The collectorless flotation of chalcopyrite ores using sodium sulfide     

Gerald H. Luttrell  Roe-Hoan Yoon 《International Journal of Mineral Processing》1984,13(4):271-283

The collectorless flotation process has been tested on six different chalcopyrite ores while monitoring the potentials ($\text{E}{}_{\mathrm{<mtext>h</mtext>}}$) of the pulp. The results show that collectorless flotation is effective only under oxidizing conditions. In addition, the flotation requires that the chalcopyrite surface be relatively free of hydrophilic oxidation products, which can be accomplished by treating the ore pulp with sodium sulfide (Na₂S). On the basis of these findings, methods of improving the collectorless flotation process are discussed.  相似文献   

Biological and Physical Attenuation of Endocrine Disruptors and Pharmaceuticals: Implications for Water Reuse   总被引：2，自引：0，他引：2  

Shane A. Snyder  Joseph Leising  Paul Westerhoff  Yeomin Yoon  Heath Mash  Brett Vanderford 《Ground Water Monitoring & Remediation》2004,24(2):108-118

A select group of endocrine disrupters, pharmaceuticals, and personal care products was studied to determine the degree of biological attenuation in water reuse applications. Laboratory investigations involved both batch reactors using biologically active sand and continuous flow simulated aquifer storage and recovery experiments. All laboratory experiments were conducted using Colorado River water spiked with various target compounds at concentrations between 10 and 100 ng/L. Field studies were also conducted to determine the occurrence and attenuation of target compounds in water reuse applications. Two golf courses irrigated with reuse water were studied to determine if turf applications led to contamination of nearby ground water. A waste water treatment facility that uses rapid infiltration basins seasonally was also tested to determine the degree of attenuation of detectable target compounds along a subsurface flowpath. A qualitative structural activity relationship model was applied to the target compounds to predict the general rate of aerobic biological degradation. Significant attenuation of many target compounds was observed in both laboratory and field experiments. Conversely, several compounds displayed limited removal during these studies. Field experiments were limited to detectable compounds and various nonbiological removal or concentration effects that may impact data interpretations, which are discussed in this paper. The predictive model was found to be moderately accurate within the confines of the project scope.  相似文献   

Broad depth range seismic imaging of the subducted Nazca Slab, North Chile     

S. Buske  S. Lüth  H. Meyer  R. Patzig  C. Reichert  S. Shapiro  P. Wigger  M. Yoon 《Tectonophysics》2002,350(4):93-282

In this paper, we present a compilation of modern seismic and seismological methods applied to image the subduction process in North Chile, South America. We use data from active and passive seismic experiments that were acquired within the framework of the German Collaborative Research Center SFB267 ‘Deformation Processes in the Andes’. The investigation area is located between 20° and 25°S and extends from the trench down to 100 km depth. In the depth range between the sea bottom and 15 km, we process an offshore seismic reflection profile using a recently developed velocity-model-independent stacking procedure. We find that the upper part of the subducting oceanic lithosphere in this depth range is characterized by a horst-and-graben structure. This structure supports an approximately 3 km thick coupling zone between the plates. In the depth range between 15 and 45 km, we analyse the spatial distribution of aftershocks of the Antofagasta earthquake (1995). The aftershock hypocenters are concentrated in an approximately 3 km thick layer. Finally, in the depth range between 45 and 100 km, we apply Kirchhoff prestack depth migration to the onshore ANCORP profile. A double reflection zone is observed between 45 and 60 km depth, which may represent the upper and lower boundary of the subducted oceanic crust. Over the whole range down to more than 80–90 km depth, we obtain an image of the subducting slab. At that depth, the hypocenters of local earthquakes deviate significantly in the direction perpendicular to the slab face from the reflective parts of the slab. Consequently, our results yield a complete seismic image of the downgoing plate and the associated seismic coupling zone.  相似文献   

Postglacial marine environmental changes in Maxwell Bay, King George Island, West Antarctica   总被引：3，自引：0，他引：3  

Boo-Keun Khim  Ho Il Yoon 《Polar research》2003,22(2):341-353

Sediment textural properties and total organic carbon (TOC) contents of three sediment cores from Maxwell Bay, King George Island, West Antarctica, record changes in Holocene glaciomarine sedimentary environments. The lower sedimentary unit is mostly composed of TOC-poor diamictons, indicating advanced coastal glacier margins and rapid iceberg discharge in proximal glaciomarine settings with limited productivity and meltwater supply. Fine-grained, TOC-rich sediments in the upper lithologic unit suggest more open water and warm conditions, leading to enhanced biological productivity due to increased nutrient-rich meltwater supply into the bay. The relationship between TOC and total sulfur (TS) indicates that the additional sulfur within the sediment has not originated from in situ pyrite formation under the reducing condition, but rather may be attributed to the detrital supply of sand-sized pyrite from the hydrothermal-origin, quartz-pyrite rocks widely distributed in King George Island. The evolution of bottom-water hydrography after deglaciation was recorded in the benthic foraminiferal stable-isotopic composition, corroborated by the TOC and lithologic changes. The ع⁸O values indicate that bottom-water in Maxwell Bay was probably mixed gradually with intruding ¹⁸O-rich seawater from Bransfield Strait. In addition, the ع³C values reflect a spatial variability in the carbon isotope distribution in Maxwell Bay, depending on marine productivity as well as terrestrial carbon fluxes by meltwater discharge. The distinct lithologic transition, dated to approximately 8000 yr BP (uncorrected) and characterized by textural and geochemical contrasts, highlights the postglacial environmental change by a major coastal glacier retreat in Maxwell Bay.  相似文献   

Investigating the Effects of Different LED Wavelengths on Aggregation and Swimming Behavior of Chub Mackerel (Scomber japonicus)     

