Soil Seed Banks and Forest Succession Direction Reflect Soil Quality in Ziwuling Mountain,Loess Plateau,China

The paper presents a study by taking the soil seed banks and vegetation successions of the forests in Ziwuling Mountain as indicators to analyze the effects of the ages, and the litter layers and soil depths at growing locations in seven types of forest communities on their seed bank formations and soil quality. The results showed that the seed banks at different growing locations in the communities increased in the order of upper slope, middle slope, and lower slope; the seed storages of the seed banks in the different layers of the communities varied, much more higher in the litter layers than in 0–15 cm, and the seed storages of the seed banks in the seven types of forest communities ranked in the increasing order of Pinus tabulaeformis forest, Pinus shenkaneusis forest, Quercus liaotungensis forest, Populus davidiana forest, Betula platyphylla forest, scrub communities, and grassland communities; in the meantime, the seed storage of seed banks peaked in 30–50 years old P. shenkaneusis forest, 30–40 years old P. tabulaeformis forest, 15–30 years old Q. liaotungensis, and P. davidiana and B. platyphylla forests, and 10–15 years old scrub and grassland communities, and the ages of the communities varied with the seed storages of the seed banks in a significantly correlative manner following a fitted exponential equation. In addition, the soil seed banks of the seven types of communities consisted of rich and diverse species with the herbaceous and shrub species greatly outnumbering the arbor species; in general, the coniferous forests were composed of 31 kinds of plants, the deciduous and broadleaf forests consisted of 20–29 plant species, the shrubs contained 27 plant species, and the herbaceous plants numbered 20 plant species; The various species compositions contained only 4–6 arbor species with most being foreign species. In each of the compositions, Bothriochloa ischemum was the grassland plant with the highest occurrence frequency, Sophora viciifolia and Hippophae reamnoides were the shrub plants with the highest occurrence frequencies, and Q. liaotungensis was the arbor plant with the highest occurrence frequency, and they followed by P. shenkaneusis and P. tabulaeformis. These results showed that soil seed banks and forest successions are better indicators for soil quality from natural successions.     

Analysis of implicit HHT‐α integration algorithm for real‐time hybrid simulation

Real‐time hybrid simulation is a viable experiment technique to evaluate the performance of structures equipped with rate‐dependent seismic devices when subject to dynamic loading. The integration algorithm used to solve the equations of motion has to be stable and accurate to achieve a successful real‐time hybrid simulation. The implicit HHT α‐algorithm is a popular integration algorithm for conducting structural dynamic time history analysis because of its desirable properties of unconditional stability for linear elastic structures and controllable numerical damping for high frequencies. The implicit form of the algorithm, however, requires iterations for nonlinear structures, which is undesirable for real‐time hybrid simulation. Consequently, the HHT α‐algorithm has been implemented for real‐time hybrid simulation using a fixed number of substep iterations. The resulting HHT α‐algorithm with a fixed number of substep iterations is believed to be unconditionally stable for linear elastic structures, but research on its stability and accuracy for nonlinear structures is quite limited. In this paper, a discrete transfer function approach is utilized to analyze the HHT α‐algorithm with a fixed number of substep iterations. The algorithm is shown to be unconditionally stable for linear elastic structures, but only conditionally stable for nonlinear softening or hardening structures. The equivalent damping of the algorithm is shown to be almost the same as that of the original HHT α‐algorithm, while the period elongation varies depending on the structural nonlinearity and the size of the integration time‐step. A modified form of the algorithm is proposed to improve its stability for use in nonlinear structures. The stability of the modified algorithm is demonstrated to be enhanced and have an accuracy that is comparable to that of the existing HHT α‐algorithm with a fixed number of substep iterations. Both numerical and real‐time hybrid simulations are conducted to verify the modified algorithm. The experimental results demonstrate the effectiveness of the modified algorithm for real‐time testing. Copyright © 2011 John Wiley & Sons, Ltd.     

Imaging the rupture process of the 10 January 2018 MW7.5 Swan island,Honduras earthquake*

The 10 January 2018 M_W7.5 Swan island, Honduras earthquake occurred on the Swan island fault, which is a transform plate boundary between the North American and Caribbean plates. Here we back-project the rupture process of the earthquake using dense seismic stations in Alaska, and find that the earthquake ruptured at least three faults (three stages) for a duration of ~40 s. The rupture speed for the longest fault (stage 3) is as fast as 5 km/s, which is much faster than the local shear wave velocity of ~4 km/s. Supershear rupture was incidentally observed on long and straight strike-slip faults. This study shows a supershear rupture that occured on a strike-slip fault with moderate length, implying that supershear rupture might commonly occur on large strike-slip earthquakes. The common occurrence of supershear rupture on strike-slip earthquakes will challenge present understanding of crack physics, as well as strong ground motion evaluation in earthquake engineering.     

