16,382 results
Search Results
2. Molecular simulation of different types of polysilsesquioxane doped cellulose insulating paper: A guide for special cellulose insulating paper
- Author
-
Zeng, Zhenglin, primary, Tan, Weimin, additional, Deng, Yanhe, additional, Cheng, Quan, additional, Fu, Liuyue, additional, and Tang, Chao, additional
- Published
- 2024
- Full Text
- View/download PDF
3. Fabrication of negative magnetostrictive Japanese traditional paper (washi) with cobalt ferrite particles
- Author
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Kurita, Hiroki, primary, Rova, Lovisa, additional, Keino, Takumi, additional, and Narita, Fumio, additional
- Published
- 2023
- Full Text
- View/download PDF
4. Fabrication and characterization of graphene-based paper for heat spreader applications.
- Author
-
Muhsan, Ali A. and Lafdi, Khalid
- Subjects
THERMAL conductivity measurement ,THERMAL conductivity ,CHEMICAL processes ,CHEMICAL vapor deposition ,SCANNING electron microscopy ,SLURRY - Abstract
In this work, in-plane thermal conductivity measurement was carried out on graphene-based papers. Graphene-based papers were fabricated using various processing techniques such as chemical vapor deposition (CVD), hot pressing of graphene slurry, and evaporation induced self-assembly. The prepared materials were characterized using scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. In-plane thermal conductivity measurement was performed via a steady state thin film thermal conductivity apparatus. The in-plane thermal conductivity measurements show that the CVD based sample has the highest thermal conductivity. COMSOL Multiphysics was used to simulate the in-plane thermal conductivity of graphene-based papers. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
5. X-ray microtomography and laser ablation in the analysis of ink distribution in coated paper.
- Author
-
Myllys, M., Häkkänen, H., Korppi-Tommola, J., Backfolk, K., Sirviö, P., and Timonen, J.
- Subjects
LASER ablation ,X-ray computed microtomography ,INK chemistry ,PERMEABILITY of paper coatings ,PROFILOMETER ,PENETRATION mechanics - Abstract
A novel method was developed for studying the ink-paper interface and the structural variations of a deposited layer of ink. Combining high-resolution x-ray tomography with laser ablation, the depth profile of ink (toner), i.e., its varying thickness, could be determined in a paper substrate. X-ray tomography was used to produce the 3D structure of paper with about 1 μm spatial resolution. Laser ablation combined with optical imaging was used to produce the 3D structure of the printed layer of ink on top of that paper with about 70 nm depth resolution. Ablation depth was calibrated with an optical profilometer. It can be concluded that a toner layer on a light-weight-coated paper substrate was strongly perturbed by protruding fibers of the base paper. Such fibers together with the surface topography of the base paper seem to be the major factors that control the leveling of toner and its penetration into a thinly coated paper substrate. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
6. Reactive molecular dynamics research on influences of water on aging characteristics of PMIA insulation paper
- Author
-
Wang, Lihan, primary, Yin, Fei, additional, Shen, Yin, additional, and Tang, Chao, additional
- Published
- 2020
- Full Text
- View/download PDF
7. Improvements of mechanical properties of multilayer open-hole graphene papers
- Author
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Xia, Yuxuan, primary, Li, Yeyuan, additional, Zhu, Chunhua, additional, Wei, Ning, additional, and Zhao, Junhua, additional
- Published
- 2019
- Full Text
- View/download PDF
8. Electrically and magnetically dual-driven Janus particles for handwriting-enabled electronic paper.
- Author
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Komazaki, Y., Hirama, H., and Torii, T.
- Subjects
- *
JANUS particles , *ELECTRONIC paper , *MICROFLUIDIC analytical techniques , *SUPERPARAMAGNETIC materials , *NANOPARTICLES , *ELECTRIC potential , *MAGNETIC fields , *INTERNET forums - Abstract
In this work, we describe the synthesis of novel electrically and magnetically dual-driven Janus particles for a handwriting-enabled twisting ball display via the microfluidic technique. One hemisphere of the Janus particles contains a charge control agent, which allows the display color to be controlled by applying a voltage and superparamagnetic nanoparticles, allows handwriting by applying a magnetic field to the display. We fabricated a twisting ball display utilizing these Janus particles and tested the electric color control and handwriting using a magnet. As a result, the display was capable of permitting handwriting with a small magnet in addition to conventional color control using an applied voltage (80 V). Handwriting performance was improved by increasing the concentration of superparamagnetic nanoparticles and was determined to be possible even when 80V was applied across the electrodes for 4 wt.% superparamagnetic nanoparticles in one hemisphere. This improvement was impossible when the concentration was reduced to 2 wt.% superparamagnetic nanoparticles. The technology presented in our work can be applied to low-cost, lightweight, highly visible, and energy-saving electronic message boards and large whiteboards because the large-size display can be fabricated easily due to its simple structure. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
9. Thin film versus paper-like reduced graphene oxide: Comparative study of structural, electrical, and thermoelectrical properties.
- Author
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Okhay, Olena, Gonçalves, Gil, Tkach, Alexander, Dias, Catarina, Ventura, Joao, da Silva, Manuel Fernando Ribeiro, Valente Gonçalves, Luís Miguel, and Titus, Elby
- Subjects
GRAPHENE oxide ,THIN films ,CHEMICAL reduction ,HYDRAZINE ,SEMICONDUCTORS - Abstract
We report fabrication of reduced graphene oxide (rGO) films using chemical reduction by hydrazine hydrate and rGO paper-like samples using low temperature treatment reduction. Structural analysis confirms the formation of the rGO structure for both samples. Current-voltage (I-V) measurements of the rGO film reveal semiconductor behavior with the maximum current value of ~3×10
-4 A. The current for the rGO paper sample is found to be, at least, one order of magnitude higher. Moreover, bipolar resistance switching, corresponding to memristive behavior of type II, is observed in the I-V data of the rGO paper. Although precise values of the rGO film conductivity and the Seebeck coefficient could not be measured, rGO paper shows an electrical conductivity of 6.7×102 S/m and Seebeck coefficient of -6μV/°C. Thus, we demonstrate a simplified way for the fabrication of rGO paper that possesses better and easier measurable macroscopic electrical properties than that of rGO thin film. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
10. Mechanism study of the conductivity characteristics of cellulose electrical insulation influenced by moisture.
- Author
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Zhao, Haoxiang, Mu, Haibao, Zhang, Daning, Baumeier, Björn, Yao, Huanmin, Guo, Guangzhi, and Zhang, Guanjun
- Subjects
ELECTRIC insulators & insulation ,FRONTIER orbitals ,MOLECULAR dynamics ,CELLULOSE ,ELECTRIC distortion ,MOISTURE ,CELLULOSE synthase ,SILICONE rubber - Abstract
Cellulose insulating paper is widely used in the power industry for its good electrical insulating properties. Moisture sharply increases its conductivity, which directly leads to the weakening of insulation performance and greatly increases the risk of subsequent electric field distortion and insulation breakdown. This paper focuses on the microscopic mechanism of moisture changing the characteristics of charge transport in cellulose insulation and attempts to reveal the related conductivity mechanism. To achieve this purpose, microscopic and macroscopic perspectives are integrated and several simulation and experimental methods are utilized comprehensively. The molecular dynamics simulation results showed that most water molecules in damped cellulose were individually and uniformly adsorbed on the hydroxyl groups by hydrogen bond, and the quantum chemistry computation results showed that the lowest unoccupied molecular orbital more appeared on the water molecule and the corresponding density of state increased. Then, experimentally, it was confirmed that the trap energy level decreased by the thermally stimulated current method. On this basis, the promotion effect of moisture on charge transport is predicted and verified by polarization and depolarization current methods. As the moisture content increased, more charge carriers escaped from the trap by hopping and participated in long-range continuous charge motion. Therefore, after dampness, the current of cellulose insulating paper increased exponentially with the increase in electric field strength, which was consistent with the hopping conductivity mechanism. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
11. Preface to Special Topic: Invited Papers from the 59th Annual Conference on Magnetism and Magnetic Materials, Honolulu, HI, USA, 3–7 November 2014
- Author
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Leighton, Chris, primary
- Published
- 2015
- Full Text
- View/download PDF
12. Biocellulose-based flexible magnetic paper
- Author
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Barud, H. S., primary, Tercjak, A., additional, Gutierrez, J., additional, Viali, W. R., additional, Nunes, E. S., additional, Ribeiro, S. J. L., additional, Jafellici, M., additional, Nalin, M., additional, and Marques, R. F. C., additional
- Published
- 2015
- Full Text
- View/download PDF
13. Preface to Special Topic: Invited Papers of the 58th Annual Conference on Magnetism and Magnetic Materials, Denver, Colorado, USA, November 2013
- Author
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Hoffmann, Axel, primary
- Published
- 2014
- Full Text
- View/download PDF
14. Electronic structure spectroscopy of organic semiconductors by energy resolved-electrochemical impedance spectroscopy (ER-EIS).
