bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability in Variable-Pitch Milling Regarding Regenerative Chatter
Authors: Olgac Nejat , Sipahi Rifat
Published: April 2008

The regenerative chatter in milling process is studied for two different variable-pitch cutters one with (a) four flutes and the other with (b) six flutes. The cutting dynamics of the process is evaluated from stability perspective. Mathematically, the problem is recognized in a general class of delay differential equations (DDE) with multiple delays, whose stability can be analyzed by a recent stability analysis methodology called the Cluster Treatment of Characteristic Roots, CTCR. This method proves to be very beneficial to surface two critical aspects of the process, which maintain chatter-free cutting: (i) the pitch angle geometry of the cutting tool and (ii) admissible cutting conditions to determine the depth-of-cut and the spindle speeds. Case studies are provided to demonstrate the capabilities.
Spontaneous Crack Propagation Along Functionally Graded Bimaterial Interfaces
Authors: Kubair Dhirendra V. , Bhanu-Chandar B.
Published: April 2008

The effects of spatially varying the material properties on the mode-3 planar crack propagation characteristics are numerically investigated. The spectral scheme that is available for homogeneous materials is modified to account for the asymmetrically varying material properties. Crack propagation along the interface of a functionally graded bimaterial system has been simulated. A parametric study was performed by systematically varying the material inhomogeneity length scale independently in the two half-spaces. Our study indicated that softening type graded materials reduce the resistance to fracture, while a hardening material offers higher fracture resistance with increase in inhomogeneity. Only the transient phase of crack propagation speed was affected by the material property variation, irrespective of whether the material was hardening, softening or an asymmetric type. The crack always reached a quasi-steady-state velocity, which remained unaffected by the material property inhomogeneity.
Exergy Transfer Criteria on Enhanced Heat Transfer Performance Evaluation
Authors: Wu Shuang-Ying , Chen Yan , Li You-Rong , Cui Wen-Zhi , Quan Liao
Published: April 2008

Based on the exergy transfer performance analysis of forced convective heat transfer through a tube with constant heat flux/ constant wall temperature for thermally and hydrodynamic fully developed turbulent flow, extended performance evaluation criteria for enhanced heat transfer surfaces based on the exergy transfer theorem have been developed. An exergy transfer performance evaluation criterion ΔNue or ΔE, which is defined as the difference of exergy-transfer Nusselt number or exergy transfer rate before and after enhanced heat transfer, is put forward. By reference to spirally grooved tube, the effect of Reynolds number, structure parameters of tube, dimensionless wall temperature difference and heat flux on the exergy transfer process is discussed. The results show that the exergy transfer performance of enhanced heat transfer with constant wall temperature is quite different from that with constant wall heat flux. An effective approach for exergy transfer performance evaluation and the optimal process parameters and configuration choice of enhanced heat transfer tube are provided.
Interfacial Fracture Characterization of Nano-Scale Thin Films Using Single-Strip Stress-Engineered Superlayer
Authors: Zheng Jiantao , Sitaraman Suresh K.
Published: April 2008

Characterization of interfacial fracture parameters for nano-scale thin films continues to be challenging due to the difficulties associated with preparing samples, fixturing and loading the samples, and extracting and analyzing the experimental data. In this paper, we propose a stress-engineered superlayer test method that can be used to measure the interfacial fracture parameters of nano-scale (as well as micro-scale) thin films without the need for loading fixtures. The proposed test employs the residual stress in sputter-deposited metals to provide the energy for interfacial crack propagation. The innovative aspect of the test is the use of an etchable release layer that is deposited between the two interfacial materials of interest. The release layer is designed such that the available energy for interfacial crack propagation will continue to decrease as the crack propagates, and at the location where the crack ceases to propagate, the available energy for crack propagation will be the critical energy for crack propagation or the interfacial fracture toughness. The proposed test method has been successfully used to characterize Ti thin film on Si substrate.
Lamb Wave Tuning Between Piezoelectric Wafer Active Sensors and Host Structure: Experiments and Modeling
Authors: Santoni Giola B. , Giurgiutiu Victor
Published: April 2008

In structural health monitoring (SHM), a network of embedded sensors permanently bonded to the structure is used to monitor the presence and extent of damage. The sensors can actively interrogate the structure through ultrasonic waves. Among the ultrasonic waves, Lamb waves are quite convenient because they can propagate at large distances in plates and then interrogate a large area. Lamb waves in a plate can be produced with piezoelectric wafer active sensors (PWAS) that are small, inexpensive, unobtrusive transducers. PWAS can be surface-mounted on an existing structured or placed inside composite materials. PWAS sensors use the piezoelectric principle. An alternating voltage applied to the PWAS terminals produces an oscillatory expansion and contraction of the PWAS. An oscillatory expansion and contraction of the PWAS produces an alternating voltage at the PWAS terminals. PWAS are bonded to the structure through an adhesive layer; the coupling with the investigated structure is higher then conventional transducers. If the PWAS bonded to the structure is excited, it couples its in-plane motion with the Lamb wave particle motion on the material surfaces. In previous studies, the Lamb wave mode tuning between PWAS and isotropic plates has been observed experimentally and theoretically. Recently experiments have been performed to verify the presence of tuning between bonded PWAS and composite plates. In the present paper, it will be discussed a method, normal mode expansion (NME), for predicting the tuning frequencies of the PWAS-plate structure. This method can be used for both isotropic and non-isotropic material. Experimental values for the tuning frequencies in isotropic plates are compared with the theoretically data obtain with integral transform solution and NME.
Pressure Distribution Within EHD Point Contacts Based on Measured Film Thickness
Authors: Poliscuk Radek , Vaverka Michal , Vrbka Martin , Krupka Ivan , Hartl Martin
Published: April 2008

