Hot Component Research Articles

Time-dependence of the effective temperatures of a two-dimensional Brownian gyrator with cold and hot components

We consider a model of a two-dimensional molecular machine—called Brownian gyrator—that consists of two coordinates coupled to each other and to separate heat baths at temperatures respectively T x and T y . We consider the limit in which one component is passive, because its bath is ‘cold’, T x → 0, while the second is in contact with a ‘hot’ bath, T y > 0, hence it entrains the passive component in a stochastic motion. We derive an asymmetry relation as a function of time, from which time dependent effective temperatures can be obtained for both components. We find that the effective temperature of the passive element tends to a constant value, which is a fraction of T y , while the effective temperature of the driving component grows without bounds, in fact exponentially in time, as the steady-state is approached.

A systematic survey for z< 0.04 CLAGNs

ABSTRACT We have conducted a systematic survey for z < 0.04 active Galactic nuclei (AGNs) that may have changed spectral class over the past decade. We use SkyMapper, Pan-STARRS and the Véron-Cetty & Véron catalogue to search the entire sky for these ‘changing-look’ AGNs (CLAGNs) using a variety of selection methods, where Pan-STARRS has a coverage of 3$\pi$ steradians (sky north of Declination −30○) and SkyMapper has coverage of ∼21000 $~\rm {deg^2}$ (sky south of Declination 0○). We use small aperture photometry to measure how colour and flux have changed over time, where a change may indicate a change in spectral type. Optical colour and flux are used as a proxy for changing Hα equivalent width, while WISE 3.4 μm flux is used to look for changes in the hot dust component. We have identified four AGNs with varying spectra selected using our optical colour selection method. Three AGNs were confirmed from recent observations with WiFeS on the 2.3 m telescope at Siding Spring and the other was identified from archival spectra alone. From this, we identify two new CLAGNs; NGC 1346 and 2MASX J20075129–1108346. We also recover Mrk 915 and Mrk 609, which are known to have varying spectra in the literature, but they do not meet our specific criteria for CLAGNs.

Numerical model to estimate subcooled flow boiling heat flux and to indicate vapor bubble interaction

There are numerous technical applications where hot components, with uneven temperature distribution, require cooling. In such applications, it is desired to provide efficient local cooling of the hot spots, while avoiding unnecessary over-cooling of the other regions. Such an approach, known as precision cooling, has several advantages. In addition to the fact that it reduces the effort for cooling, it limits the unintended heat lost to the cooling medium. In liquid cooled systems, such as Internal Combustion Engines (ICE), subcooled flow boiling offers immense potential for precision cooling. The primary challenges in extracting this potential are understanding the complexities in the subcooled flow boiling phenomenon and estimating the risk of encountering film boiling. The present study introduces a numerical model to estimate the wall heat flux in subcooled flow boiling and the model includes a mechanistic formulation to account for vapor bubble interaction. The formulation for vapor bubble interaction serves two purposes: (a) blends two well-established models in the literature, one in the isolated bubbles regime and other in the fully developed boiling regime, to estimate the wall heat flux; and (b) provides information to limit boiling in order to not encounter film boiling. The results from the new model are validated with two different experiments in the literature and the wall heat flux estimated by the model is in agreement with experimental results and responsive to different input parameters, such as bulk velocity, operating pressure and inlet subcooling. The new model requires only input of local flow quantities and hence implementation in Computational Fluid Dynamics (CFD) is straightforward.

