| 1. |
- Alin, David, 1984, et al.
(författare)
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Reducing the EPEI-Time Using Discrete Event Simulation
- 2009
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Ingår i: Proceedings of the 2009 Swedish Production Symposium. ; :2, s. 295-301
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Konferensbidrag (refereegranskat)abstract
- One of the cornerstones in LEAN production is ‘make to order’, which requires small batch sizes and, thus, short Every Part Every Interval (EPEI) times. EPEI-time is defined as the time it takes to produce all product variants, before the first variant in the cycle returns in the schedule. However, many companies are reluctant to reduce their EPEI-times due to the increased number of set-ups. This skepticism is also supported by parts of existing theory, while other research contributions mean that companies often can reduce batch-sizes without affecting productivity. This paper presents a case study which uses discrete event simulation (DES) to evaluate the relation between EPEI-time and productivity. The results show that it is possible to reduce the EPEI-time and still maintain productivity and service levels to customers, without any investments. Increased variation in the production schedule evened out the load among the machines and, hence, the time lost in set-ups was gained in more parallel work.
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| 2. |
- Andersson, John, 1993, et al.
(författare)
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Polymer Brushes on Silica Nanostructures Prepared by Aminopropylsilatrane Click Chemistry: Superior Antifouling and Biofunctionality
- 2023
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 15:7, s. 10228-10239
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Tidskriftsartikel (refereegranskat)abstract
- In nanobiotechnology, the importance of controlling interactions between biological molecules and surfaces is paramount. In recent years, many devices based on nanostructured silicon materials have been presented, such as nanopores and nanochannels. However, there is still a clear lack of simple, reliable, and efficient protocols for preventing and controlling biomolecule adsorption in such structures. In this work, we show a simple method for passivation or selective biofunctionalization of silica, without the need for polymerization reactions or vapor-phase deposition. The surface is simply exposed stepwise to three different chemicals over the course of ∼1 h. First, the use of aminopropylsilatrane is used to create a monolayer of amines, yielding more uniform layers than conventional silanization protocols. Second, a cross-linker layer and click chemistry are used to make the surface reactive toward thiols. In the third step, thick and dense poly(ethylene glycol) brushes are prepared by a grafting-to approach. The modified surfaces are shown to be superior to existing options for silica modification, exhibiting ultralow fouling (a few ng/cm2) after exposure to crude serum. In addition, by including a fraction of biotinylated polymer end groups, the surface can be functionalized further. We show that avidin can be detected label-free from a serum solution with a selectivity (compared to nonspecific binding) of more than 98% without the need for a reference channel. Furthermore, we show that our method can passivate the interior of 150 nm × 100 nm nanochannels in silica, showing complete elimination of adsorption of a sticky fluorescent protein. Additionally, our method is shown to be compatible with modifications of solid-state nanopores in 20 nm thin silicon nitride membranes and reduces the noise in the ion current. We consider these findings highly important for the broad field of nanobiotechnology, and we believe that our method will be very useful for a great variety of surface-based sensors and analytical devices.
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| 3. |
- Hellsmark, Hans, 1974, et al.
