Preliminary Design Considerations Research Articles

Traversing Situations and Contexts in Networked Learning

To meet the goals of business education and develop responsible business leaders, educators need to design networked learning environments that nurture and leverage connections. This includes connecting students to each other, their teachers, to industry and to the community. This paper aims to understand factors that support or inhibit students’ participation in networked learning in a business education context. Productive participation in learning networks is essential if students are to connect meaningfully with people and resources in ways that support their learning and experience. As the physical and digital learning environments students engage in often include complex configurations of tools, tasks, and epistemic resources, they require the skills and dispositions to effectively transition between these environments. Using a situated readiness framework by Hachmann and Dohn (2018), this study presents an analysis of focus group data from business students in higher education to identify ways in which students’ level of readiness impacts on their ability to participate effectively in learning networks. Students in the present study highlighted a range of challenges they faced when attempting to traverse between face-to-face and online learning environments. However, our study also revealed numerous other situations or contexts that business students needed to traverse as part of their networked learning experience. These were grouped into five overarching categories: domain; space and configuration; format, structure and resources; people or groups; and purpose and responsibility. Overlayed onto the situated readiness framework, these categories can be used by other researchers to gain a more nuanced understanding of how students navigate the complexities of networked learning environments. Future research conducted across a range of learning contexts would allow the categories to be refined and built upon. The study also identified skills and dispositions that contributed to students' level of readiness to navigate situations and contexts within networked learning environments, and some preliminary design considerations based on the findings. To support business students in higher education on their journey to becoming responsible business leaders, it is imperative that they are able to participate productively in complex networked learning environments. As educators, this requires us to understand their level of readiness to do so and equip them with the skills and dispositions they need to participate effectively.

Experimental investigation on alternate load path mechanisms in double-span beams with unsymmetrical span lengths and reinforcement ratios

In the design and assessment of reinforced concrete (RC) structures against progressive collapse via single column removal scenarios, also known as the “alternate load path (ALP) method”, the development of secondary mechanisms in double-span beams, i.e. compressive arch action (CAA) and catenary action (CA), has been thoroughly investigated and identified in many previous studies. The majority of the experimental tests were conducted on symmetrical double-span beams (identical span length and steel reinforcement ratio for both beams). However, variations in span length and reinforcement details of beams adjacent to one another are common in RC buildings due to architectural requirements. Hence, an experimental study with a total of 6 tests was conducted to investigate the development of ALP mechanisms (CAA and CA) in double-span RC frames with unsymmetrical 1) span length and/or 2) longitudinal reinforcement ratio. The 6 tests included 3 symmetrically-designed specimens that served as the baseline to facilitate comparison and quantification of the ALP development for the other 3 unsymmetrical continuous beams. The behaviour and development of ALP mechanisms in all the 6 specimens were analysed at structural level including general observations and measurements of the external forces, displacements, and strains. Last but not least, a simplified method that was initially developed based on symmetrical test data was employed to validate unsymmetrical test results, with the aim to provide a robust and simple tool for preliminary design considerations of the ALP mechanisms.

High Speed Permanent Magnet Assisted Synchronous Reluctance Machines – Part I: A General Design Approach

The design of synchronous reluctance machines with and without permanent magnets assistance constitutes a challenging engineering task due to the numerous design variables and performance indexes to be considered. The design complexity increases even further when the application requires high speed operation, with consequent rotor structural constraints and related effects on the electromagnetic performance. Structured as two-parts companion papers, this work proposes a comprehensive design procedure able to consider all the non-linear aspects of the machine behaviour, greatly reducing the number of independent design variables, without worsening the computational burden. In particular, the non linear behaviour of the rotor iron ribs and the effect of the permanent magnets on the structural design are all taken into account with the proposed iterative design procedure targeting the achievement of a desired power factor. The proposed method will be then used to draw some preliminary design considerations highlighting the several trade-offs involved in the design of high speed permanent magnet assisted synchronous reluctance machine. Part I is setting the theoretical bricks that will be further expanded and experimentally validated in the companion paper Part II.

