Full Electrostatic Control of Nanomechanical Buckling

Buckling at the micro and nanoscale generates distant bistable states which can be beneficial for sensing, shape-reconfiguration and mechanical computation applications. Although different approaches have been developed to access buckling at small scales, such as the use heating or pre-stressing beams, very little attention has been paid so far to dynamically and precisely control all the critical bifurcation parameters, the compressive stress and the lateral force on the beam. Precise and on-demand generation of compressive stress on individually addressable microstructures is especially critical for morphologically reconfigurable devices. Here, we develop an all-electrostatic architecture to control the compressive force, as well as the direction and amount of buckling, without significant heat generation on micro/nano structures. With this architecture, we demonstrated fundamental aspects of device function and dynamics. By applying voltages at any of the digital electronics standards, we have controlled the direction of buckling. Lateral deflections as large as 12% of the beam length were achieved. By modulating the compressive stress and lateral electrostatic force acting on the beam, we tuned the potential energy barrier between the post-bifurcation stable states and characterized snap-through transitions between these states. The proposed architecture opens avenues for further studies that can enable efficient actuators and multiplexed shape-shifting devices

Assessment of the requisites of microbiology based infectious disease training under the pressure of consultation needs

<p>Abstract</p> <p>Background</p> <p>Training of infectious disease (ID) specialists is structured on classical clinical microbiology training in Turkey and ID specialists work as clinical microbiologists at the same time. Hence, this study aimed to determine the clinical skills and knowledge required by clinical microbiologists.</p> <p>Methods</p> <p>A cross-sectional study was carried out between June 1, 2010 and September 15, 2010 in 32 ID departments in Turkey. Only patients hospitalized and followed up in the ID departments between January-June 2010 who required consultation with other disciplines were included.</p> <p>Results</p> <p>A total of 605 patients undergoing 1343 consultations were included, with pulmonology, neurology, cardiology, gastroenterology, nephrology, dermatology, haematology, and endocrinology being the most frequent consultation specialties. The consultation patterns were quite similar and were not affected by either the nature of infections or the critical clinical status of ID patients.</p> <p>Conclusions</p> <p>The results of our study show that certain internal medicine subdisciplines such as pulmonology, neurology and dermatology appear to be the principal clinical requisites in the training of ID specialists, rather than internal medicine as a whole.</p

Exergetic sustainability indicators for a high pressure hydrogen production and storage system

OZSABAN, MERT/0000-0001-6818-6428WOS: 000410010600040This study examines the exergetic sustainability effect of PEM electrolyzes (PEME) integrated high pressure hydrogen gas storage system whose capacity is 3 kg/h. For this purpose, the indicators, previously used in the literature, are taken into account and their variations are parametrically studied as a function of the PEME operating pressure and storage pressure by considering i) PEME operating temperature at 70 degrees C, ii) PEME operating pressures at 10, 30, 50 and 100 bar, hydrogen gas flow rate at 3 kg/h and iv) storage pressure between 200 and 900 bar. Consequently, the results from the parametric investigation indicate that, with the ascent of storage pressure from 200 to 900 bar at a constant PEME operating pressure (=50 bar), exergetic efficiency changes decreasingly between 0.612 and 0.607 while exergetic sustainability between 1.575 and 1.545. However, it is estimated that waste exergy ratio changes increasingly between 0.388 and 0.393 while environmental effect factor between 0.635 and 0.647. Additionally, it is said that the higher PEME outlet pressure causes the higher exergetic sustainability index, the lower environmental effect factor, the lower waste exergy output, the higher exergetic efficiency. However, the higher storage pressure causes the lower exergetic efficiency, the higher waste exergy output, the higher environmental effect factor and the lower exergetic sustainability index. Thus, it is recommended that this type of the system should be operated at higher PEME outlet pressure, and at an optimum hydrogen storage pressure. (C) 2017 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC

A Comparative Experiment Study on Precast Tunnel Segments

Increasing popularity of using fibres in concrete has brought questions about their usability in segmental tunnel linings as an alternative to the conventional lining. Prior studies have already revealed that the replacement of conventional steel reinforcement is possible with steel fibres. However, the usability of macro-synthetic fibres (MSFs) as reinforcements in precast tunnel segments is still unclear and one of the controversial questions to be answered. This study aims to evaluate the structural applicability of using MSFs in precast tunnel segments by means of an experimental program on full-scale specimens. Fourteen full-scale precast tunnel segments of four different reinforcement cases were analysed: typical conventional steel reinforcement; combination of MSFs and conventional reinforcement; combination of MSFs and glass fibre reinforced polymer rebars (GFRP); MSFs only. Flexural tests were carried out to compare the flexural capacities of specimens at the service limit state, while point load tests were conducted to observe the structural performance of precast tunnel segments under the effect of design thrust forces. The experimental results showed that combination of MSFs and GFRP could be an innovative solution for precast tunnel segments in case of using a suitable quantity that satisfied the project requirements

