Evaluation of a 256×256 Si:As IBC detector array for astronomy     

M. E. McKelvey  Robert E. McMurray Jr.  C. R. Mccreight  W. J. Forrest  J. D. Garnett  N. Lum  J. Asbrock  R. White  R. Kelchner  L. Lum  L. Pham 《Experimental Astronomy》1994,3(1-4):167-168

256×256-element IBC Si:As arrays have been evaluated for applications in IR astronomy from space-borne platforms. Basic figures of merit were measured at IR flux levels simulating those expected in space-based astronomical observations. Results include dark current <20e ^-/s, G as high as 3.8, / of 20%, and read noise below 100 rms e^-.  相似文献   

Long-wavelength infrared technology for astronomy at the Hughes Technology Center     

L. Pham  N. Lum  J. Asbrock  J. Venzon  R. Kelchner 《Experimental Astronomy》1994,3(1-4):227-234

The Hughes Technology Center (HTC) has developed a family of high-performance Si:As impurity-band conduction (IBC) hybrid focal plane arrays (FPAs) optimized for low background applications: 58×62 pixels (76-m pitch), 128×128 pixels (75- and 120-m pitch), and 256×256 pixels (30-m pitch). These FPAs exhibit state-of-the-art low noise (<100e ^-) achieved by using readout arrays fabricated on HTC's CryoCMOS process line. The IBC detector arrays, also fabricated at HTC, exhibit high quantum efficiency over a wide waveband with operating temperature of 4–12 K. In addition, Hughes is developing a 256×256 Si:As IBC FPA for high background applications as well as a 512×512 FPA. Readout development includes design and fabrication of 256×256 readouts with large well size of 1×10⁷ e ^- for the high-background FPA and 512×512 readouts with moderate well size (1×10⁶ e ^-).  相似文献   

Arsenic mobilisation in a new well field for drinking water production along the Red River,Nam Du,Hanoi     

Jenny Norrman  Charlotte J. Sparrenbom  Michael Berg  Dang Duc Nhan  Pham Quy Nhan  Håkan Rosqvist  Gunnar Jacks  Emma Sigvardsson  David Baric  Johanna Moreskog  Peter Harms-Ringdahl  Nguyen Van Hoan 《Applied Geochemistry》2008

  相似文献   

REDD+ politics in the media: a case from Nepal     

Dil B. Khatri  Thuy Thu Pham  Monica Di Gregorio  Rahul Karki  Naya S. Paudel  Maria Brockhaus  Ramesh Bhushal 《Climatic change》2016,138(1-2):309-323

  相似文献   

The Sin Quyen Cu–Fe–Au–REE deposit (northern Vietnam): composition and formation conditions     

I.V. Gas’kov  Tran Tuan Anh  Tran Trong Hoa  Pham Thi Dung  P.A. Nevol’ko  Pham Ngoc Can 《Russian Geology and Geophysics》2012,53(5):442-456

The Sin Quyen Cu–Fe–Au–REE deposit is localized in the Proterozoic deposits of the Phan Xi Pang zone, northern Vietnam. The mineralization is formed by lenticular and sheet-like bodies occurring concordantly with the host rocks. Seventeen orebodies have been recognized in the deposit, which form an ore horizon up to 140 m in total thickness, about 2 km in strike, and up to 350 m in dip. The ores are of simple mineral composition: Au-rich copper and iron sulfides (chalcopyrite, pyrite, pyrrhotite) and iron oxides (magnetite, hematite). Gold and silver are distributed unevenly in the ores: Their contents vary from hundredths and tenths of ppm to 1.8 ppm. Copper sulfide ores are the main concentrator of gold and silver. All ores are characterized by high REE contents, tens and hundreds of times exceeding the element clarkes. The highest contents have been revealed for Ce and La. Orthite is the main carrier of REE. No correlation between REE and ore elements of sulfide-oxide ores has been revealed, which points to the independent formation of the mineralization. Orebodies together with the host rocks underwent metamorphism at 500–600 to 630–685 °C and 3–7 kbar. The spatial association of the mineralization with amphibolites (metamorphosed basites) and the mineral composition of ores suggest that the Sin Quyen deposit is of Cyprian volcanogenic type.  相似文献   

Three-dimensional hydrostratigraphical modelling to support evaluation of recharge and saltwater intrusion in a coastal groundwater system in Vietnam     

Vu Thanh Tam  Okke Batelaan  Tran Thanh Le  Pham Quy Nhan 《Hydrogeology Journal》2014,22(8):1749-1762

Saltwater intrusion is generally related to seawater-level rise or induced intrusion due to excessive groundwater extraction in coastal aquifers. However, the hydrogeological heterogeneity of the subsurface plays an important role in (non-)intrusion as well. Local hydrogeological conditions for recharge and saltwater intrusion are studied in a coastal groundwater system in Vietnam where geological formations exhibit highly heterogeneous lithologies. A three-dimensional (3D) hydrostratigraphical solid model of the study area is constructed by way of a recursive classification procedure. The procedure includes a cluster analysis which uses as parameters geological formation, lithological composition, distribution depth and thickness of each lithologically distinctive drilling interval of 47 boreholes, to distinguish and map well-log intervals of similar lithological properties in different geological formations. A 3D hydrostratigraphical fence diagram is then generated from the constructed solid model and is used as a tool to evaluate recharge paths and saltwater intrusion to the groundwater system. Groundwater level and chemistry, and geophysical direct current (DC) resistivity measurements, are used to support the hydrostratigraphical model. Results of this research contribute to the explanation of why the aquifer system of the study area is almost uninfluenced by saltwater intrusion, which is otherwise relatively common in coastal aquifers of Vietnam.  相似文献   

