12,040 research outputs found
Inverted polymer fullerene solar cells exceeding 10% efficiency with poly(2-ethyl-2-oxazoline) nanodots on electron-collecting buffer layers
Polymer solar cells have been spotlighted due to their potential for low-cost manufacturing but their efficiency is still less than required for commercial application as lightweight/flexible modules. Forming a dipole layer at the electron-collecting interface has been suggested as one of the more attractive approaches for efficiency enhancement. However, only a few dipole layer material types have been reported so far, including only one non-ionic (charge neutral) polymer. Here we show that a further neutral polymer, namely poly(2-ethyl-2-oxazoline) (PEOz) can be successfully used as a dipole layer. Inclusion of a PEOz layer, in particular with a nanodot morphology, increases the effective work function at the electron-collecting interface within inverted solar cells and thermal annealing of PEOz layer leads to a state-of-the-art 10.74% efficiency for single-stack bulk heterojunction blend structures comprising poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxylate] as donor and [6,6]-phenyl-C71-butyric acid methyl ester as acceptor
Medical Cyber-Physical Systems Development: A Forensics-Driven Approach
The synthesis of technology and the medical industry has partly contributed
to the increasing interest in Medical Cyber-Physical Systems (MCPS). While
these systems provide benefits to patients and professionals, they also
introduce new attack vectors for malicious actors (e.g. financially-and/or
criminally-motivated actors). A successful breach involving a MCPS can impact
patient data and system availability. The complexity and operating requirements
of a MCPS complicates digital investigations. Coupling this information with
the potentially vast amounts of information that a MCPS produces and/or has
access to is generating discussions on, not only, how to compromise these
systems but, more importantly, how to investigate these systems. The paper
proposes the integration of forensics principles and concepts into the design
and development of a MCPS to strengthen an organization's investigative
posture. The framework sets the foundation for future research in the
refinement of specific solutions for MCPS investigations.Comment: This is the pre-print version of a paper presented at the 2nd
International Workshop on Security, Privacy, and Trustworthiness in Medical
Cyber-Physical Systems (MedSPT 2017
Light Curve Patterns and Seismology of a White Dwarf with Complex Pulsation
The ZZ Ceti star KUV 02464+3239 was observed over a whole season at the
mountain station of Konkoly Observatory. A rigorous frequency analysis revealed
6 certain periods between 619 and 1250 seconds, with no shorter period modes
present. We use the observed periods, published effective temperature and
surface gravity, along with the model grid code of Bischoff-Kim, Montgomery and
Winget (2008) to perform a seismological analysis. We find acceptable model
fits with masses between 0.60 and 0.70 M_Sun. The hydrogen layer mass of the
acceptable models are almost always between 10^-4 and 10^-6 M_*. In addition to
our seismological results, we also show our analysis of individual light curve
segments. Considering the non-sinusoidal shape of the light curve and the
Fourier spectra of segments showing large amplitude variations, the importance
of non-linear effects in the pulsation is clearly seen.Comment: 5 pages, 6 figures, in "Stellar Pulsation: Challenges for Theory and
Observation", Eds. J. Guzik and P. A. Bradley, AIP
Duality for Finite Multiple Harmonic q-Series
We define two finite q-analogs of certain multiple harmonic series with an
arbitrary number of free parameters, and prove identities for these q-analogs,
expressing them in terms of multiply nested sums involving the Gaussian
binomial coefficients. Special cases of these identities--for example, with all
parameters equal to 1--have occurred in the literature. The special case with
only one parameter reduces to an identity for the divisor generating function,
which has received some attention in connection with problems in sorting
theory. The general case can be viewed as a duality result, reminiscent of the
duality relation for the ordinary multiple zeta function.Comment: 12 pages AMSLaTeX. Submitted for publication October 26, 2003;
revised September 14, 2004. New title reflects change in emphasis and new
section devoted to connections with inverse pairs and Hoffman duality.
References added and typos correcte
Utilising the repertory grid in organisational research:exploring managers’ implicit theories of authentic leadership.
