A numerical model for Type II supernovae — The collapse stage     

Cong Xu  Zong-wei Li  Yun-zao Ge 《Chinese Astronomy and Astrophysics》1985,9(2):154-158

We use the following numerical model for the collapse stage of a Type II supernova of 15 M_⊙. Our electron capture rate includes the effects of the inverse reaction and the neutron-proton mass difference. This decreases the electron density at the collapse stage and led to rather large values of the maximum inward velocity and of the corresponding mass (Umax = 3.06 × 10⁹cm/s, Mmax=0.76 M_⊙). These larger values are more favourable for the propagation of shock after the rebounce and the triggering-off of a Type-II supernova explosion. For neutrino transport, we use a leakage model and an equilibrium diffusion model, respectively, for the thin and thick stages and a grey atmosphere model to assess the effect of neutrino precipitation on the collapse. We found this effect to be small, the energy precipitation to be not more than 10^?5 the neutrino energy loss and the momentum precipitation not more than 10^?6 the gravitational acceleration.  相似文献   

ANALYSIS OF DRIVING FORCES ON THE CHANGE OF HISTORICAL FARMLAND USE IN SHANDONG PROVINCE DURING THE QING DYNASTY （1644-1911）     

ZHANGXue-qin GEQuan-sheng ZHENGJing-yun 《中国地理科学(英文版)》2003,13(3):207-215

How land-cover has been changed by human use over the last 300 years is one of the five overarching questions guiding the Land-use/Cover Change (LUCC) Science/Research Plan. China has variety of historical docu-ments providing unique data superiority. So the characteristics of farmland area in Shandong Province during the Qing Dynasty (1644-1911) are summarized firstly: 1) the rising trend of farmland area was striking; 2) farmland area had re-markable fluctuation; 3) farmland area per capita decreased dramatically; 4) wasteland reclamation index increased rapidly. Then, the driving forces of farmland area change are analyzed. It is concluded that natural and human factors are jointly influential. Among the driving forces, human dimensions are the main factors of farmland area change,which direct the general tendency of the changes mentioned above. And the natural factors influence the stability of farmland area as well. Variation of the natural factors would act as the major contributory factor to farmland area change during years or periods of abrupt climatic changes, or during the intensive occurring periods of natural hazards.Besides, the passive aspects of human factors, such as war chaos also influenced the fluctuation of the farmland area.This research indicates that it is feasible to study the land-use/cover change by Chinese historical literatures, which has huge potential to provide a comprehensive picture of the growing dominance of human land-use and land-cover pat-terns that can be used in many global change research oroiects.  相似文献   

海带膳食纤维的提取与功能性试验   总被引：2，自引：1，他引：2  

李来好  陈培基  李刘冬  杨贤庆  吴燕燕  刁石强  薛长湖 《中国海洋大学学报(自然科学版)》2003,33(5):687-694

采用酶技术和化学处理相结合的方法 ,研究了海带膳食纤维的工艺技术 ,筛选出海带膳食纤维提取和漂白的最佳工艺条件 ,提取出海带膳食纤维产品 ,并进行人体的功能性试验。结果表明 ,海带膳食纤维的产率达 2 7.3% ,颜色为类白色 ,膳食纤维含量达 73.3% ,钙含量 7.5% ,膨胀力为55m L/ g,持水力为 2 650 % ;海带膳食纤维的功能性优于小麦麸皮膳食纤维 ,对便秘患者具有良好的疗效。  相似文献   

南黄海及相邻陆区松散沉积层磁性地层的研究     

周墨清  葛宗诗 《海洋地质与第四纪地质》1990,(4)

本文通过研究区5个钻孔松散沉积岩心磁性地层的划分对比,获知布容与松山极性带的界线,南黄海和陆区北部位于80.0—99.5m。陆区的南部此界线于270.4m深处。松山和高斯极性带的界线,海区未揭露到,其沉积起始时间都小于1.7Ma。而陆区的南、北部分别位于117m和328.2m。高斯和吉尔伯特极性带的界线,陆区北部为140m,而南部区为460.15m。沉积起始时间为3.4Ma。吉尔伯特底界仅北部陆区所揭示,为190.5m。松散沉积层与下伏白垩纪(?)石灰岩接触面位于400.35m,沉积起始时间约17.0Ma。  相似文献   

虾蟹海产品香味的前体物质的加热变化     

薛长湖  汪贻生  林洪  楼伟凤 《中国海洋大学学报(自然科学版)》1994,(4)

