GLASS and PERCEPTION

Post 170 ⇒   by Gautam Shah 

Glass has been used in Doors and Windows as translucent to transparent glazing pane, and occasionally as gloss but an opaque panel. Glass has had TWO different facets, of the day timelit from the front or outside, and that of the night time –lit from the back or inside. Both of these facets, daytime and night time are viewed from either of the sides and offer different experience.

DAY TIME VIEW -from outside, in early days had a greyish -metallic surface. It was a dull and muddy pane with wavy figures (due to flattening of a disc cut out of a bulb). In later periods, it had lesser impurities, fewer surface undulations, but was ground to a glossy finish. Modern glass is comparatively very glossy (unless specifically ordered or treated), which allows reflection of the surroundings and the sky. The reflectivity, with additional treatment, often excludes the interior view (mirror glass and photo framing glass). Polyester films and surface metallizing adds one-way opacity, permitting unhindered view from the other side.

DAY TIME VIEW -from inside, the glass of early days, and its later day modern version have had issues of colour coordination with other surface finishes. Both types of glass had a tinge that strongly affected the colours of the interiors. Fresco and other drawn art work could be re-calibrated, after fixing of the panes (or during re-installation later with superior glass). The ceramic or coloured stone mosaics of floors and walls, however, did not allow such corrections. Such interior colour schemes had to be pre-planned in consideration of the glass tinge. Colour coordination with window frames and members such as muntins, mullions, jambs, etc. with the metallic-grey tone of the glass was difficult.

Poor quality of glass was to an extent solved by colouring it. Pot glass had dark-colour presence that was effective when back lit very brilliantly usually after the sunset. Such intense interior illumination was not available in that age. The stained glass was comparatively light coloured but still filled the interior profusely. Later part of Gothic architecture saw the required sobering with use of grisaille painting technique, or use of the non stained cristallo glass.

Inside view of stained glass, St. Denis Cathedral, St. Denis, France, upper choir

Inside view of stained glass, St. Denis Cathedral, St. Denis, France, upper choir

In stained glass treatment the need to stretch the story board across many sections of the window was so strong that all framing and dividing members like muntins and cams were made slender, at least on the face side. These were also dissolved by colouring them with the same tone as the outlines in the picture.

Mosaics, Main nave of the Byzantine basilica of Sant’Apollinare Nuovo in Ravenna, Italy

Early modern-day architects had to overcome the fuzzy view through poor quality of glass. As a result small pieces of glass were used, and contrasted with the white painted mullions, muntins, jambs and rails. The typical US colonial window had subdivided glass panes which did not offer a clear or undistorted view, so were used for illumination, and covered with translucent curtains to occlude the view. Later, at the end part of Industrial revolution period as the glass became clearer, the mullions were thinned or made of metals, This dissolved their presence.

Typical US Colonial style White window house

White window architecture of US

NIGHT TIME VIEW –from outside was important to register the presence of the building. Visibility of the Churches and Cathedrals and Places at night provided an assurance of protection. The main problem was cost of illuminating the structures, whether from outside or inside. The presence of small interior light visible through a roof light, lantern window, rose window or pinnacle, was assuring. It was an economic and effective device. When windows of lighter stains and white glass became popular, it was easier to provide a visible illumination from inside.

Chrysler building USA at night

NIGHT TIME VIEW -from inside has been a problem in the absence of street or public illumination in the vicinity of buildings. The urbanisation now provides illumination to back lit the glass of the buildings. Historical monuments or modern buildings always have some background illumination. Some important buildings are specifically lit outside and from within the building to enhance the architectural quality.

450px-Campanile_Sternatia

. Campanile Sternatia Lit from Inside

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FILLERS and COMPOSITES

Post 169 ⇒   by Gautam Shah  →

Forms of Glass fiber used as Fillers

Fillers are inevitable constituents of composites. Fillers provide body, reinforcement, and impart special properties to the new material. Fillers have many forms, such as fine particulates, staple fibre (whiskers or short fibres), filaments (long or continuous fibres), unwoven (felt) and woven fabrics, knit textiles, aggregates, and sheets. Filler materials are natural (wood, plant, hair), minerals (asbestos, sand, stones, powders), and man-made (polymers, metals, ceramics) materials.

