排序方式： 共有8条查询结果，搜索用时 0 毫秒
1
1.
This paper deals with the effects of thermal stresses on selected carbonate rocks used as dimension stones. They are Mesozoic calcareous and dolomitic rocks cropping out in Apulia (southern Italy) that, for their physico-mechanical and aesthetic properties, have always been finding a large application both as ornamental stones and as simple construction materials; their use is attested not only in Italy, in works of archaeological, historical and artistic interest too. The cause–effect relationships of thermal degradation were studied by means of an artificial accelerated ageing test, in order to provide a perspective about the decay of carbonate stones due to diurnal and seasonal temperature fluctuations, as well as thermal shocks during events of fire development. The stone samples were subjected to thermal cycles in a muffle furnace, ranging from 100 to 700 °C; after each cycle, several non-destructive and semi-destructive tests were carried out: mass and volume measurements, mercury intrusion porosimetry, sclerometer tests, ultrasonic tests, thin-section observations and determination of chromatic alterations through image analysis and Munsell charts method. In this way, the qualitative and quantitative modifications induced in fabric, physical and mechanical properties were discussed. The results highlight the fundamental role of depositional and diagenetic fabric that, together with mineralogical composition, represents the most significant discriminating factor in the response of the stone to thermal stresses. 相似文献
2.
Martino Amodio Eleonora Andriani Maurizio Caselli Paolo R. Dambruoso Barbara E. Daresta Gianluigi de Gennaro Pierina Ielpo Claudia M. Placentino Maria Tutino 《Journal of Atmospheric Chemistry》2009,63(3):203-220
The chemical composition of PM10 and PM2.5 samples collected during two seasonal monitoring campaigns at residential, urban and industrial Apulia Region- sites was
investigated. Ionic fraction, carbonaceous compounds and Polycyclic Aromatic Hydrocarbons were determined for all samples.
High correlations among PM data collected in the investigated sites suggested the regional character of particulate matter.
It was also confirmed by five days back trajectories analysis. Moreover, no significant seasonal trend in PM mass concentration
was observed in the investigated sites. These results, relevant for the area under investigations, were not observed in the
North of Italy and Europe and allow to conclude that PM10 and PM2.5 cannot be considered ‘good’ indicators for the evaluation of local anthropic contributions to air quality. On the contrary,
the high levels of Polycyclic Aromatic Hydrocarbons found in Taranto sampling sites suggested that PAHs can be a better indicator
for this purpose. This result is also relevant in order to weigh the importance of industrial area and to suggest right policy
control to decision makers. 相似文献
3.
Navigation at sea is based on Electronic Chart Display and Information Systems (ECDIS) that allow for the use of a limited number of projections. As navigation in the Arctic region becomes a reality due to the progressive melting of the polar ice cap, a re-examination of the most suitable projections for navigation in the Arctic becomes timely. Several projections are proposed in the literature for this area. In our approach, the selection is based on an analytical study utilizing three criteria: the control of the magnitude of distortions within acceptable limits, the shape of great circles (GCs) and rhumb lines/loxodromes, and the shape of the graticule lines portrayed on the chart. The analysis carried out shows that to fulfill the set criteria, the arctic area should be divided into Arctic and sub-Arctic regions. More specifically, for the Arctic region the Azimuthal Polar Equidistant projection and the Azimuthal Polar Stereographic projection are the most suitable ones. For the sub-Arctic region, the Lambert Conformal Conic and the Conic Equidistant projection are considered more appropriate. All four projections proposed can be used for both the traditional nautical chart and the ECDIS, and both are considered as the starting point for further study of specific ECDIS requirements. 相似文献
4.
Exact theory for expanding density perturbations under the following assumptions: (i) Friedmann universes made of dust only; (ii) spherically-symmetric perturbations (iii) isolated perturbations; (iv) null peculiar velocity field; is reviewed and extended. The overdensity equation is derived and the related solution is determined concerning both mean overdensity and local overdensity, and including both the growing and the decreasing mode, in terms of non-dimensional variables normalized to the initial configuration. A first-order and zero-order approximation to the exact theory is also performed in view of applications to specific problems, e.g., the acquisition of angular momentum by tidal torques. The idealized case presented here makes a necessary reference in dealing with more general situations involving both analytical and numerical approaches. 相似文献
5.
