ALBERT

Description: This paper reports an experimental and numerical study of rapid solidification of a water droplet due to depressurization. During the experiment, a distilled water droplet was suspended on a thermocouple, which was also used to measure the droplet temperature, and the droplet surface temperature was captured by an infrared thermograph. The experimentally measured data indicates that freezing occurs from the droplet surface when the droplet temperature reaches a certain subcooling. A mathematical model was constructed to simulate the temperature transition and the temperature distribution within the sphere. The model considers the pressure reduction in the test vessel, the kinetic condition for undercooled solidification, and the heat transfers due to convection and sublimation at the ice surface. A coordinate transformation method was used to capture the two moving boundaries within the droplet, which are internal solidification interface and surface sublimation interface. The model-predictions agree well with the measured temperature data, demonstrating the soundness of the present model. The results show that the rapid solidification of a water droplet due to depressurization is a typical non-equilibrium phase transition, with a lower ambient pressure, the solidification speed will be faster, and the duration time for droplet center temperature keeps constant will be shorter.

Description: We describe the first measurements of the critical Marangoni number of thermocapillary flow in liquid bridges under microgravity. The experiments were conducted during the ballistic flight of rockets with small liquid bridges established by melting the equivalent cylindrical rod of solid sodium nitrate under microgravity. Fine thermocouples in the melt indicated the onset of flow oscillations by the increase of temperature oscillations. The critical Marangoni number M a c was measured to be approximately 1·10 4 for Prandtl number P r = 9. This type of experiment was especially simple, effective and suitable for execution during the short microgravity–time available during sounding rockets flights. The lessons learned from these experiments have been collected. In a second part of this paper we review five more sophisticated microgravity experiments in sounding rockets in which the surface tension driven flow was visualized by tracers and suitable illumination. Two experiments are devoted to the very first demonstration of the classical cellular Bénard-Marangoni instability of thin liquid layers with free surface, heated from below. We could demonstrate in another experiment chaotic thermocapillary flow in a cubic cuvette filled with oil up to a flat free surface. Two experiments dealt with liquid bridges (LBs); in one the LB was nearly as long as possible at all. Here we could observe the helical nature of the hydrothermal wave in the geometry of the LB and measured a much smaller critical Marangoni number than in the short liquid bridges on ground. In the other experiment we investigated particle accumulation structures (PAS) and could show that PAS develops independently from gravity forces though it was indicated that gravity has an influence on PAS–formation by changing the flow field.

Description: Requirement change propagation, if not managed, may lead to monetary losses or project failure. The a posteriori tracking of requirement dependencies is a well-established practice in project and change management. The identification of these dependencies often requires manual input by one or more individuals with intimate knowledge of the project. Moreover, the definition of these dependencies that help to predict requirement change is not currently found in the literature. This paper presents two industry case studies of predicting system requirement change propagation through three approaches: manually, linguistically, and bag-of-words. Dependencies are manually and automatically developed between requirements from textual data and computationally processed to develop surrogate models to predict change. Two types of relationship generation, manual keyword selection and part-of-speech tagging, are compared. Artificial neural networks are used to create surrogate models to predict change. These approaches are evaluated on three connectedness metrics: shortest path, path count, and maximum flow rate. The results are given in terms of search depth needed within a requirements document to identify the subsequent changes. The semi-automated approach yielded the most accurate results, requiring a search depth of 11 %, but sacrifices on automation. The fully automated approach is able to predict requirement change within a search depth of 15 % and offers the benefits of full minimal human input.

Description: Effects of Marangoni number, aspect ratio and gravity level on thermocapillary convection in a liquid layer is investigated numerically, in which the level set method is employed to capture free surface deformation. The computational results show that, with the increase of Marangoni number the free surface deformation is increased and it can lead to free surface rupture if the Marangoni number is large enough. The end walls has a damping effect on the free surface deformation, and as the aspect ratio (A =L/(0.5H)) decreases the deformability of free surface is reduced. The gravity can damp the free surface deformation, particularly as gravity level varies from 0.0001g 0 to g 0 the free surface deformability decreases steeply.

Description: SJ-10 program provides a mission of space microgravity experiments including both fields of microgravity science and space life science aboard the 24th recoverable satellite of China. Scientific purpose of the program is to promote the scientific research in the space microgravity environment by operating the satellite at lower earth orbit for 2 weeks. There are totally 27 experiments, including 17 ones in the field of microgravity science (microgravity fluid physics 6, microgravity combustion 3, and space materials science 8) and 10 in the field of space life science (radiation biology 3, gravitational biology 3, and space biotechnology 4). These experiments were selected from more than 200 applications. The satellite will be launched in the end of 2015 or a bit later. It is expected that many fruitful scientific results on microgravity science and space life science will be contributed by this program.

Description: The reuse of knowledge and information arising from the different phases of a product’s lifecycle is crucial for a company in order to achieve competitive advantage. This paper describes a case study from the oil industry investigating the transfer of knowledge within the service phase and also between the service and design phases. Interviews with engineering designers and service engineers were conducted. Knowledge arising from servicing the drilling equipment that was identified as relevant for service engineers was compared to that relevant for engineering designers. Furthermore, the mechanisms involved in the transfer of knowledge between service and design were investigated. Knowledge about changes, issues and improvements generated during service was found to be relevant to both groups; however, engineering designers were interested in knowledge of equipment at a component level whilst service engineers were more interested in obtaining an overview of the systems. The study showed that communication between the departments consisted prevalently of the service engineers pushing knowledge and information to the engineering designers. The reusing service knowledge (RSK) model is proposed based upon the findings and the understanding from a general framework for developing a knowledge management strategy. Additionally, the initial model was revised to explicitly address the factors that emerged from the case study. The RSK model was developed based on a case study from a customised industry; however, previous studies indicated that similar issues are also of relevance to a variant design industry.

Description: Capturing and managing requirements are crucial to the success of product design and development. This paper presents and analyzes the causes of requirements change during the design process of a complex aerospace system developed by Rolls-Royce during the course of 6 years. The study was part of a series of efforts ongoing at this original equipment manufacturer to improve requirements engineering practices and involved a group of engineers in the assessment of the root causes of change. A large data set was examined, containing 700 system requirements and more than 1,000 changes released during the project studied. The results showed that more than 80 % of the changes had internal root causes and change driven by the customer accounted for about 15 % of the total. The structured approach that was implemented to understand the causes of change allowed the group of engineers to identify and dissect various management guidelines aiming to further improve requirements engineering in practice. This paper thus also reports the guidelines captured at this aerospace manufacturer and intends to support practitioners across the industrial community.

Description: The reuse of knowledge and information arising from the different phases of a product’s lifecycle is crucial for a company in order to achieve competitive advantage. This paper describes a case study from the oil industry investigating the transfer of knowledge within the service phase and also between the service and design phases. Interviews with engineering designers and service engineers were conducted. Knowledge arising from servicing the drilling equipment that was identified as relevant for service engineers was compared to that relevant for engineering designers. Furthermore, the mechanisms involved in the transfer of knowledge between service and design were investigated. Knowledge about changes, issues and improvements generated during service was found to be relevant to both groups; however, engineering designers were interested in knowledge of equipment at a component level whilst service engineers were more interested in obtaining an overview of the systems. The study showed that communication between the departments consisted prevalently of the service engineers pushing knowledge and information to the engineering designers. The reusing service knowledge (RSK) model is proposed based upon the findings and the understanding from a general framework for developing a knowledge management strategy. Additionally, the initial model was revised to explicitly address the factors that emerged from the case study. The RSK model was developed based on a case study from a customised industry; however, previous studies indicated that similar issues are also of relevance to a variant design industry.

Description: Acoustic levitation is one of the levitation technique which is expected to be used for analytical chemistry and manufacturing new materials. Thus, it is important to gather the knowledge about acoustically levitated droplet. The purpose of this study is to investigate the heat transfer and flow behavior under phase change process of an acoustically levitated droplet. The following results were obtained from experiments. Evaporation process and external flow structure of the levitated droplet is visualized by a high speed camera and it is found that they differ by the type of fluid. Toroidal vortices are observed near the surface of the ethanol solution droplet. Heat transfer coefficient is estimated from the volume change and temperature gradient. It is substantially higher than that estimated by the existing experimental correlation.

Description: Fractals are defined as geometric shapes that exhibit symmetry of scale. This simply implies that fractal is a shape that it would still look the same even if somebody could zoom in on one of its parts an infinite number of times. This property is also called self-similarity with several applications including nano-pharmacology and drug nanocarriers. We are interested in the study of the properties of fractal aggregates in a microgravity environment above an orbiting spacecraft. To model the effect we use a complete expression for the gravitational acceleration. In particular on the surface of the Earth the acceleration is corrected for the effect of oblateness and rotation. In the gravitational acceleration the effect of oblateness can be modeled with the inclusion of a term that contains the J 2 harmonic coefficient, as well as a term that depends on the square of angular velocity of the Earth. In orbit the acceleration of gravity at the point of the spacecraft is a function of the orbital elements and includes only in our case the J 2 harmonic since no Coriolis force is felt by the spacecraft. Using the fitting parameter d = 3.0 we have found that the aggregate monomer number N is not significantly affected and exhibits a minute 0.0001 % difference between the geocentric and areocentric latitudes of 90° and 0°. Finally for circular and elliptical orbits around Earth and Mars of various inclinations and eccentricities the aggregate monomer number it’s not affected at all at the orbital altitude of 300 km.

Description: Numerous studies have been carried out to investigate the hypergravity effect on plants, where seedlings (4–5 days old) were continuously exposed and grown under hypergravity condition. Here, we have used a novel ‘shortterm hypergravity exposure experimental method’ where imbibed caryopses (instead of seedlings) were exposed to higher hypergravity values ranging from 500 g to 2500 g for a short interval time of 10 minutes and post short-term hypergravity treated caryopses were grown under 1 g conditions for five days. Changing patterns in caryopsis germination and growth, along with various photosynthetic and biochemical parameters were studied. Results revealed the significant inhibition of caryopsis germination and growth in short-term hypergravity treated seeds over control. Photosynthesis parameters such as chlorophyll content, rate of photosynthesis (P N ), transpiration rate (Evap) and stomatal conductance (Gs), along with intracellular CO 2 concentration (C int ) were found to be affected significantly in 5 days old seedlings exposed to short-term hypergravity treatment. In order to investigate the cause of observed inhibition, we examined the α -amylase activity and antioxidative enzyme activities. α -amylase activity was found to be inhibited, along with the reduction of sugars necessary for germination and earlier growth in short-term hypergravity treated caryopses. The activities of antioxidant enzymes such as catalase and guaiacol peroxidase were increased in short-term hypergravity treated caryopses, suggesting that caryopses might have experienced oxidative stress upon short-term hypergravity exposure.