Surface topography significantly influences the behavior of lubricated contacts between highly loaded machine elements. Most oil- or grease- lubricated machine elements such as gears, rolling bearings, cams and traction drives operate in mixed lubrication conditions and the lubricant film thickness is directly related to the main practical performance parameters such as function, wear, contact fatigue and scuffing. For determination wear and especially contact fatigue, the values and distribution of the pressure in rolling contact are required. The theoretical studies usually involve the numerical solution of pressure and film thickness in the contact, using some physical mathematical model built around the Reynolds equation to describe the flow and the theory of elastic deformation of semi-infinite bodies. Such calculations can be extremely time consuming, especially when lubricant films are very thin and/or contact load very high. This study is aimed at obtaining pressure distribution within lubricated contact from measured film thickness. Lubricant film thickness distribution within the whole concentrated contact is evaluated from chromatic interferograms by thin film colorimetric interferometry. Consequently, an elastic deformation is separated from the film thickness, geometry and mutual approach of the surfaces. Calculation of the pressure distribution is based on inverse elasticity theory. EHD lubricated contact with smooth surfaces of solids was first investigated. Calculated pressure, distributions were compared with data obtained from full numerical solution to check the accuracy. The approach was also applied to surfaces with dents and their influence on distribution of pressure in lubricant film.
Experimental Verification of Source Temperature Modulation via a Thermal Switch in Thermoelectric Energy Harvesting
Authors: McCarty R. , Monaghan D. , Hallinan K. P. , Sanders B.
Published: April 2008

This paper provides a description of research seeking to experimentally verify the effectiveness of a thermal switch used in series with TE devices for waste heat recovery for constant and variable source heat input, and for variable source thermal capacitance (mass). Using an experimental set-up comprised serially of a fixed heat source, a variable thermal resistance air gap serving as a thermal switch, a thermoelectric device and a heat sink mounted on a translation stage, the time-averaged power output to power input ratios improved up to 15% and 30% respectively for constant and variable heat input in certain design space conditions. The experimental results, as supported by model predictions, suggest that the thermal capacitance of the heat source must be greater than the thermal capacitance of the TE device in order for thermal switching to improve the time-averaged power output to power input ratios of waste heat recovery systems.
Alternative Solutions for Longitudinal Fins of Rectangular, Trapezoidal, and Concave Parabolic Profiles
Authors: Aziz A.
Published: April 2008

The traditional thermal analysis of fins is based on the assumption of specified thermal boundary conditions at the base and tip of the fin. For situations when the fin base is in contact with a fluid experiencing condensation and the fin is required to remove the energy released by the fluid, the base is subjected to two boundary conditions: a fixed temperature and a fixed heat flux. This paper develops solutions for the temperature distribution in the fins under these conditions. Solutions are provided for rectangular, trapezoidal, and concave parabolic (finite tip thickness). Results illustrating the relationship between the dimensionless heat flux, the fin parameter, and dimensionless tip temperature are provided for all three geometries. The case of convective fin tip is also considered and lead to a relationship between the dimensionless heat flux, the fin parameter, and the Biot number at the tip. The results presented here provide tools that not only complement the traditional analyses but are believed to have more direct relevance for fin designers.
Analysis of Experimental Results in Mechanics of MWNT
Authors: Zalamea Luis , Pipes R. Byron
Published: April 2008

The interaction between multiple shells in a MWNT structure is still a subject of intense research for theoreticians as well as experimentalists1-4. Uncertainties arise mainly from the difficulties in calculating the atomic interactions within the material, i.e. graphite sliding5. In contrast, the other relevant deformation mode; separation, can be modeled through a modified Lennard Jones potential6. Accepting the validity of continuum mechanics at the relevant scales7 it is possible to define a parameter that while varying from zero to one, spans from frictionless sliding to perfect bonding between individual layers8. Each individual graphene sheet making a nanotube is considered an isotropic hollow cylinder with a thickness equal to that of the equilibrium separation between layers, leaving no space between layers, in agreement with arguments presented elsewhere9. The key point of this analysis is the modeling of those interfaces through a single parameter called the shear transfer efficiency. Three loading situations are of interest: extension, twisting and bending. All three have in common that the load is introduced only to the outermost layer and somehow must be transferred to the inner shells. An implicit assumption is that the only stresses responsible for stress transfer between shells are shearing, although there is always normal stress transfer due to Poisson's effects and to the kinematics of the deformation, they are deemed to be of second order due to the low value of Poisson's ratio for graphene and are neglected in the present analysis. Their quantification would lead to the normal transfer efficiency, by analogy with our shear transfer efficiency.
Thermal Efficiency of the Cross Flow Heat Exchangers
Authors: Fakheri Ahmad
Published: April 2008

