Influence of Intrinsic Trapping on The Performance Characteristics of ZnO-Bi 2

The lumped parameter/complex plane analysis technique reveals several contributions to the ac small-signal terminal immittance of the ZnO-Bi2O3 based varistors' grain-boundary response. The terminal capacitance constitutes multiple trapping phenomena, a barrier layer contribution, and a resonance effect in the frequency range 10-2 ≤ f ≤ 109 Hz. A trapping response near to ∼105 Hz (∼10-6 s), observed via the loss-peak and a distinct depressed semicircular relaxation in the complex capacitance plane, is common to all well-formed (exhibiting good performance for applications) devices regardless of the composition recipe and processing route. This trapping is attributed to possible formation of ionized intrinsic or native defects, and believed to be predominant within the electric field falling regions across the microstructural grain-boundary electrical barriers. The nature of rapidity of this intrinsic trapping and the corresponding degree of uniformity/non-uniformity can be utilized in conjunction with relevant information on other competing trapping phenomena to assess an overall performance of these devices. The constituting elements, responsible for the average relaxation time of the intrinsic trapping, indicate some sort of possible surge arrester (i.e., suppressor/absorber) applications criteria in the power systems' protection. The factors related to materials' history, composition recipe, and processing variables influence or modify relative magnitudes and increase or decrease the visibility of the constituting elements without distorting devices' generic dielectric behavior

Immittance Spectroscopy of Smart Components and Novel Devices

AC small-signal immittance spectroscopy is employed as a viable tool to demonstrate electrical characterization, performance improvement, and quality assurance issues of smart materials-based components and novel devices. The variation in the ac response, complemented via dc measurements within a range of tolerating temperature, delineates competing phenomena occurring in the microstructures of these engineering material systems. The results are presented in a generic manner with possible explanations on the mechanisms for two selected Debye-like (nearly ideal) and non-Debye (non-ideal) low-capacitance resistors. This spectroscopic approach allows systematic development of a representative equivalent circuit, considered to be the characteristic of the devices and components, for specific applications

Influence of Multiple Trapping Phenomena on The Applications Criteria of ZnO-Bi 2

The performance characteristics of the ZnO-Bi2O3-based varistors can be assessed to meet the applications criteria on the basis of a systematic evaluation corresponding to various experimental conditions. This evaluation process employs the lumped parameter/complex plane analysis technique for the ac small-signal immittance data. An overall behavior of these devices is attributed to the microstructural effects via controlled grain-size and its distribution, existence of phases, carrier density in the grains, trapping states, and their role within the electrical thickness across the grain-boundary electrical barrier, etc. These factors are strongly dictated by the additives to ZnO in conjunction with the processing variables. Multiple device functions can result when a single set from a variety of processing parameters is chosen, provided the starting chemistry or composition/formulation remain invariant. The factors related to materials' history, composition recipe, and combined processing methods influence or modify relative magnitudes of the constituting elements of each trapping relaxation. Thus, these magnitudes either increase or decrease the visibility without distorting the devices' generic dielectric behavior. An identical set of experiments contributes to distinguish a good varistor performance over a poor response for surge arrester (i.e., suppressor/absorber) applications in the power systems' transient protection

Vegetated roofs as a means of sustainable urban development : a scoping review

Urbanisation affects the water cycle and heat balance in a negative way. Vegetated roofs have the potential to minimise the effects of urbanisation. A scoping review is presented here to examine how vegetated roofs are being evolved as an effective tool of sustainable urban stormwater management and overall urban development. It has been found that research on vegetated roofs has been increasing significantly and it can contribute towards achieving multiple sustainable de-velopment goals (SDGs). It has also been found that the uptake of vegetated roofs has been slow. A lack of regulatory acceptance caused by an absence of experimental data and a subsequent knowledge gap establishing the effectiveness of vegetated roofs are major reasons behind this slow uptake. Future research on vegetated roofs and their subsequent evolutions should put a focus on gathering experimental data towards establishing a performance benchmark for detention, retention and water quality in urban settings. Such data can be utilised towards developing a stand-alone guideline and software for green roof design

Ultra-Low Temperature Coefficient of Capacitance (Tcc) of the SrSnO

The perovskite-structured SrSnO3 possessing steady capacitance over the temperature range between 27°C and 300°C in a frequency domain spanning nearly four decades has been evaluated. The samples investigated in this study were synthesized by using solid-state reaction (SSR) and self-heat-sustained (SHS) techniques. These samples were sintered at a temperature (T ) ranging between 1200°C and 1600°C with a soak-time (t) ranging between 2 h and 60 h. The ac immittance (impedance or admittance) measurements were conducted on these sintered bodies in the frequency range 5Hz to 13 MHz. These ac electrical data were found to exhibit relaxation in more than one complex plane formalisms in a simultaneous manner. The magnitude of the terminal capacitance was found to be in a narrow window of 3 pF to 6 pF possessing very weak temperature dependence. Further analysis also revealed that this material system possessed low dielectric constant and ultra-low temperature coefficient of capacitance (TCC) or dielectric constant (TCK). The electrical behavior of these sintered bodies has been systematically correlated with the evolved microstructures. Plausible equivalent circuit elements were extracted using the lumped parameter/complex plane analysis (LP/CPA) and evaluated at various situations

