Perspectives on the simulation of micro gas and nano liquid flows

Micro- and nano-scale fluid systems can behave very differently from their macro-scale counterparts. Remarkably, there is no sufficiently accurate, computationally efficient, and — most importantly — generally agreed fluid dynamic model that encapsulates all of this important behaviour. The only thing that researchers can agree on is that the conventional Navier-Stokes fluid equations are unable to capture the unique complexity of these often locally non-thermodynamic-equilibrium flows. Here, we outline recent work on developing and exploring new models for these flows, highlighting, in particular, slip flow as a quintessential non-equilibrium (or sub-continuum) phenomenon. We describe the successes and failures of various hydrodynamic and molecular models in capturing the non-equilibrium flow physics in current test applications in micro and nano engineering, including the aerodynamic drag of a sphere in a rarefied gas, and the flow of water along carbon nanotubes

Molecular dynamics simulations of liquid flow in and around carbon nanotubes

Using recently-developed fluid state controllers [1], we apply continuum fluid boundary conditions to molecular dynamics (MD) simulations of liquid argon flow past a carbon nanotube (CNT) and through a CNT membrane. Advantages of this method are that it: is not dependent on periodic boundary conditions; can accurately generate fluid transport without any geometrical constraints; and is capable of performing as an essential part of a hybrid continuum/atomistic technique. In our simulations, a pressure gradient is applied across a CNT membrane by controlling the densities of two reservoirs located either side of the membrane. Fluid velocity and density distributions are reported and compared to other published data where possible

MD boundary conditions for pressure gradient flows : nano-mixing and nano-droplet deformation in extensional flows

We present new algorithms for simulating pressure gradient flows in molecular dynamics (MD) simulations. Nano-channel inlet and outlet non-periodic boundary conditions are implemented using hydrodynamic state reservoirs and flux boundary models at arbitrary boundaries of the domain geometry. We demonstrate the new method in a complex nano-mixer configuration and for droplet deformation in extensional flow channels. The technique which we propose is applicable to any complex nano-channel configuration, and may serve as a useful tool in engineering design of nano-scale applications

Water transport through (7,7) carbon nanotubes of different lengths using molecular dynamics

Non-equilibrium molecular dynamics simulations are used to investigate water transport through (7,7) CNTs, examining how changing the CNT length affects the internal flow dynamics. Pressure-driven water flow through CNT lengths ranging from 2.5 to 50 nm is simulated. We show that under the same applied pressure difference an increase in CNT length has a negligible effect on the resulting mass flow rate and fluid flow velocity. Flow enhancements over hydrodynamic expectations are directly proportional to the CNT length. Axial profiles of fluid properties demonstrate that entrance and exit effects are significant in the transport of water along CNTs. Large viscous losses in these entrance/exit regions lead into central “developed” regions in longer CNTs where the flow is effectively frictionless

Use and Application of Federal Advisory Committee Act (FACA) Database

University experts can offer uniquely valuable insights for informing policy based on expertise they develop through research. The application of knowledge through public service is an important and understudied mechanism for translating academic expertise to government and other communities. Today universities encourage researchers to engage in public service, and often they actively provide institutional support to create a culture and environment where such pro bono work is regarded as an important activity by the research community. Yet the question remains as to whether or not a systematic mechanism exists to track, record, and measure the value of university expertise influencing policy within the context of research. We explore a useful but underutilized administrative data source, the Federal Advisory Committee Act (FACA) database, with an eye towards linking the federal service data to other sources in order to measure research impact in a sociopolitical setting. This publicly available dataset contains rich information on federal advisory committees that play an important role in shaping national programs and policies. Each year an average of 900 advisory committees with more than 60,000 members have provided either policy or grant review advice in 40 different issue areas. Our exploratory findings suggest a steady increase of academics in federal service, the different level of federal service contribution by universities, and the association between federal service and university R&D spending. We also discuss the importance of data cleaning when using administrative data for research and data linkage methods when linking federal service data to university research spending records

The Role of Lifetime Exposures across Cognitive Domains in Barbados Using Data From the SABE Study

