Temperatures In Excess Research Articles

Predictive Maintenance of Machinery with Rotating Parts Using Convolutional Neural Networks

All kinds of vessels consist of dozens of complex machineries with rotating parts and electric motors that operate continuously in harsh environments with excess temperature, humidity, vibration, fatigue, and load. A breakdown or malfunction in one of these machineries can significantly impact a vessel’s operation and safety and, consequently, the safety of the crew and the environment. To maintain operational efficiency and seaworthiness, the shipping industry invests substantial resources in preventive maintenance and repairs. This study presents the economic and technical benefits of predictive maintenance over traditional preventive maintenance and repair by replacement approaches in the maritime domain. By leveraging modern technology and artificial intelligence, we can analyze the operating conditions of machinery by obtaining measurements either from sensors permanently installed on the machinery or by utilizing portable measuring instruments. This facilitates the early identification of potential damage, thereby enabling efficient strategizing for future maintenance and repair endeavors. In this paper, we propose and develop a convolutional neural network that is fed with raw vibration measurements acquired in a laboratory environment from the ball bearings of a motor. Then, we investigate whether the proposed network can accurately detect the functional state of ball bearings and categorize any possible failures present, contributing to improved maintenance practices in the shipping industry.

Hot-Electron Microwave Noise and Energy Relaxation in (Be)MgZnO/ZnO Heterostructures

Pulsed hot-electron microwave noise measurements of the (Be)MgZnO/ZnO heterostructures are presented in this work. The heterostructures of different barrier thicknesses and different bulk electron densities in ZnO layer are compared. Capacitance–voltage (C–V) measurements reveal the decrease in the two-dimensional electron gas (2DEG) peak in electron density profile at the Zn-polar BeMgZnO/ZnO interface as the BeMgZnO barrier layer thickness decreases. For thin-barrier heterostructures, the peak disappears and only the bulk electron density is resolved in C–V measurements. The excess noise temperature at ∼10 GHz in thick-barrier heterostructures is noticeably higher (∼10 times) compared to thin-barrier heterostructures, which is attributed to the strong noise source in the contacts of the former. In the case of thin-barrier heterostructures, at electric fields above ∼10 kV/cm and electron density ≳1×1017cm−3, strong noise source is resolved, which was also observed earlier in the Ga-doped ZnO films due to the formation of self-supporting high-field domains. However, for the low electron densities (≲6 ×1016 cm−3), the aforementioned noise source is not observed, which suggests the importance of a deep ZnO/GaN interface with 2DEG for power dissipation. The hot-electron temperature dependence on the dissipated power of those low-electron-density heterostructures is similar to that of O-polar ZnO/MgZnO. The estimated electron energy relaxation time in ZnO/MgZnO is ∼0.45 ps ± 0.05 ps at dissipated electrical power per electron of ∼0.1 nW/el and approaches ∼0.1 ps as the dissipated power is increased above ∼10 nW/el.

Multi-objective optimization of a pipe energy pile with heat exchanger pipes subjected to chaotic advection

Shallow geothermal energy extraction through an energy pile system relies on the constant temperature available below the earth's surface at shallow depths. The energy pile system transfers the heat stored in the earth to a place of utility for space heating and cooling through fluid circulation, thus extracting geothermal energy. In this study, a 3D energy pile model comprising a helical heat exchanger pipe (HHEP) was developed and validated with the existing experimental data using a FEM-based software package. Further, it was hypothesized that replacing HHEP with a chaotic configured helical heat exchanger pipe (CHEP) would enhance thermal performance. The numerical analyses supported the hypothesis, where there was about a 15 % increase in heat release rate for energy piles containing CHEP. The above results form a basis for exploring the simulation results through laboratory scale model tests. Thus, an experimental setup was fabricated to conduct geothermal energy tests on a scaled pipe energy pile (PEP) model. The investigation was carried out by considering three design-input parameters: flow rate, pitch, and inlet temperature at three different levels with water and ethylene glycol as heat exchanger fluid (HEF) in a 4:1 ratio. The heat release rate of the PEP (Qp), heat flux per unit length of HEP (qpl), soil excess temperature (θs), total thermal resistance (TTR), and energy consumed (EC) were analyzed. Furthermore, multi-objective optimization using the MO-Jaya algorithm and multiple attribute decision-making (MADM) R-method were used to predict an optimal set of design-input parameters. Finally, a confirmation test was conducted to test the competence of the predicted parameters. The percentage variation between the predicted design input parameters and the experimental values was below 10 %.

