1. Department of Electrical and Computer Engineering, University of Washington, Seattle, WA 98195, USA
2. Department of Electrical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan
3. Department of Civil and Environmental Engineering, University of Washington, Seattle, WA 98195, USA
4. Department of Engineering Science and Ocean Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan