bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Investigation on Cellulosic Biofuel Manufacturing: Effects of Biomass Particle Size on Sugar Yield
Authors: Zhang Pengfei , Zhang Qi , Pei Z. J. , Pei Linda
Published: August 2012

Biofuels made from cellulosic biomass are an alternative to petroleum-based liquid transportation fuels. A key barrier to cost-effective manufacturing of cellulosic biofuel is low sugar yield in enzymatic hydrolysis. Particle size and crystallinity index of cellulosic biomass are two important parameters in enzymatic hydrolysis. The current literature contains many experimental investigations about effects of biomass particle size on sugar yield. However, particle size, often reduced by ball milling, is correlated with crystallinity index. Changes in particle size usually cause changes in crystallinity index. Therefore, particle size and crystallinity index may have confounding effects on sugar yield. Relations between particle size and sugar yield are not clear. This paper reports an experimental investigation on sugar yields from switchgrass particles produced by three methods: cutting milling, hammer milling, and manual cutting. The particles have different sizes but the same crystallinity index. Results show that there are no significant differences among sugar yields from these particles of different sizes. Particle size within the tested range has no significant effects on sugar yield.
Project-Based Service-Learning and Student Motivation
Authors: Cooper Lauren A. , Kotys-Schwartz Daria , Reamon Derek T.
Published: August 2012

We know from motivation theory that enhanced motivation in students is positively correlated with engagement and active learning, interest, and value. We know less about the types of instructional strategies and curricular interventions that work to enhance student motivation in a typical engineering course. Grounded in motivation theory, the purpose of this research is to evaluate how the context of project-based service-learning affects aspects of student motivation in a required undergraduate Mechanical Engineering course. Our research aims to answer: 1) How does project-based service learning affect students’ motivation as compared to conventional (non-service) project-based learning? 2) How are women affected differentially by project-based service-learning? The research, which began in 2010, is being completed over a two-year period. The students and activities in Component Design, an existing junior-level course at the University of Colorado at Boulder, will serve as the research focus. Specifically, project-based service-learning curriculum will be implemented into a required design and build activity for Component Design students. Using a conventional design project as the control, how the context of project-based service learning affects aspects of student motivation will be studied. This paper will discuss the research design, theoretical framework, and the results from our first year of research. Our objective is to provide a more thorough understanding of the effects of service-learning on engineering education. Although service-learning may not be appropriate for every engineering course, we can strive to identify and implement specific elements of service-learning that are correlated with student motivation.
Surface Free Energy Change of UV Exposed Composites and Coatings via Acid-Base Interactions
Authors: Asmatulu R. , Ghaddar M.
Published: August 2012

Surface free energy of composite and coatings are critically important for the performance of the materials since the change in surface free energies can drastically affect the physical, chemical and physicochemical properties, and hence the service life of them. The characterization of the surface free energy is the key issue to understand the mechanisms of the surface degradation. Acid-base interaction is one way of determining the surface free energy change on these surfaces. In the present study, we exposed composite and coating surfaces to UV light, and then measured the contact angle values using various liquids (e.g., DI water, diiodomethane and glycerol). Using the van Oss approach, we calculated the surface energy changes of the surfaces exposed to the UV light. We found that the surface energy, acidity and basicity of the composite and coating materials were drastically changed as a function of UV exposure time. This study can be useful for the moisture uptake of composites, composite degradation, aging and service life of these products.
Hydrodynamic Behavior of Magnetic Nanocomposite Spheres Under Magnetic Fields
Authors: Wamocha H. L. , Asmatulu R. , Ravigururajan T. S.
Published: August 2012

In the present study, drug carrying magnetic nanocomposite spheres were fabricated using oil-in-oil emulsion/solvent evaporation method and characterized via different techniques. The spheres with a diameter of 200 nm and 3 μm consist of poly (lactic-co-glycolic acid) (PLGA), a drug and magnetic nanoparticles (e.g., Fe3O4 or Co0.5Zn0.5Fe2O4). The spheres were initially dispersed in both deionized (DI) water and viscous glycerol solutions, and pumped in a magnetic field at different tube diameters, pump speeds and concentrations to study the hydrodynamic behavior of drug-carrying magnetic nanocomposite spheres. The test results showed that the magnetic field, tube diameter, pump speed and magnetic nanoparticle concentrations in the spheres drastically changed the capturing efficiency of the spheres. In the in vivo tests of the spheres, these parameters should be considered in order to increase the efficiency of the drug delivery systems.
Computational Study of Slurry Flow in Pipes to Determine Profiles Sensed in Near Infrared Slurry Measurements
Authors: Pasangulapati V. , Kesana N. R. , Sharma G. , Chambers F. W. , McNally M. E. , Hoffman R. M.
Published: August 2012