The heat exchanger efficiency is defined as the ratio of the actual heat transfer in a heat exchanger to the optimum heat transfer rate. The optimum heat transfer rate, qopt, is given by the product of UA and the Arithmetic Mean Temperature Difference, which is the difference between the average temperatures of hot and cold fluids. The actual rate of heat transfer in a heat exchanger is always less than this optimum value, which takes place in an ideal balanced counter flow heat exchanger. It has been shown that for parallel flow, counter flow, and shell and tube heat exchanger the efficiency is only a function of a single nondimensional parameter called Fin Analogy Number. The function defining the efficiency of these heat exchangers is identical to that of a constant area fin with an insulated tip. This paper presents exact expressions for the efficiencies of the different cross flow heat exchangers. It is shown that by generalizing the definition of Fa, very accurate results can be obtained by using the same algebraic expression, or a single algebraic expression can be used to assess the performance of a variety of commonly used heat exchangers.
Intelligent Sensors for Integrated Health Management Systems
Authors: Oesch Christopher , Mahajan Ajay , Utterback Lucas , Padmanaban Haricharan , Chitikeshi Sanjeevi , Figueroa Fernando
Published: April 2008

This paper describes work being conducted on the development of intelligent sensors with learning capabilities as part of an integrated systems approach. The integrated systems approach treats the sensor as a complete system with its own sensing hardware (the traditional sensor), A/D converter, processing and storage capabilities, software drivers, self-assessment algorithms, communication protocols and evolutionary methodologies that allow the system to learn its own behavior. The immediate application is the monitoring of rocket test stands, but the technology should be generally applicable to the Integrated Systems Health Monitoring (ISHM) vision. This paper outlines progress made in the development of intelligent sensors by describing the work done till date on Physical Intelligent Sensors (PIS) and Virtual Intelligent Sensors (VIS). The PIS as discussed here consists of a thermocouple used to read temperature in an analog form which is then converted into digital values. A microprocessor collects the sensor readings and runs numerous embedded event detection routines on the digital data. If any event, i.e. spike, drift, noise, is detected, it is reported, stored and sent to a remote system through an Ethernet connection. Hence the output of the PIS is data coupled with a confidence factor in the reliability of the data. The VIS discussed here is a virtual implantation of the PIS in the G2 software environment. The VIS is designed to mirror the operations of the PIS; however, the VIS works on a computer at which digital data is provided as the input. This work lays the foundation for the next generation of smart devices that have embedded intelligence for distributed decision making capabilities.
Multi-Physics Modeling Approach in All Terrain Vehicle Longitudinal Dynamics
Authors: Sharaf A. Am. , Mavros G. , Rahnejat H. , King P. D.
Published: April 2008

This paper presents a detailed 4×4 off-road vehicle modelling method, based on a multi-physics approach. A full drivetrain system including all aspects of rotational inertial dynamics, friction, damping and stiffness properties is integrated with a fourteen-degrees-of-freedom vehicle model including body dynamics, kinematics, suspension and wheel dynamics as well as the terramechanical phenomena between tyres and soft soils. The interaction between all these modules is implemented in the MATLAB/SIMULINK/SimDriveline environment. The concepts of modularity, flexibility, and user-friendliness were emphasized during model development. The model is developed in order to provide design engineers with the capability to investigate effects of component selection and to develop control systems and automatic optimization processes for off-road 4×4 vehicles. While the modelling approach can be used for a wide variety of operating conditions, the present work focuses on the analysis of the contribution of different aspects on the off-road traction of 4×4 vehicles.
Effects of Texture on Thermoelectric Power in Ti-6Al-4V
Authors: Carreon Hector
Published: April 2008

Ti-6A1-4V alloy exhibits a very strong anisotropic texture caused by the existence of a preferred crystallographic orientation in the polycrystalline microstructure. This crystallographic alignment can result in anisotropic behavior of the material so that the material properties are different depending on whether they are measured in perpendicular or parallel direction. In addition to this morphological anisotropy, due to the dominantly hexagonal grain structure, the Ti-6A1-4V alloy also exhibited a substantial thermoelectric anisotropy. This study was conducted to investigate the effect of thermoelectric anisotropy on the thermoelectric power measurements in a highly textured Ti-6A1-4V specimen using a completely nondestructive technique based on the Seebeck effect. The result shows the thermoelectric power dependence associated with texturing and the macroscopic grain structure in a rolled Ti-6A1-4V specimen, which was annealed at 710°C for 2 hours and slowly cooled. The measurements clearly demonstrated that the intrinsic sensitivity of the thermoelectric contact technique is a very useful tool that could be exploited for quantitative nondestructive (QND) material characterization.
Hall Sensors Using Piezoresistive Transducer Fabrication Process
Authors: Chen Steven , Chiou J. Albert
Published: April 2008

