| 1. |
- Forchheimer, Daniel, et al.
(författare)
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Improving image contrast and material discrimination with nonlinear response in bimodal atomic force microscopy
- 2015
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Atomic force microscopy has recently been extented to bimodal operation, where increased image contrast is achieved through excitation and measurement of two cantilever eigenmodes. This enhanced material contrast is advantageous in analysis of complex heterogeneous materials with phase separation on the micro or nanometre scale. Here we show that much greater image contrast results from analysis of nonlinear response to the bimodal drive, at harmonics and mixing frequencies. The amplitude and phase of up to 17 frequencies are simultaneously measured in a single scan. Using a machine-learning algorithm we demonstrate almost threefold improvement in the ability to separate material components of a polymer blend when including this nonlinear response. Beyond the statistical analysis performed here, analysis of nonlinear response could be used to obtain quantitative material properties at high speeds and with enhanced resolution.
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| 2. |
- Abidin, Aysajan, 1983-
(författare)
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Authentication in Quantum Key Distribution : Security Proof and Universal Hash Functions
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Quantum Key Distribution (QKD) is a secret key agreement technique that consists of two parts: quantum transmission and measurement on a quantum channel, and classical post-processing on a public communication channel. It enjoys provable unconditional security provided that the public communication channel is immutable. Otherwise, QKD is vulnerable to a man-in-the-middle attack. Immutable public communication channels, however, do not exist in practice. So we need to use authentication that implements the properties of an immutable channel as well as possible. One scheme that serves this purpose well is the Wegman-Carter authentication (WCA), which is built upon Almost Strongly Universal2 (ASU2) hashing. This scheme uses a new key in each authentication attempt to select a hash function from an ASU2 family, which is then used to generate the authentication tag for a message.The main focus of this dissertation is on authentication in the context of QKD. We study ASU2 hash functions, security of QKD that employs a computationally secure authentication, and also security of authentication with a partially known key. Specifically, we study the following.First, Universal hash functions and their constructions are reviewed, and as well as a new construction of ASU2 hash functions is presented. Second, security of QKD that employs a specific computationally secure authentication is studied. We present detailed attacks on various practical implementations of QKD that employs this authentication. We also provide countermeasures and prove necessary and sufficient conditions for upgrading the security of the authentication to the level of unconditional security. Third, Universal hash function based multiple authentication is studied. This uses a fixed ASU2 hash function followed by one-time pad encryption, to keep the hash function secret. We show that the one-time pad is necessary in every round for the authentication to be unconditionally secure. Lastly, we study security of the WCA scheme, in the case of a partially known authentication key. Here we prove tight information-theoretic security bounds and also analyse security using witness indistinguishability as used in the Universal Composability framework.
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| 3. |
- Ahlberg, Jörgen, et al.
(författare)
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Face tracking for model-based coding and face animation
- 2003
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Ingår i: International journal of imaging systems and technology (Print). - : John Wiley & Sons. - 0899-9457 .- 1098-1098. ; 13:1, s. 8-22
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Tidskriftsartikel (refereegranskat)abstract
- We present a face and facial feature tracking system able to extract animation parameters describing the motion and articulation of a human face in real-time on consumer hardware. The system is based on a statistical model of face appearance and a search algorithm for adapting the model to an image. Speed and robustness is discussed, and the system evaluated in terms of accuracy.
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| 4. |
- Ahlberg, Jörgen, et al.
(författare)
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Simultaneous sensing, readout, and classification on an intensity-ranking image sensor
- 2018
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Ingår i: International journal of circuit theory and applications. - : WILEY. - 0098-9886 .- 1097-007X. ; 46:9, s. 1606-1619
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Tidskriftsartikel (refereegranskat)abstract
- We combine the near-sensor image processing concept with address-event representation leading to an intensity-ranking image sensor (IRIS) and show the benefits of using this type of sensor for image classification. The functionality of IRIS is to output pixel coordinates (X and Y values) continuously as each pixel has collected a certain number of photons. Thus, the pixel outputs will be automatically intensity ranked. By keeping track of the timing of these events, it is possible to record the full dynamic range of the image. However, in many cases, this is not necessary-the intensity ranking in itself gives the needed information for the task at hand. This paper describes techniques for classification and proposes a particular variant (groves) that fits the IRIS architecture well as it can work on the intensity rankings only. Simulation results using the CIFAR-10 dataset compare the results of the proposed method with the more conventional ferns technique. It is concluded that the simultaneous sensing and classification obtainable with the IRIS sensor yields both fast (shorter than full exposure time) and processing-efficient classification.
