248 research outputs found
Computer simulation of liquid crystals
No full textMolecular dynamics simulation performed on modern computer workstations provides a powerful tool for the investigation of the static and dynamic characteristics of liquid crystal phases. In this thesis molecular dynamics computer simulations have been performed for two model systems. Simulations of 4,4'-di-n-pentyl-bibicyclo[2.2.2]octane demonstrate the growth of a structurally ordered phase directly from an isotropic fluid. This is the first time that this has been achieved for an atomistic model. The results demonstrate a strong coupling between orientational ordering and molecular shape, but indicate that the coupling between molecular conformational changes and molecular reorientation is relatively weak. Simulations have also been performed for a hybrid Gay-Berne/Lennard-Jones model resulting in thermodynamically stable nematic and smectic phases. Frank elastic constants have been calculated for the nematic phase formed by the hybrid model through analysis of the fluctuations of the nematic director, giving results comparable with those found experimentally. Work presented in this thesis also describes the parameterisation of the torsional potential of a fragment of a dimethyl siloxane polymer chain, disiloxane diol (HOMe(_2)Si)(_2)O, using ab initio quantum mechanical calculations
A Lennard-Jones Embedded-Atom Potential and Its Application to the Study of Melting
No full textThe nearest-neighbour Lennard-Jones potential from the embedded-atom method is extended to a form that includes more than nearest neighbours. The model has been applied to study melting with molecular dynamics. The calculated melting point, fractional volume change on melting, heat of fusion and linear coefficients of thermal expansion are in good agreement with experimental data. We have found that the second and third neighbours influence the melting point distinctly
Gas-liquid phase coexistence and finite-size effects in a two-dimensional Lennard-Jones system
No full textThe gas-liquid phase coexistence in a two-dimensional Lennard-Jones system is investigated using Maxwell construction method together with molecular dynamics simulations. The results of phase coexistence in different truncations of the potential are compared with data obtained from the literature, and the corresponding critical properties calculated. The crossover from Ising-like to mean field behavior is observed and confirmed as the temperature approaches the critical point from below. Performing simulations on systems with different sizes, we find that a finite size effect is more significant than those shown in most of the previous results, and a lower critical temperature is obtained when the full extent of this finite size effect is considered
The phase equilibrium in a Lennard-Jones fluid: Possible applications in astrophysics
No full textUsing standard thermodynamics and previous results of the author, this paper
aims to discuss the conditions for phase equilibrium in a Lennard-Jones
fluid. Possibilities for astrophysical applications of the obtained results
are discussed to some extent, including an unexpected application - in
physics of extremely dense matter concerning studies of neutron stars
Nonlocal heat transfer in two-dimensional Lennard–Jones crystal: Application of the molecular dynamics method
No full textAbstractThe redistribution of heat between two subsystems in the two-dimensional crystal consisting of particles interacting by means of the Lennard–Jones potential with argon parameters is considered in the frame of molecular dynamics method. Calculations of heat flux, its time derivative and kinetic temperature gradient showed that the characteristic relaxation times of the nonequilibrium flux within the nonlocal Cattaneo model at temperatures 10K<T<40K are very small (τv<10-11s) and, comparable with the time of phonons free path
Lennard-Jones quark matter and massive quark stars
No full textQuark clustering could occur in cold quark matter because of the strong coupling between quarks at realistic baryon densities of compact stars. Although one may still not be able to calculate this conjectured matter from the first principles, the intercluster interaction might be analogized to the interaction between inert molecules. Cold quark matter would then crystallize in a solid state if the intercluster potential is deep enough to trap the clusters in the wells. We apply the Lennard-Jones potential to describe the intercluster potential and derive the equations of state, which are stiffer than those derived in conventional models (e.g. MIT bag model). If quark stars are composed of the Lennard-Jones matter, they could have high maximum masses (> 2 M(circle dot)) as well as very low masses (< 10(-3) M(circle dot)). These features could be tested by observations.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000269136800007&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Astronomy & AstrophysicsSCI(E)21ARTICLE1L31-L3539
