Thermal Analysis Of Fused Deposition

Fused Deposition processes involve successive melting, extrusion and solidification of thermoplastic polymer melts. Fluid mechanics and heat transfer of neat or particle-filled polymeric melts, viscoelastic deformation and solidification ofthe roads that are being produced, and repetitive thermal loading of the growing part are important physical processes that control the final quality of the part. Previous computational process models investigated deposition and cooling processes for single and multiple filaments. In the current study, complimentary computational models are presented for the extrusion phase of the process. Impact of liquefier and nozzle design on thermal hardware behavior and operational stability has been quantified. Also a detailed study of temperature field near the vicinity of deposition point is presented with particular emphasis on dimensional analysis and deposition ofmultiple material systems.Mechanical Engineerin

DIVERSITY OF MICROFUNGI ON FAGACEAE IN ULUDAG FORESTS

WOS: 000363091600042Forests ecosystems are sources of oxygen and wood products, also they prevent soil erosion, improve water and air quality, serve as homes for wildlife; and therefore, they preserve and increase biodiversity. Forests can host a diverse community of fungal species with various effects on their host trees. In this research, trees of Fagaceae family of Uludag forests of Bursa province were investigated between the years of 2002 and 2008. By microscopic examination we identified 38 microfungi species in 27 genera belongs to Ascomycota and 1 microfungus species in 1 genus belongs to Basidiomycota. The taxa belong to 15 families: Botryosphaeriaceae, Diaporthaceae, Diatrypaceae, Dothioraceae, Erysiphaceae, Gnomoniaceae, Incertae sedis, Melanconidaceae, Microstromataceae, Nectriaceae, Pseudovalsaceae, Rhytismataceae, Trichosphaeriaceae, Valsaceae and Xylariaceae. The distribution of species by trophic groups revealed a dominance of xylotrophic species. With this study, fungal diversity of Fagaceae family in Uludag forests was identified and included in the mycobiota of Turkey

Fixed vs. Flexible Pricing in a Competitive Market

We study the selection and dynamics of two popular pricing policies—fixed price and flexible price—in competitive markets. Our paper extends previous work in marketing, for example, Desai and Purohit (2004) by focusing on decentralized markets with a dynamic and fully competitive framework while also considering possible noneconomic aspects of bargaining. We construct and analyze a competitive search model, which allows us to endogenize the expected demand depending on pricing rules and posted prices. Our analysis reveals that fixed and flexible pricing policies generally coexist in the same marketplace, and each policy comes with its own list price and customer demographics. More specifically, if customers dislike haggling, then fixed pricing emerges as the unique equilibrium, but if customers get some additional satisfaction from the bargaining process, then both policies are offered, and the unique equilibrium exhibits full segmentation: haggler customers avoid fixed-price firms and exclusively shop at flexible firms, whereas nonhaggler customers do the opposite. We also find that prices increase in customer satisfaction, implying that sellers take advantage of the positive utility enjoyed by hagglers in the form of higher prices. Finally, considering the presence of seasonal cycles in most markets, we analyze a scenario in which market demand goes through periodic ups and downs and find that equilibrium prices remain mostly stable despite significant fluctuations in demand. This finding suggests a plausible competition-based explanation for the stability of prices

Development of phased array probes to operate in time-of-flight diffraction configuration to continuously monitor defect growth in thermal power plants

