bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulations of Compressible Multiphase Flows Through a Tube of Varying Cross-Section
Authors: Jolgam Shaban A. , Ballil Ahmed R. , Nowakowski Andrzej F. , Nicolleau Franck C. G. A.
Published: December 2013

The simulation of multiphase compressible flows through high pressure nozzles is presented. The study uses the developed numerical approach. There are many important engineering applications which are concerned with multiphase flows and convergent-divergent nozzles. This work presents the developed extension of the model and numerical algorithm based on the so called parent model earlier introduced by Saurel and Abgrall [Saurel, R. and Abgrall, R., A Multiphase Godunov Method for Compressible Multifluid and Multiphase Flows, J. Comput. Phys. 150 (1999), 425–467]. This model which consists of conservation laws for each phase complemented with the volume fraction evolution equation is modified by adding a source term to simulate area variation. The model is strictly hyperbolic and non-conservative due to the existence of non-conservative terms. The model is able to deal with compressible and incompressible flows. Moreover, it can deal with mixtures and pure fluids, where each fluid has its own pressure and velocity. The presence of velocity and pressure relaxation terms in the governing equations has made the velocity and pressure relaxation processes essential to tackle the boundary conditions at the interface. The interface separating phases is considered as a numerical diffusion zone in this method. The model is solved using an efficient Eulerian numerical method. A second order Godunov-type scheme with approximate Riemann solver is used to enable capturing of a physical interface by the resolution of the Riemann problem. The solution is obtained by splitting the hyperbolic part and source terms parts in the numerical algorithm. The source terms, including relaxation parts of the model, are tackled in succession using Strang splitting technique. The governing equations are solved at each computational cell using the same numerical algorithm for the whole domain including the interface. The main aim of this work has been to study different flow regimes with respect to pressure boundary conditions through the numerical solutions of single and multiphase flows. The performance of the programme has been verified via well established benchmark test problems for multiphase flows.
Modelling Local Dynamic Pressure Within Inflatable Sports Balls
Authors: Hanson Henry , Harland Andy , Holmes Chris , Price Dan , Lucas Tim
Published: December 2013

This study used a coupled Eulerian Lagrangian (CEL) approach to model the air within a football (soccer ball) during two types of impacts. Conventional modelling techniques (and those used in all previous football finite element models known by the author) utilize a uniform pressure method incapable of accounting for spatial pressure variation. Internal pressures and deformations for the CEL and uniform pressure models were within a few percent of each other, indicating good agreement between pressurization techniques. By necessity, the air was defined with different methods in each model and this may have contributed to a discrepancy in maximum internal pressure. Using the CEL model, the pressure wave generated at impact was observed to travel from one side of the ball to the other at the speed of sound. Though the CEL model helped illustrate the impact scenario, there were no clear distinctions that gave it an advantage over the uniform pressure method for simple impact analysis.
Real-Time Control of the Heating of an Airfoil
Authors: Rétat-Masson Francoise , Chinesta Francisco , Leygue Adrien , Cueto Elias , Dala Laurent , Law Craig
Published: December 2013

Dynamic Data-Driven Application Systems constitute nowadays one of the most challenging applications of simulation-based Engineering Science [1]. DDDAS imply a set of techniques that allow the linkage of simulation tools with measurement devices for real-time control of systems and processes [2]. DDDAS entails the ability to dynamically incorporate additional data into an executing application, and in reverse, the ability of an application to dynamically steer the measurement process. These systems need accurate and fast simulation tools, hence the off-line computations to limit as much as possible the on-line computations. In order to obtain the most efficient solver, all the sources of variability are introduced as extra-coordinates as to solve only once the model off-line to obtain its most general solution to be then considered in on-line purpose. However, such models result defined in highly multidimensional spaces. A technique recently proposed, called Proper Generalized Decomposition [3], allows circumventing this redoubtable curse of dimensionality.
Emblematic Gestures Recognition
Authors: Chellali Ryad , Renna Ilaria
Published: December 2013

This paper presents a framework allowing emblematic gestures detection, segmentation and their recognition for human-robots interaction purposes. This framework is based on a new coding of arms’ kinematics reflecting both the muscular activity of the performer and the appearance of arm seen by the recipient when a gesture is performed. Following that, gestures can be seen as sequences of torques activations leading arm’s parts to express a comprehensive meaning. In addition, these sequences have very stable topologies and shapes regardless to performers. This facilitates the generalization of the recognition process with a minimalistic learning effort for online usages. Promising results were obtained for a set of 5 classes of gestures performed by 19 different persons.
First Steps in the Space Separated Representation of Models Defined in Complex Domains
Authors: Ghnatios Chady , Ammar Amine , Cimetiere Alain , Hamdouni Aziz , Leygue Adrien , Chinesta Francisco
Published: December 2013

