Target Performance Level Research Articles

Control Theory Forecasts of Optimal Training Dosage to Facilitate Children's Arithmetic Learning in a Digital Educational Application.

Education can be viewed as a control theory problem in which students seek ongoing exogenous input-either through traditional classroom teaching or other alternative training resources-to minimize the discrepancies between their actual and target (reference) performance levels. Using illustrative data from [Formula: see text] Dutch elementary school students as measured using the Math Garden, a web-based computer adaptive practice and monitoring system, we simulate and evaluate the outcomes of using off-line and finite memory linear quadratic controllers with constraintsto forecast students' optimal training durations. By integrating population standards with each student's own latent change information, we demonstrate that adoption of the control theory-guided, person- and time-specific training dosages could yield increased training benefits at reduced costs compared to students' actual observed training durations, and a fixed-duration training scheme. The control theory approach also outperforms a linear scheme that provides training recommendations based on observed scores under noisy and the presence of missing data. Design-related issues such as ways to determine the penalty cost of input administration and the size of the control horizon window are addressed through a series of illustrative and empirically (Math Garden) motivated simulations.

Pareto-optimal performance-based robust design of braced excavations in soft clay with response surface methodology

This paper presents a methodology for robust design optimization of braced excavations in soft clay with response surface methodology based on the pareto-optimal trade-off between system performance and cost. As prediction of maximum ground settlement induced by excavation is generally accompanied by an implicit numerical model, the response surface methodology is employed to build the performance function with respect to both design parameters and uncertain geotechnical parameters. Then a pareto-optimal performance-based robust design framework of braced excavations in soft clay is formulated to find the optimal design that meets the design requirements while optimizing the system performance and construction cost. With the aid of a multi-objective optimization approach, trade-off relationship between performance robustness and cost efficiency are developed to help identify the most robust design based on the targeted performance levels. A design example of braced excavation in Taipei soft clay is used to illustrate the significance of the proposed methodology.

Performance based design of a new hybrid passive energy dissipation device for vibration control of reinforced concrete frames subjected to broad-ranging earthquake ground excitations

This paper evaluates a new hybrid passive device that comprises two different passive energy dissipation categories, namely, viscoelastic damper and friction damper. The device operates as a synergic unit using a novel locking mechanism. The hybrid passive device offsets the drawbacks of individual devices and facilitates improving the performance of structures for multiple excitation vibration levels due to wind and seismic events. Both devices are connected in a parallel combination using locking mechanisms and exhibit distinct hysteretic characteristics under small and significant deformation. The viscoelastic damper alone will be activated for extreme winds and minor to moderate earthquakes, and both devices will work simultaneously for strong earthquakes. Considering the advantages of such a new device, this article presents a new seismic design method structures equipped with a hybrid passive dampers device using the energy-balance concept. The method accounts for the structural member's inelastic behaviour, phase transformation of the stiffness and the energy dissipation capacity of the energy devices to achieve the intended performance level under the design earthquake hazard. The proposed method has been applied on a six- and a twelve-storied reinforced concrete building. The seismic performance is verified through nonlinear time history analysis using a set of near and far-field ground motions. Numerical results are investigated in terms of the inter-story drifts, the residual drifts, the floor acceleration and the yield mechanisms. The structure's performance corresponds well with the target performance levels.

