Challenges in the EM-based design of modern telecommunication satellite antennas

2018 ◽  
Vol 37 (4) ◽  
pp. 1461-1480
Author(s):  
Enrico Reiche ◽  
Michael Schneider
Keyword(s):  
High Power ◽  
Antenna System ◽  
System Level ◽  
Efficient Design ◽  
Design Issues ◽  
Satellite Antenna ◽  
Content Type ◽  
Telecommunication Satellite ◽  
Em Field ◽  
Satellite Antennas

Purpose This paper aims to introduce design challenges of modern telecommunication satellite antennas. The antenna farms accommodated on a satellite are systems of high complexity. From the radio frequency (RF) point of view, the most important design issues, e.g. high power applications in space (vacuum) or typical antenna scenarios (single/multi beam antennas), and their solution are considered. Design/methodology/approach The paper presents the application of electro-magnetic (EM) field simulation in the design and optimisation process. The design of a telecommunications satellite antenna splits into several areas, for which different types of EM field solvers are used. Findings The use of EM field solvers enables an accurate and efficient design approach of modern geostationary telecommunications satellite antennas. Due to the use of EM field solvers, an excellent agreement between predictions and measurement results on feed as well as antenna system level is achieved. Originality/value This paper gives an overview of state-of-the-art telecommunications satellite antenna architectures and their efficient RF design due to the use of EM field solvers. Typical high power effects and other design issues are explained. RF engineers are encouraged to work on this exciting topic to further improve the design process and to develop new satellite antenna and feed products.

Energy transition demand will elevate aluminium prices

2021 ◽  
Keyword(s):  
Supply Chain ◽  
Middle East ◽  
High Power ◽  
Energy Transition ◽  
Green Energy ◽  
Power Markets ◽  
Energy Sources ◽  
Content Type

Significance Aluminium smelters are being hampered by high power prices and shortages amid the switch towards green energy sources. China has been forced to start importing aluminium at record levels to tackle domestic shortages. Impacts The green energy transition will strain power markets, increasing the challenge of producing energy-intensive aluminium. Supply will gradually diversify as outputs stagnates in China but looks set to rise in Argentina, Brazil, the Middle East and Russia. Consumers and governments in importing nations will increase aluminium recovery and recycling to cut pressure on the supply chain.

Experimental study on fire resistance of a full-scale composite floor assembly in a two-story steel framed building

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Lisa Choe ◽  
Selvarajah Ramesh ◽  
Xu Dai ◽  
Matthew Hoehler ◽  
Matthew Bundy
Keyword(s):  
Natural Gas ◽  
Fire Resistance ◽  
Full Scale ◽  
System Level ◽  
Compartment Fire ◽  
Content Type ◽  
Standard Fire ◽  
Fire Experiment ◽  
The Usa ◽  
Floor System

PurposeThe purpose of this paper is to report the first of four planned fire experiments on the 9.1 × 6.1 m steel composite floor assembly as part of the two-story steel framed building constructed at the National Fire Research Laboratory.Design/methodology/approachThe fire experiment was aimed to quantify the fire resistance and behavior of full-scale steel–concrete composite floor systems commonly built in the USA. The test floor assembly, designed and constructed for the 2-h fire resistance rating, was tested to failure under a natural gas fueled compartment fire and simultaneously applied mechanical loads.FindingsAlthough the protected steel beams and girders achieved matching or superior performance compared to the prescribed limits of temperatures and displacements used in standard fire testing, the composite slab developed a central breach approximately at a half of the specified rating period. A minimum area of the shrinkage reinforcement (60 mm2/m) currently permitted in the US construction practice may be insufficient to maintain structural integrity of a full-scale composite floor system under the 2-h standard fire exposure.Originality/valueThis work was the first-of-kind fire experiment conducted in the USA to study the full system-level structural performance of a composite floor system subjected to compartment fire using natural gas as fuel to mimic a standard fire environment.

