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Search Results: 1 - 10 of 325126 matches for " S. Zimowski "
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Mechanical and tribological properties of TiC–based composites for ED machining
P. Figiel,S. Zimowski,P. Klimczyk,T. Dziwisz
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: The goal of this work is comparative study of TiC–(Mo, Ni) composites with different TiC-phase content to obtain material with an optimal mechanical and tribological properties, which can be easy shaped by Electro Discharge Machining (EDM).Design/methodology/approach: Three variants of TiC–(Mo, Ni) composites with the different hardening phase to the bonding phase ratio were sintered in vacuum. The influence of the initial TiC hard phase content in the sintered composites on their mechanical and tribological properties as well as ED machinability were investigated. The density, Young modulus, hardness, fracture toughness were measured. Tribological tests were carried out conducted using “pin-on-disc” and “ball-on-disc” methods. Wire Electro Discharge Machining (WEDM) performance preliminary test were realised also.Findings: The microstructure of sintered TiC–(Mo, Ni) materials is characterized by a ring structure of carbides. Mechanical properties and wear resistance are better for samples with higher TiC content. All variants of investigated materials are characterized by good WED machinability.Research limitations/implications: Obtained materials are characterized by good mechanical, tribological and working properties but homogeneity of microstructure should be improved. Farther works will be continued also for limitation of the metallic phase content up to 5 vol.%.Practical implications: After additional technological evaluation tests, obtained materials could be used for the different parts of machines and wear components (e.g. nozzles, plungers) shaped by EDM.Originality/value: New type of TiC–metal bonded composite with high content of hard phase which could be shaped by EDM.
Amorphous carbon layers on polymeric substrates
R.M. Nowak,S. Jonas,S. Zimowski,K. Tkacz-?miech
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: urpose: This paper is aimed to study an effect of nitrogen incorporation on the structure and tribological properties of amorphous a C:N:H layers grown on polycarbonate substrates.Design/methodology/approach: Series of the layers were deposited from CH4 + N2 gas mixture with application of Plasma Enhanced Chemical Vapour Deposition technique assisted by radio waves (RF PE CVD). An analysis of atomic-level structure of the layers was made using FT IR technique. The samples were subjected to investigations of friction coefficient and wear resistance. The respective measurements were performed using Micro-Combi-Tester and a tribometer in ball-on-disc configuration.Findings: The IR spectra of the obtained layers have demonstrated a presence of nitrogen bonded both to carbon and to hydrogen. A formation of the following bonds has been confirmed: -C≡N, -NH2, -C-NH2, >C=NH. All they are typical for a-C:N:H layers. The tribological tests have shown that the layers reduce the friction coefficient of the polycarbonate (up to 50 %) and considerably improve abrasion resistance.Research limitations/implications: Further studies in order to find relations between growing conditions and the properties of the layers should be performed. A role of the chemical composition and structure should be carefully analyzed.Practical implications: An application of carbon overcoats on polycarbonates may improve the usable properties of plastic components (hardness, scratch resistance, UV radiation resistance). This will make polycarbonates attractive materials of wide spectrum of possible applications.Originality/value: It has been shown in this research that application of RF PE CVD technique allows obtaining the a-C:N:H layers improving usable properties of plastics. The layers well adhesive to the substrate may be obtained at the temperatures below 80oC.
