bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation on Wafer Polishing of Oxide and Copper Layers
Authors: Tsai Jhy-Cherng
Published: June 2008

Polishing, in particular chemical-mechanical polishing (CMP), is a critical technology for the planarization of wafers. This paper investigates, via experiments, and compares the performance of CMP process with different process parameters for wafers with silicon-dioxide (SiO2) layer and for wafers with copper (Cu) layer. Polishing pressure (P), speed (V), and back pressure (BP) are used as process parameters in this study. Different pads and slurries are also experimented for copper layer as its properties are different from that of conventional oxide layer. Material removal rate (RR) and non-uniformity (NU) are used as indices to measure the performance. Experimental data on oxide layers show RR increases as P and V increase but NU gets worse at the same time. This condition can be improved, for both oxide and copper layers, with suitable BP. Experiments on copper CMP using slurry with abrasives show that RR increases with higher P and V. While NU gets worse with higher P, it can be reduced as V increases using a soft pad. Better NU can be obtained using soft pad though RR is lower in this case. For abrasive-free polishing of copper layer, RR, though relatively lower compared to CMP with regular slurry, is unstable using hard pad despite that NU becomes better at higher P. NU of polished wafer is best at certain pressure but becomes worse at low pressure for hard pad and at high P for soft pad. It is also observed that NU of AFP can be improved with BP and softer pad. Soft pad gives better polishing quality and performance though RR is lower than that using slurry with abrasives.
NDE of Carbon Fiber Composite Pressure Vessels
Authors: Bunsell A. R. , Blassiau S. , Mezie`re Y. , Favry Y. , Teissedre J.-Ch.
Published: June 2008

The use of advanced composites in pressure vessels requires means of periodically evaluating residual minimum lifetimes in order for them to remain in service. Tests based on the prediction of crack propagation are not applicable for composite vessels as, in the absence of stress raisers or localised damage, the failure processes are diffuse and particularly damaging if the reinforcing fibers fail. Acoustic emission has been used to detect this type of damage. At a constant pressure it has been shown that even unidirectional carbon fiber reinforced resin continues to emit which reveals a continuing failure process involving the failure of fibers. The rate of emission under a constant pressure has been shown to obey a simple law which allows the damage accumulation to be calculated as a function of time. A maximum damage threshold can be determined experimentally so that master curves corresponding to the damage accumulated by a pressure vessel under constant pressure over the lifetime required can be calculated. A comparison between these master curves and the rate of damage accumulation of any other pressure vessel of the same type reveals if it will fail before or after the desired lifetime. The effects of pressure variations during service have been seen to be minor but even if this is not the case a comparison with the master curves still allows minimum lifetimes to be predicted. The technique does not require the vessels to be removed from the vehicle which is immobilised for a minimum of time.
A Disposable PVDF Sensor Applied for the Detection of Fatigue Crack Growth in Bonded Composite Joints
Authors: Kwon Oh-Yang , Brosig Dana , Nistala Kalyan , Dzenis Yuris A.
Published: June 2008

The application of polyvinylidene di-fluoride (PVDF) film as an acoustic emission (AE) sensor appears to be practical to detect the fatigue crack growth in composite materials and structures. A commercially available PVDF film sensor was employed to detect AE due to fatigue crack growth in the single-lap joints of graphite/epoxy laminates. Although the signal-to-noise ratio is not as high as those measured by PZT sensors, the result showed that the location of crack front could be predicted by the linear location of AE signals detected by the PVDF sensors. Since the composite materials usually produce very energetic AE signals, the extremely cost-effective form of PVDF sensors can be permanently mounted on composite structures for structural health monitoring as disposable ones. Piezoelectric polymer sensors are expected to be eventually embedded in composite structures provided the current limit of use temperature being increased by introducing co-polymerization with some heat resistant constituents.
Improved Electric Resistance Change Method for Delamination Monitoring of Graphite/Epoxy Composite Laminates
Authors: Todoroki Akira , Tanaka Miho , Shimamura Yoshinobu
Published: June 2008

Laminated composite plates have low delamination resistance. Since delamination crack creation is a difficult problem for visual inspection, delamination causes low reliability for primary structure of laminated composites. To improve this low reliability, identifications of delamination cracks in-service are required. The present study employs an electric-resistance change method in an attempt to identify internal delaminations experimentally. In our previous paper, a two-prove method was adopted for the electric resistance change measurements because of the simplicity. Instead, the present paper adopts multiple-prove method for the measurements of electric resistance changes. Electric current is charged from the different electrodes to measure the voltage changes. The measurements of electric voltage change at multiple points are robust against electric resistance change at the electrodes, and the method is similar to the four-probe method for high precision measurements of electric resistance change. In the present study, high precise measurement system of electric voltage change is developed, and the electric voltage measurement method is adopted for identifications of embedded delamination location and size. As a result, the improved electric resistance change method is shown to be effective for the identifications of embedded delamination cracks of graphite/epoxy laminated composites.
Nondestructive Inspection of Corrosion and Delamination at the Concrete-Steel Reinforcement Interface
Authors: Miller Tri , Hauser Christopher J. , Kundu Tribikram
Published: June 2008