Renovation Process Challenges and Barriers
No full textThe implementation of Nearly Zero-Energy Buildings (NZEB) renovation packages in Europe needs to be accelerated to meet the decarbonisation goals. To achieve this level of performance, building renovation strategies should shift towards industrialised solutions that incorporate a multitude of passive and active components, increasing the complexity and cost of the execution. Moreover, it requires the involvement of different stakeholders of the building supply chain, resulting in additional difficulties in communication and coordination. To address this challenge, this study aims at mapping the renovation process and at addressing the respective bottlenecks. The objective is to identify the type of information that the stakeholders require during the different renovation phases and provide a framework to structure the workflow between all actors. By structuring the information along the renovation process phases, the different stakeholders can identify when the information can be provided and how the different types of information link to each other.Building Product InnovationDesign of Construtio
Binary Lennard-Jones atomic clusters: Structural features induced by large-sized atoms
No full textGlobal-minimum geometries of binary Lennard-Jones clusters (BLJN where N is the number of atoms) are previously elucidated when the size ratio of the large B atom to the small A atom is 1.05–1.3. In the present study, BLJ clusters for larger size ratios (1.4–2.0) are investigated to clarify the structural features. The heuristic method combined with geometrical perturbations and atom-type conversion is developed to search for the global minima of the BLJ clusters. In the lowest-energy geometries of the BLJ clusters (N ⩽ 50), A and B atoms form cores and outer shells, respectively. The existence of fairly large sized atoms induces complicated structural growth sequence patterns (including icosahedron, triangular orthobicupola, cuboctahedron, etc.). New global minima of BLJ59 for s = 1.15, BLJ68 for s = 1.15 and BLJ70 for s = 1.2 are also reported
The experience of patients and therapists in psychological therapy.
No full textPatients and therapists are rarely asked to describe
their subjective experiences as participants in psychological therapy. In this study 40 therapist/patient pairs
were asked to record, after each session of psychological
therapy, their subjective views concerning the helpful and
unhelpful events which took place, and also to evaluate
the helpfulness of those events and the session itself.
On completion of therapy. they described their views of
the helpful events in retrospect, and provided outcome
data. A total of 1076 events were collected from 399
therapy sessions. These were content-analysed using
Elliott's Therapeutic Impact Content Analysis System.
Results showed that during therapy. patients found the
most helpful aspects of therapy to include
reassurance/relief and problem solution events; whereas
therapists chose the gaining of cognitive and affective
insight. After the conclusion of therapy, both patients
and therapists also reported the importance of personal
contact. Although decreasing with time, the differences
between the two perspectives were highly significant.
More differences between the views were found when outcome
was poor, although the perspectives could be clearly
distinguished even when outcome was good.
It was suggested that different aspects of the therapeutic process have a different degree of salience for
therapists and patients, in that patients are most
interested in gaining a solution to their problems.
whereas therapists are more concerned with the aetiology
of the problem and its transformation through patient
insight. Despite these differences, however, most therapies seemed to be reasonably helpful. It was therefore
speculated that one mechanism of therapeutic intervention
may be the alternative way of making sense of the world
with which both patients and therapists are confronted in
therapy, suggested by the differing types of events which
the two groups of participants see as helpful
Nonlocal heat transfer in two-dimensional Lennard-Jones crystal: Application of the molecular dynamics method
No full text© 2016 The Author(s).The redistribution of heat between two subsystems in the two-dimensional crystal consisting of particles interacting by means of the Lennard-Jones potential with argon parameters is considered in the frame of molecular dynamics method. Calculations of heat flux, its time derivative and kinetic temperature gradient showed that the characteristic relaxation times of the nonequilibrium flux within the nonlocal Cattaneo model at temperatures 10. K. <. T<. 40. K are very small (τv<10-11s) and, comparable with the time of phonons free path
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