Tratamento de efluentes de sala de ordena de bovinocultura: lagoas de estabilização seguidas de leito cultivado

No Brasil, o destino dos efluentes dos confinamentos de animais foi e continua sendo os cursos de água, usando o ultrapassado método da diluição para eliminar os resíduos das instalações, o que pode resultar na eutrofização de rios, riachos, lagos e lagoas. As lavagens diárias da sala de ordenha, da Unidade Educativa de Produção (UEP) de Bovinocultura de Leite da Escola Agrotécnica Federal de Inconfidentes -MG (EAFI/MG), gerou 4,7 vezes mais efluentes poluentes do que a produção de leite, entre os meses de junho de 2006 e maio de 2007. Uma unidade-piloto composta por lagoa anaeróbia, lagoa facultativa e leito cultivado (“constructed wetland”) foi projetada para testar a eficiência no tratamento do resíduo líquido gerado pela sala de ordenha. Após o tratamento do efluente bruto no sistema proposto, ficou constatado que a retenção média de fósforo foi de 83%; a redução de nitrato de 88%; a Demanda Química de Oxigênio (DQO) ficou reduzida, em média, 89%; os sólidos totais em 67% e a redução da turbidez, analisada somente no leito cultivado ficou, em média, em 60%. O pH médio das amostras foi de 6,2. Em se tratando de efluentes oriundos de confinamento de animais, pode-se afirmar que o resultado foi positivo, demonstrando que essa opção de sistema de tratamento tem grande potencial de aplicação.

Efeito da taxa de carregamento sobre a remoção de poluentes de esgoto em sistemas alagados construídos

Objetivou-se estudar o efeito da taxa de carregamento sobre a eficiência de sistemas alagados, construídos de escoamento horizontal subsuperficial (SAC-EHSS), em remover poluentes de esgoto sanitário. Os SAC-EHSS foram alimentados com efluente proveniente de tanque séptico, sob taxas de carregamento orgânico volumétrico (TCO V) de 53 a 231 g m-3d-1 de demanda química de oxigênio (DQO total) e as associadas taxas de carregamento (TC V) de demanda química de oxigênio solúvel, sólidos suspensos totais (SST), nitrogênio total (N-Total) e fósforo total (P-Total). Para avaliação de desempenho dos SAC-EHSS, as mesmas variáveis foram quantificadas em seu efluente. Relação linear e positiva foi obtida entre as taxas de remoção de DQO total, DQO solúvel e SST, e as TC V, nas faixas em que foram aplicadas, além de não terem sido observados efeitos negativos desta variável sobre a eficiência na remoção desses poluentes. As taxas de remoção de N-Total e P-Total não apresentaram, entretanto, tendência de aumento com a TC V aplicada nos SAC- EHSS, cultivados com taboa e utilizados no tratamento de efluente sanitário. As cargas aplicadas desses nutrientes devem ser consideradas referenciais no dimensionamento desses sistemas, caso se queira maximizar a remoção global de poluentes da água residuária.

Control of ammonia emissions in naturally ventilated dairy cattle facilities in Portugal

We conducted a study of the processes associated to NH3 emission in naturally ventilated dairy cattle facilities, having described factors that regulate NH3 emission, as well as methodologies for measuring these emissions at these facilities. Appropriate techniques to mitigate NH3 emission in facilities located in regions with warm climates were also identified. The most effective mitigation techniques with simple implementation include strategies associated to: (i) installation design and flooring, which lead to reduced emissions, (ii) excreta pre-excretion, namely the use of diets with optimized crude protein content and increased milk production at farm level; and (iii) excreta post-excretion, particularly by changing the conditions of environmental monitoring within the premises, practice introduction or additive application in the management of excreta deposited on floors.

