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"Comparison of methods"
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An engineering perspective on the numerics of quasi-periodic oscillations
The phenomenon of quasi-periodicity in deterministic dynamical systems describes stationary solutions, which neither exhibit a finite period length nor are chaotic. Recently, an increasing demand for robust numerical methods is driven by applied dynamics and industrial applications. In this context, direct time integration proves to be impractical due to extensive integration intervals. Therefore, in a first step, this contribution aims on giving an application oriented survey of the basic theory as well as alternative concepts. In the following, the focus is set on the direct computation of invariant manifolds (surfaces) on which quasi-periodic solutions evolve. This approach offers a unique framework from which classical methods (e.g., the multi-harmonic-balance) can be systematically deduced and mutual similarities between different methods may be revealed. This contribution starts with a brief summary of related mathematical basics, which is followed by an overview of available methods. Subsequently, the computation of invariant manifolds by means of solving a partial differential equation is emphasized. These PDEs may be formulated using different parametrization strategies. Here, the concept of
hyper-time parametrization
is particularly interesting, since it is a promising starting point for the development of numerical schemes with general applicability in engineering problems. In order to solve the underlying PDE, various methods may be used. The implementation of a
Fourier
-
Galerkin
method as well as a finite difference method is presented and compared on the basis of computational results of the
van-der-Pol
equation (with and without forcing). Moreover, it is demonstrated that both methods apply to periodic as well as quasi-periodic solutions alike. In order to exemplify the practical use, these methods are applied to a generic rotordynamic model problem.
Journal Article
Comparison and Determination of the Content of Mosapride Citrate by Different qNMR Methods
As a salt-type compound, mosapride citrate’s metabolism and side effects are correlated with its salt-forming ratio. Several techniques were developed in this work to compare various quantitative nuclear magnetic resonance (qNMR) methodologies and to quantitatively examine the content of raw materials. Among the qNMR techniques, methods for 1H NMR and 19F NMR were developed. Appropriate solvents were chosen, and temperature, number of scans, acquisition time, and relaxation delay parameter settings were optimized. Maleic acid was chosen as the internal standard in 1H NMR, and the respective characteristic signals of mosapride and citrate were selected as quantitative peaks. The internal standard in 19F NMR analysis was 4,4′-difluoro diphenylmethanone, and the distinctive signal peak at −116.15 ppm was utilized to quantify mosapride citrate. The precision, repeatability, linearity, stability, accuracy, and robustness of the qNMR methods were all validated according to the ICH guidelines. By contrasting the outcomes with those from high-performance liquid chromatography (HPLC), the accuracy of qNMR was assessed. As a result, we created a quicker and easier qNMR approach to measure the amount of mosapride citrate and evaluated several qNMR techniques to establish a foundation for choosing quantitative peaks for the qNMR method. Concurrently, it is anticipated that various selections of distinct quantitative objects will yield the mosapride citrate salt-forming ratio.
Journal Article
Cluster randomised trials with a binary outcome and a small number of clusters: comparison of individual and cluster level analysis method
Background
Cluster randomised trials (CRTs) are often designed with a small number of clusters, but it is not clear which analysis methods are optimal when the outcome is binary. This simulation study aimed to determine (i) whether cluster-level analysis (CL), generalised linear mixed models (GLMM), and generalised estimating equations with sandwich variance (GEE) approaches maintain acceptable type-one error including the impact of non-normality of cluster effects and low prevalence, and if so (ii) which methods have the greatest power. We simulated CRTs with 8–30 clusters, altering the cluster-size, outcome prevalence, intracluster correlation coefficient, and cluster effect distribution. We analysed each dataset with weighted and unweighted CL; GLMM with adaptive quadrature and restricted pseudolikelihood; GEE with Kauermann-and-Carroll and Fay-and-Graubard sandwich variance using independent and exchangeable working correlation matrices. P-values were from a t-distribution with degrees of freedom (DoF) as clusters minus cluster-level parameters; GLMM pseudolikelihood also used Satterthwaite and Kenward-Roger DoF.
Results
Unweighted CL, GLMM pseudolikelihood, and Fay-and-Graubard GEE with independent or exchangeable working correlation matrix controlled type-one error in > 97% scenarios with clusters minus parameters DoF. Cluster-effect distribution and prevalence of outcome did not usually affect analysis method performance. GEE had the least power. With 20–30 clusters, GLMM had greater power than CL with varying cluster-size but similar power otherwise; with fewer clusters, GLMM had lower power with common cluster-size, similar power with medium variation, and greater power with large variation in cluster-size.
