Fall In Temperature Research Articles

Morphometric characteristics of glacial cirques and former glaciers in the Geyik Mountains, Western Taurus, Türkiye

Using the Glacier reconstruction (GlaRe) toolbox, reconstructions of former glaciers in the Geyik Mountains, part of the Taurus Mountain system in southern Türkiye, show that an area of 132.5 km2 was glaciated in the last major glaciation, which left clear terminal and hummocky moraines. Glaciers were 1.4 to 12 km long and those from 49 cirques merged to form a broad 75 km2 piedmont glacier in the Namaras Valley, up to 400 m thick. A thorough analysis of morphometry of the 98 Geyik cirques, using the revised Automated Cirque Metric Extraction version 2 (ACME2) toolbox, shows that they are relatively small, with limited widths: the median length/width ratio of 1.29 is unusually high. With size, length and width increase faster than depth, demonstrating strong static allometry. Maximum slope averages 59°, minimum 3.3° and axial 25°. A combination of low hypsometric integral, high axial profile closure and high axial height-length integral is proposed as a measure of cirque development.The main summits are on sharp ridges on cirque crests, showing that they have been lowered by glacial erosion (by cirque development). Glaciation was strongly asymmetric, with cirque vector mean aspect between northeast and north-northeast. This shows the dominance of solar radiation effects, with some modification from westerly winds. Glacier palaeo- Equilibrium Line Altitudes (pELAs) rise northeastwards and cirque floor minimum altitudes (CFAs) rise toward east-northeast, both showing the importance of moist air from the Mediterranean, 38–55 km to the southwest. pELA averages 2208 m above sea level (a.s.l.) (2277 m area-weighted); CFA averages 2234 m. CFA varies mainly with summit altitudes; where related palaeoglaciers are short CFA is somewhat below pELA, but for longer ones it is above. The most likely palaeoclimate to form these glaciers involves a precipitation increase of 53–72 % with a temperature fall of 8 °C compared with present-day. The cirques formed under similar or less severe conditions.

Distribution of microvascular endothelial function in different clinical and non-clinical settings in the united states and china

Abstract Background Despite the fact that microvascular (endothelial) dysfunction is associated with various diseases from cardiovascular to kidney, lung, liver, and other medical conditions, it has not been extensively studied in various clinical and non-clinical settings as blood pressure has. Digital Thermal Flowmetry (DTF) of microvascular endothelial function is a new and automated technique based on monitoring fingertip temperature fall and rebound during reactive hyperemia. Here we report distributions of microvascular function across (1) CVD patients, (2) wellness and internal medicine clinics, (3) college students, and (4) community-based healthy volunteers in China. Methods A total of 7,907 endothelial function test results were collected from various settings. Blood pressure and heart rate were measured before the tests. The tests were conducted using FDA-approved automated VENDYS devices (Endothelix Inc., Palo Alto, CA). Adjusted maximum temperature rebound was reported as Vascular Reactivity Index (VRI) and compared across different settings. Results VRI in CVD patients, wellness and internal medicine clinics, college students, and Chinese volunteers were (1.25±0.34) (1.53±0.5) (1.86±0.5) (1.95±0.44.) respectively P<0.01. Age was weakly correlated with VRI with the equation age=-0.01 VRI+2.01 (r=0.17 p<0.001) Conclusions To our knowledge, this is the largest database of finger-based endothelial function testing. VRI showed distinct distributions across various clinical and non-clinical settings with CVD patients exhibiting the lowest and Chinese healthy volunteers the highest values. The VRI trend mimics the statistically expected risk trend with CVD patients having the highest and Chinese healthy volunteers having the lowest CVD events risk.Figure 1.

