Steady Cycle Research Articles

Metabolic homeostasis and growth in abiotic cells

Metabolism constitutes the core chemistry of life. How it began on the early Earth and whether it had a cellular origin are still uncertain. A leading hypothesis for life's origins postulates that metabolism arose from geochemical CO2-fixing pathways, driven by inorganic catalysts and energy sources, long before enzymes or genes existed. The acetyl-CoA pathway and the reductive tricarboxylic acid cycle are considered ancient reaction networks that hold relics of early carbon-fixing pathways. Although transition metals can promote many steps of these pathways, whether they form a functional metabolic network in abiotic cells has not been demonstrated. Here, we formulate a nonenzymatic carbon-fixing network from these pathways and determine its functional feasibility in abiotic cells by imposing fundamental physicochemical constraints. Using first principles, we show that abiotic cells can sustain a steady carbon-fixing cycle that performs a systemic function over a relatively narrow range of conditions. Furthermore, we find that in all feasible steady states, the operation of the cycle elevates the osmotic pressure, leading to volume expansion. These results suggest that achieving homeostatic metabolic states under prebiotic conditions was possible, but challenging, and volume growth was a fundamental property of early metabolism.

Dimethyl ether fuel injection system development for a compression ignition engine for increasing the thermal efficiency and reducing emissions

In this study, a dedicated fuel injection equipment (FIE) for a 100% dimethyl ether (DME)-fueled three-cylinder engine was developed. DME has a cetane number (>55) higher than baseline diesel (40–50), making it a promising compression ignition (CI) engine fuel. However, some physicochemical properties of DME, namely lubricity, viscosity, density, calorific value, vapour pressure, incompatibility with elastomers, etc., necessitate modifications in the existing FIE to deliver a power output equivalent to baseline diesel fuelled engine. Modifications included customized DME storage tanks, supply lines, return lines, and a pneumatic pre-supply feed pump. In addition, a customized high-pressure pump (HPP) (inline mechanical pump) and a set of modified injectors with larger nozzle hole diameters were used for the DME engine. The engine speed was varied from 1000 to 2000 rpm, and off-road operating conditions were simulated using a non-road steady cycle (NRSC). A detailed evaluation of the FIE for its comparative combustion, performance, and emissions characteristics of DME was conducted vis-à-vis baseline diesel. The DME-fuelled engine showed an increase of ∼4.7% in brake thermal efficiency (BTE) under full load conditions and an increase of ∼8.32% BTE under simulated non-road-testing conditions. In addition, the DME-fuelled engine exhibited no visible smoke and negligible soot in the engine exhaust. DME combustion reduced HC emissions by ∼50% at low and medium engine speeds, and a ∼100% reduction was seen at higher engine speeds compared to baseline diesel engine. The CO emission decreased by ∼90%, and the CO2 emissions were ∼15% lower for DME. Lower exhaust gas temperature (EGT) and lower heat release rate (HRR) during premixed combustion indicated that DME-fuelled engine acted as a low heat rejection (LHR) engine. This study demonstrated a 100% DME-fueled engine with a customized FIE, delivering higher thermal efficiency and lower emissions than conventional diesel engines for on- and off-road applications.

P‐7.11: Assistance of Iron (II) Chloride and Dimethyl Sulfoxide to Liquid Electrochromic Device Based on Ammonium Metatungstate

Inspired by some previous surveys, we obtained significant electrochromic properties by hydrothermal synthesis using a solution of Iron (II) Chloride, Ammonium Metatungstate, Sodium Hydroxide and Hydrochloric Acid. The respond time of the electrochromic device was accelerated by iron (II) chloride that the coloring time was 6.5s while the bleaching time was 11.5s at the molar concentration ratio of 1:3.5 between ammonium metatungstate and iron (II) chloride, PH=2.5. Meanwhile the device had a significant optical modulation of 65% with air serving as a blank. Influenced by the acidic environment, the aqueous solution will occur hydrogen evolution reaction (HER) which dramatically deteriorated the stable of active layer over a long period of cycling. Here we innovatively apply a hydrogen bond acceptor, dimethyl sulfoxide (DMSO) to the formulation, the open circuit voltage of HER can be increased as well as the overpotential through restricting all hydrogen atoms of the water molecules in the DMSO‐H2O H‐bond network which can achieve the effect of maintaining a steady cycle of over 800 cycles.

