A two-step approach to model precipitation extremes in California based on max-stable and marginal point processes

In modeling spatial extremes, the dependence structure is classically inferred by assuming that block maxima derive from max-stable processes. Weather stations provide daily records rather than just block maxima. The point process approach for univariate extreme value analysis, which uses more historical data and is preferred by some practitioners, does not adapt easily to the spatial setting. We propose a two-step approach with a composite likelihood that utilizes site-wise daily records in addition to block maxima. The procedure separates the estimation of marginal parameters and dependence parameters into two steps. The first step estimates the marginal parameters with an independence likelihood from the point process approach using daily records. Given the marginal parameter estimates, the second step estimates the dependence parameters with a pairwise likelihood using block maxima. In a simulation study, the two-step approach was found to be more efficient than the pairwise likelihood approach using only block maxima. The method was applied to study the effect of El Ni\~{n}o-Southern Oscillation on extreme precipitation in California with maximum daily winter precipitation from 35 sites over 55 years. Using site-specific generalized extreme value models, the two-step approach led to more sites detected with the El Ni\~{n}o effect, narrower confidence intervals for return levels and tighter confidence regions for risk measures of jointly defined events.Comment: Published at http://dx.doi.org/10.1214/14-AOAS804 in the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Experimental and analytical study on heat generation characteristics of a lithium-ion power battery

This document is the Accepted Manuscript version of the following article: Yongqi Xie, Shang Shi, Jincheng Tang, Hongwei Wu, and Jianzu Yu, ‘Experimental and analytical study on heat generation characteristics of a lithium-ion power battery’, International Journal of Heat and Mass Transfer, Vol. 122: 884-894, July 2018. Under embargo until 20 February 2019. The final, definitive version is available online via: https://doi.org/10.1016/j.ijheatmasstransfer.2018.02.038A combined experimental and analytical study has been performed to investigate the transient heat generation characteristics of a lithium-ion power battery in the present work. Experimental apparatus is newly built and the investigations on the charge/discharge characteristics and temperature rise behavior are carried out at ambient temperatures of 28 °C, 35 °C and 42 °C over the period of 1 C, 2 C, 3 C and 4 C rates. The thermal conductivity of a single battery cell is experimentally measured to be 5.22 W/(m K). A new transient model of heat generation rate based on the battery air cooling system is proposed. Comparison of the battery temperature between simulated results and experimental data is performed and good agreement is achieved. The impacts of the ambient temperature and charge/discharge rate on the heat generation rate are further analyzed. It is found that both ambient temperature and charge/discharge rate have significant influences on the voltage change and temperature rise as well as the heat generation rate. During charge/discharge process, the higher the current rate, the higher the heat generation rate. The effect of the ambient temperature on the heat generation demonstrates a remarkable difference at different charge states.Peer reviewe

A class of goodness-of-fit tests for spatial extremes models based on max-stable processes

Parametric max-stable processes are increasingly used to model spatial extremes. Starting from the fact that the dependence structure of a max-stable process is completely characterized by an extreme-value copula, a class of goodness-of-fit tests is proposed based on the comparison between a nonparametric and a parametric estimator of the corresponding unknown multivariate Pickands dependence function. Because of the high-dimensional setting under consideration, these functional estimators are only compared at a specific set of points at which they coincide, up to a multiplicative constant, with estimators of the extremal coefficients. The nonparametric estimators of the Pickands dependence function used in this work are those recently studied by Gudendorf and Segers. The parametric estimators rely on the use of the {\em pairwise pseudo-likelihood} which extends the concept of pairwise (composite) likelihood to a rank-based context. Approximate $p$-values for the resulting margin-free tests are obtained by means of a {\em one- or two-level parametric bootstrap}. Conditions for the asymptotic validity of these resampling procedures are given based on the work of Genest and R\'emillard. The finite-sample performance of the tests is investigated in dimension 10 under the Smith, Schlather and geometric Gaussian models. An application of the tests to rainfall data is finally presented.Comment: 28 pages, 3 figures, 5 table

