981 resultados para Natural Gas Midstream services
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Combining headspace (HS) sampling with a needle-trap device (NTD) to determine priority volatile organic compounds (VOCs) in water samples results in improved sensitivity and efficiency when compared to conventional static HS sampling. A 22 gauge stainless steel, 51-mm needle packed with Tenax TA and Carboxen 1000 particles is used as the NTD. Three different HS-NTD sampling methodologies are evaluated and all give limits of detection for the target VOCs in the ng L1 range. Active (purge-and-trap) HS-NTD sampling is found to give the best sensitivity but requires exhaustive control of the sampling conditions. The use of the NTD to collect the headspace gas sample results in a combined adsorption/desorption mechanism. The testing of different temperatures for the HS thermostating reveals a greater desorption effect when the sample is allowed to diffuse, whether passively or actively, through the sorbent particles. The limits of detection obtained in the simplest sampling methodology, static HS-NTD (5 mL aqueous sample in 20 mL HS vials, thermostating at 50 C for 30 min with agitation), are sufficiently low as to permit its application to the analysis of 18 priority VOCs in natural and waste waters. In all cases compounds were detected below regulated levels
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Deregulation of the electricity sector liberated the electricity sale and production for competitive forces while in the network business, electricity transmission and distribution, natural monopoly positions were recognised. Deregulation was accompanied by efficiencyoriented thinking on the whole electricity supply industry. For electricity distribution this meant a transition from a public service towards profit-driven business guided by economic regulation. Regulation is the primary means to enforce societal and other goals in the regulated monopoly sector. The design of economic regulation is concerned with two main attributes; end-customer price and quality of electricity distribution services. Regulation limits the costs of the regulated company but also defines the desired quality of monopoly services. The characteristics of the regulatory framework and the incentives it provides are therefore decisive for the electricity distribution sector. Regulation is not a static factor; changes in the regulatory practices cause discontinuity points, which in turn generate risks. A variety of social and environmental concerns together with technological advancements have emphasised the relevance of quality regulation, which is expected to lead to the large-scale replacement of overhead lines with underground cables. The electricity network construction activity is therefore currently witnessing revolutionary changes in its competitive landscape. In a business characterised by high statutory involvement and a high level of sunk costs, recognising and understanding the regulatory risks becomes a key success factor. As a response, electricity distribution companies have turned into outsourcing to attain efficiency and quality goals. This doctoral thesis addresses the impacts of regulatory risks on electricity network construction, which is a commonly outsourced activity in the electricity distribution network sector. The chosen research approach is characterised as an action analytical research on account of the fact that regulatory risks are greatly dependent on the individual nature of the regulatory regime applied in the electricity distribution sector. The main contribution of this doctoral thesis is to develop a concept for recognising and managing the business risks stemming from economic regulation. The degree of outsourcing in the sector is expected to increase in years to come. The results of the research provide new knowledge to manage the regulatory risks when outsourcing services.
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Global warming is assertively the greatest environmental challenge for humans of 21st century. It is primarily caused by the anthropogenic greenhouse gas (GHG) that trap heat in the atmosphere. Because of which, the GHG emission mitigation, globally, is a critical issue in the political agenda of all high-profile nations. India, like other developing countries, is facing this threat of climate change while dealing with the challenge of sustaining its rapid economic growth. Indias economy is closely connected to its natural resource base and climate sensitive sectors like water, agriculture and forestry. Due to Climate change the quality and distribution of Indias natural resources may transform and lead to adverse effects on livelihood of its people. Therefore, India is expected to face a major threat due to the projected climate change. This study proposes possible solutions for GHG emission mitigation that are specific to the power sector of India. The methods discussed here will take Indian power sector from present coal dominant ideology to a system, centered with renewable energy sources. The study further proposes a future scenario for 2050, based on the present Indian government policies and global energy technologies advancements.
