of critical points and edges. an analysis of the qualitative behaviour of critical points in bifurcation situations. a classification of what types of blob bifurcations are possible.
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| 2. |
- Åkerman, S., et al.
(författare)
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Surface Model Generation and Segmentation of the Human Celebral Cortex for the Construction of Unfolded Cortical Maps
- 1996
-
Ingår i: Proc. 2nd International Conference on Functional Mapping of the Human Brain. ; , s. S126-S126
-
Konferensbidrag (refereegranskat)abstract
- Representing the shape of the human cerebral cortex arises as a basic subproblem in several areas of brain science, such as when describing the anatomy of the cortex and when relating functional measurements to cortical regions. Most current methods for building such representions of the cortical surface are either based on contours from two-dimensional cross sections or landmarks that have been obtained manually.In this article, we outline a methodology for semi-automatic contruction of a solely surface based representation of the human cerebral cortex in vivo for subsequent generation of (unfolded) two-dimensional brain maps.The method is based on input data in the form of three-dimensional NMR images, and comprises the following main steps:suppression of disturbing fine-scale structures by linear and non-linear scale-space techniques,generation of a triangulated surface representation based on either iso-surfaces or three-dimensional edge detection,division of the surface model into smaller segments based on differential invariants computed from the image data.When constructing an unfolded (flattened) surface representation, the instrinsic curvature of the cortex means that such a unfolding cannot be done without introducing distortions. To reduce this problem, we propose to cut the surface into smaller parts, where a ridge detector acts as guideline, and then unfold each patch individually, so as to obtain low distortions.Having a solely surface based representation of the cortex and expressing the image operations using multi-scale differential invariants in terms of scale-space derivatives as done in this work is a natural choice both in terms of conceptual and algorithmic simplicity. Moreover, explicitly handling the multi-scale nature of the data is necessary to obtain robust results.
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| 3. |
- Jonsson, Erland, 1946, et al.
(författare)
-
A quantitative model of the security intrusion process based on attacker behavior
- 1997
-
Ingår i: IEEE Transactions on Software Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 0098-5589 .- 1939-3520. ; 23:4, s. 235-245
-
Tidskriftsartikel (refereegranskat)abstract
- This paper is based on a conceptual framework in which security can be split into two generic types of characteristics, behavioral and preventive. Here, preventive security denotes the system's ability to protect itself from external attacks. One way to describe the preventive security of a system is in terms of its interaction with the alleged attacker, i.e., by describing the intrusion process. To our knowledge, very little is done to model this process in quantitative terms. Therefore, based on empirical data collected from intrusion experiments, we have worked out a hypothesis on typical attacker behavior. The hypothesis suggests that the attacking process can be split into three phases: the learning phase, the standard attack phase, and the innovative attack phase. The probability for successful attacks during the learning and innovative phases is expected to be small, although for different reasons. During the standard attack phase it is expected to be considerably higher. The collected data indicates that the breaches during the standard attack phase are statistically equivalent and that the times between breaches are exponentially distributed. This would actually imply that traditional methods for reliability modeling could be applicable.
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| 4. |
- Jonsson, Erland, 1946, et al.
(författare)
-
Security intrusion process: an empirical model
- 1997
-
Ingår i: IEEE Aerospace and Electronic Systems Magazine. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8985. ; 12:4, s. 7-17
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes a security model developed from empirical data collected from a realistic intrusion experiment in which a number of undergraduate students were invited to attack a distributed computer system. Relevant data, with respect to their intrusion activities, were recorded continuously. We have worked out a hypothesis on typical attacker behavior based on experiences from this and other similar experiments. The hypothesis suggests that the attacking process can be split into three phases: the learningphase, the standard attack phase and the innovative attack phase. The probability for successful attacks during the learning phase is expected to be small and, if a breach occurs, it is rather a result of pure luck than deliberate action. During the standard attack phase, this probability is considerably higher, whereas it decreases again in the innovative attack phase. The collected data indicates that the breaches during the standard attack phase are statistically equivalent. Furthermore, the times between breaches seem to be exponentially distributed, which means that traditional methods for reliability modelling of component failures may be applicable.
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| 5. |
- Lindeberg, Tony, 1964-, et al.
