bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and assessment of a method to determine the angle of attack on an operating wind turbine by matching onboard pressure measurements with panel method simulations
Authors: Soto-Valle Rodrigo , Noci Sara , Papi Francesco , Bartholomay Sirko , Nayeri Christian Navid , Paschereit Christian Oliver , Bianchini Alessandro
Published: October 2021

Wind Energy is substantially growing in recent years and is now one of the most competitive renewable energy sources on the market. To further foster the growth of this energy source, increasing effort is put into building accurate numerical models. Most models compute the loads acting on the turbine as a dependence of some sort to the angle of attack (AoA). Accurate AoA measurements would allow for comparison with experiments and would be of great benefit for the improvement of numerical models and the investigations of aerodynamic phenomena such as stall delay. However, the determination of the angle of attack during operation is troublesome to the present day. In addition to what was already mentioned, the AoA is key to evaluate loads acting on the wind turbine and assessing experiments, computational models, and aeroelastic models. This paper proposes a simple comparative method to estimate the AoA based on pressure distributions. The proposed method is tested using data from different numbers of pressure taps placed on the Berlin Research Turbine (BeRT) at the Hermann Föttinger Institut of the Technische Universität Berlin. The predicted results are in line with those from other methods while the operating conditions to which the model can be applied are improved.
Experimental Assessment of a Multi-Variable Control Strategy of a Micro-Cogeneration Solar-ORC Plant for Domestic Application
Authors: Vittorini Diego , Fatigati Fabio , Di Battista Davide , Di Bartolomeo Marco , Carapellucci Roberto
Published: October 2021

Suitability to off-design operation, applicability to combined thermal and electrical generation in a wide range of low temperatures and pressures and compliance with safety and environmental limitations qualify small-scale Organic Rankine Cycle plants as a viable option for combined heat and power generation in the residential sector. As the plants scale down, the electric and thermal output maximization has to account for issues, spanning from high pump power absorption, compared to the electric output of the plant, to intrinsically low plant permeability induced by the expander, to the intermittent availability of thermal power, affected by the heat demand for domestic hot water (DHW) production. The present paper accounts for a flat-plate solar thermal collector array, bottomed by an ORC unit featuring a sliding vane expander and pump and flat-plate heat exchangers. A high-temperature buffer vessel stores artificially heated water – electric heaters, simulating the solar collector - and feeds either the hot water line for domestic use or the ORC evaporator, depending on the instantaneous demand (i.e., domestic hot water or electric power), the temperature conditions inside the tank and the stored mass availability. A low-temperature receiver acts like the heat sink of the ORC unit and harvests the residual thermal power, downstream the expander: a dedicated control, modelled to properly modulate the mass addition/subtraction to this storage unit allows to restore the operating points of the cycle and to limit the incidence of off-design operation, via real-time adjustment of the cycle operating parameters. Indeed, the possibility of continuous ORC generation depends on (i) the nature of the demand and (ii) the amount of hot water withdrawn from the high-temperature buffer vessel. The time-to-temperature for the mass stored inside the buffer affects the amount of ORC unit activations and eventually the maximum attainable generation of electric energy. The plant energy performance is experimentally assessed, and various characteristic operating points are mapped, based on test runs carried out on a real-scale ORC pilot unit.
Injection of CO2/N2 gaseous mixtures into gas hydrates to contemporary perform CH4 recovery and CO2 storage
Authors: Filipponi Mirko , Gambelli Alberto Maria , Li Yan , Presciutti Andrea , Castellani Beatrice , Nicolini Andrea , Rossi Federico , Cotana Franco
Published: October 2021

Carbon dioxide injection into natural gas hydrate reservoirs represents a promising opportunity to predispose a theoretically carbon neutral energy source. This technique allows to replace methane molecules with an equal number of carbon dioxide molecules and, consequently, to balance in advance emissions associated to methane utilization. While the direct CH4/CO2 replacement has been widely investigated, more data and scientific evidences are required to well define the feasibility of recovering methane by replacing it with CO2-based gaseous mixtures. In this sense, the most promising opportunity consists in flue-gas mixtures. In some cases, the presence of nitrogen was found capable to improve the overall efficiency, due to the direct competition between CH4 and N2 molecules to fill small cages characterizing hydrate structures. Moreover, these mixtures are extremely less-expensive than pure carbon dioxide. In this work, a binary CO2/N2 (50/50 vol%) gaseous mixture was used to recover methane contained into hydrate structures. Experiments were carried out in a small-scale experimental apparatus, designed to simulate a natural gas hydrate reservoir and to intervene on it with replacement techniques. Composition of gaseous mixtures present into hydrates and in the gaseous phase present immediately above, where defined via gas-chromatographic analyses. Finally, results were compared with data currently present in literature, in order to validate their consistency.
Simulation of the HiPowAR power generation system for steam-nitrogen expansion after ammonia oxidation in a high-pressure oxygen membrane reactor
Authors: Cammarata Alberto , Colbertaldo Paolo , Campanari Stefano
Published: October 2021

