Exploratory Research on MEMS Technology for Air-Conditioning and Heat-Pumps

This report details the efforts to exploit micro-electrical-mechanical-systems (MEMS) and micro device technologies to improve control of multi-channel evaporators by reducing maldistribution among channels, and increase capacity and efficiency of current vapor-compression refrigeration chillers and heat-pumps. Besides summarizing the market potential of MEMS technology for use in evaporators and micro-heat-pumps, the report describes the accomplishments of an experimental investigation of refrigerant-side maldistribution in multi-channel plate heat exchangers (PHE's). A special test facility designed for the purpose of studying the maldistribution of refrigerant in evaporators is described in the report. The facility allows maldistribution caused by either normal superheat temperature control, or induced by the user in controlled amounts, to be measured and quantified. Four different techniques were used to detect the presence of liquid droplets in the stream of superheated vapor at the evaporator exit, an indication of maldistributed flow. They are: Helium-Neon laser, beaded thermocouple, static mixer and newly designed heated MEMS sensor. Comparison of the four techniques shows that the MEMS sensor designed and fabricated in this project has the highest potential for indicating maldistribution, manifested by entrained liquid droplets, in multi-channel evaporators. A complete set of test results in the time and frequency domain is show in graphical form in the appendices. The design, fabrication, calibration, and testing of the MEMS serpentine resistance sensor is also reported, along with a control scheme and strategy for implementing the MEMS sensor in multi-channel evaporator systems

Neural regulation of cardiovascular response to exercise: role of central command and peripheral afferents

During dynamic exercise, mechanisms controlling the cardiovascular apparatus operate to provide adequate oxygen to fulfill metabolic demand of exercising muscles and to guarantee metabolic end-products washout. Moreover, arterial blood pressure is regulated to maintain adequate perfusion of the vital organs without excessive pressure variations. The autonomic nervous system adjustments are characterized by a parasympathetic withdrawal and a sympathetic activation. In this review, we briefly summarize neural reflexes operating during dynamic exercise. The main focus of the present review will be on the central command, the arterial baroreflex and chemoreflex, and the exercise pressure reflex. The regulation and integration of these reflexes operating during dynamic exercise and their possible role in the pathophysiology of some cardiovascular diseases are also discusse

Control of a magnetically levitated ventricular assist device

This work presents theoretical and experimental means for achieving impeller stability in a magnetically levitated left ventricular assist device (LVAD). These types of medical devices are designed to boost the native heart`s ability to pump blood by means of mechanical energy transfer using a rotating impeller. Magnetic suspension of the impeller eliminates bearing friction and reduces blood damage, but it requires active controls that monitor the impeller`s position and speed in order to generate the forces and torques required to regulate its dynamic behavior. To accomplish this goal, this work includes: 1) a dynamic system model derived using energy and momentum conservation 2) dynamic analysis including stability, controllability and observability, and 3) development of two control algorithms: proportional integral derivative and sliding mode control. Experimental validation included component behavior, model accuracy, and the characterization of controller performance using a physiological simulator. The system model proved to be an adequate representation of the system while levitating in air, but additional research is needed to model hydrodynamic and gyroscopic effects. After the prototype`s subcomponents were tested, calibrated and/or modified to fit the control requirements, both control strategies were successful in controlling the rotor as it spun at 6000 rpm pumping 6L/min of water at 80mmHg. A maximum speed of 6500 rpm was achieved with speed control within 5% over most of the operating range. The control platform and many of the methods presented here are continually being used and improved towards the implantation of the device in a human subject in the future

Innovations in Traumatic Hemorrhage

Traumatic hemorrhagic injuries present a great problem to humanity and a challenge to medicine in the modern world. Current methods of treating these injuries in the field are ineffective and often extremely overkill or injurious. These methods are particularly inadequate when applied to the continuous high pressure bleeding that occurs from arterial wounds. Our project focuses on lowering the barriers to entry to innovation in the field of bleeding treatment by creating a low cost model of the human circulatory system. This model can function as a low-cost testing platform for novel bleeding treatments developed by companies and individuals that do not have the resources to regularly purchase extremely expensive cardiovascular simulators. To this end we designed a tripartite model which included a heart-simulating pump, vessel-simulating vasculature, and blood-mimicking fluid. In order to ensure our device functioned as a testing platform, we performed some preliminary solution candidate tests on it which had the ancillary benefit of identifying one effective but biologically unsafe solution that could be translated into a safe and efficacious future solution. Ultimately we found that our system functioned well as a testing platform for traumatic injury treatments and that standard silicone sealant administered by injection into the vessels had the greatest efficacy in stopping bleeding

Concomitant evaluation of cardiovascular and cerebrovascular controls via Geweke spectral causality to assess the propensity to postural syncope

