Pyrolytic characteristics and kinetics of the marine green tide macroalgae, Enteromorpha prolifera

The marine macroalgae Enteromorpha prolifera was one of the main algal genera that occurred in the widespread green tides in Qingdao, China, during the summers of 2007, 2008 and 2010. It is thus a plentiful source of biomass and could be used as a biofuel. In this study, the pyrolytic characteristics and kinetics of E. prolifera were investigated using thermogravimetric analysis (TGA) method. Cornstalk and sawdust were used as comparisons. Pyrolytic characteristics were studied using TG-DTG (thermogravimetry-derivative thermogravimetry) curves. Three stages in the pyrolytic process were determined: dehydration, dramatic weight loss and slow weight loss. E. prolifera was pyrolyzed at a lower initial temperature than the two terrestrial biomass forms. The apparent activation energy values for the three types of biomass were calculated and the mechanism functions were determined using 16 different mechanism functions, frequently used in thermal kinetics analysis. Activation energy values varied with mechanism function and the range of activation energy values for E. prolifera, cornstalk, and sawdust were 25-50 kJ/mol, 60-90 kJ/mol and 120-155 kJ/mol, respectively. This indicates that E. prolifera has low thermal stability for pyrolysis and good combustion characteristics.     

缘管浒苔和羽藻氮、磷营养生理学研究

以无性繁殖系为材料,开展了缘管浒苔和羽藻对NO₃-,NH₄+和PO₄3-的吸收动力学、生长动力学研究。吸收动力学研究结果表明缘管浒苔和羽藻对NO₃- 和PO₄3-的吸收方式为主动运输,对NH₄+的吸收方式为被动扩散。缘管浒苔对NO₃-的最大吸收速率(V_max)、对NH₄+的吸收斜率都大于羽藻,说明缘管浒苔对高浓度的NO₃-和NH₄+具有更强的吸收能力。缘管浒苔吸收NO₃-和NH₄+的a值远大于羽藻,说明在低营养盐浓度时,缘管浒苔对NO₃-和NH₄+的亲和力更强。在PO₄3-的吸收中,羽藻的最大吸收速率(V_max)远大于缘管浒苔,说明羽藻对高浓度PO₄3-的吸收能力更强,但缘管浒苔的a值远大于羽藻,说明前者在低营养盐浓度时PO₄3-的亲和力更强。生长动力学研究结果表明,硝酸氮是促进两种海藻快速生长的最适宜氮源形式,氨氮更易促进藻体叶绿素的积累。在相同氮营养条件下,羽藻表现出比缘管浒苔更强的生长优势。     

Tween 80分子在气-液界面上的吸附动力学

用滴体积法测定30℃时Tween80水溶液的平衡及动态表面张力;研究了溶液浓度对动态表面张力及吸附机理的影响。结果表明,溶液浓度越大,动态表面张力数值越小。低浓度时,分子在气-液界面上的吸附受纯扩散控制,浓度增大,表面吸附为扩散-动力学控制机理。     

Photochemical degradation of crude oil in seawater

1 INTRODUCTION Marine photochemistry is a newly developed subject in marine sciences. Photochemical degrada- tion is important in decomposing and removing various organic contaminants in oceans (Ali et al., 1995a, b; Yang, 2000; Yang and Qi, 2002; 2003). …     

A Comparison of Stiff ODE Solvers for Astrochemical Kinetics Problems

The time dependent chemical rate equations arising from astrochemical kinetics problems are described by a system of stiff ordinary differential equations (ODEs). In this paper, using three astrochemical models of varying physical and computational complexity, and hence different degrees of stiffness, we present a comprehensive performance survey of a set of well-established ODE solver packages from the ODEPACK collection, namely LSODE, LSODES, VODE and VODPK. For completeness, we include results from the GEAR package in one of the test models. The results demonstrate that significant performance improvements can be obtained over GEAR which is still being used by many astrochemists by default. We show that a simple appropriate ordering of the species set results in a substantial improvement in the performance of the tested ODE solvers. The sparsity of the associated Jacobian matrix can be exploited and results using the sparse direct solver routine LSODES show an extensive reduction in CPU time without any loss in accuracy. We compare the performance and the computed abundances of one model with a 175 species set and a reduced set of 88 species, keeping all physical and chemical parameters identical with both sets.We found that the calculated abundances using two different size models agree quite well. However, with no extra computational effort and more reliable results, it is possible for the computation to be many times faster with the larger species set than the reduced set, depending on the use of solvers, the ordering and the chosen options. It is also shown that though a particular solver with certain chosen parameters may have severe difficulty or even fail to complete a run over the required integration time, another solver can easily complete the run with a wider range of control parameters and options. As a result of the superior performance of LSODES for the solution of astrochemical kinetics systems, we have tailor-made a sparse version of the VODE solver by replacing the full numerical matrix linear algebra component of the standard VODE solver with sparse matrix solver routines. The preliminary tests from the preconditioned iterative solver package VODPK indicate very good results for one of our test models, but not for all of the models.     

