琳恩·诺塔奇《泥、河、石》中的共同体书写

《泥、河、石》是美国非裔剧作家琳恩·诺塔奇的杰出剧作之一,体现了剧作家对全球黑人困境的思考以及构建精神共同体的诉求。本文关注《泥、河、石》中的共同体思想,通过分析剧中被殖民和战争破坏的地缘共同体、多元文化背景下貌合神离的文化共同体以及对黑人生存发展至关重要的精神共同体,阐释诺塔奇对黑人生存困境的思考以及对殖民主义、种族主义的批判。

Analysis on the Dynamical Process of Donghekou Rockslide-Debris Flow Triggered by 5.12 Wenchuan Earthquake

Among the geo-hazards caused by the great Wenchuan Earthquake, the rapid and long runout rockslide-debris flow is of primary concern due to the large volume of displaced material and the resultant catastrophic impacts to the landscape and socioeconomic structure. In order to analyze the dynamical process of this kind of geo-hazard, the Donghekou rockslide-debris flow is given as an example in this paper. This event, which killed 780 people, initiated at an elevation of 1300 m with a total long run-out distance of more than 2400 m. The slide mass is mainly composed of dolomite limestone and siliceous limestone of Sinian system, together with carbon slate and phyllite of Cambrian. During the processes from slide initiation to the final cessation of slide movement, five dynamic stages took place, here identified as the initiation stage, the acceleration of movement stage, the air-blast effect stage, the impact and redirection stage and the long runout slidematerial accumulation stage. Field investigations indicate that due to the effects of the earthquake, the dynamics of the Donghekou rockslide-debris flow are apparently controlled by geologic and tectonic conditions, the local geomorphological aspects of the terrain, and the microstructural and macroscopic mechanical properties of rocks which compose the slide mass. These three main factors which dictate the Donghekou rockslide-debris flow dynamics are discussed in detail in this paper, and significant results of field investigations and tests of materials are presented. The above dynamical processes are analyzed in this paper, and some useful conclusions have been gained.

Grinding Properties of Abandoned Concrete

The grinding properties of abandoned concrete, which consists primarily of hardened cement, limestone aggregate and river sand, are studied. Theoretical models of grinding are used to explain the experimental observation. The results show that 1) The principle disintegration mechanism of hardened cement and river sand is volumetric grinding, although at later stages grinding of cement becomes difficult because of its flaked structure; 2) The lime- stone grinding process can be divided into two steps. First, volumetric grinding, with an obvious component of surface grinding, followed by primarily surface grinding as the micro-particle content increases; 3) Initially, the principle mechanism of grinding limestone and river sand is volumetric grinding, albeit less efficient grinding than if these components were ground separately, and; 4) After 10 to 20 min of grinding the grinding bottleneck phenomenon ap- pears and after 20 min of grinding the content of micro-particles is large and surface grinding is the main mechanism while the particle size of the mixture is smaller than that of separately ground river sand and cement but bigger than that of separately ground limestone.

Numerical Analysis of Emergency River Restoration Scheme for Qingping Mega Debris Flow

The mega debris flow occurred on August 13 th 2010 in Qingping town,China(hereafter called '8.13' Debris Flow) have done great damage to the local habitants as well as to the re-construction projects in the quake-hit areas,and the channel-fill deposit problem caused by the debris flow was the most destructive.Moreover,it is of high possibility that an even severe deposit problem would reappear and result in worse consequences.In order to maximize risk reduction of this problem,relevant departments of the government established a series of emergency river restoration schemes,for which the numerical analysis is an important procedure to evaluate and determine the optimized one.This study presents a numerical analysis by applying a twodimensional debris flow model combined with a relevant water-sediment model to simulate the deposit during the progress of the debris flow,and to calculate and analyze the river flow field under both the present condition and different restoration conditions.The results show that the debris flow model,which takes the confluence of the Wenjia Gully to the main river into account,could simulate the deposit process quite well.In the reproduced debris flow from the simulation of the '8.13' Debris Flow,the original river flow path has switched to a relatively lower place just along the right bank with a high speed of near 7m.s-1 after being blocked by the deposit,which is highly hazardous.To prevent this hazard,a recommended scheme is derived through inter-comparison of different restoration conditions.It shows that the recommended scheme is able to reduce the water level and as well to regulate the flow path.Based on the given conditions of the mainstream and the tributary confluence for the simulated '8.13' Debris Flow,when encountering a debris flow with deposit volume less than 0.5 million m3,the river channel can endure a 20-year return flood;however,when the deposit volume increases to 2 million m3,the flood capacity of the river will be greatly impacted and the scheme becomes invalid.The recommended scheme supported by the present study has been applied to the emergency river restoration after this mega-debris flow.

