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Engineering accreditation bodies express a strong consensus that in addition to technical and scientific skills, engineering education also needs to promote the development of professional skills. In general, team-based projects are considered to be valuable approaches to develop such skills and have been extensively added to engineering curricula. Yet, it remains unclear which skills and to what extent students learn from these interventions. The challenge of assessing the development of those skills is an important factor in this gap. In this paper, we used a standardised self-reporting questionnaire to evaluate the development of students' self-efficacy beliefs through in-course and capstone projects. Results suggest that students only marginally develop these skills when they are not explicitly addressed as part of the project, showing ways to more effectively support student learning of professional skills. The questionnaire also proved to be an effective and scalable way to assess large classes.

Multiobjective optimization is increasingly used in engineering to design new systems and to identify design tradeoffs. Yet, design problems often have objective functions and constraints that are expensive and highly nonlinear. Combinations of these features lead to poor convergence and diversity loss with common algorithms that have not been specifically designed for constrained optimization. Constrained benchmark problems exist, but they do not necessarily represent the challenges of engineering problems. In this article, a framework to design electro-mechanical actuators, called multiobjective design of actuators (MODAct), is presented and 20 constrained multiobjective optimization test problems are derived from the framework with a specific focus on constraints. The full source code is made available to ease its use. The effects of the constraints are analyzed through their impact on the Pareto front as well as on the convergence performance. A constraint landscape analysis approach is followed and extended with three new metrics to characterize the search and objective spaces. The features of MODAct are compared to existing test suites to highlight the differences. In addition, a convergence analysis using NSGA-II, NSGA-III, and C-TAEA on MODAct and existing test suites suggests that the design problems are indeed difficult due to the constraints. In particular, the number of simultaneously violated constraints in newly generated solutions seems key in understanding the convergence challenges. Thus, MODAct offers an efficient framework to analyze and handle constraints in future optimization algorithm design.

By considering a water capillary bridge confined between two flat surfaces, we investigate the thermodynamics of the triple line delimiting this solid-liquid-vapor system when supplemented in carbon dioxide. In more detail, by means of atom-scale simulations, we show that carbon dioxide accumulates at the solid walls and, preferably, at the triple lines where it plays the role of a line active agent. The line tension of the triple line, which is quantitatively assessed using an original mechanical route, is shown to be driven by the line excess concentrations of the solute (carbon dioxide) and solvent (water). Solute accumulation at the lines decreases the negative line tension (i.e., more negative) while solvent depletion from the lines has the opposite effect. Such an unprecedented quantitative assessment of gas-induced line tension modifications shows that the absolute value of the negative line tension increases upon increasing the carbon dioxide partial pressure. As a striking example, for hydrophilic surfaces, the line tension is found to increase by more than an order of magnitude when the carbon dioxide pressure exceeds 3 MPa. By considering the coupling between line and surface effects induced by gaseous adsorption, we hypothesize from the observed gas concentration-dependent line tension a nontrivial impact on heterogeneous nucleation of nanometric critical nuclei.

In the emerging field of deformable microfluidics, we propose a new geometry in which the height and angle of a channel are controlled, thanks to the deformability of the microfluidic elastomer down to thicknesses of a few microns. The particularity of our set-up is that the height of the channel under study is fully closed at rest, which reveals especially well suited to address micro-nanoconfinement problems such as clogging, transport selectivity and flow rectification. Using fluorescence microscopy and light absorption, we probe the channel shape from the measurement of the PDMS-displacement field. We demonstrate that the maximal PDMS displacement can be inferred from finite elements numerical simulations and predicted reliably with simple analytical relations from elasticity continuum mechanics.

A novel mechanical approach is developed to explore by means of atom-scale simulation the concept of line tension at a solid-liquid-vapor contact line as well as its dependence on temperature, confinement, and solid/fluid interactions. More precisely, by estimating the stresses exerted along and normal to a straight contact line formed within a partially wet pore, the line tension can be estimated while avoiding the pitfalls inherent to the geometrical scaling methodology based on hemispherical drops. The line tension for Lennard-Jones fluids is found to follow a generic behavior with temperature and chemical potential effects that are all included in a simple contact angle parameterization. Former discrepancies between theoretical modeling and molecular simulation are resolved, and the line tension concept is shown to be robust down to molecular confinements. The same qualitative behavior is observed for water but the line tension at the wetting transition diverges or converges towards a finite value depending on the range of the solid/fluid interactions at play., Comment: 8 pages, 7 figures

