Characteristics and Temperature Compensation of Non-Dispersive Infrared (NDIR) Alcohol Gas Sensors According to Incident Light Intensity

This paper discusses the output characteristics of the sensor response of infrared ethanol gas detectors based on incident radiation intensity. Sensors placed at each focal point of two elliptical waveguides were fabricated to yield two module combinations and to verify the output characteristics. A thin Parylene-C film was deposited onto the reflector surfaces of one module. The thermal properties were compared between the sensor (2.0 Ø) and sensor with a hollow disk (1.6 Ø), the disk being mounted at the end of one detector. The fabricated sensor modules were placed inside a gas chamber. The temperature was increased from 253 K to 333 K, over the concentration range from 0 to 500 ppm. As the temperature increases by 10 K, the output of sensor (2.0 Ø) without and with Parylene-C coating typically increased by 70 mV and 52 mV, respectively. However, the sensor output with the hollow disk showed an average decrement of 0.8 mV/50 ppm and 1 mV/50 ppm for module without and with Parylene-C deposition, respectively. For concentrations higher than 50 ppm, the estimation error was around ±5%. Further, the sensitivity to temperature variation and the absorbance of infrared (IR) reflection was found higher for Parylene-C coated module.

Модификация спектров фотопроводимости в композитных структурах ZnO-квантовые точки CdSe под действием дополнительного фотовозбуждения

The incorporation of CdS nanocrystals into a porous ZnO matrix results in sensitization of the composite in the visible spectral region. Studies of the photoconductivity spectra upon variable external illumination show that the spectra undergo reversible transformations. It is shown that the shape of the peak and the position of the local photoconductivity maximum corresponding to nanocrystals depend on the wavelength distribution of the incident radiation intensity. The mechanisms responsible for the process are discussed.

Saturation characteristics of SF6 absorption at the 10.4 μm band of CO2

Measurements were made of the saturation characteristics of the SF6 absorption at the 10.4 μm band of CO2, using a pulsed CO2 laser. It is shown that the observed nonlinear absorption properties can be divided into three characteristic regions, namely P(12)–P(16), P(18)–P(22), and P(24)–P(30), each of which has distinctive features in the measured transmission as a function of incident radiation intensity. In each region, this transmission behaviour, together with associated dynamical effects such as pulse shaping, are amenable to interpretation by means of a four-level model for the SF6 absorption. The relevant molecular parameters are determined by comparison of theory with experiment.

Optimization of Focusing Solar-Collector Design

A set of general graphical relationships has been developed for establishing the receiver-reflector area ratio which will provide the maximum useful heat delivery from a focusing collector. The method, applied to paraboloids and parabolic cylinders, gives the optimum area ratio in terms of incident radiation intensity, optical properties (including precision of reflector), and thermal loss rate. Use of the method for design and for evaluation of existing reflectors is illustrated; its use in economic optimization will be dependent on availability of adequate cost data.