Effects of Social Learning on Rural Farmers’ Adaptive Capacity: Empirical Insights from the Vietnamese Mekong Delta     

Thong Anh Tran  Helen James  Dang Kieu Nhan 《社会与自然资源》2020,33(9):1053-1072

Abstract

Environmental challenges in the Vietnamese Mekong Delta characterized by adverse impacts of climate change, upstream hydropower development and localized dyke expansion present imperatives for rural farmers to “learn to adapt.” However, little is known about how learning contributes to improving their capacity in adapting to these “wicked” problems. This study investigates potential effects of farmers’ learning on their adaptive capacity, utilizing nine focus group discussions, 33 interviews, and a structured survey of 300 farmers. The exploratory factor analysis produced two factors for social learning: (1) learning through social interactions and (2) self-reflection, and one factor for adaptive capacity. The regression results show that the social learning factors have significantly positive effects on adaptive capacity. Farmers with a higher level of social learning are likely to demonstrate higher adaptive capacity. The findings call for policy considerations to promote learning in a broader context of the delta to enhance local capacity.  相似文献   

Simulating the effects of induced anisotropy on liquefaction potential using a new constitutive model     

H. Than Trong Tran  H. Wong  Ph. Dubujet  T. Doanh 《国际地质力学数值与分析法杂志》2014,38(10):1013-1035

The effects of induced anisotropy on the undrained behaviour of very loose and saturated sands have been a subject of intensive investigation, both experimentally and theoretically, by several authors in the past few years. This paper proposes an original constitutive model well‐adapted to simulate the behaviour of sands subject to complex stress histories, in particular, the preloading cycle along the classical drained stress path in compression. The developed model belongs to the family of critical state models. Its construction is based on a few theoretical concepts taken from the theory of ‘Bounding Surface Plasticity’ developed among others by Y. Dafalias and Popov (1975), the ‘Clay And Sand Model’ (CASM) of H. Yu (2006), the CJS model (B. Cambou and K. Jafari (1988)) and the hyperelastic isotropic model of P. Lade (1987). To accurately simulate volume changes, which represent a key element in soil behaviour, a state‐dependent dilatancy rule is proposed, which can account for the influences of stress and void ratio. The current void ratio depends implicitly on the irreversible strains already accumulated hence the strain history. A kinematic hardening is combined with an isotropic hardening, involving rotation and distortion of the bounding surface, in order to capture correctly the experimental observations. Comparisons of experimental results to numerical simulations show that the model is able to simulate with a good precision the major trends of undrained responses of loose and presheared sands. It predicts correctly rapid static liquefaction at small or null drained preloading, as well as the progressive transition to a completely stable behaviour typical of dense sands, while the sample is loose in reality. At intermediate to large amplitudes of preloadings, the model also predicts correctly the temporary stage of instability when the deviatoric stress decreases slightly before rising up again. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Investigations on meteorological conditions for elevated PM2.5 in Fairbanks,Alaska     

Huy N.Q. Tran  Nicole Mölders 《Atmospheric Research》2011,99(1):39-49

The relationships between meteorological conditions (temperature, wind-speed and direction, relative humidity, surface-inversion depth and strength, and stability) and PM_2.5 concentrations in Fairbanks, Alaska were investigated using ten years of observational data. The results show that during wintertime (November through February) PM_2.5 concentrations exceeding the 24 h National Air Quality Standard (35 μg/m³) occurred under calm wind, extremely low temperature (≤20 °C) and moisture (water-vapor pressure < 2 hPa) multiday surface-inversion conditions that trap the pollutants in the breathing level and inhibit transport of polluted air out of Fairbanks. PM_2.5 concentrations tend to be higher under stable than other conditions, but are not sensitive to the degree of stability. The presence of a surface inversion and calm wind are necessary, but in combination with low temperatures and humidity, the conditions are sufficient for high PM_2.5 concentrations. The low temperatures are required because they lead to increased emission rates from domestic heating and power production. During multiday inversions with temperatures above ? 20 °C, high relative humidity (> 75%) partly caused by water-vapor emission reduces PM_2.5 concentrations.  相似文献   

Relationship between valve activity, microalgae concentration in the water and toxin accumulation in the digestive gland of the Pacific oyster Crassostrea gigas exposed to Alexandrium minutum     

