Economic Fluctuations and Capitalistic Production: A Case Study in Robustness Constraints

A central pursuit of macroeconomic research is to understand the source of short run variations in aggregate economic variables. To this end, the branch of macroeconomics known as Real Business Cycle (RBC) theory emphasizes the role of disturbances to the real economy while abstracting from nominal variables (e.g. money). According to RBC theory, business cycles are the result of optimal responses to exogenous stochastic disturbances on technology in a structure of capitalistic production. In this report, we contend that the structure of capitalistic production per se constrains the ability of the economy to absorb shocks. That is, even if the feedback behavior in the model is designed to mitigate fluctuation (and is not necessarily optimal relative to some inter-temporal utility), the resulting sensitivity is nevertheless constrained by a lower bound. Moreover, we show that this lower bound is exacerbated with increasing steady state consumption, capital and investment. Concretely, we show that the Ramsey model, linearized about its steady state equilibrium, has a non-minimum phase structure and therefore its sensitivity is constrained by the control theoretic design limits. Moreover, the non-minimum phase zero is given by the inverse of the discount factor. As the discount factor approaches unity, steady state consumption approaches optimal steady state consumption, but the non-minimum phase zero approaches the closed unit circle exacerbating the sensitivity constraints

SMED: El camino a la flexibilidad total (SMED: The road to total flexibility)

Este artículo presentará la metodología de SMED (Cambio de dados en un dígito de minuto) como una alternativa hacia la flexibilidad total, la cuál se propone como una herramienta vital de competencia ante las condiciones del mercado existentes. Se explicarán los pasos a seguir para implementar la herramienta y se presentará un caso de estudio en el cuál la herramienta fue aplicada exitosamente, identificándose como la decisión determinante en la reducción del tiempo de ciclo por cambios de modelo, incrementando así la eficiencia del sistema de manufactura. El mercado hoy en día, está caracterizado por elementos determinantes, tales como: la globalización, una desaceleración económica de nuestro vecino y socio comercial, los Estados Unidos de Norteamérica, y una industria Asiática emergente. Estos factores combinados, impactan de manera total la forma de operar de las empresas, debido a que las empresas requieren implementar diferentes estrategias, tales como: 1) disminuir costos de producción, 2) incrementar la calidad, e 3) incrementar la flexibilidad y tiempo de respuesta. This articles lays out the methodology of SMED (data change in a minute digit) as an alternative tool towards total flexibility that serves as a vital component for the competioion in the current market. Steps to conduct this tool are explained, a case study using this instrument is discussed, and this means is identified as an essential decision tool for time reduction due to model change, thereby enhancing the eficiency of the products. Today´s market is characterized by elements such as the globalization, a slow US economy and an emergent Asiatic industry. These components impact the way the companies operate worldwide, due to the facts that the companies must implement strategies such as: 1) reduction in production costs, 2) increase in quality, and 3) increase in flexibility and the response time

Retrospective Cost-based Adaptive Spacecraft Attitude Control.

Fixed gain attitude control laws are sensitive to modeling errors and actuator nonlinearities. Adaptive control can solve many of these challenges. We present a retrospective cost-based adaptive spacecraft attitude controller designed using the system's impulse response as modeling information. The performance metric is based on rotation matrices and thus, the controller does not suffer from singularities or discontinuities present in vector attitude representations. We demonstrate robustness to inertia and actuator scaling as well as actuator misalignment and nonlinearities, unknown disturbances, sensor noise and bias for thrusters and reaction wheels through numerical simulations. We implement an averaged Markov parameter and decentralized control to address the problem of the singular input matrix of magnetic torquers. For control moment gyros, we develop a hybrid linearization and impulse response-based Markov parameter and present new guidelines to evaluate the feasibility of desired rest-to-rest maneuvers. Finally, we address the problem of angular velocity-free attitude control of a flexible spacecraft with noncollocated sensors and actuators. We present a new approach to controlling harmonic nonminimum-phase systems using the step and impulse response of the linearized system. We demonstrate robustness to model uncertainty through system analysis and numerical simulations.PhDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111607/1/gecruz_1.pd

Retrospective Cost Adaptive Control of Spacecraft Attitude Using Magnetic Actuators

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106485/1/AIAA2013-4563.pd

Opciones reales en la evaluación financiera de proyectos de inversión cafetaleros

Este trabajo tiene como objetivo estudiar empíricamente las opciones reales como una técnica para la valuación financiera de proyectos de inversión cafetaleros de base tecnológica, además de realiza una comparación de la técnica tradicional con la técnica de opciones reales para dicha valuación. Para cumplir con el objetivo planteado se aplicó la técnica de opciones reales a cuatro proyectos de inversión de base tecnológica del sector cafetalero, cabe mencionar que dichos proyectos de inversión cuentan con flujos de efectivo correspondientes a diez años cada uno. Se utilizó la técnica de opciones reales, aplicado específicamente el modelo desarrollado por los autores Black & Scholes. El análisis que se realizó en la presente investigación está limitado a proyectos de inversión cafetaleros, los cuales fueron obtenidos de la Secretaría de Agricultura y Desarrollo Rural (SADER). La originalidad de la presente investigación radica en que en México no se tiende a utilizar esta metodología, sino que, por cuestiones de facilidad, se utilizan las técnicas tradicionales que consiste en valor presente neto, tasa interna de retorno y periodo de recuperación. Con la aplicación de la metodología de opciones reales se obtuvo un valor superior al que se obtuvo al aplicar la técnica tradicional, por lo cual se puede decir que las opciones reales favorecen a reducir el riesgo y la incertidumbre en los proyectos para una mejor evaluación de estos. Por lo tanto, se recomienda la utilización de opciones reales, ya que esta técnica da una mayor certeza de los resultados de la técnica tradicional

CTZS Thin Films Grown by a Sequential Deposition of Precursors

A comparative study of the structural, optical and morphological properties of Cu2ZnSnS4 (CZTS) thin films prepared by two different techniques was performed. One consists of sequential evaporation of the elemental metallic precursors under a flux of sulphur supplied by evaporation from an effusion cell (physical vapor deposition-PVD) and the second one is a solution-based chemical route where thin layers of CuS, SnS and ZnS are deposited sequentially by diffusion membrane- assisted chemical bath deposition techniques; the membranes are used to optimize the kinetic growth through a moderate control of the release of the metal into CBD solution by osmosis. The present comparative study is helpful to the synthesis of kesterite nanostructured thin films.Comment: Published 201