Increase In Temperature Gradient Research Articles

Comparison of effect of inhaled anaesthetic (Sevoflurane) versus intravenous (Propofol) anaesthetic on core and peripheral body temperature during general anaesthesia: A randomised control study

: The fall in core body temperature and peripheral body temperature following the administration of anaesthetic agent has been studied and demonstrated so far, along with the comparison of the same parameters following induction with propofol in contrast to that with sevoflurane. But no study so far, has compared the effects of TCI-propofol based anaesthesia with that of sevoflurane based anaesthesia for induction and maintenance, on core and peripheral body temperature and the gradient of temperature between the agents. The studies conducted so far, has shown more fall in core and peripheral body temperature from their respective baseline values when propofol was used for induction of anaesthesia in comparison to the use of sevoflurane. A total of 60 adults were randomized into two groups of 30 each; Group 1 were induced with TCI- propofol at 8mcg/ml plasma concentration and maintaind with TCI-propofol at 2-3mcg/ml plasma concentration and 66% nitrous oxide and 33% oxygen gas mixture. Group 2 were induced with intravenous thiopentone at 3-5mg/kg body weight and maintained with 1-1.5MAC sevoflurane, 66% nitrous oxide and 33% oxygen gas mixture. Core body temperature was measured inserting the temperature probe into nasophraynx and peripheral temperature was measured with the temperature probe inserted onto thenar eminence of either hand. We observed that both anaesthetic agents have caused similar fall in core temperature. However, peripheral temperature fell more with sevoflurane compared to TCI-propofol. In parallel with these observations, the increase in temperature gradient was higher in magnitude for sevoflurane based anaesthesia. The core temperature was comparable between the groups from their respective baseline values. But, the fall in peripheral temperature was more in sevoflurane group, so was the temperature gradient. Thus, TCI-propofol when used in appropriate plasma concentration for induction and maintenance of anaesthesia causes less hypothermia in contrast to sevoflurane.

Simultaneous film temperature and film thickness measurements for jet impingement applications using two-color laser-induced fluorescence

The study investigates a jet impingement cooling process of a cylindrical geometry relevant for electric and electronic applications. The applied two-color detection technique enables a simultaneous determination of film temperature and film thickness. For this purpose, the heat transfer oil Marlotherm LH was doped with the temperature-sensitive fluorescence tracer nile red. The temperature determination was realized by suitable band pass filters. Preliminary spectral investigations were carried out in terms of varying dye concentration, temperature and film thickness. At high dye concentrations (up to 37.5 mg/L), reabsorption effects lead to a spectral shift toward higher wavelengths with increasing film thickness. Low dye concentrations (0.29 mg/L, 0.59 mg/L) show no film thickness dependent spectral shift. A film temperature investigation at low dye concentration showed no bias of the intensity ratio due to film thickness, i.e., no additional spectral shift toward lower wavelengths was observed. The investigations on the jet impingement setup revealed an increasing film temperature and decreasing film thickness with increasing solid temperature. The average film temperature increases with increasing solid temperature from 298 (solid temperature 298 K) to 308 K (solid temperature 398 K). At higher solid temperatures, the film temperature increases with distance to the stagnation zone. The average film thickness decreases with increasing solid temperature from 0.24 to 0.17 mm. At high solid temperatures, the film temperature increased with radial distance to the stagnation zone. This behavior is caused by the increasing temperature gradient with increasing solid temperature and decreasing viscosity with increasing film temperature.

Detection of Internal Transport Barrier in the T-10 Tokamak Using Thomson Scattering Diagnostics

At the T-10 tokamak, the Thomson scattering diagnostics was upgraded in 2016. The new system is based on the Nd:YAG laser with the pulse repetition frequency of 100 Hz; the measurements can be performed every 10 ms during the entire plasma discharge at the spatial resolution of up to 5 mm. Using the upgraded diagnostics, the electron temperature measurements were performed during experimental campaigns of the T-10 tokamak in 2016−2018. In the regimes with the electron cyclotron resonance heating, it was demonstrated that the regions with increased temperature gradients form in the plasma, which was interpreted as the formation of internal transport barrier. The ASTRA-code-based simulations of the current profile time evolution made it possible to correlate the positions of the barrier and the rational surface q = 1.

