ELEC 301 Projects Fall 2007

This work was created using the Connexions authoring platform. This platform will be retired as of the end of 2021.  This work has been migrated to PDF format for continuous access to the educational content, however any embedded links within the text to the legacy platform may no longer be accessible

NANOCRYSTALLINE TiO2 ELECTRODES EXHIBITING HIGH STORAGE CAPACITY AND STABILITY IN RECHARGEABLE LITHIUM BATTERIES

Nanocrystalline TiO 2 films were explored for the first time as electrode material for a rechargeable lithium intercalation cell, i.e., Li/LiCF3SO3 + PC/TiO 2. Two kinds of nanocrystalline films, TiO 2 F387 (Degussa) and TiO 2 colloid-240, were investigated. These films exhibited excellent performance renderin[s them a promising choice for secondary battery applications. At a current density of 0.01 mA/cm", two voltage plateaus at 1.78 and 1.89 V were observed for TiO 2 F387 films during charge and discharge, respectively. The TiO 2 electrode charge capacity per unit weight rose with decreasing current density. The highest capacity, obtained at a current density of 0.005 mA/cm 2 and a final discharge voltage of 1.4 V, was 265 mAh/g corresponding to a lithium insertion ratio of x--0.8. Nanocrystalline TiO_ colloid-240 films showed a similar performance. The cycle life of a TiO 2 colloid-240 cell at a high current density was found to be excellent; a capacity loss lower than 14% has been observed over 100 charge/discharge cycles

VOLTAGE-CONTROLLED SMALL SIGNAL ANALYSIS OF REAL SPACE TRANSFER TRANSISTOR

The research of determining the small signal equivalent circuit of the real space transfer (RST) transistor is investigated in this work. We propose a voltage-controlled mode model, called parameter extraction, to describe the performance of RST transistors at high frequency range. Besides, we also employ the value-determined model to simulate the microwave characteristics of RST and the theoretical and experimental results are compared. The influence of variables of RF performance is analyzed and theoretical results show that the cut-off frequency ( f T ) is mainly affected by the leakage resistances and the dimension of metal contact, but the maximum available gain frequency, f max , is dependent on contact resistances

INSUFFICIENCIES OF THE SINGLE EXPONENTIAL MODEL AND EFFICIENCY OF THE DOUBLE EXPONENTIAL MODEL IN TIlE OPTIMIZATION OF SOLAR CELLS EFFICIENCY

Single and double exponential models are confronted to determine the most adapted model for optimization of solar cells efficiency. It is shown that the single exponential model (SEM) presents some insufficiencies for efficiency optimization. The interest of the double exponential model to optimize the efficiency and to achieve an adequate simulation of the operation of solar cells is demonstrated by means of I-V characteristics plotting

FLAT TYPE THICK FILM INDUCTIVE SENSORS

Two thick film flat-type inductive sensors are described and tested for distance and profile measurement. The first one is a single-layer spiral while the second one is a multi-layer structure consisting of ten spirals one over the other. The paper describes their geometric configurations together with their simulated magnetic fields and it reports the results from the characterization test i.e. the series-equivalent circuit parameters, the sensitivity and the cross-sensitivity to temperature. An experimental analysis of the sensitivity suggests that optimized values are obtained by an appropriate choice of the working frequency. The sensors are shielded against e.m. noise coming from the nonsensitive area. Moreover, two sensors have been tested in the laboratory using the single layer as a distance sensor and the multi-layer as a transducer for the measurement of a metallic object profile. The results of the tests show a maximum sensitivity of 14 mV=mm and a resolution of 0.6 mm for the single layer, while the multi layer one reconstructs the profile with an axial resolution of a few microns and a lateral resolution better than 200 mm

NEW RESULTS ON BANDWIDTH OF GaAs PIN PHOTODIODES

In this paper an equivalent circuit of a GaAs PIN photodiode for the millimeter wave range is proposed. Moreover, an approximate expression for the bandwidth of this circuit is obtained. By using the effective quality factor concept, an equation that includes the value of a hypothetical resistance involved in the circuit mentioned above, is derived. In the context of fiber optic communications, this "resistance" represents the losses due to the fiber-photodiode coupling