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Tan B.,Dalian University of Technology | Tan B.,Nanyang Normal College | Li Z.-J.,Dalian University of Technology | Lu P.,Dalian University of Technology | And 2 more authors.
Journal of Geophysical Research: Oceans | Year: 2012

To investigate the morphology and distribution of pressure ridges in the northwestern Weddell Sea, ice surface elevation profiles were measured by a helicopter-borne laser altimeter during Winter Weddell Outflow Study with the German R/V Polarstern in 2006. An optimal cutoff height of 0.62 m, derived from the best fits between the measured and theoretical ridge height and spacing distributions, was first used to separate pressure ridges from other sea ice surface undulations. It was found that the measured ridge height distribution was well modeled by a negative exponential function, and the ridge spacing distribution by a lognormal function. Next, based on the ridging intensity Ri (the ratio of mean ridge sail height to mean spacing), all profiles were clustered into three regimes by an improved k-means clustering algorithm: Ri ≤ 0.01, 0.01 < Ri 0.026, and R i > 0.026 (denoted as C1, C2, and C 3 respectively). Mean (and standard deviation) of sail height was 0.99 (±0.07) m in Regime C1, 1.12 (±0.06) m in C 2, and 1.17 (±0.04) m in C3, respectively, while the mean spacings (and standard deviations) were 232 (±240) m, 54 (±20) m, and 31 (±5.6) m. These three ice regimes coincided closely with distinct sea ice regions identified in a satellite radar image, where C1 corresponded to the broken ice in the marginal ice zone and level ice formed in the Larsen Polynya, C2 corresponded to the deformed first- and second-year ice formed by dynamic action in the center of the study region, and C3 corresponded to heavily deformed ice in the outflowing branch of the Weddell Gyre. The results of our analysis showed that the relationship between the mean ridge height and frequency was well modeled by a logarithmic function with a correlation coefficient of 0.8, although such correlation was weaker when considering each regime individually. The measured ridge height and frequency were both greater than those reported by others for the Ross Sea. Compared with reported values for other parts of the Antarctic, the present ridge heights were greater, but the ridge frequencies and ridging intensities were smaller than the most extreme of them. Meanwhile, average thickness of ridged ice in our study region was significantly larger than that of the Coastal Ross Sea showing the importance of deformation and ice age for ice conditions in the northwestern Weddell Sea. © 2012 American Geophysical Union. All Rights Reserved. Source


Gao Y.,Nankai University | Gao Y.,Nanyang Normal College | Zhou Q.,Nankai University
Yingyong Jichu yu Gongcheng Kexue Xuebao/Journal of Basic Science and Engineering | Year: 2014

Nano-phytoremediation is a joint technology combined nanotechnology with phytoremediation for remediation of contaminated environment. In this work, simulation experiments were designed for remediation of e-waste contaminated soil containing Pb and PCBs, Impatiens balsamina was selected as the tested remediation plant, and three nanoscale zero-valent irons(nZVIs)(nZVI, vermiculite supported nZVI and activated carbon supported nZVI) were applied to promote the efficiency of phytoremediation. The results indicated that I. balsamina had strong tolerance on this combined pollution. Particularly in the 1000mg/kg Pb+250μg/kg PCBs treatment, the application of activated carbon supported nZVI could significantly reduce the accumulation of Pb in roots, up to 24.4%of that without nZVI application. On the contrary, nZVI and vermiculite supported nZVI had a positive effect on the accumulation of Pb because Pb can be absorbed onto or enter into nano colloidal substances, then be internalized in cytoplasms, thus having promoted the accumulation of Pb. It is thus clear that vermiculite supported nZVI and nZVI have practical potentials in phytoremediation of Pb contaminated soils. In a word, the nano-phytoremediation method for treating e-waste contaminated soils should be a very promising method to be further explored in the future. ©, 2014, The Editorial Board of Journal of Basic Science and Engineering. All right reserved. Source