A new look into the impacts of dust radiative effects on the energetics of tropical easterly waves

Abstract. Saharan dust aerosols are often embedded in tropical easterly waves, also known as African easterly waves, and are transported thousands of kilometers across the tropical Atlantic Ocean, reaching the Caribbean Sea, Amazon Basin, and eastern USA. However, due to the complex climate dynamics of west Africa and the eastern tropical Atlantic Ocean, there is still a lack of understanding of how dust particles may influence the development of African easterly waves, which are coupled to deep convective systems over the tropical Atlantic Ocean and in some cases may seed the growth of tropical cyclones. Here we used 22 years of daily satellite observations and reanalysis data to explore the relationships between dust in the Saharan air layer and the development of African easterly waves. Our findings show that dust aerosols not merely are transported by the African easterly jet and the African easterly waves system across the tropical Atlantic Ocean, but also contribute to the changes in the eddy energetics of the African easterly waves. The efficiency of the dust radiative effect in the atmosphere is estimated to be a warming of approximately 20 W m−2 over the ocean and 35 W m−2 over land. This diabatic heating of dust aerosols in the Saharan air layer acts as an additional energy source to increase the growth of the waves. The enhanced diabatic heating of dust leads to an increase in meridional temperature gradients in the baroclinic zone, where eddies extract available potential energy from the mean flow and convert it to eddy kinetic energy. This suggests that diabatic heating of dust aerosols can increase the eddy kinetic energy of the African easterly waves and enhance the baroclinicity of the region. Our findings also show that dust outbreaks over the tropical Atlantic Ocean precede the development of baroclinic waves downstream of the African easterly jet, which suggests that the dust radiative effect has the capability to trigger the generation of the zonal and meridional transient eddies in the system comprising the African easterly jet and African easterly waves.

Surface morphology evolution mechanisms of pulse laser polishing mold steel

In this study, high-frequency nanosecond pulse laser was conducted on mold steel surfaces for solving surface defects during polishing processes. The influence of different single-pulse energy densities on surface roughness was carefully investigated through technical experiments, with the lowest roughness obtained at 2.5 J/cm2. A computational fluid dynamics (CFD) model was developed to simulate the evolution of surface morphology at different energy densities. The applicability of the model was successfully verified by comparative experiments and simulative results. The evaporation threshold for nanosecond pulse laser polishing was found to be between 2.5 and 3.0 J/cm2. The introduction of evaporation and increased temperature gradients accelerate the flow of the melt pool, thereby leading to a shift in the driving force for fluid velocity. The short pulse cycle can create a continuous melt pool that moves with the laser beam, resulting in surface flattening along the scanning path. Under a large number of overlapping pulses, the surface over melting (SOM) mechanism dominated the morphology evolution of the molten pool. Significant findings demonstrated that pulse laser-induced heat accumulated to melt the peaks and valleys of the initial surface, while convective flow reduced the height difference of the melt pool. It can provide a new insight into surface roughness improvement of metals through nanosecond pulse laser polishing.