(författare)
-
Analysis of brain activation patterns using a 3-D scale-space primal sketch
- 1999
-
Ingår i: Human Brain Mapping. - 1065-9471 .- 1097-0193. ; 7:3, s. 166-94
-
Tidskriftsartikel (refereegranskat)abstract
- A fundamental problem in brain imaging concerns how to define functional areas consisting of neurons that are activated together as populations. We propose that this issue can be ideally addressed by a computer vision tool referred to as the scale-space primal sketch. This concept has the attractive properties that it allows for automatic and simultaneous extraction of the spatial extent and the significance of regions with locally high activity. In addition, a hierarchical nested tree structure of activated regions and subregions is obtained. The subject in this article is to show how the scale-space primal sketch can be used for automatic determination of the spatial extent and the significance of rCBF changes. Experiments show the result of applying this approach to functional PET data, including a preliminary comparison with two more traditional clustering techniques. Compared to previous approaches, the method overcomes the limitations of performing the analysis at a single scale or assuming specific models of the data.
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| 6. |
- Lindeberg, Tony, 1964-, et al.
(författare)
-
Linear Scale-Space II : Early visual operations
- 1994
-
Ingår i: Geometry-Driven Diffusion in Vision. - : Kluwer Academic Publishers. ; , s. 43-77
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Vision deals with the problem of deriving information about the world from the light reflected from it. Although the active and task-oriented nature of vision is only implicit in this formulation, this view captures several of the essential aspects of vision. As Marr (1982) phrased it in his book Vision, vision is an information processing task, in which an internal representation of information is of utmost importance. Only by representation information can be captured and made available to decision processes. The purpose of a representation is to make certain aspects of the information content explicit, that is, immediately accessible without any need for additional processing.This introductory chapter deals with a fundamental aspect of early image representation---the notion of scale. As Koenderink (1984) emphasizes, the problem of scale must be faced in any imaging situation. An inherent property of objects in the world and details in images is that they only exist as meaningful entities over certain ranges of scale. A simple example of this is the concept of a branch of a tree, which makes sense only at a scale from, say, a few centimeters to at most a few meters. It is meaningless to discuss the tree concept at the nanometer or the kilometer level. At those scales it is more relevant to talk about the molecules that form the leaves of the tree, or the forest in which the tree grows. Consequently, a multi-scale representation is of crucial importance if one aims at describing the structure of the world, or more specifically the structure of projections of the three-dimensional world onto two-dimensional images.The need for multi-scale representation is well understood, for example, in cartography; maps are produced at different degrees of abstraction. A map of the world contains the largest countries and islands, and possibly, some of the major cities, whereas towns and smaller islands appear at first in a map of a country. In a city guide, the level of abstraction is changed considerably to include streets and buildings etc. In other words, maps constitute symbolic multi-scale representations of the world around us, although constructed manually and with very specific purposes in mind.To compute any type of representation from image data, it is necessary to extract information, and hence interact with the data using certain operators. Some of the most fundamental problems in low-level vision and image analysis concern: what operators to use, where to apply them, and how large they should be. If these problems are not appropriately addressed, the task of interpreting the output results can be very hard. Ultimately, the task of extracting information from real image data is severely influenced by the inherent measurement problem that real-world structures, in contrast to certain ideal mathematical entities, such as ``points'' or ``lines'', appear in different ways depending upon the scale of observation.Phrasing the problem in this way shows the intimate relation to physics. Any physical observation by necessity has to be done through some finite aperture, and the result will, in general, depend on the aperture of observation. This holds for any device that registers physical entities from the real world including a vision system based on brightness data. Whereas constant size aperture functions may be sufficient in many (controlled) physical applications, e.g., fixed measurement devices, and also the aperture functions of the basic sensors in a camera (or retina) may have to determined a priori because of practical design constraints, it is far from clear that registering data at a fixed level of resolution is sufficient. A vision system for handling objects of different sizes and at difference distances needs a way to control the scale(s) at which the world is observed.The goal of this chapter is to review some fundamental results concerning a framework known as scale-space that has been developed by the computer vision community for controlling the scale of observation and representing the multi-scale nature of image data. Starting from a set of basic constraints (axioms) on the first stages of visual processing it will be shown that under reasonable conditions it is possible to substantially restrict the class of possible operations and to derive a (unique) set of weighting profiles for the aperture functions. In fact, the operators that are obtained bear qualitative similarities to receptive fields at the very earliest stages of (human) visual processing (Koenderink 1992). We shall mainly be concerned with the operations that are performed directly on raw image data by the processing modules are collectively termed the visual front-end. The purpose of this processing is to register the information on the retina, and to make important aspects of it explicit that are to be used in later stage processes. If the operations are to be local, they have to preserve the topology at the retina; for this reason the processing can be termed retinotopic processing.Early visual operationsAn obvious problem concerns what information should be extracted and what computations should be performed at these levels. Is any type of operation feasible? An axiomatic approach that has been adopted in order to restrict the space of possibilities is to assume that the very first stages of visual processing should be able to function without any direct knowledge about what can be expected to be in the scene. As a consequence, the first stages of visual processing should be as uncommitted and make as few irreversible decisions or choices as possible.The Euclidean nature of the world around us and the perspective mapping onto images impose natural constraints on a visual system. Objects move rigidly, the illumination varies, the size of objects at the retina changes with the depth from the eye, view directions may change etc. Hence, it is natural to require early visual operations to be unaffected by certain primitive transformations (e.g. translations, rotations, and grey-scale transformations). In other words, the visual system should extract properties that are invariant with respect to these transformations.As we shall see below, these constraints leads to operations that correspond to spatio-temporal derivatives which are then used for computing (differential) geometric descriptions of the incoming data flow. Based on the output of these operations, in turn, a large number of feature detectors can be expressed as well as modules for computing surface shape.The subject of this chapter is to present a tutorial overview on the historical and current insights of linear scale-space theories as a paradigm for describing the structure of scalar images and as a basis for early vision. For other introductory texts on scale-space; see the monographs by Lindeberg (1991, 1994) and Florack (1993) as well as the overview articles by ter Haar Romeny and Florack (1993) and Lindeberg (1994).
