Temperatures In Excess Research Articles

Influence of the annealing temperature of (n) poly-Si/SiOx passivating contacts on their firing stability

Several works have been published recently regarding firing stability of passivating contacts featuring P-doped polysilicon on an interfacial oxide (poly-Si/SiOx). Therein, a degradation was reported if the (n) poly-Si/SiOx structure was capped by a dielectric passivation layer during firing due to creation of additional defects in the interfacial oxide. In part A of this study it is shown, that P-doped (n) poly-Si/SiOx structures capped by a SiNy or SiNy/AlOz stack only degrade during firing at moderate temperatures if they previously have been annealed below the optimum annealing temperature Topt. It was found that this degradation is stronger the colder the annealing temperature was below Topt. In part B of this study it is shown, that at excess firing temperatures also samples annealed at or above Topt degrade. Again, this degradation depends on the initial annealing temperature in a similar way that the degradation is stronger the colder the annealing temperature was below Topt. Furthermore, a saturation of the measured surface recombination density was observed for set firing temperatures above 900°C, which points to a saturation of the underlying defect creation mechanism in the interfacial oxide.

Effects of extreme melt events on ice flow and sea level rise of the Greenland Ice Sheet

Abstract. Over the past decade, Greenland has experienced several extreme melt events, the most pronounced ones in the years 2010, 2012 and 2019. With progressing climate change, such extreme melt events can be expected to occur more frequently and potentially become more severe and persistent. So far, however, projections of ice loss and sea level change from Greenland typically rely on scenarios which only take gradual changes in the climate into account. Using the Parallel Ice Sheet Model (PISM), we investigate the effect of extreme melt events on the overall mass balance of the Greenland Ice Sheet and the changes in ice flow, invoked by the altered surface topography. As a first constraint, this study estimates the overall effect of extreme melt events on the cumulative mass loss of the Greenland Ice Sheet. We find that the sea level contribution from Greenland might increase by 2 to 45 cm (0.2 % to 14 %) by the year 2300 if extreme events occur more frequently in the future under a Representative Concentration Pathway 8.5 (RCP8.5) scenario, and the ice sheet area might be reduced by an additional 6000 to 26 000 km2 by 2300 in comparison to future warming scenarios without extremes. In conclusion, projecting the future sea level contribution from the Greenland Ice Sheet requires consideration of the changes in both the frequency and intensity of extreme events. It is crucial to individually address these extremes at a monthly resolution as temperature forcing with the same excess temperature but evenly distributed over longer timescales (e.g., seasonal) leads to less sea level rise than for the simulations of the resolved extremes. Extremes lead to additional mass loss and thinning. This, in turn, reduces the driving stress and surface velocities, ultimately dampening the ice loss attributed to ice flow and discharge. Overall, we find that the surface elevation feedback largely amplifies melting for scenarios with and without extremes, with additional mass loss attributed to this feedback having the greatest impact on projected sea level.

Compatibility of molybdenum with high temperature hydrogen

Arc-cast Molybdenum samples were exposed to a high temperature (2200–2630 K) hydrogen (H2) environment at ∼1 atm to evaluate their chemical compatibility under extreme temperature conditions; this compatibility information is useful to examining the potential application of Mo-matrix cermets for nuclear thermal propulsion applications. Subscale samples were exposed to 1–2 L/min of flowing H2 with hold times of 80 min at temperature (2200–2630 K). The measured mass loss was observed to be slightly lower than that predicted by vapor pressure calculations, which indicates minimal chemical corrosion reactions between Mo and H2 up to temperatures in excess of 90% of the melting temperature of Mo. Grain size dramatically increases across the temperature range. Parallel surface ledges within grains are frequently observed across the sample surface following high temperature hydrogen exposure and in general are related to the orientation of the grain. The observed mass loss is sufficiently low to consider Mo cermets as a candidate fuel for NTP applications.

