31 research outputs found
Guidance algorithms for a free-flying space robot
Robotics is a promising technology for assembly, servicing, and maintenance of platforms in space. Several aspects of planning and guidance for telesupervised and fully autonomous robotic servicers are investigated. Guidance algorithms for proximity operation of a free flyer are described. Numeric trajectory optimization is combined with artificial intelligence based obstacle avoidance. An initial algorithm and the results of its simulating platform servicing scenario are discussed. A second algorithm experiment is then proposed
Artificial intelligence applications in teleoperated robotic assembly of the EASE space structure
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, and Dept. of Electrical Engineering and Computer Science, 1988.Bibliography: leaf 197.by Herbert E. M. Viggh.Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, and Dept. of Electrical Engineering and Computer Science, 1988
SPIRE algorithms
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (p. 393-396).In this thesis we address the problem of estimating changes in surface reflectance in hyperspectral image cubes, under unknown multiplicative and additive illumination noise. Rather than using the Empirical Line Method (ELM) or physics-based approaches, we assumed the presence of a prior reflectance image cube and ensembles of typical multiplicative and additive illumination noise vectors, and developed algorithms which estimate reflectance using this prior information. These algorithms were developed under the additional assumptions that the illumination effects were band limited to lower spatial frequencies and that the differences in the surface reflectance from the prior were small in area relative to the scene, and have defined edges. These new algorithms were named Surface Prior Information Reflectance Estimation (SPIRE) algorithms. Spatial SPIRE algorithms that employ spatial processing were developed for six cases defined by the presence or absence of the additive noise, and by whether or not the noise signals are spatially uniform or varying. These algorithms use high-pass spatial filtering to remove the noise effects. Spectral SPIRE algorithms that employ spectral processing were developed and use zero-padded Principal Components (PC) filtering to remove the illumination noise. Combined SPIRE algorithms that use both spatial and spectral processing were also developed. A Selective SPIRE technique that chooses between Combined and Spectral SPIRE reflectance estimates was developed; it maximizes estimation performance on both modified and unmodified pixels. The different SPIRE algorithms were tested on HYDICE airborne sensor hyperspectral data, and their reflectance estimates were compared to those from the physics-based ATmospheric REMoval (ATREM) and the Empirical Line Method atmospheric compensation algorithms. SPIRE algorithm performance was found to be nearly identical to the ELM ground-truth based results. SPIRE algorithms performed better than ATREM overall, and significantly better under high clouds and haze. Minimum-distance classification experiments demonstrated SPIRE's superior performance over both ATREM and ELM in cross-image supervised classification applications. The taxonomy of SPIRE algorithms was presented and suggestions were made concerning which SPIRE algorithm is recommended for various applications.by Herbert Erik Mattias Viggh.Ph.D
Normbrytande eller normbekrÀftande? En kvalitativ innehÄllsanalys av TV-serien "Girls" utifrÄn ett genusperspektiv
Abstract Studiens syfte Ă€r att kritiskt analysera TV-serien Girls, en serie som tillskrivits egenskaper som implicerar en normkritisk och banbrytande framstĂ€llning av unga kvinnor i dagens amerikanska medelklassamhĂ€lle. I förlĂ€ngningen syftar studien till att undersöka huruvida dagens visuella medier bidrar till att bekrĂ€fta eller utmana den rĂ„dande könsmaktsordningen och dĂ€r tillhörande normer. Ăr TV-serien Girls normkritisk och banbrytande vad gĂ€ller framstĂ€llningen av unga kvinnors livsvillkor i relation till utseende och kroppsuppfattning, sexualitet, maktstrukturer mellan könen samt de konventioner och stereotyper som existerar för mĂ€n respektive kvinnor? Studien vilar pĂ„ den hermeneutiska lĂ€ran om tolkning och förstĂ„else och prĂ€glas vidare av ett perspektivistiskt stĂ€llningstagande till vad som Ă€r befintlig sanning. Den huvudsakliga metoden i uppsatsen sorterar under diskursiv innehĂ„llsanalys som har kompletterats med observationsverktyg frĂ„n frĂ€mst semiotiken men Ă€ven frĂ„n narratologi. Analyserat material bestĂ„r av den första sĂ€songen av Girls, tio avsnitt ĂĄ ca 30 minuter. Som komplement och referenspunkt anvĂ€ndes Ă€ven samtliga tio avsnitt av SVTs paneldiskussion TV-cirkeln: Girls. Resultatet av studien visar pĂ„ en delvis normbrytande syn pĂ„ och framstĂ€llning av kvinnans kropp och sexualitet samt konventioner och maktstrukturer inom sociala relationer, men tycks Ă€ven pĂ„ mĂ„nga vis vara en reproducent av rĂ„dande normer. Resultat visar pĂ„ en dubbelsidig och komplicerad relation till genusvetenskapliga teorier om könskonventioner och köns olikartade framstĂ€llning i medier. Key words: Girls, genus, innehĂ„llsanalys, feminism, sexualitet, kroppsuppfattning, stereotyp Normbrytande eller normbekrĂ€ftande? En kvalitativ innehĂ„llsanalys av TV-serien âGirlsâ utifrĂ„n ett genusperspektiv Emma Viggh & Ida Wallin Institutionen för kommunikation och medier, Lunds universite
"Oj, mamma har friendat mig!"
