贵州中三叠世生物礁   总被引：13，自引：0，他引：13       下载免费PDF全文

贺自爱  杨宏  周经才 《地质科学》1980,15(3):256-264

贵州中三叠世生物礁,早在六十年代中期,殷鸿福、杨遵仪就已提出线索。作者在六十年代初研究贵州三叠纪地层时,已对三叠系相变带的特征和规模,以及板庚碳酸盐岩体有了初步认识。七十年代初,作者又到花江进行调查,发现一套壮观的藻礁灰岩。  相似文献   

Improving Indigenous Technologies for Sustainable Land Use in Northern Mountainous Areas of Vietnam     

LeQuocDoanh HaDinhTuan 《山地科学学报》2004,1(3):270-275

More than 30 ethnic groups are now living in northern mountainous regions, Vietnam, mainly relying on shifting cultivation with the fallow period being shortened from time to time. Naturally, soil fertility reduces from cycle to cycle, entailing the reduction of productivity. Large areas of moderately sloping lands suitable for upland agriculture have become bare after many cultivation-fallow cycles. The soils there have been severely degraded with more toxicity, low porosity, low water retention capacity and poor floral diversity. Normally, these lands cannot be used for food crop cultivation. So farmers in uplands have to rely on slash-and-burn practices for their livelihood. As there is no more forest with good soil in medium slopes, farmers go to cut forests in watershed, high slope lands and old forests up to the mountains‘ top. There are ecologically and environmentally very sensitive areas, so their destruction will inevitably cause hazardous consequences in the whole basin. Meanwhile,cultivation in these areas has low economic efficiency and sustainability because the crop yield may decrease very fast due to severe erosion as the higher the slope, the more serious erosion. Consequently living standards of highland farmers remain low and unstable. Sustainable farming on these lands in the perspective of a seriously deteriorated ecology and environmental is not an easy task. There have been many projects trying to help mountainous farmers get out of their vicious circle. However, due to different reasons, the results gained are low, and in some cases,things ceased to move after the projects phased out. During past few years, based on the farmer experiences, the Vietnam Agricultural Science Institute has cooperated with local and international partners to implement different projects in order to solve the problems by developing simple, easy and cheap cultivation technologies, which can be accepted and applied by local poor farmers for sustainable agricultural production. The first results of our activities offered good opportunities for sustain food production, improve soil health, recharge of aquifers,and enhanced household income for better rural lively hoods in the upland eco-regions of northern Vietnam.  相似文献   

Constraining the geometry of the neutron star RX J1856.5−3754     

Wynn C. G. Ho 《Monthly notices of the Royal Astronomical Society》2007,380(1):71-77

RX J1856.5−3754 is one of the brightest, nearby isolated neutron stars (NSs), and considerable observational resources have been devoted to its study. In previous work, we found that our latest models of a magnetic, hydrogen atmosphere match well the entire spectrum, from X-rays to optical (with best-fitting NS radius   R ≈ 14  km, gravitational redshift   z _g∼ 0.2  , and magnetic field   B ≈ 4 × 10¹²  G). A remaining puzzle is the non-detection of rotational modulation of the X-ray emission, despite extensive searches. The situation changed recently with XMM–Newton observations that uncovered 7-s pulsations at the     level. By comparing the predictions of our model (which includes simple dipolar-like surface distributions of magnetic field and temperature) with the observed brightness variations, we are able to constrain the geometry of RX J1856.5−3754, with one angle <6° and the other angle     , though the solutions are not definitive, given the observational and model uncertainties. These angles indicate a close alignment between the rotation and the magnetic axes or between the rotation axis and the observer. We discuss our results in the context of RX J1856.5−3754 being a normal radio pulsar and a candidate for observation by future X-ray polarization missions such as Constellation-X or XEUS .  相似文献   

Effect of abalone farming on sediment geochemistry in the Shallow Sea near Wando,South Korea     

Jeongwon Kang  Yeon Gyu Lee  Da Un Jeong  Jung Sick Lee  Yang Ho Choi  Yun Kyung Shin 《Ocean Science Journal》2015,50(4):669-682

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Retrieval of outgoing longwave radiation from COMS narrowband infrared imagery     

