bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary Design of a Calorimeter for Experimental Determination of Effective Absorptivity of Metal Substrates During Laser Powder Deposition
Authors: Koester Jacob J. , Langerman Michael A. , Korde Umesh A. , Sears James W. , Buck Gregory A.
Published: April 2008

A thermal model of the laser powder deposition (LPD) process has been developed and tested. Results obtained from the model, however, are dependent upon the magnitude of the laser energy absorbed during the process. Although spectral absorptivities of metal surfaces are described in literature, during the LPD process, the powder increases the energy delivered to the substrate. There are no published data regarding this affect. Therefore, the SDSM&T Additive Manufacturing Laboratory (AML) is developing a calorimeter to experimentally investigate the affect of the powder on laser energy absorption at the metal substrate. The preliminary design is described in this paper with discussion on measures being taken to increase the accuracy of experimental data.
Experimental and Numerical Investigations of a Split-Ring Test for Springback
Authors: Xia Z. Cedric , Miller Craig E. , Ren Feng
Published: April 2008

This paper presents an in-depth experimental and numerical investigation of a split-ring test, which provides a simple yet effective benchmark for correlating forming and springback predictive capabilities with experimental measurements. The experimental procedure consists of deep drawing a circular 6111-T4 aluminum alloy into a cylindrical cup of 55mm depth, cross-cutting 9 rings of 5mm each from the cup, splitting the rings and measuring their opening displacement, i.e. the springback amount. Experimental data obtained included punch force trajectories, drawn cup profile, thickness distribution after forming, and the ring openings after splitting. A numerical model is built to analyze the process, and both transversely-isotropic and fully-orthotropic yield criteria are investigated. Simulation results are validated against experimental data. A detailed numerical analysis is also conducted for stress distributions in each ring after each step and their relationship to springback amount. Stress and strain signatures suggested that the test is well suited for validating material models such as anisotropic yield surface models and hardening models.
A Stochastic Approach to Dynamic System Modeling With Application to Gas Turbines
Authors: Bassily Hanny , Wagner John
Published: April 2008

Dynamic system mathematical models are a cornerstone for model based fault diagnostic techniques. However, achieving a robust mathematical model, based only on analytical derivations, cannot always be a realistic task especially for dynamic systems possessing physical parameter uncertainties and modeling errors. One attractive alternative is the huge capacity of stochastic methods to model non-deterministic highly complicated dynamic systems. In this paper, a general sensor-based modeling strategy is presented using stochastic techniques with application to a stationary gas turbine. The turbine sensors are monitored and recorded in real time to implement a signal modeling technique based on time series principles and turbine operation states. A subsequent recognition strategy, based on the turbine operation states and the Markov chain approach, is implemented to estimate the different signals. To experimentally validate the developed technique, input and output sensor data for a 4.5 MW stationary gas turbine has been recorded and analyzed during the critical start up phase. The proposed modeling strategy offers a considerable capability to recreate an unobserved signal from the observation of the other signals.
High Strain Rate Tensile Behavior of Carbon Fiber Reinforced Aluminum Laminates
Authors: Zhou Yuanxin , Mao Pingwen , Uddin Mohammad F. , Jeelani Shaikh
Published: April 2008

In this paper, loading and loading-unloading tests of carbon fiber reinforced aluminum laminates (CRALL) have been carried out in a tensile impact apparatus, and quasi-static tensile tests have been performed on a MTS-810 machine. Complete stress-strain curves of composite in the strain rate range from 0.001–1200 1/s have been obtained. Experimental results show that CRALL composite is a strain rate sensitivity material, the tensile strength and failure strain both increased with increasing strain rate. A linear strain hardening model has been combined with Weibull distribution function to establish a constitutive equation for CRALL. The simulated stress-strain curves from model are in good agreement with the test data. The analysis of the model shows that the Weibull scale parameter, σ0, increased with increasing strain rate, but Weibull shape parameter, β, can be regarded as a constant.
Intelligent Sensors: Strategies for an Integrated Systems Approach
Authors: Chitikeshi Sanjeevi , Mahajan Ajay , Bandhil Pavan , Utterbach Lucas , Figueroa Fernanado
Published: April 2008

This paper proposes the development of intelligent sensors as an integrated systems approach, i.e. one treats the sensors as a complete system with its own sensing hardware (the traditional sensor), A/D converters, processing and storage capabilities, software drivers, self-assessment algorithms, communication protocols and evolutionary methodologies that allow them to get better with time. Under a project being undertaken at the Stennis Space Center, an integrated framework is being developed for the intelligent monitoring of smart elements. These smart elements can be sensors, actuators or other devices. The immediate application is the monitoring of the rocket test stands, but the technology should be generally applicable to the Intelligent 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).
Turbomachinery Performance Models (2005B)
Authors: Pelton Robert J. , Japikse David , Maynes Daniel , Oliphant Kerry N.
Published: April 2008

