Develop an Adaptive Real-Time Indoor Intrusion Detection System Based on Empirical Analysis of OFDM Subcarriers.

Device-free passive intrusion detection is a promising technology to determine whether moving subjects are present without deploying any specific sensors or devices in the area of interest. With the rapid development of wireless technology, multi-input multi-output (MIMO) and orthogonal frequency-division multiplexing (OFDM) which were originally exploited to improve the stability and bandwidth of Wi-Fi communication, can now support extensive applications such as indoor intrusion detection, patient monitoring, and healthcare monitoring for the elderly. At present, most research works use channel state information (CSI) in the IEEE 802.11n standard to analyze signals and select features. However, there are very limited studies on intrusion detection in real home environments that consider scenarios that include different motion speeds, different numbers of intruders, varying locations of devices, and whether people are present sleeping at home. In this paper, we propose an adaptive real-time indoor intrusion detection system using subcarrier correlation-based features based on the characteristics of narrow frequency spacing of adjacent subcarriers. We propose a link-pair selection algorithm for choosing an optimal link pair as a baseline for subsequent CSI processing. We prototype our system on commercial Wi-Fi devices and compare the overall performance with those of state-of-the-art approaches. The experimental results demonstrate that our system achieves impressive performance regardless of intruder's motion speeds, number of intruders, non-line-of-sight conditions, and sleeping occupant conditions.

Vertical Assembly of Giant Double- and Triple-Decker Spoked Wheel Supramolecular Structures.

The double- or triple-decker 3D metallo-hexagons were obtained by self-assembly of multitopic tris-terpyridines with Cd2+ ions in near-quantitative yield. Comprising up to 72 ionic pairs, the multiple spoked wheels display characteristic reversible gelation properties under thermodynamic conditions. The supramolecular metallo-nanoarchitectures were characterized by 1 H NMR, 2D NMR (COSY and NOESY), and diffusion-ordered spectroscopy (DOSY) and HR-ESI-MS, traveling-wave ion mobility mass spectrometry (TWIM-MS), TEM, and AFM. For the first time, the self-assembly of 45 units at once was demonstrated to yield exceptional giant triple-decker hexagons of up to circa 42 000 Da.

Chiral Self-Assembly of Nonplanar 10,10'-Dibromo-9,9'-bianthryl Molecules on Ag(111).

We report on the low-temperature scanning tunneling microscopy (STM) measurements of the self-assembly of nonplanar 10,10'-dibromo-9,9'-bianthryl (DBBA) molecules on Ag(111) combined with density functional theory (DFT) calculations. DBBA molecules have two enantiomorphous adsorption configurations, from which more chiral structures can be formed. At a low coverage [0.4 monolayer (ML)], DBBA forms racemic netlike islands consisting of molecular chains along ⟨1 2 3̅⟩Ag. Moreover, the gliding between the molecular chains gives rise to chiral windmill-like patterns in the islands. At 0.8 ML, DBBA forms a racemic row phase and a homochiral hexamer phase. The molecular appearance difference between the two coexisted phases and the DFT calculated molecular adsorption configuration reveal a decrease in the molecular dihedral angle of DBBA, which implies an enhancement in the intermolecular interactions via CH···π and halogen bonds. The transition from a racemic packing mode to a homochiral one suggests that the suitability of steric configurations is dominant in the close-packing mode under enhanced intermolecular interactions.

Metallo-Organic Ligand Designing Road for Constructing the First-Generation Dendritic Metallotriangle.

Three approaches have been carefully examined in order to develop a terpyridine-based dendritic metallotriangle: (1) direct self-assembly of two types of organic polyterpyridines with metal ions; (2) assembly of flexible metallo-organic ligands containing two uncomplexed free terpyridines with a possible 60°-V-shaped orientation; (3) assembly of functionalized metallotriangles possessing a fixed 60°-bent uncoordinated bisterpyridine. Only the third approach has successfully given rise to the desired first-generation dendritic metallotriangle. Structural characterization was accomplished by NMR, ESI-TWIM-MS, and AFM.

The Investigation of Hybrid PEDOT:PSS/ß-Ga2O3 Deep Ultraviolet Schottky Barrier Photodetectors.

In this paper, the hybrid ß-Ga2O3 Schottky diodes were fabricated with PEDOT:PSS as the anode. The electrical characteristics were investigated when the temperature changes from 298 K to 423 K. The barrier height ϕb increases, and the ideality factor n decreases as the temperature increases, indicating the presence of barrier height inhomogeneity between the polymer and ß-Ga2O3 interface. The mean barrier height and the standard deviation are 1.57 eV and 0.212 eV, respectively, after taking the Gaussian barrier height distribution model into account. Moreover, a relatively fast response speed of less than 320 ms, high reponsivity of 0.6 A/W, and rejection ratio of R254 nm/R400 nm up to 1.26 × 103 are obtained, suggesting that the hybrid PEDOT:PSS/ß-Ga2O3 Schottky barrier diodes can be used as deep ultraviolet (DUV) optical switches or photodetectors.

Experimental and Theoretical Studies of Mo/Au Schottky Contact on Mechanically Exfoliated ß-Ga2O3 Thin Film.

We studied the reverse current emission mechanism of the Mo/ß-Ga2O3 Schottky barrier diode through the temperature-dependent current-voltage (I-V) characteristics from 298 to 423 K. The variation of reverse current with the electric field indicates that the Schottky emission is the dominant carrier transport mechanism under reverse bias rather than the Frenkel-Poole trap-assisted emission model. Moreover, a breakdown voltage of 300 V was obtained in Fluorinert ambient with an average electric field of 3 MV/cm in Mo/ß-Ga2O3 Schottky barrier diode. The effects of the surface states, on the electric field distribution, were also analyzed by TCAD simulation. With the negative surface charge densities increasing, the peak electric field reduces monotonously. Furthermore, the Schottky barrier height inhomogeneity under forward bias was also discussed.