Papers by Keyword: Theoretical Calculations

Abstract: Forming limit curve (FLC) is the most common used manifestation of the failure criterion today in the sheet metal forming industry. All commercial simulation software uses this concept to evaluate the failure strains and to detect the most dangerous section(s) of the workpiece. The laboratory determination of the FLC is standardized. However, because experimental measurement is cumbersome, theoretical calculations of FLCs using mechanical properties from well-defined test conditions are still interesting. Such calculation concepts are already developed by different authors. This paper presents calculated FLCs using the models of Abspoel et al., Stören and Rice and Swift. All the equations include tensile tests data that have been measured physically at room temperature, with quasi-static strain rates. Calculated results of DC04 cold rolled steel sheet with relatively high plastic anisotropy coefficient was compared to a nearly isotropic DP800 high strength steel. Based on the results it is observed that r-value influences the shape of the left-hand side of the FLC as well as the plane strain point significantly, for the DC04 sheet. These effects are less pronounced for the DP800 material, which has lower r-value. At the same time, n-value and total elongation raise or lower the curves, generally. These observations are briefly explained by function analyses using fictitious r-values in the calculations.

Abstract: The current study was carried out by determining structural and energetic parameters to theoretically validate the experimental results of the adsorption efficiency of amine-functionalized porous carbon for the elimination of Cu²⁺ ions and Pb²⁺ and detail the reaction mechanism in the aqueous medium. The Density Functional Theory calculations, molecular dynamics, and Monte Carlo simulations were used to investigate the adsorption enhancement mechanism. The calculations were performed using the Dmol3 module of the Materials Studio program (MatS) using the exchange-correlation function M-11L2. DFT calculations were determined for porous carbon (PC) and porous carbon functionalized by ethylene diamine (PC-ED). Indeed, this study aims to reveal the functionalization influence on improving the adsorption efficiency of Cu²⁺ and Pb²⁺ by porous carbon (PC). Overall, the study attempts to explain the experimental results of the improved interactivity of porous carbon functionalized by ethylene diamine concerning Cu²⁺ and Pb²⁺ ions, compared to the reactivity of these ions with the group carboxyl characterizes the porous carbon (PC). The Molecular dynamics and Monte Carlo simulations were used to clarify the interactions between Cu²⁺ or Pb²⁺ ions and porous carbon modelled in the presence or absence of ethylene diamine (PC–ED) function. Hence, the theoretical study showed that the presence of ethylene diamine (C₂H₄(NH₂)₂)_m forms more ligands towards the ions of metal M²⁺ with the interaction bounds lower than ≤ 2.5 Å. The same result is shown by the small adsorption energy obtained in the range of -1140 to -200 kcal/mol for and -1200 to -600 kcal/mol for Pb²⁺ and Cu²⁺, respectively. Therefore, more adsorption of Cu²⁺ and Pb²⁺ ions. The theoretical results obtained agree with the experimental results.

Abstract: The novel bicycloamino acid, 1−carboxyl−4−amino−2−aza−3−oxo−[2.2.2] bicyclooctane was synthesized and its physical characteristics have been compared to those predicted using quantum chemical calculations. The crystal structure of novel compound was determined by X-ray diffraction measurements at room temperature. Unit cell is monoclinic, with space group P 2₁/n (14) and a = 5.8587(6) Ǻ, b = 11.2454(16) Ǻ, c = 13.9723(16) Ǻ, β=97.840(6)°, Z = 2. Refinement was performed using all 1598 reflections with R = 0.4085 and wR = 0.6024. Theoretical calculation of full optimization and atomic net charge, and frontier orbital energies of the title compound was carried out at the B3LYP/6−31G(d,p) level. The NMR chemical shielding tensors and vibrational frequencies were calculated with B3LYP/6-311+G(2d, p)− level in which were close values and similar spectrum structures with experimental results and used to interpret the experimental measurements.

Abstract: Despite nanosegregation of solutes at grain boundaries has been intensively studied in the past decades and numerous theoretical data as well as experimental values on characteristic energies and/or enthalpies and entropies exist some questions remain still unanswered. In this paper some of these questions – Which energetic quantities obtained in different ways, experimentally and theoretically, can be mutually compared What is the segregation site of a solute in the grain boundary core – are discussed in more detail. It will be shown that the entropy of grain boundary segregation plays an important and indisputable role in responding some issues and that understanding of its role will help us to elucidate fundamentals of the grain boundary segregation.

Abstract: In this research, methyl acrylate has been synthesized from industrial raw material methyl acetate through highly efficient and eco-friendly method, One-step aldol condensation, using acid-base bifunctional catalyst Cs, P and K as catalysts. Carbon deposits and other issues led to the catalysts deactivation in the process of fixed bed, which led to the production interruption. While, the process of circulating fluidized bed can overcome this defect and the catalyst can maintain good catalytic activity in the whole process. Cs (8%), P (5%), K (2%)/γ-Al₂O₃/ catalyst showed better performance due to its high surface area and more weak basicity and acidity. In addition, theoretical calculations and cold model experiments were also conducted in this work to determine the catalyst particle size，operation gas velocity and gas distributor plate.

Abstract: Telescope laser pointer is generally used firearms and other light weapons systems, to ensure accurate light weapons capable of targeting, this paper presents a telescope system automatically detects a laser pointer, laser pointer can be the role of the distance, the laser divergence angle of the laser spot size of the laser optical axis adjustment range and the laser optical axis deviation and other parameters were measured. In this paper, the detection system structure, optical structure was designed; proposed laser pointer detection principle of the parameters; and software design. At last, to meet the requirements of this system has been experimentally derived by experimental verification, measurement accuracy.