Quantitative mapping of service process-microstructural degradation-property deterioration for a Ni-based superalloy based on chord length distribution imaging process

Directionally solidified (DS) and single crystal (SC) Ni-based superalloys inevitably underwent microstructural degradation induced by the harsh operating environment. For the safety service and economic overhaul, constructing a quantitative mapping chain from service process to microstructural degradation and to property deterioration is critically essential. The present work started with stress-free and stress-assisted pre-service treatments of a DS Ni-based superalloy to obtain microstructures with different degraded states. An imaging process based on two-phase rotary chord length distributions was established to extract the high dimensional statistical information for identifying the morphology and size features of microstructures. To reduce the dimension of the statistical information and quantitatively characterize the microstructural states in fewer parameters, principal component analysis was employed to capture the core microstructural indicators, which was utilized to establish the response surface between the deterioration of fatigue resistance and the microstructural degradation. Finally, a multi-output support vector regression (SVR) model was constructed to map between service process and microstructural degradation. The results showed acceptable accuracy to estimate the microstructural degradation of pre-serviced alloys. Meanwhile, the framework provides a technical chain for the waste determination and microstructural degradation estimation of the hot section components made by DS and SC Ni-based superalloys.

Dispersion measure distributions of fast radio bursts due to the intergalactic medium

ABSTRACT Utilizing cosmological hydrodynamic simulations, we quantify the distributions of the dispersion measure (DM) of fast radio bursts (FRBs). We examine the contributions of cold, warm-hot, and hot gas to the total DM. We find that the hot gas component (T > 107K), on average, makes a minor contribution ($\le 5{{\ \rm per\ cent}}$) to the overall DM. Cold (T < 105K) and warm-hot (T = 105 − 107K) gas components make comparable contributions to DM for FRBs at z = 1, with the former component making an increasingly larger contribution towards higher redshift. We provide a detailed DM distribution of FRBs at z = 0.25 to z = 2 that may be compared to observations. We also compute the relation between the Compton y parameter and DM, finding a strong correlation, y∝DM4, providing an additional, independent constraint on the nature of the DM of FRBs.

Failure analysis of a gas turbine blade: A review

Blade is an essential component of a gas turbine that functions to convert thermal gas energy at a high temperature and pressure into mechanical energy. Gas in the turbine blade works at a high temperature and pressure. High temperatures and pressures cause turbine blades to be one part of turbine components that often fails. Failure of the blade results in performance and turbine efficiency. The cause of failure on the blade is influenced by several factors, including fatigue, creep, oxidation, degradation of the coating on the turbine blade, corrosion, erosion, and surface degradation due to working at high temperatures. The hot temperature on the blades work on turbines around 1927 F to 3500 F and is one of the main factors in the failure rate. Individual blade failure rates differ due to operating temperature, rotation speed, operating mode, total service time, and differences in fabrication. This article discusses several case studies of failure in turbine hot section components such as blades to support the failure investigation is the key to improving turbine efficiency.

Corrosion Behavior and Failure Prediction of YSZ Coatings Under CMAS Attack

In aeroengines, thermal barrier coatings (TBCs) are usually utilized to protect the hot components from hot gases. The ability to predict the TBC failure is crucial to avoid economic losses. In this study, plasma-sprayed 8 wt.% yttria-stabilized zirconia (YSZ) coatings were subjected to corrosion by calcium–magnesium–aluminosilicate (CMAS, 33CaO–9MgO–13Al2O3–45SiO2) glass at 1250 °C. After the test, two morphologies were observed on the coating surface. At the sample edges, the coating underwent over-sintering because of the locally high temperature: the molten glass easily penetrated the YSZ layer and reacted with it; and iron spinel was detected on the surface. In the sample central region submitted to a relatively lower temperature, a dense layer consisting of both CMAS glass and YSZ was formed. The analysis of the self-luminescence of the YSZ coating after corrosion revealed the presence of sintered regions on the coating surface, which increased as the corrosion temperature increased. This came with a decrease in the coating luminescence. This study shows that the self-luminescence properties can be used to monitor the degree of corrosion and predict the failure of the coating.

