bluuebunny/crossref_metadata_2025 huggingface dataset:
Error Metrics and the Sequential Refinement of Kriging Metamodels
Authors: Romero David A. , Marin Veronica E. , Amon Cristina H.
Published: October 2014

Metamodels, or surrogate models, have been proposed in the literature to reduce the resources (time/cost) invested in the design and optimization of engineering systems whose behavior is modeled using complex computer codes, in an area commonly known as simulation-based design optimization. Following the seminal paper of Sacks et al. (1989, “Design and Analysis of Computer Experiments,” Stat. Sci., 4(4), pp. 409–435), researchers have developed the field of design and analysis of computer experiments (DACE), focusing on different aspects of the problem such as experimental design, approximation methods, model fitting, model validation, and metamodeling-based optimization methods. Among these, model validation remains a key issue, as the reliability and trustworthiness of the results depend greatly on the quality of approximation of the metamodel. Typically, model validation involves calculating prediction errors of the metamodel using a data set different from the one used to build the model. Due to the high cost associated with computer experiments with simulation codes, validation approaches that do not require additional data points (samples) are preferable. However, it is documented that methods based on resampling, e.g., cross validation (CV), can exhibit oscillatory behavior during sequential/adaptive sampling and model refinement, thus making it difficult to quantify the approximation capabilities of the metamodels and/or to define rational stopping criteria for the metamodel refinement process. In this work, we present the results of a simulation experiment conducted to study the evolution of several error metrics during sequential model refinement, to estimate prediction errors, and to define proper stopping criteria without requiring additional samples beyond those used to build the metamodels. Our results show that it is possible to accurately estimate the predictive performance of Kriging metamodels without additional samples, and that leave-one-out CV errors perform poorly in this context. Based on our findings, we propose guidelines for choosing the sample size of computer experiments that use sequential/adaptive model refinement paradigm. We also propose a stopping criterion for sequential model refinement that does not require additional samples.
Fuel Economy of a Multimode Combustion Engine With Three-Way Catalytic Converter
Authors: Nüesch Sandro P. , Stefanopoulou Anna G. , Jiang Li , Sterniak Jeff
Published: October 2014

Highly diluted, low temperature homogeneous charge compression ignition (HCCI) combustion leads to ultralow levels of engine-out NOx emissions. A standard drive cycle, however, would require switches between HCCI and spark-ignited (SI) combustion modes. In this paper we quantify the efficiency benefits of such a multimode combustion engine, when emission constraints are to be met with a three-way catalytic converter (TWC). The TWC needs unoccupied oxygen storage sites in order to achieve acceptable performance. The lean exhaust gas during HCCI operation, however, fills the oxygen storage and leads to a drop in NOx conversion efficiency. If levels of tailpipe NOx become unacceptable, a mode switch to a fuel rich combustion mode is necessary in order to deplete the oxygen storage and restore TWC efficiency. The resulting lean-rich cycling leads to a penalty in fuel economy. Another form of penalty originates from the lower combustion efficiency during a combustion mode switch itself. In order to evaluate the impact on fuel economy of those penalties, a finite state model for combustion mode switches is combined with a longitudinal vehicle model and a phenomenological TWC model, focused on oxygen storage. The aftertreatment model is calibrated using combustion mode switch experiments from lean HCCI to rich spark-assisted HCCI (SA-HCCI) and back. Fuel and emission maps acquired in steady-state experiments are used. Different depletion strategies are compared in terms of their influence on drive cycle fuel economy and NOx emissions. It is shown that even an aggressive lean-rich cycling strategy will marginally satisfy the cumulated tailpipe NOx emission standards under warmed-up conditions. More notably, the cycling leads to substantial fuel penalties that negate most of HCCI's efficiency benefits.
Study on the Iced Quad-Bundle Transmission Lines Incorporated With Viscoelastic Antigalloping Devices
Authors: Xu Zhao-Dong , Xu Ling-Zhi , Xu Fei-Hong
Published: October 2014