Film formation of high poly(vinyl chloride) content latex particles

Although poly(vinyl chloride) (PVC) is produced on a large scale industrially by emulsion and suspension polymerization, it is usually processed from the dry state and is seldom directly used as an aqueous polymer dispersion. In this work we demonstrate that by control of particle morphology and particle size distribution it is possible to produce latexes with high PVC content from which polymer films can be cast directly. A series of hybrid PVC/acrylic latexes with a core-shell structure are produced by semi-batch emulsion polymerization using a preformed PVC latex as a seed. Although monomodal particles of this type have a minimum film formation temperature in excess of 80 °C when the content of PVC is high, it is shown that through the use of a bimodal particle size distribution the packing efficiency of the spherical PVC domains is increased such that room temperature film formation is possible with PVC content up to 80 wt%.

Kinetics of the Saponification of Mixed Fats Consisting of Olein and Stearin

This research presents the kinetics of the saponification reaction using mixed fats of olein and stearin [in the ratio (3:1)] with NaOH solution. In this reaction, excess solution of NaOH was used to ensure the reaction being irreversible. Three parameters were varied to show their effects on the reaction rate .They are: percentage excess of NaOH solution (10 % - 100 %) , temperature (100-150)oC , and stirring speed (400-1100) rpm. It was noticed that increasing the percentage excess of NaOH solution enhances the rate of reaction while increasing temperature decreases the reaction rate since it is exothermic reaction. Increasing stirring speed also improves the reaction rate because it is mass transfer controlled .Calculations of the activation energy and the frequency factor was also performed.
 A new mathematical model for calculation of the reaction – rate constant was derived. It is shown that a good approximation was obtained between the experimental and calculated values of the reaction – rate constant k .

Dimensionless prejudgment criterion of coal spontaneous combustion in longwall gobs and its application

Coal spontaneous combustion (CSC) in longwall gobs is the result of the coupling of multiple physical fields, making its development difficult to predict, so the prejudgment indicators need to be refined. In this work, the dimensionless model of CSC in the gob was established, and three prejudgment indicators such as air leakage intensity indicator, longwall advance rate indicator and exothermic intensity indicator were proposed to consist of the dimensionless prejudgment criteria of CSC in gobs. Numerical simulations were performed to obtain the relationship curves between each indicator and the dimensionless maximum excess temperature in the gob. These curves had formed a series of nomograms that can be used to prejudge the CSC. It shows that the risk of the CSC in gobs is positively correlated with the air leakage intensity indicator and the exothermic intensity indicator, but inversely proportional to the longwall advance rate indicator. The field application indicates that the prejudgment criteria and its Nomogram can be used to accurately predict whether the CSC could occur in the gob, and has good prospects for application.

One step densification of SDC—Na2CO3 nano‐composite electrolytes for SOFC applications by cold sintering process

AbstractSm0.2Ce0.8O1.9‐ 30% Na2CO3 (Sm doped ceria (SDC)‐30N) nano‐composite electrolytes were densified in a single step via cold sintering process (CSP). At 200°C and 450 MPa of uniaxial pressure, samples up to 97% of their theoretical density could be obtained. The effect of processing parameters, such as temperature, uniaxial pressure, processing duration, and moisture content, on the densification of the nano‐composite electrolytes was investigated. The thermal, microstructural, and electrical properties of nano‐composites were investigated by differential scanning calorimetry, X‐ray diffractometer, scanning electron microscope, and EIS analysis. SDC crystallite sizes were found to be around 25 nm, barely coarsened after CSP by which the true nano nature of the nano‐composite could be preserved. Because, by conventional processing high density values could not be attained and high processing temperatures in excess of 600°C had to be used, promoting particle coarsening. The highest total electrical conductivity was found to be 2.2 × 10−2 S cm−1 at 600°C, with an activation energy of 0.83 eV for SDC‐30N nano‐composites. The present investigation revealed that the implementation of cold sintering technique resulted in significant enhancements in the densification of nano‐composite electrolytes, thereby rendering them suitable for efficient utilization in SOFC applications, as compared to the conventional production methods.

