Trade-off Studies Research Articles

Trade-off study and the influence of different fuel injection strategies to enhance the engine characteristics powered with ternary fuel in CRDI diesel engine.

The effects of a diesel engine combustion chamber geometries (PB1, PB2, PB3) and fuel injection pressure (FIP) (500, 750, and 1000 bar) with ternary fuel are discussed in this paper. It is observed that at maximum load as the FIP increased, the PB3 surpasses the PB1 and PB2 in brake thermal efficiency (4.86%) and hydrocarbon (7.2% decrease). However, a minor reduction in NOx (3%) is seen with increased FIP in the PB2. The NHRR (net heat release rate), peak pressure (in-cylinder), and ROPR (rate of pressure increases) all considerably increase with an enhancement in FIP in the case of PB3 by 2.96%, 3.86%, and 1.98%, respectively. It is discovered that altering the fuel injection pressure and piston shape concurrently offers a viable substitute for raising engine output and reducing emissions.

Eliciting Societal Preferences for Non-health Outcomes: A Person Trade-Off Study in the Context of Genomics

Economic evaluations of health technologies traditionally aim to maximize population health outcomes measured by using quality-adjusted life-years (QALYs). Non-health outcomes, however, may have high social value, and their exclusion has the potential to bias decisions regarding allocation of health care resources. This research positions Australian participants as societal decision-makers to explore their willingness to trade-off health gains in adults for non-health benefits in families with a child affected by a rare disease. To estimate the social value of the different health care interventions, a person trade-off (PTO) method was used. PTOs present participants with groups of beneficiaries that vary in terms of the number of individuals who will benefit, the individuals' characteristics, their expected benefits, or a combination, and ask which group should be prioritized. Each trade-off presented health gains from the treatment of moderate physical and mental health conditions described by the 3-level version of the EuroQol 5-Dimension (EQ-5D-3L) health states. The health gains in these groups were traded-off against non-health gains in families accessing diagnostic genomic testing, and equivalence values were calculated, using median and ratio of means methods, based on the ratio of the group sizes at the point of equivalence. Participants were recruited through Prolific and were stratified according to age, sex, and education.The impact of participant characteristics on equivalence values was assessed using Kruskal-Wallis H tests and ordinary least-squares log-linear regressions. Participants (N=434) positioned as societal decision-makers were generally willing to trade-off adult health gains with the familial non-health benefits of genomic testing, showing a preference for valuing both types of outcomes within public health policy. The aggregation of preferences generated 2 weightings for genomic testing against each health treatment, an unadjusted value and a reweighted value to match target demographic characteristics. Converted into QALY value per test, it was found that participants valued the non-health benefits of genomic testing between 0.730 and 0.756 QALY. A minority of participants always prioritized diagnostic genomic testing over the physical (6.0%) or mental (4.6%) health treatments, with a larger minority always prioritizing the physical (15.4%) or mental (14.8%) health treatments. The findings indicate that participants perceived the non-health parental benefits in children experiencing rare disease to have comparable value to health gains in adults experiencing the moderate physical or mental health conditions described using EQ-5D-3L. These findings suggest that the benefits of genomic tests would be underestimated if only health benefits are included in economic evaluations.

A Systems Engineering Approach to Reducing Mis‐pulls and Misplaced Trailers for Trucking Fleets

AbstractHeavy vehicle fleets can have more than three times the number of trailers than tractors, but tractors host most of the vehicle network and tracking systems. Tractor location is readily available through telematics systems, yet trucking operations may pull the wrong trailer during operations because of the lack of trailer location information. The lack of automated trailer location data can lead to lost or mis‐placed trailers, which compromises the service of the product being shipped. Adding dedicated telematics systems to individual trailers is cost prohibitive. Therefore, we propose leveraging the tractor's existing location data with unique identifiers from the trailer to geo‐reference trailers. The goal of the proposed system is to use existing truck and trailer hardware (i.e. the braking system controllers) to identify the trailer serial numbers to the truck‐tractor, which creates geo‐referenced tractor‐trailer combinations. This work follows a system engineering approach for a trailer tracking system design beginning with a thorough review of the problem and customer need, generating concise requirements, conducting a tradeoff study of potential solutions, and demonstrating the proposed solution on a test bench. A systems engineering approach following the International Organization for Standardization (ISO) 15288 and International Council on Systems Engineering (INCOSE) technical processes is used for this design and development effort. This work demonstrates a novel approach, delivering a trailer tracking capability fielded through minimal changes to existing hardware and software. This automated trailer location system would reduce mis‐pulled and temporarily misplaced trailers, thus saving time and money for fleet operations worldwide.

