scholarly journals Mechanical Characteristics and Energy Evolution of Sandstone Three-Point Bending Test

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Tao Qin ◽  
Kai Ren ◽  
Zhi Liu ◽  
Yan-Wei Duan ◽  
Lei Wang
Keyword(s):  
Stress Field ◽  
Near Field ◽  
Peak Stress ◽  
Bending Test ◽  
Field Energy ◽  
Far Field ◽  
Peak Strain ◽  
Three Point Bending ◽  
Field Peak ◽  
Characteristic Points

With the increase of underground mining depth in coal mines, the distribution of stress fields in deep mining becomes more complex, and the stress localization characteristics are obvious. In order to obtain the local mechanical properties and energy evolution of sandstone, this article is based on the three-point bending experiment and combined with the localized failure theory to explore the evolution law of stress field, deformation field, and energy field of sandstone specimen under tensile stress during the three-point bending experiment. The results show that during the three-point bending test of sandstone, with the increase of the span of the three-point bending test, the peak stress at the characteristic point shows an increasing trend, and the peak stress has obvious regional characteristics. In the vertical direction, the peak stress at the characteristic points in the upper part of the neutral layer is larger, and the peak stress at the characteristic points in the lower part of the neutral layer is smaller. In the horizontal direction, the peak stress at the characteristic points in the near field is higher, and the peak stress at the characteristic points in the middle field and the far field is smaller. The stress field and the deformation field have a good corresponding relationship. The upper far-field peak strain tends to decrease with the increase of the span, and the upper near-field peak strain first decreases and then increases with the increase of the span. The lower near-field peak strain tends to decrease and then increase with increasing span, and the lower far-field peak strain fluctuates with increasing span. The energy field is dependent on the stress field and the deformation field, showing obvious regional characteristics. The energy storage and release capacity of the upper area are higher than those of the lower area. The overall performance of the loading energy storage, rebound energy release, and crack propagation energy release in different areas can be described as far field < mid-field << near field. The near-field energy at different spans presents the characteristics of two stages. When the span is between 140 mm and 150 mm, the near-field energy shows a rapid decreasing trend, and when the span is between 150 mm and 180 mm, the near-field energy presents an obvious increasing trend.

A 90GHz pulsed-transmitter with near-field/far-field energy cancellation using a dual-loop antenna

2011 ◽  
Author(s):  
Amin Arbabian ◽  
Shinwon Kang ◽  
Steven Callender ◽  
Bagher Afshar ◽  
Jun-Chau Chien ◽  
...  
Keyword(s):  
Near Field ◽  
Loop Antenna ◽  
Field Energy ◽  
Far Field

scholarly journals Enhancing radiative energy transfer through thermal extraction

Nanophotonics ◽  
2016 ◽  
Vol 5 (1) ◽  
pp. 22-30 ◽  
Author(s):  
Yixuan Tan ◽  
Baoan Liu ◽  
Sheng Shen ◽  
Zongfu Yu
Keyword(s):  
Thermal Radiation ◽  
Radiative Heat ◽  
Near Field ◽  
Light Output ◽  
Radiative Energy ◽  
Field Energy ◽  
Far Field ◽  
Thermal Extraction ◽  
Field Radiation ◽  
Boltzmann Law

Abstract Thermal radiation plays an increasingly important role in many emerging energy technologies, such as thermophotovoltaics, passive radiative cooling and wearable cooling clothes [1]. One of the fundamental constraints in thermal radiation is the Stefan-Boltzmann law, which limits the maximum power of far-field radiation to P0 = σT4S, where σ is the Boltzmann constant, S and T are the area and the temperature of the emitter, respectively (Fig. 1a). In order to overcome this limit, it has been shown that near-field radiations could have an energy density that is orders of magnitude greater than the Stefan-Boltzmann law [2-7]. Unfortunately, such near-field radiation transfer is spatially confined and cannot carry radiative heat to the far field. Recently, a new concept of thermal extraction was proposed [8] to enhance far-field thermal emission, which, conceptually, operates on a principle similar to oil immersion lenses and light extraction in light-emitting diodes using solid immersion lens to increase light output [62].Thermal extraction allows a blackbody to radiate more energy to the far field than the apparent limit of the Stefan-Boltzmann law without breaking the second law of thermodynamics.Thermal extraction works by using a specially designed thermal extractor to convert and guide the near-field energy to the far field, as shown in Fig. 1b. The same blackbody as shown in Fig. 1a is placed closely below the thermal extractor with a spacing smaller than the thermal wavelength. The near-field coupling transfers radiative energy with a density greater than σT4. The thermal extractor, made from transparent and high-index or structured materials, does not emit or absorb any radiation. It transforms the near-field energy and sends it toward the far field. As a result, the total amount of far-field radiative heat dissipated by the same blackbody is greatly enhanced above SσT4, where S is the area of the emitter. This paper will review the progress in thermal extraction. It is organized as follows. In Section 1, we will discuss the theory of thermal extraction [8]. In Section 2, we review an experimental implementation based on natural materials as the thermal extractor [8]. Lastly, in Section 3, we review the experiment that uses structured metamaterials as thermal extractors to enhance optical density of states and far-field emission [9].