A Magnetohydrodynamic enhanced entry system for space transportation: MEESST

This paper outlines the initial development of a novel magnetohydrodynamic (MHD) plasma control system which aims at mitigating shock-induced heating and the radio-frequency communication blackout typically encountered during (re-)entry into planetary atmospheres. An international consortium comprising universities, SMEs, research institutions, and industry has been formed in order to develop this technology within the MEESST project. The latter is funded by the Future and Emerging Technologies (FET) program of the European Commission’s Horizon 2020 scheme (grant no. 899298). Atmospheric entry imposes one of the harshest environments which a spacecraft can experience. The combination of hypersonic velocities and the rapid compression of atmospheric particles by the spacecraft leads to high-enthalpy, partially ionised gases forming around the vehicle. This inhibits radio communications and induces high thermal loads on the spacecraft surface. For the former problem, spacecraft can sometimes rely on satellite constellations for communicating through the plasma wake and therefore preventing the blackout. On the other hand, expensive, heavy, and non-reusable thermal protection systems (TPS) are needed to dissipate the severe thermal loads. Such TPS can represent up to 30% of an entry vehicles weight, and especially for manned missions they can reduce the cost- efficiency by sacrificing payload mass. Such systems are also prone to failure, putting the lives of astronauts at risk. The use of electromagnetic fields to exploit MHD principles has long been considered as an attractive solution for tackling the problems described above. By pushing the boundary layer of the ionized gas layer away from the spacecraft, the thermal loads can be reduced, while also opening a magnetic window for radio communications and mitigating the blackout phenomenon. The application of this MHD-enabled system has previously not been demonstrated in realistic conditions due to the required large magnetic fields (on the order of Tesla or more), which for conventional technologies would demand exceptionally heavy and power-hungry electromagnets. High-temperature superconductors (HTS) have reached a level of industrial maturity sufficient for them to act as a key enabling technology for this application. Thanks to superior current densities, HTS coils can offer the necessary low weight and compactness required for space applications, with the ability to generate the strong magnetic fields needed for entry purposes. This paper provides an overview of the MEESST project, including its goals, methodology and some preliminary design considerations.

Multi-chamber GEM-based concept of radiated power/SXR measurement system for use in high radiation environment of DEMO

This work describes the progress of development of total core radiation power and soft X-ray (SXR) diagnostic system designed in accordance with the DEMO control requirements. Monitoring of energy loss through the separatrix is necessary for reliable plasma control. Data gathered by this system could also be helpful for studying spatial distribution of heavy impurities, MHD modes and their localization, plasma shape and position.Gas electron multiplier (GEM) technology is assessed as a base for a new radiated SXR power measurement system. The main advantages of this technology are the compactness of GEM detector, good temporal and spatial resolution, the ability to discriminate energy of incident photons and better neutron resilience than existing systems. All of these make it potentially a good candidate for SXR diagnostic system in ITER and DEMO.The scope of the study includes analysis of the feasibility of selected approaches, the design of the diagnostic system, necessary simulations and engineering considerations, and the proposal of an integration scenario. Preliminary design considerations for the GEM-sensor-based system under development have been done. Plasma radiation intensities and spectra have been simulated using data from the appropriate DEMO scenario. A concept of the photosensitive chamber has been assessed. Photoabsorption simulations with the proposed structure and parameters have been conducted and the results have been discussed.

Gaussian-Based Machine Learning Algorithm for the Design and Characterization of a Porous Meta-Material for Acoustic Applications

The scope of this work is to consolidate research dealing with the vibroacoustics of periodic media. This investigation aims at developing and validating tools for the design and characterization of global vibroacoustic treatments based on foam cores with embedded periodic patterns, which allow passive control of acoustic paths in layered concepts. Firstly, a numerical test campaign is carried out by considering some perfectly rigid inclusions in a 3D-modeled porous structure; this causes the excitation of additional acoustic modes due to the periodic nature of the meta-core itself. Then, through the use of the Delany–Bazley–Miki equivalent fluid model, some design guidelines are provided in order to predict several possible sets of characteristic parameters (that is unit cell dimension and foam airflow resistivity) that, constrained by the imposition of the total thickness of the acoustic package, may satisfy the target functions (namely, the frequency at which the first Transmission Loss (TL) peak appears, together with its amplitude). Furthermore, when the Johnson–Champoux–Allard model is considered, a characterization task is performed, since the meta-material description is used in order to determine its response in terms of resonance frequency and the TL increase at such a frequency. Results are obtained through the implementation of machine learning algorithms, which may constitute a good basis in order to perform preliminary design considerations that could be interesting for further generalizations.

Optimizing the acoustic properties of a meta-material using machine learning techniques

The scope of this work is to consolidate research dealing with vibroacoustics of periodic media. This investigation aims at developing and validating tools for the design of global vibroacoustic treatments based on foam cores with embedded periodic patterns, which allow passive control of acoustic paths in layered concepts. Firstly, a numerical test campaign is carried out by considering some solid (but still non-perfectly rigid) inclusions in a 3D-modeled porous structure; this causes the excitation of additional acoustic modes due to the periodic nature of the meta-core itself. Then, some design guidelines are provided in order to predict several possible sets of characteristic parameters (i.e. inclusion geometry, elastic and foam properties) that, constrained by the imposition of mass and thickness of the acoustic package, may satisfy the target functions (i.e. the frequency at which the first Transmission Loss peak appears, together with its amplitude). Results are obtained through the implementation of machine learning algorithms, which may constitute a good basis in order to perform preliminary design considerations that could be interesting for further generalizations.