Extraction of the electron excess temperature in terahertz quantum cascade lasers from laser characteristics

Abstract We propose a method to extract the upper laser level’s (ULL’s) excess electronic temperature from the analysis of the maximum light output power (P max) and current dynamic range ΔJ d = (J max − J th) of terahertz quantum cascade lasers (THz QCLs). We validated this method, both through simulation and experiment, by applying it on THz QCLs supporting a clean three-level system. Detailed knowledge of electronic excess temperatures is of utmost importance in order to achieve high temperature performance of THz QCLs. Our method is simple and can be easily implemented, meaning an extraction of the excess electron temperature can be achieved without intensive experimental effort. This knowledge should pave the way toward improvement of the temperature performance of THz QCLs beyond the state-of-the-art.

Decoding the thermal history of the merging cluster Cygnus A

ABSTRACT We report on a detailed spatial and spectral analysis of the large-scale X-ray emission from the merging cluster Cygnus A. We use 2.2 Ms Chandra and 40 ks XMM–Newton archival data sets to determine the thermodynamic properties of the intracluster gas in the merger region between the two subclusters in the system. These profiles exhibit temperature enhancements that imply significant heating along the merger axis. Possible sources for this heating include the shock from the ongoing merger, past activity of the powerful AGN in the core, or a combination of both. To distinguish between these scenarios, we compare the observed X-ray properties of Cygnus A with simple, spherical cluster models. These models are constructed using azimuthally averaged density and temperature profiles determined from the undisturbed regions of the cluster and folded through marx to produce simulated Chandra observations. The thermodynamic properties in the merger region from these simulated X-ray observations were used as a baseline for comparison with the actual observations. We identify two distinct components in the temperature structure along the merger axis, a smooth, large-scale temperature excess we attribute to the ongoing merger, and a series of peaks where the temperatures are enhanced by 0.5–2.5 keV. If these peaks are attributable to the central AGN, the location, and strength of these features imply that Cygnus A has been active for the past 300 Myr injecting a total of ∼1062 erg into the merger region. This corresponds to ∼10 per cent of the energy deposited by the merger shock.

Quantifying overheating risk in English schools: A spatially coherent climate risk assessment

Climate adaptation decision making can be informed by a quantification of current and future climate risk. This is important for understanding which populations and/or infrastructures are most at risk in order to prioritise adaptation action. When assessing the risk of overheating in buildings, many studies use advanced building models to comprehensively represent the vulnerability of the building to overheating, but often use a limited representation of the meteorological (hazard) information which does not vary realistically in space. An alternative approach for quantifying risk is to use a spatial risk assessment framework which combines information about hazard, exposure and vulnerability to estimate risk in a spatially consistent way, allowing for risk to be compared across different locations. Here we present a novel application of an open-source CLIMADA-based spatial risk assessment framework to an ensemble of climate projections to assess overheating risk in ∼20,000 schools in England. In doing so, we demonstrate an approach for bringing together the advantages of open-source spatial risk assessment frameworks, data science techniques, and physics-based building models to assess climate risk in a spatially consistent way, allowing for the prioritisation of adaptation action in this vulnerable young population. Specifically, we assess the expected number of days each school overheats (internal operative temperature exceeds a high threshold) in a school-year based on three global warming levels (recent past, 2 °C and 4 °C warmer than pre-industrial). Our results indicate an increase in this risk in future warmer climates, with the relative frequency of overheating at internal temperatures in excess of 35 °C increasing more than at 26 °C. Indeed, this novel demonstration of the approach indicates that the most at-risk schools could experience up to 15 school days of internal temperature in excess of 35 °C in an average year if the climate warms to 2 °C above pre-industrial. Finally, we demonstrate how the spatial consistency in the output risk could enable the prioritisation of high risk schools for adaptation action.

Bolometric IR photoresponse based on a 3D micro-nano integrated CNT architecture.

