bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Advanced Thermal-Hydraulic System Codes for Safety Analysis of Integral Type PWR
Authors: Choi J. , Woods B.
Published: April 2014

The integral Pressurized Water Reactor (PWR) concept, which contains the nuclear steam supply systems within the reactor vessel, is one of the innovative reactor types with high possibility for near-term deployment. An IAEA International Collaborative Standard Problem (ICSP) on “Integral PWR Design Natural Circulation Flow Stability and Thermo-hydraulic Coupling of Primary System and Containment during Accidents” has been conducted since 2010. Oregon State University of USA has offered their experimental facility, which was built to demonstrate the feasibility of Multi-Application Small Light Water Reactor (MASLWR) design, and sixteen institutes from seven IAEA Member States have been participated in this ICSP. The objective of the ICSP is to assess computer codes for reactor system design and safety analysis. This objective is achieved through the production of experimental data and computer code simulation of experiment. A loss of feedwater transient with subsequent automatic depressurization system blowdown and long term cooling was selected as the reference event since many different modes of natural circulation phenomena including the coupling of primary system, high pressure containment and cooling pool are expected to occur in this transient. The ICSP has been conducted in three phases: pre-test (with designed initial & boundary conditions before the conduction of the experiment), blind (with real initial & boundary conditions after the conduction of the experiment) and open simulation (after the observation of real experimental data). Most advanced thermal-hydraulic system analysis codes like TRACE, RELAP5-3D and MARS have been assessed against experiments conducted at MASLWR test facility.
Two New Competition Indexes on the Basis of Lotka-Volterra Competition Model
Authors: Zhang Huayong , Huang Tousheng , Dai Liming
Published: April 2014

In this research, two competition indexes, competing capacity and competing tensor, are brought forward to better understand the interspecific competition between species. With the employment of the two indexes, the competitive process in Lotka-Volterra model can be described much clearly. The strength of competition for a species is divided into three competition grades according to the competing tensor. In the interspecific competition, when two species are in different competition grades, the weak species will be excluded; when two species are in the same grade, the coexistent equilibrium will present. Two cases are studied with the methods by employing the two indexes. In the second case, the stability of equilibrium point is determined by the competing tensor. The new indexes have shown potential in population dynamics analysis.
Reducing the Effects of Blast to the Head Through Load Partitioning
Authors: Rapo Mark A. , Baumer Tim , Chan Philemon C. , MacKiewicz James F.
Published: April 2014

Warfighters who survive encounters with improvised explosive devices (IEDs) may incur mild traumatic brain injury (mTBI) due to blast overpressure effects. Since existing head injury criteria are mostly based on head kinematics, head acceleration is one key metric to be measured. A blast wave travels at supersonic speed with a very sharp peak overpressure rise followed by a rapid decay within a short duration. For the surface area that is covered by the helmet, the cushion/suspension subsystem is responsible for mitigating the blast effects on the head, while the exposed area of the head or face would receive a direct blast loading. Computational fluid dynamic (CFD) simulations of a blast on an upright warfighter show a significant reduction in peak force to the head when a helmet is worn. For a helmet with an attached eye-shield, the load to the head from a front blast can be reduced further. A field study was conducted to verify that the increased load partitioned away from face and to the helmet and cushioning system would result in decreased head acceleration. Blast field tests were conducted using 4 lbs. of cylindrical C4 charges at 92″ standoff. Head acceleration was measured using combinations of a free hanging mid-size standard ISO headform fitted with Team Wendy (TW) pads, an advanced combat helmet (ACH), and an eye-shield. Tests were performed with the blast hitting the front, side and back of the helmeted headform system. Headform accelerations ranging from 120–465g were recorded based on blast direction and the amount of head protection. To validate the three-dimensional Navier-Stokes’ based CFD simulations, a custom-designed blast overpressure bust (BOB) containing 22 surface pressure sensors was mounted on top of the BTD to measure the pressure distribution over the head and face when exposed to a blast. The incident overpressure of the blast was 0.25MPa, with reflected pressures reaching 1.0MPa.
Design of Vehicle Active Suspension System Using Discrete-Time Sliding Mode Control With Parallel Genetic Algorithm
Authors: Zhu Shenjin , He Yuping , Ren Jing
Published: April 2014

Sliding mode control (SMC) has gained a wide acceptance in recent years due to its simplicity and robustness. Discrete-time sliding mode control (DSMC) is advantageous over its continuous-time counterparts due to the development in digital signal processing. However, little attention has been paid to the application of DSMC to the design of active suspensions. In this research, DSMC-based active suspensions are designed using both the SMC theory and a genetic algorithm (GA) to improve the ride quality and handling performance with the full states observed by a discrete-time Kalman filter. The extensive computation demand levied by the GA is handled by using the parallel computation technique. The proposed optimization-based SMC approach simplifies the design process and improves the overall performance of the controlled system.
An Exploration of Accuracy and Convergence of the Degenerate Uniform Strain Hexahedral Element: A Solution to the Unmeshed Void in an All-Hexahedral Mesh
Authors: Shelton Timothy R. , Crane Nathan K. , Cox James V.
Published: April 2014

