scholarly journals Photorealistic modelling of metals from first principles

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Gianluca Prandini ◽  
Gian-Marco Rignanese ◽  
Nicola Marzari
Keyword(s):  
First Principles ◽  
Noble Metals ◽  
Numerical Approach ◽  
Photorealistic Rendering ◽  
Gold Compounds ◽  
Different Types ◽  
Metallic Compounds ◽  
Ancient Times ◽  
Comprehensive Framework ◽  
Heterogeneous Alloys

AbstractThe colours of metals have attracted the attention of humanity since ancient times, and coloured metals, in particular gold compounds, have been employed for tools and objects symbolizing the aesthetics of power. In this work, we develop a comprehensive framework to obtain the reflectivity and colour of metals, and show that the trends in optical properties and the colours can be predicted by straightforward first-principles techniques based on standard approximations. We apply this to predict reflectivity and colour of several elemental metals and of different types of metallic compounds (intermetallics, solid solutions and heterogeneous alloys), considering mainly binary alloys based on noble metals. We validate the numerical approach through an extensive comparison with experimental data and the photorealistic rendering of known coloured metals.

Adsorption of the Gas Molecules (NH3, C2H6O, C3H6O, CO, H2S) on noble metal (Ag, Au, Pt, Pd, Ru)–Doped MoSe2 Monolayer: A First-Principles Study

2021 ◽  
Author(s):  
Lanjuan Zhou ◽  
Sujing Yu ◽  
Yan Yang ◽  
Qi Li ◽  
Tingting Li ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Noble Metal ◽  
First Principles ◽  
Density Functional ◽  
Noble Metals ◽  
Gas Sensing ◽  
Functional Theory ◽  
First Principles Study ◽  
Gas Molecules ◽  
Sensing Performance

In this paper, the effects of five noble metals (Au, Pt, Pd, Ag, Ru) doped MoSe2 on improving gas sensing performance were predicted through density functional theory (DFT) based on...

Assessment of flight dynamic and static aeroelastic behaviors for jet transport aircraft subjected to instantaneous high g-loads

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yonghu Wang ◽  
Ray C. Chang ◽  
Wei Jiang
Keyword(s):  
Numerical Approach ◽  
Future Research ◽  
Inspection Method ◽  
Content Type ◽  
Flight Data ◽  
Transport Aircraft ◽  
Different Types ◽  
Static Aeroelasticity ◽  
Safety Operation ◽  
Structural Inspection

Purpose The purpose of this paper is to present a quick inspection method based on the post-flight data to examine static aeroelastic behavior for transport aircraft subjected to instantaneous high g-loads. Design/methodology/approach In the present study, the numerical approach of static aeroelasticity and two verified cases will be presented. The non-linear unsteady aerodynamic models are established through flight data mining and the fuzzy-logic modeling of artificial intelligence techniques based on post-flight data. The first and second derivatives of flight dynamic and static aeroelastic behaviors, respectively, are then estimated by using these aerodynamic models. Findings The flight dynamic and static aeroelastic behaviors with instantaneous high g-load for the two transports will be analyzed and make a comparison study. The circumstance of turbulence encounter of the new twin-jet is much serious than that of four-jet transport aircraft, but the characteristic of stability and controllability for the new twin-jet is better than those of the four-jet transport aircraft; the new twin-jet transport is also shown to have very small aeroelastic effects. The static aeroelastic behaviors for the two different types can be assessed by using this method. Practical implications As the present study uses the flight data stored in a quick access recorder, an intrusive structural inspection of the post-flight can be avoided. A tentative conclusion is to prove that this method can be adapted to examine the static aeroelastic effects for transport aircraft of different weights, different sizes and different service years in tracking static aeroelastic behavior of existing different types of aircraft. In future research, one can consider to have more issues of other types of aircraft with high composite structure weight. Originality/value This method can be used to assist airlines to monitor the variations of flight dynamic and static aeroelastic behaviors as a complementary tool for management to improve aviation safety, operation and operational efficiency.

scholarly journals Influence of misalignments on the performance of externally occulted solar coronagraphs