Middle to late Miocene cooling and drying in the northern Tibetan Plateau based on evidence from plant-insect interactions

The Qaidam Basin in the northern Tibetan Plateau is currently arid, but may have had a semi-humid to semi-arid climate in Miocene times, as suggested by pollen and isotopic data; however, the lack of macroscopic fossils hinders more precise paleoclimatic calibration. In this paper, we report fossil leaves with insect damage from a late Miocene layer (HT-5) in the Huaitoutala section dated ∼11.4 Ma, and compare them with records from a middle Miocene layer (HT-1) dated ∼12.7 Ma. Results show that damage diversity dropped from 36 types in HT-1 to 24 types in HT-5, suggesting a fall in mean annual temperature. Damage frequency decreased from 70 % in HT-1 to 32 % in HT-5, pointing to a drop in the coldest month temperature. Moreover, a slight fall in the diversity of mining damage, from 5 types in HT-1 to 4 types in HT-5, suggests a shift towards a slightly more arid climate from the middle to late Miocene. The flora from HT-5 is composed mainly of Betulaceae, Populus, Ulmus, and shrubs. Based on the distribution of these taxa in modern vegetation, the climate was probably semi-humid, not entirely arid during the late Miocene. These results are corroborated by fossil mammal data from the same section. Therefore, despite a cooling and drying trend from the middle to late Miocene, the climate of the Qaidam Basin was not as extremely arid as today.

Comparative Analysis of Aerosol Direct Radiative Forcing During COVID-19 Lockdown Period in Peninsular India

AbstractThe load of aerosols in the atmosphere has been increasing gradually due to industrialization and urbanization. This increase has contributed to change in the Earth’s radiation budget through the absorption or scattering of radiation. The aerosol direct radiative forcing (ADRF) is a measurement utilized to comprehend the impact of cooling or warming up of the atmosphere directly by aerosols. Our study examined the impact of aerosols during the COVID-19 pandemic by comparing them to the average from the preceding 5-year period (2015–2019) in peninsular India. The measure of aerosols deployed in this study is the Aerosol Optical Depth (AOD), and the study was carried out on three distinct time frames: prior to lockdown, during lockdown, and post lockdown. The study revealed that the ADRF increased during all the three time frames of 2020 compared to the average of 2015–2019, and the other time scales experienced an increase in ADRF as well. The most notable rise in ADRF and decrease in temperature occurred in the tropical savanna and warm semi-arid climate regions during the pre-lockdown period. During lockdown, the increase in ADRF was seen throughout the study area, and a decrease in temperature was observed only in the tropical monsoon region. In the post-lockdown period, the decline in ADRF was accompanied by a fall in temperature in the tropical savanna region. This study provides insights into the effect of aerosols on ADRF in peninsular India and highlights the importance of monitoring and regulating aerosol emissions to mitigate the changes in temperature.

High thermal tolerance of egg clutches and potential adaptive capacity in green turtles

Climate warming threatens sea turtles, among other effects, because high temperatures increase embryo mortality. However, not all species and populations are expected to respond the same way because they could have different thermal tolerances and capacities to adapt. We tested the effect of incubation temperature on egg mortality in a population of green turtles (Chelonia mydas) previously suggested to be less affected by extreme climatic events than others. We (1) assessed the relationship between temperature and hatching success, (2) defined an optimal range of temperatures that maximized hatching success and (3) assessed the variability in the response to temperature among clutches laid by different mothers, which could allow adaptation. Hatching success was consistently high in green turtle clutches with a skew toward high values, with 50 % of clutches having a success above 94 %. Yet, it was mildly affected by temperature, declining at both low and high temperatures. The optimal range of mean incubation temperatures was between ~30.5 °C and 32.5 °C. Current mean temperatures (31.3 °C) fall within the middle of the optimal range, indicating a potential resilience to further rises in mean nest temperature. Hatching success was best described by nest temperature and the interaction between female identity and temperature. This last predictor indicated a variability in thermal tolerance among clutches laid by different mothers and therefore, a capacity to adapt. The studied population of green turtles seems to be less vulnerable than others to climate warming. Understanding how different populations could respond to increasing temperatures could help complete the picture on the potential effects of climate change on sea turtles.