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This Masters Thesis examines industrial service business and studies how Global Technical Support Center Finland, part of ABB Oy, can develop its lifecycle services based on availability related customer needs. Focus is in three most business critical industry segments OGP (Oil, Gas and Petrochemical), Power and Metals. The research was conducted as a qualitative case study, including literature review and empirical part. The literature review explores industrial service business, product lifecycle services and related customer needs, product effectiveness and maintenance. This study contains also characteristics of constructive research. Primary material was gathered through internal and external interviews. Both theme and semi-structured interviews were performed. This research has shown that customers have different needs depending of the industry segment where they operate. Most remarkable differences are related to maintenance schedules. The main outcomes of the study are the industry specific lifecycle service models that combine company recommendations with customer specific needs. Other development needs were related to proactivity, condition based monitoring, information sharing and lifecycle estimations.
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On tudie l'volution du prix d'une ressource naturelle non renouvelable dans le cas o cette ressource est durable, c'est--dire qu'une fois extraite elle devient un actif productif dtenu hors terre. On emprunte la thorie de la dtermination du prix des actifs pour ce faire. Le choix de portefeuille porte alors sur les actifs suivant : un stock de ressource non renouvelable dtenu en terre, qui ne procure aucun service productif; un stock de ressource dtenu hors terre, qui procure un flux de services productifs; un stock d'un bien composite, qui peut tre dtenu soit sous forme de capital productif, soit sous forme d'une obligation dont le rendement est donn e. Les productivits du secteur de production du bien composite et du secteur de l'extraction de la ressource voluent de faon stochastique. On montre que la prdiction que l'on peut tirer quant au sentier de prix de la ressource diffre considrablement de celle qui dcoule de la rgle d'Hotelling lmentaire et qu'aucune prdiction non ambigu quant au comportement du sentier de prix ne peut tre obtenue de faon analytique.
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Au cours des dernieres decennies, linteret pour la gazeification de biomasses a considerablement augmente, notamment en raison de la grande efficacite de recouvrement energetique de ce procede par rapport aux autres procedes de generation de bioenergies. Les composants majoritaires du gaz de synthese, le monoxyde de carbone (CO) et lhydrogene (H2) peuvent entre autres servir de substrats a divers microorganismes qui peuvent produire une variete de molecules chimiques dinterets, ou encore produire des biocarburants, particulierement le methane. Il est donc important d'etudier les consortiums methanogenes naturels qui, en syntrophie, serait en mesure de convertir le gaz de synthese en carburants utiles. Cette etude evalue principalement le potentiel de methanisation du CO par un consortium microbien issu dun reacteur de type UASB, ainsi que les voies metaboliques impliquees dans cette conversion en conditions mesophiles. Des tests dactivite ont donc ete realises avec la boue anaerobie du reacteur sous differentes pressions partielles de CO variant de 0.1 a 1,65 atm (0.09 a 1.31 mmol CO/L), en presence ou absence de certains inhibiteurs metaboliques specifiques. Des le depart, la boue non acclimatee au CO presente une activite carboxidotrophique relativement interessante et permet une croissance sur le CO. Les tests effectues avec de lacide 2- bromoethanesulfonique (BES) ou avec de la vancomycine demontrent que le CO est majoritairement consomme par les bacteries acetogenes avant detre converti en methane par les methanogenes acetotrophes. De plus, un plus grand potentiel de methanisation a pu etre atteint sous une atmosphere constituee uniquement de CO en acclimatant auparavant la boue. Cette adaptation est caracterisee par un changement dans la population microbienne desormais dominee par les methanogenes hydrogenotrophes. Ceci suggere un potentiel de production a large echelle de biomethane a partir du gaz de synthese avec laide de biofilms anaerobies.
