次生生物甲烷与生物降解作用的判识——以准噶尔盆地腹部陆梁油气田为例

“次生生物气”是指原油遭受生物降解后生成的天然气,由于其成分几乎全部为甲烷,因此又称为“次生生物甲烷”。以准噶尔盆地陆梁油气田为例,基于天然气组分和稳定碳同位素组成,结合伴生原油的轻烃地球化学特征,系统研究了次生生物甲烷和生物降解作用的判识方法。研究表明：当热成因天然气与次生生物甲烷混合时,甲烷碳同位素组成变轻,天然气组分变干。同时,此类天然气通常与埋深(地温)和生物降解油藏密切相关。通过原油的轻烃化合物特征可以有效判别油藏是否遭受生物降解。次生生物甲烷的生成常常还伴随着原生热成因气中重烃气组分的选择性降解,造成天然气干燥系数变大,重烃气碳同位素组成富集¹³C,甚至发生倒转。目前使用的各类天然气成因判识图版只适用于原生热成因气,使用时必须充分考虑是否存在各类次生改造作用的影响。     

北部湾盆地迈陈凹陷徐闻X1井油气地球化学特征

通过对北部湾盆地迈陈凹陷徐闻X 1井所产天然气和原油样品的系统分析,指出该井天然气甲烷含量低、重烃气体含量高、干燥系数低,属于原油伴生气,而乙烷和丙烷的碳同位素值小于-30‰,是典型的油型气;该井原油的三环萜烷系列呈C19>C20>C21>C23>C24>C25>C26的阶梯状分布,呈煤成油的特征,但丰富的C27甾烷的存在表明该原油属于典型的湖相原油,而非煤成油,其生物标志物组成的重要特征是富含各种重排构型化合物,表明该原油的烃源岩形成于浅水、弱还原的淡水沉积环境。     

Assessing trophic position quantification methods for three piscivorous freshwater fish using stable isotopes and stomach contents

Accurate trophic position (TP) estimates are important for the development of ecosystem-based management plans. TPs can be quantified by carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes in tissues, but these can disagree with observed and perceived feeding ecology. A recent method that has used a scaled diet-tissue discrimination factor (DTDF), reflecting the inverse relationship between DTDF and δ¹⁵N, was found to better describe TPs of predatory fish species in marine ecosystems, but this has not been tested in freshwater ecosystems. Here, we compare methods of TP estimations in the Lake Huron-Erie corridor (HEC), a system where high diversity of prey items has contributed to the concern that foraging ecology of piscivorous fish species is poorly understood. Using δ¹⁵N and δ¹³C, we quantified TP of longnose gar (Lepisosteus osseus), largemouth bass (Micropterus salmoides), and northern pike (Esox lucius) to assess the efficacy of a scaled DTDF compared to traditional DTDF isotope methods and stomach content analysis (SCA). The scaled DTDF method produced TP estimates that were at times consistent with SCA and were generally higher and with a greater range among individuals than non-scaled DTDFs. The scaled method was not sensitive to baseline choice nor influenced by incorporating carbon source in the model. Greater variability of TP estimates using a scaled DTDF suggests more complex trophic structuring in the upper trophic level guild of the HEC. These results, particularly the lack of baseline sensitivity, provide support for using the scaled DTDF in freshwater food web characterization.     

Balancing CapEx reduction and network stability with stable routing–virtual topology capacity adjustment (SR–VTCA)

This paper investigates the merits of the SR–VTCA (stable routing–virtual topology capacity adjustment) approach as a mechanism to find a beneficial trade-off between network stability and reduction in capital expenditures (CapEx). These are two main objectives for the entities that own the optical infrastructure, such as network operators (NOs), and those also acting as Internet service providers (ISPs). The SR–VTCA scheme is a novel approach to adapt transparent optical networks to time-varying traffic by adjusting the number of lightpaths between node pairs, while keeping the IP routing unchanged. Lightpath bundling (LB) and anycast (AS) switching are combined in SR–VTCA operation to advertise lightpath additions/removals to the IP layer as mere adjustments (increments or decrements) in the capacity, allowing to keep the IP routing stable, and thus, simplifying control plane operations. On the contrary, a fully-reconfigurable (FR) network design, where IP routing can be also modified, would increase the burden in the control plane, but at a higher CapEx reduction, since the optical infrastructure is used more efficiently. In this work, we investigate the CapEx overprovision introduced by SR–VTCA with respect to a FR scheme. In order to do this, SR–VTCA planning problem is first modeled as a MILP formulation. A heuristic procedure based on traffic domination is then proposed to solve large instances of the problem. Exhaustive experiments are conducted comparing the SR–VTCA solutions obtained by the aforementioned MILP and heuristic proposal with solutions found by other optimization methods presented in the literature to solve the FR planning problem. Finally, the results show that SR–VTCA can achieve similar results to the FR case in terms of CapEx reduction, while a huge number of IP reroutings are saved by maintaining IP stability. Thus, SR–VTCA provides an advantageous balance between CapEx overprovisioning and the control plane overhead associated with IP rerouting.     