A piezoresistive transducer (PRT) pressure sensor would be able to sense a magnetic field and provide an adequate Hall effect output. In this study, two different types of boron-doped transducers, X-ducer and picture-frame transducer (also called micro Wheatstone-bridge transducer) were tested for the Hall effect. It is found that the currently used fabrication process and packaging for PRT pressure sensors do not need to be altered for Hall sensors. However, a slight mask modification is necessary to use an X-ducer instead of a picture-frame transducer for the Hall effect sensing because the X-ducer is at least 50 times more sensitive than the picture-frame transducer. The sensitivity calculated using the Hall theory and estimated hole mobility velocity is in reasonably good agreement with experimental results.
Train-to-Train Impact Test of Crash Energy Management Passenger Rail Equipment: Structural Results
Authors: Tyrell David , Jacobsen Karina , Martinez Eloy , Perlman A. Benjamin
Published: April 2008

On March 23, 2006, a full-scale test was conducted on a passenger rail train retrofitted with newly developed cab end and non-cab end crush zone designs. This test was conducted as part of a larger testing program to establish the degree of enhanced performance of alternative design strategies for passenger rail crashworthiness. The alternative design strategy is referred to as crash energy management (CEM), where the collision energy is absorbed in defined unoccupied locations throughout the train in a controlled progressive manner. By controlling the deformations at critical locations the CEM train is able to protect against two dangerous modes of deformation: override and large-scale lateral buckling. The CEM train impacted a standing locomotive-led train of equal mass at 31 mph on tangent track. The interactions at the colliding in Interface and between coupled interfaces performed as expected. Crush was pushed back to subsequent crush zones and the moving passenger train remained in-line and upright on the tracks with minimal vertical and lateral motions. The added complexity associated with this test over previous full-scale tests of the CEM design was the need to control the interactions at the colliding interface. between the two very different engaging geometries. The cab end crush zone performed as intended because the locomotive coupler pushed underneath the cab car buffer beam, and the deformable anti-climber engaged the uneven geometry of the locomotive anti-climber and short hood. Space was preserved for the operator as the cab end crush zone collapsed. The coupled interfaces performed as predicted by the analysis and previous testing. The conventional interlocking anti-climbers engaged after the pushback couplers triggered and absorbed the prescribed amount of energy. Load was transferred through the integrated end frame, and progressive controlled collapsed was contained to the energy absorbers at the roof and floor level. The results of this full-scale test have clearly demonstrated the significant enhancement in safety for passengers and crew members involved in a push mode collision with a standing locomotive train.
A Time Integration Algorithm for Nonlinear Viscoelastic Behaviors of Orthotropic Media
Authors: Sawant Sourabh , Muliana Anastasia
Published: April 2008

This study develops a recursive-iterative algorithm for analyzing nonlinear viscoelastic responses of orthotropic materials. The algorithm is derived based on implicit stress integration solutions within a general displacement based finite element (FE) framework for small deformations and uncoupled thermo-mechanical problems. The Schapery's nonlinear single integral model is generalized for stress-temperature-time dependent responses of an orthotropic medium. The time-dependent compliance follows material symmetry, which leads to nine independent time integral equations. A recursive method is used to solve the time-dependent integral model. An incremental iterative algorithm is added in order to minimize error arising from the linearized strain formulation in the recursive method. Furthermore, a consistent tangent stiffness matrix is formulated to enhance equilibrium and avoid divergence. The recursive-iterative numerical formulation is implemented within the ABAQUS general purpose FE code. Available experimental data on nonlinear viscoelastic responses of orthotropic laminated composite materials are used to verify the above numerical algorithm.
Thermo-Mechanical Fatigue Life Estimation of Organic BGA Packages Using Laser Moire Interferometry
Authors: Tunga Krishna , Sitaraman Suresh K.
Published: April 2008

Accelerated Thermal Cycling (ATC) is traditionally used for assessing solder joint reliability. ATC typically takes as long as three to four months to complete. This paper proposes a new method to determine the fatigue life of solder joints using laser moire´ technique. The developed method takes about a week to complete and gives us the detailed deformation behavior of each solder ball in the package at various temperatures. The developed method has been demonstrated for a high I/O organic BGA package. To illustrate the efficacy of the method, the results have been validated using experimental thermal cycling data.
Optimizing Piston Velocity Profile for Maximum Work Output From an IC Engine
Authors: Teh Kwee-Yan , Edwards Christopher F.
Published: April 2008

