Flexible electronics have gained great attention recently. Applications such as flexible displays, artificial skin and health monitoring devices are a few examples of this technology. Looking closely at the components of these devices, although MEMS actuators and sensors can play critical role to extend the application areas of flexible electronics, fabricating movable MEMS devices on flexible substrates is highly challenging. Therefore, this thesis reports a process for fabricating free standing and movable MEMS devices on flexible silicon substrates; MEMS flexure thermal actuators have been fabricated to illustrate the viability of the process. Flexure thermal actuators consist of two arms: a thin hot arm and a wide cold arm separated by a small air gap; the arms are anchored to the substrate from one end and connected to each other from the other end. The actuator design has been modified by adding etch holes in the anchors to suit the process of releasing a thin layer of silicon from the bulk silicon substrate. Selecting materials that are compatible with the release process was challenging. Moreover, difficulties were faced in the fabrication process development; for example, the structural layer of the devices was partially etched during silicon release although it was protected by aluminum oxide which is not attacked by the releasing gas . Furthermore, the thin arm of the thermal actuator was thinned during the fabrication process but optimizing the patterning and etching steps of the structural layer successfully solved this problem. Simulation was carried out to compare the performance of the original and the modified designs for the thermal actuators and to study stress and temperature distribution across a device. A fabricated thermal actuator with a 250 μm long hot arm and a 225 μm long cold arm separated by a 3 μm gap produced a deflection of 3 μm before silicon release, however, the fabrication process must be optimized to obtain fully functioning devices on flexible silicon.

The ability to collect valuable data concerning the stress, strains, and shape profiles of aircraft and aircraft components during flight is important to fields such as structural health monitoring, gust alleviation, and flutter control. A research interest in the form of a NASA Phase I SBIR called for possible systems that would be able to take accurate shape sensing data on a flexible wing aircraft. In a joint venture between Luna Technologies Inc. and Virginia Polytechnic Institute and State University a flexible wing wind tunnel model was designed and constructed as a test article for the Luna Technologies Inc. fiber optic shape sensing system. In order to prove the capability of a fiber optic shape sensing system in a wind tunnel environment a flexible wing test article was constructed. The wing deflections and twists of the test article were modeled using a vortex lattice method called Tornado combined with simple beam theories. The beam theories were linear beam theories and the stiffness of the composite bodies was supplied by static testing of the test articles. The code was iterative in that it ran the VLM code to estimate the forces and moments on the wing and these were applied to a linear beam which gave the wing a new geometry which in turn was run through the VLM. The wind tunnel model was constructed at Virginia Tech using 3-D printing techniques for the fuselage and foam and fiberglass for the wings. On the bottom surface of the wings the Luna Technologies Inc. fiber optic shape sensing fiber was bonded along the leading and tailing edges. The swept-wing test article was experimentally tested in the Virginia Tech 6'x6' Stability Wind Tunnel at various airspeeds and the VLM based code results were in agreement, within margins of error and uncertainty, with the experimental results. The agreement of the analytical and experimental results verified the viability of using an iterative VLM code in combination with simple beam theories as a quick and relatively accurate approximation method for preliminary design and testing. The tests also showed that a fiber optic shape sensing system can be sufficiently tested in a wind tunnel environment, and if applied carefully could perhaps in the future provide useful shape and strain measurements. / Master of Science

