bluuebunny/crossref_metadata_2025 huggingface dataset:
Évaluation du suivi mensuel personnalisé mis en place par l’ANPE en 2006
Authors: Fontaine Maëlle , Le Barbanchon Thomas
Published: April 2018

In January 2006, the French public employment service (ANPE) implemented the “ SuiviMensuel Personnalisé” (SMP), a new massive follow-up programme to monitor and counsel job seekers. The programme starts four months after their registration and consists in interviewing them every month. This paper evaluates the effect of SMP on registered unemployment spells. Using a difference-in-differences method, we find that SMP shortened unemployment spells to a significant degree, by between5% and 12%. The impactwas greater in 2007 than in 2006, and for long-term recipients of unemployment benefits. Unemployment spells were shortened thanks to higher job finding rates and higher deregistration rates.
Le crédit d’impôt dédié au développement durable : une évaluation économétrique
Authors: Mauroux Amélie
Published: April 2018

This article evaluates the incentive impact of the 2006 increase from 25% to 40% in the tax credit on residential energy-efficiency improvement for homeownerswho have lived for two years or less in a dwelling built before 1977. We estimate a triple-differences model combinedwith matching on exhaustive fiscal data. If the credit rate had stayed at 25%, one in fifteen eligible households among households filing tax returns and living in buildings completed between 1969 and 1976 would not have used this tax credit in 2006 ; the proportion would have risen to one in eight in 2007 and 2008. Unless we assume substantial CO 2 emission reductions after energy conservation investments, our model shows that public spending per tonne of CO 2 not emitted would exceed € 32, the social cost of carbon in France.
L’assignation aléatoire comme méthode d’évaluation des politiques publiques
Authors: Bouguen Adrien , Seban Juliette
Published: April 2018

L’évaluation d’impact d’une politique publique se heurte au problème de l’inférence causale, qui rend inopérantes les méthodes intuitives (comparaison entre avant et après le lancement de la politique ou entre bénéficiaires et non bénéficiaires). En comparant les résultats de deux groupes constitués aléatoirement avant le lancement de la politique, l’assignation aléatoire fournit une méthode rigoureuse d’évaluation d’impact. Cet article formule le problème de l’inférence causale puis montre comment, sous certaines conditions, l’assignation aléatoire permet de le résoudre. Les différents protocoles possibles et leurs conséquences en termes d’applicabilité, d’éthique et de précision statistique sont examinés. Les menaces potentielles pesant sur les résultats d’analyse sont détaillées, distinguant celles qui sont communes à toutes les méthodes d’évaluation de celles qui sont spécifiques à l’évaluation aléatoire.
Commentaire - Le calcul de puissance en assignation aléatoire : un point de vue de statisticien
Authors: Erkel-Rousse Hélène
Published: April 2018

Le calcul de puissance revêt une grande importance pratique car il conditionne la capacité à évaluer de manière satisfaisante l’effet d’une mesure de politique économique sur la base d’un protocole expérimental, en influençant les choix de ses caractéristiques techniques. Ce commentaire vise à documenter le débat sur le type de test d’hypothèses sur lequel fonder de préférence le calcul de puissance. Il montre que le choix d’un test unilatéral ou d’un test bilatéral permet indifféremment de répondre aux questions qui se posent à l’évaluateur, dès lors que les propriétés de ces tests sont bien maîtrisées. Il rappelle en outre l’importance pour le calcul de puissance d’une bonne formulation de l’écart-type de l’estimateur de l’effet de la politique à évaluer.
Expérimentation contrôlée contre appariement : le cas d’un dispositif d’accompagnement de jeunes diplômés demandeurs d’emploi
Authors: Bléhaut Marianne , Rathelot Roland
Published: April 2018

Cette étude vise à comparer les résultats d’une évaluation expérimentale avec ceux que l’on aurait pu obtenir si le même programme avait été évalué par des méthodes non-expérimentales. Nous utilisons l’exemple d’un programme d’accompagnement visant les jeunes diplômés demandeurs d’emploi, ayant fait l’objet d’une évaluation par expérimentation aléatoire. En l’absence d’expérimentation, aucun groupe de contrôle n’aurait pu être désigné. L’évaluation aurait dû comparer les jeunes entrés dans le dispositif avec ceux qui n’y sont pas entrés. En faisant abstraction du groupe de contrôle expérimental, nous utilisons des méthodes d’appariement afin de contrôler le mieux possible l’hétérogénéité observée entre les jeunes entrés ou non dans le programme. Les résultats obtenus sont très différents de ceux de l’évaluation par expérimentation aléatoire.
L’évaluation des politiques publiques : faut-il de l’interdisciplinarité ?
Authors: Wasmer Étienne
Published: April 2018

Public policy evaluation has become a highly active field of social-science research, and evaluations increasingly influence public decisions. The choice of evaluation methodology may, however, not be neutral. More specifically, we discuss the advantages and disadvantages of inter-disciplinarity for producing an assessment that is fair, operational, empirically accurate and scientifically sound. Psychological research on the determinants of the predictive ability of experts has found that experts’ specialisation seems to reduce their predictive abilities. From this result, we draw conclusions for public policy evaluation and weigh the pros of interdisciplinarity against the transaction costs generated by interdisciplinary exchanges.
L’évaluation des politiques publiques : qui et comment ?
Authors: Gregoir Stéphane
Published: April 2018

