Hard drive, computer

FIGURE 1.7 A side view of a multiplaten computer hard drive (from Ref 34). 

FIGURE 1.8 A cross section of a typical computer hard drive disk (from Ref 35). 

In a computer hard drive, the data are stored on one or more rigid disks coated with magnetic materials. The magnetic film is coated on a planar NiP substrate. NiP film is typically electroplated on an aluminum disk. Before the coating process, the NiP must be planarized. The planarization process is similar to oxide ILD CMP except that the material is a metal. The slurry chemistry is similar to copper or tungsten CMP except that the end point is to form a perfectly planar substrate. Hydrogen peroxide can be used as an oxidizer in NiP CMP as stated in the patent by Jia and coworkers [14,15]. As shown in Fig. 7.5, the removal rate for NiP film follows the same trend as for copper. At higher concentration, the removal rate decreases because of the formation of a native protective NiO film [12]. 

Images are written directly onto a computer hard drive using the equipment described in Subheading 2.2, items 4 and 5... 

We think that we have done very well with human technology, packing information very densely on to computer hard drives, chips, and CD-ROM disks. However, these all store information on the surface, whereas DNA stores it in three dimensions. It is by far the densest information storage mechanism known in the universe. 

To get some idea how fiist some common objects rotate, consider the feUowii examples a dentist s drill runs at 400,000 rpm a current state-of-the-art computer hard drive runs at 7200 rpm the earth goes throug i one complete revolution in 24 hours, thus the rotational speed of earth is 15 d ees per hour or 1 degree every 4 minutes. 

As we explained in Chapter 12, motors run many devices and equipment that make our lives comfortable and less laborious. As an example, we identified a huge number of motors in various devices at home, including motors that run the compressor of your refrgerator, garbage disposer, exhaust fims, tape player in a VCR, vacuum cleaner, turntable of a microwave, hair dryer, electric shaver, computer fan, and computer hard drive. When selecting motors for these... 

A third currency is time, although along this dimension, there is neither a source nor a recipient. Information involves work and heat in its production, copying, and transformation. These activities do not take place instantaneously, but rather over a period of time. The amount of time is variable and depends on the machinery and circumstances. A performance of Beethoven s Ninth Symphony takes about an hour. The software that encodes the performance required several years for the composer to develop. Copying the software to a computer hard drive requires a few seconds at most. Information processing is not free on account of work and heat requirements. That these resources are expended over finite time intervals is also a critical feature. 

Optical media is more durable than electromagnetic tape and is less vulnerable to environmental conditions. With the exception of Blu-ray Discs, the speed of data retrieval is considerably slower than that of a computer hard drive. The storage capacity of optical disks is significantly less than that of hard drives. Another, less common form of optical storage is optical tape, which consists of a long, narrow strip of plastic upon which patterns can be written and fi-om which the patterns can be read back. 

The bulky nature of absorbent papers also makes them permeable to liquids. Based on this property, absorbent papers are used as filter media in coffee makers, in laboratory procedures for the recovery of crystalline solids, in fuel and oil filters for all types of machinery, in air filters for computer hard drives, and in many other similar applications. 

A backup copy of the data files on the computer disk should be made onto a formatted 3.5 in. disk before using the files in any solvent-resin calculations. It is suggested that the Lotus. WKl files be copied to the appropriate spreadsheet directory on the computer hard drive for faster operation of the spreadsheets. The directions needed for proper operation of the spreadsheet are listed at the top of each spreadsheet. Any spreadsheet data and calculations that need be saved should be saved under a different file name. Any solvent or resin/polymer numbers that are typed into the appropriate spreadsheet cells must be listed in numerical order for the lookup function to work correctly. The data files can be used with Lotus 123 Version 5.0 for Windows, Microsoft Excel Version 5.0 for Windows, or any earlier version of the spreadsheet software. Anyone familiar with the use of macros in spreadsheets can undoubtedly automate the operation of some of the spreadsheets contained on the computer disk. 

Letters that previously stood for words such as "disc," but now do not stand for three words. Taken together, they refer to a standard for digitally encoding music and video, and storing it in a CD-configured plastic medium. (Note that "disc" is spelled with a "c" when referring to music storage, but with a "k" if used for other purposes such as computer hard drive memories.)... 

Neodymium has exceptional magnetic properties and is therefore used to produce the small, very powerful magnets required for computer hard drives, audio speakers and headphones (the earpieces of mobile phones, for instance). 

Ferrofluids are a class of important ternary ferrite spinels are of the formula MFc204 (M = Co, Mn, Ni), synthesized as nano-sized particulates dispersed in a solvent. These solutions have applicatians that span electronic devices e.g., forming seals around spinning drive shafts in computer hard drives heat conduction in speaker tweeters) to medicine (hyperthermia-based cancer treatment - i.c., directing nanoparticles to a cancerous area and raising their temperature via an external magnetic field). For a review of ferrofluids, see Odenbach, S. J. Phys. Condens. Matter 2004,16, R1135. 

Data is recorded to a computer hard drive by applying a magnetic field that manipulates particles within Ae disk medium. Srnaller particles allow for a greater density of information to be stored. Nickel nanowires respond to an apphed magnetic field, making them an attractive recording material for future data storage devices (55). 

Ferromagnetic materials are also used to coat computer hard drives. Electromagnetic recording heads align spins to create domains, which remain for years. 

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