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The control bandwidth of a flexure mechanism is typically limited by parasitic resonance frequencies with low structural damping. Such resonances can be suppressed by including active material in the mechanism, which is used to dissipate energy at specified frequencies. The active material is typically placed in areas with high strain, in order to obtain the highest possible coupling and therefore dissipation. However, due to the low ultimate strain of some common active materials, the included active material will limit the deflection of the mechanism. In this work we introduce a design method that improves the closed-loop performance of a low pivot shift cross hinge mechanism by including active material in the leaf springs, without sacrificing the achievable deflection of the mechanism. The coupling between the active material and a selected undesired parasitic frequency is maximised by placing the material in locations with high modal strain. At the same time, the piezoelectric patches are only included in regions where the strain due to the nominal deflection is limited, such that the maximum deflection of ± 15 degrees is maintained. Using the patches as sensors and actuators, positive position feedback control is applied. Using simulations, it is shown that a selected resonance peak can be decreased by 16.3 dB for the considered mechanism, enabling 88% higher bandwidth.

Many precision machines, such as wafer scanners, have an internal motion stage. These stages generate reaction forces that act directly on the machine frame. A common method to minimize the effect of these reaction forces is a balance mass. To eliminate the need for this balance mass, it is proposed to use an active vibration isolation system as a virtual balance mass. Such can be achieved by constructing a force that is based on the reference of the motion stage that cancels its correlated reaction force. This appends the primary objective of an active vibration isolation system, which is to reduce the sensitivity to direct and indirect disturbances. A self-tuning algorithm is implemented to deal with parameter uncertainty and variation. The performance of the proposed method is experimentally validated on a 6-DoF active vibration isolation system, which is appended with a flexure based, straight guided motion stage. A 300 Hz frame mode is introduced of which the displacement can be measured to assess the performance of the method. The proposed method improved the tracking accuracy of the motion stage by a factor of 3.8 and reduced the settling time of the frame mode by a factor of 91, compared to the system without a virtual balance mass.

Leafsprings are commonly used in flexure mechanisms to enable repeatable motion and provide support stiffness. In various applications, the torsional stiffness needs to be increased. This paper presents the concept of using warping constraints distributed along the leafspring to increase the torsional stiffness relative to the stiffness in other directions. A beam-based model of nonuniform torsion is used to estimate the relationship between the geometrical design parameters and the expected increase in torsional stiffness. The model predicts that an order of magnitude increase in stiffness is feasible. Compared to other solutions, the distributed warping constraints have a less obtrusive shape that offer more design freedom.

In the design process of high-precision motion stages, the dynamic behavior is of paramount importance. Manual design of such a stage is a time-consuming process, involving many iterations between engineers responsible for mechanics, dynamics and control. By using topology optimization in combination with additive manufacturing, post-processing using traditional machining and parts assembly, it is possible to arrive at an optimal design in an automated manner. The printing, machining, and assembly steps are incorporated in the optimization in order to directly arrive at a manufacturable design. With a motion stage demonstrator optimized for maximum eigenfrequencies, it is shown that combining additive manufacturing and topology optimization at industry-relevant design precision is within reach and can be applied to high-performance motion systems.

Six degree of freedom manipulation provides full control over position and orientation, essential for many applications. However, six degree of freedom closed kinematic (parallel) manipulators either have a limited range of motion combined with a good repeatability when comprising flexure joints, or they have limited repeatability with a large workspace when using traditional rolling- or sliding-element bearings. Employing recent developments in large stroke flexures and design optimization, a fully flexure-based large range of motion hexapod robot has been designed. The resulting system allows for ±100 mm of translational and more than ±10 degrees of rotational range of motion in each direction combined with a small mechanism volume below 0.25 m3. Furthermore, a dedicated flexure-based design for the actuators combines high actuation forces without impairing precision, allowing for accelerations exceeding 10g. Experiments on a preliminary prototype validate the large workspace and confirm a high repeatability below 0.1 µm can be achieved, which is currently limited by electronics.