Development and engineering application of fiber bragg grating intelligent cable in large-span hyperbolic parabolic spatial cable network

In order to accurately control the prestress force of cables in long-span cable net structures, a new type of fiber Bragg grating (FBG) intelligent cable was developed. The FBG sensor was directly encapsulated inside the cable, and the sensing performance of the intelligent cable was verified by the cyclic tensile tests. The results show that the sensitivity coefficients of FBG monitoring are basically consistent, and the linearity deviation of the fiber Bragg grating is less than 4.67 %. Based on a real project Shunde Desheng Sports Center, a 114 m long-span saddle-shaped cable net structure model was established using finite element analysis, and the distribution and correlation of internal forces of cables in different tension stages were calculated and compared with the actual monitoring results of intelligent cables. The analysis results indicate that the force changes of intelligent cables is basically consistent with the value of finite element simulation. According to the data of long-term intelligent cable monitoring, the change of cable force caused by the temperature deformation of the steel ring beam is much greater than the influence of the temperature rise and fall of the cable itself on the cable force. Intelligent cables can provide a reference for cable force monitoring of long-span cable net structures.

Physiological Responses to Acute Heat Stress in Rohu, Labeo rohita: Insights from Liver Proteomics.

Heat stress is a major problem in aquaculture species, causing changes in physiology such as decreased feed intake, growth rate, reproduction, and internal cellular damage, thereby affecting fish's health. The effects of an acute heat stress simulating a daily rise and fall in temperature on summer days were evaluated in the liver proteome of rohu (Labeo rohita) fingerlings in the present study. The fish maintained at 30°C were gradually exposed to a higher temperature of 36°C at an increment rate of 1°C per 1.5h, and after 3h at that temperature, it was gradually reduced to 30°C. The liver tissue samples were collected at 5 am, 5pm, and 5 am the next day from the exposed and control fish. Protein samples were prepared from the liver tissues, and the extracted proteins were compared using 2-dimensional (2D) gel electrophoresis (2DGE) and mass spectrometry (MS) using a MALDI-TOF/TOF mass spectrometer. A total of 44 differentially expressed protein spots were visualized in 2D gel analysis from heat stress exposed fish at three time points, out of which 21 proteins including one hypothetical protein could be identified by MS. The abundance of five selected differentially expressed proteins (DEPs) was validated using qPCR. The majority of DEPs were found to be involved primarily in lipid, protein and energy metabolism, immune system regulation, cytoskeletal stability, and ROS management. The findings of this study would help in the development of strategies to mitigate heat stress in L. rohita.

PCR virtual temperature sensor design based on system modeling and identification

The reaction results of Polymerase chain reaction (PCR) are highly sensitive to temperature accuracy, but the reaction liquid temperature is hard to be measured directly. In this paper, a virtual temperature sensor is creatively designed to directly obtain the reaction liquid temperature using a model-switching approach. This study first establishes the mathematical models of the temperature control system and obtains precise system models for the heating and cooling stages. Based on this, a virtual sensor is constructed, and a closed-loop fuzzy PID control system is established. Furthermore, the accuracy of the designed virtual temperature sensor is verified through simulation and experimentation. Simulation results show that the fuzzy PID control method has higher temperature accuracy, with a deviation of 0.23 °C, making it more suitable for Peltier systems, as Peltier systems suffer from inconsistent temperature rise and fall models. The experimental results show that the control method using the virtual sensor achieves higher precision in liquid temperature control, with an accuracy of ±0.21 °C. Finally, standard PCR procedures are performed for designed chip, and the results indicate that the temperature sensor and control system designed in this study exhibit significantly higher amplification efficiency, approximately 16 times greater than traditional control methods.

