Periodic Temperature Changes Research Articles

Research on Temperature–Pressure Coupling Model of Gas Storage Well during Injection Production

Periodic changes in wellbore temperature and pressure caused by the cyclic injecting and producing of gas storage wells affect wellbore integrity. To explore the distribution and influencing factors of wellbore temperature and pressure during gas storage well injection-production processes, based on energy conservation, momentum theorem, and the transient heat transfer mechanism of the wellbore, a temperature and pressure coupling model for gas storage injection-production wellbores was established, and a piecewise iterative method was used to solve the model equations. Compared with the field data, the predicted relative errors of the wellhead temperature and pressure were 2.30% and 2.07%, respectively, indicating that the coupling model has a high predictive accuracy. The influences of the injection-production conditions, tubing diameter, and overall heat transfer coefficient on the wellbore temperature and pressure distributions were analyzed through an example. When the gas injection flow rate increased by 1.5 times, the bottomhole temperature decreased by 37%. Doubling the overall heat transfer coefficient resulted in a 10% rise in the bottomhole temperature. An increase of 0.3 times in the gas injection pressure led to a 31% increase in bottomhole pressure. With a 1.5-fold increase in the gas production flow rate, the wellhead temperature rose by 28%, and the wellhead pressure dropped by 20%. The research in this paper can serve as a guide for the optimization design and safe operation of gas storage wells.

The Problem of Heat and Mass Transfer of a Half-Space with an Air Flow with Periodic Changes in Air Temperature

A system of differential equations, boundary and initial conditions for calculating temperature and moisture content fields in a homogeneous halfspace, the boundary of which is blown by an air flow, is formulated. The heat exchange of the boundary with the air medium occurs according to the Newtonian law, and mass transfer — according to the Dalton evaporation law. In the initial state, the air and the material have the same temperature, and water vapor, both near the surface of the material and outside the boundary layer, is in a saturation state, so there is no exchange of heat and moisture between the air and the material. At some point, the air temperature begins to produce small harmonic fluctuations near its initial value. For a mathematical model of heat and mass transfer, in which the movement of moisture to the surface is considered to be caused only by a drop in moisture content, i.e. the phenomenon of thermal diffusion is neglected, an asymptotic time view of the temperature and moisture content fields is obtained. The moisture content field has the form of a damped harmonic wave, and the temperature field is represented by the superposition of two waves of the same type, which have the same frequency, but different attenuation coefficients and phase velocities. The calculation of the basic wave parameters for a material with clay characteristics is carried out, and the results obtained are compared with experimental data. The constructed solution is a generalization of the Fourier formulas known in the literature, which are valid only in a situation when the material does not contain moisture, and according to the harmonic law, not the air temperature changes, but the surface temperature. The results obtained in the article will be used in geocryology as a theoretical tool in the study of seasonal fluctuations in the thermal and physical state of the soil, which is an important task in planning economic activities in the field of the distribution of frozen rocks.

Lock-in Thermography for the Localization of Security Hard Blocks on SoC Devices

AbstractLocalizing security-relevant hard blocks on modern System-on-Chips for physical attacks, such as side-channel analysis and fault attacks, has become increasingly time-consuming due to ever-increasing chip-area and -complexity. While this development increases the effort and reverse engineering cost, it is not sufficient to withstand resolute attackers. This paper explores the application of camera-based lock-in thermography, a nondestructive testing method, for identifying and localizing security hard blocks on integrated circuits. We use a synchronous signal to periodically activate security-related functions in the firmware, which causes periodic temperature changes in the activated die areas that we detect and localize via an infrared camera. Using this method, we demonstrate the precise detection and localization of security-related hard blocks at the die level on a modern SoC.