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| 7. |
- Avatare, Anneli, et al.
(författare)
-
The APS/AMID Project
- 1991
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Bretzner, Lars, et al.
(författare)
-
Use your hand as a 3-D mouse or relative orientation from extended sequences of sparse point and line correspondances using the affine trifocal tensor
- 1998
-
Ingår i: Computer Vision — ECCV'98. - : Springer Berlin/Heidelberg. ; , s. 141-157
-
Konferensbidrag (refereegranskat)abstract
- This paper addresses the problem of computing three-dimensional structure and motion from an unknown rigid configuration of point and lines viewed by an affine projection model. An algebraic structure, analogous to the trilinear tensor for three perspective cameras, is defined for configurations of three centered affine cameras. This centered affine trifocal tensor contains 12 coefficients and involves linear relations between point correspondences and trilinear relations between line correspondences It is shown how the affine trifocal tensor relates to the perspective trilinear tensor, and how three-dimensional motion can be computed from this tensor in a straightforward manner. A factorization approach is also developed to handle point features and line features simultaneously in image sequences.This theory is applied to a specific problem of human-computer interaction of capturing three-dimensional rotations from gestures of a human hand. A qualitative model is presented, in which three fingers are represented by their position and orientation, and it is shown how three point correspondences (blobs at the finger tips) and three line correspondences (ridge features at the fingers) allow the affine trifocal tensor to be determined, from which the rotation is computed. Besides the obvious application, this test problem illustrates the usefulness of the affine trifocal tensor in a situation where sufficient information is not available to compute the perspective trilinear tensor, while the geometry requires point correspondences as well as line correspondences over at least three views.
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| 9. |
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| 10. |
- Lindeberg, Tony, 1964-, et al.
(författare)
-
Förfarande och anordning för överföring av information genom rörelsedetektering, samt användning av anordningen : [Method and arrangement for controlling means for three-dimensional transfer of information by motion detection]
- 1998
-
Patent (populärvet., debatt m.m.)abstract
- The invention concerns a method and an arrangement for controlling means (24, 26), themselves controlled by processors, for three-dimensional transfer of information by motion detection using an image capturing device (20). Features of an object (10) are detected and transferred to line and point correspondences, which are used for controlling means (22, 26) to perform rotational and translational motion.
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| 11. |
- Eriksson, Patric, et al.
(författare)
-
A role for 'sensor simulation' and 'pre-emptive learning' in computer aided robotics
- 1995
-
Ingår i: 26th International Symposium on Industrial Robots, Symposium Proceedings. - : Mechanical Engineering Publ.. - 1860580009 ; , s. 135-140
-
Konferensbidrag (refereegranskat)abstract
- Sensor simulation in Computer Aided Robotics (CAR) can enhance the capabilities of such systems to enable off-line generation of programmes for sensor driven robots. However, such sensor simulation is not commonly supported in current computer aided robotic environments. A generic sensor object model for the simulation of sensors in graphical environments is described in this paper. Such a model can be used to simulate a variety of sensors, for example photoelectric, proximity and ultrasonic sensors. Tests results presented here show that this generic sensor model can be customised to emulate the characteristics of the real sensors. The preliminary findings from the first off-line trained mobile robot are presented. The results indicate that sensor simulation within CARs can be used to train robots to adapt to changing environments.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
- Chen, Eric Zhi, 1963-
(författare)
-
Further results on difference triangle sets
- 1994
-
Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 40:4, s. 1268-1270
-
Tidskriftsartikel (refereegranskat)abstract
- Further results on the upper bounds for difference tri8nglesets (DTS) are derived from disjoint difference sets and additive sequencesof permutations, whit3 greatly improve the known bounds.
