Thermo-Optical Switching Effect Based on a Tapered Optical Fiber and Higher Alkanes Doped with ZnS:Mn

The paper investigates the effect of thermo-optic switching resulting from the hybrid combination of a tapered optical fiber (TOF) with alkanes doped with nanoparticles of zinc sulfide doped with manganese (ZnS:Mn NP). Presented measurements focused on controlling losses in an optical fiber by modification of a TOF cladding by the alkanes used, characterized by phase change. Temperature changes cause power transmission changes creating a switcher or a sensor working in an ON-OFF mode. Phase change temperatures and changes in the refractive index of the alkane used directly affected power switching. Alkanes were doped with ZnS:Mn NPs to change the hysteresis observed between ON-OFF modes in pure alkanes. The addition of nanoparticles (NPs) reduces the difference between phase changes due to improved thermal conductivity and introduces extra nucleating agents. Results are presented in the wide optical range of 550–1200 nm. In this investigation, hexadecane and heptadecane were a new cladding for TOF. The higher alkanes were doped with ZnS: Mn NPs in an alkane volume of 1 wt.% and 5 wt.%. The thermo-optic effect can be applied to manufacture a thermo-optic switcher or a temperature threshold sensor.

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Conductive transparent probes and their application to high-density phase-change data storage by using current injection

MRS Proceedings ◽

10.1557/proc-803-hh1.3 ◽

2003 ◽

Vol 803 ◽

Cited By ~ 1

Author(s):

Tooru Murashita

Keyword(s):

Phase Change ◽

Data Storage ◽

Indium Tin Oxide ◽

Amorphous Region ◽

Metal Electrode ◽

Refraction Index ◽

High Density ◽

Phase Changes ◽

Probe Current ◽

The Difference

ABSTRACTWith the goal of producing high-density terabits/inch2 storage, we are studying a method in which nanometer-sized marks are recorded on Ge2Sb2Te5 (GST) phase-change media by current beams injected from sharpened probes. The current beams can inject powers with lower transmission losses into nanometer-sized local regions that are much smaller than the refraction limit of light. Moreover, the difference in the conductivity between amorphous and crystalline GST is orders larger than the difference in their refraction index. Therefore, the current beams are advantageous for such high-density data storage with nanometer-sized marks.We have experimentally and numerically studied phase changes in GST using probe current injections. The structures of the media are composed of GST and a metal electrode stacked on a polycarbonate substrate. We simulated temperatures, crystallization rates, and mark sizes of GST as a function of power injection conditions. The results clarify that a small crystalline mark can be stably made in an amorphous region by injecting probe current pulses with the same beam sizes. For supplying higher injection powers to produce phase change, metal oxide, such as indium-tin- oxide (ITO), is more robust at high powers than metals. We have developed conductive transparent (CT) probes consisting of ITO coated on a fiber tapered to a point with a nanometer-scale radius. The CT probe can inject current in a nanometer-sized region and simultaneously illuminate the same local region. We also propose a new method of optical rewritable phase-change storage using the CT probes.

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Phase Change Materials: A Prospective Solution for Surface Layers of Building Envelopes

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.749.415 ◽

2015 ◽

Vol 749 ◽

pp. 415-419

Author(s):

Zbyšek Pavlík ◽

Anton Trník ◽

Milena Pavlíková ◽

Jan Fořt ◽

Robert Černý

Keyword(s):

Phase Change ◽

Phase Change Materials ◽

Phase Changes ◽

Surface Layers ◽

Scanning Calorimetry ◽

Powder Density ◽

The Difference ◽

And Storage ◽

Change Material

A Phase Change Material (PCM) based on paraffinic wax encapsulated in polymer shell is used for improvement of the heat storage capacity of commercially produced dry plaster, originally developed for both exterior and interior hand application. The composition of PCM modified plasters is designed with respect to the workability of fresh mixtures. Characterization of applied PCM is done using the measurement of particle size distribution, powder density, and matrix density. For the newly developed composite plasters, basic physical properties, mechanical properties, and thermal properties are accessed, whereas a specific attention is paid to the Difference Scanning Calorimetry (DSC) analysis. Using DSC measurement, temperatures of phase change transitions and phase changes enthalpies are identified. The obtained results show that the temperature induced phase change can be used for the release and storage of thermal energy in buildings, which can be beneficially utilized for saving the energy spent for the achievement of the indoor thermal comfort.

