bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anisotropies and inhomogeneities in the microstructure of the case hardening steel SAE 5120
Authors: Eisbrecher I. , Clausen B. , Hunkel M. , Rentsch R. 
Published: January 2012

AbstractDistortion is an effect of inhomogeneous strain behavior. It can be initiated by plasticity due to thermal or transformation stresses (such as yielding, creep and transformation plasticity), phase transformations or strains during phase transformations. Inhomogeneities in microstructure and anisotropies constitute a distortion potential. Based on this knowledge several investigations were carried out on forged disks with a centered hole made of low alloy steel SAE 5120 (EN 20MnCr5) because both inhomogeneity and anisotropy have been observed in the microstructure of this material. Disks have been forged from continuous cast and hot rolled bar material. They show an inhomogeneous banded microstructure that is explicitly orientated in the direction of the two manufacturing processes. By forging, the initial microstructure of the bar material is influenced significantly: the segregation bands parallel to the rolling direction are deformed into a typical pattern. Besides this inhomogeneity in microstructure also the inhomogeneities of the bar material, such as center segregations from continuous casting, can still be observed in the deformed material. Gear blanks were machined from these disk blanks. It has been shown that the original position of the gear blank inside the disk blank influences the distortion [1]. The underlying reason remained unclear and investigations on this topic are discussed in this paper.
Semi‐optical in‐process‐metrology to determine the roundness deviation of bearing rings during heat treatment
Authors: Gafsi H. , Goch G. 
Published: January 2012

AbstractThis paper presents two different systems for measuring the roundness deviation of bearing rings during heating and gas quenching. During heating in a furnace, laser triangulation is applied to measure absolute values for the ring's mean radius and ovality. Afterwards, the ring is quenched in a gas nozzle field equipped with a semi‐optical measurement system consisting of twelve tactile and twelve optical sensors independent from each other. Before quenching, the tactile sensors measure in‐situ the absolute mean radius of the near 900°C hot ring and its roundness deviation from ovality up to pentagonality. Based on this information, the optical sensors measure in‐process the change of the roundness deviation during the gas quenching, as the tactile sensors cannot be used in high speed gas jets due to turbulence.
Some recent developments in modelling of heat‐treatment phenomena in steel within the collaborative research centre SFB 570 “Distortion Engineering”
Authors: Wolff M. , Böhm M. , Bökenheide S. , Dalgiç M. 
Published: January 2012

AbstractIt is the aim to present some developments in modelling of distortion‐related phenomena during heat treatment of steel in the context of the Collaborative Research Centre SFB 570 “Distortion Engineering” at the Bremen University, Germany. Taking this into account, a survey will be given and some results will be exemplarily presented. This work is the first contribution to the session “Modelling of material behaviour within the CRC Distortion Engineering” of the 3rd International Conference on Distortion Engineering, Bremen, 2011. The following articles by Hunkel 2011 [1] and by Bökenheide et al. 2011 [2] deal in detail with the steel qualities 100Cr6 (SAE 52100) and 20MnCr5 (SAE 5120), respectively. Here, more general aspects of the subsequent phenomena are in the focus: Phase transformations (PT) and transformation‐induced plasticity (TRIP) during quenching and heating, plastic behaviour of (supercooled) austenite as well as creep during heating and austenitising. The following items will be considered in particular: Experiments and processing strategies for experimental data, model approaches and results for single phenomena of material behaviour. Many assertions have a general character not linked to special steel sorts. We will also address open questions and possible perspectives.
Modelling of phase transformations and transformation plasticity of a continuous casted steel 20MnCr5 incorporating segregations
Authors: Hunkel M. 
Published: January 2012

AbstractIn general, material data for heat treatment simulations are assumed to be isotropic and homogeneous (except the carbon dependency for case hardening simulations). But it was found for the conventional continuous casted case hardening steel 20MnCr5 (SAE 5120) that segregations lead to anisotropic and inhomogeneous properties especially during phase transformations. This paper reviews the work within the Collaborative Research Centre SFB 570 “Distortion Engineering” on determination of segregations and its influence on phase transformations and plasticity as well as the subsequent modelling and simulation.
Numerical distortion simulation of roller bearing rings
Authors: Grohmann O. , Rentsch R. , Heinzel C. , Brinksmeier E. 
Published: January 2012

