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- 저자 : Dwivedi (검색결과 140 건)
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Design and Analysis of Hybrid Multilevel Inverter for Asymmetrical Input Voltages
Dwivedi Arpan,Pahariya Yogesh 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.6
The conversion of DC to AC has emerged as a vital role in Standalone power supply system. While converting DC to AC, it is conceivable to acquire the preferred output voltage and frequency. Voltage source inverters are basically categorized on the basis of output voltage waveforms. Multilevel inverters are replacing conventional inverters by overcoming the short coming of classical topologies. In practical implementation of conversion factors that should be considered are reducing component count and performance characteristics like fault tolerance capability, charge balance control, etc. This paper deals with the design of the single phase hybrid multilevel inverter using the Three-level diode clamped leg and Three-level T-type leg using asymmetrical voltage input sources for standalone system. The entire mathematical modeling of proposed hybrid inverter is presented. The performance parameters evaluated for asymmetrical source condition are THD analysis, reliability, switching and conduction losses are carried out. The simulation and hardware implementation of proposed topology at same load conditions has been done; both the hardware and simulation results are compared.
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Dwivedi, Shipra,Agrawal, Sarita,Singh, Shraddha,Madeshiya, Amit Kumar,Singh, Devendra,Mahdi, Abbas Ali,Chandra, Abhjeet Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.13
Background: Cholelithiasis is associated in 54%-98% of patients with carcinoma of the gallbladder, and a high incidence among females suggests a role of female hormones in the etiology of the disease. Cytochrome $P450C17{\alpha}$ (CYP-17) is a key enzyme involved in estrogen metabolism and polymorphisms in CYP-17 are associated with altered serum levels of estrogens. Thus, we investigated whether the CYP-17 MspA1 gene polymorphism might impact on risk of gall bladder cancers or gallstones, as well as to determine if this gene polymorphism might be linked with estrogen serum levels and lipid profile among the North Indian gall bladder cancer or gallstone patients. Materials and Methods: CYP-17 gene polymorphisms (MspA1) were genotyped with PCR-RFLP in cancer patients (n=96), stone patients (n=102), cancer + stone patients (n=52) and age/sex matched control subjects (n= 256). Lipid profile was estimated using a commercial kit and serum estrogen was measured using ELISA. Results: The majority of the patients in all groups were females. The lipid profile and estrogen level were significantly higher among the study as compared to control groups. The frequency of mutant allele A2 of CYP17 MspA1 gene polymorphism was higher among cancer (OR=5.13, 95% CI+3.10-8.51, p=0.0001), stone (OR=5.69, 95%CI=3.46-9.37, p=0.0001) and cancer + stone (OR=3.54, 95%CI=1.90-6.60, p=0.0001) when compared with the control group. However there was no significant association between genotypes of CYP17 MspA1 gene polymorphism and circulating serum level of estrogen and lipid profile. Conclusions: A higher frequency of mutant genotype A1A2 as well as mutant allele A2 of CYP-17 gene polymorphism is significantly associated with risk of gallbladder cancer and stones. Elevated levels of estrogen and an altered lipid profile can be used as predictors ofgall bladder stones and cancer in post menopausal females in India.
