2,669 research outputs found
Reliability growth models for NASA applications
The objective of any reliability growth study is prediction of reliability at some future instant. Another objective is statistical inference, estimation of reliability for reliability demonstration. A cause of concern for the development engineer and management is that reliability demands an excessive number of tests for reliability demonstration. For example, the Space Transportation Main Engine (STME) program requirements call for .99 reliability at 90 pct. confidence for demonstration. This requires running 230 tests with zero failure if a classical binomial model is used. It is therefore also an objective to explore the reliability growth models for reliability demonstration and tracking and their applicability to NASA programs. A reliability growth model is an analytical tool used to monitor the reliability progress during the development program and to establish a test plan to demonstrate an acceptable system reliability
Reliability evaluation methodology for NASA applications
Liquid rocket engine technology has been characterized by the development of complex systems containing large number of subsystems, components, and parts. The trend to even larger and more complex system is continuing. The liquid rocket engineers have been focusing mainly on performance driven designs to increase payload delivery of a launch vehicle for a given mission. In otherwords, although the failure of a single inexpensive part or component may cause the failure of the system, reliability in general has not been considered as one of the system parameters like cost or performance. Up till now, quantification of reliability has not been a consideration during system design and development in the liquid rocket industry. Engineers and managers have long been aware of the fact that the reliability of the system increases during development, but no serious attempts have been made to quantify reliability. As a result, a method to quantify reliability during design and development is needed. This includes application of probabilistic models which utilize both engineering analysis and test data. Classical methods require the use of operating data for reliability demonstration. In contrast, the method described in this paper is based on similarity, analysis, and testing combined with Bayesian statistical analysis
Microscopic Description of Deeply Virtual Compton Scattering off Spin-0 Nuclei
We evaluate within a microscopic calculation the contributions of both
coherent and incoherent deeply virtual Compton scattering from a spin-0
nucleus. The coherent contribution is obtained when the target nucleus recoils
as a whole, whereas for incoherent scattering break-up configurations for the
final nucleus into a an outgoing nucleon and an system are considered.
The two processes encode different characteristics of generalized parton
distributions.Comment: 7 pages, 3 figure
Generalized Parton Distributions from Hadronic Observables
We propose a physically motivated parametrization for the unpolarized
generalized parton distributions, H and E, valid at both zero and non-zero
values of the skewness variable, \zeta. At \zeta=0, H and E are determined
using constraints from simultaneous fits of experimental data on both the
nucleon elastic form factors and the deep inelastic structure functions.
Lattice calculations of the higher moments constrain the parametrization at
\zeta > 0. Our method provides a step towards a model independent extraction of
generalized distributions from the data that is alternative to the mathematical
ansatz of double distributions.Comment: 4 pages, 2 figures, to appear in the proceedings of DIS 200
Evaluation of functioning of ICDS project areas under Indore and Ujjain divisions of the state of Madhya Pradesh
Background: Integrated Child Development Services (ICDS) is recognized worldwide as one of the most efficient community based programmes promoting early childhood care. Regular evaluations of the programme have been conducted to make it more effective and adequate for the beneficiaries. Objectives: To evaluate the functioning of the Anganwadi Centers under different project areas of Indore and Ujjain Divisions. Methods: Under the present evaluation system one ICDS project and five Anganwadi Centers under the project area (AWCs) were visited on a monthly basis and services provided reviewed. Findings reported are from nine project areas under Indore and Ujjain Divisions in the state of Madhya Pradesh from October 2008 – June 2009. Results: A total of 45 centers were evaluated. 29 centers were operating from rented buildings and storage facilities were lacking at 19 of the centers. Though the quality of food was acceptable to the beneficiaries shortage of food was a problem at the centers. Absence of Pre-School Education (PSE) and Nutrition and Health Education (NHED) Kits compromised PSE and NHED activities at the centers. Unavailability of medicine kits, lack of regular visits by the ANMs to the centers and absence of routine health check up of beneficiaries were other problems encountered under the project areas surveyed. Availability of a doctor under each project area was stated as a major need by the workers. Conclusion: Coordinated steps catering to different services provided at the centers are needed to optimize the functioning of the ICDS scheme
An overview of reliability growth models and their potential use for NASA applications
An overview is provided of reliability growth literature over the past 25 years. This includes a thorough literature review of different areas of the application of reliability growth such as design, prediction, tracking/management, and demonstration. Various reliability growth models use different bases on how they characterize growth. Different models are discussed. Also, the use is addressed of reliability growth models to NASA applications. This includes the application of these models to the space shuttle main engine. For potential NASA applications, we classify growth models in two groups, which are characterized
Nuclear Medium Modifications of Hadrons from Generalized Parton Distributions
We study the structure of generalized parton distributions in spin 0 nuclei
within a microscopic approach for nuclear dynamics. GPDs can be used on one
side as tools to unravel the deep inelastic transverse structure of nuclei in
terms of both transverse spatial and transverse momentum degrees of freedom. On
the other, one can obtain information on GPDs themselves by observing how they
become modified in the nuclear environment. We derive the structure of the
nuclear deeply virtual Compton scattering tensor and generalized parton
distributions at leading order in in a field-theoretical framework. The
nuclear generalized parton distributions are calculated using a two step
process -- the convolution approach -- where the scattering process happens
from a quark inside a nucleon, itself inside a nucleus, disregarding final
state interactions with both the nuclear and nucleon debris. We point out that
details of the nuclear long range interactions such as two-body currents, can
be disregarded compared to the deep inelastic induced modifications of the
bound GPDs. We show how the pattern of nuclear modifications predicted, and in
particular the deviations of off-shell effects from the longitudinal
convolution provide clear signals to be sought in experimental measurements.
Finally, we find interesting relationships by studying Mellin moments in
nuclei: in particular we predict the -dependence for the -term of GPDs
within a microscopic approach, and the behavior with of the total momentum
carried by quarks in a nucleus. The latter provides an important element for
the evaluation of nuclear hadronization phenomena which are vital for
interpreting current and future data at RHIC, HERMES and Jefferson Lab.Comment: 29 pages, 10 figure
Impact of Educational Intervention Measures on Knowledge regarding HIV/ Occupational Exposure and Post Exposure Prophylaxis among Final Year Nursing Students of a Tertiary Care Hospital in Central India
Amongst the different Health Care Personnel nurses are at a greater risk of being accidentally exposed to HIV and other Blood Borne Pathogens. The present study was conducted among 50 final year nursing students of a Medical College Hospital to assess the knowledge regarding HIV, occupational exposure and Post Exposure Prophylaxis (PEP) among the students and analyses the impact of educational intervention measures on the issues amongst the study subjects. A Pre-designed and Pre-tested semi-structured questionnaire was used to evaluate the level of knowledge before and after educational intervention sessions. Knowledge regarding risk of transmission of HIV by needle-stick injury and body fluids against which universal precautions were mandatory increased by 72% following the intervention sessions (χ2 = 53.202, p <0.001). 72% and 36% respondents correctly knew the duration within which to start PEP and the drugs available for PEP, post educational sessions 98% and 96% students were aware of it: the difference being statistically significant (χ2 = 11.294, p <0.001) and (χ2 = 37.748, p <0.001) respectively. The mean pre-intervention score was 8.32; mean post-intervention score was 14.40: statistical analysis showed the results to be significant (t= 13.857, p< 0.001). The study reflects that there is a dearth of knowledge among the study group. Incorporating the concerned issues in the academic curriculum to provide the students with adequate knowledge and information during their formative years is needed
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