bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficient implicit simulation of incremental sheet forming
Authors: Hadoush A. , van den Boogaard A.H. 
Published: December 2011

SUMMARYIn single point incremental forming (SPIF), the sheet is incrementally deformed by a small spherical tool following a lengthy tool path. The simulation by the ﬁnite element method of SPIF requires extremely long computing times that limit the application to simple academic cases. The main challenge is to perform thousands of load increments modelling the lengthy tool path with elements that are small enough to model the small contact area. Because of the localised deformation in the process, a strong nonlinearity is observed in the vicinity of the tool. The rest of the sheet experiences an elastic deformation that introduces only a weak nonlinearity because of the change of shape. The standard use of the implicit time integration scheme is ineﬃcient because it applies an iterative update (Newton–Raphson) strategy for the entire system of equations. The iterative update is recommended for the strong nonlinearity that is active in a small domain but is not required for the large part with only weak nonlinearities. It is proposed in this paper to split the ﬁnite element mesh into two domains. The ﬁrst domain models the plastically deforming zone that experiences the strong nonlinearity. It applies a full nonlinear update for the internal force vector and the stiﬀness matrix every iteration. The second domain models the large elastically deforming zone of the sheet. It applies a pseudolinear update strategy based on a linearization at the beginning of each increment. Within the increment, it reuses the stiﬀness matrix and linearly updates the internal force vector. The partly linearized update strategy is cheaper than the full nonlinear update strategy, resulting in a reduction of the overall computing. Furthermore, in this paper, adaptive reﬁnement is combined with the two domain method. It results in accelerating the standard SPIF implicit simulation of 3200 shell elements by a factor of 3.6. Copyright © 2011 John Wiley & Sons, Ltd.
Adjoint‐based optimal variable stiffness mesh deformation strategy based on bi‐elliptic equations
Authors: Wang Qiqi , Hu Rui 
Published: December 2011

SUMMARYThere are many recent advances in mesh deformation methods for computational fluid dynamics simulation in deforming geometries. We present a method of constructing dynamic mesh around deforming objects by solving the bi‐elliptic equation, an extension of the biharmonic equation. We show that introducing a stiffness coefficient field a(x) in the bi‐elliptic equation can enable mesh deformation for very large boundary movements. An indicator of the mesh quality is constructed as an objective function of a numerical optimization procedure to find the best stiffness coefficient field a(x). The optimization is efficiently solved using steepest descent along adjoint‐based, integrated Sobolev gradients. A multiscenario optimization procedure is performed to calculate the optimal stiffness coefficient field a蜧(x) for a priori unpredictable boundary movements. Copyright © 2011 John Wiley & Sons, Ltd.
Optical switching with isotropic liquid crystals
Authors: Costache Florenta , Blasl Martin 
Published: December 2011

AbstractOptical communication networks and remote optical sensing applications must include, in their architecture, optical switches to dynamically control the optical path connection. Optical switches with no moving parts can warrant high stability and reliability. This is just one of the reasons to employ electrooptical waveguides based on isotropic liquid crystals in optical switching devices. Furthermore of advantage is that, since these devices are fabricated by means of high precision silicon wafer planar technology, they can be tailored to the specific needs of a given application and are suitable for high volume manufacturing.
Laser direct writing
Authors: Häfner Matthias , Pruss Christof , Osten Wolfgang 
Published: December 2011

AbstractDiffractive optics are compact and flexible optical elements with attractive properties that conventional refractive or reflective surfaces cannot deliver. While their fabrication is still challenging, the developments over the past years in both replication and mastering have advanced their application in fields like illumination shaping, metrology, laser beam forming, polarization shaping or fraud protection. A powerful tool for mastering is the technology of laser direct writing, initially developed for applications like mask production for lithography or mastering for optical data storage. In this contribution we present recent developments in laser direct writing technology for diffractive optics.
The effect of loading rates and particle geometry on compressive properties of polypropylene/zinc oxide nanocomposites: Experimental and numerical prediction
Authors: Omar Mohd Firdaus , Akil Hazizan Md , Ahmad Zainal Arifin , Mahmud Shahrom 
Published: December 2011

