Search results for: aerodynamic tests

Authors: F. Pedro, S. Dias, A. Tadeu, J. António, Ó. López, A. Coelho

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Railway transportation is considered the most economical and sustainable way to travel. However, future mobility brings important challenges to railway operators. The main target is to develop solutions that stimulate sustainable mobility. The research and innovation goals for this domain are efficient solutions, ensuring an increased level of safety and reliability, improved resource efficiency, high availability of the means (train), and satisfied passengers with the travel comfort level. These requirements are in line with the European Strategic Agenda for the 2020 rail sector, promoted by the European Rail Research Advisory Council (ERRAC). All these aspects involve redesigning current equipment and, in particular, the interior of the carriages. Recent studies have shown that two of the most important requirements for passengers are reasonable ticket prices and comfortable interiors. Passengers tend to use their travel time to rest or to work, so train interiors and their systems need to incorporate features that meet these requirements. Among the various systems that integrate train interiors, the flooring system is one of the systems with the greatest impact on passenger safety and comfort. It is also one of the systems that takes more time to install on the train, and which contributes seriously to the weight (mass) of all interior systems. Additionally, it presents a strong impact on manufacturing costs. The design of railway floor, in the development phase, is usually made relying on a design software that allows to draw and calculate several solutions in a short period of time. After obtaining the best solution, considering the goals previously defined, experimental data is always necessary and required. This experimental phase has such great significance, that its outcome can provoke the revision of the designed solution. This paper presents the methodology and some of the results of an experimental characterisation of composite panels for railway application. The mechanical tests were made for unaged specimens and for specimens that suffered some type of aging, i.e. heat, cold and humidity cycles or freezing/thawing cycles. These conditionings aim to simulate not only the time effect, but also the impact of severe environmental conditions. Both full solutions and separated components/materials were tested. For the full solution, (panel) these were: four-point bending tests, tensile shear strength, tensile strength perpendicular to the plane, determination of the spreading of water, and impact tests. For individual characterisation of the components, more specifically for the covering, the following tests were made: determination of the tensile stress-strain properties, determination of flexibility, determination of tear strength, peel test, tensile shear strength test, adhesion resistance test and dimensional stability. The main conclusions were that experimental characterisation brings a huge contribution to understand the behaviour of the materials both individually and assembled. This knowledge contributes to the increase the quality and improvements of premium solutions. This research work was framed within the POCI-01-0247-FEDER-003474 (coMMUTe) Project funded by Portugal 2020 through the COMPETE 2020.

Keywords: durability, experimental characterization, mechanical tests, railway flooring system

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Authors: Ayda Khosravanihaghighi, Pramod Koshy, Bill Walsh, Vedran Lovric, Charles Christopher Sorrell

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There is an increasing demand for orthopedic implants owing to the increasing numbers of the aging population. Titanium alloy (Ti6Al4V) is a common material used for orthopedic implants owing to its advantageous properties in terms of good corrosion resistance, minimal elastic modulus mismatch with bone, bio-inertness, and high mechanical strength. However, it is important to improve the bioactivity and osseointegration of the titanium alloy and this can be achieved by coating the implant surface with suitable ceramic materials. In the present work, pure and doped-ceria (CeO₂) coatings were deposited by spin coating on the titanium alloy surface in order to enhance the biological interactions between the surface of the implant and the surrounding tissue. In order to examine the bone-binding ability of an implant, simulated body fluid (SBF) tests were conducted in order to assess the capability of apatite layer formation on the surface and thus predict in vivo bone bioactivity. Characterization was done using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses to determine the extent of apatite formation. Preliminary tests showed that the CeO₂ coatings were biocompatible and that the extent of apatite formation and its characteristics can be enhanced by doping with suitable metal ions.

Keywords: apatite layer, biocompatibility, ceria, orthopaedic implant, SBF, spin coater, Ti-implant

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Authors: Abdul Halim Abdullah, Nur Liyana Zainal Abidin, Mahani Mokhtar

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Problem-solving is an activity which can encourage students to use Higher Order Thinking Skills (HOTS). Learning fractions can be challenging for students since empirical evidence shows that students experience difficulties in solving the fraction problems. However, visual methods can help students to overcome the difficulties since the methods help students to make meaningful visual representations and link abstract concepts in Mathematics. Therefore, the purpose of this study was to investigate whether there were any changes in students’ HOTS at the four highest levels when learning the fractions by using Thinking Blocks. 54 students participated in a quasi-experiment using pre-tests and post-tests. Students were divided into two groups. The experimental group (n=32) received a treatment to improve the students’ HOTS and the other group acted as the control group (n=22) which used a traditional method. Data were analysed by using Mann-Whitney test. The results indicated that during post-test, students who used Thinking Blocks showed significant improvement in their HOTS level (p=0.000). In addition, the results of post-test also showed that the students’ performance improved significantly at the four highest levels of HOTS; namely, application (p=0.001), analyse (p=0.000), evaluate (p=0.000), and create (p=0.000). Therefore, it can be concluded that Thinking Blocks can effectively encourage students to use the four highest levels of HOTS which consequently enable them to solve fractions problems successfully.

Keywords: Thinking Blocks, Higher Order Thinking Skills (HOTS), fractions, problem solving

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Authors: Marzieh Amiri, Zahra Iranpour Mobarakeh, Fatemeh Mehrbakhsh, Mehran Amiri

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Introduction: Early diagnosis and intervention of congenital hearing loss is necessary to minimize the adverse effects of hearing loss. The aim of the present study was to report the results of newborn hearing screening in a centerin the south part of Iran, Fasa. Material and methods: In this study, the data related to 6,144 newbornsduring September 2018 up to September2021, was analyzed. Hearing screening was performed using transient evoked otoacoustic emissions (TEOAEs) and automated auditory brainstem response (AABR) tests. Results: From all 6144 newborns,3752 and 2392referred to the center from urban and rural part of Fasa, respectively. There were 2958 female and 3186 male in this study. Of 6144 newborns, 6098 ones passed the screening tests, and 46 neonates were referred to a diagnostic audiology clinic. Finally, nine neonates were diagnosed with congenital hearing loss (seven with sensorineural hearing loss and two with conductive hearing loss). The severity of all the hearing impaired neonates was moderate and above. The most important risk factors were family history of hearing loss, low gestational age, NICU hospitalization, and hyperbilirubinemia. Conclusion: Our results showed that the prevalence of hearing loss was 1.46 per 1000 infants. Boosting public knowledge by providing families with proper education appears to be helpful in preventing the negative effects of delayed implementation of health screening programs.

