Miracle-dz/UniFAR-FTUs huggingface dataset:
Shrinkage compensation approach proposed for ABS material in FDM process

ABSTRACT Dimensional accuracy of parts manufactured by Fused Deposition Modelling (FDM) greatly suffers from the shrinkage problems of the available polymer materials. This paper proposes a constructive idea for resolving the shrinkage issues and explains how shrinkage could be managed by interior geometry of the artifacts fabricated on desktop 3D printers. The main principle for preventing the deterioration on dimensional accuracy of the holes/slots is to utilize the auxiliary lines located from the hole’s perimeter to the outer boundaries of the artifact. Thus, the shrinkage of these auxiliary line segments simply helps to pull the original hole backward, acting against the predicted contraction. In this paper, the proposed approach will be examined using a finite element analysis tool to predict the shrinkage behavior of the fabricated samples along with necessary measurements taken on the Coordinate Measuring Machine. Additionally, an analytical framework for modeling the shrinkage behavior of ABS is to be elaborated. The coherence of the simulations and the measurements are to be analyzed regarding the effect of the geometry and material color on the shrinkage behavior. The discussion involves the improvement on the dimensional accuracy of 3D printed features.
Using Three-Level Fuzzy Space Vector Modulation Method to Improve Indirect Vector Control Strategy of a DFIG Based Wind Energy Conversion Systems

This work present a Indirect Vector Command (IVC) method with three-level space vector modulation (SVM) and Fuzzy regulator (FR) of a doubly fed induction generator (DFIG) incorporated in a wind turbine system (WTS). Classical IVC command technique using three-level SVM inverter presents considerable stator reactive and stator active powers ripples at fixed state period. In order to guaranteed a strong IVC strategy for the DFIG-rotor side converter and decrease stator active and stator reactive powers ripples, a three-level SVM inverter strategy based on fuzzy logic regulator (FSVM) is used in this work. Simulation results show the competence of the proposed strategy of command particularly on the quality of the provided energy comparatively to a classical IVC using SVM inverter.
Creating Optoelectronic Devices from Atomically Thin Materials Grown by Chemical Vapor Deposition

Two-dimensional materials such as graphene and transition metal dichalcogenides (TMDs) are ideal candidates to create ultra-thin optoelectronics that can be flexible and semitransparent. Although optoelectronic devices based on TMDs have demonstrated remarkable performance, most devices are created using techniques that are not suitable for mass production, such as mechanical exfoliation of monolayer flakes and patterning by electron-beam lithography. Here we show device fabrication processes that are suitable for mass production and based on the growth of high-quality atomically thin materials such as graphene, MoS2, WS2,MoSe2 and WSe2 by chemical vapor deposition. Using as-grown materials and photolithography, we achieved photodetectors with high sensitivity and record shot-noise limited detectivities of 8.7 ⇥ 10 Jones in ambient condition and even higher when sealed with a protective layer. We studied MoS2 based devices with gold electrodes and graphene electrodes. The devices with graphene electrodes have a tunable band alignment and are especially attractive for scalable ultra-thin flexible optoelectronics. However, these devices are hindered by a slow photoresponse caused by charge trapping. Gas adsorbates, such as H2O and O2, which create charge traps, are a main contribution to both the high responsivity and the slow photoresponse. We studied the effect of ambient conditions on the performance of MoS2 photodetectors. We show that vacuum pumping with laser illumination combined with hydrophobic substrates removes most of the
Design and Analysis of a Novel CPT System with Soft Ferromagnetic Material Cores and Electromagnetic Resonant Coupling for EVs