Tan B.,Dalian University of Technology | Tan B.,Nanyang Normal College | Lu P.,Dalian University of Technology | Li Z.,Dalian University of Technology | Li R.,Dalian University of Technology
Annals of Glaciology | Year: 2013

Surface elevation data for sea ice in the northwesternty - Weddell Sea, Antarctica, collected by a helicopter-borne laser altimeter during the Winter Weddell Outflow Study 2006, were used to estimate the form drag on pressure ridges and its contribution to the total wind drag, and the air-ice drag coefficient at a reference height of 10m under neutral stability conditions (Cdn(10)). This was achieved by partitioning the total wind drag into two components: form drag on pressure ridges and skin drag over rough sea-ice surfaces. The results reveal that for the compacted ice field, the contribution of form drag on pressure ridges to the total wind drag increases with increasing ridging intensity Ri (where Ri is the ratio of mean ridge height to spacing), while the contribution decreases with increasing roughness length. There is also an increasing trend in the air-ice drag coefficient C dn(10) as ridging intensity Ri increases. However, as roughness length increases, Cdn(10) increases at lower ridging intensities (Ri≤0.023) but decreases at lower ridging intensities (0.023 < Ri < 0.05). These opposing trends are mainly caused by the dominance of the form drag on pressure ridges and skin drag over rough ice surfaces. Generally, the form drag becomes dominant only when the ridging intensity is sufficiently large, while the skin drag is the dominant component at relatively larger ridging intensities. These results imply that a large value of Cdn(10) is caused not only by the form drag on pressure ridges, but also by the skin drag over rough ice surfaces. Additionally, the estimated drag coefficients are consistent with reported measurements in the northwestern Weddell Sea, further demonstrating the feasibility of the drag partition model. Source


Tan B.,Dalian University of Technology | Tan B.,Nanyang Normal College | Li Z.,Dalian University of Technology | Lu P.,Dalian University of Technology | And 5 more authors.
International Journal of Advancements in Computing Technology | Year: 2011

An improved k-means clustering algorithm is proposed after analyzing the disadvantages of the traditional k-means algorithm. The cluster centers are initialized by combining the sample mean and standard deviation, the optimal clustercenters are searched by the hybridizing particle swarm optimization and traditional k-means algorithm, and the criterion function is improved during the iteration process to search the optimal number of clusters. The theory analysis and experimental results show that the improved algorithm not only avoids the local optima, also has greater searching capability than the tradition alalgorithm.This improved algorithmis used to analyze the morphology of the ridge sail (the upper surface of ice ridges). The comparison with the measured datashows that the influences of the geographical locations and the growing environments on the formation of ice ridges can be perfectly reflected by theclustered results. Source


Tan B.,Dalian University of Technology | Tan B.,Nanyang Normal College | Li Z.-J.,Dalian University of Technology | Lu P.,Dalian University of Technology | And 2 more authors.
Shuikexue Jinzhan/Advances in Water Science | Year: 2012

Based on the surface elevation profiles of sea ice in the Weddell Sea measured by a helicopter-borne laser altimeter during the Winter Weddell Outflow Study 2006, an optimal model is established with the relative deviations between the theoretical and measured ridge height (spacing) distributions as the performance index and the cutoff height as a control variable. An optimal cutoff height of 0.62 m is obtained and used to separate ridges from level ice surface. Analysis on the ridge distributions implies that the best fits to the observed sail height and spacing distributions are achieved by W'80 distribution and a lognormal distribution, respectively. All profiles are clustered into three regimes by the k-means algorithm based on the ridging intensity R i (R i ≤ 0.01, 0.01 < R i ≤ 0.026 and R i > 0.026). The average sail height is 0.99 m for the profiles of R i ≤ 0.01, 1.12 m for 0.01 < R i ≤ 0.026, and 1.17 m for R i > 0.026. While the average spacing are 232m, 54 m and 31 m respectively for the three different regimes. Effective thickness within the area covered by ridged ice, average thickness of ridged ice, sail cross-section, and the areal fraction of ridged ice are also calculated by the mathematical models, and the results indicate that these parameters increase with increase of the ice ridge intensity. Source

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