Dimensional Behavior Research Articles

A semi-continuum model of saturation overshoot in one dimensional unsaturated porous media flow

A semi-continuum model for fluid flow in saturated-unsaturated porous medium in one spatial dimension is presented. The model is based on well-established physics, measurable parameters and material characteristics. The porous material is characterized by porosity, intrinsic permeability, main wetting and draining branches of the retention curve, and the saturation dependence of the relative permeability. The fluid is characterized by its density and dynamic viscosity. The only physics involved is the mass balance of fluid in porous media together with the Darcy-Buckingham Law for fluid flow in unsaturated porous media. The model is a cellular automaton based on the Macro Modified Invasion Percolation concept of dividing the porous medium into blocks which are not infinitesimal and are assumed to retain the characteristics of a porous medium. The cellular automaton repeats three successive rules: saturation update in each block, pressure update in each block, and flux update between neighboring blocks. The model tracks the evolution of the relative saturation, the fluid capillary pressure, and the fluid flux. The model is shown to reproduce qualitatively and quantitatively all features of one dimensional saturation overshoot behavior reported in the literature.

Study of vortex glass-liquid transition in superconducting Fe(Te, Se) thin films on LaAlO3 substrates

Superconducting thin films of two different thicknesses have been fabricated on (100) LaAlO3 substrates using a polycrystalline target of composition Fe1.05Te0.50Se0.50 by the pulsed laser deposition technique. The onset of superconducting transition temperatures (TConset) at 0 T magnetic field of the grown thin films of thickness of ∼74 nm and ∼185 nm are ∼12.65 and 13.15 K, respectively. The upper critical field BC2(0) values have been calculated by the Ginzburg–Landau theory as well as by the Werthamer–Helfand–Hohenberg model, and the corresponding coherence lengths have been estimated. In the present work, the thermally activated energy (TAE) has been obtained using the conventional Arrhenius law as well as by a modified thermally activated flux flow (TAFF) theory. For both models, the TAEs of vortices show a crossover at a magnetic field of ∼2 T corresponding to the transition from the single vortex pinning regime to the collective vortex pinning regime. Based on the analysis of the field dependence of TAE, the planer/point defect dominating magnetic field regions have been identified. The analysis of the magnetotransport data with the modified TAFF model reveals the dominating three dimensional behavior of vortices for both thin films. Moreover, in the vortex phase diagram, a narrow vortex melting region and a vortex glass-liquid phase transition below BC2 have been observed for both of the grown thin films. Furthermore, the X-ray photoelectron spectroscopy results show that Fe is present in Fe2+ and Fe3+ chemical states in both thin films.

Novel multiuse liquid phase promoter for PM components

AbstractThe aim of this work was to characterize the behavior of a novel multiuse B‐free alloy that was designed as a liquid phase promoter and as a filler material for sintering and brazing steels in N2‐H2. Through thermodynamic calculations, a new Cu‐Fe‐Ni‐Si alloy (named LP) has been designed showing a proper melting point suitable for being used at temperatures below 1100°C, with good wetting behavior that allows it use as brazing material and liquid phase former. This new boron‐free alloy has shown good dimensional behavior, good brazeability, and competitive mechanical properties. These demonstrated features allow the developed alloy it use as braze material for PM parts in industrial furnaces as well as master alloy to promote transient liquid phase in PM structural steels.

A model for inertial particles in curvilinear flows

The recent advent of advanced microfabrication capabilities of microfluidic devices has driven attention towards the behavior of particles in inertial flows within microchannels for applications related to the separation and concentration of bio-particles. The phenomena of inertial focusing has been demonstrated to be a robust technique in such applications, where the flow of particles in a curvilinear geometry has proven to be particularly advantageous, not only because the geometry can reduce the foot-print of a lab-on-chip device, but also because the coupling of secondary Dean flows to inertial forces allows for exquisite particle manipulations. However, the ability to design a curvilinear channel for a specific application is often based on empirical results, as theoretical models to date typically do not include the effects of a finite sized particle within the flow. Here we present a complete numerical model that directly simulates a particle within a confide curvilinear flow and using this model we investigate the three dimensional focusing behavior of inertial particles as well as the applicability of the point particle assumptions previous researchers have proposed. Finally, we propose a new model that takes into account the full physics, but relies on a perturbation expansion of the lateral forces, where the perturbation parameter is the curvature ratio of the channel. This simple model can be used to predict the behavior of particles in complex channel geometries where the curvature may not be constant.

