EFFECT OF COAL MINING ON RIVER SEDIMENTATION-A Case Study From The Shengfu-Dongsheng Coal FieldIn The Loess Plateau, North China     

Chang-xing JIN  Lian-yuan YOU 《国际泥沙研究》1999,(2)

IINTRODUCTIONTheWulanmulunheRiver(theupperreachoftheKuyeheRiver)isatributaryoftheYellowRiver(Fig.I).Ithasawatershedareaof3839km2upstreamfromtheoutletgaugingstationatWangdaohengta(ithasbeensuccessfollyoperatedsince1958).ThisisafieldinthefragileecologicalareaoftheLoessPlateau.AnnualrainfallintheWulanmulenheRiverbasinrangesfrom124mmto640rumwithanaverageof343mm.Themaincharacteristicsofrainfallarehighintensityandspatialandtemporalheterogenety.Nearly70%ofthetotalannualrainfallfallsinthefl…  相似文献   

西朝鲜湾盆地侏罗系新义州组湖相油源岩远景     

Mass.  MS 项光 《海洋地质译丛》1994,(1):1-9

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HCO emission from H II-molecular cloud interface regions     

Schenewerk MS  Snyder LE  Hollis JM  Jewell PR  Ziurys LM 《The Astrophysical journal》1988,328(2):785-796

A survey of well-known molecular clouds in the four strongest HCO NK-,K+ = 1(01)-0(00) hyperfine transitions has been carried out to determine the prevalence of HCO and to study its chemistry. HCO emission was observed in seven molecular clouds. Three of these, NGC 2264, W49, and NGC 7538, were not previously known sources of HCO. In addition, NGC 2024 and Sgr B2 were mapped and shown to have extensive HCO emission. The survey results show the HCO abundance to be enhanced in H II-molecular cloud interface regions and support a correlation between C+ and HCO emission. The strength of the HCO emission in NGC 2024 is interpreted in terms of this enhancement and the source structure and proximity to Earth.  相似文献   

Comet Sugano-Saigusa-Fujikawa (1983V)--a small, puzzling comet     

Hanner MS  Newburn RL  Spinrad H  Veeder GJ 《The Astronomical journal》1987,94(4):1081-1087

Spectroscopic and infrared observations of Comet Sugano-Saigusa-Fujikawa (1983V) were obtained during its close approach to the Earth on 11-14 June 1983. The [O I] production rates of 1.8 +/- 0.9 x 10(26) atoms/s observed on 12.3 June and 7 +/- 3.5 x 10(26) atoms/s on 13.4 June lead to derived water-production rates of 3 x 10(27) mol/s on 12 June and 1.1 x 10(28) mol/s on 13 June. The abundances of the minor species NH2, CN, C2, and C3 are unusually low relative to [O I]. The upper limit to the average nuclear radius from our infrared and visual photometry on 12-13 June (assuming that the entire signal came from the nucleus) is approximately 370 m. The dust/gas mass ratio was <0.01 on June 12 and <0.005 on June 13.  相似文献   

Growth of rural population in Punjab, 1971-81     

Gill MS 《Population geography : a journal of the Association of Population Geographers of India》1987,9(1-2):62-72

