Homogenous Expansion Research Articles

Implementing Reversible Swelling into the Numerical Model of a Lithium-Ion Pouch Cell for Short Circuit Prediction

Mechanical simulation models have become crucial for understanding Li-ion battery failure and degradation mechanisms. However, existing safety assessment models lack the implementation of SOC-dependent thickness variations referred to as reversible swelling. Reversible swelling affects the applied preload force on a constrained pouch cell, potentially impacting its safety. To investigate this, a finite element RVE model was developed in LS-Dyna. Two swelling models, simplified homogenous expansion (HE) and locally resolved expansion (LE), were implemented along with a reference basis model (BM) without expansion. Six different stress- or strain-based short circuit criteria were calibrated with abuse test simulations at different SOCs and preload forces. Short circuit prognosis improved on average by 0.8% and 0.7% for the LE and HE model compared to the BM, with minimum principal stress being the most suitable criterion. The LE model exhibited a softer mechanical response than the HE model or BM, accounting for the pouch cell surface unevenness at small indentations. This study demonstrated the feasibility and usefulness of implementing an expansion model in a commercial FE solver for improved short circuit predictions. An expansion model is crucial for simulating aged battery cells with significant geometry changes strongly affecting the preload force of a constrained battery cell.

Reinterpretation of the Geldart A powder classification based on Eulerian–Eulerian CFD simulation

Abstract Geldart classified powders into four categories and assigned each category its own unique characteristic. Geldart A particles, being easily aeratable, show a unique feature of ‘Homogenous expansion’ before bubbling. In this work, an additional feature for the Geldart chart is proposed which adds significant utility for the processing of Geldart A particles. CFD was used to characterize the entire Geldart A region of the Geldart chart based on detailed fluidization behavior. For this, Eulerian–Eulerian Two-fluid model (TFM) simulations were conducted for 25 particle systems across the entire span of the Geldart A region. The simulations (Solid volume fraction (SVF) contours) of bed evolution, taken before the appearance of multiple bubbles, were analyzed in detail. The particle systems were then sub-categorized into Red (5% average bed expansion), Orange (12.5% average bed expansion), and Green (30% average bed expansion) sub-types. The sub-types were plotted on Geldart chart, and for the first time a continuum heat map was generated, from which the ‘level of fluidizability’ of all Geldart A powders can be conveniently gaged. The map can be used for a more informed choice of powder for various industrial applications. Also, the A/B boundary proposed by Verloop was found to be a better fit for our proposed continuum when compared to the original Geldart A/B boundary. The 2D Simulation results performed in this work, found adequate validation against experimental findings in literature. Further, fine mesh 2D simulation results compared well with 3D simulations for dense bed, and were thereby deemed adequate for revealing dense bed behavior before onset of multiple bubbles.

Characteristics of Welding Residual Stress Distribution in Dissimilar Weld Joints

For the construction of ecofriendly ships, fuels such as liquefied natural gas (LNG), ammonia, and hydrogen are being discussed as alternatives. LNG fuel has recently been applied to shipbuilding. The most important aspect of an LNG propulsion ship is the LNG storage tank, because LNG is stored at a high pressure and low temperature. Cryogenic steels are needed to evaluate safety in weld joints, especially the LNG storage tank which has a dissimilar weld joint with a STS pipe. The dissimilar weld joint has a complex welding residual stress distribution. It is necessary to evaluate the effects of temperature changes that occur during the loading–unloading process of LNG. In this study, the residual stress distribution characteristics of heterogeneous welding parts welded to STS pipes using 9% Ni steel, STS, and high-manganese austenitic steel in an LNG storage tank were investigated through experimental and analytical methods. The thermal stress due to the difference in thermal expansion coefficient between cryogenic steel and the STS pipe occurred with a small amount in loading–unloading of LNG. When high-manganese austenitic steels and the STS pipe were joined, tensile stress was generated at the dissimilar weld joint owing to the temperature difference generated during the LNG loading–unloading process. STS has a homogenous weld joint and identical thermal expansion coefficients; therefore, the shrinkage and expansion were not affected by the temperature change. The welding residual stress at the dissimilar weld joints was measured via an experimental cutting method, and the results indicated that the tensile residual stress had distribution similar to the yield stress of the material. The stress generated by the temperature change and the welding residual stress overlapped and occurred during the loading–unloading process of the LNG tank; however, the final tensile stress below the tensile stress was distributed in the storage tank.