Study of Objective Assessment Indexes of Shuttle Shift Quality of Wheel Loader

The objective assessment indexes of shuttle shift quality of wheel loader are investigated. The process of shuttle shift is divided into two stages. At the deceleration stage, a large jerk value is observed, and a maximum acceleration value is reached when the shuttle clutch is synchronized. At the acceleration stage, the jerk is too small to be an index of comfortableness. The maximum acceleration, vibration dose value (VDV) and jerk of deceleration stage show a good linear correlation, meaning that the three indexes have similar representative ability for comfortableness assessment. The total duration of shuttle shift is chosen as an index because it is directly related to working efficiency. The duration, in which the torque converter plays a dominant role, is more than 50% of the total duration of shuttle shift, indicating that the duration of shuttle shift is mainly determined by torque converter’s characteristics. The overshoot distance is chosen as the index to represent the dimensional behaviour of the shuttle shift.

Analysis of the Characteristics of Monthly Rainfall Pattern in Katsina

Aims: This paper seeks to analyse the characteristics of monthly rainfall pattern in Katsina City in a view to unveiling the trends and describing its dynamics so that adequate recommendations can be made for its modelling.
 Study Design: The analysis involves a complete statistical, trend, spectral and nonlinear analysis of the monthly rainfall time series recorded in Katsina.
 Place and Duration of Study: Location: Katsina City, Katsina State, Nigeria from 1990 to 2015; a period of 26 years.
 Methodology: Secondary data of daily rainfall recorded in Katsina city from 1990 to 2015 was collected from the Nigerian Meteorological Agency (NiMet), and monthly averages were taken to obtain the monthly rainfall data. The data was then subjected to statistical, trend, spectral and nonlinear analysis techniques to reveal the behavioural patterns in the rainfall and also to reveal its underlying dynamics for its future modelling and prediction.
 Results: The outcome of this analysis indicates that the monthly rainfall in Katsina exhibits an increasing trend with high variance and right-skewed distribution requiring a maximum of 6 independent variables to model its dynamics. The correlation exponent plot reached a saturation value of 5.892 confirming that the monthly rainfall in Katsina over the last 26 years exhibits low dimensional chaotic behavior while the largest Lyapunov exponent for the monthly rainfall time series in Katsina was also computed and found to be positive, having a value of 0.006055/month confirming the presence of deterministic chaos dynamics and is predictable for the next 165 months.
 Conclusion: Since from the findings of this work it is confirmed that the rainfall in Katsina exhibits chaotic behavior with an increasing trend, it is recommended that more drainages and dams be built to provide steady supply of water for agricultural and domestic purposes as well as curtail the menace of flooding and drought which may occur as a result of global warming and climate change.

A study of fabric biasness with self developed fabric dimensional behaviour test

To achieve better fitting and snug effect ladies wear cut the fabric on bias is a common practice in the fashion industry When a fabric is cut on bias there is a great improvement in terms of extensibility The garment length however exceeds the required length due to the increased extensibility Adjustments in dimensions are necessary in order to meet garment specifications A fabric dimensional behaviour test B Test was developed and used for evaluating the biasness FAST Eb Testing method was adopted as well to compare with the results of the B Test nbsp nbsp

Cut-off for lamplighter chains on tori: dimension interpolation and Phase transition

Given a finite, connected graph $$\mathsf {G}$$ , the lamplighter chain on $$\mathsf {G}$$ is the lazy random walk $$X^\diamond $$ on the associated lamplighter graph $$\mathsf {G}^\diamond =\mathbb {Z}_2 \wr \mathsf {G}$$ . The mixing time of the lamplighter chain on the torus $$\mathbb {Z}_n^d$$ is known to have a cutoff at a time asymptotic to the cover time of $$\mathbb {Z}_n^d$$ if $$d=2$$ , and to half the cover time if $$d \ge 3$$ . We show that the mixing time of the lamplighter chain on $$\mathsf {G}_n(a)=\mathbb {Z}_n^2 \times \mathbb {Z}_{a \log n}$$ has a cutoff at $$\psi (a)$$ times the cover time of $$\mathsf {G}_n(a)$$ as $$n \rightarrow \infty $$ , where $$\psi $$ is an explicit weakly decreasing map from $$(0,\infty )$$ onto [1 / 2, 1). In particular, as $$a > 0$$ varies, the threshold continuously interpolates between the known thresholds for $$\mathbb {Z}_n^2$$ and $$\mathbb {Z}_n^3$$ . Perhaps surprisingly, we find a phase transition (non-smoothness of $$\psi $$ ) at the point $$a_*=\pi r_3 (1+\sqrt{2})$$ , where high dimensional behavior ( $$\psi (a)=1/2$$ for all $$a \ge a_*$$ ) commences. Here $$r_3$$ is the effective resistance from 0 to $$\infty $$ in $$\mathbb {Z}^3$$ .

