bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonic-Vibration Assisted Pelleting for Cellulosic Ethanol Manufacturing: An Experimental Investigation of Power Consumption
Authors: Zhang Qi , Zhang Pengfei , Pei Z. J. , Wilson Jonathan , McKinney Leland , Pritchett Graham
Published: August 2012

Ethanol produced from cellulosic biomass is an alternative to petroleum-based transportation fuels. However, its manufacturing costs are too high for cellulosic ethanol to be competitive. Cellulosic feedstocks have low density, causing their transportation and storage expensive, contributing to high manufacturing costs of cellulosic ethanol. Pelleting can increase the density of cellulosic feedstocks and reduce their transportation and storage costs. Ultrasonic vibration-assisted (UV-A) pelleting is a new pelleting method. Effects of input pelleting parameters (ultrasonic power, pelleting pressure, and particle size) on pellet quality and sugar yield have been studied. However, the effects of these parameters on power consumption in UV-A pelleting have not been studied. Since power consumption directly affects ethanol manufacturing costs, lower power consumption is desirable. The objective of this paper is to study effects of different input parameters (biomass material, particle size, ultrasonic power, and pelleting pressure) of UV-A pelleting on power consumption. Four types of biomass materials (big bluestem, corn stover, sorghum stalk, and wheat straw) were studied. Sorghum stalk consumed the least power. Pelleting pressure, particle size and ultrasonic power significantly affected power consumption of all four materials. Higher ultrasonic power and pelleting pressure resulted in lower power consumption. In addition, this paper also compares power consumption between UV-A pelleting and ring-die pelleting (a traditional pelleting method).
Surface Functionalization of an Ovarian Cancer Diagnostic Biosensor
Authors: Ahmad Asad , Gallant Nathan , Guldiken Rasim , Onen Onursal
Published: August 2012

Ovarian cancer is the fifth leading cause of death among women in United States and the disease has 1.4% (1 in 71) lifetime risk. Patients with ovarian cancer have a short median survival time after diagnosis with their 5-year survival rate being less than 40%. Early stage ovarian cancer represents an important target for screening since it is lethal in most late stage cases (1). Currently the primary screening procedure for ovarian cancer are blood levels of cancer antigen (CA) 125, however CA 125 levels can also be elevated due to other disorders and do not provide conclusive results (2). Utilizing the research done at the Cell and Molecular Biology department at the University of South Florida which conclusively revealed that urinary levels of bcl-2 are elevated in ovarian cancer patients (3), this research it the first of its kind looking to assess the capture of an analyte protein on a series of potential bioconjugated surfaces for use in a novel acoustic biosensor. Therefore, this research addresses the need for a reliable and economic testing platform to detect ovarian cancer.
Investigation of High Performance Heat Sink Characteristics in Forced Convection Cooling of Power Electronic Systems
Authors: Karimi-Moghaddam Giti , Rende Craig , Gould Richard D. , Bhattacharya Subhashish
Published: August 2012

This study presents the experimental performance of a high fin density heat sink for semiconductor power modules — such as IGBTs. As a case study a commercially available extruded heat sink has been chosen. By analyzing the steady-state maximum temperatures as well as various geometric orientations, Nusselt number correlations were found experimentally, which can be used to predict the performance of the heat sink. It was found that the experimental Nusselt number correlations can predict the performance of the heat sink to within a 10%. Furthermore, steady-state maximum temperature results showed that for low fan speeds (2 m/s–3 m/s), the device junction temperatures achieved a value no higher than 80°C, which is well below the junction temperature limit for 125°C for silicon power semiconductor devices. Furthermore, it was shown that for two heat sinks in series forced convection tests, gap spacing between the devices has a minimal effect on the overall performance. Also, a numerical simulation study using COMSOL Multiphysics simulation software to study flow and temperature fields has been conducted. These modeling results the thermal behavior of heat sink are validated by experimental measurements.
Kinematics and Tip-Over Stability Analysis for a Hybrid Serial-Parallel Mobile Manipulator
Authors: Souza-Jimenez Jose Antonio , Gonzalez-Villela Victor J.
Published: August 2012

This paper shows the geometry and the kinematical model for a compounded serial-parallel wheeled mobile manipulator. The parallel manipulator, Stewart Platform, is an interface that helps the whole system to accomplish stable motion when handling heavy objects and to improve mobility over uneven-terrain by repositioning their center of mass. To evaluate the possibility of tip over, a stability analysis is performed; some criteria are established. Computer simulations and experiments are carried out and the influences of different robotic postures on the tip-over stability are analyzed through simulation results.
Modeling Articulated Human Body Dynamics Under a Representative Blast Loading
Authors: Tan X. G. , Przekwas Andrzej J. , Rule Gregory , Iyer Kaushik , Ott Kyle , Merkle Andrew
Published: August 2012

