Real-time Temperature Measurement Research Articles

Whispering Gallery Mode Resonator Temperature Compensation and Refractive Index Sensing in Glucose Droplets.

Among the different types of photonic sensor devices, optical whispering gallery mode resonators (WGMRs) have attracted interest due to their high level of sensitivity, small size, and ability to perform real-time temperature measurements. Here we demonstrate the applicability of temperature measurements using WGMR in both air and liquid environments. We also show that WGMR allowed measurements of the refractive index variations in an evaporating glucose–water solution droplet. The thermal tuning of WGMR can be reduced by coating WGMRs with a thin layer of polymethyl methacrylate (PMMA). Dip-coating the silica microsphere multiple times significantly reduced the resonance shift, partially compensating for the positive thermo-optical coefficient of silica. The shift direction changed the sign eventually.

Hybrid Dissolved-Oxygen and Temperature Sensing: A Nanophotonic Probe for Real-Time Monitoring of Chlorella Algae.

Dissolved-oxygen concentration and temperature are amongst the crucial parameters required for the precise monitoring of biological and biomedical systems. A novel hybrid nanocomposite probe for real-time and contactless measurement of both dissolved-oxygen concentration and temperature, based on a combination of downconverting phosphorescent molecules of platinum octaethylporphyrin and lanthanide-doped upconverting nanoparticles immobilized in a host of polystyrene, is here introduced. Chlorella algae are employed here as a model to demonstrate the hybrid nanophotonic sensor’s capability to monitor the aforementioned two parameters during the photosynthesis process, since these are among the parameters impacting their production efficiency. These algae have attracted tremendous interest due to their potential to be used for diverse applications such as biofuel production; however, feasibility studies on their economic production are still underway.

Real-time temperature measurement in stochastic rotation dynamics.

Many physical and chemical processes involve energy change with rates that depend sensitively on local temperature. Important examples include heterogeneously catalyzed reactions and activated desorption. Because of the multiscale nature of such systems, it is desirable to connect the macroscopic world of continuous hydrodynamic and temperature fields to mesoscopic particle-based simulations with discrete particle events. In this work we show how to achieve real-time measurement of the local temperature in stochastic rotation dynamics (SRD), a mesoscale method particularly well suited for problems involving hydrodynamic flows with thermal fluctuations. We employ ensemble averaging to achieve local temperature measurement in dynamically changing environments. After validation by heat diffusion between two isothermal plates, heating of walls by a hot strip, and by temperature programed desorption, we apply the method to a case of a model flow reactor with temperature-sensitive heterogeneously catalyzed reactions on solid spherical catalysts. In this model, adsorption, chemical reactions, and desorption are explicitly tracked on the catalyst surface. This work opens the door for future projects where SRD is used to couple hydrodynamic flows and thermal fluctuations to solids with complex temperature-dependent surface mechanisms.

Combining High-Resolution Land Use Data With Crowdsourced Air Temperature to Investigate Intra-Urban Microclimate

The spatial variability of land cover in cities results in a heterogeneous urban microclimate, which is often not represented with regulatory meteorological sensor networks. Crowdsourced sensor networks have the potential to address this shortcoming with real-time and fine-grained temperature measurements across cities. We use crowdsourced data from over 500 citizen weather stations during summer in Sydney, Australia, combined with 100-m land use and Local Climate Zone (LCZ) maps to explore intra-urban variabilities in air temperature. Sydney presents unique drivers for spatio-temporal variability, with its climate influenced by the ocean, mountainous topography, and diverse urban land use. Here, we explore the interplay of geography with urban form and fabric on spatial variability in urban temperatures. The crowdsourced data consists of 2.3 million data points that were quality controlled and compared with reference data from five synoptic weather stations. Crowdsourced stations measured higher night-time temperatures, higher maximum temperatures on warm days, and cooler maximum temperatures on cool days compared to the reference stations. These differences are likely due to siting, with crowdsourced weather stations closer to anthropogenic heat emissions, urban materials with high thermal inertia, and in areas of reduced sky view factor. Distance from the coast was found to be the dominant factor impacting the spatial variability in urban temperatures, with diurnal temperature range greater for sensors located inland. Further differences in urban temperature could be explained by spatial variability in urban land-use and land-cover. Temperature varied both within and between LCZs across the city. Crowdsourced nocturnal temperatures were particularly sensitive to surrounding land cover, with lower temperatures in regions with higher vegetation cover, and higher temperatures in regions with more impervious surfaces. Crowdsourced weather stations provide highly relevant data for health monitoring and urban planning, however, there are several challenges to overcome to interpret this data including a lack of metadata and an uneven distribution of stations with a possible socio-economic bias. The sheer number of crowdsourced weather stations available can provide a high-resolution understanding of the variability of urban heat that is not possible to obtain via traditional networks.

