Effect of shear-span/depth ratio on cohesive crack and double-K fracture parameters of concrete

Choubey, Rajendra Kumar,Kumar, Shailendra,Rao, M.C. Techno-Press 2014 Advances in concrete construction Vol.2 No.3

A numerical study of the influence of shear-span/depth ratio on the cohesive crack fracture parameters and double - K fracture parameters of concrete is carried out in this paper. For the study the standard bending specimen geometry loaded with four point bending test is used. For four point loading, the shear - span/depth ratio is varied as 0.4, 1 and 1.75 and the ao/D ratio is varied from 0.2, 0.3 and 0.4 for laboratory specimens having size range from 100 - 500 mm. The input parameters for determining the double - K fracture parameters are taken from the developed fictitious crack model. It is found that the cohesive crack fracture parameters are independent of shear-span/depth ratio. Further, the unstable fracture toughness of double-K fracture model is independent of shear-span/depth ratio whereas, the initial cracking toughness of the material is dependent on the shear-span/depth ratio.

Advance review on the exploitation of the prominent energy-storage element Lithium. Part II: From sea water and spent lithium ion batteries (LIBs)

Choubey, Pankaj K.,Chung, Kang-Sup,Kim, Min-seuk,Lee, Jae-chun,Srivastava, Rajiv R. Elsevier 2017 Minerals engineering Vol.110 No.-

<P><B>Abstract</B></P> <P>The uncertainty in production and utilization with the availability of lithium rich minerals and brine in a limited land area has grown the attention for the exploitation of those resources not coming under a specific boundary. Approximately 230 billion tons of lithium in ubiquitous sea water and generation of a huge amount of used lithium ion batteries (spent LIBs) in different corner of the end-user countries can play a major role to change the scenario of securing lithium as a raw material for industry. Therefore, it needs to be exploited in such an effective manner that it can assure the mitigation of projected supply risk of this energy-critical element. To explore the commercial viability for their sustainable exploitation, it is imperative to review the methodologies that have been investigated and have clear potential for upscaling.</P> <P>This article deals with the processing of those resources that do not contributes yet to lithium supply in commodity market, and include the lithium recovery from sea water and spent LIBs. A purposive discussion on the electro-dialysis and reverse osmosis for the separation and recovery of lithium from sea water is of vital interest in future. A routinely disposed spent LIBs is a huge reservoir of lithium and need to be recovered as a main product along with the costlier cobalt, while recycling the spent LIBs. The various extraction and recovery processes of lithium are subdivided according to the adopted methodology, selection of lixiviant and obtaining the product in the desired form, whilst the technological and chemical perspective is also discussed. The deliberations on the edges and/or drawbacks, complications and prospects of the different processes are also included. It is believed that this state-of-the-art review can contribute in formulating the strategy for fulfilling the global energy demand by a sustainable recovery of lithium from its non-conventional resources, and can provide future research directions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Exploitation of Lithium from sea water and spent batteries are critically reviewed. </LI> <LI> Li recovery via adsorption and electrodialysis process from sea water is compared. </LI> <LI> Pretreatment follows dismantling of LIBs to enrich the metals in black mass, LiM<SUB>x</SUB>O<SUB>y.</SUB> </LI> <LI> Acid/alkali leaching followed by solvent extraction to separate the metals. </LI> <LI> Precipitation is applied as a final step to get Li<SUB>2</SUB>CO<SUB>3</SUB> from the both sources. </LI> </UL> </P>

SRD5A2 Gene Polymorphisms and the Risk of Benign Prostatic Hyperplasia but not Prostate Cancer

Choubey, Vimal Kumar,Sankhwar, Satya Narayan,Carlus, S. Justin,Singh, Anand Narayan,Dalela, Divakar,Thangaraj, Kumarasamy,Rajender, Singh Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.3

Background: Testosterone, a primary androgen in males, is converted into its most active form, dihydrotestosterone (DHT), by $5{\alpha}$-reductase type 2 (encoded by the SRD5A2 gene) in the prostate. DHT is necessary for prostatic growth and has five times higher binding affinity than testosterone for androgen receptors. We hypothesized that polymorphic variations in the SRD5A2 gene may affect the risk of benign prostatic hyperplasia and prostate cancer. Materials and Methods: We analyzed SRD5A2 gene polymorphisms in 217 BPH patients, 192 PCa cases, and 171 controls. Genotyping was undertaken using direct DNA sequencing. Genotype data were compared between cases and controls using a Chi square statistical tool. Results: We found that the A49T locus was monomorphic with 'AA' genotype in all subjects. At V89L locus, the presence of 'VV' showed a marginally significant correlation with increased BPH risk (p=0.047). At the $(TA)_n$ locus, longer TA repeats were found to be protective against BPH (p=0.003). However, neither of these polymoprhisms correlated with the risk of PCa. Conclusions: We conclude that A49T is monomorphic in the study population, VV marginally correlates with BPH risk, and longer $(TA)_n$ repeats are protective against BPH. None of these polymorphisms affect the risk of PCa.

