Friday, December 28, 2007

ASIMO

ASIMOis a humanoid robot created by Honda Motor Company. Standing at 130 centimeters (4 feet 3 inches) and weighing 54 kilograms (119 pounds), the robot resembles a small astronaut wearing a backpack and can walk on two feet at speeds up to 6 km/h (3.7 mph). ASIMO was created at Honda's Research & Development Wako Fundamental Technical Research Center in Japan. It is the current model in a line of eleven that began in 1986 with E0.

Officially, the name is an acronym for "Advanced Step in Innovative MObility". Honda's official statements indicate that the robot's name is not a reference to science fiction writer and inventor of the Three Laws of Robotics, Isaac Asimov. In Japanese, the name is pronounced ashimo and, not coincidentally, means "legs also" (from Japanese 足も).

Wednesday, December 19, 2007

Local area network

A local area network is a network that spans a relatively small space and provides services to a small amount of people. Depending on the amount of people that use a Local Area Network, a peer-to-peer or client-server method of networking may be used. A peer-to-peer network is where each client shares their resources with other workstations in the network. Examples of peer-to-peer networks are: Small office networks where resource use is minimal and a home network. A client-server network is where every client is connected to the server and each other. Client-server networks use servers in different capacities. These can be classified into two types: Single-service servers, where the server performs one task such as file server, print server, etc.; while other servers can not only perform in the capacity of file servers and print servers, but they also conduct calculations and use these to provide information to clients (Web/Intranet Server). Computers are linked via Ethernet Cable, can be joined either directly (one computer to another), or via a network hub that allows multiple connections.

Historically, LANs have featured much higher speeds than WANs. This is not necessarily the case when the WAN technology appears as Metro Ethernet, implemented over optical transmission systems.

Wednesday, December 12, 2007

Nanomaterials

A number of physical phenomena become noticeably pronounced as the size of the system decreases. These include statistical mechanical effects, as well as quantum mechanical effects, for example the “quantum size effect” where the electronic properties of solids are altered with great reductions in particle size. This effect does not come into play by going from macro to micro dimensions. However, it becomes dominant when the nanometer size range is reached. Additionally, a number of physical properties change when compared to macroscopic systems. One example is the increase in surface area to volume of materials. This catalytic activity also opens potential risks in their interaction with biomaterials.

Materials reduced to the nanoscale can suddenly show very different properties compared to what they exhibit on a macroscale, enabling unique applications. For instance, opaque substances become transparent (copper); inert materials become catalysts (platinum); stable materials turn combustible (aluminum); solids turn into liquids at room temperature (gold); insulators become conductors (silicon). A material such as gold, which is chemically inert at normal scales, can serve as a potent chemical catalyst at nanoscales. Much of the fascination with nanotechnology stems from these unique quantum and surface phenomena that matter exhibits at the nanoscale.

Thursday, December 06, 2007

Movement from cell to cell and handover

The use of multiple cells means that, if the distributed transceivers are mobile and moving from place to place, they also have to change from cell to cell. The mechanism for this differs depending on the type of network and the circumstances of the change. For example, if there is an ongoing continuous communication and we don't want to interrupt it, then great care must be taken to avoid interruption. In this case there must be clear coordination between the base station and the mobile station. Typically such systems use some kind of multiple access independently in each cell, so an early stage of such a handover (handoff) is to reserve a new channel for the mobile station on the new base station which will serve it. The mobile then moves from the channel on its current base station to the new channel and from that point on communication takes place. The exact details of the mobile system's move from one base station to the other varies considerably from system to system. For example, in all GSM handovers and W-CDMA inter-frequency handovers the mobile station will measure the channel it is meant to start using before moving over. Once the channel is confirmed okay, the network will command the mobile station to move to the new channel and at the same time start bi-directional communication there, meaning there is no break in communication. In CDMA2000 and W-CDMA same-frequency handovers, both channels will actually be in use at the same time (this is called a soft handover or soft handoff). In IS-95 inter-frequency handovers and older analog systems such as NMT it will typically be impossible to measure the target channel directly whilst communicating. In this case other techniques have to be used such as pilot beacons in IS-95. This means that there is almost always a brief break in the communication whilst searching for the new channel followed by the risk of an unexpected return to the old channel.