Public perception of climate change and disaster preparedness: Evidence from the Philippines     

Vincenzo Bollettino  Tilly Alcayna-Stevens  Manasi Sharma  Philip Dy  Phuong Pham  Patrick Vinck 《Chemie der Erde / Geochemistry》2010

The Philippines is highly susceptible to both geophysical and climate-related disasters. This article explores Filipinos knowledge and perception of climate change and their association with what action Filipinos take to prepare for rapid onset natural hazards such as typhoons. Data for this study were collected from a nationally representative random survey of 5,184 adults conducted between March and April of 2017. Filipinos self-report relatively low levels of knowledge of climate change and cited increased temperatures, shifts in seasons, and heavier rains as the most likely consequences. Levels of disaster preparedness in the Philippines differ widely by region. Although most Filipinos perceive that natural hazards are a risk to them, only a third of Filipinos undertake measures to prepare for disasters. Filipinos who perceive climate-related changes directly impacting their households report taking greater action to prepare for disasters. Filipinos who believe they have been directly impacted by climate-related changes are also more likely to prepare for disasters, take planning actions, and undertake material actions to prepare, such as dwelling improvements. Other factors associated with disaster preparedness include gender, membership in an association, wealth, risk perception, and prior exposure to and losses due to disasters. The findings imply that, while posing different challenges and requiring different responses, adaptation to climate change and disaster preparedness are inherently associated and potentially mutually reinforcing. Policies and programs would arguably benefit from a more unified intervention framework that links climate change adaptation and disaster preparedness.  相似文献   

Predicting soil erosion hazard in Lattakia Governorate(W Syria)   总被引：1，自引：0，他引：1  

Mohammed Safwan  Khallouf Alaa  Alshiehabi Omran  Bao Pham Quoc  Thi Thuy Linh Nguyen  Nam Thai Van  Tran Anh Duong  Harsányi Endre 《国际泥沙研究》2021,36(2):207-220

The main objective of this study is to predict soil erosion in the Lattakia Governorate(WSyria)using the Water Erosion Prediction Project model(WEPP)and to compare the result with that of the RUSLE.Field survey and data collection were carried out,and 44 soil samples were analyzed.In addition,all the necessary input files were prepared for use in the WEPP model and RUSLE.Results show that more than of 80%of the locations studied experience slight to moderate erosion(less than 5 t/ha/y),whereas the rest of the locations experience severe soil erosion hazard.Moreover,the volume of runoff estimated by the WEPP model is in the range of 51e321 mm,and the R^2 between the simulated soil erosion and the predicted runoff reached 0.68.Interestingly,the R^2 between the WEPP model and RUSLE is 0.56,which indicates a good correlation between the two models.  相似文献   

Influence of phosphate on the oxidation kinetics of nanomolar Fe(II) in aqueous solution at circumneutral pH     

Yanpeng Mao  A. Ninh Pham  T. David Waite 《Geochimica et cosmochimica acta》2011,75(16):4601-4610

The oxygenation kinetics of nanomolar concentrations of Fe(II) in aqueous solution have been studied in the absence and presence of millimolar concentrations of phosphate over the pH range 6.0-7.8. At each phosphate concentration investigated, the overall oxidation rate constant varied linearly with pH, and increased with increasing phosphate concentration. A model based on equilibrium speciation of Fe(II) was found to satisfactorily explain the results obtained. From this model, the rate constants for oxygenation of the Fe(II)-phosphate species FeH₂PO₄⁺, FeHPO₄ and FePO₄⁻ have been determined for the first time. FePO₄⁻ was found to be the most kinetically reactive species at circumneutral pH with an estimated oxygenation rate constant of (2.2 ± 0.2) × 10 M⁻¹ s⁻¹. FeH₂PO₄⁺ and FeHPO₄ were found to be less reactive with oxygen, with rate constants of (3.2 ± 2) × 10⁻² M⁻¹ s⁻¹ and (1.2 ± 0.8) × 10⁻¹ M⁻¹ s⁻¹, respectively.  相似文献   

Geochemistry of surface waters in the vicinity of open pit mines at the Cay Cham deposit, Thai Nguyen province, northern Vietnam     

Pham Tich Xuan  Nguyen Van Pho  O. L. Gas’kova  S. B. Bortnikova 《Geochemistry International》2013,51(11):931-938

This study provides an assessment of the environmental impact of open pit mining operations at the Cay Cham titanomagnetite-ilmenite deposit (northern Vietnam). The results of surface water sampling indicate the formation of acid mine drainage and contamination of adjacent areas by heavy metals (Cu, Zn, Ni, and Mn). The acid mine drainage is produced by oxidation leaching of sulfide minerals associated with primary mineralization owing to the low neutralization potential of the natural waters in the humid environment of tropical rainforest. The study showed that alternating dry and wet seasons typical of this climatic region promote the generation of stored acidity leading to a sharp decrease in pH of drainage water during the wet season and result in the negative impacts of this mine on both flowing and stagnant surface waters.  相似文献