Operating Regimes Research Articles

Additive Nanosecond Laser-Induced Forward Transfer of High Antibacterial Metal Nanoparticle Dose onto Foodborne Bacterial Biofilms.

Additive laser-induced forward transfer (LIFT) of metal bactericidal nanoparticles from a polymer substrate directly onto food bacterial biofilms has demonstrated its unprecedented efficiency in combating pathogenic microorganisms. Here, a comprehensive study of laser fluence, metal (gold, silver and copper) film thickness, and the transfer distance effects on the antibacterial activity regarding biofilms of Gram-negative and Gram-positive food bacteria (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Listeria monocytogenes, Salmonella spp.) indicated the optimal operation regimes of the versatile modality. LIFT-induced nanoparticle penetration into a biofilm was studied by energy-dispersion X-ray spectroscopy, which demonstrated that nanoparticles remained predominantly on the surface of the biofilm.

Accelerating the optimization of vertical flow assay performance guided by a rational systematic model-based approach

Rapid diagnostic tests (RDTs) have shown to be instrumental in healthcare and disease control. However, they have been plagued by many inefficiencies in the laborious empirical development and optimization process for the attainment of clinically relevant sensitivity. While various studies have sought to model paper-based RDTs, most have relied on continuum-based models that are not necessarily applicable to all operation regimes, and have solely focused on predicting the specific interactions between the antigen and binders. It is also unclear how the model predictions may be utilized for optimizing assay performance. Here, we propose a streamlined and simplified model-based framework, only relying on calibration with a minimal experimental dataset, for the acceleration of assay optimization. We show that our models are capable of recapitulating experimental data across different formats and antigen-binder-matrix combinations. By predicting signals due to both specific and background interactions, our facile approach enables the estimation of several pertinent assay performance metrics such as limit-of-detection, sensitivity, signal-to-noise ratio and difference. We believe that our proposed workflow would be a valuable addition to the toolset of any assay developer, regardless of the amount of resources they have in their arsenal, and aid assay optimization at any stage in their assay development process.

Characteristics of electron temperature profile stiffness in electron-heated plasmas on EAST

A very high core electron temperature (T e0 ∼ 10 keV) plasma has been established and stably sustained by applying both lower hybrid wave (LHW) and on-axis electron cyclotron resonance heating (ECRH) in the Experimental Advanced Superconducting Tokamak (EAST). In this work, power balance analysis shows that the increase of ECRH power can increase the normalized T e gradient significantly at the plasma core region (ρ < 0.6), but does not change the T e profile stiffness in the low-density L-mode plasmas. This has been considered to be due to a strong synergistic effect between ECRH and LHW. Furthermore, three distinguishable stages characterized by different T e profile stiffnesses can be identified from the density ramp-up in the electron-heated plasma on EAST. A stronger T e profile stiffness at ρ = 0.3 has been observed in the Stage-II, where the LHW power deposition gradually moves away from the plasma core region, following the electron density increases. Furthermore, the formation of an internal plasma density transport barrier inside ρ ∼ 0.6, accompanied by a sudden drop in core T e and a rise in both core plasma density and ion temperature, has been observed for the first time during the transition from the Stage-II to the Stage-III when the central line-averaged plasma density reaches a threshold of 2.2 × 1019 m−3. This finding strongly affects further development of high-performance gas-fueled electron-heated plasma scenarios in EAST and suggests an advanced operational regime with a wide internal plasma density transport barrier.

Experimental and Numerical Investigation of the Effect of Blades Number on the Dynamic Response of a Small Horizontal-Axis Wind Turbine

The new energy scenario is rising a strong interest towards the distributed production from renewable sources; among them, wind seems to be one of the most interesting and at the same time critical due to the challenges of the conversion technology. Operation of small wind energy conversion systems is generally very complex due the extremely variable regime of operation and the high turbulent wind, so that a deep knowledge of the dynamic response of such devices is crucial not only for optimising their performances but also to make them comfortable to be used in residential areas. For these reasons, the present work is focused on analysing the effect in changing the number of blades on a small horizontal axis wind turbine through an experimental campaign in the wind tunnel. The turbine dynamics has been characterised running some “wind ramp” tests and analysing the rotor capability in following the wind as well the vibrations transmitted by the turbine during the operation. Results demonstrate that a higher number of blades, despite a small decrease of performance, can make the machine more efficient in operating at low wind regimes. At the same time, a higher number of blades can make the rotor efficient even at lower speed of rotation, thus limiting the risks of having high magnitude vibrations.