Myung-Sook Park  Chang-Hoi Ho  Heeje Cho  Yong-Sang Choi 《大气科学进展》2015,32(3):375-388

Hourly outgoing longwave radiation(OLR) from the geostationary satellite Communication Oceanography Meteorological Satellite(COMS) has been retrieved since June 2010. The COMS OLR retrieval algorithms are based on regression analyses of radiative transfer simulations for spectral functions of COMS infrared channels. This study documents the accuracies of OLRs for future climate applications by making an intercomparison of four OLRs from one single-channel algorithm(OLR12.0using the 12.0 μm channel) and three multiple-channel algorithms(OLR10.8+12.0using the 10.8 and 12.0 μm channels; OLR6.7+10.8using the 6.7 and 10.8 μm channels; and OLR All using the 6.7, 10.8, and 12.0 μm channels). The COMS OLRs from these algorithms were validated with direct measurements of OLR from a broadband radiometer of the Clouds and Earth's Radiant Energy System(CERES) over the full COMS field of view [roughly(50°S–50°N, 70°–170°E)] during April 2011.Validation results show that the root-mean-square errors of COMS OLRs are 5–7 W m-2, which indicates good agreement with CERES OLR over the vast domain. OLR6.7+10.8and OLR All have much smaller errors(～ 6 W m-2) than OLR12.0and OLR10.8+12.0(～ 8 W m-2). Moreover, the small errors of OLR6.7+10.8and OLR All are systematic and can be readily reduced through additional mean bias correction and/or radiance calibration. These results indicate a noteworthy role of the6.7 μm water vapor absorption channel in improving the accuracy of the OLRs. The dependence of the accuracy of COMS OLRs on various surface, atmospheric, and observational conditions is also discussed.  相似文献   

Climatological features of WRF-simulated tropical cyclones over the western North Pacific   总被引：2，自引：0，他引：2  

Dasol Kim  Chun-Sil Jin  Chang-Hoi Ho  Jinwon Kim  Joo-Hong Kim 《Climate Dynamics》2015,44(11-12):3223-3235

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Distribution of dinoflagellate cysts in Yellow Sea sediments   总被引：1，自引：1，他引：0  

SHIN Hyeon Ho  LIM Dhongil  PARK Soung-Yun  HEO Seung  KIM So-Young 《海洋学报(英文版)》2013,32(9):91-98

To investigate the distribution,abundance,and species composition of dinoflagellate cysts in the Yellow Sea,surface sediment samples were collected at 37 sites,including the Korean dump site.Twenty-one dinoflagellate cyst taxa were identified,with the assemblages dominated mainly by Spiniferites bulloideus,Operculodinium centrocarpum,and cyst of Alexandrium catenella/tamarense type.A high frequency of O.centrocarpum in the Yellow Sea was observed for the first time,and it is likely that this can be attributed to the dynamics of the Yellow Sea Cold Water Mass and the Changjiang(Yangtze) River runoff.Total cyst concentrations ranged from 23 to 48 442 cysts/g dry weight,and high cyst concentrations were recorded adjacent to the dumping site.This result suggests that anthropogenic activities such as ocean dumping stimulate the growth of dinoflagellates in the Yellow Sea,which in turn leads to high levels of dinoflagellate cyst production.  相似文献   

Geochemistry and petrogenesis of Permian ultramafic-mafic complexes of the Jinping–Song Da rift (southeastern Asia)     

P.A. Balykin  G.V. Polyakov  A.E. Izokh  Tran Trong Hoa  Ngo Thi Phuong  Tran Quoc Hung  T.E. Petrova 《Russian Geology and Geophysics》2010,51(6):611-624