The EU project HiPowAR studies a novel power generation system based on ammonia flameless oxidation with pure oxygen in a high-pressure membrane reactor and expansion of the resulting high-temperature H2O-N2stream. The system combines the advantages of high temperature at expander inlet, typical of gas turbines, and small compression demand, typical of steam cycles. Water is injected into the reactor to control the very high adiabatic temperature, at the limited energy expenditure of liquid pumping. This work assesses the performance potential of the HiPowAR system under different design conditions, through simulations with a model developed in Aspen Plus®. The system shows a high efficiency (up to 55%) when operating at high temperature (e.g., 1350°C at expander inlet); hence, O2 membranes capable of working at very high temperature are required. The cycle features an optimal sub-atmospheric expansion pressure (in the range 0.1-0.2 bar), which requires the re-pressurization of the off-gas (steam-saturated nitrogen). The system also produces liquid water as a net output. A reduction of the expander inlet temperature to values acceptable by typical steam cycles (600°C) significantly limits the efficiency, despite allowing to demonstrate the process using conventional steam expanders.
Study of the integration of a supersonic impulse turbine in a NH3/H2O absorption heat pump for combined cooling and power production from a low temperature heat source
Authors: Braccio Simone , Phan Hai Trieu , Tauveron Nicolas , Le Pierrès Nolwenn
Published: October 2021

The present work is focused on the investigation of an absorption cycle integrated with an impulse axial turbine for the combined production of cooling and electric power. This technology holds great promise for its ability to harness low-temperature heat sources, more effciently in comparison to separate production with simple cycles. By developing a 1D model of the expander, and integrating it into a 0D model of the complete cycle, it is possible to evaluate the performance of the cycle and its variation with respect to the operating parameters, namely the temperature of the external resources. Pending an experimental validation of the results, this study showed the importance of correctly defining the temperature of the sources - namely the generator temperature - in order to satisfy the technological needs while also maximising the effciency of the cycle. Finally it was highlighted how the integration of a supersonic impulse turbine strongly limits the flexibility during operation given the constant mass flow rate treated by the expander.
Thermo-economic analysis of a supercritical CO2-based waste heat recovery system
Authors: Bonalumi Davide , Giuffrida Antonio , Sicali Federico
Published: October 2021

This work investigates the performance of a supercritical CO2cycle as the bottoming cycle of a commercial gas turbine with 4.7 MW of electric power output. In detail, the partial heating cycle is the layout chosen for the interesting trade-off between heat recovery and cycle efficiency with a limited number of components. Single-stage radial turbomachines are selected according to the theory of similitude. In particular, the compressor is a troublesome turbomachine as it works near the critical point where significant variations of the CO2properties occur. Efficiency values for turbomachinery are not fixed at first glance but result from actual size and running conditions, based on flow rates, enthalpy variations as well as rotational speeds. In addition, a limit is set for the machine Mach numbers in order to avoid heavily loaded turbomachinery. The thermodynamic study of the bottoming cycle is carried out by means of the mass and energy balance equations. A parametric analysis is carried out with particular attention to a number of specific parameters. Considering the power output calculated for the supercritical CO2cycle, economic calculations are also carried out and the related costs compared to those specific of organic Rankine cycles with similar power output.
Demand response strategies in residential buildings clusters to limit HVAC peak demand
Authors: Mugnini Alice , Polonara Fabio , Arteconi Alessia
Published: October 2021

Due to the increasing spread of residential heating systems electrically powered, buildings show a great potential in producing demand side management strategies addressing their thermal loads. Indeed, exploiting the intrinsic characteristics of the heating/cooling systems (i.e. the thermal inertia level), buildings could represent an interesting solution to reduce the electricity peak demand and to optimize the balance between demand and supply. The objective of this paper is to analyse the potential benefits that can be obtained if the electricity demand derived from the heating systems of a building cluster is managed with demand response strategies. A simulation-based analysis is presented in which a cluster of residential archetypal buildings are investigated. The buildings differ from each other for construction features and type of heating system (e.g. underfloor heating or with fan coil units). By supposing to be able to activate the energy flexibility of the single building with thermostatic load control, an optimized logic is implemented to produce programmatically an hourly electricity peak reduction. Results show how the involvement of buildings with different characteristics depends on the compromise that wants to be achieved in terms of minimization of both the rebound effects and the variation of the internal temperature setpoint.
Urban context and neighbouring lands: how reforestation could have a role in the implementation of Sustainable Energy and Climate Action Plans
Authors: Abbate Simona , Di Paolo Luca , Carapellucci Roberto , Cipollone Roberto
Published: October 2021

