Theoretical Prediction Method Research Articles

Numerical Simulation on Stress Distribution and Deformation of Large Hydro Turbine Blade with Complex Surface during Heat Treatment Process

A three dimensional finite element model of the heat treatment process of ZG06Cr13Ni4Mo stainless steel was established in this paper. The distribution of stress and deformation for large hydro turbine blade with complex surface during normalizing and tempering treatment has been simulated. The simulated results are consistent with the measured equivalent stress values by hole-drilling method, which indicates that the model is effective to predict the stress distribution of heat treated ZG06Cr13Ni4Mo material. Based on this model, the distribution law of stress field and deformation of the large hydro turbine blade of complex surface after the heat treatment were simulated. The established model provided a theoretical prediction method for designing of optimized complex surface blade and formulating a reasonable heat treatment process.

Computation of pH-dependent binding free energies.

Protein-ligand binding accompanies changes in the surrounding electrostatic environments of the two binding partners and may lead to changes in protonation upon binding. In cases where the complex formation results in a net transfer of protons, the binding process is pH-dependent. However, conventional free energy computations or molecular docking protocols typically employ fixed protonation states for the titratable groups in both binding partners set a priori, which are identical for the free and bound states. In this review, we draw attention to these important yet largely ignored binding-induced protonation changes in protein-ligand association by outlining physical origins and prevalence of the protonation changes upon binding. Following a summary of various theoretical methods for pKa prediction, we discuss the theoretical framework to examine the pH dependence of protein-ligand binding processes.

Molecular dynamics simulations of molecularly imprinted polymer approaches to the preparation of selective materials to remove norfloxacin

ABSTRACTA novel molecularly imprinted polymer (MIP) designed by molecular dynamics (MD) simulations was successfully prepared with norfloxacin as a template molecule, methyl acrylic acid as a functional monomer, and ethylene glycol dimethacrylate as a crosslinker. According to the theoretical prediction and experimental preparation methods, three kinds of molecular imprinting materials were designed and synthesized with MD simulations and molecular imprinting technology. The best ratio of the template to the functional monomer to the crosslinker was 1:8:40 in these studies. The experimental results illustrate that the MD simulations were credible in compounding the components of the MIPs. The structure of the prepared polymers were characterized with various methods. To analyze the adsorption performances, many kinds of static adsorption tests, including kinetic, isotherm, and selectivity tests, were used. The results indicate that the novel adsorbents conformed to the pseudo–second‐order kinetic equation and followed the Langmuir isotherm model. The adsorption amounts of MIP2 at a ratio of 1:8:40 were about 29.35 mg/g at 298 K. The selective adsorption and reusable performance of norfloxacin were excellent. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 132, 42817.

Structure and stability of supramolecular crown ether complexes.

Despite the fact that the complexation of ammonium cations with ionophores like crown ethers plays an important role in biological and industrial processes, there is still a lack of theoretical methods to reproduce or even predict the host-guest complex structures or their thermodynamic stabilities in an accurate manner. Hence, the development of ionophores has often relied on a trial-and-error approach and the synthetic efforts associated with this have been enormous, so far. Therefore, theoretical methods for the reliable prediction of binding affinities of crown ether derivatives with ammonium ions would be an indispensable tool for the rational design of new receptors with tailored properties. Here, we suggest a computationally efficient but still accurate theoretical approach. It is tested for a model system consisting of 18-crown-6 ether and an ammonium cation, but is invented for application to much larger complexes. The accuracy of various approximate quantum-chemical methods, based on density functional theory (DFT) and many-body perturbation theory, is evaluated against the gold standard CCSD(T) in the basis set limit as internal reference. An important aspect is the consideration of dispersion interactions in DFT methods, for which the dispersion-correction by Grimme was employed. For all selected methods, the basis-set dependence of calculated interaction energies was investigated.

Functional Exposed Amino Acids of BauA as Potential Immunogen Against Acinetobacter baumannii.

