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Register a new userEffect of Nd-YAG laser Pumping Power on Output Pulse Characteristics of Blue Ti-Sapphire Laser
تأثر وسائط نبضات الخرج لبلورة تيتان- الياقوت الأزرق بتغير استطاعة الضخ لليزر نيوديميوم- ياغ
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يقدم النموذج المقترح آلية مبسطة لدراسة تأثير تغيرات وسـائط الـدخل، مثـل معامـل التـضخيم الأعظمي، و معدل الضخ، و معامل الضياع و عموماً استطاعة الضخ، في مميزات نبضات الخـرج الآتيـة: زمن التأخير، و عرض النبضة، و مدة نشوء النبضة و قيم القمم العظمى لكثافة فوتونات ليزر الضخ Nd YAG - من ناحية، و خرج بلورة تيتان– الياقوت الأزرق المضخوخة مع مفتـاح جـودة ذاتـي للكـسب و المقترنة مع بلورة لاخطية من ناحية ثانية. بينت الحسابات العددية أن: قمم كثافة فوتونات الخرج، و عرض النبضة، و زمن التأخير و مدة أو مدة نبضة الخرج الليزري، تتأثر بشدة بتغييرات استطاعة منبع الضخ لكلا الوسطين.
sapphire oscillator in order to generate a single wavelength at 780 nm. The model offers a simple mechanism to investigate the impact of the variations of the input parameters (maximum amplification coefficient, pumping rate, loss coefficient, and pumping density) on the output pulse characteristics (delay time, pulse width, pulse build up time, duration and peaks maxima of the Nd3+ -YAG pumping laser). Moreover, this model allows studying the gain-switched Ti:sapphire output characteristics as being pumped by the second harmonic wavelength (532nm). Numerical results showed that the maxima of the output photon density, pulse width, delay time, and pulse duration are very much dependent on the power variations of the pumping source.
References used
(N. J. Vasa, M. Tanaka, T. Okada, M. Macda, O. Uchino, “Comparative study of spectral narrowing of a pulsed Ti:sapphire laser using pulsed and CW injection seeding”, J. Appl. Phys. B (Laser and Optics) 62,51-57 (1996
(G. A. Skripko, S. G. Bartoshevich, I. V. Mikhnyuk and I. G. Tarazevich, “LiB3 O5: a highly efficient frequency converter for Ti:sapphire lasers”, Opt. Lett. V(16), N(21) ,1-3, (1991
(J. E. Murray and S. E. Harris, “Pulse lengthening via internal second – harmonic generation”, Journal of Applied Physics. V(41),N(2), (1970
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The research has been done in Alassad University Hospital in Lattakia, from January 2009 to January 2011 and included 80 pseudophakic eyes of 80 patients ] 36 (45.0%) belonged to male sex and 44 (55.0%) females[ older than 15 years having PCO with
decreased best corrected Visual Acuity (VA) of two or more Snellen’s chart line. Before laser treatment, the VA was assessed and all patients were examined on slit lamp for IOP and to rule out the causes for reduced vision other than PCO. Then 2-3 mm size capsulotomy was done with Q-switched Nd: YAG Laser, with Abraham’s posterior capsulotomy lens, after topical anesthesia, by using minimum amount of energy and fewest numbers of pulses. Patients were followed for assessment of best corrected VA and for possible complications just after laser and at the end of 1st week, 2nd week and the 4th week. The post-laser treatment was advised in accordance with complications to each patient.
The types of PCO were fibrosis in 54 (67.5%) eyes, Elschnig pearls in 16 (20 %) eyes and wrinkling in 10 (12.5%) eyes. Pre-laser visual acuity was CF-6/60 in 42 (52.5%) eyes, 6/36-6/24 in 23 (28.75%) eyes and 6/18-6/12 in 15 (18.75%) eyes. Post-laser VA was improved to 6/9-6/6 in 60 (75%) eyes. Out of 80 patients, 10 (12.5%) eyes developed the complications due to YAG laser which included IOL pitting in 4 (5%) eyes, raised IOP in 1 (1.25%), uveitis in 2 (2.5%), iris bleeding (hyphema) in 1 (1.25%), vitreous in anterior chamber in 1 (1.25%), and cystoids macular edema (CME) in 01(1.25%) eye. None of the eye developed sight threatening complications like retinal detachment or macular hole. The 20 (25%) eyes did not achieve the significant improvement because of pre-existing pathology in the posterior segment that was not diagnosed at the time of screening due to thick PCO.
This means that Nd: YAG laser capsulotomy is effective and convenient method for doing capsulotomy in all types of PCO. It is free from the risk of endophthalmitis found in surgical capsulotomy.
The laser has been used as an alternative effective method of etching enamel surface for direct bonding of orthodontic brackets instead of phosphoric acid. The aim of this study was to compare shear bond strength of orthodontic brackets following Er-
YAG versus Nd-YAG Laser etching. Eighty human extracted upper premolars were collected and divided randomly into two equal groups; the buccal enamel surface of the first group was etched by Er-YAG laser while the second group was etched by Nd-YAG laser. Each group was divided into two equal subgroups according to the bonding material type (chemical cure resin or light cure resin). The mechanical test has occurred by using a universal testing machine (Instron). The finding showed that no statistically significant differences in mean of shear bond strength between (Nd-YAG, Er-YAG) Laser etching group were found regardless of the bonding type.
The work includes the development of a program in an advanced – programming
language. to solve two none linear related partial differential equation that form a
mathematical model that describes the dynamic status of laser ,so that we can study the
properties of radiation density through this type the related program ,as well as the
population inversion inside the homogeneous medium of laser . We have studied the
strength f the out put power as well as the population inversion in the case of pulse –
working of the solid state laser Nd:YAG and the population inversion change as a function
of the diameter and length of the effective medium of laser .
The broodstock of Blue tilapia (Oreochromis aureus) were reared in glass aquaria in the laboratory of the High Institute of Marine Research to study the effect of different water salinities on growth rates of those broodstocks and comparing the resul
ts with those obtained from the natural environment (freshwater).
The broodstock were transported from El-Sin Fish Farm- Banias to the culture aquaria at the beginning of April (2011). After acclimation to the three studied water salinities (7‰, 14‰ and 19 ‰) in three aquaria (the forth aquarium was left as a control: fresh water), the fish were fed on a diet containing 35 % protein till satiation, twice a day for 72 days. The results revealed that the broodstock reared at 14‰ Salinity produced the best weight gain, where the weight gain was 18.76 g/fish with a feed conversion rate (FC) of 2.04. The weight gain was 17.16 g/fish for the fish reared at 7‰ with a FC= 2.51, while broodstock reared at fresh water gained 14.63g/fish with a FC= 2.97. The worst weight gain was obtained from the broodstock reared at 19‰ (9.24 g/fish) with a FC= 3.7.
We motivate and propose a suite of simple but effective improvements for concept-to-text generation called SAPPHIRE: Set Augmentation and Post-hoc PHrase Infilling and REcombination. We demonstrate their effectiveness on generative commonsense reason
ing, a.k.a. the CommonGen task, through experiments using both BART and T5 models. Through extensive automatic and human evaluation, we show that SAPPHIRE noticeably improves model performance. An in-depth qualitative analysis illustrates that SAPPHIRE effectively addresses many issues of the baseline model generations, including lack of commonsense, insufficient specificity, and poor fluency.
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