Blast waves resulting from both industrial explosions and terrorist attacks cause devastating effects to exposed humans and structures. Blast related injuries are frequently reported in the international news and are of great interest to agencies involved in military and civilian protection. Mathematical models of explosion blast interaction with structures and humans can provide valuable input in the design of protective structures and practices, in injury diagnostics and forensics. Accurate simulation of blast wave interaction with a human body and the human body biodynamic response to the blast loading is very challenging and to the best of our knowledge has not been reported yet. A high-fidelity computational fluid dynamic (CFD) model is required to capture the reflections, diffractions, areas of stagnation, and other effects when the shock and blast waves respond to an object placed in the field. In this effort we simulated a representative free field blast event with a standing human exposed to the threat using the Second Order Hydrodynamic Automatic Mesh Refinement Code (SHAMRC). During the CFD analysis the pressure time history around the human body is calculated, along with the fragment loads. Subsequently these blast loads are applied to a fully articulated human body using the multi-physics code CoBi. In CoBi we developed a novel computational model for the articulated human body dynamics by utilizing the anatomical geometry of human body. The articulated human body dynamics are computed by an implicit multi-body solver which ensures the unconditional stability and guarantees the quadratic rate of convergence. The developed solver enforces the kinematic constraints well while imposing no limitation on the time step size. The main advantage of the model is the anatomical surface representation of a human body which can accurately account for both the surface loading and the surface interaction. The inertial properties are calculated using a finite element method. We also developed an efficient interface to apply the blast wave loading on the human body surface. The numerical results show that the developed model is capable of reasonably predicting the human body dynamics and can be used to study the primary injury mechanism. We also demonstrate that the human body response is affected by many factors such as human inertia properties, contact damping and the coefficient of friction between the human body and the environment. By comparing the computational results with the real scenario, we can calibrate these input parameters to improve the accuracy of articulated human body model.
Bubble Formation on Superhydrophobic Micropatterns
Authors: Wang Xinwei , Zhao Siwei , Wang Hao , Pan Tingrui
Published: August 2012

In this paper, boiling phenomena on a copper surface coated with superhydrophobic micropatterns have been investigated. The micropatterns consisted of chemically inert nanoparticles (PTFE) were in square patterns 180 μm on each side with contact angles above 150° for the superhydrophobic behavior. Boiling experiments were conducted on the patterned copper surface with or without degassing treatment prior to heating, from which bubbles were found to form only on the superhydrophobic sites. As controlled experiments, a uniformly-coated superhydrophobic surface as well as a bare copper surface was also tested in comparison.
A Computational Validation of Turbine Nozzle Guide Vane Aerodynamic Experiments in an HP Turbine Stage
Authors: Turgut O¨zhan H. , Camcı Cengiz
Published: August 2012

A computational validation study related to aerodynamic loss generation mechanisms is performed in an axial flow turbine nozzle guide vane (NGV). The 91.66 cm diameter axial flow turbine research facility has a stationary nozzle guide vane assembly and a 29 bladed HP turbine rotor. The NGV inlet and exit Reynolds numbers based on midspan axial chord are around 300000 and 900000, respectively. The effect of grid structure on aerodynamic loss generation is investigated. GAMBIT and TGRID combination is used for unstructured grid, whereas GRIDPRO is the structured grid generator. For both cases, y+ values are kept below unity. The finite-volume flow solver ANSYS CFX with SST k–ω turbulence model is employed. Experimental flow conditions are imposed at the boundaries. The flow transition effect and the influence of corner fillets at the vane-endwall junction are also studied in this paper. Grid independence study is performed with static pressure coefficient distribution at the mid-span of the vane and the total pressure coefficient at the NGV exit. The velocity distributions and the total pressure coefficient at the NGV exit plane are in very good agreement with the experimental data. This validation study shows that the effect of future geometrical modifications on the endwalls and the vane will be predicted reasonably accurately. The current study shows that an accurately measured turbine stage geometry, a properly prepared block structured/body fitted grid, a state of the art transitional flow implementation, and realistic boundary conditions coming from high resolution turbine experiments are all essential ingredients of a successful NGV aerodynamic loss quantification via computations.
Wall Material Effect on Total Conduction Heat Gain of Office Buildings in Hot and Dry Climate
Authors: Bahrami A. , Aidun D. K. , Marzocca P. , Valentine D. T.
Published: August 2012

The large difference between maximum and minimum daily temperatures and considerable amount of solar heat gain are characteristics of hot and dry climate. In this situation walls and roof of a building act as thermal storage elements which store heat during the day and remove it at night therefore the direction of heat transfer can change throughout a day. This should be considered in total conduction heat gain calculation. In the present study the effect of wall and insulation material is studied in a simple office building. Outside temperature is considered to change periodically with time. In addition, the outside surface of the wall is considered to be exposed to the sun during day light. A one-dimensional transient heat conduction equation with time dependent boundary conditions is solved numerically using the Crank-Nicolson method. Different wall materials and insulations were investigated in order to find the best insulation and material from total conduction heat gain viewpoint. It is shown that by using proper materials and location of insulation within the wall the heat gain and energy cost can be decreased considerably.
Contact Angle Measurement Through Atomic Force Microscopy
Authors: Yu Jiapeng , Wang Hao
Published: August 2012

