Heating Mechanism Research Articles

Visible-Light-Induced Hydrogen Generation from Mixtures of Hydrogen Boride Nanosheets and Phenanthroline Molecules.

Hydrogen boride (HB) nanosheets are recognized as a safe and lightweight hydrogen carrier, yet their hydrogen (H2) generation technique has been limited. In the present study, nitrogen-containing organic heterocycles are mixed with HB nanosheets in acetonitrile solution for visible-light-driven H2 generation. After exploring various nitrogen-containing heterocycles, the mixture of 1,10-phenanthroline molecules (Phens) and HB nanosheets exhibited significant H2 generation even under visible light irradiation. The quantum efficiency for H2 generation of the mixture of HB nanosheets and Phens is 0.6%. Based on spectroscopic and electrochemical analyses and density functional theory (DFT) calculations, it is determined that radical species generated from Phens with electrons and protons donated by HB nanosheets are responsive to visible light for H2 generation. The HB nanosheets/Phens mixture presented in this study can generate H2 using renewable energy sources such as sunlight without the need for complex electrochemical systems or heating mechanisms and is expected to serve as a lightweight hydrogen storage/release system.

Two-stage heat dissipation in plastic deformation of metals under ultra-high strain rate deformation

Understanding plastic heating at high strain rates is essential for designing material behavior. We employ molecular dynamics to analyze plastic heating and introduce a refined Taylor-Quinney coefficient (TQC) calculating approach. Our results reveal a two-stage heating behavior in high-strength systems, a relaxation stage characterized by rapid heating, stress relaxation, and increasing TQC, followed by a steady-state stage marked by linear temperature increase, constant stress, and stable TQC. The dislocation movement may behave as a plastic heating converter. During the relaxation stage, defect/dislocation nucleation dominates, leading to an increase in TQC as defect density rises upon yielding. Despite an increasing portion of plastic work being stored in defects, the data suggest that dislocations primarily act as sources of heat. In the steady-state stage, an unusual scenario emerges where defect density decreases as plastic deformation proceeds, yet TQC continues to increase due to the release of stored energy. This phenomenon is potentially explained by the annihilation of dislocation dipoles moving towards each other on the same slip plane. Additionally, TQC remains relatively insensitive to variations in temperature and strain rate over a broad range, challenging prior assumptions and expanding the understanding of plastic heating mechanisms.

Multiscale study of dynamic mode-I fracture characteristics of thermally treated granite: Comparison of conventional and microwave heating

High-temperature-assisted rock breaking is a promising technique, with conventional and microwave heating being widely used methods. Understanding the mechanisms of conventional and microwave heating on the dynamic mode-I fracture characteristics of rock is crucial for engineering applications. Dynamic mode-I fracture experiments were conducted on Notched Semi-Circular Bending (NSCB) specimens at 25, 200, 300, 400, and 500 °C under both heating methods. Additionally, a finite element-discrete element coupled numerical method was developed to simulate the dynamic mode-I fracture process in high-temperature granite. The study investigated the effects of both heating methods on the fracture process and morphological features of the rocks, revealing differences in damage mechanisms across various scales. Results indicated that both heating methods similarly influence the fracture toughness of granite, with fracture toughness initially remaining nearly unchanged and then rapidly decreasing, with 200 °C identified as the threshold temperature. Moreover, the fractal dimension increased exponentially with temperature. The fracture mechanisms associated with conventional and microwave heating were also discussed.

Heating pattern and effects of built-up land in response to influencing factors: A statistical estimation of 172 Chinese cities

The increase of the land surface temperature (LST) caused by an urban expansion poses a great threat to the humanity and society. However, the heating characteristics of built-up land and the environmental impacts on these mechanisms remain poorly understood over large areas. Therefore, the change trend (k) and structural distribution of LST during the process of increasing the built-up area in 172 cities in China was quantified. Using correlation analysis and statistical methods to analyze the correlation and possible driving characteristics of influencing factors (climate, topography, land use type, and soil) on k. The results indicated that k varied from −5.955 to 8.240 and showed a spatial characteristic of small in the northwest and large in the southeast. The research emphasized the heating difference of built-up land varied significantly in cities with different natural environmental conditions, with the maximum difference reaching 6 °C. The heating mechanism of built-up land under the interference of influencing factors was explained from the perspective of land surface heat flux, and the mitigation strategies for urban temperature were proposed. Besides, the threshold for the impact of environmental factors on the heating of built-up land was found, which provides a reference for environment-adapted urban design and planning standards tailored by considering the specific characteristics of each city.

