| 1. |
- Pettersson, Håkan, et al.
(författare)
-
Photocurrent spectroscopy on self-assembled InAs quantum dots embedded in InP
- 2005
-
Ingår i: Microelectronics Journal. - Amsterdam : Elsevier. - 0026-2692. ; 36:3-6, s. 227-230
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we report on an overview of recent results from Fourier transform photocurrent (FTPC) measurements in the infrared spectral region on ensembles of self-assembled InAs quantum dots embedded in a matrix of InP. In interband PC, clear signals related to the dots are observed. Comparing the PC- and PL spectra, we observe that the fundamental transition is absent in the PC spectra, which we interpret in terms of Pauliblocking due to a filled electron ground state of the dots. Our results furthermore suggest that an Auger process is involved in forming the interband PC signal. In intersubband PC, peaks related to transitions from the dots' ground- and first excited states to the conduction band of the matrix are observed. Using a novel approach of combining FTPC with illumination from an additional external non-modulated light source, we have measured the spectral distribution of photoionization of excitons in quantum dots and found an exciton binding energy in good agreement with theoretical calculations.
|
|
| 2. |
- Bordag, Ljudmila A., et al.
(författare)
-
Interaction of a rotational motion and an axial flow in small geometries for a Taylor-Couette problem
- 2005
-
Ingår i: Journal of Fluids and Structures. - Amsterdam : Elsevier. - 0889-9746 .- 1095-8622. ; 20:5, s. 621-641
-
Tidskriftsartikel (refereegranskat)abstract
- We analyze the stability of a Taylor-Couette flow under the imposition of a weak axial flow in the case of a very short cylinder with a narrow annulus gap. We consider an incompressible viscous fluid contained in the narrow gap between two concentric short cylinders, in which the inner cylinder rotates with constant angular velocity. The caps of the cylinders have narrow tubes conically tapering to very narrow slits, allowing an axial flow along the surface of the inner cylinder. The approximated solution for the Taylor-Couette flow for short cylinders was found and used for the stability analysis instead of the precise but bulky solution. The sensitivity of the Taylor-Couette flow to small perturbations and to weak axial flow was studied. We demonstrate that perturbations coming from the axial flow cause the propagation of dispersive waves in the Taylor-Couette flow. While in long cylinders the presence of an axial flow leads to the breaking of axial symmetry, in small cylinders it leads to the breaking of mirror symmetry. The coexistence of a rotation and an axial flow requires that, in addition to the energy and the angular momentum of the flow, the helicity must also be studied. The approximated form for the helicity formula in the case of short cylinders was derived. We found that the axial flow stabilizes the Taylor-Couette flow. The supercritical flow includes a rich variety of vortical structures, including a symmetric pair of Taylor vortices, an anomalous single vortex and quasiperiodic oscillating vortices. Pattern formation was studied at large for rated ranges of azimuthal and axial Reynolds numbers. A region where three branches of different states occur was localized. Numerical simulations in 3-D and in the axisymmetrical case of the model flow are presented, which illustrate the instabilities analyzed.
|
|
| 3. |
|
|
| 4. |
- Andersson, M., et al.
(författare)
-
The mobile–stationary divide in ubiquitous computing environments : Lessons from the transport industry
- 2005
-
Ingår i: Information systems management. - Boston, Mass. : Informa UK Limited. - 1058-0530 .- 1934-8703. ; 22:4, s. 65-79
-
Tidskriftsartikel (refereegranskat)abstract
- The emergence of ubiquitous computing offers new possibilities and opportunities for organizations attempting to improve their productivity and effectiveness. in particular, the promises of ubiquitous computing are attractive to organizations such as transport firms, in which coordination of diverse sets of mobile units is central to organizational performance. This article analyzes the use of ubiquitous transport systems in Swedish road haulage firms and discusses the opportunities and challenges for the early adopters. It pays specific attention to the mobile–stationary divide; that is, the set of challenges associated with integration of mobile and stationary people and systems into a seamless computing environment.
|
|
| 5. |
- Henfridsson, Ola, et al.
(författare)
-
Multi-Contextuality in Ubiquitous Computing : Investigating the Car Case through Action Research
- 2005
-
Ingår i: Information and organization. - New York : Pergamon Press. - 1471-7727 .- 1873-7919. ; 15:2, s. 95-124
-
Tidskriftsartikel (refereegranskat)abstract
- Ubiquitous computing envisions seamless access of mass-scale services over the multitude of contexts that users encounter in their everyday mobility. However, to be successful such computing must simultaneously be designed to provide transparent, integrated, and convenient support in localized use contexts. Thus, the issue of multi-contextuality makes the design of ubiquitous computing services and environments a challenging endeavor. While ubiquitous computing requires attention to the multi-contextuality of people’s mobile device use encompassing spatial, temporal, and social dimensions of mobility, the typical avenue for IS research studies has been the single context (e.g., team, organization, or inter-organizational).This paper reports on a grounded action research study with the objective of developing and testing design principles for handling multi-contextuality in an increasingly important ubiquitous computing environment – the car. Already supporting people’s everyday mobility and promising to provide ubiquitous availability of computing and communication infrastructure, the car is indeed a relevant setting for investigating the co-existence of different use contexts in ubiquitous computing. Contributing to the early stage of the ubiquitous computing research tradition, this paper not only empirically demonstrates that the car as a ubiquitous computing environment can improve the convenience of people’s everyday mobile device use by providing multi-contextual support. The paper also suggests our design principles and their associated socio-technical implications to be valid for other ubiquitous computing environments. Indeed, synchronizing fluid use patterns, scaling service manipulation, and signaling context-switches through awareness support lie at the heart of weaving ubiquitous computing environments conveniently into the fabric of people’s everyday mobility.
