Nanobuds

Nanotechnology has already become an important field in the medical field for diagnostic and drug delivery applications. Carbon-60 molecules which are also known as fullerene promises good appliance in medical field. Cylindrical fullerenes are known as carbon nanotubes. Carbon nanotubes can be synthesized in many forms. Single walled nanotubes and multi walled nanotubes are two important materials. A carbon nanotubes bent into a torus is known as nanotorus. Carbon nanobuds are latest member in Nanomaterials category which is created by the combination of carbon nanotubes and fullerenes. Fullerene in the form of buds is connected to carbon nanotubes by covalent bonding in nanobuds. Bonding is achieved between fullerene buds and sidewalls of carbon nanotubes. The main application of nanobuds is in field emission applications since they are excellent field emitters. Since the fullerene buds prevents slipping of nanotubes, nanobuds can be used as molecular anchors.

Spool valves

Control valves are required in pneumatic and hydraulic systems to direct and regulate the flow of fluid from compressor or pump to the various load devices. Relief valves are infinite position valves. Finite position valves are used for passage or blocking of fluid flow. There can be either two or four parts for control valves. The three major types of control valves are poppet valves, rotary valves and spool valves. Simple discs, balls and cones are used in poppet valves. The two varieties of poppet valves are 2/2 simple valve and 3/2 valve. Poppet valves are economical but require large operating force. Rotary valves are used for hand operation in pneumatic systems. They are compact and have low operating forces. Spool valves are constructed with a spool moving horizontally within the valve body. The spool can be easily moved as there is no net force acting on the spool due to system pressure. There are two types of spool valves. They are two-way spool valve and four-way spool valve. Spools are shifted during the operation of spool valves. For this, a button, lever or a solenoid is used.

Microwave tunnel diodes

Tunnel diodes can be used in microwave applications. Quantum tunneling theory is used to explain the tunneling phenomenon that take place in tunnel diodes.  Tunneling phenomenon is actually a majority carrier effect. Some of the advantages of tunnel diodes are low cost, less weight, high speed, low noise, high peak current to valley current ratio and low power operations. These parameters make tunnel diodes ideal candidate in applications like microwave amplification and microwave oscillation. The tunnel diode is a p-n junction semiconductor diode with negative resistance. Tunnel effect is responsible for this negative resistance. Heavy doping is employed during the construction of tunnel diodes. In tunnel diodes, Fermi level lie inside the valence band in p-region and inside the conduction band in n-region. While using for amplifier applications, tunnel diodes are connected either in parallel or in series with a resistive load. Another common practice is connecting tunnel diode to a microwave circulator.