AbstractCompressive properties, of particulate filled polymer matrix composites, are affected (to a certain extent) by the geometry of the particles, as well as the loadingrates. Therefore, this article presents the results on the compressive properties of polypropylene/zinc oxide nanocomposites across strain rates from 10−2 to 10−3 s−1. The specimens were tested using a Universal Testing Machine for static loading and a conventional Split Hopkinson Pressure Bar apparatus for dynamic loading. Results show that the yield stress and 2.5% flow stress, of both PP/ZnO nanocomposites, showed a positive increment with increasing strain rates. However, the yield strain shows a contradictory pattern, where it decreased with increasing strain rates. PP/ZnO‐white seal recorded higher strain rate sensitivity, dissipation energy, stiffness, and strength properties, than that of PP/ZnO‐pharmaceutical, over a wide range of strain rates investigated. Interestingly, the Eyring theory almost agreed with the experimental results. Overall, based on the experimental and numerical results, we do believe that particle geometry, as well as strain rates, has a significant influence on the compressive properties of polypropylene/zinc oxide nanocomposites specimens. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers
Evaluation of interfacial properties and microfailure mechanisms in single fiber‐reinforced epoxy composites at low temperature
Authors: Park Joung‐Man , Wang Zuo‐Jia , Kwon Dong‐Jun , Gu Ga‐Young , Um Moon‐Kwang , DeVries K. Lawrence 
Published: December 2011

AbstractIn this preliminary study, micromechanical techniques were used to compare the interfacial properties of both carbon and glass fiber composites with two structurally different epoxy matrices (YD‐114 and YDF‐175) at ambient and relatively low temperatures (25°C and −10°C). Tensile modulus of elasticity for both epoxies was higher at lower temperature. Although both fibers exhibited more bimodality at lower temperature than at ambient temperature, glass fiber composites exhibited a statistically greater improvement in tensile strength. This may be attributed to differences in inherent flaws and rigidity. A decrement in stress was observed for YDF‐175 epoxy composites under cyclic loadings at both temperatures, which was attributed to lower interfacial shear strength (IFSS). In contrast to the IFSS of conventional YD‐114 epoxy composites, the IFSS of both the carbon and glass fibers/YDF‐175 epoxy composites studied was higher at the lower temperature. The microfailure pattern observed in microdroplet pullout tests was consistent with the other IFSS results. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers
Bio‐assay Guided Isolation of α‐Glucosidase Inhibitory Constituents from Hibiscus Mutabilis Leaves
Authors: Kumar Deepak , Kumar Hemanth , Vedasiromoni J. R. , Pal Bikas C. 
Published: December 2011

ABSTRACTIntroductionThe increasing demand for natural‐product‐based medicines and health‐care products for the management of diabetes encouraged investigation of this commonly available Indian plant.ObjectivesTo establish the anti‐diabetic (α‐glucosidase inhibitory) activity of H. mutabilis leaf extract, isolate and identify the constituents responsible for the activity, and validate a HPLC method for quantification of the active constituents for standardisation of the extract.Material and methodsThe methanolic extract of leaves was partitioned between water, n‐butanol and ethyl acetate. Bio‐assay guided fractionation, based on inhibition of α‐glucosidase, allowed isolation and identification of the active components. The active components were quantified using RP‐HPLC‐DAD validated for linearity, limit of detection, limit of quantification, precision, accuracy and robustness for this plant extract and the partitioned fractions.ResultsFerulic acid and caffeic acid were identified as the α‐glucosidase inhibitors present in H. mutabilis. They were partitioned into an ethyl acetate fraction. The HPLC‐DAD calibration curve showed good linearity (r2 > 0.99). For the recovery studies the %RSD was less than 2%. The interday and intraday variations were found to be less than 4% RSD for retention time and response.ConclusionThe identification of α‐glucosidase inhibition activity in H. mutabilis supports further investigations into the possible use of the plant for the management of diabetes. The HPLC method validated for these extracts will be useful in future research with the plant. Copyright © 2011 John Wiley & Sons, Ltd.
Proteomics reveals selective regulation of proteins in response to memory‐related serotonin stimulation in Aplysia californica ganglia
Authors: Monje Francisco J. , Birner‐Gruenberger Ruth , Darnhofer Barbara , Divisch Isabella , Pollak Daniela D. , Lubec Gert 
Published: December 2011

