Effect of accelerators with waste material on the properties of cement paste and mortar

Kiran Devi,Babita Saini,Paratibha Aggarwal 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.22 No.2

Accelerators are used to speed up the construction by accelerating the setting time which helps in early removal of formwork thus leading to faster construction rate. Admixtures are used in mortar and concrete during or after mixing to improve certain properties of material which cannot be achieved in conventional cement mortar and concrete. The various industrial by products make nuisance and are hazardous to ecosystem as well. These wastes can be used in the construction industries to reduce the consumption of cement/aggregates, cost; and save the energy and environment by utilising waste and eliminate their disposal problem as well. The effect of calcium nitrate and triethanolamine (TEA) as accelerators and marble powder (MP) as waste material on the various properties of cement paste and mortar has been studied in the present work. The replacement ratio of MP was 0-10% @ 2.5% by weight of cement. The addition of calcium nitrate was 0% and 1%; and variation of addition of TEA was 0-0.1@ 0.025% and 0.1-1.0@ 0.1% by weight of cement. On the basis of setting time, some mix proportions were selected and further investigated. Setting time and soundness of cement paste; compressive strength and microstructure of mortar mix of selected mix proportions were studied experimentally at 3, 7 and 28 days aging. Results showed that use of MP, calcium nitrate, TEA and their combination reduced setting time of cement paste for all the mixes. Addition of calcium nitrate increased the compressive strength at all curing ages while MP and TEA decreased the compressive strength. The mechanism of additives was discussed through scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis of the specimens.

An Efficient Synthesis of 2,4,5-Triaryl-1H-Imidazole Derivatives Catalyzed by Boric Acid in Aqueous Media Under Ultrasound-Irradiation

Kiran F. Shelke,Suryakant B. Sapkal,Swapnil S. Sonar,Balaji R. Madje,Bapurao B. Shingate,Murlidhar S. Shingare 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.5

Boric acid (BO3H3) is an inexpensive, efficient and mild catalyst for the synthesis of 2,4,5-triaryl-1H-imidazoles in excellent yields from the one-pot three-component condensation of benzil/benzoin, an aldehydes and ammonium acetate in aqueous media under ultrasound at room temperature. The remarkable advantages offered by this method are green catalyst, mild reaction conditions, simple procedures, much faster reactions and excellent yield of products.

Three-dimensional finite element modeling of pulsed AC gas metal arc welding process

Kiran, D. V.,Cheon, J.,Arif, N.,Chung, H.,Na, S. J. Springer Science + Business Media 2016 INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TE Vol.86 No.5

<P>The behavior of the welding arc in the pulsed DC and AC gas metal arc welding processes was studied using real-time recorded current, voltage waveforms, and synchronized high-speed video at different electrode negative (EN) ratios for a constant wire feed rate. The regression equations were developed to predict the arc root dimensions as a function of welding current, voltage, time, and the EN ratio. A methodology was proposed to estimate the available energy rate distribution to the electrode and the base plate during the positive and negative cycles in pulsed AC gas metal arc welding (pulsed AC-GMAW) process. For an approximately equal peak positive current, the increase in the pulse time enhanced the molten electrode droplet diameter, arc plasma distribution, and the arc root dimensions. The fraction of the available arc energy rate supplied to the base plate was higher in positive pulse when compared to the negative pulse. A three-dimensional finite element modeling of pulsed DC-GMAW and pulsed AC-GMAW processes was performed to estimate the weld pool profile and temperature distribution in the weldment. The computed weld width, penetration, and the thermal cycles were in reasonable agreement with the corresponding experimental results. The peak temperature of the region in the weld pool near to the Gaussian distributed heat source experience fluctuations which were in synchronization with the current waveform. Increase in the EN ratio decreased the peak temperature while increased the cooling rate in the weldment. This reduced the bainite phase and enhanced the martensite phase in the weldment.</P>

4-Hydroxy-2’-Nitrodiphenyl Ether Analogues as Novel Tyrosinase Inhibitors

Kiran Sapkota,이은영,Jae-Ho Yang,권영주,최종원,나영화 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.5

Tyrosinase ubiquitously existing from microorganisms to animals and plants is known to be the most critical and rate limiting enzyme during melanin biosynthesis. In order to develop new tyrosinase inhibitor we have synthesized 14diphenyl ether compounds possessing hydroxyl, bromo, and nitro groups in the structure. Among the compounds prepared, 18 and 19 have shown much stronger inhibition of tyrosinase monophenolase function than arbutin used as a positive control. Both compounds 18 and 19 possess para-hydroxyphenyl moiety in their structure, which might reinforce the importance of p-hydroxyphenyl group in the tyrosinase inhibitory process. In the DPPH radical scavenging activity test, none of the compounds even 18 and 19 showed significant antioxidant activity. The results suggest that elaborate adjustment of diphenyl ether analogues with proper substituents have potential to be developed as new skin whitening agents working on the tyrosinase function.

