Variation Of Design Parameters Research Articles

Evaluating architectural layouts for occupancy patterns and interactions using agent-based modelling as a methodology for workplace design

This paper presents methods for evaluating layout alternatives based on occupants' interactions for workplace design during the early design phase. The research proposes a modelling framework to simulate domain-specific patterns of occupancy and social interactions, as well as the process of design evaluation. The paper introduces a framework for an agent-based model using the Unity gaming engine to incorporate both architectural and non-architectural parameters derived from existing literature on organisational spatial and social behaviour. The experiments employ systematic approaches to vary design parameters and provide a comparative evaluation of layouts based on the number of face-to-face interactions. The method proposed in this paper can assist design stakeholders in creating a workplace environment for knowledge industries, where face-to-face interactions are considered sources of innovation. The presented modelling framework can also be adopted in other domains to evaluate the influence of spatial design on occupants' social interactions.

A compact Balanced Antipodal Vivaldi Antenna with improved phase center stability for imaging and ultrawideband localization applications

This paper introduces a phase center stability improved Balanced Antipodal Vivaldi Antenna (BAVA) loaded with ‘I’ shaped non-resonant director array. The proposed antenna operates from 6 GHz to 18 GHz with S11 less than −10 dB and addresses the issue of phase reversal. The rectification of phase reversal produces enhanced phase center stability. Standard deviation is used to find least dispersed set of the phase center span calculated by varying design parameters of the director through a parametric study. By effective circumventing of phase reversal through improved coupling between the signal and ground planes, the proposed antenna achieves a maximum of 65.31% of improvement of phase center stability when compared to the reported Vivaldi antennas. In addition, further fine tuning of H-plane phase center stability for phi-components of about 6.5% at higher frequencies of operation is also attained using a meander-line section in the feed. With a size of 3.2λ0×1.6λ0×0.02032λ0 mm3, the proposed antenna exhibits sustained radiation patterns. Where λ0 is free space wavelength at 12 GHz. Full wave simulation of the design using CST microwave studio and experimental validation with a fabricated prototype are carried out.

Bearing capacity of strip footing on c-ϕ slope under rainfall condition

This paper presents a novel solution for predicting the bearing capacity of a strip footing on a c-ϕ (cohesive-frictional) slope under rainfall conditions. The commercial finite element PLAXIS code was adopted for numerical modelling purposes. The bearing capacity of the strip footing is expressed through a dimensionless bearing capacity factor. The bearing capacity was examined considering the rainfall conditions and variation of design parameters, e.g., soil strength parameters, slope angle, and setback ratio. The results show that the bearing capacity of strip footing on the slope decrease under rainfall compares to its normal condition and the effects of each parameter on the UBC. The paper’s results can be a helpful reference for practical engineering in predicting the bearing capacity of strip footing on the c-ϕ slope under rainfall conditions.

Effect of design variation in behaviour and performance of Endplate-Type intermodular connection

Intermodular connections play an important role in the constructability and performance of modular building structures. The wind-generated vertical uplift force and the lateral load on modular structures raise concerns about the tensile and shear capacity of the intermodular connection joints. This study focuses on investigating the change in load response behaviour, working mechanism and performance of endplate-type intermodular connections with varying design parameters. Initially, the paper presents the design criteria of endplate-type intermodular connections and their behaviour, with a detailed theoretical approach, to identify their performance and capacity under tensile and shear loads. Then, the capacity of the proposed connections in this study was evaluated based on both the presented theoretical design and numerical approaches. The design inspiration for the proposed connection was taken from literature using which the finite element models for 4 specimens were developed and validated. The validated connection models were then used to conduct parametric studies for 11 proposed models, focused on changes in base endplate thickness (8 mm, 10 mm and 12 mm) and steel grade (s275 and s355), bolt hole diameter (22 mm, 26 mm and 30 mm) and tolerance, bolt grade (8.8, 10.9 and 12.9) and applied preload (0, 50 kN, 90 kN and 110 kN) with and without additional plate over oversized bolt holes. The results obtained from both shear and tensile performance analysis indicate that the change in proposed design parameters has a greater impact on shear over tensile behaviour and capacity. Further, the conducted parametric studies helped in identifying the optimum design parameter combinations for enhanced connection performance which are also cost-effective and ideal for an onsite installation. Finally, the paper suggests recommendations for future research and essential advancement in the endplate-type intermodular connection design in enhancing performance and presents the practical limitations and challenges in using such techniques.

