Selçuk TEVRÜZ, 030070128, 10th week

Deflection Temperature Under Load (DTUL) (April 14, 2011 - 13:42)

Deflection temperature under load (DTUL) is a technique which follows the deflection of a beam of material under fixed stress as the temperature is increased. The temperature at which the beam deforms by a specified strain (0.2% for plastics and 0.1% for composites) is the DTUL. This technique was previously known as heat deflection temperature (HDT).

(Mulligan D.R., Cure Monitoring for Composites and Adhesives, 2003, pg.15)

Vision Control (April 14, 2011 - 20:05)

One of the principal aims of a television production is to create a stream of pictures that convinces the viewer that they are watching continous action in 'real' time. Direction, camerawork, sound, lighting, vision mixing all practise an 'invisible' technique designed to hide the mechanisms of bringing the image to the screen in order to emphasize the content of the programme. The vision controller plays a crucial part in this strategy by ensuring image continuity in exposure, colour and picture quality. In order to achieve this, he/she must contuniously monitor the output of all cameras making any appropriate adjustments to iris, black level and colour as needed. This can only be achieved if each shot is assessed on a Grade 1 monitor coupled to a waveform monitor/vectorscope.

Matching pictures is usually achieved by using a joystick control for each camera which, when depressed, switches that camera's output to the assessment monitor. Rotating the top of the joystick allows the black level to be set, and moving the joystick forwards or backwards opens/closes the iris. The ratio of joystick movement to iris movement can be altered by a FINE and a COARSE setting. For studio work, the iris control is normally operated in the FINE mode, which allows one f-stop either side of the central position; the central position having been set to the nominal lens aperture. The COARSE iris control is normally used on outside broadcasts where large changes in lighting levels can be expected.

In a studio production, exposure will be dependent on lighting levels and variation in levels. It is common practice for the lighting director to attempt to balance out lighting levels during rehearsal before vision control operator begins exposure correction. To maintain the 'invisible' technique there should be no evidence of vision control adjustments in the recorded/transmitted picture. Usually each shot will be previewed before it is used but sometimes, adjustment on shot is unavoidable. Picture matching is focused on exposure, matching face tones and background, and black level. A small adjustment of black level has a greater effect on the TV image than a similar alteration to iris. To summarize, the operational role of the vision control operator may include:

• align the cameras prior to rehearsal and transmission/recording
• align vision/lighting control room monitors
• check incoming/outgoing vision sources to the vision mixer
• adjust black level, iris setting of each shot and colour match if required
• set the appropriate contouring detail for each shot and adjust gamma and knee as appropriate
• switch appropriate mixed viexfinder feeds to camera viewfinders as required and identify any vision faults and arrange for the necessary adjustment

(Ward P., TV Technical Operations, 2000, pg.132)

Thermal Spray Coating (April 14, 2011 - 20:28)

Thermal spray processing is a well-established means of forming coatings of thickness greater than about 50 µm, so-called thick coatings. A wide range of materials can be thermally sprayed for a variety of applications, ranging from gas turbine technology (heat engines) to the electronics industry. Thermal spray coatings have been produced for at least 40 years, but the last decade has seen a virtual revolution in the capability of the technologyto produce truly high performance coatings of a great range of materials on many different substrates. This enhancement of the technology has been achieved largely through the introduction of the new spray techniques, the enhancement of spray process controls, the employment of state-of-the-art methods of feedstock materials production and the use of modern techniques of quality assurance.

Although the use of advanced thermal spray coating has largely occured within the aircraft industry, newer, extended applications of the technique have demonstrated its versatility. Applications include protection from wear, high temperatures, chemical attack, and the more mundane uses of environmental corrosion protection in infrastructure maintenance engineering.

(Stern K.H., Metallurgical and Ceramic Protective Coatings, 1996, pg.261)

Porcelain Enameling (About Coating) (April 14, 2011 - 20:36)

Porcelain enamels are glass coatings applied to products to improve appearance and protect the metal surface. Porcelain enamels are distinguished from other ceramic coatings by their predominantly vitreous nature and the types of applications for which they are used. They are distinguished from paint by their inorganic composition and the fusion of the coating matrix to the substrate metal.

Aluminum products, including tanks and vessels, architectural panels, cookware, and signs, can be finished by porcelain enameling to enhance appearance, chemical resistance, or weather resistance. The common porcelain eanameling alloys for the various forms of aluminum are the following:

• Sheet: 1100, 3003, and 6061
• Extrusions: 6061
• Casting alloys: 443 and 356

(Davis J. R., Corrosion of Aluminum and Aluminum Alloys, 2000, second edition, pg. 211)