Optimising the energy-water-CO2 nexus of a water distribution network

The digital age attracts significant challenges in the delivery of Fourth Industrial Revolution (4IR) based technologies. The energy-water-CO 2 nexus benefits of 4IR technologies are a significantly greater challenge, especially across the Water Distribution Network (WDN). A business process based energy-water-CO 2 nexus model was developed with the capacity to simulate a comprehensive WDN, and predict the impact of 4IR technologies on the energy-water-CO 2 nexus. The model was applied to the monitoring and control business process of a local water utilities water distribution network. The model simulates the baseline (as-is) energy-water-CO 2 nexus, and evaluates the impact of the adoption of variable speed drive (VSD) and the internet of things (IoT) based on three operational regimes: normal operating pressure, low pressure and high pressure. The model evaluates VSD and IoT adoption singly and in-combination. The VSD has the largest positive impact on the energy-water-CO 2 nexus, reducing the energy demand and CO 2 emissions by16% each, and the water losses by 22%. A reduction in water losses, results in an increase in revenue for the water utility enabling the upgrading of aging infrastructure, investment in digital technologies and the expansion of infrastructure to increase access to clean drinking water. Whilst the impact of IoT on the WDN water-energy-CO 2 nexus is low, it is critical towards developing a “smart” and “self-adjusting” water distribution network.

Characterization of the Propulsion System for Submersible Multimedium Robotic Vehicles

Multimedium robots are a new class of bioinspired vehicles with the ability of cross-domain transition and maneuverability across multiple domains. Such hybrid robots can transverse both in air and water, overcoming the stark differences in the motion dynamics within these mediums. Differences in the density, viscosity, and additional fluid-induced forces of the medium make the propulsion system design for multimedium robots a crucial challenge. Both unmanned aerial and remotely operated underwater vehicles rely on electrical propulsion coupled with propellers to navigate in their own respective medium of operation. However, due to the density differences in water and air, which is approximately 103 times, an aerial propeller demands higher RPM to generate significant thrust, unlike an underwater propeller. Higher water density and fluid inertia, on the other hand, demand a greater in-drive torque to spin the propeller in underwater conditions. Other critical parameters to be considered while choosing a suitable propulsion system are propeller diameter, propeller pitch, shaft torque requirements, operational RPM of motor–propeller pair, cavitation, and propeller tip deflection. This article presents an in-depth investigation and evaluation methodology to identify the feasible operating range for propellers and motors that meet the aerial and underwater thrust requirements while minimizing cavitation and propeller deflection. The thrusters (motor-propeller pair) are investigated individually, where propeller performance and physical constraints on the propeller blade are analyzed using blade elemental momentum theory (BEMT), while the motor is studied using the three-constant motor model. These subsystems are then mapped using torque equilibrium to determine their specific operational regime and overall efficiency. Numerical simulation in QPROP demonstrates that aerial thrusters can be utilized for both the mediums but with a sacrifice of overall efficiency. The optimal motor efficiency was 73.06% in aerial operation and 8.1% in underwater operation, but with increased thrust underwater due to higher fluid density, which is essentially a design tradeoff. The results of the analysis are experimentally validated and further presented as a framework for selecting an appropriate propulsion subsystem for multimedium vehicles based on the specific user-defined design requirements.

Vanishing space-charge effects in contact-limited thin-film diodes

Estimation of charge-carrier mobility and trap energy from a space-charge-limited-current measurement is a well-established technique for the characterization of electronic materials. However, classical solid-state theories referenced for parameter extraction are based on simplistic assumptions that may not be strictly valid for a new generation of devices from unconventional materials and processing. In this study, we show that contact-limited currents dominate the entire operating regime in thin-film or nanoscale diodes even at a small charge-injection barrier. This assessment can make many reported values and analysis routines debatable, because they do not generally take any contact effects into consideration. Physical origins of the validity problem and guidelines for holistic parameterization are detailed through systematic correlation of analytical models, numerical simulation, and an experimental investigation into an organic diode with a graphene contact.