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Les services cosystmiques (SE) rfrent aux bnfices que produisent et soutiennent la biodiversit et les cosystmes et qui profitent ltre humain. Dans beaucoup de cas, ils ne sont pas pris en compte dans le systme conomique. Cette externalisation des SE engendre des dcisions sur lutilisation du territoire et des ressources naturelles qui ignorent leur contribution la qualit de vie des communauts. Afin notamment de sensibiliser lopinion publique limportance des SE et de mieux les intgrer dans les processus dcisionnels, ont t dveloppes des dmarches dvaluation conomique des SE. Dans cette thse, nous avons cherch comprendre la fois comment lutilisation passe et actuelle des sols dans la rgion de Montral affecte la valeur des SE et comment ces amnits naturelles sont perues et valorises par la population, dans une perspective damnagement futur du territoire. Pour ce faire, nous avons utilis deux approches : lanalyse spatiale recourant aux systmes dinformation gographique et lanalyse des prfrences exprimes par des techniques denqute. Pour lanalyse spatiale, nous avons combin des analyses cartographiques des valeurs montaires associes aux SE publies dans la littrature. Nous avons alors estim la valeur des cosystmes dun territoire par le transfert de bnfices, de prix de marchs directs et de cots vits. Cette dmarche nous a permis de comprendre la relation entre lutilisation actuelle du territoire du Grand Montral cologique et la valeur des services fournis par les cosystmes, que nous avons estime 2,2 milliards de dollars par anne. Elle nous a permis aussi de mesurer les effets sur la valeur des SE du changement dutilisation des sols entre les annes 1960 et 2010. Nous avons montr que malgr diffrentes politiques de contrle et dencadrement de ltalement urbain au cours de cette priode, les pertes conomiques non marchandes lies aux SE slvent 236 millions de dollars par anne. Pour lanalyse des prfrences exprimes, nous avons utlilis deux mthodes, lvaluation contingente et le choix multi-attributs, avec lobjectif de mesurer le consentement payer de rpondants pour des variations dans lamnagement du territoire. Nous avons montr dune part que les rpondants valorisent significativement lincidence des pratiques agro-environnementales sur la qualit de lenvironnement et des paysages en consentant payer entre 159 et 333 dollars par mnage par anne pour une amlioration de la diversit du paysage agricole. Dautre part, leur volont payer pour lamlioration de ltat des milieux humides du Qubec est estime entre 389 et 455 dollars par mnage par anne. Lutilisation conjointe des deux mthodes nous a permis den comparer les rsultats. Nous avons en outre dmontr que le choix du format de question de valorisation de lvaluation contingente affecte la convergence des rsultats. Enfin, nous avons propos des pistes de recherches futures portant sur lintgration des dmarches danalyse biophysique, conomique et politique dans des outils de prise de dcision mieux adapts la dynamique des cosystmes, de la biodiversit et des communauts humaines.
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The research work which was carried out to characterization of wastes from natural rubber and rubber wood processing industries and their utilization for biomethanation. Environmental contamination is an inevitable consequence of human activity. The liquid and solid wastes from natural rubber based industries were: characterized and their use for the production of biogas investigated with a view to conserve conventional energy, and to mitigate environmental degradation.Rubber tree (flevea brasiliensis Muell. Arg.), is the most important commercial source of natural rubber and in india. Recently, pollution from the rubber processing factories has become very serious due to the introduction of modern methods and centralized group processing practices.The possibility of the use of spent slurry as organic manure is discussed.l0 percent level of PSD, the activity of cellulolytic, acid producing,proteolytic, lipolytic and methanogenic bacteria were more in the middle stage of methanogenesis.the liquid wastes from rubber processing used as diluents in combination with PSD, SPE promoted more biogas production with high methane content in the gas.The factors that favour methane production like TS, VS, cellulose and hemicellulose degradation were favoured in this treatment which led to higher methane biogenesis.The results further highlight ways and means to use agricultural wastes as alternative sources of energy.