Despite official discourse in favour of public policy evaluation, there is no clearly-identifiable body in France at governmental or institutional level that does so. Policy evaluation responsibility is scattered among a range of departments and agencies. Consolidating the evaluation process would pool experience in relevant evaluation methodologies as well as in the ways and means for implementing new policies. Doing so would create an environment conducive to a more professional evaluation function and the promotion of best practices, and would also facilitate regular, higher-profile policy evaluation programmes. Certain French institutions, if given additional resources and greater skill capacity, could be in a position to coordinate and promote ex-post and ex-ante public policy evaluation.
Genetic Fine‐Mapping of a Quantitative Trait Locus (QTL) Associated with Embryogenic Tissue Culture Response and Plant Regeneration Ability in Maize (Zea mays L.)
Authors: Salvo Stella , Cook Jason , Carlson Alvar R. , Hirsch Candice N. , Kaeppler Shawn M. , Kaeppler Heidi F.
Published: April 2018

Embryogenic and regenerable tissue cultures are widely utilized in plant transformation, clonal propagation, and biological research applications. Germplasm utilized in those applications are limited, however, due to genotype‐dependent culture response. The goal of this study was to identify genomic regions controlling embryogenic and regenerable tissue culture response in the globally important crop, maize (Zea mays L.), toward the long‐term objective of developing approaches for genotype‐independent plant genetic engineering and clonal propagation systems. An inbred maize line, WCIC2, nearly‐isogenic to reference inbred B73, was developed by phenotypic selection and molecular marker analysis. WCIC2 has over 50x increase in tissue culture response relative to the recurrent parent, B73. This line was used to genetically fine‐map a region on chromosome 3 controlling embryogenic and regenerable tissue culture response to a 23.9 Mb region. WCIC2 and derivatives will be useful materials to enable maize research in a genetic background similar to B73, and our genetic mapping results will advance research to identify causal genes controlling somatic embryo formation and plant regeneration in maize.
Genomic‐enabled Prediction Accuracies Increased by Modeling Genotype × Environment Interaction in Durum Wheat
Authors: Sukumaran Sivakumar , Jarquin Diego , Crossa Jose , Reynolds Matthew
Published: April 2018

Genomic prediction studies incorporating genotype × environment (G×E) interaction effects are limited in durum wheat. We tested the genomic‐enabled prediction accuracy (PA) of Genomic Best Linear Unbiased Predictor (GBLUP) models—six non‐G × E and three G × E models—on three basic cross‐validation (CV) schemes— in predicting incomplete field trials (CV2), new lines (CV1), and lines in untested environments (CV0)— in a durum wheat panel grown under yield potential, drought stress, and heat stress conditions. For CV0, three scenarios were considered: (i) leave‐one environment out (CV0‐Env); (ii) leave one site out (CV0‐Site); and (iii) leave 1 yr out (CV0‐Year). The reaction norm models with G × E effects showed higher PA than the non‐G × E models. Among the CV schemes, CV2 and CV0‐Env had higher PA (0.58 each) than the CV1 scheme (0.35). When the average of all the models and CV schemes were considered, among the eight traits— grain yield, thousand grain weight, grain number, days to anthesis, days to maturity, plant height, and normalized difference vegetation index at vegetative (NDVIvg) and grain filling (NDVIllg)—, plant height had the highest PA (0.68) and moderate values were observed for grain yield (0.34). The results indicated that genomic selection models incorporating G × E interaction show great promise for forward prediction and application in durum wheat breeding to increase genetic gains.
Taxonomic revision of the Graphipterus serrator (Forskål) group (Coleoptera, Carabidae): an increase from five to 15 valid species
Authors: Renan Ittai , Assmann Thorsten , Freidberg Amnon
Published: April 2018

The south-west PalaearcticGraphipterusserratorgroup is revised. The systematic concept of theG.serratorgroup has undergone many changes during the last two centuries, and several different classifications have been published in recent decades. Here, the numerical taxonomy approach is used with the morphological characterization similarity level of the sympatric taxa in order to delimit allopatrically occurring taxa at the species and subspecies level. A key to the species and distribution maps are provided along with analyses of the conservation status and habitat preferences of the taxa. TheGraphipterusserratorgroup currently comprises 16 taxa. Five new species are described:GraphipterusmagnusRenan & Assmann,sp. n.,GraphipterusmauretensisRenan & Assmann,sp. n.,GraphipteruspiniamitaiiRenan & Freidberg,sp. n.,GraphipterussharonaeRenan & Assmann,sp. n., andGraphipterusstagonopsisRenan & Assmann,sp. n.In addition, five taxa are revalidated to full species status:GraphipterusheydeniKraatz, 1890,stat. rest.(lectotype designated),Graphipterusmultiguttatus(Olivier, 1790),stat. rest.(lectotype designated),GraphipteruspeletieriLaporte de Castelnau, 1840,stat. rest.(the frequently used namelepeletieriis an error),GraphipterusrotundatusKlug, 1832,stat. rest.(lectotype designated), andGraphipterusvaldaniiGuérin-Méneville, 1859stat. rest., and a full species status is proposed forGraphipterusreymondiAntoine, 1953,stat. n.One new synonymy is proposed:GraphipteruskindermanniChaudoir, 1871,syn. n. ofCarabusmultiguttatusOlivier, 1790. Lectotype designations were made forGraphipterusheydeni,GraphipterusminutusDejean, 1822,Graphipterusmultiguttatus, andGraphipterusrotundatus. Neotype designations were made forGraphipterusreicheiGuérin-Méneville, 1859,GraphipterusintermediusGuérin-Méneville, 1859, andGraphipterusvaldaniiGuérin-Méneville, 1859.
Mesure de la performance des politiques européennes de développement rural par l’estimation de leur « valeur ajoutée territoriale »
Authors: Vollet Dominique , Bosc Christel , Berriet-Solliec Marielle , Lépicier Denis
Published: April 2018

