bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Rheology of Frozen Soils
Authors: Arenson Lukas U. , Springman Sarah M. , Sego Dave C. 
Published: June 2019

Abstract
The rheological behaviour of frozen soils depends on a number of factors and is complex. Stress and temperature histories as well as the actual composition of the frozen soil are only some aspects that have to be considered when analysing the mechanical response. Recent improvements in measuring methods for laboratory investigations as well as new theoretical models have assisted in developing an improved understanding of the thermo-mechanical processes at play within frozen soils and representation of their response to a range of perturbations. This review summarises earlier work and the current state of knowledge in the field of frozen soil research. Further, it presents basic concepts as well as current research gaps. Suggestions for future research in the field of frozen soil mechanics are also made. The goal of the review is to heighten awareness of the complexity of processes interacting within frozen soils and the need to understand this complexity when developing models for representing this behaviour.
On the Simulation of Kinetic Theory Models of Complex Fluids Using the Fokker-Planck Approach
Authors: Mokdad B. , Pruliere E. , Ammar A. , Chinesta F. 
Published: June 2019

Abstract
Models of kinetic theory provide a coarse-grained description of molecular configurations wherein atomistic processes are ignored. The Fokker-Planck equation related to the kinetic theory descriptions must be solved for the distribution function in both physical and configuration spaces. When the model involves high dimensional spaces (including physical and conformation spaces and time) standard discretization techniques fail due to excessive computation requirements. In this paper, we revisit some model reduction techniques recently proposed to circumvent those difficulties, exploring other new application areas related to entangled polymer models as well as the use of such reduced models for treating complex flows in which the distribution function involves both the physical and the conformation coordinates.
Free Surface Effects on Normal Stress Measurements in Cone and Plate Flow
Authors: Venerus David C. 
Published: June 2019

Abstract
The effects of free surface shape on normal stress difference measurements in cone and plate flow are investigated. The analysis shows that the stress field is significantly altered by deviations of the free surface from an ideal (spherical) shape. For the cone and partitioned plate technique, it is shown how modest deviation from a spherical free surface shape can lead to errors of roughly 10% in the measured normal stress differences.
Optimized Rheo-optical Measurements Using Fast Fourier Transform and Oversampling
Authors: Klein Christopher , Venema Paul , Sagis Leonard , van Dusschoten Dagmar , Wilhelm Manfred , Spiess Hans Wolfgang , van der Linden Erik , Rogers Salman S. , Donald Athene M. 
Published: June 2019

Abstract
Rheo-optics is a method that allows the analysis of optical properties, like birefringence and dichroism under steady and oscillatory shear. It is possible to correlate macroscopic mechanical responses with induced microscopic changes in the material. We describe how this method was improved several fold and implemented on a commercially available setup. However, the here presented ideas are applicable to any rheo-optical setup, based on modulation of the laser light. Additionally it does not need a lock-in amplifier and therefore reduces the costs of the setup.
Rheological Characterization of Shear-Thinning Fluids with a Novel Viscosity Equation of a Tank-Tube Viscometer
Authors: Kwon Kyung C. , Park YoonKook , Floyd Tamara , Vahdat Nader , Jackson Erica , Jones Paul 
Published: June 2019

Abstract
A tank-tube viscometer and its novel viscosity equation were developed to determine flow characteristics of non-Newtonian fluids. The objective of this research is to test capabilities of the tank-tube viscometer and its novel non-Newtonian viscosity equation by characterizing rheological behaviors of well-known polyethylene oxide (MW 8000000) aqueous solutions as non-Newtonian fluids with 60-w% sucrose aqueous solution as a reference calibration fluid. Non-Newtonian characteristics of 0.3 - 0.7 wt% polyethylene oxide aqueous solutions were extensively investigated with the tank-tube viscometer and its non-Newtonian viscosity equation over the 294 - 306 K temperature range, and 55 - 784 s-1 shear rate range. The 60-w% sucrose aqueous solution was used as a reference/calibration fluid for the tank-tube viscometer. Dynamic viscosity values of 60 w% sucrose aqueous solution were determined with the calibrated tank-tube viscometer and its Newtonian viscosity equation at 299.15 K, and compared with the literature values.
Effects of State Change of Liquid Crystalline Polymer on Dynamic Visco-Elasticity of its Blends with Polyethylene-Terephthalate
Authors: Hashmi S.A.R. , Kitano Takeshi 
Published: June 2019

