Numerical techniques for computational aeroacoustics

The problem of aerodynamic noise is considered following the Computational Aeroacoustics approach which is based on direct numerical simulation of the sound field. In the region of sound generation, the unsteady airflow is computed separately from the sound using Computational Fluid Dynamics (CFD) codes. Overlapping this region and extending further away is the acoustic domain where the linearised Euler equations governing the sound propagation in moving medium are solved numerically. After considering a finite volume technique of improved accuracy, preference is given to an optimised higher order finite difference scheme which is validated against analytical solutions of the governing equations. A coupling technique of two different CFD codes with the acoustic solver is demonstrated to capture the mechanism of sound generation by vortices hitting solid objects in the flow. Sub-grid turbulence and its effect 011sound generation has not been considered in this thesis. The contribution made to the knowledge of Computational Aeroacoustics can be summarised in the following: 1) Extending the order of accuracy of the staggered leap-frog method for the linearised Euler equations in both finite volume and finite difference formulations; 2) Heuristically determined optimal coefficients for the staggered dispersion relation preserving scheme; 3) A solution procedure for the linearised Euler equations involving mirroring at solid boundaries which combines the flexibility of the finite volume method with the higher accuracy of the finite difference schemes; 4) A method for identifying the sound sources in the CFD solution at solid walls and an expansion technique for sound sources inside the flow; 5) Better understanding of the three-level structure of the motions in air: mean flow, flow perturbations, and acoustic waves. It can be used, together with detailed simulation results, in the search for ways of reducing the aerodynamic noise generated by propellers, jets, wind turbines, tunnel exits, and wind-streamed buildings

Consumers' Perceptions of Organic Foods in Bulgaria: Evidence from Semantic Differentials Application

The main tendency for most countries in Central and Eastern Europe is their organic production to be developed mainly for the purpose of export. This leads to the impossibility for organic products to be adapted to the local market and their price happens to be too high for consumers from these countries. The solution to this is the quick development and expansion of the domestic market for organic agricultural products and foods. The market of organic products in Bulgaria enlarged significantly in the last few years. Although the share of organic food products in the general food market in the country is relatively small - less than 5 %, the total area under organic products in Bulgaria (cultivated and wild collected) is more than 250 thousand. The consumer decision-making with regard to organic food products is considered to be one of the priorities for development of the organic agricultural sector and market. In order to promote marketing possibilities for organic foods, it is important that we understand how consumers perceive the quality and safety attributes of organic products. The article aims to present consumers’ perception of Bulgarian organic foods (Bulgarian yoghurt case) by applying the method of semantic differentials. The empirical study is framed by the focus-groups and semantic differential approaches. The first stage of the survey (5 sessions) was carried out in the towns with the most developed market of organic foods in the country (Sofia and Plovdiv). They were conducted in the period May – June 2009. A total number of 46 people participated in the focus-groups. The second stage of the study tests the consumers’ perception of quality and safety attributes of Bulgarian yoghurt by the semantic differential method. Data were collected during April and May 2011 in Sofia. The target population of 84 bulgarians included consumers who are knowledgeable about organic foods and regularly buy organic yogurt. Principal component analysis with varimax rotations extracted six factors for these results and each of them groups around it specific concepts of the bipolar scales used in the study. They are used to build the picture of the perceptions of the respondents regarding the quality and safety of the studied products. The interpretation of the importance of the factors is done by clarifying the semantic relations between the underlying concepts (descriptors)

EFFECT OF CU AS МINORITY АLLOYING ЕLEMENT ON GLASS FORMING ABILITY AND CRYSTALLIZATION BEHAVIOR OF RAPIDLY SOLIDIFIED AL-SI-NI RIBBONS