Dans quelle mesure le programme européen Leader contribue-t-il encore à répondre aux objectifs initiaux d’un développement local ascendant et innovant ? Nous proposons une méthode pluridisciplinaire, basée sur une analyse d’évaluation de l’efficacité des projets comme de leur gouvernance à partir d’une grille originale d’analyse de la valeur ajoutée territoriale. Celle-ci est structurée autour de quatre composantes : ancrage territorial, intersectorialité, coordinations entre acteurs et caractère transversal du projet de développement territorial. L’application de cette méthode aux projets Leader mis en œuvre dans le pays d’Aurillac met en exergue la valeur ajoutée la plus importante pour les projets relatifs à l’accueil de populations et d’entreprises. Par ailleurs, le couplage de cette analyse quantitative avec une analyse qualitative de science politique permet de tenir compte du contexte local et de pointer d’autres aspects freinant la performance de Leader (rigidité administrative, stratégies notabiliaires) ou l’améliorant (création d’un pôle d’accueil et d’appui). Classification JEL : Q18, H50, R58
Doxai, Principes et Normes
Authors: Colletis Gabriel , Salles Maryse
Published: April 2018

L’article propose un outil méthodologique destiné à améliorer les méthodes d’évaluation des politiques. Le travail de recherche à la base de cet article a été mené dans une logique bidisciplinaire, associant le domaine de l’économie à celui des systèmes d’information. Le premier temps de l’article est consacré à une revue orientée de la littérature du domaine de l’évaluation des politiques publiques, visant à identifier les difficultés de l’évaluation. Dans un deuxième temps, la problématique du travail est explicitée. Puis l’outil Dpn ( doxai -principes-normes) est présenté. Son but est d’aider à révéler les chaînes qui relient les visions du monde (paradigmes, valeurs) aux indicateurs d’évaluation, en passant par le niveau structurant des principes. L’outil est situé par rapport aux difficultés de l’évaluation identifiées dans la littérature. Un exemple d’application de l’outil constitue le troisième temps de l’article, débouchant sur des propositions d’indicateurs pour l’évaluation des politiques de développement économique territorial. Classification : B41, D78, O21, R1, R58
Application of Data Mining Technology Based on Wireless Sensor Networks in Oceanographic Forecasting
Authors: Zhai Wei
Published: April 2018

This paper aims to present a desirable prediction method for oceanographic trends. Therefore, an online monitoring scheme was prepared to collect the accurate oceanographic hydrological data based on wireless sensor network (WSN) and computer technology. Then, the data collected by the WSN were processed by support vector regression algorithm. To obtain the most important parameters of the algorithm, the particle swarm optimization was introduced to search for the global optimal solution through the coopetition between the particles. After that, an oceanographic hydrological data collection and observation system was created based on the hydrological situation of New York harbour. Then, the traditional support vector regression and the proposed method were applied to predict the oceanographic trends based on water temperature, salinity and other indices. The results show that the proposed algorithm enhanced the data utilization rate of the WSN, and achieved good prediction accuracy. The research provides important insights into the application of advanced technology in oceanographic forecast.
A Fire Drill Training System Based on VR and Kinect Somatosensory Technologies
Authors: Feng Li Nian , Xiao Zhiguo
Published: April 2018

The traditional fire drill is difficult, high cost, poor effect etc. in variety of fire scene simulation; a new fire drill platform combined Somatosensory camera Kinect and VR can achieve self-construction and virtual simulation fire drill based on somatosensory interaction; the platform achieves interaction between human and the 3D objects in virtual simulation environment, 3D modeling, scene building with Unity, identified human skeletal by Kinect, and using Euclidean distance matching recognition algorithm for body movements, and finally realizes the evaluation of fire drills.; the platform shows that the system has important practical significance and use value in fire drills, fire safety teaching and other aspects.
Street Traders and “Good Officers”: Crackdowns as a Relational Form of Urban Governance in Nairobi
Authors: Dragsted-Mutengwa Brigitte
Published: April 2018

