A NEW DESIGN METHODOLOGY FOR PRINTED LOG-PERIODIC MONOPOLE ANTENNA

In theory, Log-Periodic Antenna (LPA) is a linearly polarized antenna with frequency independent properties on the input impedance and gain patterns. Owing to these characteristics, LPA has gained research interests and been employed for many wideband applications. A Printed Log-Periodic Dipole Antenna (PLPDA) with multiple notched bands is proposed for Ultra-WideBand (UWB) applications. An antenna with the notched frequencies of 1.03 GHz, 1.28 GHz, 1.72 GHz, 2.24 GHz and 2.51 GHz is designed, fabricated, and measured. An antenna model was established on the substrate of FR4 and feed by a stripline. The simulation results show that the antenna can achieve an impendence wide bandwidth from 0.89 to 2.58 GHz with return loss less than -10 dB and exhibit stable antenna gain. Furthermore, the measurement result is better consistent with simulation result.

PCB Base Log-periodic Antenna for Mobile Communications

A log-periodic antenna can provide directivity and gain when operating in a wide band.The log-periodic antenna is used in many applications where wide bandwidth is required along with direct and medium gain.This research implements a sequential approach to the design and simulation of the performance of a printed log-periodic dipole antenna(LPDA)capable of operating in the 1800 MHz frequency range.The advantage of this antenna is the compactness and easy integration into planar circuits suitable for applications requiring wide bandwidth and high gain.The dimension of the designed antenna was originally calculated taking high frequency as 1885 MHz and low frequency as 1805 MHz,then modeled using HFSS-13 electromagnetic simulation to determine the effect of substrate dielectric properties on dipole width and length for element optimization.The design was verified by creating and measuring S11 and radiation diagrams.The designed antenna has a total gain of 7.9 dB and a wide bandwidth.

Log-periodic quantum oscillations in topological or Dirac materials

As a manifestation of the underlying physical nature, quailtum oscillations with the applied magnetic field (B) are one of the most important topics in condensed matter physics. The research history can be tracked to 1930 when Lev Shubnikov and W. J. de Haas observed Shubnikov-de Haas (SdH) oscillations in the magnetoresistance (MR) of bismuth crystals. Since then, researchers have observed quantum oscillations in diverse materials, including metals, metallic compounds, semimetals, semiconductors and even insula tors, as well as in artificial mesoscopic microstructures . Nowadays, quantum oscillation detec ted by magneto transport investigation has been a powerful tool to detect the physical properties in solid-state systems.

Analysis of Onset and Development of Ore Formation in Dajishan Tungsten Ore Area,Jiangxi Province,China

The ＂theory of self-similar oscillatory finite-time singularities＂ of Sornette reflects accurately the spatio-temporal evolution and trends of development of events and processes in complex systems approaching to the singularities, and the effect of prediction for catastrophic events has been tested to be satisfactory. The authors take the contents of the chemical element tungsten as the carrier of positive feedback （or activator） in the ore formation, then try to apply the theory to studying and analyzing the onset and development of ore formation in the Dajishan （大吉山） tungsten ore area, Jiangxi （江西） Province, China. The results of the study show that during the spatio-temporal evolution from outside the ore area to its center, the contents of the chemical element tungsten and their loga- rithmic derivatives （local fractal dimension） manifest an obvious regularity： by way of the process of oscillation and the transition to power-law accelerating growth, they eventually approach the center of ore formation. The regularity makes clear that in the complex ore-forming system of the Dajishan tungsten ore deposit, the chemical element tungsten plays the role of carrier of positive and negative feedback, and by competing with each other, approaches to singularity in finite time by virtue of self-similar log-periodic oscillations and succeeded by power-law accelerating growth. In this way the onset of ore formation is realized. This regularity reflects correctly the dynamic process of ore formation of the studied ore deposit. The authors hold that Sornette＇s theory can be further applied to the prediction of perspective areas.