This paper explores the feasibility of detecting and quantifying corrosion and delamination at the interface between reinforcing steel bar and concrete using ultrasonic guided waves. The problem of corrosion and delamination of the reinforcing steel in the aging infrastructure has increased significantly in the last three decades and is likely to keep on increasing. Ultrasonic cylindrical guided waves that can propagate a long distance along the reinforcing steel bar are found to be sensitive to the interface conditions between steel bar and concrete. Ultrasonic transducers are used to launch and detect cylindrical guided waves along the steel bar. The traditional ultrasonic testing methods, for instance the pulse-echo method, where reflection, transmission, and scattering of longitudinal waves are used for detecting large voids in concrete, are not very efficient for detecting corrosion and delamination at the interface between concrete and steel bar. For this study four sets of specimens were prepared. They are rebars and plain steel bars with corrosion and physical separation. Transducers used during the experiment are the Electromagnetic Acoustic Transducer (EMAT) and the Piezoelectric Transducer (PZT). The experiment suggests that the guided wave inspection technique is feasible for the health monitoring of reinforced concrete structures. It also reveals that the ultrasonic guided waves are sensitive to the type of steel used and to the rib patterns on the reformed steel bars.
Significance of Elastance Variation on Respiratory System Dynamics
Authors: Al-Jumaily A. M. , Al-Fakhri Y.
Published: June 2008

The sensitivity of the respiratory system dynamic response to variations in the wall elastance is investigated. The acoustical approach is used to determine the impedance at the throat using impedance recursion formulas. Both symmetric and asymmetric structures are considered. The response of the lung structure indicates that when the airway wall elastance varies, as the case during an asthma attack, the overall normalized input impedance frequency spectrum could be used to give a reasonable signature for identifying such abnormality.
Vascular Impedance Analysis in Human Pulmonary Circulation
Authors: Zhou Qinlian , Gao Jian , Huang Wei , Yen R. T.
Published: June 2008

Vascular impedance in human pulmonary circulation is analyzed by the fluid dynamic approach. A model representing the entire system of pulmonary circulation is constructed based on experimentally measured morphometric and elasticity data of the vessels. The pulmonary arteries and veins are considered as elastic tubes. Their impedance follows Womersley’s theory and electric analogue. The “sheet-flow” theory is employed to describe the flow in capillaries and thus a microvascular impedance matrix is derived. The input impedance at the main pulmonary artery is calculated under both zone 3 and zone 2 conditions. The results are compared with available experimental data in the literature.
Lung-Diaphragm Behavior of the Respiratory System During Input From Excitation
Authors: Mawasha P. Ruby , Lam Paul , Kasturi Lalitha
Published: June 2008

A numerical behavior of a lung-diaphragm model of a respiratory system during input from mouth pressure and diaphragm excitation is being investigated. A lung-diaphragm is subject to constant inlet air-flow conditions into the respiratory system. The mouth pressure (Macia et. al., 1997) and diaphragm excitation (Ricci et. al., 2002) are described by a constitutive relations containing nonlinearities from rib cage muscles forces and inlet air-flow conditions. Within certain operating regimes, the model exhibits self-excited pulsatile periodic motion and the qualitative features of the response can be understood in terms of the underlying model. Further, the mathematical model is a more general approach and can be used to conduct parametric studies and determine the instability mechanisms involved in the modeling of lung-diaphragm behavior of the respiratory system during input from excitation.
Superimposed Oscillations Enhance the Clearance of Mucus Simulant at Low Air Flows in a Rigid Tracheal Model
Authors: Krumpe Peter E. , Evrensel Cahit A. , Hassan Amgad A.
Published: June 2008

Clearance of mucus by the beating action of cilia is the primary means of removing inhaled particulates and airway debris from airways in healthy people. However many pulmonary diseases are associated with impaired mucociliary clearance mechanisms. For these patients, cough is the default airway clearance mechanism. Unfortunately most pulmonary disease patients can only produce low expiratory flow rates and have difficulty coughing for this reason.
Influence of Scribe Speed and Force on Chemomechanical Nanofunctionalized Features
Authors: Cannon Bennion R. , Magleby Spencer P. , Howell Larry L. , Jiang Guilin , Niederhauser Travis L. , Linford Matthew R.
Published: June 2008

Researchers at Brigham Young University have recently developed a new method for preparing monolayer films on silicon surfaces. The method consists of wetting the wafer with a reactive organic liquid, mechanically scribing a feature on the surface of the wafer while it is immersed, and cleaning the surface to remove the organic liquid and any silicon particles that are produced by scribing. The objective of this paper is to present preliminary results on understanding how the scribed features and their performance are affected by the mechanical characteristics of the scribing system. Performance is simply judged here by the amount of water a hydrophobic square (corral) can hold. Testing was performed to determine the influence of tip force and scribing speed on the geometry and performance of the scribed lines. Lower forces produced smoother lines, however the corrals that were formed using a high force were shown to hold the most water.
Modeling Variation Propagation in Machining Systems With Different Configurations
Authors: Zhong Weiping , Huang Ying , Hu S. Jack
Published: June 2008

