Effect Of External Pressure Research Articles

Characteristic effects of substituent and external pressure on group-inclusion complexation with p-sulfonatocalix[8]arene and γ-cyclodextrin

By synthesizing unique nitroxide probes (α-substituted phenyl-2,4,6-trimethoxybenzyl(t-butyl)nitroxide), we have shown that p-sulfonatocalix[8]arene (Calix-S8) and γ-cyclodextin (γ-CD) form electron spin resonance spectroscopically separable group-inclusion complexes (α-substituted phenyl-in (R-in) and t-butyl-in complexes) and determined the group-inclusion constants of Calix-S8 and γ-CD. Using nitroxide probes, we have examined the effects of substituent and external pressure on group-inclusion complexation with Calix-S8 and γ-CD. Experiments on pressure dependence enabled us to calculate the reaction volume (Δ V) for R-in and t-butyl-in complex formations. Δ V for group-in complexation with Calix-S8 had negative values. In contrast, Δ V values for γ-CD showed positive values, which is responsible for the repelled water molecules in the CD cavity. The characteristic pressure effects on group-in complexation suggest that group recognition by γ-CD is sensitive when compared with that by Calix-S8.

Secure Software Development Assimilation

Drawing upon institutional theory, this article develops an extended model to test and verify the effects of external institutional pressures on Secure Software Development (SSD) assimilation and the roles of internal critical factors. The empirical results are based on 86 survey data from respondents of related organizations in United Kingdom, Hong Kong, and Mainland China who have related project experience about SSD. Results from partial least squares (PLS) analysis suggest that both mimetic and coercive pressures have indirect effects on SSD assimilation with the distal mediation of top management. Normative pressures positively affect SSD assimilation with the full mediation of secure software champion. Results also suggest that secure software champion plays another partial mediation between top management participation and SSD assimilation. This paper highlights the important role of secure software champion for its dually mediating effects on both external and internal forces during SSD assimilation process.

Effects of External Hydrostatic Pressure on Finished Surface in Silicon Cutting

In this paper, machining tests of silicon wafer under high hydrostatic pressure are reported. A lathe type machining tester was developed, and machining tests were conducted on the upper surface of silicon wafers whose crystal orientation was (001). Roughness of the finished surface was measured by using AFM, and the effect of hydrostatic pressure on roughness was studied. It was found that roughness decreases with increase of hydrostatic pressure. It was also found that the roughness depends on the cutting direction. The roughness is large when the cutting direction is parallel to the <100> direction, but it is small when the cutting direction is parallel to the <110> direction. Mechanism of effects of hydrostatic pressure and crystal orientation are discussed.

Thermo-elastic analysis of a non-axisymmetrically heated FGPM hollow cylinder under multi-physical fields

This study deals with the two-dimensional steady-state response of a cylindrical shell made from functionally graded piezoelectric materials under multi-physical fields. The hollow cylinder is subjected to mechanical, electrical and non-axisymmetric thermal fields. Material properties vary continuously through the thick direction of the cylinder based on the power-law distribution of the reinforcement volume fraction. Using equations of equilibrium, strain–displacement and stress–strain relations in conjunction with the potential–displacement equation, a set of coupled differential equations is derived which are then numerically solved by the differential quadrature method to obtain the mechanical stresses in cylinder. In order to obtain the thermal stress distributions in the non-axisymmetrically heated cylinder the complex variable method is applied. The effects of external pressure and material in-homogeneity on the stresses, mechanical and electrical displacements and electric potential distributions are discussed in details. It has been found that increasing the external pressure of the cylinder decreases the electric displacement, justifying industrial application of such material as efficient actuators and sensors. Moreover, dimensionless Von Mises thermal stresses decreases with increasing the material in-homogeneity.