AbstractThe marine mollusk Aplysia californica (Aplysia) is a powerful model for learning and memory due to its minimalistic nervous system. Key proteins, identified to be regulated by the neurotransmitter serotonin in Aplysia, have been successfully translated to mammalian models of learning and memory. Based upon a recently published large‐scale analysis of Aplysia proteomic data, the current study investigated the regulation of protein levels 24 and 48 h after treatment with serotonin in Aplysia ganglia using a 2‐D gel electrophoresis approach. Protein spots were quantified and protein‐level changes of selected proteins were verified by Western blotting. Among those were Rab GDP dissociation inhibitor alpha (RabGDIα), synaptotagmin‐1 and deleted in azoospermia‐associated protein (DAZAP‐1) in cerebral ganglia, calreticulin, RabGDIα, DAZAP‐1, heterogeneous nuclear ribonucleoprotein F (hnRNPF), RACK‐1 and actin‐depolymerizing factor (ADF) in pleural ganglia and DAZAP‐1, hnRNPF and ADF in pedal ganglia. Protein identity of the majority of spots was confirmed by a gel‐based mass spectrometrical method (FT‐MS). Taken together, protein‐level changes induced by the learning‐related neurotransmitter serotonin in Aplysia ganglia are described and a role for the abovementioned proteins in synaptic plasticity is proposed.
A chemical switch for detecting insect infestation
Authors: Weerakoon Kanchana A , Chin Bryan A 
Published: December 2011

AbstractBACKGROUND: Plants emit phytochemicals as a defensive mechanism against herbivores. A small sensor switch that responds to these chemicals could be used to stop insect infestation at early stages.RESULTS: Polyethylene‐co‐vinyl acetate was chosen as the best polymer for this particular application, based on its swelling response to plant volatiles. When the carbon concentration of the active layer was low enough to be near the percolation threshold, the sensor could be used as a ‘chemical switch’. The resistance of the sensor increased significantly, mimicking a ‘switch‐off’ response when exposed to the analyte vapor. When the analyte vapor was no longer present, the sensor returned back to its original condition, showing a ‘switch‐on’ response. The percolation point was obtained when the carbon concentration of the polymer/carbon composite was kept at 2.5 wt%.CONCLUSION: A low‐mass‐fraction carbon composite sensor has been designed and fabricated to detect γ‐terpinene, α‐pinene, p‐cymene, farnesene, limonene and cis‐hexenyl acetate. The sensor is inexpensive, easy to fabricate and highly stable in air. Copyright © 2011 Society of Chemical Industry
Optimization of AlGaN‐based spacer layer for InAlN/GaN interfaces
Authors: Akazawa M. , Gao B. , Hashizume T. , Hiroki M. , Yamahata S. , Shigekawa N. 
Published: December 2011

AbstractAlGaN‐based spacer layers for lattice‐matched and nearly lattice matched InAlN/GaN interfaces were examined in Al2O3/InAlN/AlGaN/AlN/GaN structures. An Al2O3 overlayer was deposited to investigate the characteristics under positive bias by capacitance‐voltage (C‐V) measurement. The C‐V characteristic for a sample with an Al0.38Ga0.62N/AlN double spacer layer indicated unfavorable electron accumulation at the InAlN/AlGaN interface inside the barrier under positive bias. To suppress the unfavorable accumulation, attempts were made to increase the Al molar fraction of the AlGaN layer to reduce the conduction band discontinuity and interface charge at InAlN/AlGaN interface. An Al0.44Ga0.56N/AlN double spacer layer and an Al0.44Ga0.56N single spacer layer of almost the same total thickness were investigated. Although both spacer layers result in normal C‐V characteristics without the indication of unfavorable electron accumulation, the InAlN layer on a 1.5‐nm‐thick Al0.44Ga0.56N single spacer layer exhibited superior surface morphology without deteriorating the mobility of the two‐dimensional electron gas despite the absence of the AlN layer. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparative study of UV electro‐absorption modulators based on bulk III‐nitride films and multiple quantum wells
Authors: Kao Chen‐kai , Bhattacharyya A. , Thomidis C. , Moldawer A. , Paiella R. , Moustakas T. D. 
Published: December 2011