ON THE INFLUENCE OF EXOGENEOUS PROCESSES ON THE RESULTS OF MEASURING MOVEMENTS OF GEODESIC MARKINGS

The influence of exogenous processes on geodetic marks is multifactorial, and in modern observation practice there is no clear scientifically based system of engineering and geodetic forecasting of neotectonics influence on the results of repeated high-precision leveling, on the basis of which it would be possible to solve the issues of stability of depth, soil and rock leveling marks, as well as modeling the mechanism of influence of exogenous processes on the results of repeated leveling. Therefore, the study of their influence is an urgent task. The study is aimed at determining the influence of exogenous processes on the results of measurements of geodetic marks displacements during observations at local geodynamic polygons in the Kryvyi Rih region. The work performed has shown that the temperature factor is periodic in nature and therefore its influence on the stability of the reps also naturally varies over time: it changes linearly in the time interval March-May and September-November, sinusoidally in June-August, if divided into separate parts. Although, in general, the temperature change can be described as a sinusoid. A linear correlation has been established, but it should be noted that it can be broken by the imposition of a stronger factor that determines the dynamics of the movement of the rappers. There is no clear connection between temperature changes Δt and exceedances Δh in the time interval May-July. The intensive increase in temperature corresponds to the lowering of soil references, which is inconsistent with the general theory of their stability. The phase shift is more than two months, which indicates the influence of another, stronger factor than temperature on the stability of soil references. Periodic changes in atmospheric temperature cause thermal deformations of rocks, which, due to differences in thermal properties and temperature conditions of rocks, have a complex differentiated structure in space and time, which is manifested in heterogeneous vertical displacements of the references underlying these rocks. The revealed regularities of the temperature factor and the instability of the references caused by this factor made it possible to predict its value and recommend a scheme of time periods for field measurements in repeated cycles.

Mesoscopic precursor anomaly characteristics of red sandstone under uniaxial compression after cyclic high-temperatures

The deformation and failure characteristics of rock caused by periodic changes of temperature are not only significantly different from that under normal temperature, but also significantly different from that produced by a single high-temperature event. Here, using a three-dimensional digital image correlation (3D-DIC) integrated test system, mechanical and micro-damage tests of red sandstone are performed under cycles of high-temperature and natural-cooling with a temperature range of 25°C to 300°C and the number of cycles varying between 0 and 25. Macroscopic, mesoscopic and microscopic characteristics such as rock strength, deformation, strain field and fracture morphology are examined and their evolution with the number of heating-cooling cycles is discussed. Using the time-history evolution of the differentiation rate of the precursor anomaly (En), the characteristic coefficient (K) and the damage variable (DF), three kinds of characteristic time points are put forward to quantify the incubation and development time of precursor abnormal characteristics and are used to divide the whole process of deformation and failure. These time points are the precursor abnormal differentiation time (PADT) tE, the precursor abnormal startup time (PAST) tK, and the precursor abnormal failure time (PAFT) tD. Test results show that: (1) The action of cyclic high-temperature natural-cooling not only shows the strengthening effect of temperature, but also shows the strengthening effect of a certain number of cycles. (2) The evolution sequence of the three precursor abnormal characteristic moments is PADT, PAST and PAFT in turn, and this sequence can intuitively describe the whole complex process of rock deformation and failure, and there are wave peaks in the evolution curve with the number of high-temperature cycle. (3) The effect of high temperature (i.e., 300°C) cyclic heating on rock properties is similar to the threshold effect of a single high-temperature heating event.

Effect on Rotation Speed on Thermal Dehydration Characteristics of Waste Gypsum Particles in a Constant Volume Rotary Vessel by Heating.

This study examined the thermal dehydration characteristics of CaSO4∙2H2O in a constant-volume rotary vessel. The experiment used CaSO4∙2H2O particles obtained from the crushed waste gypsum board. The particle size ranged from 850 to 2000 μm, and the experiment was carried out at varying rotation speeds of 1, 10, and 35 rpm, with the vessel temperature heated to 180 °C. Temperature and pressure inside the vessel were measured simultaneously using the thermocouple and the pressure sensor. The XRPD measurement analyzed the transition of CaSO4∙2H2O after the heating of particles. The result showed that the temperature growth rate was similar for high rotation speeds of 10 and 35 rpm, while periodic temperature changes occurred at the low rotation speed of 1 rpm. A distinguishing flow pattern was observed at the low rotation speed, and the particles inside the vessel collapsed periodically downward. This particle behavior was related to the temperature distribution of the rotation speed of 1 rpm. Additionally, the pressure in the vessel increased rapidly at higher rotation speeds. This trend indicates the desorption of the crystal water of CaSO4∙2H2O due to the increasing temperature in the case of high rotation speed. Also, the XRPD measurement results showed the appearance of CaSO4∙0.5H2O under the higher rotation speed conditions, and the mass fraction of CaSO4∙0.5H2O increased with the rotation speed. Overall, the present study suggests that rotation speed plays a crucial role in determining the heat conduction and heat transfer of particles in a constant-volume rotary vessel.

