bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethanol, not detectably metabolized in brain, significantly reduces brain metabolism, probably via action at specific GABA(A) receptors and has measureable metabolic effects at very low concentrations
Authors: Rae Caroline D. , Davidson Joanne E. , Maher Anthony D. , Rowlands Benjamin D. , Kashem Mohammed A. , Nasrallah Fatima A. , Rallapalli Sundari K. , Cook James M. , Balcar Vladimir J.
Published: December 2013

Ethanol is a known neuromodulatory agent with reported actions at a range of neurotransmitter receptors. Here, we measured the effect of alcohol on metabolism of [3‐13C]pyruvate in the adult Guinea pig brain cortical tissue slice and compared the outcomes to those from a library of ligands active in the GABAergic system as well as studying the metabolic fate of [1,2‐13C]ethanol. Analyses of metabolic profile clusters suggest that the significant reductions in metabolism induced by ethanol (10, 30 and 60 mM) are via action at neurotransmitter receptors, particularly α4β3δ receptors, whereas very low concentrations of ethanol may produce metabolic responses owing to release of GABA via GABA transporter 1 (GAT1) and the subsequent interaction of this GABA with local α5‐ or α1‐containing GABA(A)R. There was no measureable metabolism of [1,2‐13C]ethanol with no significant incorporation of 13C from [1,2‐13C]ethanol into any measured metabolite above natural abundance, although there were measurable effects on total metabolite sizes similar to those seen with unlabelled ethanol.

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Ethanol has many documented effects on brain neurochemistry including significantly decreasing glucose consumption. Here, we used multinuclear NMR spectroscopy and metabolomic neuropharmacology to examine alcohol effects on metabolism in cortical brain tissue slices. [1,2‐13C]Ethanol is not metabolized by brain, but very low ethanol [0.1 mM] has significant effects on brain metabolism. Higher ethanol [1.0–60 mM] likely decreases metabolism through action at α4β3δ‐containing GABA(A) receptors.
Diabetes nurse educators' experiences of providing care for women, with gestational diabetes mellitus, from disadvantaged backgrounds
Authors: Carolan Mary
Published: December 2013

Aims and objectives

To explore diabetes nurse educators' experiences of providing care for women, with gestational diabetes mellitus, from disadvantaged backgrounds and to gather information which would assist with the development of an educational programme that would support both women and diabetes educators.

Background

Rates of gestational diabetes mellitus have increased dramatically in recent years. This is concerning as gestational diabetes mellitus is linked to poorer pregnancy outcomes including hypertension, stillbirth, and nursery admission. Poorest outcomes occur among disadvantaged women. gestational diabetes mellitus is also associated with maternal type 2 diabetes and with child obesity and type 2 diabetes among offspring. Effective self‐management of gestational diabetes mellitus reduces these risks. Diabetes nurse educators provide most education and support for gestational diabetes mellitus self‐management.

Design

An interpretative phenomenological analysis approach, as espoused by Smith and Osborn (Qualitative Psychology: A Practical Guide to Research Methods, 2008, Sage, London, 51), provided the framework for this study.

Methods

The views of six diabetes educators were explored through in‐depth interviewing. Interviews were transcribed verbatim and analysed according to steps outlined by Smith and Osborn (Qualitative Psychology: A Practical Guide to Research Methods, 2008, Sage, London, 51).

Results

Three themes emerged from the data: (1) working in a suboptimal environment, (2) working to address the difficulties and (3) looking to the future. Throughout, the diabetes nurse educators sought opportunities to connect with women in their care and to make the educational content understandable and meaningful.

Conclusions

Low literacy among disadvantaged women has a significant impact on their understanding of gestational diabetes mellitus information. In turn, catering for women with low literacy contributes to increased workloads for diabetes nurse educators, making them vulnerable to burnout.

Relevance to clinical practice

There is a need for targeted educational programmes for women with low literacy. Resources should be literacy appropriate, with photographs and simple text, and include culturally appropriate foods and information. This approach should lead to an improvement in the women's uptake of gestational diabetes mellitus information and may lead to a lessening of the workload burden for diabetes nurse educators.
Melatonin synthesis in rice seedlings in vivo is enhanced at high temperatures and under dark conditions due to increased serotonin N‐acetyltransferase and N‐acetylserotonin methyltransferase activities
Authors: Byeon Yeong , Back Kyoungwhan
Published: December 2013