High accelerations of fast moving robots induce high fluctuating reaction forces and moments, resulting in undesirable vibrations and loss of accuracy. These fluctuations can be reduced or even eliminated by dynamic balancing techniques, e.g. by addition of counter-masses. However, these techniques typically disregard the flexibility of the mechanism. This flexibility potentially leads to undesirable eigenfrequencies and unbalance of an otherwise perfectly balanced mechanism. In this paper, the effect of link flexibility on the force balance quality is investigated in the frequency domain. This is done for a 2-DOF parallel manipulator with realistic stiffnesses. With the use of flexible multi-body software, the frequency transfer functions for the shaking forces are obtained for an unbalanced, a force balanced and a partially balanced case. The results show that, firstly, force balance results in a strong attenuation of the shaking forces’ frequency content up to the first eigenfrequency. Secondly, the addition of balance mass results in a reduction of the first parasitic eigenfrequency of the system leading to a worsened performance around the first eigenfrequency and a reduction in controller bandwidth. Identification of these effects leads to an optimal, intermediate solution, which mitigates the negative effects of dynamic balance, resulting in low-frequency shaking force attenuation of 30 dB without loss of controller bandwidth.

Flexure mechanisms are commonly designed to be exactly constrained to favour determinism, though at the expense of limitations on parasitic eigenfrequencies and support stiffness. This paper presents the use of viscoelastic material for providing additional stiffness without the indeterminism commonly associated with overconstraining. It is demonstrated experimentally that a custom synthesised elastomer compound can compensate for unintended misalignments without internal stress buildup, while improving the dynamic performance in terms of the first parasitic eigenfrequency. The measurements are corroborated by a nonlinear flexible multibody analysis.

Iron core torque motors provide a high power density, but require high off-axis stiffness, which is normally too demanding for flexure mechanisms especially when considering large range of motion applications. In this paper, a flexure-based suspension for a high torque iron core direct drive torque motor with a large range of motion of 60 degrees is presented. This flexure-based suspension provides the required high radial stiffness (>1000N/mm) combined with a high radial load capacity (500N) over the full range of motion. Furthermore, the suspension maintains a constant position of the pivot axis within 0.1mm, which is required to limit pull-in forces and to stay within alignment tolerances of the actuator. A prototype has been designed and constructed and experimental validations confirm the high radial stiffness and load capacity of the rotor suspension.

Interventional X-ray systems are used to acquire 2D and 3D images of complex anatomical structures (e.g. the cardiovascular system). These images provide a clinician with feedback in a medical procedure, which enables advanced minimally invasive treatments. A typical interventional X-ray system contains an X-ray source and detector, connected by a C-shaped arm. Several stacked motion systems enable the C-arm and imaging equipment to move spherically around an isocentre. This allows for 2D X-ray images to be taken at various projection angles. Other imaging techniques such as 3D computed tomography are enabled by this core functionality. Developments in interventional X-ray systems are often a compromise between performance, clinical usability, and cost. This paper presents three novel mechatronic architectures, which are designed to break through this trade-off. The proposed designs aim to improve the interventional X-ray system on multiple, application-specific levels. The first system focusses on improved image quality and clinical usability of 3D scans (high-end applications). A dual stage design allows for significantly extended and faster scanning motions, with a 55% smaller footprint in the operating room. It is based on a quasi-kinematic roll guide design, resulting in less nonlinear behaviour, and improved alignment of the imaging equipment. The second system decreases cost and installation requirements, while maintaining and adding to the current imaging capability (low-end applications). By reconsidering the degrees of freedom needed, a lightweight design is created (>50% mass reduction), with an improved stiffness to mass ratio. Both system 1 and 2 present an evolutionary improvement on existing architectures. As a revolutionary alternative, the third system pursues high-end performance and optimised workflow, at reduced overall cost. It features a compact and lightweight (~500 kg) mechatronic design which makes optimal use of the space available in the operating room. A full scale mock-up of this system has been built. Currently, a detailed design, including hardware realisation is being made for experimental performance validation at subsystem level.

