bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Apparatus for the Determination of Nusselt and Rayleigh Numbers During Natural Convection From a Heated Horizontal Cylinder
Authors: Atayılmaz S¸evket O¨zgu¨r , Dalkılıc¸ Ahmet Selim , Demir Hakan , Ku¨rekci Nuri Alpay
Published: July 2010

Determination of Nusselt and Rayleigh numbers during natural convection heat transfer from horizontal cylinders are investigated experimentally and numerically. Experiments are done by means of the test cabin inside a conditioned room at different environmental and surface temperatures. The environmental and cylinder surface temperatures are ranging between 10–40 °C and 20–60 °C respectively. 1 m long horizontal copper cylinder is used and has outer diameters of 4.8 mm including centered silicone covered cylindrical resistant wires inside it. The experimental apparatus is designed to capable of changing the different operating parameters such as heat flux and environmental temperature. The existence of the gap on the closed surfaces in the test cabin which can cause a stack effect, affected temperature and velocity fields, disturbance of the natural convection condition is also checked. The detailed description of design and development of the test apparatus, control devices, instrumentation, and the experimental procedure are reported and the study of experimental setups from the available literature survey with the existing one are compared in this paper. The uncertainty analysis method proposed by Kline and McClintock is used and explained elaborately. Detailed information and algorithm of numerical method are given to ease the understanding of the numerical part of study. Alteration of Nusselt numbers with Rayleigh numbers, the temperature distribution on the heated horizontal cylinder surface by means of Fluent CFD program are shown in the paper. In addition to this, Morgan’s correlation is used for the comparison of Nusselt number and is found in good agreement with the experimental results.
An Interdisciplinary Laboratory Experience for Sustainability
Authors: Vallee Glenn E. , Casey Philip , Pinsonneault James
Published: July 2010

A new senior level interdisciplinary lab experience has been developed at Western New England College which focuses on the use of biodiesel in an interdisciplinary engineering design and sustainability team project. A biodiesel generation system has been developed as part of two senior capstone design projects, and the system is capable of converting all of the waste vegetable oil (WVO) generated by the college food services department into biodiesel for use in diesel powered utility equipment on campus, and to heat the mechanical engineering laboratories. This fuel is also used to power vehicles designed as part of the senior level interdisciplinary lab experience which previously involved the development of a solar powered vehicle. Teams comprised of mechanical, electrical and computer engineering students are required to design and fabricate biodiesel powered vehicles designed to transport a payload across a race track in the shortest time possible using the biodiesel generated by each student team from waste cooking oil found on campus. Students gain hands on experience in the conversion of waste cooking oil into fuel and learn that the quality of the fuel generated plays an important role on vehicle performance. Students are given tight budgetary constrains to encourage the use of recycled materials and used parts found in the engineering labs. A mathematical energy model is developed to predict vehicle performance and an onboard data acquisition system is developed to measure performance parameters such as vehicle speed, engine rpm, and wind speed for comparison to the predictive energy model. Students are graded on vehicle performance on race day, the total cost of the vehicle and the vehicle weight. The experience gives students valuable insights into the interdisciplinary team dynamic and the importance of engineering for sustainability.
Thermodynamic Analysis of Fermentation and Anaerobic Growth of Baker’s Yeast
Authors: Teh Kwee-Yan
Published: July 2010

Thermodynamic concepts have been used in the past to predict microbial cell yield under various growth conditions. Cell yield may be the key consideration in some industrial biotechnology applications. It is not the case, however, in the context of biofuel production. In this paper, we examine the thermodynamics of fermentation and concomitant growth of baker’s yeast in continuous culture experiments under anaerobic, glucose-limited conditions, with emphasis on the yield and efficiency of ethanol production. We find that anaerobic metabolism of baker’s yeast is very efficient; the process destroys less than 7% of the total chemical exergy supplied to the fermentation reactor. However, the exergy of ethanol secreted constitutes less than 60% of the in-flowing exergy, or 75% that of glucose fed to the continuous culture. Effects of varying the specific adenosine 5′-triphosphate (ATP) consumption rate, which is the fundamental parameter that quantifies the energetic requirements for cell growth and maintenance, are also examined.
Drag Reduction by Culture Solutions of Dry Malted Rice
Authors: Watanabe Keizo , Ogata Satoshi
Published: July 2010

Turbulent drag reduction by culture solutions of dry malted rice was investigated in a 2.00mm-inner-diameter pipe flow of length 50 diameters at Reynolds numbers from 500 to 8000. The drag reducing abilities of the solutions were tested by comparing drag reduction effectiveness at different concentrations and culture times in water. Comparisons between polysaccharide biopolymer solutions and culture solutions of dry malted rice revealed that the test solutions exhibited Type B drag reduction, which were roughly parallel to, but displaced upwards from, the Newtonian Prandtl-Ka´rma´n law. The maximum drag reduction ration was about 30% at a Reynolds number of 8,000. It is shown also that the onset point of drag reduction phenomena was Ref = 200.
A Numerical Investigation of Ray Tracing Method in a View Factor Calculation Procedure for Zonal Radiation Heat Transfer in Complex Systems
Authors: Malikov German , Lisienko Vladimir , Koptelov Roman , Kalugin Jakov , Viskanta Raymond
Published: July 2010

