Based on the introduction of the profile of Pearl River Delta area, the strengths, weaknesses, opportunities and threats of developing urban agricultural in Pearl River Delta area are analyzed by using the SWOT analys...Based on the introduction of the profile of Pearl River Delta area, the strengths, weaknesses, opportunities and threats of developing urban agricultural in Pearl River Delta area are analyzed by using the SWOT analysis. The strengths are analyzed from three aspects, covering natural resources, geographic advantages and technological advantages; the weaknesses are analyzed from the terms of land resources, labor cost, industrial scale and quality of personnel involved; opportunities are analyzed from the aspects of potential clients, favorable policies and markets; the threats are analyzed from two aspects, including concept factor and income gap between urban and rural areas. on the basis of the above analyses, the countermeasures and suggestions on the development of urban agriculture in the Pearl River Delta area are put forward.展开更多
Pore structure of C/C （Carbon-Carbon） composite after several stages of pitch impregnation under the high pressure and heat treatment was investigated by means of low temperature nitrogen adsorption and the standard...Pore structure of C/C （Carbon-Carbon） composite after several stages of pitch impregnation under the high pressure and heat treatment was investigated by means of low temperature nitrogen adsorption and the standard contact porosimetry. Total pore volume, pore size distribution and specific surface area were calculated for samples of composite after several successive stages of treatment. The radius of pores presented in the material changes from 1 nm to 90 tam. Total pore volume and specific surface area both decrease after successive stages of pitch impregnation under the pressure, whereas heat treatment up to 1,750 ℃ and 2,000 ℃ leads to creation of some porous space and pore volume expansion. The bulk porosity of C/C composite comes down from 33.7% to 13.7% after the serial stages of treatment and the specific surface area is reduced by half compared to the initial material.展开更多
Recently, a series of basic granulite enclosures are found in the granulite gneisses along the right side of the Yarlung Zangbo River, lying west of the Namjagbarwa Mountain. Es-pecially, some high-pressure granulite ...Recently, a series of basic granulite enclosures are found in the granulite gneisses along the right side of the Yarlung Zangbo River, lying west of the Namjagbarwa Mountain. Es-pecially, some high-pressure granulite enclosures have been discovered in eastern gully of the Zhibei village. To the northwest of the high-pressure granulite belt there occur Yarlung Zangbo ophiolite zone. Southeastward the granulites change into amphibolite and green-schist facies rocks, which constitute a complete lower crust section.展开更多
New structural and petrological data unveil a very complicated ductile deformation history of the Xiongdian-Suhe HP metamorphic unit, north-western Dabie Shan, central China. The fine-grained symplectic amphibolite-fa...New structural and petrological data unveil a very complicated ductile deformation history of the Xiongdian-Suhe HP metamorphic unit, north-western Dabie Shan, central China. The fine-grained symplectic amphibolite-facies assemblage and coronal structure enveloping eclogite-facies garnet, omphacite and phengite etc., representing strain-free decompression and retrogressive metamorphism, are considered as the main criteria to distinguish between the early-stage deformation under HP metamorphic conditions related to the continental deep subduction and collision, and the late-stage deformation under amphibolite to greenschist-facies conditions occurred in the post-eclogite exhumation processes. Two late-stages of widely developed, sequential ductile deformations D 3 and D 4, are recognized on the basis of penetrative fabrics and mineral aggregates in the Xiongdian-Suhe HP metamorphic unit, which shows clear, regionally, consistent overprinting relationships. D 3 fabrics are best preserved in the Suhe tract of low post-D 3 deformation intensity and characterized by steeply dipping layered mylonitic amphibolites associated with doubly vergent folds. They are attributed to a phase of tectonism linked to the initial exhumation of the HP rocks and involved crustal shortening with the development of upright structures and the widespread emplacement of garnet-bearing granites and felsic dikes. D 4 structures are attributed to the main episode of ductile extension (D 1 4) with a gently dipping foliation to the north and common intrafolial, recumbent folds in the Xiongdian tract, followed by normal sense top-to-the north ductile shearing (D 2 4) along an important tectonic boundary, the so-called Majiawa-Hexiwan fault (MHF), the westward continuation of the Balifan-Mozitan-Xiaotian fault (BMXF) of the northern Dabie Shan. It is indicated that the two stages of ductile deformation observed in the Xiongdian-Suhe HP metamorphic unit, reflecting the post-eclogite compressional or extrusion wedge formation, the subhorizontal ductile extension and crustal thinning as well as the top-to-the north shearing along the high-angle ductile shear zones responsible for exhumation of the HP unit as a coherent slab, are consistent with those recognized in the Dabie-Sulu UHP and HP metamorphic belts, suggesting that they were closely associated in time and space. The Xiongdian-Suhe HP metamorphic unit thus forms part of the Triassic (250-230 Ma) collision orogenic belt, and can not connect with the South Altun-North Qaidam-North Qinling UHP metamorphic belt formed during the Early Paleozoic (500-400 Ma).展开更多
文摘Based on the introduction of the profile of Pearl River Delta area, the strengths, weaknesses, opportunities and threats of developing urban agricultural in Pearl River Delta area are analyzed by using the SWOT analysis. The strengths are analyzed from three aspects, covering natural resources, geographic advantages and technological advantages; the weaknesses are analyzed from the terms of land resources, labor cost, industrial scale and quality of personnel involved; opportunities are analyzed from the aspects of potential clients, favorable policies and markets; the threats are analyzed from two aspects, including concept factor and income gap between urban and rural areas. on the basis of the above analyses, the countermeasures and suggestions on the development of urban agriculture in the Pearl River Delta area are put forward.