Reliability Analysis of Rock Supports in Underground Mine Drifts: A Case Study

Support failures in mine drifts represent potential hazards that threaten underground mine safety and productivity. The aim of this study is to determine the reliability index associated with the rock supporting elements used in Ridder-Sokolny mine, an underground mine located in East Kazakhstan. Numerical simulations of the drift support and the First Order Reliability Method (FORM) were employed to carry out the analysis. Several support cases were considered including: shotcrete, bolting, concrete, bolting combined with concrete and unsupported drift case. For each support case, the Factors of Safety (FS), the reliability index (β) and the Probability of Failure (PF) were determined in accordance with the corresponding rock mass quality and the excavation geometry. The results indicate a slight variation of the average FS values for the different support cases (except for shotcrete) while β and PF vary more significantly between 0.62–3.25 and 0.05–27 (× 103%) factor depending on the rock conditions and the installed support. The probability of failure of the rock support increases with a decrease in the rock mass quality. Similar trends are observed with an increase of the width/height ratio of the excavations for the same rock domain. These results illustrate that a single FS value obtained from a deterministic method may not always provide a sufficient indication of safety. This is in agreement with the field observations which have indicated a poor performance of the supports. Hence, on the basis of the reliability index of the supports, the requirement in terms of coefficient of variability of the rock mass quality to meet the target performance level is proposed. It is concluded that the results of this study could help improving the drift support design in Ridder-Sokolny mine.

Seismic performance analysis and rehabilitation applications for a historical masonry building through field works and experimental investigations

Historical buildings are distinct structures in terms of seismic performance and extensive evaluations focusing on their seismic mechanisms and responses have yet to be clarified and presented. Thus, it was aimed to present a methodology consisting of various analysis approaches for historical buildings to increase the seismic strength. This study also covers rehabilitation applications for a historical masonry structure that was originally designed as the hospital building, however, later refunctioned to serve as the military prison, and presently in use as a university building. The pre-defined tasks in the study are implemented in three stages. Firstly, the material properties of building components were determined through field study and laboratory tests. Secondly, a series of simulations such as linear, non-linear, and kinematic analyses were performed using finite element software. As a result of the analysis, it was determined that the structure did not satisfy the targeted performance levels, as well as vertical and lateral bending mechanisms emerged. Therefore, a rehabilitation stage is presented due to the unsatisfactory seismic strength of the building. This work examines the seismic performance and proposes a rehabilitation approach for masonry buildings focusing on a particular and significant case, which includes the first structure built using solid bricks in Istanbul in the Ottoman era.

A model to support long-term building maintenance planning for multifamily housing

The authors put forward an optimization model to assist condominium managers in defining the sequence of maintenance and improvement measures to be executed within a predefined planning horizon to achieve predefined levels of the building performance. The required input are: results of the building elements survey, the desired criteria-wise measures of building performance, and the proposals of maintenance/improvement measures to select from, with the assumption that at least some of them are complementary and must be conducted in certain order to avoid rework. The product of the analysis is a schedule: a selection of technically justified and financially viable sequences of repair/improvement activities and their allocation to consecutive periods of the planning horizon. The optimization module of the model, being the focus of the paper, bases on the mixed integer linear programming. Its unique feature is the approach to constraints. The model operation is illustrated by a numerical example. Using the model, the planner is able to assess how the settings (target performance levels and the scale of the planning horizon) affect the choice and schedule of maintenance/improvement measures and the scale of the sinking fund to be systematically collected from the flat owners. The relative simplicity of the model makes it a practical tool for developing long-term maintenance plans for residential buildings as well as justifying maintenance fees.

Characterization of Dissipated Energy Demand

Performance-Based Earthquake Engineering (PBEE) aims at designing structures that are able to satisfy multiple target performance levels at different ground motion intensities. The performance levels can be introduced into the overall design process through energy concepts. It is acknowledged that the design of structures protected by control systems such as base isolation or energy dissipation devices can be efficiently optimized by using an energy-based approach. The energy-based design approach incorporated within the probabilistic framework of the performance-based design is a promising design method. In its development, three important energy-based dissipation parameters are critically needed to evaluate, which are the ratio of hysteretic energy to input energy EH/EI, normalized cumulative damage η, as well as the equivalent number of cycles neq. Therefore, this study has taken a comprehensive investigation of these parameters for four hysteretic systems of structures with the vibration period of 0.05s–4s for 7 damping ratios, that is 0.02, 0.05, 0.1, 0.2, 0.3, 0.4 and 0.5, and 6 ductility factors, that is 2, 3, 4, 5, 6 and 8. Empirical formulas of predicting the mean values and standard deviations of the energy-based dissipation parameters are proposed as a function of vibration period, damping ratio, and ductility factors. The proposed predictive models can be easily and conveniently used to evaluate the energy-based dissipation parameters in a deterministic and probabilistic manner in the energy-based design in the framework of PBEE.