Using post-processing heat treatments to elucidate precipitate strengthening of additively manufactured superalloy 718

The poor machinability and extensive work hardening of Ni-based superalloys makes additive manufacturing an attractive option for producing geometrically complex components with distinct microstructures. Although previous studies show recovery of high strength at room temperature, very few studies demonstrate successful properties at elevated temperatures required for industrial applications. The objectives of this study are to present a post-build heat treatment for high strength across a wide temperature range, determine the strength contribution of nanoscale precipitating phases to the overall mechanical properties of superalloy 718, and from these, provide a comprehensive microstructure-property relationship for wrought and AM 718 to guide efforts to simulate the properties of AM components. Laser powder bed fusion–produced superalloy 718 was characterized at multiple length scales using scanning electron microscopy and transmission electron microscopy in the as-built condition and with multiple heat treatments designed to form combinations of γʹ, γʺ, and δ precipitates. Uniaxial tensile tests performed from room temperature to 600 °C on subsize specimens determined the yield strength, elastic modulus, ultimate tensile strength, fracture stress, and uniform elongation. Precipitates in this work proved to be weak barriers to dislocation motion through a dispersed barrier model, but they provided strength to the alloy through their consistent high density. The relative contribution to the yield strength from γʺ remained consistent between 48–57% of the total strength up to 600 °C, the primary influence on the high temperature strength of superalloy 718. The strength factors for γʺ and δ precipitates were found to trend inversely with tensile test temperature and may be attributable to the differences in precipitate coherency. A post-build heat treatment is recommended to maintain high strength at elevated temperatures. A quantitative microstructure-property relationship, dependent on precipitate size, density, and morphology, was derived and can estimate the yield strength across a wide temperature range applicable to the operational regimes for superalloy 718.

Numerical Investigation of the Ramjet and Scramjet Operation Regimes of the HIFiRE-2 Combustion Chamber

Numerical Investigation of the Ramjet and Scramjet Operation Regimes of the HIFiRE-2 Combustion Chamber

THE INSTRUMENTAL ACCURACY OF KNOWN FORMULAS FOR THE CONVERSION OF OPACITY INDICATORS INTO INDICATORS OF TOXICITY OF EXHAUST GASES OF RECIPROCATING ICE

The article analyzes the nomenclature of the most widely used indicators of opacity of exhaust gases of reciprocating internal combustion engines and mathematical apparatuses of known formulas for conversion of indicators of opacity and toxicity of exhaust gases, from which the conversion formula of Prof. Igor Parsadanov as such, which takes into account not only the opacity indicators, but also the indicators of the toxicity of exhaust gases was selected. The analysis and transformation of the selected conversion formula was carried out, and the peculiarities of the influence on the magnitude of the physical value of the independent variables obtained by it were revealed. A method of calculating the instrumental accuracy of obtaining the mass hourly emission of particulate matters with the flow of exhaust gases according to the researched conversion formula in two successive approximations has been developed. According to the results of the calculated study according to the developed methodology for the basic indicator of the opacity of the exhaust gases and the passport accuracy of the measuring equipment, it was established that the average value of such accuracy was ±8.3 % for the special regimes of operation of the reciprocating internal combustion engine. The influence of the type of exhaust gas opacity indexes with its corresponding measurement units on the instrumental accuracy of the studied conversion formula was identified and analyzed. According to the sign of the value of such accuracy for the passport accuracy of the measuring equipment, the known indicators of opacity of exhaust gases are ranked.

