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David Dornfeld - One of the best experts on this subject based on the ideXlab platform.
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Finite Element Modeling of Burr Formation Process in Drilling 304 Stainless Steel
Journal of Manufacturing Science and Engineering-transactions of The Asme, 1999Co-Authors: David DornfeldAbstract:A 3D finite element model was developed for the simulation of drilling burr formation processes of 304L stainless steel. The nonlinear thermo-elastic-plastic model simultaneously accounts for dynamic effects of mass and inertia, strain hardening, strain rate, automatic mesh contact with friction capability, material ductile failure and temperature-mechanical coupling. Material ductile failure criteria were proposed to simulate drilling burr formation. Based on a series of stress contours and the progressive deformation of the workpiece edge obtained from simulation, a drilling burr formation mechanism was proposed and divided into four stages: initiation, development, Pivoting Point, and formation stages with cap formation. The burr thickness is largely determined by the distance between the pre-defined machined surface and the Pivoting Point, while the burr height is determined by the positions of the Pivoting Point and the cap formation. The FEM simulation demonstrates the dominant roles of negative shearing and bending mechanisms in the drilling burr formation process. The simulation results coincide with phenomenological observations of burr geometry from drilling 304 stainless steel and plasticine work materials.
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Analysis of Burr Formation Mechanism in Orthogonal Cutting
Journal of Manufacturing Science and Engineering-transactions of The Asme, 1999Co-Authors: Masayuki Hashimura, Y. P. Chang, David DornfeldAbstract:To prevent problems caused by burrs in machining, reduction and control of burr size is desirable. This paper presents a basic framework for and conceptual understanding of the burr formation process based upon the material properties of the workpiece. In order to verify this framework and explain the basic phenomena in the burr formation process, the deformation at the edge of the workpiece was analyzed using a finite element method (FEM). Micro-machining tests under an optical microscope and a scanning electron microscope using Al-2024-O material were also done to observe the burr formation process. The feed rate and tool edge radius were varied and the resulting burr formation observed. FEM analysis of burr formation in the 2024 material and observation of the deformation at the workpiece edge in the micro-machining tests verified the proposed conceptual understanding of the burr formation process. For the experimental conditions examined, all of the burrs in Al-2024-O were negative burrs, that is, edge breakout. As the feed was increased two effects were observed. One effect was an increase in the resulting burr thickness. Another effect, which was observed during the burr initiation stage while machining with a sharp tool, was an increase in both the distance and depth of the initial Pivoting Point of the burr from the tool edge.
Puig Polo I Càrol - One of the best experts on this subject based on the ideXlab platform.
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Evolución temporal de la vegetación en el Sahel mediante el NDVI y su relación con la precipitación en el periodo 1983-2012
Universitat Politècnica de Catalunya, 2015Co-Authors: Puig Polo I CàrolAbstract:The development and population prosperity in the transition zone between the Sahara desert in the north and the tropical humid savannah in the south, known as Sahel, depends to a great extent on the rainfall regime. The climate is defined by a long and dry season and a short season with rains between the months of June and September. Rainfalls are determined by a strong north to south gradient with small and variable precipitation in the north, which translates into continuous change of vegetation species and life forms that range from sparse thorny shrubs in between grass in the north to a greater amount of vegetal cover and ligneous species in the south. The vegetation growth shows a considerable inter-annual fluctuation that generates a generalized concern in the predominantly rural population, since their way of life is mainly based on dry land agriculture and pasturing. The severe droughts that happened during the 1970¿s, which were extended until the middle of the following decade, have been