A new 3D micro-nano integrated M-shaped carbon nanotube (CNT) architecture was designed and fabricated. It is based on vertically aligned carbon nanotube arrays composed of low-density, mainly double-walled CNTs with simple lateral external contacts to the surroundings. Standard optical lithography techniques were used to locally tailor the width of the vertical block structure. The complete sensor system, based on a broadband blackbody absorber region and a high-resistance thermistor region, can be fabricated in a single chemical vapor deposition process step. The thermistor resistance is mainly determined by the high junction resistances of the adjacent aligned CNTs. This configuration also provides low lateral thermal conductivity and a high temperature coefficient of resistance (TCR). These properties are advantageous for new bolometric sensors with high voltage responsivity and broadband absorption from the infrared (IR) to the terahertz spectrum. Preliminary performance evaluations have shown current and voltage responsivities of 2 mA/W and 30 V/W, respectively, in response to IR (980 nm) absorption for a 20 × 20 μm2 device. The device exhibits an exceptionally fast response time of ≈0.15 ms, coupled with a TCR of -0.91 %/K. These attributes underscore its high operating speed and responsivity, respectively. In particular, the device maintains excellent thermal stability and reliable operation at elevated temperatures in excess of 200 °C, extending its potential utility in challenging environmental conditions. This design allows for further device miniaturization using optical lithography techniques. Its unique properties for mass production through large-scale integration techniques make it important for real-time broadband imaging systems.

Coupling dynamic response of saturated soil with anisotropic thermal conductivity under fractional order thermoelastic theory.

In this paper, a two-dimensional (2D) thermo-hydro-mechanical dynamic (THMD) coupling analysis in the presence of a half-space medium is studied using Ezzat's fractional order generalized theory of thermoelasticity. Using normal mode analysis (NMA), the influence of the anisotropy of the thermal conduction coefficient, fractional derivatives, and frequency on the THMD response of anisotropy, fully saturated, and poroelastic subgrade is then analyzed with a time-harmonic load including mechanical load and thermal source subjected to the surface. The general relationships among the dimensionless physical variables such as the vertical displacement, excess pore water pressure, vertical stress, and temperature distribution are graphically illustrated. The NMA method does not require the integration and inverse transformation, increases the decoupling speed, and eliminates the limitation of numerical inverse transformation. The obtained results can guide the geotechnical engineering construction according to different values of load frequency, fractional order coefficient, and anisotropy of thermal conduction coefficient. This improves the subgrade stability and enriches the theoretical studies on thermo-hydro-mechanical coupling.

Modernization of an automated smoke removal control system in the silicate plant office building

The modernization of the smoke removal system in the security room of the silicate plant office building is considered. To maintain the specified excess pressure and temperature of the supply air in the security room, an air pressurization system is designed, consisting of two subsystems, one of which maintains excess pressure when the door to the security room is open, and the other when the door is closed. To select fans for the air pressurization system, the required air to ensure the maintenance of the specified excess pressure in the room is calculated. In accordance with fire safety rules, appropriate equipment for the air pressurization system is selected. Keywords safety, smoke removal, safety room, automation, automated control system, fan, fan performance, pressure, temperature

Selective Synthesis of Defect-Rich LaMnO3 by Low-Temperature Anion Cometathesis.

The synthesis of complex oxides at low temperatures brings forward aspects of chemistry not typically considered. This study focuses on perovskite LaMnO3, which is of interest for its correlated electronic behavior tied to the oxidation state and thus the spin configuration of manganese. Traditional equilibrium synthesis of these materials typically requires synthesis reaction temperatures in excess of 1000 °C, followed by subsequent annealing steps at lower temperatures and different p(O2) conditions to manipulate the oxygen content postsynthesis (e.g., LaMnO3+x). Double-ion exchange (metathesis) reactions have recently been shown to react at much lower temperatures (500-800 °C), highlighting a fundamental knowledge gap for how solids react at lower temperatures. Here, we revisit the metathesis reaction, LiMnO2 + LaOX, where X is a halide or mixture of halides, using in situ synchrotron X-ray diffraction. These experiments reveal low reaction onset temperatures (ca. 450-480 °C). The lowest reaction temperatures are achieved by a mixture of lanthanum oxyhalide precursors: 2 LiMnO2 + LaOCl + LaOBr. In all cases, the resulting products are the expected alkali halide salt and defective La1-ϵMn1-ϵO3, where ϵ = x/(3 + x). We observe a systematic variation in defect concentration, consistent with a rapid stoichiometric local equilibration of the precursors and the subsequent global thermodynamic equilibration with O2 (g), as revealed by computational thermodynamics. Together, these results reveal how the inclusion of additional elements (e.g., Li and a halide) leads to the local equilibrium, particularly at low reaction temperatures for solid-state chemistry.

