Vicinity Of Interface Research Articles

Mathematical simulation of characteristics of angular coordinate estimates of radar targets in the vicinity of interface between two media

The calculations, used for investigating the characteristics of measurement of radar targets’ angular coordinates near the interface between two media, are based on mathematical models set up as superposition (in the observation point) of two waves reflected from the object: the direct wave and the wave reflected by the surface of the interface between two media. These mathematical models are shown to be convenient and efficient for inquiries in characteristics of amplitude algorithms of measurements. The models agree well with the results of target’s elevation measurement, obtained during full-scale tests.

Numerical Simulation of 3-D Fracture Behaviors on the FRP-Strengthened Concrete Structures

A numerical code RFPA3D (Realistic Failure Process Analysis) is used to simulate the crack initiation and propagation in FRP-strengthened concrete beam under external loading. In our model, the FRP-strengthened concrete is assumed to be a three-phase composite composed of concrete, FRP, and interface between them. The displacement-controlled loading scheme is used to simulate the complete failure process of FRP-strengthened concrete the numerical simulation of failure process of the specimens. It is found that the main failure mode is the interfacial debonding and the interfacial debonding may propagate either within the adhesive layer or through concrete layer in the vicinity of bond interface. The simulation results agree well with the experiment observations. The width of the FRP sheet is considered an important factor not only to significantly influence the debonding propagation type and crack distribution but also to control the ultimate load-capacity and ultimate strain. This study is focused on the failure process of the FRP-strengthened concrete beam and the effects of the width of FRP sheet on the failure mode and on the structural load-carrying capacity of concrete structures.

Novel Characterization Technique for Oxidation Processes

A new application of the commercially-available Surface Charge Profiler (SCP) tool to evaluate metal ionic contaminants that can be brought in during device fabrication processes, including oxidation, is discussed. The SCP measures the surface photovoltage (SPV) signal, and associated depletion width (Wd) and the minority-carrier recombination lifetime (τ). The technique allows not only detect a risky level of the contaminants but also to distinguish between different impurities such as Fe, Cu, and Na. A behavior of these metals in the vicinity of Si-SiO2 interface is discussed. A novel characterization technique should be a beneficial alternative metrology to the conventional capacitance versus voltage (CV), triangular voltage sweep (TVS), and SPV methods.

Exact and approximate analysis of surface acoustic waves in an infinite elastic plate with a thin metal layer

For an accurate approximation of the effect of a thin layer over a finite substrate, we consider the displacements are continuous across the interface, while the stress components are obtained from derivatives of displacements. As a result, the stress boundary conditions are transformed to a relationship between stresses in the vicinity of the interface of two layers and density of the metal layer. Through this approximation, we eventually have four equations to solve for the surface acoustic wave dispersion relation of the two-layer structure. The approximate and accurate results are compared with good agreement for small thickness of the metal layer. These results are intended for periodic structures with separate solutions for electroded and unelectroded regions, which can be connected by the continuity boundary conditions for the analysis of the complete structure of typical surface acoustic wave resonators.

Anisotropic siloxane-based monolith prepared in confined spaces

When bicontinuous gels are prepared via sol–gel method in a 2-dimensionally (2D) confined space, the gel skeletons in the vicinity of interface of a mold are elongated perpendicular to the interface. This phenomenon was attributed to the dynamic wetting of polymerizing siloxane phase onto the interface of the mold under gravity. In this paper, we report the successful preparation of monolithic columns with an oriented pillar structure in a variety of 2D confined spaces. Starting from a solution, which consists of methyltrimethoxysilane (MTMS), the macroporous structure is prepared in situ by a completely spontaneous process. In the oriented pillar structure, bicontinuous siloxane skeletons deformed or disappeared and most pillars are oriented along the direction of gravity. Gel morphologies with the pillar structure were examined by scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM). Geometrical information on gel morphologies was numerically derived from the obtained 3D LSCM images.

Reorganization of lipid nanocapsules at air–water interface: I. Kinetics of surface film formation

The size, the electrical properties and the behaviour at air–water interface of lipid nanocapsules (LNC) with various compositions were investigated. Two populations of LNC are presented in the suspension after the preparation: with (LNC II) and without (LNC I) phospholipid molecules. After the spreading at air–water interface, a rapid disaggregation of LNC I, located in the vicinity of interface, occurs leading to formation of surface film. The phospholipid molecules stabilize the structure of nanocapsules and LNC II are more stable at the interface in comparison with LNC I. The formation of a surface film was followed after by measuring the evolution of the surface pressure, relative surface area change and surface potential. A kinetic approach describing the various processes during the surface film formation was proposed. The corresponding kinetic constants were estimated.