Review of rainwater harvesting research by a bibliometric analysis

This study presents a review of recent rainwater harvesting (RWH) research by a bibliometric analysis (based on performance analysis and science mapping method). Following the inclusion/exclusion criteria, a total of 3226 publications were selected for this bibliometric analysis. From the selected publications, the top journals were identified according to number of publications and number of citations, as well as the authors with the highest number of publications. It has been found that publication rate on RWH has been increasing steadily since 2005. Water (MDPI) journal has published the highest number of publications (128). Based on the literature considered in this review, the top five authors are found as Ghisi, E., Han, M., Rahman, A., Butler, D. and Imteaz, M.A. in that order. With respect to research collaborations, the top performing countries are USA–China, USA–Australia, USA–UK, Australia–UK and Australia–China. Although, the most dominant keywords are found to be ‘rain’, ‘rainwater’, ‘water supply’ and ‘rainwater harvesting’, since 2016, a higher emphasis has been attributed to ‘floods’, ‘efficiency’, ‘climate change’, ‘performance assessment’ and ‘housing’. It is expected that RWH research will continue to rise in future following the current trends as it is regarded as a sustainable means of water cycle management

Community-scale rural drinking water supply systems based on harvested rainwater : a case study of Australia and Vietnam

Rainwater harvesting (RWH) systems can be used to produce drinking water in rural communities, particularly in developing countries that lack a clean drinking water supply. Most previous research has focused on the application of RWH systems for individual urban households. This paper develops a yield-after-spillage water balance model (WBM) which can calculate the reliability, annual drinking water production (ADWP) and benefit-cost ratio (BCR) of a community-scale RWH system for rural drinking water supply. We consider multiple scenarios regarding community aspects, including 150-1000 users, 70-4800 kL rainwater storage, 20-50 L/capita/day (LCD) drinking water usage levels, local rainfall regimes and economic parameters of Australia (developed country) and Vietnam (developing country). The WBM analysis shows a strong correlation between water demand and water supply with 90% system reliability, which allows both Australian and Vietnamese systems to achieve the similar capability of ADWP and economic values of the produced drinking water. However, the cost of the Vietnamese system is higher due to the requirement of larger rainwater storage due to larger household size and lower rainfall in the dry season, which reduces the BCR compared to the Australian systems. It is found that the RWH systems can be feasibly implemented at the water price of 0.01 AUD/L for all the Vietnamese scenarios and for some Australian scenarios with drinking water demand over 6 kL/day

Regional flood frequency analysis using an artificial neural network model

This paper presents the results from a study on the application of an artificial neural network (ANN) model for regional flood frequency analysis (RFFA). The study was conducted using stream flow data from 88 gauging stations across New South Wales (NSW) in Australia. Five different models consisting of three to eight predictor variables (i.e., annual rainfall, drainage area, fraction forested area, potential evapotranspiration, rainfall intensity, river slope, shape factor and stream density) were tested. The results show that an ANN model with a higher number of predictor variables does not always improve the performance of RFFA models. For example, the model with three predictor variables performs considerably better than the models using a higher number of predictor variables, except for the one which contains all the eight predictor variables. The model with three predictor variables exhibits smaller median relative error values for 2- and 20-year return periods compared to the model containing eight predictor variables. However, for 5-, 10-, 50- and 100-year return periods, the model with eight predictor variables shows smaller median relative error values. The proposed ANN modelling framework can be adapted to other regions in Australia and abroad

Production of fresh water by a solar still : an experimental case study in Australia

There is a scarcity of fresh water in many rural communities where solar stills can be used to produce drinking water at a minimal cost. These stills use solar energy, which is a sustainable form of energy, and hence this can contribute towards achievement of United Nations (UN) Sustainable Development Goals (SDG). This study aims to develop empirical models of a solar stills based on experimental data obtained at Werrington South, New South Wales, Australia. Two solar stills were used in the experiment, a conventional design (Con-Still) and a con-still modified with adding extra thermal mass inside the still (mod-still). Regression analysis was adopted to develop prediction equations using Pi (productivity in L/m2/day) as the response variable and ambient temperature (Ta), sky temperature (Ts19), global radiation (Gh), and wind velocity (W) as the predictor variables. The mean and median productivity values of the mod-still were found to be 17%, and 22% higher than that those for the con-still. The proposed mod-still can be further improved and used in rural areas to produce fresh water from sea water and other forms of contaminated water