Full-scale tests of two-story RC frames retrofitted with steel plate multi-slit dampers

There is a growing need of seismic retrofit of existing non-seismically designed structures in Korea after the 2016 Gyeongju and 2017 Pohang earthquakes, especially school buildings which experienced extensive damage during those two earthquakes. To this end, a steel multi-slit damper (MSD) was developed in this research which can be installed inside of partition walls of school buildings. Full-scale two-story RC frames were tested with and without the proposed dampers. The frames had structural details similar to school buildings constructed in the 1980s in Korea. The details of the experiments were described in detail, and the test results were validated using the analysis model. The developed seismic retrofit strategy was applied to a case study school building structure, and its seismic performance was evaluated before and after retrofit using the MSD. The results show that the developed retrofit strategy can improve the seismic performance of the structure to satisfy a given target performance level.

A review of successful climate change mitigation policies in major emitting economies and the potential of global replication

This article reviews climate change mitigation policies implemented in five major emitting economies: China, the European Union, India, Japan and the United States. It analyses their historical performance in terms of energy system and greenhouse gas emissions indicators. In cases where policies aim to reduce future emissions, their target performance levels are assessed. The review centres on the sectors of electricity generation, passenger vehicles, freight transport, forestry, industry, buildings, agriculture, and oil and gas production. Most focus countries have implemented successful policies for renewable energy, fuel efficiency, electrification of passenger vehicles, and forestry. For other sectors, information is limited or very heterogeneous (e.g. buildings, appliances, agriculture) or there are few comprehensive policies in place (e.g. industry). The article further presents an explorative emissions scenario developed under the assumption that all countries will replicate both the observed trends in sector-level indicators and the trends that policies for future emissions reductions aspire to achieve. It shows that the global replication of sector progress would reduce greenhouse gas emissions by 2030 by about 20% compared to a current policies scenario. All countries analysed would overachieve the emissions reduction targets in their post-2020 climate targets. However, the resulting reduction in global emissions by 2030 would still not be sufficient to keep the world on track for a global cost-effective pathway that keeps temperature increase below 2°C. The findings of this study emphasise the need for transformative policies to keep the Paris Agreement temperature limit within reach.

Multi-level Response Modification Factor Estimation for Steel Moment-Resisting Frames Using Endurance-Time Method

ABSTRACT The computational complexity and high computational costs are the main obstacles to estimate the seismic demand and capacity of non-linear structural systems and assess their seismic performance under strong earthquake events. On the other hand, the current response modification factors for seismic design of structures are mainly based on a single performance target, and therefore, cannot be directly used in modern performance-based design procedures. In this study, a low computational cost method is adopted for seismic performance assessment of steel moment-resisting frames and development of multi-level modification factors by using the newly-developed Endurance-Time method. The efficiency of the proposed method is demonstrated for 3, 5, and 7-storey frame examples. It is shown that compared to conventional methods using time-history and pushover analysis techniques, the proposed approach can significantly (up to 80%) reduce the computational costs. The results indicate that push-over analyses may lead to inaccurate results, while a good agreement is generally observed between the seismic demands predicted by Endurance-Time and Time-History methods (less than 10% error). The results of Endurance-Time method are then used to develop multi-level response modification factors for steel moment-resisting frames by taking into account the effects of earthquake intensity and the target performance level. It is shown that Endurance-Time method can accurately estimate the response modification factors and the corresponding earthquake intensity levels with significantly less computational cost compared to the conventional methods using incremental dynamic analysis. The proposed multi-level response modification factors should prove useful in performance-based seismic design of steel moment-resisting frames.

