Influence of electrolyte co-additives on the performance of dye-sensitized solar cells

The presence of specific chemical additives in the redox electrolyte results in an efficient increase of the photovoltaic performance of dye-sensitized solar cells (DSCs). The most effective additives are 4-tert-butylpyridine (TBP), N-methylbenzimidazole (NMBI) and guanidinium thiocyanate (GuNCS) that are adsorbed onto the photoelectrode/electrolyte interface, thus shifting the semiconductor's conduction band edge and preventing recombination with triiodides. In a comparative work, we investigated in detail the action of TBP and NMBI additives in ionic liquid-based redox electrolytes with varying iodine concentrations, in order to extract the optimum additive/I₂ ratio for each system. Different optimum additive/I₂ ratios were determined for TBP and NMBI, despite the fact that both generally work in a similar way. Further addition of GuNCS in the optimized electrolytic media causes significant synergistic effects, the action of GuNCS being strongly influenced by the nature of the corresponding co-additive. Under the best operation conditions, power conversion efficiencies as high as 8% were obtained.     

Speech and Video Telephony Quality Characterization and Prediction of Live Contemporary Mobile Communication Networks

Quality of Service (QoS) characterization and prediction is of utmost importance in contemporary operating cellular communications networks. Measurements data of speech and video telephony have been collected using modern experimental equipment. More specifically, key performance indicators of radio, speech and video quality are evoked. The objective of our study is to critically investigate the performance of speech and video telephony at live cellular networks correlating significant QoS parameters from radio and the service side. Simple non-linear regression models are also proposed for speech and video quality prediction. Finally, the paper represents the splendid positive influences of the continuous performance evaluation for the optimization of the mobile networks. There are also briefly given guidelines for mobile networks benchmarking.     

Transboundary Cooperation Through Water Related EU Directives’ Implementation Process. The Case of Shared Waters Between Bulgaria and Greece

Water Resources Management - Coordination on the management of transboundary waters is crucial for the development of riparian regions; nevertheless, lack of common legislation frameworks and...     

Integration of VR with BIM to facilitate real-time creation of bill of quantities during the design phase: A proof of concept study

As building practices change, procedures that seemed indispensable at one point can be abandoned for others, one example of which is the bill of quantities (B/Q). Research into the extant literature attributes the declining use of B/Qs to a multitude of reasons, such as its complexity, the potentially long time required to produce it, the growth in popularity of non-traditional procurement systems, and the challenge of using the information within the document in a construction schedule. With these issues in mind, building information modeling (BIM) and virtual reality (VR) are combined and proposed as a potential solution that allows inclusion of the client into the design process. Following a literature review and precedent study, an experiment was carried out using this new process to simulate a client’s design decisions on window and interior furnishings. The choices made by the client using VR automatically updated a B/Q schedule built in Revit and allowed them to have a firm understanding of project costs. Besides giving the client more confidence in a pleasing final outcome, the technology also ensured an up-to-date, accurate, and easily understandable B/Q. The proposed method features great potential savings in cost and time and gives the B/Q a newfound importance in future construction processes. The research case presented in this paper is a stepping stone in exploring new opportunities offered by VR and BIM and how they could improve the reliability and accuracy of traditional procurement within construction, specifically within the B/Q document.     

CMOS tuners for mobile TV

Digital video reception is emerging as the latest feature toward multimedia-enriched handheld devices. Mobile battery-operated devices require small-size tuners that consume low power and are amenable to single-chip integration with the baseband demodulator. Following an overview of the system and circuit-level implementation challenges of mobile TV standards such as DVB-H and T-DMB, this article presents a dual-band direct conversion tuner for DVB-H. Architecture and circuit trade-offs are discussed, and detailed measurements are presented. The tuner occupies 9.7 mm² and achieves a 4 dB NF at both UHF and L-band, eliminating the need for an external LNA. By using a fractional-TV synthesizer both 470-890 MHz and 1.4-1.8 GHz bands are supported, while achieving an integrated phase noise of less than -41 dBc. Sixth-order low-pass filters support channel bandwidths from 4 to 10 MHz     

