Temperature Dependence Of Time Research Articles

Relaxation in non-Markovian models: From static to dynamic heterogeneity

Glass transition processes have often been explained in terms of wide distributions of relaxation times. By means of a simple stochastic model we here show how dynamic heterogeneity is the key to the emergence of the glass transition. A non-Markovian model representing a small open region of the amorphous material was previously shown to reproduce the time and thermal characteristic behavior of supercooled liquids and glasses. Due to the interaction of the open regions with their environment, the temperature dependence of the equilibrium relaxation times differs from the featureless behavior of the relaxation times of closed regions, whose static disorder does not lead to a glass transition, even with wider distributions of equilibrium relaxation times. The dynamic heterogeneity of the open region produces a glass transition between two different regimes: a faster-than-Arrhenius and non-diverging growth of the supercooled liquid relaxation times and an average Arrhenius behavior of the ideal glass. The Kovacs’ expansion gap was studied by evaluating the nonequilibrium distribution of relaxation times after the temperature quenches.

Optical properties, concentration and thermal quenching of luminescence of Dy3+- doped La2O3-Na2O-ZnO-TeO2 glasses

Tellurite glasses of the chemical composition: xDy2O3-(7-x)La2O3–3Na2O-25ZnO-65TeO2, where (0 < x ≤ 7) were obtained by the melt quenching technique. The spectroscopic characteristic of Dy3+- doped title glasses was carried out based on absorption and luminescence spectra as well as luminescence decay kinetics measurements. The Judd-Ofelt intensity parameters Ωλ (λ= 2, 4, 6) have been evaluated from the absorption spectrum and subsequently used to calculate the spontaneous emission probabilities, luminescence branching ratios and radiative lifetime of 4F9/2 emitting level of Dy3+. The emission cross-sections for Dy3+ transitions in the visible range have been determined applying Füchtbauer-Ladenburg formula. The luminescence decay measurements revealed strong concentration quenching of Dy3+ emission. The non-exponential decay curves have been fitted in the frame of Inokuti-Hirayma model, indicating that the dipole-dipole interaction plays an important role in luminescence quenching of 4F9/2 level. The temperature dependence of luminescence decay times of 4F9/2 state of Dy3+ has been investigated.

Temperature dependence, accuracy, and repeatability of T1 and T2 relaxation times for the ISMRM/NIST system phantom measured using MR fingerprinting.

Before MR fingerprinting (MRF) can be adopted clinically, the derived quantitative values must be proven accurate and repeatable over a range of T1 and T2 values and temperatures. Correct assessment of accuracy and precision as well as comparison between measurements can only be performed when temperature is either controlled or corrected for. The purpose of this study was to investigate the temperature dependence of T1 and T2 MRF values and evaluate the accuracy and repeatability of temperature-corrected relaxation values derived from a B1 -corrected MRF-fast imaging with steady-state precession implementation using 2 different dictionary sizes. The International Society of MR in Medicine/National Institute of Standards and Technology phantom was scanned using an MRF sequence of 2 different lengths, a variable flip angle T1 , and a multi-echo spin echo T2 at 14 temperatures ranging from 15°C to 28°C and investigated with a linear regression model. Temperature-corrected accuracy was evaluated by correlating T1 and T2 times from each MRF dictionary with reference values. Repeatability was assessed using the coefficient of variation, with measurements taken over 30 separate sessions. There was a statistically significant fit of the model for MRF-derived T1 and T2 and temperature (p < 0.05) for all the spheres with a T1 > 500 ms. Both MRF methods showed a strong linear correlation with reference values for T1 (R2 = 0.996) and T2 (R2 = 0.982). MRF repeatability for T1 values was ≤1.4% and for T2 values was ≤3.4%. MRF demonstrated relaxation times with a temperature dependence similar to that of conventional mapping methods. Temperature-corrected T1 and T2 values from both dictionaries showed adequate accuracy and excellent repeatability in this phantom study.