Description: The following article deals with the algorithm applied to recover lost microacceleration data using fractal quality of microaccelerations witch occur in the indoor environment of space laboratory. This quality was discovered by the author. Using this algorithm it is possible to check efficiency and operating conditions of measuring equipment during an orbital flight of space laboratory.

Description: We report preliminary results on experimental investigations on condensation in the framework of the European Space Agency funded programme Enhanced Condensers in Microgravity (ENCOM-2) which aims at better understanding underlying phenomena during condensation. The first experiment is a study on condensation of HFE on external curvilinear surface of 15 mm height during reduced gravity experiments. It is found that the local minimum of the film thickness exists at the conjugation area of condensed film and the meniscus at the bottom of the fin; this leads to the local maximum of the heat transfer coefficient, which we also found moves towards the fin tip. The second experiment is a study of falling films hydrodynamics inside a vertical long pipe. In particular, characteristics of wavy falling films produced employing intermittent liquid feed are examined in order to assess wave effects on film condensation. Preliminary results suggest that intermittent feed simply divides the film in two autonomous regions with the wave feature of each one depending only on its flow rate. The processing of registered film thickness data can lead to the estimation of the transverse velocity profile in the film, which is mainly responsible for heat transfer during condensation. The third experiment looks at in-tube convective condensation at low mass fluxes (typical of Loop Heat Pipes and Capillary Pumped Loops) of n-pentane inside a 0.56 mm diameter channel. The results show that the mean heat transfer in the annular zone when it is elongated may be less than the mean heat transfer when it is shorter, due to the interface deformation involved by surface tension effect. When the length of this annular zone reaches a critical value, the interface becomes unstable, and a liquid bridge forms, involving the release of a bubble. The heat transfer due to the phase-change in this isolated bubble zone appears to be very small compared to the sensible heat transfer: the bubbles evolve and collapse in a highly subcooled liquid. The last experiment concerns in-tube condensation of R134a inside a square channel of 1.23 mm hydraulic diameter at mass fluxes of 135 kg m −2 s −1 and 390 kg m −2 s −1 for three different configurations: horizontal, vertical downflow and vertical upflow. For the calculated heat transfer coefficient it is found that gravity has no effect on condensation in downflow configurations at 390 kg m −2 s −1 and in upflow conditions at both values of mass velocity. The effect of gravity on the condensation heat transfer coefficient becomes noteworthy in downflow at mass velocity G = 135 kg m −2 s −1 and vapour quality lower than 0.6.

Description: Spatial and temporal regulation of cell phenotype by mechanical forces is a growing field of research in health sciences since these stimuli influence cellular functions, such as proliferation, migration, differentiation and gene expression. In the context of the Fluolive project selected by the European Space Agency and aiming at evaluating the impact of gravity alterations on the cell phenotype, we have developed new bone-derived cell lines adapted for live-cell imaging of the cytoskeleton. Osteoblastic cells derived from human osteosarcomas were used as experimental models. U2-OS and SaoS-2 cells stably expressing TagGFP2- β -actin and mCherry- α -tubulin were established and single-cell clonal cultures were characterized in terms of recombinant proteins production and localization, fluorescence intensity, cell proliferation and migration rates. Living fluorescently-tagged cell lines allow real-time fluorescence microscopy of the cytoskeleton dynamics without bleaching and without alteration of cell morphology. U2-OS and SaoS-2 TagGFP2- β -actin and mCherry- α -tubulin clones will be used to monitor the effect of mechanical forces in models of altered gravity on Earth and possibly on the ISS.

Description: We propose a concept for future space gravity missions using cold atom interferometers for measuring the diagonal elements of the gravity gradient tensor and the spacecraft angular velocity. The aim is to achieve better performance than previous space gravity missions due to a very low white noise spectral behavior and a very high common mode rejection, with the ultimate goals of determining the fine structures of the gravity field with higher accuracy than GOCE and detecting time-variable signals in the gravity field better than GRACE.

Description: Separating gas-liquid two-phase flow is of practical importance for many space engineering systems. While droplet and bubble removal is a naturally occurring phenomenon in most terrestrial situations, the absence of buoyancy in a microgravity environment often results in situations where two disparate phases have no distinct inclination to separate from one another. Passive cyclonic separators can perform this task without moving parts and the reliability concerns of active separators. In such separation devices, separation efficiency is strongly influenced by the gas core behavior. Based on experimental and numerical investigations, the behavior of the gas core with two-phase injection is studied. A control-volume model is developed to capture the relevant physics of the flow in the separator. It is shown that the injection nozzle design, swirl number, and volumetric gas quality all have a major influence on the core size. The present investigation covers a range of volumetric quality from 0 to 0.75, and a range of swirl number from 17 to 28. Both homogeneous and non-homogeneous nozzles are used. The implications of the results are discussed in detail.

Description: The focus of the study is the estimation of the effects of microgravity on the central nervous activity and its underlying influencing mechanisms. To validate the microgravity-induced physiological and psychological effects on EEG, quantitative EEG features, cardiovascular indicators, mood state, and cognitive performances data collection was achieved during a 45 day period using a -6°head-down bed rest (HDBR) integrated approach. The results demonstrated significant differences in EEG data, as an increased Theta wave, a decreased Beta wave and a reduced complexity of brain, accompanied with an increased heart rate and pulse rate, decreased positive emotion, and degraded emotion conflict monitoring performance. The canonical correlation analysis (CCA) based cardiovascular and cognitive related EEG model showed the cardiovascular effect on EEG mainly affected bilateral temporal region and the cognitive effect impacted parietal-occipital and frontal regions. The results obtained in the study support the use of an approach which combines a multi-factor influential mechanism hypothesis. The changes in the EEG data may be influenced by both cardiovascular and cognitive effects.

Description: Nonlinear convective flows developed under the joint action of buoyant and thermocapillary effects in a two-layer system with periodic boundary conditions on the lateral walls, have been investigated. The influence of an interfacial heat release on oscillatory regimes, has been studied. It is shown that the development of oscillatory instability can lead to the appearance of different non-steady flows. Specifically, regimes of standing symmetric oscillations, traveling waves and modulated traveling waves, have been found.

Description: An investigation on the effect of lateral vibrations on the thermocapillary convection and the surface behavior of a liquid bridge for high Prandtl number fluid has been conducted numerically. The Navier-Stokes equations coupled with the energy conservation equation were solved on a staggered grid, and the mass conserving level set approach was used to capture the free surface deformation of the liquid bridge. The present results show that the positions of the vortex centers in the radial and axial directions fluctuate periodically around the equilibrium positions when the external vibration is applied. The surface velocity without lateral vibration is larger than that with lateral vibrations, which means that the lateral vibrations inhibit the surface flow.

Description: The simultaneous effect of Coriolis force due to rotation and magnetic field dependent (MFD) viscosity on the onset of Bénard-Marangoni convection in a horizontal ferrofluid layer in the presence of a uniform vertical magnetic field is studied. The lower boundary is rigid while the upper free boundary is open to the atmosphere and at which the temperature-dependent surface tension effect is allowed for. The Galerkin technique is employed to extract the critical stability parameters numerically. The results show that the onset of Bénard-Marangoni ferroconvection is delayed with an increase in the MFD viscosity parameter Λ, Taylor number T a , magnetic susceptibility χ and Biot number B i but opposite is the case with an increase in the value of magnetic number M 1 and nonlinearity of fluid magnetization M 3 . Further, increase in M 1 , M 3 and decrease in Λ, T a , χ and B i is to decrease the size of the convection cells. Comparisons of results between the present and the existing ones are made under the limiting conditions and good agreement is found.

Description: Steady thermo-solutocapillary convection in axisymmetric liquid bridge with dynamic free surface is numerically studied in the absence of gravitational effects. The upper and lower disks of liquid bridge maintain at constant temperature and solute concentration. The deformable free surface is obtained by Level set method. Numerical simulations are carried out for Prantle number Pr = 1, Capillary number Ca = 0.1, Marangoni number 1 ≤ Ma ≤ 100, and thermal to solutal Marangoni number ratio −10≤R σ ≤ 0.1. The results show that there are three modes of free surface deformation in thermo-solutocapillary convection under low Marangoni number: 1) as −10≤R σ 〈−1, the free surface bulges out near the lower disk and bulges in near the upper disk; 2) as R σ =−1 the free surface bulges out near the lower and upper disks and bulges in at the central region of the liquid bridge; 3) as −1R σ ≤−0.1, the free surface bulges out near the upper disk and bulges in near the lower disk. Moreover, the effect of Marangoni number on free surface deformation also is discussed.

Description: Evaporation of a Dichloromethane liquid film is explored with an evolution equation describing film dynamics. The film is subject to different initial conditions, smooth and uniform random perturbation. Two different gravity environments (Earth and zero gravity) and two different domain shapes (square and rectangular) have been used. The occurrence of long wave instabilities affecting film dynamics is noted in each of these cases. The evaporating Dicholormethane liquid film is destabilized via long wave instabilities in zero gravity. The thermocapillary patterns formed due to long wave destabilization show a coupling to the initial conditions and domain shape. A criterion for the occurrence of long wave instabilities based on the growth rate of perturbations is described. This equation considers a non-stationary film thickness. It predicts that long wave instabilities are always present in zero gravity environments with a growth rate that increases as the film thickness decreases due to evaporation. Our equation for growth rate of long wave instabilities may be used as an engineering design tool to confine operating parameters of zero gravity heat transfer equipment, that include or harness phase change, to safe limits.

Description: This paper describes the activities for utilization and control of ELITE S2 on board the International Space Station (ISS). ELITE S2 is a payload of the Italian Space Agency (ASI) for quantitative human movement analysis in weightlessness. Within the frame of a bilateral agreement with NASA, ASI has funded a number of facilities, enabling different scientific experiments on board the ISS. ELITE S2 has been developed by the ASI contractor Kayser Italia, delivered to the Kennedy Space Center in 2006 for pre-flight processing, launched in 2007 by the Space Shuttle Endeavour (STS-118), integrated in the U.S. lab and used during the Increments 16/17 (2008) and 33/34 (2012/2013). The ELITE S2 flight segment comprises equipment mounted into an Express Rack and a number of stowed items to be deployed for experiment performance (video cameras and accessories). The ground segment consists in a User Support Operations Center (based at Kayser Italia) enabling real-time payload control and a number of User Home Bases (located at the ASI and PIs premises), for the scientific assessment of the experiment performance. Two scientific protocols on reaching and cognitive processing have been successfully performed in eight sessions involving three ISS crewmembers: IMAGINE 2 and MOVE.

