133 research outputs found
Distributions and Sources of Sedimentary Sterols as well as Their Indications of Sewage Contamination in the Guanting Reservoir, Beijing
No full textIn this study, domestic sewage contamination in the Guanting Reservoir, one of the major water source reservoirs of Beijing, was examined using sterols as tracing molecular markers. Nineteen sediment samples in seven cross-sections in the Guanting Reservoir were collected, extracted, and analyzed by gas chromatography-mass spectrometry (GC-MS). Seven different sterols were identified and quantified from the surface sediment samples in the Guanting Reservoir. The total sterols in sediments of the reservoir ranged from 2.78 μg g−1 to 40.31 μg g−1 with the average concentration of 13.53 μg g−1. Concentrations of fecal sterols, coprostanol and epicoprostanol in the Guishui River reservoir area were generally higher than in the Yongding River reservoir area. The average concentrations of coprostanol and epicoprostanol in the Yongding River reservoir area were 0.41 μg g−1 and 0.34 μg g−1, respectively. The average concentrations of coprostanol and epicoprostanol in the Guishui River reservoir area were 0.72 μg g−1 and 0.70 μg g−1, respectively. Ratios of sterols indicated higher sewage pollution in regions close to river mouths and reservoir banks. Principal component analysis (PCA) indicated three distinct sources of sterols from domestic sewage, phytoplankton, and terrestrial higher plants. This article identified the current situation of sewage contamination in sediments of the Guanting Reservoir, which could provide important references for further implementation of pollution control and basin management in the region
Seasonal River Export of Nitrogen to Guanting and Baiyangdian Lakes in the Hai He Basin
No full textEutrophication refers to the nutrient enrichment, leading to blooms of algae. Such blooms in lakes can happen throughout the year because of the changes in nutrient and hydrological cycles. Nutrient export to lakes from rivers is the main cause of eutrophication problems. Seasonal trends in nitrogen (N) export by rivers to lakes are still not well understood. The objective of this study is, therefore, to better understand the seasonal trends in river export of dissolved inorganic N (DIN) to lakes of the Hai He Basin. To this end, we selected Guanting and Baiyangdian as representative lakes, whose drainage areas include various cropping systems. We developed a seasonal version of the Model to Assess River Inputs of Nutrients to lAkes (MARINA-Lakes) model for Guanting and Baiyangdian while assessing N flows from the land to the lakes. The model accounts for the seasonality in human activities (e.g., cropping systems and fertilizer practices), climate, and hydrology. The effective seasons are winter (December–February), spring (March–May), summer (June–August), and fall (September–November). The model results for the year 2012 indicate that river export of DIN was highest in winter and lowest in summer. Point sources accounted for over 50% of DIN exports to Guanting and Baiyangdian across seasons. Avoiding direct discharges of animal manure (point source) in winter is needed to reduce future lake pollution. We argue that effective lake pollution control requires accounting for seasonal N cycles. Our study can support effective nutrient management and environmental policies
Occurrence of pharmaceuticals and personal care products, and their associated environmental risks in Guanting Reservoir and its upstream rivers in north China
No full textEighteen selected pharmaceuticals and personal care products (PPCPs) were detected in surface water and sediments from the Guanting Reservoir (GTR) and its upstream rivers.</p
Simple and Ingenious Manner To Build Li-Rich Layered Materials with Surface Layered/Spinel Heterostructures and Li Deficiencies
No full textThe voltage and capacity attenuation is one of the main
bottlenecks
limiting the commercialization of Li-rich layered materials, the introduction
of a spinel structure and Li deficiencies into materials may mitigate
or suppress these shortcoming. The Li-rich layered materials with
surface layered/spinel heterostructures and Li deficiencies (LR-S)
are prepared by a simple and ingenious manner; that is, the 10 wt
% precursors are added to uptake the volatilize of Li ions, which
produced from the Li-rich material (LR-0) in a high-temperature post-treatment
process. The generation of the spinel structure and Li deficiencies
in the LR-S sample are confirmed by the inductively coupled plasma
mass spectrometry, X-ray diffraction, Raman spectra, and high-resolution
transmission electron microscopy characterizations. The LR-S sample
displayed excellent electrochemical performances; that is, the capacity
