Conservative Results Research Articles

Evaluation of Pencycuron Residue Dynamics in Eggplant Using LC-MS/MS and Establishment of Pre-Harvest Residue Limits

Pencycuron is a fungicide whose maximum residue limit (MRL) in eggplant is either set at very low levels (0.02 mg/kg in European Union) or remains unestablished in many countries, necessitating stringent pesticide management. To enable timely interventions by farmers and regulators, pre-harvest residue limits (PHRLs) propose maximum allowable pesticide concentrations for each day during the pre-harvest period. An analytical method was developed to conduct residue determination trials, demonstrating that graphitized carbon black (GCB) effectively removes eggplant matrices during sample preparation. The LC-MS/MS method was established with a limit of quantification (LOQ) of 0.005 mg/kg, recovery rates ranging from 102.6% to 106.1% with relative standard deviation (RSD; 2.3–6.4%), and a matrix effect (%ME) of +8.1%. Residue analysis revealed a concentration of 0.045 mg/kg at 0 days after treatment (DAT), decreasing to 0.006 mg/kg at 14 DAT. The residue dynamics followed a first-order kinetic model, as confirmed by the F-test, with a rate constant of 0.1405. Therefore, the half-life was determined to be 4.9 d. Based on the MRL value of 0.02 mg/kg at 0 days before harvest (DBH), the PHRL was determined using both k and kmin, resulting in values of 0.04 mg/kg and 0.02 mg/kg at 5 days and 0.08 mg/kg and 0.03 mg/kg at 10 DBH, respectively. Using kmin yields more conservative results, which ensures food safety under conditions of slower degradation rates.

Distributionally Robust Optimal Scheduling of Hybrid Ship Microgrids Considering Uncertain Wind and Wave Conditions

A hybrid ship uses integrated generators, an energy storage system (ESS), and photovoltaics (PV) to match its propulsion and service loads, and together with optimal power and voyage scheduling, this can lead to a substantial improvement in ship operation cost, ensuring compliance with the environmental constraints and enhancing ship sustainability. During the operation, significant uncertainties such as waves, wind, and PV result in considerable speed loss, which may lead to voyage delays and operation cost increases. To address this issue, a distributionally robust optimization (DRO) model is proposed to schedule power generation and voyage. The problem is decoupled into a bi-level optimization model, the slave level can be solved directly by commercial solvers, the master level is further formulated as a two-stage DRO model, and linear decision rules and column and constraint generation algorithms are adopted to solve the model. The algorithm aims at minimizing the operation cost, limiting greenhouse gas (GHG) emissions, and satisfying the technical and operational constraints considering the uncertainty. Extensive simulations demonstrate that the expected total cost under the worst-case distribution is minimized, and compared with the conventional robust optimization methods, some distribution information can be incorporated into the ambiguity sets to generate fewer conservative results. This method can fully ensure the on-time arrival of hybrid ships in various uncertain scenarios while achieving expected operation cost minimization and limiting greenhouse gas (GHG) emissions.

Review of the NRC Canada studies on fire resistance of floor assemblies: Results, design guidelines and research gaps

AbstractThe National Research Council Canada conducted two major fire resistance studies on floor assemblies over the past two decades. Despite the publication of the experimental results, there is a lack of suggested guidelines for design practitioners and gaps for future research. Thus, this paper comprehensively reviews the fire resistance results of 85 full‐scale floor tests, suggests design guidelines, and identifies research gaps. These efforts aim to enhance the understanding and support the potential improvement of the fire performance of floor assemblies. The review of the results covers the impact of various design parameters on the fire resistance of floor assemblies, such as framing type and spacing, insulation type, subfloor configuration, resilient channel spacing, number of gypsum board layers, and screw spacing from the board edge. Although the interaction of these factors is complex, some of them play significant roles in determining the overall fire resistance of floor assemblies. For instance, rock and cellulose insulation outperformed glass fibre, a wider resilient channel spacing lowered fire resistance, whilst an increased distance of screws from the board edge improved the fire resistance. More importantly, detailed explanations are provided for the influences these parameters exert on fire resistance. Following this detailed examination of the results, design guidelines are provided for practitioners' consideration. A comparison is made between the experimental results and predictions from the component additive methods in the Canadian and Euro Codes, demonstrating that both methods yield conservative results. Finally, this paper concludes by identifying research gaps and providing recommendations for future investigations, including the necessity of experimental studies on floor assemblies with new design configurations and the promising role of machine learning in fire resistance evaluation.

