High-power mode-locked external cavity semiconductor laser usinginverse bow-tie semiconductor optical amplifiers

This paper presents experimental results of using an inverse bow-tie gain guided semiconductor optical amplifier (SOA) as the optical gain element in a high-power external cavity semiconductor laser. An average output power of 700 mW is demonstrated in continuous-wave (CW) operation while 400 mW of average power is obtained in both passive and hybrid mode-locked operation, with subsequent optical amplification in an identical SOA. The mode-locked laser operates at a repetition rate of 1.062 GHz, owing to the interplay between the gain and saturable absorber dynamics. Optical pulses are generated with a temporal duration of 5 ps, which implies a pulse energy of 376 pJ, and a peak power of 60 W. Further reduction of the optical pulsewidth to 1.3 ps is also achieved by using dispersion compensation techniques. These results show the promise of novel SOA devices for use as gain elements in external cavity semiconductor lasers. The generated output pulse characteristics from mode-locked operation is sufficient for use in novel three-dimensional data storage applications, and in large-scale commercial printing and marking applications     

Communication control and leadership in telecommunications by small groups

. Sixteen teams of four persons each solved four realistic problems, one on each of 4 days, by communicating over a closed-circuit television system with an audio capacity. Teams were assigned to conditions which either did or did not have centrally controlled switching so that only one person could talk at a time, and which either did or did not have one subject appointed to help perform some of the experimenter's tasks. Teams were paid bonuses depending on how well they solved each problem. Dependent measures include time to solution, the quality of solution, measures of verbal communication and questionnaire responses. Teams in the switched condition took longer to solve problems and used fewer but longer messages than did subjects in the non-switched condition. There were no striking differences between the quality of the solutions achieved in the two conditions. Designating a helper for the experiment produced fewer significant results than anticipated. It appears that mechanical variables such as those manipulated here are less important than other variables, perhaps personality, in the emergence of leadership.     

Studies in interactive communication: V. Cooperative problem solving by skilled and unskilled typists in a teletypewriter mode.

2-person teams of 8 skilled and unskilled typists each (female high school students) cooperated to solve credible, real-world problems by communicating through interconnected typewriters or, as a control, by conversing face-to-face. Performance was assessed by (a) the time taken to solve a problem, (b) measures of behavioral activity, and (c) several measures of verbal output. All 3 criteria showed large differences between face-to-face conversation and communication via typewriter. There were, however, no differences between the 2 groups of typists on any criteria even when they communicated by typewriter, in part because 1/3 or less of the total time was spent typing, and in part because Ss composed their own messages. Findings have implications for the use of keyboard terminals in telecommunications and interactive computer system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An exact multinomial one-sample test of significance.

The exact multinomial test described in this article can be used to test the significance of variations in the numbers of observations distributed into 2 or more mutually-exclusive categories. When there are only 2 categories the test reduces to the binomial test. The test is valid for samples of any size but it quickly becomes prohibitively difficult to apply as the total number of categories increases. A comparison with the chi-square test shows how seriously the latter may be in error when the number of observations is small. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Specifying human-computer interface requirements†

Human factors principles are often not incorporated into the design of human-computer interfaces for a number of reasons, among them: Human factors is not part of main stream engineering, human factors has no binding way to influence development, and present guidelines and standards are too general. This article describes the rationale and technical features of a specification that provides a solution to these and other difficulties. The specification documents the results of translating standards and guidelines into project-specific requirements. Designs that meet requirements should be 'easy to use' and can be produced by designers without any human factors expertise. It puts human factors directly in the main stream of development and makes human factors more directly responsible and accountable for the usability of systems.     

Knowledge of performance as an incentive in repetitive, monotonous tasks.

This experiment tried to isolate the purely motivational effect of knowledge of performance from its informational and rewarding aspects. The Ss worked an hour a day, for 24 days, punching random digits into a teletype tape. They were told they were programming a computer and efforts were made to lend credibility to this ficion. 16 males undergraduate sudents were assigned to 1 of 4 groups. Ss in 1 group received no information about their output. In 2 other groups, the Ss could see a counter which taillied every stroke on the perforator and could, if they so chose, determine their daily work output. In the 4th group Ss were required to write down their output at the end of 15, 30, and 45 minutes, "for accounting purposes only." No significant differences were discovered among the 4 groups. Suggestions are offered to account for the discrepancy between the results of this experiment and those of a similar experiment reported by Gibbs and Brown in 1955. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

168 channels /spl times/ 6 GHz from a multiwavelength mode-locked semiconductor laser

A gain-flattened multiwavelength mode-locked semiconductor laser generates 168 discrete wavelength channels at 6 GHz. Intracavity etalon filtering delineates the 0.12-nm-spaced channels while spatial filtering inside a spectrometer broadens the laser spectrum to 20 nm. Mode locking produces 85-ps pulses in each channel at 750 MHz. The pulse-repetition rate is multiplied to 6 GHz per channel via optical time-division multiplexing to yield an aggregate pulse rate of 1 THz.     

Creep of Single Crystals of Nickel-Based Superalloys at Ultra-High Homologous Temperature

The creep behavior of single crystals of the nickel-based superalloy CMSX-4 was investigated at 1288 °C, which is the temperature of the hot isostatic pressing treatment applied to this superalloy in the industry. It was found that at this super-solvus temperature, where no γ′-strengthening occurs, the superalloy is very soft and rapidly deforms under stresses between 4 and 16 MPa. The creep resistance was found to be very anisotropic, e.g., the creep rate of [001] crystals was about 11 times higher than that of a [111] crystal. The specimens of different orientations also showed a very different necking behavior. The reduction of the cross-sectional area ψ of [001] crystals reached nearly 100 pct, while for a [111] crystal ψ?=?62 pct. The EBSD analysis of deformed specimens showed that despite such a large local strain the [001] crystals did not recrystallize, while a less deformed [111] crystal totally recrystallized within the necking zone. The recrystallization degree was found to be correlated with deformation behavior as well as with dwell time at high temperature. From the analysis of the obtained results (creep anisotropy, stress dependence of the creep rate, traces of shear deformation, and TEM observations), it was concluded that the main strain contribution resulted from 〈\( 0 1\bar{1} \)〉{111} octahedral slip.