Haberkorn H  Tran D  Massabuau JC  Ciret P  Savar V  Soudant P 《Marine pollution bulletin》2011,62(6):1191-1197

The complexity of the relationships between Alexandrium minutum (A.m.) concentration in the water ([A.m.]_w), Paralytic Shellfish Poisoning contamination in the digestive gland ([PSP]_dg) and valve behavior was explored in oysters Crassostrea gigas. Two experiments were conducted, during which oysters’ valve behaviour were analyzed. Oysters, first acclimated for 10-days with the non harmful microalgae Heterocapsa triquetra (H.t.), were exposed to four microalgae mixtures at constant total concentrations of 10 × 10³ cells ml⁻¹ (experiment-1) and 5 × 10³ cells ml⁻¹ (experiment-2): 100% A.m.; 50% A.m.-50% H.t.; 25% A.m.-75% H.t.; 100% H.t. At the end of experiment-2, [PSP]_dg were measured.At 10 × 10³ cells ml⁻¹, the microalgal ingestion decreased (p < 0.05) with increasing [A.m.]_w but not at 5 × 10³ cells ml⁻¹ (p > 0.05). The frequency of microclosures specifically increased with [A.m.]_w (p < 0.05) and the opening duration with [PSP]_dg (p < 0.0001). Oysters exhibiting the maximum increase in opening duration also exhibited the highest [PSP]_dg. The results are discussed in terms of oyster physiology and origin of the behavioral response.  相似文献   

Early Mesozoic lamprophyres in Gorny Altai: petrology and age boundaries     

E.A. Vasyukova  A.E. Izokh  A.S. Borisenko  G.G. Pavlova  V.P. Sukhorukov  Tran Tuan Anh 《Russian Geology and Geophysics》2011,52(12):1574-1591

The Mesozoic Chuya dike complex was recognized by R.V. Obolenskaya based on the similar mineral composition of dikes and their age characteristics. Lamprophyres occur along the large Terekta–Tolbonur and Kurai–Kobda shear zones. The Chuya complex was studied by the example of two areas, South Chuya and Yustyd, with different levels of erosional truncation. The dikes of the first area are localized in the South Chuya Ridge, where they cut Cambrian–Ordovician metamorphic rocks, and the dikes of the Yustyd area occur in the Devonian terrigenous blackshale deposits of the Yustyd trough. The dikes of these areas differ in structures, textures, the degree of carbonatization, and mineral composition. The performed studies of rocks and minerals confirmed that the dikes of both areas belong to the same complex. They helped to establish the regularities of the lithologic composition of the entire complex and its local areas and to substantiate the recognition of areas not only from their geologic position but also by the composition, structures, and textures of rocks and their mineral composition. Geochronological data show two stages of the complex formation: 236–234 and 250–242 Ma. The results of studies also demonstrate that the lamprophyres and coeval syenites of the Tarkhata massif are fractionates of the same parental melt and can be united into a hypabyssal-plutonic complex. Comparison with other Permo-Triassic lamprophyre complexes showed that the wide variations of the composition of the Chuya rocks and its trend as well as the geochemical anomalies are specific features of complexes of high-K lamprophyres.  相似文献   

Thermochronology of the PoSen complex,northern Vietnam: Implications for tectonic evolution in SE Asia     

Pei-Ling Wang  Ching-Hua Lo  Ching-Ying Lan  Sun-Lin Chung  Tung-Yi Lee  Tran Ngoc Nam  Yuji Sano 《Journal of Asian Earth Sciences》2011,40(5):1044-1055