Summary Background Maternal vitamin D status has been associated with bone mass of offspring in many, but not all, observational studies. However, maternal vitamin D repletion during pregnancy has not yet been proven to improve offspring bone mass in a randomised controlled trial. We aimed to assess whether neonates born to mothers supplemented with vitamin D during pregnancy have greater whole-body bone mineral content (BMC) at birth than those of mothers who had not received supplementation. Methods The Maternal Vitamin D Osteoporosis Study (MAVIDOS) was a multicentre, double-blind, randomised, placebo-controlled trial that recruited pregnant women from three study sites in the UK (Southampton, Oxford, and Sheffield). Eligible participants were older than 18 years, with a singleton pregnancy, gestation of less than 17 weeks, and a serum 25-hydroxyvitamin D (25[OH]D) concentration of 25–100 nmol/L at 10–17 weeks' gestation. P'articipants were randomly assigned (1:1), in randomly permuted blocks of ten, to either cholecalciferol 1000 IU/day or matched placebo, taken orally, from 14 weeks' gestation (or as soon as possible before 17 weeks' gestation if recruited later) until delivery. Participants and the research team were masked to treatment allocation. The primary outcome was neonatal whole-body BMC, assessed within 2 weeks of birth by dual-energy x-ray absorptiometry (DXA), analysed in all randomly assigned neonates who had a usable DXA scan. Safety outcomes were assessed in all randomly assigned participants. This trial is registered with the International Standard Randomised Controlled Trial registry, ISRCTN 82927713, and the European Clinical Trials Database, EudraCT 2007–001716–23. Findings Between Oct 10, 2008, and Feb 11, 2014, we randomly assigned 569 pregnant women to placebo and 565 to cholecalciferol 1000 IU/day. 370 (65%) neonates in the placebo group and 367 (65%) neonates in the cholecalciferol group had a usable DXA scan and were analysed for the primary endpoint. Neonatal whole-body BMC of infants born to mothers assigned to cholecalciferol 1000 IU/day did not significantly differ from that of infants born to mothers assigned to placebo (61·6 g [95% CI 60·3–62·8] vs 60·5 g [59·3–61·7], respectively; p=0·21). We noted no significant differences in safety outcomes, apart from a greater proportion of women in the placebo group with severe post-partum haemorrhage than those in the cholecalciferol group (96 [17%] of 569 mothers in the placebo group vs 65 [12%] of 565 mothers in the cholecalciferol group; p=0·01). No adverse events were deemed to be treatment related. Interpretation Supplementation of women with cholecalciferol 1000 IU/day during pregnancy did not lead to increased offspring whole-body BMC compared with placebo, but did show that 1000 IU of cholecalciferol daily is sufficient to ensure that most pregnant women are vitamin D replete, and it is safe. These findings support current approaches to vitamin D supplementation in pregnancy. Results of the ongoing MAVIDOS childhood follow-up study are awaited. Funding Arthritis Research UK, Medical Research Council, Bupa Foundation, and National Institute for Health Research.

