Fabry-Perot resonance-suppressed double-layer metal mesh window for electromagnetic interference shielding.

Traditional electromagnetic interference shielding windows that can simultaneously reflect microwaves and transmit visible light are usually fabricated by depositing one metal mesh layer on the surface of the window. However, such a structure always suffers from strong Fabry-Perot resonance (FPR), which leads to the decline of shielding effectiveness (SE). Here, we analyze the mechanism of FPR from a perspective of the equivalent circuit model and further report a facile approach to minimize the FPR by depositing another high-resistance mesh layer on the back side of the shielding window, which can greatly reduce reflected waves, ensuring that interference cannot be formed. Simulation results prove that FPR can be effectively eliminated by the proposed method, and experiments further show that for a shielding window made with Schott B270 glass plate, the SE can be enhanced by 6.3 dB (76.6% energy attenuation) at declining points, while transmittance is only reduced by 1.6%.

Transparent ultra-wideband double-resonance-layer metamaterial absorber designed by a semiempirical optimization method.

In this study, a transparent ultra-wideband double-resonance-layer absorber was designed using a semiempirical optimization method. In this method, an equivalent circuit model, genetic algorithm, and parameter fitting are employed to reduce the computation time and improve the design flexibility. Simulations and measurements show that the as-designed absorber can achieve ultrawide microwave absorption in the range of 2.00 to 11.37 GHz with a fractional bandwidth of 140.2%. Furthermore, electric field and surface current distributions show that the broad bandwidth was derived from the good matching of the absorption peaks in the two resonance layers. In addition, the target waveband of the as-designed absorber covered the wavebands of WiFi and radio-frequency identification, as well as part of the 5G waveband. This makes the proposed absorber a good candidate for daily electromagnetic pollution reduction.

Numerical investigation of an ultra-broadband, wide-angle, and polarization-independent metasurface light absorber.

In this paper, we propose and numerically investigate an ultra-broadband, wide-angle, and polarization-independent metasurface absorber based on periodic hexagon-latticed titanium (Ti) nanoring arrays over a continuous Ti film. The proposed absorber can achieve more than 90% absorptivity under normal incidence, ranging from 350 to 1453 nm, and the average absorption is up to 95.6%. Additionally, the absorptivity still remained beyond 70% when the incident angles varied from 0° to 60°. The simulations of electric field distributions indicate that the broadband absorption performance can be ascribed to the superposition of the localized surface plasmon resonance (LSPR) originated from the nanopillars and nanoholes, respectively. The proposed approach is simple and inexpensive, and the metal material is optional. Therefore, we believe that the proposed absorber will be a candidate for many potential applications, such as thermophotovoltaic cells, thermal emitters, and optoelectronic devices.

MXene as a Cation-Selective Cathode Material for Asymmetric Capacitive Deionization.

Capacitive deionization (CDI) has become a promising method to solve the shortage of freshwater resources recently. However, the co-ion expulsion effect obviously hinders electrosorption capacity and charge efficiency of CDI. In this work, an asymmetric CDI cell is assembled in which Na+-intercalated Ti3C2Tx (NaOH-Ti3C2Tx) serves as a cation-selective cathode, while the activated carbon (AC) serves as the anode. The NaOH-Ti3C2Tx with negatively charged surface groups (-OH, -O, and -F) is adopted to weaken the co-ion expulsion effect. Benefited from the synergistic effect of the reduced co-ion expulsion effect and expanded interlayer space, the asymmetric CDI cell achieves a higher electrosorption capacity of 12.19 mg g-1 and a higher charge efficiency of 0.826 compared with the symmetric one composed of AC (4.55 mg g-1 and 0.306) in 100 mg L-1 NaCl solution. High cyclic stability of the as-prepared asymmetric CDI cell is also observed. The improved desalination performance indicates that NaOH-Ti3C2Tx is a promising alternative as cation-selective cathode material for asymmetric CDI cells. The desalination mechanism is discussed in detail to lay the foundation for further improvement of the CDI performance of other 2D materials like MXene.

Broadband Near-Infrared Absorber Based on All Metallic Metasurface.

Perfect broadband absorbers have increasingly been considered as important components for controllable thermal emission, energy harvesting, modulators, etc. However, perfect absorbers which can operate over a wide optical regime is still a big challenge to achieve. Here, we propose and numerically investigate a perfect broadband near-infrared absorber based on periodic array of four isosceles trapezoid prism (FITP) unit cell made of titanium (Ti) over a continuous silver film. The structure operates with low quality (Q) factor of the localized surface plasmon resonance (LSPR) because of the intrinsic high loss, which is the foundation of the broadband absorption. The high absorption of metal nanostructures mainly comes from the power loss caused by the continuous electron transition excited by the incident light inside the metal, and the resistance loss depends on the enhanced localized electric field caused by the FITP structure. Under normal incidence, the simulated absorption is over 90% in the spectrum ranging from 895 nm to 2269 nm. The absorber is polarization-independent at normal incidence, and has more than 80% high absorption persisting up to the incident angle of ~45° at TM polarization.

