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- Blokpoel, Sjoerd, et al.
(författare)
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Cooperation and product modelling systems
- 2004
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Ingår i: Proceedings of the 5th European Conference of Product and Process Modelling in the Building and Construction Industry. - : Balkema Publishers, A.A. / Taylor & Francis The Netherlands. - 0415359384 ; , s. 423-430
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the introduction of product modelling in today's building process. The main potentials of these systems are facilitating open communication, configuration management, reuse of information, virtual prototyping in 4D and allowing numerous analyses on e.g. life cycle, energy use and accurate estimates of project costs. The modelling systems have prerequisites for application that are not fulfilled by the construction industry. Therefore, the potential benefits cannot be derived at the moment. Most unfulfilled prerequisites are related to the way of cooperation. New building process organisation types, like partnering, offer a better way to approach a project and a good basis to use the systems. The development of these organisation types should be integrated in the application of models because the systems could be a good tool, and maybe even an enabler. Legal issues are no roadblock for application, but need attention. The current contracts are sufficient, but need an add-on for procedures in the use of ICT. A third party should keep an encrypted logfile to ensure tracebility of changes. Model errors in exchange files can occur and cause problems. Producers of data should be responsible for the produced data and check its consistency. Middleware is needed to exchange only core model information and to allow company based ICT systems that connect through a shared modelling system. The main strength of the application is configuration management and a database with information to improve communication. The main weakness is the lack of clear, measurable benefits and costs Key Performance Indexes (KPI's). The main opportunities are current developments in partnering, which make the application of systems better possible. Main threats are the fragmentised view in the sector, both in phases, in a project and of projects by a company and the lack of good cooperation.
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| 2. |
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| 3. |
- Enochsson, Ola, et al.
(författare)
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Bro över Luossajokk : beräkning med säkerhetsindexmetod, böjdragkapacitet i överkant i mittsnittet i korta spannet
- 2002
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I samband med projektet "30 ton på Malmbanan", Paulson-Töyrä (1996), konstaterades att bron över Luossajokk i Kiruna inte klarade de nya förhöjda lasterna. Bron har två spann och en utkragande konsol 10,25 + 6,3 + 3,4 m. Överbyggnaden utgörs av ett slakarmerat betongtråg med ett nytt mellanstöd som uppfördes 1965 då en äldre överbyggnad byttes ut. En klassningsberäkning och en utredning av förstärkningsbehov utfördes. Efter en förnyad översyn av brons bärförmåga utfördes töjningsmätningar vintern och sommaren 2001. Töjningsmätningarna indikerade förvånansvärt små påkänningar i bron. En närmare utredning av brons säkerhet att bära uppträdande laster genomförs därför i denna rapport. Detta sker med hjälp av en nyanserad säkerhetsberäkning med säkerhetsindexmetod. Den nya genomgången visar att medelvärdet för bärförmågan för moment är 2,89 MNm med standardavvikelsen 0,19 MNm i det mest utsatta snittet med dragpåkänningar i överkant i korta spannet. Detta kan jämföras med det formella dimensioneringsvärdet 1,99 MNm som erhölls i klassningsberäkningen med beaktande av aktuella partialkoefficienter. I det nya medelvärdet har en lägre uppmätt effektiv höjd beaktats, att ett av tolv armeringsjärn borrats av samt att betong- och armeringshållfastheterna är högre än de nominella dimensioneringsvärdena. På lastsidan gav klassningsberäkningen i motsvarande snitt att det formella dimensioneringsvärdet för momentet är 2,79 MNm. En analys av verkliga uppträdande laster ger att medelvärdet maximalt uppgår till 2,05 MNm. Detta lastfall utgörs av ett lok placerat med tre axlar i längsta spannet och tre axlar placerade på konsolen, om såväl bromslast som ojämn temperaturlast och dynamiskt tillskott uppträder samtidigt. Enligt BV Bärighet (1996) behöver ojämn temperatur inte beaktas, vilket är rimligt med tanke på att detta är ett statiskt obestämt lastfall som försvinner vid uppsprickning i brottstadiet. Det har heller inte medräknats i tidigare klassningsberäkningar. I så fall fås att lasten har medelvärdet 1,66 MNm och att säkerhetsindex β varierar mellan 3,8 och 6,0 beroende på vilka antaganden som görs om lasternas statistiska fördelning. För en rimlig fördelning innehålls kravet i säkerhetsklass 3 att säkerhetsindex β 4,75. Bron visar sig därför, enligt vår bedömning och med beaktande av erhållna mätresultat, ha erforderlig bärförmåga om hastigheten begränsas på bron så att eventuella dynamiska tillskott blir låga och/eller inverkan av ojämn temperatur försummas. Brons fortsatta uppförande bör kontrolleras genom ett mätprogram. Detta bör förutom armeringstöjningar med befintliga givare även inkludera mätningar av nedböjningar för att säkerställa att använda beräkningsmodeller och randvillkor på ett korrekt sätt återger brons beteende. Storleken på den dynamiska förstoringsfaktorn D bör även mätas liksom inverkan av bromskrafter och ojämn temperaturfördelning. På så sätt kan ett säkrare underlag erhållas för bedömning av frekvensfunktionerna för dessa vanliga lasteffekter. Dessa värden borde även vara av intresse vid säkerhetsbedömning av likartade järnvägsbroar.
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| 4. |
- Georg, Dietmar, et al.
