Browsing by Author "Naveen, K."

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An X-ray visualization technique has been used for the quantitative determination of local liquid holdups distribution and liquid holdup hysteresis in a nonwetting two-dimensional (2-D) packed bed. A medical diagnostic X-ray unit has been used to image the local holdups in a 2-D cold model having a random packing of expanded polystyrene beads. An aqueous barium chloride solution was used as a fluid to achieve good contrast on X-ray images. To quantify the local liquid holdup, a simple calibration technique has been developed that can be used for most of the radiological methods such as gamma ray and neutron radiography. The global value of total liquid holdup, obtained by X-ray method, has been compared with two conventional methods: drainage and tracer response. The X-ray technique, after validation, has been used to visualize and quantify the liquid hysteresis phenomena in a packed bed. The liquid flows in preferred paths or channels that carry droplets/rivulets of increasing size and number as the liquid flow rate is increased. When the flow is reduced, these paths are retained and the higher liquid holdup that persists in these regions leads to the holdup hysteresis effect. Holdup in some regions of the packed bed may be an order of magnitude higher than average at a particular flow rate. © 2005 American Institute of Chemical Engineers.
(Local liquid holdups and hysteresis in a 2-D packed bed using X-ray radiography) Basavaraj, M.G.; Gupta, G.S.; Naveen, K.; Rudolph, V.; Bali, R.
2005
Design and development of microneedle array-based electrode for bio-potential measurement
(2017) Balashanmugam, N.; Naveen, K.; Krishna, P.; Mohankumar, G.C.
Conventional wet electrodes used in bio-potential measurement like EEG, ECG, etc., require the need for conductivity gel application on skin to wet the surface so that more contact area exist between skin and electrode resulting in better signal acquisition. Wet electrodes have certain drawbacks like the gel tends to underperform within one to two hours after application due to reasons like body heat. To overcome this drawbacks, dry electrodes are being developed which can be classified into two types; one penetrating skin and the other not. Both this type of electrodes has the advantages and limitations. The major drawback of filament type non-penetrating dry electrodes is that if the interest is in acquiring signals during motion, these electrodes tend to move relative to the skin resulting in noisy signal where as the microneedle can overcome this drawback by being continuously in contact with skin in all circumstances. In present work we have used micromachining technique to fabricate PMMA microneedle array. The study involves design of microneedle array, fabrication and mechanical testing of microneedles for skin insertion. It was found that for skin insertion upto 150 ?m microneedles 7.5 N load was required and microneedles were structurally stable at this load. Copyright 2017 Inderscience Enterprises Ltd.
Design and development of microneedle array-based electrode for bio-potential measurement
(Inderscience Publishers, 2017) Balashanmugam, N.; Naveen, K.; Krishna, K.; Mohan Kumar, G.C.
Conventional wet electrodes used in bio-potential measurement like EEG, ECG, etc., require the need for conductivity gel application on skin to wet the surface so that more contact area exist between skin and electrode resulting in better signal acquisition. Wet electrodes have certain drawbacks like the gel tends to underperform within one to two hours after application due to reasons like body heat. To overcome this drawbacks, dry electrodes are being developed which can be classified into two types; one penetrating skin and the other not. Both this type of electrodes has the advantages and limitations. The major drawback of filament type non-penetrating dry electrodes is that if the interest is in acquiring signals during motion, these electrodes tend to move relative to the skin resulting in noisy signal where as the microneedle can overcome this drawback by being continuously in contact with skin in all circumstances. In present work we have used micromachining technique to fabricate PMMA microneedle array. The study involves design of microneedle array, fabrication and mechanical testing of microneedles for skin insertion. It was found that for skin insertion upto 150 ?m microneedles 7.5 N load was required and microneedles were structurally stable at this load. © © 2017 Inderscience Enterprises Ltd.
Local liquid holdups and hysteresis in a 2-D packed bed using X-ray radiography
(2005) Basavaraj, M.G.; Gupta, G.S.; Naveen, K.; Rudolph, V.; Bali, R.
An X-ray visualization technique has been used for the quantitative determination of local liquid holdups distribution and liquid holdup hysteresis in a nonwetting two-dimensional (2-D) packed bed. A medical diagnostic X-ray unit has been used to image the local holdups in a 2-D cold model having a random packing of expanded polystyrene beads. An aqueous barium chloride solution was used as a fluid to achieve good contrast on X-ray images. To quantify the local liquid holdup, a simple calibration technique has been developed that can be used for most of the radiological methods such as gamma ray and neutron radiography. The global value of total liquid holdup, obtained by X-ray method, has been compared with two conventional methods: drainage and tracer response. The X-ray technique, after validation, has been used to visualize and quantify the liquid hysteresis phenomena in a packed bed. The liquid flows in preferred paths or channels that carry droplets/rivulets of increasing size and number as the liquid flow rate is increased. When the flow is reduced, these paths are retained and the higher liquid holdup that persists in these regions leads to the holdup hysteresis effect. Holdup in some regions of the packed bed may be an order of magnitude higher than average at a particular flow rate. 2005 American Institute of Chemical Engineers.