The uniform strain hexahedral element mesh has long been a work horse for getting accurate and convergent answers in high deformation solid mechanics analyses. Obtaining an all-hexahedral mesh can be a difficult and time consuming process thus limiting the element’s use in design phase computations. Unconstrained paving and plastering offers a technique to get an all-hexahedral mesh automatically but still can leave un-meshable voids [1]. While degenerated forms of the uniform strain hexahedral element such as the wedge have been used sparingly, they have garnered limited general acceptance. We present a more exhaustive numerical exploration of the degenerated hexes with the hope of encouraging their use to resolve the un-meshable voids. The results of patch tests are used to numerically demonstrate linear completeness of the degenerate elements. A manufactured solution analysis is then used to show optimal convergence rates for meshes containing degenerate elements. Additionally, applications to a torsion rod and high velocity impact are used to highlight the accuracy and applicability of degenerates for solving more complex problems.
Waves of Acoustically Induced Transparency in Bubbly Liquids: Theoretical Prediction and Experimental Validation
Authors: Gumerov Nail A. , Akhatov Iskander S. , Ohl Claus-Dieter , Sametov Sergei P. , Khasimulin Maxim V. , Gilmanova Galia I.
Published: April 2014

Self-organization of bubbles in acoustic fields, or self-action of the acoustic waves in bubbly liquids is a strongly nonlinear phenomenon due to two-way interaction of the bubbles and the acoustic field. Theoretical model and preliminary computations predict that waves of self-induced acoustic transparency may exist. Such effect is confirmed in the experiments presented in this paper. Formation of a wave of void fraction which rapidly propagates through the bubbly medium leaving a region almost free of bubbles behind its front is observed in the experiments. Measurements of the dynamics of such a wave at different acoustic frequencies and amplitudes are carried out. A three dimensional model of self-organization of a polydisperse bubble continuum in acoustic field is developed and the results of simulations are compared with experiments. A good agreement of the theory and experiment is found.
Measurements of Car Vibrations Under Real-Life Driving Conditions and Assessment of Energy Harvesting for Wireless Sensor Nodes
Authors: Dompierre A. , Traore M. S. , Fréchette L. G.
Published: April 2014

This work presents a study of car vibrations measured under typical driving conditions to assess the potential of powering automotive sensors incorporated in cars via vibration energy harvesting (VEH). The locations where sensors or switches are currently used and the requirements of potential automotive wireless sensor nodes were used as criteria to narrow down the location of the measurements. A total of 20 locations were retained after keeping the sensors with lower requirements. Random vibrations due to the road perturbations as well as part of the structural responses of the vehicle from changing vehicle speed were observed through vibration peaks which shift in frequency and others which are steady despite the changing conditions. The spectral analyses indicate that most of the available vibration energy is in a frequency range below 200 Hz, with harvestable consistent peaks below 140 Hz on the front chassis, the rear and front plastic bumpers and the brake fluid tank. An analytical model is used to assess the power output from several linear harvester MEMS designs and we estimate that continuous power over 100 nW are achievable from those sources.
Acoustics and Computational Models for Diagnosing Arterial Blockages
Authors: Al-Rawi M. A. , Al-Jumaily A. M.
Published: April 2014

Arterial blockages can occur in small or large arteries for a variety of reasons, such as obesity, stress, smoking and high cholesterol. This paper presents a feasibility study on a novel method to detect the behaviour of the blood pressure wave propagation for arteries in both healthy and diseased conditions in order to develop a relatively inexpensive method for early detection of arterial disease. The trend of this behaviour is correlated to the early development of the arterial blockage at various locations. Invasive sets of data (gathered from experiments performed on animals) are implemented into a 3D Computational Fluid Dynamic (CFD) model to determine how the arterial wall compliance changes when any abnormalities occur to the blood flow profile. At the same time, a 1D acoustical model is developed to transfer the information gathered (wave propagation for blood pressure, flow and arterial wall displacement) from the CFD model. Wave forms were collected at a location which was invasively accessible (the femoral artery). The computational and acoustical models are validated against the clinical trials and show good agreement. Any changes to the arterial wall displacement could be detected by systolic and diastolic blood pressure values at the femoral artery.
Elements of a Graduate Course in Computational Fluid Dynamics: Successful Assimilation and Implementation
Authors: Kumpaty Subha
Published: April 2014