(Keynote) Polyoxometallate Functionalized Membranes for Next Generation Fuel Cells, Electrolyzers and Other Devices

Using polyoxometalate moieties we are developing proton conducting membranes for proton exchange membrane fuel cells, electrolyzers and other devices that can solve the durability and environmental challenges and temperature limitations facing the state of the state-of-the-art perfluorinated sulfonic acid-based membranes. During recent work with perfluorinated membranes we have shown how to achieve stability enhancement that easily exceeds the Fuel Cell DOE accelerated stress tests (AST) for chemical stability and mechanical durability requirements for light duty vehicles. This indicates the potential of these For this perfluorinated polymer-HPA combination we obtained higher performance than the current state-of-the-art PFSAs under high humidity conditionsHPA moieties to give oxidative stability to hydrocarbon membranes as well. New membrane technology we are working on will utilize covalently bound heteropoly acids (HPA), inorganic super acids, that have both some of the highest proton conductivities when wet and have been proven to catalytically decompose oxygenated radicals that destroy existing membranes. We have already demonstrated similar membranes in fuel cells with high performance and some of the most stable long term durability ever demonstrated. In fuel cells, the materials always performed beyond state-of the-art when in humid conditions but struggled when the cells became dry, as electrolysis applications feeds water to the cell we have very high confidence that we will be able to easily exceed electrolyzer performance targets. We are improving upon this polymer chemistry and are now tailoring it specifically to electrolysis. When configured correctly within a hydrocarbon polymer membrane these HPA-hydrocarbon polymers will outperform perfluorosulfonic acid (PFSA) polymers. The correct HPA chemistry must be chosen, and we have shown that silicotungstic acid derivatives act as strong proton conducting moieties and also catalytically decompose oxygenated radicals. This will then enable hydrocarbon membranes with practical lifetimes and performance using the silicotungstic functionality. We are aiming to control the HPA channel morphology and allow for maximum proton conductivity with minimum water uptake. The engineered structures will facilitate proton conduction from ambient conditions to temperatures in excess of 120°C (the polymeric materials chosen are stable to 200°C when dry and potentially much higher when wet and pressurized), as well as achieving cost and durability targets for PEM membranes in electrolyzer applications. Our approach will also allow for development of an ionomer for optimal interfacing with the electrodes.

Numerical study on combustion characteristics of ammonia mixture under different combustion modes

Ammonia, an emerging carbon-free fuel, exhibits promising potential within the energy field. Nevertheless, it faces challenges such as unstable combustion and high NOx emissions that necessitate resolution. In this paper, numerical simulation methods are used to compare the combustion characteristics under different modes. Furthermore, the numerical research is carried out by adding ammonia gas in different combustion modes. The results indicated that regardless of the combustion mode, induction of ammonia elicits a significant surge in NOx emissions, but the combustion characteristics of different combustion modes are different. When ammonia is introduced into conventional combustion mode, ignition is significantly delayed. It is proved that the excess enthalpy combustion technology is effective in facilitating the combustion of ammonia mixtures. However, excess enthalpy combustion temperature will lead to elevate NO emissions. In contrast, MILD combustion and oxy-fuel MILD combustion technologies effectively suppress NO formation within ammonia mixtures. This is because in MILD combustion mode, the reaction rate becomes slow, which inhibits the formation of NO.

The geodynamic origin of Los Humeros volcanic field in Mexico: insights from numerical simulations

Compared to normal arc-related volcanic eruptions, the formation of a volcanic caldera is a relatively atypical event. During caldera formation a series of large volumes of magma are erupted, reducing the structural support for the rock above the magma chamber and creating a large depression at the surface called caldera. Los Humeros volcanic field (LHVF) represents one of the largest volcanic calderas in Mexico. It is located some 400 km from the trench at the eastern edge of the Trans Mexican Volcanic Belt where the depth to the Cocos slab is more than 300 km. In this study we employ high-resolution two-dimensional thermomechanical numerical simulations of magma intrusions and a horizontal tectonic strain rate to better understand the influence of crustal deformation for the formation of Los Humeros caldera. A minimum number of three thermal anomaly pulses of hydrated mantle material (with diameter of 15 km or more) and a regional strain rate of 7.927 × 10–16 s−1 are required for magma to reach the surface. Modeling results show that regional extension coupled with deep thermal anomalies (with a temperature excess of ΔT ≥ 100 °C) that come in a specific chain-type sequence produce surface deformation patterns similar to LHVF. We propose an asthenospheric sub-slab deep source (> 300 km depth) for the thermal anomalies where previous studies showed the existence of a gap or tear in the Cocos slab.