The viscoelastic damper is one of the most promising devices for vibration mitigation. In order to reduce dynamic responses of iced transmission lines due to strong wind, a new kind of viscoelastic antigalloping device (VEAGD) is developed. Experimental and theoretical studies indicate that the device has fine energy dissipation capacity and high damping characteristic. Then, the motion equations of the iced quad-bundle transmission lines incorporated with VEAGDs are established by employing Lagrange equation based on the assumed mode method. At the same time, the parameters and positions of the VEAGDs are determined optimally by the genetic algorithm. Numerical analysis results show that VEAGDs have excellent antigalloping effect, and the dynamic responses of the transmission lines with optimally designed VEAGDs are mitigated more effectively.
The Application of Laser Cladding to Marine Crankshaft Journal Repair and Renovation
Authors: Torims Toms , Bruckner Frank , Ratkus Andris , Fokejevs Artjoms , Logins Andris
Published: October 2014

This article presents the development and design of a laser cladding machine for in-situ marine diesel engine crankshaft repairs. The described technology and device is designed to perform crankpin journal renovation operations directly in the engine housing, without removing the crankshaft from the engine. This paper outlines the novel, in-situ concept of applying laser cladding to marine crankshaft repairs. Laser cladding technology is described along with the state of laser cladding implementation in modern production engineering. The principal design of the in-situ laser cladding machine is presented and accompanied by a detailed description of the in-situ laser cladding machine construction. Arguments for the selection of appropriate laser nozzles are provided based on state-of-the-art technology. Technological challenges deriving from the industrial use of the laser equipment are outlined. The proposed device and method satisfy ship-board crankshaft surface renovation needs and open up an entirely new dimension for the industrial application of laser cladding technologies. This technology provides clear economic benefits and many technological advantages.
Computational Investigations of Thermal Simulation of Shell and Tube Heat Exchanger
Authors: Yehia Mahmoud Galal , Attia Ahmed A. A. , Abdelatif Osama Ezzat , Khalil Essam E.
Published: October 2014

In the present paper, simulation for shell and tube heat exchanger investigated using CFD techniques. Numerical simulations of the turbulent, three-dimensional fluid flow and heat transfer are performed using Ansys Fluent 6.3. The effect of friction characteristics on the model of heat exchanger is discussed. A RNG κ-ε turbulence model with non-equilibrium wall function and 2nd order upwind is used. The present model is validated with the experimental literature and show a good agreement. The numerical results of the present study predict reasonably agree well with available correlations. Finally the present study model can be used to model a shell and tube heat exchanger with a satisfactory accuracy level in predictions.
Mechatronic Modeling and Optimization of the Structural Layout of the Electric Arc Furnace
Authors: Brusa Eugenio G. M. , Morsut Stefano
Published: October 2014

Vibration of electrodes in Electric Arc Furnace (EAF) fed by AC current for steel melting is usually fairly large. It might be dangerous for the EAF operation and often reduces the efficiency of melting process. Vibration amplitude depends on the vertical position control operated to keep the arc length constant as much as possible and to the electromechanical actions due to the mutual magnetic induction among the three electric phases. Since designer of the EAF system needs a clear correlation between each design parameter and the dynamics observed a first modeling activity was performed. A mechatronic approach was implemented, by including the electromechanical coupling into the structural analysis performed to predict the system dynamics. A Multi Body Dynamics (MBD) code was used in cooperation with the Finite Element Method (FEM). A preliminary experimental validation on a real plant was tentatively performed.
Analysis of Stiffening Effect and Rupture in Dynamics of Graphite Electrodes of the Electric Arc Furnace
Authors: Brusa Eugenio G. M.
Published: October 2014

Prediction of dynamic behavior of electrodes of the Electric Arc Furnace (EAF) fed by AC current is rather difficult because of several phenomena superposed, particularly during the first step of melting process, i.e. the so-called perforation, and in case of melting of metallic scrap. Unexpected ruptures of electrodes are often observed as a consequence of vibration. Dynamic excitation is applied by the vertical position control of the mast supporting the electrodes and by the Lorentz’s forces generated by the magnetic flux provided by each electric phase. Moreover, the irregular distribution of stiffness along the electrode, being due to the sensitivity of material properties upon temperature, affects quite a lot the dynamic response of the structure. To identify the origin of the observed ruptures and to suitably predict the dynamic behavior of the whole system a modeling activity was performed. A numerical model of the EAF structures was built, by resorting to an integrated approach based on the Finite Element Method and on the Multi Body Dynamics, then it was preliminarily validated on an existing plant. It demonstrated that stiffening effect upon the graphite electrode induced by temperature distribution makes dangerous the action of the vertical position control, when it is applied too fast and excites the flexural modes of the electrode. Numerical model allowed refining the design of the electrode and improving the safety factor as well as finding some design requirement to suitably limit the operation of the position control system.
Numerical Simulation of Lubrication System in a Hermetic Reciprocating Compressor
Authors: Ozsipahi Mustafa , Cadirci Sertac , Gunes Hasan , Sarioglu Kemal , Kerpicci Husnu
Published: October 2014

