Fatih GÜNDÜZ 030060144 8th week Answers

Liquid Laser : (Previous)

Lasers that use liquids as active medium have advantages of being more concantretad than a gas and of being able to be circulated and cooled. In 1966 Peter, P. Sorokin and J.R Lankard at IBM corporation's watson Research center in Yorktown heights. New york, demonstared the first dye laser. Since then hundreds of flourecent dyes have been found  to produce laser action. Dyes can emit laser beams with with a wide range of wavelenghts and thus have the great advantage being tuneable.  Liquid dye lasers can emit the laser beams from about the 250 nanometers in the ultraviolent throught the whole visible spectrum to 1,800 nanometers in the infrared.
 In a liquid dye laser, the dye is active medium. It is usually dissolved in a liquid solvent such as
alcohol or ethylene glycol. The source of energy for a liquid dye laser is usually a flashlamb  of another laser. 
(Charlene W Billings, Lasers: New Technology Of Light. P. 25)

Liquid laser : (New) (Better) (Laser Technologies)
 One of the most important characteristics of a laser medium is its degree of optical perfection. Liquids offer certain unique advantagesn as a laser medium. Although they are prone to large changes in reflection index brought about by changes in temperature, one can eleminate such temperature gradients and any associated variations in refrection index by circulating the liquid.
Liquid lasers have obvious inherent advantages over solid state lasers: they cannot be permanently damaged even at extremely high power levels of about 10^10 watts that have been generated by solid state lasers in mode lock operation. At these levels the laser materials are often permanently damaged . Liquids can be circulated and cooled in heat exchangers. Their avarage power output is not dependent on heat dissipation by thermal conductivity. Finally the cost of their preparation is a small fraction of the cost of solid materials.
(Lasers in Medicine, Taylor & Francis, p.77)

Dial Indicators : (Previous) (Better)

Dial Indicatorsmagnify small movements of a plunger or lever and show this magnified movement by means of a pointer on a graduated dial. This direct reading from the pointer and graduated dial gives the operator a quick, complete and accurate picture of condition of item under test. Dial Indicators are used to check the dimensional accuracy, of workpieces in conjuction with other equipment such as gauge blocks, to check straightness and alignments of machines and equipment, to set workpieces in machines to ensure paralelism and concernity and for a host of other uses too numerous to list completely.

(Workshop Processes, Practices and Materials, B. J. Black, p.108)

Dial Indicators : (New) (Measurement comparing)
 A dial indicator is the most commonly used mechanical type comparator. Comparators are used to transfer or compare a measurement with a known standart with a high degree of accuracy. Dial indicator is used to make a comparative measurement between the workpiece and indicator block from same reference plane.
The two main functions of a dial indicator are:
- To measure a lenght. This is the distance between a standart dimension to wich the dial indicator is set and the length of the part being measured.
-To determine the errors in geometrical form (Ovality, out of roundness, lobed form, taper etc.) or positional errors of surface (in paralelism, squareness, alignment etc.)
(Basic Mechanical Engineering, Mohan Sen, p.76)




The Unified Numbering System (UNS) for Metals and Alloys : (Previous)
In nOrth America, the accepted designations for copper and copper alloys are now part of the unified Numbering System (UNS) for Metals and Alloys (Ref 1), which is managed jointly by American Society for testing and Materials (ASTM) and the Society of Automotive Engineers (SAE) International Under the UNS system, coppers and copper alloys are desigrated by five-digit numbers preceded by the letter "C". The five-digit codes are based on and supersede, an older three-digit system developed by the U.S. copper and brass industry. The older system was administered by the Copper Development Association (CDA) and alloys are still sometimes identified by their "CDA numbers" The UNS designations are simply two-digit extensions of the CDA numbers to accommodate new compositions.
In the UNS system from C10000 through C79999 demote wrought alloys, while cast alloy designations range from C80000 through C99999. As shown in Table1, within these two categories, the compositions are grouped into distinct families of coppers and copper alloys, including the six major branches-coppers, high alloy coppers, brases, bronzes, copper nickels, and nickel silvers.(Davis R.J.,Copper and copper alloys, 2001, p.14) 


