In this paper, the prephase method and the prephased unit cell designs for 1-bit reflective metasurfaces are discussed. Focusing on the symmetrical beam in 1-bit reflective metasurfaces under incident plane waves, the prephase method can break the even symmetrical array factor. With random prephase distributions, the symmetrical beam is effectively suppressed, and a single beam is formed. Moreover, the customized prephase distribution with equivalent amplitude tailoring further suppresses the sidelobe levels as beam scanning. For the realization of prephase, two kinds of methods are presented for the prephased unit cell designs. The proposed prephase method and prephased unit cells provide the foundation for 1-bit reconfigurable intelligence surface designs.

Realization (probability)

10.1109/iwat57058.2023.10171683

Cite

Citations (0)

Envision of evolvable antenna array

Qi Wu Zhong Lin Gong

In this paper we envision the evolvable antenna array system (EAA) based on the development of tunable or reconfigurable antenna element and the concepts that drawn from evolvable hardware. The general system architecture and the working scheme of EAA system are outlined. Two different ways of evolving: element-level evolving and array-level evolving are illustrated by examples. Further discussions in terms of the system implementation and performance improvement are then followed.

Evolvable Hardware

Reconfigurable antenna

10.1109/isape.2003.1276674

Cite

Citations (0)

Car assembly line fault diagnosis based on modified support vector classifier machine

Expert Systems with Applications (2010)

Qi Wu

Margin classifier

10.1016/j.eswa.2010.02.085

Cite

Citations (4)

Millimeter-wave wideband circularly polarized antenna arrays using travelling-wave elements

Qi Wu Jiexi Yin Yu Chen Haiming Wang Wei Hong

Using travelling-wave elements, two planar antenna arrays are developed for millimeter-wave wideband circularly polarized (CP) applications. First, the aperture-fed travelling-wave element is designed. Stacked curl element is printed on the surface of the substrate to realize wideband axial ratio (AR) and impedance performance. Then, two antenna arrays using substrate integrated waveguide (SIW) and microstrip feeding networks are developed, respectively. Performance comparison between these two arrays are discussed. Finally, the wideband CP antenna array which is fed by the SIW network is fabricated and measured. The measured impedance bandwidth of the array is 35.4%, 3-dB AR bandwidth is 33.8%, and 3-dB gain bandwidth is 32.2% with a peak gain of 23.5 dBic. The overall bandwidth is 30.6% and good efficiency of about 70% is obtained because of the low-loss full-corporate SIW feeding scheme.

Wideband

Extremely high frequency

10.1109/iwat.2018.8379135

Cite

Citations (3)

Research on Probability Mean-Lower Semivariance-Entropy Portfolio Model with Background Risk

Mathematical Problems in Engineering (2020)

Qi Wu Yuelin Gao Ying Sun

In the financial market, investors must deal with uncertain risk, and they also face background risk and many uncertain factors caused by their own characteristics. Considering the fuzzy nature of these factors as well as investors’ risk preferences, transaction costs, and so on, in order to reduce investment risk, an improved probability entropy measure is introduced, and a probability mean-lower semivariance-entropy model with different risk attitudes is established by using fuzzy sets and probability theory. To solve the portfolio model, an improved differential evolution algorithm is proposed and a numerical example is given. The numerical results show that the proposed algorithm is effective and that the model can disperse the financial risk to a certain extent and reasonably solve the portfolio problem under many different conditions.

Semivariance

Downside risk

Spectral risk measure

10.1155/2020/2769617

Cite

Citations (4)

Dynamical heterogeneities and defects in two-dimensional soft colloidal crystals

Soft Matter (2015)

Berend van der Meer Qi Wu Joris Sprakel Laura Filion Marjolein Dijkstra

In this paper we study a two-dimensional system of charged colloidal particles using Brownian dynamics simulations. We determine the phase diagram and investigate the dynamics of this system in the density regime where hexatic and solid phases are stable. We find that the dynamics in these phases is heterogeneous by means of the spontaneous formation and diffusion of highly mobile defects. We identify two key mechanisms associated with the areas of high mobility. The first mechanism involves the highly cooperative motion of a closed loop of particles which shift coherently along the loop until each particle has replaced the position of its predecessor in the chain. The second mechanism involves the spontaneous creation of vacancy-interstitial pairs which diffuse within the hexatic and solid phases. We further explore quantitatively the properties of the open-ended and closed rearrangement strings and find that in the crystal phase the string-size distribution can be approximately matched with a simple, random walk description of vacancies and interstitials on a lattice.

Brownian dynamics

Lattice (music)

Colloidal particle

Colloidal crystal

10.1039/c5sm01520k

Cite

Citations (18)

Broadband Planar SIW Cavity-Backed Slot Antennas Aided by Unbalanced Shorting Vias

IEEE Antennas and Wireless Propagation Letters (2019)

Qi Wu Jiexi Yin Yu Chen Haiming Wang Wei Hong

Two types of substrate integrated waveguide (SIW) cavity-backed slot (CBS) antennas are proposed for bandwidth enhancement. First, a quad-resonance SIW CBS antenna is proposed using a cross-shaped slot and loading unbalanced shorting vias. Additional half-TE ₁₂₀ mode is successfully excited along with three other independent modes including half-TE ₁₁₀ and odd and even TE ₂₁₀ modes. Next, a penta-resonance SIW CBS antenna with a cross-shaped slot is proposed, in which two pairs of shorting vias are loaded. Two additional hybrid modes of half-TE ₂₁₀ and half-TE ₁₂₀ modes are introduced along with three other independent modes including half-TE ₁₁₀ and odd and even TE ₃₁₀ modes. Furthermore, the working mechanism of these two types of SIW CBS antennas is explained. Finally, prototypes of these two antennas are fabricated and measured at X-band. Their measured fractional bandwidths are 20.0% and 20.8%, respectively. Simulation and measurement results agree very well, which confirms the validity of the proposed designs.

10.1109/lawp.2019.2891108

Cite

Citations (65)

A self-adaptive embedded chaotic particle swarm optimization for parameters selection of W v -SVM

Expert Systems with Applications (2010)

Qi Wu

Ergodicity

Logistic map

10.1016/j.eswa.2010.06.038

Cite

Citations (34)

Dual-band circularly polarized antenna fed by SICL coupler

Qi Wu Haiming Wang Yu Chen Xiaowei Zhang Wei Hong

A dual-band dual-circularly polarized patch antenna which is excited by two L-probes and fed by substrate integrated coaxial line (SICL) branch-line coupler is designed, fabricated, and measured. Simulation and measurement results show that, considering reflection coefficient, gain, and axial-ratio (AR) together, the bandwidths are 10% and 4%, and the antenna gains are 7 dBi and 8.2 dBi, respectively, at 1.6 GHz and 2.5 GHz bands.

Reflection coefficient

Multi-band device

Coaxial

Turnstile antenna

Axial ratio

10.1109/aps.2014.6905265

Cite

Citations (1)