High dimensional asymptotics for the naive Hotelling T2 statistic in pattern recognition

This paper examines the high dimensional asymptotics of the naive Hotelling T2 statistic. Naive Bayes has been utilized in high dimensional pattern recognition as a method to avoid singularities in the estimated covariance matrix. The naive Hotelling T2 statistic, which is equivalent to the estimator of the naive canonical correlation, is a statistically important quantity in naive Bayes and its high dimensional behavior has been studied under several conditions. In this paper, asymptotic normality of the naive Hotelling T2 statistic under a high dimension low sample size setting is developed using the central limit theorem of a martingale difference sequence.

Intrasinus Bone Gain with the Osteotome Sinus Floor Elevation Technique: A Review of the Literature.

To evaluate the mean amount of intrasinus bone obtainable with the osteotome technique for transcrestal maxillary sinus elevation combined with simultaneous implant insertion, with and without the use of grafting materials. A review was conducted on PubMed, Scopus, and Cochrane central databases. Only human studies in which implant placement was contextual to the sinus elevation procedure, without additional crestal regenerative procedures and with a minimum 1-year follow-up, were selected. Seventeen studies were found to meet the selection criteria. No statistically significant difference between the two procedures was detected. The mean intrasinus bone gain at 3 years after surgery was 2.99 mm in cases where no grafting material was used and 4.24 mm in cases in which grafting materials were used. The mean percentage of crestal height increase at the implant site at 3 years after surgery, referring to a selection of studies with initial bone height > 4 mm, was 47.28% in procedures without grafting material and 62.68% in procedures with grafting material. A different dimensional behavior of the newly formed bone during the first 3 years after surgery was found: a slight volumetric shrinkage in grafting procedures and a slight bone increase in procedures without grafting material. No statistically significant difference in implant survival rate was found. Both osteotome transcrestal sinus elevation procedures seem to guarantee predictable short- and medium-term results with reference to the intrasinus bone gain. However, the use of grafting materials, compared with their nonuse, does not seem to have substantial advantages in the short and medium term as far as mean intrasinus bone gain is concerned.

Creep and thermal behavior of quarry dust-silicon carbide hybrid particles reinforced ZA-27 alloy composites using stir casting technique

In this research, creep and thermal behavior of stir cast ZA-27 alloy-based hybrid composites modified with quarry dust (QD) and silicon carbide (SiCp) particles was investigated. ZA-27 hybrid composite samples reinforced with 10 wt% QD-SiCp particles containing varied weight percentage 0, 25, 50, 75, and 100% quarry dust was developed using stir casting technique. Dimensional stability (creep) evaluation and thermal behavior were performed to assess the performance of the produced modified composites. Thermal behavior was carried out using DSC thermal analyzer at operating temperatures of 0–500 °C to determine the behavior of the composites relative to temperatures, while the creep behavior (dimensional stability) was conducted using Dynamic Mechanical Analyzer (DMA 242E) at elevated temperature of 100 °C under a load of 3 N for 70 min. The results show that hybrid composites with designation B2 (50% SiCp:50%QD) and B3 (25% SiCp:75% QD) displayed superior creep resistance without dimensional instability; the highest dimensional change of 0.11 pct was observed in Bo (100% SiCp), while dimensional changes of < 0.05 pct was observed for unmodified alloy, B1 (75% SiCp:25% QD) and B4 (100% QD), respectively. However, superior elevated temperature was observed in sample designations Bo and B2, respectively, when compared with unmodified (unreinforced) alloy.

Two Dimensional (2D) P-Aramid Dry Multi-Layered Woven Fabrics Deformational Behaviour for Technical Applications

In today’s scenario for the various technical applications, from composites to body armour, the material mouldability along with its mechanical property become very important. In the present study, two dimensional (2D) woven fabrics made of para-aramid high performance fibres in multi-layer dry structure were used for investigating different forming characteristics. The different layers were arranged with 0°/90° orientation for deep drawing formability test to analyse the effect of number of layers and blank-holder pressure (BHP) during the test. Specific preforming device with low speed forming process and predefined hemispherical shape of punch has been applied. Using fine photographic analysis, some important 2D multi-layer fabrics forming characteristics i.e., material drawing-in, surface shear angle etc. from the imposed deformation have been observed, measured and analysed for better understanding and co MPa rison. The result revealed that the mouldability behaviour of the multi-layered dry textile fabric preforms is directional, and closely dependent on blank-holding pressure and number of layers. This indicates both parameters should be carefully considered while material deformation to avoid the formation of wrinkling and maintain other mechanical properties on final application.