Indentation and external pressure on subsea single wall pipe and pipe-in-pipe

A trawl gear impact on an underwater pipeline can create a dent that pushes part of the pipe wall inward. External pressure also tends to push the wall inward. Because of that interaction, an impact under external pressure dents the pipeline more severely than the same impact with no external pressure. The interaction has been investigated as part of a wider study of overtrawlability of pipe-in-pipe systems carried out by the National University of Singapore. The problem is important because the need to protect pipelines against trawl gear impact leads to a requirement to trench medium and small-diameter pipelines. Trenching is costly and a frequent source of delays and disputes, and so it is worthwhile to search for ways to eliminate unnecessary trenching. A finite-element model of denting under external pressure for single wall pipe and pipe-in-pipe using hydrostatic fluid element has been established and verified by comparison against published data and current experiment data. Parametric study of different external pressures shows the effect of external pressure on the denting process. The combinations of the internal pressure, external pressure and indentation are considered. The study shows that when the internal pressure of a dented subsea pipe is decreasing, the possibility of buckle propagation for the single wall pipe is higher than it is for the pipe-in-pipe.

Chemical pressure effect on Tc in BiS2-based Ce1−xNdxO0.5F0.5BiS2

We have investigated the crystal structure and superconducting properties of the BiS2-based layered superconductor Ce1−xNdxO0.5F0.5BiS2.Bulk superconductivity was observed for x⩾0.4, and the transition temperature was enhanced with increasing Nd concentration. The highest transition temperature was 4.8K for x=1.0. With increasing Nd concentration, the length of the a axis decreased, while the length of the c axis did not show a remarkable change. The chemical pressure along the a axis upon Nd substitution seemed to be linked with the inducement of bulk superconductivity. We found that the chemical pressure effect did not completely correspond to the external pressure effect.

Magnetic transitions and the magnetocaloric effect in the Pr1−xYxMn2Ge2 system

Layered rare earth compounds in the RMn2X2 series (R = rare‐earth; X = Ge, Si) are of interest for potential cooling applications at lower temperatures as they enable the structural and magnetic behavior to be controlled via substitution of R, Mn, and X atoms on the 2a, 4d, and 4e sites respectively. We continue investigations of the Pr1−xYxMn2Ge2 magnetic phase diagram as functions of both composition and Mn–Mn spacing using X‐ray and neutron diffraction, magnetization and differential scanning calorimetry measurements. Pr1−xYxMn2Ge2 exhibits an extended region of re‐entrant ferromagnetism around x ∼ 0.5 with re‐entrant ferromagnetism at for Pr0.5Y0.5Mn2Ge2. The entropy values −ΔSM around the ferromagnetic transition temperatures from the layered antiferromagnetic AFl structure to the canted ferromagnetic structure Fmc (typically ) have been derived for Pr1−xYxMn2Ge2 with x = 0.0, 0.2, and 0.5 for ΔB = 0–5 T. The changes in magnetic states due to Y substitution for Pr are discussed in terms of chemical pressure, external pressure, and electronic effects.

Influence of chemical substitution, magnetic field, and hydrostatic pressure effect on martensitic and intermartensitic transition in bulk Ni49-xCuxMn38Sn13(0.5≤ x ≤ 2) Heusler alloys

In this work, we report the influence of chemical substitution of Ni site by Cu, magnetic field of 50 kOe, and external pressure effect on martensite and intermartensite transformations in Ni49-xCuxMn38Sn13 (0.5 ≤ x ≤ 2) Heusler alloys. The substitution of Cu for Ni decreases the lattice parameter and introduces the intermartensitic transformation in this alloy series. Further, the intermartensitic transformation vanishes for higher Cu content (x = 2). The application of external magnetic field and hydrostatic pressure suppresses the intermartensitic transformation in Ni49-xCuxMn38Sn13 (0.5 ≤ x ≤ 1.5) and Ni49-xCuxMn38Sn13 (x = 0.5) alloys, respectively. Also, the external magnetic field favors the stabilization of austenite phase while the external hydrostatic pressure favors the martensite phase.

Deformation analysis of double-sided tube hydroforming in square-section die

In this paper, in order to explore the deformation behavior of double-sided tube hydroforming in square-section die, effect of external pressure on the critical effective strain was theoretically analyzed firstly. And then a special experimental setup was designed for double-sided tube hydroforming in which the difficulty of simultaneous loading was overcome using two independent intensifiers and servo controlling while the sealing of external pressure was guaranteed by the O rings assembled in the interfaces of mandrel/base plate and outer cylinder/base plate. Furthermore, 5A02-O aluminum alloy tubes with outer diameter of 63mm and thickness of 2mm were investigated under different external pressures varying from 0 to 80MPa. At the same time, numerical simulation was conducted using the Abaqus/Explicit software. It is shown that increasing of external pressure has an effect on the fraction of grain boundaries, the number and size of the microvoids and the microhardness in the transition zone, and thus increases the critical effective strain in the transition zone. It can be concluded that the deformation ability of the transition zone is improved by the external pressure in double-sided tube hydroforming of square-section. This investigation shows that double-sided tube hydroforming is a potential forming method for the fabrication of lightweight hollow structures using the tubes with low ductility.