Description: The average force acting on a cylindrical or spherical body placed near the boundary of cylindrical cavity filled with liquid and executing rotational vibrations is experimentally studied. The repulsive lift force acting on solid is found and measured using the method of body suspension in the gravity field. In horizontal cavity the repulsive force provides steady state of light cylinder near the upper boundary at a distance comparable with the thickness of the Stokes layer. The heavy sphere which hangs on thread repulses from the wall of vertical cylindrical cavity under torsional vibration. The dependence of the average lift force on the amplitude and frequency of vibrations and on distance between the body and the boundary has been investigated. Results are presented on the plane of dimensionless parameters. In the examined frequency range the lift force acting on cylinder decreases exponentially with distance from the boundary. Lift force acting on sphere decreases with distance and strongly depends on dimensionless frequency of vibration. Conclusion that lift force is generated by body oscillations excited by its viscous interaction with the oscillating boundary is done. The found phenomenon is important for control of inclusions under microgravity conditions.

Description: This research addresses a need in systems engineering to verify that a system can meet performance requirements; this is done by integrating failure behavior into the system’s nominal model during the initial stages of design. In general, failure behavior is not used in early assessments, lending toward increased uncertainty in the model’s validity. Current libraries do not model failures and thus cannot confidently address how a design will function in the intended operational environments. Since failures occur from effects on the environment, they should be included during verification and validation efforts. Current approaches capture off-nominal behavior using parameter variation where flow variables and parameters are varied to measure the system-level effect. This approach is ad hoc and does not accurately capture failure mode behavior. To address this limitation, an approach is developed to understand and implement failure mode behavior into nominal models. The Modelica Standard Library (MSL) is used as an example for the component library of nominal models. MSL has a significant amount of basic nominal component behavior and therefore is desirable for this research. Two approaches are developed to implement failure mode behavior; the first uses transfer function and use case graphs, and the second uses existing literature. In addition, complex systems often have a large number of components and an even larger number of failure modes. Since the goal is to limit the development time, we generate an approach to identify high-risk failure modes. This captures an early system-level effect of each failure mode and uses an occurrence to calculate risk. To show the usefulness of each method, two examples are provided including a vehicle drivetrain subsystem with a variety of failures and a diesel engine with fuel injector and valve failures.

Description: In this article, new experimental data of the thermal diffusion coefficient ( D T ) of 20 binary mixtures of hexane-hexadecane, decane-hexadecane, toluene-hexadecane and 1-metilnaphtalene-hexadecane at several different compositions and at 298K and atmospheric pressure, are reported. Thermal diffusion coefficients were measured in a thermogravitational column with rectangular configuration. The results obtained show that the mass fraction dependence of thermodiffusion coefficients of the mixture is linear in all the cases. The studied mixtures have a common component, hexadecane, and they can be classified into two groups according to their mass and to the morphology of their components. We also show that the thermal diffusion coefficient and mixture viscosity are related in a different way for mixtures of n-alkanes and for mixtures of aromatic rings.

Description: This paper introduces metrics derived from application of a Markov decision process to evaluate a design’s changeability. Changeability is known to improve product performance if conscientious early-stage design decisions are matched with structured management of the system in response to exogenous disturbances—shifts which may be environmental, market, technological, and political in nature. Included in the paper is a brief discussion of changeability’s role in ensuring strategic product performance as well as a review of past metrics developed, highlighting the open design challenge to more fully capture the managerial and process dimensions inherent to changeability. The proposed metrics are featured in a case study related to the ballast water system of an ocean-going vessel. The result of such application is greater context for the value changeability offers and an improved understanding of the resources required to manage uncertainty over the product’s life cycle.

Description: This research addresses a need in systems engineering to verify that a system can meet performance requirements; this is done by integrating failure behavior into the system’s nominal model during the initial stages of design. In general, failure behavior is not used in early assessments, lending toward increased uncertainty in the model’s validity. Current libraries do not model failures and thus cannot confidently address how a design will function in the intended operational environments. Since failures occur from effects on the environment, they should be included during verification and validation efforts. Current approaches capture off-nominal behavior using parameter variation where flow variables and parameters are varied to measure the system-level effect. This approach is ad hoc and does not accurately capture failure mode behavior. To address this limitation, an approach is developed to understand and implement failure mode behavior into nominal models. The Modelica Standard Library (MSL) is used as an example for the component library of nominal models. MSL has a significant amount of basic nominal component behavior and therefore is desirable for this research. Two approaches are developed to implement failure mode behavior; the first uses transfer function and use case graphs, and the second uses existing literature. In addition, complex systems often have a large number of components and an even larger number of failure modes. Since the goal is to limit the development time, we generate an approach to identify high-risk failure modes. This captures an early system-level effect of each failure mode and uses an occurrence to calculate risk. To show the usefulness of each method, two examples are provided including a vehicle drivetrain subsystem with a variety of failures and a diesel engine with fuel injector and valve failures.

Description: This paper introduces metrics derived from application of a Markov decision process to evaluate a design’s changeability. Changeability is known to improve product performance if conscientious early-stage design decisions are matched with structured management of the system in response to exogenous disturbances—shifts which may be environmental, market, technological, and political in nature. Included in the paper is a brief discussion of changeability’s role in ensuring strategic product performance as well as a review of past metrics developed, highlighting the open design challenge to more fully capture the managerial and process dimensions inherent to changeability. The proposed metrics are featured in a case study related to the ballast water system of an ocean-going vessel. The result of such application is greater context for the value changeability offers and an improved understanding of the resources required to manage uncertainty over the product’s life cycle.

Description: Requirement change propagation, if not managed, may lead to monetary losses or project failure. The a posteriori tracking of requirement dependencies is a well-established practice in project and change management. The identification of these dependencies often requires manual input by one or more individuals with intimate knowledge of the project. Moreover, the definition of these dependencies that help to predict requirement change is not currently found in the literature. This paper presents two industry case studies of predicting system requirement change propagation through three approaches: manually, linguistically, and bag-of-words. Dependencies are manually and automatically developed between requirements from textual data and computationally processed to develop surrogate models to predict change. Two types of relationship generation, manual keyword selection and part-of-speech tagging, are compared. Artificial neural networks are used to create surrogate models to predict change. These approaches are evaluated on three connectedness metrics: shortest path, path count, and maximum flow rate. The results are given in terms of search depth needed within a requirements document to identify the subsequent changes. The semi-automated approach yielded the most accurate results, requiring a search depth of 11 %, but sacrifices on automation. The fully automated approach is able to predict requirement change within a search depth of 15 % and offers the benefits of full minimal human input.

Description: Managing uncertainty levels is important for organizations carrying out complex product development processes since it fosters design process improvements and optimization. Among the different uncertainties, design imprecision is known to represent uncertainty in decision-making that typically triggers changes to the value assigned to design variables during the early stages of the development process. This paper presents a method aiming to support large organizations understanding, quantifying and communicating this type of uncertainty. The imprecision management method that is proposed relies on five main steps: collection of historical records of change, time evolution reconstruction, statistical characterization of the typical levels of imprecision that should be expected, communication to new projects and continuous knowledge update. In addition, we present results from a case-study performed at Rolls–Royce that tested the method’s applicability in practice. The study shed light to interesting empirical findings about the typical level of imprecision in design variables and its evolution during real product development projects. The results from this initial evaluation suggest that the method provides useful support for design process management and thus has industrial value.

Description: This paper presents a model of the way that designers move between situations when interpreting during design activity. Three hypotheses are presented that arise from this model: that designers change their situation during interpretation, that small changes in a source can lead to large changes in the representation and that changes to the situation have their origins in the experience of the designer. The paper demonstrates how this internal movement between situations can be computationally implemented using three examples. The systems implemented demonstrate the way that interpretation can lead to changes in the situation and present an example of how the changes to a designer’s situation can be guided by past experiences.

Description: The variability of products affects customers’ satisfaction by increasing flexibility in decision-making for choosing a product based on their preferences in competitive market environments. In product family design, decision-making for determining a platform design strategy or the degree of commonality in a platform can be considered as a multidisciplinary optimization problem with respect to design variables, production cost, company’s revenue, and customers’ satisfaction. In this paper, we investigate evolutionary algorithms and module-based design approaches to identify an optimal platform strategy in a product family. The objective of this paper is to apply a multi-objective particle swarm optimization (MOPSO) approach to determine design variables for the best platform design strategy based on commonality and design variation within the product family. We describe modifications to apply the proposed MOPSO to the multi-objective problem of product family design and allow designers to evaluate varying levels of platform strategies. To demonstrate the effectiveness of the proposed approach, we use a case study involving a family of General Aviation Aircraft. We show that the proposed optimization algorithm can provide a proper solution in product family design process through experiments. The limitations of the approach and future work are also discussed.

Description: Search of design spaces to generate solutions affects the design outcomes during conceptual design. This research aims to understand the different types of search that occurs during conceptual design and their effect on the design outcomes. Additionally, we study the effect of other factors, such as creativity, problem-solving style, and experience of designers, on the design outcomes. Two sets of design experiments, with experienced and novice designers, are used in this study. We find that designers employ twelve different types of searches during conceptual design for problem understanding, solution generation, and solution evaluation activities. Results also suggest that creativity is influenced positively by the type and amount of searches, duration of designing, and experience of designers.

Description: This paper addresses the problem of describing the decision-making process of a committee of engineers based upon their verbalized linguistic appraisals of alternatives. First, we show a way to model an individual’s evaluation of an alternative through natural language based on the Systemic-Functional Linguistics system of APPRAISAL. The linguistic model accounts for both the degree of intensity and the uncertainty of expressed evaluations. Second, this multi-dimensional linguistic model is converted into a scalar to represent the degree of intensity and a probability distribution function for the stated evaluation. Finally, we present a Markovian model to calculate the time-varying change in preferential probability, the probability that an alternative is the most preferred alternative. We further demonstrate how preferential probability toward attributes of alternatives correspond to preferential probability toward alternatives. We illustrate the method on two case studies to highlight the time-variant dynamics of preferences toward alternatives and attributes. This research contributes to process tracing in descriptive decision science to understand how engineers actually take decisions.

Description: Benefits of modularity are often achieved from module independence that allows for independent development to reduce overall lead time and economies of scale due to sharing similar modules across products in a product family. Current modularity methods tend to describe only one of these views, either the module–module independence or the product–product shared module similarity. This paper proposes a new hybrid module generation algorithm that balances both module independence and product similarity, allowing product similarity strategy to influence the coupling-driven architecture considerations. The proposed method builds on two popular matrix-based methods: the design structure matrix approach and modular function deployment that each has been developed to support these two different aspects of the module generation. This paper presents a novel algorithm that integrates both views and allows a balanced clustering that takes both interactions and company portfolio strategy into account. Usefulness of the algorithm is presented using a cordless handheld vacuum cleaner as a case study and by comparing it to alternative approaches.

