A predictive maintenance system for integral type faults based on support vector machines:An application to ion implantation

In semiconductor fabrication processes, effective management of maintenance operations is fundamental to decrease costs associated with failures and downtime. Predictive Maintenance (PdM) approaches, based on statistical methods and historical data, are becoming popular for their predictive capabilities and low (potentially zero) added costs. We present here a PdM module based on Support Vector Machines for prediction of integral type faults, that is, the kind of failures that happen due to machine usage and stress of equipment parts. The proposed module may also be employed as a health factor indicator. The module has been applied to a frequent maintenance problem in semiconductor manufacturing industry, namely the breaking of the filament in the ion-source of ion-implantation tools. The PdM has been tested on a real production dataset. © 2013 IEEE.

Superluminous supernovae from PESSTO

We present optical spectra and light curves for three hydrogen-poor superluminous supernovae followed by the Public ESO Spectroscopic Survey of Transient Objects (PESSTO). Time series spectroscopy from a fewdays aftermaximum light to 100 d later shows them to be fairly typical of this class, with spectra dominated by Ca II, MgII, FeII, and Si II, which evolve slowly over most of the post-peak photospheric phase. We determine bolometric light curves and apply simple fitting tools, based on the diffusion of energy input by magnetar spin-down, Ni-56 decay, and collision of the ejecta with an opaque circumstellar shell. We investigate how the heterogeneous light curves of our sample (combined with others from the literature) can help to constrain the possible mechanisms behind these events. We have followed these events to beyond 100-200 d after peak, to disentangle host galaxy light from fading supernova flux and to differentiate between the models, which predict diverse behaviour at this phase. Models powered by radioactivity require unrealistic parameters to reproduce the observed light curves, as found by previous studies. Both magnetar heating and circumstellar interaction still appear to be viable candidates. A large diversity is emerging in observed tail-phase luminosities, with magnetar models failing in some cases to predict the rapid drop in flux. This would suggest either that magnetars are not responsible, or that the X-ray flux from the magnetar wind is not fully trapped. The light curve of one object shows a distinct rebrightening at around 100 d after maximum light. We argue that this could result either from multiple shells of circumstellar material, or from a magnetar ionization front breaking out of the ejecta.

Thermal decomposition mechanism of levoglucosan during cellulose pyrolysis

Levoglucosan (1,6-anhydro-β-d-glucopyranose) decomposition is an important step during cellulose pyrolysis and for secondary tar reactions. The mechanism of levoglucosan thermal decomposition was studied in this paper using density functional theory methods. The decomposition included direct CO bond breaking, direct CC bond breaking, and dehydration. In total, 9 different pathways, including 16 elementary reactions, were studied, in which levoglucosan serves as a reactant. The properties of the reactants, transition states, intermediates, and products for every elementary reaction were obtained. It was found that 1-pentene-3,4-dione, acetaldehyde, 2,3-dihydroxypropanal, and propanedialdehyde can be formed from the CO bond breaking decomposition reactions. 1,2-Dihydroxyethene and hydroxyacetic acid vinyl ester can be formed from the CC bond breaking decomposition reactions. It was concluded that CO bond breaking is easier than CC bond breaking due to a lower activation energy and a higher released energy. During the 6 levoglucosan dehydration pathways, one water molecule which composed of a hydrogen atom from C3 and a hydroxyl group from C2 is the preferred pathway due to a lower activation energy and higher product stability. © 2012 Elsevier B.V. All rights reserved.

Kinetics study on thermal dissociation of levoglucosan during cellulose pyrolysis

(Chemical Equation Presented) The mechanisms and kinetics studies of the levoglucosan (LG) primary decomposition during cellulose pyrolysis have been carried out theoretically in this paper. Three decomposition mechanisms (C-O bond scission, C-C bond scission, and LG dehydration) including nine pathways and 16 elementary reactions were studied at the B3LYP/6-31 + G(D,P) level based on quantum mechanics. The variational transi-tion- state rate constants for every elementary reaction and every pathway were calculated within 298-1550 K. The first-order Arrhenius expressions for these 16 elementary reactions and nine pathways were suggested. It was concluded that computational method using transition state theory (TST) without tunneling correction gives good description for LG decomposition by comparing with the experimental result. With the temperature range of 667-1327 K, one dehydration pathway, with one water molecule composed of a hydrogen atom from C3 and a hydroxyl group from C2, is a preferred LG decomposition pathway by fitting well with the experimental results. The calculated Arrhenius plot of C-O bond scission mechanism is better agreed with the experimental Arrhenius plot than that of C-C bond scission. This C-O bond scission mechanism starts with breaking of C1-O5 and C6-O1 bonds with formation of CO molecule (C1-O1) simultaneously. C-C bond scission mechanism is the highest energetic barrier pathway for LG decomposition. © 2013 Elsevier Ltd. All rights reserved.

