Browsing by Subject "Mechanical Engineering"

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Aerosol particle electroscavenging by droplets.
(2012-06) Zhang, Meng
When water droplets precipitate under the action of gravity and frictional forces, they will collide with smaller aerosol particles and fall to the ground. Usually, either droplets or aerosol particles carry some electric charges, and some may be highly charged. Therefore, the electrostatic effect is a very important factor in particle scavenging. Wet scrubbers as air pollution control devices use the same theory as scavenging to remove both particulate and gas contaminants from the industrial exhaust streams. Electrostatic wet scrubbers were developed in an attempt to improve collection efficiency by raising the attraction force between droplets and particles. Very few numerical models have been developed to describe the phenomenon of particle collection by highly charged droplets when electrostatic force is dominant. In an attempt to understand the physics of scavenging, a new three-dimensional model has been developed to simulate neutral or charged particles collected by a group of neutral or charged droplets. The model can simulate the particle traveling through a matrix of droplets. Both the inertial effect and the electrostatic effect on particle scavenging have been considered. The collection efficiency can be estimated by utilizing this developed model. The effect on the collection efficiency by the size of the particle and of the droplet, the charges of the particle the droplet, and droplet distance have been investigated. A validation approach has also been developed and the study results have achieved good agreement with published data.
Air as a Condensing Medium in a Surface Condenser
(1923-06) Becker, Lewis Michael
Analysis of a Treadmill Based Human Power Electricity Generator
(2012-08-27) Mankodi, Harsh;
The modern challenge faced with the global energy situation is the growing energy demand and the strong dependence on unsustainable fossil fuels. Another concurrent issue is the adverse health and socio-economic implications of adult obesity. Human Power Generation, which uses metabolized human energy to generate electrical power, could potentially address both these challenges. The treadmill, one of the most popular exercise machines, presently consumes large amounts of energy while dissipating a majority as heat. The purpose of this thesis project was to design and develop a human powered treadmill generator and determine its power generation potential. The developed treadmill was based on a manual flatbed treadmill using an electromagnetic dynamo generator coupled to a front axle flywheel. A heavy duty rechargeable battery pack was used to store the generated energy and additional components to measure the generated power were included. The power generating potential of the generator was determined for varying belt speeds and angles of inclination, and compared with the American College of Sports Medicine (ACSM) metabolic walking and running prediction equations to determine efficiency. The generator was able to deliver 140W peak power for a short period of time. Regression equations related the power generated to the belt speed, covering values ranging from an average 10.8±0.36W at 1.83±0.045m/s to 90.3±3.04W at 2.38±0.054m/s. The angle of inclination did not have a significant impact on energy generation. The max average efficiency obtained for the system in this study was 37.9±2.63%, assuming 25% gait efficiency. Possible applications for this concept include energy saving equipment in a gym, low-cost, simple to operate, and low maintenance solutions for developing nations, and as a tool to educate energy conservation. Also, the need for exercise in space with low gravity makes the treadmill generator a possible source for secondary power in future extraterrestrial environments.
Application of the GSSSS family of algorithms to the natural index 3 differential-algebraic equations of multibody dynamics.
(2011-07) Hoitink, Andrew John
Growing interest in the simulation of constrained multibody systems has prompted the development of a variety of time integration methods for the differential-algebraic equations (DAEs) inherent to these systems. The vast majority of these methods require reformulation of the natural index 3 equations of motion leading to additional computational cost and the need to control drift phenomena, citing instability of direct index 3 methods. This research sought within the generalized single step single solve (GSSSS) family of algorithms an algorithm and framework capable of overcoming the instability and problems encountered by previous researchers. A precise understanding of the equation of motion time level concept as well as novel methods for extending linear parent algorithms to nonlinear dynamic applications enabled a depth of search unique to the area. In the end, an algorithmic framework is identified which overcomes previous limitations and is capable of providing stable, robust, and accurate integration of index 3 DAEs for both rigid and rigid/flexible multibody dynamics applications.