Advanced meanline turbomachinery performance models are presented based on an extensive database for centrifugal and mixed-flow compressors and pumps. The methodology of processing the data is briefly discussed here, and in more depth in a companion paper. In this investigation, the detailed steps of building the highly non-linear, multi-variable, coupled models are presented. This modeling includes the impeller, a vaneless diffuser, and/or a volute. In future papers, diverse classes of diffusers, guide vanes, and return channels will be added as well. Using genetic expression programming, models of very high order are developed. These models are then tested against neural network models that are built using the same database. Several different classes of performance models are built to meet global modeling requirements, specific discipline domain requirements, and to meet specific designers’ requirements. This paper is one in a set of four papers. Papers No. 1 and 4 were presented at the ASME/IGTI Conference in Reno, Nevada, on June 6–9, 2005, and the remaining two (Papers No. 2 and No. 3) are being presented at the 2005 ASME International Mechanical Engineering Congress on November 5–11, 2005, in Orlando, Florida.
Blood Glucose Regulation for Diabetic Mellitus Using a Hybrid Intelligent Techniques
Authors: Nandikolla Vidya , Naidu Desineni
Published: April 2008

In this paper, we use a mathematical model for the interaction between the blood glucose and insulin concentration and investigates the on-line control schemes necessary to accomplish an external blood glucose regulation. The dynamic model is described in terms of blood glucose level, and net insulin level in blood as two state variables and external rate of blood glucose concentration as control variable. Using optimal regulation results, an objective is chosen to minimize the deviation of blood glucose from a preset level. The closed-loop optimal control scheme is developed for the biosystem in which a blood glucose sensor feeds information to a pump to release computed amount of insulin into the circulation system. The performance of the proposed optimal control scheme is compared with experimental results. Further to improve the closed-loop optimal performance, a soft control strategy based on adaptive neuro-fuzzy inference system (ANFIS) is devised leading to synergy of hard (optimal) and soft (artificial intelligent) control. ANFIS is a simple learning technique which is implemented in the framework of adaptive neural networks that provides the best optimization tool to find parameters that best fits the data. The application of this synergetic (hard and soft) control strategy to the diabetic regulation system shows good agreement between the experimental data and the theoretical/simulated results.
From Project Management to Project Design: A Research Proposal
Authors: Kamel Michael , Guirguis Hani
Published: April 2008

Project Management has had an increasingly important role in industrial organization, new product development and innovation theories over the last few decades. The majority of the current project management research and literature are focused on the post contract award phase as well as the skills and know-how of the project manager. Empirical research shows that, despite strict adherence to the best management norms and best practices, many projects still fail to achieve their objectives while others are aborted before they are completed. The authors argue that this project failute is due to the lack of an analytical and systematic process of designing the project prior to its award and that this phase of Project Design plays a major role in predetermining the project’s outcome. The following paper is a research proposal for presenting the literature review, theoretical basis and empirical evidence of the need for a theoretical framework for designing projects. This framework will encompass a dynamic model for the interactions between the various project success factors across different project categories.
Characterization and Design of Quartz Rate Sensors
Authors: Wang Frank , Smith Marc
Published: April 2008

The BEI Systron Donner’s quartz rate sensor (QRS) uses double-ended quartz tuning fork to sense angular rate. The drive fork, acting as a Coriolis sensor, is coupled to a similar fork as a pickup to produce the rate output signal. In this paper, the theoretical analysis of the quartz fork model is presented. Following that, FEA analysis results are discussed. The consideration to optimize fork design is detailed. Experiments from mechanical testing and electrical testing are presented to show the improvement of the fork design.
A High-Fidelity Electrokinetic Flow Model for the Prediction of Electrophoregrams in On-Chip Eletrophoresis Applications
Authors: Lin Hao , Bharadwaj Rajiv , Santiago Juan G. , Mohammadi Bijan
Published: April 2008

On-chip electrophoresis is a growing field with increasing chemical and bioanalytical applications such as genomics and proteomics. The use of multicomponent and heterogeneous electrolyte configurations can often lead to complex flow behavior. In this work, we present a high-fidelity, low computational cost electrokinetic flow model for the modeling and optimization of electrophoretic separations. The model adopts a depth-averaged approach that captures convective-dispersion processes, and includes important physical effects such as electrical body force and fully nonlinear multi-species electromigration. The corresponding numerical scheme is based on a finite volume approach using a monotonic upstream-centered construction (MUSCL). The numerical model can simulate arbitrary electrolyte and sample configurations, and capture the complex evolution of sharp, narrow sample peaks and high pre-concentration (stacking) ratios. Exemplary results showing both field amplified sample stacking and isotachophoresis processes are presented. The development of such models is critical to the efficient design and optimization of on-chip CE methods and devices.
A Metrological Traceability System for Microflowrate Measurement
Authors: Yang C.-T. , Lin W.-T. , Yang F.-R. , Feng C.-C.
Published: April 2008