International audience; We present a unique rheometer allowing the study of fluid systems from the macrosco-pic scale to the microscopic scale. This rheometer developed from a surface forces apparatus geometry allows the equilibrium measurement of the mechanical response of the studied system. From this state of equilibrium, we impose a small harmonic perturbation of the gap between surfaces to measure the rheological response in linear regime. It is possible for continuous confinement from 10 micrometers to nanometer in a single experiment, the study of the transition from macrocopic to the microscopic. MOTS-CLÉS : rhéomètre, confinement, nanofluidique, SFA; Nous présentons ici un rhéomètre original permettant l'étude de systèmes fluides de l'échelle macroscopique à l'échelle microscopique. Ce rhéomètre développé à partir d'une géo-métrie de machine à forces de surface permet la mesure de la réponse mécanique à l'équilibre du système étudié en fonction du confinement. À partir de cet état d'équilibre, nous imposons une petite oscillation de la distance entre les surfaces afin de mesurer la réponse rhéologique proche de l'équilibre. Cette mesure est possible pour des confinements variant de 10 micro-mètres au nanomètre permettant en continu et dans une même expérience, l'étude du passage du macrocopique au microscopique.

Fluids in large and small pores display different behaviors with a crossover described through the concept of critical capillarity. Here we report experimental and simulation data for various siliceous zeolites and adsorbates that show unexpected reminiscent capillarity for such nanoporous materials. For pore sizes D exceeding the fluid molecule size, the filling pressures p are found to follow a generic behavior kBT ln p ∼ γ/ρD where γ and ρ are the fluid surface tension and density. This result is rationalized by showing that the filling chemical potential for such ultra-small pores is the sum of an adsorption energy and a capillary energy that remains meaningful even for severe confinements. A phenomenological model, based on Derjaguin’s formalism to bridge macroscopic and molecular theories for condensation in porous materials, is developed to account for the behavior of fluids confined down to the molecular scale from simple parameters., Confined fluids in porous media exhibit different behaviors in large and small pores, the crossover between the two regimes being not well understood. Here the authors show, by experiments and simulations, that capillarity is reminiscent even for very small pore diameters, providing a unified picture.

The slippage of polymer solutions on solid surfaces is often attributed to a depletion layer whose origin, thickness, and interaction with the flow are poorly understood. Using a Dynamic Surface Force Apparatus we report a structural and nanorheological study of the interface between hydrolyzed poly-acrylamide solutions and platinum surfaces. Polyelectrolyte chains adsorb on the surfaces in a thin charged layer, acting as a nonattractive wall for the bulk solution. We investigate the flow of the visco-elastic solution on the adsorbed layer from the nanometer to 10 micrometers, bridging microscopic to macroscopic properties. At distances larger than 200 nanometers, the flow is well described by an apparent slip boundary condition. At smaller distance the apparent slip is found to decrease with the gap. In contrast to the apparent slip model, we show that a 2-fluids model taking into account the finite thickness of depletion layers at the non-attractive wall describes accurately the dynamic forces over 4 spatial decades of confinement. Depletion layers are found to be an equilibrium property of the interface, independent on the flow and on the confinement. Their thickness is phenomenologically described by ξ + 2lD with ξ the correlation length of the semi-dilute solutions and lD the Debye length. We interpret this result in terms of screened repulsion between the charged adsorbed layer and the bulk polyions.

Using a dynamic Surface Force Apparatus, we demonstrate that the notion of slip length used to describe the boundary flow of simple liquids, is not appropriate for viscoelastic liquids. Rather, the appropriate description lies in the original Navier's partial slip boundary condition, formulated in terms of an interfacial friction coefficient. We establish an exact analytical expression to extract the interfacial friction coefficient from oscillatory drainage forces between a sphere and a plane, suitable for dynamic SFA or Atomic Force Microscopy non-contact measurements. We use this model to investigate the boundary friction of viscoelastic polymer solutions over 5 decades of film thicknesses and one decade in frequency. The proper use of the original Navier's condition describes accurately the complex hydrodynamic force up to scales of tens of micrometers, with a simple "Newtonian-like" friction coefficient, not frequency dependent, and reflecting closely the dynamics of an interfacial depletion layer at the solution/solid interface., Comment: 7 pages, 5 figures

International audience; We present experimental and theoretical results concerning the forced filling and spontaneous drying ofhydrophobic cylindrical mesopores in dynamical regime. Pores are structured with organic/inorganic moieties responsible for a periodicity of the surface energy along their axis.We find that the forced intrusion of water in these hydrophobic pores presents a slow dynamics: the intrusion pressure decreases as the logarithm of the intrusion time. We find that this slow dynamics is well described quantitatively by a classical model of activated wetting at the nanoscale, giving access to the structural length scales and surface energies of the mesoporous material.