A Novel Battery Temperature-Locking Method Based on Self-Heating Implemented with an Original Driving Circuit While Electric Vehicle Driving: A Numerical Investigation

In extremely cold environments, when battery electric vehicles (BEVs) are navigating urban roads at low speeds, the limited heating capacity of the on-board heat pump system and positive temperature coefficient (PTC) device can lead to an inevitable decline in battery temperature, potentially falling below its permissible operating range. This situation can subsequently result in vehicle malfunctions and, in severe cases, traffic accidents. Henceforth, a novel battery self-heating method during driving is proposed to maintain battery temperature. This approach is ingeniously embedded within the heating mechanism within the motor driving system without any necessity to alter or modify the existing driving circuitry. In the meantime, the battery voltage can be regulated to prevent it from surpassing the limit, thereby ensuring the battery’s safety. This method introduces the dead zone into the space vector pulse width modulation (SVPWM) algorithm to form the newly proposed dSVPWM algorithm, which successfully changes the direction of the bus current in a PWM period and forms AC, and the amplitude of the battery alternating current (AC) can also be controlled by adjusting the heating intensity defined by the ratio of the dead zone and the compensation vector to the original zero vector. Through the Simulink model of the motor driving system, the temperature hysteresis locking strategy, grounded in the field-oriented control (FOC) method and employing the dSVPWM algorithm, has been confirmed to provide controllable and sufficiently stable motor speed regulation. During the low-speed phase of the China Light Vehicle Test Cycle (CLTC), the battery temperature fluctuation is meticulously maintained within a range of ±0.2 °C. The battery’s minimum temperature has been successfully locked at around −10 °C. In contrast, the battery temperature would decrease by a significant 1.44 °C per minute without the implementation of the temperature-locking strategy. The voltage of the battery pack is always regulated within the range of 255~378 V. It remains within the specified upper and lower thresholds. The battery voltage overrun can be effectively avoided.

Discrimination of vibrational modes in Ni2MnGa thin films

Vibrational properties in magnetic shape memory alloys are intrinsically connected to the topologies formed due to temperature-dependent breakdown of symmetry. In this sense, herein, we apply Raman spectroscopy in the study of Ni2MnGa films prepared by sputtering on glass and gallium arsenide substrates. Different laser wavelengths probe the Raman active vibrational modes. The non-equilibrium heating mechanisms of the electronic lattice induced by excitation laser power within the thermal penetration depth are used to explain the formation of higher order vibrational modes resulting from phonon-assisted intra-band electronic excitations. The discrimination of the Raman active modes is performed based on calculations carried out within the framework of the density functional theory considering the coexistence of austenite and martensite phases as a function of temperature in films with different crystalline textures and residual stresses. More importantly, this work presents a simple way to discriminate the vibrational modes of the austenite and martensite phases in Ni2MnGa thin films that can be easily applied in the nanodevice development process.

