Controlling dispersed state and exfoliation process of clay in polymer matrix

In the present review, the authors do not try to provide a comprehensive review of researches on polymer/clay nanocomposites (PCNs), but some examples to demonstrate different exfoliation processes of the clay in various polymer matrixes and the dispersed state of clay. Interaction between polymers and layered silicates plays an important role in adjusting the exfoliation process of layered silicates and the microstructure of polymer nanocomposites. Properties of polymer/layered silicate nanocomposites mainly depend on the dispersed state of layered silicates. The authors will also address the outline of the present research in the direction of PCNs including the discussion of technical problems and their possible solutions.

基于信息重建技术的地震信号处理方法研究

The dissertation addressed the problems of signals reconstruction and data restoration in seismic data processing, which takes the representation methods of signal as the main clue, and take the seismic information reconstruction (signals separation and trace interpolation) as the core. On the natural bases signal representation, I present the ICA fundamentals, algorithms and its original applications to nature earth quake signals separation and survey seismic signals separation. On determinative bases signal representation, the paper proposed seismic dada reconstruction least square inversion regularization methods, sparseness constraints, pre-conditioned conjugate gradient methods, and their applications to seismic de-convolution, Radon transformation, et. al. The core contents are about de-alias uneven seismic data reconstruction algorithm and its application to seismic interpolation. Although the dissertation discussed two cases of signal representation, they can be integrated into one frame, because they both deal with the signals or information restoration, the former reconstructing original signals from mixed signals, the later reconstructing whole data from sparse or irregular data. The goal of them is same to provide pre-processing methods and post-processing method for seismic pre-stack depth migration. ICA can separate the original signals from mixed signals by them, or abstract the basic structure from analyzed data. I surveyed the fundamental, algorithms and applications of ICA. Compared with KL transformation, I proposed the independent components transformation concept (ICT). On basis of the ne-entropy measurement of independence, I implemented the FastICA and improved it by covariance matrix. By analyzing the characteristics of the seismic signals, I introduced ICA into seismic signal processing firstly in Geophysical community, and implemented the noise separation from seismic signal. Synthetic and real data examples show the usability of ICA to seismic signal processing and initial effects are achieved. The application of ICA to separation quake conversion wave from multiple in sedimentary area is made, which demonstrates good effects, so more reasonable interpretation of underground un-continuity is got. The results show the perspective of application of ICA to Geophysical signal processing. By virtue of the relationship between ICA and Blind Deconvolution , I surveyed the seismic blind deconvolution, and discussed the perspective of applying ICA to seismic blind deconvolution with two possible solutions. The relationship of PC A, ICA and wavelet transform is claimed. It is proved that reconstruction of wavelet prototype functions is Lie group representation. By the way, over-sampled wavelet transform is proposed to enhance the seismic data resolution, which is validated by numerical examples. The key of pre-stack depth migration is the regularization of pre-stack seismic data. As a main procedure, seismic interpolation and missing data reconstruction are necessary. Firstly, I review the seismic imaging methods in order to argue the critical effect of regularization. By review of the seismic interpolation algorithms, I acclaim that de-alias uneven data reconstruction is still a challenge. The fundamental of seismic reconstruction is discussed firstly. Then sparseness constraint on least square inversion and preconditioned conjugate gradient solver are studied and implemented. Choosing constraint item with Cauchy distribution, I programmed PCG algorithm and implement sparse seismic deconvolution, high resolution Radon Transformation by PCG, which is prepared for seismic data reconstruction. About seismic interpolation, dealias even data interpolation and uneven data reconstruction are very good respectively, however they can not be combined each other. In this paper, a novel Fourier transform based method and a algorithm have been proposed, which could reconstruct both uneven and alias seismic data. I formulated band-limited data reconstruction as minimum norm least squares inversion problem where an adaptive DFT-weighted norm regularization term is used. The inverse problem is solved by pre-conditional conjugate gradient method, which makes the solutions stable and convergent quickly. Based on the assumption that seismic data are consisted of finite linear events, from sampling theorem, alias events can be attenuated via LS weight predicted linearly from low frequency. Three application issues are discussed on even gap trace interpolation, uneven gap filling, high frequency trace reconstruction from low frequency data trace constrained by few high frequency traces. Both synthetic and real data numerical examples show the proposed method is valid, efficient and applicable. The research is valuable to seismic data regularization and cross well seismic. To meet 3D shot profile depth migration request for data, schemes must be taken to make the data even and fitting the velocity dataset. The methods of this paper are used to interpolate and extrapolate the shot gathers instead of simply embedding zero traces. So, the aperture of migration is enlarged and the migration effect is improved. The results show the effectiveness and the practicability.

