Determination of the complex refractive indices of Titan haze analogs using photothermal deflection spectroscopy     

Véronique Vuitton  Buu N. Tran  James P. Ferris 《Icarus》2009,203(2):663-671

The spectrometers of the Cassini mission to the Saturn system have detected haze layers reaching up to 800 km in Titan’s atmosphere. Knowledge of the complex refractive index (k) of the haze is important for modeling the surface and atmosphere of Titan and retrieving some information about the functional groups present in the aerosols. Plasma discharges or ultraviolet radiation are commonly used to drive the formation of solid organics assumed to be good analogs of the Titan aerosols. [Tran, B.N., Ferris, J.P., Chera, J.J., 2003a. The photochemical formation of a Titan haze analog. Structural analysis by X-ray photoelectron and infrared spectroscopy. Icarus 162, 114-124; Tran, B.N., Force, M., Briggs, R., Ferris J.P., Persans, P., Chera, J.J., 2008. Photochemical processes on Titan: Irradiation of mixtures of gases that simulate Titan’s atmosphere. Icarus 177, 106-115] reported the index of refraction of analogs synthesized by far ultraviolet irradiation of various gas mixtures. k was determined in the 200-800 nm wavelength range from transmission and reflection spectroscopy. However, this technique is limited by (i) uncertainties in the absorption values because of the small amounts of organics available, (ii) light scattering by the surface roughness and particulates in the sample. These limitations prompted us to perform new measurements using photothermal deflection spectroscopy (PDS), a technique based on the conversion of absorbed light into heat in the material of interest. By combining traditional spectroscopy (λ < 500 nm) and PDS (λ > 500 nm), we determined values of k over the 375-1550 nm range. k values as low as 10⁻⁴ above 1000 nm were determined. This is one order of magnitude lower than the measurements generally used as a reference for Titan’s aerosols analogs [Khare, B.N., Sagan, C., Arakawa, E.T., Suits, F., Callicott, T.A., Williams, M.W., 1984. Optical-constants of organic Tholins produced in a simulated Titanian atmosphere—from soft-X-ray to microwave-frequencies. Icarus 60(1), 127-137]. We recommend that these results were used in models to describe the optical properties of the aerosols produced in Titan’s stratosphere.  相似文献   

Use of comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry for the characterization of biodegradation and unresolved complex mixtures in petroleum     

Tin C. Tran  Emmanuelle Grosjean  Philip J. Marriott 《Geochimica et cosmochimica acta》2010,74(22):6468-6484

A comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOFMS) method has been developed for separation of a series of petroleum samples using a polar/non-polar column set configuration. Groups of oils were selected to provide samples from the same oil family to assist in comparison of compositional changes during biodegradation. The groups also represented different sources and ages to allow an assessment of the application of GC × GC for the differentiation of oil source, as well as fluid history. The increased resolution and separation afforded by the GC × GC technique provides more complete compositional information on complex biodegraded oil samples than one-dimensional GC, and improves the ability to study biodegradation trends. Among the components identified, it is proposed that alkyl-decahydronaphthalenes constitute a significant contribution to the UCM.  相似文献   

Stanniferrous granites of Vietnam: Rb-Sr and Ar-Ar isotope age,composition, sources,and geodynamic formation conditions     

Anh  Phan Luu  Vladimirov  A. G.  Kruk  N. N.  Polyakov  G. V.  Ponomarchuk  V. A.  Hoa  Tran Trong  Phuong  Ngo Thi  Kuibida  M. L.  Annikova  I. Yu.  Pavlova  G. G.  Kiseleva  V. Yu. 《Doklady Earth Sciences》2010,432(2):839-845

Doklady Earth Sciences - Stanniferrous granite-leucogranite massifs in Vietnam to which the bedrock and placer commercial deposits of cassiterite are associated (Timtuc etc.) are of late Cretaceous...  相似文献   

ISO Spectroscopy of Ultraluminous Infrared Galaxies     

D. Lutz  R. Genzel  D. Kunze  D. Rigopoulou  H.W.W. Spoon  E. Sturm  D. Tran  A.F.M. Moorwood 《Astrophysics and Space Science》1999,266(1-2):85-90

Spectroscopy from the Infrared Space Observatory ISO has for the first timeprovided the sensitivity to exploit the diagnostic power ofmid-infrared fine structure lines and PAH features for the study ofultraluminous infrared galaxies (L_IR >10¹² L ). We report on observations obtainedwith SWS, ISOPHOT-S, and the CVF option of ISOCAM. From both fine structure lines and PAH features, we find that the majority of ULIRGs is predominantlypowered by star formation. Our total sample of about 75 ULIRGs allows tosearch for trends within the class of ULIRGs: The fraction of AGNs increaseswith luminosity above 3 × 10¹²L but there is no obvioustrend for ULIRGs to be more AGN-like with more advanced merger phase.  相似文献   