widely studied because of their serious consequences on the population, and because it is considered as one of the first signs of global climatic changes. Sahel is the region that has shown greater precipitation and vegetation variations in the last three to four decades. Technological advances in remote sensing have allowed constant monitoring of ecosystems, mainly because of the availability of improved spatial, time and spectral data. The present thesis investigates the time and spatial vegetation patterns and the precipitation variability in Sahel through interrelations based on the analysis of temporary series from the normalized vegetation difference index (NDVI) for the period 1983-2012 and rainfall satellite estimations. Whereas the precipitation emerges as a dominant cause from the increase of the vegetation, there is evidence of other anthropogenic factors overlapping the climatologic trend. Measuring rainfall in the semi-arid regions continues to be a Pivoting Point because of great spatial and weather variability. On top of this, note that the number of available weather stations in Sahel is quite limited. Satellite data, along with meteorological stations measurements, are currently the best source of information with regards to spatial-temporary precipitation in Sahel. Three temporary series of precipitation have been analyzed to cover the period between 1983 and 2012: GPCC, ARC2 and TAMSAT. These series have been compared with more recent ones to provide better quality estimations: RFE2, TRMM 3B42 and GPCP-1dd. The result shows a good correlation between series GPCC, ARC2, RFE2 and TRMM 3B42. The analysis of 30 years of precipitation data shows a recovering of the annual precipitation, although the trends in the annual temporary distribution have changed: nowadays it rains more but during less time. There are NDVI data available coming from the AVHRR sensor since 1981, as well as from its newer GIMMS3g version. Nevertheless, there are aspects in the design and processing of the sensor data that result in noise. There are data sets of the most recent NDVI coming from the sensors VEGETATION and MODIS installed in the SPOT and Terra satellites respectively, which are considered to be an improvement on the AVHRR GIMMS3g data. These sensors provide the possibility of evaluating the accuracy of the tendency analysis of the series of time of the AVHRR GIMMS3g in the period of time in which data overlap, from 2001 to 2012. This evaluation shows that the AVHRR GIMMS3g data set is correct in temporary studies of the vegetation in areas that do not record rainfalls greater than 1,000 mm, whereas the temporary tendencies in more humid zones should be interpreted with reservations.Al Sahel, la zona de transició entre el desert del Sàhara al nord i la sabana humida tropical al sud, el desenvolupament i la prosperitat de la població depenen en gran mesura del règim de pluges. El clima es caracteritza per una estació seca i llarga i una temporada curta de pluges entre els mesos de juny i setembre. La precipitació està determinada per un fort gradient de nord a sud amb pluges escasses i variables al nord, cosa que es tradueix en una gran diversitat d'espècies de vegetació i formes de vida: des d'arbustos espinosos de cobertura molt escassa intercalats entre pastures al nord a més quantitat de cobertura vegetal i espècies llenyoses al sud. El creixement de la vegetació mostra fluctuacions interanuals considerables, la qual cosa suscita una preocupació generalitzada en la població -predominantment rural-, ja que el seu modus vivendi es basa principalment en l'agricultura de secà i el pasturatge. Les greus sequeres que van tenir lloc durant la dècada de 1970 i que es van allargar fins a mitja dècada de 1980, han estat àmpliament estudiades no només per les greus conseqüències sobre la població, sinó perquè es consideren un dels primers signes de canvi climàtic global. El Sahel és la regió on s'han evidenciat les grans variacions de precipitació i vegetació al llarg de les últimes tres o quatre dècades. Els avenços tecnològics en el camp de la teledetecció han permès la vigilància dels ecosistemes gràcies a la disponibilitat de dades amb resolucions espacials, temporals i espectrals cada vegada més acurades. En aquesta tesi s'investiguen els patrons temporals i espacials de la vegetació i la variabilitat de les precipitacions al Sahel a partir de les interrelacions basades en l'anàlisi de sèries temporals de l'índex de vegetació normalitzat (NDVI) en el període 1983-2012 i de les estimacions de precipitació procedents de satèl·lit. Mentre