scholarly journals 221 K Local Photothermal Heating in a Si Plasmonic Waveguide Loaded with a Co Thin Film

Sensors ◽  
2021 ◽  
Vol 21 (19) ◽  
pp. 6634
Author(s):  
Nana Ota ◽  
Tomohiro Miyauchi ◽  
Hiromasa Shimizu
Keyword(s):  
Buffer Layer ◽  
Optical Sensors ◽  
Temperature Rise ◽  
Phase Change Materials ◽  
Optical Switches ◽  
Maximum Temperature ◽  
Plasmonic Waveguides ◽  
Resistance Change ◽  
Tm Mode ◽  
Photothermal Heating

Photothermal heaters are important devices for optical switches and memories based on the thermo-optic/magneto-optic effect and phase change materials. We demonstrated photothermal heating in Si plasmonic waveguides loaded with Co thin films by measuring the resistance change upon inputting transverse-magnetic (TM) mode light. Temperature rise is proportional to the light intensity with clear polarization dependence. The photothermal conversion efficiency was estimated at 36 K/mW and maximum temperature rise was estimated at 221 K at steady state upon the inputting 6.3 mW TM mode light for the 400 nm-wide, 8 µm-long and 189 nm-thick Co film deposited on the Si wire waveguide with 129 nm-thick SiO2 buffer layer. The method to increase the efficiency is discussed based on the experimental and simulation results considering the thickness of the SiO2 buffer layer, Co layer and Si core layer, waveguide width, and wavelength. Local photothermal heaters in this study can be applied to a variety of fields including optical switches/memories without electrical control signals in photonic integrated circuits, on-chip optical sensors, and a lab-on-a-chip in biology, chemistry, and medicine.

Modeling temperature rise in multi-track reciprocating frictional sliding

2021 ◽  
pp. 135065012098823
Author(s):  
Thierry A Blanchet
Keyword(s):  
Temperature Rise ◽  
Peclet Number ◽  
Maximum Temperature ◽  
Uniform Heat Flux ◽  
Heat Accumulation ◽  
Stroke Length ◽  
Péclet Number ◽  
Maximum Temperature Rise ◽  
Rectangular Patch ◽  
Accumulation Effect

As in various manufacturing processes, in sliding tests with scanning motions to extend the sliding distance over fresh countersurface, temperature rise during any pass is bolstered by heating during prior passes over neighboring tracks, providing a “heat accumulation effect” with persisting temperature rises contributing to an overall temperature rise of the current pass. Conduction modeling is developed for surface temperature rise as a function of numerous inputs: power and size of heat source; speed and stroke length, and track increment of scanning motion; and countersurface thermal properties. Analysis focused on mid-stroke location for passes of a square uniform heat flux sufficiently far into the rectangular patch being scanned from the first pass at its edge that steady heat accumulation effect response is adopted, focusing on maximum temperature rise experienced across the pass' track. The model is non-dimensionalized to broaden the applicability of the output of its runs. Focusing on practical “high” scanning speeds, represented non-dimensionally by Peclet number (in excess of 40), applicability is further broadened by multiplying non-dimensional maximum temperature rise by the square root of Peclet number as model output. Additionally, investigating model runs at various non-dimensional speed (Peclet number) and reciprocation period values, it appears these do not act as independent inputs, but instead with their product (non-dimensional stroke length) as a single independent input. Modified maximum temperature rise output appears to be a function of only two inputs, increasing with decreasing non-dimensional values of stroke length and scanning increment, with outputs of models runs summarized compactly in a simple chart.

scholarly journals Low-energy optical switching of SO2 linkage isomerisation in single crystals of a ruthenium-based coordination complex

RSC Advances ◽  
2021 ◽  
Vol 11 (22) ◽  
pp. 13183-13192
Author(s):  
Jacqueline M. Cole ◽  
David J. Gosztola ◽  
Sven O. Sylvester
Keyword(s):  
Single Crystals ◽  
Optical Sensors ◽  
Optical Switching ◽  
Optical Switches ◽  
Low Energy ◽  
Coordination Complex ◽  
Wide Range

Single crystals that behave as optical switches are desirable for a wide range of applications, from optical sensors to read–write memory media.

