bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exergy and Thermoeconomic Analysis of a Solar Air Heating Plant
Authors: Lozano Miguel A. , Mancini Carla , Serra Luis M. , Verda Vittorio 
Published: October 2014

The aim of this work is to present the energy, exergy and thermoeconomic analysis of a hypothetical solar air heating plant located in Zaragoza, Spain. The plant consists mainly of four parts: 1) a field of solar collectors, 2) a water tank storage, 3) a heat exchanger where heat energy is transferred from the collectors to the water storage tank, and 4) a water to air heater heat exchanger. Circulating pumps, pipes and fan have also been considered. In a previous work of the authors the design variables of the system were optimally determined from a conventional economic approach.
In this paper, a productive structure for the plant has been proposed and energy losses and exergy destructions (or irreversibility) have been calculated. Energy and exergy efficiencies have also been determined for each of the components and the whole system. Moreover, the costs of internal flows have been dynamically calculated for the time period under consideration. The very specific features of solar heating systems: thermal energy storage as well as continuous variation of solar radiation and energy demand (seasonal and throughout the day) impose important difficulties, which in our opinion have not been deeply studied yet in current methodologies.
The major conclusions are: i) energy, exergy and thermoeconomic analyses following a dynamic approach is very sensitive to the reference environment (ambient air temperature), ii) the same productive structure can and must be used for all of them, iii) solar energy should be considered as a high quality source and thermodynamic efficiency of solar heating plants is very low (2.5% in our case), and iv) a dynamic analysis of the process of cost formation through the different components reveals interesting and valuable information about the physics and economics of solar energy conversion systems.
Estimating the Effect of Chirality and Size on the Mechanical Properties of Carbon Nanotubes Through Finite Element Modelling
Authors: Zuberi Muhammad Jibran Shahzad , Esat Volkan 
Published: October 2014

Carbon nanotubes (CNTs) are considered to be one of the contemporary materials exhibiting superior mechanical, thermal and electrical properties. A new generation state-of-the-art composite material, carbon nanotube reinforced polymer (CNTRP), utilizes carbon nanotubes as the reinforcing fibre element. CNTRPs are highly promising composite materials possessing the potential to be used in various areas such as automotive, aerospace, defence, and energy sectors.
The CNTRP composite owes its frontline mechanical material properties mainly to the improvement provided by the CNT filler. There are challenging issues regarding CNTRPs such as determination of material properties, and effect of chirality and size on the mechanical material properties of carbon nanotube fibres, which warrant development of computational models. Along with the difficulties associated with experimentation on CNTs, there is paucity in the literature on the effects of chirality and size on the mechanical properties of CNTs. Insight into the aforementioned issues may be brought through computational modelling time- and cost-effectively when compared to experimentation.
This study aims to investigate the effect of chirality and size of single-walled carbon nanotubes (SWNTs) on its mechanical material properties so that their contribution to the mechanical properties of CNTRP composite may be understood more clearly. Nonlinear finite element models based on molecular mechanics using various element types substituting C-C bond are generated to develop zigzag, armchair and chiral SWNTs over a range of diameters. The predictions collected from simulations are compared to the experimental and computational studies available in the literature.
Design of a Semi Active Differential to Improve the Vehicle Dynamics
Authors: Annicchiarico Claudio , Rinchi Mirko , Pellari Stefano , Capitani Renzo 
Published: October 2014

Suppressing or limiting the differential action of the differential mechanism is the mostly adopted technique to avoid the skidding of a driving wheel of a vehicle riding on a poorly adherent surface. The devices carrying out this function unbalance the traction force distribution in the differential, generating a yaw torque acting on the vehicle as a secondary effect. If the unbalancing action is electronically controlled, this yaw torque can be used to affect the attitude of car as a torque vectoring technique.
In this paper, a purpose built differential is presented and its technical features are highlighted, including the electrohydraulic actuation. Moreover, its torque vectoring capabilities are discussed, basing on the numerical simulation campaign performed deploying this device in a 7 DOFs model of a race car with low ground effect.
The results of these simulations are compared with the behavior of the same vehicle equipped with a common passive locking differential, to show that the proposed one and its control logic (which relies on only measurable inputs) are able of improving the handling of the vehicle, in terms of both vehicle stability and linearity with the driver’s inputs. Therefore, this system could be considered as a completion of the common ESC (“Electronic Stability Control) systems to control the vehicle attitude when using the brake system is an inefficient solution.
A New Methodology for the Experimental Study of Scuffing on Gears for Advanced Applications
Authors: Bartilotta Ida , Strambi Marco , Ciulli Enrico , Gravina Michele 
Published: October 2014

