Hz Of Frequency Research Articles

Experimental and numerical investigation of static and fatigue behavior of mortar with blast furnace slag sand as fine aggregates in air and water

The experimental and analytical study are attempted to clarify the static and fatigue behavior of mortar with blast furnace slag (BFS) sand as fine aggregates in compression in air and water. The cylindrical BFS mortar specimens were used for static and fatigue compression tests in air and water and results are compared with those of mortar using crushed sand (CS). The fatigue load was applied in the form of sine signal with a constant amplitude and the frequency of 5Hz. The stress level is varied from 60%, 70% and 80% of the uniaxial compressive strength. The experimental results disclose that BFS mortar exhibits more fatigue life compared to CS mortar in air, while it is similar in water. Thereafter, the stress-strain relationships for each mortar under monotonic loading are formulated. Moreover, a simplified fatigue model for the assessment of plastic strain, total strain and fracture parameter at different number of loading cycles and for prediction of fatigue life is also proposed.

Cyclic compression stimulates osteoblast differentiation via activation of the Wnt/β-catenin signaling pathway.

It is widely accepted that mechanical stress is an important factor in bone associated cell differentiation, including that of mesenchymal stem cells, osteoblasts and osteocytes. The present study aimed to determine the effect of mechanical cyclic compressive load on osteoblast differentiation, and whether this was associated with activation of the wingless‑type (Wnt)/β-catenin signaling pathway. Using a 3D scaffold model, MC3T3‑E1 cells were exposed to cyclic compressive loading via the Flexcell‑5000C™ Compression system. Sinusoidal wave magnitudes of 0.33, 0.5and1MPa were applied for 4, 6 and 8h, at 1Hz frequency. Expression levels of genes associated with osteoblast differentiation were enhanced following compression, including alkaline phosphatase, osteocalcin, runt‑related transcription factor2 and osterix. Optimal compression was observed using a magnitude of 0.5MPa for 6h, whereas a magnitude of 1MPa had no effect on osteoblast differentiation, and had a negative effect when applied for prolonged time periods. Compressive loading additionally enhanced the mRNA expression levels of the Wnt/β‑catenin signaling pathway component, low density lipoprotein receptor‑related protein 5, and the protein expression levels of Wnt1, disheveled segment polarity protein‑2 (DVL2) and β-catenin. By contrast, mRNA expression levels of sclerostin and the inactive form of β-catenin (phosphorylated at Ser33/37/Thr41) were reduced following compressive loading. Following compressive loading of cells, dickkopf-related protein1 (DKK‑1), an inhibitor of the Wnt signaling pathway, increased protein expression levels of the inactive form of the Wnt‑associated protein, phosphorylated‑β‑catenin, compared with compression alone. However, DVL2 and Wnt1 protein expression levels were unaffected, suggesting that the loading‑induced activation of Wnt/β‑catenin signaling decreased however, it was not prevented by DKK‑1 treatment. In conclusion, the present study demonstrated that cyclic compressive load promoted osteoblast differentiation and may be dependent on the Wnt/β-catenin signaling pathway in regard to magnitude and duration.

PVDF based flexible piezoelectric nanogenerators using conjugated polymer:PCBM blend systems

Piezoelectric energy harvesting technology has received much attention as a powerful source of energy for a self-powered system. In this study, three main conjugated polymers that have delocalized π-electrons and excellent charge transport properties were studied: poly(3-hexylthiophene) (P1), poly[(4,8-di-(2-ethylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(5,5′-yl-4,4′-bis(dodecyl)-2,2′-bithiophene)] (P2) and poly[(4,8-di-(2-ethylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(5,5′-yl-4,4′-bis(2-ethylhexyl)-2,2′-bithiophene)] (P3). Each of three polymers was blended with phenyl-C61-butyric acid methyl ester (PCBM61), and the blend systems were used to make PVDF based piezoelectric nanogenerators (PNG-0–3). Polymers showed bimodal structures that have a majority edge-on orientation, forming a minority face-on orientation. At a 2Hz frequency and 0.2mm displacement, the output voltages (peak-to-peak) of PNG-(0–3) were 35.0V, 41.2V, 42.2V and 43.1V, respectively, and the output currents (peak-to-peak) were 558.5nA, 569.5nA, 572nA and 589nA, respectively. The energy conversion efficiencies of PNGs (0–3) were 6.47%, 11.62%, 13.36%, and 14.33%, respectively; therefore, the efficiency was improved by up to about 2.2 times.

