bluuebunny/crossref_metadata_2025 huggingface dataset:
CFD Modeling of Free Surface and Entrainment of Buoyant Particles From Free Surface for Submerged Jet Systems
Authors: Khan Md. N. H. , Fletcher Clive , Evans Geoffrey , He Qinglin
Published: November 2021

For a submerged jet, there are many design characteristics to explore for better mixing of buoyant particles (BP). Industries are facing difficulties in mixing of BP. Higher turbulence favors mixing [1], but mixing of BP has always been an art. Submerged jet (SJ) or impinged jet (IJ) is one of the ways to disperse BPs. For a SJ, modeling of free surface is important when the jet is not deeply submerged (∼ 10 mm) in the liquid bath. In this research project, the free surface (surface between air and liquid) for a SJ system in a cylindrical liquid bath and entrainment of BPs has been studied with CFD analysis. The solution parameters (velocity profile and center line velocity) are validated against experimental LDV data generated. The use of 2D axisymmetric geometries minimized the computational cost. To overcome the computational burden of tracking individual particles, the dispersion of particles/ turbulent fluctuations were determined by a Particle Cloud Model [2].
Instantaneous Velocity Profiles and Characteristics of Pressure-Driven Flow in Microchannels
Authors: Kawaji M. , Chung P. M.-Y. , Kawahara A.
Published: November 2021

This paper presents a review of the flow characteristics in microchannels and our own flow visualization work using a photochromic dye activation technique. The review reveals differences in flow behaviour between micro- and macro-channels, and the need to measure instantaneous velocity profiles to explain these differences. In the experiment, de-ionized water containing a photochromic dye was pumped through a square capillary tube with inner dimensions of 96 μm × 96 μm to yield a Reynolds number of 0.1. A pulsed ultraviolet laser beam was used to create dye traces in the flowing liquid, and images of the traces were recorded with a video camera. Friction factor in laminar flow was also determined from pressure drop measurements at several Reynolds numbers using tap water. The experimental results showed the flow in intermediate-sized microchannels at low Reynolds numbers to still conform to conventional fluid mechanics theory, possibly with slight deviation. The success in obtaining quantitative results with this approach holds promise for further studies of flows in microchannels with smaller diameters.
Controlling Drop Rebound With Solid Target Motion
Authors: Kim Ho-Young , Lee Heon Ju
Published: November 2021

Drops having a high surface tension and a low viscosity, such as water and molten metal drops, exhibit a vigorous recoiling and a long-lasting oscillation upon impacting with nonwetting solid surfaces. Here we report the study of controlling drop rebound using target movement. Our experimental study reveals that drop rebound is highly enhanced in such a condition that the target moves upward at the moment of impact and reverses its motion when the recoiling starts. On the other hand, an effective suppression of drop rebound is achieved by moving the target downward upon drop impact and reversing its direction well in the middle of the recoiling process. This controlling scheme of drop rebound can be employed in such practical applications as the spray deposition processes and the solder jet bumping.
Heat Transfer and Critical Heat Flux of Forced Flow Boiling in Vertical-Narrow-Annular Passages
Authors: Koizumi Yasuo , Ohtake Hiroyasu , Fujita Yosinobu
Published: November 2021

The forced-convection flow boiling heat transfer in narrow-annular flow passages was experimentally examined by using R-113. The gap clearance and the mass flux were δ = 0.5 ∼ 10.0 mm and G = 102 ∼ 103 kg/m2s, respectively. When the clearance was narrow (δ = 0.5 and 1.0 mm), the critical heat flux (CHF) condition which was defined as the deviation from the fully developed nucleate boiling state occurred in the first place, then the wall temperature excursion (EXC) was initiated after a further increase in the heat flux. At the CHF condition, the wall temperature did not rise sharply. The difference between those heat fluxes, qCHF and qEXC, became small as the flow rate was increased. When the clearance became wide (δ ≥ 2.0 mm), the CHF condition and the EXC occurred simultaneously. The EXC heat flux qEXC increased sharply with an increase in δ until δ = 2.0 mm. In δ > 2.0 mm, the increasing rate calmed down to show tendency reaching some asymptotical value, qEXC of the co-current flow was considerably higher, approximately ten times, than qEXC of the counter-current flow. The difference decreased as δ became wide. The critical heat flux, qCHF, correlation, which was developed by considering that whether the dried area which was created because of wearing-out of the liquid layer under a bubble could be rewetted or not decide the critical condition, predicted well the present experimental results of qCHF. However, when δ was extremely narrow such as δ = 0.5 and 1.0 mm, the heat transfer deterioration due to the appearance of a coalescent bubble occurred before the condition defined above, thus the correlation overpredicted qCHF.
Study on Velocity Profile Measurement Using Ultrasound Time-Domain Correlation Method
Authors: Yamanaka Gentaro , Kikura Hiroshige , Aritomi Masanori
Published: November 2021

This paper presents a velocity profile measurement technique using a ultrasound time-domain correlation method (UTDC). The system is based on the cross correlation between two consecutive echoes of ultrasonic pulses to detect the velocity. The UTDC has two advantages over a conventional ultrasound pulse Doppler method. First the system has a higher time resolution than the pulse Doppler method. Second, the system does not have a limitation in maximum measurable velocity, which is limited by Nyquist’s sampling theorem.