  • Straw, hair, coir, hemp, jute, papyrus, rice-husk etc., have been mixed with clay to form bricks. Sand, ash, and mineral dust were added to mud to reduce the plasticity for plaster work. Wood planks were glued together to form block board or plywood like construction in 15th C BC.
  • Man-made materials include: Fibreglass, quartz, Kevlar, Dyneema or carbon fibre, graphite, carbon-graphite, silicon carbide, titanium carbide, aluminium oxide, boron, coated boron, boron carbide, alumina, alumina-silica, niobium-titanium, niobium-tin, etc.

Fillers Particles (of 10 t0 250 μm in diameter) help block the movement of dislocations in the composites and provide distinctive strength properties. Staple fibres used as fillers have high length to a diameter ratio, and are generally in their random orientations, whereas filaments are used for high performance structural applications and are prearranged (for a particular structural use) before introduction of matrix, or in certain cases a fixing compound.

Depending on the load conditions, fibre arrangements for reinforcement are random, unidirectional (aligned in a single direction), or multi-directional (oriented in two or three directions). Continuous fibres are more efficient at resisting loads than are short ones, but it is more difficult to fabricate complex shapes from materials containing continuous fibres, than from short-fibre or particle-reinforced materials.

Insulator_railways

Ceramic-Metal composite -Electric Insulator

Particles (fillers) of one material are dispersed in another material (matrix) in many different ways. 1 -Particles are mixed in a liquid phase of the matrix, and allowed to harden to a solid phase, 2 -particles are allowed to grow in the matrix, or 3 -articles are pressed into the matrix and inter-diffusion is encouraged by mechanical working or other energy input.

Particulate fillers in ceramic matrices enhance characteristics such as electrical conductivity, thermal conductivity, thermal expansion, and hardness. Particles of Alumina, Silicon carbide and Boron nitride embedded in a polymer matrix and formed as abrading tools are used for grinding and polishing stone floors, tools etc. Carbon black (as powder) added to vulcanised rubber provides hardness and toughness for automobile tyres. The rubber is further reinforced with metal, rayon, polyester and other threads as continuous fibre filler.

Silver_mica_capacitors

High end Ceramic composites

  • High-performance ceramic composites are strengthened with filaments that are bundled into yarns. Each yarn, strand or tow may contain thousands of filaments, each of which with a diameter of approximately 10 micrometers (0.01 millimetres).

Often components are formed that are strong in all directions, by creating a three-dimensional lattice of filler component. The filler component itself could be a composite material.

Fillers affect the quality of a composite. Fillers are usually combined with ductile matrix materials, such as metals and polymers, to make them stiffer. Fillers are added to brittle-matrix materials like ceramics to increase toughness. The length-to diameter ratio of the fibre, the strength of the bond between the fibre and the matrix, and the amounts of fibre are variables that affect the mechanical properties. It is important to have a high length-to-diameter aspect ratio so that the applied load is effectively transferred from the matrix to the fibre.

A variety of reinforcements can be used, including particles, whiskers (very fine single crystals), discontinuous fibres (short), continuous fibres, and textiles preform (made by braiding, weaving, or knitting fibres together in specified designs).

  • Glass is the most common and inexpensive fibre and is usually use for the reinforcement of polymer matrices. Glass has a high tensile strength and fairly low density (2.5 g/cc).

  • Carbon-graphite: In advance composites, carbon fibres are the material of choice. Carbon is a very light element, with a density of about 2.3 g/cc and its stiffness is considerable higher than glass. Carbon fibres can have up to 3 times the stiffness of steel and up to 15 times the strength of construction steel. The graphitic structure is preferred to the diamond-like crystalline forms for making carbon fibre because the graphietic structure is made of densely packed hexagonal layers, stacked in a lamellar style. This structure results in mechanical and thermal properties are highly anisotropic and this gives component designers the ability to control the strength and stiffness of components by varying the orientation of the fibre.

  • Polymers: A variety of polymer materials are used as filler material for composites. The strong covalent bonds of polymers offer tailor-made properties in the form of bristles, whiskers, staple fibres, filaments, yarns or tows, spun yarns, threads, ropes, unwoven and woven fabrics, knitted compositions. Nylons, polyesters, rayon, acrylic, Kevlar and many other fibres are used for composite formation.

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  • Ceramics: Ceramic fibres made from materials such as Alumina and Silicon carbides are used in very high temperature applications, and also where environmental attacks are severe. Tungsten-boron filaments, Ceramics have poor properties in tension and shear, so most applications as reinforcement are in the particulate form.