A prototype recuperated supercritical co2 cycle: Part-load and dynamic assessment

High efficiency, flexibility and competitive capital costs make supercritical CO2 (sCO2) systems a promising technology for renewable power generation in a low carbon energy scenario. Recently, innovative supercritical systems have been studied in the literature and proposed by DOE-NETL (STEP project) and by a few projects in the EU Horizon 2020 (H2020) program aiming to demonstrate supercritical CO2 Brayton power plants, promising superior techno-economic features than steam cycles particularly at high temperatures.The H2020 SOLARSCO2OL project, which started in 2020, is building the first European MW-scale sCO2 demonstration plant and has been specifically tailored for Concentrating Solar Power (CSP) applications. After a detailed explanation of the modelling approach for steady and unsteady cycle simulations, this paper presents the off-design and dynamic analysis of such plant layout, which is based on a simply recuperated sCO2 cycle. The entire system model has been developed in TRANSEO environment. The part-load analysis ranged from 50% of nominal up to a 105% peak load, discussing the impact on compressor and turbine operating conditions. Full operational envelop has been determined considering cycle main constraints, such as maximum turbine inlet temperature and minimum pressure at compressor inlet.The off-design performance analysis highlights the most relevant relationships among the main part-load regulating parameters, namely molten salt mass flow rate, CO2 mass flow rate, total CO2 mass in the loop, and shaft line speed. The results show specific features of different control approaches, discussing the pros and cons of each solution, considering also its upscale towards commercial applications. In particular, the analysis shows that at 51% of load an efficiency decrease of 20% is expected. Finally, the dynamic characterization of the closed loop shows the relatively fast responsiveness of the plant to compressor speed variations, causing quick changes in CO2 mass flow rate, together with longer time scale phenomena related to the plant heat exchangers. In this respect, sCO2 plants demonstrate to have the potential to provide primary reserve for the electrical grid, as far as thermal stresses on main plant components are kept under acceptable limits.

Modelling the net environmental and economic impacts of urban nature-based solutions by combining ecosystem services, system dynamics and life cycle thinking: An application to urban forests

Nature-based solutions (NBS) are gaining relevance as sustainable urban actions because of their potential to provide multiple benefits in the form of ecosystem services (ES), and thus mitigate urban challenges. This paper presents an original semi-dynamic modelling framework that simultaneously considers i) ES supply and demand dynamics, ii) negative environmental impacts, externalities, and financial costs derived from NBS, and iii) life cycle NBS impacts beyond the use phase. Compared to other models, it also aims to be valuable for urban planning actions at site level, i.e., for evaluating the net impacts of specific urban NBS projects. To validate the modelling framework, a proof-of-concept model for urban forests is developed and tested for a case study in Madrid (Spain). The modelling framework is split in two interrelated parts: foreground (dynamic modelling) and background (static modelling). In the foreground, the environmental impacts derived from the use phase of an NBS project are quantified considering its spatio-temporal dynamism, by making use of system dynamics. In the background, the environmental impacts derived from the rest of the life cycle phases of the NBS are quantified making use of steady state life cycle impact assessment. The net economic impact of the NBS project, considering both financial values and externalities, is eventually calculated in the background encompassing all the life cycle phases. Results from the case study illustrate how planning, design, and management decisions over the entire life cycle of an urban forest can influence the net environmental and economic performance of this type of NBS. A discussion is provided to inform on how the modelling framework can help moving beyond the state-of-the-art, and how the derived model can be used for sustainability assessments of urban NBS projects.

