| 1. |
- Isaksson, Ola, et al.
(författare)
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Trends in product modelling : an ENDREA perspective
- 2000
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Ingår i: Proceedings / Produktmodeller 2000. - Linköping : Linköping universitet.
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Konferensbidrag (refereegranskat)abstract
- The success of engineering companies is highly dependent on how well product information is managed, engineered and communicated. From marketing through development to after sales activities, data needs to be accessible and used in the best way. Today, geographical distance, the need for close co-operation and data complexity are all natural parts of the working environment. Product modelling techniques are continuously evolving with new requirements and opportunities emerging daily. This paper will outline and discuss some of these trends, and at the same time present some of the areas where research is being carried out within projects in the Product Model Cluster in the national graduate school - The Swedish Engineering Design Research and Education Agenda (ENDREA).
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| 2. |
- Olsson, Jan-Ola, et al.
(författare)
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Closed-loop System Identification of an HCCI Engine
- 2004
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Ingår i: Advances in Automotive Control. - 0080442501 ; 37:22, s. 239-244
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Konferensbidrag (refereegranskat)abstract
- Homogeneous Charge Compression Ignition (HCCI) is a promising but challenging combustion engine concept. The potential for good fuel economy and low emissions is high but the transient performance required for automotive applications presents a few problems still to be solved. The focus of this work is identification of the process dynamics. An ARX type model is fitted to input-output data. A method applicable under closed-loop control is suggested and demonstrated. The resulting models are evaluated in terms of the repeatability of model characteristics, prediction accuracy, residual characteristics and comparison to spectral models is made.
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| 3. |
- Pfeiffer, Roland, et al.
(författare)
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System Identification and LQG Control of Variable-Compression HCCI Engine Dynamics
- 2004
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Ingår i: Proceedings of the 2004 IEEE International Conference on Control Applications.. - 1085-1992. - 0780386337 ; 2, s. 1442-1447
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Konferensbidrag (refereegranskat)abstract
- The Homogenous Charge Compression Ignition (HCCI) combustion engine has potential to replace the spark ignition and compression ignition engines of today. One of the main problems in making the engine commercially attractive is the lack of direct means of controlling the ignition phasing. In this paper, we investigate the potential of inlet air temperature as a means to ignition actuation. This article describes a method for system identification of the HCCI process, and development of an effective LQG regulator for the combustion process, Matlab and Simulink being used in computations and simulations.
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| 4. |
- Tunestål, Per, et al.
(författare)
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Closed-Loop Combustion Control of HCCI Engines
- 2003
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Ingår i: Nonlinear and Hybrid Systems in Automotive Control. ; , s. 321-334
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The HCCI engine, with its excellent potential for high efficiency and low NOx emissions, is investigated from a control perspective. Combustion timing, i.e., where in the thermodynamic cycle combustion takes place, is identified as the most challenging problem with HCCI engine control. A number of different means for controlling combustion timing are suggested, and results using a dual-fuel solution are presented. This solution uses two fuels with different ignition characteristics to control the time of autoignition. Cylinder pressure measurement is suggested for feedback of combustion timing. A simple net-heat release algorithm is applied to the measurements, and the crank angle of 50% burnt is extracted. Open-loop instability is detected in some high-load regions of the operating range. This phenomenon is explained by positive feedback between the cylinder wall heating and ignition timing processes. Closed-loop performance is hampered by time delays and model uncertainties. This problem is particularly pronounced at operating points that are open-loop unstable.
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| 5. |
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| 6. |
- Andgart, Niklas, et al.
(författare)
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PSD-constrained PAR reduction for DMT/OFDM
- 2004
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Ingår i: Eurasip Journal on Applied Signal Processing. - 1110-8657. ; 2004:10
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Tidskriftsartikel (refereegranskat)abstract
- Common to all DMT/OFDM systems is a large peak-to-average ratio (PAR), which can lead to low power efficiency and nonlinear distortion. Tone reservation uses unused or reserved tones to design a peak-canceling signal to lower the PAR of a transmit block. In DMT ADSL systems, the power allocated to these tones may be limited due to crosstalk issues with many users in one twisted pair bundle. This PSD limitation not only limits PAR reduction ability, but also makes the optimization problem more challenging to solve. Extending the recently proposed active set tone reservation method, we develop an efficient algorithm with performance close to the optimal solution.
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| 7. |
- Bachrach-Lindström, Margareta, et al.