It is desired to perform accurate Near Infrared sensor measurements of slurries flowing in pipes leaving large batch reactors. A concern with these measurements is the degree to which the slurry sensed is representative of the material in the reactor and flowing through the pipe. Computational Fluid Dynamics (CFD) has been applied to the flow in the pipe to determine the flow fields and the concentration profiles seen by the sensors. The slurry was comprised of a xylene liquid phase and an ADP (2-amino-4, 6-dimethylpyrimidine) solid phase with a density ratio of 1.7. Computations were performed for a horizontal pipe with diameter 50.8 mm, length 2.032 m, and 1.76 m/s and 3.26 m/s mixture velocities. The corresponding pipe Reynolds numbers were 1.19E+05 and 2.21E+05. The flow through a slotted cylindrical probe inserted radially in the pipe also was considered. Spherical slurry particles with diameters from 10 μm to 1000 μm were considered with solid volume fractions of 12%, 24%, and 35%. Computations were performed with ANSYS FLUENT 12 software using the Realizable k-ε turbulence model and the enhanced wall treatment function. Comparisons of computed vertical profiles of solid volume fraction to results in the literature showed good agreement. Symmetric, nearly flat solid volume fraction profiles were observed for 38 μm particles for all three initial solid volume fractions. Asymmetric solid volume fraction profiles with greater values toward the bottom were observed for the larger particles. Changes in the profiles of turbulent kinetic energy also were observed. These changes are important for optical measurements which depend upon the mean concentration profiles as well as the turbulent motion of the slurry particles.
Minimizing Geometric Variation in Multistage Assembly Lines by Geometrical Decoupling
Authors: Edholm Peter , Lindkvist Lars , So¨derberg Rikard
Published: August 2012

Geometrical part robustness is used today as an engineering criterion in many manufacturing companies. The goal is to minimize the effect of geometrical variation by optimizing the locating schemes for the parts. Several methods and tools now exist to support geometrical robustness optimization for parts, but also for assemblies. In this paper the focus is on geometrical decoupling, which is one parameter of geometrical robustness of the different locating strategies in a complete assembly line. A goodness value is proposed that describes the level of geometrical couplings in a complete assembly line together with the part robustness value. By calculating this goodness value it is possible to predict the geometrical sensitivity of a complete assembly line as well as predicting the risk of geometrical variation in the final product. To illustrate the definition of this goodness value, and also the purpose of calculating it, a case study is used where a part of a sheet metal assembly line is described. Several different scenarios (assembly concepts) are applied to clarify the meaning and to validate this definition of the goodness value. The case study shows that the goodness value gives a good indication of the level of geometrical couplings within the assembly line and that this value can be used to evaluate different assembly concepts, with their locating concepts, against each other. The goal is to have a more robust and also geometrically decoupled assembly line which enables root-cause analysis in production, and also optimizes the geometrical quality minimizing the effect of geometrical variation of the final product from the plant.
Development of a Tridimensional Visualization and Model Reconstruction System Based on Computed Tomographic Data
Authors: Medelli´n Castillo Hugo I. , Alfaro Manuel A. Ochoa
Published: August 2012

Medical image processing constitutes an important research area of the biomedical engineering since it provides accurate human body information for 3D visualization and analysis, diagnostic, surgical treatment planning, surgical training, prosthesis and implant design, wafer and surgical guides design. Computed tomography (CT) and magnetic resonance imaging (MRI) have had a great impact in the medicine since they can represent complex three dimensional (3D) anomalities or deformities. In this paper, the development of a system for tridimensional visualization and model reconstruction based on CT data is presented. The aim is to provide a system capable to assist the design process of prosthesis, implants and surgical guides by reconstructing anatomical 3D models which can be exported to any CAD program or computer aided surgery (CAS) system. A complete description of the proposed system is presented. The new system is able to visualize and reconstruct bone and/or soft tissues. Three types of renders are used: one for 3D visualization based on three planes, other for 3D surface reconstruction based on the well known marching cubes algorithm, and the other for 3D volume visualization based on the ray-casting algorithm. The functionality and performance of the system are evaluated by means of four case studies. The results have proved the capability of the system to visualize and reconstruct anatomical 3D models from medical images.
Experimental Study on the Thermal Boundary Resistance Between an Individual Carbon Nanotube End and a Au Surface
Authors: Hirotani Jun , Ikuta Tatsuya , Nishiyama Takashi , Takahashi Koji
Published: August 2012

In the past decade, the very high intrinsic thermal conductivity of a carbon nanotube (CNT) has been successfully unveiled through experimental studies, but the thermal boundary resistance (TBR) between a CNT and ambient material still remains unclear. Some analytical and molecular dynamics studies have been reported on the TBR between a CNT and a surrounding material but there is no reliable experiment method to quantitatively investigate TBR between a CNT and a solid surface because of technical difficulties.
Advanced Kinematic Scheme of Structural Calculation of Thin Multilayer Laminate With Essentially Diverse Layer’s Stiffness
Authors: Gaynutdinov V. G.
Published: August 2012

Composite structure consists of a system of layers bonded together. The layers can have different mechanical properties and thicknesses. The main task is to predict the behavior of a laminate as a system of layers with given properties. We suggest advanced kinematic scheme for structural calculation and heuristic numerical algorithm of prediction behavior of a multilayer structures with essentially diverse layer’s stiffness. Kinematic scheme can be compared in adequacy with three-dimensional approach of structural calculation of thin multilayer laminate, but is more economical in view of required resource for numerical calculation.
Helium as a Carrier Gas in Humidification Dehumidification Desalination Systems
Authors: Narayan G. Prakash , McGovern Ronan H. , Lienhard John H. , Zubair Syed M.
Published: August 2012