Performance-Vesting Share Award Outcomes and CEO Incentives

ABSTRACTI investigate the incentives provided by performance-vested stock awards (PVSAs) and the accuracy of ex ante PVSA valuations. In PVSAs, the number of shares awarded to the CEO varies based on how firm performance compares to target performance levels. The incentives provided by PVSAs and their valuations depend on the difficulty of the performance targets, which cannot be easily determined using ex ante disclosures. Using a hand-collected dataset of PVSA outcomes, I find that target difficulty is such that CEOs have incentives to earn additional shares from improved firm performance in 75 percent of PVSAs. In contrast, findings in prior studies using methodologies that rely on comparisons of PVSA targets to similarly named financial statement metrics suggest only 12 percent of awards provide such incentives. I further find that, on average, PVSAs pay out 115 percent of shares disclosed in ex ante valuations, suggesting the valuations of awards are understated.Data Availability: Data are available from sources cited in the text. PVSA outcome data are available upon request from the author.JEL Classifications: G34; J33; M12.

Operating Theatre Ventilation Systems and Their Performance in Contamination Control: "At Rest" and "In Operation" Particle and Microbial Measurements Made in an Italian Large and Multi-Year Inspection Campaign.

In Operating Theatres (OT), the ventilation system plays an important role in controlling airborne contamination and reducing the risks of Surgical Site Infections (SSIs). The air cleanliness is really crucial in this field and different measurements are used in order to characterize the situation in terms of both airborne microbiological pollutants and particle size and concentration. Although the ventilation systems and airborne contamination are strictly linked, different air diffusion schemes (in particular, the Partial Unidirectional Airflow, P-UDAF, and the Mixing Airflow, MAF) and various design parameters are used, and there is still no consensus on real performance and optimum solutions. This study presents measurements procedures and results obtained during Inspection and Periodic Performance Testing (1228 observations) in a large sample of Italian OTs (175 OTs in 31 Italian hospitals) in their operative life (period from 2010 to 2018). The inspections were made after a cleaning procedure, both in “at-rest” conditions and “in operation” state. Inert and microbial contamination data (in air and on surfaces) are analyzed and commented according to four relevant air diffusion schemes and design classes. Related data on Recovery Time (RT) and personnel presence were picked up and are commented. The results confirm that the ventilation systems are able to maintain the targeted performance levels in the OT operative life. However, they attest that significant differences in real OT contamination control capabilities do exist and could be ascribed to various design choices and to different operation and maintenance practices. The study shows and confirms that the air diffusion scheme and the design airflow rate are critical factors. Beside large variations in measurements, the performance values, in terms of control of airborne particle and microbial contamination (in air and on surfaces), for P-UDAF systems are better than those that were assessed for the MAF air diffusion solution. The average performances do increase with increasing airflows, and the results offer a better insight on this relationship leading to some possible optimization.

Optimal strategies for floating anchored information with partial infrastructure support

Floating Content (FC) is a communication paradigm to locally share ephemeral content without direct support from infrastructure. It is based on constraining the opportunistic replication of content in a way that strikes a balance between minimizing resource usage and maximizing content availability among the intended recipients. However, existing approaches to management of FC schemes are unfit for realistic scenarios with non-uniform user distributions, resulting in heavy overdimensioning of resources allocated to FC. In this work, we propose a new version of FC, called Cellular Floating Content (CFC), which optimizes the use of bandwidth and memory by adapting the content replication and storage strategies to the spatial distribution of users, and to their mobility patterns. The main idea underlying our approach is to partition users into small “local communities”, and to optimally weight their contributions to the FC paradigm according to their specific mobility features, and to the resources required to achieve a target performance level. We characterize numerically the properties of the optimal strategies in a variety of mobility patterns and traffic conditions, showing the accuracy of our approach, and the significant savings it enables in the amount of resources necessary to run FC, which in a realistic setup can be as high as 27% with respect to traditional FC dimensioning strategies.

