Zhu Changping

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.

Yield of Ozone, Nitrite Nitrogen and Hydrogen Peroxide Versus Discharge Parameter Using APPJ Under Water ⁄

Discharge plasma in and in contact with water can be accompanied with ultraviolet radiation and electron impact, thus can generate hydroxyl radicals, ozone, nitrite nitrogen and hydrogen peroxide. In this paper, a non-equilibrium plasma processing system was established by means of an atmospheric pressure plasma jet immersed in water. The hydroxyl intensities and discharge energy waveforms were tested. The results show that the positive and negative discharge energy peaks were asymmetric, where the positive discharge energy peak was greater than the negative one. Meanwhile, the yield of ozone and nitrite nitrogen was enhanced with the increase of both the treatment time and the discharge energy. Moreover, the pH value of treated water was reduced rapidly and maintained at a lower level. The residual concentration of hydrogen peroxide in APPJ treated water was kept at a low level. Additionally, both the efficiency energy ratio of the yield of ozone and nitrite nitrogen and that of the removal of p-nitrophenol increased as a function of discharge energy and discharge voltage. The experimental results were fully analyzed and the chemical reaction equations and the physical processes of discharges in water were given.

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.

Water Content Effect on Oxides Yield in Gas and Liquid Phase Using DBD Arrays in Mist Spray

Electric discharge in and in contact with water can accompany ultraviolet (UV) radiation and electron impact, which can generate a large number of active species such as hydroxyl radicals (OH), oxygen radical (O), ozone (O3) and hydrogen peroxide (H2O2). In this paper, a nonthermal plasma processing system was established by means of dielectric barrier discharge (DBD) arrays in water mist spray. The relationship between droplet size and water content was examined, and the effects of the concentrations of oxides in both treated water and gas were investigated under different water content and discharge time. The relative intensity of UV spectra from DBD in water mist was a function of water content. The concentrations of both O3 and nitrogen dioxide (NO2) in DBD room decreased with increasing water content. Moreover, the concentrations of H2O2, O3 and nitrogen oxides (NOx) in treated water decreased with increasing water content, and all the ones enhanced after discharge. The experimental results were further analyzed by chemical reaction equations and commented by physical principles as much as possible. At last, the water containing phenol was tested in this system for the concentration from 100 mg/L to 9.8 mg/L in a period of 35 min.

Electric parameter measurement of dielectric barrier discharge

The electrical parameter method and computer data processing based on Lissajous figures were used to investigate the characteristics of dielectric barrier discharge (DBD), analyze the discharge voltage-current waveform, and evaluate the discharge energy under different discharge power. Meanwhile, the efficiency energy ratio of quantum yield for active substance in DBD was examined by optical emission spectroscopy (OES). The results demonstrate that the discharge voltage-current waveform, discharge energy, equivalent capacitance of the discharge gap and the dielectric layer of DBD can be obtained quickly. The discharge energy and equivalent capacitance both increased, and the dielectric capacitance decreased with increasing input power of high voltage power supply. Additionally, the quantum yield of active substance in DBD is a function related to discharge energy.

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.

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.

Yield of hydrogen peroxide, ozone and nitrite nitrogen with DBD arrays in water mist spray

Summary form only given. Electric discharge in water can accompany UV radiation and electron impact, and can generate oxidants such as hydroxyl radicals, ozone and hydrogen peroxide. Here, a non-thermal plasma processing system was established by means of dielectric barrier discharge (DBD) arrays in water mist spray. The yield of hydrogen peroxide (H₂O₂), ozone (O₃) and nitrite nitrogen (NO_x) were both enhanced after discharge in water. The effects of water-air flow ratio, discharge time and high voltage power were investigated. The intensities in the ultraviolet region were measured by optical emission spectroscopy (OES) with different power input and moisture content. Experimental results show that there exist intense emissions of OH (309-317.8 nm), O⁺ (372.3, 375.1, 394.7, 397.6 nm), N₂ (335.5, 352.1 nm), and NO (296, 357.7, 378.9 nm) in the plasma and the intensity increases with both increasing input power and moisture. The concentration of H₂O₂, O₃ and NO_x was measured after discharge. The yield of H₂O₂, O₃ and NO_x in water and O₃ and NO₂ in DBD changed as a function of water-air flow ratio and treatment time. For same treatment time, the yield of O₃ and NO₂ in the DBD increased initially and then decreased with increasing water-air flow ratio, and the yield of H₂O₂, O₃ and NO_x in water decreased slowly with increasing water-air flow ratio. For same water-air flow ratio, the yield of O₃ and NO_x in water increases initially then remains constant with increasing treatment time; the yield of H₂O₂ in water increases significantly and sustained with increasing treatment time, and the pH value of treated water slightly decreases with increasing treatment time. The experimental results were fully analyzed by the chemical reaction equations and commented by the physical principles as much as possible. Finally, the water containing phenol was tested in this system. The degradation rate came to 86% in 30 min.

Dual-frequency ultrasonic washing machine for fruits and vegetables

This paper presents a fruits and vegetables washing machine using ultrasonic technology. The pesticide residues on fruits or vegetables can be peeled off by ultrasonic waves effectively. The washing machine produces two frequencies ultrasonic, 140 kHz f or washing fruits or vegetables and decomposing pesticides, 80 kHz for other cleaning such as dishes. Cleaning experiment and its results are shown in this paper.

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.