In this paper a variety of well known computer graphics algorithms (Binary Spatial Partitioning-BSP, Bounding Box-BB, and direct method of sequential search) for ray tracing are studied numerically in the context of the view factor calculations for the zonal method of radiation heat transfer analysis in complex industrial furnace geometries. The paper reports on a modified BSP algorithm which takes into account the specific types of obstructions and their arrangement in different types of metallurgical furnaces. The modified algorithm enhances the ray tracing calculations by two to three orders of magnitude. An universal algorithm to obtain an intersection with a polyhedron obstruction is developed. The method is tested for simple three dimensional and complex furnace geometries.
Sensitivity Analysis of Dissipative Reversible and Hamiltonian Systems: A Survey
Authors: Kirillov Oleg N. , Verhulst Ferdinand
Published: July 2010

The paradox of destabilization of a conservative or non-conservative system by small dissipation, or Ziegler’s paradox (1952), has stimulated an ever growing interest in the sensitivity of reversible and Hamiltonian systems with respect to dissipative perturbations. Since the last decade it has been widely accepted that dissipation-induced instabilities are closely related to singularities arising on the stability boundary. What is less known is that the first complete explanation of Ziegler’s paradox by means of the Whitney umbrella singularity dates back to 1956. We revisit this undeservedly forgotten pioneering result by Oene Bottema that outstripped later findings for about half a century. We discuss subsequent developments of the perturbation analysis of dissipation-induced instabilities and applications over this period, involving structural stability of matrices, Krein collision, Hamilton-Hopf bifurcation and related bifurcations.
LNG-Based Cogeneration Systems: Part 1—Comparison of Gas-Turbine-Based Concepts
Authors: Tsatsaronis G. , Morosuk T.
Published: July 2010

Liquefied Natural Gas (LNG) is expected to contribute in future more than in the past to the overall energy supply in the world. The paper is the first part of a two-part presentation. In the first one, some novel concepts for combining LNG regasification with the generation of electricity are discussed, whereas in the second part advanced exergy-based analyses are applied to the most favorable LNG–based cogeneration system. All concepts to be evaluated in the first part use gas turbines, to keep the overall investment cost relatively low. The comparisons are conducted based on thermodynamic efficiency and on the potential for improving this efficiency.
LNG-Based Cogeneration Systems: Part 2—Advanced Exergy-Based Analyses of a Concept
Authors: Tsatsaronis G. , Morosuk T. , Cziesla F.
Published: July 2010

Liquefied Natural Gas (LNG) is expected to contribute in future more than in the past to the overall energy supply in the world. The paper is the second part of a two-part presentation. In the first one, some novel concepts for combining LNG regasification with the generation of electricity are discussed, whereas in the second part advanced exergy-based analyses are applied to the most favorable LNG–based cogeneration system. These analyses include an advanced exergy analysis and an advanced exergoeconomic analysis. With the aid of these analyses the interactions among system components as well as the potential for improving the thermodynamic efficiency and the potential for reducing the overall cost will be revealed. The objective of this paper is to demonstrate (a) the potential for generating electricity while regasifying LNG, and (b) the capabilities associated with advanced exergy-based methods.
Advanced Exergetic Analysis of Chemical Processes
Authors: Boyano A. , Tsatsaronis G. , Morosuk T. , Blanco-Marigorta A. M.
Published: July 2010

In this paper, a steam methane reforming (SMR) process for the production of hydrogen is studied. The process is based on two chemical reactions (reforming and water-gas-shift reaction). For each component but especially focusing on the chemical reactors, the avoidable part of the exergy destruction is estimated. The assumptions required for these calculations are discussed in detail and represent the main contribution of this work to the development of exergy-based methods for the analysis of chemical processes. In an advanced exergy analysis, the exergy destruction within a component is split into avoidable/unavoidable parts. This splitting improves understanding of the sources of thermodynamic inefficiencies and facilitates a subsequent optimization of the overall process. The overall SMR process is characterized by high energetic and exergetic efficiencies. However, the majority of the exergy destruction is caused by the irreversibility of chemical reactions and heat transfer. Results of this paper suggest options for improving the efficiency of the overall process.
Complex Pressure Pulses in Micro-Channels Magnetically Induced
Authors: Letelier Mario F. , Siginer Dennis A. , Stockle Juan S. , Ulloa Francisco A.
Published: July 2010