- Author
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Schauer, Franz
- Subjects
ORGANIC semiconductors ,ELECTRONIC structure ,IMPEDANCE spectroscopy ,SEMICONDUCTOR materials ,MATERIALS science ,FULLERENES ,ELECTRONIC paper ,TIME-resolved spectroscopy - Abstract
Organic electronic applications are envisioned to address broad markets, which includes flexible displays, electronic papers, sensors, disposable and wearable electronics, and medical and biophysical applications, leading to a tremendous amount of interest from both academia and industry in the study of devices. These fields of science and technology constitute interdisciplinary fields that cover physics, chemistry, biology, and materials science, leading, as a wanted output, to the elucidation of physical and chemical properties, as well as structures, fabrication, and performance evaluation of devices and the creation of new knowledge underlying the operation of organic devices using new synthesized organic materials—organic semiconductors. We testify the situation when the available organic electronic applications sometimes lack a theoretical background. The cause may be the complicated properties of disordered, weak bounded, molecular materials with properties different from their inorganic counterparts. One of the basic information-rich resources is the electronic structure of organic semiconductors, elucidated by the methods, hardly possible to be transferred from the branch of inorganic semiconductors. Electrochemical spectroscopic methods, in general, and electrochemical impedance spectroscopy, in particular, tend and seem to fill this gap. In this Perspective article, the energy resolved-electrochemical impedance spectroscopic method for electronic structure studies of surface and bulk of organic semiconductors is presented, and its theoretical and implementation background is highlighted. To show the method's properties and strength, both as to the wide energy and excessive dynamic range, the basic measurements on polymeric materials and D–A blends are introduced, and to highlight its broad applicability, the results on polysilanes degradability, gap engineering of non-fullerene D–A blends, and electron structure spectroscopy of an inorganic nanocrystalline film are highlighted. In the outlook and perspective, the electrolyte/polymer interface will be studied in general and specifically devoted to the morphological, transport, and recombination properties of organic semiconductors and biophysical materials. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
15. Paper-based ultracapacitors with carbon nanotubes-graphene composites
- Author
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Li, Jian, primary, Cheng, Xiaoqian, additional, Sun, Jianwei, additional, Brand, Cameron, additional, Shashurin, Alexey, additional, Reeves, Mark, additional, and Keidar, Michael, additional
- Published
- 2014
- Full Text
- View/download PDF
16. Paper-based ultracapacitors with carbon nanotubes-graphene composites.
- Author
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Jian Li, Xiaoqian Cheng, Jianwei Sun, Brand, Cameron, Shashurin, Alexey, Reeves, Mark, and Keidar, Michael
- Subjects
- *
SUPERCAPACITORS , *CARBON nanotubes , *GRAPHENE , *SCANNING electron microscopes , *TRANSMISSION electron microscopes , *RAMAN spectroscopy , *THIN films - Abstract
In this paper, a paper-based ultracapacitors were fabricated by the rod-rolling method with the ink of carbon nanomaterials, which were synthesized by arc discharge under various magnetic conditions. Composites of carbon nanostructures, including high-purity single-walled carbon nanotubes (SWCNTs) and graphene flakes were synthesized simultaneously in a magnetically enhanced arc. These two nanostructures have promising electrical properties and synergistic effects in the application of ultracapacitors. Scanning electron microscope, transmission electron microscope, and Raman spectroscopy were employed to characterize the properties of carbon nanostructures and their thin films. The sheet resistance of the SWCNT and composite thin films was also evaluated by four-point probe from room temperature to the cryogenic temperature as low as 90 K. In addition, measurements of cyclic voltammetery and galvanostatic charging/discharging showed the ultracapacitor based on composites possessed a superior specific capacitance of up to 100 F/g, which is around three times higher than the ultracapacitor entirely fabricated with SWCNT. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
17. Reactive molecular dynamics research on influences of water on aging characteristics of PMIA insulation paper
- Author
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Fei Yin, Lihan Wang, Yin Shen, and Chao Tang
- Subjects
010302 applied physics ,Materials science ,Moisture ,Thermal decomposition ,General Physics and Astronomy ,02 engineering and technology ,Activation energy ,021001 nanoscience & nanotechnology ,01 natural sciences ,Decomposition ,Molecular dynamics ,Chemical engineering ,Insulation system ,0103 physical sciences ,Molecule ,Fiber ,0210 nano-technology - Abstract
The diffusion of moisture in the meta-aramid fiber (PMIA) oil-paper insulation system and the thermal decomposition of PMIA insulation paper in different moisture contents were studied via molecular dynamics simulations. The results showed that the PMIA insulation paper had a stronger ability to absorb water molecules than the insulating oil; therefore, water molecules in the insulating oil diffuse to the insulation paper, which further affects the thermal decomposition of the PMIA insulation paper. The activation energy of the water-bearing composite model was 129.96 kJ/mol, which was 5.5% lower than that of the pure PMIA (137.61 kJ/mol). It indicated that moisture could promote PMIA decomposition. The micromechanism of the enhanced thermal decomposition of PMIA with moisture contents could be described as follows: The O–H bond of the water can easily break to generate H atoms and hydroxyl radicals (•OH). The strong activity of H atoms allows it to easily combine with the ammonia base at the end of PMIA to generate NH3. Additionally, the free •OH radical can easily combine with the amido and carbonyl bonds at two ends of PMIA, undergo an oxidation reaction, and generate an oxhydryl. Therefore, it can reduce the chemical stability of the PMIA chain and further drive thermal decomposition. Statistical data on fragments generated by the thermal decomposition of the water-bearing PMIA composite system show that the main products include H2, C/H/O-containing molecules, hydrocarbon molecules, N-bearing molecules, and free radicals.
- Published
- 2020
18. Development of a differential photoacoustic system for the determination of the effective water diffusion and water vapor permeability coefficients in thin films.
- Author
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Martinez-Munoz, P. E., Martinez-Hernandez, H. D., Rojas-Beltran, C. F., Perez-Ospina, J. L., and Rodriguez-Garcia, M. E.
