追摹、混搭與穿越 : 晚清畫報中的古今對話

學界多看重晚清畫報的“中外互動”，若能同時兼及“古今對話”，論述將更具張力。因爲，思接千古乃人類思考及文化創造的基本模式，只不過不同時代，古今之間的對立／ 對峙／對話的强度與頻率有很大差異。本文將畫報作爲一個“大文本”看待，討論其中新聞與古事如何騰挪趨避，趣味與筆法怎樣互相交融，並借此造成某種新奇感與陌生化效果

The strain softening model of rock damage under compression and tension

Deformation and failure of brittle material under compression are different from those under tension. The differences are characteristic for the brittle material such as rock, concrete and others. At present, few constitutive models for rock can reflect the differences. A damage-induced softening model for rock constitutive relations is presented based on statistical strength theory, continuum damage mechanics and elastic mechanics. The model can consider properties of rock mechanics such as strain softening, difference in strength between compression and tension, non-liner stress-strain relation, compressive hardening, brittleness and so on. The model is well-adapted, simple and practical as it is flexible and has only 7 parameters which can be easily obtained from uniaxial test under compression and tension. Under triaxial compression, uniaxial compression and uniaxial tension, the stress-strain relations obtained from the presented model are compared with those obtained from laboratory tests. The comparisons show that the differences between results obtained respectively from the presented model and laboratory tests are small. The presented model is rational

The Magnetic mechanism of S₅ paleosol in Baoji section

The magnetic susceptibility（MS）has been widely used as a proxy of summer monsoon,whicla is Daseu on an important fact that the MS achieves the highest value in the most developed paleosol S5 ,while lower values in less weathered loess layer in the Central Chinese Loess Plateau（CLP）. However,in Baoji loess section, the MS of Ss is the lowest value within the top 6 paleosols（ S0, S1 ...S5）, which contradicts above normal situation. Baoji（34°25 ＇N, 107°07＇E） is located in the southern edge of CLP, north foot of Qinling Mountains. The present climate is warm temperate semi-humid with mean annual precipitation （MAP） of more than 700ram （ up to 1100mm in Qinling areas） ,the rain distribution is uneven （60% rain falls between July and Sep. ）, and mean annual temperature （MAT）of 12℃ （25.4℃ in July）. Pedogenic condition in Baoji,such as precipitation,is better than the Central Loess Plateau,for example MAP 654mm in Xifeng （35°46＇N, 107°41 ＇E） and MAP 555mm in Lingtai （ 35°33＇N, 107°31＇E）. In order to find out its mechanism,the samples were collected from the Baoji loess-paleosol sequence since S5, with sampling interval 30cm. The results of rock magnetism and geochemical measurements for Baoji S5 and S3 samples show, that ratio Rb/Sr of Ss samples was higher than that of S3, indicating that S5 was a better-developed paleosol unit, stronger chemical weathering than S3. The climate condition during S5 period was confirmed to be the warmest and wettest for the last O. 5Ma. The S3 paleosol was formed under oxidation environment, under such pedogenic conditions, maghemite and hematite were formed simultaneouly, the anti-ferromagnetic minerals are mainly hematite, superparamagnetic（SP） maghemite is the main contributor to the magnetic properties. However, the contents of ferrimagnetic minerals in S5 samples are lower than that of S3 samples. With pedogenic developing,the proportion of ferrimagnetic component reduces in S5 while the content of anti-ferromagnetic minerals （ mainly goethite） increases. There are amounts of dark brown Fe-Mn film on the cranny surface of Ss paleosol, which indicates where the iron in S1 went to and why MS in S5 becomes lower. This phenomenon seems to suggest different pedogenic condition between S3 and S5 development. S3 pedogenic environment was under oxidizing conditions： so that extra fine grain ferrimagnetic minerals produce with pedogenic development; while S5 development in Baoji was under condition of moisture over much, pedogenesis actually occurs under waterlogged conditions. So that fine- grained magnetite ,maghemite and hematite are gradually dissolved, and finally converted into goethite and limonite and other weak magnetic minerals. Such transformation of magnetic minerals ,from high MS minerals（ magnetite and maghemite） to low MS minerals （such as goethite）due to over moisture （gleying） , results in the lower MS value for Baoji S5 paleosol.10 page(s