The aim of this numerical study is to investigate the lubrication system of a household hermetic reciprocating compressor. The effects of the rotational speed, oil viscosity and crankshaft-to-oil sump bottom distance on the oil-air two phase flows are investigated in detail. Necessary oil to lubricate the components of the compressor is sucked from the oil sump through an asymmetrically opened suction hole of the crankshaft by its rotational movement and climbs as an oil film on the helical channel carved on the shaft wall. This oil film is directed to crankshaft outlet. The oil forms an immiscible mixture with air, thus a two phase flow model should be analyzed using Volume of Fluid (VoF) method in the flow solver. Main findings related to the oil mass flow rate released from the crankshaft outlet reveal that with increasing rotational speed, the mass flow rate from the crankshaft outlet also increases, but with increasing viscosity and decreasing crankshaft-to-oil sump bottom distance, the oil mass flow rate decreases.
Experimental Investigation of Oil Flowrate in a Hermetic Reciprocating Compressor
Authors: Tas Sibel , Cadirci Sertac , Gunes Hasan , Sarioglu Kemal , Kerpicci Husnu
Published: October 2014

The aim of this experimental study is to investigate the mass flow rate of the lubricating oil in a hermetic reciprocating compressor. Essential parameters affecting the performance of the lubrication are the rotational speed of the crankshaft, the viscosity of the oil, the operating temperature and the submersion depth of the crankshaft. An experimental setup was built as to measure the oil mass flow rate with respect to the oil temperature variation during different operating conditions. The influence of the governing parameters such as the rotational speed, temperature (viscosity) and the submersion depth on the mass flow rate from crankshaft outlet are studied in detail. In addition, the oil flow visualization from the upper hole of the crankshaft is performed using a high-speed camera in order to observe the effectiveness of the lubrication of the various parts of the compressor. This study reveals that with increasing rotational speed, the submersion depth of the crankshaft and with decreasing viscosity of the lubricant, the mass flow rate from the crankshaft increases.
The Effect of Contact Ratio on the Cooling Performance of an Aluminum-Foam Heat Sink With a Solid Aluminum Core
Authors: Shih Wei-Hung , Liu Chin-Chia , Hsieh Wen-Hsin
Published: October 2014

To enhance the cooling performance of a metal-foam heat sink, this work increases the surface area of the heat sink wall in contact with the electronic component by vertically placing a solid aluminum cylinder in the center (i.e., core) of an aluminum-foam heat sink. The contact ratio, defined as the ratio of the surface area of the extended heat sink wall in contact with the electronic component to the solid-fluid interface area inside the aluminum-foam heat sink, was systematically varied to experimentally investigate the heat transfer characteristics. The experimental results on the measured Nusselt number, solid-phase and gas-phase temperatures and temperature difference between the solid and gas of the aluminum foam under different contact ratios were reported and discussed in this work.
Teaching Product Design Through Industry Collaboration
Authors: Costello Gabriel J.
Published: October 2014

There has been increased interest in using problem-based pedagogies to enable design engineering undergraduates obtain a more relevant learning experience. Furthermore organizations, such as Engineers Ireland, are calling for graduate engineers to have more rounded skills in the areas of presentation, communication and team-work. However some scholars argue that design “is hard to learn and harder still to teach”. This paper provides an example of using student-industry collaboration in the teaching of product design to Mechanical Engineering final year students at the Galway-Mayo Institute of Technology (GMIT) based in Ireland. The work proposes to make an original contribution by directly interfacing with industry in order to simulate a real-life client-designer interaction for students. Finally we argue that this work contributes new insights to the debate on “pedagogies of engagement”.
The Effects of Groundwater Flow on Vertical-Borehole Ground Source Heat Pump Systems
Authors: Funabiki Ayako , Oguma Masahito , Yabuki Taisei , Kakizaki Takao
Published: October 2014