- Subjects
THIN films ,PERMEABILITY ,WATER vapor ,HUMIDITY ,ELECTRONIC noise ,DIFFUSION coefficients ,RESERVOIRS - Abstract
This paper focused on developing a methodology and metrology using a differential photoacoustic (PA) system to determine the effective water vapor diffusion coefficient (D e f f ) and the effective permeability coefficient (Π) in thin films as a piece of paper and standard polystyrene for a controlled relative humidity. The methodology proposes a new differential photoacoustic system, including the water reservoir, relative humidity, and temperature detectors. Two cells, reference/sample, were used to obtain the instrumental function to reduce the electronic and environmental noises. A method based on the study of ln [ 1 − (S − S 0) / Δ S ] = t / τ D and the behaviors of R
2 as a function of the number of data was proposed to assess the region in which the photoacoustic signal should be processed to determine each effective coefficient. S is the amplitude of the PA signal, S 0 is the initial amplitude value, Δ S is the change, t (time), and τ D is the water vapor diffusion time. The effective water diffusion coefficient (D e f f ) for water and polystyrene was 1.90 × 10−11 m2 /s and 3.09 × 10−11 m2 /s, respectively. The permeability coefficient value for the piece of paper was 4.18 × 10−9 mol kg−1 cm−2 s−1 Pa−1 , while for polystyrene, it was 6.80 × 10−9 mol kg−1 cm−2 s−1 Pa−1 for 70% of relative humidity. This methodology can be extended by changing the moisture content on the chamber to obtain the dependence of D e f f as a function of relative humidity. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
19. Fabrication and characterization of graphene-based paper for heat spreader applications
- Author
-
Ali A. Muhsan and Khalid Lafdi
- Subjects
010302 applied physics ,Materials science ,F300 ,Graphene ,F200 ,General Physics and Astronomy ,H800 ,02 engineering and technology ,Chemical vapor deposition ,021001 nanoscience & nanotechnology ,Hot pressing ,01 natural sciences ,Evaporation (deposition) ,law.invention ,Thermal conductivity measurement ,Thermal conductivity ,law ,0103 physical sciences ,Heat spreader ,Thin film ,Composite material ,0210 nano-technology - Abstract
In this work, in-plane thermal conductivity measurement was carried out on graphene-based papers. Graphene-based papers were fabricated using various processing techniques such as chemical vapor deposition (CVD), hot pressing of graphene slurry, and evaporation induced self-assembly. The prepared materials were characterized using scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. In-plane thermal conductivity measurement was performed via a steady state thin film thermal conductivity apparatus. The in-plane thermal conductivity measurements show that the CVD based sample has the highest thermal conductivity. COMSOL Multiphysics was used to simulate the in-plane thermal conductivity of graphene-based papers.
- Published
- 2019
20. Microwave driven atmospheric water harvesting with common sorbents.
- Author
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Nepal, Suman, Shahrokhian, Aida, and King, Hunter
- Subjects
WATER harvesting ,SORBENTS ,MASS transfer ,MICROWAVES ,HUMIDITY ,MICROWAVE heating ,SORPTION - Abstract
Using sorbent materials to separate and concentrate ambient humidity is a promising option for atmospheric water harvesting in the face of impending worldwide freshwater scarcity. The method of cycled sorption and forced release can facilitate efficient condensation, but performance strongly depends on device-scale issues of heat and mass transfer. We examine the potential of using microwave radiation to liberate sorbed vapor, in proof-of-concept experiments with hygroscopic salt-infused paper towel as simple sorbents. We quantify performance as a function of tunable system parameters and ambient humidity. Our results demonstrate promising aspects: both rapid desorption and regeneration, owing to water-tuned dielectric heating and directing flow through fibrous sorbent, respectively; substantial efficiency of moisture separation toward very low (∼ 25 %) relative humidity; and robust repeatability over many cycles, due to the targeted energy input and retention of hygroscopic salt within the paper scaffold. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
21. Improvements of mechanical properties of multilayer open-hole graphene papers
- Author
-
Junhua Zhao, Yeyuan Li, Chunhua Zhu, Yuxuan Xia, and Ning Wei
- Subjects
010302 applied physics ,Materials science ,Nanocomposite ,Graphene ,General Physics and Astronomy ,02 engineering and technology ,Edge (geometry) ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Molecular dynamics ,law ,Covalent bond ,0103 physical sciences ,Ultimate tensile strength ,Shear strength ,Composite material ,0210 nano-technology ,Stress concentration - Abstract
Holes and defects can greatly reduce the mechanical properties of multilayer graphene sheets under different loading conditions due to the stress concentration near the hole edge in each in-plane sheet and the lack of interlayer carbon–carbon bonds between the layers. Here, we report a novel design of multilayer open-hole graphene papers (MLGPs) formed through interlayer covalent bonding at the hole edges of multilayer open-hole graphene sheets (MLGSs) under high temperature using molecular dynamics (MD) simulations. Our MD results show that the hybrid sp2–sp3 interlayer bonds of MLGPs can significantly improve their both tensile strength and interlayer shear strength. The tensile strength and interlayer shear strength of MLGPs increase by around 20% and 3 times by comparison with those of MLGSs with the same number of layers, respectively, which mainly depends on the uniformity of their interlayer bond distribution. This study can provide an effective way to improve the mechanical performances of multilayer graphene sheets with flaws and also offer corresponding guidance for the design of MLGS-based nanocomposites.
- Published
- 2019
22. X-ray microtomography and laser ablation in the analysis of ink distribution in coated paper
- Author
-
Heikki Häkkänen, Jussi Timonen, Kaj Backfolk, Petri Sirviö, Markko Myllys, and Jouko Korppi-Tommola
- Subjects
Topography ,Coated paper ,Laser ablation ,X-ray microtomography ,Materials science ,ta114 ,Inkwell ,business.industry ,medicine.medical_treatment ,General Physics and Astronomy ,Surface structure ,Laser ,Ablation ,Image analysis ,law.invention ,Optics ,law ,medicine ,Profilometer ,ta216 ,business ,Tomography ,Image resolution - Abstract
A novel method was developed for studying the ink-paper interface and the structural variations of a deposited layer of ink. Combining high-resolution x-ray tomography with laser ablation, the depth profile of ink (toner), i.e., its varying thickness, could be determined in a paper substrate. X-ray tomography was used to produce the 3D structure of paper with about 1 μm spatial resolution. Laser ablation combined with optical imaging was used to produce the 3D structure of the printed layer of ink on top of that paper with about 70 nm depth resolution. Ablation depth was calibrated with an optical profilometer. It can be concluded that a toner layer on a light-weight-coated paper substrate was strongly perturbed by protruding fibers of the base paper. Such fibers together with the surface topography of the base paper seem to be the major factors that control the leveling of toner and its penetration into a thinly coated paper substrate.
- Published
- 2015
23. Electrically and magnetically dual-driven Janus particles for handwriting-enabled electronic paper
- Author
-
H. Hirama, Toru Torii, and Yusuke Komazaki
- Subjects
Materials science ,law ,Magnet ,Microfluidics ,General Physics and Astronomy ,Magnetic nanoparticles ,Nanoparticle ,Nanotechnology ,Janus particles ,Electronic paper ,law.invention ,Voltage ,Superparamagnetism - Abstract
In this work, we describe the synthesis of novel electrically and magnetically dual-driven Janus particles for a handwriting-enabled twisting ball display via the microfluidic technique. One hemisphere of the Janus particles contains a charge control agent, which allows the display color to be controlled by applying a voltage and superparamagnetic nanoparticles, allows handwriting by applying a magnetic field to the display. We fabricated a twisting ball display utilizing these Janus particles and tested the electric color control and handwriting using a magnet. As a result, the display was capable of permitting handwriting with a small magnet in addition to conventional color control using an applied voltage (80 V). Handwriting performance was improved by increasing the concentration of superparamagnetic nanoparticles and was determined to be possible even when 80 V was applied across the electrodes for 4 wt. % superparamagnetic nanoparticles in one hemisphere. This improvement was impossible when the concentration was reduced to 2 wt. % superparamagnetic nanoparticles. The technology presented in our work can be applied to low-cost, lightweight, highly visible, and energy-saving electronic message boards and large whiteboards because the large-size display can be fabricated easily due to its simple structure.