Understanding the structure near the three-phase contact line is critical for a comprehensive understanding of the thin-film region when a liquid partially wets a planer substrate. Despite numerous theoretical and simulation efforts found literature, an accurate experiment is difficult to conduct because of how small its scale. In the present work the accurate geometry of the region near the three-phase contact line was obtained by directly scanning the thin-film region with atomic force microscopy (AFM). The contact angles were directly extracted from the results and compared with the ones measured from traditional optical methods.
A Nonaxisymmetric Endwall Design Methodology for Turbine Nozzle Guide Vanes and its Computational Fluid Dynamics Evaluation
Authors: Turgut O¨zhan H. , Camcı Cengiz
Published: August 2012

Nonaxisymmetric endwall contouring has recently become one of the ways to minimize the secondary flow related losses in a turbine nozzle guide vane (NGV) passage. In this study, a specific nonaxisymmetric endwall contouring design methodology is introduced. Fourier series based splines at different axial locations are generated and combined with the help of stream-wise B-splines within solid modeling program. Eight different contoured endwalls are presented in this paper. Computational study of these designs are performed by the finite-volume flow solver. The SST k–ω turbulence model is selected and a body-fitted structured grid is used. Total pressure distribution at the NGV exit shows that contouring the endwall effectively changes the results. Among from these various designs, the most promising one is with the contouring extended in the upstream of the vane leading edge. Mass-averaged value of 3.2% total pressure loss reduction is achieved at the NGV exit plane. The current study was performed in a rotating turbine rig simulating a state of the art HP turbine stage. An NGV only simulation is performed. This approach is helpful in isolating rotor-stator influence and the possible upstream flow modifications of the rim seal cavity flow existing in the rotating turbine research rig. The investigation including the rotor-stator interaction and rim seal cavity flow is the topic of a subsequent paper currently under progress.
Configuration Optimization of Cross Wave Primary Surface Sheet in the Recuperator Using Particle Swarm Algorithm
Authors: Ma T. , Chen Y. T. , Zhang D. J. , Ji Y. P. , Zeng M. , Wang Q. W.
Published: August 2012

Highly efficient and compact primary surface recuperators are widely used in the microturbine system. However, creep deformation may occur in the passages of the primary surface sheet due to its thin thickness and long operating time. In this paper, the stress and creep deformation of cross wave (CW) primary surface sheet operating for 40000h is numerically studied. In order to improve the creep resistance, the configuration optimization of CW primary surface sheet is carried out using the APDL language in the software ANSYS combined with additional particle swarm optimization (PSO) algorithm. With the object function of minimum creep deformation, the optimal configuration of the CW primary surface sheet is recommended. Compared with the baseline design, the von mises stress and total deformation of the optimal configuration are decreased by 55% and 41%, respectively. The results indicate that the procedure based on PSO algorithm has a significant potential to reduce the creep deformation and it is recommended to be used for configuration optimization.
Performance of a Turbine Driven by a Pulsed Detonation Combustor
Authors: Rouser Kurt P. , King Paul I. , Schauer Frederick R. , Sondergaard Rolf , Hoke John L.
Published: August 2012

There is longstanding government and industry interest in pressure-gain combustion for use in Brayton cycle-based engines. Theoretically, pressure-gain combustion allows heat addition with reduced entropy loss. The pulsed detonation combustor (PDC) is a device that can provide such pressure-gain combustion and possibly replace the typical steady deflagration combustor. The PDC is inherently unsteady, however, and comparisons with steady deflagration combustors must be based upon time-integrated performance variables. In this study, the radial turbine of a Garrett automotive turbocharger was coupled directly to and driven, full admission, by a hydrogen-fueled PDC fueled. Data included pulsed-cycle time histories of turbine inlet and exit temperature, pressure, velocity, mass flow, and enthalpy. The unsteady inlet flowfield showed momentary reverse flow, and thus unsteady accumulation and expulsion of mass and enthalpy within the device. The coupled turbine-driven compressor provided a time-resolved measure of turbine power. Duty cycle increased with PDC frequency. Power and cycle-average specific work increased with PDC frequency and fill fraction.
Adhesive and Mechanical Properties of Carbon Nanotube Probes Contacting Chemically-Treated Surfaces
Authors: Barker Kane M. , Ferri Al , Bottomley Lawrence A.
Published: August 2012

