Investigating Reliability on Fuel Cell Model Identification. Part II: An Estimation Method for Stochastic Parameters

An alternative way to process data from polarization measurements for fuel cell model validation is proposed. The method is based on re‐ and subsampling of I–V data, with which repetitive estimations are obtained for the model parameters. This way statistics such as standard deviations and correlations between the parameters may be experimentally derived. Histograms may also be produced, approximating the probability distributions that they follow. Two experimental case studies are discussed. In the first case, observations are made on the behavior of the parameter values for two mathematical models. As the number of data points (measurement points) employed in the estimation of the parameters increases, parameters with high variances converge to specific values. On the contrary, parameters with small variances diverge linearly. The parameters' histograms do not usually follow normal distributions rather they show a connection between the number of peaks in the graphs and correlations of the parameters. The second case study is an application on a fast degraded SOFC button cell, where the values and the histograms of the parameters are compared before and after degradation.     

XH715型数控立式加工中心床身动态优化设计的研究

首先设计出了三种形式的立式加工中心的床身,然后利用Pro/E强大的三维建模功能对XH715立式加工中心床身及整机进行了参数化建模,通过对床身有限元模型的动力学分析,得到了较优的模型,最后对该机床床身进行了动力学试验验证了设计结果.     

A new methodology for the design of low energy buildings

The Kyoto protocol binded the developed countries to reduce the greenhouse gas emissions at least by 5% by 2008-2012 in order to tackle global warming and climate change. Some of the measures of the governments to achieve this goal are to promote new buildings construction and to retrofit existing buildings while satisfying low energy criteria. This means improving energy efficiency of buildings and energy systems, developing sustainable building concepts and promoting renewable energy sources.The design of a low energy building requires parametric studies via simulation tools in order to optimize the design of the building envelope and HVAC systems. These studies are often complex and time consuming due to a large number of parameters to consider. Hence, this paper aims to set up a methodology that simplifies parametrical studies during the design process of a low energy building. The methodology is based on the Design of Experiments (DOE) method which is a statistical method widely used in industry to perform parametric studies that reduces the required number of experiments.     

碳纤维增强可果美晶格核芯的夹芯板

设计和制造了用碳纤维增强的中等拉伸的可果美晶格,以粘贴片作为表皮装配成夹芯板。通过面外受压、面内受压和3点弯曲试验,对夹芯板的力学性能进行了测试,揭示了夹芯板结构的不同破坏模式。试验结果显示,碳纤维增强可果美晶格比泡沫和蜂巢具有更高的刚度和强度。研究发现,弯曲和剥离决定了夹芯结构的力学性能,表面越平越能提高夹芯板的整体力学性能。     

Buckling experiments on steel silo transition junctions: II: Finite element modeling

This paper is concerned with the finite element modeling of the experiments on cone–cylinder–skirt–ring transition junctions in steel silos under simulated bulk solid loading presented in the companion paper. Before presenting the finite element results, the issue of modeling the interaction between the stored solid and the shell wall throughout the loading process is first examined. Results from nonlinear bifurcation analyses using the perfect shapes and nonlinear analyses using the measured imperfect shapes are then presented and compared with the experimental results. These comparisons show that despite the structural complexity of steel silo transition junctions, their behavior can be satisfactorily predicted by finite element analyses taking into account a number of important factors including geometric imperfections, effects of welding and the interaction between the junction and the stored solid. Next, the paper presents results of nonlinear analyses of these junctions with assumed eigenmode-affine imperfections. These results shed considerable light on the effect of ring buckling on the load-carrying capacity of transition junctions. Finally, the implications of the experimental and finite element results for the design of steel silo transition junctions are discussed.     

Buckling experiments on steel silo transition junctions: I: Experimental results

Large elevated steel silos for the storage of bulk solids generally consist of a cylindrical vessel above a conical discharge hopper supported on a cylindrical skirt. The cone–cylinder–skirt transition junction is subject to a large circumferential compressive force which is derived from the horizontal component of the meridional tension in the conical hopper, so either a ring is provided or the shell walls are locally thickened to strengthen the junction. Extensive theoretical studies have examined the buckling and collapse strengths of these junctions, leading to theoretically based design proposals. However, no previous experimental study on steel silo transition junctions has been reported due to the considerable difficulties associated with testing these thin-shell junctions at model scale. This paper presents the results of a series of tests on cone–cylinder–skirt–ring junctions in steel silos under simulated bulk solid loading. In addition to the presentation of test results including geometric imperfections and failure behavior, the determination of buckling modes and loads based on displacement measurements is examined in detail.     