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Land use is a crucial link between human activities and the natural environment and one of the main driving forces of global environmental change. Large parts of the terrestrial land surface are used for agriculture, forestry, settlements and infrastructure. Given the importance of land use, it is essential to understand the multitude of influential factors and resulting land use patterns. An essential methodology to study and quantify such interactions is provided by the adoption of land-use models. By the application of land-use models, it is possible to analyze the complex structure of linkages and feedbacks and to also determine the relevance of driving forces. Modeling land use and land use changes has a long-term tradition. In particular on the regional scale, a variety of models for different regions and research questions has been created. Modeling capabilities grow with steady advances in computer technology, which on the one hand are driven by increasing computing power on the other hand by new methods in software development, e.g. object- and component-oriented architectures. In this thesis, SITE (Simulation of Terrestrial Environments), a novel framework for integrated regional sland-use modeling, will be introduced and discussed. Particular features of SITE are the notably extended capability to integrate models and the strict separation of application and implementation. These features enable efficient development, test and usage of integrated land-use models. On its system side, SITE provides generic data structures (grid, grid cells, attributes etc.) and takes over the responsibility for their administration. By means of a scripting language (Python) that has been extended by language features specific for land-use modeling, these data structures can be utilized and manipulated by modeling applications. The scripting language interpreter is embedded in SITE. The integration of sub models can be achieved via the scripting language or by usage of a generic interface provided by SITE. Furthermore, functionalities important for land-use modeling like model calibration, model tests and analysis support of simulation results have been integrated into the generic framework. During the implementation of SITE, specific emphasis was laid on expandability, maintainability and usability. Along with the modeling framework a land use model for the analysis of the stability of tropical rainforest margins was developed in the context of the collaborative research project STORMA (SFB 552). In a research area in Central Sulawesi, Indonesia, socio-environmental impacts of land-use changes were examined. SITE was used to simulate land-use dynamics in the historical period of 1981 to 2002. Analogous to that, a scenario that did not consider migration in the population dynamics, was analyzed. For the calculation of crop yields and trace gas emissions, the DAYCENT agro-ecosystem model was integrated. In this case study, it could be shown that land-use changes in the Indonesian research area could mainly be characterized by the expansion of agricultural areas at the expense of natural forest. For this reason, the situation had to be interpreted as unsustainable even though increased agricultural use implied economic improvements and higher farmers' incomes. Due to the importance of model calibration, it was explicitly addressed in the SITE architecture through the introduction of a specific component. The calibration functionality can be used by all SITE applications and enables largely automated model calibration. Calibration in SITE is understood as a process that finds an optimal or at least adequate solution for a set of arbitrarily selectable model parameters with respect to an objective function. In SITE, an objective function typically is a map comparison algorithm capable of comparing a simulation result to a reference map. Several map optimization and map comparison methodologies are available and can be combined. The STORMA land-use model was calibrated using a genetic algorithm for optimization and the figure of merit map comparison measure as objective function. The time period for the calibration ranged from 1981 to 2002. For this period, respective reference land-use maps were compiled. It could be shown, that an efficient automated model calibration with SITE is possible. Nevertheless, the selection of the calibration parameters required detailed knowledge about the underlying land-use model and cannot be automated. In another case study decreases in crop yields and resulting losses in income from coffee cultivation were analyzed and quantified under the assumption of four different deforestation scenarios. For this task, an empirical model, describing the dependence of bee pollination and resulting coffee fruit set from the distance to the closest natural forest, was integrated. Land-use simulations showed, that depending on the magnitude and location of ongoing forest conversion, pollination services are expected to decline continuously. This results in a reduction of coffee yields of up to 18% and a loss of net revenues per hectare of up to 14%. However, the study also showed that ecological and economic values can be preserved if patches of natural vegetation are conservated in the agricultural landscape. -----------------------------------------------------------------------
