Multiscale modelling of mesoscopic behaviour in soft matter systems

Soft matter modelling has a wide range of applications, such as polymer additive manufacturing, organics electronics, and biomolecular engineering. Many physical properties and phenomena of soft matter are determined by interactions and processes at a wide range of length and time scales. Therefore, it is challenging for theoretical models to simulate processes involving features from multiple scales. To reach the mesoscopic scales for soft matter behaviour, coarse-grained models have been developed to accelerate the atomistic models by projecting out the relevant degrees of freedom, allowing coverage of a wider range of scales. However, due to the lack of a formalism to capture the dynamics and anisotropy of the system, conventional coarse-grained model shows significant errors in dynamical properties and inconsistent soft matter behaviour. In this thesis, a generalised systematic formalism for coarse-graining is presented. The Mori-Zwanzig formalism provides a dynamically-guided projection to construct a mesoscopic system directly from the underlying microscopic system. Moreover, the Gay-Berne functional is introduced to describe the anisotropic effect of the pairwise interactions at mesoscopic level. The performance of the model is demonstrated by comparing it to other coarse-grained models using benzene as an example, which shows significant improvement in both static and dynamical properties. For application, crystallization of pentacene is studied by treating pentacene molecule as ellipsoidal particle. Furthermore, a modified atomistic model and a modified continuum model are employed to simulate mesosopic behaviour of polymers in electrospinning and electro-optical poling, demonstrating mesoscopic modelling from the atomistic and continuum limits

Phase Equilibria of Ethylene Copolymers in Sub- And Supercritical Fluids.

Phase equilibria of polyethylene and ethylene-copolymers in sub- and supercritical solutions are investigated in this work. Fluid-liquid and fluid-solid phase transitions data are measured for tetracontane, a prototype of linear polyethylene, in sub- and supercritical propane, poly(ethylene-co -hexene-1) in suband supercritical. propane and ethylene + 1-hexene mixture, and poly(ethylene-co-octene-1) in sub- and supercritical propane and ethylene. The experiments are carried out in a batch optical cell equipped with a transmitted-light probe. The experimental data are correlated and predicted using two equations of state derived from of the Statistical Associating Fluid Theory (SAFT). In the case of tetracontane + propane, increasing the tetracontane concentration and increasing pressure increase the fluid-solid transition temperature. Also, increasing the long-chain-n-alkane molecular weight increases the fluid-liquid transition pressure. The SAFT predictions are in a reasonable agreement with the experimental data for both fluid-liquid and fluid-solid transitions. For poly(ethylene-co-hexene-1), both poly(ethylene- co-hexene-1) concentration and molecular weight have a relatively weak effect on the phase behavior. The fluid-liquid pressure and fluid-solid temperature decrease as branch density increases. The fluid-liquid pressure depends strongly on the solvent type. When the ethylene concentration increases in poly(ethylene-co-hexene-1)+ethylene+hexene-1 mixtures, the fluid-liquid pressure increases, whereas the fluid-solid temperature decreases. For poly(ethylene-co-octene-1)+propane, the poly(ethylene- co-octene-1) concentration has a weak effect on both fluid-liquid and fluid-solid transitions in the range of 0.01 to 0.1 polymer fraction. Increasing the poly(ethylene-co-octene-1) molecular weight increases both fluid-liquid and fluid-solid transitions, whereas increasing the poly(ethylene-co-octene-1) branch density decreases both transitions in poly(ethylene-co-octene-1)+propane system. Only fluid-liquid, cloud-point pressure, is measured for poly(ethylene- co-octene-1)+ethylene. Furthermore, the fluid-liquid pressure strongly depends on molecular weight and short-chain branch density, but weakly on polymer concentration in the range from 0.05 to 0.15 polymer fraction. Poly(ethylene- co-octene-1) solutions in ethylene exhibit upper- and lower-critical-solution-temperature behavior only. Once again, SAFT calculations are in reasonable agreement with the experimental data

TOM: Why Isn’t Price Enough?