Atmospheric nucleation : development and application of nanoparticle measurements to assess the roles of ion-induced and neutral processes
(2008-01) Iida, Kenjiro
The major purpose of my Ph.D. study was to enhance our current understanding of new particle formation (NPF) processes in the atmosphere. My contributions include: (1) performing field measurements of atmospheric aerosols and subsequent data analysis of nucleation events, and (2) improving the performance of instruments commonly used for atmospheric aerosol measurements. My acquisition and analysis of atmospheric data involved studying the fraction of electrically charged particles, f , in the 3-25 nm range to obtain information on nucleation and subsequent growth process in the atmospheric boundary layer. Chapter 2 shows that the initial charge states of nucleated particles can be inferred from known diameter growth rates and measured values of charged fractions f in the 3-6nm range. By this means I was able to show that ion-induced nucleation did not contribute significantly to NPF events observed in Boulder, Colorado. Chapter 3 applies and extends the concepts that were introduced in Chapter 2. In this chapter I show that the diameter growth rates of particles during NPF events can be estimated from the measured size dependent charged fractions of particles in the 4-25 nm range and applied the technique to infer growth rates during NPF events observed in Mexico City. My work on instrument development involved theoretical and experimental studies aimed at reducing the size detection limit of a laminar flow condensation particle counter (CPC). Theoretical studies showed that preferred CPC working fluids for activating the growth of the smallest possible size are those having high surface tension and low vapor pressure. Experiments were performed using selected working fluids in the prototype ultrafine CPC developed by Stolzenburg and McMurry. Results show that diethylene glycol and oleic acid can sometimes activate the growth of particles having geometric diameter as small as 1 nm, and can always efficiently detect particles down to 1.5 nm.
Base Line Testing of 10kw GEK Power Pallet
(2012-04-18) Adams, John
Background: The Power Pallet is a generator system which uses a gasifier to convert wood chips into a low energy density gas which can be burned in a spark fired Kubota Engine turning a generator. Biomass gasification was widely used in Europe during World War II. Interest in biomass gasification is returning. Objectives: Develop testing method for the Power Pallet System; preform initial testing in order to plan future testing capabilities; test the effectiveness of a butterfly valve in changing reactor oxygen ratio.
Biofuel combustion: a single particle approach including new tandem measurements.
(2011-10) Dutcher, Dabrina D
The physicochemical properties of aerosol particles are complex. They are often irregular in shape, and can contain complex mixtures of liquids and solids. By measuring multiple properties of a particle, it is possible to describe it more completely than is possible if only one property is evaluated. This is the principle behind the theme of this chapter: tandem aerosol measurements. The Aerosol Time-of-Flight Mass Spectrometer carries out tandem measurements of a particle's vacuum aerodynamic diameter and its composition. I describe here the use of the ATOFMS in series with instruments that measure other properties so as to provide still more information. These additional properties include particle mobility, mass, and "brightness" (i.e., the amount of light that it scatters when illuminated by a laser). In addition, we show that when the ATOFMS is used downstream of tandem differential mobility analyzer systems (TDMA), new information can be gained about species that affect a particle's hygroscopicity (HTDMA) or volatility (VTDMA). These novel instrument combinations yield information regarding the dependence of particle effective density, volatility, and hygroscopicity on particle composition. Additional information is presented about the relationship between particle mobility size and vacuum aerodynamic size for assorted particle types and about the unanticipated difficulties that I encountered when using the ATOFMS for tandem measurements. I discovered that the rotating seals in the aerosol particle mass analyzer (APM) contain compounds that volatilize and react with acidic particles. The ATOFMS is exceedingly sensitive to these reaction products, so much so that it is not possible to obtain meaningful information about the composition of the particles under investigation. This sensitivity may provide a sensitive means, however, to assess the particle acidity.
