Basic concepts of the crystallization from aqueous solutions: The example of aluminum oxy(hydroxi)des and aluminosilicates     

Jean-Pierre Jolivet  Corinne Chanéac  David Chiche  Sophie Cassaignon  Olivier Durupthy  Julien Hernandez 《Comptes Rendus Geoscience》2011,343(2-3):113-122

This overview features the chemical background on condensation phenomena of the aluminum cation in aqueous solution. The formation of polycationic molecular clusters and nanosized solid phases of aluminum oxy(hydroxi)des is interpreted with illustrative mechanisms, building a bridge between solution chemistry and solid-state chemistry. The formation of the main structural types of aluminosilicates (zeolites, clays, imogolite) is also illustrated through the aqueous chemistry of aluminum and silicates.  相似文献   

Autopilot control synthesis for path tracking maneuvers of underwater vehicles     

Sam-Sang YOU  Hyeung-Sik CHOI  Hwan-Seong KIM  Han-Il PARK 《中国海洋工程》2011,25(2):237-249

This paper is concerned with the robust control synthesis of autonomous underwater vehicle(AUV) for general path following maneuvers.First,we present maneuvering kinematics and vehicle dynamics in a unified framework.Based on H∞ loop-shaping procedure,the 2-DOF autopilot controller has been presented to enhance stability and path tracking.By use of model reduction,the high-order control system is reduced to one with reasonable order,and further the scaled low-order controller has been analyzed in both the frequency and the time domains.Finally,it is shown that the autopilot control system provides robust performance and stability against prescribed levels of uncertainty.  相似文献   

Application of Dempster-Shafer theory of evidence to GIS-based landslide susceptibility analysis   总被引：9，自引：2，他引：7  

No-Wook Park 《Environmental Earth Sciences》2011,62(2):367-376

GIS-based spatial data integration tasks for predictive geological applications, such as landslide susceptibility analysis, have been regarded as one of the primary geological application issues of GIS. An efficient framework for proper representation and integration is required for this kind of application. This paper presents a data integration framework based on the Dempster-Shafer theory of evidence for landslide susceptibility mapping with multiple geospatial data. A data-driven information representation approach based on spatial association between known landslide occurrences and input geospatial data layers is used to assign mass functions. After defining mass functions for multiple geospatial data layers, Dempster’s rule of combination is applied to obtain a series of combined mass functions. Landslide susceptibility mapping using multiple geospatial data sets from Jangheung in Korea was conducted to illustrate the application of this methodology. The results of the case study indicated that the proposed methodology efficiently represented and integrated multiple data sets and showed better prediction capability than that of a traditional logistic regression model.  相似文献   

南京城市湖泊湿地的水质动态及其评价   总被引：4，自引：1，他引：3  

张波  翟路  林杰  孙婵  傅致远 《湿地科学与管理》2011,7(1):29-32,39

选取南京市玄武湖、莫愁湖、内秦淮河湿地为对象,通过定点、定时采样和水质分析等方法,对城市湖泊湿地水质的季节动态、水质影响因素及其富营养化评价等进行了研究。结果表明,TN、TP、BOD和COD是反映城市湖泊水体污染度的重要指标,TP含量过高是造成城市河湖湿地水体富营养化的主要原因。水体污染程度随季节动态表现为:夏季>春季>秋季>冬季。相对封闭的莫愁湖湿地水质的季节变化较小,但水质较差,各个季节均表现出重富营养化—严重富营养化状态;受工业或生活污水影响较大的内秦淮河湿地,水体受污染严重,全年均属严重富营养—异常富营养化;玄武湖湿地的水体,在春季和秋季均已达到富营养化水平,夏季相对较好,TN、TP为富营养化水平,其余指标为中—富营养水平。  相似文献   

A developed soil column test device for measuring the electrical conductivity breakthrough curves     

Xiaoqiang Dong  Xiaofeng Liu  Heesoo Woo  Junboum Park 《Environmental Earth Sciences》2014,72(9):3715-3722

