Search results

Attitude determination and control subsystem (ADCS) is a vital part of earth observation satellites (EO-Satellites) that governs the satellite’s rotational motion and pointing. In designing such a complicated sub-system, many parameters including mission, system and performance requirements (PRs), as well as system design parameters (DPs), should be considered. Design cycles which prolong the time-duration and consequently increase the cost of the design process are due to the dependence of these parameters to each other. This paper aims to describe a rapid-sizing method based on the design for performance strategy, which could minimize the design cycles imposed by conventional methods.

The proposed technique is an adaptation from that used in the aircraft industries for aircraft design and provides a ball-park figure with little engineering man-hours. The authors have shown how such a design technique could be generalized to cover the EO-satellites platform ADCS. The authors divided the system requirements into five categories, including maneuverability, agility, accuracy, stability and durability. These requirements have been formulated as functions of spatial resolution that is the highest level of EO-missions PRs. To size, the ADCS main components, parametric characteristics of the matching diagram were determined by means of the design drivers.

Integrating the design boundaries based on the PRs in critical phases of the mission allowed selecting the best point in the design space as the baseline design with only two iterations. The ADCS of an operational agile EO-satellite is sized using the proposed method. The results show that the proposed method can significantly reduce the complexity and time duration of the performance sizing process of ADCS in EO-satellites with an acceptable level of accuracy.

Rapid performance sizing of EO-satellites ADCS using matching diagram technique and consequently, a drastic reduction in design time via minimization of design cycles makes this study novel and represents a valuable contribution in this field.

The purpose of this paper is to develop a behavioral mode (as opposed to a numerical one), which considers any parasitic behavior as an indication of a potentially contributing element in the overall system deficiency.

Similar to that associated with general systems theory, this paper concentrates on the organization and functions of natural systems which exhibit a loss of efficiency due to some general parasitic behavior. Based on the philosophy of “Bionics”, it clarifies the functional architecture and root-cause of this behavior in living systems in order to model subsystems characteristics which exhibit the same behavior in a complex system. In addition, a case study is done on the so-called “Eurozone financial difficulties” to examine the idea of this paper. However, limited access to proprietary financial data limits the generalization of the theory and therefore special case studies seem to be necessary.

The study of “parasites” and their associated functions introduces one possible explanation for the shortage of resources in systems. This concept could also help understand “interfaces” in a new perspective, where changing the system boundary could alter the type of interfaces in the system.

This work is applicable where there is a competition for the limited resources. Resource-based systems, such as financial systems, could be the subject of parasitic attack, and therefore, this work could build an appropriate foundation to understand and prevent this kind of danger to the system.

The presented behavioral model would be very useful to predict failures in systems which are rich in the resources. Detailed analysis on the subject, presented in this paper, provides initial knowledge to prevent shortage in system resources, caused by a general parasitic behavior.

Conventional powder bed fusion systems, with their high costs, proprietary nature and restrictive fees, limit research opportunities. This study aims to unveil an affordable, open-source hardware, open-source software laser-based metal powder bed fusion system. Recognizing the distinction between DIY and open-source hardware is crucial for widespread acceptance.

The authors present a comprehensive system architecture using object process methodology for functions and architecture, a design structure matrix to model system dependencies and classical technical drawing exploded views for select subsystems. Modularization enables high adaptability, fostering potential adoption.

The fully open system enables unrestricted research, mirroring common industrial metal laser-based powder bed fusion (L-PBF) systems. While “open” systems are available for purchase, they remain closed-source, lacking source code and technical drawings sharing, hindering contribution and co-development. The authors’ is the pioneering and sole open-source metal L-PBF system, boasting 1,500+ print hours. A series of industrial and academic adopters are currently implementing the system.

The open system, slicer software and controller offer unique process control, supporting multimaterial printing. The authors shared the design on the OpenAM GitHub page under the CERN-OHL-P v2 Open Source Hardware license. While it is functional for additive manufacturing (e.g. aluminum, tool steel, titanium and stainless steel), the entire process chain is actively evolving, ideal for co-development with the additive manufacturing community.

This paper aims to investigate the possibility of lowering the time taken during the aircraft design for unmanned aerial vehicles by using machine learning (ML) for the configuration selection phase. In this work, a database of unmanned aircraft is compiled and is proposed that decision tree classifiers (DTC) can understand the relations between mission and operational requirements and the resulting aircraft configuration.

This paper presents a ML-based approach to configuration selection of unmanned aircraft. Multiple DTC are built to predict the overall configuration. The classifiers are trained with a database of 118 unmanned aircraft with 57 characteristics, 47 of which are inputs for the classification problem, and 10 are the desired outputs, such as wing configuration or engine type.

This paper shows that DTC can be used for the configuration selection of unmanned aircraft with reasonable accuracy, understanding the connections between the different mission requirements and the culminating configuration. The framework is also capable of dealing with incomplete databases, maximizing the available knowledge.

This paper increases the computational usage for the aircraft design while retaining requirements’ traceability and increasing decision awareness.

As one of the fastest growing countries in the Middle East, and the one most vulnerable to climate change, the main challenge now facing Iran today is how to house its growing population in a socially, economically, and environmentally sustainable way. However, in the absence of a national framework to guide the sustainable development of the built environment, responding to this challenge is problematic. The articulation of a comprehensive assessment method that would enable issues of sustainability to be addressed and incorporated within building construction projects is urgently required. The research that underpins this paper takes account of current tools in aiming to support the development of a national building sustainability assessment method (BSAM) for use in Iran that involves the identification of sources of impact, specific benchmarks, and priorities for a weighting system for assessment criteria. This paper profiles the basis of a contextual framework that will inform the development of such a regional-based tool, taking account of Iran’s current climate change adaptation policies and priorities, its environmental conditions and socio-economic challenges, building typologies, standards and benchmarks.

