1,358,666 research outputs found
Intelligent Control for Aerospace Engineers: A Novel Educational Framework
No full textThe integration of intelligent control techniques into aerospace engineering education remains a challenge. This paper presents a novel approach for teaching intelligent control specifically designed for aerospace engineers, bridging the gap between theoretical foundations and practical applications. The proposed framework encompasses a comprehensive curriculum covering model-based and model-free approaches, leveraging neural networks, reinforcement learning, and other computational intelligence techniques. It emphasizes hands-on experiences through simulation-based exercises, hardware-in-the-loop experiments, and design projects tailored to different aerospace vehicle categories, including multi-rotor UAVs, helicopters, fixed-wing aircraft, and Hypersonic Flight Vehicles. The framework also addresses assessment methods, industry collaborations, and case studies to enhance student learning outcomes
Neural Network-based Flight Control Systems: Present and Future
No full textAs the first review in this field, this paper presents an in-depth
mathematical view of Intelligent Flight Control Systems (IFCSs), particularly
those based on artificial neural networks. The rapid evolution of IFCSs in the
last two decades in both the methodological and technical aspects necessitates
a comprehensive view of them to better demonstrate the current stage and the
crucial remaining steps towards developing a truly intelligent flight
management unit. To this end, in this paper, we will provide a detailed
mathematical view of Neural Network (NN)-based flight control systems and the
challenging problems that still remain. The paper will cover both the
model-based and model-free IFCSs. The model-based methods consist of the basic
feedback error learning scheme, the pseudocontrol strategy, and the neural
backstepping method. Besides, different approaches to analyze the closed-loop
stability in IFCSs, their requirements, and their limitations will be discussed
in detail. Various supplementary features, which can be integrated with a basic
IFCS such as the fault-tolerance capability, the consideration of system
constraints, and the combination of NNs with other robust and adaptive elements
like disturbance observers, would be covered, as well. On the other hand,
concerning model-free flight controllers, both the indirect and direct adaptive
control systems including indirect adaptive control using NN-based system
identification, the approximate dynamic programming using NN, and the
reinforcement learning-based adaptive optimal control will be carefully
addressed. Finally, by demonstrating a well-organized view of the current stage
in the development of IFCSs, the challenging issues, which are critical to be
addressed in the future, are thoroughly identified.Comment: 163 page
Gender risk preference in entrepreneurial opportunity: evidence from Iran
No full textThis paper examines how different representations of entrepreneurial opportunity can influence the risk preference of entrepreneurs and non-entrepreneurs, and whether this differs between men and women. A survey methodology was used with a random sample of 135 entrepreneurs and 126 non-entrepreneurs. The methodology was presented through a new risky choice framework containing five entrepreneurial opportunities. The first results indicate that framing information of opportunity caused significant differences in risk preferences between the entrepreneurs and non-entrepreneurs and also between the males and females. In negative situations, except for the lowest risk level of the experiment, the male entrepreneurs tended to choose higher risky opportunities than the female entrepreneurs. However, neither group showed a preference for the lowest opportunity return in certainty. In addition, a comparative analysis showed that there were more differences between the four groups in the negative situations than in the positive situations. The detailed differences and risk preferences of each of the four groups were also analysed. The results have been discussed with emphasis on entrepreneurship
Constituents of New Value Creation in the Course of Entrepreneurial Opportunity Development
No full textEntrepreneurship is a young field of study that rests at the heart of modern theories of economic development. Several studies have had immense endeavors to explain many of phenomena in entrepreneurship as well as entrepreneurial opportunity and entrepreneur’s economic function. Still, we know little about how entrepreneurial action takes place under the condition of risk and uncertainty. Having value proposition as a central construct and building upon entrepreneurship literature, this dissertation is a further contribution to our current knowledge, particularly in entrepreneurial opportunity evaluation. It embodies four distinct but interrelated studies. Using a variety of independent and mediating variables and constructs such as gender, risk disposition, expertise, innovativeness, intention, self-efficacy, attitude, subjective norms, empathy, learning, and opportunity style, it seeks to address the challenge these factors create in the course of opportunity development for entrepreneurs.
The study No.1 examines “how different representations of entrepreneurial opportunity can influence the risk preference of entrepreneurs and non-entrepreneurs, and whether this differs between men and women”. A survey methodology was used with a random sample of 135 entrepreneurs and 126 non-entrepreneurs. The methodology was presented through a new risky choice framework containing five entrepreneurial opportunities. The first results indicate that framing information of opportunity caused significant differences in risk preferences between the entrepreneurs and non-entrepreneurs and also between the males and females. In negative situations, except for the lowest risk level of the experiment, the male entrepreneurs tended to choose higher risky opportunities than the female entrepreneurs. However, neither group showed a preference for the lowest opportunity return in certainty. In addition, a comparative analysis showed that there were more differences between the four groups in the negative situations than in the positive situations. The detailed differences and risk preferences of each of the four groups were also analyzed.
The study No.2 inspects the moderating roles of the founder’s experience and innovation degree on the relationship between opportunity confidence and new value creation intention (NVCI) at the pre-founding stage of a business. For this purpose, it uses survey data from 157 prospective entrepreneurs in the ICT industry from university incubators in Iran. Using SEM, result show that experience, alone, does not moderate the relationship between opportunity confidence and NVCI. However, if entrepreneurs have required opportunity confidence, then medium and high-level innovation can increase the likelihood of acting on the opportunity for novice and experienced entrepreneurs, respectively. For novice entrepreneurs, the innovation variance from low to medium moderates the relationship between opportunity confidence and intent. In fact, this relationship is strengthened by the medium novelty level. Whereas, for experienced entrepreneurs, the variance from medium to high, moderates the relationship that is strengthened by the high novelty level.