The transformational influence of authentic leadership on followers in early career relationships
Characterizing the pulsations of the ZZ Ceti star KUV 02464+3239
We present the results on period search and modeling of the cool DAV star KUV
02464+3239. Our observations resolved the multiperiodic pulsational behaviour
of the star. In agreement with its position near the red edge of the DAV
instability strip, it shows large amplitude, long period pulsation modes, and
has a strongly non-sinusoidal light curve. We determined 6 frequencies as
normal modes and revealed remarkable short-term amplitude variations. A
rigorous test was performed for the possible source of amplitude variation:
beating of modes, effect of noise, unresolved frequencies or rotational
triplets. Among the best-fit models resulting from a grid search, we selected 3
that gave l=1 solutions for the largest amplitude modes. These models had
masses of 0.645, 0.650 and 0.680 M_Sun. The 3 `favoured' models have M_H
between 2.5x10^-5 - 6.3x10^-6 M_* and give 14.2 - 14.8 mas seismological
parallax. The 0.645 M_Sun (11400 K) model also matches the spectroscopic log g
and T_eff within 1 sigma. We investigated the possibility of mode trapping and
concluded that while it can explain high amplitude modes, it is not required.Comment: 11 pages, 8 figures, accepted for publication in MNRA
Equivalent Linear Two-Body Equations for Many-Body Systems
A method has been developed for obtaining equivalent linear two-body
equations (ELTBE) for the system of many () bosons using the variational
principle. The method has been applied to the one-dimensional N-body problem
with pair-wise contact interactions (McGurie-Yang N-body problem) and to the
dilute Bose-Einstein condensation (BEC) of atoms in anisotropic harmonic traps
at zero temperature. For both cases, it is shown that the method gives
excellent results for large N.Comment: 12 pages, Late
On-Chip Cavity Optomechanical Coupling
On-chip cavity optomechanics, in which strong co-localization of light and
mechanical motion is engineered, relies on efficient coupling of light both
into and out of the on-chip optical resonator. Here we detail our particular
style of tapered and dimpled optical fibers, pioneered by the Painter group at
Caltech, which are a versatile and reliable solution to efficient on-chip
coupling. First, a brief overview of tapered, single mode fibers is presented,
in which the single mode cutoff diameter is highlighted. The apparatus used to
create a dimpled tapered fiber is then described, followed by a comprehensive
account of the procedure by which a dimpled tapered fiber is produced and
mounted in our system. The custom-built optical access vacuum chambers in which
our on-chip optomechanical measurements are performed are then discussed.
Finally, the process by which our optomechanical devices are fabricated and the
method by which we explore their optical and mechanical properties is
explained. It is our expectation that this manuscript will enable the novice to
develop advanced optomechanical experiments.Comment: 31 pages, 9 figure
The Well Organised Working Environment: A mixed methods study
Background: The English National Health Service Institute for Innovation and Improvement designed a series of programmes called The Productive Series. These are innovations designed to help healthcare staff reduce inefficiency and improve quality, and have been implemented in healthcare organisations in at least 14 different countries. This paper examines an implementation of the first module of the Productive Community Services programme called 'The Well Organised Working Environment'. Objective: The quantitative component aims to identify the quantitative outcomes and impact of the implementation of the Well Organised Working Environment module. The qualitative component aims to describe the contexts, mechanisms and outcomes evident during the implementation, and to consider the implication of these findings for healthcare staff, commissioners and implementation teams. Design: Mixed methods explanatory sequential design. Settings: Community Healthcare Organisation in East Anglia, England. Participants: For the quantitative data, participants were 73 staff members that completed End of Module Assessments. Data from 25 services that carried out an inventory of stock items stored were also analysed. For the qualitative element, participants were 45 staff members working in the organisation during the implementation, and four members of the Productive Community Services Implementation Team. Methods: Staff completed assessments at the end of the module implementation, and the value of items stored by clinical services was recorded. After the programme concluded, semi-structured interviews with staff and a focus group with members of the Productive Community Services implementation team were analysed using Framework Analysis employing the principles of Realist Evaluation. Results: 62.5% respondents (n = 45) to the module assessment reported an improvement in their working environment, 37.5% (n = 27) reported that their working environment stayed the same or deteriorated. The reduction of the value of items stored by services ranged from £4 to £5039 across different services. Results of the qualitative analysis suggests explanations for why the programme worked in some contexts and not others, for instance due to varying levels of management support, and varying levels of resources allocated to carrying out or sustaining the improvement work. Conclusions: Quantitative analysis of data generated during healthcare improvement initiatives can give an impression of the benefits realised, but additional qualitative analysis also provides opportunity for learning to improve future implementations. Targets set by commissioners for innovation should focus on sustaining improvement rather demonstrating one-off benefits, and implementation teams should not let their preconceptions of what will and what will not work prevent them from trying interventions that may benefit staff
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