- Published
- 2015
24. Understanding ac losses in CORC cables of YBCO superconducting tapes by numerical simulations.
- Author
-
Nguyen, Linh N., Shields, Nathaniel, Ashworth, Stephen, and Nguyen, Doan N.
- Subjects
SUPERCONDUCTING coils ,SUPERCONDUCTING cables ,HIGH temperature superconductors ,CABLES ,FINITE element method ,COMPUTER simulation ,ADHESIVE tape ,CURRENT distribution - Abstract
Alternating current (ac) losses in conductor-on-rounded-core (CORC) cables of YBCO high-temperature superconducting (HTS) tapes are a significant challenge in HTS power applications. This study employs two finite element analysis (FEA) models to investigate the contributions from different ac loss components and provide approaches for reducing ac losses in cables. An FEA model based on the T-A formulation treats the cross section of thin superconducting layers as 1D lines and, therefore, only can predict the ac loss generated by the perpendicular magnetic field. In contrast, the model based on H-formulation can be performed on the actual 2D rectangular cross section HTS tapes to provide the total ac losses generated by magnetic fluxes penetrating from both the edges and surfaces of HTS tapes, although this model requires more computing time and memory. The 1D and 2D simulation models were validated by cross comparing the results from both models and by comparing sub-section and full cross section models. Subsequently, two models relate cable design and operational parameters to the surface and edge losses of a two-layer CORC cable by considering the (1) relative contributions of edge and surface losses to the overall ac losses; (2) effect of the current distribution between inner and outer HTS layers on ac losses; (3) impact of the tape alignment on ac losses in each HTS layer; (4) influence of the thickness of HTS layers on ac losses; (5) effect of size and number of inter-tape gaps on ac losses; and (6) contribution frequency on the ac losses. The research results given in this paper are therefore not only valuable to suggest strategies for reducing ac loss in multi-layer cables but also for developing more accurate and effective methods to calculate ac loss in CORC HTS cables. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
25. A programmable metasurface based on acoustic black hole for real-time control of flexural waves.
- Author
-
Su, Kun and Li, Lixia
- Subjects
FREQUENCY changers ,REAL-time control ,ELASTIC waves ,STRUCTURAL engineering ,ACTIVE medium ,SOLAR atmosphere ,SMART structures - Abstract
The time-modulated active medium with linear independent frequency conversion method has been demonstrated to enable wave orientation and reconstruction. However, due to the symmetric scattering field, this technique requires intricate microcircuit designs. To overcome this limitation, this paper proposes a tunable piezoelectric metasurface based on acoustic black holes (ABHs) to redirect flexural wave reflections. The system can convert an incident flexural wave into a reflected wave of any direction and frequency. This is accomplished through the linear time modulation of the sensing signal, which breaks the constraints of Snell's law inherent in traditional designs and is insensitive to the incident amplitude. The coupling of the ABH damping system with a linear independent frequency conversion mechanism allows for the conversion of an incident flexural wave into a reflected wave in any direction and frequency while also eliminating the influence of second harmonic reflection on the wave field and simplifying the time modulation circuit. In addition, this paper demonstrates arbitrary angle reflection, focusing, beam splitting, and frequency conversion of the incident wave. By improving the flexibility of elastic wave manipulation, this paper introduces a new approach for active control of elastic waves and provides a design method that can be employed in a variety of applications ranging from vibration protection of engineering structures to vibration sensing and evaluation. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
26. Copper ion concentration detection based on quantum weak measurement of circular dichroism.
- Author
-
Tang, Tingting, Huang, Hua, Li, Jun, He, Yu, Li, Jie, Liang, Xiao, and Li, Chaoyang
- Subjects
COPPER ions ,CIRCULAR dichroism ,TECHNOLOGICAL innovations ,METAL detectors ,TERNARY forms - Abstract
In this paper, a high precision detection method of copper ion (C u 2 + ) concentration based on weak measurement is proposed. The ternary complex formed by C u 2 + with L-tryptophan and phenanthroline reagents has circular dichroism (CD) signal at 605 nm in visible light. The CD signal can be obtained using the intensity contrast as a pointer in the imaginary weak-value amplification scheme. The measured sensitivity and resolution are 0.3417 mrad l/mg and 0.058 mg/l, respectively, which is improved by an order of magnitude compared to the traditional CD measurement method. It is also more accurate and less costly than commonly used C u 2 + detection methods. The C u 2 + concentration detection based on the weak measurement of CD signal detection proposed in this paper not only brings technological breakthroughs in the field of heavy metal ion detection, but also is of great significance in promoting the cross-development of chemistry, biomedicine, and life sciences. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
27. Metasurface-based wireless communication technology and its applications.
- Author
-
Cheng, Xinyue, Li, Chenxia, Fang, Bo, Hong, Zhi, Jin, Yongxing, and Jing, Xufeng
- Subjects
WIRELESS communications ,TELECOMMUNICATION ,WIRELESS power transmission ,COMMUNICATION of technical information ,LITERATURE reviews - Abstract
Metasurfaces, due to their outstanding ability to control electromagnetic waves, have great application prospects in the field of wireless communication. This paper provides a comprehensive review of research work based on metasurface in three aspects: wireless power transfer, wireless information transmission, and novel wireless transceiver architectures. In the domain of wireless power transfer, several focusing metasurfaces and systems with unique performance are presented along with a new formula for calculating wireless power transfer. Concerning wireless information transmission section, the direct digital information transmission based on metasurface and the information transmission based on space-time-coding digital metasurface are introduced. Lastly, a simplified wireless transceiver with metasurfaces was introduced. The paper concludes with a discussion on the future directions of metasurfaces in the wireless communication domain. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
28. Multi-scale modeling of shock initiation of a pressed energetic material III: Effect of Arrhenius chemical kinetic rates on macro-scale shock sensitivity.
- Author
-
Parepalli, P., Nguyen, Yen T., Sen, O., Hardin, D. B., Molek, C. D., Welle, E. J., and Udaykumar, H. S.
- Subjects
MULTISCALE modeling ,CHEMICAL kinetics ,CHEMICAL models ,PREDICTION models - Abstract
Multi-scale predictive models for the shock sensitivity of energetic materials connect energy localization ("hotspots") in the microstructure to macro-scale detonation phenomena. Calculations of hotspot ignition and growth rely on models for chemical reaction rates expressed in Arrhenius forms; these chemical kinetic models, therefore, are foundational to the construction of physics-based, simulation-derived meso-informed closure (reactive burn) models. However, even for commonly used energetic materials (e.g., HMX in this paper) there are a wide variety of reaction rate models available. These available reaction rate models produce reaction time scales that vary by several orders of magnitude. From a multi-scale modeling standpoint, it is important to determine which model best represents the reactive response of the material. In this paper, we examine three global Arrhenius-form rate models that span the range of reaction time scales, namely, the Tarver 3-equation, the Henson 1-equation, and the Menikoff 1-equation models. They are employed in a meso-informed ignition and growth model which allows for connecting meso-scale hotspot dynamics to macro-scale shock-to-detonation transition. The ability of the three reaction models to reproduce experimentally observed sensitivity is assessed by comparing the predicted criticality envelope (Walker–Wasley curve) with experimental data for pressed HMX Class V microstructures. The results provide a guideline for model developers on the plausible range of time-to-ignition that are produced by physically correct Arrhenius rate models for HMX. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