Objective To compare the effectiveness of insulin pumps with multiple daily injections for adults with type 1 diabetes, with both groups receiving equivalent training in flexible insulin treatment.Design Pragmatic, multicentre, open label, parallel group, cluster randomised controlled trial (Relative Effectiveness of Pumps Over MDI and Structured Education (REPOSE) trial).Setting Eight secondary care centres in England and Scotland.Participants Adults with type 1 diabetes who were willing to undertake intensive insulin treatment, with no preference for pumps or multiple daily injections. Participants were allocated a place on established group training courses that taught flexible intensive insulin treatment (“dose adjustment for normal eating,” DAFNE). The course groups (the clusters) were then randomly allocated in pairs to either pump or multiple daily injections.Interventions Participants attended training in flexible insulin treatment (using insulin analogues) structured around the use of pump or injections, followed for two years.Main outcome measures The primary outcomes were a change in glycated haemoglobin (HbA1c) values (%) at two years in participants with baseline HbA1c value of ≥7.5% (58 mmol/mol), and the proportion of participants achieving an HbA1c value of Results 317 participants (46 courses) were randomised (156 pump and 161 injections). 267 attended courses and 260 were included in the intention to treat analysis, of which 235 (119 pump and 116 injection) had baseline HbA1c values of ≥7.5%. Glycaemic control and rates of severe hypoglycaemia improved in both groups. The mean change in HbA1c at two years was −0.85% with pump treatment and −0.42% with multiple daily injections. Adjusting for course, centre, age, sex, and accounting for missing values, the difference was −0.24% (−2.7 mmol/mol) in favour of pump users (95% confidence interval −0.53 to 0.05, P=0.10). Most psychosocial measures showed no difference, but pump users showed greater improvement in treatment satisfaction and some quality of life domains (dietary freedom and daily hassle) at 12 and 24 months.Conclusions Both groups showed clinically relevant and long lasting decreases in HbA1c, rates of severe hypoglycaemia, and improved psychological measures, although few participants achieved glucose levels currently recommended by national and international guidelines. Adding pump treatment to structured training in flexible intensive insulin treatment did not substantially enhance educational benefits on glycaemic control, hypoglycaemia, or psychosocial outcomes in adults with type 1 diabetes. These results do not support a policy of providing insulin pumps to adults with poor glycaemic control until the effects of training on participants’ level of engagement in intensive self management have been determined.Trial Registration Current Controlled Trials ISRCTN61215213.

In this study, malondialdehyde (MDA), ceruloplasmine (CER) and adenozine deaminase (ADA) concentrations were investigated in cattle with cystic echinococcosis. Group I consisted of 15 cattle with cystic echinococcosis whereas Group II consisted of 10 clinically healthy cattle aged 2-3 years. Venous blood samples were taken from the animals before being slaughtered in the Samsun province. At necropsy, suspiciousstructurs in lesions were examined parazitologically concerning cystic echinococcosis in various organs and animals with protoscolex formed the experimental group and the control group consisted of animals which were found clinically healthy and without any lesions in their examinations. Serum MDA, CER and ADA levels were measured in positive animals and compared with the levels of healthy animals. Serum concentrations of MDA, CER and ADA (mean ± standard deviation) of Group I were determined as 1.9 ± 0.6 nmol/ml, 10.2 ± 1.8 mg/dl and 43.2 ± 3.9 U/L whereas in the control group, they were 1.4 ± 0.7 nmol/ml, 5.6 ± 1.4 mg/dl and 19.5 ± 4.1 U/L respectively. There was a statistically significant difference in MDA (p < 0.05) and ADA (p < 0.001) values between Group I and II while the difference in CER value (p > 0.05) was not significant., Bu çalışmada, kistik ekinokokkozisli sığırlarda serum malondialdehit (MDA), seruloplazmin (CER) ve adenozin deaminaz (ADA) konsantrasyonlarının araştırılması amaçlanmıştır. Çalışmada 2-3 yaşlarında 15 adet kist hidatik (E.granulosus) ile enfekte hayvan Grup I’i ve 10 adet sağlıklı ve kist hidatik negative hayvan da Grup II’yi oluşturdu. Samsun yöresinde mezbahaneye gelen sığırlar venöz kan alındıktan sonra kesime sevk edildi. Nekropsi sonucu değişik organlarda kistik ekinokokkozis açısından şüpheli lezyonlardaki kistik yapılar parazitolojik olarak incelendi ve protoskoleks yönünden pozitif olan sığırlar çalışmanın deneme grubunu, klinik olarak sağlıklı ve organ muayenelerinde herhangi bir lezyon bulunmayan sığırlar ise kontrol grubunu oluşturdu. Pozitifliği saptanan hayvanların serum MDA, CER ve ADA düzeyleri ölçülerek sağlıklı hayvanlar ile kıyaslandı. Kistik ekinokokozis ile enfekte sığırlarda serum MDA, CER ve ADA düzeyleri sırası ile, 1,9 ± 0,6 nmol/ml, 10,2 ± 1,8 mg/dl ve 43,2 ± 3,9 U/L, kontrol grubu sığırlarda ise, 1,4 ± 0,7 nmol/ml, 5,6 ± 1,4 mg/dl ve 19,5 ± 4,1 U/L bulundu. Enfekte ve sağlıklı gruplar arasında serum MDA (p < 0,05) ve ADA (p < 0,001) düzeyleri yönünden fark önemli bulunurken, CER değerleri yönünden fark önemsiz bulundu