Reforestation is the appropriate natural tool to mitigate the climate change. The authors illustrate how to manage cuts and plantations of trees making profit from unused lands, to reach different carbon capture goals. Unused lands, moreover, are frequently in the neighbouring of Municipalities which often are politically responsible of these territories. Their destination as carbon sink inside the implementation of the Sustainable Energy and Climate Action Plans (SECAPs) is particularly suitable, participating in a synergic way to reduce the CO2 municipal emissions by 55 % in 2030 with respect to the 1990 datum. In the framework of a SECAP, this level is mandatory and participates to the common huge effort to decarbonize energy needs. After having modelled some intrinsic aspects related to the dynamics of the carbon capture due to the growth of trees, the research demonstrated how, with a proper management of cuts and plantations, a new concept of mutualism between city and territory can be designed, recognizing the crucial role of neighbouring unused lands alongside those direct actions usually implemented to reduce the carbon intensity of a city.
An engineering approach for the fast simulation of radial inflow turbines with vaneless spiral casing by single-channel CFD models
Authors: Danieli Piero , Masi Massimo , Lazzaretto Andrea , Carraro Gianluca
Published: October 2021

The basic RANS-CFD analysis of the simplest radial-inflow turbine configuration is the subject of this paper. An original technique is here proposed to model the effect of the vaneless spiral casing using single-channel CFD calculations and providing an effective alternative to the more complex simulation of the 360-degree domain otherwise required to simulate this turbine configuration. The aim of the paper is to verify the effectiveness of the proposed modelling technique as a reliable engineering approach conceived to support the preliminary design phase of radial-inflow turbines with time-effective CFD calculations. To this end, the open-source CFD code MULTALL has been used to predict the aerodynamic performance of optimal designs of radial-inflow turbines with different specific speed and diameter and working with air as ideal gas. The MULTALL predictions are compared with the corresponding steady-state results obtained by calculations suited to the preliminary assessment of radial turbines designs performed on fully 360-degree turbine domains using the commercial code Star CCM+®. The investigation is conducted on two turbines that are designed in accordance with a widely validated method. The results show that the proposed CFD approach predicts well the trends and values of the aerodynamic performance of both the turbine designs: a 5% overestimation of the performance predicted by the fully 360-degree CFD models was never exceeded. The suggested turbine modelling approach implemented in MULTALL requires a three times lower computation time than the corresponding traditional 360-degree model.
Analysis of the partially premixed combustion in a labscale swirl-stabilized burner fueled by a methane-hydrogen mixture
Authors: Stefanizzi Michele , Stefanizzi Saverio , Ceglie Vito , Capurso Tommaso , Torresi Marco , Camporeale Sergio Mario
Published: October 2021

Nowadays hydrogen is gaining more and more attention by Industry, Academia and Politics. Being a carbon free fuel, it is supposed to have a key role in the future energy scenario, especially if produced by renewable sources. The use of mixtures of hydrogen and conventional hydrocarbons in gas turbines is one of the most promising technical solutions for obtaining a sustainable combustion during the transition toward a full decarbonization. For this reason, it is fundamental to investigate the behaviour of fuels enriched with hydrogen in combustion processes. In this work, a lab-scale swirled premixed burner has been investigated by means of a fully 3D URANS approach. Firstly, a numerical simulation with cold flow has been performed to validate the model against experimental data. Then, reactive flow simulations have been performed. Initially, a combustion with 100% methane was considered. Then, a 30% by volume hydrogen blending has been investigated. The partially premixed combustion model has been implemented to take into account the inhomogeneities of the mixture at the chamber inlet. The variation of the flame structure due to the hydrogen enrichment will be described in terms of the temperature and species concentration distributions.
Off-line washing effectiveness on a multistage axial compressor
Authors: Aldi Nicola , Casari Nicola , Fadiga Ettore , Friso Riccardo , Oliani Stefano , Pinelli Michele , Spina Pier Ruggero , Suman Alessio , Vulpio Alessandro , Zanini Nicola
Published: October 2021

The interaction between gas turbines and airborne particles determines detrimental effects on the performance, efficiency, and reliability of the power unit. When it is possible, the interaction is reduced by the use of inlet separators and filtration systems. In an aero engine, these barriers are difficult to implement, and only bigger particles (usually greater than 10 μm) are separated from the airflow. Small units, especially those equips helicopters, are usually affected by fouling issues, especially when the aircraft is employed in harsh environments such as firefighting and rescue activities. To recover this contamination, the unit is washed after the mission by ground operations to restore the unit performance by removing the deposits. This operation occurs during a sub-idle unit operation, and the washing process has to be effective when the engine operates in this off-design condition. In this paper, the evaluation of the washing performance during a sub-idle unit operation is carried out. The compressor unit is a multistage axial compressor that equips the Allison 250-C18 engine. The washing operation was performed by water, and a sensitivity analysis is carried out to discover the capability of water droplets to remove the contaminants. The experimental analysis involves the contamination of the unit by micro-sized soot particles and a washing operation by micro-sized water droplets. These experimental results are compared to numerical simulations to discover the effects of the washing operation on a small power unit during sub-idle operating conditions. The off-design regime imposes a specific evaluation of the proper setup of the washing strategy: flow separations involve wider regions in the compressor unit, and the removal capability is strongly related to the droplet path through the stages. The results show how in the off-design washing operation, the droplet diameter has greater importance than the water flow rate for reducing the deposits over the compressor stages.
Application of a completely organic and bio-degradable sugar-based insulating coating to vine shoots, to prevent late frost damages
Authors: Di Giuseppe Alessia , Gambelli Alberto Maria , Palliotti Alberto , Nicolini Andrea , Rossi Federico
Published: October 2021