Braking performance of a novel frictional-magnetic compound disc brake for automobiles

2018 ◽  
Vol 233 (10) ◽  
pp. 2443-2454 ◽  
Author(s):  
Yan Yin ◽  
Jiusheng Bao ◽  
Jinge Liu ◽  
Chaoxun Guo ◽  
Tonggang Liu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Temperature Rise ◽  
Friction Material ◽  
Maximum Temperature ◽  
Interface Temperature ◽  
Disc Brake ◽  
Braking Performance ◽  
Maximum Temperature Rise ◽  
Disc Brakes ◽  
Braking Torque

Disc brakes have been applied in various automobiles widely and their braking performance has vitally important effects on the safe operation of automobiles. Although numerous researches have been conducted to find out the influential law and mechanism of working condition parameters like braking pressure, initial braking speed, and interface temperature on braking performance of disc brakes, the influence of magnetic field is seldom taken into consideration. In this paper, based on the novel automotive frictional-magnetic compound disc brake, the influential law of magnetic field on braking performance was investigated deeply. First, braking simulation tests of disc brakes were carried out, and then dynamic variation laws and mechanisms of braking torque and interface temperature were discussed. Furthermore, some parameters including average braking torque, trend coefficient and fluctuation coefficient of braking torque, average temperature, maximum temperature rise, and the time corresponding to the maximum temperature rise were extracted to characterize the braking performance of disc brakes. Finally, the influential law and mechanism of excitation voltage on braking performance were analyzed through braking simulation tests and surface topography analysis of friction material. It is concluded that the performance of frictional-magnetic compound disc brake is prior to common brake. Magnetic field is greatly beneficial for improving the braking performance of frictional-magnetic compound disc brake.

scholarly journals Revisiting the Effect of Slag in Reducing Heat of Hydration in Concrete in Comparison to Other Supplementary Cementitious Materials

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1847 ◽  
Author(s):  
Hoon Moon ◽  
Sivakumar Ramanathan ◽  
Prannoy Suraneni ◽  
Chang-Seon Shon ◽  
Chang-Joon Lee ◽  
...  
Keyword(s):  
Blast Furnace ◽  
Temperature Rise ◽  
Adiabatic Calorimetry ◽  
Blast Furnace Slag ◽  
Isothermal Calorimetry ◽  
Heat Of Hydration ◽  
Supplementary Cementitious Materials ◽  
Maximum Temperature ◽  
Mass Concrete ◽  
Furnace Slag

Blast furnace slag (SL) is an amorphous calcium aluminosilicate material that exhibits both pozzolanic and latent hydraulic activities. It has been successfully used to reduce the heat of hydration in mass concrete. However, SL currently available in the market generally experiences pre-treatment to increase its reactivity to be closer to that of portland cement. Therefore, using such pre-treated SL may not be applicable for reducing the heat of hydration in mass concrete. In this work, the adiabatic and semi-adiabatic temperature rise of concretes with 20% and 40% SL (mass replacement of cement) containing calcium sulfate were investigated. Isothermal calorimetry and thermal analysis (TGA) were used to study the hydration kinetics of cement paste at 23 and 50 °C. Results were compared with those with control cement and 20% replacements of silica fume, fly ash, and metakaolin. Results obtained from adiabatic calorimetry and isothermal calorimetry testing showed that the concrete with SL had somewhat higher maximum temperature rise and heat release compared to other materials, regardless of SL replacement levels. However, there was a delay in time to reach maximum temperature with increasing SL replacement level. At 50 °C, a significant acceleration was observed for SL, which is more likely related to the pozzolanic reaction than the hydraulic reaction. Semi-adiabatic calorimetry did not show a greater temperature rise for the SL compared to other materials; the differences in results between semi-adiabatic and adiabatic calorimetry are important and should be noted. Based on these results, it is concluded that the use of blast furnace slag should be carefully considered if used for mass concrete applications.

scholarly journals Thermal Analysis of AlGaN/GaN HEMTs Considering Anisotropic And Inhomogeneous Thermal Conductivity

2021 ◽  
Author(s):  
Yao Li ◽  
Zixuan Zheng ◽  
Qun Li ◽  
Hongbin Pu
Keyword(s):  
Thermal Conductivity ◽  
Temperature Rise ◽  
Power Dissipation ◽  
Thermal Characteristics ◽  
Maximum Temperature ◽  
Base Temperature ◽  
Initial Growth ◽  
Boltzmann Transport ◽  
Growth Interface ◽  
Anisotropic Thermal Conductivity