 

  • Metallic fibres: Metallic fibres have high strengths but since their density is very high they are of little use in weight critical applications. Drawing very thin metallic fibres (less than 100 microns) is also very expensive.

 

Following are some of the earlier posts on related Topics

1   MATRIX and COMPOSITES

2   COMPOSITES Part – 1

Next week post in this series will be

INTERFACE OF MATRIX AND FILLER

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MATRIX of COMPOSITES

Post 168  ⇒  by Gautam Shah  →

The constituents of a composite are ordinarily classified as Matrix and Filler. It is the nature of relationship between the filler and matrix, or the Interface that defines the composite. Fillers serve to resist stresses, mainly tension, and the Matrix serves to resist the shear, and all materials present including any aggregates, serve to resist the compression.

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Matrix and Filler each are of three types: Metals, Ceramics and Polymers.

These three provide nine possible combinations.

Composite materials’ combinations: Possibilities of combinations and type-examples.

Matrix (m) + Filler(f) = Composite Type-Examples

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Metal matrix composites MMC

Metal (m)+ Metal (f) = Aluminium-Tin are non miscible metals, yet can be alloyed as a composite

Metal (m) + Ceramic (f) = Electrical semi conductors, Carbide cutting tool tips, Scissors, knives

Metal (m) + Polymer (f) = Not feasible, Metals become soft at very high temperature -unsuitable for polymer filler

Sandwiched metals

Ceramic matrix composites CMC

Ceramic (m) + Ceramic (f) = Carbon-carbon composites 

Ceramic (m) + Metal (f) = Metal sprayed optic glass fiber cables

Ceramic (m) + Polymer (f) = Not feasible, Ceramics require high temperature for formation -unsuitable for polymer filler

Brake lining

●  Polymer matrix composites PMC

Polymer (m) + Polymer (f) = Polyester or rayon fibre reinforced plastics

Polymer (m) + Metal (f) = Grinding and polishing abrasives

Polymer (m) + Ceramic (f) = Fibreglass, Fibre reinforced plastic FRP Asphalt roads, imitation granite, cultured marble sinks and counter tops

Wool fibre composite

MATRICES

A matrix is an environment or material within which an interface is desired. A matrix surrounds the Filler material while creating a bond with it. A matrix thus creates a network within which the filler components are supported by maintaining or reinforcing their intended positions. For a matrix to be affective, it must at some stage have a lower phase than the filler material. The lower phase may occur before or while the filler material is being formed or introduced. The matrix material may turn to a higher phase by evaporation of the solvent, removal of the heat or pressure, and polymerization or action of a catalyst. Polymer matrices are most common, followed by metals and ceramics. However, paper pulp, mud, wax, etc. are some matrix materials that do not fit into any of the above-mentioned categories. Ceramic matrix composites though difficult to form, show greatest promise in material sciences.

Wood Particles in Resin Matrix

  • Portland cement, Gypsum plaster, mud (clay), and Bitumens are widely used matrix materials. Polymer matrix materials are thermosetting resins such as polymers, poly-amides, epoxies, or thermoplastic resins such as polycarbonate or polysulphones. Typically a polymer matrix composite of Epoxy and carbon fibres is of two thirds the weight of aluminium, and two and a half times as stiff.
  • For metal matrices most commonly used metals are aluminium, titanium, magnesium, and copper. Composites with metal matrices generally have metal or ceramic as filler materials. Aluminium reinforced with fibres of the ceramic silicon carbide is a classic example of a metal matrix with ceramic filler. The composite material combines the strength and stiffness of a silicon carbide with the ductility of aluminium. Metal to metal composites consist of two immiscible metals (metals that do not form alloys), such as magnesium and titanium. Such metal-metal composites with bronze matrices have been in use since Bronze Age to create many useful materials.

 

Next article in the series -about FILLERS in COMPOSITES

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FENCES

Post 167  ⇒  by Gautam Shah  →

Swaziland_-_Traditional_homes

Twig Fence Swaziland

Fences are barriers to confine or exclude people or animals, to define boundaries, or to decorate. Fort walls and compound or estate walls are solid and heavy structures, but are not considered fences. Fences are lighter and of limited height. Fences are transparent to translucent to allow unrestricted flow of vision, water and air.

