U.S. Food Aid and Agricultural Cargo Preference Policy

Replaced with revised version of paper 07/20/10.Food Aid Policy, Cargo Preference, Agricultural and Food Policy, Food Security and Poverty,

Measurement and Process Control in Precision Hot Embossing

Microfluidic technologies hold a great deal of promise in advancing the medical field, but transitioning them from research to commercial production has proven problematic. We propose precision hot embossing as a process to produce high volumes of devices with low capital cost and a high degree of flexibility. Hot embossing has not been widely applied to precision forming of hard polymers at viable production rates. To this end we have developed experimental equipment capable of maintaining the necessary precision in forming parameters while minimizing cycle time. In addition, since equipment precision alone does not guarantee consistent product quality, our work also focuses on real-time sensing and diagnosis of the process. This paper covers both the basic details for a novel embossing machine, and the utilization of the force and displacement data acquired during the embossing cycle to diagnose the state of the material and process. The precision necessary in both the forming machine and the instrumentation will be covered in detail. It will be shown that variation in the material properties (e.g. thickness, glass transition temperature) as well as the degree of bulk deformation of the substrate can be detected from these measurements. If these data are correlated with subsequent downstream functional tests, a total measure of quality may be determined and used to apply closed-loop cycle-to-cycle control to the entire process. By incorporating automation and specialized precision equipment into a tabletop “microfactory” setting, we aim to demonstrate a high degree of process control and disturbance rejection for the process of hot embossing as applied at the micron scale.Singapore-MIT Alliance. Manufacturing Systems and Technology Programm

Gender Differences In Demand For Index Based Livestock Insurance

Risk management is an important aspect of helping households avoid and escape chronic poverty throughout the world. In many settings, women and their dependents are disproportionately negatively affected by poverty and shocks, suggesting particular applicability of improved risk management. Indexbased insurance products are an innovative approach to risk management that circumvents difficulties associated with transactions costs and information asymmetries that plague standard insurance products in developing countries. General demand for index-based insurance products remains limited despite its theoretical strengths, and very little is known about women's demand. This paper examines the relationship between gender and demand for index-based livestock insurance (IBLI) among Boran pastoralists in southern Ethiopia. It uses three years of household survey data and a series of qualitative interviews to investigate which demand factors for IBLI vary by gender. Results suggest that, though IBLI appears to be equitably accessed by men and women alike, the factors determining access may indeed vary by gender. Risk aversion and informal insurance influence IBLI demand differently for men and women. At the same time, baseline differences in financial literacy and herd size have a negative impact on women's demand, but lower education and smaller shares of income from livestock have a positive effect on IBLI demand by women

Balancing a two-wheeled Segway robot

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 57).In this thesis, I designed and constructed hardware for a two-wheeled balancing Segway robot. Because the robot could not be balanced based on a control system derived from the original analytical model, additional system dynamics in the form of frictional losses in the motors were incorporated. A SISO PID compensator and a SISO lead-lag compensator were designed to balance the robot based on the new model; both showed acceptable system responses but were subject to high-frequency oscillation. A SISO state feedback controller was also designed, and it was successful in creating stability in simulation and removing the high-frequency oscillation effects. The robot was rebuilt using new parts that better represented its ideal model, and software was created using National Instruments LabVIEW to control the robot.by Maia R. Bageant.S.B

