bluuebunny/crossref_metadata_2025 huggingface dataset:
Controlled Flow Evaporation in Complex Microchannels With Non-Uniform Wall Temperatures
Authors: Arslan Selin , Fre´chette Luc. G.
Published: July 2010

This paper presents an experimental study of flow evaporation in non-uniform microchannels, demonstrating the ability to provide a stable flow of evaporated fluid for energy conversion and chip cooling applications. Two mechanisms are proposed to stabilize the internal flow evaporation. The first mechanism is to establish a temperature gradient along the channel to separate the room temperature inlet fluid from the steam exit flow. The second mechanism is to change the direction of the surface tension forces acting on the meniscus to fix its position along the channel. To achieve this, shaped channels are formed of contractions and expansions with varied wall angles. The device consists of a silicon wafer with through-etched complex microchannels, that is anodically bonded to a glass wafer on each side. Inlet and exit holes for the fluid are machined in the glass wafers. Water is forced through the chip while it is heated on the exit side of the three layer chip. The qualitative nature of the two-phase flow along the shaped channels is observed through the glass cover wafer, for different flow rates and wall temperatures. The temperature gradient achieved with different thickness of channel walls shows agreement with the modeling results. Also, the benefit of having multiple expansions in the channels was demonstrated. By using these two mechanisms the onset of water evaporation was fixed along the channel. This will lead to the development of adequate two-phase flow micro heat exchangers.
Passive In-Plane Micromixer for Slow Diffusing Liquids
Authors: Yakhshi Tafti Ehsan , Kumar Ranganathan , Cho Hyoung J.
Published: July 2010

The problem of passive micromixing has been analyzed. Laminar flow in microchannels implies that transport processes including mass transfer are dominated by diffusion; inertial effects and have little to no effect on mixing in small scale conduits. Study of the diffusion theory shows that the velocity at the interface of fluids intended to be mixed is a determining factor. Higher velocity at the diffusion interface increases the mass flux across. By means of unique sidewall design, the laminar velocity profile can be passively altered such that the maximum of the profile coincides with the transversely progressing diffusion fronts repeatedly through the mixing channel. Based on the idea of increasing diffusion interfacial velocity, a passive mixing channel has been designed using numerical simulation tools, fabricated and characterized.
Self Assembly of Thermo Electric Coolers Using Solder and Fluid Based Methods
Authors: Tuckerman James , Hendrick Gary , Crane Nathan B.
Published: July 2010

Thermoelectric coolers (TECs) are solid state cooling devices that produce a temperature difference under an applied voltage. Thermo electric coolers are made by assembling P and N type Bismuth Telluride elements in series. Previous work has shown that microscale components can achieve higher performance in many applications than macroscale devices. [1, 2]. However, current assembly techniques cannot assemble and produce the smaller devices effectively. This paper will look at a water-based method to compare to prior solder-based assemblies.
Dispenser Printed Microscale Thermoelectric Generators for Powering Wireless Sensor Networks
Authors: Chen Alic , Koplow Michael , Madan Deepa , Wright Paul K. , Evans James W.
Published: July 2010

Wireless sensor networks (WSN) are a promising technology for ubiquitous, active monitoring in residential, industrial and medical applications. These nodes combine a radio transceiver, microcontroller and sensors into a low power package. A current bottleneck for widespread adoption of WSN’s is the power supplies. While the power demands can be somewhat alleviated through novel electronics, any primary battery will have a finite lifetime. Energy harvesting, from ambient vibration, light, and heat sources, offers an opportunity to significantly extend the lifetime of the nodes and possibly provide perpetual power. Thermal energy is an ideal source for WSNs due to the availability of low-grade ambient waste heat sources. Thermoelectric devices convert temperature gradients into DC electric power in compact form factors. Efficient device designs require hundreds of high-aspect ratio semi-conductor microelements fabricated electrically in series and thermally in parallel. This design requirement presents problems for standard microfabrication techniques due to thickness limitations of standard semiconductor processes. We present a new method of contact dispenser printing, specifically developed to additively create microscale generators. Initial materials performance results show promising results and are further detailed in this work.
Decision-Making Under Model Uncertainty of Damaged Aircraft Systems
Authors: Lopez Israel , Sarigul-Klijn Nesrin
Published: July 2010

When in-flight failures occur, rapid and precise decision-making under imprecise information is required in order to regain and maintain control of the aircraft. To achieve planned aircraft trajectory and complete landing safely, the uncertainties in vehicle parameters of the damaged aircraft need to be learned and incorporated at the level of motion planning. Uncertainty is a very important concern in recovery of damaged aircraft since it can cause false diagnosis and prognosis that may lead to further performance degradation and mission failure. The mathematical and statistical approaches to analyzing uncertainty are first presented. The damaged aircraft is simulated via a simplified kinematics model. The different sources and perspectives of uncertainties under a damage assessment process and post-failure trajectory planning are presented and classified. The decision-making process for an emergency motion planning to landing site is developed via the Dempster-Shafer evidence theory. The objective of the trajectory planning is to arrive at a target position while maximizing the safety of the aircraft under uncertain conditions. Simulations are presented for an emergency motion planning and landing that takes into account aircraft dynamics, path complexity, distance to landing site, runway characteristics, and subjective human decision.
Depth Profiling of Polymer Composites by Ultrafast Laser Ablation
Authors: Young Christopher N. , Clayton Clive R. , Longtin Jon P. , Granata Richard D.
Published: July 2010