Effect of fabrication method and surface roughness on spray characteristics for small pressure-swirl atomizers

The paper investigates the effect of the fabrication method, precision and surface roughness on atomization nozzle performance. A comprehensive review of the available knowledge on the topic is an integral part and an indispensable prerequisite of the study. It focuses on the requirements for atomizing nozzles and their production from the point of view of surface quality, dimensional and shape accuracy. The published results on the influence of surface quality and roughness on internal flow and atomizer performance are discussed. Available atomizer manufacturing techniques are reviewed with a focus on Rapid prototyping methods, accuracy and geometrical imperfections.Classical Machining and two 3D printing techniques were applied to produce small pressure-swirl atomizers. They were fabricated in a number of versions. The machined nozzles featured several specific defects. Spray quality measurements of these atomizers, at selected operation regimes, were made on a cold test bench using PDA and mechanical patternation to evaluate discharge coefficient (CD), Sauter mean diameter, spray cone angle, nozzle efficiency (ηn), breakup length and liquid distribution in the spray.The results show the important and systematic effects of surface quality and manufacturing imperfections on the atomizer characteristics. The exit orifice imperfections harm the circumferential uniformity and other spray characteristics. The effect becomes significant when the exit orifice shifted out of the nozzle axis by >2 % of the chamber diameter, and the orifice edge is chamfered by >20 % of the orifice length. The swirl chamber surface modified by scratches has a minor effect.Replacement of machining with current commercial 3D printing techniques, namely Selective laser melting and PolyJet technique, is associated with increased surface roughness. It worsens spray quality, liquid distribution uniformity and ηn and increases the CD when relative surface roughness exceeds 0.007.The result presentation using dimensionless criteria allows for generalisation of the outcomes to other atomizer types and scales.

Multi-objective optimization of the ORC axial turbine for a waste heat recovery system working in two modes: cogeneration and condensation

Due to the demand of the district heating network and electric power grid ORC turbines can operate in the condensation and cogeneration modes. This approach requires the design of an expander which is characterized by high efficiency in each mode of operation. The paper is devoted to a multi-objective efficiency optimization of a one stage axial ORC turbine working on MM (Hexamethyldisiloxane). An Implicit Filtering algorithm (IF) is used to find a flowpath with maximum efficiency. During the optimization the rotor profiles (at the hub and shroud) and the shape of endwall contours of the rotor domain are changed. Five optimization tasks are carried out with different weights of the efficiency of both modes of operation. Pareto fronts are obtained and a decision-making method is used to select an optimum solution. The optimization of the rotor row allows for significant efficiency improvements in two regimes of operation, with respect to a baseline geometric configuration designed with the help of classical methods.

Strategies of socio-ecological transition for a sustainable urban metabolism

Urbanization plays a key role in the human activities causing and feeding climate change. At present, climate change and other environmental issues are directly or indirectly related to the metabolism of cities. However, cities may also play a central role in the fight against climate change. This is the reason why Urban Metabolism (UM) has become a powerful concept to account for and understand the way in which complex systems such as cities use and dispose of material resources, also suggesting measures to change their operational regimes. The rightsizing and optimization of UM is basically a matter of social innovation. It implies changes in the way a city collectively produces and reproduces its physical stocks and provides services to its inhabitants. This article aims at identifying strategies, scenarios, and pathways to slow down urban metabolic processes while improving their efficiency, thus managing a successful transition to an urban (more) circular economy, as well as decreasing the material intensity of the urban economy. The main objectives of the article are the following:1. The development of a renewed approach for studying Urban Metabolism based on transdisciplinary approaches and methods aimed to model metabolic agents' patterns of practices.2. The definition of urban patterns of resource use of different agents shaping urban metabolism (households, corporate agents, communities, and public authorities).3. The exploration of the main policies and administrative tools that cities use to manage environmental problems leading to different urban regulation regimes.4. A tool for generating future scenarios and roadmaps to reach a low-carbon future. This tool is crucial for engaging experts, stakeholders and the public looking for new solutions.

High current short pulse driver using a high power diode laser for optoacoustic biomedical imaging techniques.