(författare)
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Teknologiska innovationssystem inom energiområdet: En praktisk vägledning till identifiering av systemsvagheter som motiverar särskilda politiska åtaganden
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med denna rapport är att illustrera hur ett praktiskt inriktat ramverk, tekno- logiska innovationssystem (TIS), kan användas av analytiker och beslutsfattare vid departement och myndigheter för att analysera strategiskt viktiga teknikområden ?????????????????????????????????????????????????????????????????????????????I rapporten analyseras fem TIS centrerade kring havsbaserad vindkraft, marin energi, ????????????????????????????????????????????????????????????????????????????????????? systemsvagheter som bromsar områdets vidare utveckling, vilka som kan åtgärdas av systemets aktörer och vilka som motiverar särskilda politiska åtaganden. Rapporten utgör därmed ett underlag för att formulera åtgärder för att åstadkomma ökad innova- tion, teknikspridning och industrialisering inom ovan nämnda teknikområden.Studien har även möjliggjort en jämförande analys av likheter och skillnader ???????????????????????????????????????????????????????????????????????????????? ?????????????????????????????????????????????????????????????????????????????????????? mellan områdena – de är starka respektive svaga av olika orsaker. Detta visar att ???????????????????????????????????????????????????????????????????????Samtidigt har områdena gemensamma drag. Systemets aktörer, där även politiska ???????????????????????????????????????????????????????????????????????????????????? ?????????????????????????????????????????????????????????????????????????????- skapsnätverk. Men de har varit sämre på att skapa tidiga nischmarknader som ger utrymme för fortsatt lärande och kostnadsreduktion. Sådana nischer kan ibland skapas av marknadens aktörer, men ofta krävs politiska styrmedel. De behövs för att investeringar i kunskapsutveckling ska kunna nyttiggöras och för att en bred industriell utveckling inom nya områden skall göras möjlig i Sverige.Vidare presenteras lärdomar kring vad en aktiv teknikpolitik innebär. Två huvud- ??????????????????????????????????????????????????????????????????????????????- hällsbygget och därför bör vara ett politikområde bland många samt att den skarpa ??????????????????????????????????????????????????????????????????????????????- ?????????????????????????????????????????????????????????????????????????????????? ?????????????????????????????????????????????????????????????????????????????????? olika faser av innovationssystemets utveckling.För att lyckas med en aktiv teknikpolitik behövs en hög grad av koordinering ??????????????????????????????????????????????????????????????????????? teknikområden så att ”rätt” typ av åtgärder kan sättas in vid ”rätt” tidpunkt av ”rätt” aktör. TIS-ramverket lyfts här fram som en metod för att skapa ett sådant underlag. Slutligen presenteras en metod för projektbedömningar som syftar till att stötta handläggare i utvärderingar av projekt inom nya teknikområden.Rapporten i sin helhet riktar sig särskilt till beslutsfattare och handläggare vid myndigheter, departement och politiker, men även andra organisationer och indi- vider med intresse av att högt ställda klimatmål ska kunna nås samtidigt som en positiv näringslivsutveckling möjliggörs.
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| 4. |
- Napoleone, Antonino, et al.
(författare)
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Fed-batch production assessment of a tetravalent bispecific antibody : A case study on piggyBac stably transfected HEK293 cells
- 2021
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Ingår i: New Biotechnology. - : Elsevier BV. - 1871-6784 .- 1876-4347. ; 65, s. 9-19
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Tidskriftsartikel (refereegranskat)abstract
- The transition from preclinical biological drug development into clinical trials requires an efficient upscaling process. In this context, bispecific antibody drugs are particularly challenging due to their propensity to form aggregates and generally produce low titers. Here, the upscaling process for a tetravalent bispecific antibody expressed by a piggyBac transposon-mediated stable HEK293 cell pool has been evaluated. The project was performed as a case study at Testa Center, a non-GMP facility for scale-up testing of biologics in Sweden, and encompassed media adaptation strategies, fed-batch optimization and a novel antibody purification technology. The cell pool was adapted to different culture media for evaluation in terms of cell viability and titers compared to its original Expi293 Expression Medium. These parameters were assessed in both sequential stepwise adaption and direct media exchanges. By this, a more affordable medium was identified that did not require stepwise adaptation and with similar titers and viability as in the Expi293 Expression Medium. Fed-batch optimizations resulted in culture densities reaching up to 20 x 106 viable cells/mL with over 90 % viability 12 days postinoculum, and antibody titers three times higher than corresponding batch cultures. By implementing a novel high-speed protein A fiber technology (Fibro PrismA) with a capture residence time of only 7.5 s, 8 L of supernatant could be purified in 4.5 h without compromising the purity, structural integrity and function of the bispecific antibody. Results from this study related to medium adaptation and design of fed-batch protocols will be highly beneficial during the forthcoming scale-up of this therapeutic antibody.
