Top PDF On the influence of chemical kinetics on the combustion of fuels

n is the order of the overall reaction rate. Therefore, at high pressure burnine rates have large values and they are close lo their asymptotic values obtained by taking an infinitely fast reaction rate. This assumption of taking an infinitely fast reaction rate disregards chemical kinetics, and therefore, this might explain why chemical kinetics could be of secondary importance m the combustion processes of Diesel I want also to point out one of the main conclusions of the paper in connection with the influence of chemical kinetics. When the droplets are small, or at low pressure, they do not sustain individual flames but they evaporate together within a common flame. This is due to the influence of chemical kinetics and such in- fluence has been theoretically obtained and it has also been experimentally verified by observing spray combustion.

It is known that one of the most important objects relating nature and mankind is fire. Broadly speaking there are two types of fire, flaming and smoldering fires. Flaming fires involve the rapid oxidation of a fuel with associated flame, heat, and light. The flame itself occurs within a region of gas where intense exothermic reactions are taking place. An exothermic reaction is a chemical reaction that takes place within a substance whereby heat and energy are released as the substance change to a simpler chemical form. As chemical reaction occur within the fuel being burned, light is usu- ally emitted as photons are released by the oxidation of the fuel. Depending upon the specific chemical and physical change taking place within the fuel the flame may or may not emit light. The visible flame has no mass; what it is seen as visible flame is actually energy (photons) being released in the form of light by the oxidation of the fuel. The color of the flame is dependent upon the energy level of the photons emitted. Lower energy levels produce colors toward the red end of the light spectrum while higher energy levels produce colors toward the blue end of the spectrum. The hottest flames are white in appearance. A smoldering fire is a flameless form of combustion, deriving its heat from oxidation occurring in the surface of a solid fuel.

Transport processes and chemical reactions were implemented using a two-steps sequential split- operator scheme [15]. In the first step, the transport equation system (accounting for diffusion, electromigration and electroosmosis and the water electrolysis reactions at the electrode, under electroneutrality conditions) is numerically integrated by means of a finite element method. In the second step, the chemical reactions are calculated. The aqueous formation of complexes, precipitation and dissolution reactions were calculated using the PHREEQC code. For brevity, the reaction equations are not reported here, as they can be found in Parkhurst and Appelo, 1999 [16].

The results presented in [13] showed that in narrow channels, for mixtures with Lewis num- ber smaller than one, symmetric and non-symmetric solutions may co-exist for the same set of parameters. It was demonstrated by means of global stability analysis that when this is the case, the non-symmetric solution is stable while the symmetric solution is usually unstable. This effect of symmetry breaking was first demonstrated in the context of a constant density (diffusive-thermal) model and using a global one-step Arrhenius kinetics with a single reac- tant characterized by a constant Lewis number, so that it could be unmistakably linked to the diffusive-thermal instability [4, 13–16]. A similar effect was reported in [11], based on the com- plete Navier-Stokes equations in isothermal and appreciably wider ducts. These results have been validated recently within a more realistic direct simulation model including the detailed chemical kinetics and transport for lean hydrogen-air flames propagating in adiabatic channels and channels with heat losses [20, 21].

The definition of the term creativity is complex that is why the idea of developing it in students could be considered complicated. Nevertheless, the attempts of definition there are related it with the concept of bilingualism which has been linked to the ability to speak two different languages. According to Riotta (2015) “People who learn to speak more than one language throughout their lives have essentially trained their brains to be stronger muscles, making them smarter and more creative”. As a consequence, it is possible to say that creativity can be increased by managing two or more languages if we consider creativity as a way of forming new ideas different from the conventional ones, in addition Ghonsooly and Showqi (2012) stated that “mastering a foreign language in a classroom context dramatically increases the four components of divergent thinking (fluency, elaboration, originality and flexibility)”

Understanding the frame as an interactive process of social articulation through a shared discourse in specific contexts allows the addressing of sub- jects that are of public interest from two facets: as an expression of interpre- tative schemes and as a symbolic construction process, where the type of par- ticipation plays a fundamental role in the individual cognitive effects (Gam - son and Modigliani, 1989; Gamson et al., 1992). From this perspective, this type of study using frames can contribute to the pondering on the influence of the new processes of production and consumption of information on cu - rrent affairs; about the effects of the social networks on the quality of pu blic debate, and about the transformation that the new arenas for deliberation introduce in the political and media spheres.