Past work has shown femtosecond laser ablation to be a non-thermal process at low fluences in polymer systems. The ablation rate in this low fluence regime is very low, allowing for micro-scale removal of material. We have taken advantage of this fact to perform shallow depth profiling ablation on carbon fiber reinforced polymer (CFRP) composites. Neat resin and composite samples were studied to establish reference ablation profiles. These profiles and the effects of the heterogeneous distribution of carbon fibers were observed through optical and scanning electron microscopy. Weathered materials that have been subjected to accelerated tests in artificial sunlight or high temperature conditions were ablated to evaluate any correlation between exposure and change in ablation characteristics. Preliminary Raman and micro-ATR analysis performed before and after ablation shows no chemical changes indicative of thermal effects. The low-volume-ablation property was utilized in an attempt to expose the sizing-matrix interphase for analysis.
Ionic Current Through a 3 NM in Diameter Nanopore
Authors: Ge Yanyan , Chen Yunfei , Xu Dongyan , Yang Juekuan , Li Deyu
Published: July 2010

Ionic current through highly confined nanochannels receives significant attention over the past decade because of the novel phenomena from the overlapped electric double layers. In addition, nanoscale Coulter-type single molecule sensors detect the modulation of ionic current through individual nanopores to sense the translocation of single molecules or nanoparticles. The baseline ionic current and its noise determine the sensitivity of the Coulter-type single molecule sensors. All published research on ionic current through nanochannels focuses on the effects of overlapped electric double layers without paying much attention to the ionic transport through nanopores for high concentration electrolytes with non-overlapped double layer. Therefore, the ionic current data for high concentration electrolytes through nanochannels are limited and not systematic.
Dielectrophoretic Focusing of Microparticles in Curved Microchannels
Authors: Zhu Junjie , Tzeng Tzuen-Rong Jeremy , Xuan Xiangchun Schwann
Published: July 2010

Focusing particles into a tight stream is usually a necessary step prior to counting, detecting and sorting them in microfluidic devices such as flow cytometers [1] and continuous-flow separators [2]. The diverse approaches to particle focusing may be classified as active or passive ones in nature. Active focusing utilizes external force field(s) to manipulate particles other than the force to pump the particle solution. This category covers the conventional sheath flow focusing method and the various sheathless focusing methods where a transverse acoustic, AC dielectrophoretic, or magnetic force must be externally imposed. Passive focusing exploits the geometric topology-induced internal force(s) to alter the particle motion. So far dielectrophoretic, hydrodynamic and inertial forces have been demonstrated to focus particles [3]. Here, we introduce a novel passive particle focusing technique in electrokinetic flow through curved microchannels. This focusing stems from the cross-stream dielectrophoretic motion induced by channel curvatures [4], and is demonstrated in a serpentine and a spiral microchannel.
A Novel Way to Characterize the Non-Specific Surface Adhesion of Cancer Cells and Understand Cancer Metastasis
Authors: Tang Xin , Cappa Tony , Kuhlenschmidt Theresa , Kuhlenschmidt Mark , Saif Taher A.
Published: July 2010

Cancer deaths are mostly caused by the metastasis of the malignant cells, not by the primary tumor itself. During metastasis, cancer cells detach from the primary tumor, spread to different tissues via blood circulation or lymph system, and reattach to invade new tissues and organs. In this project, we hypothesize that cancer cells manage their invasion by changing their surface adhesivity. To study the cell surface adhesivity, a novel and versatile microelectromechanical systems (MEMS) force sensor is developed to quantify the strength of adhesion between living cancer cells and a probe. The Silicon sensors consist of a probe and 2 flexible cantilever beams, while the probe is used to contact the cancer cell and the flexible beams are used to measure the cell force response in the range from nN to uN. The spring constant of the sensor is 14 nN/ μm. Our results demonstrate that the aggressive HCT-8 cells (from human colon adenocarcinoma) show high nonspecific adhesivity when they aggregate into cell islands, and low surface non-specific adhesivity after they disassociate from the cell islands. The surface adhesivity of less aggressive Caco-2 cells (from human colon carcinoma) and normal MA104 cell (from monkey kidney) are found to be lower than that of before-disassociation HCT-8 cells. Furthermore, the adhesion force response of cancer cells is found to show 2-slope force behavior, which is different from previous results of focal-adhesion detachment experiments. The 2-stage force bearing model is proposed to interpret the underlying mechanism.
Dimensionality Analysis of Thermal Transport in Multilayer Thin Film Systems
Authors: Hopkins Patrick E. , Serrano Justin R. , Phinney Leslie M. , Kearney Sean P. , Grasser Thomas W. , Harris C. Thomas
Published: July 2010

