Conceptual Design Considerations Research Articles

Transient analysis of megawatt-level space gas-cooled reactor coupled with He-Xe Brayton cycle system

The development of the aerospace industry and advancements in aerospace technology have created an urgent need for space power supply. A self-developed thermal hydraulic system analysis program is utilized to examine the transient response safety of gas-cooled reactors and investigate the performance of the coupled Brayton cycle overall system. The typical transient accident conditions were simulated, including positive reactivity insertion, turbine-alternator-compressor shaft speed drop, and loop coolant flow rate reduction. By considering cladding integrity as the safety criterion, it is determined that the reactor studied in this work has a safety margin of 0.152$ when introducing reactivity. The introduction of positive reactivity enhances reactor power output and heat generation. As more heat is carried away by He-Xe gas into the turbine, both operating temperature and heat transfer efficiency within the thermal cycle system are further improved. With an introduction of 0.13 % positive reactivity into the core, reactor thermal power can be stabilized at 110 % of its rated value while increasing system thermoelectric conversion efficiency by 2.7 %. During a continuous turbine-alternator-compressor shaft speed drop incident (from 100 % to 80 % rated speed), the total electrical power drops to 580 kWe along with reductions in temperature ratio and pressure ratio for both turbine and compressor. System cycle efficiency shows a positive correlation with turbine-alternator-compressor shaft speed within an appropriate range. In a sudden coolant flow rate drop incident, when the loop flow rate decreases to 60 % of its rated value, both reactor power and turbine-alternator-compressor shaft power decline significantly: the total electrical power drops from 1096 kWe to 216 kWe while the system’s cycle efficiency decreases from 32.1 % to 12.13 %. This work provides valuable insights into conceptual design considerations as well as safety assessment aspects pertaining to megawatt-class space.

Digital Twin-Enabled Response Function Analysis: A Synthetic Approach to Ship's Propulsion System Assessment

Analyzing the behavior of vessels in actual sea conditions is crucial for conceptual system design, safety and energy efficiency considerations. However, the essential seakeeping problem is reduced to the analysis of wave-hull interactions often neglecting consideration of the propulsion. But in the meantime, the synthetic consideration of wave–propulsion interactions is a key for safety and energy efficiency. Furthermore, safety evaluation of a ship's design with reduced propulsion power in adverse seas is vital for risk management. Response functions are commonly used to estimate propulsion system responses in incoming seaways. This paper proposes a synthetic approach using digital twin technology for rapid response function estimation. It introduces a companion linearized state-space model linked with the digital twin, enabling immediate retrieval of coefficients for response function analysis at the desired operating point. This integrated methodology provides a comprehensive representation of ship propulsion behavior in wave environments, offering a comprehensive framework for system performance assessment.

Conceptual Design and Performance Considerations for Superconducting Magnets in the Material Plasma Exposure eXperiment

An important step toward the advent of nuclear fusion as a future power source is the development of plasmafacing materials that can function as designed for a long period of time. While ITER and other devices including Wendelstein 7-X and the Joint European Torus will provide insight into divertor and first wall performance, a dedicated device to advance the understanding of material performance in the representative plasma environments is needed. The Material Plasma Exposure eXperiment has been proposed as a linear plasma device to generate and to direct fusion reactor-like plasma energy and particle flux at the target materials with electron temperatures of 1-15 eV and electron densities of 10 20 -10 21 m -3 . Given that the requirements for radio frequency (RF) heating on-axis field are no greater than 2.5 T and the warm bore diameters must be between 60 cm and 1.5 m, the conceptual design was developed for the experiments on a set of superconducting magnets carried out using commercially available NbTi superconductors. This conceptual design evaluated the cryogenic heat loads, mechanical loads, and quench protection to ensure that the current design is compatible with current technologies. In addition, an alternative evaluation of this design relative to ReBCO high-temperature superconducting magnets determined the conditions under which these technologies could be advantageous.