In this paper, an optimal control problem is set up to maximize the work output from a piston engine via piston motion shaping. The empirical heat transfer correlation and global reaction kinetics used in the engine model result in a stiff, non-smooth dynamical system. The algorithm used to transcribe this system to a constrained nonlinear program is described. The optimal solution is obtained using the gradient-based optimization solver SNOPT. At optimality, the total heat transfer loss is lower due to the shorter time spent at elevated temperatures after combustion, leading to a modest increase (less than 3%) in work output as compared to a conventional slider-crank piston engine.
Fretting Wear Between Supporting Grids and Cladding Tubes of Nuclear Fuel Rod
Authors: Park Young-Chang , Kim Yong-Hwan , Lee Seung-Jae , Lee Young-Ze
Published: April 2008

The experimental investigation was performed to find the associated changes in characteristics of fretting wear with various water temperatures. Fretting can be defined as the oscillatory motion with very small amplitudes, which usually occur between two contacting surfaces. The fretting wear, which occurs between cladding tubes of nuclear fuel rod and grids, causes in damages the cladding tubes by flow induced vibration in a nuclear reactor. In this paper, the fretting wear tests were carried out using the zirconium alloy tubes and the grids with increasing the water temperature. The tube materials in water of 20°C, 50°C and 80°C were tested with the applied loads from 5N up to 25N and the relative amplitude of 200μm. The worn surfaces were observed by SEM, EDX analysis and 2D surface profiler. As the water temperature increased, the wear volume was decreased, but oxide layer was increased on the worn surface. The abrasive wear mechanism was observed at water temperature of 20°C and adhesive wear mechanism occurred at water temperature of 50°C, 80°C. As the water temperature increased, surface micro-hardness was decreased, but wear depth and wear width were decreased due to increasing stick phenomenon. Stick regime occurred due to the formation of oxide layer on the worn surface with increasing water temperatures.
Characterization of Defect Nucleation and Propagation in Fe2O3+FCC-Al Nanocomposites During Uniaxial Tensile and Compressive Deformations
Authors: Tomar Vikas , Zhou Min
Published: April 2008

The objective of this research is to analyze uniaxial tensile and compressive mechanical deformations of α-Fe2O3 + fcc Al nanoceramic-metal composites using classical molecular dynamics (MD). Specifically, variations in the nucleation and the propagation of defects (such as dislocations and stacking faults etc.) with variation in the nanocomposite phase morphology and their effect on observed tensile and compressive strengths of the nanocomposites are analyzed. For this purpose, a classical molecular dynamics (MD) potential that includes an embedded atom method (EAM) cluster functional, a Morse type pair function, and a second order electrostatic interaction function is developed, see Tomar and Zhou (2004) and Tomar and Zhou (2006b). The nanocrystalline structures (nanocrystalline Al, nanocrystalline Fe2O3 and the nanocomposites with 40% and 60% Al by volume) with average grain sizes of 3.9 nm, 4.7 nm, and 7.2 nm are generated using a combination of the well established Voronoi tessellation method with the Inverse Monte-Carlo method to conform to prescribed log-normal grain size distributions. For comparison purposes, nanocrystalline structures with a specific average grain size have the same grain morphologies and the same grain orientation distribution. MD simulations are performed at the room temperature (300 K). Calculations show that the deformation mechanism is affected by a combination of factors including the fraction of grain boundary (GB) atoms and the electrostatic forces between atoms. The significance of each factor is dependent on the volume fractions of the Al and Fe2O3 phases. Depending on the relative orientations of the two phases at an interface, the contribution of the interface to the defect formation varies. The interfaces have stronger effect in structures with smaller average grain sizes than in structures with larger average grain sizes.
A Hybrid Parallelizable Algorithm for Computer Simulation of the Motion Behaviors of a Branched Multibody System
Authors: Duan Shanzhong (Shawn) , Patel Yogesh
Published: April 2008

This paper presents a hybrid parallelizable algorithm for the computer-aided modeling of the dynamic behavior of multibody open tree systems. The method is based on cutting certain system interbody joints at branched bodies so that a system of largely independent multibody subchains is formed. These subchains interact with one another through associated unknown constraint forces fc at the cut joints. The increased parallelism is obtainable through cutting joints and the explicit determination of associated constraint forces combined with a sequential O(n) procedure. Consequently, the sequential O(n) procedure is carried out within each subchain to form and solve the equations of motion, while parallel strategies are performed between the subchains to form and solve constraint equations concurrently. Two extreme cutting procedures are further discussed to conduct a comparison of computational efficiency. One case is to cut the joints at branched bodies so that the longest lengths of subchains are obtained and the other is to cut the joints at branched bodies so that the shortest lengths of subchains are formed. The algorithm can easily accommodate the available number of processors while maintaining high efficiency. The algorithm will also be implemented on both parallel homogeneous computing (PHC) systems and network-distributed heterogeneous computing (DHC) environment. The implementation of the algorithm in a DHC environment will permit engineers and researchers to conduct distributed simulation of dynamic behaviors of large and complex multibody systems on ubiquitous network-distributed PC workstations in their workplace. In short, the exploration of the parallelizable algorithm for a multibody tree system will provide a deep understanding of the relationship between computational load balancing and optimal joint locations to be cut. The computational efficiency of the algorithm can be increased further.
Local Flow Control Using a Field Effect Transistor
Authors: Horiuchi Keisuke , Dutta Prashanta
Published: April 2008