Pump-probe transient thermoreflectance (TTR) techniques are powerful tools for measuring thermophysical properties of thin films, such as thermal conductivity, Λ, or thermal boundary conductance, G. This paper examines the assumption of one-dimensional heating on Λ and G determination in nanostructures using a pump-probe transient thermoreflectance technique. The traditionally used one dimensional and radial (3D) models are reviewed. To test the assumptions of the thermal models, experimental data from Al films on bulk substrates (Si and glass) are taken with the TTR technique. This analysis is extended to thin film multilayer structures. Results show that at 11 MHz modulation frequency, thermal transport is indeed one dimensional. Error among the various models arises due to pulse accumulation and not accounting for residual heating.
A Smart Device for Harnessing Energy From Aerodynamic Flow Fields
Authors: St. Clair Daniel , Stabler Christopher , Daqaq Mohammed F. , Luo Jian , Li Gang
Published: July 2010

In this work, inspired by music playing harmonicas, we conduct a conceptual investigation of a coupled aero-electromechanical system for wind energy harvesting. The system consists of a piezoelectric cantilever unimorph structure embedded within an air chamber to mimic the vibration of the reeds in a harmonica when subjected to air flow. In principle, when wind blows into the air chamber, the air pressure in the chamber increases and bends the cantilever beam opening an air path between the chamber and the environment. When the volumetric flow rate of air past the cantilever is large enough, the energy pumped into the structure via the nonlinear pressure forces offset the intrinsic damping in the system setting the beam into self-sustained limit-cycle oscillations. These oscillations induce a periodic strain in the piezoelectric layer which produces a voltage difference that can be channeled into an electric load. Unlike traditional vibratory energy harvesters where the excitation frequency needs to match the resonant frequency of the device for efficient energy extraction, the nonlinearly coupled aero-elasto dynamics of this device guarantees autonomous vibration of the cantilever beam near its natural frequency as long as the volumetric flow rate is larger than a certain threshold. Experimental results are presented to demonstrate the ability of this device to harvest wind energy under normal wind conditions.
Three-Point Bending Testing of Sandwich Beams and Finite Element Comparison
Authors: Champliaud Henri , Feng Zhengkun , Bersee Harald
Published: July 2010

The results of 3-point bending tests applied on 4 different types of composite beam structure and their comparison with Finite Element Modeling (FEM) are presented. Three different layups have been applied on rectangular and hexagonal foam cross sections. Experiments are realized and compared with FEM results in order to create a more confident design of an adaptive wind turbine blade that will be built using a foam core and a fiber glass/epoxy skin. Even if torsion loads and centrifugal loads are present on wind turbine blade during operation, the major loads are due to bending moments, so emphasis is put on 3-point bending tests of sandwich like composite beams. Tests and FEM show that the sandwich beam behavior is closely related to the skin and foam thicknesses.
Acoustic Travel-Time Tomography of the Atmospheric Surface Layer
Authors: Ostashev Vladimir E. , Bedard Alfred J. , Vecherin Sergey N. , Wilson D. Keith
Published: July 2010

Acoustic travel-time tomography of the atmospheric surface layer (ASL) is based on measurements of travel time of sound impulse propagation between different pairs of sources (speakers) and receivers (microphones), which constitute the tomography array. Then, the temperature and wind velocity fields inside the tomography array are reconstructed with inverse algorithms. Improved knowledge about these fields is important in many applications: validation and input data for atmospheric models, studies of turbulence over complex topography and heterogeneous surfaces, input data for wave propagation models, etc.
Shaft Crack Detection Using Statistical Analysis
Authors: Li Zhuang , Jin Lei , Zhang Ning , Zhou Yang
Published: July 2010

Cracks and voids are common defects in rotating systems and are a precursor to fatigue-induced failure. The application of statistical analysis, as a tool for damage identification and health monitoring in rotating machinery, is investigated. Experimental vibration data were collected for a set of health and cracked shafts. Formal statistical models have been proposed to describe the relationship between the vibration signals and the existence of damage. Damage detection and diagnosis are implemented based on statistical estimation and hypothesis testing. Such a statistical model provides a screening technique to detect other damage types. As a result, the proposed methods can improve the power of damage detection.
A Contact Model Between Tyre and Pavement at Low Speed for Periodic Motor Vehicle Inspection
Authors: Garci´a-Pozuelo Ramos Daniel , Di´az Lo´pez Vicente , Boada Mari´a Jesu´s Lo´pez
Published: July 2010

