Sporopollen analysis of Core B10 in the southern Yellow Sea and the reflected characteristics of climate changes

Eight sporopollen zones have been divided based on the results of high-resolution sporopollen analysis of Core B10 in the southern Yellow Sea. Based on the results along with C-14 datings and the subbottom profiling data, climatic and environmental changes since the last stage of late Pleistocene are discussed. The main conclusions are drawn as follows: (1) the vegetation evolved in the process of coniferous forest-grassland containing broad-leaved treesconiferous and broad-leaved mixed forest --> coniferous and broad-leaved mixed forest-grassland prevailed by coniferous trees --> coniferous and broad-leaved mixed forest-grassland containing evergreen broad-leaved trees- coniferous and broad-leaved mixed forest-grassland prevailed by broad-leaved trees-deciduous broad-leaved forest-meadow containing evergreen broad-leaved trees- coniferous and broadleaved mixed forest-grassland prevailed by broad-leaved trees- coniferous and broad-leaved mixed forest containing evergreen broad-leaved trees; (2) eight stages of climate changes are identified as the cold and dry stage, the temperate and wet stage, the cold and dry stage, the warm and dry stage, the temperate and wet stage, the hot and dry stage, the temperate and dry stage, then the warm and dry stage in turn; (3) the sedimentary environment developed from land, to littoral zone, to land again, then to shore-neritic zone; and (4) the Yellow Sea Warm Current formed during early-Holocene rather than Atlantic stage.

北京地区15000年以来植被与环境变迁的初步研究

本文通过高时间分辨率的孢粉分析、14C测年、烧失量测定(600℃)及炭片统计分析，结合表土孢粉分析、古地磁特性等，对北京地区房山东甘池剖面（40.2ºN，116ºE)进行了较为系统的研究，从而揭示了距今15000年以来北京地区植被演替及环境变迁的关系，讨论了气候突变性事件及火因子对森林植被的影响等，同时借助于考古材料及历史地理文献对7000年以来人类活动导致植被的破坏及环境变化进行了讨论。 考虑到本剖面的特殊地貌单元，在分析流水地貌中花粉沉积和沉积物沉积的特殊性后，将北京地区15000年以来植被与环境变化划分为8个阶段： 1．约15780-14767aB.P.，属晚冰期的最盛期，乔木稀疏，草本类以蒿、藜为优势，缺乏反映隐域性环境的沼泽植被，气候冷干。 2．约14767-13482a B.P.，由于降雨增多，湿度加大，平原区形成小的沼泽环境，香蒲、眼子菜、黑三棱等沼生、水生植物得以在水体中生长繁盛，泥炭发育。由于山区生长的针阔叶混交林中盖度不大，并以针叶树种为主，反映气候以寒冷湿润为特征。此段中约14066aB.P.处出现的冷干环境与哥德堡漂移事件相对应，13520aB.P.，则反映出泥炭积累的暂时中断，为一干冷的气候突变点。 3．约13482-12625a B.P.，针阔叶混交林进一步发展，水生植物减少，沼泽逐渐消失，反映气候趋向暖干。 4．约12625-11418aB.P.，乔木减少，针阔叶混交林中针叶、阔叶出现优势交替现象。水生植物也有波动，反映气候趋于干凉，并有冷暖的波动。环境中湿度变化明显。 5．约11418-9607aB.P.，植被稀疏，气候呈现进一步干冷的特征。其中在 10619-10318aB.P.，孢粉及炭片浓度、年沉积率和烧失量均很低，出现了约相当于新仙女木期的冷干气候特征。 6. 9607—7270aB.P.，落叶阔叶树种有所增加，但其盖度不大。水生植物不繁盛，反映由草原植被向森林草原的演替。气候特征由冷向温干转变。 7、7270-3395aB.P.，阔叶树种明显增多，盖度增大，可视为温暖时期的特征，在5771aB.P.和4563aB.P.，曾出现乔木树种的下降，可视为高温期的短暂冷期。 8. 3395-lOOOaB.P.，气候变干变凉，加之人类活动的加剧，导致植被覆盖度的下降。考古学及史料记载，反映出这段发生了多次冷暖干湿交替出现的情形，加之人类对森林的砍伐、焚烧和拓荒，因而使北京山区的森林植被逐渐发生逆向演替、成为现存的次生植被类型。