Separated representations allow substituting the resolution of 3D models by a sequence of three one-dimensional problems [1]. This route is especially suitable when models are defined in hexahedral domains. When it is not the case, different possibilities exist. In a former work [2], we explored the route of immersing the domain into a hexahedral domain, and then use a kind of penalty method to solve the model whilst enforcing the boundary conditions. In the present work, we are analyzing two alternative routes. The first one consists of using an inverse technique in order to compute the boundary conditions on the border of the hexahedra in which the complex domain is immersed. The second one consists in solving the model in a regular domain for a number of geometrical parameters considered as extra-coordinates from which we could have access to the solution in any geometry resulting from a choice of those parameters.
On a RSM Approach to the Multihead Weigher Configuration
Authors: Beretta Alessia , Semeraro Quirico
Published: December 2013

The multihead weigher is a complex machine which has to be properly configured and managed by taking into account the uncertainty of the load cells. Specifically, this paper focuses on the configuration problem of the multihead weigher First an objective function is proposed. This function considers both the costs of “non conforming” packages (i.e. packages that have to be scrapped or reworked because their weight is below the law lower limit) and the cost of extra product (i.e. cost of material that exceeds the target weight). Secondly, the paper presents an approach to select the average weight to be set for each hopper by combining a RSM (Response Surface Methodology) and a multihead weighing machine simulator. The performance of the proposed approach is presented and discussed.
Real-Time Simulation for Virtual Surgery in a PGD Framework
Authors: Niroomandi Siamak , Bordeu Felipe , Alfaro Iciar , Gonzalez David , Leygue Adrien , Cueto Elias , Chinesta Francisco
Published: December 2013

We analyze here the use of proper generalized decompositions (PGD) for real-time simulation of living soft tissues in virtual surgery environments. These tissues are usually modeled as hyperelastic solids, and therefore present important difficulties for their simulation under real-time constraints (i.e., feedback rates on the order of1 kHz).

PGD techniques provide with physics-based meta-models without any prior computer experiment, that can be used on-line for the simulation under such severe constraints. These metemodels are constructed on the assumption of the problem to be multi-dimensional, with parameters as additional space dimensions. These parameters, in this case, are taken as the position of contact of surgical tool and organ, modulus of the contact force and orientation (a 9D problem). PGD techniques allow to solve efficiently these high-dimensional problems without the burden associated to the application of mesh-based techniques to these problems.
Active Flow Control With an Oscillating Backward Facing Step
Authors: Cadirci Sertac , Gunes Hasan
Published: December 2013

An oscillatory, zero-net-mass flux actuator system, Jet and Vortex Actuator (JaVA), is implemented on the step wall of a backward facing step. JaVA is shown previously both experimentally and numerically that it can energize the boundary layer by creating jets or vortices thus it may delay flow separation when used properly. The main part of JaVA is a rectangular cavity with a moving actuator plate. The actuator plate is mounted asymmetrically inside the cavity of the JaVA box, such that there are one narrow and one wide gap between the plate and the box. The main governing parameters are the actuator plate’s width (b), the amplitude (a) and the operating frequency (f). The main target of the control with active jets on the step wall is to influence directly the main recirculation zone, thus as the actuator plate or the step’s vertical wall moves periodically in horizontal direction, a jet emerges into the recirculation zone. Non-dimensional numbers such as the scaled amplitude (Sa = 2πa/b) and the jet Reynolds number (ReJ = 4abf/ν) as well as the maximum cross flow velocity characterize the JaVA-induced flow types and effects on the recirculation zone. One period consists of one blowing and one suction phase into the recirculation zone. The actuator plate has a sinusoidal motion determined by the amplitude and the operating frequency. Time-averaged flow fields and boundary layer profiles for actuated and not actuated cases at various operating frequencies indicate the effect of active flow control. The control effectiveness is given by the ratio of the jet Reynolds number to the Reynolds number of the incoming flow (r = ReJ/Re). A transient finite-volume-based laminar, incompressible Navier-Stokes solver (Fluent) has been used to study the flow fields generated by JaVA. The computational domain consists of a moving zone along the channel and the motion of the actuator plate is generated by a moving grid imposing appropriate boundary conditions with User-Defined-Functions (UDF). Numerical simulations reveal the JaVA-boundary layer interaction in the narrow channel for various governing parameters such as frequencies (jet Reynolds numbers) and channel flow velocities (Reynolds numbers, Re = 200, 400 and 800). The proposed control method based on suction and blowing with an oscillating backward facing step (OsBFS) seems to be effective in shortening the recirculation zone length and delaying the flow separation downstream of the backward facing step.
Injection Pressures of a Bio-Oil Driven Non-Road Diesel Engine: Experiments and Simulations
Authors: Niemi Seppo , Kiijärvi Jukka , Laurén Mika , Hiltunen Erkki
Published: December 2013

The depletion of global crude oil reserves, increases in fossil fuel prices and environmental issues have encouraged the search for and study of bio-derived fuels. For years, fatty acid methyl esters (FAME) have already been used successfully. High-quality hydrogenated vegetable oil and Fischer-Tropsch biofuels have also been developed.