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Influence of Metal Substitution on the Pressure-Induced Phase Change in Flexible Zeolitic Imidazolate Frameworks

10.26434/chemrxiv.7108706.v1 ◽

2018 ◽

Author(s):

C. Michael McGuirk ◽

Tomče Runčevski ◽

Julia Oktawiec ◽

Ari Turkiewicz ◽

mercedes K. taylor ◽

...

Keyword(s):

Phase Change ◽

Single Crystal ◽

Gas Adsorption ◽

High Capacity ◽

Phase Changes ◽

Zeolitic Imidazolate Frameworks ◽

Metal Substitution ◽

Heat Management ◽

Metal Organic ◽

First Time

Metal–organic frameworks that display step-shaped adsorption profiles arising from discrete pressure-induced phase changes are promising materials for applications in both high-capacity gas storage and energy-efficient gas separations. The thorough investigation of such materials through chemical diversification, gas adsorption measurements, and in situ structural characterization is therefore crucial for broadening their utility. We examine a series of isoreticular, flexible zeolitic imidazolate frameworks (ZIFs) of the type M(bim)2 (SOD; M = Zn (ZIF-7), Co (ZIF-9), Cd (CdIF-13); bim– = benzimidazolate), and elucidate the effects of metal substitution on the pressure-responsive phase changes and the resulting CO2 and CH4 step positions, pre-step uptakes, and step capacities. Using ZIF-7 as a benchmark, we reexamine the poorly understood structural transition responsible for its adsorption steps and, through high-pressure adsorption measurements, verify that it displays a step in its CH4 adsorption isotherms. The ZIF-9 material is shown to undergo an analogous phase change, yielding adsorption steps for CO2 and CH4 with similar profiles and capacities to ZIF-7, but with shifted threshold pressures. Further, the Cd2+ analogue CdIF-13 is reported here for the first time, and shown to display adsorption behavior distinct from both ZIF-7 and ZIF-9, with negligible pre-step adsorption, a ~50% increase in CO2 and CH4 capacity, and dramatically higher threshold adsorption pressures. Remarkably, a single-crystal-to-single-crystal phase change to a pore-gated phase is also achieved with CdIF-13, providing insight into the phase change that yields step-shaped adsorption in these flexible ZIFs. Finally, we show that the endothermic phase change of these frameworks provides intrinsic heat management during gas adsorption.

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Numerical Study of a Cooling System Using Phase Change of a Refrigerant in a Thermosyphon

Energies ◽

10.3390/en14123634 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3634

Author(s):

Grzegorz Czerwiński ◽

Jerzy Wołoszyn

Keyword(s):

Mass Transfer ◽

Phase Change ◽

Heat Dissipation ◽

Cooling System ◽

Numerical Study ◽

Relaxation Parameter ◽

Phase Changes ◽

Transfer Time ◽

Two Phase ◽

Time Relaxation

With the increasing trend toward the miniaturization of electronic devices, the issue of heat dissipation becomes essential. The use of phase changes in a two-phase closed thermosyphon (TPCT) enables a significant reduction in the heat generated even at high temperatures. In this paper, we propose a modification of the evaporation–condensation model implemented in ANSYS Fluent. The modification was to manipulate the value of the mass transfer time relaxation parameter for evaporation and condensation. The developed model in the form of a UDF script allowed the introduction of additional source equations, and the obtained solution is compared with the results available in the literature. The variable value of the mass transfer time relaxation parameter during condensation rc depending on the density of the liquid and vapour phase was taken into account in the calculations. However, compared to previous numerical studies, more accurate modelling of the phase change phenomenon of the medium in the thermosyphon was possible by adopting a mass transfer time relaxation parameter during evaporation re = 1. The assumption of ten-fold higher values resulted in overestimated temperature values in all sections of the thermosyphon. Hence, the coefficient re should be selected individually depending on the case under study. A too large value may cause difficulties in obtaining the convergence of solutions, which, in the case of numerical grids with many elements (especially three-dimensional), significantly increases the computation time.