WOS: 000311653300001 In this study, the evaluation of therapeutic effects of probiotic bacteria, in comparison with single supportive and symptomatic therapy. in CPV (canine parvovirus) infection was aimed. A total of 20 naturally infected dogs, 1-6 months old, exhibiting enteritis and for which the diagnosis were confirmed by an ELISA commercially available test, were randomly divided into two equal groups. Only supportive and symptomatic therapy was applied in group I, whereas a commercial probiotic product which contained different probiotic bacteria (VSL#3) was used as adjuvant oral therapy in the group II. Clinical scores established from complete clinical examinations performed at the beginning and on every subsequent day during the therapy and haematological parameters determined before and 5 days after treatments were compared between the 2 groups. A moderate anaemia (low haemoglobinemia) coupled to reduction in the mean corpuscular volume and haemoglobin concentration was evidenced in 55% of parvovirus infected clogs and a relatively leukopenia when compared with after the treatment was observed in all diseased animals. Seven (70%) and nine (90%) dogs in the groups I and II respectively, survived during the trial. Moreover, the clinical scores have declined significantly more rapidly in the group II than in the group I. While the erythrocyte parameters have not significantly differed between the 2 groups, leukocyte and lymphocyte numerations were significantly improved during the treatment course only in clogs additionally treated with probiotics. The present study indicates that probiotics may be beneficial in CPV therapy. especially for shortening the recovery time, under optimal care conditions. Commission of Scientific Research Projects of Ondokuz Mayis UniversityOndokuz Mayis University [VET- 014] This study was supported by the Commission of Scientific Research Projects of Ondokuz Mayis University (Project No: VET- 014).

WOS: 000287897300001 In this study, the effects of florfenicol and tulathromycin on clinical recovery and acute-phase proteins in bovine respiratory diseases (BRD) were evaluated under the field conditions. A total of 30 local race feedlot cattle were used in the study. Twenty naturally infected beef and 10 healthy beef were used for the experimental and control groups, respectively. Sick animals were randomly divided into two groups of 10 and subcutaneously 40 mg per kg florfenicol was administrated in group I and 2.5 mg per kg tulathromycin was administrated in group II as single dose. The animals were clinically examined before (0 h) and 9 days after the treatment. Also, blood samples were taken and serum haptoglobin and serum amyloid A concentrations were measured before and 9 days after the treatment. It was concluded that although the clinical findings and recovery were not always correlated with serum acute phase proteins levels, florfenicol and tulathromycin can be effective for BRD therapy under field conditions.

PubMed: 20001994 The aim of this study was to describe and quantify the therapeutic value of honey in oral mucosal ulcers healing in comparison with Glyceroloxytriester (TGO). We also aimed to biochemically evaluate the healing effects of honey which had been collected from the Blacksea region flora on mucosal ulcers resulting in material loss. Thirty wistar rats (240±30 g) were enrolled in this study. Excisional wounds were performed in all rats for animal oral mucosal ulcer model. They were randomly allocated to three groups: group 1 was treated with Apitherapeutic agent or honey (0,1 ml, 2x1), group 2 was treated with TGO (0,1ml, 2×1) locally, Group 3 served as the control group. Following the surgical procedure on day 7, biopsy specimens were taken from right buccal mucosa and on day 14 biopsy specimens were taken from left bucal mucosa in all rats. Afterwards, hydroxy pyroline levels were measured. Data were analyzed statistically There was no statistically significant difference between Group 1 and 2, and also between Group 2 and 3, but there was statistically significant difference between Group 1 and 3 on day 7. There was no statistically significant difference between Group 1, 2 and 3 on day 14.