Исследование влияния химического состава воздушной среды на аэродинамику полета малых летательных аппаратов

The work is devoted to the study of the influence of an air environment with different chemical composition on the aerodynamics of small aircrafts of the airplane type used for reconnaissance purposes in case of fires. The thermodynamic properties of the combustion products formed during the combustion of rubber and foam rubber were calculated. The properties of the medium were taken into account in the mathematical modeling of the flight aerodynamics of an unmanned aerial vehicle. The mathematical model is based on solving conservation equations in a non-isothermal formulation for a turbulent viscous compressible flow using the k-ε turbulence model. The pressure and velocity fields of the environment were obtained during the flow around the wing, and the values of drag and lift forces were compared in the presence of combustion products in the air and without them. In particular, the numerical calculations were carried out in the presence of a vertical temperature gradient in the design area simulating the heating of air masses during fires with the study of the influence of these gradients on the aerodynamic characteristics of the wing. The calculations show that with an increase in the vertical temperature gradient by 60 K/m, the values of lift and drag decrease by 5 %.

Antarctic polar vortex dynamics in 2019 and 2020 under the influence of the subtropical stratosphere

The trend of strengthening of the Antarctic polar vortex in late spring and early summer (November–December) has been observed in recent decades. A good example of this trend is the dynamics of the Antarctic polar vortex in 2020 when it existed until the last week of December. In 2019, conversely, on the contrary, an unusually early breakup of the polar vortex occurred, a minor sudden stratospheric warming was recorded. Strengthening (or weakening) of the Antarctic polar vortex occurs as a result of an increase (or decrease) in the stratospheric meridional temperature gradient under conditions of growth (or decline) in the temperature of the lower subtropical stratosphere. We considered the temperature variations in the lower subtropical stratosphere in the spring of 2019 and 2020 and the corresponding response of the Antarctic polar vortex. The dynamics of the Antarctic polar vortex in September–October 2019 and November 2020 was largely synchronized with the temperature changes in the lower subtropical stratosphere relative to climatological means. Using correlation analysis, we show that the Antarctic polar vortex dynamics in December is largely due to the temperature changes in the lower subtropical stratosphere that occurred in the second half of November, which manifested itself in 2020.

Solidification behavior of Sn crystals − Under different temperature gradients

Lead-free solder alloys typically comprise β-Sn, known for its anisotropy. Our experiments revealed that under standard solidification conditions （Room temperature cooling）, characterized by an angular distribution spanning 20–60°, β-Sn crystals exhibited minimal nucleation and lacked a distinct optimal orientation. However, when a temperature gradient of 295 K/cm was applied during the solidification of β-Sn crystals, a conspicuous selective orientation emerged. This orientation favored the growth along the [110] grain axis. However, with the further increase in temperature gradient, a significant transition occurs in the growth mechanism of Sn crystals: multiple nucleation centers emerge, leading to dendritic crystal growth. With the further increase in temperature gradient, a significant transformation occurs in the growth mechanism of Sn crystals: multiple-nucleation centers emerge, leading to dendritic crystal growth, and subsequently transitioning towards equiaxed growth. Consequently, the expansion of the temperature gradient results in an increase in undercooling, triggering a series of changes in crystal growth patterns: the solidification front transitions from planar to dendritic growth and further to equiaxed growth. This is because, with the increasing prominence of undercooling, the transport of solutes from the tin solution to the tin melt diminishes. The atomic saturation in the tin melt decreases, causing a decline in the grain growth rate and promoting the formation of equiaxed crystals.

Effect of defects on flux expulsion of pure niobium superconducting radio frequency cavities via spatial temperature gradient

Since flux vortices are easily pinned by defects in superconducting radio frequency (SRF) cavities, trapped magnetic flux increases the surface resistance of the SRF cavity. It has been experimentally demonstrated that trapped magnetic flux can be expelled by cooling down a superconducting cavity under a large spatial temperature gradient. In this paper, we use the time-dependent Ginzburg–Landau (TDGL) theory to theoretically investigate the effect of defects on the flux expulsion ability of pure niobium superconducting cavities with an applied spatial temperature gradient. It is shown that the residual flux vortex density displays a notable stepwise decreasing trend with increasing temperature gradient at smaller residual fields, while it shows a stepwise rising with increasing defect size. Both larger defect number and size make vortices difficult to be expelled. Moreover, long cooling time is beneficial for vortices to be expelled, and the cooling time has nearly no significant effect on flux expulsion under conditions of large cooling times. The results in this paper provide some theoretical guidelines for improving the performance of superconducting cavities in practical situations.