The evaluation of propensity to postural syncope necessitates the concomitant characterization of the cardiovascular and cerebrovascular controls and a method capable of disentangling closed loop relationships and decomposing causal links in the frequency domain. We applied Geweke spectral causality (GSC) to assess cardiovascular control from heart period and systolic arterial pressure variability and cerebrovascular regulation from mean arterial pressure and mean cerebral blood velocity variability in 13 control subjects and 13 individuals prone to develop orthostatic syncope. Analysis was made at rest in supine position and during head-up tilt at 60°, well before observing presyncope signs. Two different linear model structures were compared, namely bivariate autoregressive and bivariate dynamic adjustment classes. We found that (i) GSC markers did not depend on the model structure; (ii) the concomitant assessment of cardiovascular and cerebrovascular controls was useful for a deeper comprehension of postural disturbances; (iii) orthostatic syncope appeared to be favored by the loss of a coordinated behavior between the baroreflex feedback and mechanical feedforward pathway in the frequency band typical of the baroreflex functioning during the postural challenge, and by a weak cerebral autoregulation as revealed by the increased strength of the pressure-to-flow link in the respiratory band. GSC applied to spontaneous cardiovascular and cerebrovascular oscillations is a promising tool for describing and monitoring disturbances associated with posture modification

Testialustan suunnittelu hybridiajoneuvojen hardware-in-the-loop simulaatioihin

Recent changes to vehicle type-approval regulations have increased demand for testing methods, which better represent real-world driving conditions. Hardware-in-the-Loop (HIL) simulation is seen as an attractive alternative for pure simulations and real-world operation measurements. The goal of this work was to provide a functional testbed for engine testing, as well as for HIL simulations of Hybrid Electric Vehicles (HEVs). In addition, a state-of-the-art review of HIL was considered an important goal of the work. The theory behind HIL, and real-time systems in general, is depicted using a wide variety of examples from automotive applications relating to hybrid power sources. The knowledge gained from the literature was used to design and build a testbed in a form of an engine dynamometer. The testbed can be used to emulate rotational forces, such as load torques on a driveshaft. The testbed’s fast hardware connections enable real-time testing. The scope of the design was in mechanical design and in specification of the hardware components. Initial Internal Combustion Engine (ICE) steady-state and transient tests were done to partially validate the testbed. However, the performance was assessed to not be at an acceptable level. For example, only speed tracking passed the non-road transient cycle tracking assessment. Torque tracking and the derived power curves failed the assessment narrowly. However, the test results indicate that with proper tuning of the control software, the system performance should get better. The system response was slow at this point, but the transient behavior itself was fast. Also, in steady-state, torque and speed ripple were low. Only the preparations for HIL simulation were carried out, since the testbed was not validated to be functional enough for the much more demanding HIL tests. The preparations involved building a simulation model of a series-parallel hybrid Refuse-Collecting Vehicle (RCV), which is to be used for the verification of the designed system’s HIL capabilities. The model was independently verified to be suitable to be used for the physical tests.Viimeaikaiset muutokset ajoneuvojen tyyppihyväksyntään ovat lisänneet tarvetta testausmetodeille, jotka paremmin vastaavat oikean elämän ajo-olosuhteita. HIL-simulaatio nähdään houkuttelevana vaihtoehtona pelkälle simulaatiolle sekä ajoneuvon ajonaikaisille mittauksille. Tämän työn tavoitteena on tarjota toimiva testilaite moottoridynamometritestaukseen sekä hybridiajoneuvojen HIL-simulaatioihin. Lisäksi, HIL:in nykytilanteen kuvausta pidettiin tärkeänä työn tavoitteena. HIL:in, ja yleisemmin reaaliaikaisen testauksen, tausta ja teoria selvitettiin laaja alaisesti käyttäen esimerkkejä hybridivoimanlähteisiin liittyvistä ajoneuvoalan käyttökohteista. Kirjallisuutta hyödyntäen, testipenkki suunniteltiin ja rakennettiin. Testipenkkiä voidaan käyttää emuloimaan pyöriviä voimia, kuten vetoakseliin kohdistuvia vääntöjä. Testipenkin nopeat yhteydet mahdollistavat reaaliaikaisen testauksen. Suunnittelu oli rajattu pääasiassa mekaaniseen suunnitteluun ja komponenttien määrittelyyn. Sähkö- ja ohjelmistosuunnittelu määriteltiin yleisellä tasolla. Alustavat polttomoottorilla tehdyt vakaiden ajopisteiden ja transienttiajojen testit toteutettiin testipenkin osittaiseksi validoinniksi. Kuitenkin, laitteen suorituskyky ei yltänyt halutulle tasolle. Esimerkiksi, ainoastaan nopeusseuranta läpäisi transienttiajo testin, mutta vääntö- ja voimaseurannat epäonnistuivat täpärästi. Tulokset kuitenkin osoittavat luottamusta siitä että testipenkki saadaan aikanaan halutulle tasolle ohjelmistopuolen kontrollereja säätämällä. Tällä hetkellä systeemin vasteaika on liian pitkä, vaikka muuten dynamiikka on nopeaa. Lisäksi, vakaissa ajopisteissä vääntö- ja nopeushuojunta ovat alhaisia. Ainoastaan valmistelut HIL-simulaatiota varten saatiin toteutettua, sillä testipenkkiä ei saatu reaaliaikasta testausta vaativalle tasolle. Valmistelut sisälsivät hybridijäteauton simulaatiomallin rakentamisen, jota tullaan aikanaan käyttämään testipenkin HIL toimivuuden validointiin. Simulaatiomalli varmistettiin itsenäisenä toimivaksi, ja siten soveltuvaksi tuleviin fyysisiin testiajoihin