/0000-0002-0636-4214 WOS: 000268128600005 PubMed: 25903514 This randomized study was designed to establish the efficacy of platelet-rich plasma (PRP) gel and topical estradiol alone, or in combination, on healing of full-thickness wounds created on the trunk of rabbits. Fifteen New Zealand white female rabbits and 60 wounds were studied. Four 2.25-cm(2) full-thickness wounds were created using a template and treatments including a sterile saline solution that were assigned randomly to the wounds. Wounds were bandaged, dressed intermittently, and assessed by wound measurements and a collection, of samples at 7, 14, and 21 days to evaluate healing. Variables of interest were hydroxyproline concentration and scored gross and microscopic morphologic characteristics reflective of wound healing. PRP gel + estradiol-treated wounds completely healed faster than wounds given other treatments. Granulation tissue growth to the skin level was faster (P < 0.05) in the PRP gel + estradiol group than the other groups. Only the PRP gel + estradiol group had a significantly lower collagen level than the sterile saline solutions on day 7 (P < 0.05). The PRP gel + estradiol group and estradiol group led to an increase in angiogenesis on day 14 (P < 0.05). Complete epithelization was observed only in the PRP gel + estradiol group compared with the other groups on day 7. PRP gel + estradiol-treatment enhanced healing in full-thickness wounds by reducing the contraction rate with a trend toward accelerating both epithelial migration and the angiogenic response.

34th Congress of the Federation-of-European-Biochemical-Societies -- JUL 04-09, 2009 -- Prague, CZECH REPUBLIC WOS: 000267069900927 … Federat European Biochem Soc

Guvenc, Tolga/0000-0003-1468-3415 WOS: 000254907600039 Clinical signs and necropsy findings were described in a four-year-old female rhesus macaque with diabetes mellitus, resulting from spontaneous amyloidosis. Weakness, polyphagia, polydipsia, and polyuria, which lasted for a few weeks, were determined from anamnesis and clinical investigations. Highly increased serum BUN, AST, ALP levels, glycosuria, and proteinuria was detected in the biochemical analysis. According to these clinical, haematological, and biochemical data, it was thought that the monkey was affected with diabetes mellitus. Despite all efforts to cure the animal, the patient died. Diffuse amyloidosis was detected in the kidney and pancreas at the necropsy and histopathological examinations.

GULER, Ahmet/0000-0003-0167-2346; /0000-0002-0636-4214 WOS: 000284734700003 PubMed: 25901517 Aim. To evaluate the effects of three types of honey (chestnut, blossom, and rhododendron) on the healing of full-thickness wounds. Methods. Twenty-four (24) New Zealand White female rabbits were used. Four 1.5 cm x 1.5 cm full-thickness skin wounds were created on the back of each animal and treated with pure honey or sterile saline, respectively. Wounds were assessed by wound measurements and collection of samples at 7, 14, and 21 days post wounding to evaluate the healing process. Variables of interest were hydroxyproline concentration and gross and microscopic morphological characteristics reflective of wound healing. Wounds of the honey-treated groups healed much faster than the control group. Results. On day 7, the formation of granulation tissue, epithelization, angiogenesis, and fibroplasia levels increased in the honey-treated groups (P < 0.05). A statistical difference between the honeys was not detected. Conclusion. The present results suggest that honey accelerates the inflammatory reaction and initiates healing early on in the treatment process.

Additive manufacturing (AM) has recently gained popularity over the conventional manufacturing methods as it allows for innovative design solutions in terms of geometric complexity and shape optimization. As a result of the geometry, size and heterogeneous microstructure of the AM samples, conventional macroscale experiments are, however, frequently inadequate in determining the resulting material parameters. In such cases, nanoindentation represents a viable non- destructive technique for determining the mechanical properties such as Young’s modulus (EIT) and hardness (HIT) of small samples’ volumes. The nanoindentation measurements on a Keysight G200 machine equipped with a standard Berkovich tip are performed in this study on AISI 316L wrought samples as well as samples obtained via the laser-powder bed fusion (L-PBF) AM process. The standard depth-controlled loading- unloading method is used. With the aim of comparing the material properties on the macro- and microscale, conventional monotonic uniaxial tensile tests are also performed on both samples types. The possibility of calibrating the material parameters of finite element (FE) numerical models using nanoindentation test results to obtain the load vs. the indentation depth curve is finally discussed. Experimentally obtained load- displacement curves are used to calibrate the elastic and plastic material parameters of the FE model. Since FE modelling of the nanoindentation process is a nonlinear elasto-plastic contact problem, Young’s modulus and hardness alone are, in fact, not sufficient to characterize properly the overall material behaviour.

