A set-based approach to passenger aircraft family design

In today's highly competitive civil aviation market, aircraft manufacturers develop aircraft families in order to satisfy a wide range of requirements from multiple airlines, with reduced costs of ownership and shorter lead time. Traditional methods for designing passenger aircraft families employ a sequential, optimisation-based approach, where a single configuration and systems architecture is selected fairly early which is then iteratively analysed and modified until all the requirements are met. The problem with such an approach is the tendency of the optimisers to exploit assumptions already 'hard-wired' in the computational models. Subsequently the design is driven towards a solution which, while promising to the optimiser, may be infeasible due to the factors not considered by the models, e.g. integration and installation of promising novel technological solutions, which result in costly design rework later in the design process. Within this context, the aim is to develop a methodology for designing passenger aircraft families, which provides an environment for designers to interactively explore wider design space and foster innovation. To achieve this aim, a novel methodology for passenger aircraft family design is proposed where multiple aircraft family solutions are synthesised from the outset by integrating major components sets and systems architectures set. This is facilitated by integrating set theory principles and model-based design exploration methods. As more design knowledge is gained through analysis, the set of aircraft family solutions is gradually narrowed-down by discarding infeasible and inferior solutions. This is achieved through constraint analysis using iso-contours. The evaluation has been carried out through an application case-study (of a three-member passenger aircraft family design) which was executed with both the proposed methodology and the traditional approach for comparison. The proposed methodology and the case-study (along with the comparison results) were presented to a panel of industrial experts who were asked to comment on the merits and potential challenges of the proposed methodology. The conclusion is that the proposed methodology is expected to reduce the number of costly design changes, enabling designers to consider novel systems technologies and gain knowledge through interactive design space exploration. It was pointed out, however, that while the computational enablers behind the proposed approach are reaching a stage of maturity, allowing a multitude of concepts to be analysed rapidly and simultaneously, this still is expected to present a challenge from organisational process and resource point of view. It was agreed that by considering a set of aircraft family solutions, the proposed approach would enable the designers to delay critical decisions until more knowledge is available, which helps to mitigate risks associated with innovative systems architectures and technologies

Set-based approach to passenger aircraft family design

Presented is a method for the design of passenger aircraft families. Existing point-based methods found in the literature employ sequential approaches in which a single design solution is selected early and is then iteratively modified until all requirements are satisfied. The challenge with such approaches is that the design is driven toward a solution that, although promising to the optimizer, may be infeasible due to factors not considered by the models. The proposed method generates multiple solutions at the outset. Then, the infeasible solutions are discarded gradually through constraint satisfaction and set intersection. The method has been evaluated through a notional example of a three-member aircraft family design. The conclusion is that point-based design is still seen as preferable for incremental (conventional) designs based on a wealth of validated empirical methods, whereas the proposed approach, although resource-intensive, is seen as more suited to innovative designs

INS/GPS Based State Estimation of Micro Air Vehicles Using Inertial Sensors

The most attractive and attention seeking topic of aerospace world is Micro Air Vehicle (MAV) which broadly speaking it can be categorized as significantly smaller aircraft than conventional aircrafts. Micro Air Vehicles can be divided as autonomous, semi-autonomous and remote controlled flying machines which can be fixed wing MAV, Flapping wing MAV and rotary wing MAV. One of the crucial problems regarding Micro Air Vehicle is its stability which is basically concerned with the guidance, navigation and control. State Estimation is an important aspect of navigation and this paper deals with the state estimation problem of micro Air vehicle. Inertial sensors are being used including MEMS Gyro, MEMS Accelerometer, Magnetometer and GPS in Inertial Measurement Unit (IMU) and three Discrete Time Extended Kalman Filter Schemes have been used for the state estimation purpose. Trajectory and required data is recorded in Flight Simulator and MATLAB has been used for the simulations. A comprehensive parametric study is carried out and results are analyzed and briefly discussed. Keywords: Micro Electro Mechanical System (MEMS), Micro Air Vehicle (MAV), Measurement Covariance Matrix, Process Covariance Matri

Residual barriers for utilization of maternal and child health services: community perceptions from rural Pakistan.