Effect of Thermal Overload Relay (TOR) as Overheating Protection on BSR-10 Type Biofuel Pelletizer Molding Machine

BSR-10 type biofuel pellet forming machine is widely used in renewable energy industry to produce high quality biofuel pellets. However, prolonged operation and heavy loads on these engines can cause their temperature to rise excessively and potentially damage the electric motors. To overcome this problem, this study aims to investigate the effect of using a Thermal Overload Relay (TOR) as a protection against overheating in a BSR-10 type biofuel pellet forming machine. This research involves measuring temperature and engine performance when operated with and without TOR. Motor temperature and engine ambient temperature are observed and recorded during normal operation and heavy load situations. In addition, engine performance in terms of rotational speed, energy consumption and pellet production were also evaluated with and without TOR. The results showed that the use of TOR significantly reduced the motor temperature in the BSR-10 type biofuel pellet forming machine. When given a heavy load, the engine that is protected by TOR shows a more stable and controlled temperature compared to the engine without TOR. In addition, TOR-equipped machines also show improvements in overall performance, including more stable rotational speeds, more efficient energy consumption and consistent pellet production. In conclusion, the use of Thermal Overload Relay (TOR) as protection against overheating in the BSR-10 type biofuel pellet forming machine is effective in controlling motor temperature, improving engine performance, and preventing damage caused by excess temperature. This research provides a better understanding of the use of TOR in the context of biofuel pelletizing machines and can provide useful guidance to the renewable energy industry in improving the operational efficiency and reliability of their machines..

Improving the methodology for determining the main parameters of solar batteries

The article cites the need for a reliable and economical power supply to rural consumers. At the same time, it is important to develop distributed generation, including on the basis of renewable sources, using solar and wind energy to reduce costs. The necessity of choosing solar panels with optimal parameters, taking into account the influence of external factors, is shown. To determine the actual generated power of solar batteries, the concept of "power loss during the conversion of the solar radiation flux into electrical power" is introduced. It has been established that insufficient studies of the regime parameters of photocells, in particular, the temperature of its heating and the corresponding change in efficiency, taking into account external factors, do not allow choosing a module with effective power. To study the parameters of solar batteries, an equivalent circuit and methods for determining its parameters are presented. The established dependence of the excess of the SM temperature over the ambient temperature on the power of solar radiation is presented, which formed the basis of an improved method for determining the parameters of solar batteries. The presented results of the study allow at the design stages to determine the expected power of a solar photovoltaic installation and choose its optimal parameters.

Change in transition balance between durable tetragonal phase and stress-induced phase of cobalt surface-layered in Bi-2212 materials by semi-empirical mechanical models

This study has indicated the positive effect of sintering temperature on the mechanical durability, strength, critical stress, deformation degrees, durable tetragonal phase, failure and fracture by fatigue, and mechanical characteristic behavior to the applied test loads for the Co surface-layered Bi-2212 ceramic materials produced by the standard solid-state reaction method. The sintering mechanism has been used as the driving force for the penetration of cobalt ions in the Bi-2212 ceramic matrix. The microindentation hardness test measurements have been performed at the load intervals 0.245 N-2.940 N. The experimental findings have also been examined by the six different semi-empirical mechanical and indentation-induced cracking models. It has been found that all the mechanical performance parameters are improved considerably with increasing the diffusion sintering temperature up to 650 °C. On this basis, the Co surface-layered Bi-2212 sample produced at the sintering temperature of 650 °C has been observed to improve dramatically the mechanical durability and resistance to the applied test loads as a consequence of the formation of new force barrier regions, surface residual compressive stress regions, and slip systems in the Bi-2212 ceramic system. Similarly, the optimum sintering temperature has extensively enhanced the elastic recovery mechanism, critical stress values, and deformation degree levels, stored internal strain, and crack surface energy through the Bi-2212 ceramic materials. Accordingly, it has been noted that the best sample produced at 650 °C is more hardly broken than the other ceramics. Namely, the optimum sintering temperature has decreased the sensitivity to the applied test loads as a result of delaying the beginning of the plateau limit regions. On the other hand, all the mechanism has been found to reverse completely depending on the excess sintering temperature. Lastly, the indentation-induced cracking model has been found to exhibit the closest results to the original Vickers microhardness parameters in the plateau limit regions.