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| 16. |
- Chen, Eric Zhi, 1963-
(författare)
-
Six new binary quasi-cyclic codes
- 1994
-
Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 40:5, s. 1666-1667
-
Tidskriftsartikel (refereegranskat)abstract
- Six new quasi-cyclic codes are presented, which improve thelower bounds on the minimum distance for a binary code. A localexhaustive search is used to find these codes and many other quasi-cycliccodes which attain the lower bounds.
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| 17. |
- Chen, Wende, et al.
(författare)
-
New constructions of disjoint distinct difference sets
- 1998
-
Ingår i: Designs, Codes and Cryptography. - 0925-1022 .- 1573-7586. ; 15:2, s. 157-165
-
Tidskriftsartikel (refereegranskat)abstract
- New constructions of regular disjoint distinct difference sets (DDDS) are presented. In particular,multiplicative and additive DDDS are considered.
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| 18. |
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| 19. |
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| 20. |
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| 21. |
- Einarson, Daniel, 1960-
(författare)
-
Inheritance and coroutines
- 1998
-
Ingår i: ASU Newsletter. ; 24:3
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 22. |
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Eriksson, Lars-Henrik, et al.
(författare)
-
Formal specification and validation of a cache-coherence protocol
- 1995. - 1
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We specify a cache coherence protocol for cache-only shared memory multiprocessor architectures using the $\pi$-calculus. The analysis of the specification of the protocol is discussed, with emphasis on the use of the modal $\mu$-calculus to express correctness properties. The protocol specification is expressed using recursion variables inside parallel composition and thus it does not adhere to the syntactic requirements for finite control. We argue that the specification still belongs to a class of $\pi$-calculus processes for which model checking and bisimilarity checking is decidable. The relaxation of the syntactical requirement for finite control permits more natural specifications to be made. We expect that specifications which are naturally expressed using recursion variables inside parallel compositions but still permit decidable analyses are common in practise.
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| 27. |
- Eriksson, Magnus, et al.
(författare)
-
Dynamic Radio Resource Management Schemes for Interactive Services in DVB-T and DAB
- 1999
-
Ingår i: Proceedings of Radiovetenskap och kommunikation. - Karlskrona : Högskolan i Karlskrona/Ronneby. - 9163081563
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The topic of this paper is dynamic schemes for downlink packet radio resource management. The results can be applied to personal communication services in the terrestrial digital video and audio broadcasting systems (DVB-T and DAB). Dynamic single frequency networks (DSFN) are investigated, meaning that the macro diversity capability of the COFDM modulation scheme is utilised for cellular communication. The concept of PARPS (Packet and Resource Plan Scheduling) is introduced. PARPS reduces the combined problem of dynamic radio resource management, including DSFN, dynamic channel allocation, power control, link adaptation, etc, to a scheduling problem. We propose several optimised and heuristic PARPS schemes. Our results show that some of the heuristic schemes have near-optimal delay performance. We also have results indicating that the capacity of the PARPS schemes for 2D Poisson traffic can be evaluated with static analyses, i.e. without simulation of a queuing system.
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| 28. |
- Eriksson, Magnus
(författare)
-
Internet och multimedia
- 1996
-
Ingår i: Grunderna i IT. - Stockholm : Utbildningsradion. - 9126963949 ; , s. 12-25
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
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| 29. |
- Eriksson, Magnus, et al.
(författare)
-
The Concepts of PARPS : Packet and Resource Plan Scheduling
- 1999
-
Ingår i: Multiaccess, Mobility and Teletraffic for Wireless Communications (MMT '99), Venice, Italy, October 6-8, 1999.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Dynamic schemes for downlink packet radio resource management (RRM) are the topic of this paper. The concept of PARPS (Packet And Resource Plan Scheduling) is introduced. PARPS reduces the combined proble m of dynamic RRM, including statistical multiplex, dynamic channel allocation, power control, link adaptation, reuse partitioning, soft handover, admission control, etc, to a scheduling problem. PARPS makes it possible to achieve dynamic RRM individually for each data packet, without performing signal-to-interference ratio calculations for every single packet. A PARPS algorithm assigns a so-called resource plan to each timeslot, and assigns data packets to timeslots and transmitters. A resource plan is a combination of several radio parameters, e.g. transmitter power levels, coding rates and modulation schemes, for a group of centrally controlled and synchronised transmitters. We propose several optimised and heuristic PARPS algorithms. Optimised PARPS is NP hard, i.e. it is not realistic to solve in real time for a big system, but it can be used for finding an upper bound for the compound effect of several RRM techniques by means of computer simulations. The heuristic algorithms are realistic to implement in real systems. Our results show that some of the heuristic algorithms have delay performance very near an optimised algorithm, and that the capacity and coverage of a set of resource plans for 2D Poisson traffic can be evaluated with static analyses, i.e. without queuing system simulation. We apply PARPS to cellular systems based on the COFDM modulation scheme. Especially, we have personal communication services in the MEMO system in mind, where the terrestrial digital audio or video broadcasting system (DAB or DVB-T) is used as a broadband downlink, in combination with some narrowband uplink, e.g. GSM.
