Fatigue failure in metal bellows due to flow-induced vibrations

To prevent fatigue due to flow-induced vibrations in metal bellows connected to ducts carrying liquid hydrogen, a study was made which shows that the flexure lines are in general a function of the vibration coupling between the fluid and bellows structure, and the nature of the external environment

Local properties of patterned vegetation: quantifying endogenous and exogenous effects

Dryland ecosystems commonly exhibit periodic bands of vegetation, thought to form due to competition between individual plants for heterogeneously distributed water. In this paper, we develop a Fourier method for locally identifying the pattern wavenumber and orientation, and apply it to aerial images from a region of vegetation patterning near Fort Stockton, Texas. We find that the local pattern wavelength and orientation are typically coherent, but exhibit both rapid and gradual variation driven by changes in hillslope gradient and orientation, the potential for water accumulation, or soil type. Endogenous pattern dynamics, when simulated for spatially homogeneous topographic and vegetation conditions, predict pattern properties that are much less variable than the orientation and wavelength observed in natural systems. Our local pattern analysis, combined with ancillary datasets describing soil and topographic variation, highlights a largely unexplored correlation between soil depth, pattern coherence, vegetation cover and pattern wavelength. It also, surprisingly, suggests that downslope accumulation of water may play a role in changing vegetation pattern properties

Local origins of volume fraction fluctuations in dense granular materials

Fluctuations of the local volume fraction within granular materials have previously been observed to decrease as the system approaches jamming. We experimentally examine the role of boundary conditions and inter-particle friction $\mu$ on this relationship for a dense granular material of bidisperse particles driven under either constant volume or constant pressure. Using a radical Vorono\"i tessellation, we find the variance of the local volume fraction $\phi$ monotonically decreases as the system becomes more dense, independent of boundary condition and $\mu$. We examine the universality and origins of this trend using experiments and the recent granocentric model \cite{Clusel-2009-GMR,Corwin-2010-MRP}, modified to draw particle locations from an arbitrary distribution ${\cal P}(s)$ of neighbor distances $s$. The mean and variance of the observed ${\cal P}(s)$ are described by a single length scale controlled by $\bar \phi$. Through the granocentric model, we observe that diverse functional forms of ${\cal P}(s)$ all produce the trend of decreasing fluctuations, but only the experimentally-observed ${\cal P}(s)$ provides quantitative agreement with the measured $\phi$ fluctuations. Thus, we find that both ${\cal P}(s)$ and ${\cal P}(\phi)$ encode similar information about the ensemble of observed packings, and are connected to each other by the local granocentric model

Preliminary evaluation of a thin organic film coating Final report

High temperature and humidity resistance of thin siloxane films on metal substrate

Hysteresis and competition between disorder and crystallization in sheared and vibrated granular flow

Experiments on spherical particles in a 3D Couette cell vibrated from below and sheared from above show a hysteretic freezing/melting transition. Under sufficient vibration a crystallized state is observed, which can be melted by sufficient shear. The critical line for this transition coincides with equal kinetic energies for vibration and shear. The force distribution is double-peaked in the crystalline state and single-peaked with an approximately exponential tail in the disordered state. A linear relation between pressure and volume ($dP/dV > 0$) exists for a continuum of partially and/or intermittently melted states over a range of parameters

Evolution of Network Architecture in a Granular Material Under Compression

As a granular material is compressed, the particles and forces within the system arrange to form complex and heterogeneous collective structures. Force chains are a prime example of such structures, and are thought to constrain bulk properties such as mechanical stability and acoustic transmission. However, capturing and characterizing the evolving nature of the intrinsic inhomogeneity and mesoscale architecture of granular systems can be challenging. A growing body of work has shown that graph theoretic approaches may provide a useful foundation for tackling these problems. Here, we extend the current approaches by utilizing multilayer networks as a framework for directly quantifying the progression of mesoscale architecture in a compressed granular system. We examine a quasi-two-dimensional aggregate of photoelastic disks, subject to biaxial compressions through a series of small, quasistatic steps. Treating particles as network nodes and interparticle forces as network edges, we construct a multilayer network for the system by linking together the series of static force networks that exist at each strain step. We then extract the inherent mesoscale structure from the system by using a generalization of community detection methods to multilayer networks, and we define quantitative measures to characterize the changes in this structure throughout the compression process. We separately consider the network of normal and tangential forces, and find that they display a different progression throughout compression. To test the sensitivity of the network model to particle properties, we examine whether the method can distinguish a subsystem of low-friction particles within a bath of higher-friction particles. We find that this can be achieved by considering the network of tangential forces, and that the community structure is better able to separate the subsystem than a purely local measure of interparticle forces alone. The results discussed throughout this study suggest that these network science techniques may provide a direct way to compare and classify data from systems under different external conditions or with different physical makeup

Judicial Review of the Fact Findings of the Federal Trade Commission

Section 5 of the Trade Commission Act (15 U. S. C. § 45) and Section 11 of the Clayton Act (15 U. S. C. § 21) provide that The findings of the Commission as to facts, if supported by testimony, shall be conclusive. This follows the form of the usual statutory provision, and its settled interpretation is that the findings of the administrative board, if supported by substantial evidence, are conclusive as to issues of fact. The purpose of the creation of the Trade Commission was largely to establish an administrative tribunal consisting of a body of persons especially qualified by reason of information, experience and study to administer the federal program against unfair competition and monopoly. The Trade Commission Act took the function of gathering evidence entirely out of the hands of the courts and vested it in the Commission. The Commission was given the power to employ experts and examiners, including attorneys, economists, accountants and specialists in various fields. It would seem, therefore, that by the terms conclusive, if supported by testimony Congress had it in mind that the administrative specialist rather than the court would determine the facts and draw the inferences therefrom. The test, then, which both logic and reason would seem to require the courts to adopt in determining whether or not the order of the Commission is to be upheld is simply this: Are the findings supported by substantial evidence? The court should not go beyond this to weigh the evidence or review the findings of fact found by the Commission. In a number of cases the Circuit Courts of Appeal have treated the findings of the Commission with due respect and have held that the findings were supported by evidence and as such were conclusive upon the courts. But the courts seem to have a natural suspicion of the functions of administrative officers and bodies and when the Commission presents a case which is not as strong as the court feels it should be it is more likely than not to set aside the administrative order and substitute therefor its own opinion. The courts have, of course, developed and evoked certain doctrines and rationalizations whereby to achieve their ends, while ostensibly obeying the legislative command. A study of the use of these rationalizations is necessary in order to determine to what extent the courts actually consider the fact findings of the Commission sufficient bases for decisions. This may perhaps best be done by first considering some of the more illustrative of those cases in which it has been found that the findings of the Commission were not supported by substantial evidence

The Impact Life Experience Has On Leadership Development

The purpose of this qualitative study was to address the problem of ineffective leadership by focusing on the impact life experiences have on leadership development. Participants in this qualitative study were educational leaders (principals) located in a central North Carolina school district. The researcher sought to study how select leaders’ life experiences impacted their leadership development, identify common themes that influenced select leaders, use the results to address the need for effective leadership in educational environments, and use the results to bring awareness of the importance of leadership development through experiential learning. Qualitative data in this study revealed that that life experiences are vital in developing a leader’s growth, and findings in the study are consistent with research that our “life experiences and our response to them are of critical importance in how leaders are formed and the kind of leaders we become” (Ambler, 2012, para. 6). As a result of this research, educational systems, companies, and/or organizations seeking effective leaders may find this study beneficial when seeking and developing leaders