Temperature Affects the Time Required to Discern the Relationship between Primary Production and Export Production in the Ocean

Knowledge of the relationship between net primary production (NPP) and export production (EP) in the ocean is required to estimate how the ocean’s biological pump is likely to respond to climate change effects. Here, we show with a theoretical food web model that the relationship between NPP and EP is obscured by the following phenomena: (1) food web dynamics, which cause EP to be a weighted average of new production (NP) over a previous temperature-dependent time interval that can vary between several weeks at 25 °C to several months at 0 °C and, hence, to be much less temporally variable than NP and (2) the temperature dependence of the resiliency of the food web to perturbations, which causes the return to equilibrium to vary from roughly 50 days at 0 °C to 5–10 days at 25 °C. The implication is that the relationship between NPP and EP can be discerned at tropical and subtropical latitudes if measurements of NPP and EP are averages or climatologies over a timeframe of roughly one month. At high latitudes, however, measurements may need to be averaged over a timeframe of roughly one year because the food webs at high latitudes are very likely far from equilibrium with respect to NPP and EP much of the time, and the model can describe only the average behavior of such physically dynamic systems.

Numerical Study on the Temporal Evolution of a Helicon Discharge

A numerical model is developed to study the temporal evolution of helicon discharge. The initiation of helicon discharge is first presented in terms of time-dependent electron density and temperature, electric and magnetic fields, and power deposition; then, their steady-state values are compared with experimental data and previous simulations for benchmark. It is found that the evolutions of electron density and temperature arrive steady state around 100 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.5~\mu \text{s}$ </tex-math></inline-formula> , respectively, while electric and magnetic fields become steady prior to 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> . The spatial distributions of power deposition indicate that RF power is absorbed mostly near the edge, similar to those of electron temperature. Parameter studies show that high background pressure, confining magnetic field strength, and RF power are beneficial to obtaining high-density helicon plasma, while the driving frequency has little effect. These findings are interesting for the design and optimization of helicon plasma source.

Preparation of a novel oligomer type compatibilizer for polypropylene/polystyrene blend

A polystyrene–g–2,2,6,6-tetramethylpiperidine 1-oxyl radical (PS–g–TEMPO) copolymer was formed during thermal-oxidative degradation of PS/hindered amine light stabilizer (HALS) under heat treatment by thermal equilibrium. The optimum preparation condition was identified at 150 °C for 21 h by assessment of the temperature and aging time dependences of the molecular weight and thermal properties. The optimized copolymer was reacted with polypropylene (PP). A PS–g–PP grafted copolymer-type compatibilizer was reactively prepared with the copolymer/PP at 200 °C melt mixing temperature. The tetrahydrofuran-soluble part of the PP/PS/PS–g–TEMPO blend was analyzed as the PS–g–PP copolymer. The PS–g–PP showed a broad melting peak in the range from 125 °C to 160 °C. The PP grafting ratio was approximately 4%, as calculated by pyrolysis gas chromatography mass spectrometry (Py-GC/MS) analysis. The reactive polymer blend of the PP/PS/PS–g–TEMPO showed significant improvement in mechanical properties and ductile fracture surface as compared with PP/PS. The HALS loading easily produced an excellent compatibilizer for PP/PS mechanical improvement.

Crystallization kinetics and molecular dynamics of binary coamorphous systems of nimesulide and profen analogs