Fuel refining processes, however, consume energy increasing CO2 emissions. For profitability reasons, large-scale industrial production is also required. Several distributed energy producers are instead willing to utilize various local waste materials as fuel feedstock. The target is local fuel production without any complicated manufacturing processes.

Crude bio-oils are therefore also interesting fuel options, in particular for medium-speed diesel engines capable of burning such bio-oils without any major problems. Nevertheless, waste-derived crude bio-oils have also been studied in Finland in high-speed non-road diesel engines. One option has been mustard seed oil (MSO). Mustard has been cultivated in fallow fields. Non-food mustard seeds have been used for fuel manufacturing.

In the performed studies with MSO, the exhaust smoke and HC emissions decreased, NOx remained approximately constant, and the thermal efficiency was competitive compared with operation on ordinary diesel fuel oil (DFO). The number of exhaust particles tended, however, to increase and deposits were formed in the combustion chamber, particularly if the engine was also run at low loads with MSO. On the whole, the results were so promising that deeper analyses of engine operation with MSO were considered reasonable.

The kinematic viscosity of crude bio-oils is much higher than that of FAMEs or DFO. Consequently, the injection pressure tends to increase especially at the injection pump side of an in-line injection pump system. The flow characteristics of crude bio-oil also differ from those of DFO in the high-pressure pipe. With bio-oil, the flow seems to be laminar. The bulk modulus of bio-oils is also different from that of DFO affecting the rate of the injection pressure rise.

In the present study, a turbocharged, inter-cooled direct-injection non-road diesel engine was driven with a mixture of MSO (95%) and rape seed methyl ester (RME, 5%), and standard DFO. The engine was equipped with an in-line injection pump.

First, the injection pressures at pump and injector ends of the high-pressure injection pipe were measured for both fuels as a function of crank angle. Furthermore, a model was created for the injection system based on the method of characteristics.

Free software called Scilab was adopted for numerical simulation of the model. Despite a few limitations in the built model, the results showed clear trends and the model can be used to predict changes in the fuel injection process when the fuel is changed.
Numerical Investigation on the Thermal Performance Enhancement in a Latent Heat Thermal Storage Unit
Authors: Sciacovelli Adriano , Verda Vittorio , Colella Francesco
Published: December 2013

The present paper describes the application of computational fluid-dynamics (CFD) for the analysis of the melting process in a single vertical shell-and-tube heat exchanger. The computations are based on a 2D axial-symmetric model that takes in account the phase change phenomenon by means of the enthalpy method. The numerical studies aimed at clarifying the importance of the different heat transfer mechanisms with a particular focus on natural convection demonstrating its fundamental importance on the phase change process by enhancing the heat transfer between HTF and solid PCM. the paper discusses the effect of two different common performance enhancement techniques: dispersion of high conductive nano-particles in the PCM and the introduction of radial fins. An extensive thermo-fluid dynamic study has been undertaken exploring the effect on the thermal performance enhancement of particle volume fraction and fins. The analysis shows that in comparison to the standard design, the performances of the LHTS unit in terms of charging time could be improved by up to 40 % for nano-particle enhancement. When fins are considered charging time can be reduced to one-third of its original value. Significant improvements are also achieved during the solidification process: discharge time is reduced of 33% with fins enhancement.
The Role of Placental Locations on Fetus Mortality in Road Traffic Accidents
Authors: Moustafa Moustafa , Acar B. Serpil , Acar Memis
Published: December 2013

The aim of this study is to investigate the possible role of placental location on the risk of placental abruption in road traffic accidents involving a pregnant driver. Placental abruption accounts for around 50–70% of fetal deaths in motor vehicle accidents. The computational pregnant occupant model, ‘Expecting’, which has a multi-body fetus and a finite element uterus model was developed at Loughborough University and is used in this investigation.