The Building Bridges service was implemented as the result of an assessment of the psychological and mental health needs of black and minority ethnic children and families in Liverpool. This article describes the development of the service, and draws links between the existing literature, government legislation and implications for CAMHS.

Expert systems have come to the forefront in the modeling of problems. One of the major problems facing the expert system designers is to develop an accurate knowledge base and a meaningful model of uncertainty associated with complex models. Decision-making is based on knowledge, and decision system support needs a knowledge base as well. An adequate knowledge acquisition (KA) process leads to accurate knowledge and improves the decision-making process. To manage the risk of a medical service (twin pregnancy in this case) a knowledge management system was created. The captured knowledge may be associated with an uncertainty. This study aims to introduce a method for evaluating the reliability of a tacit KA model. It assisted engineering managers in assessing and prioritizing risks. The study tried to use this method in risk management and new case in the health domain.

In this study, relevant variables were identified in the knowledge management literature reviews and the domain of expertise management. They are validated by a group of domain experts. Kendall’s W indicator was used to assess the degree of consensus. On the basis of combined cognitive maps, a cognitive network was constructed. Using Bayesian belief networks and fuzzy cognitive maps, an uncertainty assessment method of tacit KA was introduced. To help managers focus on major variables, a sensitivity analysis was conducted. Reliability of model was calculated for optimistic and pessimistic values. The applicability and efficacy of the proposed method were verified and validated with data from a medical university.

Results show that tacit KA uncertainty can be defined by independent variables, including environmental factors, personality and acquisition process factors. The reliability value shows the accuracy of the captured knowledge and the effectiveness of the acquisition process. The proposed uncertainty assessment method provides the reliability value of the acquisition model for knowledge engineers, so it can be used to implement the project and prevent failures in vital factors through necessary actions. If there is not a satisficed level of reliability, the KA project reliability can be improved by risk factors. The sensitivity analysis can help to select proper factors based on the resources. This approach mitigated some of the disadvantages of other risk evaluation methods.

The contribution of this study is to combine the uncertainty assessment with tacit KA based on fuzzy cognitive maps and the Bayesian belief networks approach. This approach used the capabilities of both narrative and computational approaches.

In this paper, a closed-form analytical solution for the prediction of moment-rotation and the rotational stiffness-rotation curves of I-shaped beam to cylindrical column connections, commonly used on offshore platforms, at room and elevated temperatures, are presented.

An analytical solution for the prediction of moment-rotation and the rotational stiffness-rotation curves of I-shaped beam to cylindrical column connections is presented. The results of this model are compared with those of a non-linear coupled mechanical-thermal finite element model and small-scale experimental tests previously provided by the authors.

In this paper, a closed-form analytical solution for the prediction of moment-rotation and the rotational stiffness-rotation curves of I-shaped beam to cylindrical column connections, commonly used on offshore platforms, at room and elevated temperatures, is presented. The required yield and plastic moments in this model are provided as an extension to Roark's relationships. The results of this model are compared with those of a non-linear coupled mechanical-thermal finite element model and small-scale experimental tests previously provided by the authors. A reasonable agreement has been found between the analytical model results and the experimental/numerical modeling results.

This article is extracted from the author’s doctoral thesis, and all its achievements belong to the authors of the article.

The purpose of this paper is to analyze the firm’s capital market benefits in a high-quality information setting. More specifically, the authors address the question of whether the commonly documented IFRS benefits are capable of influencing inducing shareholders to increase their equity investment in adopting firms.

This study is performed on publicly listed firms in three emerging countries, namely, Morocco, South Africa and Turkey. The design of the ownership database allows a panel analysis for the years 2001 through 2011. The trend approach is suitable to account for concurrent effects that are unrelated to financial reporting while controlling for time-lasting behavior of investors. Overall, a minimum of four-year periods before and after the IFRS adoption date are warranted.

Overall, the findings support evidence of increases in equity holdings following a firm’s IFRS adoption. More specifically, institutional investors and institutional blockholders (both domestic and foreign) invest more heavily in the stocks of the firms that have committed to IFRS. By contrast, the authors fail to report evidence for ownership by blockholders and controlling shareholders.

The current empirical work should be of value to international investors, policy makers and market authorities. As for international investors facing reduced information disadvantage and comparable financial information across worldwide markets, they will find it easier to select and invest in value-creating stocks. This study may be useful for policy makers in acquiring a clear view of advantages, challenges and relevance of IFRS adoption to emerging markets. In particular, this study contributes to an understanding of potential capital market consequences of IFRS adoption. Furthermore, market authorities should be aware of the importance of institutional framework to enhance IFRS implementation and usage.

This work contributes to the ongoing empirical research on the intended capital market benefits of IFRS. The authors provide deeper insight into shareholdings changes of a number of key investors in a context where supply and demand of information are stained with asymmetry and mostly, influenced by differences in accounting practices. A major contribution of this study is the use of a methodological approach that outperforms commonly used approaches in the way how it considers concurrent events (compared to the shift specification) and time-lasting investor behavior (compared to the difference-in-differences analysis).