Resumo:
Energy production from biomass and the conservation of ecologically valuable grassland habitats are two important issues of agriculture today. The combination of a bioenergy production, which minimises environmental impacts and competition with food production for land with a conversion of semi-natural grasslands through new utilization alternatives for the biomass, led to the development of the IFBB process. Its basic principle is the separation of biomass into a liquid fraction (press fluid, PF) for the production of electric and thermal energy after anaerobic digestion to biogas and a solid fraction (press cake, PC) for the production of thermal energy through combustion. This study was undertaken to explore mass and energy flows as well as quality aspects of energy carriers within the IFBB process and determine their dependency on biomass-related and technical parameters. Two experiments were conducted, in which biomass from semi-natural grassland was conserved as silage and subjected to a hydrothermal conditioning and a subsequent mechanical dehydration with a screw press. Methane yield of the PF and the untreated silage was determined in anaerobic digestion experiments in batch fermenters at 37C with a fermentation time of 13-15 and 27-35 days for the PF and the silage, respectively. Concentrations of dry matter (DM), ash, crude protein (CP), crude fibre (CF), ether extract (EE), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent ligning (ADL) and elements (K, Mg, Ca, Cl, N, S, P, C, H, N) were determined in the untreated biomass and the PC. Higher heating value (HHV) and ash softening temperature (AST) were calculated based on elemental concentration. Chemical composition of the PF and mass flows of all plant compounds into the PF were calculated. In the first experiment, biomass from five different semi-natural grassland swards (Arrhenaterion I and II, Caricion fuscae, Filipendulion ulmariae, Polygono-Trisetion) was harvested at one late sampling (19 July or 31 August) and ensiled. Each silage was subjected to three different temperature treatments (5C, 60C, 80C) during hydrothermal conditioning. Based on observed methane yields and HHV as energy output parameters as well as literature-based and observed energy input parameters, energy and green house gas (GHG) balances were calculated for IFBB and two reference conversion processes, whole-crop digestion of untreated silage (WCD) and combustion of hay (CH). In the second experiment, biomass from one single semi-natural grassland sward (Arrhenaterion) was harvested at eight consecutive dates (27/04, 02/05, 09/05, 16/05, 24/05, 31/05, 11/06, 21/06) and ensiled. Each silage was subjected to six different treatments (no hydrothermal conditioning and hydrothermal conditioning at 10C, 30C, 50C, 70C, 90C). Energy balance was calculated for IFBB and WCD. Multiple regression models were developed to predict mass flows, concentrations of elements in the PC, concentration of organic compounds in the PF and energy conversion efficiency of the IFBB process from temperature of hydrothermal conditioning as well as NDF and DM concentration in the silage. Results showed a relative reduction of ash and all elements detrimental for combustion in the PC compared to the untreated biomass of 20-90%. Reduction was highest for K and Cl and lowest for N. HHV of PC and untreated biomass were in a comparable range (17.8-19.5 MJ kg-1 DM), but AST of PC was higher (1156-1254C). Methane yields of PF were higher compared to those of WCD when the biomass was harvested late (end of May and later) and in a comparable range when the biomass was harvested early and ranged from 332 to 458 LN kg-1 VS. Regarding energy and GHG balances, IFBB, with a net energy yield of 11.9-14.1 MWh ha-1, a conversion efficiency of 0.43-0.51, and GHG mitigation of 3.6-4.4 t CO2eq ha-1, performed better than WCD, but worse than CH. WCD produces thermal and electric energy with low efficiency, CH produces only thermal energy with a low quality solid fuel with high efficiency, IFBB produces thermal and electric energy with a solid fuel of high quality with medium efficiency. Regression models were able to predict target parameters with high accuracy (R2=0.70-0.99). The influence of increasing temperature of hydrothermal conditioning was an increase of mass flows, a decrease of element concentrations in the PC and a differing effect on energy conversion efficiency. The influence of increasing NDF concentration of the silage was a differing effect on mass flows, a decrease of element concentrations in the PC and an increase of energy conversion efficiency. The influence of increasing DM concentration of the silage was a decrease of mass flows, an increase of element concentrations in the PC and an increase of energy conversion efficiency. Based on the models an optimised IFBB process would be obtained with a medium temperature of hydrothermal conditioning (50C), high NDF concentrations in the silage and medium DM concentrations of the silage.
