196746 research outputs found
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A technology assessment and implementation model for evaluating socio-cultural and technical factors for the successful deployment of Logistics 4.0 technologies
No full textThe Logistics 4.0 research stream has been heavily focused on the use of new digital technologies to achieve higher degrees of productivity and flexibility in logistics processes and operations. Whereas in many cases impacting positively the business performance, their introduction also affects the nature of the work of human logistics operators. Furthermore, the interactions between technical (logistics) systems and socio-cultural factors have been widely overlooked in the Industry 4.0 literature. This makes it difficult to provide univocal, tactical, and structured approaches to successfully guide the introduction of Logistics 4.0 technologies on the shop floors and warehouses, while securing the employees' trust, motivation, and engagement, and consequently, improving not only business performance but also employees' job satisfaction. This paper proposes a Technology Assessment and Implementation Model, with particular consideration of socio-cultural factors, to serve as a functional guiding tool to follow during the deployment of Logistics 4.0 technologies to ensure operators' smooth acceptance of the newly digitalized workplace
A novel yaw wake model for wind farm control applications
No full textYaw control is a potential control strategy to redirect the wakes of wind turbines for the purpose of improving the wind farm performance. Because of its time-consuming nature, high fidelity numerical simulations are hard to be applied in engineering applications. Instead, a simple and efficient engineering wake model is preferable. In this paper, a novel yaw wake model is developed in the following three steps: a novel wake velocity model for non-yawed wind turbines is first developed; second, a novel wake deflection model is developed to overcome the shortcomings in existing models; and third, a novel wake model for yawed wind turbines is developed. To verify its accuracy, the results of the novel yaw wake model implemented in the in-house Analytical Wake Model Calculator (AWMC) are validated against experimental data and simulation results. Moreover, the comparisons with a few existing yaw wake models show its superiority. In terms of error, the overall accuracy of the wake deflection model is enhanced by more than 20 % compared to other models in all cases. In addition, the overall accuracy of the novel yaw wake distribution model is improved by at least 10 % in most cases as compared to state-of-the-art yaw wake models
Constituents of Human Particle, Microbial and Chemical Emissions and Exposures in Indoor Environments: An experimental overview
No full textThis study presents the preliminary findings on the human contribution to particle, microbe and gas-phase chemical burden of indoor air, as well as the effect of ozone on malondialdehyde (MDA) levels, a biomarker of lipid peroxidation
Resilient cooling strategies: an all-air HVAC case study
No full textResilient cooling is the ability of a building-plant system to withstand and recover after a disruptive event. In particular, heatwaves and power outages have been considered in this study as perturbations of a building-plant system. The present work investigated the operation of an all-air HVAC system combined with two air to water heat pumps in Copenhagen, Denmark. TRNSYS simulations considered both current and future outdoor climatic conditions, both in mid and long term, to evaluate building’s energy use. The results showed that during heatwaves operative temperatures higher than 28 °C were registered, but only for 5 to 20% of the occupied time in the worst scenario. The variation was due to the cooling load, which increased as the heatwave increased in length and intensity. Nevertheless, the energy use did not considerably increase with values between 33 to 39 kWh/(m2 y) but the system resulted to be non-resilient in most of the cases that combine heatwaves with power outages
Regionalized environmental damages and life cycle cost of chickpea production using LC-IMPACT assessment
No full textModern intensive agriculture worldwide is generating increasing environmental and economic pressures that hinder its sustainable development. This study proposes the joint use life cycle assessment (LCA) and life cycle costing (LCC) to evaluate irrigated chickpea production (ICP) and the eco-environmental situation of dry farming (DFCP). Data are collected from 625 chickpea farmers in in the Kermanshah province of Iran. The most updated approach, LC-IMPACT, is applied for the first time globally in agricultural activity LCA. Results indicate that most impact categories of ICP have higher rates than DFCP. On-Field emissions and pesticides in DFCP, and nitrogen and phosphate in ICP, are identified as the main hotspots. The LCC analysis reveals that the total emissions cost (EC) for DFCP and ICP is 130 and 53 1TCP−1. The eco-efficiency rate of damage categories in DFCP shows a better situation compared to the ICP scenario. The findings indicate that the DFCP scenario exhibits a higher level of environmental friendliness compared to the ICP scenario. Finally, it can be concluded that the joint use of LC-IMPACT assessment method and LCC can contribute to achieving better eco-environmental conditions in chickpea production
A comprehensive review on the current technologies and recent developments in high-temperature heat exchangers
No full textHigh-temperature heat exchangers are extensively studied today due to their benefits for industrial processes. In most cases, there is a threshold for the maximum operating temperature of heat exchangers. Beyond this temperature level, special design and material considerations are required. This threshold is 600 °C today, which is higher than in the past due to recent advances in heat transfer and materials. This study presents extensive information about various designs of high-temperature heat exchangers, their materials and heat transfer fluids, and the most significant technical issues and scientific gaps in this field. The aim is to shed light on the pathway to improving high-temperature heat exchanger efficiency, economic feasibility, and safety. The research survey shows that i) molten salts, liquid metals, helium, supercritical carbon dioxide, etc. are the most appropriate heat transfer fluids for high-temperature heat exchangers; ii) shell and tube, plate, plate and fin, helical coil, finned tube, printed circuit, double-pipe, and bayonet tube heat exchangers are the most commonly used configurations for high-temperature applications; and iii) iron- and nickel-based alloys, and ceramics are the most commonly used materials. The critical issues in high-temperature heat exchangers are corrosion, material degradation over time, quality degradation, and limited lifetime. The main benchmarks needed for high-temperature heat exchanger design are fluid types, working conditions, required heat transfer rate, and costs. The study represents a brief yet informative state-of-the-art and discusses the gaps for each of these parameters, providing readers with a clear line of future research