Total X-Ray Emission from the LMC Observed with HaloSat

Abstract We constrain the global parameters of the Large Magellanic Cloud (LMC) by modeling the first soft X-ray (0.4–6.8 keV) observations of the entire LMC produced in a single pointing with moderate spectral resolution by the HaloSat CubeSat. These data are best fit with the sum of two thermal plasma components in collisional ionization equilibrium and a power law. We find cool (0.210 ± 0.014 keV) and hot (0.89 ± 0.14 keV) components. The total X-ray luminosity of the LMC is (1.08 ± 0.14) × 1039 erg s−1. X-ray binaries make up a large fraction of the emission with a luminosity of (6.0 ± 0.8) × 1038 erg s−1, followed by cool gas from superbubbles, supernovae, and diffuse emission with a luminosity of (3.0 ± 0.3) × 1038 erg s−1. The hot gas from star formation contributes the smallest fraction, with a luminosity of (1.9 ± 0.5) × 1038 erg s−1. We estimate the total volume of the cool gas to be between (0.2–1.2) × 1010 pc3 and the hot gas to be between (1.0–5) × 107 pc3 for filling factors of f = 1 and 0.2. These volumes result in a total thermal energy for the cool gas between (1.4–3) × 1054 erg for electron densities of 0.017–0.04 cm−3, and a thermal energy for the hot gas between (1.7–4) × 1053 erg for electron densities of 0.12–0.3 cm−3. This yields cooling timescales for the cool and hot gas of (1.5–3) × 108 yr and (1.8–6) × 107 yr, respectively.

Combination of PIP and LSI processes for SiC/SiC ceramic matrix composites

Silicon carbide fiber-reinforced silicon carbide matrix composites (SiC/SiC CMCs) are promising candidates for hot gas components in jet engines. Three common manufacturing routes are chemical vapor infiltration, reactive melt infiltration (RMI) and polymer infiltration and pyrolysis (PIP). A combination of the processes seems attractive: the remaining porosity after PIP process can be closed by subsequent siliconization, resulting in a dense material. This work describes a new approach of a combined PIP and RMI process. SiC/SiC CMCs were manufactured by PIP process using Hi-Nicalon Type S fibers. An additional RMI was carried out after a reduced number of PIP cycles. Microstructure was examined via μCT, SEM and EDS. Bending strength was determined to 433 ​MPa; strain to failure was 0.60%. The overall processing time was reduced by 55% compared to standard PIP route. The hybrid material contained 70% less unreacted carbon than material produced by LSI process alone.

About solvents used in the preparation of oils for cosmetic products complying with the Cosmos standard

Solvents have a bad reputation in the cosmetics world, at least as regards the production of specialty vegetable oils used in this market. In order to do without these solvents, the cosmetics industry tends to use only mechanically produced oils. However, there is a range of seeds for which mechanical extraction is not satisfactory. This is the case with rare, expensive, and oil-poor seeds for which pressing does not give good yields, and results in high production costs. These are also hard seeds that cannot be pressed without causing the presses to become intensely hot, and this affects the quality of the oils. In recent years, our laboratory has worked on the development of extraction techniques with ethanol and the EcoXtract® solvent (2-methyloxolane) in order to provide professionals with production methods compatible with the COSMOS standard. Ethanol is not a good solvent for oils, especially in the presence of water and at low temperature. This drawback can be turned into an advantage to recover the oil (without distillation of the solvent) by cold decantation. The extraction is carried out on the hot components, and the oil is recovered by cooling the saturated miscella for the precipitation of the lipid phase. This process makes it possible to limit the energy consumption necessary for the recovery of the oil and the regeneration of the solvent. The great advantage for oils intended for the cosmetic market is that ethanol has a better solvent power for polar lipids compared to hexane and mechanical extraction. It is possible to split the lipid extract into neutral lipids and polar lipids by adjusting the precipitation temperature or by partial distillation. At the refining step, it is also possible to deacidify and remove contaminants from crude oil by liquid-liquid extraction with ethanol. We have recently obtained interesting results by reducing the phthalate concentration of walnut oils by 90%. The use of ethanol for oil neutralization is a process which generates less loss of neutral oil than the alkaline neutralization of a mixture with high acidity, and this is less harmful than physical refining during the production of 3-MCPD esters, esters of glycidol, and trans fatty acids. EcoXtract® is a solvent derived from the chemistry of pentoses in biomass. This solvent has very good oil solvation capacities and less biological toxicity than hexane. Its production has an acceptable carbon footprint and good sustainability characteristics. It is recognised by Ecocert as suitable for producing COSMOS ingredients. Compared to ethanol, its use requires fewer preparation steps (ethanol requires rigorous drying before extraction) and it requires less circulating solvent per kilo of oil extracted. The solvent removal from the meal requires less energy and allows the use of direct steam to aid in the removal of the solvent since the miscibility of water in this solvent is limited to 4.5 g/100g.