Multidrug-resistant Acinetobacter baumannii is recognized to be among the most difficult antimicrobial-resistant gram negative bacilli to control and treat. One of the major challenges that the pathogenic bacteria face in their host is the scarcity of freely available iron. To survive under such conditions, bacteria express new proteins on their outer membrane and also secrete iron chelators called siderophores. Antibodies directed against these proteins associated with iron uptake exert a bacteriostatic or bactericidal effect against A. baumanii in vitro, by blocking siderophore mediated iron uptake pathways. Attempts should be made to discover peptides that could mimic protein epitopes and possess the same immunogenicity as the whole protein. Subsequently, theoretical methods for epitope prediction have been developed leading to synthesis of such peptides that are important for development of immunodiagnostic tests and vaccines. The present study was designed to in silico resolving the major obstacles in the control or in prevention of the diseases caused by A. baumannii. We exploited bioinformatic tools to better understand and characterize the Baumannii acinetobactin utilization structure of A. baumannii and select appropriate regions as effective B cell epitopes. In conclusion, amino acids 26-191 of cork domain and 321-635 of part of the barrel domain including L4-L9, were selected as vaccine candidates. These two regions contain functional exposed amino acids with higher score of B cell epitopes properties. Majority of amino acids are hydrophilic, flexible, accessible, and favorable for B cells from secondary structure point of view.

On the possibility of predicting seismogram and accelerogram of strong motions of the soil for an earthquake model considered as an instantaneous rupture of the Earth’s surface

Problems of the prediction of displacement and acceleration values for strong soil displacements are considered for the case where an earthquake is regarded as an instantaneous mechanical rupture of the Earth’s surface. We have attempted to develop, based on recent concepts of earthquake generation process, simplified theoretical methods for the quantitative prediction of soil displacement parameters during strong earthquakes. As an illustrative example, we consider an earthquake originating as a consequence of relative displacements of suddenly ruptured blocks in a horizontal direction with a given initial velocity. An empirical relationship between soil particle motion velocity near the rupture and at a certain distance from it, on one hand, and the earthquake magnitude, on the other hand, was established. It is assumed that the impact of inertial motions of a deep soil stratum on the inertial motions of upper subsurface soil stratum at instantaneous break of a medium can be neglected. By solving a wave problem for a multilayer near-surface stratum, analytical relations were developed for a soil seismogram and accelerogram on the surface depending on the physical-mechanical and dynamic characteristics of the soil at all layers of the stratum; attenuation coefficients of mechanical soil vibrations; the distance to the rupture; and the magnitude of the predicted earthquake. The results obtained enable us to determine the maximum displacement and acceleration values of the soil, taking into account local soil conditions and their variations over time, as well as the values of the predominant vibration periods in the soil. The method was applied for solid and loose soil basements.

Mathematical Modeling of Relaxation and Creep for Medical-Grade Polymer Yarns

We have studied the deformation properties of medical-grade polymer yarns (categorized as viscoelastic solids) in the region of action of nondestructive loads close to their usage conditions, based on a mathematical model of the deformation processes. Advances in methods for theoretical prediction of the stress–strain state of the indicated materials can be attributed to their expanding application. Development of procedures for calculation of deformation processes in the studied materials is inseparably connected with solving problems of comparative analysis of their deformation properties, with studies of the correlation between properties and structure, with targeted processing control of properties, and also with prediction of short-term and long-term mechanical effects.

Influence of Secondary Flow Injection Angle on a Fluidic Shock Control Technique

The influence of the secondary flow injection angle on a fluidic shock control technique that is used to control the ramp shock of supersonic and hypersonic inlets is studied in this paper. The differential equation of the momentum thickness of the boundary layer, the injection ratio, and the secondary flow injection angle is first deduced. Then, the relation of the secondary flow injection ratio with the displacement of the first ramp shock is established. Based on this, a theoretical prediction method of the required secondary mass flow ratio for a given shock control requirement is developed in an iterative manner and then validated by both numerical simulations and wind-tunnel tests. The theoretical analysis shows that the momentum thickness development rate of the boundary layer is closely related to the dimensionless tangential velocity of the secondary flow and the injection ratio. Although the desired displacement of the first ramp shock remains the same, the required secondary mass flow ratio decreases substantially with the increase of injection angle. The results obtained by wind-tunnel tests and three-dimensional computations also show that the accuracy of the prediction method is satisfactory.