In central Nairobi, crackdowns on illegal street trading by officers from the local authorities are a daily occurrence. Based on an ethnographic study of encounters between street traders and officers during crackdown operations in and around the Nairobi CBD, this article argues that crackdowns work as a platform for exchanges and thereby for the formation of social relationships. It explores how such relationships are formed and maintained during crackdowns, and how a range of urban actors has interests invested in them. The article contributes to regional literature on street trading by proposing a view of urban governance as emerging through everyday interactions and relations between urban actors. Furthermore, the article contributes to scholarship on relational urban governance by exemplifying how anthropological notions of exchange provide an analytical avenue through which such everyday interactions and relations can be explored.
Galling Generation Mechanism in Upsetting-Ball Ironing Test
Authors: Wang Zhi Gang , Komiyama Shinobu
Published: April 2018

An upsetting-ball ironing test has been developed to investigate the lubricating performance of coatings in multi-stage cold forging. By using this test, the lubricating performance of a zinc phosphate free coating called “dry in-place coating” was evaluated and improved, and now the dry in-place coating is used worldwide due to its high anti-galling ability and low environmental impact. In this study, galling generation mechanism in the upsetting-ball ironing test is investigated by using the point tracking function in FEM simulation. Scratches on ironed surface are generated at the starting point of ironing and the width and depth of scratches increase gradually with the increasing ironing stroke. It is revealed that all points on a scratch have been in contact with the same point of the ball. The lubrication coating on the billet surface peels off locally with the onset of ironing and some contamination particles enter the interface between the billet and the ball and thus cause scratches. Galling takes place at the ironing stroke of around 10 mm when the billet of 14 mm in diameter and 32 mm in height is upset to 45 percent reduction in height and then ironed by the ball of 10 mm in diameter. It is found that all points on the ironed surface at the starting position of galling are not on the initial billet surface but come from the inside of the billet. These points come out at the ironing stroke of 4 mm due to the dividing flow in the surface layer. It is concluded that galling in the upsetting-ball ironing test is generated by the extremely large surface expansion.
An Insight in Friction and Wear Mechanisms during Hot Stamping
Authors: Venema Jenny , Hazrati Marangalou Javad , Matthews David , van den Boogaard Ton
Published: April 2018

Hot stamping is often used in the automotive industry to combine formability and strength. However, during forming process at high temperatures, friction and tool wear are determining factors that can affect the efficiency of the whole process. The goal of this paper is to investigate the effects of temperature on the local coefficient of friction and tool wear and to provide an insight in the phenomena which take place at the tool-sheet metal interface during hot stamping processes. For this purpose, hot friction draw tests between uncoated tool steel and Al-Si coated press hardening steel were carried out at several temperatures between 500-700°C. Consecutive tests were performed to mimic industrial hot stamping process and to investigate the effect of tool wear on the friction phenomenon. Finally, tool-sheet metal tribological behavior and the interaction between the friction and tool wear mechanisms were analyzed using different imaging and chemical characterization techniques. The results show that several stages can be distinguished at the interface between tool and sheet metal coating during hot stamping: flattening due to initial normal contact, ploughing of tool asperities through coating, secondary ploughing in the coating by adhered material on the tooling, and abrasive wear in the tool by embedded particles in the sheet metal coating. Furthermore, tool wear shows some major differences in the temperature range of 500-700°C. At high temperature a larger abrasive area and more severe compaction galling occurs that can be explained by material properties of Al-Si coating at elevated temperatures. The results of this study can be used for more efficient process design and a more realistic modelling of the hot stamping process.
Effect of Workpiece Surface Topography on Friction in Cold Forging Using Environmentally-Friendly Lubricant
Authors: Hayakawa Kunio , Nakamura Tamotsu
Published: April 2018

An optimal surface topography for the use of an environmentally friendly lubricant was elucidated, by making a wide combination of surface roughnesses Ra and RSm representing height and frequency of surface asperity, using the wet blast treatment. A forward conical can - backward straight can extruded friction test method proposed by the present authors was used. Coulomb friction coefficient was evaluated using a calibration curve representing the relationship between the surface friction coefficient of the conical punch and the front/back extrusion height of the workpiece. It was found that the surface topography of workpiece largely affects the lubricating property when the friction coefficient is large. Especially, the surface treatment with larger Ra and smaller RSm is effective for improving the friction. Furthermore, the correlation between the friction coefficient and the proposed parameter for the surface topography Ra/RSm was shown to be better than the Ra.
Joining by Plastic Deformation
Authors: Alves Luis , Silva Carlos , Martins Paulo A.F.
Published: April 2018

This paper draws from the existing processes and applications of joining by plastic deformation to a comprehensive overview of a new set of processes that have been recently developed by the authors. The presentation includes solutions for connecting tubes, sheets and tubes to sheets and provides information on the tooling systems, operating variables, deformation mechanics and workability limits. Results from analytical modelling, finite element analysis and experimentation give support to the presentation and prove the feasibility of the new joining by plastic deformation processes for connecting tubes, sheets and tubes to sheets made from dissimilar materials, at room temperature, without having to use addition materials or adhesives. The resulting joints are easy to disassembly at the end of live, thereby allowing recyclability of the individual parts.
A Simple Model Linking Surface Roughness with Friction Coefficient and Manufacturing Cost
Authors: De Chiffre Leonardo , Kücükyildiz Ö.C. , Bay Nils
Published: April 2018