Surface Chemical Reactions in Processes of Diffusion Mass Transfer

The phenomenological theory for describing high-temperature interaction between metal and diluted gaseous medium has been developed. The theory is based on the assumption of duplex contact layer existence in the vicinity of interface (with relative thickness 2 d), where chemical reactions and processes of gas component migration occur. The non-stationary conditions of mass transfer at the interface are described involving effective average parameters. These conditions allow considering a wide spectrum of boundary diffusion phenomena (in a short and prolonged time ranges), in order to describe the kinetics of accumulation of diffusing component close to the interface. The description of the kinetic of gaseous saturation of metal (nitriding and borating) in the diluted medium becomes a partial proof of the suggested models. In order to approach the diffusion phenomena, boundary conditions, which contain, besides the coordinate derivative of concentration function, also the time derivative, were suggested. The derived equations describe the time dependence of change of surface concentration of gaseous component, the kinetics of its accumulation owing to chemical reaction, the specimen mass change owing to both, the diffusive addition dissolution in metal and its chemical interaction. The role of temperature is also discussed.

Long-Lived Transient Vacancy Distribution in Multilayers

Modeling the vacancy concentration in bi-metallic systems is a key step to understand thermal interdiffusion phenomena. For instance in the kinetics of precipitation, a strong difference between vacancy concentration in the precipitates and in the matrix, may change the precipitate mobility and the coarsening mechanism, the precipitate composition and morphology [1]. The origin of this inhomogeneous vacancy concentration is mainly due to the differences in migration energies ∆E and in formation energies ∆E of the vacancy in the two phases. The distribution of vacancy sinks and sources or the local lattice deformation should also play an important role. In this work, we focus on the influence of both ∆E and ∆E terms on the vacancy concentration profile in a phase separating a multilayer with planar (111) interfaces. The atomic diffusion model is a kinetic Ising-like model with a vacancy exchange mechanism. We perform both kinetic Mean-field and kinetic Monte-Carlo simulations in order to discuss how the vacancy concentration profile (VCP) reaches its steady-state. In the figure, we report the quasistationary VCP found at the vicinity of an (111) interface for ∆E = 0eV. As expected the vacancy strongly segregates into the two interface planes (p=-1,0) because of the tendency of the system to phase separate (the vacancy tends to reduce the number of AB pairs). More surprising is the decrease of the concentration in adjacent planes (p=-3,2,1,2). This marked decrease, that becomes asymmetric for ∆E = -0.1eV (see figure), is rationalized by invoking local correlation effects.

炭素鋼摩擦圧接部の温度分布の数値解析

The purpose of this study is to estimate temperature distribution in the vicinity of weld interface during a friction welding process involving an upset process. On the base of a simple model of friction heat input, a non-steady heat conduction analysis was carried out by finite element method. As a result from a comparison of the estimated temperature distribution with the experimental data, it turned out that the friction heat input model that allowed for the effects of temperature and linear velocity on the friction coefficient was appropriate. This heat input model could simulate adequately the change in friction heat input and temperature distribution in a friction welding process. As a result, the relationship between burn-off length and temperature distribution in upset process has been explained and also the relationship between temperature distribution and width of heat-affected zone has been obtained. This heat input model allows us to estimate temperature distribution in friction welding, from friction pressure, rotation speed and the thermal property of base metal, even where a friction-welding machine does not have a function of torque measurement.

Quantification of macrobenthic effects on diagenesis using a multicomponent inversemodel in salt marsh sediments

Using a multicomponent inverse model, we quantified the rates of organic matter (OM) remineralization and the relative importance of major terminal electron acceptors [Fe(III)–(oxy)hydroxides and SO4∐3] in salt marsh sediments with varying degrees of bioturbation and vegetation at Skidaway Island, Georgia. The model determined the rates of OM diagenesis by seeking simultaneous agreement between measured and model‐calculated depth‐concentration profiles of multiple major redox species while using the biological transport parameters determined from direct field observations. The OM degradation rates are found to be greater and penetrate deeper in sediments with vegetation or bioturbation than in sediments with limited macrobenthic components, in which organic matter degradation is restricted to the immediate vicinity of water‐sediment interface. The results also confirmed previous observations that Fe(III)–(oxy)hydroxides are much more important than sulfate as terminal electron acceptors in the heavily bioturbated station and provided the numerical values to the depth‐dependent relative importance. Solid‐phase Fe is recycled as a terminal electron acceptor >=30 times in the bioturbated station, because biological mixing repeatedly moves reduced Fe(II) back into the aerobic environment, where it is reoxidized to form Fe(III)–(oxy)hydroxides and is reused as a terminal electron acceptor. Vegetation appears to have little influence on net solute transport, but it stimulates microbial activities and significantly enhances the remineralization of OM at depths.

