Constant Energy Input Research Articles

Quasar outflow deceleration or acceleration: predictions and a search

ABSTRACT Quasar winds can shock and sweep up ambient interstellar medium (ISM) gas, contributing to galactic quenching. We combine and extend past models of energy-conserving shock bubbles around quasars, investigate model implications from an observational standpoint, and test model predictions using new high-resolution spectroscopic observations of the broad absorption-line quasar SDSS J030000.56+004828.0 (J0300). Even with constant energy input from the wind, a bubble’s expansion decelerates over time as more ISM gas is swept up. Our new observations enable a direct search for this deceleration. We obtain the tightest reported 3σ limit on the average rest-frame deceleration (or acceleration) of a quasar outflow: |a| < 0.1 km s−1 yr−1 (<3 × 10−4 cm s−2) in the relatively low-velocity Ca ii outflow of J0300 over 9.65 rest-frame years. We can satisfy these limits with certain parameter choices in our model, but the large velocity range of the Ca ii absorption in J0300 rules out the hypothesis that such gas shares the velocity of the swept-up ISM gas in a self-similar shock bubble. We investigate the possibility of ram-pressure acceleration of preexisting ISM clouds and conclude that the velocity range seen in Ca ii in J0300 is potentially consistent with such an explanation. The Ca ii-absorbing gas clouds in J0300 have been inferred to have high densities by Choi et al., in which case they can only have been accelerated to their current speeds if they were originally at least an order of magnitude less dense than they are today.

Numerical analysis of the enrichment of CH4/H2 in ammonia combustion in a hot co-flow environment

A numerical investigation is conducted using OpenFOAM to study the characteristics of ammonia flames enriched with methane and hydrogen, influenced by a diluted co-flow (exhaust gas). The study aims to explore various flame characteristics, including fuel consumption, ignition delay time, lift-off height and position, temperature, and CO and NO emissions while maintaining a constant energy input of 5 kW. Non-stabilized flames are identified by analyzing the OH peak in the computational domain among ammonia flames enriched with CH4/H2 for different dilutions of O2 (6 %, 9 %, and 12 %). The study is structured into three stages of numerical simulations corresponding to stabilized flames: (1) no reaction, (2) reaction in the absence of O2, and (3) reaction with O2 to see the sole impact of the hot co-flow and local turbulence mixing on the primary cracking of ammonia. Furthermore, the rates of H2 and N2 formation resulting from the utilization of ammonia in the presence of hot co-flow are thoroughly examined. Additionally, the behavior of ammonia flames and CH4/H2-enriched ammonia flames under preheated air conditions (23 % O2) is analysed. Stable flames are observed in the co-flow at 12 % O2, displaying characteristics of Moderate or Intense Low-oxygen Dilution (MILD) combustion. Conversely, ammonia flames under preheated air conditions exhibit conventional flame behavior. Pure ammonia flames exhibit stronger temperature gradients and higher levels of CO and NO emissions. As the enrichment of NH3 with CH4/H2 increases, peak temperatures decrease while lift-off heights increase, indicating a transition towards more distributed flame structures. Notably, the instance with 40 % H2 enrichment exhibits lower NO emissions and a higher rate of ammonia consumption along with more distributive flame characteristics.

Nanoplastics from disposable paper cups and microwavable food containers

Nanoplastics (NPs, <1 µm) pose greater risks due to their increased absorption rates in biological systems. In this study, we investigated the release of NPs from paper cups and microwavable food containers coated with low-density polyethylene (LDPE) and polylactic acid (PLA). For disposable paper cups, we found that LDPE-coated cups released up to 26-fold more NPs (maximum 1.9 × 107 per cup) than PLA-coated ones. The NPs release from LDPE-coated cups was increased at high temperatures above 80 °C, and further increased by physical agitation. However, negligible NP release was observed when the inner coating thickness exceeded 1 mm. For microwavable food containers, those with PLA coatings were more susceptible to the effects of microwave. Depending on the cooking time, we noticed a significant difference (up to 40000 times) in the number of released NPs between LDPE and PLA coatings. Additionally, higher microwave power level led to an increase of NPs, even with constant total energy input. Considering the release of NP, PLA coatings for disposable paper cups and LDPE coatings for microwavable food containers seem more suitable. Furthermore, our results suggest that multi-use cups significantly reduce NPs release due to their material thickness, making them a safer alternative to disposable ones.

