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- Espinoza, Fredrik, et al.
(författare)
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GeoNotes: social and navigational aspects of location-based information systems
- 2001. - 1
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Ingår i: UBICOMP 2001. - : Swedish Institute of Computer Science.
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Location-based information systems allow the user to access information in relation to the user's position in geographical space. This paper outlines navigational and social aspects of such systems. It is argued that location-based systems must allow users to participate as content providers in order to achieve a social and dynamic information space. Moreover, as these systems allow commercial and private users to annotate space with information on a mass-scale, information filtering techniques will become essential in order to prevent information overload and user disturbance. We present a number of content-based and social filtering techniques to support this. We discuss implications for implementation and we describe a system (GeoNotes), which takes some of these aspects into account.
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- Magnusson, Alf, 1958, et al.
(författare)
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A Comparison of Spray Properties for Model Fuel and Diesel Using Several Optical Methods
- 2004
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Ingår i: 19th Ilass Europe.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Many experiments are carried out using a model fuel, for instance for measurement technique reasons. These data are usually transferred to situations where standard diesel fuel is used. The objective of this work is to characterize the liquid and vapour phase penetration of two different diesel fuels, one two-component model fuel, IDEA (70% n-decane and 30% α-methylnaphthalene) and one standard diesel fuel (Swedish Environmental Class I), when injected into air with density corresponding to early injections up to self ignition conditions in diesel engines. The experimental study was carried out in the high-pressure, high-temperature (HP/HT) spray rig at Chalmers, which was pressurized in the range of 4 to 85 bar and with temperature ranging from 400 to 800 K.A common-rail injection system with a single hole nozzle was used. Several optical methods (Schlieren, Shadowgraph, LIF (Laser Induced Fluorescence) and Mie-scattering) were used together or separately which allow a comparison of the output. Phase Doppler Anemometry (PDA) was used for the two fuels as a complement to the planar methods. Results from measurements show that there are differences in liquid penetration, fuel vaporization and droplet distribution in between the fuels and relatively good agreement between the methods
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| 8. |
- 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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