Description: Complex systems are increasingly being developed as part of portfolios or sets of related complex systems. This enables synergies such as commonality between portfolio systems that can significantly reduce portfolio life-cycle cost and risk. While offering these benefits, commonality usually also incurs up-front as well as life-cycle penalties in cost and risk due to increased design complexity. The resulting trade-off needs to be carried out during the architecting stage of the portfolio life cycle when there is maximum leverage to improve life-cycle properties due to degrees of freedom available in architectural and design decisions. This paper outlines a 4-step methodology for the identification and assessment of commonality opportunities in complex systems portfolios during the architecting stage of the portfolio life cycle. The methodology transforms a solution-neutral description of a portfolio of aerospace systems based on system functionality, requirements, and metrics into a set of preferred portfolio design solutions with commonality. The methodology is based on a 2-stage approach that identifies preferred architectures for each system in the portfolio individually prior to heuristic commonality analysis between systems based on a pairwise assessment of system overlap in functionality, technologies, operational environments, and scale. Application of the methodology is demonstrated with a retrospective analysis of NASA’s Saturn launch vehicle portfolio.

Description: Introduced nearly 25 years ago, the paradigm of mass customization (MC) has largely not lived up to its promise. Despite great strides in information technology, engineering design practice and manufacturing production, the necessary process innovations that can produce products and systems with sufficient customization and economic efficiency have yet to be found in wide application. In this paper, the state-of-the-art in MC is explored in the context of an envisioned MC development process for both the firm and the customer. Specifically, 130 references are reviewed within the process frameworks (Sect. 3 ) and/or to highlight opportunities for future development in MC (Sect. 4 ) based on the review. This review yields opportunities in four primary areas that challenge MC development: (1) customer needs and preference assessment tools, (2) approaches for requirement specification and conceptual design, (3) insights from methodologies focused on the development of durable MC goods and (4) enhancements in information mapping and handling.

Description: While cyber–physical system sciences are developing methods for studying reliability that span domains such as mechanics, electronics and control, there remains a lack of methods for investigating the impact of the environment on the system. External conditions such as flooding, fire or toxic gas may damage equipment and failing to foresee such possibilities will result in invalid worst-case estimates of the safety and reliability of the system. Even if single component failures are anticipated, abnormal environmental conditions may result in common cause failures that cripple the system. This paper proposes a framework for modeling interactions between a cyber–physical system and its environment. The framework is limited to environments consisting of spaces with clear physical boundaries, such as power plants, buildings, mines and urban underground infrastructures. The purpose of the framework is to support simulation-based risk analysis of an initiating event such as an equipment failure or flooding. The functional failure identification and propagation (FFIP) framework is extended for this purpose, so that the simulation is able to detect component failures arising from abnormal environmental conditions and vice versa: Flooding could be caused by a failure in a pipe or valve component. As abnormal flow states propagate through the system and its environment, the goal of the simulation is to identify the system-wide cumulative effect of the initiating event and any related common cause failure scenario. FFIP determines this effect in terms of degradation or loss of the functionality of the system. The method is demonstrated with a nuclear reactor’s redundant coolant supply system.

Description: ‘Someone else has patented this before’. This is the last thing you would want to hear after months of intensive engineering design work. Yet, this is not uncommon. There is a link between engineering design and intellectual property (IP). However, the boundary between them is not always well defined, especially on when and how IP infringement checks should be conducted during the engineering design process. Hence, this letter seeks to reach out to researchers in the engineering design community to come together and tackle this common design issue.

Description: Structural material properties are strongly related to the solidified microstructures, thus precise control of microstructural formation and selection are crucial in engineering. As most of the phenomena involved during solidification are dynamic, in situ and real-time X-ray imaging should be retained as the method of choice for investigating the solidification front evolution of metallic alloys grown from the melt. On Earth, natural convection in the melt is the major source of various disturbing effects. Solidification under microgravity conditions is an efficient way to eliminate buoyancy and convection, providing valuable benchmark data for the validation of analytical models and numerical simulations. In addition, a comparative study of solidification experiments carried out on Earth and in space can also enlighten the effects of gravity. In the frameworks of the ESA - MAP programme entitled XRMON, an experimental apparatus has been developed to perform directional and equiaxed solidification in microgravity conditions with in situ X-ray radiography observation. In the first part of this paper, we will present a brief review of some effects induced by gravity on the solidification process and investigated by mean of synchrotron X-ray radiography at ESRF (European Synchrotron Radiation Facility). In the second part of this paper, we will describe the key elements of the XRMON-GF device, and some scientific results achieved during the MASER-12 sounding rocket mission and the 58 th ESA Parabolic flight campaign are finally presented in the third and last part of the paper.

Description: We propose a framework for measuring the complexity of aerospace systems and demonstrate its application. A measure that incorporates size, coupling, and modularity aspects of complexity is developed that emphasizes the importance of indirect coupling and feedback loops in the system. We demonstrate how hierarchical modular structure in the system reduces complexity and present an algorithm to decompose the system into modules. The measure is tested and found to be scalable for large-scale systems involving thousands of components and interactions (typical in modern aerospace systems). We investigate the sensitivity of the measure and demonstrate the ability of the framework to identify incorrectness in system representation. The merits of the framework are exemplified through a case study comparing three spacecraft. The framework provides the designer with three key capabilities that can positively influence the aerospace (or other) design process: the ability to identify complex subsystems, the ability to classify misrepresentations, and the ability to trade-off commercially of the shelf (COTS) and non-COTS components.

Description: We present a comprehensive robot development process and its evaluation. We designed this process in the context of a robotics course in high schools. The motivation for designing this new process was improving the robustness and reliability of robots developed by students and preparing students for becoming better designers. The newly designed process proved to be highly successful in designing top quality robots. In the process design, we explored and adapted existing design tools and methods to the specific designers, the nature of the product, the environment, the product needs, and the design context goals. At the end of this thorough design, we selected a synergetic integration of six tools and methods to compose the new comprehensive development process for this product context: conceptual design, fault-tolerant design, atomic requirements, fuzzy logic for control, creative thinking, and microprogramming-based design. The design skills of the students that learned the design process and the performance of robots they designed and participated in an international robotics contest were examined. The high school teams that studied the proposed process won the first places in an international contest. The robots developed by the students had better performance than robots built by engineers and faculty teams. Professional experts rated the robots’ designs as excellent. The students that studied the process demonstrated high level of diverse design skills including creativity and design management capabilities. Additionally, they improved their science subject grades and their attitude toward engineering. Both the results obtained by the study and the authors’ experience in teaching robotics demonstrate that the proposed robot development process could be taught successfully in high school and that it leads to superior robotic products. Our experience also indicates that this process could serve industry design by improving the robustness of robots operating in uncertain environments and supporting fast change management practices.

Description: To demystify the debate about the validity of selection methods that utilize aggregation procedures, it is necessary that contributors to the debate are explicit about (a) their personal goals and (b) their methodological aims. We introduce three additional points of clarification: (1) the need to differentiate between the aggregation of preferences and of performances, (2) the application of Arrow’s theorem to performance measures rather than to preferences, and (3) the assumptions made about the information that is available in applying selection methods. The debate about decision methods in engineering design would be improved if all contributors were more explicit about these issues.

Description: When designing mechatronic products, ‘complex dependencies’ are often reported to be a major challenge. This paper focuses on managing dependencies between attributes of the product during the design process. The literature study shows that there is a gap in the literature with regard to the classification of product-related dependencies. Traditionally, these dependencies have been described as appearing between the following product attributes: function, properties and structure. By analysing three mechatronic projects from industry, we identified and classified 13 types of product-related dependencies. Each product-related dependency is described and illustrated using the practical examples from the industrial projects. The value of the classification is evaluated by applying it to an industrial development setting not used for the analysis. The evaluation shows that delays in the project schedule, loss of functionality and quality issues can be avoided if attention is directed toward the product-related dependencies in the development process.

Description: The addition of ferroelectric microparticles embedded in a nanostructured silica aerogel modifies the dry gel microstructure in a measurable way. The pore size distribution changes as well as the specific surface area. This indicates a possible positive effect of particles on the gelation characteristics. These modifications were observed in solutions gelling during a sounding rocket experiment in which approximately three minutes microgravity provided sufficient time for a convection and sedimentation free gelation to occur. The paper describes the synthesis procedures and the microstructures obtained for the gels under microgravity conditions.

Description: HiDOSE (Heavy ion DOSimetry Experiment) and nDOSE (neutron DOSimetry Experiment) experiments conducted as a part of BIOKIS (Biokon in Space) payload were designed to measure the dose equivalent due to charged particles and to neutron field, on the entire energy range, during STS-134 mission. Given the complexity of the radiation field in space environment, dose measurements should be considered an asset of any space mission, and for this reason HiDOSE and nDOSE experiments represent an important contribution to the radiation environment assessment during this mission, a short duration flight. The results of these experiments, obtained using Thermo Luminescence Dosimeters (TLDs) to evaluate the charged particles dosimetry and neutron bubbles dosimeters and stack bismuth track dosimeters for neutron dosimetry, indicate that the dose equivalent rate due to space radiation exposure during the STS-134 mission is in accordance with the results obtained from long duration flights.

Description: The present work aims to complete the analysis of the vibrational impact generated by the Influence of VIbrations on DIffusion of Liquids, IVIDIL, experiment in a global way. To do so, we have analysed all the episodes which, along the active period between September 2009 and January 2010, accounts for simultaneous accelerometric signals coming from the Columbus (ESA) module, the Destiny (NASA) module and the Pressurized module of the Kibo complex, PM-Kibo, (JAXA) respectively. Signals have been downloaded thanks to the NASA Principal Investigator Microgravity Services, PIMS, website. Vibrational analysis involved the consideration of second and higher order statistical techniques. In addition, a comparative study of the RMS acceleration integrated over one-third octave frequency bands enabled to check if the ISS vibratory limit requirements are everywhere accomplished. In summary it can be concluded that, in the vibratory regime, the experiment in the Columbus module is isolated enough of the Destiny and PM-Kibo ones. In addition, concerning only the Columbus data, the study also concluded that the peculiar energy exchange detected between the nominal frequency of the movement and its third harmonic is due to nonlinearities probably originated by the shaker, the module of translational arrangement mounted on the SODI instrument. All these results introduce an interesting generic question: is it always correct to consider that the accelerometric data only coming from one module can offer to the Space Station customers a suitable global scenario of the ISS environment?, if not, what is the real extent of these data?

