Temperature Amplitude Research Articles

Arrhenius activation energy and thermal radiation effects on oscillatory heat-mass transfer of Darcy Forchheimer nanofluid along heat generating cone

The main goal of present research is to illustrate the frequency and amplitude behavior of heat and mass transfer of Darcy Forchheimer nanofluid flow with Arrhenius activation energy and thermal radiation effects. The impact of heat generation and chemical reaction on Darcy Forchheimer nanofluid along vertical porous cone is investigated to improve heating durability of thermodynamic systems in this research. The governing mathematical model is moderated in suitable format to construct physical coefficients. The oscillating stokes and primitive coefficients are used to differentiate the model into oscillating and steady forms. The Gaussian elimination and implicit finite difference techniques are used to address the numerical findings. To construct pertinent algorithm in FORTRAN system, the primitive-type variables are used on steady and oscillating models with first law of thermodynamics, nanoparticles and heat generation. The results under defined conditions are reported in numerical and graphical sequence through Tec-plot 360. It is found that the amplitude of surface temperature increases as heat generation increases because heat generation improves the excessive thermal transport. It is depicted that the Darcy-Forchheimer porous material decreases the fluid temperature. It is found that amplitude of mass transfer increases as activation energy and chemical reaction coefficient increases. The oscillating frequency of heat and mass transfer increases as Prandtl number increases. The current mechanism of mass and heat transfer of nanofluid has several uses in mineralogy, cutting tools, lubricating oils, machining operations, heat exchangers, coating sheets, petroleum drilling and cooling of metallic cones.

Geocryological Conditions of Small Mountain Catchment in the Upper Kolyma Highland (Northeastern Asia)

This research presents a comprehensive environmental assessment of a small mountain permafrost catchment of the Anmangynda River in the Upper Kolyma Highland (Northeastern Asia) over the period of 2021–2023. The study reveals significant diversity in climatic, geocryological, and hydrogeological conditions within this confined area, emphasizing the need for extensive field data collection and monitoring in vast permafrost regions with limited data availability. Key findings include variations in ground temperature, maximum seasonal thaw depth, and depths of zero annual amplitudes of ground temperature at different elevations and landscape types. Groundwater and surface flow dynamics within spring aufeis basins exhibit complex geocryological regimes influenced by icing processes. The presence of aufeis and its impact on local hydrology highlight the ecological significance of this phenomenon. Future research should focus on long-term trends in permafrost dynamics and their relationship with climate change, as well as the ecological effects of aufeis formation on local ecosystems. The study underscores the importance of a multi-faceted approach to environmental assessment, incorporating various environmental parameters and processes, to gain a comprehensive understanding of the intricate interactions within the cryosphere and their responses to changing climate conditions. Such knowledge is essential for addressing broader questions related to climate change, ecosystem resilience, and sustainable resource management in Northeastern Siberia.

Thermal shakedown in granular materials with irregular particle shapes

Granular materials with irregular particle shapes undergo a myriad of temperature variations in natural and engineered systems. However, the impacts of cyclic temperature variations on the mechanics of granular materials remain poorly understood. Specifically, little is known about the response of granular materials to cyclic temperature variations as a function of the following central variables: particle shape, applied stress level, relative density, and temperature amplitude. This paper presents advanced laboratory experiments to explore the impacts of cyclic temperature variations on the mechanics of granular materials, with a focus on sands. The results show that cyclic temperature variations applied to sands induce thermal shakedown: the accumulation of irreversible bulk deformations due to microstructural rearrangements caused by thermal expansions and contractions of the constituting particles. The deformation of sands caused by thermal shakedown strongly depends on particle shape, stress level, relative density, and temperature amplitude. This deformation is limited for individual thermal cycles but accumulates and becomes significant for multiple thermal cycles, leading to substantial compaction in sands and other granular materials, which can affect various natural and engineered systems.