Real-time measurement of temperature and volume of the weld pool in wire-arc additive manufacturing

The quality of the material deposition and contour accuracy produced by WAAM (Wire Arc Additive Manufacturing) depends on process parameters such as the temperature and the volume of the weld pool. The control of the welding process can be substantially improved by obtaining real-time signals of the weld-pool temperature and volume. In this paper, we present a new optical sensor that can measure the quantities through the welding arc. We have developed a ratio pyrometer with narrowband filters that suppresses the radiation from the plasma. We present our new sensor in this paper and demonstrate its capability to measure the weld-pool temperature pyrometrically and the weld-pool area by digital image processing as a real-time signal through the arc. In addition, we estimate the weld-pool volume from its area and the known material inflow.

Study on the Characteristics of Schottky Temperature Detector Based on Metal/n-ZnO/n-Si Structures

Background: At present, the main problems of Micro-Electro-Mechanical Systems (MEMS) based temperature detector are the narrow range of temperature detection and difficulty in the measurement of high temperature. Besides, MEMS devices have different response characteristics for various surrounding temperature in the petrochemical and metallurgy application fields with hightemperature and harsh conditions. To evaluate the performance stability of the high-temperature MEMS devices, the real-time temperature measurement is necessary. Objective: A Schottky temperature detector based on the metal/n-ZnO/n-Si structures is designed to measure high temperature (523~873K) for MEMS devices with a large temperature range. Methods: By using the Finite Element Method (FEM), three different work function metals (Cu, Ni and Pt) contacting the n-ZnO were investigated to realize Schottky. At room temperature (298K) and high temperature (523~873K), the current densities with various bias voltages (J-V) were studied. Results: The simulation results show that the high-temperature response power consumption of three Schottky detectors of Cu, Ni and Pt decreases successively, which is 1.16 mW, 63.63 μW and 0.14 μW. The response temperature sensitivities of 6.35 μA/K, 0.78 μA/K, and 2.29 nA/K are achieved. Conclusion: The Cu/n-ZnO/n-Si Schottky structure could be used as a high-temperature detector (523~873K) for the high-temperature MEMS devices. It has a large temperature range (350K) and a high response sensitivity of 6.35 μA/K. Compared with the traditional devices, the Cu/n-ZnO/n-Si Schottky structure-based temperature detector has a low energy consumption of 1.16 mW, having potential applications in the high-temperature measurement of the MEMS devices.

Error analysis of contactless optical temperature probing methods for cryogenic Yb:YAG

In this work, we have investigated six different in situ optical contactless temperature probing methods for cryogenic Yb:YAG systems. All the methods are based on variation of fluorescence spectra with temperature, and they either look at the width of the emission line, the ratio of the emission intensity at different wavelengths and to the overall spectral change at selected wavelength intervals. We have shown that, for Yb:YAG crystal with homogeneous temperature distribution, one can perform real-time contactless optical temperature measurements with a ± 1 K accuracy in the 78–300 K range. We have further tested the methods in measuring the average temperature of Yb:YAG rods at up to 500 W absorbed pump power level. We have seen that, a real-time temperature measurement accuracy of ± 5 K is feasible in both lasing and non-lasing situations for estimating the average temperature of crystals under nonhomogeneous thermal load. The techniques are quite valuable in evaluating the bonding quality of Yb:YAG crystals in cryogenic systems. Moreover, the real-time temperature information provides feedback on parameters like cavity alignment status and extraction efficiency to the laser engineers while optimizing the system.

A thin-film temperature sensor based on a flexible electrode and substrate

Accurate temperature measurements can efficiently solve numerous critical problems and provide key information. Herein, a flexible micro-three-dimensional sensor, with a combination of platinum and indium oxide to form thermocouples, is designed and fabricated by a microfabrication process to achieve in situ real-time temperature measurements. The stability and reliability of the sensor are greatly improved by optimizing the process parameters, structural design, and preparation methods. A novel micro-three-dimensional structure with better malleability is designed, which also takes advantage of the fast response of a two-dimensional thin film. The as-obtained flexible temperature sensor with excellent stability and reliability is expected to greatly contribute to the development of essential components in various emerging research fields, including bio-robot and healthcare systems. The model of the application sensor in a mask is further proposed and designed to realize the collection of health information, reducing the number of deaths caused by the lack of timely detection and treatment of patients.

