Data analytics and stochastic modeling in a semiconductor fab

The scale, scope and complexity of the manufacturing operations in a semiconductor fab lead to some unique challenges in ensuring product quality and production efficiency. We describe the use of various analytical techniques, based on data mining, process trace data analysis, stochastic simulation and production optimization, to address these manufacturing issues, motivated by the following two objectives. The first objective is to identify the sub‐optimal process conditions or tool settings that potentially affect the process performance and product quality. The second objective is to improve the overall production efficiency through better planning and resource scheduling, in an environment where the product mix and process flow requirements are complex and constantly changing. Copyright © 2010 John Wiley & Sons, Ltd.     

Sensitivity of school-aged children to pitch-related cues

Two experiments investigated the ability of 17 school-aged children to process purely temporal and spectro-temporal cues that signal changes in pitch. Percentage correct was measured for the discrimination of sinusoidal amplitude modulation rate (AMR) of broadband noise in experiment 1 and for the discrimination of fundamental frequency (F0) of broadband sine-phase harmonic complexes in experiment 2. The reference AMR was 100 Hz as was the reference F0. A child-friendly interface helped listeners to remain attentive to the task. Data were fitted using a maximum-likelihood technique that extracted threshold, slope, and lapse rate. All thresholds were subsequently standardized to a common d' value equal to 0.77. There were relatively large individual differences across listeners: eight had relatively adult-like thresholds in both tasks and nine had higher thresholds. However, these individual differences did not vary systematically with age, over the span of 6-16 yr. Thresholds were correlated across the two tasks and were about nine times finer for F0 discrimination than for AMR discrimination as has been previously observed in adults.     

Strong jump-traceability II: <Emphasis Type="Italic">K</Emphasis>-triviality

We show that every strongly jump-traceable set is K-trivial. Unlike other results, we do not assume that the sets in question are computably enumerable.     

Current density imaging by pulsed conduction electron spin resonance

In analogy with Nuclear MRI, the ESR signal phase shift of conduction electrons moving in electrical currents along controlled magnetic field gradients can be used to generate spatial electronic current density maps. First two-dimensional images of the current density distribution in quasi-one-dimensional organic conductors are presented.     

Functional MRI using super-resolved spatiotemporal encoding

Recently, new ultrafast imaging sequences such as rapid acquisition by sequential excitation and refocusing (RASER) and hybrid spatiotemporal encoding (SPEN) magnetic resonance imaging (MRI) have been proposed, in which the phase encoding of conventional echo planar imaging (EPI) is replaced with a SPEN. In contrast to EPI, SPEN provides significantly higher immunity to frequency heterogeneities including those caused by B₀ inhomogeneities and chemical shift offsets. Utilizing the inherent robustness of SPEN, it was previously shown that RASER can be used to successfully perform functional MRI (fMRI) experiments in the orbitofrontal cortex — a task which is challenging using EPI due to strong magnetic susceptibility variation near the air-filled sinuses. Despite this superior performance, systematic analyses have shown that, in its initial implementation, the use of SPEN was penalized by lower signal-to-noise ratio (SNR) and higher radiofrequency power deposition as compared to EPI-based methods. A recently developed reconstruction algorithm based on super-resolution principles is able to alleviate both of these shortcomings; the use of this algorithm is hereby explored within an fMRI context. Specifically, a series of fMRI measurements on the human visual cortex confirmed that the super-resolution algorithm retains the statistical significance of the blood oxygenation level dependent (BOLD) response, while significantly reducing the power deposition associated with SPEN and restoring the SNR to levels that are comparable with those of EPI.     

Synchronization of mutually versus unidirectionally coupled chaotic semiconductor lasers

Synchronization dynamics of mutually coupled chaotic semiconductor lasers are investigated experimentally and compared to identical synchronization of unidirectionally coupled lasers. Mutual coupling shows high quality synchronization in a broad range of self-feedback and coupling strengths. It is found to be tolerant to significant parameter mismatch which for unidirectional coupling would result in loss of synchronization. The advantages of mutual coupling are emphasized in light of its potential use in chaos communications.     

Electrostatics by Brownian dynamics: solving the Poisson equation near dielectric interfaces

The isomorphism between electrostatics and diffusion is discussed and utilized to develop a Brownian dynamics algorithm for solving the Poisson equation near dielectric interfaces. The electrostatic potential behaves as if carried by noninteracting, randomly moving pseudo-particles whose residence time in a given region of space is proportional to the electrostatic potential there. By applying random numbers from the exact solution for diffusion near a planar discontinuity, the Brownian motion of these particles can be propagated for large time steps, independent of spatial grids or artificial boundary conditions. The applicability of the Brownian algorithm is demonstrated in simple illustrative calculations.     

Some insight into the acoustics of the didjeridu

The Australian didjeridu is a unique and interesting instrument. Despite the fact that the bore shape is almost random in nature and varies considerably across different instruments, the didjeridu timbre is readily recognizable. This is also true despite the fact that the player can manipulate the timbre more than in most wind instruments, by changing the shape of his vocal tract. In this study we examine the didjeridu spectrum in detail, in order to determine the characteristics that are similar across different instruments, those that are constant for a given instrument, and those that are readily influenced by the player. To this end we recorded and analyzed the sounds of eight instruments of different quality, all of them played across a range of timbres. Examining the resultant spectra, along with the resonance frequencies of these instruments, leads to a number of interesting conclusions. One of these is that the random nature of the instrument bore is actually conducive to creating its typical timbre. We also give a preliminary explanation of the differences between good and poor instruments.