Double coaxial pipe jet control using DBD-PA and bluff body

In this study, a double-tube burner nozzle with a DBD-PA (dielectric barrier discharge plasma actuator) and flame holder was employed to regulate the lifted flame. The flame holder held the lifted flame and the DBD-PA regulated the lifted flame to suppress the lifted flame’s vertical oscillation. To form a lifted flame, pseudo-biogas, a mixture of CH4 and CO2 in the ratio of 6:4, was jetted out through an inner nozzle and air through an annular nozzle. To control the air jet and prevent the lifted flame’s vertical oscillation, the DBD-PA was installed inside an annular nozzle. The DBD-PA was driven intermittently at regular intervals to produce a tangential flow in the same direction as the jetting gas, and the flame holder was placed above the nozzle outlet on the nozzle center axis. The finding indicated that by driving the DBD-PA at the slightly lower frequency than the frequency of the naturally shedding vortices in the free jet, the lifted flame’s vertical oscillation can be reduced by collapsing the jet’s vortex ring at a steady position and with a steady cycle. By impeding the lifted flame’s vertical oscillation, it is forecasted to reduce the blowout of the lifted flame and combustion noise.

Nitrogen-doped carbon fibers loaded with Co/Co2Mn3O8 alloy nanoparticles as bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries

The lack of low-cost and high-activity bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is an important factor restricting the massive application of rechargeable zinc-air batteries (ZABs). Herein, nitrogen-doped carbon fibers (NCFs) loaded with Co/Co2Mn3O8 alloy nanoparticles (Co/Co2Mn3O8@NCFs) were reported as a bifunctional oxygen electrocatalyst for rechargeable ZABs. The hierarchical porous structure of NCFs and strong synergetic coupling between Co/Co2Mn3O8 alloys and Co-Nx sites accelerated the kinetics of ORR reaction. The abundant lattice oxygen and N-doped sites promoted the efficient OER process. Benefiting from the above advantages, a rechargeable ZAB assembled with Co/Co2Mn3O8@NCFs delivered an excellent energy density of 968.10 Wh kg−1 (normalized to the mass of consumed zinc) and outstanding stable cyclability (steady cycle charge and discharge at 10 mA cm−2 for 120 h), surpassing state-of-the-art Pt/C catalyst (830.86 Wh kg−1/75 h). This study demonstrated the potential value of Co/Co2Mn3O8 alloys in energy conversion and storage.

Experimental investigation on emission characteristics of high reactivity gasoline compression ignition with different EGR and injection pressure strategies

Using a High Reactivity Gasoline (HRG) in diesel engines is a promising approach to reduce NOx and soot emissions simultaneously without modifying the engine hardware. In this study, an experimental investigation on HRG and diesel emission characteristics was conducted in a six-cylinder heavy duty diesel engine with different exhaust gas recirculation (EGR) rate and injection pressure strategies. Four operation points, A25, A75, C25, and C75 in the European Steady Cycle (ESC), were studied. The pilot-main injection strategy was applied, and injection timing was adjusted to maintain a constant Crank Angle of 50 % heat release (CA50). The results show that, compared with diesel, HRG can achieve lower soot mass emission while maintaining an ultra-low NOx emission level (2–3 g/kWh) with a lower injection pressure, indicating lower cost in the fuel injection and aftertreatment systems. The particle size distribution was also analyzed for both fuels. Under high EGR rates, the accumulation mode particles were dominant for both HRG and diesel. However, under low EGR rates, diesel produced much more nucleation mode particles than HRG. The phenomenon can be explained by the difference in the pyrene and acetylene productions between paraffin and aromatic compositions.

Combating Li metal deposits in all-solid-state battery via the piezoelectric and ferroelectric effects

All-solid-state Li-metal batteries (ASSLBs) are highly desirable, due to their inherent safety and high energy density; however, the irregular and uncontrolled growth of Li filaments is detrimental to interfacial stability and safety. Herein, we report on the incorporation of piezo-/ferroelectric BaTiO3 (BTO) nanofibers into solid electrolytes and determination of electric-field distribution due to BTO inclusion that effectively regulates the nucleation and growth of Li dendrites. Theoretical simulations predict that the piezoelectric effect of BTO embedded in solid electrolyte reduces the driving force of dendrite growth at high curvatures, while its ferroelectricity reduces the overpotential, which helps to regularize Li deposition and Li+ flux. Polarization reversal of soft solid electrolytes was identified, confirming a regular deposition and morphology alteration of Li. As expected, the ASSLBs operating with LiFePO4/Li and poly(ethylene oxide) (PEO)/garnet solid electrolyte containing 10% BTO additive showed a steady and long cycle life with a reversible capacity of 103.2 mAh g-1 over 500 cycles at 1 C. Furthermore, the comparable cyclability and flexibility of the scalable pouch cells prepared and the successful validation in the sulfide electrolytes, demonstrating its universal and promising application for the integration of Li metal anodes in solid-state batteries.

