Effect of gas flow rate on breakdown voltage in a rotating gliding arc reactor

Understanding breakdown phenomena in rotating gliding arc discharge (RGA) is of interest to tailor them for specific applications. This work revealed that the breakdown voltage in a RGA reactor was not dictated by collisional effects i.e., change in flow rate. The observation was consistent for both the discharge gas medium argon and nitrogen. The collisional effect variation was implemented by varying the operating flow rates i.e., 5 SLPM which is transitional in nature, and 50 SLPM which is turbulent in nature having localized micro-eddies. The observation also indicated failure of Paschen law in RGA having shortest gap between the electrodes of order of mm, operated under atmospheric pressure conditions. Collisional ineffectiveness indicates possibility of streamer formation which needs to be further investigated in future. This work marks preliminary and important step towards understanding the breakdown phenomena in atmospheric RGAs operated under different flow regimes such as laminar/transitional and turbulent.

UV Treatment on Inactivation of Fungal Contamination of Sri Lankan Black Pepper (Piper nigrum) seed and powder

A study was carried out to test the efficacy of UV- C treatment to decontaminate fungal species in black pepper. After preliminary tests carried out using a UV-C drum, a canopy type UV-C sterilization unit was designed and fabricated. Black pepper seed and powder samples were given 10, 15, and 20 minutes UV- C treatments. Results showed that UV-C canopy is effective on inactivation of yeast and moulds in black pepper seeds complying the international microbiological standard requirements for spices. Improvement of UV-C Design modification have been carrying out to obtain the potential inactivation level by UV-C light for black pepper powder and improve the inactivation level of bacteria in black pepper seed and powder.

Degradation of Methylene Blue Using Microplasma Discharge – A Relative Study with Photodegradation

Large-scale production and application of synthetic dyes have become a matter of concern as it is a major factor responsible for environmental pollution. Most dyeing effluents are discharged into water bodies and lands without being treated, which ultimately pollutes the groundwater making it unfit for consumption. The present study explains the degradation of one of such synthetic dyes Methylene blue (MB), using non-thermal Microplasma treatment. The aqueous solution of MB was treated with an array of air microplasma discharge at atmospheric pressure. Different concentrations (10 ppm, 20 ppm) of MB solution were treated for various treatment time and chemical parameters like pH, electrical conductivity, total dissolved solids and salinity was measured. The degradation percentage reached 100% in 15 min of treatment for 10 ppm MB solution, and 20 min of treatment for 20 ppm MB solution indicated by the color change from blue to a clear solution. The reactive oxygen species (ROS) and reactive nitrogen species (RNS) formed during the microplasma treatment are responsible for MB degradation. Same volume of MB solution was irradiated by direct sunlight for photodegradation and was found to degrade the solution of 10 ppm by 96% and 20 ppm by 93% in 10 hours of treatment. Experimental results indicated that microplasma treatment was effective for dye degradation, without the need for pretreatment process or chemicals.

In package control of Rhyzopertha dominica in wheat using a continuous atmospheric jet cold plasma system

Cold plasma is recognized and explored for a plethora of applications in the food and agricultural industry. This study investigated the influence of a continuous atmospheric pressure non-thermal jet plasma system on the mortality of Rhyzopertha dominica adults in whole wheat kernels and the changes in the milling and physicochemical attributes of the treated whole wheat. Air-filled packets of whole wheat kernels were artificially infested with R. dominica adults. The packages were carried by a continuous conveyor belt and treated with plasma at voltages ranging from 44-47 kV for 4-7 min. The mortality was determined after 24 h and milling yield, particle size, proximate composition, and color of plasma-treated and untreated wheat grains were also evaluated. The maximum mortality was 88.33% at 47 kV for 7 min. The milling yield, protein, and fiber content of wheat were enhanced with plasma treatment significantly. Thus the continuous atmospheric pressure jet plasma used in this study could be one of the practically implementable emerging techniques for the commercial disinfestation of packaged food products.

Surface Roughness Analysis of Cotton Fabric by Laser Speckle Technique

In the textile industry, disposing the waste products after dyeing causes a major environmental issue. The mordants used leads to adverse effect for the human and other living organisms. Plasma processing is ecofriendly and it does not produce any waste, pollution free on the environment. Therefore, low temperature plasma treatments are set to make a revolution in textile industry. The present work is to modify the surface of cotton fabric by oxygen plasma treatment with operating parameters such as exposure time, discharge potential and base pressure are kept constant as 5 min, 400V and 9 Pascal respectively. The surface roughness of the fabric is analyzed by laser speckle technique for plasma treated and mordanted fabric and then corresponding results were reported. Further, we observed the increase in surface roughness of the fabric after plasma treatment.