Paleoclimatic evolution of Holocene loess and discussion of the sensitivity of magnetic susceptibility and median diameter

Climate changes are closely related to peoples' livelihoods. Holocene climate changes are therefore particularly important to humans. It is known that eolian loess deposits in China are one of the best geological records for paleoclimatic change. As it is the top layer of loess sequence, Holocene loess may be easily disturbed by human activities. For that reason, it has not been studied thoroughly. Recently, a continuously deposited, high-resolution and well-preserved Holocene loess section has been found in Baicaoyuan, Huining County, Gansu Province, located in the northwest edge of the Chinese Loess Plateau. The magnetic and grain size signals of the section reflect Holocene paleoclimate variations and are comparable to the stalagmite oxygen isotope records of Sanbao and Hulu caves. They consistently record the general evolution process of Holocene paleoclimate in Eastern Asia. During the period 14.2-12.8 ka BP, Last Glacial Maximum turned into Holocene transition phase. During 12.8-11.5 ka BP, the climate was cold and dry, dominated by the Younger Dryas. Between 11.5 and 10.5 ka BP, the climate rapidly turned warm and wet, and 10.5-5.2 ka BP was the Holocene Optimum Period, during which some relatively dry-cold events could be observed. Since 5.2 ka BP, the climate slowly became dry and cold. In summary, the climate showed a general drying trend from the early Holocene to the late Holocene, which was controlled by variation of solar radiation. Compared with magnetic susceptibility, the median diameter curve fluctuates frequently. Some climate events were recorded by the median diameter curve, but not observed in the magnetic susceptibility curve. It is suggested that the grain size parameter is more sensitive to paleoclimate changes than susceptibility at the Baicaoyuan section during the Holocene.8 page(s

Magnetic properties of Romanian quaternary loess deposits and its significances

The Mircea Voda loess paleosol sequence in Romania is located in the Dobrudja Plateau at a distance of about 13km from the Danube and 40km from the Black Sea coast(44°19'15″N,28°11'21″E).The climate of the Mircea Voda area is affected by the Mediterranean climate: hot and dry summer and wet and cold winter.Every year it generally has 6 months of dryness and 3months of drought.The meteorological data show that the average annual rainfall of the Dobrudja Plateau is 600~800mm,and the average annual evaporation is 476mm.About 30m of Quaternary aeolian deposits including five strongly developed pedo-complexes can be observed.The loess-paleosol sequences overlie limnic sediments of presumably lower Pleistocene age on Tertiary and Mesozoic sediments.By analyzing several magnetic parameters,such as Xlf,Xfd%,XARM,IRM,SIRM,J-T and hysteresis loop of Mircea Voda loess samples,their results show that the magnetic minerals of Mircea Voda loess-paleosol sequence are similar with that of Chinese loess,which are predominated by magnetite and maghemite,meanwhile,and goethite.Romanian loess shows a consistent loess paleosol pattern with the Xifeng loess in Chinese Loess Plateau,the pedogenic process was completed in a strongly oxidized environment,and the magnetic susceptibility has a positive correlation with the pedogenic process in general.The values of magnetic susceptibility are low in loess and high in paleosol,indicating that the glacial-interglacial circulation had a global influence.The pedogenic producing SP and SD ferrimagnetic minerals is the main reason for increasing magnetic susceptibility in paleosol.But the values of magnetic susceptibility in Mircea Voda section are low compared with Xifeng section in Chinese Loess Plateau.The X0 is the magnetic susceptibility when the Xfd% is zero. The X0 of Romanian loess is lower than that of Xifeng loess,so the difference of their original materials is likely to be one of the reasons why the magnetic susceptibility of Romanian loess is lower than that of Xifeng loess.Despite the effective moisture in Mircea Voda section is higher than that of Xifeng section.The pedogenesis in Romanian is weaker than that in Xifeng,different climatic condition: precipitation coupling various temperatures in China and Romania,could be another reason why the magnetic susceptibility of Mircea Voda section is lower than the Xifeng section’s.11 page(s