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

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

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

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

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

The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.Comment: Major update of previous version. This is the reference document for LBNE science program and current status. Chapters 1, 3, and 9 provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess. 288 pages, 116 figure

Nitrous oxide as a function of oxygen and archaeal gene abundance in the North Pacific

Natural Environment Research Council (NERC) (NE/E01559X/1)