With an increasing amount of volatile renewable electrical energy, the balancing of demand and supply becomes more and more demanding. Demand response is one of the emerging tools in this new landscape. Targeting service sector buildings, we investigated a tariff driven demand response model as a means to shave electrical peak loads and thus reducing grid balancing energy. In this paper is presented a software framework for load shifting which uses a tariff signal for the electric energy as minimization target. The framework can be used both on top of an existing building management system to shift heat generation towards low-tariff times, as well as to simulate load shifting for different buildings, heat pumps and storage configurations. Its modular architecture allows us to easily replace optimizers, weather data providers or building management system adapters. Our results show that even with the current TOU tariff system, up to 34 % of cost savings and up to 20 % reduction in energy consumption can be achieved. With Sub-MPC, a modified MPC optimizer, we could reduce computing times by a factor 50, while only slightly affecting the quality of the optimization.

Nanofluidics finds its root in the study of fluids and flows at the nanoscale. Flow rate is a quantity that is both central when dealing with flows and notoriously difficult to measure experimentally at the scale of an individual nanopore or nanochannel. We show in this letter that minute flow rate can be directly measured accumulating liquid over time within the compliant membrane of a commercial piezoresistive pressure sensor. Our flow rate sensor is versatile and can be operated independently of the nature of the liquid, flow profile, and type of nanochannel. We demonstrate this method by measuring the pressure-driven flow of silicon oil in a single nanochannel of average radius 200 nm. This approach gives reliable measurement of the flow rate up to 1 pL/min. Unlike other nanoscale flow measurements methods based, for instance, on particle tracking, our sensor delivers a direct voltage output suitable for nanoflow control applications.

Multi-objective optimization tools are becoming increasingly popular in mechanical engineering and allow decision-makers to better understand the inevitable trade-offs. Mechanical design problems can however combine properties that make the use of optimization more complex: (i) expensive cost functions; (ii) discrete or step-like behavior of the cost functions; and (iii) non-linear constraints. The latter in particular has a great impact on the convergence and the diversity of the obtained Pareto front. In this paper, we present five bi-objective mechanical design optimization problems with various levels of constraint complexity. They are used to rigorously benchmark two common constraint handling strategies (constrained-dominance and penalty function). The results suggest that both strategies have similar performance, and that as constraints become more intricate, convergence to the best-known Pareto front is not guaranteed. Indeed, analyzing the evolution of the hypervolume along generations reveals that the optimizer can get trapped in local optima. A detailed analysis of the obtained Pareto fronts for the proposed problems allows us to qualify the effects of the different constraints.

Domestic scale heat pumps and air conditioners are mainly driven by volumetric compressors. Yet the use of reduced scale centrifugal compressors is reconsidered due to their high efficiency and power density. Recent work has demonstrated the technical feasibility of a 20 mm centrifugal compressor on gas lubricated bearings operated with R134a by achieving isentropic efficiencies in excess of 75%. The design procedure of such centrifugal compressor starts by using pre-design tools based on the Cordier line. However, the optimality of the obtained pre-design, which is the starting point of a complex and iterative process, is not guaranteed, especially when small-scale compressors operating with organic fluids are targeted. This paper proposes an updated data-driven pre-design tool tailored for small-scale centrifugal compressors used in refrigeration applications. The pre-design model is generated using an experimentally validated 1D code which evaluates the compressor performance as a function of its detailed geometry and operating conditions. Using a symbolic regression tool, a reduced order model that predicts the performance of a given compressor geometry has been built. The proposed pre-design model offers an alternative to the tools available in literature by providing a higher level of detail and flexibility. Particularly, the model includes the effect of the pressure ratio PR and additional geometrical features such as blade height ratio b4 and the shroud to tip radius ratio r2s for addressing the inlet and exhaust areas. The analysis of the centrifugal compressor losses allows identifying the underlying phenomena that shape the new isentropic efficiency contours. As a consequence, for a specific operating condition, a compressor can have different geometries that yield the same efficiency. Low Ns compressors with high b4 are limited by blade loading and recirculation losses and operate closer to the surge limit. Compressors with low b4 and high Ns are exposed to high tip clearance and skin friction losses. Finally, the design space is limited at high Ns due to choke at the compressor inlet, while high incidence losses occur at low Ns at a constant r2s. Since incidence losses relate to the impeller inlet area, increasing r2s enables to achieve higher Ns, while decreasing r2s enables to explore lower Ns conditions. Compared to the 1D model the new pre-design model yields deviations below 4% on the isentropic efficiency, while running 1500 times faster. The new pre-design model is therefore of significant interest when the compressor is part of an integrated system design process.