Temperature and light are important environmental factors for plant growth and development. The final two enzymes in the melatonin synthesis pathway in plants are serotonin N‐acetyltransferase (SNAT) and N‐acetylserotonin methyltransferase (ASMT), which have thermophilic characteristics. Thus, the effects of temperature and light on melatonin synthesis in rice seedlings were investigated. Here, we demonstrated that melatonin levels increased as temperature increased when rice seedlings were exposed to various temperatures for 1 hr. Moreover, the relative melatonin levels were higher in the dark. For example, exposure of rice seedlings to 1‐hr darkness at 55°C resulted in a melatonin yield of 4.9 ng/g fresh weight (fw), compared with 2.95 ng/g fw under light conditions. Temperature‐dependent melatonin synthesis was closely associated with an increase in both SNAT and ASMT activities, but not with transcript levels of melatonin biosynthetic genes. The daily melatonin levels in field‐grown rice plants were unaffected as the positive effect of the relatively high temperature during the day was counteracted by the negative effect of the high light. The opposite effect occurred during the night, in which the positive effect of darkness on melatonin synthesis was counteracted by the negative effect of a low temperature.
Differentiating Suicide Attempters from Suicide Ideators: A Critical Frontier for Suicidology Research
Authors: Klonsky E. David , May Alexis M.
Published: December 2013

Most individuals who consider suicide do not make suicide attempts. It is therefore critical to identify which suicide ideators are at greatest risk of acting on their thoughts. However, few seminal theories of suicide address which ideators go on to make attempts. In addition, perhaps surprisingly, most oft‐cited risk factors for suicide—such as psychiatric disorders, depression, hopelessness, and even impulsivity—distinguish poorly between those who attempt suicide and those who only consider suicide. This special section of Suicide and Life‐Threatening Behavior serves to highlight this knowledge gap and provide new data on differences (and similarities) between suicide attempters and suicide ideators.
The Effect of Shame‐Proneness, Guilt‐Proneness, and Internalizing Tendencies on Nonsuicidal Self‐Injury
Authors: VanDerhei Susan , Rojahn Johannes , Stuewig Jeffrey , McKnight Patrick E.
Published: December 2013

Nonsuicidal self‐injury is especially common in adolescents and young adults. Self‐injury may be related to shame or guilt—two moral emotions—as these differentially predict other maladaptive behaviors. Using a college sample, we examined not only how shame‐proneness, guilt‐proneness, and internalizing emotional tendencies related to self‐injury, but also whether these moral emotions moderate the relation between internalizing tendencies and self‐injury. High shame‐proneness was associated with higher frequencies of self‐injury. High guilt‐proneness was associated with less self‐injury, although this effect was mitigated at higher levels of internalizing tendencies. These results suggest shame‐proneness is a risk factor for self‐injury, while guilt‐proneness is protective.
Full‐Field Measurements on Low‐Strained Geomaterials Using Environmental Scanning Electron Microscopy and Digital Image Correlation: Improved Imaging Conditions
Authors: Wang L. L. , Bornert M. , Héripré E. , Chanchole S. , Tanguy A.
Published: December 2013

Full‐field strain measurement at microscale on geomaterials by means of hydromechanical in situ testing and imaging in an environmental scanning electron microscope and digital image correlation techniques is a challenging task because of both low magnitude of investigated strains (typically of the order of 10−3) and unfavourable imaging conditions. In view of improving strain measurement accuracy, three major sources of measurement errors are evaluated, and methods to minimise their effects are proposed. First, a fast and simple procedure to accurately quantify image noise is proposed and subsequently used to optimise various environmental scanning electron microscope setting parameters, such as dwell time, spot size, working distance and chamber pressure. Second, a specific procedure to limit magnification fluctuations to a sufficiently low level is described. Finally, digital image correlation systematic errors are quantified on real images, and several ways to reduce their amplitude are compared. The combination of these improvements finally allows us to reach an appropriate accuracy for overall strain measurements and characterisation of microscale heterogeneities.
Nonintrusive Structural Dynamic Reduced Order Modeling for Large Deformations: Enhancements for Complex Structures
Authors: Perez Ricardo , Wang X. Q. , Mignolet Marc P.
Published: December 2013

This paper focuses on the development of nonlinear reduced order modeling techniques for the prediction of the response of complex structures exhibiting “large” deformations, i.e., a geometrically nonlinear behavior, which are nonintrusive, i.e., the structure is originally modeled within a commercial finite element code. The present investigation builds on a general methodology successfully validated in recent years on simpler beam and plate structures by: (i) developing a novel identification strategy of the reduced order model parameters that enables the consideration of the large number of modes (>50 say) that would be needed for complex structures, and (ii) extending a step-by-step strategy for the selection of the basis functions used to represent accurately the displacement field. The above novel developments are successfully validated on the nonlinear static response of a nine-bay panel structure modeled with 96,000 degrees of freedom within Nastran.
A Mechanistic Multibody Model for Simulating the Dynamics of a Vertical Piano Action
Authors: Masoudi Ramin , Birkett Stephen , McPhee John
Published: December 2013