Abstract To examine the differences of thermal characteristics introduced by material thermal conductivity, anisotropic polycrystalline diamond (PCD) and GaN are analyzed based on the accurate model of grain sizes in the directions of parallel and vertical to the interface and an approximate solution of the phonon Boltzmann transport equation. Due to the space-variant grain structures of PCD, the inhomogeneous-anisotropic local thermal conductivity, homogeneous-anisotropic thermal conductivity averaged over the whole layer and the typical values of inhomogeneous-isotropic thermal conductivity are compared with/without anisotropic GaN thermal conductivity. The results show that the considerations of inhomogeneous-anisotropic PCD thermal conductivity and anisotropic GaN thermal conductivity are necessary for the accurate prediction of temperature rise in the GaN HEMT devices, and when ignoring both, the maximum temperature rise is undervalued by over 16 K for thermal boundary resistance (TBR) of 6.5 to 60 m2K/GW at power dissipation of 10 W/mm. Then the dependences of channel temperature on several parameters are discussed and the relations of thermal resistance with power dissipation are extracted at different base temperature. Compared with GaN, SiC and Si substrates, PCD is the most effective heat spreading layer though limited by the grain size at initial growth interface.

scholarly journals Comparison and Combination of Thermal, Fluorescence, and Hyperspectral Imaging for Monitoring Fusarium Head Blight of Wheat on Spikelet Scale

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2281 ◽  
Author(s):  
Anne-Katrin Mahlein ◽  
Elias Alisaac ◽  
Ali Al Masri ◽  
Jan Behmann ◽  
Heinz-Wilhelm Dehne ◽  
...  
Keyword(s):  
Fusarium Head Blight ◽  
Hyperspectral Imaging ◽  
Optical Sensors ◽  
Fusarium Culmorum ◽  
Maximum Temperature ◽  
Support Vector ◽  
Head Blight ◽  
Maximum Temperature Difference ◽  
Simple Ratio

Optical sensors have shown high capabilities to improve the detection and monitoring of plant disease development. This study was designed to compare the feasibility of different sensors to characterize Fusarium head blight (FHB) caused by Fusarium graminearum and Fusarium culmorum. Under controlled conditions, time-series measurements were performed with infrared thermography (IRT), chlorophyll fluorescence imaging (CFI), and hyperspectral imaging (HSI) starting 3 days after inoculation (dai). IRT allowed the visualization of temperature differences within the infected spikelets beginning 5 dai. At the same time, a disorder of the photosynthetic activity was confirmed by CFI via maximal fluorescence yields of spikelets (Fm) 5 dai. Pigment-specific simple ratio PSSRa and PSSRb derived from HSI allowed discrimination between Fusarium-infected and non-inoculated spikelets 3 dai. This effect on assimilation started earlier and was more pronounced with F. graminearum. Except the maximum temperature difference (MTD), all parameters derived from different sensors were significantly correlated with each other and with disease severity (DS). A support vector machine (SVM) classification of parameters derived from IRT, CFI, or HSI allowed the differentiation between non-inoculated and infected spikelets 3 dai with an accuracy of 78, 56 and 78%, respectively. Combining the IRT-HSI or CFI-HSI parameters improved the accuracy to 89% 30 dai.

scholarly journals Aluminum Inserts for Enhancing Heat Transfer in PCM Accumulator

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 415 ◽  
Author(s):  
Anna Dmitruk ◽  
Krzysztof Naplocha ◽  
Jakub Grzęda ◽  
Jacek W. Kaczmar
Keyword(s):  
Phase Change Materials ◽  
Heat Storage ◽  
Storage System ◽  
Volume Ratio ◽  
Energy Storage System ◽  
Heat Fluxes ◽  
Heat Of Fusion ◽  
Maximum Temperature ◽  
Release Time ◽  
Storage Unit

