Automatic CX Tool for Electrical Building

Commissioning (Cx) consists in specifying building system performance requirements set by the owner, auditing different judgments and actions performed by the Cx related parties in order to achieve the performance, writing necessary and sufficient documentation, and verifying that the system enables proper operation and maintenance through functional performance testing. The process of Cx is the whole set of tasks ensuring that the performance of buildings meet the awaited performance. This process comes within the scope of Kyoto's protocol by reducing energy consumption and also emission of green house gases (GHG). This study is carried out for an exemplary electrical building of educational facilities. The objectives of the project are to develop and test a Cx tool in order to increase the energy efficiency of the building while ensuring indoor comfort. This study shows that an appropriate design of a building is not sufficient to ensure an effective management of energy. The Cx of installations is an essential step to meet the required energy performances

Stopping of Charged Particles in a Magnetized Classical Plasma

The analytical and numerical investigations of the energy loss rate of the test particle in a magnetized electron plasma are developed on the basis of the Vlasov-Poisson equations, and the main results are presented. The Larmor rotation of a test particle in a magnetic field is taken into account. The analysis is based on the assumption that the energy variation of the test particle is much less than its kinetic energy. The obtained general expression for stopping power is analyzed for three cases: (i) the particle moves through a collisionless plasma in a strong homogeneous magnetic field; (ii) the fast particle moves through a magnetized collisionless plasma along the magnetic field; and (iii) the particle moves through a magnetized collisional plasma across a magnetic field. Calculations are carried out for the arbitrary test particle velocities in the first case, and for fast particles in the second and third cases. It is shown that the rate at which a fast test particle loses energy while moving across a magnetic field may be much higher than the loss in the case of motion through plasma without magnetic field.Comment: 14 pages, 3 figures, LaTe

Slow Light in Doppler Broadened Two level Systems

We show that the propagation of light in a Doppler broadened medium can be slowed down considerably eventhough such medium exhibits very flat dispersion. The slowing down is achieved by the application of a saturating counter propagating beam that produces a hole in the inhomogeneous line shape. In atomic vapors, we calculate group indices of the order of 10^3. The calculations include all coherence effects.Comment: 6 pages, 5 figure

From Bengali to English: sequential bilingualism of a second-generation British Bangladeshi

The paper discusses sequential language acquisition of the researcher's daughter Safa who transformed from a monolingual Bengali speaker to an almost monolingual English speaker in a few months after moving to the UK. Safa was born in Bangladesh and was a monolingual Bengali speaker until she was three years and nine months when the family moved to the UK. Unlike most research on sequential bilingualism, Safa's transition from Bengali to English went through a period of an invented language, which she developed and used for a few months. Safa then underwent language shift as Bengali became her passive language. Safa's loss of fluency in Bengali was mainly due to the absence of Bengali linguistic environment, because her family lived outside the community. Safa's mother's indifference to Bangladeshi ethnicity and her parents’ positive attitude towards Britishness meant that her decline in Bengali did not cause them much concern. Despite the lack of proficiency in Bengali, Safa still retains a strong ethnic Bangladeshi identity. Tabors and Snow’s four-stage developmental process of sequential second-language acquisition has been applied to find the similarities and differences in Safa's case, while language maintenance and shift theories have contributed to the analysis of the process of her language shift

STARTING AND GENERATION OF SUB-100fs PULSES IN Ti:Al2O3 BY SELF-FOCUSING

Ti:Al2O3 has the available bandwidth for directly generating very short tunable pulses at high average power. We introduce a modelocking technique based on self-focusing that has been used to modelock titanium sapphire in an aligned, GVD compensated cavity. When the peak power levels are sufficiently high we demonstrate that self-focusing takes place in the sapphire due to the optical Kerr effect. We show how the mode changing aspects of this self-focusing can be harnessed to drive and sustain the modelocking process. We also describe how the self-phase modulation resulting from the Kerr effect, in conjunction with the negative GVD introduced by the intracavity prism dispersion delay line leads to a quasi-soliton pulse whose parameters can be modified and its properties can be understood based on non-linear solution solutions previously described We report 800 mW at sub- 100fs (when pumped with 8W) and 2.1W output with 120fs pulsewidth (pumped with 14W). Passive modelocking techniques are generally not self starting. We have developed a method based on mode-dragging to generate the intensity fluctuations required to initiate the modelocking process in Kerr Lens Modelocked lasers

GENERATION OF CW COHERENT RADIATION IN THE NEAR U.V.

Following the demonstration of the second harmonic generation in 1961 by Franken, numerous non linear methods have been used associated with pulsed lasers to generate U.V. radiation in the range 200-300 nm. The corresponding sources are now widely used in the spectroscopic studies, but their limited monochromaticity makes them of poor interest in high resolution spectroscopy. There is for long time now a pronounced interest to have at one's disposal a radiation source which provides extremely narrow bandwith, convenient intensity and tunability, but it is only recently, with the advent of powerful CW dye lasers, and the development of enhancement technics that the first reliable sources have been demonstrated, and the first high resolution spectroscopy studies performed. We give in this paper a brief and then certainly incomplete review of the different progress that have been done in the generation of highly monochromatic U.V. radiation, as well as a review of the different experiments that have been performed in this frequency domain. We mainly deal with the use of non linear crystals in second harmonic generation and sum frequency mixing schemes, leaving for the conclusion the listing of the other possibilities of coherent CW U.V. generation that could be used in a near future

Production d'impulsions picosecondes et subpicosecondes par lasers à colorant continus à modes bloqués

An analysis of the operation of mode-locked lasers producing picosecond pulses is given, with emphasis on the CW dye laser which is alone capable of delivering subpicosecond pulses. First, it is shown how the locking of the phases of the modes of a laser is necessary for the compression of light energy into a short time interval. Then, the various methods of mode-locking are analyzed with the aid of very simple qualitative descriptions and physical pictures. Experimental realizations of each method are also given. After describing how the pulse durations are measured, the performances of the various picosecond laser systems are compared. By way of conclusion, a few brief ideas of the most recently research developments in the field are given.Une analyse du fonctionnement d'un laser en régime modes bloqués, permettant la production d'impulsions picosecondes, est présentée ; on insiste particulièrement sur le cas des lasers à colorant continus, seuls capables de délivrer des impulsions subpicosecondes. On montre tout d'abord la nécessité de bloquer entre elles les phases des modes d'un laser pour obtenir une concentration de l'énergie dans le temps. Les différentes méthodes de blocage sont alors analysées à l'aide d'images et de considérations qualitatives très simples. Les principaux lasers picosecondes à colorant sont décrits à titre d'application de ces méthodes. Après avoir indiqué comment l'on mesure les durées d'impulsions, on compare leurs performances à celles d'autres types de lasers picosecondes. Enfin on donne en conclusion une idée des développements les plus récents des recherches dans ce domaine