Multilevel (ML-ICLV) & Single Level Integrated Discrete Choice and Latent Variable (ICLV) Models Using Alternative Latent Structures' Conceptualizations

The aim of the present endeavor is to experiment on integrating discrete choice with latent variable (ICVL) models using alternative factorial structures’ conceptualizations and do so at both Single Level (Level 0) and Multilevel (ML-ICVL). In doing, specific independent variables amenable to alternative latent variables’ conceptualization were selected. These included: a) 1st-order latent variables (1st-order factors) (FM; FW), b) 1st-order latent variables (1st-order factors) (FM; FW) forming a 2nd-order factor (F), c) Multi-level (two-level) factorial structures (FML0; FML1 and FWL0; FWL1), and d) Bi-Factor factorial structures (FM; FW; FG). The results may be of use to researchers interested in using valid, reliable, and accurate structures of latent variables in ICLV models. We confirm that alternative latent structures of divergent factorial nature exist for the same observed variables, and may have different impact upon the dependent observed choice variable in the ICLV models. Second, DCE utility is conceptualized and estimated at both Level 0 and Level 1 and the differences are evident

Multilevel (ML-ICLV) & Single Level Integrated Discrete Choice and Latent Variable (ICLV) Models Using Alternative Latent Structures' Conceptualizations

The aim of the present endeavor is to experiment on integrating discrete choice with latent variable (ICVL) models using alternative factorial structures’ conceptualizations and do so at both Single Level (Level 0) and Multilevel (ML-ICVL). In doing, specific independent variables amenable to alternative latent variables’ conceptualization were selected. These included: a) 1st-order latent variables (1st-order factors) (FM; FW), b) 1st-order latent variables (1st-order factors) (FM; FW) forming a 2nd-order factor (F), c) Multi-level (two-level) factorial structures (FML0; FML1 and FWL0; FWL1), and d) Bi-Factor factorial structures (FM; FW; FG). The results may be of use to researchers interested in using valid, reliable, and accurate structures of latent variables in ICLV models. We confirm that alternative latent structures of divergent factorial nature exist for the same observed variables, and may have different impact upon the dependent observed choice variable in the ICLV models. Second, DCE utility is conceptualized and estimated at both Level 0 and Level 1 and the differences are evident

Objective 2: Conduct Experimental Activities on Performance of Sensor‐Equipped Composite Elements

In this report we present the basic principles of our exploratory research for embedding sensors and energy-harvesting devices in sandwich composite structures. A range of piezopolymer sensors where used, varying in their dimensions, their capacitance and the electrode coating material. Sensors were tested in the surface-attached and embedded formats on composite sandwich laminates. Specimens were tested under three-point bending configuration to measure both the sensor voltages and the generated laminate strains. The electromechanical sensitivity performance with respect to frequency and strain amplitude were the key performance parameters investigated. Primary conclusions, of a practical nature, were extracted concerning the appropriate type of sensor for embedding applications as well as the parameters affecting the sensitivity and efficiency of the devices to perform as energy both strain gauges and energy-harvesting devices.JRC.G.5-European laboratory for structural assessmen

Wind assessment for micro wind turbines in an urban environment

Wind flow in urban environments could be seen as a potential source of energy. This form of energy could be exploited by means of micro wind turbines placed along the existing infrastructures. To test this, an outdoor campaign was organised, which recorded the wind characteristics at different locations around a highway noise barrier in Delft, the Netherlands. The real-time data set was validated with a two-dimensional Computational Fluid Dynamics study. Both the influence of the high turbulence and the inflow angle on the positioning of the micro wind turbines are assessed for the case of perpendicular flow towards the plane of the noise barrier. Results indicated that integrating micro wind turbines with the noise barriers proves advantageous due to the flow velocity increment downstream. Lastly, a noise assessment was conducted in order to determine the optimal spacing between micro wind turbines, which impacts its social acceptance

Performance of the Five European Union Most Important Nutritional Labels

The efforts to reverse the overweight/obesity epidemic have largely been based on the premise that the “more the information provided to consumers, the better”. Nutritional labeling schemes have been instrumental in implementing such premise and different such schemes have been developed and used both in the US and elsewhere. US-based evidence shows that there is no winner regarding overall performance for consumer protection among the tested US labeling formats. The question is: Do the labeling schemes adopted in EU perform better

Rotorcraft engine maintenance costs analysis based on flight profile and usage.