Keywords: newborn hearing screening, hearing loss, risk factor, prevalence

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Authors: Erkan Polat, Barlas Ozden Caglayan

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By day-to-day developed techniques, it is possible to pass through larger openings by using smaller beam-column sections. Parallel to this trend, it is aimed to produce not only smaller but also economical and architecturally more attractive beams. This study aims to explain the structural behavior of arch steel beam reinforced by using post-tension cable. Due to the effect of post-stressed cable, the arch beam load carrying capacity increases and an optimized section in a smaller size can be obtained with a better architectural view. It also allows better mechanical and applicational solutions for buildings. For better understanding the behavior of the reinforced beam, steel beam and arch steel beam with post-tensioned cable are all modeled and analyzed by using SAP2000 Finite element computer program and compared with each other. Also, full scale test specimens were prepared to test for figuring out the structural behavior and compare the results with the computer model results. Test results are very promising. The similarity of the results between the test and computer analysis shows us that there are no extra knowledge and effort of engineer is needed to calculate such beams. The predicted (and proved by tests) beam carrying capacity is 35% higher than the unreinforced beam carrying capacity. Even just three full scale tests were completed, it is seen that the ratio (%35) may be increased ahead by adjusting the cable post-tension force of beams in much smaller sizes.

Keywords: arch steel beams, pre-stressed cables, finite element, specimen Test

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Authors: Nureni O. Adeboye, Dawud A. Agunbiade

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This research attempts to investigate the effects of heteroscedasticity and periodicity in a Panel Data Regression Model (PDRM) by extending previous works on balanced panel data estimation within the context of fitting PDRM for Banks audit fee. The estimation of such model was achieved through the derivation of Joint Lagrange Multiplier (LM) test for homoscedasticity and zero-serial correlation, a conditional LM test for zero serial correlation given heteroscedasticity of varying degrees as well as conditional LM test for homoscedasticity given first order positive serial correlation via a two-way error component model. Monte Carlo simulations were carried out for 81 different variations, of which its design assumed a uniform distribution under a linear heteroscedasticity function. Each of the variation was iterated 1000 times and the assessment of the three estimators considered are based on Variance, Absolute bias (ABIAS), Mean square error (MSE) and the Root Mean Square (RMSE) of parameters estimates. Eighteen different models at different specified conditions were fitted, and the best-fitted model is that of within estimator when heteroscedasticity is severe at either zero or positive serial correlation value. LM test results showed that the tests have good size and power as all the three tests are significant at 5% for the specified linear form of heteroscedasticity function which established the facts that Banks operations are severely heteroscedastic in nature with little or no periodicity effects.

Keywords: audit fee lagrange multiplier test, heteroscedasticity, lagrange multiplier test, Monte-Carlo scheme, periodicity

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Authors: Yael Neumann

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Attention deficits are common in people with aphasia (PWA). Two treatment approaches address these deficits: domain-general methods like Play Attention, which focus on cognitive functioning, and domain-specific methods like Language-Specific Attention Treatment (L-SAT), which use linguistically based tasks. Research indicates that L-SAT can improve both attentional deficits and functional language skills, while Play Attention has shown success in enhancing attentional capabilities among school-aged children with attention issues compared to standard cognitive training. This study employed a randomized controlled cross-over single-subject design to evaluate the effectiveness of these two attention treatments over 25 weeks. Four PWA participated, undergoing a battery of eight standardized tests measuring language and cognitive skills. The treatments were counterbalanced. Play Attention used EEG sensors to detect brainwaves, enabling participants to manipulate items in a computer game while learning to suppress theta activity and increase beta activity. An algorithm tracked changes in the theta-to-beta ratio, allowing points to be earned during the games. L-SAT, on the other hand, involved hierarchical language tasks that increased in complexity, requiring greater attention from participants. Results showed that for language tests, Participant 1 (moderate aphasia) aligned with existing literature, showing L-SAT was more effective than Play Attention. However, Participants 2 (very severe) and 3 and 4 (mild) did not conform to this pattern; both treatments yielded similar outcomes. This may be due to the extremes of aphasia severity: the very severe participant faced significant overall deficits, making both approaches equally challenging, while the mild participant performed well initially, leaving limited room for improvement. In attention tests, Participants 1 and 4 exhibited results consistent with prior research, indicating Play Attention was superior to L-SAT. Participant 2, however, showed no significant improvement with either program, although L-SAT had a slight edge on the Visual Elevator task, measuring switching and mental flexibility. This advantage was not sustained at the one-month follow-up, likely due to the participant’s struggles with complex attention tasks. Participant 3's results similarly did not align with prior studies, revealing no difference between the two treatments, possibly due to the challenging nature of the attention measures used. Regarding participation and ecological tests, all participants showed similar mild improvements with both treatments. This limited progress could stem from the short study duration, with only five weeks allocated for each treatment, which may not have been enough time to achieve meaningful changes affecting life participation. In conclusion, the performance of participants appeared influenced by their level of aphasia severity. The moderate PWA’s results were most aligned with existing literature, indicating better attention improvement from the domain-general approach (Play Attention) and better language improvement from the domain-specific approach (L-SAT).

Keywords: attention, language, cognitive rehabilitation, neurofeedback

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Authors: Jone Ibarruri, Mikel Manso, Marta Cebrián

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A high amount of food is lost or discarded in the World every year. In addition, in the last decades, an increasing demand of new alternative and sustainable sources of proteins and other valuable compounds is being observed in the food and feeding sectors and, therefore, the use of food by-products as nutrients for these purposes sounds very interesting from the environmental and economical point of view. However, the direct use of discarded fruit and vegetables that present, in general, a low protein content is not interesting as feeding ingredient except if they are used as a source of fiber for ruminants. Especially in the case of aquaculture, several alternatives to the use of fish meal and other vegetable protein sources have been extensively explored due to the scarcity of fish stocks and the unsustainability of fishing for these purposes. Fish mortality is also of great concern in this sector as this problem highly reduces their economic feasibility. So, the development of new functional and natural ingredients that could reduce the need for vaccination is also of great interest. In this work, several fermentation tests were developed at lab scale using a selected mixture of fruit and vegetable discards from a wholesale market located in the Basque Country to increase their protein content and also to produce some bioactive extracts that could be used as additives in aquaculture. Fruit and vegetable mixtures (60/40 ww) were centrifugated for humidity reduction and crushed to 2-5 mm particle size. Samples were inoculated with a selected Rhizopus oryzae strain and fermented for 7 days in controlled conditions (humidity between 65 and 75% and 28ºC) in Petri plates (120 mm) by triplicate. Obtained results indicated that the final fermented product presented a twofold protein content (from 13 to 28% d.w). Fermented product was further processed to determine their possible functionality as a feed additive. Extraction tests were carried out to obtain an ethanolic extract (60:40 ethanol: water, v.v) and remaining biomass that also could present applications in food or feed sectors. The extract presented a polyphenol content of about 27 mg GAE/gr d.w with antioxidant activity of 8.4 mg TEAC/g d.w. Remining biomass is mainly composed of fiber (51%), protein (24%) and fat (10%). Extracts also presented antibacterial activity according to the results obtained in Agar Diffusion and to the Minimum Inhibitory Concentration (MIC) tests determined against several food and fish pathogen strains. In vitro, digestibility was also assessed to obtain preliminary information about the expected effect of extraction procedure on fermented product digestibility. First results indicated that remaining biomass after extraction doesn´t seem to improve digestibility in comparison to the initial fermented product. These preliminary results show that fermented fruit and vegetables can be a useful source of functional ingredients for aquaculture applications and a substitute of other protein sources in the feeding sector. Further validation will be also carried out through “in vivo” tests with trout and bass.