The study No.3 explores the crucial factors that form the pre and post intentionality to create new values, particularly the post intention factors that facilitate opportunity enactment. It shows how intention impacts motivation-mustering to learn about practical knowledge concerning value proposition facilitator (VPF), which in turn influences value creation enactment. A survey methodology has been applied to a randomly selected sample of 213 entrepreneurs from 16 incubators in Iran. Using SEM and longitudinal data, the results showed that attitudes toward value creation and value creation self-efficacy significantly impacted the intentionality to create new value. Moreover, VPF has a direct effect on value creation enactment so that, it partially mediates the relationship between new value creation intention (NVCI) and value creation enactment. The findings did not support the influence of subjective norms neither on NVCI nor on value creation enactment.
Finally, the study No.4 seeks to shade light on the black-box of value co-creation in entrepreneurship and on the process through which the entrepreneur’s new value proposition meets the customer’s problem and pain in particular. Later I will discuss that successful entrepreneurs are often more empathic than unsuccessful entrepreneurs. Those entrepreneurs that offer their new values through an empathic relationship, learn a vital market knowledge (practical knowledge) that in turn shapes a shared mental model between them and the beneficiary that increases the likelihood of value co-creation engagement. Moreover, the performance of this relationship improves if there is a match between entrepreneurs’ learning approach and their initial opportunity insight. Furthermore, there is another matching mechanism between learning skills and the dimensions of empathy that enhances empathy capacity for entrepreneurs. These two matching mechanism at the end have a paramount influence on the value co-creation effectiveness
Internationalization of SMEs and Organizational Factors in Emerging Economies: High –Tech Industry of Iran
No full textSMEs as an engine of growth play an important role in emerging economies for poverty
reduction, the role which has attracted the attention of scholars in recent years. This study
explores the effect of firm characteristics, resources and top management team (TMT)
characteristics on the internationalization of SMEs. According to our conceptual model, we
assumed that firm resources mediate the link between international performance of SMEs and
characteristics of firms and of TMT. To test our model, we asked top managers of international
SMEs in Iran ICT sector to fill in a questionnaire. The data was analyzed through structural
equation modeling which leads us to codifying a causal model accordingly. The findings show a
direct and indirect positive effect of TMT characteristics on internationalization of SMEs,
however, it indicates that indirect effect of firm characteristics is not significant. Finally, a set of
guidelines are proposed for internationalization of SMEs in emerging economies
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Robust Attitude Control of an Agile Aircraft Using Improved Q-Learning
No full textAttitude control of a novel regional truss-braced wing (TBW) aircraft with low stability characteristics is addressed in this paper using Reinforcement Learning (RL). In recent years, RL has been increasingly employed in challenging applications, particularly, autonomous flight control. However, a significant predicament confronting discrete RL algorithms is the dimension limitation of the state-action table and difficulties in defining the elements of the RL environment. To address these issues, in this paper, a detailed mathematical model of the mentioned aircraft is first developed to shape an RL environment. Subsequently, Q-learning, the most prevalent discrete RL algorithm, will be implemented in both the Markov Decision Process (MDP) and Partially Observable Markov Decision Process (POMDP) frameworks to control the longitudinal mode of the proposed aircraft. In order to eliminate residual fluctuations that are a consequence of discrete action selection, and simultaneously track variable pitch angles, a Fuzzy Action Assignment (FAA) method is proposed to generate continuous control commands using the trained optimal Q-table. Accordingly, it will be proved that by defining a comprehensive reward function based on dynamic behavior considerations, along with observing all crucial states (equivalent to satisfying the Markov Property), the air vehicle would be capable of tracking the desired attitude in the presence of different uncertain dynamics including measurement noises, atmospheric disturbances, actuator faults, and model uncertainties where the performance of the introduced control system surpasses a well-tuned Proportional–Integral–Derivative (PID) controller
Export growth and firm survival
No full textThis paper uses plant-level data from Chile to show that an increase in sector-wide exports decreases the survival probability of exporters, but not that of non-exporters. We argue that this result can be explained by the fact that exporters and non-exporters use factors of production in different intensities
Iron deficiency and risk of early readmission following a hospitalization for acute heart failure
No full textCosmological tests of an axiverse-inspired quintessence field
No full textInspired by the string axiverse idea, it has been suggested that the recent transition from decelerated to accelerated cosmic expansion is driven by an axion-like quintessence field with a sub-Planckian decay constant. The scenario requires that the axion field be rather near the maximum of its potential but is less finely tuned than other explanations of cosmic acceleration. The model is parametrized by an axion decay constant f, the axion mass m, and an initial misalignment angle |θi| which is close to π. In order to determine the m and θi values consistent with observations, these parameters are mapped onto observables: the Hubble parameter H(z) at an angular-diameter distance dA(z) to redshift z=0.57, as well as the angular sound horizon of the cosmic microwave background (CMB). Measurements of the baryon acoustic oscillation (BAO) scale at z≃0.57 by the BOSS survey and Planck measurements of CMB temperature anisotropies are then used to probe the {m,f,θi} parameter space. With current data, CMB constraints are the most powerful, allowing a fraction of only ∼0.2 of the parameter-space volume. Measurements of the BAO scale made using the SPHEREx or SKA experiments could go further, observationally distinguishing all but ∼10-2 or ∼10-5 of the parameter-space volume (allowed by simple priors) from the ΛCDM model
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