10,870 research outputs found
Optimizing an array of antennas for cellular coverage from a high altitude platform
In a wireless communications network served by a high altitude platform (HAP) the cochannel interference is a function of the antenna beamwidth, angular separation and. sidelobe level. At the millimeter wave frequencies proposed for HAPs, an array of aperture type antennas on the platform is a practicable solution for serving the cells. We present a method for predicting cochannel interference based on curve-fit approximations for radiation patterns of elliptic beams which illuminate cell edges with optimum power, and a means of estimating optimum beamwidths for each cell of a regular hexagonal layout. The method is then applied to a 121 cell architecture. Where sidelobes are modeled As a flat floor at 40-dB below peak directivity, a cell cluster size of four yields carrier-to-interference ratios (CIRs), which vary from 15 dB at cell edges to 27 dB at cell centers. On adopting a cluster size of seven, these figures increase, respectively, to 19 and 30 dB. On reducing the sidelobe level, the. improvement in CIR can be quantified. The method also readily allows for regions of overlapping channel coverage to be shown
Process Capability Database Usage In Industry: Myth vs. Reality
Process capability data (PCD) is needed for robust design, optimal tolerance allocation, and variation
simulation analysis. Process capability databases (PCDBs) have been developed in many industries and are
being used by the manufacturing community to monitor quality; however, they are not being effectively
utilized by design. When the PCDBs1 were developed, the intent was for design to use PCD for
optimization and product cost minimization, but this ideal situation has not been realized.
A survey of a variety of design and manufacturing companies was circulated to determine both the state-ofthe-
art in PCDBs and the barriers preventing design from fully utilizing PCD. Two key barriers were
identified for internal PCDBs: lack of a company-wide vision for PCD usage and poor communication
between manufacturing and design. Supplier PCDBs have the additional barriers of lack of trust between
suppliers and customers and time lag for data entry. Management support, training, database population,
and common systems were identified as potential solutions to the identified barriers
An exploratory study on the effect of positive (warmth appeal) and negative (guilt appeal) print imagery on donation behaviour in animal welfare
Very few studies in social marketing empirically compare the effectiveness of positive and negative appeals. This study examines the effect of positive (warmth appeal) and negative (guilt appeal) print imagery on donation behaviour to an animal welfare organisation. A quasiexperimental design was used to test the appeals, using a convenience sample of 282 university students, with each experimental group being exposed to only one type of appeal. The results indicated that negative imagery which evoked guilt was more effective than positive imagery which evoked warmth, on intention to donate money and time to the animal welfare organisation
Do people âpop outâ?
The human body is a highly familiar and socially very important object. Does this mean that the human body has a special status with respect to visual attention? In the current paper we tested whether people in natural scenes attract attention and âpop outâ or, alternatively, are at least searched for more efficiently than targets of another category (machines). Observers in our study searched a visual array for dynamic or static scenes containing humans amidst scenes containing machines and vice versa. The arrays consisted of 2, 4, 6 or 8 scenes arranged in a circular array, with targets being present or absent. Search times increased with set size for dynamic and static human and machine targets, arguing against pop out. However, search for human targets was more efficient than for machine targets as indicated by shallower search slopes for human targets. Eye tracking further revealed that observers made more first fixations to human than to machine targets and that their on-target fixation durations were shorter for human compared to machine targets. In summary, our results suggest that searching for people in natural scenes is more efficient than searching for other categories even though people do not pop out.peer-reviewe
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Factors influencing utilisation of âfree-standingâ and âalongsideâ midwifery units for low-risk births in England: a mixed-methods study
Background
Midwifery-led units (MUs) are recommended for âlow-riskâ births by the National Institute for Health and Care Excellence but according to the National Audit Office were not available in one-quarter of trusts in England in 2013 and, when available, were used by only a minority of the low-risk women for whom they should be suitable. This study explores why.
Objectives
To map the provision of MUs in England and explore barriers to and facilitators of their development and use; and to ascertain stakeholder views of interventions to address these barriers and facilitators.
Design
Mixed methods â first, MU access and utilisation across England was mapped; second, local media coverage of the closure of free-standing midwifery units (FMUs) were analysed; third, case studies were undertaken in six sites to explore the barriers and facilitators that have an impact on the development of MUs; and, fourth, by convening a stakeholder workshop, interventions to address the barriers and facilitators were discussed.
Setting
English NHS maternity services.
Participants
All trusts with maternity services.
Interventions
Establishing MUs.
Main outcome measures
Numbers and types of MUs and utilisation of MUs.
Results
Births in MUs across England have nearly tripled since 2011, to 15% of all births. However, this increase has occurred almost exclusively in alongside units, numbers of which have doubled. Births in FMUs have stayed the same and these units are more susceptible to closure. One-quarter of trusts in England have no MUs; in those that do, nearly all MUs are underutilised. The study findings indicate that most trust managers, senior midwifery managers and obstetricians do not regard their MU provision as being as important as their obstetric-led unit provision and therefore it does not get embedded as an equal and parallel component in the trustâs overall maternity package of care. The analysis illuminates how provision and utilisation are influenced by a complex range of factors, including the medicalisation of childbirth, financial constraints and institutional norms protecting the status quo.
Limitations
When undertaking the case studies, we were unable to achieve representativeness across social class in the womenâs focus groups and struggled to recruit finance directors for individual interviews. This may affect the transferability of our findings.
Conclusions
Although there has been an increase in the numbers and utilisation of MUs since 2011, significant obstacles remain to MUs reaching their full potential, especially FMUs. This includes the capacity and willingness of providers to address womenâs information needs. If these remain unaddressed at commissioner and provider level, childbearing womenâs access to MUs will continue to be restricted.
Future work
Work is needed on optimum approaches to improve decision-makersâ understanding and use of clinical and economic evidence in service design. Increasing womenâs access to information about MUs requires further studies of professionalsâ understanding and communication of evidence. The role of FMUs in the context of rural populations needs further evaluation to take into account user and community impact.
Funding
This project was funded by the National Institute for Health Research (NIHR) Health Services and Delivery Research programme and will be published in full in Health Services and Delivery Research; Vol. 8, No. 12. See the NIHR Journals Library website for further project information
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