aIr ROckETs?????

Flying model rockets is a relatively safe and inexpensive way for students to learn the basics of forces and the response of a vehicle to external forces. A model rocket is subjected to four forces in flight; weight, thrust, and the aerodynamic forces, lift and drag. There are many different types of model rockets. The first and simplest type of rocket that a student encounters is the compressed air, or stomp rocket. The air rocket system consists of two main parts, the launcher and the rocket.
On the figure we show a generic launcher, although launchers come in a wide variety of shapes and sizes. The launcher has a base to support the rocket during launch. A hollow launch tube is mounted perpendicular to the base and is inserted into the base of the rocket before launch. The launch tube is connected to an air pump by a hollow feeder line. The pump is used to pressurize the inside of the body tube to provide thrust for the rocket. We have attached a pressure gage to the feeder line to display the change in pressure in the system. For many air rockets, the pump is simply a cylinder which can be collapsed by striking with your hand or foot, which is where the "stomp" rocket got its name. In our simulation, we are going to pump up the system, and then launch the rocket, to better control and explain how the system works.
The other part of the compressed air rocket system is the rocket itself. The rocket has a hollow body tube which is opened on one end and closed at the other end by the nose cone. The body tube is only slightly larger than the launch tube. When the rocket is placed on the launch tube, the body tube becomes a closed pressure vessel. The pressure inside the body tube equals the pressure produced by the air pump. Fins are attached to the bottom of the body tube to provide stability during the flight.
The flight of a compressed air rocket is similar to the flight of a ballistic shell or a bullet fired from a gun. Unlike a model rocket, bottle rocket, or full scale rocket for which the thrust force is applied to the rocket for a large portion of the flight, the thrust of a stomp rocket is completely expended in the first instance of flight. During the entire flight, only the weight and aerodynamic forces act on the rocket.
The launch of a compressed air rocket proceeds in three stages; the pressurization of the body tube, the initial acceleration along the launch tube, and the expulsion of the compressed air from the rear of the rocket. Here is a computer animation of the launch of a compressed air rocket:

jeNAyAH SiBer!!!!

Kemunculan Internet sebagai alat komunikasi terkini menjanjikan satu wadah penyebaran maklumat yang memantapkan ilmu dan maklumat. Oleh kerana tiada siapa yang dapat mengawal perjalanan maklumat di dunia siber, berjuta-juta laman web telah dihidupkan. Bermacam-macam maklumat (sama ada benar atau salah), idea, ideologi, propaganda dan tidak kurang juga pornografi disebarkan melalui Internet.
Pada masa yang sama, kebebasan maklumat yang dijanjikan oleh dunia siber ini menimbulkan rasa gerun bagi pihak pentadbir sesetengah negara yang selama ini mahu mengongkong kebebasan bersuara, berfikir dan berpendapat penduduk mereka.

BUS tOpoLOgY???????

A bus network topology is a network architecture in which a set of clients are connected via a shared communications line, called a bus. There are several common instances of the bus architecture, including one in the motherboard of most computers, and those in some versions ofEthernet networks.

ring TOPoloGy??????????

A ring network is a network topology in which each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node - a ring. Data travels from node to node, with each node along the way handling every packet.

Because a ring topology provides only one pathway between any two nodes, ring networks may be disrupted by the failure of a single link^[1]. A node failure or cable break might isolate every node attached to the ring. FDDI networks overcome this vulnerability by sending data on a clockwise and a counterclockwise ring: in the event of a break data is wrapped back onto the complementary ring before it reaches the end of the cable, maintaining a path to every node along the resulting "C-Ring". 802.5 networks -- also known as IBM Token Ring networks -- avoid the weakness of a ring topology altogether: they actually use a star topology at the physical layer and a Multistation Access Unit (MAU) to imitate a ring at the datalink layer.

STar TopOLOgy????

Star networks are one of the most common computer network topologies. In its simplest form, a star network consists of one central switch, hub or computer, which acts as a conduit to transmit messages.^[1] Thus, the hub and leaf nodes, and the transmission lines between them, form a graph with the topology of a star. If the central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way transmission time (i.e. to and from the central node) plus any delay generated in the central node. An active star network has an active central node that usually has the means to prevent echo-related problems.
The star topology reduces the chance of network failure by connecting all of the systems to a central node. When applied to a bus-based network, this central hub rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the rest of the systems will be unaffected. ^[2]
It is also designed with each node (file servers, workstations, and peripherals) connected directly to a central network hub, switch, or concentrator.

Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. The hub, switch, or concentrator manages and controls all functions of the network. It is also acts as a repeater for the data flow. This configuration is common with twisted pair cable. However, it can also be used with coaxial cable or optical fibre cable.