Phase change materials (PCMs) are applied in heat storage units, as they are able to accumulate the energy in the form of the latent heat of fusion. Thus, they can be used in recovering the excess of heat from various industrial processes. Their main weakness is their low thermal conductivity coefficient, which strongly limits their usage. In this paper, the benefits of the application of metallic inserts in heat storage PCM-based units were elaborated. Two kinds of Al–Si spatial elements (foams and honeycomb structures) were produced with the use of means of the investment casting method. Key factors influencing the technological process were established. The surface’s roughness was measured in order to compare the obtained structures with their patterns in terms of the casting’s accuracy. The compressive strength of the samples was tested, and their fatigue resistance was considered. The thermal performance of manufactured inserts in the PCM (paraffin)-based accumulator, supported by the calculation of heat fluxes, was analyzed and adjusted. Finally, further optimization was conducted in terms of the volume ratio of the metal insert to the PCM. Metallic inserts were found to significantly affect the performance of the entire energy storage system, as their use results in reduced charging time, a longer heat release time, increased maximum temperature, and a significant reduction in the temperature gradient in the heat storage unit.

Maximum temperature rise of fire plume ejected out of the compartment window with a horizontal eave

2020 ◽  
Vol 44 (8) ◽  
pp. 1108-1117
Author(s):  
Linjie Li ◽  
Zihe Gao ◽  
Yilin Li ◽  
Pai Xu ◽  
Ningyu Zhao ◽  
...  
Keyword(s):  
Temperature Rise ◽  
Maximum Temperature ◽  
Fire Plume ◽  
Maximum Temperature Rise

scholarly journals Controllable Polarization of Lasing Emission From a Polymer Microfiber Laser

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Van Duong Ta ◽  
Rui Chen ◽  
Handong Sun
Keyword(s):  
Optical Sensors ◽  
Transverse Magnetic ◽  
Optical Switches ◽  
Pulse Excitation ◽  
Whispering Gallery ◽  
Low Threshold ◽  
Output Laser ◽  
On Chip ◽  
Doped Polymer ◽  
Lasing Modes

AbstractMicrolasers with controllable polarization of output emission are vital for on-chip optical communications, optical sensors and optical switches. In this work, we report a high quality (Q) factor, low-threshold polymer microfiber laser and the possibility of achieving laser emission with a desired polarization. The microfiber is fabricated by direct drawing from a dye-doped polymer solution and it can generate whispering gallery mode (WGM) lasing under optical pulse excitation. When the microfiber is pumped from the side with pumping direction perpendicular to the microfiber’s axis, the polarization direction of the output laser is found to be the same as that of the pump laser. Lasing emission with either transverse electric (TE) or transverse magnetic (TM) modes can be obtained and these two polarization states can be switched over by tuning the pumping laser. Furthermore, emission with both TE and TM modes can also be observed by changing the orientation of the microfiber relatively to pumping direction. Our finding provides an effective approach for achieving microlasers that have high Q lasing modes with anticipated polarization.

Battery Thermal Management System Design: Role of Influence of Nanofluids, Flow Directions, and Channels

2019 ◽  
Vol 17 (2) ◽  
Author(s):  
Sanjay Srinivaas ◽  
Wei Li ◽  
Akhil Garg ◽  
Xiongbin Peng ◽  
Liang Gao
Keyword(s):  
Pressure Drop ◽  
Thermal Management ◽  
Temperature Rise ◽  
Management System ◽  
Battery Pack ◽  
Maximum Temperature ◽  
Temperature Deviation ◽  
Battery Thermal Management ◽  
Thermal Management System ◽  
Battery Thermal Management System

Abstract Lithium-ion batteries are currently being produced and used in large quantities in the automobile sector as a clean alternative to fossil fuels. The thermal behavior of the battery pack is a very important criterion, which is not only essential for safety but also has an equally important role in the capacity and life cycle of the batteries. The liquid battery thermal management system is a very efficient type of thermal management system, and mini-channel-based liquid cooling systems are one of the most popular type of the battery thermal management system and have been researched extensively. This paper mainly intends to study the effects of tapering, the addition of grooves to the channel, the use of different nanofluids, and the flow direction of coolant on the thermal performance of the battery pack using a three-dimensional computational fluid dynamics model. The results suggest that converging channels can be used to control the temperature rise, while diverging channels can be used to control the temperature deviation. The addition of grooves and the use of nanofluids were beneficial in reducing the temperature rise. The final setups were able to reduce the maximum temperature rise by 2.267 K with a substantial pressure drop increase and by 1.513 K with an increase in pressure drop of only 19.92%.

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