132 research outputs found

    Radiotherapy Treatment Planning With Dose Volume Constraints By Linear Programming Approach

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    Optimization has become an important tool in treatment planning for cancer radiation therapy.  It may be used to determine beam weights, beam directions, and appropriate use of beam modifiers such as wedges and blocks, with the aim of delivering a required dose to the tumor while sparing nearby critical structures and normal tissue. Linear programming formulations are a core computation in many approaches to treatment planning, because of the abundance of highly developed linear programming software. Moreover the choices of formulation, algorithm, and pivot rule that perform best from a computational view point are sometimes not obvious, and the software’s default choices are sometimes poor.  Here we present some linear programming formulations of treatment planning problem with dose volume constraints, conclusions are drawn about the formulations and variants

    President George W. Bush’s Policy Towards Iraq: Change or Continuity?

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    A substantial amount of commentary has been dedicated to George W. Bush’s policy towards Iraq, with many perceiving it as a departure from traditional US foreign policy practice. The objective of this research is to address and challenge this contention. This thesis takes 1979 as the launching point from which to examine this assertion, as it is both the year in which Saddam Hussein gained power as president of Iraq and also the year when the United States began tilting favourably towards, and reviving its relations with, this country. To embark on this study a descriptive and analytical narrative of the evolution of US foreign policy towards Iraq is presented, ending with the George W. Bush terms of office. This study contends that US policy towards Iraq has two major dimensions: the first is US policy towards Arab Iraq and the second its de facto policy towards Iraqi Kurdistan; both are defined by US strategy at the supra-national level. To guide this study, continuity and change were used as guiding concepts for analysing US Iraq policy at the national and sub-national levels. The study argues that US Iraq policy is primarily one of continuity rather than change, as US national interests and security, as regards Iraq, are defined by the same fundamental concerns, regardless of the nature of the American administration in office. The research concludes that, from the inception of the Bush administration, and the attacks on 9/11 that followed, the actual invasion of Iraq and US actions in its aftermath were all guided by the same considerations and goals

    The Perception of Chinese Construction Professionals Towards the Obstacles Implementing Green Construction

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    Green construction plays a key role as building block of sustainable development. The economy is significantly affected by the construction industry of the country. There are certain stakeholders in the green construction industry, however project managers (PMs) play significant role in the process of a construction/ rehabilitation project. Generally, the initiative for change or implementing a new system is very challenging issue to deal with. Project manager has to encounter certain obstacles either at several stages of the green construction projects. The present study deals with the identification of the most critical obstacles that have the greatest influence on a project’s outcome in general and particularly in China. To rank the different obstacles extracted from the literature, we use multi criteria decision making (MCDM) tool i.e. TOPSIS. For obtaining input data a team of six experts (project managers) from top Chinese construction companies with an experience of more than 12 years were selected. The results depicts that the most relevant and important obstacles which are critical for green project management are managerial and psychological obstacles and they need to be addressed to improve the project management performance. Keywords: green construction, project management, topsis, project managers

