An Erbium Fiber Fabricated by the “Core-Suction” Technique

An erbium doped fiber preform having a lead germanate erbium glass core with silica cladding was fabricated by a newly developed technique named “Core-Suction”. This preform was then drawn into fiber and fiber cross-section, loss spectrum and refractive index profile measured. A 30 cm piece of the manufactured fiber was spliced to a standard silica fiber using a commercial available splicer. This spliced fiber was then used to setup an erbium doped fiber amplifier (EDFA) and gain spectrum of the amplifier measured. Distributed gain of the manufactured erbium fiber was measured using an optical frequency domain reflectometry (OFDR) based optical backscatter reflectometer (OBR). It is demonstrated that the “Core-Suction” technique can be used to make a high-gain amplifier that is compatible with conventional silica fibers.      

Comments on “A Hierarchy of Importance Indices”

The paper by Hwang (IEEE Trans. Reliability, vol. 54, pp. 169–172, 2005) presented structural importance measures in terms of cutsets or pathsets, and investigated how they are related. Hwang's paper has made contributions to importance measures. However, several errors which cause confusions are found in the paper. This note is to clarify these errors, and discuss the suspicions.      

Comments on “A Class of Fault-Tolerant Multiprocessor Networks”

A. Ghafoor presented node-disjoint paths of even networks using Figs. 4, 5, 6,and 7 (Ghafoor, IEEE Trans. Reliability, vol. 38, no. 1, pp. 5-15). However, the paper contains errors which cause confusion. We show that the node-disjoint paths, and Theorem 4 (Ghafoor, IEEE Trans. Reliability, vol. 38, no. 1, pp. 5-15), are not correct. We propose advanced node-disjoint paths, and prove that the fault diameter of even networks is d+1. This is optimal.     

A Piezo-Sensor-Based “Smart Tire” System for Mobile Robots and Vehicles

In this paper, we present the development of a tire rubber deformation sensing system that provides the critical information for understanding and estimation of wheel/ground interactions for mobile robots and vehicles. Polyvinylidene fluoride (PVDF)-based sensors are designed and fabricated to embed on the inner tread surface to measure the tire rubber tread deformation. Analytical models of the PVDF-based sensing system are presented to capture the wheel/ground contact information and friction characteristics. The sensed deformation measurements are integrated with the onboard control system through a wireless data transmission module. Experimental results on a skid-steered mobile robot are presented to show the feasibility and estimation of wheel/ground friction characteristics using the developed sensing system.     

A “Flying-Adder” On-Chip Frequency Generator for Complex SoC Environment

The spirit of system-on-chip (SoC) approach is to integrate more and more system functions into one single chip. Consequently, the on-chip clock requirement could be very complicated due to the various functions the chip has to support. To fulfill those clock needs, it is not uncommon for more than several phase-locked loop (PLLs) to be used within one such large chip. Designing these on-chip PLLs is a very challenging task in term of cost and performance. To solve this problem for a HDTV SoC of over 50 millions transistors, a ldquoflying-adderrdquo architecture based PLL (FAPLL) is constructed. This generic FAPLL is instantiated multiple times in this SoC for different functions, resulting in significant chip cost reduction.     

Digital Background-Calibration Algorithm for “Split ADC” Architecture

The “split ADC” architecture enables continuous digital background calibration by splitting the die area of a single ADC design into two independent halves, each converting the same input signal. The two independent outputs are averaged to produce the ADC output code. The difference of the two outputs provides information for a background-calibration algorithm. Since both ADCs convert the same input, when correctly calibrated, their outputs should be equal, and the difference should be zero. Any nonzero difference provides information to an error-estimation algorithm, which adjusts digital-calibration parameters in an adaptive process similar to a least mean square algorithm. This paper describes the calibration algorithm implemented in the specific realization of a 16-bit 1-MS/s algorithmic cyclic ADC. In addition to correcting ADC linearity, the calibration and estimation algorithms are tolerant of offset error and remove linear scale-factor-error mismatch between the ADC channels. Simulated results are presented confirming self-calibration in approximately 10 000 conversions, which represents an improvement of four orders of magnitude over previous statistically based calibration algorithms.      

