Comparison of microbial activity in some Brazilian soils by microcalorimetric and respirometric methods

The microbial activity in a Rhodic eutrudox (R), a Typic eutrudox (V) and a Quartzipsamment (Q) was monitored by respirometric and calorimetric methods. CO₂ evolution was monitored for 98 days by titrimetry and conductimetry for control amended samples (A) with 25% of cattle manure (E), municipal refuse compost (L), earthworm casts (H) or 1.25 kg ha⁻¹ of trifluralin (T). Average values of all treatments through respiration at the end of the incubation period were 5.24±0.34, 6.13±0.31 and 6.50±0.33, in mg CO₂ g⁻¹ soil, for R, V and Q, respectively, by titrimetry and 8.89±0.44, 10.41±0.54 and 10.41±0.52, in mg CO₂ g⁻¹ soil, for R, V and Q, respectively, for conductimetry. Excellent correlation (r=1.00) between titrimetry and conductimetry was observed. The decreasing order for respiration was E, H, L and T. After each incubation time, the conductimetric values were higher than those for titrimetry, for all treatments of these Brazilian soils. Average values of the exothermic thermal effect were: 0.58±0.02, 0.60±0.02 and 0.67±0.01 kJ g⁻¹ soil, for R, V and Q, respectively, for 103 days. A significant correlation coefficient of 0.91 and P<0.0001 between calorimetric and respirometric values over 98 days was observed. Based on the obtained calorimetric results, it can be proposed that this technique should be as a useful analytical method for determining the microbial activity in soils.     

Chemometrics in fuel science: demonstration of the feasibility of chemometrics analyses applied to physicochemical parameters to screen solvent tracers in Brazilian commercial gasoline

Samples of commercial gasoline, from the National Program of Fuel Quality Monitoring of the National Petroleum Agency, were collected from gas stations located in the Midwestern state of Sao Paulo, Brazil, and analyzed by several physicochemical standard methods established by ANP Resolution no. 309. Also, important information related to tampering was analyzed with the marker solvent. Statistical analysis and exploratory chemometric were employed to discriminate the presence of markers of solvents in commercial gasoline. The results showed that statistical and chemometric parameters such as atmospheric distillation temperatures T10 and T90, RON, benzene and saturated and aromatic hydrocarbons satisfactorily describe the presence of marker solvent, usually with a probability exceeding 70%. Furthermore, after optimizing the SIMCA algorithm, sensitivity in the training set with cross‐validation leave‐one‐out (83.8%) and the set of prediction (77.1%) were revealed. The proposed method will become indispensable and recommended for discriminating samples of fuels for commercial applications in routine monitoring programs and quality control. Copyright © 2011 John Wiley & Sons, Ltd.     

巴西劈裂试验应力场解析解应力函数解法

巴西圆盘试验是国际岩石力学学会推荐的用于测量岩石抗拉强度的间接实验,其理论基础是圆盘在荷载作用下应力场的分布。本文以平面应力状态为基础,根据弹性理论中的Airy应力函数和线弹性叠加原理,采用与Н. И. Мусхелишьили所用的复变函数方法完全不同的方法,给出了巴西圆盘内部任意一点应力的直角坐标形式的解析表达式。将得到的应力场解析解和Н.И. Мусхелишьили 采用复变函数方法给出的经典解对比发现,两者完全吻合一致,从而表明本文所采用的方法是合理正确的。     

Differential nonhomogeneous models for elastic randomly cracked solids

A differential scheme is developed to approximate the elastic behaviour of randomly cracked solids, accounting for possible locally nonhomogeneous distribution of the cracks. Certain inclusion or matrix spaces within the solids are modelled as forbidden regions for the cracks. At small to intermediate values of the crack density and proportion of forbidden regions, the effective elastic moduli of the models do not differ much from each other, but the differences become profound at higher values of those parameters: the effective moduli can be very small and large (toward those of the uncracked solids) depending upon the particular nonhomogeneous arrangements of the cracks.     

国产能谱仪快速分析球团矿

本文使用国产能量色散X射线荧光光谱仪对分析球团矿进行了方法试验研究,建立了适当的卫作条件,经试验,该方法速度快,精密度满足使用要求.     

