| 31. |
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| 32. |
- Persson, Fredrik, 1971-, et al.
(författare)
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The Effect of Differentiation on Prison Population : A Simulation Study of the Swedish Prison System
- 2004
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Ingår i: European Simulation Symposium,2004. - San Diego, USA : SCS International. ; , s. 144-
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Konferensbidrag (refereegranskat)abstract
- This paper describes the case of a simulation study of the Swedish Prison and Probation system regarded as a queuing system. The situation in Swedish prisons today is not acceptable with a utilisation over 100 per cent. The short-term solution of the problem has been to overcrowd the prisons. The purpose of this work is to describe the relations between waiting time in remand prison, the official number of cells in prisons and the degree of differentiation regarding to the expected torrent of criminals. Differentiation is the attempt to keep different categories of clients apart during their prison time. The degree of differentiation is defined as the number of defined categories used for client placement. The conclusions from this study is that there are not enough number of prison cell available. The situation for male inmates/clients is more critical than for female clients. The results from the study suggest that there needs to be approximately 11,000 prison cells in total to meet the unofficial recommendation of a maximum of seven days in remand prison.
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| 33. |
- Persson, Fredrik
(författare)
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The impact of different levels of detail in manufacturing systems simulation models
- 2002
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Ingår i: Robotics and Computer-Integrated Manufacturing. - : Pergamon Press. - 0736-5845 .- 1879-2537. ; 18:3-4, s. 319-325
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Tidskriftsartikel (refereegranskat)abstract
- Modelling and simulating manufacturing systems often involves several different organisational units. This can make data collection difficult and it can be hard to obtain data that allows for the model to be built with a consistent level of detail. To investigate the impact of a varying level of detail, a manufacturing system was modelled using different levels of detail. The first model was modelled at a high level of detail containing all elements in the system. The second model was an aggregation of some of the processes in the system and the third model consisted only of the main processes. The experiments performed with the models, aimed at finding differences between models' outputs that originated from the choice of the level of detail. The results show that there are significant differences between the models. The simulation models used for this paper are made in collaboration with a company in the mobile communications industry and deals with supply chain problems.
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| 34. |
- Persson, Niclas
(författare)
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Event Based Sampling with Application to Spectral Estimation
- 2002
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis event based sampling, estimation of a single resonance frequency and the application indirect tire pressure monitoring system are studied.Event based sampling is an alternative to traditional uniform or equidistant sampling. In event based sampled systems, signals are sampled only when certain pre-defined events take place. Event based sampling occurs naturally in many contexts such as motion systems where angles and positions are measured. In this thesis special attention is paid to rotating axles where the position is measured with a rotational speed sensor. Due to production tolerances such a sensor has a nonideal performance. This causes a periodic error in the event based sampled signal which in many cases cannot be neglected. Two different methods for elimitating the sensor errors are proposed.To be able to use standard tools for analyzing the signal from the rotational speed sensor, the signal is interpolated to a uniformly sampled signal. A desirable feature of the interpolation is to incorporate a lowpass filter to avoid aliasing. We investigate and compare three different methods, all based on a non-parametric regression.A survey of different methods to estimate a single resonance frequency in the rotational speed signal is presented including aspects of estimation accuracy and computational complexity.As an application of event based sampling and spectral estimation, a Tire Pressure Monitoring System (TPMS) is designed and analyzed. The TPMS is based on event based sampled measurements from a wheel speed sensor. The tire is modeled as a spring-damper system. The idea is to monitor the resonance frequency caused by the spring-damper system. This frequency is correlated with the inflation pressure, and by monitoring the resonance frequency, it is possible to detect inflation pressure changes. The system is implemented and tested in a real vehicle with promising results.
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| 35. |
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| 36. |
- Persson, Per, et al.
(författare)
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GeoNotes: social enhancement of physical space
- 2001. - 1
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Ingår i: Proceeding CHI EA '01 CHI '01 Extended Abstracts on Human Factors in Computing Systems. - Seattle, Washington, USA : ACM Publications.
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Konferensbidrag (refereegranskat)abstract
- The GeoNotes system allows users to annotate physical locations with virtual 'notes', which are then pushed to or accessed by other users when in the vicinity. GeoNotes employs a number of social filtering techniques, which all rely on logging of usage rather than content.
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| 37. |
- Persson, Per, et al.
(författare)
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GeoNotes: social enhancement of physical space
- 2001. - 1
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Ingår i: ERCIM News. ; :47
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Positioning technology is often associated with locating people in geographical space. The GeoNotes system, however, positions pieces of information. GeoNotes allows all users to annotate physical locations with virtual "notes", which are then pushed to or accessed by other users when in the vicinity.
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| 38. |
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| 39. |
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| 40. |
- Repp, Jascha, et al.
(författare)
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Controlling the Charge State of Individual Gold Adatoms
- 2004
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 305, s. 493-
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Tidskriftsartikel (refereegranskat)abstract
- The nature and control of individual metal atoms on insulators are of great importance in emerging atomic-scale technologies. Individual gold atoms on an ultrathin insulating sodium chloride film supported by a copper surface exhibit two different charge states, which are stabilized by the large ionic polarizability of the film. The charge state and associated physical and chemical properties such as diffusion can be controlled by adding or removing a single electron to or from the adatom with a scanning tunneling microscope tip. The simple physical mechanism behind the charge bistability in this case suggests that this is a common phenomenon for adsorbates on polar insulating films.
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