Indian spectroscopic and imaging space telescope (INSIST): An optics design trade-off study

Indian spectroscopic and imaging space telescope (INSIST): An optics design trade-off study

PCR3 Pain-Free Injections for Growth Hormone Deficiency (GHD) Improve Quality of Life: A Time Trade-Off (TTO) Study in the UK and Canada

Growth hormone deficiency (GHD) in children causes decreased growth and markedly reduced adult height. The treatment for GHD has been given as daily subcutaneous injections. However, new GH formulations can be given weekly. Injections are a burden for children and caregivers, but to our knowledge, the impact on quality of life (QoL) has not been investigated using time trade-off (TTO) methodology. This study evaluates the impact of type of injections on QoL using a TTO survey.

PCR67 Health State Utilities for Achondroplasia: A Time Trade-Off Study

Achondroplasia is a rare genetic disorder that prevents the changing of cartilage to bone, leading to disproportionate short stature, which can have serious complications that impact quality of life. The aim of this study is to elicit health state utility values (HSUV) corresponding to health states describing the burden of achondroplasia, via a TTO valuation approach with the general public.

An interactive framework to facilitate probabilistic set-based multidisciplinary design optimisation studies

The upcoming stringent environmental aircraft regulations and the environmental, social and governance (ESG) framework targeting net zero emissions has forced aircraft manufacturers to seek innovative feasible technical solutions. Often, there is the need to consider entirely radical solutions, such as hybrid-electric aircraft, which are not fully understood when compared with conventional kerosene driven aircraft. The recent development of a probabilistic set-based multidisciplinary optimisation methodology has demonstrated the ability to explore trade-offs when the requirements are uncertain. In this way, the weaknesses and potential to enable the feasibility of hybrid-electric aircraft can be studied from a systems perspective but maintaining the connection with more detailed trade-off studies of components of the sub-systems. We have developed an interactive interface, where the user is guided through the steps of the design methodology and the produced data is visualised to aid an informative decision-making process. In our illustrative case study, decision-makers are enabled to interactively explore the hybrid-electric propulsion design space while considering the impact to the figures of merit from expected improvements in the coming years of key enabling technologies, such as energy storage.

PCR63 A Time Trade-Off Study to Estimate Respiratory Syncytial Virus (RSV) Related Utility Values for Older Adults (OA) in the United States (US)

RSV is a highly contagious human pathogen that causes acute respiratory infections. The objective of this study was to estimate RSV-specific health utilities for US adults ≥60 years of age.

Deep Reinforcement Learning for Joint Trajectory Planning, Transmission Scheduling, and Access Control in UAV-Assisted Wireless Sensor Networks.

Unmanned aerial vehicles (UAVs) can be used to relay sensing information and computational workloads from ground users (GUs) to a remote base station (RBS) for further processing. In this paper, we employ multiple UAVs to assist with the collection of sensing information in a terrestrial wireless sensor network. All of the information collected by the UAVs can be forwarded to the RBS. We aim to improve the energy efficiency for sensing-data collection and transmission by optimizing UAV trajectory, scheduling, and access-control strategies. Considering a time-slotted frame structure, UAV flight, sensing, and information-forwarding sub-slots are confined to each time slot. This motivates the trade-off study between UAV access-control and trajectory planning. More sensing data in one time slot will take up more UAV buffer space and require a longer transmission time for information forwarding. We solve this problem by a multi-agent deep reinforcement learning approach that takes into consideration a dynamic network environment with uncertain information about the GU spatial distribution and traffic demands. We further devise a hierarchical learning framework with reduced action and state spaces to improve the learning efficiency by exploiting the distributed structure of the UAV-assisted wireless sensor network. Simulation results show that UAV trajectory planning with access control can significantly improve UAV energy efficiency. The hierarchical learning method is more stable in learning and can also achieve higher sensing performance.