The stability issue of fractured rock mass slope under the influences of freeze–thaw cycle

Freeze–thaw failure of frozen rock slope often occurs during engineering construction and mining in cold area, which poses a great threat to engineering construction and people's life safety. The properties of rock mass in cold region will change with the periodic change of temperature, which makes it difficult to accurately evaluate the stability of slope under the action of freeze–thaw cycle by conventional methods. Based on field investigation and literature review, this paper discusses the characteristics of frozen rock mass and the failure mechanism of frozen rock slope, and gives the types and failure modes of frozen rock slope. Then, the research status of frozen rock slope is analyzed. It is pointed out that the failure of frozen rock slope is the result of thermo-hydro-mechanical (THM) coupling. It is considered that freeze–thaw cycle, rainfall infiltration and fracture propagation have significant effects on the stability of frozen rock slope, and numerical simulation is used to demonstrate. The research shows that the safety factor of frozen rock slope changes dynamically with the surface temperature, and the safety factor of slope decreases year by year with the increase of freeze–thaw cycles, and the fracture expansion will significantly reduce the safety factor. Based on the above knowledge, a time-varying evaluation method of frozen rock slope stability based on THM coupling theory is proposed. This paper can deepen scholars' understanding of rock fracture slope in cold area and promote related research work.

Novel high thermal conductivity alumina/salt composites for thermal energy storage: Effect of wettability on microstructure and properties

In this work, alumina foam ceramics (AFC) were prepared by foaming method, and AFC/salt composite phase change materials were prepared by melt infiltration method using AFC as skeleton materials. The results showed that AFC had good chemical compatibility with Na2SO4 and NaCl. The salt contents of AFC/Na2SO4 and AFC/NaCl were 37.8 wt% and 31.7 wt%, respectively, with compressive strength of 100.1 MPa and 72.8 MPa, thermal conductivity of 5.53 W/m·K and 6.40 W/m·K, and energy density of 1129 J/g and 1019 J/g, respectively. Due to the better wettability, AFC and Na2SO4 form a chimeric structure, which has better binding and bonding strength, and is not prone to molten salt leakage. AFC/ Na2SO4 is expected to be applied to industrial waste heat recovery and solar thermal power generation with periodic temperature changes.

Influences of seasonal changes of the ground temperature on the performance of ground heat exchangers embedded in diaphragm walls: A cold climate case from North China

Compared with ground heat exchangers (GHEs) in typical vertical boreholes with depth of 100–120 m, GHEs embedded in the diaphragm wall of buildings are more easily affected by periodic changes of the shallow ground temperature. Here we numerically solve the heat transfer model of the diaphragm wall with GHEs considering actual ground temperature boundary conditions in cold climate region, North China, and investigate the influences of seasonal variations of the ground temperature on heat transfer performance of GHEs. Results show that due to the above seasonal effect, the heat exchange performance of GHEs may decrease to different extent especially in relatively shallow diaphragm walls, thereby causing non-negligible design deviations. Under the present geometric and climate conditions, as the depth of GHEs increases, the maximum thermal influence distance from the diaphragm wall tends to increase during the cooling season and decrease during the heating season, respectively. The optimal spacing between GHE groups ranges from 0.5 to 0.9 m, and though a high construction cost, a smaller spacing is more favorable for improving the overall energy efficiency. The present work is expected to provide useful references for optimal design and performance prediction of GHEs embedded in diaphragm walls with similar climate conditions.