Conceptual design considerations for a wireless intraocular pressure sensor system for effective glaucoma management

As a leading form of preventable visual impairment, it is imperative to assess glaucoma treatment as a function of intraocular pressure (IOP). IOP can spike throughout the day. This necessitates a device that can (1) monitor IOP outside of clinical visits by providing a memory when IOP exceeds a set threshold indicating the possibility for glaucomatous damage to occur; and (2) accurately assess IOP. Both requirements point ultimately towards the development of an implantable device. The Wireless Intraocular Pressure Sensor System (WIPSS) devised by our team uses optical technologies and may assist an overseeing clinician with assessing glaucoma treatment efficacy and avoiding irreversible glaucomatous visual field loss downstream.

Actively facilitated permeable reactive barrier for remediation of TCE from a low permeability aquifer: Field application

Proven in situ treatment and remediation approaches are limited for low-permeability aquifers materials, particularly because of limitations to the delivery of reactive chemicals or access to contaminated plumes. In this paper, we describe the development of a cutting-edge solution for the remediation of contaminated groundwater in a low-permeability and low water-bearing aquifer contaminated with the chlorinated hydrocarbon trichloroethylene (TCE). The remediation technique introduced coupling of large-diameter permeable reactive barrier wells (PRB wells) with: (1) extraction wells through in a highly impacted plume; and (2) re-injection wells at the fringe of the plume. A pump-and-treat system (PTS) was employed at the site in a separate plume to reduce the mass of TCE near the second source zone. This research focuses only on the large diameter PRB well system. Conceptual site model development, design considerations, implementation and performance evaluation demonstrated how each of these elements were applied in the field. Approaches for coupling technologies to increase technical and economic feasibility are presented. Extraction and reinjection wells of treated groundwater at the fringe of the plume promoted a positive hydraulic gradient, facilitated groundwater transport through the reactive media, and contained the plume. Detailed geospatial and statistical analysis with over 10 years’ monitoring data showed that dissolved TCE plume delineation shrank, and still concentration continues to decline, and were projected to meet the demands of remediation compliance regulations in the next few years. The results of this study indicate that significant remediation was achieved despite the challenging hydraulic conditions of the aquifer. The developed the remediation technology and conclusions indicate the system’s usefulness at other sites.

Boron-10 lined RPCs for sub-millimeter resolution thermal neutron detectors: conceptual design and performance considerations

A novel concept for position-sensitive thermal neutron detectors based on thin-gap Resistive Plate Chambers (RPC) lined with a neutron converter layer is presented and its feasibility is discussed. Several detector architectures implementing a stack of RPCs in multilayer and inclined geometries are introduced. The results of a Monte Carlo simulation study are presented demonstrating the effect of the main detector design parameters on the expected detection efficiency and spatial resolution.

Integrated analysis of kinematic form active structures for architectural applications: Design of a representative case study

Today’s architecture is characterized by a growing demand for flexibility and adaptability, allowing to adjust to meet the current needs. Both covering spaces for weather protection and improving energy performance of buildings ask for dynamic architectural solutions. The integration of lightweight technical textiles offers great possibilities for these kinematic structures, due to their inherently high flexibility.Unfortunately, until now, there is a lack of in-depth knowledge on the material properties of technical textiles, their structural behaviour during deformation and the use of available design tools. The inability to keep the fabric properly pretensioned in all deployment stages within the structure’s limitations, obstructs the use of fabric structures for kinematic applications.In order to make a good design and analysis possible, we investigated the material properties of a standard polyester-PVC fabric and implemented these properties in a simple linear elastic computer model of a case study. Afterwards, we performed a parameter study to derive a set of conceptual design considerations for the kinematic prestressed fabric structure. The specified parameters to verify in the design process are (i) the boundary configuration in which form-finding is conducted (i.e. the reference state), (ii) the prestress levels and ratios, (iii) the control of the deployment and (iv) the used material parameters. The paper discusses how the computed model can serve as a design tool.An exhaustive preliminary study is essential to enhance the overall structural behaviour of the membrane structure in all stages of its transformation, within the application range, keeping the membrane properly tensioned and avoiding excessive stress concentrations.In a next step, a large-scale experimental model is set up, measuring the geometry, reaction forces and strains in the membrane. This model will serve as an experimental validation of the numerically obtained results.