|
|
| 6. |
|
|
| 7. |
- Agelis, Sacki
(författare)
-
Reconfigurable Optical Interconnection Networks for High-Performance Embedded
- 2005
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In embedded computer and communication system the capacity demand for interconnection networks is increasing continuously in order to achieve high-performance systems. Recent breakthroughs show that by using reconfigurability inside a single chip substantial performance gains can be added. However, in this thesis the focus is on system level reconfigurability (between chips or modules) and the performance gains that potentially can be achieved by having support for runtime reconfigurability on the system level.This thesis addresses the field of runtime system level reconfigurability with the use of optics in switches and routers for data- and telecommunications, and in multi-processor systems used for embedded signal processing. Several reconfigurable systems for switching and routing with support to adapt for asymmetric traffic patterns are proposed and compared to identify how design choices affect flexibility, performance etc. The proposed solutions are characterized by their multistage optical interconnection networks with reconfigurable shuffle patterns, where the reconfigurability is provided by micro-optical-electrical mechanical systems. More specifically, application-specific bottlenecks can be resolved by reconfiguring the interconnection network according to the current application demands. The benefits of the architectural solutions are confirmed by simulations that clearly show that the architectures can achieve high performance for both symmetric application characteristics and for several classes of asymmetric application characteristics. The final architectural solution is characterized by electronic packet-switches interconnected through an optical backplane, which is reconfigurable. Moreover, the thesis presents how several signal processing applications can be mapped to run concurrently in a time-shared scheme on a single reconfigurable multi-processor system that has high flexibility to adapt for the application currently at hand. The interconnection network is then adapted (reconfigured) according to the demands of the currently executed application in each time instance. The analysis shows that it is feasible to build such a system with today’s components.
|
|
| 8. |
- Babich, M. V., et al.
(författare)
-
Quasi periodic vortex structures in two-dimensional flows in an inviscid incompressible fluid
- 2005
-
Ingår i: Russian journal of mathematical physics. - New York : John Wiley & Sons. - 1061-9208 .- 1555-6638. ; 12:2, s. 121-156
-
Tidskriftsartikel (refereegranskat)abstract
- We consider a two-dimensional steady motion of an inviscid incompressible fluid described by the equation &UDelta; u(x,y) = F(u(x,y)), where u(x,y) is the streamfunction, &UDelta; is the Laplace operator, and F((.)) an arbitrary function measuring the flow vorticity. Apparently, until now, the only way to treat an equation of the above type with nontrivial function F analytically is to use the algebro-geometric method for integrable equations. In particular, we investigate the Cosh-Laplace equation (ChL) &UDelta; u(x,y) = ± 4cosh(u(x,y)) by means of the special technique of finite-gap integration, which allows us to obtain real solutions of the ChL equation by using a Riemann surface with appropriate symmetry. We study the first nontrivial case corresponding to a Riemann surface of genus g = 3. The hydrodynamical interpretation of finite-gap solutions is meaningful, and we try to understand the fluid processes described by these solutions. To this end, we take a Riemann surface with additional symmetry properties. We present four five-parameter families of exact solutions. These solutions are given in terms of Jacobi elliptic functions, which enables us to directly investigate the relevant properties. We also find explicit formulas for the lines of singularity. It is of interest from the point of view of algebraic geometry that the structure of the theta divisor can be described.
|
|
| 9. |
- Byttner, Stefan, et al.
(författare)
-
Using Multiple Cylinder Ion Measurements for Improved Estimation of Combustion Variability
- 2005
-
Ingår i: Proceedings of the SAE 2005 World Congress & Exhibition. - Warrendale, PA : SAE Inc..
-
Konferensbidrag (refereegranskat)abstract
- Estimation of combustion variability can be performed by using ion currents measured at the spark plug. A scheme is here proposed that exploits the potential of using measurements from multiple cylinders to improve the estimation accuracy of combustion variability (measured by the coefficient of variation of IMEP). This is realised by dividing combustion variability into categories and having one classifier running for each cylinder with the ion current as input signal. The final estimate of combustion variability is then formed by a majority vote among the classifiers. This scheme is shown to improve estimation accuracy by up to 15% on measurements taken from highway driving in a production vehicle.
|
|
| 10. |
- Fan, Xing, 1975-, et al.
(författare)
-
Guaranteed real-time services over standard switched Ethernet
- 2005
-
Ingår i: The IEEE Conference on Local Computer Networks, 30th Anniversary. - New York, NY : IEEE Computer Society. - 0769524214 ; , s. 490-492
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we contribute with an approach to support guaranteed real-time services over standard switched Ethernet without additional hardware or software modification of the switch and the underlying standard. In our proposal, the traffic differentiation mechanism introduced by the IEEE 802.1D/Q standard and the standard hardware-implemented first come first served (FCFS) priority queuing are used in the switch and the source nodes. We have derived a feasibility analysis algorithm that can be used to ensure that the real-time requirements can be met. The algorithm also gives, as a sub-result, the needed buffer space in the end nodes and the switch. Moreover, our feasibility analysis supports variable-sized frames and switches with different bit-rates ports. The simulation analysis verifies our feasibility analysis.
|
|