Effect of a simulated heat wave in thermal and aerial environment broiler-rearing environment

ABSTRACT Global warming increases the occurrence of events such as extreme heat waves. Research on thermal and air conditions affecting broiler-rearing environment are important to evaluate the animal welfare under extreme heat aiming mitigation measures. This study aimed at evaluating the effect of a simulated heat wave, in a climatic chamber, on the thermal and air environment of 42-day-old broilers. One hundred and sixty broilers were housed and reared for 42 days in a climatic chamber; the animals were divided into eight pens. Heat wave simulation was performed on the 42nd day, the period of great impact and data sampling. The analyzed variables were room and litter temperatures, relative humidity, concentrations of oxygen, carbon monoxide and ammonia at each pen. These variables were assessed each two hours, starting at 8 am, simulating a day heating up to 4 pm, when it is reached the maximum temperature. By the results, we concluded that increasing room temperatures promoted a proportional raise in litter temperatures, contributing to ammonia volatilization. In addition, oxygen concentrations decreased with increasing temperatures; and the carbon monoxide was only observed at temperatures above 27.0 °C, relative humidity higher than 88.4% and litter temperatures superior to 30.3 °C.

HYDROPHOBIC MEMBRANE TECHNOLOGY FOR AMMONIA EXTRACTION FROM WASTEWATERS

ABSTRACT Total Ammoniacal Nitrogen - TAN (NH3 + NH4+) in wastewaters cause environmental degradation concerns due to their negative impacts on air, soil and water. Several technologies are available for TAN removal from the wastewaters. One emerging technology is the use of hydrophobic membrane as non-destructive NH3 extraction. In this paper the authors discuss the uses of gas permeable membrane (GPM) and its physicochemical characteristics that influence gas mass transfer rate, diffusion and recovery mechanisms of NH3 from liquid sources (e.g. animal wastewater). Several aspects of NH3 extraction from liquid manure and other TAN generation sources using GPM technology as well as its applicability for NH3 mitigation from liquid effluents and possible recovery as a nutrient for plant growth are also discussed in this review.

Testate amoebae (thecamoebians) as indicators of aquatic mine impact

The environmental impacts of a single mine often remain local, but acidic and metal-rich acid mine drainage (AMD) from the waste materials may pose a serious threat to adjacent surface waters and their ecosystems. Testate amoebae (thecamoebian) analysis was used together with lake sediment geochemistry to study and evaluate the ecological effects of sulphidic metal mines on aquatic environments. Three different mines were included in the study: Luikonlahti Cu-mine in Kaavi, eastern Finland, Haveri Cu-Au mine in Ylöjärvi, southern Finland and Pyhäsalmi Zn-Cu-S mine in Pyhäjärvi, central Finland. Luikonlahti and Haveri are closed mines, but Pyhäsalmi is still operating. The sampling strategy was case specific, and planned to provide a representative sediment sample series to define natural background conditions, to detect spatial and temporal variations in mine impacts, to evaluate the possible recovery after the peak contamination, and to distinguish the effects of other environmental factors from the mining impacts. In the Haveri case, diatom analyses were performed alongside thecamoebian analysis to evaluate the similarities and differences between the two proxies. The results of the analyses were investigated with multivariate methods (direct and indirect ordinations, diversity and distance measure indices). Finally, the results of each case study were harmonized, pooled, and jointly analyzed to summarize the results for this dissertation. Geochemical results showed broadly similar temporal patterns in each case. Concentrations of ions in the pre-disturbance samples defined the natural baseline against which other results were compared. The beginning of the mining activities had only minor impacts on sediment geochemistry, mainly appearing as an increased clastic input into the lakes at Haveri and Pyhäsalmi. The active mining phase was followed by the metallic contamination and, subsequently, by the most recent change towards decreased but still elevated metal concentrations in the sediments. Because of the delay in the oxidation of waste material and formation of AMD, the most intense, but transient metal contamination phase occurred in the post-mining period at Luikonlahti and Haveri. At Pyhäsalmi, the highest metal contamination preceded effluent mitigation actions. Spatial gradients were observed besides the temporal evolution in both the pre-disturbance and mine-impacted samples from Luikonlahti and Pyhäsalmi. The geochemical gradients varied with distance from the main source of contaminants (dispersion and dilution) and with water depth (redox and pH). The spatial extent of the highest metal contamination associated with these mines remained rather limited. At Haveri, the metallic impact was widespread, with the upstream site in another lake basin found to be contaminated. Changes in thecamoebian assemblages corresponded well with the geochemical results. Despite some differences, the general features and ecological responses of the faunal assemblages were rather similar in each lake. Constantly abundant strains of Difflugia oblonga, Difflugia protaeiformis and centropyxids formed the core of these assemblages. Increasing proportions of Cucurbitella tricuspis towards the surface samples were found in all of the cases. The results affirmed the indicator value of some already known indicator forms, but such as C. tricuspis and higher nutrient levels, but also elicited possible new ones such as D. oblonga ‘spinosa’ and clayey substrate, high conductivity and/or alkalinity, D. protaeiformis ‘multicornis’ and pH, water hardness and the amount of clastic material and Centropyxis constricta ‘aerophila’ and high metal and S concentrations. In each case, eutrophication appeared to be the most important environmental factor, masking the effects of other variables. Faunal responses to high metal inputs in sediments remained minor, but were nevertheless detectable. Besides the trophic state of the lake, numerical methods suggested overall geochemical conditions (pH, redox) to be the most important factor at Luikonlahti, whereas the Haveri results showed the clearest connection between metals and amoebae. At Pyhäsalmi, the strongest relationships were found between Ca- and S-rich present loading, redox conditions and substrate composition. Sediment geochemistry and testate amoeba analysis proved to be a suitable combination of methods to detect and describe the aquatic mine impacts in each specific case, to evaluate recovery and to differentiate between the effects of different anthropogenic and natural environmental factors. It was also suggested that aquatic mine impacts can be significantly mitigated by careful design and after-care of the waste facilities, especially by reducing and preventing AMD. The case-specific approach is nevertheless necessary because of the unique characteristics of each mine and variations in the environmental background conditions.

