Power Characteristics of Wireless Charging for Sensor Networks in Tunnels

In order to generate wireless microwave power charging technology in coal mine tunnels, it is necessary to know the power characteristics of wireless electromagnetic wave along the tunnel walls. In this paper, the experimental results of narrowband wireless electromagnetic wave propagation measurements are presented, and a statistical model of the power characteristics at 2.4 GHz in real rectangular mine tunnels is proposed. Two standard half-wave dipole antennas were used to perform the field experiments in tunnels with different wall materials. A 10-meter wireless charging distance belongs to the free-space propagation zone. The path loss exponents rely heavily on the location of the receiver and antenna polarizations. To obtain more power, the locations of the receiver should match the corresponding polarizations

Research of mico/nano methane sensing technology

For design requests of low power consumption, miniaturization and low cost about methane sensor because of development of mine Internet of things, a carrier catalytic combustion type methane sensor based on mico/namo meter technology was researched. Existing research status and corresponding achievements of the methane sensor were introduced in details on inspects of microheaters and low- dimensional methane sensing, and a metal oxide semiconductor methane sensor with a new metal-insulator-metal structure was introduced. The methane sensor has characteristics of low power consumption and miniaturization, which meets with development requests of mine Internet of things

2.4 GHz Radio Wave Propagation Characteristics in Coal Mine Workface Tunnels

We proposed a novel ray-tracing based radio waves propagation (RTRWP) Law suitable for under-tunnel complex coal mine workface. The energy consumption model evaluation in complex coal mine workface is derived. Theoretical analysis about calculating the multiple reflections of the radio waves in coal mine workface is also provided. Computer simulations and field tests in workface tunnels show that this proposed RTRWP law can work effectively to describe the actual radio wave propagation environments in complex coal mine workface

Multiple-Input Single-Output Wireless Power Transmission System for Coal Mine

In Wireless Power Transmission (WPT) systems, the proportion of energy received by the load is critical and the efficiency is the more significant parameter. The magnetic multiple input algorithms as well as many multiple overlapping coils structures in the transmitter side are proposed for the coal mine Internet of the Things (IOT) nodes. Different phase shifts cases for the input signal were considered to study their effect on the efficiency. Simulation results showed that the axial component of magnetic induction resulted from the multiple overlapping coils structure has preferable homogeneous distribution over the traditional single input coil. The proposed system achieved an efficiency value of 60 % for a receiver placed 40 cm away from a 4 coils transmitter comparing to an efficiency value of 50% for the same distance using a single coil transmitter. Simulation results shows that the proposed model is well adapted for the movable charging mode for the IOT nodes in coal mine. DOI : http://dx.doi.org/10.11591/telkomnika.v12i6.543

Dual-Band Sensor Network for Accurate Device-Free Localization in Indoor Environment with WiFi Interference

International audienceRadio Frequency based Device-Free Localization (RFDFL) is an emerging localization technique without requirements of attaching any electronic device to a target. The target can be localized by means of measuring the shadowing of received signal strength caused by the target. However, the accuracy of RFDFL deteriorates seriously in environment with WiFi interference. State-of-the-art methods do not efficiently solve this problem. In this paper, we propose a dual-band method to improve the accuracy of RFDFL in environment without/with severe WiFi interference. We introduce an algorithm of fusing dual-band images in order to obtain an enhanced image inferring more precise location and propose a timestamp-based synchronization method to associate the dual-band images to ensure their one-one correspondence. With real-world experiments, we show that our method outperforms traditional single-band localization methods and improves the localization accuracy by up to 40.4% in real indoor environment with high WiFi interference

Coal-rock interface recognition based on terahertz time-domain spectroscopy

In order to study feasibility of coal-rock interface recognition based on terahertz time-domain spectroscopy, some experiments were taken out by using terahertz time-domain spectroscopy, which used gas coal and sandstone powder tablet as samples. Time delay and attenuation amplitude that caused by terahertz pulse transmission between different samples were obtained. Hilbert-Huang transform was used to make time-frequency analysis of the samples' terahertz spectrum, and the analysis results were compared with the ones by traditional fast Fourier transform method. The comparison results show that resolution of terahertz spectrum is higher in time-frequency domain, and frequency and energy components of terahertz pulse can be analyzed better and more intuitively at any time as well as absorption effect of any frequency at different time. Coal-rock interface recognition process based on terahertz time-domain spectroscopy was introduced. The experimental results show that coal-rock medium can be well distinguished by characteristic value extracted by Hilbert spectrum and marginal spectrum

Prospect of perception mine internet of things and its development trend

Prospect of mine internet of things was given, which was realizing connection among objects in mine, decreasing even eliminating monitoring blind area, and adopting could computing and big data technologies to get useful monitoring information, so as to realize intrinsically safe mine. Development trend of mine internet of things was sorted out from aspects of technologies and service mode. Corresponding concepts were expounded including fog computing technology, network fractal structure, ontology of mine things and intellectualization, cloud computing and big data technologies and so on as well as their application and development in mine internet of things, and cooperative working mode and buying services mode were expected

Top-down design of mine Internet of things

Current status of mine Internet of things technology and its industrial development pattern were introduced. It was pointed out that top-down design of mine Internet of things was for designing perception mine from the state safe production supervision, realizing objects connection of mine Internet of things, and confirming service essence of mine Internet of things. Development trend of mine Internet of things was discussed, namely key technologies would be broken through continuously, service carrying pattern would appear gradually, and the government and enterprises would promote development of mine Internet of things jointly. Following development fields of mine Internet of things were focused on: breakthrough of core and key technologies including intelligent equipments with micromation and energy capturing technology, mine network, communication and post-disaster reconstruction technology, cloud computing, big data and safe production management technology, mine semanteme and virtualization technology, and safety, privacy and credible network technology; five sensing application including sensing miner, sensing disaster, sensing equipment, sensing mine area and sensing management; construction of cloud service hierarchy; standardization construction. Safeguard measures and construction route of mine Internet of things were proposed