AbstractResearch within the collaborative research center SFB 570 “Distortion Engineering” has identified effects of the material flow and the strain distribution in metal forming on the distortion of parts. Within this paper the influence of the distortion potential of roller bearings resulting from the hot metal forming process in the industrial manufacturing chain is of special interest. In an experimental study an out‐of‐roundness of the bearings was detected, possibly caused by the shearing process of bar stocks. As a result of the shearing condition both front ends of the cylindrical billet are deformed and oval in shape. This shape deviation is taken into account and transferred into a FE‐model. However, this completes the boundary conditions for the hot metal forming simulation. As a result the simulation proved that the inaccurate geometry causes ring distortion and results in stresses due to a varying strain distribution in the rings.
Influence of austenitisation and transformation hardening on the residual stress development of laser beam treated components made of 20MnCr5
Authors: Sakkiettibutra J. , Kamau E. N. 
Published: January 2012

AbstractIn steel forming process chains residual stresses affect the final form of work pieces. This may have a detrimental effect, e. g. in the case of released residual stresses during laser welding of a shaft‐hub connection, or may be used purposefully, as in the case of a selective application of residual stresses in thermal pre‐stressing. During final heat treatment or rather hardening, distortion is essentially changed. In order to control or exploit the effect of residual stresses, they must be determined at first and their formation has also to be understood. One often neglected influence on the residual stresses is the dependence of the local flow stress, which strongly changes due to the structural transformation. Especially for processes with a high heating and cooling rate the incomplete austenitisation limits the structural hardening during cooling. For both of the applications mentioned above, it will be demonstrated how this influence can be taken into account based on a model and how this influence affects the absolute quantity of residual stresses. The modeled shape changes and residual stresses results are substantiated using speckle photography, laser triangulation, x‐ray and neutron diffraction measurements.
Method to describe interdependencies of state characteristics related to distortion
Authors: Wuest T. , Klein D. , Seifert M. , Thoben K.‐D. 
Published: January 2012

AbstractThe product state can be described through its state characteristics. In each process step some state characteristics are changed to add value to the product. It is also important to be aware of how state characteristics change over time and valuable to understand the interdependencies between different state characteristics. The purpose of this paper is to develop a method, which describes and illustrates interdependencies between relevant state characteristics along a production process chain with the goal to increase transparency for the stakeholders of the product. The process chain of a bearing ring within the project CRC 570 Distortion Engineering and interdependencies of relevant state characteristics connected to distortion and distortion potential will be used as an example to illustrate the above‐mentioned method. A discussion on limitations and benefits of this approach will serve as a conclusion.
Stability Studies of Crude Plant Material of Bacopa monnieri and Quantitative Determination of Bacopaside I and Bacoside A by HPLC
Authors: Srivastava Pratibha , Raut Hema N. , Puntambekar Hemalata M. , Desai Anagha C. 
Published: January 2012

ABSTRACTIntroductionBacopa monnieri (BM) contains several dammarane‐type triterpenoid saponins including bacopaside I and bacoside A. These bioactive compounds may be used as chemical markers for the quality control of different BM products used for promoting mental health and intellect.ObjectiveQuantification of bacopaside I and bacoside A in crude plant material of BM stored under the stability study conditions by HPLC.MethodologyCrude BM samples were stored at long‐term (LS; 30°C and 65% RH), accelerated (AS; 40°C and 75% RH) and real‐time (RT) study conditions. HPLC of BM extracts was carried out using a LiChroCART Purospher® STAR RP‐18 endcapped column along with a guard column, Purospher STAR RP 18e 4.0 4.0 mm 5 µm using a gradient of acetonitrile (A) and water containing 0.05% (v/v) orthophosphoric acid (B) at a flow rate 1.5 mL/min with UV detection at 205 nm.ResultsThe linear range of bacopaside I and bacoside A was 0.2 to 1 mg/mL. With the help of a regression equation the coefficient of determination (r2) values for bacopaside I and bacoside A were found to be > 0.999 and > 0.994 respectively. Relative standard deviation (RSD) values were < 4.0 for all the concentrations injected (n = 3). The HPLC study indicated that BM samples kept under LS condition are rich in saponin contents as compared with the samples stored under AS and RT study conditions.ConclusionThe study indicated that BM plant material should be used fresh to obtain maximum concentration of active saponins or it should be stored under LS conditions up to 3 months. Copyright © 2012 John Wiley & Sons, Ltd.
Performance ratio revisited: is PR > 90% realistic?
Authors: Reich Nils H. , Mueller Bjoern , Armbruster Alfons , van Sark Wilfried G. J. H. M. , Kiefer Klaus , Reise Christian 
Published: January 2012

