785 resultados para engine performance


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Compression ignition (CI) engine design is subject to many constraints which presents a multi-criteria optimisation problem that the engine researcher must solve. In particular, the modern CI engine must not only be efficient, but must also deliver low gaseous, particulate and life cycle greenhouse gas emissions so that its impact on urban air quality, human health, and global warming are minimised. Consequently, this study undertakes a multi-criteria analysis which seeks to identify alternative fuels, injection technologies and combustion strategies that could potentially satisfy these CI engine design constraints. Three datasets are analysed with the Preference Ranking Organization Method for Enrichment Evaluations and Geometrical Analysis for Interactive Aid (PROMETHEE-GAIA) algorithm to explore the impact of 1): an ethanol fumigation system, 2): alternative fuels (20 % biodiesel and synthetic diesel) and alternative injection technologies (mechanical direct injection and common rail injection), and 3): various biodiesel fuels made from 3 feedstocks (i.e. soy, tallow, and canola) tested at several blend percentages (20-100 %) on the resulting emissions and efficiency profile of the various test engines. The results show that moderate ethanol substitutions (~20 % by energy) at moderate load, high percentage soy blends (60-100 %), and alternative fuels (biodiesel and synthetic diesel) provide an efficiency and emissions profile that yields the most “preferred” solutions to this multi-criteria engine design problem. Further research is, however, required to reduce Reactive Oxygen Species (ROS) emissions with alternative fuels, and to deliver technologies that do not significantly reduce the median diameter of particle emissions.

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The effects of ethanol fumigation on the inter-cycle variability of key in-cylinder pressure parameters in a modern common rail diesel engine have been investigated. Specifically, maximum rate of pressure rise, peak pressure, peak pressure timing and ignition delay were investigated. A new methodology for investigating the start of combustion was also proposed and demonstrated—which is particularly useful with noisy in-cylinder pressure data as it can have a significant effect on the calculation of an accurate net rate of heat release indicator diagram. Inter-cycle variability has been traditionally investigated using the coefficient of variation. However, deeper insight into engine operation is given by presenting the results as kernel density estimates; hence, allowing investigation of otherwise unnoticed phenomena, including: multi-modal and skewed behaviour. This study has found that operation of a common rail diesel engine with high ethanol substitutions (>20% at full load, >30% at three quarter load) results in a significant reduction in ignition delay. Further, this study also concluded that if the engine is operated with absolute air to fuel ratios (mole basis) less than 80, the inter-cycle variability is substantially increased compared to normal operation.

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In this paper, we present how a thin RF sputtered layer of lanthanum oxide (La2O3) can alter electrical and improve hydrogen gas sensing characteristics of Pt/molybdenum oxide (MoO3) nanostructures Schottky diodes. We derived the barrier height, ideality factor and dielectric constant from the measured I–V characteristics at operating temperatures in the range of 25–300 ◦C. The dynamic response, response and recovery times were obtained upon exposure to hydrogen gas at different concentrations. Analysis of the results indicated a substantial improvement to the voltage shift sensitivity of the sensors incorporating the La2O3 layer. We associate this enhancement to the formation of numerous trap states due to the presence of the La2O3 thin film on the MoO3 nanoplatelets. These trap states increase the intensity of the dipolar charges at the metal–semiconductor interface, which induce greater bending of the energy bands. However, results also indicate that the presence of La2O3 trap states also increases response and recover times as electrons trapping and de-trapping processes occur before they can pass through this thin dielectric layer.

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This study investigated the influence of interpersonal coordination tendencies on performance outcomes of 1-vs-1 subphases in youth soccer. Eight male developing soccer players (age: 11.8+0.4 years; training experience: 3.6+1.1 years) performed an in situ simulation of a 1-vs-1 sub-phase of soccer. Data from 82 trials were obtained with motion-analysis techniques, and relative phase used to measure the space-time coordination tendencies of attacker-defender dyads. Approximate entropy (ApEn) was then used to quantify the unpredictability of interpersonal interactions over trials. Results revealed how different modes of interpersonal coordination emerging from attacker-defender dyads influenced the 1-vs-1 performance outcomes. High levels of space-time synchronisation (47%) and unpredictability in interpersonal coordination processes (ApEn: 0.91+0.34) were identified as key features of an attacking player’s success. A lead-lag relation attributed to a defending player (34% around 7308 values) and a more predictable coordination mode (ApEn: 0.65+0.27, P50.001), demonstrated the coordination tendencies underlying the success of defending players in 1-vs-1 sub-phases. These findings revealed how the mutual influence of each player on the behaviour of dyadic systems shaped emergent performance outcomes. More specifically, the findings showed that attacking players should be constrained to exploit the space-time synchrony with defenders in an unpredictable and creative way, while defenders should be encouraged to adopt postures and behaviours that actively constrain the attacker’s actions.