Les systemes nanoporeux lyophobes, utilisables comme accumulateurs hydrauliques, s’apparentent a des anti-eponges. Les materiaux nanoporeux, employes comme anti-eponges, sont presentes dans cet article qui vise plus largement a decrire le principe de fonctionnement des systemes nanoporeux lyophobes et les mecanismes physiques qui leurs sont sous-jacents. L’article s’attache par ailleurs a comparer les systemes nanoporeux lyophobes aux solutions de stockage et de conversion d’energie actuelles, de facon a etablir leurs points forts et leur limitations. Les aspects exploratoires et perspectives en vue de futures ameliorations sont egalement abordes.

International audience; This paper reports hollow MEMS plate oscillators for the characterization of liquid samples, with a one-fold improvement in both Q-factor and Allan deviation compared to previous alike structures, and fluidic constriction larger than 1μm. These new characteristics make the devices amenable for the first time to liquid weighing with a 100 Hz.(g.L-1)-1 sensitivity and a few g.L-1 detection floor.

International audience; We present a nano-rheometer based on the dynamic drainage flow between a sphere and a plane from bulk regime to highly confined regime. The instrument gives absolute measurements of the viscosity of simple liquids in both regime. For complex fluids, the measurements involves the viscosity and the elastic modulus. The device operates on distances ranging over four orders of magnitude from 1 nanometer to 10 micrometers, bridging rheological properties from the macroscopic to the molecular scale. This allows to measure an hydrodynamic or visco-elastic boundary condition and to explore the causes of the boundary condition at the microscopic level.

The underground network of arbuscular mycorrhizal (AM) fungi is decisive for the above-ground diversity of many plant ecosystems, but tools to investigate the population structure of AM fungi are sorely lacking. Here, we present a bioinformatics approach to identify microsatellite markers in the AM fungus Glomus intraradices. Based on 1958 contigs of this fungus, assembled from public databases, we identified 842 microsatellites. One hundred of them were subjected to closer scrutiny by designing flanking primers and performing an extensive screen to identify polymorphic loci. We obtained 18 polymorphic microsatellite markers, and we found that seven out of eight individual single-spore cultures of G. intraradices could readily be identified by at least five allelic differences, as compared to all other strains. Two single-spore cultures, however, nominally originating from completely different locations, displayed identity at all 18 loci, suggesting with 99.999999% probability that they represent a single clone.

International audience; The forced intrusion of water in hydrophobic nanoporous pulverulent material is of interest for quick storage of energy. With nanometric pores the energy storage capacity is controlled by interfacial phenomena. With subnanometric pores, we demonstrate that a breakdown occurs with the emergence of molecular exclusion as a leading contribution. This bulk exclusion effect leads to an osmotic contribution to the pressure that can reach levels never previously sustained. We illustrate on various electrolytes and different microporous materials, that a simple osmotic pressure law accounts quantitatively for the enhancement of the intrusion and extrusion pressures governing the forced wetting and spontaneous drying of the nanopores. Using electrolyte solutions, energy storage and power capacities can be widely enhanced.

International audience; A low-cost micro-incubator for the imaging of dynamic processes in living cells and tissues has been developed. This micro-incubator provides a tunable environment which can be altered to study the response of cell monolayers for several days as well as relatively thick tissue samples and tissue engineered epithelial tissues in experiments lasting several hours. Samples within the incubator are contained in a sterile cavity closed by a gas permeable membrane. The incubator can be positioned in any direction and used on an inverted as well as on an upright microscope. The temperature is regulated with a Peltier system controlled with a sensor positioned close to the sample to be able to compensate for any changes in temperature. Rapid changes in the environment can be applied to the sample because of the fast response of the Peltier system and the sample's adaptations to induced changes in the environment can be monitored. To evaluate the performance of the micro-incubator we report on studies using cultured cells in monolayers, on monolayers of cells stretched to breaking point on a distensible membrane, on cells in open 3D fibrous scaffolds and on fluorescently labelled polymersome penetration into 3D tissue engineered oral mucosa.

