Computational Study of the Structure and Thermodynamic Properties of Ammonium Chloride Clusters Using a Parallel J-Walking Approach

The thermodynamic and structural properties of (NH$_4$Cl)$_n$ clusters, n=3-10 are studied. Using the method of simulated annealing, the geometries of several isomers for each cluster size are examined. Jump-walking Monte Carlo simulations are then used to compute the constant-volume heat capacity for each cluster size over a wide temperature range. To carry out these simulations a new parallel algorithm is developed using the Parallel Virtual Machine (PVM) software package. Features of the cluster potential energy surfaces, such as energy differences among isomers and rotational barriers of the ammonium ions, are found to play important roles in determining the shape of the heat capacity curves.Comment: Journal of Chemical Physics, accepted for publicatio

We\u27re One For Uncle Sam

https://digitalcommons.library.umaine.edu/mmb-vp/5349/thumbnail.jp

Fouling mechanisms in constant flux crossflow ultrafiltration

Four fouling models due to Hermia (complete pore blocking, intermediate pore blocking, cake filtration and standard pore blocking), have long been used to describe membrane filtration and fouling in constant transmembrane pressure (ΔP) operation of membranes. A few studies apply these models to constant flux dead-end filtration systems. However, these models have not been reported for constant flux crossflow filtration, despite the frequent use of this mode of membrane operation in practical applications. We report derivation of these models for constant flux crossflow filtration. Of the four models, complete pore blocking and standard pore blocking were deemed inapplicable due to contradicting assumptions and relevance, respectively. Constant flux crossflow fouling experiments of dilute latex bead suspensions and soybean oil emulsions were conducted on commercial poly (ether sulfone) flat sheet ultrafiltration membranes to explore the models’ abilities to describe such data. A model combining intermediate pore blocking and cake filtration appeared to give the best agreement with the experimental data. Below the threshold flux, both the intermediate pore blocking model and the combined model fit the data well. As permeate flux approached and passed the threshold flux, the combined model was required for accurate fits. Based on this observation, a physical interpretation of the threshold flux is proposed: the threshold flux is the flux below which cake buildup is negligible and above which cake filtration becomes the dominant fouling mechanism

Corporate Citizenship and Community Stakeholders

Stipulating that work on corporate citizenship is intended to add to the conversation around the role of business in society, it is reasonable to assume that scholars adopting (and adapting) the language of corporate citizenship find something there that allows for better description, analysis and synthesis of this role. Though what \u27better\u27 may mean here remains an open question, a sensible place to begin considering the question is to compare and contrast corporate citizenship with more established ways of conceiving business\u27s role in society such as, in the case of this chapter, stakeholder theory

Stakeholders

This landmark book takes a retrospective look at the most important and influential works in the study of stakeholders since Freeman’s 1984 publication, Strategic Management: A Stakeholder Approach. 2009 marked the 25th anniversary of this watershed in organizational scholarship, so now is an excellent time for Phillips and Freeman to revisit this topical and exciting subject. From the tremendous upsurge in the literature, the editors have carefully selected ground-breaking works on topics including corporate governance, stakeholder-agency theory, management models, ethical theory and stakeholder orientation. This invaluable volume will shape the thinking of scholars and academics for the next 25 years.https://scholarship.richmond.edu/bookshelf/1048/thumbnail.jp

Rates of erosion and landscape change along the Blue Ridge escarpment, southern Appalachian Mountains, estimated from in situ cosmogenic 10Be

The Blue Ridge escarpment, located within the southern Appalachian Mountains of Virginia and North Carolina, forms a distinct, steep boundary between the lower-elevation Piedmont and higher-elevation Blue Ridge physiographic provinces. To understand better the rate at which this landform and the adjacent landscape are changing, we measured cosmogenic 10Be in quartz separated from sediment samples (n = 50) collected in thirty-two streams and from three exposed bedrock outcrops along four transects normal to the escarpment, allowing us to calculate erosion rates integrated over 104–105 years. These basin-averaged erosion rates (5.4–49 m My-1) are consistent with those measured elsewhere in the southern Appalachians and show a positive relationship between erosion rate and average basin slope. Erosion rates show no relationship with basin size or relative position of the Brevard fault zone, a fundamental structural element of the region. The cosmogenic isotopic data, when considered along with the distribution of average basin slopes in each physiographic province, suggest that the escarpment is eroding on average more rapidly than the Blue Ridge uplands, which are eroding more rapidly than the Piedmont lowlands. This difference in erosion rates by geomorphic setting suggests that the elevation difference between the uplands and lowlands adjacent to the escarpment is being reduced but at extremely slow rates

Momentum analysis of complex time-periodic flows

Several methods have been proposed to characterize the complex interactions in turbulent wakes, especially for flows with strong cyclic dynamics. This paper introduces the concept of Fourier-Averaged Navier-Stokes (FANS) equations as a framework to obtain direct insights into the dynamics of complex coherent wake interactions. The method simplifies the interpretations of flow physics by identifying terms contributing to momentum transport at different timescales. The method also allows for direct interpretation of non-linear interactions of the terms in the Navier-Stokes equations. By analysing well-known cases, the characteristics of FANS are evaluated. Particularly, we focus on physical interpretation of the terms as they relate to the interactions between modes at different timescales. Through comparison with established physics and other methods, FANS is shown to provide insight into the transfer of momentum between modes by extracting information about the contributing pressure, convective, and diffusive forces. FANS provides a simply calculated and easily interpreted set of equations to analyse flow physics by leveraging momentum conservation principles and Fourier analysis. The method is applicable to flows with complex cyclic waveforms, including broadband spectral energy distributions.Comment: 28 pages, 23 figures. Submitted to the Journal of Fluid Mechanic

What Stakeholder Theory Is Not

The term stakeholder is a powerful one. this is due, to a significant degree, to its conceptual breadth. The term means many different things to many different people and hence evokes praise or scorn for a wide variety of scholars and practitioners of myriad academic disciplines and backgrounds. Such breadth of interpretation, though one of stakeholder theory\u27s greatest strengths, is also one of its most prominent theoretical liabilities as a topic of reasoned discourse. Much of the power of stakeholder theory is a direct result of the fact that, when used unreflectively, its managerial prescriptions and implications are nearly limitless. When discussed in its instrumental variation (i.e., that managers should attend to stakeholders as a means to achieving other organizational goals such as profit or shareholder wealth maximization) stakeholder theory stands virtually unopposed. The goal of the current paper is like that of a controlled burn that clears away some of the underbrush of misinterpretation in the hope of denying easy fuel to the critical conflagration that would attempt to raze the theory. The aim is to attempt to narrow its technical meaning for greater facility of use in management and organizational studies. By elaborating a number of common misinterpretations of the theory, we hope to render a stronger and more convincing stakeholder theory as a starting place for future research