An innovative method against late frosts in vineyard has been developed at CIRIAF, University of Perugia. It consists of an organic coating made by cotton candy and straw to prevent the vine shoots freezing due to late frosts. This technique has already tested at lab-scale with very encouraging results. This paper aims to experiment the effect of the organic coating applied on young shoots of grapevine during artificially controlled frost events. A vine shoot covered by the organic coating was positioned in the climatic chamber and a thermocouple was rolled up to the vine shoot to control its temperature. Also, a vine shoot rolled up to the thermocouple and without organic coating was positioned inside the climatic chamber, used as a reference case. Results show that the temperature gap, gained with the adoption of the insulating layer was approximately in the range 0.2 – 3.2 °C, but the organic coating was not enough to maintain temperature above the ice-point able to prevent the vine shoot freezing in lab. Even thought, the experimental application of the present technique allowed to detect some crucial challenges which need to be solved before to test this technology in real situations.
Changing commuters’ mobility behaviors of university campuses: environmental and energy comparisons
Authors: Cirrincione Laura , Di Dio Salvatore , La Gennusa Maria , Peri Giorgia , Rizzo Gianfranco , Scaccianoce Gianluca
Published: October 2021

Governments are required to take proper measures to promote the use of electric and hybrid vehicles and, more generally, to push people towards sweeter modalities including walking and biking. To reach such tight and challenging goals, local institutions should be deeply involved, and universities among them. The promotion of sustainable mobility practices among commuter students must be considered indeed an effective contribution to facilitating the transition towards greener cities. On purpose, students of the University of Palermo that daily commute from their residences to the campus are considered here. These commuters, in fact, mainly adopt traditional polluting transportation means. Avoiding the recourse to these means by supporting the use of sweeter modalities such as walking, biking, public transport and vehicle pooling and sharing, would contribute to significantly reducing the associated polluting emissions. This task might be accomplished by involving students in app-based games that would reward their greener mobility behaviors. Results of a couple of in-field campaigns including a significant sample of commuter students is presented here, along with the obtainable environmental and energy benefits. The proposed method thus candidates itself as an effective tool that not only academic institutions but also local administrations could adopt to make their decarbonization pathways. Finally, it is argued whether universities (as well as local administrations) could be candidate for carbon or energy credits within the existing trading schemes because of the reduction of their energy consumption and greenhouse gases release.
Indoor environmental quality of the Valli Theatre: outcomes on sound, light and thermo-hygrometry
Authors: Bevilacqua Antonella , Gelati Sara Francesca , Merli Francesca
Published: October 2021

The characteristics of a performing arts space have a great influence on the experience that both artists and audiences have during a show. Therefore, it is of great importance to understand the sound field behaviour, the lighting, and the thermo-hygrometry of the ambient conditions existing inside this cultural heritage. The aim of this paper is the presentation of a complete assessment in relation to the comfort of an Opera theatre on its whole. As such, it has been undertaken a study in relation to the acoustic listening situations other than to the parameters related to the light level and temperature comfort of the Valli Theatre of Reggio Emilia. The acoustic characterization has been undertaken in line with the ISO 3382 standard measurements procedure by capturing the room impulse response (RIR), while the light intensity has been studied by using the lux meter. In addition, the thermo-hygrometer has been used to photograph the comfort related to temperature and relative humidity inside the main hall.
Parametric Evaluation of Wobble-Yoke Stirling Engine State Space Model
Authors: Abdullah Ermira Junita , Lee Rick Kit
Published: October 2021

A conceptual design of Stirling engine suitable for onboard aircraft application is the motivation behind this study. The aim is to evaluate the suitability of the system to be integrated in aircraft as part of energy contributor by recycling the waste thermal energy. A parametric evaluation of an established Wobble-Yoke Stirling Engine state space model was performed to determine a suitable pre-compensator design that is able to produce the highest power output given the size and mass constraint. Simulation was performed using MATLAB in order to analyze the dynamic properties of the engine as a closed-loop system, with temperature, pressure and damping coefficient acting as controlling parameters. The parametric evaluation was conducted to determine the effect of assemble mass of piston, maximum displacement of piston and viscous damping coefficient to the performance of the system. The methodology can be used in the conceptual design process in order to determine the sizing and power output of the stirling engine system.
Numerical evaluation of finite length tubes effects in Stirling engines heaters
Authors: Marra Francesco Saverio , Acampora Luigi
Published: October 2021

