Compact high-power tunable three-level operation of double cladding Nd-doped fiber laser

We present a compact high-power continuous-wave tunable neodymium-doped double cladding fiber laser operating on three-level 4F3/2 - 4I9/2 transition with a maximum output power up to 810 mW. At 926.7 nm, it has a maximum slope efficiency of 49.3% against absorbed 808-nm pump. By compressing the fiber Bragg grating, 15-nm tuning range is achieved

Effects of resonant single-particle states on pairing correlations

Effects of resonant single-particle (s.p.) states on the pairing correlations are investigated by an exact treatment of the pairing Hamiltonian on the Gamow shell model basis. We introduce the s.p. states with complex energies into the Richardson equations. The solution shows the property that the resonant s.p. states with large widths are less occupied. The importance of many-body correlations between bound and resonant prticle pairs is shown.Comment: 4 pages, 3 figures, to be published in Phys. Rev.

Soliton generation using erbium doped fibre based circuitry

The invention of the erbium doped fibre amplifier (EDFA) has led to a revolution in telecommunications permitting data transfer at rates previously unimaginable with conventional regenerator technology. With the problem of loss largely eliminated it is now dispersion and nonlinearity that represent the principle barriers to utilizing the enormous bandwidth offered by optical fibre. Soliton transmission in which the nonlinear and dispersive effects within the fibre can be made to balance and effectively cancel provide one means of getting access to more of that potential transmission capacity. As the field has advanced further limiting issues have been identified, e.g. Gordon Haus jitter, soliton interactions, acousto-optic interactions etc., requiring more advanced solutions such as soliton control to be sought

50-fs pulse generation in an integrated erbium-doped fiber-laser/amplifier module

We report the generation of 50 - 90fs solitons from an all-fibre passively mode-locked erbium-doped fibre laser in combination with an erbium fibre amplifier

Picosecond pulse generation in erbium-doped fibre based circuits

Fibre circuits offer great potential for the development of convenient, compact, diode-pumpable ultrashort pulse suitable for a broad range of applications spanning from telecommunications, all-optical processing down to their use as basic laboratory tools. The principle advantages of the fibre environment for short pulse generation lie: (a) in the mode-confinement which results in low (~10 mW) laser thresholds, high efficiencies and ready access to fibre non-linearities (which are suitable for passive mode-locking and pulse processing), and (b) in the simple integratability of fibre devices which facilitate the construction of complex but compact functional circuits for the generation of specific optical pulse output

Amplification of femtosecond pulses in a passive, all-fibre soliton source

We report a theoretical and experimental study of the amplification of femtosecond soliton pulses generated by a passively mode-locked fiber laser in a high-gain erbium-doped fiber amplifier (EDFA). Results on the spectral and temporal evolution of 450-fs soliton pulses propagating within an EDFA are presented. Power gains as high as 30 dB and the generation of sub-100-fs Raman colored solitons are observed. The results are found to be well described by the theoretical model presented

Caretaker mental health and family environment factors are associated with adolescent psychiatric problems in a Vietnamese sample

Little is known about risk factors for adolescent mental health in Vietnam. The present study investigated the relationship between caretaker mental health and adolescent mental health in a cross-sectional Vietnamese sample. Primary caretakers completed measures of their own mental distress and general health status using the Self-Reporting Questionnaire-20 (SRQ-20) as well as reports of adolescent mental health using the parent version of the Strengths and Difficulties Questionnaire (SDQ). Multivariate regression models were used to examine the relationships between the caretaker and adolescent health variables. The demographic factors of age, sex, ethnicity, religious affiliation, and household wealth status demonstrated significant relationships with SDQ subscale scores. Caretaker mental health was positively associated with adolescent mental health, and this association remained significant even after accounting for other relevant demographic variables and caretaker general health status. Understanding correlates of adolescent mental health difficulties may help identify youth and families at risk for developing psychiatric problems and inform mental health interventions in Vietnam

Nutritive value of forages as affected by soil and climatic differences

Effects of environment on the performance of beef steers in Kansas have been studied since 1962. The experiments, in three phases, have included seven feedlot trials and one digestion trial

A functional model, eigenvalues, and finite singular critical points for indefinite Sturm-Liouville operators

Eigenvalues in the essential spectrum of a weighted Sturm-Liouville operator are studied under the assumption that the weight function has one turning point. An abstract approach to the problem is given via a functional model for indefinite Sturm-Liouville operators. Algebraic multiplicities of eigenvalues are obtained. Also, operators with finite singular critical points are considered.Comment: 38 pages, Proposition 2.2 and its proof corrected, Remarks 2.5, 3.4, and 3.12 extended, details added in subsections 2.3 and 4.2, section 6 rearranged, typos corrected, references adde

Fuzzy cluster validation using the partition negentropy criterion

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-04277-5_24Proceedings of the 19th International Conference, Limassol, Cyprus, September 14-17, 2009We introduce the Partition Negentropy Criterion (PNC) for cluster validation. It is a cluster validity index that rewards the average normality of the clusters, measured by means of the negentropy, and penalizes the overlap, measured by the partition entropy. The PNC is aimed at finding well separated clusters whose shape is approximately Gaussian. We use the new index to validate fuzzy partitions in a set of synthetic clustering problems, and compare the results to those obtained by the AIC, BIC and ICL criteria. The partitions are obtained by fitting a Gaussian Mixture Model to the data using the EM algorithm. We show that, when the real clusters are normally distributed, all the criteria are able to correctly assess the number of components, with AIC and BIC allowing a higher cluster overlap. However, when the real cluster distributions are not Gaussian (i.e. the distribution assumed by the mixture model) the PNC outperforms the other indices, being able to correctly evaluate the number of clusters while the other criteria (specially AIC and BIC) tend to overestimate it.This work has been partially supported with funds from MEC BFU2006-07902/BFI, CAM S-SEM-0255-2006 and CAM/UAM project CCG08-UAM/TIC-442