Description: Methodologies are developed for evaluating uncertainties in droplet size measurements and burning rates for droplet combustion experiments that have been performed on the International Space Station. Different uncertainty sources are considered and propagated into the combined standard uncertainties via the Taylor series method. The local polynomial method is used to provide estimates of instantaneous burning rates. Results from analyses of non-sooting (methanol) or lightly sooting (heptane) droplets as well as moderately sooting (decane/propylbenzene) droplets are presented. Ninety-five percent expanded uncertainties in droplet diameters and burning rates are typically about 0.1 mm and 0.005 mm 2 /s, respectively, for methanol and heptane droplets and 0.1 mm and 0.02 mm 2 /s for decane/propylbenzene droplets, though uncertainties can be larger during ignition and extinction events.

Description: The classical capillary stability problem in a vertical circular cylinder is a special case of the more general problem of the stability of liquid above a capillary surface in a circular cylinder with arbitrary orientation of gravity. This problem can, of course, also be viewed as arbitrary cylinder orientation in a steadily accelerating spacecraft. The general (tilted) circular cylinder capillary stability problem is solved numerically by use of the Surface Evolver code for general tilt and general contact angle. Tens of thousands of combinations of contact angle, tilt angle, and Bond number are solved for with a global volunteer computing network running Surface Evolver . The results appear to be symmetric about 90 degree contact angle, as in the previous vertical cylinder studies, and not symmetric about 45 degree tilt.

Description: We present a comprehensive robot development process and its evaluation. We designed this process in the context of a robotics course in high schools. The motivation for designing this new process was improving the robustness and reliability of robots developed by students and preparing students for becoming better designers. The newly designed process proved to be highly successful in designing top quality robots. In the process design, we explored and adapted existing design tools and methods to the specific designers, the nature of the product, the environment, the product needs, and the design context goals. At the end of this thorough design, we selected a synergetic integration of six tools and methods to compose the new comprehensive development process for this product context: conceptual design, fault-tolerant design, atomic requirements, fuzzy logic for control, creative thinking, and microprogramming-based design. The design skills of the students that learned the design process and the performance of robots they designed and participated in an international robotics contest were examined. The high school teams that studied the proposed process won the first places in an international contest. The robots developed by the students had better performance than robots built by engineers and faculty teams. Professional experts rated the robots’ designs as excellent. The students that studied the process demonstrated high level of diverse design skills including creativity and design management capabilities. Additionally, they improved their science subject grades and their attitude toward engineering. Both the results obtained by the study and the authors’ experience in teaching robotics demonstrate that the proposed robot development process could be taught successfully in high school and that it leads to superior robotic products. Our experience also indicates that this process could serve industry design by improving the robustness of robots operating in uncertain environments and supporting fast change management practices.

Description: Since the first flight of humans into space it is known that space flight affects the immune system; especially a weakening of the reactivity of T-lymphocytes after flight has been observed. In an in vitro experiment, proposed by Augusto Cogoli and flown in Spacelab-1 in 1983, the activation of T-lymphocytes was found to be strongly inhibited in microgravity. This surprising result triggered extended investigations in space and on the ground by us and other research teams. T-cells are that subpopulation of lymphocytes responsible for the activation of the specific immune system. The mechanism of T-cell activation is very complex; 3 different signals are required as well as an interaction between T-lymphocytes and monocytes. Cell motility based on a continuous rearrangement of the cytoskeletal network within the cell is essential for cell-cell contacts. The objective of all our experiments performed on different platforms in space as well as in simulated microgravity on ground was to understand and explain the dysfunction of the cell activation under reduced gravity conditions. On sounding rockets we have studied the influence of microgravity on the delivery of the first signal, the motility of lymphocytes as well as changes in the cytoskeletal structure and early gene expression. On long term missions we investigated many aspects of the delivery of the 2 nd and 3 rd signal, including motility and aggregate formation of lymphocytes, interaction of lymphocytes with monocytes, motility of monocytes and changes in different cytoskeletal structures.

Description: Search of design spaces to generate solutions affects the design outcomes during conceptual design. This research aims to understand the different types of search that occurs during conceptual design and their effect on the design outcomes. Additionally, we study the effect of other factors, such as creativity, problem-solving style, and experience of designers, on the design outcomes. Two sets of design experiments, with experienced and novice designers, are used in this study. We find that designers employ twelve different types of searches during conceptual design for problem understanding, solution generation, and solution evaluation activities. Results also suggest that creativity is influenced positively by the type and amount of searches, duration of designing, and experience of designers.

Description: Design-by-analogy is a growing field of study and practice, due to its power to augment and extend traditional concept generation methods by expanding the set of generated ideas using similarity relationships from solutions to analogous problems. This paper presents the results of experimentally testing a new method for extracting functional analogies from general data sources, such as patent databases, to assist designers in systematically seeking and identifying analogies. In summary, the approach produces significantly improved results on the novelty of solutions generated and no significant change in the total quantity of solutions generated. Computationally, this design-by-analogy facilitation methodology uses a novel functional vector space representation to quantify the functional similarity between represented design problems and, in this case, patent descriptions of products. The mapping of the patents into the functional analogous words enables the generation of functionally relevant novel ideas that can be customized in various ways. Overall, this approach provides functionally relevant novel sources of design-by-analogy inspiration to designers and design teams.

Description: Capillary channel techniques with free liquid surfaces provide very reliable means for liquid management in space. However, capillary channel flow is subject to limitation due to liquid surface instabilities when a critical flow rate is reached. Steady flow rate limitation is a consequence of the choking effect and well understood. Critical steady flow rate computation with a one-dimensional model is related to a numerical singularity which occurs at critical flow. For transient flow the singularity does not occur. Therefore, a new transient stability model is defined. It is based on the steady model, a simplified transient momentum balance, the consideration of the capillary pressure of typical observed surface shapes, and on a simplified dynamic inside the channel. The balance and dynamic are defined by liquid and geometrical properties only and therefore significantly easier to compute than a transient differential equation system. In 2011, experiments were performed in cooperation with NASA on the International Space Station (ISS) to confirm the model for steady flow and validate the new transient model. A new phenomenon is discussed, the flexibility effect, which provides significant additional transient stability for channels of sufficient length. An undesired feedback effect, provoked by the reuse of the liquid in a circular loop of the experimental setup, and which influenced the measurements, is compensated by a semi-empirical model for a feedback ratio.

Description: Exposure to microgravity during space flight (SF) of variable length induces suffering of the endothelium (the cells lining all blood vessels), mostly responsible for health problems found in astronauts and animals returning from space. Of interest to pre-nosological medicine, the effects of microgravity on astronauts are strikingly similar to the consequences of sedentary life, senescence and degenerative diseases on Earth, although SF effects are accelerated and reversible. Thus, microgravity is a significant novel model for better understanding of common pathologies. A comprehensive cell and molecular biology study is needed in order to explain pathophysiological findings after SFs. This project will study the effects of microgravity and cosmic radiation on endothelial cells (ECs) cultured on the International Space Station through analysis of 1) cell transcriptome, 2) DNA methylome, 3) DNA damage and cell senescence, 4) variations in cell cycle and cell morphology. This project has been selected by the European Space Agency and the Italian Space Agency and is presently in preparation. The ground study presented here was performed to determine the biological and engineering requirements that will allow us to retrieve suitable samples after culturing, fixing and storing ECs in space. We expect to identify molecular pathways activated by space microgravity in microvascular ECs, which may shed light on pathogenic molecular mechanisms responsible for endothelial suffering shared by astronauts and individuals affected with aging, degenerative and sedentary life-associated pathologies on Earth.

Description: A series of experiments has been performed under earth’s gravity to study formation of particle accumulation structures (PAS) in a supercritical flow driven by the combined effects of buoyancy and thermocapillary forces. The test flow was created in a non-isothermal cylindrical column (liquid bridge) made of n-decane and heated from above. The objective of the experiment was to answer two major questions: (1) how strong is the influence of the shape of the interface on the process of formation of PAS; (2) what temperature of the ambient air fits better for PAS to occur. Considering these questions, we developed a method based on changing both the volume of the liquid bridge and temperature at the external walls of the experimental chamber to set and to keep constant the shape of the interface and the temperature inside the setup, respectively. The experimental observations are presented in the form of diagrams in the parameters’ space showing ranges of the PAS formation. The findings show that a liquid bridge with an interface as close to the straight cylindrical as possible and surrounded by air at low temperature is the best terrain for PAS formation. The results of the chaos analysis of the recorded temperature time series and their correlation with the obtained diagrams allow for showing that accumulation of particles in coherent structures is possible only in a periodic oscillatory flow characterized by a small value of the translation error not exceeding 0.01. It is demonstrated that presence of either any spectral noise or of several modes with incommensurate frequencies makes formation of a PAS impossible.

Description: Thermocapillary flows in thin films are considered which are differentially heated from lateral side walls. The competition between two different types of motion is addressed. One type is the so-called return flow in which a return flow opposes the thermocapillary free-surface flow to preserve mass conservation. The other type of motion is a large-scale flow which arises as a plug flow in which the velocity is independent of the coordinate perpendicular to the film. We provide physical arguments, based on the minimization of the surface energy, for the preference of the large scale flow over the return flow as the film thickness decreases. The large scale motion arises as a cellular flow with alternating vorticity perpendicular to the film surface. The direction of rotation of these vortices is not determined when the film is adiabatic and of constant thickness. If, however, the film thickness varies perpendicular to the applied temperature gradient the flow direction is dictated by the minimization of the surface energy. Our predictions are consistent with independent experiments and numerical simulations.

Description: The behavior of matter near a 2 nd order phase transition is expected to obey universal features. In particular, fluids, liquid mixtures, polymers, which belong to the same class of universality (the class of fluids) should exhibit the same universal scaling laws for many thermodynamics and kinetic parameters. Critical point slowing down is the most notorious. Such divergence or convergence makes the class of fluids extremely sensitive to even minute external disturbances and especially gravity: on earth the fluid becomes compressed under its own weight. Compensating for these effects by space experiments and/or magnetic forces or isotopic density matching has led to enlarge our vision of universality for phase transition. New phenomena have been discovered by suppressing gravity effects, as the thermal “Piston Effect”, which leads to a paradoxical critical point speeding up and the apparent violation of the 2 nd thermodynamic law. Another finding is concerned with the use of critical slowing down and weightlessness to investigate the dynamics of phase separation with no gravity-induced sedimentation. The key role of the coalescence of domains makes valid only two simple growth laws. The latter can be successfully applied to a quite different situation, the evolution laws in the well-known biological problem of sorting of embryonic cells. Due to the extreme sensitivity of fluids near their critical point, the effect of vibration can be investigated in much detail, using only one fluid, which represents the whole class of fluids. The investigation of the above thermal and phase transition problems under vibrations indeed suggests that a periodic excitation can act as a kind of artificial gravity, which induces thermal convection, speeds up phase transition and localizes the liquid and vapor phases perpendicular to it.

