Luanda bay has been acting as a sink for the untreated municipal and industrial effluents from a part of the city. Sediment samples were analyzed for their total organic carbon contents and pseudo-total concentrations...Luanda bay has been acting as a sink for the untreated municipal and industrial effluents from a part of the city. Sediment samples were analyzed for their total organic carbon contents and pseudo-total concentrations ofFe, Mn, Hg, Cd, Pb, Cu, Zn, Ni and Cr The highest concentrations of organic carbon and Hg, Cd, Pb, Cu and Zn were found near the sewerage discharge outlets, exceeding in these points the lowest Sediment Quality Guidelines for the occurrence of adverse biological effects. A further study, based on the latest version of the BCR sequential extraction procedure, was undertaken in order to assess the physical/chemical binding and bioavailability ofFe, Mn, Cd, Pb, Cu and Zn in these sediments. The toxic metals Cd, Zn, Pb and Cu pose a potential environmental risk, because they were extracted from the sediment labile fractions in concentrations that exceeded the corresponding ERL （Effects Range Low） values, entering the range within which adverse biological effects occur. The non-residual fractions of metals ranged from 91 to 100% for Cd, 89 to 94% for Zn, 67 to 100% for Pb, 71 to 82% for Cu, 30 to 77% for Mn and 39 to 48% for Fe. Measures to be taken for the disposal of the polluted dredged sediments are shown in this work.展开更多
The numerical prediction of added resistance and vertical ship motions of one ITTC （Intemational Towing Tank Conference） S-175 containership in regular head waves by our own in-house unsteady RANS solver naoe-FOAM-S...The numerical prediction of added resistance and vertical ship motions of one ITTC （Intemational Towing Tank Conference） S-175 containership in regular head waves by our own in-house unsteady RANS solver naoe-FOAM-SJTU is presented in this paper. The development of the solver naoe-FOAM-SJTU is based on the open source CFD tool, OpenFOAM. Numerical analysis is focused on the added resistance and vertical ship motions （heave and pitch motions） with four very different wavelengths （ 0.8Lpp 〈 2 〈 1.5L ） in regular head waves. Once the wavelength is near the length of the ship model, the responses of the resistance and ship motions become strongly influenced by nonlinear factors, as a result difficulties within simulations occur. In the paper, a comparison of the experimental results and the nonlinear strip theory was reviewed and based on the findings, the RANS simulations by the solver naoe-FOAM-SJTU were considered competent with the prediction of added resistance and vertical ship motions in a wide range of wave lengths.展开更多
In this paper the performance of a BOC-50＇ sailing yacht model in calm water and in realistic sea states is investigated experimentally. A scaled model of the hull form with the keel-bulb configuration has been teste...In this paper the performance of a BOC-50＇ sailing yacht model in calm water and in realistic sea states is investigated experimentally. A scaled model of the hull form with the keel-bulb configuration has been tested in the towing tank of the LSMH of NTUA. During the tests the calm water resistance and the dynamic responses, including the added resistance in waves were recorded. Results referring to the resistance, the side force, the CG displacement, the pitch as well as the vertical accelerations of the model at the bow, the CG and the stern are presented. Moreover, by using a Velocity Prediction Program the polar and the stability diagram of the tested sailing yacht were calculated. Useful conclusions about the dynamic behavior of the model were obtained.展开更多
Comprehensive statistical analysis was performed on the basic features of focal mechanisms of 619 ML≥2. 0 earthquakes which occurred in the capital circle area from January 2002 to June 2010. By dividing the capital ...Comprehensive statistical analysis was performed on the basic features of focal mechanisms of 619 ML≥2. 0 earthquakes which occurred in the capital circle area from January 2002 to June 2010. By dividing the capital area into three studying regions based on regional tectonic characteristics,cluster analysis was conducted on the focal mechanisms of all subregions using the longest distance method in the statistical cluster analysis to study the characteristics of tectonic stress tensors. The result shows that dominant P-axis azimuth distribution is NNE-NEE and that of T-axis is NNW-NWW,most of the focal areas are controlled by a horizontal stress field and rupture is mainly of horizontal strike-slip. The maximum principal compression stress orientation is NE75° in the west,NE62° in the middle,and near EW in the east of the capital area. The regional tectonic stress field is characterized by horizontal compression.展开更多
The Internet and mobile internet have made the transaction of a huge number of products and services possible in ways previously unimaginable, exerting an extensive and profound influence on commercial, industrial, fi...The Internet and mobile internet have made the transaction of a huge number of products and services possible in ways previously unimaginable, exerting an extensive and profound influence on commercial, industrial, financial and even medical enterprises, universities and government agencies. All of this wide variety of transformations can be distilled into the concept of ＂Internet thinking. ＂ This paper poses that internet thinking consists of the following three levels. First is lnternet spirit, i.e., openness, equality, collaboration and sharing. Second is Internet philosophy, including interconnection between virtual and real entities, elimination of restrictions of time and space, modularization, personal imperialism, crowdsourcing and user-centered approaches. Third is the Internet economy, featuring long-tail theory at a technical level, market equilibrium theory at the level of transaction structure and consumer sovereignty theory at the level of transaction performance. According to Internet thinking, traditional firms must be transformed towards smart organizations characterized by network-based ecosystem, global integration, platform-based operation, users as contributors, borderless development and self- organizing management. As rightly pointed out by the CEO of Haier Group Zhang Ruimin, ＂There is no such a thing as a successful firm; there are only firms defined by their times. ＂ Adapting to the times is key to the survival of all firms.展开更多
文摘Luanda bay has been acting as a sink for the untreated municipal and industrial effluents from a part of the city. Sediment samples were analyzed for their total organic carbon contents and pseudo-total concentrations ofFe, Mn, Hg, Cd, Pb, Cu, Zn, Ni and Cr The highest concentrations of organic carbon and Hg, Cd, Pb, Cu and Zn were found near the sewerage discharge outlets, exceeding in these points the lowest Sediment Quality Guidelines for the occurrence of adverse biological effects. A further study, based on the latest version of the BCR sequential extraction procedure, was undertaken in order to assess the physical/chemical binding and bioavailability ofFe, Mn, Cd, Pb, Cu and Zn in these sediments. The toxic metals Cd, Zn, Pb and Cu pose a potential environmental risk, because they were extracted from the sediment labile fractions in concentrations that exceeded the corresponding ERL （Effects Range Low） values, entering the range within which adverse biological effects occur. The non-residual fractions of metals ranged from 91 to 100% for Cd, 89 to 94% for Zn, 67 to 100% for Pb, 71 to 82% for Cu, 30 to 77% for Mn and 39 to 48% for Fe. Measures to be taken for the disposal of the polluted dredged sediments are shown in this work.
