This paper presents a macroelement formulation for the prediction of the planar dynamic response of inelastic deformable rocking bodies. The formulation is based on a previous macroelement developed by the authors able to describe the cyclic response of inelastic rocking bodies, which takes into account the deformability both along the height of the member, as well as near the rocking end. Modifications of this formulation to account for other motion modes of rocking members during their dynamic response, namely, sliding and upthrow, as well as modifications to account for damping in a uniform manner during the whole motion, including impacts, are introduced. The dynamic response predicted by the macroelement for free-standing rigid and deformable rocking bodies is presented and compared with existing theoretical solutions, and the effect of deformability, damping, inelasticity, and friction on the response is discussed. 相似文献
The resource-based view (RBV) of the firm has been established as one of the main approaches to strategy formulation for the development of sustainable competitive advantage. Moreover, human resource management can be conceptualised as a source of competitiveness. This paper proposes that RBV could contribute to the confrontation of the hindrances that shipping companies face in the management of their human resources, and to the formation of sustainable competitive advantage. The paper analyses the findings of a field study, regarding the different human resource and crew management practices that are applied by Greek-owned shipping companies. Finally, based on the RBV of the firm, it proposes an integrated framework for managing human resources in the shipping industry in a way that could lead to the formation of sustainable competitive advantage. 相似文献
The quick response of civil authorities after a major disaster event in an urban area is essential for the reduction of damages
and impacts to human lives. One of the first critical problems to be solved at the very early stages of response is the optimum
management of emergency vehicles and real time knowledge of the accessibility of the road network. In this article the concept
of using a number of emergency vehicles as sensors for monitoring the traffic conditions in an urban area after a major disaster
event is described. The fleet management system used for this taks is working with ral time DGPS. The system makes use of
existing vehicle fleets in the urban area, rapidly collecting data and covering the whole road network. It records travel
times with the help of the GPS system for every road segment driven through by each vehicle sensor, thus providing a digital
time database from which traffic parameters can be also computed. It can be used for real time monitoring of traffic conditions
under disaster or emergency situations where all the previously available data become invalid or unreliable. ? 2002 Wiley
Periodicals, Inc. 相似文献
We study the effects of a non-singular gravitational potential on satellite orbits by deriving the corresponding time rates
of change of its orbital elements. This is achieved by expanding the non-singular potential into power series up to second
order. This series contains three terms, the first been the Newtonian potential and the other two, here R1 (first order term) and R2 (second order term), express deviations of the singular potential from the Newtonian. These deviations from the Newtonian
potential are taken as disturbing potential terms in the Lagrange planetary equations that provide the time rates of change
of the orbital elements of a satellite in a non-singular gravitational field. We split these effects into secular, low and
high frequency components and we evaluate them numerically using the low Earth orbiting mission Gravity Recovery and Climate
Experiment (GRACE). We show that the secular effect of the second-order disturbing term R2 on the perigee and the mean anomaly are 4″.307×10−9/a, and −2″.533×10−15/a, respectively. These effects are far too small and most likely cannot easily be observed with today’s technology. Numerical
evaluation of the low and high frequency effects of the disturbing term R2 on low Earth orbiters like GRACE are very small and undetectable by current observational means. 相似文献
Surficial and sub-surficial sediments obtained from the lower course of the Kifissos River, which drains the Athens Basin,
have been analyzed for heavy metals and aliphatic and polycyclic hydrocarbons. Oddly, the calculated enrichment factors for
the identified heavy metals, with the baseline taken from a pristine area in the adjacent Saronikos Gulf, are very low excluding
only those related to Cu and Zn. In contrast, the enrichment factors for the measured hydrocarbons are particularly high.
However, physicochemical water conditions and annual flushing episodes of the Kifissos River may have reduced significantly
the sediment chemical fingerprint found out by the present study. Moreover, an evaluation of the fluvial sediment quality
based on the enriched Cu and Zn amounts and concentration of PAH fraction with a consideration of the biological thresholds
proposed by the National Oceanic and Atmospheric Administration (USA) reveals little probability for serious biological impairments.