Experimental study on the effects of hydrochemistry and periodic changes in temperature and humidity on sandstone weathering in the Longshan Grottoes

Changes in precipitation, temperature and humidity can lead to the weathering of rock masses in grottoes; these changes are common in sandstone grottoes. To simulate this cyclic process, different salt solutions were designed according to the main precipitated components. Sandstone specimens taken from Longshan Grottoes were soaked in these solutions for 48 h and then placed in a simulated environment with temperature and humidity changes for 5 cycles (50 h) to study the effects of hydrochemical, temperature and humidity changes on the sandstone. Physical indexes, such as mass, wave velocity, surface hardness and tensile strength, of the rock samples were measured every three cycles, and the damage characteristics and mechanisms of the sandstone were discussed based on SEM and XRD test results. The results showed that the macroindicators and microstructures of the samples gradually decreased with increasing number of cycles. The physical indexes of the rock samples in different solutions changed at different rates, the changes in surface hardness and tensile strength were consistent, and the responses were less sensitive to deterioration than to longitudinal wave velocity. In different solutions, the microstructures and mineral compositions of the samples showed different trends with increasing number of cycles. This damage was caused by a combination of various actions, such as feldspar dissolution, chemical erosion, water scouring, clay mineral expansion and disintegration, and salt crystallization, which increased the number of pores, enlarged the holes and expanded the cracks inside the rock samples.

Structural Phenomena in a Vesicle Membrane Obtained through an Evolution Experiment: A Study Based on MD Simulations.

The chemical evolution of biomolecules was clearly affected by the overall extreme environmental conditions found on Early Earth. Periodic temperature changes inside the Earth's crust may have played a role in the emergence and survival of functional peptides embedded in vesicular compartments. In this study, all-atom molecular dynamic (MD) simulations were used to elucidate the effect of temperature on the properties of functionalized vesicle membranes. A plausible prebiotic system was selected, constituted by a model membrane bilayer from an equimolar mixture of long-chain fatty acids and fatty amines, and an octapeptide, KSPFPFAA, previously identified as an optimized functional peptide in an evolution experiment. This peptide tends to form the largest spontaneous aggregates at higher temperatures, thereby enhancing the pore-formation process and the eventual transfer of essential molecules in a prebiotic scenario. The analyses also suggest that peptide-amphiphile interactions affect the structural properties of the membrane, with a significant increase in the degree of interdigitation at the lowest temperatures under study.

Experimental study of the thermal probing depth of a skin calorimeter

In this work we perform an experimental study of the thermal probing depth of a skin calorimeter developed to measure in vivo the heat capacity and the thermal resistance of a 4 cm2 skin region. To determine these properties, a small thermal excitation is applied to the skin and then, the static and dynamic response of the calorimetric signal is studied. This excitation consists of a periodic change of the calorimeter thermostat temperature while the device is applied on the skin. We have found that the thermal penetration depth depends mainly on the period of this periodic thermal excitation. This time dependence is exponential for non-semi-infinite domains. Using a time–variant model, we performed measurements on the dorsal and volar areas of the left wrist of a healthy 64-year-old male subject. For a 4 cm2 region of skin, the results show that the heat capacity in both zones are of the same order of magnitude. Its initial value is 4 J/K and increases exponentially up to 7 J/K with a time constant of 6.5 min. Thermal resistance also increases exponentially with time: from 27 to 36 K/W for the volar zone, and from 32 to 45 K/W for the dorsal zone.

Conversion of stable crystals to metastable crystals in a solution by periodic change of temperature.

Using a Becker-Döring-type model including cluster incorporation, we study the possibility of conversion of stable crystals to metastable crystals in a solution by a periodic change of temperature. At low temperature, both stable and metastable crystals are assumed to grow by coalescence with monomers and corresponding small clusters. At high temperature, a large amount of small clusters produced by the dissolution of crystals inhibits the dissolution of crystals, and the imbalance in the amount of crystals increases. By repeating this process, the periodic temperature change can convert stable crystals into metastable crystals.

Dynamic Cross-Linking Network Construction of Carboxymethyl Starch Enabling Temperature and Strain Bimodal Film Sensors

Building stimulus-responsive units in the hydrogel coatings remains challenging for film sensors consisting of alternated layers of inert substrates and hydrogel coatings. An interesting film sensor with a carboxymethyl starch-based hydrogel coating was developed here. The cross-linking networks of carboxymethyl starch play the roles of structure-constructing units and stimulus-controlling units simultaneously, endowing the coatings with thermal sensing and strain sensing capabilities. The dynamic cross-links formed via the boronic ester bonds are temperature-sensitive, releasing or consuming additional acid ions with temperature alteration, and also as primary networks give the hydrogel strength and stretchability with the assistance of semi-penetrated polyacrylamide chains. Therefore, as-prepared flexible film sensors can be used to detect the periodic changes of human temperature and small-scale motion with multiple working modes, discriminating the physical states related to human health. Moreover, this kind of starch-based coating is degradable in a strongly alkaline solution and the inert substrate layer can protect the skin from erosion caused by direct hydrogel-skin contact, and thereby the film sensor is human- and environmentally friendly. This work also proposes a strategy of building temperature-sensitive units in the film sensor via regulating the chemical networks, instead of tuning physical structures.

