变速变姿态下飞机燃油体积解算技术

为准确测量飞机不规则油箱内的燃油体积,在传统的查表插值法基础上,提出了基于等效传感器的自适应步长切割法(ASCM),用于建立燃油质量特性数据库,通过引入等效传感器概念,实现了不同姿态下多传感器的信息融合;该方法根据切片截面积的变化率调整切割步长,从而减小了燃油体积解算时的插值误差;利用多传感器的输出值实现了燃油平面的最小二乘(LMS)拟合,当有效传感器较少时,再结合等效燃油平面姿态角拟合燃油平面,消除了加速度对燃油平面的影响;对传统的三维查表插值法进行改进,减小了由于燃油平面姿态角插值引起的误差。基于UG二次开发,设计了燃油体积解算平台。实际油箱CAD仿真验证结果表明:该方法所建的数据库数据规模小,燃油解算速度快,实现了加速度和姿态误差修正,并减小了差值误差,进一步提高了燃油的测量精度。

二维不规则域内紊流有限体积解

本文针对M.Faghri等计算某一类二维不规则域内层流方法在工程中应用范围窄的特点,结合本文推出的物面正交曲线座标系中的控制方程,用代数变换法发展了一个二维不规则域内紊流的计算方法。它既达到了适用范围广,同时又避免了数值求解偏微分方程生成适体坐标的目的。采用紊流K-ε两方程模型并用有限体积法进行方程离散化。文中最后通过若干算例对该方法进行说明。计算与实验结果比较表明,二者吻合较好。

范德华方程体积解的公式化与程序化

范德华方程是最早的立方型状态方程,通过该方程求解实际气体在确定温度、压力下的体积,既是物理化学的重要教学内容,同时,也是一个教学难点。本文对这一问题的公式化、程序化进行了探讨,为应用一般微型计算器求解上述方程进行了有益的探索。并将所得结果应用于饱和蒸汽的体积计算,结果表明范氏方程对实际气体的行为有较好的吻合,至今仍有较大的应用空间。

二维带非线性源项单个守恒律的有限体积方法的收敛性

本文讨论在无结构网格下用有限体积方法离散二维带非线性源项的单个守恒律,在测度值解与Diperna唯一性结果的框架下,证明了估计解在L_(loc)~l(R^2×(0,T))意义下收敛到单个守恒律的熵解。

飞机燃油测量传感器优化布局技术

实时、准确地测量出飞机各油箱的剩余油量,对飞机飞行安全十分重要.为了提高飞机燃油的测量精度,设计了一种基于粒子群算法(PSO)的燃油测量传感器优化布局方法.首先,引入燃油实体的概念,建立了某机翼复杂、带隔断多腔油箱CAD模型及箱内燃油实体模型;其次,基于Unigraphics NX(UG)二次开发,完成了飞机不同姿态下、复杂不规则多腔油箱燃油体积的解算;再次,提出了飞机油箱最大燃油可测区(LMR)的概念,并以此作为优化目标进行传感器优化布局;最后,引入可设置边界距离因子(BDF),解决了传感器布局时与油箱壁距离过近的问题.结果表明,该方法实现了多根燃油传感器的布局,可以不受油箱形状和大小的限制,有效避开了油箱内部的干涉区域,保证不同飞行姿态下油量测量的连续性,并使得飞机燃油的可测范围达到较高水平.

地勘期间煤层气含量测定中损失量的误差分析

地勘期间煤层气含量测定过程中,损失量的测定一直存在误差。测定工作的不同阶段都隐含误差因素,如提芯过程的提钻暴露时间、装样过程的装样暴露时间,解吸过程的数据测定等。再具体举例而言,对于绳索取芯其提钻过程不是匀速过程,而是随绳索缠绕半径增大其提芯速度变大;在装样过程中,由于煤芯样品在不断解吸出煤层气,这部分气体不应该纳入初始时刻解吸气体积;解吸阶段当煤岩样品解吸速率较小,或是由于人为误差都有可能使解吸数据造成偏差。文章通过对煤层气含量测定过程中,各阶段损失量推定可能带来的误差因素进行定性或定量分析,进一步修正煤层气损失量计算数据,提高其计算精度。