The influence of copper as a minority alloying element in the process of rapid solidification of Al-Si-Ni ribbons produced by Chill Block Melt Spinning (CBMS) was investigated. XRD and TEM analyses proved a completely amorphous structure of the alloys Al74Ni16Si10 and (Al74Ni16Si10)98Cu2. The crystallization behaviour of these alloys was studied by DSC analysis. It was found that the crystallization of the amorphous alloys (Al74Ni16Si10)100-xCux, x=0, 2 runs in two steps. The temperatures Tx1 and Tx2 of each of the crystallization steps were determined. It was proven that the addition of 2 at. % copper does not significantly change Tx temperatures. The temperature difference ΔTx was calculated and it showed that more thermally stable is the copper containing alloy. Crystalline analogues of the amorphous alloys were obtained by annealing of the melt-spun amorphous ribbons at a temperature which exceeded by 170°C the onset crystallization temperature. The type and size of separated crystalline phases were determined by XRD. It was found that the addition of 2 at. % Cu to Al74Ni16Si10 alloy causes a separation of new phases - Cu3.8Ni and (Al, Cu)Ni3 and 54%, 24% and 7% size increase of the phases Al, Al3Ni, NiSi2 respectively

Artificial neural network (ANN) approach to predicting micro hardness profile values of iron-based sintered alloys

Recent interest in artificial neural networks has considerably extended their use in the field of powder metallurgy. Advanced in the paper is a model for predicting the micro hardness of sintered compacts made from iron powders and powder mixtures through the process of sintering performed in different atmospheres. The proposed model is based on three layer neural network with backpropagation learning algorithm. Specially developed software has been used to provide for the proper functioning of the neural network. Moreover, it should also be noted that the training data used to carry out the research has been collected by a laboratory controlled experimental testing. Finally, the paper concludes that the presented neural network model is applicable for hardness profile prediction of iron-based sintered alloys as confirmed by the experimental results

Pseudomyxoma peritonei - a report of two cases and a review of the literature

Introduction: PMP is a rare disease with a slow but progressive course leading to death. According to the literature PMP encompass wide variety of conditions. To avoid the confusion and to facilitate the treatment and comparison of the results several authors suggested that the term `PMP` should include only the cases with appendiceal origin.Case report: We report two cases with low-grade paseudomyxoma peritonei. The first case was managed by debulking surgery alone with survival 2 years. The second case underwent complete cytoreduction plus HIPEC and 3 years later is still alive and free of disease. There was one patient with a benign appendiceal mucocele treated by appendectomy, who is free of disease 3 years later.Introduction: PMP is a rare disease with a slow but progressive course leading to death. According to the literature PMP encompass wide variety of conditions. To avoid confusion and to facilitate treatment and comparison of the results several authors suggested that the term `PMP` should include only the cases with appendiceal origin.Case report: We report two cases with low-grade paseudomyxoma peritonei. The first case was managed by debulking surgery alone with survival 2 years. The second case underwent complete cytoreduction plus HIPEC and 3 years later is still alive and free of disease. There was one patient with a benign appendiceal mucocele treated by appendectomy, who is free of disease 3 years later.Conclusion: Despite the high complication rate, cytoreductive surgery with HIPEC remains the gold standard in the treatment of pseudomyxoma peritonei. The tumor grade and completeness of cytoreduction are the main prognostic factors. Due to the rarity of the condition most of the surgeons are not experienced enough to manage these patients. Additionally, the incomplete cytoreduction is associated with poorer prognosis and significantly hampers the subsequent interventions. Thus, in the cases when it is found incidentally, the best strategy is the taking of biopsy, appendectomy and subsequent referral to a specialized center for a treatment by multidisciplinary team