Keywords: fungal solid state fermentation, protein increase, functional extracts, feed ingredients

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Authors: Maxime Alex Junior Kuitche, Ruxandra Mihaela Botez, Jean-Chirstophe Maunand

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The evolution of aircraft is closely linked to the study and improvement of propulsion systems. Determining the propulsion performance is a real challenge in aircraft modeling and design. In addition to theoretical methodologies, experimental procedures are used to obtain a good estimation of the propulsion performances. For piston-propeller propulsion, the propeller needs several experimental tests which could be extremely demanding in terms of time and money. This paper presents a new procedure to estimate the performance of a propeller from a numerical approach using computational fluid dynamic analysis. The propeller was initially scanned, and then, its 3D model was represented using CATIA. A structured meshing and Shear Stress Transition k-ω turbulence model were applied to describe accurately the flow pattern around the propeller. Thus, the Partial Differential Equations were solved using ANSYS FLUENT software. The method was applied on the UAS-S45’s propeller designed and manufactured by Hydra Technologies in Mexico. An extensive investigation was performed for several flight conditions in terms of altitudes and airspeeds with the aim to determine thrust coefficients, power coefficients and efficiency of the propeller. The Computational Fluid Dynamics results were compared with experimental data acquired from wind tunnel tests performed at the LARCASE Price-Paidoussis wind tunnel. The results of this comparison have demonstrated that our approach was highly accurate.

Keywords: CFD analysis, propeller performance, unmanned aerial system propeller, UAS-S45

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Authors: Nassier A. Nassir, Robert Birch, D. Rico Sierra, S. P. Edwardson, G. Dearden, Zhongwei Guan

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The effect of laser surface treatment parameters on the residual strength of titanium alloy has been investigated. The influence of the laser surface treatment on the bonding strength between the titanium and poly-ether-ketone-ketone (PEKK) surfaces was also evaluated and compared to those offered by titanium foils without surface treatment to optimize the laser parameters. Material characterization using an optical microscope was carried out to study the microstructure and to measure the mean roughness value of the titanium surface. The results showed that the surface roughness shows a significant dependency on the laser power parameters in which surface roughness increases with the laser power increment. Moreover, the results of the tensile tests have shown that there is no significant dropping in tensile strength for the treated samples comparing to the virgin ones. In order to optimize the laser parameter as well as the corresponding surface roughness, single-lap shear tests were conducted on pairs of the laser treated titanium stripes. The results showed that the bonding shear strength between titanium alloy and PEKK film increased with the surface roughness increment to a specific limit. After this point, it is interesting to note that there was no significant effect for the laser parameter on the bonding strength. This evidence suggests that it is not necessary to use very high power of laser to treat titanium surface to achieve a good bonding strength between titanium alloy and the PEKK film.

Keywords: bonding strength, laser surface treatment, PEKK, poly-ether-ketone-ketone, titanium alloy

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Authors: Shantha Kumari Muniyandi, Johan Sohaili, Siti Suhaila Mohamad

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The aim of this study was to investigate the suitability of reusing nonmetallic printed circuit boards (PCBs) waste in recycled HDPE (rHDPE) in terms of toxicity and mechanical properties. A series of X-ray Fluorescence Spectrometry (XRF) analysis tests have been conducted on raw nonmetallic PCBs waste to determine the chemical compositions. It can be seen that the nonmetallic PCBs approximately 72% of glass fiber reinforced epoxy resin materials such as SiO2, Al2O3, CaO, MgO, BaO, Na2O, and SrO, 9.4% of metallic materials such as CuO, SnO2, and Fe2O3, and 6.53% of Br. Total Threshold Limit Concentration (TTLC) and Toxicity Characteristic Leaching Procedure (TCLP) tests also have been done to study the toxicity characteristics of raw nonmetallic PCB powders, rHDPE/PCB and virgin HDPE for comparison purposes. For both of the testing, Cu was identified as the highest metal element contained in raw PCBs with the concentration of 905 mg/kg and 59.09 mg/L for TTLC and TCLP, respectively. However, once the nonmetallic PCB was filled in rHDPE composites, the concentrations of Cu were reduced to 134 mg/kg for TTLC and to 3 mg/L for TCLP testing. For mechanical properties testing, incorporation of 40 wt% nonmetallic PCB into rHDPE has increased the flexural modulus and flexural strength by 140% and 36%, respectively. While, Izod Impact strength decreased steadily with incorporation of 10 – 40 wt% nonmetallic PCBs.

Keywords: nonmetallic printed circuit board, recycled HDPE, composites, mechanical properties, total threshold limit concentration, toxicity characteristic leaching procedure

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Authors: Begüm Terzi, Özlem Ateş Sönmezoğlu, Ahmet Yildirim

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Drought is the most important factor that limiting the production and productivity of wheat in the world. The yield of wheat, which is one of the most important crop in the world, reduced depend on drought. Researches to minimize effects of drought are one of the most important about breeding of drought resistant varieties. In recent years, benefiting from the drought resistance wild species and rapid advances in molecular biology studies, researches about drought have been accelerated and number of studies were made on molecular plant breeding which included the molecular mechanisms related to drought resistance. The aim of the present study was characterization of some bread wheat lines for drought tolerance which commonly cultivated in different location of Turkey. In this study, registered 9 bread wheat varieties which on the physiological tests about drought tolerance and 10 bread wheat line has been developed by Transitional Zone Agricultural Research Institute were used. SSR, STS, RAPD and SNP markers that associated with drought tolerance were used. The polymorphisms of the markers were determined by screening of two control varieties. For these purpose 40 molecular markers were used and 12 markers of them were polymorphic among the drought tolerance and the drought sensitive varieties. Control varieties were screened using polymorphic markers. All the DNAs on the genotypes will be searched for the presence of QTLs mapped to different chromosomes. Result of the research, the studied genotypes will be grouped according to drought tolerance and will be detected drought tolerance varieties by molecular markers. In addition, the results will be compared also with physiological tests. The drought tolerant wheat genotypes may be used in breeding studies related to drought stress.