Boiling of Dilute Emulsions.
(2010-06) Roesle, Matthew Lind
Although boiling in pure liquids has been studied thoroughly, boiling in other circumstances is less well understood. One area that has received little attention is boiling of dilute emulsions in which the dispersed component has a lower boiling point than the continuous component. These mixtures exhibit several surprising behaviors that were unknown until the 1970's. Generally, boiling of the dispersed component enhances heat transfer over a wide range of surface temperatures without transition to film boiling, but a high degree of superheat is required to initiate boiling. In single-phase convection the dispersed component has little effect on heat transfer. These behaviors appear to occur in part because few droplets in the emulsion contact nucleation sites on the heated surface. No detailed and physically consistent model of boiling in dilute emulsions exists at present. The unusual behavior of boiling dilute emulsions makes them potentially useful for high heat flux cooling of electronics. High-power electronic devices must be maintained at temperatures below ~85 °C to operate reliably, even while generating heat fluxes of 100 W/cm2 or more. Current research, generally focusing on single phase convection or flow boiling in small diameter channels, has not yet identified an adequate solution. An emulsion of refrigerant in water would be well-suited to this application. The emulsion retains the high specific heat and thermal conductivity of water, while boiling of the refrigerant enhances the heat transfer coefficient at temperatures below the saturation temperature of water. To better understand boiling dilute emulsions and expand the experimental database, an experimental study of boiling heat transfer from a horizontal heated wire, including visual observations, is performed. Emulsions of pentane in water and FC-72 in water are studied. These emulsions have properties suitable for practical use in high heat flux cooling applications, unlike most emulsions that have previously been studied. The range of the experimental study is extended to include enhanced boiling of the continuous component, which has not previously been observed, in addition to boiling of the dispersed component. In both regimes the heat transfer coefficient is enhanced compared to that of water. Visual observations reveal the presence of large attached bubbles on the heated wire, the formation of which coincides with the inception of boiling in the heat transfer data. At very low dispersed component fractions and low temperatures, boiling of individual dispersed droplets is not observed. The large attached bubbles represent a new boiling mode that has not been reported in previous studies and is, under some circumstances, the dominant mode of boiling heat transfer. A model of boiling dilute emulsions is developed based upon the Euler-Euler model of multiphase flows. The general balance equations as developed by Drew and Passman are applied to the present situation, thus providing a rigorous and physically consistent framework. The model contains three phases that represent the continuous component, liquid droplets of the dispersed component, and bubbles that result from boiling of individual droplets. Mass, momentum, and energy transfer between the phases are modeled based upon the behavior of and interaction between individual elements of the dispersed phases. One-dimensional simulations of a single boiling droplet in superheated liquid are also performed, and the results are used to develop the closure equations of the larger model. Droplet boiling is assumed to occur when a droplet contacts a heated surface or a vapor bubble. Collisions between droplets and bubbles and chain-boiling of closely-spaced droplets are considered. The model is limited to the dispersed component boiling regime, and thus it does not account for phase change of the continuous component. The model also does not include the large attached bubbles revealed in the visualization experiments. However, simulations of boiling match several trends observed in the experimental data. The model thus provides a physically consistent and partially validated platform for future analytical and numerical work.