Precision control of continuous microcontact printing

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis. Due to the condition of the original material, there are unavoidable flaws in this reproduction. Pages 257 to 263 in the original document contain text that runs off the edge of the page.Includes bibliographical references (pages 265-271).This work focuses on the development of experimental equipment enabling the scale-up of microcontact printing for industrial use. An examination of existing experimental microcontact printing hardware and identification of its deficiencies are given, and the design and implementation of improvements are detailed. In particular, these improvements focus on the enabling of closed-loop force control of the printing process by the establishment of a deterministic computational platform and additional sensing. An understanding and rationale for the overall control design of the microcontact printing process is developed. Though the goal is to control the compression of each individual microscale feature on the microcontact printing stamp, force control is shown to offer significant advantages over displacement control. Analytical dynamic models of the system are developed, iterated, and verified experimentally. Initially, a simple model consisting of two separable single-input, single-output (SISO) systems was developed, but this model was shown to fail to capture relevant dynamics. A twelfth-order multi-input, multi-output (MIMO) model describing the system was then developed and verified experimentally using specially constructed frequency response measurement tools. Controller design was then undertaken for both the simple and complex model. The simple model was accommodated with proportional-integral and pure integral designs. The complex model required an augmented full-state feedback controller with a Kalman state estimator, which was designed and implemented in discrete time. Nonideal properties inherent to the printhead system, including uncontrollability and unobservability, were quickly identified. Maximum potential control performance under these constraints was explored and demonstrated experimentally, and it was shown that the inherent limitations made satisfactory closed-loop performance impossible. A conceptual printhead design for control is also presented. Mechanical design principles based on the lessons indicated by the system model and control design are laid out. A conceptual design is developed based on these principles, and basic geometry, packaging, and component selection is completed, allowing for a dynamic system model to be evaluated. The new printhead design is found to offer a significantly improved dynamic response, making the force control problem very tractable, and additionally solves a number of other design flaws inherent to the original printhead. An example control design and resulting performance is presented.by Maia R. Bageant.Ph. D

Development of a precision hot embossing machine with in-process sensing

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 121-123).Microuidic technologies show great promise in simplifying and speeding biological, medical, and fluidic tasks, but transitioning these technologies from a laboratory environment to a production environment has proven difficult. This work focuses on hot embossing as a process suitable to produce these devices. In this work, a precision micro-embossing machine capable of maintaining precise setpoints in force and temperature input as well as displaying highly linear, repeatable motion and force application is developed and characterized. Additionally, this equipment is then outfitted with additional sensors that allow for three measurements relevant to process physics and product quality to be captured: initial substrate geometry; substrate bulk deformation; and glass transition temperature of the material. These measurements can be captured in-process without modifying the production cycle. The end goal is to incorporate this precision micro-embossing machine into a micro-factory cell and to implement closed-loop cycle-to-cycle process control.by Maia R. Bageant.S.M

Index insurance and climate risk management: addressing social equity

Motivation Fair distribution of benefits from index insurance matters. Lack of attention to social equity can reinforce inequalities and undermine the potential index insurance holds as a tool for climate risk management that is also pro-poor. Purpose The aims are to: (i) examine social equity concerns raised by index insurance in the context of climate risk management; (ii) consider how greater attention can be given to social equity in index insurance initiatives; and (iii) reflect on the policy challenges raised by seeking to take social equity into account as a mechanism for climate risk reduction. Approach and methods The article draws on learning from the CGIAR’s Research Program on Climate Change, Agriculture and Food Security (CCAFS) and presents the cases of the Index Based Livelihoods Insurance (IBLI) and Agriculture and Climate Risk Enterprise Ltd. (ACRE) in East Africa. It proposes a framework for unpacking social equity related to equitable access, procedures, representation and distribution within index insurance schemes Findings Systematically addressing social equity raises hard policy choices for index insurance initiatives without straightforward solutions. Attention to how benefits and burdens of index insurance are distributed raises the unpalateable truth for development policy that the poorest members of rural society can be excluded. Nevertheless, a focus on social equity may open up opportunities to ensure index insurance is linked to more socially just climate risk management. At the very least, it may prevent index insurance from generating greater inequality. Taking social equity into account thus, shifts the focus from agricultural systems in transition per se to systems with potential to incorporate societal transformation through distributive justice. Policy implications A framework is presented for unpacking different dimensions of social equity in index insurance schemes. It is intended to facilitate identification of opportunities for building outcomes that are more equitable, with greater potential for inclusion and fairer distribution

Free surface flows emerging from beneath a semi-infinite plate with constant vorticity

The free surface flow past a semi-infinite horizontal plate in a finite-depth fluid is considered. It is assumed that the fluid is incompressible and inviscid and that the flow approaches a uniform shear flow downstream. Exact relations are derived using conservation of mass and momentum for the case where the downstream free surface is flat. The complete nonlinear problem is solved numerically using a boundary integral method and these waveless solutions are shown to exist only when the height of the plate above the bottom is greater than the height of the uniform shear flow. Interesting results are found for various values of the constant vorticity. Solutions with downstream surface waves are also considered, and nonlinear results of this type are compared with linear results found previously. These solutions can be used to model the flow near the stern of a (two-dimensional) ship