Abstract: Disclosed herein are a surge prevention apparatus and method for a centrifugal compressor. The surge prevention apparatus includes a control unit for controlling a gas provision operation based on a flow rate and pressure on an inlet side of a compressor and pressure on an outlet side of the compressor, and a gas provision unit for storing a part of gas flowing into the inlet side of the compressor and providing the stored gas to the inlet side in response to a control signal from the control unit.

Abstract: A multi-hop relay maritime communication apparatus installed in a ship is disclosed. The maritime communication apparatus includes a first access module configured to comprise a plurality of directional antennas integrally formed; a second access module configured to comprise an omni-directional antenna; and a bridge configured to be connected to the first access module and the second access module via an Ethernet interface.

Abstract: A multi-hop relay maritime communication apparatus installed in a ship is disclosed. The maritime communication apparatus includes a first access module configured to comprise a plurality of directional antennas integrally formed; a second access module configured to comprise an omni-directional antenna; and a bridge configured to be connected to the first access module and the second access module via an Ethernet interface.

Abstract: The present invention relates to an apparatus and method of performing wireless communication using multiple directional antennas. The transportation means according to the present invention includes at least two communication devices, wherein one of the at least two communication devices, communication device A, includes a directional antenna group 1, and the other communication device, communication device B, includes a directional antenna group 2, and wherein the communication device A performs directional antenna selection control of the directional antenna group 1 included in the communication device A depending on whether the communication device B is connected with a network. According to the present invention, one of the communication devices gains access to a satellite station, a base station, or other ships, at least one antenna of another communication device may be used to relay wireless communication and may play a role as a base station or an AP.

Abstract: Disclosed herein are a maritime communication apparatus and method. The maritime communication apparatus includes a land-based network communication unit, a maritime network communication unit, and a communication control unit. The land-based network communication unit communicates with a land-based communication network. The maritime network communication unit communicates with a maritime communication network. The communication control unit links the communication of the land-based network communication unit with the communication of the maritime network communication unit in accordance with a destination address of data provided by any one of the land-based network communication unit and the maritime network communication unit.

Abstract: Disclosed herein are a surge prevention apparatus and method for a centrifugal compressor. The surge prevention apparatus includes a control unit for controlling a gas provision operation based on a flow rate and pressure on an inlet side of a compressor and pressure on an outlet side of the compressor, and a gas provision unit for storing a part of gas flowing into the inlet side of the compressor and providing the stored gas to the inlet side in response to a control signal from the control unit.

Abstract: An antenna switching system according to an exemplary embodiment of the present invention includes a plurality of directional antenna which is mounted in a ship to receive a wireless signal; an antenna switch which selects one of the plurality of directional antennas; a modem which is connected to the directional antennas through the antenna switch to extract a strength of a received signal; and a switching determining unit which outputs an antenna selection signal to the antenna switch based on the strength of the received signal and GPS/DR information of a transmission side ship and its own ship.

Abstract: Disclosed herein are a method and apparatus for generating multiband Radio Frequency (RF) signals in maritime wireless communication. The apparatus includes a baseband conversion unit, a phase compensation unit, a Direct Current (DC) offset compensation unit, and an RF transmission unit. The baseband conversion unit converts RF signals corresponding to a baseband modulation signal having a negative frequency and a baseband modulation signal having a positive frequency into baseband signals, respectively. The phase compensation unit eliminates the images of multiband signals so as to correspond to the baseband signals. The DC offset compensation unit compensates the baseband modulation signals for DC offsets using the multiband signals from which the images have been eliminated. The RF transmission unit generates the RF signals using the signals which have been compensated for the DC offsets, and sends the RF signals via an antenna.

Abstract: A time synchronization method in a wireless sensor network, a low power routing method using a reservation scheme, and an apparatus for performing the method are provided. The time synchronization method in the wireless sensor network may include: receiving a first synchronization request command packet from a parent node that manages time synchronization for a predetermined synchronization region; receiving, from the parent node, a second synchronization request command packet that has a transmission timestamp value of the first synchronization request command packet; and performing time synchronization for a child node based on a reception time of the first synchronization request command packet, a reception time of the second synchronization request command packet, and the transmission timestamp value of the first synchronization request command packet.

Abstract: The present invention relates to an apparatus and method of performing wireless communication using multiple directional antennas. The transportation means according to the present invention includes at least two communication devices, wherein one of the at least two communication devices, communication device A, includes a directional antenna group 1, and the other communication device, communication device B, includes a directional antenna group 2, and wherein the communication device A performs directional antenna selection control of the directional antenna group 1 included in the communication device A depending on whether the communication device B is connected with a network. According to the present invention, one of the communication devices gains access to a satellite station, a base station, or other ships, at least one antenna of another communication device may be used to relay wireless communication and may play a role as a base station or an AP.