The placenta is located in the upper region of the uterus near the fundus in ‘Expecting’. Four locations for the placenta; anterior, posterior, lateral left, lateral right cases are modelled and used in simulations in this study. These models are used to simulate a range of frontal impacts of severity 15 kph and 30 kph. Three cases of occupant restraint: three-point seatbelt with an airbag, three-point seatbelt only and airbag only conditions are investigated. The maximum strains developed in the uterus and utero-placental interface (UPI) have been estimated and compared for these scenarios in order to investigate placental abruption that leads to fetal loss. Placenta located at anterior position is found to be at higher risk than other positions considered.
Natural Element Simulation of Extrusion of Hollow Profiles
Authors: Alfaro Iciar , Gagliardi Francesco , Greco Francesco , Filice Luigino , Cueto E.
Published: December 2013

Numerical simulation of the extrusion of hollow profiles is a particularly challenging process due to the inherent flow patterns in this type of procedure. Aluminium must flow round the central part of the die and join again prior to exit the die. The quality of this welding line is highly affected by the mechanical conditions within the die, which depend crucially on geometry. In this paper we present a review of our work on the topic, where the Natural Element Method (NEM), a meshless technique, has been applied towards an efficient analysis of the conditions necessary to give a quality welding of the flows giving rise to the final geometry of the extrudate. The use of meshless methods is precisely the novel ingredient in our analysis, since it provides with an accurate description of the position of the flow front and the mechanical conditions (stress, strain, temperature) at the interface. Numerical results are also compared with experimental measures showing the impact of die geometry on the quality of the final design.
Design of a Recommender System Based on Customer Preferences: A Comparison Between Two Approaches
Authors: Jomaa Inès , Poirson Emilie , Da Cunha Catherine , Petiot Jean-François
Published: December 2013

This work addresses the design of a preference based system that suggests relevant products to customers. It aims at helping them with their purchase decision (on electronic commerce websites). A use case that consists in making spontaneous recommendations to the customers, on the basis of their previous ratings is described. The product considered to illustrate the approach is a comic. This paper is focused on two recommender approaches. The first approach, “the traditional” approach, is based on the collaborative filtering while the second approach, is based on a new proposed algorithm. Collaborative filtering is a technique to making recommendations by matching people with the same preferences (preferential similarity). The second approach which is proposed is a combination of the traditional collaborative filtering and the perceptual similarities approach between customers (perceptual similarity). Perceptive data include emotional, sensory and semantic ratings of the products. The purpose of this paper is to evaluate the performance of the proposed approach and to compare it with the traditional approach. A test procedure is thus implemented. It consists in simulating customers’ behavior according to a set of products, and to compute a performance criterion of the recommender system, measuring the relevance of the proposed products. The performance of the proposed algorithm is compared with that of the traditional one. The results show that the consideration of perceptual assessments of products by customers generally helps in the relevance of the propositions of the system.
Numerical Calculation of Two-Phase Flow Based on a Two-Fluid Model With Flow Regime Transitions
Authors: Chung Moon-Sun , Jung Youn-Gyu , Yi Sung-Jae
Published: December 2013

Numerical test and eigenvalue analysis for a two-phase channel flows for energy conversion systems like fuel cells or water electrolysers with flow regime transitions are performed by using the well-posed system of equation that takes into account the pressure jump at the phasic interface. The interfacial pressure jump terms derived from the definition of surface tension which is based on the surface physics make the conventional two-fluid model hyperbolic without any additive terms, i.e., virtual mass or artificial viscosity terms. The four-equation system has three sets of eigenvalues; each of them has an analytical form of real eigenvalues relevant to the sonic speeds with phasic velocities of three typical flow regimes such as dispersed, slug, and separated flows. Further, the eigenvalues for the flow transition regions can also be obtained numerically for smooth calculation of flow regime transitions. The sonic speeds agree well not only with the earlier experimental data but also with those of an analytical model. Owing to the hyperbolicity of this model, we can adopt an upwind method, which is one of the well-known Godunov type upwind methods. A typical example of two-phase flows shows that the present model can simulate the phase separation caused by density difference of two-phase fluids.
The MobilAR Robot, Ubiquitous, Unobtrusive, Augmented Reality Device
Authors: Bernier Emmanuel , Chellali Ryad , Thouvenin Indira Mouttapa
Published: December 2013

We present a new mobile Augmented Reality device that combines mobile robotics, human-robots interactions, and 3D modeling to augment users’ perception of their environment. The developed device, the MobilAR, provides minimally intrusive AR, where users do not need to wear any apparatus and no markers are used to align real and virtual entities. The mobilAR design is as follow: a projector is mounted on the end-effector of a robotic arm, itself mounted on a wheeled platform. The robotic arm allows to project undistorted content on any part of the environment such as walls, floor, ceiling and objects by using the right image transformation. The mobile base makes it possible to have the projector anywhere inside a building. The device uses self-localization and computer vision techniques to model the physical world and augment it. The mobilAR platform also encompasses a gesture recognition module for user interaction. As a proof-of-concept, we implemented a simple guided tour scenario of our laboratory where the MobilAR follows a user and projects contents on any surface. Results and extensions of this work are also discussed.
Non-Associative Finite Strain Plasticity Coupled With Anisotropic Ductile Damage for Metal Forming
Authors: Nguyen T. Dung , Badreddine Houssem , Saanouni Khémais
Published: December 2013