Role of Q-heterochromatin and thermal conductivity of the human body in the development of obesity

Introduction and Aim: Obesity, commonly known as a complex multifactorial disease, has emerged as a significant medical and societal issue in recent decades. The objective of this study is to assess if there is a significant impact of Q-heterochromatin (Q-HR) and thermal conductivity (k) in the body on the risk of obesity. Methods: This prospective analytical cohort study included 300 individuals from both genders aged 35.24 4.21 years who do not have oncological, hormonal, or other forms of diseases that predispose to morbid obesity. Results: In obese individuals, the temperature distribution in the peripheral and central parts of the body has a high level of variability relative to the control. In the main group, Q HR has a clear gradient from 0 to 2, and the average numerical parameter is 1.21 0.11, which is more than twice as low as in the control group (2.94 0.14). In obese individuals, the chromatin concentration decreased with increasing temperature gradient (X2 = -16.8; p0.001). Conclusion: The level of Q-HR is considerably lower in obese people compared to the control group. When compared to the control, obese people had a higher k between the central and peripheral sections. The level of Q-HR and k were shown to be inversely correlated.

Subchannel thermal–hydraulic analysis of a wire-wrapped 19-pin rod bundle in the NACIE-UP facility

Based on the experimental campaign performed on the NACIE-UP (NAtural Circulation Experiment-Upgraded) facility, the benchmark activity was proposed by ENEA to qualify and validate the numerical tools for the Heavy Liquid Metal (HLM) system. Xi’an Jiaotong University participated in the benchmark exercise of subchannel validation and the self-developed subchannel code YAOGUANG was applied to the thermal hydraulic analysis. The performed two tests with different power distributions on the Fuel Pin bundle Simulator (FPS) were simulated, characterized by transition from forced to natural circulation. The applicability of this code to the stable state and mass flow rate transient was evaluated by comparing the numerical outcomes with the experimental results. Then the effect of the non-uniform heating on the thermal field was analyzed. The results indicate that this subchannel code has good accuracy in simulating both steady state and transient conditions with uniform power distribution. For the non-uniform case, the subchannel calculations can capture the general trend of temperature distributions, with a larger simulation deviation observed. This discrepancy is mainly due to the limitations of existing models adopted because they didn’t consider the impacts of non-uniform conditions on the flow and heat transfer in rod bundles. Finally, the influence of non-uniform heating is mainly manifested as the increase of axial and radial temperature gradients and it helps to flatten the radial thermal field to some degree.

Influence of thermal stratification on the transport of polydispersed expiratory particles

The fluid dynamics of expiratory events are complex, and understanding how indoor air conditions affect this and the spread of exhaled material is crucial to the prevention of large-scale spread of diseases. It is known that thermal stratification can trap contaminants in the lower levels of a room; however, there is a lack of studies that investigate the influence of vertical temperature gradients on the transport of expiratory particles at room scale. To this effect, we used Eulerian–Lagrangian large-eddy simulations to investigate the effect of thermal stratification on the transport of polydispersed expiratory particles during speaking in two different sized rooms. Cases with increasing temperature gradient were compared to an isothermal base case, and the influence of stratification on the exhalation jet and the particles suspended within is analyzed. The particle volume fraction was computed to quantify the spatiotemporal evolution of different particle size categories. Our results show that thermal stratification leads to an increased concentration of aerosols in the breathing zone and extends their forward reach. Aerosols up to a size threshold between 12 and 20 μm are locked up at different heights by stratification—beyond this threshold, they fall out continuously. In all cases, aerosols <20 μm traveled up to 4 m from the source, showing that physical distancing guidelines alone may be inadequate for controlling cross-infection risk for long-term exposures. Particles >60 μm are unaffected by stratification and do not follow a ballistic trajectory, falling out within 0.5 m of the infectious individual in all cases.

