Chun Yu

University of Kentucky, Lexington, Kentucky, United States

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Publications (6)4.34 Total impact

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    ABSTRACT: An electromagnetic (EM) heating system is developed to achieve the rapid and uniform warming of cryopreserved biomaterials. Using the heating system, a rectangular resonant cavity is excited in TE101 mode at frequencies near 434 MHz. In experiments, a spherical phantom of biomaterial with a diameter of 36 mm is placed at the center of the cavity. The phantom is first cooled down to about -80 degrees C within the cavity and then thawed by EM absorption. Results show that EM warming can produce much higher warming rate than conventional water-bath warming method. The spatial temperature distribution in the phantom during EM warming is also more uniform than that during the water-bath warming.
    Cryobiology 11/2006; 53(2):288-93. DOI:10.1016/j.cryobiol.2006.07.001 · 1.59 Impact Factor
  • Chun Yu · Cai‐Cheng Lu
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    ABSTRACT: In practical applications, frequency-selective surfaces (FSSs) are finite, and sometimes even curved. In this paper, we present a hybrid volume-surface integral-equation approach to analyze the transmission and reflection characteristics of finite and curved FFS structures. The hybrid integral equations are established using the surface- and volume-equivalent principles. This approach has two advantages. One is the capability of modeling arbitrarily shaped FSS structures in detail, the other one allows us to easily apply the multilevel fast multiple algorithm to speed up the solution process. The scattering characteristics and frequency responses of several FSSs are analyzed. The simulation results show that for a finite-sized FSS, reducing the radius of curvature causes amplitude variation, frequency shift, and bandwidth change in the reflection and transmission responses. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 107–112, 2005; Published online in Wiley InterScience ( DOI 10.1002/mop.20738
    Microwave and Optical Technology Letters 04/2005; 45(2):107 - 112. DOI:10.1002/mop.20738 · 0.57 Impact Factor
  • Chun Yu · Cai-Cheng Lu · Chong Luo
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    ABSTRACT: Solving integral equation by iterative methods for cavity scattering problems can encounter slow convergence due to several factors, such as internal resonance, near resonance and multiple wave bounces. A numerical study is presented on the solution of the TETH-type (short for tˆ·E and tˆ·H) combined field integral equation in the context of the near-resonance decoupling approach (NRDA), in which the TETH-type formulation is discretized by the method of moments with roof-top basis and testing functions over quadrilateral shaped meshes.
    Antennas and Propagation Society International Symposium, 2004. IEEE; 07/2004
  • Cai-Cheng Lu · Chun Yu
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    ABSTRACT: The input impedances of a microstrip antenna with finite and curved substrates are calculated using the hybrid volume surface integral equation approach. The results for flat and large substrate cases are compared with the measurement as well as the method of moment solution based on the spectral domain Green's function for infinitely large ground plane. Numerical results show that the input impedance can be significantly influenced when the substrate of a patch antenna is reduced in size or curved in shape.
    IEEE Transactions on Antennas and Propagation 03/2004; 52(2-52):615 - 619. DOI:10.1109/TAP.2004.823894 · 2.18 Impact Factor
  • Cai-Cheng Lu · Chun Yu
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    ABSTRACT: The hybrid volume-surface integral equation approach is implemented to calculate the radiation and scattering by large microstrip arrays on curved substrate and ground plane. The multilevel fast multipole algorithm is applied to reduce the memory and CPU requirements for solving the matrix equation. Numerical results for input impedances of single patch and the scattering pattern for an array are presented.
    Microwave and Millimeter Wave Technology, 2002. Proceedings. ICMMT 2002. 2002 3rd International Conference on; 09/2002
  • Cai-Cheng Lu · Chun Yu
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    ABSTRACT: The hybrid volume-surface integral equation (VSIE) approach has been applied to calculate the input impedance of the printed structure with finite ground plane. The calculated results for a rectangular patch antenna have been compared with experiment and good agreement is observed. When the ground plane size increases, the input impedance converges to the result of infinite ground plane. An important advantage of the VSIE algorithm is that it can be used to simulate the printed structure of finite, arbitrary shaped ground plane.
    Antennas and Propagation Society International Symposium, 2002. IEEE; 02/2002