Stochastic velocity modeling of Magneto-Hydrodynamics Non-Darcy flow between two stationary parallel plates

A stochastic model for the Magneto-Hydrodynamics (MHD) of a non-Darcy flow between two parallel plates has been presented in this paper. This is due to the significant importance and the wide range applications of such fluid along with the need for more real-life representative models, which are relatively few in the literature. The introduced novel model considered the included uncertainties in all parameters where a general numerical solution was derived using the Stochastic Finite Difference method based on Homogenous Chaos expansion (SFDHC). Four cases were studied in the investigation; stochastic medium porosity, stochastic Hartmann number, stochastic Forchheimer number, and stochastic pressure gradient. In each of the cases mentioned, the probability density function (PDF) of the resulting stochastic flow velocity was derived and evaluated concerning their mean and Standard Deviation (SD). In addition, the results in all of the four cases were further validated with the corresponding Monte Carlo Simulation (MCS) showing strong conformity. Moreover, the results of the model solution were tabulated and plotted using two common values for each parameter and a Gaussian stochastic process with 10% coefficient of variation for the uncertain one. Consequently, the velocity mean, SD and approximate range varied between 0.8175,0.8204, 0.0018,0.0573, and 0.0144,0.4881 respectively. The results showed also that the largest effect of the uncertain parameters on the fluid velocity is caused by; the pressure gradient, the medium porosity, the Hartmann number and the Forchheimer number respectively. Furthermore, the results of this study provide the required uncertainty quantification for the problem under consideration.

An Infinite-Light and Infinite-Frequency in Cosmology and Neurosciences

The aim of this paper is to introduce the new concept of an infinite-light and infinite-frequency. Research methodology includes literature review, new hypotheses and scientific explanations to support it are stated and clarified, and finally, suggestions are proposed on how to study it. In brief, this paper discusses a widely accepted big bang theory on creation of our universe which mentions formation of glowing or light before particle-formation phase, and concept of duality for an atom and light in relation to an infinite-light. These two notions clearly brought out light as a fundamental subject to discuss. In this manuscript, I hypothesize an existence of an infinite-light which has several peculiar features: 1) infinite-energy, 2) infinite frequency (waveless energy), 3) infinite time (timeless), and 4) infinite-space (infinite-universe). In connection with these features, an infinite-light can be theorized to exist either immediately after the big bang or prior to big bang. Interestingly, its existence can explain creation of the universe in further details. It might be able to unravel what has already existed before the big bang, what drives the isotropic and homogenous universe expansion, why there is cosmological constant and finally it may clarify matters related to consciousness, invisibility, black hole and dark energy. Nonetheless, one must bear in mind that most written in this manuscript are hypothetical and remain to be proven.

An Autocrine TNFα-Tumor Necrosis Factor Receptor 2 Loop Promotes Epigenetic Effects Inducing Human Treg Stability In Vitro.

A crucial issue for Treg-based immunotherapy is to maintain a bona fide Treg phenotype as well as suppressive function during and after ex vivo expansion. Several strategies have been applied to harness Treg lineage stability. For instance, CD28 superagonist stimulation in vitro, in the absence of CD3 ligation, is more efficient in promoting Treg proliferation, and prevention of pro-inflammatory cytokine expression, such as IL-17, as compared to CD3/CD28-stimulated Treg. Addition of the mTOR inhibitor rapamycin to Treg cultures enhances FOXP3 expression and Treg stability, but does impair proliferative capacity. A tumor necrosis factor receptor 2 (TNFR2) agonist antibody was recently shown to favor homogenous expansion of Treg in vitro. Combined stimulation with rapamycin and TNFR2 agonist antibody enhanced hypo-methylation of the FOXP3 gene, and thus promoting Treg stability. To further explore the underlying mechanisms of rapamycin and TNFR2 agonist-mediated Treg stability, we here stimulated FACS-sorted human Treg with a CD28 superagonist, in the presence of rapamycin and a TNFR2 agonist. Phenotypic analysis of expanded Treg revealed an autocrine loop of TNFα–TNFR2 underlying the maintenance of Treg stability in vitro. Addition of rapamycin to CD28 superagonist-stimulated Treg led to a high expression of TNFR2, the main TNFR expressed on Treg, and additional stimulation with a TNFR2 agonist enhanced the production of soluble as well as membrane-bound TNFα. Moreover, our data showed that the expression of histone methyltransferase EZH2, a crucial epigenetic modulator for potent Treg suppressor function, was enhanced upon stimulation with CD28 superagonist. Interestingly, rapamycin seemed to downregulate CD28 superagonist-induced EZH2 expression, which could be rescued by the additional addition of TNFR2 agonist antibody. This process appeared TNFα-dependent manner, since depletion of TNFα using Etanercept inhibited EZH2 expression. To summarize, we propose that an autocrine TNFα–TNFR2 loop plays an important role in endorsing Treg stability.

