| 1. |
- Alic, Vedad, et al.
(författare)
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Bi-directional Algebraic Graphic Statics : On Force Diagram Constraints
- 2017
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Konferensbidrag (refereegranskat)abstract
- This paper presents a study exploring the capabilities of a new method, described by Åkesson and Alic [1], which extends the capabilities of the algebraic graphic statics method, by Van Mele and Block [11]. The new method extends the algebraic graphic statics method by making it bi-directional i.e. allowing for determination of an updated form diagram by making direct interactive manipulations of the force diagram. In the new method, Newton’s method is used for solving a set of non-linear equations, to find an updated form diagram from given changes in the force diagram. Additional geometric constraints are introduced on the form diagram to obtain desired solutions. The implementation of the method as a back-end to an interactive application is discussed, and the usability of the method is shown in examples where the qualities of directly manipulating the force diagram are discussed. The main part of this paper will supplement Åkesson and Alic [1] by presenting further studies of the application of constraints to the force diagram, and which shapes this leads to in the form diagram. Further, the paper will present how to adapt force and form diagrams for interactive graphical representations suitable for computers.
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| 2. |
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| 3. |
- Axell, Erik, et al.
(författare)
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GNSS spoofing detection using multiple mobile COTS receivers
- 2015
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Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781467369978 ; , s. 3192-3196
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Konferensbidrag (refereegranskat)abstract
- In this paper we deal with spoofing detection in GNSS receivers. We derive the optimal genie detector when the true positions are perfectly known, and the observation errors are Gaussian, as a benchmark for other detectors. The system model considers three dimensional positions, and includes correlated errors. In addition, we propose several detectors that do not need any position knowledge, that outperform recently proposed detectors in many interesting cases.
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| 4. |
- Bao, Ling, 1980, et al.
(författare)
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Rigid Calabi-Yau threefolds, Picard Eisenstein series and instantons
- 2013
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 462:1
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Konferensbidrag (refereegranskat)abstract
- Type IIA string theory compactified on a rigid Calabi-Yau threefold gives rise to a classical moduli space that carries an isometric action of U(2, 1). Various quantum corrections break this continuous isometry to a discrete subgroup. Focussing on the case where the intermediate Jacobian of the Calabi-Yau admits complex multiplication by the ring of quadratic imaginary integers script O signd, we argue that the remaining quantum duality group is an arithmetic Picard modular group PU(2, 1; script O signd). Based on this proposal we construct an Eisenstein series invariant under this duality group and study its non-Abelian Fourier expansion. This allows the prediction of non-perturbative effects, notably the contribution of D2- and NS5-brane instantons. The present work extends our previous analysis in 0909.4299 which was restricted to the special case of the Gaussian integers script O sign1 = ℤ[i].
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| 5. |
- Cheng, Hei Victor, et al.
(författare)
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Massive MIMO at Night : On the Operation of Massive MIMO in Low Traffic Scenarios
- 2015
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Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - : IEEE. - 9781467364324 - 9781467364317 - 9781467364300 ; , s. 1697-1702
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Konferensbidrag (refereegranskat)abstract
- For both maximum ratio transmission (MRT) and zero forcing (ZF) precoding schemes and given any specific rate requirement the optimal transmit power, number of antennas to be used, number of users to be served and number of pilots spent on channel training are found with the objective to minimize the total consumed power at the base station. The optimization problem is solved by finding closed form expressions of the optimal transmit power and then search over the remaining discrete variables. The analysis consists of two parts, the first part investigates the situation when only power consumed in the RF amplifiers is considered. The second part includes both the power consumed in the RF amplifiers and in other transceiver circuits. In the former case having all antennas active while reducing the transmit power is optimal. Adaptive scheme to switch off some of the antennas at the base stations is found to be optimal in the latter case.
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| 6. |
- Cheng, Hei Victor, et al.