Difference between static and dynamic angle of repose of uniform sediment grains

In the investigation of sediment transport, it is necessary to differentiate various definitions of angle of repose (AoR) available in the literature. The static AoR, composed of upper and lower angle of slope, forms just before and after slope instability, while the dynamic AoR can be observed when sediment grains are moving continuously down an inclined plane. In the present study, a series of laboratory experiments was conducted to measure static and dynamic angle of repose for uniform natural sedi-ments with median diameter of 0.28–4.38 mm. The results show that the different slope angles have different characteristics. The upper and dynamic AoR increase slightly with increasing grain diameter, while the lower AoR is not sensitive to changes in sediment size and may assume a constant value. The average of the upper and lower AoR is equivalent to the dynamic AoR, and the difference between them increases with increasing grain diameter. The present study suggests that the different angles of repose should be treated with caution when applying in investigations of bedload transport, dune migration and local scour development.     

坦噶尼喀湖东北部入湖河流表层沉积物中磷的形态和分布特征

磷是坦噶尼喀湖生态系统中必不可少的营养元素,直接决定湖体初级生产力的高低,进而影响到周边居民对于动物蛋白的获取来源.为了解坦噶尼喀湖磷的外源输入,选择湖泊东北部的入湖河流,对表层沉积物(16个样点)中总磷(TP)和各形态磷含量及其分布特征进行分析,并探讨磷的形态分布特征与土地利用方式之间的相关关系.结果表明,入湖河流沉积物TP含量为73.05~239.94 mg/kg,平均含量为152.64±55.37 mg/kg,其中最高值出现在马拉加拉西河口.采用Psenner法对磷进行连续浸提并比较不同形态磷含量,由高及低依次为铁铝结合态磷(Fe/Al-P)钙结合态磷(CaP)有机磷(Org-P)残渣态磷(Res-P)弱吸附态磷(Labile-P).土地利用类型对TP及各形态磷含量影响较大,其中TP含量表现为河口湿地城镇附近林草地区,表明地表径流和人类活动会对TP含量产生影响,而对于不同形态磷含量,Laible-P、Fe/Al-P、Org-P含量均表现为河口湿地林草地城镇附近,Ca-P、Res-P含量均表现为城镇附近河口湿地林草地.分析沉积物理化性质与各磷形态之间的相关性,发现沉积物总氮(TN)、有机质和总有机碳与Fe/Al-P、LabileP和TP相关性较好,与Org-P、Ca-P和Res-P相关性较差,表明TN和有机质的输入,会伴随沉积物中磷含量的升高,其增量的赋存形态主要为氧化还原敏感态磷和Labile-P.沉积物粒径组成与各磷形态含量存在相关性,细粒径沉积物与各形态磷含量呈显著正相关,粗粒径沉积物与各形态磷呈显著负相关,表明细小颗粒更易吸附磷.     

Paleomagnetic results from Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane,Tibet, China,and their tectonic implications

Results of a systematic paleomagnetic study are reported based on Late Carboniferous to Early Permian sedimentary rocks on the north slope of the Tanggula Mountains,in the northern Qiangtang terrane(NQT),Tibet,China.Data revealed that magnetic minerals in limestone samples from the Zarigen Formation(CP^z)are primarily composed of magnetite,while those in sandstone samples from the Nuoribagaribao Formation(Pnr)are dominated by hematite alone,or hematite and magnetite in combination.Progressive thermal,or alternating field,demagnetization allowed us to isolate a stable high temperature component(HTC)in 127 specimens from 16 sites which successfully passed the conglomerate test,consistent with primary remnance.The tilt-corrected mean direction for Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane is D_s=30.2°,I_s=-40.9°,k_s=269.0,a_(95)=2.3°,N=16,which yields a corresponding paleomagnetic pole at 25.7°N,241.5°E(dp/dm=2.8°/1.7°),and a paleolatitude of 23.4°S.Our results,together with previously reported paleomagnetic data,indicate that:(1)the NQT in Tibet,China,was located at a low latitude in the southern hemisphere,and may have belonged to the northern margin of Gondwana during the Late Carboniferous to Early Permian;(2)the Paleo-Tethys Ocean was large during the Late Carboniferous to Early Permian,and(3)the NQT subsequently moved rapidly northwards,perhaps related to the fact that the Paleo-Tethys Ocean was rapidly contracting from the Late Permian to Late Triassic while the Bangong Lake-Nujiang Ocean,the northern branch of the Neo-Tethys Ocean,expanded rapidly during this time.     

Market risk in carbon market: an empirical analysis of the EUA and sCER

The paper uses a capital asset pricing model to analyze the market risk in the European Union Emission Trading System (EU ETS) and clean development mechanisms (CDM) and Zipf analysis technology to analyze the carbon price volatility in different expectations of returns in the two markets. The results show that the systematic risk of the EU ETS market is around 0.07 %, but the CDM market is clearly divided into two stages; the systematic risk of the futures contracts in the first stage (DEC09–DEC12) is less than the EU ETS market, but the systematic risk of the futures contracts that enter the market is greater than the EU ETS market and has a higher market sensitivity, although on the unsystematic risk. The CDM market is always greater than the EU ETS market. Abnormal returns in the two carbon markets are both lower than 0.02 %, but CDM is higher. The probability of price down is greater than that of price up. The carbon price is affected by market mechanisms and external factors (economic crisis and environmental policies) in the low expectations of returns. However, in the high expectations of returns, compared with the CDM market, the carbon price change in the EU ETS market is less stable and has higher risks.