The behaviour of the tyre plays an important role in the vehicle handling. Thus for the analysis of vehicles and road safety it is necessary to take into account the forces and moments generated at contact patch. An accurate tyre model that estimates these forces and moments is highly essential for the studies of vehicle dynamics and control. Most of the tyre models have been developed for high speed, combined forces, etc. But, usually, automobile vehicles run at low speeds during an important part of their operating life (less than 60 km/h) and in steady state conditions. Furthermore, during vehicle inspection and maintenance of the steering and brake system, by means of sideslip tester and roller brake tester respectively, the forces transmitted by the tyres are measured, all of these inspections are carried out at low speeds. Therefore, it is particularly interesting to develop a model of the contact patch tyre-pavement for low speeds without the complexity of models that cover a wide speed range but with a bigger precision at low speeds. The dynamometer plate has proved to be an appropriate test equipment to characterise the tyre-pavement contact at low speed and the steering geometry and wheel alignment. It has the feature of being able to carry out tests for any type of tyre allowing to test with a great flexibility and operating speed. For this reason, the dynamometer plate has been chosen as test equipment. The main aim of this research is to set up a contact model between tyre and pavement at low speed, based on the measurement of longitudinal and lateral forces. The experimental tests carried out by means of the dynamometer plate have allowed to establish a relationship between influence variables and the longitudinal and lateral forces in the contact patch for steady state low speeds. A sensibility study has shown that the most influential variables in the forces of the contact patch are the pressure, the vertical force and the toe angle. However, the influence of temperature and camber angle is lower for the defined model conditions. A test methodology that allows carrying out the experimental tests in a systematic and controlled way in the dynamometer plate has also been developed.
A Theoretical Study of Submarining Tendency of a Hybrid III 5th Percentile Female Dummy
Authors: Tang Liang , Zhou Qing
Published: July 2010

This paper presents a theoretical study on the assessment of submarining tendency of a Hybrid III 5th percentile female crash dummy in frontal impact crash tests. Three candidate criteria for submarining tendency assessment were presented and examined. The first two criteria were derived based on the kinematic relationship between the lap-belt and the pelvis. The third criterion was derived based on the force equilibrium of the lap-belt and pelvis system. Nonlinear finite element models were used together with the use of a Hybrid III 5th percentile female crash dummy model to evaluate these candidate analysis methods.
Effect of Heat Treating Temperature on Chemical and Physical Properties of Natural Hydroxyapatite Produced From Bovine Bone
Authors: Younesi Mousa , Javidi Mehdi , Bahrololoom Mohammad Ebrahim , Fooladfar Hamidreza
Published: July 2010

This study focused on chemical and physical properties of Hydroxyapatite powder was prepared by burning bone and heat treating the obtained bone ash at different temperatures (600, 700, 800, and 1100 °C) in an air furnace. The black ash was converted to a white powder after heat treatment. Results of X-ray diffraction analysis and Fourier transform infra-red spectroscopy that were done on heat treated powders in different temperatures indicated that the white powder was hydroxyapatite and did not contain any organic components of the bone. Furthermore, results of X-ray diffraction analysis were shown that phase transformation of the resulted hydroxyapatite to other calcium phosphate phases did not occur up to 1100 °C. X-ray fluorescence analyses revealed that calcium and phosphorous were the main elements and magnesium and sodium were present as minor impurities. The results of the energy dispersive X-ray analysis showed that Ca/P ratio of this natural hydroxyapatite varies between 1.46 and 2.01. The resulted material was found to be thermally stable up to 1100 °C. The density of natural hydroxyapatite heat treated at 800 °C was measured to be 3.187 g/cm3.
The Study of RBC Deformation in Capillaries With a Lattice Boltzmann Method for Surfactant Covered Droplets
Authors: Farhat Hassan , Lee Joon Sang
Published: July 2010

This study aims at analyzing the shape change of red blood cells in the process of streaming through a capillary smaller than the red blood cell diameter. The characteristics of its shape change and velocity can potentially lead to an indicator of a variety of diseases. We approach this problem with considering red blood cells as surfactant covered droplets. This assumption is justified by the fact that the cell membrane liquefies under high pressure in small capillaries, and this allows the marginalization of the mechanical properties of the membrane. The red blood cell membrane is in fact a macro-colloid containing lipid surfactant. When liquefied, it can be treated as a droplet of immiscible hemoglobin covered with lipid surfactant in plasma surrounding. The merit is to analyze the effect of the flow condition and domain geometry on the surfactant concentration change over the droplet interface, and the effect of this change on the surface tension of the droplet. The distribution of the surfactant is calculated by enforcing conservation of the surfactant mass concentration on the interface, leading to a convection diffusion equation. The equation takes account of the effects of the normal and Marangoni stresses as a boundary condition on the interface between the immiscible fluids. The gradient in the surface tension adversely determines the droplet shape by effecting a local change in the capillary number, and influences its velocity by retarding the local surface velocity. The choice of the Gunstensen model is motivated by its capability of handling incompressible fluids, and the locality of the application of the surface tension. We used the same concept to investigate the dynamic shape change of the RBC while flowing through the microvasculature, and explore the physics of the Fahraeus, and the Fahraeus-Lindqvist effects.
Mechanical Design and Vibro-Acoustic Testing of Ultrathin Carbon Foils for a Spacecraft Instrument
Authors: Bernardin John D. , Baca Allen G.
Published: July 2010

