Search results for "Transient"

Photodynamics studies of ligand-protected gold nanoclusters by using ultrafast transient infrared spectroscopy

2015

Highly monodisperse samples of three ligand-protected gold nanoclusters Au102(pMBA)44, Au144(SC2H4Ph)60, and a cluster tentatively identified as Au130(pMBA)50, were characterized by UV/vis and infrared spectroscopy, and their photodynamics was studied by transient absorption spectroscopy. The dynamics study for each cluster was performed by electronically exciting the cluster with a pump pulse in the visible or near infrared region and by monitoring the transient absorption of vibrational modes of the ligands with a mid-IR probe pulse. The photodynamics studies were used to determine the molecular or metallic behavior of the cluster, and also to gain important size dependent information abo…

On Stability of a Concentrated Fiber Suspension Flow

2014

Linear stability analysis of a fiber suspension flow in a channel domain is performed using a modified Folgar-Tucker equation. Two kinds of potential instability are identified: one is associated with overcritical Reynolds number and another is associated with certain perturbations in fiber orientation field and is present for any Reynolds numbers. The second type of instability leads to initially growing transient perturbations in the microstructure. It is shown that both types of instability lead to instability of the bulk velocity field. As for the perturbed Orr-Sommerfeld eigenvalues, the presence of fibers increases the stability region; the stability region increases with growing C i …

Improved Quadratic Time-frequency Distributions for Detecting Inter-turn Short Circuits of PMSMs in Transient States

2020

This paper aims to improve quadratic time-frequency distributions to adapt condition monitoring of electrical machines in transient states. Short-Time Fourier transform (STFT) has been a baseline signal processing technique for detecting fault characteristic frequencies. However, limits of window sizes due to loss of frequency- or time-resolution, make it hard to capture rapid changes in frequencies. Within this study, Choi-Williams and Wigner-Ville distributions are proposed to effectively detect peaks at characteristic frequencies while still maintaining low computation time. The improved quadratic time-frequency distributions allow for generating spectrograms of a longer lasting data sig…

Ultrafast electronic relaxation and vibrational cooling dynamics of Au 144(SC2H4Ph)60 nanocluster probed by transient mid-IR spectroscopy

2014

Energy relaxation dynamics of a gold nanocluster with atomically precise composition, Au144(SC2H4Ph)60, is studied by transient mid-IR spectroscopy. The experiment is designed to simultaneously pro...

Molecule-like photodynamics of Au102(pMBA)44 nanocluster.

2015

Photophysical properties of a water-soluble cluster Au102(pMBA)44 (pMBA = para-mercaptobenzoic acid) are studied by ultrafast time-resolved mid-IR spectroscopy and density functional theory calculations in order to distinguish between molecular and metallic behavior. In the mid-IR transient absorption studies, visible or near-infrared light is used to electronically excite the sample, and the subsequent relaxation is monitored by studying the transient absorption of a vibrational mode in the ligands. Based on these studies, a complete picture of energy relaxation dynamics is obtained: (1) 0.5-1.5 ps electronic relaxation, (2) 6.8 ps vibrational cooling, (3) intersystem crossing from the low…

Mathematical models and stability analysis of three-phase synchronous machines

2013

THE POTENTIALS OF A TRANSIENT TRANSNATIONAL COMMUNITY FOR TEACHER EDUCATORS’ PROFESSIONAL LEARNING AND DEVELOPMENT

2020

Although there has been a rising interest in the profession of teacher educators, there is still a lack of research looking at the professional learning and development of teacher educators. Taking a European perspective, we intend to contribute to the field of teacher education. At the outset we outline current literature and research findings, indicating various challenges that teacher education professionals face in today’s society, which are prominent in many contexts of language teacher education. Choosing to study a transient transnational community of 11 teacher educators as an autoethnographic case, we draw on qualitative data collected in the context of the ERASMUS+ project proPIC …

Mathematical models and stability analysis of induction motors under sudden changes of load

2013

A Time-Non-Homogeneous Double-Ended Queue with Failures and Repairs and Its Continuous Approximation

2018

We consider a time-non-homogeneous double-ended queue subject to catastrophes and repairs. The catastrophes occur according to a non-homogeneous Poisson process and lead the system into a state of failure. Instantaneously, the system is put under repair, such that repair time is governed by a time-varying intensity function. We analyze the transient and the asymptotic behavior of the queueing system. Moreover, we derive a heavy-traffic approximation that allows approximating the state of the systems by a time-non-homogeneous Wiener process subject to jumps to a spurious state (due to catastrophes) and random returns to the zero state (due to repairs). Special attention is devoted to the cas…

HIPPOCAMPAL REVERSIBLE LESIONS IN A CASE OF TRANSIENT GLOBAL AMNESIA

2013

PURPOSE: We present a case of transient global amnesia (TGA) onset in a 52-year-old male with a medical history of migraine. METHODS: Patient was taken to ER by his colleagues which reported that after an emotional stress he suddenly appeared perplexed and started asking repetitive questions. In ER a neurological examination excluded other neurological signs or symptoms and it was confirmed that cognitive impairment was limited to the amnesia domain; electroencephalography was unremarkable and he had no history of epileptic seizures or head trauma. At the neurologic examination Capland and Hodges criteria were fulfilled and the diagnostic hypothesis of TGA was placed. He underwent to a brai…