Optoacoustic biomedical imaging combines the high spatial resolution of the ultrasound imaging with the specificity of the optical absorption spectroscopy techniques. It is being used in various scenarios such as anatomical, functional and molecular imaging. Typically light sources for this imaging technique is based on solid state lasers since they can produce high energy short optical pulses. However, they are bulky, expensive and the imaging speed is limited because their low pulse repetition rate. High power diode lasers (HPDLs) are a promising alternative for imaging small volume absorbers as they are compact, affordable and allow high repetition rates. However, HPDLs provide relative low peak optical power compared to solid state lasers. Therefore, imaging systems based on diode lasers require much longer pulse duration resulting in lower in-depth resolution and optoacoustic conversion efficiency. HPDLs need dedicated fast electronics to generate short optical pulses. In this work, we have designed, built and test a pulsed diode laser driver based on RF power MOSFETs, specifically considering the optimization of the current pulse in order to maximize the optical peak power, achieving current pulses of more than 900 A with a duration of 50 ns. We have studied the operation of a low cost HPDL out of the manufacturers datasheet ratings without noticeable degradation at high current (> 250 A) and short pulse duration (< 60 ns). We have obtained an optical peak power of 750 W and a energy per pulse of 31.2 µJ at 40 ns optical pulse duration. The optoacoustic images obtained in this operation regime shown a clear enhancement respect to the ones obtained in standard operation of the HPDL.

Dynamic control of the mode-locked fiber laser using a GO/PS modulator.

This Letter proposes a novel, to the best of our knowledge, transistor-like optical fiber modulator composed of graphene oxide (GO) and polystyrene (PS) microspheres. Unlike previously proposed schemes based on waveguides or cavity enhancement, the proposed method can directly enhance the photoelectric interaction with the PS microspheres to form a light local field. The designed modulator exhibits a distinct optical transmission change (62.8%), with a power consumption of <10 nW. Such low power consumption enables electrically controllable fiber lasers to be switched in various operational regimes, including continuous wave (CW), Q switched mode-locked (QML), and mode-locked (ML). With this all-fiber modulator, the pulse width of the mode-locked signal can be compressed to 12.9 ps, and the corresponding repetition rate is 21.4 MHz.

Bandwidth tunable vibration energy harvester based on hybrid triboelectric-piezoelectric array

In this work, we present a highly effective and scalable design strategy of a triboelectric-piezoelectric hybrid array of three cantilever beams stacked over each other (wideband operation regime), which can also be rotated around their mean position to vibrate freely without impacting any other layer (narrowband operation regime). Contrary to a unique frequency response exhibited by conventional devices, the proposed device can switch between narrowband and wideband frequency responses around different central frequencies. This work elaborately discusses the frequency response of mechanical stopper-based PEG and TEGs at varying gap lengths, excitations, and resonant frequencies, and the design of the hybrid array is optimized based on it. The performance of this device is characterized using simulation analysis and experimental validation. Experimentally, the device generates net power greater than 0.3 μW (Piezoelectric) and 0.4 μW (Triboelectric) continually between the frequencies of 30 to 60 Hz in the wideband operation regime and output power of 0.81 μW, 0.65 μW, and 0.62 μW at 27,36 and 45 Hz in the narrowband operation regime under mechanical excitation of 0.75g. The remarkable performance of the device at different frequency ranges demonstrates its potential in various harvesting and sensing applications.

Body Force Model Implementation of Transonic Rotor for Fan/Airframe Simulations

Three-dimensional throughflow models represent a turbomachinery cascade via a force distribution without the need for detailed geometric modelling in the numerical solution, saving consistent computational resources. In this paper, we present the application of a body force method on an axial transonic fan implemented into an in-house tool for axisymmetric throughflow simulations. By a systematic comparison of local and integral quantities with a validated numerical solution, the capabilities and limitations of the model are discussed for different operating regimes. The implementation is first validated at the peak efficiency calibration point, providing a good duplication of blade flow variables and radial profiles. The design total pressure is matched with a 0.6% absolute difference and a slightly higher slope of the characteristic towards the stall. The isentropic efficiency curve is penalised after the choking mass flow rate calibration, presenting an absolute difference close to 2%, although with a consistent off-design trend. In general, the model provides a satisfactory representation of the flow field and the outflow spanwise distributions, with locally larger discrepancies near the endwalls. Finally, the method is applied to simulate the fan and outlet guide vanes installed into an isolated turbofan nacelle. The onset of intake stall at a high angle of attack is compared between the body force and a boundary conditions-based approaches, highlighting the importance of adopting fully coupled solution methods to study fan/airframe interaction problems.