Carbon nanotubes are useful in a variety of measurement applications. In the case of Atomic Force Microscopes (AFMs), carbon nanotubes can be affixed to the tip of the AFM cantilever to improve image resolution and enable images of surfaces with deep crevices and trench structures. In this paper, the mechanical response of long, straight, small walled carbon nanotubes (SWNTs) under compressive and tensile load is examined with an atomic force microscope. Multi-dimensional force spectroscopy (MDFS) is used to simultaneously measure the cantilever resonant frequency, deflection, and scanner motion. The acquired force curves reveal that the SWNT buckles shortly after contact is initiated. As the scanner continues to rise and then reverses direction, the SWNT undergoes a number of adhesion/sticking episodes, buckling, and slip events. The bulk properties of the nanotube are estimated by measuring the shift in natural frequency during tension. Finally, the carbon nanotube is modeled as an elastica in order to predict the post-buckled shape of the SWNT. By comparing the model results with MDFS results, the static coefficient of friction between the SWNT and a variety of surfaces is estimated. The study suggests that MDFS has a wide applicability for studying the mechanical and adhesive properties of various nanotubes, nanorods and nanofibers.
A Method for Detecting the Occurrence of Chainsaw Kickback
Authors: Arnold Drew , Parmigiani John
Published: August 2012

One of the most dangerous phenomena associated with chainsaw use is kickback. This occurs when the upper quadrant of the chainsaw bar’s tip catches on the work-piece, accelerating the saw toward the user. Safety devices currently installed on chainsaws rely on the rotational acceleration of the saw to move a difficult-to-design mechanical linkage and activate a band brake. Even with a well-designed braking linkage, the saw must rotate through a large angle (approximately 45°) before actuating the brake. A more effective kickback detection and chain-braking system is needed—one that is capable of (i) early detection of the kickback event and (ii) rapid braking of the moving chain. This paper deals with a method of detecting such a kickback event. The approach taken in this work determines the key kinematic parameters associated with kickback using an electronics package of accelerometers and a gyroscope attached to a typical chainsaw. Testing consisted of (i) performing a series of normal cuts through wooden poles, and (ii) purposely initiating kickback via several common scenarios. Data analysis consisted of comparing magnitude, duration, and frequency of sensor output between normal cutting and kickback scenarios. After data filtering, a method of scaling factor variation was used to extract the optimum detection algorithm of a single gyroscope with appropriate signal conditioning, Kickback is detected within 30 milliseconds, before the saw loses contact with the work-piece. The gyroscope magnifies the signal corresponding to the kickback event while attenuating signals corresponding to normal use. This method presents the possibility of a significantly improved chainsaw kickback control system.
Hydrogenation of Magnesium Nanoblades: The Effect of Concentration Dependent Hydrogen Diffusion
Authors: Yang Bo , He Yuping , Zhao Yiping
Published: August 2012

By assuming the H diffusion coefficient and H adsorption rate to be exponentially and linearly dependent on H concentration, a physical model is developed to predict the hydrogenation process of Mg nanoblades. The predicted H uptake curves agree well with the experimental data from V-coated Mg nanoblades. The obtained H diffusion coefficients in MgHx between Mg and MgH2 have nearly three orders of magnitude variation. The characteristic time of H surface adsorption is longer than that of H diffusion in Mg but shorter than that in MgH2 for 100 nm thick nanoblades. Thus, as it proceeds, the hydrogenation process gradually changes from surface reaction-limited to diffusion-limited. In both one- and two-dimensional simulations, it is shown that a hydride shell is not formed during hydrogenation. In contrast, a hydride core is formed during dehydrogenation. The strong (exponential) concentration dependence of H diffusion coefficient throws profound influence on the stability and instability of a diffusion front, i.e., a H diffusion front in hydrogenation, and a H-vacancy diffusion front in dehydrogenation. In the latter case, the front tends to corrugate forming islands when the H2 release rate is high.
Bioinspiration From Biodiversity in Sensor Design
Authors: Mu¨ller Rolf , Ma Jianguo , Yan Zhen , Grimm Cindy , Mio Washington
Published: August 2012

Biodiversity is a notable outcome of biological evolution. In the process of adaptive radiation, functional principles of sensing in biology have been adapted to suit different tasks and constraints. The biosonar system of bats is an example of such an adaptive radiation in sensing that also offers particularly advantageous conditions for a biodiversity-level analysis of adaptation principles with potential engineering relevance. The beam-forming capabilities of bat biosonar are tied to the geometries of external baffle structures, i.e., the outer ears used for reception and the noseleaves used to shape the emitted biosonar pulses. Since the geometries of these baffles determine their functions, which in turn can also be expressed by a shape (the beampattern), biosonar beamforming can be described by two interrelated shape spaces, one for biological form and the other for biological function. A shape space representation for the outer ears can be obtained by a cylindrical transform of the ear surfaces followed by principal component analysis. The results of this analysis are in a form that is suitable to inform the design of technical baffle shapes. However, additional analysis methods need to be developed for noseleaves, beampatterns, as well as the link between form and function.
Effect of Prismatic Skylight on the Power Consumption and Air-Conditioning Loads
Authors: Munera Sebastian , Tao Yong X.
Published: August 2012