Design and validation of impedance probe for platform-independent ionospheric plasma diagnostics

The design of an impedance probe (IP), which is one of the instruments in the package called IAMMAP for the CAS500-3 satellite, and related plasma chamber experiments are introduced. The characteristics of the IP were estimated based on plasma and antenna theory. Trade-off studies on the possible geometry and on the circuit configuration were carried out. It was shown that the combination of a short wave monopole antenna and a capacitor bridge with a heterodyne configuration is suitable for ionospheric plasma diagnostics. The plasma chamber experiments reveal that the upper hybrid resonance frequency measured by the IP is compatible with the plasma model and with the Ne values estimated by the Langmuir probe (LP). This suggests that the compactly-designed IP and LP can serve as a good combination for in-situ measurement of the ionospheric plasma providing self-calibrated plasma parameters.

Implementation of in-rod axially heterogeneous thorium-uranium fuel in a typical PWR

Given the potential of the thorium fuel cycle and the predominance of PWRs in today’s commercial fleet of nuclear power plants, further investigations on the introduction of thorium-based fuel in open-cycle reactors such as PWRs are warranted. The benefits of microheterogeneous thoria-urania fuel (e.g. increased burnup / fuel cycle length, reduced radiotoxicity and increased stability of spent fuel, proliferation advantages due, feasibility of converting UO2-based fuel manufacturing plants to ThO2-UO2), are diminished by fuel manufacturing costs, the need to denature thorium sections of the fuel, thermo-hydraulic design requirements, higher fission gas release and cladding temperature gradients.This paper presents results of the neutronic performance of homogeneous and multiple heterogeneous fuel pin cell designs and explores the fundamental reasons and reaction balances between the different fuel models. The work utilises fuel models with variations in the length and composition of thorium and uranium sections. We compare the various urania-thoria fuel models with a reference PWR (North-Anna 1) with similar fissile content. We postulate a number of fuel design criteria, to appraise fuel models in trade-off studies, including improved burnup and cycle length, limitations on fuel enrichment grade and excess reactivity during burnup (typically at beginning of cycle), safety requirements such as limitations on total burnup, power peaking and feedback mechanisms. In addition, criteria are set for proliferation resistance and radiotoxicity.Verification studies were performed on fuel with homogeneous and axially heterogeneous fuel cell pins, followed by initial assembly and full-core analyses, to affirm confidence in the models employed. Our results confirm significant conversion of thorium to 233U, resulting in an improved burnup and fuel cycle length. Shut down margins and neutron economy are improved by significantly reducing beginning of cycle excess reactivity and hence reducing the need for burnable and soluble neutron absorbers. The conversion of thorium to 233U then leads to an increase in reactivity later in the cycle. To address proliferation concerns, fuel models with denatured thorium sections are introduced.We conclude that among the well-performing fuel models, fuel comprising heterogeneous pins repeating 3 cm thorium and 1 cm uranium sections, with the uranium region enriched to 20 at% 235U, and the thorium region denatured to a specific degree, performed best in terms of the fuel criteria considered. The promising results for the fuel pin cell models were confirmed with initial assembly and full core models: Burnup improvement rendered by the 3Th1U fuel models is 25.6% / 22.3% / 17.9% for the pin cell / assembly / full core models respectively, in spite of employing denaturing of thorium sections, while also fulfilling the other stated fuel criteria.