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| 30. |
- Fodor, George A., 1954-, et al.
(författare)
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The implications of the object/unified modeling language approach to the problem of fault detection and isolation in dynamical systems
- 1999
-
Ingår i: Proceedings of the 1999 IEEE International Symposium on Computer Aided Control System Design. - New York, USA : IEEE conference proceedings. - 0780355008 ; , s. 176-181
-
Konferensbidrag (refereegranskat)abstract
- There is a growing trend to use object-based implementations and modeling in industrial control applications. However, the object-based approach imposes new theoretical and practical problems. Those problems are due to a higher abstraction level that is achievable with objects as compared to the more traditional, state-based fault detection and isolation methods (FDI) approaches. This paper presents a description of the problems and solutions to them in the framework of a discrete FDI method referred to as ontological control. The results are also relevant in respect to domain-independent failure recovery methods... (Fodor et al., 1997)
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| 31. |
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| 32. |
- Jonsson, Magnus, 1969-
(författare)
-
High performance fiber-optic interconnection networks for real-time computing systems
- 1999
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Parallel and distributed computing systems become more and more powerful and hence place increasingly higher demands on the networks that interconnect their processors or processing nodes. Many of the applications running on such systems, especially embedded systems applications, have real-time requirements and, with increasing application demands, high-performance networks are the hearts of these systems. Fiber-optic networks are good candidates for use in such systems in the future. This thesis contributes to the relatively unexplored area of fiber-optic networks for parallel and distributed real-time computer systems and suggests and evaluates several fiber-optic networks and protocols. Two different technologies are used in the networks, WDM (Wavelength Division Multiplexing) and fiber-ribbon point-to-point links. WDM offers multiple channels, each with a capacity of several Gbit/s. A WDM star network in which protocols and services are efficiently integrated to support different kinds of real-time demands, especially hard ones, has been developed. The star-of-stars topology can be chosen to offer better network scalability. The WDM star architecture is attractive but its future success depends on components becoming more commercially mature. Fiber-ribbon links, offering instead an aggregated bandwidth of several Gbit/s, have already reached the market with a promising price/performance ratio. This has motivated the development and investigation of two new ring networks based on fiber-ribbon links. The networks take advantage of spatial bandwidth reuse, which can greatly enhance performance in applications with a significant amount of nearest downstream neighbor communication. One of the ring networks is control channel based and not only has support for real-time services like the WDM star network but also low level support for, e.g., group communication. The approach has been to develop network protocols with support for dynamic real-time services, out of time-deterministic static TDMA systems. The focus has been on functionality more than pure performance figures, mostly on real-time features but also on other types of functionality for parallel and distributed systems. Worst-case analyses, some simulations, and case studies are reported for the networks. The focus has been on embedded supercomputer applications, where each node itself can be a parallel computer, and it is shown that the networks are well suited for use in the radar signal processing systems studied. Other application examples in which these kinds of networks are valuable are distributed multimedia systems, satellite imaging and other image processing applications.
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| 33. |
- Karlgren, Jussi, et al.
(författare)
-
Recognizing Text Genres with Simple Metrics Using Discriminant Analysis
- 1994
-
Ingår i: Proceedings of the 15th International Conference on Computational Linguistics. - Morristown, NJ, USA : Association for Computational Linguistics. ; , s. 1071-1075
-
Konferensbidrag (refereegranskat)abstract
- A simple method for categorizing texts into pre-determined text genre categories using the statistical standard technique of discriminant analysis is demonstrated with application to the Brown corpus. Discriminant analysis makes it possible use a large number of parameters that may be specific for a certain corpus or information stream, and combine them into a small number of functions, with the parameters weighted on basis of how useful they are for discriminating text genres. An application to information retrieval is discussed.
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| 34. |
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| 35. |
- Lindberg, Johan, et al.
