A Semi-Evolutive Partially Local Filter for Data Assimilation     

Ibrahim Hoteit  Dinh-Tuan Pham  Jacques Blum 《Marine pollution bulletin》2001,43(7-12):164-174

The singular evolutive extended Kalman (SEEK) filter has been proposed recently by Pham et al. (1997) for data assimilation into numerical oceanic models. This filter has been applied in different realistic ocean frameworks and has provided satisfactory results ( Pham et al., 1997; Verron et al., 1998). However, the SEEK filter remains expensive in real operational assimilation. To reduce cost and obtain a better representativity, we introduce the idea ‘local correction basis'. Such basis however cannot be made to evolve according to the model without destroying its locality property. Therefore we shall keep this basis fixed and we augment it by a few global basis vectors which evolve. The resulting semi-evolutive partially local filter is much less costly to implement than the SEEK filter and yet can yield better results. In the first application, validation twin experiments are conducted in a realistic setting of the OPA model over the tropical Pacific Ocean.  相似文献   

Crustal anatexis and formation of two types of granitic magmas in the Kontum massif, central Vietnam: Implications for magma processes in collision zones   总被引：1，自引：0，他引：1  

M. Owada  Y. Osanai  N. Nakano  T. Matsushita  Tran Ngoc Nam  T. Tsunogae  T. Toyoshima  Pham Binh  H. Kagami 《Gondwana Research》2007,12(4):428-437

Asia grew in the Late Permian by the collision of a number of micro-continents. Syn- to post-collisional magmatism occurred along the continental collision zones . In this study, we report two types of granitic rocks, garnet granite (Grt granite) and orthopyroxene granite (Opx granite), from the Kontum massif, central Vietnam, which is situated on the continental collision zone between the South China and Indochina cratons. These granitic rocks were formed at ca. 250 Ma when high-temperature (HT) and ultrahigh-temperature (UHT) metamorphism took place in the same zone. Based on the petrological and geochemical features compared with previously reported experimental results, garnet-bearing granite is derived from pelitic gneisses by partial melting, whereas orthopyroxene-bearing granite is produced by the partial melting of garnet-bearing mafic granulites. We inferred that a significantly high-geothermal gradient is required to produce Vietnamese granitic magmatism and related HT to UHT metamorphism. This geotherm may be attributed to upwelling mantle plume beneath the Kontum massif during the Late Permian.  相似文献   

Sources of anomalous transient electric signals (ATESs) in the ULF band in the Lamia region (central Greece): electrochemical mechanisms for their generation   总被引：1，自引：0，他引：1  

V. -N. Pham  D. Boyer  G. Chouliaras  A. Savvaidis  G. Stavrakakis  J. -L. Le Mouël 《Physics of the Earth and Planetary Interiors》2002,130(3-4):209-233

Anomalous transient electric signals (ATESs) in the ultra low frequency (ULF) band have been often observed during magnetotelluric (MT) investigations [Nature 319 (1986) 310; Phys. Earth Planet. Int. 114 (1999) 141; Geophys. J. Int. 142 (2000) 948], but their origin was unknown until now. They have the same characteristics as the so-called seismic electric signals (SES) claimed to be earthquake precursors by the VAN group (e.g. [Tectonophysics 110 (1984) 73] and later works by this group). Our analysis suggests that the so-called SES could be of anthropic origin. Following the devastating 7 September 1999 Athens earthquake, the VAN group claimed that a SES had been recorded at LAM station (Lamia, central Greece) some days prior to the main shock and that a second SES, which might correspond to an impending even larger earthquake, had been observed after the main shock. In the 2 years after the Athens main shock, no subsequent large earthquakes have occurred near Athens. We conducted a campaign of measurement in the Lamia region in May and June 2001. The results show that ATESs, which look like SES, have several different sources: pump-stations for ground-water, high power electric lines, and factories located to the SE of Lamia city. The ATESs can be generated by two electrochemical mechanisms of metallic electrode polarization: the “galvanic cell” and the “ac electrolytic cell” which are studied by simulated field experiments and discussed in detail in Appendix A. These two mechanisms can occur over a wide range of length scales in the field. Any isolation failure in buried metallic conductors, such as electrical and telecommunication networks, oil, water and gas pipes, railways, high power electric lines, factories and so on, can produce a galvanic cell or an ac electrolytic cell, or both, which could generate, under some circumstances, an “overvoltage”, the ATES. Finally, the absence of a magnetic signal has been observed during ATES and does not constitute a firm criterion for SES [Acta Geophys. Pol. 44 (1996b) 301]. Thus, great care must be taken when claiming the existence of electric precursors of seismic or volcanic events.  相似文献   

Mapping and surveillance of active fissure zones on a volcano by the self-potential method, Etna, Sicily     

F. Massenet  Pham Van Ngoc 《Journal of Volcanology and Geothermal Research》1985,24(3-4)

The self-potential (S.P.) method, often employed in base-metal exploration, has successfully been applied to volcanological problems.Test surveys on the site of Mount Etna (Sicily) have revealed some positive anomalies as high as a few hundred millivolts over recent and old eruptive fissures. The S.P. technique allows one to determine the precise location of the fissures.The interpretation of the geophysical results (including S.P.), taking into account the structure of Mount Etna, has shown two important zones upon which several S.P. investigations have been carried out.Studies of the causes of these S.P. anomalies have shown the importance of the streaming potential as the principal source mechanism.  相似文献   

