The case for epistocratic republicanism

In recent years, the fortunes of democracy have waned both in theory and practice. This has added impetus not only to the republican case for strengthening democratic institutions but also to new anti-democratic thought. This article examines the claim made by Jason Brennan that epistocracy, rule by the ‘knowledgeable’, is compatible with freedom from domination. It begins by briefly explaining epistocracy and republicanism. It then presents the argument for epistocratic republicanism: that democracy can be a source of domination and that freedom from domination can be secured through non-democratic political institutions. The case against epistocratic republicanism is grounded in concerns about systemic domination and the ability of epistocrats to arbitrarily set the terms of social cooperation. These two arguments are judged on the basis of which better minimises domination while respecting its value to all people. Epistocratic republicanism is found to be less reliable because of the risks of epistemic injustice that accompanies systemic domination; democracy, accompanied by other republican institutions, is better at minimising domination and respecting persons. It concludes that republicans ought to be democrats

The topographic development and areal parametric characterization of a stratified surface polished by mass finishing

Mass finishing is amongst the most widely used finishing processes in modern manufacturing, in applications from deburring to edge radiusing and polishing. Processing objectives are varied, ranging from the cosmetic to the functionally critical. One such critical application is the hydraulically smooth polishing of aero engine component gas-washed surfaces. In this, and many other applications the drive to improve process control and finish tolerance is ever present. Considering its widespread use mass finishing has seen limited research activity, particularly with respect to surface characterization. The objectives of the current paper are to; characterise the mass finished stratified surface and its development process using areal surface parameters, provide guidance on the optimal parameters and sampling method to characterise this surface type for a given application, and detail the spatial variation in surface topography due to coupon edge shadowing. Blasted and peened square plate coupons in titanium alloy are wet (vibro) mass finished iteratively with increasing duration. Measurement fields are precisely relocated between iterations by fixturing and an image superimposition alignment technique. Surface topography development is detailed with ‘log of process duration’ plots of the ‘areal parameters for scale-limited stratified functional surfaces’, (the Sk family). Characteristic features of the Smr2 plot are seen to map out the processing of peak, core and dale regions in turn. These surface process regions also become apparent in the ‘log of process duration’ plot for Sq, where lower core and dale regions are well modelled by logarithmic functions. Surface finish (Ra or Sa) with mass finishing duration is currently predicted with an exponential model. This model is shown to be limited for the current surface type at a critical range of surface finishes. Statistical analysis provides a group of areal parameters including; Vvc, Sq, and Sdq, showing optimal discrimination for a specific range of surface finish outcomes. As a consequence of edge shadowing surface segregation is suggested for characterization purposes

The application of Taguchi approach to optimise the processing conditions on bonnet polishing of CoCr

This paper applied the Taguchi approach to investigate the effects of each polishing parameter and obtain the optimal processing conditions for CoCr alloy polishing. The polishing medium was 1µm diamond paste with Microcloth(polishing cloth). Surface finish parameter Sa was chosen as criterion for optimization. The experimental result indicates that the optimal polishing condition for CoCr alloy polishing is 5deg of precess angle, 800 rpm of head speed, 0.2mm of tool offset and 1.5 bar of tool pressure. With this optimal condition, a confirmatory experiment was conducted. The surface roughness Sa reduced from initial 24nm to 7nm and reduction ratio was 72.5% which was very close to the estimated ratio 64%

Material removal investigation in bonnet polishing of CoCr alloy

The manufacture of orthopaedic joint bearings surfaces requires exceptionally high levels of control of not only the surface finish but also the surface form. In the case of hip joints, the form of femoral head should be controlled to within ± 50ìm from a given diameter. It has been shown that a better form control of bearing component could enhance clearances creating the correct volume of lubrication to fill the bearing surface gap and reduce wear particle generation. This element is especially critical for the new generation non-spherical head designs. Bonnet polishing which is used successfully in the area of optics is potentially an excellent finishing process to control the form and finish of artificial joints. In the process of form control polishing an “influence function” which defines the material removal rate is of vital importance in developing a corrective polishing procedure. However, the effects of polishing parameters (such as precess angle, head speed, tool pressure and tool offset) on influence function are not very clear for CoCr alloys. These elements must be assessed if a deterministic polishing process is to be developed. Therefore, it is of paramount importance to understand the contribution of each polishing factors to influence function and consequent part polishing. This study has investigated the effects of polishing parameters on influence function, including geometric size and volumetric material removal rate (MRR). The experimental results indicate that the polishing parameter of precess angle and tool offset affect the geometric size of influence function significantly; the polishing parameter of head speed and tool pressure affect the geometric size of influence function to a lesser degree; the polishing parameter of precess angle, head speed and tool offset affect MRR greatly