To obtain the breakthrough curves without efforts required in the sampling and chemical analysis, a new soil column test device was developed. The device can conduct time-continuous electrical conductivity (EC) measurements without disturbing the soil matrix at all stages of the test. This device is composed of soil column, channel selector, LCR meter, and data logger. The soil column employs three 4-electrode sensors installed at different positions. To verify its applicability, the electrical conductivity breakthrough curves at different distances have been obtained with the use of five different species influent solutions (KCl, NaCl, CaCl₂, MgCl₂, and seawater). Results showed that the EC breakthrough curves and the transport parameters (the pore-water velocity, the dispersion coefficient, and the dispersivity) are very reasonable, and understand the one-dimensional steady flow exactly. The developed soil column test device proposed in this study provides a nondestructive, convenient, and inexpensive means of obtaining EC breakthrough curves.  相似文献   

Comparison of Helicity Signs in Interplanetary CMEs and Their Solar Source Regions     

K.-S. Cho  S.-H. Park  K. Marubashi  N. Gopalswamy  S. Akiyama  S. Yashiro  R.-S. Kim  E.-K. Lim 《Solar physics》2013,284(1):105-127

If all coronal mass ejections (CMEs) have flux ropes, then the CMEs should keep their helicity signs from the Sun to the Earth according to the helicity conservation principle. This study presents an attempt to answer the question from the Coordinated Data Analysis Workshop (CDAW), “Do all CMEs have flux ropes?”, by using a qualitative helicity sign comparison between interplanetary CMEs (ICMEs) and their CME source regions. For this, we select 34 CME–ICME pairs whose source active regions (ARs) have continuous SOHO/MDI magnetogram data covering more than 24 hr without data gap during the passage of the ARs near the solar disk center. The helicity signs in the ARs are determined by estimation of cumulative magnetic helicity injected through the photosphere in the entire source ARs. The helicity signs in the ICMEs are estimated by applying the cylinder model developed by Marubashi (Adv. Space. Res., 26, 55, 2000) to 16 second resolution magnetic field data from the MAG instrument onboard the ACE spacecraft. It is found that 30 out of 34 events (88 %) are helicity sign-consistent events, while four events (12 %) are sign-inconsistent. Through a detailed investigation of the source ARs of the four sign-inconsistent events, we find that those events can be explained by the local helicity sign opposite to that of the entire AR helicity (28 July 2000 ICME), incorrectly reported solar source region in the CDAW list (20 May 2005 ICME), or the helicity sign of the pre-existing coronal magnetic field (13 October 2000 and 20 November 2003 ICMEs). We conclude that the helicity signs of the ICMEs are quite consistent with those of the injected helicities in the AR regions from where the CMEs erupted.  相似文献   

Determination of Trace Elements in Geological Reference Materials G‐3, GSP‐2 and SGD‐1a by Low‐Dilution Glass Bead Digestion and ICP‐MS     

Chan‐Soo Park  Hyung Seon Shin  Haeyoung Oh  Jong Hwa Moon  Hana Cho  Chang‐sik Cheong 《Geostandards and Geoanalytical Research》2013,37(3):361-368

We present a revised alkali fusion method for the determination of trace elements in geological samples. Our procedure is based on simple acid digestion of powdered low‐dilution (flux : sample ≈ 2 : 1) glass beads where large sample dilution demanded by high total dissolved solids, a main drawback of conventional alkali fusion, could be circumvented. Three geological reference materials (G‐3 granite, GSP‐2 granodiorite and SGD‐1a gabbro) decomposed by this technique and routine tabletop acid digestion were analysed for thirty trace elements using a quadrupole ICP‐MS. Results by conventional acid digestion distinctly showed poor recoveries of Zr, Hf and rare earth elements due to incomplete dissolution of resistant minerals. On the other hand, results obtained by our method were in reasonable agreement with reference data for most analytes, indicating that refractory minerals were efficiently dissolved and volatile loss was insignificant.  相似文献   