ABSTRACTIn this study, we investigate the performance ratio (PR) of about 100 German photovoltaic system installations. Monitored PR is found to be systematically lower by ~2–4% when calculated with irradiation data obtained by pyranometers (henceforth denoted as PRPyr) as compared with irradiation amounts measured by reference cells (denoted as PRSi). Annual PRSi for the ~100 systems is found to be between ~70% and ~90% for the year 2010, with a median PR of ~84%. Next, simulations were performed to determine loss mechanisms of the top 10 performing systems, revealing a number of these loss mechanisms may still allow for some optimization. Despite the fact that we do not see such values from our monitoring data base up to now, we believe PRSi values above 90% are realistic even today, using today's commercially available components, and should be expected more frequently in the future. This contribution may help in deepening our knowledge on both energy loss mechanisms and efficiency limits on the system level and standardization processes of system‐related aspects. Copyright © 2012 John Wiley & Sons, Ltd.
Influence of surface texture on the defect‐induced breakdown behavior of multicrystalline silicon solar cells
Authors: Kwapil Wolfram , Nievendick Jan , Zuschlag Annika , Gundel Paul , Schubert Martin C. , Warta Wilhelm 
Published: January 2012

ABSTRACTThe defect‐induced diode breakdown behavior in multicrystalline silicon solar cells, which is located at recombination active crystal defects, is influenced by the surface texturization because the wet chemical treatment selectively etches grain boundaries and dislocations, resulting in etch pits. On textured surfaces, the defect‐induced breakdown voltage is decreased, and the slope of the local reverse I–V characteristics in breakdown is steeper. We find that the local defect‐induced breakdown voltage correlates with the depth of the etch pits. It is suggested that the enhanced electric field in the space charge region at the tip could be superimposed by an electric field around metallic precipitates because of the internal Schottky contact formation with the surrounding silicon. The combined electric field could be responsible for the dependence of the defect‐induced breakdown behavior on the surface texture. Copyright © 2012 John Wiley & Sons, Ltd.
Molecular modeling of hair keratin/peptide complex: Using MM‐PBSA calculations to describe experimental binding results
Authors: Azoia Nuno G. , Fernandes Margarida M. , Micaêlo Nuno M. , Soares Cláudio M. , Cavaco‐Paulo Artur 
Published: January 2012

AbstractMolecular dynamics simulations of a keratin/peptide complex have been conducted to predict the binding affinity of four different peptides toward human hair. Free energy calculations on the peptides' interaction with the keratin model demonstrated that electrostatic interactions are believed to be the main driving force stabilizing the complex. The molecular mechanics–Poisson‐Boltzmann surface area methodology used for the free energy calculations demonstrated that the dielectric constant in the protein's interior plays a major role in the free energy calculations, and the only way to obtain accordance between the free energy calculations and the experimental binding results was to use the average dielectric constant. Proteins 2012;. © 2012 Wiley Periodicals, Inc.
MAPPING RIVER DEPTH FROM PUBLICLY AVAILABLE AERIAL IMAGES
Authors: Legleiter C. J. 
Published: January 2012