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| 5. |
- Nilsson, Andreas, 1974, et al.
(författare)
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Effects of continuous feedback on households’ electricity consumption: Potentials and barriers
- 2014
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 122, s. 17-23
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Tidskriftsartikel (refereegranskat)abstract
- Two field experiments were carried out to study (a) the effects on energy savings of continuous visual feedback via in-home displays, and (b) the motives for responding or not. In study 1, 40 participants living in separate or semi-detached houses in two different towns participated. All participants received a questionnaire and a list of possible energy saving measures. Households were then randomly assigned to an experimental condition (display) or a control condition (no display). In study 2, 32 households in rented apartments participated. No significant differences between the conditions were found for either of the studies. In study 2, semi-structured interviews were conducted among nine of the households. Through an analysis of interview transcripts barriers were identified explaining why the feedback intervention was not sufficient to change behaviour and reduce consumption. The barriers experienced indicate that there is a risk of overconfidence in IHDs. For the development of energy policies and more wide-scale implementation, it is important to be aware of the potential obstacles to success.
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| 6. |
- Aggestam, Emil, 1992, et al.
(författare)
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Multi-objective design optimisation of transition zones between different railway track forms
- 2018
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Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems, CM 2018. - : TU Delft. - 2590-0609. - 9789461869630 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- The vertical dynamic interaction between vehicle and railway track is simulated in the time domain using an extended state space vector approach. The track model includes a transition zone between slab track on a bridge and ballasted track on an embankment. By considering a multi-objective optimisation problem, solved using a genetic algorithm, selected vehicle and track responses are simultaneously minimised by optimising the distributions of rail pad stiffness and sleeper spacing in the transition zone. It is shown that the magnitudes of the maximum dynamic loads in the optimised transition zone can be reduced to be similar as the magnitudes far away from the transition zone.
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| 7. |
- Albright, Ann, et al.
(författare)
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Dynamic soil-structure interaction of a single-span railway bridge, forced vibration testing and simulation
- 2023
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Ingår i: Structure and Infrastructure Engineering. - : Informa UK Limited. - 1573-2479 .- 1744-8980. ; , s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- High-speed railway is expanding drastically in Sweden, necessitating new technology, and improve-ments of existing structures. End-shield bridges are a common and under-tested bridge type inSweden. Their dynamic performance is significantly impacted by their boundary conditions due to thesoil–structure interaction (SSI) and their large masses cantilevering beyond the footings. A specificend-shield bridge was tested under low (5 kN) and high (20kN) amplitude-forced hydraulic excitationfor a wide range of frequencies. Several train passages for typical passenger trains,‘X62’, were meas-ured with the same experimental setup. The results were analysed to isolate the significant modes ofthe system and the natural frequencies. A full 3D numerical model was calibrated and updated inAbaqus, along with a brief sensitivity study to determine the most influential parameters. Finally, theresponse to passing trains and Eurocode design HSLM trains was calculated. The experimental studyshowed that higher loading amplitudes resulted in higher damping and lower natural frequencies. Thenumerical analysis showed that for this bridge type the SSI cannot be neglected and can be success-fully introduced in the model.
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| 8. |
- Allahvirdizadeh, Reza, et al.
(författare)
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A framework recommendation for updating running safety design criteria of non-ballasted railway bridges using statistical investigations
- 2024
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Ingår i: Proceedings 12th European Conference on Structural Dynamics (EURODYN 2023). - : IOP Publishing. ; , s. 102008-
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Konferensbidrag (refereegranskat)abstract
- As far as the authors are aware, the threshold for vertical acceleration of the bridge deck was chosen based on the assumption that the induced dynamic loads would overcome gravity at higher accelerations, resulting in loss of contact between wheels and rail; however, the previous studies do not support this hypothesis. Considering these inconsistencies, a better understanding of the simplified design criteria is essential before conducting further studies suchas the calibration of partial safety factors. Therefore, this study considers a set of representative design scenarios to statistically compare wheel-rail contact loss with other criteria that can bederived from moving load models, such as vertical accelerations and bridge deck deflections. Based on the analyzes performed, deflection seems to be a better criterion than acceleration to control the running safety limit-state; although the results presented do not necessarily show avery strong correlation between these two criteria. Therefore, the k-means clustering approach isused together with 5% lower quantiles of the collected data to propose potential new thresholds. It should be noted that due to the limited number of analyzes, the approach presented in this study can be considered as a possible framework for further updates of the current design method rather than drawing general conclusions.