 

Fences are nominally erected over the ground but any physical obstruction, natural or man-made can function as fencing. So a ditch or dry or water filled moats can work as a fence. Fences of vegetation such as plants, hedges, climbers, cactus and dry thorny shrubs are used in farms and fields. Timber, earth, stones, and lattices, wires and nets of metals are widely used for fencing.

 

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Water filled Moat

In 19 C North America, many varieties of timber fencings were developed, such as the split rail laid zigzag, the post rail, and the picket. Other common fences are chain-link fence, hurricane fences, and white picket fences. In comparatively low rainfall areas like East Europe and in W. USA, turf was dumped to form a fence.

 

Split rail or Zigzag fences

 

Twig Fence

Looped wire fence

 

The first patents on barbed wire fencings were taken out in the United States in 1867. However, it was in 1874, when its production by machines, made its use widespread. Woven wire fences and expanded metal lattices, affixed to wood, steel, or concrete posts, proved economical and durable.

Berlin Germany Dividing Y shaped Fence

 

Electrified fences, frequently a single strand of barbed wire, are sometimes used for temporary confinement of animals. A mild shock is given to the animal at intervals of a few seconds if it is in contact with the fence. Fence wire usually consists of two longitudinal wires twisted together to form an entwined cable and having wire barbs wound around either or both of the cable wires at regular intervals. The varieties of barbed wires are numerous, with cables being single or double, round, half-round, or flat and having a range of gauges. The twisted double wire provides extra strength and permits contraction and expansion without breakage. Barbs are diagonally cut in order to provide sharper points and they may be formed of one or two pieces (two or four points) and are generally spaced at intervals of 100 to 130 mm.

 

Lattice Fence

Fences are considered as safety barricades against animals, insects, humans and vehicles. These pose Height and Width factored hazards. Barbed wire fences have straight head, inward, outward bend or double head (Y form) at the top to make the crossover difficult. Armed forces place extended coils of barbed wire loops on ground without any posts. During world war-II barbed wire fence posts were spiked to prevent air craft landing.

Bent head Fence with Electric current

 

Hitler’s concentration camps are grim-reminder of fencing used for forceful confinement. Berlin, Germany was first divided by barbed wire fencing, which however did not prevent people escaping through it, so were replaced with massive RCC walls. Yet nations of the world still put up barbed wire fences to demarcate boundaries, as it provides a cheap and fast way of erection. India and Pakistan boundaries are fenced with double rows fencing, with an inspection path in the middle, and recognised no-man’s land across it.

 

Ownership of a fence between two properties is matter of dispute. The person who builds the fence first, remains the owner of it, and is also responsible for its upkeep. This, however, does not prevent the neighbour to place a patch at places of break. Ownership of a fence is often marked on title deeds with horizontal ‘T’ symbol, with the leg of T shown towards and in the property of the owner. Nominally fencing wires, lattices, or the cladding is placed on the non-owners side, to enable repairs or straightening of posts as and when required.

Other posts on Similar Topics

1.  Environmental Barricades

2   Barrier Systems in Buildings

3   Barrier Systems

4   Use of Barriers in Performing Arts

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DESIGN ORGANIZATIONS and QUALITY of LEADERSHIP

Post 166  ⇒  by Gautam Shah  →

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Design organizations are substantially a person centric entity. Even in partnerships, group or corporates practices the owners / conveners or leaders, each have a very sharply defined responsibility. It is the quality of leadership varies according to the nature of work in the organization. Inversely it is the quality of leadership that defines the work style of the organization.

White_stag_candidates_learn

The object has TWO facets: 1- The domain of leadership required for the functioning of the organization, and 2 – The domain of leadership required to handle a project. An organization operating efficiently has already this mode in place. The first aspect is more or less constant, till the organization changes its scope of business or is forced to re-evaluate it. The second aspect requires a leader to be as versatile as the project demands.

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Design organizations that handle highly variable situations or non-repeating projects need a very Radical leader. On the other hand design organizations with routine projects will function well under a Methodical leader.

For design organizations handling projects that are critical in time, resources and extent, need an Autocratic leader. Autocratic leader can override the situational differences, and imposes a pre-set style. The autocratic leader expects complete obedience of the subordinates.

Very large or multi divisioned organizations need a Democratic leader. Democratic leaders are ideal for projects involving large user base. Such leaders mould the situation, so that it can be handled within the ambience of the personal (leadership) qualities. Employees show responsible behaviour and self-discipline as they get due recognition and full support.

