排序方式： 共有10条查询结果，搜索用时 15 毫秒
1
1.
2.
The search for methods to reduce the fuel consumption in orbital transfers is something relevant and always current in astrodynamics. Therefore, the maneuvers assisted by the gravity, also called Swing-by maneuvers, can be an advantageous option to save fuel. The proposal of the present research is to explore the influence of some parameters in a Swing-by of an artificial satellite orbiting a planet with one of the moons of this mother planet, with the goal of changing the inclination of the artificial satellite around the main body of the system. The fuel consumption of this maneuver is compared with the required consumption to perform the same change of inclination using the classical approach of impulsive maneuvers. 相似文献
3.
4.
Stefano Tavani Stefano Vitale Celestino Grifa Alessandro Iannace Mariano Parente Stefano Mazzoli 《地学学报》2016,28(3):195-201
Bedding‐parallel dolomite seams occur in a clay‐poor carbonate succession of the Apennines. The seams are composed of a high concentration of dolomite crystals compared to the hosting dolomitic limestone. SEM images document microcracking, and in many cases even crushing and fragmentation, of dolomite crystals and accumulation of non‐carbonate insoluble material both along micro‐stylolites within the seams and around dolomite crystals of the seams. We interpret the seams as hybrid structures between pressure‐solution seams and compaction bands, which formed during burial. The euhedral dolomite crystals scattered in the micritic matrix represent the insoluble residue produced by the progressive dissolution of calcite. As calcite dissolution proceeds, the concentration of dolomite crystals increases, eventually resulting in a dolomite seam in which locally a dolomite crystal‐supported texture is attained. At this stage, the dolomite crystals within the seam start to collide, crush and fragment, so that the dolomite seam behaves like a compaction band. 相似文献
5.
Alberto De Bonis Stefania Febbraro Chiara Germinario Daniela Giampaola Celestino Grifa Vincenza Guarino Alessio Langella Vincenzo Morra 《Geoarchaeology》2016,31(6):437-466
Recent transportation infrastructure works in Naples, Italy, provided important discoveries related to the production of pottery in the Hellenistic workshop area of Piazza Nicola Amore. A minero‐petrographic investigation was conducted on 35 samples belonging to the widespread Campana A ware and production indicators (clayey raw materials, unfired Graeco‐Italic amphorae, kiln wastes, workshop tools). Additional analysis was conducted on black‐glaze and common ware samples for comparison. The analyses reveal compositional and technological homogeneity of Campana A ware. Samples are characterized by low CaO content with evidence of both volcanic and sedimentary components, suggesting that different clay sources were properly mixed to prepare a standard recipe. Production indicators, black‐glaze and common wares, have a composition well consistent with the calcareous clays from the island of Ischia. Leucite‐ and garnet‐bearing temper from the Somma Volcano were used for the preparation of coarse‐grained pastes, unfired Graeco‐Italic amphorae, and clayey raw materials, thus suggesting that they represented the clay sources for amphorae production. Our results reveal new technological and socioeconomic aspects of Hellenistic pottery production in the Bay of Naples, in particular for the Campana A ware, now representing a new reference group: Neapolis. 相似文献
6.
Celestino Gonzalez-Nicieza M. Inmaculada Alvarez-Fernandez M. Belen Prendes-Gero Consuelo Pizarro-Garcia Aldo O. Oliva-Gonzalez 《Environmental Earth Sciences》2014,71(8):3673-3684
The storage of CO2 in unused coal mines is a viable option for reducing emissions of CO2, whose accumulation in the atmosphere is one of the main contributors to global warming. Understanding CO2 behaviour and storage capacity of the coal is an important first step before injecting the CO2. We used experimental equipment to extract coal from a mine and to obtain a representative sample of both its internal structure (in terms of cleats, macropores, mesopores and micropores) and occluded gases. Storage capacity was studied in terms of variations in gas pressure. The adsorption isotherm was experimentally obtained applying a procedure specifically designed to avoid altering the coal. An unused coal bed was selected to determine how much CO2 it could adsorb and to study the feasibility of storing power plant CO2 in this kind of mine. 相似文献
7.