Heat advection by groundwater flow is known to improve the performance of ground heat exchangers (GHEs), but the effect of groundwater advection on performance is not yet fully understood. This study examined how parameters related to groundwater flow, such as aquifer thickness, porosity, lithology, and groundwater flow velocity, affect the performance of a borehole GHE. Under the thin-aquifer condition (10 m, or 10% of the entire GHE length in this study), groundwater flow velocity had the greatest effect on heat flux. With a groundwater flow velocity of at least 10−4 m/s through a low-porosity aquifer filled with gravel with high thermal conductivity, the heat flux of a GHE was as much as 60% higher than that of a non-aquifer GHE. If the aquifer is as thick as 50 m (50% of the entire GHE length), the high thermal conductivity of gravel doubled the heat flux of the GHE with a groundwater flow velocity of at least 10−5 m/s. Thus, not only groundwater flow velocity, but also aquifer thickness and thermal conductivity were important factors. However, groundwater seldom flows at such high velocities, and porosity, gravel size, and aquifer thickness vary regionally. Thus, in the design of ground source heat pump systems, it is not appropriate to assume a large groundwater effect.
An Investigation of the Relation Between Combustion Phase and Emissions of ULSD and RME Biodiesel With a Common-Rail HSDI Diesel Engine
Authors: Dhahad Hayder A. , Abdulhadi Mohammed A. , Alfayyadh Ekhlas M. , Megaritis T.
Published: October 2014

This study investigates the effect of combustion phase (premixed and diffusion phases) duration on the emissions emitted from a high speed direct injection (HSDI) diesel engine fueled with neat (100%) rapeseed methyl ester (RME) and run at a constant speed (1500 rpm) with single injection strategy at constant fuel injection pressure (800 bar) and varying fuel injection timings (−12,−9,−6,−3,0) ATDC, for two loads (2.5 and 5 bars) BMEP. The obtained results were compared with those obtained when the engine run at the same conditions but with ultra-low sulfur diesel fuel (ULSD). In-cylinder pressure was measured and analyzed using (LABVIWE) program. calculation program specially written in (MATLAB) software was used to extract the apparent heat release rate, the ignition delay, combustion duration and specify the amount of heat released during the premixed and diffusion combustion phases (premixed burn fraction PMBF) and (diffusion burn fraction DBF). Emission measurements included; NOx, CO, THC, CO2 and smoke number (SN). The results showed that at high load, RME generate higher NOx, CO and THC. Measurements and calculations indicated that ignition delay of RME was shorter than that of ULSD, which means less PMBF. This conflicting effect is probably due to the advanced start of combustion (SOC) leading to higher combustion temperature inside the combustion chamber and there will be less time available to complete the combustion. The emission results at low load showed that NOx and CO, generated by RME were less than those generated by USLD. USLD produced soot more than RME at high load and less at low load.
Determination of Maximum Loads for Drive Train Components in Thrusters Using Flexible Multibody-System Models
Authors: Schlecht B. , Rosenlöcher Thomas
Published: October 2014

The usage of modern thrusters allows to combine the functions of the drive and the ship rudder in one assembly, which are separated in conventional ship propulsions. The horizontally oriented propeller is supported in a vertically rotatable nacelle, which is mounted underneath the ship hull. The propeller can directly or indirectly driven by an electric motor or combustion engine. The direct drive requires the installation of a low speed electric motor in the nacelle. The present paper concentrates on indirect drives where the driving torque is transferred by bevel gear stages and shafts from the ship to the propeller. Due to the closed and inaccessible construction high demands on the reliability have to be achieved. Especially for the design of the highly loaded bevel gear stages accurate information to the occurring loads are required. The available experience to the operation of thrusters show, that primarily rarely occurring special load cases must be considered in the design process. Such operational conditions can only be determined by expensive long-term measurements. By means of a detailed multibody system simulation model of the thruster it is already possible to develop a basic knowledge to the dynamic properties of the drive train and to determine design loads for drivetrain components.
Compliant Device for Hand Rehabilitation of Stroke Patient
Authors: Borboni Alberto , Faglia Rodolfo , Mor Maurizio
Published: October 2014

A new device for hand rehabilitation of stroke patient is presented. Its main innovative features are: lightness, real safety guaranteed by its structural elasticity, smoothness and easiness of movements. The kinematic behavior of the system hand-plus-rehabilitation-device is analyzed. The device applicability is confirmed by positive testing.

Cerebrovascular diseases are the third cause of mortality and the second cause of long term disability in Western countries. The 60% of survived individuals shows a sensitive/motor deficit of one or both hands and must be subjected to a rehabilitative treatment to recover the use of the upper limb.