Conclusion
We recommend that CRTs with ≤ 30 clusters and a binary outcome use an unweighted CL or restricted pseudolikelihood GLMM both with DoF clusters minus cluster-level parameters.
Journal Article
Household food waste quantification: comparison of two methods
Purpose
The purpose of this paper is to quantify household food waste by using two different methods. A comparison of the results highlights a divergence between the perceived contribution to the problem and more objective measurements.
Design/methodology/approach
Self-reported quantities, collected by means of a postal survey sent out to a random sample of the French- and German-speaking Swiss population, were compared to extrapolations from a national waste compositional analysis report.
Findings
The results of the self-reported survey showed 8.9 kg of avoidable and possibly avoidable household food waste per capita per year, whereas calculations based on the second method resulted in a total of 89.4 kg of mostly avoidable household food waste per capita per year.
Research limitations/implications
This striking tenfold discrepancy between the two sets of results highlights the extent of under-reporting in self-assessment and speaks in favour of using more objective methods to quantify food waste, building on the example of the second method used in this study.
Practical implications
The discrepancy highlighted here could be used as a hook in an awareness-raising campaign to highlight everyone’s contribution to the food waste issue and encourage citizens to reconsider their behaviour and adopt recommended behavioural changes.
Originality/value
By highlighting the divergence between self-reported and actual waste management facts and figures, this paper justifies the need to develop measures to encourage citizens to reconsider their attitudes and practices.
Journal Article
Construction and empirical testing of comprehensive risk evaluation methods from a multi-dimensional risk matrix perspective: taking specific types of natural disasters risk in China as an example
Global climate change, continuous economic development and accelerated urbanisation have increased the frequency and complexity of various incidents. Risk assessment is an important means to deal with different crises and incidents. Based on the systematic analysis of the basic connotation, attribute relationship and main contents of risk assessment, this study extends the traditional two-dimensional risk matrix to multi-dimensional risk matrix. On this basis, this study further proposes four comprehensive risk assessment methods, including total ordinal, weighted average, Euclidean distance and two-norm methods. Empirical research was conducted by selecting three types of natural disasters, regional agro-meteorological disasters, geological disasters and forest fires, in 30 related regions in China between 2010 and 2019. The results indicated that compared to the two-dimensional risk matrix, the multi-dimensional risk matrix can intuitively characterise and compare the all-round risk situation of different regions, periods, types and dimensions, which is more helpful for a systematic analysis and risk comparison. All four evaluation methods proposed in this paper proved able to effectively conduct comprehensive regional risk evaluations with consistent results. However, when considering the fitting coefficient between the results obtained by various evaluation methods and the comprehensive evaluation results, it can be found that the accuracy (i.e. fitting coefficient) of Euclidean distance method is significantly higher than that of the other three methods. In the last 10 years, the temporal order of natural disaster risk in China has been more volatile, with Beijing, Shanxi, Tianjin, Hebei, Liaoning, Ningxia, Zhejiang, Shaanxi, Fujian and Gansu experiencing higher volatility in the ranking of natural disaster risk.
Journal Article
A Systematic Review of Remotely Operated Vehicle Surveys for Visually Assessing Fish Assemblages
Anthropogenic activities and greater demands for marine natural resources has led to increases in the spatial extent and duration of pressures on marine ecosystems. Remotely operated vehicles (ROVs) offer a robust survey tool for quantifying these pressures and tracking the success of management intervention while at a range of depths, including those inaccessible to most SCUBA diver-based survey methods (~>30 m). As the strengths, limitations, and biases of ROVs for visually monitoring fish assemblages remain unclear, this review aims to evaluate ROVs as a survey technique and to suggest optimal sampling strategies for use in typical ROV-based studies. Using the search engines Scopus™ and Google Scholar™, 119 publications were identified that used ROVs for visual surveys of fish assemblages. While the sampling strategies and sampling metrics used to annotate the imagery in these publications varied considerably, the total abundance of fish recorded over strip transects of varying dimensions was the most common sampling design. The choice of ROV system appears to be a strong indicator of both the types of surveys available to studies and the success of ROV deployments. For instance, larger, more powerful working-class systems can complete longer and more complex designs (e.g. swath, cloverleaf, and polygonal transects) at greater depths, whereas observation-class systems are less expensive and easier to deploy but are more susceptible to delays or cancelations of deployments. In more severe sea state conditions, radial transects, or strip transects that employ live-boating or a weight to anchor the tether to the seafloor, can be used to improve the performance of observation-class systems. As these systems often employ shorter tethers, radial transects can also be used to maximize sampling area at deeper depths and on large vessels that may rotate substantially while anchored. For highly mobile species, and in survey designs where individuals are likely to be recounted (e.g. transects along oil and gas pipelines), relative abundance (MaxN) may be a more robust sampling metric. By identifying subtle, yet important, differences in the application of ROVs as a tool for visually surveying marine ecosystems, we identified key areas for improvement for best practice for future studies.