New Incremental Actuators Based on Electroactive Polymer: Conceptual, Control, and Driver Design Considerations

This paper presents an overview of the widely used conventional linear actuator technologies and existing electroactive polymer-based linear and rotary actuators. It also provides the conceptual, control, and driver design considerations for a new dielectric electroactive polymer (DEAP)-based incremental actuator. The DEAP incremental actuator consists of three independent DEAP actuators with a unique cylindrical design that potentially simplifies mass production and scalability compared to existing DEAP actuators. To accomplish the incremental motion, a high-voltage (HV) bidirectional dc–dc converter independently charges and discharges each capacitive DEAP actuator. The topology used for the HV driver is a peak current controlled bidirectional flyback converter. The scalability of the proposed DEAP incremental actuator is discussed, and different scaled designs are provided. The estimated speeds and forces for various scaled incremental actuator designs are provided. The HV drivers are experimentally tested with a prototype of the DEAP incremental actuator. The energy efficiency measurement results of one of the HV driver are presented. The DEAP incremental actuator prototype achieved bidirectional motion with a maximum velocity of 1.5 mm/s, at 2.87 Hz incremental driving frequency, when all actuators are driven with 1.8 kV. Finally, two new improved concepts of DEAP-based incremental actuator are presented.

Positive Education in Asia and Beyond

Positive education is the application of positive psychology principles to the education domain. Relative to positive psychology, positive education has not received a great deal of theoretical and empirical attention. In addition, there is a significant dearth of positive education theory and research focusing on students in the Asian region. This article explores positive education, its links to positive psychology, and its relevance and importance to wellbeing and learning in the Asian context. Building on the series of studies in this Special Issue, the article then outlines critical conceptual, measurement, and research design considerations for positive education research going forward.

Behavior of a steel coupled beam moment frame based on nonlinear analyses

A steel coupled beam moment frame (CBMF) is an innovative seismic resisting moment resisting frame that is composed of coupled beams and steel columns. A coupled beam features a pair of steel beams, post-tensioning elements, and energy dissipation devices. Coupled beams can be fabricated in shop and pin-connected to columns on site, facilitating the field construction. Energy dissipation is provided by a special energy dissipation device, not by damage to the main structural members or to the energy dissipation device itself. Rotations at beam–column joints are the result of a relative slide mechanism of the coupled beams, not the result of beam plastic hinges. During unloading, the force in the PT elements eliminates coupled beam relative slide as well as rotations at beam–column joints, offering the potential of minimal residual rotations to coupled beam–column connections. This paper presents conceptual details, conceptual behavior, and design considerations for CBMFs. For behavior study, a prototype building using CBMFs as the lateral resisting frames was designed. A nonlinear analysis model for the prototype building was created. Static pushover and cyclic push analyses were conducted to assess the concepts. Dynamic time history analyses using a 44-ground motion record set were performed to study the post-earthquake residual story drift and residual connection rotation response of the prototype CBMF building. Analysis results showed that the global behavior and connection response of the prototype CBMF supported the conceptual behavior and design considerations, and that post-earthquake story drifts and connection rotations of the prototype CBMF building are ignorably small.

Model-based structural optimization of seawater desalination plants

Membrane-based processes and thermal desalination plants are two alternatives to overcome the problem of fresh water supply by means of seawater desalination. In this work the combination of two types of desalination technologies, a reverse osmosis network (RON) and a forward-feed multi-effect distillation (FF-MED), in a hybrid plant is considered as a structural optimization problem. Deterministic mixed-integer non-linear programming techniques (MINLP) are used to rigorously optimize operational parameters and process structure simultaneously. A generalized superstructure for the hybrid desalination plant is constructed and conceptual design considerations are used to reduce its complexity. A mathematical model for the whole plant and an economical objective function are provided. The resulting model is highly nonlinear and non-convex. A stepwise optimization strategy is proposed, including a specialized initialization scheme to robustly compute good initial solutions with a minimum of user interaction. Results for various specifications illustrate the application of the proposed optimization model. The performance of the suggested method is compared to that obtained with the global solver BARON.