Applications of MEMS have prompted the design and manufacture of fluidic devices for sub-microliter fluid flow measurement. The accuracy of flowrate in terms of traceability and repeatability provides key information for successful micro-fluidics applications. To establish a measurement standard for microflow sensors and microflow controller for liquid handling and microfluidic monitoring, a traceable measurement system at Taiwan’s NMI has been sponsoring since 2002. The applied approaches included a gravimetric approach, a virtual piston approach, and a velocity-based approach. The expected flowrate ranges from 10 mL/min down to 10 nL/min, and the measurement uncertainty is evaluated. In this paper, the gravimetric approach and the chip based volumetric approach were demonstrated of their measurement setup and capability.
A Micro-Fabricated Electrical Impedance Based Hematology Analyzer
Authors: Sullivan Stephanie M. , Jamieson Brian G. , Layton Bradley E.
Published: April 2008

Our work proposes a device to monitor and measure three key hematology parameters: red blood cell count (RBC), mean red blood cell volume (MCV), and red blood cell distribution width (RDW). This device will be a microfabricated microchannel unit. Cellular detection will be performed using an impedance device through a series of filter beds with channel dimensions of approximately 2–7 μm wide × 5 μm high × 5–15 μm long.
Design Process Error-Proofing: Lessons From and Challenges for NASA
Authors: Chao Lawrence P. , Tumer Irem , Ishii Kosuke
Published: April 2008

This report describes the state of design observed at NASA and collaborative research between NASA and Stanford University into improving design practices. Just as there are many types of missions and projects, there are many types of design practices and reviews at NASA. Through exploration of the NASA life-cycle across the organization and deeper case studies of specific missions, the goal of this work is to identify best practices and lessons learned from NASA’s review experience, benchmark against industry techniques, and develop methodologies to improve the process. By introducing design process error-proofing methods based on FMEA and QFD into the NASA framework, more robust corrective actions and solutions can better detect and prevent design errors. This paper demonstrates the methods through retroactive exploration and implementation on the Mars Climate Orbiter.
Adaptive Neural Network in Compensation the Dynamics and Position Control of a Servo-Hydraulic System With a Flexible Load
Authors: Yousefi Hassan , Handroos Heikki
Published: April 2008

Asymmetrical servo-hydraulic systems are commonly used in industry. These kinds of systems are nonlinear in nature and generally difficult to control. Because of changing system parameters, using the same gain will cause overshoot or even loss of system stability. The highly nonlinear behavior of these devises makes them idea subjects for applying different types of sophisticated controllers. This paper is concerned with using two artificial neural networks in compensation the dynamics and position tracking of a second order model reference in a flexible servo-hydraulic system. In present study, a neural network as an acceleration feedforward and another one as a gain scheduling of a proportional controller are proposed. Differential evolution algorithm is used to find the weights and biases to avoid the local minima. The proposed controller was verified with a commonly used p-controller. The results suggest that if the neural networks choose and train well, they improve all performance evaluation criteria such as stability, fast response, and accurate reference model tracking in servo-hydraulic systems.
On-Line Remaining Life Assessment of Hot Reheat Pipe Bend
Authors: Dutta B. K. , Guin S. , Samal M. K.
Published: April 2008

An ageing in-service Hot Reheat (HRH) pipe bend before Intermediate Pressure (IP) Stop/ Control Valve of a Utility was identified for real-time creep-fatigue damage assessment. A data acquisition system has been installed to record thermal hydraulic parameters, such as pressure, temperature and flow on real time basis. The HRH piping including low pressure bypass line incorporating various supports such as directional restraints, constant weight hangers and spring hangers, was modeled using straight and bend elements. Static stress analysis was performed to find out the forces and moments at either ends of the pipe-bend for sustained and expansion loadings using piping analysis program CAESAR-II. A detailed 3-D Finite Element Model of the pipe bend was also developed using 20-noded brick elements. The 3-D FE model along with material parameters and loading are used by code BOSSES for on-line monitoring of damage. The nodal temperatures (obtained by temperature transient analysis), recorded internal pressure, associated piping loads, etc. are then used in a stress analysis module to calculate stresses at different gauss points of the pipe bend. The temperatures and stresses at different time are then used to compute fatigue and creep damage and to assess growth of different postulated cracks at various locations of pipe bend, as well as remaining life. All the information are upgraded and restart files are saved for successive computation. The real-time process data of the pipe bend are made available to the Researcher’s Desk through Client-Server Network.
Technical Performance Modeling of Hybrid and Plug-In Hybrid Electric School Buses Using ADVISOR
Authors: Pritchard Ewan , Johnson Richard R.
Published: April 2008