Modeling Solubility of Nitrogen in Clean Fire Extinguishing Agent by Peng-Robinson Equation of State and a Correlation of Henry’s Law Constants

This document is the Accepted Manuscript version of the following article: Mengdong Chen, Yongqi Xie, Hongwei Wu, Shang Shi, and Jianzu Yu, ‘Modelling solubility of Nitrogen in clean fire extinguishing agent by Peng-Robinson equation of state and a correlation of Henry’s law constants’, Applied Thermal Engineering, Vol. 110, pp. 457-468, first published online 29 August 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ The version of record is available online at doi: http://dx.doi.org/10.1016/j.applthermaleng.2016.08.179 © 2016 Elsevier Ltd. All rights reserved.Nitrogen is usually used to increase the total pressure of the fluid in aircraft fire suppression bottle. The amount of nitrogen required in the bottle is a significant factor to assure complete and effective discharge into the protected area and it depends on the solubility of the nitrogen in the fire extinguishing agent. In this article, the Peng-Robinson equation of state (PR EOS) including both the classical van der Waals mixing rule and the Wong-Sandler mixing rule is utilized to correlate the Gas-Liquid Equilibrium (GLE) data from available open published literature and to analyze the solubility of nitrogen in halon alternatives such as HFC227ea (C3HF7), CF3I, FC218 (C3F8), and HFC125 (C2HF5) with Halon1301 (CF3Br) as a reference. A new method is proposed to compute the adjustable interaction parameters in the van der Waals mixing rule and in the Wong-Sandler mixing rule based on the measurements of nitrogen required to pressurize the fire suppression bottle to a specified equilibrium pressure at room temperature. Results show that the PR EOS reproduces the GLE data very well with both van der Waals mixing rule and the Wong-Sandler mixing rule and it is then utilized to predict the temperature dependence of the Henry’s law constants of nitrogen dissolved in the fire extinguishing agents. The PR EOS with van der Waals mixing rule is much more appropriate for determining the Henry’s constants than that with the Wong-Sandler mixing rule and the results calculated by the current model are used to establish a new correlation for the Henry’s law constants. This correlation will be very helpful for fire extinguishing bottle designers to acquire the pressure-temperature relationships for the mixture of nitrogen and agents.Peer reviewe

Understanding the digestibility and nutritional functions of rice starch subjected to heat-moisture treatment

In this study, rice starch with well-controlled digestion resistibility achieved by heat-moisture treatment (HMT) was chosen as a supplementary diet for high-fat-diet-fed mice. Then, the nutritional functions of HMT-modified rice starch were evaluated by the physiological and biochemical indices, proliferation and distribution of intestinal microflora, and functional diversity by putative metagenomes analysis. Compared with the native-rice-starch mice (DM) group, the blood glucose, serum lipid, oxidative stress, and liver function metabolic levels/indices of the HMT-rice-starch mice (HMT-DM) group were worse due to the declined level of slowly digestible starch (SDS) in HMT-modified rice starch. Meanwhile, the species diversity index was observed to be higher in the DM group and Bifidobacteria was identified as a type of bacteria related to the relatively higher content of RS in HMT-modified rice starch. Overall, our results provide important information for the rational design of rice starch-based health-promoting foods with nutritional functions

Kinect-Based Vision System of Mine Rescue Robot for Low Illuminous Environment

This paper presents Kinect-based vision system of mine rescue robot working in illuminous underground environment. The somatosensory system of Kinect is used to realize the hand gesture recognition involving static hand gesture and action. A K-curvature based convex detection method is proposed to fit the hand contour with polygon. In addition, the hand action is completed by using the NiTE library with the framework of hand gesture recognition. In addition, the proposed method is compared with BP neural network and template matching. Furthermore, taking advantage of the information of the depth map, the interface of hand gesture recognition is established for human machine interaction of rescue robot. Experimental results verify the effectiveness of Kinect-based vision system as a feasible and alternative technology for HMI of mine rescue robot