Sustainability in design: now! Challenges and opportunities for design research, education and practice in the XXI century

Copyright @ 2010 Greenleaf PublicationsLeNS project funded by the Asia Link Programme, EuropeAid, European Commission

Bubble Rise Dynamics in Complex Fluids

Formation of gas bubbles in complex fluids and their subsequent rise due to buoyancy is a very important fundamental phenomenon both in nature and industry. Bubble size and bubble velocity are critical parameters which govern the interfacial transport phenomena and play an important role in gas-solid contact. These characteristics affect the operating parameters as well as the design of equipment in industrial applications. Non-Newtonian, Shear-thickening fluids have been studied extensively due to their immense potential for commercial use in shock absorbing and force damping applications, such as liquid body armor, sports and personal protection. Furthermore, a better understanding of shear-thickening fluid is pertinent to industrial processing for enhancing flow, preventing the breakage or clogging of mixing equipment, and preventing clogging in narrow orifices. Despite their significance, many aspects of the flow of these non-Newtonian fluids remain poorly understood. In the first part of this dissertation, we study the dynamics of rising bubbles in three dimensional fluidized beds using computational fluid dynamics-discrete element method (CFD-DEM) to shed light on the physics underpinning phenomena uncovered previously using magnetic resonance imaging (MRI). We were able to understand the underlying mechanism behind the anomalous collapse of a bubble in side-by-side injection as well as an alternating asynchronous pinch-off pattern due to jet interaction in a fluidized bed by looking into the gas streamlines and the drag force on the particles. In the second part of this dissertation, we study dynamics of rising bubbles in Newtonian fluids and non-Newtonian cornstarch-water suspensions experimentally using optical imaging. We were able to identify that Capillary number (Ca) is a key dimensionless parameter governing the regimes of interacting jets in water. We also observed a periodic coalescence of bubbles at the same points in space in cornstarch-water suspensions and attributed this behavior to leading bubbles entering a shear thickening regime. Further, we identified the key dimensionless parameters for wobbling behavior of single bubbles in cornstarch suspensions to be Bond (Bo), and Reynolds (Re) number, regardless of the bubble being in a Newtonian or a shear-thinning regime. We believe our findings can be applied in industry to optimize the mass transport and liquid mixing for a range of applications

DEFINING DIGITAL PRESERVATION WORK: A CASE STUDY OF THE DEVELOPMENT OF THE REFERENCE MODEL FOR AN OPEN ARCHIVAL INFORMATION SYSTEM

I report on a multi-method case study of the development of a standard called the Reference Model for an Open Archival Information System (OAIS), which describes components and services required to develop and maintain archives in order to support long-term access and understanding of the information in those archives. The development of the OAIS took place within a standards development organization called the Consultative Committee for Space Data Systems (CCSDS), whose formal purview is the work of space agencies, but the effort reached far beyond the traditional CCSDS interests and stakeholders. It has become a fundamental component of digital archive research and development in a variety of disciplines and sectors. Through document analysis, social network analysis and qualitative analysis of interview data, I explain how and why the OAIS development effort, which took place within a space data standards body, was transformed into a standard of much wider scope, relevant to a diverse set of actors. The OAIS development process involved substantial enrollment of resources from the environment, including skills and expertise; social ties; documentary artifacts; structures and routines; physical facilities and proximity; and funding streams. Enrollment from the environment did not occur automatically. It was based on concerted efforts by actors who searched for relevant literature, framed the process as open, and promoted it at professional events. Their acts of participation also helped to enroll resources, contributing to what structuration theory calls the signification and legitimation of the Reference Model, i.e. enactment of what the document means, and why and to whom it is important. Documentary artifacts were most successfully incorporated into the OAIS when they were perceived to support modularity and to be at an appropriate level of abstraction. The content of the Reference Model was subject to stabilization over time, making changes less likely and more limited in scope. A major factor in the success of the OAIS was the timing of its development. Actors within several streams of activity related to digital preservation perceived the need for a highlevel model but had not themselves developed one. At the same time, several actors now felt they had knowledge from their own recent digital archiving efforts, which could inform the development of the OAIS. This study has important implications for research on standardization, and it provides many lessons for those engaged in future standards development efforts.Ph.D.InformationUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/39372/2/dissertation_callee.pd