The hybrid electric vehicle is changing the automotive market at an impressive rate. While not as highly publicized, the transit bus market is being transformed at an equally great rate. As these markets move forward, the school bus market remains largely unchanged. As an unchanged market, there is still the opportunity to optimize a hybrid vehicle platform for school buses. This study models an existing class C school bus and investigates the potential of both series and parallel hybrids to reduce fuel consumption and emissions. The primary focus of this study is to investigate the potential benefits of adding an electric grid interconnection to hybrid electric school buses, allowing them to add to the hybrid potential to a pre-charged battery pack. These vehicles are known as plug-in hybrids. The school bus models shown in this paper were generated in a Matlab/Simulink-based program developed by NREL called ADVISOR. ADVISOR is used by vehicle manufacturers as a tool to experiment with different vehicle configurations. In this study both a generic series hybrid and a generic parallel hybrid are generated and used in both charge-sustaining and charge-depleting scenarios with varying sizes of battery packs to increase the “grid energy.” The results of each model are presented by fuel economy and emissions reductions taking into account the power plant emissions and electricity costs. The results of the study show that by adding a plug-in connection to existing hybrids, significant savings can be achieved, both in fuel costs and in overall emissions. By analyzing the emissions at the power plant level and at the vehicle level we show that emission of NOx, Particulate Matter and Carbon Dioxide can all be reduced while saving on fuel costs. This study also shows that some models of traditional hybrid can be operated as plug-in models with little or no change to the system to gain significant benefit from the initial charge.
A Shape Reconstruction Method for Two Phase Materials Using Resistance Tomography Data
Authors: Soleimani Manuchehr
Published: April 2008

Electrical resistance tomography (ERT) has great potential to be used for multi-phase flow monitoring. The Image reconstruction in ERT is computationally costly, so the online monitoring is a difficult task. The linear reconstruction methods are currently used as fast methods. The image reconstruction is a nonlinear inverse problem and the linear methods are not sufficient in many cases. The application of a recently proposed non-iterative inversion method for two-phase materials in has been studied. The method works based on Monotonicity property of the resistance matrix in ERT and it requires modest computational cost. In this paper we explain the application of this inversion method. We demonstrate the capabilities and drawbacks of the method by using 2D test examples. A major contribution of this paper is to optimize the software program for the inversion (by doing most of the computations offline), so it can be used for online application.
Prediction of Erosion Due to Solid Particle Impact in Single-Phase and Multiphase Flows
Authors: Mazumder Quamrul H.
Published: April 2008

Solid particle erosion of metal surfaces is a major problem in several fluid handling industries due to unpredicted equipment failure and production loss. Prediction of erosion is difficult even in single-phase flow. The complexity of the problem increases significantly in multiphase flow due to existence of different flow patterns where the spatial distribution of the phases changes with the change of phase flow rates. Earlier predictive means of erosion in single and multiphase flows were primarily based on empirical data and were limited to the flow conditions of the experiments. A model has been developed for predicting erosion in single-phase multiphase flows considering the effects of solid particle impact velocities that causes erosion. Local fluid velocities and simplified equations are used to calculate erosion rates assuming uniform distribution of solid particles in the liquid phase in multiphase flow. Another assumption was that the solid particle velocities are similar to the velocity of the fluids surrounding the particles. As the model is based on physics of multiphase flow and erosion phenomenon, it is more general than the previous models. The predicted erosion rates obtained by the mechanistic model are compared to experiments data available in the literature and show good agreement.
Dynamic Analysis of a Hyperbolic Composite Coupling
Authors: Ghoneim H. , Lawrie D. J.
Published: April 2008

A novel hyperbolic composite coupling is proposed. In addition to enjoying the advantages of composite materials, the proposed coupling can be readily integrated with composite drive shaft into a single unit. A mathematical model of the coupling is developed based on the Timoshenko beam theory using the energy approach and the extended Lagrange’s equations. The corresponding discrete equation of vibration is obtained using the finite element method and solved for the natural frequencies using MATLAB. The dynamic characteristics of the coupling (Axial, torsional and bending natural frequencies) are studied in order to assess the merits and potential of the proposed coupling.
Vibrational Characteristics of Micro Beams
Authors: Onipede Oladipo , Avdeev Ilya , Khalilollahi Amir , Buziewicz Lisa
Published: April 2008

Several high frequency MEMS devices such as resonators and filters can be modeled as electrostatically driven micro-beams. While their static structural response depends solely on the magnitude of the applied voltage and their elastic stiffness, their dynamic response also depends on their mass, damping properties and the applied voltage frequency. In designing these devices, critical parameters must include the maximum voltage, voltage frequency and the natural frequency of the system. Even though the electrostatic force developed by the voltage is non-linear, the system can be modeled as a harmonic system due to the periodic nature of the response. Results from a non-linear structural-electrostatic dynamic model show the importance of the dynamic properties and the non-linear electrostatic force. The results show significantly lower limiting voltages, especially when the driving voltage is close to the natural frequency of the system. The effect of damping is also addressed.
A Control-Oriented Mean-Value Model of HCCI Diesel Engines With External Mixture Formation
Authors: Canova Marcello , Garzarella Luca , Ghisolfi Marco , Midlam-Mohler Shawn , Guezennec Yann , Rizzoni Giorgio
Published: April 2008