Oxidative potential of size-segregated PM in an urban and an industrial area of Italy

This work is focused on the relationship between the size distribution of some source tracers of atmospheric particulate matter (PM) and the oxidative potential (OP) of each PM size fraction. Size-segregated PM samples were collected by a multistage impactor (cut-sizes: 0.18, 0.32, 0.56, 1.0, 1.8, 3.2, 5.6, 10 and 18 μm) in two geographical areas of Italy (Rome and Ferrara), characterized by different strength of the main PM sources. The samples were analysed by three different acellular OP methods: dithiothreitol (DTT), dichlorofluorescein diacetate (DCFH) and ascorbate (AA) assay.Elemental (Li, Be, B, Na, Mg, Al, Si, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Zr, Nb, Mo, Cd, Sn, Sb, Te, Cs, Ba, La, Ce, W, Tl, Pb, Bi and U) and ionic (Cl−, NO3−, SO42−, Na+, NH4+, K+, Mg2+, Ca2+) composition of the same samples was also determined, in order to trace the contribution of the main PM sources. The size distribution of the OP values was compared to the size distribution of some PM source tracers, with the aim of identifying the PM sources that mostly influence the oxidative properties of atmospheric dust.AA assay resulted to be more sensitive towards coarse particles and OPAA showed a size distribution very similar to that of brake dust tracers. DTT and DCFH assays resulted instead more sensitive towards fine particles. OPDTT and OPDCFH values were comparable at the two sites; sources whose strength was very different in the two monitored areas (secondary contribution and, to a less extent, industrial sources) did not then contribute significantly to the measured OP values. The dimensional behaviour of OPDTT and OPDCFH was consistent with the contribution of biomass burning.

Ba4[Mn3N6], a Quasi-One-Dimensional Mixed-Valent Nitridomanganate (II, IV)

The mixed-valent nitridomanganate Ba4[Mn3N6] was prepared using a gas–solid high temperature route. The crystal structure was determined employing high resolution synchrotron powder diffraction data: space group Pbcn, a = 9.9930(1) Å, b = 6.17126(8) Å, c = 14.4692(2) Å, V = 892.31(2) Å3, Z = 4. The manganese atoms in the structure of Ba4[Mn3N6] are four-fold coordinated by nitrogen forming infinite corrugated chains of edge-sharing [MnN4] tetrahedra. The chains demonstrate a complete charge order of Mn species. Magnetization measurements and first principle calculations indicate quasi-one dimensional magnetic behavior. In addition, chemical bonding analysis revealed pronounced Mn–Mn interactions along the chains.

Influence of Water and Temperature on Ionomer in Catalytic Layers and Membranes of Fuel Cells and Electrolyzers Evaluated by AFM

AbstractThe major difference for the durability of the materials in PEM fuel cells and PEM electrolyzers is the exposure to humidified gases and to liquid water, respectively. Aquivion and Nafion ionomer was investigated at surfaces of membranes and cross‐sections of electrodes by material‐sensitive atomic force microscopy. The dimensional behavior of electrodes and membranes in a membrane‐electrode assembly cross section was studied as a function of combined humidity and temperature changes. The observed opposite effects of ionomer dimensional changes in membrane and catalytic layers are important for understanding mechanical stress factors and degradation. For the lamellar polymer phase at moderate humidity, a linear swelling behavior and the enclosure of multiples of 0.8 nm‐thick water layers was observed. Submersed in water, 3 nm‐thick enclosed water layers were found. At the water‐immersed Aquivion membrane derived from alcoholic dispersion larger 30–50 nm sized water‐rich areas were found. In contrast, for membranes derived from water‐based dispersion the water‐rich phase was smaller with 11 nm. The thickness of the ultrathin ionomer layers in the electrode was investigated as a function of humidity and temperature. A linear swelling was found for humidity changes whereas nonlinear behavior with 100% expansion and hysteresis was seen for temperature cycles.