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In the process of urbanization, natural and semi-natural landscapes are increasingly cherished as open space and recreational resource. Urban rivers are part of this kind of resource and thus play an important role in managing urban resilience and health. Employing the example of Tianjin, this doctoral dissertation research aims at learning to understand how to plan and design for the interface zones between urban water courses and for the land areas adjacent to such water courses. This research also aims at learning how to link waterfront space with other urban space in order to make a recreational space system for the benefit of people. Five questions of this dissertation are: 1) what is the role of rivers in spatial and open space planning? 2) What are the human needs regarding outdoor open space? 3) How do river and water front spatial structures affect people's recreational activities? 4) How to define the recreational service of urban river and waterfront open space? 5) How might answering these question change planning and design of urban open space? Quantitative and qualitative empirical approaches were combined in this study for which literature review and theoretical explorations provide the basis. Empirical investigations were conducted in the city of Tianjin. The quantitative approach includes conducting 267 quantitative interviews, and the qualitative approach includes carrying out field observations and mappings. GIS served to support analysis and visualization of empirical information that was generated through this study. By responding to the five research questions, findings and lessons include the following: 1) In the course of time rivers have gained importance in all levels and scales of spatial planning and decision making. Regarding the development of ecological networks, mainly at national scale, rivers are considered significant linear elements. Regarding regional and comprehensive development, river basins and watersheds are often considered as the structural link for strategic ecological, economic, social and recreational planning. For purposes of urban planning, particularly regarding recreational services in cities, the distribution of urban open spaces often follows the structure of river systems. 2) For the purpose of classifying human recreational needs that relate to outdoor open space Maslow's hierarchy of human needs serves as theoretical basis. The classes include geographical, safety, physiological, social and aesthetic need. These classes serve as references while analyzing river and waterfront open space and other kinds of open space. 3) Regarding the question how river and waterfront spatial structures might affect people's recreational activities, eight different landscape units were identified and compared in the case study area. Considering the thermal conditions of Tianjin, one of these landscape units was identified as affording the optimal spatial arrangement which mostly meets recreational needs. The size and the shape of open space, and the plants present in an open space have been observed as being most relevant regarding recreational activities. 4) Regarding the recreational service of urban river and waterfront open space the results of this research suggest that the recreational service is felt less intensively as the distances between water 183 front and open space users places of residence are increasing. As a method for estimating this Service Distance Effect the following formula may be used: Y = a*ebx. In this equation Y means the Service Distance between homes and open space, and X means the percentage of the people who live within this service distance. Coefficient "a" represents the distance of the residential area nearest to the water front. The coefficient "b" is a comprehensive capability index that refers to the size of the available and suitable recreational area. 5) Answers found to the questions above have implications for the planning and design of urban open space. The results from the quantitative study of recreational services of waterfront open space were applied to the assessment of river-based open space systems. It is recommended that such assessments might be done employing the network analysis function available with any GIS. In addition, several practical planning and designing suggestions are made that would help remedy any insufficient base for satisfying recreational needs. The understanding of recreational need is considered helpful for the proposing planning and designing ideas and for the changing of urban landscapes. In the course of time Tianjin's urban water system has shrunk considerably. At the same time rivers and water courses have shaped Tianjin's urban structure in noticeable ways. In the process of urbanization water has become increasingly important to the citizens and their everyday recreations. Much needs to be changed in order to improve recreational opportunities and to better provide for a livable city, most importantly when considering the increasing number of old people. Suggestions made that are based on results of this study, might be implemented in Tianjin. They are 1) to promote the quality of the waterfront open space and to make all linear waterfront area accessible recreational spaces. Then, 2), it is advisable to advocate the concept of green streets and to combine green streets with river open space in order to form an everyday recreational network. And 3) any sound urban everyday recreational service made cannot rely on only urban rivers; the whole urban structure needs to be improved, including adding small open space and optimize the form of urban communities, finally producing a multi-functional urban recreational network.
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The identification of compositional changes in fumarolic gases of active and quiescent volcanoes is one of the most important targets in monitoring programs. From a general point of view, many systematic (often cyclic) and random processes control the chemistry of gas discharges, making difficult to produce a convincing mathematical-statistical modelling. Changes in the chemical composition of volcanic gases sampled at Vulcano Island (Aeolian Arc, Sicily, Italy) from eight different fumaroles located in the northern sector of the summit crater (La Fossa) have been analysed by considering their dependence from time in the period 2000-2007. Each intermediate chemical composition has been considered as potentially derived from the contribution of the two temporal extremes represented by the 2000 and 2007 samples, respectively, by using inverse modelling methodologies for compositional data. Data pertaining to fumaroles F5 and F27, located on the rim and in the inner part of La Fossa crater, respectively, have been used to achieve the proposed aim. The statistical approach has allowed us to highlight the presence of random and not random fluctuations, features useful to understand how the volcanic system works, opening new perspectives in sampling strategies and in the evaluation of the natural risk related to a quiescent volcano
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Esta monografa tiene como propsito analizar la manera en que el gas influenci las relaciones bilaterales entre Rusia y la Unin Europea en el periodo del 2003 al 2008. La deficiencia de Fuentes energticas propias en la Unin Europea, sobre todo de hidrocarburos, contribuy a que en este periodo, la Federacin Rusa alcanzara algunas de las metas que se haba propuesto a nivel poltico y econmico desde la llegada del presidente Vladimir Putin al poder, con el fin de hacer un reposicionamiento de Rusia a nivel regional, basado en la reciprocity (reciprocidad), donde Rusia brinda gas a la UE pero a su vez, la UE debe brindar seguridad en otros sectores. A travs de la teora de Barry Buzan Regional Security Complex se muestra la influencia del sector energtico (energetic) en el campo poltico y econmico en las relaciones bilaterales de estas dos unidades del sistema internacional.