Comments on “Phase-Shifting for Nonseparable 2-D Haar Wavelets”

In their recent paper, Alnasser and Foroosh derive a wavelet-domain (in-band) method for phase-shifting of 2-D “nonseparable” Haar transform coefficients. Their approach is parametrical to the (a priori known) image translation. In this correspondence, we show that the utilized transform is in fact the separable Haar discrete wavelet transform (DWT). As such, wavelet-domain phase shifting can be performed using previously-proposed phase-shifting approaches that utilize the overcomplete DWT (ODWT), if the given image translation is mapped to the phase component and in-band position within the ODWT.      

Improvement on “Sequential Testing” in MIL-HDBK-781A and IEC 61124

This paper presents results of an analysis of the sequential test (ST) procedures described in MIL-HDBK-781A, and IEC 61124, intended for checking the mean Time Between Failures (TBF) value under an exponential distribution of the TBF. The methodological basis of the calculations consists in discretization of the ST process through subdivision of the time axis in small segments. By this means, the process is converted into a binomial for which an algorithm, and a fast computer program have been developed; and most important of all, a tool is provided for searching for the optimal truncation. The influence of truncation by time on the Expected Test Time (ETT) characteristics was studied; and an improved truncation method, minimizing this influence, was developed. The distributions of the test times were determined. The type A plan characteristics in IEC 61124:2006 have substantial inconsistencies in the probabilities of types I & II errors (up to a factor of 2), and in the ETT (up to 17%). We checked these results by using the binomial-recursive method, and by simulation. The Type C plans, reproduced from GOST R27.402:2005, are consistent; but there is scope (and need) for substantial improvement of the search algorithm for the optimal parameters.     

Repeat Bidding on Internet-Based Multiple-Item “Name-Your-Own-Price” Auctions

Name-Your-Own-Price (NYOP) auctions have gained recent popularity on the Internet. In many NYOP settings, the auction firm displays multiple bidding items for the bidders (such as multiple options of airline tickets) and restricts them to place a single offer. Recent studies have, however, shown that the Internet environment enables many customers to engage in repeat bidding. Our purpose in this paper is: 1) to analyze the consumer value gained by repeat bidding on multiple-item NYOP auctions under different-bidding strategies; 2) to derive an upper bound on the value gained by repeat bidding when multiple items are present; and 3) to analyze the multiple-item NYOP auction from a consumer-firm perspective. We use Monte Carlo simulation to discuss the effects of various auction parameters on the firm's expected profit, and show that the presence of multiple bidding items provides a win–win situation for both the auction firm and the bidders. In particular, we show that multiple items increase the expected value for the consumers and also help firms mitigate potential losses due to repeat bidding.      

The “Bayesian Anomaly” and Its Practical Mitigation

A fundamental logical problem in the Bayesian inference of a series system's failure probability is described, a practical means for its mitigation is discussed, and its application to space launch vehicles is illustrated. The problem is the ldquoBayesian Anomaly,rdquo the difference in the system's failure probability per operation inferred from prior estimates, and test or operational experience applied at a lower-level of the system; and from the convolution of the same priors, and of the same experience applied at the system level (or any level above the first). In particular, unlike in a classical inference, the mean estimates differ critically. Although it is not possible to entirely resolve the problem, a practical procedure for mitigating it, establishing consistency among the mean and variance estimates at the two levels, is delineated.     

Wafer-Level Defect Screening for “Big-D/Small-A” Mixed-Signal SoCs

Product cost is a key driver in the consumer electronics market, which is characterized by low profit margins and the use of a variety of “big-D/small-A” mixed-signal system-on-chip (SoC) designs. Packaging cost has recently emerged as a major contributor to the product cost for such SoCs. Wafer-level testing can be used to screen defective dies, thereby reducing packaging cost. We propose a new correlation-based signature analysis technique that is especially suitable for mixed-signal test at the wafer-level using low-cost digital testers. The proposed method overcomes the limitations of measurement inaccuracies at the wafer-level. A generic cost model is used to evaluate the effectiveness of wafer-level testing of analog and digital cores in a mixed-signal SoC, and to study its impact on test escapes, yield loss, and packaging costs. Experimental results are presented for a typical mixed-signal “big-D/small-A” SoC, which contains a large section of flattened digital logic and several large mixed-signal cores.      