AbstractIn this paper we present studies and compare the performance of UV electroabsorption modulators based on bulk GaN films and GaN/AlGaN multiple quantum wells. In both types of devices, the absorption edge at room temperature is dominated by excitonic effects and can be strongly modified through the application of an external electric field. We find that when similar active layer thicknesses and device geometries are employed, the electroabsorption modulators based on bulk nitride films can provide similar performance levels as those of GaN/AlGaN multiple quantum well devices. This should be compared to the case of arsenide, phosphide, or antimonide semiconductors, where the electroabsorption effect in quantum wells is an order of magnitude stronger than in the bulk. This is primarily due to the strong ionic character of the nitride semiconductors, which lead to very large exciton binding energies at room temperature (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of inversion domain formation in AlN grown on sapphire by MOVPE
Authors: Kueller Viola , Knauer Arne , Brunner Frank , Mogilatenko Anna , Kneissl Michael , Weyers Markus 
Published: December 2011

AbstractFor certain growth conditions pronounced roughening has been observed for AlN layers grown on c‐plane sapphire by metal‐organic vapour phase epitaxy. TEM investigations revealed inversion domains correlated with the rough regions of the wafer. Al‐polar material was found at hillocks and N‐polar AlN in the valleys. We have investigated the early stages of growth and found three determining factors for the polarity development in AlN on c‐plane sapphire: substrate treatment by NH3 (nitridation) or TMAl preflow, substrate treatment by annealing under H2 atmosphere and the influence of parasitic depositions in the reactor. We propose a correlation between the sapphire surface termination and the polarity of AlN. Oxygen termination of sapphire is suggested to lead to N‐polarity and aluminium termination to Al‐polar AlN. By optimising the reactor condition, substrate treatment and growth conditions, smooth Al‐polar AlN layers were obtained for the subsequent growth of deep UV‐LED heterostructures. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of vertically propagating convectively coupled equatorial waves using observations and a non‐hydrostatic Boussinesq model on the equatorial beta‐plane
Authors: Roundy Paul E. , Janiga Matthew A. 
Published: December 2011

AbstractA non‐hydrostatic model on the equatorial beta‐plane is solved for the most basic solutions of vertically and zonally propagating internal plane waves. Solutions tilt in the vertical and propagate upward, with buoyancy as a principal restoring force. Results indicate that when frequency is of the same order of magnitude as a reduced buoyancy frequency, the shallow‐water model equivalent depth depends on frequency. One consequence of this dependence is that Kelvin waves become dispersive at high frequencies. In a complementary observational analysis, linear regression and a space‐time wavelet spectrum analysis of observed convectively coupled mixed Rossby gravity (MRG) waves are applied to estimate vertical wavelengths that are consistent with the strongest signals associated with observed convectively coupled waves at specific zonal wave numbers and frequencies. Substitution of these dispersion parameters into the model yields theoretical structures characterized by vertical and horizontal wavenumbers and frequencies similar to those observed in the lower and middle troposphere. These model solutions demonstrate that the Coriolis terms associated with the horizontal component of the earth's angular momentum explain substantial meridional tilts and phase shifts between quantities associated with observed convectively coupled waves, especially proximate to the surface of the Earth. Copyright © 2011 Royal Meteorological Society
Boundary‐layer flow within and above a forest canopy of variable density
Authors: Ross Andrew N. 
Published: December 2011