Description: Random Positioning Machines (RPM) were introduced decades ago to simulate microgravity. Since then numerous experiments have been carried out to study its influence on biological samples. The machine is valued by the scientific community involved in space relevant topics as an excellent experimental tool to conduct pre-studies, for example, before sending samples into space. We have developed a novel version of the traditional RPM to broaden its operative range. This novel version has now become interesting to researchers who are working in the field of tissue engineering, particularly those interested in alternative methods for three-dimensional (3D) cell culturing. The main modifications concern the cell culture condition and the algorithm that controls the movement of the frames for the nullification of gravity. An incubator was integrated into the inner frame of the RPM allowing precise control over the cell culture environment. Furthermore, several feed-throughs now allow a permanent supply of gas like CO 2 . All these modifications substantially improve conditions to culture cells; furthermore, the rewritten software responsible for controlling the movement of the frames enhances the quality of the generated microgravity. Cell culture experiments were carried out with human lymphocytes on the novel RPM model to compare the obtained response to the results gathered on an older well-established RPM as well as to data from space flights. The overall outcome of the tests validates this novel RPM for cell cultivation under simulated microgravity conditions.

Description: The study of heat transfer during the free fall of PbSn droplets is important to optimize the alloy solidification conditions in drop tubes. In this paper a model of heat transfer by conduction is applied in the solidification of PbSn eutectic alloys in a 3 m length drop tube installed at Associate Laboratory of Sensors and Materials of the Brazilian Space Research Institute (LAS/INPE). Drop tubes are one of the most suitable and low cost options to provide a microgravity environment on the ground.

Description: We examined periodical oscillation phenomena that were observed during salt-water oscillator experiments under a small gravity condition. This condition was realized by situating a lower-density gadolinium chloride (GdCl 3 ) aqueous solution on a higher-density sodium chloride (NaCl) aqueous solution and applying a downward magnetic force. The GdCl 3 solution concentration was 0.15 mol/kg (density ρ =1.03×10 3 kg/m 3 ), and the NaCl concentration was varied to (A) 4.35 mol/kg ( ρ =1.15×10 3 kg/m 3 ), (B) 3.79 mol/kg ( ρ =1.12×10 3 kg/m 3 ), and (C) 2.49 mol/kg ( ρ = 1.09×10 3 kg/m 3 ). The magnitude of magnetic flux density was varied from 0 to 4.00 T. As the magnetic flux density grew larger, the GdCl 3 solution was pulled downward by the magnetic force, and upward and downward flows were generated simultaneously at the orifice. These flows were accompanied by a periodical, locally thickened part. The thickened part was only observed when the magnetic force magnitude was small in cases (A) and (B). This flow pattern was not observed in case (C), in which a conventional salt-water oscillation was induced instead (C). In this paper we discuss new experimental results in which the oscillation cycles in cases (A) and (B) are strongly associated with the magnitude of the magnetic force and the density difference in the biphase solutions.

Description: In July 2013, the German Aerospace Center (DLR) in Cologne, Germany, commissioned its new medical research facility :envihab. One central element of the facility is a new type of short radius centrifuge called DLR-SAHC 1 (formerly known as :enviFuge), which has been developed in collaboration with AMST Systemtechnik GmbH, Ranshofen, Austria. The shift of subjects above heart-level on a short arm centrifuge allows unique studies on, e.g., the cardiovascular regulation in surroundings with a high gradient of artificial gravity. Equipped with the capacity to move the four nacelles along the acceleration axis simultaneously and independently from each other, the centrifuge allows the possibility to perform up to four complex trials in parallel. The maximal acceleration is 6 g at the foot level and each nacelle can accomodate an up to 150kg payload. Additional equipment can be mounted on two payload bays with a capacity of 100kg each. Standard features of the centrifuge include a motion capturing system with six cameras and two triaxial force plates to study the kinematics of physical exercise (e.g., squatting, jumping or vibration training) under increased gravity. Future projects involving SAHC 1 will allow the development and testing of potential countermeasures and training methods against the negative effects of weightlessness in space on human physiology. Due to the centrifuge’s capability to hold heavy equipment, carrying out a variety of non-human life science experiments requiring complex and heavy hardware is also fully feasible.

Description: The paper is concerned with dynamics of light solid in cavity with liquid subjected to rotational vibration in the external force field. New vibrational phenomenon – diving of a light cylinder to the cavity bottom is found. The experimental investigation of a horizontal annulus with a partition has shown that under vibration a light body situated in the upper part of the layer is displaced in a threshold manner some distance away from the boundary. In this case the body executes symmetric tangential oscillations. An increase of the vibration intensity leads to a tangential displacement of the body near the external boundary. This displacement is caused by the tangential component of the vibrational lift force, which appears as soon as the oscillations lose symmetry. In this case the trajectory of the body oscillatory motion has the form of a loop. The tangential lift force makes stable the position of the body on the inclined section of the layer and even in its lower part. A theoretical interpretation has been proposed, which explains stabilization of a quasi-equilibrium state of a light body near the cavity bottom in the framework of vibrational hydromechanics.

Description: The complex macroscopic rheological behavior of granular flow contains elements of both solid and liquid flow. Furthermore, under microgravity, granular flow exhibits novel flow features. To overcome a lack of comprehensive analyses of granular flow under microgravity, this study reviews the microgravity platforms and devices under which granular flow can be observed, the experimental findings made in such settings, and the range of numerical simulations that can be used to examine granular flow under microgravity. Differences in experimental research between normal gravity and microgravity are highlighted. These differences are found in the modifications made to conventional granular flow experimental devices, in new or unique granular flow behaviors, and in the numerical simulation methods needed for microgravity modeling. Additionally, the benefits of numerical simulation methods for examining rapid and dense flows under microgravity are also discussed. This study may have wide-ranging implications in such fields as investigations of the surface geology of asteroids or the efficient design and development of anchoring mechanisms or space vehicles.

Description: We report the results of residual acceleration obtained from initial tests of parabolic flights (more than 100 hours) performed with a small single-engine aerobatic aircraft (CAP10B), and propose a method that improves these figures. Such aircraft have proved capable of providing researchers with periods of up to 8 seconds of reduced gravity in the cockpit, with a gravity quality in the range of 0.1 g 0 , where g 0 is the gravitational acceleration of the Earth. Such parabolas may be of interest to experimenters in the reduced gravity field, when this range of reduced gravity is acceptable for the experiment undertaken. They have also proven to be useful for motivational and educational campaigns. Furthermore, these flights may be of interest to researchers as a test-bed for obtaining a proof-of-concept for subsequent access to parabolic flights with larger aircraft or other microgravity platforms. The limited cost of the operations with these small aircraft allows us to perform them as part of a non-commercial joint venture between the Universitat Politècnica de Catalunya - BarcelonaTech (UPC), the Barcelona cluster BAIE and the Aeroclub Barcelona-Sabadell. Any improvements in the length and quality of reduced gravity would increase the capabilities of these small aircraft. To that end, we have developed a method based on a simulator for training aerobatic pilots. The simulation is performed with the CAD software for mechanical design Solidworks Motion \({\circledR }\) , which is widely distributed in industry and in universities. It specifically simulates the parabolic flight manoeuvre for our small aircraft and enables us to improve different aspects of the manoeuvre. The simulator is first validated with experimental data from the test flights. We have conducted an initial intensive period of specific pilot training with the aid of the simulator output. After such initial simulation-aided training, results show that the reduced gravity quality has significantly improved from 0.1 g 0 to 0.05 g 0 . We conclude that single-engine aerobatic aircraft are capable of conducting small hypogravity experiments with the limitations described in the paper.

Description: The influence of a static gravity level on Soret-driven convection of a ternary mixture in a square cavity heated from above is investigated. The problem is solved by the finite difference method using the equations of thermosolutal convection in multicomponent mixtures. These equation are transformed to a set of equations to eliminate the cross-diffusion effects and to reduce the number of governing parameters. Calculations are performed to study a ternary mixture with the components having different signs of the separation ratios at different levels of gravity. Due to the thermodiffusion effect, the component with a negative separation ratio moves to the upper (hot) wall. This leads to the development of instability accompanied by a sharp increase in the flow intensity and a sharp decrease in the concentration difference between the upper and lower boundaries. Numerical data on the time evolution of integral characteristics of flow and heat and mass transfer, and data on the structure fields of stream function and concentration at different times for different values of the Rayleigh number (different levels of gravity) are obtained.

Description: The parameter analysis method of conceptual design is studied in this paper with the help of C–K theory. Each of the fundamental design activities—idea generation, implementation of the idea as hardware and evaluation—is explained and defined as a specific sequence of C–K operators. A case study of designing airborne decelerators is used to demonstrate the modeling of the parameter analysis process in C–K terms. The theory is used to explain how recovery from an initial fixation took place, leading to a breakthrough in the design process. It is shown that the innovative power of parameter analysis is based on C-space “de-partitioning” and that the efficient strategy exhibited by parameter analysis can be interpreted as steepest-first, controlled by an evaluation function of the design path. This logic is explained as generalization of branch-and-bound algorithms by a learning-based, dynamically evolving evaluation function and exploration of a state space that keeps changing during the actual process of designing.

Description: Capturing and managing requirements are crucial to the success of product design and development. This paper presents and analyzes the causes of requirements change during the design process of a complex aerospace system developed by Rolls-Royce during the course of 6 years. The study was part of a series of efforts ongoing at this original equipment manufacturer to improve requirements engineering practices and involved a group of engineers in the assessment of the root causes of change. A large data set was examined, containing 700 system requirements and more than 1,000 changes released during the project studied. The results showed that more than 80 % of the changes had internal root causes and change driven by the customer accounted for about 15 % of the total. The structured approach that was implemented to understand the causes of change allowed the group of engineers to identify and dissect various management guidelines aiming to further improve requirements engineering in practice. This paper thus also reports the guidelines captured at this aerospace manufacturer and intends to support practitioners across the industrial community.