Experimental investigation of the combustion characteristics in oxy-fuel combustion of hydrogen-enriched natural gas on a semi-industrial scale

The present paper deals with the influence of different hydrogen enrichment on oxy-fuel combustion of natural gas, enabling important insights regarding decarbonization of high-temperature processes. Experiments were conducted using a high-impulse multifuel burner for industrial applications for hydrogen contents between 0 and 100%. The fuel input varied between 100 and 140 kW, while water-cooled lances were used to simulatethermal loads. The analysis included temperature measurement points, atomic and energy balances and the cooling capacity of the thermal load for steady-state operation. The obtained results show that the flue gas temperature decreases by up to 126 K for pure hydrogen, while the cooling capacities of the thermal load increased by up to 16.3% at constant calorific energy input. The flames for different hydrogen enrichments were also compared visually. Overall, all investigated fuel blends were highly interchangeable with the investigated burner and showed high potential for a timely decarbonization of industrial heating.

Influence of Electron Beam Powder Bed Fusion Process Parameters on Transformation Temperatures and Pseudoelasticity of Shape Memory Nickel Titanium

Electron beam powder bed fusion (PBF‐EB) is used to manufacture dense nickel titanium parts using various parameter sets, including the beam current, scan speed, and postcooling condition. The density of manufactured NiTi parts is investigated in relation to the linear energy input. The results imply that the part density increases with increasing linear energy density to over 98% of the bulk density. With a constant energy input, a combination of low power and low scan speed leads to denser parts. This is attributed to lower electrostatic repulsive forces from lower number density of the impacting electrons. After manufacturing, the densest parts with distinct parameter sets are categorized into three groups: 1) high power with high scan speed and vacuum slow cooling, 2) low power with low scan speed and vacuum slow cooling, and 3) low power with low scan speed and medium cooling rate in helium gas. Among these, a faster cooling rate suppresses phase transformation temperatures, while vacuum cooling combinations do not affect the phase transformation temperatures significantly. Herein, all the printed parts exhibit almost 8% pseudoelasticity regardless of the process parameters, while the parts cooled in helium have a higher energy dissipation efficiency (1 − η), which implies faster damping of oscillations.

Robust loose nanofiltration membrane with fast solute transfer for dye/salt separation

In today's energy crisis and shortage of resources, resource recycling on the premise of saving energy is a crucial topic. Large volumes of wastewater containing dye/salt mixtures in the textile industry are generated. In the process of treating textile wastewater, a membrane with better solute transport properties can be used to selectively remove solutes at constant energy input to save energy. Moreover, due to the challenging environment of typical textile wastewater, the membrane also needs to have a certain robustness. In this study, β-cyclodextrin and mussel-inspired polydopamine were combined using host-guest chemistry and then cross-linked by glutaraldehyde to form a robust loose separation layer. The results show that the membranes obtained by this process have a dye rejection greater than 99% and a salt rejection of about 16%. With the high degree of crosslinking at the surface, the membrane was found to exhibit excellent robustness in corrosive media at different pH values. Due to the high degree of cross-linking of the surface, the modified membrane also has good anti-fouling and anti-bacterial properties. Filtration using different concentrations of dye/salt mixed solutions demonstrated the stability of the membrane for filtration in highly concentrated salt solutions. In addition, a long-term stability test proved that the membrane operates stably for more than 60 h, maintaining its selectivity. This membrane with excellent robustness can provide technical guidance and theoretical support for the large-scale application of loose nanofiltration membranes.