B-uppsats i Medie- och kommunikationsvetenskap vid Institutionen för Kommunikation och Medier; âOj, mamma har friendat mig!â. En kvalitativ studie i förĂ€ldrar- barnrelationen pĂ„ facebookâ, författad av Emma Viggh & Ida Wallin vid Lunds Universitet. Nyckelord: Facebook, Sociala medier, Identitet, Relationer, Ungdomar, FörĂ€ldrar Samtidens medievardag bĂ€ddar för en helt ny situation dĂ„ tidigare Ă„tskilda parter, som arbetsgivare och anstĂ€llda, förĂ€ldrar och barn, nu möts och interagerar i samma sociala nĂ€tforum. En process som sĂ€rskilt avspeglas i vĂ„rt valda medium, Facebook. Vi har i följande studie valt att se djupare vid just det sistnĂ€mnda; förĂ€ldra- barnrelationen och den komplexa situation som kan komma att uppstĂ„ dĂ„ förĂ€ldrar nĂ€rvarar och bevakar sin ungdoms skapande av det egna jaget, detta i en tid dĂ„ autonomi och frigörelse frĂ„n tidigare nĂ€ra hĂ„llna parter Ă€r en viktig process för ungdomen. VĂ„rt syfte med studien Ă€r att undersöka hur tonĂ„ringar i Ă„ldern 16-18 Ă„r anvĂ€nder och upplever mediet Facebook i relation till förĂ€ldrarnas nĂ€rvaro i samma nĂ€tverk. Vi har i studien utgĂ„tt ifrĂ„n ett kvalitativt tillvĂ€gagĂ„ngssĂ€tt och utfört semistrukturerade och personliga intervjuer med sju (7) utvalda respondenter. Vi framstĂ€llde till intervjutillfĂ€llet en övergripande intervjuguide som inleddes med kartlĂ€ggande frĂ„gor och avslutades med frĂ„gor av mer öppen karaktĂ€r. Respondenterna Ă€r alla mellan 16-18 Ă„r och har en eller flera förĂ€ldrar som âvĂ€nâ pĂ„ Facebook. Vi kan efter studiens genomförande konstatera att vĂ„ra respondenters instĂ€llning till förĂ€ldrarnas nĂ€rvaro pĂ„ mediet Facebook prĂ€glas av viss komplexitet. Det finns en problematik i den uppkomna situtationen dĂ„ somliga av ungdomarna kĂ€nner sig pĂ„passade och obekvĂ€ma med förĂ€ldrarnas nĂ€rvaro. Tillika vittnar vissa respondenter om konflikter som uppstĂ„tt mellan dem och förĂ€ldrarna rörande publicerat material pĂ„ mediet. Vi kan samtidigt se en Ă„terkommande positiv instĂ€llning till förĂ€ldranĂ€rvaron, bland annat genom respondentens upplevelse av att förĂ€ldern kan uppnĂ„ en ökad tilltro till hen genom den nya uppsiktsmöjligheten, men Ă€ven genom en mer tilltagen vardagskontakt förĂ€lder och barn emellan. Vi reflekterar kring möjligheten att ungdomarna inte lĂ€ngre befinner sig i ett frigörelsestadium gentemot förĂ€ldern utan snarare Ă€r pĂ„ vĂ€g in i en fas av Ă„teranknytning
Mission planning for space based satellite surveillance experiments with the MSX
The Midcourse Space Experiment is a BMDO-sponsored scientific satellite set for launch within the year. The satellite will collect phenomenology data on missile targets, plumes, earth limb backgrounds and deep space backgrounds in the LWIR, visible and ultra-violet spectral bands. It will also conduct functional demonstrations for space-based space surveillance. The Space-Based Visible sensor, built by Lincoln Laboratory, Massachusetts Institute of Technology, is the primary sensor on board the MSX for demonstration of space surveillance. The SBV Processing, Operations and Control Center (SPOCC) is the mission planning and commanding center for all space surveillance experiments using the SBV and other MSX instruments. The guiding principle in the SPOCC Mission Planning System was that all routine functions be automated. Manual analyst input should be minimal. Major concepts are: (I) A high level language, called SLED, for user interface to the system; (2) A group of independent software processes which would generally be run in a pipe-line mode for experiment commanding but can be run independently for analyst assessment; (3) An integrated experiment cost computation function that permits assessment of the feasibility of the experiment. This paper will report on the design, implementation and testing of the Mission Planning System
Production and hydration of calcium sulfoaluminate-belite cements derived from aluminium anodising sludge
Calcium sulfoaluminate-belite cement (CSAB) offers lower CO2 emissions in its production, compared with Portland cement. However, for the production of CSAB a high amount of alumina is required, and the scarcity and high cost of high-purity bauxite make these cements costly at present. In this study, the use of uncalcined aluminium anodising sludge (AAS) as the main source of alumina to produce CSAB clinkers, replacing bauxite, was assessed. The CSAB clinkers produced were mainly composed of yeâelimite and belite, along with minor traces of alite, and/or brownmillerite, depending on the alumina source. Clinkers derived from AAS as a source of aluminium showed a lower content of yeâelimite (35.5%), as well as the formation of alite (8.2%) when compared to a reference clinker produced with reagent-grade materials. Comparable hydration products were identified in the hydrated cements independent of the alumina source used. The use of AAS to produce CSAB cement was proven to be technically feasible, and the cement thus produced has desirable technical characteristics, presenting high mechanical strength (>40 MPa in paste samples)
