Program design features that can improve participation in health education interventions

<p>Abstract</p> <p>Background</p> <p>Although there have been reported benefits of health education interventions across various health issues, the key to program effectiveness is participation and retention. Unfortunately, not everyone is willing to participate in health interventions upon invitation. In fact, health education interventions are vulnerable to low participation rates. The objective of this study was to identify design features that may increase participation in health education interventions and evaluation surveys, and to maximize recruitment and retention efforts in a general ambulatory population.</p> <p>Methods</p> <p>A cross-sectional questionnaire was administered to 175 individuals in waiting rooms of two hospitals diagnostic centres in Toronto, Canada. Subjects were asked about their willingness to participate, in principle, and the extent of their participation (frequency and duration) in health education interventions under various settings and in intervention evaluation surveys using various survey methods.</p> <p>Results</p> <p>The majority of respondents preferred to participate in one 30–60 minutes education intervention session a year, in hospital either with a group or one-on-one with an educator. Also, the majority of respondents preferred to spend 20–30 minutes each time, completing one to two evaluation surveys per year in hospital or by mail.</p> <p>Conclusion</p> <p>When designing interventions and their evaluation surveys, it is important to consider the preferences for setting, length of participation and survey method of your target population, in order to maximize recruitment and retention efforts. Study respondents preferred short and convenient health education interventions and surveys. Therefore, brevity, convenience and choice appear to be important when designing education interventions and evaluation surveys from the perspective of our target population.</p

Ply thickness tolerances in stacking sequence optimization of multilayered laminate plates

The paper deals with the impact of manufacturing tolerances of plies thicknesses on optimal design of multi-layered laminated plates in compression. It is assumed that the considered tolerances are represented by the maximum acceptable deviation of every individual ply thickness from its nominal design value. The robustness of the optimum is achieved diminishing the buckling load amplitude factor by the product of arbitrary assumed tolerances and appropriate sensitivities. The discussed optimization problem is solved numerically by the direct enumeration method. The proposed approach is illustrated with examples of the rectangular multi-layered laminated plate design under uni- and biaxial compression. The achieved results emphasise the robustness of the proposed method compared to the approaches with ignored tolerances

Modelowanie w systemie ABAQUS piezoelektrycznych elementów aktywnych typu MFC

W pracy przedstawiono sposób efektywnego modelowania kompozytowych elementów piezoelektrycznych metodą elementów skończonych. W systemie ABAQUS przygotowano makroskopowy model elementu aktywnego typu MFC wykorzystującego efekt piezoelektryczny d33. W dalszej kolejności przeanalizowano wielowarstwową belkę kompozytową z naklejonym badanym elementem aktywnym. Numerycznie zbadano prosty i odwrotny efekt piezoelektryczny, wyznaczając odpowiednio wartości napięć na zaciskach elementu aktywnego przy wymuszonym odkształceniu układu oraz ugięcia statyczne przy różnych wartościach napięcia zasilającego. Rezultaty tych analiz porównano z wynikami rzeczywistych pomiarów przeprowadzonych na stanowisku laboratoryjnym. Opracowany model numeryczny wykorzystano do próby wykrycia symulowanego uszkodzenia materiału kompozytowego.The paper presents an approach to effective modelling of piezoelectric transducers in finite element method based software. A macroscopic model of an active element made of macro fiber composite (MFC type) exhibiting d33 effect is developed in ABAQUS system. Next, a multilayer composite beam with the discussed piezoelectric actuator is analysed. Both a direct and a converse piezo effects are analyzed numerically, calculating respectively charge on transducer's poles subject to forced displacements and beam static deflections with respect to assumed supply voltage. The outcomes of the numerical simulations are compared to the laboratory test results. Next, the worked-out FEM model of MFC actuator/sensor is used to detect the simulated defect in composite material