Simulation of Velocity Evolution of a Cold Collision-less Non-Magnetised Plasma by Particle-in-Cell Method

This work presents simple numerical simulation algorithm to analyse the velocity evolution of high density non-magnetized glow discharge (cold) collision-less plasma using Particle-in-Cell (PIC) method. In the place of millions of physical electrons and background ions, fewer particles called super particles are used for simulation to capture the plasma properties such as particle velocity, particle energy and electrical field of the plasma system. The plasma system which is of interest in this work is weakly coupled plasma having quasi-neutrality nature. Simulation results showed symmetric velocity distribution about zero with slight left skewness, indicating static system. The order of directional velocity of individual particle seems to agree with the input electron temperature of the considered plasma system. The particle and field energy evolution were observed having fluctuations about zero which indicates that the system is equilibrating. This work marks the preliminary work to study the transport of plasma species in plasma column of gliding arc discharge.

Spectroscopic diagnostic complex based on the magnetron sputtering device with a digital method of the data mining

A diagnostic complex based on a magnetron sputtering device is proposed for studying a magnetron discharge plasma parameter by optical emission spectroscopy, using two spectroscopic systems: photographic and photoelectric. Software for digital processing of the obtained emission spectra is developed. The results obtained by the two spectroscopic systems are compared.

Spray Drying of Ginger and Physical and Micro Structural Properties of Spray Dried Ginger Powder - An Advance Food Material

The objective of this work was to optimize the spray drying of ginger juice using maltodextrin and to investigate the effect of carrier agent on physical and micro-structural properties of spray dried ginger powder. A laborator ypilot scale spray dryer was employed for spray drying process and commercial maltodextrin was used as carrier agents. Ginger powder obtained under optimized condition of maltodxtrin concentration and 165oC inlet temperature was evaluated for moisture content, water activity, particle size distribution, bulk density, true density, porosity, wettability flowability, dispersibility, and powder morphology. Micro-structural analysis revealed powder particles of various sizes and shapes however properties were within the desired range. Spray dried ginger powder can be used as natural ginger flavouring. Optimized spray drying parameters and powder properties pave the way for testing high sticky food material and mixing of different spray dried powders by surface modification for more advance powder processing.

Mortality of Tribolium castaneum and quality changes in Oryza sativa by indirect exposure to Non-Thermal Plasma

The management of stored product pests is a serious concern as it contributes to postharvest product losses. This study investigated the influence of NTP on the control of Tribolium castaneum adults and the quality of Oryza sativa and compared with phosphine fumigation. The experiments were performed at 100 - 200 V of NTP and 100 - 200 ppm of phosphine for the exposure periods of 8, 16, and 24 h. Mortality of 100 % and 86.67 % was obtained at 24 h of exposure for plasma treatment (200 V) and phosphine (200 ppm), respectively. The quality changes in rice during the mortality studies were also evaluated for treated samples. The cooking properties, texture, hydration behavior, and pasting profile along with color and moisture content were investigated. The statistical analysis did not report any significant quality changes for plasma and phosphine treated rice compared to the untreated samples. The microstructural changes in the rice was also examined by scanning electron microscope. The results suggest that NTP treatment can be used as a useful tool for the control of T. castaneum without affecting the properties of rice. However, large scale studies have to be explored for practical usage of NTP in management of stored product pests.

Effect of Sintering Temperature on Metal-Insulator Phase Transition in La1-xCaxMnO3 Perovskites

Lanthanum calcium based perovskites are found to be advantageous for the possible applications in magnetic sensors/reading heads, cathodes in solid oxide fuel cells, and frequency switching devices. In the present investigation La0.3Ca0.7MnO3 perovskites were synthesised through solid state reaction and sintered at four different temperatures such as 900, 1000, 1100 and 1200˚ C. X-ray powder diffraction pattern confirms that the prepared La0.3Ca0.7MnO3 perovskites have orthorhombic structure with Pnma space group. Ultrasonic in-situ measurements have been carried out on the La0.3Ca0.7MnO3 perovskites over wide range of temperature and elastic constants such as bulk modulus of the prepared La0.3Ca0.7MnO3 perovskites was obtained as function of temperature. The temperature-dependent bulk modulus has shown an interesting anomaly at the metal-insulator phase transition. The metal insulator transition temperature derived from temperature-dependent bulk modulus increases from temperature 352˚ C to 367˚ C with the increase of sintering temperature from 900 to 1200˚ C.