Low utilization of maternal and child care services in rural areas has constrained Pakistan from meeting targets of Millennium Development Goals (MDGs) 4 and 5. This study explores community barriers in accessing Maternal and Child Health (MCH) services in ten remote rural districts of Pakistan. It further presents how the barriers differ across a range of MCH services, and also whether the presence of Community Health Workers (CHWs) reduces client barriers. Qualitative methods were used involving altogether sixty focus group discussions with mothers, their spouses and community health workers. Low awareness, formidable distances, expense, and poorly functional services were the main barriers reported, while cultural and religious restrictions were lesser reported. For preventive services including antenatal care (ANC), facility deliveries, postnatal care (PNC), childhood immunization and family planning, the main barrier was low awareness. Conversely, formidable distances and poorly functional services were the main reported constraints in the event of maternal complications and acute child illnesses. The study also found that clients residing in areas served by CHWs had better awareness only of ANC and family planning, while other MCH services were overlooked by the health worker program. The paper highlights that traditional policy emphasis on health facility infrastructure expansion is not likely to address poor utilization rates in remote rural areas. Preventive MCH services require concerted attention to building community awareness, task shifting from facility to community for services provision, and re-energization of CHW program. For maternal and child emergencies there is strong community demand to utilize health facilities, but this will require catalytic support for transport networks and functional health care centers

Perceived barriers to utilizing maternal and neonatal health services in contracted-out versus government-managed health facilities in the rural districts of Pakistan

Background: A number of developing countries have contracted out public health facilities to the Non-Government Organizations (NGOs) in order to improve service utilization. However, there is a paucity of in-depth qualitative information on barriers to access services as a result of contracting from service users’ perspective. The objective of this study was to explore perceived barriers to utilizing Maternal and Neonatal Health (MNH) services, in health facilities contracted out by government to NGO for service provision versus in those which are managed by government (non-contracted). Methods: A community-based qualitative exploratory study was conducted between April to September 2012 at two contracted-out and four matched non-contracted primary healthcare facilities in Thatta and Chitral, rural districts of Pakistan. Using semi-structured guide, the data were collected through thirty-six Focus Group Discussions (FGDs) conducted with mothers and their spouses in the catchment areas of selected facilities. Thematic analysis was performed using NVivo version 10.0 in which themes and sub-themes emerged. Results: Key barriers reported in contracted sites included physical distance, user charges and familial influences. Whereas, poor functionality of health centres was the main barrier for non-contracted sites with other issues being comparatively less salient. Decision-making patterns for participants of both catchments were largely similar. Spouses and mother-in-laws particularly influenced the decision to utilize health facilities. Conclusion: Contracting out of health facility reduces supply side barriers to MNH services for the community served but distance, user charges and low awareness remain significant barriers. Contracting needs to be accompanied by measures for transportation in remote settings, oversight on user fee charges by contractor, and strong community-based behavior change strategies

Perceived barriers to utilizing maternal and neonatal health services in contracted-out versus government-managed health facilities in the rural districts of Pakistan

Background: A number of developing countries have contracted out public health facilities to the Non-Government Organizations (NGOs) in order to improve service utilization. However, there is a paucity of in-depth qualitative information on barriers to access services as a result of contracting from service users’ perspective. The objective of this study was to explore perceived barriers to utilizing Maternal and Neonatal Health (MNH) services, in health facilities contracted out by government to NGO for service provision versus in those which are managed by government (non-contracted). Methods: A community-based qualitative exploratory study was conducted between April to September 2012 at two contracted-out and four matched non-contracted primary healthcare facilities in Thatta and Chitral, rural districts of Pakistan. Using semi-structured guide, the data were collected through thirty-six Focus Group Discussions (FGDs) conducted with mothers and their spouses in the catchment areas of selected facilities. Thematic analysis was performed using NVivo version 10.0 in which themes and sub-themes emerged. Results: Key barriers reported in contracted sites included physical distance, user charges and familial influences. Whereas, poor functionality of health centres was the main barrier for non-contracted sites with other issues being comparatively less salient. Decision-making patterns for participants of both catchments were largely similar. Spouses and mother-in-laws particularly influenced the decision to utilize health facilities. Conclusion: Contracting out of health facility reduces supply side barriers to MNH services for the community served but distance, user charges and low awareness remain significant barriers. Contracting needs to be accompanied by measures for transportation in remote settings, oversight on user fee charges by contractor, and strong community- based behavior change strategies