A simple theoretical model linking surface micro geometry, friction and manufacturing cost is presented. Combining a basic geometrical relationship of plastic deformation of workpiece surface asperities by a hard tool with an assumption of adhesive friction, the friction coefficient of a soft, rough surface sliding against a hard, smooth tool surface can be calculated, linking surface roughness with friction coefficient. The simple model can also link the cost related to manufacturing with a surface characterized by a given friction coefficient value. Results are presented from tests carried out to verify the simple model. Several test pieces were manufactured by turning, or grooving, an aluminum alloy and brass using different feeds, tool nose radii, and tool nose angles, achieving different surface profiles. The surfaces were characterized using a stylus profilometer and a digital microscope. The static friction coefficient was determined in terms of angle of repose using a rotary table. The experimentally determined values of the friction coefficient were compared with those predicted from feed, tool radius, and asperity angle. The tests have shown a good reproducibility, and a clear determination of the friction coefficient was possible. However, due to the low normal loads involved in this set up, the influence from the surface roughness was not clear. Further investigations are therefore proposed.
Quantitative Evolution of WC-Co Cemented Carbide Tool Surface during the Cold Forming of Steel Parts
Authors: Dubar Laurent , Debras Colin , Dubar Mirentxu , Dubois André
Published: April 2018

The present paper investigates the evolution of the WC grain size and morphology with the number of produced parts. Four reduction dies used in cold forward extrusion of steel are taken from the production line: a brand new die and three dies which have respectively produced 100.000, 150.000 and 220.000 parts. 3D roughness measurements and SEM micrographs are performed on the contact surface of each die. Results of these analyses highlight that WC grains are subject to plastic strain and are removed from the surface as the number of produced parts increase, leading to a growth of WC free areas where steel adhesion may occur. When analyzing the size of the WC grains, it appears that the population of small grains increases with the number of produced parts until 150.000. Then the population of small grains decreases. A wear mechanism is proposed to explain this variation of WC grains size with the number of extruded parts.
A New Coupled Thermal Stress FE-Model for Investigating the Influence of Non-Isothermal Conditions on Bond Strength and Bonding Status of the First Pass in Roll Bonding
Authors: Liu Zhao , Kraemer Alexander , Karhausen Kai F. , Aretz Holger , Teller Marco , Hirt Gerhard
Published: April 2018

Roll bonding is a joining-by-forming process to permanently join two or more layers of different materials by hot or cold rolling. One of the typical industrial applications is aluminium sheets for heat exchangers in automobiles. During roll bonding the layers are fed into the rolling stand with parallel surfaces. Due to the plastic deformation in the roll gap metallic bonds between the layers are achieved. Several theoretical models have been published to describe the process, e.g. Zhang & Bay. These models have mostly been developed for cold rolling and describe the bond strength based on surface enlargement, contact pressure and flow stress. Since these models are developed for cold rolling, they are not temperature depending. Heat exchange is usually neglected and de-bonding after the roll gap is not accounted for. However, for hot roll bonding the above mentioned assumptions do not hold true. To understand the mechanisms of hot roll bonding industrial and laboratory scale investigations have previously been conducted. Based on the findings a FE framework for hot roll bonding was developed. This FE framework accounts for the possibility of de-bonding after the roll gap but is restricted to isothermal conditions. However, for a roll bonding simulation it is essential to take the temperature influence into consideration. Therefore, this paper presents an extended version of the FE framework which accounts for temperature dependent material flow, compatible definition of thermal & mechanical interactions and bonding status related heat exchange. To verify the new features of the extended FE framework a roll bonding test case is employed. Mechanical and thermal interactions as well as the current flow stress are calculated in subroutines in order to enable a fully coupled thermal stress simulation. The results show that with this extended FE framework the influence of non-isothermal conditions on material flow and bonding status as well as the feedback effects of bonding status to heat exchange have been successfully integrated in hot roll bonding simulations. This fully coupled thermal stress simulation is the first step towards multi-pass roll bonding simulations.
Brushing for High Performance Cold Pressure Welded Bonds
Authors: Gerlitzky Christiane , Volz Stefan , Groche Peter
Published: April 2018

Joining of steel and aluminum is a commonly applied manufacturing process to obtain lightweight components. Cold pressure welding by means of direct extrusion allows gaining high bond strengths between these two materials. The contacting surfaces are usually prepared by using scratch brushing to enhance the bond strength. Most studies have shown the benefit of the brushing whereas the resulting bond strength scatters. Variations in the parameters of the brush treatment are presumed to be a major cause for the variations in strength. Within the presented work, scratch brushing parameters are adjusted to further improve the resulting bond strength. Cracking of the surfaces at low strains is a beneficial effect to enhance the bond strength. Therefore, the crack formation of the surfaces brushed under different conditions is analyzed in tensile tests. Roughness, residual stresses and microstructural changes of the aluminum surfaces resulting from brushing processes are evaluated to enhance the understanding of the cracking mechanism. Concluding, the brushing parameters are adjusted to improve bond strengths up to the material strength of the used aluminum.
Influence of Stacking Sequence and Intermediate Layer Thickness in AA6082-IF Steel Tri-Layered Cold Roll Bonded Composite Sheets
Authors: Arbo Siri Marthe , Westermann Ida , Holmedal Bjørn
Published: April 2018

