Thesis: M.S., Massachusetts Institute of Technology, Department of Civil Engineering, 1978 / Bibliography: p. 195-199. / M.S. / M.S. Massachusetts Institute of Technology, Department of Civil Engineering

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A fundamental result in the theory of elliptic PDEs shows that the hessian of solutions of uniformly elliptic PDEs belong to the Sobolev space ��^2,ε. New results show that for the right choice of c, the optimal hessain integrability exponent ε* is given by ε* = ������ ����(1−������) / ����(1−��), �� ∈ (0,1) Through the techniques of asymptotic analysis, the behavior and properties of this function are better understood to establish improved quantitative estimates for the optimal integrability exponent in the ��^2,ε-regularity theory.

Due to the global loss of tidal marsh area, potential anthropogenic and natural disturbances to these systems, and coastal marshes’ affinity for trapping environmental pollutants, understanding how marsh birds inhabiting these ecosystems will adapt to these changes is paramount. To quantify future changes, I first needed to have something to compare against – baseline estimates. To this end, I performed distance sampling line transect surveys during the nonbreeding season to estimate species-specific population abundance, density, and habitat associations and captured two species of marsh bird, Clapper Rail (Rallus crepitans) and Seaside Sparrow (Ammospiza maritima), to estimate baseline ingestion of one such environmental pollutant – microplastics. By providing the first baseline population and density estimates for numerous nonbreeding marsh birds, my findings suggest that the tidal marshes of Mississippi provide critical habitat for many of these species. Additionally, I was able to document the first evidence of microplastic ingestion by resident tidal marsh birds.

Interior Double-crested cormorant reproduction was examined on a large geographical scale to evaluate management actions. Three distinct breeding areas across Ontario were selected. Beginning in 2002, over 11,000 preledged cormorants have been marked. During 2006 and 2007, re-observation of banded birds, colony data such as nest, egg, and chick measurements, and island morphology, were collected. Data revealed no significant regional differences in adult size. However, eggs in eastern Lake Ontario (ELO) were larger than North Channel of Lake Huron (NChan) and Lake of the Woods (LOW). Chicks in ELO throughout development were smaller than NChan and LOW. Number of gulls was correlated inversely to cormorant fledge rate. Survival estimates were <20% for young of the year, but increased to >80% after year 2. Elasticity analysis revealed that a 50% reduction in adult survival combined with 100% fecundity reduction would result in a 42% reduction in population growth.

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This thesis presents the results of a research effort investigating the effect of belt usage reporting errors of National Automotive Sampling System-Crash Data System (NASS-CDS) investigators on injury risk estimates. Current estimates of injury risk are developed under the assumption that NASS-CDS investigators are always accurate at determining seat belt usage. The primary purpose of this research is to determine the accuracy of NASS-CDS investigators using event data recorders (EDRs) as the baseline for accuracy, and then recalculating injury risk estimates based on our findings. The analysis of a 107 EDR dataset, from vehicle tests conducted by the National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS), was conducted to determine the accuracy of Chrysler, Ford, GM and Toyota EDRs. This accuracy was examined by both EDR module type and vehicle make. EDR accuracy was determined for crash delta-V, seat belt buckle status, pre-impact speed, airbag deployment status and front seat position. From this analysis we were able to conclude that EDRs were accurate, within 4.5%, when comparing maximum delta-V of EDRs that recorded the entire crash pulse length. We also determined that EDRs were 100% accurate when reporting driver seat belt status for EDRs that completely recorded the event and recorded a status for the driver's seat belt. All GM, Ford and Chrysler EDRs in our database reported a pre-impact velocity less than 6 mph different than the NHTSA and IIHS reported pre-impact velocities. We also found that all but 2 (101 out of 103) of the GM, Ford, and Toyota EDRs correctly reported airbag deployment status. Lastly we were able to conclude that seat position status was useful in determining when a smaller sized occupant was the driver or right front occupant. EDRs reported seat position of 5% Hybrid III females as "forward" in every case that seat position was recorded for this smaller occupant size. Based on the analysis of seat belt status accuracy, a comparison of NASS-CDS investigator driver seat belt status and EDR driver seat belt status was conducted to determine the accuracy of the NASS-CDS investigators. This same comparison was conducted on reports of driver seat belt status provided by police. We found that NASS-CDS investigators had an overall error of 9.5% when determining driver seat belt status. When the EDR stated that the driver was unbuckled, investigators incorrectly coded buckled in of 29.5% of the cases. When the EDR stated that the driver was buckled, NASS-CDS error was only 1.2%. Police officers were less accurate than NASS-CDS investigators, with an overall error of 21.7%. When the EDR stated that the driver was buckled, police had an error of 2.4%. When the EDR stated that the driver's belt was unbuckled, police had an error of around 69%. In 2008, NASS-CDS investigators reported that drivers had an overall belt usage rate during accidents of 82%. After correcting for the errors we discovered, we estimate that the driver belt buckle status during a crash is around 72.6%. Injury risk estimates and odd ratio point estimates were then calculated for NASS-CDS investigator and EDR buckled versus unbuckled cases. The cases included only frontal collisions in which there was no rollover event or fire. Injury was defined as AIS 2+. The risk ratios and point estimates were then compared between investigators and EDRs. We found that injury risk for unbelted drivers may be over estimated by NASS-CDS investigators. The unbuckled to buckled risk ratio for EDRs was 8%-12% lower than the risk ratio calculated for NASS-CDS investigators. / Master of Science