This paper describes a novel contactless power transfer (CPT) system with geometrically improved H-shape ferromagnetic cores and electromagnetically prospective modelling analysis methods for wireless power transmitting (WPT) applications of electric vehicles (EVs). A CPT prototype, using optimized H-shaped magnetic couplers and series-to-series (SS) compensation, is proposed to address and ensure the maximization of system efficiency, power transfer ratings, and air gaps of coupling coils. By focusing on the main factors such as various system operating frequencies, different geometric designs of coils, changeable inductive coupling distances, electromagnetic field performances and actual phase angle deviations when the inductive coupling system tends to be stable with its waveforms, this small-sized H-shape CPT system has been analytically considered and modelled in a finite-element method (FEM) environment, resulting in a maximum system efficiency of 59.5%, a coil transmitting efficiency of 83.8% and a maximum power output of 42.81 kW on the load end when the resonant coupling of CPT system tends to occur within a range of calculated resonant frequencies, with an air gap of 10 mm. Moreover, the system efficiency and coil transmitting efficiency can reach 47.75% and 77.22%, respectively, and the highest RMS real power to load can achieve 31.95 kW with an air gap of 20 mm. Besides, with an air gap of 30mm, this H-shape CPT system is measured to output 20.39-kW RMS power, along with the maximum system efficiency and coil efficiency of 41.78% and 63.23%, respectively. Furthermore, the improvements of flux linkage, magnetic flux density regarding the actual electromagnetic performance produced and the issues on the calculated natural resonant frequencies have been studied by result analysis and comparison of electromagnetic field parameters generated. In addition, the current limitations and further design considerations have been discussed in this paper.
Influence of temperature on multiaxial creep behaviour of 304HCu austenitic stainless steel

ABSTRACT Effect of temperature on multiaxial creep behaviour of 304HCu austenitic stainless steel has been investigated. The multiaxiality was introduced by incorporating notches in smooth specimens. Creep rupture life increased with notch acuity ratio having a saturation/decline tendency. Notch strengthening increased with temperature, stress and notch sharpness. Multiaxial ductility decreased rapidly with notch sharpness and tended towards saturation. Fracture mode was found to change from transgranular ductile to intergranular creep depending on the stress, temperature and notch sharpness. Finite element analysis of notched specimens along with orientation imaging microscopic study was carried out to assess the deformation and damage at different normalised stress ratio. A temperature independent unique master plot for multiaxial rupture life as a function of stress has been established.
Surface alteration of aluminium alloy by an exfoliated graphitic tribolayer during friction surfacing using a consumable graphite rich tool

In present study, a strategy for mechanical exfoliation of graphite to a few layered graphene (FLG) coupled with its mechanical infusion onto aluminium (Al6061) substrate through a solid-state friction surfacing (FS) methodology is developed and documented. Here, a graphite-rich and expendable FS tool fabricated through conventional powder metallurgy is used as a source of graphite. Later on, this expendable tool is utilized for impregnating graphite on the aluminium alloy surface through FS. The high frictional shear stress during FS results in the exfoliation of graphite to FLG which is confirmed by the characteristic wrinkled morphology through FE-SEM studies. Experimental results revealed successful impregnation of FLG flakes up to ∼165 μm depth on the surface of aluminium matrix. The effect of graphite flake size (60 mesh (max. 250 μm) and 325 mesh (max. 44 μm)) on specific wear rate and its ability to mechanically exfoliate into a FLG structure is also analysed. Dynamic recrystallization due to plastic deformation during FS results in ∼ 90% grain size reduction relative to the as-received aluminium alloy (reference Al). Excellent interfacial bonding with mechanical intercalation between graphite flake and aluminium matrix is also observed through TEM studies. Intermetallic phase such as Al4C3 is observed at the Al/graphite interface with larger flake size. The tribological properties are significantly improved with the graphite reinforcement leading to the decrease in coefficient of friction by ∼12.5 and 26.7% with graphite of 250 (FS250) and 44 μm (FS44) flake size respectively as compared to the reference Al. The least specific wear rate is observed for FS44 which is about ∼53.4 % and ∼ 28.57 % less than the wear rate of reference Al and FS250, respectively. The microhardness, nano-hardness and XRD studies further corroborate the results.
Morphological, mechanical, and thermal properties of PP/SEBS/talc composites