Description: The investigation of systemic blood pressure (BP) responses under partial-g conditions is of particular importance with respect to post-space-flight orthostatic intolerance. In this study, changes in vessel diameter and wall distension of the common carotid artery (CCA) were assessed under graded gravity. Measurements were performed on 8 healthy subjects in standing position under lunar (0.16 g), Martian (0.38 g), 1.0 g and hypergravity (1.8 g) during partial-g parabolic flights. Data are reported as means ± SE estimated by linear mixed effects modeling. The CCA diameter was significantly enlarged under Martian and lunar-g (6.55 ± 0.2 and 6.54 ± 0.2 mm; p 〈 0.001 each) with respect to 1.0 g (6.39 ± 0.2 mm). The CCA distension showed significant enlargement under Martian-g (622 ± 91 μ m) with respect to 1.0 g (603 ± 82 μ m; p 〈 0.05). Furthermore, the distension was significantly lower under hyper-g with respect to 1.0 g (550 ± 88 μ m; p 〈 0.001). These results show that rapid changes of gravitational stress induce significant modifications of hemodynamic parameters reflected in the CCA vessel wall diameter and distension. The increased vessel wall diameter under partial-g is likely due to the rise in mean BP at the CCA level caused by the absence of hydrostatic pressure and may trigger the baroreflex to maintain homeostatis. We can assume that the increase in distension during the partial-g phase originates from a larger stroke volume and enhanced BP reflections. Furthermore, this study demonstrates the reliability of functional high resolution vascular ultrasound technique during parabolic flights.

Description: When developing an artifact, designers must first capture and represent user needs. These needs can then be transformed into system requirements or objectives. The contribution of this work is rooted in the formalization of the affordance-based approach for capturing user needs in the early stages of design. This formalization comes in three forms: the first affordance basis for engineering design (a defined set of affordances), a formal structure for affordance statements, and a new relational model structure. This formalization is intended to improve model quality and consistency, while managing model creation resources. Further, this affordance-based approach to capturing user needs imposes a level of abstraction that forces solution independence yet is capable of capturing the large range of user needs. As such, the approach provides a structured approach to problem abstraction—the process of specifying user needs without reference to specific solutions. This affordance-based problem representation relies on other design process tools to help develop the actual artifact, which is also discussed.

Description: Engineering changes are essential for any product development, and their management has become a crucial discipline. Research in engineering change management has brought about some methods and tools to support dealing with changes. This work extends the change prediction method through incorporation of a function–behaviour–structure (FBS) scheme. These additional levels of detail provide the rationales for change propagation and allow a more proactive management of changes. First, we develop the ontology of this method based on a comprehensive comparison of three seminal functional reasoning schemes. Then, we demonstrate the FBS Linkage technique by applying it to a diesel engine. Finally, we evaluate the method.

Description: Managing uncertainty levels is important for organizations carrying out complex product development processes since it fosters design process improvements and optimization. Among the different uncertainties, design imprecision is known to represent uncertainty in decision-making that typically triggers changes to the value assigned to design variables during the early stages of the development process. This paper presents a method aiming to support large organizations understanding, quantifying and communicating this type of uncertainty. The imprecision management method that is proposed relies on five main steps: collection of historical records of change, time evolution reconstruction, statistical characterization of the typical levels of imprecision that should be expected, communication to new projects and continuous knowledge update. In addition, we present results from a case-study performed at Rolls–Royce that tested the method’s applicability in practice. The study shed light to interesting empirical findings about the typical level of imprecision in design variables and its evolution during real product development projects. The results from this initial evaluation suggest that the method provides useful support for design process management and thus has industrial value.

Description: In the design process of products or systems, a current trend consists in taking into account judgments of users. In this context, a multiobjective optimisation method taking into account judgments of a panel of subjects is proposed. It is aimed at identifying the best trade-offs between quantitative objectives and judgments of users. The method is divided in two steps: (1) judgment data acquisition and (2) integration of the judgment data into the multiobjective optimisation process. The method is based on a stochastic Pareto-based evolutionary algorithm for optimisation and on a multilinear interpolation for judgment modelling. The combination of these techniques makes it possible to solve complex problems, with up to eight decision variables and up to at least eight objectives. Relevant applications of the method include optimisation with judgments about various aspects of the product or system, identification of the best trade-offs satisfying at the same time several groups with different judgments, and analysis of the interest of market segmentation. For illustration purpose, a pilot study about an individual office lighting design problem is processed.

Description: Despite the development of a variety of decision-aid tools for assessing the value of a conceptual design, humans continue to play a dominant role in this process. Researchers have identified two major challenges to automation, namely the subjectivity of value and the existence of multiple and conflicting customer needs. A third challenge is however arising as the amount of data (e.g., expert judgment, requirements, and engineering models) required to assess value increases. This brings two challenges. First, it becomes harder to modify existing knowledge or add new knowledge into the knowledge base. Second, it becomes harder to trace the results provided by the tool back to the design variables and model parameters. Current tools lack the scalability and traceability required to tackle these knowledge-intensive design evaluation problems. This work proposes a traceable and scalable rule-based architecture evaluation tool called VASSAR that is especially tailored to tackle knowledge-intensive problems that can be formulated as configuration design problems, which is demonstrated using the conceptual design task for a laptop. The methodology has three main steps. First, facts containing the capabilities and performance of different architectures are computed using rules containing physical and logical models. Second, capabilities are compared with requirements to assess satisfaction of each requirement. Third, requirement satisfaction is aggregated to yield a manageable number of metrics. An explanation facility keeps track of the value chain all along this process. This paper describes the methodology in detail and discusses in particular different implementations of preference functions as logical rules. A full-scale example around the design of Earth observing satellites is presented.

Description: In upper stages of spacecrafts, Propellant Management Devices (PMD’s) can be used to position liquid propellant over the outlet in the absence of gravity. Centrifugal forces due to spin of the upper stage can drive the liquid away from the desired location resulting in malfunction of the stage. In this study, a simplified model consisting of two parallel, segmented and unsegmented disks and a central tube assembled at the center of the upper disk is analyzed experimentally during rotation in microgravity. For each drop tower experiment, the angular speed caused by a centrifugal stage in the drop capsule is kept constant. Steady-states for the menisci between the disks are observed for moderate rotation. For larger angular speeds, a stable shape of the free surfaces fail to sustain and the liquid is driven away. Additionally, tests were performed without rotation to quantify two effects: the removal of a metallic cylinder around the model to establish the liquid column and the determination of the the settling time from terrestrial to microgravity conditions.

Description: When an astronaut transitions from a low to high gravitational environment, fluid shifts from the head towards the feet resulting in orthostatic intolerance and syncope. Ground based experiments have shown that by stimulating the cardiovascular system via simple mental stressors, syncope can be delayed, potentially enabling astronauts to reach assistance before loss of consciousness. However, the effect of mental stressors on the stimulation of the cardiovascular system in gravitational environments different than that of Earth’s is unknown. As such, this paper investigates the effects that mental stressors under various gravitational environments. To do this, a pilot study was performed in which two participants were flown on two separate parabolic flights that simulated hyper and hypogravity conditions. The plane used was an Aerobatic Single-Engine Cap-10B plane (twin seater), and each participant executed 11 parabolas. The participants were the winners of the Barcelona Zero-G Challenge 2011 organized by UPC Universitat Politècnica de Catalunya-BarcelonaTech and Aeroclub Barcelona-Sabadell. Measurements were made of the participants’ hemodynamic and autonomic response throughout the parabolas, using a Chronocord: high precision HRV monitor. Comparisons of the baseline response without mental stressors, and the response with mental stressors during different gravitational loading conditions were made. It was observed that there is an increase in cardiovascular activity during hypo- and hyper-gravity when performing mental arithmetic. Our results show that the twin seater aerobatic single engine CAP-10B aicraft can provide changing gravitational loading conditions for enough periods to study changes in physiological systems.

Description: An experimental device with three crystallization cells, each with two working positions, was designed to study growth kinetics and structural transformation of colloidal crystals under microgravity condition. The device is capable of remote control of experimental procedures. It uses direct-space imaging with white light to monitor morphology of the crystals and reciprocal-space laser diffraction (Kossel lines) to reveal lattice structure. The device, intended for colloidal crystal growth kinetics and structural transformation on Tiangong-1 target spacecraft, had run on-orbit for more than one year till the end of the mission. Hundreds of images and diffraction patterns were collected via the on-ground data receiving station. The data showed that single crystalline samples were successfully grown on the orbit. Structural transformation was carefully studied under electric and thermal field. Using a backup device, control experiments were also performed on the ground under similar conditions except for the microgravity. Preliminary results indicated that the on-orbit crystals were more stable than the on-ground ones.

Description: This paper summarizes the first results from isolated droplet combustion experiments performed on the International Space Station (ISS). The long durations of microgravity provided in the ISS enable the measurement of droplet and flame histories over an unprecedented range of conditions. The first experiments were with heptane and methanol as fuels, initial droplet droplet diameters between 1.5 and 5.0 m m , ambient oxygen mole fractions between 0.1 and 0.4, ambient pressures between 0.7 and 3.0 a t m and ambient environments containing oxygen and nitrogen diluted with both carbon dioxide and helium. The experiments show both radiative and diffusive extinction. For both fuels, the flames exhibited pre-extinction flame oscillations during radiative extinction with a frequency of approximately 1 H z . The results revealed that as the ambient oxygen mole fraction was reduced, the diffusive-extinction droplet diameter increased and the radiative-extinction droplet diameter decreased. In between these two limiting extinction conditions, quasi-steady combustion was observed. Another important measurement that is related to spacecraft fire safety is the limiting oxygen index (LOI), the oxygen concentration below which quasi-steady combustion cannot be supported. This is also the ambient oxygen mole fraction for which the radiative and diffusive extinction diameters become equal. For oxygen/nitrogen mixtures, the LOI is 0.12 and 0.15 for methanol and heptane, respectively. The LOI increases to approximately 0.14 (0.14 O 2 /0.56 N 2 /0.30 C O 2 ) and 0.17 (0.17 O 2 /0.63 N 2 /0.20 C O 2 ) for methanol and heptane, respectively, for ambient environments that simulated dispersing an inert-gas suppressant (carbon dioxide) into a nominally air (1.0 a t m ) ambient environment. The LOI is approximately 0.14 and 0.15 for methanol and heptane, respectively, when helium is dispersed into air at 1 atm. The experiments also showed unique burning behavior for large heptane droplets. After the visible hot flame radiatively extinguished around a large heptane droplet, the droplet continued to burn with a cool flame. This phenomena was observed repeatably over a wide range of ambient conditions. These cool flames were invisible to the experiment imaging system but their behavior was inferred by the sustained quasi-steady burning after visible flame extinction. Verification of this new burning regime was established by both theoretical and numerical analysis of the experimental results. These innovative experiments have provided a wealth of new data for improving the understanding of droplet combustion and related aspects of fire safety, as well as offering important measurements that can be used to test sophisticated evolving computational models and theories of droplet combustion.