The three-dimension model for the rock-breaking mechanism of disc cutter and analysis of rock-breaking forces

To study the rock deformation with threedimensional model under rolling forces of disc cutter,by carrying out the circular-grooving test with disc cutter rollingaround on the rock,the rock mechanical behavior underrolling disc cutter is studied,the mechanical model of disccutter rolling around the groove is established,and the theory of single-point and double-angle variables is proposed.Based on this theory,the physics equations and geometricequations of rock mechanical behavior under disc cutters oftunnel boring machine(TBM) are studied,and then the balance equations of interactive forces between disc cutter androck are established.Accordingly,formulas about normalforce,rolling force and side force of a disc cutter are derived,and their validity is studied by tests.Therefore,a newmethod and theory is proposed to study rock-breaking mechanism of disc cutters.     

Polycyclic aromatic and aliphatic hydrocarbons in Mytella charruana, a bivalve mollusk from Mundaú Lagoon, Brazil

The levels of selected organic markers, such as 17 polycyclic aromatic hydrocarbons (PAHs), 16 of which are classified as priority pollutants by the US-EPA, perylene, aliphatic hydrocarbons (linear alkanes) and petroleum biomarkers (hopanes and steranes) were assessed in Mytella charruana, a common bivalve mollusk from the convergence of the Mundaú Lagoon, Maceió, Alagoas, Brazil. The organic markers were evaluated in three campaigns (Jul/2006, Oct/2007 and Feb/2008) aiming to identify pollution sources, understand their status of contamination and determine baseline data looking for future management strategies. Higher Σ16HPAs concentration was observed in organisms with 10-30 mm (80% of the total mass of organisms from Mundaú Lagoon) collected in Feb/2008, whereas in individuals with 30-40 mm, the PAH concentrations were higher during Jul/2006 and Oct/2007. The sugarcane burning in Maceió-AL occurs between October and March. The Flt/(Flt + Py) and BaA/(BaA + Chry) ratios in Feb/2008 indicated a combustion process source. The PAH concentrations in Mytella charruana are below of the limit value considered by the WHO (10 ng g⁻¹ for BaP). However, the results suggest that the sugarcane burning process lead to higher PAH concentrations in these organisms in Feb/2008. Many samples showed significant contamination by petroleum biomarkers, hopanes and steranes. Also, the aliphatic hydrocarbon chromatographic profiles were characteristic of petrogenic sources. The hydrocarbons measured in Mytella charruana from Mundaú Lagoon seems to be impacted by PAH in sugarcane burning periods. On the other hand, urban residues and fishing boats could be pointed as important petrogenic sources of aliphatic hydrocarbons in the same bivalve mollusk.     

一种高精度的增量式光学编码器

本文介绍了一种14位增量式光学编码器,包括光学部分和电气部分的组成及工作原理。作为应用实例,还介绍了用单片机(MCU)对输出的编码进行计数并加以显示。     

EXTENSIONS OF HILBERT MODULES AND HANKEL OPERATORS

1.IntroductionInthepresentpaper,wewillcontinuethestudyofHilbertmodules[1-5].LetHbeaHilbertspaceandAafunctionalgebra.WesaythatHisaHilbertmoduleoverAifthereisamultiplication(a,f)-affromAxHtoH,makingHintoanXmoduleandif,inaddition,theactionisjointlycontinuousinthesup-normonAandtheHilbertspacenormonH.ThecategoryHofallHilbertNmodulesisanaturalsettingfornumerousquestionsinoperatortheory.In[9],DouglasandPaulseninitiatedasystematicstudyofHilbertmodules'theywereabletotranslatemanyconceptsandpro…     

Anisotropic effective higher-order response of heterogeneous Cauchy elastic materials

The homogenization results obtained by Bacca et al. (2013a), to identify the effective second-gradient elastic materials from heterogeneous Cauchy elastic solids, are extended here to the case of phases having non-isotropic tensors of inertia. It is shown that the nonlocal constitutive tensor for the homogenized material depends on both the inertia properties of the RVE and the difference between the effective and the matrix local elastic tensors. Results show that: (i) orthotropic nonlocal effects follow from homogenization of a dilute distribution of aligned elliptical holes and, in the limit case, of cracks; (ii) even under the dilute assumption and isotropic local effective behaviour, homogenization may lead to effective nonlocal orthotropic properties.