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High speed optical switching gain based EDFA model with 30 Gb/s NRZ modulation code in optical systems

Journal of Optical Communications ◽

10.1515/joc-2020-0223 ◽

2020 ◽

Vol 0 (0) ◽

Author(s):

Mahmoud M. A. Eid ◽

Ahmed Nabih Zaki Rashed ◽

Keyword(s):

Optical Fiber ◽

High Speed ◽

Optical Switching ◽

Fiber Amplifier ◽

Optical Systems ◽

Power Budget ◽

Erbium Doped Fiber Amplifier ◽

Amplifier Model ◽

Modulation Rate ◽

Modulation Code

AbstractThis study presents high speed optical switching gain based Erbium doped fiber amplifier model. By using the proposed model the optical fiber loss can be minimized. The system is stabilized with the power budget of 25.875 mW a long 75 km as a length of optical fiber in this study can be verified. The modulation rate of 10 Gb/s can be upgrade up to reach 30 Gb/s. The suitable power for the optical transmitter is −2.440 dBm and NRZ modulation code is verified. The receiver sensitivity can be upgraded with the minimum bit error rate and max Q factor are 1.806 e−009 and 5.899.

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In-Process Diameter Measurement Technique for Micro-Optical Fiber with Standing Wave Illumination

Nanomanufacturing and Metrology ◽

10.1007/s41871-020-00081-4 ◽

2021 ◽

Author(s):

Masaki Michihata ◽

Zhao Zheng ◽

Daiki Funaiwa ◽

Sojiro Murakami ◽

Shotaro Kadoya ◽

...

Keyword(s):

Optical Fiber ◽

Standing Wave ◽

Dynamic Range ◽

Scattered Light ◽

High Dynamic Range ◽

Measurement Range ◽

Diameter Distribution ◽

Process Measurement ◽

Air Turbulence ◽

Tapered Optical Fiber

AbstractIn this paper, we propose an in-process measurement method of the diameter of micro-optical fiber such as a tapered optical fiber. The proposed technique is based on analyzing optically scattered light generated by standing wave illumination. The proposed method is significant in that it requires an only limited measurement range and does not require a high dynamic range sensor. These properties are suitable for in-process measurement. This experiment verified that the proposed method could measure a fiber diameter as stable as ± 0.01 μm under an air turbulence environment. As a result of comparing the measured diameter distribution with those by scanning electron microscopy, it was confirmed that the proposed method has a measurement accuracy better than several hundred nanometers.

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Phase changes and convection in the Earth’s mantle

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1965.0040 ◽

1965 ◽

Vol 258 (1088) ◽

pp. 276-283 ◽

Cited By ~ 76

Keyword(s):

Temperature Gradient ◽

Phase Change ◽

Initial Temperature ◽

Phase Changes ◽

Homogeneous Layer ◽

Transformation Zone ◽

Earth’S Mantle ◽

Transition Level ◽

Transformation Rates

A phase change may hinder or enhance convection, depending on its characteristics. Univariant transformations such as may occur in the mantle constitute a barrier to convection unless the motion starts at some distance above or below the transition level; an initial temperature gradient in excess of the adiabatic value is also required. Multivariant transformations only require, in the transformation zone, an initial gradient slightly greater than the adiabatic value for a homogeneous layer. The effect on convection of transformation rates is not likely to be serious.

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