Numerical investigations about the sound transmission loss of a fuselage panel section with embedded periodic foams

The scope of this paper is to investigate the sound transmission loss of a typical fuselage panel section, as well as to propose solutions based on the inclusion of a periodic pattern inside its foam core, which aim at passively improving the acoustic performance in a mid-high range of frequencies. In detail, a new fuselage panel configuration is numerically studied, starting from the state of the art regarding the acoustic packages based on porous meta-materials. The main novelties of the present work are represented by the application of a meta-core solution inside an acoustic package of aeronautical interest, as well as a systematic investigation of the effects deriving from its geometrical parameters. In order to reach this goal, a numerical model of a fuselage panel section is studied, and the effect of several periodic patterns are simulated; more specifically, twelve configurations are taken into account, each with different radius of the inclusions and number of unit cells along the thickness. For each of these layouts, the mass increase of the so-called meta-core, compared to that of its classical homogeneous counterpart, is estimated, together with the associated mid-band frequency and amplitude of the sound transmission loss peak, which is caused by the additional acoustic modes excited by the periodic nature of the meta-core itself. Results are presented in terms of tables and graphs, which may constitute a good basis in order to perform preliminary design considerations that could be interesting for further generalizations.

Concentrating solar power multi-effect desalination in Al Khobar, Saudi Arabia

As about two-thirds of the thermal energy to the power cycle of a concentrated solar power plant is dumped to the condenser, typically air or evaporative cooling, there is the opportunity to achieve energy savings by using a multi-effect distillation system to condensate the steam and at the same time produce desalinized water. Preliminary design considerations and computations for a concentrated solar power plant located in Al Khobar, Saudi Arabia, are here proposed. The solar field has an aperture of 1,230,000 m2, it uses oil as the receiver fluid, it uses a six hours’ thermal energy storage by molten salt, and it features a 140 MW turbine. It is expected production of up to 413 GWh of electricity annually, for a capacity factor of 0.36, by using an air-cooled condenser. Adoption of a glass enclosure and a multi-effect distillation plant replacing the air-cooled condenser may permit the same electricity production plus the production of desalinized water in an environment protected by sand and dust.

Numerical analysis of liquefaction-induced differential settlement of shallow foundations on an island slope

Seismic differential settlement of shallow foundations on an island slope with a liquefiable sand stratum can significantly reduce the foundation's bearing capacity. Now, most studies focused on the settlement of foundation, while few efforts have provided a description of the differential settlement of foundation. In this study, we therefore adopted an approach using three-dimensional (3D) nonlinear finite element (FE) simulation. A special case that the water table located at the interface between the liquefiable sand layer and the clay layer was employed in this model. A series of parametric studies involving soil properties, surcharge load, foundation location, and the typical shaking characteristics of earthquake events were conducted to identify their impact on liquefaction-induced differential settlement. Generally, a more permeable sand stratum and a larger cohesion of the upper clay stratum were found effective at decreasing differential settlement. A foundation's length/width ratio also played an important role in reducing differential settlement and, when the distance of the foundation from the crest of an island slope reached a critical value, the differential settlement tends towards a steady value. Heavily-loaded shallow foundations resulted in more differential settlement, leading to a reduction in their seismic bearing capacity. The peak ground acceleration and Arias intensity of an earthquake had a significant effect as well. In addition, some preliminary design considerations for shallow foundation under the earthquakes were proposed. Overall, the numerical results offer some valuable references to improve the design and construction of foundations on an island slope under the seismic loadings.

Wind Trawler: operation of a wind energy system in the far offshore environment

A great untapped wind resource lies within the deep oceanic environment far from shore. Considering the technological and economic challenges of fixed offshore wind platforms to operate at great offshore depths and distances, we propose that this resource best be exploited by the use of a mobile floating wind-and-hydro power producing plant, termed the Wind Trawler. This paper explores preliminary design considerations for wind turbine, hydro turbine, and hull to optimize power performance ensure stability. The wind speed is modelled using long term averages from hindcast software to compare power production of a Wind Trawler and fixed wind turbine in the offshore environment.