2018 ◽  
Vol 612 ◽  
pp. A82 ◽  
Author(s):  
S. V. Shestov ◽  
A. N. Zhukov
Keyword(s):  
European Space Agency ◽  
Numerical Approach ◽  
Primary Objective ◽  
Optical Elements ◽  
Trade Off ◽  
Space Agency ◽  
Minimal Height ◽  
Different Types ◽  
Points Of View ◽  
Quantitative Influence

Context. The ASPIICS instrument is a novel externally occulted coronagraph that will be launched on board the PROBA-3 mission of the European Space Agency. The external occulter will be placed on one satellite ~150 m ahead of the second satellite that will carry an optical instrument. During 6 h out of 19.38 h of orbit, the satellites will fly in a precise (accuracy around a few millimeters) formation, constituting a giant externally occulted coronagraph. The large distance between the external occulter and the primary objective will allow observations of the white-light solar corona starting from extremely low heights ~ 1.1R⊙. Aims. We intend to analyze influence of shifts of the satellites and misalignments of optical elements on the ASPIICS performance in terms of diffracted light. Based on the quantitative influence of misalignments on diffracted light, we provide a recipe for choosing the size of the internal occulter (IO) to achieve a trade-off between the minimal height of observations and sustainability to possible misalignments. Methods. We considered different types of misalignments and analyzed their influence from optical and computational points of view. We implemented a numerical model of the diffracted light and its propagation through the optical system and computed intensities of diffracted light throughout the instrument. Our numerical approach is based on a model from the literature that considered the axisymmetrical case. Here we extend the model to include nonsymmetrical cases and possible misalignments. Results. The numerical computations fully confirm the main properties of the diffracted light that we obtained from semi-analytical consideration. We obtain that relative influences of various misalignments are significantly different. We show that the internal occulter with RIO = 1.694 mm = 1.1R⊙ is large enough to compensate possible misalignments expected to occur in PROBA-3/ASPIICS. Besides that we show that apodizing the edge of the internal occulter leads to additional suppression of the diffracted light. Conclusions. We conclude that the most important misalignment is the tilt of the telescope with respect to the line connecting the center of the external occulter and the entrance aperture. Special care should be taken to co-align the external occulter and the coronagraph, which means co-aligning the diffraction fringe from the external occulter and the internal occulter. We suggest that the best orientation strategy is to point the coronagraph to the center of the external occulter.

Talent management in government organizations: identification of challenges and ranking the solutions to address them

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohammad-Hadi Sehatpour ◽  
Behnam Abedin ◽  
Aliyeh Kazemi
Keyword(s):  
Human Resources ◽  
Talent Management ◽  
Successful Implementation ◽  
Senior Managers ◽  
Related Factors ◽  
Content Type ◽  
Government Organizations ◽  
Top Managers ◽  
Different Types ◽  
Comprehensive Framework

PurposeThe main aim of this research is to rank and prioritize the solutions to address the challenges for the successful implementation of talent management (TM) in government banks in Iran.Design/methodology/approachThis paper has identified the challenges of TM implementation in government banks and proposed the solutions to address these challenges through a review of the extant literature. The identified challenges and solutions were ranked using two multi-criteria decision-making (MCDM) methods called PROMETHEE and VIKOR based on the insights from 20 senior managers of government banks in Iran.FindingsThe challenges and solutions were categorized into cultural, managerial, human resources and environmental-related factors. “Building culture of TM in organizations”, “making TM as an ongoing process in organizations”, “commitment of senior managers to TM process”, “managing TM pipeline” and “focusing on meritocracy in recruitment and selections” were ranked as the top solutions to address cultural, managerial, human resources and environmental challenges, respectively.Research limitations/implicationsThe findings can provide a comprehensive view of different types of challenges and solutions in the TM process for government organizations and institutions. It also provides helpful insights for top managers to define their organizations' strategies effectively and to implement the TM process by ranking and prioritizing the solutions to address their challenges.Originality/valueThe main contribution of this study is to develop a comprehensive framework in which, identification of different types of challenges in the implementation of TM processes can be addressed and the approaches to remove or mitigate the effects of these challenges are ranked by using two well-established MCDM techniques.

scholarly journals Chocolate, “Food of the Gods”: History, Science, and Human Health