A Data-constrained Analysis for Joule Heating as a Solar Active Region Atmosphere Heating Mechanism. I. Sunspot Umbral Light Bridge

Understanding the mechanisms underlying the heating of the solar atmosphere is a fundamental problem in solar physics. The lower atmosphere of the Sun (i.e., photosphere and chromosphere) is composed of weakly ionized plasma. This results in anisotropic dissipation of electric currents by Coulomb and Cowling resistivities. Joule heating due to dissipation of currents perpendicular to the magnetic field by Cowling resistivity has been demonstrated to be the main mechanism for the heating of a sunspot umbral light bridge located in NOAA AR 12002 on 2014 March 13. Here, we focus on the same target region and demonstrate the importance of further constraining our Joule heating model using observational data in addition to magnetic field, namely plasma temperature calculated from the inversion of spectroscopic data obtained from the Interferometric BI-dimensional Spectrometer instrument of the ground-based Dunn Solar Telescope. As a parameter in our analysis, temperature is demonstrated to have the highest sensitivity after magnetic field. We show that the heating of the light bridge is a highly dynamic event that necessitates utilization of 3D spatially resolved observational data for temperature rather than a 1D temperature stratification based on theoretical/semiempirical solar atmosphere models. Our improved data-constrained analysis using spatially resolved temperatures shows that the entire light bridge is heated by the proposed mechanism, and yields heating rate values that are consistent with our previous study.

Thermosensitive Liposomes for Gemcitabine Delivery to Pancreatic Ductal Adenocarcinoma.

Treatment of pancreatic ductal adenocarcinoma with gemcitabine is limited by an increased desmoplasia, poor vascularization, and short plasma half-life. Heat-sensitive liposomes modified by polyethylene glycol (PEG; PEGylated liposomes) can increase plasma stability, reduce clearance, and decrease side effects. Nevertheless, translation of heat-sensitive liposomes to the clinic has been hindered by the low loading efficiency of gemcitabine and by the difficulty of inducing hyperthermia in vivo. This study was designed to investigate the effect of phospholipid content on the stability of liposomes at 37 °C and their release under hyperthermia conditions; this was accomplished by employing a two-stage heating approach. First the liposomes were heated at a fast rate, then they were transferred to a holding bath. Thermosensitive liposomes formulated with DPPC: DSPC: PEG2k (80:15:5, mole%) exhibited minimal release of carboxyfluorescein at 37 °C over 30 min, indicating stability under physiological conditions. However, upon exposure to hyperthermic conditions (43 °C and 45 °C), these liposomes demonstrated a rapid and significant release of their encapsulated content. The encapsulation efficiency for gemcitabine was calculated at 16.9%. Additionally, fluorescent analysis during the removal of unencapsulated gemcitabine revealed an increase in pH. In vitro tests with BxPC3 and KPC cell models showed that these thermosensitive liposomes induced a heat-dependent cytotoxic effect comparable to free gemcitabine at temperatures above 41 °C. This study highlights the effectiveness of the heating mechanism and cell models in understanding the current challenges in developing gemcitabine-loaded heat-sensitive liposomes.

Evolutionary distribution and mode transition in medium frequency from 50 kHz to 5 MHz of argon atmospheric pressure dielectric barrier discharge plasma

Dielectric barrier discharges (DBDs) provide a promising technology for generating non-equilibrium cold plasmas at atmospheric pressure. For both application-focused and fundamental research, it is important to explore the discharge mode transition and electron heating mechanism to enable effective independent tuning of key plasma parameters in a DBD system. In this work, we report numerical studies of the effects of single-frequency excitation on atmospheric argon DBDs, which are carried out in the medium driving frequency (MF) range from 50 kHz to 5 MHz by using a one-dimensional hydrodynamics coupling model. The spatio-temporal evolution of particle density associated with the discharge mode transition and electron dynamic behavior has been investigated. By tuning different components of a single frequency, we observe the electron heating behaviors of the individual modes and mode transitions from the Townsend discharge to the glow discharge in the low frequency to the Ω mode and the hybrid mode in the medium frequency to the α-mode and the γ-mode in the radio frequency. The physical analysis is understood based on these fundamental insights into the plasma physics.