Full-scale tests on composite steel-concrete beams with steel trapezoidal decking

This paper describes the detailed testing of two full-scale steel-concrete composite beams comprised of composite slabs with deep trapezoidal decking connected to universal beams by welded stud shear connectors. The ribs of the decking were orthogonal to the longitudinal axes of the steel beams. This situation exists in secondary beams in flooring systems of steel framed buildings, and beams with deep trapezoidal slabs of this type are economic since they are able to span large distances, with or without propping. Despite the popularity of these decks and many useful research contributions over several decades, there are some concerns related to the strength and ductility of the shear connection because of the large voids in the slab and the need to place the studs off-centre to circumvent welding them through the longitudinal stiffener in the rib. There is also significant disquiet as to the applicability of push test results on much smaller specimens to the design of full-scale beams. The experimental work in this paper therefore intends to provide benchmark data for the calibration of theoretical models and of design recommendations. The beams were 8 m long with low degrees of shear connection. The tests showed that both beams behaved in a very ductile fashion with the ultimate moment capacities being above those predicted from the Eurocode 4 guidelines.     

On the applicability of the laminar flow index when selecting surgical lighting

In modern operating rooms ultraclean air is supplied through the ceiling to prevent bacteria from entering an operating wound and cause infections. Operating lamps can disturb this flow of clean air. In this paper the accuracy of some aspects of the Laminar Flow Index of operating lamps was tested. The disturbance of the airflow was determined for different shapes and sizes of operating lamps in an isothermal situation. To accomplish this, an experimental study and a simulation study of a small room with an operating lamp were performed. The infection risk was found to be proportional to the projected surface area of the lamp. Although different lamp shapes resulted in a distinctly different flow pattern in the room, this did not affect the infection risk in a significant way. Operating lamps with a projected area smaller than 0.1 m² do not disturb the airflow at all in this particular setup.     

Interdisciplinary safety analysis of complex socio-technological systems based on the functional resonance accident model: An application to railway trafficsupervision

This paper presents an application of functional resonance accident models (FRAM) for the safety analysis of complex socio-technological systems, i.e. systems which include not only technological, but also human and organizational components. The supervision of certain industrial domains provides a good example of such systems, because although more and more actions for piloting installations are now automatized, there always remains a decision level (at least in the management of degraded modes) involving human behavior and organizations. The field of application of the study presented here is railway traffic supervision, using modern automatic train supervision (ATS) systems. Examples taken from railway traffic supervision illustrate the principal advantage of FRAM in comparison to classical safety analysis models, i.e. their ability to take into account technical as well as human and organizational aspects within a single model, thus allowing a true multidisciplinary cooperation between specialists from the different domains involved.A FRAM analysis is used to interpret experimental results obtained from a real ATS system linked to a railway simulator that places operators (experimental subjects) in simulated situations involving incidents. The first results show a significant dispersion in performances among different operators when detecting incidents. Some subsequent work in progress aims to make these “performance conditions” more homogeneous, mainly by ergonomic modifications. It is clear that the current human-machine interface (HMI) in ATS systems (a legacy of past technologies that used LED displays) has reached its limits and needs to be improved, for example, by highlighting the most pertinent information for a given situation (and, conversely, by removing irrelevant information likely to distract operators).     

Experimental study and numerical simulation of pipe-on-pipe impact

Experiments and numerical simulations were conducted to investigate the dynamic response in a pipe-on-pipe impact event, in which a missile (swinging) pipe with one end hinged and the other end free impinges on an orthogonal simply-supported/clamped target pipe at its centre. This study focuses on the effects of the impact location on the missile pipe and the wall thickness of the pipes. The experiments were carried out by using a spring-powered catapult impact setup, the specimens used were made of seamless steel pipes of two different thicknesses, 1 mm and 3 mm respectively, and the target pipes were clamped. Seven tests were carried out using the catapult. Numerical simulations using the explicit finite element code LS-DYNA were performed on an HPC360 workstation for each of the seven test cases. The results of the experiments and numerical simulations were compared, showing good agreement. Having confirmed the validity of the numerical model, numerical simulations were applied to the cases of a simply-supported target pipe, and the partitioning of the energy dissipation was calculated. As the response mode depends significantly on the initial impact position, the evolution of the response mode was examined numerically as the point of impact on the missile pipe was moved from the hinged end to the free end. It was found that there is a particular impact location for which the target pipe was most seriously damaged using the same impact speed.