Dynamics of Magnetized Spherical Accretion Flows

Transonic accretion flow with self-consistent treatment of random magnetic field is presented.Comment: in proceedings to "Astrophysics of Compact Objects", Huangshan, China, 200

A Business Application of the System Dynamics Approach: Word-of-Mouth and Its Effect in an Online Environment

In this article, we illustrate the use of system dynamics modeling approach to study a complex system: word-of-mouth. Word-of-mouth plays an important role in reducing risk and uncertainty in purchase and consumption. Most of the prior research on word-of-mouth focused on studying either the factors that trigger consumers’ participation (sending or receiving) in word-of-mouth activities or the impact word-of-mouth information has on consumers’ buying decisions. The relationship between the two decision processes, however, is recursive and dynamic. Most prior studies have not focused on a recursive relationship. Our objective is to present a system dynamics model for the study of the relationship between the buying decision and the decision to participate in word-of-mouth communication. We also discuss how system dynamics modeling can be used in other complex problems in business such as the creation of a global business

Electronic phase separation in insulating (Ga,Mn)As with low compensation: Super-paramagnetism and hopping conduction

In the present work, low compensated insulating (Ga,Mn)As with 0.7% Mn is obtained by ion implantation combined with pulsed laser melting. The sample shows variable-range hopping transport behavior with a Coulomb gap in the vicinity of the Fermi energy, and the activation energy is reduced by an external magnetic field. A blocking super-paramagnetism is observed rather than ferromagnetism. Below the blocking temperature, the sample exhibits a colossal negative magnetoresistance. Our studies confirm that the disorder-induced electronic phase separation occurs in (Ga,Mn)As samples with a Mn concentration in the insulator-metal transition regime, and it can account for the observed superparamagnetism and the colossal magnetoresistance.Comment: 14 pages, 7 figure

Investigation of a possible electronic phase separation in the magnetic semiconductors Ga1−x_{1-x}Mnx_{x}As and Ga1−x_{1-x}Mnx_{x}P by means of fluctuation spectroscopy

We present systematic temperature-dependent resistance noise measurements on a series of ferromagnetic Ga$_{1-x}$Mn$_{x}$As epitaxial thin films covering a large parameter space in terms of the Mn content $x$ and other variations regarding sample fabrication. We infer that the electronic noise is dominated by switching processes related to impurities in the entire temperature range. While metallic compounds with $x>2$ % do not exhibit any significant change in the low-frequency resistance noise around the Curie temperature $T_\mathrm{C}$, we find indications for an electronic phase separation in films with $x<2$ % in the vicinity of $T_\mathrm{C}$, manifesting itself in a maximum in the noise power spectral density. These results are compared with noise measurements on an insulating Ga$_{1-x}$Mn$_{x}$P reference sample, for which the evidence for an electronic phase separation is even stronger and a possible percolation of bound magnetic polarons is discussed. Another aspect addressed in this work is the effect of ion-irradiation induced disorder on the electronic properties of Ga$_{1-x}$Mn$_{x}$As films and, in particular, whether any electronic inhomogeneities can be observed in this case. Finally, we put our findings into the context of the ongoing debate on the electronic structure and the development of spontaneous magnetization in these materials

Dublin City University video track experiments for TREC 2002

Dublin City University participated in the Feature Extraction task and the Search task of the TREC-2002 Video Track. In the Feature Extraction task, we submitted 3 features: Face, Speech, and Music. In the Search task, we developed an interactive video retrieval system, which incorporated the 40 hours of the video search test collection and supported user searching using our own feature extraction data along with the donated feature data and ASR transcript from other Video Track groups. This video retrieval system allows a user to specify a query based on the 10 features and ASR transcript, and the query result is a ranked list of videos that can be further browsed at the shot level. To evaluate the usefulness of the feature-based query, we have developed a second system interface that provides only ASR transcript-based querying, and we conducted an experiment with 12 test users to compare these 2 systems. Results were submitted to NIST and we are currently conducting further analysis of user performance with these 2 systems