基金Foundation item： Supported by the National Natural Science Foundation of China （Grant No. 50739004 and 11072154）
文摘The numerical prediction of added resistance and vertical ship motions of one ITTC （Intemational Towing Tank Conference） S-175 containership in regular head waves by our own in-house unsteady RANS solver naoe-FOAM-SJTU is presented in this paper. The development of the solver naoe-FOAM-SJTU is based on the open source CFD tool, OpenFOAM. Numerical analysis is focused on the added resistance and vertical ship motions （heave and pitch motions） with four very different wavelengths （ 0.8Lpp 〈 2 〈 1.5L ） in regular head waves. Once the wavelength is near the length of the ship model, the responses of the resistance and ship motions become strongly influenced by nonlinear factors, as a result difficulties within simulations occur. In the paper, a comparison of the experimental results and the nonlinear strip theory was reviewed and based on the findings, the RANS simulations by the solver naoe-FOAM-SJTU were considered competent with the prediction of added resistance and vertical ship motions in a wide range of wave lengths.
文摘In this paper the performance of a BOC-50＇ sailing yacht model in calm water and in realistic sea states is investigated experimentally. A scaled model of the hull form with the keel-bulb configuration has been tested in the towing tank of the LSMH of NTUA. During the tests the calm water resistance and the dynamic responses, including the added resistance in waves were recorded. Results referring to the resistance, the side force, the CG displacement, the pitch as well as the vertical accelerations of the model at the bow, the CG and the stern are presented. Moreover, by using a Velocity Prediction Program the polar and the stability diagram of the tested sailing yacht were calculated. Useful conclusions about the dynamic behavior of the model were obtained.
基金funded jointly by China Spark Program of Earthquake Science and Technology(XH12001)Special research fund and Task contract of earthquake trend tracing in 2013 of Beijing Earthquake Administration(2013020109)
文摘Comprehensive statistical analysis was performed on the basic features of focal mechanisms of 619 ML≥2. 0 earthquakes which occurred in the capital circle area from January 2002 to June 2010. By dividing the capital area into three studying regions based on regional tectonic characteristics,cluster analysis was conducted on the focal mechanisms of all subregions using the longest distance method in the statistical cluster analysis to study the characteristics of tectonic stress tensors. The result shows that dominant P-axis azimuth distribution is NNE-NEE and that of T-axis is NNW-NWW,most of the focal areas are controlled by a horizontal stress field and rupture is mainly of horizontal strike-slip. The maximum principal compression stress orientation is NE75° in the west,NE62° in the middle,and near EW in the east of the capital area. The regional tectonic stress field is characterized by horizontal compression.
文摘The Internet and mobile internet have made the transaction of a huge number of products and services possible in ways previously unimaginable, exerting an extensive and profound influence on commercial, industrial, financial and even medical enterprises, universities and government agencies. All of this wide variety of transformations can be distilled into the concept of ＂Internet thinking. ＂ This paper poses that internet thinking consists of the following three levels. First is lnternet spirit, i.e., openness, equality, collaboration and sharing. Second is Internet philosophy, including interconnection between virtual and real entities, elimination of restrictions of time and space, modularization, personal imperialism, crowdsourcing and user-centered approaches. Third is the Internet economy, featuring long-tail theory at a technical level, market equilibrium theory at the level of transaction structure and consumer sovereignty theory at the level of transaction performance. According to Internet thinking, traditional firms must be transformed towards smart organizations characterized by network-based ecosystem, global integration, platform-based operation, users as contributors, borderless development and self- organizing management. As rightly pointed out by the CEO of Haier Group Zhang Ruimin, ＂There is no such a thing as a successful firm; there are only firms defined by their times. ＂ Adapting to the times is key to the survival of all firms.
