Papers by Keyword: Dual Frequency

Abstract: Biodiesel production from waste-or by-product oils having high free fatty acid (FFA) contents is required oil pretreatment. Esterification has been used to reduce FFA contents of crude oils prior to transesterification. In this present work, palm empty fruit bunch (EFB) oil which is a by-product from the palm oil industry was used as feedstock for biodiesel production. The EFB oil has very high FFA contents. Thus, esterification of the oil was carried out. The esterification was enhanced by dual frequency ultrasound waves (28 kHz + 40 kHz). Zeolite was used as a heterogenous acid catalyst. Methanol to oil (M:O) molar ratio, catalyst loading, and reaction were main factors affecting on the process and were investigated using central composite design (CCD) of experiment. Response surface methodology (RSM) was used to optimise these parameters. The results showed that at the optimised condition of 12:1 M:O molar ratio, 11.36 %wt catalyst loading and 60 min of reaction time, the FFA conversion was highest at 91.69% compared with the predicted value of 93.56% which was only 1.99% difference between tested and predicted values.

Abstract: With the rapid development of RFID (radio frequency identification) application, the design requirements of RFID tag antenna are also increasing. A design of dual-frequency or multi-frequency tag antenna has become fashionable. In the present paper, we design a dual-band RFID tag antenna, which consists of a bent microstrip patch and rectangular microstrip patch. The designed antenna is analyzed and optimized by HFSS13. Simulation results indicate that the tag antenna has the characteristics of double band, high gain, and good radiation pattern.

Abstract: The newly broadcast GPS L2C signal will be extensively used due to its superiority. In order to acquire L2C signal fast in a dual-frequency GPS receiver, this paper firstly discusses two traditional acquisition algorithms, then proposes and implements a new algorithm based on the fixed phase relationships among C/A code, CM code and CL code and the fixed relationships of Doppler shift between the L1 channel and L2 channel. The experimental result demonstrates that the new acquisition algorithm can speed up the acquisition process substantially. It also suits other dual-frequency navigation receivers.

Abstract: A study of thermal field in induction melting with cold crucible and dual induction frequencies is presented in this paper. Numerical simulation was done by finite element based software COMSOL with use of multi-physical modeling. A method of superposing of magnetic vector potential is proposed to solve the complexity of dual induction frequencies. Different conditions of high and low frequencies were given in the calculation to find the effects on distribution of thermal fields. The computed temperature distribution was compared with the macro etched section of solidified ingots and the results showed that the orientation of dendritic grain structures follow to the similar direction of heat flow. This indicates that proper set of induction coils could enable more uniform thermal field distribution and attaining controlled solidification morphology in the ingots.