The aim of this study is to evaluate the effect of some experimental variables such as the content of styrene–ethylene–butylene–styrene (SEBS) and talc, processing conditions and mixing protocol on the properties of polypropylene (PP). To achieve this objective, PP/SEBS blends and PP/SEBS/talc composites were processed in a corotating twin-screw extruder. A masterbatch of PP/talc was prepared before the extrusion of PP/SEBS/talc composites. The morphology of blends and composites was evaluated by scanning electron microscopy, which revealed the dispersion of small rubber droplets in the PP matrix. Moreover, the micrographs also showed that SEBS and talc particles were uniformly dispersed and distributed in the polymer matrix. Results of thermal properties showed that talc had a nucleating effect, which promoted the increase of both PP crystallization temperature and crystallinity degree. The incorporation of talc in PP/SEBS blends led to an expressive increase in the impact resistance by 70% as compared with the reference blend: PP/SEBS 80/20% (w/w). This result reveals that although the PP/SEBS/talc composites showed a separated morphology, the good dispersion and distribution of this mineral filler in the polymers contributed to avoid crack propagation and increase the impact properties. The tensile properties in the elastic region were not significantly affected.
How to Help Older Adults Move the Focus on a Smart TV? Exploring the Effects of Arrow Hints and Element Size Consistency

ABSTRACT The current interfaces of smart TVs (STVs) lack an effective customization that is consistent with the needs of older adults. Accordingly, this study investigates the usability problems encountered by older adults when using STVs, and it identifies solutions to the most frequent problem. In the pilot study, a usability test was conducted and the difficulty of focus manipulation was found to be the most frequent one. Then in the main study, an experiment was conducted to evaluate two solutions (i.e., maintaining consistent element size and adding arrow hints), which involved remote control (RC) and touchscreen interaction (TI) input methods. Fifty-three older adults were recruited to participate in the study and thus four findings were found. First, the task completion time for manipulating focus increases with age and it rapidly increases after 75 years of age. Second, using a simplified RC can significantly improve the task effectiveness and decrease the number of keystrokes and the completion time for manipulating focus when compared with TI. While when using TI, after adding arrow hints to the STV interface the task completion time and the number of keystrokes are reduced. Third, for both input methods, when the interface comprises elements with inconsistent sizes, adding arrow hints was observed to enhance the task effectiveness and shorten the task completion time. However, the arrow hints were counterproductive when the element sizes were consistent. Fourth, the majority of elderly participants preferred to use arrow hints in the STV interface.
Pathways to Proficiency: Examining the Coherence of Initial Second Language Acquisition Patterns within the Language Difficulty Categorization Framework