Abstract
The dynamic viscoelastic properties of liquid crystalline polymer (LCP) and polyethylene terephthalate (PET) blends were studied at two different temperatures: 265°C at which LCP was in solid state and 285°C at which LCP was in molten state. The PET was in molten state at both the temperatures. The storage modulus, G’, loss modulus, G’’, dynamic viscosity, h’, of blends with different compositions were evaluated and compared. The morphology of these samples was studied using scanning electron microscope, which exhibited composition dependency. A maxima was observed in the viscosity versus composition plot corresponding to 90/10 LCP/PET blend at 285°C. The G’ versus G’’ plots demonstrated the composition dependency of LCP/PET blends.
Error Introduced by a Popular Method of Processing Parallel-Disk Viscometry Data
Authors: Yeow Y. Leong , Leong Yee-Kwong , Khan Ash 
Published: June 2019

Abstract
The assumptions implicit in the simplified expressions used to convert the torque-rotational speed data of parallel-disk viscometry into rim shear rate and rim shear stress are identified. The rim shear stress generated by the simplified expression is compared against the actual rim shear stress. The error involved is quantified for two standard rheological models and for a set of laboratory data. Under normal operation conditions of parallel-disk viscometers this error was found to be within the acceptable limit. However, for highly shear thinning fluids and for fluids exhibiting yield stress this error can become very large. The suitability of the approximate rim shear stress in wall slip determination is then briefly discussed.
Genetic Programming Approach for Flow of Steady State Fluid Between Two Eccentric Spheres
Authors: El-Bakry Mostafa Y. , Radi Amr 
Published: June 2019

Abstract
Genetic Programming (GP) is used to estimate the functions that describe the torque and the force acting on the external sphere due to steady state motion of viscoelastic fluid between two eccentric spheres. The GP has been running based on experimental data of the torque at different eccentricities to produce torque for each target eccentricity. The angular velocity of the inner sphere and the eccentricity of the two spheres have been used as input variables to find the discovered functions. The experimental, calculated and predicted torque and forces are compared. The discovered function shows a good match to the experimental data. We find that the GP technique is a good new mechanism of determination of the force and torque of fluid in eccentric sphere model.
Shear Rate Corrections for Herschel-Bulkley Fluids in Couette Geometry
Authors: Kelessidis Vassilios C. , Maglione Roberto 
Published: June 2019

AbstractA methodology is presented to invert the flow equation of a Herschel-Bulkley fluid in Couette concentric cylinder geometry, thus enabling simultaneous computation of the true shear rates, γ̇HB, and of the three Herschel-Bulkley rheological parameters. The errors made when these rheological parameters are computed using Newtonian shear rates, γ̇N, as it is normal practice by research and industry personnel, can then be estimated. Quantification of these errors has been performed using narrow gap viscometer data from literature, with most of them taken with oil-field rheometers. The results indicate that significant differences exist between the yield stress and the flow behavior index computed using γ̇HB versus the parameters obtained using γ̇N and this is an outcome of the higher γ̇HB values. Predicted true shear rates and rheological parameters are in very good agreement with results reported by other investigators, who have followed different approaches to invert the flow equation, both for yield-pseudoplastic and power-law fluids.
Aging, Rejuvenation and Thixotropy in Complex Fluids: Time-dependence of the Viscosity at Rest and under Constant Shear Rate or Shear Stress
Authors: Quemada Daniel 
Published: June 2019

