Bearing servicing tool

A tool for removing and/or replacing bearings in situ is presented. The tool is comprised of a brace having a first end adapted to engage a first end of the bearing housing, and a second end adapted to engage a second end of the bearing housing. If the two ends of the bearing housing are different in configuration, then the respective ends of the brace are configured accordingly. An elongate guide member integral with the brace has two parts, each projecting endwise from a respective end of the brace. A removable pressure plate can be mounted on either part of the guide member for longitudinal movement therealong and has first and second ends of different configurations adapted to engage the first and second ends of the bearing. A threaded-type drive is cooperative between the guide and the pressure plate to move the pressure plate longitudinally along the guide and apply a force to the bearing, either to remove the bearing from its housing, or to emplace a new bearing in the housing

Interference effects during burning in air for stationary n-heptane, ethyl alcohol, and methyl alcohol droplets

Experiments have been conducted for the determination of the evaporation constant and flame shapes of two and of five closely spaced droplets burning in air. Droplets of approximately the same and of different diameters were used at various distances between the droplet centers. The apparent flame shape, which was observed only for n-heptane droplets, changes very little during burning. The square of the droplet diameter decreases linearly with time for fixed spacing between droplet centers, at least within the experimental limits of accuracy. In general, the average evaporation constant for two droplets, K', must be assumed either to vary continuously during burning or else to be a function of average initial drop diameter, D^0. The change of K' with time corresponds to the second derivative in plots of the square of the diameter vs. time. These second derivatives are not defined in our work because of unavoidable scatter of the experimental data. Attempts at understanding the observed results by considering published theories for single droplets, as well as groupings obtained from dimensional analysis, have been unsuccessful. It appears that the diffusion model for the heterogeneous burning of single fuel droplets will require serious revision and extension before the burning of droplets arrays and sprays can be understood quantitatively. Furthermore, the effective value of K' for a spray probably depends not only on the fuel-oxidizer system but also on the injection pattern. For this reason additional studies had best be carried out under conditions corresponding to those existing in service models

Monetary transmission in Africa: a review of official sources

This paper focuses on the subject of monetary transmission in Africa. It begins with a report on the effects of the financial crisis of 2008 in Africa. In the countries with more developed financial systems the financial channel proved to be the most important in transmitting the crisis. In the more peripheral countries the trade channel proved to be the most important. Where countries were able to withstand the global shock coming from the financial crisis they did so with a diversified group of trading partners in fast growing economies. The paper then turns to examine three post crisis institutional developments and asks, how are: a) an increased momentum towards regional integration, b) the rise of Pan African banking and, c) an increase in cross border flows, affecting the monetary transmission mechanism (MTM) in Africa. It is clear from the literature that the rise of Pan African banking and the regionalization thrust of the authorities are deepening the financial channels between countries. But with respect to cross border flows, the huge size of deposits maintained by Africa’s BIS reporting banks suggest relatively low levels of bank intermediation and competition. Thus the benefits that are assumed to accrue as a result of increased cross border flows are withdrawn from the local economy and stored up in the BIS banks. We know large deposits reflect the expectations of the deposit holders. But beyond that very little is known about the role of expectations and the workings of the expectations channel in monetary transmission in Africa. Even less is known about how such expectations would interact with those formed as a result of operations in the large informal sectors which characterise African macro economies. Until research can bridge this gap, the increasing cross border flows with the large deposits held in BIS banks form the basis yet another explanation for the historical weakness of the MTM in Africa

Entanglement Entropy and Spectra of the One-dimensional Kugel-Khomskii Model

We study the quantum entanglement of the spin and orbital degrees of freedom in the one- dimensional Kugel-Khomskii model, which includes both gapless and gapped phases, using analytical techniques and exact diagonalization with up to 16 sites. We compute the entanglement entropy, and the entanglement spectra using a variety of partitions or "cuts" of the Hilbert space, including two distinct real-space cuts and a momentum-space cut. Our results show the Kugel-Khomski model possesses a number of new features not previously encountered in studies of the entanglement spectra. Notably, we find robust gaps in the entanglement spectra for both gapped and gapless phases with the orbital partition, and show these are not connected to each other. We observe the counting of the low-lying entanglement eigenvalues shows that the "virtual edge" picture which equates the low-energy Hamiltonian of a virtual edge, here one gapless leg of a two-leg ladder, to the "low-energy" entanglement Hamiltonian breaks down for this model, even though the equivalence has been shown to hold for similar cut in a large class of closely related models. In addition, we show that a momentum space cut in the gapless phase leads to qualitative differences in the entanglement spectrum when compared with the same cut in the gapless spin-1/2 Heisenberg spin chain. We emphasize the new information content in the entanglement spectra compared to the entanglement entropy, and using quantum entanglement present a refined phase diagram of the model. Using analytical arguments, exploiting various symmetries of the model, and applying arguments of adiabatic continuity from two exactly solvable points of the model, we are also able to prove several results regarding the structure of the low-lying entanglement eigenvalues.Comment: 25 pages, 19 figure

The Africa Rising Narrative - Whither development?

Over the last ten years the mainstream press have put together an Africa Rising narrative which tells us that because of a series of “good” governance reforms and more responsible economic management (by technocratic and not ideological leaders), African countries have managed to transform their economies into growing vibrant engines of growth. Robust growth rates that averaged 5.8% a year between 2002 and 2012 formed the basis of expectations that there was more to come. In 2011 The Economist (Dec 3rd) reported that, after decades of slow growth ‘Africa now has the real chance to follow Asia in embarking on fast growth in a very short period.’ After years of repose - Africa was rising. Basing its predictions on data from the IMF, The Economist (ibid) declared that Ghana, Mozambique, Nigeria and Zambia would be among this decade’s star performers. Recent events (like Ghana’s 2015 IMF bailout) may have dented the narrative but it persists because although Africa’s 2015 GDP declined 1.2% to 3.4% from 4.6% in 2014, it is still among the fastest growing regions in world. There is clearly a huge disconnect between the narrative and the images of African migrants risking life and limb to get away from Africa and into Europe. This article explores the sources of the disconnect and evaluates the narrative. How and why did The Economist (and others in the media and the economics profession) manage to put forward the bold claim that the 21st Century belonged to Africa

Dynamical density functional theory with hydrodynamic interactions and colloids in unstable traps

A density functional theory for colloidal dynamics is presented which includes hydrodynamic interactions between the colloidal particles. The theory is applied to the dynamics of colloidal particles in an optical trap which switches periodically in time from a stable to unstable confining potential. In the absence of hydrodynamic interactions, the resulting density breathing mode, exhibits huge oscillations in the trap center which are almost completely damped by hydrodynamic interactions. The predicted dynamical density fields are in good agreement with Brownian dynamics computer simulations