ABSTRACTRemote sensing could facilitate efficient characterization of river systems for research and management purposes, provided that suitable image data are available and that the information derived therefrom is reliable. This study evaluated the utility of public domain multispectral images for estimating flow depths in a small stream and a larger gravel‐bed river, using data acquired through a task‐oriented consortium and the National Agricultural Imagery Program (NAIP). Field measurements were used to calibrate image‐derived quantities to observed depths and to assess depth retrieval accuracy. A band ratio‐based algorithm yielded coherent, hydraulically reasonable bathymetric maps for both field sites and three different types of image data. Applying a spatial filter reduced image noise and improved depth retrieval performance, with a strong calibration relationship (R2 = 0.68) and an observed (field‐surveyed) versus predicted (image‐derived) R2 of 0.6 for tasked images of the smaller stream. The NAIP data were less useful in this environment because of geo‐referencing errors and a coarser spatial resolution. On the larger river, NAIP‐derived bathymetry was more accurate, with an observed versus predicted R2 value of 0.64 for a compressed county mosaic easily accessible via the Internet. Comparison of remotely sensed bathymetric maps with field surveys indicated that although the locations of pools were determined accurately, their full depth could not be detected because of limited sensor radiometric resolution. Although a number of other constraints also must be considered, such as the need for local calibration data, depth retrieval from publicly available image data is feasible under appropriate conditions. Copyright © 2012 John Wiley & Sons, Ltd.
Secure communication for the Internet of Things—a comparison of link‐layer security and IPsec for 6LoWPAN
Authors: Raza Shahid , Duquennoy Simon , Höglund Joel , Roedig Utz , Voigt Thiemo 
Published: January 2012

ABSTRACTThe future Internet is an IPv6 network interconnecting traditional computers and a large number of smart objects. This Internet of Things (IoT) will be the foundation of many services and our daily life will depend on its availability and reliable operation. Therefore, among many other issues, the challenge of implementing secure communication in the IoT must be addressed. In the traditional Internet, IPsec is the established and tested way of securing networks. It is therefore reasonable to explore the option of using IPsec as a security mechanism for the IoT. Smart objects are generally added to the Internet using IPv6 over Low‐power Wireless Personal Area Networks (6LoWPAN), which defines IP communication for resource‐constrained networks. Thus, to provide security for the IoT based on the trusted and tested IPsec mechanism, it is necessary to define an IPsec extension of 6LoWPAN. In this paper, we present such a 6LoWPAN/IPsec extension and show the viability of this approach. We describe our 6LoWPAN/IPsec implementation, which we evaluate and compare with our implementation of IEEE 802.15.4 link‐layer security. We also show that it is possible to reuse crypto hardware within existing IEEE 802.15.4 transceivers for 6LoWPAN/IPsec. The evaluation results show that IPsec is a feasible option for securing the IoT in terms of packet size, energy consumption, memory usage, and processing time. Furthermore, we demonstrate that in contrast to common belief, IPsec scales better than link‐layer security as the data size and the number of hops grow, resulting in time and energy savings. Copyright © 2012 John Wiley & Sons, Ltd.
Perinatal outcomes associated with subsequent pregnancy among adolescent mothers in Peru
Authors: Ventura Walter , Ventura‐Laveriano Jessica , Nazario‐Redondo Conny 
Published: January 2012

AbstractObjectiveTo assess the perinatal outcomes of a subsequent pregnancy among adolescent mothers living in Peru.MethodsA large hospital‐based retrospective cohort study was conducted to evaluate singleton births during a 9‐year period (2001–2009). The study population was divided into 3 groups: adolescents aged 15–19 years who had 1 previous parturition (n = 2074), nulliparous adolescents (n = 20 721), and multiparous adults aged 20–29 years (n = 23 129).ResultsNo significant differences were found between multiparous adolescents and the 2 control groups with regard to preterm delivery, perinatal death, and 5‐minute Apgar score below 7. Logistic regression analysis showed no significant differences in the rates of cesarean delivery or preterm birth before 34 or 37 weeks. After adjusting for confounding factors, low birth weight (LBW) and small for gestational age (SGA) were more likely to occur during a subsequent pregnancy among adolescent mothers than during the 1st pregnancy among nulliparous adolescents. The odds ratios were 1.38 (95% CI, 1.14–1.67) and 1.27 (95% CI, 1.02–1.56), respectively.ConclusionMultiparous adolescents are more likely to experience LBW or SGA than are nulliparous adolescents. No significant differences in other perinatal outcomes were found among the 3 study groups.
Evaluation of the biocompatibility of a coating material for an implantable bladder volume sensor
Authors: Kim Su‐Jin , Lee Dong‐Sup , Kim In‐Gul , Sohn Dong‐Wan , Park Jung‐Yul , Choi Bum‐Kyoo , Kim Sae‐Woong 
Published: January 2012