Can neural networks predict steady annual cycles of marine ecosystems?

We used artificial neural networks to replace the complete spin-up procedure that computes a steady annual cycle of a marine ecosystem driven by ocean transport. The networks took only the few biogeochemical model parameters and attempted to predict the spatially distributed concentrations of the ecosystem, in this case only nutrients, for one time point of the annual cycle. The ocean circulation was fixed for all parameters. Different network topologies, sparse networks, and hyperparameter optimization using a genetic algorithm were used. This showed that all studied networks can produce a distribution that is point-wise close to the original spin-up result. However, these predictions were far from being annually periodic, such that a subsequent spin-up was necessary. In this way, the overall runtime of the spin-up could be reduced by 13% on average. It is debatable whether this procedure is useful for the generation of initial values, or whether simpler methods can achieve faster convergence.

Stabilizing Li metal anode by constructing lithiophilic N-doped carbon nanotubes on flexible carbon felt host

The Li metal anode is regarded as the most ideal anode material for the next-generation high-energy-density rechargeable Li batteries. Unfortunately, infinite volume change, “dead” Li formation, and continuous dendrite growth, severely hamper its commercial applications. Constructing 3D hosts has been widely developed to address these issues. Herein, nitrogen-doped carbon nanotubes (NCNTs) are grown in the carbon felt (CF) as the host material for Li metal anode via economic chemical vapor deposition was developed. Carbon felt provides a fast and uniform ion/electron pathway and alleviates the volume expansion during the charge/discharge process. With the introduction of NCNTs, lithiophilic functional groups like pyridine and pyrrole distributed uniformly on the surface of carbon felt, providing adequate lithiophilic sites to guide Li nucleation, ensuring the smooth Li deposition with dendrite-free morphology. As a result, excellent cycling stability is realized in symmetric cells with low overpotential and long lifespan. In addition, when the composite Li electrode is paired with the sulfur cathode (8.7 mg cm−2), the full cell displays a steady cycle life in coulombic efficiency retention of 93 % and a high specific capacity of 3.32 mAh cm−2 after 270 cycles at 0.2C.

Experimental investigation on the effects of DPF Cs-V-based non-precious metal catalysts and their coating forms on non-road diesel engine emission characteristics.

Non-precious metal catalysts with good soot catalytic properties and a low cost have great potential for application in diesel particulate filters (DPF). In this study, we compared the effects of DPF supported by Cs2V4O11 (Cs-V-based) non-precious metal catalysts and conventional Pt-Pd-based precious metal catalysts on the performance of a non-road diesel engine. Furthermore, the effects of on-wall coating and in-wall coating of Cs-V-based catalysts on DPF performance were also investigated. The results indicated that the particulate emissions from DPF with Cs-V-based catalysts were reduced slightly less than that with Pt-Pd-based catalysts; however, the particle number (PN) and particulate matter (PM) emissions were still reduced by 94.4% and 91.7%, respectively, meeting the non-road China IV limits under the non-road steady cycle (NRSC). In addition, CO, HC, and NO can also be slightly oxidized by the non-precious metal catalysts. On the other hand, the DPF with in-wall coating induced comparatively higher gaseous substances and particulate emissions and caused a higher exhaust back pressure (EBP), which was 9.6% higher than the on-wall coating under NRSC, negatively affecting engine performance. Additionally, the geometric mean diameter (GMD) for the DPF with in-wall coating was only 33.3nm because of the large emission proportion of nuclear mode particles.