The thermal effect of snow cover on ground surface temperature in the Northern Hemisphere

Snow cover is critical to the ground thermal regime because it affects surface conditions and the energy balance. Prior work inherently included confounding effects from vegetation and the soil when estimating the snow’s effect by using the differences between air and ground surface or soil temperature. Here we use the Kudryavtsev model including a snow module to isolate the effect of only the snow cover during winter, based on observational sites across the Northern Hemisphere. We find that snow’s damping of annual mean ground surface temperature averages 5.06 ± 3.15 °C and ranges 0 °C–10 °C, while damping of the annual ground surface temperature amplitude is 7.95 ± 4.95 °C, ranging 0 °C–20 °C. Greater insulation occurs in the high-latitudes. The insulating effect is primarily driven by snow depth, but also the combination of air temperature and its amplitude, snow depth, and duration. Snow cover duration and low air temperature enhance snow’s insulating ability. These observational results that isolate the damping effect of only the snow could play a significant role in better understanding the energy change between air and the ground.

Surface plasmon resonance temperature sensor based on the conjoined-tube hollow-core anti-resonant fiber with ultra-high temperature sensitivity

A surface plasmon resonance (SPR) temperature sensor based on the conjoined-tube hollow-core anti-resonant fiber (HC-ARF) is designed and analyzed. The conjoined-tube HC-ARF contains two connecting tubes with a cross arrangement in the cladding. The SPR temperature sensor is constructed by inserting a metal into one of the inner layer tubes and injecting a thermo-sensitive liquid into the hollow core of the HC-ARF to enhance the temperature sensitivity by exploiting the SPR effect. The effects of the structural parameters and thermo-sensitive media and metals on the sensing properties such as the temperature sensitivity, peak loss, resolution, amplitude sensitivity, and figure of merit (FOM) are analyzed systematically. Numerical analysis reveals ultra-high temperature sensitivity of 38.8 nm/°C and FOM of 673.84∘C−1, which are approximately 10 times higher than those of sensors described in the recent literature. In addition, the sensor is capable of detecting a wide temperature range from −5∘C to 60°C with good linearity. The SPR temperature sensor with high precision, a wide temperature detection range, a simple and easily modifiable structure, as well as good manufacturing tolerance has large potential in high-precision temperature monitoring in the petrochemical and biomedical industries.

Low cycle fatigue behavior and life prediction of a directionally solidified alloy

Low cycle fatigue behavior and life prediction of a directionally solidified alloy

The synergy between pollution reduction and carbon reduction in Chinese cities and its influencing factors

The synergy between pollution reduction (PR) and carbon reduction (CR) is crucial for cities facing both climate change and environmental pollution in achieving sustainable development. This study evaluates the PR-CR synergy in 295 Chinese cities from 2014 to 2022. Utilizing the improved Tapio Decoupling Principle and the Probit model, the study reveals that: (1) About 51.5 % (152) of the cities demonstrated a synergy between PR and CR. This synergy varied across the years; for instance, 102 cities exhibited it in 2018 and 2020, but only 14 in 2019. (2) The remaining 48.5 % (143 cities) did not exhibit this synergy, largely due to increased carbon emissions. These cities fall into three categories: those affected primarily by air pollution, carbon emissions, or both. (3) Environmental regulation emerged as the most influential factor promoting this synergy, with a significant coefficient of 81.47. Other positive influences included annual precipitation (0.000284), altitude (0.000650), Normalized Difference Vegetation Index (2.024), proportion of secondary industry (0.0168), proportion of construction land area (0.0182), and green patents (0.0000571). Conversely, average annual temperature (-0.0620) and relief amplitude (-0.0705) negatively impacted the synergy. This study enriches the discourse on PR-CR synergy, offering valuable insights for shaping sustainable development policies in cities.

Development of optic disc edema during 30 days of hypercapnic head-down tilt bed rest is associated with short sleep duration and blunted temperature amplitude.