Recent technologies have facilitated the use of robots as assistive tools to patients, providing safe and highly personalized rehabilitation sessions, thus making therapist contribution to recovery much more intensive and effective.

We propose in this work a wearable glove with an incorporated compliant mechanical transmission over the hand.

The glove is composed by two main modules with well-defined mechanical characteristics. One is the actuator on the upper side of the forearm, close to the wrist (and to the impaired hand) and still separated from it; the other (the transmission) is composed by several elastic transmissions which, moved by the actuator, properly transmit displacements, speed and forces to one or more impaired fingers during a rehabilitation session. While the actuator module has a rigid and defined structure and is fixed to the forearm section of the glove, the “transmission” module has in fact a labile and extended structure as it has to reach all five fingers (one, some, or all might be impaired and in need of rehabilitation) up to their tips and move them in an effective and reliable way.

A kinematical characterization of the compliant transmission is proposed to dimension the actuators and to define the correct commanded motion profile at actuator level.
Prediction of the Rolling Contact Fatigue Behavior of Pre-Indented Hybrid Bearings
Authors: Robitaille Corentin , Nelias Daniel , Tonicello Emmanuel , Chaise Thibaut
Published: October 2014

The objective of this work is to study the Rolling Contact Fatigue (RCF) behavior of hybrid bearings. The studied bearings are composed of Si3N4 balls rolling on steel raceways. The raceways are made out of nitrided 32CrMoV13 steel. The nitriding treatment aims at reinforcing the surface mechanical properties. As the presence of an indent on the raceway surface will dramatically decrease the fatigue life of the rolling element [1], this study focuses on the RCF behavior of pre-indented rolling element bearings.

It is thus necessary to study the fatigue behavior of both the steel and the ceramic material under fatigue loading. The study presented here focuses on the fatigue behavior of nitrided 32CrMoV13 steel under rolling contact and aims at proposing a crack initiation criterion based on experimental results.

Fatigue tests are performed on a bi-disks machine with indented 32CrMoV13 samples to observe the damage evolution and crack initiation stages under various indent dimensions and test conditions.

In parallel simulations are performed with a semi-analytical method to accurately determine the stress history under elastic-plastic rolling contact. Semi analytical methods, classically used for the simulation of elastic contacts, have recently been extended to the consideration of plasticity [2], allowing to simulate the ball-raceway interaction in ball bearings [3] and wear or running in [4]. The main advantage of these methods is their ability to simulate the coupling between the contact conditions and the plastic behavior in reasonable computational time.

Based on the experimental and simulation results, a crack initiation criterion based on the dislocation theory proposed by Tanaka and Mura [5] is proposed allowing to predict the number of cycles for crack initiation for the given material.
Optimization of the Roll and Steer Systems of a Four-Wheeled Tilting Vehicle
Authors: Caneri Massimiliano , Lot Roberto , Cossalter Vittore , Massaro Matteo
Published: October 2014

The work addresses the optimization of the steering and roll systems of an innovative four-wheeled tilting vehicle, which is currently being built at the University of Padova. The vehicle is a combination of traditional two and four-wheeled forms, with the driver operating a bike handlebar to steer, and throttle and brake inputs to control speed. Two pedals control the roll movement, while the gearshifts are made automatically. The steering system consists of a handlebar, column, pinion, rack and track-rods to the wheels. In the resulting spatial mechanism, roll and steer motions of the wheels are coupled. The kinematic optimization presented in this paper, aims at minimizing undesired roll to steer behaviour, and provides appropriate outer/inner wheel steer angles. The natural coordinate approach is employed to efficiently simulate and optimize the mechanism.
Comparing Interface Elements on a Tablet for Intuitive Teleoperation of a Mobile Manipulator
Authors: Lopez David A. , Frank Jared A. , Kapila Vikram
Published: October 2014

