In this study we investigated the effect of tidal forcing on iron cycling in intertidal saltmarsh sediments (ISS). Historically, sulfate has been considered the major terminal electron acceptor involved in organic carbon remineralization in ISS. Although sulfate is a more efficient electron acceptor for organic matter degradation in anoxic ISS, irons rapid recycling at the surface of ISS may allow it also to be an important electron acceptor for the remineralization of organic matter. Bioturbation, macrophyte-mediated irrigation, and semidiurnal tidal forcing in this environment may increase the abundance of O2 in the top few cm of the sediment, rapidly oxidizing iron and inhibiting sulfate reduction. To determine if the cycling of iron may be faster than previously thought in these sediments, we combined sediment core chemical profiles of reduced and oxidized insoluble iron with in-situ electrochemical profiles of O2, Fe2+, soluble organic-Fe3+ complexes, FeS(aq), and hydrogen sulfide in the top few centimeters of unvegetated creek bank sediments over several tidal cycles. We also installed monitoring wells in the tidal creek bank to quantify tidal forcing and to investigate tidal direction in the sediments. We built a transient, reactive transport model to simulate measured geochemical profiles and test our understanding of diagenetic processes. Additional tests were run on the model to investigate the importance of bioirrigation compared to tidally-induced porewater advection. Results indicate that tidal action is a more dominant transport process. It affects the cycling of iron in ISS by flushing reduced species out of the sediment during flood tide, and allowing oxygen and oxidized species deeper into the sediment during ebb tide. As a result, amorphous iron oxides are replenished at the sediment surface, and microbial iron reduction may be the main respiratory process in the first tens of centimeters of creek bank saltmarsh sediments subjected to intense tidal forcing.

Continental margin sediments play an important role in marine biogeochemical cycles, partly due to high primary production rates and efficient export of organic matter to sediments in margin environments. This thesis presents studies of solute exchange in fine-grained sediments representative of slope and rise environments, and carbon and nitrogen cycling in sandy sediments dominant in continental shelves worldwide. Results of these studies advance understanding of the role of benthic processes on marine ecosystems. In fine-grained sediments, solute exchange by diffusion, biological mixing and bioirrigation can be quantified using in situ flux chambers with inert tracer additions. Mechanistic models of chamber tracer transport across the seabed indicate that in organic-rich sediments, bioirrigation and mixing dominate over a wide range of bottom water oxygen levels, reflecting the patchiness and versatility of benthic macrofaunal communities. Positive correlations between benthic oxygen and tracer fluxes appear site-specific. Reliable chamber volume estimates derived from mechanistic models reveal that empirical fits to chamber tracer datasets may overestimate chamber volume and benthic solute fluxes. The biogeochemistry of sandy, highly permeable sediments that dominate continental shelves is largely unknown because of the difficulty in sampling and studying them under natural conditions. Novel sediment reactors were developed and used to mimic in situ porewater advection and natural sedimentary conditions. Compositional changes of natural seawater, with and without the addition of

Network coding and duty-cycling are two popular techniques for saving energy in wireless sensor networks. To the best of our knowledge, the idea to combine these two techniques, for even more aggressive energy savings, has not been explored. One explanation is that these two techniques achieve energy efficiency through conflicting means, e.g., network coding saves energy by exploiting overhearing, whereas dutycycling saves energy by cutting idle listening and, thus, overhearing. In this thesis, we thoroughly evaluate the use of network coding in duty-cycled sensor networks. We propose a scheme called DutyCode, in which a MAC protocol implements packet streaming and allows the application to decide when a node can sleep. Additionally, a novel, efficient coding scheme decision algorithm, ECSDT, assists DutyCode to reduce further energy consumption by minimizing redundant packet transmissions, while an adaptive mode switching algorithm allows smooth and timely transition between DutyCode and the default MAC protocol, without any packet loss. We investigate our solution analytically, implement it on mote hardware, and evaluate it in a 42-node indoor testbed. Performance evaluation results show that our scheme saves 30-46% more energy than solutions that use network coding, without using duty-cycling.