Output-feedback control design for Takagi-Sugeno fuzzy systems through Lyapunov functions depending polynomially on the states

This paper proposes a new strategy based on linear matrix inequalities (LMIs) for the synthesis of state- and output-feedback controllers through parallel distributed compensation for continuous-time Takagi-Sugeno fuzzy systems. The main novelty of the proposed design technique is the use of homogeneous polynomial Lyapunov functions of degree larger than two on the states, generalizing the results based on quadratic functions. Parametrized in terms of a constant matrix, those homogeneous polynomial Lyapunov functions provide less conservative results in terms of stability and decay rate of trajectories when dealing with membership functions whose time-derivatives have unknown bounds. The synthesis procedure is formulated in terms of a locally convergent iterative algorithm, where a set of LMIs defined in an augmented parameter space is solved at each iteration. Numerical examples are used to compare the proposed method with quadratic stabilizability techniques available in the literature, illustrating the advantages of higher degree Lyapunov functions.

Premise‐Variable‐Domain‐Partition‐Dependent Output Feedback Switched Controllers Design for Switched IT2 Fuzzy Systems With Switching Signal Transmission Delays and Local Nonlinear Model

ABSTRACTThis article studies the guaranteed cost extended dissipative stabilization problem of switched IT2 fuzzy systems (SIT2FSs) with switching signal transmission delays and local nonlinear model. The guaranteed cost performance, guaranteed cost strict dissipative performance, guaranteed cost − performance and guaranteed cost passivity performance are considered for SIT2FSs in a unified form. First, a novel asynchronous control scheme is proposed for SIT2FSs with local nonlinear model. The controller gains in mismatched interval are designed separately. By using a premise‐variable‐domain‐partition‐dependent switched fuzzy Lyapunov functions (PDSFLFs) approach, the membership‐function‐shape‐independent (MFSI) existence conditions of a class of IT2 fuzzy switched controllers, which can ensure the guaranteed cost extended dissipative performance of SIT2FSs, are established. Then, by utilizing the shape information of membership functions and dividing the premise variable domain into multiple partitions, the membership‐function‐shape‐dependent (MFSD) existence conditions of a class of premise‐variable‐domain‐partition‐dependent (PVDPD) IT2 fuzzy switched controllers are presented. The results indicate that less conservative results can be achieved by using the PVDPD IT2 fuzzy switched controllers, and better system performance can be gotten compared with the Type‐1 fuzzy switched controllers. Finally, the effectiveness of the results is demonstrated through a robot arm model.

Guidance for structural integrity assessment of smooth pipe elbows containing defects using R6

Recently, guidance for fracture assessment of defective elbows using the R6 failure assessment diagram (FAD) method has been included in R6 Revision 4 Amendment 13 (2023). This paper provides an overview of the new guidance and supporting validation. The guidance is validated using 75 cases of 3-D finite element (FE) elastic-plastic J results of smooth pipe elbows of various geometries with axial/circumferential internal/external semi-elliptical/extended/fully-circumferential surface cracks under internal pressure, in-plane/out-of-plane bending moment, torsion and various load combinations, by comparing the FE-based Option 3 failure assessment curves (FAC) with the R6 Option 2 FAC. The results show that, for 74 out of 75 cases, the FE-based Option 3 data points are above the R6 Option 2 FAC with reasonable conservatism when the guidance for evaluating the elbow stress intensity factor and limit load is followed. In other words, following the new guidance can lead to reasonably conservative assessment results.

Stability analysis of aperiodic impulsive delay systems using sum of squares approach

AbstractThe stability problem of aperiodic impulsive delay systems with unstable continuous and discrete dynamics is addressed in this article. New delay‐dependent stability conditions are proposed by employing a clock‐dependent Lyapunov–Krasovskii‐like functional composed of a Lyapunov–Krasovskii functional and a high‐order polynomial matrix function. The stability conditions are then solved using sum of squares programming techniques, yielding less conservative results than the looped‐functionals approach. Finally, the simulation results demonstrate the effectiveness of the results.