Except for the decade 1941-1951, in which Punjab's population declined because of a huge exchange of population between India and Pakistan and a large loss of life, the decade 1971-1981 was the 1st decade since 1911 to experience a deceleration in the growth rate of the rural population of Punjab, India. The deceleration was due to out-migration to urban areas. The scheduled caste population increased 28.37% between 1971 and 1981, while the nonscheduled caste population increased by only 13.32%, which was considerably below the rate of natural increase. Nonscheduled castes had experienced substantial out-migration because of 1) improved transport and communication facilities which enabled them to move to urban centers; 2) mechanization of main farming operations and easy availability of migrant laborers which lessened the need for family labor; 3) the rise of a relatively mobile younger generation with a high literacy rate; 4) rapidly decreasing land holdings which strengthened the push factor in the countryside; and 5) rising aspirations, especially among the younger generation. In 1981, Sikhs constituted 71.3% of the rural population in Punjab, followed by Hindus (26.51%), Christians (1.25%), and Muslims (.89%). From 1971-1981, Muslims experienced the greatest increase (49.29%). Sikhs grew by 20.74% and Hindus by 9.02%. The Sikhs high growth rate was due to 1) a new technique for counting religious affiliation in which all members of a household are considered the same religion as the head of household and 2) conversion of Hindus to Sikhism. Hindus had a low growth rate because 1) the new method of counting religious affiliation and 2) rural-urban migration. The area with the lowest population increase resulted from industrialists and other nonagriculturists buying farmland, causing the agriculturists to move away to less desirable land. Conclusions are 1) the sharp rural-urban division along religious lines should be lessened, 2) Sikhs' lag in urbanization and upward mobility should be decreased, and 3) nonagriculturalists should be prevented from buying farm land from peasants along main roads and around urban centers.  相似文献   

Hard Burst Emission from the Soft Gamma Repeater SGR 1900+14     

Woods PM  Kouveliotou C  van Paradijs J  Briggs MS  Hurley K  Gö&gbreve;ü&scedil; E  Preece RD  Giblin TW  Thompson C  Duncan RC 《The Astrophysical journal》1999,527(1):L47-L50

We present evidence for burst emission from SGR 1900+14 with a power-law high-energy spectrum extending beyond 500 keV. Unlike previous detections of high-energy photons during bursts from soft gamma repeaters (SGRs), these emissions are not associated with extraordinarily bright flares. Not only is the emission hard, but the spectra are better fitted by D. Band's gamma-ray burst (GRB) function rather than by the traditional optically thin thermal bremsstrahlung model. We find that the spectral evolution within these hard events obeys a hardness/intensity anticorrelation. Temporally, these events are distinct from typical SGR burst emissions in that they are longer ( approximately 1 s) and have relatively smooth profiles. Despite a difference in peak luminosity of greater, similar1011 between these bursts from SGR 1900+14 and cosmological GRBs, there are striking temporal and spectral similarities between the two kinds of bursts, aside from spectral evolution. We outline an interpretation of these events in the context of the magnetar model.  相似文献   

晚新生代大陆裂谷作用期间前寒武纪火山成因硫化物矿源再活化形成的？…     

Fulp.  MS 程翔 《国外地质与勘测》1991,(3):41-45

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煌斑岩与中温热液型金矿床的成因关系     

Nich.  MS  刘蒙华 《东北地质科技情报》1989,(1):38-41

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地震波形非线性反演的替代方法     

Samb.  MS 刘瑞文 《世界地震译丛》1994,(1):15-22

大型非线性反演问题的一个普通例子是地震波形反演，通常解这类问题的方法涉及到求出观测与理论预测值之间某一失配函数的极小值。随着问题规模的增大，需要反演大矩阵的一些方法变得很麻烦，要执行反演并避免稳定性方面的问题就需要相当大的储存量和计算工作。因此，不需要任何大型矩阵反演的方法是很受欢迎的。目前，下降型算法正被广泛使用着。通常，在每次迭代时，由失配函数的梯度得出下降方向，并且根据这个方向或者还有以前的  相似文献   

朝鲜半岛及黄海板内地震的体波分析     

Jun.  MS 郭金城 《世界地震译丛》1994,(1):37-43

本文研究了朝鲜半岛及黄海板内４次中强度浅震，求出它们的震源机制、震源深度、震源时间函数及地震矩。结是要发现，用短周期合成地震图与观测结果对比求得的震源深度是很浅的，在６－９ｋｍ之间。为了测定震源机制、震源时间函数及地震矩，我们根据ＧＤＳＮ资料反演了远震长周期Ｐ与ＳＨ波。反演虽仅依据少数远震体波作出，但矩张量的辐射图形与在近震及远震距离上观测到的大多数Ｐ波初动方向一致。相对振幅及波形在观测结果与合成  相似文献