443,910 research outputs found
Laboratory surveillance of communicable diseases : enteric pathogens
Laboratories represent a crucial link in the surveillance chain. Since only a small proportion of cases of enteric infections are asked to submit a stool sample, one needs to assess the practices for testing for enteric pathogens and their notification practices. Five local laboratories participated in this study. This included a description of the laboratory practices; capacity for stool sample analysis; awareness of the notification system and the factors which could improve the system at laboratory level.peer-reviewe
Wavelet-Based Kernel Construction for Heart Disease Classification
© 2019 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERINGHeart disease classification plays an important role in clinical diagnoses. The performance improvement of an Electrocardiogram classifier is therefore of great relevance, but it is a challenging task too. This paper proposes a novel classification algorithm using the kernel method. A kernel is constructed based on wavelet coefficients of heartbeat signals for a classifier with high performance. In particular, a wavelet packet decomposition algorithm is applied to heartbeat signals to obtain the Approximation and Detail coefficients, which are used to calculate the parameters of the kernel. A principal component analysis algorithm with the wavelet-based kernel is employed to choose the main features of the heartbeat signals for the input of the classifier. In addition, a neural network with three hidden layers in the classifier is utilized for classifying five types of heart disease. The electrocardiogram signals in nine patients obtained from the MIT-BIH database are used to test the proposed classifier. In order to evaluate the performance of the classifier, a multi-class confusion matrix is applied to produce the performance indexes, including the Accuracy, Recall, Precision, and F1 score. The experimental results show that the proposed method gives good results for the classification of the five mentioned types of heart disease.Peer reviewedFinal Published versio
Weblogs in Higher Education - Why Do Students (Not) Blog?
Positive impacts on learning through blogging, such as active knowledge construction and reflective writing, have been reported. However, not many students use weblogs in informal contexts, even when appropriate facilities are offered by their universities. While motivations for blogging have been subject to empirical studies, little research has addressed the issue of why students choose not to blog. This paper presents an empirical study undertaken to gain insights into the decision making process of students when deciding whether to keep a blog or not. A better understanding of students' motivations for (not) blogging may help decision makers at universities in the process of selecting, introducing, and maintaining similar services. As informal learning gains increased recognition, results of this study can help to advance appropriate designs of informal learning contexts in Higher Education. The method of ethnographic decision tree modelling was applied in an empirical study conducted at the Vienna University of Technology, Austria. Since 2004, the university has been offering free weblog accounts for all students and staff members upon entering school, not bound to any course or exam. Qualitative, open interviews were held with 3 active bloggers, 3 former bloggers, and 3 non‑ bloggers to elicit their decision criteria. Decision tree models were developed out of the interviews. It turned out that the modelling worked best when splitting the decision process into two parts: one model representing decisions on whether to start a weblog at all, and a second model representing criteria on whether to continue with a weblog once it was set up. The models were tested for their validity through questionnaires developed out of the decision tree models. 30 questionnaires have been distributed to bloggers, former bloggers and non‑ bloggers. Results show that the main reasons for students not to keep a weblog include a preference for direct (online) communication, and concerns about the loss of privacy through blogging. Furthermore, the results indicate that intrinsic motivation factors keep students blogging, whereas stopping a weblog is mostly attributable to external factors
DSOGI-PLL based power control method to mitigate control errors under disturbances of grid connected hybrid renewable power systems
The control of power converter devices is
one of the main research lines in interfaced renewable
energy sources, such as solar cells and wind turbines.
Therefore, suitable control algorithms should be
designed in order to regulate power or current properly
and attain a good power quality for some disturbances,
such as voltage sag/swell, voltage unbalances and fluctuations,
long interruptions, and harmonics. Various
synchronisation techniques based control strategies
are implemented for the hybrid power system applications
under unbalanced conditions in literature studies.
In this paper, synchronisation algorithms based
Proportional-Resonant (PR) power/current controller
is applied to the hybrid power system (solar cell + wind
turbine + grid), and Dual Second Order Generalized
Integrator-Phase Locked Loop (DSOGI-PLL) based PR
controller in stationary reference frame provides a solution
to overcome these problems. The influence of
various cases, such as unbalance, and harmonic conditions,
is examined, analysed and compared to the PR
controllers based on DSOGI-PLL and SRF-PLL. The
results verify the effectiveness and correctness of the
proposed DSOGI-PLL based power control method
Contextual Sensitivity in Grounded Theory: The Role of Pilot Studies
Grounded Theory is an established methodological approach for context specific inductive theory building. The grounded nature of the methodology refers to these specific contexts from which emergent propositions are drawn. Thus, any grounded theory study requires not only theoretical sensitivity, but also a good insight on how to design the research in the human activity systems to be studied. The lack of this insight may result in inefficient theoretical sampling or even erroneous purposeful sampling. These problems would not necessarily be critical, as it could be argued that through the elliptical process that characterizes grounded theory, remedial loops would always bring the researcher to the core of the theory. However, these elliptical remedial processes can take very long periods of time and result in catastrophic delays in research projects. As a strategy, this paper discusses, contrasts and compares the use of pilot studies in four different grounded theory projects. Each pilot brought different insights about the context, resulting in changes of focus, guidance to improve data collection instruments and informing theoretical sampling. Additionally, as all four projects were undertaken by researchers with little experience of inductive approaches in general and grounded theory in particular, the pilot studies also served the purpose of training in interviewing, relating to interviewees, memoing, constant comparison and coding. This last outcome of the pilot study was actually not planned initially, but revealed itself to be a crucial success factor in the running of the projects. The paper concludes with a theoretical proposition for the concept of contextual sensitivity and for the inclusion of the pilot study in grounded theory research designs
Optimization of the position of single-lead wireless sensor with low electrodes separation distance for ECG-derived respiration
A classical method for estimation of respiratory information from electrocardiogram (ECG), called ECG - derived respiration (EDR), is using flexible electrodes located at standard electrocardiography positions. This work introduces an alternative approach suitable for miniaturized sensors with low inter-electrode separation and electrodes fixed to the sensor encapsulation. Application of amplitude EDR algorithm on single-lead wireless sensor system with optimized electrode positions shows results comparable with standard robust systems. The modified method can be applied in daily physiological monitoring, in sleep studies or implemented in smart clothes when standard respiration techniques are not suitable
Fabrication And Thermoelectric Characterization Of Stretchable Conductive Latex-Based Composites
Miniaturized stretchable electronic devices that can be bent and strained elastically without breaking, have drawn considerable research interest in recent years for wearable computers and integrated bio-sensor applications. Portable electrical power harvesting remains a critical challenge in flexible electronics materials. One proposed solution has been to convert waste heat from the human body into electricity using thermoelectric materials. Traditionally, however, these materials are brittle ceramic semiconductors with limited fracture resistance under deformation. The primary objective of this thesis is to address this challenge by fabricating and studying the mechanical, thermal and electrical performance of stretchable composites combining natural latex polymer with either metallic (Ni) or thermoelectric (InSb) powders. Ni-based and InSb-based latex specimens were synthesized with different powder concentrations up to 36 vol.%. The effects of the powder concentration on tensile elongation, electrical conductivity, and thermal conductivity of the composites were measured at ambient temperature. Strong dependences of mechanical and electrical properties on powder concentration were found. By contrast, thermal conductivity was observed to remain low at all concentrations, suggesting that the predominant heat transport process is through the low-conductivity latex matrix rather than the conductive particles.
This thesis was conducted with the support of a Vermont Space Grant Consortium graduate research assistantship
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