(författare)
-
Techniques for a priori decision threshold estimation in speaker verification
- 1998
-
Konferensbidrag (refereegranskat)abstract
- A key problem for field applications in speaker verification is the issue of a priori threshold setting. In the context of the CAVE project several methods for estimating speakerindependent and speaker-dependent decision thresholds were compared. Relevant parameters are estimated from development data only, i.e. without resorting to additional client data. The various approaches were tested on the Dutch SESP database.
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| 36. |
- Palme, Jacob, et al.
(författare)
-
Issues when designing filters in messaging systems
- 1996
-
Ingår i: Computer Communications. - : Elsevier BV. - 0140-3664 .- 1873-703X. ; 19:2, s. 95-101
-
Tidskriftsartikel (refereegranskat)abstract
- The increasing size of messaging communities increases the risk of information overload, especially when group communication tools like mailing lists or asynchronous conferencing systems (like Usenet News) are used. Future messaging systems will require more capable filters to aid users in the selection of what to read. The increasing use of networks by non-computer professionals requires filters that are easier to use and manage than most filtering software today. Filters might use evaluations of messages made by certain users as an aid to filtering these messages for other users.
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| 37. |
- Pettersson, Stefan
(författare)
-
A Comparison of Radio Resource Management Strategies in Bunched Systems for Indoor Communication
- 1999
-
Ingår i: Vehicular Technology Conference, 1999 IEEE 49th. - New York : IEEE. - 0780355652 ; , s. 402-406
-
Konferensbidrag (refereegranskat)abstract
- In this paper we investigate the performance of different channel selection strategies in a 3-dimensional indoor environment. The selection strategies are part of a locally centralized or bunched radio communication system using the SIR as a basis for the channel selection decisions. We evaluate the capacity and the complexity of the system for the different strategies. In the performance evaluation, Fixed Channel Assignment (FCA) is used as a reference. The result show that the capacity is more than five times higher in the bunched system compared with the FCA system for the LNF (Lowest Number First) strategy. We also investigate the impact power control has on the system performance.
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| 38. |
- Schelén, Olov, et al.
(författare)
-
Resource reservation agents in the Internet
- 1998
-
Ingår i: 8th International Workshop on Network and Operating Systems Support for Digital Audio and Video. - Cambridge.
-
Konferensbidrag (refereegranskat)
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| 39. |
- Höök, Kristina, et al.
(författare)
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A glass box approach to adaptive hypermedia
- 1996
-
Ingår i: User Modeling and User-Adapted Interaction. - 0924-1868 .- 1573-1391. ; 6, s. 157-184
-
Tidskriftsartikel (refereegranskat)abstract
- Utilising adaptive interface techniques in the design of systems introduces certain risks. An adaptive interface is not static, but will actively adapt to the perceived needs of the user. Unless carefully designed, these changes may lead to an unpredictable, obscure and uncontrollable interface. Therefore the design of adaptive interfaces must ensure that users can inspect the adaptivity mechanisms, and control their results. One way to do this is to rely on the user’s understanding of the application and the domain, and relate the adaptivity mechanisms to domain-specific concepts. We present an example of an adaptive hypertext help system POP, which is being built according to these principles, and discuss the design considerations and empirical findings that lead to this design.
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| 40. |
- Höök, Kristina, et al.
(författare)
-
Inferring complex plans
- 1993
-
Ingår i: 1st International Workshop on Intelligent User Interfaces.
-
Konferensbidrag (refereegranskat)abstract
- We examine the need for plan inference in intelligent help mechanisms. We argue that previous approaches have drawbacks that need to be overcome to make plan inference useful. Firstly, plans have to be inferred - not extracted from the users? help requests. Secondly, the plans inferred must be more than a single goal or solitary user command.
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| 41. |
- Karlgren, Jussi
(författare)
-
Sublanguages and Registers : A Note On Terminology
- 1993
-
Ingår i: Interacting with computers. - 0953-5438 .- 1873-7951. ; 5:3, s. 348-350
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Tidskriftsartikel (refereegranskat)abstract
- The term sublanguage from mathematical linguistics confuses interaction researchers and leads them to believe that implementing natural language interfaces is easier than it is. The term register from sociolinguistics is proposed instead.
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| 42. |
- Karlgren, Jussi, et al.
(författare)
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The glass box user model for filtering
- 1994. - 3
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The first requirement on an interactive system in a domain such as information filtering is to be an interface to knowledge, rather than just a knowledgeable interface. We borrow the computation instruction metaphor of a system as "a black box in a glass box" as a means to conceptualize the problem of giving a user control over the actions of an interactive system. The application domain we work in is that of information filtering. In the "black box", we hide complex knowledge of the domain objects such as facts and assumptions about text genre identification, while the "glass box", which is what the user sees, only shows the neat top level knowledge of the domain conceptual categories such as e.g. categorization rules.
