Temperature-induced Variation Research Articles

A pseudo resistor with temperature self-adaptive scheme

A temperature self-adaptive ultra-high-resistance pseudo-resistor (PR) circuit is proposed for a wide range of biomedical applications. It acts as a relatively constant resistor over a wide temperature range (−40 °C–85 °C) due to its potential to compensate for the impact of the temperature-induced current. Hence, the performance of many biomedical analog intellectual property (IP) circuits can be effectively improved with temperature variations. The proposed circuit consists of a gate-voltage-controlled pseudo-resistor and a proportional-to- absolute-temperature (PTAT) circuit. Besides, its analysis and proof of concept with the self-adaptive scheme are presented. The circuit is designed in standard 0.18 μm CMOS technology and occupies a silicon area of 18.5 × 43.7 μm2. It consumes 12 nW with a single power supply of 1.8 V. The post-layout simulation results demonstrate that the proposed pseudo-resistor could adequately improve the temperature-induced resistance variation by up to 18X while consuming ultra-low power and providing relatively high-temperature independence compared to the prior art.

Bubble-water/catalyst triphase interface microenvironment accelerates photocatalytic OER via optimizing semi-hydrophobic OH radical

Photocatalytic water splitting (PWS) as the holy grail reaction for solar-to-chemical energy conversion is challenged by sluggish oxygen evolution reaction (OER) at water/catalyst interface. Experimental evidence interestingly shows that temperature can significantly accelerate OER, but the atomic-level mechanism remains elusive in both experiment and theory. In contrast to the traditional Arrhenius-type temperature dependence, we quantitatively prove for the first time that the temperature-induced interface microenvironment variation, particularly the formation of bubble-water/TiO2(110) triphase interface, has a drastic influence on optimizing the OER kinetics. We demonstrate that liquid-vapor coexistence state creates a disordered and loose hydrogen-bond network while preserving the proton transfer channel, which greatly facilitates the formation of semi-hydrophobic •OH radical and O-O coupling, thereby accelerating OER. Furthermore, we propose that adding a hydrophobic substance onto TiO2(110) can manipulate the local microenvironment to enhance OER without additional thermal energy input. This result could open new possibilities for PWS catalyst design.

Effects of temperature-induced variation of the second phase on the microstructure, texture and properties of Mg-RE-Zn alloys

In this paper, the Mg-9.32Gd-3.72Y-1.68Zn-0.72Zr (wt%) alloy has undergone three times of repetitive upsetting extrusion deformation. Alloys with different morphologies and distribution patterns of the second phase have been prepared by varying the deformation temperature in each pass. The effects of the second phase on microstructure, texture and mechanical properties are investigated. The results show that (i) the second phase, including Mg5Gd and LPSO phase, has an important effect on the dynamic recrystallization (DRX) behavior of the alloy. (ii) Appropriate lamella distance and block phase size can promote the activation of the slip system and effectively weaken the texture strength. (iii) The DT sample has an effective combination of fine grain strengthening and second phase strengthening due to the reasonable second phase distribution and size, which greatly improves the UTS and YS of the alloy.

Global temperature behavior monitoring and analysis of a three-tower cable-stayed bridge

Varying temperature is a major load of long-span cable-stayed bridges. The temperature effect on the structural behavior may mask the influences of other loads. Conventional studies on the thermal behavior of bridges are limited to regression analyses based on measurement or numerical studies of 2D or local 3D models. This study investigated the global 3D temperature behaviors of a three-tower cable-stayed bridge through the integration of field monitoring and unified numerical simulation. A 3D refined model of the bridge with thermal elements was built, and the thermal boundary conditions were determined from environmental field monitoring data for the global 3D heat-transfer analysis. The calculated temperatures agreed well with the field monitoring counterparts. The temperatures were then input into the same global finite element model with mechanical elements for structural analysis. The temperature-induced structural responses, including the structural displacements and forces, agreed well with the measurement counterparts. The temperature-induced structural response variation pattern and sensitivity were summarized and quantified. This unified numerical simulation enables an efficient and accurate analysis of the global 3D thermal behavior of bridges, as compared with the conventional 2D or local 3D simulation.