Instantaneous 3D tomography-based convection beneath the Rungwe Volcanic Province, East Africa: implications for melt generation

SUMMARY Within the Western Branch of the East African Rift (EAR), volcanism is highly localized, which is distinct from the voluminous magmatism seen throughout the Eastern Branch of the EAR. A possible mechanism for the source of melt beneath the EAR is decompression melting in response to lithospheric stretching. However, the presence of pre-rift magmatism in both branches of the EAR suggest an important role of plume-lithosphere interactions, which validates the presence of voluminous magmatism in the Eastern Branch, but not the localized magmatism in the Western Branch. We hypothesize that the interaction of a thermally heterogeneous asthenosphere (plume material) with the base of the lithosphere enables localization of deep melt sources beneath the Western Branch where there are sharp variations in lithospheric thickness. To test our hypothesis, we investigate sublithospheric mantle flow beneath the Rungwe Volcanic Province (RVP), which is the southernmost volcanic center in the Western Branch. We use seismically constrained lithospheric thickness and sublithospheric mantle structure to develop an instantaneous 3D thermomechanical model of tomography-based convection (TBC) with melt generation beneath the RVP using ASPECT. Shear wave velocity anomalies suggest excess temperatures reach ∼250 K beneath the RVP. We use the excess temperatures to constrain parameters for melt generation beneath the RVP and find that melt generation occurs at a maximum depth of ∼140 km. The TBC models reveal mantle flow patterns not evident in lithospheric modulated convection (LMC) that do not incorporate upper mantle constraints. The LMC model indicates lateral mantle flow at the base of the lithosphere over a longer interval than the TBC model, which suggests that mantle tractions from LMC might be overestimated. The TBC model provides higher melt fractions with a slightly displaced melting region when compared to LMC models. Our results suggest that upwellings from a thermally heterogeneous asthenosphere distribute and localize deep melt sources beneath the Western Branch in locations where there are sharp variations in lithospheric thickness. Even in the presence of a uniform lithospheric thickness in our TBC models, we still find a characteristic upwelling and melt localization beneath the RVP, which suggest that sublithospheric heterogeneities exert a dominant control on upper mantle flow and melt localization than lithospheric thickness variations. Our TBC models demonstrate the need to incorporate upper mantle constraints in mantle convection models and have global implications in that small-scale convection models without upper mantle constraints should be interpreted with caution.

Fractional derivative modelling for rheological characteristics of multilayered saturated porous rock with interfacial thermal contact resistance

AbstractIn this paper, the one‐dimensional rheological characteristics of multilayered saturated porous rock subjected to a ramp‐type heating is investigated. By introducing the fractional order parameter and material parameters, a viscoelastic constitutive model is proposed to describe the rheological characteristics of multilayered saturated porous rock. The general incomplete thermal contact model is established to predict the interfacial thermal contact resistance of multilayered saturated porous rock. Based on the coupled thermo‐hydro‐mechanical theory, the semi‐analytical solutions of the excess pore water pressure, temperature increment and displacement are obtained by using the Laplace transform method. The accuracy of the present solutions is verified by comparing with the classic elastic and viscoelastic models, and existing solutions. In addition, the influence of fractional order parameter, material parameter ratio, thermal contact transfer coefficient and thermal partition coefficient on the excess pore water pressure, temperature increment and displacement of multilayered saturated porous rock are investigated.

Alpine Viticulture and Climate Change: Environmental Resources and Limitations for Grapevine Ripening in Valtellina, Italy.

The effects of the spatial and temporal variability of environmental factors on viticulture are particularly important in mountainous wine regions due to their complex geomorphology. A typical example is Valtellina, an Italian valley in the middle of the Alpine chain known for its wine production. The aim of this work was to assess the effects of the current climatic conditions on Alpine viticultural production by evaluating the relationship between sugar accumulation, acid degradation, and environmental factors. To achieve this objective, a 21-year time series of ripening curves from 15 vineyards (cv Nebbiolo) along the Valtellina wine-growing belt was collected. The ripening curves were then analysed in conjunction with meteorological data to assess the influence of geographical and climatic characteristics, as well as other limiting environmental factors, on grape ripening. Valtellina is currently characterised by a stable warm phase, with yearly precipitation slightly higher than in the past. In this context, the timing of ripening and the level of total acidity are correlated with altitude, temperature, and summer thermal excess. Precipitation shows good correlations with all the maturity indices, so higher precipitation leads to late ripening and higher total acidity. Considering the oenological goal of local wineries, the results suggest that the Alpine area of Valtellina is currently facing favourable environmental conditions, with early development and increased levels of sugar while maintaining good levels of acidity.