Description: Design tasks need to be rescheduled and reprioritised frequently during product development. Inappropriate priority decisions generate rework; thus, the policy used to guide such decisions may have a significant effect on design cost and lead time. Generic priority rules provide easily implementable guidelines for task prioritisation and are theoretically effective for many planning problems. But can they be used in design processes, which include iteration, rework and changes? In this article, a discrete-event simulation model is developed to investigate priority policies in design. The model explores the combined effects of progressive iteration, rework and change propagation during design of interconnected parts in a product architecture. Design progression is modelled as an increase in the maturity of parts; rework and change propagation cause maturity levels in certain parts to reduce. Twelve product architecture models ranging in size from 7 to 32 elements are simulated to draw qualitative and general insights. Sensitivity of the findings to assumptions and model inputs is tested. Generally effective priority policies are identified, and their impact is shown to depend on the interconnectedness and organisation of product architecture, as well as the degree of concurrency in the design process.

Description: Nonlinear oscillatory convective flows developed under the joint action of buoyant and thermocapillary effects in the 47v2 silicone oil - water system with periodic boundary conditions on the lateral walls, have been studied. The influence of an inclined temperature gradient on convective regimes, has been investigated. Different values of parameter, characterizing the horizontal component of the temperature gradient, have been considered. Regimes of standing symmetric oscillations, traveling waves, pulsating traveling waves moving in the opposite directions, and modulated traveling waves, have been found.

Description: An experimental investigation has been performed to study a supercritical flow driven by the combined effects of buoyancy and thermocapillary forces, in a non-isothermal liquid cylindrical column heated from above (liquid bridge). The liquid zone was of 3 mm in radius and 2.58 mm in height made of n-decane. Changing temperature of air in the experimental chamber via controlling the temperature at its external wall, the conditions at the onset of instability of the flow, as characterized by the critical value of the imposed temperature difference, were determined for several values of the liquid volume. Performing ”chaos analysis” of the obtained data, different regimes of the supercritical flow were identified. The experimental observations are supported by a computer modeling of the thermoconvective flow made for the experimental conditions neglecting deformations of the liquid-gas interface. It is shown that the spatial structure of the flow may change with external conditions in the ambient gas.

Description: When developing an artifact, designers must first capture and represent user needs. These needs can then be transformed into system requirements or objectives. The contribution of this work is rooted in the formalization of the affordance-based approach for capturing user needs in the early stages of design. This formalization comes in three forms: the first affordance basis for engineering design (a defined set of affordances), a formal structure for affordance statements, and a new relational model structure. This formalization is intended to improve model quality and consistency, while managing model creation resources. Further, this affordance-based approach to capturing user needs imposes a level of abstraction that forces solution independence yet is capable of capturing the large range of user needs. As such, the approach provides a structured approach to problem abstraction—the process of specifying user needs without reference to specific solutions. This affordance-based problem representation relies on other design process tools to help develop the actual artifact, which is also discussed.

Description: Design tasks need to be rescheduled and reprioritised frequently during product development. Inappropriate priority decisions generate rework; thus, the policy used to guide such decisions may have a significant effect on design cost and lead time. Generic priority rules provide easily implementable guidelines for task prioritisation and are theoretically effective for many planning problems. But can they be used in design processes, which include iteration, rework and changes? In this article, a discrete-event simulation model is developed to investigate priority policies in design. The model explores the combined effects of progressive iteration, rework and change propagation during design of interconnected parts in a product architecture. Design progression is modelled as an increase in the maturity of parts; rework and change propagation cause maturity levels in certain parts to reduce. Twelve product architecture models ranging in size from 7 to 32 elements are simulated to draw qualitative and general insights. Sensitivity of the findings to assumptions and model inputs is tested. Generally effective priority policies are identified, and their impact is shown to depend on the interconnectedness and organisation of product architecture, as well as the degree of concurrency in the design process.

Description: The stability of a front of chemoconvective finger structures being spontaneously formed in a two-layer system of fluids filling a vertical Hele-Shaw cell, each of them containing a reactant of an exothermic A + B → S reaction is examined. If the configuration consists of more dense acid (or salt) on top of less dense base in the presence of gravity, the development of the Rayleigh- Taylor instability leads to the standard scenario of density fingering. Despite the widespread perception of fingering as an irregular process, we show that, at least in some cases, the exact balance between the instabilities involved can result quasi-regular fingering pattern formation. In the case of immiscible fluids, we demonstrate that the Rayleigh-Bénard mechanism associated with intensive heat release during the reaction performs fine-tuning of the envelope of salt fingers. The mathematical model we develop consists in a set of reaction-diffusion-convection equations governing the evolution of concentrations and temperature coupled to Navier-Stokes and energy equations, written in a Hele-Shaw approximation. The results of linear stability analysis and direct numerical simulations of the fully nonlinear system are presented.

Description: In the design process of products or systems, a current trend consists in taking into account judgments of users. In this context, a multiobjective optimisation method taking into account judgments of a panel of subjects is proposed. It is aimed at identifying the best trade-offs between quantitative objectives and judgments of users. The method is divided in two steps: (1) judgment data acquisition and (2) integration of the judgment data into the multiobjective optimisation process. The method is based on a stochastic Pareto-based evolutionary algorithm for optimisation and on a multilinear interpolation for judgment modelling. The combination of these techniques makes it possible to solve complex problems, with up to eight decision variables and up to at least eight objectives. Relevant applications of the method include optimisation with judgments about various aspects of the product or system, identification of the best trade-offs satisfying at the same time several groups with different judgments, and analysis of the interest of market segmentation. For illustration purpose, a pilot study about an individual office lighting design problem is processed.

Description: We investigate numerically the effect of a linearly polarized, harmonic vibration on a 2-D incompressible fluid confined in a square cavity when a sudden change of temperature is imposed at the walls under zero static gravity. A thermal front propagates from the wall, which can become unstable and develop as fingers. The study is performed in the framework of the Boussinesq approximation where the density variations are taken into account only in the vibrational force. The calculations carried out by finite difference method show that the direction of vibrations has a major impact on the thermal front propagation. When vibrations are parallel to the wall, the flow is induced in the same direction and a thermal vibrational instability develops. In contrast, when vibrations are normal to the wall, it is observed a parametric instability is observed.

Description: The parameter analysis method of conceptual design is studied in this paper with the help of C–K theory. Each of the fundamental design activities—idea generation, implementation of the idea as hardware and evaluation—is explained and defined as a specific sequence of C–K operators. A case study of designing airborne decelerators is used to demonstrate the modeling of the parameter analysis process in C–K terms. The theory is used to explain how recovery from an initial fixation took place, leading to a breakthrough in the design process. It is shown that the innovative power of parameter analysis is based on C-space “de-partitioning” and that the efficient strategy exhibited by parameter analysis can be interpreted as steepest-first, controlled by an evaluation function of the design path. This logic is explained as generalization of branch-and-bound algorithms by a learning-based, dynamically evolving evaluation function and exploration of a state space that keeps changing during the actual process of designing.

Description: Engineering changes are essential for any product development, and their management has become a crucial discipline. Research in engineering change management has brought about some methods and tools to support dealing with changes. This work extends the change prediction method through incorporation of a function–behaviour–structure (FBS) scheme. These additional levels of detail provide the rationales for change propagation and allow a more proactive management of changes. First, we develop the ontology of this method based on a comprehensive comparison of three seminal functional reasoning schemes. Then, we demonstrate the FBS Linkage technique by applying it to a diesel engine. Finally, we evaluate the method.

Description: Despite the development of a variety of decision-aid tools for assessing the value of a conceptual design, humans continue to play a dominant role in this process. Researchers have identified two major challenges to automation, namely the subjectivity of value and the existence of multiple and conflicting customer needs. A third challenge is however arising as the amount of data (e.g., expert judgment, requirements, and engineering models) required to assess value increases. This brings two challenges. First, it becomes harder to modify existing knowledge or add new knowledge into the knowledge base. Second, it becomes harder to trace the results provided by the tool back to the design variables and model parameters. Current tools lack the scalability and traceability required to tackle these knowledge-intensive design evaluation problems. This work proposes a traceable and scalable rule-based architecture evaluation tool called VASSAR that is especially tailored to tackle knowledge-intensive problems that can be formulated as configuration design problems, which is demonstrated using the conceptual design task for a laptop. The methodology has three main steps. First, facts containing the capabilities and performance of different architectures are computed using rules containing physical and logical models. Second, capabilities are compared with requirements to assess satisfaction of each requirement. Third, requirement satisfaction is aggregated to yield a manageable number of metrics. An explanation facility keeps track of the value chain all along this process. This paper describes the methodology in detail and discusses in particular different implementations of preference functions as logical rules. A full-scale example around the design of Earth observing satellites is presented.

Description: As of 2013, a number of companies had announced their intention to start flying suborbital vehicles, capable of transporting people to high altitudes out of any airport or launch site, on a commercial and regular basis. According to several studies, a market for suborbital “space tourism” exists. Another very promising application of suborbital flight is scientific research. The present paper provides an overview of the potential of commercial suborbital flight for science, including microgravity research. Suborbital flight provides a much-needed intermediate-duration opportunity between research performed in Earth orbit and more affordable but shorter duration alternatives, such as drop towers and zero-g parabolic flights. Moreover, suborbital flight will be less expensive and more frequent than both orbital flight and sounding rockets, and it has the capability to fly into sub-orbit the researcher together with the payload, and thus enable on-site interaction with the experiment. In the United States, both the National Aeronautics and Space Administration (NASA) and a number of private institutions have already shown interest in conducting scientific experiments, particularly microgravity research, aboard these new platforms. Researchers who intend to participate in future suborbital flights as payload specialists will need training, given the physical challenges posed by the flight. Finally, suborbital researchers may also want to have a basic knowledge of the legal status that will apply to them as passengers of such flights.

Description: Gravity supports all the life activities present on earth. Microgravity environments have effect on the biological functions and physiological status of an individual. The present study was undertaken to investigate the effect of simulated microgravity on important regulatory enzymes of carbohydrate metabolism in liver using HLS mice model. Following hind limb unloading of mice for 11 days the animal’s average body weights were found to be not different, while the liver weights were decreased and found to be significantly different ( p 〈 0.05) from control mice. Further, in liver the specific activity of hexokinase enzyme was reduced ( p 〈 0.02) and the phosphoenolpyruvate carboxykinase activity was significantly increased in simulated microgravity subjected mice compared to control ( p 〈 0.003). Immunoblot analysis show decreased phosphofructokinase-2 activity in HLS mice compared to control. Liver lactate dehydrogenase activity significantly reduced in simulated microgravity subjected mice ( p 〈 0.005). Thus in our study the rodents have adapted to simulated microgravity conditions, with decreased glycolysis and increased gluconeogenesis in liver and reciprocally regulated.