Conceptual Seismic Design of Cable-Stayed Bridges

Cable-stayed bridges can be a very effective means of bridging large distances in both seismic and non-seismic regions. Their design, analysis, and construction can be very challenging, and fortunately there is a considerable amount of literature that can assist engineers with both the analysis and detailed design of cable-stayed bridges. It is less common, however, to find simple recommendations for the conceptual design of cable-stayed bridges, in particular for seismic loading. As such, this article reviews and discusses some of the important conceptual design considerations for cable-stayed bridges, first for gravity loads and then for seismic excitation. The advantages and disadvantages of different cable-stayed bridge solutions are highlighted, with review of deck sections, tower configurations in both the longitudinal and transverse direction, deck-to-pier connections, and cable arrangements, amongst other things. Reference is made to a number of real cable-stayed bridge solutions. After reviewing the important conceptual design considerations for cable-stayed bridges, a simple preliminary sizing procedure is proposed. The preliminary sizing procedure is intended to offer designers a quick but rational means of identifying reasonable member sizes for cable-stayed bridges that should then be verified through advanced analyses in the developed and detailed design stages of the project. A case study application of the preliminary sizing procedure is made for a three-tower cable-stayed bridge in Ecuador, and by comparing preliminary and final design member sizes it is concluded that the preliminary sizing procedure may be a useful tool for design.

Conceptual Design Considerations for Microwave- and Solar-Powered Fuel-Less Aircraft

Unmanned aerial vehicles typically have limited flight duration, particularly at smaller scales. A microwave-/ solar-powered flight vehicle, on the other hand, can remain in theater continuously by harvesting electromagnetic radiation using onboard antennas and solar panels. Moreover, these seemingly disparate power sources are complementary in that they are both heavily dependent on the wing area. Rectifying antennas are used to harvest power and convert it into electrical energy usable by the onboard motors and other electronics. To supplement this energy source, photovoltaic cells are used to harness incoming solar radiation. Discussed herein are design features of fuel-less air vehicles and their sensitivity to several key performance metrics for this class of aircraft. In this study, aircraft with wingspans in the range 3-5 m and cruise Re = 5 × 10 5 -5 × 10 6 are considered. New metrics are presented that are unique to a microwave-powered aircraft and are useful in the development of its missions. These metrics relate the design of the aircraft and the energy transmitter to the duration and range of the vehicle's missions. The addition of solar power harvesting to a microwave-powered aircraft is examined. Furthermore, an examination of the strong coupling among the aircraft's flight performance, power harvesting abilities, and its mission capabilities is given. Traditional and nontraditional wing shapes are presented to motivate a discussion of this coupling. In particular, tradeoffs between flight performance and power harvesting performance are discussed.

Conceptual design considerations for the acoustical design of an animal research facility.

Conceptual design considerations from the acoustical design of an animal research facility are presented in this paper. Animals in laboratory settings are experimentally stressed to observe outcomes. Stressors external to the experiment confound data and reduce research productivity. Among these experimental contaminants is acoustical noise, which has well‐documented extra‐auditory effects in animals. Both steady‐state and transient sounds can affect development, sleep, reproduction, behavior, and other parameters important to animal models. Reasonably comprehensive sensitivity data exist in the medical and laboratory literature; however, there are few treatments of the acoustical design of vivarium and animal laboratory facilities. Acoustical design of these facilities is challenging due to the broad array of sensitivities (including ultrasonic frequencies), scarcity of high‐frequency data for noise sources, contamination control and cleanliness requirements, and surface durability concerns. Acoustical d...

Cargo Aircraft Conceptual Design Optimisation Using a Flexible Computer-Based Scaling Approach

In the early design stages of a new aircraft, there is a strong need to broaden the knowledge base of the evolving aircraft project, allowing a profound analysis of the solution concepts and of the design driving requirements. The methodology presented in this paper provides a tool for increasing and improving in an exemplary manner the necessary information on cargo aircraft. By exchanging or adapting a few particular modules of the entire program system, the tool is applicable to a range scale of different aircraft types. In an extended requirement model, performance requirements are represented along with other operational requirements. An aircraft model is introduced in sufficient detail for conceptual design considerations. The computer-aided scaling methodology is explained, which, controlled by an optimisation module, automatically resizes the aircraft model until it optimally satisfies the requirements in terms of a selectable figure of merit. Typical results obtained at the end of the scaling are discussed together with knowledge gained during the process, and an example is given.