Effects of humic acid on heavy metal uptake by herbaceous plants in soils simultaneously contaminated by petroleum hydrocarbons   总被引：2，自引：0，他引：2  

Soyoung Park  Ki Seob Kim  Daesok Kang  Hansam Yoon  Kijune Sung 《Environmental Earth Sciences》2013,68(8):2375-2384

The effects of humic acid (HA) on heavy metal uptake by herbaceous plants in soil simultaneously contaminated with heavy metals and petroleum hydrocarbons were investigated. The results showed that HA reduced readily soluble and exchangeable forms of heavy metals in the contaminated soil but increased their plant-available forms. Potential bioavailability and leachability factors became larger than 1 after adding HA to the soil, except for those of Ni, suggesting that more heavy metals could be potentially phytoavailable for plant uptake. Furthermore, HA increased the accumulation of Pb, Cu, Cd, and Ni in the shoots and roots of selected plants. The greatest increase in the accumulation of heavy metals was 264.7 % in the shoot of Festuca arundinacea, with the bioconcentration factor (BCF) increasing from 0.30 to 1.10. Humic acid also increased the BCFs of the roots of Brassica campestris for Ni and Pb. These results suggest that HA amendment could enhance plant uptake of heavy metals, while concurrently reducing heavy metal leachability and preventing subsurface contamination, even in soils simultaneously contaminated with petroleum hydrocarbons.  相似文献   

3-D acoustic modeling by a Hartley method     

Yang Qi-qiang  Lin Chan  Zhong Cheng  Zhang Shulu  Wang Changlong 《Journal of Applied Geophysics》2010,70(2):169-180

Numerical methods using the Hartley transform are described for the simulation of 3-D wave phenomena with application to the modeling of seismic data. Four topics are covered. The first deals with the solution of the 3-D acoustic wave equation. The second handles the solution of the 3-D two way nonreflecting wave equation. The third involves modeling with an areal source. The fourth treats wave phenomena whose direction of propagation is restricted within ± 90° from a given axis.The numerical methods developed here are similar to the Fourier methods. Time stepping is performed with a second-order differencing operator. The difference is that expressions including space derivative terms are computed by the Hartley transforms rather than the Fourier transforms. Being a real-valued function and equivalent to the Fourier transform, the Hartley transform avoids computational redundancies in terms of the number of operations and memory requirements and thus is more efficient and economical than the Fourier transform. These features are crucial when dealing with 3-D seismic data. The numerical results agree with the analytical results. The use of areal source in modeling can efficiently provide data for testing some schemes that deal with the areal shot-records. Using the transform methods, we can impose constraints on the direction of the wave propagation most precisely in the wavenumber domain when attempting to restrict propagation to upward moving waves. The implementation of the methods is demonstrated on numerical examples.  相似文献   

Kinematic modelling of shear band localization using discrete finite elements     

X. Wang  D. Chan  N. Morgenstern 《国际地质力学数值与分析法杂志》2003,27(4):289-324

Modelling shear band is an important problem in analysing failure of earth structures in soil mechanics. Shear banding is the result of localization of deformation in soil masses. Most finite element schemes are unable to model discrete shear band formation and propagation due to the difficulties in modelling strain and displacement discontinuities. In this paper, a framework to generate shear band elements automatically and continuously is developed. The propagating shear band is modelled using discrete shear band elements by splitting the original finite element mesh. The location or orientation of the shear band is not predetermined in the original finite element mesh. Based on the elasto‐perfect plasticity with an associated flow rule, empirical bifurcation and location criteria are proposed which make band propagation as realistic as possible. Using the Mohr–Coulomb material model, various results from numerical simulations of biaxial tests and passive earth pressure problems have shown that the proposed framework is able to display actual patterns of shear banding in geomaterials. In the numerical examples, the occurrence of multiple shear bands in biaxial test and in the passive earth pressure problem is confirmed by field and laboratory observations. The effects of mesh density and mesh alignment on the shear band patterns and limit loads are also investigated. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献