Component-level Approach Research Articles

Synergetic and Performance Characteristics of A High-Speed Pre-Cooled Propulsion Concept

Abstract Pre-cooled air-breathing cycles are promising candidates to power future high-speed flight as well as Single-Stage-To-Orbit vehicles, due to their increased efficiency over contemporary propulsion systems and launch vehicles. These concepts usually feature complex interactions in the synergy of their thermodynamic cycles. In this study, a performance model of such a cycle is developed for its air-breathing mode of operation. One-dimensional thermodynamic modeling is employed within a component-level approach, to evaluate the performance and operation of the cycle under investigation in the range of 1.35 = ≤ 8 = 5 and conditions of up to 26 kilometers altitude. The model is validated quantitatively and qualitatively for both design and off-design conditions. The specific impulse Isp and specific thrust, as predicted by the model, agree within less than 5% for both design and off-design point conditions, while it captures the trend of Isp for the range modeled. Moreover the maximum gross thrust point is predicted correctly at M∞ = 4. The fundamental operating principles and synergetic characteristics of the engine at design and off-design conditions are investigated and reported. A model which does not feature a bypass duct is created and compared for the same inflow conditions and mission profile. It is found that the engine without the bypass duct exhibits reduced specific impulse up to 32% lower at off-design conditions while the overall trend of engine efficiency cannot be properly captured without modeling of the bypass duct, especially at the region of M∞ < 3.5.

Design of Low Cost Bio-impedance Measuring Instrument

It is a well-established fact that the electrical bio-impedance of a part of the human body can provide valuable information regarding physiological parameters of the human body, if the signal is correctly detected and interpreted. Accord-ingly, an efficient low-cost bio-electrical impedance measuring instrument was developed, implemented, and tested in this study. Primarily, it is based upon the low-cost component-level approach so that it can be easily used by researchers and investigators in the specific domain. The measurement setup of instrument was tested on adult human subjects to obtain the impedance signal of the forearm which is under investigation in this case. However, depending on the illness or activity under examination, the instrument can be used on any other part of the body. The current injected by the instrument is within the safe limits and the gain of the biomedical instrumentation amplifier is highly reasonable. The technique is easy and user-friendly, and it does not necessitate any special training, therefore it can be effectively used to collect bio-impedance data and interpret the findings for medical diagnostics. Moreover, in this paper, several existing methods and associated approaches have been extensively explored, with in-depth coverage of their working principles, implementations, merits, and disadvantages, as well as focused on other technical aspects. Lastly, the paper also deliberates upon the present status, future challenges and scope of various other possible bio-impedance methods and techniques.

OC6 Phase Ib: Floating Wind Component Experiment for Difference-Frequency Hydrodynamic Load Validation

A new validation campaign was conducted at the W2 Harold Alfond Ocean Engineering Laboratory at the University of Maine to investigate the hydrodynamic loading on floating offshore wind substructures, with a focus on the low-frequency contributions that tend to drive extreme and fatigue loading in semisubmersible designs. A component-level approach was taken to examine the hydrodynamic loads on individual parts of the semisubmersible in isolation and then in the presence of other members to assess the change in hydrodynamic loading. A variety of wave conditions were investigated, including bichromatic waves, to provide a direct assessment of difference-frequency wave loading. An assessment of the impact of wave uncertainty on the loading was performed, with the goal of enabling validation with this dataset of numerical models with different levels of fidelity. The dataset is openly available for public use and can be downloaded from the U.S. Department of Energy Data Archive and Portal.

Revisiting the lumbosacral orthosis from the perspective of dynamical systems theory: a preliminary randomized clinical trial on patients with chronic low back pain.