In this paper, the velocity profile measurement using the UTDC is performed, and the velocity profiles measured by the UTDC is compared with the one obtained using the pulse Doppler method.

The result showed that aliasing effect occured by the measurement of the pulse Doppler method but does not occured by that of the UTDC at the same pulse repetation frequency.
Generalized Mechanistic Force System Model of Ball-End Milling for Sculpture Surface Machining
Authors: Lazoglu Ismail
Published: November 2021

In this paper, a new mechanistic model is developed for the prediction of cutting force system in ball-end milling process. The key feature of the model includes the ability to calculate the workpiece / cutter intersection domain automatically for a given cutter location (CL) file, cutter and workpiece geometries. Moreover, an analytical approach is used to determine the instantaneous chip load and cutting forces. The model also employs a Boolean approach for given cutter, workpiece geometries, and the CL file in order to determine the surface topography and scallop height variations along the workpiece surface which can be visualized in 3-D. Some of the typical results from the model validation experiments performed on Ti-6A1-4V are also reported in the paper. Comparisons of the predicted and measured forces as well as the surface topographies show good agreement.
Geometry Analysis and Simulation in Shoe Centerless Grinding
Authors: Zhang Hong , Lieh Jungshen , Yen David , Song Xiaozhong , Rui Xiaojian
Published: November 2021

In this paper, the geometry relationship of shoe centerless grinding for predicting the profile of workpiece is presented. Based on the model, critical parameters are studied. The model was compared with experimental results obtained from grinding trials.
Grading and Motivation of Student Teams Working on Industry-Sponsored Mechanical Design Projects
Authors: Beale David G. , Simionescu P. A. , Dyer David
Published: November 2021

The guiding principles adopted for teaching the Comprehensive Mechanical Design course in the Department of Mechanical Engineering of Auburn University are presented. These were introduced to better serve the need for well-trained engineering personnel, where technical skills must be combined with good communication and management skills.
Pre-Processing of Heterogeneous Objects for Layered Manufacturing
Authors: Shin Ki-Hoon , Dutta Debasish
Published: November 2021

Layered manufacturing (LM) is emerging as a new technology that enables fabrication of three dimensional heterogeneous objects (such as Multi-materials and Functionally Gradient Materials). The steps for fabricating heterogeneous objects include model representation and material process planning. This paper introduces a method for processing the material information. It includes pre-processing (discretization), orientation (build direction selection), and adaptive slicing of heterogeneous objects. The discretization process converts all material information inside a heterogeneous object to material features like geometric features, thus it makes it possible to determine build direction by estimating build time based on geometric features and material features. It also allows adaptive slicing of heterogeneous objects to minimize surface finish and material resolution error. In addition, tool path planning can be simplified to fill pattern generation. Examples are shown.
On the Driving Mechanism Design for Large Amplitude Electrostatic Actuation
Authors: Hsieh Jerwei , Chu Chien-Cheng , Fang Weileun
Published: November 2021

This study intends to improve the performances of conventional electrostatic actuator regarding its amplitude and driving force. Two approaches including the oblique-comb actuator design and 2-DOF vibration system for amplitude amplification are proposed. The former has advantages in both generated force and allowable stroke, while the latter has the nature of larger output amplitude driven by smaller input stroke. Base on the advantages of both methods, the combination of these two designs can further improve the performance regarding output amplitude and driving voltage.
Flip-Chip Fabrication of Advanced MEMS Using a Novel Latching Off-Chip Hinge Mechanism
Authors: Michalicek M. Adrian , Bright Victor M.
Published: November 2021

This paper presents the design, fabrication and implementation of a novel off-chip hinge mechanism that can be latched in place to hold surface-micromachined structures off the edge of the chip. This mechanism was designed to enable fast, reliable, accurate, simple, and low-cost fabrication of advanced flip-chip MEMS structures. The upper layers of a flip-chip device can be commercially prefabricated on a host module attached to the hinge mechanism while the lower layers can be prefabricated on virtually any desired receiving module. This paper presents the design, fabrication and testing of a variety of advanced micromirror arrays assembled using this mechanism. This research demonstrates that structures comprised of several surface-micromachined layers can be positioned and bonded onto a variety of work surfaces such as ceramic substrates, MEMS chips and even CMOS electronics using adhesives, solder, gold bonding or mechanical latches. The hinge mechanism is designed to be easily disabled by a variety of methods should another bonding technique be desired. All flip-chip modules are designed with the mechanism to enable multiple flip-chip assembly options.
A Magnetically Actuated, Electrostatically Clamped High Current MEMS Switch
Authors: Choi Yoonsu , Kim Kieun , Allen Mark G.
Published: November 2021

