Simulation of the urban climate variations in connection with the transformations of the city of Nantes since the 17th century

The paper seeks to quantify the effect of urban politics on the microclimate of the city of Nantes (France), in particular those initiated by the sanitarians in the mid-19th century to find a remedy for the insalubrity that had been developing with urban densification since the late 17th century. Intensive historical research was first carried out in order to define and date the major transformations undergone by the city, its structure (densification, then widening of the streets, filling of water courses), the lifestyle habits (heating) or the building practices (appearance of stone and paving, higher buildings, insulation). This led to the definition of 5 characteristic states of the city, in 1680, 1756, 1835, 1880 and 1945.     

Issues in the assimilation of the sources of a trace gas by inverse modelling

The problem of reconstructing the (otherwise unknown) source and sink field of a tracer in a fluid is studied by developing and testing a simple tracer transport model of a single-level global atmosphere and a dynamic data assimilation system. The source/sink field (taken to be constant over a 10-day assimilation window) and initial tracer field are analysed together by assimilating imperfect tracer observations over the window.Experiments show that useful information about the source/sink field may be determined from relatively few observations when the initial tracer field is known very accurately a-priori, even when a-priori source/sink information is biased (the source/sink a-priori is set to zero). In this case each observation provides information about the source/sink field at positions upstream and the assimilation of many observations together can reasonably determine the location and strength of a test source.     

Desorption kinetics of trichloroethylene and perchloroethylene from aged dense nonaqueous phase liquid-contaminated soil

Batch experiments were conducted to investigate the desorption kinetics of a contaminated soil collected from a field site at Hill Air Force Base (AFB), Utah. The site has been contaminated with many dense nonaqueous phase liquids (DNAPLs), primarily trichloroethylene (TCE) and perchloroethylene (PCE), for more than 60 years. Similar desorptive behaviour of both TCE and PCE was observed: a stage of fast release of the contaminant at the start followed by a very slow stage. Moreover, it is suggested that not all the contaminant in the solid phase may be released to the aqueous phase, apparently due to the age factor. Local variations were observed in the effective diffusivity and other sorption-related parameters across the site due to aquifer heterogeneity. Experimental results were then simulated using a numerical code based on the intraparticle diffusion model. Good agreement was found between both results.     

Seeker optimization algorithm for global optimization: A case study on optimal modelling of proton exchange membrane fuel cell (PEMFC)

In order to optimize the proton exchange membrane fuel cell (PEMFC) model parameters, a novel approach based on seeker optimization algorithm (SOA) is proposed. The SOA is based on the concept of simulating human searching behaviors, where the choice of search direction is based on the empirical gradient by evaluating the response to the position changes and the decision of step length is based on uncertainty reasoning by using a simple Fuzzy rule. In this study, after evaluated on benchmark function optimization, the SOA is applied to optimal modelling of the PEMFC by using a fuel cell test system in Fuel Cell Application Centre (FAC) at the Temasek Polytechnic, and compared with several state-of-the-art versions of differential evolution (DE) and particle swarm optimization (PSO) algorithms. The simulation results show that the proposed approach is superior to other compared algorithms, and the PEMFC model with optimized parameters by SOA fitted experimental data well. Hence, SOA is an effective and reliable technique for optimizing the parameters of PEMFC model, and can be helpful for system analysis, optimization design and real-time control of the PEMFCs.     

A Novel Approach to Analyzing the Occupancy of the Geo/Geo/∞ Queueing System

Discrete time queueing systems have been successfully used to model packet queues in computer and digital communications systems. In this article we introduce a novel approach to analyzing the Geo^X/Geo^Y/∞ queueing system, which is suitable for modelling high speed computer and communications systems. The approach is based on characterizing the system by a functional equation which is then solved recursively to give identical results to those obtained using other approaches.     

狭缝调相式分置斯特林制冷机理论模型与模拟

自从分置式斯特林制冷机出现以来,工程设计对可靠的整机理论模型有着迫切需求。给出狭缝调相式气动分置式斯特林制冷机热动力学模型及控制方程,直线压缩机采用了绝热模型,压缩活塞的运动规律采用了试验修正,模型中考虑了活塞驱动电机运动特征和回热不完全、轴向导热、穿梭运动、气体泵热、辐射等主要冷损,排出器运动采用单自由度强迫运动模型,并运用数值计算方法模拟整机性能。该模型可用来对整机性能进行预测并帮助设计者深入理解整机物理过程。     

一种改进的基于经验模态分解的小波阈值滤波方法

经验模态分解是一种新的信号分解方法,该方法可将非线性非平稳信号分解成若干个单分量的本征模态函数,使得每个本征模态函数都具有一定的物理意义。本文探索了该方法在语音增强方面的应用.在文献[8]的基础上,对其方法进行了有效改进。首先将带噪语音进行经验模态分解,得到六个本征模态函数和一个余量信号,对这七个信号分别进行小波阈值滤波,并由滤波后的七个信号重构语音。结果表明,该方法的滤波效果明显优于对带噪语音直接采用小波阈值滤波的方法,并且较之文献[8]的滤波方法也具有一定的优势。     

Improved empirical relations for estimating original oil in place recovered during microbial enhanced oil recovery under varied salinity conditions

During microbial enhanced oil recovery (MEOR) processes, the interaction between injection water (IW) and formation water (FW) salinity causes in-situ salinity variation which affects the final oil recovery. The present study explicitly quantifies the Original Oil in Place (OOIP) recovered for different IW and FW salinity conditions through numerical simulation. Based on simulation results, user-friendly empirical correlations were deduced to quickly estimate the OOIP. The results suggest that the OOIP increases drastically in all reservoirs with any initial FW salinity as the adopted salinity of IW is lowered. The study would serve as a tool for making reservoir management decisions.     

BURIAL HISTORY AND THERMAL MATURITY EVOLUTION OF THE TERMIT BASIN,NIGER

Reconstruction of the burial history and thermal evolution of the Cretaceous – Tertiary Termit Basin, a sub‐basin within the larger Eastern Niger Basin of Niger, indicates spatially and temporally variable conditions for organic matter maturation during the basin's multi‐phased evolution. Three episodes of tectonic subsidence which correspond to the observed fault mechanical stratigraphy within the Termit Basin are identified: Late Cretaceous, Maastrichtian to early Paleocene, and Oligocene. These episodes fall within the regional tectonic phases of the West African Rift System delineated by previous studies. The basin exhibits substantial heterogeneity in the magnitude of the tectonic episodes and in consequent thermal maturities. For this paper, 1D burial and thermal histories of eight widely dispersed wells in the Agadem permit area in the SW of the Termit Graben were modelled to investigate the maturation of organic matter in source rocks ranging from Santonian to Oligocene in age. The kinetic modelled maturities match with maturities based on Rock‐Eval T_max values for four wells if present‐day heat flows are elevated. Future exploration strategies in the Termit Basin should take into consideration these heterogeneities in thermal histories and tectonic pulses, which may lead to the development of hydrocarbon accumulations with different oil‐gas compositions in different reservoir compartments.