The paper proposes a brief overview of the commonly adopted approaches for the experimental study of scuffing on gears for advanced applications and suggests a new methodology for the design of an experimental campaign aimed at determining the scuffing resistance of an innovative aerospace gear material.
The present study has been carried out by AM Testing srl in collaboration with Avio Aero within the VHLGM (Validation of High Load Capacity Gear Material) project of the Clean Sky Sustainable and Green Engines framework.
Potential of the Variable Valve Actuation (VVA) Strategy on a Heavy Duty CNG Engine
Authors: Baratta Mirko , Finesso Roberto , Misul Daniela , Spessa Ezio , Tong Yifei , Peletto Cesare 
Published: October 2014

The environmental concerns officially aroused in 1970s made the control of the engine emissions a major issue for the automotive industry. The corresponding reduction in fuel consumption has become a challenge so as to meet the current and future emission legislations.
Given the increasing interest retained by the optimal use of a Variable Valve Actuation (VVA) technology, the present paper investigates into the potentials of combining the VVA solution to CNG fuelling. Experiments and simulations were carried out on a heavy duty 6-cylinders CNG engine equipped with a turbocharger displaying a twin-entry waste-gate-controlled turbine. The analysis aimed at exploring the potentials of the Early Intake Valve Closure (EIVC) mode and to identify advanced solutions for the combustion management as well as for the turbo-matching. The engine model was developed within the GT-Power environment and was finely tuned to reproduce the experimental readings under steady state operations. The 0D-1D model was hence run to reproduce the engine operating conditions at different speeds and loads and to highlight the effect of the VVA on the engine performance as well as on the fuel consumption and engine emissions. Pumping losses proved to reduce to a great extent, thus decreasing the brake specific fuel consumption (BSFC) with respect to the throttled engine. The exhaust temperature at the turbine inlet was kept to an almost constant value and minor variations were allowed. This was meant to avoid an excessive worsening in the TWC working conditions, as well as deterioration in the turbocharger performance during load transients. The numerical results also proved that full load torque increases can be achieved by reducing the spark advance so that a higher enthalpy is delivered to the turbocharger. Similar torque levels were also obtained by means of Early Intake Valve Closing strategy. For the latter case, negligible penalties in the fuel consumption were detected. Moreover, for a given combustion phasing, the IVC angle directly controls the mass-flow rate and thus the torque. On the other hand, a slight dependence on the combustion phasing can be detected at part load. Finally, the simulations assessed for almost constant fuel consumption for a wide range of IVC and SA values.
Specific attention was also paid to the turbocharger group functioning and to its correct matching to the engine working point. The simulations showed that the working point on the compressor map can be optimized by properly setting the spark advance (SA) as referred to the adopted intake-valve closing angle. It is anyhow worth observing that the engine high loads set a constraint deriving from the need to meet the limits on the peak firing pressure (PFP), thus limiting the possibility to optimize the working point once the turbo-matching is defined.
Problem-Based Learning Approach in Marine Engineering Education Using Mobile Devices and Internet Tools
Authors: Mora Luis Carlos E. , Marrero Antonio González , Mellado Reyes Carrau , Añorbe-Diaz Beatriz , Martín-Gutierrez Jorge 
Published: October 2014

The skills of Marine Engineering graduates should be strongly oriented to problem solving for situations without external direct assistance. Marine professionals should also be able to take the right decisions under difficult situations like emergencies.
Work-group and job planning is an every day requirement, especially when doing maintenance and reparation tasks. Besides, marine technology has advanced quickly and knowledge recycling is a must on every shipping company, but operation and maintenance procedures have usually to be learnt on the go. During last decades, marine engineering students had not got immersed into a real challenge work environment until going onboard for the first time when finishing their studies. The adoption of a problem-based learning is intended to solve this situation, so students will have a closer contact with real decision-taking and auto-learning situations on earlier stages. We pretend to create more engaging experiences and introduce our students into real collaborative environments using technologies; especially those based on mobile devices and Internet tools.
Grounded in motivation theory, this research evaluates how the context of problem-based learning (PBL) affects aspects of motivation in students of marine engineering. Our research aims to answer: 1) How does the context of service in project-based learning affect student motivation? 2) What factors are most influential on student motivation to persist in project-based learning experiences?
The results show different behavior in freshmen and senior students.
Multiobjective Pareto-Based Optimization of pMUT Hydrophone With Piezoelectric Active Diaphragm
Authors: Shevtsov Sergey , Chang Shun-Hsyung (Stephen) , Kalinchuk Valery , Zhilyaev Igor , Shevtsova Maria 
Published: October 2014