Necessity of feedback control for the quantum Maxwell demon in a finite-time steady feedback cycle

We revisit quantum Maxwell demon in thermodynamic feedback cycle in the steady-state regime. We derive a generalized version of the Clausius inequality for a finite-time steady feedback cycle with a single heat bath. It is shown to be tighter than previously known ones, and allows us to clarify that feedback control is necessary to violate the standard Clausius inequality.

Long Shelf-Life Efficient Electrolytes Based on Trace l-Cysteine Additives toward Stable Zinc Metal Anodes.

The unstable anode/electrolyte interface (AEI) triggers the corrosion reaction and dendrite formation during cycling, hindering the practical application of zinc metal batteries. Herein, for the first time, l-cysteine (Cys) is employed to serve as an electrolyte additive for stabilizing the Zn/electrolyte interface. It is revealed that Cys additives tend to initially approach the Zn surface and then decompose into multiple effective components for suppressing parasitic reactions and Zn dendrites. As a consequence, Zn|Zn symmetric cells using trace Cys additives (0.83mm) exhibit a steady cycle life of 1600 h, outperforming that of prior studies. Additionally, an average Coulombic efficiency of 99.6% for 250 cycles is also obtained under critical test conditions (10mA cm-2 /5 mAh cm-2 ). Cys additives also enable Zn-V2 O5 and Zn-MnO2 full cells with an enhanced cycle stability at a low N/P ratio. More importantly, Cys/ZnSO4 electrolytes are demonstrated to be still effective after resting for half year, favoring the practical production.

Robotic Process Automation using Virtual Environment

Abstract: Ventures are starting to see a computerized labor force as a feature of their computerized change technique by joining components of RPA, man-made reasoning (AI), and examination to mechanize business processes. While carrying out associations receive the above rewards of effective RPA execution, the RPA item sellers and specialist co-ops likewise go through a steady development cycle to handle specialized hindrances that taking on associations face in mechanizing processes and RPA apparatus mix/communication with all applications/frameworks inside their current circumstance. The RPA market is growing quickly, yet to be maintained, RPA should offer more extensive help for application types, and for both virtual and cloud-based frameworks. As RPA keeps on advancing both in capacity and extension, business use cases are growing past centralized servers, heritage, work areas, and web applications into the domain of remote and virtualized conditions. We are now seeing a solid blend of robotization conditions like actual machines, Windows servers, terminal servers, virtual machines (VMs), virtual work area framework (VDI), and distant work area convention (RDP).

Phase and amplitude evolution in the network of triadic interactions of the Hasegawa–Wakatani system

The Hasegawa–Wakatani system, commonly used as a toy model of dissipative drift waves in fusion devices, is revisited with considerations of phase and amplitude dynamics of its triadic interactions. It is observed that a single resonant triad can saturate via three way phase locking, where the phase differences between dominant modes converge to constant values as individual phases increase in time. This allows the system to have approximately constant amplitude solutions. Non-resonant triads show similar behavior only when one of its legs is a zonal wave number. However, when an additional triad, which is a reflection of the original one with respect to the y axis is included, the behavior of the resulting triad pair is shown to be more complex. In particular, it is found that triads involving small radial wave numbers (large scale zonal flows) end up transferring their energy to the subdominant mode which keeps growing exponentially, while those involving larger radial wave numbers (small scale zonal flows) tend to find steady chaotic or limit cycle states (or decay to zero). In order to study the dynamics in a connected network of triads, a network formulation is considered, including a pump mode, and a number of zonal and non-zonal subdominant modes as a dynamical system. It was observed that the zonal modes become clearly dominant only when a large number of triads are connected. When the zonal flow becomes dominant as a “collective mean field,” individual interactions between modes become less important, which is consistent with the inhomogeneous wave-kinetic picture. Finally, the results of direct numerical simulation are discussed for the same parameters, and various forms of the order parameter are computed. It is observed that nonlinear phase dynamics results in a flattening of the large scale phase velocity as a function of scale in direct numerical simulations.

