Search

Este libro emana de la Conferencia Internacional "Agua, Megaciudades y Cambio Global", celebrada en París en diciembre de 2015 en ocasión de la COP21 y contiene los resúmenes de monografías de 15 megaciudades: Beijing, Buenos Aires, Chicago, Ciudad Ho Chi Minh, Estambul, Lagos, Londres, Los Ángeles, Manila, México, Mumbai, Nueva York, París, Seúl y Tokio.

Ce livre, issu de la conférence internationale « Eau, mégapoles et changement global », est le résultat d’un travail collectif de 33 auteurs et co-auteurs et contient les résumés de monographies de 15 mégapoles emblématiques - Beijing, Buenos Aires, Chicago, Ho Chi Minh Ville, Istanbul, Lagos, London, Los Angeles, Manille, Mexico, Mumbai, New York, Paris, Séoul et Tokyo. Cet ouvrage offre des informations précieuses et uniques concernant la gestion de l’eau dans ces 15 mégapoles.

This book is the outcome of the International Conference ‘Water, Megacities and Global Change’, and represents the collective work of 33 authors and co-authors. It contains summaries of monographs on 15 emblematic megacities: Beijing, Buenos Aires, Chicago, Ho Chi Minh City, Istanbul, Lagos, London, Los Angeles, Manila, Mexico, Mumbai, New York, Paris, Seoul and Tokyo. This edition provides unique information about water management in these megacities.

Thermoelektrische Elemente können zur Erzeugung elektrischer Energie aus einer Temperaturdifferenz verwendet werden. Traditionell basieren thermoelektrische Generatoren auf komplementär dotierten Halbleitern, welche elektrisch in Serie und thermisch parallel verschaltet werden. Bei dem herkömmlichen Aufbau werden auf der Kalt- und auf der Heißseite sowohl elektrische als auch mechanische Kontakte auf einem Keramiksubstrat realisiert. In dieser Arbeit wird ein großflächiger pn-Übergang zur elektrischen Verbindung der komplementären Halbleiter auf der Heißseite verwendet. Damit erübrigt sich dort das verbindende Substrat, und dessen Verzicht führt zu einer Steigerung der Heißseitentemperatur. Darüberhinaus werden Probleme in Hinblick auf die Stabilität von elektro-mechanischem Kontakt sowie chemische Wechselwirkungen stark reduziert. Es zeigt sich, dass ein derartiges pn-Übergangs-Thermoelektrikelement ein zweidimensionales Transportverhalten aufweist, welches sich nicht durch das sonst übliche, eindimensionale „Constant property“-Modell beschreiben lässt. Hier wird nun ein grundsätzliches physikalisches Modell vorgeschlagen und mittels Simulationen auf Basis der Onsager-Theorie überprüft. Die simulierten thermischen und elektrischen Flüsse zeigen insbesondere auf, dass elektrische Verluste durch Kreisströme innerhalb des pn-Elementes hervorgerufen werden. Ferner geben die Simulationen Hinweise auf mögliche geometrische Optimierungen zur Reduzierung der Verluste, und eine entsprechende positive Wirkung konnte von uns tatsächlich experimentell nachgewiesen werden. Wir verwenden nanostrukturiertes Silizium aufgrund der im Vergleich zu kristallinem Material verringerten thermischen Leitfähigkeit. Die nanostrukturierten Proben wurden aus Nanopartikeln in der Gasphase hergestellt und durch ein „Spark-Plasma“-Sinterverfahren verdichtet. Zusätzlich zu den nanostrukturierten Siliziumproben wurden pn-Übergänge durch Lasersinterung von dotierten Nanopartikeln auf einem entgegengesetzt dotierten Siliziumwafer bzw. durch Verschweißen komplementärer Wafer hergestellt. Ein geeigneter Messplatz wurde entwickelt und eingerichtet, und es wurde gezeigt, dass die nanostrukturierten pn-Übergänge wiederholte Heizzyklen mit einer Heißseitentemperatur von 780°C überstehen. Somit wurde gezeigt, dass thermoelektrische Elemente auf Basis von pn-Übergängen bei höheren Temperaturen verwendet werden können als herkömmliche Generatoren. Und trotz der internen Verluste zeigen pn-Übergangselemente bei hohen Temperaturen vergleichbare Ausgangsleistungen wie die konventionellen Generatoren. Thermoelectric devices can be used to produce electricity given a temperature difference. Traditionally, thermoelectric devices are built by connecting complementary doped semiconductor materials electrically in series and thermally in parallel. In this architecture a ceramic substrate on both the cold and hot sides provides support for the electrical and mechanical connections. In this work, a large area pn junction is used to provide an electrical connection between the complementary semiconductors on the hot side. Having a pn junction means that the hot side electrical contacts are not required. The dismissal of the hot side substrate translates to higher hot side temperatures since problems associated with the stability of the electrical, mechanical and chemical properties on the hot side of the thermoelectric generator are largely reduced. A pn junction thermoelectric device is demonstrated to be a two dimensional transport device which cannot be described by the one dimensional constant property model commonly used in thermoelectrics theory. A basic working principle is proposed and further verified using simulations based on Onsager’s theory. The simulations describe the behavior of the pn junction device in terms of thermal and electrical fluxes and indicate that electrical losses arise due to internal current vortices within the pn thermoelectric device. The simulations also indicate that a geometrical optimization can be done to reduce such losses, and this we could verify experimentally. Nanostructured silicon is used as the primary material system due to its relatively low thermal conductivity with respect to crystalline silicon. The nanostructured samples are produced from nanoparticles produced from a gas phase, and densified by a spark plasma sintering method. In addition to the nanostructured silicon samples, pn junctions are produced by laser sintering of doped nanoparticles on a complementary doped silicon wafer, and by welding of complementary silicon wafers together. The metrology system is developed and it is shown that the nanostructured pn junctions can sustain repeated heating cycles with a hot side temperature of 780°C. It is shown that pn junction devices can be operated in higher temperatures than conventional devices and despite the internal losses of a pn junction device, it has comparable output power characteristic than a conventional device given high temperatures.

