2,767 research outputs found
Generic guide concepts for the European Spallation Source
The construction of the European Spallation Source (ESS) faces many
challenges from the neutron beam transport point of view: The spallation source
is specified as being driven by a 5 MW beam of protons, each with 2 GeV energy,
and yet the requirements in instrument background suppression relative to
measured signal vary between 10 and 10. The energetic particles,
particularly above 20 MeV, which are expected to be produced in abundance in
the target, have to be filtered in order to make the beamlines safe,
operational and provide good quality measurements with low background.
We present generic neutron guides of short and medium length instruments
which are optimized for good performance at minimal cost. Direct line of sight
to the source is avoided twice, with either the first point out of line of
sight or both being inside the bunker (20\,m) to minimize shielding costs.
These guide geometries are regarded as a baseline to define standards for
instruments to be constructed at ESS. They are used to find commonalities and
develop principles and solutions for common problems. Lastly, we report the
impact of employing the over-illumination concept to mitigate losses from
random misalignment passively, and that over-illumination should be used
sparingly in key locations to be effective. For more widespread alignment
issues, a more direct, active approach is likely to be needed
Correction of Optical Aberrations in Elliptic Neutron Guides
Modern, nonlinear ballistic neutron guides are an attractive concept in
neutron beam delivery and instrumentation, because they offer increased
performance over straight or linearly tapered guides. However, like other
ballistic geometries they have the potential to create significantly
non-trivial instrumental resolution functions. We address the source of the
most prominent optical aberration, namely coma, and we show that for extended
sources the off-axis rays have a different focal length from on-axis rays,
leading to multiple reflections in the guide system. We illustrate how the
interplay between coma, sources of finite size, and mirrors with non-perfect
reflectivity can therefore conspire to produce uneven distributions in the
neutron beam divergence, the source of complicated resolution functions. To
solve these problems, we propose a hybrid elliptic-parabolic guide geometry.
Using this new kind of neutron guide shape, it is possible to condition the
neutron beam and remove almost all of the aberrations, whilst providing the
same performance in beam current as a standard elliptic neutron guide. We
highlight the positive implications for a number of neutron scattering
instrument types that this new shape can bring.Comment: Presented at NOP2010 Conference in Alpe d'Huez, France, in March 201
Advanced wet-dry cooling tower concept
Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering.The purpose of this years' work has been to test and analyze the new dry cooling tower surface previously developed. The model heat transfer test apparatus built last year has been instrumented for temperature, humidity and flow measurement and performance has been measured under a variety of operating conditions.
Tower Tests showed approximately 40-50% of the total energy transfer as taking place due to evaporation. This can be compared to approximately 80 to 85% for a conventional wet cooling tower. Comparison of the model
tower test results with those of a computer simulation has demonstrated the validity of that simulation and its use as a design tool. Computer predictions have been made for a full-size tower system operating at
several locations.
Experience with this counterflow model tower has suggested that several design problems may be avoided by blowing the cooling air horizontally through the packing section. This crossflow concept was built from the previous counterflow apparatus and included the design and fabrication of new packing plates.
Instrumentation and testing of the counterflow model produced data with an average experimental error of 10%. These results were compared to the predictions of a computer model written for the crossflow configuration. In 14 test runs the predicted total heat transfer differed from the
measured total heat transfer by no more than 8% with most runs coming well within 5%. With the computer analogy's validity established, it may now be used to help predict the performance of fullscale wet-dry
towers
A Capstone Project: A way to Integrate Knowledge and Empower Students to Become Change Agents in the Practice Setting.
Nursing education today calls for creative and innovative ways in preparing students for the future. The growing complexity in the practice setting demands that nursing students gain exposure to skill sets that empower them to be change agents. A capstone project in the final year of an Undergraduate Nursing Program enabled students to integrate their knowledge from all areas of their curriculum to address quality improvement (QI) issues. While the students’ projects were not QI projects, they functioned as precursors or ideas for future QI initiatives. The capstone projects were graded using a designed marking rubric that addressed the Undergraduate Degree Level Expectations and the entry to practice competencies for the Registered Nurse in Ontario. The students presented their work at a capstone conference that invited personnel from both academia and clinical practice organizations. The capstone project became a way to acknowledge ideas and accomplishments of future nursing graduates.