As mobile robots experience increased commercialization, development of intuitive interfaces for human-robot interaction gains paramount importance to promote pervasive adoption of such robots in society. Although smart devices may be useful to operate robots, prior research has not fully investigated the appropriateness of various interaction elements (e.g., touch, gestures, sensors, etc.) to render an effective human-robot interface. This paper provides overviews of a mobile manipulator and a tablet-based application to operate the mobile manipulator. In particular, a mobile manipulator is designed to navigate an obstacle course and to pick and place objects around the course, all under the control of a human operator who uses a tablet-based application. The tablet application provides the user live videos that are captured and streamed by a camera onboard the robot and an overhead camera. In addition, to remotely operate the mobile manipulator, the tablet application provides the user a menu of four interface element options, including, virtual buttons, virtual joysticks, touchscreen gesture, and tilting the device. To evaluate the intuitiveness of the four interface elements for operating the mobile manipulator, a user study is conducted in which participants’ performance is monitored as they operate the mobile manipulator using the designed interfaces. The analysis of the user study shows that the tablet-based application allows even non-experienced users to operate the mobile manipulator without the need for extensive training.
Dynamics of Externally Pressurized Air Bearing With High Values of Clearance
Authors: Dal Abdurrahim , Karaçay Tuncay
Published: October 2014

Performance parameters such as critical speed and stability are affected by various design parameters such as supply pressure, clearance between shaft and rotor (air film thickness), bearing diameter and length etc. for externally pressurized gas lubricated bearing. Literature about effects of supply pressure is generally analyzed with clearances which are lower than 100 μm. Externally pressurized gas lubricated bearings with small clearance have some practical disadvantages such as difficulties in manufacturing process and price. So, externally pressurized air bearing may become widespread with usage of higher values of clearance in the bearing. However, there is limited number of study investigating the dynamics of externally pressurized air bearing with high values of clearance. In this study the effect of supply pressure was investigated on the dynamic of an externally pressurized gas lubricated bearing with increased clearance. The flow between shaft and rotor was modeled using Reynold’s Equation which is known fluid equation of motion. And this model was solved by Alternating Direction Implicit (ADI) numerical solution method. Dynamics of the rotor was investigated for different elevated (increased) clearances.
Proposals to Maximize Electricity Generation From Sugar Cane in Brazil
Authors: Pina Eduardo Antonio , Modesto Marcelo
Published: October 2014

Brazil’s sugarcane industry has been characterized by low efficiency in energy production as it consumes large amounts of bagasse as fuel in its cogeneration system, considering its low price and abundance. The possibility of selling surplus electricity to the grid has motivated investments in improvements, such as reduction of steam demand by means of process thermal integration and double distillation systems, and employment of condensing instead of back pressure steam turbines. Four different cogeneration systems were analyzed in this work: two traditional Rankine Cycles, the first presenting back pressure steam turbine and the second featuring condensing steam turbine configuration; a BIGCC (Biomass Gasification Combined Cycle) and an altered model of the BIGCC, comprised by an extra gas turbine set operating with ethanol. Thermoeconomic analyses determining exergy based costs of electricity and ethanol for all cases were carried out. The main objective of this work is to assess the proposal to maximize electricity production from the sugarcane industry in Brazil.
Investigations on the Performance of a Mechatronic System for Water Well Rehabilitation Using High Power Ultrasonics
Authors: Brehm Robert , Locher Peer , Linderberg Johan
Published: October 2014

In Denmark the public water supply is practically 100% served by groundwater abstracted from nearly 20.000 water wells. During time of operation the productivity from a well will often decrease drastically. This impaired performance is usually caused by well clogging. This clogging makes the well economically inefficient for the operator and therefore needs to be rehabilitated. This article examines the performance and evaluates the effectiveness of high power ultrasonics for water well rehabilitation. Special focus is drawn to the inconsistent efficiency of the currently, rarely used ultrasonic cleaning method caused by the specific varying conditions in water wells and correlated ultrasound intensity losses. The scope for improving the, in Denmark, rarely used ultrasonic cleaning method efficiency is investigated and suggestions for improvements based on a proof-of-concept prototype are given based on empirical- as well as theoretical studies.
Modeling Performance of a Production Line and Optimizing Its Efficiency by Means of Genetic Algorithm
Authors: Bartkowiak Tomasz , Gessner Andrzej
Published: October 2014