IBEX-Hi is an electrostatic analyzer spacecraft instrument designed to measure the energy and flux distribution of energetic neutral atoms (ENAs) emanating from the interaction zone between the Earth’s solar system and the Milky Way galaxy. A key element to this electro-optic instrument is an array of fourteen carbon foils that are used to ionize the ENAs. The foils are comprised of an ultrathin (50–100Å thick) layer of carbon suspended across the surface of an electroformed Nickel wire screen, which in turn is held taught by a metal frame holder. The electroformed orthogonal screen has square wire elements, 12.7 μm thick, with a pitch of 131.1 wires/cm. Each foil holder has an open aperture approximately 5 cm by 2.5 cm. Designing and implementing foil holders with such a large surface area has not been attempted for spaceflight in the past and has proven to be extremely challenging. The delicate carbon foils are subject to fatigue failure from the large acoustic and vibration loads that they will be exposed to during launch of the spacecraft. This paper describes the evolution of the foil holder design from previous space instrument applications to a flight-like IBEX-Hi prototype. Vibro-acoustic qualification tests of the IBEX-Hi prototype instrument and the resulting failure of several foils are summarized. This is followed by a discussion of iterative foil holder design modifications and laser vibrometer modal testing to support future fatigue failure analyses. The results of these activities indicate that there is no strong dependency of the natural frequencies or transmissibilities of the foils on the different foil holder and screen configurations. However, for all foil holder designs, the natural frequencies of the foils were observed to decrease noticeably from exposure to acoustic testing. These test results, when combined with foil holder assembly considerations, suggest that the welded frame and integrated screen designs should be incorporated into the architecture of the IBEX-Hi flight instrument.
A New Method for Line Spectra Reduction of Vibration Isolation System Based on Flexible Base
Authors: Zhang Zhenhai , Zhu Shijian , Liu Shuyong
Published: July 2010

Line spectra in the radiated noise of marine vessels are the most visible signs, which can be detected, tracked and identified by enemy’s passive sonar, and hence it is of great significance to reduce the line spectra for improving the acoustic stealth of marine vessels. Insertion of resilient isolators between the machinery and the base is one of the most common methods for controlling unwanted vibration of the hull of submarine. Isolators in service are usually assumed to be linear and almost all the vibration isolation-n systems (VIS) are designed with linear theory, which satisfies engineering requirements in most situations. However, the nonlinear dynamical characteristics of VIS have attracted increasing attention in recent years due to the facts that onboard machinery trends towards more powerful and lighter, and that the demands in engineering for reducing vibration become more rigorous. Furthermore, some distinguishing features of nonlinear systems can be applied to achieve some special functions, among which the most important one is using chaos to reduce line spectra in the radiated noise of submarines based on the fact that response spectrum of a nonlinear system under harmonic excitation is a continuous one when chaos occurs. In this paper, a chaos synthesis method based on tracking control is prososed for a vibration isolation system (VIS) of on board machinery to make the chaotic motion in nonlinear VIS persistent. In this way, the line spectra in the radiated noise can be reduced effectively because the response spectrum of a chaotic system under harmonic excitations is a continuous and reduced one. Numerical simulations were carried out and the results showed that utilizing this method the nonlinear VIS not only possesses an excellent isolation performance of vibration and line spectra, but also reduces the amplitude of the isolated equipment notably.
Determination of Contact Condition at Elevated Temperature
Authors: St-Georges L. , Kiss L. I. , de Varennes E.
Published: July 2010

To model complex structure with numerous components and solids, the condition of contact between two solids must be adequately described. In this investigation, a special apparatus developed to analyze the condition of contact between two solids is presented. With this apparatus, experimental tests can be performed to determine the condition of friction (static and dynamic and the transition from one to the other) and the thermal and electrical contact resistances between two disk shaped rotating samples of different nature at various temperatures (from ambient up to 1000°C) and contact pressures. To determine the evolution of the friction mechanism as a function of the relative displacement between the solids, an inverse mathematical method has been developed and is presented. The results obtained with the apparatus proposed will provide a better understanding of the contact condition and could be easily incorporated in future mathematical models describing the behaviour of complex, multi layered structures.
Topology-Boundary Optimization of Coupled Structural-Acoustic Systems
Authors: Shu Lei , Ma Zhengdong , Fang Zongde
Published: July 2010

A new topology optimization technique is presented in this paper for optimal design of coupled structural-acoustic system with a current focus on interior noise reduction of automotive vehicles. The new topology optimization technique is based on an earlier published work on the analysis and sensitivity analysis of the coupled structural-acoustic system [1–2]. It is extended in this paper to consider the optimum material distribution in the structural domain as well as the optimum boundary shape between the structural and acoustic domains for the purpose of interior noise reduction. Firstly, a fixed boundary problem was considered with a focus on the material distribution in the structural domain to achieve the desired acoustic response inside the acoustic domain. The general formulation developed accounts for the full coupling effect of the structural vibration and acoustic pressure and can consider multiple (structural and acoustic) inputs and outputs over a predefined frequency domain. Secondly, optimization of the boundary shape between the structural domain and acoustic domain is considered with a focus on modifying acoustic resonant modes as well as the interaction between the structure and acoustic field. Finally, optimal material distribution and boundary determination are simultaneously considered to obtain a truly optimum structural-acoustic system for the desired performance requirements of the coupled system. Examples will be given to demonstrate the feasibility and effectiveness of the new topology optimization technique for various applications.
Remote Control Jackleg Drills Reduce Operators’ Overall Noise Exposures
Authors: Argirakis Anthony S.
Published: July 2010