Thermographic imaging of mouse across circadian time reveals body surface temperature elevation associated with non-locomotor body movements.

Circadian clocks orchestrate multiple different physiological rhythms in a well-synchronized manner. However, how these separate rhythms are interconnected is not exactly understood. Here, we developed a method that allows for the real-time simultaneous measurement of locomotor activity and body temperature of mice using infrared video camera imaging. As expected from the literature, temporal profiles of body temperature and locomotor activity were positively correlated with each other. Basically, body temperatures were high when animals were in locomotion. However, interestingly, increases in body temperature were not always associated with the appearance of locomotor activity. Video imaging revealed that mice exhibit non-locomotor activities such as grooming and postural adjustments, which alone induce considerable elevation of body temperature. Noticeably, non-locomotor movements always preceded the initiation of locomotor activity. Nevertheless, non-locomotor movements were not always accompanied by locomotor movements, suggesting that non-locomotor movements provide a mechanism of thermoregulation independent of locomotor activity. In addition, in the current study, we also report the development of a machine learning-based recording method for the detection of circadian feeding and drinking behaviors of mice. Our data illustrate the potential utility of thermal video imaging in the investigation of different physiological rhythms.

Laser-Induced Breakdown Spectroscopy (LIBS) For The Characterization Of Methane-Air Laminar Diffusion Flame

Laser-induced breakdown spectroscopy (LIBS) was applied for the characterization of the methane-air laminar diffusion flame, revealing the spatial distribution of its composition. From the measurement, it was found that distribution of the atomic and ionic N emissions produced by the flame had obvious differences, which were mainly distributed in the air area and flame area, respectively. A comparison of the LIBS spectra of air, methane gas, and methane-air laminar diffusion flame showed that the atomic N emissions were mainly produced by the excitation of N2, and the ionic N emissions were more related to the N-containing combustion products. In addition, the correlation between typical emissions and the flame temperature measured by thermocouple was estimated to show that the tendency of the changes in temperature can be characterized by C2 emission intensities. This work provides a new method for real-time online flame temperature measurement, and also provides a reference for revealing the formation process and conversion pathway of each component in the flame.

Assessment of the thermal outcome during steam-pulse ablation for sheep tissue

Thermal ablation has attracted attention as a minimally invasive tissue ablation treatment. Steam flow was recently introduced as a novel ablation procedure. This work aimed to assess the applicability of pulsated steam flow for tumor ablation. Ex vivo ablation was performed using liver, muscle, and fat tissues of sheep. Three experimental protocols of pulse number were administered to these tissues, while computational simulation was conducted according to the ex vivo tests for each tissue. Real-time measurements of temperature revealed heat propagation during and subsequent to ablation. The peak temperature was achieved after ablation. The time to reach the peak (highest temperature) increased with the distance from the thermal sensor to the steam needle according to thermal conductivity, except for steam leakage along to gap between the tissue and blood vessel. A cross-section of the ablated specimen clearly revealed the boundaries of cell defects. The ablated area was droplet shaped up to the steam needle. Computational simulations revealed that the ablated area was consistent with the area with the highest temperature. Though several limitations still remain such as no blood circulation, pulsated steam flow can ablate diverse animal tissues.

Real-time temperature measurement of living cells exposed to microwaves using a temperature-dependent fluorescent dye

Real-time measurement of temperature in living cells exposed to microwaves is challenging because of the low spatial resolution of conventional temperature probes. Here, we established a noninvasive method by using a temperature-dependent fluorescent dye, Rhodamine B (Rho-B) to stain living cells that were exposed to a customized microwave exposure device. The relationship between Rho-B fluorescence and the temperature of living cells, and between Fluo4/AM and the inward inflow of Ca2+ were established. The results showed that the fluorescence intensity changed by 7.9%/°C as the temperature rose from 25 °C to 37 °C. The spatial resolution and temporal resolution of this method were 225 × 225 µm 2 and 1.5 s, respectively. In conclusion, the real-time temperature measurement technique is simple to use and requires no specialized equipment beyond a LSCM. This method can provide real-time information of the temperature changes in cells simultaneously with the investigation of calcium concentration.