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Dwivedi, Amarendra Dhar,Permana, Rega,Singh, Jitendra Pal,Yoon, Hakwon,Chae, Keun Hwa,Chang, Yoon-Seok,Hwang, Dong Soo American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.23
<P>Tunicate, a filter-feeder in seawater, is able to accumulate high amount of metals using intracellular polymer matrices. The woven pyrogallol structures of tunichrome, a small peptide contained in tunicate's blood;Cells, is believed to, be responsible for selective. metal sequestration in tunicates from seawater. However, the intriguing tunichrome matrix is difficult both to harvest from the tunicate and to synthesize massively due to the-extreme oxidation sensitivity of the pyrogallol, moiety which limits the study scope. Here, we succeeded to mimic tunichrome by conjugating two cheap and naturally occurring components: pyrogallol-5-carboxylic acid (gallic acid) and chitin. nanofiber A tunicate-mimetic infiltration matrix of surface-tailored chitin nanofibers with pyrogallol moieties (CGa) demonstrated the versatility of this strategy in generation of ingenious filtration material, especially for unprecedented fine and-Clean gold recovery inside of the tunicate-mimetic infiltration matrix (>99%, 533 mg gold per gram weight), which exceeds that of the,presently most popular materials. Complexation between pyrogallol on the nanofiber and gold-was similar to that of a tunichrome's metal sequestration. Extended X-ray absorption fine Structure, (EXAFS); spectroscopy and data-fitting, elucidated the decreased coordination numbers for Au-Au nearest neighbors, demonstrating that gold coordinated to pyrogallol units, followed by an intramolecular association of Au-0. A catalytic reduction of 4-nitrophenol mediated by the-tunicate-mimetic matrix with harvested gold revealed excellent recyclability up to 30 cycles (similar to 95% reduction), which together with methylene-blue reduction and antimicrobial performances indicates the versatile characteristics,of sustainable processes by the tunichrome mimetics. This strategy opens the door for fast-developing new biomimetic alternatives for precious metal recovery, which is not restricted to gold and can offer a tool for multifaceted soft/hard nanomaterials..</P>
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Dwivedi, Shailendra,Singh, Sarvesh,Goel, Apul,Khattri, Sanjay,Mandhani, Anil,Sharma, Praveen,Misra, Sanjeev,Pant, Kamlesh Kumar Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.8
Background: It has been hypothesized that IL-18 (pro-) and IL-10 (anti-) inflammatory genetic variants at -607 C/A-137G/C and -819C/T,-592C/A, respectively, may generate susceptibility and severity risk with various modes of tobacco exposure in prostate carcinoma (PCa) patients. IL-18 is a pro-inflammatory cytokine expressed on various cells including prostate gland elements, and is a key mediator of immune responses with anti-cancerous properties. IL-10 is an anti-inflammatory cytokine that is associated with tumour malignancy which causes immune escape. Materials and Methods: The present study was conducted with 540 subjects, comprising 269 prostate carcinoma patients and 271 controls. Genotyping was performed by PCR-RFLP and confirmed by real time PCR probe-based methods. Results: The findings indicated that the mutant heterozygous and homozygous genotype CC and GC+CC showed significant negative associations (p=0.01, OR=0.21; 95% CI: 0.08-0.51 and p=0.011, OR=0.43; 95% CI: 0.22-0.81, respectively) thus, less chance to be diagnosed as cancer against GG genotype of tobacco smoking patients. In addition, a heterozygous GC genotype at the same locus of IL-18 pro-inflammatory cytokine may aggravate the severity (OR=2.82; 95%CI 1.09-7.29 :p=001) so that patients are more likely to be diagnosed in advanced stage than with the GG wild homozygous genotype. Our results also illustrated that anti-inflammatory cytokine (IL-10) genetic variants, although showing no significant association with susceptibility to cancer of the prostate, may gave profound effects on severity of the disease, as -819 TC (OR=4.60; 95%CI 1.35-15.73), and -592 AC (OR=5.04; 95%CI 1.08-25.43) of IL-10 in tobacco chewers and combined users (both chewers and smokers) respectively, are associated with diagnosis in more advanced stage than with other variants. Conclusions: We conclude that promoter genetic variants of IL-18 and IL-10 with various modes of tobacco exposure may affect not only susceptibility risk but also severity in prostate cancer.