MEMS switches based on a dual actuation scheme that simultaneously allows for large standoff heights and low clamping voltages have been fabricated. The switches consist of a magnetically-driven component and an electrostatically-driven component. These devices are based on the use of a transient external magnetic field to bring the actuating portion of the switch (made of electroplated NiFe) close to a dielectric-coated clamping electrode, followed by application of an electrostatic clamping voltage to keep the switch closed. Since the clamping voltage is applied when the switch is closed, this voltage can be relatively small. This approach is particularly attractive for reconfigurable arrays of switches. Arrays of switches are simultaneously closed by the magnetic field generated by an off-substrate magnetic source. Selected switches are clamped by electrostatic force using low voltages to maintain the ON state. With this scheme, reconfigurable patterns on an array of switches are possible. These switches possess a large open state air gap (25–35 μm), and are able to pass high currents in excess of 1 A. The large OFF state impedance, then, allows for their usage in switching applications in reconfigurable aperture antennas.
Pirani Pressure Sensor With Distributed Temperature Sensing
Authors: van Baar J. J. , Wiegerink R. J. , Lammerink T. S. J. , Krijnen G. J. M. , Elwenspoek M.
Published: November 2021

A Pirani pressure sensor is based on the fact that the thermal conductivity of a gas is dependent on the pressure. The structure presented in this paper consists of a heated microbeam, which is placed above a v-groove in a heat sink. The temperature distribution along the microbeam is a measure for the thermal conductivity of the surrounding gas. Measuring the temperature distribution instead of the average temperature of the beam has two advantages: the measurement becomes independent of the Temperature Coefficient of Resistance of the temperature sensing resistors and the heat loss to the substrate is implicitly taken in account, which extends the lower pressure range.
Omnidirectional Walking Microrobot Realized by Thermal Microactuator Arrays
Authors: Mohebbi Matthew H. , Terry Mason L. , Böhringer Karl F. , Kovacs Gregory T. A. , Suh John W.
Published: November 2021

An omnidirectional mobile microrobot realized by micro-electromechanical system (MEMS) actuator arrays is presented. The microrobot consists of two rigidly connected microcilia array chips, each having an 8 × 8 array of “motion pixels,” which are composed of four orthogonally oriented thermal bimorph actuators. This allows for reliable, accurate motion in three degrees of freedom (x,y,θ) in the plane, a first for a microrobot of this kind. The microrobot is approximately 3cm in length, 1cm in width, 1mm in height, and has a mass of less than half a gram. By varying the input power, actuation frequency and motion gait strategy the velocity of the chip can be precisely controlled. Motion in three degrees of freedom has been demonstrated and a maximum velocity of 635 μm/s and carrying capacity greater than 1.448 g (two 8-pin ICs) has been observed. The microrobot has been characterized extensively and a model for its performance is described.
Design and Fabrication of High Power Electromagnetic Microactuator With Perpendicular Magnetic Anisotropy
Authors: Pan C. T. , Shen S.-C. , Chou H.-P.
Published: November 2021

A novel microactuator has presented by this research. The high power electromagnetic microactuator combines of innovative hard magnetic Fe/Pt process, high Ni/Fe permalloy magnetic circuit design technique, bulk micromachining and excimer laser ablation. The hard magnetic material is Fe/Pt which is deposited under low temperature by sputter on the suspension diaphragm to offer perpendicular magnetic anisotropy field. The magnetic circuit with close loop is applied to concentrate the magnetic flux and increases magnetic force. Therefore, the magnetic field induced by the magnetic field of the planar coil and Ni/Fe permalloy can be enhanced, which will interact with Fe/Pt and induce huge displacement, large force output and high frequency. The high power electromagnetic microactuator has been demonstrated magnetic force 2 times larger than conventional magnetic microactuator.
MEMS Metrology Using Resonant Structures
Authors: Allen A. Miller , Johnson George C.
Published: November 2021

We present an analytical method and experiment to determine the “as-built” geometry of surface micro-machined micro-electromechanical structures. The analysis is based on the use of the lateral resonant frequencies of electrostatic comb drive resonators. The method can be used in situ and does not require a priori knowledge of the mechanical material properties of the structure. The variation between designed geometry and “as-built” geometry is determined from a fit of experimental results to the analytical model.
Building a ‘Design-to-Analysis’ Interface for Summit™-Based Microsystem Development
Authors: Wong C. Channy , Jorgensen Craig R. , Yarberry Victor R. , Ho Pauline , Pawlowski Roger P. , Freymiller James , Melander Darryl J.
Published: November 2021

As the design for microsystems becomes increasingly more complex, the ability to predict and visualize thin-film structures during the design phase becomes correspondingly important. Virtual prototyping is definitely needed. However, accurately predicting the dimensions of the final product will require that the true effects of the surface micromachining processes be modeled. At Sandia, we are developing an integrated software package that links microsystem design with visualization and performance analysis. This integrated package consists of physical models that can generate the correct shape of micro-features. This paper describes our initial effort, which is twofold: (1) to build a generalized 3-D CAD package that interfaces between the microsystem design tools and analysis tools, and (2) to develop a modeling capability that predicts the general shape of fundamental micro-features from the fabrication process. A demonstration to illustrate how the ‘design-to-analysis’ infrastructure is being integrated will also be presented.
Achieving Close Frequency Match Without Incurring Instabilities in Micro Gyros
Authors: Haney J. D. , Feng Z. C.
Published: November 2021