retentions is 88.92% at 1 C after 200 cycles, and the voltage drop
for each cycle is 1.91 mV, respectively. The reason is mainly attributed
to the spinel structure serving as a pillar structure and the Li deficiencies
modulating the oxidation products of the oxygen ion in the removal/uptake
process
Water Resources Vulnerability Assessment based on the Parametric-system Method: a Case Study of the Zhangjiakou Region of Guanting Reservoir Basin, North China
No full textAbstractA water resources vulnerability (WRV) assessment is important to maintain water resources safety in a basin. In this paper, an index system, including four subsystems -- the hydrological subsystem, the socioeconomic subsystem, the eco-environment subsystem and the hydraulic engineering subsystem, is constructed for an integrated WRV assessment of the Zhangjiakou region of the Guanting Reservoir Basin, North China. The parametric-system (PS) method based on background value is used for the quantitative WRV assessment of each subsystem and of the integrated water resources system. The results of the calculations show that the degree of vulnerability of Guanting Reservoir Basin is quite serious, with Zhangjiakou City being extremely vulnerable, and Yanqing County and Zhuolu County mildly vulnerable. The assessment process and results, as well as the characteristics of the method used, have been compared with those of the fuzzy optimization (FO) method and the grey relational analysis (GRA) method. The parametric-system (PS) method is appropriate for level classification and rank analysis of many samples in the system, with the obvious advantage of employing the simple process of linear calculation for both the assessment and reference systems. In practical calculation, multiple methods should be used comprehensively, so as to provide a more rational decision-making basis for water resources management
Polycyclic aromatic hydrocarbons in soils around Guanting Reservoir, Beijing, China
No full textThe concentrations of 16 polycyclic aromatic hydrocarbons ( 16PAHs) were measured by gas chromatography equipped with a mass spectrometry detector (GC-MS) in 56 topsoil samples around Guanting Reservior (GTR), which is an important water source for Beijing. Low to medium levels of PAH contamination (mean=394.2580.7ngg-1 dry weight (d.w.)) was evident throughout the region. In addition, localised areas of high PAH contamination near steel and cement factories were identified, with 16PAHs concentrations as high as 4110ng/g, dry weight (d.w.). There was a significant positive correlation (r2=0.570, p0.01) between total organic carbon content and 16PAHs concentrations. Phenanthrene was the predominant compound, accounting for 27.2% of the PAH concentration, followed by chrysenepyrenebenzo[a]anthracene benzo[b]fluoranthene benzo[a]pyrene. Four-ring PAH homologues (39%) were dominant. The higher proportion of 4-6 ring homologues, molecular indices, and the spatial distribution of PAH indicated that industrial discharges, incineration of wastes and traffic discharges were the major sources of soil PAHs around the water reservoir
Bei Mei Jidu jiao Zhongguo xue sheng hui ge an yan jiu (1909-1951)
No full textOne of the most striking phenomena in the first half of the 20th century was the influx of Chinese intellectuals into America to receive Western education. Studies in the past, however, often depicted the history of American-educated Chinese students simply as the history of Chinese students returning from America. For a long time the foreign exposure and experience of the Chinese intellectuals did not draw enough attention from the academia. If we agree that one of the valuable contributions that the West can make to China was the spiritual values in Western civilization, the encounter between the intellectuals and the Christian idealism would probably be a very important issue. It is not the purpose of this research to re-write the history of American-returned students in any depth. The author would like to focus on a group of "China's American-educated youths" who has encountered modern Christianity. Although they were not all followers or baptized Christians, they adhered to the principles of Christianity as the highest standard for measuring the changing circumstances in China and in the world.To unite the Chinese Christians in the United States, the Chinese Students' Christian Association in North America was founded in 1909 by a group of Chinese Christian students. The objective of the Association was similar to the Young Men's Christian Association. Through a case study of the Chinese Students' Christian Association in North America, the author attempts to depict the spiritual feature of the American-educated Chinese students as a single group. This dissertation argues that they intentionally chose the social gospel, which adopted the Kingdom of God as the key concept, in the quest fort he modern religious belief. By making critical assessment and judgment on the non-Christian order in the society, political arena and the internationals cene, they longed for the realization of the earthly democratic kingdom which suited to the home country and the world. Disappointed in politics, the China's American-educated youths did not turn into mere spectators. The Christian idealism made them profoundly aware of the sociopolitical realm of China and the world. This thirst for a Kingdom of God became the driving force for the continuous development of the students' Christian movement.