The use of Prismatic Skylights and its effects as a passive Energy Conservation Strategy in “Residential” and “Big Box Commercial Buildings” in hot and humid climate has been evaluated throughout this project. The potential benefits of using skylights reside in the fact that it reduces electrical lighting necessities but at the same time it contributes to an upsurge of the Cooling Loads of the conditioned space. Acknowledging the impact of skylights is fundamental to elaborate an optimized design of a building’s energy efficient mechanical system. To reach a sound conclusion, the evaluated buildings were modeled and their performance was simulated using the Department of Energy Simulation Program “Energy Plus”. To be able to compare the Energy Conservation Measure case (Using Skylights) with the Base Line (No Skylights), a photometric sensor was modeled to ensure that both cases sourced the same amount of light visible in the electromagnetic spectrum. Considering the Heating, Cooling and lighting energy consumption as variables, the variance between the ECM and the Base line for the residential case was 5% more energy consumption with skylights. For the Big Box Commercial Building there was a 5% deduction in energy consumption in the ECM case using 5% roof area covered with skylights. The results obtained from this investigation reveal a very promising effect in the implementation of skylights in “Big Box Commercial Buildings”, but not so optimistic in the case of “Residential Buildings” for hot and humid climate as shown by the simulation and monitoring data from the experimental case.
Influence of Nanochannel Inlet Structure Upon DNA Capture Ratio
Authors: Wu Jiahao , Wang Hong , Kim Jinsoo , Murphy Freddy , Soper Steven A. , Park Sunggook
Published: August 2012

DNA molecule will be stretched to its near full contour length inside a nanochannel when the channel diameter is less than the DNA persistence length.1–3 It provides the possibility of real time lab-free-analysis of analysis, such as screening of sequence variations of DNA molecules.3 The key process for this nanochannel-based analysis is to drive DNA molecule electrophoretically through the nanochannel and read out the information of the DNA chain while it is passing the channel.2, 3
The Combustion Characteristics of n-Decane/Iso-Octane/Toluene Mixture and Jet-A Fuel Droplets in the Absence of Convection
Authors: Liu Yu-Cheng , Savas Anthony J. , Avedisian C. Thomas
Published: August 2012

This study examines the extent to which a ternary mixture of n-decane/iso-octane/toluene in the specific mixture fraction of 42.67/33.02/24.31 (mole fraction), respectively, can replicate the droplet burning characteristics of an aviation fuel, Jet-A (designated by the Air Force as “POSF4658”). Experiments were carried out to examine the droplet combustion characteristics in an environment which minimizes convection to promote spherical symmetry in the burning process. The evolution of droplet diameter, burning rate and flame and soot stand-off ratios were compared to Jet-A to evaluate the potential of this ternary to serve as a Jet-A surrogate regarding the droplet burning process. The results show that the ternary blend has a shorter transient droplet heating period than Jet-A and it closely replicates the evolution of droplet diameter and burning rate. The burning rates for these two fuels are close at the end of burning, and flame and soot standoff ratios for the ternary are also reasonably close to those of Jet-A. The results also suggest that the spherical droplet flame configuration can be a useful tool to evaluate the extent to which a mixture of single component fuels may serve as a surrogate of a real transportation fuel.
A Product Realization Approach to Creativity in Engineering Education
Authors: El-Sayed Mohamed E. M. , El-Sayed Jacqueline A. J.
Published: August 2012

Product realization, which is the goal of any product development process from concept to production, usually means bringing a product to physical reality. Problem solving and design are two of the engineering activities for achieving the product development process goal. For this reason engineering education efforts are usually focused on problem solving as a building block for any educational course or program activities. In addition, some courses and curriculum threads are usually dedicated to design education and practices. The common restriction of realization to mean physical reality, however, limits the full understanding and potential of better problem solving and design education in engineering. In this paper, the realization process is expanded to include the virtual and perceptual realities as valid domains of the product realization process. These domains of realization and their interactions with the physical reality are studied. Also, the relationships between research, problem solving, and design are examined in the context of engineering product realization. Focus, in this study, is directed to the understanding of research, engineering problem solving, and design activities as a result of the expanded realization concept. This understanding aims at improving engineering education by focusing on the key issue of creativity in program and course design, delivery, and assessment. To illustrate the concepts, presented in the paper, several examples are included.
An Interactive Design Space Supporting Development of Vehicle Architecture Concept Models
Authors: Osborne Gary , Prater Glen , Lesiv Rostyslav , Lamb David , Castanier Matthew
Published: August 2012

Due to a lack of suitable analysis tools, automotive engineers are often forced to forego quantitative optimization early in the development process, when fundamental decisions establishing vehicle architecture are made. This lack of tools arises because traditional analysis models require detailed geometric descriptions of components and assembly joints in order to yield accurate results, but this information is simply not available early in the development cycle. Optimization taking place later in the cycle usually occurs at the detail design level, and tends to result in expedient solutions to performance problems that might have been more effectively addressed at the architecture level. Alternatively, late-cycle architecture changes may be imposed, but such modifications are equivalent to a huge optimization cycle covering almost the entire design process, and require discarding the detail design work used originally as the basis of the NVH model. Optimizing at the architecture level can both shorten and improve the results of a vehicle development process. In this paper we describe the requirements and implementation of a user interface for a software package supporting vehicle architecture conceptual design and analysis.
Dispersion of Particles on Liquid Surfaces
Authors: Pillapakkam Shriram B. , Singh Pushpendra
Published: August 2012