Discontinuity Mapping using Terrestrial Laser Scanner and Kinematic Method

This study presents the results of discontinuity mapping using terrestrial laser scanning (TLS) survey and the kinematic method. The results provide the current site and slope condition of comprehensive geological study using terrestrial laser scanning and discontinuity survey at Simpang Pulai, Perak. From the results obtained, it can be concluded that the major potential failures in this area are wedge and plane failures, but there are some area had the potential of toppling failure. This study, however, constitutes a preliminary design consideration and not intended for use in final design or construction. The final design shall be made by the engineer based on the further detail site investigation (S.I.) and other design factors to be used in the actual design of the project.

Preliminary Design and System Considerations for an Active Hybrid Laminar Flow Control System

Hybrid laminar flow control or HLFC design is a complex and multi-disciplinary process, which demands a thorough understanding of all aspects from a global systems viewpoint. The objective of the paper is to present a preliminary design of important components of an HLFC system that helps in quick assessment of conceptual system architectures. This is important to evaluate feasibility, system performance, and overall aircraft benefits at early stages of system development. This paper also discusses the various important system requirements and issues concerning the design of active HLFC systems, and the interfaces between various disciplines are presented. It can be emphasized from the study that the future compressor design for the HLFC system should consider the thermal management aspects and additional mass flow requirements from the aerodynamics-structure design optimization and also from water drain system solutions. A method to calculate the accumulated water content inside the plenum chambers is presented, and the effect of a drain hole on the power consumption is studied. A low order thermal management study of the HLFC compressor motor shows a high temperature rise in the windings for very high speed motors for long duration operation and calls for effective cooling solutions.

Effect of farmers’ management on movable sprinkler solid-set systems

Farmer's management is considered a key factor for efficient, cost-effective irrigation. In this study, the effect of proper irrigation management in the solid-set systems of Kurdistan province in Iran was investigated. Performance indices including Coefficient of Uniformity (CU), Potential Application Efficiency of the Low Quarter (PELQ), Wind Drift and Evaporation Loss (WDEL), Adequacy of Irrigation (ADirr), Deep Percolation Losses (DP), and Application Efficiency (AE) were measured in ten different local plots in 2007 and 2017. The performance of selected systems remained similar in 2007 and 2017. The management of the plots evaluated in 2017 was modified, taking into account the preliminary design considerations and applying changes such as irrigation scheduling and sprinkler type. These plots with improved management were re-evaluated. Results showed that CU and PELQ were improved by 29% and 82%, respectively, in all systems. In addition, deep percolation losses (DP) were reduced by more than 40%. Insufficient training for farmers and the use of unskilled labor are of the main reasons for sustained underperformance in the study area. Actions are required in farmers’ education and in public performance monitoring. Additionally, the results of this research have shown that management improvement measurements are urgently required for the satisfactory performance of the above-mentioned systems.

Optimization of Thermal Protection Panels Subjected to Intense Heating and Mechanical Loading

In this work we solve a higly-nonlinear structural optimization problem for the sandwich panel with external thermal protection layer that can be used in the spacecraft systems. Objective function of the problem is the mass per unit area of the panel. Constraints are formulated based on the simplified analytical solutions of structural mechanics and heat transfer problems, which are suitable for the preliminary design considerations. The set of design variables includes the geometric parameters of the panel and additional microstructural parameter—porosity of the heat protection material. Direct random search and simulated annealing method are applied to solve considered problem. Change of limit states and optimal configurations of the panel are studied for different levels of the mechanical loading.

Application of Wireless Power Transfer to Railway Parking Functionality: Preliminary Design Considerations with Series-Series and LCC Topologies

There is a wide literature concerning the application of inductive power transfer (IPT) to light railway systems. In this work, proposed application is innovative with respect to existing literature: static current collection on conventional railway lines is proposed in order to replace the functionalities implemented by conventional battery chargers and the so-called railway “parking” system. According to standards in force, current collection in standstill conditions is limited since pantograph contact shoes and catenary wires have to be protected by thermal overload. These limitations have to be considered since power demand for all the services installed on modern coaches should be higher than 20-40kW. This is a critical technical issue especially for long compositions that have to be prepared for service by activating on-board subsystems such as heating and air conditioning. Additional possible applications should be related to refrigerated wagons in freight compositions. In all these cases the availability of a simple, safe, and compact system should be useful to ensure a wireless power collection to on-board equipment. In this work authors introduce the proposed application and perform some preliminary design considerations. With respect to current literature on IPT systems, authors also introduce some innovative design criteria based on the analogy between resonant electrical system and corresponding mechanical ones. In this way, sizing of the proposed IPT system can be performed using modal methods that are also used for the proper sizing of mechanical vibrating systems, such as example, vehicle suspensions, or pantograph systems.