Bubble size effect on effervescent atomization.
(2011-07) Shepard, Thomas G.
This paper presents the results from a number of studies conducted in an effort to gain insight into how to control bubble size during gas injection through a porous media into a liquid cross-flow, what effect bubble size has on the spray characteristics from an effervescent atomizer, and to provide input for future effervescent atomizer designs and studies. Experiments were performed in a specially designed atomizer which allowed for manipulation of the air injector geometry in order to vary bubble size from sizes much smaller than the nozzle exit diameter to much larger than the exit diameter. A parametric study was conducted to examine how three different bubble control mechanisms affect the average bubble size, bubble size standard deviation, and gas to liquid mass flow ratio (GLR) at the transition point between bubbly flow and slug flow. It was found that changing the channel hydraulic diameter at the air injection site had the largest effect while pore size and electrolyte concentration had smaller, though still significant, effects. A dimensional analysis was performed which arrived at a similarity parameter which correlates to bubble size for air injected through a porous media into a cross-flow. Bubble size was seen to have an effect on the stability, spray half cone angle, and Sauter mean diameter of the liquid droplets produced by an effervescent atomizer. The effect of bubble size on improving spray characteristics was shown to be optimal for bubble sizes on the order of the exit diameter. The mechanism by which bubble size has an affect is suggested to be due to liquid velocity fluctuations at the exit of the nozzle as opposed to the often cited mechanism of causing the flow to choke thus allowing gas to expand beyond the exit. A comparison of bubbly and annular flows at identical conditions further suggests that effervescent atomizer design and operation may benefit from trying to produce annular flow conditions at low GLRs rather than bubbly flow conditions at high GLRs.
Carbon nanotube based carbon dioxide gas sensors for respiratory monitoring.
(2009-12) Sivaramakrishnan, Shyam
The objective of this work is to create a new sensor for monitoring the concentration of exhaled CO2 gas in human breath. Limitations such as high power, large size, lack of portability and undesirable use of sampling tubes are experienced currently during respiratory CO2 monitoring. CO2 being a very important biomarker, it is desirable to extend the scope of CO2 monitoring beyond clinical use to home and ambulatory monitoring. Due to the vast amount of prior research effort put into currently used non-dispersive infra red (NDIR) CO2 sensors, it was deemed unnecessary to further investigate this technique. The sensor development approach in this thesis has been creation of a solid-state CO2 sensor through merging of state-of-the-art research in different disciplines - namely materials science, nanotechnology, chemistry, mechanical engineering and electrical engineering. Early promise for development of such a sensor is shown by use of functionalized carbon nanotube (CNT) materials. Single-walled carbon nanotubes (SWNTs) functionalized with polyethylene imine (PEI) is used as the CO2 sensitive material. A conductivity measurement technique using surface acoustic wave (SAW) sensors enables measurement of SWNT conductivity with very high resolution. While sensitive to CO2, this embodiment is several times more sensitive to humidity in the environment. Since humidity variation happens simultaneously with CO2 variation in exhaled breath, this is found not to be a viable technique for respiratory CO2 measurement. This early failure suggested a need for a sensor that was equally or more sensitive to CO2 than to other environmental analytes. In looking for such an alternative sensor, a CO2 sensor based on stiffness measurement of bare SWNTs was reported to be sensitive and selective to CO2. However, current techniques used for film-stiffness measurement are too bulky, unreliable or expensive. Hence, a new stiffness sensing transducer is developed using an electret microphone. This stiffness measurement technique is based on the extreme sensitivity of an electret microphone's capacitance to the stiffness of its membrane. A CO2 sensor is obtained by coating such a microphone with SWNTs. This embodiment shows good sensitivity to CO2 but unpredictable response to humidity changes. While some microphones show excellent humidity resistance, others show large response to humidity. This behavior is traced to the fabrication of the microphones. Since commercial microphones are used in this work, it is not possible to control manufacturing specifications. Thus, practical difficulties with obtaining a reliable microphone are a major impediment. It was also judged that the sensitivity of stiffness changes to CO2 might be insufficient for respiratory monitoring. The above two sensor embodiments suggest the difficulty in obtaining a selective yet sensitive solid-state CO2 sensor using carbon nanotubes. Hence, an alternative approach is tested using sensitive, selective but slow commercial CO2 sensors. CO2 sensors made using an electrolytic sensing technique are commercially sold for indoor air-quality monitoring. While reliable, such sensors are too slow for respiratory monitoring. But, development of a (second order) mathematical model for the sensor's slow response enables detection of fast CO2 changes during breathing. This is achieved by inverting the mathematical model to predict the fast CO2 input based on the sensor's slow output. The resulting embodiment is the first reliable respiratory CO2 sensor developed in this work. Though better than NDIR sensors, the power requirements and size of electrolytic CO2 sensors are still unacceptable for portable and wireless respiratory CO2 monitoring. Finally, based on research into CNTs and electrolytic CO2 sensors, a new nanocomposite-material based CO2 sensor is fabricated. This sensor combines advantages of high sensitivity and fast response of CNTs with the selectivity of metal carbonates to CO2. The nanocomposite material is fabricated by attaching nanoparticles of calcium carbonate (CaCO3) to SWNTs. CO2 sensing is achieved by measuring the resistance of the SWNT film which changes due to the reaction between CaCO3 and CO2. Cross-sensitivity to humidity, while present, is small enough to be removed using a reference CNT sensor that does not respond to CO2 but responds to humidity. While reliable in operation, this sensor however suffers from slow response due to chemisorption of CO2 on some of the CNTs. Since resistance of the entire nanocomposite can be controlled by a few CNTs, such slow-responding CNTs cause very poor overall response times (>100s). Model inversion techniques developed earlier are not effective with such response times to predict breath-by-breath CO2 changes. In order to enhance the response time, a capacitance based sensor is developed using a similar nanocomposite (SWNT-BaCO3). This sensor's speed of response is found to be much better compared to the previous embodiment which results in the development of a low-power, small, fast and inexpensive CO2 sensor. However, the sensor's capacitance is still found to be sensitive to environmental humidity. Further, the developed nanocomposites are also found to require humidity in the environment for sensing CO2. Thus, the sensor needs constant humidity to respond to CO2 reliably during breath sensing. This is achieved by completely removing humidity from the exhaled breath (using a molecular sieve) before it reaches the sensor. Simultaneously, humid air sampled away from the face is supplied using a low-power pump to humidify the sensing chamber. Using these designs, a reliable respiratory CO2 sensor is fabricated that is compared with a NDIR CO2 analyzer. Results show that the sensor reliably monitors CO2 concentration in the breath. The developed embodiment could potentially be improved with drift-correcting techniques (hardware and software); but is currently unique in its ability to perform low-power, portable and low-cost respiratory CO2 sensing.
Case studies in bio-thermal management.
(2011-12) Lovik, Ryan D.