Abstract
Complex fluids exhibit time-dependent changes in viscosity that have been ascribed to both thixotropy and aging. However, there is no consensus for which phenomenon is the origin of which changes. A novel thixotropic model is defined that incorporates aging. Conditions under which viscosity changes are due to thixotropy and aging are unambiguously defined. Viscosity changes in a complex fluid during a period of rest after destructuring exhibit a bifurcation at a critical volume fraction ϕc2. For volume fractions less than ϕc2 the viscosity remains finite in the limit t →∞. For volume fractions above critical the viscosity grows without limit, so aging occurs at rest. At constant shear rate there is no bifurcation, whereas under constant shear stress the model predicts a new bifurcation in the viscosity at a critical stress σB, identical to the yield stress σy observed under steady conditions. The divergence of the viscosity for σ≤σB is best defined as aging. However, for σ > σB, where the viscosity remains finite, it seems preferable to use the concepts of restructuring and destructuring, rather than aging and rejuvenation. Nevertheless, when a stress σA(≤σB) is applied during aging, slower aging is predicted and discussed as true rejuvenation. Plastic behaviour is predicted under steady conditions when σ > σB. The Herschel-Bulkley model fits the flow curve for stresses close to σB, whereas the Bingham model gives a better fit for σ >> σB. Finally, the model’s predictions are shown to be consistent with experimental data from the literature for the transient behaviour of laponite gels.
New Driving Unit for the Direct Measurement of Yield Stress with a Stress Controlled Rheometer
Authors: Shahnazian Hamid , Odenbach Stefan 
Published: June 2019

Abstract
Investigations of rheological properties of ferrofluids have shown strong changes of the viscosity in magnetic fluids with an applied magnetic field. The change of the viscosity – the magnetoviscous effect – can theoretically be described with chain and structure formation under the influence of a magnetic field. Moreover, the formation of these structures leads to the appearance of viscoelastic effects or other non-Newtonian features like yield stress in ferrofluids with an applied magnetic field. With a shear rate controlled rheometer – as it as been used in former experiments – the yield stress could not be investigated directly. Therefore the results concerning a field dependent yield stress based on an extrapolation of shear controlled measurements. For the direct investigations of the yield stress, a dedicated stress controlled rheometer is required, allowing direct investigations of the magnitude and field dependence of this effect. In this work the design of the stress controlled rheometer with its main parameters has been described in detail. The rheological investigations with differently composed fluids show that the stress controlled rheometer enables direct measurements of even small yield stresses in ferrofluids as well as large effects like they are found in magnetorheological fluids (MRF).
Evaluation of Slip Effects in the Capillary Flow of Foams
Authors: Bekkour Karim 
Published: June 2019

Abstract
Foams have been prepared from water added with a surfactant (Sodium-Dodecyl-Sulfate, SDS) and a polymer (Poly-Ethylene-Oxide, PEO) at different concentrations. This work was devoted to a study of the flow properties of the foams. The pressure drops were measured during flow in capillary tubes (2.5, 3.5 and 4 mm) in laminar regime. It was found a strong dependence of the flow curves on capillary diameter showing that pronounced wall slip effects exist. Two known approaches were applied to quantify the slip velocity: (a) the Mooney method, in which the key assumption is that the slip velocity depends only on the wall shear stress, was not applicable and (b) the Oldroyd-Jastrzebski method, in which the assumption is that the slip velocity depends not only on the wall shear stress but also on the flow geometry, yielded satisfactory results. The determination of the pressure drop coefficient showed that the Metzner and Reed correlation, i.e., the Reynolds analogy based on the generalised Reynolds number, could be applied if the data are corrected for slip effects.
Rheological Study of the Interfacial Crosslinking Reaction in Reactive Polymer Blends
Authors: Cirman C. , Bouquey M. , Terrisse J. , Muller R. 
Published: June 2019

Abstract
Two reactive methacrylic polymers were synthesized by copolymerization of isobutylmethacrylate with a small amount of either methacrylic acid or glycidyl methacrylate. In a molten blend, the condensation reaction between the acid and epoxy groups leads to crosslinking at the interface between the domains formed by the two polymers. This reaction was followed by dynamic mechanical measurements in the melt. Blends were prepared by compression molding a mixture of pellets of controlled size and then by shearing these samples in a cone and plate rheometer up to different values of total shear strain, thus achieving different values of interfacial area per unit volume. Since the two copolymers are miscible, a homogeneous blend could be obtained by coprecipitation and was considered as a limiting case for high values of interfacial area. The glass transition temperature of the polymers was well below the temperature at which the kinetics of the condensation reaction becomes significant. It was therefore possible to separate the creation of interface by shearing from the interfacial crosslinking reaction, which was induced by increasing the temperature. For the blends with the highest values of interfacial area, the viscoelastic properties in the melt after reaction revealed a low frequency plateau for the storage modulus G’, whose level increases almost linearly with the amount of applied shear strain.
On the importance of cryptographic agility for industrial automation
Authors: Paul Sebastian , Niethammer Melanie 
Published: June 2019

