不同景观条件下机械剥蚀与化学剥蚀间之比

机械剥蚀和化学剥蚀的数量是地形形成变化的主要指标,早在上一世纪末就已开始对其进行定量评定。通常,评定剥蚀的基础是离子径流和悬移泥沙径流。当认为这种方法是最客观和最精确时,还必须指出其极大局限性,这种局限性首先是由于机械剥蚀物和化学剥蚀物的形成与搬运的不同机制的缘故。     

Effect of Ploughing Depth on the Growth and Yield of Heracleum candicans： a Threatened Medicinal Herb and a Less-explored Potential Crop of the Himalayan Region

This paper examines the effect of ploughing depths （A -- 60 cm, B -- 45 cm and C -- 30 cm） on the growth and yield of Heracleum candicans Wall （Apiaceae）, a threatened medicinal herb of the Himalayan region. This less-explored plant is being suggested as a potential crop for the mountain agriculture. The study was carried out in an orchard in Himachal Pradesh, India at 2500 m altitude, for two successive growth years. During the first year, all plants remained in juvenile state; in the second year, nearly 65 % plants produced flowers only under 60cm ploughing depth. Among its morphological traits, plant height, collar diameter and aboveground flesh weight were found to be strongly correlated （P 〈 0.01） with the belowground biomass during the first year （r =0.968, 0.925 and 0.973, respectively） and during the second year （r=0.945, 0.928 and 0.775, respectively）. Increase in the ploughing depth was significantly correlated （P〈0.01） with all growth parameters, including the belowground dry weight, marketable portion of the produce. The belowground biomass （commercial yield; 16.28 Qt/hec） at depth A was about 2.6 and 4.7 times higher than those recorded at depths B and C, respectively. The results clearly justify the importance of deep ploughing and this paper strongly recommends it for economically sustainable cropping.     

遥感技术与美国的人口普查

引言 D.布鲁金尼的论文《可用空间时代技术进行更精确的人口普查》提出了一些有趣的问题。我们为能够在《摄影测量工程和遥感》杂志上看到这篇有关遥感在社会科学领城内的应用的论文而高兴。我们认为只有了解人口普查数据的多种用途之后,再来检验那些改进人口普查的方法才是合适的,众所周知,每十年一次的人口普查数据的精度和完备性并不是没有缺点的。无疑地,许多人口普查人员将首先承认,每次由点数     

The responses of different ethnic groups in the Sudan to rural-urban migration

The ethnic identities of the various population groups in the Sudan are a product of their specific natural and social environments. The migration of these groups to the towns, especially to Greater Khartoum, involves a drastic change of cultural norms and values. However, the capability of change and the subsequent results are strongly conditioned by the specific background of each ethnic group and by the conditions in its area of origin. This is being proved by a comparative study on three ethnic groups in the Sudan: the Nuba, the Zaghawa and the Hadandawa.     

Identification of the interstellar cyanomethyl radical (CH2CN) in the molecular clouds TMC-1 and Sagittarius B2

We report the astronomical identification of the cyanomethyl radical, CH2CN, the heaviest nonlinear molecular radical to be identified in interstellar clouds. The complex fine and hyperfine structures of the lowest rotational transitions at about 20.12 and 40.24 GHz are resolved in TMC-1, where the abundance appears to be about 5 x 10(-9) relative to that of H2. This is significantly greater than the observed abundance of CH3CN (methyl cyanide) in TMC-1. In Sgr B2 the hyperfine structure is blended in the higher frequency transitions at 40, 80, and 100 GHz, although the spin-rotation doubling is clearly evident. Preliminary searches in other sources indicate that the distribution of CH2CN is similar to that for such carbon chain species as HC3N or C4H.     

Changing population concentration in India: a macro-regional scenario

There are great spatial variations in the distribution of the fast growing populations of India. About 70% of the 1981 population is concentrated in only 40% of the geographical area. Such a pattern of population concentration, with its spatio-temporal dimension, can be understood better if examined at the macro-regional level considering the physico-climatic and socio-economic diversity of the country. This is done by way of analyzing district level data for India as a whole and also for its various macro-regions. The study reveals that the Great Plains and Coastal Plains and Islands have a homogenous distribution and a higher population increase. The Deccan Plateau shows the most homogenous dispersion of population. The population is declining in the Northern Mountains and the Great Plains but accentuating in the Coastal Plains and Islands and the Deccan Plateau. The north and south of India are showing opposite trends in population concentration.