A production line is a fundament of modern high scale FMCG industry. The performance of the line depends on various factors, out of which breakdowns, cleanings and changeovers play the most important role. The paper describes the idea of modeling production line performance by its decomposition into discrete subsystems. Every machine or workstation together with preceding buffer constitute a single subsystem, which is characterized by statistical distributions of time to repair, time between failures, processing speed and capacity. Time dedicated for cleaning and changing format parts between different production batches is also considered in the model. Subsystems are connected with each other by conveyors. The model was simulated by the given time step. In order to verify the simulation results, the data from the real production line were compared and used for adjusting the parameters of the model. The described specimen consisted of six workstations connected with conveyors. There was one high capacity buffer between the second and third station. The efficiency of the whole line as well breakdown time characterizing every machine was captured by data acquisition system. Based on the given data, the parameters of statistical distributions of time to repair and time between failures were estimated by approximation to known distributions. In addition, statistical distributions of cleaning and changeover time were derived in order to provide general performance of the production line. Genetic algorithm was introduced to optimize the line parameters in order to achieve higher efficiency and to identify potential bottlenecks.
Web-Based Assessment of CAD Data in Undergraduate Design Education
Authors: Krüger Daniel Benjamin , Wartzack Sandro
Published: October 2014

In this contribution a web-based assessment framework for CAD data is proposed which has been developed based on the experience the authors made giving undergraduate courses at a German university. The framework is the backbone of a hybrid teaching concept combining conventional classroom lessons with e-learning elements. In-between the classroom lessons the students receive instructions on a particular modeling task via a web-interface. The same interface is used to hand in solutions in form of CAD files. Teachers who need to assess these solutions are supported by a semi-automated analysis of the CAD geometry. An algorithm compares each solution with a reference solution in order to reveal typical modeling mistakes. After the assessment is completed the students receive a feedback on their work. A case study on the application of the teaching concept in a course with 691 participants held during summer term 2013 reveals the positive experience the authors made using the system and points to some issues that need to be improved in the future.
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.
Experimental Investigation of a Dual Fuel Diesel Engine Run on Scrubbed Biogas Using the Method of Adsorption
Authors: Verma Vijay S. , Bora Bhaskor J. , Sarkar Achinta , Saha Ujjwal K.
Published: October 2014

Global warming and depletion of fossil fuels have compelled the researchers to study the sources of renewable energy. Biogas, one of the most promising alternative renewable biofuel, is produced from anaerobic digestion. It mainly consists of methane and carbon dioxide (CO2) with traces of water vapor, hydrogen sulfide (H2S), siloxanes, hydrocarbons, ammonia, oxygen, carbon monoxide and nitrogen. The presence of high concentration of CO2 in biogas lowers the energy content per unit mass/volume. This limits its utility to only low quality energy applications where as H2S is a highly toxic and corrosive gas. Therefore, it is extremely difficult to transport and store biogas. Thus, the need emerges for a unified approach for scrubbing, compression and subsequent storage of biogas for wider applications. The current work presents the scrubbing of biogas using the method of adsorption. The quality of the scrubbed biogas studied by gas chromatography is presented. The scrubbed biogas is then tested in a dual fuel diesel engine as a primary fuel to evaluate the performance and emission characteristics of the engine. The data obtained are compared with those of raw biogas run dual fuel diesel engine.
Minimum Energy Control of Redundant Manipulators With Axes Coupling and Compounded Path
Authors: Alpert Lior , Halevi Yoram
Published: October 2014

In redundant manipulation systems the end-effector path does not completely determine the trajectories of all the individual degrees of freedom and this freedom can be used to enhance the performance in some sense. The paper deals with utilizing the redundancy to minimize energy consumption. It extends previous results by considering more general cases of possible coupling between the axes, e.g. three axes for planar motion, and more general paths comprising of several primitive motions connected dynamically. The solution is based on projections into lower subspaces that separate the system and the input into two parts. One that is completely determined by the end-effector path and the other that is free for optimization. Simulation results show that redundancy, even with limited joint motion, can lead to a considerable reduction in energy consumption.
A Multi-Body Model of a Mechanical Transmission to Simulate Failures on Bearings
Authors: Cinquemani Simone , Gorla Carlo , Rosa Francesco , Sabbioni Edoardo , Osto Emanuele
Published: October 2014

The paper deals with a project aimed to improve the reliability of a condition monitoring system applied on gearboxes installed on rolling mills. In this context, to properly set up the algorithm, it is necessary to have measurements associated both to standard operating conditions and to malfunctioning. The latter, not being able to be experimentally generated, can be simulated by developing numerical models of the machine under varying conditions. The outputs generated, corresponding to different fault conditions associated with the main common failures of the elements that constitute the transmission, will provide a useful data base to tune the algorithm of condition monitoring.
Active Performance Optimization of Cantilever Piezoelectric Energy Harvester
Authors: Anbarani M. Tavakkoli , Alasty A.
Published: October 2014

