The Experts below are selected from a list of 12105 Experts worldwide ranked by ideXlab platform
Philip D. Mannheim - One of the best experts on this subject based on the ideXlab platform.
-
Arbitrary force-constant changes in the Crystal Impurity problem
Physical Review B, 2006Co-Authors: Philip D. MannheimAbstract:To calculate the response to an external probe of an Impurity in a host Crystal, one needs to determine both the frequencies and the amplitudes of the perturbed Crystal vibrational modes in which the defect participates. When the introduction of the defect leads to force-constant changes, the complexity of the problem often necessitates a numerical treatment. However, in a previous study we had actually obtained simple and exact analytic expressions for the positions and intensities of the perturbed modes in the case in which the host-host and the host-Impurity force constants were taken to be both central and nearest neighbor. Such expressions required knowledge of only one pure Crystal lattice Green's function, the one at the defect site itself. In this paper we extend our previous study to incorporate nearest-neighbor noncentral force constants as well. By analytically constructing the perturbed Crystal lattice Green's function at the defect site, we find that the same simple expressions, which we had previously obtained in the nearest-neighbor central force-constant case, also hold without any modification at all in the case of isotropic force-constant changes in Crystals whose host-host force constants are isotropic, and in the particular mixed case in which the fractional changes inmore » the central and isotropic components of the force constants are equal to each other. In the most general arbitrary nearest-neighbor force-constant change case we obtain a reasonably compact exact expression for the dynamics of the perturbed modes which only involves a total of two pure Crystal lattice Green's functions.« less
-
Bounds on localized modes in the Crystal Impurity problem
Physical Review B, 2006Co-Authors: Harry J. Lipkin, Philip D. MannheimAbstract:Using general properties of the Crystal site representation normal mode matrix, we provide some very simple bounds on localized modes in simple, body-centered, and face-centered cubic Crystals with substitutional point defects. We derive a trace condition constraint on the net change in Crystal eigenfrequencies caused by the introduction of a defect, with the condition being a completely general one which holds for any combination of central and noncentral Crystal force constants and for all-neighbor interactions. Using this condition we show that the sufficient condition for producing localized modes in an arbitrary cubic Crystal by a mass change at the defect site is that the defect mass be less than one half of that of the host atom mass which it replaces, and that the sufficient condition for producing localized modes in an arbitrary cubic Crystal by force-constant changes alone is that the defect site self-force constant be greater than twice that of the pure Crystal self-force constant of the host atom which it replaces.
Osamu Wada - One of the best experts on this subject based on the ideXlab platform.
-
Leveraging deep photonic band gaps in photonic Crystal Impurity bands
Applied Physics Letters, 2001Co-Authors: Sheng Lan, Satoshi Nishikawa, Osamu WadaAbstract:Photonic band gaps can be generated in the Impurity bands of photonic Crystals formed by periodically placed defects. Even slight periodic modulation of the properties of these defects can open up very deep band gaps in the Impurity bands. This phenomenon originates from the concentration of electromagnetic field at the defect regions, making electromagnetic wave extremely sensitive to the small changes of the defects. A dynamical photonic band gap in the Impurity band created by a control light, provides a mechanism for constructing high-efficiency optical switches.
Rongqing Zhang - One of the best experts on this subject based on the ideXlab platform.
-
Tuning calcite magnesium content by soluble shell matrices: Insights into biomineral Impurity control
Materials Science and Engineering: C, 2010Co-Authors: Fangjie Zhu, Yawei Kong, Jian Liang, Yujuan Zhou, Xiaojun Liu, Liping Xie, Rongqing ZhangAbstract:Abstract In this study, the prismatic EDTA-soluble matrix (ESM) of Pinctada fucata was found to significantly reduce calcite Mg content when presented as an additive. Together with the Mg exclusion effect identified in the prismatic layer of P. fucata , a novel mechanism was proposed that organisms might use the additive effect to control the Crystal Impurity content in a solution of defined element composition. The precipitation inhibition assay and the direct ion-binding assay demonstrated that the ESM effect is realized neither by altering the precipitation rate nor by regulating the relative ion activity in the Crystallizing solution. A plausible correlation between Crystal Impurity control and polymorphism determination was also discussed.
Sheng Lan - One of the best experts on this subject based on the ideXlab platform.
-
Leveraging deep photonic band gaps in photonic Crystal Impurity bands
Applied Physics Letters, 2001Co-Authors: Sheng Lan, Satoshi Nishikawa, Osamu WadaAbstract:Photonic band gaps can be generated in the Impurity bands of photonic Crystals formed by periodically placed defects. Even slight periodic modulation of the properties of these defects can open up very deep band gaps in the Impurity bands. This phenomenon originates from the concentration of electromagnetic field at the defect regions, making electromagnetic wave extremely sensitive to the small changes of the defects. A dynamical photonic band gap in the Impurity band created by a control light, provides a mechanism for constructing high-efficiency optical switches.
