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Asian countries face various developmental issues such as natural disasters, water concerns, urbanization, healthcare, and climate change, and there is the need to develop infrastructure to resolve these issues. This paper first introduces the system of Taiwan's infrastructure quality management and then provides a study on the countermeasures to improve quality management. The findings of the discussions will be collected as an infrastructure maintenance and management reference.

The performances of metamaterial absorbers can be affected by the incidence angle of electromagnetic wave. It is difficult to design the incidence angle-insensitive metamaterial absorbers. In this paper, we propose a metamaterial absorber with wide-angle incidence based on the equivalent medium theory. The absorber unit consists of a double-sided split resonant ring placed vertically on the ground. The resistors and capacitors are loaded at the opening of the resonant ring. The resistor is used to adjust the equivalent electromagnetic parameters of the metamaterial, and the capacitor is used to control the resonant frequency of the metamaterial and miniaturize the unit. When the transverse electric (TE) plane wave impinges on the surface of the absorber, R = 4000 Ohm and C = 1.5 pF, the proposed absorber can achieve an absorptivity greater than 90% at 1.59 GHz up to an incidence angle reaching 70°. Besides, the absorber can achieve an 85% absorptivity under an incidence angle of 75°. when the transverse magnetic (TM) plane wave impinges on the surface of the absorbers, R = 1200 Ω and C = 1.5 pF, the proposed absorber can achieve an absorptivity of greater than 90% at 1.59 GHz up to a 70°incidence angle. Besides, the absorber can also achieve an absorptivity of 85% up to 75°. The results show that the measurement results are basically consistent with the simulation results. In addition, when the capacitance is changed while the other parameters are fixed, the metamaterial absorber proposed in this paper still has the same wide-angle absorbing performance at the new resonant frequency. In other words, the proposed absorber has broadband operating characteristics. A frequency-tunable metamaterial absorber with wide-angle incidence can be designed based on the aforementioned results. The results in this paper provide a method of tuning capacitance. The opening is set at the other end of the split ring, and the same fixed-value resistor and variable capacitor are loaded on the left opening, and the corresponding DC bias feeder is designed. One end of the DC bias line is directly connected to the ground, and the other end needs to be separately connected to the other DC bias feeder of each unit to realize the control of the variable capacitors of each unit.

In the past decade, most of researchers have been devoted to broadening the bandwidth of absorber. There are few researches on how to achieve wide-angle absorbing materials by detailed theoretical analysis and design guidance. It is still difficult to design wide-angle absorbers. In this paper, based on the equivalent medium theory, the reflectivity of the metamaterial absorber with a single-layered medium backed with metal reflector is analyzed in detail. Starting from the basic electromagnetic theory, the reflection coefficient of the absorber under transverse electric(TE) plane wave and transverse magnetic (TM) plan wave irradiation are derived. And the equivalent electromagnetic parameters of realizing the wide-angle absorbing effect are analyzed, which provide a theoretical basis for designing the wide-angle metamaterial absorber. The theoretical analysis results show that the equivalent electromagnetic parameters required for the medium to achieve low-profile and wide-angle absorbing effect are mainly related to the equivalent permeability and have little relationship with the equivalent permittivity. Moreover, the equivalent electromagnetic parameter value for achieving ultra-wide-angle absorber under TE wave and that under TM wave irradiation are different from each other. In other words, the anisotropic metamaterial with appropriate equivalent permeability has the potential to be used to design the ultra-wide-angle absorbers which are not sensitive to TE waves nor TM waves. In addition, in order to find the theoretically achievable widest absorbing angle value under TE wave and TM wave irradiation, the reflection coefficients at all angles must be less than or equal to –10 dB to obtain the relationship among the equivalent electromagnetic parameters, thickness and angle. The results show that the theoretically achievable widest absorbing angle value is 86.56° under TE wave and TM wave irradiation. The designer can choose the corresponding thickness and permeability from the data obtained from the analysis according to the design requirements. The narrow-band absorbers have limited applications. Therefore, in this paper we also theoretically analyze the values of the equivalent electromagnetic parameters for ahcieving wide-band and wide-angle absorbing materials, and make theoretical verification. The results show that the wide-band and wide-angle absorber can be achieved theoretically, while the equivalent electromagnetic parameters of the medium vary with frequency as some special curves indicate. Although this method is based on the equivalent medium theory and has no direct relationship with the actual structure, it does provide theoretical guidance for designing the wide-angle absorbers.