Micro-channels are presently used extensively in applications related to biomedicine and others. These applications commonly involve flow patterns apt for separating particles in suspension, or fluid layers or fluid portions. In order to find a desired optimum performance it is necessary, among other factors, to determine the pressure gradients that would generate the required flow patterns. Presently the driving pressure gradients are produced by means of mechanical devices, such as syringe pumps, which have obvious limitations in the case where the flow time-pattern is complex. High frequency flows with varying amplitude or swift changes in acceleration imply overcoming big inertia forces in mechanisms. In this paper it is presented a novel and alternative methods for providing complex pressure pulses for the case were the working fluid changes properties when affected by magnetic fields. It is shown that an appropriate arrangement of parallel tubes, subject to different magnetic fields, can induce a wide variety of pressure pulses in selected stations of the system. These stations can be used for connecting the working channel. An analytical model is presented together with several applications.
The Effects of the Distance Between Nozzle and Substrate on Cold Gas Dynamic Spray Process
Authors: Li Longjian , Chen Qinghua , Cui Wenzhi , Jen Tien-Chien , Yen Yi-Hsin , Liao Quan , Zhu Lin
Published: July 2010

In this paper, numerical simulations were performed for the gas-particle two phase flow in the Cold Gas Dynamic Spray (CGDS) process to investigate the acceleration of micro- and nanoparticles with diameters ranging from 100nm to 50μm. Nitrogen (N2) and Helium (He) were chosen as the carrier gas, respectively. The acceleration of carrier gas to particles in the De-Laval-Type supersonic nozzle was strongly dependent on the characteristics of flow field, as well as the densities and the size of the particles. Copper particles (Cu) were chosen as the spraying materials. The computed results showed that the flow structures of the carrier gas were very different for different gas and different spraying distance, which resulted in consequently different accelerating features. The cone-shape weak shocks (compression waves) occurred at the exit of divergent section, and the bow-shaped strong shock wave was found right before the substrate, which played a resistance role to the particles and prevented the smaller particles from approaching on the substrate.
Numerical Modeling of Velocity and Temperature Distributions in a Bipolar Plate of PEM Electrolysis Cell With Greatly Improved Flow Uniformity
Authors: Kasukurthi Jephanya , Veepuri K. M. , Nie Jianhu , Chen Yitung
Published: July 2010

In this present work, finite volume method was used to simulate the three-dimensional water flow and heat transfer in a flow field plate of the proton exchange membrane (PEM) electrolysis cell. The standard k-ε model together with standard wall function method was used to model three-dimensional fluid flow and heat transfer. First, numerical simulations were performed for a basic bipolar plate and it was found that the flow distribution inside the channels in not uniform. The design of the basic bipolar plate has been changed to a new model, which is featured with multiple inlets and multiple outlets. Numerical results show that the flow and temperature distributions for the new design become much homogeneous.
An Avionics Integrity Program Approach to Preventing Aircraft Electronics Humidity and Moisture Problems
Authors: Lide Charles , Glista Stefan
Published: July 2010

Analysis of the causes of airborne electronics field failures indicates that humidity, moisture, and corrosion are significant contributors to the total field failure population. In spite of this fact, analysis methods, test methods and standard procedures to address these problems are less mature than those for other electronics failure mechanisms such as low and high cycle fatigue. An Avionics Integrity Program (AVIP) approach to address humidity and moisture issues is outlined. Programmatic and technical issues associated with achieving humidity and moisture resistance are discussed. The paper focuses on the steps to be taken at each stage of the development and verification process to reduce the probability of moisture related problems escaping to later stages of development and verification. Design and development process improvements are discussed along with areas of need for improved methods. Sources of moisture including the influence of cooling interface temperatures are presented along with mitigations to moisture sources. Examples of moisture-related failures are discussed along with corrective actions to the electronic equipment. Design criteria to prevent moisture-related failures and achieve a moisture-resistant design are presented. Limitations of humidity test methods are covered along with suggested improvements to increase realism of testing to match the severe environmental and operating conditions. Finally, field life management moisture screening is proposed.
Motion Performance Analysis of Double-Cylinder Parallel Manipulators
Authors: Zhou Hong , Alimi Shehu T. , Ravindranath Aravind , Vepuri Hareesh
Published: July 2010

Double-cylinder parallel manipulators are closed-loop two-degree-of-freedom linkages. They are preferred to use because of their simplicity plus the common advantages of parallel manipulators such as high stiffness, load-bearing, operation speed and precision positioning. Like other parallel manipulators, the output motion of double-cylinder parallel manipulators is not as flexible as two-degree-of-freedom serial manipulators. The motion performance analysis plays a critical role for this type of parallel manipulator to be applied successfully. In this paper, the linkage feasibility conditions are established based on the transmission angle. When feasibility conditions are satisfied, there is no dead position during operation. The workspace is generated by using curve-enveloping theory. The singularity characteristics are analyzed within the workspace. The motion performance index contours within the workspace are produced using the condition number of the manipulator Jacobian matrix. The results of this paper provide guidelines to apply this type of parallel manipulator.
Effects of Silicon Substrate on the Growth of Carbon Nanotubes
Authors: Yung K. P. , Tay R. Y. J. , Wei J. , Tay B. K.
Published: July 2010