开关电容DC－DC变换器的分析

本文提出等效电量关系法，并采用这一新的方法对众多的开关电容ＤＣ－ＤＣ变换器进行了统一分析，避免了求解复杂的状态方程的繁琐过程，且简化了分析．     

红外/毫米波多模寻的系统关键技术分析

概述了红外／毫米波多模寻的系统的主要技术特点，对多谱段头罩的选材，外形与厚度的设计进行了计算与理论分析；探讨了适宜于多模导引头的多种类型稳定位标器和复合天线系统系统方案；重点对外／毫米波融合处理器系统进行了研究，针对红外，毫米波探测系统的输出信息，确定了多模寻的系统的融合层次与融合准则。     

Spark discharge generator as a stable and reliable nanoparticle synthesis device: Analysis of the impact of process and circuit variables on the characteristics of synthesized nanoparticles

Nanotechnology offers the promise of harnessing quantum properties not available in the bulk phase. These desirable properties are highly dependent on size and composition. Generators that control these variables are therefore essential for progress in the field. The spark discharge generator (SDG) is an outstanding aerosol route for nanoparticle synthesis, which stands out due to its fast kinetics, scalability, high purity, accuracy and reproducibility, with the added advantage of allowing the synthesis of nanoparticles of any conducting material. These advantages are a consequence of its vast heating and cooling rates, its intrinsic and easily controllable electronic variables at the reach of a click. However, the mechanistic impact of these variables on the actual aerosol generated is still not fully understood. In this work, we constructed an SDG and systematically studied its behavior with particular interest in the effect that resistance, capacitance, inductance, flow rate, gap separation and current have on the electrical behavior of the spark. Our model system produced primarily Fe and Cu nanoparticles with measured concentrations ranging 5*10⁵ – 2*10⁷ part/cm³, and mean agglomerate sizes of 5 – 80 nm. We discuss how the spark influences particle size and number concentration and provide useful correlations that link dependent with independent variables. Remarkably, a finite resistance produces a maximum in the output of the generated aerosols. This suggests a direct link between RLC properties of the circuit and cabling into the frequency of the spark, and nanoparticle number concentration, indicating potential for exploiting such behavior towards maximizing nanoparticle generation. Furthermore, we discuss a link between spark oscillations and energy release with its consequent aerosol generation.     

南海南部天然气水合物稳定带厚度及资源量估算

为了估算南海南部天然气水合物资源量,文章分析了中外科学家的研究成果,认为南海南部具有天然气水合物形成、发育的有利条件：发育的沉积盆地、有利的水深和充足的物源供应,地震剖面揭示的BSR、泥底辟和断裂构造等印证了这一点；同时利用相关的计算公式，对南海南部4个重点区域的水合物稳定带厚度进行了计算，并在此基础上对南海南部的水合物资源前景进行了预测。结果表明，4 个研究区域内的绝大部分海域具有天然气水合物形成的温度、压力条件，水合物稳定带厚度67~833 m。各个海域差异较大，南海南部水合物体积及甲烷资源量分别为2.32×10¹³m³和4.78×10¹⁵m³。     

Trophodynamics of mercury and other trace elements in a pelagic food chain from the Baltic Sea

Mercury (Hg) and 13 other trace elements (Al, Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, As, Cd, and Pb) were measured in phytoplankton, zooplankton, mysis and herring in order to examine the trophodynamics in a well-studied pelagic food chain in the Baltic Sea. The fractionation of nitrogen isotopes (δ¹⁵N) was used to evaluate food web structure and to estimate the extent of trophic biomagnification of the various trace elements. Trophic magnification factors (TMFs) for each trace element were determined from the slope of the regression between trace element concentrations and δ¹⁵N. Calculated TMFs showed fundamental differences in the trophodynamics of the trace elements in the pelagic food chain studied. Concentrations of Al, Fe, Ni, Zn, Pb and Cd showed statistically significant decreases (TMF < 1) with increasing trophic levels and thus these trace elements tropically dilute or biodilute in this Baltic food chain. Cu, As, Cr, Mn, V, Ti and Co showed no significant relationships with trophic levels. Hg was unique among the trace elements studied in demonstrating a statistically significant increase (TMF > 1) in concentration with trophic level i.e. Hg biomagnifies in this Baltic food chain. The estimated TMF for Hg in this food chain was comparable to TMFs observed elsewhere for diverse food chains and locations.     

Sedimentary records of sewage pollution using faecal markers in contrasting peri-urban shallow lakes

Sewage contamination in shallow lake sediments is of concern because the pathogens, organic matter and nutrients contribute to the deterioration of the water-bodies' health and ecology. Sediment cores from three shallow lakes (Coneries, Church and Clifton Ponds) within Attenborough nature reserve located downstream of sewage treatment works were analysed for TOC, C/N, δ¹³C, δ¹⁵N, bacterial coliforms and faecal sterols. ²¹⁰Pb and ¹³⁷Cs activities were used to date the sediments. Elemental analysis suggests that the source of organic matter was algal and down profile changes in δ¹³C indicate a possible decrease in productivity with time which could be due to improvements in sewage treatment. δ¹⁵N for Coneries Pond are slightly higher than those observed in Church or Clifton and are consistent with a sewage-derived nitrate source which has been diluted by non-sewage sources of N. The similarity in δ¹⁵N values (+ 12‰ to + 10‰) indicates that the three ponds were not entirely hydrologically isolated. Analysis by gas chromatography/mass spectrometry (GC/MS) reveals that Coneries Pond had sterol concentrations in the range 20 to 30 μg/g (dry wt.), whereas, those from Clifton and Church Ponds were lower. The highest concentrations of the human-sourced sewage marker 5β-coprostanol were observed in the top 40 cm of Coneries Pond with values up to 2.2 μg/g. In contrast, Church and Clifton Pond sediments contain only trace amounts throughout. Down-profile comparison of 5β-coprostanol/cholesterol, 5β-coprostanol/(5β-coprostanol + 5α-cholestanol) and 5β-epicoprostanol/coprostanol as well as 5α-cholestanol/cholesterol suggests that Coneries Pond has received appreciable amounts of faecal contamination. Examination of 5β-stigmastanol (marker for herbivorous/ruminant animals) down core concentrations suggests a recent decrease in manure slurry input to Coneries Pond. The greater concentration of β-sitosterol in sediments from Church and Clifton Ponds as compared to Coneries is attributed in part to their greater diversity and extent of aquatic plants and avian faeces.