383 resultados para mould


Relevância:

10.00% 10.00%

Publicador:

Resumo:

The Crowned Harp provides a detailed analysis of policing in Northern Ireland. Tracing its history from 1922, Ellison and Smyth portray the Royal Ulster Constabulary (RUC) as an organisation burdened by its past as a colonial police force. They analyse its perceived close relationship with unionism and why, for many nationalists, the RUC embodied the problem of the legitimacy of Northern Ireland, arguing that decisions made on the organisation, composition and ideology of policing in the early years of the state had consequences which went beyond the everyday practice of policing.

The authors provide an extended discussion of policing after the outbreak of civil unrest in 1969, ask why policing was cast in a paramilitary mould, and look at the use of special constabularies and the way in which the police dealt with social unrest which threatened to break down sectarian divisions. Examining the reorganisations of the RUC in the 1970s and 1980s, Ellison and Smyth focus on the various structural, legal and ideological components, the professionalisation of the force and the development of a coherent, if contradictory, ideology. The analysis of the RUC during this period sheds light on the problematic nature of using the police as a counter insurgency force in a divided society. Perceptions of the police, and the opinions of rank and file members are examined and an assessment is made of the various alternative models of policing, such as community policing and local control. This book offers important lessons about the nature of policing in divided societies.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A study undertaken at the University of Liverpool has investigated the potential for using construction and demolition waste (C&DW) derived aggregate in the manufacture of a range of precast concrete products, i.e. building and paving blocks and pavement flags. Phase III, which is reported here, investigated
concrete pavement flags. This was subsequent to studies on building and paving blocks. Recycled demolition aggregate can be used to replace newly quarried limestone aggregate, usually used in coarse (6 mm) and fine (4 mm-to-dust) gradings. The first objective was, as was the case with concrete building
and paving blocks, to replicate the process used by industry in fabricating concrete pavement flags in the laboratory. The ‘‘wet’’ casting technique used by industry for making concrete flags requires a very workable mix so that the concrete flows into the mould before it is compressed. Compression squeezes out water from the top as well as the bottom of the mould. This industrial casting procedure was successfully replicated in the laboratory by using an appropriately modified cube crushing machine and a special mould typical of what is used by industry. The mould could be filled outside of the cube crushing machine and then rolled onto a steel frame and into the machine for it to be compressed. The texture and mechanical properties of the laboratory concrete flags were found to be similar to the factory ones. The experimental work involved two main series of tests, i.e. concrete flags made with concrete- and
masonry-derived aggregate. Investigation of flexural strength was required for concrete paving flags. This is different from building blocks and paving blocks which required compressive and tensile splitting strength respectively. Upper levels of replacement with recycled demolition aggregate were determined
that produced similar flexural strength to paving flags made with newly quarried aggregates, without requiring an increase in the cement content. With up to 60% of the coarse or 40% of the fine fractions replaced with concrete-derived aggregates, the target mean flexural strength of 5.0 N/mm2 was still
achieved at the age of 28 days. There was similar detrimental effect by incorporating the fine masonry-derived aggregate. A replacement level of 70% for coarse was found to be satisfactory and also conservative. However, the fine fraction replacement could only be up to 30% and even reduced to 15% when used for mixes where 60% of the coarse fraction was also masonry-derived aggregate.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Pre-consolidated carbon fibre-reinforced polyphenylene sulphide (CF/PPS) laminates were
thermoformed into V-shaped parts via designed out of autoclave thermoforming experiments.
The different processing conditions tested in the experiment have resulted in final
part angles whose differences ranged from 2.087 to 3.431 from the original mould angle.
The test results show that processing conditions influenced finished part dimensions as the
final sample angles were found to decrease relative to the tooling dimensions, as mould
temperature increases. Higher mould temperature conditions produce thinner parts due
to the thermal expansion of mould tools. The mould temperature of 170C, which can
produce parts with high degree of crystallinity as well as small size of crystal, has been
established as the optimal thermoforming condition for CF/PPS composites.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

