Enhanced thermoelectric performance of n-type bismuth selenide doped with nickel

Chiranjit Kulsi,Kajari Kargupta,Saibal Ganguly,Dipali Banerjee 한국물리학회 2017 Current Applied Physics Vol.17 No.12

Bismuth selenide (Bi2Se3) and transition metal (nickel) doped (5 and 7.5 mol %) Bi2Se3 have been prepared by solvothermal approach for investigation of thermoelectric properties of the materials. The morphological characterization reveals plate and flake like structures for undoped and doped samples respectively. There is a decrease in lattice constant, computed from Rietveld refinement data and crystallite size, found using Debye-Scherrer equation for doped samples. Doping by nickel increases the electrical conductivity and reduces both thermo power and thermal conductivity of the materials than pure Bi2Se3. Reduction in thermal conductivity of the doped samples by 42%, results in an increase in figure of merit (ZT) of nickel doped (5%) materials by one order of magnitude (0.02e0.22) compared to pure Bi2Se3.

Analytical and Experimental Modal Analysis of Electrical Transmission Tower to Study the Dynamic Characteristics and Behaviors

Chiranjit Bhowmik,Prasun Chakraborti 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.3

Experimental modal analysis of electrical transmission tower has been a challenging task for transmission tower researchers and design engineers in industry all over the world. Requirement of large numbers of sensors and accelerometers have been major constrain. In this study an innovative approach has been developed to investigate the dynamic characteristics and behavior of tower structure through analytical and experimental modal analysis. Firstly, a scale down (1:15) prototype model of transmission tower structure has been constructed with mild steel straps, joint together by welding, for modal testing. Modal hammer test has been conducted on the prototype tower model for extracting modal parameters; modal frequency, modal damping and modes, of the tower model which representing the actual tower structure. Secondly, the transmission tower structure has been modeled in standard finite element tools and analyzed analytically for natural frequencies. The first six natural frequencies and corresponding mode shapes have been determined analytically and first six natural frequencies have also been determined experimentally and compared with each other. The first six natural frequencies are determined analytically, the frequency range of 2–9 Hz has been found. The analytical and experimental modal analysis of transmission tower structure has been found to be in correlation with some differences. The maximum natural frequencies percentage difference 11.1% has been found; between the scale down model and the stand software model. Additionally, the tower structure has been modified and optimized to improve the stiffness of the diaphragm as per specification and practical limitations. The first order natural frequency of the modified tower has been reduced to 2.171 Hz from the 2.1773 Hz.

Isozymes of α-amylases from Newly Isolated Bacillus thuringiensis CKB19: Production from Immobilized cells

Chiranjit Maity,Saptadip Samanta,Suman K. Halder,Pradeep K. Das Mohapatra,Bikas R. Pati,Malabendu Jana,Keshab C. Mondal 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.2

The aim of this study was to produce two isozymes of α-amylase by immobilization of a newly isolated soil bacterium. The bacterium was identified as Bacillus thuringiensis CKB19 on the basis of its 16S rRNA profile. Enzyme production by free cells increased linearly with cell growth up to 34 h in starch containing enriched liquid media. The active bacterial cells were immobilized in Caalginate beads, and operational stability of the entrapped cell was optimized for amylase production. Enzyme production was optimal at an alginate concentration of 2 g%(w/v), calcium chloride concentration of 1 M, and with 300beads (each bead contained 2 × 10^7 cells)/250 mL flask. Amylase production by the immobilized cells was about 3times higher than free cell fermentation after 34 h of incubation. It was observed that the immobilized bacterium secreted two different amylases (Am-I and Am-II) into the culture fluid. The molecular masses of Am-I and Am-II were 59.6 and 44.7 kd, respectively, and showed optimum activity at pH 5.0 and 9.0. Both amylases showed optimum activity at 40℃ and were stable at the same temperature,with losses of only 10 and 20% (for Am I and Am II,respectively) of their original activities after 24 h of incubation. Further, both amylases were salt tolerant (up to 4 M NaCl) and hydrolyzed raw starchy foods into glucose. All these characteristics make this enzyme mixture suitable for use as a digestive aid and for the improvement of digestibility of animal feed ingredients.