This paper presents the formulation of an advanced mechanical model describing a wide class of anisotropic elastoplastic constitutive equations accounting for the strong coupling with the anisotropic ductile damage. This model is developed within the framework of thermodynamics of irreversible processes with state variables and the continuum damage mechanics. The plastic anisotropy is accounted for through a non-associative theory for which a plasticity yield criterion and the plastic potential are defined separately but considering the strong coupling between both phenomena. The damage anisotropy is defined by using a second rank tensor. The effect of damage on the mechanical fields (stress, hardening, plastic strain, etc…) is described by a fourth rank damage effect operator that is defined in the context of the hypothesis of total energy equivalence. A rotating frame formulation is used to fulfil the objectivity of the constitutive equations under finite transformation. Finally, in order to illustrate the predictive capabilities of the model, the parametric studies with some simple loading case are investigated and the results discussed on the light of the anisotropic character of the ductile damage and its interaction with the anisotropy of plastic flow.
A Continuum Damage and Failure Model Based on Stress-State-Dependent Criteria
Authors: Brünig Michael , Gerke Steffen , Hagenbrock Vanessa
Published: December 2013

The paper deals with the effect of stress state on inelastic deformation and failure behavior of ductile solids. The continuum model takes into account stress-state-dependence of the damage and failure criteria with different branches corresponding to different micro-mechanical mechanisms depending on the stress triaxiality and the Lode parameter. Basic material parameters are identified using various tests with smooth and differently notched tension and shear specimens. To get more insight in the complex damage and failure mechanisms on the micro-scale additional series of three-dimensional micro-mechanical numerical analyses of void-containing unit cells have been performed. These calculations cover a wide range of stress triaxialities and Lode parameters in tension, shear and compression domains. The numerical results are used to discuss general trends, to develop equations for the damage and failure criteria, and to identify corresponding parameters of the continuum model.
Multidimensional Hyper-Reduction of Large Mechanical Models Involving Internal Variables
Authors: Ryckelynck David
Published: December 2013

We propose to incorporate a Response Surface (RS) approximation of variables over a parametric domain into a weak form of parametric Partial Differential Equations (PDEs). Hence a multidimensional model-reduction can be achieved. We propose a multidimensional a priori model reduction method to generate or to enrich RSs. It is coined multidimensional because the fields to forecast are defined over an augmented domain in term of dimension. They are functions of both space variables and parameters that simultaneously evolve in time. This changes the functional space related to the weak form of the PDEs and the definition of the reduced bases. It has a significant impact on the proposed model reduction method. In particular, a new point of view on interpolation of variables has to be addressed. A Multidimensional Reduced Integration Domain (MRID) is proposed to reduce the complexity of the reduced formulation. A multidimensional Hyper-Reduction method extract from the MRID truncated equilibrium equations, truncated residuals and a truncated error indicator.
Ecological Interface for Assessing Cardiac Disease
Authors: McEwen Tim , Flach John , Elder Nancy
Published: December 2013

Using the ecological interface design approach, a graphical user interface was developed to show how different factors (e.g., LDL, HDL, triglycerides, systolic blood pressure) contribute to cardiac health. The display is based on an epidemiological model derived from the Framingham study and additional treatment guidelines in the medical literature. This interactive display allows physicians and patients to see how different factors contribute to overall cardiac health and to see the impact of interventions on reducing risk. The display also graphically associates the state of the patient with treatment categories to help physicians to select the best treatment method based on empirical models. It also has the potential to enrich the dialogue between physician and patient through interactive ‘experiments’ that illustrate the potential benefits of various treatment options.
A Data Compression Approach for PGD Reduced-Order Modeling
Authors: Néron David , Ladevèze Pierre
Published: December 2013

This work concerns the Proper Generalized Decomposition (PGD) which is used to solve problems defined over the time-space domain and which are possibly nonlinear. The PGD is an a priori model reduction technique which allows to decrease CPU costs drastically by seeking the solution of a problem in a reduced-order basis generated automatically by a dedicated algorithm. The algorithm which is used herein is the LATIN method, a non incremental iterative strategy which enables to generate the approximations of the solution over the entire time-space domain by successive enrichments. The problematics which is addressed in this paper is the construction of the resulting reduced-order models along the iterations, which can represent a large part of the remaining global CPU cost. To make easier the construction of these models, we propose an algebraic framework adapted to PGD which allows to define a “compressed” version of the data. The space of the compressed fields exhibits some very interesting properties that lead to an important increase of the performances of the global strategy.
Task Based Pose Optimization of Modular Mobile Manipulators
Authors: He Liang , Phillips Sean , Waslander Steven , Melek William
Published: December 2013