Two Heat Source Models to Simulate Welding Processes with Magnetic Deflection

Abstract The technique of weaving by magnetic arc deflection was developed a few years ago to enable the oscillation of the weld pool, thus, causing grain refinement and improving the properties on the welded joint. This paper aims to propose two heat source models that include effects of magnetic arc deflection on a bead-on-plate GTAW process in numerical simulations by using the finite element method. Two cases are studied. In the first case, non-deflected arc and straigth magnectic deflected arc along the torch movement are carried out and compared to numerical simulations. Temperatures at three different points on the backside of the plates (two away from the welding center line and one in its center) and weld pools of SAE 1020 3.2 mm and 6 mm thick steel plates are analyzed. Results obtained by numerical simulations are close to the experimental ones. In the second case, welding with weaving (frequency of 1Hz) on 3 mm thick steel plates is analyzed. The bead width and its visual presentation are compared to experimental results, which show good agreement with both proposed models.

Exclusion of fish and invertebrates from benthic patches of artificial aquatic environments across water conductivity levels using high-frequency (10 Hz) pulses and adjustable electrical settings

Livestock fence chargers are often used to generate pulsed electrical fields in freshwater environments to exclude fish and invertebrates from benthic patches so that their ecological function can be investigated. Such devices appear to be effective, but the precise characteristics of the electrical fields they generate and specific settings needed to exclude organisms across water conductivity levels have not been described. We present an electrical engineering and experimental framework to predict and evaluate the effectiveness of a modified device at different combinations of electrical settings and water conductivities. We avoided toxic materials and considered safety issues. We conducted laboratory experiments to identify the electrical fields with a 10-Hz pulse frequency needed to exclude adult Fathead Minnows (Pimephales promelas) and crayfish (Procambarus clarkii) from electrical exclosures across a range of water conductivities (13–800 µS/cm). Fish and crayfish in waters of low conductivity (≤50 µS/cm) were excluded from exclosures at ≥200 V of electric potential. In water of higher conductivity (≥250 µS/cm), similar settings caused consumer immobilization. Electrical pulse durations of 150 µs were more effective than 50-µs pulse durations at excluding organisms. Further refinement toward standardized methods requires analogous experimentation in the field, but our findings emphasize the importance of comprehensively considering electrical fields (voltage, pulse frequency and duration), water conductivity, and electrode configuration a priori when using these devices to optimize designs.

A fast integrated mobility spectrometer for rapid measurement of sub-micrometer aerosol size distribution, Part I: Design and model evaluation

A fast integrated mobility spectrometer (FIMS) was previously developed to characterize submicron aerosol size distributions at a frequency of 1Hz and with high size resolution and counting statistics (Kulkarni & Wang, 2006a, 2006b; Olfert, Kulkarni, & Wang, 2008). However, the dynamic size range of the FIMS was limited to one decade in particle electrical mobility. It was proposed that the FIMS dynamic size range can be greatly increased by using a spatially varying electric field (Wang, 2009). This electric field creates regions with drastically different field strengths in the separator, such that particles of a wide diameter range can be simultaneously classified and subsequently measured. A FIMS incorporating this spatially varying electric field is developed. This paper describes the theoretical frame work and numerical simulations of the FIMS with extended dynamic size range, including the spatially varying electric field, particle trajectories, activation of separated particles in the condenser, and the transfer function, transmission efficiency, and mobility resolution. The influences of the particle Brownian motion on FIMS transfer function and mobility resolution are examined. The simulation results indicate that the FIMS incorporating the spatially varying electric field is capable of measuring aerosol size distribution from 8 to 600nm with high time resolution. The experimental characterization of the FIMS is presented in an accompanying paper.