Health systems for rare diseases: financial sustainability

Introduction. Distribution of public spending on health depends on a variety of factors, from disease burden and system priorities to organisational aspects and costs. Nowadays, virtually all health care systems face serious sustainability challenges. This is particularly true for rare diseases, where priority setting involves complex and often controversial value-laden choices. Method. The theoretical framework underlying the approach of this work is based upon the State of Health in the EU, a two-year initiative undertaken by the European Commission and developed in cooperation with the Organisation for Economic Co-operation and Development and the European Observatory on Health Systems and Policies. Results. The 2017 report identified five cross-cutting sustainability issues: health promotion and disease prevention, primary care, integrated care, health workforce planning  and forecasting, person-centred health data. Implications and recommendations. Rare diseases have been one of the priorities of the Community’s programmes for research and development. The EU has stimulated a series of actions in the field of rare diseases. These project activities could set up the practical cooperation and come up with the knowledge to translate and to work on the identified five key challenges of EU Member States health systems’ sustainability and resilience

Uticaj dodavanja neorganskog i organskog selena na kvalitet i količinu sperme ovnova severoistočne bugarske merino rase

Selenium is a trace element, which stimulates antioxidant defenses and improves reproductive functions in human and animals, under the form of selenoproteins. The objective of the study was to evaluate the effect of selenium, supplemented as inorganic or organic form in the diet of stud rams, on some of their semen parameters. The experiment was performed with 15 clinically healthy rams from North East Bulgarian merino breed. The animals were divided in three groups (5 per group). The rams from first experimental group (G1) received a diet with supplementation of 4,0mg sodium selenite (Na2SeO3) per animal per day, while the animals of the second experimental group (G2) obtained diet with 1.83g L-selenomethionine (Sel-Plex, Alltech, USA) per animal per day. Eventually, each animal from the G1 and G2 received 1.83g selenium per day. The control group (GC) received a diet without supplementation of selenium. The principal composition of the diet in each group was the same. The ejaculates were obtained via artificial vagina. The evaluated parameters were volume and pH of the ejaculates and motility, concentration and in vitro survivability of the spermatozoa at 39˚S for 360 min. It was found that the supplementation of ram studs diet either with inorganic and organic selenium led to increase in the volume of the ejaculates, motility and survivability of the spermatozoa. The pH of the freshly obtained semen was not affected by selenium treatment.Selen je element u tragovima, koji stimuliše antioksidantske odbrane i poboljšava reproduktivne funkcije kod ljudi i životinja, u obliku selenoproteina. Cilj studije je bio da se proceni efekat selena, dopunjenog u neorganskom ili organskom oblik u ishrani ovnova, na neke parametre semena. Eksperiment je obavljen sa 15 klinički zdravih ovnova severnoistočne bugarske merino rase. Životinje su podeljene u tri grupe (5 po grupi). Ovnovi prve eksperimentalne grupe (G1) dobijali su obrok sa dodatkom 4,0 mg natrijum selenita (Na2SeO3) po grlu dnevno, dok su životinje druge eksperimentalne grupe (G2) hranjene obrokom sa 1,83 g L-selenometionina (Sel- Plek, Alltech, SAD) po grlu dnevno. Na kraju, svaka životinja iz G1 i G2 dobijala je 1,83g selena dnevno. Kontrolna grupa (GC) dobila je obrok bez dodatka selena. Glavni sastav obroka u svakoj grupi bio je isti. Ejakulati su dobijeni preko veštačke vagine. Ocenjivani su sledeći parametri: volumen i pH ejakulata i pokretljivosti, koncentracija i preživljavanje in vitro spermatozoida na 39°C tokom 360 min. Utvrđeno je da dodatak obroku neorganskog i organskog selena doveo do povećanja zapremine ejakulata, pokretljivosti i preživljavanja spermatozoida. Na sveže dobijeno seme nije uticao tretman sa selenom

Comparative characteristics of some methods for estimating energy expenditure in critically ill mechanically ventilated patients