Photosynthetic efficiency, cell volume, and elemental stoichiometric ratios in Thalassirosira weissflogii under phosphorus limitation

Nutrient limitation is known to inhibit growth and metabolism and to alter elemental stoichiometric ratios in phytoplankton. In this study, physiological changes in Thalassirosira weissflogii were measured under different dissolved inorganic phosphate (DIP) regimes in semi-continuous cultures to revisit the utility of the Redfield ratio for assessing nutrient limitation. The results showed that cell size increased with decreasing DIP availability. In the P-depleted treatment (f/2-P) the cell size was 1.48 times larger than that in the P-limited (f/100) treatment and 2.67 times larger than that in the P-saturated treatment (f/2 and f/10). The fucoxanthin to chlorophyll a ratio (Fuco/chl a) was relatively stable (about 0.3) in P-saturated cultures and was 10 times higher than that in P-limited and P-depleted cultures. During the experimental period, the photosynthetic efficiency index, ?F/Fm′, was relatively stable at ~0.50 in the P-saturated cultures, but quickly declined with decreasing DIP availability. Although cellular P content showed a significant difference between the P-saturated culture (1.6 pg/cell) and the P-limited culture (0.7 pg/cell), the N/P ratio in T. weissflogii did not show a trend with DIP availability and fluctuated slightly around 25. Our results suggest that cell division in T. weissflogii is not strictly size-gated but is probably regulated by a biochemical, and hence, an elemental stoichiometric ratio threshold, and that deviation of the cellular N/P ratio from the Redfield ratio is not a reliable indicator of algal nutrient stress.

Kinetics of Chlorine Decay in Water Distribution Systems

A combined first and second-order model, which includes bulk decay and wall decay, was developed to describe chlorine decay in water distribution systems. In the model the bulk decay has complex relationships with total organic carbon (TOC), the initial chlorine concentration and the temperature. Except for the initial stages they can be simplified into a linear increase with TOC, a linear decrease with initial chlorine concentration and an exponential relationship with the temperature. The model also explains why chlorine decays rapidly in the initial stages. The parameters of model are determined by deriving the best fitness with experimental data. And the accuracy of model has been verified by using the experimental data and the monitoring data in a distribution system.

Effects of Freeze–thaw Cycles on Soil Mechanical and Physical Properties in the Qinghai–Tibet Plateau

Extreme freeze-thaw action occurs on the Qinghai-Tibet Plateau due to its unique climate resulting from high elevation and cold temperature.This action causes damage to the surface soil structure, as soil erosion in the Qinghai-Tibet Plateau is dominated by freeze-thaw erosion.In this research,freezing–thawing process of the soil samples collected from the Qinghai–Tibet Plateau was carried out by laboratory experiments to determinate the volume variation of soil as well as physical and mechanical properties, such as porosity, granularity and uniaxial compressive strength, after the soil experiences various freeze–thaw cycles.Results show that cohesion and uniaxial compressive strength decreased as the volume and porosity of the soil increased after experiencing various freeze–thaw cycles, especially in the first six freeze–thaw cycles.Consequently, the physical and mechanical properties of the soil were altered.However, granularity and internal friction angle did not vary significantly with an increase in the freeze–thaw cycle.The structural damage among soil particles due to frozen water expansion was the major cause of changes in soil mechanical behavior in the Qinghai–Tibet Plateau.

Crystals of suspended marine barite in the eastern equatorial Pacific:processes of dissolution and effects on crystal morphology

Suspended particulate substances were sampled in the eastem equatorial Pacific in water column from surface to near bottom in five stations in 2005, from which 868 barite crystals were recovered. The barite crystals were examined under scanning electron microscopy. About 61% of the total barites crystals contained detectable Sr by energy dispersive X-ray spectrometry. Barite crystals could be classified into four groups based on their morphology： 1） bladed; 2） ovoid or rounded; 3） arrow-like; and 4） irregularly shaped. The arrow-like barite crystals in natural environment has never been reported before. In addition, about a half of the studied crystals showed features of dissolution as cavities or holes inside of the crystals or around their edges. We found that differential dissolution of barite crystals is consequence of heterogeneous Sr distribution in barite crystals. Our results would help in understanding the biogeochemical processes of marine barite formation and preservation in seawater and marine sediments.