Waste heat recovery potential in the thermochemical copper–chlorine cycle for hydrogen production: Development of an efficient and cost-effective heat exchanger network

With the finite nature of fossil fuel resources and related environmental issues, it is necessary to replace fossil-fuel-based hydrogen production methods with more sustainable ones. For the clean production of hydrogen, the copper-chlorine (Cu–Cl) thermochemical cycle is a favorable choice. However, internal waste heat recovery of the cycle is essential to improve the efficacy of the system. In this paper, the waste heat recovery potential of the four-step Cu–Cl cycle is investigated, to support the design of a new cost-effective and high-performance heat exchanger network. Pinch analysis is executed to find the optimum rates of cold and hot utilities for this cycle. Three heat exchanger network cases are investigated which include case 1, without heat recovery; case 2, with 16 heat exchangers; and case 3, with 11 heat exchangers. The effect of varying design parameters on the energy system's efficiency and cost-related parameters are also explored here. Based on the pinch analysis results, the minimum heating and cooling and the maximum recoverable heat, on a normalized basis, are 333.3 kJ/mol H2, 76.9 kJ/mol H2, and 134.4 kJ/mol H2, respectively. Moreover, for cases 1, 2, and 3 the thermal efficiencies are calculated as 33.3%, 41.1%, and 40.5%, respectively. Additionally, it is observed that, when the thermal energy of the cycle is supplied from a solar power tower plant, the levelized cost of hydrogen for case 1 is 9.6 $/kg H2, for case 2 is 7.9 $/kg H2, and for case 3 is 7.8 $/kg H2.

Maximizing supercontinuum bandwidths in gas-filled hollow-core fibers using artificial neural networks

Machine learning has been used to accelerate studies in the dynamics of optical pulses. In this study, we use machine learning to investigate the optimal design of supercontinuum-generating hollow-core antiresonant fibers (HC-ARFs) pressurized and filled with methane. Artificial neural networks (ANNs) are trained to replace the numerical solvers, accelerate the simulation of fibers, and provide a more rapid fiber design procedure. We first use an analytical model to approximate the dispersion and loss of the methane-filled silica HC-ARF. This approximation is used by the generalized unidirectional pulse propagation equation solver to simulate the pulse propagation and generate training data for our ANNs by varying design parameters including the pump center wavelength, fiber hollow-core radius, fiber length, cladding strut thickness, and gas pressure. We evaluate the performance of different spectral-predicting ANN architectures and use the trained ANN along with a custom fiber performance function to search the full parameter space. Subsequently, the regions with design parameters with predicted high performance are identified, and these high-performance HC-ARF designs are further optimized for supercontinuum generation at target supercontinuum bandwidths. We also extend our effort to maximizing the total spectral energy outside of the input pump wavelength by integrating the ANN with a global optimization technique for the search of an optimal HC-ARF design.

A miniaturized UWB bandpass filter with tunable cut-off frequencies employing rectangular open-loop defected ground structure

AbstractThis article presents a compact rectangular impedance resonator (RIR)–based ultra-wideband bandpass filter with an improved reflection coefficient within the passband and controllable cut-off frequencies. The proposed filter consists of anti-parallel coupled RIR coupled with rectangular open-loop defected ground structure (ROL-DGS) etched on the ground plane. The ROL-DGS ensures better in-band and out-off-band characteristics with reduced size due to its high Q-factor. The short- and open-circuit stubs control the lower (fCL) and upper (fCU) 3-dB cut-off frequencies, respectively, by originating transmission zeros independently with the help of variations in design parameters. As a result, the filter having a compact size of 0.216λCL × 0.176λCL is achieved, where λCL is the corresponding guided wavelength at the lower cut-off frequency fCL of 2.95 GHz. Further, an equivalent circuit is also modeled to explain the working of the proposed filter, and equivalent lumped parameters were extracted. Simulated results reveal that the reported filter passes the frequencies effectively within 2.95–11.44 GHz with fractional bandwidth of 117.9%. The simulated insertion loss values within the passband are less than 1.17 dB, and the reflection coefficient is better than −19.6 dB. Further, the proposed filter is fabricated, and it was found that the measured and simulation results are in well agreement.