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| 43. |
- Waern, Yvonne, et al.
(författare)
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Office automation and users need for support
- 1991
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Ingår i: Behaviour and Information Technology. - London : Taylor & Francis. - 0144-929X .- 1362-3001. ; 10:6, s. 501-514
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Tidskriftsartikel (refereegranskat)abstract
- We investigated a recently introduced office automation system at Swedish Telecom. In a first study, where 275 users answered an inventory, the users indicated that they found the system useful, but that they would like better user support. Paper and on-line support were most often used at the syntax level, but were not regarded to be very satisfactory. Human advisors were found to be consulted most often, as well as being reported the most satisfactory means of support at the task and conceptual levels. In an interview study concerning the electronic mail system, the results from 35 users showed that the users were satisfied with the system, but that they knew fairly little about it, particularly at the semantic level. A third study showed that the system support personnel knew their users rather well. When asked to describe the system, system support personnel mainly described the system in computer terms, whereas many other users described it non-informatively. It is concluded that knowledgeable human advisors are needed lo support the efficient use of a system by illuminating task and semantic aspects. At the same time, easy-to-use manuals are needed to support the reminding about syntactic and interaction details.
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| 44. |
- Almansa, Andrés, et al.
(författare)
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Enhancement of Fingerprint Images by Shape-Adapted Scale-Space Operators
- 1996
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Ingår i: Gaussian Scale-Space Theory. Part I. - Dordrecht : Springer Science+Business Media B.V.. - 9789401588027 ; , s. 21-30
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Bokkapitel (refereegranskat)abstract
- This work presents a novel technique for preprocessing fingerprint images. The method is based on the measurements of second moment descriptors and shape adaptation of scale-space operators with automatic scale selection (Lindeberg 1994). This procedure, which has been successfully used in the context of shape-from-texture and shape from disparity gradients, has several advantages when applied to fingerprint image enhancement, as observed by (Weickert 1995). For example, it is capable of joining interrupted ridges, and enforces continuity of their directional fields.In this work, these abovementioned general ideas are applied and extended in the following ways: Two methods for estimating local ridge width are explored and tuned to the problem of fingerprint enhancement. A ridgeness measure is defined, which reflects how well the local image structure agrees with a qualitative ridge model. This information is used for guiding a scale-selection mechanism, and for spreading the results of shape adaptation into noisy areas.The combined approach makes it possible to resolve fine scale structures in clear areas while reducing the risk of enhancing noise in blurred or fragmented areas. To a large extent, the scheme has the desirable property of joining interrupted lines without destroying essential singularities such as branching points. Thus, the result is a reliable and adaptively detailed estimate of the ridge orientation field and ridge width, as well as a smoothed grey-level version of the input image.A detailed experimental evaluation is presented, including a comparison with other techniques. We propose that the techniques presented provide mechanisms of interest to developers of automatic fingerprint identification systems.
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| 45. |
- Brunnström, Kjell, et al.
(författare)
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On Scale and Resolution in the Analysis of Local Image Structure
- 1990
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Ingår i: Proc. 1st European Conf. on Computer Vision. ; , s. 3-12
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Konferensbidrag (refereegranskat)abstract
- Focus-of-attention is extremely important in human visual perception. If computer vision systems are to perform tasks in a complex, dynamic world they will have to be able to control processing in a way that is analogous to visual attention in humans.In this paper we will investigate problems in connection with foveation, that is examining selected regions of the world at high resolution. We will especially consider the problem of finding and classifying junctions from this aspect. We will show that foveation as simulated by controlled, active zooming in conjunction with scale-space techniques allows robust detection and classification of junctions.
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| 46. |
- Brunnström, Kjell, et al.
(författare)
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Scale and Resolution in Active Analysis of Local Image Structure
- 1990
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Ingår i: Image and Vision Computing. - : Elsevier. ; 8:4, s. 289-296
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Tidskriftsartikel (refereegranskat)abstract
- Focus-of-attention is extremely important in human visual perception. If computer vision systems are to perform tasks in a complex, dynamic world they will have to be able to control processing in a way that is analogous to visual attention in humans. Problems connected to foveation (examination of selected regions of the world at high resolution) are examined. In particular, the problem of finding and classifying junctions from this aspect is considered. It is shown that foveation as simulated by controlled, active zooming in conjunction with scale-space techniques allows for robust detection and classification of junctions.