Role of Motif III in Catalysis by Acetyl-CoA Synthetase
Cheryl Ingram-Smith,Jerry L. Thurman Jr.,Karen Zimowski,Kerry S. Smith
Archaea , 2012, DOI: 10.1155/2012/509579
Abstract: The acyl-adenylate-forming enzyme superfamily, consisting of acyl- and aryl-CoA synthetases, the adenylation domain of the nonribosomal peptide synthetases, and luciferase, has three signature motifs (I–III) and ten conserved core motifs (A1–A10), some of which overlap the signature motifs. The consensus sequence for signature motif III (core motif A7) in acetyl-CoA synthetase is Y-X-S/T/A-G-D, with an invariant fifth position, highly conserved first and fourth positions, and variable second and third positions. Kinetic studies of enzyme variants revealed that an alteration at any position resulted in a strong decrease in the catalytic rate, although the most deleterious effects were observed when the first or fifth positions were changed. Structural modeling suggests that the highly conserved Tyr in the first position plays a key role in active site architecture through interaction with a highly conserved active-site Gln, and the invariant Asp in the fifth position plays a critical role in ATP binding and catalysis through interaction with the 2′- and 3′-OH groups of the ribose moiety. Interactions between these Asp and ATP are observed in all structures available for members of the superfamily, consistent with a critical role in substrate binding and catalysis for this invariant residue.
Role of Motif III in Catalysis by Acetyl-CoA Synthetase
Cheryl Ingram-Smith,Jerry L. Thurman Jr.,Karen Zimowski,Kerry S. Smith
Archaea , 2012, DOI: 10.1155/2012/509579
Abstract: The acyl-adenylate-forming enzyme superfamily, consisting of acyl- and aryl-CoA synthetases, the adenylation domain of the nonribosomal peptide synthetases, and luciferase, has three signature motifs (I–III) and ten conserved core motifs (A1–A10), some of which overlap the signature motifs. The consensus sequence for signature motif III (core motif A7) in acetyl-CoA synthetase is Y-X-S/T/A-G-D, with an invariant fifth position, highly conserved first and fourth positions, and variable second and third positions. Kinetic studies of enzyme variants revealed that an alteration at any position resulted in a strong decrease in the catalytic rate, although the most deleterious effects were observed when the first or fifth positions were changed. Structural modeling suggests that the highly conserved Tyr in the first position plays a key role in active site architecture through interaction with a highly conserved active-site Gln, and the invariant Asp in the fifth position plays a critical role in ATP binding and catalysis through interaction with the 2′- and 3′-OH groups of the ribose moiety. Interactions between these Asp and ATP are observed in all structures available for members of the superfamily, consistent with a critical role in substrate binding and catalysis for this invariant residue. 1. Introduction AMP-forming acetyl-CoA synthetase (Acs, EC 6.2.1.1), which catalyzes the formation of acetyl-CoA from acetate, ATP, and CoASH (acetate + ATP + CoASH ? acetyl-CoA + AMP + PPi), belongs to the acyl-adenylate-forming enzyme superfamily, which has newly been designated by Gulick [1] as the ANL superfamily of adenylating enzymes to reflect the three subfamilies, the acyl- and aryl-CoA synthetases, the adenylation domain of the nonribosomal peptide synthetases, and luciferase. Although distant members of this superfamily catalyze wholly unrelated reactions and employ different substrates, they share the property of formation of an enzyme-bound acyl-adenylate intermediate in the first step via activation with ATP with concurrent release of pyrophosphate. Sequence alignment of members of this superfamily has revealed the presence of three signature motifs as defined by Chang et al. [2]:??motif I: T[S/G]-S[G]-[G]-[S/T]-T[S/E]-G[S]-[X]-P[M]-[K]-G[L/F],??motif II: Y[L/W/F]-G[S/M/W]-X-T[A]-E, ??motif III: Y[F/L]-R[T/K/X]-T[S/V/A]-G-D, (boldfaced residues are the predominant residue at each position, and alternative residues are indicated in bracket.) Marahiel et al. [3] further identified ten conserved core motifs in the superfamily, in which the A3, A5, and A7
Study of the Structural and Electrical Properties of Cr-Doped BiFeO3 Ceramic  [PDF]
S. S. Arafat, S. Ibrahim
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.810051
Abstract: Multiferroic BiFe1-xCrxO3 (x = 0.2 and 0.4) ceramics were synthesized in a single phase. The effects of Cr3+ substitution on the crystal structure, dielectric permittivity and leakage current were investigated. Preliminary X-ray structural studies revealed that the samples had a rhombohedral perovskite crystal structure. The dielectric constant ε' significantly increased while the dielectric loss tanδ was substantially decreased with the increase in Cr3+ substitution. The temperature effect on the dielectric properties exhibited an anomaly corresponding to magneto-electric coupling in the samples and was shifted to lower temperatures with the increase in Cr3+ substitution. The leakage current density also reduced in magnitude with the increase in the Cr3+ substitution.
