Device operation improving power efficiency

Besides the two main characteristics of sensitivity as well as specificity of a sensor, the industrial, military, and other standards demand the device to be portable, economical, autonomous, and power efficient. In order to address some of these characteristics, the authors in their respective laboratories have been working on improving the design of the prototype, as shown in Figs. 15.6 and 15.7, respectively. The necessaiy electronics consisting of local oscillators, beat oscillators, smaller cavities, mixers, and phase-locking loops have been assembled in prototypes. As of this date the device needs further evaluation in an operational environment to establish a set of encyclopedic data and for comparison with unknown toxins. 

At maximum power, a typical fuel cell operating on hydrogen is only 50% efficient. This translates into 1W of thermal power that needs to be dissipated for every watt of electricity produced. A battery typically operates at an efficiency of 80%i or more. Therefore, the use of a fuel cell can increase the thermal load in an electronic device by 60-100%i. The fuel cell efficiency can be improved by operating the stack at a higher voltage. However, this requires oversizing the stack, which increases the mass and the volume of the power supply, and also, perhaps more significantly, increased cost. 

When a transformer-rectifier operates at full current but below its rated output voltage, its power efficiency declines. This is because the losses remain virtually unchanged while the power output falls proportionately with voltage. If the same transformer-rectifier operates at full voltage but below its rated output current, the reverse is true. The power efficiency increases because the resistive losses decrease with the square of the current while the power output falls only linearly. The efficiency improvement is not as great as might be expected from this statement, because the no-load (iron) losses of a transformer do not reduce at all and the rectifier losses are only partly resistive. The latter reflects the fact that semiconductor devices have fixed voltage drops in addition to their resistive losses. 

The interface between the organic layer and metallic anode of an OLED is crucial to the stability and the performance of the device. The a-septithiophene (a-7T) has been used as the buffer layer at the interface between the ITO electrode and the hole transport layer (HTL). The insertion of a-7T layer lowered the operating voltage and improved the external power efficiency. Moreover EL emission was not saturated up to 1600mA/cm. The Maximum EL intensity was over 17000cd/m and the maximum external power efficiency at 2000cd/m is 6.41m/W and that at lOOcd/m is 9.341m/W. The EL intensity and external power efficiency of OLEDs depend on the thickness of the a-7T layer. 

Compact and stable devices are available that take advantage of the improved quality of the crystal lasers, as well as increased pump efficiencies. Hundreds of different models of Nd + based lasers have demonstrated laser action (Kaminskii, 1981). It is possible to operate these Nd + solid state lasers in the continuous regime, with output powers ranging from 1 W to 1000 W. Pulsed operation is also possible, with a pulse length from the picosecond range, via mode-locking, to tens of nanoseconds by Q-switch operation. 

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