Organic light-emitting diode


An organic light emitting diode (OLED) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compounds which emit light in response to an electric current. This layer of organic semiconductor material is situated between two electrodes. Generally, at least one of these electrodes is transparent.

OLEDs are used in television screens, computer monitors, small, portable system screens such as mobile phones and PDAs, watches, advertising, information and indication. OLEDs are also used in light sources for general space illumination and in large-area light-emitting elements. Due to their comparatively early stage of development, they typically emit less light per unit area than inorganic solid-state based LED point-light sources.

How a Disc Brake System Works

Brake systems are designed to slow the vehicles wheel movement through friction. There are primarily two brake systems, ABS and non ABS (anti brake skid). Both systems work on basic hydraulics and utilize a brake master cylinder (connected to the brake pedal in the car) that supplies brake fluid pressure to the front brake calipers and rear wheel cylinder or brake calipers if so equipped.

Typical Non ABS Brake System

The brake system requires hydraulic force which is many times greater than the force applied by the foot. This added hydraulic force is achieved by leverage multiplication. The multiplying force can be changed by varying the relative location of the brake master cylinder rod pivot as it relates to the lever.

In the hydraulic force multiplication method, the force which is applied at one point is transmitted by incompressible brake fluid to another point. This basic system consists of two pistons (master cylinder and wheel caliper or cylinder), which are filled with brake fluid and are connected by a brake line of any length or shape. When the brake pedal is forced down brake fluid from the master cylinder is transferred to the brake caliper piston, pressurized fluid is transmitted through the brake caliper to the brake pads or shoes, which are mounted to the brake caliper or wheel cylinder.

A major problem to the brake system is a brake fluid leak, if there is a slow leak in the system it will affect the brake master cylinder by allowing air into the system creating a low pedal and eventual brake operation failure. If a large brake fluid leak is present, fluid escapes, leading to a major brake failure on one half of the system (front or rear). A master cylinder has a built in safety device, two separate hydraulic systems a primary and secondary, separating front and rear brake operation incase of front or rear brake operation failure, one system will still be present.