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| 47. |
- Lindeberg, Tony, 1964-
(författare)
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A scale selection principle for estimating image deformations
- 1998
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Ingår i: Image and Vision Computing. - 0262-8856 .- 1872-8138. ; 16, s. 961-977
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Tidskriftsartikel (refereegranskat)abstract
- A basic functionality of a vision system concerns the ability to compute deformation fields between different images of the same physical structure. This article advocates the need for incorporating explicit mechanisms for scale selection in this context, in algorithms for computing descriptors such as optic flow and for performing stereo matching. A basic reason why such a mechanism is essential is the fact that in a coarse-to-fine propagation of disparity or flow information, it is not necessarily the case that the most accurate estimates are obtained at the finest scales. The existence of interfering structures at fine scales may make it impossible to accurately match the image data at fine scales. selecting deformation estimates from the scales that minimize the (suitably normalized) uncertainty over scales. A specific implementation of this idea is presented for a region based differential flow estimation scheme. It is shown that the integrated scale selection and flow estimation algorithm has the qualitative properties of leading to the selection of coarser scales for larger size image structures and increasing noise level, whereas it leads to the selection of finer scales in the neighbourhood of flow field discontinuities
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| 48. |
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| 49. |
- Lindeberg, Tony, 1964-
(författare)
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Edge detection and ridge detection with automatic scale selection
- 1998
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Ingår i: International Journal of Computer Vision. - : Kluwer Academic Publishers. - 0920-5691 .- 1573-1405. ; 30:2, s. 117-154
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Tidskriftsartikel (refereegranskat)abstract
- When computing descriptors of image data, the type of information that can be extracted may be strongly dependent on the scales at which the image operators are applied. This article presents a systematic methodology for addressing this problem. A mechanism is presented for automatic selection of scale levels when detecting one-dimensional image features, such as edges and ridges.A concept of a scale-space edge is introduced, defined as a connected set of points in scale-space at which: (i) the gradient magnitude assumes a local maximum in the gradient direction, and (ii) a normalized measure of the strength of the edge response is locally maximal over scales. An important consequence of this definition is that it allows the scale levels to vary along the edge.Two specific measures of edge strength are analysed in detail, the gradient magnitude and a differential expression derived from the third-order derivative in the gradient direction. For a certain way of normalizing these differential descriptors, by expressing them in terms of so-called gamma-normalized derivatives, an immediate consequence of this definition is that the edge detector will adapt its scale levels to the local image structure. Specifically, sharp edges will be detected at fine scales so as to reduce the shape distortions due to scale-space smoothing, whereas sufficiently coarse scales will be selected at diffuse edges, such that an edge model is a valid abstraction of the intensity profile across the edge.Since the scale-space edge is defined from the intersection of two zero-crossing surfaces in scale-space, the edges will by definition form closed curves. This simplifies selection of salient edges, and a novel significance measure is proposed, by integrating the edge strength along the edge. Moreover, the scale information associated with each edge provides useful clues to the physical nature of the edge.With just slight modifications, similar ideas can be used for formulating ridge detectors with automatic selection, having the characteristic property that the selected scales on a scale-space ridge instead reflect the width of the ridge.It is shown how the methodology can be implemented in terms of straightforward visual front-end operations, and the validity of the approach is supported by theoretical analysis as well as experiments on real-world and synthetic data.
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| 50. |
- Lindeberg, Tony
(författare)
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Edge detection and ridge detection with automatic scale selection
- 1996
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Ingår i: Proc Computer Vision and Pattern Recognition (CPR’96). ; , s. 465-470
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Konferensbidrag (refereegranskat)abstract
- When extracting features from image data, the type of information that can be extracted may be strongly dependent on the scales at which the feature detectors are applied. This article presents a systematic methodology for addressing this problem. A mechanism is presented for automatic selection of scale levels when detecting one-dimensional features, such as edges and ridges. A novel concept of a scale-space edge is introduced, defined as a connected set of points in scale-space at which: (i) the gradient magnitude assumes a local maximum in the gradient direction, and (ii) a normalized measure of the strength of the edge response is locally maximal over scales. An important property of this definition is that it allows the scale levels to vary along the edge. Two specific measures of edge strength are analysed in detail. It is shown that by expressing these in terms of γ-normalized derivatives, an immediate consequence of this definition is that fine scales are selected for sharp edges (so as to reduce the shape distortions due to scale-space smoothing), whereas coarse scales are selected for diffuse edges, such that an edge model constitutes a valid abstraction of the intensity profile across the edge. With slight modifications, this idea can be used for formulating a ridge detector with automatic scale selection, having the characteristic property that the selected scales on a scale-space ridge instead reflect the width of the ridge.
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