The human body is an engineered system that utilizes an extensive range of interconnected processes to perform tasks. One category of processes relevant to mechanical engineering is thermal science, which includes both heat transfer and fluid flow. There are a great many organs and interconnecting vessels where such processes occur. Here, a selected group of thermal/fluid processes are set forth and subjected to synergistic analysis by numerical simulation and experimentation. In this thesis, two case studies are described. One of these involves the heat transfer and fluid flow in association with the removal of plaque from partially blocked arteries. This work necessarily involves the assessment of the temperature rise created by the frictional interaction of the plaque-removal tool and the surface of the plaque material. This process takes place in the presence of flowing blood. The work involved in vitro and in vivo experiments, the latter with respect to a cadaver. The experimentation also involves means for determining the geometric configurations of arteries before and after plaque removal. The geometric configuration of the artery is of importance due to its effects on the flow of blood through the vessel. The experimental findings were post-processed and subsequently employed as input information to appropriate numerical simulation models. In the case of heat transfer, a bioheat model was employed to evaluate local temperatures in human tissue. In turn, the local-temperature information was employed to evaluate a thermal tissue injury model. The outcome of that evaluation indicated that temperatures produced by a plaque-removal device would not create tissue necrosis. The efficacy of plaque removal as a means for ameliorating cardiovascular insufficiency was investigated by means of numerical simulation. The geometric configurations of both a highly stenosed blood vessel and subsequently debulked vessel were determined by means of intravenous ultrasound (IVUS) imaging. These images were reconstituted to create solid models which were subsequently utilized as the basis of numerical simulation. The simulation took account of heart-induced pressure pulsations which were employed as input information to the time-dependent, three-dimensional Navier-Stokes equations. The ratio of the volumetric rates of blood flow passing through the originally stenosed vessel and the subsequently debulked vessel enabled the formulation of a metric to describe the efficacy of the plaque removal therapy. For the posterior tibial artery, an increase of 2.5 fold in the volumetric flow rate was discovered. The second case study investigates the thermal effects of the presence of rechargeable implants in the body. It is well established that implants may be sources of heat generation. In the situation to be considered here, the implant does not contain a long-lived internal battery to power its functional activities. Rather, the needed power is provided by means of a transformer whose primary (antenna) is situated externally. The secondary of the transformer is contained within the implant. Both the antenna and the implant generate heat. Both of these heat sources may increase the tissue temperature in the subcutaneous zone and may also increase the temperature in the deeper tissue. To determine the magnitude of the rate of heat generation by these heat sources, a unique experimental facility was created and implemented. The facility was designed to accommodate antennas and implants of varying geometrical characteristics. A calorimetric method was employed as the means for the determination of the magnitude of the energy transferred from the heat generating devices to their respective environments. Experiments were performed for both the case in which the axes of the implant and the antenna are collinear and for the case in which the axes are misaligned. The criticality of the alignment issue stems from the fact that patients, rather than medical professionals, are required to perform the alignment task. It was found that alignment is, in fact, a major factor with regard to the rates of heat generation and the concomitant temperature elevation of the tissue neighboring these devices. Attention was focused on neuromodulation implants and their related antennas. For the study, the leading therapeutic neuromodulation devices were employed. For each of these, independent evaluations of heat generation rates were performed. The obtained information provided critical inputs to enable a reliable numerical simulation activity to be performed. The purpose of the simulation was to obtain temporal and spatial variations of temperatures within the relevant tissue beds. The temperature results were then utilized to assess the likelihood of tissue necrosis resulting from excessive temperatures imposed over lengthy durations. It was found that there were substantial differences in the outcomes of the various neuromodulation devices. In particular, issues of safety were discovered for at least two of the evaluated devices. It was also found that misalignment aggravated safety issues which were of marginal concern when the implant and its antenna were perfectly aligned.
Characteristics of a Rotary Pump for Oils of Different Viscosities
(1922-06) Vaule, Sven A.
Characteristics of particles downstream of a partially failed diesel particulate filter.
(2011-02) Ragatz, Adam C.
A diesel particulate filter (DPF) can be used to reduce the particulate matter (PM) emissions from a vehicle. However, when these devices fail the tailpipe emissions can change. The main goal of this project was to determine if a soot sensor provided by Honeywell could detect a failed filter, defined as an exhaust aerosol concentration downstream of the DPF greater than the current US heavy duty PM standard of 13 mg/kWh (10 mg/bhp-hr). In this study a DPF failure was first simulated on an engine dynamometer test stand using an exhaust bypass valve. Then the valve was removed and the filter was actually failed in a series of steps by drilling out individual channel end caps. Exhaust was cooled and diluted using a partial flow air ejector dilution tunnel, and dilution ratios were determined using raw and dilute nitric oxide (NO) measurements. Dilute diesel exhaust aerosol was characterized upstream and downstream of a DPF. Filter samples and an AVL photo-acoustic soot sensor were used to estimate PM mass emissions, and TSI aerosol instruments were used to measure aerosol size distributions and total number concentrations. An electrostatic precipitator, DMA, electrometer and CPC were used to evaluate the aerosol charge distribution. Downstream measurements were repeated as the filter was progressively failed in a series of steps. These measurements were then used to evaluate the response of the Honeywell exhaust soot sensor. Under certain steady state conditions the sensor output showed a statistically significant increase as the filter was failed but the output was susceptible to interference from mechanical vibration and was dependent on engine operating conditions, and the exhaust system used. Exhaust aerosol charge measurements showed the concept is viable but further work is required to refine the sensor.
Charge and energy interactions between nanoparticles and low pressure plasmas.