Modellering av inverkan av magnesium frÄn alternativa rÄmaterial pÄ Portland cementklinker kemi
The methods used in this thesis work were a combination of computational and modeling based laboratory experiments. Thermodynamic process modeling of the cement clinker process offers a tool for evaluating how changes in raw materials and process parameters affect the clinker quality. Work with finding suitable replacement raw materials involves investigating the chemical compatibility of potential alternative materials. Such replacement materials may be metallurgical slags, although there are some unsolved issues with the quantities of certain metals and particularly Mg in these materials. For predicting the formation of clinker mineral phases, cooling calculations are used in order to reproduce the temperature history in the full scale process. A chemistry model including a solid solution phase based on C2S and phosphate was developed along with the recommendation for continued work on clinker phases with solid solutions to include MgO. A thermodynamic database for phase chemistry calculations of clinkering reactions was created and evaluated. Suitable compounds and solution species were selected from the thermochemical database included in FactSage software. The extent and quality of the required thermodynamic data via available databases is generally satisfactory, except for certain properties of some of the main clinker phases. One example is the lack of a thermodynamic model for the alite solid solution. That is, the composition of the phase available in the database representing alite does not contain the minor elements Al, Fe and Mg. Therefore, it is difficult to predict the quantity and distribution of Mg in the clinker, with varying total content of MgO. Thus, one of the goals/objectives was to improve thethermodynamic model of alite as a solid solution of 3CaO-SiO2-xAl2O3-yFe2O3-zMgO. To achieve this, it was assumed that a mix of compounds with adjusted Henrian coefficients representing the solid solution clinker phase alite was in equilibrium with the clinker melt. The distribution of MgO was studied in synthetic clinker compositions with quantities ranging from 0.5 to 10 wt-%. Synthetic clinker mixes were heated to 1450°C and studied with Rietveld refinements of X-ray diffraction data and SEM-EDS analysis. In addition, the mechanisms of how slag and lime particles react facilitating the diffusion of MgO into the developing clinker melt and the formation of incipient belite were studied. The calculated results provide a good prediction of the quantities and composition of the clinker phases formed during heating and non-equilibrium cooling. The solubility of MgO in the clinker and the quantity of periclase formed is in fair agreement with published data. Thus, this thesis work shows that using a mix of compounds with adjusted activities in alite together with available standard thermodynamic data and the Scheil cooling method had good potential for evaluating alternative raw materials. Also, the work has identified weak points in the process modeling and suggest improvements to be made in future research work
Mangan i cementdamm
Manganese is a heavy metal that acts an essential micronutrient for plants and animals, as well as it is toxic in great amounts. Mn2+ is the form of manganese that is biologically available for plants and micro organisms living in soil. How much manganese a plant needs and tolerates varies greatly among different species. The amount of available manganese in soil also varies among different soil types, depending on the origin of the minerals in the soil. The available amount of manganese also depends on the plant it self, as different species affect their environment in different ways. The research that has been made on the effects of cement plants on the environment shows similar results. The content of manganese in the air, in dust deposition and in soil is slightly higher around a cement plant. In most cases itâs not obvious that this is due to the cement production, as it is difficult to separate which contamination is due to the actual cement production and what is coming from other activities around the plant such as transports. There are