    Oral health of older people

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    Introduction and objectives The population of older people in New Zealand is increasing. With advancing age, older people are more likely to develop some form of disability. More and more older people are retaining their teeth, but epidemiological evidence indicates that oral disease continues older people are considered a caries-active group. There are marked differences in the oral health status of community dwelling and nursing home residents, with treatment needs higher in the latter. To date, little is known about clinical presentations of older people (community dwelling and nursing home residents) to hospital dental departments in New Zealand. There are currently no data describing the demographic characteristics, sources of referral and the nature of dental treatment provided to older people presenting to hospital dental departments in New Zealand. Keeping this theme in mind, I undertook this study to answer the following research questions: 1. What is the status of oral health among older people living in New Zealand; and 2. What are the barriers to dental care among older people living in New Zealand? This study was conducted in two parts. The first part of this study was an 8-month clinical audit at Waikato Hospital Dental Department to determine: 1. The demographic characteristics, source and reasons for referral, dentition status of the older people (>65 years of age) presenting to the Dental Department of Waikato Hospital; and 2. The nature of their dental problems, the treatment received and the follow-up care. The second part of this study was a secondary analysis of the 2012 older peoples’ national oral health survey data. The second part of this study was conducted to: 1. Describe older New Zealanders’ use of dental services; and 2. Determine any difference in the nature of dental problems, and barriers to dental care among older adults in community-dwelling and Residential care facilities. Method For the first part of the study, information on patients aged 65 or more who presented to the dental department from 1st February to 31st October 2018 was abstracted from the Waikato DHB clinical database. Data analysed included demographic characteristics, dentition status, source of referral, medical history, treating clinician, treatment delivered and whether there was follow-up care. This information was then entered a data capture form and numerically coded. The IBM SPSS (Statistical Package for the Social Sciences) for Windows program was used for the analysis of the data. The data for the second part of this study were obtained from the 2012 New Zealand Older People’s Oral Health Survey (OPOHS) data dictionary. The 2012 OPOHS was part of the Study into Older People’s Oral Health Issues; an umbrella project funded by the Ministry of Health. The 2012 OPOHS was the first nationwide survey to collect information on the oral health status of older adults in New Zealand, residing in community-dwelling and residential aged-care facilities. In addition to ascertaining the clinical and self-reported oral health status of vulnerable older adults, the 2012 OPOHS also reported on the oral health services accessed by them. The Stata statistical software package (Stata Corp for Windows) was used to analyse the older people’s use of oral health services from the 2012 OPOHS data-set . Results Part 1 – Clinical audit Among the 203 identified patients (in the 8-month clinical audit), there was a male-to-female ratio of almost 3:2, and 90% were of European origin. Overall, 80% of the patients were living in their own homes; 80% were dentate. Some 30% presented with at least two medical conditions, and those living in a rest home had a higher mean number of medical conditions. General dental practitioners had referred more than 40% of patients in the 85+ age group whereas general medical practitioners (GP) had referred 33% in that age group. More than 50% of rest home patient referrals to the dental department were from their GP. Some 33% were oncology referrals (internal), while 33% were acute referrals and 60% had presented for elective dental treatment. Swollen face, odontogenic infection and irreversible pulpitis were the most likely reasons for acute referrals. Around 10% of patients had teeth extracted. Two-thirds of patients were referred to their general dental practitioner for follow-up. Part 2- Secondary analysis of 2012 NZOPOHS data More than half of the overall study population were edentulous. The proportion of edentulous participants was higher in the RC population than the HB group. Overall, twice as many residents living in their own homes than those in the RC population had visited a dentist in private practice, with dental check-up being the main reason for visit. Likewise, 30% of the participants received a dental clean and similar proportion also had their teeth filled. Around 20% of the participants had a dental extraction. A higher proportion of residents from HB category than those in the RC population also visited a DHB dental clinic and a dental technician. On the other hand, at least three in four residents from the residential care population (dentate and edentulous) had not visited a dentist in the previous 12 months. Lack of perceived need and cost were reported as the two main reasons not visiting a dental professional in the past 12 months. Almost one in three participants from both the HB and RC facility reported “Moderate” or “A lot of difficulty” in paying a $150.00 dental bill. On the other hand, 25% of the Residential-care participants reported travel distance as the main reason for not seeking dental care in the past 12 months. Conclusion Around 25 older patients per month are referred to the waikato hospital dental department, for care from diverse referral sources, and the proportion of acute referrals is relatively high, suggesting that poor oral health among older adults is an important problem. Those living in residential care are unable to access professional dental care as easily as those in their own homes. Lack of perceived need, costs of the dental treatment and travel distance are reported as the major reasons for not visiting a dental professional. These findings show that older people presenting at hospital dental clinics have oral health needs and dental treatment needs that require urgent attention. Their inability to access dental care raises serious concerns about their oral health

