Architectural windows that smartly regulate indoor solar radiation by changing their optical transmittance in response to thermo-stimuli have been developed as a promising solution toward reducing the energy consumption of buildings. Recently, energy-efficient smart window technology has attracted increasing scientific interest, with the exploration of energyefficient novel materials as well as integration with practical techniques to generate various desired multi-functionalities. This review systematically summarizes emerging thermoresponsive materials for smart window applications, including hydrogels, ionic liquids, perovskites, metamaterials, and liquid crystals. These are compared with vanadium dioxide (VO2), a conventional and extensively studied material for thermochromic smart window applications. In addition, recent progress on cutting-edge integrated techniques for smart windows is covered, including electro-thermal techniques, self-cleaning, wettability and also 2 integration with solar cells for bifunctional energy conservation and generation. Finally, opportunities and challenges relating to thermochromic smart windows and prospects for future development are discussed. features (Figure 1b); (2) passivity, with their automatic response to temperature cutting down the need for switch systems, for example electrical control requiring external energy and human manipulation; (3) rational stimulus-response, with regulation by indoor temperature rather than UV-triggered optical modulation in photochromic materials. The table of contents entry:Smart windows are promised significant contribution to the economization of building energy consumption. The rapid development of thermoresonsive materials and integrated techniques provide novel directions beyond conventional pure VO2-based thermochromic smart windows. The review summarizes emerging materials, including hydrogels, ionic liquids, perovskites, and metamaterials and integrated techniques, covering electro-thermal devices, self-cleaning, wettability, and integration with solar cells.

Abstract-Slow-wave structures using distributed periodic inductive and capacitive loadings have found many microwave circuit applications as left-handed (bandpass) or right-handed (lowpass) transmission lines. A large slow-wave factor (SWF) could result in a much smaller passive component, but also a much lower bandgap (cutoff) frequency and a larger dispersion. This paper addresses the issues and the design tradeoff between the SWF, group delay (dispersion), and the cutoff frequency of a right-handed (lowpass) quasi-lumped transmission line. A new two-layer transmission line structure using 3-D substrate metallization with an SWF of 5.8 is designed. A prototype of a 3-GHz branch-line coupler with a 70% size reduction using such a transmission line structure is fabricated and tested.Index Terms-Branch-line coupler, dispersion, electromagnetic bandgap (EBG), periodic structures, slow wave.

Vanadium dioxide (VO2) based thermochromic smart window is considered as the most promising approach for economizing building energy consumption. However, the high phase transition temperature (τc), low luminous transmission (Tlum), and solar modulation (ΔTsol) impose an invertible challenge for commercialization. Currently, smart window research surprisingly assumes that the sunlight radiates in one direction which is obviously not valid as most regions receive solar radiation at various angles in different seasons. For the first time, solar elevation angle is considered and 3D printing technology is employed to fabricate tilted microstructures for modulating solar transmission dynamically. To maximize energy‐saving performance, the architecture of the structures (tilt, thickness, spacing, and width) and tungsten (W) doped VO2 can be custom‐designed according to the solar elevation angle variation at the midday between seasons and tackle the issue of compromised Tlum and ΔTsol with W‐doping. The energy consumption simulations in different cities prove the efficiency of such dynamic modulation. This first attempt to adaptively regulate the solar modulation by considering the solar elevation angle together with one of the best reported thermochromic properties (τc = 40 °C, Tlum(average) = 40.8%, ΔTsol = 23.3%) may open a new era of real‐world‐scenario smart window research.

We have fabricated a bamboo-derived composite with enhanced radiative cooling via a simple solution-based process. The long-wavelength infrared emissivity (ε LWIR ) for one side is as low as 0.3, to prevent the heat exchange, and the ε LWIR of the other side is near unity (0.95), to promote the radiative cooling. The energy saving simulations have been performed in Singapore, suggesting up to 89% energy savings enhancement, when compared with commercial low-E glass.

Thermo-responsive smart windows that control solar transmission are expected to be the promising solution to excessive building energy consumption and overheating of solar cell devices. The two performance indices, namely, the luminous transmission (T lum ) and the solar modulation (ΔT sol ), are often intrinsically limited by conventional thermo-responsive materials, which restrict their applications in smart windows. Alternatively, constructing a deformable surface morphology of smart windows can be an effective strategy to modulate the solar transmission.Here, we report a new category of thermo-responsive smart windows with a deformable surface morphology, which can be custom designed to achieve both desirable ΔT sol and T lum according to the sunlight incident angles of actual applications. This design is based on a thermo-responsive shape memory polymer and an optical coating, which is termed the butterfly-wing-like smart window (BSW). The BSW reversibly transforms from a temporary shape of flat topography to a predefined original shape of tilted configuration upon heating. It is demonstrated that the BSW has a high ΔT sol of 32.6% and an excellent T lum(average) of 64.5%. This work provides a new design strategy and mechanism for thermo-responsive smart windows.

Abstract-The design of miniaturized printed wire antennas using multilayer vias loaded periodic metallization is presented. The proposed structure is evolved from a periodic slow-wave transmission line, where each unit cell is made of a patch and two loops spread over two metal layers connected in series through vias. A section of the periodic metallization is used as a quarter-wave monopole antenna protruded over a truncated ground plane and fed by a microstrip line. The design prototype at 2.4 GHz band shows that it is possible to obtain 24% 10 dB bandwidth with 80% efficiency at an antenna length of 12 mm long without tuning inductors, more than a 50% reduction from a normal printed straight monopole.Index Terms-Electromagnetic band-gap, monopole antennas, slow wave structures, small antennas, wideband.

No abstract

Fabrication and testing technologies of super-smooth X-ray optical elements of synchrotron radiation is a new field.It works in the short-waveband and is one of the basic contents of optical foundation engineering research of soft X-ray. This article describes optical system characteristics of synchrotron radiation light beam, research goal, significance, background, present situation of our country and comparison with overseas level in fabrication and testing technology of super-smooth synchrotron radiation optical elements. It presents domestic and foreign present situation of super-smooth optical surface fabrication technology, as well as each kind of measurement technologies of synchrotron radiation optical elements. This article relates on fabrication and testing of super-smooth optical elements made of monocrystalline silicon emphatically, systematically introduces fabrication, test method and result of the optical elements. All test results meet with the design specification. The paper also demonstrates the progress approached or achieved both at home and abroad.