环渤海地区地壳和上地幔地震层析成像研究

In Circum-Bohai region (112°~124°E, 34°~42°N ), there exists rich gas-petroleum while inner-plate seismic activity is robust. Although the tectonic structure of this region is very complicated, plenty of geological, geophysical and geochemical researches have been carried out.In this paper, guided by the ideas of "One, Two, Three and Many" and "The depth controls the shallow, the regional constrains the local", I fully take advantage of previous results so as to establish a general image of this region. After collecting the arrival-time of P-wave phases of local events and tele-seismic events recorded by the stations within this region from 1966 to 2004, I process all these data and build an initial model. Then, a tomography image of crust and upper-mantle of this region is obtained. With reference to previous results, we compare the image of various depths and five cross-profiles traverse this region along different direction. And finally, a discussion and conclusion is made.The principle contents is listed as below: 1) in the first chapter, the purpose and meaning of this thesis, the advance in seismic tomography, and the research contents and blue-print is stated; 2) in the second chapter, I introduce the regional geological setting of Circum-Bohai region, describe the tectonic and evolutionary characteristics of principle tectonic units, including Bohai Bay Basin, Yanshan Fold Zone, Taihangshan Uplifted Zone, Jiao-Niao Uplifted Zone and Luxi Uplifted Zone, and primary deep faults; 3) In the third chapter, the previous geophysical researches, i.e., gravity and geomagnetic characters, geothermal flow, seismic activity, physical character of rocks, deep seismic sounding, and previous seismic tomography, are discussed; 4) in the fourth chapter, the fundamental theory and approach of seismic tomography is introduced; 5) in the fifth chapter, the technology and approaches used in this thesis, including collecting and pre-processing of data, the establishment of initial velocity model and relocation of all events; 6) in the sixth chapter, I discuss and analyze the tomography image of various depth and five cross-sections; 7)in the seventh chapter, I make a conclusion of the results, state the existing problems and possible solutions.

Observation of charge-dependent azimuthal correlations and possible local strong parity violation in heavy-ion collisions

Parity (P)-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the orbital momentum of the system created in noncentral collisions. To study this effect, we investigate a three-particle mixed-harmonics azimuthal correlator which is a P-even observable, but directly sensitive to the charge-separation effect. We report measurements of this observable using the STAR detector in Au + Au and Cu + Cu collisions at root s(NN) = 200 and 62 GeV. The results are presented as a function of collision centrality, particle separation in rapidity, and particle transverse momentum. A signal consistent with several of the theoretical expectations is detected in all four data sets. We compare our results to the predictions of existing event generators and discuss in detail possible contributions from other effects that are not related to P violation.