2019 ◽  
Vol 16 (24) ◽  
pp. 4960 ◽  
Author(s):  
Maria Teresa Montagna ◽  
Giusy Diella ◽  
Francesco Triggiano ◽  
Giusy Rita Caponio ◽  
Osvalda De Giglio ◽  
...  
Keyword(s):  
Food Industry ◽  
Epidemiologic Studies ◽  
Hot Water ◽  
Potential Health ◽  
Oxidation Processes ◽  
Daily Diet ◽  
Different Types ◽  
Ancient Times ◽  
Regulation Of Blood Pressure

Chocolate is well known for its fine flavor, and its history began in ancient times, when the Maya considered chocolate (a cocoa drink prepared with hot water) the “Food of the Gods”. The food industry produces many different types of chocolate: in recent years, dark chocolate, in particular, has gained great popularity. Interest in chocolate has grown, owing to its physiological and potential health effects, such as regulation of blood pressure, insulin levels, vascular functions, oxidation processes, prebiotic effects, glucose homeostasis, and lipid metabolism. However, further translational and epidemiologic studies are needed to confirm available results and to evaluate other possible effects related to the consumption of cocoa and chocolate, verifying in humans the effects hitherto demonstrated only in vitro, and suggesting how best to consume (in terms of dose, mode, and time) chocolate in the daily diet.

The adsorption of nitrogen oxides on noble metal-doped graphene: The first-principles study

2019 ◽  
Vol 33 (04) ◽  
pp. 1950044 ◽  
Author(s):  
X. Jia ◽  
L. An
Keyword(s):  
Gas Sensors ◽  
First Principles ◽  
Density Functional ◽  
Noble Metals ◽  
Functional Theory ◽  
Adsorption Effect ◽  
Charge Densities ◽  
Adsorption Of Nitrogen ◽  
Doped Graphene ◽  
Metal Doped

The first-principles method based on density functional theory has been used to investigate the adsorption performance of NO/NO2 molecules on intrinsic, Ag-doped, Pt-doped and Au-doped graphene. Results show that graphene doped with Ag/Pt/Au has shorter final adsorption distance, larger adsorption energy and charge transfer amount with NO/NO2 molecules than intrinsic graphene, and the charge densities of doped graphene and NO/NO2 molecules overlap effectively. Therefore, doping graphene with noble metals can greatly enhance the adsorption between graphene and NO/NO2 molecules. Analysis also reveals that Au-doped graphene has the strongest adsorption effect on NO/NO2 molecules, followed by Ag-doped graphene, while Pt-doped graphene has the weakest role on the adsorption of NO/NO2 molecules. The work conducted in this research provides a theoretical guidance for the application of NO/NO2 gas sensors based on graphene.

scholarly journals DFT calculations of the structure and stability of copper clusters on MoS2

2020 ◽  
Vol 11 ◽  
pp. 391-406
Author(s):  
Cara-Lena Nies ◽  
Michael Nolan
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Noble Metals ◽  
Semiconductor Device ◽  
2D Materials ◽  
Single Atom ◽  
Copper Binding ◽  
Adsorption Sites ◽  
Potential Applications ◽  
Low Dimensional

Layered materials, such as MoS2, are being intensely studied due to their interesting properties and wide variety of potential applications. These materials are also interesting as supports for low-dimensional metals for catalysis, while recent work has shown increased interest in using 2D materials in the electronics industry as a Cu diffusion barrier in semiconductor device interconnects. The interaction between different metal structures and MoS2 monolayers is therefore of significant importance and first-principles simulations can probe aspects of this interaction not easily accessible to experiment. Previous theoretical studies have focused particularly on the adsorption of a range of metallic elements, including first-row transition metals, as well as Ag and Au. However, most studies have examined single-atom adsorption or adsorbed nanoparticles of noble metals. This means there is a knowledge gap in terms of thin film nucleation on 2D materials. To begin addressing this issue, we present in this paper a first-principles density functional theory (DFT) study of the adsorption of small Cu n (n = 1–4) structures on 2D MoS2 as a model system. We find on a perfect MoS2 monolayer that a single Cu atom prefers an adsorption site above the Mo atom. With increasing nanocluster size the nanocluster binds more strongly when Cu atoms adsorb atop the S atoms. Stability is driven by the number of Cu–Cu interactions and the distance between adsorption sites, with no obvious preference towards 2D or 3D structures. The introduction of a single S vacancy in the monolayer enhances the copper binding energy, although some Cu n nanoclusters are actually unstable. The effect of the vacancy is localised around the vacancy site. Finally, on both the pristine and the defective MoS2 monolayer, the density-of-states analysis shows that the adsorption of Cu introduces new electronic states as a result of partial Cu oxidation, but the metallic character of Cu nanoclusters is preserved.