Numerical Study of Combustion and Emission Characteristics for Hydrogen Mixed Fuel in the Methane-Fueled Gas Turbine Combustor

The aeroderivative gas turbine is widely used as it demonstrates many advantages. Adding hydrogen to natural gas fuels can improve the performance of combustion. Following this, the effects of hydrogen enrichment on combustion characteristics were analyzed in an aeroderivative gas turbine combustor using CFD simulations. The numerical model was validated with experimental results. The conditions of the constant mass flow rate and the constant energy input were studied. The results indicate that adding hydrogen reduced the fuel residues significantly (fuel mass at the combustion chamber outlet was reduced up to 60.9%). In addition, the discharge of C2H2 and other pollutants was reduced. Increasing the volume fraction of hydrogen in the fuel also reduced CO emissions at the constant energy input while increasing CO emissions at the constant fuel mass flow rate. An excess in the volume fraction of added hydrogen changed the combustion mode in the combustion chamber, resulting in fuel-rich combustion (at constant mass flow rate) and diffusion combustion (at constant input power). Hydrogen addition increased the pattern factor and NOx emissions at the outlet of the combustion chamber.

Investigation of reactions occurring in waste combustion ash using thermal analysis coupled with gas analysis and characterization.

Waste-to-energy (WtE) ash was investigated for thermal reactions that generate gas components such as hydrogen and carbon dioxide. An evolved gas detection method coupled with thermal gravimetric analysis and differential scanning calorimetry provided insight into the possible reactions occurring in WtE ash at temperatures ranging from 90°C to 600°C in an inert environment. The combined analysis shows that H2 is produced from WtE ash at temperatures ~298°C and is detected until ~480°C. CO2 appears in the evolved gas starting at 290°C and continues to increase as the temperature is increased. The results reveal that the processes releasing H2 and the CO2 are independent of each other, and the CO2 generation depends on the constant input of energy. These results enable the identification of the possible processes occurring in WtE ash decomposition of Friedel's salt at 280°C and dehydration of Ca(OH)2 at 410°C, both of which release H2O that reacts with the aluminium present to release H2. At temperatures higher than 480°C, an alumina layer is formed preventing further production of H2. X-ray diffraction analysis done on the WtE ash verifies the presence of chemical phases that support the proposed reactions. The outcome of this study enables identifying the possible reactions in WtE ash that can be causing the energy changes seen during disposal, storage and transportation of ash. These results can give direction for detailed understanding and development of the kinetics and the mechanisms of the reactions occurring in WtE ash which is important for optimization of reuse and disposal of ash.

Impact of the Power-Dependent Beam Diameter during Electron Beam Additive Manufacturing: A Case Study with γ-TiAl

The development of process parameters for electron beam powder bed fusion (PBF-EB) is usually made with simple geometries and uniform scan lengths. The transfer to complex parts with various scan lengths can be achieved by adapting beam parameters such as beam power and scan speed. Under ideal conditions, this adaption results in a constant energy input into the powder bed despite of the local scan length. However, numerous PBF-EB machines show deviations from the ideal situation because the beam diameter is subject to significant changes if the beam power is changed. This study aims to demonstrate typical scaling issues when applying process parameters to scan lengths up to 45 mm using a fourth generation γ-TiAl alloy. Line energy, area energy, return time, and lateral velocity are kept constant during the additive manufacturing process by adjusting beam power and beam velocity to various scan lengths. Samples produced in this way are examined by light microscopy regarding lateral melt pool extension, melt pool depth, porosity, and microstructure. The process-induced aluminum evaporation is measured by electron probe microanalysis. The experiments reveal undesired changes in melt pool geometry, gas porosity, and aluminum evaporation by increasing the beam power. In detail, beam widening is identified as the reason for the change in melt pool dimensions and microstructure. This finding is supported by numerical calculations from a semi-analytic heat conduction model. This study demonstrates that in-depth knowledge of the electron beam diameter is required to thoroughly control the PBF-EB process, especially when scaling process parameters from simply shaped geometries to complex parts with various scan lengths.

Is There a Fourth Law for Non-Ergodic Systems That Do Work to Construct Their Expanding Phase Space?