Homogeneous Charge Compression Ignition (HCCI) is considered a promising concepts to achieve low NOx and Particulate Matter emissions in traditional Spark Ignition and Diesel engines. However, understanding and controlling the complex mechanisms which govern the combustion process is still extremely difficult. A viable method to obtain HCCI combustion in DI Diesel engines consists of premixing the charge by applying an additional fuel injector in the intake port, thus decoupling the HCCI mixture formation from the traditional in-cylinder injection. The system allows high load operation in DI mode without compromising performance, low to mid-load operation in HCCI mode, and a region in between where both systems operate together. To manage HCCI combustion with external mixture formation it is essential to identify the most important control parameters and understand their influence on the auto-ignition process. The proposed paper deals with the analysis of HCCI combustion with external mixture formation through experimental investigation and a Control-Oriented mean-value model. The model provides the data required by a combustion calculation algorithm to perform a first-law analysis that estimates the in-cylinder heat release and pressure. The tool developed was then validated on data provided by an extensive experimental activity on a 4-cylinder Diesel engine equipped with an external fuel atomizer to operate in HCCI mode.
An Investigation of Temperature Characteristics of Pulsating Heat Pipe
Authors: Cai Qingjun , Chen Chung-Lung , Asfia Julie F.
Published: April 2008

Pulsating heat pipe (PHP) is an interesting heat transfer device. This paper focuses on PHP heat transfer characteristics versus its operating temperature. In experiments of copper and stainless steel PHPs, results indicate that, at a same input power, both temperature differences (from the evaporator to condenser) and evaporator temperature fluctuations are relevant to operating temperature. The minimal temperature difference and fluctuation appear at an operating temperature ranging from 120 to 160°C. Experimental analysis of the evaporator temperature fluctuations show that single phase cooling in PHP causes a large temperature difference (between the evaporator and condenser) and fluctuation. Phase change proportion increases at the optimal operation condition. Static mechanical balance combining with dynamic elastic oscillation system is used to interpret PHP temperature variations versus operating temperature.
3D Micro-Metrology Using a Nanofocus X-Ray Source
Authors: Antolak Arlyn , Morse Daniel , Aigeldinger Georg , Ceremuga Joseph
Published: April 2008

Metrology applied to microsystems accelerates yield improvement and sustains performance at all stages of processing thereby ensuring manufacturability. One measure of the manufactured part quality in micro-structures, e.g., microfluidic channels or LIGA-fabricated parts and assemblies, is the side-wall verticality and/or curvature. In this paper, we report on initial investigations to directly obtain three-dimensional metrological information with micron-scale spatial resolution. Using a lab-based nanofocus x-ray source (0.5 micron spot size), samples a few millimeters in diameter can be examined with high volumetric resolution by collecting thousands of (tomographic) projections. Following reconstruction of the projection data, dimensional information is extracted directly from the object’s 3D rendering. A test part was used to verify and optimize the tomographic inspection process, and the application of this method to a LIGA-fabricated part is presented.
Axial-Flux Motor System Efficiency in a Solar Powered Vehicle
Authors: Hammack Scott , Schinstock Dale
Published: April 2008

This paper presents a study of maximizing motor system efficiency for a solar powered vehicle by providing guidelines for the setup and operation of the motor system. It describes the vehicle, the motor system, and the dynamometer used for testing. Solar racecars use the axial flux motor described in the work because of its high efficiency, direct drive feature, and lead screw driven variable air gap. We present efficiency test results at a range of operating points. Motor operation in drive and regeneration modes is covered. During regeneration mode testing, the axial flux motor system converts mechanical energy provided by the dynamometer to electrical energy. In drive mode, the dynamometer absorbs the mechanical energy produced by the axial flux motor. The parameters varied in studying motor efficiency are battery voltage, speed, torque, and air gap size. Regeneration efficiency as influenced by back EMF is discussed. Guidelines for motor operation are developed. For example, guidelines for setting the motor air gap as a function of speed are given. The users of solar powered vehicles can employ these guidelines to setup and operate the motor more efficiently through improved regenerative energy capture and decreased drive losses. Application of the guidelines may be extended to other electric and hybrid vehicles, thus improving automotive energy efficiency.
A Subgrid Physics Model for Multi-Length Scale Thermal Analysis of MEMS
Authors: Wong C. Channy
Published: April 2008

