The influence of atmospheric conditions on the leakage current of ceramic insulators on the Colombian Caribbean coast

The contamination of electrical insulators is one of the major contributors to the risk of operation outages in electrical substations, especially in coastal zones with high salinity levels and atmospheric pollution. By using the measurement of leakage-currents, which is one of the main indicators of contamination in insulators, this work seeks to the determine the correlation with climatic variables, such as ambient temperature, relative humidity, solar irradiance, atmospheric pressure, and wind speed and direction. The results obtained provide an input to the behaviour of the leakage current under atmospheric conditions that are particular to the Caribbean coast of Colombia. Spearman’s rank correlation coefficients and principal component analysis are utilised to determine the significant relationships among the different variables under consideration. The necessary information for the study was obtained via historical databases of both atmospheric variables and the leakage current measured in over a period of one year in a 220-kV potential transformer insulator. We identified the influencing factors of temperature, humidity, radiation, wind speed and direction on the magnitude of the leakage current as the most relevant.

Analysis of ancient pottery and ceramic objects using X-ray fluorescence spectrometry

Archaeology has been called 'the science of the artefact' and nothing demonstrates this point better than the current interest displayed in provenance studies of archaeological objects. In theory, every vessel carries a chemical compositional pattern or 'fingerprint' identical with the clay from which it was made and this relationship is basic to provenance studies. The reasoning behind provenance or sourcing studies is to probe into this past and attempt to re-create prehistory by obtaining information on exchange and social interaction. This paper discusses the use of XRF spectrometry for the analysis of ancient pottery and ceramics to examine whether it is possible to predict prehictoric cultural exchanges.

Nanoscale texture on glass and titanium substrates by physical vapor deposition process

The aim of the paper is to give a feasibility study on the material deposition of Nanoscale textured morphology of titanium and titanium oxide layers on titanium and glass substrates. As a recent development in nanoscale deposition, Physical Vapor Deposition (PVD) based DC magnetron sputtering has been the choice for the deposition process. The nanoscale morphology and surface roughness of the samples have been characterized using Atomic Force Microscope (AFM). The surface roughnesses obtained from AFM have been compared using surface profiler. From the results we can say that the roughness values are dependent on the surface roughness of the substrate. The glass substrate was relatively smoother than the titanium plate and hence lower layer roughness was obtained. From AFM a unique nano-pattern of a boomerang shaped titanium oxide layer on glass substrate have been obtained. The boomerang shaped nano-scale pattern was found to be smaller when the layer was deposited at higher sputtering power. This indicated that the morphology of the deposited titanium oxide layer has been influenced by the sputtering power.

Response of laminated glass panels to near field blast events

This thesis develops and applies an analytical method to treat the blast response of glass façades and studies the influence of controlling parameters such as all component materials and geometric properties, support conditions and energy absorption, and hence establishes a framework for their design for a credible blast event.

Influence of interlayer properties on the blast performance of laminated glass panels

This paper investigates the influence of interlayer properties on the blast performance of laminated glass (LG) panels. A parametric study is carried out by varying the thickness and Young’s modulus (E) of the interlayer under two different blast loads. Results indicate the existence of a critical interlayer thickness (or E) that causes the onset of interlayer failure. This should be achieved in the design to enhance energy absorption, reduce support reactions and initiate a safer failure mode. Present findings provide information to achieve such design targets and enable safe and efficient performance of LGs under credible blast loads.

Influence of structural sealant joints on the blast performance of laminated glass panels

This paper investigates the influence of structural sealant joints on the blast performance of laminated glass (LG) panels, using a comprehensive numerical procedure. A parametric study was carried out by varying the width, thickness and the Young’s modulus (E) of the structural silicone sealant joints and the behavior of the LG panel was studied under two different blast loads. Results show that these parameters influence the blast response of LG panels, especially under the higher blast load. Sealant joints that are thicker, have smaller widths and lower E values increase the flexibility at the supports and hence increase the energy absorption of the LG panel while reducing the support reactions. Results also confirmed that sealant joints designed according to current standards perform well under blast loads. Modeling techniques presented in this paper could be used to complement and supplement the guidance in existing design standards. The new information generated in this paper will contribute towards safer and more economical designs of entire facade systems including window glazing, frames and supporting structures.