29. A compensation method of carrier magnetic interference under pathological conditions for geomagnetic navigation.
- Author
-
Ji, Caijuan, Song, Chengying, Li, Sheng, Gao, Yang, and Chen, Qingwei
- Subjects
LEAST squares ,MEASUREMENT errors ,GEOMAGNETISM ,ELECTRONIC equipment ,MAGNETOMETERS ,NAVIGATION - Abstract
Geomagnetic navigation has become a hot spot in current research because of its characteristics of passiveness and good concealment. However, the magnetic interference from various ferromagnetic substances, electronic equipment, etc., of the carrier will be superimposed on the geomagnetic field, causing magnetometer measurement errors, thus affecting navigation accuracy. In practice, due to the limited maneuverability of the carrier, sufficient geomagnetic observation data cannot be obtained, resulting in the observation equation used for carrier magnetic interference compensation to be seriously pathological. To achieve the compensation of carrier magnetic interference, this paper proposes the total least squares method based on the ridge regression using the L curve to solve ridge parameters. This method can effectively suppress the measurement noise that exists on both sides of the observation equation, and is suitable for alleviating the pathological effects of carrier magnetic interference compensation. Experimental results show that the compensated magnetometer measurement error is reduced to 3% of the carrier magnetic interference by using the method proposed in this paper, which obtains more stable and accurate parameter estimates. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
30. Biocellulose-based flexible magnetic paper
- Author
-
Sjl Ribeiro, Eloiza da Silva Nunes, Marcelo Nalin, M. Jafellici, Rodrigo Fernando Costa Marques, Wesley Renato Viali, Junkal Gutierrez, Hernane da Silva Barud, and Agnieszka Tercjak
- Subjects
Nanocomposite ,Materials science ,technology, industry, and agriculture ,General Physics and Astronomy ,Nanoparticle ,Nanotechnology ,Magnetization ,chemistry.chemical_compound ,Membrane ,chemistry ,Chemical engineering ,Bacterial cellulose ,Permeability (electromagnetism) ,Magnetic nanoparticles ,Superparamagnetism - Abstract
Biocellulose or bacterial cellulose (BC) is a biocompatible (nano) material produced with a three-dimensional network structure composed of microfibrils having nanometric diameters obtained by the Gluconacetobacter xylinus bacteria. BC membranes present relatively high porosity, allowing the incorporation or synthesis in situ of inorganic nanoparticles for multifunctional applications and have been used as flexible membranes for incorporation of magnetic nanocomposite. In this work, highly stable superparamagnetic iron oxide nanoparticles (SPION), functionalized with polyethylene glycol (PEG), with an average diameter of 5 nm and a saturation magnetization of 41 emu/g at 300 K were prepared. PEG-Fe2O3 hybrid was dispersed by mixing a pristine BC membrane in a stable aqueous dispersion of PEG-SPION. The PEG chains at PEG-SPION's surface provide a good permeability and strong affinity between the BC chains and SPION through hydrogen-bonding interactions. PEG-SPION also allow the incorporation of higher content of nanoparticles without compromising the mechanical properties of the nanocomposite. Structural and magnetic properties of the composite have been characterized by XRD, SEM, energy-dispersive X-ray spectroscopy (EDX), magnetization, Raman spectroscopy, and magnetic force microscopy.
- Published
- 2015
31. Paper-based ultracapacitors with carbon nanotubes-graphene composites
- Author
-
Alexey Shashurin, Cameron Brand, Jian Li, Mark Reeves, Michael Keidar, Xiaoqian Cheng, and Jianwei Sun
- Subjects
Supercapacitor ,Nanocomposite ,Materials science ,Scanning electron microscope ,Graphene ,General Physics and Astronomy ,Carbon nanotube ,law.invention ,Electric arc ,symbols.namesake ,law ,symbols ,Composite material ,Raman spectroscopy ,Sheet resistance - Abstract
In this paper, a paper-based ultracapacitors were fabricated by the rod-rolling method with the ink of carbon nanomaterials, which were synthesized by arc discharge under various magnetic conditions. Composites of carbon nanostructures, including high-purity single-walled carbon nanotubes (SWCNTs) and graphene flakes were synthesized simultaneously in a magnetically enhanced arc. These two nanostructures have promising electrical properties and synergistic effects in the application of ultracapacitors. Scanning electron microscope, transmission electron microscope, and Raman spectroscopy were employed to characterize the properties of carbon nanostructures and their thin films. The sheet resistance of the SWCNT and composite thin films was also evaluated by four-point probe from room temperature to the cryogenic temperature as low as 90 K. In addition, measurements of cyclic voltammetery and galvanostatic charging/discharging showed the ultracapacitor based on composites possessed a superior specific capacitance of up to 100 F/g, which is around three times higher than the ultracapacitor entirely fabricated with SWCNT.
- Published
- 2014
32. 2D Quantum materials: Magnetism and superconductivity.
- Author
-
Milošević, M. V. and Mandrus, D.
- Subjects
MAGNETISM ,SUPERCONDUCTIVITY ,INELASTIC neutron scattering ,MAGNETIC impurities ,MAGNETIC materials ,MAGNETIC traps ,CUPRATES - Abstract
Although the study of quasi-2D magnetism is well-established in bulk materials, the study of literal 2D magnets - consisting of a single layer of magnetic ions - is quite limited. Four of the contributed papers report experimental work on nanostructures: three of these involve superconductivity and one is on magnetism. Proximity effects in superconductors have been known for nearly 90 years,[13] but until recently proximity effects in magnets have been harder to study due to the much smaller range of the proximity effect in magnets compared to superconductors. One of the most exciting recent developments in quantum materials is the discovery and characterization of magnetism and superconductivity in exfoliated single-layer materials. [Extracted from the article]
- Published
- 2021
- Full Text
- View/download PDF
33. Piezoelectric energy harvester with outstanding output performance at low frequency vibration based on concentrating force on the piezoelectric element by parallel springs.
- Author
-
Hao, Yifan, Luo, Hongzhi, Lu, Xinyue, Huang, Jiawei, Chen, Hang, and Yang, Tongqing
- Subjects
FREQUENCIES of oscillating systems ,PIEZOELECTRIC ceramics ,STAINLESS steel ,LEAD titanate ,LEAD zirconate titanate - Abstract
This paper proposes a piezoelectric energy harvester that concentrates force on the piezoelectric element by parallel springs. When vibrating, the force exerted by the mass is released at three equal points on the surface of the brass substrate through three parallel springs. This concentrated release of energy through the spring amplification effect facilitates large deformation of the piezoelectric ceramic sheet, resulting in a higher charge output. The results show that under the combined action of a 14 g annular hollow mass and a 0.3 mm wire diameter stainless steel spring, the energy harvester based on the lead zirconate titanate ceramic exhibited an outstanding output power of 1.0–32.1 mW at a low resonance frequency with acceleration amplitudes of 0.5–3 g (1 g = 9.8 m/s
2 ). More importantly, to match the vibration frequency of the actual environment, this paper optimized the structure of the harvester and proposed that the harvester can be designed by selecting the weight of the mass block, the parameters and number of springs, and the shape of the brass substrate. The energy harvester designed in this study is expected to capture energy from low-frequency natural environments and exhibit outstanding output performance, which can provide guidelines for future efforts in this direction. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
34. High-volume biological sample processing using microwaves.
- Author
-
Wilson-Garner, S., Alzeer, S., Baillie, L., and Porch, A.
- Subjects
SAMPLING (Process) ,BACTERIAL DNA ,MICROWAVES ,DNA probes ,CAVITY resonators - Abstract
This paper describes the design and optimization of a 10 ml cartridge for patient sample processing using a 3.5 GHz (empty resonant frequency) TM
010 cylindrical microwave cavity. The cartridge has been designed to augment a novel approach for the rapid diagnosis of M. tuberculosis (the causative agent of Ttuberculosis), which uses the direct application of microwaves to a bacteria-containing sample to release pathogen-specific DNA. The target bacterial DNA is then captured and recovered using magnetic nanoparticles coated with pathogen-specific DNA probes. Excitation parameters were optimized using three surrogates for M. tuberculosis, namely, M. smegmatis, M. abscessus, and M. bovis suspended in water and simulated sputum. The paper also explores the mechanism of microwave-mediated DNA release from bacteria using scanning electron microscopy. Examination of bacteria exposed to microwaves at power levels known to mediate the release of DNA reveals no obvious signs of permanent cell disruption, suggesting that a more subtle interaction is taking place. Finally, the presence of microwave-liberated M. bovis DNA was able to be detected at a level of sensitivity comparable to that achieved using microscopy. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
35. Study of electric-field induced ionic migration on all-inorganic perovskite CsPbBr3 single crystal nuclear radiation detector.