Losing hand functions due to ischemic or haemorrhaging stroke, often resulting in spasticity, causes difficulties in the activities of daily living (ADL), making rehabilitation challenging and important. Using robotic rehabilitation devices is a promising novel approach to exercise the hands, promote patient volition and increase the neural connections. The human hand, with its many degrees of freedom (DOFs), evolutionary formed for precision and power gripping, introduces, however, difficulties in developing specialized rehabilitation devices. Grasp-oriented modelling of hand’s kinematics with simplified but effective mathematical representations is, therefore, critical. The kinematic characterisation performed in this work simplifies the available 24 DOFs biomechanical model to 9 DOFs by constraining the joints via synergies specific to different grasp types and fingers’ inclination angles.The acquired model is compared to the anatomical one, and the effects of intra- and inter-dependent joints are studied. Although the used dependencies reduce slightly the joints’ ranges of motion (ROMs), the important grasping types and the ROMs used in ADL are preserved. The proposed model increases also positioning accuracy.

Autonomous sensor nodes, enabled by the integration of energy harvesting principles, create the preconditions for a significant simplification and mass reduction in aircraft structural health monitoring. A promising energy harvesting approach to collect and convert the energy from random aircraft vibrations during operation, is to use piezoelectric energy harvesters. Due to the narrow operating frequency bandwidth of the considered harvesters, a frequency up-conversion mechanism, based on plucking the free end of the piezoelectric devices by using rotating plectra, and letting the transducers oscillate at their eigenfrequencies, is introduced in order to enable their utilization while operating in the considered random excitation environment. An experimental investigation of fused deposition modelling 3D printed plectra is therefore carried on to better understand the effects of the respective design parameters, i.e., their size, stiffness and material types, on the resulting performances of the piezoelectric energy harvesters in terms of the obtainable specific power outputs. The voltages generated by the harvesters, as well as their maximal free end deflections, are thus measured for different plectrum materials, different plucking frequencies and different geometries of the plectra. Design-of-experiments (DoE) methods are employed in the setup of the experiments, whereas advanced numerical algorithms are used for the analysis of the hence obtained results. A comprehensive insight into the effects of plectrum properties on the responses of the piezoelectric energy harvesters is therefore provided, which represents another step towards the design of autonomous energy harvester powered sensor nodes to be used in aircraft structural health monitoring applications.

Frictional characteristics are an important factor in the design and exploitation of precision positioning systems and components. In fact, friction is a complex stochastic phenomenon depending on an intricate interplay between materials’ physical and chemical properties, as well as on the contact conditions influenced by the exerted normal forces, sliding velocities, contact area, temperature etc. Experimental measurements of the nanoscale friction force of an X39CrMo17-1 high-alloy steel thin film, deposited on a silicon wafer, are obtained in this work via elaborated lateral force microscopy (LFM) measurements performed on a scanning probe microscope using silicon-nitride microcantilever probes. The thin-film samples are synthesised by using pulsed laser deposition, which enables obtaining precise stochiometric elemental properties. The LFM measurements allow obtaining single-asperity contact conditions in the studied tribo-pair, which is studied experimentally considering the mentioned external influences as the variable process parameters. In order to obtain an in-depth insight into the dependencies of nanoscale friction on these parameters, the obtained experimental data is used to train various machine learning (ML) algorithms. The resulting predicted values of the nanoscale friction force are therefore obtained by using random forest, multilayer perceptron and support vector regression ML methods. In order to assess their predictive performances, all the used algorithms are validated on a separately measured test dataset. The best predictive performances are obtained by using the support vector regression algorithm, resulting in the highest achieved coefficient of determination (R2), allowing the prediction of 90 % of the variance of the experimental measurements.