There have been different degrees of exchange rate disequilibrium in the developing countries during recent transition or reform periods. The level of the exchange rate and its misalignment can have significant impacts on agricultural policy measures such as the Producer Support Estimates (PSEs). However, little efforts have been made to explicitly take into account the issue of exchange rate misalignment. In the conventional PSE studies the prevailing actual (nominal) exchange rates are usually used. There is general agreement that the use of actual exchange rates may introduce a bias in the PSE calculations, and that this bias can be substantial when the actual rates are significantly out of equilibrium, but there is much less agreement on the most appropriate alternative. This dissertation proposes a theoretical and an empirical model for estimating equilibrium exchange rates. Within the context of these models, the equilibrium exchange rates are argued to be determined by a group of real economic fundamentals. These fundamentals within this study include technological progress (Balassa-Samuelson effect), levels of government expenditure, world interest rate, net capital inflows, terms of trade, and openness of the economy. Base on various time series techniques and using data from India and China, sensible long-run relationships are identified between the real exchange rate and these economic fundamentals. The long-run co-integrating relationships are used to derive the equilibrium exchange rates and to gauge corresponding misalignments for the currencies in the two countries. The relevance and usefulness of the exchange rate equilibrium and disequilibrium in the calculation of the PSEs for India and China are then discussed. Results from the commodity-specific measures including the Market Price Support (MPS) and the PSE show that agricultural support levels are quite sensitive to alternative exchange rate assumptions. Specifically, exchange rate misalignments have either amplified or counteracted the direct effect on agriculture from sectoral-specific policies. With a few commodity exceptions such an indirect effect in both countries is relatively small in magnitude and dominated by the direct effect. This is also the case when the indirect effect rises substantially as a result of more misaligned exchange rates. Counterfactual MPS measure calculated assuming the exchange rate is in equilibrium with different exchange rate pass-through is also presented. It is shown that when no exchange rate pass-through to domestic prices occurs, the transfer of the indirect effect of exchange rate misalignment into the counterfactual MPS is full. But when there is exchange rate pass-through, even though partially, the transfer of indirect effect is significantly smaller. Results based on the commodity-specific PSE show that the exchange rate effect also depends on the relative importance of different PSE components. In addition to a positive impact on the direct effects measured by commodity-specific PSE compared to those measured by commodity-specific MPS, the increasing share of budgetary expenditures in India's agricultural support in recent years has resulted in more pronounced indirect effects. For China, the exchange rate effects are more similar between the PSE and the MPS measures at the commodity level because of the dominance of the MPS component relative to the budgetary payments in the PSEs. Moving from commodity-specific to aggregate measures, one can observe a similar pattern of agricultural support. However, the exchange rate effect measured by the total PSE appears to be more important: it becomes several times larger in magnitude than the direct effect in periods of severe exchange rate misalignment. The exchange rate effect when the PSE is "scaled up" from covered commodities to an estimate for the total agricultural sector is also demonstrated even though the assumption imposed by scaling-up may be unrealistic if price support is concentrated among those products included in the analysis. Since the commodity coverage in both countries tends to be incomplete and the scaling-up procedure leads to a total MPS component of greater magnitude, larger exchange rate effects are found in the scaled-up than the non-scaled-up version of the total PSEs. The impact of scaling-up on the indirect effect is proportional to the share of covered commodities in the total value of agricultural production. Again for the PSEs at both the commodity and aggregate levels, the counter factual measures indicate a full transfer of indirect effect of exchange rate when no exchange rate pass-through is assumed. A large portion of the indirect effect disappears when incomplete exchange rate pass-through is assumed resulting in a smaller transfer of the effect to the counter factual PSEs. / Ph. D.

We study the relationship of dominance for sequences and trees in Banach spaces. In the context of sequences, we prove that domination of weakly null sequences is a uniform property. More precisely, if $(v_i)$ is a normalized basic sequence and $X$ is a Banach space such that every normalized weakly null sequence in $X$ has a subsequence that is dominated by $(v_i)$, then there exists a uniform constant $C\geq1$ such that every normalized weakly null sequence in $X$ has a subsequence that is $C$-dominated by $(v_i)$. We prove as well that if $V=(v_i)_{i=1}^\infty$ satisfies some general conditions, then a Banach space $X$ with separable dual has subsequential $V$ upper tree estimates if and only if it embeds into a Banach space with a shrinking FDD which satisfies subsequential $V$ upper block estimates. We apply this theorem to Tsirelson spaces to prove that for all countable ordinals $\alpha$ there exists a Banach space $X$ with Szlenk index at most $\omega^{\alpha \omega +1}$ which is universal for all Banach spaces with Szlenk index at most $\omega^{\alpha\omega}$.