The density of the warm ionized gas in high-redshift galaxies is known to be higher than what is typical in local galaxies on similar scales. At the same time, the mean global properties of the high- ...and low-redshift galaxies are quite different. Here, we present a detailed differential analysis of the ionization parameters of 14 star-forming galaxies at redshift 2.6-3.4, compiled from the literature. For each of those high-redshift galaxies, we construct a comparison sample of low-redshift galaxies closely matched in specific star formation rate (sSFR) and stellar mass, thus ensuring that their global physical conditions are similar to the high-redshift galaxy. We find that the median logOIII 5007/OII 3727 line ratio of the high-redshift galaxies is 0.5 dex higher than their local counterparts. We construct a new calibration between the OIII 5007/OII 3727 emission line ratio and ionization parameter to estimate the difference between the ionization parameters in the high- and low-redshift samples. Using this, we show that the typical density of the warm ionized gas in star-forming regions decreases by a median factor of 7.1 super(+10.2) sub(-5.4) from z ~ 3.3 to z ~ 0 at fixed mass and sSFR. We show that metallicity differences cannot explain the observed density differences. Because the high- and low-redshift samples are comparable in size, we infer that the relationship between star formation rate density and gas density must have been significantly less efficient at z ~ 2-3 than what is observed in nearby galaxies with similar levels of star formation activity.
Phase-shifted carrier (PSC) pulsewidth modulation (PWM) in its conventional form is a good solution for single-phase Cascaded inverters as alternative phase opposition disposition (APOD) PWM for ...single-phase diode clamped inverters. PSC distributes the switching angles of APOD PWM waveform among the legs uniformly and reduces the switching frequency of each leg. This paper proposes a modified PSC technique based on partly shifted carriers for all disposition types including phase disposition (PD) which is suitable for three-phase cascaded inverters. Simulation results are also included for using carrier-based space-vector PWM (SVPWM).
•Investigating a k-out-of-N system to minimize costs of spare parts supplying.•Considering quality of spares part.•Quality and cost tradeoff of suppliers.•Implementing probably tree, Markov chain and ...Monte Carlo simulation methods implemented to model the problem.
Spare parts management is one of the most important aspects in industrial systems where a large number of spare parts are stocked to replace with failed parts and reduce the system's downtime. In this study, it is supposed that the quality of spare parts can differ from the quality of the original parts since they might be supplied from different suppliers. This problem is modeled by using the probability tree and Markov chains approach to determine the optimal number of spare parts, their supplier, and appropriate quality, leading to minimization of the system's total cost and or system's total availability. Meanwhile, highly expensive parts cause large investment. In this study, a k-out-of-N redundant system is modeled in which by failing each part it is replaced by a stocked spare part if exists. Otherwise, in case of spare parts lacking the system continues to its operation with failed part(s) which reduces system performance. If the number of failed parts reaches a predetermined threshold level (N-k+1) it leads to system shutdown. All suggesting models are applied on numerical samples for to show the representation of the state and determine optimal spare parts supply strategies and inventory policies in large-scale industrial systems.
Integrated consideration of production planning and maintenance processes is a real world assumption. Specifically, by improving the monitoring equipment such as various sensors or product-embedded ...information devices in recent years, joint assessment of these processes is inevitable for enhancing the level of the system optimization. By means of this equipment, managers can benefit from a condition-based maintenance (CBM) for monitoring and managing their system. The chief aim of the paper is to develop a stochastic maintenance problem based on CBM activities engaged with a complex applied production problem called flexible job shop scheduling problem (FJSP). This integrated problem considers two maintenance scenarios in terms of corrective maintenance (CM) and preventive maintenance (PM). The activation of scenario is done by monitoring the degradation condition of the system and comparing the associated value by predetermined PM and CM levels. Moreover, to make it more realistic, the developed problem allows breakdown of the system between inspection intervals. The event time and duration of performing the maintenance activities are also considered stochastic. The developed methodology copes with high stochastic complexity of proposed problem through simulation-based optimization (SBO) approach, which works based on harmony search optimization algorithm. The developed items of SBO are discussed on different generated test problems and assessed through statistical methods and new visualization approach. Numerical example shows that the proposed method is practical for proposed integrated CBM and FJSP problem. It also offers a basis for any implementation of CBM on production problems.