Jackleg drills have proven to be a problem when it comes to overexposures to noise for coal miners as well as metal/nonmetal miners. These pneumatic drills are used to drill holes for roof bolting or blast holes in developmental and stoper mining. They are used when mining vertically or steeply inclined deposits. The “Leg” is a heavy metal support which allows the driller to keep the rig steady when collaring the hole as well as keeping it steady while drilling into the hard rock. Since drilling is done basically by hand, the operator remains in close proximity to the noise associated with the pneumatic hammer. Up until now, little has been done with the exception of Original Equipment Manufacturer (OEM) and retrofit mufflers to achieve compliance with the noise standards stated in Code of Federal Regulations (CFR) Title 30, part 62 for the drills of the type. Just recently an anthracite coal mining company, having noise problems associated with their jackleg drills, purchased a “Remote In-Stope Drill Rig” from a manufacturer in South Africa. A noise study was conducted by the Mine Safety & Health Administration (MSHA) and the cooperative mining company to determine the effectiveness of the remote control jackleg drill in reducing the operator’s overall noise exposure. The baseline test was conducted on the original jackleg drill. Once the new remote unit was received, it was tested as received from the manufacturer with their hammer and again with the company’s original hammer retrofitted to the drill rig. The company also made modifications to the 8 ft. hose extending it to 20 ft. to allow operation further from the noise source. The study was conducted to determine the effectiveness of the remote control unit in reducing not only the sound level, but also the overall noise dose. The unit was found to not only reduce the operator’s overall noise exposure when used with either hammer, but allowed drilling to be conducted from a location under permanently supported roof with no vibration on the operator’s hands.
Measuring the Temperature of Topology Optimized Electrothermal Microgrippers Using Raman Spectroscopy
Authors: Sardan Sukas O. , Liu J. , Bo̸ggild P.
Published: July 2010

In this paper, we present the results of the temperature measurements performed on topology optimized polysilicon microgrippers using Raman spectroscopy. The results reveal that the temperature profile along the actuators is in correspondence with the finite element simulation results presented in [1] except an offset of ∼250 °C due to chip heating. In order to predict this behavior, we included a section of the carrier chip into the finite element model. We also fabricated new devices with wider electrodes to reduce the overall Joule heating. Both finite element simulations and experimental results show that the devices with a wider electrodes design lead to a temperature drop of ∼50 °C as compared to the devices with the previous electrode design.
Multi-Tuned Optimum Vibration Absorbers for Curved Beams
Authors: Yang Fan , Sedaghati Ramin , Esmailzadeh Ebrahim
Published: July 2010

Detailed investigations on the vibration suppression of beam-type structures using Multiple Tuned Mass Damper (MTMD) technology has been carried out in this study. A general curved beam has been utilized as a case study to illustrate the developed optimum design methodology. The governing differential equations of motion for the curved beam with the attached MTMD systems have been derived, and then solved using the finite element method. A hybrid optimization methodology, which combines the global optimization method based on Genetic Algorithm (GA) and the local optimization technique based on Sequential Quadratic Programming (SQP), has been developed. This has been utilized to find the optimum design parameters (damping coefficient, spring stiffness and position coordinate) of the attached Tuned Mass Damper (TMD) systems in order to suppress the vibration levels at a particular mode or several modes, simultaneously. Finally, a design principle for vibration suppression of beam-type structures using the MTMD technology has been proposed through extensive numerical investigations.
TiO2 Nanofibers Based Dye-Sensitized Solar Cells
Authors: Li Jinwei , Xu Shiyou , Shi Yong
Published: July 2010

Dye sensitized solar cells (DSSCs) are promising photovoltaic devices as they offer advantages such as low cost and easy for fabrication et al. The key part of the original DSSC is a sintered film of nanoparticles which has a large surface area for the absorption of dyes. It has been reported that boundaries of nanoparticles diminish the efficiency of charge transport in the nanoparticle network, and lead to charge–carrier recombination. The one dimensional morphology of the nanofiber is believed to improve electron transport efficiency without sacrificing the high specific surface area for the adsorption of dyes. In this paper, TiO2 nanofibers are used to replace TiO2 nanoparticles in the DSSC. The film of nanofibers was synthesized by electrospinning process and collected on the transparent conductive glass substrate. The precursor used for the electrospinning of the nanofiber consists of titanium (IV) isopropoxide, acetate acid, ethanol and polyvinylpyrrolidone(PVP). After the electrospinning process, nanofibers were pretreated at 120°C for 2 hours and annealed at 500°C in atmosphere for another 2 hours. Then DSSC with the film of TiO2 nanofibers were assembled and characterized through electrical measurements. Open circuit voltage of 0.7V and short circuit current densities of 0.45mA/cm2 were achieved.
Nanofluids Evaporation Kinetics on Microstructured Superhydrophobic Surfaces
Authors: Xu Wei , Choi Chang-Hwan
Published: July 2010