Viscous behaviour of dry sand     

D. Pham Van Bang  H. Di Benedetto  A. Duttine  A. Ezaoui 《国际地质力学数值与分析法杂志》2007,31(15):1631-1658

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An Improved Formula of Fundamental Resonance Frequency of a Layered Half-Space Model Used in H/V Ratio Technique     

Tran Thanh Tuan  Pham Chi Vinh  Matthias Ohrnberger  Peter Malischewsky  Abdelkrim Aoudia 《Pure and Applied Geophysics》2016,173(8):2803-2812

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Steel buckling‐restrained braced frames with single and dual corner gusset connections: seismic tests and analyses     

Chung‐Che Chou  Jia‐Hau Liu  Dinh‐Hai Pham 《地震工程与结构动力学》2012,41(7):1137-1156

The design of a three‐story buckling‐restrained braced frame (BRBF) with a single‐diagonal sandwiched BRB and corner gusset was evaluated in cyclic tests of a one‐story, one‐bay BRBF subassembly and dynamic analyses of the frame subjected to earthquakes. The test focused on evaluating (1) the seismic performance of a sandwiched BRB installed in a frame, (2) the effects of free‐edge stiffeners and dual gusset configurations on the corner gusset behavior, (3) the frame and brace action forces in the corner gusset, and (4) the failure mode of the BRBF under the maximum considerable earthquake level. The subassembly frame performed well up to a drift of 2.5% with a maximum axial strain of 1.7% in the BRB. Without free‐edge stiffeners, the single corner gusset plate buckled at a significantly lower strength than that predicted by the specificationof American Institute of Steel Construction (2005). The buckling could be eliminated by using dual corner gusset plates similar in size to the single gusset plate. At low drifts, the frame action force on the corner gusset was of the same magnitude as the brace force. At high drifts, however, the frame action force significantly increased and caused weld fractures at column‐to‐gusset edges. Nonlinear time history analyses were performed on the three‐story BRBF to obtain seismic demands under both design and maximum considerable levels of earthquake loading. The analytical results confirmed that the BRB and corner gusset plate achieved peak drift under cyclic loading test. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Evaluation of Two Low‐Cost–High‐Performance Adsorbent Materials in the Waste‐to‐Product Approach for the Removal of Pesticides from Drinking Water     

Pham Thi Thuy  Nguyen Viet Anh  Bart van der Bruggen 《洁净——土壤、空气、水》2012,40(3):246-253

This study evaluates the performance of two low cost and high performance adsorption materials, i.e., activated carbon produced from two natural waste products: Bamboo and coconut shell, in the removal of three pesticides from drinking water sources. Due to the fact that bamboo and coconut shell are abundant and inexpensive materials in many parts of the world, they respond to the “low‐cost” aspect. The adsorption capacities of two local adsorbents have been compared with commercial activated carbon to explore their potential to respond to the “high quality” aspect. Two pesticides were selected, namely dieldrin and chlorpyrifos, because they are commonly used in agriculture activities, and may remain in high concentrations in surface water used as drinking water sources. The results indicate that the adsorption of pesticides on activated carbons is influenced by physico‐chemical properties of the activated carbon and the pesticides such as the presence of an aromatic ring, and their molar mass. The activated carbon produced from bamboo can be employed as low‐cost and high performance adsorbent, alternative to commercial activated carbon for the removal of pesticides during drinking water production. The performance of activated carbon from bamboo was better due to its relatively large macroporosity and planar surface. The effect of adsorbent and pesticide characteristics on the performance was derived from batch experiments in which the adsorption behavior was studied on the basis of Freundlich isotherms.  相似文献   

Cs baseline levels in the Mediterranean and Black Sea: A cross-basin survey of the CIESM Mediterranean Mussel Watch programme     

Herv Thbault  Alessia M. Rodriguez y Baena  Bruno Andral  Delko Barisic  Jos Benedicto Albaladejo  Alexandru S. Bologa  Redouane Boudjenoun  Roberta Delfanti  Victor N. Egorov  Tahar El Khoukhi  Heleni Florou  Goran Kniewald  Abdelkader Noureddine  Vasile Patrascu  Mai Khanh Pham  Alfonso Scarpato  Nikolay A. Stokozov  Sayhan Topcuoglu  Michel Warnau 《Marine pollution bulletin》2008,57(6-12):801

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify ¹³⁷Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured ¹³⁷Cs levels were found to be very low (usually <1 Bq kg⁻¹ wet wt) ¹³⁷Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.  相似文献   

Modeling complex aquifer systems: a case study in Baton Rouge,Louisiana (USA)     

Pham  Hai V.  Tsai  Frank T.-C. 《Hydrogeology Journal》2017,25(3):601-615

Hydrogeology Journal - This study targets two challenges in groundwater model development: grid generation and model calibration for aquifer systems that are fluvial in origin. Realistic...  相似文献