Macro-step-size selection and monitoring of the coupling error for weak coupled subsystems in the frequency-domain

A rather general approach to establish a multiphysic simulation is referred to as non-iterative co-simulation or weak coupled simulation. The involved subsystems are coupled in a weak sense and thus stepwise extrapolation of the coupling signals is required. Extrapolation is associated with an error which may influence the dynamical behavior of the coupled system. This coupling error depends significantly on the coupling step-size, i.e. the macro-step-size, and is one of the most critical parameter of a noniterative co-simulation. In practice, appropriate macro-step-sizes are determined by some numerical tests or chosen according to the experience of domain-specific engineers. But who assesses the results of a non-iterative co-simulation? Comparison between reference and co-simulation results in the time-domain is often practiced in case studies using complex subsystems to validate co-simulation performance and accuracy of the achieved results. But this approach is counter-productive and mostly not applicable in practice. In this work we consider the coupling process as single source of distortion and analyse it in the frequency-domain. As a consequence, a relation between the macro-step-size and the coupling signals is available which leads to a ’rule-of-thumb’ for a adequate macro-stepsize selection. In addition, the gained insight into the coupling process itself enables new possibilities to monitor the coupling error leading to the ability to assess the results of a weak coupled simulation. The proposed methodologies are examined using a complex mechatronic system describing a vehicle (multi-body system, MBS), which is controlled via an anti-lock braking system (ABS) during different scenarios

On the difficulities of real-time co-simulation

In a co-simulation, subsystems are coupled via their in- and outputs to simulate the overall system behaviour. The subsystems are modelled in their domain specfic simulation tools. The task changes if one coupled subsystem represents a real-time system. A real-time system which has to guarantees hard-real-time conditions influences the co-simulation concept: now the co-simulation also has to fulfill hard-real-time conditions. This type of co-simulation is called real-time co-simulation. The most important difference to a non-real-time co-simulation is the time correct overall simulation speed with respect to the involved real-time systems. To achieve this, all subsystems in form of non-real-time systems have to be synchronised to the involved real-time systems. The focus of this work lies on the problems that occur in a real-time co-simulation environment compared to a classical one. A concept to handle the additional problems is outlined and tested on an example real-time co-simulation

Fluid-dynamic study on a multi-stage fluidized bed column for continuous CO2 capture via temperature swing adsorption

Adsorption based processes have a great potential to significantly reduce the overall costs of CO2 separation from stack flue gas as compared to currently available technologies. One of the main challenges in the development of these processes is certainly the provision of adequate adsorbents. Hence, in the last decade a great effort has been put into screening and testing of various adsorbent materials. However, beside the identification of suitable adsorbent materials it is of equal importance to develop suitable reactor designs that allow for effective and most cost efficient utilization of these materials and so far only little work has been attributed to this subject. Nevertheless, it was shown that for thermodynamic reasons it is essential to provide counter-current contact between adsorbent and gas streams in order to allow for efficient operation of any Temperature Swing Adsorption (TSA) CO2 capture process. It was further highlighted that effective heat transfer with the used adsorbent material is necessary as the reported values of their corresponding adsorption enthalpies are typically rather large. Please click Additional Files below to see the full abstract

LEAN PANEL BENDER – Einige mechanische Aspekte der Modellierung in Echtzeit für Produktion in Losgröße 1

Nachfolgend werden einige wissenschaftliche Aspekte der Echtzeit-Materialerkennungsstrategie MAC diskutiert, die in der neuen Maschinenfamilie LEAN PANEL BENDER der Firma Salvagnini Maschinenbau realisiert ist und die eine hochpräzise und hocheffiziente Herstellung von komplex geformten Blechprodukten sowohl bei Losgröße 1 als auch in der Serie erlaubt.(VLID)342339