Effect and mechanism of phase change lightweight aggregate on temperature control and crack resistance in high-strength mass concrete

Under temperature stress, high-strength mass concrete is brittle due to its high total heat of hydration. In this study, a control mixture of C55 high-strength mass concrete meeting the performance requirements was prepared. The effects of different functional aggregates on the thermal properties, such as setting and hardening rate, peak temperature, and temperature rise and fall rate in the early stage of cement hydration, as well as the effects of functional lightweight aggregates on the workability, mechanical properties, and deformation properties of concrete, were investigated in this paper using two types of aggregates with thermal insulation and phase change energy storage functions. The study shows that, in addition to having some early strength impacts and temperature management capabilities, thermal storage coarse lightweight aggregate (PCCLA) and thermal insulation fine lightweight aggregate (TIFLA) can both increase the workability and crack resistance of concrete. When it comes to temperature regulation, thermal storage coarse aggregate outperforms thermal insulation functional aggregate significantly. Thermal insulation fine aggregate can improve the rate of setting and hardening, while coarse thermal storage aggregate may work as in-situ self-heating curing in the early stages due to its phase change energy storage. This quickens the rate of setting and hardening and increases the resistivity of the set period, which in turn increases the rate of drying shrinkage.

Implementation of Rapid Nucleic Acid Amplification Based on the Super Large Thermoelectric Cooler Rapid Temperature Rise and Fall Heating Module.

In the rapid development of molecular biology, nucleic acid amplification detection technology has received more and more attention. The traditional polymerase chain reaction (PCR) instrument has poor refrigeration performance during its transition from a high temperature to a low temperature in the temperature cycle, resulting in a longer PCR amplification cycle. Peltier element equipped with both heating and cooling functions was used, while the robust adaptive fuzzy proportional integral derivative (PID) algorithm was also utilized as the fundamental temperature control mechanism. The heating and cooling functions were switched through the state machine mode, and the PCR temperature control module was designed to achieve rapid temperature change. Cycle temperature test results showed that the fuzzy PID control algorithm was used to accurately control the temperature and achieve rapid temperature rise and fall (average rising speed = 11 °C/s, average falling speed = 8 °C/s) while preventing temperature overcharging, maintaining temperature stability, and achieving ultra-fast PCR amplification processes (45 temperature cycle time < 19 min). The quantitative results show that different amounts of fluorescence signals can be observed according to the different concentrations of added viral particles, and an analytical detection limit (LoD) as low as 10 copies per μL can be achieved with no false positive in the negative control. The results show that the TEC amplification of nucleic acid has a high detection rate, sensitivity, and stability. This study intended to solve the problem where the existing thermal cycle temperature control technology finds it difficult to meet various new development requirements, such as the rapid, efficient, and miniaturization of PCR.

Chorological abductive inferring: case studies of tracing spatial dissemination of COVID-19

Abstract COVID-19 did not disappear in the third year (2022) of the global pandemic. On the contrary, the number of infected people several times exceeded the highs of previous years, but the greater morbidity was not accompanied by a relatively comparable number of deaths. Some studies showed that the SARS-CoV-2 virus impact, e.g. in CEE EU countries, characterizes the seasonal intensity as temperatures fall or rise in relative humidity. All researchers agree that the number of COVID-19-infected people is only an estimate based on the volume of tests performed and that the true numbers are usually much higher. The implementation of spatial interaction modeling could potentially aid in the control of the COVID-19 pandemic due to the inherently spatial nature of its diffusion. The gravity models used in this investigation to simulate the regional spread of the COVID-19 epidemic are based methodologically on previous empirical studies. The proposed methodology uses techniques for modeling spatial interactions due to the epidemics described above, which are a direct result of the number of contacts between individuals. The COVID-19 pandemic can be studied regionally using spatial diffusion methods as well as population potential models (spatial interaction models) and visualized using geographic information system software. Empirical verification and geovisualizations are based on available recent population and pandemic statistics that are possible to acquire from national health services. Methodologically, this type of modeling and simulation aimed at reconstructing a factual situation can be defined as abductive chorological inferring.

