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In this work, we propose a method for distinction of edible oils by using a terahertz (THz) spectrum combined with chemometrics.

This paper proposes a methane sensor based on localized surface plasmon resonance (LSPR) of a hexagonal periodic gold nanoring array. The effects of structural parameters on the extinction spectrum and refractive index (RI) sensitivity are analyzed to obtain optimal parameters. In particular, the RI sensitivity can reach 550.08 nm/RIU through improvement of the sensor structure, which is an increase of 17.4% over the original value. After coating a methane-sensitive membrane on the inner and outer surfaces of the gold rings, the methane concentration can be accurately measured with a gas sensitivity of −1.02 nm/%. The proposed method is also applicable to quantitative analyses of components concentration and qualitative analyses of gas composition.

A high-sensitive and transverse-stress compensated methane sensor based on a photonic crystal fiber long-period grating (PCF-LPG) is proposed. The outermost layer of the PCF consists of six large sideholes, five of which are coated with methane-sensitive compound film to achieve methane measurement. Such side-hole structure is helpful for gas sensitive reaction, but not conducive to avoiding external stress interference. Therefore, the last large hole is plated with silver layer to eliminate the cross-sensitivity effect through adding a Surface Plasmon Resonance (SPR) sensing channel with the consideration of photo-elastic effect and material deformation. Results show that the methane gas sensitivity can reach up to 6.39nm/% with the transverse-stress compensation. The sensor is very simple and effective, which provides a new method of gas measurement combined with different actual conditions. INDEX TERMS Methane sensor, transverse-stress compensation, photonic crystal fiber long period grating, surface plasmon resonance.

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In view of the underground monitoring and monitoring system of coal mine, wired data transmission has been used in the past, but there are some disadvantages such as complicated wiring work, large amount of labor, fixed network structure which is not convenient to meet the dynamic requirements and low stability. Therefore, this study designs a monitoring system based on ZigBee wireless sensor network, wireless transmission, strong mobility, high reliability, low power consumption, strong real-time performance, etc, can be real-time monitoring of the coal mine environment parameters, including downhole temperature, humidity and gas concentration, and the acquisition of information sent by ZigBee wireless transmission way. STM32F103RBT6 is adopted as the wireless network processor in the system, which is responsible for establishing the network and transmitting data. NDIR HC sjh-5 CUBIC gas concentration sensor to collect underground mine data; Wireless SZOS embedded wireless communication module is used as the wireless sending and receiving port to enhance the wireless sending power. The software architecture adopts ZigBee protocol stack. The research shows that the proposed ZigBee wireless sensor network based coal mine underground gas monitoring system can help improve the real-time monitoring level and reduce safety risks in the complex and special environment of coal mine underground.

A highly sensitive and temperature-compensated methane sensor based on a liquid-infiltrated photonic crystal fiber (PCF) is proposed. Two bigger holes near the core area are coated with a methane-sensitive compound film, and specific cladding air holes are infiltrated into the liquid material to form new defective channels. The proposed sensor can achieve accurate measurement of methane concentration through temperature compensation. The sensitivity can reach to 20.07 nm/% with a high linearity as the methane concentration is within the range of 0%-3.5% by volume. The proposed methane sensor can not only improve the measurement accuracy, but also reduce the metrical difficulty and simplify the process.

In this paper, a novel 22.5°fan-shaped half-mode substrate integrated waveguide resonator (FSHMSIWR) is presented firstly. Based on it, a filter design method by suppression or utilization of higher-order modes is proposed. When feeding on magnetic wall, the fundamental mode (TM 101) is excited to generate passband response, while the higherorder modes (TM 201 and TM 301) can be suppressed. A pair of complementary split-ring resonators (CSRRs) are introduced to strengthen the out-band rejection. Then a single-band bandpass filter (BPF) with ultrawide and deep stopband is realized. When feeding on electric wall, the higher-order modes can be well excited, which provides flexibility to realize multi-band BPFs only by changing the feeding position. As verification, a single-band BPF and a tri-band BPF with source-load coupling are designed and fabricated. The measured results show good agreement with the simulated ones.