International audience; The mechanical behaviour of adherent cells cultured in vitro is known to be dependent on the mechanical properties of the substrate. We show that this mechanical behaviour is also strongly affected by the cells' environment. We focus here on the impact of temperature and pH. Experiments carried out on individual cells in a tuneable environment reveal that the intra-cellular mechanical behaviour exhibits large and fast changes when the external cell environment is changed. Fast passive microrheometry measurements allow for the precise characterisation of the transient regime observed during a temperature drop. When maintained at a non physiological temperature, the cells reach a stabilised state distinct from the state observed in physiological conditions. The perturbation can be reversed but exhibits hysteretic behaviour when physiological conditions are restored. The transient regime observed during the recovery process is found to be different from the transient regime observed when leaving physiological conditions. A modified generalized Stokes-Einstein equation taking into account the cell activity through an effective temperature is proposed here to fit the experimental results. Excellent agreement between the model and the measurements is obtained for time lags from 10 −3 to 1 s considered in this study. PACS. 87.17.Rt Cell adhesion and cell mechanics – 87.16.dm Mechanical properties and rheology – 87.16.Ln Cytoskeleton

Label-free techniques are now identified as relevant tools to detect any biological material which cannot be grafted by a fluorescent tag, for instance. In this growing context, a new detection strategy based on the resonance of micrometric capillary waves is proposed to detect biomolecules. The sensitivity of the surface rheology to the (bio)chemical content of a liquid surface is found to behave as an original transduction means to convert any slight change in the surface composition into a detectable change in the surface geometry. Micrometric deformations are promoted steadily along a functionalised liquid surface by generating linear meniscus waves from a capillary boundary layer which develops all around the outer circular edge. The geometry of the subsequent nearly standing waves net is accurately characterised using refractometry and interferometry techniques. This paper focuses on this last technique which is especially developed to characterise the waves amplitude at the surface centre with a sensitivity of a few hundreds of nanometers. As such, local interferometry allows us to follow in real-time the resonance frequencies of the wave net and finally, to detect any slight change in surface tension induced during the trapping of solubilised biomolecules at the functionalised surface. In order to clearly illustrate the potentialities of a resonant wavy meniscus, use is made of two complementary oligonucleotides. This label-free technique is demonstrated to deliver useful information on the adsorption rate of initially solubilised DNA strands to a lipidic matrix. By following the time-dependent frequency spectrum of the surface waves, it is possible to discriminate between single-stranded DNA strands and double-stranded DNA strands. This new label-free sensor can therefore be considered as a liquid analogy of the well-known cantilever technique.

This article discusses the aging of a liquid surface enriched with surface active species and suddenly perturbed by standing capillary waves. Special attention is paid to deriving an accurate initial condition of the surface elevation. Due to the arising of the waves, the sub-phase and surface concentrations, C and Γ, which were initially uniform and controlled by thermodynamic equilibrium, are modified by a transient oscillatory regime. A complete analytical description of the time-dependent carrier wave and oscillating chemical modulations associated with these concentrations is proposed for: (1) a small surface elevation, (2) a weak coupling with momentum transport, (3) but a strong coupling between all chemical transport phenomena which might be involved during transient regime: surface adsorption/desorption, 3-D diffusion within the sub-phase as well as near the liquid surface, and 2-D chemical diffusion along the surface. Analytical expressions resulting from regular perturbation series are compared to the limit aging regimes most commonly invoked in the literature, namely, diffusion- or sorption-limited surface aging. Finally, the (surface) compositional elasticity due to the arising of surface tension gradients is derived.

This paper presents a liquid surface biosensor whose potential applications are analogue to the well-known quartz crystal microbalance. The technique involved is based on the resonance of meniscus capillary waves here excited at a functionalized air-water interface. The strategy proposed in this paper can be seen as a promising way to avoid as much as possible any transfer of Blodgett type. Meniscus capillary waves supplied by the electrodynamical vibration of a brimful cylinder filled with water are used as a way to characterize the surface aging of an air-water interface covered by a lipidic monolayer. An optical technique based on one-dimensional interferometry is developed to measure continuously the resonant behavior of the surface elevation at the center of the cell around the natural frequencies of the meniscus waves. The frequency dependence of the wave amplitude is investigated during the transient regime associated to the immobilization of DNA strands at the lipidic matrix. Resonant frequencies are found to be very sensitive to the chemical loading supported by the air-water interface. The technique is seen as a mean to discriminate between single- and double-stranded DNA.