Dynamic reservoir-condition microtomography of reactive transport in complex carbonates: effect of initial pore structure and initial brine pH

We study the impact of brine acidity and initial pore structure on the dynamics of fluid/solid reaction at high Péclet numbers and low Damköhler numbers. A laboratory μ-CT scanner was used to image the dissolution of Ketton, Estaillades, and Portland limestones in the presence of CO2-acidified brine at reservoir conditions (10 MPa and 50°C) at two injected acid strengths for a period of 4 hours. Each sample was scanned between 6 and 10 times at ∼4 μm resolution and multiple effluent samples were extracted. The images were used as inputs into flow simulations, and analysed for dynamic changes in porosity, permeability, and reaction rate. Additionally, the effluent samples were used to verify the image-measured porosity changes. We find that initial brine acidity and pore structure determine the type of dissolution. Dissolution is either uniform where the porosity increases evenly both spatially and temporally, or occurs as channelling where the porosity increase is concentrated in preferential flow paths. Ketton, which has a relatively homogeneous pore structure, dissolved uniformly at pH = 3.6 but showed more channelized flow at pH = 3.1. In Estaillades and Portland, increasingly complex carbonates, channelized flow was observed at both acidities with the channel forming faster at lower pH. It was found that the effluent pH, which is higher than that injected, is a reasonably good indicator of effective reaction rate during uniform dissolution, but a poor indicator during channelling. The overall effective reaction rate was up to 18 times lower than the batch reaction rate measured on a flat surface at the effluent pH, with the lowest reaction rates in the samples with the most channelized flow, confirming that transport limitations are the dominant mechanism in determining reaction dynamics at the fluid/solid boundary

Flexible shape extraction for micro/nano scale structured surfaces.

Surface feature is the one of the most important factors affecting the functionality and reliability of micro scale patterned surfaces. For micro scale patterned surface characterisation, it’s important to extract the surface feature effectively and accurately. The active contours, known as “snakes”, have been successfully used to segment, match and track the objects of interest. The active contours have been applied to facial boundary detection, medical image processing, motion correction, etc. In this paper, surface feature extraction techniques based on active contours have been investigated. Parametric active contour models and geometric active contour models have been presented. Also, a group of examples has been selected here to demonstrate the feasibility and applicability of the surface pattern extraction techniques based on active contours. At last, experimental results will be given and discussed

Functional Modelling of Water Vapour Transmission through Surface Defects Using Surface Segmentation Analysis

Flexible photovoltaic films have been recently shown to have efficiencies comparable to those of solid Si based photovoltaics. Flexible PV films have significant advantages in terms of ease of manufacture by roll-to-roll (R2R) techniques and in easy building integration. A significant challenge is the protection of the flexible solar cells from water vapour ingress, which seriously reduces cell life and efficiency. Transparent barrier films are a possible solution to addressing the water vapour transmission rate (WVTR) challenge. Consequently thin barrier films such as those made from Al2O3 are the subject of increasing research interest when used for the encapsulation of flexible PV modules. The film can be produced by several thin film deposition processes such as atomic layer deposition (ALD). However, micro-scale defects in the barrier film such as pinholes and particulate debris have been shown to have serious consequences in terms of WVTR. Our previous research has empirically shown that small defects (≤3μm lateral dimension) were less significant in determining water vapour ingress. In contrast, larger defects (≥3 μm lateral dimension) have been shown to have a greater effect on the barrier functionality. The present paper illustrates the use of surface segmentation techniques to efficiently extract defect data from measured surface topography of barrier film sheets. Experimental results are presented where the defect information is correlated with the WVTR tests. A model is then presented to test the hypothesis that the major contributing defects to water vapour transmission rate (WVTR) are small numbers of large defects. The model presented in the paper shows excellent correlation with experimental results and provides a theoretical basis for the development of in process surface measurement for thin film R2R manufacture