We study the nonlinear dynamics of the MEMS micro gyro to guide the structural design of the sensor. The nonlinearity is a result of the small but finite rotations of the gyro structure. The equations of motion are studied numerically. Nonlinearity of the gyro system is demonstrated through the determination of the resonance frequencies. The resonance frequencies are shown to be affected by the oscillations in the other modes. Even though the frequency variations are small, they are significant because the micro gyro structures have an unusually high Q value (i.e. low damping ratio). The nonlinear coupling between the drive mode and the sense mode has been shown to give rise to instability of the drive mode motions. Numerical solution further verifies that. Moreover, we determined the region in the parameter space containing the frequency detuning in which instability occurs. For parameters outside the region, the instability can be avoided.
Micro-Isolation Valve for Fuel Tank Array
Authors: Takahashi Koji , Nagayama Kunihito , Yasaka Tetsuo , Asano Tanemasa
Published: November 2021

Isolation valve system for low-cost liquid tank array is designed and demonstrated. This valve is normally closed and opens only once for liquid injection. This array system can supply precise amount of liquid at each operation as many times as the number of tanks. In order to tolerate the ambient high pressure and to accomplish the perfect injection, a large and thick membrane is fabricated and tested as valve. Without any special structure, our valves are found to open just by applying low AC voltage to a pair of electrodes that are apart from each other by tens of micrometers. Dielectric breakdown and pressure increase inside tank are found to work effectively to form a large hole.
A Novel Attitude Control Technique for Miniature Spacecraft
Authors: Li Jun , Koh Sung K. , Ananthasuresh G. K. , Ayyaswamy P. S. , Ananthakrishnan S.
Published: November 2021

A novel attitude control technique for miniature spacecraft using MEMS actuators is presented in this paper. In this technique, a permanent net change in the orientation of the spacecraft is achieved even though the individual microactuators are all brought to their unactivated state at the end of an attitude-changing maneuver. This is ideally suited for untethered systems such as spacecraft because continuous supply of power is not necessary to retain the new orientation. The technique exploits the non-commutative property of finite rotations of a rigid-body. That is, a sequence of fully-reversed rotations about three orthogonal axes results in net change in the orientation of the spacecraft. The limited torque capacity of microactuators is overcome by using an array of actuators and accomplishing the attitude-change maneuver in several small steps. An ensuing problem of planning such a maneuver is stated. The practical feasibility of the technique is demonstrated using electro-thermal microactuators.
A Large-Angle and Large-Mirror Microscanner Based on Thermal Actuators
Authors: Tu Ching-Chen , Liu Cheng-Hsien , Du Chen-Hsun , Tsaur Jiunn-jye , Lee Chengkuo
Published: November 2021

In this paper, we present a large-scanning-angle and large-mirror microscanner actuated by the thermal actuators. The thermal actuators are based on bimorph effect and consist of three thin film layers, Polyimide, Au, and SiO2. The large mirror is released rapidly by using poly-pad combined with surface micromachining and bulk micromachining. The actuator has the adventure of low power consumption from our design. Furthermore, our microscanner can achieve the purposes of self-assembly and out-of-plane by residual stress after curing processes.
Effects of Stress Induced by the Underlying Layers on the Micro-Structures and Characteristic Phase Transformation Temperatures of Sputtered TiNi Thin Films
Authors: Wang Rong Xin , Zohar Yitshak , Wong Man
Published: November 2021

The micro-structures and the phase transformation temperatures of sputtered titanium-nickel (TiNi) thin films, both free-standing and attached on different underlying multi-layer substrates have been studied. Differences in the micro-structures, such as the lattice constants and the relative concentrations of TiNi, Ti2Ni and TiNi3 phases, were observed (1) among the free-standing and the attached films, (2) among the films attached on different underlying multi-layers and (3) among films with different relative orders of aging and release. Not surprisingly, the corresponding phase transformation temperatures are also different. It is proposed that both substrate- and process-induced stress significantly affect the micro-structures, hence the phase transformation characteristics, of the resulting shape-memory alloy thin films.
Calibration of MEMS Strain Sensors Fabricated on Silicon
Authors: Cao Li , Hautamaki Chuck , Zhou Jia , Kim Tae Song , Mantell Sue
Published: November 2021