The design of high-sensitive hydrophones is one of the research interests in underwater acoustics. Due to progress of micro- and nanotechnology the most attention of researchers is attracted by the transducers that use the micro-electromechanical system (MEMS) concept. Piezoelectric micro-machined ultrasonic transducers (pMUTs) present a new approach to sound detection and generation that can overcome the shortcomings of conventional transducers. For accurate ultrasound field measurement, small size hydrophones which are smaller than the acoustic wavelength are required for providing an omnidirectional response and avoid spatial averaging.
This paper presents some results of multiobjective optimization for membrane-type piezoceramic MEMS based transducers. We investigate the miniaturized membrane-type sensor with perforated holes in the active PZT and intermediate membranes, with the protective plates and a vacuum chamber. An influence of the protective plate elastic and viscous properties, the dimensions and the relative area of the perforated holes on the sensitivity’s frequency response of the hydrophone was studied for the broadening and equalizes the operating frequency band. We optimize these key parameters using the Pareto approach with the finite element (FE) model of coupled piezoelectric-acoustic problem. Finally, the set of optimized hydrophone structures and some examples of obtained sensitivity frequency response are demonstrated.
Finite Element Method Modelling and Analysis on Compressor Coupling Integrity Review
Authors: Hamdi Edi , Dirgantara Tatacipta , Setiawan Hery 
Published: October 2014

Finite element method modeling for flexible coupling of gas turbine compressor package installed in one of PT. Pertamina Hulu Energi Offshore North West Java (PHE ONWJ) facility has been completed. The model delivered result which is in acceptable level of accuracy as compared to manufacturer operating guideline as well as follows in general to guidance of API 671 widely used as industrial code and standard for coupling.
The scope of modeling is including the static and dynamic analysis for both perfectly aligned (used as base reference) and for misaligned condition. The scope covers as well the cyclic stresses which in turns determining the disc pack life time. The major challenge on the modeling is mainly to vary the degree of misalignment and how to distribute the additional load to the flexible part of the coupling causing deformation of disc pack.
The static analysis modeling reveals that the stresses are still below the yield point when aligned perfectly even in high vibration situation, but when it reaches up to 0.1 degree of misalignment with maximum torque the Von-Misses stress has exceeded the yield. The dynamic analysis shows that for similar 0.1 degree the fatigue factor of safety also has exceeded API 671 requirement.
Following the actual coupling failure events, the model has successfully indicated the location of highest stress correlated to crack initiation as compared to actual cracks found in existing discs specimen. The model has been validated as well with the result of material analysis of the damaged flexible discs showing that the failure occurred due to over misalignment.
In addition to manufacturer manual description, the model is capable to recommend maximum angular misalignment that need to be monitored during compressor operation and provide basis to calculate safety factor to comply API 671 guideline.
As oil and gas exploration and production company which focus on possible highest energy efficiency of its operating platforms — which all is located offshore, the work leads a way in integrity management of turbo-machinery equipment in order to maximize running time and minimize production shutdown.
Applying Novel Future-Internet-Based Supply Chain Control Towers to the Transport and Logistics Domain
Authors: Alias Cyril , Jawale Mandar , Goudz Alexander , Noche Bernd 
Published: October 2014

Competing supply chain networks all around the globe are under scrutiny due to ever-growing demand for service improvement and cost reduction. A major field of action in this respect is the realization of real-time monitoring means for supply chain processes including a constant comparison of the respective progress status with the planning guidelines and the best possible management of deviations and exceptions.
Control towers have been named as the future tool of supply chain monitoring for quite a while. They are defined as decision-support systems merging different data streams from various subordinate levels and displaying the consolidated information at a higher level for the purpose of monitoring and control of processes while pursuing the goal of optimal process operation. Contrary to the technological constraints of the past which prevented a continuous and fully transparent real-time monitoring of supply chain processes, innovative evolving so-called Future Internet technologies enable genuine transparency and the handling of exceptions in a timely and cost-efficient manner nowadays. With the help of such technologies, newly designed and built control towers are supposed to assist actors on the planning and execution levels of their respective supply chain networks in their decision-making in case of relevant deviations or exceptions. This again raises the market acceptance of such control towers.
This paper presents a novel approach to the functional principle of Future-Internet-based control tower solutions and describes the different components therein. Especially, the incorporation of manifold information sources from the Future Internet technologies for the purpose of real-time monitoring and control of supply chain processes is highlighted in the paper.
Application of Structural Integrity Concepts to NPP Piping and Equipment During Design, Commissioning and Operation
Authors: Arzhaev Alexey , Sivakov Sergey , Arzhaev Kirill , Butorin Sergey , Makhanev Valentin 
Published: October 2014