文摘Pore structure of C/C （Carbon-Carbon） composite after several stages of pitch impregnation under the high pressure and heat treatment was investigated by means of low temperature nitrogen adsorption and the standard contact porosimetry. Total pore volume, pore size distribution and specific surface area were calculated for samples of composite after several successive stages of treatment. The radius of pores presented in the material changes from 1 nm to 90 tam. Total pore volume and specific surface area both decrease after successive stages of pitch impregnation under the pressure, whereas heat treatment up to 1,750 ℃ and 2,000 ℃ leads to creation of some porous space and pore volume expansion. The bulk porosity of C/C composite comes down from 33.7% to 13.7% after the serial stages of treatment and the specific surface area is reduced by half compared to the initial material.
基金Project supported by the National Natural Science Foundation of China and the National Key Project KJ 85-07-01-04.
文摘Recently, a series of basic granulite enclosures are found in the granulite gneisses along the right side of the Yarlung Zangbo River, lying west of the Namjagbarwa Mountain. Es-pecially, some high-pressure granulite enclosures have been discovered in eastern gully of the Zhibei village. To the northwest of the high-pressure granulite belt there occur Yarlung Zangbo ophiolite zone. Southeastward the granulites change into amphibolite and green-schist facies rocks, which constitute a complete lower crust section.
文摘New structural and petrological data unveil a very complicated ductile deformation history of the Xiongdian-Suhe HP metamorphic unit, north-western Dabie Shan, central China. The fine-grained symplectic amphibolite-facies assemblage and coronal structure enveloping eclogite-facies garnet, omphacite and phengite etc., representing strain-free decompression and retrogressive metamorphism, are considered as the main criteria to distinguish between the early-stage deformation under HP metamorphic conditions related to the continental deep subduction and collision, and the late-stage deformation under amphibolite to greenschist-facies conditions occurred in the post-eclogite exhumation processes. Two late-stages of widely developed, sequential ductile deformations D 3 and D 4, are recognized on the basis of penetrative fabrics and mineral aggregates in the Xiongdian-Suhe HP metamorphic unit, which shows clear, regionally, consistent overprinting relationships. D 3 fabrics are best preserved in the Suhe tract of low post-D 3 deformation intensity and characterized by steeply dipping layered mylonitic amphibolites associated with doubly vergent folds. They are attributed to a phase of tectonism linked to the initial exhumation of the HP rocks and involved crustal shortening with the development of upright structures and the widespread emplacement of garnet-bearing granites and felsic dikes. D 4 structures are attributed to the main episode of ductile extension (D 1 4) with a gently dipping foliation to the north and common intrafolial, recumbent folds in the Xiongdian tract, followed by normal sense top-to-the north ductile shearing (D 2 4) along an important tectonic boundary, the so-called Majiawa-Hexiwan fault (MHF), the westward continuation of the Balifan-Mozitan-Xiaotian fault (BMXF) of the northern Dabie Shan. It is indicated that the two stages of ductile deformation observed in the Xiongdian-Suhe HP metamorphic unit, reflecting the post-eclogite compressional or extrusion wedge formation, the subhorizontal ductile extension and crustal thinning as well as the top-to-the north shearing along the high-angle ductile shear zones responsible for exhumation of the HP unit as a coherent slab, are consistent with those recognized in the Dabie-Sulu UHP and HP metamorphic belts, suggesting that they were closely associated in time and space. The Xiongdian-Suhe HP metamorphic unit thus forms part of the Triassic (250-230 Ma) collision orogenic belt, and can not connect with the South Altun-North Qaidam-North Qinling UHP metamorphic belt formed during the Early Paleozoic (500-400 Ma).