(2010-05) Galli, Federico
In this work, the interactions between low-pressure plasmas and nanoparticles are studied with numerical models aimed at understanding the phenomena that affect the nanoparticles charge, charge distribution, heating, and crystallization dinamycs. At the same time other phenomena that affect the plasma properties resulting from the presence of nanoparticles are also studied: they include the power-coupling to the plasmas, the ion energy distribution and the electron energy distribution. An analytical model predicting the nano-particle charge and temperature distributions in a low pressure plasma is developed. The model includes the effect of collisions between ions and neutrals in proximity of the particles. In agreement with experimental evidence for pressures of a few Torr a charge distribution that is less negative than the prediction from the collisionless orbital motion limited theory is obtained. Under similar plasma conditions an enhanced ion current to the particle is found. Ion-electron recombination at the particle surface, together with other particle heating and cooling mechanisms typical of silane-argon plasmas, is included in a particle heating model which predicts the nano-particle temperature. The effect of plasma parameters on the nano-particle temperature distribution is discussed and the predictive power of the model is demonstrated against experimental evidence of temperature induced crystallization of silicon nano-particles. The power coupled to the plasma is measured together with the impedance nature of the plasma, in the case of a pristine and dusty plasma. Nanoparticles are shown to strongly affect the electrical properties of the plasma, resulting in a much more resistive discharge. A study of the ion energy distribution of ions impinging the sruface of nanoparticles is carried out and shows that ion-neutral collisions in proximity of the surface of the nanoparticle not only affects the particle charge but also the average energy of ions bombarding the particle surface. Finally the presence of nanaparticle in the plasma and their ability to selectively interact with electrons in a specific energy range is studied to the extent of investigating the effects of the presence of particles on the electron energy distribution of electrons.
Charge and momentum transfer processes for gas-phase nanoparticles.
(2011-05) Premnath, Vinay
Charge and momentum transfer processes between aerosol particles and gas molecules proceed via collisions. There is a need to better understand such collision driven phenomena in order to predict particle dynamics and growth processes. This dissertation consists of two research projects focusing on charge and momentum transfer processes for aerosol particles in the sub 20 nm size range. The research on particle charging was aimed at bridging the gap between diffusion charging theory (traditionally used in aerosol physics) and chemical ionization, both of which are collision based reactions. In diffusion charging theory, the occurrence of a back charging reaction is neglected, i.e. once an ion collides with a particle, charge is transferred to the particle, and the charged particle does not lose charge on colliding with uncharged vapor molecules. However, in chemical ionization, charge transfer can occur in both directions - from charge-donating ion to vapor molecule and back from charged vapor molecule to the original charge-donating species. We examined the occurrence and the rate of this back charging reaction using a combination of experimental methods (electrospray ionization- mass spectrometry) and collision kinetics models. Studies conducted with charged amino acid clusters (~0.5 nm in size) and trimethylamine vapor molecules illustrated that charge transfer could occur from aerosol cluster ions to neutral vapor molecules upon collision. The second set of studies conducted involved ion mobility measurements of protein ions generated via electrospray ionization (ESI) with charge reduction from both non-denaturing and denaturing ESI solutions. A critical examination of the ESI process on gas-phase protein structure was carried out. Mobility diameters (dp) and collision cross sections (Ω) were inferred from the mobility spectra. An effective gas molecule diameter of 0.3 nm was accounted for in these calculations. While calculating collision cross sections, a non unity momentum scattering coefficient (ξ = 1.36) was considered to account for diffuse collisions between gas molecules and protein ions. The effective density of protein ions electrosprayed from non-denaturing solution was 0.96 g cm-3 while that from denaturing was 0.98 g cm-3.
Colles’ fracture creation on cadaveric arms by impact loading.
(2010-12) Magnuson, Thomas David
Among the most common causes of upper extremity fracture is a fall on an outstretched hand. The result of this is often a fracture of the distal radius, and the most common of these is the two part Colles’ fracture. Understanding the fracture in greater detail can lead to better clinical treatment of the injury. Much study has been done in an attempt to understand the biomechanical factors that lead to the fracture and to recreate the event in multiple media with varying boundary conditions. In this study, we focused our efforts on the impact loading of forearm cadavera in an attempt to recreate, as best as possible, the physiologic events of a forward fall onto an outstretched hand. Fluoroscopic data was taken prior to testing to dimension the cortical bone of the radius, and afterwards to assess and characterize fracture patterns. A custom drop tower was designed and constructed to dynamically load cadaveric forearms to failure. Furthermore, impact mechanics theory was used to estimate the effective load applied with each test. It was determined that 3046 N ± 650 N, with a ratio of axial to bending loads of 2.8 ± 1.0, was necessary to impart a Colles’ fracture in completely intact cadaveric forearms. This load fell within published ranges associated with distal radius fractures. Testing included 15 cadaveric samples (11 female and 4 males). Though considered at first, no direct correlation was found between the body mass index of each donor and the load required to fracture the radius. Results also indicated that females were more susceptible to Colles’ fractures than were males. This may be due in part to the higher average age of the female donors. We concluded that it is possible to produce Colles’ fractures with a relatively high rate of success. However, uncontrollable biological factors provided variation such that a completely repeatable fracture pattern across the sample population was not achieved. Furthermore, while an impact model could be the most accurate recreation of a forward fall, more research is needed to truly validate the results obtained through this impact based body of work.