Simplification of KDS 14 Design Method for Slab–Column Connections Subjected to Unbalanced Moment

The current KDS 14 design method yields reasonable accuracy with acceptable safety in assessing the unbalanced moment-carrying capacity of slab–column connections. However, the model requires considerable computational effort owing to the effects of various design parameters, particularly the gravity-load effect. This study proposes a method to simplify the KDS 14 model to evaluate the unbalanced moment-carrying capacity of slab–column connections. In the proposed method, the gravity-load effect is decoupled from equations used for evaluating unbalanced moment-carrying capacity components. Subsequently, the total unbalanced moment-carrying capacity is determined by establishing an interaction between the gravity shear ratio and unbalanced moment components without considering the gravity-load effect. For practical design purposes, final simplified design equations are proposed. The reliability of the simplified method is validated based on a comparison with the current KDS 14 design code using a comprehensive database encompassing interior, exterior, and corner slab–column connections. Furthermore, a parametric study based on the proposed simplified approach, current design codes, combined with finite-element (FE) analysis is performed to elucidate the effects of constituents on the unbalanced moment-carrying capacity of corner slab–column connections. The results show that the proposed simplified model and KDS design method are strongly correlated with the experimental and FE results for a range of design parameters. Meanwhile, the ACI 318 model consistently provides a lower limit for strength prediction, thus yielding overly conservative and safe results compared with the test and FE results in most cases.

Analysis of the tooth-root stress of external spur gears with high effective contact ratio

For spur gears with contact ratio close to 2, the extension of the contact interval resulting from loaded tooth deflections and local contact deformations may result in an effective contact ratio above 2. In these cases, the load is transmitted by at least two tooth-pairs, the maximum load and tooth-root stress decrease, and therefore the calculation methods of the gear rating Standards ISO and AGMA provide very conservative results. In this work, two models are applied to the calculation of the tooth-root stress of load-induced high contact ratio external gears: (i) an analytic model of load sharing, based on the minimum energy method, and (ii) a finite element model, which validates the results obtained from the previous model. Obtained values of the stress are compared with those provided by ISO and AGMA rating methods, which do not account for the stress reduction due to the higher contact ratio. A new modification coefficient is proposed to correct these conservative values, which allows the AGMA and ISO geometry factors to remain as no load-dependent factors and keep their actual calculation methods and significance.

Relaxed conditions for parameterized linear matrix inequality in the form of nested fuzzy summations

The aim of this study is to investigate less conservative conditions for parameterized linear matrix inequalities (PLMIs) that are formulated as nested fuzzy summations. Such PLMIs are commonly encountered in stability analysis and control design problems for Takagi-Sugeno (T-S) fuzzy systems. Utilizing the weighted inequality of arithmetic and geometric means (AM-GM inequality), we develop new, less conservative linear matrix inequalities for the PLMIs. This methodology enables us to efficiently handle the product of membership functions that have intersecting indices. Through empirical case studies, we demonstrate that our proposed conditions produce less conservative results compared to existing approaches in the literature.

Reliability analysis of an aircraft load mechanism considering multi-site damage dependency

Aircraft load mechanisms are the important actuators of the aircraft rudder control systems. By sharing the same operation circumstances and working conditions, the damage processes at multiple sites are dependent. In this paper, we firstly conduct a wear experiment and a stress relaxation experiment of an aircraft load mechanism. To consider the individual variability of the damage processes, the stochastic processes are adopted. Then, vine copula function is introduced to analyze the multivariate dependence of the damage processes. Furthermore, a time-varying dependent model is formed to model the dynamic damage interaction. The reliability of the aircraft load mechanism is assessed by using the Rosenblatt transformation and Monte Carlo method. The obtained results show that overlooking the dependency will lead to a conservative reliability result. Finally, the effect of the damage processes on the mechanism is analyzed, which provides effective guidance for the maintenance of the mechanism.

Monitoring the effectiveness of fauna sensitive infrastructure along the Peak Downs Highway in Central Queensland reveals mixed results for koala conservation

ABSTRACT The koala is endangered in Queensland, New South Wales and the Australian Capital Territory. Collisions with vehicles are a major threat to the survival of the species. At the end of October 2022, a 1-month-long project was undertaken to monitor the use of habitat by koalas near fauna sensitive infrastructures consisting of between 160 and 400 m wildlife exclusion fencing leading to multi-span bridges (underpasses) along the Peak Downs Highway in Central Queensland. Three underpasses were monitored using 12 wildlife surveillance cameras operating 24 h/day. Video footage was analysed by artificial intelligence. Day-time walked transects were used to survey koalas in the surrounding habitat and individual koalas were photographed and identified. The surveillance cameras recorded several thousand animals across several groups/species, but only one koala was observed. Altogether 51 koala sightings were made during the walked transects. Three male koalas are presumed to have crossed the highway without using the underpasses as they were observed on both sides of the road. The cameras showed no evidence of these animals using the underpass. We recommend expanding the length of the fences to increase the likelihood of use of underpasses and a repeat of the survey at the beginning of the breeding season.