第23回名古屋大学年代測定総合研究センターシンポジウム平成22(2010)年度報告

The variations of residual stress distributions on solder balls under the cyclic thermal load and aging processes are investigated in this thesis. The solidification phenomena for different shapes and materials of the solder balls during the reflow process are predicted by using the Surface Evolver program. The distribution of residual stress in the solder ball is calculated by employing the MARC finite element package. The temperature dependent material properties of the solders, i.e. 63Sn/37Pb and 96.5Sn/3.5Ag, are used in the residual stresses calculations. The variation of the residual stresses distributions of different solder balls under the temperature cycling test ( between ¡V40¢J and 85¢J ) and the aging test ( at 85¢J ) are simulated and studied. The effects of the solder parameters, i.e. the solder height and the pad geometry shapes on the residual stresses distribution are also studied. Besides, the same simulation and analysis has also applied on the solder ball with an unleaded solder 96.5Sn/3.5Ag. A better understanding about the variation of the residual stress in a solder ball is expected from this analysis.

Abstract The effects of residual stresses distribution and post-weld-shift on the signal coupling efficiency of an Optical Add & Drop Multiplex (OADM) are investigated in this thesis. The position variations between the two collimators in the OADM under the temperature cycling test and high temperature aging test have been simulated and studied. The finite element method package, i.e. MARC, is used for the stresses and deformation simulations of an OADM under different load cases. The coupled thermal-elastic-plastic model is employed in the analysis, and the creep effect of the solder is considered in the numerical simulations. The temperature dependent material properties of the 63Sn/37Pb and 96.5Sn/3.5Ag solder are used for the solder solidification, temperature cycling and aging tests. The effects of the OADM packaging parameters, i.e. the different offset angles between collimators, different solder are also studied. Besides, the same simulation and analysis has also applied on the soldering with and without cavity. A comparison between the simulated and measured results indicates that the proposed finite element model is feasible for analyzing the OADM packaging problems.

Thesis (M.S.)--James Madison University, 2009. / Includes bibliographical references.

ABSTRACT During the last decades, environmental impacts have increased significantly, much due to the great traffic flows within cities. Therefore, to reduce these impacts and encourage a healthy way of living, it has in recent years become vital to generate safer and more sustainable and flexible modes of transportation. In order to do so, authorities and physical planners must work together to find viable solutions to incorporate in the infrastructure and offer alternative transport modes – such as walking, cycling and public transportation.  The purpose of this thesis is to examine the development of the cycling infrastructure in the city of Västerås and whether it is possible to expand bicycle commuting alongside public transportation. The thesis consequently aims to study how different physical planners within Västerås municipality work with traffic related questions. The thesis is based on interviews with relevant physical planners, data from scientific literature and different strategy documents intended for Västerås municipality.  The results are based on a thematic coding system to analyse specific categories frequently mentioned during the interviews. These results have later been put into context with related literature regarding sustainable cycling infrastructure.  The results show that there is a common goal for traffic planning within the municipality, even if the authorities express different actions concerning its development.

Coral reefs thrive in nutrient-deficient environments yet function among the most productive ecosystems on Earth as a consequence of the symbiosis between coral hosts and their symbiotic zooxanthellae. The symbiotic unit (holobiont) can utilize both inorganic and organic sources of nutrients for the accumulation of carbon and nitrogen required for metabolism, growth, and reproduction. An iterative model was created to describe the flux of carbon and nitrogen between a host and its algae. The model design is based on a previously published conceptual model of algal symbioses; functions and values of input parameters are based on published studies of the coral species Stylophora pistillata. The model is designed to simulate responses of the coral, zooxanthellae and the holobiont to different environmental variables, either one at a time or changing simultaneously. Simulations presented are for default values based on previously published data for S. pistillata adapted to high-light (shallow-euphotic) and low-light (deep-euphotic) environments, and for single-variable manipulations of rates of a) host feeding, b) photosynthesis, and c) dissolved inorganic nitrogen (DIN) uptake. Simulations examining feeding rates between 0% and 6.5% of host biomass indicate that biomass of both high-light and low-light adapted holobionts increase exponentially with increased feeding, with benefit to the high-light holobiont ~8 times greater than to the low-light holobiont. Increasing rates of photosynthesis illustrated that a low-light holobiont is carbon limited, is primarily dependent upon host feeding, and can benefit from a small increase in photosynthesis rate. Simulations examining rates of DIN input indicate that the high-light holobiont functions optimally when inorganic nitrogen input is very low. Increase in DIN up to 0.5% resulted in benefit to the holobiont, but more resulted in unrealistically excessive growth by the zooxanthellae until a function to maintain a fixed range for the host-zooxanthellae biomass ration function was included in the model. Simulations for the low-light holobiont did not indicate any benefit from DIN input. The model was originally designed using a spreadsheet-based program which frequently became overloaded when testing multiple variables. Modification of the model in software better designed for modeling is recommended for future work.

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