Sleep and circadian temperature disturbances occur with spaceflight and may, in part, result from the chronically elevated carbon dioxide (CO2) levels on the international space station. Impaired sleep may contribute to decreased glymphatic clearance and, when combined with the chronic headward fluid shift during actual spaceflight or the spaceflight analog head-down tilt bed rest (HDTBR), may contribute to the development of optic disc edema. We determined if strict HDTBR combined with mildly elevated CO2 levels influenced sleep and core temperature and was associated with the development of optic disc edema. Healthy participants (5 females) aged 25-50 yr, underwent 30 days of strict 6° HDTBR with ambient Pco2 = 4 mmHg. Measures of sleep, 24-h core temperature, overnight transcutaneous CO2, and Frisén grade edema were made pre-HDTBR, on HDTBR days 4, 17, 28, and post-HDTBR days 4 and 10. During all HDTBR time points, sleep, core temperature, and overnight transcutaneous CO2 were not different than the pre-HDTBR measurements. However, independent of the HDTBR intervention, the odds ratios {mean [95% confidence interval (CI)]} for developing Frisén grade optic disc edema were statistically significant for each hour below the mean total sleep time (2.2 [1.1-4.4]) and stage 2 nonrapid eye movement (NREM) sleep (4.8 [1.3-18.6]), and above the mean for wake after sleep onset (3.6 [1.2-10.6]) and for each 0.1°C decrease in core temperature amplitude below the mean (4.0 [1.4-11.7]). These data suggest that optic disc edema occurring during HDTBR was more likely to occur in those with short sleep duration and/or blunted temperature amplitude.NEW & NOTEWORTHY We determined that sleep and 24-h core body temperature were unaltered by 30 days exposure to the spaceflight analog strict 6° head-down tilt bed rest (HDTBR) in a 0.5% CO2 environment. However, shorter sleep duration, greater wake after sleep onset, and lower core temperature amplitude present throughout the study were associated with the development of optic disc edema, a key finding of spaceflight-associated neuro-ocular syndrome.

Elevated body temperature is associated with depressive symptoms: results from the TemPredict Study

Correlations between altered body temperature and depression have been reported in small samples; greater confidence in these associations would provide a rationale for further examining potential mechanisms of depression related to body temperature regulation. We sought to test the hypotheses that greater depression symptom severity is associated with (1) higher body temperature, (2) smaller differences between body temperature when awake versus asleep, and (3) lower diurnal body temperature amplitude. Data collected included both self-reported body temperature (using standard thermometers), wearable sensor-assessed distal body temperature (using an off-the-shelf wearable sensor that collected minute-level physiological data), and self-reported depressive symptoms from > 20,000 participants over the course of ~ 7 months as part of the TemPredict Study. Higher self-reported and wearable sensor-assessed body temperatures when awake were associated with greater depression symptom severity. Lower diurnal body temperature amplitude, computed using wearable sensor-assessed distal body temperature data, tended to be associated with greater depression symptom severity, though this association did not achieve statistical significance. These findings, drawn from a large sample, replicate and expand upon prior data pointing to body temperature alterations as potentially relevant factors in depression etiology and may hold implications for development of novel approaches to the treatment of major depressive disorder.

Earlier Flowering Phenology and Pollinator Visitation on Urban Green Roofs Compared to Ground-Level Gardens

Urban green space, green infrastructure, and horticultural installations are gaining recognition for their potential to foster biodiversity. Green roofs are challenging growing environments for plants, characterized by extreme substrate temperatures, high light intensity, limited moisture availability, and limited substrate depth. Plants have a variety of physiological responses to these unique conditions, but little is known about how green roof growing conditions affect ecological characteristics like plant flowering phenology. Meanwhile, studies are only just uncovering the degree to which green roofs can provide habitat and support urban pollinator biodiversity. We evaluated the flowering phenology and made in situ pollinator observations of 15 plant taxa growing both on green roof systems and at ground level in Denver, Colorado, over two growing seasons. We found that flowering phenology occurs substantially earlier on green roofs compared to ground level among the observed plant taxa and observed a greater number of pollinators on green roofs early in the season, compared to ground level, presumably due to the availability of floral resources among the observed plant taxa. We observed significantly higher substrate temperatures along with wider diurnal temperature amplitude during the growing season that may contribute to the observed phenological patterns. Divergence in flowering phenology between individual plants of the same species on green roofs and plants at ground-level may have implications for organisms that rely on floral resources in urban environments. Earlier flower initiation on green roofs may provide pollinators with unique foraging opportunities and aid targeted conservation where early-season floral resources are limited.