Participatory discussions

Projects that are in extremely dynamic situation need a Bohemian leader. Such a leader has a fast response and develops a style to suit the situation on hand. They are well suited for tackling continuously variable situations.

A Custodial leader has extra ordinary economic resources and public contacts to get things done. Such a leader dispenses organizational resources and makes employees dependent on the organization. Resulting performance, however, may not be adequate.

Autocratic leadership at Rural Council meet India

An Autocratic leader may stimulate an organization towards an acute specialization in only one or few fields, whereas a Bohemian leader may dissipate the energy and de-focus the goals of the organization. A Democratic leader will continuously review and revise the aims of the organization, and plan the resources, to make the organizations creative.

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GP – General Purpose Paints

Post 165  ⇒  by Gautam Shah  →

HK_Sai_Ying_Pun_Des_Voeux_Road_West_Dulux_Painting_Material_Shop_3

In Building Industry many different types of finishes are used for covering non-masonry surfaces such as Ferrous Metals, alloys, aluminium, wood, and wood composites. In many cases the surfaces are composed of many different types of materials, textures and forms. Often the extent of each individual type of surface is so small and its composition so complex that it may not be feasible to attend to different surfaces.

Most paint manufacturers offer a General purpose coating systems (GP) for such situations. The coatings are nominally conceived to be multi layer systems (at least of primer, inner and top-final coat). GP coating systems work for the inner and top coat, however, a primer coat is specific for the surface. It is specifically designed for the substrates such as masonry-cement primer, wood primer, mild-steel or iron primer.

Building_Painting_6253

GP or General Purpose coatings are used for following situations:

On items that are difficult to coat– Such as deep grooves, undersides, inaccessible areas, narrow stripes, engravings, sharp corners and edges, very smooth surfaces, small parts like lattices.

On locations with difficult access– High level ceilings, external sides of windows in multi storey buildings, roof trusses.

In variable atmospheric conditions– Rain and snow storms, very high to very low humidity environments, dust, sun rays, wind, flying insects, very high to very low temperatures.

In single or multi coat systems– Some initial coatings at plant level as specific coating system and rest on the site as GP system.

For specific purpose– As a fresh system (on a virgin surface), as a re-application system (re-coating with a similar but over an aged surface) or as a renovation system (removal of aged coating layer, repairs and coating).

With peripheral hazards– Fire, chemical vapour and odours, colour dropping or running, and over-sprays.

Such site applicable finishes are designed to dry out at normal atmospheric conditions. Most of the GP finishes allow multiple methods of application, and are applicable in widely variable atmospheric conditions.

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CONTRAST EFFECT – PERCEPTION

Post 164   by Gautam Shah ➔

Contrast simultaneity

We perceive things by different sensorial faculties and against many diverse contexts. In addition we perceive things and happenings in time and space scale. Whenever some details are required, the other senses fill-up the specifics. Typically our bilateral faculties like eyes and ears continuously back up the space position details. Similarly multilateral nodes of touch also support such a process.

1024px-Night_vision_goggles_experimental

experimental Night vision goggles

Space position or time marking details are affected by the quality of context. Where the context is dulled or rapidly changing the particulars of things and happenings fail to register effectively. The ‘back or fore’ grounds offer a scale to size-up the perception, and also format relationships in terms of now-then, here-there, far-near, etc. The time factor operates as ‘Concurrent and Sequential contrasts. These two aspects are affected by our past experiences and expectations (desires). The aberrations of perception arise from here. The way colours are seen or weights are felt is due to such contrasts. Our past experience and desires make us see or experience things before they happen at closer locations.

Contrast

Contrast or contextual effects created or employed in our daily life, are in home arrangements, food menus, dressing, expression and communication, etc. We create visual emphasis by accentuation of colour, illumination, texture, patterns, surface exposure duration and extent, etc. We generate audio accents by sound pitch, pressure, time gaping, replaying in different frequencies, etc. Touch experience is controlled by proximity, duration, exposure of body-limbs, extent and additional information such as temperature (warmth-cold), moisture, breeze, etc.

Camouflage

The contrast effects can be attuned manipulating the time and space fields. TV programmes often separate out the interviewer and interviewee in time separated frames, within same frame by superior-inferior positioning, or by comparative sizing. Additional information such as audio-video clips can break the relationship developing between the two time and space consecutive items. In a formal party tea, coffee or pre-post dinner drinks are served in different rooms-ambience.

Colour contrast due to colour blindness

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