     

Geochemistry,and zircon U–Pb and molybdenite Re–Os geochronology of Jilongshan Cu–Au deposit,southeastern Hubei Province,China

The Jilongshan skarn Cu–Au deposit is located at the Jiurui ore cluster region in the southwestern part of the Middle–Lower Yangtze River valley metallogenic belt. The region is characterized by NW‐, NNW‐ and EW‐trending faults and the mineralization occurs at the contact of lower Triassic carbonate rocks and Jurassic granodiorite porphyry intrusions. The intrusives are characterized by SiO₂, K₂O, and Na₂O concentrations ranging from 61.66 to 67.8 wt.%, 3.29 to 5.65 wt.%, and 2.83 to 3.9 wt.%, respectively. Their A/CNK (A/CNK = n(Al₂O₃)/[n(CaO) + n(Na₂O) + n(K₂O)]) ratio, δEu, and δCe vary from 0.77 to 1.17, 0.86 to 1, and 0.88 to 0.96, respectively. The rocks show enrichment in light rare earth elements ((La/Yb)_N = 7.61–12.94) and large ion lithophile elements (LILE), and depletion in high field strength elements (HFSE), such as Zr, Ti. They also display a peraluminous, high‐K calc‐alkaline signature typical of intrusives associated with skarn and porphyry Cu–Au–Mo polymetallic deposits. Laser ablation inductively coupled plasma spectrometry (LA‐ICP‐MS) zircon U–Pb age indicates that the granodiorite porphyry formed at 151.75 ± 0.70 Ma. A few inherited zircons with older ages (677 ± 10 Ma, 848 ± 11 Ma, 2645 ± 38 Ma, and 3411 ± 36 Ma) suggest the existence of an Archaean basement beneath the Middle–Lower Yangtze River region. The temperature of crystallization of the porphyry estimated from zircon thermometer ranges from 744.3 °C to 751.5 °C, and 634.04 °C to 823.8 °C. Molybdenite Re–Os dating shows that the Jilongshan deposit formed at 150.79 ± 0.82 Ma. The metallogeny and magmatism are correlated to mantle–crust interaction, associated with the subduction of the Pacific Plate from the east. Copyright © 2013 John Wiley & Sons, Ltd.     

Greenhouse gases abatement by catalytic dry reforming of methane to syngas over samarium oxide-supported cobalt catalyst

Anthropogenic activities often result in the emissions of methane (CH₄) and carbon dioxide (CO₂) which are the principal components of greenhouse gases. The mitigation of these gases to avert further occurrence of global warming has attracted a lot of research interest. In this study, the potential of greenhouse gases abatement via catalytic CO₂ (dry) reforming of methane to syngas over samarium oxide-supported cobalt (20 wt% Co/80 wt% Sm₂O₃) catalyst was investigated. The 20 wt% Co/80 wt% Sm₂O₃ material was synthesized via wet impregnation method and characterized using different instrument techniques. The methane dry reforming reaction, as well as its kinetics over the catalyst, was studied in a stainless steel fixed-bed continuous flow reactor at feed (CH₄:CO₂) ratios range of 0.1–1.0, temperature range of 923–1023 K and gas hourly space velocity (GHSV) of 30,000 h^?1. The 20 wt% Co/80 wt% Sm₂O₃ catalyst showed promising catalytic activity evident from the highest CH₄ and CO₂ conversion of ~71 and ~74% as well as the highest hydrogen (H₂) and carbon monoxide (CO) yield of ~62 and ~73%, respectively. Moreover, the methane dry reforming over the 20 wt% Co/80 wt% Sm₂O₃ catalyst produces H₂/CO ratio close to unity hence suitable for use as a chemical intermediate for synthesis of oxygenated fuels. The kinetic data obtained from the methane dry reforming were fitted to power law model. Apparent activation energies of 88.62, 80.12, 108.12 and 100.91 kJ mol^?1 were obtained for CH₄, CO₂, H₂ and CO, respectively. The characterization of the spent 20 wt% Co/80 wt% Sm₂O₃ catalyst after 4 h of time-on-stream has confirmed the presence of amorphous carbon which can easily be gasified.     

便携式钻机在水泥灰岩矿勘查中的应用

便携式钻机已广泛应用于地质与工程勘查中,为了进一步扩大便携式钻机的应用范围,倡导绿色勘查,在湖南省东安县王师岭矿区水泥灰岩矿勘查中,采用ZY-25型便携式钻机以钻代槽进行地表取样,取得了较好的效果。应用实践表明,当矿区构造简单,岩层产状较平缓且稳定,矿体厚度较大,矿石有用组分含量较高且分布均匀,有害组分含量较低时,采用便携式钻机取样代替槽探取样评价矿床是可行的。