Active inverter output filtering methods

Frequency converters are widely used in the industry to enable better controllability and efficiency of variable speed AC motor drives. Despite these advantages, certain challenges concerning the inverter and motor interfacing have been present for decades. As insulated gate bipolar transistors entered the market, the inverter output voltage transition rate significantly increased compared with their predecessors. Inverters operate based on pulse width modulation of the output voltage, and the steep voltage edge fed by the inverter produces a motor terminal overvoltage. The overvoltage causes extra stress to the motor insulation, which may lead to a prematuremotor failure. The overvoltage is not generated by the inverter alone, but also by the sum effect of the motor cable length and the impedance mismatch between the cable and the motor. Many solutions have been shown to limit the overvoltage, and the mainstream products focus on passive filters. This doctoral thesis studies an alternative methodology for motor overvoltage reduction. The focus is on minimization of the passive filter dimensions, physical and electrical, or better yet, on operation without any filter. This is achieved by additional inverter control and modulation. The studied methods are implemented on different inverter topologies, varying in nominal voltage and current.For two-level inverters, the studied method is termed active du/dt. It consists of a small output LC filter, which is controlled by an independent modulator. The overvoltage is limited by a reduced voltage transition rate. For multilevel inverters, an overvoltage mitigation method operating without a passive filter, called edge modulation, is implemented. The method uses the capability of the inverter to produce two switching operations in the same direction to cancel the oscillating voltages of opposite phases. For parallel inverters, two methods are studied. They are both intended for two-level inverters, but the first uses individual motor cables from each inverter while the other topology applies output inductors. The overvoltage is reduced by interleaving the switching operations to produce a similar oscillation accumulation as with the edge modulation. The implementation of these methods is discussed in detail, and the necessary modifications to the control system of the inverter are presented. Each method is experimentally verified by operating industrial frequency converters with the modified control. All the methods are found feasible, and they provide sufficient overvoltage protection. The limitations and challenges brought about by the methods are discussed.