In a recent study we have shown that when small particles, e.g., flour, pollen, glass, etc., contact an air-liquid interface, they disperse rapidly as if they were in an explosion. The rapid dispersion is due to the fact that the capillary force pulls particles into the interface causing them to accelerate to a large velocity. The vertical motion of a particle during its adsorption causes a radially-outward lateral (secondary) flow on the interface that causes nearby particles to move away. We present direct numerical simulation results for the adsorption of particles and show that the inertia of a particle plays an important role in its motion in the direction normal to a fluid-liquid interface. Although the importance of inertia diminishes with decreasing particle size, on an air-water interface the inertia continues to be important even when the size is as small as a few nanometers.
A Review of Fuzzy Logic Based Control of Robotic Manipulators
Authors: Khurpade Jayant B. , Dhami Sukhdeep S. , Banwait Sukhwant S.
Published: August 2012

Robotic manipulators are complex mechanisms due to which their kinematics and dynamics are nonlinear in nature and computationally intensive. Fuzzy logic based approach provides an alternative for modeling and control of non-linear systems and hence has been extensively applied in the field of robotics. This paper presents a review of fuzzy logic based techniques for modeling and control of robotic manipulators. The survey is reported in terms of objectives, types of robotic manipulators, types and structures of fuzzy systems employed. A summary of quantitative results is presented as performance indicators of fuzzy modeling and control of robotic manipulators.
Cellular Photosynthetic Rate of Fully and Partially Pigmented Chlamydomonas reinhardtii as a Function of Irradiance
Authors: Murphy Thomas E. , Berberog˘lu Halil
Published: August 2012

This paper reports the cellular photosynthetic rates of the green algae Chlamydomonas reinhardtii wild strain and its truncated chlorophyll antenna transformant, tla1, as a function of local irradiance. It is hypothesized that reduction in the pigmentation of algae cells can enhance light peneration in mass cultures and increase productivity. Thus, an experimental setup was designed to expose each cell within planktonic algae cultures to a nearly uniform irradiance. An oxygen microsensor was used to monitor the photosynthetic rate as the irradiance onto the sample was varied. The results showed that the cellular photosynthetic rate of the wild strain, CC125, was greater than that of tla1 at all irradiances, by a factor that ranged from 1.7 to 4. Photoinhibition was observed in both strains, although the effect was more pronounced in CC125. Although less pigmented cells enable deeper light penetration in photobioreactors, their reduced phosotynthetic rate can negate this benefit.
Online Thermal Properties Database for Structure-Property Correlated Materials
Authors: Srivastava Ishan , Fisher Timothy S. , Fernando Sudheera , Catlin Ann Christine , Gupta Puneet , Rao Preeti S.
Published: August 2012

New data for thermophysical properties of materials are being discovered and measured routinely throughout the world, but sometimes conflicts exist in the published data from various sources. We introduce an online thermal properties database intended for use as a repository for experimentally obtained thermophysical properties of materials by researchers across the globe. This online database is a part of www.thermalhub.org, which is a NSF-funded cyber infrastructure initiative aimed at serving the global heat transfer community. The relevant details associated with an experiment, such as the material type and composition, the thermophysical property measured, the test methods employed, the test conditions of the experiment, the results of the experiments, the uncertainty associated with the experimental results, and the literature where the results are published, are included as fields in the online database. It is known that one thermophysical property can be tested by various methods whose results may differ. Similarly, one thermophysical property can be experimentally measured under varying test conditions to produce different results.
Thermodynamic Analyses of Single Brayton and Combined Brayton–Rankine Cycles for Distributed Solar Thermal Power Generation
Authors: Dunham Marc , Lipinski Wojciech
Published: August 2012

This paper explores the theoretical efficiencies of single Brayton and combined Brayton-Rankine thermodynamic power cycles for distributed solar thermal power generation. Thermodynamic analyses are conducted for the nominal solar power input to the receiver of 75 kW, concentration ratio in the range 50–100 suns, and for selected heat transfer fluids including air, argon, carbon dioxide, helium, and hydrogen for the Brayton cycle and for the topping cycle of the combined system. C6-fluoroketone, cyclohexane, n-pentane, R-141b, R-245fa, HFE-7000, and steam are examined as working fluids in the bottoming segment of the combined cycle. A single Brayton cycle is found to reach a peak efficiency of 13.3% with carbon dioxide and 100 suns solar input. The four top-performing Brayton cycle fluids are examined as topping cycle fluids in the combined cycle. Each of the four fluids is paired with seven potential bottoming fluids, resulting in 28 heat transfer fluid configurations. The combination of the Brayton topping cycle using carbon dioxide and the Rankine bottoming cycle using R-141b gives the highest thermal efficiency of 22.3% for 100 suns.
Analytical Thermal Model of a Generic Multi-Layer Spacerless 3D Package
Authors: Rodrigo Nuwan , Ghalambor Saeed , Haji-Sheikh Abdolhossein , Agonafer Dereje
Published: August 2012

