Pulse characteristics of passively mode-locked diode lasers

For the first time to our knowledge, asymmetric pulse shapes and the linear and nonlinear chirp from a passively mode-locked semiconductor laser are directly measured. For the laser tuned to various center wavelengths, fall-time-to-rise-time ratios of 2.0 to 2.5 are measured. With the laser tuned to the shorter-wavelength side of its tuning range, a significant quadratic chirp of -60 fs/nm^2 is measured, along with a linear chirp of -800 fs/nm. The nonlinear chirp is responsible for the asymmetrically shaped compressed pulses that produce long-tailed autocorrelations

Supermodes of high-repetition-rate passively mode-locked semiconductor lasers

We present a steady-state analysis of high-repetition-rate passively mode-locked semiconductor lasers. The analysis includes effects of amplitude-to-phase coupling in both gain and absorber sections. A many-mode eigenvalue approach is presented to obtain supermode solutions. Using a nearest-neighbor mode coupling approximation, chirp-free pulse generation and electrically chirp-controlled operation are explained for the first time. The presence of a nonzero alpha parameter is found to change the symmetry of the supermode and significantly reduce the mode-locking range over which the lowest order supermode remains the minimum gain solution. An increase in absorber strength tends to lead to downchirped pulses. The effects of individual laser parameters are considered, and agreement with recent experimental results is discussed

Improved Iptv Channel Change times Through Multicast Caching of Pre-selected Channels

Name: RAY, THOMAS Date of Degree: DECEMBER, 2014 Title of Study: IMPROVED IPTV CHANNEL CHANGE TIMES THROUGH MULTICAST CACHING OF PRE-SELECTED CHANNELSMajor Field: ELECTRICAL ENGINEERINGAbstract: IPTV has grown in recent years to an estimated 100 million users worldwide. IPTV uses IGMP processes to stream an individual channel to a user until the next channel change when the current channel is stopped and the new selection begins streaming. One of the critical factors determining customer satisfaction is the requirement to have reasonably rapid channel change times of 2 seconds or less, but current channel change times are frequently above that threshold. Numerous research efforts have been ongoing to reduce these times including edge servers, I-frame management, buffering improvements, dynamic video coding, and pre-selecting channels. Channel pre-selection involves sending additional channels in hopes that the user's next selection will already be present at the user's set top box to reduce the channel change time. While this pre-selection technique has previously been proposed, the proposals have been limited in scope, typically based on set top box replacement, and lack specific details regarding the expected channel change reductions attained. This research addressed all of these shortcomings beginning with laboratory testing to verify that the channel change time reduction for successful pre-selection is two times the network delay plus the IGMP processing time which equates to an average of 320 millisecond reduction per channel change. Several pre-selection models were developed and evaluated using theoretical calculations, functional testing, and performance simulations. Sample data was generated to reflect a wide range of user IPTV viewing behavior for use in the performance simulations. The top two models resulted in an average of well over 70% success rates in accurately pre-streaming the user's next selection in the multicast cache output. This approach also has the benefit of being implemented on IPTV provider equipment and would typically only require firmware upgrades without the need for expensive new equipment or changes to existing standards. Operational considerations were also discussed to reduce problems and delays during the implementation phase of the system. Additional applications and future improvements were also presented.Electrical Engineerin

Method and system for fault accommodation of machines

A method for multi-objective fault accommodation using predictive modeling is disclosed. The method includes using a simulated machine that simulates a faulted actual machine, and using a simulated controller that simulates an actual controller. A multi-objective optimization process is performed, based on specified control settings for the simulated controller and specified operational scenarios for the simulated machine controlled by the simulated controller, to generate a Pareto frontier-based solution space relating performance of the simulated machine to settings of the simulated controller, including adjustment to the operational scenarios to represent a fault condition of the simulated machine. Control settings of the actual controller are adjusted, represented by the simulated controller, for controlling the actual machine, represented by the simulated machine, in response to a fault condition of the actual machine, based on the Pareto frontier-based solution space, to maximize desirable operational conditions and minimize undesirable operational conditions while operating the actual machine in a region of the solution space defined by the Pareto frontier

Generalized Mantel–Haenszel estimators for simultaneous differential item functioning tests

The Mantel–Haenszel estimator is one of the most popular techniques for measuring differential item functioning (DIF). A generalization of this estimator is applied to the context of DIF to compare items by taking the covariance of odds ratio estimators between dependent items into account. Unlike the Item Response Theory, the method does not rely on the local item independence assumption which is likely to be violated when one item provides clues about the answer of another item. Furthermore, we use these (co)variance estimators to construct a hypothesis test to assess DIF for multiple items simultaneously. A simulation study is presented to assess the performance of several tests. Finally, the use of these DIF tests is illustrated via application to two real data setsPeer ReviewedPostprint (author's final draft

Prophylactic and Therapeutic Breast Conservation in BRCA1/2 Mutation Carriers

Breast-conserving therapy (BCT) for sporadic breast cancer has been widely accepted by surgeons and patients alike. While BCT is associated with a higher risk of ipsilateral breast tumor recurrence (IBTR), it has not been shown to decrease overall survival (OS) in comparison with mastectomy. Many women with a BRCA1/2 mutation opt for mastectomy instead of breast-conserving measures at the time of a breast cancer diagnosis. In some cases, this is due to fear of aggressive disease, but to date, there have been no studies offering strong evidence that breast conservation should not be offered to these women. BRCA1/2-associated breast cancer has not been found to be more aggressive or resistant to treatment than comparable sporadic tumors, and no study has shown an actual survival advantage for mastectomy in appropriately treated affected mutation carriers. This paper reviews the available literature for breast conservation and surgical decision making in BRCA1/2 mutation carriers

Wavelength tunable source of subpicosecond pulses from CW passively mode-locked two-section multiple-quantum-well laser

A wavelength-tunable passively-mode-locked semiconductor laser source of subpicosecond pulses is demonstrated. The system includes a two-section multiple-quantum-well laser which is coupled to an external grating for tuning and is followed by an external grating pair for pulse compression. A tuning range of 16 nm round 846 nm is obtained, resulting in compressed pulse widths as short as 260 fs and pulse widths shorter than 600 fs for all wavelength values within this tuning range. Time-bandwidth products are one to two times the transform limit