Substantial grounds exist to doubt the universal validity of the Newtonian Paradigm that requires a pre-stated, fixed phase space. Therefore, the Second Law of Thermodynamics, stated only for fixed phase spaces, is also in doubt. The validity of the Newtonian Paradigm may stop at the onset of evolving life. Living cells and organisms are Kantian Wholes that achieve constraint closure, so do thermodynamic work to construct themselves. Evolution constructs an ever-expanding phase space. Thus, we can ask the free energy cost per added degree of freedom. That cost is roughly linear or sublinear in the mass constructed. However, the resulting expansion of the phase space is exponential or even hyperbolic. Thus, the evolving biosphere does thermodynamic work to construct itself into an ever-smaller sub-domain of its ever-expanding phase space at ever less free energy cost per added degree of freedom. The universe is not correspondingly disordered. Entropy, remarkably, really does decrease. A testable implication of this, termed here the Fourth Law of Thermodynamics, is that at constant energy input, the biosphere will construct itself into an ever more localized subregion of its ever-expanding phase space. This is confirmed. The energy input from the sun has been roughly constant for the 4 billion years since life started to evolve. The localization of our current biosphere in its protein phase space is at least 10–2540. The localization of our biosphere with respect to all possible molecules of CHNOPS comprised of up to 350,000 atoms is also extremely high. The universe has not been correspondingly disordered. Entropy has decreased. The universality of the Second Law fails.

Experimental characterization of a small wind turbine with variable blades angle

Small wind turbines with fixed blades present a significant disadvantage when operating at low wind speeds. Wind speed increase proportionally with the height to the ground and such wind turbines are installed at most on rooftops, so they face low wind speeds < 10 m/s. This work shows the experimental characterization of a wind turbine prototype with three flat blades and variable orientation angle, to measure the least wind velocity that drives the turbine from the rest. Experimental tests were carried out in a wind tunnel defining two essential points of interest: first, the angle at which it is possible to start the movement of the turbine with the minimum energy; second, the angle that captures the most power from the wind, based on a constant energy input (wind velocity constant).

Durable Superoleophobic Janus Fabric with Oil Repellence and Anisotropic Water-Transport Integration toward Energetic-Efficient Oil–Water Separation

Porous materials with opposing superwettability toward oil and water have aroused widespread interest for their selective-wetting advantage in oil-water separation. The separation process, however, requires constant energy input to maintain the driving force. Further reducing the external energy consumption or accelerating the liquid transport during separation is still a challenge. The Janus membrane is an emerging porous material with opposing wettability toward a specific liquid on each side. The asymmetric wettability distribution leads to a surface energy gradient-driven liquid-transport behavior through the thickness, which significantly facilitates liquid transportation. It is conceived that porous materials possessing both Janus features and selective superwettability would reduce energy consumption and strengthen the efficiency in oil-water separation. Herein, a novel durable superoleophobic (SOHB) Janus fabric which possesses oil-repellent and surface energy gradient-driven water-transport properties was developed through one-side superoleophobic/superhydrophilic modification of the superamphiphobic fabric. The SOHB Janus fabric exhibits high mechanical durability and significant superior capacity than the homogeneous superoleophobic/superhydrophilic fabric in separating various oil-water mixtures. Moreover, the SOHB Janus fabric repels oil contaminants and pumps perspiration from the human skin, exhibiting prospects in physical moisture regulation and comfort improvement. Our novel Janus fabric, along with the fabrication principle, provides a feasible solution for energetic-efficient oil-water remediations and would have implications for the fabrication of advanced separation membranes and intelligent functional clothing.

Studies on the behaviour of a passive containment cooling system for the Indian Advanced Heavy Water Reactor

Abstract A passive containment cooling system has been proposed for the advanced heavy water reactor being designed in India. This is to provide long term cooling for the reactor containment following a loss of coolant accident. The system removes energy released into the containment through immersed condensers kept in a pool of water. An important aspect of immersed condenser’s working is the potential degradation of immersed condenser’s performance due to the presence of noncondensable gases. An experimental programme to investigate the passive containment cooling system behaviour and performance has been undertaken in a phased manner. In the first phase, system response tests were conducted on a small scale model to under­stand the phenomena involved. Tests were conducted with constant energy input rate and with varying energy input rate simulating decay heat. With constant energy input rate, pressures in volume V1 and V2 reached almost steady value. With varying energy input rate V1 pressure dropped below the pressure in V2. The system could efficiently purge air from V1 to V2. The paper deals with the details of the tests conducted and the results obtained.

