Chaotic dynamic analysis of viscoelastic plates

The dynamic buckling of viscoelastic plates with large deflection is investigated in this paper by using chaotic and fractal theory. The material behavior is given in terms of the Boltzmann superposition principle. in order to obtain accurate computation results, the nonlinear integro-differential dynamic equation is changed into an autonomic four-dimensional dynamical system. The numerical time integrations of equations are performed by using the fourth-order Runge-Kutta method. And the Lyapunov exponent spectrum, the fractal dimension of strange attractors and the time evolution of deflection are obtained. The influence of geometry nonlinearity and viscoelastic parameter on the dynamic buckling of viscoelastic plates is discussed.

Expanding adoption of drinking water treatment systems in developing countries: a case study from Tamil Nadu, India

Household-level water treatment and safe storage systems (HWTS) are simple, local, user-friendly, and low cost options to improve drinking water quality at the point of use. However, despite conclusive evidence of the health and economic benefits of HWTS, and promotion efforts in over 50 countries in the past 20 years, implementation outcomes have been slow, reaching only 5-10 million regular users. This study attempts to understand the barriers and drivers affecting HWTS implementation. Using a case study example of a biosand filter program in southern India, system dynamics modelling is shown to be a useful tool to map the inter-relationships of different critical factors and to understand the dissemination dynamics. It is found that the co-existence of expanding quickly and achieving financial sustainability appears to be difficult to achieve under the current program structure.

A systems approach to characterise the dissemination process of household water treatment systems in developing countries

Abstract: Starting in the 1980s, household-level water treatment and safe storage systems (HWTS) have been developed as simple, local, user-friendly, and low cost options to improve drinking water quality at the point of use. However, despite conclusive evidence of the health and economic benefits of HWTS, and promotion efforts in over 50 countries in the past 20 years, implementation outcomes have been slow, reaching only 5-10 million regular users. This study attempts to understand the barriers and drivers affecting HWTS implementation. Although existing literature related to HWTS and innovation diffusion theories proposed ample critical factors and recommendations, there is a lack of holistic and systemic approach to integrate these findings. It is proposed that system dynamics modelling can be a promising tool to map the inter-relationships of different critical factors and to understand the structure of HWTS dissemination process, which may lead to identifying high impact, leveraged mitigation strategies to scale-up HWTS adoption and sustained use.

Improvements to Data Collection in Commercial Fisheries Using Electronic Reporting Methods: Cost/Efficiency and Implications for Use in Ecosystem Management.

Data have been collected on fisheries catch and effort trends since the latter half of the 1800s. With current trends in declining stocks and stricter management regimes, data need to be collected and analyzed over shorter periods and at finer spatial resolution than in the past. New methods of electronic reporting may reduce the lag time in data collection and provide more accurate spatial resolution. In this study I evaluated the differences between fish dealer and vessel reporting systems for federal fisheries in the US New England and Mid-Atlantic areas. Using data on landing date, report date, gear used, port landed, number of hauls, number of fish sampled and species quotas from available catch and effort records I compared dealer and vessel electronically collected data against paper collected dealer and vessel data to determine if electronically collected data are timelier and more accurate. To determine if vessel or dealer electronic reporting is more useful for management, I determined differences in timeliness and accuracy between vessel and dealer electronic reports. I also compared the cost and efficiency of these new methods with less technology intensive reporting methods using available cost data and surveys of seafood dealers for cost information. Using this information I identified potentially unnecessary duplication of effort and identified applications in ecosystem-based fisheries management. This information can be used to guide the decisions of fisheries managers in the United States and other countries that are attempting to identify appropriate fisheries reporting methods for the management regimes under consideration. (PDF contains 370 pages)