- Author
-
Zhang, Mingzhi, Xia, Guotu, Huang, Chentao, Liu, Juan, Deng, Wenjuan, Tian, Fang, Zou, Jijun, and Tang, Bin
- Subjects
NUCLEAR counters ,SINGLE crystals ,PEROVSKITE ,HYSTERESIS ,ACTIVATION energy ,ELECTRIC fields ,PHOTOELECTRICITY - Abstract
As one of the promising room temperature nuclear radiation detection materials, the all-inorganic perovskite CsPbBr
3 single crystal has been receiving much attention in recent years. Even though the performance of the CsPbBr3 detector is improving continuously, the disadvantages of detection instability have not been solved fundamentally, and this instability is mainly caused by ionic migration in the CsPbBr3 single crystal itself. In this paper, a reasonable ionic migration model is proposed based on an in-depth study of the current hysteresis phenomenon and ionic migration mechanism in the Ti/CsPbBr3 /Ti detector. The model shows that the ions migrate to the anode or cathode under an external electric field, and the accumulated ions subsequently form an inverted internal electric field inside the crystal and carrier transport barriers at the metal–semiconductor interface simultaneously. The photoelectric characteristic and ionic migration activation energy (E a i o n) fitting results also prove the rationality of the ionic migration model. Furthermore, the ionic migration model can also be used to explain the left-shift of the energy response peak and the decrease in the normalized charge collection efficiency in the Ti/CsPbBr3 /Ti detector. This paper systematically investigates the intrinsic origin of migrated ions and the influence of ionic migration on detection stability, which will provide a potential solution to improve detection stability by suppressing ionic migration in the near future. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
36. Research on the encounter motion of super-cavitating vehicles.
- Author
-
Zhou, Feng, Fan, Chunyong, Tian, Ying, Wang, Min, and Luan, Hengxuan
- Subjects
CAVITATION ,MOTION - Abstract
In this paper, the super-cavitating phenomenon under the effect of two vehicles' encounter motion processes is numerically studied. Particular attention is given to the influence of the vertical gaps between the vehicle, the cavitation number, and the slenderness ratio on the cavity profile and radial force of the object. Several numerical models are built to study the cavity evolution process and the force acting on the vehicle to explore the influence mechanism of two vehicles' encounter motion on supercavitating flow. The study shows that the cavity around the vehicle is primarily affected by the vertical gaps and cavitation number, but is relatively weakly affected by the slenderness ratio. Several impact laws are acquired in the paper. The relationship between cavity fracture time and vertical gaps is approximately a power function and obeys the law of t = 5.433h
0.3688 . The concept of the time of the maximum radial force occurrence and the cavitation number follows the formula of t = 4.86e0.3688σ . The relationship between the maximum radial force occurrence position and the cavitation number is a function of Ln and consistent with the law n = −0.799ln(σ) + 8.427. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
37. Quantifying uncertainty in analysis of shockless dynamic compression experiments on platinum. II. Bayesian model calibration.
- Author
-
Brown, Justin L., Davis, Jean-Paul, Tucker, J. Derek, Huerta, Gabriel, and Shuler, Kurtis W.
- Subjects
PLATINUM ,CALIBRATION ,LOW temperatures - Abstract
Dynamic shockless compression experiments provide the ability to explore material behavior at extreme pressures but relatively low temperatures. Typically, the data from these types of experiments are interpreted through an analytic method called Lagrangian analysis. In this work, alternative analysis methods are explored using modern statistical methods. Specifically, Bayesian model calibration is applied to a new set of platinum data shocklessly compressed to 570 GPa. Several platinum equation-of-state models are evaluated, including traditional parametric forms as well as a novel non-parametric model concept. The results are compared to those in Paper I obtained by inverse Lagrangian analysis. The comparisons suggest that Bayesian calibration is not only a viable framework for precise quantification of the compression path, but also reveals insights pertaining to trade-offs surrounding model form selection, sensitivities of the relevant experimental uncertainties, and assumptions and limitations within Lagrangian analysis. The non-parametric model method, in particular, is found to give precise unbiased results and is expected to be useful over a wide range of applications. The calibration results in estimates of the platinum principal isentrope over the full range of experimental pressures to a standard error of 1.6%, which extends the results from Paper I while maintaining the high precision required for the platinum pressure standard. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
38. Self-consistent model and numerical approach for laser-induced non-equilibrium plasma.
- Author
-
Pokharel, S. and Tropina, A. A.
- Subjects
NONEQUILIBRIUM plasmas ,LASER plasmas ,LASER-induced breakdown spectroscopy ,PLASMA production ,ATMOSPHERIC nitrogen ,FEMTOSECOND pulses - Abstract
This paper presents a self-consistent multi-dimensional mathematical model and a numerical approach for simulating the low-temperature plasma induced by the femtosecond laser filament. Addressing limitations in current models, we analyze key aspects of the laser plasma behavior, including plasma generation, detailed chemical kinetics, energy exchange channels, total energy balance, and hydrodynamics. The developed model and LOTASFOAM code are applied to study the temporal and spatial decay of the plasma produced by a femtosecond laser pulse in pure nitrogen at atmospheric pressure. The paper also includes a discussion on the spatial and temporal dynamics of electronically excited states of nitrogen in the decaying laser plasma. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
39. Realization of an ultra-thin absorber with fragmented magnetic structure at L-, S-, and partial C-bands.
- Author
-
E, Liujia, Liu, Zhongqing, Zhang, Jingwei, Xu, Zhaoxuan, Yuan, Zhenliang, Mei, Zhonglei, and Niu, Tiaoming
- Subjects
MAGNETIC structure ,RADAR cross sections ,METAMATERIALS ,EVOLUTIONARY algorithms ,COPPER plating ,MAGNETIC materials ,POLARIZATION (Nuclear physics) - Abstract
In this paper, an ultra-thin absorber with a total thickness of 9.2 mm is designed and verified at the frequency band of 1–5.34 GHz. The absorber is composed of a layer of metasurface, multi-layered magnetic substrate, a layer of fragmented magnetic structure obtained by improved MOEA/D-GO (Multi-Objective Evolutionary Algorithm based on Decomposition combined with Enhanced Genetic Operators), and a copper back plate. The absorber is achieved by two steps. First, we designed and measured an ultra-thin absorber at 0.78–2.04 GHz by adding a layer metasurface onto the top of a basic multi-layer absorber composed of magnetic materials. The fractional bandwidth (FBW) of the absorber is 89.4%, and the electrical thickness is only 0.024 λ 0 at the lowest operating frequency. Second, to broaden the bandwidth, we use an improved MOEA/D-GO to optimize one magnetic layer of the absorber. The working frequency band of the optimized absorber is 1–5.34 GHz, covering L- (1–2 GHz), S- (2–4 GHz), and partial C-bands (4–8 GHz). Furthermore, we modified the structure of the metasurface to make the absorber polarization-independent. The FBW of the final absorber is 136.4%, and the electrical thickness is 0.031 λ 0 at the lowest operating frequency. The prototype of the absorber is measured, and the experimental results agree well with the simulated performance. The results show that the improved MOEA/D-GO can be used to design and optimize sophisticated electromagnetic (EM) structures with the predesigned properties, and the absorber with ultrathin thickness and light weight verified in this paper have great application potentials in EM compatibility, EM shielding, and radar cross section reduction at the low bands of the microwave spectrum. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