Postacie drgań belki kompozytowej z elementami piezoelektrycznymi

In this paper the modal shapes of a light, thin laminate beam with active elements were evaluated. Cases with one or two Macro Fiber Composite (MFC) active elements adhered onto a glassepoxy cantilever beam were analyzed. The systems under consideration were modeled in ABAQUS finite element software to derive mode shapes numerically. Next, the modes were compared to each other to estimate the influence of PZT patches. First 20 modes of natural vibrations were examined including bending, torsion and axial ones. The comparisons of mode shapes were performed according to Modal Assurance Criterion (MAC) analysis. The examination of changes of mode shapes of the original beam with placement of active elements is the starting point in prior of optimal placements of PZTs with final goal the control of dynamics of helicopter blades.W pracy przedstawiono wyniki analizy modalnej lekkiej, cienkiej belki kompozytowej, jednostronnie utwierdzonej, z osadzonymi elementami aktywnymi. Na wstępie przeanalizowano belkę wzorcową – tj. wykonaną z laminatu żywiczno-szklanego bez elementów aktywnych. Następnie zbadano tę samą belkę z dodanym jednym, a w dalszej kolejności także z dwoma kompozytowymi elementami aktywnymi typu MFC (Macro Fiber Composite). Częstości i postacie drgań własnych badanych układów określono numerycznie za pomocą metody elementów skończonych – wykorzystano w tym celu oprogramowanie ABAQUS. Wyznaczono i zbadano 20 pierwszych postaci drgań zawierających zarówno mody giętne oraz skrętne, jak i jedną modę wzdłużną. Do oceny wpływu elementów aktywnych na uzyskane postacie drgań badanej belki wykorzystano kryterium dopasowania modalnego (ang. Modal Assurance Criterion, MAC). Zaprezentowana praca stanowi wstępny etap badań, których celem jest wyznaczenie optymalnego położenia elementów aktywnych sterujących dynamiką łopat wirnika śmigłowca

Control of Bending-Bending Coupled Vibrations of a rRotating Thin-Walled Composite Beam

The paper presents a study of a possible application of structure embedded piezoelectric actuators to enhance the performance of a rotating composite beam exhibiting the coupled flexural-flexural vibrations. The discussed transversal and lateral bending modal coupling results from the directional properties of the beam’s laminate and ply stacking distribution. The mathematical model of the beam is based on an assumption of cross-sectional non-deformability and it incorporates a number of non-classical effects. The final 1-D governing equations of an active composite beam include both orthotropic properties of the laminate and transversely isotropic properties of piezoelectric layers. The system’s control capabilities resulting from embedded Macro Fiber Composite piezoelectric actuators are represented by the boundary bending moment. To enhance the dynamic properties of the composite specimen under consideration a combination of linear proportional control strategies has been used. Comparison studies have been performed, including the impact on modal coupling magnitude and cross-over frequency shift

Numerical analysis of composite structures with embedded piezoelectric active elements

The paper presents a numerical simulation of active multiple layer composite beams in bending test. Within framework of performed analysis glass-epoxy and carbon-epoxy laminates with integrated piezoelectric actuators were considered. In the research macro fiber composite (MFC) type transducers exhibiting d33 effect were used. The numerical models and further calculations were done in ABAQUS/Standard FEM software. Discrete models of the considered composite beam structures were formulated according to the Layup-Ply technique. In performed tests nonlinear geometric effects corresponding to large structural deflections were taken into account. The resulting state equations were solved by means of Newton-Raphson iterative method. Finally, the findings of numerical simulations were compared to the outcomes of laboratory experiments. A very good agreement of numerical and experimental results was achieved; this confirmed the assumptions made to the numerical model and further modelling technique. Numerical model of the piezoelement, analysis of a composite beam with piezoelectric patch, numerical tests for the separated M-8503-P1 piezoelement, electric boundary conditions for the examined actuator, strain state of a glass-epoxy laminate, laboratory test-stand, numerical and laboratory experiment results are presented

Vibration of a mistuned three-bladed rotor under regular and chaotic excitations

This study considers forced vibrations of a rotating structure consisting of a rigid hub and three flexible beams. The blades are nominally made of a multilayered laminate with a specific stacking sequence resulting in full isotropic macroscopic material behaviour. However, in the performed analysis it is assumed that the rotor has been mistuned because of manufacturing tolerances of the composite material. These inaccuracies are represented by deviations of reinforcing fibres orientations from their nominal values. The considered tolerances break the intended macroscopic material isotropy and make the laminate to exhibit the fully orthotropic behaviour. Based on previous authors research, the system of four mutually coupled dimensionless ordinary differential governing equations is adopted. Forced responses of the system under regular and chaotic excitations are investigated

Nonlinear dynamics and synchronisation of pendula attached to a rotating hub

A model of a nonlinear system composed of a hub with attached two pendula rotating in a horizontal plane is studied in the paper. Each single pendulum, treated as a stiff and massless rod with a lumped mass, is connected to the hub by a flapping hinge. Nonlinear stiffness and viscous damping of the hinge is taken into consideration. The system is excited by an external torque generated by a DC motor which is considered as an ideal system with torque given by a harmonic function. For small oscillations the problem is linearised and then solved analytically. An influence of the structural parameters like mass of the hub and pendula length on natural end excited vibrations is presented. Large oscillations are studied by a continuation technique, directly from the original Ordinary Differential Equations of motion (ODE). The complete synchronisation, phase synchronisation, bifurcations and transition through resonances are analysed considering the influence of the mass of the hub. The existence of chaotic oscillations of the system and paths leading to chaos are demonstrated as well