The dual functionality of plasmonic light harvesting and barrier spacing between Au nanoparticles (NPs) and ZnO nanorod arrays (NRsA) are spotlighted to investigate their impact on the ...photoconversion and optical nonlinearity in the present study. The passivating Al
2
O
3
barrier layer permits high-energy hot electron tunneling and injection from Au to the ZnO NRsA. The structural, vibrational, morphological/elemental, and optical properties of ZnO NRsA/a-Al
2
O
3
/Au were characterized by X-ray diffraction (XRD), Raman scattering, field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDX), and ultraviolet-visible-near IR (UV-Vis-near IR) absorption, respectively. The optoelectronic and nonlinear optical properties were analyzed by current-voltage measurement and z-scan tests under red laser (655 nm) irradiation, respectively. To highlight the effect of surface plasmon charge transport-based photosensing and photo-harvesting, the irradiated light source is selected to have a photon energy lower than the ZnO bandgap energy and detuning from LSPR. The transfer of photo-induced hot electrons from the Au NPs localized surface plasmon resonance (LSPR) to the ZnO NRsA translates into photocurrent generation in photosensing performance. The reverse saturable absorption process is changed to saturable absorption after intercalating the Al
2
O
3
spacing layer into the ZnO NRsA/Au interface. The typical values of the nonlinear refraction index and absorption coefficient are calculated as
n
2
= +2.38 × 10
−5
cm
2
W
−1
and
β
= −0.17 cm W
−1
for the sandwiched ZnO NRsA/Al
2
O
3
/Au heterostructure, respectively. The sandwiched ZnO NRsA/amorphous Al
2
O
3
/Au heterostructure exhibits strong nonresonant optical nonlinearity, which has an excellent figure of merit for optical switching.
The collaboration of surface plasmon resonance and barrier spacing are spotlighted to investigate on the photoconversion and optical nonlinearity of ZnO nanorods array.
Ti–Cu–N thin films have been grown on Si(111), KBr (potassium bromide), quartz and glass slide substrates using a TiCu (13:87
at. %) single multi-component target by reactive DC magnetron sputtering ...at nitrogen ambient. This study provides insight into the importance of nitrogen pressure on the characteristic of Ti–Cu–N thin films. Crystalline phases of these films are identified by X-ray diffraction (XRD) technique. The titanium atoms were inserted into the Cu
3N unit cell. The results from XRD show that the observed phases are nano-crystallite cubic anti-Rhenium oxide (anti-ReO
3) structure of Ti doped Cu
3N (Ti:Cu
3N) and nano-crystallite face centre cubic (fcc) structure of Cu. Formation of copper vacancies in Cu
3N cell substituted by titanium atoms and subsequent excess of interstitial nitrogen (N-rich) result in lattice constant expansion and optical energy gap widening. Surface morphology of the films studied by scanning electron microscope (SEM) indicates agglomeration of grains. Ti:Cu atomic ratio of Ti–Cu–N films, determined by energy dispersive X-ray (EDX) spectroscopy, is less than that of the original TiCu single multi-component target and nearly independent of nitrogen pressure. Optical study is performed by Vis-near IR transmittance spectroscopy. Film thickness, refractive index and extinction coefficient are extracted from the measured transmittance using a reverse engineering method. Absorption coefficient indicates that the nitrided films are direct semiconductor. The films electrically show quasi-metallic behavior. The effect of sputtering pressure on deposition rate is investigated. Compared with the Ti free Cu
3N film, the Ti:Cu
3N films possesses fine thermal stability in vacuum.
► Ti–Cu–N nano-composite thin films prepared usingreactive DC magnetron sputter deposited at nitrogen ambient. ► Investigation of deposition pressure on target composition and discharge characteristic. ► Ti addition to Copper nitride thin films and newly prepared ternary compound. ► The effect of deposition pressure on structural, morphological, optical and electrical properties. ► The effect of N concentration on absorption and granularity of thin films.
The high temperatures and strong magnetic fields of the solar corona form streams of solar wind that expand through the Solar System into interstellar space. At 09:33 UT on 28 April 2021 Parker Solar ...Probe entered the magnetized atmosphere of the Sun 13 million km above the photosphere, crossing below the Alfvén critical surface for five hours into plasma in casual contact with the Sun with an Alfvén Mach number of 0.79 and magnetic pressure dominating both ion and electron pressure. The spectrum of turbulence below the Alfvén critical surface is reported. Magnetic mapping suggests the region was a steady flow emerging on rapidly expanding coronal magnetic field lines lying above a pseudostreamer. The sub-Alfvénic nature of the flow may be due to suppressed magnetic reconnection at the base of the pseudostreamer, as evidenced by unusually low densities in this region and the magnetic mapping.