Identification of butt welded joint penetration based on infrared thermal imaging

In the gas metal arc welding (GMAW) process, the intense arc light and high temperature conditions bring great difficulties to the online identification of welded joint penetration. At present, visual sensing method and arc sound detection method are mainly used to identify the welded joint penetration, there are few reports about using welding temperature field to identify welded joint penetration. In this paper, a method of using infrared thermal imaging to identify the welded joint penetration was proposed, a single infrared thermal imager was used to monitor the welding temperature field in real time, the solidified weld area outside the weld pool area was selected as the region of interest (ROI) for real-time temperature measurement. The temperature field distribution features of ROI were extracted, taking these features as input and welded joint penetration as output, the identification model for welded joint penetration was established based on artificial neural network (ANN). The identification accuracy and generalization ability of the identification model were verified by a variety of butt welding experiments, the experimental results show that the identification accuracy of the established model for three penetration states of welded joint is higher than 96%, which can be applied in the online identification of welded joint penetration.

Fatigue reliability evaluation of Q460 welded joints using fracture fatigue entropy method

In this paper, the fracture fatigue entropy (FFE) was used to evaluate the fatigue reliability of Q460 welded joints during high-cycle fatigue. The Q460 butt welded joint fatigue tests were conducted under different loads. Meanwhile, the real-time temperature measurement, monitored by an infrared thermal scanner, was completed. The fatigue limit can be well estimated according to the cumulative damage entropy production rate in Phase II, and compared with the fatigue limit prediction value by the traditional staircase method, a good consistency is achieved. Furthermore, the P-S-N curves of 5%, 50%, and 95% survival probability rate are well predicted, which is consistent with the experimental data. Therefore, based on this, the accurate fatigue reliability evaluation based on the proposed method has been achieved.

Multi-wavelength radiometric thermometry data processing algorithm based on the BFGS algorithm.

Multi-wavelength radiometric thermometry has a wide application prospect in many fields. However, due to unknown emissivity, the data processing algorithm remains a difficult problem. The Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm is proposed to inverse true temperature and spectral emissivity without assuming the emissivity model. The BFGS algorithm can automatically identify the emissivity models of different trends. These simulation results show that given different initial emissivity has no significant influence on the inverse temperature and emissivity. Then, we select 0.5 as the initial emissivity and carry out the simulation experiments at 800 and 900 K, respectively. The maximum absolute error of temperature is less than 3.5 K and the computation time is less than 0.2 s. Thus, the algorithm has high precision and efficiency. Finally, the verification experiment indicates that the BFGS algorithm is effective and reliable. The proposed method can be applied to real-time temperature measurement in many industrial processes.

Development of experimental methodology for estimation of thermo-physical properties of engineering materials using inverse method

In the present article, a novel experimental methodology is proposed for the simultaneous estimation of unknown thermal conductivity (k) and specific heat capacity (cp) of engineering materials. The experimental method involves radiative heating of the test sample and measuring its temperature response at two different locations. Proper arrangements have been made to realize one-dimensional heat conduction within the test sample. The one-dimensional heat conduction equation with convection-radiation heat loss boundary condition is considered as the forward model as it best mimics the experimental heat transfer. The inverse problem is formulated as a parameter estimation problem, and solved using Levenberg-Marquardt algorithm. First, numerical estimations were carried out with synthetic temperature data. It was found that the time-dependent heat flux boundary condition is more suitable to estimate the properties of higher thermal conductivity materials. Then, real-time temperature measurements were carried out on Stainless Steel (SS), Mild Steel (MS), Brass (BS), Aluminium (Al), and Copper (Cu) test samples. The estimated k of SS, MS, BS, Al, and Cu in (W/(m K)) is 14.03, 54.63, 103.21, 221.53 and 379.89, respectively. And, the estimated cp of SS, MS, BS, Al, and Cu in (J/(kg K)) is 500.44, 460.84, 395.01, 939.58, and 398.43 respectively. The estimated thermal properties are also validated against experimentally measured values obtained using the Modified Transient Plane Source (MTPS) sensor. It was found that the estimated k and cp in case of SS has a deviation of 7% and 4%, respectively.