A calibration technique for measuring MEMS strain sensor performance is described. The sensor calibration technique entails developing a repeatable relationship (gage factor) between the change in sensor nominal resistance and the strain measured at the sensor. The calibration technique involves creating a “pseudo” strain sensor consisting of a strain gage mounted on a silicon wafer. Two identical test specimens are evaluated: the pseudo sensor mounted (with adhesive) on an aluminum specimen (or embedded in a specimen), and a MEMS strain sensor mounted on an aluminum specimen (or embedded in a specimen). The dimensions of the silicon wafer for both the pseudo sensor and MEMS sensor are identical. The specimens are loaded by tensile test. For the pseudo sensor specimen, a relationship is established between the strain applied to the specimen (far field strain) and the strain at the sensor (near field strain). Once the relationship between near field and far field strain is known, a relationship between near field strain and change in resistance of the uncalibrated MEMs sensor is established. This relationship between strain at the sensor and change in resistance is the gage factor. Two different MEMS strain sensor designs were fabricated by patterning polysilicon on a 500 micron thick silicon wafer: monofilament and membrane sensors. Gage factors for the MEMS sensors were determined following the calibration procedure. The results also lead to a conclusion that wafer geometry influences the strain transfer to the sensor.
Friction and Tribological Considerations for Nanometer Range Machining
Authors: Chattopadhyay Som
Published: November 2021

Positioning accuracy within the range of nanometers is required for high precision machining applications. The implementation of such a range is difficult through the slides because of (a) irregular nature of friction at the slider-guideway interface, and (b) complex motion characteristic at very low speeds. The complexity arises due to the local deformation at the interface prior to breakaway, which is known as microdynamics. In this work prior experimental results exhibiting microdynamics have been appraised, and mathematical model developed to understand this behavior.
Deep Reactive Ion Etched Submicron Beam/Trench Characterization
Authors: O’Brien Gary , Cheng Xing , Guo L. J.
Published: November 2021

Sub-micron width high aspect ratio beam/trench arrays are etched into silicon substrates using a Surface Technology Systems (STS) deep reactive ion etch (RIE) tool equipped with a time multiplexed plasma etch/passivation cycle scheme. The oxide mask is patterned by nanoimprint lithography and minimizes lateral trench etching by adjusting the significant etch parameters. High aspect ratio trench arrays 350nm wide with a 700nm period are etched to a depth of 10 μm with typical sidewall asperities on the order of 30nm. A dual etch process is used to reduce scalloping near the trench surface using HBr/Cl to etch the initial 500nm followed by the STS process using C4F8/SF6 chemistry. The dual etch process resulted in a reduction of sidewall asperities from 75nm to less than 25nm. In addition, the dual etch process reduced the trench array depth variation from a measured standard deviation of 0.7 to 0.1 representing significant improvement of etch repeatability across the wafer sample.
Analysis of Time Periodic Electroosmotic Flows
Authors: Dutta Prashanta , Beskok Ali
Published: November 2021

Analytical solutions of time periodic electroosmotic flow in two dimensional straight channels are obtained as a function of a nondimensional parameter k, which is based on the electric double layer (EDL) thickness, kinematic viscosity and the frequency of the externally applied electric field. A parametric study as a function of k reveals interesting physics, ranging from oscillatory “plug-like” flow in the quasi-steady state to flows analogous to the oscillating flat plate in unbounded flow domain (Stokes’ second problem). The latter case differs from Stokes’ second solution within the EDL, since the flow is driven with oscillatory electric field, rather than a moving surface. Utilization of the instantaneous Helmholtz Smoluchowski velocity as the slip boundary condition on the wall matches the bulk flow solution accurately, even for high, frequency excitations. Unlike the steady electroosmotic flows, the vorticity for time periodic electroosmotic flows is not confined in the EDL.
Numerical Simulation of Gas Flows in Micro-Filters
Authors: Ahmed Imtiaz , Beskok Ali
Published: November 2021

Gas flows through micro-filters are simulated in the continuum and slip flow regimes as a function of the Knudsen, Reynolds and Mach numbers. The numerical simulations are based on the spectral element formulation of compressible Navier-Stokes equations, which utilize previously developed high-order velocity slip and temperature jump boundary conditions. Both slip and no-slip simulations are used to identify the rarefaction effects. The simulation results show skin friction and form-drag reduction with increased Knudsen number. Pressure drops across the filters are compared against several empirical scaling laws, available in the literature. Compressibility becomes important for high-speed flows, creating large density fluctuations across the micro-filter elements. For high Mach number flows, interactions between thermal and kinetic energies of the fluid are observed. It is also shown that viscous heating plays a significant role for highspeed gas flows, impacting heat transfer characteristics of micro-filters.
A Fast Algorithm for Particulate Micro-Flows in Complex Geometries
Authors: Liu D. , Maxey M. , Karniadakis G. E.
Published: November 2021

An approximate description for the motion of particles in a liquid flow is pesented that forms the basis for an efficient numerical simulation procedure. The method is based on a spatial distribution of finite force multipoles and requires much less resolution than full DNS. The numerical implementation is summarised and example results given for Stokes flow and low Reynolds number flow in a channel and in a channel with a contraction. Comparisons are made with DNS results and experimental data.
Two-Phase Flow Boiling in a Microchannel Heat Sink
Authors: Lee Man , Wong Yiu Yan , Wong Man , Zohar Yitshak
Published: November 2021