Enterprise applications migration to the cloud: risks and opportunities

Millions of enterprises move their applications to a cloud every year. According to Forrester Research “the global cloud computing market will grow from a $40.7 billion in 2011 to $241 billion in 2020”. Due to increased interests and demand broad range of providers and solutions have appeared in the market. It is vital to be able to predict possible problems correctly and to classify and mitigate risks associated with the migration process. The study will show the main criteria that should be taken into consideration while making decision of moving enterprise applications to the cloud and choosing appropriate vendor. The main goal of the research is to identify main problems during the migration to a cloud and propose a solution for their prevention and mitigation of consequences in case of occurrence. The research provides an overview of existing cloud solutions and deployment models for enterprise applications. It identifies decision drivers of an applications migration to a cloud and potential risks and benefits associated with this. Finally, the best practices for the successful enterprise-to-cloud migration based on the case studies analysis are formulated.

Managing business risk relating to pending patent applications – A comparison U.S. and European practices

This thesis presents different IPR risk mitigation actions as well as enforcement practices and evaluates their usability in different situations. The focus is on pending patent applications, where the right is not officially recognized or established yet, but some references are made to granted patents as well. The thesis presents the different aspects when assessing the risk level created by patents and pending applications. At all times it compares the patent law of the United States and European Patent Convention. Occasionally some references are made to national law, when the European Patent Convention cannot be applied. The thesis presents two case examples, which bring the risk mitigation actions and enforcement practices closer to practice.

Spatial multicriteria decision analysis for the siting of on-shore wind power in Kemiönsaari

Wind power is a low-carbon energy production form that reduces the dependence of society on fossil fuels. Finland has adopted wind energy production into its climate change mitigation policy, and that has lead to changes in legislation, guidelines, regional wind power areas allocation and establishing a feed-in tariff. Wind power production has indeed boosted in Finland after two decades of relatively slow growth, for instance from 2010 to 2011 wind energy production increased with 64 %, but there is still a long way to the national goal of 6 TWh by 2020. This thesis introduces a GIS-based decision-support methodology for the preliminary identification of suitable areas for wind energy production including estimation of their level of risk. The goal of this study was to define the least risky places for wind energy development within Kemiönsaari municipality in Southwest Finland. Spatial multicriteria decision analysis (SMCDA) has been used for searching suitable wind power areas along with many other location-allocation problems. SMCDA scrutinizes complex ill-structured decision problems in GIS environment using constraints and evaluation criteria, which are aggregated using weighted linear combination (WLC). Weights for the evaluation criteria were acquired using analytic hierarchy process (AHP) with nine expert interviews. Subsequently, feasible alternatives were ranked in order to provide a recommendation and finally, a sensitivity analysis was conducted for the determination of recommendation robustness. The first study aim was to scrutinize the suitability and necessity of existing data for this SMCDA study. Most of the available data sets were of sufficient resolution and quality. Input data necessity was evaluated qualitatively for each data set based on e.g. constraint coverage and attribute weights. Attribute quality was estimated mainly qualitatively by attribute comprehensiveness, operationality, measurability, completeness, decomposability, minimality and redundancy. The most significant quality issue was redundancy as interdependencies are not tolerated by WLC and AHP does not include measures to detect them. The third aim was to define the least risky areas for wind power development within the study area. The two highest ranking areas were Nordanå-Lövböle and Påvalsby followed by Helgeboda, Degerdal, Pungböle, Björkboda, and Östanå-Labböle. The fourth aim was to assess the recommendation reliability, and the top-ranking two areas proved robust whereas the other ones were more sensitive.

