Improved land tenure not the driver of economic development in a Vietnamese community     

Christian M. S. Knudsen  Ole Mertz 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2016,116(1):82-84

During the restructuring of the Vietnamese economy in 1986, the Communist party of Vietnam (CPV) took the decision to leave central planning and build a market economy in Vietnam. In order to promote rural development and deal with deforestation, poverty and declining agricultural profitability, the government implemented the forestland allocation policies (FLA) and started a process of decentralization. This research note examines the impact of FLA policies on the agricultural practices of an upland community in central Vietnam and discusses the effects of increased tenure security. It is shown that the promotion of a sedentary production system has altered the sustainability of swidden agriculture leading to declining profitability and that a transition towards new crops and specialized crop cultivation has compensated for the loss. Furthermore, it is argued that the FLA policies have increased the villagers’ incentive to invest, their access to credit and the forest area of the village, but that the CPV has been the main driver of these changes rather than the increased tenure security.  相似文献   

Strong gravitational lensing by spiral galaxies     

Ole Mo¨ller  & A. W. Blain 《Monthly notices of the Royal Astronomical Society》1998,299(3):845-850

We investigate gravitational lensing using a realistic model of disc galaxies. Most of the mass is contained in a large spherical isothermal dark matter halo, but the potential is modified significantly in the core by a gravitationally dominant exponential disc. The method used is adapted from a very general multilens ray-tracing technique developed by Mo¨ller. We investigate the effects of the disc-to-halo mass ratio, the disc scalelength, the disc inclination to the line of sight and the lens redshift on two strong-lensing cross-sections: the cross-section for multiple imaging and the cross-section for large magnifications, in excess of a factor of 10. We find that the multiple-imaging cross-section can be enhanced significantly by an almost edge-on Milky Way disc compared with a singular isothermal sphere (SIS) in individual cases; however, when averaged over all disc inclinations, the cross-section is only increased by about 50 per cent. These results are consistent with other recent work. The presence of a disc, however, increases the inclination-averaged high-magnification cross-section by an order of magnitude compared with a SIS. This result has important implications for magnification bias in future lens surveys, particularly those in the submillimetre waveband, where dust extinction in the lensing galaxy has no effect on the brightness of the images.  相似文献   

IAG Newsletter     

Ole Baltazar Andersen 《Journal of Geodesy》1998,72(6):364-371

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Reactions of Cl Atoms with Selected VOCs: Kinetics, Products and Mechanisms   总被引：1，自引：0，他引：1  

Gaia Fantechi  Niels R. Jensen  Ole Saastad  Jens Hjorth  Jozef Peeters 《Journal of Atmospheric Chemistry》1998,31(3):247-267

The reactions of isoprene, MBO (2-methyl-3-buten-2-ol) and toluene with chlorine atoms have been studied at 298 ± 5 K and 740 ± 5 Torr with the use of FTIR spectroscopy. Major products of the isoprene-Cl reaction and of the MBO-Cl reaction have been identified and quantified, and reaction mechanisms have been tentatively proposed in order to explain the products formed. The reaction between isoprene and Cl atoms yields mainly HCl, formyl chloride, formic acid, methylglyoxal (pyruvic aldehyde), CO and CO2, while the MBO-Cl reaction forms acetone, HCl, formyl chloride, formic acid, CO, CO2. As products from the reaction between toluene and Cl we identified and quantified HCl and benzaldehyde. The rate constants for the reactions of isoprene and toluene with Cl atoms have also been determined using a relative rate method. The measured values are: kisoprene = (5.5 ± 1.0) × 10–10 cm3 molecule–1 s–1 and ktoluene = (5.6 ± 1.3) × 10–11 cm3 molecule–1 s–1. Atmospheric lifetimes have been estimated from these values.  相似文献   

Effect of grain scale alignment on seismic anisotropy and reflectivity of shales   总被引：1，自引：0，他引：1  