A simple load model based on hybrid mechanism and data-driven approach for district heating in building complex

Accurate prediction of heating loads in district heating systems is essential for the implementation of demand-driven heating. This work presents a novel heating load prediction model that is particularly suitable for complex multi-user buildings. The input characteristics of the model are established through the heat transfer mechanism, considering factors such as the cumulative impact of outdoor temperature and user demand (indoor temperature). The specific form of the heating load function is determined using the MLR-PSO (Multiple Linear Regression-Particle Swarm Optimization) method. Only the indoor and outdoor temperatures need to be provided for the model to calculate future heating loads. Practical engineering tests demonstrated that the model achieved normalized mean bias errors of daily loads between 4.98 % and 5.54 % across different heating seasons, with a minimum annual relative deviation of 0.75 % for annual loads. Additionally, the model helps guide the operation of heating systems. For example, during the 2021–2022 heating season, setting the target indoor temperature at 18 °C reduced weekly energy consumption by 15.3 % compared to the previous season. This approach may be employed to construct a simple load model for existing heating systems to accurately predict both short-term and long-term loads, providing valuable insights into the management and control of heating systems.

Recent Applications of Photothermal Conversion in Organic Synthesis.

Photothermal conversion is a novel heating method that has emerged in recent years, wherein certain species can convert light to heat with great efficiency. These photothermal agents have shown immense promise for generating nanoscale thermal gradients under mild, visible light irradiation, providing a pathway for combining photochemistry with thermally driven reactivity. While this novel heating mechanism has been leveraged to great effect for applications such as photothermal therapeutics and steam water purification, it has seen limited use in organic synthesis. This outlook explores instances wherein the photothermal effect was used directly or as a synergistic component to drive organic reactions and postulates how it may be used moving forward.

Modeling Transition Region Hot Loops on the Sun: The Necessity of Rapid, Complex Spatiotemporal Heating and Nonequilibrium Ionization

The study examines the heating profile of hot solar transition region loops, particularly focusing on transient brightenings observed in IRIS 1400 Å slit-jaw images. The findings challenge the adequacy of simplistic, singular heating mechanisms, revealing that the heating is temporally impulsive and requires a spatially complex profile with multiple heating scales. A forward-modeling code is utilized to generate synthetic Interface Region Imaging Spectrograph (IRIS) emission spectra of these loops based on HYDRAD model output, confirming that emitting ions are out of equilibrium. The modeling further indicates that density-dependent dielectronic recombination rates must be included to reproduce the observed line ratios. Collectively, this evidence substantiates that the loops are subject to impulsive heating and that the components of the transiently brightened plasma are driven far from thermal equilibrium. Heating events such as these are ubiquitous in the transition region, and the analysis described above provides a robust observational diagnostic tool for characterizing the plasma.

Fiber laser tuning by means of nonthermal plasma as a temperature regulator

AbstractThis work presents a technique to obtain wavelength tuning for a fiber laser with a nonthermal plasma‐based temperature regulator system and a fiber Bragg grating (FBG). The plasma effect was generated in a dielectric barrier discharge (DBD) reactor filled with helium as the carrier gas for plasma generation. The temperature characterization of the DBD reactor had shown that the nonthermal heating mechanism of plasma could manipulate gas temperature from 25°C to around 145°C in ~10 min. By exploiting the rapid temperature change of plasma, the reflected wavelength of the FBG can be tuned accordingly. At a discharge voltage of 3 kV, the fiber laser was tuned within a range of 2 nm with 11.9 pm/°C tuning resolution. The fiber laser exhibits a thermally stable emission with very low shifting at a constant temperature value.

On the Intermittency of Hot Plasma Loops in the Solar Corona

A recent analysis has suggested that the heating of plasma loops in the solar corona depends not just on the Poynting flux but also on processes yet to be identified. This discovery reflects and refines earlier questions such as, Why and how are entire hydromagnetic structures only intermittently loaded with bright coronal plasma? The present work scrutinizes more chromospheric and coronal data, with the aim of finding reproducible observational constraints on coronal heating mechanisms. Six independent scans of chromospheric active-region magnetic fields are investigated and correlated to overlying hot plasma loops. For the first time, the footpoints of over 30 bright plasma loops are thus related to scalar proxies for the Poynting fluxes measured from the upper chromosphere. Although imperfect, the proxies all indicate a general lack of correlation between footpoint Poynting flux and loop brightness. Our findings consolidate the claim that unobserved physical processes are at work, which govern the heating of long-lived coronal loops.