An exploratory study of the potential of LIBS for visualizing gunshot residue patterns

The study of gunshot residue (GSR) patterns can assist in the reconstruction of shooting incidences. Currently, there is a real need of methods capable of furnishing simultaneous elemental analysis with higher specificity for the GSR pattern visualization. Laser-Induced Breakdown Spectroscopy (LIBS) provides a multi-elemental analysis of the sample, requiring very small amounts of material and no sample preparation. Due to these advantages, this study aims at exploring the potential of LIBS imaging for the visualization of GSR patterns. After the spectral characterization of individual GSR particles, the distribution of Pb, Sb and Ba over clothing targets, shot from different distances, were measured in laser raster mode. In particular, an array of spots evenly spaced at 800μm, using a stage displacement velocity of 4mm/s and a laser frequency of 5Hz was employed (e.g. an area of 130×165mm2 was measured in less than 3h). A LIBS set-up based on the simultaneous use of two spectrographs with iCCD cameras and a motorized stage was used. This set-up allows obtaining information from two different wavelength regions (258–289 and 446–463nm) from the same laser induced plasma, enabling the simultaneous detection of the three characteristic elements (Pb, Sb, and Ba) of GSR particles from conventional ammunitions. The ability to visualize the 2D distribution GSR pattern by LIBS may have an important application in the forensic field, especially for the ballistics area.

Oscillatory fluid flow induces the osteogenic lineage commitment of mesenchymal stem cells: The effect of shear stress magnitude, frequency, and duration

A potent regulator of bone anabolism is physical loading. However, it is currently unclear whether physical stimuli such as fluid shear within the marrow cavity is sufficient to directly drive the osteogenic lineage commitment of resident mesenchymal stem cells (MSC). Therefore, the objective of the study is to employ a systematic analysis of oscillatory fluid flow (OFF) parameters predicted to occur in vivo on early MSC osteogenic responses and late stage lineage commitment. MSCs were exposed to OFF of 1Pa, 2Pa and 5Pa magnitudes at frequencies of 0.5Hz, 1Hz and 2Hz for 1h, 2h and 4h of stimulation. Our findings demonstrate that OFF elicits a positive osteogenic response in MSCs in a shear stress magnitude, frequency, and duration dependent manner that is gene specific. Based on the mRNA expression of osteogenic markers Cox2, Runx2 and Opn after short-term fluid flow stimulation, we identified that a regime of 2Pa shear magnitude and 2Hz frequency induces the most robust and reliable upregulation in osteogenic gene expression. Furthermore, long-term mechanical stimulation utilising this regime, elicits a significant increase in collagen and mineral deposition when compared to static control demonstrating that mechanical stimuli predicted within the marrow is sufficient to directly drive osteogenesis.

Comparison of BOLD, diffusion-weighted fMRI and ADC-fMRI for stimulation of the primary visual system with a block paradigm

The blood oxygen level-dependent (BOLD) effect is extensively used for functional MRI (fMRI) but presents some limitations. Diffusion-weighted fMRI (DfMRI) has been proposed as a method more tightly linked to neuronal activity. This work proposes a protocol of DfMRI acquired for several b-values and diffusion directions that is compared to gradient-echo BOLD (GE-BOLD) and to repeated spin-echo BOLD (SE-BOLD, acquisitions performed with b=0s/mm2), which was also used to ensure the reproducibility of the response.A block stimulation paradigm of the primary visual system (V1) was performed in 12 healthy subjects with checkerboard alternations (2Hz frequency). DfMRI was performed at 3T with 5 b-values (b=1500, 1000, 500, 250, 0s/mm2) with TR/TE=1004/93ms, Δ/δ=45.4ms/30ms, and 6 spatial directions for diffusion measures. GE-BOLD was performed with a similar block stimulation design timing. Apparent Diffusion Coefficient (ADC)-fMRI was computed with all b-values used. An identical Z-score level was used for all fMRI modalities for the comparison of volumes of activation. ADC-fMRI and SE-BOLD fMRI activation locations were compared in a voxel-based analysis to a cytoarchitectural probability map of V1.SE-BOLD activation volumes represented only 55% of the GE-BOLD activation volumes (P<0.0001). DfMRI activation volumes averaged for all b-values acquired represented only 12% of GE-BOLD (P<0.0001) and only 22% of SE-BOLD activation volumes (P<0.005). Compared to SE-BOLD-fMRI, ADC-fMRI activations showed fewer pixels outside of V1 and a higher average probability of belonging to V1.DfMRI and ADC-fMRI acquisition at 3T could be easily post-processed with common neuro-imaging software. DfMRI and ADC-fMRI activation volumes were significantly smaller than those obtained with SE-BOLD. ADC-fMRI activations were more precisely localized in V1 than those of SE-BOLD-fMRI. This validated the increased capability of ADC-fMRI compared to BOLD to enhance the precision of localizing an fMRI activation in the cyto-architectural zone V1, thereby justifying the use of ADC-fMRI for neuro-scientific studies.