A micro heat sink comprising 10 microchannels integrated with a local heater and a temperature microsensor array has been fabricated on a silicon wafer using standard micromachining techniques. A glass wafer was anodically bonded to the silicon wafer in order to cap the trapezoidal microchannels, about 14μm in depth and 120μm in average width. DI water was pressurized through the heat sink serving as the working fluid. Boiling curves of device temperature, at a few locations along the centerline, were measured as a function of the input power. In contrast to previously reported results, the boiling plateau associated with latent heat of phase change from liquid to vapor was detected. The transparent glass ceiling allowed the visualizations of flow phenomena dominated by surface effects. The classical bubble dynamics of bubble formation, growth, and detachment was observed at relatively low input power. However, this mode was completely suppressed at moderate power levels. Further increase of the input power resulted in a clear separation between the upstream vapor and the downstream liquid. The average location of the vapor/liquid interface shifted downstream with the input power, and near the critical heat flux condition the interface was located at the channel outlet. Thus, the added heat resulted in increased quality of the two-phase flow rather than increasing the mixture temperature.
Dynamics of Field Amplified Sample Stacking
Authors: Bharadwaj Rajiv , Santiago Juan G.
Published: November 2021

We present an analysis and an experimental study of field amplified sample stacking. The analysis consists of a one dimensional, unsteady electromigration model of the concentration fields in sample stacking. The model predicts that the sample concentration develops as a non-linear concentration wave with a peak concentration increasing with time that reaches a maximum value determined by ratio of electric fields in the sample and the buffer region. The experimental work is a preliminary study of the effects of electroosmotic flow on sample stacking for a single fluid-fluid interface within a glass microchannel. Using a simple cross-channel configuration a high-gradient initial step-function in the buffer concentration field was established which causes an unsteady sample concentration process. The experimental results qualitatively confirm the wave-like profile of the stacked analyte predicted by the analytical model. Experiments also provide evidence of internal pressure generation due to mis-matched electroosmotic velocities during stacking. The effect of electric field strength and sample-to-background buffer concentration ratio, γ, are also presented. Stacked sample concentration at γ = 4 is found to initially increase with increasing electric field but saturates at higher electric fields. Stacking rates at higher γ ratios indicate that concentration enhancement is quickly limited by dispersion due to internally generated pressure gradients.
A Large Flowrate Electroosmotic Pump With Micron Pores
Authors: Yao Shuhuai , Huber David , Mikkelsen James C. , Santiago Juan G.
Published: November 2021

This paper presents a description of the design, fabrication, and characterization of a novel, high flowrate electroosmotic pump designed for microcooling applications. The prototype pumps demonstrated a flowrate of 7 ml/min for 200 V applied potential that is suitable for two-phase heat exchangers with a capacity approaching 100 W. This pump uses electroosimotic flow (EOF) to drive the flow and is compact with no moving parts. The pump structure is produced by chemically treating and further sintering an ultrafine glass frit (filter). The frits we use are porous cylinders 30 mm in diameter and 3 mm (varying from 1.5 to 3 mm) thick and provide the high wetted-surface-to-volume ratio required to generate pressures exceeding 2 arm. Both deionized (DI) water and buffered aqueous solutions have been used as working fluids. Experiments have been conducted to characterize the pump performance and investigate its physical properties such as the structure porosity, tortuosity, effective pore size, finite double layer effects, and the dependence of zeta potential on ionic conductivity of the working solution.
Velocity Measurements of Flow Over Hydrophobic Microchannel Walls
Authors: Tretheway Derek C. , Meinhart Carl D.
Published: November 2021

This work addresses the controversy of slip of a hydrophilic fluid over a hydrophobic boundary by applying micron resolution particle image velocimetry (μ-PIV) to measure the flow profiles of water flowing through 30 × 300 micron channels that have a clean surface (hydrophilic) and channels coated with hydrophobic molecules, OTS (octadecyltrichlorosilane). The results for hydrophilic liquids flowing over hydrophilic boundaries are consistent with the no-slip boundary condition. However, the results show that the no-slip boundary condition is not necessarily valid for hydrophilic liquids flowing over hydrophobic boundaries. Thus, modeling fluid flow at the micro-scale with the assumption of no-slip may or may not be valid, but will depend on the interactions between the fluid and the surface properties of the wall.
Selective Induction Heating for MEMS Packaging and Fabrication
Authors: Cao Andrew , Lin Liwei
Published: November 2021

Selective induction heating has been applied to metallic micro-loops patterned on a glass substrate. These aluminum loops enclosed areas ranging from 300 × 300μm2 to 1000 × 1000μm2. They have a thickness of 4μm and widths ranging from 30μm to 150μm. Induction heating is achieved remotely by using a helical coil driven at 14.2 MHz. When 1kW of heating power is applied for 150ms, it is found that the 1000 × 1000μm2 aluminum loops are heated to a high temperature of at least 1100°C. A finite element model is established to estimate the heat transfer process and it is found that the heat generation rate should be at least 9 × 1012 W/m3 and at least 8 watts of power is induced in the aluminum loop locally and selectively. Furthermore, Pyrex substrate does not heat up under induction heating and heating of silicon substrate is highly dependent on the doping level. It is believed that with proper design and material selection, this remotely applied selective heating method can be applied for MEMS bonding and fabrication process.
A Novel Device-Level Micropackaging Using Micro Assembly Transfer
Authors: Chen Jen-Yi , Huang Long-Sun , Chu Chia-Hua , Kuo Yao-Hui , Chang Peizen
Published: November 2021