Harmonic models and molecular dynamics simulations of isomorph behavior of Lennard-Jones fluids: Excess entropy and high temperature limiting behavior

Henchman’s approximate harmonic model of liquids is extended to predict the thermodynamic behavior along lines of constant excess entropy (“isomorphs”) in the liquid and supercritical fluid regimes of the Lennard-Jones (LJ) potential phase diagram. Simple analytic expressions based on harmonic cell models of fluids are derived for the isomorph lines, one accurate version of which only requires as input parameters the average repulsive and attractive parts of the potential energy per particle at a single reference state point on the isomorph. The new harmonic cell routes for generating the isomorph lines are compared with those predicted by the literature molecular dynamics (MD) methods, the small step MD method giving typically the best agreement over a wide density and temperature range. Four routes to calculate the excess entropy in the MD simulations are compared, which includes employing Henchman’s formulation, Widom’s particle insertion method, thermodynamic integration, and parameterized LJ equations of state. The thermodynamic integration method proves to be the most computationally efficient. The excess entropy is resolved into contributions from the repulsive and attractive parts of the potential. The repulsive and attractive components of the potential energy, excess Helmholtz free energy, and excess entropy along a fluid isomorph are predicted to vary as ∼T−1/2 in the high temperature limit by an extension of classical inverse power potential perturbation theory statistical mechanics, trends that are confirmed by the MD simulations.

Rafting and redissolution of γʹ phase in Ni–Al alloy under external stress

The volume fraction and rafting degree of the γʹ-Ni3Al phase under stress and high temperature are the key characteristics of mechanical properties in Ni-based superalloys, the rafting and redissolution of γʹ phase caused by the creep at high temperature damage the morphology and properties of Ni-based superalloys. The phase-field simulation is performed to study the rafting accompany with the redissolution of γʹ phase under high temperature and loading stress in Ni–Al alloy, the driving force and kinetics evolution of the γʹ rafting were revealed. During the rafting under continuous heating, the elastic energy in the vertical γ channel is different to that of the horizontal γ channel, this difference in elastic energy drives the elements diffusion directionally to form the γʹ rafts morphology. With the increased tensile stress, the decrease of specific surface of the γʹ phase slows down the redissolution, a higher volume fraction is reserved for the rafted γʹ phase. With temperature increases, the interface of γ/γʹ phase becomes more diffusional and wider under stress. The results give an insight on the rafting mechanism of γʹ phase and the kinetics evolution in Ni-based superalloys under excess temperature.

Effect of initial generating eddy height on temperature, velocity and air entrainment of fire whirl

In this paper, we present an experimental effort to reveal the effect of the initially generated eddy height on the thermal, velocity, and air entrainment properties of the fire vortex plume. Experiments were performed by a fixed-frame facility with variable channel wall height (h), using propane as the fuel (20 cm in burner exit diameter, 50.0–100.0 kW in heat release rate). Results show that the growth rates of centerline excess temperature and axial velocity tend to increase with h in the continuous flame below h. It is found that the radial distribution of excess temperature is always of hump-type and little affected by h at lower levels, while the radial profile of axial velocity changes from the plateau-type into the hump-type as h is increased. In the upper continuous and intermittent flames, the radial profile of excess temperature evolves from the hump type into the unimodal type, and that of axial velocity develops into the unimodal type from the plateau type as h is increased. The growth rates of excess temperature radius and axial velocity radius with the normalized height decrease with h for the continuous and intermittent flames. The axial position corresponding to the significant increase in the growth rate moves upstream with the increase of the heat release rate (Q˙). Under small h, the tangential velocity within the vortex core decreases with height, suggesting that the rotational strength becomes weakened. It is found that the air entrainment is weak at the flame bottom within the initial generating eddy height, and the entrained air is insufficient for complete combustion. The axial mass flow rate increases obviously as the channel wall disappears. With the increase of h, turbulence suppression is enhanced, and its role in flame elongation becomes more significant. The reduction of flame height is probably attributed to the greater turbulent mixing length under lower initial generating eddy height.