“Spiked” GaInP Quantum Wells for Shorter Red Wavelength Emission

Compositional and strain limitations are often restricting the emission wavelength from quantum-well (QW) lasers. The letter presents simulation and experimental results on the effects of including thin higher bandgap layers into GalnP QWs emitting in the short red wavelength range. These were considered "spiked" single QWs since the thin higher bandgap layers used in our studies varied in composition and led to carrier wavefunctions that are like perturbed single QW wavefunctions rather than wavefunctions of coupled QWs. The edge-emitting lasers having up to four-monolayer AlGalnP "spikes" in the QWs had an emission blueshift of up to 25 nm, whereas the degradation of other laser characteristics was in line with the degradation observed when similar emission blueshift was generated by conventional QW modification.     

Comments on “On the Self-Generation of Electrical Soliton Pulses”

A recent paper on soliton oscillators gave a parsimonious account of earlier work and omitted a critical reference.     

“Split ADC” Calibration for All-Digital Correction of Time-Interleaved ADC Errors

The “split analog-to-digital converter (ADC)” architecture enables fully digital calibration and correction of offset, gain, and aperture-delay mismatch errors in time-interleaved ADCs. The calibration of $M$ interleaved ADCs requires $2M + 1$ half-sized ADCs, a minimal increase in analog complexity. Each conversion is performed by a pair of half-sized ADCs, generating two independent outputs that are digitally corrected using estimates of offset, gain, and aperture-delay errors. The ADC outputs are averaged to produce the ADC output code. The difference of the outputs is used in a calibration algorithm that estimates the error in the correction parameters. Any nonzero difference drives a least-mean-square feedback loop toward zero difference, which can only occur when the average error in each correction parameter is zero. A simulation of a 4 : 1-time-interleaved 16-bit 12-MSps successive-approximation-register ADC shows calibration convergence within 400 000 samples.      

Fast Recovery Blind Equalization for Time-Varying Channels Using “Run-and-Go” Approach

In this paper, we propose a blind adaptive equalization scheme for time-varying channels, which combines a blind algorithm based on high order statistics (HOS) and decision-directed (DD) LMS algorithm. In contrast to the ldquostop-and-gordquo algorithm , where DD-LMS adaptation is stopped for unreliable decisions, the proposed algorithm applies a blind algorithm based on HOS for the unreliable decisions. Furthermore, the region of reliable decisions is updated corresponding to the estimated signal quality. Hence, the proposed ldquorun-and-gordquo algorithm inherits MMSE performance of DD-LMS and the (re)acquisition ability of the blind algorithm. Especially, for decision feedback equalizers (DFEs) the proposed algorithm provides robust blind initialization and reacquisition ability under time varying multipath environments.     

A Note on “Global Robust Stability Criteria for Interval Delayed Neural Networks Via an LMI Approach”

A recently reported result concerning the global exponential robust stability of delayed neural networks is revisited. It is shown by a counter example that the result is invalid because the proof is incorrect, and then a modified version is given. The paper also presents an improved sufficient condition for global exponential robust stability of the neural networks with unbounded activation functions and time-varying delays. Finally, a numerical simulation is given to show the effectiveness of the obtained result.      

Comments on “Semi-Blind Channel Estimation and Equalization for MIMO Space–Time Coded OFDM”

A semiblind channel estimation scheme of the multiple-input–multiple-output space–time coded orthogonal frequency-division multiplexing system was proposed in the aforementioned paper for either real or complex with symmetric signals. We point out that this scheme cannot work correctly for complex signal scenario.      

Comments on “Improved Sufficient Conditions for Global Asymptotic Stability of Delayed Neural Networks”

In this note, we point out that the results given in the paper by Wu and Cui (2007) can be obtained by using the results given in Lu (2003). Moreover, the results given in the second paper are much stronger under less restrictive conditions.