Alberto De Bonis Celestino Grifa Giuseppe Cultrone Pantaleone De Vita Alessio Langella Vincenzo Morra 《Geoarchaeology》2013,28(5):478-503
We performed petrophysical analyses on 34 clayey samples of different geological origin within the Campania region of Italy in order to determine possible sources of raw materials used to produce ancient pottery. Possible raw material sources can be grouped into high‐CaO clays (HCC) and low‐CaO clays (LCC). HCC are mainly represented by more recent (Miocene‐Pleistocene) basinal sediments whereas LCC tend to be associated with basinal, alluvial, and pyroclastic deposits. A chemical comparison between clayey raw materials, modern ceramic replicas, and Campanian archaeological ceramics of several typologies (common ware, cooking ware, fine tableware, amphorae, and bricks) from 8th century B.C. to the Middle Ages (a total of 350 ceramic samples) indicates that HCC were extensively used for common wares and that these were either mixed with temper or levigated. In contrast, most of the LCC were used for the production of cookware. We also analyzed the technological potential of the sampled raw materials, taking into consideration their actual and possible uses. We observed that most HCC deposits were well suited for tableware and amphorae, whereas LCC were better for cookware and some fine tableware. 相似文献
8.
A combined single range and single image device for low-cost measurement of building façade features
Celestino Ordóñez Pedro Arias José Herráez Jaime Rodríguez María T. Martín 《The Photogrammetric Record》2008,23(122):228-240
The dimensions of building façades and window apertures are usually determined by making direct measurements using tapes and plummets. This approach, however, has a number of drawbacks including the physical risk to which the persons making the measurements are exposed. This paper proposes an indirect approach based on close range photogrammetry that is inexpensive, simple, fast and safe, and which does not require specialist staff or direct ground control measurements. The method is based on taking a picture using a digital camera and measuring the distance to the object using a handheld laser distance meter. Both items of equipment are mounted on a specially designed support that allows the laser distance meter to move independently of the camera. 相似文献
9.
Gian Franco Napa-García André Teófilo Beck Tarcisio B. Celestino 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2018,12(2):123-134
Recent accidents in underground structures have raised the risk awareness of the geotechnical engineering community. Geotechnical design is subject to significant uncertainties in load and strength parameters as well as in engineering models. However, engineering models which objectively address such uncertainties in design are still scarce. This paper presents an objective framework for the quantification of the risks involved in underground structures excavated in fractured rock masses, where structural failures may occur due to block falls. The framework considers the structure as a distributed system, where falling block probabilities are integrated over the main structural dimension. Random block size and geometry, arising from random joint orientation, are taken into account, as well as uncertainties in joint strength and geometrical parameters. A cost function is used to quantify failure consequences in terms of the block size. The framework is demonstrated in an application to a case study involving a real structure: the Paulo Afonso IV power station cavern. Results of the case study show that the studied cavern presents high reliability and very low risk. The framework proposed herein is shown to be a practical tool for the risk evaluation of underground structures constructed in rock masses, such as caverns and tunnels. 相似文献
10.
Summary A weathering classification for granitic rock materials from southeastern Brazil was framed based on core characteristics.
The classification was substantiated by a detailed petrographic study. Indirect assessment of weathering grades by density,
ultrasonic and Schmidt hammer index tests was performed. Rebound values due to Schmidt hammer multiple impacts at one representative
point were more efficient in predicting weathering grades than averaged single impact rebound values, P-wave velocities and
densities.
Uniaxial compression tests revealed that a large range of uniaxial compressive strength (214–153 MPa) exists in Grade I category
where weathering does not seem to have played any role. It was concluded that variability in occurrences of quartz intragranular
cracks and in biotite percentage, distribution and orientation might have played a key role in accelerating or decelerating
the failure processes of the Grade I specimens. Deterioration of uniaxial compressive strength and elastic modulus and increase
in Poisson’s ratio with increasing weathering intensity could be attributed to alteration of minerals, disruption of rock
skeleton and microcrack augmentation. A crude relation between failure modes and weathering grades also emerged.
Correspondence: Prof. T. B. Celestino, Universidade de S?o Paulo, S?o Carlos, Brazil 相似文献
1