que la precipitació emergeix com una causa dominant de l'augment de la vegetació, hi ha evidències d'altres factors de caràcter antropogènic superposats a la tendència del clima. Mesurar la precipitació en les regions semiàrides continua sent una feina crítica a causa de la seva gran variabilitat espacial i temporal; d'altra banda, cal afegir que al Sahel el nombre d'estacions meteorològiques disponibles és molt escàs. Les dades de satèl·lit, en combinació amb els mesuraments de les estacions meteorològiques, són actualment el millor mitjà per adquirir informació espaciotemporal de la precipitació a la regió. S'han analitzat tres sèries temporals de precipitació que cobreixen el període comprès entre 1983 i 2012: GPCC, ARC2, TAMSAT. Aquestes sèries s'han comparat amb altres de més recents i que proporcionen estimacions de més qualitat: RFE2, TRMM 3B42 i GPCP-1dd. El resultat mostra una bona correspondència entre les sèries GPCC, ARC2, RFE2 i TRMM 3B42. L'anàlisi de 30 anys de precipitació mostra que la precipitació anual s'ha recuperat, tot i que la tendència en la distribució temporal anual ha canviat: ara plou més però durant menys temps. Des de 1981 es disposa de dades del NDVI procedents del sensor AVHRR en la seva versió GIMMS3g. No obstant això, hi ha aspectes en el disseny i processament de les dades del sensor que hi introdueixen soroll. Hi ha conjunts de dades del NDVI més recents procedents dels sensors VEGETATION i MODIS -embarcats en els satèl·lits SPOT i Terra, respectivament- que es consideren una versió millorada respecte de les dades AVHRR GIMMS3g. A més, aquests productes ofereixen la possibilitat d'avaluar l'exactitud en l'anàlisi de la tendència de les sèries temporals de l'AVHRR GIMMS3g en el període de temps en què les dades se solapen, de 2001 a 2012, i a partir d'això s'observa que el conjunt de dades AVHRR GIMMS3g és adequat en estudis temporals de la vegetació en àrees que no reben més de 1.000 mm de precipitació, mentre que la interpretació de les tendències temporals en les zones més humides s'ha de fer amb certes reserves.En el Sahel, la zona de transición entre el desierto del Sahara en el norte y la sabana húmeda tropical en el sur, el desarrollo y la prosperidad de la población depende en gran medida del régimen de lluvias. El clima se caracteriza por una estación seca y larga y una corta temporada de lluvias entre los meses de junio y septiembre. La lluvia está determinada por un fuerte gradiente de norte a sur con una precipitación escasa y variable en el norte, que se traduce en un continuo cambio de especies de vegetación y formas de vida que van desde arbustos espinosos de cobertura muy escasa intercalados entre pastos en el norte a una mayor cantidad de cobertura vegetal y especies leñosas en el sur. El crecimiento de la vegetación muestra fluctuaciones interanuales considerables que generan una preocupación generalizada en la población, predominantemente rural, ya que su modo de vida se basa principalmente en la agricultura de secano y el pastoreo. Las graves sequías ocurridas durante la década de 1970, que se alargaron hasta mediados de la década siguiente, han sido ampliamente estudiadas tanto por sus graves consecuencias sobre la población, como porque se considera uno de los primeros signos de cambio climático global. El Sahel es la región donde se han evidenciado las mayores variaciones de precipitación y vegetación en las últimas tres o cuatro décadas. Los avances tecnológicos en el campo de la teledetección han permitido la vigilancia de los ecosistemas gracias a la disponibilidad de datos con resoluciones espaciales, temporales y espectrales cada vez mejores. En esta tesis se investigan los patrones temporales y espaciales de la vegetación y la variabilidad de las precipitaciones en el Sahel a través de las interrelaciones basadas en el análisis de series temporales del índice de vegetación normalizado (NDVI) en el periodo 1983-2012 y las estimaciones de precipitación procedentes de satélite. Mientras que la precipitación emerge como una causa dominante del aumento de la vegetación, hay evidencias de otros factores de carácter antropogénico superpuestos a la tendencia del clima. Medir la precipitación en las regiones semiáridas sigue siendo un punto crítico por la gran variabilidad espacial y temporal de la misma, a esto hay que añadir que el número de estaciones meteorológicas disponibles es muy escaso en el Sahel. Los datos de satélite, en combinación con las mediciones de las estaciones meteorológicas, son actualmente el mejor medio de adquisición de información