Due to their extraordinary electrical, thermal and mechanical properties, carbon nanotubes (CNTs) have been foreseen as potential materials for electronics devices in the future. To integrate CNTs in electronic applications, CNTs would need to be deposited on different types of Si substrate. In this study, CNTs were grown on Ni catalyst layer with four types of substrates, namely Si, n++ Si, p++ Si and SiO2, using Plasma Enhanced Chemical Vapor Deposition (PECVD). The morphology and microstructure of the CNT films were analyzed by scanning electron microscopy (SEM) and Raman spectroscope. It was found that the type of Si substrate has significant effects on CNT growing characteristics. The possible mechanisms for the observed results are proposed. These findings add significant reference value to select deposition conditions suitable for deposition of CNTs on different types of Si substrate.
Organic Monolayers for Room Temperature Copper Bonding
Authors: Ang X. F. , Foo Q. H. , Wei J. , Chen Z. , Wong C. C.
Published: July 2010

Wafer level bonding process is a key fabrication step in several integration systems including microelectromechanical (MEMs) and nanoelectromechanical (NEMs). Often, harsh bonding conditions used result in large thermomechanical stresses built-up which leads to undesired degradation in device performance. Our recent study revealed the capability of nanostructured organic coatings (NSOCs) in reducing the bonding temperature needed to bond copper surfaces from 300°C to 60°C. In this study, room temperature copper bonding is demonstrated successfully with the help of the organic layers. Further investigation is made to evaluate the influence of thickness of NSOCs to alleviate bonding temperature. We found that all NSOCs (1, 2, 3) showed superior bond strength (>25MPa) as compared to that of the uncoated copper (<23MPa) at bonding temperatures from 25°C to 80°C. Since it is imperative that surface oxide has to be removed for bonding to take place, the enhancement exhibited is attributed to an effective surface passivation by the organic layer. It is postulated that this ultrathin layer, which behaves as a milder layer as compared to the bulk oxide layer, can be easily displaced for bond formation.
An Overview of Reverse Osmosis Water Desalination and the Solution Diffusion Mathematical Model
Authors: Hessami Mir-Akbar , Hall Nathan , Robb Adam
Published: July 2010

The planet Earth has an abundant supply of saline water but it requires special treatment to ensure the supply of potable water to sustain life on Earth. Water desalination can be used to achieve this objective. In order to understand this process, research was undertaken on water desalination with a focus on reverse osmosis (RO) in order to develop a simple mathematical model of this process. Mathematical modelling can be used to describe, explain and calculate the solvent and solute fluxes through RO membranes. Such techniques are commonly used by membrane manufacturers to develop proprietary software to study their product’s performance. Two such software packages were used to study the effects of the operating conditions on the performance of RO membrane. Good agreement was achieved between the salt rejection results of the mathematical model and the computer software.
A Template for the Integration of Teaching and Learning of Communication Skills in the Engineering Course
Authors: Hessami Mir-Akbar
Published: July 2010

Published studies in the open literature and experience of new engineering graduates have shown that employees who are able to clearly communicate their thoughts and ideas to their employers through written reports and oral presentations advance more quickly in the organisation compared to those who lack these skills even if they possess superior technical knowledge. Also, surveys of engineering employers have shown that while the technical knowledge of engineering graduates is considered to be adequate, the perception is that graduates lack the personal communication skills required of them in the work place. The traditional method of teaching communication skills to engineering students is through especially designed units which are taught by specialists in the field of communication. Engineering students generally consider these units to be of little importance due to a lack of engineering relevance. In order to overcome such shortcomings, teaching and learning of communication skills was integrated with the teaching of technical contents to final year students in a two-semester long Final Year Project (FYP) core unit in the undergraduate engineering degree during 2003 to 2008. The assessments tasks for the FYP unit included submission of a Project Proposal, a Progress Report, a Research Paper and a Final Report, plus an Oral Presentation. Students were given instruction on how to prepare for these activities at appropriate times during the semester. This paper describes the details of the approach used and the results obtained by students who have completed this unit.
Liquid Crystal Polymer (LCP) for Characterization of Millimer-Wave Transmission Lines and Bandpass Filters
Authors: Lu H. J. , Guo Y. X. , Faeyz K. , Cheng C. K. , Wei J.
Published: July 2010

In this paper, a multi-layer LCP substrate fabrication process was described and millimeter wave transmission lines and filters were designed and fabricated on the LCP substrate. Various transitions from a CPW to a microstrip line with their characteristic impedance being 50 ohms were investigated. The characteristics of the wirebonding assembly for connecting two transmission lines was also examined. The measurement results show that an insertion loss of 1.3 dB at 60 GHz can be achieved for the two-wire bonding trasmisssion line including two transitions from a CPW to a microstrip line.
Energy Saving by ESCO (Energy Service Company) Project in Japanese Hospital
Authors: Okamoto S.
Published: July 2010