While a course in Computational Fluid Dynamics (CFD) is a common offering in many universities and for several decades, the author of this paper learnt interesting patterns from the students’ assimilation of the principles and implemented the pedagogical build-up for positive experiences during the recent offering in winter 2012–13. With precise assignments that highlight the appropriate concepts to be learnt and put to coding, the students have progressed in gaining the confidence to tackle a variety of flow problems. Students felt that they could always learn using software and solve problems but the intricate details in understanding and applying the governing fluid dynamics equations was what they were able to gain from the course. The topical treatment given, the problems solved, the techniques applied, the software used are presented in this paper as an example of successful implementation of and enhanced student learning in a graduate course in CFD. Industry-relevant course projects culminated the positive experience, as confirmed by the course evaluation results.
Time-Frequency Analysis of Disc Brake Squeal in a Brake Experiment
Authors: Liu X. D. , Wang H. X. , Wan Z. S. , Shan Y. C.
Published: April 2014

Automotive brake squeal has become a challenging issue to reduce traffic noise and improve the vehicle quality. Since the generation mechanism of brake squeal is extremely complex, involving multiple disciplines such as nonlinear dynamics, contact mechanics, tribology and acoustics, it is still not well understood. The brake bench experiment is an important method to investigate the evolution of squeal and the transient nonlinear dynamic behavior of brake system, because of the difficulties in modeling the nonlinear time-varying system parameters in braking, such as friction coefficient, contact stiffness and damping in brake pads, for analytical and numerical method. Here a laboratory experiment is constructed to simulate vehicle disc brake squeal. The rotation speed, brake pressure, torque, temperature and sound pressure are measure during the braking process with squeal events. The variations of friction coefficient versus temperature and brake pressure are investigated respectively. It is obtained that the friction coefficient increases with the increasing temperature and brake pressure. The evolution of brake squeal and its transient dynamic behavior are analyzed and discussed through three time-frequency analysis methods including STFT, CWT and HHT. The results demonstrate that the squeal signal is composed of several frequency components and may be dominated by one or two components with high energy which are related to the vibration modes of physical brake parts. The instantaneous frequencies of IMFs vibrate substantially with time induced by the nonlinear friction and contact between the disc and pad pairs.
Modeling of Coal-Biomass Fluidization Using Computational Fluid Dynamics
Authors: Estejab Bahareh , Battaglia Francine
Published: April 2014

In an effort to assess the fluidization characteristics of coal-biomass mixtures, computational fluid dynamics (CFD) was used and validated. The gas and solids phases were modeled using an Eulerian-Eulerian approach to efficiently simulate the physics. The computational platform Multiphase Flow with Interphase eXchanges (MFIX) was employed to simulate the particle-particle interactions of coal-biomass mixtures and compare the predictions with experimental data. The coal-biomass mixtures included sub-bituminous coal and hybrid poplar wood. Particles properties of both materials fall within the Geldart A classification. Of particular interest to this study was predicting particle mixing in fluidized beds and biomass hydrodynamics. Both materials and two mass ratio mixtures were studied and pressure drop across the bed for various gas inlet velocities and bed height were analyzed and compared to the experiments.
Nonlinear Free Vibration of a Beam With Off-Axis Attached Mass
Authors: Hassanpour Pezhman A.
Published: April 2014

A model of a clamped-clamped beam with an attached lumped mass is presented in this paper. The system is modeled using the Euler-Bernoulli beam theory. In the models presented in literature, it is assumed that the center of mass of the attached mass is located on the neutral axis of the beam. In this paper, this assumption is relaxed. The governing equations of motion are derived. It has been shown that the off-axis center of mass of the attached mass generates an amplitude-dependent transverse force in the beam, which introduces a quadratic nonlinearity. The nonlinear governing equations of motion are solved using the Multiple Scales method. The nonlinear free vibration frequencies are determined.
On the General Characterization of Machined Springs and Their Manufacturing Processes
Authors: Calderon Juan de Dios , Perez Carlos
Published: April 2014

Springs are among the most important and common mechanical elements used. When springs are designed, it is important to make certain considerations and procedures in order to select the optimum spring configuration, fixturing system and other assembly features for a specific function. In conventional springs or wire wound springs, these individual features increase time and complexity of assembly. Machined springs have been developed as mean of solution for multi-objective design like reliability, repeatability and integration of multiple components, which results in a significative reduction of complexity of assembly.

On the other hand, machined springs have precise performance as well as additional capabilities and features that are not obtained with conventional springs. The key behind the versatility of machined springs is the capability of integration of special geometries for fixation, the possibility of usage of multiple entry coil geometries and obtention of accurate spring values.