Thermodynamics of Alfvénic slow solar wind produced by Alfvénic turbulence

ABSTRACT Alfvén-wave turbulence is known as a plasma heating mechanism associated with the acceleration of fast solar wind, found emanating from open magnetic fields adjacent to coronal holes. In this study, we expand the scope of this mechanism to investigate the thermodynamics of Alfvénic slow solar wind, a phenomenon originating from open fields near a streamer, as observed in recent inner heliospheric missions. We demonstrate a one-dimensional two-fluid model that incorporates three components: (1) low-frequency Alfvén-wave turbulence, serving as the primary dissipation mechanism, (2) a curved magnetic field that reproduces the streamer’s boundary, and (3) the kinetic instabilities to address proton temperature anisotropy. Our findings suggest that this dissipation mechanism can be applied in common to both fast and Alfvénic slow solar winds. We identify the proton-cyclotron instability near the Sun and the oblique and parallel firehose instabilities occurring close to 1 au as crucial factors governing temperature anisotropy. This study contributes to our understanding of the complex thermodynamics of solar winds and provides valuable insights for future space missions.

Effect of temperature and particle size on dielectric property of vanadium-titanium magnetite

The current body of research on microwave-assisted grinding of vanadium-titanium magnetite (VTM) predominantly focuses on the analysis of changes in particle size and dissociation degree of the grinding products. Nonetheless, the microwave heating mechanism of the ore remains inadequately explored. In this study, the dielectric property of VTM with different particle sizes were measured at a frequency of 2.45 GHz and temperatures ranging from ambient to 800 °C. The results indicate that the dielectric constants (ε′) and dielectric loss factors (ε″) of VTM increase with temperature. The loss tangent coefficients (tan δ) initially increase and then decrease, reaching a maximum value of 0.44 at approximately 500 °C. The values of dielectric property parameters increase as the particle size decreases. By calculating the penetration depth equation, it can be determined that the optimal particle size for uniform heating in microwave of VTM is approximately 15 ∼ 30 mm. The heating rate of the ore in the microwave field is divided into two stages. Initially, the heating rate is very fast due to the ore being a strong magnetic mineral. However, when the ore temperature reaches 500 °C, the tan δ of the ore decreases, leading to a decrease in the heating rate.

Temperature-reducing shocks in optically thin radiative MHD—Analytical and numerical results

Shocks are often invoked as heating mechanisms in astrophysical systems, with both adiabatic compression and dissipative heating that leading to the increase in temperature. While shocks are reasonably well understood for ideal magnetohydrodynamic (MHD) systems, in many astrophysical plasmas, radiation is an important phenomena, which can allow energy to leave the system. As such, energy becomes non-conservative, which can fundamentally change the behavior of shocks. The energy emitted through optically thin radiation post-shock can exceed the thermal energy increase, resulting in shocks that reduce the temperature of the medium, i.e., cooling shocks that have a net decrease in temperature across the interface. In this paper, semi-analytical solutions for radiative shocks are derived to demonstrate that both cooling (temperature decreasing) and heating (temperature increasing) shock solutions are possible across the whole temperature range in optically thin radiative MHD. Numerical simulations of magnetic reconnection for solar-like temperatures and plasma-β with optically thin radiative losses also yield both heating and cooling shocks in roughly equal abundances. The detected cooling shocks feature a significantly lower pressure jump across the shock than their heating counterparts. The compression at the shock front leads to locally enhanced radiative losses, resulting in significant cooling within a few grid cells in the upstream and downstream directions. The presence of temperature-reducing (cooling) shocks is critical in determining the thermal evolution, and heating or cooling, across a wealth of radiative astrophysical plasmas including magnetic reconnection in the solar corona.