OBJECTIVE: To determine the prevalence of experiencing intra-familial violence among Mexican and Egyptian youth and to describe its associated risk factors. METHODS: Data from questionnaires applied to 12,862 Mexican and 5,662 Egyptian youth, aged 10 to 19, who attended public schools were analyzed. Biviarate and logistic regression analysis were used to determine the relationship between socio-demographics, the experience of intra-familial violence and violence perpetration. RESULTS: The prevalence of having experienced intra-familial violence was comparable across the Mexican and Egyptian populations (14% and 17%, respectively). In Mexico, young men were more likely to have experienced such violence (OR=2.36) than women, whereas in Egypt, young women were at slightly greater risk than young men (OR=1.25). Older age, male gender and urban residence were independent correlates of experiencing intra-familial violence among Mexican youth. For Egyptian adolescents, in contrast, younger age, female gender and having non-married parents were independent correlates of victimization. Intra-familial violence victims were also more likely than non-victims to perpetrate violence (Mexico: OR=13.13; Egypt: OR=6.58). CONCLUSIONS: Mexican and Egyptian youth experienced intra-familial violence at a relatively low prevalence when compared with youth of other countries. A strong association was found between experiencing intra-familial violence and perpetrating violence. OBJETIVO: Determinar a prevalência da violência intra-familiar sofrida por jovens mexicanos e egípcios, e descrever os fatores de risco associados. MÉTODOS: Os dados analisados foram obtidos de questionários aplicados a 12.862 mexicanos e 5.662 egípcios, jovens de 10 a 19 anos, que freqüentam escolas públicas. O relacionamento entre fatores sociodemográficos, a violência sofrida e sua perpetração foram investigados por meio de análise bivariada e regressão logística. RESULTADOS: A prevalência de violência intra-familiar foi comparável entre as populações mexicana e egípcia (14% e 17%, respectivamente). No México, essa violência foi muito mais provável entre os homens jovens do que entre mulheres (OR=2,36), enquanto que no Egito era mais provável entre as mulheres jovens do que homens (OR=1,25). Idade mais elevada, gênero masculino e residência urbana são fatores associados a violência intra-familiar entre jovens mexicanos. Entre jovens egípcios, a idade mais baixa,o gênero feminino e pais não casados foram fatores associados a essa violência. Foi mais provável a repetição da violência pelos jovens que eram vítimas da violência intra-familiar (México: OR=13,13; Egito: OR=6,58). CONCLUSÕES: A prevalência de experimentar a violência intra-familiar de jovens mexicanos e egípcios foi baixa em comparação com jovens em outros países. Houve forte associação entre vítimas de violência intra-familiar e a repetição da violência.