Numerical Study of Crack Propagation Path in Three-Point Bending Beam Using Extended Finite Element Method

2013 ◽  
Vol 353-356 ◽  
pp. 3615-3618 ◽  
Author(s):  
Cheng Fan ◽  
Xue Qing Jing
Keyword(s):  
Finite Element ◽  
Fracture Energy ◽  
Numerical Study ◽  
Peak Stress ◽  
Bending Test ◽  
Propagation Path ◽  
Extended Finite Element ◽  
Basic Principles ◽  
Three Point Bending ◽  
Expansion Path

This paper is based on the basic principles of the extended finite element in the large commercial software ABAQUS on the platform of different fracture energy of three point bending test of concrete are numerically simulated, and three-point bending crack initiation, through expansion path analysis. The results show that has a direct impact on the size of the fracture energy of concrete specimens destruction, Fracture of brittle fracture can be small more obvious, produce more harmful. When softening decline stage after peak stress occurred in the "jump back" phenomenon.

scholarly journals Radiationless anapole states in on-chip photonics

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Evelyn Díaz-Escobar ◽  
Thomas Bauer ◽  
Elena Pinilla-Cienfuegos ◽  
Ángela I. Barreda ◽  
Amadeu Griol ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Near Field ◽  
Field Measurements ◽  
High Index ◽  
Field Energy ◽  
Far Field ◽  
Interference Effects ◽  
Strong Reduction ◽  
On Chip ◽  
Integrated Circuitry

AbstractHigh-index nanoparticles are known to support radiationless states called anapoles, where dipolar and toroidal moments interfere to inhibit scattering to the far field. In order to exploit the striking properties arising from these interference conditions in photonic integrated circuits, the particles must be driven in-plane via integrated waveguides. Here, we address the excitation of electric anapole states in silicon disks when excited on-chip at telecom wavelengths. In contrast to normal illumination, we find that the anapole condition—identified by a strong reduction of the scattering—does not overlap with the near-field energy maximum, an observation attributed to retardation effects. We experimentally verify the two distinct spectral regions in individual disks illuminated in-plane from closely placed waveguide terminations via far-field and near-field measurements. Our finding has important consequences concerning the use of anapole states and interference effects of other Mie-type resonances in high-index nanoparticles for building complex photonic integrated circuitry.

Estimation of the Zone of Failure Extent in Quasi-Brittle Specimens with Different Crack-Tip Constraint Conditions from Stress Field

2013 ◽  
Vol 592-593 ◽  
pp. 262-265 ◽  
Author(s):  
Václav Veselý ◽  
Jakub Sobek ◽  
Petr Frantík ◽  
Michal Štafa ◽  
Lucie Šestáková ◽  
...  
Keyword(s):  
Stress Field ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Crack Tip ◽  
Bending Test ◽  
Stress Fields ◽  
Three Point Bending ◽  
Higher Order Terms ◽  
Crack Tip Constraint

A multi-parameter fracture mechanics concept based on the Williams power series is applied on novel cracked specimen geometries utilizing combined boundary conditions of the wedge splitting and the three-point bending test. Crack tip stress fields for various configurations (causing different constraint conditions at the crack tip and thus also different fracture process zone extents) are numerically investigated and subsequently analytically reconstructed using developed procedure. An importance of using higher order terms of the Williams series is demonstrated.

Magnetic Tag Antenna for UHF Near-field and Far-Field RFID Applications

2015 ◽  
Vol 5 (2) ◽  
pp. 119
Author(s):  
Mondher Dhaouadi ◽  
M. Mabrouk ◽  
T. Vuong ◽  
A. Ghazel
Keyword(s):  
Near Field ◽  
Far Field ◽  
Rfid Applications
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