    Photochemical air quality modelling in arid regions

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    Despite continuous measures to control air pollution, large fractions of the population across the world are still exposed to potentially dangerous pollutant concentration levels. Research continues to increase in the area of air pollution with focus on different pollutants and regions. A particular emphasis is on the understanding of the formation of secondary pollutants as their relationships with primary pollutants are complex. One of the key factors that influences these complex relationships is the regional characteristics, such as temperature, humidity, and solar radiations. Arid regions are of particular concern as the characteristics, especially, extreme temperatures and dust storms, deteriorate air quality significantly. The study area chosen for this research is the Riyadh region in Saudi Arabia. Improving the air quality in this region requires further understanding of the formation of secondary pollutants, particularly ozone (O₃). Generally, Photochemical Air Quality Models (PAQM) are employed to study the formation of secondary pollutants in the atmosphere. This research configured high-resolution Community Multiscale Air Quality (CMAQ) model over the area to study the research objectives. This model could be utilized to study various strategies to mitigate photochemical smog formation in the region. The regional characteristics have significant roles in atmospheric chemical mechanisms, and an effective mitigation plan is important for successful air quality management; hence getting a better understanding of the chemical mechanisms is pivotal. This thesis investigated various chemical mechanisms that are present in PAQM constraining with the observed data resulting in the identification of the most appropriate mechanism for arid regions. The key chemical reactions and corresponding kinetics were also ascertained. The identified chemical mechanism will serve as a benchmark for any future implementation of PAQM in Riyadh as well as similar regions. Conventionally, deterministic PAQMs are applied to evaluate the efficacy of a control strategy to achieve air quality standards. Uncertainties are inherent in any mathematical model, including PAQM, and are specific to regional characteristics. Ignoring model uncertainties might yield a false sense of precision about pollutant response to emission controls. Hence, such uncertainties must be identified and quantified for the selection of control policies. This research identified key factors influencing the O₃ precursor responsiveness and characterized the parametric uncertainties influencing the prediction of O₃ to precursor emissions. Devising an appropriate mitigation plan also requires running PAQM for a number of scenarios, which is computationally challenging. To overcome this computational burden, an efficient Reduced Form Model (RFM) was developed. It characterizes the impact of uncertainties in model input parameters on O₃ response to not only precursor emissions (NOₓ and VOCs) but also to dust emissions. The development of an efficient RFM allowed the use of a probabilistic framework to study the impact of various emission mitigation and dust increase scenarios. This RFM enabled the understanding of the impact of various emission reductions on the formation of O₃. The newly incorporated dust parameter in the RFM revealed that the relationship of dust concentrations with O₃ formation is nonlinear. Initially, O₃ concentration decreased with the increase of dust and later increased. The configured PAQM, the identified atmospheric chemical mechanism, and the developed RFM (incorporating the new dust parameter) would facilitate the responsible authorities in devising appropriate O₃ reduction strategies for the study area and similar regions. The endeavour undertaken in this research to advance the understanding of PAQM in arid conditions opens up several avenues of further research. The developed RFM has a potential to be improved, such as adding more types of uncertainties (structural and meteorological) and further validating with comprehensive observed data. Additionally, the RFM could be integrated with economics and health uncertainty models to study the cost of mitigation plans and health impacts. Moreover, air chambers can be setup to get more insight into chemical kinetics under arid conditions especially the role of heterogeneous reactions of NOₓ with dust particles

    Finite Element Analysis of Horizontal Axis Wind Turbine Blades Using NACA 4412 Series

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    Wind turbine technology is one of the rapid growth sectors of renewable energy all over the world. The ultimate objective of the project work is to increase the output power under specified atmospheric conditions. From the technical point of view, the output power depends on the shape of the blade. The blade plays a pivotal role, because it is the most important part of the energy absorption system. Finite element analysis was conducted by different materials used for blade fabrication namely glass fiber with epoxy resin, Aluminum and teak wood. The research work focuses on NACA4412. Also, the performance of a wind turbine blade is highly dependent on the structure Total deformation, Stress and Strain of the blade is critical to the wind turbine system service life. So, the wind turbine blades are analyzed taking these parameters into account
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