One very important environmental influence in the child’s cognitive develop- ment is the parents’level of education. Parents with a higher education create a more intellectually stimulating environment for their children (Hoff, 2003a, 2003b). It has been demonstrated that highly educated parents (professionals) have a different way of interaction with their children particularly in respect to their language used (Hoff, Laursen, & Tardif, 2002). College-educated mothers talk more, use a richer vocabu- lary, and read more to their children than those mothers limited to a high school edu- cation (Hoff-Ginsberg, 1991). Parents’s educational level has also been related to children’s school attendance and general cognitive development (e.g., Ganzach, 2000; Teachman, 1987; White, 1982). Children from parents with higher education tend to have a larger vocabulary, more rapid language development, better perfor- mance in cognitive tests, and higher school attendance. Portes, Cuentas, and Zady (2000) assessed the relation of parent–child interaction to children’s intellectual achievement. The results demonstrated that although interaction characteristics are related to children’s intellectual achievement, that relation is moderated by context factors that may vary in each culture. Some differences in educational systems among different countries have to be considered. Further, the association between parents’ education and private versus public schools may vary across countries.

Regarding the apparent contradiction in the amount of NiO formed when comparing gravimetric (Fig. 3) and crystallographic (Fig. 7) results, we propose that the differences are related to the formation of nanocrystalline material, with characteristics lengths below 3 nm. An estimation of its relative quantity can be provided by the samples oxidized during 300–600 s (Fig. 7a): by XRD the amounts of NiO grown from small (Ni–WOP) and large Ni(111) CS (Ni–WP) were approximately 12 vs. 18 cps deg, respectively. Considering that the oxygen uptake is similar within each oxida- tion condition, we can conclude that the differences given by XRD correspond to the differences in relative amount of nanocrys- talline NiO material, i.e. 50%. This hypothesis concerning the for- mation of nanocrystallite oxide and its relation to the initial Ni substrate can be also extended to the samples that displayed sim- ilar amounts of crystalline oxide formed (Fig. 7a, 60–180 s). On the one hand, according to RS (Fig. 7b) the crystallinity is enhanced in the oxides grown from improved Ni CS layers. On the other hand, the electrical characterizations showed that the current density values differ much depending on the initial Ni substrate (Fig. 8a, 60 s), which we propose to be a consequence of the amount of grain boundaries present in the oxide films: higher current densi- ties (meaning lower resistance) would correspond to a lower amount of NiO grains in series as compared to oxide formed by a larger amount of nanocrystalline oxide. In the same way, R sheet

A great variety of products are available to improve the moisture damage resistance of the mixtures. These products include the use of mineral fillers (mineral powders with physical size passing the 0.063 mm sieve) which have a decisive influence on the adhesion between the aggregate and the binder for two reasons [15]. The first reason is that the mineral filler fill the voids in the bituminous mixtures, thereby preventing water entry. The second reason is that several mineral fillers exhibit a better chemical affinity with the bitumen than with the aggregate. In this regard, some authors indicate that the use of Portland cement as filler leads to an improvement in the water resistance of the mixture [8, 16]. Other authors stated that using fly ash as mineral filler also improves the water resistance of HMA [5, 16]. Nevertheless, hydrated lime is the most used anti-stripping agent, generally in percentages of 1% to 2% by dry weight of the aggregate [3, 5, 16-17].

cooling down to 37°C, the rheological parameters remain higher than after direct dissolution at low temperature in relation with the temperature range for clear gel stability. The change in the behaviour of methylcellulose is also clearly shown by DSC as presented in figure 6; on heating, the phase transition has a peak at 59.5°C (formation of the turbid gel corresponding to a large increase in G’) and on cooling the peak occurs at 31.7°C (gel-sol transition). The temperature of 37°C is still in the range of the clear gel.

