Large-scale and facial fabrication of PbS nanorods by sulfuration of a Pb sheet

PbS nanostructures were synthesized by sulfuration of lead sheets in a tube furnace under sulfur ambiance. The lead sheets were placed in different temperature zones, between 330 and 470 °C. Field emission scanning electron microscope (FESEM) images showed that only the lead sheet placed at 330 °C showed nanorods morphology. The prepared nanorods exhibited a rectangular shape with an average diameter of 95 nm and an average length of 400 nm. The phase and composition of the product were identified by x-ray diffraction (XRD) pattern and x-ray photoelectron spectra (XPS). The pattern indicated that these PbS nanorods were with a cubic phase and the XPS result showed binding energy for lead and sulfur that belonged to PbS structure. In addition, Raman measurements confirmed the XRD pattern and XPS results and indicated three Raman active modes, which belonged to PbS phase for the nanorods. The optical properties of the products were characterized by UV–visible and room temperature photoluminescence (PL) spectrometers. The optical characterization results showed a band gap for the PbS nanorods in the infrared region.     

Investigating hazard recognition in augmented virtuality for personalized feedback in construction safety education and training

Accidents resulting from poorly planned or set up work environments are a major concern within the construction industry. While traditional education and training of personnel offer well-known approaches for establishing safe work practices, serious games in virtual reality (VR) are used more often as a complementary approach for active, personalized learning experiences. Their designs yet have to take full advantage of how trainees can potentially manipulate and interact with virtual objects. In addition, little construction safety research has focused on generating and analyzing the inherent data that can be collected about the trainees’ actions in the virtual environment. The objective analysis of their performance in the virtual environment offers precise feedback to sensitize their work behavior later in real practice. This research presents a novel framework for the generation and assessment of the trainees’ data in augmented virtuality (AV). The proposed approach is tested in a virtual work environment consisting of multiple stages and hazards that are consistent within today’s construction sites and workshops. A real angle grinder has been reworked and repurposed as an interactive AV controller to further enhance immersion. Results on the performance in the proposed system and the experiences of two groups of volunteering participants are presented and discussed. An outlook presents future avenues towards enhancing existing construction safety education and focus points on correlating objective tracking data with self-assessment.     

Comparative studies of experimental and numerical techniques in measurement of corrosion rate and time-to-corrosion-initiation of rebar in concrete in marine environments

The evaluation of the corrosion process for estimating the service life of concrete structure is of great importance to civil engineers. In this paper, the effects of different exposure conditions (i.e., tidal and splash zones) on macrocell and microcell corrosion of rebar in concrete were examined on concrete specimens with different w/c ratios in the Persian Gulf region. Experimental techniques such as macrocell corrosion rate measurement, Galvanostatic pulse, electrical resistivity, half-cell potential measurement, and numerical techniques were used to determine the corrosion rate and time-to-corrosion-initiation of rebar. Results showed that corrosion rates in the splash zone were higher than the ones in the tidal zone. This indicates that the propagation of corrosion in the splash zone is faster than the one in the tidal zone. There was also a strong correlation between the experimental results and those obtained from a numerical model in both tidal and splash zones.     

A geospatially-enabled web tool for urban water demand forecasting and assessment of alternative urban water management strategies

This study develops and demonstrates the Integrated Urban Water Model (IUWM) for forecasting urban water demand with options to assess effects of water conservation and reuse. While water and energy balance drive hydrologic, storage and recycling simulations on a daily timestep, social and infrastructural processes are resolved by spatially distributed parameters. IUWM is deployed as an online tool with geographical information system (GIS) interfaces, enhancing its ease of use and applicability at building to municipal scales. The performance of the model at varying spatial scales was evaluated with extensive water metering data for the City of Fort Collins, Colorado. The calibrated model provided very good estimates of demands at individual block group as well as the municipal service area. The capacity of IUWM for the assessment of the spatiotemporal variability of water consumption and effects of water demand management strategies under climate and urban growth scenarios is discussed.     

Crack detection limits in unit based masonry with terrestrial laser scanning

This paper presents the fundamental mathematics to determine the minimum crack width detectable with a terrestrial laser scanner in unit-based masonry. Orthogonal offset, interval scan angle, crack orientation, and crack depth are the main parameters. The theoretical work is benchmarked against laboratory tests using 4 samples with predesigned crack widths of 1–7 mm scanned at orthogonal distances of 5.0–12.5 m and at angles of 0°–30°. Results showed that absolute errors of crack width were mostly less than 1.37 mm when the orthogonal distance varied 5.0–7.5 m but significantly increased for greater distances. The orthogonal distance had a disproportionately negative effect compared to the scan angle.     

