Free-Space Optical Link as a Model Undergraduate Design Project

An undergraduate design project is described in which a free-space optical communications link is constructed. The interest and motivation for the students is achieved by using a visible laser and constructing a complete system by using the digital output of a CD/DVD player and an audio receiver to transmit music over the free-space link. In addition to providing a high-level technical experience, the project also teaches multidisciplinary teamwork and emulates a real working environment; it is relatively low cost, divisible into modules, and adaptable. An overview of the project is included with representative designs and information.     

A unified Green's function analysis of complicated DFB lasers

An efficient full-wave analysis technique for one-dimensional optical domains, known as the recursive Green's function method (RGFM), is presented for evaluation of distributed feedback (DFB) laser cavities with arbitrary material profiles. The method first constructs the Green's function of an inhomogeneous domain and subsequently uses Green's theorem to determine the laser optical field, lasing wavelength, and threshold gain. The technique is applied to investigate the performance of three DFB laser structures: a chirped-grating configuration, a modulated stripe width design, and a reduced duty cycle complex-coupled device. These structures are evaluated in terms of their single-mode lasing behavior and the uniformity of the optical field within the cavity     

Elevated free fatty acids induce uncoupling protein 3 expression in muscle: a potential explanation for the effect of fasting

The newly described uncoupling protein 3 (UCP3) may make an important contribution to thermogenesis in humans because of its high level of expression in skeletal muscle. Contrary to expectations, fasting, a condition that reduces resting energy expenditure, has been reported to increase UCP3 expression in muscle. We have confirmed that a 10-fold increase in UCP3 mRNA levels occurs in rat quadriceps muscle between 12 and 24 h of food removal. A less consistent twofold increase in muscle UCP2 mRNA levels was observed in animals fasted for up to 72 h. Administration of recombinant leptin to prevent a fall in circulating leptin levels did not eliminate the fasting-induced increase in quadriceps UCP3 expression. Administration of a high dose of glucocorticoid to fed animals to mimic the increase in corticosterone induced by fasting did not reproduce the increase in UCP3 expression observed in fasted animals. In contrast, elevation of circulating free fatty acid levels in fed animals by Intralipid plus heparin infusion caused significant increases in the UCP3/actin mRNA ratio compared with saline-infused fed controls in both extensor digitorum longus (2.01 +/- 0.34 vs. 0.68 +/- 0.11, P = 0.002) and soleus muscles (0.31 +/- 0.07 vs. 0.09 +/- 0.02, P = 0.014). We conclude that free fatty acids are a potential mediator of the increase in muscle UCP3 expression that occurs during fasting. This seemingly paradoxical induction of UCP3 may be linked to the use of free fatty acid as a fuel rather than an increased need of the organism to dissipate energy.     

Artificial Intelligence and Software Engineering: Breaking the Toy Mold

The application of AI techniques to software engineering has suffered, from the perspective of practising software engineers, due to a tradition of testing ideas and theories on small, toy domains. At the IJCAI-95 Workshop on AI and Software Engineering we focused onthis issue, and here we discuss some of the results of that workshop, identifying the major weaknesses in AI&SE research, and offer some insight into the future of the field.     

Learning and education: a continuing frontier for AI

Learning is the most important part of artificial intelligence. A basic research effort can explore how to build software that can learn and be educated very broadly.     

Sensitivity-oriented versus didactically oriented in-service counselor training.

Compared the effectiveness of 2 different in-service training workshops for counselors. 18 male and 15 female secondary school counselors with a mean age of 37.3 yrs and mean counseling experience of 6.3 yrs served as Ss. 22 Ss were given a 16-hr Carkhuff-type refresher in facilitative interpersonal process plus 8 hrs either of sensitivity experiences or traditional didactic learning. 11 volunteers whose schedules could not be accommodated served as controls. Pre-post criteria of relationship skill were assessed in actual and simulated interviews. Results demonstrate the usefulness of Carkhuff-based training supplemented by group encounter as a professional-skills enhancer, and underscored the transferability of sensitivity training gains to counseling. It is concluded that the interpersonal learning that occurs in a sensitivity context may be a more valuable resource in real-life counseling situations than the learning effected by didactic materials. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compound gear trains of minimum equivalent inertia

This paper develops the radii of the gears in a compound gear train of specified length and overall ratio for minimum equivalent inertia. The resultant equation set that completely solves the problem requires iterative solution, for which a FORTRAN program is supplied.     

Optical fibers coated with non-linear Langmuir-Blodgett films

We report second harmonic generation (SHG) in structures composed of optical fiber cores coated with Langmuir-Blodgett non-linear films. Such structures may serve as attractive alternatives to currently available coated slab non-linear waveguides. The fabrication of frequency doublers, couplers and modulators on optical fibers would eliminate the difficult problems of coupling from planar signal conditioners, sensors and detectors onto fiber transmission systems. In addition, the small size of fibers allows for the high energy densities required for non-linear interactions to exist over large distances.

Our results confirm that fibers can be coated and the deposition ratio monitored, provided that a sufficient number are dipped simultaneously. The dependence of SHG on distance as well as the variation with number of layers for a hemicyanine dye deposited on multimode fiber cores are discussed.     

Forward analysis of some special Stewart platforms

A closed forward displacement analysis is performed for a parallel mechanism where a triangular platform is joined to a hexagonal base, with two legs from each triangle vertex connected to an adjacent pair of base vertices. A new approach, based on symbolic manipulation computer techniques, is used to show there are 16 solutions for any given set of leg lengths. If the platform is an equilateral triangle, the base a hexagon with a rotational symmetry, and the legs put in two natural groups, this approach can show that one of these sets may be replaced by cables (so the leg can only “pull”), and the other set can be rods that are only under compression (we refer to this subsequently as only “push”). If the base is further constrained to be planar the rod/cable values are related by a simple equation such that once the base and platform dimensions are known a wide range of rod/cable values may be picked. In these cases it can also be proved that the chosen solutions are the only physically realizable solutions (in the non‐planar case this can only be demonstrated computationally). Examples are provided for several cases. © 2000 John Wiley & Sons, Inc.     

Electro-optic sensor from high Q resonance between optical D-fiber and slab waveguide

An electro-optic sensor capable of detecting electric fields with a high degree of sensitivity and linearity is fabricated using optical D-fiber. The slab coupled optical sensor utilizes weak coupling and long evanescent interaction with a lithium niobate waveguide. Transmission dips from mode resonances have a linewidth of 0.12 nm and a Q factor of approximately 13,000. These sharp resonances improve device sensitivity and are achieved due to the unique fabrication process possible with D-shaped fibers. The sensor deviates <0.1% from linearity while monitoring fields between 200 V/m and 20 kV/m and promises high sensitivity to fields well beyond that range.