We present 65 optical spectra of the Type Ia supernova SN 2012fr, of which 33 were obtained before maximum light. At early times SN 2012fr shows clear evidence of a high-velocity feature (HVF) in the Si II 6355 line which can be cleanly decoupled from the lower velocity "photospheric" component. This Si II 6355 HVF fades by phase -5; subsequently, the photospheric component exhibits a very narrow velocity width and remains at a nearly constant velocity of v~12,000 km/s until at least 5 weeks after maximum brightness. The Ca II infrared (IR) triplet exhibits similar evidence for both a photospheric component at v~12,000 km/s with narrow line width and long velocity plateau, as well as a high-velocity component beginning at v~31,000 km/s two weeks before maximum. SN 2012fr resides on the border between the "shallow silicon" and "core-normal" subclasses in the Branch et al. (2009) classification scheme, and on the border between normal and "high-velocity" SNe Ia in the Wang et al. (2009a) system. Though it is a clear member of the "low velocity gradient" (LVG; Benetii et al., 2005) group of SNe Ia and exhibits a very slow light-curve decline, it shows key dissimilarities with the overluminous SN 1991T or SN 1999aa subclasses of SNe Ia. SN 2012fr represents a well-observed SN Ia at the luminous end of the normal SN Ia distribution, and a key transitional event between nominal spectroscopic subclasses of SNe Ia.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This paper reports the findings from internal mould cooling trials using a water spray configuration applied at various internal mould air temperatures from 120°C to 180°C for an aluminium mould. To achieve maximum benefit in terms of cycle time reduction, internal mould water cooling was used in conjunction with a combination of external forced air and water cooling. Savings in cooling times of up to 30% were achieved compared to conventional external only forced air cooling.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The aim of this work has been to adapt and apply the advantages of rapid prototyping and electroforming technologies to try to achieve an innovative mould design for rotational moulding. The new innovative design integrates an electroformed shell, manufactured starting from a rapid prototyping mandrel, with different designed standard aluminium tools. The shell holder enables mould assembly with high precision manufacture of a shell in a few minutes. The overall mould cost is significantly decreased because it is only necessary to manufacture one or two shells each time; however, the rest of the elements of the mould are standard and usable for an infinite number of shells, depending on size.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Polymer extrusion, in which a polymer is melted and conveyed to a mould or die, forms the basis of most polymer processing techniques. Extruders frequently run at non-optimised conditions and can account for 15–20% of overall process energy losses. In times of increasing energy efficiency such losses are a major concern for the industry. Product quality, which depends on the homogeneity and stability of the melt flow which in turn depends on melt temperature and screw speed, is also an issue of concern of processors. Gear pumps can be used to improve the stability of the production line, but the cost is usually high. Likewise it is possible to introduce energy meters but they also add to the capital cost of the machine. Advanced control incorporating soft sensing capabilities offers opportunities to this industry to improve both quality and energy efficiency. Due to strong correlations between the critical variables, such as the melt temperature and melt pressure, traditional decentralized PID (Proportional–Integral–Derivative) control is incapable of handling such processes if stricter product specifications are imposed or the material is changed from one batch to another. In this paper, new real-time energy monitoring methods have been introduced without the need to install power meters or develop data-driven models. The effects of process settings on energy efficiency and melt quality are then studied based on developed monitoring methods. Process variables include barrel heating temperature, water cooling temperature, and screw speed. Finally, a fuzzy logic controller is developed for a single screw extruder to achieve high melt quality. The resultant performance of the developed controller has shown it to be a satisfactory alternative to the expensive gear pump. Energy efficiency of the extruder can further be achieved by optimising the temperature settings. Experimental results from open-loop control and fuzzy control on a Killion 25 mm single screw extruder are presented to confirm the efficacy of the proposed approach.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The injection stretch blow moulding process involves the inflation and stretching of a hot preform into a mould to form bottles. A critical process variable and an essential input for process simulations is the rate of pressure increase within the preform during forming, which is regulated by an air flow restrictor valve. The paper describes a set of experiments for measuring the air flow rate within an industrial ISBM machine and the subsequent modelling of it with the FEA package ABAQUS. Two rigid containers were inserted into a Sidel SBO1 blow moulding machine and subjected to different supply pressures and air flow restrictor settings. The pressure and air temperature were recorded for each experiment enabling the mass flow rate of air to be determined along with an important machine characteristic known as the ‘dead volume’. The experimental setup was simulated within the commercial FEA package ABAQUS/Explicit using a combination of structural, fluid and fluid link elements that idealize the air flowing through an orifice behaving as an ideal gas under isothermal conditions. Results between experiment and simulation are compared and show a good correlation.