ChemInform Abstract: Structure‐Property Relationships of Curved Aromatic Materials from First Principles

AbstractReview: 77 refs.

The Study on Theoretical Prediction Method of Corrosion-Induced Cracking of the Concrete Cover

The concrete covercorrosion-induced cracking is the key to service life predicting of reinforcedconcrete structures. The existing research results make engineering andtechnical personnel in specific applications bewilderment. In this paper, therepresentative theoretical analysis methods of existing have been classifiedand the characteristics of various methods have been analyzed, the accuracy ofvarious methods has been comparatively analyzed by a concrete case.

Structure-property relationships of curved aromatic materials from first principles.

CONSPECTUS: Considerable effort in the past decade has been extended toward achieving computationally affordable theoretical methods for accurate prediction of the structure and properties of materials. Theoretical predictions of solids began decades ago, but only recently have solid-state quantum techniques become sufficiently reliable to be routinely chosen for investigation of solids as quantum chemistry techniques are for isolated molecules. Of great interest are ab initio predictive theories for solids that can provide atomic scale insights into properties of bulk materials, interfaces, and nanostructures. Adaption of the quantum chemical framework is challenging in that no single theory exists that provides prediction of all observables for every material type. However, through a combination of interdisciplinary efforts, a richly textured and substantive portfolio of methods is developing, which promise quantitative predictions of materials and device properties as well as associated performance analysis. Particularly relevant for device applications are organic semiconductors (OSC), with electrical conductivity between that of insulators and that of metals. Semiconducting small molecules, such as aromatic hydrocarbons, tend to have high polarizabilities, small band-gaps, and delocalized π electrons that support mobile charge carriers. Most importantly, the special nature of optical excitations in the form of a bound electron-hole pairs (excitons) holds significant promise for use in devices, such as organic light emitting diodes (OLEDs), organic photovoltaics (OPVs), and molecular nanojunctions. Added morphological features, such as curvature in aromatic hydrocarbon structure, can further confine the electronic states in one or more directions leading to additional physical phenomena in materials. Such structures offer exploration of a wealth of phenomenology as a function of their environment, particularly due to the ability to tune their electronic character through functionalization. This Account offers discussion of current state-of-the-art electronic structure approaches for prediction of structural, electronic, optical, and transport properties of materials, with illustration of these capabilities from a series of investigations involving curved aromatic materials. The class of curved aromatic materials offers the ability to investigate methodology across a wide range of materials complexity, including (a) molecules, (b) molecular crystals, (c) molecular adsorbates on metal surfaces, and (d) molecular nanojunctions. A reliable pallet of theoretical tools for such a wide array relies on expertise spanning multiple fields. Working together with experimental experts, advancements in the fundamental understanding of structural and dynamical properties are enabling focused design of functional materials. Most importantly, these studies provide an opportunity to compare experimental and theoretical capabilities and open the way for continual improvement of these capabilities.

Mechanisms of thermal process of zinc ultrafine powder preparation by inert gas condensation

Zinc ultrafine powder is widely used as key raw material for anti-corrosion paint in recent years. Inert gas condensation (IGC) is one of the primary means for preparing zinc ultrafine powder with a clean interface. As condensation is the most important process that determines the powder's size, this paper presents new models for radiative and convective cooling in condensation process by studying the microphysical mechanisms. In order to study the microphysical mechanisms of zinc nucleation process in the inert gas condensation, this paper established mathematical expressions to deduce the bonding probability of collisions between condensation nuclei particles and vapor molecules during the nucleation process. The two models have been used to predict the diameter of zinc condensation nucleus. Compared with experiments that have been done, the prediction errors are only less than 7%. This may provide a theoretical method for prediction of ultrafine powder diameter in IGC.

