Public-space planning in four Nordic cities: Symbolic values in tension     

Merle Jacob  Tomas Hellström 《Geoforum》2010,41(4):657-665

This article takes its point of departure in the assumption that values shape planning practices and that alternatively one can reconstruct such values from the way planning interventions are argued and evaluated. We contend that planners’ discourses involve implicit value commitments that are observable in their representations of public space and implicated in the results of public-space planning. The paper builds an empirical case from representations of public space elaborated in planning documents developed by planners in four medium-sized Nordic cities. We show how these planning representations form four thematic value clusters concerning urban public space, namely leisure-play, identity-unity, power-organization and unruliness-change. Together these clusters constitute a value framework which reveals a number of central tensions relating to the way that planners seek to balance order and spontaneity in public space. The paper concludes by outlining and discussing these values and the tensions they represent.  相似文献   

Volcanoes as possible indicators of tectonic stress orientation — Aleutians and Alaska     

Kazuaki Nakamura  Klaus H. Jacob  John N. Davies 《Pure and Applied Geophysics》1977,115(1-2):87-112

A new method for obtaining from volcanic surface features the orientations of the principal tectonic stresses is applied to Aleutian and Alaskan volcanoes. The underlying concept for this method is that flank eruptions for polygenetic volcanoes can be regarded as the result of a large-scale natural magmafracturing experiment. The method essentially relies on the recognition of the preferred orientation of radial and parallel dike swarms, primarily using the distribution of monogenetic craters including flank volcanoes. Since dikes tend to propagate in a direction normal to the minimum principal stress (T-axis), the method primarily yields the direction of the maximum horizontal compression (MHC) of regional origin. The direction of the MHC may correspond to either the maximum (P-axis) or intermediate (B-axis) principal stress.The direction of MHC obtained at 20 volcanoes in the Aleutian arc coincides well with the direction of convergence between the Pacific and North American plates. This result provides evidence that in the island arc the inferred direction of MHC is parallel to the maximum principal tectonic stress. In the back-arc region, general E-W trends of MHC are obtained from seven volcanic fields on islands on the Bering Sea shelf and the mainland coast of Alaska. These volcanic fields consist mostly of clusters of monogenetic volcanoes of alkali basalt. In the back-arc region, the trends of MHC may correspond to an E-W intermediate, a vertical maximum, and a N-S minimum principal stress.Implications for the tectonics of island arcs and back-arc regions are: (1) volcanic belts of some island arcs, including the Aleutian arc, are under compressional deviatoric stress in the direction of plate convergence. It is improbable that such arcs would split along the volcanic axis to form actively spreading marginal basins. (2) This compressional stress at the arc, probably generated by underthrusting, appears to be transmitted across the entire arc structure, but is apparently replaced within several hundred kilometers by a stress system characterized by horizontal extension (tensional deviatoric stress) in the back-arc region. (3) The volcanoes associated with these two stress systems differ in type (polygenetic vs. monogenetic) and in the chemistry of their magmas (andesitic vs. basaltic). These differences and the regional differences in orientation of the principal tectonic stresses suggest that the back-arc stress system has its own source at considerable depth beneath the crust.Lamont-Doherty Geological Observatory Contribution No. 2503.  相似文献   

Monitoring coastal evolution and associated littoral hazards of French Guiana shoreline with radar images     

Hervé Trebossen  Benoît Deffontaines  Nicolas Classeau  Jacob Kouame  Jean-Paul Rudant 《Comptes Rendus Geoscience》2005,337(13):1140-1153

This paper aims at illustrating different case examples of monitoring active coastal evolutions using remote sensing synthetic aperture radar images (ERS 1–2 and Envisat) in humid tropical areas. Effectively, the radar satellite images may be acquired under most climate conditions, especially in cloudy tropical areas. As case examples, we studied herein French Guiana shoreline and its fast evolution under the combined influences of sea currents, sediments and swells. We focused on two aspects of French Guiana littoral evolution: (1) sedimentation and erosion processes linked to mud banks displacements around Kourou City, and (2) around Iracoubo village. Lastly, we compared this short-term sedimentation balance with long-term data showing the discrepancies of short- and long-term littoral evolutions on whole French Guiana. To conclude, this work demonstrates the importance of SAR imagery to provide high-quality and high-frequency update geographic information for coastal management and littoral hazards especially in such tropical humid and cloudy areas. To cite this article: H. Trebossen et al., C. R. Geoscience 337 (2005).  相似文献   

A Review and Evaluation of Specific Heat Capacities of Rocks,Minerals, and Subsurface Fluids. Part 2: Fluids and Porous Rocks     

Waples  Douglas W.  Waples  Jacob S. 《Natural Resources Research》2004,13(2):123-130

Heat capacities of solid sediments and pore fluids within a basin can influence geothermal gradients when sedimentation or erosion is rapid. This paper provides data on specific heat capacities of pore fluids and porous rocks. It includes data on specific heat capacities of water, ice, and gas hydrates at reference temperatures, as well as equations for calculating the specific heat capacity of those substances as a function of temperature. It also provides values for specific heat capacities of oil and natural gases at low temperatures, as well as equations describing the temperature and pressure dependence of the specific heat capacities of those substances. Finally, it shows how to calculate the specific heat capacity of mixtures of solid materials, or of mixtures of solids and pore fluids. The data and equations provided herein can be incorporated directly into existing modeling software by users and software developers.  相似文献   

Three-Dimensional Numerical Modeling of Steam Override Observed at a Full-Scale Remediation of an Unconfined Aquifer     

Jacob Gudbjerg  Tom Heron  Torben O. Sonnenborg  Karsten H. Jensen 《Ground Water Monitoring & Remediation》2005,25(3):116-127