A high temperature (HT) structural health monitoring system for pipes that utilises phased array (PA) probes in time-of-flight diffraction (TOFD) configuration to continuously monitor the defect growth over time is being developed, so that when the defect reaches a critical size the plant can be shut down and maintenance can take place before failure. The numerical models for PA/TOFD inspection technique in either symmetric or asymmetric pitch-catch configuration were developed using the CIVA simulation platform. The probe characteristics were selected and the ultrasonic beam profile was predicted for different points in the volume of interest i.e. the weld and the heat affected zone (HAZ). The probes positions and interspacing between the probes in emission and reception were also selected in order to achieve maximum inspection coverage. The PA probes use piezoelectric elements for generation and reception of ultrasound beam. Single crystal gallium orthophosphate (GaPO4) has been selected for impedance analysis as a candidate for application in the PA probes operating at HT. Impedance characteristics of GAPO4 elements were investigated up to 580°C and together with measured capacitance (at 1 kHz), density and dimensions of the GAPO4 elements used to calculate material properties of these elements at HT as a function of time. The calculated material properties were used to evaluate the developed PA on TOFD technique at HT using COMSOL simulation package. The simulated and experimental results are encouraging for proceeding with development of PA/TOFD probes using GaPO4, for inspection and condition monitoring of HT pipelines in power plants at temperatures up to 580°C.European Commission through the FP7 Programme (FP7-SME-2013-1) under the grant agreement no. 605267, iKnowHow Informatics, CeramTec, InnoTecUK, Brunel University, Enkon, Vermon, Tecnitest Ingenieros and INETEC

Assessment of material properties of gallium orthophosphate piezoelectric elements for development of phased array probes for continuous operation at 580 degrees C

In this paper, the thickness extension mode gallium orthophosphate single crystal elements were characterised using the impedance analyser. Impedance characteristics of piezoelectric elements were investigated at temperatures from 25°C up to 580°C at first and then at a constant temperature of 580°C for a period of 25 days. The resonant and anti-resonant frequencies extracted from the impedance characteristics, capacitance (measured at 1 kHz), density and dimensions of the gallium orthophosphate elements were used to calculate electromechanical, piezoelectric and elastic properties of these elements at high temperatures as a function of time. The tested gallium orthophosphate elements proved to possess very stable efficiency and sensing capability when subjected to high temperature. The results are very encouraging for proceeding with development of phased array probes using gallium orthophosphate, for inspection and condition monitoring of high temperature pipelines in power plants at a temperature up to 580°C

The Effect of Flipped Instruction on Special Education Preservice Teachers\u27 Perceptions

This study analyzes the flipped instruction model used in three special education educator preparation courses to examine which components preservice teachers perceived most contributed to their content knowledge, motivation, and engagement (n=50). Weekly pre-class asynchronous assignments included the use of educational technology tools such as an interactive e-textbook site, Perusall, and online academic activities such as Khan Academy to strengthen their content knowledge. This allowed more time for a student-centered approach during synchronous instruction to incorporate tools such as Nearpod, Pear Deck, Flipgrid and digital badges to strength-en their motivation and engagement. Data were collected through a post-course survey; results indicate that preservice teachers perceived this model was motivating, engaging, and contributed significantly to their content knowledge. They also identified hands-on activities during class as a significant component of their learning. This article discusses the project, limitations, and implications for future flipped instruction research in special education educator preparation programs

The Effect of Flipped Instruction on Special Education Preservice Teachers\u27 Perceptions

This study analyzes the flipped instruction model used in three special education educator preparation courses to examine which components preservice teachers perceived most contributed to their content knowledge, motivation, and engagement (n=50). Weekly pre-class asynchronous assignments included the use of educational technology tools such as an interactive e-textbook site, Perusall, and online academic activities such as Khan Academy to strengthen their content knowledge. This allowed more time for a student-centered approach during synchronous instruction to incorporate tools such as Nearpod, Pear Deck, Flipgrid and digital badges to strength-en their motivation and engagement. Data were collected through a post-course survey; results indicate that preservice teachers perceived this model was motivating, engaging, and contributed significantly to their content knowledge. They also identified hands-on activities during class as a significant component of their learning. This article discusses the project, limitations, and implications for future flipped instruction research in special education educator preparation programs

Perceived partner responsiveness, daily negative affect reactivity, and all-cause mortality:A 20-year longitudinal study

