Hakan YORULMUŞ 030070111 week8th

1) Solid Foil Polymerization  (Group: Manufacturing method)

(previous)

 The process is based on complete polymerization of semipolymerized plastic foil on exposure to suitable light source. The semipolymerized foil is first stacked on previously solidified part and illuminated such that bonding is achieved after complete polymerization. The excess foil which is not illuminated can be removed by dissolving into suitable solvent leaving behind the desired part.

(Narenda B. Dahorte, Sandip P. Harimkar,Laser Fabrication and machining of materials, pg. 358)

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This process applies solid-to-solid, rather than liquid-to-solid, poly-merization. The part is built up using semipolymerized plastic foilsprogressively stacked on top of each other. Upon exposure to ultraviolet light, the semipolymerized foil solidifies and bonds to the previouslayer. The areas of the foil that do not constitute the eventual part areused to support it during the building process but remain soluble andso are easy to remove once the part is complete.

(Hassan Abdel-Gawad El-Hofy, Hassan El-Hofy,Advanced Machining Processes: Nontraditional and Hybrid Machining Processes, McGraw-Hill  | March 1, 2005, page 245)

2)High Speed Plating  (Group: High speed process)
(previous)
Plating at high speed, at high current density, can usually only be justified if the process is cheaper or the product superior to a conventional rate plating procedure. The advantages of high speed plating are obvious in that a greater throughout can be achieved with a particular plant, or a smaller plant can be employed to provide a given output. The details of capital investment and overheads become the concern of the accountant but only if a technically viable process can be developed. High-speed processes are more demanding with regard to plant requirements, and some attempts have failed due to equipment deficiencies. The properties of electrodeposits produced at high current density are differnt from those of deposits obtained at conventional rates and they are superior for some purposes.

(Nickel and Chromium Plating, J.K.Dennis, T.E.Such, Page 423)

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The high speed plating technique is used in reel-to-reel or strip-to-strip plating where the current densities are (typically) greater than 5-10 A/dm*. The major obstacle to high speed plating is mass transport limitation. This can be overcome by maintaining sufficient electrolyte circulation past the plated part, and by increasing the bulk concentration of the active ions. High speed plating involves high electrolyte flow, typically in the turbulent flow region. Design of plating cells is not a simple task and theoretical calculation requires a knowledge of fluid mechanics, particularly since the uniform flow rate over the entire plated region is often required. The situation is complicated and occasionally is critical with regard to plating additives which are typically present in minute amounts, and therefore are considered more sensitive to flow variations than the major metal ions. The composition of the plating solution for high speed plating is thus different from that of barrel or rack plating.

( A. C. Tan, Tin and Solder Plating in the Semiconductor Industry: A Technical Guide,page319)

3)Workability  (Group: Management)
(previous)

Workability is a vital aspect of the processing of materials, having posts in both material behaviour and process design. Whether a part can be produced by plastic deformation without cracking or the generation of other defects is of important economic consequence. Because of the complex natüre of the workability of metals, there is no single test can be used to evaluate it. Several laboratory tests have been developed that are useful in screening materials for workability, but in other instances, very specialized tests that are specific to the process are commonly used.

(G.E.Dieter, H.A.Kuhn, S. L. Semiatin, Handbook of workability and process design, p.1)

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The diverse requirements of mixability, stability, transportability, placeability, mobility, compactability and finishability of fresh concrete mentioned above are collectively referred to as workability. The workability of fresh concrete is thus a composite property. It is difficult to define precisely all the aspects of the workability in a single definition. IS: 6461 (Part-VII)-1973 defines workability as that property of freshly mixed concrete or mortar which determines the ease and homogeneity with which it can be mixed, placed compacted and finished.

(M L Gambhir, Concrete Technology,,page 125)

4)Vision Control  (Group: Electronic equipment)
(previous)

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)

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It is important that the cameras are adjusted to produce the best possible pictures for each shot, and also to ensure that the shots match from camera to camera and from shot to shot. e.g. face tones look the same. This is the basic function of vision control.
Lightweight cameras
Lightweight cameras usually have auto-white balance, auto-black level and auto-iris facilities, three of the main areas of interest for vision control. It should be remembered that the auto-iris control can give rise to errors when the camera is presented with scenes containing large areas of excessive highlights, e.g. white clouds. Ideally the camera operator should adjust the lens iris manually to suit each shot, using the viewfinder to judge the correct exposure.
Full-facility vision control
Cameras equipped with remote control of camera processing (such as iris, black level, gamma correction, fine detail enhancement, and colour correction in highlight and black areas) will enable the vision controller to achieve greater precision in control of picture quality and ensure that the pictures match one shot to the next. This is important even when shooting 'single camera*. At the beginning of rehearsal the camera iris should be set to its nominal value  and the lighting levels balanced to achieve a satisfactory picture. Minor adjustments to iris and black level are made subsequently to ensure picture matching. Some shots may require more or less fine detail correction, which should be adjusted shot by shot. Any colour cast introduced by reflection of light from costumes or the set can be removed by means of the colour correction controls, and similarly for any variation in the colour temperature (whiteness) of the light sources used for each scene. Alternatively, the vision controller can deliberately introduce a colour cast, and produce warm pictures or cool pictures to match the mood of the scene as appropriate.

Further duties of the vision control engineer include camera line-up. the checking of all vision sources routed to the switcher, alignment of all the picture monitors in the studio control complex, and as a liaison point for camera crew when technical problems arise.The vision controller works very closely with the lighting director, and in a small studio these duties may well be handled by one person.

Vision control

This is a typical opwational control panel tOCP) (or a fulMecilitiea camera.

1. Remote control of filter wheels located between lens and light-splitting system (colour correction, neutral density and effocts filters).

2. Master gam control; extra gain is used when operating in low light.

3. Gain and black trims, used for minor adjustment of colour gain and black level when matching pictures

4. Auto/manual ins control.

5. Detail enhancement.

6. Contrast control, used to modify the 'law', i.e. lo stretch/crush appropriate parts of the grey scale.

7. Range control, adjusts the range over which the joystick will operate, and selects the mean aperture.

8. Readout of lens aperture.

9 Joystick, the main operational control, has three functions. Twist to adjust master black

level forward/back 

to open/close iris.Depress to switch channel to preview monitor.

(Alan Bermingham,Ken Angold-Stephens,The Video Studio;1994;page62-63)