High temperature, COVID-19, and mortality excess in the 2022 summer: a cohort study on data from Italian surveillances

We aimed to assess whether the effect of high temperature on mortality differed in COVID-19 survivors and naive. We used data from the summer mortality and COVID-19 surveillances. We found 3.8 % excess risk in 2022 summer, compared to 2015–2019, while 20 % in the last fortnight of July, the period with the highest temperature. The increase in mortality rates during the second fortnight of July was higher among naïve compared to COVID-19 survivors. The time series analysis confirmed the association between temperatures and mortality in naïve people, showing an 8 % excess (95%CI 2 to 13) for a one-degree increase of Thom Discomfort Index while in COVID-19 survivors the effect was almost null with −1 % (95%CI −9 to 9). Our results suggest that the high fatality rate of COVID-19 in fragile people has decreased the proportion of susceptible people who can be affected by the extremely high temperature.

Imaging system aberrations through optical windows with nonuniform laser heating.

An optical window is a critical component of an imaging system. When operating in harsh environments with extreme heating, nonuniform temperature changes occur throughout the window and cause nonuniform refractive index changes and mechanical deformations due to thermal expansion, which can degrade the imaging system's performance. In this paper, we present results collected from an experimental setup developed to characterize these aberrations. This setup includes a C O 2 laser for sample heating, an infrared camera for measuring front and back surface temperatures, and a visible imaging system and a wavefront sensor for measuring degradations of a collimated beam from a point source transmitted through the heated window. Sapphire samples are laser heated with a Gaussian profile to temperatures in excess of 500K with surface temperature gradients in excess of 15K/mm. These measurements are compared with first principles models, which show quantitative agreement for window temperatures and qualitative agreement with the transmitted wavefront and imaged point source.

Impact of Adsorption Swelling and Slippage Effects on Changes in Coal’s Permeability at Different Temperatures

As a critical parameter, coal’s permeability influences the coalbed’s methane (CBM) production efficiency, which, in turn, is affected by a slippage effect, adsorption swelling, and effective stress in the CBM exploitation process. In this paper, an isothermal adsorption experiment under various temperatures, including seepage tests comprising CH4 and He in coal at different temperatures under constant effective stress, was carried out separately. We established a modified Shi&Duruca (S&D) model that considered constant effective stress and a modified adsorption model, in which the effect of excess adsorption capacity and temperature was considered. The results revealed that swelling deformation occurred when coal adsorbed CH4, which would result in the permeability of CH4 being lower than that of He under similar conditions. With an increase in pore pressure, coal’s permeability decreased gradually under the combined effects of slippage and adsorption swelling. Temperature is an important factor that affects the movement and storage of gas. Any change in temperature and pore pressure would result in coal’s permeability being comprehensively affected by thermal expansion, thermal cracking, and adsorption swelling, including the effects of slippage. Thermal expansion and thermal cracking increase coal’s permeability under low pressure and decrease coal’s permeability under high pressure. The modified adsorption model and permeability model could better characterize the adsorption and permeability properties of coal. The calculation results illustrated that the slippage effect and adsorption swelling are two important factors affecting permeability, with its permeability increment sharing a similar change trend with changes in permeability. Under the condition of low pressure, the adsorption swelling effect was dominant, and the contributary rate of the slippage effect on permeability would increase, obviously, with an increase in temperature.

Concretionary cementation of a Scottish Middle Jurassic sandstone by hot, Paleocene fluids: a clumped isotope study