Design Aspects of Conical Coaxial Magnetic Gears

In this paper, a new design of a conical coaxial magnetic gear was proposed. Conical magnetic gears are considered a logical link between the radial- and axial-field coaxial designs. The modeling of magnetic torques based on the 3D finite element method was developed. The design parameter variations of the conical coaxial magnetic gear were determined and discussed. The magnetic torque density was calculated and compared with that of a cylindrical coaxial magnetic gear with the same size and materials used. An optimal cone angle based on the air-gap length was proposed. Multistage conical coaxial magnetic gears were proposed as a sequence of coupled rotors with increased torque density and reduced magnetic reluctance. The proposed conical coaxial magnetic gears are more compact in size and suitable for integration with electrical machines and variable transmissions.

Hybrid single-phase immersion cooling structure for battery thermal management under fast-charging conditions

Immersion cooling technology shows the potential for high-energy–density battery thermal management under extreme charging/discharging conditions. In this study, a hybrid immersion cooling structure is proposed for overcoming challenges of conventional indirect liquid cooling methods. A simulation model for the hybrid immersion cooling design is developed based on experiments. The performance of the proposed design is investigated with variations in key design parameters, such as the flow directions, gaps between the batteries, pass partitions, and heat transfer materials. Ultimately, a hybrid immersion structure with one pass partition and graphite fins shows the best performance regarding the overall weight and temperature uniformity. This hybrid structure reduces the pressure drop and power consumption by 45.4% and 61.0%, respectively, thereby reaching a preferred battery temperature condition relative to a baseline structure under a 3C charging condition. In addition, the hybrid immersion structure provides a 6.7 °C lower maximum temperature and 3.0 K lower temperature difference relative to those of a conventional structure with a nearly identical weight. This structure can also reduce the battery temperature effectively under thermal abuse conditions; thus, it can be regarded as more reliable in terms of safety.

Electrically controlled liquid crystal nonlinear optical devices prepared by multi-layer composite structures

In this study, a multi-layer composite structure is used to prepare nonlinear optical devices from multi-walled carbon nanotubes (MWCNTs)/liquid crystal (LC) composite systems. Their third-order optical nonlinearity is investigated. The MWCNTs were coated and modified to improve their dispersion in the solvent. The coated and modified MWCNTs were characterized by IR absorption spectroscopy and transmission electron microscopy (TEM). The nonlinear optical (NLO) properties of the devices prepared by the multi-layer composite structures with varying design parameters were studied. The conventional devices were also prepared by mixed doping method for comparison with the proposed devices. Both devices underwent Z-scan testing. The third-order nonlinear polarizability of the conventional hybrid-doped devices was calculated with a value of 5.39 × 10-10 esu. The third-order nonlinear polarizability of the proposed devices prepared by the multi-layer composite structures has a value of 2.97 × 10-9 esu, which is about five times the corresponding value for the hybrid-doped devices. So, the devices prepared by the multi-layer composite structures have better NLO properties. Moreover, the third-order nonlinear polarizability of the proposed devices was further increased up to 3.88 × 10-9 esu, which is an increase of almost 31% after applying voltage to these devices prepared by the multi-layer composite structures. The limiting threshold of S-CTAB/MWCNTs@BHR33400 is 0.245 J/cm2 after voltage application. Applying voltage plays a role in promoting the NLO properties of the devices. Using the multi-layer composite structure to prepare the liquid crystal nonlinear optical devices can significantly improve the NLO properties of the devices. Such prepared devices can be electrically tuned, providing new avenues for preparing nonlinear optical devices.