40. Dynamic deformation behavior and constitutive model of a Zr–W alloy.
- Author
-
Ma, Yue, Wang, Chuanting, Guo, Zhiping, Chen, Ying, Gao, Hongyin, Meng, Yuanpei, Yang, Yansong, He, Yuan, Guo, Lei, and He, Yong
- Subjects
MECHANICAL behavior of materials ,HOPKINSON bars (Testing) ,MATERIAL plasticity ,DEFORMATIONS (Mechanics) ,ALLOYS - Abstract
In this paper, a Zr–5W alloy was fabricated via casting. In order to obtain the mechanical properties of the material, quasi-static compression tests at room temperature and split Hopkinson pressure bar tests at various temperatures were carried out. The x-ray diffraction result showed that the main components of the alloy were αZr and W
2 Zr, where αZr is the matrix and W2 Zr is the reinforcement. The metallographic characterization results showed that there were two main forms of W2 Zr in the material, namely, large particle boundary and small diffuse submicrometer precipitates. The reinforcements of both distributions have the effect of increasing the strength of the material, but the small submicrometer W2 Zr precipitates would cause microcrack nucleation during the late plastic deformation stage, resulting in damage softening. In order to make theoretical calculations of the mechanical properties of materials, the Johnson–Cook (JC) constitutive model and Zerilli–Armstrong (ZAM) constitutive model of the material were obtained. It was found that the JC constitutive model had poor consistency in describing material properties. Although the consistency of the ZAM constitutive model was higher than that of the JC constitutive model, it still had obvious shortcomings. Combined with the deformation mechanism of the alloy, a modified constitutive relation was established by adding damage softening terms based on the hexagonal close-packed metal constitutive model inferred by the kinetics of heat-activated dislocations. The relative error results of all working conditions show that the correlation consistency of the improved constitutive model in this paper is significantly better than that of JC constitutive and ZAM constitutive. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
41. Phase shifting profilometry based on Hilbert transform: An efficient phase unwrapping algorithm.
- Author
-
Meng, Xianglin, Wang, Fei, Liu, Junyan, Chen, Mingjun, and Wang, Yang
- Subjects
HILBERT transform ,SHAPE measurement ,PHASE coding ,ALGORITHMS ,COMPUTATIONAL complexity ,TIME measurements - Abstract
Digital fringe projection profilometry based on phase-shifting technology is a reliable method for complex shape measurement, and the phase is one of the most important factors affecting measurement accuracy. The calculation of the absolute phase depends on the calculation of the wrapped phase and encoding technology. In this paper, a technique of obtaining the absolute phase of multi-frequency heterodyne fringe images using the Hilbert transform is presented. Since the wrapped phase can be calculated from only one fringe image of each frequency, the method does not need phase-shifting. The absolute phase can be obtained from the wrapped phase by applying the heterodyne method. The measurement time and computational complexity are dramatically reduced, the measurement efficiency is greatly improved, and this benefit from the number of images is greatly reduced. The experimental results show that the method presented in this paper performs well in the application, and the accuracy is no different from that of the phase-shifting method while the efficiency is greatly improved. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
42. The criterion of planar instability in alloy solidification under varying conditions: A viewpoint from free energy.
- Author
-
Yu, Fengyi
- Subjects
SOLIDIFICATION ,ALLOYS - Abstract
In alloy solidification, the transport processes of heat and solute result in morphological instability of the interface, forming different patterns of the solidification structure and determining the mechanical properties of components. As the first observable phenomenon of morphological instabilities, planar instability influences the subsequent stages significantly, deserving in-depth investigations. In this paper, the planar instability in alloy solidification under varying conditions is studied. First, the dynamical evolution of the planar instability is performed by the theoretical model and the phase-field model, respectively. Second, to represent the history-dependence of solidification, varying parameters are adopted in the simulations. Then, the criterion of planar instability under varying conditions is discussed. This paper considers that the critical parameters of planar instability are the excess free energy at the interface and the corresponding interfacial energy. Finally, to validate the criterion, comparisons between the phase-field and theoretical models are carried out, showing good consistency. Moreover, solidification processes with different preferred crystallographic orientations are performed, demonstrating the effect mechanism of the excess free energy and interfacial energy on planar instability. The idea of the interfacial energy influencing the planar instability could be applied to investigating other patterns induced by interfacial instability. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
43. Topological optimization of a composite square lattice structure for bandgap property based on an improved multi-parameter genetic algorithm.
- Author
-
Wang, Xueqi and Li, Dong
- Subjects
PHONONIC crystals ,GENETIC algorithms ,FINITE element method ,ENERGY bands ,COMPOSITE structures ,THEORY of wave motion - Abstract
This paper proposed a two-dimensional composite square lattice structure containing two kinds of inclusions (polymethylmethacrylate and T2 copper). To maximize the relative widths of the gaps between the adjacent energy bands of the phononic crystals (PnCs), an improved multi-parameter genetic algorithm was adopted in this paper. The material distribution and ligament sizes were considered simultaneously by ternary encoding and binary encoding. The propagation wave behaviors of the composite lattice structures were studied by the finite element method. The effects of different lattice shapes and other relevant influencing parameters on the bandgaps were discussed. The results showed that the lattice shape, ligament width, and material density affect the width and the location of the bandgaps, and the effectiveness of the proposed method was demonstrated by a transmission spectrum experiment. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
44. An improved hybrid quantum-classical convolutional neural network for multi-class brain tumor MRI classification.
- Author
-
Dong, Yumin, Fu, Yanying, Liu, Hengrui, Che, Xuanxuan, Sun, Lina, and Luo, Yi
- Subjects
CONVOLUTIONAL neural networks ,BRAIN tumors ,TUMOR classification ,MAGNETIC resonance imaging ,QUANTUM computing - Abstract
The efficiency of quantum computing has recently been extended to machine learning, which has made a significant impact on quantum machine learning. The hybrid structure of quantum and classical ones has developed into the most successful application mode currently due to noisy intermediate scale quantum limitations. In this paper, an improved hybrid quantum-classic convolutional neural network (HQC-CNN) with fast training speed, lightweight, and high performance is proposed. Its convolution layer realizes feature mapping through parameterized quantum circuit, while other layers keep classic operation and finally complete the task of four classifications of brain tumors. The experiment in this paper is based on kaggle brain tumor magnetic resonance imaging public dataset. The final experimental results show that HQC-CNN can effectively classify meningioma, glioma, pituitary, and no tumor with a classification accuracy of 97.8%. When compared to numerous well-known landmark models, HQC-CNN has obvious advantages. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
45. Flexoelectric aging effect in ferroelectric materials.
- Author
-
Zhang, Zhen, Wen, Zhaokuan, Li, Ting, Wang, Zhiguo, Liu, Zhiyong, Liao, Xiaxia, Ke, Shanming, and Shu, Longlong
- Subjects
FERROELECTRICITY ,FERROELECTRIC materials ,FLEXOELECTRICITY ,STRAINS & stresses (Mechanics) ,PERMITTIVITY ,CERAMICS - Abstract
In spite of the flexoelectric effect being a universal phenomenon in the ferroelectric perovskites, the current understanding of flexoelectric aging in ferroelectrics is, actually, rather incomplete. In this paper, we have fabricated a series of Mn-doped BaTiO
3 perovskite ceramics (BaTi1–x Mnx O3 , x = 0.1% and 1%, BTMO) to systematically investigate the corresponding flexoelectric aging behavior by controlling the concentration of Mn. We found that the variation of Mn dopant significantly effects the Curie temperature, dielectric constant, flexoelectric aging, and flexoelectric coefficient of the BTMO ceramics. Especially for the BTMO (0.1%) ceramics, obvious ferroelectric aging and flexoelectric aging phenomenon are observed at room temperature. The main reason for aging of BTMO ceramics is that the doping of Mn introduces oxygen vacancies, which tend to be stable under the action of strain gradient and electric field. Therefore, the results presented in this paper verify that the flexoelectric aging in Mn-doped BTO ceramics is closely related to ferroelectric fatigue. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