The performance of Stirling engines is directly related to the amount of energy that, in the form of heat, participates in the thermodynamic cycle. A peculiar characteristic of this type of engine is the closed circuit of the working fluid, implying a periodic admission and extraction, ideally involving the whole working fluid, of the heat exchanged during the cycle without any exchange of material with the external environment. Several correlations have been proposed in the literature to predict the heat exchange in the hot side heat exchangers, but most of them are based on nondimensional numbers, usually expressed in terms of an oscillatory Reynolds number and a non-dimensional length, that even if they take into account the amplitude and frequency of the oscillating flow inside the tube with respect to its diameter, do not include any dependency upon the length of the tube. Nevertheless, the length of the tube can have a great impact on the performance of a Stirling engine. The heater forms a significant part of the dead volume of the engine, making the optimization of the volume to surface ratio necessary. The friction losses increase by increasing the length of the tubes, determining a negative impact while the exchange surface increases. Even the Nusselt number in the inner side of the tubes changes along the length, achieving the largest values alternatively in the first portions of the tube lengths because of entrance effects (Graetz problem). The picture is made even more complex because of the special velocity profiles that develop in oscillating flows in tubes. One of the effects less investigated in previous studies, which we could call a “breathing effect”, regards the amount of working fluid that, in a real engine, can effectively travel from the hot side to the cold side, thus reaching the conditions of nominal heat exchange with the thermal source and sink of the cycle. An idealized configuration has been devised to investigate, using CFD simulations, these effects. Results reporting how the friction coefficient and the Nusselt number depend on the finite length of the tube will be illustrated.
Generation of compressed air by cascaded thermocompressors – project status
Authors: Fischer Fabian , Kühl Hans-Detlev
Published: October 2021

Compressed air is one of the most widely used industrial energy sources, and its production by mechanical compressors is extremely expensive and, in addition, inefficient. Therefore, the utilization of waste heat, which accrues on a large scale in many industrial applications, by means of a thermocompressor is an obvious alternative. This contribution presents a design approach to experimentally investigate a reciprocating thermocompressor with a self-actuated overdriven free displacer. These experiments shall be the basis for the design and realization of a cascade of identical stages, which has so far only been investigated by means of analytical modelling and theoretical similarity considerations. The main advantage of this approach is its extreme constructive simplicity and the expected self-regulating effect, which both facilitate a cost-effective production and operation. As the minimization of dead volume and fluid friction losses is essential, the heat exchangers and the regenerator are plainly realized by an annular gap around the displacer in the proposed design, thus further increasing its simplicity. The design parameters are determined by an optimization based on an analytical model extended by various losses and heat transfer limitations.
A Study of Mesh Sheets of 3-kW Stirling Engine
Authors: Enomoto Takeshi , Matsuguchi Atsushi , Kagawa Noboru
Published: October 2021

In recent years, the interest in low-pollution and high-efficiency heat engines has been increasing due to the growing awareness of environmental protection, and power generation at relatively low temperatures, such as use of exhaust heat and sunlight, has been attracting attention. Compared with other heat engines, Stirling engine is very important because it can be driven by any heat source at low temperatures, such as exhaust heat, and it does not emit exhaust gas. In order to realize a more efficient Stirling engine, it is essential to design a heat exchange system that is suitable for each component.

Performance measurement and analysis on a new mesh regenerator material at low temperature difference using a 2-piston alpha-type 3-kW Stirling engine, NS03T are carried out. Mesh sheets developed for high performance Stirling engines can be designed with CAD and CAM technologies by etching process. For this study, M5 and M7 mesh sheets which are thin sheets of stainless steel with square holes in a grid arrangement, are used. With nitrogen and helium as the working fluid, the engine performance is measured by changing the charge pressure, heating temperature, and engine speed to clarify the flow resistance and heat transfer characteristics of the M5 and M7.
Development of a 100-Watt-Scale Beta-Type Low Temperature Difference Stirling Engine Prototype
Authors: Lottmann Matthias , de Rouyan Zachary , Hasanovich Linda , Middleton Steven , Nicol-Seto Michael , Speer Connor , Nobes David
Published: October 2021

This paper documents the ongoing design process of a Stirling engine prototype for a source temperature of 95 °C, aiming to achieve shaft power on the order of 100 Watts. The engine will serve to produce experimental data for the validation of a numerical low temperature Stirling model. The higher-level motivation is to assess the technical and economical potential of producing power from abundant sources of low temperature heat by using Stirling engines. Design decisions are governed by the goals of minimizing energy losses and maximizing the variability of operating points through variable heat exchanger geometry, compression ratio and charge pressure. The resulting design is a beta engine with a total gas volume around 100 liters. It features displacer and power pistons in a combined cylindrical working space and a mechanism using pivoting links similar to a bellcrank. The stroke of the power piston is adjustable while maintaining a constant top dead center position. A component critical for friction is the power piston seal, for which a low friction rolling seal and a conventional sliding seal were considered. As of June 2021, the development is at an advanced state and the first set of components are entering production.
A novel model and design of a MEMS Stirling cooler for local refrigeration
Authors: Bégot Sylvie , GETIE Muluken , Diallo Alpha , Lanzetta François , Barthès Magali , de Labachelerie Michel
Published: October 2021