This study characterized the effects of aging on individual cognitive domains and how sex, job type, and years of education alter the age effect on older adults from Barbados. This was an analysis of the cross-sectional data collected as part of the SABE Study (Health, Well-being and Ageing) in 2006. The loss of a single point in each of the individual cognitive domains assessed using the mini-mental state exam served as dependent variables. Independent variables included age, sex, years of education, job type, and the interactions with age in a series of logistic regression analyses. The study aimed to identify which factors altered the effect of age on cognitive performance and which directly affected performance. Results demonstrated that the effect of age differed across the cognitive domains. In addition, sex, education, and job type all differentially affected cognitive performance in an additive, formative manner. The most consistent finding was that high years of education coupled with employment requiring mostly mental effort was the best combination for maintaining high levels of cognitive performance in late life. The results demonstrate that adverse age effects on cognitive performance may be minimized or delayed through modifiable lifetime exposures in the people of Barbados

Ready to Roll: New Zealand wheelchair users' preparedness for emergencies.

Background: People with disabilities are disproportionally affected by emergency situations compared to the general population, with higher mortality rates and increased vulnerability to disrupted infrastructure and services. The 2010-2011 Canterbury earthquakes highlighted issues regarding personal and organisational preparedness for people with disabilities in New Zealand (NZ). The Ready to Roll (RTR) study investigates issues of emergency preparedness by wheelchair users in NZ, seeks their opinions about a proposed register of vulnerable people for use in emergencies, and also surveys information communication technology (ICT) use patterns amongst this group to determine whether such technology could augment emergency response planning. Aims: This study focused on four key questions: 1. What is the current state of emergency preparedness amongst NZ wheelchair users? 2. What are their perceived barriers to emergency preparedness? 3. What is the level of support for, and concerns about, a Disabled Persons Emergency Response Register in this group? 4. What types of ICT, able to support emergency planning and response, are currently being accessed and used by this group? Methods: A nationwide survey of adult, community dwelling wheelchair users was conducted using SurveyMonkey™ or a postal questionnaire. Survey questions were developed through a process of engagement with disabled people. A snowball sampling recruitment method using Disabled Persons Organisations and disability service providers was used to disseminate the survey. Results: The key findings from the 101 people who completed the survey revealed less than 30% had an emergency plan and less than 20% were planning for their disability related needs. Personal preparedness barriers identified included the need for assistance from someone else to carry out planning activities (n = 50), lack of disability relevant information (n = 37), limited accessibility to information (n = 24), cost (n = 23), and being unable to stockpile medications (n = 20) or consumables (n 11). Ninety participants supported the concept of a Disabled Persons Emergency Response Register but fewer (n = 76) thought they would personally participate in such an initiative. The participants of this study reported high levels of internet engagement including internet searches, emails and downloading/installing software (n= 91), online financial transactions (n = 84) and using social media (n = 80). Seventy nine participants were currently smart phone users. Conclusions RTR participants reported much lower levels of personal emergency preparedness and a higher incidence of barriers to preparedness than that reported for the general NZ population, a concerning finding given the increased vulnerability of people with disabilities in emergencies. Findings of this study indicated that adjuncts to assist emergency planners respond to the needs of people with disabilities such as a register system or ICT enabled tools could be useful, well utilised and accessible to this group of participants. However the small scale and limitations of the study produce an inability to generalise findings beyond participants to people with disabilities more broadly. As such, further research into the issues raised by this and previous studies is recommended to improve the personal and organisational emergency preparedness for disabled New Zealanders

Co-evolved genetic program for stock market trading

This thesis compares the profitability of trading rules evolved by a single population genetic program (GP), a co-operative co-evolved GP, and a competitive co-evolved GP. Profitability was determined by trading thirteen listed shares on the Johannesburg Stock Exchange (JSE) over a period of April 2003 to June 2008. The GP parameters were optimised using a response surface methodology known as factorial design. A compound excess return over the buy-and-hold strategy was determined as the preferred fitness function via an empirical process. Various selection strategies to select individuals for the crossover and mutation operators were compared. It was found rank selection was the preferred strategy. The optimised GPs were tested on market data using a real world fee structure. The results were compared to a buy-and-hold strategy and a random-walk. The results of this thesis show that the co-operative co-evolved GP generates trading rules that perform significantly worse than a single population GP and a competitively co-evolved GP. The results also show that a competitive co-evolved GP and the single population GP produce similar trading rules. The evolved trading rules significantly outperform the buy-and-hold strategy when the market, including fees, was trending downwards. No significant difference was found between the buy-and-hold strategy, the competitive co-evolved GP, and single population GP when the market (including fees) was trending upwards.Dissertation (MSc)--University of Pretoria, 2018.Computer ScienceMScUnrestricte