Microwave-Assisted Synthesis of 3-Styrylchromones in Alkaline Ionic Liquid

Kiran F. Shelke,Suryakant B. Sapkal,Nana V. Shitole,Bapurao B. Shingate,Murlidhar S. Shingare 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

A simple, highly efficient and environmentally benign method for the synthesis of 3-styrylchromones from 3-formylchromones and 4-nitrophenylacetic acid/4-nitrotolune in the presence of catalytic amount of basic ionic liquid 1-butyl-3-methylimidazolium hydroxide [(bmim)OH] carried out under the influence of microwave irradiation. This method gives remarkable advantages such as, short reaction times, simple work-up procedure and moderate to good yields. The ionic liquid was successfully reused for four cycles without significant loss of activity.

Biocompatability of carbon nanotubes with stem cells to treat CNS injuries

Kiran Kumar Bokara,Jong Youl Kim,Young Il Lee,Kyungeun Yun,Tom J Webster,Jong Eun Lee 대한해부학회 2013 Anatomy & Cell Biology Vol.46 No.2

Cases reporting traumatic injuries to the brain and spinal cord are extended range of disorders that affect a large percentage of the world's population. But, there are only few effective treatments available for central nervous system (CNS) injuries because the CNS is refractory to axonal regeneration and relatively inaccessible to many pharmacological treatments. The use of stem cell therapy in regenerative medicine has been extensively examined to replace lost cells during CNS injuries. But, given the complexity of CNS injuries oxidative stress, toxic byproducts, which prevails in the microenvironment during the diseased condition, may limit the survival of the transplanted stem cells affecting tissue regeneration and even longevity. Carbon nanotubes (CNT) are a new class of nanomaterials, which have been shown to be promising in different areas of nanomedicine for the prevention, diagnosis and therapy of certain diseases, including CNS diseases. In particular, the use of CNTs as substrates/scaffolds for supporting the stem cell differentiation has been an area of active research. Single-walled and multi-walled CNT's have been increasingly used as scaffolds for neuronal growth and more recently for neural stem cell growth and differentiation. This review summarizes recent research on the application of CNT-based materials to direct the differentiation of progenitor and stem cells toward specific neurons and to enhance axon regeneration and synaptogenesis for the effective treatment of CNS injuries. Nonetheless, accumulating data support the use of CNTs as a biocompatible and permissive substrate/scaffold for neural cells and such application holds great potential in neurological research.

Occupational Health Could be the New Normal Challenge in the Trade and Health Cycle: Keywords Analysis Between 1990 and 2020

Kiran, Sibel Occupational Safety and Health Research Institute 2021 Safety and health at work Vol.12 No.2

This brief report aims to establish the keyword content of studies on occupational health and safety-the key framework of the world of work in the trade and health domain. Data were collected from the SCOPUS database, focusing on articles on occupational health and safety and related keywords, with an emphasis on abstracts and titles. Data were analyzed and summarized based on keywords included from the MeSH database. There were 24,499 manuscripts in the domain and 1,346 (5.40%) occupational health-related keywords, including those that overlapped. The most frequently referenced occupational health-related keyword was "occupational health" (452 articles), followed by "occupational safety" (141 articles). There were fewer keywords on occupational health in the trade and health literature. As the world of work has been prioritized because of the recent new normal of work life since the COVID-19 pandemic, examining the focus of occupational health priorities within the global perspective is crucial.

Designing novel chalcone single crystals with ultrafast nonlinear optical responses and large multi-photon absorption coefficients

Kiran, A.J.,Lee, H.W.,Ravindra, H.J.,Dharmaprakash, S.M.,Kim, K.,Lim, H.,Rotermund, F. Elsevier 2010 Current Applied Physics Vol.10 No.5

A chalcone single crystal, 1-(4-chlorophenyl)-3-(4-methoxyphenyl)prop-2-en-1-one that is transparent over the visible to infrared region is introduced as a new potential material to third-order nonlinear optical applications. The crystal exhibits ultrafast optical response (@?90 fs) and large optical nonlinearity in the wavelength range 800-1200 nm. A very large effective two-photon absorption coefficient β<SUB>eff</SUB>exceeding 120 cm/GW can be obtained with this chalcone crystal, at a low intensity threshold of 41 MW/cm<SUP>2</SUP> The mechanism of nonlinear absorption at different levels of intensity has been discussed. The crystal shows no damage against the laser pulse intensity as high as 8 GW/cm<SUP>2</SUP> We discuss the molecular and crystal designing of chalcones with large and ultrafast optical nonlinearity combined with low optical cut-off (<450 nm).

A study on the quality of two-wire tandem submerged arc welds under iso-heat input conditions

Kiran, Degala Venkata,Cho, Dae-Won,Lee, Hee-Keun,Kang, Chung Yun,Na, Suck-Joo Springer-Verlag 2015 INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TE Vol.78 No.1

Numerical Studies on Submerged Arc Welding Process

Kiran, Degala Ventaka,Na, Suck-Joo The Korean Welding and Joining Society 2014 대한용접·접합학회지 Vol.32 No.4

A quantitative understanding on the effect of the welding conditions on weld joint dimensions and weld thermal cycle is difficult through experimental studies alone. The experimental realization of temperature distribution in the weld pool is proved to be extremely difficult due to the small size of welds, high peak temperature and steep temperature gradients in weld pool. This review deals with the heat transfer and fluid flow analysis to understand the parametric influence of a single wire submerged arc welding (SAW) and multi-wire SAW processes on the weld bead dimensions, temperature and fluid flow distribution in the weldment.