Long-term nutrient load management and lake restoration: Case of Säkylän Pyhäjärvi (SW Finland)

Eutrophication caused by anthropogenic nutrient pollution has become one of the most severe threats to water bodies. Nutrients enter water bodies from atmospheric precipitation, industrial and domestic wastewaters and surface runoff from agricultural and forest areas. As point pollution has been significantly reduced in developed countries in recent decades, agricultural non-point sources have been increasingly identified as the largest source of nutrient loading in water bodies. In this study, Lake Säkylän Pyhäjärvi and its catchment are studied as an example of a long-term, voluntary-based, co-operative model of lake and catchment management. Lake Pyhäjärvi is located in the centre of an intensive agricultural area in southwestern Finland. More than 20 professional fishermen operate in the lake area, and the lake is used as a drinking water source and for various recreational activities. Lake Pyhäjärvi is a good example of a large and shallow lake that suffers from eutrophication and is subject to measures to improve this undesired state under changing conditions. Climate change is one of the most important challenges faced by Lake Pyhäjärvi and other water bodies. The results show that climatic variation affects the amounts of runoff and nutrient loading and their timing during the year. The findings from the study area concerning warm winters and their influences on nutrient loading are in accordance with the IPCC scenarios of future climate change. In addition to nutrient reduction measures, the restoration of food chains (biomanipulation) is a key method in water quality management. The food-web structure in Lake Pyhäjärvi has, however, become disturbed due to mild winters, short ice cover and low fish catch. Ice cover that enables winter seining is extremely important to the water quality and ecosystem of Lake Pyhäjärvi, as the vendace stock is one of the key factors affecting the food web and the state of the lake. New methods for the reduction of nutrient loading and the treatment of runoff waters from agriculture, such as sand filters, were tested in field conditions. The results confirm that the filter technique is an applicable method for nutrient reduction, but further development is needed. The ability of sand filters to absorb nutrients can be improved with nutrient binding compounds, such as lime. Long-term hydrological, chemical and biological research and monitoring data on Lake Pyhäjärvi and its catchment provide a basis for water protection measures and improve our understanding of the complicated physical, chemical and biological interactions between the terrestrial and aquatic realms. In addition to measurements carried out in field conditions, Lake Pyhäjärvi and its catchment were studied using various modelling methods. In the calibration and validation of models, long-term and wide-ranging time series data proved to be valuable. Collaboration between researchers, modellers and local water managers further improves the reliability and usefulness of models. Lake Pyhäjärvi and its catchment can also be regarded as a good research laboratory from the point of view of the Baltic Sea. The main problem in both of them is eutrophication caused by excess nutrients, and nutrient loading has to be reduced – especially from agriculture. Mitigation measures are also similar in both cases.

Greenhouse gas emissions from peat and biomass-derived fuels, electricity and heat — Estimation of various production chains by using LCA methodology

More discussion is required on how and which types of biomass should be used to achieve a significant reduction in the carbon load released into the atmosphere in the short term. The energy sector is one of the largest greenhouse gas (GHG) emitters and thus its role in climate change mitigation is important. Replacing fossil fuels with biomass has been a simple way to reduce carbon emissions because the carbon bonded to biomass is considered as carbon neutral. With this in mind, this thesis has the following objectives: (1) to study the significance of the different GHG emission sources related to energy production from peat and biomass, (2) to explore opportunities to develop more climate friendly biomass energy options and (3) to discuss the importance of biogenic emissions of biomass systems. The discussion on biogenic carbon and other GHG emissions comprises four case studies of which two consider peat utilization, one forest biomass and one cultivated biomasses. Various different biomass types (peat, pine logs and forest residues, palm oil, rapeseed oil and jatropha oil) are used as examples to demonstrate the importance of biogenic carbon to life cycle GHG emissions. The biogenic carbon emissions of biomass are defined as the difference in the carbon stock between the utilization and the non-utilization scenarios of biomass. Forestry-drained peatlands were studied by using the high emission values of the peatland types in question to discuss the emission reduction potential of the peatlands. The results are presented in terms of global warming potential (GWP) values. Based on the results, the climate impact of the peat production can be reduced by selecting high-emission-level peatlands for peat production. The comparison of the two different types of forest biomass in integrated ethanol production in pulp mill shows that the type of forest biomass impacts the biogenic carbon emissions of biofuel production. The assessment of cultivated biomasses demonstrates that several selections made in the production chain significantly affect the GHG emissions of biofuels. The emissions caused by biofuel can exceed the emissions from fossil-based fuels in the short term if biomass is in part consumed in the process itself and does not end up in the final product. Including biogenic carbon and other land use carbon emissions into the carbon footprint calculations of biofuel reveals the importance of the time frame and of the efficiency of biomass carbon content utilization. As regards the climate impact of biomass energy use, the net impact on carbon stocks (in organic matter of soils and biomass), compared to the impact of the replaced energy source, is the key issue. Promoting renewable biomass regardless of biogenic GHG emissions can increase GHG emissions in the short term and also possibly in the long term.