Coding for Relay Networks with Parallel Gaussian Channels

A wireless relay network consists of multiple source nodes, multiple destination nodes, and possibly many relay nodes in between to facilitate its transmission. It is clear that the performance of such networks highly depends on information for- warding strategies adopted at the relay nodes. This dissertation studies a particular information forwarding strategy called compute-and-forward. Compute-and-forward is a novel paradigm that tries to incorporate the idea of network coding within the physical layer and hence is often referred to as physical layer network coding. The main idea is to exploit the superposition nature of the wireless medium to directly compute or decode functions of transmitted signals at intermediate relays in a net- work. Thus, the coding performed at the physical layer serves the purpose of error correction as well as permits recovery of functions of transmitted signals. For the bidirectional relaying problem with Gaussian channels, it has been shown by Wilson et al. and Nam et al. that the compute-and-forward paradigm is asymptotically optimal and achieves the capacity region to within 1 bit; however, similar results beyond the memoryless case are still lacking. This is mainly because channels with memory would destroy the lattice structure that is most crucial for the compute-and-forward paradigm. Hence, how to extend compute-and-forward to such channels has been a challenging issue. This motivates this study of the extension of compute-and-forward to channels with memory, such as inter-symbol interference. The bidirectional relaying problem with parallel Gaussian channels is also studied, which is a relevant model for the Gaussian bidirectional channel with inter-symbol interference and that with multiple-input multiple-output channels. Motivated by the recent success of linear finite-field deterministic model, we first investigate the corresponding deterministic parallel bidirectional relay channel and fully characterize its capacity region. Two compute-and-forward schemes are then proposed for the Gaussian model and the capacity region is approximately characterized to within a constant gap. The design of coding schemes for the compute-and-forward paradigm with low decoding complexity is then considered. Based on the separation-based framework proposed previously by Tunali et al., this study proposes a family of constellations that are suitable for the compute-and-forward paradigm. Moreover, by using Chinese remainder theorem, it is shown that the proposed constellations are isomorphic to product fields and therefore can be put into a multilevel coding framework. This study then proposes multilevel coding for the proposed constellations and uses multistage decoding to further reduce decoding complexity

The long-term impact of a loyalty program: An evaluation from a Las Vegas casino hotel

Loyalty programs are popular marketing strategies intended to attract, maintain, and enhance customer relationships. Despite the widespread usage of loyalty programs across various businesses, its effectiveness has not been well validated. Few empirical studies attempted to evaluate the value of loyalty programs but the findings have been conflicting with each other. Given the competitive climate of such a highly saturated competitive market of the hospitality industry, it is meaningful for hospitality marketers to evaluate the effectiveness of loyalty programs to increase customer retention and profitability. Therefore, the main purpose of this study was to examine the effectiveness of a hospitality loyalty program from a longitudinal perspective. The literature review is separated in four sections. The first section is the theory building section, which examined social exchange theory, equity theory, and the relationship marketing theory to understand the development of customer loyalty. The second section describes the definition of loyalty and the factors that affect customer loyalty. It gives an understanding about loyalty marketing from a general perspective. The third section describes the purpose of loyalty programs, and finally the last section summarized the investigation of loyalty programs from previous studies. Overall, the literature review section suggested that despite the prevailing usage and attention on loyalty programs, the effectiveness from the customers\u27 behavioral standpoint has not been well understood. For this reason, this study aims to find out the effectiveness of loyalty programs from a longitudinal perspective and study hypotheses were advanced. This study obtained secondary data from a Las Vegas casino hotel and performed time series ARIMA modeling to test the study hypotheses. Results of this study supported the research hypotheses and indicated that loyalty programs do have a positive impact on customers\u27 behavioral loyalty. The findings are expected to provide valuable insights for casino marketers to understand the impact of loyalty programs and develop marketing tactics to maintain loyal customers and maximize profitability as well