In this work, description of some of the general characteristics of machined springs in terms of material and process selection is made; moreover, certain considerations during the design and manufacturing stages are pointed. A comparative study between a wire spring and machined spring for a specific application is performed as mean of evidence of the advantages of machined springs.
A Small-Scale ORC Energy Recovery System for Vehicular Application: Feasibility Analysis and Preliminary Components Design
Authors: Capata Roberto , Sciubba Enrico
Published: April 2014

The paper analyses the feasibility of an “on-board” innovative and patented (patent ID RM2011 A 000671) ORC recovery system. The vehicle thermal source can be either a typical diesel engine (1400 cc) or a small gas turbine set (15–30 kW). The sensible heat recovered from the exhaust gases feeds the energy recovery system that can produce sufficient extra power to sustain the conditioning system and other auxiliaries. The concept is suitable for all types of thermally propelled vehicles, but it is studied here for automotive applications.

The characteristics of the organic cycle-based recovery system are discussed, and a preliminary design of the main components, such as condenser, evaporator and pre-heater is presented. The main challenge are the imposed size and weight limitations that require a particular design for this compact heat exchangers. A possible system layout is analysed and the requirements for a prototypal application are investigated.

At this stage of the project, no components costs evaluation is provided, in part because our scope is to demonstrate feasibility, and secondly most of the components are built in our own shop.
Vibration Absorber and Harvester for Energy Efficient Structures
Authors: Gonzalez-Buelga A. , Clare L. , Neild S. A. , Cammarano A. , Wagg D. J. , Burrow S. , Inman D. J.
Published: April 2014

Most work has been conducted on vibration absorbers, such as tuned mass dampers, where significant energy is extracted from a structure. We investigate the concept of recovering some of this energy electrically. We present experimental results from a vibration absorber/harvester. Our results suggest that sufficient energy might be harvested such the device can be self tuning and self powered to optimize vibration suppression.
Optimization of Process Parameters in Profile Forming of Al 3003(O) Aluminium Alloy
Authors: Senthil Kumar V. S. , Shanmugnatan S. P.
Published: April 2014

Rapidly changing product design and specifications to meet highly dynamic customer requirements demands flexibility in manufacturing, in contrast to the rigid, automated manufacturing. Concept of lean manufacturing for small batch production is gaining momentum. Application of CNC machines find wide acceptance. Therefore, the profile forming technique that caters to rapidly changing product specifications with increasing need for productivity, flexibility and quality requirements can be a promising solution. This paper presents the forming process demonstrating the formation of the sheet metal part using computer coordinated hemispherical tool. The statistical method of analysis based on the design of experiments (DOE) and response surface has been used to evaluate the optimum conditions of the formability of an Aluminium sheet. The parameters considered for the experiments are tool size, step size, spindle speed and feed rate. The Process performance indicators are the surface finish, wall angle, and average thickness of profile part. An empirical model has been created for predicting the indicators through response surface methodology (RSM). The influence of the different parameters and their interactions are studied in detail.
Analysis of Impedance for Water Management in Proton Exchange Membrane Fuel Cells Using Factorial Design of Experiment (DoE) Methodology
Authors: Mammar Khaled , Ould-Bouamama Belkacem
Published: April 2014

Electrochemical impedance spectroscopy (EIS) is a very powerful tool for exploitation as a rich source of Proton Exchange Membrane Fuel Cell (PEMFC) diagnostic information.

A primary goal of this work was to develop a suitable PEMFC impedance model, which can be used in the analysis for flooding and drying of fuel cell. For this one a novel optimization method based on factorial Design methodology is used. It was applied for parametric analysis of electrochemical impedance Thus it is possible to evaluate the relative importance of each parameter to the simulation accuracy. Furthermore this work presents an analysis of the PEMFC impedance behavior in the case of flooding and drying.
Experimental and CFD Investigations of Heat Transfer in Helical Coils for the Development of Correlations for Newtonian and Non-Newtonian Fluids in Transient State-Space Conditions
Authors: Pawar Sandipan S. , Sunnapwar Vivek K. , Yakkundi Vivek K.
Published: April 2014

Experimental studies and CFD investigations were carried out under laminar and turbulent flow regimes in isothermal steady state and non-isothermal unsteady state conditions in helical coils for Newtonian and non-Newtonian fluids. Water and glycerol-water mixture (10 and 20 % glycerol) as Newtonian fluids and dilute aqueous polymer solutions of sodium carboxymethyl cellulose (SCMC), sodium alginate (SA) as non-Newtonian fluids were used in this study. The experiments were performed for three helical coils of coil curvature ratios as 0.0757, 0.064 and 0.055 in laminar and turbulent flow regimes. For the first time, two innovative correlations to calculate Nusselt number (Nu) in terms of new dimensionless ‘M’ number, Prandtl number and coil curvature ratio under different conditions for Newtonian fluids are proposed in this paper. Third correlation of Nu vs. Graetz number (Gz) including the effects of coil curvature on heat transfer coefficient which was not considered by earlier investigators is developed based on tests conducted in laminar flow for Newtonian fluids. All these three innovative correlations developed based on experimental data which were not found in the literature. These correlations were compared with the work of earlier investigators and were found to be in good agreement. The CFD analysis for laminar and turbulent flow was carried out using the CFD package FLUENT 12.0.16. The CFD calculation results (Nui, U) for laminar and turbulent flows were compared with the experimental results, and also the work of earlier investigators was found to be in excellent agreement. Further, the effect of helix diameter on heat transfer for Newtonian and Non-Newtonian fluids are also presented in this paper and it was observed that as helix diameter increases, overall heat transfer coefficient decreases.
Feedwater Repowering of Coal Fired Power Plants: Effects of Steam Turbine Overloads on Energy and Economic Performance of the Integrated Power System
Authors: Carapellucci Roberto , Giordano Lorena
Published: April 2014