Power semiconductor nonlinearities in active du/dt output filtering

This doctoral thesis introduces an improved control principle for active du/dt output filtering in variable-speed AC drives, together with performance comparisons with previous filtering methods. The effects of power semiconductor nonlinearities on the output filtering performance are investigated. The nonlinearities include the timing deviation and the voltage pulse waveform distortion in the variable-speed AC drive output bridge. Active du/dt output filtering (ADUDT) is a method to mitigate motor overvoltages in variable-speed AC drives with long motor cables. It is a quite recent addition to the du/dt reduction methods available. This thesis improves on the existing control method for the filter, and concentrates on the lowvoltage (below 1 kV AC) two-level voltage-source inverter implementation of the method. The ADUDT uses narrow voltage pulses having a duration in the order of a microsecond from an IGBT (insulated gate bipolar transistor) inverter to control the output voltage of a tuned LC filter circuit. The filter output voltage has thus increased slope transition times at the rising and falling edges, with an opportunity of no overshoot. The effect of the longer slope transition times is a reduction in the du/dt of the voltage fed to the motor cable. Lower du/dt values result in a reduction in the overvoltage effects on the motor terminals. Compared with traditional output filtering methods to accomplish this task, the active du/dt filtering provides lower inductance values and a smaller physical size of the filter itself. The filter circuit weight can also be reduced. However, the power semiconductor nonlinearities skew the filter control pulse pattern, resulting in control deviation. This deviation introduces unwanted overshoot and resonance in the filter. The controlmethod proposed in this thesis is able to directly compensate for the dead time-induced zero-current clamping (ZCC) effect in the pulse pattern. It gives more flexibility to the pattern structure, which could help in the timing deviation compensation design. Previous studies have shown that when a motor load current flows in the filter circuit and the inverter, the phase leg blanking times distort the voltage pulse sequence fed to the filter input. These blanking times are caused by excessively large dead time values between the IGBT control pulses. Moreover, the various switching timing distortions, present in realworld electronics when operating with a microsecond timescale, bring additional skew to the control. Left uncompensated, this results in distortion of the filter input voltage and a filter self-induced overvoltage in the form of an overshoot. This overshoot adds to the voltage appearing at the motor terminals, thus increasing the transient voltage amplitude at the motor. This doctoral thesis investigates the magnitude of such timing deviation effects. If the motor load current is left uncompensated in the control, the filter output voltage can overshoot up to double the input voltage amplitude. IGBT nonlinearities were observed to cause a smaller overshoot, in the order of 30%. This thesis introduces an improved ADUDT control method that is able to compensate for phase leg blanking times, giving flexibility to the pulse pattern structure and dead times. The control method is still sensitive to timing deviations, and their effect is investigated. A simple approach of using a fixed delay compensation value was tried in the test setup measurements. The ADUDT method with the new control algorithm was found to work in an actual motor drive application. Judging by the simulation results, with the delay compensation, the method should ultimately enable an output voltage performance and a du/dt reduction that are free from residual overshoot effects. The proposed control algorithm is not strictly required for successful ADUDT operation: It is possible to precalculate the pulse patterns by iteration and then for instance store them into a look-up table inside the control electronics. Rather, the newly developed control method is a mathematical tool for solving the ADUDT control pulses. It does not contain the timing deviation compensation (from the logic-level command to the phase leg output voltage), and as such is not able to remove the timing deviation effects that cause error and overshoot in the filter. When the timing deviation compensation has to be tuned-in in the control pattern, the precalculated iteration method could prove simpler and equally good (or even better) compared with the mathematical solution with a separate timing compensation module. One of the key findings in this thesis is the conclusion that the correctness of the pulse pattern structure, in the sense of ZCC and predicted pulse timings, cannot be separated from the timing deviations. The usefulness of the correctly calculated pattern is reduced by the voltage edge timing errors. The doctoral thesis provides an introductory background chapter on variable-speed AC drives and the problem of motor overvoltages and takes a look at traditional solutions for overvoltage mitigation. Previous results related to the active du/dt filtering are discussed. The basic operation principle and design of the filter have been studied previously. The effect of load current in the filter and the basic idea of compensation have been presented in the past. However, there was no direct way of including the dead time in the control (except for solving the pulse pattern manually by iteration), and the magnitude of nonlinearity effects had not been investigated. The enhanced control principle with the dead time handling capability and a case study of the test setup timing deviations are the main contributions of this doctoral thesis. The simulation and experimental setup results show that the proposed control method can be used in an actual drive. Loss measurements and a comparison of active du/dt output filtering with traditional output filtering methods are also presented in the work. Two different ADUDT filter designs are included, with ferrite core and air core inductors. Other filters included in the tests were a passive du/dtfilter and a passive sine filter. The loss measurements incorporated a silicon carbide diode-equipped IGBT module, and the results show lower losses with these new device technologies. The new control principle was measured in a 43 A load current motor drive system and was able to bring the filter output peak voltage from 980 V (the previous control principle) down to 680 V in a 540 V average DC link voltage variable-speed drive. A 200 m motor cable was used, and the filter losses for the active du/dt methods were 111W–126 W versus 184 W for the passive du/dt. In terms of inverter and filter losses, the active du/dt filtering method had a 1.82-fold increase in losses compared with an all-passive traditional du/dt output filter. The filter mass with the active du/dt method was 17% (2.4 kg, air-core inductors) compared with 14 kg of the passive du/dt method filter. Silicon carbide freewheeling diodes were found to reduce the inverter losses in the active du/dt filtering by 18% compared with the same IGBT module with silicon diodes. For a 200 m cable length, the average peak voltage at the motor terminals was 1050 V with no filter, 960 V for the all-passive du/dt filter, and 700 V for the active du/dt filtering applying the new control principle.