Aim: To compare the energy expenditure (EE) assessed by ventilator-derived carbon dioxide production (EE–VCO2-ventilator) and the energy expenditure calculated from six predictive equations with the gold standard energy expenditure measured with indirect calorimetry (IC) in mechanically ventilated patients. Materials and methods: This is a prospective, non-randomized, one-month study which included six mechanically ventilated patients with FiO2 <60% and PEEP <10 mbar. Thirty-minute measurements were taken using a Cosmed Q-NRG+ metabolic monitor. The average ventilator-derived VCO2 from the Drager Evita Infinity V500 respirator (VʹCO2, ml/min) was calculated for the same period. The IC-measured EE (MEE-IC) was compared with EE–VCO2-ventilator by a formula proposed in ESPEN (8.19×VCO2) and with six predictive equations. Results: Mean MEE-IC was 1650±365 kcal. Mean measured EE–VCO2-ventilator was 1669±340 kcal. A statistically nonsignificant difference was found between the two measurements (p=0.84, correlation coefficient 0.98). Of the predictive equations we compared, the best correlation to the reference method was the Penn State 3 with mean EE of 1679±356 (p=0.81, correlation coefficient of 0.78). Conclusions: In critically ill mechanically ventilated patients, the assessment of EE based on a ventilator-derived VCO2 is an alternative to IC and is more accurate than most predictive equations

Effect of supplementation with inorganic and organic selenium on sperm quality and quantity in North-East Bulgarian merino rams

Selenium is a trace element, which stimulates antioxidant defenses and improves reproductive functions in human and animals, under the form of selenoproteins. The objective of the study was to evaluate the effect of selenium, supplemented as inorganic or organic form in the diet of stud rams, on some of their semen parameters. The experiment was performed with 15 clinically healthy rams from North East Bulgarian merino breed. The animals were divided in three groups (5 per group). The rams from first experimental group (G1) received a diet with supplementation of 4,0mg sodium selenite (Na2SeO3) per animal per day, while the animals of the second experimental group (G2) obtained diet with 1.83g L-selenomethionine (Sel-Plex, Alltech, USA) per animal per day. Eventually, each animal from the G1 and G2 received 1.83g selenium per day. The control group (GC) received a diet without supplementation of selenium. The principal composition of the diet in each group was the same. The ejaculates were obtained via artificial vagina. The evaluated parameters were volume and pH of the ejaculates and motility, concentration and in vitro survivability of the spermatozoa at 39˚S for 360 min. It was found that the supplementation of ram studs diet either with inorganic and organic selenium led to increase in the volume of the ejaculates, motility and survivability of the spermatozoa. The pH of the freshly obtained semen was not affected by selenium treatment

Ultra-short laser surface properties optimization of biocompatibility characteristics of 3D poly-ε-caprolactone and hydroxyapatite composite scaffolds

The use of laser processing for the creation of diverse morphological patterns onto the surface of polymer scaffolds represents a method for overcoming bacterial biofilm formation and inducing enhanced cellular dynamics. We have investigated the influence of ultra-short laser parameters on 3D-printed poly-ε-caprolactone (PCL) and poly-ε-caprolactone/hydroxyapatite (PCL/HA) scaffolds with the aim of creating submicron geometrical features to improve the matrix biocompatibility properties. Specifically, the present research was focused on monitoring the effect of the laser fluence (F) and the number of applied pulses (N) on the morphological, chemical and mechanical properties of the scaffolds. SEM analysis revealed that the femtosecond laser treatment of the scaffolds led to the formation of two distinct surface geometrical patterns, microchannels and single microprotrusions, without triggering collateral damage to the surrounding zones. We found that the microchannel structures favor the hydrophilicity properties. As demonstrated by the computer tomography results, surface roughness of the modified zones increases compared to the non-modified surface, without influencing the mechanical stability of the 3D matrices. The X-ray diffraction analysis confirmed that the laser structuring of the matrices did not lead to a change in the semi-crystalline phase of the PCL. The combinations of two types of geometrical designs—wood pile and snowflake—with laser-induced morphologies in the form of channels and columns are considered for optimizing the conditions for establishing an ideal scaffold, namely, precise dimensional form, mechanical stability, improved cytocompatibility and antibacterial behavior