In recent years, the environmental concerns and the need to improve the competitiveness of existing coal-fired power plants have renewed the interest for the repowering option. Repowering techniques based on combustion turbines allow to increase thermodynamic performances of the steam power plant, as well as to reduce emissions of greenhouse gases, due to efficiency improvement and partial fuel-shift from coal to natural gas.

This paper aims to evaluate performances of feedwater repowering of a coal fired power plant, considering various steam turbine overloads. Two types of analysis are here proposed. First, thermodynamic and environmental benefits of feedwater repowering are evaluated in terms of efficiency gain and CO2 emission reduction, with reference to the steam power plant only. Then, effects of the integration of a gas turbine into the existing coal fired power plant are highlighted. Different feedwater repowering options, varying the operating mode of the coal fired power plant, are compared from the energy, economic and environmental point of view. The attention is focused on performance parameters of the integrated steam-gas power plant, as well as on marginal indices defining the efficiency and unit cost of electricity of the additional power production.
Numerical Simulation of a Microencapsulated Phase Change Material Slurry Flowing in a Helical Coil Heat Exchanger
Authors: Languri Ehsan M. , Shaaban Aly H. , Kong Minsuk , Alvarado Jorge L.
Published: April 2014

Heat transfer analysis of microencapsulated phase change material (MCPM) slurry flowing through a helical coil heat exchanger was carried out numerically. MPCM slurry at different mass fractions with known thermal and physical properties was chosen as heat transfer fluid (HTF). MPCM slurries can carry significantly higher thermal load when the PCM undergoes phase change within a specified temperature range. However, little is known as to how MPCM behave in helical coil heat exchangers. Helical coil heat exchangers are being used widely in many industrial applications including air conditioning systems due to their compactness and high thermal effectiveness. Enhancing the heat transfer rate of coil heat exchanger by using MPCM slurry without altering the existing parameters of coil heat exchangers such as shell diameter should lead to energy savings due to reductions in HTF pumping energy demands at identical heat loads. The ultimate goal of this study is to show a significant enhancement in heat transfer when MPCM slurry is pumped through helical coil heat exchangers. Unlike traditional HTF used in helical coil heat exchangers, the proposed MPCM slurry could alter the flow structure and the internal convection by inducing and enhancing the formation of secondary flows, as a result of phase change in the microencapsulated phase change material. Specifically, a three dimensional numerical study was undertaken to understand the effects of the helical coil heat exchanger geometry and the HTF flow characteristics on heat transfer enhancement. Baseline numerical simulations were conducted using water as HTF in order to compare with MPCM slurry numerical results. The numerical model was solved based on the finite volume method. The temperature-dependent properties of MPCM slurry and boundary conditions were considered. The promising results of this numerical study demonstrate the importance of formulated HTF and the geometry of the heat exchanger on the heat transfer enhancement and energy savings.
A Study of High-Pressure CO2 Recycling Using Pinewood Char Gasification
Authors: Sircar Indraneel , Sane Anup , Gore Jay
Published: April 2014

Measurements of the reaction rates at high-pressures for gasification of low-ash pinewood char with CO2 are presented. A fixed-bed reactor operated at 1140–1260 K and 1–10 atm was utilized in the present study. Product gas sampling and gas chromatograph measurements enabled tracking of the gasification progress and mass loss data. The mass loss data are interpreted using the volumetric and non-reactive core models. Activation energy, collision frequency and reaction order are reported for each model. The experimental data show high sensitivity to temperature. The data also show an increase of the apparent gasification rates with higher CO2 pressures. Comparison of computed char conversion profiles and experimental data are discussed in the context of mass transport and effects on the gasification rates. The findings from this study have applications to gasification modeling and design of large-scale gasification systems.
Event-Driven CNC Modularized Sewing Platform
Authors: Xie Xiaohui , Ma Cui , Han Bingzhe , Du Ruxu
Published: April 2014

With ever increased demand for quality and productivity, modern industrial sewing machine is becoming very complex and requiring sophisticated control. This paper presents a control platform that can be used for all kinds of lockstitch sewing machines. This event-driven control platform can support various kinds of sewing operations, from simple lockstitches, to X-Y lockstitches, as well as thread cutting. The key to the control platform is the precision cooperative control. First, for each motion axis, both the position and the velocity must be precisely controlled. In addition, the multi-axis motions must be synchronized to achieve high accuracy stitches.