This paper describes a study starting from an analysis of typical energy demand profiles in a hospital setting followed by the case study of a cogeneration system (CGS) by an ESCO (Energy Service Company) project. The concept is a future autonomous system for the combined generation of electrical, heating and cooling energy in the hospital. The driving cogeneration units are two high-efficiency gas engines; this is used to produce the electrical and heat energy. Gas engine is used as a driving unit because of high needs for electrical and heating energy. The natural gas-fuelled reciprocating engine is used to generate 735kW of power. In our case electrical energy will be used only in the Hospital. A deficit in electricity can be also purchased from the public network. The generated steam will be used to drive three steam-fired absorption chillers and delivered to individual consumers of heat. This system is capable of doing simultaneous heating and cooling. No obstacles were recognized for the technical feasibility of CGS. The average ratio between electric and thermal load in the Hospital is suitable to make CGS system operate. An analysis performed for a non-optimized CGS system predicted a large potential for energy savings.
Surface Runoff and Its Erosion Energy in a Partially Continuous System: An Ecological Hydraulic Model
Authors: Zhang Huayong , Dai Liming
Published: July 2010

Plant community and ground surface form a partially continuous ecosystem in conveying surface runoff and its erosion energy. It is one of the mechanisms for maintaining the stable development of a partially continuous ecosystem that the plant community and ground surface dissipate the erosion energy produced by surface runoff so as to control the soil erosion process of the ecosystem. Based on the energy fundamentals of hydraulics and by idealizing the structure of plant community, we obtain an ecological hydraulic model in this paper through a series of mathematical deductions, which includes three equations: (1) the equation on approaching energy balance of surface runoff moving across plant community and ground surface; (2) the equation on the process of dissipating energy of surface runoff by plant community and ground surface in an ecosystem; (3) the equation on the relationship among the pattern of plant community, ground surface and energy dissipation of surface runoff. Theoretically, the ecological hydraulic model can be used to calculate the dynamical process of energy dissipation of surface runoff by plant community and ground surface in a partially continuous ecosystem and to discuss the optimization of plant community pattern in a given section of the ecosystem.
Development of Faculty Course Assessment Reports for ME Program ABET Accreditation
Authors: Duan Shanzhong Shawn , Bassett Kurt
Published: July 2010

The assessment of program outcomes for ABET accreditation has become a challenge for engineering programs nationwide. Various methods and approaches have been investigated to develop good practices for program assessment. At South Dakota State University (SDSU), an approach called Faculty Course Assessment Reports (FCAR) has been explored for mechanical engineering (ME) program assessment. FCAR provides an assessment tool to correlate the ME program outcomes with the outcomes of the core ME courses, and to evaluate student performance at the course level based on ABET outcome criterion. This process begins with the development of course objectives and outcomes. Then these course objectives and outcomes are directly mapped with the ME program objectives and outcomes respectively. Further the quantitative and qualitative details generated in the FCAR are lined up directly to ABET program outcome a to k criterion through FCAR rubrics. By use of the FCAR process, all ME program outcomes are evaluated at the course level based on the ABET program outcomes. The assessment results are being used for improvement of the ME curriculum. The process was developed to provide an effective tool for the ME program outcome assessment at the course level with reasonable effort.
Effects of Tube Diameter, Length and Tube Numbers on Condensation of Steam in Vertical Tube Condenser
Authors: Revankar Shripad T. , Henderson Gavin
Published: July 2010

A heat and mass analogy study was performed for the steam condensation in a vertical tube where steam is completely condensed. In the analysis a single tube, tube bundle with four tubes and two different diameter tubes were considered. The two condensing tubes of same height (0.9m) but different inside diameters, 26.6mm and 52.5mm, were used whereas the tube bundle was made of four tubes of height 1.8 m and 52.5 mm diameter. The results showed that the operating pressure is uniquely determined by inlet steam flow rate for the complete condensation. The condensation heat transfer rate increases and the condensation heat transfer coefficient decreases with the system pressure. The condensation heat transfer coefficients (HTC) were obtained as function various parameters such as different primary pressure (150–450 kPa) and inlet steam flow rate, single tube and tube bundle and tube diameters. Comparison with experimental condensation rates for single tube of 26.6 mm and 52.5 mm and four tube bundle of tube diameter 52.5 mm were made and the agreement was good. The effects of these parameters to condensation performance were evaluated.
High Throughput Nanofluidic Architectures for Nanoparticle Separation
Authors: Prabhu Anmiv S. , Jubery Talukder Zaki , Freedman Kevin , Mulero Rafael , Dutta Prashanta , Kim Min Jun
Published: July 2010

High blood cholesterol levels and associated complications are a major health concern the world over and current techniques to deal with this, especially low density lipoprotein (LDL) apheresis, have significant room for improvement. We had previously reported a proof of concept technique that relies on silicon nitride based solid state nanopores to separate high density lipoprotein (HDL) like particles from LDL like particles. A mathematical model to describe the setup is reported. This model revealed that charge density of the pore surface was critical in determining the efficiency of separation. Accordingly we chemically modified our nanopores with (3-aminopropyl)-triethoxysilane (APTES) to achieve more efficient, high throughput particle separation. Such a technique could make it possible to develop safe and affordable LDL apheresis devices in the future.
Response of Electrostatically Actuated Sensors Near Half of the Natural Frequency
Authors: Caruntu Dumitru I. , Knecht Martin W.
Published: July 2010