In tri-layered Cold Roll Bonded (CRB) composite sheets of dissimilar metals, uneven thickness reduction of the different layers have been observed. This has been explained by the difference in yield strength/flow stress of the metals. The aim of this research was to study if these observations also depend on different parameters such as stacking sequence and initial sheet thickness, as opposed to only material properties. Hence, tri-layered CRB composite sheets consisting of AA6082 and IF-steel were produced with two different stacking sequences, St/Al/St vs Al/St/Al. Two different layer thicknesses of the intermediate layer were used. Rolling was performed in a single pass achieving approximately 55-65% total thickness reduction. Comparisons between the samples are given, focusing on the reduction of thickness achieved in each layer, the roll bonded interface characteristics and the bond strength of the joints. The overall thickness reduction achieved in each layer was found to be similar for both metals in both stacking sequences for the considered material combination. The stacking sequence is statistically found not to have any effect on the bond strength of the joints. The thickness of the intermediate layer does not significantly affect the overall bond strength of the composite sheet for both stacking sequences. These findings are opposed to earlier results found in the literature.
Thermomechanical Modelling of Direct-Drive Friction Welding Applying a Thermal Pseudo Mechanical Model for the Generation of Heat
Authors: Sonne Mads Rostgaard , Hattel Jesper Henri
Published: April 2018

In the present work a 2D axisymmetric thermomechanical model of the direct-drive friction welding process is developed, taking the temperature dependent shear yield stress into account in the description of the heat generation, utilizing a recent thermal pseudo mechanical model originally developed for the friction stir welding (FSW) process. The model is implemented in ABAQUS/Explicit via a subroutine. The application in this case is joining of austenitic stainless steel rods with an outer diameter of 112 mm, used for manufacturing of exhaust gas valves for large two stroke marine engines. The material properties in terms of the temperature dependent flow stress curves used both in the thermal and the mechanical constitutive description are extracted from compression tests performed between 20 °C and 1200°C on a Gleeble 1500 thermomechanical simulator. Comparison between measured and simulated transient temperatures shows relatively good agreement and furthermore, the simulated deformations in terms of upsetting length and flash formation are also in good agreement with the observations from the experiment.
Temperature Control for Friction Stir Welding of Dissimilar Metal Joints and Influence on the Joint Properties
Authors: Krutzlinger Markus , Marstatt Roland , Costanzi Giacomo , Bachmann Andreas , Haider Ferdinand , Zaeh Michael F.
Published: April 2018

Friction Stir Welding (FSW) is a suitable technology to join dissimilar metals such as aluminum and copper or aluminum and titanium. Since it is a solid state welding process, the solidus temperature is typically not exceeded and the formation of intermetallic phases can be minimized compared to fusion welding processes. However, an intermetallic layer is still formed at the joining interface. This layer determines the seam properties such as the joint strength or the electrical conductivity. The thickness of the layer is in the nanometer range and is mainly influenced by the welding temperature via an Arrhenius law. The process temperature mainly depends on the rotational speed and on the feed rate of the machine tool. In this study, a temperature control system for aluminum-copper lap joints was developed. A PI control system was used for this purpose to maintain the given welding temperature by adjusting the rotational speed. Consequently, a constant welding temperature was ensured along the entire seam and influences such as changes in workpiece geometry, environmental conditions, or material variations could be mitigated. Experiments with six different temperature levels (low – high) were conducted for one exemplary welding task in order to verify the proposed constant welding conditions. The joints were investigated by tensile shear tests as well as optical and electron microscopy. It was proven that temperature-controlled FSW ensures a constant thickness of the intermetallic compound layer.
Numerical Investigation of the Tool Load in Joining by Forming of Dissimilar Materials Using Shear-Clinching Technology
Authors: Wiesenmayer Sebastian , Müller Martin , Dornberger Peter , Han Daxin , Hörhold Réjane , Meschut Gerson , Merklein Marion
Published: April 2018