Self-similar properties of avalanche statistics in a simple turbulent model.

In this paper, we consider a simplified model of turbulence for large Reynolds numbers driven by a constant power energy input on large scales. In the statistical stationary regime, the behaviour of the kinetic energy is characterized by two well-defined phases: a laminar phase where the kinetic energy grows linearly for a (random) time [Formula: see text] followed by abrupt avalanche-like energy drops of sizes [Formula: see text] due to strong intermittent fluctuations of energy dissipation. We study the probability distribution [Formula: see text] and [Formula: see text] which both exhibit a quite well-defined scaling behaviour. Although [Formula: see text] and [Formula: see text] are not statistically correlated, we suggest and numerically checked that their scaling properties are related based on a simple, but non-trivial, scaling argument. We propose that the same approach can be used for other systems showing avalanche-like behaviour such as amorphous solids and seismic events. This article is part of the theme issue 'Scaling the turbulence edifice (part 1)'.

Light-powered soft steam engines for self-adaptive oscillation and biomimetic swimming.

Oscillation plays a vital role in the survival of living organisms in changing environments, and its relevant research has inspired many biomimetic approaches to soft autonomous robotics. However, it remains challenging to create mechanical oscillation that can work under constant energy input and actively adjust the oscillation mode. Here, a steam-driven photothermal oscillator operating under constant light irradiation has been developed to perform continuous or pulsed, damped harmonic mechanical oscillations. The key component of the oscillator comprises a hydrogel containing Fe3O4/Cu hybrid nanorods, which can convert light into heat and generate steam bubbles. Controllable perturbation to the thermomechanical equilibrium of the oscillator can thus be achieved, leading to either continuous or pulsed oscillation depending on the light intensity. Resembling the conventional heat steam engine, this environment-dictated multimodal oscillator uses steam as the working fluid, enabling the design of self-adaptive soft robots that can actively adjust their body functions and working modes in response to environmental changes. An untethered biomimetic neuston-like robot is further developed based on this soft steam engine, which can adapt its locomotion mechanics between uniform and recurrent swimming to light intensity changes and perform on-demand turning under continuous light irradiation. Fueled by water and remotely powered by light, this unique hydrogel oscillator enables easy control over the oscillation dynamics and modes, offering an effective approach to self-adaptive soft robots and solar steam engines.

Design and Optimal Control of a Multistable, Cooperative Microactuator

In order to satisfy the demand for the high functionality of future microdevices, research on new concepts for multistable microactuators with enlarged working ranges becomes increasingly important. A challenge for the design of such actuators lies in overcoming the mechanical connections of the moved object, which limit its deflection angle or traveling distance. Although numerous approaches have already been proposed to solve this issue, only a few have considered multiple asymptotically stable resting positions. In order to fill this gap, we present a microactuator that allows large vertical displacements of a freely moving permanent magnet on a millimeter-scale. Multiple stable equilibria are generated at predefined positions by superimposing permanent magnetic fields, thus removing the need for constant energy input. In order to achieve fast object movements with low solenoid currents, we apply a combination of piezoelectric and electromagnetic actuation, which work as cooperative manipulators. Optimal trajectory planning and flatness-based control ensure time- and energy-efficient motion while being able to compensate for disturbances. We demonstrate the advantage of the proposed actuator in terms of its expandability and show the effectiveness of the controller with regard to the initial state uncertainty.

Energy, Entropy and Quantum Tunneling of Protons and Electrons in Brain Mitochondria: Relation to Mitochondrial Impairment in Aging-Related Human Brain Diseases and Therapeutic Measures.