espacio-temporal de la precipitación en el Sahel. Se han analizado tres series temporales de precipitación que cubren el periodo comprendido entre 1983 y 2012: GPCC, ARC2, TAMSAT. Estas series se han comparado con otras más recientes y que proporcionan estimaciones de mejor calidad: RFE2, TRMM 3B42 y GPCP-1dd. El resultado muestra una buena correspondencia entre las series GPCC, ARC2, RFE2 y TRMM 3B42. El análisis de 30 años de precipitación muestra que la precipitación anual se ha recuperado, aunque la tendencia en la distribución temporal anual ha cambiado: ahora llueve más pero durante menos tiempo. Desde 1981 se dispone de datos del NDVI procedentes del sensor AVHRR y en su versión GIMMS3g. Sin embargo, hay aspectos en el diseño y procesado de los datos del sensor que introducen ruido en los datos. Existen conjuntos de datos del NDVI más recientes procedentes de los sensores VEGETATION y MODIS embarcados en los satélites SPOT y Terra, respectivamente, que se consideran una mejora sobre los datos AVHRR GIMMS3g, y estos productos ofrecen la posibilidad de evaluar la exactitud en el análisis de la tendencia de las series de tiempo del AVHRR GIMMS3g en el periodo de tiempo en el que los datos se solapan, de 2001 a 2012, a partir de lo cual se observa que el conjunto de datos AVHRR GIMMS3g es adecuado en estudios temporales de la vegetación en áreas que no reciben más de 1.000 mm de precipitación, mientras que en la interpretación de las tendencias temporales en las zonas más húmedas debe de hacerse con ciertas reservas
Steur Annemiek - One of the best experts on this subject based on the ideXlab platform.
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China’s Foreign Investment Law: reform to rebrand foreign trade and investment
2020Co-Authors: Steur AnnemiekAbstract:On January 1st 2020 China will enact a new Foreign Investment Law. Even before its enactment, this law is already a hot topic of debate: it is the first time in 40 years since the Foreign Investment Laws were fundamentally updated, it is an attempt to ease trade and diplomatic relations with the U.S. and it is supposed to ease market access and improve the business environment, the latter elements being a source of friction between China and other countries. Because China’s previous economic and foreign investment policies have allowed it to become a major player in global trade, this change in legislature can be seen as both a natural extension of its current policies to adjust to its changing domestic economy as well as a Pivoting Point in its competition for dominance in the global trade market. While this law has not been enacted yet, it is interesting to put it in context of everchanging legislature in China and its process of “opening up”. That was one of the slogans of the great reforms in 1978, but appears to still be a major theme today. Foreign investment is a matter of relations of China with other countries, and the most recent and compelling tensions involve China-U.S. trade relations. This law therefore has the potential to reshape relations between two major powers. China changing its foreign policy undoubtedly has effects on global trade, and while it is difficult to measure its real effects, global actors are already responding. This thesis will look into the relation between China and the U.S. in particular. The central friction between China and the U.S. has not changed since President Trump took office in 2016, but the issues between China and the U.S. have taken on new forms with the imposed tariffs that marked the beginning of a trade dispute in 2018. Other issues that the U.S. has with China are the licensing process, as a business start-up has to be approved by the government and businesses have to give a lot of information, which is feared to increase Chinese competition and China’s “negative investment list”, which describes some industries that are not open for investment, and forced technology transfer. In addition, the U.S. has accused China before of undervaluing the RMB (the Chinese currency) and has complained about an uneven trade surplus for China, while the U.S. is left with a trade deficit. On the other hand, there are differences since President Trump took office in the White House. A very straightforward difference is that President Trump uses twitter to announce and change his mind on policies towards China in terms of trade, making China-U.S. relations unstable. Also, placing tariffs on Chinese goods is a measure not easily resorted to by previous presidents of the U.S. Still, this measure is an extension of the already