Search results for "CHS"
showing 10 items of 313 documents
Effects of Frequency Dependence of the External Quantum Efficiency of Perovskite Solar Cells
2018
Perovskite solar cells are known to show very long response time scales, on the order of milliseconds to seconds. This generates considerable doubt over the validity of the measured external quantum efficiency (EQE) and consequently the estimation of the short-circuit current density. We observe a variation as high as 10% in the values of the EQE of perovskite solar cells for different optical chopper frequencies between 10 and 500 Hz, indicating a need to establish well-defined protocols of EQE measurement. We also corroborate these values and obtain new insights regarding the working mechanisms of perovskite solar cells from intensity-modulated photocurrent spectroscopy measurements, iden…
Metal frame as local protection of superconducting films from thermomagnetic avalanches
2016
Thermomagnetic avalanches in superconducting films propagating extremely fast while forming unpredictable patterns, represent a serious threat for the performance of devices based on such materials. It is shown here that a normal-metal frame surrounding a selected region inside the film area can provide efficient protection from the avalanches during their propagation stage. Protective behavior is confirmed by magneto-optical imaging experiments on NbN films equipped with Cu and Al frames, and also by performing numerical simulations. Experimentally, it is found that while conventional flux creep is not affected by the frames, the dendritic avalanches are partially or fully screened by them…
Error Estimates of Uzawa Iteration Method for a Class of Bingham Fluids
2015
The paper is concerned with fully guaranteed and computable bounds of errors generated by Uzawa type methods for variational problems in the theory of visco-plastic fluids. The respective estimates have two forms. The first form contains global constants (such as the constant in the Friedrichs inequality for the respective domain), and the second one is based upon decomposition of the domain into a collection of subdomains and uses local constants associated with subdomains.
We need more replication research – A case for test-retest reliability
2017
Following debates in psychology on the importance of replication research, we have also started to see pleas for a more prominent role for replication research in medical education. To enable replication research, it is of paramount importance to carefully study the reliability of the instruments we use. Cronbach’s alpha has been the most widely used estimator of reliability in the field of medical education, notably as some kind of quality label of test or questionnaire scores based on multiple items or of the reliability of assessment across exam stations. However, as this narrative review outlines, Cronbach’s alpha or alternative reliability statistics may complement but not replace psyc…
VET workers’ problem-solving skills in technology-rich environments: European approach
2014
International journal for research in vocational education and training 1 (2014) 1, S. 57-80
Teacher trainees' experiences of the components of ICT competencies and key factors in ICT competence development in work-based vocational teacher tr…
2022
International journal for research in vocational education and training 9 (2022) 2, S. 146-166
Meiofauna as indicator for assessing the impact of fish farming at exposed marine site
2012
This study aimed to detect the impact of organic loads due to biodeposition from a fish farm in an exposed area of the Strait of Sicily, Mediterranean Sea. Sediment chemistry and meiofaunal assemblages were investigated on a seasonal basis at four stations: two from the impacted area and two control stations. The presence of the cages induced a significant accumulation of proteins, lipids and biopolymeric carbon, resulting in a reduction in meiofaunal density at the impacted stations. Changes in community structure were also evident, as meiofauna under the cages were characterized by increased importance of polychaetes and copepods in comparison with a much lower importance of gastrotrichs …
Merkels Briefwechsel
2018
Informācija par G. H. Merķeļa vēstuļu kolekciju Latvijas Universitātes Akadēmiskajā bibliotēkā
Early history of European domestic cattle as revealed by ancient DNA
2006
We present an extensive ancient DNA analysis of mainly Neolithic cattle bones sampled from archaeological sites along the route of Neolithic expansion, from Turkey to North-Central Europe and Britain. We place this first reasonable population sample of Neolithic cattle mitochondrial DNA sequence diversity in context to illustrate the continuity of haplotype variation patterns from the first European domestic cattle to the present. Interestingly, the dominant Central European pattern, a starburst phylogeny around the modal sequence, T3, has a Neolithic origin, and the reduced diversity within this cluster in the ancient samples accords with their shorter history of post-domestic accumulation…
A Positive Definite Advection Scheme for Use in Long Range Transport Models: Extension to Monotonicity
1992
Numerical modeling of atmospheric transport processes requires the solution of the continuity equation for prognostic variables such as momentum, heat, water vapor, liquid water or chemical species of the atmosphere. Although in the literature many advection schemes are known to solve this problem (Lax and Wendroff 1964, Crowley 1968, Tremback et al. 1987, Bott 1989a,b), these algorithms show different disadvantages, which sometimes yield undesirably poor numerical results. For instance, the upstream method is known to produce large numerical diffusion. The higher order versions of the advection schemes of Tremback et al. (1987) are much less diffusive. Unfortunately, the schemes are not po…