Degree Splitting of Root Square Mean Graphs  [PDF]
S. S. Sandhya, S. Somasundaram, S. Anusa
Applied Mathematics (AM) , 2015, DOI: 10.4236/am.2015.66086
Abstract: Let \"\" be an injective function. For a vertex labeling f, the induced edge labeling \"\" is defined by, \"\" or \"\"; then, the edge labels are distinct and are from \"\". Then f is called a root square mean labeling of G. In this paper, we prove root square mean labeling of some degree splitting graphs.
A Parameter Estimation Model of G-CSF: Mathematical Model of Cyclical Neutropenia  [PDF]
S. Balamuralitharan, S. Rajasekaran
American Journal of Computational Mathematics (AJCM) , 2012, DOI: 10.4236/ajcm.2012.21002
Abstract: We investigate the FFT (Fast Fourier Transform) model and G-CSF (granulocyte colony-stimulating factor) treatment of CN (Cyclical Neutropenia). We collect grey collies and normal dog’s data from CN and analyze the G-CSF treatment. The model develops the dynamics of circulating blood cells before and after the G-CSF treatment. This is quite natural and useful for the collection of laboratory data for investigation. The proposed interventions are practical. This reduces the quantity of G-CSF required for potential maintenance. This model gives us good result in treatment. The changes would be practical and reduce the risk side as well as the cost of treatment in G-CSF.
Synthesis, Thermal Behaviour, XRD, and Luminescent Properties of Lighter Lanthanidethiodipropionate Hydrates Containing Aminogunidine as Neutral Ligand  [PDF]
S. Packiaraj, S. Govindarajan
Open Journal of Inorganic Chemistry (OJIC) , 2014, DOI: 10.4236/ojic.2014.43006
Abstract:
Aminoguanidine lanthanide thiodipropionate hydrates of composition [Ln(Agun)2(tdp)3·nH2O], Agun = Aminoguanidine, tdp = thiodipropionic acid, where Ln = La, Pr, Nd and Sm if n = 2, have been prepared and characterized by physic-chemical techniques.
Fuzzy Based Intelligent Monitoring of Critical Lines in the Restructured Power Market  [PDF]
S. Rajasekaran, S. Sathiyamoorthy
Circuits and Systems (CS) , 2016, DOI: 10.4236/cs.2016.79191
Abstract: Restructured electric market environment allows the power wheeling transactions between the power producers and customers to meet the growing load demand. This will lead to the possible of congestion in the transmission lines. The possible contingencies of power components further worsen the scenario. This paper describes the methodology for the identification of critical transmission line by computing the real power and reactive power performance indices. It also demonstrates the importance of fuzzy logic technique used to rank the transmission lines according to the severity and demonstrated on IEEE-30 bus system.
Error Correction Circuit for Single-Event Hardening of Delay Locked Loops  [PDF]
S. Balaji, S. Ramasamy
Circuits and Systems (CS) , 2016, DOI: 10.4236/cs.2016.79210
Abstract: In scaled CMOS processes, the single-event effects generate missing output pulses in Delay-Locked Loop (DLL). Due to its effective sequence detection of the missing pulses in the proposed Error Correction Circuit (ECC) and its portability to be applied to any DLL type, the ECC mitigates the impact of single-event effects and completes its operation with less design complexity without any concern about losing the information. The ECC has been implemented in 180 nm CMOS process and measured the accuracy of mitigation on simulations at LETs up to 100 MeV-cm2/mg. The robustness and portability of the mitigation technique are validated through the results obtained by implementing proposed ECC in XilinxArtix 7 FPGA.
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