The theoretical framework for constructing a fully mechanistic multibody dynamic model of a vertical piano action is described, and its general validity is established. Equations of motion are derived symbolically using a graph-theoretic formulation. Model fidelity is increased by introducing several novel features: (i) a new contact model for representing the compression of the felt-lined interfaces between interacting parts, capable of capturing the intermittent loading and unloading of these contacts occurring through the key stroke, as well as providing smooth transitions between these states; (ii) models for two important components that are unique to the vertical action, the bridle strap and the butt spring; (iii) a sophisticated key pivot model that captures both the rotational motion and the vertical translation of the key as it can lift off the balance rail under some conditions; (iv) flexible beam models for backcheck wire and hammer shank so as to predict observed vibrations in the response accurately; and (v) coupling of the mechanism model to a flexible stiff string model for realistic hammer impact. For simulation, parameters were obtained by experimental testing and measurement of a physical prototype vertical action. Techniques are described for the virtual regulation of the model to ensure that initial conditions and pseudostatic response accurately represent the precise configuration and desired relationships between the parts during the key stroke. Two input force profiles were used for simulations, a forte pressed (hard) and piano pressed touch (soft), typical of those measured at the key surface when activated by a pianist. Simulated response to these quite different inputs is described, and compared to experimental observations obtained from a physical prototype.
Adaptive Actuator Failure and Structural Damage Compensation of NASA Generic Transport Model
Authors: Guo Jiaxing , Tao Gang , Liu Yu
Published: December 2013

This paper studies design and evaluation of a multivariable model reference adaptive control (MRAC) scheme for aircraft systems under simultaneous actuator failures and structural damage. A key design condition–system infinite zero structure is investigated for nominal and posthazard aircraft systems and the invariance of this essential condition is concluded under realistic failure and damage conditions. The multivariable model reference adaptive control scheme is developed to ensure stability and asymptotic output tracking for the aircraft in the presence of uncertain actuator failures and structural damage. The developed fault-tolerant control design is evaluated by a high-fidelity nonlinear aircraft model–the NASA generic transport model.
Effects of H2 Addition to Compressed Natural Gas Blends on Cycle-to-Cycle and Cylinder-to-Cylinder Combustion Variation in a Spark-Ignition Engine
Authors: Baratta Mirko , d'Ambrosio Stefano , Misul Daniela , Spessa Ezio
Published: December 2013

An experimental investigation and a burning-rate analysis have been performed on a production 1.4 liter compressed natural gas (CNG) engine fueled with methane-hydrogen blends. The engine features a pent-roof combustion chamber, four valves per cylinder, and a centrally located spark plug. The experimental tests have been carried out in order to quantify the cycle-to-cycle and the cylinder-to-cylinder combustion variation. Therefore, the engine has been equipped with four dedicated piezoelectric pressure transducers placed on each cylinder and located by the spark plug. At each test point, in-cylinder pressure, fuel consumption, induced air mass flow rate, pressure, and temperature at different locations on the engine intake and exhaust systems as well as “engine-out” pollutant emissions have been measured. The signals related to engine operation have been acquired by means of a National Instruments PXI-DAQ system and software developed in house. The acquired data have then been processed through a combustion diagnostic tool resulting from the integration of an original multizone thermodynamic model with a computer-aided design (CAD) procedure for the evaluation of the burned-gas front geometry. The diagnostic tool allows the burning velocities to be computed. The tests have been performed over a wide range of engine speeds, loads, and relative air-fuel ratios (up to the lean operation limit (LOL)). For stoichiometric operation, the addition of hydrogen to CNG has produced a brake-specific fuel combustion (bsfc) reduction ranging between 2% and 7% and a brake-specific total unburned hydrocarbons (bsTHCs) decrease up to 40%. These benefits have appeared to be even higher for lean mixtures. Hydrogen has shown to significantly enhance the combustion process, thus leading to a sensibly lower cycle-to-cycle variability. Hydrogen addition has generally resulted in extended operation up to relative air-to-fuel ratio (RAFR) = 1.8. Still, the LOL consistently varies depending on the considered cylinder.
Nonparametric Stochastic Modeling of Structural Uncertainty in Rotordynamics: Unbalance and Balancing Aspects
Authors: Murthy Raghavendra , Tomei Joseph C. , Wang X. Q. , Mignolet Marc P. , El-Shafei Aly
Published: December 2013

This paper focuses on extending an earlier investigation on the systematic and rational consideration of uncertainty in reduced order models of rotordynamics systems. The current effort concentrates on the consistent introduction of uncertainty in mass properties on the modal mass and gyroscopic matrices and on the unbalance force vector. The uncertainty in mass is separated into uncertainty that maintains the rotor symmetry and the one which disrupts it. Both types of uncertainties lead to variations in the system modal matrices but only the latter induces an unbalance. Accordingly, the approach permits the selection of separate levels on the uncertainty on the system properties (e.g., natural frequencies) and on the unbalance. It was first found that the unbalanced response is increased by considering the uncertainty in the rotor modal mass matrices. It was next noted that the approach presented not only permits the analysis of uncertain rotors but it also provides a computational framework for the assessment of various balancing strategies. To demonstrate this unique feature, a numerical experiment was conducted in which a population of rotors were balanced at low speed and their responses were predicted at their first critical speed. These response predictions were carried with the uncertainty in the system modal mass matrices but with or without the balancing weights effects on these matrices. It was found that the balancing at low speed may, in fact, lead to an increase in both the mean and 95th percentile of the response at critical speed.
An Exploration of Transport Within Microdroplet and Nanodroplet Clusters During Dropwise Condensation of Water on Nanostructured Surfaces
Authors: Mendoza Hector , Beaini Sara , Carey Van P.
Published: December 2013