Basically, the target of synthesizing was the creation of the same three sets of notes as recorded sounds. Of course the envelope curves of partials should be same for all three sets for each note. The first step of synthesizing was generation of sinusoidal waves. All waves were made to have the frequencies that were seen in the recording and analyzing process. Each wave was matched to an envelope curve as its partial number and the envelope curve was multiplied to the matched sinusoidal wave.

conditions of female journalists are analyzed, it can be seen that 62.5% of those hired earn less than €1000, as compared to 46.4% of men. A glass ceiling also exists, which serves as a barrier to executive positions; only 15.9% of these positions are held by women, a percentage which has held steady over time since before the crisis (Caro-González, García-Gordillo, Rodríguez-Rad & Jiménez-Marín, 2007). In this context, one third of the journalists indicate that they have been forced to do freelance work (Palacio, 2015). It would appear that most of these freelancers are women, as the precarious labor conditions are an incentive for self-employment (Dyer, 1994). Creating their own business would allow them to break through the glass ceiling, accessing more equal pay and executive positions in the organizations. However, the aforementioned report from the Madrid Press Association (Palacio, 2015) indicates that only 40.3% of freelance workers are women. This figure does not seem to make sense if we take into consideration that between 2011 and 2014 a total of 15,807 journalists earned their degrees in Spain, of whom more than 65% are women. This information is in line with the data from the GEM (Global Entrepreneurship Monitor) report for Spain (Peña et al., 2016, pp. 126), where 58.5% of the new and fledgling entrepreneurs are men.

Recently, Y. Shen, et al., studied the effect of several degrees of cyclic fatigue on torsional fracture and tor- sional preload on K3 and K3XF heat treated instru- ments. The fatigue behavior of the NiTi instruments was tested with the rotary instruments immersed in an aqueous medium. Therefore, to determine the resistance to cyclic fatigue, new instruments 25/04 K3XF and K3 (n = 15 for each group) were used in an apparatus for folding in 3 points, with a radius of 7 mm and a curvature of 45 degrees in deionized water. To evaluate the effect of cyclic fatigue on torsion, cyclic preloads were performed in the files under 4 condi- tions. 15 new instruments from each group were exposed to 0%, 25%, 50% and 75% of their respective average of number of revolutions to fracture (Nf). Among the obtained results in the cyclic fatigue test, the average number of rotations to the fracture of K3XF without torsional preload was 2 times more than Nf of K3 under similar conditions.

The objective of this exercise, which focuses on regional variants from Argentina, is for students to practice circumlocution in the form of a definition or paraphrase. To complete the exercise in (17), students will work in pairs. The materials needed are a set of cards with the items depicted, labeled with the Argentinean lexical variant, and an- other set with only the Argentinean term, without any picture. Students should receive have of each, and take turns in the exchange of information. As the student who only has the lexical item written in his/her card ask about the meaning of this word, his/her partner should produce explanations and definitions that will allow them to make the connection between the neutral terms and the dialectally marked ones. Once the stu- dent understands the term, s/he is to give the neutral term.

The following parameters determine the trans ition point in. tho Hart's sphere of influenoe and the velooity of the probe[r]

The aim of the present study is to determine the influence of the position of the collecting channels on intraocular pressure and its contribution to the development of glaucoma. Numerical simulations were performed using the finite element method for two case studies. The first case is a simplified model of rectangular section that simulates the flow between two collecting channels. The second model describes flow throughout the Schlemm channel (CS), considering that it is a rigid ring of constant thickness, with four distributions of the collector channels. The pres- sure and velocity profiles are shown for both cases. In the simplified case, there are differences of 10 Pa between the average pressures. The second model shows that the symmetric arrangement has a constant pressure distribution while the asymmetric cases have variations of 2 Pa. The results confirm that the position of the collecting channels influences the intraocular pressure. This study shows that a transient analysis is needed to understand the whole process, considering the elastic properties of the CS as well as the variations of diameter of the collecting channels.