Accurate Prediction of IrH Bond Dissociation Enthalpies by Density Functional Theory Methods

AbstractThe iridium hydride complexes have been extensively used in organic reactions, such as oxidation and hydrogenation reactions. In many of these reactions, the dissociation or formation of IrH bond plays an important role in determining the overall reaction rates and yields. In the present study, the accuracy of different theoretical methods for prediction of IrH bond strengths has been examined on the basis of the previously reported IrH BDEs of 17 different complexes. Comparing the performance of different DFT functionals (e.g. B3LYP, TPSS, M06), different basis sets (including the different effective core potentials (ECP) on Ir and I atoms, and the total electron basis sets on the other atoms), and different solvation models (SMD, CPCM, and IEFPCM) in solution phase single point calculations, we found that the gas‐phase calculation with TPSS/(LanL2DZ: 6‐31G(d)) method is relatively more accurate than the other gas‐phase calculation methods, and can well simulate the IrH BDEs in low‐polarity solvents (such as chlorobenzene and dichloroethane). Finally, efforts were put in analyzing the structure‐activity relationships between the ligand structure (around Ir center) and the IrH BDEs. We wish the present study could benefit future studies on the Ir‐H complexes involved organic reactions.

Investigations on water condensation in the main steam pipe of a pressurized water reactor nuclear power station: Part II—Theoretical studies

A theoretical method based on heat transfer theories and numerical simulations was presented to predict the water condensation rates in the main steam pipe for the pressurized water reactor nuclear power station during the stable and starting up operation processes. Firstly, the complex heat transfer processes, including the steady heat transfer and transient heat transfer, in the main steam pipe were analyzed in detail. Then, the theoretical prediction methods were presented to compute the heat loss in the main steam pipe during stable and starting up operation processes, respectively. In order to verify the present theoretical method as well as visualize the flow fields in the main steam pipe, corresponding computational fluid dynamics computations based on conjugate heat transfer and equilibrium condensation model were performed. To validate the reliability of the present theoretical method, experiments (see Part I of this two-part paper) were carried out to measure the water condensation rates in the main steam pipe during the starting up and stable operation processes. The comparisons were made between the theoretical predictions, computational fluid dynamics computations, and the experimental tests. It shows that the present theoretical method has a good accuracy in predicting the water condensation rates for these two different operation conditions. For the startup process, the difference between the theoretical prediction and experimental data is only 0.16%. For the stable operation condition, the difference between the prediction and experimental data reaches 30.24% for the theoretical method whereas 23.55% for the computational fluid dynamics method.

Theoretical prediction of crystal structures of rubrene

We theoretically predict crystal structures and molecular arrangements for rubrene molecule using CONFLEX program and compare them with the experimental ones. The most, second-most, and fourth-most stable predicted crystal structures show good agreement with the triclinic, orthorhombic, and monoclinic polymorphs of rubrene, respectively. The change in molecular conformation is also predicted between crystalline and gas phases: the tetracene backbone takes flat conformation in crystalline phase as in the observed structure. Meanwhile, it is twisted in gas phase. The theoretical prediction method used in this work provides the successful results on the determination of the three kinds of crystal structures and molecular arrangements for rubrene molecule.

Remarkably fast coupled folding and binding of the intrinsically disordered transactivation domain of cMyb to CBP KIX.