Machining systems designed in different configurations have different quality performance in terms of product geometric variation. However, there exists no systematic method to predict the end-of-line product variation due to the complexity of machining processes. This paper presents a modeling methodology to analyze the variation propagation for machining systems and the impact of system configuration on quality variation. Two important sources of variations, i.e., kinematic and static variations, are included in the modeling. Kinematic deviation due to part locating and relocating is modeled using the Homogeneous Transformation Matrix. Deformation due to clamping and machining forces are modeled using the Finite Element Method, either the compliance matrix approach or the reduced stiffness matrix approach. The Monte Carlo simulation method is integrated to generate a number of workpieces with geometric dimensions and variation. Experiments are conducted to verify the model. The application is illustrated using three differently configured machining systems.
A Novel Bioreactor for the Flexural Stimulation of Tissue Engineered Heart Valve Biomaterials
Authors: Engelmayr George , Sutherland Fraser W. H. , Mayer John E. , Sacks Michael S.
Published: June 2008

A novel bioreactor was developed for the purpose of studying the effect of dynamic flexural stimulation on the properties of tissue engineered heart valve (TEHV) scaffolds and constructs. While pulse duplicator and flow loop bioreactors have shown promise in the development of functional tissue engineered cardiovascular constructs [1–3], these devices present several drawbacks when applied to the study of fundamental biomechanical phenomena, including: small sample capacity, anatomical sample geometry, and coupled mechanical stimuli. In contrast, our bioreactor was designed to provide a simple, user-controllable mode of mechanical stimulation; cyclic three-point bending; offer a sufficient sample capacity for statistically significant comparisons at multiple time points, and accommodate a simple sample geometry amenable to mechanical testing. The bioreactor has the capacity to dynamically flex twelve rectangular samples (2.5 × 0.75 × 0.2 cm) under sterile conditions in a humidified cell culture incubator operating at 37 °C and 5% CO2 (Figure 1).
A Kinematic Approach to the Design and Analysis of Optimal Machining Fixtures
Authors: Marin Rodrigo A. , Ferreira Placid M.
Published: June 2008

This paper discusses the design and analysis of machining fixtures from a kinematics perspective. We use screw theory to model the fixture elements, the motions and forces/moments involved. We present linear algebraic methods that are quick and reasonably accurate, as opposed to existing methods. First, we study the determinism of 3-2-1 locator schemes and present simple formal geometric conditions to verify it. They also give an insight into the design issues influencing the robustness of the locator scheme. Next, we discuss the problem of synthesizing optimal clamping schemes that minimize the maximum clamping force. We present linear programs to solve this problem with and without friction. Finally, we focus our attention on the robustness of the fixturing scheme and discuss the use of form closure to provide it. We present linear algebraic methods to compute the regions of the workpart within which the clamps can be placed to produce form closure, both dependently and independently of each other. The method is easily incorporated in the linear program to compute optimal clamping schemes.
Strategy for Tissue Engineering of Osteochondral Constructs
Authors: Takai Erica , Guo X. Edward , Lu Helen H. , LeRoux Michelle A. , Raina Priya , Ateshian Gerard A. , Hung Clark T.
Published: June 2008

Damage to articular cartilage is a common condition affecting the joints of millions of people. This is a major problem considering the poor regenerative capacity of adult articular cartilage and the disability and pain that accompanies these injuries [13]. There exists a range of options that have been applied in clinical practice, with variable degrees of success, for repair of focal lesions and damage of the articular surface, including tissue adhesives [1,6,11,12,18], enzymatic treatments [8] and laser solder welding [21], autograft cell/tissue transfer via osteoperiosteal grafts [17], osteochondral grafts (mosaicplasty) [10] and Carticel [4,5]. The poor healing capacity of articular cartilage [13], potential for donor site pain and morbidity in autograft procedures, risk of disease transmission in allograft procedures, and the limited longevity of arthroplasty systems (i.e., ∼15 years for a total knee arthroplasty), has generated considerable research efforts to develop cell-based therapies for articular cartilage repair and replacement.
A New System for Cyclical Tensile Loading of Cultured Connective Tissue Cells in a Three-Dimensional Gel Matrix
Authors: Dussault Chantal , Young Dominic I. , Duncan Neil A.
Published: June 2008

Cells can sense and respond to the mechanical load present in connective tissue. Cell shape has been correlated to the local mechanical environment in a variety of connective tissue cells [1,2], and cell deformation has been suggested as a mechanism to transduce tissue mechanical signals to the nucleus via the cytoskeleton [3,4]. Though many connective tissues are subjected to tensile loads, to date very limited investigations have been reported on the effect of tensile loads on the mechano-biology of isolated cells. To apply tensile loads to isolated connective tissue cells requires a three-dimensional (3D) matrix to maintain cell phenotype, and a highly elastic matrix to enable the large deformations that the cells experience in situ.
On Modeling of Piezoelectric Patches in Aeroelastic Vibrations
Authors: Agneni Alessandro , Mastroddi Franco , Polli Gian Mario
Published: June 2008