The need for more functions in a single device has led to die stacking architecture. Although the number of die increases further to accommodate package functionality, the overall package dimensions have not increased; they have stayed the same or decreased (roughly 1.4mm). If this trend continues, in order to keep the same package height, alternate stacking structures need to be investigated. One such opportunity is the spacerless die stacking architecture. Using dummy silicon spacers add to the cost of a package and do not increase the memory or functionality, although they serve as enablers for wire bonding of same size die. Spacerless architecture reduces the package height by eliminating spacers or dummy die. This allows for an increased number of active die to be stacked directly on one another without changing the overall package height, or in some cases reducing the package height. Previous work [1] has been done to develop a steady-state heat conduction model in a two-layer body. This analytical model will be extended to the current multi-layered generic spacerless three dimensional packages (3DP) enabling the computation of temperature for uniform or non-uniform powered die. The computation will account for the contact resistance created by the die attach and the solder balls. Finally validation of this analytically developed model will be carried out with a numerical model.
Scatter of Bolt Preloads in Pipe Flange Connection Tightened by Impact Wrench and the Effect on Sealing Performance
Authors: Kondo Koji , Omiya Yuya , Kobayashi Takashi , Sawa Toshiyuki
Published: August 2012

Pipe flange connections have been used in chemical plants, petro-chemical industry and so on. They are tightened with a lot of bolts and nuts by torque wrench, impact wrench and so on. When the impact wrench is used for tightening a lot of bolts and nuts in pipe flange connection with gaskets, it is well known that a large scatter is assumed to occur in tightening the lots of bolts in the connection using the impact wrench. In the present paper, the scatter in bolt preloads in a pipe flange connection with 20″ nominal diameter using impact wrenches was measured. The ratio of the maximum and the minimum bolt force is called the tightening coefficient. The tightening coefficient is calculated taking into account the interference of the adjacent bolts. The value of the coefficient is compared with the measured results obtained from torque wrench tightening. Then, FEM calculation for analyzing the gasket stress distribution in the process of bolt tightening is carried out. Using the obtained gasket stress distribution and the data obtained from the fundamental gasket characteristics, an amount of leakage is estimated. In addition, the bubble leak testing was carried out. The estimated result is in a fairly good agreement with the measured result. Discussion is made on the tightening coefficient by impact wrenches and the effect of the scatter in bolt preloads on the sealing performance.
Quality Factors of Crystalline Semiconductor Nanocomposite Resonators
Authors: Chakravarthy Puroorava , Li Gang
Published: August 2012

A nanocomposite can generally be regarded as a solid combining a bulk matrix and nano-scale phases. The phases can be nanoparticles, nanowires, nanoplatelets and etc. The addition of nanosized phases into the bulk matrix can lead to significantly different material properties compared to their macrocomposite counterparts. In this work, we investigate the characteristics of energy dissipation in nanocomposite resonators. By using classical molecular dynamics (MD), we calculate the quality factors of layered and fibrous crystalline semiconductor nanocomposite resonators. Key factors that determine the quality factor of the nanocomposite resonators are identified and analyzed.
Probabilistic Multibody Modeling of Gearboxes for Wind Turbines
Authors: Alemayehu Fisseha M. , Ekwaro-Osire Stephen
Published: August 2012

Gearboxes have been prone to early failure rather than any mechanical part of modern wind turbines, much earlier than their predicted design life. Some studies indicated that gearboxes of wind turbines fail during the first 3 to 5 years of operation of the system as opposed to the total design life of the wind turbine, which usually is 20 years. Consequently, such failures cause the highest down time and extremely expensive replacement activities. Gearboxes are subjected to torsional, bending and axial wind loads which are yet not fully defined. The uncertainty in loading conditions and system design parameters has brought about the importance of considering probabilistic design and modeling approach than the traditional deterministic approach. Accordingly, the motivation of this study is to improve the reliability of gearboxes for wind turbine applications. A probabilistic multibody dynamic modeling of the gearbox, that fully integrates uncertainties in wind loading and design parameters, is sought. This paper presents previous studies and finally proposes the above mentioned approach as a potential way of improving, in general, the reliability of wind energy and, in particular, the gearboxes in wind turbines.
Probabilistic Analysis of Steel Roof Damage From Hail Strike
Authors: Shimek Evan , Ekwaro-Osire Stephen , Rasty Jahan
Published: August 2012