Association rates for interactions between folded proteins have been investigated extensively, allowing the development of computational and theoretical prediction methods. Less is known about association rates for complexes where one or more partner is initially disordered, despite much speculation about how they may compare to those for folded proteins. We have attached a fluorophore to the N-terminus of the 25 amino acid cMyb peptide used previously in NMR and equilibrium studies (termed FITC-cMyb), and used this to monitor the kinetics of its interaction with the KIX protein. We have investigated the ionic strength and temperature dependence of the kinetics, and conclude that the association process is extremely fast, apparently exceeding the rates predicted by formulations applicable to interactions between pairs of folded proteins. This is despite the fact that not all collisions result in complex formation (there is an observable activation energy for the association process). We propose that this is partially a result of the disordered nature of the FITC-cMyb peptide itself.

A torsional hollow cylinder research apparatus for studying the permanent deformation characteristics of asphalt

A large, innovative torsional hollow cylinder apparatus has been designed and commissioned for research investigations on asphalt. It can apply the complex shear and normal stress paths experienced in a pavement under a moving wheel load. The resulting high-quality data on permanent shear and volumetric strains will assist with the development of theoretical methods for rut depth prediction and act as an accurate reference to assess the performance of simpler test equipment. A wide range of repeated load stress paths can be applied under constant temperature conditions. The 350 mm long test specimens have a wall thickness of 50 mm. They are produced by accurate coring from a roller compacted test slab of asphalt. A detailed description of the apparatus is presented along with some preliminary results.

Experimental validation of the novel theory explaining self-organization in porous anodic alumina films

The lack of a reliable method for theoretical prediction of nanoporous anodic alumina films obtained from non-familiar electrolytes prompted the search of a viable solution to this problem. The theory explaining the self-assembly mechanism was described in our preceding work. Here, the results of an extensive validation test are presented.

Accurate Prediction of AuP Bond Strengths by Density Functional Theory Methods

AbstractThe recent development of Au‐catalyzed reactions has greatly enriched the methods of organic synthesis. The phosphine or phosphate‐coordinated Au complexes have shown high efficiency in catalyzing various CC and CH activations. In many of these reactions, the AuP bond strength was found to play an important role in determining the catalytic efficiency. In the present study, the accuracy of different theoretical methods for prediction of AuP strengths has been examined on basis of the experimental enthalpy changes between different ClAu(PR3) and ClAu(THT) (THT=tetrahydrothiophene). By comparing the different DFT functionals (e.g. B3LYP, TPSS, M06), different basis sets (including the different effective core potentials on Au and the total electron basis sets on all other atoms), and different solution phase single point calculations, we found that the TPSS/(CPE‐121G+f:6‐311+G(d,p)(SMD)//TPSS/(CPE‐121G:6‐31G(d) (M1) method gives the best correlations with the available experimental results. Meanwhile, the calculations with B3LYP//TPSS and M05//TPSS also give comparable calculation results. Finally, the specified method (M1) is used to calculate the AuP bond dissociation enthalpies and energies of different ClAu(PR3)/ClAu(P(OR)3) complexes. By accurately reproducing the available experimental results, we believe that the method (M1) is reliable for the theoretical analysis of Au‐P systems.

Theoretical, numerical and experimental prediction of pump as turbine performance

Abstract Insufficient understanding of the correlation between pump and pump as turbine (PAT) performance is a major problem encountered in the PAT selection and design. Therefore, establishment of accurate PAT performance prediction methods is necessary. In this paper, theoretical analysis of the relationship between pump and PAT performance was first performed. A theoretical method of predicting PAT performance is developed using theoretical analysis and empirical correlation. In the next step, computational fluid dynamics (CFD) was adopted in the direct and reverse modes performance prediction of a single stage centrifugal pump. To give a more accurate CFD result, all domains within the PAT control volume were modeled and hexahedral structured mesh was generated during CFD simulation. Complete performance curves of its pump and turbine modes were acquired. To verify the accuracy of theoretical and numerical prediction methods, the pump was manufactured and tested on a PAT open test rig. Results comparison and discussion of the theoretical, numerical and some other methods with experimental data were carried out. Eventually, relatively accurate theoretical and numerical PAT performance prediction methods were developed.