Preliminary Design Considerations for Variable Geometry Radial Turbines with Multi-Points Specifications

Radial turbines’ preliminary designs are usually carried out through some dimensionless approaches, such as the loading-to-flow-diagram and/or the blade speed ratio. In case of variable nozzle radial turbines, multi-points specifications must be considered, related to the improvement of the operating range. As preliminary design correlations and standards usually taken into consideration arise from studies dedicated to fixed geometry radial turbines, they need to be updated with regard to nozzle off-design opening configurations. This paper provides some theoretical basics in order to help designers considering variable geometry problems. Some complementary elements about the dimensionless methods are given by taking into account the nozzle opening effect. Then, useful considerations are brought regarding the preliminary design of variable geometry radial turbines with multi-points specifications.

Shear Performance Assessment of Timber Log-House Walls under In-Plane Lateral Loads via Numerical and Analytical Modelling

Log-house is an ancient construction technology based on the superposition of linear timber logs, connected to the orthogonal walls by a system of carvings, notches and corner joints. Due to the fact that this solution is widely used in constructions located in seismic or windy areas, the in-plane behaviour of walls represents an attractive research topic. In this paper, major outcomes of a Finite-Element (FE) numerical investigation carried out on single corner joints currently in use for log-house buildings are discussed under different loading conditions (i.e., in-plane lateral and vertical compressive loads), including parametric analyses to capture the key aspects of their typical structural response. Careful consideration is paid for the elastic stiffness of such joints, being of primary interest for design purposed. At the same time, a linear analytical formulation is presented, with the aim of providing a simple but useful tool in support of design, and especially to estimate the maximum lateral displacement/resistance for a given log-house wall when subjected to in-plane lateral forces. There, the intrinsic mechanical features of corner joints and related aspects are properly considered (i.e., static friction phenomena, as well as the presence of small gaps, etc.). The analytical model, in addition, takes advantage of the numerically predicted joint stiffness values, being dependent on several parameters. As shown, rather good agreement is obtained between the FE model output, the analytical predictions and past reference experimental/numerical results available in the literature for full-scale log-house walls under in-plane lateral loads, hence suggesting the potential of the proposed approach. In conclusion, possible Force-Preload-Displacement (FPD) charts are presented, to act as simplified tools for preliminary design considerations.

모터구동 밸브 액추에이터의 위치 제어

In this paper, we address the preliminary design considerations to develop a motor-operated valve (MOV) actuator. Both a lead compensator (LC) and a linear proportional-derivative (PD) controller are considered as a tool for controlling the opening and closing of a valve. The LC is designed using the frequency response characteristics to satisfy the given design specifications. The PD controller with a first-order filter in the denominator is optimally tuned so that a genetic algorithm (GA) minimizes an objective function. There is nonlinear saturation in the valve due to its physical structure and the signals applied to the motor are limited. To assess the stability of the overall feedback system when one of the designed controllers is used in operations in a nonlinear section, this study applies Popov’s stability criterion. Simulation works are performed to validate the effectiveness of the proposed methods.

A Comparison of Organic and Steam Rankine Cycle Power Systems for Waste Heat Recovery on Large Ships

This paper presents a comparison of the conventional dual pressure steam Rankine cycle process and the organic Rankine cycle process for marine engine waste heat recovery. The comparison was based on a container vessel, and results are presented for a high-sulfur (3 wt %) and low-sulfur (0.5 wt %) fuel case. The processes were compared based on their off-design performance for diesel engine loads in the range between 25% and 100%. The fluids considered in the organic Rankine cycle process were MM(hexamethyldisiloxane), toluene, n-pentane, i-pentane and c-pentane. The results of the comparison indicate that the net power output of the steam Rankine cycle process is higher at high engine loads, while the performance of the organic Rankine cycle units is higher at lower loads. Preliminary turbine design considerations suggest that higher turbine efficiencies can be obtained for the ORC unit turbines compared to the steam turbines. When the efficiency of the c-pentane turbine was allowed to be 10% points larger than the steam turbine efficiency, the organic Rankine cycle unit reaches higher net power outputs than the steam Rankine cycle unit at all engine loads for the low-sulfur fuel case. The net power production from the waste heat recovery units is generally higher for the low-sulfur fuel case. The steam Rankine cycle unit produces 18% more power at design compared to the high-sulfur fuel case, while the organic Rankine cycle unit using MM produces 33% more power.