Title of Dissertation: PATHWAYS TO PROFICIENCY: EXAMINING THE COHERENCE OF INITIAL SECOND LANGUAGE ACQUISITION PATTERNS WITHIN THE LANGUAGE DIFFICULTY CATEGORIZATION FRAMEWORK Megan Christina Masters, Doctor of Philosophy, 2018 Dissertation directed by: Dr. Steven J. Ross, Professor, Second Language Acquisition It has perhaps never been clearer that in order to effectively communicate with global governments and develop reasoned foreign policy, the United States Intelligence Community requires the support of trained linguists. The development of foreign language proficiency is a complex process requiring a significant investment of time and resources. For learners involved in intensive foreign language training within the United States Government (USG), the Department of Defense (DoD) has developed various Language Difficulty Categorization (LDC) frameworks aimed at standardizing the amount of time learners are given to meet established proficiency criteria. Despite the widespread adoption of LDC frameworks over the past 60 years, few empirical studies have examined the systematicity in proficiency patterns for languages grouped within the same difficulty category. By situating the analysis within the framework of a logic model, data-mining techniques were used to statistically model, via path analysis, the relationships between program inputs, activities, and outcomes. Two main studies comprised the investigation. Study 1 employed a contrastiveanalytic approach to examine the coherence with which both cognitive (e.g., general aptitude, language-specific aptitude, and average coursework outcomes) and noncognitive (e.g., language preference self-assessment scores) variables contributed to the development of foreign language achievement and proficiency outcomes for three languages grouped within the same category. For Study 1, only learners who completed the entire foreign language-training program were included in the analysis. Results of Study 1 found a great deal of coherence in the role that language-specific aptitude and 300-level average coursework grades play in predicting end-of-program proficiency outcomes. To examine the potential hidden effects of non-random attrition, Study 2 followed the same methodological procedures as Study 1, but it imputed missing coursework and proficiency test score data for learners who attrited (that is, “dropped out”) during the intensive foreign language-training program. Results of the imputation procedure confirmed that language-specific aptitude plays a robust role in predicting average coursework outcomes across languages. Study 2 also revealed substantial differences in the role that cognitive and non-cognitive variables play in predicting endof-program proficiency outcomes between the observed and imputed datasets as well as across languages and skills. PATHWAYS TO PROFCIENCY: EXAMINING THE COHERENCE OF INITIAL SECOND LANGUAGE ACQUISITION PATTERNS WITHIN THE LANGUAGE DIFFICULTY CATEGORIZATION FRAMEWORK
Influence of Sputtering Power of ZrB2 Target on Structure and Properties of Nanocomposite Zr-B-O Films

The nanocomposite Zr-B-O films based on ZrB2 and ZrO2 are successfully deposited on Si (100) and stainless-steel substrates via a multi-target magnetron co-sputtering system. The influence of the sputtering power of ZrB2 target on sample structure and performance was analyzed by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectrometer (XPS). Nano scratch tests were conducted to measure the films’ mechanical properties. Their oxidation resistance in an aerobic environment was tested by high-temperature oxidation in a muffle furnace. Corrosion behaviors of the Zr-B-O films were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy. It shows that the interior of the composite films has a high degree of non-crystallization. The maximum hardness (26.76 GPa) and corresponding elastic modulus (268.05 Gpa) of the film were obtained at the sputtering power of 120 W. The hardest film also shows the better oxidation resistance with a mass change of around 0.1% before and after oxidation under 1000 °C for 1 h. However, the corrosion resistance of Zr-B-O nanocomposite films is negatively correlated with the power of ZrB2, which is related to the microstructure of the composite film.
Low velocity oblique impact behavior of adhesively bonded single lap joints

Abstract This article addresses the low velocity oblique impact behavior of adhesively bonded single lap joints, and the effects of adherend strength and plastic ductility, impact energy, overlap length and oblique impact angle on the damage initiation and propagation in the adhesive layer. The experimental contact force-time, contact force-central displacement variations, axial separation lengths through the adhesive layer and permanent central deflections of overlap region, adhesive fracture surfaces were evaluated in detail. In the explicit finite element analyses, the adhesive layer was divided into three zones: upper and lower adhesive interfaces and the adhesive layer between these interfaces. The adhesive interfaces were modeled with cohesive zone approach to predict the failure initiation and propagation along both upper and lower adhesive–adherend interfaces, whereas the elastic-plastic material model was implemented for the middle adhesive region between the upper and lower adhesive interfaces. The proposed finite element model predicted reasonably the damage initiation and propagation through the adhesive layer, and the contact force-time/central displacement variations. Especially, the test and analysis results were compared with those of the adhesively bonded single lap joints under a normal transverse impact load. Increasing oblique impact angle resulted in lower peak contact forces, shorter contact durations and earlier damage initiation and propagation through the adhesive layer. The peak contact forces increased, the contact duration decreased with increasing impact energy. The strength and plastic deformation capability of adherend materials also affected the damage initiation and propagation through the adhesive layer as well as the after-impact joint geometry.
Predictive models of auditory perception in human electrophysiology