A field-effect transistor is developed on PDMS microchannel to control flow in microfluidic chips by modifying the surface charge condition. By applying a gate voltage to one side of the microchannel wall, zeta potential at that side is altered, while the zeta potential at the other side is maintained at the original value. This non-uniform zeta potential results in a secondary electroosmotic flow in lateral direction, which is used for flow control in microchannel geometries. The flow control is observed both quantitatively and qualitatively at relatively low voltage (less than 50 [V]), and this local flow control is primarily due to the leakage current through the interface between PDMS and glass layers. To verify the experimental results, a leakage capacitance model is introduced to estimate the modified zeta potential for the straight channel case, and excellent agreement is obtained between the predicted and experimental zeta potential results.
Exergy as an Indicator for Resources Scarcity: The Exergy Loss of Australian Mineral Capital — A Case Study
Authors: Valero Alicia , Valero Antonio , Arauzo Inmaculada
Published: April 2008

Over the span of the 20th century, the global demand for metals and minerals has increased dramatically. This is associated with a general trend of declining ore grades from most commodities, meaning higher quantities of ore needed to be processed and thus more energy. Hence, quantifying the loss of mineral capital in terms of mass is not enough since it does not take into account the quality of the minerals in the mine. Exergy is a better indicator than mass because it measures at the same time the three features that describe any natural resource: quantity, composition and a particular concentration. For the sake of better understanding the exergy results, they are expressed in tons of Metal equivalent, tMe, which are analogously defined to tons of oil equivalent, toe. The aim of this paper is 1) to show the methodology for obtaining the exergy loss of mineral resources throughout a certain period of time and 2) to apply it to the Australian case. From the available data of production and ore grade trends of Australian mining history, the tons of Metal equivalent lost, the cumulative exergy consumption, the exergy decrease of the economic demonstrated reserves and the estimated years until depletion of the main base-precious metals are provided, namely: for gold, copper nickel, silver lead and zinc.
Development of Advanced amd Customized Absorption Chillers From Indian Industry
Authors: Ranade Mukund , Balu R. , Babu P. , Nataraj M.
Published: April 2008

Indian absorption industry started customizing chillers first based on material or electrical requirements, like chillers for hazardous areas or using materials such as titanium, cupronickel, stainless steel, cladded plates etc. However, as knowledge about chiller technology has improved, many cycle variations have been designed and fabricated to suit customer requirements. This is commercially possible due to lower technical manpower costs in India. Such efforts have resulted in over 20 % market share of absorption chillers in spite of unfavorable fuel prices (higher gas and oil prices than electricity cost). This paper describes some of the cycles used for different applications based on customers' requirement such as double absorbers, various types of single double-effect chillers, twin hot water machines, and absorption heat pumps. Double absorbers used in India are of two types: Horizontal double absorbers and vertical double absorbers. The cycle COP of such chillers can exceed 1.46.
An Investigation Into the Effect of Inclusion of Cerium Oxide Nanoparticles on the Physicochemical Properties of Diesel Oil
Authors: Sajith V. , Sandhya M. , Sobhan C. B.
Published: April 2008

Because of its excellent catalytic activity and its ability to act as oxygen buffer causing simultaneous oxidation of hydrocarbons as well as the reduction of Nitrogen Oxide, Cerium Oxide (CeO2) is very special as a fuel additive for internal combustion engines. The present work investigates, through a series of experiments, the influence of the addition of CeO2 in the nanoparticle form on various physicochemical properties of Diesel oil, such as the cloud and pour points, the flash and fire points, the viscosity and the volatility which influence not only the spray characteristic but also the fuel atomization. Diesel oil samples, containing various percentage dosing levels of CeO2 nanoparticles of size range 20-30 nanometers are prepared using standard procedures of ultrasonic mixing, and used in the experiments. The physicochemical properties of the base fuel and the modified fuel are measured accurately using ASTM standard test methods. The effects on the individual fuel properties and the overall performance on a Diesel engine are studied, leading to inferences on the optimum dosing level.
Endogenous and Exogenous Exergy Destruction in Thermal Systems
Authors: Tsatsaronis George , Kelly Solange O. , Morosuk Tatiana V.
Published: April 2008