Experimental studies of dropwise condensation have generally indicated that higher heat transfer coefficients correspond to smaller mean sizes for droplets growing through condensation on the surface. Recent investigations of dropwise condensation on nanostructured surfaces suggest that optimizing the design of such surfaces can push mean droplet sizes down to smaller values and significantly enhance heat transfer. This paper summarizes a theoretical exploration of the limits of heat transfer enhancement that can be achieved by pushing mean droplet size to progressively smaller sizes. A model analysis is developed that predicts transport near clusters of water droplets undergoing dropwise condensation. The model accounts for interfacial tension effects on thermodynamic equilibrium and noncontinuum transport effects, which become increasingly important as droplet size becomes progressively smaller. In this investigation, the variation of condensing heat transfer coefficient for droplet clusters of different sizes was explored for droplet diameters ranging from hundreds of microns to tens of nanometers. The model predictions indicate that the larger droplet transport trend of increasing heat transfer coefficient with decreasing mean droplet size breaks down as droplet size becomes smaller. The model further predicts that as drop size becomes smaller, a peak heat transfer coefficient is reached, beyond which the coefficient drops as the size continues to diminish. This maximum heat transfer coefficient results from the increasing importance of surface tension effects and noncontinuum effects as droplet size becomes smaller. The impact of these predictions on the interpretation of dropwise condensation heat transfer data, and the implications for design of nanostructured surfaces to enhance dropwise condensation are discussed in detail.
Comparisons of Radiative Heat Transfer Calculations in a Jet Diffusion Flame Using Spherical Harmonics and k-Distributions
Authors: Cai Jian , Marquez Ricardo , Modest Michael F.
Published: December 2013

A new nongray radiation modeling library for combustion gases has been implemented in OpenFOAM. The spectral models for single species include gray, correlation tables and full spectrum k-distributions (FSK) assembled from a narrow-band database. Mixing models for k-distributions include the multiplication and uncorrelated mixture models. Radiative transfer equation solvers for the library include spherical harmonics such as P1, P3, SP3 and SP5 as well as the optically thin approximation. The performance of the different solution methods is compared for accuracy and speed as a tool for future model strategy selection.
An Improved Mixing-Plane Method for Analyzing Steady Flow Through Multiple-Blade-Row Turbomachines
Authors: Wang Ding Xi
Published: December 2013

Presented in this paper is an improved method for dealing with a mixing plane that exists between computational domains of two adjacent blade rows of a multiple-blade-row turbomachine. The method makes use of the semidiscrete flow equation updating scheme to convert flux differences across an interrow interface to conservative flow variable incrementals then to characteristic variable perturbations. Therefore, the proposed method bears more physics and is much more robust than any known method of its kind. As a result, reverse flow can be accommodated by this method naturally without any special treatment. Two existing methods are also included to provide a clear illustration of the differences and advantages of the new method. Two numerical test cases using a transonic compressor stage are presented to investigate the robustness of the new method and its influence on solution convergence, accuracy, and time cost in comparison with the two existing methods.
Eigenvalues and Eigenvalue Sensitivities of a Beam Supported by Viscoelastic Solids
Authors: Cha Philip D. , Carbon Kyle C. , Hsieh Richard
Published: December 2013

The eigenvalues and the first and second-order eigenvalue sensitivities of a uniform Euler–Bernoulli beam supported by the standard linear solid model for viscoelastic solids are studied in detail. A method is proposed that yields the approximate eigenvalues and allows the formulation of a frequency equation that can be used to obtain approximate eigenvalue sensitivities. The eigenvalue sensitivities are further exploited to solve for the perturbed eigenvalues due to system modifications, using both a first- and second-order Taylor series expansion. The proposed method is easy to formulate, systematic to apply, and simple to code. Numerical experiments consisting of various beams supported by a single or multiple viscoelastic solids validated the proposed scheme and showed that the approximate eigenvalues and their sensitivities closely track the exact results.
The Influence of Inaccuracies in Carotid MRI Segmentation on Atherosclerotic Plaque Stress Computations
Authors: Nieuwstadt Harm A. , Speelman Lambert , Breeuwer Marcel , van der Lugt Aad , van der Steen Anton F. W. , Wentzel Jolanda J. , Gijsen Frank J. H.
Published: December 2013