The First Mid-infrared Detection of HNC in the Interstellar Medium: Probing the Extreme Environment toward the Orion Hot Core

Abstract We present the first mid-infrared (MIR) detections of HNC and in the interstellar medium, and numerous resolved HCN rovibrational transitions. Our observations span 12.8–22.9 μm toward the hot core Orion IRc2, obtained with the Echelon-Cross-Echelle Spectrograph aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). In particular, ∼5 km s−1 resolution distinguishes individual rovibrational transitions of the HNC and HCN P, Q, and R branches; and the R branch. This allows direct measurement of the species’ excitation temperatures, column densities, and relative abundances. HNC and exhibit a local standard of rest velocity of −7 km s−1 that may be associated with an outflow from nearby radio source I and an excitation temperature of about 100 K. We resolve two velocity components for HCN, the primary component also being at −7 km s−1 with a temperature of 165 K. The hottest component, which had never before been observed, is at 1 km s−1 with a temperature of 309 K. This is the closest component to the hot core’s center measured to date. The derived is below expectation for Orion’s Galactocentric distance, but the derived HCN/HNC = 72 ± 7 is expected for this extreme environment. Compared to previous sub-millimeter and millimeter observations, our SOFIA line survey of this region shows that the resolved MIR molecular transitions are probing a distinct physical component and isolating the chemistry closest to the hot core.

Development of a form-flexible handling technology with active cooling for hybrid components in forging processes

Tailored Forming is a novel manufacturing process for the production of forged hybrid components. In contrast to components made of mono-materials, hybrid components can be adapted to the respective loads by combining different materials with contradictory properties. Short processing times and high component quality, however, lead to the demand for automated handling and local active cooling within the forming process, since the appropriate processing temperature is particularly important. Due to the fact that the hybrid components are differently hot and change their shape during the forming process, a special gripper system must be provided, which can withstand high temperatures, and ensures both shape variability and local cooling. Nowadays, however, there is a gap between shape variable grippers and rigid grippers for temperature-sensitive processes without any integrated cooling functionalities. Therefore, this paper presents an approach for the development of shape variable high temperature grippers with the use-case of handling hot steel-aluminium hybrid components.

Empirical Modeling of Abrasive Waterjet Process for Controlled Depth Machining of Dense Segmented Ceramic Thermal Barrier Coatings

Abrasive waterjet (AWJ) controlled depth machining shows promise to be one of the most efficient non-conventional structuring techniques for dense segmented Thermal Barrier Coatings (STBC) on turbomachinery hot gas components made of Yttria-Stabilized Zirconia. Exemplary applications in the field of gas turbine technology are engraving of structures to optimize gas turbine performance and the stripping process of TBC within the repair process chain. As there are no comprehensive process models available, the development of an appropriate AWJ machining process is demanding. Thus, deeper process understanding and modeling need to be investigated.This paper shows an empirical modeling of AWJ process for controlled depth machining of dense segmented TBC material. The practical trials are based on a Design of Experiments (DoE). The investigated influencing parameters are water pressure, abrasive mass flow, feed rate, hatch distance and machining angle. The considered target variables are ablation depth and surface roughness. Furthermore, the process stability is investigated. The developed empirical model results in an acceleration of process parameter determinations.