A laboratory and theoretical framework for systematic non-equilibrium turbulence studies
No full textThe cornerstone assumption of equilibrium of the small and intermediate scales in the classical view of turbulence (K41 - the combined efforts of Kolmogorov, Batchelor and Richardson) is under ever increased scrutiny. Although the K41 based models do appear to apply well to some flows, there exist many important flows that are problematic for these turbulence models. In particular, it is interesting to note that the most challenging applications appear to have one thing in common - rapid changes of the flow in the mean in time and/or space. It is thus interesting to systematically investigate what the bounds of validity of the classical K41-view of turbulence are, if any. And if the K41-picture of turbulence does indeed break down, what are the non-linear spectral energy transfer mechanisms that lead to nonequilibrium turbulence behavior (local vs. non-local)? Does the non-linear energy exchange between scales divert from the classically assumed Richardson cascade? And is the constancy of the spectral flux across the inertial range interrupted? In order to answer these questions, a new facility for the systematic study of non-equilibrium turbulence in a controlled setting has been established along with an accompanying theoretical framework that is tailored for addressing these specific issues
Online SPE-LC-MS-MS method for eight hydroxylated metabolites of polycyclic aromatic hydrocarbons in urine and determination of optimal sampling time after firefighter training
No full textPolycyclic aromatic compounds (PAHs) are formed during incomplete combustion and firefighters are inadvertently at risk of being exposed to these and other hazardous compounds. Exposure to PAHs is often estimated by measuring their hydroxylated metabolites (OH-PAH) in urine. Here, an online-SPE LC-MS-MS method was set up for eight OH-PAHs thus increasing sample throughput and minimizing manual handling. The method was validated over a 5-month period and showed good reproducibility with intra- and inter-day variation of 2.4-8.1% and 1.6-6.5%, respectively, of low-level samples and accuracy (91.6-104.8%) for a standard reference material. The method was applied to urine samples from conscripts training to become firefighters to determine the optimal sampling time for this training activity before a large intervention study. In total, six conscripts sampled urine 6-8 times over a 40-hr period during a 3-day training course. All eight metabolites were detected in ≥ 97% of the samples and showed peak excretion 4-6 hrs after the training corresponding to 8-10 hrs after first exposure. Samples taken the morning after the exercise contained low levels of most metabolites. Consequently, 4-6 hrs post exposure is recommended as the optimal sampling time for quantification of PAH exposure and monitoring of potential differences in exposure
Stabilizing metastable ferroelectric tungsten trioxide phase at room temperature via solvothermal synthesis and millisecond pulsed laser irradiation
No full textEpsilon tungsten trioxide (ε-WO3) has drawn much attention for its unique gas sensing and ferroelectric properties. However, the strong metastability of ε-phase makes it extremely difficult to stabilize the phase at room temperature. For a long time, it was believed that the ε-phase can only be stabilized by rapid solidification processing. In this study, ε-WO3 was stabilized by employing solvothermal synthesis and subsequent annealing, with the help of Cr- and Ti-dopants. Structural characterization using XRD, Raman and TEM analysis revealed that the as-annealed powders are a mixture of ε-WO3 and γ-WO3 and the fraction of ε-WO3 is directly correlated with the Cr- and Ti-doping levels. Rietveld refinement suggests that the maximum obtainable fractions of ε-phase in as-annealed WO3 are ∼68 % for Cr-doping and ∼87 % for Ti-doping. The growth mechanism is that solvothermal synthesis produced Cr- and Ti-doped W18O49 and subsequent annealing resulted in phase transition from W18O49 to ε-WO3. The XPS analysis reveals the phase stabilization mechanism to involve the interstitial sites of WO3 being occupied by Cr3+ and Ti4+ dopants, resulting in structure distortions. The fraction of ε-WO3 can be further improved to almost 100 % by introducing kinetic constraints using pulsed laser irradiation to rapidly melt and solidify the WO3 (in several milliseconds). A viable solvothermal synthesis route for ε-WO3 and the feasibility to produce ε-phase via additive manufacturing are illustrated in this work.</p
Zearalenone removal using inactivated yeast embedded in porous modified yam starch aerogels and its application in corn silk tea
No full textZearalenone contaminates food and poses a threat to human health. It is vital to develop cost-effective and environmentally-friendly adsorbents for its removal. By screening Sporobolomyces pararoseus (SZ4) and modified yam starch (adsorption capacity (qe) of 1.33 and 0.94 mg/g, respectively), this study prepared a novel composite aerogel adsorbent (P-YSA@SZ410). The compressive strength of P-YSA@SZ410 was 1.35-fold higher than unloaded yeast. It contained several functional groups and three-dimensional interconnected channels, achieving a 0° contact angle within 0.18 s, thereby demonstrating excellent water-absorbent properties. With a qe of 2.96 mg/g at 308 K, the adsorption process of P-YSA@SZ410 was spontaneous, endothermic, and matched pseudo-second-order and Langmuir models. The composite adsorbed zearalenone via electrostatic attraction and hydrogen bonding, maintaining a qe of 2.24 mg/g after five cycles. P-YSA@SZ410 was found to remove zearalenone effectively under various conditions and could be applied to corn silk tea, indicating its great potential as an adsorbent material