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| 9. |
- Allahvirdizadeh, Reza, et al.
(författare)
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Applicability of meta-model assisted reliability assessment for dynamic problems: a comparison between regression-based methods
- 2023
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Ingår i: Proceedings 14th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP14. - : Trinity College Dublin.
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Konferensbidrag (refereegranskat)abstract
- There is a growing intent among engineers, stakeholders, and decision makers to use probabilistic methods for infrastructure assessment or design objectives. However, the corresponding limit state for such problems usually requires the construction of complex computational models, usually using commercial software without parallelization capability. Such a requirement makes performing reliability analysis computationally prohibitive, which is even more challenging for dynamic problems, since a very short time step is required to obtain sufficiently accurate predictions. This concern has led to several methods being proposed to surrogate the limit state function with a generally black box called a meta-model. A variety of them, such as Kriging, Polynomial Chaos Expansion (PCE), Artificial Neural Networks (ANN), and response surfaces (e.g., polynomial, spline, or radial-base functions), have been adopted for this purpose. These meta-models are typically trained on a limited data set collected by computing the true responses of carefully selected input variables. Their applicability for assessing the probability of failure has been studied individually in the literature for both benchmark and practical problems. However, as far as the authors are aware, no comparison has been made between them for dynamic problems. This comparison needs to be made from the point of view of both accuracy and performance (number of calls to the limit state function). In this context, this paper takes a systematic approach to evaluate their performance under identical conditions, i.e., with similar training datasets. For this purpose, the dynamic response of railway bridges with different spans excited by the passage of trains with a wide range of speeds is used as a reference problem.
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| 10. |
- Allahvirdizadeh, Reza, et al.
(författare)
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Ensemble Meta-Models for Running Safety Assessment ofHigh-Speed Railway Bridges Considering Soil-StructureInteraction Effects
- 2022
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Konferensbidrag (refereegranskat)abstract
- Increasing operating speeds and axle loads of trains may induce higher verticaldeck accelerations on bridges, which may subsequently lead to the occurrence of ballast instabilities.This phenomenon not only increases maintenance costs but also leads to speed restrictionsunder operating conditions. In severe cases, it can also cause train derailment. Thishas been shown to be the governing criterion for the design of short to medium span lengthhigh-speed railway bridges, especially from the dynamic behaviour point of view. Despiteits substantial importance in the design of railway bridges, the conventional deterministic approachescannot achieve the desired level of safety (Allahvirdizadeh et al. 2020). Therefore,this article is devoted to the evaluation of the probability of violating running safety usingsimulation-based methods. In this context, different variables, including those for the bridge(span length, flexural rigidity, and geometric properties), for the train (axle load, dominantfrequency and damping ratio) and for the boundary conditions (soil and foundation properties)are considered. Due to the high computational cost and complexity of the consideredperformance function, a low-cost meta-model is trained using stack modelling concept as acombination of support vector machines (SVM), k-nearest neighbours (k-NN) and decisiontrees. Then, the range of maximum and minimum probabilities of exceeding the verticalacceleration threshold are evaluated as a function of train speed and bridge span length. Comparingthese boundaries with corresponding results of simply-supported bridges showed thatneglecting soil-structure interaction effects in shorter span bridges may result an underestimatedsafety of the system; however, for longer span bridges it may result in overestimatedsafeties.
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