(författare)
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Nutritional status and functional capacity after femoral neck fractures : a prospective randomized one-year follow-up study
- 2000
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Ingår i: Aging. - 1945-4589. ; 12:5, s. 366-374
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Tidskriftsartikel (refereegranskat)abstract
- The primary aim of this study was to evaluate the effect of two different surgical methods on nutritional status and functional capacity during the first postoperative year in patients with displaced femoral neck fractures. A further aim was to evaluate the effect of nutritional support. One hundred patients were randomly assigned to treatment with either primary total hip arthroplasty (THA) or osteosynthesis. Half of the patients in each treatment group received protein- and energy-enriched food in the hospital in addition to individual nutritional advice in order to optimize their intake of protein- and energy-rich food. Nutritional state and functional capacity were examined at baseline, one and three months, and one year after the operation. Pain was examined at three months and one year. The effect of nutritional intervention was equal within both surgical groups. Logistic regression showed that the dependent variable "living at one year" was significantly associated with serum albumin levels at one month. Advanced age, mental impairment and deteriorated nutritional status were predominant in the non-survivors. Overall, the primary THA group performed better compared with the osteosynthesis group concerning weight change over time, locomotion and pain. This study also showed that primary THA could safely be performed in the elderly without an increased postoperative mortality rate.
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| 8. |
- Boiesen, P, et al.
(författare)
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Histologic grading in breast cancer--reproducibility between seven pathologic departments. South Sweden Breast Cancer Group
- 2000
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 1651-226X .- 0284-186X. ; 39:1, s. 41-45
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Tidskriftsartikel (refereegranskat)abstract
- Histologic grade, including tubular formations, nuclear grade, and mitotic activity, is a well-documented prognostic factor in breast cancer. In comparison with other prognostic parameters, the evaluation of histologic grade is cheap and can be performed, in principle, in all cases of breast cancer. One possible disadvantage is that the evaluation may vary between different pathological departments. The aim of the present work was therefore to study the reproducibility of the histologic grading system by distributing haematoxylin-erythrosin-stained slides from 93 invasive breast cancers to the seven pathology departments within the southern healthcare region of Sweden. The evaluation was performed blindly and without any knowledge of other clinical parameters. In 31% of the cases the same histologic grade was obtained for all departments. The overall mean kappa was 0.54, indicating a moderate reproducibility. Of the three factors included in histologic grade, the agreement was best for tubular formations and poorest for nuclear grade and mitotic activity. The overall moderate reproducibility should be considered when the clinical usefulness of histologic grading is compared with other prognostic instruments.
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| 9. |
- Broome, Michael, et al.
(författare)
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Splanchnic vasoconstriction by angiotensin II is arterial pressure dependent
- 2002
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 46:1, s. 57-63
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Our hypothesis was that splanchnic vasoconstriction by exogenous angiotensin II (Ang II) is significantly potentiated by local mechanisms increasing vasomotor tone and that splanchnic tissue oxygenation during administration of Ang II is perfusion pressure dependent. The aim was to study local splanchnic circulatory effects and tissue oxygenation during intravenous infusion of Ang II at different levels of regional arterial driving pressure in a whole-body large animal model. METHODS: Ang II was infused in incremental doses (0-200 microg x h-1) in anaesthetised instrumented pigs (n=8). Mean superior mesenteric arterial pressure (PSMA) was adjusted by a local variable perivascular occluder. Perivascular ultrasound and laser-Doppler flowmetry were used for measurements of mesenteric venous blood flow and superficial intestinal blood flow, respectively. Intestinal oxygenation was evaluated by oxygen tissue tension (PtiO2) and lactate fluxes. RESULTS: Ang II produced prominent and dose-dependent increases in mesenteric vascular resistance (RSMA) when the intestine was exposed to systemic arterial pressure, but Ang II increased RSMA only minimally when PSMA was artificially kept constant at a lower level (50 mmHg) by the occluder. Although Ang II decreased PtiO2 at a PSMA of 50 mmHg, splanchnic lactate production was not observed. CONCLUSION: We demonstrate that splanchnic vasoconstriction by exogenous Ang II is dependent on arterial driving pressure, suggesting significant potentiation through autoregulatory increases in vasomotor tone. Intestinal hypoxaemia does not seem to occur during short-term infusion of Ang II in doses that significantly increases systemic arterial pressure.
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| 10. |
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