Papers by Keyword: Evolution

Abstract: The examination of the primary climatic indicators, air temperature and rainfall, at the Drobeta Turnu Severin meteorological station for the period 2011-2022, allowed for the identification of increasing or declining trends. The entire study was developed using three different time frames of analysis: monthly, seasonal, and annual. The results indicate the specificities for each climate parameter on each of the three-time scales. The yearly trends for mean temperature are primarily increasing, while the annual trends for rainfall are generally decreasing. Because of the fluctuation of meteorological elements, air pollution has varying characteristics based on the geographical and topographical qualities of the urban region. This study's findings help to understand the seasonality of the overall air quality and the interaction between meteorological conditions and air contaminants. The Air Quality Index (AQI) was used to assess air quality. The AQI revealed that the air quality in Drobeta Turnu Severin is normal.

Abstract: We investigate the structural evolution of the single-walled carbon nanotubes (SWNTs) by molecular dynamics (MD) simulation using the Gao-Weber potential. The structural evolution of SWNTs is analyzed through the total energy per atom, the radial distribution function, coordination number, bond angle and the distribution of ring statistics. The results show that the melting temperature of SWNTs occurs at around T_m=5620 K. This value is in good agreement with the result of Zhang and co-workers. The visualization indicates that the initially perfect SWNTs is broken resulting in the ring of various.

Abstract: The early stage development of the cement microstructure is a crucial aspect affecting the overall performance of cementitious materials. The formation of hydration products depends on the presence of water and carbon dioxide, as well as on the distribution and re-crystallization of the cement particles. In this paper we evaluate the micromechanical properties evolution of cement phases over first 28 days after casting by the electron microscopy and static areal indentation.

Abstract: The microstructure morphology of SAF2205 steel during single direction torsion is studied at room temperature by optical microscope. The microstructure evolution indicates that different austenite morphologies on selected longitudinal sections are observed from the subsample close to clamp end, the subsample close to the fracture end and the subsample from the undeformed specimen. The austenite is elongated gradually on longitudinal sections which caused by shear stress. Concurrently, the elongation degree is more obvious in L1 section (near to the center of the sample) than that of L2 section (away from the center of the sample), which is attributed to the gradient distribution of plastic strain. The finite element analysis shows the plastic strain distribution law of the torsional deformation and the results from the fracture appearance indicate the dimples with different depths and types are observed.

Abstract: The organizations and phase composition after forging and heat treatment of the stacking fault energy for the three high manganese steel with 2.99 mJ/m²,7.9 mJ/m²and23 mJ/m² were observed. It’s analysised that the microstructure and orientation change of three high manganese steel by SEM and EBSD and the effect of alloy elements and the composition of the material on microstructure of high manganese steel; Through Static compressive deformation of cylindrical specimen under different strain rates experimental, the effect of strain rate on the deformation mechanism of different components of high manganese steel was analysised. Cylindrical specimens by static compression at different strain rates, analysis of strain rate on the different components of high manganese steel impact deformation mechanism; The mechanical performance characteristics are analyzed under different strain rate of three components high-manganese steel by stress - strain curves. By Compressive Split-Hopkinson Pressure Bar experiments to study the mechanism of high manganese steel deformation at high strain rates. The study found: the exclusion of the impact of the martensitic transformation can produce 18Mn high manganese TRIP or TWIP effect after deformation. Through observation and calculation, it found C, Al's content of alloying elements on the grain sizes less affected, but the starting temperature of martensitic transformation and layer greatly affects high manganese wrong size possible. Through analysis, found C, Al decides that the high content of alloying elements manganese organization original phase composition and deformation mechanism; organizations γ + ε-M + α'-M high manganese TRIP effect occurs, organizations γ + ε-M's high manganese TRIP effect occurs, tissue TWIP effect of high manganese steel γ.