Little evidence of hysteresis in regional precipitation, when indexed by global temperature rise and fall in an overshoot climate simulation

Abstract Society has set the aim of stabilising climate at key temperature thresholds, such as global warming at or below 1.5°C or 2.0°C above preindustrial levels. However, greenhouse gas emissions are failing to decline, and if they continue on their current trajectory it is likely that such thresholds will be crossed in the decades ahead. Because of this risk, there is an emerging focus on overshoot, where, for a temporary period, global warming is allowed to cross critical thresholds to reach a peak value before decreasing to the desired limit. A key question about overshoots is whether there are hysteresis effects—that is, whether global or regional climate has properties that differ between the phase of global warming increase and the phase of decreasing. Here, we analyse temperature and precipitation data from five Earth System Models (ESMs) forced by the SSP5-3.4-OS CMIP6 overshoot scenario. We look at the level of precipitation during two periods of near-identical global warming: one whilst temperatures are rising, and the other when they are falling. For global means, we find a statistically significant difference between precipitation values during the two periods. This is an example of hysteresis, as the reversion to an earlier global warming state results in a level of global rainfall which is different from that observed when warming was increasing. Spatial disaggregation of rainfall differences between the two near-identical warming levels shows the largest differences in the tropical region, which are statistically significant for four of the five ESMs. When considering much smaller regions, including parts of the tropics, there remains some evidence of hysteresis. However, the differences are no longer statistically significant against a background of substantial interannual rainfall variability. We discuss the implications of our findings for climate impacts assesments.&amp;#xD;

Bio-based composite phase change material utilizing wood fiber and coconut oil for thermal management in building envelopes

Bio-based materials are attracting substantial attention for their eco-friendly attributes within the construction field, where they facilitate energy saving and emissions reduction. However, the performance of it, such as thermal properties, needs to be improved. Fully utilizing bio-based materials, we developed a novel composite phase change material (PCM), A-WF/CO/h-BN, with high thermal storage properties designed for application in building envelopes. It incorporates coconut oil (CO) as the PCM featuring an optimal phase change temperature. Hexagonal boron nitride (h-BN) was chosen to enhance the thermal conductivity. Acetylated wood fiber (A-WF) was employed as the supporting material. The prepared A-WF/CO/h-BN sample exhibits excellent and rapid heat storage and exothermic capabilities. In the experiment of thermal performance evaluation, the cold end of the A-WF/CO/h-BN sample is cooler than that of the A-WF when both hot ends are heated. Results indicate that the proposed A-WF/CO/h-BN sample can effectively delay the heat transfer and inhibit the temperature rise and fall. For these superior properties, when the A-WF/CO/h-BN sample is applied in building envelopes, it can minimize the heat transfer from the envelope to the interior and inhibit indoor temperature fluctuation. Thus, it can reduce building energy consumption and carbon emissions while achieving indoor thermal comfort.

Mechanical property and frost resistance of phase–change/NanoSiO2 concrete in a low–temperature environment

To study the effect of phase–change materials and nanomaterials as new composite materials on the mechanical properties and frost resistance of concrete, it is beneficial for low–carbon and environmentally friendly buildings to be achieved. The effects of freeze–thaw cycles and different preloading strains were considered. ICT scanning was performed, and the compression performance of composite–modified concrete (CMC) were tested. The internal pore structure and strength indicators of the CMC were analyzed during uniaxial compression. Meanwhile, by conducting uniaxial compression tests on CMC at different temperatures, changes in the mechanical properties during real–time freezing and thawing processes were obtained. The results demonstrated that the fractal dimension grows and the compressive performance of the CMC declines as the number of freeze–thaw cycles and preloading strain increases. The proportion of spheroids in the internal pore shape gradually decreases, whereas the proportions of rods, discs, and blades increases. CMC effectively delays the rise or fall of internal temperature during the freeze–thaw process and reduces its internal structural deterioration. Compared with the freeze–thaw effect, an increase in the preloading strain has a more notable impact on the compressive performance of CMC. A stress–strain constitutive model is proposed for a 10 % microencapsulated phase–change materials and a 1.5 % nanoSiO2 composite–modified concrete (10 mPCMs/1.5 NS CMC), influenced by temperature, through regression analysis. Meanwhile, under low temperatures, the degradation of mechanical properties of 10 mPCMs/1.5 NS CMC and the influence of different preloading strains are considered, leading to the development of stress–strain constitutive models for freeze–thaw cycles and different preloading conditions.