Fluidization of solids with water in supercritical conditions – Characteristics of pressure fluctuations

Three flow pattern evolution processes of fixed-homogeneous, fixed-homogeneous-bubbling and fixed-bubbling have been observed in a water–solid fluidized bed in supercritical conditions. In this paper, pressure fluctuation signals of each fluidization regimes were analyzed by time domain, frequency domain, and time–frequency methods. The characteristics of standard deviation of absolute pressure (AP), power density spectrum (PDS) of differential pressure (DP), multi-resolution decomposed signals and decomposed signals of three scales (macro-scale, meso-scale and micro-scale) were obtained in different flow regimes. The plot of AP standard deviation vs. superficial velocity showed a peak on the transition from fixed bed to homogenous expansion. The dominant frequency of homogenous regime (at ambient, high pressure and sub-critical conditions) was close to zero. In the bubbling regime (some supercritical conditions), a band of frequency between 0 and 1Hz was observed, which was smaller than the classical gas–solid bubbling fluidized bed. The energy proportion of macro-scale signal component was the highest among the three scales components of signals, which indicated that the macro-scale flow dynamic was dominant.

Implementation of capacitive probes for ultra-high precision machine for cylindricity measurement with nanometre level of accuracy

Capacitive probes are widely used on new ultra-high precision machines to perform measurements with an uncertainty of few nanometres, especially for cylindricity measuring machines. For this reason, their insitu calibration has to be carried out by using a specific structure. Therefore, a preliminary high precision set-up has been designed and manufactured to investigate the behaviour and the implementation of the capacitive probes. Both the number and the locations of the capacitive probes in the set-up are presented and detailed, to justify how they minimize the homogenous thermal expansion effects. The experimental set-up allows validating the insitu calibration principle of the capacitive probes with regard to the laser interferometers. The recorded residual errors are about 2 nm over the 80 µm-travel range. The effect of a transverse offset of the capacitive probe from the cylinder's generatrix has been investigated both experimentally and theoretically, as well as they present a good agreement.

Studies of Si-Fe-C Electrode Materials Prepared By Combinatorial Sputter Deposition

Introduction Based on our previous studies (e.g. [1]) and other work [2], it is our opinion that silicon-based amorphous alloys are promising for use as a negative electrode. This is due to the fact that the volume expansion of amorphous silicon (a-Si) upon Li insertion is homogeneous and causes less pulverization as compared to the crystalline material. In addition to the homogenous expansion, the two-phase regions are inhibited once a-Si is used.Herein, a combinatorial study, on Si-Fe-C sputtered films covering a wide range of compositions is presented. The intention is to study the effect of both Fe and C within the electrode on the electrochemical performance. Carbon was added in the hope that some carbon would remain “free” and could transport intercalated Li effectively to the interior of the particles, whereas iron can form an inactive matrix that reduces the overall volume expansion. Experimental Four combinatorial libraries in the Si-Fe-C system were produced using a Corona Vacuum Coaters model V3-T multi-target sputtering system described in [3]. Different targets, two inches in diameter, were used: a Si target, an Fe target and a C target. The targets and a plasma scrubber were mounted on magnetrons. The desired deposition profile was be achieved by using different stationary masks placed over the targets. Figure 1 summarizes the produced compositions.X-ray diffraction was used to study the structure of these libraries and Mossbauer spectroscopy was employed to probe the atomic environment. Cyclic voltammetry measurements were performed using a multichannel pseudopotentiostat to study the behavior of these materials as negative electrodes for Li-ion batteries Results and Discussion Structural Studies: X-ray patterns obtained from all compositions produced in this study were amorphous or nanostructured and no Bragg peaks indicative of any crystalline phases.In order to understand the microstructure, as XRD measurements provide little detailed structural information, room temperature Mössbauer spectroscopy was performed on two libraries denoted by solid triangles and circles. The formation of Si-Fe phases were evident. Electrochemical Analysis: Figure 1(b) shows the potential versus capacity of the library denoted by the solid circles in Figure 1(a). Data for 64 electrode material are shown. Our combinatorial measurement setup allows for a simultaneous and rapid measurement. The impact of adding iron and carbon on the resulting capacity is illustrated clearly in Figure 1(b).Through a combined consideration of Mössbauer effect measurements and electrochemical data, the formation of nanoscale regions of inactive Si-Fe and SiC phases was evident.