Microstructure and Mechanical Properties of DBC on Sputter Deposited Copper on Alumina Substrate

The process of Direct Bonding Copper (DBC) is performed by a spinel reaction between CuO and Al2O3. In order to develop DBC on alumina substrate with high bonding strength, alumina substrate was preformed as follows: Cu was sputter-deposited on alumina substrate. Sputter-Deposited Cu (SDC) on alumina substrate was oxidized at 673K for 30min in air atmosphere and then stabilized at 1273K for 30min in N2 gas atmosphere to improve bonding strtrength between preformed alumina substrate and SDC layer. Subsequently, the Cu-foil (300µm) was bonded on preformed-alumina substrate in N2 gas atmosphere at 1342~1345K. It was found that optimum condition of DBC on preformed-alumina substrate could be successfully obtained at 1345K for 30min. Consequently, bonding strength of DBC on alumina substrate was the high value of 80N/cm. Observation and analysis of microstructure for Cu sputtered DBC showed that reaction compounds such as CuAlO2 and CuAl2O4 approved to be formed in the vicinity of interface between Cu and alumina substrate.

Microstructure at/around Interface between Plasma-Sprayed Hydroxyapatite and Ti Alloy

Microstructures of the interface between plasma-spray coated hydroxyapatite (HAp) and Ti-alloy substrate have been investigated mainly by means of transmission electron microscopy. The results obtained are as follows; HAp coating exhibits a high crystallinity. The interface of HAp/Ti-alloy is winding at an interval of about 100µm and thickness of HAp coating is about 50µm. Al2O3 abrasives remained in both HAp coating and Ti-alloy substrate around the interface. Amorphous phase was not observed at the interface. The grain size of Ti-alloy in the vicinity of the interface is about 10 to 100nm in diameter, while that far from the interface is about 3µm in diameter. Miniaturization of Ti-alloy grain around the interface was occurred by plasma spraying. There is no specific crystallographical orientation relationship between HAp and Ti-alloy at the interface, indicating bonding of the interface is essentially mechanical one such as an anchor effect.

Microstructural analysis of Ga1−Mn N films grown by PEMBE

Abstract The microstructural changes of Ga 1− x Mn x N films grown at various substrate temperatures (350–700°C) by a PEMBE system have been investigated using transmission electron microscopy. Ga 1− x Mn x N film with low dislocation density was grown epitaxially at 700°C but dislocation density increased with the decrease of substrate temperature. Moreover, HCP and FCC structures coexisted in the vicinity of interface between GaN and Ga 1− x Mn x N films grown below 450°C.

Aging Characteristics of Short Mullite Fiber Reinforced Al-4.0Cu-1.85Mg Metal Matrix Composite

Mullite short fiber reinforced Al-4.0Cu-1.85Mg composite and its base alloy were fabricated by squeeze casting. The age-hardening behavior, precipitation procedure, microstructure of dislocation and precipitates, and the interfacial structure have been studied by means of hardness measurement (HB), differential scanning calorimetry (DSC), and analytical transmission electron microscope (ATEM), respectively. The short mullite fiber in the composite induces high dislocation density in the near vicinity of the interface after it is solutionized and quenched in ice water, and suppresses or delays the formation of GPB zones. The aged hardness of the composite is always higher than that of its base alloy, but there appears little difference between the time needed in the composite and in the base alloy to reach the peak hardness, which means that the acceleration effect of mullite fiber in the precipitation of Al-Cu-Mg alloy is not great enough. Mg also reacts with Al and SiO2, resulting in the formation of spinel (MgAl2O4), which depletes Mg in the matrix and finally hinders the aging acceleration in the testing composite.

