scholarly journals Approaches to modelling the shape of nanocrystals

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Christina Boukouvala ◽  
Joshua Daniel ◽  
Emilie Ringe

AbstractUnlike in the bulk, at the nanoscale shape dictates properties. The imperative to understand and predict nanocrystal shape led to the development, over several decades, of a large number of mathematical models and, later, their software implementations. In this review, the various mathematical approaches used to model crystal shapes are first overviewed, from the century-old Wulff construction to the year-old (2020) approach to describe supported twinned nanocrystals, together with a discussion and disambiguation of the terminology. Then, the multitude of published software implementations of these Wulff-based shape models are described in detail, describing their technical aspects, advantages and limitations. Finally, a discussion of the scientific applications of shape models to either predict shape or use shape to deduce thermodynamic and/or kinetic parameters is offered, followed by a conclusion. This review provides a guide for scientists looking to model crystal shape in a field where ever-increasingly complex crystal shapes and compositions are required to fulfil the exciting promises of nanotechnology.

Author(s):  
Johann U. Zimmermann ◽  
Siegmar Haasis ◽  
Fred J. A. M. van Houten

The bi-directional communication of CAD programs with subsequent applications such as process planning remains a key challenge in design-for-the-lifecycle. While it seems sensible that individual applications use their own collection of feature types and thereby allow users to have their specific perspective of the product, it is still difficult to automatically close the gap between the variety of applications. Universal Linking of Engineering Objects (ULEO) targets this concern. It is general enough to facilitate informational integration of the applications along the process chain. This paper examines a number of scenarios for exploiting ULEO’s benefits in the field of automotive development and reports on the associated prototypical software implementations. Principle alternatives and technical aspects relevant for applying ULEO are discussed in some detail beforehand.


Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 925 ◽  
Author(s):  
Victor Ciribeni ◽  
Regina Bertero ◽  
Andrea Tello ◽  
Matías Puerta ◽  
Enzo Avellá ◽  
...  

Over the last decades, several reliable mathematical models have been developed for simulating ore comminution processes and determining the Work Index. Since Fred Chester Bond developed the Work Index standard procedure in 1961, numerous attempts have been made to find simpler, faster, and economically more advantageous alternative tests. In this paper, a Bond test simulation based on the cumulative kinetic model (CKM) has been checked on a spreadsheet. The research has been accomplished by conventionally determining the kinetic parameters for some Ag and Au ores and for three pure minerals and one rock that are common constituents of the gangue rock. Analysis of the results obtained allowed to develop a simplified procedure for calculating the kinetic parameters and their application to Work Index determination through simulation.


2011 ◽  
Vol 50 (8) ◽  
pp. 1740-1755 ◽  
Author(s):  
Krzysztof M. Markowicz ◽  
Marcin L. Witek

AbstractThe aim of this study is to investigate the sensitivity of radiative-forcing computations to various contrail crystal shape models. Contrail optical properties in the shortwave and longwave ranges are derived using a ray-tracing geometric method and the discrete dipole approximation method, respectively. Both methods present good correspondence of the single-scattering albedo and the asymmetry parameter in a transition range (3–8 μm). There are substantial differences in single-scattering properties among 10 crystal models investigated here (e.g., hexagonal columns and plates with different aspect ratios, and spherical particles). The single-scattering albedo and the asymmetry parameter both vary by up to 0.1 among various crystal shapes. The computed single-scattering properties are incorporated in the moderate-resolution atmospheric radiance and transmittance model (MODTRAN) radiative transfer code to simulate solar and infrared fluxes at the top of the atmosphere. Particle shapes have a strong impact on the contrail radiative forcing in both the shortwave and longwave ranges. The differences in the net radiative forcing among optical models reach 50% with respect to the mean model value. The hexagonal-column and hexagonal-plate particles show the smallest net radiative forcing, and the largest forcing is obtained for the spheres. The balance between the shortwave forcing and longwave forcing is highly sensitive with respect to the assumed crystal shape and may even change the sign of the net forcing. The optical depth at which the mean diurnal radiative forcing changes sign from positive to negative varies from 4.5 to 10 for a surface albedo of 0.2 and from 2 to 6.5 for a surface albedo of 0.05. Contrails are probably never that optically thick (except for some aged contrail cirrus), however, and so will not have a cooling effect on climate.


CrystEngComm ◽  
2021 ◽  
Vol 23 (6) ◽  
pp. 1423-1428
Author(s):  
Daichi Yosho ◽  
Yuriko Matsuo ◽  
Akira Kusaba ◽  
Pawel Kempisty ◽  
Yoshihiro Kangawa ◽  
...  

An ab initio-based approach is used to study the facet stability of GaN during THVPE. The surface phase diagrams as functions of temperature and pressure are determined. Wulff construction is used to predict the crystal shape.


Author(s):  
P. Huhtanen ◽  
U. Kukkonen

Potentially digestible fibre leaves the rumen either by enzymatic breakdown or by passage to the lower tract. The digestibility of potentially digestible fibre is a function of the rate at which fibre is digested and its retention time in the rumen. The procedures used for estimating the rate of fibre digestion (kd) and the rate of passage of feed particles (kp) are extremely variable. The estimates for kdand kpderived by using different procedures can have a large effect on the fibre digestibility calculated from kinetic parameters of fibre. The objective of the present study was to evaluate the different methods in estimating the kinetic parameters of mathematical models that will describe cell wall digestion in the rumen.


2021 ◽  
Vol 346 ◽  
pp. 03066
Author(s):  
Alexander Romanov ◽  
Alexey Shchenyatsky ◽  
Oxana Zorina

The study object - technological process of interference fits assembling is identified, the scheme with oil supply from the end face is adopted as the technological scheme. Technological pressing equipment is considered, its applicability for hydropress assembling is evaluated. The main aspects of hydropress joints assembling on a base of mechatronic press are established: increasing of assembling performance, its stability. Mathematical models and an algorithm that regulate the process of liquid friction and formation of an oil layer between the contacting surfaces of joint mating parts are developed. The basic requirements for the regulation channels of control system that ensure the quality of hydropress fits during automated assembling are established.


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