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Las comunicaciones mviles, no aparecen a nivel comercial sino hasta finales del siglo XX. Las redes mviles terrestres se iniciaron en mbitos restringidos para el establecimiento de comunicaciones en tareas de despacho, para la gestin de las actividades de flotas de vehculos en aplicaciones tales como servicios de polica, mantenimiento de servicios pblicos de distribucin de agua, gas, electricidad, servicios de emergencia, ambulancias, etc. Radiobsquedas, redes mviles privadas o Trunking, y sistemas de telefona mvil mejorados fueron el siguiente paso. Despus lleg la telefona mvil digital, las agendas personales, miniordenadores, laptops y un sinfn de dispositivos dispuestos a conectarse va radio con otros dispositivos o redes. Y finalmente la unin entre comunicaciones mviles e Internet, el verdadero punto de inflexin tanto para uno como para otro. En la actualidad, las tcnicas digitales para las comunicaciones mviles, permiten la utilizacin de nuevos mtodos de acceso, como son las de acceso mltiple por divisin en el tiempo (Time Division Multiple Access, TDMA), con tcnicas de banda estrecha, y el acceso mltiple por divisin de cdigo (Code Division Multiple Access, CDMA) con tcnicas de espectro ensanchado. Las primeras sufren un conocido problema denominado propagacin multi-trayectoria Bsicamente este fenmeno consiste en que la seal que llega al receptor se compone de la suma de un conjunto de seales idnticas en amplitud pero con fases distintas. En el peor caso la seal en el receptor puede llegar a ser nula, producindose un fenmeno de fading importante. Las tcnicas de espectro ensanchado (CDMA) no sufren este tipo de problemas.
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La exposicin a polvo de cemento y slice ha sido estudiada por aos en pases como Estados Unidos y Canad, cuando el polvo de cemento se inhala durante diferentes actividades, se puede ocasionar afectacin del tracto respiratorio de las personas expuestas. El estudio Perfil de exposicin ocupacional a polvo de cemento y slice cristalina en procesos de cementacin y Fracturamiento hidrulico en el sector Oil & Gas en Colombia: un estudio retrospectivo (2009 2013). Permiti identificar las actividades funcionales que representan un riesgo potencial por la presencia de partculas aerosuspendidas, analizar una base de datos que rene cerca de 18298 registros de evaluaciones higinicas en el sector Oil & Gas, realizar posteriormente el clculo de material particulado en la fraccin respirable y slice cristalina aplicables para cada proceso y el procesamiento de los datos estadsticamente, confrontar estos estimadores estadsticos con los valores lmites permisibles definidos por el gobierno nacional, los resultados incluyeron la caracterizacin de un perfil de exposicin ocupacional por actividad funcional para el proceso de cementacin, la identificacin de los trabajadores ms expuestos segn las condiciones de exposicin y cules de estos perfiles superan los lmites mximos permisibles para un turno de trabajo de 12 horas, esta informacin permitir a los profesionales de la salud e higiene laboral orientar actividades de seguimiento, vigilancia y control en los grupos de exposicin similar especficos. Para el proceso de fracturamiento hidrulico los datos encontrados no fueron estadsticamente significativos.