Al, Mg Co-doped ZnO thin films: Effect of the annealing temperature on the resistivity and ultraviolet photoconductivity

Interesting electrical and optical properties can be obtained from sol-gel doped Zinc Oxide (ZnO) materials by controlled introduction of dopants in the precursor solution. In this work we investigate the effects of annealing temperature on Al and Mg co-doped ZnO thin films. All samples were dip coated from the same solution, using identical techniques and pre-heating temperature, but were annealed in air at various temperatures ranging from 500°C to 650°C. A three-order magnitude reduction in electrical resistivity was achieved for an increase of 100°C annealing temperature. The structural properties and the energy band-gap remained relatively unchanged during this process. Photocurrent measurements carried out using an ultraviolet excitation source indicate a 5x increase in magnitude, along with increase in persistence behavior. The mechanism behind these effects has been linked to temperature-induced variation in Mg to Al ratio in the films, measured using energy dispersive spectroscopy. Our results indicate that strong in-plane variation of resistivity in ZnO thin films can be carried out using localized heating, opening the way to simpler fabrication processes.

A 17.7–19.2-GHz Receiver Front End With an Adaptive Analog Temperature- Compensation Scheme

This article presents an eight-element 17.7–19.2-GHz receiver front end with 1–2 concurrent beams in a 65-nm CMOS technology. Each output beam utilizes a temperature-compensation variable-gain amplifier (TC-VGA) to minimize the temperature-induced gain variation. The concept of the proposed TC-VGA and the realization of corresponding adaptive analog control are introduced in detail. The front-end architecture and circuit-level design to enable a flat wideband gain response, precise phase and amplitude control, low power consumption, and adaptive analog temperature compensation are presented. Wafer probing is conducted to measure the performance of the receiver front end. The measured gain-temperature coefficient is ±0.005 dB/°C from −15°C to 85 °C at 17.7–19.2 GHz, while the counterpart without temperature compensation is −0.1 dB/°C. The chip demonstrates a 28-dB power gain, a 26% 3-dB fractional bandwidth, a 3.2–4.1-dB noise figure (NF), and a −27.4-dBm input 1-dB gain compression point (IP <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {1\,dB}}$ </tex-math></inline-formula> ) for each element. In addition, each channel provides 7-bit phase-shifting resolution and 6-bit attenuation for a 15.75-dB gain range with a <1.5° root-mean-square (rms) phase error, and a < 0.22-dB rms amplitude error. The chip occupies <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.65\times2.77$ </tex-math></inline-formula> mm2 area with pads, equivalent to 1.61 mm2 per element (for two beams), and consumes 37.2 mW per element per beam. To the best of our knowledge, the receiver front end demonstrates the minimum gain variation with temperature among silicon RF-beamforming front ends.

Determining the Zero-Temperature-Coefficient Point From Device Simulation to Circuit for Improving Temperature Variation Immunity

Thermal issue emerges as one of the critical reliability concerns in integrated circuit design, especially for advanced technology. To improve the temperature immunity and reduce the thermal-related timing guard bands in digital circuits, in this work, we offer a new insight into the zero-temperature-coefficient (ZTC) based design strategy featuring minimizing the temperature-induced delay variation. An effective current-based method to facilitate the ZTC point ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {ZTC}}$ </tex-math></inline-formula> ) determination for standard cells is developed, which is demonstrated on advanced gate-all-around (GAA) nanosheet (NS) FETs from 300 to 425 K using the calibrated TCAD simulation. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {ZTC}}$ </tex-math></inline-formula> dependencies on the signal input slew rate, output capacitance, and self-heating effects (SHEs) are further investigated from the perspective of the effective current by tracing the voltage trajectory. The mixed-mode TCAD simulation results show that the frequency variation of ring oscillator (RO) reduces nearly ten times when operating near <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {ZTC}}$ </tex-math></inline-formula> and great power-performance trade-offs can also be achieved. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {ZTC}}$ </tex-math></inline-formula> determination for standard cells combined with the compensation effect among different standard cells benefits selecting the optimal zero-temperature-delay (ZTD) point in the target path, thereby helping to implement a robust digital design against temperature variation.

Real-Time Intelligent Prediction Method of Cable’s Fundamental Frequency for Intelligent Maintenance of Cable-Stayed Bridges

Cable’s fundamental frequency (CFF) is an important characteristic of the working state of long-span cable-stayed bridges. The change in the bridge’s temperature field will influence CFF by altering the cable’s tension and the cables’ sags. An accurate regression model between the temperature-induced variation of CFF and the real-time changing temperature field should be established. Then, the reference value of the temperature-induced variation of CFF can be obtained after inputting the real-time temperature data. In this study, an intelligent real-time prediction model for CFF is proposed based on the full-bridge temperature field, including the average temperature of the main beam, the vertical temperature difference of the main beam, and the temperature of the cable tower. Besides, a machine learning method named the long short-term memory (LSTM) network is exploited to ensure the nonlinear fitting performance of the model, and a paradigm for optimal hyperparameter selection and training strategy selection is provided. To verify the superiority of the LSTM-based model, the output accuracy of the linear regression, BP network, and LSTM network was tested and compared using the monitoring data collected from cable sensors in the main span and side span, which provides an important basis for the intelligent maintenance and sustainable operation of the bridge cables.