In this paper, we experimentally studied the evaporation kinetics of sessile droplets of nanofluids with systematically varying particle sizes on superhydrophobic surfaces of well-defined micro-post structures. The superhydrophobic surface patterns were fabricated on a silicon wafer by photolithography and deep reactive ion etching (DRIE) at cryogenic temperature followed by Teflon coating. The 0.01 wt% suspensions of gold (Au) nanoparticles with varying sizes (5, 50, and 250 nm in diameter) were tested as nanofluids for the evaporation kinetics including the contact angle, base diameter, height, volume and evaporation rate by using a goniometer. The dryout patterns were investigated by using scanning electron microscopy (SEM). The results show that the surface topography and nanoparticle sizes have significant effects on the initial contact angle, profile evolution, wetting transition, evaporation rate, and dryout deposition pattern of the nanofluid droplets.
Responsive Biosensors for Biodegradable Magnesium Implants
Authors: Schulz Mark J. , Doepke Amos , Guo Xuefei , Kuhlmann Julia , Halsall Brian , Heineman William , Dong Zhongyun , Tan Zongqin , Xue Dingchuan , Lee Namheon , Yun Yeoheung , Liu Yijun , Hurd Douglas , Shanov Vesselin , Rai Durgesh , Witte Frank , Kumar Dhananjay , Yarmolenko Sergey , Pixley Sarah K. , Hopkins Tracy , Jayasinghe Chaminda , Sundaramurthy Surya
Published: July 2010

A biosensor is an electronic device that measures biologically important parameters. An example is a sensor that measures the chemicals and materials released during corrosion of a biodegradable magnesium implant that impact surrounding cells, tissues and organs. A responsive biosensor is a biosensor that responds to its own measurements. An example is a sensor that measures the corrosion of an implant and automatically adjusts (slows down or speeds up) the corrosion rate. The University of Cincinnati, the University of Pittsburgh, North Carolina A&T State University, and the Hannover Medical Institute are collaborators in an NSF Engineering Research Center (ERC) for Revolutionizing Metallic Biomaterials (RBM). The center will use responsive sensors in experimental test beds to develop biodegradable magnesium implants. Our goal is to develop biodegradable implants that combine novel bioengineered materials based on magnesium alloys, miniature sensor devices that monitor and control the corrosion, and coatings that slow corrosion and release biological factors and drugs that will promote healing in surrounding tissues. Responsive biosensors will monitor what is happening at the interface between the implant and tissue to ensure that the implant is effective, biosafe, and provides appropriate strength while degrading. Corrosion behavior is a critical factor in the design of the implant. The corrosion behavior of implants will be studied using biosensors and through mathematical modeling. Design guidelines will be developed to predict the degradation rate of implants, and to predict and further study toxicity arising from corrosion products (i.e., Mg ion concentrations, pH levels, and hydrogen gas evolution). Knowing the corrosion rate will allow estimations to be made of implant strength and toxicity risk throughout the degradation process.
Influence of Hot Pressing Parameters on Mechanical Properties of PP-HA Bio-Composites
Authors: Younesi Mousa , Bahrololoom Mohammad Ebrahim , Fooladfar Hamidreza
Published: July 2010

This paper focuses on the effects of pressure and temperature in hot press molding on the mechanical properties of polypropylene-hydroxyapatite composites with two different types of silanated and unsilanated hydroxyapatite. Density, crystallinity, ultimate tensile strength, Young’s modulus and impact resistance were evaluated for the two types of composites. Increasing pressure caused enhancement of density, crystallinity, MFI, ultimate tensile strength and Young’s modulus. Increases in temperature increased MFI, ultimate tensile strength and Young’s modulus whilst decreased impact resistance of composites. Effects of increasing pressure and temperature on the mechanical properties of polypropylene-silanated hydroxyapatite were less than their effects on the mechanical properties of polypropylene-unsilanated hydroxyapatite. Micrographs showed changes in fracture mode from ductile to brittle with increasing pressure and temperature during hot press molding.
Fiber Orientation in Injection-Compression Molded Short-Fiber-Reinforced Polypropylene Parts
Authors: Huang Han-Xiong , Yang Can , Li Kun
Published: July 2010

Four processing parameters, including compression force, compression time, compression distance, and delay time, were investigated in terms of their effects on the fiber orientation in injection-compression molded (ICM) short-fiber-reinforced polypropylene parts. The results reveal that the fiber orientation pattern in ICM parts is different from that in conventional injection molded parts. Compression force plays an important role in determining the fiber orientation, whereas the effect of compression time can be neglected. Moreover, the fiber orientation changes obviously in the width direction, with most fibers arranging orderly in the flow direction at positions near the mold cavity wall.
Track and Trace Multiple Incoherent Sound Sources in 3D Space in Real Time
Authors: Zhu Na , Wu Sean
Published: July 2010