One of the roles of exergy analysis is to provide thermal system designers and operators with information useful for the system optimization. An exergy analysis identifies the sources of thermodynamic inefficiencies by evaluating the exergy destruction within each system component. However, care must be taken when using the total exergy destruction within a component to reach conclusions regarding the optimization of the overall energy system. The reason is that the total exergy destruction occurring in a component is not due exclusively to that component but is also caused by the inefficiencies within the remaining system components. The endogenous exergy destruction within a component is defined as that part of the component's exergy destruction that is independent of any change in the exergy destruction within the remaining components. The part of the component's exergy destruction which depends upon the changes of the exergy destruction within the other components is defined as the exogenous exergy destruction. It is apparent that the sum of endogenous and exogenous exergy destruction is equal to the total exergy destruction within the component being considered. Knowledge of the exogenous and endogenous exergy destruction for the most important components can further assist the engineer in deciding whether an adjustment in that component or in the structure of the system (i.e. in the remaining components) is required to improve the overall system. The paper presents the general concept of endogenous and exogenous exergy destruction. Using a graphical approach, the endogenous and exogenous exergy destruction of a simple gas turbine process and simple refrigeration machine are investigated.
A Comparison of Machine Risk Acceptance Results Among Trained Users of ANSI B11-TR3
Authors: Etherton J.
Published: April 2008

The ANSI guideline on machine risk assessment, B11-TR3, describes risk assessment as an iterative process. This implies that protective measures of varied levels of technology can be successively evaluated until a risk that is acceptable is attained. The theories of risk acceptance are many. Reducing risk to a level that is agreed to be 'as low as reasonably practicable' (ALARP) is said to give focus to making a decision about when risk has been adequately reduced. Main (2004) says that "Although the concept of acceptable risk is becoming more commonly adopted throughout the world, a single level of acceptability cannot be universally applied. Acceptable risk is a function of many factors, and is specific to a company, culture, and time-era." Fischhoff et al. (1981) have argued that "the risk associated with the most acceptable option is not acceptable in any absolute sense. One accepts options, not risks, which are only one feature of options." This paper describes risk assessment groups in five manufacturing workplaces and discusses training that led to acceptable risk decisions for a hazardous machine system in each workplace. The composition of the five teams in this study ranged from a team with just a single engineer to teams involving several workplace personnel. The applied preventive measures ranged from measures that were tailored to meet corporate safety goals to measures that evolved from the local risk assessment team's ingenuity. The paper concludes with suggestions on how to make the risk acceptance concept meaningful in the training of future machine risk assessment teams.
Prediction of Gas Permeability Through Multiple-Ply Composite Laminates
Authors: Xu Jianlong , Sankar Bhavani V.
Published: April 2008

Polymer matrix composites are candidate materials for cryogenic tanks for Crew Exploration Vehicles and Crew Launch Vehicles planned by NASA for future space missions. However gas leakage through microcracks and delaminations remains as a critical problem that needs to be solved. In the present work, gas permeability mechanism through multiple ply laminates is investigated. Different from the through matrix cracks in cross ply laminates, stitch cracks are observed in angle-ply laminates during experimentation. Stacking sequences [0/θn/90]s are investigated. From experimental observations presented in the literature, stitch cracks seem to develop in angle plies depending on the value of θ and n. A representative volume element (RVE) is analyzed by three-dimensional finite element method (FEM). Two methods are used to calculate the energy release rate: three-dimensional J-integral by ABAQUS 6.5™ and strain energy difference of RVEs before and after crack propagation. Based on energy release rate, the mechanisms and other parameters that control the creation and propagation of stitch cracks are investigated. The results will lead to the development of a relation between loads and the number of stitch cracks and their lengths. The permeation model is based on Darcy's law for porous materials. By integrating Darcy's law in the thickness direction of the composite laminate, the gas permeability can finally be expressed in terms of crack densities and crack opening displacements (COD). Three-dimensional FE analyses will be performed to find out COD for a given crack density and crack length. The results for gas permeability obtained through the simulations will be compared to the experimental results of cross ply laminates from previous work to understand the effects of laminate configuration on gas permeability.
Osmosis: Characteristics of Liquid at an Interface
Authors: Howlett Larry D.
Published: April 2008

Many explanations for the movement of water across a membrane have been presented. One idea proposes that osmosis is the movement of water in response to a vapor pressure difference. It is difficult to accept this model for osmosis without a good understanding of the existence of a vapor in a liquid. We propose a model for a vapor in a liquid. The model is based upon the kinetic theory of gas and Maxwell's predicted speed distribution. Since vapor pressure and total kinetic energy are both expressions of the energy of a gas, we compare the model to published values of vapor pressure for water, ice, and several other liquids. Based upon this limited comparison, it appears that this model may be a universal model for the continuous existence of a vapor in a liquid or a solid.
Hydraulic Assist Power System
Authors: Sun Zongxuan , Miao Hsu-Chiang
Published: April 2008