Sohrab Rohani - One of the best experts on this subject based on the ideXlab platform.
-
dynamic modeling of continuous evaporative cooling kcl nacl Crystallizers
Canadian Journal of Chemical Engineering, 1999Co-Authors: Abdulsamad Tadayyon, Sohrab RohaniAbstract:Previous work on the modeling of potash Crystallizers has been mainly limited to the estimation of Crystal size distribution (CSD) in the presence of only one solid component (KCl). In the present study, an attempt has been made to develop a model that incorporates NaCl as a second component that may co-precipitate along with KCl under certain operating conditions. Addition of water to prevent co-saturation or as a means of internal fines dissolution is also taken into consideration. External fines dissolution using a heat exchanger is incorporated in the model. In addition to the CSD, the model is able to predict Crystal Impurity resulting from co-saturation with NaCl. The predictive capability of the model is tested using limited dynamic experimental data obtained from a 1 m3 pilot plant continuous evaporative Crystallizer and the steady-state experimental data from a two-stage evaporative Swenson DTB industrial potash Crystallizer circuit. In both cases, a good agreement between the model predictions and the experimental data was noticed. Les travaux anterieurs sur la modelisation des cristallisoirs de potasse se sont principalement limites a l'estimation de la distribution de taille des cristaux (CSD) en presence d'un seul composant solide (KCl). Dans la presente etude, on propose un modele qui introduit le NaCl comme second composant pouvant co-precipiter avec le KCl dans certaines conditions de fonctionnement. On prend egalement en consideration l'addition d'eau afin d'empecher la co-saturation ou comme moyen de dissolution des fines internes. La dissolution des fines externes a l'aide d'un echangeur de chaleur est introduite dans le modele. Outre la CSD, le modele est capable de predire l'impurete des cristaux resultant de la co-saturation avec le NaCl. La capacite predictive du modele est verifiee a l'aide de donnees emperiques experimentales limitees provenant d'un cristallisoir a evaporation continu pilote de 1 m3 et de donnees experimentales en regime permanent provenant d'un cristallisoir de potasse industriel DTB de Swenson. Dans les deux cas, on a note un bon accord entre les predictions du modele et les donnees experimentales.
-
Dynamic modeling of continuous evaporative cooling KCl‐NaCl Crystallizers
The Canadian Journal of Chemical Engineering, 1999Co-Authors: Abdulsamad Tadayyon, Sohrab RohaniAbstract:Previous work on the modeling of potash Crystallizers has been mainly limited to the estimation of Crystal size distribution (CSD) in the presence of only one solid component (KCl). In the present study, an attempt has been made to develop a model that incorporates NaCl as a second component that may co-precipitate along with KCl under certain operating conditions. Addition of water to prevent co-saturation or as a means of internal fines dissolution is also taken into consideration. External fines dissolution using a heat exchanger is incorporated in the model. In addition to the CSD, the model is able to predict Crystal Impurity resulting from co-saturation with NaCl. The predictive capability of the model is tested using limited dynamic experimental data obtained from a 1 m3 pilot plant continuous evaporative Crystallizer and the steady-state experimental data from a two-stage evaporative Swenson DTB industrial potash Crystallizer circuit. In both cases, a good agreement between the model predictions and the experimental data was noticed. Les travaux anterieurs sur la modelisation des cristallisoirs de potasse se sont principalement limites a l'estimation de la distribution de taille des cristaux (CSD) en presence d'un seul composant solide (KCl). Dans la presente etude, on propose un modele qui introduit le NaCl comme second composant pouvant co-precipiter avec le KCl dans certaines conditions de fonctionnement. On prend egalement en consideration l'addition d'eau afin d'empecher la co-saturation ou comme moyen de dissolution des fines internes. La dissolution des fines externes a l'aide d'un echangeur de chaleur est introduite dans le modele. Outre la CSD, le modele est capable de predire l'impurete des cristaux resultant de la co-saturation avec le NaCl. La capacite predictive du modele est verifiee a l'aide de donnees emperiques experimentales limitees provenant d'un cristallisoir a evaporation continu pilote de 1 m3 et de donnees experimentales en regime permanent provenant d'un cristallisoir de potasse industriel DTB de Swenson. Dans les deux cas, on a note un bon accord entre les predictions du modele et les donnees experimentales.