Modern developments in the automotive sector are motivated by the objective of lowering the emission of pollutants. In contrast, growing demands for safety and comfort lead to a potential increase of the weight of vehicles. Thus, the consequent use of lightweight design is indispensable. This includes the use of different materials for the construction of car bodies. Because of various material properties, joining of dissimilar materials is challenging and requires often the application of non-thermic processes like riveting or clinching. These processes are limited by the mechanical properties of the joining partners. Especially the increasing use of ultra-high strength alloys, like the hot stamped steel 22MnB5, makes the development of new joining technologies necessary. One of these innovative technologies is shear-clinching. By combining shear-cutting and clinching in one process, this technology produces durable and tight connections of dissimilar materials with high differences regarding strength and formability. In contrast to shear-cutting the die-sided material has no contact with the punch. Since the process of shear-clinching is a combination of cutting and joining using the same tool, the tool loads differ from common shear-cutting. Especially cutting hot stamped steels is a challenge due to their high ultimate strength which leads to high tool loads. Thus, the analysis of the load condition is essential for the dimensioning of durable and wear resistant tools. Hence, the scope of this paper is a numerical investigation of the tool loads during the indirect cutting process and the subsequent step of joining by forming during shear-clinching. Since an experimental investigation of the occurring tool loads in the closed process is not practicable, the finite element method has to be used. Therefore, a damage-based numerical model is set up to enable the coupled simulation of the combined cutting and joining process and the resulting tool loads. This allows the analysis of the loads during the whole process, identifying the influences of materials and sheet thicknesses.
Joining by Forming of Tubes to Sheets with Counterbored Holes
Authors: Alves Luis , Afonso Rafael M. , Silva Carlos , Martins Paulo A.F.
Published: April 2018

This paper presents a new joining by forming process for connecting tubes to sheets. The process consists of forming an annular flange with rectangular cross section by partial sheet-bulk of the tube wall thickness and performing the mechanical interlock by upsetting the free tube end against a flat-bottomed (counterbored) sheet hole. The presentation identifies the variables and the workability limits of the process and includes an analytical model to assist readers in the design of the new joints. The new proposed joining by forming process and the corresponding analytical model are validated by experimentation and numerical simulation using finite element analysis. The process allows connecting tubes to sheets made from dissimilar materials at room temperature, avoids the utilization of addition materials or adhesives and produces joints that are easy to disassembly at the end of live, allowing recyclability of the tubes and sheets.
Parameter Identification for Magnetic Pulse Welding Applications
Authors: Bellmann Joerg , Lueg-Althoff Joern , Schulze Sebastian , Gies Soeren , Beyer Eckhard , Tekkaya A. Erman
Published: April 2018

Magnetic pulse welding (MPW) is a promising technology to join dissimilar metals and to produce multi-material structures, e.g. to fulfill lightweight requirements. During this impact welding process, proper collision conditions between both joining partners are essential for a sound weld formation. Controlling these conditions is difficult due to a huge number of influencing and interacting factors. Many of them are related to the pulse welding setup and the material properties of the moving part, the so-called flyer. In this paper, a new measurement system is applied that takes advantage of the high velocity impact flash. The flash is a side effect of the MPW process and its intensity depends on the impact velocity of the flyer. Thus, the intensity level can be used as a welding criterion. A procedure is described that enables the user to realize a fast parameter development with only a few experiments. The minimum energy level and the optimum distance between the parts to be joined can be identified. This is of importance since a low energy input decreases the thermal and mechanical shock loading on the tool coil and thus increases its lifetime. In a second step, the axial position of the flyer in the tool coil is adjusted to ensure a proper collision angle and a circumferential weld seam.
Proofs and Contradictions for Wave Formation Theories in Collision Welding
Authors: Niessen Benedikt , Franceschi Alessandro , Groche Peter
Published: April 2018

Joining processes initiated by collisions provide several advantages in comparison to conventional welding techniques. Although collision welding is already used industrially, some effects during the bond formation, like the occurrence of waves in the interface, have not been fully understood, yet. In order to describe these effects, a number of theories have been developed that can be divided into three categories by the governing mechanism: 1) indentation theory 2) stress wave theory and 3) fluid theories. However, none of these theories has so far been conclusively proved or disproved. A unique test rig allows specifically targeted examinations of the wave formation and the transition region from straight to wavy interface as well as the evolution of the waves. Within the presented investigation, the kinetic energy and the hardness as process and material parameters have been examined regarding their influence to wave formation. For a specific investigation of the overall deformation of the bond zone a parameter, bond length elongation Φ, was introduced to connect wave length and wave amplitude. The results of the experiments provide arguments for wave formation being caused by both stress waves and fluidic effects.
Comparison of efficacy of mulligan's mobilization with movement with maitland mobilization along with conventional therapy in the patients with knee osteoarthritis: A randomized clinical trial
Authors: Kiran Aniqa , Ijaz Muhammad , Qamar Muhammad , Basharat Ayesha , Rasul Akhtar , Ahmed Waqas
Published: April 2018

Objective: The objective of this study is to determine the outcome and efficacy of Mulligan's mobilization with movement (MWM) with Maitland mobilization along with conventional therapy in the patients with knee osteoarthritis (OA). Materials and Methods: A randomized controlled trial study was performed at the Department of Physiotherapy, Mayo Hospital, Lahore, Pakistan. Sixty-two patients were selected for the study. MWM was introduced in half of the patients and Maitland mobilizations in the second half for 2 weeks. The goniometry, visual analog scale (VAS), knee range of motion (ROM), and Western Ontario McMaster OA (WOMAC) Index for knee OA were the assessment tools used to assess all patients before and after 2 weeks of intervention. Paired sample t-test was used for analysis of results. Results: The mean pre- and postdifferences in MWM group were 4.06 ± 0.99, 10.19 ± 3.87, and 19.41 ± 7.58 for VAS, ROM flexion, and WOMAC Index, respectively, while the pre- and postmean difference values for Maitland mobilization group were 3.355 ± 1.05, 10.19 ± 5.5, and 12.28 ± 7.029 for VAS, ROM flexion, and WOMAC Index, respectively. The mean differences of both treatment interventions individually were significant and showed that both were clinically effective in treating the patients of knee OA. Conclusion: It was concluded that patients in both groups showed improvement in pain, ROM, and functions.
Prevalence of metabolic syndrome and its components in nondiabetic Libyan females
Authors: El-Shareif Hawa
Published: April 2018