Research on tunnel vehicle fire temperature field simulation considering the latent heat of vaporization inside concrete linings

The high temperatures and non-uniform temperature fields caused by fires can lead to the rapid failure of linings, severely affecting tunnel safety. To obtain the temperature distribution of the lining under different fire conditions, simulation research is conducted by CFD technology. First, the fire resistance test of lining is simulated, and a furnace temperature simulation method based on PID control and a lining heat transfer model considering the latent heat of vaporization (LHV) are proposed. Second, the experimentally verified method is applied to a full-scale tunnel model to study the vehicle fire temperature field considering the LHV. The results show that the method based on the PID control can accurately simulate the furnace temperature. By introducing a LHV energy source, the 100 °C temperature plateau within the lining can be effectively simulated to prevent prematurely determining component failure. Compared to traditional methods, the lining-gas heat exchange boundary considering the LHV is more accurate. The temperature rise at the lining surface and rebar is slower, with maximum temperature differences of 80 K and 125 K, respectively. The aim of this research is to provide a complete temperature rise and fall process for the fire protection analysis and design of tunnel linings.

Temperature trends in the Arctic and Antarctic

This work considers global temperature trends and their prediction in the world and polar regions in particular. Global warming covered the period from the 17th till the end of 20th centuries. The mechanisms of this process remain obscure; however, it is clear that abiotic factors controlling climate make the most significant contribution. Starting from 1997, the global fall of temperature has been observed, with instability becoming the major trend. Climate depends on the interaction of abiotic (hydrosphere, lithosphere, atmosphere), biotic (biosphere), and social (noosphere) spheres of the Earth. All these spheres are characterized by a highly stable system. Human activity has no essential impact on global climatic processes. The consequences of contemporary temperature changes, which are to manifest themselves in the coming years, will not be extreme for all mankind. However, they may be of particular importance for the polar regions. The temperature in the Arctic will increase, while the climate of the Antarctic will become colder. The global average temperature will decrease and become more variable. Modern science is capable of predicting climate change. Serious climate research should be free from political and economic pressures.

Design and application of high-precision calibration blackbody for space optical remote sensing sensor

Radiation calibration is a crucial step in producing high-quality images for spaceborne infrared cameras. Blackbody radiation sources, as the standard equipment for infrared thermometers, play an increasingly important role in radiation calibration. But as the camera aperture increases, blackbody faces challenges such as poor temperature uniformity, slow heating and cooling rates, large mass, and large volume. This article proposes a design scheme for spaceborne calibration blackbody based on a combination of rope pull fixation and limit block positioning. The temperature uniformity, temperature stability, temperature rise and fall rate, thermal stress characteristics, and anti-emission vibration characteristics of the blackbody under this scheme are analyzed and optimized in detail. The analysis results show that the conduction thermal resistance between the blackbody and the environment is nearly two orders of magnitude higher than that of the conventional scheme. The blackbody has excellent temperature uniformity, temperature stability, wide calibration temperature range, light weight, small volume, and fast temperature rise and fall speed. The blackbody scheme with a thickness of only 1.5 mm was implemented and applied on orbit.

Anti-UV Passive Radiative Cooling Chiral Nematic Liquid Crystal Films for Thermal Management.

Passive radiative cooling (PRC) can spontaneously dissipate heat to outer space through atmospheric transparent windows, providing a promising path to meet sustainable development goals. However, achieving simultaneously high transparency, color-customizable, and thermal management of PRC anti ultraviolet (anti-UV) films remains a challenge. Herein, a simple strategy is proposed to utilize liquid crystalline polymer, with high mid-infrared emissive, forming customizable structural color film by molecular self-assembly and polymerization-induced pitch gradient, which guarantees the balance of transparency in visible spectrum and sunlight reflection, rendering anti-UV colored window for thermal management. By performing tests, temperature fall of 5.4 and 7.9°C are demonstrated at noon with solar intensity of 717Wm-2 and night, respectively. Vivid red-, green-, blue-structured colors, and colorless films are designed and implemented to suppress the solar input and control the effective visible light transmissivity considering the efficiency function of human vision. In addition, temperature rise of 11.1°C is achieved by applying an alternating current field on the PRC film. This study provides a new perspective on the thermal management and aesthetic functionalities of smart windows and wearables.

