Abstract: Disclosed are polyvinylidene fluoride hollow fiber separation membranes and a preparation method thereof, and more particularly, to polyvinylidene fluoride hollow fiber separation membranes, which may be usefully used not only for water treatment, but also in the sewage treatment field, such as domestic waste water, industrial wastewater, or the like because the polyvinylidene fluoride hollow fiber separation membranes possess excellent pure water permeability and chemical resistance such as alkali resistance, etc.

Abstract: We propose overhear-based transmitting control system in WLANs to improve performance of 802.11 wireless LANs. The main idea of this scheme is that when the transmission of a node fails, one of neighboring nodes with better channel quality retransmits the lost frame in substitution. To do so, every node should maintain overhear table to buffer the transmitted packets that is not yet acknowledged. We also present algorithms to retransmit lost packets, to maintain the overhear table and to compensate for the retransmission of packets of other nodes. The performance of this scheme is evaluated via simulations in terms of MPDU size and average path loss. It shows that in environments where the packet is likely to be lost more, the throughput gain of our proposed scheme performs better.

Abstract: We propose overhear-based transmitting control system in WLANs to improve performance of 802.11 wireless LANs. The main idea of this scheme is that when the transmission of a node fails, one of neighboring nodes with better channel quality retransmits the lost frame in substitution. To do so, every node should maintain overhear table to buffer the transmitted packets that is not yet acknowledged. We also present algorithms to retransmit lost packets, to maintain the overhear table and to compensate for the retransmission of packets of other nodes. The performance of this scheme is evaluated via simulations in terms of MPDU size and average path loss. It shows that in environments where the packet is likely to be lost more, the throughput gain of our proposed scheme performs better.

Abstract: A domestic nanofiltration membrane based water purifier without a storage tank. The water purifier according to the present invention uses a nanofiltration membrane filter as a main filtering section and does not have a storage tank for containment of purified water. Although conventional reverse osmosis membrane based water purification systems provide good quality water, they have problems in that installation of the storage tanks due to insufficient flow rate results in the increased volumes of water purifiers, and at the same time, secondary pollution may be caused by microorganism propagation upon prolonged storage. In this regard, the present invention provides a domestic nanofiltration membrane based water purifier without a storage tank, in which a nanofiltration membrane filter with a pore size of approximately 0.1 to 10 nm is used as a main filtering section.