Measurement and analysis of earth's magnetic field based on low-magnetic field standards
The Cheongyang (CYG) observatory has been built to measure earth's magnetic field and to study prediction of earthquake and space weather. The equipments of the CYG observatory are a 3-axis fluxgate magnetometer, an overhauser effect proton magnetometer, a declination/inclination magnetometer and a data logger. A Cs-4He atomic magnetic resonance magnetometer was used to correct the measured data obtained by the proton magnetometer. All the measurement equipments were calibrated using magnetic field standard system maintained at KRISS. The Measurement results show a variation of the baselines less than 5 nT within one year, which is the most critical requirement criteria for joining the INTERMAGNET (International Real-time Magnetic Observatory Network).
An algorithm which can obtain the global walking direction
This paper proposes an algorithm to obtain the global walking direction despite magnetic field interferences indoor. This algorithm can be applied to the phone's compass. If the user is walking in the opposite direction of the phone's compass (North). The user's global walking direction would be “South”. The phone's compass equipped a magnetometer collects data. This algorithm treats these data as signals and eliminates some high frequency components by passing them through a low pass filter. This algorithm opportunistically selects three consecutive vectors which are not parallel. Then it decomposes the three vectors into two directions. One is the earth's magnetic field vector. The other is the interference vector. It subtracts the earth's magnetic field vector from the compass reading vector and offers the interference vector. Then this algorithm calculates the coordinates of the pairwise intersections of the three interference vectors. Experiments show that the right geomagnetic north vector makes the locus of intersection points forms likes an oval or a closed loop. The accuracy of this algorithm is higher than the traditional compass. The global walking direction can be outputted by comparing the walking direction against this geomagnetic north vector.
Simulation study of high power microwave generation by virtual cathode oscillation in coaxial vircator
Summary form only given, as follows. We have numerically simulated the high power microwave generation by virtual cathode oscillation in a coaxial vircator with 3 dimensional PIC code Magic. It is noted that the coaxial vircator has the advantage of an enhancement of power efficiency and gaining of narrow bandwidth frequency. The study is focused on the design of a diode structure for a coaxial vircator suitable for Chundoong IREB pulser (Max. 600 kV, 85 kA, 60 ns). It consists of a center annular cathode, a cylindrical meshed-anode and a reflector. The simulation results showed that the coaxial vircator can indeed be operated at the selected frequency with the narrow bandwidth and the microwave output power strongly depends on the position and geometry of the reflector. From this simulation results we expect that the maximum microwave output power will be obtained by the reflector of 4 cm in width and also 4 cm in distance away from the IREB, where the resonant frequency of microwave from coaxial vircator is simulated to be 6.577 GHz.