A cantilever micro-resonator electrostatically actuated near half of the natural frequency is investigated. Hamilton’s principle is used to derive the partial-differential equation of motion for a general non-uniform sensor. Nonlinearities arise due to the electrostatic and Casimir forces. The electrostatic actuation introduces parametric coefficients in both linear and nonlinear parts of the governing equation. A direct approach is taken using the method of multiple scales resulting in a phase-amplitude relationship for the system. Numerical results for a uniform capacitive resonator micro-sensor are provided and tested numerically using a reduced-order model of the governing equation of motion.
Closed-Form Solutions of Axisymmetrical Transverse Vibrations of Concave Parabolic Thickness Annular Plates
Authors: Caruntu Dumitru I.
Published: July 2010

This paper deals with transverse vibrations of axisymmetrical annular plates of concave parabolic thickness. A closed-form solution of the partial differential equation of motion is reported. An approach in which both method of multiple scales and method of factorization have been employed is presented. The method of multiple scales is used to reduce the partial differential equation of motion to two simpler partial differential equations that can be analytically solved. The solutions of the two differential equations are two levels of approximation of the exact solution of the problem. Using the factorization method for solving the first differential equation, which is homogeneous and includes a fourth-order spatial-dependent operator and second-order time-dependent operator, the general solution is obtained in terms of hypergeometric functions. The first diferential equation and the second differential equation (nonhomogeneous) along with the given boundary conditions give so-called zero-order and first-order approximations, respectively, of the natural frequencies and mode shapes. Any boundary conditions could be considered. The influence of Poisson’s ratio on the natural frequencies and mode shapes could be further studied using the first-order approximations reported here. This approach can be extended to nonlinear, and/or forced vibrations.
Growth of Delamination for Laminates Circular Plates Subjected to Transverse Loads
Authors: Chen Deliang , Chen Changping , Fu Yiming , Dai Liming
Published: July 2010

By using movable boundary variational principle, a set of nonlinear governing equations for the delaminated circular plate including the transverse shear deformation and contact effect between the delaminations subjected to transverse load are derived and the corresponding boundary and matching conditions are given. At the same time, according to the Griffith criterion, the formulas of total energy release rate and its individual mode components along the delamination front are obtained and the delamination growth is studied. In the numerical calculation, the delamination growth of axisymmetrical laminated circular plates with various delamination radiuses, delamination depths, and the different material properties are discussed.
Authentic Innovation: The Role of Apprenctice Learning in Engineering Education
Authors: Vernon Tanya , Werner Brandon
Published: July 2010

In 2000, the Accreditation Board of Engineering and Technology (ABET) adopted an outcomes based approach to the US engineering curriculum. The new accreditation criteria, commonly called EC2000, call for program outcomes and assessment that provide for a ‘well rounded engineer’. Approaching nearly a decade now, are students reaping the benefits of the reform? Are students able to design better? Apply knowledge of mathematics, science, and engineering better? Are they able to communicate better and use techniques, skills and modern engineering tools necessary for engineering practice? Most importantly, are they more “well-rounded?” It may be argued that despite ABET accreditation reform, the undergraduate mechanical engineering curriculum has remained relatively static over the last decade, adjusting for obvious changes in cross-disciplinary study and some emergent technologies. Girt with hundreds of hours of core and required subjects such as calculus, physics, dynamics, fluid mechanics, strength of materials, thermodynamics, etc. the undergraduate mechanical engineering student generally has but one occasion to flex his/her intellectual and innovative acuity—the senior design project. While students occasionally work in teams, rarely are students exposed to genuine challenges of group interaction, delivery schedules and cost constraints as catalyzed in industry. How is authentic innovation achieved in a learning environment?
Analysis and Optimization of Rectangular Longitudinal and Circular Pin Fins With Space Variable Heat Transfer Coefficient
Authors: Das S. , Razelos P.
Published: July 2010

Extended surfaces, referred in the literature as fins, are usually metallic strips of different shapes and forms. These fins are attached to a primary surface of a structure, for the specific purpose of enhancing the heat transfer between the surface and the surrounding ambient fluid. For the last sixty three years, fins have attracted considerable attention and a vast literature exists on this subject. The aim of this study is to portray the analysis and optimization of rectangular longitudinal and pin fins of cylindrical cross sections. For this purpose a new method of analyzing fins is briefly discussed. Herein, specifically we examine the analysis and optimization of longitudinal fins with linear, exponential and other forms of space variable heat transfer coefficients taken from the existing literature. For pin fins, we examine the case where the heat transfer coefficient depends on the pin fin’s diameter. The results from the optimization process are presented in a concise fashion with practical examples.
Thrust Characterization for Bio-Inspired Pulsatile Vortex Ring Thrusters With Variable Exit Nozzle Diameter
Authors: Thomas Tyler M. , Kreig Mike , Mohseni Kamran
Published: July 2010