Coamorphous drug delivery systems have emerged as a promising formulation technique for improving the solubility and oral bioavailability of poorly soluble drugs. The selection of a suitable coformer is the key to obtaining a successful coamorphous formulation. This study aims to investigate the impacts of coformers with similar chemical structures but different physical properties on the crystallization behavior and molecular dynamics of binary amorphous systems. The addition of three profen analogs, ibuprofen (IBU), ketoprofen (KETO) and indoprofen (INDO) leads to significantly different effects on the crystallization kinetics of amorphous nimesulide (NIME). The crystal growth rates for amorphous NIME are substantially accelerated in the presence of IBU, but drastically reduced in the presence of INDO, while the incorporation of KETO results in a negligible effect. Broadband dielectric spectroscopy is employed to characterize the molecular dynamics of neat amorphous NIME and coamorphous systems. The addition of three structural analogs alters the molecular mobility of amorphous NIME in different ways, which is consistent with the trend observed for their impacts on the crystallization kinetics, suggesting that the relative mobility between the components of coamorphous mixtures governs the physical stability. In addition, it is found that the temperature dependence of the α-relaxation times for NIME with and without coformers is superimposed once the temperature is scaled by Tg/T, whereas the crystallization kinetics do not overlap on a Tg/T scale. This deviation can result from a complex interplay of thermodynamic and kinetic factors involved in multicomponent amorphous systems. This study provides insights into the crystallization kinetics and molecular dynamics of coamorphous systems containing drug analogs, which can potentially offer more flexibility for the control of physical stability without sacrificing therapeutic efficacy.

Investigation of Micromorphology and Carrier Recombination Dynamics for InGaN/GaN Multi-Quantum Dots Grown by Molecular Beam Epitaxy

InGaN quantum dots (QDs) are promising candidates for GaN-based all-visible optoelectronic devices such as micro light-emitting diode and laser. In this study, self-assembled InGaN/GaN multi-quantum dots (MQDs) have been grown by plasma-assisted molecular beam epitaxy on c-plane GaN-on-sapphire template. A high density of over 3.8 × 1010 cm−2 is achieved and InGaN QDs exhibit a relatively uniform size distribution and good dispersity. Strong localization effect in as-grown InGaN QDs has been evidenced by temperature-dependent photoluminescence (PL). The variation of peak energy is as small as 35 meV with increasing temperature from 10 K to 300 K, implying excellent temperature stability of emission wavelength for InGaN MQDs. Moreover, the radiative and nonradiative recombination times were calculated by time-resolved PL (TRPL) measurements, and the temperature dependence of PL decay times reveal that radiative recombination dominates the recombination process due to the low dislocation density of QDs structure.

Thermal analysis of unsteady convective flows over a vertical cylinder with time-dependent temperature using the generalized Atangana–Baleanu derivative

Unsteady convective flows, over an infinite, vertical, heated, circular cylinder is investigated by considering the generalized Fourier's law of the thermal process. The generalized constitutive equation of thermal flux is a partial fractional differential equation based on the generalized time-fractional derivative with Mittag–Leffler kernel, namely the generalized Atangana–Baleanu derivative. Closed forms of the analytical solutions for the temperature and velocity fields, expressed with Bessel and Struve functions, are determined using the Laplace transform and the Weber–Dirichlet transform. The ordinary case corresponding to classical Fourier's law is also obtained. Numerical simulations, obtained with the Mathcad software, are carried out and graphically illustrated to analyze the heat transfer and fluid motion. The influence of the fractional orders of the time-derivative and of the Prandtl and Grashof numbers on the fluid temperature and velocity is studied.

Recent Advances in Pyroelectric Materials and Applications.

As one important subclass of piezoelectric materials, pyroelectric materials have caused increasing attention owing to the unique pyroelectric effect induced by spontaneous polarization, showing broad promising application prospects due to various electrical responses induced by time-dependent temperature variation. This review systematically introduces the pyroelectric effect and evaluation of pyroelectric materials and follows by analyzing and concluding the novel properties corresponding to four kinds of main pyroelectric materials. The emphasis of this review focuses on several significant and practical applications of pyroelectric materials in thermal energy harvesting from the external environment, pyroelectric sensing, and imaging, even some electrochemical applications including hydrogen generation, wastewater treatment, sterilization, and disinfection. Finally, the development direction of pyroelectric materials, potential challenges and opportunities in the future are all discussed and proposed. Through systematical conclusion and analysis of the latest research progress in the recent two decades, this review may provide significant guide and inspiration in the development of pyroelectric materials.