In order to increase the machine flexibility and decrease variety, a generalized and modularized sewing platform is proposed in this paper. It can be assembled with common lockstitch sewing machine and achieve several kinds of sewing functions. This platform module has independent driving capability to fulfill special movement and the communication ability to collaborate with other modules. Besides the modularized mechanism, the reusable and reconfigurable control system is the key point. For industry sewing machine, the important functions are the single-axis precise control and multi-axis cooperative control. In the X-Y moving platform, the closed-loop stepper motor system is adopted for each axis to obtain precise speed and position control. On the other hand, the cooperative control between modules is realized by event-based control method which uses a time-independent parameter to avoid the uncertain time-delay. To verify the system, the corresponding experiments are taken. And the results satisfy the requirements very well.
The Dynamic Modeling and Simulation on a Shell Gasifier
Authors: Zhang Huisheng , Huang Di , Zhou Dengji , Weng Shilie , Lu Zhenhua
Published: April 2014

As the conventional model of gasifier, the model based on the lumped slag layer method can only give the lumped parameters in gasifier. However, the distribution characteristics of the various parameters in gasifier is obvious. To remedy the defect in conventional model, this paper presents a compartment-slag layer model in the modeling of the shell gasifier, which takes the advantage of the lumped slag layer method and the compartment method used in the simulation of the CWS gasifier. The simulation results were validated by the experimental data. The dynamic results show that the new model can reflect the response of some key parameters. This could provide references for the future investigation of the dynamic characteristics of the IGCC system.
VAV System Operating in an Educational Building Under Tropical Conditions: Modeling and Simulation
Authors: Alvarez Oscar , Sanjuan Marco , Amaya Fabian , Bula Antonio
Published: April 2014

An educational building located in the Caribbean area of Colombia that uses a VAV system has been modeled and simulated in order to quantify the energy consumption. The energy values attained has been compared with the real energy consumption obtained from the data system. The results show that the error introduced are sensitive to the building mass at the beginning of the transient process, never the less, as the transient continues, the software shows good agreement with the experimental data. The maximum error at the beginning is 25% and decreases to 10%.
Halloysite Clay Nanotubes With PCM for Thermal Energy Storage and Efficiency
Authors: Thapa S. , Zhao Y. , Lvov Y. , Weiss L.
Published: April 2014

There is opportunity to achieve energy savings and increasing energy sustainability through new techniques addressing thermal storage challenges. New materials may be useful to a wide variety of applications including solar thermal as well as building heating and cooling systems. This present work focuses on new thermal storage technology that may be utilized across a wide spectrum of structures. The technology itself relies on implementation of a phase-change insulation material that combines unique characteristics of naturally occurring halloysite clay nanotubes with low-cost eicosane-type waxes. This combination results in a microtube skeleton supported material. This allows for material shape preservation during phase transition heat conversion.

Investigations further consider the addition of thermal conductivity enhancement via graphite-based nano particles or tubes. In this manner a unique material is presented that is capable of maintaining shape during wax phase change while exhibiting increase in thermal conductivity. Unlike wax-based phase change material systems that allow the wax to change structure during phase change, the use of halloysite nanotubes also maintains the overall thermal conductivity increase through numerous phase change cycles. Multiple material combinations that vary included percentages of both halloysite and conductivity enhancement are investigated. Thermal conductivity of wax-halloysite-graphite (45/45/10 %) composite showed increased conductivity to 1.35 W/mK. This was nearly 3 times higher than the base wax-halloysite composite. Wax-halloysite-graphite-carbon nanotubes (45/45/5/5 %) composite showed thermal conductivity of 0.83 W/mK while maintaining original shape until 81°C (above the wax melting point).
Static Pull-In Analysis of an Electrically Actuated Piezoelectric Viscoelastic Microbeam
Authors: Chen Changping , Li Shoujian , Dai Liming
Published: April 2014

Nonlinear piezoelectric viscoelastic model is used to account for a DC load and a pizeoelectric voltage. On the basis of the Euler-Bernoulli hypothesis, nonlinear static pull-in phenomena of a piezoelectric viscoelastic microbeam under a DC load and a pizeoelectric voltage is studied and the corresponding numerical analyses are performed. The influences of piezoelectric effect on the static pull-in voltages of the piezoelectric viscoelastic microbeam are discussed.
Static and Dynamic Analysis of Aircraft Structures by Component-Wise Approach
Authors: Carrera E. , Pagani A. , Petrolo M.
Published: April 2014