A Proposed Stochastic Finite Difference Approach Based on Homogenous Chaos Expansion

This paper proposes a stochastic finite difference approach, based on homogenous chaos expansion (SFDHC). The said approach can handle time dependent nonlinear as well as linear systems with deterministic or stochastic initial and boundary conditions. In this approach, included stochastic parameters are modeled as second-order stochastic processes and are expanded using Karhunen-Loève expansion, while the response function is approximated using homogenous chaos expansion. Galerkin projection is used in converting the original stochastic partial differential equation (PDE) into a set of coupled deterministic partial differential equations and then solved using finite difference method. Two well-known equations were used for efficiency validation of the method proposed. First one being the linear diffusion equation with stochastic parameter and the second is the nonlinear Burger's equation with stochastic parameter and stochastic initial and boundary conditions. In both of these examples, the probability distribution function of the response manifested close conformity to the results obtained from Monte Carlo simulation with optimized computational cost.

Structural and optical study of irradiation effect in GaN epilayers induced by 308 MeV Xe ions

Wurtzite GaN epilayers irradiated at room temperature with 308 MeV 129Xe 35+ ions to fluences of 1 × 10 13 and 3 × 10 13 cm −2 have been studied by contact mode atomic force microscopy (AFM), high-resolution X-ray diffraction (HRXRD), micro-Raman scattering and photoluminescence (PL) spectroscopy. The AFM images showed that the surface of GaN films was etched efficiently due to the Xe ion irradiation. The initial step-terrace structure on GaN surface was eliminated completely at a fluence of 3 × 10 13 cm −2. HRXRD and Raman results indicated that the Xe ion irradiation led to a homogenous lattice expansion throughout the entire ∼3 μm-thick GaN films. The lattice expansion as well as the biaxial compressive stress of the films was increasing with the increase of ion fluence. PL measurements showed that a dominant yellow luminescence band in the as-grown GaN films disappeared, but a blue and a green luminescence bands were produced after irradiation. Based on these results, the strong electronic excitation effect of 308 MeV Xe ions in GaN is discussed.

HRXRD and Raman study of irradiation effects in InGaN/GaN layers induced by 2.3 MeV Ne and 5.3 MeV Kr ions

In 0.15Ga 0.85N/GaN bilayers irradiated with 2.3 MeV Ne and 5.3 MeV Kr ions at room temperature were studied by high-resolution X-ray diffraction (HRXRD) and micro-Raman scattering. The Ne ion fluences were in the range from 1 × 10 12 to 1 × 10 15 cm −2, and the Kr ion fluences were in the range from 1 × 10 11 to 1 × 10 13 cm −2. Results show that the structures of both In 0.15Ga 0.85N and GaN layers remained almost unchanged for increasing fluences up to 1 × 10 13 and 1 × 10 12 cm −2 for Ne and Kr ion irradiations, respectively. After irradiation to higher fluences, the GaN layer was divided into several damaged layers with different extents of lattice expansion, while the In 0.15Ga 0.85N layer exhibited homogenous lattice expansion. The layered structure of GaN and the different responses to irradiation of the GaN and In 0.15Ga 0.85N layers are discussed.

