• Title, Summary, Keyword: Rectangular Cavity

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Long Range UHF RFID Tag with a Rectangular Metallic Cavity Structure

  • Yeo, Jun-Ho
    • Journal of electromagnetic engineering and science
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    • v.10 no.3
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    • pp.121-126
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    • 2010
  • A long range UHF RFID tag with a rectangular metallic cavity structure is proposed for various applications with metallic objects. The proposed tag consists of a rectangular metallic cavity structure and a folded dipole antenna which is located on top of the cavity. The tag is designed for Korean UHF RFID band(910~914 MHz) and the bandwidth, which satisfies the -10 dB input reflection coefficient requirement, is approximately 1.3 %(904~916 MHz). Measurement demonstrates that the proposed tag shows long reading range up to 15 m when it is placed on a metallic plate.

Measurements of multimode characteristics including surface wave mode in a dielectrically loaded rectangular cavity (직육면체 캐비티의 다중 모드 특성및 표면파 모드 특성 측정)

  • 김채영;김윤명;라정웅
    • 전기의세계
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    • v.28 no.4
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    • pp.47-52
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    • 1979
  • Total number of resonant modes in a microwave oven cavity may be maximized for a given frequency bandwidth to obtain more uniform power distribution by choosing proper size of the cavity. The total number of modes is calculated for a dielectrically loaded rectangular cavity and its size is suggested here for which the change in the number of modes is less sensitive to the change of dielectric layer thickness and its total number of modes is maximized in a given range of cavity sizes. A prove coupled rectangular cavity is constructed and the total existing modes are measured to see the change of modes depending on the dielectric layer thickness and the cavity size. Surface wave mode existing in the dielectric layer is confirmed by measuring Q and the input impedance of the cavity for this mode, which closely compares with the calculation.

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Effect of surface bolt on the collapse mechanism of a shallow rectangular cavity

  • Huang, Fu;Zhao, Lian-heng;Zhang, Sheng
    • Geomechanics and Engineering
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    • v.13 no.3
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    • pp.505-515
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    • 2017
  • Based on the collapse characteristics of a shallow rectangular cavity, a three-dimensional failure mechanism which can be used to study the collapsing region of the rock mass above a shallow cavity roof is constructed. Considering the effects of surcharge pressure and surface bolt on the collapsing block, the external rate of works produced by surcharge pressure and surface bolt are included in the energy dissipation calculation. Using variational approach, an analytic expression of surface equation for the collapsing block, which can be used to study the collapsing region of the rock mass above a shallow cavity roof, is derived in the framework of upper bound theorem. Based on the analytic expression of surface equation, the shape of the collapsing block for shallow cavity is drawn. Moreover, the changing law of the collapsing region for different parameters indicates that the collapsing region of rock mass decreases with the increase of the density of surface bolt. This conclusion can provide reference for practicing geotechnical engineers to achieve an optimal design of supporting structure for a shallow cavity.

Modelling and experimental investigations on stepped beam with cavity for energy harvesting

  • Reddya, A. Rami;Umapathy, M.;Ezhilarasib, D.;Uma, G.
    • Smart Structures and Systems
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    • v.16 no.4
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    • pp.623-640
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    • 2015
  • This paper presents techniques to harvest higher voltage from piezoelectric cantilever energy harvester by structural alteration. Three different energy harvesting structures are considered namely, stepped cantilever beam, stepped cantilever beam with rectangular and trapezoidal cavity. The analytical model of three energy harvesting structures are developed using Euler-Bernoulli beam theory. The thickness, position of the rectangular cavity and the taper angle of the trapezoidal cavity is found to shift the neutral axis away from the surface of the piezoelectric element which in turn increases the generated voltage. The performance of the energy harvesters is evaluated experimentally and is compared with regular piezoelectric cantilever energy harvester. The analytical and experimental investigations reveal that, the proposed energy harvesting structures generate higher output voltage as compared to the regular piezoelectric cantilever energy harvesting structure. This work suggests that through simple structural modifications higher energy can be harvested from the widely reported piezoelectric cantilever energy harvester.

Numerical Investigation of the Cover-Plates Effects on the Rectangular Open Cavity (직사격형 공동에서 덮개 효과에 대한 수치적 연구)

  • 허대녕;이덕주
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.457-464
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    • 2001
  • The aeroacoustic phenomena in the simple rectangular open cavity are well published by many researchers. But the geometry shapes of aircraft landing gear wells, weapon bays, etc. are more complicate than that of the simple retangular cavity. They are more similar to the cavity having cover-plates at adges, or Helmholtz resonator. Therefore, the effects of cover-plates existing on edges of rectangular open cavity are numerically investigated in this paper. The compressible Navier-Stokes equations are solved for two-dimensional cavities with laminar boundary layers upstream. The high-order and high-resolution numerical schemes are used for the evaluation of spatial derivatives and the time integration. Physically correct numerical boundary conditions and buffer zone techniques are implemented to produce time-accurate solutions in the whole computation domain. The computational domain is large enough to directly resolve a portion of the radiated acoustic field. Results show that the cover-plates existing on edges of cavity reduce the noise convected from cavity, make the frequency of noise become higher, and change the directivity pattern. So these results can be used in the design of a low noise cavity.