Abstract
Cryptographic primitives do not remain secure, they deteriorate over time. On the one hand increasing computing power leads to more powerful attacks on their underlying mathematical problems. On the other hand quantum computing threatens to break many widely used cryptographic primitives. The main goal of cryptographic agility is to enable an easy transition to alternative cryptographic schemes. Considering the long lifetime of products within industrial automation, we argue that vendors should strive for cryptographic agility in their products. In this work we motivate cryptographic agility by discussing the threat of quantum computers to modern cryptography. Additionally, we introduce the reader to the concept of post-quantum cryptography. Ultimately, we demonstrate that cryptographic agility requires three elements: 1) cryptographic application programming interfaces, 2) secure update mechanisms and 3) documentation of cryptographic primitives. By providing practical concepts we show how to meet these requirements in software-based systems.
Cyber security and Industry 4.0
Authors: Mehrfeld Jens 
Published: June 2019

Abstract
“Stagnation is death“. This quote can be applied to two aspects. First, it is bad for a company if an outage occurs since then it cannot produce goods anymore and thus can make no more profit. Second, this quote can also refer to the developments leading to Industry 4.0. But what happens if technological progress creates more risks? The following article explores this issue with respect to IT security.
Diagnostic performance of cerebrospinal fluid free light chains in Lyme neuroborreliosis – a pilot study
Authors: Tjernberg Ivar , Johansson Marcus , Henningsson Anna J. 
Published: June 2019

Abstract

Background
The aim of this study was to evaluate the diagnostic performance of cerebrospinal fluid (CSF) free light chains (FLCs) in the diagnosis of Lyme neuroborreliosis (LNB).

Methods
Serum and CSF levels of κ- and λ-FLC, albumin and total concentration of immunoglobulin M (IgM) were determined together with CSF chemokine CXCL13 in 23 patients with definite LNB, 35 inflammatory neurological disease control (INDC) and 18 non-inflammatory control (NIC) patients. Indices and intrathecal fractions (IFs) of FLC and IgM were calculated.

Results
Significant differences in FLC indices and IFs were found between the LNB group and both control groups, p ≤ 0.007. Sensitivity of intrathecal κ- and λ-FLC synthesis reached 78%–87% in LNB patients with a specificity of 94%–100% in NIC patients, whereas specificity in INDC patients was 69%. The corresponding frequencies of positive results for IF and index of IgM and CSF CXCL13 in these three diagnostic groups were 74%–96% in LNB patients, 0% in NIC patients and 3%–6% in INDC patients at the chosen cut-off levels.

Conclusions
The findings of this study show a moderate to high sensitivity of CSF κ- and λ-FLC in LNB patients with a high specificity in NIC patients. However, overlap in CSF κ- and λ-FLC levels between LNB and INDC patients calls for caution in the interpretation and limits the diagnostic usefulness in the LNB diagnosis. CSF CXCL13 appears to be the most valuable additional biomarker of LNB aside from routine parameters such as CSF pleocytosis and anti-Borrelia antibody index.
Effect of confined electrolyte volumes on galvanic corrosion kinetics in statically loaded materials
Authors: Policastro Steven A. , Hangarter Carlos M. , Anderson Rachel M. , Friedersdorf Fritz 
Published: June 2019

Abstract
This work investigates the effects that the confined volume of atmospheric electrolytes has on the galvanic corrosion kinetics of a martensitic stainless steel alloy, UNS S13800, coupled with UNS A97075 in simulated atmospheric environments at relative humidity values that span the range of operational exposures. Restricted volumes found in thin films and droplets have been shown to control reduction reaction kinetics and are an ongoing challenge to characterize and standardize. This, along with the dynamic and high concentration of aggressive ions found in confined electrolytes, creates a unique corrosion system that requires a multifaceted approach to evaluate varied conditions, compare them with traditional measurements, and more accurately predict galvanic atmospheric corrosion. In this work, corrosion currents in galvanic couples were obtained under two environmental conditions: (1) bulk electrolytes, in a standardized test configuration, with chemistries relevant to atmospheric electrolytes; and (2) deliquesced droplets formed and equilibrated at a given temperature and relative humidity value. The corrosion currents for the same galvanic couple specimens were evaluated, using an atmospheric corrosion model, under a thin film electrolyte while statically loaded and unloaded, at two nominally different locations, e.g. Alexandria, VA, and Miami, FL, on the same date, using recorded weather conditions. The modeled corrosion currents were then compared with the currents obtained from the experimental conditions.
When do small fatigue cracks propagate and when are they arrested?
Authors: Stanzl-Tschegg Stefanie E. 
Published: June 2019