A novel device-level micropackaging that may encapsulate functional devices in post packaging has been developed. The encapsulation is formed with a metallic microcap like a dome shape to shield necessary micro devices from external impact or contamination. The metal cap is initially fabricated on a carrier glass and then transferred onto a host substrate. In this micropackaging, the micro assembly transfer and cap leg-snapped techniques are utilized in successfully demonstrating the transferred cap on the selected area of the host substrate that is aligned through the transparent glass. The low temperature solder bonding also allows this technique to be compatible with existing integrated circuit and micromachined devices. Furthermore, the robustness of the electroplated micro cap is even superior to the reported surface micromachining technique due to the high stiffness of a thicker structure by controllable electroplating. With the effective aid of the numerical analysis of the cap leg, the fracture can be expected at a desirable spot in which the stress concentration occurs under pulling forces for separation of the carrier glass and the cap. As a result, the micro encapsulation presents a successful, new packaging technique with advantages of selective 3D micro packaging, sealing, robustness, back-end process compatibility and potentially low cost.
An Acoustic Procedure for Measuring Blade-Frequency Forces Generated by Model Ship Propellers
Authors: Strasberg M.
Published: November 2021

An acoustic procedure is described for measuring the blade-frequency fluctuating forces developed by a powered model propeller operating behind a model of a ship’s hull or a wake generator in the anechoic test section of a wind tunnel. The sound pressure radiated by the propeller in a given direction is measured and its magnitude inserted into a simple theoretical relation to determine the alternating force developed by the propeller in that direction. Although the procedure was developed years ago, the details and limitations have not previously been described in the literature. Restrictions are discussed on the size of the propeller, location of the measurement point, measurement frequency, and the wind speed. Measurements determining the validity of the procedure are described, including comparisons of the magnitude of forces determined by this acoustic procedure with direct measurements made with a force dynamometer in a water tunnel.
Array-Based Methods of Characterizing Piping Component Acoustic Behavior
Authors: Conti Matthew , Stokes Ann , Corrado Charles
Published: November 2021

We present recently developed experimental methods of estimating acoustic scattering matrix representations of piping components such as valves and bends. Scattering matrices quantify the frequency dependent reflection and transmission coefficients for a wave incident on a device, and include terms representing the conversion of energy from one wave type to another. Scattering matrix representations of individual components can be embedded in a transmission line model to numerically assess acoustic transmission through a full piping system. This paper addresses both the experiment design and signal processing algorithms required to measure the scattering matrix.
Efficient Component-Based Vibration and Power Flow Analysis of a Vehicle Structure
Authors: Tan Yung-Chang , Lee Soo-Yeol , Castanier Matthew P. , Pierre Christophe
Published: November 2021

A case study on the efficient prediction of vibration and power flow in a vehicle structure is presented. The modeling and analysis technique is based on component mode synthesis (CMS). First, the finite element model (FEM) of the entire vehicle structure is partitioned into component models. Then, the Craig-Bampton method is used to assemble a CMS model of the vehicle. The CMS matrices are further reduced by finding characteristic constraint (CC) modes. A relatively small number of CC modes are selected to capture the primary motion of the interface between components, yielding a highly reduced order model of the vehicle vibration in the low- to mid-frequency range. Using this reduced order model (ROM), the power flow and vibration response of the vehicle is analyzed for several design configurations. A design change in one component structure requires a re-analysis of the FEM for that component only, in order to generate a new ROM of the entire vehicle. It is found that this component-based approach allows efficient evaluation of the effectiveness of the vehicle design changes.
Computation of Sound Transmission Loss and Absorption Coefficient of Multi-Layer Systems
Authors: Hong K. L. , Raveendra S. T.
Published: November 2021

Sound transmission and absorption of multi-layer sound absorbents are discussed in this manuscript. A new matrix formulation based on four pole parameters is utilized to derive the transmission loss and absorption coefficient of the absorbents. A transfer matrix relating pressure to acoustic velocity provides the required information to calculate the transmission loss and absorption coefficient. The multi-layer sound absorbents considered are structural panels, elastic porous linings and air-gaps. No limitations are imposed on the number of layers. Some realistic configurations of a multi-layer sound absorbent are studied to demonstrate the applicability of the four-pole parameter technique.
Variable Gap-Reluctance Linear Motor With Application to Linear Resonance Compressors
Authors: Popham Vernon W. , Lawrenson Christopher C. , Burr Ronald F. , Lipkens Bart
Published: November 2021