ELECTRO HYDRAULIC SUSPENSION SYSTEM DESIGN WITH OPTIMAL STATE DERIVATIVE FEEDBACK CONTROLLER

This paper is concerned with a control design of an electro-hydraulic suspension system. In some practical problems, for instance in the active suspension design, the state derivative signals such as acceleration and velocity are easier to obtain rather than the state variables such as displacement and velocity, since the most commonly used sensors are the accelerometers. Hence, design of an optimal state derivative feedback controller is proposed by employing the linear matrix inequalities framework. In order to demonstrate the effectiveness of the proposed controller, a two-degree-of-freedom quarter vehicle suspension model equipped with an electro hydraulic actuator is preferred. Throughout the numerical simulation studies, bump type road irregularities at different vehicle forward velocities are applied to evaluate the performances of the controller in terms of ride comfort and safety

Resonance frequency analysis assessment of implant stability in labial onlay grafted posterior mandibles:A pilot clinical study

Purpose: The objectives of this study were ( 1) to compare the stability, evaluated by means of resonance frequency analysis (RFA), of implants placed posterior mandibles augmented with autogenous bone harvested from the mandibular symphysis with that of implants placed in nongrafted edentulous posterior mandibles and ( 2) to compare peri-implant marginal bone height changes and implant failure for the 2 groups. Materials and Methods: Eight patients with thin posterior mandibular ridges (buccolingual crestal width less than 4 mm) underwent labial onlay alveolar grafting with symphyseal bone blocks 4 months prior to placement of 17 implants. Seven nongrafted patients received 18 implants in the edentulous posterior mandible; these patients served as a control group. RFA was performed the day of implant placement ( baseline), 1 month postplacement, 4 months postplacement ( after prosthesis delivery), and 12 months postloading. Peri-implant bone height changes at a level of 0.01 mm were assessed using periapical radiographs at baseline, the 1-month follow-up, and the 4-month follow-up. Analysis of variance was used to evaluate statistical differences within the groups, and t test was used to make comparisons between groups. Results: None of the patients presented postoperative complications or implant failure. Mean implant stability quotient (ISQ) was 63.0 +/- 6.0 to 70.2 +/- 3.5 for the grafted group and 64.1 +/- 4.1 ISQ to 70.1 +/- 3.9 for the nongrafted group. No significant difference was found in mean ISQ between the grafted and nongrafted groups at baseline, the 1-month follow-up, 4 months postplacement, or 12 months postloading ( P =.211, P =.873, P =.925, P =.735, respectively). Mean peri-implant bone loss was 0.16 +/- 0.04 mm mesially and 0.16 +/- 0.05 mm distally. Conclusion: RFA revealed no difference in implant stability between mandibular ridges augmented with autologous bone grafts at baseline or after loading

Effectiveness of the “pain-free dental injection” (PaFein) teaching model in reducing children's pain: A randomized, controlled study

Purpose: This study explores the effectiveness of a comprehensive structured teaching model – the “PaFein” – for instructing postgraduate pediatric dental residents in the provision of pain-free local anesthesia to children. Methods: Ten postgraduate pediatric dental residents and 172 children between the ages 5 and 13 participated in the study following ethical approval. The previously measured baselines guided the randomization of study and control groups. The study group (five residents) attended the PaFein course (9 hours). Based on power calculations, residents performed dental injections (8 mandibular block, 8 palatal/lingual and 14 buccal infiltrations) in randomly assigned child patients. Demographic data of residents/children, parental and self-report anxiety scores and Visual Analogue Scale (VAS) pain scores were noted to examine children's anxiety and pain during dental injections. Results: Children's mean anxiety score did not differ significantly between groups; however, VAS pain reports during dental injections (a, b, c, d) were found lower in the PaFein study group than the control group (p < 0.05). VAS pain reports for (a) buccal injections were 1.08 and 1.9 (p = 0.02); (b) inferior alveolar nerve blocks were 1.58 and 3.37 (p = 0.0002); (c) palatal/lingual injections were 1.34 and 3.02 (p < 0.0001); (d) total means were 1.28 and 2.59, respectively (p = 0.0001). VAS pain reports of anxious and non-anxious children in the PaFein study group (1.63 and 1.17) were also lower than the control group (3.33 and 2.39) (p < 0.0001 and p = 0.005). Conclusion: The “PaFein” teaching model was found to be effective in training dental residents to reduce dental injection pain in children, including the anxious ones