Conversion of chalcopyrite to copper oxide in hypochlorite solution for selective leaching of copper in dilute sulfuric acid solution

Choubey, Pankaj Kumar,Lee, Jae-chun,Kim, Min-seuk,Kim, Hyung-Seok Elsevier 2018 Hydrometallurgy Vol.178 No.-

<P><B>Abstract</B></P> <P>In the present study, development of a novel oxidation route to convert chalcopyrite to tenorite for leaching of copper has been described. Initially chalcopyrite was converted into tenorite/copper oxide (CuO) under alkaline region using electro-generated chlorine as an oxidant. Various process parameters such as chlorine sparging rate, temperature, and reaction time were investigated. It was found that 93.8% chalcopyrite converted to tenorite at 60 °C in 300 min when chlorine sparging rate was 0.69 mmol min<SUP>−1</SUP> while, maintaining the pulp density of 10 g/L and pH of the solution between 11−12.7 using dilute sodium hydroxide solution. The oxidized sample containing tenorite phase was leached in dilute sulfuric acid solution at 30 °C and 10 g/L pulp density for 60 min. It was observed that pH of the solution plays a crucial role to enhance the selective recovery of copper. Almost 88% of copper along with 43.1% iron were leached out when pH of the leaching solution was varied between 0.9−1.2. However, negligible dissolution of iron with almost same percentage of copper leaching (88.2%) was observed with the solution having pH 2.7−3.2. Enhanced copper leaching efficiency of up to 99.3% was achieved in the same pH range (2.7−3.2) at 60 °C within 30 min.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Conversion of chalcopyrite to tenorite in alkaline medium was investigated. </LI> <LI> Electro-generated chlorine was used as an oxidant to assist the phase transformation. </LI> <LI> Subsequent leaching of tenorite yielding a selective recovery of copper. </LI> <LI> Linear relationship between degree of conversion to leaching efficiency was established. </LI> </UL> </P>

INTUITIONISTIC FUZZY AUTOMATA AND INTUITIONISTIC FUZZY REGULAR EXPRESSIONS

Choubey, Alka,K M, Rayi The Korean Society for Computational and Applied M 2009 Journal of applied mathematics & informatics Vol.27 No.1

A definition of finite automaton (DFA and NDFA) with intuitionistic fuzzy (final) states is proposed. Acceptance of intuitionistic fuzzy regular language by the finite automaton (DFA and NDFA) with intuitionistic fuzzy (final) states are examined. It is found that the finite automaton (DFA and NDFA) with intuitionistic fuzzy (final) states is more suitable for recognizing intuitionistic fuzzy regular language than earlier model. The paper also gives an idea of intuitionistic fuzzy regular expressions through possible definitions.

Study of nonlinear optical properties of organic dye by Z-scan technique using He–Ne laser

Choubey, R. K.,Medhekar, S.,Kumar, R.,Mukherjee, S.,Kumar, Sunil Springer-Verlag 2014 Journal of materials science Materials in electron Vol.25 No.3

Effect of tunnel fire: Analysis and remedial measures

Bishwajeet Choubey,Sekhar C. Dutta,Virendra Kumar 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.6

