Variational iteration method — a promising technique for constructing equivalent integral equations of fractional order

The variational iteration method is newly used to construct various integral equations of fractional order. Some iterative schemes are proposed which fully use the method and the predictor-corrector approach. The fractional Bagley-Torvik equation is then illustrated as an example of multi-order and the results show the efficiency of the variational iteration method’s new role.     

基于非分散红外(NDIR)技术的土壤剖面二氧化碳浓度的测定

为了探索土壤剖面CO₂浓度以及不同土壤层(腐殖质H层、A层、B层、C层)土壤呼吸的变化规律,应用非分散红外(NDIR)技术的新方法,持续不间断的测量土壤剖面二氧化碳浓度。实验所用的主要仪器为硅基非分散红外测量仪,能在高湿、高粉尘、污垢及其他恶劣环境中进行光谱数据采集。通过2013年全年光谱测定值的采集,并应用梯度法模型计算不同深度土壤碳通量,同时利用LI-8100碳通量自动监测系统持续监测的土壤碳通量值进行回归分析。结果显示：土壤剖面CO₂浓度呈现明显的梯度变化,即随着土壤深度的增加,土壤CO₂浓度增大;梯度法模型得出的不同土壤层的土壤呼吸模拟值与实测土壤呼吸值之间具有较好的线性相关,H,A,B,C层的模型预测的决定系数(R2)分别为0.906 9,0.718 5,0.838 2,0.903 0,均方根误差(RMSE)分别为0.206 7,0.104 1,0.015 6,0.009 6。均达到了较好的预测结果,表明该方法对定量分析不同土壤层碳通量是可行的。该方法具有清晰揭示土壤CO₂在不同土壤层之间的传输规律,以及有助于分析不同土壤层土壤呼吸特性的优点,能为全球土壤剖面碳通量计算提供基础数据,是一种具有发展前途的传感器。     

Convex hulls of piecewise-smooth Jordan curves

Several linear-time algorithms for finding the convex hull of a simple polygon in the plane are known. This paper extends a linear-time algorithm for polygons to a linear-time algorithm for input that includes smooth, convex, curved edges, such as conic sections.     

The response of two-degree-of-freedom systems with quadratic and cubic non-linearities to multifrequency parametric excitations

The response of two d.o.f. systems with quadratic and cubic non-linearities to multi-frequency parametric excitations is determined by using the method of multiple scales. Four first-order ordinary differential equations are derived to describe the modulation of the amplitudes and the phases when principal parametric resonances of both modes and combination resonances of the additive and difference type occur simultaneously. In all cases the steady state solutions and their stability are determined. Numerical results depicting the various resonances are presented.     

Comparing study on hydration properties of various cementitious systems

The hydration properties of slag sulfate cement (SSC), slag Portland cement (PSC), and ordinary Portland cement (POC) were compared in this study by determining the compressive strength of pastes, the hydration heat of binders within 72 h, the pore structure, the hydration products, and the hydration degree. The results indicated that main hydration products of PSC paste and POC paste are calcium hydroxide and C–S–H gel, while those of SSC paste are ettringite and C–S–H gel from the analyses of XRD, TG–DTA, and SEM. At the early curing age, the compressive strength depends on the clinker content in the cementitious system, while at the late curing age, which is related to the potential reactivity of slag. From hydration heat analysis, the cumulative hydration heat of PSC is lower than that of POC, but higher than that of SSC. Slag can limit chemical reaction and the delayed coagulation of gypsum, which also plays a role in the early hydration. So SSC shows the lowest heat release and slag can’t be simulated without a suitable alkaline solution. Based on MIP analysis, the porosity of POC paste is the smallest while the average pore size is the biggest. At the age of 90 days, the compressive strength of SSC can get higher development because of its relative smaller pore size than that of PSC and POC paste.     

The “Fingerprint” of a freshwater microalga Scenedesmus sp. LX1: Visualizing the composition of its soluble algal products

The composition of soluble algal products was visualized by a fingerprint analytical method.     

Viabilite des piles a combustible pour l'application automobile

Viability of fuel cells for automotive applications. In order to demonstrate the technical, environmental and economic viability of fuel cells for road vehicle applications, PSA Peugeot Citroën and Renault have decided to unite their forces. A common program was started in September 1999 for evaluating the potential of a fuel cell vehicle. This program is expected to allow the participants to gain the necessary know-how, and to determine the feasibility and competitivity conditions for the real commercialization of a serial fuel cell vehicle, in a highly competitive market. The work carried out during the first phase of the program will be presented.     

Application of a search algorithm to stream assimilative capacity management

This paper presents an efficient method for solving the model of stream assimilative capacity management problem. The optimization method employed is very easy to comprehend as it is intuitively similar to the manual solution process. Besides, the method is very easy to program and has good ability of obtaining the optimal or at least a good candidate solution in an efficient manner. The usefulness of the proposed method is demonstrated through an example available in the literature.