Additionally, sediment toxicity due to the sediment PAH load may be considered as minimum. 相似文献
The Profitis Ilias gold deposit, located on the western part of Milos Island, Greece, is the first epithermal gold deposit
discovered in the Pliocene–Pleistocene Aegean volcanic arc. Estimated ore reserves are 5 million tonnes grading 4.4 g/tonne
Au and 43 g/tonne Ag. The deposit is closely associated with a horst and graben structure, and occurs in a series of steep
interconnected crustiform-banded quartz veins up to 3 m wide, extending to depths of at least 300 m. The mineralisation occurs
in three stages and is hosted by 3.5–2.5 Ma old silicified and sericitised rhyolitic lapilli-tuffs and ignimbrites. It consists
of pyrite, galena, chalcopyrite, electrum and native gold. Additionally, adularia occurs with quartz mainly in veins. Homogenisation
temperatures of primary liquid-rich inclusions vary from 145 to 399 °C for the ore stage, and 112 to 263 °C for the post-ore
stage. Salinities range between 0.1 and 11.4 wt% NaCl equiv. and 0.93 to 8.5 wt% NaCl equiv. for the ore stage and the post-ore
stage, respectively. Rare vapour-rich inclusions in ore stage quartz homogenise between 368 and 399 °C and estimates of eutectic
melting (−25 to −38 °C) indicate the presence of Ca and Mg in the ore fluids. Sample elevation versus fluid inclusion Th–salinity relationships show (1) a high-salinity trend, where moderate-temperature (300–250 °C) and moderate-salinity brines
(∼3 wt% NaCl equiv.) trend to high-salinity (up to 15 wt% NaCl equiv.) fluids with lower (∼25–50 °C) homogenisation temperatures,
and (2) a high-Th trend where moderate-salinity and moderate-temperature brines (200–250 °C; 3 wt% NaCl equiv.) develop into low-salinity (<1 wt%
NaCl equiv.), high-temperature (>350 °C) fluids. These trends are best explained by extreme boiling and vapourisation phenomena
between 200 and 250 °C. The 430–450 m asl (metres above sea level) level marks the transition between a lower liquid-dominated
segment of the system where only the steep high-salinity trend is seen, and an upper vapour-dominated segment where the high-Th trend or a combination of both are seen. There is a close spatial association between mineable gold grades and the upper
segment of the system. Depth-to-boiling curves suggest that the paleo-surface was ∼200 m above the present summit of Profitis
Ilias. Comparison of the mineralisation and fluid geochemistry at Profitis Ilias with that of the nearby modern geothermal
system indicates that the processes of metal mineralisation have probably been continuous since the Late Pliocene.
Received: 24 February 2000 / Accepted: 15 July 2000 相似文献
Macroinvertebrates play a key role in freshwater lentic and lotic ecosystems. The macroinvertebrate benthic community of a shallow Mediterranean lake (Lake Pamvotis, NW Greece) was studied. The benthic assemblage was sampled monthly at five sites during a period of 1 year (Apr. 1998–Mar. 1999). In addition hypolimnetic water quality variables were monitored over the same period at each site.
The aim of the study was (a) to describe the intra-annual and spatial variability in benthic communities, (b) to relate possible community changes to environmental conditions and (c) to evaluate the responses of the lake's ecological status on community indices.
The benthic fauna of Lake Pamvotis was found to be very limited with a total of 10 species belonging to five taxonomic groups. The oligochaete community comprised 80% of the total benthic fauna with Potamothrix bavaricus as a new record for the Lake Pamvotis and Potamothrix hammoniensis, being the dominant benthic species represented more than 61% of the total benthic fauna. Chironomus plumosus was the most abundant chironomid species contributing with about 6% of the total benthic fauna, and Chaoborus flavicans with 19% was the important dipteran. Almost all benthic species showed the same intra-annual seasonal pattern, with peak population densities during spring and early summer except P. hammoniensis which predominated during the whole sampling period. Dissolved oxygen and temperature seemed to be the main environmental factors affecting community indices.
Benthic communities are affected by human disturbances in Lake Pamvotis shifting their composition to more tolerant taxa, reflecting also the eutrophic to hypertophic character of the lake. 相似文献