Interactions among density, climate, and food web effects determine long-term life cycle dynamics of a key copepod

Increasing pressure on animal populations through climate change and anthro- pogenic exploitation fuel the need to understand complex life cycle dynamics of key ecosystem species and their responses to external factors. Here, we provide a novel, integrative study on the long-term population dynamics of Pseudocalanus acuspes, a key species in the Baltic Sea, explic- itly considering its distinct life-history stages, and testing for linear, non-linear, and non-additive climate and food web effects. Based on a unique data set of stage-specific abundance covering almost 5 decades of sampling (1960 to 2008, with 1408 samples), we use generalized additive mod- eling (GAM) and its respective non-additive threshold (TGAM) formulation to test for (1) density effects on subsequent life-history stages within the internal life cycle, (2) the effect of exogenous bottom-up (i.e. hydro-climatic) and top-down (i.e. predation) pressures, and (3) changes between bottom-up and top-down regulation. We show that linear density effects are always present, explaining a high proportion of interannual variability, while effects of external pressures are non- linear or non-additive and strongly stage- and season-specific. In general, younger stages of P. acuspes are more affected by atmospheric winter conditions and water temperature, whereas older stages are influenced by conditions of deepwater salinity and predation pressure. These bot- tom-up processes, however, are not necessarily stable, and can depend on the level of top-down predation pressure. Our study demonstrates the complex and non-stationary interplay between internal and external factors regulating long-term animal population dynamics.

Extending environmental management beyond the firm boundaries: An empirical study of Dutch food and beverage firms

Consumer demand for environmental sustainability and for affordable prices calls for cooperation and information exchange in food chains to reduce joint environmental impact, known as externally-oriented environmental management (E-EM). E-EM is increasingly regarded as a management tool to simultaneously improve environmental, operational, and business performance. Understanding the factors that influence managers to develop E-EM helps to design environmentally and economically sustainable food chains. The prior research regarding these factors is not exhaustive and demanded a multi-period approach. This study expands the understanding of the factors that influence managers to develop E-EM with a multi-period empirical research. We address the effects of external institutional pressures (regulative, normative, and culturally-cognitive) and the level of in-company environmental management (I-EM) on E-EM, which involves information exchange in the chain, cooperation with suppliers and customers. The analysis relies on survey data of 255 and 96 Dutch food and beverage (F&B) processors from 2002 and 2010 respectively. The findings indicate that respondents have considerably improved I-EM over time. I-EM requires in-company pzrocedures ranging from environmental strategy formulation to the managerial review of achieved results to assure continuous improvement of environmental performance. F&B processors that had already achieved a high level of I-EM are more likely to develop E-EM. Also growing normative and culturally-cognitive pressures from supply chain partners and increasingly from long-term public–private environmental covenants significantly influenced E-EM implementation. However, regulative pressure from public authorities had no impact. It appeared that E-EM is influenced mostly by institutional pressures when the firms are less experienced with I-EM.

Nonlinear axisymmetric response of FGM shallow spherical shells on elastic foundations under uniform external pressure and temperature

Abstract Based on the classical shell theory taking into account geometrical nonlinearity, initial geometrical imperfection and Pasternak type elastic foundation, the nonlinear axisymmetric response of shallow spherical FGM shells under mechanical, thermal loads and different boundary conditions is considered in this paper. Using the Bubnov–Galerkin method and stress function, obtained results show effects of elastic foundations, external pressure, temperature, material and geometrical properties on the nonlinear buckling and postbuckling of the shells. The snap-through behaviors of the FGM spherical shallow shells on elastic foundations also are analyzed carefully in this paper. Some results were compared with the ones of other authors.