Water structure and chaotropicity: their uses, abuses and biological implications

The concept of "water structure" has been invoked to explain all manner of aqueous phenomena. Here we look at the origins of this tendency to understand solute hydration in terms of structural changes in bulk water, and consider the validity of one particular example: the classification of small solutes as chaotropic or kosmotropic, and the putative relation of this terminology to notions of structure-making and structure-breaking in the solvent. We doubt whether complex phenomena such as Hofmeister and osmolyte effects on macromolecules can be understood simply on the basis of a change in solvent structure. Rather, we argue that chaotropicity, if understood in the original sense, arises from the activities that solutes exert on macromolecular systems, as well as from deviations of solvation water from bulk-like behaviour. If applied judiciously, chaotropicity remains a potent, biologically pertinent parameter useful for classifying and understanding solution phenomena in all types of living system.

Oltre il "Momento dell'Abolizione":Saggio in memoria di Louk Hulsman

This article is written to celebrate the fine contribution and constant optimism of Louk Hulsman to the debate about penal abolition, the rethinking of popular and political discourses on ‘crime’, and the institutionalised responses of the ‘criminal justice system’. Reflecting on his experiences of incarceration and on his critical analysis of the political economic relations of power, Louk Hulsman talked of the defining ‘moment of abolition’ – his reading of Thomas Mathiesen’s ground-breaking text, The Politics of Abolition. Having considered the key elements of Louk Hulsman’s work and its critical challenge to the criminological enterprise, the article explores the apparent political contradiction in campaigning for humane conditions while seeking abolition within the context of an ever-expanding, global prison-industrial complex.

The Characteristics of Wave Impacts on an Oscillating Wave Surge Converter

Wave impacts on an Oscillating Wave Surge Converter are examined using experimental and numerical methods. The mechanics of the impact event are identified experimentally with the use of images recorded with a high speed camera. It is shown that it is the device which impacts the wave rather than a breaking wave impacting the device. Numerical simulations using two different approaches are used to further understand the issue. Good agreement is shown between numerical simulations and experimental measurements at 25th scale.

CO oxidation on Pt(111):An ab initio density functional theory study

CO oxidation on Pt(111) is studied with ab initio density functional theory. The low energy pathway and transition state for the reaction are identified. The key event is the breaking of an O-metal bond prior to the formation of a chemisorbed CO2 molecule. The pathway can be rationalized in terms of competition of the O and C atoms for bonding with the underlying surface, and the predominant energetic barrier is the strength of the O-metal bond.

The first major step in the peace process’? Exploring the impact of the Anglo-Irish Agreement on Irish republican thinking

This article supports interpretations of the Anglo-Irish Agreement of 1985 as a significant factor contributing towards the development of the Northern Ireland peace process. However, it also emphasises a certain serendipity in the Agreement’s effect on northern nationalist, and more specifically republican, politics in the region. In particular, it stresses that a specific interpretation of the Agreement promoted by the SDLP inspired a dialogue with republicanism, encouraging an ongoing re-appraisal within the latter about the nature of Britain’s role in Northern Ireland. This, the article argues, reinforced the movement towards a more political approach that republicans had begun in the 1980s, and encouraged their eventual embrace of a constitutional strategy in the 1990s. However, in advancing this argument, the article notes that such an outcome was far from the minds of the British and Irish officials who negotiated the Anglo-Irish Agreement. The Agreement was intended to marginalise rather than accommodate republicans. Despite this, it provided an inadvertent incentive to draw militant republicanism into the democratic process in Northern Ireland.

The Application of Digital Photogrammetric Techniques and Aerial Photography to the Preservation of Archaeological Detail. Case Study: The Copney Stone Circle Complex, Co. Tyrone, N. Ireland

The Copney Stone Circle Complex, Co. Tyrone, N. Ireland, is an important Bronze Age site forming part of the Mid-Ulster Stone Circle Complex. The Environment Service: Historic Monuments and Buildings (ESHMB) initiated a program of bog-clearance in August 1994 to excavate the stone circles. This work was completed by October 1994 and the excavated site was surveyed in August 1995. Almost immediately, the rate at which the stones forming the circles were breaking down was noted and a program of study initiated to make recommendations upon the conservation of this important site. Digital photogrammetric techniques were applied to aerial images of the stone circles and digital terrain models created from the images at a range of scales. These provide base data sets for comparison with identical surveys to be completed in successive years and will allow the rate of deterioration, and the areas most affected, of the circles to be determined. In addition, a 2D analysis of the stones provides an accurate analysis of the absolute 2D dimensions of the stones for rapid desktop computer analysis by researchers remote from the digital photogrammetric workstation used in the survey.