In an efficient market, differences in quality should be fully reflected in differences in price. This paper examines a highly active residential property market and verifies whether housing attributes can explain time on the market (TOM) in addition to prices. In contrast to the previous literature, only the price ratio and inflation factor are found to be critical in affecting TOM. An interpretation of the results is suggested, along with some directions for future research.TOM, price ratio, inflation factor, physical attribute, time aggregation

The regulation of the residential property market in Hong Kong : a study of government strategies and tools

published_or_final_versionPolitics and Public AdministrationMasterMaster of Public Administratio

Return migration and re-migration of Brazilian-Japanese and the role of identity in their migration

published_or_final_versionInternational and Public AffairsMasterMaster of International and Public Affair

Use of switching barriers to retain customers: Online retail stock traders in Hong Kong

Why some customers decide to stay withexisting service provider after having thought of switchinghas apparently not been examined adequately in extantresearch. The purpose of this research is to identifyfactors relevant to building constructs to representswitching barriers in online retail stock trading industryin Hong Kong. Review of extant literature, development ofa questionnaire and focus group interviews are the threeprincipal methods used for this research. Four factors thatare relevant for measuring switching barriers areidentified: two positive barriers involve service recoveryand trust and two negative barriers relate to higherswitching costs and lack of attractive alternatives

Increasing the civil service retirement age in Hong Kong : a study of policy processes and dynamics

published_or_final_versionPolitics and Public AdministrationMasterMaster of Public Administratio

Prevalence and heritability of handedness in a Hong Kong Chinese twin and singleton sample

Funding: Research Grants Council of the Hong Kong Special Administration Region (CUHK8/CRF/13G & C4054-17WF), by an internal grant entitled “Reading Development in Chinese and in English: Genetics and Neuroscience Correlates”(4930703) from The Chinese University of Hong Kong (CM is the PI on both grants), by a Hong Kong: Scotland Collaborative Research Partnership award from the Hong Kong Grants Council (CMis the PI for the Hong Kong side) and the Scottish Funding Council (SP is the PI for the Scotland side). It was additionally funded by an International Exchange Kan Tongo Po Visiting Fellowship to SP. SP is a Royal Society University Research Fellow.Background Left-handedness prevalence has been consistently reported at around 10% with heritability estimates at around 25%. Higher left-handedness prevalence has been reported in males and in twins. Lower prevalence has been reported in Asia, but it remains unclear whether this is due to biological or cultural factors. Most studies are based on samples with European ethnicities and using the preferred hand for writing as key assessment. Here, we investigated handedness in a sample of Chinese school children in Hong Kong, including 426 singletons and 205 pairs of twins, using both the Edinburgh Handedness Inventory and Pegboard Task. Results Based on a binary definition of writing hand, we found a higher prevalence of left-handedness (8%) than what was previously reported in Asian datasets. We found no evidence of increased left-handedness in twins, but our results were in line with previous findings showing that males have a higher tendency to be left-handed than females. Heritability was similar for both hand preference (21%) and laterality indexes (22%). However, these two handedness measures present only a moderate correlation (.42) and appear to be underpinned by different genetic factors. Conclusion In summary, we report new reference data for an ethnic group usually underrepresented in the literature. Our heritability analysis supports the idea that different measures will capture different components of handedness and, as a consequence, datasets assessed with heterogeneous criteria are not easily combined or compared.PreprintPublisher PDFPeer reviewe

Combining CD4 recovery and CD4: CD8 ratio restoration as an indicator for evaluating the outcome of continued antiretroviral therapy: an observational cohort study

Immune recovery following highly active antiretroviral therapy (HAART) is commonly assessed by the degree of CD4 reconstitution alone. In this study, we aimed to assess immune recovery by incorporating both CD4 count and CD4:CD8 ratio