Cliff-edge forests: Xerothermic hotspots of local biodiversity and models for future climate change.

Cliffs are remarkable environments that enable the existence of microclimates. These small, isolated sites, decoupled from the regional macroclimate, play a significant role in maintaining species biodiversity, particularly in topographically homogeneous landscapes. Our study investigated the microclimate of south-exposed forests situated at the edge of sandstone cliffs in the western part of the North Alpine Foreland Basin in Switzerland and its role in local forest community composition. Using direct measurements from data loggers, as well as vegetation analyses, it was possible to quantify the microclimate of the cliff-edge forests and compare it with that of the surrounding forests. Our results highlighted the significant xerothermic and more variable nature of the cliff-edge forest microclimate, with a mean soil temperature up to 3.72°C warmer in the summer, higher annual (+28%) and daily (+250%) amplitudes of soil temperature, which frequently expose vegetation to extreme temperatures, and an 83% higher soil drying rate. These differences have a distinct influence on forest communities: cliff-edge forests are significantly different from surrounding forests. The site particularities of cliff edges support the presence of locally rare species and forest types, particularly of Scots pine. Cliff edges must therefore be considered microrefugia with a high conservation value for both xerothermic species and flora adapted to more continental climates. Moreover, the microclimate of cliff-edge forests could resemble the future climate in many ways. We argue that these small areas, which are already experiencing the future climate, can be seen as natural laboratories to better answer the following question: what will our forests look like in a few decades with accelerated climate change?

Long-range ordering of velocity-aligned active polymers.

In this work, we study the effect of covalent bonding on the behavior of non-equilibrium systems with the active force acting on particles along their velocity. Self-ordering of single particles does not occur in this model. However, starting from some critical polymerization degree, the ordered state is observed. It is homogeneous and exhibits no phase separation. In the ordered state, the chains prefer a near-two-dimensional configuration and all move in one direction. Importantly, the self-ordering is obtained only at intermediate active force magnitudes. At high magnitudes, the transition from the disordered to ordered state is suppressed by the swelling of the chains during the transition, as we show by the transition kinetics analysis. We demonstrate the bistable behavior of the system in a particular range of polymerization degrees, amplitudes of active force, densities, and thermostat temperatures. Overall, we show that covalent bonding greatly aids the self-ordering in this active particle model, in contrast to active Brownian particles.

NONTUBERCULOUS MYCOBACTERIA DIVERSITY IN KARST WATERS AND BIOFILMS IN BULGARIAN CAVES

Background: Nontuberculous Mycobacteria (NTM) are emerging pathogens causing opportunistic infections in humans and animals. Their distribution in the waters and caves of Bulgaria is poorly studied. Climatic changes are associated with changes in the amplitudes of ambient and water temperature, as well as changes in the amount of precipitation which play an essential role in the creation of reservoirs of some types of NTM in the environment. Material and Methods: We optimized the methods for successful isolation of environmental NTM and then used molecular genetic methods for identification. Results: A total of 235 samples (karst water, sediments, soil, bat guano) were collected in some caves of the following karst regions: 203 in Vratsa Karst area, 204 in Ponor Karst area, 205 in Bezdenski area and 303 in Karst and caves of Bosnek region. Primary isolation of mycobacteria by Löwenstein–Jensen at room temperature was more successful than on liquid media at 37°C. We identified NTM in 10% (n=24) from these materials. Diverse NTM included: M. chelonae (n=3), M. gordonae (n=2), M. intermedium (n=3), M. scrofulaceum (n=1), M. szulgai (n=4), M. fortuitum group (n=4), NTM mix culture (n=5), M. terrae complex (n=1), Mycobacterium sp. (n=1). Rapidly growing NTM (M. chelonae, M. fortuitum group) were the most common. The isolates belonged to group of environmental saprophytes (Risk group 1) and potential pathogens (Risk group 2). Conclusions: We successfully implemented a procedure for decontamination and isolation of NTM from the environment. For the first time in the country, NTM species were identified in biofilms, karst waters, soil and bat guano within caves. The presence of NTM in cave ecosystems represents a potential source for human infection.