We propose a task based pose optimization method for modular mobile manipulators. The modular mobile manipulators are designed and prototyped by researchers at University of Waterloo. The intended application of the modular mobile manipulator is to assist urban search and rescue in unstructured environments. A single mobile manipulator with limited capability cannot achieve complex tasks in this application. When several modular mobile manipulators are linked to one another, they can perform complex tasks through decentralized collaboration. The focus of this research is to develop and simulate a task based pose optimization algorithm for several mobile robots linked by dexterous arms. A genetic algorithm is a bio-inspired optimization technique that mimics the process of evolution. In nature, many living organisms, such as ants and birds use genetic algorithms to forge for food and achieve complex tasks. The advantages of the genetic algorithm are its simplicity and effectiveness. The proposed genetic algorithm in this research optimizes the manipulability measure of the onboard mechanical manipulator arms. To verify the proposed task based pose optimization algorithm, a formation of three mobile manipulators serially connected through their onboard mechanical manipulators is considered in this research. The control architecture is organized into a three level hierarchy. On the top level, a human operator sends guiding commands to the lead module in the formation through a wireless communication channel. The median level control aims at optimizing the manipulator pose. The base level control is established with the input-output linearization. To add realistic considerations into the simulation environment, fractal terrains are generated with the popular Diamond-Square algorithm. The inclination angle of each mobile manipulator on the terrain is estimated through a four-point terrain-matching algorithm. The simulation is completed in MATLAB. Repetitive simulations are pursued in this research to confirm the simplicity and effectiveness of our approach to control machines that interact with the natural environment. The simulation program established in this research serves as a test environment for the task based pose optimization of modular mobile manipulators. The major contributions of this research are the optimization algorithm and the novel hardware design for the specified tasks.
Silencer With Tunable Resonators for Active Noise Control
Authors: Cherrier Olivier , Pommier-Budinger V.
Published: December 2013

The article deals with active noise control and presents a silencer made of tunable acoustic resonators to reduce variable tonal noises. The silencer is composed of baffles with acoustic resonators made of two superposed and identically perforated plates associated with cavities. One of the plates is mobile and its displacement is controlled by an electromechanical system, allowing changing the internal shapes of the holes of the perforated layers. Consequently the impedance of the resonators and their resonance frequencies can be controlled. These tunable resonators can be used for noise control of variable tonal noises such as those generated by fans for example. The advantages of the proposed system are the simplicity of the actuation and the compactness of the system.
Carriage of Clostridium difficile by Wild Urban Norway Rats (Rattus norvegicus) and Black Rats (Rattus rattus)
Authors: Himsworth Chelsea G. , Patrick David M. , Mak Sunny , Jardine Claire M. , Tang Patrick , Weese J. Scott
Published: December 2013

Clostridium difficile
is an important cause of enteric infections in humans. Recently, concerns have been raised regarding whether animals could be a source of
C. difficile
spores. Although colonization has been identified in a number of domestic species, the ability of commensal pests to serve as a reservoir for
C. difficile
has not been well investigated. The objective of this study was to determine whether urban rats (
Rattus
spp.) from Vancouver, Canada, carry
C. difficile
.
Clostridium difficile
was isolated from the colon contents of trapped rats and was characterized using ribotyping, toxinotyping, and toxin gene identification. Generalized linear mixed models and spatial analysis were used to characterize the ecology of
C. difficile
in rats.
Clostridium difficile
was isolated from 95 of 724 (13.1%) rats, although prevalence differed from 0% to 46.7% among city blocks. The odds of being
C. difficile
positive decreased with increasing weight (odds ratio [OR], 0.67; 95% confidence interval [CI], 0.53 to 0.87), suggesting that carriage is more common in younger animals. The strains isolated included 9 ribotypes that matched recognized international designations, 5 identified by our laboratory in previous studies, and 21 “novel” ribotypes. Some strains were clustered geographically; however, the majority were dispersed throughout the study area, supporting environmental sources of exposure and widespread environmental contamination with a variety of
C. difficile
strains. Given that urban rats are the source of a number of other pathogens responsible for human morbidity and mortality, the potential for rats to be a source of
C. difficile
for humans deserves further consideration.
An
rhs
Gene Linked to the Second Type VI Secretion Cluster Is a Feature of the Pseudomonas aeruginosa Strain PA14
Authors: Jones Cerith , Hachani Abderrahman , Manoli Eleni , Filloux Alain
Published: December 2013