A procedure for the analysis of the effectiveness of shunted piezoelectric devices in increasing passive damping on aeroelastic systems is presented. The proposed methodology is based on the description of aeroelastic systems composed by a flexible fixed-wing in a linear potential flow bonded with several piezo-electric devices in order to achieve a selective control of critical aeroelastic modes. The aeroelastic application has shown the capability of improving the stability margin and reducing the response amplitude in the parametric operative range of the system assigned in term of flight speed, air density, and Mach number. Indeed, a relevant issue emphasizing the complexity of the aeroelastic vibrations is represented by the explicit parametric dependency of the system to such parameters. Thus, a suitable performance of the piezo damper should be designed for any flight speed, altitude and Mach number. Moreover, a control law has been used for the optimal tuning of piezo devices within the parameters ranges by means of a resistive-inductive shunt of such devices. The modal model, the stiffness matrices of piezo elements and also the aerodynamic model have been calculated by a commercial finite element code. The use of a finite-state form for the aerodynamics allows to get the solution of the problem by a standard first-order state-space representation.
Method for Flutter Aeroservoelastic Open Loop Analysis
Authors: Botez Ruxandra , Doin Alexandre , Cotoi Iulian
Published: June 2008

Aeroservoelasticity (ASE) is a multidisciplinary study of interactions between structural dynamics, unsteady aerodynamics and control systems. In this paper, the Aircraft Test Model ATM developed by NASA Dryden Flight Research Center is used, and the velocities at which flutter occurs are calculated by use of the STARS aeroservoelastic software. For the validation of our aeroservoelastic study, STARS aeroservoelastic software developed also by NASA is used. We develop a new aeroservoelastic tool in Matlab to consider these interactions, and the obtained results through our method are compared to the ones obtained in STARS.
The Optimization of Continuous Indentation Technique Parameters
Authors: Jeon Eun-chae , Kwon Dongil , Park Joo-Seung
Published: June 2008

Continuous indentation technique has been widely studied because of its various merits, such as simple experiments, short experiment time and nondestructive technique. It is proved that the technique can produce tensile properties from the load-depth curves without optical observation by many researches. When the experiment is performed, it is, however, very difficult to determine the values of various experimental parameters that affect derived tensile properties by inserted in numerical analysis procedure. In this study, the effects of the parameters were studied using Taguchi method which is a kind of design of experiment (DOE). The ratio of indentation depth to indenter radius, the indenter radius, the number of unloads and the unloading ratio were selected as the main parameters. The changes of derived tensile properties by the main parameters were analyzed by calculating signal-to-noise (SN) ratio. Finally, the optimum values of each parameter were determined. The tensile properties evaluated with the optimum values showed much better agreement to those from uniaxial tensile test.
Flow Phenomena and Time Resolved Concentration Measurements in an Axial Flow Mixer
Authors: Campbell Jared E. , Coppom Richard W.
Published: June 2008

Experiments were conducted to better understand the flow physics associated with axial flow mixers in pipes. Specifically, the dependence of the downstream mixing evolution on the velocity ratio of the secondary to primary stream was explored. Experiments were conducted in a 25.4 mm diameter water pipe flow loop (25,700 ≤ RD ≤ 28,500), in which a fluorescein dye was coaxially injected. The injection tube diameter was 1.5 mm. Three velocity ratios, VR = 0.5, 1.0 and 2.0 were explored, where VR = Vjet/Vmain. The present results indicate that the effects of velocity ratio on the mean concentration are primarily evident in the near-field flow downstream of the injector, while concentration variance measurements indicate a primary influence at intermediate axial locations. Analysis of higher order moments and flow visualizations suggest that these influences are associated with the injected flow conditions. Two-dimensional LIF analysis of the coherent jet breakup region showed an instability in this transition related to injector flow Reynolds number. The present concentration measurements do not indicate the exponential variance decay commonly used for modelling mixing in pipes. Far field data exhibit low wavenumber motions as predicted by the recent theory of Guilkey et al. (1997).
Computer-Aided Analysis of Transient and Steady State Temperature Distribution in Human Brain During Selective Cooling of Head Surface and Rewarming for Head Injury Patients
Authors: Zhu Liang , Diao Chenguang
Published: June 2008

