030070094 Buğra Çetinkaya 10th week Definitions

Injected metal assembly (Group: Manufacturing)

There is no old definition.

 

Injected metal assembly can reduce the costs normally encountered when using conventional approaches. Typical components shown hero are provided with surfaces around which the injected metal can shrink. Governor case and plate for a telephone dial, 
a. has two locking grooves in the case; a cooling fan for a small power drill, 

b. has four locking lugs around which the center hub is cast. Mechanical lock is produced on damping-disc/shaft assembly.

c. by providing dovetail shape in disc. Injected metal is forced into porous abrasive material, 

d. to lock the mandrel to the abrasive wheel. Similarly, as brake cable fastener is injected directly onto braided cable, 

e. and injected metal solidifies around Irregular cable shape, thus locking itself to the cable. Knurled shaft,

f. provides locking surface for small gear/shaft assembly
(Roger William Bolz, Production Processes: The Productivity Handbook, p. 3-04)

Intrinsic Viscosity (Group: Material Properties)

There is no old definition.

The viscosity of a polymer solution or polymer melt, in general, is a measure of the fluid's resistance to flow. Intrinsic viscosity is a measure of the hydrodynamic volume of a polymer molecule in solution. It is sensitive to molecular weight conformation as well as molecular size.

For a given set of polyethylene resins produced with the same process, intrinsic viscosity can he used as an indicator of the average molecular weight of the polymer. Because intrinsic viscosity is affected by molecular conformation, LDPE (with their long-chain branching) will assume a hydrodynamic volume in solution smaller than that of a linear PE of equivalent molecular weight. PE produced by different processes will have different linear relationships between ln(melt index) and intrinsic viscosity. The molecular weight distribution may be a factor as well. The dilute solution viscosity test defines what is known as the viscosity-average molecular weight.

Intrinsic viscosity (dl/g) measurements are normally made by using a three-point zero-concentration extrapolation. Because it is a zero-concentration measurement, it is independent of concentration; the intrinsic viscosity is dependent on the solvent used in the test. Measurements of PE dilute solution viscosity have been made at 140 C and at concentrations of 0.1, 0.2 and 0.3 g polymer/100 cm3 decalin.

(Elsayed Abdel-Bary, Handbook Of Plastic Films, p. 46)

Continuous Casting (Group: Manufacturing Process)

There is no old definition.
 

Continuous casting process can be used for producing castings of large length with a uniform cross-section. Castings of different cross-section can be produced by changing the mould. This process essentially consists of pouring the molten metal into one end of a metal mould, open at both ends, cooling it rapidly till the metal solidifies, and removing the solidified product in a continuous length from the other end of the mould. Continuous casting process is illustrated in Fig. 11.19.

 

In this process, the pouring die (the mould) and cooling jacket are made, sometimes, integral with the furnace. It also incorporates an integrated valve to stop the metal flow into the mould when desired. The molten metal flows into the mould from the bottom of the furnace so that impurities are not included in it. As it flows down, it is cooled rapidly by quick dissipation of heat by circulating water in the jacket around the metal mould. Withdrawing rolls below the mould help in pulling down the solidified casting at a controlled speed. A saw is fitted to cut the casting into desired lengths. The shapes that can be produced by this process are: square, rectangular, and hexagonal.

(B. S. Nagendra Parashar,R. K. Mittal, Elements Of Manufacturing Processes, p. 234)

Data Integrity (Group: Database System)

There is no old definition.
 

Fragmentation does not just have an effect on the system's performance. There is also an impact on the integrity of the data that the system stores and processes. As a system's disk becomes Fragmented (whether slowly over time or rapidly due to significant data throughput), the number of discrete read-and-write operations necessary to manage the data increases. Each operation is an opportunity or the disk to fail and puts a little more strain on the mechanics of the drive.

Consider your car. If you keep your car at peak performance, it is less likely to break down. Regularly changing the oil means that the engine encounters less friction and requires less effort to move the car. It' the oil gets dirty and old, the engine has to work harder because there's resistance. Harder work means shorter life for engine components, and as a result, you're more likely to encounter a breakdown or mechanical failure.

Although disk drives aren't nearly as reliant on this type of upkeep, there is a measurable difference between a well-maintained drive and one that has had no maintenance. A drive that has severe fragmentation works very hard to read and write data compared with a similar drive without fragmentation. Less work means less likelihood of failure, which means increased data availability and integrity.

Unfortunately, data integrity issues usually do not provide advanced warning. They usually manifest when a user tries to access data and the file is missing or corrupt. At that point, the best alternative is usually restoring from a backup or looking for a copy (for example. a recent copy sent via email). Once this initial data integrity issue is recognized, most administrators will immediately take steps to verify the integrity of other data and proactively mitigate any other data integrity issues (for example. get a complete backup of the data, repair the drive, and so on).

(Mike Danseglio, The Shortcut Guide to Managing Disk Fragmentation, p. 55)

Shape Memory Alloys (Group: Material)

There is no old definition.

Shape memory alloys are worth mentioning in this overview of actuator technologies because, despite a number of drawbacks, they are unmatched in work density and, as is not so well known, can be extremely high in power to mass. These metal alloys undergo temperature driven phase transformation. Temperature change is frequently achieved using a current pulse, particularly in nickel—titanium alloys, where resistivity is reasonable. A change in crystal structure results in dimensional changes that are typically between 1% and 8%. These strains can be induced under very high loads, leading to high work densities (>1 MJ/m3). Furthermore, by employing effective cooling (e.g. operating in a water bath and employing short current pulses to induce heating), millisecond time scale impulse responses can be induced by heating, lbRowed by quick cooling from nucleate boiling. Typically the shape memory alloy contracts at high temperature. and a tensile stress is needed to return it to its elongated state following cooling. A simplified version of the shape memory cycle is shown in Fig. 2.3. Mechanical elongation can be avoided when a two-way shape memory effect is induced . 
Apart from the smaller strain, shape memory alloy performance generally exceeds that of dielectric elastomers. However, shape memory alloys suffer from low efficiency (<5%). Furthermore, these actuators are difficult to position control because of their hysteretic and stress dependent response. Rates of actuation can be low when used in air. Finally, lifetime is relatively short at high strain. Materials are readily available and produced in quantity.
 

(Federico Carpi,Danilo De Rossi,Roy Kornbluh, Dielectric Elastomers as Electromechanical Transducers, p. 19)