A study on the preparation of fine and low soda alumina     

Yi Yong Park  Suong Oh Lee  Tam Tran  Seong Jun Kim  Myong Jun Kim   《International Journal of Mineral Processing》2006,80(2-4):126-132

A simple process to produce fine and low soda α-alumina (α-Al₂O₃) from a commercial grade aluminium trihydroxide (gibbsite, Al(OH)₃) produced by KC Corporation Ltd was developed. There are two options for this process with the first one producing low soda α-alumina (< 0.05% Na₂O) having a mean particle size of 50 μm. The second option yields a fine product with a mean size of less than 10 μm. In the first option, a plant aluminium trihydroxide containing 0.20% Na₂O was first fluidized with nitrogen at 400–600 °C to yield an amorphous activated alumina. This intermediate product was then treated with acetic or oxalic acid, washed with water and heated to 1200 °C to form calcined α-alumina, having a Na₂O content of less than 0.05%. A 20 min leaching using 0.2 M acetic or oxalic acid could yield an alumina product containing 0.04% Na₂O. In the second option, a new technique for the preparation of fine and low soda α-alumina was evaluated using an attrition mill working also as a leaching vessel at 80 °C. Fine (< 10 μm in mean particle size) and low soda (< 0.04% Na₂O) alumina was produced by a 20 min leaching step with 0.2 M acetic acid and concurrent attrition milling.  相似文献   

Dispersion and cost analysis of some finite difference schemes in one-parameter acoustic wave modeling     

Laurent Anné  Quang Huy Tran  William W. Symes 《Computational Geosciences》1997,1(1):1-33

Given a precision threshold to be imposed on the group velocity error and a finite difference scheme for the acoustic wave equation, it is possible to determine time-step and grid-spacing in an optimal manner, i.e., so as to minimize the computational cost. Using this optimal cost as a criterion, it becomes easy to compare schemes for efficiency in homogeneous media. Heterogeneous media with constant density can be accommodated to a certain extent by minimizing the cost over a range of Courant numbers. Such analysis shows that, amongst the second-order Taylor series schemes in time, higher-order schemes are generally more efficient than lower-order schemes. However, this result does not extend to very high order schemes.  相似文献   

Predicting Blast-Induced Ground Vibration in Open-Pit Mines Using Different Nature-Inspired Optimization Algorithms and Deep Neural Network     

Nguyen  Hoang  Bui  Xuan-Nam  Tran  Quang-Hieu  Nguyen  Dinh-An  Hoa  Le Thi Thu  Le  Qui-Thao  Giang  Le Thi Huong 《Natural Resources Research》2021,30(6):4695-4717

Natural Resources Research - Blast-induced ground vibration (GV) is a hazardous phenomenon in open-pit mines, and it has unquestionable effects, such as slope instability, deformation of...  相似文献   

Polarization comparison between on-axis and off-axis dual reflector telescopes: Zemax and Grasp8 simulations     

Huan T. Tran 《New Astronomy Reviews》2003,47(11-12):1091

The cross-polarization performance for an off-axis dual reflector telescope is shown to be equivalent to an on-axis telescope when used for a large-format focal plane array. The need for low sidelobes forces the on-axis designs to high curvature, which in turn leads to high cross-polarization at the edge of the field. A scheme for correcting instrumental-polarization is presented, as well as a full design for a polarization-pure optical system capable of supporting a 1000-element focal plane array.  相似文献   

Anisotropic Time-Dependent Modeling of Tunnel Excavation in Squeezing Ground     

Huy Tran Manh  Jean Sulem  Didier Subrin  Daniel Billaux 《Rock Mechanics and Rock Engineering》2015,48(6):2301-2317

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A new species Lobophora tsengii sp. nov. (Dictyotales; Phaeophyceae) from Bach Long Vy (Bailongwei) Island,Vietnam     

Sun  Zhongmin  Dao  Minh Dong  Tran  Quoc Toan  Dam  Duc Tien 《中国海洋湖沼学报》2021,39(6):2363-2369

Journal of Oceanology and Limnology - A new species Lobophora tsengii is described from Bach Long Vy (Bailongwei) Island, Haiphong Province, Vietnam. The plants inhabit the subtidal zone and have...  相似文献