Systems methods for analyzing trade-offs between food security and conserving biodiversity

The endeavor for greater food security has caused trade-offs between increasing agricultural production and conserving habitat of threatened species. We take a novel approach to analyze these trade-offs by applying and comparing three systems methods (systems diagrams, influence matrices, and land use modeling) in a case study of Uganda. The first two methods were used to scope out the trade-off system and identify the most important variables influencing trade-offs. These variables were agricultural yield, land governance processes, and change in land use and land cover. The third method was used to quantify trade-offs and evaluate policy scenarios to alleviate them. A reference scenario indicated that increasing agricultural production by expanding agricultural land provided food for 79% more people in 2050 (compared to 2005) but with a 48% loss of habitat of threatened species. A scenario assuming strong investments to augment agricultural yield increased the number of people fed in 2050 up to 157%, while reducing the loss of habitat down to 27%. We use a novel “trade-off coefficient” for a consistent comparison of scenario results. A scenario assuming yield improvement and ring-fencing protected areas reduced the trade-off coefficient from − 0.62 in the reference case to − 0.15. This coefficient can be used as a common basis to compare results from different trade-off studies. It was found that the three systems methods are useful, but have limitations as stand-alone tools. Combining the methods into a single methodology increases their collective utility by maximizing the transparency and comprehensiveness and potential stakeholder engagement of a trade-off analysis.

Scoring Approach to Assess Maintenance Risk for Aircraft Systems in Conceptual Design

Ease of maintenance can significantly contribute to reducing aircraft operational cost. Maintenance risk is defined as the opposite of maintenance ease; it is impacted by many factors, most of which are decided upon during the aircraft’s conceptual design. This paper proposes a novel method to assess the maintainability risks of aircraft systems by combining various aspects on the component level, intercomponent level, bay level, and aircraft level. For each level, all contributing factors to maintenance risk are analyzed and integrated into several scores. These maintenance risk scores can be used to assess the various aspects contributing to maintenance risk, using input parameters available during the conceptual design phase. This paper presents the validation of the scores using different components and aircraft equipment bays, such as avionic racks, the nose cone, and a complex aft equipment bay of a business jet. The proposed maintenance risk scoring method will enhance multidisciplinary tradeoff studies during aircraft conceptual design, considering competing design aspects such as system placement, thermal aspects, impact on aircraft balancing, or even the overall aircraft shape. Therefore, this new conceptual design capability enables designing novel aircraft configurations featuring unconventional system component placement or component bay shapes while considering maintenance aspects upfront.

Influence of split injection strategies and Trade-off study on the CRDI engine characteristics powered with waste cooking Oil/Diesel blend

An investigation has been conducted on a CRDI (common-rail diesel injection) engine utilizing a blended fuel with waste cooking oil (WCO20) to explore the influence of fuel injection strategies (i.e., split injection strategy with different fuel injection pressure) on the engine characteristics. It is observed that specific fuel consumption (BSFC) and nitrogen oxide emission (NOx) increased with a decrease in brake thermal efficiency (BTE) in the case of WCO20 at a base FIP of 40 MPa. The volatility and viscosity (physical properties) of the WCO20 fuel blend influenced the combustion phenomena resulting in a reduction in engine performance. The higher viscosity of the methyl ester blend restricts the fuel atomization process during the injection. Fuel injection pressure (Pinj) was raised from 40 to 100 MPa in increments of 25 MPa in the first phase to maximize the use of the WCO20 blend. High injection pressures (100 MPa) have higher BTE (12.33%) and better combustion characteristics (2.86 %) than lower fuel injection pressures (40 MPa). The concentrations of smoke (3.62 %), CO (15.6 %), and HC (2.8 %) were reduced as injection pressure was raised, owing to the better formation of the mixture and improved spray atomization. When used as a pilot injection before the main injection (BMI), 5% WCO20 reduces HC and CO emissions and NOx (7.82%) and smoke emissions while compromising only a marginal amount of thermal efficiency in the second phase.

