Dynamic Thermal Analysis of a Power Amplifier

This paper presents dynamic thermal analyses of a power amplifier. All the investigations are based on the transient junction temperature measurements performed during the circuit cooling process. The presented results include the cooling curves, the structure functions, the thermal time constant distribution and the Nyquist plot of the thermal impedance. The experiments carried out demonstrated the influence of the contact resistance and the position of the entire cooling assembly on the obtained results.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Syntheses and Properties of Two-Dimensional, Dicationic Nonlinear Optical Chromophores Based on Pyrazinyl Cores

Six new dicationic 2D nonlinear optical (NLO) chromophores with pyrazinyl-pyridinium electron acceptors have been synthesized by nucleophilic substitutions of 2,6-dichloropyrazine with pyridyl derivatives. These compounds have been characterized as their PF_6^− salts by using various techniques including electronic absorption spectroscopy and cyclic voltammetry. Large red shifts in the intense, π → π* intramolecular charge-transfer (ICT) transitions on replacing −OMe with –Nme_2 substituents arise from the stronger π-electron donor ability of the latter. Each compound shows a number of redox processes which are largely irreversible. Single crystal X-ray structures have been determined for five salts, including two nitrates, all of which adopt centrosymmetric packing arrangements. Molecular first hyperpolarizabilities β have been determined by using femtosecond hyper-Rayleigh scattering at 880 and 800 nm, and depolarization studies show that the NLO responses of the symmetric species are strongly 2D, with dominant “off-diagonal” β_(zyy) components. Stark (electroabsorption) spectroscopic measurements on the ICT bands afford estimated static first hyperpolarizabilities β_0. The directly and indirectly derived β values are large, and the Stark-derived β_0 response for one of the new salts is several times greater than that determined for (E)-4′-(dimethylamino)-N-methyl-4-stilbazolium hexafluorophosphate. These Stark spectroscopic studies also permit quantitative comparisons with related 2D, binuclear RuII ammine complex salts

Novel software for medical and technical Thermal Object Identification (TOI) using dynamic temperature measurements by fast IR cameras

This paper presents a thermal analysis and methodology of thermal parameters identification of thermal multilayer structures using thermographic measurements after dynamic heating (or cooling) the investigated objects. During the thermal transient process, thermal images are recorded, with the highest possible frame rate of the camera. Then, temperature and power signals are transformed into the frequency domain, to get finally the thermal time constants distribution corresponding to the thermal parameters of the structure. A brief description of TOI program developed in MATLAB environment as well as the exemplary identifications of 2 different thermal objects are shown

Evidence of increased axillary blood flow velocity without increased handgrip strength and endurance in persons with a fibromuscular axillary arch

Background: The purpose of this in vivo study was to compare axillary artery blood flow velocity, and maximal handgrip strength and endurance performance in young subjects with and without an axillary arch (AA). Materials and methods: One hundred and fifty-six young adults were screened for the presence of an AA on their dominant arm side. After physical examination subjects were checked using diagnostic echography for the presence of an AA. Sixteen subjects with an AA and 15 without an AA had their axillary artery peak systolic velocity quantified in 3 different arm positions using Doppler ultrasound. Maximal handgrip strength and endurance performance was quantified in the same positions using a functional rehabilitation system. Results: Mean peak systolic velocity was significantly higher in the AA group compared to controls in abduction/external rotation of the arm during muscle relaxation (p = 0.003) and contraction (p = 0.01). No significant differences between groups were found for maximal handgrip strength and endurance performance. Conclusions: This study provides evidence for a transient axillary artery compression by the AA in a throwing position. This is not reinforced by additional contraction of the shoulder muscles along with the AA. Axillary artery compression does not influence maximal handgrip strength and endurance performance in symptom-free young adults

Multilevel use of image repository in the field of veterinary imaging and dissemination of training tools

[Extract] Until now the veterinary teaching environment is limited to static two dimensional materials. In order to improve the teaching experience we decided to adapt our educational PACS to build 2D and 3D viewing veterinary datasets. As entry level of education we setup a knowledge base consisting out of normal anatomy [1, 2]. The second step is the construction of an imaging atlas compared with the normal anatomy of every animal. The third step is the construction of a database containing a wide variety of radiopathology cases. The final level is the integration in an e-learning platform namely WikiVet [3] which is a collaborative initiative involving UK veterinary schools. The project is creating a comprehensive online knowledge base and will provide a reliable reference source to supersede Wikipedia for veterinary students, paramedics and graduates anywhere in the world, improving diagnostic skills using diagnostic imaging