The emissions of nitrogen oxides (NOx) are a serious environmental problem due to its relationship with the formation of smog, acid rain and because they are dangerous for human and animal health. These gases are produced in high quantities in diesel engines used for automotive applications, and different strategies are being used to reduce them, among which are the Selective Catalytic Reduction (SCR) systems. For its operation, it is necessary a supply of ammonia as NOx reducing agent, but the inefficiency at low temperatures of the systems used nowadays has led to the conception of the solid ammonia storage units (ASS). Unfortunately, the materials currently used, i.e. metal halides, do not meet the ammonia supply requirements at low temperatures and have problems of swelling and agglomeration. In order to find a material with better properties for its application as an ammonia sorbent material, MgCl2 composites with different carbon materials (graphite, graphene, and SWCNTs) were prepared by direct mixing and wet impregnation methods, and characterized in this work. Despite the decrease of total storage capacity, improvements were found in thermal stability and mass retention, as well as in sorption and desorption kinetics, making these materials a first result towards the improvement of the solid ammonia storage units.

Este trabalho propõe uma metodologia para enumerar soluções, que indiquem a barra e a compensação de potência reativa necessária para o sistema elétrico sob análise, que atendam aos requisitos avaliados pela função objetivo e as restrições. Nessa alocação de compensação ótima de potência reativa, obtemos as melhores barras e configurações de potências e tecnologias de dispositivos de compensação, minimizando as perdas totais de potência ativa da rede. Em redes fracas com conversores de frequência (por exemplo, para conexão de fontes renováveis, ou interligações utilizando conversores HVDC), esta metodologia proposta busca a melhor relação de curto-circuito trifásico (SCR) no ponto de conexão do conversor de frequência, melhorando a conexão da barra de interesse. O método busca soluções para alocar um único dispositivo de compensação, e soluções alocando simultaneamente dois dispositivos. A metodologia proposta baseia-se na enumeração exaustiva das soluções, e o estudo de caso nos sistemas de 14 e 30 barras do IEEE mostrou a aplicabilidade e funcionalidade da metodologia proposta. / This work proposes a methodology to enumerate solutions, which indicate the bar and the reactive power compensation required for the electrical system under analysis, that meet the requirements evaluated by the objective function and the constraints. In this allocation of optimal compensation of reactive power, we obtain the optimal bars and technologies of compensation devices, minimizing the total losses of active power of the network. In weak networks with frequency converters (e.g. for connection of renewable sources, or interconnections using HVDC converters), the proposed methodology seeks the best threephase short-circuit (SCR) relation at the connection point, improving the connection of the new generation. The method looks for solutions to allocate a single compensation device, and solutions to allocate two devices simultaneously. The proposed methodology is based on the exhaustive enumeration of the solutions. A case study carried out in the IEEE 14 and 30 bus systems shows the applicability and performance of the proposed methodology.

A formal specification language used during the requirements phase can reduce errors and rework, but formal specifications are regarded as expensive to maintain, discouraging their adoption. This work presents a single-subject experiment that explores the costs of modifying specifications written in two different languages: a tabular notation, Software Cost Reduction (SCR), and a state-of-the-practice notation, Real-time Unified Modeling Language (UML). The study records the person-hours required to write each specification, the number of defects made during each specification effort, and the amount of time repairing these defects. Two different problems are specified&mdash;a Bidirectional Formatter (BDF), and a Bicycle Computer (BC)&mdash;to balance a learning effect from specifying the same problem twice with different specification languages. During the experiment, an updated feature for each problem is sent to the subject and each specification is modified to reflect the changes. <br /><br /> The results show that the cost to modify a specification are highly dependent on both the problem and the language used. There is no evidence that a tabular notation is easier to modify than a state-of-the-practice notation. <br /><br /> A side-effect of the experiment indicates there is a strong learning effect, independent of the language: in the BDF problem, the second time specifying the problem required more time, but resulted in a better-quality specification than the first time; in the BC problem, the second time specifying the problem required less time and resulted in the same quality specification as the first time. <br /><br /> This work demonstrates also that single-subject experiments can add important information to the growing body of empirical data about the use of formal requirements specifications in software development.

Samples of SCR catalysts were impregnated with the following alkali salts; KCl, K2SO4 and ZnCl2 at two different concentrations in a wet impregnation method. The activities of the six samples were measured in a test reactor and at different temperatures between 250-350 ºC. Compared to fresh catalyst, the impregnated samples all had lower activity. It seems like KCl is the most poisoning salt, depending on the lowest value of the activity. The experimental results are expected as compared to earlier articles, which reports that all alkali salts has deactivating effects on a catalyst and that KCl is among the most poisoning ones. By making a cross-section SEM analysis, the penetration of the metals at different depths in to the catalyst material wall was evaluated. An ICP-AES analysis was carried out in order to see the concentration of K and Zn of the test samples. Finally, the pore diameter and active surface was measured by BET method. Since the values of the active surface didn’t change compared to a fresh catalyst and the pore diameter was only slightly decreased we can suppose that the alkali salts deactivates the catalyst by coating of the catalyst pore structure and not as a pore blocking.

