Sunday, May 27, 2007
Saturday, May 19, 2007
Moore machine
The name Moore machine comes from that of its supporter, Edward F. Moore, a state-machine pioneer who wrote "Gedanken-experiments on Sequential Machines".
Most digital electronic systems are designed as clocked sequential systems. Clocked sequential systems are a limited form of Moore machine where the state changes only when the global clock signal changes. Typically the current state is stored in flip-flops, and a global clock signal is connected to the "clock" input of the flip-flops. Clocked chronological systems are one way to solve met stability problems.
A typical electronic Moore machine includes a combinatorial logic chain to decode the current state into the outputs. The instant the current state changes, those changes ripple through that chain, and almost instantaneously the outputs change. There are design techniques to ensure that no glitches occur on the outputs during that brief period while those changes are rippling through the chain, but most systems are designed so that glitches during that brief transition time are ignored or are irrelevant. The outputs then stay the same indefinitely, until the Moore machine changes state again.
Monday, May 14, 2007
Sunglass
Many people find direct sunlight too bright to be comfortable, particularly when reading from paper on which the sun directly shines. In outdoor activities like skiing and flying, the eye can receive more light than usual. It has been recommended to wear these kinds of glasses on sunny days to protect the eyes from ultraviolet radiation, which can lead to the development of a cataract. Sunglasses have also been linked with celebrities and film actors mainly due to the desire to mask identity, but in part due to the lighting involved in production being typically stronger than natural light and uncomfortable to the naked eye.
Wednesday, May 09, 2007
Mod chip
Almost all modern console gaming systems have hardware-based schemes which ensure that only officially authorized games may be used with the system and implement regional lockout similar to the scheme used in DVD movies. The specific technical nature of these DRM systems varies by system, and may include cryptographic signing, intentionally unreadable sectors, custom optical media, or some combination thereof. Mod chips are available also for some DVD players, to defeat region code enforcement and user.
Tuesday, May 01, 2007
Description of Willamette Valley
The agricultural wealth of the valley is considered to be in no small measure a result of the Missoula Floods, which swamped the valley approximately forty times between 15,000 and 13,000 years ago at the end of the last ice age. The floods were caused by the episodic rupturing of the ice dam of Glacial Lake Missoula, the waters of which swept down the Columbia and flooded the Willamette Valley as far south as Eugene. The floodwaters carried rich volcanic and glacial soil from Eastern Washington, which was deposited across the valley floor when the waters subsided.