present displeasure of the trade deficit between the U.S. and China. For the sake of the scope and conciseness, this thesis will limit itself to the period of the Trump administration (from 2016 onward). Usually, analyses are made of how economics, or rather economic development, influences International Relations, but in this thesis, since the mutual influence of IR and economics is considered self-evident and the law is meant to send a message to the international community, I will look at the language aspect of law, how the newly adopted Foreign Investment Law is interpreted in China and the U.S. and how it translates itself to China-U.S. relations. This thesis therefore will try to answer the following question: What does China try to communicate with the new Foreign Investment Law and how is it received in the United States? In the attempt to answer this question I will discuss the new Foreign Investment Law, compare it with the three existing ones, look at statements and speeches from the U.S. government on China’s new Foreign Investment Law, comments on the draft and final versions and other files that are representative of the situation and view of the U.S. government on China’s Foreign Investment Law. This will be put under the framework of expressive and communicative functions of law, as it helps us understand why a law and this specific law has relevance: it does not exist on its own, but tells a story of what China hopes to achieve with the alteration and how a global actor like the U.S. reacts. In addition, Beijing and Washington consensus will be briefly discussed, as to give some background to help understand from which the root of differences and similarities in statements from China and the U.S. about each other originates in an economic sense, since they are commenting on foreign investment
Masayuki Hashimura - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Burr Formation Mechanism in Orthogonal Cutting
Journal of Manufacturing Science and Engineering-transactions of The Asme, 1999Co-Authors: Masayuki Hashimura, Y. P. Chang, David DornfeldAbstract:To prevent problems caused by burrs in machining, reduction and control of burr size is desirable. This paper presents a basic framework for and conceptual understanding of the burr formation process based upon the material properties of the workpiece. In order to verify this framework and explain the basic phenomena in the burr formation process, the deformation at the edge of the workpiece was analyzed using a finite element method (FEM). Micro-machining tests under an optical microscope and a scanning electron microscope using Al-2024-O material were also done to observe the burr formation process. The feed rate and tool edge radius were varied and the resulting burr formation observed. FEM analysis of burr formation in the 2024 material and observation of the deformation at the workpiece edge in the micro-machining tests verified the proposed conceptual understanding of the burr formation process. For the experimental conditions examined, all of the burrs in Al-2024-O were negative burrs, that is, edge breakout. As the feed was increased two effects were observed. One effect was an increase in the resulting burr thickness. Another effect, which was observed during the burr initiation stage while machining with a sharp tool, was an increase in both the distance and depth of the initial Pivoting Point of the burr from the tool edge.
Donald Loose - One of the best experts on this subject based on the ideXlab platform.
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The Dynamic Sublime as the Pivoting Point between Nature and Freedomin Kant
The Sublime and its Teleology, 2011Co-Authors: Donald LooseAbstract:The author corrects classic view of Kantian dualism in general and readjusting the characterization of the dynamic sublime as mere conflict and resistance to the supremacy of nature or as indication of the collapse of the mental faculties. This chapter shows how the analysis of the sublime forms the pivot in The Critique of the Power of Judgment (CPJ). It sketches nature as a recalcitrant ally of freedom, and the interaction of freedom with nature as its lasting ally at the level of freedom itself. The chapter explains how symbolic representation constitutes the climax of the mediation between nature and freedom. The chapter views analytics of the sublime as the pivot in the diptych of the analytic of the aesthetic power of judgment and the critique of the teleological power of judgment. Keywords:dynamic sublime; freedom; Kantian dualism; nature