Hydraulic assist power system (HAPS) is a low-cost system that converts vehicle kinetic energy during vehicle deceleration or braking into hydraulic energy and then uses it to assist vehicle propulsion. Unlike conventional hybrid electrical vehicles (HEV) or hydraulic hybrid vehicles (HHV), where a separate motor/generator or motor/pump set is required, the present concept uses the existing hydraulic pump of the transmission unit as the motor/pump set directly. This leads to reduced size, lower weight and less cost. Typical applications of HAPS include energy recovery, engine restart, and hill-holding, etc.
Platform Protection Through Acoustic Signature Management
Authors: Seto Mae L.
Published: April 2008

A naval ship's acoustic signature is known after a ranging but changes the longer it is in-service away from a range. The Ship Signatures Management System (SSMS) provides an organic real-time capability to predict their own signature and enough information to mitigate signature issues. SSMS provides the Commanding Officer with a tool to determine the ship's acoustic signature in order to evaluate the impact of his/her proposed actions on the ship's counter-detection range and sensor performance. In this manner, the ship's protection is enhanced through insightful and timely signature management. DRDC has upgraded the SSMS hardware to state-of-the-art components to increase the number of sensors, the fidelity of the logged data, the dynamic range, and the processing power. This paper discusses some of the advanced SSMS features developed like tonal detection and tracking, tonal association, and the diagnostics used to determine the cause of features in the acoustic signature.
Near-Field Characteristics of a Jet With a Coil-Insert Injector
Authors: Rahai Hamid R. , Alware Ayaz , Carpio Daniel , Khansa Eyass
Published: April 2008

Simultaneous time resolved measurements of two components of turbulent velocity and their cross moments are made at the exit and downstream of an axisymmetric jet with a coil-insert injector. The coil-insert injector is a coil shaped tube with ratios of coil diameter, pitch spacing and length to the jet inside diameter of 0.1, 1.0, and 1.5 respectively. The coil had three round holes of 0.2 mm diameter at the middle of each pitch for radial injection. The volume flow ratios of the radial blowing to the axial flow were 0.075, 0.10, 0.125, and 0.15. Results indicate that the radial blowing enhances asymmetry and increased generation of turbulence intensities at the jet outlet. However, increased entrainment and mixing between the injected flow and the axial flow reduces the asymmetry downstream, resulting in relatively constant intensities in the region with high axial momentum.
The Nonlinear Internal Resonance Analysis of a Rotary Truncated Conical Shell
Authors: Chen Changping , Dai Liming
Published: April 2008

Truncated conical shell is an important structure that has been widely applied in many engineering fields. The present paper studies the internal dynamic properties of a truncated rotary conical shell with considerations of intercoupling the high and low order modals by utilizing Harmonic Balance Method. To disclosure the detailed intercoupling characteristics of high order modal and low order modal of the system, a truncated shallow shell is studied and the internal response properties of the system is investigated by using the Multiple Scale Method. Abundant dynamic characteristics are found in the research of this paper. It is found in the research of the paper that the high-order modals of rotating conical shells have significant effects to the amplitude and frequency of the shells.
A Problem Solving Approach for Teaching Engineering Laboratories
Authors: Ciocanel Constantin , Elahinia Mohammad H.
Published: April 2008

This paper presents the redevelopment method and process of the laboratory experiments for the Mechanics and Vibration Laboratory, MIME3390, in the Mechanical, Industrial, and Manufacturing Engineering Department at the University of Toledo. The redevelopment objective was to transform the learning process from a subject-based learning to a problem-solving learning. Particular objective was to provide the students with more hands-on experience and to challenge them by requesting the procedure for each laboratory experiment to be designed and carried out by each group of students. This senior level laboratory course consists of experiments in deformable solid mechanics including stress and deflection analysis, fatigue life evaluation, stability and mechanical vibration. Prerequisite courses for this laboratory are Mechanical Design I and Mechanical Vibrations. In line with the program objectives of the department, the following list of objectives has been defined for this course: "Upon successful completion of this course, the students should have: (1) become knowledgeable in the use of standard instrumentation for static and dynamic structural testing, such as strain gages, load frames, impact hammers, and spectrum analyzers; (2) reinforced material studied in previous mechanics and vibrations courses; (3) improved data analysis skills, and (4) further developed laboratory and technical writing skills." Prior to this redevelopment, as part of the subject-based approach, a classroom lecture preceded each laboratory session. The lecture consisted of the review of the theory pertaining to each experiment to help students refresh their knowledge on the subject. Additionally the description and procedure of the laboratory experiment was covered during this lecture. Prior to each class, the lecture notes, along with the laboratory procedures, were posted on the course website. The step-by-step instructions for each experiment were provided to assist the students in setting up and conducting each experiment. Throughout the semester, eleven experiments were performed. The students wrote individual reports on the experiments consisting of a summary of the acquired data, data analysis, and observations. However, due to the number of students and limited number of lab sessions it was difficult to provide the students with the real hands-on experience with the instrumentation and lab setup. As a result, during the lab the student mostly collected data according to the lab procedure and compiled a report that sometimes was inspired by samples of reports written by former students.