Wyniki wyszukiwania - BazTech

1

Remote Sensing Monitoring of Volcanic Ash Clouds Based on PCA Method

Li Ch., Dai Y., Zhao J., Zhou S., Yin J., Xue D.

Acta Geophysica

|

2015

|

Vol. 63, no. 2

432--450

EN

Volcanic ash clouds threaten the aviation safety and cause global environmental effects. It is possible to effectively monitor the volcanic ash cloud with the aid of thermal infrared remote sensing technology. Principal component analysis (PCA) is able to remove the inter-band correlation and eliminate the data redundancy of remote sensing data. Taking the Eyjafjallajokull volcanic ash clouds formed on 15 and 19 April 2010 as an example, in this paper, the PCA method is used to monitor the volcanic ash cloud based on MODIS bands selection; the USGS standard spectral database and the volcanic absorbing aerosol index (AAI) are applied as contrasts to the monitoring result. The results indicate that: the PCA method is much simpler; its spectral matching rates reach 74.65 and 76.35%, respectively; and the PCA method has higher consistency with volcanic AAI distribution.

2

Vibrational Spectra, Phase Transition and Nonlinear Optical Properties of Anilinium Perchlorate Molecular-Ionic Solid

Marchewka M., Debrus S., Drozd M., Baran J., Barnes A. J., Xue D., Ratajczak H.

Polish Journal of Chemistry

|

2003

|

Vol. 77 / nr 11

1625-1636

EN

Crystals of anilinium perchlorate, C6H5NH ClO 3 4 + , were obtained by slow evaporation of an aqueous solution at room temperature. Powder Kurtz-Perry measurements were performed for the title material. The efficiency of second harmonic generation was estimated relative to KDP: d = 0.21dKDP. Room temperature powder infrared and Raman measurements for the title solid and its deuterated analogue were carried out. The vibrational spectra in the regions of the internal vibrations of the ions corroborate the X-ray data (reported by Paixao et al. [1]). Differential scanning measurements performed on the powder sample indicate a first order phase transition at about 220 K.Apossible mechanism of the phase transition is suggested in relation to disorder of the hydrogen atoms on nitrogen atoms (reported in [1]). The role of the aniline molecule in the second harmonic generation is discussed.

3

Predicting optical properties of potassium hydrogen bis-trichloroacetate crystal

Xue D., Ratajczak H.

Bulletin of the Polish Academy of Sciences. Chemistry

|

2003

|

Vol. 51, No. 2

71-75

EN

The second order nonlinear optical coefficient dsg of potassium hydrogen bis-trichloroacetate molecular crystal is theoretically predicted by the chemical bond method, which shows that optical responses of this crystal originate from the C-C1 bonds. The predicted value of d(36) is in agreement with the experimental observation.

4

Ab initio study of urea crystal

Xue D., Ratajczak H.

Bulletin of the Polish Academy of Sciences. Chemistry

|

2003

|

Vol. 51, No. 3-4

143-153

EN

Dielectric properties - linear (refractive indices) and nonlinear optical responses - of urea crystal are quantitatively calculated using static ab initio quantum chemistry calculations at the self-consistent field (SCF) level of theory. The polarizabili-ties and first hyperpolarizabilities of the urea molecule are used to calculate macroscopic susceptibilities of the urea crystal. The calculated values of the urea crystal can agree well with experimental data and other reports. The effect of hydrogen bonds on the susceptibilities of the urea crystal may be neglected. The present work provides us a useful way to deal with quantum chemistry calculations of such molecular crystals as urea.

5

Chemical bond analysis on second order nonlinear optical properties of Na2SeO4źH2O

Xue D., Betzler K., Hesse H., Ratajczak H.

Bulletin of the Polish Academy of Sciences. Chemistry

|

2002

|

Vol. 50, No. 3

289-297

EN

Second order nonlinear optical properties of Na(2)SeO(4)-H(2)SeO(3)-H(2)O crystals with hydrogen bonds have been quantitatively studied from the chemical bond viewpoint. Contributions of all constituent chemical bonds to the total linear and nonlinear optical properties of this crystal at Lambda = 0.8716 um have been determined. The chemical bond method quantitatively expresses those contributions. The current calculation shows that hydrogen bonds play a very important role in contributing to the total linear-and nonlinear optical properties of Na(2)SeO(4)-H(2)SeO(3)-H(2)O. Our results show that the coordination environments of the hydrogen bonds strongly affect their contributions to the optical response of the host crystal. Therefore, a successful selection of the excellent coordination environment of hydrogen bonds would help us to find good materials suitable for efficient second harmonic generation.

6

Theoretical analysis of chemical bonding behaviors and dielectric properties of different phases of ice

Xue D., Betzler K., Hesse H., Ratajczak H.

Bulletin of the Polish Academy of Sciences. Chemistry

|

2001

|

Vol. 49, No. 4

289-298

EN

From the chemical bond viewpoint, the chemical bond parameters, linear optical properties and geometrical characteristics of constituent chemical bonds (i.e., O-H and H.. .O bonds) in the single-crystalline ice phases I, II, III, VI, VII and VIII have been quantitatively studied. At the same time, the chemical bonding situations of constituent H(D) atoms in different phases of ice have been numerically scaled. The calculated results show that the different lengths and directions of the hydrogen bonding O-H(D).. .O (including two parts: H(D)-O and H(D).. .O bonds) in the different phases of ice cause a large variation in the linear optical properties. Their characteristics found in single-crystalline phases of ice can be used as a guideline for the application of this special kind of functional chemical bond as linkage in materials design.