Large workspace is one of the promising advantages possessed by the cable-driven parallel robots (CDPR) over the conventional rigid-link robots. This paper focuses on the dynamic analysis and ...workspace classification based on the general motion equation of cable robot and the unilateral property of cables. The combinations of different types of two conditions lead to several different types of workspace, including static equilibrium workspace, wrench closure workspace, wrench feasible workspace, dynamic workspace, and collision-free workspace. A qualitative comparison of different types of workspaces is performed. The simulation results verify the relationship between the several types of workspaces.
•We propose the quantitative relationship between fracture toughness and impact toughness in high-strength steels.•Both impact toughness and fracture toughness of materials obey the minimum energy ...density criterion.•The relation is affected by two aspects: the energy consumption pattern and specimen size.•It would provide a more economical and faster way to quantitatively predict the fracture toughness of high-strength steels.
In this paper, the fracture toughness and impact toughness were systematically studied in high-strength steels. The results show that the two types of toughness are both the representative of the competition between flat fracture and shear fracture, which follows the minimum energy density criterion. Accordingly, we established the quantitative relation between impact toughness and fracture toughness in high-strength steels through theoretical derivations. The relation is affected by two aspects: the energy consumption pattern and specimen size. It would provide a more economical and faster way to quantitatively predict the fracture toughness of high-strength steels, which can be further applied to some new materials such as high-entropy alloys, nanostructured materials and metallic glasses.
AUTOMATIC MODEL CALIBRATION Duan, Q.; Di, Z.; Quan, J. ...
Bulletin of the American Meteorological Society,
05/2017, Letnik:
98, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Weather forecasting skill has been improved over recent years owing to advances in the representation of physical processes by numerical weather prediction (NWP) models, observational systems, data ...assimilation and postprocessing, new computational capability, and effective communications and training. There is an area that has received less attention so far but can bring significant improvement to weather forecasting—the calibration of NWP models, a process in which model parameters are tuned using certain mathematical methods to minimize the difference between predictions and observations. Model calibration of the NWP models is difficult because 1) there are a formidable number of model parameters and meteorological variables to tune, and 2) a typical NWP model is very expensive to run, and conventional model calibration methods require many model runs (up to tens of thousands) or cannot handle the high dimensionality of NWP models. This study demonstrates that a newly developed automatic model calibration platform can overcome these difficulties and improve weather forecasting through parameter optimization. We illustrate how this is done with a case study involving 5-day weather forecasting during the summer monsoon in the greater Beijing region using the Weather Research and Forecasting Model. The keys to automatic model calibration are to use global sensitivity analysis to screen out the most important parameters influencing model performance and to employ surrogate models to reduce the need for a large number of model runs. Through several optimization and validation studies, we have shown that automatic model calibration can improve precipitation and temperature forecasting significantly according to a number of performance measures.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Background and Aims: Anthocyanins are a group of important phenolic compounds which are responsible for the colour of red grape and wine. This study aimed to confirm the existence of ...pelargonidin‐3‐O‐glucoside in Vitis vinifera grape berry skins.
Methods and Results: The anthocyanin profiles in the berry skins of Cabernet Sauvignon and Pinot Noir were analysed by high performance liquid chromatography – electronic spray ionization – tandem mass spectrometry. Besides 17 anthocyanins that are commonly determined in the berries of these two varieties, pelargonidin‐3‐O‐glucoside was also detected at trace levels.
Conclusions: The mass‐spectrometry evidence confirmed the existence of pelargonidin‐3‐O‐glucoside in non‐teinturier V. vinifera grapes.
Significance of the Study: This finding will be beneficial for the further understanding of anthocyanin profile and its biosynthesis in grape berries.
Mineral salt bricks are often used in cow raising as compensation for mineral losses to improve milk yield, growth, and metabolic activity. Generally, effects of minerals are partially thought to ...result from improvement of microbial metabolism, but their influence on the rumen microbiota has rarely been documented to date. In this study, we investigated the response of microbiota to mineral salt in heifer and adult cows and evaluated ruminal fermentation and enteric methane emissions of cows fed mineral salts. Twelve lactating Holstein cows and twelve heifers fed a total mixed ration (TMR) diet were randomly allocated into two groups, respectively: a treatment group comprising half of the adults and heifers that were fed mineral salt and a control group containing the other half fed a diet with no mineral salt supplement. Enteric methane emissions were reduced by 9.6% (P < 0.05) in adults ingesting a mineral salt diet, while concentrations of ruminal ammonia, butyrate, and propionate were increased to a significant extent (P < 0.05). Enteric methane emissions were also reduced in heifers ingesting a mineral salt diet, but not to a significant extent (P > 0.05). Moreover, the concentrations of ammonia and volatile fatty acids (VFAs) were not significantly altered in heifers (P > 0.05). Based on these results, we performed high-throughput sequencing to explore the bacterial and archaeal communities of the rumen samples. Succiniclasticum and Prevotella, two propionate-producing bacteria, were predominant in samples of both adults and heifers. At the phylotype level, mineral salt intake led to a significant shift from Succiniclasticum to Prevotella and Prevotellaceae populations in adults. In contrast, reduced abundance of Succiniclasticum and Prevotella phylotypes was observed, with no marked shift in propionate-producing bacteria in heifers. Methanogenic archaea were not significantly abundant between groups, either in adult cows or heifers. The shift of Succiniclasticum to Prevotella and Prevotellaceae in adults suggests a response of microbiota to mineral salt that contributes to higher propionate production, which competes for hydrogen utilized by methanogens. Our data collectively indicate that a mineral salt diet can alter interactions of bacterial taxa that result in enteric methane reduction, and this effect is also influenced in an age-dependent manner.