Comparison of In-Vehicle Technologies with Traditional Safety Measures to Prevent Crashes along Curves and Shoulders
(2010-12) Pitale, Jaswandi Tushar
Five hundred and ten people were killed in the state of Minnesota in 2007. Using MN/Dot values for crashes this costs the state more than $3.5 billions. Forty percent of these fatal crashes are road departure crashes and they mainly occur on rural roads. To prevent these road departure crashes and reduce the financial losses occurring due to them, safety systems have to be implemented. There are two types of systems which could be implemented: · Traditional civil engineering solutions such as adding rumble strips, curve flattening, shoulder paving etc. · Emerging technology-based solutions. The technology-based safety systems consist of both infrastructure-based and in-vehicle systems. The technology-based infrastructure solutions involve radar based advanced curve warnings where the speed of the vehicle is calculated and if necessary the driver is warned. In-vehicle technologies include both vision-based and DGPS-based lane departure warning systems. Owing to the limited budget and necessity in curtailing the number of fatal crashes, these safety systems have been compared and studied to suggest an optimal solution which would be cost-effective and also effective in reducing traffic fatalities due to lane departures. Presented herein is a follow up on a research initiated by CH2MHill [1.]. A sample set of 204 curves and 137 tangential sections was studied by them. Their research mainly consisted of two parts: iv · A cross-sectional study to evaluate the effect of road geometry such as curve radius, width of shoulders, etc. on road departure crashes. · A before:after analysis which studies the effect of certain civil engineering treatments in form of crash rate on the road section before and after implementing the treatment. Based on the cross-sectional and the before:after analysis, the traditional safety treatments identified on road sections were evaluated against new technology-based safety systems through the following approach: · Effectiveness – Effectiveness of any system is the extent to which it meets the purpose, in this case, the extent to which it reduces crashes. The effectiveness was quantified for each safety system using either the before:after analysis, values provided by FHWA or analogies drawn on reduction in fatalities due to existing technologies such as seat belts and ABS. · Exposure – Effectiveness of any technology is always a function of its exposure. This exposure is measured in terms of the number of vehicle miles the system is exposed to, public acceptability and market penetration. · Cost-effectiveness –It is necessary to implement safety systems which are cost-effective for the government as well as the public to ensure effective use of the financial resources. Any change on the roads is cost-effective for the state if the money spent on implementing the change is compensated for by the reduction in losses occurred to the state due to crashes and fatalities. Benefit:cost ratios have been calculated to evaluate this cost-effectiveness. · Contribution to TZD – The state expends a fixed amount of safety budget every year. Thus, given a fixed amount of money, the treatment giving the most reduced number of fatalities was evaluated. This was defined as the deployment factor. The treatment having the highest deployment factor was the optimal solution which would help to move towards Mn/DOT’s goal of Towards Zero Deaths (TZD). Result In this study, new emerging technologies were studied against traditional infrastructure based safety systems. These studies were evaluated based on their effectiveness in reducing crashes, market penetration, legal implications, cost effectiveness and their contribution to TZD and an optimum solution has been provided. For curves, curve flattening produced highest effectiveness of 66%. However, curve flattening is among the most expensive safety treatment. Using effectiveness numbers from the FHWA, static curve warning systems would appear to provide the highest benefit:cost ratio. However, it is important to note that as a result of the cross-sectional and before:after analyses, approximately 80% of the curves studied were already equipped with static curve warning signs, and these intersections still had high crash and fatality rates. Hence the deployment factor was calculated for all the remaining safety systems maintaining the static signs as the baseline. For a given fixed safety budget, vi adding rumble strips gives the highest reduced number of fatalities or the highest deployment factor. Similarly, for tangential sections, enhancing them gave the highest deployment factor. Also, evaluation of the in-vehicle technologies showed that the vision-based lane departure warning systems have deployment factors comparable to that of enhancing the road sections. These results were obtained based on the data set that has been the background for our research. The above approach however should not be limited to one particular data set and can be used by engineers as a generic tool and approach to evaluate different safety systems for their cost-effectiveness and contribution to reduction in fatalities.
Computational modeling of drug transport in the posterior eye.
(2010-01) Balachandran, Ram K.