This study focuses on new clumped isotope data from concretionary calcite cements in the Middle Jurassic Valtos Sandstone Formation (Great Estuarine Group) of the Inner Hebrides. Clumped isotopes show that concretion cementation began at 45 ± 6°C increasing to temperatures in excess of 70°C before cooling slightly to 57 ± 7°C at the concretion margin. In the early stages of cementation, calculated δ 18 O FLUID values were c. −12‰ VSMOW, identical to an estimate of Paleocene Hebridean meteoric water based on hydrothermal reactions close to Paleocene igneous centres. These δ 18 O FLUID values imply that concretion cementation started in the Paleocene probably during the earliest stages of phreato-magmatic effusive igneous activity. As the concretion grew, temperature changes were accompanied by progressively evolving δ 18 O FLUID compositions up to +2.1 ± 1.1‰ VMOW. These evolving δ 18 O FLUID compositions were caused by isotope exchange reactions between 18 O-rich lithologies and hot basinal fluids migrating upward along faults. This fluid flow was driven by progressive crustal loading from the thickening Paleocene lava pile, which also caused sandstone compaction. Published radiometric dates that constrain the emplacement time of the Skye Lava Group, and its subsequent rapid erosion, suggest that concretion formation and final compaction was completed in no more than 2.6 myr, far more rapidly than modelled previously. Initial concretion growth that predates development of volcanic topography shows that the strongly negative compositions of Hebridean Paleocene meteoric water are mainly of latitudinal rather than orographic origin. Supplementary material: Clumped isotope data correction and uncertainties, sample details and additional figures are available at https://doi.org/10.6084/m9.figshare.c.6459860

NO-chemistry during methanol combustion from rich to lean conditions—exploring the fuel property influence mechanisms on different NO pathways

Methanol is a favorable hydrogen-based energy storage media, and fire methanol in industrial boiler and furnace can achieve renewable and carbon-free energy supplies in industrial heating field. Knowledges about NO formation during methanol combustion are very limited, and in particular that under furnace combustion condition with excess oxygen and high temperature (up to 1500 °C) was lacked. This paper examined NO generation of methanol under broader operation range. By comparing its behavior with the well-studied methane, the NO-chemistry dependence on methanol fuel property was analyzed. Results showed the fuel property of methanol has opposite influence on NO generation between rich and lean combustion. During lean combustion, the O atom concentration was greatly increased to promote the conversion of N2 to NO via N2+O↔N+NO under high temperature. This fuel-related mechanism makes NO generation being independent on residence time but closely correlated to fuel concentration. This proposed O enhanced mechanism also explains some previous observations that the contribution from NNH and N2O pathway is larger for methanol than methane at lean condition. Under fuel rich combustion, however, methanol generates NO mainly via prompt pathway, sharing the similar mechanism to methane but with much reduced level due to the decreased CHi concentration.

Study on the maximum excess temperature and temperature distribution under the influence of lateral smoke exhaust in tunnel fires

This paper numerically investigates the temperature characteristics of tunnel fire under the ceiling with the effect of lateral smoke exhaust. In the past, analyses of maximum excess temperature under the ceiling and temperature distribution with extraction flows have been conducted. However, the lateral exhaust has a different impact on temperature than the ceiling exhaust. Consequently, several simulations were run in a tunnel (60m long, 9m wide, and 6m high). The lateral exhaust velocity is set by 0 – 10 m/s with a fire heat release rate of 5 – 20 MW. The temperature beneath the tunnel ceiling is measured by 9 rows of thermocouples. The results show that there is a linear relationship between the maximum excess temperature and the lateral exhaust velocity. The longitudinal temperature distributions at different transverse positions are distinct because of the lateral smoke exhaust especially when the hot smoke passes by the vent. The transverse temperature difference expands with the lateral exhaust velocity increases and the heat release rate decreases. Several modified models are proposed to provide references for predicting the temperature characteristics of tunnel fires with lateral smoke exhaust.

An Empirical Performance Assessment of Infrared Thermography for Real-time Monitoring of Electrical Systems in the Coco Fibre Industry

The quality of the electrical network, which includes MV panels, DBs, MCBs, sub-circuits with fuse units, and electrical motors for machine tools, determines production in any sector. Most drive systems employ inductionmotors. System temperature indicates health. Excess temperature is rarely detected due to breakdown. This case study presents real-time data for a leading coir industry from each electrical circuit and motor in several machine tools. Every section is thermographed and compared to the allowed temperature range. Thermographic analysis is non-contact and uses fewer meters and instruments. A harmonic analyzer measures THD using data from the full testing period. Modern energy audits save 10–15% on energy. Suggestions include modest restructuring of electrical network load distribution, little investment in capacitor banks in each section of induction motors, and thorough analysis and corrective measures based on customer needs.