This paper proposes an advanced approach to the analysis of reinforced-shell aircraft structures. This approach, denoted as Component-Wise (CW), is developed by using the Carrera Unified Formulation (CUF). CUF is a hierarchical formulation allowing for the straightforward implementation of any-order one-dimensional (1D) beam theories. Lagrange-like polynomials are used to discretize the displacement field on the cross-section of each component of the structure. Depending on the geometrical and material characteristics of the component, the capabilities of the model can be enhanced and the computational costs can be kept low through smart discretization strategies. The global mathematical model of complex structures (e.g. wings or fuselages) is obtained by assembling each component model at the cross-section level. Next, a classical 1D finite element (FE) formulation is used to develop numerical applications. It is shown that MSC/PATRAN can be used as pre- and post-processor for the CW models, whereas MSC/NASTRAN DMAP alters can be used to solve both static and dynamic problems. A number of typical aeronautical structures are analyzed and CW results are compared to classical beam theories (Euler-Bernoulli and Timoshenko), refined models and classical solid/shell FE solutions from the commercial code MSC/NASTRAN. The results highlight the enhanced capabilities of the proposed formulation. In fact, the CW approach is clearly the natural tool to analyze wing structures, since it leads to results that can be only obtained through three-dimensional elasticity (solid) elements whose computational costs are at least one-order of magnitude higher than CW models.
Aspects of Fixture Clamp Modeling in Non-Rigid Variation Simulation of Sheet Metal Assemblies
Authors: Lindau Björn , Wärmefjord Kristina , Lindkvist Lars , Söderberg Rikard
Published: April 2014

Today there is an increased use of CAT-tools (Computer Aided Tolerancing) within the automotive industry. These kinds of virtual tools are getting increasingly important to ensure robust solutions as early as possible in the development processes, to minimize the use of test series and thereby reduce lead times and development costs.

This paper focuses upon modeling of fixture locating scheme and the aspect of how many degrees of freedoms (DoF) a clamp actually locks. The clamps control part movement allowance, and it is of importance to investigate the influence from the friction forces between the clamping units and the fixated parts. Simulated forces in non-steering directions are compared to friction forces measured in real body shop production equipment. The non-rigid variation simulations have been performed based upon the Method of Influence Coefficients (MIC) and additional functionality for contact modeling, force estimation and weld sequence analysis.

There are a variety of alternatives of how to build the simulation model and the made choices obviously influence the simulation results. The industrial case study shows significant differences in both estimated in-plane forces and geometric results after springback for different choices of modeling alternatives. It demonstrates the difficulties in taking the friction force into consideration in variation simulation of sheet metal assembly processes.
A Method for Computation of Wave Propagation in Heterogeneous Solids: Algorithm Description
Authors: Park K. C. , Cho S. S.
Published: April 2014

An explicit integration algorithm for computations of wave propagation in solids is presented, which is designed to trace extensional and shear waves in accordance with their respective propagation speeds. This has been possible by an orthogonal decomposition of the total displacement into extensional and shear components. The two decoupled wave equations are integrated with a newly developed algorithm[1, 2] that is proven to be effective in mitigating spurious oscillations. The essence of the present algorithm consists of a combination of two wave capturing characteristics: a new integration formula that is designed to filter post-shock oscillations and the central difference method that is known to intrinsically filter out front-shock oscillations. A judicious combination of these two wave capturing characteristics is shown to reduce substantially both spurious front-shock and post-shock oscillations. Numerical experiments have demonstrated that the present algorithm traces the stress wave fronts with high-fidelity for both linear and nonlinear wave propagation problems.
Design of a Counterweight Walker Active Therapeutic Movement Rehabilitation Rig
Authors: Aguilera Navarrete Israel , Lozano Guzmán Alejandro A.
Published: April 2014

According to INEGI (National Institute for Statistics and Geography), in 2004 there were around 730,000 people in Mexico with the need of some kind of mechanical aid to regain ability to walk. Support equipment for regaining the ability to walk normally is manufactured outside of Mexico. This equipment is complex and very expensive. In this work, the design of a walking ability rehabilitation aid is presented. This work is carried out applying the modular design concept. This ensures that all client needs are fulfilled by the resultant product, and that these needs are measurable and controllable. Basic idea behind this design is supporting part of patient’s weight and that of an exoskeleton on a mechanical device. Basic kinematics and dynamic calculation are presented, as well as simulations results. This information shows the feasibility of building and operating this rehabilitation walking aid.
Flow Boiling in an In Line Set of Short Narrow Gap Channels
Authors: Janssen D. D. , Dixon J. M. , Young S. J. , Kulacki F. A.
Published: April 2014