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Characteristics of the Mixed Convection Flow and Heat Transfer in a Channel with Open Cavity (개방된 캐비티를 가진 채널 내에서의 혼합대류 유동과 열전달 특성)

  • Ko, Y.C.;Bae, D.S.;Kim, N.S.
    • Journal of Power System Engineering
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    • v.11 no.4
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    • pp.56-64
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    • 2007
  • A numerical simulation is carried out mixed convection in horizontal channel with a heat source from below of rectangular cavity. Finite volume method was employed for the discretization and PISO algorithm was used for calculating pressure term. The parameters governing the problem are the Reynolds number ($10^{-2}{\leq}Re{\leq}50$), the Rayleigh number ($10^3{\leq}Ra{\leq}2.06{\times}10^5$), the Prandtl number ($0.72{\leq}Pr{\leq}909$), the aspect ratio ($0.5{\leq}AR=W/H{\leq}2$) and the angle of inclination ($0^{\circ}{\theta}60^{\circ}$). Mean Nusselt number distributions were obtained and effect of Reynolds number, Rayleigh number and Prandtl number on mixed convection in the horizontal channel with rectangular cavity were investigated.

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Bow-tie Mode Lasing in a Grooved Rectangular Semiconductor Microcavity

  • Moon, Hee-Jong;Hyun, Kyung-Sook
    • Journal of the Optical Society of Korea
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    • v.16 no.2
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    • pp.162-165
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    • 2012
  • Bow-tie modes were proposed in a grooved rectangular resonator and their lasing characteristics were investigated in semiconductor microcavities. The observed spacing between two adjacent lasing peaks from the grooved cavity was reduced compared to that of 4-bounce whispering gallery modes (WGMs) from the same-sized simple rectangular cavity due to increased round-trip path length of the bow-tie modes. The lasing spectra of bow-tie modes obtained from two adjacent corners showed highly correlated patterns while those of 4-bounce WGMs did not.

Theoretical Consideration on Influences of Cavity or Pillar Shape on Band Structures of Silicon-Based Photonic Crystals

  • Ogawa, Yoshifumi;Tamura, Issei;Omura, Yasuhisa;Iida, Yukio
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.7 no.1
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    • pp.56-65
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    • 2007
  • This paper describes physical meanings of various influences of cavity (or pillar) shape and filling factor of dielectric material on band structures in two-dimensional photonic crystals. Influences of circular and rectangular cross-sections of cavity (or pillar) arrays on photonic band structures are considered theoretically, and significant aspects of square and triangular lattices are compared. It is shown that both averaged dielectric constant of the photonic crystal and distribution profile of photon energy play important roles in designing optical properties. For the triangular lattice, especially, it is shown that cavity array with a rectangular cross-section breaks the band structure symmetry. So, we discuss this point from the band structure and address optical properties of lattice with a circular cross-section cavity.

Numerical Investigation of Mixing Characteristics in Cavity Flow at Various Aspect Ratios (종횡비에 따른 공동형상 내부에서의 혼합특성에 관한 수치적 연구)

  • Shin, Myung Seob;Yang, Seung Deok;Yoon, Joon Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.1
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    • pp.79-88
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    • 2015
  • This study numerically examined the mixing characteristics of rectangular cavity flows by using the hybrid lattice Boltzmann method (HLBM) applied to the finite difference method (FDM). Multi-relaxation time was used along with a passive scalar method which assumes that two substances have the same mass and that there is no interaction. First, we studied numerical results such as the stream function, position of vortices, and velocity profile for a square cavity and rectangular cavity with an aspect ratio of 2. The data were compared with previous numerical results that have been proven to be reliable. We also studied the mixing characteristics of a rectangular cavity flow such as the concentration profile and average Sherwood number at various Pe numbers and aspect ratios.

Forced Convection Heat Transfer from an Inner Surface of a Two-Dimensional Rectangular Cavity (이차원 사각형 공동 내부에서의 강제 대류 열전달)

  • Seo, T.B.;Han, K.Y.;Kange, Y.H.
    • Journal of the Korean Solar Energy Society
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    • v.22 no.4
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    • pp.77-84
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    • 2002
  • In order to investigate forced convection heat transfer due to the wind from the inner surface of a cavity receiver for a parabolic dish type solar energy collecting system, a two-dimensional rectangular cavity receiver is prepared and installed in a wind tunnel. The convection heat transfer coefficient of the inner surface of the receiver is dependent on the direction and the velocity of the wind. The attack angle of the cavity and the air velocity in the tunnel are controlled in a wide range so that the effects of the attack angle and the wind velocity on the heat transfer coefficient can be studied. The skirt is installed at the aperture of the cavity in order to reduce convective heat loss. The effects of the length and the installation angle of the skirt on convection heat transfer of the cavity are tested. It is found that convection heat loss can be significantly reduced by installing the skirt. Also, it is known that heat transfer from the cavity can be minimized if the angle of the skirt is $90^{\circ}$ to the outer surface of the cavity.