Rotorcraft cover all sectors of human activity, supporting military, civil and government needs. Their design allows them to: i) deploy at different operating environments, ii) support power-demanding flight profiles, and iii) be agile and highly maneuverable. Compared to a civil aircraft turbofan engine, which typically operates at 35,000 feet for several hours, turboshaft engines found on rotorcraft usually experience high-frequency power changes. This results in a decrease of the useful life of critical components, due to low cycle fatigue (LCF) considerations. Methods developed so far, regarding the effects of engine degradation on engine performance and the estimation of the life of critical components, relate to aircraft turbofan engines, and therefore are not directly transferable to rotorcraft engines. Moreover, the current methods available to assess engine life cycle maintenance cost are also based on aircraft-related considerations and therefore are inapplicable to rotorcraft operations. Specifically, the current erroneous assessment premise is that the rotorcraft engine experiences two fatigue cycles per flight. This may be true for an aircraft due to its simple flight profile, but it does not apply to a rotorcraft due to the inherent diversity of the mission. After a thorough literature review, this work identified a gap in the existing knowledge regarding the life cycle cost assessment of rotorcraft, which may operate on a plethora of mission profiles within a given timeframe. In addition, the review did not reveal any evidence of a tool that could be deployed in these cases, particularly to assess the effect of different component designs on life. To address the aforementioned limitations, this doctoral work established a new methodology to estimate turbine fatigue cycles according to the peculiarities of every mission profile. The method also assesses engine life cycle maintenance costs considering a mixture of several different flight profiles within a certain timeframe (instead of a single flight profile). The new toolset created can provide useful information to an operator, regarding turbine life limit estimations and incurred maintenance costs, also considering factors such as: i) the fleet operating environment, ii) the flight profiles used, iii) fleet numbers and expected availability and, iv) pilot experience and flight attitude. The proposed methodology regarding the turbine life estimation integrates: i) an in-house helicopter flight mechanics code, ii) an in-house tool, which calculates engine performance, and iii) a tool to assess the turbine life developed from the author. It creates a set of life-limits for three different flight profiles and then uses a newly developed method, named Weight Usage Flight Profile Method (WU-FPM). This estimates an ‘equivalent’ life-limit in flight hours based on the fatigue cycles limit, which was estimated from the three different flight profiles, over the duration of a year. The life-limit data set is based on a Design Of Experiment (DOE) approach. The DOE estimates a representative turbine life for a reference flight profile, based on a design space which considers two operating (payload and climb rate) and one environmental parameter (ISA deviation). These are chosen within the rotrocraft Original Equipment Manufacturer (OEM) -defined capabilities. The parameters used for this life-limit are used to estimate the life limit for a Search and Rescue (SAR ) and Oil and Gas ( OAG) flight profile. Regarding the maintenance cost assessment the methodology uses two scenarios to estimate the life cycle costs: i) the Minimum Shop Visit (MINSV), and ii) the maximum Life Limited Part (LLP) usage. The previously estimated ‘equivalent’ engine life due to turbine failure and the OEM-specified Time between Overhaul (TBO) are used to assess maintenance intervals, which support these scenarios. The new method established was applied to selected test cases to demonstrate and assess its functionality. Results showed that regarding the operational and environmental parameters that affect Turbine Entry Temperature (TET), the payload and the ISA deviation are the most significant in hover and cruise, while the climb rate is the more influential parameter in the climb segment. Results also showed that the number of fatigue cycles per flight change according to the mission flight profile. For example, for a passenger flight, the turbine experiences 4 fatigue cycles, while it experiences 10 on a Search and Rescue (SAR) and 12 on an Oil and Gas (OAG) flight. Regarding maintenance cost prediction, the results show that the diversity of the missions influences the incurred cost significantly. For example, the costs incurred for a mission distribution of Passenger/OAG/SAR of 80/10/10% respectively, compared to a distribution of 50/40/10% can increase engine service life by 17.5%. The developed methodology, combined with a surrogate model, can be a useful tool for a rotorcraft operator to support informed financial planning decisions, based on a short or longer-term analysis.PhD in Aerospac

The influence of internal pressure and neuromuscular agents on C. elegans biomechanics: an empirical and multi-compartmental in silico modelling study

The function of a specific tissue and its biomechanics are interdependent, with pathologies or ageing often being intertwined with structural decline. The biomechanics of Caenorhabditis elegans, a model organism widely used in pharmacological and ageing research, has been established as biomarker for healthy ageing. However, the properties of the constituent tissues, and their contribution to the overall mechanical characteristics of the organism, remain relatively unknown. In this study we investigated the biomechanics of healthy C. elegans cuticle, muscle tissue, and pseudocoelom using a combination of indentation experiments and in silico modelling. We performed stiffness measurements using an atomic force microscope. To approximate the nematode’s cylindrical body we used a novel three-compartment nonlinear finite element model, enabling us to analyse of how changes in the elasticity of individual compartments affect the bulk stiffness. We then fine-tuned the parameters of the model to match the simulation force-indentation output to the experimental data. To test the finite element model, we modified distinct compartments experimentally. Our in silico results, in agreement with previous studies, suggest that hyperosmotic shock reduces stiffness by decreasing the internal pressure. Unexpectedly, treatment with the neuromuscular agent aldicarb, traditionally associated with muscle contraction, reduced stiffness by decreasing the internal pressure. Furthermore, our finite element model can offer insights into how drugs, mutations, or processes such as ageing target individual tissues

Ευστάθεια των βραχωδών πρανών και δυνατότητες αποκατάστασης και αξιοποίησης του εγκαταλειμμένου λατομείου «ΒΛΑΧΟΥ» στην περιοχή της Άνω Γλυφάδας

The short vase life of Acacia holosericea cut stems needs to be improved before they are marketable as cut foliage for floral arrangement. The effects of citric acid, Cu and sucrose were investigated for their efficacy in postharvest treatments to extend vase life of the cut stems. Five experiments were conducted involved combinations of citric acid either with Cu or sucrose. Vase life, relative fresh weight (RFW), and vase solution uptake were measured as indicators of cut stem quality. The effect of Cu alone was shown to be consistently superior in improving vase life by up to 1.9-fold as compared with deionised water control. Citric acid had a smaller effect than Cu and did not act synergistically with Cu. Sucrose on its own or in combination with citric acid did not improve vase life significantly; instead sucrose promoted early wilting or desiccation of the cut foliage