The thrust response of a bio-inspired pulsatile vortex ring thruster is explored for variable diameter exit nozzle profiles. Our pulsatile vortex ring thruster is composed of a plunger in a submerged cavity that oscillates to intake and expel fluid through an exit nozzle creating vortex rings which generate thrust. The diameter of the exit nozzle is expanded upon fluid intake to increase volume flow. Upon fluid expulsion the nozzle diameter is reduced to increase flow velocity. This allows for an increase in total thrust. The effect is a thrusting force from a positive net flux in momentum with a zero net flux in mass. This is loosely inspired by jellyfish which utilize the same orifice for both mass intake and expulsion. The thrust is directly measured for multiple diameter profiles. A selected diameter profile is either a constant exit nozzle diameter or a sinusoidal oscillation of exit nozzle diameter that corresponds to the plunger motion. The increase in thrust is analyzed with respect to variable diameter effects and compared to thrust results of constant exit diameter nozzles.
Bilateral Teleoperation With Time Delay Using Modified Wave Variable Based Controller
Authors: Kawashima K. , Tadano K. , Fofana M. S.
Published: July 2010

Very often in teleoperation of surgical robots, we discover that there is some degree of uncertainty in terms of locating critical time delays necessary to establish criteria sustaining stable and safe surgical regimes. Within the stable and safe regimes optimal performance indices and critical time delays combine to deliver a greater motion rhythm for the teleoperation of surgical robots. In this paper, we apply a bilateral controller of the modified wave variable (MWV) type to locate critical time delays maintaining stable and safe teleoperation of a specific surgical robot. The controller implemented additional wave impedance in the wave variable transformations in order to focus more closely on force tracking. The effectiveness of the proposed controller and locate dynamics of specific phenomena that align with the cumulative energy density required to operate the surgical robot are investigated. Firstly, the stability of MWV is investigated in detail. Then, the effect of additional wave impedance is discussed theoretically. Finally, experiments are conducted for three degrees of freedom master and slave manipulators to demonstrate the effectiveness of the MWV. The controller provides superior position and force tracking performance compared to the traditional wave variable-based method. The proposed method can improve position and force tracking errors between the master and slave caused by the communication channel time delay.
Experimental and Numerical Investigations on Drag and Torque Characteristics of Three-Bladed Savonius Wind Turbine
Authors: Rahman Mosfequr , Morshed Khandakar N. , Lewis Jeffery , Fuller Mark
Published: July 2010

With the growing demand of energy worldwide, conventional energy is becoming more and more scarce and expensive. The United States is already facing an energy crunch as the fuel price soars. Therefore, there is an obvious need for alternative sources of energy—perhaps more than ever. Wind is among the most popular and fastest-growing forms of electricity generation in the world, which is pollution free and available almost at any time of the day, especially in the coastal regions. The main attraction of the vertical-axis wind turbine is its manufacturing simplicity compared to that of the horizontal-axis wind turbine. Among all different vertical axis wind turbines, Savonius wind turbine is the simplest one. Operation of the Savonius wind turbine is based on the difference of the drag force on its semi-spherical blades, depending on whether the wind is striking the convex or the concave part of the blades. The advantage of this type of wind turbine is its good self-starting and wind directional independence characteristic. It, however, has a relatively lower efficiency in comparison with the lift type vertical-axis wind turbines. Due to its simple design and low construction cost, Savonius rotors are primarily used for water pumping and wind power on a small scale. The main objective of this ongoing research work is to improve the aerodynamic performance of vertical axis Savonius wind turbine. Wind tunnel investigation has been performed on aerodynamic characteristics, such as drag coefficients, and static torque coefficient of three-bladed Savonius rotor model. Also the computational fluid dynamics (CFD) simulation has been performed using FLUENT software to analyze the static rotor aerodynamics such as drag coefficients and torque coefficient, and these results are compared with the corresponding experimental results for verification.
Entropy Generation Analysis of Microchannel Heat
Authors: Jung Jaehoon , Kim Sung Jin
Published: July 2010

Analytical solutions for entropy generation rate distribution associated with heat transfer and fluid friction in microchannel heat sinks are examined. Microchannel heat sinks are modeled as a porous medium through which fluid flows. Analytical solutions are obtained by using velocity and temperature distributions of microchannel heat sinks, which are based on the modified Darcy model for fluid flow and the two-equation model for heat transfer. Using the analytical solution, the entropy generation of heat sinks was obtained. The effects of height, channel width, and fin thickness on the entropy generation rate were studied and thermal optimization of heat sink was performed.
Thermal Modeling of a Mini Rotor-Stator System
Authors: Dikmen Emre , van der Hoogt Peter , de Boer Andre´ , Aarts Ronald , Jonker Ben
Published: July 2010