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Dwivedi, Amarendra Dhar,Yoon, Hakwon,Singh, Jitendra Pal,Chae, Keun Hwa,Rho, Sang-chul,Hwang, Dong Soo,Chang, Yoon-Seok American Chemical Society 2018 Environmental science & technology Vol.52 No.17
<P>Here, we investigated the fate of nanoscale zerovalent iron (nZVI) on the <I>Cucumis sativus</I> under both hydroponic and soil conditions. Seedlings were exposed to 0, 250, and 1000 mg/L (or mg/kg soil) nZVI during 6-9 weeks of a growth period. Ionic controls were prepared using Fe-EDTA. None of the nZVI treatments affected the plant biomass. On the basis of the total iron contents and the superparamagnetic property of nZVI-exposed roots, there was no evidence of pristine nZVI translocation from the roots to shoots. Electron microscopy revealed that the transformed iron nanoparticles are stored in the root cell membrane and the vacuoles of the leaf parenchymal cells. X-ray absorption spectroscopy identified ferric citrate (41%) and iron (oxyhydr)oxides (59%) as the main transformed products in the roots. The shoot samples indicated a larger proportion of ferric citrate (60%) compared to iron (oxyhydr)oxides (40%). The 1.8-fold higher expression of the <I>CsHA1</I> gene indicated that the plant-promoted transformation of nZVI was driven by protons released from the root layers. The current data provide a basis for two potential nZVI transformation pathways in <I>Cucumis sativus</I>: (1) interaction with low molecular weight organic acid ligands and (2) dissolution-precipitation of the mineral products.</P> [FIG OMISSION]</BR>
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Polymorphic stages of the fresh water blue-green alga, Gomphosphaeria aponina
Dwivedi, V.K.,Tandon, Richa,Tiwari, G.L. The Korean Society of Phycology 2010 ALGAE Vol.25 No.3
The natural growth of a population of Gomphosphaeria aponina Kutzing (Chroococcales, Cyanoprocaryota) was studied in a cemented freshwater tank in Allahabad, India. This population appeared to be a polymorphic species. Different species of the genus Gomphosphaeria have been segregated based on morphological features of colonies, cells and mucilage. However, these features are not well defined for different species. Our observations revealed many feature variations and, interestingly, certain features that have been described for different Gomphosphaeria species were seen in a single population. In this study, records of such variable morphological features were possible due to the availability of numerous specimens and continuous observations for more than two years. Further, this study revealed two points: (i) more detailed morphological studies are required both from nature as well as in culture to identify critical differences among the species, and (ii) molecular characterization of taxa appears to be necessary for final species settlement.
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Dwivedi, Amarendra Dhar,Permana, Rega,Singh, Jitendra Pal,Yoon, Hakwon,Chae, Keun Hwa,Chang, Yoon-Seok,Hwang, Dong Soo Elsevier 2017 Chemical engineering journal Vol.328 No.-
<P><B>Abstract</B></P> <P>Inspired by naturally occurring metal chelation strategy by pyrogallol moiety of tunichromes of marine tunicates, a strong retention of carcinogenic chromium (Cr<SUP>VI</SUP>) is described by mimicking tunichrome matrix as a proof-of-concept investigation in water treatment applications. Harvesting tunichromes tailored with the pyrogallol moiety are extremely difficult owing to aerial sensitivity and purification difficulties, thus proving a challenging synthesis problem. Despite significant interest, knowledge of specific metal coordination in tunicate’s matrix is still ambiguous, hindering study scope. We planned to fabricate a promising tunichrome matrix (TM) tailored with pyrogallol moieties from the Earth-abundant raw materials (gallic acid and chitin nanofiber) at mass scale without artificial aid. Specifically, we aimed at atomistic understanding of contaminant and pyrogallol moiety of TM by examining the structural parameters (redox change, geometrical distortion, coordination bond). Cr <I>K</I>-edge extended X-ray absorption fine structure (EXAFS) corresponds well to nontoxic Cr<SUP>III</SUP> (average four CrO bond lengths of 1.91Å) and a small fraction of Cr<SUP>VI</SUP> (average two CrO bond lengths of 1.62Å). A coupled reductive complexation mechanism was identified by combining near edge X-ray absorption fine structure (NEXAFS) and linear combination fits. From the viewpoint of practical utility and effective performance (nearly 119mg chromium per g weight of TM), the impacts of water chemistry conditions were investigated from a variety of contaminated waters, showing a distinct improvement compared to conventional popular materials. The gained knowledge would be beneficial for utilizing a pyrogallol moiety as an alternative greener and sustainable scavenger, specifically for toxic chromium.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A newly designed nano-bio tool inspired by marine tunicate, a filter feeder. </LI> <LI> Superior retention of Cr<SUP>VI</SUP> by mimicking tunichrome matrix in remediation treatment. </LI> <LI> Pyrogallol – a primary factor in increased efficiency as a proof-of-concept study. </LI> <LI> First comprehensive report on tunichrome’s chromium metal coordination chemistry. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Non-axisymmetric dynamic response of imperfectly bonded buried orthotropic pipelines
Dwivedi, J.P.,Mishra, B.K.,Upadhyay, P.C. Techno-Press 1998 Structural Engineering and Mechanics, An Int'l Jou Vol.6 No.3
This paper deals with the non-axisymmetric dynamic response of an imperfectly bonded buried orthotropic pipeline subjected to longitudinal wave (P-wave) excitation. An infinite cylindrical shell model, including the rotary inertia and shear deformation effects, has been used for the pipeline. For some cases comparison of axisymmetric and non-axisymmetric responses have also been furnished.
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