Human resource optimisation through semantically enriched data

The industrial domain is experiencing a so-called fourth industrial revolution in which the evergrowing complexity of manufacturing information, the increasing amount of knowledge and the use of web-oriented techniques, represent three crucial factors that are accelerating the growth of complexity of industrial systems. On the other hand, continuous-evolving requirements in industrial environments, due to technology outbreaks and a new global marketplace, have led to an on-going evolution of human resource management through the creation and adoption of alternative business models. In the past decade, semantic models such as ontologies have been proven to be effective for many knowledge-intensive applications, since they provide formal models of domain knowledge that can be exploited in different ways. For all these reasons, an innovative human resource optimisation (HRO) engine is introduced, which employs semantically enhanced information and conditional random field (CRFs) probabilistic models with knowledge derived from industrial shop floor level, and proposes the right person for the right job in real-time shop floor operations towards optimising decisions on how to implement and schedule either repeatedly or non-occurring tasks. Industrial information data flow and semantic enrichment were ensured through the combined use of a common interface data exchange model (CIDEM) and ontologies, after which a feasibility study at a chemical plant presented interesting preliminary results.     

The promoting effect of Fe on Ni/GDC for the Solid Oxide H2O electrolysis

The study deals with the modification of commercial Ni/GDC powder with iron and its use as fuel functional electrode for Solid Oxide H₂O electrolysis. The Fe-NiO/GDC samples were prepared with the Deposition-Precipitation method and characterized, in their oxidized and reduced form, by using BET, HR-TEM, SAED, XRD, XPS and TG analysis in the presence of H₂O. The electrochemical investigation deals with the comparison of single SOECs at 900°C, under various pH₂O/pH₂ ratios. In the oxidized powders iron was detected, both in the bulk and on the surface, in the form of crystallized Fe₂O₃ species, which during H₂-reduction interacted with NiO towards the formation of a Ni-Fe alloy. The latter promoted the electrochemical performance of the Fe-Ni/GDC electrodes, where there are indications of strong dependence on the Fe wt% content. Specifically, the performance of the cell with 0.5 wt% Fe-Ni/GDC was threefold higher than that with Ni/GDC. On the other hand, the cell with 2 wt% Fe-Ni/GDC was worse, implying that the promoting effect of Fe lies on quite low wt% content. Finally, the examined Fe-doped electrodes exhibited increase of polarization in high pH₂O. This is primarily ascribed to the fact that Fe-Ni/GDC electrodes seem more susceptible to H₂O oxidation. Overall, Fe is considered as a promising Ni/GDC dopant, capable to substitute noble metals like Au, but further investigation is required for the elucidation of key preparation and performance parameters.     

Comparison of examination methods based on multiple-choice questions and constructed-response questions using personal computers

The aim of the present research was to compare the use of multiple-choice questions (MCQs) as an examination method, to the examination based on constructed-response questions (CRQs). Despite that MCQs have an advantage concerning objectivity in the grading process and speed in production of results, they also introduce an error in the final formulation of the score. The error is traced to the probability of answering a question by chance or based on an instinctive feeling, which does not enable the ascertainment of the knowledge of the whole background included in the question. In the present study, both MCQ and CRQ tests were given to examinees, in the framework of a computer-based learning system. Avoiding the procedure of mixed scoring, e.g. both positive and negative markings, a set of pairs of MCQs was composed. The MCQs in each pair were similar concerning the same topic, but this similarity was not evident for an examinee that did not possess adequate knowledge on the topic addressed in the questions of the pair. The examination based on these “paired” MCQs, by using a suitable scoring rule, when made to the same sample of students, οn the same topics and with the same levels of difficulty, gave results that were statistically indistinguishable with the grades produced by an examination based on CRQs, while both the “paired” MCQ test results and the CRQ test results differed significantly from those obtained from a MCQ test using positive-only scoring rule.     

Application of microwave-assisted extraction to the fast extraction of plant phenolic compounds

The analysis of phenolic compounds in plants attracts considerable attention. Conventional (reflux) extraction as well as microwave-assisted extraction of phenolic substances from aromatic plants using different solvents has been studied. RP-HPLC with UV detection was employed for the analysis of phenolic compounds. Total phenolic compounds were determined by the Folin-Ciocalteu assay. The amount of extractable phenolic substances for this method decreased with decreasing polarity of the solvent in the order water, 60% methanol, 60% acetone, and ethyl acetate/water (60:30, v/v) by using the conventional method. When microwave-assisted extraction was performed, the previous order was changed to 60% acetone, 60% methanol, water and ethyl acetate/water. The HPLC results have shown similar solvent effect for the two extraction methods. It was also proved that microwave-assisted extraction is a more effective technique compared to the conventional method. The extraction time was reduced, less solvent was used and the amount of extracted phenolic compounds was increased.