Biomechanical finite element analysis (FEA) based on in vivo carotid magnetic resonance imaging (MRI) can be used to assess carotid plaque vulnerability noninvasively by computing peak cap stress. However, the accuracy of MRI plaque segmentation and the influence this has on FEA has remained unreported due to the lack of a reliable submillimeter ground truth. In this study, we quantify this influence using novel numerical simulations of carotid MRI. Histological sections from carotid plaques from 12 patients were used to create 33 ground truth plaque models. These models were subjected to numerical computer simulations of a currently used clinically applied 3.0 T T1-weighted black-blood carotid MRI protocol (in-plane acquisition voxel size of 0.62 × 0.62 mm2) to generate simulated in vivo MR images from a known underlying ground truth. The simulated images were manually segmented by three MRI readers. FEA models based on the MRI segmentations were compared with the FEA models based on the ground truth. MRI-based FEA model peak cap stress was consistently underestimated, but still correlated (R) moderately with the ground truth stress: R = 0.71, R = 0.47, and R = 0.76 for the three MRI readers respectively (p < 0.01). Peak plaque stretch was underestimated as well. The peak cap stress in thick-cap, low stress plaques was substantially more accurately and precisely predicted (error of −12 ± 44 kPa) than the peak cap stress in plaques with caps thinner than the acquisition voxel size (error of −177 ± 168 kPa). For reliable MRI-based FEA to compute the peak cap stress of carotid plaques with thin caps, the current clinically used in-plane acquisition voxel size (∼0.6 mm) is inadequate. FEA plaque stress computations would be considerably more reliable if they would be used to identify thick-cap carotid plaques with low stresses instead.
Measurement of Spatiotemporal Intracellular Deformation of Cells Adhered to Collagen Matrix During Freezing of Biomaterials
Authors: Ghosh Soham , Craig Dutton J. , Han Bumsoo
Published: December 2013

Preservation of structural integrity inside cells and at cell-extracellular matrix (ECM) interfaces is a key challenge during freezing of biomaterials. Since the post-thaw functionality of cells depends on the extent of change in the cytoskeletal structure caused by complex cell-ECM adhesion, spatiotemporal deformation inside the cell was measured using a newly developed microbead-mediated particle tracking deformetry (PTD) technique using fibroblast-seeded dermal equivalents as a model tissue. Fibronectin-coated 500 nm diameter microbeads were internalized in cells, and the microbead-labeled cells were used to prepare engineered tissue with type I collagen matrices. After a 24 h incubation the engineered tissues were directionally frozen, and the cells were imaged during the process. The microbeads were tracked, and spatiotemporal deformation inside the cells was computed from the tracking data using the PTD method. Effects of particle size on the deformation measurement method were tested, and it was found that microbeads represent cell deformation to acceptable accuracy. The results showed complex spatiotemporal deformation patterns in the cells. Large deformation in the cells and detachments of cells from the ECM were observed. At the cellular scale, variable directionality of the deformation was found in contrast to the one-dimensional deformation pattern observed at the tissue scale, as found from earlier studies. In summary, this method can quantify the spatiotemporal deformation in cells and can be correlated to the freezing-induced change in the structure of cytosplasm and of the cell-ECM interface. As a broader application, this method may be used to compute deformation of cells in the ECM environment for physiological processes, namely cell migration, stem cell differentiation, vasculogenesis, and cancer metastasis, which have relevance to quantify mechanotransduction.
Injection Pump Analysis
Authors: Schultz William W. , Johnsen Eric , Han Bosuk , Park Sung
Published: December 2013

An injection pump is one of the simplest mechanics devices imaginable with no moving parts and a very simple geometry. We examine the device performance for steam injectors using primarily a control volume analysis and consider to what extent this simplified analysis represents optimal performance. We seek the rationale for performing CFD studies and develop optimization scenarios.
Modelling and Control of a Hydraulically Actuated Shaking Table Employed for Vibration Absorber Testing
Authors: Pagano Stefano , Russo Riccardo , Strano Salvatore , Terzo Mario
Published: December 2013

This paper presents an activity concerning the modelling and control of an unidirectional electro-hydraulically actuated table adopted to test vibration isolators. The test rig consists of a hydraulic actuation system that drives a sliding table mounted on linear bearings. The system is characterized by nonlinearities such as valve dead zone and frictions. A nonlinear model is derived and then employed for parameters identification procedure. The results concerning the model validation are illustrated. They fully confirm the effectiveness of the proposed model able to capture the system behavior.

The testing procedure of the isolation systems is based on the definition of a target displacement time history of the table and, consequently, the precision of the table positioning is of primary importance. In order to minimize the positioning error, a suitable control system has to be adopted. The system non-linearities limit highly the performances of the classical linear control, so a non-linear one is proposed. The sliding table mathematical model is employed for a non-linear control design able to minimize the error between the target position and the current one. The controller synthesis is made taking into account no isolator under test. The proposed approach consists in a non-linear optimal control based on the state-dependent Riccati equation (SDRE). Numerical simulations have been performed in order to evaluate the goodness of the designed control with and without the specimen under test. The results confirm that the performances of the proposed non-linear controller are not invalidated because of the presence of the specimen and highlight the controller robustness.
Determination of Pressure in the Mold Cavity of Injected Semi-Crystalline Thermoplastics
Authors: Tardif Xavier , Sobotka Vincent , Boyard Nicolas , Le Bot Philippe , Delaunay Didier
Published: December 2013