A Study on Fundamental Combustion Properties of Oxymethylene Ether-2

Abstract Oxymethylene ethers (OMEn, n = 1–5) are a promising class of synthetic fuels that have the potential to be used as additives or substitutes to diesel in compression ignition engines. A comprehensive understanding of their combustion properties is required for their safe and efficient utilization. In this study, the results of a combined experimental and modeling work on oxidation of OME2 are reported: (i) Ignition delay time measurements of stoichiometric OME2/synthetic air mixtures diluted 1:5 with nitrogen using the shock tube method at pressures of 1, 4, and 16 bar, and (ii) laminar flame speeds of OME2/air mixtures using the cone angle method at atmospheric and elevated pressures of 3 and 6 bar. The experimental data sets obtained have been used for validation of three detailed reaction mechanisms of OME2 obtained from literature. The results of ignition delay time measurements showed that ignition of OME2 is characterized by pre-ignition activity at the low temperature side of the measurements regardless of the pressure. Regarding the performance of the different reaction mechanisms, the model from Cai et al. (2020, “Auto-Ignition of Oxymethylene Ethers (OMEn, n = 2–4) as Promising Synthetic e-Fuels From Renewable Electricity: Shock Tube Experiments and Automatic Mechanism Generation,” Fuel, 264, p. 116711) best predicted the temperature and pressure dependence of ignition delay times. For laminar flame speeds, the experimental data were well matched by the mechanism from Ren et al. (2019) at p = 1, 3, and 6 bar and for all equivalence ratios considered. From sensitivity analyses calculations, it was observed that chain reactions involving small radicals, i.e., H, O, OH, HO2, and CH3 control the oxidation of OME2. The comparison of the results of this work and our previous work (Ngugi et al. (2021)) on OME1 show that these two fuels have similar oxidation pathways. The results obtained in this work will contribute to a better understanding of the combustion of oxymethylene ethers, and thus, to the design and optimization of burners and engines as well.

Conformal maps of viscous electron flow in the Gurzhi crossover

We investigate the impact of geometric constriction on the viscous flow of electron liquid through quantum point contacts. We provide analysis on the electric potential distribution given the setup of a slit configuration and use the method of conformal mapping to obtain analytical results. The potential profile can be tested and contrasted experimentally with the scanning tunneling potentiometry technique. We discuss intricate physics that underlies the Gurzhi effect, i.e., the enhancement of conductivity in the viscous flow, and compare results for different boundary conditions. In addition, we calculate the temperature dependence of the momentum relaxation time as a result of impurity assisted quasiballistic interference effects and discuss various correlational corrections that lead to the violation of Matthiessen's rule in the hydrodynamic regime. We caution that spatially inhomogeneous profiles of current in the Gurzhi crossover between Ohmic and Stokes flows might also appear in the nonhydrodynamic limit where nonlocality plays an important role. This conclusion is corroborated by calculation of dispersive conductivity in the weakly impure limit.

Numerical study on the effect of residual stress on mechanical properties of laser welds of aluminum alloy 2024

The fusion zone is the weak area of weld joint which will experience complex thermal mechanical process during laser welding aluminum alloy 2024-T4. The resulting residual stress in the weld joint may exceed the yield stress, which will significantly affect the hardness and tensile strength. The purpose of this study is to predict the residual stress, and analyze its relationship with hardness and yield stress of the aluminum alloy 2024-T4 weld joint. Herein, three sequential models are established: (i) a thermal finite element model using double cone combined heat source that allows the prediction of time-dependent temperature distribution during laser welding of aluminum alloy 2024; (ii) a mechanical model using sequential coupling method and loading temperature in each increment to predict strain and residual stress; (iii) a theoretical empirical model to link the residual stress, hardness and yield stress. The simulated temperature field from the thermal model is in good agreement with the experimental result. The predicted stress field shows that the average von Mises stress at the center of the Al 2024-T4 and Al 2024-O weld joints are 303.60 MPa and 62.85 MPa, respectively, which are close to their yield stress. Moreover, it is found that the hardness decreases by 6 HV0.1 under the influence of residual stress in Al 2024-T4 fusion zone. The results indicate that the yield stress of 2024-T4 weld joint decreases by 16.5 MPa as a result of the residual stress. Above results indicate that residual stress has non-negligible influences on the mechanical properties of laser weld joint.