As an attempt to develop a sensitive device for biomolecule detection, a micromechanical methodology based on the rheological change of an air–water interface is put forward (Berthier and Davoust, CEA/CNRS patent, PCT International Application WO 2003/080209 A3, 2003). Capillary waves induced from the vertical electrodynamic vibration of a brimful cylindrical tank filled with water stand as a good way to identify dilational elasticity and viscosity of an aging interface. Before, we were interested of the fact that complex wave number and the frequency of waves are obtained through an optical technique, which allows us to accurately recognize the whole interface geometry. These two parameters, a modeling based on a dispersion relation (Lucassen-Reynders and Lucassen, Adv Colloid Interface Sci, 2:347, 1969) and the surface mass transport equation, are jointly used to identify the surface diffusivity and the dilational rheology of the interface for a nonsoluble biochemical surfactant. Preliminary results obtained from a water surface functionalized by DNA, thanks to a lipidic monolayer, demonstrate the capabilities of the proposed methodology. The sensitivity of dilational rheology and the surface diffusivity on DNA adsorption on lipids is made evident.

This paper aims at modelling the interfacial ageing induced by the sudden arising of standing capillary waves at a contaminated air/water interface. Here is thus considered a brimful cylindrical reactor filled with a water bath in which surfactants are solubilized. The cylindrical capillary waves at the air/water free surface are responsible for further production of interfacial area. The surface diffusion being supposed instantaneous, Marangoni effect does not play any damping role. The thermodynamical equilibrium achieved when the interface is at rest, is considered as initial condition. The time-dependence of the surface concentration in surfactants, Γ ( t ) , and of the bulk concentration in surfactants at the vicinity of the interface, C s ( t ) , is analytically modelled taking into account the serial coupling between bulk diffusion and sorption phenomena. As recommended by Yariv and Frankel [E. Yariv, I. Frankel, Phys. Rev. Lett. 89 (2002) 26], none assumption on the source of the ageing is formulated in the transient regime under consideration.

In order to better understand the influence of gas evolution on the performance of the direct methanol fuel cell (DMFC) anode, a visual DMFC, comprising of a transparent anode and a cathode endplate with an integrated heat exchanger, and a picture analysis methodology were developed. The result was an inexpensive, but very powerful, tool for analyzing the role of two-phase flow. An important finding is that gas bubbles do not appear uniformly throughout the fluid flow matrix, but rather only at a few active sites. Another important finding is that the gas saturation (volume fraction of gas/volume fraction of liquid) increases along the streamwise direction.

Summary We have developed a software, Cell Database, for archiving records about cells stored in liquid nitrogen tanks. Once installed on a web server, the database is accessed through a standard web browser. This user-friendly and self-explanatory application is independent of computer platform and periodic upgrades of a commercial software. Our web application allows import of data from other database programs and adaptation to different tank formats, types of samples, and archiving needs.

An isothermal two-phase ternary mixture model that takes into account conservation of momentum, mass, and species in the anode of a direct methanol fuel cell (DMFC) is presented and analyzed. The slenderness of the anode allows a considerable reduction of the mathematical formulation, without sacrificing the essential physics. The reduced model is then verified and validated against data obtained from an experimental DMFC outfitted with a transparent end plate. Good agreement is achieved. The effect of mass-transfer resistances in the flow field and porous backing are highlighted. The presence of a gas phase is shown to improve the mass transfer of methanol at higher temperatures (>30 degreesC). It is also found that at a temperature of around 30 degreesC, a one-phase model predicts the same current density distribution as a more sophisticated two-phase model. Analysis of the results from the two-phase model, in combination with the experiments, results in a suggestion for an optimal flow field for the liquid-fed DMFC.

Automated design tools are seldom used in industry. Their potential, however, is high, especially in companies mostly active in variant design, where custom tools could help cut down development time in the early stages. The design of geared electro-mechanical actuators for the automotive industry is such a case. These actuators are simple examples of coupled multi-disciplinary systems that can be hard to design, since they need to follow strict specifications in terms of performance and packaging. This paper presents an automated design and optimization tool tailored for such systems based on an integrated modeling approach, multi-objective optimization and an interactive reporting tool. The focus is set on the impact of system-level constraints on the usability by industry of the generated designs. In two case studies, the tool is able to find competitive actuator candidates that are cheaper (−3.6% and −11%) and more compact than similar existing products in less than an hour on a state-of-the-art laptop computer. More powerful options or actuators using different technologies have also been proposed. Compared to optimizations done without system-level constraints, the generated actuators are immediately usable by engineers to get accurate insights into the design problem and promote informed decision-making.