In this paper, we present a new model design and parametric studies of a miniature Stirling cooler machine for on-site refrigeration. The MEMS (Microelectromechanical systems) technology is investigated to design this machine. The concept could be used to provide cooling at chip scale and mitigate hot spots in electronic devices. Whereas numerous works deal with Stirling engines at a macroscopic scale, only a few works concern miniaturized Stirling engines. Therefore, a model analysis giving insights of the impact of the technological choices and downsizing of the machine is needed. A base design model is presented. The model results lead to a cooling power of 10 mW and a Coefficient Of Performance of 1.45. A parametric study is conducted for operational and design parameters. Compared to macro-scale design, the same trend is observed for the influence of the thermal performance regenerator. Different trends from macroscopic engines were observed for hysteresis losses importance, and the choice of the working gas. The raise in power due to the raise in frequency expected for micro-scale devices is counterbalanced by the degradation of the COP due to the increase in thermofluidic losses. Squeeze film damping and finite speed losses can be neglected at this scale.
External heat transfer enhancement of a beta-type Stirling engine with fins as regenerator
Authors: Kumaravelu Thavamalar , Saadon Syamimi
Published: October 2021

The Stirling engine is an externally heat engine closed loop with a high theoretical performance and low emissions compared to other conventional engines. This property nowadays becomes very advantageous due to its multi-fuel capacity including solar, biogas and geothermal energy. In this study, a numerical investigation of the effect of a circular, pin, and rectangular fins on the performance of the Stirling engine is introduced. The 3D CFD model was performed and validated with previous experimental study. The power output, heat transfer rate and efficiency were studied for all cases of fins. The results indicated a close agreement between the numerical and the experimental results with average difference for power of the engine approximately around 2.8%. The efficiency decrease with the increase of the rotational speed of the engine and the highest efficiency is indicated for rectangular fins.
Hoodia gordonii (Masson) Sweet ex Decaisne
Authors: Latté Klaus Peter
Published: October 2021

Hoodia gordonii wird seit Langem von den indigenen Einwohnern des südlichen Afrikas, den Khoisan, zur Stillung des Hungers und des Durstes während langer Jagdreisen angewendet. Zahlreiche seltene Steroidglykoside wurden isoliert, u.a. auch die Substanz „P57“, die als wirksamer Stoff angesehen wurde. Einige Wirkmechanismen wurden für die Steroidglykoside und für Extrakte beschrieben, die die appetitunterdrückende Wirkung belegen. Ausgehend von diesem Wissen wurden von internationalen Firmen in den 1990er und 2000er Jahren Produkte mit H. gordonii bzw. „P57“ zur Gewichtsreduktion bei Übergewicht entwickelt. Nur eine klinische Studie ist jedoch in voller Länge veröffentlicht, in der eine Gewichtsreduktion bei Übergewicht nicht bestätigt werden konnte. Die Nutzung und Vermarktung dieser Pflanze war aufgrund von Fragen zu den „intellectual property rights“ und zum sog. „benefit sharing“ sehr umstritten.
Diagnostic Accuracy of SWAN in the Diagnosis of Low-Flow Brain Vascular Malformations in Childhood
Authors: Akyel Nazlı Gülsüm , Alımlı Ayşe Gül , Sivri Mesut , Akmaz Ünlü Havva , Tiftik Mehmet
Published: October 2021

Purpose The main objective of this study is to demonstrate the diagnostic accuracy of susceptibility-weighted angiography (SWAN) in the diagnosis of slow-flow cerebral vascular malformations, especially developmental venous anomaly (DVA). We also aimed to determine the prevalence of DVAs identified by SWAN at 1.5 T.

Methods We retrospectively evaluated 1,760 axial SWAN images for the diagnosis of low-flow vascular anomaly. Among them were 305 patients who underwent contrast-enhanced examination due to different indications. Postcontrast images were analyzed by different radiologists who were blinded to patients. The presence of DVA and other features such as location, length, depth, and direction of drainage vein was evaluated.

Results Twenty-six patients with DVA had both SWAN and postcontrast images. There were four false-negative patients with SWAN. The sensitivity of the SWAN sequence was 84.6%. In addition, totally 77 DVA (4.36%), 2 capillary telangiectasia (0.11%), and 2 cavernous malformations (0.11%) were detected in 1,760 patients.

Conclusion SWAN is an effective method for the diagnosis of developmental venous anomalies and other low-flow cerebral vascular malformations. Especially in the pediatric age, susceptibility-weighted imaging sequences are useful to limit contrast use.
Acute Ischemic Stroke in a Young Child and Its Association with SARS-CoV-2 Infection
Authors: Shree Nivya , Kommalur Anitha , M. Lakshmi , Kariyappa Mallesh , Devadas Sahana , Kumble Dhanalakshmi , Sajjan Sushma Veeranna , Rangegowda Ravichandra Kothur , Patel Ashray Sudarshan
Published: October 2021