Variable gap-reluctance linear motors operate on the principle of electromagnetic attraction across an air gap between a moving armature and a stator and coil, which minimizes reluctance or stored magnetic energy. The direction of motion, force and magnetic field are aligned and are perpendicular to the air gap. When the air gap and corresponding stroke are moderate, large amounts of force and power can be delivered from a compact design. Several sizes of a new variable gap-reluctance linear motor design have been developed, characterized and applied. Practical application is demonstrated for linear resonance diaphragm refrigerant and gas compressors. A leaf spring suspension is used to dynamically match the motor to the resonance compressor load. Analysis and experimental results are combined to develop and characterize both the basic motor and integrated compressor designs.
Recent Developments in Thermoacoustic Engine-Generators
Authors: Corey John A.
Published: November 2021

The simplicity of thermoacoustic engines promises power at low cost and high reliability, but demands a second output conversion, from acoustic to more useful form. Electric output is the most highly prized form. At CFIC, and now Q drive, we have been experimenting with our resonant linear alternators as active dynamic components in thermoacoustic machines, providing this conversion. This paper presents the reasons for considering such a system, implications on design, and the results of CFIC’s prototype testing so far.
Simplified Dynamic Models of Submerged Objects From Limited Scattering Data
Authors: McDaniel J. Gregory , Clarke Cory L.
Published: November 2021

This paper investigates dynamic models of submerged objects which are obtained by acoustically ensonifying an object and measuring the scattered field at a single point while varying frequency. From such measurements, one can compute an effective impedance that physically represents the impedance of a half-space that would reflect a normally incident plane wave with the same amplitude as the wave scattered by the object. This effective impedance is shown to be passive and causal when the magnitude of the scattered wave is less than one. The effective impedance is related to reflection and impedance matrices matrices that arise in network formulations for the scattering of plane and spherical waves.
Acoustic Diffraction by a Half-Plane in a Viscous Fluid Medium
Authors: Davis Anthony M. J. , Nagem Raymond J.
Published: November 2021

We consider the diffraction of a time-harmonic acoustic plane wave by a rigid half-plane in a viscous fluid medium. The linearized equations of viscous fluid flow and the no-slip condition on the half-plane are used to derive a pair of disjoint Wiener-Hopf equations for the fluid stresses and velocities. The Wiener-Hopf equations are solved in conjunction with a requirement that the stresses are integrable near the edge of the half-plane. Specific wave components of the scattered velocity field are given explicitly, and the complete scattered velocity field is given in a form that is suitable for numerical computation.
Tuning a Replica of the Liberty Bell via Material Tailoring: An Application of a Method for Optimal Acoustic Design
Authors: Koopmann G. H. , Ericson David , Olchowski Adam , Salesky Eric
Published: November 2021

In this paper we describe a method for optimally tuning a bell to ‘best fit’ a specified sound spectrum. The method links the disciplines of structural dynamics, acoustics and optimization into a unified methodology. The design variables center on the addition of masses (size, number and location). The design variables are treated as external forces (via their impedances) in the equation that describes the bell dynamics as a series expansion of eigen functions. This step eliminates the need for solution of large matrix eigenvalue problems. An acoustic program POWER is used to assess the bell’s radiated sound power as a function of the design variables. Various search engines are used within the computer program MATLAB® to determine which design variables give the ‘best fit’ to the acoustic specifications.
On the Safety of Infeeding Vertical Garden Shredders
Authors: Brickman Dennis B. , Barnett Ralph L.
Published: November 2021

This paper addresses consumer garden shredders of the hammermill type with vertical hoppers that are manually fed. The purpose of this paper is to show that garden materials presented to a vertical garden shredder through the inlet hopper will not pull an erectly standing operator’s hand into the flails. In order for an erectly standing operator to contact the flails, it is necessary for the shoulder to move downward. Experiments demonstrate that the operator’s shoulder moves insignificantly downward during pull-in excursions using various garden materials that are attached to the operator’s hand through snagging mechanisms, hand friction, and entanglement.
Children’s Outerwear Drawstrings and Sliding Board Safety Analysis
Authors: Brickman Dennis B.
Published: November 2021

A two year old child strangled to death when the drawstrings of her jacket became lodged in a catch point hazard at the top of a residential sliding board. Approaches utilized in the safety analysis include accident reconstruction, safety literature review, standards research, an accident statistics survey, and an evaluation of alternative jacket and sliding board designs. Results of the analysis indicate there are technically and economically feasible design alternatives which prevent the child strangulation hazard associated with the jacket drawstrings and sliding board.
Use of Qualitative Risk Analysis to Prioritize Project Risk Reduction Efforts
Authors: Lindsey Pamelyn G. , Soczek Charlie A.
Published: November 2021

The risk associated with a highly toxic bulk storage facility was evaluated using a DuPont Qualitative Risk Assessment Protocol. The protocol used for the evaluation will be presented along with the results of the assessment. By application of this method a capital savings opportunity of over $500,000 can be realized as compared to the initial project scope estimate. These potential savings result from implementation of risk reduction measures based on an evaluation of both acute and chronic health effects on workers and the community. Additional process hazards analyses will be conducted to ensure adequate risk mitigation is implemented as the project design is finalized.