Keywords: bread wheat, drought, molecular marker, Triticum aestivum

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Authors: Himali Gunasekara, Baddika Jayaratne

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Haematological abnormalities are known to cause Ischemic Stroke or Transient Ischemic Attack (TIA). The identification of haematological correlates plays an important role in a management and secondary prevention. The objective of this study was to describe haematological correlates of stroke and their association between stroke profile. The haematological correlates screened were Lupus Anticoagulant, Dysfibroginemia, Paroxysmal nocturnal haemoglobinurea (PNH), Sickle cell disease, Systemic Lupus Erythematosis (SLE) and Myeloploriferative Neoplasms (MPN). A cross sectional descriptive study was conducted in a sample of 152 stroke patients referred to haematology department of National Hospital of Sri Lanka for thrombophilia screening. Different tests were performed to assess each hematological correlate. Diluted Russels Viper Venom Test and Kaolin clotting time were done to assess Lupus anticoagulant. Full blood count (FBC), blood picture, Sickling test and High Performance Liquid Chromatography were the tests used for detection of Sickle cell disease. Paroxysmal nocturnal haemoglobinurea was assessed by FBC, blood picture, Ham test and Flowcytometry. FBC, blood picture, Janus Kinase 2 (V617F) mutation analysis, erythropoietin level and bone marrow examination were done to look for the Myeloproliferative neoplasms. Dysfibrinogenaemia was assessed by TT, fibrinogen antigen test, clot observation and clauss test. Anti nuclear antibody test was done to look for systemic lupus erythematosis. Among study sample, 134 patients had strokes and only 18 had TIA. The recurrence of stroke/TIA was observed in 13.2% of patients. The majority of patients (94.7%) have had radiological evidence of thrombotic event. One fourth of patients had past thrombotic events while 12.5% had family history of thrombosis. Out of haematological correlates screened, Lupus anticoagulant was the commonest haematological correlate (n=16 ) and dysfibrigonaemia(n=11 ) had the next high prevalence. One patient was diagnosed with Essential thrombocythaemia and one with SLE. None of the patients were positive for screening tests done for sickle cell disease and PNH. The Haematological correlates were identified in 19% of our study sample. Among stroke profile only presence of past thrombotic history was statistically significantly associated with haematological disorders (P= 0.04). Therefore, hematological disorders appear to be an important factor in etiological work-up of stroke patients particularly in patients with past thrombotic events.

Keywords: stroke, transient ischemic attack, hematological correlates, hematological disorders

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Authors: Vishaal Subramanian, Annuatha Vinod Kumar, Santosh Kumar Budankayala, M. Senthil Kumar

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This paper discusses the aerodynamic and structural design, simulation and optimization of a mini-High Altitude Long Endurance (HALE) UAV. The applications of this mini HALE UAV vary from aerial topological surveys, quick first aid supply, emergency medical blood transport, search and relief activates to border patrol, surveillance and estimation of forest fire progression. Although classified as a mini UAV according to UVS International, our design is an amalgamation of the features of ‘mini’ and ‘HALE’ categories, combining the light weight of the ‘mini’ and the high altitude ceiling and endurance of the HALE. Designed with the idea of implementation in India, it is in strict compliance with the UAS rules proposed by the office of the Director General of Civil Aviation. The plane can be completely automated or have partial override control and is equipped with an Infra-Red camera and a multi coloured camera with on-board storage or live telemetry, GPS system with Geo Fencing and fail safe measures. An additional of 1.5 kg payload can be attached to three major hard points on the aircraft and can comprise of delicate equipment or releasable payloads. The paper details the design, optimization process and the simulations performed using various software such as Design Foil, XFLR5, Solidworks and Ansys.

Keywords: aircraft, endurance, HALE, high altitude, long range, UAV, unmanned aerial vehicle

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Authors: W. Wen, G. Jackson, S. Maskill, D. G. McCartney, W. Sun

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CoNiCrAlY alloys have been widely used as bond coats for thermal barrier coating (TBC) systems because of low cost, improved control of composition, and the feasibility to tailor the coatings microstructures. Coatings are in general very thin structures, and therefore it is impossible to characterize the mechanical responses of the materials via conventional mechanical testing methods. Due to this reason, miniature specimen testing methods, such as the small punch test technique, have been developed. This paper presents some of the recent research in evaluating the mechanical properties of the CoNiCrAlY coatings at room and high temperatures, through the use of small punch testing and the developed miniature specimen tensile testing, applicable to a range of temperature, to investigate the elastic-plastic and creep behavior as well as ductile-brittle transition temperature (DBTT) behavior. An inverse procedure was developed to derive the mechanical properties from such tests for the coating materials. A two-layer specimen test method is also described. The key findings include: 1) the temperature-dependent coating properties can be accurately determined by the miniature tensile testing within a wide range of temperature; 2) consistent DBTTs can be identified by both the SPT and miniature tensile tests (~ 650 °C); and 3) the FE SPT modelling has shown good capability of simulating the early local cracking. In general, the temperature-dependent material behaviors of the CoNiCrAlY coating has been effectively characterized using miniature specimen testing and inverse method.

Keywords: NiCoCrAlY coatings, mechanical properties, DBTT, miniature specimen testing

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Authors: Anil Nis, Nilufer Ozyurt Zihnioglu

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The object of the study is to investigate fresh state properties of the steel fiber reinforced self-compacting concrete (SFR-SCC). Three different steel fibers; straight (Vf:0.5%), hooked-end long (Vf:0.5% and 1%) and hybrid fibers (0.5%short+0.5%long) were used in the research aiming to obtain flow properties of non-fibrous self-compacting concrete. Fly ash was used as a supplementary with an optimum dosage of 30% of the total cementitious materials. Polycarboxylic ether based high-performance concrete superplasticizer was used to get high flowability with percentages ranging from 0.81% (non-fibrous SCC) to 1.07% (hybrid SF-SCC) of the cement weight. The flowability properties of SCCs were measured via slump flow and V-funnel tests; passing ability properties of SCCs were measured with J-Ring, L-Box, and U-Box tests. Workability results indicate that small increase on the superplasticizer dosages compensate the adverse effects of steel fibers on flowability properties of SSC. However, higher dosage fiber addition has a negative effect on passing ability properties, causing blocking of the mixes. In addition, compressive strength, tensile strength, and four point bending results were given. Results indicate that SCCs including steel fibers have superior performances on tensile and bending strength of concrete. Crack bridging capability of steel fibers prevents concrete from splitting, yields higher deformation and energy absorption capacities than non-fibrous SCCs.