Résumé
La formation en sciences infirmières actuelle a besoin de moyens créateurs et novateurs pour préparer les étudiantes pour l’avenir. En raison de la complexité croissante de la pratique clinique, il importe que les étudiantes en sciences infirmières développement des compétences qui les habilitent à devenir des agentes de changement. Un projet de synthèse de dernière année d’un programme de premier cycle en sciences infirmières a permis à des étudiantes d’intégrer leurs connaissances acquises dans les divers domaines de leur programme d’étude afin de répondre à des questions d’amélioration de la qualité (AQ). Même si les projets des étudiantes n’étaient pas des projets d’AQ, ils ont fait office de précurseurs ou ont permis de mettre de l’avant des idées pour de futures initiatives d’AQ. Les projets de synthèse ont été notés au moyen d’une grille d’évaluation conçue pour tenir compte des attentes de fin d’études de premier cycle et des compétences pour accéder à la pratique pour infirmières autorisées en Ontario. Les étudiantes ont présenté leurs travaux lors d’une conférence de couronnement à laquelle étaient conviés des membres du personnel des milieux clinique et universitaire. Le projet de synthèse est devenu un moyen de reconnaître les idées et les réalisations des futures diplômées en sciences infirmières
Post-CCSD(T) corrections to bond distances and vibrational frequencies: the power of
The importance of post-CCSD(T) corrections as high as CCSDTQ56 for
ground-state spectroscopic constants (, , , and
) has been surveyed for a sample of two dozen mostly heavy-atom
diatomics spanning a broad range of static correlation strength. While CCSD(T)
is known to be an unusually felicitous `Pauling point' between accuracy and
computational cost, performance leaves something to be desired for molecules
with strong static correlation. We find CCSDT(Q) to be the next
`sweet spot' up, of comparable or superior quality to the much more expensive
CCSDTQ. A similar comparison applies to CCSDTQ(5) vs. CCSDTQ5, while
CCSDTQ5(6) is essentially indistinguishable from CCSDTQ56. A
composite of CCSD(T)-X2C/ACV5Z-X2C with [CCSDT(Q) -- CCSD(T)]/cc-pVTZ
or even cc-pVDZ basis sets appears highly effective for computational
vibrational spectroscopy. Unlike CCSDT(Q) which breaks down for the ozone
vibrational frequencies, CCSDT(Q) handles them gracefully.Comment: Mol. Phys., in press [Timothy J. Lee memorial issue
Users’ attitudes towards personal health records a cross-sectional pilot study
Background: Prevention and management of chronic conditions is a priority for many healthcare systems. Personal health records have been suggested to facilitate implementation of chronic care programs. However, patients’ attitude towards personal health records (PHRs) can significantly affect the adoption rates and use of PHRs. Objectives: to evaluate the attitude of patients with Type II diabetes towards using a PHR to manage their condition. Methods: We used a cross-sectional exploratory pilot study. Fifty-four (54) patients used a PHR to monitor and record their blood glucose levels, diet, and activities for 30 days, and to communicate with their clinicians. At the end of the study, patients responded to a survey based on three constructs borrowed from different technology acceptance frameworks: relative advantage, job fit, and perceived usefulness. A multivariate predictive model was formed using partial least squaring technique (PLS) and the effect of each construct on the patients’ attitude towards system use was evaluated. Patients also participated in a semi-structured interview. Results: We found a significant positive correlation between job fit and attitude (JF?ATT = +0.318, p less than 0.01). There was no statistical evidence of any moderating or mediating effect of other main constructs or any of the confounding factors (i.e., age, gender, time after diagnosed) on attitude. Conclusion: The attitude of patients towards using PHR in management of their diabetes was positive. Their attitude was mainly influenced by the extent to which the system helped them better perform activities and self-manage their condition. © Schattauer 2016
Optimization of moderators and beam extraction at the ESS
A global approach coupling the moderator to the beam extraction system has been applied for the design optimization of the thermal and cold moderators of the European Spallation Source (ESS), which will be the brightest neutron source in the world for condensed-matter studies. The design is based on the recently developed high-brightness low-dimensional moderator concepts. Para-hydrogen is used for the cold neutron source, while thermal neutrons are provided by moderation in water. The overall moderation configuration was chosen in order to satisfy a range of requirements on bispectral extraction, beamport configuration and instrument performance. All instruments are served by a single moderator assembly above the target, arranged in a 'butterfly' geometry with a height of 3 cm. This was determined to be the optimal height for trade-off between high brightness and efficient guide illumination, by analysis of the performance of 23 instruments, based on the reference suite of the ESS Technical Design Report. The concept of 'brilliance transfer' is introduced to quantify the performance of the neutron optical system from the source to the sample. The target monolith incorporates a grid of 42 neutron beamports with an average separation of 6°, allowing a free choice between cold and thermal neutron sources at all instrument positions. With the large number of beamports and the space below the target available for future moderators, ample opportunities are available for future upgrades
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