Decision aid function for restoration of transmission power systems: conceptual design and real time considerations

This paper deals with the conceptual design of a decision aid function for restoration (DAFFOR) of transmission networks after major black-outs, and in particular with real time considerations. Some important characteristics of the proposed DAFFOR are: (a) capability of taking into account the dynamic evolution of the network state, due to either a control action or an unforeseen event; (b) interactive mode, which permits users to request a validation of their own suggestion; (c) coupling with an internal dynamic simulator which is solicited to validate any suggestion. At present, the DAFFOR is coupled with the French National Utility Operator Training Simulator (EDF OTS). After intensive testing within the OTS environment, the operational version of the DAFFOR will be developed.

Design-Construction of Fox Hollow Pedestrian Bridge

The basic structure of this $920,000 pedestrian crossing in Calgary, Alberta, Canada, is a two-span symmetrical cable-stayed bridge supported by a single A-frame tower. The bridge deck and tower use precast concrete components. The resulting bridge is an elegant design solution to the functional, aesthetic, structural and budgetary requirements set by the City of Calgary. In addition, the project was completed on schedule and with reduced traffic disruption. This article presents the design challenge, conceptual design and design considerations, as well as the production and erection highlights of the project.

A multi-crucible core-catcher concept: Design considerations and basic results

A pulti-crucible core-catcher concept to be implemented in new light water reactor containments has recently been proposed. This paper deals with conceptual design considerations and the various ways this type of core-catcher could be designed to meet requirements for reactor application. A systematic functional analysis of the multi-crucible core-catcher concept and the results of the preliminary design calculation are presented. Finally, the adequacy of the multi-crucible core-catcher concept for reactor application is discussed.

Use of Navy External Combustion Engine Technology

ABSTRACT Conceptual design considerations specifically for the application of United States Navy external combustion engine technology in ultra high altitude aircraft including general feasibility study results are presented. The performance data available on existing engines is scaled to identify the system performance of a theoretical application. The results of the studies are used for comparison to ultra high altitude aircraft systems presently in operation. This technology represents an existing low cost alternative to development of high performance turbine or multiple stage turbocharged internal combustion engines for short duration missions at altitudes up to 100,000 feet.

Design and Performance of Vaneless Volutes for Radial Inflow Turbines: Part 1: Non-Dimensional Conceptual Design Considerations

The requirements for the volute of a radial inflow turbine are that it should collect the working fluid, deliver it to the turbine rotor as efficiently as possible and provide the desired rotor inlet conditions. The design requirements of the turbine leads to the rotor design and the identification of the desired flow conditions at rotor inlet in terms of the magnitude and direction of the absolute Mach number. The volute must then be designed to ensure that the desired rotor inlet conditions are attained. A non-dimensional design procedure for a vaneless turbine volute is described. Based on a knowledge of the flow direction and magnitude of the absolute Mach number at rotor inlet the overall dimensions of the volute in terms of the radius ratio and flow area ratio are first established. The overall design is then developed to provide the variation of the volute centroid radius and area ratio with azimuth angle. A trapezoidal cross-sectional shape is then used to establish the outer dimensions of the volute. The non-dimensional procedure assumes a one-dimensional compressible flow and as such relies on the empirical specification of the dissipation of angular momentum, the dissipation of energy and the deviation of the swirling flow from that of a free vortex. The effect of the uncertainties associated with the empirical data on the volute design geometry is assessed. A complementary experimental investigation to develop and substantiate the required empiricism is presented in Part 2, which follows. As the design procedure is essentially one-dimensional it must be interpreted with a knowledge of the actual three-dimensional flow within a volute passage. Supportive experimental studies will be presented in Part 3 in the next issue.