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The purpose of this study was to test a model of the relationship between temperament, character and job performance, in order to better understand the cause of stable individual differences in job performance. Personality was conceptualized in terms of Cloninger, Svrakic and Przybeck’s (1993) theoretical framework of personality. It was expected that Self Directedness (character) would mediate Harm Avoidance and Persistence (temperament) in the prediction of job performance. In order to test the hypotheses, a sample of 94 employee/supervisor pairs was recruited from several organizations across Australia. Participants completed a number of questionnaires online, regarding their personality traits (completed by employees) and Job Performance (completed by Supervisors). Consistent with the hypothesis, Self Directedness was found to be a moderate, direct predictor of job performance. Also consistent with the hypothesis, Self Directedness mediated Harm Avoidance in the prediction of job performance. Results show that character (Self Directedness) is important in the prediction of job performance, and also suggests that fearful, avoidant individuals are less likely to perform well in the workplace, based on their low level of character development.

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The well-known power system stabilizer (PSS) is used to generate supplementary control signals for the excitation system of a generator so as to damp low frequency oscillations in the power system concerned. Up to now, various kinds of PSS design methods have been proposed and some of them applied in actual power systems with different degrees. Given this background, the small-disturbance eigenvalue analysis and large-disturbance dynamic simulations in the time domain are carried out to evaluate the performances of four different PSS design methods, including the Conventional PSS (CPSS), Single-Neuron PSS (SNPSS), Adaptive PSS (APSS) and Multi-band PSS (MBPSS). To make the comparisons equitable, the parameters of the four kinds of PSSs are all determined by the steepest descent method. Finally, an 8-unit 24-bus power system is employed to demonstrate the performances of the four kinds of PSSs by the well-established eigenvalue analysis as well as numerous digital simulations, and some useful conclusions obtained.

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Dynamic capabilities are widely considered to incorporate those processes that enable organizations to sustain superior performance over time. In this paper, we argue theoretically and demonstrate empirically that these effects are contingent on organizational structure and the competitive intensity in the market. Results from partial least square structural equation modeling (PLS-SEM) analyses indicate that organic organizational structures facilitate the impact of dynamic capabilities on organizational performance. Furthermore, we find that the performance effects of dynamic capabilities are contingent on the competitive intensity faced by firms. Our findings demonstrate the performance effects of internal alignment between organizational structure and dynamic capabilities, as well as the external fit of dynamic capabilities with competitive intensity. We outline the advantages of PLS-SEM for modeling latent constructs, such as dynamic capabilities, and conclude with managerial implications.

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As the Indonesian construction industry is now promising to become the engine of national economic development, achieving quality and higher performance, not only domestically but also in the international market, are becoming crucial issues. Implementing quality management systems (QMSs) based on ISO 9001 are important in helping Indonesian construction companies become more competitive, for it is acknowledged that quality in construction is a major concern in the global construction industry. However, the possession of ISO 9001 certification does not reflect the presence of a well-operated QMS, which is capable of giving customer and project end-users satisfaction. The review of literature found that there is a significant correlation between a company.s organisational culture and the quality performance of contractors. While research into this area has involved many researchers, there is no critical mass of information specifically related to the Indonesian situation. Studies based on contemporary perspectives of the characteristics of the Indonesian construction organisational culture using Cameron and Quinn.s Organizational Culture Assessment Instrument (OCAI) and its relationship with the contractor.s ISO 9001 practices, have not been previously undertaken. This thesis research, therefore, investigated the culture profiles in Indonesian construction organisations, together with the current implementation of ISO 9001 and their performance during implementing QMSs, as information in these areas has a bearing on the poor performance and low levels of competitiveness of Indonesian construction companies. Questionnaire surveys were distributed to selected representative grade 7 civil engineering contractors located in the two provincial capitals of Makassar and Manado, and the national capital, Jakarta, in order to collect responses designed to examine the effectiveness of their QMSs implementation. The survey also aimed to identify current problems within the systems, and examine the performance of companies while implementing their QMSs. The questionnaire contained questions to assess the organisational culture profiles of Indonesian construction companies, adopting the OCAI. The survey results were then used to analyse the influence of different organisational culture profiles on QMSs implementation among respondent companies. The results from the questionnaire survey supported the development of a Culture-based Quality Management System Improvement Implementation Framework, designed to help Indonesian construction companies identify some typical barriers associated with impacting on effective QMSs implementation; to assist them to develop cultural values that can drive effective QMSs implementation; to undertake effective QMSs practices; and to recognise the potential results and longer-term benefits obtainable from implementing effective QMSs. A Focus Group Discussion was conducted with the assistance of a panel of professional construction practitioners, policy makers and academic experts, which further considered and validated the usefulness and applicability of the framework. Based on the outcome from this discussion and on the results of the earlier data analysis, a final version of the framework was developed to assist Indonesian construction companies in improving their capability of construction project delivery, and thereby contribute to providing or improving the competitive advantage of Indonesian construction companies in the local, national and global construction market.