Journal Article
A comparative study of overlapping community detection methods from the perspective of the structural properties
Community detection is one of the most important tasks in network analysis. It is increasingly clear that quality measures are not sufficient for assessing communities and structural properties play a key hole in understanding how nodes are organized in the network. This work presents a comparative study of some representative state-of-the-art methods for overlapping community detection from the perspective of the structural properties of the communities identified by them. Experiments with synthetic and real-world benchmark Ground-Truth networks show that, although the methods are able to identify modular communities, they often miss many structural properties of the communities, such as the number of nodes in the overlapping region and the memberships of the nodes. This is a strong suggestion that a deeper comprehension of the overlapping properties of the communities is needed for the design of more efficient community detection methods.
Journal Article
Serological diagnosis of toxoplasmosis in pregnancy: comparison between a manual commercial ELISA assay and the automated VIDAS® kit
Knowledge of the toxoplasmosis serological status in pregnant women is important to allow adequate management for the prevention of congenital toxoplasmosis of those who are not immunized. Serological screening is generally carried out using commercial kits to determine the presence or absence of immunoglobulins M or G in the maternal blood. Robust results are therefore needed. We evaluated the performances of a commercial ELISA assay composed of several recombinant parasite antigens and of a commercial assay using parasite lysate to determine the serological status against
Toxoplasma gondii
of African pregnant women. A recruitment of 106 pregnant women during their third trimester of pregnancy was carried out in Benin. Serologies were performed with
recom
Well
Toxoplasma
IgM and IgG kits. Subsequently, the serological assays were carried out by an automaton method with the VIDAS
®
TOXO IgM and IgG II kits. Here we compared
recom
Well
Toxoplasma
to VIDAS
®
TOXO results. Reproducibility tests of the
recom
Well kits were assessed following the discrepancies observed in the results. Of 106 plasmas tested, 47 showed anti-
T.
gondii
IgG (44.3%), including 5 with IgM and high IgG avidity (4.7%). Of the two techniques, VIDAS
®
TOXO was more robust and specific for IgG while the
recom
Well
Toxoplasma
gave more false positive results. The combination of several techniques for the determination of serological toxoplasmosis status remains relevant. Methods using native proteins are closer to the reality of the environment. Therefore, kits using recombinant proteins should be tested on highly geographically diverse populations to refine their composition.
Journal Article
Variations in Phenology Identification Strategies across the Mongolian Plateau Using Multiple Data Sources and Methods
Satellite data and algorithms directly affect the accuracy of phenological estimation; therefore, it is necessary to compare and verify existing phenological models to identify the optimal combination of data and algorithms across the Mongolian Plateau (MP). This study used five phenology fitting algorithms—double logistic (DL) and polynomial fitting (Poly) combined with the dynamic threshold method at thresholds of 35% and 50% (DL-G35, DL-G50, Poly-G35, and Poly-G50) and DL combined with the cumulative curvature extreme value method (DL-CUM)—and two data types—the enhanced vegetation index (EVI) and solar-induced chlorophyll fluorescence (SIF)—to identify the start (SOS), peak (POS), and end (EOS) of the growing season in alpine meadow (ALM), desert steppe (DRS), forest vegetation (FV), meadow grassland (MEG), and typical grassland (TYG) of the MP. The optimal methods for identifying the SOS, POS, and EOS of typical grassland areas were Poly-G50 (NSE = 0.12, Pbias = 0.22%), DL-G35/50 (NSE = −0.01, Pbias = −0.06%), and Poly-G35 (NSE = 0.02, Pbias = 0.08%), respectively, based on SIF data. The best methods for identifying the SOS, POS, and EOS of desert steppe areas were Poly-G35 (NSE = −0.27, Pbias = −1.49%), Poly-G35/50 (NSE = −0.58, Pbias = −1.39%), and Poly-G35 (NSE = 0.29, Pbias = −0.61%), respectively, based on EVI data. The data source explained most of the differences in phenological estimates. The accuracy of polynomial fitting was significantly greater than that of the DL method, while all methods were better at identifying SOS and POS than they were at identifying EOS. Our findings can help to facilitate the establishment of a phenological estimation system suitable for the Mongolian Plateau and improve the observation methods of vegetation phenology.
Journal Article