Injection molding is the most used process for thermoplastic part manufacturing. This process is commonly divided into four steps: injection, packing, cooling and ejection. During the packing step, an amount of material gets into the mold cavity to compensate for shrinkage of the polymer mainly due to the crystallization. Once the gate is frozen, polymer is subjected to isochoric cooling while the pressure of the polymer is higher than atmospheric pressure. Improving the quality of the injected part requires prediction of the shrinkage, warpage and residual stress and pressure impacts deeply on the morphology and consequently on the shape of the final part. The pressure decrease during the isochoric phase also determines the ejection time. However, description of the behavior of the polymer during packing and isochoric steps needs an accurate model that considers coupling between heat transfer and crystallization and also a good knowledge of the behavior (specific volume and crystallization kinetics) of the polymer under high pressure. Some studies have already underlined the influence of shear rate on the kinetics of crystallization. Here, based on a pressure analysis and an experimental-numerical comparison, we confirm crystallization is strongly coupled to flow history.
Nonlinear Controller for a Modified Design of the Ball and Beam System
Authors: Salas Oscar , Riachy Samer , Barbot Jean-Pierre
Published: December 2013

The global stabilization of the classical ball & beam has been approached in the literature through saturated control which imposes restrictions on the reactivity of the closed loop. In this work a modified design for the classical ball & beam system is presented. The beam is driven by two actuators (see figure 1). In comparison to the classical system, this design offers an additional degree of freedom which is the vertical motion of the beam. We show that the new design offers the possibility to get rid of the closed loop low reactivity restriction. We propose two nonlinear controllers to steer the trajectories of the system towards a final desired position. The first controller adapts, to the new design, existing controllers from the literature for the classical ball & beam. The second controller uses the additional degree of freedom to provide a faster stabilization.
Mathematical Modelling and Parameter Identification of an Electro-Magneto-Mechanical Actuator for Vibration Control
Authors: Darula Radoslav , Stein George Juraj , Kallesøe Carsten Skovmose , Sorokin Sergey
Published: December 2013

An electro-magneto-mechanical system, composed of the electromagnet, having an iron core with a coil and a movable yoke, is analyzed in the paper. Exposing the yoke to mechanical motion, the variation of the magnetic flux due to change of the air gap height induces alternating voltage at the coil terminals. If the electrical circuit is closed, the so generated electrical power is dissipated via the internal coil losses, treated in this paper. Thanks to the interaction between the electrical and mechanical system (i.e. via magnetic force), the power dissipation in electrical circuit influences the dynamical response of the mechanical system. And so the mechanical vibrations can be controlled by these means.

The mathematical model of the simplified dynamical system, which describes behavior of the experimental set-up, is derived using a lumped parameter approach.

The aim of the article is to identify parameters of the derived mathematical model, focused mainly on electrical circuit. Based on measured experimental data, the static constants as well as dynamic losses were analyzed.
Uncertainty Quantification in Computational Nonlinear Elasticity
Authors: Capiez-Lernout E. , Soize C. , Mignolet M.-P.
Published: December 2013

This work presents a methodology for the construction of an uncertain nonlinear computational model adapted to the static analysis of a complex mechanical system. The deterministic nonlinear computational model is constructed with the finite element method using a total Lagrangian formulation. The finite element nonlinear response is then considered as a reference deterministic solution from which a reduced-order basis is constructed using the POD (Proper Orthogonal Decomposition) methodology. The mean reduced nonlinear computational model is thus obtained by projecting the reference deterministic solution on this basis. The explicit construction of the mean reduced nonlinear computational model is proposed for any type of structure modeled with three-dimensional solid finite elements. A procedure for the robust identification of the uncertain nonlinear computational model with respect to experimental responses is then given. Finally, the methodology is applied to a structure for which simulated experiments are given.
Optimal Spring Balancing Cylinder Design of an Industrial Robot Using Multi-Disciplinary and Multi-Objective Optimization
Authors: Weström Jakob , Feng Xiaolong , Andersson Hans , Lunderius Stefan
Published: December 2013

This article presents an automated approach in optimal design of the spring balancing cylinder of an industrial robot using multi-disciplinary and multi-objective design optimization.

Spring balancing cylinder is a mechanical device typically used in industrial robots of high load handling capacity. The objective of use of such device is to effectively balance one of main axes (typically axis-2) subject to the most severe gravitational torque.

The spring balancing cylinder consists typically of multiple springs (two or three) co-axially installed inside the cylinder. Design of such balancing device involves about 16 design parameters, including both geometric parameters (free length, wire diameter, spring outer diameter, and number of turns) and parameters defining mounting positions of the device on a robot. Optimal design of such device is to achieve desired balancing, measured by maximum unbalanced static torque of the balanced axis, with minimum weight and volume of the cylinder. More desirably, the trade-off relationship between the maximum static torque measured by a balancing degree index and weight of the balancing cylinder is explored. Design of such balancing device is subject to a number of hard constraints defining fatigue lifetime of the springs and geometric interference between adjacent springs both in radial and axial directions.