Time trade-off study to establish utility decrements in individuals with a spinal cord injury who perform intermittent catheterization

AimsTo generate utility decrements for three attributes associated with catheterization for individuals with a spinal cord injury (SCI): the process of catheterization, the physical impact of urinary tract infections (UTIs) and worry associated with hospitalization.Materials and methodsHealth state vignettes comprising various levels of the three attributes were developed. Two cohorts of respondents, corresponding to people with SCIs and a sample broadly representative of the UK population, were presented with nine vignettes (three vignettes for the mild, moderate and severe health states in addition to a random set of six vignettes). It was assumed no or a nominal decrement was associated with the mild health state. Utility decrements were derived from analysing the data obtained from the online time trade-off (TTO). A proportion of the SCI cohort (n = 57) also completed the EQ-5D-5L questionnaire.ResultsUtility decrements were generated using statistical models for the general population (n = 358), the SCI population (n = 48) and the two populations combined (merged model, n = 406). Results from the two cohorts showed minimal differences. For the merged model, SCI status was not statistically significant. All interaction terms, excluding SCI and the severe level of the physical attribute, were not statistically significant. Compared to the mild level, the greatest utility decrement calculated was the severe level of the emotional (worry) attribute (0.09, p < .001) for the SCI population. A significant decrement of 0.02 (p < .001) was calculated for the moderate level of the emotional attribute for all models. The mean utility score for those with SCI having completed the EQ-5D-5L was 0.371.LimitationsModest sample size of respondents from the SCI population (n = 48).ConclusionsWorry associated with hospitalization had the greatest impact on patients’ health-related quality of life (HRQoL). The catheterization process, such as the lubrication and repositioning of the catheter, also impacted on patients’ HRQoL.

Analysis of heat transfer characteristics and optimization of U-tube based solar evacuated tube collector system with different flow conditioning inserts

In the present study, the performance of a U-tube based evacuated tube collector (ETC) for a forced circulation system is tested. The collector tilt angle is varied to analyse the optimum tilt angle to get the higher thermal performance of the solar U-tube ETC regardless of the sun's location. Different flow conditioning inserts are introduced, and its feasibility study is accomplished for the ETC in the place of a conventional plain U-tube ETC to obtain higher system performance. Further, a computational fluid dynamics (CFD) based thermal model is developed in Ansys-fluent R14.5 platform and validated with in-house experimental datasets. Based on the developed CFD model, a detailed parametric study is carried out to optimize the model geometry and operating parameters of solar ETC. CFD results revealed that increasing U-tube diameter from 1/8“ to 3/8” enhances the net temperature gain by about 39%. Consequently, the proposed flow conditioning inserts models showed a better performance with higher net temperature gain and thermal efficiency under the same condition with acceptable pressure drop penalty. Among the different studied geometries, twisted taped with square holes proved to be the most effective design for obtaining a higher thermal efficiency compared to the plain U-tube design. The temperature contour with streamlines and pressure contour of the best flow conditioning model is also discussed. Furthermore, a trade-off study is accomplished to visualize the thermal efficiency in contrast to pressure drop and net temperature gain.

Predicting and Reinforcing the Critical Buckling Loads of Flexible Corrugated Panels

Corrugated panels are promising in the field of morphing structures due to their high anisotropy. A low stiffness in the morphing direction allows for a reduced actuation force, which provides the benefit of reducing the system weight. However, a low stiffness also leads to reduced critical buckling loads, which makes it easier for corrugated panels to buckle in the morphing process. The conflict between the actuation force and the critical buckling load requires an efficient method to predict the critical buckling load, which can then be applied in a trade-off study to find the optimal design. In the current study, a simplified method to predict the critical buckling load is proposed based on the derivation of equivalent properties. The method is verified using the finite element analysis and applied for the optimisation of corrugated panels. A conceptual design to reinforce corrugated panels is also proposed, which shows a significant increase in the critical buckling load of flexible corrugated panels.