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Increasing awareness of the benefits of stimulating entrepreneurial behaviour in small and medium enterprises has fostered strong interest in innovation programs. Recently many western countries have invested in design innovation for better firm performance. This research presents some early findings from a study of companies that participated in a holistic approach to design innovation, where the outcomes include better business performance and better market positioning in global markets. Preliminary findings from in-depth semi-structured interviews indicate the importance of firm openness to new ways of working and to developing new processes of strategic entrepreneurship. Implications for theory and practice are discussed.

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Debate about the relationships between business planning and performance has been active for decades (Bhidé, 2000; Mintzberg, 1994). While results have been inconclusive, this topic still strongly divides the research community (Brinckmann et al., 2010; Chwolka & Raith, 2011; Delmar & Shane, 2004; Frese, 2009; Gruber, 2007; Honig & Karlsson, 2004). Previous research explored the relationships between innovation and the venture creation process (Amason et al., 2006, Dewar & Dutton, 1986; Jennings et al., 2009). However, the relationships between business planning and innovation have mostly been invoked indirectly in the strategy and entrepreneurship literatures through the notion of uncertainty surrounding the development of innovation. Some posited that planning may be irrelevant due to the iterative process, the numerous changes innovation development entails and the need to be flexible (Brews & Hunt, 1999). Others suggested that planning may facilitate the achievement of goals and overcoming of obstacles (Locke and Latham, 2000), guide the venture in its allocation of resources (Delmar and Shane, 2003) and help to foster the communication about the innovation being developed (Liao & Welsh, 2008). However, the nature and extents of the relationships between business planning, innovation and performance are still largely unknown. Moreover, if the reasons why ventures should engage (Frese, 2009) –or not- (Honig, 2004) in business planning have been investigated quite extensively (Brinckmann et al., 2010), the specific value of business planning for nascent firms developing innovation is still unclear. The objective of this paper is to shed some light on these important aspects by investigating the two following questions on a large sample of random nascent firms: 1) how is business planning use over time by new ventures developing different types and degrees of innovation? 2) how do business planning and innovation impact the performance of the nascent firms? Methods & Key propositions This PSED-type study draws its data from the first three waves of the CAUSEE project where 30,105 Australian households were randomly contacted by phone using a methodology to capture emerging firms (Davidsson, Steffens, Gordon, Reynolds, 2008). This screening led to the identification of 594 nascent ventures (i.e., firms that were not operating yet at the time of the identification) that were willing to participate in the study. Comprehensive phone interviews were conducted with these 594 ventures. Likewise, two comprehensive follow-ups were organised 12 months and 24 months later where 80% of the eligible cases of the previous wave completed the interview. The questionnaire contains specific sections investigating business plans such as: presence or absence, degree of formality and updates of the plan. Four types of innovation are measured along three degrees of intensity to produce a comprehensive continuous measure ranging from 0 to 12 (Dahlqvist & Wiklund, 2011). Other sections informing on the gestation activities, industry and different types of experiences will be used as controls to measure the relationships and the impacts of business planning and innovation on the performance of nascent firms overtime. Results from two rounds of pre-testing informed the design of the instrument included in the main survey. The three waves of data are used to first test and compare the use of planning amongst nascent firms by their degrees of innovation and then to examine their impact on performance overtime through regression analyses. Results and Implications Three waves of data collection have been completed. Preliminary results show that on average, innovative firms are more likely to have a business plans than their low innovative counterpart. They are also most likely to update their plan suggesting a more continuous use of the plan over time than previously thought. Further analyses regarding the relationships between business planning, innovation and performance are undergoing. This paper is expected to contribute to the literature on business planning and innovation by measuring quantitatively their impact on nascent firms activities and performance at different stages of their development. In addition, this study will shed a new light on the business planning-performance relationship by disentangling plans, types of nascent firms regarding their innovation degres and their performance over time. Finally, we expect to increase the understanding of the venture creation process by analysing those questions on nascent firms from a large longitudinal sample of randomly selected ventures. We acknowledge the results from this study will be preliminary and will have to be interpreted with caution as the business planning-performance is not a straightforward relationship (Brinckmann et al., 2010). Meanwhile, we believe that this study is important to the field of entrepreneurship as it provides some much needed insights on the processes used by nascent firms during their creation and early operating stages.