Adult human brains consume a disproportionate amount of energy substrates (2–3% of body weight; 20–25% of total glucose and oxygen). Adenosine triphosphate (ATP) is a universal energy currency in brains and is produced by oxidative phosphorylation (OXPHOS) using ATP synthase, a nano-rotor powered by the proton gradient generated from proton-coupled electron transfer (PCET) in the multi-complex electron transport chain (ETC). ETC catalysis rates are reduced in brains from humans with neurodegenerative diseases (NDDs). Declines of ETC function in NDDs may result from combinations of nitrative stress (NS)–oxidative stress (OS) damage; mitochondrial and/or nuclear genomic mutations of ETC/OXPHOS genes; epigenetic modifications of ETC/OXPHOS genes; or defects in importation or assembly of ETC/OXPHOS proteins or complexes, respectively; or alterations in mitochondrial dynamics (fusion, fission, mitophagy). Substantial free energy is gained by direct O2-mediated oxidation of NADH. Traditional ETC mechanisms require separation between O2 and electrons flowing from NADH/FADH2 through the ETC. Quantum tunneling of electrons and much larger protons may facilitate this separation. Neuronal death may be viewed as a local increase in entropy requiring constant energy input to avoid. The ATP requirement of the brain may partially be used for avoidance of local entropy increase. Mitochondrial therapeutics seeks to correct deficiencies in ETC and OXPHOS.

High power piezoelectric characterization system (HiPoCS™)

The bottleneck of the piezoelectric devices in miniaturization is the heat generation owing to the losses. There are three losses in a piezoelectric material; dielectric, elastic and piezoelectric losses. The development of high-power density piezoelectrics is directly relevant to the clarification of the loss mechanisms in such materials. This article describes the characterization methodologies of high-power piezoelectrics, in particular, in determining the three losses separately. There are two categories for the measuring methods: (1) electrical excitation method, and (2) mechanical excitation method. The former is basically admittance/impedance measurement via the output current over the input voltage, further classified into four methods; (a) constant voltage, (b) constant current, (c) constant vibration velocity, and (d) constant input energy. To the contrary, the latter is basically the transient mechanical vibration ring-down measurement under various electrical constraint conditions. The key is to obtain precise values of both mechanical quality factors at resonance QA and at antiresonance QB, regardless of measuring techniques, so that we can determine the piezoelectric loss precisely. The difference of QM between the resonance and antiresonance is originated from the electromechanical coupling factor k2 loss, Depending on the sign of the k2 loss, more efficient driving frequency can be derived rather than the conventional ‘resonance’ frequency.

Electron beam melting of Ti6Al4V: Role of the process parameters under the same energy density

• Influence of process parameters under constant energy input on microstructure and microhardness was elucidated. • Influence of processing conditions on top surface roughness was discussed. • The link between process parameters and properties was studied considering the interaction between beam and material. • Guidelines to choose the process parameters were released. The role of the process parameters under a fixed energy density in Electron Beam Melting of Ti6Al4V was investigated. The beam current, scan speed and line offset were varied in a wide range keeping constant the energy density achieved, aiming to highlight the influence of each parameter on the properties of the printed parts. Microstructure, microhardness and top surface roughness were chosen as measured output. The results obtained showed that the amount of energy adsorbed by the metal is depending on beam current and scan speed, this due to the complex interaction between the electrons of the beam and the atoms of the material. As a consequence, the samples showed different properties, even if the adopted energy density was the same, the influence of the process parameters on the above-mentioned measured output was assessed.

Selective laser melting (SLM) of AISI 316L\u2014impact of laser power, layer thickness, and hatch spacing on roughness, density, and microhardness at constant input energy density

In selective laser melting (SLM) the variation of process parameters significantly impacts the resulting workpiece characteristics. In this study, AISI 316L was manufactured by SLM with varying laser power, layer thickness, and hatch spacing. Contrary to most studies, the input energy density was kept constant for all variations by adjusting the scanning speed. The varied parameters were evaluated at two different input energy densities. The investigations reveal that a constant energy density with varying laser parameters results into considerable differences of the workpieces’ roughness, density, and microhardness. The density and the microhardness of the manufactured components can be improved by selecting appropriate parameters of the laser power, the layer thickness, and the hatch spacing. For this reason, the input energy density alone is no indicator for the resulting workpiece characteristics, but rather the ratio of scanning speed, layer thickness, or hatch spacing to laser power. Furthermore, it was found that the microhardness of an additively manufactured material correlates with its relative density. In the parameter study presented in this paper, relative densities of the additively manufactured workpieces of up to 99.9% were achieved.