A parametric study was performed to determine the effect of flexible foundations on the response of timber shear walls. Timber shear walls, which typically consist of structural-use panels, such as plywood or oriented strand board (OSB), attached to a frame made from dimension lumber with dowel-type fasteners such as nails, provide resistance to lateral loading for many low-rise structures in North America. Research performed on shear walls has assumed that a wall is supported by a relatively stiff foundation, such as a concrete block wall, along the entire length of the wall. However, walls are sometimes supported by a relatively flexible foundation, such as a floor joist, which would alter the stiffness, and therefore the response of the wall. Research on flexible foundations is limited at best, and there is a string need to examine the behavior of shear walls on flexible foundations. The study consisted of creating a shear wall numerical model, varying the conditions at the foundation of the model, and analyzing the model when subjected to both monotonic and dynamic loading for each foundation. The system modeled corresponded to a 2.4 m (8 ft) high by 3.7 m (12 ft) long shear wall supported by and parallel to a 7.3 m (24 ft) long joist with hold-downs at each chord of the wall. The joist was supported at each end, with one chord of the wall at an end of the joist and the other chord located at the center of the joist. Eleven joist cross-sections, with sizes determined based on deflection criteria ranging from L/180 to L/720, and a rigid base were included in the study, along with three different hold-down bolt sizes, for a total of thirty-six different foundations. The wall model was analyzed using WALSEIZ1, which is a modified version of the finite element program WALSEIZ (White and Dolan, 1995). Maximum displacements, internal forces, and maximum load were recorded when the model was subjected to monotonic loading, while the maximum displacements and base shear were recorded when the model was subjected to dynamic loading. Results from the study were examined to determine if modifications to the current design practices should be considered. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / Recent innovations in portable electronics, electric vehicles and power generation by wind and solar have expanded the need for effcient battery storage. Lithium-ion batteries have been the frontline contender of battery storage yet are not able to match current demands. Alternatively, lithium-sulfur batteries are a promising technology to match the consumer demands. Elemental sulfur cathodes incur a variety of problems during cycling including the dissolution of intermediate lithium polysul- fides, an undesirable volume change (~ 80%) when completely reduced and a high dependence on liquid electrolyte, which quickly degrades the cell's available energy density. Due to these problems, the high theoretical capacity and energy density of lithium sulfur cells are unattainable. In this work, A new class of phenyl polysul- fides, C6H5SxC6H5(4 < x <6), are developed as liquid sulfur containing cathode materials. This technology was taken a step further to fulfill and emerging need for exible electronics in technology. Phenyl tetrasulfide (C6H5S4C6H5) was polymerized to form a high energy density battery with acute mobility. Lithium half-cell testing shows that phenyl hexasulfide (C6H5S6C6H5) can provide a specific capacity of 650mAh/g and capacity retention of 80% through 500 cycles at 1C rate along with superlative performance up to 10C. Furthermore, 1, 302W h/ kg and 1, 720W h/L are achievable at a low electrolyte/active material ratio. Electrochemical testing of polymer phenyl tetrasulfide reveals high specific capacities of 634mAh /g at 1C, while reaching 600mAh /g upon mechanical strain testing. This work introduces novel cathode materials for lithium-sulfur batteries and provides a new direction for the development of alternative high-capacity flexible cathode materials.

To effectively analyze and design a flexible supply chain (FSC), a variety of variables need to be considered. This research presents a framework, an extension of Chan et al. (2009) that identifies a more extensive yet salient set of variables for designing FSCs. This framework provides a basis for using simulation to better understand, and to better design, FSCs. Conceptual simulation models are developed to represent general flexible supply chains in terms of using design and system variables. The proposed conceptual model incorporates many elements from the framework considering a wide variety of variables to demonstrate the approach for building a FSC model. This research provides a general FSC simulation model, built in FlexSim, that implements many variables from the framework and aspects of the conceptual framework. Variability plays an important role in FSC model. Two key supply-chain performance measures are lead time and variability in lead time. One way that has been proposed to improve both measures is to increase supplier flexibility. Through simulation this research provides a means to assess the effects of various manufacturing and logistics flexibility-related variables on lead time and its variability. This research includes effect of several experiments that consider the effect of supplier flexibility level, proportion of process time that is production and transportation time, and level of variability in process time on lead time. The triangular distribution is used often in simulation when process data are not available. Thus, the triangular distribution is used in the FSC simulation model. This research provides a means to effectively consider alternative values of the parameters of the triangular distribution during experimentation. The method facilitates specification of both moment and location parameters.

No description available.