Enhanced Dielectric Relaxation in Self-Organized Layers of Polypeptides Coupled to Platinum Nanoparticles: Temperature Dependence and Effect of Bias Voltage

Using alternative current impedance spectroscopy, we investigate the dynamical conductivity of hybrid nanomaterials composed of helical polypeptide layers containing platinum nanoparticles (PtNP). The electrical characteristics of the self-organized poly(γ-benzyl-l-glutamate) (PBGL) in bidimensional lamellar assembly in the presence of Pt nanoparticles are well modeled and described by a single equivalent circuit of parallel resistance and capacitance. The latter are determined using a comparison between the measured and calculated Nyquist plots, which allows extracting the characteristic relaxation time and frequency of the dipolar relaxation process. We found that the relaxation frequency in the PBLG–PtNP hybrid materials is enhanced by 4 orders of magnitudes compared to pure PBLG, which indicates a much faster dielectric relaxation in PBLG–PtNP due to dipole orientation and dipole–dipole interactions. The temperature dependence of the relaxation time is analyzed using Arrhenius plots, from which the activation energy of the relaxation process is found to be around 0.1 eV. Such a value close to the peptide vibration energy of the PBLG indicates a vibration-assisted relaxation process and a polaronic charge transport mechanism. An advantage of the PBLG–PtNP nanocomposite material is that the activation energy can be finely tuned by the PBLG degree of polymerization. Finally, an important outcome of this work is the investigation of the dielectric relaxation process in PBLG–PtNP under applied DC bias. We found that the activation energy decreases with increasing bias voltage for all degrees of polymerization of the PBLG molecule. This effect is interpreted in terms of electric field-induced alignment of the dipoles and of increased mobility of the polaronic charge carriers. The presence of piezoelectricity in the hybrid material gives the possibility to use the DC bias as a simple mean of monitoring the dynamical conductivity involving polaronic states.

Emergence of large thermal noise close to a temperature-driven metal-insulator transition