In this paper, two probabilistic analyses are performed to try to gain a better understanding of the damage inflicted on galvanized roofs from hail strikes. The first analysis addresses the probability that a hailstone will have the energy required to cause yielding in steel sheets. The second probability study lays the theoretical groundwork for determining the probability of a loss in structural integrity of the steel roof. Data and equations are combined from various sources to create a separate limit state function for each analysis. The probabilistic analyses are performed in NESSUS. For determining probability of yielding, an energy related method for determining stress in an impacted plate is used in conjunction with LS-DYNA finite element software to discover that all perpendicular hail strikes will induce some degree of plastic deformation on simply supported steel sheets in the gauge range of galvanized steel roofs. More data is still required for successful determination of probability of a loss in structural integrity, but the foundation is established, which would allow probabilistic determination of the most economic roof gauges in a given region. There appears to be a logarithmic relationship between the analytically determined initial impact force of a hailstone and the indentation diameter that remains after striking in which the thickness of the sheet plays an important role, but more data points need to be collected to verify this.
Ultra-High Thermal Conductivity Polyethylene Nanofibers
Authors: Shen Sheng , Tong Jonathan , Zheng Ruiting , Chen Gang
Published: August 2012

Highly stretched polyethylene nanofibers are demonstrated to have thermal conductivities as high as ∼ 100 W/m.K along the fiber direction, which is comparable to many metals and is 3 orders of magnitude larger than the typical thermal conductivity of bulk polymers. The high thermal conductivity is attributed to the restructure of polymer chains in nanofibers by stretching, which improves the fiber quality toward the “ideal” single crystalline fibers. Our results suggest that high thermal conductivity polyethylene nanofibers may be able to serve as a cheaper alternative to conventional metal-based heat transfer materials in a wide range of applications.
Observation of Surface Structure of Kyo-Kawara (Ceramic Material for Roof Component) Fabricated by Traditional Skillful Technique
Authors: Asada Masahisa , Sakata Masaki , Shiono Takeshi , Takai Yuka , Goto Akihiko , Hamada Hiroyuki
Published: August 2012

Kyo-gawara is one of traditional crafts, one of Japanese roof tile made in Kyoto by using traditional techniques. The characteristics of Kyo-gawara is gloss on surface available in “Migaki” process. Migaki process is that craftsman strokes half-dry surface with paddle one by one. Number of products that a craftsman has to finish the process is decided. In previous study, investigation about the relationship between number of times of Migaki process and surface properties of Kyo-gawara cannot be seen [1]. In this study, specimens having different number of time of Migaki process (none, once, twice) were used, surface structure and properties were analyzed, and investigation about the relationship between Migaki process and surface characteristics was performed. Measurement items are surface roughness (Ra), contact angle, water absorption. As a result, surface roughness tended to decrease, and with increase of number of times of Migaki process. From the result of measurement of contact angle and water absorption, it was clarified that Migaki could improve waterproofness.
Modeling and Fabrication of Hollowed Scaffolds With Interconnected Variational Porosity Architecture
Authors: Khoda Bashir , Ozbolat Ibrahim T. , Koc Bahattin
Published: August 2012

This paper presents a novel computer-aided modeling of 3D hollowed tissue scaffolds with a controlled internal architecture. Functionally gradient variational porosity architecture is proposed with continuous material deposition planning scheme. The complex internal architecture of scaffolds is discritized into sub-regions accumulated from ruling lines that are generated from outer to inner features. The desired pore size and hence the porosity have been achieved by geometrically partitioning those sub-regions based on the area while meeting the tissue scaffold design constraint. Thus the desired controlled variational porosity along the scaffold architecture has been achieved with the combination of two geometrically oriented consecutive layers. A continuous, interconnected and optimized tool-path has been generated for both layers aiming at the standard solid free form fabrication process. A zigzag pattern tool-path has been proposed for accumulated sub-region layer. And a concentric spiral like optimal tool-path pattern has been derived for the successive layer to ensure fabricatable continuity along the structure. A micro-nozzle biomaterial deposition system driven by NC motion control has been used to fabricate sample designed structure with desired pore size and porosity level. Besides proper characterization of the fabrication sample has been performed to validate the proposed methodology. Moreover a comparative study between proposed design and conventional cartesian coordinate scaffolds has been performed. The results demonstrate significant reduction in design error with the proposed method.
Simulations of Impulsive Dynamics in RF MEMS Capacitive Switches
Authors: Venkattraman Ayyaswamy , Alexeenko Alina
Published: August 2012

Radio Frequency Micro-Electro-Mechanical Systems (RF MEMS) have emerged as a promising enabling technology for low-cost and low-power switches, actuators, and sensors. However, the reliability of these devices, especially those involving repeated contacting events, remains a major stumbling block for their widespread adaptation. In this work we present dynamic simulations of RF MEMS switch response due to electrostatic actuation in the presence of gas damping and residual stress. The dynamics emerging from the interaction between the beam structure and gas environment shows generation of stress waves induced by contact. It has been observed that these impulsive effects could lead to transient stresses that are significantly greater than the steady state bending stress. S-N curves for LIGA Nickel are used to make predictions for the lifetime at various voltages and operating gas pressures that show pressure dependence consistent with earlier experimental observations.