A promising technology for small scale seawater desalination is the humidification dehumidification (HDH) system. This technology has been widely investigated in recent years. Since existing HDH systems have very high specific energy consumption, the authors have previously invented several ways to increase the energy efficiency of these systems. Even for these relatively higher efficiency systems the dehumidifier is expected to be large, owing to the large thermal resistance associated with the presence of non-condensable carrier gas (air) in the system. In this manuscript, we demonstrate that changing the carrier gas from air to helium a potential solution to this problem. In addition, the energy performance of a brine heated HDH system using helium relative to those using air is analysed in detail through well established on-design models for the components in the system.
Performance Characteristics of a Variable Density Pin Array Micro-Heat Exchanger
Authors: Papadopoulos George , Tiliakos Nicholas , Benel Gabriel
Published: August 2012

The design, fabrication and preliminary performance of a variable density pin array micro heat exchanger for micro-cooling applications is reported. Various pin diameters and density configurations were analyzed for their ability to provide maximum uniform heat transfer over the active area of the micro-heat exchanger using air as the working fluid for maximum mass flow rates through the micro-heat exchanger in the range of 40 mg/sec to 60 mg/sec. Fabrication of the micro-heat exchanger was performed using deep reactive ion etching (DRIE) technique on a 0.5 mm thick silicon wafer with nominal feature sizes in the range of 5 microns to 20 microns. Performance data is presented based on analysis and comparison to a baseline configuration with no pins.
Technique to Improve Performance of Positive Pressure Ventilation Tactic in High-Rise Fires
Authors: Panindre Prabodh , Kumar Sunil , Narendranath Atulya , Manjunath Vinay Kanive , Ceriello John
Published: August 2012

Positive Pressure Ventilation (PPV) is a firefighting tactic that can assist firefighters in venting of smoke and high temperature combustion products in a more efficient manner and make the fire-rescue /suppression operation safer than without PPV. The pressure created by PPV operation must be greater than that of created by spread of fire. In real-life structures such as high-rise buildings, considering the leakages and size of stairwells, it becomes difficult to achieve the desired pressure at upper floors using PPV operation. With the help from FDNY (Fire Department of New York), on-site tests and computer simulation techniques were performed to study the behavior of PPV tactic. A technique was developed that significantly increases the positive pressure level achieved by a typical PPV operation. The efficacy of this technique was tested by conducting on-site experiments and numerical simulation methods using computational fluid dynamics software - Fluent 12.0 and NIST’s Fire dynamic simulator (FDS 5.0). The results of on-site experiments and numerical simulation methods found to be in close agreement with each other and confirmed the efficacy of this technique in improving the performance of typical PPV operation. This paper describes the results obtained from these on-site tests and numerical simulation methods. As FDNY is in the phase of implementing this instrument to ease and improve the PPV deployment operation, numerical simulation methods have been used to optimize this technique and the analysis discussed in this study also simplifies the PPV fan deployment operation for firefighters.
Analytical Models for Radiative Heat Transfer in Radioisotope Thermophotovoltaic (RTPV) Cell
Authors: Panindre Prabodh , Mousavi Kh. Narges Susan , Kumar Sunil
Published: August 2012

A Radioisotope Thermophotovoltaic (RTPV) Cell is a device used to convert heat energy into electrical energy. The electric generation capacity of RTPV cell depends on the radiative heat transfer between its two surfaces: the emitter surface heated by radioisotope thermal source and the receiving photovoltaic (PV) cell surface. The spectral directional surface properties and the surface temperatures of emitter and PV cell surface play important roles in quantifying the radiative heat flux of RTPV cell. This paper establishes the required analytic flat plate solutions to calculate the radiative heat flux of RTPV cell. The results obtained using the analytic solutions developed in this study have been qualitatively validated with the results of numerical simulations performed by a commercially available software. The effect of the surface temperatures and emitter surface coating on RTPV cell capacity is also studied and analyzed by both the methods. The results obtained from both the methods show that PV cell surface temperature has negligible effect on RTPV cell capacity as compared to the emitter surface temperature. Also, the radiative heat flux of RTPV cell with coated emitter is found to be significantly higher than that of RTPV cell with uncoated emitter surface. The analytical methods can be used to estimate the net radiative heat flux of RTPV cell for different surface temperatures and are independent of the dimensions of RTPV cell.
Considerations on Ultra-Thin Substrate-Less Micro and Nano Systems
Authors: Gatzen Hans H. , Griesbach Tim , Wurz Marc C. , Rissing Lutz
Published: August 2012