Application of Structural Integrity Concepts to RF NPP piping and equipment have started in Russia in the beginning of 1990s from requirements to Leak Before Break (LBB) calculation studies adopted by regulatory body. Results of first practical LBB Concept application to RF NPP piping have been reported at Lyon LBB Conference in year 1995.
Experience of LBB Concept practical application in Russia during 1990s formed strong basis for issuing comprehensive guideline RD 95 10547-99 which stated LBB Concept basic principles and requirements applicable to RF NPPs with Light Water Reactors (LWR) at all stages of Life Cycle: design, commissioning and operation. Requirements of RD 95 10547-99 guideline have been in good correspondence to classic LBB principles used in many European countries, USA, Japan and to IAEA Technical Documents as well.
RF NPP piping operation experience analysis have revealed necessity of producing more general methodology — Break Preclusion (BP) Concept — to substantiate structural integrity of piping potentially susceptible to active degradation mechanisms like Flow Accelerated Corrosion (FAC), Intergranular Stress Corrosion Cracking (IGSCC), etc. BP and LBB Concepts are based on the same major principles: (a) quality of design, manufacturing, assembling, (b) monitoring of degradation and operating conditions, (c) enveloping loading conditions with respect to maximum design loads, (d) calculation and experimental substantiation of failure according to LBB scenario. LBB Concept requires full implementation of principles (a)÷(d) and BP Concept allows to achieve balance in implementation of principles (a) and (b) while principles (c) and (d) should be fully implemented.
Memorandum of 8th International Scientific and Technical Conference “Safety of VVER NPPs” in year 2013 stated as a 1st priority goal to substantiate structural integrity of main components for Long-Term Operation (LTO) during 60–80 years. Actual regulatory demands to operating NPPs also produce strong demand to provide structural integrity arguments for safety important piping and equipment as a part of periodic safety justification of NPP Unit needed for license extension.
Peculiarities of structural integrity concepts application to safety important piping and equipment at different stages of NPP Unit Life Cycle (design. commissioning and operation) are discussed in paper with emphasis on technical measures providing conditions for effective degradation monitoring and prevention during LTO. Perspectives of regulatory documents improvement are also discussed.
Performance Evaluation and Environmental Analysis of an Electrically Assisted Bicycle Under Real Driving Conditions
Authors: Iodice Paolo , Abagnale Carmelina , Cardone Massimo , Strano Salvatore , Terzo Mario , Vorraro Giovanni 
Published: October 2014

This paper describes the on-road test program that was used for a performance study and environmental analysis of an electrically assisted bicycle in the urban area of Naples. For this purpose, the vehicle was tested on different test tracks, cycling over 2000 km, and then making a general assessment about the driving behavior under real conditions.
Based on the findings obtained during the different test samples, an appraisal of the electric traction offered by this bicycle on the driving comfort was evaluated for different conditions: electrical assistance at start, on a flat road and when riding uphill. The power requirements in different typical riding situations were also calculated: these results were estimated by experimental kinematic parameters that describe the driving dynamics collected during the real-life applications. An environmental analysis was made and also put against the environmental impact of a thermal moped.
A Numerical Model to Investigate Evaporative Condensers Behaviour at Tube Scale
Authors: Fiorentino Maria , Starace Giuseppe 
Published: October 2014

Evaporative condensers operate at lower temperatures and with a higher efficiency compared to air condensers, as heat rejection is limited by air wet bulb temperature and mainly caused by water vaporization. This reduces the compressor pressure-lift and improves refrigeration cycle performance.
Due to complex phenomena of heat and mass transfer on the tube bundles, modeling the evaporative condensers is a hard task and fine grids in numerical simulations are requested to reach acceptable results.
A two-dimensional steady state numerical model at the single tube scale has been developed in Ansys-Fluent (release- 14.5), adopting the VOF multiphase model.
Moist air has been treated as a mixture of air and water vapor species, while water vaporization and latent heat have been modeled with a C++ User Defined Function.
The tube wall temperature has been assumed constant.
The aim of this work is to describe the developed numerical model and to validate it by comparing results obtained at different operating conditions with empirical relationships found in the literature in terms of combined and overall heat transfer coefficients.
Combined heat transfer coefficient variation along the tube surface has been analyzed, observing that the heat transfer coefficient is higher in the impingement zone, becomes approximately uniform and rises approaching the trailing edge.
Moisture content distributions at different sections through the heat exchanger have been examined in detail as well.
This study will be the basis to investigate the performance of the whole condenser taking into account the real evolution of the operating conditions of each single tube in the bundle, whatever its arrangement.
Zooming in to see the bigger picture: Microfluidic and nanofabrication tools to study bacteria
Authors: Hol Felix J. H. , Dekker Cees 
Published: October 2014

Experimental platforms for probing bacteria
Bacteria respond to a host of changing cues provided by their environment. Hol and Dekker review how microfluidic and nanofabricated devices can provide a platform to deliver different stimuli in a variety of environments. Bacterial quorum sensing and electron transport are among the problems that can be studied in this way.

Science
, this issue
10.1126/science.1251821