A subgrid physics model has been developed to analyze heat transfer in an integrated microsystem. By modeling the ‘multi-mode’ phonon scattering process in microstructures, the dominant microscale heat transfer mechanisms such as phonon scattering at thin-film boundaries and at grain boundaries will be captured. Thus a localized anisotropic thermal conductivity can be calculated for use in system analysis. With this new capability, a continuum thermal analysis tool can address thermal problems with multiple characteristic length scales. To demonstrate its capability, this subgrid physics model has been applied to simulate the thermal response of a microscale optical shutter. Result shows that internal material structures such as grain size can significantly change the thermal response of a microsystem.
Simulation of Humidification Within a Breather
Authors: Sun Y. C. , Al-Jumaily A. M. , Makinson D.
Published: April 2008

A typical breather consists of an air delivery unit (ADU), a humidifying chamber, a connecting tube and a heated delivery tube. For an effective treatment of several respiratory syndromes such as sleep apnea, the chamber is recommended to generate the required moisture content and temperature of the air delivered by the breather. In this paper a mathematical model is developed for a complete breather with a focus on the humidification process. The model is simulated using Simulink™ in a Matlab™ environment. A series of experiments are conducted on various components of the breather for validation as well as to facilitate the necessary empirical relationships for the simulation process. The main outcomes of this work are: the ADU settings significantly alter the delivered air humidity level; the humidifier settings indirectly control the reservoir evaporation rate by controlling the chamber vapor pressure difference; the heated air delivering tube power input effectively controls the nasal mask airflow temperature; the ambient relative humidity level has a linear relationship with the nasal mask humidity level; and the ambient temperature variation can effectively influence the delivered air conditions.
Measurement of the Propagation Velocity of Pulse Wave Generated by Ultrasound in Arteries
Authors: Zhang Xiaoming , Greenleaf James F.
Published: April 2008

Arterial wall stiffness can be associated with various diseases. The stiffness of an artery can be assessed by measurement of the pulse wave velocity (PWV). Usually, PWV is estimated using the foot-to-foot method. However, the foot of the pressure wave is not very clear due to reflected waves. Also, the blood pressure wave generated by the heart is normally a low frequency wave, hence the time resolution is low. PWV is an average indicator of artery stiffness between two measuring locations, therefore, it is not easy to identify local stiffness. In this paper a short external pulse is generated in an artery by the radiation force of ultrasound. The propagation velocity of the pulse wave is measured along the artery. The temporal resolution of this method, which is in the range of microseconds, is much higher than the conventional pressure PWV method, and therefore allows the wave velocity to be measured accurately over a few millimeters.
Phase Field Simulation of Ferroelectric Single Crystals
Authors: Liu T. , Lynch C. S.
Published: April 2008

Ferroelectric materials exhibit spontaneous polarization and domain structures below the Curie temperature. In this study a cubic to tetragonal phase transformation and the evolution of domain structures in ferroelectric crystals are simulated by using the time-dependent Ginzburg-Landau equation. The effects of electric boundary conditions on the formation of domain patterns and field induced polarization switching are discussed. The phase field model is used to simulate the formation of domain structures, domain wall motion and the macroscopic response of ferroelectric materials under external fields.
Torque Ripple Attenuation of an Axial Piston Pump by Continuous Swash Plate Adjustment
Authors: Mehta Viral S. , Manring Noah D.
Published: April 2008

One of the major drawbacks of a hydraulic system is the disturbing noise generated by the hydraulic pump. Based on the accepted theory about noise generation in an axial piston pump, various studies suggesting modification of the port-plate relief groove geometry and addition of hydraulic attenuators have shown a limited success in reducing the noise. The noise level is still high and may not be acceptable for future applications. A recent industrial study shows that the noise apparently has relation with the torque acting on the input shaft of the axial piston pump. The primary objective of this paper is to describe a new method to reduce the noise level by varying the swash plate of the pump continuously to eliminate the torque ripple. The paper begins by deriving the equation of torque acting on the input shaft as a function of the average torque and the total number of pistons that are used within the rotating group. A control law is derived according to which if the swash plate is dithered, should give a constant shaft torque. By attenuating the torque ripple characteristics of the pump, other vibrational aspects of the pump are also expected to be reduced. The secondary objective of this paper is to present a Simulink® model of a nine piston pump to describe a functional pump. The swash plate control law earlier derived will be applied to this model to see the behavior of the output parameters like the shaft torque, output flow and pressure. The results will be investigated to see if any relationship exist between the pump torque ripple and pressure ripple, and the theory of pump noise attenuation by reduction in torque ripple will be corroborated.
Charged Droplets Emitted by Standing Capillary Waves in a Liquid Film: Part 1 — Theoretical Considerations
Authors: Song W.
Published: April 2008

This paper presents a method of producing charged droplets using standing capillary waves in a thin liquid film on a vibrating surface. Capillary waves with wavelengths on the order of microns are set to reach a critical stable condition and an electric field is applied to extract charged droplets from the crest of unstable waves. This method is more efficient than the method based on stable Taylor cones working in the cone-jet mode in producing a large quantity of uniformly charged droplets. Theoretical analyses on the droplet diameter, charge-to-mass ratio and the total current emitted from capillary waves are also presented.
2D PIV Experiments on Non-Uniform Flow in a Rectangular Open Model Pump Suction Passage
Authors: Xu Zhaofeng , Yi Fan , Liu Shuhong , Wu Yulin
Published: April 2008