For accomplishing ultra-thin micro and nano electromechanical mechanical systems (MEMS / NEMS), we are proposing an approach with substrate-less devices. Instead of fabricating thin devices on regular thickness wafers and thinning down the wafer at the end, the new devices are still fabricated on a thick handling wafer, but are released from them. This is done by means of a sacrificial layer below the device dissolved at the end of the wafer fabrication process. For still achieving sufficient device stiffness, an organic carrier-foil is integrated into the component, resulting in a flexible part with similarities to a macroscopic decal. For avoiding a warping particularly for multilayer devices, a compensation of the film is necessary.
Water-Hydrocarbon Emulsion Flow in Microchannels
Authors: Akhmetov Alfir , Mavletov Marat , Rakhimov Artur , Sametov Sergey , Akhatov Iskander S.
Published: August 2012

Water-hydrocarbon emulsions are widely used in various oil production processes, for example for blocking drill holes and managing fluid flows. From rheology view point the typical distinctive feature of such emulsions is their higher viscosity and non-Newtonian behavior as compared to that of carrier liquid. However, the flow of emulsions in capillary structures and microchannels reveals a remarkable, quite unexpected phenomenon called “dynamic blocking”, whereby the flow of emulsion through microchannel ceases in time despite the presence of the applied constant pressure gradient. The terminology “dynamic blocking” is due to the fact that, despite an apparent macroscopic flow arrest, the flow can nevertheless be observed on a microscopic scale at a much lower (by three to four orders of magnitude) flow rate and with a significantly modified structure of microflows. It should be noted that the size of water microdrops is significantly (by more than an order of magnitude) smaller than the characteristic size of the channel. No clear understanding exists today for the behavior of emulsions as they move through the microstructure. In this paper some experimental results of “dynamic blocking” are presented, and some plausible mechanisms explaining its physical nature are discussed.
Experimental Heat Transfer Spectrum Shift Prevention of a Portable Radiation Spectrometry System
Authors: Brandys Irad , Levin Yeshayahu , Atias Rahamim , Ifergan Yair , Cohen Yosef
Published: August 2012

Each radioactive material has its unique energy signature (spectrum). Spectrum shift during measurements is a well know phenomenon which occurs due to environmental temperature changes which affect the electronics, and can lead to misidentification of the radioactive material. We developed a new portable spectroscopy workstation based on Digital Signal Processing (DSP) technology, which includes an analog circuit, a Multi Channel Analyzer (MCA), 7 power suppliers and a laptop. The designed system, to which wide range of radioactive detectors can be attached, uses to identify a sampled radioactive material according to its spectrum. In order to prevent the spectrum shift phenomena, both natural and forced convection heat transfer experiments were carried out. Few configurations were tested during these experiments whose results yielded the final electronic packaging configuration of the system as well as the definition of the stabilization time of the system.
Design and Industrial Elaboration of Thermal Energy Storage Units Made of Recycled Vitrified Industrial Wastes
Authors: Meffre A. , Olives R. , Py X. , Bessada C. , Echegut P. , Michon U.
Published: August 2012

New sensible heat storage materials for CSP (Concentrated Solar Power-plant) made of recycled ceramics from vitrified asbestos containing wastes are considered. Up to now, those inert ceramics are only used for road construction and the raw vitrified product is cooled industrially in cast-iron ingot mould without any particular care. Nevertheless, all obtained industrial glass-ceramic ingots present similar macro and micro structures. The present work is first focused on macro and micro structural properties of those materials related to cooling conditions and secondly on a comprehensive model of the current industrial cooling step. One of the major advantages of this storage material is the possibility to shape it directly at the outlet of the vitrification process to produce the thermal storage elements. Therefore, various geometries of the storage material could be obtained leading to a possible optimization of heat transfer performances and reduction in pressure drop. On the basis of the relationship between cooling conditions and properties, the cooling protocol needed to manufacture efficient thermal storage modules can be considered.
Methodology to Study Attenuation of a Blast Wave Through the Cranium
Authors: Shah Alok S. , Stemper Brian D. , Yoganandan Narayan , Pintar Frank A. , Rangarajan Nagarajan , Hallman Jason , Shender Barry S.
Published: August 2012

The purpose of the study was to quantify attenuation of open field shockwaves passing through the PMHS (Post Mortem Human Subject) cranium. A better understanding of the relationship between shockwave characteristics external to the cranium and insults experienced by the brain is essential for understanding injury mechanisms, validation of finite element models, and development of military safety devices for soldiers in the field. These relationships are being developed using experimental PMHS techniques. Our existing shock tube produced open field shockwaves by increasing input pressure behind a Mylar membrane using compressed nitrogen until the membrane burst. Increasing membrane thickness resulted in greater bursting pressure and peak shockwave pressure. Peak pressure decreased predictably with greater distance from the shock tube outlet. Input pressures between 1.6 and 3.2 MPa resulted in peak shockwave pressures between 45 kPa and 90 kPa measured between 40 and 60 cm from the shock tube exit. The experimental protocol consisted of obtaining a PMHS head, filling the voided cranium with Sylgard gel, and securing the head in front of the shock tube using a Hybrid III dummy neck. Pressure transducers were mounted on the external cranium surface on the ipsilateral side and on the internal cranium surface on the ipsilateral and contralateral sides. Because the specimen was tested in multiple orientations, the ipsilateral side referred to the frontal or temporal sides. Transducers were mounted prior to adding the Sylgard gel. Data from all tests indicated shockwave rise times less than 10 μs external to the skull and internal to the skull on the ipsilateral side. Therefore, the sampling rate was 10 MHz using a digital oscilloscope. Shockwave characteristics were quantified including peak overpressure, peak underpressure, and duration of positive phase. The results show peak overpressure attenuations between 14 and 26% from the external ipsilateral transducer to the contralateral transducers in frontal and lateral orientation. In addition, there was a 93–96% reduction in the rate of onset between those transducers. Each characteristic may affect injury type/severity. This setup can be used to understand injury mechanisms for blast-induced mTBI, to quantify effects of interventions (e.g., helmets) on attenuation of open field blast waves, and for validation of finite element models.
Dynamic Optimization of District Energy Generation
Authors: Salsbery Scott J.
Published: August 2012