The effect of process parameters on floating zone crystal growth of selected cuprates

Process parameters for floating zone crystal growth with optical heating were analyzed with special emphasis to the effect of external gas pressure. The cuprates are grown at low velocities ≤1mm/h and with a traveling solvent floating zone enriched in CuO. Elevated oxygen pressure up to 15MPa can affect phase equilibria and solidification modes, which enabled crystal growth of various novel compounds, which are not stable at normal pressure. Analyses of quenched zones suggest that crystals grow from oxygen depleted melts. Upon melting at the interface of the feed rod oxygen is released. Undesired formation of gas bubbles in the melt can be partly inhibited by growing under O2/Ar mixed gas atmosphere. Highly anisotropic antiferromagnetic ordering and strong effects of Ca doping in selected cuprates were revealed on single crystalline samples.

Hydrogen diffusivity, kinetics of H2O/H2 charge transfer and corrosion properties of LaNi5-powder, composite electrodes in 6 M KOH solution

Meticulous analysis of galvanostatic charge/discharge dependencies of the LaNi5-based, powder composite electrode, in terms of determination of characteristic kinetic parameters of hydrogen storage electrode materials working in concentrated alkaline solution has been carried out. A special attention has been paid to the precise determination of charge and discharge times. The cathodic curves reveal their stepwise nature which allows to receive information of hydride material corrosion phenomena and determine the real time of atomic hydrogen absorption. The graphical way of determining of reduction times, based on differential cathodic curves is proposed. The knowledge of hydrogen absorption and desorption times allows to determine hydrogen diffusivity within the tested material with acceptable accuracy. The effect of external pressure (0.5–4 bar) on hydrogen absorption ability of LaNi5-based material is also discussed. The exchange current density of H2O/H2 system distinctly increases with external pressure, at the same time, kind of gas atmosphere (Ar or H2) scarcely affects the exchange current on the LaNi5 electrode. The hydrogen capacity increases when the charge/discharge rate decreases. The reduction times of oxide phases formed during electrode discharge can be a measure of material corrosion rate. It is shown that the rate of LaNi5 corrosion process strongly increases with the electrode cycling.

Pressure effect and electron diffraction on the anomalous transition in ternary superconductor Bi2Rh3Se2

The effect of external hydrostatic pressure up to 22.23kbar on the temperature-dependent transport properties of the ternary compound Bi2Rh3Se2 is investigated. Interestingly, the resistive anomaly at Ts~250K, previously proposed as a charge-density-wave (CDW) transition, is shifted to higher temperature with increasing pressure, in distinct contrast to an established knowledge for CDW. Using temperature-dependent electron-diffraction characterizations, we have unraveled that this transition is, in effect, of a structural phase-transformation nature, experiencing the symmetry reduction from a high-symmetry C-centered monoclinic lattice to a low-symmetry primitive one below Ts. A more elaborately determined room-temperature C-centered lattice was also proposed.

Effects of Diameter to Thickness Ratio and External Pressure on the Velocity of Dynamic Buckle Propagation in Offshore Pipelines

In this paper, a numerical study of the dynamic buckle propagation, initiated in long pipes under external pressure, is presented. For a long pipe, due to the high exerted pressure, local instability is likely to occur; therefore, the prevention of its occurrence and propagation are very important subjects in the design of pipelines. The 3D finite element modeling of the buckle propagation is presented by considering the inertia of the pipeline and the nonlinearity introduced by the contact between its collapsing walls. The buckling and collapse are assumed to take place in the vacuum. The numerical results of the nonlinear finite element analysis are compared with the experimental results obtained by Kyriakides and Netto (2000, “On the Dynamics of Propagating Buckle in Pipelines,” Int. J. Solids Struct., 37, pp. 6843–6878) from a study on the small-scale models. Comparison shows that the finite element results have very close agreement with those of the experimental study. Therefore, it is concluded that the finite element model is reliable enough to be used for nonlinear collapse analysis of the dynamic buckle propagation in the pipelines. In this study, the effects of external pressure on the velocity of dynamic buckle propagation for different diameter to thickness ratios are investigated. In addition, the mathematical relations, based on the initiation pressure, are derived for the velocity of buckle propagation considering the diameter to thickness ratio of the pipeline. Finally, a relation for the buckle velocity as a function of the pressure and diameter to thickness ratio is presented.