Water quality and harmful algae in Southeastern coastal stormwater ponds

Several long-term monitoring studies describing the water quality and biological condition of Southeastern estuaries (National Estuarine Eutrophication Assessment Project, South Carolina Estuarine and Coastal Assessment Program (SCECAP), Environmental Monitoring and Assessment Program (EMAP), South Carolina Harmful Algal Bloom Program (SCHAB), South Carolina Tidal Creek Project, and others) have been developed. Many of the same water quality issues determined for open estuaries are also found in coastal stormwater ponds, and there are important interactions between the man-made ponds and the natural systems. Researchers have highlighted problems such as nutrient eutrophication, bacterial and chemical contamination, hypoxia, and harmful algal blooms (HABs). This technical memorandum summarizes the state-of-the-knowledge of water quality indicators (dissolved oxygen, nutrients, and chlorophyll a), and harmful algae in Southeastern coastal stormwater ponds. (PDF contains 31 pages)

Coral Remote Sensing Workshop: Proceedings and Recommendations, 17-18 September, Sheraton, Brickell Ave, Miami FL

Coral reefs exist in warm, clear, and relatively shallow marine waters worldwide. These complex assemblages of marine organisms are unique, in that they support highly diverse, luxuriant, and essentially self-sustaining ecosystems in otherwise nutrient-poor and unproductive waters. Coral reefs are highly valued for their great beauty and for their contribution to marine productivity. Coral reefs are favorite destinations for recreational diving and snorkeling, as well as commercial and recreational fishing activities. The Florida Keys reef tract draws an estimated 2 million tourists each year, contributing nearly $800 million to the economy. However, these reef systems represent a very delicate ecological balance, and can be easily damaged and degraded by direct or indirect human contact. Indirect impacts from human activity occurs in a number of different forms, including runoff of sediments, nutrients, and other pollutants associated with forest harvesting, agricultural practices, urbanization, coastal construction, and industrial activities. Direct impacts occur through overfishing and other destructive fishing practices, mining of corals, and overuse of many reef areas, including damage from souvenir collection, boat anchoring, and diver contact. In order to protect and manage coral reefs within U.S. territorial waters, the National Oceanic and Atmospheric Administration (NOAA) of the U.S. Department of Commerce has been directed to establish and maintain a system of national marine sanctuaries and reserves, and to monitor the condition of corals and other marine organisms within these areas. To help carry out this mandate the NOAA Coastal Services Center convened a workshop in September, 1996, to identify current and emerging sensor technologies, including satellite, airborne, and underwater systems with potential application for detecting and monitoring corals. For reef systems occurring within depths of 10 meters or less (Figure 1), mapping location and monitoring the condition of corals can be accomplished through use of aerial photography combined with diver surveys. However, corals can exist in depths greater than 90 meters (Figure 2), well below the limits of traditional optical imaging systems such as aerial or surface photography or videography. Although specialized scuba systems can allow diving to these depths, the thousands of square kilometers included within these management areas make diver surveys for deeper coral monitoring impractical. For these reasons, NOAA is investigating satellite and airborne sensor systems, as well as technologies which can facilitate the location, mapping, and monitoring of corals in deeper waters. The following systems were discussed as having potential application for detecting, mapping, and assessing the condition of corals. However, no single system is capable of accomplishing all three of these objectives under all depths and conditions within which corals exist. Systems were evaluated for their capabilities, including advantages and disadvantages, relative to their ability to detect and discriminate corals under a variety of conditions. (PDF contains 55 pages)

Design,optimization and in vivo evaluation of non-viral vectors for gene therapy. Applications in ocular disorders

227 págs.

Two mechanisms for population inversion via two-colour coherent excitation in three-level systems

We analyse the physical origin of population inversion via continuous wave two-colour coherent excitation in three-level systems by dressing the inverted transition. Two different mechanisms are identified as being responsible for the population inversion. For V-configured systems and cascade (E) configured systems with inversion on the lower transition, the responsible mechanism is the selective trapping of dressed states, and the population inversion approaches the ideal value of 1. For Lambda-configured systems and Xi-configured systems with inversion on the upper transition, population inversion is based on the selective excitation of dressed states, with the population inversion tending towards 0.5. As the essential difference between these two mechanisms, the selective trapping of dressed states occurs in systems with strong decay into dressed states while the selective excitation appears in systems with strong decay out of dressed states.