Solving of this design problem requires use of two different design tools. The first design tool is a robot static design tool. The entire robot statics is modeled. The maximum static torque of the balanced axis is calculated by finding the maximum value of static torques of the axis as function rotational angles of the axis within its limits. The maximum static torque is used as one of the design objectives. The second design tool is a detailed spring dimensioning tool. The overall spring constant and pre-loading force are determined subject to constraints of geometric and fatigue lifetime. The integration of the design tools is accomplished using a commercial software tool modeFrontier.

This challenging design problem is formulated into an optimization problem of mixed design variables, multi-objective and multi-constraint nature and solved fully automatically using Multi-Objective Genetic Algorithm (MOGA) implemented in the modeFrontier modeling and optimization environment. The trade-off relationship between the balancing degree and the weight of the springs have been quantitatively explored. Even though some limitations of the developed methodology do exist and need further improvement, it is convinced that the developed approach is ready to be applied in industrial design practice.
Setup of Virtual Experiments and Critical Analysis of Conventional Thermoeconomic Diagnosis of Multiple Faults in Air-Condensed Rooftop Systems
Authors: Piacentino Antonio , Talamo Miriam
Published: December 2013

The diagnosis of soft faults in vapor compression cooling systems is a crucial activity, since malfunctions may provoke heavy degradation in plant performance and increase the power consumption for space cooling. Among the various Faults Detection and Diagnosis techniques developed over the last two decades, thermoeconomic diagnosis has been playing only a marginal role due to the difficulties encountered when applying the conventional thermoeconomic approaches to vapor compression refrigeration plants. In this paper a critical analysis on capabilities and limits of thermoeconomic diagnosis of refrigeration systems is proposed. The reference plant assumed for this study is a 116 kWc air-condensed rooftop systems charged with R407C as refrigerant. A reliable 1-D steady-state simulator is used to calculate thermodynamic and performance data in “off-design” operating conditions; since the simulator has no specific capabilities to simulate faulty systems, literature-derived results were used to adjust the input settings for each specific fault simulated. Among the most common faults in rooftop air conditioners, four different malfunctions are examined: fouling at condenser, fouling at evaporator, refrigerant undercharge (either due to leakage or erroneous charging during service) and extra-superheating along the suction line; the faults are imposed both individually and simultaneously. The thermoeconomic diagnosis is performed basing on the “fuel impact” approach; the need to split physical exergy into its thermal and mechanical fractions and the presence of dissipative components suggested us to formulate some methodological premises, discussed in detail in the paper. The results testify that the adopted conventional approach is not very reliable; although some faults are properly identified, in fact, false fault signals and erroneous causalization eventually resulted, due to the presence of system-level faults (i.e. faults not strictly associated with any specific plant component, like refrigerant undercharge), the subjective assumptions made as concerns the cost allocation of residues and some controversial aspects concerning the productive structure.
Evaluation of Drivers’ Attention Level by a Driving Simulator
Authors: Bartolozzi Riccardo , Frendo Francesco
Published: December 2013

Diagnosis systems for evaluating driver’s attention level have become very important in the last years and have gained an increasing attention from automotive manufacturers; indeed, traffic crashes represent worldwide one of the main public health problems and many accidents are demonstrated to be due to drivers’ hypovilance. In this work a driving simulator and specific test tools were developed to validate the possibility of monitoring the drivers’ attention level and capability.

The driving simulator is equipped with a fixed cockpit and a single front screen. The cockpit reproduces the man-machine interface of a typical medium class car with automatic transmission, i.e. the driver interacts with the simulator by means of the throttle and brake pedals and the steering wheel. The pedals are endowed with passive feedback systems, whereas an electric motor applies an active feedback torque on the steering wheel.

From the software point of view, the simulator is managed by four PCs connected by a LAN. Two of them are dedicated to the simulation of vehicle dynamics and for data logging, while the other two run the graphical scenario software. This includes a motorway area connected to an urban area with an autonomous traffic.

The vehicle model was built with a block architecture in the Matlab/Simulink environment and is run in real-time by using the xPC Target toolbox. A specific block, consisting of an in-house developed 14 d.o.f. model, was set up to represents vehicle dynamics.

The driving simulator is currently employed in experimental campaigns acquiring about 60 signals of driver’s input and vehicle quantities. In order to evaluate the drivers’ attention level, two specific tests were developed, which aim at measuring the drivers’ reaction time and ability in sudden events such as a brake manoeuvre or a sudden lateral skid.

In the paper the driving simulator hardware and software are presented. The tests procedures, which were developed to investigate the driver’s attention, are also discussed with reference to some tests.
CFD Evaluation of the Pressure Losses in a Reciprocating Compressor: A Flexible Approach
Authors: Balduzzi Francesco , Ferrara Giovanni , Babbini Alberto , Pratelli Guido
Published: December 2013

Pressure losses in the suction and discharge components of a reciprocating compressor are the main irreversibilities that affect the global system efficiency; their prediction is a critical issue for the evaluation of the absorbed power.