Zinc-chelated Vitamin C Stimulates Adipogenesis of 3T3-L1 Cells

Ghosh, Chiranjit,Yang, Seung Hak,Kim, Jong Geun,Jeon, Tae-Il,Yoon, Byung Hyun,Lee, Jai Young,Lee, Eun Young,Choi, Seok Geun,Hwang, Seong Gu Asian Australasian Association of Animal Productio 2013 Animal Bioscience Vol.26 No.8

Adipose tissue development and function play a critical role in the regulation of energy balance, lipid metabolism, and the pathophysiology of metabolic syndromes. Although the effect of zinc ascorbate supplementation in diabetes or glycemic control is known in humans, the underlying mechanism is not well described. Here, we investigated the effect of a zinc-chelated vitamin C (ZnC) compound on the adipogenic differentiation of 3T3-L1 preadipocytes. Treatment with ZnC for 8 d significantly promoted adipogenesis, which was characterized by increased glycerol-3-phosphate dehydrogenase activity and intracellular lipid accumulation in 3T3-L1 cells. Meanwhile, ZnC induced a pronounced up-regulation of the expression of glucose transporter type 4 (GLUT4) and the adipocyte-specific gene adipocyte protein 2 (aP2). Analysis of mRNA and protein levels further showed that ZnC increased the sequential expression of peroxisome proliferator-activated receptor gamma ($PPAR{\gamma}$) and CCAAT/enhancer-binding protein alpha (C/$EBP{\alpha}$), the key transcription factors of adipogenesis. These results indicate that ZnC could promote adipogenesis through $PPAR{\gamma}$ and C/$EBP{\alpha}$, which act synergistically for the expression of aP2 and GLUT4, leading to the generation of insulin-responsive adipocytes and can thereby be useful as a novel therapeutic agent for the management of diabetes and related metabolic disorders.

Characterization and thermophysical properties of Zr_0.8Nd_0.2O_1.9-MgO composite

Nandi, Chiranjit,Kaity, Santu,Jain, Dheeraj,Grover, V.,Prakash, Amrit,Behere, P.G. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.2

The major drawback of zirconia-based materials, in view of their applications as targets for minor actinide transmutation, is their poor thermal conductivity. The addition of MgO, which has high thermal conductivity, to zirconia-based materials is expected to improve their thermal conductivity. On these grounds, the present study aims at phase characterization and thermophysical property evaluation of neodymium-substituted zirconia (Zr_0.8Nd_0.2O_1.9; using Nd₂O₃ as a surrogate for Am₂O₃) and its composites with MgO. The composite was prepared by a solid-state reaction of Zr_0.8Nd_0.2O_1.9 (synthesized by gel combustion) and commercial MgO powders at 1773 K. Phase characterization was carried out by X-ray diffraction and the microstructural investigation was performed using a scanning electron microscope equipped with energy dispersive spectroscopy. The linear thermal expansion coefficient of Zr_0.8Nd_0.2O_1.9 increases upon composite formation with MgO, which is attributed to a higher thermal expansivity of MgO. Similarly, specific heat also increases with the addition of MgO to Zr_0.8Nd_0.2O_1.9. Thermal conductivity was calculated from measured thermal diffusivity, temperature-dependent density and specific heat values. Thermal conductivity of Zr_0.8Nd_0.2O_1.9-MgO (50 wt%) composite is more than that of typical UO₂ fuel, supporting the potential of Zr_0.8Nd_0.2O_1.9-MgO composites as target materials for minor actinides transmutation.

Characterization of highly stable water-based magnetorheological gel using OPTIGEL-WX as an additive: The study of magneto-induced rheological and viscoelastic properties

Chandra Shekhar Maurya,Chiranjit Sarkar 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.110 No.-

In this work novel kinds of highly stable MR gels were prepared by suspending flake-shaped micron-sizedcarbonyl iron (CI) particles into water/OPTIGEL-WX suspension, OPTIGEL-WX is a promising additive thatforms a gel-like structure with water. We found that surface tension decreases when the concentration ofOPTIGEL-WX was raised, and the contact angle increased due to a stronger adhesive force at the liquid–air interface between the host liquid molecules and the CI particles. We examined magneto-induced rheologicaland viscoelastic properties using Anton-Paar (MCR-102) rheometer. The theoretical Binghammodel was used to fit the experimental shear stress versus shear rate curves and observed static anddynamic yield stress values were substantially identical. Amplitude sweep showed that the linear viscoelasticregion (LVE) was obtained approximately at 0.1% of shear strain. A crossover point, modulusG0& G} , and yield stress were enhanced as the magnetic field was increased. Frequency sweepshowed that the storage modulus shows an increasing trend with the increase of frequency at first, whileat higher frequency range storage modulus shows a steady plateau area. Time-dependent shear flow andamplitude sweep tests revealed complete reversibility of rheological and viscoelastic properties of theMR gel with time after destroying the microstructures.

