The Perturbations of a Hyperbolic Orbit by an Oblate Planet

Perturbation of hyperbolic orbit by oblate planet and escape hyperbola from eart

Interplanetary Trajectory Optimization with Powerlimited Propulsion Systems

A trajectory-optimization process is described in which the optimum thrust equations are derived using the calculus of variations. The magnitude of the thrust is constrained within an upper and a lower bound, but the thrust direction is arbitrary. This formulation allows both the constant-thrust program and the variable-thrust program to be considered. For the constant-thrust program, certain propulsion-system parameters are optimized for maximum final vehicle mass. This theory has been used to study interplanetary missions to Venus and Mars using a power-limited propulsion system. Both one-way and round trip rendezvous trajectories are considered. The analysis employs a two-body inverse-square force-field model of three dimensions. An iterative routine used to solve the two-point boundary-value problem is described in the Appendix

Performance characteristics of a tubular regenerative heat exchanger

The term regenerator is widely used to define any type of heat exchanger in which the heat is alternately stored and removed...The present investigation is concerned with the calculation of the characteristics of the single-blow , tubular regenerative heater, its dimensions and performance. In the analysis in this thesis, the heat is considered to be stored in bundles of tubes initially preheated by hot gases flowing through the heater and subsequently cooled by the flow of air. This paper makes no attempt to deal with the effects of radiation from the outer row of tubes to the heater shell --Introduction, page 1-3

‘Land grabbing’ e ‘Green grabbing’: Uma leitura da ‘corrida na produção acadêmica’ sobre a apropriação global de terras

A partir de 2008, houve uma extensa produção e publicação de artigos acadêmicos, basicamente em inglês, sobre um fenômeno denominado corrida mundial por terras ou land grabbing (apropriação de terras). Depois de cinco ou seis anos, essa produção se mantém, mas com construções teórico-empíricas mais elaboradas – inclusive com a reformulação de conceitos e criação de outros como green grabbing (apropriação verde) e water grabbing (apropriação da água) –, especialmente porque as primeiras reflexões eram excessivamente centradas em dados quantitativos e escala (quantidade de hectares transacionados), em grandes investimentos estrangeiros em terras agrícolas e voltados para estudos de casos sobre a compra de terras no Continente Africano. O objetivo deste artigo é retomar os termos do debate, relendo argumentos e discutindo formulações teóricas (inclusive o próprio conceito de land grabbing), procurando construir diálogos teóricos e agendas de pesquisas acadêmicas no Brasil, pois o mesmo – além ser um país com históricos problemas agrários como a concentração da terra – é marcado por investimentos externos, mas também incentiva a apropriação privada de terras em outros lugares e países, o que resulta na expansão das fronteiras agrícolas e gera conflitos e disputas territoriais. After 2008, there has been an extensive production and publication of academic articles in English, dealing with a phenomenon called global land rush or land grabbing. After five or six years, such academic production continuous but more elaborated theoretically and with larger empirical evidences, including some conceptual reformulations and creation other concepts like green grabbing and water grabbing. This happened especially because the first studies were overly focused on quantitative data and scale (land deals in hectares), considering large foreign investment in agricultural land and focused on case studies on the purchase of land on the African continent. This article aims to resume the terms of the debate, discussing some arguments and theoretical formulations – including the concept of land grabbing –, looking for reflexions, theoretical dialogue and academic research agenda in Brazil. Besides being a country with historical agrarian problems, like the concentration of landownership, Brazil is has foreign investments, but it also encourages private investments and land deals, resulting in the expansion of the agricultural frontier, generating conflicts and territorial disputes in other countries

Control by Code of Energy Usage in Building Systems

Space heating, air-conditioning and refrigeration accounts for over 30% of the total energy use in the U.S. ASHRAE Standard 90P, ENERGY CONSERVATION IN NEW BUILDING DESIGN, sets forth requirements for the design of all types of new buildings, covering their exterior envelopes and selection of their HVAC, service water heating, electrical distribution and illuminating systems and equipment for efficient use of energy. This paper reviews the current status, content, and implications of the proposed energy standard and reports some experience with its use