also studies carried out in the same purpose that does not analyze the effects of manganese but of other metals. There is no research available on Swedish cement plants and nothing that specializes in manganese. In literature describing the process of cement manufacturing manganese is considered a non volatile compound that will be incorporated in the burnt clinker. Today the use of renewable fuel and raw material is increasing to lower carbon dioxide emissions and replace the fossil fuel used by the mineral industries. Limestone used as raw material contains significantly more manganese then the renewable fuel. Limestone contains manganese as manganese oxides which are not volatile in the cement manufacturing process, which means that no great emissions will occur. A very small amount of heavy metals will always evaporate but will be caught in the electro filters in the chimney. A certain amount of dust will also be emitted, how much varies greatly and depends on the type of process used. Emissions from industries and activities are regulated by Swedish law and the European Union. Manganese is often grouped together with other metals, for example Sb, As, Pb, Cr, Co, Cu, Ni and V, and the emission of the total amount of all these metals including manganese is limited. This can pose a problem for the development and use of renewable fuel and raw material for the mineral industries as manganese is present in sedimentary rocks in greater amounts then the other metals it is often grouped with
Modellering av inverkan av magnesium frÄn alternativa rÄmaterial pÄ Portland cementklinker kemi
The methods used in this thesis work were a combination of computational and modeling based laboratory experiments. Thermodynamic process modeling of the cement clinker process offers a tool for evaluating how changes in raw materials and process parameters affect the clinker quality. Work with finding suitable replacement raw materials involves investigating the chemical compatibility of potential alternative materials. Such replacement materials may be metallurgical slags, although there are some unsolved issues with the quantities of certain metals and particularly Mg in these materials. For predicting the formation of clinker mineral phases, cooling calculations are used in order to reproduce the temperature history in the full scale process. A chemistry model including a solid solution phase based on C2S and phosphate was developed along with the recommendation for continued work on clinker phases with solid solutions to include MgO. A thermodynamic database for phase chemistry calculations of clinkering reactions was created and evaluated. Suitable compounds and solution species were selected from the thermochemical database included in FactSage software. The extent and quality of the required thermodynamic data via available databases is generally satisfactory, except for certain properties of some of the main clinker phases. One example is the lack of a thermodynamic model for the alite solid solution. That is, the composition of the phase available in the database representing alite does not contain the minor elements Al, Fe and Mg. Therefore, it is difficult to predict the quantity and distribution of Mg in the clinker, with varying total content of MgO. Thus, one of the goals/objectives was to improve thethermodynamic model of alite as a solid solution of 3CaO-SiO2-xAl2O3-yFe2O3-zMgO. To achieve this, it was assumed that a mix of compounds with adjusted Henrian coefficients representing the solid solution clinker phase alite was in equilibrium with the clinker melt. The distribution of MgO was studied in synthetic clinker compositions with quantities ranging from 0.5 to 10 wt-%. Synthetic clinker mixes were heated to 1450°C and studied with Rietveld refinements of X-ray diffraction data and SEM-EDS analysis. In addition, the mechanisms of how slag and lime particles react facilitating the diffusion of MgO into the developing clinker melt and the formation of incipient belite were studied. The calculated results provide a good prediction of the quantities and composition of the clinker phases formed during heating and non-equilibrium cooling. The solubility of MgO in the clinker and the quantity of periclase formed is in fair agreement with published data. Thus, this thesis work shows that using a mix of compounds with adjusted activities in alite together with available standard thermodynamic data and the Scheil cooling method had good potential for evaluating alternative raw materials. Also, the work has identified weak points in the process modeling and suggest improvements to be made in future research work