Shan Minglei

Gas concentration detection using ultrasonic based on wireless sensor networks

In this article, a low power consumption wireless sensor for binary gas mixtures real-time quantitative analysis is presented. This small size wireless gas sensor, which is developed based on an improved time-of-flight (TOF) method, can evaluate target gas in gas mixtures with high resolution. And the wireless sensor network system reduce power consumption using a power control IEEE802.15.4 standard, which can provide an effective mechanism for improving energy efficiency by decreasing the transmitting power directly. In contrast with some other gas analysis techniques, it avoids the problem of the secondary pollution and the short sensor life of using chemic sensor, and the high power consumption problem of traditional TOF methods, makes ultrasonic wireless gas sensor available. Currently, this gas quantitative analysis system consists of several Wireless Ultrasonic Gas Sensor nodes (WUGS) and a master node. The WUGS hardware consists of a microcontroller for obtaining measuring data from the ultrasonic channel, and a Zigbee transceiver for transmitting the data sets to a master sensor node. Furthermore, an environmental monitoring chamber was designed for testing this WUGS using sulfur hexafluoride (SF6) and hydrogen (H2) mixed with air respectively. The resolutions of the tests were within 30µV/V and 500µV/V, respectively. The power cost of the WUGS during the detection period is lower than 90mW. The main advantages of this gas concentration measurement are high accuracy to the gas of which molecular weight is different largely from air, low power consumption and ease of network setup. The sensors have shown good stability for more than three months in a high-voltage substation, for an SF6 leak alarm system test.

Atmospheric Pressure Plasma Jet in Organic Solution: Spectra, Degradation Effects of Solution Flow Rate and Initial pH Value

The organic compounds of p-nitrophenol (PNP) solution was treated by the active species generated in a stirred reactor by an atmospheric pressure plasma jet (APPJ). The emission intensities of hydroxyl (OH), oxygen (O), nitric oxide (NO), hydrogen (H) and molecular (N2) were measured by optical emission spectroscopy (OES). The relations between the flow rates of the PNP solution and degradation, the degradation effects and initial pH value of the solution were also investigated. Experimental results show that there exist intense emissions of O (777.1 nm), N2 (337.1 nm), OH (306–310 nm) and NO band (200–290 nm) in the region of plasma. Given the treatment time and gas flow rate, the degradation increased as a function of discharge energy and solution flow rate, respectively. The solution flow rate for the most efficient degradation ranged from 1.414 m/s to 1.702 m/s, and contributed very little when it exceeded 2.199 m/s. This indicates the existence of diffusion-controlled reactions at a low solution flow rate and activation-controlled reactions at a high solution flow rate. Moreover, increasing or decreasing the initial pH value of neutral PNP solution (pH=5.95) could improve the degradation efficiency. Treated by APPJ, the PNP solutions with different initial pH values of 5.95, 7.47 and 2.78 turned more acidic in the end, while the neutral solution had the lowest degradation efficiency. This work clearly demonstrates the close coupling of active species, photolysis of ultraviolet, the organic solution flow rate and the initial pH value, and thus is helpful in the study of the mechanism and application of plasma in wastewater treatment.

The research of moisture detection in transformer oil based on ultrasonic method

Transformer is one of the most important equipment in the power industry. The moisture content of a power transformer insulation system is a key parameter for the estimation of its aging condition and operation reliability. Therefore detection of the moisture content is a very essential task within power transformer diagnostics. This paper puts forward a moisture detection method in transformer oil based on the ultrasonic transit time difference. The ultrasonic velocity of oil is closer to the water, but has a relatively large difference with ice; the oil-water mixture is frozen to enable the water to become ice in this paper. Because different moisture content will lead to change of propagation time, the moisture content will be obtained from ultrasonic transit time difference. This paper analyses ultrasonic transmit time in the suspension in theory, then verify the theoretical analysis in experimental. The experimental results are in agreement with theoretical analysis. It is clearly showed that the use of ultrasonic on transformer oil moisture detection is feasible.

