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Samples of burley, sun-cured, and flue-cured tobacco from the main producing areas of relevant tobacco types in China were collected to study the changes in tobacco-specific nitrosamine (TSNA) contents during storage and to investigate the effect of storage temperature and tobacco nitrate level on TSNA formation of cured tobacco. Contents of TSNAs in burley and sun-cured tobacco increased substantially during 1 year under natural storage environment, with total TSNA content increasing about 215% for both tobacco types. The most rapid increase occurred during the high temperature season. Temperature had a significant promoting effect on TSNA formation during storage. Storage temperature as high as 27 °C for 12 days was enough to induce the increase of TSNA formation, while the most significant effect was shown when the temperature was above 30 °C. The increased rate of accumulation became greater as the temperature increased. Total TSNA content in air-cured burley tobacco after the treatment of 60 °C for 24 days was 772% higher than that in the low temperature control. Different types of tobacco showed different results in terms of the response of TSNA formation to high temperature. TSNA formation in flue-cured tobacco did not increase after high-temperature treatment for 36 days, while burley and sun-cured tobacco saw a dramatic increase of TSNA content. This difference could be explained by the fact that burley tobacco and sun-cured tobacco usually had more than 10 times the nitrate content than flue-cured tobacco. As the nitrate nitrogen increased in cured burley tobacco, TSNA formation during leaf storage at high temperature significantly increased. Addition of nitrate onto flue-cured tobacco to the level equivalent to burley tobacco followed by high-temperature treatment increased the TSNA concentration comparable to burley tobacco. The interaction between high temperature and abundant nitrate content in cured tobacco could be responsible for TSNA formation during storage.

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Research on dynamics of streamer propagation along different dielectric materials under a uniform electric field is presented. In the three-electrode arrangement, the variation of the streamer propagation probability, velocity and light intensity with electric field in the air and along the different dielectric materials was measured through three photomultipliers. The photographs of the streamer propagation in the air and along the different dielectric materials were taken with an ultraviolet camera. The test results have shown that the electric field required for streamer propagation in air alone is less than along the insulation surface. Furthermore, for electric fields higher than streamer 'stability' propagation fields, the streamer propagates along insulation surface with a 'fast' and a 'slow' component. However, the streamer propagates in air alone without a 'fast' component, only with a 'slow' component. The velocity of the streamer propagating in air alone is significantly less than the velocity of the 'fast' component, and is higher than the velocity of the 'slow' component. The streamer 'stability' propagation field and velocity depend upon the nature of the dielectric material. Specifically, higher electric fields are required for streamers to propagate along a dielectric material with larger permittivity. The velocity of streamer propagation along the dielectric material is also affected by attachment of charge to the surface and photoemission of secondary electrons from the surface so much. Consequently, under the same electric field, the relationship between streamer propagation velocity and permittivity of dielectric material is not very evident, roughly inverse proportion.Index Terms -Streamer propagation, dielectric material, three-electrode arrangement, streamer propagation electric field, streamer propagation velocity, streamer propagation light intensity.

Over the past decades, imaging and spectroscopy techniques have been rapidly developing and widely applied in nondestructive fruit and vegetable quality assessment. The physical properties (including size, shape, color, position, and temperature) and biological properties (including cultivar, season, maturity level and geographical origin) of fruits and vegetables vary from one to another. A great variety of physical and biological properties of agricultural products influence the optical propagation properties and interaction behaviors with incident light, thus decreasing the quality inspection accuracy. Many attempts have been made in image correction and spectral compensation methods to improve the inspection accuracy. This paper gives a detailed summary about influence of physical and biological variability, as well as the correction and compensation methods for eliminating or reducing the effects in fruit and vegetable quality nondestructive inspection by using imaging and spectroscopy techniques. The advantages and disadvantages of the solution methods are discussed and summarized. Additionally, the future challenges and potential trends are also reported.

Ice accumulation on high voltage insulators can cause accidents by flashover across the ice-covered insulators. The ice accumulation can be reduced by changing the insulator surface properties by application of a semiconducting RTV silicone coating. This method is based on the hydrophobicity and semiconductivity properties of the coating. The mechanism for reducing ice accretion is analyzed theoretically. Experimental results are presented to validate the effectiveness of the semiconducting RTV coating at reducing ice on insulator strings. The results show that the coating on the insulators delays ice formation and reduces the amount of ice.