Reflection phase modification by metamaterial interface: an understanding of design criteria for ultrathin multispectral absorber.

We introduce a metasurface to modify the reflection phase for multispectral microwave absorbers. General quantitive design criteria are proposed by carrying out field analysis, so that design of multispectral microwave absorber can be effectively realized. Optimal design process is discussed to develop an understanding of the absorbing mechanism. Experiment results show that the absorber having only 0.015 times the wavelength at the center frequency can simultaneously achieve high absorption in the microwave, visible light and near-infrared light bands. Multispectral absorption comes with added features of flexibility, ultrathin thickness and a light weight that make it a powerful candidate in advanced stealth application.

Theoretical Analysis and Design of Ultrathin Broadband Optically Transparent Microwave Metamaterial Absorbers.

Optically Transparent Microwave Metamaterial Absorber (OTMMA) is of significant use in both civil and military field. In this paper, equivalent circuit model is adopted as springboard to navigate the design of OTMMA. The physical model and absorption mechanisms of ideal lightweight ultrathin OTMMA are comprehensively researched. Both the theoretical value of equivalent resistance and the quantitative relation between the equivalent inductance and equivalent capacitance are derived for design. Frequency-dependent characteristics of theoretical equivalent resistance are also investigated. Based on these theoretical works, an effective and controllable design approach is proposed. To validate the approach, a wideband OTMMA is designed, fabricated, analyzed and tested. The results reveal that high absorption more than 90% can be achieved in the whole 6~18 GHz band. The fabricated OTMMA also has an optical transparency up to 78% at 600 nm and is much thinner and lighter than its counterparts.

Characteristics of participants' and caregivers' influence on non-response in a cross-sectional study of dementia in an older population.

OBJECTIVE: The issue of non-response in dementia epidemiological studies, which may result in the underestimation of the prevalence of dementia, has attracted little attention. We aimed to explore the causes and related factors of non-response in a dementia survey among Chinese veterans. METHODS: A two-phase, cross-sectional study investigated the prevalence of dementia and mild cognitive impairment in Chinese veterans aged ≥ 60 years. We collected the socio-demographic data and prior medical history, evaluated the health status of veterans and their caregivers, assessed the cognitive status of veterans, and evaluated the care burden of caregivers by Caregiver Burden Inventory (CBI). RESULTS: Of 9676 eligible participants, 525 (5.4%) veterans in phase 1 and 1706 (35.0%) veterans among 4875 veterans in phase 2 did not respond. Illness, hospitalization and death accounted for 63.0% and 75.5% non-response in phases 1 and 2, respectively. Non-participation in social activities, self-perceived poor health status, worsened health changes, self-reported need for life care, and history of hearing loss or glaucoma independently predicted non-response in phase 1 or 2. The heavy care burden, suggested by the higher CBI scores and self-reported health deterioration of the primary caregivers, predicted non-response in phase 1 or 2. CONCLUSIONS: The negative factors from both the participants and their caregivers independently predicted the non-response in the dementia study in an older population. Preventative strategies from the perspectives of the participants and caregivers should be developed to improve the response rates in both phases in a cross-sectional study.

Construction of the Chinese Veteran Clinical Research (CVCR) platform for the assessment of non-communicable diseases.

BACKGROUND: Based on the excellent medical care and management system for Chinese veterans, as well as the detailed medical documentation available, we aim to construct a Chinese Veteran Clinical Research (CVCR) platform on non-communicable diseases (NCDs) and carry out studies of the primary disabling NCDs. METHODS: The Geriatric Neurology Department of Chinese People's Liberation Army General Hospital and veterans' hospitals serve as the leading and participating units in the platform construction. The fundamental constituents of the platform are veteran communities. Stratified typical cluster sampling is adopted to recruit veteran communities. A cross-sectional study of mental, neurological, and substance use (MNS) disorders are performed in two stages using screening scale such as the Mini-Mental State Examination and Montreal cognitive assessment, followed by systematic neuropsychological assessments to make clinical diagnoses, evaluated disease awareness and care situation. RESULTS: A total of 9 676 among 277 veteran communities from 18 cities are recruited into this platform, yielding a response rate of 83.86%. 8 812 subjects complete the MNS subproject screening and total response rate is 91.70%. The average participant age is (82.01±4.61) years, 69.47% of veterans are 80 years or older. Most participants are male (94.01%), 83.36% of subjects have at least a junior high school degree. The overall health status of veterans is good and stable. The most common NCD are cardiovascular disorders (86.44%), urinary and genital diseases (73.14%), eye and ear problems (66.25%), endocrine (56.56%) and neuro-psychiatric disturbances (50.78%). CONCLUSION: We first construct a veterans' comprehensive clinical research platform for the study of NCDs that is primarily composed of highly educated Chinese males of advanced age and utilize this platform to complete a cross-sectional national investigation of MNS disorders among veterans. The good and stable health condition of the veterans could facilitate the long-term follow-up studies of NCDs and provide prospective data to the prevention and management of NCDs.