An Empirical Formula for Suspended Sediment Delivery Ratio of Main River after Confluence of Debris flow

In order to calculate the suspended sediment discharge of the flood debris flows into the main river,a small scale flume test was designed to simulate the process of confluence of Jiangjia Ravine and Xiangjiang River in Yunnan province,China.By test observation and data analysis,suspended sediment discharge of Debris flow after its entry into the main river was found to have a close relation with the bulk density,the confluence angle of the Debris flow and the main river,the ratio between per unit width discharge of Debris flow and main river.Based on the measured and simulated results,and statistical analysis,an empirical formula was proposed for the suspended SDR(Sediment Delivery Ratio) of the main river after the confluence of Debris flow.Compared with the observed results of Debris flow in 2009,the error between the data calculated by the empirical formula and the monitored data is only about 10%.

Role of debris flow on the change of^10Be concentration in rapidly eroding watersheds:a case study on the Seti River,central Nepal

The concentration of cosmogenic loBe in riverine sediments has been widely used as a proxy for catchment-wide denudation rate （CWDR）. One of the key assumptions of this approach is that sediments originating from sub-basins with different erosional histories are well mixed. A tragic debris flow occurred in the Seti River watershed, central Nepal, on May 5, 2012. This catastrophic debris flow was triggered by slope failure on the peak of Annapurna IV and resulted in many casualties in the lower Seti Khola. However, it provided an opportunity to test the assumption of equal mixing of sediments in an understudied rapidly eroding watershed. This study documents the CWDR of ^10Be to evaluate the extent of the influence of episodic erosional processes such as debris flow on the spatio-temporal redistribution of loBe concentrations. Our data show that the debris flow caused little change in CWDR across the debris flow event. In addition to isotopic measurement, we calculated denudation rates by using the modeled concentrations in pre- and post-landslide sediments based on the local ^10Be production rate. The modeled result showed little change across the event, indicating that the debris flow in May 2012 played a minor role in sediment evacuation, despite the rapid erosion in the catchment. Our study concludes that although the 2012 event caused many casualties and severe damage, it was a low-magnitude, high frequency event.

CLAY MINERAL ASSEMBLAGES AND THEIR IMPLICATIONS IN SHIHEZI FORMATION FROM THE HUAIBEI COAL-BEARING STRATA

Clay mineral assemblages in Shihezi Formation of Huaibei coal-bearing strata are determined by X-ray diffraction and Differential Thermal Analyzer, that is restated to the sediment faces and climatic changes in the source area, and to a lesser extent, alterations during burial diagenesis. In the Upper Shihezi Formation, the clay fraction is dominated by kaolinite in northern part of the coal field, which was formed in alluvial sediment environment. But in the South of Huaibei coal field, the clay mineral assemblage consists of mainly illite that reflects the influence of sea water. The predominately kaolinite and sederite composition of the clay fraction in the lower Shihezi Formation sediments documents less relief and gentle erosion of kaolinite rich soils developing under warm source area. In the lower part of Shihezi Formation, some chlorite is detected, which suggests transformation of illite or kaolinite to chlorite under conditions of burial diagenesis.