The products of this work are readily incorporated into web sites, educational packages and databases. The technique provides a rapid and user friendly method of presentation of a large body of information and measurements, and a reliable method of storage of the information from Copney should it become necessary to re-cover the site.

Reviewing the Literature on the Breakdown of Foster Care Placements for Young People: Complexity and the Social Work Task

Young people in long-term foster care are at risk of experiencing poor social, emotional, behavioural and educational outcomes. Moreover, these placements have a significantly greater chance of breaking down compared to those involving children. This article critically evaluates the factors associated with this particular outcome. It was carried out through a literature review conducted by a social work practitioner in one Health and Social Care Trust in Northern Ireland. The findings evidenced that, apart from overriding safety concerns, placement breakdown was not a one-off event but rather a complex process involving the interplay between a range of dynamic risk and protective factors over time, operating in the wider context of the young person’s history and life experiences. The significance of these findings for social work practitioners is finally considered by identifying key theories to inform understanding and intervention.

Processability, structural evolution and properties of melt processed biaxially stretched HDPE/MWCNT nanocomposites

Biaxial stretching of melt mixed high density polyethylene (HDPE)/multiwalled carbon nanotube (MWCNT) nanocomposites was conducted in the melt state at different stretching ratios (SRs). The addition of MWCNTs leads to significant strain hardening in the HDPE, greatly improving the stability and thus processability of the stretching process. Scanning electron microscopy shows that the MWCNTs in the polymer matrix are gradually disentangled and randomly oriented in the stretching plane with increasing SRs. All the stretched samples exhibit an increase in crystallinity (about 10%) due to strain induced crystallization and a broadened distribution of crystallite size according to the XRD and DSC results. The mechanical properties of the composites improve with increasing SRs, while they drop off after a SR of 2.5 for the neat HDPE which is likely to be due to the relaxation of polymer chains prior to solidification. The presence of the MWCNTs appears to inhibit this relaxation thus helping to maintain the orientation and mechanical properties at high SRs. The modulus, yield strength and breaking strength of stretched composites with 8 wt% MWCNTs increase by approximately 54%, 85% and 193% respectively compared with the neat HDPE at a SR of 3. The electrical percolation threshold for the unstretched material occurs at 1.9 wt% MWCNTs. As SR increases, the values of critical concentration increase from 1.9 wt% to 4.9 wt% implying the destruction of conductive networks due to an increased inter-particle distance. A loading of 6 wt% MWCNTs is sufficient to ensure that the sheet conductivity is robust to changes in the SR. Decreased values of critical exponent from 1.9 to 1.1 and morphological investigation reveal a transformation of the system structure from three dimensional to two dimensional as SR increases.

Structure, mechanical, and electrical properties of high-density polyethylene/multi-walled carbon nanotube composites processed by compression molding and blown film extrusion

The structure and properties of melt mixed high-density polyethylene/multi-walled carbon nanotube (HDPE/MWCNT) composites processed by compression molding and blown film extrusion were investigated to assess the influence of processing route on properties. The addition of MWCNTs leads to a more elastic response during deformations that result in a more uniform thick-ness distribution in the blown films. Blown film composites exhibit better mechanical properties due to the enhanced orientation and disentanglement of MWCNTs. At a blow up ratio (BUR) of 3 the breaking strength and elongation in the machine direction of the film with 4 wt % MWCNTs are 239% and 1054% higher than those of compression molded (CM) samples. Resistivity of the composite films increases significantly with increasing BURs due to the destruction of conductive pathways. These pathways can be recovered partially using an appropriate annealing process. At 8 wt % MWCNTs, there is a sufficient density of nanotubes to maintain a robust network even at high BURs.

Understanding the Interaction between Low-Energy Electrons and DNA Nucleotides in Aqueous Solution

Reactions that can damage DNA have been simulated using a combination of molecular dynamics and density functional theory. In particular, the damage caused by the attachment of a low energy electron to the nucleobase. Simulations of anionic single nucleotides of DNA in an aqueous environment that was modeled explicitly have been performed. This has allowed us to examine the role played by the water molecules that surround the DNA in radiation damage mechanisms. Our simulations show that hydrogen bonding and protonation of the nucleotide by the water can have a significant effect on the barriers to strand breaking reactions. Furthermore, these effects are not the same for all four of the bases.

Method for separating emulsions.

A method for breaking an emulsion of an ionic liq. which is a salt that is in the liq. state at a temp. below 1500°, and an oil, comprising the steps of (a) irradiating the emulsion with microwave radiation; (b) sepg. the emulsion into an ionic liq. phase and an oil phase; and (c) recovering at least one of the phases. The microwave radiation may occur in the presence of an addnl. heating source, an electrostatic field, an acoustic field, or a combination thereof. [on SciFinder(R)]