Exploring the Limits of Empirical Correlations for the Design of Energy Systems With Complex Fluids: Liquid Sulfur Thermal Energy Storage as a Case Study

Abstract Sustainable energy technologies often use fluids with complex properties. As an example, sulfur is a promising fluid for use in thermal energy storage (TES) systems, with highly nonlinear thermophysical properties. The viscosity of liquid-phase sulfur varies by four orders of magnitude due to polymerization of sulfur rings between 400 K and 500 K, followed by depolymerization of long rigid chains, and a decrease in viscosity, as temperature increases. These properties may compromise the accuracy of long-established empirical correlations in the design of TES systems. This work uses computational fluid dynamics to compute steady-state free convection heat transfer coefficients of sulfur in concentric cylinders at temperatures between 400 K and 600 K. The results show that uneven distributions of high and low-viscosity sulfur in the system cause variations in flow patterns and highly nonlinear heat transfer coefficients as temperature gradients increase. As a result, existing empirical correlations for describing system performance become inaccurate. Comparisons of simulation results to predictions from well-established literature correlations show that deviations may surpass 50%. Nusselt versus Rayleigh number correlations for heat transfer are significantly affected by the loss of self-similarity. The analysis proves that existing correlations are not able to capture the complex properties of sulfur in this temperature range, suggesting that alternative modeling techniques are needed for the design and optimization of sulfur TES systems. These challenges are unlikely to be limited to sulfur as a working fluid or TES but will appear in a range of energy systems.

Achieving optimal magnetic flux expulsion of a Nb3Sn superconducting radio-frequency cavity via spatial temperature gradient

The trapped magnetic flux leads to residual resistance, thereby reducing the quality factor of the superconducting cavity and affecting its power consumption. It has been experimentally shown that the trapped magnetic flux of the superconducting radio-frequency cavity can be expelled during cooldown under a spatial temperature gradient. In the present paper, we simulate the magnetic flux expulsion behavior during the cooling process of a Nb3Sn superconducting cavity using time-dependent Ginzburg-Landau (TDGL) theory. In order to achieve optimal magnetic flux expulsion, the effect of grain size, grain boundary strength |ψ|GB, and cooling time on flux expulsion ratio ε for different temperature gradients are studied theoretically. The results show that ε first increases rapidly and then varies slightly to a steady value with increasing temperature gradient, which is in good agreement with the experimental results. In general, for larger |ψ|GB, ε decreases with increasing grain size. While for smaller |ψ|GB, ε first increases to the maximum then decreases with increasing grain size. Moreover, It is found that a larger cooling time is more beneficial for the expulsion of the flux vortices from the sample. The results of this paper The vortex dynamics behavior can give an insight into the mechanism of magnetic flux expulsion, which can provide a theoretical basis for further enhancing the performance of superconducting cavities.

Steam-side heat transfer analysis in spirally corrugated tube for grate furnace superheater

In the case of low Reynolds number, the structure of the spirally corrugated tube will make the solid particles in the fluid be affected by the centrifugal force, and be more evenly distributed in the fluid to achieve anti-fouling effect. Therefore, it can be used in heat exchangers with serious fouling problems to improve heat exchange efficiency. In this paper, the first stage low-temperature superheater in the grate furnace is selected as application equipment. The local resistance coefficient, local Nusselt number and local heat flux are analyzed, the thermal-hydraulic characteristics of different sample points are evaluated. Combinatorial method of central composite design and Latin hypercube design is used to select four representative sample points, and effect of the corrugation pitch ratio and depth ratio on the convective heat transfer intensity, fluid resistance and fluid work consumption of the steam side is studied. The research results show that as the corrugation depth increases, the local heat transfer coefficient in the circumferential direction increases, and more heat is transferred from the flue gas to the steam, but the pump power consumed in the flow process has also increased. Due to the existence of spiral structure, the local heat flux density of the wall is symmetrically distributed in the circumferential direction, which represents that the temperature gradient increases, and the heat flow is improved.