Functional connectivity alterations in epilepsy from resting-state functional MRI

The study of functional brain connectivity alterations induced by neurological disorders and their analysis from resting state functional Magnetic Resonance Imaging (rfMRI) is generally considered to be a challenging task. The main challenge lies in determining and interpreting the large-scale connectivity of brain regions when studying neurological disorders such as epilepsy. We tackle this challenging task by studying the cortical region connectivity using a novel approach for clustering the rfMRI time series signals and by identifying discriminant functional connections using a novel difference statistic measure. The proposed approach is then used in conjunction with the difference statistic to conduct automatic classification experiments for epileptic and healthy subjects using the rfMRI data. Our results show that the proposed difference statistic measure has the potential to extract promising discriminant neuroimaging markers. The extracted neuroimaging markers yield 93.08% classification accuracy on unseen data as compared to 80.20% accuracy on the same dataset by a recent state-of-the-art algorithm. The results demonstrate that for epilepsy the proposed approach confirms known functional connectivity alterations between cortical regions, reveals some new connectivity alterations, suggests potential neuroimaging markers, and predicts epilepsy with high accuracy from rfMRI scans.Scopu

Provider cost analysis supports results-based contracting out of maternal and newborn health services: an evidence-based policy perspective

Background There is dearth of evidence on provider cost of contracted out services particularly for Maternal and Newborn Health (MNH). The evidence base is weak for policy makers to estimate resources required for scaling up contracting. This paper ascertains provider unit costs and expenditure distribution at contracted out government primary health centers to inform the development of optimal resource envelopes for contracting out MNH services. Methods This is a case study of provider costs of MNH services at two government Rural Health Centers (RHCs) contracted out to a non-governmental organization in Pakistan. It reports on four selected Basic Emergency Obstetrical and Newborn Care (BEmONC) services provided in one RHC and six Comprehensive Emergency Obstetrical and Newborn Care (CEmONC) services in the other. Data were collected using staff interviews and record review to compile resource inputs and service volumes, and analyzed using the CORE Plus tool. Unit costs are based on actual costs of MNH services and are calculated for actual volumes in 2011 and for volumes projected to meet need with optimal resource inputs. Results The unit costs per service for actual 2011 volumes at the BEmONC RHC were antenatal care (ANC) visit USD$18.78, normal delivery US$ 84.61, newborn care US$16.86 and a postnatal care (PNC) visit US$ 13.86; and at the CEmONC RHC were ANC visit US$45.50, Normal Delivery US$ 148.43, assisted delivery US$167.43, C-section US$ 183.34, Newborn Care US$41.07, and PNC visit US$ 27.34. The unit costs for the projected volumes needed were lower due to optimal utilization of resources. The percentage distribution of expenditures at both RHCs was largest for salaries of technical staff, followed by salaries of administrative staff, and then operating costs, medicines, medical and diagnostic supplies. Conclusions The unit costs of MNH services at the two contracted out government rural facilities remain higher than is optimal, primarily due to underutilization. Provider cost analysis using standard treatment guideline (STG) based service costing frameworks should be applied across a number of health facilities to calculate the cost of services and guide development of evidence based resource envelopes and performance based contracting

Efficient method for variance-based sensitivity analysis

Presented is an efficient method for variance-based sensitivity analysis. It provides a general approach to transforming a sensitivity problem into one uncertainty propagation process, so that various existing approximation techniques (for uncertainty propagation) can be applied to speed up the computation. In this paper, formulations are deduced to implement the proposed approach with one specific technique named Univariate Reduced Quadrature (URQ). This implementation was evaluated with a number of numerical test-cases. Comparison with the traditional (benchmark) Monte Carlo approach demonstrated the accuracy and efficiency of the proposed method, which performs particularly well on the linear models, and reasonably well on most non-linear models. The current limitations with regard to non-linearity are mainly due to the limitations of the URQ method used