As a result, most of them think that they will not need university studies to promote in their jobs. It is logical that they decide to give up university when they find a job, if they believe that these studies will not be necessary in the future. Nevertheless, stands out that 10% more of current students believe that will not need studies to promote. The reason is that they answered in reference to those jobs they have done until now, jobs that are not related with what they want to do in the future when they obtain the academic title. However, it will depend on the personal ambition of each one because if somebody aspires to be an important manager or to have an important position in a company, university titles are normally required.

Today, it is clear that language cannot be considered in isolation from the person who uses it as a means of communication, the implementation of cognitive processes, in isolation from the national community, within which a specific national language system has been formed, in isolation from the historical, natural and environmental context in which the national language systems were being established. In modern scientific literature, the provision that the language is always nationally labeled is not in doubt. Researchers emphasize that the formation of the national language system is influenced by the history of the nation, its environment, peculiarities of the national mentality, worldview and world understanding. At the same time, up to the present day, numerous aspects of the world language picture, its interrelations with the natural and social context in which it is formed, remain poorly studied and studied in fragments. In particular, to date, it is not entirely clear how the environment affects the formation of the national language picture of the world, which means the environment for representatives of a particular linguistic culture, what associations causes the concept in the minds of individuals. Meanwhile, taking into account the great importance of the environment for the life of the nation, the understanding of the content of the concept in the minds of representatives of a certain linguistic culture will allow to better understand the features of the national picture of the world as such, to identify patterns and mechanisms of interaction between the environment and the national worldview, which determines the relevance of the chosen theme of the study. The aim of the research is to study the influence of the environment on the formation of the national language picture of the world.

3.1. Fuel Cell Fundamentals. Among the most interesting alternative propulsion systems for UAVs are those based on fuel cells. It is still an immature but growing technology, with room for improvement in weight, volume, and cost reduction. Fuel cells are electrochemical systems that convert the chem- ical energy contained in fuels directly into electric energy. When fed with hydrogen, they produce no greenhouse gases, the only products being water and heat, and the level of noise generation by the engine is low. Water, as well as heat and low oxygen-containing exhaust air, is side product of the fuel cell that could have other applications to compensate the weight disadvantages (particularly in large UAVs), such as water supply for other subsystems, deicing, or inerting of a fossil fuel tank [18]. Unlike batteries, a fuel cell does not need to be recharged; it keeps operating while fuel and oxidizer are supplied from the outside. The fuel cell itself consists of an anode where fuel is injected (usually hydrogen, ammonia, or methanol) and a cathode where an oxidant is introduced (usually air or oxygen), separated by an electrolyte ionic conductor [29]. Usually, fuel cells produce low voltages and must be assembled into a fuel cell stack in order to reach the power required for most UAV applications. Since fuel cells are by their nature modular devices, their power can go from microwatts to megawatts, making them useful in a variety of applications.

Another suffix used to create non recorded adjectives is -al, which is normally added to mean group as in instrumental, meaning group of instruments (Gómez, 2002:23). This suffix can also indicate relationship or ownership according to the DRAE, 2001. In the corpus the second meaning of the suffix is the one recognized in the adjective atencional (e.g. “Asimismo, se investigan la integración perceptiva en el tiempo debida a la atención, la evolución diacrónica del sesgo atencional o la naturaleza de la orientación atencional en el tiempo…”). Similarly, in the previously unattested adjective comportamental, the meaning of the suffix implying group is not recognized (“Entonces y tal como señalábamos en la introducción las personas liberales son más erotofílicas y las conservadoras más erotofóbicas, aunque esto no tenga porque ser siempre así, dado que los componentes de las actitudes (cognoscitivo, afectivo y comportamental)…”). Thus, taking the example into account the adjective comportamental seems to be a loan translation of the English term behavioral rather than to only a case of derivation.