The PoSen complex, located closely adjacent to the southwestern margin of the Red River shear zone represents the uplifted basement of north Vietnam and may record the motion of the shear zone. However, its thermochronological history has not been fully examined yet. Here we applied U–Pb and ⁴⁰Ar/³⁹Ar dating methods to reveal its thermochronological history. U–Pb analysis of composite zircon grains by TIMS yielded an average age of 760 ± 25 Ma, clustering on the concordia line. Twelve SHRIMP U–Pb analyses also yielded a consistent result of 751 ± 7 Ma. Along with the geochemical features, the U–Pb dating results suggest the PoSen complex was a late Proterozoic magmatic complex, which could correspond to the Chengjiang orogeny, a widespread thermal event in southwest China. Results of ⁴⁰Ar/³⁹Ar dating of micas and K-feldspars were in the range of 36–30 Ma, revealing a rapid cooling and exhumation history of the PoSen complex during the late Paleogene. The time span of cooling and exhumation of the PoSen complex is slightly older than the main cooling phases of the Ailao Shan–Red River (ASRR) metamorphic massifs (28–17 Ma), but is synchronous with the early igneous activity stage in the eastern Indo-Asian collision zone of southeast China and north Vietnam. Owing to the ongoing debate about the initiation and offset of the ASRR shear zone, the tectonic force for the late Paleogene cooling of the PoSen complex is still inconclusive. The rapid exhumation of the PoSen complex could be in response to either the detachment of the Neo-Tethyan slab or a transpressional phase of continental subduction along the ASRR shear system in the eastern Indo-Asian collision zone.  相似文献   

Spatial smoothing and minimum variance beamforming on data fromlarge aperture vertical line arrays     

Tran  J.-M.Q.D. Hodgkiss  W.S. 《Oceanic Engineering, IEEE Journal of》1993,18(1):15-24

Various approaches to the beamforming of data from large aperture vertical line arrays are investigated. Attention is focused on the conventional beamforming problem where the angular power spectrum is estimated, in this case by the adaptive minimum variance processor. The data to be processed are 200 Hz CW transmissions collected at sea by a 900 m vertical line array with 120 equally spaced sensors. Correlated multipath arrivals result in signal cancellation for the adaptive processor, and spatial smoothing techniques must be used prior to beamforming. The processing of subapertures is proposed. Full aperture and subaperture processing techniques are used on the 200 Hz data. Multipath arrivals are found to illuminate only parts of the array, thus indicating that the wavefield can be highly inhomogeneous with depth  相似文献   

Three-dimensional,time-dependent modeling of rainfall-induced landslides over a digital landscape: a case study     

The Viet Tran  Massimiliano Alvioli  Giha Lee  Hyun Uk An 《Landslides》2018,15(6):1071-1084

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Using SARAL/AltiKa to Improve Ka-band Altimeter Measurements for Coastal Zones,Hydrology and Ice: The PEACHI Prototype     

G. Valladeau  P. Thibaut  B. Picard  J. C. Poisson  N. Tran  N. Picot 《Marine Geodesy》2015,38(3):124-142

Following the successful launch of the SARAL space mission in February 2013, the reliability of the innovative AltiKa altimeter has been demonstrated for deep ocean applications, where Ka-band performances are excellent. With the objective to ensure the complementarity but also the continuity with the altimeter Level-2 products provided in the open ocean, the Prototype for Expertise on AltiKa for Coastal, Hydrology and Ice (PEACHI) project has been set up as an initiative of the French space agency, CNES, to provide a data set of research-grade Level-2 parameters that might be interesting for SARAL secondary objectives on the study of coastal dynamics, inland waters, polar oceans, or continental and sea ices. Thus, the PEACHI prototype has been developed to process and accurately tune dedicated algorithms for the assessment of Ka-band parameters, from the instrument processing to geophysical corrections. As a result, the PEACHI prototype routinely provides end users with new or improved altimeter corrections for scientific applications dedicated to mesoscale monitoring but also synergistic science.  相似文献   

Climatic hazards,health risk and response in Vietnam: Case studies on social dimensions of vulnerability     

Roger Few  Pham Gia Tran 《Global Environmental Change》2010,20(3):529-538

Vietnam is highly prone to climatic hazards, including extreme weather events and marked seasonal changes. Climatic hazards have wide-ranging implications for human health, but in most hazard-prone countries there has been little household level research on health risks. Drawing on the results of exploratory research in low-income communities in the Central Provinces and the Mekong Delta, this paper uses a qualitative approach to examine how the social dimensions of vulnerability can come into play in the generation of health outcomes associated with hazards. It explores particularly how aspects of economic livelihood, physical location, education and protective behaviour combined to influence the exposure and susceptibility of households, as well as to shape their capability to avoid adverse health impacts. These aspects were closely linked with, but not solely determined by, income-poverty: underlining the argument that understanding of risks to health in low-income settings requires careful analysis of this complex shaping of vulnerability. It also requires recognition that health protection for the poor may be articulated more in terms of protection of wider livelihood assets than preventive health actions per se.  相似文献