In recent years, mild or moderate hypothermia during which brain temperature is reduced to 30–35°C has been proposed for clinical use as an adjunct for achieving protection from cerebral ischemia and traumatic brain injury. There are two approaches for achieving a reduction in brain temperature. One is via systemic hypothermia where the whole body is cooled. This approach may produce deleterious systemic complications and require intensive monitoring. Another approach is called selective brain cooling (SBC) in which the brain is selectively cooled while the rest of the body is kept at normal temperature. Clinically feasible SBC protocols include head hood or helmet with water or chemical cooling, head immersion in iced water, nasophyaryngeal cooling after tracheal intubation, and intro-carotid flushing. Simply packing ice or wearing cooling helmet is easy to implement. Previous theoretical study [Zhu and Diao, 2001] suggests that it is feasible to achieve mild hypothermia via head surface cooling. However, most physicians believe that it takes a much longer time to reduce the brain temperature using head surface cooling. In this study, a three-dimensional theoretical model is developed to study the transient and steady state temperature distribution in the brain during SBC. The effect of regionally varying local blood perfusion rate in the brain tissue on the temporal and spatial temperature gradient is examined. Other factors including the brain size and the thermal contact resistance between the cooling medium and the head scalp are evaluated in the simulation.
Fractal Reconstruction of Breast Perfusion Before and After Hyperthermia Treatments
Authors: Craciunescu Oana I. , Das Shiva K. , Wong Terrence Z. , Samulski Thaddeus V.
Published: June 2008

Thermal modeling for hyperthermia breast patients can provide relevant information to better understand the temperatures achieved during treatment. However, human breast is much perfused, making knowledge of the perfusion crucial to the accuracy of the temperature computations. It has been shown that the perfusion of blood in tumor tissue can be approximated using the relative perfusion index (RPI) determined from dynamic contrast-enhanced magnetic resonance imaging (DE-MRI). It was also concluded that the 3D reconstruction of tumor perfusion can be performed using fractal interpolation functions (FIF). The technique used was called piecewise hidden variable fractal interpolation (PHVFI). Changes in the protocol parameters for the dynamic MRI sequences in breast patients allowed us to be able to acquire more spatial slices, hence the possibility to actually verify the accuracy of the fractal interpolation. The interpolated slices were compared to the imaged slices in the original set. The accuracy of the interpolation was tested on post-hyperthermia treatment data set. The difference between the reconstruction and the original slice varied from 2 to 5%. Significantly, the fractal dimension of the interpolated slices is within 2–3% from the original images, thus preserving the fractality of the perfusion maps. The use of such a method becomes crucial when tumor size and imaging restrictions limits the number of spatial slices, requiring interpolation to fill the data between the slices.
Investigation of Thermal Effect of Packaged CMOS Compatible Pressure Sensor
Authors: Peng Chih-Tang , Lin Ji-Cheng , Lin Chun-Te , Chiang Kuo-Ning
Published: June 2008

In this study, a packaged silicon base piezoresistive pressure sensor with thermal stress buffer is designed, fabricated, and measured. A finite element method (FEM) is adopted for design and experimental validation of the sensor performance. Thermal and pressure loading on the sensor is applied to make a comparison between sensor experimental and simulation results. Furthermore, a method that transfers simulation stress data into output voltage is proposed in this study, the results indicate that the experimental result coincides with simulation data.
Failure Mechanism Study of Anisotropic Conductive Film (ACF) Packages
Authors: Mercado Lei L. , White Jerry , Sarihan Vijay , Lee Tom
Published: June 2008

Anisotropic Conductive Film (ACF) consists of an adhesive polymer matrix with dispersed conductive particles. In Flip-Chip technology, ACF has been used in place of solder and underfill for chip attachment to glass or organic substrates. The filler particles establish the electrical contacts between the interconnecting areas. ACF Flip-Chip bonding provides finer pitch, higher package density, reduced package size and improved lead-free compatibility. Nevertheless, the interconnection is different from traditional solder joints, the integrity and durability of the ACF interconnects have major concerns. Failures in Anisotropic Conductive Film (ACF) parts have been reported after temperature cycling, moisture preconditioning and autoclave. The failures have not been well understood and have been attributed to a wide variety of causes. This paper investigates the failure mechanism of ACF using finite element simulation. From a failure-initiation point of view, the response of ACF packages to environmental (temperature and humidity) exposure is very different from standard underfilled packages. These differences cause the ACF package to fail in different ways from an underfilled package. Simulation results have shown that moisture-induced ACF swelling and delamination is the major cause of ACF failure. With moisture absorption, the loading condition at the interface is tensile-dominant, which corresponds to lower interface toughness (or fracture resistance). This condition is more prone to interface delamination. Therefore, the reliability of ACF packages is highly dependent on the ACF materials. The paper suggests a new approach towards material selection for reliable ACF packages. This approach has very good correlation with experimental results and reliability testing of various ACF materials.
Dynamic Analysis of Airflow in Air-Jet Filling Insertion: Part II — Air Velocity Measurements
Authors: Adanur Sabit , Bakhtiyarov Sayavur I. , Turel Tacibaht
Published: June 2008