The type VI secretion system (T6SS) of Gram-negative bacteria has been involved in various processes, notably bacterial competition and eukaryotic cell subversion. Most
Pseudomonas aeruginosa
strains possess three T6SS gene clusters, but only the function of the first T6SS (H1-T6SS) has been clearly elucidated. It is involved in the secretion of three toxins (Tse1 to -3) that target bacterial competitors. In the case of the H2- and H3-T6SS, no clear function has been assigned, and only one effector has been associated with these systems. Yet the H2-T6SS was proposed to promote
P. aeruginosa
internalization in nonphagocytic epithelial cells. Although the H2-T6SS genetic organization is conserved across
P. aeruginosa
isolates, one feature is the presence of an additional transcriptional unit in the PA14 strain H2-T6SS cluster, which is divergent from the core H2-T6SS genes. A specific set of four genes encodes an Hcp protein (Hcp2), a VgrG protein (VgrG14), an Rhs element (PA14_43100 or RhsP2), and a protein with no homologies with previously characterized proteins (PA14_43090). In this study, we engineered a
P. aeruginosa
PA14 strain carrying an arabinose-inducible H2-T6SS on the chromosome. We showed that arabinose induction readily promotes assembly of the H2-T6SS, as seen by monitoring Hcp2 secretion. We further studied the secretion fate of VgrG14 and RhsP2, but these were not detectable in the extracellular medium. We finally investigated whether activation of the PA14 H2-T6SS gene cluster could influence phenotypic traits such as internalization in eukaryotic cells, and we reported noteworthy differences compared to strain PAO1, which may be accounted for by the described genetic differences.
Essentiality of DevR/DosR Interaction with SigA for the Dormancy Survival Program in Mycobacterium tuberculosis
Authors: Gautam Uma S. , Sikri Kriti , Vashist Atul , Singh Varshneya , Tyagi Jaya S.
Published: December 2013

The DevR/DosR regulator is believed to play a key role in dormancy adaptation mechanisms of
Mycobacterium tuberculosis
in response to a multitude of gaseous stresses, including hypoxia, which prevails within granulomas. DevR activates transcription by binding to target promoters containing a minimum of two binding sites. The proximal site overlaps with the SigA −35 element, suggesting that DevR-SigA interaction is required for activating transcription. We evaluated the roles of 14 charged residues of DevR in transcriptional activation under hypoxic stress. Seven of the 14 alanine substitution mutants were defective in regulon activation, of which K191A, R197A, and K179A+K168A (designated K179A*) mutants were significantly or completely compromised in DNA binding. Four mutants, namely, E154A, R155A, E178A, and K208A, were activation defective in spite of binding to DNA and were classified as positive-control (pc) mutants. The SigA interaction defect of the E154A and E178A proteins was established by
in vitro
and
in vivo
assays and implies that these substitutions lead to an activation defect because they disrupt an interaction(s) with SigA. The relevance of DevR interaction to the transcriptional machinery was further established by the hypoxia survival phenotype displayed by SigA interaction-defective mutants. Our findings demonstrate the role of DevR-SigA interaction in the activation mechanism and in bacterial survival under hypoxia and establish the housekeeping sigma factor SigA as a molecular target of DevR. The interaction of DevR and RNA polymerase suggests a new and novel interceptable molecular interface for future antidormancy strategies for
Mycobacterium tuberculosis
.
Interactions between microfinance programmes and non-economic empowerment of women associated with intimate partner violence in Bangladesh: a cross-sectional study
Authors: Dalal Koustuv , Dahlström Örjan , Timpka Toomas
Published: December 2013

Objective

This study aims to examine the associations between microfinance programme membership and intimate partner violence (IPV) in different socioeconomic strata of a nationally representative sample of women in Bangladesh.

Methods

The cross-sectional study was based on a nationally representative interview survey of 11 178 ever-married women of reproductive age (15–49 years). A total of 4465 women who answered the IPV-related questions were analysed separately using χ2tests and Cramer's V as a measure of effect size to identify the differences in proportions of exposure to IPV with regard to microfinance programme membership, and demographic variables and interactions between microfinance programme membership and factors related to non-economic empowerment were considered.

Results

Only 39% of women were members of microfinance programmes. The prevalence of a history of IPV was 48% for moderate physical violence, 16% for severe physical violence and 16% for sexual violence. For women with secondary or higher education, and women at the two wealthiest levels of the wealth index, microfinance programme membership increased the exposure to IPV two and three times, respectively. The least educated and poorest groups showed no change in exposure to IPV associated with microfinance programmes. The educated women who were more equal with their spouses in their family relationships by participating in decision-making increased their exposure to IPV by membership in microfinance programmes.

Conclusions

Microfinance plans are associated with an increased exposure to IPV among educated and empowered women in Bangladesh. Microfinance firms should consider providing information about the associations between microfinance and IPV to the women belonging to the risk groups.
Suitability of emergency department attenders to be assessed in primary care: survey of general practitioner agreement in a random sample of triage records analysed in a service evaluation project
Authors: Thompson Mary I W , Lasserson Daniel , McCann Lloyd , Thompson Matthew , Heneghan Carl
Published: December 2013

Objectives

To assess the proportion of emergency department (ED) attendances that would be suitable for primary care and the inter-rater reliability of general practitioner (GP) assessment of primary care suitability.