Effects of temperature and strain amplitude on low-cycle fatigue behavior of 12Cr13 martensitic stainless steel

12Cr13 martensitic stainless steel has been selected as the structural material for steam turbine blade which is frequently subjected to low-cycle fatigue (LCF) damage. The study involved conducting low-cycle fatigue (LCF) tests under strain control at various temperatures (25 °C, 250 °C, 350 °C, 450 °C) and strain amplitudes (±0.3 %, ±0.4 %, ±0.5 %, ±0.6 %). The cyclic deformation behavior, primarily indicating cyclic stress response and the Massing effect is thoroughly analyzed based on the characterization of dislocation microstructure and electron backscatter diffraction maps. The mechanism of crack initiation and the propagation behavior are discussed based on the SEM observations of microcracks on the specimen surface and the fracture surface morphology. The influence of temperature and strain amplitude on fatigue life behavior is determined, and the underlying mechanisms are revealed. Moreover, the life prediction is performed by using the classical Basquin-Coffin-Manson model at ambient temperature.

Study on the steady-oscillatory transition of three-dimensional (3D) natural convection via Hopf bifurcation

The transition from steady-state flow to periodic oscillatory flow for the natural convection by Hopf bifurcation is investigated in a three-dimensional (3D) cavity. The spectral collocation method (SCM) in combination with the artificial compressibility method (ACM), which is developed by ourselves as a numerical method SCM-ACM with high accuracy, is employed to solve the governing equations directly instead of linear stability analysis method that is commonly used for the research on flow instability. The results show that the amplitude decays exponentially with time and the decay rate is linear with the Grashof number (Gr). The critical Grashof number for steady-oscillatory transition is obtained as Grcr = 3.423 × 106. The dimensionless angular frequency ωcr = 0.24 is also determined by Fourier analysis. In this work, we also examine the heat-momentum interactions within the boundary layers, visualize the periodic oscillations of temperature and velocity amplitudes, and analyze the origin of instability from multiple angles. The results show that large oscillations of velocity and temperature are observed near the isothermal walls. The oscillation is enhanced by the increase of thermal boundary layer thickness and flow velocity at both ends of isothermal walls. The maximum velocity and temperature amplitudes appear at the lower left and upper right corners of the mid-plane (Z = 0.5), where are the origin of instability, and the spanwise walls are almost independent of oscillations. The oscillatory flow of natural convection in three-dimensional cavity originates from the continuously increasing buoyancy force, and its transition occurs by Hopf bifurcation. Moreover, the temperature amplitude exhibits a wavy distribution on the mid-plane (X = 0.5) and strongly depends on the depth Z. These results provide benchmark data for future numerical studies and engineering application.

Performance of the phase-change material (PCM) to reduce freeze–thaw effect in cementitious composites

One of the contemporary approaches to reduce the damage to cementitious composite resulting from the freeze–thaw effect is the incorporation of phase-change materials (PCM). In this study, the composites were produced adding n-tetradecane, which is a microencapsulated organic PCM, at rates of 0, 2, 4, 6 and 8% of the cement weight. In two different simulations representing the climate conditions of the two distinct regions in Türkiye, its effect on restricting the temperature amplitudes that the composite experienced was determined. It was determined that the PCM, with a working range similar to the temperature range applied to the composite in simulation, was successful in reducing the temperature amplitudes, and the rate and type of the PCM should be chosen with care according to the climate conditions likely to be experienced by the composite when in use. In addition to PCM's thermal properties, its effects on the mechanical properties and consistency results were investigated.