The prevalent method for investigating the effect of therapeutic interventions on walking in the individuals with chronic low back pain (CLBP) is component-level approach in which all measurements focus on the spine component alone. However, this approach cannot disclose information about the overall function of the movement system such as complex walking patterns, which, in turn, reveal the underlying movement control. To compare the effect of 3-week wearing of lumbosacral orthosis (LSO) along with routine physical therapy with routine physical therapy alone on walking complexity in the individuals with nonspecific CLBP on the basis of the systems approach. Preliminary randomized clinical trial. Twenty-four subjects were randomly allocated to two groups. The control group received the routine physical therapy for 3 weeks. The intervention group received the same program plus an LSO. Nonlinear analysis was used to quantify walking complexity, as behavior of the entire movement system, before and after the intervention and at 1-month follow-up. An average of 496 strides during ten minutes of walking was used for analysis. There was no significant difference (p > 0.05) in degree of walking complexity between two groups during all evaluation periods. The administered orthotic intervention did not alter walking complexity. This suggests that therapeutic goal of current LSOs, which is not based on the systems approach, cannot recover the emergent behavior of the movement system. This may be a potential source of controversies. To achieve an effective treatment, orthotists should focus on the individuals themselves, not only on their CLBP symptoms. Although the component-level approach aims to decrease the symptoms, the systems approach focuses on the whole context that fosters LBP symptoms.

Comparison of the Total Ionizing Dose Sensitivity of a System in Package Point of Load Converter Using Both Component- and System-Level Test Approaches

Testing at system level is evaluated by measuring the sensitivity of point-of-load (PoL) converter parameters, submitted to total ionizing dose (TID) irradiations, at both system and component levels. Testing at system level shows that the complete system can be fully functional at the TID level more than two times higher than the qualification level obtained using a standard-based component-level approach. Analysis of the failure processes shows that the TID tolerance during testing at system level is increased due to internal compensation in the system. Finally, advantages and shortcomings of the testing at system level are discussed.

Multi-platform app-embedded model for hybrid air-breathing rocket-cycle engine in hypersonic atmospheric ascent

ABSTRACTThis paper presents a performance analysis on a novel engine concept, currently under development, in order to achieve hybrid air-breathing rocket technology. A component-level approach has been developed to simulate the performance of the engine at Mach 5, and the thermodynamic interaction of the different working fluids has been analysed. The bypass ramjet duct has also been included in the model. This facilitates the improved evaluation of performance parameters. The impact of ram drag induced by the intake of the engine has also been demonstrated. The whole model is introduced into a multi-platform application for aeroengine simulation to make it accessible to the interested reader. Results show that the bypass duct modelling increases the overall efficiency by approximately 7%. The model calculates the specific impulse at approximately 1800 seconds, which is 4 times higher than any chemical rocket.

Key Components of Interventions for Grandparents Raising Grandchildren: A Systematic Review

Increasingly grandparents provide primary or supplementary care for their grandchildren globally. In view of the challenges faced by grandparent caregivers, a number of intervention programs were designed to act as a buffer to the potential negative impacts on their well-beings. A recent meta-analysis (Chan et al., 2019) shows that interventions for grandparent caregivers have small to moderate effect sizes for increases in social support and parenting skills. However, little is known how the multi-component interventions work. The aim of this review is to categorize the key components of intervention programs and determine the direct effect of components on grandparent caregivers’ outcomes (i.e., physical, mental health and well-being). A component-level approach is adopted to disentangle the ‘active ingredients’ of the interventions. Peer-reviewed articles were searched via five electronic database (published before January 2020). A keyword search was performed based on combinations of two groups of terms: (1) grandparent caregivers and (2) intervention, training, and support group. Studies adopting an experimental or pre/post design and reporting quantitative changes in grandparents’ outcomes were included. Studies focusing on the special needs of grandchildren were excluded. Fourteen interventions were identified from over 20 included studies. Preliminary analyses show that different physical and mental outcomes of grandparent caregivers were predicted from key components of education, skills training, relaxation and psychosocial support. With the goal of developing evidence-based interventions for grandparents raising grandchildren, this synthesis offers insight into the mechanisms of an intervention, which informs its generalizability or applicability to a new context.

Performance-based decision-making of buildings under seismic hazard considering long-term loss, sustainability, and resilience

It is of vital importance to incorporate sustainability and resilience in the performance-based decision-making of civil infrastructure under seismic hazard. However, a performance-based engineering framework utilizing component-level approach, integrating seismic loss, sustainability, and resilience in a multi-criteria decision-making (MCDM) is not yet extensively developed particularly for retrofit selection in a long-term perspective. This paper introduces a framework utilizing performance-based approach to couple seismic loss, sustainability, and resilience in decision-making framework for selection of different retrofit alternatives. A component-based probabilistic approach is developed for the seismic loss, sustainability, and resilience assessment in a long-term perspective. The resulting social, economic, and environmental consequences are converted to expected annual consequences (EACs) by considering the full range of seismic hazards, and are utilized as a multi-criterion in the technique for order preference by similarity to ideal solution (TOPSIS). The proposed long-term performance-based multi-criteria decision-making (PB-MCDM) framework considers five consequences, which include cost, casualties, equivalent carbon emissions, embodied energy, and repair time. Based on the illustrative example, it may be concluded that incorporating seismic sustainability and resilience in PB-MCDM approach in a long-term perspective can provide ideal solutions and better decision-making against retrofit alternatives.