Effect of water regime on the dynamics of free ammonia during high solid anaerobic digestion of pig manure

Free ammonia (FAN) inhibition is commonly encountered during high solid anaerobic digestion (HSAD) of pig manure. The performance of HSAD is highly related to its operational water regime; however, little information is available regarding the dynamics of free ammonia with varied water regimes. In this work, four treatments were set with equal amount of water supply but varied addition frequencies, i.e. add once but at different times in treatments T1 and T2, add twice in T3 while it was three times in treatment T4. Results showed that the whole methanogenic process ran smoothly with the average methane gas production rate maintaining at 191.1 LCH4/kgVSadded. Although a higher methane gas production rate of 217.4 LCH4/kgVSadded was achieved in T1, one time water addition triggered a higher ammonia inhibition potential. Cumulative FAN release was 6.03 mgFAN/kgVSadded in T1 while the balance between FAN and ammonia tended to the fraction of FAN. In T4, cumulative FAN of 5.07 mgFAN/kgVSadded was evolved, which was lower than that in T1 but similar to the situation in T2. The lowest FAN was observed in T3, indicating that a moderate frequency of dilution might be conducive to alleviate free ammonia inhibition.

The influence of full drifts on density shoulder formation at the midplane by numerical modeling

The density shoulder at the midplane may influence core plasma confinement during H-mode discharge, thus affecting long-pulse steady-state discharge. Drifts in the edge plasma play a remarkable role in plasma transport and the divertor operation regime, which determine density shoulder formation (DSF). In this work, the SOLPS-ITER code package is used to evaluate the influence of full drifts on DSF in poloidal and radial coordinates. An open divertor of DIII-D-like geometry with weak neutral compression is chosen for the modeling. Cases without drifts, with only E × B drifts in forward B t and with full drifts in both forward and reversed B t are simulated for comparison. It is confirmed that the high upstream density promotes DSF when the drift is not considered, which has also been observed in various investigations. When the drifts are taken into account, the divertor in/out asymmetry (or upstream ionization source) is determined by the direction of B t due to the variation of particle transport, thus the shoulder can be facilitated or suppressed. Two mechanisms of DSF with full drifts are elucidated: (1) E × B and B × ∇B drifts promote DSF at the inner midplane (IMP) by raising the ionization source (at IMP) in forward B t; (2) the drifts contribute to DSF at the outer midplane by enhancing the particle transport loss in reversed B t. In a high-recycling regime, ionization is the dominant term for DSF, while in the low-recycling regime enhanced particle transport loss plays a more important role. Comprehensively understanding the mechanisms of DSF is of great importance for the improvement of core–edge compatibility in fusion reactors.

Mitigation of environmental effects of frequent flow ramping scenarios in a regulated river

In the transition to a society based on renewable energy, flexibility is important in balancing the energy supply as more intermittent sources like wind and solar are included in the energy mix. The storage-based hydropower systems are a renewable energy source that provides the needed flexibility since a hydropower plant can be started and stopped in minutes, and the reservoirs provide stored energy that can be utilized when the demand arises. Thereby, the hydropower plants can balance the variability in other energy sources, e.g., when there is no wind or when solar input is low. This need for increased flexibility has led research toward new hydropower turbines to provide larger ramping rates, more frequent starts and stops, and other system services. A possible drawback of the ramping operation of hydropower plants (often termed “hydropeaking”) are the adverse effects on the environment in receiving water bodies downstream of the power plant outlet, particularly when the hydropower outlets are in rivers. Rapid changes in flow can lead to stranding of fish and other biota during the shutdown of turbines and flushing of biota during the start of turbines. These effects can also be caused by other sudden episodes of water withdrawal, such as during accidental turbine shutdowns. The main objective of this study is to describe a method of designing the necessary volume of water required to mitigate a fast ramping turbine, and present the effect this has on the downstream river reach. We used a 2D hydraulic model to find the areas affected by hydropeaking operation and, furthermore, to define areas with a faster ramping rate than 13 cm/h which is used as a limit in Norwegian guidelines. Based on this, we developed a ramping regime that would prevent fast dewatering of critical areas and provide this as a basis for mitigating the effects of fast dewatering in the downstream river (River Nidelva in Norway was used as a test case). Furthermore, the effect of increasing the frequency of start–stop cycles was studied, and the proposed mitigation was evaluated for the new operational regime.