Flow coefficients for automatic valves are often derived from experimental data obtained on a dedicated test bench. Conversely, there is a lack of information concerning the flow behavior in the other components along the gas path and their losses are often taken into account by correcting the valve’s flow coefficient by means of an empirical correlation.

CFD simulation of the entirety of the suction and discharge systems is a viable alternative for the prediction of the global pressure losses, although these simulations are very demanding in terms of computational resources.

This paper presents an approach to reducing the computational effort required to perform the CFD analysis of a reciprocating compressor.

A set of CFD simulations with different suction system geometry configurations has been performed in order to evaluate the dependence of a component pressure loss on the losses of the upstream components. The losses along the suction system can then be evaluated separately from the valve loss by neglecting the presence of the valve itself. The valve can be replaced by an equivalent porous region that straightens the outgoing flow. This approach leads to a decrease in both the mesh size and complexity, and an increase in general applicability.
A Regression Based Non-Intrusive Method Using Separated Representation for Uncertainty Quantification
Authors: Rai Prashant , Chevreuil Mathilde , Nouy Anthony , Sen Gupta Jayant
Published: December 2013

This paper aims at handling high dimensional uncertainty propagation problems by proposing a tensor product approximation method based on regression techniques. The underlying assumption is that the model output functional can be well represented in a separated form, as a sum of elementary tensors in the stochastic tensor product space. The proposed method consists in constructing a tensor basis with a greedy algorithm and then in computing an approximation in the generated approximation space using regression with sparse regularization. Using appropriate regularization techniques, the regression problems are well posed for only few sample evaluations and they provide accurate approximations of model outputs.
Numerical Simulation Based on Meshless Formulation: Application to 2D Solid Mechanics
Authors: Ghozzi Y. , Labergere C. , Villon P.
Published: December 2013

This paper presents the development of Meshless Methods based on Moving Least Square Approximation (MLSA) [3][10][14]. In the case of solid mechanics, the shape displacement functions are computed for each node with a centered scheme approximation [3][12] associated with a specific weight function [10]. Both interpolated and approximated weight functions are studied [10][9][15]. We propose to build a new C1 weight function based on a 2d boundary line. The Galerkin Method is used to solve the mechanical equilibrium balance problems [14]. A 2-dimensional example is presented to validate the Meshless Method.
Effects of Microjets in Flow Over a Backward-Facing Step
Authors: Kanchi H. , Mashayek F.
Published: December 2013

Large eddy simulation is used to study the flow over a backward-facing step interacting with a periodic array of streamwise microjets emenating from the step at a 45° angle to the step face. Averaged streamwise velocity profiles are in good agreement with experimental data. A well defined turbulent inlet profile for the microjet is found to be important to obtain correct streamwise normal fluctuations near the step. To simulate cases as per the experimental setup a microjet inlet pipe section is necessary for the simulations. The studies with passive scalars need to be conducted to quantify scalar mixing. The monotonicity problem of simulating passive scalar can be overcome by simply clipping the unbounded values. This technique works because the volume occupied by overshoot values of passive scalar are small compared to the total volume of the backward-facing step geometry.
Optimization of the Global Static and Dynamic Performance of a Vehicle Body by Means of Response Surface Models
Authors: Mihaylova Pavlina , Pratellesi Alessandro , Baldanzini Niccolò , Pierini Marco
Published: December 2013

Concept FE models of the vehicle structure are often used to optimize it in terms of static and dynamic stiffness, as they are parametric and computationally inexpensive. On the other hand they introduce modeling errors with respect to their detailed FE equivalents due to the simplifications made. Even worse, the link between the concept and the detailed FE model can be sometimes lost after optimization.

The aim of this paper is to present and validate an alternative optimization approach that uses the detailed FE model of the vehicle body-in-white instead of its concept representation. Structural modifications of this model were applied in two different ways — by local joint modifications and by using mesh morphing techniques. The first choice was motivated by the strong influence of the structural joints on the global vehicle performance. For this type of modification the plate thicknesses of the most influent car body joints were changed. In the second case the overall car dimensions were modified.

The drawback of using detailed FE models of the vehicle body is that they can be times bigger than their concept counterparts and can thus require considerably more time for structural analysis. To make the approach proposed in this work a feasible alternative for optimization in the concept phase response surface models were introduced. With them the global static and dynamic performance of the body-in-white was represented by means of approximating polynomials. Optimization on such mathematical models is fast, so the choice of the optimization algorithm is not limited only among local-search strategies.

In the current study Genetic Algorithm was used to increase the chances for finding better design alternatives. Two different optimization problems were defined and solved. Their final solutions were presented and compared in terms of structural modifications and resulting responses. The approach in this paper can be successfully used in the concept phase as it is fast and reliable and at the same time it avoids the problems typical for concept models.