Simultaneous desalination and power generation using solar energy

Using solar energy to produce fresh water and electricity simultaneously is a prospective way to solve the problems combining fresh water shortage, energy crisis and farm land degradation in Northern Victoria. This paper records the process of calculating the performance of the nozzle applying homogenous equilibrium model, designing and testing the prototype of such system using three different types of the nozzles in static and rotary systems. The research on the project is divided into two steps: first is about static system in which the spray nozzle is proved to be the best in both production of fresh water and power generation; while on the second stage, the convergent–divergent (C–D) nozzles are the best in rotary system. Some data were analyzed theoretically based on the test and the results found that the percentage of fresh water measured by experiment is consistent with the calculation using homogenous equilibrium expansion model (HEM), however, there is big difference in power generation between theory and experiments. Based on our experimental figures and analysis, the reasons for low power generation are found and a new model is proposed. According to the new model, a different reaction turbine using curve length C–D nozzles is designed to overcome the problems which were encountered in the previous prototype. After analyzing the efficiency of the cycle by T– s diagram, the evacuated tube solar collector integrated heat pipe is suggested to be applied on this system.

Modelling Pressurized Deformation Source for Changbaishan Volcano with Homogenous Expansion Point Source

AbstractIn view of the fact that the horizontal displacements in Changbaishan volcanic region during 2002~2003 lacked centric symmetric distribution caused by spherical pressurized magma chamber, three mutually orthogonal tensile point sources at the same depth are used to simulate the pressurized deformation source in the volcano region. In a homogenous elastic half‐space with media parameters of Vp=6.700 km/s, Vs=3.8700 km/s, and ρ=2900 kg/m3, GPS and leveling data during 2002~2003 are jointly used to invert for the pressurized deformation source in Changbaishan volcanic region with PSGRN/PSCMP code and genetic algorithm. The results show that an ellipsoid point source model composed of unequal tensile ones in three orthogonal directions can represent the magma chamber in Changbaishan volcanic region. The magma chamber is located in about 9.2 km depth, the largest volume expansion is up to 7.0 × 106 m3 in the direction normal to the fault plane with strike angle 34.4° and dip angle 82.2°, the second one is 6.6 × 106 m3 in the direction normal to the fault plane with strike angle 302.8° and dip angle 78.5°, the last one is 5.2×106 m3 in the direction normal to the fault plane with strike angle 337.7° and dip angle 14.0°.

Cold Perfluorochemical-Induced Hypothermia Protects Lung Integrity in Normal Rabbits

To test the hypothesis that intrapulmonary perfluorochemical (PFC) liquid may induce hypothermia, and to compare the effects of internal (IC), external (EC), and combined cooling techniques (EC + IC), 14 juvenile rabbits were randomized to EC by a cold blanket (4°C, n = 5), IC by intrapulmonary cold PFC liquid lavage (4°C, n = 5), or combined IC with PFC and EC (n = 4). Arterial blood gas, blood pressure, and lung mechanics were monitored, and lung histology was examined by light microscopy. The results showed that cooling rates and the time needed to be cooled down to 30°C were significantly faster in EC and EC + IC than IC (p < 0.05). Blood gas analysis and cardiopulmonary function were within the normal range in all groups. Histological assessment revealed varied atelectasis in all lung regions in EC, whereas PFC-filled lungs (IC and EC + IC) demonstrated more homogenous expansion and no evidence of atelectasis. The results indicate that intrapulmonary PFC may be an effective technique to induce and/or augment hypothermia while supporting gas exchange, lung volume and pulmonary architecture.

