30,567 research outputs found
Theory of magnetism with temporal disorder applied to magnetically doped ZnO
A dynamic model of the asymmetric Ising glass is presented: an Ising model
with antiferromagnet bonds with probabilities q arranged at random in a
ferromagnetic matrix. The dynamics is introduced by changing the arrangement of
the antiferromagnetic bonds after n Monte Carlo steps but keeping the same
value of q and spin configuration. In the region where there is a second order
transition between the ferromagnetic and paramagnetic states the dynamic
behaviour follows that expected for motional narrowing and reverts to the
static behaviour only for large n. There is a different dynamic behaviour where
there is a first order transition between the ferromagnetic and spin glass
states where it shows no effects of motional narrowing. The implications of
this are discussed. This model is devised to explain the properties of doped
ZnO where the magnetisation is reduced when the exchange interactions change
with time.Comment: Paper was presented at MMM 2008 and is accepted for publication in
J.A.
Systematic Literature Review of Project Manager’s Leadership Competencies
Purpose: Over the last few decades, a large number of research studies have been carried out on project manager’s leadership competencies. However, systematic literature reviews are still scarce in the project management literature. Therefore, the purpose of this article is to conduct a systematic literature review on project manager’s leadership competencies based on published empirical research studies.
Methodology: We employed a systematic literature review (SLR) methodology to synthesize research in a rigorous manner and a total of 1,780 articles were identified in the first step and a final sample of 60 research studies were synthesized.
Findings: Synthesis of the findings in this SLR on project manager’s leadership competencies revealed: a) there is a lack of categorization or ranking of leadership competencies; b) 20 research studies (46%) were conducted with sample sizes of less than 100; c) only a few research studies (<10%) used interview data for analysis; and d) none of the research studies reported adoption of a triangulation method.
Implications/Limitations: This study prioritized project manager’s leadership competencies as ‘high priority’, ‘moderate priority’, and ‘low priority’. We recommend a sample size between 200 and 300 to produce sophisticated results and enhance the credibility, generalizability and validity of future research.
Originality: Future research studies are suggested to consider systematic literature review combined with face-to-face and group interview in addition to employing triangulation methods. Besides highlighting implications for practitioners, this SLR has advanced the understanding of how to conduct systematic literature reviews in a robust manner
Review of Heavy Quark Physics - theory
Recent progress in the theory of B-meson decays is reviewed with emphasis on
the aspects related to the B-factory data.Comment: 15 pages; Invited Plenary Talk at the 32nd International Conference
on High Energy Physics (ICHEP'04), Beijing, China, Aug. 16-22, 200
On-orbit assembly using superquadric potential fields
The autonomous on-orbit assembly of a large space structure is presented using a method based on superquadric artificial potential fields. The final configuration of the elements which form the structure is represented as the minimum of some attractive potential field. Each element of the structure is then considered as presenting an obstacle to the others using a superquadric potential field attached to the body axes of the element. A controller is developed which ensures that the global potential field decreases monotonically during the assembly process. An error quaternion representation is used to define both the attractive and superquadric obstacle potentials allowing the final configuration of the elements to be defined through both relative position and orientation. Through the use of superquadric potentials, a wide range of geometric objects can be represented using a common formalism, while collision avoidance can make use of both translational and rotation maneuvers to reduce total maneuver cost for the assembly process
Comparing Food and Cash Transfers to the Ultra-Poor in Bangladesh
"Bangladesh has some social safety net programs that transfer food to the poor, some that transfer cash, and some that provide a combination of both. This study evaluates the relative impacts of food and cash transfers on food security and livelihood outcomes among the ultra poor in Bangladesh. The programs impacts are evaluated according to various measures, including how well transfers are delivered; which transfers beneficiaries prefer; how accurately the programs target the extremely poor; effects on food security, livelihoods, and women’s empowerment; and cost effectiveness. The report identifies what has and has not worked in food and cash transfers and recommends ways of improving these programs. This study will be valuable to policymakers and others concerned with poverty reduction in Bangladesh and elsewhere." from textCash transfers, cost effectiveness, food security, Poverty, Poverty reduction, safety net programs, women empowerment,
Some issues related to power generation using wind energy conversion systems: An overview
Design and successful operation of wind energy conversion systems (WECs) is a very complex task and requires the skills of many interdisciplinary skills, e.g., civil, mechanical, electrical and electronics, geography, aerospace, environmental etc. Performance of WECs depends upon subsystems like wind turbine (aerodynamic), gears (mechanical), generator (electrical); whereas the availability of wind resources are governed by the climatic conditions of the region concerned for which wind survey is extremely important to exploit wind energy. This paper presents a number of issues related to the power generation from WECs e.g. factors affecting wind power, their classification, choice of generators, main design considerations in wind turbine design, problems related with grid connections, wind-diesel autonomous hybrid power systems, reactive power control of wind system, environmental aspects of power generation, economics of wind power generation, and latest trend of wind power generation from off shore sites
Unitarization of Gluon Exchange Amplitudes and Rapidity Gaps at the Tevatron
Rapidity gaps between two hard jets at the Tevatron have been interpreted as
being due to the exchange of two gluons which are in an overall color-singlet
state. We show that this simple picture involves unitarity violating
amplitudes. Unitarizing the gluon exchange amplitude leads to qualitatively
different predictions for the fraction of -channel color singlet exchange
events in forward , or scattering, which better fit Tevatron
data.Comment: 21 pages, Revtex, 7 postscript figures included via epsf.sty.