Periodic temperature changes drive the proliferation of self-replicating RNAs in vesicle populations

Growth and division of biological cells are based on the complex orchestration of spatiotemporally controlled reactions driven by highly evolved proteins. In contrast, it remains unknown how their primordial predecessors could achieve a stable inheritance of cytosolic components before the advent of translation. An attractive scenario assumes that periodic changes of environmental conditions acted as pacemakers for the proliferation of early protocells. Using catalytic RNA (ribozymes) as models for primitive biocatalytic molecules, we demonstrate that the repeated freezing and thawing of aqueous solutions enables the assembly of active ribozymes from inactive precursors encapsulated in separate lipid vesicle populations. Furthermore, we show that encapsulated ribozyme replicators can overcome freezing-induced content loss and successive dilution by freeze-thaw driven propagation in feedstock vesicles. Thus, cyclic freezing and melting of aqueous solvents – a plausible physicochemical driver likely present on early Earth – provides a simple scenario that uncouples compartment growth and division from RNA self-replication, while maintaining the propagation of these replicators inside new vesicle populations.

Performance Comparison of Break and Seat and Rubblization Rehabilitation Techniques for Reflection-Crack Mitigation: Case Study in Louisiana

Hot mix asphalt (HMA) overlays are constructed on Portland cement concrete (PCC) pavements to improve long-term performance. A significant disadvantage of using HMA overlays on PCC pavements is the development of reflection cracks. Reflection cracks are influenced by traffic loads and periodic temperature changes. The objective of the study was to compare field performance of two slab-fracturing (i.e., break and seat, and rubblization) techniques commonly used in Louisiana, U.S. Four PCC pavement rehabilitation projects with at least one slab-fracturing technique and a corresponding control section were evaluated. Field structural capacity and performance data were collected and analyzed to determine the effect of each reflection-crack mitigation technique on performance. Resilient modulus (Mr) of the existing subgrade was found to significantly influence the structural and functional performance of the pavement sections evaluated. Pavement sections with weaker subgrades were shown to be not suitable for slab-fracturing rehabilitation techniques. For the four field projects evaluated, rubblized test sections showed higher cracking resistance than the control sections. The break and seat technique did not consistently improve or reduce the crack resistance of pavement sections compared with their corresponding control sections because of variations in subgrade Mr values. Sections with smaller sized (i.e., 6 in. break pattern and rubblized particles) fractured particles exhibited higher cracking resistance. Rubblized and selected break and seat sections for the field projects evaluated exhibited lower overall performance compared with their corresponding control sections, which is attributed to other underlying subsurface conditions. Additional study is required to continuously monitor the pavement sections.

Magnetite texture and trace element evolution in the Shaquanzi Fe-Cu deposit, Eastern Tianshan, NW China