Keywords: fiber reinforced self-compacting concrete, fly ash, fresh state properties, steel fiber

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Authors: Mrunal Phatak

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Introduction: Thyroid hormone is important for the normal function of the auditory system. Hearing impairment can occur insidiously in subclinical hypothyroidism. The present study was undertaken with the aim of evaluating audiological tests like tuning fork tests, pure tone audiometry, brainstem evoked auditory potentials (BAEPs), and auditory reaction time (ART) in hypothyroid women and in age and sex-matched controls to evaluate the effect of thyroid hormone on hearing. The objective of the study was to investigate hearing status by the audiological profile in hypothyroidism (group 1) and healthy controls (group 2) to compare the audiological profile between these groups and find the correlation of levels of TSH, T3 and T4 with the above parameters. Material and methods: A total sample size of 124 women in the age group of 30 to 50 years was recruited and divided into the Cases group comprising 62 newly diagnosed hypothyroid women and a Control group having 62 women with normal thyroid profiles. Otoscopic examination, tuning fork tests, Pure tone audiometry tests (PTA). Brain Stem Auditory Evoked Potential (BAEP) and Auditory Reaction Time (ART) were done in both ears, i.e., a total of 248 ears of all subjects. Results: By BAEPs, hearing impairment was detected in a total of 64 years (51.61%). A significant increase was seen in Wave V latency, IPL I-V and IPL III-V, and the decrease was seen in the amplitude of Wave I and V in both the ears cases. A positive correlation of Wave V latency of the Right and Left ears is seen with TSH levels (p < 0.001) and a negative correlation with T3 (>0.05) and with T4 (p < 0.01). The negative correlation of wave V amplitude of the Right and Left ears is seen with TSH levels (p < 0.001), and a significant positive correlation is seen with T3 and T4. Pure tone audiometry parameters showed hearing impairment of conductive (31.29%), sensorineural (36.29%), as well as mixed type (15.32%). Hearing loss was mild in 65.32% of ears and moderate in 17.74% of ears. Pure tone averages (PTA) were significantly increased in cases than in controls in both ears. A significant positive correlation of PTA of Right and Left ears is seen with TSH levels (p<0.05). A negative correlation between T3 and T4 is seen. A significant increase in HF ART and LF ART is seen in cases as compared to controls. A positive correlation between ART of high frequency and low frequency is seen with TSH levels and a negative correlation with T3 and T4 (p > 0.05). Conclusion: The abnormal BAEPs in hypothyroid women suggest an impaired central auditory pathway. BAEP abnormalities are indicative of a nonspecific injury in the bulbo-ponto-mesencephalic centers. The results of auditory investigations suggest a causal relationship between hypothyroidism and hearing loss. The site of lesion in the auditory pathway is probably at several levels, namely, in the middle ear and at cochlear and retrocochlear sites. Prolonged ART also suggests an impairment in central processing mechanisms. The results of the present study conclude that the probable reason for hearing impairment in hypothyroidism may be delayed impulse conduction in the acoustic nerve up to the level of the midbrain (IPL I-V, III-V), particularly the inferior colliculus (wave V). There is also impairment in central processing mechanisms, as shown by prolonged ART.

Keywords: hypothyroidism, deafness, pure tone audiometry, brain stem auditory evoked potential

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Authors: A. Djoudi, R. Djibaou, H. A. Reguieg Yssaad

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Our study focuses on the study of a bacteria belonging to Pseudomonas solubilizing tricalcium phosphate. They were isolated from rhizosphere of a variety of broad bean grown in salt-affected soils (electrical conductivity between 4 and 8 mmhos/cm) of the irrigated perimeter of Mina in northwestern Algeria. Isolates which have advantageous results in the calcium phosphate solubilization index test were subjected to identification using API20 then used to re-inoculate the same soil in pots experimentation to assess the effects of inoculation on the growth of the broad bean (Vicia faba). Based on the results obtained from the in-vitro tests, two isolates P5 and P8 showed a significant effect on the solubilization of tricalcium phosphate with an index I estimated at 314% and 283% sequentially. According to the results of in-vivo tests, the inoculation of the soil with P5 and P8 were significantly and positively influencing the growth in biometric parameters of the broad bean. Inoculation with strain P5 has promoted the growth of the broad bean in stem height, stem fresh weight and stem dry weight of 108.59%, 115.28%, 104.33%, respectively. Inoculation with strain P8 has fostered the growth of the broad bean stem fresh weight of 112.47%. The effect of Pseudomonas on the development of Vicia faba is considered as an interesting process by which PGPR can increase biological production and crop protection.

Keywords: Pseudomonas, Vicia faba, promoting of plant growth, solubilization tricalcium phosphate

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Authors: Asmaa Al Shafiee, Erdin Ibraim

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Stabilizing slopes by using vegetation is considered as a cost-effective and eco-friendly alternative to the conventional methods. The main aim of this study is to investigate the mechanical effect of analogue root systems on the shear strength of different soil types. Three objectives were defined to achieve the main aim of this paper. Firstly, explore the effect of root architectural design to shear strength parameters. Secondly, study the effect of root area ratio (RAR) on the shear strength of two different soil types. Finally, to investigate how different kinds of soil can affect the behavior of the roots during shear failure. 3D printing tool was used to develop different analogue tap root models with different architectural designs. Direct shear tests were performed on Leighton Buzzard (LB) fraction B sand, which represents a coarse sand and Huston sand, which represent medium-coarse sand. All tests were done with the same relative density for both kinds of sand. The results of the direct shear test indicated that using plant roots will increase both friction angle and cohesion of soil. Additionally, different root designs affected differently the shear strength of the soil. Furthermore, the directly proportional relationship was found between root area ratio for the same root design and shear strength parameters of soil. Finally, the root area ratio effect should be combined with branches penetrating the shear plane to get the highest results.