A formal specification language used during the requirements phase can reduce errors and rework, but formal specifications are regarded as expensive to maintain, discouraging their adoption. This work presents a single-subject experiment that explores the costs of modifying specifications written in two different languages: a tabular notation, Software Cost Reduction (SCR), and a state-of-the-practice notation, Real-time Unified Modeling Language (UML). The study records the person-hours required to write each specification, the number of defects made during each specification effort, and the amount of time repairing these defects. Two different problems are specified&mdash;a Bidirectional Formatter (BDF), and a Bicycle Computer (BC)&mdash;to balance a learning effect from specifying the same problem twice with different specification languages. During the experiment, an updated feature for each problem is sent to the subject and each specification is modified to reflect the changes. <br /><br /> The results show that the cost to modify a specification are highly dependent on both the problem and the language used. There is no evidence that a tabular notation is easier to modify than a state-of-the-practice notation. <br /><br /> A side-effect of the experiment indicates there is a strong learning effect, independent of the language: in the BDF problem, the second time specifying the problem required more time, but resulted in a better-quality specification than the first time; in the BC problem, the second time specifying the problem required less time and resulted in the same quality specification as the first time. <br /><br /> This work demonstrates also that single-subject experiments can add important information to the growing body of empirical data about the use of formal requirements specifications in software development.

In modern integrated circuits, electrostatic discharge (ESD) is a major problem that influences the reliability of operation, yield and cost of fabrication. ESD discharge events can generate static voltages beyond a few kilo volts. If these voltages are dissipated in the chip, high electric field and high current are generated and will destroy the gate oxide material or melt the metal interconnects. In order to protect the chip from these unexpected ESD events, special protection devices are designed and connect to each pin of the IC for this purpose. With the scaling of nano-metric processing technologies, the ESD design window has become more critical. That leaves little room for designers to maneuver. A good ESD protection device must have superior current sinking ability and also does not affect the normal operation of the IC. The two main categories of ESD devices are snapback and non-snapback ones. Non-snapback designs usually consist of forward biased diode strings with properties, such as low heat and power, high current carrying ability. Snapback devices use MOSFET and silicon controlled rectifier (SCR). They exploit avalanche breakdown to conduct current. In order to investigate the properties of various devices, they need to be modeled in device simulators. That process begins with realizing a technology specific NMOS and PMOS in the device simulators. The MOSFET process parameters are exported to build ESD structures. Then, by inserting ESD devices into different simulation test-benches, such as human-body model or charged-device model, their performance is evaluated through a series of figures of merit, which include peak current, voltage overshoot, capacitance, latch-up immunity and current dissipation time. A successful design can sink a large amount of current within an extremely short duration, while it should demonstrate a low voltage overshoot and capacitance. In this research work, an inter-weaving diode and SCR hybrid device demonstrated its effectiveness against tight ESD test standards is shown.

Two flow reactor studies, using an electrically heated laminar flow reactor over Vanadia based (V2O5-WO3/TiO2) honeycomb catalyst, were performed at 1 atm pressure and various temperatures. The experiments were conducted using simulated exhaust gas compositions for different exhaust gases. A quartz tube was used in order to establish inert conditions inside the reactor. The experiments utilized a Fourier transform infrared (FTIR) spectrometer in order to perform both qualitative and quantitative analysis of the reaction products. Urea-water solution decomposition was investigated over V2O5-WO3/TiO2 catalyst over the entire SCR temperature range using the temperature controlled flow reactor. The solution was preheated and then injected into pure nitrogen (N2) stream. The decomposition experiments were conducted with a number of oxygen (O2) compositions (0, 1, 10, and 15%) over the temperature range of 227oC to 477oC. The study showed ammonia (NH3), carbon-dioxide (CO2) and nitric oxide (NO) as the major products of decomposition along with other products such as nitrous oxide (N2O) and nitrogen dioxide (NO2). The selective catalytic reduction (SCR) of nitric oxide (NO) with urea-water solution over V2O5-WO3/TiO2 catalyst using a laboratory laminar-flow reactor was investigated. Urea-water solution was injected at a temperature higher than the vaporization temperature of water and the flow reactor temperature was varied from 127oC to 477oC. A FTIR spectrometer was used to determine the concentrations of the product species. The major products of SCR reduction were NH3, NO and CO2 along with the presence of other minor products NO2 and N2O. NO removal of up to 87% was observed. The aim of the urea-water decomposition experiments was to study the decomposition process as close to the SCR configuration as possible. The aim of the SCR experiments was to delineate the effect of various parameters including reaction temperature and O2 concentration on the reduction process. The SCR investigation showed that changing parameter values significantly affected the NO removal, the residual NH3 concentration, the temperature of the maximum NO reduction, and the temperature of complete NH3 conversion. In the presence of O2, the reaction temperature for maximum NO reduction was 377?C for ratio of 1.0.