The University of Iowa Power Plant operates utility generation and distribution for campus facilities, including electricity, steam, and chilled water. It is desirable to evaluate the optimal load combination of boilers, engines and chillers to meet the demand at minimal cost, particularly for future demand scenarios. An algorithm is under development which will take into account the performance of individual units as part of the mix which ultimately supplies the campus and determine the degree that each should be operating to most efficiently meet demand. The algorithm will be part of an integrated simulation tool which is specifically designed to apply traditional optimization techniques for a given (both current and possible) circumstance. The second component is to couple the algorithm with accurate estimates and historical data through which expected demand could be predicted. The process will be able to account for theoretical circumstances which will be highly beneficial for strategic planning. It is also necessary to determine the unique operating characteristics of the system components. The algorithm will rely upon performance curves of individual system components (boiler, chiller, etc) and those must be developed and refined when possible using the most accurate information from experimental testing and commissioning or manufacturer supplied data. The heuristics that will be examined include combinatorial approach, a gradient-based incremental method, and simulated annealing.
Chaotic Synchronization of a Controlled, Noised, Gyroscope System With an Expected Gyroscope System
Authors: Min Fuhong , Luo Albert C. J.
Published: August 2012

In this paper, chaotic synchronization of a controlled, noised gyroscope system with an expected gyroscope system is investigated. From the theory of discontinuous dynamical systems, the necessary and sufficient conditions of such synchronization are presented. Numerical simulations for non-synchronization, partial and full chaotic synchronizations of two gyroscope systems are carried out.
Lockout/Tagout and Operational Risks in the Production Control of a Transfer Line With Passive Redundancy
Authors: Emami-Mehrgani Behnam , Nadeau Sylvie , Kenne´ Jean-Pierre
Published: August 2012

This paper presents an analytical model for the joint determination of optimal production and occupational safety for a failure prone manufacturing system consisting of three machines (two machines as passive redundancy and a third machine in series with the previous ones) producing one type of part. These machines are subject to breakdowns and repairs and the control problem is subject to non-negative constraints on work-in-processes (WIP). The decision variables are the production rate of two main machines and a standby machine. The decision variables influence the WIP levels, the inventory levels and the system’s capacity. The system capacity is assumed to be described by a finite state Markov chain. The aim of this paper is to minimize the cost of WIP, inventory while respecting occupational safety. The proposed approach is based on the combination of analytical formalism, simulation modeling, design of experiments and response surface methodology to optimize a transfer line in passive redundancy producing one part type. The usefulness of the proposed approach is illustrated through a numerical example.
FEM Stress Analysis and Strength Prediction of Stepped-Lap Adhesive Joints of Similar Hollow Cylinders Under Static Tensile Loadings
Authors: Kotajima Kazunari , Sekiguchi Yasuhisa , Kobayashi Takashi , Ueda Yuta , Sawa Toshiyuki
Published: August 2012

This paper deals with an FEM stress analysis of stepped-lap adhesive joints of similar hollow cylinders under static tensile loadings. The effects of Young’s modulus ratio between the adherends and adhesive, the thickness of the adhesive, scarf angle, the number of steps, and singular stress on the interface stress distributions are calculated using FEM. The code of FEM employed is ANSYS. The singular stress is found to occur at the edge of the interfaces. The singular stress at the inside edge is larger than that at the outside edge. It is shown that the maximum principal stress at the edge of the interface decreases as Young’s modulus ratio between the adherend and the adhesive and the adhesive thickness decreases while it decreases as the number of steps increases. Using the obtained interface stress distribution, we can predict the joint strength. For verification of the strength prediction, experiments to measure the joint strength were carried out. The numerical results of the joint strength are in a fairly good agreement with the experimental results.
Concentration Distribution Research of a Special DC Pulverized Coal Burner
Authors: Yang Mo , Guo Chunsun , Zhang Yuwen , Kang Zhangyang
Published: August 2012