Keywords: leighton buzzard sand, root area ratio, rooted soil, shear strength, slope stabilization

Procedia PDF Downloads 151

Authors: Chaoqun Tan, Naiyun Gao, Xiaoyan Xin

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Perxymonosulfate (PMS)-based oxidation processes, as an alternative of hydrogen peroxide-based oxidation processes, are more and more popular because of reactive radical species (SO4-•, OH•) produced in systems. Magnetic nano-scaled particles Fe3O4 and ferrous anion (Fe2+) were studied for the activation of PMS for degradation of acetaminophen (APAP) in water. The Fe3O4 MNPs were found to effectively catalyze PMS for APAP and the reactions well followed a pseudo-first-order kinetics pattern (R2>0.95). While the degradation of APAP in PMS-Fe2+ system proceeds through two stages: a fast stage and a much slower stage. Within 5 min, approximately 7% and 18% of 10 ppm APAP was accomplished by 0.2 mM PMS in Fe3O4 (0.8g/L) and Fe2+ (0.1mM) activation process. However, as reaction proceed to 120 min, approximately 75% and 35% of APAP was removed in Fe3O4 activation process and Fe2+ activation process, respectively. Within 120 min, the mineralization of APAP was about 7.5% and 5.0% (initial APAP of 10 ppm and [PMS]0 of 0.2 mM) in Fe3O4-PMS and Fe2+-PMS system, while the mineralization could be greatly increased to about 31% and 40% as [PMS]0 increased to 2.0 mM in in Fe3O4-PMS and Fe2+-PMS system, respectively. At last, the production of reactive radical species were validated directly from Electron Paramagnetic Resonance (ESR) tests with 0.1 M 5,5-Dimethyl-1-pyrrolidine N-oxide (DMPO). Plausible mechanisms on the radical generation from Fe3O4 and Fe2+ activation of PMS are proposed on the results of radial identification tests. The results demonstrated that Fe3O4 MNPs activated PMS and Fe2+ anion activated PMS systems are promising technologies for water pollution caused by contaminants such as pharmaceutical. Fe3O4-PMS system is more suitable for slowly remediation, while Fe2+-PMS system is more suitable for fast remediation.

Keywords: acetaminophen, peroxymonosulfate, radicals, Electron Paramagnetic Resonance (ESR)

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Authors: Bernhard Widhalm, Cornelia Rieder-Gradinger, Ewald Srebotnik

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Pine wood (Pinus sylvestris L.) is the basic raw material for the production of Oriented Strand Boards (OSB) and the major source of volatile organic compounds, especially terpenes (like α- and β-pinene). To lower the total emission level of OSB, terpene metabolising microorganisms were therefore applied onto pine wood strands for the production of emission-reduced boards. Suitable microorganisms were identified during preliminary tests under laboratory conditions. At first, their terpene degrading potential was investigated in liquid culture, followed by laboratory tests using unsterile pine wood particles and strands. The main focus was laid on an adoptable terpene reduction in a short incubation time. An optimised bacterial mixture of Pseudomonas putida and Pseudomonas fluorescens showed the best results and was therefore used for further experiments on a larger scale. In an industry-compatible testing procedure, pine wood strands were incubated with the bacterial mixture for a period of 2 to 4 days. Incubation time was stopped by drying the strands. OSB were then manufactured from the pre-treated strands and emissions were measured by means of SPME/GC-MS analysis. Bacterial pre-treatment of strands resulted in a reduction of α-pinene- and β-pinene-emissions from OSB by 40% and 70%, respectively, even after only 2 days of incubation. The results of the investigation provide a basis for the application of microbial treatment within the industrial OSB production line, where shortest possible incubation times are required. For this purpose, the performance of the bacterial mixture will have to be further optimised.

Keywords: GC-MS, OSB, Pseudomonas sp., terpene degradation

Procedia PDF Downloads 268

Authors: Mrunal Phatak, Suvarna Raut

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Introduction: Thyroid hormone is important for the normal function of the auditory system. Hearing impairment can occur insidiously in subclinical hypothyroidism. The present study was undertaken with the aims of evaluating audiological tests like tuning fork tests, pure tone audiometry, brainstem evoked auditory potentials (BAEPs), and auditory reaction time (ART) in hypothyroid women and in age and sex matched controls so as to evaluate the effect of thyroid hormone on hearing. The objective of the study was to investigate hearing status by the audiological profile in hypothyroidism (group 1) and healthy controls ( group 2) to compare the audiological profile between these groups and find the correlation of levels of TSH, T3, and T4 with the above parameters. Material and methods: A total sample size of 124 women in the age group of 30 to 50 years was recruited and divided into the Cases group comprising of 62 newly diagnosed hypothyroid women and the Control group having 62 women with normal thyroid profile. Otoscopic examination, tuning fork tests, Pure tone audiometry tests (PTA). Brain Stem Auditory Evoked Potential (BAEP) and Auditory Reaction Time (ART) were done in both ears, i.e. total 248 ears of all subjects. Results: By BAEPs, hearing impairment was detected in total 64 ears (51.61%). A significant increase was seen in Wave V latency, IPL I-V, and IPL III-V, and the decrease was seen in the amplitude of Wave I and V in both the ears in cases. Positive correlation of Wave V latency of Right and Left ears is seen with TSH levels (p < 0.001) and a negative correlation with T3 (>0.05) and with T4 (p < 0.01). Negative correlation of wave V amplitude of Right and Left ears is seen with TSH levels (p < 0.001), and a significant positive correlation is seen with T3 and T4. Pure tone audiometry parameters showed hearing impairment of conductive (31.29%), sensorineural (36.29%), as well as the mixed type (15.32%). Hearing loss was mild in 65.32% of ears and moderate in 17.74% of ears. Pure tone averages (PTA) were significantly increased in cases than in controls in both the ears. Significant positive correlation of PTA of Right and Left ears is seen with TSH levels (p<0.05). Negative correlation with T3 and T4 is seen. A significant increase in HF ART and LF ART is seen in cases as compared to controls. Positive correlation of ART of high frequency and low frequency is seen with TSH levels and a negative correlation with T3 and T4 (p > 0.05). Conclusion: The abnormal BAEPs in hypothyroid women suggest an impaired central auditory pathway. BAEP abnormalities are indicative of a nonspecific injury in the bulbo-ponto-mesencephalic centres. The results of auditory investigations suggest a causal relationship between hypothyroidism and hearing loss. The site of lesion in the auditory pathway is probably at several levels, namely, in the middle ear and at cochlear and retrocochlear sites. Prolonged ART also suggests the impairment in central processing mechanisms. The results of the present study conclude that the probable reason for hearing impairment in hypothyroidism may be delayed impulse conduction in acoustic nerve up to the level of the midbrain (IPL I-V, III-V), particularly inferior colliculus (wave V). There is also impairment in central processing mechanisms, as shown by prolonged ART.

Keywords: deafness, pure tone audiometry, brain stem auditory evoked potential, hyopothyroidism

Procedia PDF Downloads 132

Authors: Ferit Çakıcı, M. Kemal Leblebicioğlu

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In this study, characteristics and flight test analysis of a fixed-wing unmanned aerial vehicle (UAV) with hover capability is analyzed. The base platform is chosen as a conventional airplane with throttle, ailerons, elevator and rudder control surfaces, that inherently allows level flight. Then this aircraft is mechanically modified by the integration of vertical propellers as in multi rotors in order to provide hover capability. The aircraft is modeled using basic aerodynamical principles and linear models are constructed utilizing small perturbation theory for trim conditions. Flight characteristics are analyzed by benefiting from linear control theory’s state space approach. Distinctive features of the aircraft are discussed based on analysis results with comparison to conventional aircraft platform types. A hybrid control system is proposed in order to reveal unique flight characteristics. The main approach includes design of different controllers for different modes of operation and a hand-over logic that makes flight in an enlarged flight envelope viable. Simulation tests are performed on mathematical models that verify asserted algorithms. Flight tests conducted in real world revealed the applicability of the proposed methods in exploiting fixed-wing and rotary wing characteristics of the aircraft, which provide agility, survivability and functionality.