Estimation of Seismic Expected Annual Losses for Multi-Span Continuous RC Bridge Portfolios Using a Component-Level Approach

ABSTRACT A method for the estimation of expected annual losses under seismic action, using a component-level approach, is proposed. The method follows the general steps of current Performance-Based Earthquake Engineering approaches and two distinct alternatives are evaluated depending on how the collapse cases are identified. Results are compared with a commonly implemented structure level approach, showing that the latter presents an upper bound in loss estimation. The accuracy of simplified structural analysis alternatives, such as nonlinear static procedures, is also evaluated. The method is found to be suitable for economic loss assessment under seismic hazards, producing performance measures easy to understand for different decision makers.

A metamodeling based seismic life-cycle cost assessment framework for highway bridge structures

This study presents a novel framework for seismic life-cycle cost assessment of highway bridges using parameterized fragility models rooted in modern statistical learning techniques. Unlike traditional fragility curves, often used for seismic loss assessment, the parameterized fragility models are multi-dimensional functions conditioned on ground motion intensity as well as critical field measurable bridge parameters. Such functions are particularly useful for prompt vulnerability estimation and life-cycle cost assessment of structurally dissimilar highway bridges across bridge portfolios in regions characterized by moderate to high seismicity. Consequently, the proposed framework can aid decision makers and stakeholders for efficient channeling of monetary resources for necessary seismic upgrade of highway bridges within a transportation network. As a case-study example, this study chooses the non-seismically designed multi-span simply supported concrete girders highway bridge class that constitutes a significant portion of the highway bridge inventory within Central and Southeastern US. The proposed parameterized fragility functions for this bridge are used along with seismic hazard data and probabilistic repair cost information for seismic loss assessment through a component-level approach. In addition to near-instant seismic life-cycle cost assessment, as demonstrated through several examples, this approach also helps avert potential double counting from multiple component damage while calculating system-level losses.

Strategies for structural modelling of CLT panels under cyclic loading conditions

Cross Laminated Timber (CLT) is an extensively used technology to build medium- and high-rise buildings, especially thanks to the rapidity of execution, environmental sustainability, and good mechanical performances. Since this material is presently employed also in seismic-prone areas, the assessment of numerical modelling strategies to reproduce the cyclic behavior of CLT-wall systems has become a relevant research topic within the structural engineering field. Two different modelling approaches can be adopted to model the seismic behavior of such systems: the phenomenological approach and the component-level one. After a comparative presentation of the two approaches, the paper focuses on the different strategies used to create reliable component-level models able to reproduce the CLT panel-connection system behavior both at the global and local level (i.e., in terms of force-displacement curve and cumulative energy, as well as uplift and slip displacements). The experimental tests carried out at CNR-IVALSA during the SOFIE project – after a preliminary phase of interpretation of the experimental dataset, necessary to identify the peculiarities of the test procedures – are used as a comparative basis to assess the quality of the numerical results. The obtained outcomes demonstrate that the component-level approach could be a feasible and reliable method to reproduce the CLT panel connection systems cyclic behavior, also at a local level, provided that the behavior of each individual component is properly calibrated.

