Baud rate response: characterizing modal dispersion for digitalfiber optic systems

A method of characterizing modal dispersion in optical fibers, for baseband digital applications, is developed. Pulse distortion due to modal dispersion is simulated using modal transfer functions and pseudorandom pulsetrains. The extent of the distortion at given baud rates is identified with eye diagrams. Received optical power penalties are calculated from eye diagrams for a spectrum of baud rates, resulting in a penalty-versus-baud rate function called a baud rate response (BRR). Three useful parameters are derived from the BRR. The BRR magnitude parameter and shape parameter are used accurately to calculate a fiber's modal-dispersion power penalty for any given baud rate. The maximum baud-rate length product provides a mechanism for specifying modal dispersion quality along fibers     

The timing of psychosocial transitions and changes in women's lives: An examination of women aged 45 to 60.

64 middle-class women from 4 age cohorts (45, 50, 55, and 60 yrs) participated in retrospective interviews to examine major psychosocial transitions (PTs) and the specific changes that were related to chronological age (CA) and/or to phases of the family cycle, the nature of the PTs, and the characteristics of the Ss who experienced them. Judges read the interview protocols and provided independent ratings of major PTs. Results indicate the following: (a) Major PTs were more likely to be associated with phases of the family cycle than with CA. (b) Within the family cycle, PTs were more likely to occur during the preschool (28% of the Ss), launching (42%), and postparental (33%) phases than during the no children, school-age, or adolescent phases. (c) PTs associated with the preschool and launching phases were characterized by dissatisfaction, personal disruption, marital unhappiness, and decreased personal development, whereas transitions associated with the post-parental phase were characterized by personal mellowing and improved marital relations. (d) Numerous self-reported psychosocial changes were associated with family cycle phase, and a small number of changes was associated with CA. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ultra-shallow raised p+−n junctions formed by diffusion from selectively depositedIn-situ doped Si0.7Ge0.3

In this paper, a novel raised p⁺−n junction formation technique is presented. The technique makes use ofin- situ doped, selectively deposited Si_0.7Ge_0.3 as a solid diffusion source. In this study, the films were deposited in a tungsten halogen lamp heated cold-walled rapid thermal processor using SiCl₂H₂, GeH₄, and B₂H₆. The microstructure of the Si_0.7Ge_0.3 layer resembles that of a heavily defected epitaxial layer with a high density of misfit dislocations, micro-twins, and stacking faults. Conventional furnace annealing or rapid thermal annealing were used to drive the boron from thein- situ doped Si_0.7Ge_0.3 source into silicon to form ultra-shallow p⁺−n junctions. Segregation at the Si_0.7Ge_0.3/Si interface was observed resulting in an approximately 3:1 boron concentration discontinuity at the interface. Junction profiles as shallow as a few hundred angstroms were formed at a background concentration of 10¹⁷ cm⁻³.     

On the energy dissipation and velocity discontinuities in granular materials and solution of a boundary value problem in geophysics

Summary Consider the plane-strain rigid-perfectly plastic deformation of a granular material which satisfies the stress equilibrium equations and the Coulomb yield criterion. An expression is derived which enables the rate of energy dissipation to be calculated for any pair of stress and velocity fields. This is specialised to the Spencer-Mehrabadi-Cowin model and a kinematic inequality is obtained. Jump conditions are derived for velocity discontinuities on the boundary and in the interior of the plastic region. A simple analytic solution of the equations of the Mehrabadi-Cowin model is presented for the deformation of a granular material filled joint or fracture separating two rock masses undergoing a shearing motion.With 5 Figures     

Influences of student background and teacher authoritarianism on teacher expectations.

Asked 25 White elementary school teachers to predict the academic grades and occupational attainment of 6 students: a middle-class White boy; a middle-class White girl; a lower-class White boy; a lower-class White girl; a middle-class Asian boy; and a middle-class Asian girl. In addition, teachers were classified as high or low in authoritarianism based on their tolerance of ambiguity and cognitive complexity. It was found that higher grade and occupational expectations were held for middle-class than for lower-class students. Grade expectations were higher for girls than boys and tended to be higher for Asians than Whites. White females were expected to attain higher occupational status than Asian females, but Asian males were expected to surpass White males on this measure. Finally, teachers who were high authoritarians were more likely than low-authoritarian teachers to utilize stereotypes that favored ingroups and tended to be less likely to use stereotypes that favored outgroups. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Therapy/counseling practices of urban school psychologists.

A questionnaire survey of 146 school psychologists showed that over half of the Ss provided therapy-counseling services. Over 90% viewed behavioral-learning orientations, reality therapy, and client-centered therapy as useful. Techniques that were considered useful included behavioral contracts, role plays, cognitive skills training, and relaxation techniques. Referrals were most frequently related to academic problems, relationship difficulties, and fighting. More time was spent with male students. Only 11% of the Ss reported that they received professional supervision for the therapy-counseling they provided, but 68% indicated that they evaluated treatment outcome. Implications for the training and professional role of school counselors are discussed. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On Effective Methods to Teach Mechanical Design

The Mechanical Engineering Department of the Pennsylvania State University has created a “real world” approach to the teaching of mechanical design. This paper describes the efforts to restructure the teaching methods and integrate more effectively the knowledge of the design of machine elements through an open-ended case study approach. It is a “just-in-time” learning method which uses the text book as a reference and prepares the students for their “capstone” design course, The “capstone” design course also has been redesigned to emphasize teamwork, scheduling, communication, ethics, and economics as well as application of analysis and prototype construction.     

The production of a Nd-Fe-B permanent magnet by a hydrogen decrepitation/attritor milling route

A bulk ingot of a Nd-Fe-B alloy has been powdered by a combination of hydrogen decrepitation and attritor milling. The powder was aligned and pressed in the hydrided condition and the green compact sintered at 1080? C for 1 h after an appropriate heating rate. Excellent densities were achieved after this procedure and the magnets produced by this method exhibited energy products in the region of 250 kJm^?3 (32 M GOe).