Air-jet filling insertion is the most popular way of insertion systems in weaving. The heart of the air-jet filling insertion is the air flow, which provides the necessary propelling force for the yarn. In this work, the characteristics of airflow in air-jet filling insertion are discussed. The procedure and experimental system that is developed at Auburn University to measure the air flow characteristics is described.
Effects of Pulsatility on the Laminar Mixing Surface in Converging Microchannel Flows
Authors: Hitt D. L. , McGarry M. , Prabhu R. D.
Published: June 2008

With the growing interest and development of microfluidic systems, the need for micro-scale laminar flow mixing techniques is evident. Traditional mixing methods often rely upon turbulent flow for mixing which is generally not present on the micro-scale and so alternative approaches must be sought. In this work, we report on the impact of flow pulsatility on the laminar mixing surface/interface formed between two converging microchannel flows. The motivation behind the study is to assess the potential for pulsatility as a possible MEMS-mixing strategy. A 3-D computational model of the converging flow at a 90° junction is developed using the Fluent6® CFD software and the volume-of-fluid algorithm is used to track time-dependent behavior of the interface downstream of the junction. Results thus far have shown that for certain parametric regimes a complex, evolving interfacial distortion can form which propagates and persists downstream of the junction. Time-series for the total interfacial area and the interfacial motion have been extracted from numerical data and spectral analyses have been performed; some interesting nonlinear behavior has been observed. Of particular importance, the results also show that the complexity of the interfacial structure is only significant at higher frequencies (order of kHz) which is appropriate for MEMS-based pumping devices.
Piezoelectrically Actuated Microvalves for Micropropulsion Applications
Authors: Yang Eui-Hyeok , Lee Choonsup
Published: June 2008

This paper presents a piezoelectric microvalve technology with a high pressure handling capability for micropropulsion applications. The device is a normally closed valve fabricated mostly by the micromachining of silicon. The valve consists of a custom designed piezoelectric stack actuator bonded onto silicon valve components in a stainless steel housing. Major elements of the silicon valve design include narrow edge seating rings and tensile-stressed silicon tethers that contribute to the desired normally closed leak-tight operation. No leak has been detected from a soap solution test at differential pressures of 0∼500 psi for a normally closed valve structure, indicating a leak rate of 0.001sccm or lower has been achieved. Piezoelectric operation has been successfully demonstrated at a differential pressure of 500 psi. A flow rate of 20 sccm at 100 psi has been obtained at 50 V.
Investigation of the Formation and the Applications of Ice Powder
Authors: Shishkin D. V. , Geskin E. S. , Goldenberg B.
Published: June 2008

Water ice powder constitutes a potentially important manufacturing tool. Availability and cleanliness of this powder constitute its major advantage. It was shown that the ice particles can be used as an abrasive in the course of waterjet machining. Although the erosion potential of ice particle is inferior to that of the conventional abrasives the environmental soundness of ice enables us to expend the use of the ice abrasive jets on food industry, medicine, precision machining, etc. The principal issue in the use of the ice abrasives is particles formation. Analysis of various technologies showed that the most effective avenue in particles production is integration of the water freezing and ice decomposition. As the results, the desired flow rate of ice particles at the desired temperature and size distribution can be generated. The objective of the presented paper was the experimental investigation of the production of ice particles. An experimental set up was constructed and used for particles fabrication at controlled conditions. The acquired information was applied for the analysis of the phenomena leading to the particles formation. As the result a hypothetical mechanism of the ice decomposition was suggested and validated. The experiments involving the decontamination of the electronic devices, semiconductors, fabric, leather, food products, polished metal, soft plastics, rusted auto parts, etc were carried out in order to demonstrate the potential application of the ice blasting.
Numerical Modeling of Si0.15Ge0.85 by the Traveling Solvent Method
Authors: Makriyannis T. J. , Saghir M. Z. , Labrie D.
Published: June 2008

The traveling solvent method (TSM) is a relatively new and promising technique for the production of high quality semiconductors. TSM has been tested on many alloys producing pure and homogeneous crystals. In the present study the effect of buoyancy convection on the growth of the Si0.15Ge0.85 crystal grown by the traveling solvent method is investigated under different heating conditions. The full Navier-Stokes equations together with the energy and solutal equations were solved numerically using the finite element technique. The model take into consideration the losses of heat by radiation and the use of the phase diagram to determine the silicon concentration at the growth interface. Results revealed a strong convection in the solvent, which in turn is detrimental to the growth uniformity in the crystal rod. Additional numerical results showed that the convective heat transfer significantly influences the solute distribution in the liquid zone and the growth rate increases substantially.
Improved Prediction of Indoor Contaminant Distribution for Entire Buildings
Authors: Yuan Jinchao , Srebric Jelena
Published: June 2008

This paper presents a study on improvements of multi-zone models for predicting building contaminant distribution by combining a multi-zone model with a Computational Fluid Dynamic (CFD) model. The motivation is to avoid the long computations in the CFD model that are required for predicting concentrations in entire buildings. Two cases are investigated using the combined model and the results are compared to reliable experimental or CFD data. The comparisons show that the combined model provides better results than the multi-zone model alone in one of the cases, while in the other no major improvements were observed. Further investigation and development of the combined model is needed.
The Development and the Use of Fiber Optic Sensors for the Structural Health Monitoring of Composite (GFRP) Structures
Authors: Rivera Evageline , Polyzois Dimos , Thomson Douglas J. , Xu Ningguang
Published: June 2008