Numerical Simulations of Dusty Colliding Wind Binaries

Colliding Wind Binary (CWB) systems are relatively rare phenomena, but have a significant influence on galactic evolution in terms of dust production -- especially in the early universe. The mechanisms behind this dust production, however, are poorly understood. The strong winds from both partners in the binary system drive shocks that heat the dust forming region to temperatures in excess of 100 million Kelvin; whilst this region does rapidly cool, the initial shock temperatures would destroy any dust grains that formed outside the collision region. Furthermore, this collision region is difficult to observe and simulate, limiting our understanding of how grains form and evolve in this region. This thesis attempts to improve our understanding of the evolution of dust grains within these systems, particularly growth of these grains from small dust grain cores to micron-scale grains. A co-moving dust grain model was implemented that simulates growth through accretion of gas onto the dust grains, as well as destruction through gas-grain sputtering. The model also simulates cooling through collisional excitation and subsequent emission for both dust grains and gas. Overall, the goal of this model was to determine how dust growth was influenced by the wind and orbital characteristics of the system, and which of these characteristics were most important for dust growth. First, a parameter space exploration of dust producing CWB systems (WCd systems) was conducted, varying the orbital separation, the wind terminal velocity and the mass loss rate of each star. It was found that dust production is strongly influenced by the ratio of wind terminal velocities between each star, as well as the orbital separation. Following up on this, a limited simulation of the episodic dust forming system WR140 was conducted, in order to understand how variance in orbital separation through eccentricity changed dust production rates over the course of a periastron passage. Furthermore, it was determined that dust production occurs over a very short period immediately prior to periastron passage and a small period after, with an ``active'' phase of approximately 1 year, or an eighth of the systems orbital period Whilst there is much to be done in the future, and many more systems to be simulated (in particular the recently discovered WR+WR CWB systems WR48a and WR70-16) this model is a good first step towards shedding light on these elusive and dust-shrouded systems

Lithium Depletion Boundary Ages of Young Planet-Hosting Stellar Associations

Stellar associations - groups of coeval, co-moving stars - are fundamental to our understanding of stellar ages and critical for the study of stellar and planetary evolution. All stellar age measurements, with the sole exception of the Sun, are based on the ages of stellar associations or on methods developed through studies of associations. Young associations in particular provide excellent benchmarks to study stellar and planetary evolution, as many important evolutionary steps occur during the first billion years of a star's existence.The combination of the Gaia, Kepler, and TESS missions have ushered in a golden age for studying stellar and planetary evolution. These studies will require both robust, accurate age measurements for stellar associations and numerous planets within those associations to study. However, commonly used methods of measuring age, such as isochrone fitting, are imprecise and depend strongly on poorly-understood physical parameters such as magnetic fields. An alternative, more precise way to achieve association ages, the Lithium Depletion Boundary (LDB) method is less model-dependent but requires observationally expensive spectra of low-mass association members. Moreover, less than one hundred young (<1 Gyr) planets have yet been discovered, offering few vantage points into a highly important and dynamic time period. In this thesis I characterize several nearby, planet-hosting associations and planets within them. I clarify the associations' membership and kinematics using 6D astrometric data available from the Gaia mission, and the \banyan{} tool for association membership. I measure the ages of the associations using the LDB method and spectra obtained on the Goodman HTS on the SOAR telescope. When possible these ages are confirmed using additional age-measurement methods, making the resulting ages robust and accurate. The products of this thesis are new ages and membership lists for several previously known associations and subpopulations (Musca, LCC-A, LCC-B, LCC-C, Carina, Theia 92, Theia 113), the discovery and characterization of an entirely new association (MELANGE-4), and the discovery or confirmation of three exoplanets within those associations. Collectively, the associations studied here contain thousands of stars and 7 known planets, forming an impressive sample of accurately age-dated stars and planets on which future studies can rely.Doctor of Philosoph

Development of Microwave/Droplet-Microfluidics Integrated Heating and Sensing Platforms for Biomedical and Pharmaceutical Lab-on-a-Chip Applications