Comparative Study of Temperature Impact in Spin-Torque Switched Perpendicular and Easy-Cone MTJs

The writing performance of the easy-cone magnetic tunnel junction (MTJ) and perpendicularly magnetized MTJ (pMTJ) under various temperatures was investigated based on the macrospin model. When the temperature is changed from 273 K to 373 K, the switching current density of the pMTJ changes by 56%, whereas this value is only 8% in the easy-cone MTJ. Similarly, the temperature-induced variation of the switching delay is more significant in the pMTJ. This indicates that the easy-cone MTJ has a more stable writing performance under temperature variations, resulting in a wider operating temperature range. In addition, these two types of MTJs exhibit opposite temperature dependence in the current overdrive and write error rate. In the easy cone MTJ, these two performance metrics will reduce as temperature is increased. The results shown in this work demonstrate that the easy-cone MTJ is more suitable to work at high temperatures compared with the pMTJ. Our work provides a guidance for the design of STT-MRAM that is required to operate at high temperatures.

Mitigation of lamp oven and cavity oven temperature-induced frequency variation in rubidium atomic clock.

The long-term frequency stability of the rubidium atomic clock is primarily affected by temperature variations in the lamp oven and the cavity oven, which cause changes in light intensity, which are then converted into frequency variations. Therefore, we propose using light intensity variations to actively improve the cavity oven and lamp oven temperature sensitivity of the rubidium atomic clock. This is accomplished through research into the theory of the rubidium atomic frequency standard, specifically the effect of light intensity, lamp oven temperature, and cavity oven temperature on the frequency deviation. In previous work, we discovered the relationship between the light intensity and frequency deviation by combining this with our engineering expertise. Furthermore, some related experiments show that the method is feasible with the lamp oven and cavity oven temperature sensitivity of the rubidium atomic clock greatly improved, providing an effective way to improve the rubidium atomic clock's long-term frequency stability.

The Rainbow Arching over the Fluorescent Thienoviologen Mesophases.

Thermofluorochromic materials exhibit tunable fluorescence emission on heating or cooling. They are highly desirable for applications ranging from temperature sensing to high-security anti-counterfeiting. Luminescent matrices based on liquid crystals are very promising, particularly those based on liquid crystals with intrinsic fluorescence. However, only a few examples have been reported, suggesting ample margins for development in the field, due to the wide range of fluorophores and supramolecular organizations to be explored. Moreover, thermofluorochromic liquid crystals can be tailored with further functionalities to afford multi-stimuli responsive materials. For the first time, herein we report the thermofluorochromism of thienoviologen liquid crystals, already known to show bulk electrochromism and electrofluorochromism. In particular, we studied their photophysics in the 25 °C-220 °C range and as a function of the length of the N-linear alkyl chains, m (9 ≤ m ≤ 12 C atoms), and the type of anion, X (X = OTs-, OTf-, BF4-, NTf2-). Interestingly, by changing the parameters m, X and T, their fluorescence can be finely tuned in the whole visible spectral range up to the NIR, by switching among different mesophases. Importantly, by fixing the structural parameters m and X, an interesting thermofluorochromism can be achieved for each thienoviologen in a homologous series, leading to a switch of the emitted light from red to green and from white to blue as a consequence of the temperature-induced variation in the supramolecular interactions in the self-assembled phases.

Reversible Transformation between Isolated Skyrmions and Bimerons.

Skyrmions and bimerons are versatile topological spin textures that can be used as information bits for both classical and quantum computing. The transformation between isolated skyrmions and bimerons is an essential operation for computing architecture based on multiple different topological bits. Here we report the creation of isolated skyrmions and their subsequent transformation to bimerons by harnessing the electric current-induced Oersted field and temperature-induced perpendicular magnetic anisotropy variation. The transformation between skyrmions and bimerons is reversible, which is controlled by the current amplitude and scanning direction. Both skyrmions and bimerons can be created in the same system through the skyrmion-bimeron transformation and magnetization switching. Deformed skyrmion bubbles and chiral labyrinth domains are found as nontrivial intermediate transition states. Our results may provide a unique way for building advanced information-processing devices using different types of topological spin textures in the same system.