Posterior segment eye diseases cause vision impairment and blindness in millions of people. A number of these diseases including age-related macular degeneration, glaucoma, and retinopathy can cause irreversible blindness and are currently treated with the help of drugs. Delivering drugs to the posterior eye is a challenge because of the presence of various physiological and anatomical barriers. Systemic delivery is infeasible due to the size of the eye. Topical delivery is also ineffective due to various barriers and elimination routes associated with the anterior eye. Intravitreal delivery, which is currently the preferred mode of drug delivery, provides a localized drug depot in the vitreous, but the method is invasive and frequent interventions can lead to endophthalmitis, retinal detachment, and hemorrhage. Recently, delivering drug via the transscleral route has gained attention as the sclera has been shown to be permeable to drug molecules and the method is invasive and provides a localized drug source as well. The objective of the dissertation was to provide better understanding of drug transport in the posterior eye with the help of a computational model. In particular, the following specific aims were pursued. 1. Quantification of the relative importance of the tissue related barriers and elimination factors in the posterior tissues like the sclera, choroid, and the retina and its pigment epithelium. 2. Investigation of the effect of saccade induced sloshing of the vitreous following vitreous liquefaction or vitrectomy, on drug distribution in the posterior eye Posterior segment eye diseases cause vision impairment and blindness in millions of people. A number of these diseases including age-related macular degeneration, glaucoma, and retinopathy can cause irreversible blindness and are currently treated with the help of drugs. Delivering drugs to the posterior eye is a challenge because of the presence of various physiological and anatomical barriers. Systemic delivery is infeasible due to the size of the eye. Topical delivery is also ineffective due to various barriers and elimination routes associated with the anterior eye. Intravitreal delivery, which is currently the preferred mode of drug delivery, provides a localized drug depot in the vitreous, but the method is invasive and frequent interventions can lead to endophthalmitis, retinal detachment, and hemorrhage. Recently, delivering drug via the transscleral route has gained attention as the sclera has been shown to be permeable to drug molecules and the method is invasive and provides a localized drug source as well. The objective of the dissertation was to provide better understanding of drug transport in the posterior eye with the help of a computational model. In particular, the following specific aims were pursued. 1. Quantification of the relative importance of the tissue related barriers and elimination factors in the posterior tissues like the sclera, choroid, and the retina and its pigment epithelium. 2. Investigation of the effect of saccade induced sloshing of the vitreous following vitreous liquefaction or vitrectomy, on drug distribution in the posterior eye animal data, which are mostly done on an intact vitreous, to old patients whose vitreous might be liquefied. The model developed could also drive design of delivery systems in order to increase the efficiency of the treatment.
Creation and In Vivo evaluation of a porous electrode for pacing in a coronary vein: an assessment of the potential for improved electrical performance and chronic stability of coronary venous pacing leads.
(2009-05) Koop, Brendan Early
In this work, a porous electrode was fabricated and evaluated in a chronic animal study on a coronary venous pacing lead in order to assess its potential for mitigating chronic lead dislodgements and reducing the characteristic rise in pacing thresholds after implant, both of which being important issues that impact safety and efficacy of implanted cardiac resynchronization therapy systems. Eight test leads were assembled with a porous tip electrode with an average pore size of approximately 30 micrometers, created via a novel fabrication method, and eight control leads were assembled with a standard solid tip electrode design. Both groups were created without steroid-eluting collars and without a capacitive coating on the tip electrodes in order to isolate the affects of electrode porosity. Leads were implanted in canines, and electrical data and x-rays of lead position were taken regularly throughout the 60-day study. Tissue histology was performed for each lead. Significantly lower (p<0.05) mean rise in pacing threshold after implant was observed at day 3 and day 21 for the test group leads (with porous electrodes) as compared to the control group leads. Despite the higher surface area of the porous tip electrodes, pacing impedance was not statistically different between the groups throughout the study, a result likely due to decreased chronic inflammatory response at the surface of porous electrodes. The test group had no lead retractions after day 3 as determined by inspection of x-ray radiographs, while 3-6 (of 8) control group leads retracted after day 3, a result likely due to anchoring of the lead tip due to observed tissue growth into porous electrodes. Mean fibrous capsule thickness at pre-defined measurement points on the tip electrode was not statistically different between the groups, which correlates with the nearly equal mean pacing thresholds for the groups at day 60. The lack of lead retractions for the test groups leads after day 3 is a promising result which should be investigated further, along with investigations of lead extraction force and further electrical data evaluations, using larger sample sizes and more challenging implant conditions.
Dependence of Fire Detection Systems to Mass Concentrations and Particle Size Distributions
(2012-04-18) Hart, Colin
Combustion of common household items containing plastic and cellulosic solid and liquid materials results in flaming and smoldering fires. Products of combustion of these fires include H2O, CO2, energy release, visible or infrared radiation, gaseous hydrocarbons, and solid and semi-volatile particles. Commercial and household smoke detectors rely on ionization and photoelectric techniques to detect particles generated by flaming and smoldering fires and the National Fire Protection Association recommends using both techniques in parallel to improve detection capabilities. The purpose of this study is to improve the understanding of how the response of commercial smoke detectors depends on the physical and chemical characteristics of smoke particles, i.e. varying number concentration and size distribution. Our data, in turn, will support the development, analysis, and optimization of the complete fire detection systems used by commercial aircrafts in the future.

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