Lee  Donggil  Oh  Wooseok  Gim  Byeong-Mo  Lee  Jung Suk  Yoon  Euna  Lee  Kyounghoon 《Ocean Science Journal》2019,54(4):573-579

Ocean Science Journal - Efficient fish aggregation systems are essential for catching chub mackerel (Scomber japonicus), which is a major target of purse seine fisheries in South Korea. To aid the...  相似文献   

Core-based reconstruction of paleoenvironmental conditions in the southern Drake Passage (West Antarctica) over the last 150 ka     

Ho Il Yoon  Kyu-Cheul Yoo  Young-Suk Bak  Yong Il Lee  Jae Il Lee 《Geo-Marine Letters》2009,29(5):309-320

A deep-sea sediment core (GC98-06) from the southernmost Drake Passage, West Antarctica, shows late Quaternary depositional environments distinctly different from sedimentary drifts commonly found along the southwestern Pacific margin of the Drake Passage. The chronology of the core has been inferred using geochemical tracers of paleoproductivity and diatom biostratigraphy, and represents the paleoceanographic conditions in a continental rise setting during the last 150,000 years. Three dominant sediment types associated with distinct sedimentary processes have been identified using textural/compositional analyses: (1) hemipelagic mud (interglacial sediments) deposited from pelagic settling of bioclasts, meltwater plumes, and ice-rafted detritus; (2) terrigenous mud (glacial sediments) delivered by turbid meltwater plumes; and (3) massive muds marking the boundaries from interglacial to glacial periods. The succession of the sedimentary facies in core GC98-06 is interpreted to reflect temporal changes in environmental conditions prevailing on the continental rise of the southern Drake Passage in the course of successive climatic stages over the last 150 ka: from the bottom upward, these are glacial, interglacial, glaciation, glacial, and interglacial episodes. Variability in sediment flux and diatom abundance seem to have been related to changes in glacial advance, sea-ice extent, and specific sedimentary environments, collectively influenced by mid- to late Quaternary climatic changes.  相似文献   

Modeling of the branches of the Tsushima Warm Current in the Eastern Japan Sea     

Hideyuki Kawamura  Toshimichi Ito  Naoki Hirose  Tetsutaro Takikawa  Jong-Hwan Yoon 《Journal of Oceanography》2009,65(4):439-454

The branches of the Tsushima Warm Current (TWC) are realistically reproduced using a three-dimensional ocean general circulation model (OGCM). Simulated structures of the First Branch and the Second Branch of the TWC (FBTWC and SBTWC) in the eastern Japan Sea are mainly addressed in this study, being compared with measurement in the period September–October 2000. This is the first numerical experiment so far in which the OGCM is laterally exerted by real volume transports measured by acoustic Doppler current profiler (ADCP) through the Tsushima Straits and the Tsugaru Strait. In addition, sea level variation measured by tide-stations along the Japanese coast as well as satellite altimeters is assimilated into the OGCM through a sequential data assimilation method. It is demonstrated that the assimilation of sea level variation at the coastal tide-stations is useful in reproducing oceanic conditions in the nearshore region. We also examine the seasonal variation of the branches of the TWC in the eastern Japan Sea in 2000. It is suggested as a consequence that the FBTWC is continuous along northwestern Honshu Island in summertime, while it degenerates along the coast between the Sado Strait and the Oga Peninsula in other seasons. On the other hand, a mainstream of the SBTWC exists with meanders and eddies in the offshore region deeper than 1000 m to the north of the Sado Island throughout the year.  相似文献   

Recent moon jelly (Aurelia sp.1) blooms in Korean coastal waters suggest global expansion: examples inferred from mitochondrial COI and nuclear ITS-5.8S rDNA sequences     

Ki  Jang-Seu; Hwang  Dae-Sik; Shin  Kyoungsoon; Yoon  Won Duk; Lim  Donghyun; Kang  Young Shil; Lee  Yoon; Lee  Jae-Seong 《ICES Journal of Marine Science》2008,65(3):443-452

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Remnant evolution after a carbon–oxygen white dwarf merger     

S.-C. Yoon  Ph. Podsiadlowski  S. Rosswog 《Monthly notices of the Royal Astronomical Society》2007,380(3):933-948

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Seasonal characteristics of the Tsushima Current in the Tsushima/Korea Strait obtained by a fine-resolution numerical model     

Y.H. Seung  Y.-J. Kim  J.-H. Yoon 《Continental Shelf Research》2007

The horizontal distribution of the Tsushima Current in the Tsushima/Korea Strait is assessed by a fine-resolution numerical experiment. The comparison of the model results with the observations along a section crossing the strait shows that the model represents relatively well, the general tendency of what was observed, such as the separation of the Tsushima Current into the western and eastern streams by the Tsushima Island. In summer, strong and relatively uniformly distributed surface currents enhance the formation of the wake downstream of the Tsushima Island. The axis of the countercurrent, embedded in the wake, is closer to the western stream. Anti-cyclonic eddies are shed near the downstream tip of the Tsushima Island and propagate along the boundary between the western stream and the wake. The exchange of water between the western stream and the wake takes place through the intermediation of these eddies. There is a net water supply from the western stream to the wake, which is then carried to the eastern stream by the countercurrent via the eastern coast of the Tsushima Island. In winter, currents, strongly barotropic, tend to have banded structures, especially in the region downstream of the western channel where isobaths converge in the downstream direction. The eddies found in this region in winter appear to be fundamentally different from those associated with the Tsushima Island wake. The necessary condition for barotropic instability is satisfied for the monthly mean currents in this region, suggesting that the currents are barotropically unstable in this region in winter.  相似文献