  相似文献   

Black Rock by Peter Goin and Paul Starrs     

Jacob Sowers 《The Professional geographer》2006,58(4):502-503

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High Sensitivity Analysis of Trace Element-Poor Geological Reference Glasses by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS)   总被引：2，自引：0，他引：2  

Dorrit E. Jacob 《Geostandards and Geoanalytical Research》2006,30(3):221-235

Fifty-two trace elements in NIST SRM 614, 616 and MPI-DING BM90/21-G glass reference materials as well as in NIST SRM 612, USGS BCR2-G and other MPI-DING reference glasses (KL2-G, GOR132-G, GOR128-G, ATHO-G, Tl-G, StHs6/80-G and ML3B-G) were determined by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Accurate ultra-low trace element abundances in the NIST SRM 614, 616 and BM90/21-G reference glasses down to lower ng g⁻¹ levels were determined with relative standard deviations (RSD) of less than 10%. Limits of detection using He as carrier gas were up to two times lower than with Ar and were 0.004 to 0.12 μg g⁻¹ for elements of lower mass numbers (amu < 85) and 0.002 to 0.06 μg g⁻¹ for elements having amu < 85. The measured concentrations generally agree within 15% with previous studies except for B in NIST SRM 614 and 616, which appears to be heterogeneously distributed, and Co, Zn, Ga and Ag in NIST SRM 616 for which the existing data set is too small to evaluate the discrepancies. New values for As (0.593 μg g⁻¹), Ag (0.361 μg g⁻¹) and Cd (0.566 μg g⁻¹) in NIST SRM 614 and new values for Na (94864 μg g⁻¹) and As (0.276 μg g⁻¹) in NIST SRM 616 are reported.  相似文献   

Performance comparison of semicodeless GPS receivers for LEO satellites   总被引：1，自引：0，他引：1  

Oliver Montenbruck  Miquel Garcia-Fernandez  Jacob Williams 《GPS Solutions》2006,10(4):249-261

This report provides a detailed performance analysis of three semicodeless dual-frequency GPS receivers for use in low Earth orbit (LEO). The test set comprises the IGOR receiver, which represents a follow-on of the flight-proven BlackJack receiver, as well as two geodetic receivers (NovAtel OEM4-G2 and Septentrio PolaRx2), which are entirely based on commercial-off-the-shelf technology (COTS). All three receivers are considered for upcoming flight projects or experiments and have undergone at least a preliminary environmental qualification program. Using extensive signal simulator tests, the cold start signal acquisition, tracking sensitivity, differential code biases, raw measurement accuracy, and navigation accuracy of each receiver have been assessed. All tests are based on a common scenario that is representative of an actual space mission and provides a realistic simulation of the signal dynamics and quality on a scientific LEO satellite. Compared to the other receivers, the IGOR instrument exhibits a superior tracking sensitivity and is thus best suited for occultation measurements with low tangent point altitudes. The OEM4-G2 and PolaRx2 receivers are likewise shown to properly track dual-frequency GPS signals and normal signal levels and to provide accurate code and carrier phase measurements. Given their limited resource requirements, these receivers appear well suited for precise orbit determination applications and ionospheric sounding onboard of microsatellites with tight mission budgets.  相似文献   

A wide-angle seismic traverse through the Variscan of southwest Ireland     

F. Masson  A. W. B. Jacob  C. Prodehl  P. W. Readman  P. M. Shannon  A. Schulze  & U. Enderle 《Geophysical Journal International》1998,134(3):689-705

A wide-angle seismic profile across the western peninsulas of SW Ireland was performed. This region corresponds to the northernmost Variscan thrust and fold deformation. The dense set of 13 shots and 109 stations along the 120  km long profile provides a detailed velocity model of the crust.
  The seismic velocity model, obtained by forward and inverse modelling, defines a five-layer crust. A sedimentary layer, 5–8  km thick, is underlain by an upper-crustal layer of variable thickness, with a base generally at a depth of 10–12  km. Two mid-crustal layers are defined, and a lower-crustal layer below 22  km. The Moho lies at a depth of 30–32  km. A low-velocity zone, which coincides with a well-defined gravity low, is observed in the central part of the region and is modelled as a Caledonian granite which intruded upper-crustal basement. The granite may have acted as a buffer to northward-directed Variscan thrusting. The Dingle–Dungarvan Line (DDL) marks a major change in sedimentary and crustal velocity and structure. It lies immediately to the north of the velocity and gravity low, and shows thickness and velocity differences in many of the underlying crustal layers and even in the Moho. This suggests a deep, pre-Variscan control of the structural development of this area. The model is compatible with thin-skinned tectonics, which terminated at the DDL and which incorporated thrusts involving the sedimentary and upper-crustal layers.  相似文献   

Self-organization of recent rhythmic iron-manganese precipitations in underground mines in the Harz mountains     

S. Dietrich  K. -H. Jacob 《International Journal of Earth Sciences》1996,85(1):29-37

A recent early diagenetic banded iron-manganese mud has been forming underground in a closed lead-zinc mine for approximately 40 years. The processes leading to the banded structure of the precipitate were studied during a period of 2 years. Therefore, 19 physical and chemical parameters were measured regularly in short intervals. The resulting time series were analysed with respect to the data sets of the monthly chemical analyses of the descendent mine water, the daily rainfall and the mineral content. The results reveal that the precipitated material undergoes internal self-organization due to interaction of redox, colloid-chemical, microbial, electrical and ripening processes, and not exclusively produced by seasonal fluctuations of material input. Thus, the primary banding of the material, caused by externally forced fluctuations of the redox conditions within the mine water, is reorganized after a short time. The finally observed bands are controlled by non-linear coupling of reaction and transport processes within the mud. A genetic model for the banded mineralization was developed and verified by numerical simulation.  相似文献