Modelling the diffuse fraction of global solar radiation on a horizontal surface

For various applications it is necessary to know not only global solar radiation values, but also the diffuse and beam components. Because often only global values are available, there have been several models developed to establish correlations between the diffuse fraction and various predictors. These typically include the clearness index, but also may include the solar angle, temperature and humidity. The clearness index is the proportion of extraterrestrial radiation reaching a location, where the extraterrestrial value used in the calculation varies with latitude and time of year. These correlations have been developed using data principally from latitudes greater than 40°, often using only data from a few locations and with few exceptions have not used solar altitude as a predictor. Generally the data consist of hourly integrated values. A model has been developed using hourly data from a weather station set up at Deakin University, Geelong. Another model has also been developed for 15 minute data values in order to ascertain if the smoothing generated by using hourly data makes a significant difference to overall results. The construction of such models has been investigated, enabling an extension to the research, inclusive of other stations, to be performed systematically. A final investigation was carried out, using data from other Australian locations, to explain some of the considerable scatter by adding apparent solar time as a predictor, which proved to be significantly better than solar altitude.

Evaluating the performance of different media in a horizontal subsurface flow constructed wetland

The treatment efficiency of a wetland system requires a balance between pollutant loading rate and hydraulic retention time (HRT), hydraulic loading rate (HLR) and the suitable substrate to be used. The aim of this study was to investigate the treatment efficiency of horizontal subsurface flow constructed wetland planted with phragmites australis and scirpus maritimus containing three different substrates to treat agricultural wastewater under short term operation. Alum sludge and zeolite were used as substrates and gravel was used as a control for a laboratory-scale horizontal flow constructed wetland (CW) units that were made of high-density Polyethylene. The units were operated under 2, 3 and 4 days of HRTs and at different HLR for each substrate. Each beds received 0.012 m3/d to 0.08 m3/d of synthetic wastewater corresponding to a HLR of 0.035 to 0.243 m/d and a COD loading rate of 0.0148 kg COD (m2.d)-1 to 0.026 kg COD (m2.d)-1. The relationships between the substrate, retention time and removal efficiency, especially of organic matter and nutrient removal were investigated. All units showed relatively stable removal for COD during the entire operational period. The COD removal for all units and HRT were in ranged from 67% to 93%. The zeolite unit achieved significantly higher removal of TN, NH4-N and TSS compared to alum sludge and gravel unit at all HRT. The unit with zeolite was highly effective in removing TN (54 to 96%), NH4-N (50 to 99%) and TSS (91 to 96%) respectively, at 2, 3 and 4 days of HRT. Meanwhile, alum sludge was highly effective in removing phosphate. The removal of phosphate from alum sludge unit was ranged from 94 to 97% for all HRT. Compared to gravel CW unit, zeolite and alum sludge CW were proved to be tolerant to high organic loadings and nutrients, suggesting these substrates as viable options for biological treatment of agricultural wastewater.

Urban surface temperature behaviour and heat island effect in a tropical planned city

 Putrajaya is a model city planned with concepts of a "city in the garden" and an "intelligent city" in the tropics. This study presents the behaviour of the surface temperature and the heat island effect of Putrajaya. Findings show that heat island intensity is 2 °C on average at nighttime and negligible at daytime. But high surface temperature values were recorded at the main boulevard due to direct solar radiation incident, street orientation in the direction of northeast and southwest and low building height-to-street width ratio. Buildings facing each other had cooling effect on surfaces during the morning and evening hours; conversely, they had a warming effect at noon. Clustered trees along the street are effective in reducing the surface temperature compared to scattered and isolated trees. Surface temperature of built up areas was highest at noon, while walls and sidewalks facing northwest were hottest later in the day. Walls and sidewalks that face northwest were warmer than those that face southeast. The surface temperatures of the horizontal street surfaces and of vertical façades are at acceptable levels relative to the surface temperature of similar surfaces in mature cities in subtropical, temperate and Mediterranean climates. © 2014 Springer-Verlag Wien.

sEMG-based single-joint active training with iLeg—A horizontal exoskeleton for lower limb rehabilitation

In this paper, surface electromyography (sEMG) from muscles of the lower limb is acquired and processed to estimate the singlejoint voluntary motion intention, based on which, two single-joint active training strategies are proposed with iLeg, a horizontal exoskeleton for lower limb rehabilitation newly developed at our laboratory. In damping active training, the joint angular velocity is proportionally controlled by the voluntary effort derived from sEMG, performing as an ideal damper, while spring active training aims to create a spring-like environment where the joint angular displacement from the constant reference is proportionally controlled by the voluntary effort. Experiments are conducted with iLeg and one healthy male subject to validate the feasibility of the two single-joint active training strategies.