Friday, June 29, 2007

Locks

Locks are advisory locks, where each thread cooperates by acquiring the lock before accessing the equivalent data. Some systems also implement mandatory locks, where attempting unauthorized access to a locked resource will force exclusion in the entity attempting to make the access.

In terms of access to the data, no difference is made between shared or exclusive modes. Other schemes provide for a shared mode, where several threads can obtain a shared lock for read-only access to the data. Other modes such as exclusive, intend-to-exclude and intend-to-upgrade are also widely implemented.

Independent of the type of lock chosen above, locks can be confidential by what happens when the lock strategy prevents progress of a thread. Most locking designs block the finishing of the process requesting the lock until it is allowed to access the locked resource. A spin lock is a lock where the thread simply waits until the lock becomes accessible. It is very efficient if threads are only likely to be uncreative for a short period of time, as it avoids the overhead of operating system process re-scheduling. It is wasteful if the padlock is held for a long period of time.

Monday, June 25, 2007

Honey

Honey is a sweet and thick fluid produced by honey bees from the nectar of flowers. According to the United States National Honey Board and various international food system, honey stipulates a pure product that does not allow for the addition of any other substance...this includes, but is not limited to, water or other sweeteners. This article refers exclusively to the honey produced by honey bees honey twisted by other bees or other insect have very different properties. Honey is significantly sweeter than table sugar and has attractive chemical properties for baking. Honey has a typical flavor which leads some people to prefer it over sugar and other sweeteners.

Most microorganisms do not grow in honey because of its low water movement of 0.6[2]. However, it is important to note that honey frequently contains dormant end spores of the bacteria Clostridium outline, which can be perilous to infants as the end spores can transform into toxin-producing bacteria in the infant's immature intestinal tract, leading to disease and even death. The study of pollens and spores in raw honey can determine floral sources of honey. Because bees carry an electrostatic charge, and can attract other particles, the same techniques of melissopalynology can be used in area ecological studies of radioactive particles, sand, or particulate pollution.

Friday, June 15, 2007

Color

Color is the visual perceptual property corresponding in humans to the category called red, yellow, white, etc. Color derives from variety of light distribution of light energy versus wavelength interacting in the eye with the spectral sensitivities of the light receptors. Color categories and physical specifications of color are also associated with objects, materials, light sources, etc., based on their physical properties such as light combination, reflection, or emission spectra.

Typically, only features of the composition of light that are measurable by humans wavelength spectrum from 400 nm to 700 nm, roughly are included, thereby objectively relating the psychological phenomenon of color to its physical specification. Because perception of color stems from the varying sensitivity of different types of cone cells in the retina to different parts of the spectrum, colors may be defined and quantify by the degree to which they inspire these cells. These physical or physiological quantifications of color, however, do not fully clarify the psychophysical perception of color appearance