Raman microscopy of formamide-intercalated kaolinites treated by controlled-rate thermal analysis technology

Raman spectroscopy of formamide-intercalated kaolinites treated using controlled-rate thermal analysis technology (CRTA), allowing the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites, is reported. The Raman spectra of the CRTA-treated formamide-intercalated kaolinites are significantly different from those of the intercalated kaolinites, which display a combination of both intercalated and adsorbed formamide. An intense band is observed at 3629 cm-1, attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm-1, assigned to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl-stretching band of the inner hydroxyl is observed at 3621 cm-1 in the Raman spectra of the CRTA-treated formamide-intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. Significant differences are observed in the CO stretching region between the adsorbed and intercalated formamide.

Detailed analysis of a conservative difference approximation for the time fractional diffusion equation

Diffusion equations that use time fractional derivatives are attractive because they describe a wealth of problems involving non-Markovian Random walks. The time fractional diffusion equation (TFDE) is obtained from the standard diffusion equation by replacing the first-order time derivative with a fractional derivative of order α ∈ (0, 1). Developing numerical methods for solving fractional partial differential equations is a new research field and the theoretical analysis of the numerical methods associated with them is not fully developed. In this paper an explicit conservative difference approximation (ECDA) for TFDE is proposed. We give a detailed analysis for this ECDA and generate discrete models of random walk suitable for simulating random variables whose spatial probability density evolves in time according to this fractional diffusion equation. The stability and convergence of the ECDA for TFDE in a bounded domain are discussed. Finally, some numerical examples are presented to show the application of the present technique.

Determination of preventive maintenance lead time using hybrid analysis

The time for conducting Preventive Maintenance (PM) on an asset is often determined using a predefined alarm limit based on trends of a hazard function. In this paper, the authors propose using both hazard and reliability functions to improve the accuracy of the prediction particularly when the failure characteristic of the asset whole life is modelled using different failure distributions for the different stages of the life of the asset. The proposed method is validated using simulations and case studies.

Hydrazine-hydrate intercalated halloysite under controlled-rate thermal analysis conditions

The thermal behaviour of halloysite fully expanded with hydrazine-hydrate has been investigated in nitrogen atmosphere under dynamic heating and at a constant, pre-set decomposition rate of 0.15 mg min-1. Under controlled-rate thermal analysis (CRTA) conditions it was possible to resolve the closely overlapping decomposition stages and to distinguish between adsorbed and bonded reagent. Three types of bonded reagent could be identified. The loosely bonded reagent amounting to 0.20 mol hydrazine-hydrate per mol inner surface hydroxyl is connected to the internal and external surfaces of the expanded mineral and is present as a space filler between the sheets of the delaminated mineral. The strongly bonded (intercalated) hydrazine-hydrate is connected to the kaolinite inner surface OH groups by the formation of hydrogen bonds. Based on the thermoanalytical results two different types of bonded reagent could be distinguished in the complex. Type 1 reagent (approx. 0.06 mol hydrazine-hydrate/mol inner surface OH) is liberated between 77 and 103°C. Type 2 reagent is lost between 103 and 227°C, corresponding to a quantity of 0.36 mol hydrazine/mol inner surface OH. When heating the complex to 77°C under CRTA conditions a new reflection appears in the XRD pattern with a d-value of 9.6 Å, in addition to the 10.2 Ĺ reflection. This new reflection disappears in contact with moist air and the complex re-expands to the original d-value of 10.2 Å in a few h. The appearance of the 9.6 Å reflection is interpreted as the expansion of kaolinite with hydrazine alone, while the 10.2 Å one is due to expansion with hydrazine-hydrate. FTIR (DRIFT) spectroscopic results showed that the treated mineral after intercalation/deintercalation and heat treatment to 300°C is slightly more ordered than the original (untreated) clay.