Abstract: Disclosed herein are a maritime communication apparatus and method. The maritime communication apparatus includes a land-based network communication unit, a maritime network communication unit, and a communication control unit. The land-based network communication unit communicates with a land-based communication network. The maritime network communication unit communicates with a maritime communication network. The communication control unit links the communication of the land-based network communication unit with the communication of the maritime network communication unit in accordance with a destination address of data provided by any one of the land-based network communication unit and the maritime network communication unit.

Abstract: A vessel block arranging device extracts image information on a vessel block loaded on a transporter, and determines whether to arrange the vessel block in an area in which the vessel block will be arranged by using location information of the arranged vessel block in the area and extracted image information, thereby reducing errors caused by determining the vessel block arrangement.

Abstract: Disclosed herein is a circularly polarized antenna with a wide beam width, in which four U-shaped metal strips are disposed in a circular shape, and four signals having the same magnitude and phase difference intervals of 90 degrees are fed to the respective metal strips so as to transceive circularly polarized waves. The disclosed circularly polarized antenna includes a ground plane, a central patch formed in the center of an upper surface of the ground plane, and a plurality of radiation patches disposed above the ground plane and around the central patch in a circular shape, wherein signals having the same magnitude and preset phase differences are fed to respective radiation patches.

Abstract: A method includes: placing a Radio Frequency Identification (RFID) tag for underground use under a ground surface, wherein a ground plate which has a diameter greater than that of the RFID tag or a tag antenna and on a top of which the RFID tag is mounted is placed underground such that the RFID tag protrudes above the ground surface or a bottom of the RFID tag is aligned with the ground surface.

Abstract: There are provided an apparatus and method for traffic performance improvement and traffic security in an interactive satellite communication system. The method for traffic performance improvement of an interactive satellite communication system includes the steps of: a) storing an Internet protocol (IP) packet that is received from a user terminal connected to a satellite mobile terminal of the interactive satellite communication system and is to be transmitted to a central station through a satellite; b) transmitting acknowledgement for the stored IP packet to the user terminal by acting for the central station, before the stored IP packet is transmitted to the central station; and c) transmitting the stored IP packet through the satellite to the central station, and retransmitting an unacknowledged IP packet according to a retransmission request of the central station.

Abstract: A time synchronization method in a wireless sensor network, a low power routing method using a reservation scheme, and an apparatus for performing the method are provided. The time synchronization method in the wireless sensor network may include: receiving a first synchronization request command packet from a parent node that manages time synchronization for a predetermined synchronization region; receiving, from the parent node, a second synchronization request command packet that has a transmission timestamp value of the first synchronization request command packet; and performing time synchronization for a child node based on a reception time of the first synchronization request command packet, a reception time of the second synchronization request command packet, and the transmission timestamp value of the first synchronization request command packet.

Abstract: Provided are a system and method for guiding a visitor using a sensor network. The system includes: an entry approval requesting unit for requesting an entry approval of the visitor to the visitee terminal according to destination information; a route setting unit for setting a route along which the visitor terminal is to move to the destination, based on the destination information of the visitor, according to an entry approval result of the visitee terminal; a location detecting unit for detecting a current location of the visitor terminal based on identification information of the visitor terminal and location information of the sensor node, the identification information and the location information being obtained through the sensor network on the route; and a location confirming unit for confirming if the detected current location of the visitor terminal is out of a preset area.

Abstract: A vessel block arranging device extracts image information on a vessel block loaded on a transporter, and determines whether to arrange the vessel block in an area in which the vessel block will be arranged by using location information of the arranged vessel block in the area and extracted image information, thereby reducing errors caused by determining the vessel block arrangement.

Abstract: A transmitter of an apparatus position in a moving body transmits a first move command signal for moving a radio frequency identification tag to a location within an identification distance to a receiver positioned within a communication distance. A radio frequency identification reader of the moving body transmits an information request signal to the radio frequency identification tag that moves from a first location to a second location corresponding to a location within an identification distance in accordance with a first move command signal and receives a response signal corresponding to the information request signal from the radio frequency identification tag.

Abstract: Provided is a wireless sensor network using a dynamic message routing algorithm and a method of controlling the wireless sensor network. Therefore, a network system can be provided, in which each sensor node calculates a relay probability, periodically updates the relay probability, and dynamically determines a node for relaying a message on the basis of the relay probability, so that throughput per node is improved and a media access control (MAC) layer is not needed.