The development of a fiber optic sensor system for the long-term monitoring of composite glass fiber-reinforced polymer (GFRP) poles will be presented. There is a growing interest in developing techniques for evaluating and monitoring their structural integrity. In the past few years, fiber optic sensor technology has emerged as a promising alternative to conventional methods of monitoring such as strain gauges. Fiber optic sensors can be attached to or embedded in civil structures such as bridges, dams and buildings. They operate by responding to changes in temperature and strain on the structure. The long gauge fiber optic sensor measures the average strain between two points on a structure. Long gauges are interferometric sensors that involve phase matching two optical paths to create a maximum interference pattern at the photodetector. The strain is calculated using the distance in which the reference arm of the interferometer is moved in order to match the optical path lengths.
Comparison of Cost Factors in Laser Processing of Materials and Traditional Metal Cutting Processes
Authors: Verma Alok K. , Bao Han P. , Nagarathnam Kartik
Published: June 2008

Comparison of cost factors between traditional metal cutting process and laser cutting process has been made. The paper presents a generic cost estimation model for laser cutting of metals. Various types of lasers used in cutting have been discussed as well as the parameters affecting the cutting process.
Leading an Academic Department Through a Period of Dramatic Change
Authors: Untener Joseph A.
Published: June 2008

An academic department can be a complex organization and one that requires specific attention and skills to manage properly. Like any organization, there are forces that tend an academic department toward change and countering forces that tend to maintain the status quo. The dynamics of these issues during a time of fast moving and dramatic change are important and, quite often, misunderstood.
Building Effective Bridges Between Academic Departments and Admissions Staff
Authors: Gyure James F. , Samples Jerry W.
Published: June 2008

This paper describes a successful collaboration between the Chairman of an Engineering Technology Department and the Admissions and Enrollment administrator, each looking for increased enrollment. The focus will include the strategic advantages and the practical logistics of the coordinated recruiting program. Specific examples and recommendations will be provided to assist in adapting this program to other institutions.
The Good, Bad, and the Ugly of the Divide Between Engineering and Engineering Technology
Authors: Vajpayee S. Kant , Loflin David H.
Published: June 2008

Engineering technology programs in U.S colleges and universities were established by the 1970s. Their separate existence from engineering has resulted in mixed outcomes—some good, some bad, and some outright ugly. By ugly we mean the confusions generated by the divide between engineering and engineering technology. In this paper, critical analysis of the good, the bad, and the ugly is presented. It begins with a brief history of engineering technology as a discipline, discusses the current situation, points out the fact that few advanced countries practice such a divide, and offers some suggestions for improvement.
Absolute and Convective Instabilities of a Collapsible Tube
Authors: Mahmoud Hamadiche
Published: June 2008

In this paper we extend a numerical method, developed previously by the author, to compute the eigen modes of collapsible viscoelastic duct convening a fowing fuid. A new technique is developed in order to eliminate the need for recurrence formula used in the old method. This gives a more powerful and tractable method to find the eigen modes of the system. The new method has allowed the identification of a new unstable modes in a collapsible tube. It is found that there is a set of standing non axisymmetric waves representing an absolute instabilities and a set of unstable upstream and downstream propagated waves representing a convective instabilities. Two standing waves have equal frequency in their cusp points. The frequency of the other standing waves, in their cusp points, are a multiple of the frequency of the first wave and that in good agreement with experimental finding available in the literature. It is found that the first absolute unstable mode becomes convective at high Reynolds number while the other standing wave remain absolutely unstable modes for Re higher than 100. The frequency ratio of the absolute unstable modes in their cusp point are preserved for all Reynolds number and that with an good agreement with the experience. The absolute unstable mode which becomes convective at high Reynolds number keeps a monochromatic wave with a frequency equal to the frequency of the second absolute unstable mode, in its cusp point, and that for all Reynolds number higher than the limit of absolute instability of the first mode in surprising agreement with the experimental results. It is founded that the viscosity of the solid stabilizes the standing wavesat different degree. The boundary separating the absolute instabilities zone from the convective instabilities zone are found.
Stochastic Stability of Linear Gyroscopic Systems: Application to Pipes Conveying Fluid
Authors: Vedula Lalit , Sri Namachchivaya N.
Published: June 2008

In this paper we obtain asymptotic approximations for the moment Lyapunov exponent, g(p), and the Lyapunov exponent,λ, for a two-degree-of-freedom gyroscopic system close to a double zero resonance and subjected to small damping and noisy disturbances. Using a perturbation approach, we show analytically that the moment and the top Lyapunov exponent grow in proportion to ε1/3 when the damping and noise respectively are of O(ε) and O(ε). These results, pertaining to pth moment stability and almost-sure stability of the trivial solution, are applied to study the stochastic stability of a pipe conveying pulsating fluid.
Self-Excited Oscillations in a Fluid-Beam Collapsible Channel
Authors: Cai Z. X. , Luo X. Y.
Published: June 2008