A família Lemnaceae Gray no Pantanal (Mato Grosso e Mato Grosso do Sul), Brasil

Realizou-se o levantamento de plantas aquáticas da família Lemnaceae no Pantanal do Mato Grosso e Mato Grosso do Sul, a qual está representada por nove espécies, distribuídas em quatro gêneros. Das espécies encontradas somente Wolffia brasiliensis Wedd. e Lemna valdiviana Phil. haviam sido registradas no Pantanal. As demais espécies são Spirodela intermedia W. Koch, Lemna aequinoctialis Welw., L. minuta Kunth, in Humb., Bonp. & Kunth, Wolffiella welwitschii (Hegelm.) Monod, W. lingulata (Hegelm.) Hegelm., W. oblonga (Phil.) Hegelm. e Wolffia columbiana H. Karst. As Lemnaceae ocorrem em todas as 10 sub-regiões do Pantanal, com o maior número de espécies na sub-região do Nabileque, de solos mais férteis.

Distribuição e quantificação de classes de vegetação do Pantanal através de levantamento aéreo

O método de levantamento aéreo foi adaptado e utilizado pela primeira vez para a elaboração de mapas de distribuição e quantificação de classes de vegetação no Pantanal Mato-Grossense por sub-região. Foram identificadas 16 classes, baseando-se em aspectos fitofisionômicos, sendo as principais campo (31,1%), cerradão (22,1%), cerrado (14,3%), brejos (7,4%), mata semidecídua (4,0%), mata de galeria e 2,4% de baceiro ou batume. Estas informações podem subsidiar a escolha de áreas de conservação ou preservação, bem como auxiliar o monitoramento de áreas com grande extensão e difícil acesso.