A modelling study of the role of marine protected areas in metapopulation genetic connectivity in Delaware Bay oysters

ABSTRACTManagement decisions concerning location and extent of marine protected areas (MPAs) both for exploited and unexploited resources rely on understanding how populations are interconnected.The potential effects of MPA location and external fishing pressure on genetic connectivity of eastern oyster (Crassostrea virginica) populations in Delaware Bay were examined.An individual‐based metapopulation model that includes post‐settlement population dynamics, larval dispersal, and genetic structure was used to simulate four oyster populations for two periods (1970s and 2000s) with distinct population and environmental conditions. Sensitivity analysis examined the influence of larval dispersal, and simulations included combinations of MPA location (which population was protected) and three fishing mortality rates for non‐MPA populations: low (4%), medium (8%) and high (30%); no fishing was allowed in the MPAs.Results showed (i) salinity‐driven changes in larval dispersal led to relatively small, population‐specific connectivity changes, (ii) MPAs can enhance the frequency of genotypes originating within protected populations in unprotected populations when fishing rates are high (30%), and (iii) demographic shifts can impose temporal variability on the influence of MPAs on connectivity.These results suggest that genetic consequences of siting MPAs must be considered in terms of present population and environmental conditions, as well as allowing for changes in population and genetic connectivity that may shift fundamentally over time.Simulation results indicate that siting protected areas for oyster restoration in low salinity (<12ppt) regions may interact with development of disease resistance in the metapopulation by altering genotype transfer from protected to unprotected downestuary populations. Copyright © 2013 John Wiley & Sons, Ltd.

Comparative crystal field study of Ni2+ energy levels and crystal field effects in CsCdBr3 and CsMgBr3 crystals

The exchange charge model of crystal field theory has been used to analyze the ground state absorption of Ni2+ ions in CsCdBr3 and CsMgBr3 crystals. The parameters of crystal field were calculated from the available crystal structure data. The obtained Ni2+ energy level schemes were compared with the experimental absorption spectra; good agreement between the calculated and experimental data was demonstrated. Dependencies of the crystal field strength 10Dq on the “impurity ion—ligand” distance of the nearest Br− ions from Ni2+ ions were derived for both crystals and used to estimate the Stokes shift values for these crystals; all calculated results are close to the experimental data. The “critical” Ni–Br distances leading to the Ni2+ energy levels crossing were estimated; these results can be used for the analysis of the external hydrostatic pressure effects on the optical properties of the studied crystals.

Linear study of Rayleigh-Taylor instability in a diffusive quantum plasma

The linear Rayleigh-Taylor (RT) instability in an incompressible quantum plasma is investigated on the basis of quantum magnetohydrodynamic model. It is shown that the occurrence of RT instability depends on density-temperature inhomogeneity (characteristic lengths) on one hand, and the system layer size on the other. It is also observed that the combined effects of external magnetic field, diffusivity, and quantum pressure significantly modify the dispersion properties of system in both the parallel and perpendicular directions. For any case, the imaginary and real parts of dispersion relation are presented and the possibility and conditions for the instability growth rate are discussed.

External temperature and pressure effects on thermodynamic properties and mechanical stability of yttrium chalcogenides YX (X=S, Se and Te)

The full potential linearized augmented plane wave method within the framework of density functional theory is employed to investigate the structural, thermodynamic and elastic properties of the yttrium chalcogenides (YX: X=S, Se, and Te) in their low-pressure phase (Fm3¯m) and high-pressure phase (Pm3¯m). The exchange-correlation potential is treated with the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE). Temperature dependence of the volume and both adiabatic and isothermal bulk moduli is predicted for a temperature range from 0to1200K for the both phases of the herein considered materials. Furthermore, we have analyzed the thermodynamic properties such as the heat capacities, CV and CP, thermal expansion, α, and Debye temperature, ΘD, under variable pressure and temperature. We have calculated the isothermal elastic constants CijT of the YX monochalcogenides in both NaCl-B1 and CsCl-B2 phases at zero pressure and a temperature range 0−1200K. The results show that rare earth yttrium monochalcogenides are mechanically stable at high temperature. The elastic anisotropy of all studied materials in the two phases has been studied using three different methods.