Toward Confocal Chromatic Sensing in Nuclear Reactors: In Situ Optical Refractive Index Measurements of Bulk Glass

To measure fuel rod swelling in a nuclear research reactor, our research has focused on the development of an optical confocal chromatic sensor, allowing contactless measurements of radial changes in fuel rods. This sensor must be able to operate in the harsh and hot environment of a reactor, especially under high neutron fluences up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{19}~{n}_{\mathrm{ fast}}/\text {cm}^{2}$ </tex-math></inline-formula> and gamma doses of a few GGy. When exposed to such radiation levels, the properties of bulk optical glasses are known to be affected by two main phenomena: radiation-induced attenuation (RIA) and radiation-induced refractive index change (RIRIC). With the objective of testing glasses as candidates for a future confocal chromatic sensor, we created a dedicated setup for the online monitoring of the glasses’ RIRIC in the core reactor with a measurement principle relying on interferometry. Since not only the refractive index (RI) but also the length of the samples changes under neutron radiation through compaction, we measured the variation of the optical path (OP) ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$nL$ </tex-math></inline-formula> ). To assess the performance of our setup, preliminary in-lab tests were performed to evaluate the feasibility of measuring the small RI changes caused by external temperature changes. Due to this study, we were able to obtain data that were not yet available in the literature regarding the temperature-induced RI variation of several bulk glasses, including radiation-hardened glasses, up to 350 °C. This information is crucial for the targeted application, as the confocal chromatic sensor will have to operate at such elevated temperatures.

A novel wireless ECG system for prolonged monitoring of multiple zebrafish for heart disease and drug screening studies

Zebrafish and their mutant lines have been extensively used in cardiovascular studies. In the current study, the novel system, Zebra II, is presented for prolonged electrocardiogram (ECG) acquisition and analysis for multiple zebrafish within controllable working environments. The Zebra II is composed of a perfusion system, apparatuses, sensors, and an in-house electronic system. First, the Zebra II is validated in comparison with a benchmark system, namely iWORX, through various experiments. The validation displayed comparable results in terms of data quality and ECG changes in response to drug treatment. The effects of anesthetic drugs and temperature variation on zebrafish ECG were subsequently investigated in experiments that need real-time data assessment. The Zebra II's capability of continuous anesthetic administration enabled prolonged ECG acquisition up to 1 h compared to that of 5 min in existing systems. The novel, cloud-based, automated analysis with data obtained from four fish further provided a useful solution for combinatorial experiments and helped save significant time and effort. The system showed robust ECG acquisition and analytics for various applications including arrhythmia in sodium induced sinus arrest, temperature-induced heart rate variation, and drug-induced arrhythmia in Tg(SCN5A-D1275N) mutant and wildtype fish. The multiple channel acquisition also enabled the implementation of randomized controlled trials on zebrafish models. The developed ECG system holds promise and solves current drawbacks in order to greatly accelerate drug screening applications and other cardiovascular studies using zebrafish.

A novel low pressure-difference fluctuation electro-hydraulic large flowrate control valve for fuel flowrate control of aeroengine afterburner system

To address the control accuracy of large fuel flowrate during pressure fluctuation, a novel electro-hydraulic fuel metering unit (FMU) is constructed for afterburner fuel system of military aeroengine. Different from the previous FMU, the proposed FMU can achieve the higher precision opening control by a new metering valve with double control chambers (MVDCC), and realize the lower pressure difference fluctuation regulating by a novel two-stage constant pressure difference compensated valve (CPDCV) with dynamic damping orifice and damping piston. The experimental and AMESim simulation results verify the validity and superiority of the novel FMU. Since the temperature-induced variation in fuel properties and device capabilities may degrade or even impair the properties of novel FMU, the discharge flowrate is analyzed by global sensitivity analysis to research the effect proportion of each factor, the temperature effect is explored to ensure the working reliability in long-span temperature variation. Finally, the optimization of structure parameters for novel CPDCV can further reduce pressure difference fluctuation during pressure regulation, and the overshoot, adjust time and the integral of time multiplied by absolute value of error (ITAE) can be reduced by 24%, 30% and 26%, respectively. This paper provides a reference for improving the stability of large flowrate during pressure fluctuation.

Evolvability under climate change: Bone development and shape plasticity are heritable and correspond with performance in Arctic charr (Salvelinus alpinus).