Research on hot spot temperature monitoring technology of transformer winding

A temperature monitoring system based on fiber grating is designed to realize real-time measurement of the hot spot temperature of transformer windings. This paper introduces the principle of fiber grating temperature measurement, and use the Maxwell and Fluent modules in ANSYS to simulate and analyze the electromagnetic field-fluid field-temperature field of the transformer to obtain specific information about hot spots so that the fiber grating can be placed reasonably. Through the fiber grating wavelength demodulation system based on volume phase grating, the center wavelength value of the grating is obtained, and the quantitative relationship between the center wavelength and temperature is found, which proves the feasibility of the system.

A Comparative Studyon Characteristics of Inconel-625 Joints Developed through Microwave Hybrid Heating and Tungsten Inert Gas Welding

In recent years, microwave welding has received attention for joining of similar and dissimilar metals due to its major advantages like volumetric heating, selective heating of target materials, energy saving and sustainability. In the present work, the microstructural characteristics and mechanical properties of Inconel-625-welded joints developed through microwave hybrid heating and those produced by TIG welding have been compared. Welding through microwave hybrid heating (MHH) was carried out using Inconel-625 interface filler powder of 50 μm size, while TIG welding was carried out using ERNiCrMo-3 filler wire of 2.5 mm diameter which had a composition similar to that of Inconel-625 alloy. The welded samples were characterized in terms of microstructural observations and tensile and microhardness properties. The study reveals that the joining of bulk metals through MHH has potential in manufacturing industries in the near future. TIG-welded joints exhibit superior strength compared to MHH joints because of fine grain structure, lower amount of segregation in the weld zone and also smaller width of the weld zone in joints developed through MHH. The hardness in the weld zone of welded joints in both the cases is observed to be almost the same. Use of a finer interface filler of 20–25 μm particle size may further contribute to improving the mechanical properties of the joints developed through MHH. Furthermore, the use of industrial microwave furnace may improve the strength of MHH-welded joints as the process may be integrated with real-time temperature measurement of the joint zone so as to achieve better control over the process.

Real-time measurement method for the skin temperature of the human arm via large lateral shearing interferometry.

This paper presents a real-time measurement method for the skin temperature of the human arm. In this method, the air temperature close to the arm skin is measured via large lateral shearing interferometry, thus avoiding the possible influences of the different physical characteristics of different people, while maintaining the advantages of optical measurement, including its noncontact, noninvasive, and rapid features. The method captures the real-time fringe patterns generated using a parallel-sided plate when a collimated laser light beam transfers through the air surrounding the arm to be measured. Additionally, the phase difference distribution caused by the temperature difference is calculated in combination with the background fringe patterns. The phase difference in the light close to the arm skin is then estimated via a linear fitting method. Accordingly, based on the size parameters of the arm cross section and the ambient temperature monitored in real time, the air temperature close to the arm skin, which is considered equal to the arm skin temperature, is determined while considering the heat conduction effect. Experimental measurements of the temperature of human arm skin were conducted using the proposed method, and the axillary temperatures of the same person before and after the experiments were also measured using an electronic thermometer and a mercury thermometer. Good agreements were found, verifying the reliability of the proposed method. Moreover, based on this method, the possibility for the construction of a real-time body temperature measurement system is also discussed.

A thermal-driven method based on Brillouin fiber-optic sensors for the quantitative identification of subsurface cavities in concrete-filled steel tube structures

In the composite structure of a concrete-filled steel tube (CFST), because the concrete is concealed inside the steel tube, subsurface cavities can occur and are difficult to identify. In this study, a thermal-driven method based on Brillouin fiber-optic sensors (BFOSs) was proposed to quantitatively identify subsurface cavities in CFSTs. By performing a thermodynamic analysis of subsurface cavities in CFSTs, a thermal model related to the relationship between the subsurface cavity size and the temperature rise at the top surface of the CFST was established for the first time. Then, a sensing scheme based on the BFOS was proposed, and its feasibility was evaluated through an experimental program. The experimental program involved the use of an active heating layer for inputting heat flow into the CFST structure and BFOSs for the distributed measurement of temperature to identify subsurface cavities in CFSTs. The experimental results indicated that the BFOSs can achieve real-time distributed measurements of the surface temperature of the CFSTs. According to the temperature anomalies in the temperature rise curves of the CFSTs, the subsurface cavities can be accurately located in the longitudinal direction of the CFST, and its length can be quantified. There is an obvious linear relationship between the temperature rise and the square root of the heating time, from which the equivalent heat absorption coefficient (EHAC) can be determined. Furthermore, according to the relationship between the subsurface cavity height and the EHAC in the thermodynamic theoretical analysis, the subsurface cavity height can be obtained quantitatively.