Objective This study tested longitudinal associations between absolute levels of perceived partner responsiveness (PPR; how much people perceive that their romantic partners understand, care for, and appreciate them), daily negative affect reactivity and positive affect reactivity, and all-cause mortality in a sample of 1,208 adults for three waves of data collection spanning 20 years. We also tested whether longitudinal changes in PPR predicted mortality via affect reactivity. Methods Data were taken from the National Survey of Midlife Development in the United States. PPR was assessed at waves 1 and 2, affect reactivity to stressors was assessed by daily diary reports at wave 2, and mortality status was obtained at wave 3. Results Mediation analyses revealed absolute levels of PPR at wave 1 predicted wave 3 mortality via wave 2 affective reactivity in the predicted direction, but this did not remain robust when statistically accounting for covariates (e.g., marital risk, neuroticism), beta = .004, 95% confidence interval = -.03 to .04. However, wave 1-2 PPR change predicted negative affect (but not positive affect) reactivity to daily stressors at wave 2, which then predicted mortality risk a decade later (wave 3); these results held when adjusting for relevant demographic, health, and psychosocial covariates, beta = -.04, 95% confidence interval = -.09 to -.002. Conclusions These findings are among the first to provide direct evidence of psychological mechanisms underlying the links between intimate relationships and mortality and have implications for research aiming to develop interventions that increase or maintain responsiveness in relationships over time

Fuel tank leakage detection based on acoustic emission

The Plastic Fuel Tanks are widely used in the automotive industry besides steel tanks as they offer numerous advantages such as lower weight, higher corrosion resistance, better crash performance and lower total system costs. Tank manufacturing from plastics and composites has been adapted to mass production to meet the ever growing demand. The management of quality control (QC) systems for the factory environment poses challenges in the absence of relevant experience in the development and use of insitu non-destructive evaluation technologies. The problem currently faced by the automotive industry is that most techniques that meet accepted leak detection sensitivity requirements are operator-dependent. Mechanized leak detection techniques are characterized by high investment and operational costs. Hence, their implementation is not economically feasible as the related costs outweigh their benefits for automotive QC purposes. The proposed Leak Detection project was targeted at bringing a low cost leak detection system that is fast, accurate, traceable and automated for the mass production environment of the fuel tank production industry. The system eliminates the disadvantages associated with the manual-intensive and operator dependent techniques currently employed by the industry, through the use of Acoustic Emission. In this approach, hydrophones were used to listen to the sound induced by gas escaping from tanks under pressure. When pressurized gas leaks from a tank it creates an acoustic signal that can travel through the liquid medium. At the core of the system denoising techniques were designed and developed in order to obtain the highest possible signal to noise ratio (SNR) in the noisy industrial conditions. Experiments were carried out at different conditions including bubble size, distance from hydrophone to the bubble source. Furthermore, experiments were carried out at real industrial plant in order to validate the signal processing techniques and the hardware to detect the bubbles produced by leakage in the real scenario.This work was supported by the EU Horizon 2020 funded project Leak detection, Development of a reliable quality control system using advanced Non-Destructive Evaluation (NDE) technologies for the production environment of leak-free fuel tanks from plastics and composites, (Project reference: 673155)

Ultrasonic guided waves propagation analysis under different load tension levels in multi-wire cables

Power line structures made of multi-wire cables are normally subject to adverse environmental conditions that can affect their integrity. The applicability of several techniques has been studied as a possible structural health monitoring solution. Amongst these, Ultrasonic Guided Waves have shown great potential. The complex geometry of the multi-element cable structures complicates the waves’ propagation behaviour and therefore the signal analysis, making the monitoring of the structural integrity of the cables a challenging task. This research presents the enhancements obtained through the use of a specially designed multiple transducer collar for the inspection of the wires. The waves’ excitation capabilities of the system are experimentally evaluated under different axial unload and load tension levels. The influence of these conditions on wave propagation is analysed. The results show the technique’s long range capabilities as well as its limitations and will thereby contribute towards the design of a future structural health monitoring system.This work is part of MOSAIC project, funded by the UK government under the Innovate UK Programme. MOSAIC is a collaboration between the following organisations: Plant Integrity Ltd (Pi), Brunel Innovation Centre (BIC) Brunel University London, and Applied Inspection® (AI)