There is a burner which bias block is located in different place compared with other pulverized coal burners. This special DC pulverized coal burner is used to achieve uniform distribution of the export concentration. By numerical method, this article has studied the concentration of this special distribution burner and analyzed internal characteristics. In order to research the effect of bias block in concentration distribution, this special distribution burner has been compared with the structure having no bias block. Euler-Lagrange method and discrete phase model (DPM) are employed to study the gas-solid two phase flow. Solid-phase is simulated in discrete phase model (DPM) and gas-phase in separation vortex (DES).
A Numerical Study of Fast Pyrolysis of Beetle Killed Pine Trees
Authors: Kenarsari Saeed Danaei , Zheng Yuan
Published: August 2012

Since 1990s, as a result of unprecedented drought and warm winters, mountain pine beetles have devastated mature pine trees in the forests of western North America from Mexico to Canada. Especially, in the State of Wyoming, there are more than 1 million acres of dead forest now. These beetle killed trees are a source of wildfire and if left unharvested will decay and release carbon back to the atmosphere. Fast pyrolysis is a promising method to transfer the beetle killed pine trees into bio-oils. In the present study, an unsteady state mathematical model is developed to simulate the fast pyrolysis process, which converts solid pine wood pellets into char (solid), bio-oils (liquid) and gaseous products in the absence of oxidizer in a temperature range from 500°C to 1000°C within short residence time. The main goal of the study is to advance the understanding of kinetics and convective and radiative heat transfer in biomass fast pyrolysis process. Conservation equations of total mass, species, momentum, and energy, coupled with the chemical kinetics model, have been developed and solved numerically to simulate fast pyrolysis of various cylindrical beetle killed pine pellets (10 mm diameter and 3 mm thickness) in a reactor (30 mm inside diameter and 50 mm height) exposed to various radiative heating flux (0.2 MW/m2 to 0.8 MW/m2). A fast pyrolysis kinetics model for pine wood that includes competitive path ways for the formation of solid, liquid, and gaseous products plus secondary reactions of primary products has been adapted. Several heat transfer correlations and thermo property models available in the literature have been evaluated and adapted in the simulation. Finite element method is used to solve the conservation equations and a 4th order Runge-Kutta method is used to solve the chemical kinetics. Unsteady-state two dimensional temperature and product distributions throughout the entire pyrolysis process were simulated and the simulated product yields were compared to the experimental data available in the literature. This study demonstrates the importance of the secondary reactions and appropriate convective and radiative modeling in the numerical simulation of biomass fast pyrolysis.
Numerical Investigation of Gas-Solid Two Phase Flow Over Composite Structures of Elbow and Venturi Tube
Authors: Kang Zhangyang , Yang Mo , Zhang Yuwen , Guo Chunsun
Published: August 2012

The Euler-Lagrange method and Dispersed Phase Model (DPM) are adopted in the numerical simulation of gas-solid two-phase flow inside elbow, venturi tube and a new rich-lean pulverized coal burner combined elbow and venturi tube. It is to study the characteristic of coal distribution and the outlet characteristics of rich/lean separation influenced by pulverized coal particle diameter and density. he Detached-eddy-simulation (DES) approach is involved in the calculation of turbulence dispersion of gas phase. The Discrete random walk model (DRW) is used in the turbulence of solid phase. The results show that, for the particles of smaller diameter (10μm), the effect of rich-lean separation of three types of structure is unobvious; for the particles of larger diameter (50μm), this new structure burner can achieve rich-lean separation and the maximum concentration rises as the Stokes number increases; for the particles of more larger diameter 100μm, with the increasing number of St, there will be more than one core of concentration.
Numerical Simulation of Gas-Particle Two-Phase Flow in Corners Tangential Streams Gasifier
Authors: Yang Mo , Su Dan , Zhang Yuwen , Kang Zhangyang
Published: August 2012

Numerical simulation of anti-rich/lean burner jet flow is carried out to simulate two forms of gas-solid two-phase jet fields. One is a single burners and its exit of certain areas gas-solid two-phase jet field. Another one is gas-solid two-phase jet field in the single-layer combustion region. Predication of the particle dispersion in the burner jet is of great importance in industrial application and in the designing of coal burner with good performance. The objective of this study is to numerically investigate the particle dispersion mechanisms in the gas–solid two-phase jet from an anti-rich/lean burner. The detached-eddy-simulation (DES) approach is employed to study the turbulent flow in the fuel rich/lean separator and the gas–solid multiphase jet from the exit of an anti-rich/lean burner. The numerical results show that adding bias current of anti-rich/lean burner exit jet flow keeps anti-rich/lean of properties. Since the exit of boundary air speed is almost twice of primary air velocity, boundary air act on coal powder flow in acceleration and conveying, coal powder flow can keep boiler of inscribed circle position.
Razi Acceleration in Kinematics
Authors: Jazar Reza N. , Khazaei A. , Mahinfalah M.
Published: August 2012

The time derivative of vectors depends on the coordinate frame in which the vector is expresses and the coordinate frame in which the derivative is taken. By redefining and expanding the Euler’s derivative transformation formula, we introduce the general theory of derivative and coordinate frames using a proper notation method. Introducing three coordinate frames, we show that the Coriolis acceleration is actually the addition of two different accelerations. Furthermore, a new acceleration term appears that we call it Razi acceleration.
Effect of Ni-Coated Carbon Nanotubes on the Creep Behavior of Sn-Ag-Cu Solder by Nanoindentation
Authors: Wei J. , Han Y. D. , Jing H. Y. , Nai S. M. L. , Xu L. Y.
Published: August 2012