High fertigation frequency: the effects on uptake of nutrients, water and plant growth

The objective of the present research was to explore the effects of combined irrigation and fertilization (fertigation) frequency on growth, yield and uptake of water and nutritional elements by plants. Lettuce (Lactuca sativa L., cv. Iceberg) was used as the model plant. Two experiments were conducted in a screen-house: compound fertilizer at a constant N:P:K ratio at different concentrations was used in the first, while in the second the concentration of P varied solely while the concentration of the other nutritional elements was kept constant. The lettuce was planted in pots filled with perlite and irrigated daily with a constant volume of nutrient solution at different frequencies. The major finding in the two experiments was that high fertigation frequency induced a significant increase in yield, mainly at low nutrients concentration level. Yield improvement was primarily related to enhancement of nutrient uptake, especially P. It was suggested that the yield reduction obtained at low frequency resulted from nutrient deficiency, rather than water shortage, and that high irrigation frequency can compensate for nutrient deficiency. Frequent fertigation improved the uptake of nutrients through two main mechanisms: continuous replenishment of nutrients in the depletion zone at the vicinity of root interface and enhanced transport of dissolved nutrients by mass flow, due to the higher averaged water content in the medium. As such, an increase in fertigation frequency enables to reduce the concentrations of immobile elements such as P, K and trace metals in irrigation water, and to lessen the environment pollution by discharge.

炭素鋼の位相制御摩擦圧接に関する研究

It is difficult to match joint phases at the particular position of a rotation side a fixed side using a conventional friction welding machine, because the rotating spindle does not control the exact stop position. A development of positioning controlled friction welding meets to be solved such difficulties as stop at the specified position during duration of braking. This positioning control friction welding was achieved by installing servo motor positioning system. A phenomenon of positioning control was examined by the friction welding of carbon steel. The positioning control was satisfactory performed with sufficient accuracy. The undershoot and the overshoot behaviors were observed to the specified position during operation. Heavy metal flow was observed in the vicinity of weld interface in case of positioning control. Characteristic flash was formed by the heavy metal flow during positioning control. The metal flow became heavy with the stopping period increase. The direction of metal flow was circumferential, when positioning control friction welding. The rotative direction of metal flow was changed due to the overshoot or the undershoot behavior. When stopping period was optimized, metal flow became minimized. In this examination, 0.3 s was optimum stopping period. The fracture of tensile test specimens occurred at the base metal, when the position was controlled. However, tensile strength of positioning controlled joints was equal to the strength of base metal. The positioning control did not affect on the tensile strength of welded joints.

114 異種材料接合界面近傍に存在する回転だ円体状介在物による応力集中

114 異種材料接合界面近傍に存在する回転だ円体状介在物による応力集中

Fracturing behaviors of FRP-strengthened concrete structures

In this paper, we focus on the study of concrete cracking behavior and interfacial debonding fracture in fiber reinforced polymer (FRP)-strengthened concrete beams. An experimental program is systematically reviewed according to the observed failure modes, in which it is found that the interfacial debonding may propagate either within the adhesive layer or through concrete layer in the vicinity of bond interface. A finite element analysis is performed to investigate the different types of debonding propagation along FRP–concrete interface and crack distribution in concrete. For the numerical fracture models, interfacial debonding that initiates and propagates in adhesive layer is modeled by fictitious interfacial crack model. And concrete cracking, including the debonding fracture through interfacial concrete, is modeled by smeared crack model. Properties of the interfacial adhesive layer and concrete are considered to significantly influence the debonding propagation types and crack distribution. The interactions between interfacial bond strength, interfacial fracture energy of bond adhesive layer and tensile strength, fracture energy of concrete are discussed in detail through a parametric study. According to the results, the effects of these properties on different types of interfacial debonding, concrete cracking behavior and structural load-carrying capacity are clearly understood.

341 異種接合界面近傍の 3 次元き裂の √<area> パラメータによる評価

341 異種接合界面近傍の 3 次元き裂の √<area> パラメータによる評価

Orientation of crystalline lamellae in the vicinity of interface of immiscible polyethylene/poly(methyl methacrylate) blends containing polyethylene- block-poly(methyl methacrylate)

Morphologies in the vicinity of interfaces of immiscible linear-low-density polyethylene/poly(methyl methacrylate) (LLDPE/PMMA)=80/20 (w/w) blends containing polyethylene- block-poly(methyl methacrylate) (PE- b-PMMA) were investigated by transmission electron microscopy (TEM). It was found that crystalline lamellae of polyethylene was oriented vertically to the interface between LLDPE and PMMA phases in LLDPE/PMMA blends containing PE- b-PMMA. In addition, length of lamellae oriented vertically to the interface became longer with increasing content of PE- b-PMMA in the blends.