An Umbrella Review for Assessment of Treatment Effectiveness of Clear Aligners Compared to Conventional Fixed Appliances in Orthodontic Patients

Introduction Orthodontic improvements, mainly through the previous decade, have led to a substantial rise in patients’ esthetic needs. Traditional orthodontic procedures have been linked with a compromise in facial appearance, which increases concern among patients pursuing orthodontic treatment. Methods PubMed, MEDLINE, Google Scholar, and Cochrane Library of Systematic Reviews databases were searched using appropriate entry terms and Boolean operators. Search strategy was conducted till June 2022 for systematic reviews and meta-analyses. Publications were systematically assessed for eligibility, and two observers independently graded the methodologic quality using AMSTAR-2 tool. For each meta-analysis, we estimated the summary effect size by the use of random-effects and fixed-effects models and the 95% confidence interval. We estimated the between-study heterogeneity expressed by I 2 (defined as large for I 2 ≥50%), evidence of small-study effects (i.e., large studies had significantly more conservative results than smaller studies), and evidence of excess significance bias (i.e., more studies than expected with significant results). Results Overall, 16 unique systematic reviews and meta-analyses following the eligibility criteria were selected for umbrella review. The results of qualitative analysis of studies revealed that 4 studies had a critically low risk of bias, 11 showed low risk, and 1 study had moderate risk. The results of the meta-analysis favored clear aligners with respect to oral hygiene and root resorption parameters. When tooth movements were considered, the results favored conventional orthodontic treatment. Conclusion Clear aligner therapy (CAT) has significant advantages with regard to efficiency (treatment time, chair time) in mild-moderate malocclusion cases. The overall accuracy of CAT when compared to fixed orthodontic treatment was found to be 55-82%.

Non-parametric Bayesian approach to multiple treatment comparisons in network meta-analysis with application to comparisons of anti-depressants.

Network meta-analysis is a powerful tool to synthesize evidence from independent studies and compare multiple treatments simultaneously. A critical task of performing a network meta-analysis is to offer ranks of all available treatment options for a specific disease outcome. Frequently, the estimated treatment rankings are accompanied by a large amount of uncertainty, suffer from multiplicity issues, and rarely permit possible ties of treatments with similar performance. These issues make interpreting rankings problematic as they are often treated as absolute metrics. To address these shortcomings, we formulate a ranking strategy that adapts to scenarios with high-order uncertainty by producing more conservative results. This improves the interpretability while simultaneously accounting for multiple comparisons. To admit ties between treatment effects in cases where differences between treatment effects are negligible, we also develop a Bayesian non-parametric approach for network meta-analysis. The approach capitalizes on the induced clustering mechanism of Bayesian non-parametric methods, producing a positive probability that two treatment effects are equal. We demonstrate the utility of the procedure through numerical experiments and a network meta-analysis designed to study antidepressant treatments.

New Stability Criterion for Positive Impulsive Fuzzy Systems by Applying Polynomial Impulse-Time-Dependent Method.

The problems of exponential stability and L1 -gain for positive impulsive Takagi-Sugeno (T-S) fuzzy systems are further studied in this article. Different from the Lyapunov function in the literature, where the Lyapunov matrices are time-invariant or only linearly dependent on the impulse interval, in this article, a novel polynomial impulse-dependent (ID) copositive Lyapunov function (CLF) is constructed by using the polynomial impulse time function. In addition, the binomial coefficients are applied to derive new finite linear programming conditions. Less conservative results are obtained since the polynomial ID CLF contains more impulse interval information. Three examples demonstrate the influence of the polynomial degree on the results and the effectiveness of the developed new results.

Design and Analysis of Curved Steel Bridges Using 3D Shell Modelling

AbstractSteel bridge designers and erectors primarily rely on approximate methods, such as 1D line girder analyses and 2D grid analyses. For curved or skewed bridges, this can give erroneous indications of the structure's true behaviour. Refined methods of analysis, such as 3D shell modelling, aim to bring a significant change in the practice of bridge engineering. By moving the industry away from simplistic design assumptions, refined analysis methods lead to more accurate, less conservative results, which in turn brings true benefits such as improved structural safety and increased economy. In this paper, several case studies on curved plate girder and tub girder bridges are presented, which cover the full bridge life cycle, from erection of the steel structure and placement of the concrete deck, down to live load analyses using influence surfaces and load rating. The case studies will be modelled with mBrace3D, a dedicated FEA software for curved steel bridges.