Tribological properties of γ-Y2Si2O7 ceramic against AISI 52100 steel and Si3N4 ceramic counterparts

Reciprocating ball-on-flat dry sliding friction and wear experiments have been conducted on singlephase γ-Y2Si2O7 ceramic flats in contact with AISI 52100 bearing steel and Si3N4 ceramic balls at 5-15N normal loads in an ambient environment. The kinetic friction coefficients of γ-Y2Si2O7 varied in the range over 0.53-0.63 against AISI 52100 steel and between 0.51-0.56 against Si3N4 ceramic. We found thatwear occurred predominantly during the running-in period and it almost ceased at the steady friction stage. The wear rates of γ-Y2Si2O7 were in the order of 10-4mm3/(N m). Besides, wear debris strongly influenced the friction and wear processes. The strong chemical affinity between γ-Y2Si2O7 and AISI 52100 balls led to a thick transfer layer formed on both contact surfaces of the flat and counterpart ball, which changed the direct sliding between the ball and the flat into a shearing within the transfer layer. For the γ-Y2Si2O7/Si3N4 pair, a thin silica hydrate lubricant tribofilm presented above the compressed debris entrapped in the worn track and contact ball surface. This transfer layer and the tribofilm separated the sliding couple from direct contact and contributed to the low friction coefficient and wear rate.

γ-Y2Si2O7, a machinable silicate ceramic: Mechanical properties and machinability

In this paper, the mechanical properties of bulk single-phase γ-Y2Si2O7 ceramic are reported. γ-Y2Si2O7 exhibits low shear modulus, excellent damage tolerance, and thus has a good machinability ready for metal working tools. To understand the underlying mechanism of machinability, drilling test, Hertzian contact test, and density functional theory (DFT) calculation are employed. Hertzian contact test demonstrates that γ-Y2Si2O7 is a "quasi-plastic" ceramic and the intrinsically weak interfaces contribute to its machinability. Crystal structure characteristics and DFT calculations of γ-Y2Si2O7 suggest that some weakly bonded planes, which involve Y-O bonds that can be easily broken, are the sources of the low shear deformation resistance and good machinability.

Edge of Danger: electric light and the negotiation of public and private domestic space in Philip Johnson's Glass and Guest House

In the first half of the twentieth century the dematerializing of boundaries between enclosure and exposure problematized traditional expectations of the domestic environment. At the same time, as a space of escalating technological control, the modern domestic interior also offered new potential to redefine the meaning and means of habitation. The inherent tension between these opposing forces is particularly evident in the introduction of new electric lighting technology and applications into the modern domestic interior in the mid-twentieth century. Addressing this nexus of technology and domestic psychology, this article examines the critical role of electric lighting in regulating and framing both the public and private occupation of Philip Johnson's New Canaan estate. Exploring the dialectically paired transparent Glass House and opaque Guest House, this study illustrates how Johnson employed electric light to negotiate the visual environment of the estate as well as to help sustain a highly aestheticized domestic lifestyle. Contextualized within the existing literature, this analysis provides a more nuanced understanding of the New Canaan estate as an expression of Johnson's interests as a designer as well as a subversion of traditional suburban conventions.

Illuminating the glass box: The lighting designs of Richard Kelly

A promotional brochure celebrating the completion of the Seagram Building in spring 1957 features on its cover intense portraits of seven men bisected by a single line of bold text that asks, “Who are these Men?” The answer appears on the next page: “They Dreamed of a Tower of Light” (Figures 1, 2). Each photograph is reproduced with the respective man’s name and project credit: architects, Mies van der Rohe and Philip Johnson; associate architect, Eli Jacques Kahn; electrical contractor, Harry F. Fischbach; lighting consultant, Richard Kelly; and electrical engineer, Clifton E. Smith. To the right, a rendering of the new Seagram Tower anchors the composition, standing luminous against a star-speckled night sky; its glass walls and bronze mullions are transformed into a gossamer skin that reveals the tower’s structural skeleton. Lightolier, the contract lighting manufacturer, produced the brochure to promote its role in the lighting of the Seagram Building, but Lightolier’s promotional copy was not far from the truth.

The Edge of Danger: artificial lighting and the dialectics of domestic occupation in Philip Johnson's Glass and Guest Houses

In the first half of the twentieth century the dematerializing of boundaries between enclosure and exposure problematized traditional acts of “occupation” and understandings of the domestic environment. As a space of escalating technological control, the modern domestic interior offered new potential to re-define the meaning and means of habitation. This shift is clearly expressed in the transformation of electric lighting technology and applications for the modern interior in the mid-twentieth century. Addressing these issues, this paper examines the critical role of electric lighting in regulating and framing both the public and private occupation of Philip Johnson’s New Canaan estate. Exploring the dialectically paired transparent Glass House and opaque Guest House (both 1949), this study illustrates how Johnson employed artificial light to control the visual environment of the estate as well as to aestheticize the performance of domestic space. Looking closely at the use of artificial light to create emotive effects as well as to intensify the experience of occupation, this revisiting of the iconic Glass House and lesser-known Guest House provides a more complex understanding of Johnson’s work and the means with which he inhabited his own architecture. Calling attention to the importance of Johnson serving as both architect and client, and his particular interest in exploring the new potential of architectural lighting in this period, this paper investigates Johnson’s use of electric light to support architectural narratives, maintain visual order and control, and to suit the nuanced desires of domestic occupation.