Keywords: flight test, flight characteristics, hybrid aircraft, unmanned aerial vehicle

Procedia PDF Downloads 329

Authors: Riccardo Fratini, Riccardo Santini, Jacopo Serafini, Massimo Gennaretti, Stefano Panzieri

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This paper presents a nonlinear differential model, for a three-bladed horizontal axis wind turbine (HAWT) suited for control applications. It is based on a 8-dofs, lumped parameters structural dynamics coupled with a quasi-steady sectional aerodynamics. In particular, using the Euler-Lagrange Equation (Energetic Variation approach), the authors derive, and successively validate, such model. For the derivation of the aerodynamic model, the Greenbergs theory, an extension of the theory proposed by Theodorsen to the case of thin airfoils undergoing pulsating flows, is used. Specifically, in this work, the authors restricted that theory under the hypothesis of low perturbation reduced frequency k, which causes the lift deficiency function C(k) to be real and equal to 1. Furthermore, the expressions of the aerodynamic loads are obtained using the quasi-steady strip theory (Hodges and Ormiston), as a function of the chordwise and normal components of relative velocity between flow and airfoil Ut, Up, their derivatives, and section angular velocity ε˙. For the validation of the proposed model, the authors carried out open and closed-loop simulations of a 5 MW HAWT, characterized by radius R =61.5 m and by mean chord c = 3 m, with a nominal angular velocity Ωn = 1.266rad/sec. The first analysis performed is the steady state solution, where a uniform wind Vw = 11.4 m/s is considered and a collective pitch angle θ = 0.88◦ is imposed. During this step, the authors noticed that the proposed model is intrinsically periodic due to the effect of the wind and of the gravitational force. In order to reject this periodic trend in the model dynamics, the authors propose a collective repetitive control algorithm coupled with a PD controller. In particular, when the reference command to be tracked and/or the disturbance to be rejected are periodic signals with a fixed period, the repetitive control strategies can be applied due to their high precision, simple implementation and little performance dependency on system parameters. The functional scheme of a repetitive controller is quite simple and, given a periodic reference command, is composed of a control block Crc(s) usually added to an existing feedback control system. The control block contains and a free time-delay system eτs in a positive feedback loop, and a low-pass filter q(s). It should be noticed that, while the time delay term reduces the stability margin, on the other hand the low pass filter is added to ensure stability. It is worth noting that, in this work, the authors propose a phase shifting for the controller and the delay system has been modified as e^(−(T−γk)), where T is the period of the signal and γk is a phase shifting of k samples of the same periodic signal. It should be noticed that, the phase shifting technique is particularly useful in non-minimum phase systems, such as flexible structures. In fact, using the phase shifting, the iterative algorithm could reach the convergence also at high frequencies. Notice that, in our case study, the shifting of k samples depends both on the rotor angular velocity Ω and on the rotor azimuth angle Ψ: we refer to this controller as a spatial repetitive controller. The collective repetitive controller has also been coupled with a C(s) = PD(s), in order to dampen oscillations of the blades. The performance of the spatial repetitive controller is compared with an industrial PI controller. In particular, starting from wind speed velocity Vw = 11.4 m/s the controller is asked to maintain the nominal angular velocity Ωn = 1.266rad/s after an instantaneous increase of wind speed (Vw = 15 m/s). Then, a purely periodic external disturbance is introduced in order to stress the capabilities of the repetitive controller. The results of the simulations show that, contrary to a simple PI controller, the spatial repetitive-PD controller has the capability to reject both external disturbances and periodic trend in the model dynamics. Finally, the nominal value of the angular velocity is reached, in accordance with results obtained with commercial software for a turbine of the same type.

Keywords: wind turbines, aeroelasticity, repetitive control, periodic systems

Procedia PDF Downloads 249

Authors: V. Keim, J. Spachtholz, J. Hammer

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The importance of fibre reinforced plastics continually increases due to the excellent mechanical properties, low material and manufacturing costs combined with significant weight reduction. Today, components are usually designed and calculated numerically by using finite element methods (FEM) to avoid expensive laboratory tests. These programs are based on material models including material specific deformation characteristics. In this research project, material models for short glass fibre reinforced plastics are presented to simulate the visco-elasto-plastic deformation behaviour. Prior to modelling specimens of the material EMS Grivory HTV-5H1, consisting of a Polyphthalamide matrix reinforced by 50wt.-% of short glass fibres, are characterized experimentally in terms of the highly time dependent deformation behaviour of the matrix material. To minimize the experimental effort, the cyclic deformation behaviour under tensile and compressive loading (R = −1) is characterized by isothermal complex low cycle fatigue (CLCF) tests. Combining cycles under two strain amplitudes and strain rates within three orders of magnitude and relaxation intervals into one experiment the visco-elastic deformation is characterized. To identify visco-plastic deformation monotonous tensile tests either displacement controlled or strain controlled (CERT) are compared. All relevant modelling parameters for this complex superposition of simultaneously varying mechanical loadings are quantified by these experiments. Subsequently, two different material models are compared with respect to their accuracy describing the visco-elasto-plastic deformation behaviour. First, based on Chaboche an extended 12 parameter model (EVP-KV2) is used to model cyclic visco-elasto-plasticity at two time scales. The parameters of the model including a total separation of elastic and plastic deformation are obtained by computational optimization using an evolutionary algorithm based on a fitness function called genetic algorithm. Second, the 12 parameter visco-elasto-plastic material model by Launay is used. In detail, the model contains a different type of a flow function based on the definition of the visco-plastic deformation as a part of the overall deformation. The accuracy of the models is verified by corresponding experimental LCF testing.