Field observations of debris-flow initiation processes on sediment deposits in a previous deep-seated landslide site

Although information regarding the initiation processes of debris flows is important for the development of mitigation measures,field data regarding these processes are scarce.We conducted field observations of debris-flow initiation processes in the upper Ichinosawa catchment of the Ohya landslide,central Japan.On 19 June 2012,our videocamera monitoring systems recorded the moment of debris-flow initiation on channel deposits(nine surges) and talus slopes(eight surges).The initiation mechanisms of these surges were classified into three types by analyzing the video images: erosion by the surface flow,movement of deposits as a mass,and upward development of the fluid area.The first type was associated with the progress of surface flow from the upper stream on unsaturated channel deposits.The second type was likely caused by an increase in the pore water pressure associated with the rising in the groundwater level in channel deposits;a continuous water supply from the upper stream by the surface flow might have induced this saturation.The third type was associated with changes in the downstream topography caused by erosion.The flow velocity of most surges was less than 3 m s^(-1) and they usually stopped within 100 m from the initiation point.Surges with abundant pore fluid had a higher flow velocity(about 3- 5 m s^(-1)) and could travel for alonger duration.Our observations indicate that the surface flow plays an important role in the initiation of debris flows on channel deposits and talus slopes.

Mutual Interference of Two Debris Flow Deposits Delivered in a Downstream River Reach

We investigate experimentally the depositions of two contiguous debris flows flowing into a main river reach.The aim of the present experimental research is to analyze the geometry and the mutual interactions of debris flow deposits conveyed by these tributaries in the main channel.A set of 19 experiments has been conducted considering three values of the confluence angle,two slopes of the tributary,and three different triggering conditions(debris flows occurring simultaneously in the tributaries,or occurring first either in the upstream or in the downstream tributary).The flow rate along the main channel was always kept constant.During each experiment the two tributaries had the same slope and confluence angle.The analysis of the data collected during the experimental tests indicates that the volume of the debris fan is mainly controlled by the slope angle,as expected,while the shape of the debris deposit is strongly influenced by the confluence angle.Moreover,in the case of multiple debris flows,the deposit shape is sensitive to the triggering conditions.Critical index for damming formation available in literature has been considered and applied to the present case,and,on the basis of the collected data,considerations about possible extension of such indexes to the case of multiple confluences are finally proposed.

New fossils of the Early Pleistocene Equus huanghoensis(Equidae,Perissodactyla)from Nihewan in Hebei Province of China

This paper describes new fossils of Equus huanghoensis from an Early Pleistocene bed in Nihewan, Hebei Province, which confirms the classification of E. huanghoensis by Chinese researchers. The new fossils include a relatively complete male skull and mandible with all upper and lower dentition, a broken female skull with fragment of mandible and a broken Mc III of Equus sp. The fossils were collected from the Yangshuizhan site of Nihewan. The age of the formation is about 1.6 Ma. The new materials verify some classification characteristics based on teeth published in previous descriptions. These characteristics include large teeth size, short protocone, and tilted protoloph and metaloph. We have added to these characteristics of large skull size, a developed protuberantia supramagna, pentagonal nuchal side, weak Pli cabaline, simple enamel plications; a series of new characteristics strikingly different from the other Equus horses. The broken Mc III is similar to Equus qingyangensis from Qingyang, Gansu.

Magnetostratigraphic dating of the Hougou Paleolithic site in the Nihewan Basin,North China

The fluvio-lacustrine sedimentary sequences in the Nihewan Basin, northern China, are important for studying Quaternary land mammal evolution and Paleolithic settlements in the high-latitude temperate East Asia. Here we report new magnetostrati- graphic results that constrain age of the Hougou Paleolithic site in this basin. Magnetite and hematite were identified as carriers of the characteristic remanent magnetizations, with the former being dominant. Magnetic polarity stratigraphy shows that the Hougou sequence recorded the very late Matuyama reverse chron and the Brunhes normal chron. The age of the Hougou Paleolithic site was estimated to be 395 ka based on an averaged rate of sediment accumulation. The combination of our mag- netostratigraphy and previously published chronological data for early Paleolithic or human sites in the high-latitude northern China may document a persistent colonization of the hostile high-latitude areas of the eastern Old World during the mid- die-early Pleistocene.