Author(s): Holdgraf, Christopher | Advisor(s): Knight, Robert T | Abstract: It has long been thought that sensory systems operate by representing information in a hierarchy of sensory features, and that these features build upon one another. From low-level information such as spectral content, to high-level information such as word content, the sensory system must rapidly extract all of these features from the world. However, the precise nature of these levels of representation, as well as how they interact with one another, is not well-understood. In audition, intermediate sensory representations are often studied in animals, using techniques that treat neurons as a linear filter for incoming sensory inputs. If those inputs are spectro-temporal features (e.g., a spectrogram), then the result is a Spectro Temporal Receptive Field (STRF). This describes how the neural unit in question (e.g., a neuron) will respond to patterns in spectro-temporal space. It has been a crucial tool in understanding sensory processing in low-level neural activity. Using this approach it is also possible to study how this neural representation changes under different experimental conditions. STRF plasticity has been shown in both reward- and context-modulated experiments in animals.In recent years, it has been suggested that similar techniques may work in modeling the activity of neural signals recorded from humans. As we cannot generally record from single unit activity in humans, this approach relies on proxies for neural activity – specifically in the high-frequency activity (HFA) of electrocorticography electrodes. This poses a unique opportunity for two reasons: First, human language is a natural stimulus set for studying hierarchical feature representations in the brain. There are many ways to decompose speech into both auditory and linguistic components, and each of these could serve as inputs to the modeling technique described above. Second, humans are especially skilled at using high-level context such as their experience and assumptions about the world in order to change their behavior. This poses a unique opportunity to study the plasticity of speech representations in the brain.This thesis reports several new approaches towards studying the sensory representation of speech in the human brain, as well as how these representations may change due to experience. It aims to bridge the literature in rodents and songbirds with ideas in human electrophysiology in order to pursue new approaches to studying perception in humans.
Probability of Detection (POD)-Oriented View to Fault Diagnosis for Reliability Assessment of FDI Approaches

Reliability assessment of Structural Health Monitoring systems applied to the diagnosis of faults in elastic structures is discussed in this contribution. In the field of Non Destructive Testing (NDT), Probability of Detection (POD) is used as a performance measure for quantifying the reliability of NDT approaches. However, reliability measures applied to Fault Detection and Isolation (FDI) is not discussed much in this research area. In this contribution the reliability of vibration-based monitoring approaches with respect to their principal ability to detect changes, realize diagnosis, and isolate causes (as FDI) is discussed. Using eigenfrequency and band power as attributes, a novel feature-based POD is proposed and implemented as a reliability measure for vibration-based FDI. The a90/95 criteria which represents 90% probability of detecting a fault with 95% level of confidence is successfully implemented to an experimentally realized monitoring system. Emphases is made on improving the detection quality through sensor/information fusion. Acceleration, strain, and deflection measurement paths are utilized for diagnosis purposes based on experimental results.
Scaling Effective Learning Strategies: Retrieval Practice and Long-Term Knowledge Retention in MOOCs

Scientific evidence for effective learning strategies is primarily derived from studies conducted in controlled laboratory or classroom settings with homogeneous populations. Large-scale online learning environments such as MOOCs provide an opportunity to evaluate the efficacy of these learning strategies in an informal learning context with a diverse student population. Retrieval practice, a learning strategy focused on actively recalling information, is recognized as one of the most effective learning strategies in the literature. In this study, we evaluate the extent to which retrieval practice facilitates long-term knowledge retention among MOOC learners using an instructional intervention. We conducted a pre-registered randomized encouragement experiment to test how retrieval practice affects learning outcomes in a MOOC. We observed no effect on learning outcomes and high levels of treatment non-compliance. This suggests that even evidence-based strategies may not work "out of the box" in new learning contexts and require context-aware research on effective implementation approaches. We conducted a series of exploratory studies on the extent to which learners recall knowledge gained in MOOCs over the long term. To our surprise, passing and non-passing learners scored similarly on a knowledge post-test, and both retained approximately two-thirds of what they learned over the long term.