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This paper evaluates the role of magnetic reconnection in the dayside ionosphere of Mars in the collisional regime and presents some relevant data from the MAVEN (Mars Atmosphere and Volatile ...EvolutioN) mission. Magnetic reconnection is an important process operating in the solar corona, planetary magnetospheres, and astrophysical plasmas, but most of the literature focuses on collisionless plasmas. However, at Mars the reconnection should often occur in regions where collisions are important. Mars does not have a large‐scale global magnetic field; however, Mars has locally large magnetic fields associated with remnant crustal magnetization, particularly in the highland regions of the southern hemisphere. The crustal fields provide a “target” for reconnection both in the ionosphere and in the magnetotail of Mars. The current paper emphasizes the dayside ionosphere. Magnetic reconnection is associated with topological changes in the magnetic field and is also a source of energy for the plasma and can thus affect the ionospheric dynamics and ion loss at Mars. Both theoretical concepts and MAVEN particle and field data from several instruments are considered in this paper.
Plain Language Summary
Magnetic reconnection is an important physical process in solar system and astrophysical plasmas (i.e., magnetized charged particle gases). During this process, the topology of the field lines is generally altered. For example, two sets of field lines—one connected at both ends to the Sun (i.e., interplanetary field lines advected into the ionosphere by the solar wind flow) and a second set connecting at both ends to the interior of Mars, “reconnect” in the relatively small “diffusion region.” The resulting field lines reach from the Sun into the surface of Mars (i.e., “open” field lines). Energy stored in the magnetic field is released during the reconnection process, thus providing kinetic energy to the electrons and ions in the plasma. The purpose of this paper is to explore some theoretical ideas of how collisions could affect magnetic reconnection in the Martian ionosphere and then to present one observational example using MAVEN (Mars Atmosphere and Volatile EvolutioN) data.
Key Points
Magnetic reconnection in the Martian ionosphere affects the transition between solar wind and crustal magnetic fields
The efficiency of magnetic reconnection is reduced by collisions at lower altitudes in the Martian ionosphere
Magnetic reconnection in the ionosphere is evident in data collected by the MAVEN spacecraft orbiting Mars
Abstract
During the thirteenth encounter of the Parker Solar Probe (PSP) mission, the spacecraft traveled through a topologically complex interplanetary coronal mass ejection (ICME) beginning on 2022 ...September 5. PSP traversed through the flank and wake of the ICME while observing the event for nearly two days. The Solar Probe ANalyzer and FIELDS instruments collected in situ measurements of the plasma particles and magnetic field at ∼13.3
R
S
from the Sun. We observe classical ICME signatures, such as a fast-forward shock, bidirectional electrons, low proton temperatures, low plasma
β
, and high alpha particle to proton number density ratios. In addition, PSP traveled through two magnetic inversion lines, a magnetic reconnection exhaust, and multiple sub-Alfvénic regions. We compare these in situ measurements to remote-sensing observations from the Wide-field Imager for Solar PRobe Plus instrument on board PSP and the Sun Earth Connection Coronal and Heliospheric Investigation on the Solar Terrestrial Relations Observatory. Based on white-light coronagraphs, two CMEs are forward modeled to best fit the extent of the event. Furthermore, Air Force Data Assimilative Flux Transport magnetograms modeled from Global Oscillation Network Group magnetograms and Potential Field Source Surface modeling portray a global reconfiguration of the heliospheric current sheet (HCS) after the CME event, suggesting that these eruptions play a significant role in the evolution of the HCS.
This study aimed to investigate the increase in heat transfer in the indirect heater at a city gate station (CGS) with the addition of copper oxide (CuO) nanoparticles to water–ethylene glycol base ...fluids. Indirect heaters are typically used at CGSs to raise the heat transfer coefficient of output gas flow from − 5 to 15 °C. Moreover, manufacturing laboratory equipment in the presence of water–ethylene glycol base fluid and the nanoparticle in volume fractions of 0.05, 0.1, 0.2, and 0.3 at a temperature of 40–70 °C was discussed using dimensional simulation and analysis. The physical properties of the base fluid and nanofluid were measured using precise devices. Heat transfer tests for the base and nanofluid, as well as replacing of the air by gas, were conducted in a simulated and developed device. According to the obtained results with respect to the changes in convection and conduction heat transfer, enhancement of temperature difference at a rate of 36% was observed in the indirect heater with nanoparticle volume concentration of 0.2% at a temperature of 70 °C. Moreover, the Nusselt number showed a relatively good agreement with theoretical discussions.
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