In the present study, the powder metallurgy route was used to successfully incorporate Ni-coated carbon nanotubes into Sn-Ag-Cu solder, to form a nanocomposite solder. Nanoindentation tests were performed on both composite and Sn-Ag-Cu solder samples to investigate their creep behaviour at room temperature. Characterization results revealed that with the addition of Ni-coated carbon nanotubes, the creep behaviour of composite solder improved significantly as compared to that of the unreinforced solder alloy. Moreover, increasing the maximum load from 20 mN to 100 mN increased the percentage reduction in creep strain rate from 4% to 28%, for the composite compared to its monolithic counterpart after 300 s of holding.
Industrial Applications of a System for Chatter Stability Prediction and Monitoring
Authors: Lu K. B. , Jing M. Q. , Zhang Y. Q. , Liu H.
Published: August 2012

Chatter vibrations result in poor surface finish, reduced productivity, and shortened tool life in metal cutting. Although chatter stability and monitoring techniques are broadly studied in literature, the deployment of process monitoring system in the shop floor still presents a challenge. In this paper, an online prototype system including two independent modules of chatter stability prediction and monitoring for industrial applications has been constructed cooperatively. Turning and milling processes are considered. Firstly, the stability charts are evaluated by the application of the Laplace transform and the semi-discretization method. The obtained charts can assist the operators in choosing appropriate cutting parameters before operations start. Secondly, the characteristics of chatter are extracted in the time and frequency domains. The norm of chatter arising is formulated in accordance with the variance and spectrum of vibration signals. The corresponding threshold is confirmed relatively in comparison with the characteristics of the stable cutting states recorded in the reference database. Thirdly, the algorithms and modules are implemented with the combination of the advantages of MATLAB and C# programming, in which delay strategy and overlap processing enable to improve the accuracy and rapidity of the monitoring system. Finally, the effectiveness of the proposed system has been verified by experimental results of the industrial trials.
A Diagonal Piezoelectric Energy Harvester on Clamped-Free Conical Shells
Authors: Li H. , Hu S. D. , Tzou H. S.
Published: August 2012

Thin shells are common engineering structures and they have great potentials to harvest more energy from ambient vibrations. The conical shells are forced to vibrate due to the external excitation, and this kinetic energy can be extracted using piezoelectric materials. Recent sensing analyses indicate that a straight piezoelectric patch may output no voltage due to the axisymmetric of conical shells. This study is to address this issue and to overcome the zero output problems. A diagonal piezoelectric patch is proposed for conical energy transduction and harvesting. The diagonal harvester patch shows no symmetry in the longitudinal or circumferential direction for all shell modes. This configuration guarantees the energy output for all natural modes. A mathematic model of the diagonal piezoelectric harvester is given and an open-circuit output voltage of the diagonal energy harvester is derived based on the thin-shell theory and the Donnel-Mushtari-Valsov theory. Then, the distributed modal energy harvesting characteristics of the proposed diagonal piezoelectric conical shell harvester are evaluated in case studies. Numerical results prove that the proposed diagonal piezoelectric energy harvester outputs energy for all known modes. The energy amplitudes vary with the modal shapes. Next the diagonal stripe is divided into several small patches, each patch has separate electrodes. Therefore the output energy amplitudes indicate the energy distribution over the conical harvester surface. The results show that, for each mode with unit modal amplitude, the distribution depends on the mode shape, harvester location, and geometric parameters. The regions with high strain outputs yield higher modal energies.
Combustion Characteristics of Pool Fires Under Low Atmospheric Pressures
Authors: Tao Changfa , Wang Xishi , Cai Xin
Published: August 2012

In order to study the effects of low atmospheric pressure conditions on combustion characteristics of liquid pool fires, a 1.0m×1.0m×1.0m airtight steel box was constructed and used for altering the ambient pressure with a vacuum pump. Gasoline, diesel oil and n-heptane were tested as the liquid fuels. The mass burning rate, flame pulsation frequency and flame local temperature history of the small scale pool fires were experimentally determined. The results show that the mass burning rate, flame pulsation frequency decrease with the decrease of ambient pressure, while the pulsating intensity is strengthened slightly for the n-heptane flame and weakened for the gasoline flame. It is also shown that the high temperature area of the flame moves upward with the decrease of ambient pressure.
Stability of Non-Newtonian Taylor-Couette With Axial Flow
Authors: Ashrafi N. , Hazbavi A.
Published: August 2012