Revealing thermal behavior, cracking behavior, phase and microstructure formation of a ternary equiatomic alloy additively manufactured using directed energy deposition

Additive manufacturing (AM) of multi-principal element alloys (MPEAs) has recently attracted considerable attention. However, few studies focus on the thermal behavior, cracking behavior, and microstructure tunability of AM-processed MPEAs, which can significantly affect the final performance of AM MPEA parts. In this study, a ternary equiatomic MPEA CrCoNi, with a single-phase face-centered-cubic (FCC) structure, was fabricated by the AM process via directed energy deposition (DED) at different laser scan speeds (10, 30, and 50 mm/s), and special focus was given to the thermal behavior, cracking behavior and microstructure formation. The increase in the laser scan speed from 10 to 50 mm/s causes a sharp increase in temperature gradients and cooling rates by five-fold and seventeen-fold, reaching up to 1148 K/mm and 57,778 K/s, respectively, as in-situ measured by a high-speed and high-resolution thermal pyrometer. Furthermore, the increased laser scan speed induces the severe cracking, which propagates along high angle grain boundaries and is classified as solidification cracking based on the observed protruding dendrites from the cracked plane. Although the Scheil-Gulliver solidification predicts a very narrow critical temperature range of 16 K which is indicative of a low solidification cracking susceptibility, the high temperature gradient and the resulting high thermal stress, as evidenced from the high density of dislocations and stacking faults, are believed to trigger the severe solidification cracking of the CrCoNi MPEA deposited at a high laser scan speed of 50 mm/s. With increasing the laser scan speed, the grain structure changes from elongated grains, which are roughly oriented along the build direction, to a more heterogenous grain structure with elongated grains converging towards the centerline and equiaxed grains arranged between the columns of elongated grains. Furthermore, with increasing the laser scan speed, the cellular structures are refined down to ∼ 2 µm due to the increased cooling rates. These findings not only contribute to better understanding the thermal behavior, cracking behavior, and microstructure formation of the AM-processed MPEAs, but also pave a road for further enhancing the mechanical properties of AM parts via tuning the thermal behavior and microstructures.

Modeling and Simulation of a High Temperature Proton Exchange Membrane Fuel Cell

High temperature (HT) (around 120-200°C) PEM FCs are predicted to be the next generation of PEMFCs particularly for hydrogen-powered automobiles and combined heat and power (CHP) systems because the water management can be simplified at such temperatures as only a single phase of water vapor needs to be considered. Additionally, the cooling system can be streamlined due to an increase in temperature gradient between the coolant and the FC stack. This will also allow easy recovery of waste heat that can be used as a practical heat source. Furthermore, the CO tolerance improves dramatically at high temperatures thereby allowing HT PEMFCs to utilize reformed and impure hydrogen.A single phase three-dimensional, steady-state, isothermal model for a single 5 HT PEM fuel cell with serpentine flow channels is implemented in COMSOL to investigate the effect of various operating conditions like temperature, back pressure and cathode flow rate and design parameters like catalyst layer loading, cathode GDL porosity, and flow field channels including parallel and interdigitated channels. Different performance indicators in terms of polarization curve, loss mechanisms, oxygen molar concentration, and anode and cathode pressure are represented for a complete overall analysis. In fact, the breakdown of different overpotential loss mechanism for HT PEMFC presented here is unique that not only quantifies these losses but also provides an accurate comparison with corresponding low temperature counterpart. The result from the computational model follows the experimental result very closely, thus, validating our model. The simulations stipulates that the performance of a HT PEMFC improves with increasing temperature, back pressure, and air flow rate. Increasing catalyst layer loading improves the performance up to a point after which it starts to drop at low voltages because of hindered gas diffusion. Similarly, a comparative study among different flow field channel is also presented indicating improved performance when going from parallel to interdigitated and serpentine channels. Furthermore, this study provides guidelines to optimize HT PEMFC performance through comprehensive parametric study.