Compressed postscript file of complete paper also available at
http://pheno.physics.wisc.edu/pub/preprints/1998/madph-98-1024.ps.Z or at
ftp://pheno.physics.wisc.edu/pub/preprints/1998/madph-98-1024.ps.
Pseudo-Hermitian Hamiltonians, indefinite inner product spaces and their symmetries
We extend the definition of generalized parity , charge-conjugation
and time-reversal operators to nondiagonalizable pseudo-Hermitian
Hamiltonians, and we use these generalized operators to describe the full set
of symmetries of a pseudo-Hermitian Hamiltonian according to a fourfold
classification. In particular we show that and are the generators of
the antiunitary symmetries; moreover, a necessary and sufficient condition is
provided for a pseudo-Hermitian Hamiltonian to admit a -reflecting
symmetry which generates the -pseudounitary and the -pseudoantiunitary
symmetries. Finally, a physical example is considered and some hints on the
-unitary evolution of a physical system are also given.Comment: 20 page
Assessment of the feasibility of an ultra-low power, wireless digital patch for the continuous ambulatory monitoring of vital signs.
BACKGROUND AND OBJECTIVES: Vital signs are usually recorded at 4–8 h intervals in hospital patients, and deterioration between measurements can have serious consequences. The primary study objective was to assess agreement between a new ultra-low power, wireless and wearable surveillance system for continuous ambulatory monitoring of vital signs and a widely used clinical vital signs monitor. The secondary objective was to examine the system's ability to automatically identify and reject invalid physiological data. SETTING: Single hospital centre. PARTICIPANTS: Heart and respiratory rate were recorded over 2 h in 20 patients undergoing elective surgery and a second group of 41 patients with comorbid conditions, in the general ward. OUTCOME MEASURES: Primary outcome measures were limits of agreement and bias. The secondary outcome measure was proportion of data rejected. RESULTS: The digital patch provided reliable heart rate values in the majority of patients (about 80%) with normal sinus rhythm, and in the presence of abnormal ECG recordings (excluding aperiodic arrhythmias such as atrial fibrillation). The mean difference between systems was less than ±1 bpm in all patient groups studied. Although respiratory data were more frequently rejected as invalid because of the high sensitivity of impedance pneumography to motion artefacts, valid rates were reported for 50% of recordings with a mean difference of less than ±1 brpm compared with the bedside monitor. Correlation between systems was statistically significant (p<0.0001) for heart and respiratory rate, apart from respiratory rate in patients with atrial fibrillation (p=0.02). CONCLUSIONS: Overall agreement between digital patch and clinical monitor was satisfactory, as was the efficacy of the system for automatic rejection of invalid data. Wireless monitoring technologies, such as the one tested, may offer clinical value when implemented as part of wider hospital systems that integrate and support existing clinical protocols and workflows
Cost impact of a non-invasive, portable device for patient self-administration of chronic migraine in a UK National Health Service setting
Background Chronic migraine (CM) is a neurological disorder associated with
substantial disability. Botulinum toxin type A (Botox) is an approved and
effective preventive treatment option for adult patients with CM. Transcranial
magnetic stimulation (TMS) is an alternative treatment device delivering a
brief pre-set magnetic pulse used for self-administration by the patient at
home. Despite being available in a risk share scheme TMS is perceived to be
more costly in the UK. The objective of this study was to analyse the
incremental costs of TMS compared to Botox in refractory CM patients both for
a UK individual funding request setting as well as for an average UK
specialist center setting. Methods Cost impact results were derived from a
decision-tree model simulating treatment pathways over 1 year. Costs were
applied from the most recently available UK data sources. Sensitivity analysis
was performed for all variables. Results Based on published utilisation data
45.5 % of CM patients would continuously receive Botox over 1 year, whereas
53.7 % of TMS patients would be still on treatment at the end of year one.
Total costs of Botox treatment accrue to £2923 in an individual funding
request NHS cost setting, whereas TMS treatment results in £1466 in the first
year. Applying a time-based NHS cost setting expenditures accrue to £1747 for
the Botox treatment and to £1361 for the TMS treatment. In both cost settings
variation of cost assumptions did have a minor impact on the cost increment
from Botox to TMS. Conclusion The current risk share based remuneration model
of TMS allows the UK NHS to reimburse only the cost of those patients
experiencing reduction in migraine days resulting in lower costs for treating
migraine attacks. Treatment of chronic refractory migraine using TMS implies a
substantial cost reduction potential for the management of chronic treatment
of refractory migraine patients compared to conventional Botox treatment
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