Unsteady behaviour of a new fluid-beam model for flow in collapsible channels is studied in this paper. A finite element code is developed to solve the fully fluid-structure interaction unsteady problem with method of rotating spines. The self-excited oscillations for different parameters are calculated and compared with these of the earlier fluid-membrane model by Luo & Pedley (1996). A stability line in the tension – wall stiffness space is identified which seems to associate with the small amplitude oscillations which are found only in the new model. As tension is reduced from the stability line, the oscillations undergo a change in amplitude and through to period doubling, highly irregular oscillations with chaotic-like behaviour, and finally divergent. The transition of these different types of oscillations, however, depends on the value of the wall stiffness which is new in this model.
Vibrations of Circular Cylindrical Shells With Nonuniform Constraints, Elastic Bed and Added Mass Coupled to Internal, External and Annular Flow
Authors: Amabili M. , Garziera R.
Published: June 2008

The effect of steady viscous forces on vibrations of shell with internal and annular flow has been considered by using the time-mean Navier-Stokes equations. The model developed by Amabili & Garziera (2000), capable of simulating shells with non-uniform boundary conditions, added masses and partial elastic bed, has been extended to include non-uniform prestress. The effect of steady viscous forces has been added to the inviscid flow formulation considered by Amabili & Garziera (2002). The computer code DIVA has been developed by using the model developed in the present study. It has been validated by comparison with available results for shells with uniform constraints and has been used to study shells with non-uniform constraints and added lumped masses.
Mesh Shape Preservation for Flow-Induced Vibration Problems
Authors: So R. M. C. , Liu Y. , Lai Y. G.
Published: June 2008

This paper describes a numerical technique that can prevent the mesh from severe distortion in flow-induced vibration calculations. An orthogonal transformed space that is related to the physical space through a Laplacian equation is introduced. At each time step, the mesh may deform significantly in the physical space due to structural vibration, but the mesh nodal value in the transformed space remains constant. As long as the coordinates in the physical space can be adjusted to render the transformed space independent of time, the mesh shape in the physical space is preserved, even though the mesh area may enlarge or reduce significantly. For simplicity, a two-dimensional flow-induced vibration problem is used to illustrate this method. Two side-by-side elastic cylinders in a cross flow are considered. The Reynolds number is fixed at 200 so that a laminar wake is still available. The mass ratio is chosen to be small so that large displacements of the cylinders can be realized. The predictions with and without mesh preservation are compared. The difference between the two results could be as large as 25% in the prediction of the mean transverse displacements of the cylinders. The method could be extended to three-dimensional flow-induced vibration problems without much difficulty.
Smart Materials-Based Structural Vibration Isolation for Minimizing Product Quality Variation Using H∞-Based Optimal Control
Authors: Turso J. A. , Roth J. T.
Published: June 2008

An H∞-Based optimal vibration isolation system using patch-type piezoelectric actuators and sensors, suitable for application on high-precision manufacturing equipment that is being affected by external disturbances, has been designed. Reductions of the force transmitted through the structure range from approximately 5 to 30 dB in the frequency band of interest. Robust stability, nominal performance and robust performance have all been verified using the structured singular value, μ, and simulation testing for the set of plants within a derived uncertainty set. In addition, the H∞ controller is compared to an LQG-optimal controller designed for the same structure. The LQG controller, while achieving nominal performance comparable to the H∞ controller and being of significantly lower order, was shown to be unstable via μ-analysis and simulation testing. Thus, the LQG design should not be applied to a machine where there is significant in-band model uncertainty. Use of light-weight patch-type piezoelectric actuators and sensors provides a low-cost, easily-installable way of applying this technique to manufacturing equipment requiring isolation from low-frequency disturbances.
Self-Pierced Rivet (SPR) Modeling in Aluminum Structure Crash Analysis
Authors: Tang Dan X. , Barthelemy Bruno , Yuan Heng
Published: June 2008

A finite element method has been developed for modeling the characteristics of self-pierced rivets (SPR) in the aluminum parts and structures subjected to impact. It considers SPR elastic, inelastic and separation behaviors and was developed based on the coupon test results in lap shear, coach peel, and tension modes. The method consists of establishing baseline strength characteristics in the six degrees of freedom; and then modifying the baseline properties with coefficient factors (Ki) factors that influence the performance of SPR (thickness, differences in material, temperature, impact velocity, size of connection). The resulting combination is a material damage function that is utilized as the material properties of beam-type spring elements simulating the SPR connection in a FE model. The baseline properties and the equations for coefficient factors (Ki) developed in this study are provided. The material damage functions were developed in the RADIOSS environment, but can be applied to other codes as well. The method was validated at the component level using various configuration of a hat section tube. The CAE prediction using the new method correlates with the test results well in all the cases.