AbstractAn analytical model is developed for flow within and above a forest canopy with a slowly varying canopy density. Results are compared with existing analytical models for flow over a surface with slowly varying roughness length, and also with numerical simulations. The results show that the analytical solution is successful in capturing the behaviour of the flow for small and slowly changing variations in canopy density. Previous models which only vary the roughness length and neglect changes in displacement height fail to capture the near‐surface flow accurately. Including changes in displacement height as well as roughness length changes gives results closer to those obtained with the full canopy model, but even then the flow induced in the canopy leads to significant differences. The analytical model also highlights the sensitivity of the results to the parametrization of the vertical component of the turbulent stress tensor, τzz. For shorter wavelength variations in the canopy density, the analytical model breaks down as the more rapid changes in density induce larger flow perturbations which lead to increased flow into and out of the canopy. This kind of idealised analytical study provides important insights into the role of canopy heterogeneities on boundary‐layer flow. This is important both for understanding near‐surface winds and transport, and also for parametrizing the effects of surface heterogeneities in large‐scale weather and climate models. Copyright © 2011 Royal Meteorological Society
Wave‐breaking characteristics of midlatitude blocking
Authors: Masato G. , Hoskins B. J. , Woollings T. J. 
Published: December 2011

AbstractIn this article, Northern Hemisphere winter midlatitude blocking is analysed through its wave‐breaking characteristics. Rossby wave breaking is identified as a key process in blocking occurrence, as it provides the mechanism for the meridional reversal pattern typical of blocking. Two indices are designed to detect the major properties of wave breaking, i.e. the orientation (cyclonic/anticyclonic–direction of breaking or DB index) and the relative contribution of air masses (warm/cold–relative intensity or RI index). The use of the DB index differentiates between the anticyclonic cases over Europe and Asia and the cyclonic events over the oceanic basins. One of the three regions displaying cyclonic type was found over the Atlantic Ocean, the other two being over the Pacific Ocean. The first of these is located over the western side of the Pacific and is dominated by warm air extrusions, whereas the second is placed northward of the exit region of the jet stream, where the meridional θ gradient is much weaker. Two European blocking types have been detected using the RI index, which separates out the cases dominated by warm and cold air masses. The latter cases in particular exhibited a well‐structured dipole, with associated strong anomalies in both temperature and precipitation. Copyright © 2011 Royal Meteorological Society
Preparation of water‐soluble starch oligomers from variable starch species in 1‐allyl‐3‐methylimidazolium chloride
Authors: Lappalainen Katja , Kärkkäinen Johanna , Panula‐Perälä Johanna , Lajunen Marja 
Published: December 2011

AbstractNative wheat, barley, rice, maize, wx maize, and potato starch species were modified by depolymerization in 1‐allyl‐3‐methylimidazolium chloride ([AMIM]Cl) ionic liquid (IL) using oil bath or microwave heating. Reactions were catalyzed with p‐toluenesulfonic acid (p‐TsOH). Reaction times varied depending on the starch species and its concentration, the heating method, and volume of the reaction mixture. Depolymerization products were analyzed with HPLC‐ELSD. All starch species mostly degraded into water‐soluble 1500–2000 Da‐sized starch oligomers. Glucose and other short‐chained sugars did not precipitate along with starch oligomers due to their high solubility in IL. This property was utilized in the purification of commercial maltodextrins. Produced water‐soluble, low MW starch oligomers might be used, e.g., in bacterial cultivations as a glucose source.
Gendiagnostikgesetz
Authors: Gillessen-Kaesbach G. , Glaubitz R. , Eiben B. 
Published: December 2011

Zusammenfassung
Die enormen Fortschritte im Bereich der Humangenetik tragen fast täglich zur Identifizierung neuer krankheitsverursachender Gene bei. Die Konsequenzen aus diesen genetischen Informationen haben eine erhebliche Bedeutung im Hinblick auf den persönlichen Umgang mit Krankheiten und auf die individuelle Lebensplanung. In der genetischen Beratung werden dem Ratsuchenden Informationen im Hinblick auf das Wesen der Erkrankung, der Bedeutung genetischer Befunde sowie Möglichkeiten der Prävention, Therapie und Diagnostik vermittelt, die dann Grundlage für eine autonome Entscheidung sind. Das am 1. Februar 2010 in Kraft getretene Gendiagnostikgesetz (GenDG) regelt den Umgang mit genetischen Untersuchungen sowie die Verwendung genetischer Proben und Daten beim Menschen und stellt die Anforderungen an die genetische Beratung dar. Ab dem 1. Februar 2012 dürfen nur Ärzte eine genetische Beratung durchführen, die eine entsprechende Qualifikation erworben haben.