Industrial application of advanced adaptive concepts for automatic panel benders

Recently, the requirements on sheet metal production processes have increased significantly. Highest precision and flexibility with efficient energy consumption and short cycle times can be achieved by advanced concepts only. This requires a deep insight into the non-linear bending process. For this sake, efficient simulation models have been implemented to model the bending process: two and three dimensional finite element models combined with multibody simulation tools, contact mechanics algorithms and substructure techniques. The simulation tools have been successfully calibrated by measurement results. With the obtained detailed process knowledge, new adaptive concepts have been introduced, e.g. a smart crowning system in order to achieve straight profiles. The industrial application has shown the advantage of utilizing the above mentioned techniques. The straightness of the bends has been significantly increased, while energy consumption and cycle times have been reduced. Secondly, the development time of new machine concepts has been drastically reduced, such that the first prototype can be transferred to series production within short time. Moreover, the applied strategies show a large potential for future developments

Advanced mechanical simulation models for automatic panel benders

With automatic panel benders complete products are manufactured from sheet metal. In order to achieve short cycle times with high flexibility, a deep insight into the non-linear bending process is required. For this reason, efficient mechanical simulation models have been implemented, combining Finite Element Method, multibody dynamics simulation tools, contact mechanics algorithms and substructuring. Scope of this work is the comparison of several simulation models with measurement results performed on a Salvagnini P4XeD automatic panel bender

Counter-regulatory responses to postprandial hypoglycaemia in patients with post-bariatric hypoglycaemia vs surgical and non-surgical control individuals

Aims/hypothesis Post-bariatric hypoglycaemia is an increasingly recognised complication of bariatric surgery, manifesting particularly after Roux-en-Y gastric bypass. While hyperinsulinaemia is an established pathophysiological feature, the role of counter-regulation remains unclear. We aimed to assess counter-regulatory hormones and glucose fluxes during insulin-induced postprandial hypoglycaemia in patients with post-bariatric hypoglycaemia after Roux-en-Y gastric bypass vs surgical and non-surgical control individuals. Methods In this case–control study, 32 adults belonging to four groups with comparable age, sex and BMI (patients with post-bariatric hypoglycaemia, Roux-en-Y gastric bypass, sleeve gastrectomy and non-surgical control individuals) underwent a postprandial hypoglycaemic clamp in our clinical research unit to reach the glycaemic target of 2.5 mmol/l 150–170 min after ingesting 15 g of glucose. Glucose fluxes were assessed during the postprandial and hypoglycaemic period using a dual-tracer approach. The primary outcome was the incremental AUC of glucagon during hypoglycaemia. Catecholamines, cortisol, growth hormone, pancreatic polypeptide and endogenous glucose production were also analysed during hypoglycaemia. Results The rate of glucose appearance after oral administration, as well as the rates of total glucose appearance and glucose disappearance, were higher in both Roux-en-Y gastric bypass groups vs the non-surgical control group in the early postprandial period (all p<0.05). During hypoglycaemia, glucagon exposure was significantly lower in all surgical groups vs the non-surgical control group (all p<0.01). Pancreatic polypeptide levels were significantly lower in patients with post-bariatric hypoglycaemia vs the non-surgical control group (median [IQR]: 24.7 [10.9, 38.7] pmol/l vs 238.7 [186.3, 288.9] pmol/l) (p=0.005). Other hormonal responses to hypoglycaemia and endogenous glucose production did not significantly differ between the groups. Conclusions/interpretation The glucagon response to insulin-induced postprandial hypoglycaemia is lower in post-bariatric surgery individuals compared with non-surgical control individuals, irrespective of the surgical modality. No significant differences were found between patients with post-bariatric hypoglycaemia and surgical control individuals, suggesting that impaired counter-regulation is not a root cause of post-bariatric hypoglycaemia

Oxygen Tension Regulates Pancreatic β-Cell Differentiation Through Hypoxia-Inducible Factor 1α

International audienceThese data demonstrate that beta-cell differentiation is controlled by pO2 through HIF1alpha. Modifying pO2 should now be tested in protocols aiming to differentiate beta-cells from embryonic stem cells