Polypyrrole-intercalation tuning lamellar structure of V2O5·nH2O boosts fast zinc-ion kinetics for aqueous zinc-ion battery

The layered structure of vanadium oxide is an ideal cathode material for aqueous rechargeable zinc-ion batteries (ARZIBs) owing to its tunable structures, high specific capacity and high energy density. It has been shown that the regulation of the layer spacing of the layered vanadium oxide can effectively improve the electrochemical performance of ARZIBs. Most of the literatures have adjusted the layer spacing by chemical pre-insertion of metal ions and the expanded layer spacing is very limited. However, other guests, like polymer, might play a critical role in tuning the lamellar structure of vanadium oxides showing fast Zn-ion kinetics for ARZIBs. Herein, a two-step synthesis is developed to insert the conductive polymer polypyrrole (PPy) into the vanadium oxide layers, resulting in a layer spacing up to 14.0 Å. Large interlayer spacing is beneficial to the rapid (de)intercalation of zinc ions, leading to greatly promote the electrochemical performance of V2O5·nH2O (VOH). The Zn//PPy/VOH battery has an advanced specific capacity up to 383 mAh·g−1 at 0.1 A g−1 and a steady cycle performance. This strategy of pre-insertion of conducting polymer into the host material provides a novel synthesis scheme for the use of vanadium oxide as cathode material for ARZIBs.

Five performance indicators for a universal generalized irreversible steady flow cycle including seven specific refrigeration cycles

Five performance indicators for a universal generalized irreversible steady flow cycle including seven specific refrigeration cycles

Exhaust emissions from a prototype non-road natural gas engine

Since gas engines are considered a future solution to improve air quality and to mitigate climate impacts, there is an urgent need to understand their emissions. The aim for this study was to understand the phenomena affecting the formation of particulate emissions of a non-road natural gas engine. To achieve this, the engine’s exhaust emissions were characterized under different operating conditions. The regulated pollutants (gaseous CO, HC, and NOx; particulate matter (PM) and particle number (PN)) were determined experimentally and a detailed characterization of particulate pollutants over a wide particle size range (particles down to 1.2 nm) was conducted with state-of-the-art instrumentation considering both physical and chemical properties of the exhaust aerosol. The test engine was a prototype non-road spark-ignited natural gas engine, which was studied over the non-road steady test cycle (NRSC). The role of the three-way catalyst (TWC) was studied by sampling and characterizing the exhaust aerosol both with and without the TWC. The TWC was observed to efficiently remove the vast majority of the regulated gaseous (96% CO, 98% HC, 98% NOx) and particulate mass emissions (98%). In general, the measured particle number emission factors were highly dependent on the cut-off sizes of the condensation particle counters. Using CPCs with smaller cut-off sizes resulted in higher particle number emission factors. For black carbon (BC), the intermediate engine speed conditions (modes 5–7) led to lower BC emissions than the high speed conditions (modes 1–3). In contrast, highest BC emissions on a work basis were observed during idling. TWC did not influence BC levels. Without the TWC, PM was comprised mostly of organic compounds (70–100%). Downstream of the TWC, the majority of PM was, depending on the load, composed of organic compounds, sulfate, or black carbon. A statistical source apportionment based on mass spectra revealed that the PM1 was mostly related to unburned and burned lubricating oil, indicating a minor role of fuel in PM formation.

Impact of Condensation on the System Performance of a Fuel Cell Turbocharger

A mobile fuel cell systems power output can be increased by pressure amplification using an electric turbocharger. These devices are subject to frequent transient manoeuvres due to a multitude of load changes during the mission in automotive applications. In this paper, the authors describe a simulation approach for an electric turbocharger, considering the impact of moist air and condensation within the cathode gas supply system. Therefore, two simulation approaches are used: an iterative simulation method and one based on a set of ordinary differential equations. Additional information is included from turbine performance maps taking into account condensation using Euler–Lagrange CFD simulations, which are presented. The iterative calculation approach is well suited to show the impact of condensation and moist air on the steady state thermodynamic cycle and yields a significant shift of the steady state operating line towards the surge line. It is shown that a substantial risk of surge occurs during transient deceleration manoeuvres triggered by a load step.