The Shaquanzi deposit is an important Fe-Cu deposit in the Yamansu Fe mineralization belt, Eastern Tianshan. Three types of magnetite were distinguished based on the textural and mineral assemblages, including the platy mushketovite (TA), granular magnetite coexisting with K-feldspar and epidote (TB), and granular magnetite intergrown with pyrite (TC). TA magnetite consists of three generations, including a bright core (TA-1), a dark-gray inner rim (TA-2), and a light-gray outer rim (TA-3), under BSE observations. TA-1 magnetite was transformed from the primary hematite due to a sharply reduced oxygen fugacity and retains its platy pseudomorph. With the changing temperature (increase or decrease), TA-1 magnetite underwent dissolution and re-precipitation (DRP) processes to form TA-2 and TA-3 magnetite. TB magnetite consists of two generations (TB-1 and TB-2). TB-1 magnetite contains abundant mineral inclusions and microporosity. With the decrease of fO2 and temperature, TB-1 magnetite underwent a fluid-assisted recrystallization process to form TB-2 magnetite with foam texture. TC magnetite consists of four different generations (TC-1, TC-2, TC-3, and TC-4). TC-1 magnetite with densely-distributed oscillatory zonings (generally smaller than 1 μm) is surrounded by the darker TC-2 magnetite. TC-2 magnetite with foam texture may be formed by recrystallization of TC-1 magnetite. TC-3 magnetite replaced or cut TC-2 magnetite, indicating that it was formed by the DRP process of TC-2 magnetite. Following periodic changes of fO2 and temperature, TC-4 magnetite with oscillatory zones formed around TC-3 magnetite.This study proposes a new Fe/(Mg + Al + Mn) vs Ti discrimination diagram to distinguish hydrothermal and magmatic magnetite. Magnetite compositions of the Shaquanzi deposit are quite different from those of magmatic magnetite, but very similar to those observed in the hydrothermal system such as IOCG and skarn deposit, indicating that magnetite of the Shaquanzi deposit was formed by hydrothermal process rather than magmatic differentiation.

Adjustable Thermo-Responsive, Cell-Adhesive Tissue Engineering Scaffolds for Cell Stimulation through Periodic Changes in Culture Temperature.

A three-dimensional (3D) scaffold ideally provides hierarchical complexity and imitates the chemistry and mechanical properties of the natural cell environment. Here, we report on a stimuli-responsive photo-cross-linkable resin formulation for the fabrication of scaffolds by continuous digital light processing (cDLP), which allows for the mechano-stimulation of adherent cells. The resin comprises a network-forming trifunctional acrylate ester monomer (trimethylolpropane triacrylate, or TMPTA), N-isopropyl acrylamide (NiPAAm), cationic dimethylaminoethyl acrylate (DMAEA) for enhanced cell interaction, and 4-acryloyl morpholine (AMO) to adjust the phase transition temperature (Ttrans) of the equilibrium swollen cross-polymerized scaffold. With glycofurol as a biocompatible solvent, controlled three-dimensional structures were fabricated and the transition temperatures were adjusted by resin composition. The effects of the thermally induced mechano-stimulation were investigated with mouse fibroblasts (L929) and myoblasts (C2C12) on printed constructs. Periodic changes in the culture temperature stimulated the myoblast proliferation.

Research of the influence of climatic factors on the properties and characteristics of carbon plastics

The results of accelerated tests on the influence of climatic factors on the operational and technical parameters and characteristics of carbon fiber reinforced plastics are presented, among which the main attention is paid to thermal and moisture aging, thermal aging, joint periodic changes in temperature and humidity, as well as immersion in water on the state of polymer composite materials in order to check physical and mechanical properties and improving their quality. The results of the experimental studies made it possible to establish how much and in what direction the strength characteristics of the materials under study changed as a percentage of the initial value. Ref. 24. Tab. 6.

Study on the correlation between hyperventilation syndrome and climate and air quality

ObjectiveTo further explore the relationship between the number of patients with hyperventilation syndrome (HVS) and meteorological factors such as temperature, weather, humidity, wind speed and air quality. MethodsA total of 1,868 patients diagnosed with HVS from 1 January 2014 to 30 September 2020 were analysed by bivariate correlation analysis. Using the daily visits of patients with HVS as the dependant variable and meteorological factors and air quality as the independent variables, the multiple linear regression model was fitted to study the effect of climatic factors and air quality on the number of patients with HVS. ResultsThere were more female patients with HVS than males. The average monthly visits of patients with HVS showed a periodic change in the monthly average temperature. The monthly visits of patients with HVS in Shijiazhuang were higher from May to September. The monthly visits of patients with HVS in Urumqi were higher in May and June. The goodness of fit of the multivariate linear regression equation was 0.292, belonging to the medium effect. Adjusted R2 of the multivariate linear regression equation was 0.084. This meant that these statistically significant independent variables could explain 8.4% of the variance in the dependant variable. The overall test of the entire regression equation was statistically significant (F = 65.430, P = 0.000). The average temperature, humidity, air pressure and ozone (O3) levels were positively correlated with the number of visits of patients with HVS; humidity and pressure had the greatest impact. ConclusionMeteorological factors and air quality are associated with the number of visits of patients with HVS.