Study on the preparation and properties of TiO2@n-octadecane phase change microcapsules for regulating building temperature

Aiming at regulating building temperature in summer, the preparation and optimization of TiO2@n-octadecane microcapsules were studied in this paper, which is significant to energy conservation. N-octadecane and TiO2 act as the core material and shell material, respectively. The SEM, FT-IR, DSC, TGA, and infrared thermal imaging were used to analyze the TiO2@n-octadecane microcapsules. Aiming at the enthalpy of phase transition and encapsulation rate of microcapsules, the reaction vessel, emulsifier, stirring rate, amount of acetic acid, and droplet-adding rate for preparing microcapsules were optimized. Furthermore, the microcapsules with the best properties were mixed into concrete to analyze their temperature regulation performance, mechanical strength, fire resistance, thermogravimetry, and cyclic stability. The effect of microcapsule proportions on the temperature regulation ability of concrete at different temperatures was also studied. The key findings are as follows: Firstly, the TiO2@n-octadecane microcapsules exhibit a stable core–shell structure and a size of about 1 μm. The highest melting enthalpy, crystallization enthalpy, and encapsulation rate of TiO2@n-octadecane microcapsules are 120 J/g, 116 J/g, and 54.1 %, respectively. The microcapsules only consist of TiO2 and n-octadecane without any chemical reactions. Secondly, the concrete incorporating the TiO2@n-octadecane microcapsules shows a faster phase change reaction, inhibiting temperature rise or fall effectively, and preventing leakage. Thirdly, compared with ordinary concrete, 5 mm concrete with 20 % TiO2@n-octadecane microcapsules can extend its temperature below 28.5 °C for 15.7, 14.0, and 7.6 min at 30 °C, 35 °C, and 40 °C, respectively. Finally, the compressive strength of concrete with 0 %∼20 % MPCMs satisfies the requirements for concrete applications. It also has excellent fire resistance and thermal stability. Moreover, incorporating MPCMs into concrete can significantly reduce the pyrolysis of MPCMs.

Combined use of mullite and basalt fiber to inhibit the strength decline of oil well cement stone under alternating conditions of temperature rise and fall

During the development process of heavy oil with steam huff and puff, the wellbore undergoes alternating conditions of temperature rise and fall, leading to a significant decline in the strength of the cement sheath. This work studied the inhibition effect and mechanism of the composite material composed of mullite and basalt fiber on the strength decline of cement stone (the hardened body of cement slurry) under simulated wellbore temperature alternating conditions from 80 °C to 260 °C. The pore structure distribution of cement stone was investigated by mercury intrusion porosimetry (MIP), the microstructure and phase composition of cement stone was characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), together with quantitative X-ray diffraction (XRD) analysis. After 4 rounds of curing under alternating temperature conditions, the compressive strength of cement stone containing mullite and basalt fiber composite material was 28.6 MPa at 260 °C, which was only 9.2 % lower than that at 80 °C. However, the compressive strength of the blank cement stone without composite materials decreased to 22.5 MPa at 260 °C, which was 20 % lower than that at 80 °C. After 4 rounds of alternating temperature cured, the harmful pores of the cement stone without composite materials increase, and the xonotlite flakes and stacks together. The cement stone added with mullite has a finer pore structure after 4 rounds of alternating temperature cured because mullite reacts with portlandite to form C-A-S-H gel. The xonotlite remains fibrous, and a small amount of new phase hibschite is formed. Furthermore, basalt fiber can react with C-A-S-H gel at high temperatures, and the two phases are closely combined to further improve the high-temperature resistance of cement stone.