(författare)
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MIMO Capacity under Power Amplifiers Consumed Power and Per-Antenna Radiated Power Constraints
- 2014
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Ingår i: 2014 IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781479949038 - 9781479939121 - 9781479949021 ; , s. 179-183
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Konferensbidrag (refereegranskat)abstract
- We investigate the capacity of the multiple-input-multiple-output channel taking into account the consumed power in the power amplifiers. The mutual information is optimized with a limitation of total consumed power and per-antenna radiated power for a fixed channel with full channel state information at both the transmitter and receiver. The capacity is thus obtained by optimizing the input distribution to maximize the mutual information. Since the optimization problem is non-convex, direct computation of the capacity suffers from high computational complexity. Hence upper and lower bounds on the capacity are given as benchmarks for different ad-hoc schemes. An efficient suboptimal algorithm is also presented. Numerical results show that the suboptimal algorithm performs close to the capacity.
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| 7. |
- Čirkić, Mirsad, 1984-, et al.
(författare)
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Gaussian Approximation of the LLR Distribution for the ML and Partial Marginalization MIMO detectors
- 2011
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Ingår i: Proceedings of the IEEE International Conference on Acoustics, Speech and SignalProcessing (ICASSP). - : IEEE conference proceedings. - 9781457705373 ; , s. 3232-3235
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Konferensbidrag (refereegranskat)abstract
- We derive a Gaussian approximation of the LLR distribution conditioned on the transmitted signal and the channel matrix for the soft-output via partial marginalization MIMO detector. This detector performs exact ML as a special case. Our main results consist of discussing the operational meaning of this approximation and a proof that, in the limit of high SNR, the LLR distribution of interest converges in probability towards a Gaussian distribution.
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| 8. |
- Čirkić, Mirsad, 1984-, et al.
(författare)
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New Results on Adaptive Computational Resource Allocation in Soft MIMO Detection
- 2011
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Ingår i: Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). - : IEEE conference proceedings. ; , s. 2972-2975
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Konferensbidrag (refereegranskat)abstract
- The fundamental problem of our interest is soft MIMO detection for the case of block fading, i.e., when the transmitted codeword spans over several independent channel realizations. We develop methods that adaptively allocate computational resources to the detection problems of each channel realization, under a total per-codeword complexity constraint. The new results consist of a new algorithm, a new performance measure, and a thorough complexity discussion.
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| 9. |
- Čirkić, Mirsad, et al.
(författare)
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Optimization of Computational Resource Allocation for Soft MIMO Detection
- 2009
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Ingår i: Proceedings of the 43rd Asilomar Conference on Signals, Systems, and Computers (ACSSC'09). - : IEEE. - 9781424458264 - 9781424458257 - 9781424458271 ; , s. 1488-1492
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Konferensbidrag (refereegranskat)abstract
- We consider soft MIMO detection for the case of block fading. That is, the transmitted codeword spans over several independent channel realizations and several instances of the detection problem must be solved for each such realization. We develop methods that adaptively allocate the computational resources to the detection problems of each channel realization, under a total per-codeword complexity constraint. Our main results are a formulation of the problem as a mathematical optimization problem and a greedy algorithm to approximate it in a computationally feasible fashion.
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| 10. |
- Connolly, David, et al.
(författare)
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The role of district heating in decarbonising the EU energy system and a comparison with existing strategies
- 2013
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Ingår i: Book of Abstracts.
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Konferensbidrag (refereegranskat)abstract
- Many strategies have already been proposed for the decarbonisation of the EU energy system by the year 2050. These typically focus on the expansion of renewable energy in the electricity sector and subsequently, electrifying both the heat and transport sectors as much as possible. In these strategies, the role of district heating has never been fully explored system, nor have the benefits of district heating been quantified at the EU level. This study combines the mapping of local heat demands and local heat supplies across the EU27. Using this local knowledge, new district heating potentials are identified and then, the EU27 energy system is modelled to investigate the impact of district heating. The results indicate that a combination of heat savings, district heating in urban areas, and individual heat pumps in rural areas will enable the EU27 to reach its greenhouse gas emissions targets by 2050, but at a cheaper price than a scenario which focuses primarily on the implementation of heat savings.
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