FPGA-SPICE: A Simulation-Based Architecture Evaluation Framework for FPGAs

In this paper, we developed a simulation-based architecture evaluation framework for field-programmable gate arrays (FPGAs), called FPGA-SPICE, which enables automatic layout-level estimation and electrical simulations of FPGA architectures. FPGA-SPICE can automatically generate Verilog and SPICE netlists based on realistic FPGA configurations and a high-level eTtensible Markup Language-based FPGA architectural description language. The outputted Verilog netlists can be used to generate layouts of full FPGA fabrics through a semicustom design flow. SPICE simulation decks can be generated at three levels of complexity, namely, full-chip-level, grid-level, and component-level, providing different tradeoff between accuracy and simulation time. In order to enable such level of analysis, we presented two SPICE netlist partitioning techniques: loads extraction and parasitic net activity estimation. Electrical simulations showed that averaged over the selected benchmarks, the grid-/component-level approach can achieve $6.1\times /7.5\times $ execution speed-up with 9.9%/8.3% accuracy loss, respectively, compared to the full-chip level simulation. FPGA-SPICE was showcased through three different case studies: 1) an area breakdown analysis for static random access memory-based FPGAs, showing that configuration memories are a dominant factor; 2) a power breakdown comparison to analytical models, analyzing the source of accuracy loss; and 3) a robustness evaluation against process corners, studying their impact on energy consumption of full FPGA fabrics.

IC-engine acoustic source characterization in-situ with capsule tube method

Typically, a component level approach is used in control of internal combustion engine (IC-engine) exhaust noise. This has enabled the development of new, cost-efficient silencers, for example. However, prediction of sound emission from a tailpipe or insertion loss of a silencer requires a more extensive, system level approach. Therefore, valid IC-engine source characteristics and a valid model of the whole transmission path are needed. When characterizing an IC-engine as a source with the commonly used in-duct multi-load method, the requirements for load impedance variation must be fulfilled. It is fairly easy to vary the load in automotive cases, whereas new methods must be developed for large IC-engines, used e.g. in power plants. In this study, the source data determination process is investigated in detail, a novel “capsule tube method” is developed further and used for experimental acoustic source data determination of medium speed IC-engine exhaust system in harsh environment. With suitable filtration and statistical outlier rejection methods presented in this paper, the source data of a test IC-engine exhaust system was derived with success.

Investigation into the benefits of reduced oil flows in internal combustion engines

The engine lubrication system is a vital element for engine health but causes a parasitic load on the engine which increases the fuel consumption: this load can be reduced by matching the oil flow to lubricating requirements using a variable displacement oil pump. In a first stage, two variable displacement oil pumps were installed on a 2.4-L diesel engine; experiments over the New European Drive cycle showed reductions in fuel consumption of up to 3.4% and up to 5.8% over the urban phase of the cycle. A variable displacement oil pump was subsequently installed on an instrumented engine capturing over 100 metal and fluid temperatures within the engine structure. This showed that reducing oil flows resulted in lower oil temperature by up to 4 °C during cold-start New European Drive cycle but hotter cylinder liner temperatures by up to 6 °C. The higher cylinder wall temperatures caused an increase of 3% in oxides of nitrogen emissions but a reduction of 3%−5% in carbon monoxide and hydrocarbon emissions. Finally, an energy flow analysis showed that the variable displacement oil pump can reduce oil pump energy consumption by 160 kJ (32%) but that this led to a 400-kJ reduction in friction and accessory work. These findings highlight the need for a system-level rather than a component-level approach to engine lubrication design to capture key thermal interactions.

Seismic fragility methodology for highway bridges using a component level approach

AbstractBridge fragility curves, which express the probability of a bridge reaching a certain damage state for a given ground motion parameter, play an important role in the overall seismic risk assessment of a transportation network. Current analytical methodologies for generating bridge fragility curves do not adequately account for all major contributing bridge components. Studies have shown that for some bridge types, neglecting to account for all of these components can lead to a misrepresentation of the bridges' overall fragilities.In this study, an expanded methodology for the generation of analytical fragility curves for highway bridges is presented. This methodology considers the contribution of the major components of the bridge, such as the columns, bearings and abutments, to its overall bridge system fragility. In particular, this methodology utilizes probability tools to directly estimate the bridge system fragility from the individual component fragilities. This is illustrated using a bridge whose construction and configuration are typical to the Central and Southeastern United States and the results are presented and discussed herein. This study shows that the bridge as a system is more fragile than any one of the individual components. Assuming that the columns represent the entire bridge system can result in errors as large as 50% at higher damage states. This provides support to the assertion that multiple bridge components should be considered in the development of bridge fragility curves. The findings also show that estimation of the bridge fragilities by their first‐order bounds could result in errors of up to 40%. Copyright © 2006 John Wiley & Sons, Ltd.