Abstract WMP47: Robot-assisted Mechanical Therapy Protects Against Stroke-induced Skeletal Muscle Injury

Introduction: A growing body of literature supports acute changes to skeletal muscle physiology in response to stroke-induced central nervous system injury. While stroke survivors depend on rehabilitation to facilitate functional recovery, study of post-stroke rehabilitation and mechanisms of recovery remains limited. The current work addresses development of a Robot-Assisted Mechanical Therapy (RAMT) device and facilitation of reproducible, objective analysis of post-stroke rehabilitation. We hypothesize that RAMT permits systematic study of post-stroke mechano-physiotherapy and restores hindlimb function after stroke by protecting against skeletal muscle injury. Methods: Wistar rats (male, N=26) were subjected to middle cerebral artery occlusion (MCAO), after which they received daily RAMT (RAMT+; 0.5N force, 1Hz frequency, 10mm linear motion over medial stroke-affected gastrocnemius) or none (RAMT-; anesthesia only) for 14 days. Assessment of gait, sensorimotor behavior, and muscle perfusion quantified effects of RAMT on post-stroke function, while skeletal muscle analysis (RT-PCR, immunohistochemistry) evaluated expression of myostatin, a molecular target of stroke. Results: Compared to RAMT- controls, RAMT+ rats benefited from higher perfusion in stroke-affected gastrocnemius (47.7%, p&lt;0.05). RAMT+ improved post-stroke gait and sensorimotor behavior, evidenced by better track width (11.9%, p&lt;0.05), less time in quad support (54.4%, p&lt;0.05), greater travel distance (60.5%, p&lt;0.05), and more time mobile (41.7%, p&lt;0.05). Additionally, RAMT+ protected from post-stroke induction of myostatin, decreasing mRNA and protein expression (39.1% and 88.6% respectively, p&lt;0.05). Conclusion: RAMT facilitates reproducible, objective, pre-clinical study of post-stroke mechano-physiotherapy. RAMT successfully improves muscle perfusion, rescues gait deficits, preserves sensorimotor behavior, and attenuates the stroke-induced rise in myostatin. Ongoing efforts focus to characterize the mechano-sensitive miRNA transcriptome in skeletal muscle and employ electrophysiology to quantitatively map post-stroke neuroplasticity in response to RAMT.

Investigating the spatial extent of acoustically activated echogenic liposomes

The purpose of this work was to investigate the ability of bubbles entrapped within echogenic liposomes (ELIP) to serve as foci for cavitational events that would cause leakage in neighboring non-echogenic liposomes (NELIP). Previous studies have shown that entrapping bubbles into liposomes increases ultrasound-mediated leakage of hydrophilic components at ultrasound settings known to induce inertial cavitation, specifically 20kHz and 2.2W/cm2. Using tone-burst approach and pulse repetition frequency of 10Hz would bring this intensity level to the one accepted (220mW/cm2) in clinical imaging. Mixed populations of ELIP and NELIP were simultaneously exposed to ultrasound at varying ratios to examine the effect of ELIP concentration on release of a hydrophilic dye, calcein, from NELIP. Calcein release from NELIP was observed to be independent of ELIP concentration, suggesting that the release enhancement from echogenicity is strictly a localized event. Additionally, it was observed that the release mechanisms independent of echogenicity were active for the duration of experiment whereas those associated with echogenicity were active for only the initial 1–2min.