Congruences modulo powers of 2 for overpartition pairs into odd parts

Zakir Ahmed,Rupam Barman,Chiranjit Ray 대한수학회 2020 대한수학회지 Vol.57 No.2

We find congruences modulo $32$, $64$ and $128$ for the partition function $\overline{pp}_o(n)$, the number of overpartition pairs of $n$ into odd parts, with the aid of Ramamnujan's theta function identities and some known identities of $t_k(n)$, for $k=6, 7$, where $t_k(n)$ denotes the number of representations of $n$ as a sum of $k$ triangular numbers. We also find two Ramanujan-like congruences for $\overline{pp}_o(n)$ modulo $128$.

In-situ braking torque and temperature analysis of two-wheeler drum brake in friction braking

Rakesh Kumar Singh,Chiranjit Sarkar 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.4

Generally, two-wheelers consist of a drum brake on the rear wheel. The performance of the brake deteriorates drastically due to the continuous use of brakes during driving. Thus, studying brake performance in the worst conditions, where brakes are applied back to back after a fixed time interval, becomes essential. To fulfill this, the in-situ braking torque behavior of the two-wheeler drum brake is studied experimentally, and the in-situ thermal behavior is studied experimentally and numerically in the present paper. A new test rig is designed using a motor, torque sensor, data acquisition system, and drum brake of the twowheeler. The effect of speed and braking cycles on the torque and thermal behavior of drum brake is studied. The torque required for approximately the same deceleration is dependent on the speed of drum and brake cycles. Similarly, results are found for thermal analysis, and drum surface temperature depends on the speed of the drum. Moreover, the drum surface temperature increases steadily with the increase of brake cycles.

CONGRUENCES MODULO POWERS OF 2 FOR OVERPARTITION PAIRS INTO ODD PARTS

Ahmed, Zakir,Barman, Rupam,Ray, Chiranjit Korean Mathematical Society 2020 대한수학회지 Vol.57 No.2

We find congruences modulo 32, 64 and 128 for the partition function ${\overline{PP}_o}(n)$, the number of overpartition pairs of n into odd parts, with the aid of Ramamnujan's theta function identities and some known identities of t_k(n), for k = 6, 7, where t_k(n) denotes the number of representations of n as a sum of k triangular numbers. We also find two Ramanujan-like congruences for ${\overline{PP}_o}(n)$ modulo 128.

Isolation and Characterization of Novel Denitrifying Bacterium Geobacillus sp. SG-01 Strain from Wood Chips Composted with Swine Manure

Yang, Seung-Hak,Cho, Jin-Kook,Lee, Soon-Youl,Abanto, Oliver D.,Kim, Soo-Ki,Ghosh, Chiranjit,Lim, Joung-Soo,Hwang, Seong-Gu Asian Australasian Association of Animal Productio 2013 Animal Bioscience Vol.26 No.11

Nitrate contamination in ground and surface water is an increasingly serious environmental problem and only a few bacterial strains have been identified that have the ability to remove nitrogen pollutants from wastewater under thermophilic conditions. We therefore isolated thermophilic facultative bacterial strains from wood chips that had been composted with swine manure under aerated high temperature conditions so as to identify strains with denitrifying ability. Nine different colonies were screened and 3 long rod-shaped bacterial strains designated as SG-01, SG-02, and SG-03 were selected. The strain SG-01 could be differentiated from SG-02 and SG-03 on the basis of the method that it used for sugar utilization. The 16S rRNA genes of this strain also had high sequence similarity with Geobacillus thermodenitrificans $465^T$ (99.6%). The optimal growth temperatures ($55^{\circ}C$), pH values (pH 7.0), and NaCl concentrations (1%) required for the growth of strain SG-01 were established. This strain reduced 1.18 mM nitrate and 1.45 mM nitrite in LB broth after 48 h of incubation. These results suggest that the G. thermodenitrificans SG-01 strain may be useful in the removal of nitrates and nitrites from wastewater generated as a result of livestock farming.