Ethiopian new public universities

2016 ◽  
Vol 24 (2) ◽  
pp. 158-172 ◽  
Author(s):  
Rita Van Deuren ◽  
Tsegazeab Kahsu ◽  
Seid Mohammed ◽  
Wondimu Woldie
Keyword(s):  
Higher Education ◽  
Case Studies ◽  
Public Universities ◽  
Secondary Data ◽  
System Level ◽  
Illustrative Case ◽  
Content Type ◽  
Higher Education System ◽  
New Public ◽  
And Gender

Purpose – This paper aims to analyze and illustrate achievements and challenges of Ethiopian higher education, both at the system level and at the level of new public universities. Design/methodology/approach – Achievements and challenges at the system level are based on literature review and secondary data. Illustrative case studies are based on university data and interviews with university representatives. Findings – The Ethiopian higher education system has increased its enrollments substantially. The construction of 13 new universities that started enrolling students around 2007 contributed greatly to this achievement. Challenges accompanying this growth lie in funding, quality and quantity of staffing, teaching practices, research and community service, quality assurance and gender balance. Originality/value – The present study contributes to existing literature by describing case studies illustrating challenges and achievements in new public universities in Ethiopian higher education.

Design optimisation for cold-formed steel residential roof truss using genetic algorithm

2018 ◽  
Vol 15 (5) ◽  
pp. 575-583
Author(s):  
Ka Yee Kok ◽  
Hieng Ho Lau ◽  
Thanh Duoc Phan ◽  
TIina Chui Huon Ting
Keyword(s):  
Genetic Algorithm ◽  
Industrial Application ◽  
Steel Structures ◽  
Single Type ◽  
Efficient Design ◽  
Design Optimisation ◽  
Content Type ◽  
Roof Truss ◽  
Cold Formed Steel ◽  
Multi Level

Purpose This paper aims to present the design optimisation using genetic algorithm (GA) to achieve the highest strength to weight (S/W) ratio, for cold-formed steel residential roof truss. Design/methodology/approach The GA developed in this research simultaneously optimises roof pitch, truss configurations, joint coordinates and applied loading of typical dual-pitched symmetrical residential roof truss. The residential roof truss was considered with incremental uniform distributed loading, in both gravitational and uplift directions. The structural analyses of trusses were executed in this GA using finite element toolbox. The ultimate strength and serviceability of trusses were checked through the design formulation implemented in GA, according to the Australian standard, AS/NZS 4600 Cold-formed Steel Structures. Findings An optimum double-Fink roof truss which possess highest S/W ratio using GA was determined, with optimum roof pitch of 15°. The optimised roof truss is suitable for industrial application with its higher S/W ratio and cost-effectiveness. The combined methodology of multi-level optimisation and simultaneous optimisation developed in this research could determine optimum roof truss with consistent S/W ratio, although with huge GA search space. Research limitations/implications The sizing of roof truss member is not optimised in this paper. Only single type of cold-formed steel section is used throughout the whole optimisation. The design of truss connection is not considered in this paper. The corresponding connection costs are not included in the proposed optimisation. Practical implications The optimum roof truss presented in this paper is suitable for industrial application with higher S/W ratio and lower cost, in either gravitational or uplift loading configurations. Originality/value This research demonstrates the approaches in combining multi-level optimisation and simultaneous optimisation to handle large number of variables and hence executed an efficient design optimisation. The GA designed in this research determines the optimum residential roof truss with highest S/W ratio, instead of lightest truss weight in previous studies.

Operationalising resilience in tropical agricultural value chains

2019 ◽  
Vol 24 (2) ◽  
pp. 271-300 ◽  
Author(s):  
Joshua Aboah ◽  
Mark M.J. Wilson ◽  
Karl M. Rich ◽  
Michael C. Lyne
Keyword(s):  
Value Chain ◽  
Food System ◽  
Raw Materials ◽  
Citation Network ◽  
System Level ◽  
Value Chains ◽  
Common Source ◽  
Content Type ◽  
The Individual ◽  
Stakeholder Interactions