Supporting regional coastal and ocean managers: Linking ocean observing tools and capabilities to the priority needs of managers and users in the southeast region

Ocean observing has been recognized by the US Commission on Ocean Policy, the Ocean Research and Resources Advisory Panel, the Joint Ocean Commission Initiative, and many other ocean policy entities and initiatives as foundational to meeting the nation’s need for more effective coastal and ocean management. The Interim Report of the Interagency Task Force on Ocean Policy (September 2009) has called for strengthening the nation’s capacity for observing the nation’s ocean, coastal, and Great Lakes systems. (PDF contains 3 pages)

Spatial filtering in tone reproduction and vision

This thesis is concerned with spatial filtering. What is its utility in tone reproduction? Does it exist in vision, and if so, what constraints does it impose on the nervous system?

Tone reproduction is just the art and science of taking a picture and then displaying it. The sensors available to capture an image have a greater dynamic range than the media that may be used to display it. Conventionally, spatial filtering is used to boost contrast; it ameliorates the loss of contrast that results when the sensor signal range is scaled down to fit the display range. In this thesis, a type of nonlinear spatial filtering is discussed that results in direct range reduction without range scaling. This filtering process is instantiated in a real-time image processor built using analog CMOS VLSI.

Spatial filtering must be applied with care in both artificial and natural vision systems. It is argued that the nervous system does not simply filter linearly across an image. Rather, the way that we see things implies that the nervous system filters nonlinearly. Further, many models for color vision include a high-pass filtering step in which the DC information is lost. A real-time study of filtering in color space leads to the conclusion that the nervous system is not that simple, and that it maintains DC information by referencing to white.

Synthetic molecular machines for active self-assembly : prototype algorithms, designs, and experimental study

Computer science and electrical engineering have been the great success story of the twentieth century. The neat modularity and mapping of a language onto circuits has led to robots on Mars, desktop computers and smartphones. But these devices are not yet able to do some of the things that life takes for granted: repair a scratch, reproduce, regenerate, or grow exponentially fast–all while remaining functional.

This thesis explores and develops algorithms, molecular implementations, and theoretical proofs in the context of “active self-assembly” of molecular systems. The long-term vision of active self-assembly is the theoretical and physical implementation of materials that are composed of reconfigurable units with the programmability and adaptability of biology’s numerous molecular machines. En route to this goal, we must first find a way to overcome the memory limitations of molecular systems, and to discover the limits of complexity that can be achieved with individual molecules.

One of the main thrusts in molecular programming is to use computer science as a tool for figuring out what can be achieved. While molecular systems that are Turing-complete have been demonstrated [Winfree, 1996], these systems still cannot achieve some of the feats biology has achieved.

One might think that because a system is Turing-complete, capable of computing “anything,” that it can do any arbitrary task. But while it can simulate any digital computational problem, there are many behaviors that are not “computations” in a classical sense, and cannot be directly implemented. Examples include exponential growth and molecular motion relative to a surface.

Passive self-assembly systems cannot implement these behaviors because (a) molecular motion relative to a surface requires a source of fuel that is external to the system, and (b) passive systems are too slow to assemble exponentially-fast-growing structures. We call these behaviors “energetically incomplete” programmable behaviors. This class of behaviors includes any behavior where a passive physical system simply does not have enough physical energy to perform the specified tasks in the requisite amount of time.

As we will demonstrate and prove, a sufficiently expressive implementation of an “active” molecular self-assembly approach can achieve these behaviors. Using an external source of fuel solves part of the the problem, so the system is not “energetically incomplete.” But the programmable system also needs to have sufficient expressive power to achieve the specified behaviors. Perhaps surprisingly, some of these systems do not even require Turing completeness to be sufficiently expressive.