The global and regional impacts of climate change under Representative Concentration Pathway forcings and Shared Socioeconomic Pathway socioeconomic scenarios

This paper presents an evaluation of the global and regional consequences of climate change for heat extremes, water resources, river and coastal flooding, droughts, agriculture and energy use. It presents change in hazard and resource base under different rates of climate change (Representative Concentration Pathways: RCP), and socio-economic impacts are estimated for each combination of RCP and Shared Socioeconomic Pathway. Uncertainty in the regional pattern of climate change is characterised by CMIP5 climate model projections. The analysis adopts a novel approach using relationships between level of warming and impact to rapidly estimate impacts under any climate forcing. The projections provided here can be used to inform assessments of the implications of climate change. At the global scale all the consequences of climate change considered here are adverse, with large increases under the highest rates of warming. Under the highest forcing the global average annual chance of a major heatwave increases from 5% now to 97% in 2100, the average proportion of time in drought increases from 7% to 27%, and the average chance of the current 50-year flood increases from 2% to 7%. The socio-economic impacts of these climate changes are determined by socio-economic scenario. There is variability in impact across regions, reflecting variability in projected changes in precipitation and temperature. The range in the estimated impacts can be large, due to uncertainty in future emissions and future socio-economic conditions and scientific uncertainty in how climate changes in response to future emissions. For the temperature-based indicators, the largest source of scientific uncertainty is in the estimated magnitude of equilibrium climate sensitivity, but for the indicators determined by precipitation the largest source is in the estimated spatial and seasonal pattern of changes in precipitation. By 2100 the range across socio-economic scenario is often greater than the range across the forcing levels

A protocol for a scoping review of equity measurement in mental health care for children and youth

Background: Mental health (MH) problems are among the most important causes of morbidity and mortality for children and youth. Problems of lack of equity in child and youth MH services (CYMHS)-including, but not limited to, problems in inaccessibility and quality of services-are widespread. Characterizing the nature of equity in CYMHS is an ongoing challenge because the field lacks a consistent approach to conceptualizing equity. We will conduct a scoping review of how equity in MH services for children and youth has been defined, operationalized, and measured. Our objectives are to discover: (1) What conceptual definitions of equity are used by observational studies of CYMHS?; (2) What service characteristics of CYMHS care do indices of equity cover?; (3) What population dimensions have been used to operationalize equity?; (4) What statistical constructs have been used in indices that measure CYMHS equity?; and (5) What were the numerical values of those indices? Methods: The following databases will be searched: Medline, Embase, PsycINFO, Cochrane Controlled Register of Trials, CINAHL, EconLit, and Sociological Abstracts. Searches will be conducted from the date of inception to the end of the last full calendar year (December 2019). Studies will be included if they include an evaluation of a mental health service for children or youth (defined as those under 19 years of age) and which quantify variation in some aspect of child or youth mental health services (e.g., accessibility, volume, duration, or quality) as a function of socio-demographic and/or geographic variables. Study selection will occur over two stages. Stage one will select articles based on title and abstract using the liberal-accelerated method. Stage two will review the full texts of selected titles. Two reviewers will work independently on full-text reviewing, with each study screened twice using pre-specified eligibility criteria. One reviewer will chart study characteristics and indices to be verified by a second reviewer. Reviewers will resolve full-text screening and data extraction disagreements through discussion. Synthesis of the collected data will focus on compiling and mapping the types and characteristics of the indices used to evaluate MH services equity. Discussion: The planned, systematic scoping review will survey the literature regarding how equity in MH services for children and youth has been operationalized and help inform future studies of equity in CYMHS. Systematic review registration: Open Science Foundation ID SYSR-D-19-00371, https://osf.io/58srv/