To analyze the factors affecting the efficacy of mite subcutaneous immunotherapy (SCIT) in allergic asthma patients aged 5-18 years, and to find the best predictive model for the curative effect.
The ...data of 688 patients aged 5-18 years with allergic asthma who completed more than 3 years of mite SCIT from December 2006 to November 2021 in the Department of Respiratory Medicine, Children's Hospital Affiliated to Nanjing Medical University were retrospectively analyzed. Male, results of skin prick test (SPT), age, daily medication score (DMS), visual analogue scale (VAS) score, and enrollment season were defined as independent variables. R language models, including Logistic regression model, random forest model and extreme gradient boosting (XGboost) model, were used to analyze the impact of these independent variables on the outcomes. The receiver operating characteristic curve was applied to compare the predictive ability of the models. Hypothesis testing of the area under curve (AUC) of the 3 models was pe
Pain after burns is a very common problem in children. Severe pain will not only hinder treatment, but also damage children's mental health if not handled in time. Therefore, pain management is very ...important in treating children with burns. As a safe, effective, and convenient non-drug therapy, music therapy has great advantages in relieving pain and is widely used in a variety of clinical fields. This paper focused on music therapy and its mechanism of pain relief, the current status of research on pain management of pediatric burns, the application and prospect of music therapy in pain management of pediatric burns, etc., to provide reference for clinical application.
The analysis of polycrystalline materials benefits greatly from accurate quantitative descriptions of their grain structures. Laguerre tessellations approximate such grain structures very well. ...However, it is a quite challenging problem to fit a Laguerre tessellation to tomographic data, as a high-dimensional optimization problem with many local minima must be solved. In this paper, we formulate a version of this optimization problem that can be solved quickly using the cross-entropy method, a robust stochastic optimization technique that can avoid becoming trapped in local minima. We demonstrate the effectiveness of our approach by applying it to both artificially generated and experimentally produced tomographic data.
•The effect of the aging state on the corrosion fatigue properties of Al alloy is related to the stress level.•Under high-stress range where fatigue damage dominates, the over aged state shows better ...corrosion fatigue performance.•Under low-stress range, the over aged state has lower corrosion fatigue lives for its facilitation on the pitting-induced cracking.
The corrosion fatigue performance of Al alloy components is crucial for their engineering applications. This study focuses on the corrosion fatigue properties of 7075 Al alloys in three different aging states, i.e. over-aging (OA), peak-aging (PA) and under-aging (UA) states. The results show that the fatigue damage mechanism of the Al alloy is greatly affected by the stress level. In the high-stress region where the cyclic number is short, the fatigue damage is mainly caused by dislocations accumulation and stress concentration on the grain boundary. Compared with the UA state, the wave slip dislocations at the OA state are easy to accumulate and annihilate at the second phase boundaries, which reduces the fatigue damage degree at the grain boundaries. However, in the low-stress range where the cyclic number is large, the corrosion fatigue life of the Al alloy is mainly controlled by pitting-induced crack initiation. For the OA state, the spacing and size of the precipitated phase are large, so it is easy to trigger corrosive pitting, which reduces the corrosion fatigue performance of the alloy.
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► This paper is the first comprehensive comparative study of local search application strategies in hybrid metaheuristic algorithms. ► The hybrid metaheuristic algorithm employed in ...the study is state-of-the-art, composed of two cooperative metaheuristic algorithms (differential evolution and harmony search) enhanced by the Hooke and Jeeves local search. ► The top three best out of 18 different strategies are identified based on the results obtained in testing a suite of 19 problems. The results are expected to be useful for deciding how to design a hybrid metaheuristic algorithm.
This paper presents results of a comparative study with the objective to identify the most effective and efficient way of applying a local search method embedded in a hybrid algorithm. The hybrid metaheuristic employed in this study is called “DE–HS–HJ” because it is comprised of two cooperative metaheusitic algorithms, i.e., differential evolution (DE) and harmony search (HS), and one local search (LS) method, i.e., Hooke and Jeeves (HJ) direct search. Eighteen different ways of using HJ local search were implemented and all of them were evaluated with 19 problems, in terms of six performance indices, covering both accuracy and efficiency. Statistic analyses were conducted accordingly to determine the significance in performance differences. The test results show that overall the best three LS application strategies are applying local search to every generated solution with a specified probability and also to each newly updated solution (NUS+ESP), applying local search to every generated solution with a specified probability (ESP), and applying local search to every generated solution with probability and also to the updated current global best solution (EUGbest+ESP). ESP is found to be the best local search application strategy in terms of success rate. Integrating it with NUS further improve the overall performance. EUGbest+ESP is the most efficient and it is also able to achieve high level of accuracy (the fourth place in terms of success rate with an average above 0.9).
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