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Ejector-equipped transcritical R744 condensing units are believed to lead to a low-to-zero commercial refrigeration sector. In order to overcome the persisting barrier to their wider adoption represented by the lack of an affordable ejector control technique, the novel pulse-width modulation (PWM) ejector, being low cost, simple and invulnerable to clogging was recently implemented. However, additional experimental evaluations are needed. Therefore, in this experimental work the performance of two PWM ejector-equipped transcritical R744 condensing units, i.e. with and without overfed evaporator, was carried out. The experimental assessment was implemented at the medium temperature (MT) of about -5°C, heat sink temperatures from 30°C to 40°C and compressor speeds from 40 Hz to 60 Hz. The outcomes obtained revealed that the PWM ejector can effectively control the high pressure in transcritical operating conditions, regardless of the selected heat sink temperature and compressor speed. In addition, at the same cooling capacity, the PWM ejector-equipped R744 system was found to permit energy savings between 7.0 % and 11.1 % without overfed evaporator and between 11.5 % and 16.3 % with overfed evaporator compared to the standard R744 unit (i.e. with vapour by-pass valve and without ejector), respectively. Finally, higher values of coefficient of performance (COP) were found to be offered by the PWM ejector compared with its today's available competitors

In standard critical care practice, cuff sphygmomanometry is widely used for intermittent blood pressure (BP) measurements. However, cuff devices offer ample possibility of modulating blood flow and pulse propagation along the artery. We explore underutilized arrangements of sensors involving cuff devices which could be of use in critical care to reveal additional information on compensatory mechanisms. In our previous work, we analyzed the response of the vasculature to occlusion perturbations by means of observations obtained non-invasively. In this study, our aim is to (1) acquire additional insights by means of invasive measurements and (2) based on these insights, further develop cuff-based measurement strategies. Invasive BP experimental data is collected downstream from the cuff in two patients monitored in the OR. It is found that highly dynamic processes occur in the distal arm during cuff inflation. Mean arterial pressure increases in the distal artery by 20 mmHg, leading to a decrease in pulse transit time by 20 ms. Previous characterizations neglected such distal vasculature effects. A model is developed to reproduce the observed behaviors and to provide a possible explanation of the factors that influence the distal arm mechanisms. We apply the new findings to further develop measurement strategies aimed at acquiring information on pulse arrival time vs. BP calibration, artery compliance, peripheral resistance, artery-vein interaction.

In standard critical care practice, cuff sphygmomanometry is widely used for intermittent blood pressure (BP) measurements. However, cuff devices offer ample possibility of modulating blood flow and pulse propagation along the artery. We explore underutilized arrangements of sensors involving cuff devices which could be of use in critical care to reveal additional information on compensatory mechanisms. In our previous work, we analyzed the response of the vasculature to occlusion perturbations by means of observations obtained non-invasively. In this study, our aim is to (1) acquire additional insights by means of invasive measurements and (2) based on these insights, further develop cuff-based measurement strategies. Invasive BP experimental data is collected downstream from the cuff in two patients monitored in the OR. It is found that highly dynamic processes occur in the distal arm during cuff inflation. Mean arterial pressure increases in the distal artery by 20 mmHg, leading to a decrease in pulse transit time by 20 ms. Previous characterizations neglected such distal vasculature effects. A model is developed to reproduce the observed behaviors and to provide a possible explanation of the factors that influence the distal arm mechanisms. We apply the new findings to further develop measurement strategies aimed at acquiring information on pulse arrival time vs. BP calibration, artery compliance, peripheral resistance, artery-vein interaction.

The design of bioinspired systems for chemical sensing is an engaging line of research in machine olfaction. Developments in this line could increase the lifetime and sensitivity of artificial chemo-sensory systems. Such approach is based on the sensory systems known in live organisms, and the resulting developed artificial systems are targeted to reproduce the biological mechanisms to some extent. Sniffing behaviour, sampling odours actively, has been studied recently in neuroscience, and it has been suggested that the respiration frequency is an important parameter of the olfactory system, since the odour perception, especially in complex scenarios such as novel odourants exploration, depends on both the stimulus identity and the sampling method. In this work we propose a chemical sensing system based on an array of 16 metal-oxide gas sensors that we combined with an external mechanical ventilator to simulate the biological respiration cycle. The tested gas classes formed a relatively broad combination of two analytes, acetone and ethanol, in binary mixtures. Two sets of low-frequency and high-frequency features were extracted from the acquired signals to show that the high-frequency features contain information related to the gas class. In addition, such information is available at early stages of the measurement, which could make the technique suitable in early detection scenarios. The full data set is made publicly available to the community. (C) 2014 Elsevier B.V. All rights reserved., Postprint (author's final draft)

High-quality crack-free GaN-based light-emitting diodes (LEDs) were grown on patterned Si substrate using a flow modulation method and a high-temperature (HT)-AlN/AlGaN superlattice structure (SLs) interlayer. The effects of these two techniques on material properties and device performance were studied. The enhanced crystalline quality can be attributed to a 3D to 2D coalescence process with fewer dislocations initiated from the interlayers. The light output power of blue LEDs was improved by 66% after successful implementation of flow modulation and new interlayers. After substrate removal and packaging, the optical power of circle LEDs with diameter of 300 μm could reach as high as 6.30 mW at 20 mA. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In this paper, the use of a new technique to obtain transient sensor information is introduced and its usefulness to improve the selectivity of metal oxide gas sensors is discussed. The method is based on modulating the flow of the carrier gas that brings the species to be measured into the sensor chamber. In such a way, the analytes' concentration at the surface of the sensors is altered. As a result, reproducible patterns in the sensor response develop, which carry important information for helping the sensor system, not only to discriminate among the volatiles considered but also to semi-quantify them. This has been proved by extracting features from sensor dynamics using the discrete wavelet transform (DWT) and by building and validating support vector machine (SVM) classification models. The good results obtained (100% correct identification among 5 volatile compounds and nearly a 89% correct simultaneous identification and quantification of these volatiles), which clearly outperform those obtained when the steady-state response is used, prove the concept behind flow modulation. © 2008 by the authors.

See also Part 2, AD-A139 979.