Abstract: The effects of Co additions on the evolution of γ' precipitates and topologically close-packed (TCP) phases during thermal exposure at 950 °C were investigated for two Ni-based single crystal superalloys with 7.9 wt.% Co and 9.1 wt.% Co. The results indicated that the γ′ morphology was not affected by Co content, whereas γ′ volume fraction decreased and precipitate size increased due to lower Co addition after standard heat treatment. The coarsening of γ′ precipitates in both alloys was controlled by diffusion. The γ′ coarsening rate increased, while the stability of γ′ volume fraction decreased due to lower level of Co addition during 950 °C thermal exposure because more Co addition suppressed the diffusion process. High Co addition promoted the formation of μ phase after thermal exposure at 950 °C for 1000 h due to higher γ′ volume fraction, more stable γ′ volume fraction and higher electron vacancy number. The experimental results of μ phase precipitation showed good agreement with thermodynamic calculation by JMatPro.

Abstract: This paper reports some research findings on the parallel evolutions of microstructural properties and thermal diffusivity in strontium titanate. Strontium titanate samples have been prepared via the high energy ball milling technique and subsequently moulded by a hydraulic pressing and followed by cold isostatic pressing. Nanometer-sized compacted powder samples were sintered from 500 to 1400°C using 100°C increments. Strontium titanate formation was observed at as early as 500°C sintering temperature alongside secondary phases. The full formation of strontium titanate was observed at 800°C sintering temperature and above. Average grain sizes showed a fluctuating trend with increased sintering temperatures due to carbonate decomposition at lower sintering temperatures (500 to 800°C) and grain growth phenomenon at higher sintering temperatures (900 to 1400°C). Parallel characterization of evolving thermal diffusivity showed the same trend of fluctuation at low sintering temperatures as indirect relationship but increased with increased grain size due to a lesser amount of phonon scattering. However, thermal diffusivity values decreased with increased temperatures because of increased phonon-phonon scattering.

Abstract: The formation of the molluscan shell nacre is regulated to a large extent by a matrix of extracellular macromolecules that are secreted by the shell forming tissue, the mantle. This so called “calcifying matrix” is a complex mixture of proteins and glycoproteins that is assembled and occluded within the mineral phase during the calcification process. While the importance of the calcifying matrix to shell formation has long been appreciated, the molecular basis that dictates nacre formation remains largely uncharacterized.Recent expressed sequence tag (EST) investigations of the freshwater mussels (Elliptio complanata and Villosa leinosa) provide an opportunity to further characterize the proteins in the bivalve shell by a proteomic approach. In this study, we have identified a total of 15 proteins from their nacre insoluble matrices. Few of these proteins, such as Pif, MSI60, Nacrein-like, Shematrin, Kunitz-like containing, Papilin-like, LamG containing, Chitin-binding containing, M-rich and Q-rich proteins, appear to be analogs, if not true homologs, of proteins previously described from the pearl oyster or the edible mussel nacre matrices. This work constitutes a comprehensive EST-based nacre proteomic study of non-pteriomorphid bivalves that concretely gives us the opportunity to describe the molecular basis of deeply conserved nacre biomineralization toolkit within nacreous shell bearing bivalves.

Abstract: Inland plain shallow saline water has great exploitation potentiality. Based on field water testing, water level monitoring, pumping test, as well as indoor leaching experiment, applying mathematical statistics, Pipers trilinear nomograph and PHREEQC chemistry simulation methods, saline water area of the town of Sungeng Jiyang was studied. The results showed as follows: (1) Inland shallow groundwater presents “weather-evaporative” dynamic type; (2)The shallow saline water and middle-deep groundwater belonging to different flow system; (3) Because of the creeping flow and aqueous medium riched in clay, inland shallow groundwater mineralized significantly. In saline water area inland plain, the unique features of groundwater circulation result in brackish water dynamic relative stability.

Abstract: In order to solute the problems of selection and improvement of parts when the product family architecture to adapt to the diverse needs, the selection method of parts in product family evolution was proposed herein. The part’s performance and the Matching degree of demand characteristics were analyzed. The parts CSM model in product family was defined and established, the clustering method based on fuzzy C-means (FCM) for parts was used in CSM coupling space of parts. Finally, the wheel loader’s manipulator product family as an example was employed to demonstrate the feasibility of the proposed method.