Development of CFD simulation model of earth air heat exchanger for space cooling of a 36 M2 house in tropical climate Banda Aceh, Indonesia

The global warming makes the ambient temperature hotter and greater efforts are made to reach a comfortable temperature. The continuous use of air conditioners that consume electricity is also unsustainable for the surrounding environment. Several studies on thermal comfort have been conducted by various researchers. Earth-air heat exchangers (EAHE) with air-working fluids can be used as a passive contribution to reduce building energy requirements for heating or cooling purposes. It should be noted that there is very little information in the literature on the development of a CFD (Computational Fluid Dynamic) simulation model of an EAHE for space cooling of a 36 m2 house in a tropical climate, such as Banda Aceh, Indonesia. Therefore, this study aims to examine the performance of EAHE with several variations in design parameters, such as pipe length, pipe diameter, number of pipe bends, and the type of soil where the EAHE is installed, as well as the thermal regime of a 36 m2 house either with or without the use of EAHE. The simulation in this study was conducted with CFD ANSYS Fluent software. The inlet air temperature of EAHE was set to be the same as the ambient air temperature, namely 31.4oC. The simulation results reveal that for variations in pipe length, the highest drop in outlet air temperature was yielded by the 47 m pipe length, which is 26.8°C. In which an increase in pipe length causes a decrease in air outlet temperature. The variation in pipe diameter does not significantly affect the outlet air temperature. Where the average air temperature drop at the EAHE exit is 0.046oC. The variation in number of turns shows that the drop in outlet air temperature is identical, namely 28.2°C, despite the fact that their pressure drop values are different. In addition, it was found that the performance of EAHE buried under different types of soil is distinct. The highest drop in outlet air temperature was generated when the EAHE was buried in silty soil, namely 26.1°C. A case study on a 36 m2 house shows that the utilization an underground heat exchanger can reduce the house’s indoor temperature by 2°C, with an average house temperature of 30.4°C compared to that with a natural ventilation.

Effect of a Secondary Injection on the Performance of Three-Dimensional Over-under TBCC Exhaust Nozzles

A numerical simulation is used to investigate the flow field characteristics of a three-dimensional over-under turbine-based combined cycle circular-to-rectangular transition exhaust nozzle when only the turbojet flowpath is in operation. The effect on the exhaust nozzle performance of there being a secondary injection on the ramp of the expansion section of the turbojet flow path is then examined. Finally, the impact of variations in the secondary injection design parameters is further investigated. The results show that a secondary injection can improve the exhaust nozzle's performance by reducing the axial force on the inner wall of the flow path. However, changes in flight status can undermine this improvement. Under the baseline operating condition, a secondary injection with a larger angle and close to the ramp outlet can produce a more significant improvement in nozzle performance. In this study, the axial thrust coefficient, lift and pitch moment of the nozzle can be improved by a maximum of 9.312%, 66.007% and 10.975%, respectively.

Performance Investigation of a Vertical TFET with Inverted-T Channel for Improved DC and Analog/Radio-Frequency Parameters

In this manuscript, a novel line tunneling based gate-on-source-only TFET with inverted T-shaped channel (ITGOSO-VTFET) is proposed and investigated using Synopsis TCAD 2-D simulator. The GOSO configuration along with dual counter-doped pockets (CDP) improve the ON-state current by enhancing the tunneling rate of charge carriers at source/channel interface while inverted T-shaped channel helps the proposed device in reducing the OFF-state (IOFF) and ambipolar (IAMB) currents. In comparison with double-gate (DG) and GoSo-CDP TFET, the order of IOFF (IAMB) in ITGOSO-VTFET are found to be improved by ∼6 (∼4) and ∼7(∼3), respectively. Furthermore, the impact of varying design parameters is analyzed in order to obtain the optimized performance of the proposed device. Apart from improvement in DC performance, ITGOSO-VTFET is also found to offering a much better analog/RF performance in terms of various parameters like gm, fT, TFP, GBP, and τ, which eventually makes the proposed device more suitable for low power and high-speed applications.

Impact of yttrium hydride formation on multi-isotopic hydrogen retention by a getter trap for the DONES lithium loop