Purpose The analysis of the concept of resilience in supply chain management studies mostly focuses on the downstream side of the value chain and tacitly assumes an unlimited supply of raw materials. This assumption is unreasonable for agricultural value chains, as upstream disruptions clearly have a material impact on the availability of raw materials, and indeed, are a common source of supply problems. This paper aims to present a framework for the operationalisation of the concept of socioecological resilience in agricultural value chains that incorporates upstream activities. Design/methodology/approach A citation network analysis was adopted to review articles. A conceptual framework is then advanced to identify elements of resilience and indicators relevant to tropical agricultural value chains. Findings There are limited studies that assess resilience in the food chain context. Flexibility, collaboration, adaptability and resourcefulness are key elements for assessing resilience at the individual chain actor level. However, the paper argues that adaptability is the relevant element for the assessment of resilience at an aggregate food system level because it considers the alteration of a system’s state of resilience. Practical implications The proposed framework and propositions accommodate stakeholder interactions in the value chain and could serve as a tool to guide the assessment of resilience in agricultural value chains. Originality/value This paper is one of the few to extend resilience to cover the socioecological interaction aspects for supply chains that yield the raw materials needed for continuity in channel-wide value creation processes.

scholarly journals The naming of the Permian System

2021 ◽  
pp. jgs2021-037
Author(s):  
Michael J. Benton ◽  
Andrey G. Sennikov
Keyword(s):  
System Level ◽  
Naming Time ◽  
Content Type ◽  
Red Sandstone ◽  
Link Type ◽  
Permian System ◽  
Urgent Task ◽  
Great Leader ◽  
Supplementary Material ◽  
Access To Documents

The naming of the Permian by Roderick Murchison in 1841 is well known. This is partly because he ‘completed’ the stratigraphic column at system level, but also because of the exotic aspects of his extended fieldwork in remote parts of Russia and Murchison's reputed character. Here, we explore several debated and controversial aspects of this act, benefiting from access to documents and reports notably from Russian sources. Murchison or Sedgwick could have provided a name for the unnamed lower New Red Sandstone in 1835 based on British successions or those in Germany, so perhaps the Imperial aim of naming time from British geology was not the urgent task some have assumed. Murchison has been painted as arrogant and Imperialistic, which was doubtless true, but at the time many saw him as a great leader, even an attractive individual. Others suggest he succeeded because he stood on the shoulders of local geologists; however, his abilities at brilliant and rapid geological synthesis are undoubted. Two unexpected consequences of his work are that this arch conservative is revered in Russia as a hero of geological endeavours, and, for all his bombast, his ‘Permian’ was not widely accepted until 100 years after its naming.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5412079

Vigilant resilience: the possibilities for renewal through preparedness

2018 ◽  
Vol 23 (2) ◽  
pp. 212-225 ◽  
Author(s):  
Elizabeth Carlson
Keyword(s):  
Public Relations ◽  
Design Methodology ◽  
Renewal Theory ◽  
Theory Building ◽  
System Level ◽  
Content Type ◽  
The Public ◽  
Energy Company ◽  
Resilience Process

Purpose Post-crisis renewal discourse (Ulmer et al., 2007) is one form of communication that stakeholders may use as they attempt to organize for resilience. The purpose of this paper propose extending Discourse of Renewal Theory to explain how it could enact a different kind of resilience than scholars typically consider. Organizational resilience strategies often focus on the recovery or prevention stages of crisis management. Under conditions of persistent threat, it would be more productive for renewal discourse to emphasize greater preparedness. Design/methodology/approach To illustrate the need for this kind of theorizing, the author analyzes a case study that follows the public relations efforts of Canadian energy company Enbridge, Inc., in the aftermath of the 2010 Kalamazoo River oil spill. Findings By the criteria of Discourse of Renewal Theory, Enbridge attempted a renewal strategy, but it failed. By other criteria, however, it succeeded: it created the opportunity for richer dialogue among stakeholders about their interdependence and their competing interests. Originality/value By considering how elements of the resilience process may vary, this paper offers resources for more nuanced theory-building and theory-testing related to organizational and system-level resilience.