The Jinping–Song Da rift structure in the Emeishan Large Igneous Province is composed of Permian high- and low-Ti volcanic and volcanoplutonic ultramafic-mafic associations of different compositions and genesis. High-Ti picrites, picrobasalts, basalts, and dolerites are enriched in LREE and depleted in HREE and show low Al₂O₃/TiO₂ ratios (~4), commensurate ε_Nd(T) values (+0.5 to +1.1), and low (Th/Nb)_PM ratios similar to those of OIB-enriched mantle source. The established geochemical characteristics evidence that the parental melts of these rocks were generated from garnet lherzolite at the depths of garnet stability (~200 to 400 km). Later, high-Mg low-Ti volcanics (komatiites, komatiitic basalts, and basalts) and associating small peridotite-gabbro massifs and komatiite-basalt dikes were produced as a result of ~20% partial melting of depleted water-poor (≤0.03 wt.% H₂O) peridotite substratum from the hottest upper part of mantle plume at relatively shallow depths (100–120 km). The LREE-depleted komatiites and komatiitic basalts are characterized by low (Ce/Yb)_CH values, ¹⁸⁷Re/¹⁸⁸Os = 0.05–1.2, ⁸⁷Sr/⁸⁶Sr = 0.704–0.706, positive ε_Nd(T) values (+3 to +8), γ_Os = –0.5 to +0.9, and strong negative anomalies of Ba, K, and Sr on the spidergrams. The scarcer LREE-enriched komatiites, komatiitic basalts, and basalts vary greatly in chemical composition and values of ε_Nd(t) (+6.4 to –10.2), ⁸⁷Sr/⁸⁶Sr (0.706–0.712), and γ_Os (+14.8 to +56), which is due to the different degrees of crustal contamination of parental magmas. The Rb-Sr isotopic age of basaltic komatiite is 257 ± 24 Ma. The Re-Os age determined by analysis of 12 komatiite samples is 270 ± 21 Ma. These data agree with the age of flood basalts of the Emeishan Large Igneous Province. The komatiite-basalt complex of the Song Da rift is still the only Phanerozoic PGE-Cu-Ni-complex of this composition. The geochemistry of accompanying Cu-Ni-PGE-ores confirms their relationship with komatiite-basaltic magmatism.  相似文献   

Indian summer monsoon onset vortex formation during recent decades     

R. Deepa  Jai Ho Oh 《Theoretical and Applied Climatology》2014,118(1-2):237-249

This study investigates the decrease in the frequency of onset vortex of summer monsoon during recent decades using the National Center for Environmental Prediction–National Center for Atmospheric Research reanalysis (1982–2011) data. Onset vortices are known to occur over the Arabian Sea mini warm pool where the sea surface temperature peaks just before the onset of monsoon. Even though the Arabian Sea mini warm pool intensifies during the recent decades, they are not seen as a regular feature. It is found from the analysis of irrotational and non-divergent wind component at 850 and 200 hPa that during the recent decades, convergent winds dominate at upper levels and divergent winds at lower levels which inhibits convection. Moreover, the cyclonic shear vorticity shows a decrease in the recent decades which tend to reduce the boundary layer moisture convergence and lower tropospheric humidity which is an important component for the initiation of a cyclonic system. The recent decades are characterized by weak convection due to the presence of strong northerlies and descending motion at lower levels in the southeast Arabian Sea. The response of atmospheric circulation to the interdecadal variations in the warm pool and the corresponding decrease in the frequency of onset vortex formation is analyzed in detail.  相似文献   

Discharge prediction using hydraulic characteristics of mean velocity equation     

Tai Ho Choo  Soo Kwon Chae  Hyeon Cheol Yoon  Yeon Moon Choo 《Environmental Earth Sciences》2014,71(2):675-683

Discharge is an important factor in river design for water utilization, water control and hydraulic structures; therefore, an accurate estimation of the discharge is required. At present, a rating curve depicting the relationship between a stage and discharge is used to calculate the discharge from river systems. Although the rating curve has an advantage in that it can predict and use the discharge during the flood season in which the measurement is difficult, there is room for improvement as it does not reflect the hydraulic characteristics of rivers. Therefore, in this study, discharge was predicted using the convenient calculation method with empirical mediating variables of the Manning and Chezy equations which were proposed by the author’s previous research as a new methodology for estimating discharge in an open channel. This was proven, based on the data measured in a meandering open channel system in a lab at the Mississippi River in the US and at the Columbia Del Dique Canal, and an accuracy level at a coefficient of 0.8 was demonstrated. Thus, this method, which reflects the hydraulic characteristics and predicts the discharge in a simple manner, is expected to be convenient in practice.  相似文献