Compliance with imposed hydrogen concentration limits in the lithium loop of the DEMO-Oriented Neutron Source (DONES) requires the installation of an yttrium-based hydrogen trap. To determine an appropriate H-trap design, it is essential to have access to a numerical tool capable of simulating hydrogen transport in the DONES lithium loop connected to an yttrium pebble-bed. In the past, a simplified model was created that allows such calculations when hydrogen concentrations in the lithium are low. However, in certain DONES operating phases, the concentration in the lithium is high and in a range where yttrium dihydride (YH2) formation is likely. Due to the anticipated great impact of YH2 formation on the H-trap performance a new model is developed that includes the mechanism of hydride formation. It is based on a mathematical reproduction of complete pressure-composition isotherms of the Li–H and Y–H systems. Thus, the conditions that trigger YH2 formation are determined and the variation of hydrogen solubility in different yttrium hydride phases is deduced. An approximate concentration-dependent relationship of hydrogen diffusivity in yttrium is derived and incorporated into the model. Simulations are performed to analyze the dynamics of the concentration decrease during purification of the lithium circuit prior to the experimental DONES phase by varying design parameters of the trap. It is found that hydride formation greatly increases the hydrogen gettering capacity of the H-trap and limits the maximum concentration in the lithium. Indeed, YH2 formation may be purposefully triggered to exploit its beneficial properties for DONES. Simulations of the hydrogen purification process during the experimental phase of DONES show that the H-trap must be replaced at least every 28 days to meet tritium limits. This work sets the conditions for the required pebble-bed mass of the H-trap at a given temperature to comply with the DONES safety requirements. Finally, the model is validated by numerical reproduction of experimental results.

Modelling and simulation of a novel nitinol-aluminium composite beam to achieve high damping capacity

Alloys demonstrating non-linear hyperelastic hysteretic behaviour, such as Nitinol, attract a lot of attention in the aerospace and other industries due to their high damping capacity. To overcome limitations due to the high cost and density of Nitinol, we explore its use in combination with aluminium alloys to produce an affordable lightweight composite structure with high damping capacity. The challenge is that Nitinol should operate in its hyperelastic range at strains well over the yield point of aluminium, often at large vibration amplitudes, while aluminium should remain well below its elastic limit. To overcome this limitation, this paper proposes a novel beam topology with two Nitinol skins connected with transversal strips made from aluminium alloy, which acts as a lightweight core to the composite structure. A numerical parametric study is conducted to estimate the stiffness, load capacity and loss factor of the material with varying design parameters, including the thickness of the skins and that of the core. Analytical models are also developed as a preliminary design guideline from the fundamental principles of the theory of bending, based on which non-dimensional design parameters are established, and their results are compared. From the study, it is shown that at specific configurations of the design parameters, there is a potential to achieve not only high damping capacity at the skins even at small vibration amplitudes while keeping the core in its elastic region, but also high system stiffness at the same time.

An experimental study of NOx emissions from a Helmholtz resonator

A detailed experimental investigation of NOx emissions was conducted in order to get more precise combustion data for a Helmholtz resonator valveless pulse combustor. A laboratory-scale model of the combustor was designed and operated with a non-premixed input of air and propane. The effects of fuel flow rate, temperature, and pressure amplitude on NOx emissions through a variety of experimental tests were studied. The tests were carried out for three tailpipe lengths, two inlet pipe lengths, and two combustion chamber volumes. The results revealed that the variations in operational and design parameters have a significant impact on NOx emissions. NOx emissions reach a maximum value near the stoichiometric condition as temperature and pressure, which are related to the fuel flow rate, reach their maximum values. Experiments show inverse relationships between CO and NOx emissions. Furthermore, the findings show that NOx reduction increases with increasing tailpipe and inlet pipe lengths, as well as small volume combustion chambers.

Surrogate modeling of structural seismic response using probabilistic learning on manifolds

AbstractNonlinear response history analysis (NLRHA) is generally considered to be a reliable and robust method to assess the seismic performance of buildings under strong ground motions. While NLRHA is fairly straightforward to evaluate individual structures for a select set of ground motions at a specific building site, it becomes less practical for performing large numbers of analyses to evaluate either (1) multiple models of alternative design realizations with a site‐specific set of ground motions, or (2) individual archetype building models at multiple sites with multiple sets of ground motions. In this regard, surrogate models offer an alternative to running repeated NLRHAs for variable design realizations or ground motions. In this paper, a recently developed surrogate modeling technique, called probabilistic learning on manifolds (PLoM), is presented to estimate structural seismic response. Essentially, the PLoM method provides an efficient stochastic model to develop mappings between random variables, which can then be used to efficiently estimate the structural responses for systems with variations in design/modeling parameters or ground motion characteristics. The PLoM algorithm is introduced and then used in two case studies of 12‐story buildings for estimating probability distributions of structural responses. The first example focuses on the mapping between variable design parameters of a multidegree‐of‐freedom analysis model and its peak story drift and acceleration responses. The second example applies the PLoM technique to estimate structural responses for variations in site‐specific ground motion characteristics. In both examples, training data sets are generated for orthogonal input parameter grids, and test data sets are developed for input parameters with prescribed statistical distributions. Validation studies are performed to examine the accuracy and efficiency of the PLoM models. Overall, both examples show good agreement between the PLoM model estimates and verification data sets. Moreover, in contrast to other common surrogate modeling techniques, the PLoM model is able to preserve correlation structure between peak responses. Parametric studies are conducted to understand the influence of different PLoM tuning parameters on its prediction accuracy.