AbstractAs the applications for implantable medical devices have increased, the need for biocompatible packaging materials has become important. Recently, we reported an implantable sensor for real‐time monitoring of the changes in bladder volume, which necessitated finding a safe coating material for use in bladder tissue. At present, materials like polyethylene glycol (PEG), polydimethylsiloxane (PDMS) and parylene‐C are used in biomedical devices or as coating materials, owing to their excellent safety in various medical fields. However, few studies have assessed their safety in bladder tissue, therefore, we evaluated the biocompatibility of PEG, PDMS and parylene‐C in the bladder. All three materials turned out to be safe in in vitro tests of live/dead staining and cell viability. In vivo tests with hematoxylin and eosin and immunofluorescence staining with MAC387 showed no persistent inflammation. Therefore, we consider that the three materials are biocompatible in bladder tissue. Despite this safety, however, PEG has biodegradable characteristics and thus is not suitable for use as packaging. We suggest that PDMS and parylene‐C can be used as safe coating materials for the implantable bladder volume sensor reported previously.
Sedimentation of a sphere in a viscoelastic fluid: a multiscale simulation approach
Authors: Abedijaberi A. , Khomami B. 
Published: January 2012

AbstractA long-standing problem in non-Newtonian fluid mechanics, namely the relationship between drag experienced by a sphere settling in a tube filled with a dilute polymeric solution and the sphere sedimentation velocity, is investigated via self-consistent multiscale flow simulations. Comparison with experimental measurements by Arigo et al. (J. Non-Newtonian Fluid Mech., vol. 60, 1995, pp. 225–257) have revealed that the evolution of the drag coefficient as a function of fluid elasticity can be accurately predicted when the macromolecular dynamics is described by realistic micromechanical models that closely capture the transient extensional viscosity of the experimental fluid at high extension rates. Specifically, for the first time we have computed the drag coefficient on the sphere at high Weissenberg number $\mathit{Wi}$ utilizing multi-segment bead–spring chain models with appropriate molecular parameters and have demonstrated that a hi-fidelity multiscale simulation is not only capable of accurately describing the drag on the sphere as a function of $\mathit{Wi}$ at various sphere-to-tube diameter ratios but also it can closely reproduce the experimentally observed velocity and stresses in the wake of the sphere.
SOWING STRATEGIES FOR BARLEY (HORDEUM VULGARE L.) BASED ON MODELLED YIELD RESPONSE TO WATER WITH AQUACROP
Authors: ABRHA BERHANU , DELBECQUE NELE , RAES DIRK , TSEGAY ALEMTSEHAY , TODOROVIC MLADEN , HENG LEE , VANUTRECHT ELINE , GEERTS SAM , GARCIA-VILA MARGA , DECKERS SEPPE 
Published: January 2012

SUMMARYAquaCrop, the FAO water productivity model, is used as a tool to predict crop production under water limiting conditions. In the first step AquaCrop was calibrated and validated for barley (Hordeum vulgare L.). Data sets of field experiments at seven different locations in four countries (Ethiopia, Italy, Syria and Montana, USA) with different climates in different years and with five different cultivars were used for model calibration and validation. The goodness-of-fit between observed and simulated soil water content, green canopy cover, biomass and grain yield was assessed by means of the coefficient of determination (R2), the Nash–Sutcliff efficiency (E), the index of agreement (d) and the root mean square error (RMSE). The statistical parameters indicated an adequate accuracy of simulations (validation regression of yield: R2 = 0.95, E = 0.94, d = 0.99, RMSE = 0.34). Subsequently, sowing strategies in the semi-arid environment of northern Ethiopia were evaluated with the validated model. Dry sowing had a probability of 47% germination failure attributable to false start of the rainy season. On the other hand, delay sowing at the start of the rainy season to eliminate germinating weeds should be kept as short as possible because grain yields strongly reduce in the season due to water stress when sowing is delayed on shallow soils. This research demonstrates the ability of AquaCrop to predict accurately crop performance with only a limited set of input variables, and the robustness of the model under various environmental and climatic conditions.