Microwave irradiation-induced deterioration of rock mechanical properties and implications for mechanized hard rock excavation

In this study, a novel microwave-water cooling-assisted mechanical rock breakage method was proposed to address the issues of severe tool wear at elevated temperatures, poor rock microwave absorption, and excessive microwave energy consumption. The investigation object was sandstone, which was irradiated at 4 kW microwave power for 60 s, 180 s, 300 s, and 420 s, followed by air and water cooling. Subsequently, uniaxial compression, Brazilian tension, and fracture tests were conducted. The evolution of damage in sandstone was measured using active and passive nondestructive acoustic detection methods. The roughness of the fracture surfaces of the specimens was quantified using the box-counting method. The damage mechanisms of microwave heating and water cooling on sandstone were discussed from both macroscopic and microscopic perspectives. The experimental results demonstrated that as the duration of the microwave irradiation increased, the P-wave velocity, uniaxial compressive strength (UCS), elastic modulus (E), tensile strength, and fracture toughness of sandstone exhibited various degrees of weakness and were further weakened by water cooling. Furthermore, an increase in the microwave irradiation duration enhanced the damaging effect of water cooling. The P-wave velocity of the sandstone was proportional to the mechanical parameters. Microwave heating and water cooling weakened the brittleness of the sandstone to a certain extent. The fractal dimension of the fracture surface was correlated with the duration of microwave heating, and the water-cooling treatment resulted in a rougher fracture surface. An analysis of the instantaneous cutting rate revealed that water cooling can substantially enhance the efficiency of microwave-assisted rock breakage.

Plasma heating characterization of the large area inductively coupled plasma etchers with the plasma information for managing the mass production

Meter-scale of the large area inductively coupled plasma etchers with the capacitive power coupling are widely applied for the mass production of OLED (organic light emitting diode) display panels. Because of the large area-to-volume ratio of the etcher, the balance between the power loss and absorption is easily located in the capacitive coupling mode rather than the ideal inductively coupled mode. Therefore, the process results are sensitively governed by the power absorption and plasma heating properties of the reactors. We have introduced a new PI (plasma information) parameter, the ratio of the stochastic heating to Ohmic heating of the plasmas, which is monitorable by using the optical emission spectroscopy data of the processing etchers. With the help of this plasma heating characteristic index, we could optimize the process recipes with the detailed control of the etched hole sidewall passivation and related species generation rate in the plasmas; thus, chamber-to-chamber matching in the huge mass production fab with the higher efficiency was possible. It was demonstrated that the introduced PI index with plasma heating mechanism characterization could be applicable to the VM (virtual metrology) modeling as one of the good information supplying core variables. This PI index has shown a very high correlation with the plasma sheath and ion flux governing phenomena for a large number of mass-produced OLED display glasses. From these results, the introduced plasma heating mechanism-based PI index is expected to be utilized as a good reference index for their performance analysis or PI-VM modelings.

Rancang Bangun Alat Pengemas Biji Kopi Otomatis Berbasis Arduino Uno

Before coffee products are marketed, packaging is generally carried out first. Apart from protecting against damage, the packaging also aims to make it easier to carry while traveling. The conventional packaging process is quite time and energy consuming. This results in the packaging process being less efficient. With an automatic packaging system, it is hoped that it will make things easier and save time and energy. Automatic coffee bean packaging tools are built using several electronic devices. Arduino Uno is used as a controller, a load cell sensor to weigh the coffee packaging, a DS18B20 temperature sensor to measure the temperature of the packaging sealer and a proximity sensor to detect plastic packaging. In the actuator section, a servo motor is used to open the coffee bean reservoir valve (hopper tank), a DC motor is used to pull the packaging plastic and a stepper motor is used to press the packaging plastic. The plastic press is equipped with a heating mechanism using nickel wire so that the two layers of plastic can stick together. An LCD module is used to display information on the weight value of the coffee packaging, the temperature value of the sealer and the status of the packaging process. From the test results, it is known that the coffee bean packaging tool is capable of packaging coffee beans automatically. Coffee beans can be packaged in plastic with the weight and length of the packaging according to the design with a success rate of up to 87.5%