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ТЕХНОЛОГИИ ПРОИЗВОДСТВА МАГНЕТРОННЫХ МИШЕНЕЙ НА МИКРОСТРУКТУРУ И ФАЗОВЫЙ СОСТАВ СПЛАВА СИСТЕМЫ Zr–Y

The Zr–Y-based alloy targets are used for spraying of heat-resisting ceramic coatings on the gas-turbine hot section components surface by the plasma-chemical deposition techniques. The comparative study of the microstructure and phase composition for target specimens, which manufactured by vacuum-induction melting or vacuum-arc melting, are performed. The patterns of change in a microstructure and a phase composition in the experimental Zr–Y-based alloy, depending of manufacturing technology are shown. The aspects which have led to transformation of microstructure and phase composition of VTsM-1 Zr–Y-based alloy at the change of the manufacturing technology of targets are detected.

The Consequence of Drinking Water, in Air and Soil with the Presence of Natural Radioactive Elements

The current work was evaluated so as to assess the impact of naturally hot components in soil and water samples. The majority of the world's covers were made up of emitting radiation components. We have taken eight consecutive research previous studied article related with the present work what we are focused. The first source of hot isotopes is deposits that can be enriched in 238 U and its girl isotopes. All the foremost necessary natural resources are water. Natural radiation and its effects on human health, plants, and mining have recently become a major environmental concern as a result of the invention of widespread inert gas levels in home air at concentrations that exceed each location. Precise activity and gamma-absorbed dose rates of terrestrial present radionuclides in edge soil were determined through gamma-ray chemical analysis. The purpose of this study was to collect baseline data on natural environmental electromagnetic radiation and radiation levels, as well as to assess the corresponding tomography health effects on individuals. precise activity and gamma-absorbed dose rates of terrestrial present radionuclides in edge soil were determined through gamma-ray chemical analysis. The goal of this study was also to collect baseline data on natural environmental electromagnetic radiation and radiation levels, as well as to assess the health effects of tomography on individuals.

IDEAL MARRIAGE IN HANUM SALSABILA RAIS AND RANGGA ALMAHENDRA’S NOVEL I AM SARAHZA

This study constituted an analysis of an ideal marriage in the novel published in 2018. The significant components of the marriage relationship found in the novel that could be categorized into an ideal marriage were the topics to discuss. One of the significant theories of an ideal marriage used in this study was A Triangular of Love that appears in three significant components: intimacy, passion and commitment that reflected the subjective experience. Intimacy could be considered the warm component because it encompassed the feeling of comfort and tenderness in a relationship. Then, passion consisted of motivational and was considered the hot component, in that it usually included the most intense feeling. Finally, commitment involved deliberate choice to love someone and to maintain that love. It was considered the cold component (Sternberg: 1986). The research was conducted by descriptive qualitative method. The research results showed that the three points of an ideal marriage in the novel, i.e. intimacy, passion, and commitment were clearly reflected by the major characters in the novel.

Simulation and experimental study on microstructure evolution of 5CrNiMoV steel during multi-directional non-isothermal forging

Microstructure evolution during the hot forming shows a significant impact on material’s mechanical properties. To explore the deformation characteristics of 5CrNiMoV steel, numerical simulation and microscopic phase-field simulation of the multi-direction forgings were carried out. The strain distribution at each pass was investigated and the evolution of temperature, effective strain, effective strain rate, and grain size was acquired. The hot forging trials were carried out and three typical regions of forgings were taken to study the microstructure evolution. Detailed microstructure characterizations showed that the constructed parent austenite grain size of the forging in typical regions was slightly larger than the simulation results due to the grain coarsening during the air cooling. There were large amounts of high angle grain boundaries (HAGBs) for the occurrence of complete dynamic recrystallization and many bulging grain boundaries showed that discontinuous dynamic recrystallization (DDRX) could be the governing mechanism of nucleation and growth of dynamic recrystallization (DRX). Besides, the hot deformation texture changed significantly during the non-isothermal forging and the texture component differed remarkably at different regions of the forging. The main hot deformation texture components were Cube {001}<100> and Goss{011}<100>.