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Aesthetics of concrete structures is directly related to the quality of their surface finish. The objective of this investigation was to examine the effect of rheological properties of cement-based mortars on the quality of their surface finish. The study was divided into two phases. Firstly, the influence of the mix composition of mortars, viz. the water to cement (w/c) ratio, the sand content and the superplasticiser (SP) dosage on their rheology was evaluated. Secondly, the surface finish quality was characterised and related to the rheology of the studied systems. Rheology of these materials, i.e. the yield value, was measured using a vane viscometer. The quality of the surface finish was assessed by quantification of the surface air voids by analysing digital photographs of the mould finished sample surfaces. It was found that an increase in the w/c ratio and the SP content decreased the yield value, whilst the increase in the sand content had an opposite effect. When the surface quality is concerned, an increase in the yield value was found to increase the total content of the surface air voids and especially those with size smaller than 1 mm in diameter. Moreover, the analysis of the location of the surface air voids along the height of the sample revealed that with the increase in the yield value their concentration was higher in the bottom section of the analysed samples.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Objectives: To quantify variability in hand proportioning of zinc phosphate cement among a cohort of dental undergraduates and to determine the effect of any such variability on the diametral tensile strength (DTS) of the set cement. The null hypothesis was that such variability has no effect on DTS. 
Methods: Thirty-four operators dispensed a zinc phosphate cement [Fleck's® Cement] according to the manufacturers' instructions. The mass of powder and liquid dispensed was recorded. Cylindrical specimens (n = 2 x 34) of dimensions 6mm x 3mm were prepared using a stainless steel split mould. The maximum mass of powder and the minimum volume of liquid were used as one extreme ratio and the minimum mass of powder and the maximum volume of liquid used on the other extreme. The manufacturers' recommended ratio was also tested (n=34).The samples were left to set for one hour before being transferred into distilled water for 48 hours. Compression across a diameter was carried out using a universal testing machine, H10KS [Tinius Olsen], at a constant crosshead speed of 0.75 ±0.25 mm/min. Statistical analyses (α = 0.05) were by Student's t-test for the powder/liquid ratio and one-way ANOVA and Tukey HSD for for pair-wise comparisons of mean DTS. Tests were carried out for normality and constant variability. 
Results: The mean (range) amount of powder dispensed was 0.863g (0.531-1.216)g. The mean (range) amount of liquid dispensed was 0.341ml (0.265-0.394)ml. The manufacturer's recommended amounts were 0.8g of powder and 0.3ml of liquid. The mean powder/liquid ratio was not significantly different from the manufacturer's recommended value (p=0.64). Mean (SD) DTS were (MPa) max: 7.19(1.50), min: 2.65(1.01), manufacturer: 6.01(1.30). All pair-wise comparisons were significantly different (p<0.001). 
Conclusions: Variability exists in the hand proportioning powder and liquid components of zinc phosphate cement. This variability can affect the DTS of zinc phosphate cement.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This article argues that the expansion of individual employment rights is presenting a series of challenges to the collective model of economic citizenship that prevailed in most of the Anglo-American world during the last century. We examine developments in the management of workplace conflict in Anglo-American countries to highlight the institutional manoeuvrings that have been taking place to mould the nature of national regimes of employment rights. We argue that Governments almost everywhere are actively seeking to create institutional regimes that weaken the impact of employment legislation and we find that statutory dispute resolution agencies are eagerly trying to develop organizational identities that are aligned with rights-based employment disputes.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The interaction between the face coat material of a mould and the titanium alloy will cause oxygen penetration during the casting and solidification process, resulting in the formation of an α-case interaction layer at the metal surface that influences the mechanical properties of the cast components. In this study, the influence of α-case thickness and loading positions in a Ti–6Al–4V (Ti64) alloy on metal hardness, impact properties and bending strength was investigated. The results showed that the metal surface α-case consisted of many coarse α laths which has a higher hardness than metal matrix. The mechanical properties of the alloy are influenced by the α-case. The alloy bending strength was observed to have changed linearly with the thickness of sample.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Esta tese tem como objectivo comparar aspectos da recepção da literatura britânica durante o Estado Novo em Portugal, e na Hungria durante a era comunista. Na primeira parte da dissertação fica contextualizada e analisada a alteração da posição da literatura britânica nos dois países, enquanto na segunda parte se comparam facetas da recepção da mesma, contrastando as traduções literárias publicadas em Portugal e na Hungria entre 1949 e 1974, altura em que ambos os países foram dirigidos simultaneamente por regimes autocratas. Este estudo faz-se, em parte, através da comparação de manuais escolares e seletas, a fim de examinar os diferentes métodos usados pelos dois regimes ditatoriais politicamente opostos na tentativa de moldarem os seus leitores. É dada especial atenção à literatura proibida e aos motivos para as atitudes restritivas diferenciadas em relação a certos escritores na era de Salazar e na Hungria durante o período de Bloco de Leste. A tese conclui que a abordagem divergente em relação às obras literárias britânicas, bem como à literatura em geral, é principalmente enraizada na ideologia de governação diametralmente oposta dos dois regimes ditatoriais. A crença idealista no poder educativo da literatura em estabelecer o socialismo na Hungria está em nítido contraste com a política de cultura obscurantista do Estado Novo. Mesmo quando o apoio à literatura britânica não era uma das principais prioridades da esfera cultural húngara, parece evidente que a literatura canónica britânica teve uma recepção mais favorável na Hungria comunista do que no Estado Novo.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