46. Impact of thermal annealing on deep levels in nitrogen-implanted β-Ga2O3 Schottky barrier diodes.
- Author
-
Fregolent, Manuel, De Santi, Carlo, Buffolo, Matteo, Higashiwaki, Masataka, Meneghesso, Gaudenzio, Zanoni, Enrico, and Meneghini, Matteo
- Subjects
SCHOTTKY barrier diodes ,ELECTRON traps ,ACTIVATION energy ,CURRENT-voltage characteristics ,GALLIUM nitride films ,BASE isolation system - Abstract
Understanding the properties of N-implanted β-Ga
2 O3 is fundamental for the optimization of doping and isolation structures based on gallium oxide. This paper reports an extensive analysis of the impact of thermal annealing on the concentration and properties of deep levels in N-implanted β-Ga2 O3 Schottky barrier diodes by means of capacitance isothermal transient spectroscopy. Samples with annealing temperatures from 800 to 1200 °C were considered. The original results presented in this paper demonstrate the following: (a) The instability of current–voltage characteristics detected for all the samples under test can be attributed to the presence of three electron traps with activation energies of 0.6, 0.7, and 1 eV, consistent with previous reports in β-Ga2 O3 . (b) The detected traps are not the nitrogen level but intrinsic defects whose concentration is increased by the implantation process. (c) The concentration of deep levels decreases as the annealing temperature increases, demonstrating that the annealing process can effectively restore the quality of the material while keeping the conductivity decrease related to the presence of the nitrogen. Finally, (d) we demonstrate that the residual leakage and the turn-on voltage shift are correlated with the Arrhenius signature of the detected deep levels. An interpretation is proposed to explain the measurement results. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
47. Magnetization mechanism of a hybrid high temperature superconducting trapped field magnet.
- Author
-
Liao, Hengpei, Yuan, Weijia, Zhang, Zhiwei, and Zhang, Min
- Subjects
HIGH temperature superconductors ,MAGNETIZATION ,ELECTROMAGNETIC interactions ,SUPERCONDUCTING magnets ,MAGNETS - Abstract
This paper studies the magnetization mechanism of a hybrid high temperature superconducting (HTS) trapped field magnet. To address the size limitation of traditional HTS bulk materials, hybridization between HTS-stacked ring magnets and HTS bulks is proposed here. A jointless HTS-stacked ring magnet is used to increase the trapped field area for HTS bulks. A hybrid HTS magnet with 90 mm in length and 60 mm in width was tested to provide a trapped field of 7.35 T in a field cooling magnetization. The paper focuses mainly on understanding the novel magnetization mechanism of this hybrid HTS trapped field magnet. A numerical model based on homogenized H formulation was used to compare with experimental results, and a good match was found. Our experimental and numerical study of the electromagnetic interaction between the HTS-stacked ring magnet and the HTS bulks reveals that there are two magnetization stages, and the magnetization speed differs in these two stages by a sing criterion: whether the HTS-stacked ring magnet is fully penetrated or not. This study confirms that hybridization helps to build large HTS trapped field magnets. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
48. Calculation of tunneling current across trapezoidal potential barrier in a scanning tunneling microscope.
- Author
-
Dessai, Malati and Kulkarni, Arun V.
- Subjects
SCANNING tunneling microscopy ,QUANTUM tunneling ,POTENTIAL barrier ,TUNNEL design & construction ,AIRY functions ,FERMI level - Abstract
Accurate calculation of the tunneling currents in a scanning tunneling microscope (STM) is needed for developing image processing algorithms that convert raw data of the STM into surface topographic images. In this paper, an accurate calculation of the tunneling current for several tip–sample distances, bias voltages, and tips of a hyperboloidal shape with several radii of curvature is carried out. The main features of this calculation are the following. Non-WKB exact solutions to the trapezoidal (linear) potential in the barrier region are used to calculate the tunneling probabilities. Pauli blocking effects on both forward and reverse current densities are introduced. Finite temperature (viz. 300 K) calculation in which electrons belonging to a narrow band of energy about the Fermi level contribute to tunneling is carried out. Integration over a field line method is used to obtain tunneling currents for the nonplanar hyperboloidal shaped tips, using the expressions obtained in the paper, for planar model current densities. An estimate of the lateral resolution is introduced. Earlier works do not consider all these aspects together in a single calculation. Tunneling currents are found to increase rapidly with increasing bias voltage and decrease exponentially with increasing tip–sample distances. Airy function determined currents are a more accurate function of a tip–sample distance than the WKB determined currents. Pauli effects are found to not always reduce currents from their non-Pauli values. The lateral resolution is found to be degraded for blunter tips, larger bias voltages, and larger tip–sample distances. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
49. CNT/Cu composite cathode: A new approach to long lifetime for explosive emission cathode.
- Author
-
Wu, Ping, Yang, Wenshu, Sun, Jun, and Wu, Gaohui
- Subjects
CARBON nanotubes ,CATHODES ,MICROWAVE generation ,MICROSCOPY - Abstract
Carbon nanotube (CNT) cathodes have attracted much attention in recent years due to the advantages of large field enhancement factor and low emission threshold. However, the severe ablation under intense emission makes the lifetime short and therefore limits the application in the field such as high power microwave generation. To resolve this problem, this paper proposes to mix CNTs with metals, and a novel CNT/Cu composite cathode is manufactured. The lifetime experiments under voltage of 940 kV and repetition frequency of 20 Hz demonstrate that the lifetime of the CNT/Cu composite cathode is over 3 × 10
5 pulses, which is much longer than that of the normal copper cathode by at least one order of magnitude. The microscopic morphology analysis reveals that the CNT micro-protrusions and whiskers should be vital for the good emission property of the new cathode. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
50. Mode conversion of Lamb waves in a composite phononic crystal plate: Numerical analysis and experimental validation.
- Author
-
Ding, Taotao, Song, Ailing, Sun, Chaoyu, Xiang, Yanxun, and Xuan, Fu-Zhen
- Subjects
LAMB waves ,PHONONIC crystals ,NUMERICAL analysis ,COMPOSITE plates ,POLYVINYLIDENE fluoride - Abstract
The mode manipulation of Lamb waves plays an important role in damage detection and identification of damage types, location, and size. In this paper, we propose a composite phononic crystal (PC) plate with antisymmetric and symmetric PCs for realizing mode conversion from A0 to S0 mode of Lamb waves. The theoretical analysis, numerical simulations, and experimental validation are introduced and the mode conversion mechanism of the composite PC plate is systematically investigated. The effect of geometrical parameters on band structures of antisymmetric and symmetric PCs is first discussed. Then multi-physics field simulation models are developed and in-plane displacement fields are obtained in numerical simulations, which shows that the mode conversion is enhanced when the period number of the antisymmetric PC decreases and that of symmetric the PC increases. The composite PC plate specimens are fabricated with precision wire cutting technology for experimental measurements and the self-designed polyvinylidene fluoride (PVDF) comb transducer is used to stimulate the Lamb waves. The experimental results are consistent with the numerical simulations, which demonstrate that the proposed composite PC plate can achieve the mode conversion from A0 to S0 mode of Lamb waves. Our proposed structures have applicable values for the mode manipulation of Lamb waves in damage detection. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
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