We report that close to a Mott transition there is an emergence of large thermal noise (${S}_{\mathrm{th}}$) which occurs concomitantly with large correlated flicker noise ($\frac{1}{f}$ noise) with significant non-Gaussian content. This was observed in films of ${\text{NdNiO}}_{3}$ (thickness 15 nm) grown on crystalline ${\text{SrTiO}}_{3}$ substrates with different crystallographic orientations that show a hysteretic transition from a high temperature metallic phase to a low temperature insulating phase in the temperature range 160 to 211 K depending on the substrate orientation and the heating and cooling cycle. The thermal noise, which is distinct from the flicker noise, deviates from the canonical Johnson-Nyquist value of $4{k}_{B}TR$ as measured through the ratio $\ensuremath{\zeta}(T)(\ensuremath{\equiv}\frac{{S}_{\mathrm{th}}(T)}{4{k}_{B}TR})$. The ratio $\ensuremath{\zeta}$ reaches a maximum value of ${\ensuremath{\zeta}}_{M}$ at a temperature ${T}^{*}$ that is close to but distinct from the metal-insulator transition (MIT) temperature ${T}_{\mathrm{MI}}$. In all the films near ${T}^{*}$, the scaled thermal noise maxima ${\ensuremath{\zeta}}_{M}\ensuremath{\gg}1$. The films were found to be largely strain relaxed with residual in-plane and out-of-plane strain as measured by x-ray reciprocal space mapping. It has been observed that the ratio $\frac{{T}^{*}}{{T}_{\mathrm{MI}}}$ as well as ${\ensuremath{\zeta}}_{M}$ have a close dependence on the in-plane-strain in the film. The enhanced thermal noise that occurs along with large correlated flicker noise both arise from slow kinetics of relaxation as established from temperature dependence of the correlation time ($\ensuremath{\tau}$) that gets significantly larger in the temperature range around ${T}^{*}$, reaching a maxima at $T={T}^{*}$. It has been proposed that the existence of large noise (both thermal and flicker noise) owes its origin to electronic phase separation (EPS) that exists near the MIT. A physical model has been suggested that EPS near MIT temperature can give rise to a sparse phase of nanometric small pockets of metallic phases (nanopuddles) that are surrounded by and embedded within the minority insulating phase. The nanopuddles act as a source of charge fluctuations and are coupled weakly to the majority metallic phase by tunneling through the layer of the minority insulating phase. Such isolated metallic nanopuddles can be Coulomb charged if the charging energy ${E}_{C}\ensuremath{\ge}{k}_{B}T$ and can have slow relaxation of fluctuations acting as a source of large noise. It has been argued that the size distribution of the nanopuddles, their average size $\ensuremath{\langle}d\ensuremath{\rangle}$, as well as the temperature dependence of their number density ${N}_{d}$ can determine the temperature ${T}^{*}$.

Heat Transfer-Based Non-isothermal Healing Model for the Interfacial Bonding Strength of Fused Filament Fabricated Polyetheretherketone.

Fused Filament Fabrication (FFF) as an Additive Manufacturing (AM) method for Polyetheretherketone (PEEK) has established a promising future for medical applications so far, however interlayer delamination as a failure mechanism for FFF implants has raised critical concerns. A one-dimensional (1D) heat transfer model (HTM) was developed to compute the layer and interlayer temperatures by considering the nature of 3D printing for FFF PEEK builds. The HTM was then coupled with a non-isothermal healing model to predict the interlayer strength through thickness of a FFF PEEK part. We then conducted a parametric study of the primary temperature effects of the FFF system, including the print bed, nozzle, and chamber temperatures, on layer healing. The heat transfer component of the model for the FFF PEEK layer healing assessment was validated separately. An idealized PEEK cube design (10x10x10 mm3) was used for model development and 3D printed in commercially available industrial and medical FFF machines. During the printing and cooling processes of FFF, thermal videos were recorded in both printers using a calibrated infrared camera. Thermal images were then processed to obtain time-dependent layer temperature profiles of FFF PEEK prints. Both the theoretical model and experiments confirmed that the upper layers in reference to the print bed exhibited higher temperatures, thus higher healing degrees than the lower layers. Increasing the print bed temperature increased the healing of the layers allowing more layers to heal 100%. The nozzle temperature showed the most significant effect on the layer healing, and under certain nozzle temperature, none of the layers healed adequately. Although environment temperature had less impact on the lower layers closer to the print bed, 100% healed layer number increased when the chamber temperature increased. The model predictions were in good agreement with the experimental data, particularly for the mid-part of FFF PEEK cubes printed in both FFF machines.