Interpreting effects of TOC_(inert) organic content on source rock potential using S_2 vs. TOC graph in Maamba Coalfield,southern Zambia

The authors present the effects of the total organic carbon( TOCinert) during pyrolysis and how it overall affects the estimates of the hydrocarbon index( HI) using the cross plot S2 vs. TOC graph. A total of 21 drillcore samples consisting of the non-carbonaceous mudstones,carbonaceous mudstones,coaly mudstones and coals with S2> 0. 35 are selected and used. The average TOC for the sampled population is 10. 36 wt%.TOCinertmeasured from the S2 vs. TOC graph is 2. 97 wt% and the average pyrolysable TOCliveis 7. 39 wt%. The HI is 102 mg HC / g TOC and the pyrolysable HI is 175 mg HC / g TOC,indicating that the TOCinertor mi-neral matrix adsorbs some of the hydrocarbons liberated during pyrolysis resulting into the low HI values which affects the correct determination of the source rock potential. Other applications of the S2 vs. TOC cross plot have been used to determine the depositional system tracts. The high stand system tract is also determined through this method.

Global Existence of Positive Solutions for Volterra Integral Equations

This paper considers the global existence and nonexistence of positive solutions for the following volterra integral equations wbers Matrix B is called a positive definite one, if all the principal minors have positive detechants. By considering the existence of positivve solutions for algebra equations, it is proved that if I-A is a positive definite matrix,where I is an identity matrix, then (I) bas global positive solution 1 Otherwise, (I)has no continous nbndeereasing positive solution.

A Modified Fixed Point Method for the Perona Malik Equation

In this work we present a new method to solve the Perona Malik equation for the image denoising. The method is based on a modified fixed point algorithm which is fast and stable. We discretize the equation using a finite volume method by integrating the equation using a fuzzy measure on the control volume. To make our algorithm move faster in time, we have used an optimized domain decomposition which generalize the wave relaxation method. Several test of noised images illustrate this approach and show the efficiency of the proposed new method.

Cathodic Hydrogen as Electron Donor in Enhanced Reductive Dechlorination

In situ capping is an attractive and cost-effective method for remediation of contaminated sediments,but few studies on enhancing contaminant degradation in sediment caps have been reported,especially for chlorinated benzenes.Electrically enhanced bioactive barrier is a new process for in situ remediation for reducible compounds in soil or sediments.The primary objective of this study is to determine if electrodes in sediment could create a redox gradient and provide electron acceptor/donor to stimulate degradation of chlorinated contaminant.The results demonstrate that graphite electrodes lead to sustainable evolution of hydrogen,displaying zero-order kinetics in the initial stages with different voltages.The constant rates of hydrogen evolution at 3,4,and 5 V are1.05,2.54,and 4.3 nmol·L 1·d 1,respectively.Even higher voltage can produce more hydrogen,but it could not keep long time because the over potentials on electrode surfaces prevent its function.The study shows that 4 V is more appropriate for hydrogen evolution.The measured and evaluated concentration of 1,2,3,5-tetrachlorobenzene in pore water of sediment and concentration of sulfate show that dechlorination is inhibited at higher concentration of sulfate.

Intraday Volume Percentages Forecasting Using a Dynamic SVM-Based Approach

This paper proposes a dynamic model to forecast intraday volume percentages by decomposing the trade volume into two parts: The average part as the intraday volume pattern and the residual term as the abnormal changes. An empirical test on data spanning half-a-year gold futures and S&P 500 futures reveals that a rolling average of the previous days' volume percentages shows great predictive ability for the average part. An SVM approach with the input pattern consisting of two categories is employed to forecast the residual term. One is the previous days' volume percentages in the same time interval and the other is the most recent volume percentages. The study shows that this dynamic SVM-based forecasting approach outperforms the other commonly used statistical methods and enhances the tracking performance of a VWAP strategy greatly.