Experimental dehydration kinetics of serpentinite using pore volumometry

A series of dehydration experiments was carried out on both intact rock and cold-pressed powdered samples of serpentinite at temperatures in the range 535–610 °C, 100–170 °C above the onset of the breakdown temperature of 435 °C. Pore water pressures near 120 MPa were servo-controlled using a pore volumometer that also allowed dehydration reaction progress to be monitored through measurement of the amount of evolved water. Effective hydrostatic confining pressures were varied between 0 and 113 MPa. The reaction rate of intact specimens of initially near-zero porosity was constant up to 50–80% reaction progress at any given temperature, but decreased progressively as transformation approached completion. Water expulsion rates were not substantially affected by elevation of effective pressures that remained insufficient to cause major pore collapse. An Arrhenius relation links reaction rate to temperature with an activation enthalpy of 429 ± 201 and 521 ± 52 kJ mol⁻¹ for powdered and intact specimens, respectively. Microstructural study of intact specimens showed extensive nucleation beginning at pre-existing cracks, veins and grain boundaries, and progressing into the interior of the lizardite grains. Extrapolation of these data towards equilibrium temperature provides an upper bound on the kinetics of this reaction in nature.     

Analysis for reflector aluminum mesh panels of five-hundred meter aperture spherical telescope

In this paper, an analysis of the aluminum reflector mesh panels for the Five-hundred meter Aperture Spherical Telescope (FAST) is described. The study concentrates on one element of the reflector surface with the shape of a triangle. For the analysis, the panel is modelled as a mesh of cables so that it can be treated as continuous. It is demonstrated that the results so obtained are reasonable. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of Ni exchangeable pool speciation in ultramafic and mining environments with isotopic exchange kinetic data and models

Soils and ore samples influenced by mining and metallurgical activity were collected in ultramafic soils (UM) complexes of Barro Alto and Niquelândia, in order to determine the contribution of each Ni bearing phases to the total exchangeable pool of Ni, and to point out if this pool was affected by anthropic activities. For this purpose, the IEK-model previously developed by the group (Zelano et al., submitted) was applied, on the basis of IEK experiments performed on pure typical Ni scavengers (serpentines, chlorite, smectite and iron oxydes) from ultramafic systems. For each typical scavenger, this model describes the percentage of Ni associated to exchangeable pool(s) as well as their corresponding kinetic constant(s) of exchange. The mineralogical composition of soil and ore samples and Ni solid speciation were first determined, and the IEK-model was applied on these bases. In almost all samples, an important contribution of serpentine to Ni exchangeable pool was highlighted, ranging between 10% and 45%. The important amount of organic matter (OM) in one of the studied soil samples, allowed to extrapolate generic OM E_Ni and k parameters, which were introduced in the IEK-model to improve its predictive capability. Obtained results provided evidences of how even a small content (3 wt%) of organic carbon (OC), can represent an important contribution of OM to the total E_Ni pool (60%). In the investigated ore samples, up to the 60% of E_Ni was attribute to smectite, responsible for fast E_Ni pool kinetic evolution. In addition, the model highlighted the role of the Fine Black Ash (FBA), by-products of the pyrometallurgical activity, detected into a soil sample, that is responsible for the 15% of E_Ni. This approach allowed to determine, for the first time, the relative contribution of each Ni bearing phase to the total exchangeable pool, in terms of concentration and kinetics.     

海相碳酸盐岩干酪根热解成气过程及其碳同位素演化特征

应用高压封闭体系,对海相碳酸盐岩干酪根进行了热裂解模拟实验,并从气态烃、非气态烃产率及碳同位素演化特征等方面,探讨了海相碳酸盐岩烃源岩干酪根作为气源的生气机理。在模拟实验基础上,结合专用Kinetics软件求取碳酸盐岩烃源岩干酪根裂解产气动力学参数(活化能和指前因子),并将模拟实验结果外推至地质条件下,探讨其动力学模型的实际应用。结果表明,在该地质条件下,甲烷在EasyRo为0.9%时进入主生气期(转化率为10%),2.9%时主生气期结束(转化率为90%)。乙烷至戊烷在EasyRo为1.1%时进入主生气期(转化率10%),2.7%时主生气期结束(转化率90%)。该研究成果为我国海相碳酸盐岩裂解气的判识、资源评价提供了可靠的实验依据。     

基于自适应遗传算法的MRS-TEM联合反演方法研究

地面磁共振法(MRS)因具有定性、定量分析地下水能力,而备受关注.传统磁共振地层含水量反演多采用均匀半空间模型,忽略电阻率分布信息对结果的影响.针对这一问题,本文基于多层电介质中磁共振响应理论,提出MRS与瞬变电磁(TEM)联合反演方法,通过电阻率分布信息对含水量反演过程的实时修正,提高了解释结果的准确度.反演算法采用自适应遗传算法(AGA)进行,基于繁殖规则,动态调整交叉概率和变异概率,解决了标准遗传算法易未成熟收敛而难以得到全局最优解问题.模型数据表明,含噪10%情况下,联合反演仍能较准确地反映地下含水单元模型结构,对比MRS单独反演优势明显.同时,内蒙古白旗野外观测数据联合反演结果与钻井资料基本一致,充分验证了AGA反演算法的实用性及MRS-TEM联合反演的实际意义.