Current researchers have looked to nature to learn how self-assembly processes occur. By understanding the self-assembly process, designers can begin to build strong structural materials that are extremely light weight. The discrete element modeling method was used to gain a better understanding of the directed self-assembly of M13 bacteriophage. This model was parameterized from molecular dynamics simulations at the nanometer scale. Three types of functionalized bacteriophage were studied: Wild-type, 4E, and CLP8. Results showed that Wild-type phage are attracted in a head-to-tail orientation, but repelled in head-to-head orientation. The 4E bacteriophage behaved similarly with a stronger bond in the head-to-tail orientation, and CLP8 showed to physically repel in either orientation. The overall finding was that the electrostatic physics dominated as the controlling forces of the phage interactions.

Målet med vårt examensarbete var att ta reda på vad elever i grundskolans tidigare år har för attityd till matematik. Vi ville även veta varför och hur attityden förändras, om den förändras genom åren. Som bakgrund till undersökningen har vi använt oss av litte-ratur som handlar om elevers attityd och motivation till matematik. För att ta reda på vår problemställning besökte vi två olika skolor i södra Sverige där vi gjorde observationer och eleverna fick besvara enkäter. När vi sedan sammanställde resultaten och analyse-rade dem jämförde vi de svaren vi fått in genom våra enkäter med det vi såg när vi ob-serverade, samt de teorier vi använt oss av. Resultatet vi fick visade att elevers attityd och intresse för matematiken minskar både från skolår 2 till 4 och skolår 4 till 6. Det kan finnas flera olika anledningar till detta. Men en viktig del för att förhindra det är att som lärare vara flexibel i sin undervisning och vara noggrann med svårighetsgraden på uppgifter man ger eleverna.

abstract My project has been a reflection on; our consumer society, what a home is, and how we are supposed to live. It all started with an interest in flexible living, looking at buildings and the cities in a new way, and a new interpretation of the already built environment. My research question was “What do we really need?” and “ What is the minimum requirement for making a home?”. The project touches on the topics of housing, housing shortage mainly but also sustainability, minimalism, and reactivation of space. This manifested itself in the way that I designed a portable, flexible unit that is your interior space and that also cloud store one’s belongings. The unit was explored in a 1:1 scale model and drawings, exploring both design and different contexts such as; student rooms, small living for couples, and temporary living (mainly students and refugees in mind). I was inspired by Tokyo nomad woman, Shigeru Ban’s paper log house, and Ibiza instant city.

Flexible packaging is a growing successful market and the majority of flexible package applications are for the food industry. The demand for process optimization and reduced production costs, has led to an increase in flexible packaging. However, fast production lines can result in contamination in the seal area. For flexible food packaging, contamination is considered any food particle or substance trapped in the seal area. Current quality control processes can detect contamination in the seal area, but it is not determined if seal contamination effects seal quality. Oil-based and sodium based snack foods are two common categories that can be packaged on a horizontal flow film and seal (HFFS) flow-wrap machine. The study uses vegetable oil and a salt water solution to simulate the effect of liquid contamination along the T-point of flexible pouches made on an HFFS. The T-point refers to where the fin seal meets the end seal and requires the seal jaw to seal through four layers of film, which is the most difficult point to seal. The study tests a combination of different sealing temperatures and dwell time to determine the optimal sealing condition for a hermetic seal. A quality hermetic seal provides an enclosed seal with no leaks due to successful polymer chain entanglement between the two sealant layers. The different test categories of the study are non-contaminated (control), salt water solution for salt based foods, and vegetable oil for oil-based foods. Given the test parameters of the study, 140⁰C sealing temperature and 0.3 seconds dwell time are considered to be the optimal sealing condition for all three test categories. For Phase 1 of the study, salt water has a lower hermeticity pass rate compared to vegetable oil and non-contaminated seals. In addition, the effect of refrigerated storage temperature and ambient storage temperature did not show to be significant for any of the test categories. However, refrigerated conditions showed a higher hermeticity pass rate, but it was not statistically different. The findings for seal strength indicated no test category had higher or lower seal strength over the 14 day test period. Overall, the study shows there is no effect of liquid contaminant on hermeticity and seal strength for flexible film with LLDPE sealant layer.