6.
Tropical deforestation through logging activities poses a direct threat to biodiversity. However, the detection of logging has remained a challenge. Based on study sites in Zimbabwe and Zambia, we tested whether the Normalized Difference Vegetation Index (NDVI) and the Coefficient of Variation in NDVI (CVNDVI) derived from high and medium spatial resolution satellite data could be used to detect logging in dry and wet miombo woodlands. Separately, we integrated NDVI and CVNDVI in logistic regression to test whether each can be used to successfully predict logging in the study sites. We tested whether the spatial resolution of satellite data has an effect in detection of logging using NDVI and CVNDVI derived from Landsat 8 and Worldview-2. Based on the ROC curves, we concluded that remotely sensed data could provide an effective predictive tool for detecting logging. However, in wet miombo woodlands the predictive power of remotely sensed data is weak. 相似文献
7.
An example of the effects of anthropogenic changes on natural environment in the Apulian karst (southern Italy) 总被引：1，自引：0，他引：1
This paper examines a case study regarding a site in the Murge karst (Apulia, southern Italy) where, in the course of time,
anthropogenic activity has caused significant damage to the natural landscape and environment, also in terms of loss of human
lives. The study site comprises the city of Bari and the neighbouring towns, belonging to the same catchment basin, which
is characterised by a low-relief karst very rich in natural cavities and dry valleys, the latter locally called lame. From the second half of the 1500s until today, in the whole area, short rainfall storms (lasting less than 6 h) with disastrous
and mortal consequences have been recorded many times. In the last decades, human activities, such as urbanization, stone
clearing for agricultural purposes, quarrying and deforestation induced severe changes in the karst landscape causing the
modification of the surficial and underground drainage. In particular, an examination is made of the factors causing the complete
destruction of the “di Maso” Park on the night between 22 and 23 October 2005, in consequence of a high-intensity rainfall
(152.6 mm in a 6-h period) accompanied by flash flooding. Finally, the need for a better understanding of natural processes
and patterns in karst areas, and the interactions with human activities through to the development of environmental management
systems ensuring further steps towards sustainable development is remarked. 相似文献
8.
This paper aims to investigate what kind of density perturbations did lead to elliptical galaxies and what kind to spiral galaxies, in the context of a CDM scenario. Previous work by HP (Heavens and Peacock, 1988) is reviewed and extended; more particularly: (i) a theoreticalJM
relation is derived for virialized configurations, with a slope increasing with the mass, in the range 5/3<<2, and compared with its counterpart deduced by HP for expanding configurations; (ii) an non-dimensional angular momentum =J/(G
2
M
5
t
ff
)1/3; witht
ff
free-fall time at turnaround, is calculated explicitly and compared with the usual spin parameter =J(–E)
1/2/(GM
5/2), in the special case of polytropic spheres and for different peak heights; (iii) a model is built up where the ellipsoidal density perturbations described by HP are approximated as spherical density perturbations with the same mass and the same rate of acquisition of angular momentum, and the contribution of the latter to the expansion is also taken into account. The calculations are limited to the special case of Einstein-de Sitter universes (of dust only), in the whole range of HP distributions of angular momenta. If a massM=1012
m
is typical for galaxies, the results are consistent with both an inferred difference roughly in a factor of six times between angular momenta of ellipticals and spirals, and a continuous transition from the former to the latter, for each peak height. It is argued that star formation together with angular momentum, instead of peak height alone, makes the fate of a given proto-object; more specifically, if star formation is high enough and/or angular momentum is low enough, the system will be frozen as an elliptical galaxy; if, on the other hand, the rate of star formation is low enough, and/or angular momentum is high enough, the system will be frozen as a spiral galaxy. In addition, the results lead to an obvious trend: more ellipticals are associated with higher peak heights and more spirals with lower peak heights. 相似文献
1