The Unified Numbering System (UNS) for Metals and Alloys : (New)(Better)(Numbering System)
A combined numbering system created by the ASTM and the SAE was established ain an effort to coordinate all the different numbering systems into one system. This system avoids the possibility that the same number might be used for two different metals. This combined system is the the Unified Numbering System (UNS). The UNS is an identification numbering system for commercial metals and alloys; it does not provide metal and alloy specifications. The UNS system is divided into the following categories.
(Engineering Drawing and Design, David A. Madsen, p.290)

 



Polycarbonate (Lexan) : (Previous)
Polycarbonates show excellent dimensional stability, with good impact resistance and ductility. They are employed as a base for photographic film and also for lenses. Their toughness makes them appropriate for the manufacture of safety helmets .     ( John Martin, Materials For Engineering, Third Edition, P.160 )Polycarbonates, one of the strongest, toughest, and most rigid thermoplastics, are not generally considered good barrier materials. It is possible to use polycarbonate as the structural layer in a composite (co-extruded) film for use in barrier application. In such cases, polycarbonate contributes
toughness and heat resistance to the final product while other components in the composite film may provide the barrier properties
Processing Methods : Injection molding, extrusion, blow molding, and rotational molding
Applications:
• Packaging. Milk bottles, baby bottles, food containers.
• Medical. Dialysers, artery cannulas.
• Electrical. Distribution box lids, fuses, sockets, lamp holders, and covers.  
(Liesl K. Massey, Permability properties of Plastics And Elastomers. Chapter 26)

Polycarbonate (Lexan): (New) (Better) (Polymer)
Standart polycarbonates is made from bisphenol A and phosgene via an interfacial polymerization process. The polymer back bone has an aromatic polycarbonate structure with a recurring carbonate, moiety which, uniquely acoounts for the outstanding toughness of the polycarbonate and rigid aromatic unit contributes to its high glass transition temperature.
Although a large number of applications of polycarbonate have been based on its unique combination of high impact strenght, heat resistence and clearity there are still a few property deficiencies in the neat polymer which can be overcome by blending with other polymers on additives.
(Polymer Blends Handbook, 1. cilt, L. A. Utracki, p.1082)

Teflon (PTFE) : (Previous) (Better)

Poly(tetrafluoroethylene) is a highly crystalline polymer which is produced by the polymerization of tetrafluoroethylene. PTFE offers very high heat resistance (up to 250 C), exceptional chemical resistance, and outstanding flame resistance. The broad chemical resistance includes strong acids and strong bases. In addition, PTFE has the lowest coefficient of friction of any polymer.

PTFE has a high melting point and extremely high melt viscosity and hence cannot be melt processed by normal techniques. Therefore PTFE has to be processed by unconventional techniques (PTFE powder is compacted to the desired shape and sintered).

Uses:

Typically PTFE is used in applications requiring long-term performance in extremeservice

environments. PTFE applications include electrical (high-temperature, high performance wire and cable insulation, sockets, pins, connectors), mechanical (bushings,

rider rings, seals, bearing pads, valve seats, chemical resistance processing equipment and

pipe, nonlubricated bearings, pump parts, gaskets, and packings), nonstick coatings (home

cookware, tools, food-processing equipment), and miscellaneous (conveyor parts, packaging,

flame-retardant laminates).

(Kutz M., Mechanical engineers' handbook: Materials and mechanical design, p. 370)

Teflon (PTFE) : (New) (Polymer)
Description and uses.-Polytetrafluoroethylene (PTFE) is a vinyl polymer similar to polyethylene and made from the monomer tetrafluoroethylene. Better known by its trade name, Teflon. PTFE is highly resistant to oxidation, possesses high temperature stability, acts as an excellent insulator, and has superrior anti-stick properties. PTFE is used to make non-stick cooking pans and other slyppery or non-stick surfaces, as a stain resistant treatment for carpets and fabrics, and to produce artificial body parts because it is seldom rejected.
(Advice Concerning Possible Modifications to the U.S. Generalized System of Preferences,
U.S. International Trade Commission, p.21)