Gaia18aen: First symbiotic star discovered by Gaia

Context. Besides the astrometric mission of the Gaia satellite, its repeated and high-precision measurements also serve as an all-sky photometric transient survey. The sudden brightenings of the sources are published as Gaia Photometric Science Alerts and are made publicly available, allowing the community to photometrically and spectroscopically follow up on the object. Aims. The goal of this paper is to analyze the nature and derive the basic parameters of Gaia18aen, a transient detected at the beginning of 2018. This object coincides with the position of the emission-line star WRAY 15-136. The brightening was classified as a “nova?” on the basis of a subsequent spectroscopic observation. Methods. We analyzed two spectra of Gaia18aen and collected the available photometry of the object covering the brightenings in 2018 and also the preceding and following periods of quiescence. Based on this observational data, we derived the parameters of Gaia18aen and discussed the nature of the object. Results. Gaia18aen is the first symbiotic star discovered by Gaia satellite. The system is an S-type symbiotic star and consists of an M giant of a slightly super-solar metallicity, where Teff ∼ 3500 K, a radius of ∼230 R⊙, and a high luminosity L ∼ 7400 L⊙. The hot component is a hot white dwarf. We tentatively determined the orbital period of the system ∼487 d. The main outburst of Gaia18aen in 2018 was accompanied by a decrease in the temperature of the hot component. The first phase of the outburst was characterized by the high luminosity L ∼ 27 000 L⊙, which remained constant for about three weeks after the optical maximum, later followed by the gradual decline of luminosity and increase of temperature. Several re-brightenings have been detected on the timescales of hundreds of days.

Pt thin-film resistance temperature detector on flexible Hastelloy tapes

Platinum (Pt) thin-film resistance temperature detector was fabricated on the flexible Hastelloy tapes using magnetron sputtering and MEMS processes. NiCrAlY buffer layer and AlON/Al2O3 insulating layer were deposited on the tapes for stress release and electrical insulation. Post annealing was applied to improve the stability of the sensors. The performance of the sensor was calibrated with temperature up to 550 °C. Compared with the sensor on the alumina ceramic substrate, the sensor on Hastelloy tapes have much smaller thermal hysteresis, higher linearity and excellent stability. Moreover, this flexible sensor can be easily integrated with the metallic components by the welding and the maximum curvature of the sensor is 2 cm−1. This Pt thin-film temperature sensor has great potential in the surface temperature measurement of hot components in harsh environment.

Galactic 26Al traces metal loss through hot chimneys

ABSTRACT Radioactive 26Al is an excellent tracer for metal ejection in the Milky Way, and can provide a direct constraint on the modelling of supernova feedback in galaxy evolution. Gamma-ray observations of the 26Al decay line have found high velocities and hence require a significant fraction of the Galactic 26Al in the hot component. At the same time, meteoritic data combined with simulation results suggest that a significant amount of 26Al makes its way into stars before decay. We investigated the distribution into hot and cold channels with a simulation of a Milky-Way-like galaxy with massive-star feedback in superbubbles and with ejecta traced by 26Al. About 30–40 per cent of the ejecta remain hot, with typical cooling times of the order Gyr. 26Al traces the footpoints of a chimney-fed outflow that mixes metals turbulently into the halo of the model galaxy on a scale of at least 50 kpc. The rest diffuses into cold gas ≲ 104 K, and may therefore be quickly available for star formation. We discuss the robustness of the result by comparison to a simulation with a different global flow pattern. The branching ratio into hot and cold components is comparable to that of longer term average results from chemical evolution modelling of galaxies, clusters, and the intracluster medium.