Abstract
The formation of small and long cracks and their propagation or arrest are treated drawing special attention to the (a) impact of environment and (b) several loading parameters (R-ratio, stress/strain-amplitude, constant-amplitude and variable-amplitude loading, superimposed loading, ultrasonic fatigue loading, and frequency effects) for three groups of metallic materials (two high-strength steels, 7075 and 2024 Al alloys, polycrystalline copper). The influence of these parameters on lifetimes and fatigue crack propagation behavior being determined by microstructural features on all levels of magnification (ranging from several millimeters to nanometers) is presented. A review of the state of knowledge according to literature is given in the introduction. The following results were obtained, and models for their interpretation were presented: The development (growth or arrest) of small cracks into a long crack is driven by several competing processes (due to material, way of loading, environment, etc.). The environment plays a predominant role. Especially in the high-cycle and very-high cycle regime, the complexity of interacting processes needs further – mainly experimental – investigations. Some further studies relate to different loading conditions and possibilities of testing considering newly developed material. Experiments in high vacuum have to form the basis for studying environmentally assisted fatigue response.
Synthesis and characterization of a polyisocyanide with thioether pendant caused an oxidation-triggered helix-to-helix transition
Authors: Guo Li-Yuan , Zhang Han , Huang Sheng-Tang , Di Man , Yao Gang , Wu Shi 
Published: June 2019

AbstractStimuli responsive helical polymers have attracted wide attention and many polymers responsive to the external stimuli have been synthesized. But, only a few examples have been reported regarding the redox-induced helicity inversion helical polymers. The polyisocyanide including thioether pendant (poly-MBTIP) was synthesized by polymerization of methyl (R)-3-(benzylthio)-2-isocyanopropanoate (MBTIP) monomer using NiCl2·6H2O as catalytic agent in dry DCM. The chiroptical and oxidation properties of the poly-MBTIP are investigated. The poly-MBTIPs exhibit intense specific optical rotations and Cotton effects compared to the monomer, strongly suggesting a helical conformation of the polymer backbone. Additionally, the thioether pendant of poly-MBTIP backbone was oxidized to sulfoxide group by H2O2. Interestingly, the specific optical rotations and Cotton effects of poly-MBTIP oxidized are reversed, probably suggesting a helical conformation inversion.
Conetworks on the base of polystyrene with poly(methyl methacrylate) paired polymers
Authors: Kizhnyaev Valery N. , Pokatilov Fedor A. , Shabalin Alexey I. , Zhitov Roman G. 
Published: June 2019

AbstractIt is found that forced (reactive) blending of polystyrene (PS) with polymethylmethacrylate (PMMA) involves the covalent binding of heterogeneous macromolecules to afford the paired polymers. For this purpose, the “anchor” N-H unsubstituted tetrazole or oxirane functional groups are preliminarily introduced in the structure of both polymers in a small amount that leads to a covalent binding of the heterogeneous macromolecules. The reaction between the modified PS and PMMA is carried out in dimethylformamide (DMF), toluene and dichloroethane (DCE) at a high total concentration of polymers (10-20 g dL-1). The process is accompanied by gel-formation to deliver cross-linked paired polymers It is established that the highest rate of the paired polymer is attained in the DCE medium, while the lowest rate is observed in DMF. For paired polymers synthesized in DMF, two glass transition temperatures (Tg) of 92°C and 104°C correspond to the original PS and PMMA, respectively. The products of forced blending of PS and PMMA in toluene have one averaged Tg value (99°C), whereas those obtained in DCE show no pronounced glass transition region at 90 ÷ 115°C. In toluene or DCE, the paired polymers are formed, which represent single-phase systems having one glass transition region.