Environmental conditions can impact the development of phenotypes and in turn the performance of individuals. Climate change, therefore, provides a pressing need to extend our understanding of how temperature will influence phenotypic variation. To address this, we assessed the impact of increased temperatures on ecologically significant phenotypic traits in Arctic charr (Salvelinus alpinus). We raised Arctic charr at 5°C and 9°C to simulate a predicted climate change scenario and examined temperature-induced variation in ossification, bone metabolism, skeletal morphology, and escape response. Fish reared at 9°C exhibited less cartilage and bone development at the same developmental stage, but also higher bone metabolism in localized regions. The higher temperature treatment also resulted in significant differences in craniofacial morphology, changes in the degree of variation, and fewer vertebrae. Both temperature regime and vertebral number affected escape response performance, with higher temperature leading to decreased latency. These findings demonstrate that climate change has the potential to impact development through multiple routes with the potential for plasticity and the release of cryptic genetic variation to have strong impacts on function through ecological performance and survival.

Temperature-driven 5f itinerant–localized crossover in the heavy-fermion compound PuIn3

The temperature-dependent evolution pattern of 5f electrons helps to elucidate the long-standing itinerant-localized dual nature in plutonium-based compounds. In this work, we investigate the correlated electronic states of PuIn3 dependence on temperature by using a combination of the density functional theory and the dynamical mean-field theory. Not only the experimental photoemission spectroscopy is correctly reproduced, but also a possible hidden 5f itinerant-localized crossover is identified. Moreover, it is found that the quasiparticle multiplets from the many-body transitions gradually enhance with decreasing temperature, accompanied by the hybridizations with 5f electrons and conduction bands. The temperature-induced variation of Fermi surface topology suggests a possible electronic Lifshitz transition and the onset of magnetic order at low temperature. Finally, the ubiquitous existence orbital selective 5f electron correlation is also discovered in PuIn3. These illuminating results shall enrich the understanding on Pu-based compounds and serve as critical predictions for ongoing experimental research.

Large-dynamic-range athermal lithium niobite on insulator/ TiO2 nanobeam electric field sensor

An integrated optical electric field (E-field) sensor based on a one-dimensional photonic crystal nanobeam cavity on a lithium niobite on insulator (LNOI) platform is reported here. It has a large dynamic range and extreme sensitivity. The dielectric resonant mode has a quality factor Q ≳ 105. The waveguide-coupled structure, only 25 μm long, is beneficial for future on-chip integration. The use of TiO2 compensates for the thermo-optical effect of lithium niobite (LN), while the high dielectric constant of TiO2 influences the E-field distribution. A tri-layer TiO2/LNOI/TiO2 nanobeam structure is proposed to improve electro-optical modulation efficiency in LN. Detailed analysis of noise sources shows the theoretical minimum detectable E-field to be 0.15 V m−1 with a dynamic range of 83 dB. The temperature-induced resonant wavelength variation is within 3 pm °C−1 in the range of −40 °C to 40 °C.

Stability and Lattice Dynamics of Ruddlesden–Popper Tetragonal Sr2TiO4

We report a combined experimental and theoretical lattice dynamics study of the Ruddlesden–Popper layered compound Sr2TiO4. From inelastic neutron scattering experiments, we derive the generalized phonon density of states of Sr2TiO4. We also report its heat capacity, thermal expansion, and thermodynamic Gruneisen parameters using the calculated bulk modulus and find a large value of about 2. Using Raman scattering experiments under pressure, we discuss a potential structural distortion of the tetragonal structure above 11 GPa, which could be due to nonhydrostatic compression. The mode Gruneisen parameters of the four Raman-active modes are determined and shown to be in reasonable agreement with those obtained by density functional perturbation theory (DFPT) calculations. The temperature behavior of the Raman-active modes was studied, allowing us to determine the implicit volume and explicit anharmonic contributions. Above 400 K, the implicit volume contribution dominates the temperature-induced variation of the four Raman-active modes, whereas, below this temperature, the explicit anharmonic contribution is the dominant contributor to the highest energy mode. Our results underline the importance of anharmonicity in vibration-related properties of Sr2TiO4.

Electron impact processes in voltage-controlled phase transition in vanadium dioxide thin films

Abstract A study of the voltage-controlled phase transition mechanism in vanadium dioxide thin films was performed in the temperature range 65 – 295 K. Temperature-induced variation of I-V characteristics indicates the type of conductivity defined by space-charge limited currents (SCLC). Based on the analysis of the temperature dependence of sample resistivity, it was found that the dominant transport mechanism is a small polaron hopping conduction. The results of modeling together with obtained experimental data justify the influence of the parameters of trap distribution, associated with oxygen vacancies and hydrogen impurities, on the mechanism of the instability development in vanadium dioxide thin films. At relatively low trap density, the phase transition is more likely initiated electronically. At temperatures below 100 K an appearance of switching with memory is observed. An increase in the trap concentration provokes the prevalence of thermal process in the phase transition triggering.