Richardson extrapolation and defect correction of mixed finite element methods for integro-differential equations in porous media

Asymptotic error expansions in the sense of L ^∞-norm for the Raviart-Thomas mixed finite element approximation by the lowest-order rectangular element associated with a class of parabolic integro-differential equations on a rectangular domain are derived, such that the Richardson extrapolation of two different schemes and an interpolation defect correction can be applied to increase the accuracy of the approximations for both the vector field and the scalar field by the aid of an interpolation postprocessing technique, and the key point in deriving them is the establishment of the error estimates for the mixed regularized Green’s functions with memory terms presented in R. Ewing at al., Int. J. Numer. Anal. Model 2 (2005), 301–328. As a result of all these higher order numerical approximations, they can be used to generate a posteriori error estimators for this mixed finite element approximation. This project was supported in part by the Special Funds for Major State Basic Research Project (2007CB8149), the National Natural Science Foundation of China (10471103 and 10771158), the Social Science Foundation of the Ministry of Education of China (Numerical methods for convertible bonds, 06JA630047), the NSERC, Tianjin Natural Science Foundation (07JCYBJC14300), and Tianjin University of Finance and Economics.     

Numerical study on heat loss from the surface of solar collector tube filled by oil-NE-PCM/Al2O3 in the presence of the magnetic field

Journal of Thermal Analysis and Calorimetry - The natural convection of the oil-NE-PCM/Al2O3 inside the parabolic trough collector is studied. To simulate nanoencapsulate-phase change material...     

Development of a knowledge‐based medical expert system to infer supportive treatment suggestions for pediatric patients

This paper discusses the design, implementation, and potential use of an ontology‐based mobile pediatric consultation and monitoring system, which is a smart healthcare expert system for pediatric patients. The proposed system provides remote consultation and monitoring of pediatric patients during their illness at places distant from medical service areas. The system not only shares instant medical data with a pediatrician but also examines the data as a smart medical assistant to detect any emergency situation. In addition, it uses an inference engine to infer instant suggestions for performing certain initial medical treatment steps when necessary. The applied methodologies and main technical contributions have three aspects: (a) pediatric consultation and monitoring ontology, (b) semantic Web rule knowledge base, and (c) inference engine. Two case studies with real pediatric patients are provided and discussed. The reported results of the applied case studies are promising, and they demonstrate the applicability, effectiveness, and efficiency of the proposed approach.     

Potential of Applying the Geometry-Based Rover Slip Prediction Model Learned on the Earth to the Moon

Russian Physics Journal - Wheeled ground robots are widely used in planetary exploration missions, where slip can measure problems during driving and pre-acquisition slips play an important role....     

The effects of heat transfer on the exergy efficiency of an air-standard otto cycle

The exergy analysis of an air-standard Otto cycle with heat transfer loss is analyzed by using finite-time thermodynamics. The results showed that the heat transfer loss is responsible for a significant destruction of exergy. It is also shown that exergy efficiency and maximum power output increase with decreasing heat transfer loss. The results obtained in this paper may provide useful information for the maximum work available.     

Various polycarbonate graft copolymers via diels–alder click reaction

In this work, we used Diels–Alder click reaction for the preparation of various types of aliphatic polycarbonates (PCs). We first prepared a novel anthracene‐functionalized cyclic carbonate monomer, anthracen‐9‐ylmethyl 5‐methyl‐2‐oxo‐1,3‐dioxane‐5‐carboxylate (2), followed by ring‐opening polymerization of this monomer to prepare PC with pendant anthracene groups (PC‐anthracene) using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU)/1‐(3,5‐bis(trifloromethyl)phenyl)‐3‐cyclohexylthiourea (TU) as the catalyst and benzyl alcohol as the initiator in CH₂Cl₂ at room temperature. Subsequently, the resulting PC‐anthracene (M_n,TDGPC = 6000 g/mol, M_w/M_n = 1.22) was grafted with a linear α‐furan protected‐maleimide terminated‐poly(methyl methacrylate) (PMMA‐MI) (M_n,GPC = 3100 g/mol, M_w/M_n = 1.31), or poly(ethylene glycol) (PEG‐MI) (M_n,GPC = 550 g/mol, M_w/M_n = 1.09), or a mixture of PMMA‐MI and PEG‐MI to yield well‐defined PC graft or hetero graft copolymers, PC‐g‐PMMA (M_n,TDGPC = 59000 g/mol, M_w/M_n = 1.22) or PC‐g‐PEG, or PC‐g‐(PMMA)‐co‐PC‐g‐(PEG) (M_n,TDGPC = 39900 g/mol, M_w/M_n = 1.16), respectively, using Diels–Alder click reaction in toluene at 110°C. The Diels–Alder grafting efficiencies were found to be over 97% using UV spectroscopy. Moreover, the structural analyses and the molecular weights of resulting graft copolymers were determined via ¹H NMR and triple detection GPC (TD‐GPC), respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Experiments on the synthesis of carotenoid glycosides

Isozeaxanthin was treated with trifluoroacetic acid and tetra-O-benzoyl-1-thio-β-d-glucose to afford β,β-carotene-4,4′-bisthioglucoside isomers in good yields. The deprotected compounds are mimetics of naturally occurring thermoxanthins and can show favourable effects against oxidation stress.     

On the Kolmogorov–Feller law for exchangeable random variables

We prove a Kolmogorov–Feller weak law of large numbers for exchangeable sequences, under a second order hypothesis on the truncated mixands.     

1–8 GHz high efficiency single-stage travelling wave power amplifier

This paper describes a Class-A/AB wideband power amplifier that comprises of a single-stage transistor travelling wave structure in which capacitive coupling and frequency dependent lossy artificial-line are employed at the input of the active device. The proposed technique significantly enhances the amplifier’s gain-bandwidth product, input match and gain flatness performance. To ensure the amplifier delivers a predefined power to the load over its entire operating band 2-to-8 GHz a broadband load-pull technique was applied at the output of the amplifier. To avoid reduction in the amplifier’s bandwidth resulting from parasitic capacitive effects associated with the off-chip choke inductor a wideband RF choke was designed. The 1.31 × 2.93 mm² power amplifier was fabricated using 0.25 μm GaAs pHEMT MMIC process. The measurement results show that the proposed amplifier delivers an average P _sat of 29.5 dBm and P _out,1 dB of 26 dBm, and the corresponding PAE levels are 55 and 35 % for the P _sat and P _out,1 dB, respectively.     

基于非等温能量平衡模型的 GTR 二次击穿特性研究

基于非等温能量平衡传输模型,利用 Silvaco-TCAD 全面系统地分析了发射区半宽度(LE)、发射区边缘刻蚀结构以及浮空发射区结构对 NPN 型硅大功率晶体管(GTR)直流正偏二次击穿特性的影响。结果表明：当 LE为 130μm 时,GTR 直流正偏二次击穿临界点电压(VSB)最高。对于 LE为 150 μm 的 GTR,当发射区边缘横向刻蚀距离为10 μm 时,对直流正偏二次击穿的改善效果最好。当浮空发射区与发射区边缘间距减小到 17 μm 时,浮空发射区开始发挥改善直流正偏二次击穿特性的作用。