A proximal sensing cart and custom cooling box for improved hyperspectral sensing in a desert environment

BackgroundAdvancements in field spectrometry have the potential to increase understanding of crop growth and development in response to hot and dry environments. However, as with any instrument used for scientific advancement, it is important to continue developing and optimizing data collection protocols to promote efficiency, safety, and data quality. The goal of this study was to develop a novel data collection method, involving a proximal sensing cart with onboard cooling equipment, to improve deployments of a field spectroradiometer in a hot and dry environment. Advantages and disadvantages of the new method were compared with the traditional backpack approach and other approaches reported in literature.ResultsThe novel method prevented the spectroradiometer from overheating and nearly eliminated the need to halt data collection for battery changes. It also enabled data collection from a significantly larger field area and from more field plots as compared to the traditional backpack method. Use of a custom cooling box to stabilize operating temperatures for the field spectroradiometer also improved stability of white panel data both within and among collections despite outside air temperatures in excess of 30°C.ConclusionsAs compared to traditional data collection approaches for measuring spectral reflectance of field crops in a hot and dry environment, use of a proximal sensing cart with a customized equipment cooling box improved spectroradiometer performance, increased practicality of equipment transport, and reduced operator safety concerns.

Perancangan Alat Pengering Pada Proses Produksi Kapsul Daun Kelor bagi Kelompok Tani Desa Guntung Manggis

Guntung Manggis Village is one of the sub-districts located in Landasan Ulin District, Banjarbaru City, South Kalimantan Province. Some of the problems in the Guntung Mangosteen subdistrict that were obtained based on the survey results were that the drying process for making moringa leaf capsules was quite time consuming because they could not be dried directly in the sun. And the hygienic and clean drying process for Moringa leaves meets health standards. The method for solving this problem is to design and manufacture a hygienic Moringa leaf dryer. To perfect the manufacture of a Moringa leaf dryer, it is necessary to carry out a simulation first. The simulation results show that a dryer that uses 15 Watt lamp power has a better heating process because the entire heating area is a homogeneous blue color so that the drying process will take place evenly. This drying process is the best where there is no excess temperature at the base of the tool so it does not require a blower to remove heat. The dryer is more efficient because the lamp power is small and does not require a blower to homogenize the temperature of the dryer.

Investigation of using BSPT for ring-dot piezoelectric transformers for use in high-temperature resonant power supplies

SiC and GaN devices are gaining in popularity in both research and commercial applications. One of the many benefits of these devices is the possibility of power converter operation at temperatures in excess of that possible with Si-based devices (>200°C). A bismuth scandium lead titanate (BSPT) piezoelectric transformer is analysed for use in high temperature (up to 250°C), resonant converters using impedance spectroscopy and power converter measurements. The PT shows declining losses with temperatures during testing, translating into an improvement of 15% points in efficiency whilst more than doubling the output power across the temperature range. A peak performance of 0.7W output power and 53% efficiency at 225°C was achieved, giving comparable performance to previous work but at higher temperatures.

Effects of one-sided thermal shock and hold on alumina-based oxide/oxide ceramic matrix composites for temperatures in excess of 1200 °C

Nextel™720/alumina based ceramic matrix composite plates were subjected to one-sided thermal shock and 30-minute hold at 1100 °C, 1250 °C, 1400 °C and 1550 °C. Post exposure, the plates were evaluated for physical, structural, and microstructural changes using state-of-the art characterization techniques as well as standard mechanical testing procedures. Physically, no significant mass or dimensional changes were noted, while the surface roughness decreased on the exposed side for all the cases. Structurally, both the tensile and flexural strengths decreased for the 1550 °C case, but not for the other temperatures. In addition, short-beam strength tests showed no effect on interlaminar strength as a result of the elevated temperature exposures for the 30-minute duration considered. Microstructurally, SEM/EDS evaluations showed no significant change in the microstructure or element composition on the exposed and back sides. However, mercury intrusion porosity measurements did show a change in pore size distribution due to the combined effect of matrix shrinkage and further matrix microcracking. Combined results show that the operational limit of the composite can be pushed significantly beyond 1200 °C for shorter (in minutes) durations provided it is structurally viable for the application sought.