Heat transfer coefficients in a set of three symmetrically heated narrow gap channels arranged in line are reported at watt densities of 1 kW/cm3. This experimental configuration emulates an electronics system wherein power dissipation can vary across an array of processors, memory chips, or other components. Three pairs of parallel ceramic resistance heaters in a nearly adiabatic housing form the flow passage, and length-to-gap ratios for each pair of heaters is 34.1 at a gap of 0.36 mm. Novec™ 7200 and 7300 are used as the heat transfer fluids. Non-uniform longitudinal power distributions are designed with the center heater pair at 1.5X and 2X the level of the first and third heater pairs. At all levels of inlet sub-cooling, single-phase heat transfer dominates heat transfer over the first two heater pairs, while the third pair exhibits significant increases because of the presence of flow boiling. Reynolds numbers range from 250 to 1200, Weber numbers from 2 to 15, and boiling numbers from O(10−4) to O(10−3). Exit quality can reach 30 percent in some cases. Overall heat transfer coefficients of 40 kW/m2K are obtained. Pressure drops for both Novec™ heat transfer fluids are approximately equal at a given mass flux, and a high coefficient of performance is obtained. With a mass flux of 250 kg/m2s, heater temperatures can exceed 95 °C, which is the acceptable limit of steady operation for contemporary high performance electronics. Thus, an optimal operating point involving power density, power distribution, mass flux, and inlet sub-cooling is suggested by the data set for this benchmark multi-heater configuration.
PDM (Personal Design and Manufacturing) for Active Customers
Authors: Fukuda Shuichi
Published: April 2014

As diversification is quickly increasing, industries are making tremendous efforts to cope with it. But this paper points out that these efforts are too much producer-centric.

Our customers are not passive consumers as most industries assume. They are very active and would like to customize our products to their own needs and to their preferences. We should note that this act of customization is deeply associated with our basic need of self actualization. That is why their requirements are diversifying. We have to change our product development much more to customer-centric.

New emerging technologies such as 3D printers enable them to get involved in product design and manufacturing. But if we consider the capabilities of the present states of these technologies and expertise of our customers, it is much easier to realize such customer-centric product development, if we extract the feature parts or feature points from a product that relate to personalization and let our customers develop them with the help of us, experts. The parts that do not substantially contribute to personalization may be developed as a common platform and these parts can be developed by experts without customer’s involvements. In this way, customers would feel they are actualizing themselves and would be more satisfied.
Flow Accelerated Degradation of Corrosion Protective Organic Coatings
Authors: Zhou Qixin , Wang Yechun
Published: April 2014

Water percolation into coating-metal interface is usually the main cause for the deterioration of corrosion protective property of organic coatings, which leads to coating delamination and under film corrosion. Recently, flowing fluid has received attention due to its capability to accelerate the degradation of materials. A plethora of works have focused on the corrosion of metallic materials accelerated by the flow of working fluids, while few studies have investigated the flow accelerated degrading behavior of organic coatings. For organic coatings, flowing fluid above the coating surface affects corrosion by enhancing the water percolation and by abrading the surface due to wall shear stress. Hence, it is of great importance to understand the influence of flowing fluids on the degradation of corrosion protective organic coatings.

In this study, a commercially available epoxy based clear coating and pigmented marine coating were exposed to the laminar flow as well as stationary immersion. The laminar flow was pressure driven and confined in a newly designed flow channel. A 3.5 wt% sodium chloride solution was employed as the working fluid with a variety of flow rates. The corrosion protective properties of organic coatings were monitored inline by Electrochemical Impedance Spectroscopy (EIS) measurement. Equivalent circuit models were employed to interpret the EIS spectra. The time evolution of coating resistance and capacitance obtained from the model was studied to demonstrate the coating degradation. Thickness, gloss, and other topography characterizations were conducted to facilitate the assessment of the corrosion. The immersing solutions were measured by pH and conductivity meters as well as Fourier Transform Infrared Spectrometer (FTIR) to trace coating degradation products as they leached out from the coating. Initial attempts to acquire acceleration factors and predict service lifetime of organic coatings were also conducted.
Geysering Gasoline: The Hidden Hazard
Authors: Berry Thomas A. , Sevart Kevin B.
Published: April 2014

Gasoline is known to be a volatile fuel. Specific instructions are many times provided with respect to refueling procedures. Almost no information is provided about the potential for gasoline to erupt from the fuel filler neck when the gas cap is removed or dislodged. Temperatures higher than the boiling point of gasoline can be expected with the use of tractors and lawn mowing equipment, particularly when the machines are used in the summer and have gas tanks exposed to the sun. In the past many tractors and lawn mowers used a small hole to allow vapor pressure in the tank to try and equalize with the atmosphere either as gas was used from the tank or due to heating of the gasoline. This small vent hole can become plugged due to the intake of dirt and debris from use in the field, as well as, from corrosion. Some caps have a screw that can be closed to prevent any venting. When the venting provided by the cap can no longer keep up with the production of vapor the pressure in the tank builds up causing the lighter hydrocarbons in gasoline to superheat. If the cap is dislodged or removed the superheated gasoline will suddenly expand and force gasoline to erupt from the filler neck. Gasoline must be prevented from super-heating to avoid the risk associated with this hazard. Design steps to address this hazard will be presented and discussed.