Interplay between localization and magnetism in (Ga,Mn)As and (In,Mn)As

Ion implantation of Mn combined with pulsed laser melting is employed to obtain two representative compounds of dilute ferromagnetic semiconductors (DFSs): Ga1-xMnxAs and In1-xMnxAs. In contrast to films deposited by the widely used molecular beam epitaxy, neither Mn interstitials nor As antisites are present in samples prepared by the method employed here. Under these conditions the influence of localization on the hole-mediated ferromagnetism is examined in two DFSs with a differing strength of p-d coupling. On the insulating side of the transition, ferromagnetic signatures persist to higher temperatures in In1-xMnxAs compared to Ga1-xMnxAs with the same Mn concentration x. This substantiates theoretical suggestions that stronger p-d coupling results in an enhanced contribution to localization, which reduces hole-mediated ferromagnetism. Furthermore, the findings support strongly the heterogeneous model of electronic states at the localization boundary and point to the crucial role of weakly localized holes in mediating efficient spin-spin interactions even on the insulator side of the metal-insulator transition.Comment: 23 pages, 10 figures, to appear at Phys. Rev. Mate

Contact Line Instability and Pattern Selection in Thermally Driven Liquid Films

Liquids spreading over a solid substrate under the action of various forces are known to exhibit a long wavelength contact line instability. We use an example of thermally driven spreading on a horizontal surface to study how the stability of the flow can be altered, or patterns selected, using feedback control. We show that thermal perturbations of certain spatial structure imposed behind the contact line and proportional to the deviation of the contact line from its mean position can completely suppress the instability. Due to the presence of mean flow and a spatially nonuniform nature of spreading liquid films the dynamics of disturbances is governed by a nonnormal evolution operator, opening up a possibility of transient amplification and nonlinear instabilities. We show that in the case of thermal driving the nonnormality can be significant, especially for small wavenumber disturbances, and trace the origin of transient amplification to a close alignment of a large group of eigenfunctions of the evolution operator. However, for values of noise likely to occur in experiments we find that the transient amplification is not sufficiently strong to either change the predictions of the linear stability analysis or invalidate the proposed control approach.Comment: 13 pages, 14 figure

The many-year fluctuations of air temperature in the Shatsk national natural park

За даними 63-річних спостережень на метеостанції Світязь, встановлено закономірності багаторічних коливань середніх температур повітря: річних, за холодний (ХІ-ІІІ) і теплий (ІV-Х) періоди та найхолодніший (січень) і найтепліший (липень) місяці на території Шацького національного природного парку.As a result of the 63 year long observations at the Svityaz meteorological station we have established some regularition of the many-year fluctuation of the average air temperatures: within a year within, a cold (ХІ-ІІІ) and warm (ІV-Х) phase as well as during the coldest (Janyary) and warmest (July) months. The study was carried out in the area of the Shatsk national natural park

The Tourist Infrastructure as Part of the Tourism and Recreational Potential of the Starovyzhivskiy District of Volyn Region

У статті зроблена спроба здійснити комплексну оцінку сучасного стану туристичної інфраструктури Старовижівського району Волинської області за окремими підсистемами: заклади розміщення, заклади харчування, заклади дозвілля та побутового обслуговування, транспортна інфраструктура, звʼязок та інформаційне забезпечення, людський потенціал. Окреслені проблеми елементів туристичної інфраструктури району та можливі шляхи їх вирішення.This article attempts to make a comprehensive assessment of the current state of tourism infrastructure in Starovyzhivskiy district of Volyn region in separate subsystems: placement establishments, food establishments, leisure establishments and consumer service, transport infrastructure, communication and information services, human potential. Problems elements of tourism infrastructure in the district and possible ways of their solution are outlined

Оцінка сучасного стану та перспектив розвитку туристської інфраструктури Ківерцівського району Волинської області

Сучасна система індустрії туризму дозволяє забезпечити багатовекторний розвиток підприємств і організацій сфери оздоровлення та відпочинку, культури, транспорту, природоохоронної діяльності тощо. Поступово галузь стає містком до соціально-економічного розвитку країни загалом і регіонів зокрема. Волинь – туристська „мекка” України, адже край багатий пам’ятками археолого-архітектурної та культурної спадщини та природно-ресурсними можливостями, тому завданням фахівців у галузі туризму і рекреації є забезпечення сприятливих умов для пересування та перебування потенційних іноземних та внутрішніх туристів на волинській землі