Learning by failure vs learning by habits

2017 ◽  
Vol 23 (3) ◽  
pp. 524-546 ◽  
Author(s):  
Lorella Cannavacciuolo ◽  
Luca Iandoli ◽  
Cristina Ponsiglione ◽  
Giuseppe Zollo
Keyword(s):  
Learning Strategies ◽  
Diffusion Of Innovation ◽  
System Level ◽  
Alternative View ◽  
Agent Based Model ◽  
Content Type ◽  
Agent Based ◽  
Business Transactions ◽  
Virtual Lab ◽  
Start Up

Purpose The purpose of this paper is to explain the emergence of collaboration networks in entrepreneurial clusters as determined by the way entrepreneurs exchange knowledge and learn through business transactions needed to implement temporary supply chains in networks of co-located firms. Design/methodology/approach A socio-computational approach is adopted to model business transactions and supply chain formation in Marshallian industrial districts (IDs). An agent-based model is presented and used as a virtual lab to test the hypotheses between the firms’ behaviour and the emergence of structural properties at the system level. Findings The simulation findings and their validation based on the comparison with a real world cluster show that the topological properties of the emerging network are influenced by the learning strategies and decision-making criteria firms use when choosing partners. With reference to the specific case of Marshallian IDs it is shown that inertial learning based on history and past collaboration represents in the long term a major impediment for the emergence of hubs and of a network topology that is more conducive to innovation and growth. Research limitations/implications The paper offers an alternative view of entrepreneurial learning (EL) as opposed to the dominant view in which learning occurs as a result of exceptional circumstances (e.g. failure). The results presented in this work show that adaptive, situated, and day-by-day learning has a profound impact on the performance of entrepreneurial clusters. These results are encouraging to motivate additional research in areas such as in modelling learning or in the application of the proposed approach to the analysis of other types of entrepreneurial ecosystems, such as start-up networks and makers’ communities. Practical implications Agent-based model can support policymakers in identifying situated factors that can be leveraged to produce changes at the macro-level through the identification of suitable incentives and social networks re-engineering. Originality/value The paper presents a novel perspective on EL and offers evidence that micro-learning strategies adopted and developed in routine business transactions do have an impact on firms’ performances (survival and growth) as well as on systemic performances related to the creation and diffusion of innovation in firms networks.

Advanced aircraft performance analysis

2018 ◽  
Vol 90 (4) ◽  
pp. 627-638 ◽  
Author(s):  
Marc Immer ◽  
Philipp Georg Juretzko
Keyword(s):  
Performance Analysis ◽  
Design Process ◽  
Performance Optimization ◽  
Electric Propulsion ◽  
Vertical Plane ◽  
Aircraft Design ◽  
Efficient Design ◽  
Content Type ◽  
Aircraft Performance ◽  
Hybrid Electric

Purpose The preliminary aircraft design process comprises multiple disciplines. During performance analysis, parameters of the design mission have to be optimized. Mission performance optimization is often challenging, especially for complex mission profiles (e.g. for unmanned aerial vehicles [UAVs]) or hybrid-electric propulsion. Therefore, the purpose of this study is to find a methodology that supports aircraft performance analysis and that is applicable to complex profiles and to novel designs. Design/methodology/approach As its core element, the developed method uses a computationally efficient C++ software “Aircraft Performance Program” (APP), which performs a segment-based mission computation. APP performs a time integration of the equations of motion of a point mass in the vertical plane. APP is called via a command line interface from a flexible scripting language (Python). On top of APP’s internal radius of action optimization, state-of-the-art optimization packages (SciPy) are used. Findings The application of the method to a conventional climb schedule shows that the definition of the top of climb has a significant influence on the resulting optimum. Application of the method to a complex UAV mission optimization, which included maximizing the radius of action, was successful. Low computation time enables to perform large parametric studies. This greatly improves the interpretation of the results. Research limitations/implications The scope of the paper is limited to the methodology that allows for advanced performance analysis at the conceptual and preliminary design stages with an emphasis on novel propulsion concepts. The methodology is developed using existing, validated methods, and therefore, this paper does not contain comprehensive validation. Other disciplines, such as cost analysis, life-cycle assessment or market analysis, are not considered. Practical implications With the proposed method, it is possible to obtain not only the desired optimum mission performance but also off-design performance of the investigated design. A thorough analysis of the mission performance provides insight into the design’s capabilities and shortcomings, ultimately aiding in obtaining a more efficient design. Originality/value Recent developments in the area of hybrid or hybrid-electric propulsion systems have shown the need for performance computation tools aiding the related design process. The presented method is especially valuable when novel design concepts with complex mission profiles are investigated.

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