Effects of Neuromuscular Electrical Stimulation During Hemodialysis on Peripheral Muscle Strength and Exercise Capacity: A Randomized Clinical Trial

ObjectiveTo evaluate the effects of neuromuscular electrical stimulation of high and low frequency and intensity, performed during hemodialysis, on physical function and inflammation markers in patients with chronic kidney disease (CKD). DesignRandomized clinical trial. SettingHemodialysis clinic. ParticipantsPatients with CKD (N=51) were randomized into blocks of 4 using opaque sealed envelopes. They were divided into a group of high frequency and intensity neuromuscular electrical stimulation and a group of low frequency and intensity neuromuscular electrical stimulation. InterventionsThe high frequency and intensity neuromuscular electrical stimulation group was submitted to neuromuscular electrical stimulation at a frequency of 50Hz and a medium intensity of 72.90mA, and the low frequency and intensity neuromuscular electrical stimulation group used a frequency of 5Hz and a medium intensity of 13.85mA, 3 times per week for 1 hour, during 12 sessions. Main Outcome MeasuresPeripheral muscle strength, exercise capacity, levels of muscle trophism marker (insulin growth factor 1) and levels of proinflammatory (tumor necrosis factor α) and anti-inflammatory (interleukin 10) cytokines. ResultsThe high frequency and intensity neuromuscular electrical stimulation group showed a significant increase in right peripheral muscle strength (155.35±65.32Nm initial vs 161.60±68.73Nm final; P=.01) and left peripheral muscle strength (156.60±66.51Nm initial vs 164.10±69.76Nm final; P=.02) after the training, which did not occur in the low frequency and intensity neuromuscular electrical stimulation group for both right muscle strength (109.40±32.08Nm initial vs 112.65±38.44Nm final; P=.50) and left muscle strength (113.65±37.79Nm initial vs 116.15±43.01Nm final; P=.61). The 6-minute walk test distance (6MWTD) increased in both groups: high frequency and intensity neuromuscular electrical stimulation group (435.55±95.81m initial vs 457.25±90.64m final; P=.02) and low frequency and intensity neuromuscular electrical stimulation group (403.80±90.56m initial vs 428.90±87.42m final; P=.007). The groups did not differ in peripheral muscle strength and 6MWTD after the training protocol. In the high frequency and intensity neuromuscular electrical stimulation group, a correlation was observed between the initial and final values of 6MWTD and muscle strength. In the low frequency and intensity neuromuscular electrical stimulation group, correlations occurred only between the 6MWTD and the initial muscle strength. Only the low frequency and intensity neuromuscular electrical stimulation group increased levels of insulin growth factor 1 (252.38±156.35pg/mL initial vs 336.97±207.34pg/mL final; P=.03), and only the high frequency and intensity neuromuscular electrical stimulation group reduced levels of interleukin 10 (7.26±1.81pg/mL vs 6.32±1.54pg/mL; P=.03). The groups showed no differences in tumor necrosis factor α levels. ConclusionsPatients with CKD on hemodialysis improve exercise capacity after peripheral neuromuscular electrical stimulation of high and low frequency and intensity. However, the benefits on muscle and inflammatory outcomes seem to be specific for the adopted electrical stimulation strategy.

Tribocorrosion behavior of bio-functionalized highly porous titanium

Titanium and its alloys are widely used in orthopedic and dental implants, however, some major clinical concerns such as poor wear resistance, lack of bioactivity, and bone resorption due to stress shielding are yet to be overcome. In order to improve these drawbacks, highly porous Ti samples having functionalized surfaces were developed by powder metallurgy with space holder technique followed by anodic treatment. Tribocorrosion tests were performed in 9g/L NaCl solution using a unidirectional pin-on-disc tribometer under 3N normal load, 1Hz frequency and 4mm track diameter. Open circuit potential (OCP) was measured before, during and after sliding. Worn surfaces investigated by field emission gun scanning electron microscope (FEG-SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Results suggested bio-functionalized highly porous samples presented lower tendency to corrosion under sliding against zirconia pin, mainly due to the load carrying effect given by the hard protruded oxide surfaces formed by the anodic treatment.