Flows in the suction passage are important for pump working, which can influent the flow conditions in the pump. Some bad flow patterns in the suction passage may do damages to the pump, inducing cavitation, vibration, low efficiency and so on. Flow patterns of non-uniform flows in a rectangular open suction passage, such as distribution of velocity, streamline, turbulence kinetic energy and vortex, were studied by a 2D PIV method under different conditions. The results show that the non-uniformity of flow increases and the flow pattern gets deteriorate when the flow ratio of the two sub-passages rises or the total flow velocity increases. So the best operation condition can be chosen to avoid non-uniformity in the open pump suction passage.
Correspondence Between Notched and Unnotched Specimen’s Fatigue Data: Fundamental Concept and Formulation of Equivalent Stress Ratio REQ
Authors: Matsuno Hiroshi
Published: April 2008

In the present study, a creative consideration is developed for the problem of the correspondence between notched and unnotched specimen’s fatigue data. The proposed concept is essentially different from that of volumetric damage, and it has the great advantage of being avoidable to encounter the fatally invalid point of the volumetric approach, such as determination of damage-volume sizes. Moreover, the fatigue criteria derived are very easy to be applied to practical notch problems. The approach is developed as follows; (1) A hypothesis of plastic adaptation in a surface layer is proposed and mechanical models reflecting the hypothesis are constructed. (2) From these models, equivalent stress ratios REQ are derived as the new parameter for the correspondence between the cyclic stress conditions of the notched and unnotched specimens. REQ is generalized for proportional multiaxial cyclic loading through the consideration for the case of torsional cyclic loading. Moreover, REQ is derived from the mechanical model for the stress field of the mode I fatigue crack tip. (3) Experimental data on fatigue strength and fatigue crack propagation rates are rearranged on the basis of REQ and are formulated. (4) Practical criteria are proposed for the fatigue strength and the fatigue crack propagation rates.
Simple Models for Cyclic Variations Spark Ignition Engines
Authors: Chandrashekar T. K. , Antony A. J.
Published: April 2008

Cycle to Cycle variations in SI engines have increased our attention as reducing these CBC fluctuations will lead to better drivability, increased power output, better fuel economy, reduced emissions. As auto industry is growing at an alarming rate, numbers of users of automobiles are increasing day by day & strict emission standards have led people to think about the ways of increasing power with the same input. In this aspect evaluating the reasons for CBC variations has become the urgent need. In the present work a C-program has been written to simulate the same and pressure crank angle diagrams and MFB-crank angle diagrams for three different models & three different burn rates. The results are plotted & analyzed so that the best operating conditions are developed. The effects of Equivalence ratio, speed, throttle etc are studied.
Path Planning of Multiple UAV’s in an Environment of Restricted Regions
Authors: Shanmugavel Madhavan , Tsourdos Antonios , Zbikowski Rafal , White Brian
Published: April 2008

This paper describes a novel idea of path planning for multiple UAVs (Unmanned Aerial Vehicles). The path planning ensures safe and simultaneous arrival of the UAVs to the target while meeting curvature and safety constraints. Pythagorean Hodograph (PH) curve is used for path planning. The PH curve provides continuous curvature of the paths. The offset curves of the PH paths define safety margins around and along each flight path. The simultaneous arrival is satisfied by generation of paths of equal lengths. This paper highlights the mathematical property — changing path-shape and path-length by manipulating the curvature and utilises this to achieve the following constraints: (i) Generation of paths of equal length, (ii) Achieving maximum bound on curvature, and, (iii) Meeting the safety constraints by offset paths.
A 100 Motor Study: Investigating Pre-EPA Motors as a Subset of the Industrial Motor Population for Its Effects on the Economic of Motor Replacement, Preliminary Results
Authors: Kaufman Nicole M. , Welch Daniel , Johnson Richard R.
Published: April 2008

In the absence of hard data, the engineering world tends to be overly conservative in estimating benefits of change. The hypothesis herein discussed is that with hard data, the economics of motor repair/replace decisions could change significantly. If true, this could appreciably boost the efficiency of the industrial motor population by affecting the penetration of high-efficiency motors, such as NEMA Premiums. The energy savings from motor replacement depend on the difference between the efficiency of the new motor and the old motor. There has been a great deal of work investigating new motor efficiency and very little work investigating the actual running efficiency of older motors in the field. Motors that have operated for years experiencing failures and repairs may operate below their original nameplate or assumed efficiency. This study is a preliminary investigation of the efficiency of motors in industrial settings with the purpose of updating currently available motor analysis software tools to more accurately reflect the economic benefits of utilizing high-efficiency industrial induction motors.
Numerical Studies on Band-Gap Structures and Resonant-Mode Wave-Guides of Typical Sonic Crystals Made of Rigid Cylinders in Fluid by Means of Elastic FDTD Method
Authors: Miyashita Toyokatsu
Published: April 2008