In this study the temperature increase and heat dissipation in the air gap of a cylindrical mini rotor stator system has been analyzed. A simple thermal model based on lumped parameter thermal networks has been developed. With this model the temperature dependent air properties for the fluid-rotor interaction models have been calculated. Next the complete system has also been modeled by using computational fluid dynamics (CFD) with Ansys-CFX and Ansys. The results have been compared and the capability of the thermal networks method to calculate the temperature of the air between the rotor and stator of a high speed micro rotor has been discussed.
Mixed Convection and Entropy Generation Characteristics Inside a Porous Cavity With Viscous Dissipation Effect
Authors: Islam A. K. M. Sadrul , Amin M. Ruhul , Barna Shama F. , Bhuiyan Arafat A. , Banna M. H.
Published: July 2010

This paper examines and explains two-dimensional, steady mixed convection flow in a porous square vented cavity. The interaction between the buoyancy stemming from one or more heated elements inside a microstructure filled vented enclosure and an imposed forced flow forms the topic of this investigation. Analysis has been carried out for two different boundary conditions. Initial investigations are carried out for walls of the enclosure being isothermal. A second stage of analysis is performed keeping only the left wall isothermal and other three walls adiabatic. Natural convection takes place due to temperature difference between the isothermal wall and the fluid. Forced convection condition is imposed by providing an inlet and a square vent inside the enclosure filled with fluid saturated porous medium. The mathematical model is developed using modified Darcy flow model and energy equation. Through the adaptation of the well known finite element method, solution to this numerical problem is obtained. Governing parameters chosen are Peclet Number (Pe), Rayleigh Number (Ra), Aspect ratio (AR) and the width of the inlet as a fraction of the width (I/W) of the enclosure. For detailed analysis different value of these parameters such as five Rayleigh Numbers (1, 50, 100, 500 and 1000) and seven different Peclet Numbers (0.1, 1, 5, 10, 20, 50 and 100) are considered. Effect of inlet to cavity width ratio is examined within the range 0.1 ≤ I/W ≤ 0.5 for a particular aspect ratio. The performance of the enclosure in both cases; are determined by flow visualization and by analyzing different parameters such as Bejan Number, Nusselt Number and Entropy Generation Number. Isotherms, streamlines show substantial variation in their pattern or magnitude. Average Nusselt number and average Bejan Number increases whereas Average energy flux density decreases with increasing I/W. These fluctuations also vary for different Rayleigh or Peclet numbers. The results for both the boundary conditions are also compared to find the most effective value of I/W.
Nonlinear Vibrations of Circular Cylindrical Shells With Different Boundary Conditions
Authors: Amabili M. , Kurylov Ye.
Published: July 2010

Large-amplitude nonlinear vibrations of circular cylindrical shells with different boundary conditions are investigated. The Sanders-Koiter nonlinear shell theory, which includes shear deformation, is used to calculate the elastic strain energy. Shell’s displacement fields (longitudinal, circumferential and radial) are expanded by means of a double mixed series: harmonic functions for the circumferential variable; Chebyshev polynomials for the longitudinal variable. Boundary conditions for both simply supported and clamped-clamped shells are exactly satisfied. The Lagrangian approach is applied to obtain a system of nonlinear ordinary differential equations. Different expansions involving from 14 to 34 generalized co-ordinates, associated with natural modes of both simply supported and clamped-clamped shells are used to study the convergence of the solution. The nonlinear equations of motion are studied by using arclength continuation method and bifurcation analysis. Numerical responses obtained in the spectral neighborhood of the lowest natural frequency are compared with the results available in literature.
First Year Engineering Projects to Senior Capstone Design: Are Students Gaining Technical and Professional Skills?
Authors: Kotys-Schwartz Daria , Knight Daniel , Pawlas Gary
Published: July 2010

Innovative curriculum reforms have been instituted at several universities and colleges with the intention of developing the technical competence and professional skills of engineering students. First Year Engineering Project (FYEP), or Freshman Design courses have been integrated into undergraduate engineering curricula across the country. Many of these courses provide students with hands-on engineering opportunities early in the curriculum. Senior Capstone Design (SCD) courses are ubiquitous in engineering programs, incorporating technical knowledge and real-world problem solving. Previous research has shown that project-driven classes like FYEP and SCD increase the professional and technical design skills of students. While research into first year and senior design skills development has been more robust, scant research investigating the transformation of skills between freshman design experiences and senior design experiences has been performed. This research project investigates the longitudinal technical and professional skill development of mechanical engineering students at the University of Colorado at Boulder. An overview of First-Year Engineering Projects and the mechanical engineering Senior Capstone Design project course is detailed. Technical and professional skill objectives are discussed within the paper. Pre and post skill surveys were utilized in both First-Year Engineering Projects and the Senior Capstone Design classes. Initial results indicate that student skills deteriorate between the end of the first-year and beginning of the senior year.