Design of an Intelligent Book Conveyor based on RFID

In view of the problems existed in library management and service work, we designed a RFID Intelligent Book Conveyor using Radio Frequency Identification (RFID) technology and embedded technology, we also exploited GUI using Qt integrated development environment. This book conveyor is a portable equipment with complete functions, friendly interface and convenient operation. It can greatly improve the work efficiency of librarians and the service quality of the library.

Sound intensity measurement in focal region of HIFU transducer adopting narrow-pulse method

To meet the requirement for more efficient and convenient method of high-intensity focused ultrasound (HIFU for short) sound field measurement, which is propelled by the development of HIFU therapy, this paper theoretically discusses the feasibility to measure the focal region sound intensity of HIFU transducer by hydrophone method that uses narrow modulated wave as inspiring signal. It is proved through experiments to be a quick, efficient, safe and reliable method for the measurement of HIFU sound intensity.

Design of time-delay detection equipment for signal circuit

Time-delay is a key electrical parameter of the electronic circuitry or devices, and the measurement of time-delay is significant. This paper proposed a measurement method of phase time-delay. In this method, a direct digital synthesis (DDS) was used to generate a standard sinusoidal signal, and a complex programmable logic device (CPLD) was used as the high speed time counter. The sinusoidal signal was processed by waveform adjustment and had passed through zero crossing comparator previously. The standard sinusoidal signal was input into the device under test (DUT) and the trigger port of the high speed time counter at the same time. The time-delay of DUT was obtained when the time-delay output signal was used as the stop signal of high speed time counter. The system was controlled by a MCU. The conversion amplifiers of single-ended to differential and differential to single-ended were used as the time parameter and polarity adjusting unit of the standard sinusoidal signal separately. The test results for the time-delay of this system showed the range from 0 to 650 us and the resolution with 0.01 us. This equipment can be applied widely in many signal circuit, such as a digital subscriber line (DSL) separator and a MODEM.

Transmission time in the reflectionless complex potential

A phase time definition directly obtained from the Schrodinger equation is used to investigate the time delay of a particle scattered by complex reflectionless potential. The artifacts introduced by truncating in the numerical simulation are clarified. The time delay of the transmitted wave packet is found to be equal to the reflection time of the truncated potential. Both time delays are the same as the traversal time in the free space, but shorter than the time taken by a classical particle to pass the same potential.

An acoustic method on sulfur hexafluoride concentration detection

A dual-channel detection method based on the acoustic attenuation characteristics in gas for sulfur hexafluoride concentration is presented. The difference of classical attenuation coefficients of two channels as a function of sulfur hexafluoride concentration is derived and numerically simulated. A dual-channel detection device is designed using ultrasonic transducers with specific center frequency to build up the experimental platform to verify the effectiveness of the proposed scheme experimentally. Experiments demonstrated that the dual-channel acoustic detection method is nearly linear when sulfur hexafluoride concentration changes in the mixture.

All-optical modulator based on a ferrofluid core metal cladding waveguide chip

We propose a novel optical intensity modulator based on the combination of a symmetrical metal cladding optical waveguide (SMCW) and ferrofluid, where the ferrofluid is sealed in the waveguide to act as a guiding layer. The light matter interaction in the ferrofluid film leads to the formation of a regular nanoparticle pattern, which changes the phase match condition of the ultrahigh order modes in return. When two lasers are incident on the same spot of the waveguide chip, experiments illustrate all-optical modulation of one laser beam by adjusting the intensity of the other laser. A possible theoretical explanation may be due to the optical trapping and Soret effect since the phenomenon is considerable only when the control laser is effectively coupled into the waveguide.

The design of wireless monitoring systems based on ultrasonic method for metro power transmission and distribution

In recent years, with continuous growth in the scale of both metro systems and their power transmission and distribution equipments, the traditional power facility safety monitoring technology fails to meet the safety requirements. This paper designs an ultrasonic detection based on wireless monitoring system for metro power transmission and distribution equipments, where both the sulfur hexafluoride (SF6) concentration and moisture content in transformer oil are monitored by using acoustic sensors. We present the principle of ultrasonic detection in monitoring SF6 and moisture contents in transformer oil, and take the use of wireless methods in transmitting the detected concentration of the SF6 and moisture in consideration.