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This paper presents material and gas sensing properties of Pt/SnO2 nanowires/SiC metal oxide semiconductor devices towards hydrogen. The SnO2 nanowires were deposited onto the SiC substrates by vapour-liquid-solid growth mechanism. The material properties of the sensors were investigated using scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The current-voltage characteristics have been analysed. The effective change in the barrier height for 1% hydrogen was found to be 142.91 meV. The dynamic response of the sensors towards hydrogen at different temperatures has also been studied. At 530°C, voltage shift of 310 mV for 1% hydrogen was observed.

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In this work, we investigate how hydrogen sensing performance of thermally evaporated MoO3 nanoplatelets can be further improved by RF sputtering a thin layer of tantalum oxide (Ta2O5) or lanthanum oxide (La2O3). We show that dissociated hydrogen atoms cause the thin film layer to be polarised, inducing a measurable potential difference greater than that as reported previously. We attribute these observations to the presence of numerous traps in the thin layer; their states allow a stronger trapping of charge at the Pt-thin film oxide interface as compared to the MoO3 sensors without the coating. Under exposure to H2 (10 000 ppm) the maximum change in dielectric constant of 45.6 (at 260 °C) for the Ta2O5/MoO3 nanoplatelets and 31.6 (at 220 °C) for La2O3/MoO3 nanoplatelets. Subsequently, the maximum sensitivity for the Ta2O5/MoO3 is 16.87 (at 260 °C) and La2O3/MoO3 is 7.52 (at 300 °C).

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Entrepreneurship research and practice places emphasis on company growth as a measure of entrepreneurial success. In many cases, there has been a tendency to give growth a very central role, with some researchers even seeing growth as the very essence of entrepreneurship (Cole, 1949; Sexton, 1997; Stevenson & Gumpert, 1991). A large number of empirical studies of the performance of young and/or small firms use growth as the dependent variable (see reviews by Ardishvili, Cardozo, Harmon, & Vadakath, 1998; Delmar, 1997; Wiklund, 1998). By contrast, the two most prominent views of strategic management – strategic positioning (Porter, 1980) and the resource-based view (Barney, 1991; Wernerfelt, 1984) – are both concerned with achieving competitive advantage and regard achieving economic rents and profitability relative to other competitors as the central measures of firm performance. Strategic entrepreneurship integrates these two perspectives and is simultaneously concerned with opportunity seeking and advantage seeking (Hitt, Ireland, Camp, & Sexton, 2002; Ireland, Hitt, & Sirmon, 2003). Consequently, both company growth and relative profitability are together relevant measures of firm performance in the domain of strategic entrepreneurship.

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In this work, we present an investigation on Pt/graphene/GaN devices for hydrogen gas sensing applications. The graphene layer was deposited on GaN substrate using a chemical vapour deposition (CVD) technique and was characterised via Raman and X-ray photoelectron spectroscopy. The current-voltage (I-V) and dynamic response of the developed devices were investigated in forward and reverse bias operation at an optimum temperature of 160°C. Voltage shifts of 661.1 and 484.9 mV were recorded towards 1% hydrogen at forward and reverse constant bias current of 1 mA, respectively.

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While academic interest in destination branding has been gathering momentum since the field commenced in the late 1990s, one important gap in this literature that has received relatively little attention to date is the measurement of destination brand performance. This paper sets out one method for assessing the performance of a destination brand over time. The intent is to present an approach that will appeal to marketing practitioners, and which is also conceptually sound. The method is underpinned by Decision Set Theory and the concept of Consumer-Based Brand Equity (CBBE), while the key variables mirror the branding objectives used by many destination marketing organisations (DMO). The approach is demonstrated in this paper to measure brand performance for Australia in the New Zealand market. It is suggested the findings provide indicators of both i) the success of previous marketing communications, and ii) future performance, which can be easily communicated to a DMO’s stakeholders.