An Examination of Power Converter Architectures for Utility-Scale Hybrid Solar Photovoltaic and Battery Energy Storage Systems: The Features of Several Power Conversion Architectures

Recently, the falling costs of photovoltaic (PV) and battery storage (BS) technologies have raised interest in the creation of hybrid PV+BS power plants. Together with increasing energy storage capacity by storing clipped energy, hybrid plants broaden a power plant’s grid services by featuring fast dispatch flexibility and voltage-ampere reactive support. Although many proposed PV plants are being developed with colocated batteries, the dominant architecture of ­utility-scale PV+BS power plants is uncertain. Moreover, power architectures are expected to evolve over time based on future trends. The primary goal of this article is to critically examine and compare several dc–dc and dc–ac power converter architectures that are suitable candidates for hybrid PV+BS power plants. In particular, the article presents characteristics of several power conversion architectures from the point of view of power semiconductor requirements, efficiency, reactive component requirements, modularity, control complexity, and so forth. Detailed analytical models are utilized, along with a benchmark design example to present a comparative evaluation of the alternatives for performing engineering tradeoff studies.

A microstructure-based fatigue model for additively manufactured Ti-6Al-4V, including the role of prior [formula omitted] boundaries

Microstructure-based models of additive manufactured (AM) Ti-6Al-4V should faithfully represent the unique microstructural features of these materials to provide a more thorough understanding of their role in the mechanical performance of the material. For AM Ti-6Al-4V, the prior β boundaries are likely sites of microscopic plastic strain localization, often leading to fatigue crack initiation. Within the context of crystal plasticity finite element methods, there is an existing gap in the current literature for creating synthetic microstructures of Ti-6Al-4V that capture both the prior β boundaries and α laths. This work focuses on generating such statistically equivalent microstructures, where the prior β boundaries and α laths are explicitly modeled. The framework can generate synthetic microstructures that consider one prior β grain or multiple β grains (and thus prior β grain boundaries) and their associated α laths forming a Widmanstätten microstructure, which are used as inputs for fatigue simulations. Within the fatigue model, the critical accumulated plastic strain energy density (APSED) is a metric used to predict the location and number of cycles of crack initiation. From a statistical average perspective, the presence of prior β grain boundaries was detrimental to the fatigue performance. The effectiveness of the prior β grain boundary in impeding slip, and therefore localizing APSED, is dependent on the loading conditions, prior β orientations, and α variants present in neighboring prior β grains. A higher percentage of failures occurred at the prior β grain boundary in the case of lower applied stress amplitudes, where the applied loads were below the percolation limit of the material and microplasticity was localized to a few locations relative to the microstructure. Additionally, for the case of crack initiation associated with the α variants within a given prior β grain, a combination of soft-hard α lath orientations resulted in sites of APSED localization and predicted fatigue crack initiation. The framework generated in this paper to create representative synthetic microstructures of the Widmanstätten microstructures associated with AM Ti-6Al-4V and the associated fatigue modeling enables trade-off studies between microstructural features and fatigue performance.

Application of a q-rung orthopair hesitant fuzzy aggregated Type-3 fuzzy logic in the characterization of performance-emission profile of a single cylinder CI-engine operating with hydrogen in dual fuel mode

The experimental investigation was carried out in a single-cylinder, 4-stroke diesel engine which using hydrogen and diesel under dual fuel strategy to study the performance and emission spectra on the existing engine platforms. A TMI (timed manifold injection) system was designed employing an ECU (electronic control unit) for hydrogen induction into the engine manifold. The results showed a significant enhancement in BTHE (12.44% Max. enhancement at 85% full load condition under DH4 strategy) compared to base-diesel operation. The NOx emissions was enhanced to a maximum of 10.33 g/kw-hr at full load under DH4 strategy. The emissions of UHC was found to be higher at lower loads and gets significantly reduced to a maximum of 3.98 g/kw-hr at full load under DH2 strategy, while soot emissions decreases substantially and reduced to a maximum of 0.02 g/kw-hr at 85% full load condition under DH5 strategy. The trade-off study along-with an advanced q-Rung Orthopair Hesitant Fuzzy Aggregated Type-3 Fuzzy Logic System consolidated the suitable prediction for the performance and emission paradigms which confirms the verity that Diesel-H2 dual fuel operation was for high performance-low emission paradox. Thus an impending platform is developed with H2-disel dual fuel operation for the existing engine set-up.