梁冠霆.Adviser: Tze-Ming Ng.Source: Dissertation Abstracts International, Volume: 70-06, Section: A, page: 2073.Thesis (doctoral)--Chinese University of Hong Kong, 2008.Includes bibliographical references (p. 159-167).Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Abstracts in Chinese and English.School code: 1307.Liang Guanting
Regional differences and sources of organochlorine pesticides in soils surrounding chemical industrial parks
No full textConcentrations of organochlorine pesticides (OCPs; dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB)) were investigated in 105 soil samples collected in vicinity of the chemical industrial parks in Tianjin, China. OCP concentrations significantly varied in the study area, high HCH and DDT levels were found close to the chemical industrial parks. The intensity of agricultural activity and distance from the potential OCP emitters have important influences on the OCP residue distributions. Principal component analysis indicates that HCH pollution is a mix of historical technical HCH and current lindane pollution and DDT pollution input is only due to technical DDT sources. The significant correlations of OCP compounds reveal that HCHs, DDTs and HCB could have some similar sources of origin
Directional ice templating for cathode and anode of lithium ion batteries
No full textThis thesis investigates the development of sustainable and scalable fabrication strategies for lithium-ion battery electrodes using Directional Ice Templating (DIT). The aim was to overcome the limitations of conventional slurry coating, particularly the use of toxic NMP solvents and the lack of microstructural control. Chapter 1 outlined the background and motivation, emphasising the importance of thick, low-tortuosity electrodes for next-generation energy storage. Chapter 2 described the materials and experimental methods, including aqueous slurry design, fabrication procedures, and characterisation techniques.Chapter 3 demonstrated the feasibility of an aqueous DIT process to fabricate NMC811 cathodes with vertically aligned structures. This architecture enhanced electronic and ionic transport kinetics while eliminating the need for NMP solvent. Surface-sensitive characterisation confirmed the chemical stability of NMC811 during aqueous processing, and electrochemical testing showed that DIT cathodes delivered higher capacities and energy densities than slurry-coated electrodes. Chapter 4 addressed scalability and developed a directional extreme supercooling process to fabricate ultra-thick electrodes with mass loadings up to 70 mg cm⁻² at large scale. A systematic calendaring study identified 30% reduction as the critical threshold for balancing vertical alignment and packing density. At this point, DIT cathodes achieved high volumetric capacity, low impedance, and superior pouch-cell energy density compared to slurry-coating controls, demonstrating industrial relevance.
Chapter 5 extended DIT to graphite anodes. Thick, free-standing DIT anodes exhibited high mass loading, excellent reversibility, and lithium-ion diffusion coefficients several orders of magnitude higher than slurry-coated electrodes, demonstrating that DIT can overcome thickness limitations on both cathode and anode sides. Together, these results establish DIT as a sustainable, scalable, and versatile electrode fabrication strategy with significant implications for high-energy-density lithium-ion batteries in electric vehicles and grid-scale storage.Open Acces
P2P LENDING MARKET: DETERMINANTS OF INTEREST RATE AND DEFAULT RISK
No full textThe peer to peer (p2p) lending industry has grown fast in recent years. This study put an eye on the credit evaluation system of one of the p2p platform named lending club. The author used the empirical method and discussed the determinants of the interest rate and the default risk in the p2p lending market. The author concluded that the evaluation system founded by lending club could predict the risk of loans. Collecting more information about borrowers’ credit history may increase the accuracy of the model
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