Tor Arne Johansen  Bent Ole Ruud  Morten Jakobsen 《Geophysical Prospecting》2004,52(2):133-149

The elastic properties and anisotropy of shales are strongly influenced by the degree of alignment of the grain scale texture. In general, an orientation distribution function (ODF) can be used to describe this alignment, which, in practice, can be characterized by two Legendre coefficients. We discuss various statistical ODFs that define the alignment by spreading from a mean value; in particular, the Gaussian, Fisher and Bingham distributions. We compare the statistical models with an ODF resulting from pure vertical compaction (no shear strain) of a sediment. The compaction ODF may be used to estimate how the elastic properties and anisotropy evolve due to burial of clayey sediments. Our study shows that the three statistical ODFs produce almost identical correspondence between the two Legendre coefficients as a function of the spreading parameter, so that the spreading parameter of one ODF can be converted to the spreading parameter of another ODF. In most cases it is then sufficient to apply the spreading parameter for the ODF instead of the two Legendre coefficients. The effect of compaction on the ODF gives a slightly different correspondence between the two Legendre coefficients from that for the other models. In principle, this opens up the possibility of distinguishing anisotropy effects due to compaction from those due to other processes. We also study reflection amplitudes versus angle of incidence (AVA) for all wave modes, where shales having various ODFs overlie an isotropic medium. The AVA responses are modelled using both exact and approximation formulae, and their intercepts and gradients are compared. The modelling shows that the S‐wave velocity is sensitive to any perturbation in the spreading parameter, while the P‐wave velocity becomes increasingly sensitive to a perturbation of a less ordered system. Similar observations are found for the AVA of the P‐P and P‐SV waves. Modelling indicates that a combined use of the amplitude versus offset of P‐P and P‐SV reflected waves may reveal certain grain scale alignment properties of shale‐like rocks.  相似文献   

Impact of technological creep on fishing effort and fishing mortality, for a selection of European fleets     

Marchal  Paul; Andersen  Bo; Caillart  B.; Eigaard  Ole; Guyader  Olivier; Hovgaard  Holger; Iriondo  Ane; Le Fur  Fanny; Sacchi  Jacques; Santurtun  Marina 《ICES Journal of Marine Science》2007,64(1):192-209

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Cod in fjords and coastal waters of North Norway: distribution and variation in length and maturity at age   总被引：1，自引：3，他引：1  

Berg  Erik; Albert  Ole Thomas 《ICES Journal of Marine Science》2003,60(4):787-797

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Improved mapping of schooling fish near the surface: comparison of abundance estimates obtained by sonar and echo integration     

Misund  Ole Arve; Aglen  Asgeir; Hamre  Johannes; Ona  Egil; Rottingen  Ingolf; Skagen  Dankert; Valdemarsen  John Willy 《ICES Journal of Marine Science》1996,53(2):383-388

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Relationships between the geometric dimensions and biomass of schools   总被引：1，自引：1，他引：1  

Misund  Ole Arve; Aglen  Asgeir; Beltestad  Arvid K.; Dalen  John 《ICES Journal of Marine Science》1992,49(3):305-315

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Seabed shear stress and bedload transport due to asymmetric and skewed waves   总被引：1，自引：0，他引：1  

David Gonzalez-Rodriguez  Ole Secher Madsen   《Coastal Engineering》2007,54(12):914-929

A simple conceptual formulation to compute seabed shear stress due to asymmetric and skewed waves is presented. This formulation generalizes the sinusoidal wave case and uses a variable friction factor to describe the physics of the boundary layer and to parameterize the effects of wave shape. Predictions of bed shear stresses agree with numerical computations using a standard boundary layer model with a k–ε turbulence closure. The bed shear stress formulation is combined with a Meyer-Peter and Müller-type formula to predict sheet flow bedload transport under asymmetric and skewed waves for a horizontal or sloping bed. The predictions agree with oscillatory water tunnel measurements from the literature.  相似文献