Interest in Lab-on-a-chip and droplet-based microfluidics has grown recently because of their promise to facilitate a broad range of scientific research and biological/chemical processes such as cell analysis, DNA hybridization, drug screening and diagnostics. Major advantages of droplet-based microfluidics versus traditional bioassays include its capability to provide highly monodispersed, well-isolated environment for reactions with magnitude higher throughput (i.e. kHz) than traditional high throughput systems, as well as its low reagent consumption and elimination of cross contamination. Major functions required for deploying droplet microfluidics include droplet generation, merging, sorting, splitting, trapping, sensing, heating and storing, among which sensing and heating of individual droplets remain great challenges and demand for new technology. This thesis focuses on developing novel microwave technology that can be integrated with droplet-based microfluidic platforms to address these challenges. This thesis is structured to consider both fundamentals and applications of microwave sensing and heating of individual droplets very broadly. It starts with developing a label-free, sensitive, inexpensive and portable microwave system that can be integrated with microfluidic platforms for detection and content sensing of individual droplets for high-throughput applications. This is, indeed, important since most droplet-based microfluidic studies rely on optical imaging, which usually requires expensive and bulky systems, the use of fluorescent dyes and exhaustive post-imaging analysis. Although electrical detection systems can be made inexpensive, label-free and portable, most of them usually work at low frequencies, which limits their applications to fast moving droplets. The developed microwave circuitry is inexpensive due to the use of off-the-shelf components, and is compact and capable of detecting droplet presence at kHz rates and droplet content sensing of biological materials such as penicillin antibiotic, fetal bovine serum solutions and variations in a drug compound concentration (e.g., for Alzheimer’s Disease). Subsequently, a numerical model is developed based on which parametrical analysis is performed in order to understand better the sensing and heating performance of the integrated platform. Specifically, the microwave resonator structure, which operates at GHz frequency affecting sensing performance significantly, and the dielectric properties of the microfluidic chip components that highly influence the internal electromagnetic field and energy dissipation, are studied systematically for their effects on sensing and heating efficiency. The results provide important findings and understanding on the integrated device operation and optimization strategies. Next, driven by the need for on-demand, rapid mixing inside droplets in many applications such as biochemical assays and material synthesis, a microwave-based microfluidic mixer is developed. Rapid mixing in droplets can be achieved within each half of the droplet, but not the entire droplet. Cross-center mixing is still dominated by diffusion. In this project, the microwave mixer, which works essentially as a resonator, accumulates an intensive, nonuniform electromagnetic field into a spiral capacitive gap (around 200 μm) over which a microchannel is aligned. As droplets pass by the gap region, they receive spatially non-uniform energy and thus have non-uniform temperature distribution, which induces non-uniform Marangoni stresses on the interface and thus three-dimensional (3D) chaotic motion inside the droplet. The 3D chaotic motion inside the droplet enables fast mixing within the entire droplet. The mixing efficiency is evaluated by varying the applied power, droplet length and fluid viscosity. In spite of various existing thermometry methods for microfluidic applications, it remains challenging to measure the temperature of individual fast moving droplets because they do not allow sufficient exposure time demanded by both fluorescence based techniques and resistance temperature detectors. A microwave thermometry method is thus developed here, which relies on correlating fluid temperature with the resonance frequency and the reflection coefficient of the microwave sensor, based on the fact that liquid permittivity is a function of temperature. It is demonstrated that the sensor can detect the temperature of individual droplets with ±1.2 °C accuracy. At the final part of the thesis, I extend my platform technology further to applications such as disease diagnosis and drug delivery. First, I develop a microfluidic chip for controlled synthesis of poly (acrylamide-co-sodium acrylate) copolymer hydrogel microparticles whose structure varies with temperature, chemical composition and pH values. This project investigates the effects of monomer compositions and cross-linker concentrations on the swelling ratio. The results are validated through the Fourier transform infrared spectra (FTIR), SEM and swelling test. Second, a preliminary study on DNA hybridization detection through microwave sensors for disease diagnosis is conducted. Gold sensors and biological protocols of DNA hybridization event are explored. The event of DNA hybridization with the immobilized thiol-modified ss-DNA oligos and complimentary DNA (c-DNA) are monitored. The results are promising, and suggests that microwave integrated Lab-on-a-chip platforms can perform disease diagnosis studies