Temperature Extreme Value Evaluation of Composite Beams Based on Copula Functions

The solar temperature field of steel-concrete composite girder bridges has a significant impact on structural stress. To evaluate the distribution of solar temperatures, this paper conducted analyses of the solar temperature field of the Xuefeng Lake Bridge through on-site measurements and numerical simulations. The study investigated the temperature field characteristics of the composite girders according to the temperature data. Based on the numerical simulation results, a finite element computational model for the vertical temperature gradient of the steel-concrete composite girder bridge was established, and the maximum gradient temperature values of the composite girders were calculated by using the 24-year historical data from 2000 to 2023. The extreme value parameters related to the GEV distribution model were determined. Taking into account the correlation between the annual maximum environmental temperature and wind speed, a joint distribution model was established using Copula functions. The results indicate that the average error of the numerical model is within 5%. The wind-temperature joint distribution model, considering the effects of wind speed, tends to provide more conservative results. The calculated extreme values of temperature gradient load show an expanding trend, with the exceedance probabilities for recurrence periods of 100 years, 50 years, 20 years, 10 years, and 5 years being 0.64%, 1.34%, 2.29%, 3.51%, and 7.32%, respectively.

A re-analysis of about 60,000 sparse data meta-analyses suggests that using an adequate method for pooling matters.

In sparse data meta-analyses (with few trials or zero events), conventional methods may distort results. Although better-performing one-stage methods have become available in recent years, their implementation remains limited in practice. This study examines the impact of using conventional methods compared to one-stage models by re-analysing meta-analyses from the Cochrane Database of Systematic Reviews in scenarios with zero event trials and few trials. For each scenario, we computed one-stage methods (Generalised linear mixed model [GLMM], Beta-binomial model [BBM], Bayesian binomial-normal hierarchical model using a weakly informative prior [BNHM-WIP]) and compared them with conventional methods (Peto-Odds-ratio [PETO], DerSimonian-Laird method [DL] for zero event trials; DL, Paule-Mandel [PM], Restricted maximum likelihood [REML] method for few trials). While all methods showed similar treatment effect estimates, substantial variability in statistical precision emerged. Conventional methods generally resulted in smaller confidence intervals (CIs) compared to one-stage models in the zero event situation. In the few trials scenario, the CI lengths were widest for the BBM on average and significance often changed compared to the PM and REML, despite the relatively wide CIs of the latter. In agreement with simulations and guidelines for meta-analyses with zero event trials, our results suggest that one-stage models are preferable. The best model can be either selected based on the data situation or, using a method that can be used in various situations. In the few trial situation, using BBM and additionally PM or REML for sensitivity analyses appears reasonable when conservative results are desired. Overall, our results encourage careful method selection.

Interval operative management in patients admitted with acute obstruction due to incarcerated paraesophageal hernia.

Acute incarcerated paraesophageal hernias (PEH) have historically been considered a surgical emergency. Emergent operations have a higher rate of morbidity and mortality compared to elective surgery. Our institution has adopted a strategy of initial conservative management in patients presenting with acute obstruction from an incarcerated PEH who are clinically stable. Patients are given at least 24h for their symptoms to improve (selective nasogastric decompression). If symptoms resolve, contrast on an upper GI study passes to the small bowel, and liquids are tolerated, patients are discharged with planned interval repair. We sought to characterize the outcomes of this interval surgical strategy for incarcerated PEH. A retrospective chart review was performed to identify patients admitted to a single institution between October 2019 and September 2023 with an incarcerated PEH. Patients taken directly to surgery within 24h were excluded. A total of 45 patients admitted with obstruction from an incarcerated PEH were identified. Ten patients (22%) were taken urgently to surgery due to clinical instability and were excluded. Of the remaining 35 patients, 23 (66%) resolved their obstruction with conservative non-operative management and were offered planned interval PEH repair (successful conservative management). In the successful conservative management cohort, there was one unplanned readmission before interval PEH repair. Average time between discharge and repair was 25days. Complication rates did not differ in those who failed and in those who had a successful conservative management result. The cumulative length of stay for those who succeeded in conservative management (including days for the interval surgery) was equivalent with those who underwent PEH repair during the index admission. A trial of conservative management in clinically stable patients with symptomatic incarcerated PEH appears to be safe and often avoids emergent repair without increasing perioperative complications or total days in the hospital.

Subintuitionistic logics and their modal companions: a nested approach

In the present paper we deal with subintuitionistic logics and their modal companions. In particular, we introduce nested calculi for subintuitionistic systems and for modal logics in the S 5 modal cube ranging from K to S 4 . The latter calculi differ from standard nested systems, as there are multiple rules handling the modal operator. As an upshot, we get a purely syntactic proof of the Gödel-McKinsey-Tarski embedding which preserves the structure and the height of the derivations. Finally, we obtain a conservativity result for classical logic over a weak subintuitionistic system.