Assessment of the validity of using a radiant panel in the low-height floor heating

This paper examines the viability of using a radiant panel in lightweight low-height floor heating. In this structure, a dry screed with high thermal resistance is replaced by a low-resistance adhesive layer with reinforcement mesh. The absence of the radiant panel results in a reduction in heat output of 5%–17% for floor finishes with a thermal resistance of 0.001 m2K/W, 50%–54% for 0.05 m2K/W and 60%–62% for 0.1 m2K/W. A structure with a panel is characterised by a lower surface temperature amplitude (maximum 2.4 K) compared to a structure without it (8.8 K), which improves the comfort of floor users. The annual heating cost in a building equipped with the analysed structures was determined. The absence of the panel resulted in a cost increase of 13%, 37% and 79% for floor finish resistances of 0.001, 0.05 and 0.1 m2K/W, respectively. The SPBT for the purchase of radiant panels is 40 years for a floor resistance of 0.001 m2K/W, demonstrating the unprofitability of this solution. For resistances of 0.05 and 0.1 m2K/W, SPBT was 14 and 6 years, respectively. The choice of floor heating system should take into account the required heat output, thermal comfort and economic aspects. Practical application This paper assesses the validity of using radiant panels in a low-height floor heating structure, where the dry screed layer is replaced by an adhesive layer with reinforcement mesh. This structure is gaining popularity due to its quick installation and low height but has the disadvantage of the high panel cost. The paper evaluates the effect of panels on heat output and identifies the conditions under which their use is economically justified. Recipients of results are designers and contractors of heating systems. The recommendations can be the basis for selecting the optimum design solution for a lightweight floor heating system.

Mechanisms of non-stationary influence of urban form on the diurnal thermal environment based on machine learning and MGWR analysis

The non-stationary impact of urban form at block scale on the diurnal thermal environment has not been extensively studied. To fill the gap, a comprehensive multi-scale research framework was constructed, integrating machine learning algorithms and multiscale geographically weighted regression (MGWR) analysis. The urban form types were extracted by machine learning algorithms from 2282 blocks of Dalian, a coastal city, and the contribution to the diurnal land surface temperature (LST) was evaluated. Based on MGWR, the non-stationary effects of urban form, human activity and spatial location on the diurnal LST were quantified, which indicated the contributing factors to the diurnal thermal differences among the form types. The result was as follows: 1) Blocks characterized by low vegetation and mid/low-rise buildings had the highest warming contribution for diurnal LST. 2) The impact of sky view factor (SVF) on diurnal temperature amplitude exhibited no significant spatial-temporal heterogeneity. 3) Building density had a prominent effect on diurnal temperature amplitude. 4) High-vegetation and open (SVF > 0.5) mid/mid-high/low-rise (15–50 m) buildings were recommended. This study provides a more precise basis for policymakers to develop climate adaptation strategies throughout day and night, particularly for coastal cities.

Influence of convective heat transfer on the AC temperature amplitude of a microheater on glass or polyimide substrate

Influence of convective heat transfer on the AC temperature amplitude of a microheater on glass or polyimide substrate

Анализ индекса континентальности климата на территории Северо-Востока России

Analysis of climate continentality is a powerful tool for studying and forecasting weath­er. Considering the continentality index enables determining current climate characteristics and predicting potential changes. This study aims to assess climate change in Russia’s North-East by analysing the continentality index as a complex integral indicator of these changes applicable to vast territories. Although there are many methods for assessing climate continentality, there is no uni­versal methodology. It is proposed in this contribution to employ two of the existing tech­niques. The first focuses on the area’s annual temperature amplitude and geographic latitude. The second involves a calculation of the index based on average January and July tempera­tures, the sum of seasonal precipitation and the area’s latitude. An analysis of the index val­ues of the base and calculation periods leads one to conclude that these values do not change significantly towards either weaker or stronger continentality across the study area.