The Evolving Basis for the Design of Light Gauge Steel Systems

2020 ◽  
Vol 20 (13) ◽  
pp. 2041008
Author(s):  
Pinelopi Kyvelou ◽  
David A. Nethercot ◽  
Nicolas Hadjipantelis ◽  
Constantinos Kyprianou ◽  
Leroy Gardner
Keyword(s):  
Numerical Models ◽  
Numerical Approach ◽  
Superior Performance ◽  
Exact Nature ◽  
Beneficial Effects ◽  
Plate Elements ◽  
Different Types ◽  
Test Behavior ◽  
General Basis ◽  
The Many

The importance of allowing for the many different types of structural interaction that have an effect on the performance of light gauge members when used in practical situations is emphasized. A distinction is drawn between internal interactions involving the various plate elements of the steel profiles and external interactions involving the other components in the system. Although full-scale testing of representative systems can capture this behavior, the costs involved make this an impractical general basis for design; codified methods generally consider only isolated plates within members and isolated members within systems, thereby neglecting the potentially beneficial effects of both forms of interaction. Properly used, modern methods of numerical analysis offer the potential to systematically allow for both forms of interaction — provided the numerical models used have been adequately validated against suitable tests. The use of such an approach is explained and illustrated for three commonly used structural systems: roof purlins, floor beams, and columns in stud walls. In each case, it is shown that, provided sufficient care is taken, the numerical approach can yield accurate predictions of the observed test behavior. The subsequently generated large portfolio of numerical results can then provide clear insights into the exact nature of the various interactions and, thus, form the basis for more realistic design approaches that are both more accurate in their predictions and which lead to more economic designs. Building on this, modifying existing arrangements so as to yield superior performance through specific modifications is now possible. Two such examples, one in which improved interconnection between the components in a system is investigated and a second in which prestressing is shown to provide substantial enhancement for relatively small and simple changes, are presented.

Italian travertine in building heritage

2020 ◽  
Author(s):  
Rossana Bellopede ◽  
Paola Marini
Keyword(s):  
Roman Empire ◽  
Los Angeles ◽  
Urban Areas ◽  
Art Museum ◽  
Building Construction ◽  
Thermal Bath ◽  
Petrographic Analysis ◽  
Artificial Ageing ◽  
Different Types ◽  
Ancient Times

<p>Travertine is one of the most common stone for building construction used in many countries starting from ancient times. It was one of the favorite stones of the Roman empire: the main example is  the Colosseum in Rome. All over the world travertine is found in important monuments and in various modern structures: for example, the Conservation Center of the J. Paul Getty museum in Los Angeles and Jiangsu Provincial Art Museum in Nanjing, China and it is very appreciated and requested in the construction of recent thermal bath. In addition to Italian travertine, the other famous types of this stone are known throughout Europe (i.e. Germany, Hungary) and Asia (i.e. Turkey, China, Iran).</p><p>Travertine is considered a durable stone despite the weathering caused by air pollution. It is observed in urban areas that the facades may be covered with a black crust where gypsum and calcite are the main minerals .</p><p>Nine different types of travertine coming from Tuscany and Umbria (Italy) have been investigated. Petrographic analysis, physical mechanical and artificial ageing test have been performed.</p><p>Among the different kind of travertine different texture can be identified as: not laminated, laminated: laminated with sub parallel sheets, laminated with concentric sheets. The various travertine depositional structures have been in compared to the different answer to artificial ageing. Finally, it can be asserted that the durability is not connected only with porosity and the analysis of the complex texture of this kind of stone cannot give a simple solution related to its durability.</p><p> </p>

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