Effect of Repetitive Transcranial Magnetic Stimulation on Hand Function of Spastic Cerebral Palsy Children

Repetitive Transcranial magnetic stimulation (rTMS) is emerging as a new investigation as well as treatment tool for various neurological and psychiatric diseases. Recent studies showed its application as treatment tool in movement disorders, where rTMS stimulation on primary motor cortex alters physiological patterns of motor threshold; motor evoked potential and cortical plasticity which induces motor activity. Recent studies on rTMS combined with rehabilitation therapy demonstrated functional improvement in motor activities of spastic cerebral palsy (sCP) children. Thus, this study was designed to evaluate the effect of rTMS on hand function of sCP patients. Forty-five children diagnosed as sCP participated in this study after written consent from their parents or guardians. They were divided into three groups- control (CG) and interventional group (IG-A and IG-B). Participants in CG were provided only physical therapy (PT) of 30 minutes duration daily for 20 days and those in IG were administered rTMS frequency of 5Hz (IG-A) and 10Hz (IG-B) for 15 minutes consisting of 1500 pulses daily for 20 days; followed by PT as given to CG. Quality of upper extremity skill test (QUEST) scoring was used for evaluating the improvement in hand function of sCP patients. The pre (before starting any therapy) versus post (after completion of 20 sessions) mean QUEST score between different groups were statistically significant (p<0.01) and the mean change was 0.61, 2.46 and 2.87 in CG, IG-A and IG-B respectively. However, encouraging functional improvement in hand function was observed in diplegic patients in the age group of 2-6 years employing 5Hz frequency and higher frequency (10Hz) induced better activity in hemiplegic and quadriplegic patient of older age groups (7-16 years).

A hybridized electromagnetic-triboelectric self-powered sensor for traffic monitoring: concept, modelling, and optimization

We report a hybridized electromagnetic-triboelectric generator that consists of four units of freestanding triboelectric nano generators (TENG) and four electromagnetic generators (EMG) that can be used as a self-powered sensor for road traffic monitoring. The proposed hybridized nano generator converts the periodical mechanical load over the speed bumper into electricity. We optimize the geometry of the electromagnetic component for the purpose of high power generation. With combination of TENG and EMG, it is shown that the proposed device is capable of the power and voltage generation even with very small displacements and low frequencies. Depending to the triggering frequency, TENG or EMG dominates the power generation considering different mechanical loads. The hybridized nanogenerator can deliver output volume power density of 20.96Wm3 and 50.81Wm3 for TENG and EMG components in frequency of 1Hz, respectively. The proposed nano generator not only has the potential to be implemented for sensing applications and traffic monitoring due to its high output voltage, but also is capable of power harvesting to act as a self-powered monitoring system. With the global interest toward developing smart cities, the proposed self-powered device can address the traffic monitoring challenges of those cities by providing online traffic information.

Effects of transient receptor potential canonical 1 (TRPC1) on the mechanical stretch-induced expression of airway remodeling-associated factors in human bronchial epithelioid cells

Research has shown that mechanical stress stimulation can cause airway remodeling. We investigate the effects of mechanical stretch on the expression of the airway remodeling-associated factors interleukin-13 (IL-13) and matrix metalloprotein-9 (MMP-9) and signaling pathways in human bronchial epithelioid (16HBE) cells under mechanical stretch. A Flexcell FX-4000 Tension System with a flexible substrate was applied to stretch 16HBE cells at a 15% elongation amplitude and 1Hz frequency, with stretching for 0.5h, 1h, 1.5h and 2h. The experimental group with higher IL-13, MMP-9, and TRPC1 expression and higher Ca2+ levels was selected for performing intervention experiment. These cells were pretreated with the transient receptor potential canonical 1 (TRPC1) channel antagonist SKF96365 and TRPC1-specific siRNA, and then mechanical stretch was applied. Our results provided evidences that mechanical pressure significantly increased IL-13, MMP-9, and TRPC1 protein and mRNA expression levels and intracellular Ca2+ fluorescence intensity at 4 time points compared with the control group. The peak IL-13, MMP-9, and TRPC1 expression levels were observed at 0.5h after exposure to mechanical pressure. IL-13 and MMP-9 expression levels and Ca2+ fluorescence intensity in the stretch+SKF96365 group and in the stretch+TRPC1 siRNA group were significantly lower than those were in the mechanical stretch group. By incubating the cells with the intracellular calcium chelator BAPTA-AM, the expression of IL-13 and MMP9 was significantly decreased, and the expression level of TRPC1 remained unchanged. These observations suggest that mechanical stretch may induce an influx of Ca2+ and up-regulation of IL-13 and MMP-9 expression in 16HBE cells via activation of TRPC1.