The influence of axial flow on stability of the Taylor-Couette flow is carried for shear thinning fluids. The fluid is assumed to follow the Carreau-Bird model and mixed boundary conditions are imposed. The four-dimensional low-order dynamical system, resulted from Galerkin projection of the conservation of mass and momentum equations, includes additional nonlinear terms in the velocity components originated from the shear-dependent viscosity. In absence of axial flow the base flow loses its radial flow stability to the vortex structure at a lower critical Taylor number, as the shear thinning effects increases. The emergence of the vortices corresponds to the onset of a supercritical bifurcation which is also seen in the flow of a linear fluid. However, unlike the Newtonian case, shear-thinning Taylor vortices lose their stability as the Taylor number reaches a second critical number corresponding to the onset of a Hopf bifurcation. Existence of an axial flow, manifested by a pressure gradient appears to further advance each critical point on the bifurcation diagram. Complete flow field together with viscosity maps are given for different scenarios in the bifurcation diagram.
Design and Evaluation of MEMS-Based Stirling Cycle Micro-Refrigeration System
Authors: Guo Dongzhi , Gao Jingsheng , McGaughey Alan J. H. , Moran Matthew , Santhanam Suresh , Fedder Gary K. , Anderson Bill , Yao Shi-Chune
Published: August 2012

A Stirling cycle micro-refrigeration system composed of arrays of silicon MEMS cooling elements has been designed and evaluated thermodynamically. The cooling elements are each 5 mm-long, 2.25 mm-wide, have a thickness of 300 μm, and are fabricated in a stacked array on a silicon wafer. A 0.5 mm-long regenerator is placed between the compression (hot side) and expansion (cold side) diaphragms. The diaphragms are 2.25 mm circles driven electrostatically. Helium is the working fluid, pressurized at 2 bar and sealed in the system. Under operating conditions, the hot and cold diaphragms oscillate sinusoidally 90° out of phase such that heat is extracted to the expansion space and released from the compression space. The bulk silicon substrate on which the device is grown is etched with “zipping” shaped chambers under the diaphragms. The silicon enables efficient heat transfer between the gas and heat source/sink as well as reduces the dead volume of the system, thus enhancing the cooling capacity. In addition, the “zipping” shaped substrates reduce the voltage required to actuate the diaphragms. An array of vertical silicon pillars in the regenerator serves as a thermal capacitor transferring heat to and from the working gas during a cycle. In operation, the push-pull motion of the diaphragm makes a 300 μm stroke and actuates at a frequency of 2 kHz. Parametric study of the design shows the effects of phase lag, swept volume ratio between the hot space and cold space, and dead volume ratio on cooling capacity. At TH = 313.15 K and TC = 288.15 K and assuming a perfect regenerator, the thermodynamic optimization analysis gives a heat extraction rate of 0.22 W per element and cooling capacity of 30 W/cm2 for the stacked system. Evaluation of the stacked system shows that the COP will reach 6.3 if the expansion work from the cold side is recovered electrostatically and used to drive the hot side diaphragm.
Effect of Clay on Tensile, Flex and Fatigue Behavior of Carbon Fiber Reinforced Epoxy
Authors: Zhou Yuanxin , Hosur Mahesh , Shaik Zainuddin , Jeelani Shaik
Published: August 2012

In this study, the nanophased epoxy with 2 wt.% clay was utilized in a vacuum assisted resin transfer molding (VARTM) set up with carbon fabric to fabricate laminated composites. The effectiveness of clay addition on mechanical properties of composites has been evaluated by tensile, flexural and fatigue test. The tensile and flexural strengths improved by 5.7% and 13.5%, respectively as compared to the neat composite. The fatigue strength was also improved significantly. Based on the experimental result, a linear damage model combined with the Weibull distribution function has been established to describe static failure processing of neat and nanophased carbon/epoxy. The simulated stress strain curves from the model are in good agreement with the test data. Simulated results show that damage processing of neat and nanophased carbon/epoxy described by bimodal Weibull distribution function.
A Four-Rigid-Body Element Model and Computer Simulation for Flexible Components of Wind Turbines
Authors: Jiang Songyi , Duan Shanzhong Shawn
Published: August 2012

In this paper, a four-rigid-body element model is presented for description of flexible components of a horizontal axis wind turbine (HAWT). The element consists of four rigid bodies arranged in a chain structure fashion. The bodies of each element are linked by two universal joints at two ends, and one cylindrical joint at the middle. Thus each element has six degrees of freedom. They are four degrees of freedom for bending, one degree of freedom for torsion, and one degree of freedom for axial stretching. For each degree of freedom, a spring is used to describe the stiffness of the component. Stiffness of each spring is obtained by using potential energy equivalence between a Timoshenko beam and these springs. With these considerations, flexible components of a HAWT such as blades and tower may then be represented by connecting several such elements together. Based on four-rigid-body element model, the tower and blades of a HAWT are constructed. Their equations of motion are then derived via Kane’s dynamical method. Commercial computational multibody dynamic analysis software Autolev has been used for motion simulation of tower and blades under given initial conditions. Simulation results associated with the tower indicate that four-rigid-body element model is suitable for analysis of dynamic loads, modal, and vibration of wind turbines with respect to fixed and moving references at high computational efficiency and low simulation costs. The approach is also a good candidate for simulating dynamical behaviors of wind turbines and preventing their fatigue failures in time domain.