A generalized 2-DOF model for optimal design of MDOF structures controlled by Tuned Mass Damper Inerter (TMDI)

The paper illustrates a methodology to perform the optimal design of a Tuned Mass Damper Inerter (TMDI) equipped on a multi degree of freedom (MDOF) structure through a generalized model. The TMDI is considered in both configurations grounded and ungrounded. A generalized 2-DOF model is obtained: the primary oscillator, representing the original MDOF structure and the secondary oscillator, representing the control system. A Gaussian zero mean white noise random process is adopted for the excitation. The TMDI design is carried out adopting an energy objective function, maximized over the space of the design parameters which are: the mass and inertance ratios, the frequency ratio, the damping factor and a parameter that accounts for the TMDI location on the MDOF structure. Synthetic performance-based design maps of the TMDI parameters are carried out. It is shown that is possible to have different design configurations to achieve a target performance level. The maps furnish, as limit cases, the design of a Tuned Inerter Damper (TID) and a Tuned Mass Damper (TMD), when the mass or the inertance ratios are respectively assumed null. It is shown straightforwardly the regions of the design parameters where the inerter enhances the performances achievable by classical TMD. Furthermore, an analytical expression which links the optimal design variables necessary to obtain a desired target performance is proposed. Frequency response functions and modal parameters of certain 2-DOF models with optimally designed control system are reported and considerations on how the design parameters influence the system dynamics and the damping capabilities are highlighted. Comparisons of the TMDI optimally designed with cases of no control and same mass TMD are evidenced throughout the paper. Finally, the main responses of the primary structure and the TMDI are estimated in the space of variation of the design parameters in order to assess the effectiveness of the control system.

Multi-stage optimization and meta-model analysis with sequential parameter range adjustment for the low-energy house in Korea

The demand for low-energy building in the market is growing in Korea. However, transition of the market is slow mainly due to shortage of relevant information regarding the selection of energy saving design and technical elements with their subsequent impact on energy performance. Recent development of optimization tools has tried to integrate energy performance simulation with conventional architectural design process. However, these new optimization techniques such as stochastic optimization, sensitivity analysis, and meta-model analysis failed to provide sufficient knowledge base for all stakeholders during the design process despite their potentials. The objective of this study was to test an integrated process of optimization analysis and information production. An integrated automatic simulation framework was established with Passive House Planning Package (PHPP) and modeFrontier. Sequential adjustment of ranges of influential parameters was then performed until the median value of heating demand in randomly constructed design of experiment (DOE) cases reached two target performance levels. 2D plot charts for influential parameters in each target performance level were obtained based on meta-model analysis satisfying low-energy target objects.Main findings of this study are as follows: 1) Technical parameters are more influential than design parameters. Thus, it is necessary to establish technical levels for selected primary parameters such as SHGC and linear thermal transmittance; 2) The influential priority of parameters changes through eight simulation phases. Thus, the reliability of the sensitivity analysis is largely dependent on the defining realistic and feasible ranges for every planning parameter; 3) In the case of newly-introduced parameters and technologies, the proposed methodology of multi-stage optimization analysis for advising technical level has potential to provide enough information regarding the selection of appropriate technical levels and the interrelationship among other parameters.Comparative analysis of simulation results and experts’ cognition was conducted. Results of analysis show that education for thermal bridge free design is required and solar heat gain coefficient (SHGC) of glazing should be addressed more seriously. The final design decision advisory 2D charts of influential parameters in two performance target levels showed potential of knowledge platform for all stakeholders during the design process. Although this study simulated and tested the potential of multi-stage optimization based on heating demand of the prototype rural house, the methodology could be expanded to the multi-objective optimization, including cooling and lighting consumptions.

Customization scenarios for de-identification of clinical notes

BackgroundAutomated machine-learning systems are able to de-identify electronic medical records, including free-text clinical notes. Use of such systems would greatly boost the amount of data available to researchers, yet their deployment has been limited due to uncertainty about their performance when applied to new datasets.ObjectiveWe present practical options for clinical note de-identification, assessing performance of machine learning systems ranging from off-the-shelf to fully customized.MethodsWe implement a state-of-the-art machine learning de-identification system, training and testing on pairs of datasets that match the deployment scenarios. We use clinical notes from two i2b2 competition corpora, the Physionet Gold Standard corpus, and parts of the MIMIC-III dataset.ResultsFully customized systems remove 97–99% of personally identifying information. Performance of off-the-shelf systems varies by dataset, with performance mostly above 90%. Providing a small labeled dataset or large unlabeled dataset allows for fine-tuning that improves performance over off-the-shelf systems.ConclusionHealth organizations should be aware of the levels of customization available when selecting a de-identification deployment solution, in order to choose the one that best matches their resources and target performance level.