A Piezoelectric Energy Harvester (PEH) of cantilever beam type is developed to optimize the generated power by means of active control of moment of inertia of the beam. Distributed parameter equations of vibration of the beam are developed. Then the electromechanical response of the piezoelectric actuator is discussed. The harvester configuration is then described and it is shown that such a configuration can avoid the drastic power drop in presence of uncertainty around resonance frequency by applying voltage to the piezoelectric actuator. Finally the proposed harvester output power working frequency span is compared to conventional methods to show that the significant performance optimization in proposed method is achieved.
Development of a Computer Vision Tracking System for Automated 3D Reconstruction of Concrete Bridges
Authors: Zanoni Andrea , Maninetti Giacomo , Cheli Federico , Garozzo Marco
Published: October 2014

Concrete bridge inspection is nowadays primarily a slow, subjective, non-comprehensive and costly set of procedures. Automation of the acquisition method is especially desirable for economical and repeatability reasons. Digital data is normally derived from well established non-destructive testing techniques, high resolution cameras and, more recently, by 3D laser scanning. This latter technique has some advantageous aspects in terms of reliability, repeatability, completeness and intuitiveness of the analysis of the resulting 3D reconstruction of the concrete structure. Statical laser scanning is, though, impractical for a variety of different reasons. A possible way of overcoming such difficulties is represented by dynamical measurement, achieved by moving in a prescribed manner the laser scanner during the scanning process. This procedure, on the other hand, requires a reliable tracking system for the laser scanner position and orientation. This work focuses on the development of such system, based primarily on computer vision measurement systems. A compact and lightweight 3D laser scanner has been placed on an automated carrier able to move along a standard inspection by-bridge, and a system of cameras and transducers has been designed to measure the carrier position and orientation based on the assumption of rigid body motion of the by-bridge multi-link arm during inspection operations. Several experimental tests have been performed to assess the viability of the proposed system and to evaluate its performance.
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.
Design and Control of an Active Humanoid Leg for Testing Lower-Limb Prostheses
Authors: Marinelli Cristiano , Giberti Hermes , Resta Ferruccio
Published: October 2014

The present paper deals with the development of a bench for testing different types of lower limb prostheses. Aim of the bench is to test the prosthetic devices considering working conditions as much as possible similar to the real ones with respect to methodologies provided by International Standards. These standards merely identify structural tests whose purpose is just to verify that the prosthesis, or their individual components, are able to ensure adequate strength properties during their use. The only functional test concern just the ankle-foot units. Test methods for the assessment of the functional performances of the whole prostheses are missing. There are no criterions for such tests and no benches. From this the need to build new test machines that, simulating both the stance and the swing phase according to sought gait standards, allow to assess the functional properties of different lower limb prostheses and to make comparison between them. According to this, the purpose of the present work is to assess the feasibility of such a bench, evaluating, by mean of a co-simulation executed considering a Multi-Body model of the bench developed using MSC ADAMS and a model of the control system developed using MATLAB/Simulink, its capability in guaranteeing the sequential replication of movements and loads that distinguish a leg during the execution of the stride. The obtained results demonstrate the feasibility of the machine, encouraging therefore the development of more refined models, considering technological solutions closer to reality.
Indirect Solar Cooking Using a Novel Fresnel Lens and Determination of its Energy and Exergy Efficiencies
Authors: Islam Md. Didarul , Banat Fawzi , Pal Priyabrata , Younas Obaid
Published: October 2014

This paper proposes a new kind of system for effective indirect solar cooking by utilizing a novel Fresnel lens. A semi-cylindrical vessel (solar boiler) for producing steam and a jacketed cooker was designed, fabricated and tested experimentally for cooking applications. The solar boiler produced high temperature steam of 146°C and pressure of 3.15 barg which was used for cooking purposes. The international standard for evaluating cooker performance was implemented on this system and heating power was determined to be 51.2 Watt at a temperature difference of 50°C. The maximum energy and exergy efficiencies for boiler were found to be 30.18 % and 2.86%, respectively. This represents a 92% increment in energy efficiency and 128.8% increment in exergy efficiency as compared to solar parabolic cookers. The maximum energy efficiency of 5.02% and maximum exergy efficiency of 0.378% were achieved in this cooking system.