The coronavirus disease 2019 (COVID-19) in children has been shown to have lower morbidity and mortality in children as compared with adults. The neurological complications related to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are increasingly reported in children, yet the cerebrovascular complications are rare. We report a case of a toddler who presented with right-sided hemiparesis and motor aphasia, with an antecedent history suggestive of COVID-19 infection. The child tested negative on the nasopharyngeal swab for real-time reverse transcription-polymerase chain reaction (RT-PCR), but the serology for anti-SARS-CoV-2 IgG assay was positive. The neuroimaging showed an acute infarct in the left middle cerebral artery territory. A detailed evaluation for causes of childhood stroke was unrevealing, except for the presence of severe iron deficiency anemia (IDA). The child was diagnosed as acute ischemic stroke (AIS) most probably secondary to mild COVID-19 infection. The objective of this case report is to explain the possibility of AIS after a mild COVID-19 infection, complicated by the underlying severe IDA. Therefore, an association between COVID-19 and stroke in children needs to be emphasized and RT-PCR for SARS-CoV-2 as well as serological assay must be included in the workup of stroke in the young.
Rapid microwave growth of mesoporous TiO2 nano-tripods for efficient photocatalysis and adsorption
Authors: Chamoli Pankaj , Shukla Ravi K. , Bezbaruah Achintya N. , Kar Kamal K. , Raina K. K.
Published: October 2021

A rapid microwave (180 s, 100 W) green approach has been demonstrated for the synthesis of TiO2 tripods (TITPs) using Mangifera indica leaf extracts. In this process, mangiferin acts as an efficient reducing agent while microwave radiations control the nucleation and growth of anisotropic TiO2 nanostructure. Surface morphological analyses reveal that synthesized TiO2 nanomaterial has a unique resilient shape of tripods with porosity. The photocatalytic ability of synthesized TITPs has been examined using Methylene blue (MB) as the target contaminant, and ∼75% (under visible light in 75 min) and 96% (under UV in 9 min) dye degradation has been achieved. The TITPs show recyclability for up to three cycles. Moreover, TITPs exhibit good adsorbent property that varies with the change of temperature and pH. The adsorption of the MB by TITPs follows the pseudo-first-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity of TITPs is found to be 17.54 mg/g based on the Langmuir model. The present multi-facet TITPs prepared via a simple and quick (180 s) microwave method has the potential for application in photocatalytic/adsorption for aqueous contaminant remediation.
Isomerization and reorientation of Disperse Red 1 in poly(ethyl methacrylate)
Authors: Grebenkin S. , Syutkin V. M.
Published: October 2021

Irradiation of azobenzene-containing polymer materials with light causes cis–trans isomerization and reorientation of azobenzene moieties and thereby changes in the optical properties of the materials. In this study, the film of poly(ethyl methacrylate) doped with the azobenzene derivative Disperse Red 1 (DR1) has been irradiated with the linearly polarized light of 546 nm. The time profiles of optical anisotropy and absorbance measured during irradiation have been analyzed using a kinetic model. Based on the analysis of the time profiles, we conclude that the light-induced reorientation of DR1 molecules occurs in confined environments where trans → cis isomerization is hindered, while in roomy environments, there is no reorientation. In the confined environment, reorientation occurs due to the environmental changes caused by the isomerization attempts of the DR1 molecule. The polymer environment affects thermal cis → trans and light-induced trans → cis isomerizations of the DR1 molecule differently, suggesting that the spatial requirements for these processes to proceed are different. The thermal isomerization does not result in the reorientation of DR1 molecules in roomy environments.
Leveraging lifetime information to perform real-time 3D single-particle tracking in noisy environments
Authors: Zhao Tian , Beckwith Joseph S. , Amin M. Junaid , Pálmai Marcell , Snee Preston T. , Tien Ming , Yang Haw
Published: October 2021

A microscopy platform that leverages the arrival time of individual photons to enable 3D single-particle tracking of fast-moving (translational diffusion coefficient of ≃3.3 µm2/s) particles in high-background environments is reported here. It combines a hardware-based time-gating module, which enables the rate of photon processing to be as high as 100 MHz, with a two-photon-excited 3D single-particle tracking confocal microscope to enable high sample penetration depth. Proof-of-principle experiments where single quantum dots are tracked in solutions containing dye-stained cellulose, are shown with tracking performance markedly improved using the hardware-based time-gating module. Such a microscope design is anticipated to be of use to a variety of communities who wish to track single particles in cellular environments, which commonly have high fluorescence and scattering background.
Egg viability of green turtles nesting on Raine Island, the world’s largest nesting aggregation of green turtles
Authors: Booth David T. , Dunstan Andrew , Robertson Katharine , Tedeschi Jamie
Published: October 2021

Egg inviability at oviposition is a possible explanation for the high rate of early-stage embryo death of eggs laid by green turtles at Raine Island, the largest green turtle nesting aggregation in the world. We tested this possibility by assessing egg viability of freshly laid eggs. We found that green turtle eggs laid at Raine Island have high viability at their time of laying, and that there was no relationship between egg viability and early-stage embryo death or hatching success within a clutch. Hence, the inviable egg at oviposition hypothesis cannot explain the high death rate of early-stage embryos that is characteristic of green turtle clutches laid at Raine Island.
Tungsten enzymes play a role in detoxifying food and antimicrobial aldehydes in the human gut microbiome
Authors: Schut Gerrit J. , Thorgersen Michael P. , Poole Farris L. , Haja Dominik K. , Putumbaka Saisuki , Adams Michael W. W.
Published: October 2021