Co-Simulation and Dynamic Assessment of Thermal Management Strategies Aboard Naval Surface Ships

The US Navy has committed to technology development for an all-electric ship (AES) that incorporates significant advances in power management, advanced sensors and weaponry, re-configurability, and survivability. Quantifying the close relationship between ship-board thermal, mechanical, and electrical sub-systems is of fundamental importance to understanding the nature of a large integrated system like the AES.United States Office of Naval ResearchCenter for Electromechanic

Hemodynamics and Endothelial Cell Biology in Cardiovascular Diseases

Atherosclerotic plaques develop preferentially in curved and branching arteries in-vivo. Lipids and inflammatory cells accumulation in the intimal layer of the arterial wall is considered as the main driving mechanism in the disease progression. Evidences suggest that this focal distribution of plaques may result from the combination of systemic risk factors including high plasma cholesterol, smoking, diabetis, hypertension or genetic pre-disposition and local hemodynamic risk factors such as low and oscillatory flows. The exact mechanism of the biological and biomechanical interactions between the endothelium, blood flow and the growing lesion underneath still remains unclear. This thesis is a study on the relationship between biomechanical factors found in proatherogenic flow and endothelial inflammation. The thesis focuses in particular on the effect of secondary flows on wall shear stress and mass transport distribution. To that end, we have combined different techniques from flow imaging, 3D flow reconstruction, vascular biology and mathematical simulation of biological network. In particular, shear stress is involved in the regulation of the pro-inflammatory transcription factor nuclear factor -kB (NF-kB) and the vasoregulator Nitric Oxide. The role of endothelial Nitric Oxide and wall shear stress on NF-kB activation is still controversial. We investigated here the hypothesis that NO negatively regulates NF- kB activation in flow chamber with sheared endothelial cells and using a mathematical model of the NF-kB-NO pathway. Understanding the underlying relationship between hemodynamic factors and inflammatory cells transport to the wall may contribute to the development of better therapies or interventional practices to treat patients with atherosclerotic diseases

Development of biomedical devices for the extracorporeal real-time monitoring and perfusion of transplant organs

The goal of this Thesis is to develop a range of technologies that could enable a paradigm shift in organ preservation for renal transplantation, transitioning from static cold storage to warm normothermic blood perfusion. This transition could enable the development of novel pre-implantation therapies, and even serve as the foundation for a global donor pool. A low-hæmolysis pump was developed, based on a design first proposed by Nikola Tesla in 1913. Simulations demonstrated the theoretical superiority of this design over existing centrifugal pumps for blood recirculation, and provided insights for future avenues of research into this technology. A miniature, battery-powered, multimodal sensor suite for the in-line monitoring of a blood perfusion circuit was designed and implemented. This was named the ‘SmartPipe’, and proved capable of simultaneously monitoring temperature, pressure and blood oxygen saturations over the biologically-relevant ranges of each modality. Finally, the Thesis details the successful implementation and optimisation of a combined microfluidic and microdialysis system for the real-time quantitation of creatinine in blood or urine through amperometric sensing, to act as a live renal function monitor. The range of detection was 4.3μM – 500μM, with the possibility of extending this in both directions. This work also details and explores a novel methodology for functional monitoring in closed-loop systems which avoids the need for sensor calibration, and potentially overcomes the problems of sensor drift and desensitisation.Open Acces

Flow Assessment Using Optical Coherence Microscopy Based Particle Image Velocimetry

Congenital heart diseases (CHDs) are the most common forms of congenital malformation in newborns. Among all types of CHDs, a large portion is contributed by malformation of endocardial cushion malformation during early heart development. Although the etiology of endocardial cushion malformation is unclear, it is a result of interactions between genetic and environmental factors has been confirmed. There is hypothesis indicating that malformation of endocardial cushion is caused by altered shear stress conditions where in cushion forming area the shear stress is supposed to be high compare with other area in congenital heart. However it is difficult to justify due to lack of in vivo imaging modality that is able to monitor structure and hemodynamic conditions simultaneously and over long time period. To address this problem, we present an optical coherence microscopy based particle image velocimetry system. This system is capable of invasively imaging biological sample structures at micrometer resolution and providing velocity information at the same time. With this imaging set up we successfully assessed velocity profile in a microfluidic system with simultaneous structure details demonstration of the microfluidic channel. Both flow measurement and structural information were verified using conventional microscopy. As a result, OCM-based PIV imaging modality not only makes it feasible to study in detail the process of congenital heart remodeling in response to environmental alterations, but also provides new options for measuring fluid flow in live tissue