Water depercolation of setting cement paste evaluated by diffuse ultrasound

Microstructural evolution during setting of cement-based materials explains its solidification. While various studies have attempted to reveal the microstructural evolution, many questions still remain. The setting process refers to the phase change from a cement suspension to a poroelastic solid. This study proposes a diffuse ultrasound method to investigate microstructural evolution and to determine the setting of cement paste. The diffuse ultrasound refers the propagation of an incoherent component on P-waves through-transmission. Its velocity and attenuation reflect the tortuous paths in early-age cement paste. Closing the tortuous paths by cement hydration and coagulation causes the diffuse ultrasound to combine with the propagated P-wave. The combined time is then an indicator of the setting point. The diffusivity, dissipation, and permeability evaluated by the diffuse ultrasound also shed light on the microstructural evolution of fresh cement paste.     

Response surface design to study the influence of inoculum,particle size and inoculum to substrate ratio on the methane production from Ulex sp.

Ulex europaeus is one of the world worst invaders vegetal species and its suitability for biogas production is significant. The effect of three factors affecting the Biochemical Methane Potential (BMP, expressed as volume of CH₄ per mass of volatile solids of waste) and the biodegradability rate (k, expressed in volume of CH₄ per mass of VS and time) of U. europaeus was assessed by a Central Composite Face Centred Design. The BMP varied from 153 L kg⁻¹ to 308 L kg⁻¹. Inoculum to substrate ratio (ISR) and the type of inoculum had high influence on the final results. k varied from 14 L kg⁻¹ d⁻¹ to 49 L kg⁻¹ d⁻¹. The conditions that simultaneously maximized the BMP and k were an inoculum consisting in 55% (v) of granular sludge and 45 % (v) of suspended sludge from a sludge digester, an ISR of 4 g g⁻¹, and a particle size of 1.9 mm. Considering the average biomass production in shrub land areas, the potential energy production from U. europaeus is estimated in (36.9 ± 19.3) GJ ha⁻¹ yr⁻¹. For example, in Europe, a maximum energy supply of 7 EJ yr⁻¹ could be achieved from potentially harvestable shrub land areas.     

Experimental study of web crippling behaviour of hollow flange channel beams under two flange load cases

This paper presents the details of an experimental study of a cold-formed steel hollow flange channel beam known as LiteSteel beam (LSB) subject to web crippling under End Two Flange (ETF) and Interior Two Flange (ITF) load cases. The LSB sections with two rectangular hollow flanges are made using a simultaneous cold-forming and electric resistance welding process. Due to the geometry of the LSB, and its unique residual stress characteristics and initial geometric imperfections, much of the existing research for common cold-formed steel sections is not directly applicable to LSB. Experimental and numerical studies have been carried out to evaluate the behaviour and design of LSBs subject to pure bending, predominant shear and combined actions. To date, however, no investigation has been conducted on the web crippling behaviour and strength of LSB sections. Hence an experimental study was conducted to investigate the web crippling behaviour and capacities of LSBs. Twenty-eight web crippling tests were conducted under ETF and ITF load cases, and the ultimate web crippling capacities were compared with the predictions from the design equations in AS/NZS 4600 and AISI S100. This comparison showed that AS/NZS 4600 and AISI S100 web crippling design equations are unconservative for LSB sections under ETF and ITF load cases. Hence new equations were proposed to determine the web crippling capacities of LSBs based on experimental results. Suitable design rules were also developed under the direct strength method (DSM) format.     

Identifying key design parameters of the integrated energy system for a residential Zero Emission Building in Norway

This study examined an integrated solution of the building energy supply system consisting of flat plate solar thermal collectors in combination with a ground-source heat pump and an exhaust air heat pump for the heating and cooling, and production of domestic hot water. The supply energy system was proposed to a 202 m² single-family demo dwelling (SFD), which is defined by the Norwegian Zero Emission Building standard. The main design parameters were analyzed in order to find the most essential parameters, which could significantly influenced the total energy use. This study found that 85% of the total heating demand of the SFD was covered by renewable energy. The results showed that the solar energy generated by the system could cover 85–92% and 12–70% of the domestic hot water demand in summer and winter respectively. In addition, the solar energy may cover 2.5–100% of the space heating demand. The results showed that the supply air volume, supply air and zone set point temperatures, auxiliary electrical volume, volume of the DHW tank, orientation and tilt angle and the collector area could influenced mostly the total energy use.