Significance

The diverse microorganisms contained within the human gut are known to have significant effects on human health. Herein, we show that genes encoding members of the tungsten oxidoreductase (WOR) family of enzymes and a tungstate-specific transporter are prevalent in the human gut microbiome and metagenome. We demonstrate that two model gut microbes assimilate tungsten into multiple WOR enzymes and that some of these enzymes catalyze the conversion of gut aldehydes to the corresponding acid, likely as a detoxification strategy to remove these reactive compounds.
Roe-inspired stem cell microcapsules for inflammatory bowel disease treatment
Authors: Chen Guopu , Wang Fengyuan , Nie Min , Zhang Hui , Zhang Han , Zhao Yuanjin
Published: October 2021

Significance

We present roe-inspired microcapsules for therapeutic mesenchymal stem cells (MSCs) encapsulation with immune-isolating, wet-adhesive, and nutrient-rich capabilities. Due to the core-shell structure, the encapsulated MSCs could escape from the immune system and maintain immunomodulating functions. Furthermore, the roe proteins encapsulated with MSCs in the core phase provided adequate nutritional supply. By adding epsilon-poly-L-lysine-graft-methacrylamide and dopamine methacrylamide in the shell phase, the microcapsules might securely attach to the surface of the bowels. The encapsulated MSCs could relieve inflammatory bowel disease through modulating macrophage polarization. Based on these features, the roe-inspired microcapsules have great research value in clinical application.
Large uncertainties in global hydroxyl projections tied to fate of reactive nitrogen and carbon
Authors: Murray Lee T. , Fiore Arlene M. , Shindell Drew T. , Naik Vaishali , Horowitz Larry W.
Published: October 2021

Significance

Reaction with the hydroxyl radical (OH) is the dominant loss mechanism for many atmospheric gases of interest for air quality, climate change, and stratospheric ozone. Understanding how and why OH may change in the future is therefore paramount for predicting changes in the societal impacts associated with such changes. Future models’ projections strongly disagree in how OH responds to changing emissions and climate—even in the sign. Here, we demonstrate that intermodel differences in OH are best explained by disparate implementations of chemical and physical processes that affect reactive oxides of nitrogen and organic chemical species. Targeted observations can reduce uncertainty in the chemical budgets of these key species to increase confidence in future projections of composition and its impacts.
Otium litteratum en la novel·la cavalleresca
Curial e Güelfa
Authors: Gros Lladós Sònia
Published: October 2021

Resum

L’episodi nord-africà del llibre tercer de la
novel·la ha estat ja revisat per diversos estudiosos com una
recreació de la història de Dido i Eneas que ens transmet
l’Eneida. Els especialistes han subratllat els
trets particulars de la reescriptura d’aquest episodi virgilià, tot
suggerint la intermediació d’autors italians com Petrarca o
Boccaccio. En aquesta contribució pretenem explorar els aspectes que
relacionen aquest passatge amb el nou concepte
d’otium que els humanistes italians
desenvolupen a partir del redescobriment d’alguns textos clàssics.
En particular, suggerim l’anàlisi dels paral·lels amb De vita
solitaria de Petrarca, autor ben present en la novel·la,
com han mostrat els estudis de Francisco Rico o Júlia Butinyà.
Les construccions temporals de progressió narrativa en el
Curial e Güelfa
Authors: Garcia Sebastià Josep Vicent
Published: October 2021

Resum

El present estudi descriu algunes expressions
temporals del Curial e Güelfa. Concretament, se
centra en les formes de temps transcorregut que realitzen una
funció discursiva de ‘continuïtat’. Aquestes construccions expressen el transcurs d'un determinat període de temps entre dos moments referencials i, a més, aporten informació discursiva i fan que la trama avance. D’acord amb les dades
obtingudes del corpus emprat, el CIGCA, aquests constructes
s’utilitzen en passatges narratius d’altres textos medievals en
català. Les ocurrències del corpus també demostren que els usos de
les construccions temporals continuatives del
Curial són més diversos i equilibrats que els
d’altres obres semblants.
Baldament en el Curial e
Güelfa
Authors: Martínez Martínez Caterina
Published: October 2021

Resum

El present estudi se centra en el procés de
gramaticalització del connector de contrast
baldament des del sentit inicial d’adverbi
desideratiu fins al valor de marcador discursiu concessiu
actual. Ací, parem especial atenció a un valuós exemple del Curial e
Güelfa que suggereix quin degué ser el punt de partida d’aquest
procés. Examinem l’evolució del connector d’acord amb Lingüística
Cognitiva i, concretament, amb la Teoria de la Gramaticalització.
Tenim en compte, a més, la Teoria de l’Argumentació. La Teoria de la
(Inter)subjectivació i la Teoria de la Inferència Invitada del Canvi Semàntic ens
ajuden a revisar les fonts i els valors de
baldament en català des del segle XIV al segle
XIX.