本文研究了虾蟹海产品香味的前体物质在加热前后的变化。实验结果表明：对虾和蟹肌肉中的糖原和不饱和脂肪酸在加热前后含量下降，糖原是Ｍａｉｌｌａｒｄ反应的基础物质．不饱和脂肪酸是虾蟹肌肉香味中羰基化合物的前体物质。虾蟹肌肉中主要积累的核苷酸成分ＡＭＰ在加热后减少，而肌肉提取物中的游离氨基酸和结合氨基酸，特别是疏水氨基酸含量均增加。  相似文献   

胶州湾海鞘类 Ⅱ、柄海鞘科Styelidae     

葛国昌  臧衍蓝 《中国海洋大学学报(自然科学版)》1987,(4)

本文为胶州湾海鞘类区系研究之一,涉及柄海鞘科2属7种,其中二种为新种。  相似文献   

Gradation affects basic mechanical characteristics of Chinese calcareous sand as airport subgrade of reefs     

Shen Yang  Xue Shen  Hanlong Liu  Huayang Ge  Xiaoxi Rui 《Marine Georesources & Geotechnology》2020,38(6):706-715

Abstract

Construction of the reefs in the South China Sea is a significant foundation to the secure stability and economic development of China. The construction of an airport runway is necessary for this realization. The calcareous sand is the main primary material in the runway construction. A certain type of calcareous sand near a certain reef of the South China Sea was studied in this paper. To investigate this specific calcareous sand, quartz sand was used as a reference for comparison. Microscopic 3-D imaging, compression and triaxial tests were conducted to test the micro, squeezing and shear properties. The effect mechanism of gradation on the calcareous sand’s compressibility and shear characteristics are discussed from a mesoscopic viewpoint using 3-D morphology. Calcareous sand particles are multiangular and flatter in comparison with quartz sand. The larger the particle sizes are, the more different the two sands’ morphologies are. The compressibility of calcareous sand is greater, and the effect of the coarse fraction (5–1?mm) content in the gradation plays the most significant role in this feature. When the coarse particles’ content is less than 25% and the mass ratio of the middle and fine particles (M) is constant, there is the worst coarse fraction content causing the calcareous sand to be most likely compressed. The worst coarse fraction content decreases with the increase in M, and an empirical formula is proposed. When the gradation, relative density and confining pressure are the same, the peak shear stress and strain of calcareous sand are all at a high level. The effect of confining pressure is manifested in calcareous sand. The shear strength and dilation of calcareous sand are also most affected by the medium coarse fraction (5–0.25?mm) content.  相似文献   

弧后盆地的形成与演化探讨：以东亚陆缘区为例   总被引：3，自引：2，他引：3  

吴有林  林舸 《海洋地质与第四纪地质》1996,16(4):63-69

通过对弧后盆地大地构造体制的讨论，作者认为基属活化作用的产物根据地质，地球物理，地球化学等资料的分析，作者提出结论认为，由于东亚岛弧系岩石圈的均衡作用及海沟外侧冷却大洋岩石圈块体的下沉拖曳牵引等作用，使软流圈在岛弧系下方发生分异，这种分异作用带动东亚陆缘向东扩张，从而产生弧后的张开。  相似文献   

国外渔具选择性研究进展   总被引：2，自引：1，他引：2  

梁振林  葛长字  刘英光 《中国海洋大学学报(自然科学版)》2001,31(6):835-841

为了保护和可持续利用渔业资源 ,渔具选择性的研究在国际上倍受重视。该文以比较作业法中渔具选择性曲线的推导 ,特别是利用扩张 SEL ECT模型推导渔具选择性曲线为例 ,介绍国外渔具选择性研究的最新进展 ,以期作为我国开展这方面研究工作的参考  相似文献   

黄条鰤贮藏挥发性化合物的研究     

林洪  薛长湖  李兆杰  楼伟风  陈修白 《中国海洋大学学报(自然科学版)》1995,(4)

用气相色谱仪和气—质联机等方法对黄条鱼师的腐败挥发性化合物进行了定性和定量分析。这将有利于对黄条做一步的生化性质分析和制定其鲜品的国家标准。样品在２５℃贮藏５ｄ期间，测定了某些化学指标。结果表明在贮藏１ｄ后，鱼肉变腐臭，挥发性碱基化合物三甲胺和二甲基在贮藏中增加。在５ｄ的贮藏期间发现的挥发性有机酸包括乙酸、丙酸、丁酸、异丁酸、戊酸、异成酸，并且它们的含量不断增加，检测出脂肪氧化产物和含硫化合物，正己醛、３—辛酮、３，５—丰二烯—２—酮，２—壬酮辛烯—３—醇，二甲基三硫化物、１Ｈ—吲哚等都是黄条腐败时产生的重要挥发性化合物。应指出的是，２—甲基丁醇、庚醇、苯酚、辛烯—３—醇己醛是黄条中所特有的化合物，其余化合物与其它鱼类的挥发性化合物几乎相近。  相似文献