(författare)
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A practical method to calculate head scatter factors in wedged rectangular and irregular MLC shaped beams for external and internal wedges
- 2004
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 49:20, s. 4689-4700
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Tidskriftsartikel (refereegranskat)abstract
- Factor based methods for absorbed dose or monitor unit calculations are often based on separate data sets for open and wedged beams. The determination of basic beam parameters can be rather time consuming, unless equivalent square methods are applied. When considering irregular wedged beams shaped with a multileaf collimator, parametrization methods for dosimetric quantities, e.g. output ratios or wedge factors as a function of field size and shape, become even more important. A practical method is presented to derive wedged output ratios in air (S-c,S-w) for any rectangular field and for any irregular MLC shaped beam. This method was based on open field output ratios in air (Sc) for a field with the same collimator setting, and a relation f(w) between S-c,S-w and S-c. The relation f(w) can be determined from measured output ratios in air for a few open and wedged fields including the maximum wedged field size. The function fw and its parametrization were dependent on wedge angle and treatment head design, i.e. they were different for internal and external wedges. The proposed method was tested for rectangular wedged fields on three accelerators with internal wedges (GE, Elekta, BBC) and two accelerators with external wedges (Varian). For symmetric regular beams the average deviation between calculated and measured S-c,S-w/S-c ratios was 0.3% for external wedges and about 0.6% for internal wedges. Maximum deviations of 1.8% were obtained for elongated rectangular fields on the GE and ELEKTA linacs with an internal wedge. The same accuracy was achieved for irregular MLC shaped wedged beams on the accelerators with MLC and internal wedges (GE and Elekta), with an average deviation < 1 % for the fields tested. The proposed method to determine output ratios in air for wedged beams from output ratios of open beams, combined with equivalent square approaches, can be easily integrated in empirical or semi-empirical methods for monitor unit calculations.
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| 5. |
- Georg, Dietmar, et al.
(författare)
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On empirical methods to determine scatter factors for irregular MLC shaped beams
- 2004
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Ingår i: Medical physics (Lancaster). - : Wiley. - 0094-2405. ; 31:8, s. 2222-2229
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Tidskriftsartikel (refereegranskat)abstract
- Multileaf collimators (MLCs) are in clinical use for more than a decade and are a well accepted tool in radiotherapy. For almost each MLC design different empirical or semianalytical methods have been presented for calculating output ratios in air for irregularly shaped beams. However, until now no clear recommendations have been given on how to handle irregular fields shaped by multileaf collimators for independent monitor unit (MU) verification. The present article compares different empirical methods, which have been proposed for independent MU verification, to determine (1) output ratios in air (S-P) and (2) phantom scatter factors (Sp) for irregular MLC shaped fields. Ten dedicated field shapes were applied to five different types of MLCs (Elekta, Siemens, Varian, Scanditronix, General Electric). All calculations based on empirical relations were compared with measurements and with calculations performed by a treatment planning system with a fluence based algorithm. For most irregular MLC shaped beams output ratios in air could be adequately modeled with an accuracy of about 1%-1.5% applying a method based on the open field aperture defined by the leaf and jaw setting combined with the equivalent square formula suggested by Vadash and Bjarngard [P. Vadash and B. E. Bjarngard, Med. Phys. 20, 733-734 (1993)]. The accuracy of this approach strongly depends on the inherent head scatter characteristics of the accelerator in use and on the irregular field under consideration. Deviations of up to 3% were obtained for fields where leaves obscure central parts of the flattening filter. Simple equivalent square methods for S-P calculations in irregular fields did not provide acceptable results (deviations mostly >3%). S-P values derived from Clarkson integration, based on published tables of phantom scatter correction factors, showed the same accuracy level as calculations performed using a pencil beam algorithm of a treatment planning system (in a homogeneous media). The separation of head scatter and phantom scatter contributions is strongly recommended for irregular MLC shaped beams as both contributions have different factors of influence. With rather simple methods S, and SP can be determined for independent MU calculation with an accuracy better than 1.5% for most clinical situations encountered in conformal radiotherapy. (C) 2004 American Association of Physicists in Medicine.
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| 9. |
- Hultqvist, Malin, et al.
(författare)
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Enhanced autoimmunity, arthritis, and encephalomyelitis in mice with a reduced oxidative burst due to a mutation in the Ncf1 gene.
- 2004
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 101:34, s. 12646-12651
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Tidskriftsartikel (refereegranskat)abstract
- The Ncf1 gene was recently identified as a strong regulator of severe arthritis in rat. This finding was surprising, because the disease-promoting allele mediated a lower level of reactive oxygen species in NADPH oxidase-expressing cells. We have now investigated a splice mutation of the Ncf1 gene in B10.Q mice, causing a truncated and nonfunctional Ncf1 protein. We found that the mutated Ncf1 led to a more severe and chronic relapsing collagen-induced arthritis. Enhanced IgG and delayed-type hypersensitivity responses against type II collagen were seen, indicating increased activity of autoreactive T cells. Interestingly, female Ncf1-mutated mice spontaneously developed severe arthritis during the postpartum period. The arthritis was accompanied by an increased antibody response to type II collagen, with the same fine specificity as in collagen-induced arthritis. The enhancing effect of the mutated Ncf1 could also be shown to be more general in that it enhanced myelin oligodendrocyte glycoprotein protein-induced experimental autoimmune encephalomyelitis, a model for multiple sclerosis. These results show that Ncf1, a gene important for oxidative burst, regulates the susceptibility and severity of both arthritis and encephalomyelitis and modulates, directly or indirectly, the level of T cell-dependent autoimmune responses.
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