Ultrafast vibrational and thermal relaxation of dye molecules in solutions

Intra- and intermolecular relaxations of dye molecules are studied after the excitation to the high-lying excited states by a femtosecond laser pulse, using femtosecond time-resolved stimulated emission pumping fluorescence depletion spectroscopy (FS TR SEP FD). The biexponential decays indicate a rapid intramolecular vibrational redistribution (IVR) depopulation followed by a slower process, which was contributed by the energy transfer to the solvents and the solvation of the excited solutes. The time constants of IVR in both oxazine 750 and rhodamine 700 are at the 290-360 fs range, which are insensitive to the characters of solvents. The solvation of the excited solutes and the cooling of the hot solute molecules by collisional energy transfer to the surrounding takes place in the several picoseconds that strongly depend on the properties of solvents. The difference of Lewis basicity and states density of solvents is a possible reason to explain this solvent dependence. The more basic the solvent is, which means the more interaction between the solute and the neighboring solvent shell, the more rapid the intermolecular vibrational excess energy transfer from the solute to the surroundings and the solvation of the solutes are. The higher the states density of the solvent is, the more favorable the energy transfer between the solute and solvent molecules is.

Solvent extraction of scandium(III), yttrium(III), lanthanum(III) and gadolinium(III) using Cyanex 302 in heptane from hydrochloric acid solutions

The extractions of the selected rare earths (Sc, Y, La and Gd) from hydrochloric acid solutions have been investigated using bis(2,4,4-trimethylpentyl)-mono thiophosphinic acid (Cyanex 302, HL) in heptane as an extractant. The results demonstrate that the extractions of rare earths occur via the following reaction: Sc(OH)(2+) + 2[(HL)(2)]((O)) double left right arrow [Sc(OH)L-2 (.) 2(HL)]((O)) + 2H(+) Y3+ + 3[(HL)(2)]((O)) double left right arrow [Y(HL2)(3)]((O)) + 3H(+) La(OH)(2)(+) + 3[(HL)(2)](O) double left right arrow [La(OH)(2)L (.) 5(HL)]((O)) + H+ Gd(OH)(2+) + 3[(HL)(2)]((O)) double left right arrow [Gd(OH)L-2 (.) 4(HL)]((O)) + 2H(+) The pH(1/2) values and equilibrium constants of the extracted complexes have been deduced by taking into account the aqueous phase complexation of the metal ion with hydroxyl ligands and plausible complexes extracted into the organic phase. According to the pH(1/2) values, it is possible to realize mutual separation among Sc(III), Y(III), La(III) and Gd(III) with Cyanex 302 by controlling aqueous acidity.

Extraction and separation of cerium(IV) from nitric acid solutions containing thorium(IV) and rare earths(III) by DEHEHP

The extraction behaviour of Ce(IV), Th(IV) and part of RE(III), viz., La, Ce, Nd and Yb, has been investigated using di(2-ethylhexyl) 2-ethylhexyl phosphonate (DEHEHP,B) in heptane as an extractant. Results show that extractability varies in the order: Ce(IV) > Th(IV) much greater than RE(III). Therefore, it is possible to find the appropriate conditions under which Ce(IV) can be effectively separated from Th(IV) and RE(III). Furthermore, stripping Ce(IV) from the loaded organic phase can be carried out by dilute H2SO4 with an aliquot of H2O2.Roasted bastnasite made in Baotou (China) by Na2CO3 and leached by HNO3, there is about 50% Ce mainly as tetravalent nitrate along with other RE(III) and Th(IV) in the leachings. Through fractional extraction, taking nitric acid leachings of roasted Bastnasite as feed and DEHEHP as an extractant, we can obtain the CeO2 products with high purity of 99.9-99.99%, with a yield of >85%, in which ThO2/CeO2 < 10(-4).

Studies on extracting solutions of endohedral rare-earth metallofullerenes by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Thirteen extracting solutions of rare-earth metallofullerenes containing La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb respectively have been investigated by means of matrix-assisted laser desorption/ionization time-of-night, mass spectrometry. The influences of the positive-ion/negative-ion mode, laser intensity, matrix and mass discrimination to the analytical results are studied, based on which the optimal analytical conditions have been determined. The results show that the extracting solutions contain large quantities of rare-earth metallofullerenes brs;des empty fullerenes, On the basis of comparing their relative intensities, the different structure stabilities and solubilities of metallofullerenes with different rare-earth metals encapsulated into the fullerene cages, as well as some possible reasons to those differences, are discussed.