This paper presents a methodology for tracking and tracing multiple incoherent sound sources in 3D space in real time. A salient feature of this methodology is its capability of handling all types of sound signals, including broadband, narrowband, continuous, impulsive, and tonal (sinusoidal) sounds over the audible frequency range (20 to 20,000 Hz). Locations of sound sources are indicated in terms of the Cartesian coordinates in real time. The target sources are viewed through an automatic tracking camera covering 350 degree solid angle. The hardware includes four microphones, a thermometer, a webcam, a five-channel signal conditioner and a laptop. Thus, the system can be made light, portable, easy to setup and use and inexpensive. The underlying algorithm is a hybrid approach consisting of modeling of sound radiation from a point source in a free field, triangulation and signal processing techniques. To acquire better understanding of the performance of the device, numerical simulations are conducted to study the impacts of signal noise ratio, microphone spacing, source distance and frequency on the spatial resolution and accuracy of the results. Experiments are carried out to validate results over a wide variety of real-world sound signals such as helicopter noise, human conversations, truck pass-by noise, gun shots, impact sounds, clapping, coughing, etc. Satisfactory results are obtained in most cases, even when a source is behind the measurement microphones.
Nanoscale Heat Transfer and Phase Transformation Surrounding Intensely Heated Nanoparticles
Authors: Keblinski Pawel , Merabia Samy , Barrat Jean-Louis , Shenogin Sergei , Cahil David G.
Published: July 2010

Using molecular dynamics simulations and theoretical analysis we study heat flow and phase behavior at the interface between high power-density, nanoscale heat sources and an embedding fluid medium. We show that the fluid next to the nanoparticle can be heated well above its boiling point without a phase change. Under increasing nanoparticle temperature, the heat flux saturates, which is in sharp contrast with the case of flat interfaces, where a critical heat flux is observed followed by development of a vapor layer and heat flux drop. These differences in heat transfer are explained by the curvature-induced pressure close to the nanoparticle, which inhibits boiling. We observe similar behavior for water, organic fluid, as well as generic model fluid underscoring generality of the results. We will also discuss the limits of the spatial and temporal localization of extreme temperature excursions and the limits to the applicability of the linear response theory to heat transfer at extremely large heat fluxes.
Investigating Nonlinear Models for Health Monitoring in Vibrating Structures
Authors: Doughty Timothy A. , Leineweber Matthew J.
Published: July 2010

This paper investigates a method of nondestructive health monitoring based on mapping variations in a system’s estimated nonlinear parametric model. The studied system is a slender cantilever beam harmonically excited around its second natural frequency. Known significant nonlinear parameters for this system including quadratic damping and terms due to bending and inertia are considered. This study uses the Continuous Time based nonlinear system identification technique. The method used here has advantages over mappings of the system’s linear parameters, such as natural frequency whose apparent value is shown to change as the amplitude of excitation is increased for physical systems behaving nonlinearly. Crack initiation and growth was effectively identified, but the effectiveness of the method was shown to be a function of the number and nature of the terms included in the model, and the number of records used in the identification process. The use of a simple nonlinear stiffness term and frequency records near resonance produced the best results. This method is shown to identify changes in the system’s behavior well before the failure of the system being studied, suggesting the method may lead users to avoid catastrophic failure in practice.
Integrated Physics-Based Approach for the Reliability Prediction of Thermal Systems
Authors: Al-Habahbeh O. M. , Aidun D. K. , Marzocca P. , Lee H.
Published: July 2010

A broad reliability prediction method that can deal with complex thermo-fluidic systems is introduced. The procedure provides an engineering tool by integrating multiple computational packages to enable the simulation of a wide array of systems, especially those involving physics interactions such as fluid flow and solid medium. Computational Fluid Dynamics (CFD), Finite Element Method (FEM), Monte Carlo Simulation (MCS), and Fatigue analysis tools are integrated within this approach. CFD simulation is used to determine the heat convection terms used for the transient FEM analysis. Maximum thermal stress is provided by the FEM analysis whereby the fatigue life of the component is evaluated. Due to uncertainty of input parameters, the fatigue life will be in a Probability Density Function (PDF) form, which provides the relationship between the reliability and the service life of the system. The complete procedure is demonstrated using a cylindrical ring model, and then validated using experimental data gathered for power plant boiler pipes. The results show good agreement between the two methods.
Single-Crystal X-ray Structure of 1,3-Dimethylcyclobutadiene by Confinement in a Crystalline Matrix
Authors: Legrand Yves-Marie , van der Lee Arie , Barboiu Mihail
Published: July 2010

Snapshot of a Strained Ring

Benzene and cyclobutadiene possess diametrically opposed properties. The former, a hexagonal hydrocarbon with a geometry perfectly suited to its bonding arrangement, exhibits unusual stability. The latter, with its two fewer carbons tightly squeezed into the right angles of a 4-membered ring, rapidly forms a dimer to relieve its considerable geometric and electronic strain. Monomeric cyclobutadiene was first isolated in substantial quantity by confining it within a molecular shell, but it has eluded full structural characterization.

Legrand
et al.

(p.
299
) have now found a host lattice that stabilizes a dimethyl-substituted derivative of the molecule sufficiently to allow analysis of its structure and bonding motif by x-ray diffraction.