An in situ experiment on a full-scale timber frame test building was carried out to study the hygrothermal performance of wood-hemp composite insulation in timber frame wall panels with and without a vapour barrier. The heat transfer properties and the likelihood of mould growth and condensation in the panels were compared. Step changes in the internal relative humidity were performed to explore the effects of high, normal and low internal moisture loads on the wall panels. No significant difference in the average equivalent thermal transmittance (U-values) between the panels with and without a vapour barrier was observed. The average equivalent U-values of the panels were close to the U-values calculated from the manufacturers’ declared thermal conductivity values of the insulation. The likelihood of condensation was higher at the interface of the wood-hemp insulation and the oriented strand board (OSB) in the panel without a vapour barrier. In terms of the parametric assessment of the mould germination potential, the relative humidity, the temperature and the exposure conditions in the insulation-OSB interfaces of the panel without a vapour barrier were found to be more favourable to the germination of mould spores. Nonetheless, when the insulations were dismantled, no mould was visually detected.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

When developmental vernacular practice is telescoped into industrial activity, the role played by construction workers in the honing of a craft is rapidly bypassed. An almost political act is required to maintain the contribution that the hand makes to the uniformity of result that is demanded by the standard classification of typologies of building and technique. Research into fabric formwork techniques conducted by Alan Chandler utilises the flexibility of the concrete mould to explore the meaning of the making ‘process’ and the workers’ role in relation to the formal ‘result’. Chandler’s ‘Wall One’ exemplifies the exploratory prototype and its potential for variety and the trace of the hand in making. The shift to a mass production typology involved in realising the 325,000 square-metre Heatherwick studio project in Shanghai, presented the problem of how to orchestrate the fabric into a fully industrialised process. Part of the research then became how to make the shift from play to profit - and can anything of craft survive the transition into the international development marketplace? Through managing the inherent variety available to the fabric itself, a fabric based formwork solution for realising a building at the scale of a landscape offered the Chinese form work maker the opportunity to be present within the results of a fully industrialised process – a ghost in the machine.