The hydrogen atom in α -dimensional space

The hydrogen atom system can be solved strictly by the eigenvalue equation and get analytical solutions, which is uncommon as a quantum mechanics system. In this study, we obtained wave functions and bound state energies of the hydrogen atom by the Schrödinger equation of the hydrogen atom in the noninteger-dimensional space. And we discussed dimensional behavior in binding energy, angular momentum, and radial density. The dimension α is given by the degree of anisotropy of the actual physical system. The excitons in solids are similar to the hydrogen atoms, except that the mass of their center positive charge is different, so the results obtained in this study were also applicable to excitons in anisotropic solids and hydrogenic impurities, which have application value.

Evaluation of dimensional behavior of peri-implant tissues in implants immediately exposed or submerged in fresh extraction and healed sites: a histological study in dogs

BackgroundThe aim of this study was to compare histologically the dimensional behavior of peri-implant tissues during osseointegration of immediately exposed or submerged implant placement in fresh extraction and healed sites.MethodsFour fresh extraction and four delayed implant sites were placed in each hemimandible of five dogs at the bone crest level. In 2 implants of each side were installed a healing abutment (exposed) and two cover screw (submerged) and formed four groups: implant installed in fresh extraction submerged (group 1), implants in fresh extraction immediately exposed (group 2), implants installed in healed site submerged (group 3), and implants in healed site immediately exposed (group 4). After 12 weeks of healing period, histomorphometric analyses of the specimens were carried out to measure the crestal bone level values and the tissue thickness in the implant shoulder portion.ResultsThe measure of crestal bone level showed some higher values for implants installed in fresh extraction sites in the buccal aspect: 1.88 ± 0.42 mm for group 1 and 2.33 ± 0.33 mm for group 2, with statistical significance among all four groups tested (P < 0.001). For peri-implant tissue thickness, a significative higher statistical difference (P < 0.001) for implants installed in healed sites (groups 3 and 4) was found.ConclusionsWithin the limitations of the present animal study, our findings suggest that the implants placed in fresh extraction or healed site and with regards to the moment of exposition (immediately or no) are important factors to the amount of peri-implant tissues after remodeling over a period of 12 weeks. The null hypothesis was rejected.

300MPa 級SPCC を母材とする十字引張型スポット溶接継手の三次元的内部疲労損傷挙動および疲労特性に及ぼす模擬溶接欠陥の影響

300MPa 級SPCC を母材とする十字引張型スポット溶接継手の三次元的内部疲労損傷挙動および疲労特性に及ぼす模擬溶接欠陥の影響

Development of a biaxial stretching test machine and its applications

Abstract The evaluation method for a biaxially oriented film was developed using in-situ measurement during the stretching process. It can obtain basic data such as stress-strain curves, birefringence, light scattering, three dimensional refractive indexes and birefringence distribution. Stress and strain as functions of stretching speed and stretching temperature, as well as the deformation of spherulite of semi-crystalline polymer can be obtained by measuring the birefringence and light scattering during the biaxial stretching process with a small piece of polymer sample. The experimental results show the stress, retardation and three dimensional molecular orientations behavior during the simultaneous biaxial stretching and the sequential biaxial stretching process. Stretchability, thickness uniformity and spherulite size can be obtained simultaneously. In this paper, advantages and details of the newly developed system will be discussed with some experimental data.

A confinement-dependent load-induced thermal strain constitutive model for concrete subjected to temperatures up to 500 °C

This paper proves that, given a Load-Induced Thermal Strain (LITS) curve able to accurately describe the uniaxial LITS development for a specific type of concrete and temperatures up to 500 °C, a more accurate prediction of the 3D LITS state is obtained through a confinement-dependent 3D implementation than through the classic confinement-independent approach. In particular, a new model is presented, obtained by extending to 3D a fourth order polynomial LITS derivative function in a way that allows the effects of the stress confinement to be taken into account. For comparison purposes, the same fourth order polynomial LITS derivative function is also implemented in 3D through the classic confinement-independent modelling approach. These constitutive relationships are adopted to model transient experiments performed on concrete subjected to constant uniaxial and biaxial compressive loads. The results show that the confinement-dependent modelling approach gives a better prediction of the LITS state developing in the case of biaxial compression than the classic confinement-independent approach. Finally, the validated confinement-dependent model is applied to evaluate the LITS-related stress redistribution taking place in a typical Prestressed Concrete Pressure Vessel (PCPV) subjected to heating to 500 °C and cooling back to the normal operating temperature of 50 °C. It is found that including the effects of three dimensional LITS behaviour has significant effects on the predicted stress states.