In modern integrated circuits, electrostatic discharge (ESD) is a major problem that influences the reliability of operation, yield and cost of fabrication. ESD discharge events can generate static voltages beyond a few kilo volts. If these voltages are dissipated in the chip, high electric field and high current are generated and will destroy the gate oxide material or melt the metal interconnects. In order to protect the chip from these unexpected ESD events, special protection devices are designed and connect to each pin of the IC for this purpose. With the scaling of nano-metric processing technologies, the ESD design window has become more critical. That leaves little room for designers to maneuver. A good ESD protection device must have superior current sinking ability and also does not affect the normal operation of the IC. The two main categories of ESD devices are snapback and non-snapback ones. Non-snapback designs usually consist of forward biased diode strings with properties, such as low heat and power, high current carrying ability. Snapback devices use MOSFET and silicon controlled rectifier (SCR). They exploit avalanche breakdown to conduct current. In order to investigate the properties of various devices, they need to be modeled in device simulators. That process begins with realizing a technology specific NMOS and PMOS in the device simulators. The MOSFET process parameters are exported to build ESD structures. Then, by inserting ESD devices into different simulation test-benches, such as human-body model or charged-device model, their performance is evaluated through a series of figures of merit, which include peak current, voltage overshoot, capacitance, latch-up immunity and current dissipation time. A successful design can sink a large amount of current within an extremely short duration, while it should demonstrate a low voltage overshoot and capacitance. In this research work, an inter-weaving diode and SCR hybrid device demonstrated its effectiveness against tight ESD test standards is shown.

The reaction mechanism for the Selective Catalytic Reduction (SCR) of NO by NH3 on V2O5 surface was simulated by means of density functional theory (DFT) calculations performed at B3LYP/6-31G** level. As the initiation reaction, ammonia activation on V2O5 was investigated. Coordinate driving calculations showed that ammonia is adsorbed on Br&oslash / nsted acidic V-OH site as NH4 + species by a nonactivated process with a relative energy of -23.6kcal/mol. Vibration frequencies were calculated as 1421, 1650, 2857 and 2900cm-1 for the optimized geometry, in agreement with the experimental literature. Transition state with a relative energy of -17.1kcal/mol was also obtained. At the end of the Lewis acidic ammonia interaction calculations, it was observed that ammonia is hardly adsorbed on the surface. Therefore, it is concluded that the SCR reaction is initiated more favorably by the Br&oslash / nsted acidic ammonia adsorption. As the second step of the SCR reaction, NO interaction with the preadsorbed NH4 + species was investigated. Accordingly, NO interaction results in the formation of gas phase NH2NO molecule with a relative energy difference of 6.4kcal/mol. For the rest of the reaction sequence, gas phase decomposition of NH2NO was considered. Firstly, one of the hydrogen atoms of NH2NO migrates to oxygen. It then isomerizes in the second step. After that, the reaction proceeds with the isomerization of the other hydrogen. Finally, a second hydrogen atom migration to the oxygen leads to the formation of N2 and H2O. Total relative energy for this reaction series was obtained as -60.12kcal/mol, in agreement with the literature.

Realistic predictions of service life of steel catenary risers (SCR) require an accurate characterization of seafloor stiffness in the zone where the riser contacts the seafloor, the so- called touchdown area (TDA). This paper describes the key features of a seafloor-riser interaction model based on the previous experimental model tests. The seafloor is represented in terms of non-linear load-deflection (P-y) relationships, which are also able to account for soil stiffness degradation due to vertical cyclic loading. The P-y approach has some limitations, but simulations show good agreement with experimental data. Hence, stiffness degradation and rate effects during penetration and uplift motion (suction force increase) of the riser are well captured through comparison with previous experimental tests carried out at the Centre for Offshore Foundation Systems (COFS) and Norwegian Geotechnical Institute (NGI). The analytical framework considers the riser-seafloor interaction problem in terms of a pipe resting on a bed of springs, and requires the iterative solution of a fourth-order ordinary differential equation. A series of simulations is used to illustrate the capabilities of the model. Due to the non-linear soil springs with stiffness degradation it is possible to simulate the trench formation process and estimate deflections and moments along the riser length. The seabed model is used to perform parametric studies to assess the effects of stiffness, soil strength, amplitude of pipe displacements, and riser tension on pipe deflections and bending stresses. The input parameters include the material properties (usually pipe and soil), model parameters, and loading conditions such as the amplitude of imposed dis- placements, tension, and moment. Primary outputs from this model include the deflected shape of the riser pipe and bending moments along riser length. The code also provides the location of maximum trench depth and the position where the maximum bending moment occurs and any point where user is interested in.