In vitro Biocompatibility Analyses of Stents Coated with Diamond-Like Carbon by Flow Cytometry, Cell Growth Assays and Electron Microscopy

Background: Coronary artery stents can induce platelet activation by shear forces and contact to the biomaterial. This activation is one important trigger for thrombosis. Coating of stents is a possible approach to prevent this side effect. The purpose of this study was to evaluate in vitro the biocompatibility of stents coated with diamond-like carbon (DLC). Materials and Methods: For in vitro testing, DLC-coated stents were compared with noncoated 316L stainless steel stents. For this purpose, cell culture assays, videomorphometric, electron microscopic and flow-cytometric techniques were applied. Results: Growth assays with smooth muscle cells and endothelial cells revealed that DLC did not affect proliferation rates and did not have cytotoxic effects. Video-based morphometry and scanning electron microscopy showed an ultrasmooth surface and homogenous expansion patterns of the DLC stents. For analysis of platelet antigens in a circulating loop model, flow cytometry was applied. Our experiments showed no significant changes in mean channel fluorescence intensity for the structural antigens CD41a (p = 0.6) and CD42b (p = 0.1). In contrast, the expression of the activation-dependent antigens CD62p and CD63 increased significantly in noncoated stents compared to DLC-coated stents (p < 0.05). Conclusion: Coating of intracoronary stents with DLC significantly reduces platelet activation. Hereby, biocompatibility is improved.

Delayed ettringite formation — Processes and problems

The scope of the delayed ettringite formation (DEF) problem is reviewed. Based on the experience of the writer and others, DEF is to be expected in both steam cured and non-steam cured concrete. The microstructural details appear identical. The common association with alkalisilica reactions is explored, and explained in terms of both prior cracking providing space for ettringite and in terms of the reduction in alkali hydroxide concentration in the pore solution attendant on ASR. The controversy concerning basic DEF mechanism between proponents of ‘homogenous paste expansion’ and ‘crystal pressure’ is explored. In the writer's opinion the microstructural evidence is not compatible with homogeneous expansion, but is a distinct consequence of crystal pressure developed by ettringite. The thermodynamic analysis that limits expansive pressure in terms of the degree of supersaturation that can be supported may be applicable to ettringite in air voids, but is inapplicable to ettringite in cracks. Fracture mechanics considerations predict local stress concentrations at the crack tips that are many times those that can be generated in open spaces. An apparent example of such effects in opening up space between mica lamellae in steam cured concrete by ettringite deposition is provided.

Immediate Reconstruction with Tissue Expander after Mastectomy by Periareolar Approach

: Breast reconstruction in patients submitted to mastectomy for breast cancer treatment restores their physical integrity, reducing the stigma of malignant disease. From March 1992 to January 1995, a tissue expander was used for breast cancer reconstruction in five patients submitted to mastectomy by periareolar approach. This approach allowed the mastologist to remove the entire mammary gland: areola, anteromammary fatty tissue, and axillary lymph nodes in monoblock, keeping a large part of the breast cutaneous lining. The expander was introduced in a subrnuscular pocket consisting of pectoralis major and minor muscles, anterior ser- atus, and anterior aponeurosis of the rectus abdominus, and was partially insufflated with saline solution in the intraoperative stage. The patients were submitted to a second surgery when the expander was removed and a textured silicone gel prosthesis was introduced. The nipple-areola complex was reconstructed and when necessary the opposite breast made symmetrical. The muscular pocket and homogenous expansion directed to the necessary site was associated to the greater amount of better quality skin. This contributed to the achievement of very satisfactory results over a period of 9 months at the minimum and 3 years at the maximum.

Analyses of sequential filling and emptying of the lung

We simulated sequential filling and emptying of a lung lobe Fukuchi et al., 1980) by solving a differential equation for simultaneous convection and diffusion within a solid expansile model of an asymmetrical acinus. For a given degree of asymmetry subtended at a fixed branch point the shorter units are consistently better ventilated (by diffusion) despite homogenous lung expansion. Thus a helium bolus inhaled at 80% of vital capacity (VC) results in a higher helium concentration (FHe) at full inflation within the shorter units. A bolus inhaled at 20% VC results in relatively greater FHe in longer units. On expiration diffusive interaction between parallel pathways at the branch point results in a range of alveolar plateaus whose slope varies inversely with the volume at which the helium bolus is inhaled. This interdependence of gas transport among parallel pathways contributes to the ‘first in-last out’ pattern observed experimentally. Comparison of radially expansile with an axial-radially expansile models does not produce qualitatively significant differences. However, equilibration of gas concentrations during breathholding in the model occurs more rapidly than under experimental conditions. indicating that other mechanisms may also contribute to the observed pattern of lung filling and emptying.