Keywords: complex low cycle fatigue, material modelling, short glass fibre reinforced polyphthalamides, visco-elasto-plastic deformation

Procedia PDF Downloads 215

Authors: Suk Woo Hong, Chang Sung Seok, Jae Mean Koo

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Recently, the welding is widely used in modern industry for joining the structures. However, the waterworks pipes are exposed to the fatigue load by cars, earthquake and etc because of being buried underground. Moreover, the residual stress exists in weld zone by welding process and it is well known that the fatigue life of welded structures is degraded by residual stress. Due to such reasons, the crack can occur in the weld zone of pipeline. In this case, The ground subsidence or sinkhole can occur, if the soil and sand are washed down by fluid leaked from the crack of water pipe. These problems can lead to property damage and endangering lives. For these reasons, the estimation of fatigue characteristics for water pipeline weld zone is needed. Therefore, in this study, for fatigue characteristics estimation of spiral welded waterworks pipe, ASTM standard specimens and Curved Plate specimens were collected from the spiral welded waterworks pipe and the fatigue tests were performed. The S-N curves of each specimen were estimated, and then the fatigue life of weldment Curved Plate specimen was predicted by theoretical and analytical methods. After that, the weldment Curved Plate specimens were collected from the pipe and verification fatigue tests were performed. Finally, it was verified that the predicted S-N curve of weldment Curved Plate specimen was good agreement with fatigue test data.

Keywords: spiral welded pipe, prediction fatigue life, endurance limit modifying factors, residual stress

Procedia PDF Downloads 299

Authors: Fatin Khairani Khairul 'Azam

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Reading comprehension requires the formation of an articulate mental representation of the information in a text. It involves three interdepended elements—the reader, the text, and the activity, all situated into an extensive sociocultural context. Incorporating metacognitive think-aloud strategy into teaching reading comprehension would improve learners’ reading comprehension skills as it helps to monitor their thinking as they read. Furthermore, by integrating Digital Educational Learning Initiative Malaysia (DELIMa) platform in teaching reading comprehension, it can make the process interactive and fun. A quasi-experimental one-group pre-test post-test design was used to identify the effectiveness of using metacognitive think-aloud strategy via DELIMa platform in improving pupils’ reading comprehension performance and their perceptions towards reading comprehension. The participants of the study comprised 82 of form 1 pupils from a secondary school in Pasir Gudang, Johor, Malaysia. All participants were required to sit for pre-and post-tests to track their reading comprehension performance and perceptions. The findings revealed that incorporating metacognitive think-aloud strategy is an effective strategy in teaching reading comprehension as the performance of pupils in reading comprehension and their perceptions towards reading comprehension were improved during the post tests. It is hoped that the findings of the study would be useful to the teachers incorporating the same strategy in teaching to improve pupils' reading skills. It is suggested that future study should involve the motivation factor of the participants on incorporating think-aloud strategy into teaching reading comprehension as well.

Keywords: DELIMa Platform, ESL Learners, Metacognitive Strategy, Pupils' Perceptions, Reading Comprehension, Think-Aloud Strategy

Procedia PDF Downloads 210

Authors: Habib Alehossein, M. S. K. Fernando

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Soil density depends on the volume of the voids and the proportion of the water and air in the voids. However, there is a limit to the contraction of the voids at any given compaction energy, whereby additional water is used to reduce the void volume further by lubricating the particles' frictional contacts. Hence, at an optimum moisture content and specific compaction energy, the density of unsaturated soil can be maximized where the void volume is minimum. However, when considering a full compaction curve and permutations and variations of all these components (soil, air, water, and energy), laboratory soil compaction tests can become expensive, time-consuming, and exhausting. Therefore, analytical methods constructed on a few test data can be developed and used to reduce such unnecessary efforts significantly. Concentrating on the compaction testing results, this study discusses the analytical modelling method developed for some fine-grained and coarse-grained soils of Queensland. Soil properties and characteristics, such as full functional compaction curves under various compaction energy conditions, were studied and developed for a few soil types. Using MATLAB, several generic analytical codes were created for this study, covering all possible compaction parameters and results as they occur in a soil mechanics lab. These MATLAB codes produce a family of curves to determine the relationships between the density, moisture content, void ratio, saturation, and compaction energy.

Keywords: analytical, MATLAB, modelling, compaction curve, void ratio, saturation, moisture content

Procedia PDF Downloads 90

Authors: Richard Nyanzi, Maupi E. Letsoalo, Jacobus N. Eloff, Piet J. Jooste

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Candida albicans naturally occurs in the gastrointestinal tract (GIT) of more than 50% of humans. Overgrowth of the fungus causes several forms of candidiasis including oral thrush. Overgrowth tends to occur in immunocompromised humans such as diabetic, cancer and HIV patients. Antifungal treatment is available, but not without shortcomings. In this study, inhibitory activity of five probiotic Lactobacillus strains was demonstrated against the growth of seven clinical strains of Candida albicans by co-culturing of the organisms in a maize gruel (MG) medium. Phenotypic tests, molecular techniques and phylogenetic analysis have enabled precise identification of the organisms used in the study. The quantitative pour plate technique was used to enumerate colonies of the yeasts and the lactobacilli and the Kruskal-Wallis test and ANOVA tests were employed to compare the distributions of the colonies of the organisms. The cereal medium, containing added carbon sources, was inoculated with a Candida and a Lactobacillus strain in combination and incubated at 37 °C for 168 h. Aliquots were regularly taken and subjected to pH determination and colony enumeration. Certain Lactobacillus strains proved to be inhibitory and also lethal to some Candida albicans strains. A low pH due to Lactobacillus acid production resulted in significant low Candida colony counts. Higher Lactobacillus colony counts did not necessarily result in lower Candida counts suggesting that inhibitory factors besides low pH and competitive growth by lactobacilli contributed to the reduction in Candida counts. Such anti-Candida efficacy however needs to be confirmed by in vivo studies.

Keywords: candida albicans, oral thrush, candidiasis, lactobacillus, probiotics

Procedia PDF Downloads 399

Authors: Lei Xue, Liye Zhao, Jundong Wang, Yu Xue

Abstract:

A hybrid energy conversion system composed of a floating offshore wind turbine (FOWT) and wave energy converters (WECs) may possibly reduce the levelized cost of energy, improving the platform dynamics and increasing the capacity to harvest energy. This paper investigates the aerodynamic performance and dynamic responses of the combined semi-submersible FOWT and point-absorber WECs in frequency and time domains using synthetic optimizing control under turbulent wind and irregular wave conditions. Individual pitch control is applied to the FOWT part, while spring–damping control is used on the WECs part, as well as the synergistic control effect of both are studied. The effect of the above control optimization is analyzed under several typical working conditions, such as below-rated wind speed, rated wind speed, and above-rated wind speed by OpenFAST and WEC-Sim software. Particularly, the wind-wave misalignment is also comparatively investigated, which has demonstrated the importance of applying proper integrated optimal control in this hybrid energy system. More specifically, the combination of individual pitch control and spring–damping control is able to mitigate the platform pitch motion and improve output power. However, the increase in blade root load needs to be considered which needs further investigations in the future.

Keywords: floating offshore wind turbine, wave energy converters, control optimization, individual pitch control, dynamic response

Procedia PDF Downloads 53