A Feedback Control Strategy for Energy-Harvesting in Diffusion-Based Molecular Communication Systems

Piezoelectric nanogenerators recently emerged as a turning point in the design of energy-aware and energy harvesting transmission scheme at the nanoscale. This work considers their adoption in diffusion-based molecular communications, proposing a power control strategy based on feedback control theory. In particular, the transmission power of an electrochemical nanodevice fed by a piezoelectric nanogenerator is dynamically set proportionally to the available energy budget, by using a closed-loop control scheme. The resulting system is analytically modeled with a discrete-time nonlinear state equation. The range of acceptable values of the proportional gain is theoretically derived by studying technological constraints and global asymptotic stability. The impact of the proportional gain on both output variance and time constant of the linearized system around the equilibrium point is also investigated. Computer simulations validate the theoretical analysis under different parameter settings. The comparison against state of the art transmission scheme also demonstrates the unique ability of the conceived approach to ensure, at the equilibrium, the targeted performance level.

An Investigation on Process Capability Analysis for Fused Filament Fabrication

Additive manufacturing (AM) has become a popular manufacturing technology today. Many companies have been investing in AM technologies and skill development to carefully integrate them into their capabilities. Despite its benefits, AM has several disadvantages that require in-depth analysis and process engineering. This research focuses on the reproducibility issue of fused filament fabrication (FFF) for polylactic acid printing to reveal whether the AM technology can produce parts comparable to those by traditional or subtractive manufacturing. For this purpose, identification of optimal process parameters and process capability analysis are integrated to achieve repeatable minimum deviation from target dimensions. First, a design of experiments is planned and performed to determine the optimal combination of significant factors to ensure dimensional accuracy. Then, process capability analysis under optimal factor settings is performed to examine whether the printed part dimensions satisfy the target performance levels. Findings from this study show the FFF process can match the reproducibility of manufacturing parts produced by traditional manufacturing technologies.

He is smarter when he looks smart in front of many versus a few others: Impact of audience size on target appraisals in a cross-cultural context.

Will a person be seen as more superior if he or she receives an award in front of a large audience in comparison with a small audience? We predicted that this would hold true for East Asians, whose cultural logic of face asserts that a person's worth can only be conferred by collective others, but would not hold true for European Americans, whose cultural logic of dignity promotes the judgement of a person's worth based on their own perspective. This study found an audience-size effect for East Asians, in which participants gave higher appraisals to a target when they imagined the target's high performance to have been seen by 10 other people (vs. one other person) even when the target's performance level remained constant. In contrast, Westerners were not affected by the size of the audience witnessing the target's performance. In addition, perceived social reputation was found to mediate the audience-size effect; the participants imagining the target performing well in front of 10 others (vs. one other) perceived others as thinking more highly of the target; this in turn led participants to give higher appraisals to the target. As expected, this mediation effect was only found for East Asians.

Performance-Based Assessment Methodology for Retrofit of Buildings

Postearthquake reconnaissance and recent research on seismic risk analysis have shown that nonductile concrete frame structures are much more susceptible to collapse than modern code-conforming frames. The performance-based assessment paradigm has been a persistent research theme over the last decade within the earthquake engineering community in order to estimate seismic fragilities and earthquake loss for these nonductile concrete frames. This paper proposes a nonlinear performance-based methodology to evaluate different retrofit methods considering hazard level, target performance levels, and life-cycle cost estimates. The structural performance is the main parameter considered for the optimization, although a life-cycle cost analysis is also presented. As a case study, the longitudinal frame of an existing building was modeled considering the effect of flexural-shear-axial load interaction in order to capture column shear and axial failures. The presented performance-based procedure identifies the most economic retrofit solution that satisfies structural response requirements for a given performance level.