Study of the tribocorrosion behaviour of Ti6Al4V – HA biocomposites

This study is concern with tribocorrosion behaviour of Ti6Al4V-HA biocomposites. The Ti6Al4V composites reinforced with different contents of hydroxyapatite (HA) particles 5–15%, vol%) were produced by hot pressing technique. The tribocorrosion tests were performed by using a ball-on-plate configuration in artificial saliva at 37°C. The tests were carried out under open circuit potential (OCP), with a sliding duration of 1800s, 1N normal load and 1Hz frequency. The open circuit potential and wear mechanisms for all tested biocomposites are presented and discussed. The results suggest that HA plays a relevant role on tribocorrosion behaviour of Ti6Al4V-HA composites. All composites samples presented better wear resistance and also a relatively lower tendency to corrosion with increasing HA content.

Energy harvesting behaviour for aircraft composites structures using macro-fibre composite: Part I – Integration and experiment

This paper investigates new ways to integrate piezoelectric energy harvesting elements onto carbon-fibre composite structures, using a new bonding technique with a vacuum bag system and co-curing process, for fabrication onto airframe structures. Dynamic mechanical vibration tests were performed to characterise the energy harvested by the various integration methods across a range of different vibration frequencies and applied mechanical input loadings. An analytical model was also introduced to predict the power harvested under the mechanical vibrations as a benchmark to evaluate the proposed methods. The developed co-curing showed a high efficiency for energy harvesting at a range of low frequencies, where the co-curing method offered a maximum improvement of 14.3% compared to the mechanical bonding approach at a frequency of 10Hz. Furthermore, co-curing exhibited potential at high frequency by performing the sweep test between frequencies of 1 and 100Hz. Therefore, this research work offers potential integration technology for energy harvesting in complicated airframe structures in aerospace applications, to obtain the power required for environmental or structural health monitoring.

High-performance reverse electrowetting energy harvesting using atomic-layer-deposited dielectric film

Reverse electrowetting-on-dielectric (REWOD), which is a novel technology for energy harvesting, was demonstrated by depositing Al2O3 via atomic layer deposition (ALD). Specifically, thin layers of Al2O3 about 100nm-thick were successfully formed by ALD to obtain dense films with high capacitances. REWOD with the ALD Al2O3 thin films exhibited high performances under low-voltage and low-excitation-frequency conditions. The maximum power density was 11mW/cm2 with a DC bias of 24V and an external excitation frequency of 2Hz. Moreover, ALD and sputtered thin films were compared by investigating their capacitances and leakage current densities. Due to the differences between the film densities and growth methods, the ALD thin films exhibited higher capacitances and lower leakage current densities. It was also determined that the leakage current affects the REWOD energy harvesting performance. By analyzing these features, it was confirmed that ALD thin films are suitable for REWOD energy harvesting.

Temperature dependent cyclic deformation and fatigue life of EN-GJS-600 (ASTM 80-55-06) ductile cast iron

The ductile cast iron EN-GJS-600 (ASTM 80-55-06) provides several beneficial properties for a wide spectrum of applications. Its near-net shaping capabilities combined with beneficial physical and mechanical properties even at elevated temperatures result in a wide use for components of internal combustion engines. Under service conditions, fatigue loading at different temperatures occurs. In this context, the present paper focuses on the isothermal high cycle fatigue behavior of ductile cast iron EN-GJS-600 in the temperature range from ambient temperature up to 400°C at a frequency of 5Hz. At elevated temperatures, the consideration of dynamic strain aging effects on cyclic deformation and lifetime behavior is of major importance. It was proved that only one temperature increase test is necessary to determine the temperature range of pronounced dynamic strain aging effects. The physically based fatigue lifetime calculation approach “PhyBaLSIT” (SIT=strain increase test) was applied and validated for total strain controlled fatigue tests. To receive maximum information with minimum effort, both test procedures were combined enabling calculation of fatigue life in the temperature range from ambient temperature up to 400°C based on only thirteen fatigue experiments.