Design of study

Survey of GPs’ agreement of suitability for primary care on a random anonymised sample of all ED patients attending over a 1-month period.

Setting

ED of a UK Hospital serving a population of 600 000.

Method

Four GPs independently used data extracted from clinical notes to rate the appropriateness for management in primary care as well as need for investigations, specialist review or admission. Agreement was assessed using Cohen's κ.

Results

The mean percentage of patients that GPs considered suitable for primary care management was 43% (range 38–47%). The κ for agreement was 0.54 (95% CI 0.44 to 0.64) and 0.47(95% CI 0.38 to 0.59). In patients deemed not suitable for primary care, GPs were more likely to determine the need for specialist review (relative risks (RR)=3.5, 95% CI 3.0 to 4.2, p<0.001) and admission (RR=3.9, 95% CI 3.2 to 4.7, p<0.001). In patients assessed as suitable for primary care, GPs would initiate investigations in 51% of cases. Consensus over primary care appropriateness was higher for paediatric than for adult attenders.

Conclusions

A significant number of patients attending ED could be managed by GPs, including those requiring investigations at triage. A stronger agreement among GPs over place of care may be seen for paediatric than for adult attenders. More effective signposting of patients presenting with acute or urgent problems and supporting a greater role for primary care in relieving the severe workflow pressures in ED in the UK are potential solutions.
Assisting a child with tuberous sclerosis complex (TSC): a qualitative deep analysis of parents’ experience and caring needs
Authors: Graffigna Guendalina , Bosio Caterina , Cecchini Isabella
Published: December 2013

Objective

This study was aimed to explore parents’ experience of assisting children affected by tuberous sclerosis complex (TSC) with subependymal giant-cell astrocytoma (SEGA) manifestation, in order to understand their caring needs and expectation of support.

Setting and procedure

The study was designed according to the qualitative method of interpretative description and implied two sequential phases of data collection. The first phase was based on in-depth interviews with 18 Italian caregivers of children living with TSC. The second phase of the research was based on an online forum with 30 caregivers of children living with TSC.

Participants

48 Italian caregivers, assisting patients with TSC with SEGA manifestation have been involved in the study.

Results

When a TSC diagnosis is made, the whole family is affected psychologically. TSC has a great impact on families’ quality of life and on their ability to cope with the disease and support the child's ability to recover and reach an acceptable level of well-being. Caregivers report the experience of losing control and the feeling of loneliness and abandon from the healthcare system.

Conclusion and practice implications

Families of children affected by TSC need targeted psychosocial assistance in order to support patients and caregivers and facilitate their social integration.
The complexity of managing COPD exacerbations: a grounded theory study of European general practice
Authors: Risør Mette Bech , Spigt Mark , Iversen R , Godycki-Cwirko M , Francis N , Altiner A , Andreeva E , Kung K , Melbye H
Published: December 2013

Objectives

To understand the concerns and challenges faced by general practitioners (GPs) and respiratory physicians about primary care management of acute exacerbations in patients with chronic obstructive pulmonary disease (COPD).

Design

21 focus group discussions (FGDs) were performed in seven countries with a Grounded Theory approach. Each country performed three rounds of FGDs.

Setting

Primary and secondary care in Norway, Germany, Wales, Poland, Russia, The Netherlands, China (Hong Kong).

Participants

142 GPs and respiratory physicians were chosen to include urban and rural GPs as well as hospital-based and out patient-clinic respiratory physicians.

Results

Management of acute COPD exacerbations is dealt with within a scope of concerns. These concerns range from ‘dealing with comorbidity’ through ‘having difficult patients’ to ‘confronting a hopeless disease’.The first concern displays medical uncertainty regarding diagnosis, medication and hospitalisation. These clinical processes become blurred by comorbidity and the social context of the patient. The second concern shows how patients receive the label ‘difficult’ exactly because they need complex attention, but even more because they are time consuming, do not take responsibility and are non-compliant. The third concern relates to the emotional reactions by the physicians when confronted with ‘a hopeless disease’ due to the fact that most of the patients do not improve and the treatment slows down the process at best. GPs and respiratory physicians balance these concerns with medical knowledge and practical, situational knowledge, trying to encompass the complexity of a medical condition.

Conclusions

Knowing the patient is essential when dealing with comorbidities as well as with difficult relations in the consultations on exacerbations. This study suggests that it is crucial to improve the collaboration between primary and secondary care, in terms of, for example, shared consultations and defined work tasks, which may enhance shared knowledge of patients, medical decision-making and improved management planning.