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| 5. |
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| 6. |
- Ajmal, Muhammad, et al.
(författare)
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An Optimization Model for Dynamic Bulk Provisioning in Elastic Optical Networks
- 2014
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Ingår i: Asia Communications and Photonics Conference 2014. - : Optics Info Base, Optical Society of America. - 9781557528520 ; , s. AF3E.6-
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Konferensbidrag (refereegranskat)abstract
- We investigate benefits of setup-delay tolerance in elastic optical networks and propose an optimization model for dynamic and concurrent connection provisioning. Simulation shows that the proposed strategy offers significant improvement of the network blocking performance.
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| 7. |
- Ajmal, Muhammad, et al.
(författare)
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Flexible and Synthetic SDM Networks with Multi-core-Fibers Implemented by Programmable ROADMs
- 2014
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Ingår i: Proceedings of European Conference on Optical Communication ECOC2014, Cannes, France, September 21-25 September 2014. - : IEEE. ; , s. 1-3
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Konferensbidrag (refereegranskat)abstract
- This study looks into network planning issues for synthetic MCF-based SDM networks implemented through programmable ROADMs. The results show that significant savings in switching modules and energy can be attained by exploiting the flexibility inherent in programmable ROADM through a proper network design.
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| 8. |
- Ajmal, Muhammad, et al.
(författare)
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Routing, Spectrum and Core Allocation in Flexgrid SDM Networks with Multi-core Fibers
- 2014
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Ingår i: 2014 INTERNATIONAL CONFERENCE ON OPTICAL NETWORK DESIGN AND MODELING. - : IEEE. - 9783901882609 ; , s. 192-197
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Konferensbidrag (refereegranskat)abstract
- Space division multiplexing (SDM) over multi-core fiber (MCF) is advocated as a promising technology to overcome the capacity limit of the current single-core optical networks. However, employing the MCF for flexgrid networks necessitates the development of new concepts, such as routing, spectrum and core allocation (RSCA) for traffic demands. The introduction of MCF in the networks mitigates the spectrum continuity constraint of the routing and spectrum assignment (RSA) problem. In fact cores can be switched freely on different links during routing of the network traffic. Similarly, the route disjointness for demands with same allocated spectrum diminishes to core disjointness at the link level. On the other hand, some new issues such as the inter-core crosstalk should be taken into account while solving the RSCA problem. This paper formulates the RSCA network planning problem using the integer linear programming (ILP) formulation. The aim is to optimally minimize the maximum number of spectrum slices required on any core of MCF of a flexgrid SDM network. Furthermore, a scalable and effective heuristic is proposed for the same problem and its performance is compared with the optimal solution. The results show that the proposed algorithm is able to well approximate the optimal solution based on ILP model.
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| 9. |
- Ajmal, Muhammad, et al.
(författare)
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Trading Quality of Transmission for Improved Blocking Performance in All-Optical Networks
- 2013
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Ingår i: Asia Communications and Photonics Conference 2013. - 9781557529893 ; , s. AF4E.5-
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Konferensbidrag (refereegranskat)abstract
- We propose a connection provisioning strategy in dynamic all-optical networks, which exploit the possibility to allow a tolerable signal quality degradation during a small fraction of holding-time resulting in a significant improvement of blocking performance.
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| 10. |
- Anders, A., et al.
(författare)
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High speed and high dynamic range difference imaging based on the near sensor image processing concept
- 2009
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X. ; 7249, s. 72490G-
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes the Near Sensor Image Processing (NSIP) paradigm developed in the early 1990s and shows that it was a precursor to recent architectures proposed for direct (in the sensor) image processing and high dynamic range (HDR) image sensing. Both of these architectures are based on the specific properties of CMOS light sensors, in particular the ability to continuously monitor the accumulation of photon-induced charge as a function of time. We further propose an extension of the original NSIP pixel to include a circuit that facilitates temporal and spatio-temporal processing.
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