Studies on parametric sensitivity and safe operation criteria of batch processes

Heat accumulation in batch reactors may eventually lead to a temperature runaway. Critical values of process parameters were used to investigate process safety. Parameter sensitivity is discussed for a wide range of operating conditions. Two criteria for safe operation are presented, based on critical values of process parameters.     

A Convergence-Free Predistortion Technique for Adaptive Linearisation of RF Power Amplifiers

Adaptive digital baseband predistortion is a well-known linearisation technique for removing intermodulation products that radio frequency power amplifiers (PAs) introduce. This paper proposes a new baseband predistortion method that is based on a non-iterative, fast adaptation algorithm without convergence restrictions. The response of the PA in a batch of training magnitude stimuli is used for the computation of the predistortion gain. The latter is directly extracted in rectangular form without prior transformations and AM/AM and AM/PM non-linearities sequential estimation. The influence of the gain table size and the imperfections of the modulator and demodulator in the method's performance are examined. Experimental measurements of an in-house prototype show a linearity improvement of about 25 dB.     

On the high temperature electrical resistivity behaviour of Cu55-Ni45 alloy

Resistivity measurements supplemented with electron microscopy investigation in a Cu₅₅-Ni₄₅ alloy are reported, in the temperature range 273–700 K. An anomalous high temperature resistivity minimum is observed at 673 K whereas at the same temperature diffuse intensity maxima appear. It is suggested that the resistivity minimum could be attributed to the effect of short range order cluster formation.     

On the structural and transport properties of the Ni-Fe invar alloy system

Several experiments concerning structural, electrical and magnetic properties of the NiFe alloy system near the composition range Fe₃Ni and temperatures ranging from 300 to 1000 K have been conducted. TEM studies using a heating stage showed transformation α→v upon heating and v→α upon cooling. Electrical resistivity measurements in the same temperature range indicate also the presence of (α+v) phase, whereas magnetic measurements in the temperature range 4,2–1000 K and fields up to 100 kOe show no indication of an ordered state.     

A correlation for the thermal delay of buildings

A correlation is developed which expresses the thermal delay of buildings in terms of mean indoor temperature increase over mean outdoor temperature, heating power density including solar radiation, and size of building, for various building types. The correlation is based on a finite-difference solution of a system of coupled differential equations describing the transient heat transfer and energy balance in buildings.     

Preparation of a selective receptor for ephedrine for the development of an optical spot test for the detection of ephedrine in human urine using stabilized in air lipid films with incorporated receptor

The present technique describes the preparation of a selective receptor for ephedrine and a simple sensitive spot optical test for the rapid one-shot detection of ephedrine in human urine using lipid films with an incorporated receptor that are synthesized by a chemical reaction with a methacrylate polymer on a glass fiber filter. The selective receptor was synthesized using a resorcin[4]arene receptor and by transforming all the -OH groups into methoxy groups. The lipid films without this receptor provided fluorescence under a UV lamp. The use of the receptor in these films quenched this fluorescence, and the color became similar to that of the filters without the lipid films. A drop of aqueous solution of ephedrine provided a "switching on" of the fluorescence, which allows the rapid detection of this stimulant in human urine at the levels of 10(-8) M concentrations. The effect of potent interferences (i.e., proteins, lipids, ascorbic aid, glucose, leucine, glycine, tartrate, citrate, bicarbonate, and caffeine) was examined. The results showed no interferences from these compounds in concentration levels usually found in human urine samples. Dopamine was also investigated as a potent interfering agent, and the results have shown that the transformation of the hydroxy to methoxy groups has altered the selectivity of the receptor. This species does not cause interference at concentration levels lower than 10(-6) M. A drop of urine containing ephedrine provided also a "switching on" of the fluorescence, which allows the rapid detection of this stimulant in human urine at the levels of 10(-8) M concentrations. The reproducibility of the method was checked in approximately 100 samples, and all of them were found to provide similar results. Note that the colors of the filters remain stable for periods of more than 2 months.     

The net effect of ultraviolet radiation on atmospheric dimethylsulphide over the Southern Indian Ocean

Dimethylsulphide (DMS) in the atmosphere may play an important role in the climate system. This study shows an inverse relationship between ultraviolet extremes and atmospheric DMS, independent of changes in wind speed, sea-surface temperature and photosynthetically active radiation, as measured at Amsterdam Island in the Southern Indian Ocean.