Fluid Antenna Enabling Secret Communications

Recent researches have revealed that fluid antenna, a new position-switchable antenna technology, can make use of the spatial moments of deep fades of the interference signal occurred naturally due to multipath for multiple access. In this letter, this phenomenon is exploited in a physical layer security setup where a base station (BS) transmits an information-bearing signal to a legitimate user and an artificial noise (AN) signal to a potential eavesdropper while the user is equipped with a fluid antenna to overcome the AN signal. The proposed approach needs no effort from the base station (BS) to avoid the AN signal from harming the legitimate user. Trying to enhance the secrecy rate, we study the power allocation of the information-bearing and AN signals if the channel state information (CSI) is available at the BS. Both perfect and imperfect CSI scenarios are investigated. Simulation results demonstrate that the proposed system, with a single fluid antenna with one radio-frequency (RF) chain at the user, achieves the secrecy rate that is achievable by the user utilizing maximal ratio combining (MRC) with many antennas instead, and is the only approach robust to CSI uncertainties of the eavesdropper, requiring no power allocation nor beamforming at the BS

Formation of nanodiamonds at near-ambient conditions via microplasma dissociation of ethanol vapour

Clusters of diamond-phase carbon, known as nanodiamonds, exhibit novel mechanical, optical and biological properties that have elicited interest for a wide range of technological applications. Although diamond is predicted to be more stable than graphite at the nanoscale, extreme environments are typically used to produce nanodiamonds. Here we show that nanodiamonds can be stably formed in the gas phase at atmospheric pressure and neutral gas temperatures \u3c100 °C by dissociation of ethanol vapour in a novel microplasma process. Addition of hydrogen gas to the process allows in flight purification by selective etching of the non-diamond carbon and stabilization of the nanodiamonds. The nanodiamond particles are predominantly between 2 and 5 nm in diameter, and exhibit cubic diamond, n-diamond and lonsdaleite crystal structures, similar to nanodiamonds recovered from meteoritic residues. These results may help explain the origin of nanodiamonds in the cosmos, and offer a simple and inexpensive route for the production of high-purity nanodiamonds

New flexible channels for room temperature tunneling field effect transistors

Tunneling field effect transistors (TFETs) have been proposed to overcome the fundamental issues of Si based transistors, such as short channel effect, finite leakage current, and high contact resistance. Unfortunately, most if not all TFETs are operational only at cryogenic temperatures. Here we report that iron (Fe) quantum dots functionalized boron nitride nanotubes (QDs-BNNTs) can be used as the flexible tunneling channels of TFETs at room temperatures. The electrical insulating BNNTs are used as the one-dimensional (1D) substrates to confine the uniform formation of Fe QDs on their surface as the flexible tunneling channel. Consistent semiconductor-like transport behaviors under various bending conditions are detected by scanning tunneling spectroscopy in a transmission electron microscopy system (in-situ STM-TEM). As suggested by computer simulation, the uniform distribution of Fe QDs enable an averaging effect on the possible electron tunneling pathways, which is responsible for the consistent transport properties that are not sensitive to bending

Switching behaviors of graphene-boron nitride nanotube heterojunctions

High electron mobility of graphene has enabled their application in high-frequency analogue devices but their gapless nature has hindered their use in digital switches. In contrast, the structural analogous, h-BN sheets and BN nanotubes (BNNTs) are wide band gap insulators. Here we show that the growth of electrically insulating BNNTs on graphene can enable the use of graphene as effective digital switches. These graphene-BNNT heterojunctions were characterized at room temperature by four-probe scanning tunneling microscopy (4-probe STM) under real-time monitoring of scanning electron microscopy (SEM). A switching ratio as high as 105 at a turn-on voltage as low as 0.5 V were recorded. Simulation by density functional theory (DFT) suggests that mismatch of the density of states (DOS) is responsible for these novel switching behaviors

FUNCTIONALIZED BORON NITRIDE NANOTUBES FOR ELECTRONIC APPLICATIONS

Boron nitride nanotubes (BNNTs) have been well known for their structural similarity to carbon nanotubes (CNTs), as well as for their superior mechanical properties. However, BNNTs are wide band gap semiconductors (band gap ~6eV), this hinders their applications in electronic devices. In this dissertation, different methodologies to functionalize the insulating BNNTs have been demonstrated and discussed, including metallic quantum dots (QDs-BNNTs), graphene (graphene-BNNTs), CNTs (CNT-BNNT). Furthermore, research effort on the exploration of fabricating gold quantum dots decorated BNNTs based one dimensional plasmonic devices will also be discussed

Guardian Map Approach to Feasible Range of Static Stability Margin of Hypersonic Flight Vehicles with Input Saturation

Static stability margin is a critical parameter in flight control design. The feasible range of it must cover the uncertainty through the flight. To reasonably identify the feasible range of static stability margin in advance, an approach based on guardian maps is proposed for flight control of hypersonic flight vehicles with input saturation. First, the model of hypersonic flight vehicle (HFV) is established as a parametric plant. Then, flying quality requirements for the closed-loop system are formulated as inequality constraints using guardian maps. Moreover, by using linear matrix inequality, the saturation of elevators is taken into account in the integrated control of attitude control. The prescribed minimum of static stability margin that ensures the flying quality of hypersonic flight vehicles with input saturation is obtained. Furthermore, from the prospective of integrated control, it is shown that the feasible range of static stability margin can be enlarged by changing aerodynamic characteristics. The effectiveness of the proposed approach is validated by numerical simulation

Laboratory Study on Corrosion Mechanism of Production System in In Situ Combustion

The corrosion problem of a production system has been affecting the normal operation of an in situ combustion project. Because the environment of production system is significantly different in tubing, gas, liquid, and temperature in in situ combustion, the problem of the corrosion should be treated differently according to its origin. Based on the main environment of gas-liquid of the production system of in situ combustion, the corrosion of steel in N80 and J95, which are commonly used in oilfield, is studied in different temperature and pressure conditions. The results show that under the condition of 50°C and 3 MPa, the corrosion of the well is the most serious. Based on the analysis of corrosion causes in the production system, the corrosion under the protection of modified sacrificial anode in the liquid phase environment was studied. The results of comparative analysis show that the modified material had the dual protection effect of sacrificial anode and film-forming protection and could slow down the corrosion in different temperature ranges

In situ electrical conductivity measurement for functionalized boron nitride nanotubes by transmission electron microscopy

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012