Search Results (5)

A passive microwave instrument will be carried by China’s geostationary microwave satellite. A microwave hyper-spectral band included by the instrument ranges from 52.6 to 57.3 GHz, and totally has 89 channels in this spectral domain. The design of the hyper-spectral band is described from the aspects of scientific objectives and specifications. The weighting functions for each channel are calculated utilizing radiative transfer simulations under clear sky conditions. Then, the information content as well as the degree of freedom for signal are computed and analyzed to characterize this hyper-spectral sounding for atmospheric temperature profiling. Both the vertical distribution of the weighting functions and the width of retrieval averaging kernels indicate that the hyper-spectral band can provide more denser sampling for atmospheric temperature. The information content for the hyper-spectral band is approximately 46% higher than that of the ATMS-type channel 3 to 15, indicating that hyper-spectral measurement can improve the accuracy of retrieval. The most informative channels mainly locate near 57 GHz, having good consistency with the existing channels. The height range where the retrieval using the hyper-spectral observations is sensitive to the true profile, begins from about 800 to 1 hPa. Some channels can be considered as alternatives to each other since they have very similar information content and weighting functions. These results are expected to provide a valuable reference for future applications of the microwave hyper-spectral measurements. Full article

On-chip polarization control is in high demand for novel integrated photonic applications such as polarization division multiplexing and quantum communications. However, due to the sensitive scaling of the device dimension with wavelength and the visible-light absorption properties, traditional passive silicon photonic devices with asymmetric waveguide structures cannot achieve polarization control at visible wavelengths. In this paper, a new polarization-splitting mechanism based on energy distributions of the fundamental polarized modes in the r-TiO₂ ridge waveguide is investigated. The bending loss for different bending radii and the optical coupling properties of the fundamental modes in different r-TiO₂ ridge waveguide configurations are analyzed. In particular, a polarization splitter with a high extinction ratio operating at visible wavelengths based on directional couplers (DCs) in the r-TiO₂ ridge waveguide is proposed. Polarization-selective filters based on micro-ring resonators (MRRs) with resonances of only TE or TM polarizations are designed and operated. Our results show that polarization-splitters for visible wavelengths with a high extinction ratio in DC or MRR configurations can be achieved with a simple r-TiO₂ ridge waveguide structure. Full article

In this work, a novel wire-shaped supercapacitor based on nylon yarn with a high specific capacitance and energy density was developed by designing an asymmetric configuration and integrating pseudocapacitive materials for both electrodes. The nylon/Ag/MnO₂ yarn was prepared as a positive electrode by electrochemically depositing MnO₂ on a silver-paste-coated nylon yarn. Additionally, PPy was prepared on nylon/Ag yarn by chemical polymerization firstly to enlarge the surface roughness of nylon/Ag, and then the PPy could be easily coated on the chemically polymerized nylon/Ag/PPy by electrochemical polymerization to obtain a nylon/Ag/PPy yarn-shaped negative electrode. The wire-shaped asymmetric supercapacitor (WASC) was fabricated by assembling the nylon/Ag/MnO₂ electrode, nylon/Ag/PPy electrode and PAANa/Na₂SO₄ gel electrolyte. This WASC showed a wide potential window of 1.6 V and a high energy density varying from 13.9 to 4.2 μWh cm⁻² with the corresponding power density changing from 290 to 2902 μW cm⁻². Meanwhile, because of the high flexibility of the nylon substrate and superior adhesion of active materials, the WASC showed a good electrochemical performance stability under different bending conditions, suggesting its good flexibility. The promising performance of this novel WASC is of great potential for wearable/portable devices in the future. Full article

With the growing implementation of smart city projects and the significance of the research problem related to effective design thinking, the opinion of the ordinary citizens have become very relevant and contemporary. The current paper presents a quantitative empirical study focused on the attitudes towards and the readiness to accept smart cities in the specific context of Qatar. The study employs a survey questionnaire as a data collection tool. The survey is distributed online among a sample of 40 respondents from Qatar, including both residents and non-residents of smart cities in the country. Even though the sample is not representative of the Qatari population, the present study provides preliminary findings and fundamental insights into this novel topic in a specific socio-economic context. The major findings of the study uncovered that the respondents show quite positive attitudes toward diverse aspects related to smart economy, smart people, smart governance, smart mobility, smart environment, and smart living, as well as significant readiness to accept this lifestyle. However, the respondents demonstrate concerns related to the privacy and security of the people living in smart cities. The superiority of fundamental aspects of life like housing and healthcare in smart cities compared to conventional ones are also questioned by the respondents. Full article

Due to the wide deployment of wireless local area networks (WLAN), received signal strength (RSS)-based indoor WLAN localization has attracted considerable attention in both academia and industry. In this paper, we propose a novel page rank-based indoor mapping and localization (PRIMAL) by using the gene-sequenced unlabeled WLAN RSS for simultaneous localization and mapping (SLAM). Specifically, first of all, based on the observation of the motion patterns of the people in the target environment, we use the Allen logic to construct the mobility graph to characterize the connectivity among different areas of interest. Second, the concept of gene sequencing is utilized to assemble the sporadically-collected RSS sequences into a signal graph based on the transition relations among different RSS sequences. Third, we apply the graph drawing approach to exhibit both the mobility graph and signal graph in a more readable manner. Finally, the page rank (PR) algorithm is proposed to construct the mapping from the signal graph into the mobility graph. The experimental results show that the proposed approach achieves satisfactory localization accuracy and meanwhile avoids the intensive time and labor cost involved in the conventional location fingerprinting-based indoor WLAN localization. Full article