Ethylene glycol associated facile preparation and luminescent behaviors of RE (RE = Sm3+, Dy3+) ions activated NaLuF4 nanoparticles

To achieve high quality luminescent nanomaterials, we synthesized series of rare-earth (RE; RE = Sm3+, Dy3+) ions activated NaLuF4 nanoparticles via a facile synthetic technique at room temperature. The phase category, microstructure and luminescent behaviors of the resultant samples were detailedly investigated. Under a certain excitation wavelength, these prepared nanoparticles can emit glaring visible light and the emission intensities are determined to be sensitive to the doping content. The optimal doping concentration for Sm3+ and Dy3+ ions in the NaLuF4 host lattices are 1 and 3 mol%, respectively, and the involved concentration quenching mechanisms are all contributed by the electric dipole-dipole interaction. The synthesized nanoparticles exhibit splendid thermal stability and the activation energies of the NaLuF:0.01Sm3+ and NaLuF4:0.03Dy3+ nanoparticles are 0.16 and 0.17 eV, respectively. Furthermore, the temperature-dependent decay time reveals that the thermal quenching mechanism of the designed nanoparticles is responsible by the crossover process between the excited level and ground state. These results indicate that the resultant nanoparticles with good luminescent materials and high thermal stability are potential candidates for white light-emitting diode.

Heat Transfer in Double Annular due to Natural Convection

Presented paper is focused on 2D numerical simulation of turboprop engine cooling in the section of a gas turbine. The paper describes the issue of heat transfer by natural cooling of a turboprop engine in the turbine region in order to determine the time-dependent temperature field in the engine. The analysis is represented on a simplified double annular geometry, where the inner tube represents the engine rotor, the middle tube represents the flow path and the outer ring replaces the engine case. Simultaneous heat transfer by natural convection (Boussinesq model) and radiation (model S2S) is solved on this geometry. Numerical data were compared with data that was gained from measuring on an experimental stand. The surface temperatures of the tubes were measured on the experiment stand during the cooling of the engine model. The temperatures on the walls of the flow path were based on real temperatures of the running engine as initial conditions together with the temperature of the outer tube. The results will be further applied to the study of temperature-dependent deformation of aircraft engine parts, which have a significant effect on the safety and trouble-free operation of the aircraft engine.

Temperature Impacts on Endurance and Read Disturbs in Charge-Trap 3D NAND Flash Memories.

Temperature effects should be well considered when designing flash-based memory systems, because they are a fundamental factor that affect both the performance and the reliability of NAND flash memories. In this work, aiming to comprehensively understanding the temperature effects on 3D NAND flash memory, triple-level-cell (TLC) mode charge-trap (CT) 3D NAND flash memory chips were characterized systematically in a wide temperature range (−30~70 °C), by focusing on the raw bit error rate (RBER) degradation during program/erase (P/E) cycling (endurance) and frequent reading (read disturb). It was observed that (1) the program time showed strong dependences on the temperature and P/E cycles, which could be well fitted by the proposed temperature-dependent cycling program time (TCPT) model; (2) RBER could be suppressed at higher temperatures, while its degradation weakly depended on the temperature, indicating that high-temperature operations would not accelerate the memory cells’ degradation; (3) read disturbs were much more serious at low temperatures, while it helped to recover a part of RBER at high temperatures.

Life-cycle environmental and economic benefits of jointless bridges considering climate change

The damage of expansion joints is a common problem of bridges, which adversely affects not only driving comfort and safety but also the durability of the structure. Jointless bridges can fundamentally solve this fragile problem. However, how to accurately assess its environmental and economic benefits has not been studied, specifically as climate change intensifies. To address these issues, this study first examines the effects of climate change on design expansion allowance of bridge expansion joints based on climate projections. Subsequently, the life-cycle environmental and economic benefits of two jointless bridges located in Beijing–Hong Kong–Macau Expressway are quantified under climate change scenarios. Moreover, uncertainty and random forest algorithm-based importance analyses are carried out to help decision-makers identify major environmental and economic factors and develop eco-friendly plans to facilitate jointless bridge construction. Results indicate the following: (1) the design expansion allowance of bridge expansion joints tends to increase with the time-dependent temperature and humidity; (2) the avoidance of traffic detours caused by the maintenance and replacement of expansion joints is a major source of life-cycle environmental and economic benefits; (3) traffic detour distance is the most important factor influencing the life-cycle environmental and economic benefits.