Background: The metabolic syndrome (MS) is defined as a cluster of cardiovascular risk factors, including central obesity, dysglycemia, hypertension (HPN), elevated triglycerides (TGs), and reduced high-density lipoprotein cholesterol (HDL-C). MS increases the risk of cardiovascular disease and all-cause mortality. Objective: This study aims to estimate the prevalence of MS and its components among nondiabetic Libyan females using the definition proposed by National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III). Methods: A total of 122 randomly selected nondiabetic Libyan females were included in the study. Detailed medical history was obtained from all participants. Blood pressure, weight, height, waist and hip circumference were measured. Body mass index and waist–hip ratio were calculated. Fasting blood glucose (FBG) and lipid profile were collected. Standard oral glucose tolerance test with 75 GM glucose was performed. The MS was defined by ATP III and International Diabetes Federation criteria. Results: According to NCEP definition, the prevalence of the MS in the study group was 42.6%. The most common component was abdominal obesity (67.2%). FBG was ≥ 100 mg/dl in 47.5%. The prevalence of both HPN and low HDL-C was 45.9%. About 26.2% of the participants have their TG ≥ 150 mg/dl; all were MS patients. Conclusions: The prevalence of MS and cardiovascular risk factors were high among Libyan females. Public health authorities and health-care providers should implement strategies for prevention, screening, and management of cardiovascular risk factors to reduce the burden of its potential complications.
Stability for parabolic quasi minimizers in metric measure spaces
Authors: Fujishima Yohei , Habermann Jens
Published: April 2018

We are concerned with the stability property for parabolic quasi minimizers in metric measure spaces. More precisely we consider a doubling metric measure space

\mathcal X

which supports a weak Poincaré inequality and a parabolic domain

\Omega_T = \Omega \times (0,T)

on the product space

\mathcal X \times \mathbb R

, where

\Omega \subset \mathcal X

is a domain whose boundary

\partial \Omega

is regular in the sense that its complement satisfies a uniform capacity density condition. We then show that a parabolic

\mathcal Q

quasi minimizer of the

p

energy,

p \ge 2

, with fixed initial boundary data on the parabolic boundary of

\Omega_T

is stable with respect to the variation of

\mathcal Q

and

p

. The manuscript at hand is an extension of the result [7] to the setting of metric measure spaces.
Vienna Construction Projects: Redirection of Project Management Critical Success Factors—More Focus on Stakeholders and Soft Skills Development
Authors: Wanivenhaus Helmut , Kovač Jure , Žnidaršič Anja , Vrečko Igor
Published: April 2018

Although research interest in project management is increasingly directed at analyzing development trends in different business environments, the public sector in this respect has received surprisingly little intention. This paper analyzes the perception of the relevance of particular project management critical success factors among project managers and other project stakeholders in the public sector with relatively high organizational project management maturity. The main focus of research is the city of Vienna and its construction projects. An extensive quantitative survey showed the changing perceptions of the key projects’ success factors—namely, strengthening the importance of developing soft skills and stakeholders’ management.
Influence of the Public Procurement Procedure Type on the Duration of Public Procurement
Authors: Čudanov Mladen , Jovanović Predrag , Jaško Ondrej
Published: April 2018

This study analyses how important is the influence of the procedure type and a number of received bids on the duration of the public procedure process. Efficiency and speed of public procurement process diminish inventory turnaround times, direct and indirect costs of procurement, hastens and improves manageability of core processes in the organizations obliged to the public procurement process. Our study focuses on the quantitative analysis of the influence of the procedural public procurement framework mostly determined by the central government and describes potential other factors of efficiency which can be influenced at the local level. Dataset was obtained from the Public Procurement Office of Serbia, and it included 42,850 cases of public procurement after the correction of missing and “dirty” data. Using statistical methods we have presented two linear models, where the type of procedure and number of received bids account for roughly 23% of the variability in the dependent variable. This paper provides suggestions for improvement of efficiency of public procurement, as well as for data that needs to be tracked to develop more comprehensive, accurate and reliable prediction model of the duration of the public procurement process.
Impact of Local Government Revenue Structure on Income Growth and Employment in Croatia
Authors: Drezgić Saša , Grdinić Maja , Blažić Helena
Published: April 2018

The paper researches effects of local government revenue structure on income growth and employment in Croatia. The results confirm highly positive and significant effects of personal income taxation. This differs dramatically from the previous research based on central government level, which show that property and consumptions taxes are growth-friendly. The most probable explanation of such results could be in narrow revenue structure defined by the vertical fiscal equalisation and the fact that particular local revenue structure does not affect competitiveness in the same way as overall revenue structure of the country.