Optimization of a Blended-Wing-Body Unmanned Aerial Vehicle Design for Maximum Aerodynamic Lift-to-Drag Ratio

Although unmanned aerial vehicle (UAV) has found many applications in various fields, its operation has been constrained by its low flight endurance. To date, several design efforts are pursued to improve this performance and one of them is the exploration of blended-wing-body (BWB) design. In this study, parametric study is conducted on the BWB UAV design of Baseline-VII that is developed by Flight Technology and Test Center (FTTC), Universiti Teknologi MARA Shah Alam, Malaysia. The primary goal is to optimize the current Baseline-VII design for maximum lift-to-drag ratio, which in turn implies a higher flight endurance. Three design parameters are considered: inboard wing sweep angle, outboard wing sweep angle and also inboard wing span. A full-factorial design of experiments (DoE) is applied to set the total 27 design case settings for this study, with three different values considered for each design parameter: 10°, 25° and 50° for inboard and outboard wing sweep angles, and 200 mm, 300 mm and 400 mm for the inboard wing span. The computer-aided design (CAD) models for the design cases are constructed using Solidworks and the resultant aerodynamic lift-to-drag ratio is found through computational fluid dynamics (CFD) simulation analysis using ANSYS Fluent. The collected data is then statistically analysed using regression analysis in MINITAB to construct a representative regression model that aptly capture the effects of the varied design parameters on the design aerodynamic lift-to-drag ratio. Based on the results, it has been found that the maximum lift-to-drag ratio for the modified Baseline-VII UAV design is 2.8119, which is obtained with optimal settings of inboard wing sweep angle = 17.2727°, outboard wing sweep angle = 20.9091° and inboard wing span = 400 mm. This is about 28.4% increment of lift-to-drag ratio from the original Baseline-VII design.

Screening Critical Design Parameters for Electromechanical Products Performance Matching Based on Energy and Causal Model

The design parameters are the most momentous factors in carrying out performance matching. For complex electromechanical products with a large number of design parameters, determining a set of critical design parameters which have a great influence on the performance is the premise of performance matching. In this paper, from a systematic perspective, a screening method of critical design parameters based on energy and a causal model is proposed. Since energy is the driving force of the product operation to achieve performance, the design parameters affect the performance through energy flow in the product. Therefore, the causal model among design parameters, characteristic energy, and performance is established, where its path coefficients are determined based on the quantitative calculation of the energy flow simulation model. Then, the performance pertinence is defined and calculated to describe the comprehensive influence of the design parameters on performance and to screen the critical parameters. Finally, the performance matching process is presented to support the performance matching. With a refrigerator as an example, 5 parameters were screened from 11 variable design parameters, and day power consumption decreased by 6.85%, which verifies the effectiveness of the method.

The load carrying capacity of reinforced concrete columns subjected to elevated temperature using simplified method

The present work proposes a method to determine the load-carrying capacity of the reinforced concrete column at elevated temperatures. The method uses the zone method mentioned in Eurocode to determine the temperature-dependent material properties of steel and concrete. Later the design equations, as per Indian standard guidelines, are used to determine the load-carrying capacity of the column. The loads considered here include both axial loads as well as uniaxial moments. The results obtained are validated with experimental data from the literature. Once Pu and Mu are determined using temperature-dependent materials properties, interaction curves are plotted at various temperatures mentioned in the standard time–temperature curve. The results obtained are validated against the experimental results from the literature. The Paper also investigates the behaviour of reinforced columns by varying design parameters like the size of the column and the grade of concrete. The work also discusses the relevancy of the 500° Isotherm method and the zone method mentioned in Eurocode when designing columns at elevated temperatures per Indian Standard guidelines.