Simplified Numerical Study of Evaporation Processes Inside Vertical Tubes

The paper presents a simplified numerical model of evaporation processes inside vertical tubes.In this model only the temperature fields in the fluid domain(the liquid or two-phase mixture) and solid domain(a tube wall) are determined.Therefore its performance and efficiency is high.The analytical formulas,which allow calculating the pressure drop and the distribution of heat transfer coefficient along the tube length,are used in this model.The energy equation for the fluid domain is solved with the Control Volume Method and for the solid domain with the Finite Element Method in order to determine the temperature field for the fluid and solid domains.

The Singular Integral of an Analytic Polyhedron

Combining R.Harvey and J.Porking′s methods and traditional methods, we define the current Cauchy principal values in this paper by using homotopy formula and integral transformations. We study the boundary value of Weil type polyhedron integrals and obtain Plemelj formulas, which are different from the methods usually in the studies of boundary value problems.

High order sub-cell finite volume schemes for solving hyperbolic conservation laws I: basic formulation and one-dimensional analysis

In this paper, a family of sub-cell finite volume schemes for solving the hyperbolic conservation laws is proposed and analyzed in one-dimensional cases. The basic idea of this method is to subdivide a control volume(main cell) into several sub-cells and the finite volume discretization is applied to each of the sub-cells. The averaged values on the sub-cells of current and face neighboring main cells are used to reconstruct the polynomial distributions of the dependent variables. This method can achieve arbitrarily high order of accuracy using a compact stencil. It is similar to the spectral volume method incorporating with PNPM technique but with fundamental differences. An elaborate utilization of these differences overcomes some shortcomings of the spectral volume method and results in a family of accurate and robust schemes for solving the hyperbolic conservation laws. In this paper, the basic formulation of the proposed method is presented. The Fourier analysis is performed to study the properties of the one-dimensional schemes. A WENO limiter based on the secondary reconstruction is constructed.

An investigation of non-Newtonian fluid flow due to metachronal beating of cilia in a tube

The aim of this study is to explain theoretically the role of ciliary motion on the transport of epididymal fluid through the ductus efferentes of the male reproductive track. For this purpose, a mathematical model has been developed for the flow of a non-Newtonian fluid in an axisymmetric tube due to metachronal wave of cilia motion for the more realistic consequences. Carreau viscous fluid model is considered to see the rheological effects on the pumping characteristics of the flow. Regular perturbation method has been employed to obtain the analytical expressions for the stream function, the velocity field and a relation between the pressure difference and the volume flow rate. It is found that the volume flow rate is influenced significantly by Weissenberg number We and the cilia length parameter ε. The computational results are presented graphically to see the effects of various physical parameters. Finally, the analysis is applied and compared with the observed value of the flow rate of spermatic fluid in the ductus efferentes of the male reproductive track. The volume flow rate is reported closed to the estimated value 6 × 10^-3 ml/h in the human ductus efferentes when We = 0.5 and e is near by 0.25.

Integrable Hierarchy Covering the Lattice Burgers Equation in Fluid Mechanics:N-fold Darboux Transformation and Conservation Laws

Burgers-type equations can describe some phenomena in fluids,plasmas,gas dynamics,traffic,etc.In this paper,an integrable hierarchy covering the lattice Burgers equation is derived from a discrete spectral problem.N-fold Darboux transformation(DT) and conservation laws for the lattice Burgers equation are constructed based on its Lax pair.N-soliton solutions in the form of Vandermonde-like determinant are derived via the resulting DT with symbolic computation,structures of which are shown graphically.Coexistence of the elastic-inelastic interaction among the three solitons is firstly reported for the lattice Burgers equation,even if the similar phenomenon for certern continuous systems is known.Results in this paper might be helpful for understanding some ecological problems describing the evolution of competing species and the propagation of nonlinear waves in fluids.