Building on a large variety of work by other scientists in the fields of DNA nanotechnology, chemistry and reconfigurable robotics, this thesis introduces several research contributions in the context of active self-assembly.

We show that simple primitives such as insertion and deletion are able to generate complex and interesting results such as the growth of a linear polymer in logarithmic time and the ability of a linear polymer to treadmill. To this end we developed a formal model for active-self assembly that is directly implementable with DNA molecules. We show that this model is computationally equivalent to a machine capable of producing strings that are stronger than regular languages and, at most, as strong as context-free grammars. This is a great advance in the theory of active self- assembly as prior models were either entirely theoretical or only implementable in the context of macro-scale robotics.

We developed a chain reaction method for the autonomous exponential growth of a linear DNA polymer. Our method is based on the insertion of molecules into the assembly, which generates two new insertion sites for every initial one employed. The building of a line in logarithmic time is a first step toward building a shape in logarithmic time. We demonstrate the first construction of a synthetic linear polymer that grows exponentially fast via insertion. We show that monomer molecules are converted into the polymer in logarithmic time via spectrofluorimetry and gel electrophoresis experiments. We also demonstrate the division of these polymers via the addition of a single DNA complex that competes with the insertion mechanism. This shows the growth of a population of polymers in logarithmic time. We characterize the DNA insertion mechanism that we utilize in Chapter 4. We experimentally demonstrate that we can control the kinetics of this re- action over at least seven orders of magnitude, by programming the sequences of DNA that initiate the reaction.

In addition, we review co-authored work on programming molecular robots using prescriptive landscapes of DNA origami; this was the first microscopic demonstration of programming a molec- ular robot to walk on a 2-dimensional surface. We developed a snapshot method for imaging these random walking molecular robots and a CAPTCHA-like analysis method for difficult-to-interpret imaging data.

Interplay of martensitic phase transformation and plastic slip in polycrystals

Inspired by key experimental and analytical results regarding Shape Memory Alloys (SMAs), we propose a modelling framework to explore the interplay between martensitic phase transformations and plastic slip in polycrystalline materials, with an eye towards computational efficiency. The resulting framework uses a convexified potential for the internal energy density to capture the stored energy associated with transformation at the meso-scale, and introduces kinetic potentials to govern the evolution of transformation and plastic slip. The framework is novel in the way it treats plasticity on par with transformation.

We implement the framework in the setting of anti-plane shear, using a staggered implicit/explict update: we first use a Fast-Fourier Transform (FFT) solver based on an Augmented Lagrangian formulation to implicitly solve for the full-field displacements of a simulated polycrystal, then explicitly update the volume fraction of martensite and plastic slip using their respective stick-slip type kinetic laws. We observe that, even in this simple setting with an idealized material comprising four martensitic variants and four slip systems, the model recovers a rich variety of SMA type behaviors. We use this model to gain insight into the isothermal behavior of stress-stabilized martensite, looking at the effects of the relative plastic yield strength, the memory of deformation history under non-proportional loading, and several others.

We extend the framework to the generalized 3-D setting, for which the convexified potential is a lower bound on the actual internal energy, and show that the fully implicit discrete time formulation of the framework is governed by a variational principle for mechanical equilibrium. We further propose an extension of the method to finite deformations via an exponential mapping. We implement the generalized framework using an existing Optimal Transport Mesh-free (OTM) solver. We then model the $\alpha$--$\gamma$ and $\alpha$--$\varepsilon$ transformations in pure iron, with an initial attempt in the latter to account for twinning in the parent phase. We demonstrate the scalability of the framework to large scale computing by simulating Taylor impact experiments, observing nearly linear (ideal) speed-up through 256 MPI tasks. Finally, we present preliminary results of a simulated Split-Hopkinson Pressure Bar (SHPB) experiment using the $\alpha$--$\varepsilon$ model.