The paper aims at improving the understanding and mitigating the effects of tunnel fires that may breakout due to the burning fuel and/or explosion within the tunnel. This study particularly focuses on the behavior of the commonly used horse shoe geometry of tunnel systems. The problem has been obtained using an adequate well-established program incorporating the Lagrangian approach. A transient-thermo-coupled static structural analysis is carried out. The effects of radiation and convection to the outer walls of the tunnel is studied. The paper also presents the impact of the hazard on the structural integrity of the tunnel. A methodology is proposed to study the tunnel fire using a model which uses equivalent steel sheet to represent the presence of reinforcements to improve the computational efficiency with adequate validation. A parametric study has been carried out and the effect of suitable lining property for mitigating the fire hazard is arrived at. Detailed analysis is done for the threshold limits of the properties of the lining material to check if it is acceptable in all aspects for the integrity of the tunnel. The study may prove useful for developing insights for ensuring tunnel fire safety. To conduct such studies experimentally are tremendously costly but are required to gain confidence. But, scaled models, as well as loading and testing conditions, cannot be studied by many trials experimentally as the cost will shoot up sharply. In this context, the results obtained from such computational studies with a feasible variation of various combinations of parameters may act as a set of guidelines to freeze the adequate combination of various parameters to conduct one or two costly experiments for confidence building.

Intuitionistic fuzzy automata and intuitionistic fuzzy regular expressions

Alka Choubey,Ravi K M 한국전산응용수학회 2009 Journal of applied mathematics & informatics Vol.27 No.1

A definition of finite automaton (DFA and NDFA) with intuitionistic fuzzy (final) states is proposed. Acceptance of intuitionistic fuzzy regular language by the finite automaton (DFA and NDFA) with intuitionistic fuzzy (final) states are examined. It is found that the finite automaton (DFA and NDFA) with intuitionistic fuzzy (final) states is more suitable for recognizing intuitionistic fuzzy regular language than earlier model. The paper also gives an idea of intuitionistic fuzzy regular expressions through possible definitions. A definition of finite automaton (DFA and NDFA) with intuitionistic fuzzy (final) states is proposed. Acceptance of intuitionistic fuzzy regular language by the finite automaton (DFA and NDFA) with intuitionistic fuzzy (final) states are examined. It is found that the finite automaton (DFA and NDFA) with intuitionistic fuzzy (final) states is more suitable for recognizing intuitionistic fuzzy regular language than earlier model. The paper also gives an idea of intuitionistic fuzzy regular expressions through possible definitions.

Effects of unconfined blast on strategic structures and its protective measures

Bishwajeet Choubey,Sekhar C. Dutta,Md. Ahsaan Hussain 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.2

A strategic structure when exposed to direct hit of conventional bomb/projectile are severely damaged because of large amounts of energy released by the impact and penetration of bomb. When massive concrete slabs suffer a direct hit, the energy released during impact and penetration process are able to easily break up large mass of concrete. When over stressed under such impact of bombs, the concrete structure fails showing brittle behavioural nature. This paper is intended to study and suggest the protective measures for structures used for strategic application by adopting a means to dissipate the large quantum of energy released. To quantitatively evaluate the force, displacement and energy in such scenario, a fine numerical model of the proposed layered structure of different combinations was built in ANSYS programme in which tri-nitrotoluene (TNT) explosive was detonated at penetration depth calculated for GP1000 Lbs bomb. The distinct blast mitigation effect of the proposed structure was demonstrated by adopting various layers/barriers created as protective measures for the strategic structure. The calculated result shows that the blast effect on the structure is potentially reduced due to provision of buster slab with sand cushioning provided as protective measure to the main structure. This concept of layered protective measures may be adopted for safeguarding strategic structures such as Domes, Tunnels and Underground Structures.

Experimental and mathematical analysis of simulation results for sheet metal parts in deep drawing

Ajay Kumar Choubey,Geeta Agnihotri,C. Sasikumar 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.9

In this paper, deep drawing of conical and cylindrical cups without blank holder is investigated using a conical die design. These cups are produced by pushing circular blanks by pushing the flat head punch in a single stroke. ANSYS APDL 14.0 was then used to investigate the effects of die and punch geometry, half-cone angle, die and punch fillet radius, and drawing load. The thickness distribution of the cup was numerically investigated to determine the optimal process design, and mathematical analysis was adopted to determine the thickness distribution and longitudinal stress calculation. An experimental set-up was designed to validate the simulation results for conical and cylindrical shaped sheet-metal cups. Tensile tests were carried out to obtain the flow of the stress-strain curve for the simulation. The drawing characteristics of materials were investigated by performing Erichsen cupping and Vickers hardness tests. Experiments were conducted on blanks of aluminum alloys and stainless steel with initial thicknesses of 1.5 mm. A cylindrical cup of ss304 with LDR of up to 2.2 and conical cup of AA1100 with LDR of up to 2.7 were successfully achieved. Finite element simulation results showed good agreement with the mathematical and experimental results.