We have investigated band-gap structures of three typical sonic/phononic crystals, namely periodic arrays of methacrylic resin cylinders in air, aluminum cylinders in air, and steel cylinders in water, by two different FDTD methods; one method is a sonic one that deals with only longitudinal waves, and the other is an elastic one that includes also shear waves. We show that both FDTD methods give almost the same band-gap structures for the former two crystals. Namely, the band-gaps by the sonic FDTD method lie at higher frequency only by 0.01 ~ 0.02 in the normalized frequency than those by the elastic one. The theoretical band-gap structures agree well with the experimental ones. In contrast, it is shown that the third crystal should be analyzed by the elastic FDTD method. Resonant-mode wave-guides are made by a periodic repetition of single-defects along a line in a sonic crystal of rigid cylinders in air. The obtained resonant and well-guided transmission band lies inside the full band-gap of the original bulk crystal. A combination of such wave-guides with a line-defect wave-guide is shown to have desirable characteristics for filtered wave-guides and wave-couplers.
The Analysis of Tensegrity Structures for the Design of a Morphing Wing
Authors: Moored Keith W. , Bart-Smith Hilary
Published: April 2008

Tensegrity structures have become of engineering interest in recent years, but very few have found practical use. This lack of integration is attributed to the lack of a well formulated design procedure. In this paper, a preliminary procedure is presented for developing morphing tensegrity structures that include actuating elements. To do this, the virtual work method has been modified to allow for individual actuation of struts and cables. A generalized connectivity matrix for a cantilever beam constructed from either a single 4-strut cell or multiple 4-strut cells has been developed. Global deflections resulting from actuation of specific elements have been calculated with or without external loads. Furthermore, the force density method is expanded to include a necessary upper bound condition such that a physically feasible structure can be designed. Finally, the importance of relative force density values on the overall shape of a structure comprising of multiple unit cells is discussed.
Exergy Evaluation of the Mineral Capital on Earth: Influence of the Reference Environment
Authors: Valero Alicia , Valero Antonio , Marti´nez Amaya
Published: April 2008

The mineral capital on Earth is assessed from a 2nd law of thermodynamics approach. This requires to define precisely the Reference Environment (R.E.). Therefore, the exergy difference of the mineral capital generated from different R.E. is calculated. A sensitivity analysis is done to measure the influence of the element chemical exergy and other physical parameters of the R.E. on the mineral’s exergy. The exergy of the world mineral reserves, base reserves and world resources is obtained: 0.75, 1.08 and 6.59 Gtoe, respectively.
Reliability Analysis of WLCSP Using Tie-Release Crack Prediction Finite Element Technique
Authors: Lee Chang-Chun , Chiang Kuo-Ning
Published: April 2008

For the purpose of enhancing the solder joint reliability of a wafer level chip scaling package (WLCSP), the WLCSP adopted the familiar design structure where both the stress compliant layer with low elastic modulus and the dummy solder joints are considered as structural supports. However, the predicted fatigue life of the solder joints at the internal part of the packaging structure using the conventional procedures of finite element simulation are higher than under actual conditions as a result of the perfect bonding assumption in the modeling. In this research, in order to improve the thermo-mechanical reliability of the solder joints, a node tie-release crack prediction technique, based on non-linear finite element analysis (FEA), is developed and compared with the estimation of the solder joint reliability using conventional methodology. The predicted results of reliability, using the novel prediction technique, show a lower fatigue life of the solder joint than that when using conventional one when the fracture regions in the dummy solder joints are simulated under quasi-steady state. At the same time, the result of the thermal cycling test also shows good agreement with the simulated result when using the proposed node tie-release crack prediction analysis.
Development of an Experimental Facility for Investigating Critical Heat Flux of Saturated Flow Boiling of Refrigerant-123 in Microchannels
Authors: Kuan Wai Keat , Kandlikar Satish G.
Published: April 2008

An experimental facility is developed to investigate critical heat flux (CHF) of saturated flow boiling of Refrigerant-123 (R-123) in microchannels. Six parallel Microchannels with cross sectional area of 0.2 mm × 0.2 mm are fabricated on a copper block, and a Polyvinyl Chloride (PVC) cover is then placed on top of the copper block to serve as a transparent cover through which flow patterns and boiling phenomena could be observed. A resistive cartridge heater is used to provide a uniform heat flux to the microchannels. The experimental test facility is designed to accommodate test sections with different microchannel geometries. The mass flow rate, inlet pressure, inlet temperature of Refrigerant-123, and the electric current supplied to the resistive cartridge heater are controlled to provide quantitative information near the CHF condition in microchannels. A high-speed camera is used to observe and interpret flow characteristics of CHF condition in microchannels.