Effect of hydrogen pressure on pore growth and microstructure of GASAR porous Mg–Ag eutectic alloys

In order to study the effect of hydrogen, as a third non-metallic component, on the macroscopic pore growth and eutectic solidification structure in the directional solidification process, GASAR porous Mg–Ag eutectic alloy ingots were prepared by mould casting technology at different hydrogen pressures. The results show that with an increasing hydrogen pressure, the increased temperature gradient promotes the nucleation and growth of pores; for the microstructure, the increased temperature gradient cause an increasing driving force for solidification structure growth, which leads to the instability of the eutectic cells, and the eutectic structure transitions from lamellar to rod-like.

Warping deformation of the track slab and their influence on the interlayer stiffness and vibration transmission characteristics of the unit ballastless track

The unit ballastless track partially segments the concrete track bed in the longitudinal direction, and relieves the concrete temperature stress by isolating the upper and lower layers. However, the layer isolation leads to the incompatible deformation of the upper and lower track structures under the effect of the temperature gradient. A large temperature gradient on the track slab will cause local contact between layers, the contact area between layers will then decrease, thus leading to “stiffness softening” between layers. When the vehicle passes, the contact area between layers will gradually increase, which, in turn, leads to “stiffness hardening”. The analysis results show that the greater the design stiffness between layers, the more significant the “stiffness softening” effect will be under the temperature gradient. When k0 = 400 × 106 (N·m−1)·m−2 and Tg = 90 °C·m−1, the interlayer stiffness decreases by 88%.The simulation analysis results of the wheel-drop impact test show that under a positive temperature gradient, the peak value of rail vibration acceleration increases, and the peak value of the track slab and base plate vibration acceleration decreases. The greater the stiffness designed between layers, the more obvious the influence will be. With the increase of the positive temperature gradient, the vibration acceleration of the rail and the track slab will be reduced in the 1–30 Hz and 40–100 Hz frequency domains. With the increase of the negative temperature gradient, the vibration acceleration of the rail in the 4–10 Hz, 20–50 Hz frequency domains, and the vibration acceleration of the track slab in the 70–200 Hz frequency domains will be increased. A large positive temperature gradient inhibits the transmission of high-frequency vibrations above 40 Hz to the substructure, while a negative temperature gradient inhibits the transmission of low-frequency vibrations within 30 Hz and 70–200 Hz to the substructure. A positive temperature gradient is beneficial to restrain the downward transmission of low-frequency vibration. When k0 = 200 × 106 (N·m−1)·m−2, the low-frequency vibration transmission loss of the track slab to the base plate is close to 0 dB without temperature gradient, but the positive temperature gradient increases the transmission loss by about 10 dB, the greater the temperature gradient, the higher the transmission loss of the track slab to the base plate under high stiffness.

Response of high-altitude clouds to the galactic cosmic ray cycles in tropical regions

Galactic cosmic rays are one of the possible mediators of the solar influence on climate. However, the impacts of GCR on clouds and climate systems are not fully understood. In this paper, we show that the high-altitude clouds associated with deep convective activities are responding to the decadal-scale cycles of GCRs and that the susceptible areas are seasonally variable. Most notable responses were found in August over tropical land areas, suggesting that the susceptivity of clouds to GCRs depends on the depth of convective activities and the abundance of aerosol precursor materials. Furthermore, following the activation of high-altitude cloud formation, an increase in sea surface temperature (SST) gradient was observed over the Pacific. Although the response of sea surface temperature to solar activity has mostly been discussed as mediated by solar radiations, we propose that another mechanism is possible: through the impact of GCRs on clouds and the resultant changes in atmospheric circulations.