The structure and management of service level agreements innetworks

The paper proposes a structure for quality-of-service (QoS)-centered service level agreements (SLA), and a framework for their real-time management in multiservice packet networks. The SLA is structured to be fair to both parties, the service provider and their customer. The SLA considered here are for QoS assured delivery of aggregate bandwidth from ingress to egress nodes; however, the control and signaling is for the more granular flows or calls. A SLA monitoring scheme is presented in which revenue is generated by the admission of flows into the network, and penalty incurred when flows are lost in periods when the service provider is not SLA compliant. In the SLA management scheme proposed, the results of a prior off-line design are used, in conjunction with measurements taken locally at ingress nodes, to classify the loading status of routes. The routing and resource management are based on virtual partitioning and its supporting mechanism of bandwidth protection. The effectiveness of SLA management is measured by the robustness in performance in the presence of substantial diversity in actual traffic conditions. A simulation testbed called D'ARTAGNAN has been built from which we report numerical results for a case study. The results show that the SLA management scheme is robust, fair and efficient over a broad range of traffic conditions     

An artificial neural network approach on parametric optimization of laser micro-machining of die-steel

In the present research, laser micro machining (LMM) of tungsten-molybdenum general purpose high speed steel (Rex M2) has been studied. Selection of optimum machining parameter combinations for obtaining higher depth of groove and smaller height of recast layer is a challenging task in LMM due to the presence of a large number of process variables. There is no perfect combination of parameters which can simultaneously result in both the highest depth of groove and lowest height of recast layer. This paper presents an attempt to develop a strategy for predicting the optimum machining parameter setting for the generation of the maximum depth of groove with minimum height of recast layer. A feed forward back-propagation neural network has been developed to model the machining process. The model, after proper training, is capable of predicting the response parameters as a function of four different control parameters. Experimental results demonstrate that the machining model is suitable and the optimization strategy satisfies practical requirements. The developed model has been found to be quite unique, powerful and flexible.     

Modified CMA based blind multiuser equaliser with decision directed scheme

A modified constant modulus (CM) algorithm based blind multiuser equaliser with a decision directed (DD) scheme is developed that does not require any mutual decorrelation and is suitable for downlink direct sequence code division multiple access systems. The performance of the proposed time domain adaptive equaliser is evaluated with respect to usual parameters and is found to perform better than the concurrent CM algorithm and DD scheme.     

Performance analysis of an improved MMSE multiuser receiver formismatched delay channels

Motivated by the fact that time delays in a practical direct-sequence code-division multiple-access (DS-CDMA) system can never be perfectly estimated, an improved minimum-mean squared-error (MMSE)-based receiver is proposed and analyzed. Via the simple assumption of a probability distribution for the delay estimation errors, the proposed receiver can achieve a performance superior to that of the conventional MMSE (CMMSE) receiver. The performances of this improved receiver and the CMMSE receiver are compared in terms of the mean squared error (MSE), probability of error, and asymptotic multiuser efficiency (AME). As the original definition of AME does not consider mismatched channels, the behavior of three single-user receivers bearing imperfect delay estimation is also investigated. These single-user receivers are employed to define a more appropriate AME. Finally, an efficient update mechanism to accommodate dynamic channel statistics, and thus practical implementation, is proposed     

A common precursor to neurotensin and LANT6 and its differential processing in chicken tissues

Antisera towards neurotensin (NT) and the structurally related peptide, LANT6, were used to characterize immunoreactive peptides and proteins in extracts of chicken tissues. A 17 kDa protein was identified by Western blotting as a potential precursor to NT and LANT6. However, the posttranslational processing of this common precursor appeared to be tissue specific, giving rise to disproportionate amounts of NT and LANT6, along with varying expression of a large molecular LANT6 (M(r), 15 kDa). The intestinal cells containing immunoreactive NT, LANT6, and large molecular LANT6 behaved similarly during fractionation by size and density. These activities also banded together in particles resembling vesicles during centrifugation of isotonic homogenates of tissue. These results suggest that chicken NT and LANT6 are biosynthesized as parts of the same precursor, the processing of which can give rise to a variety of products stored within secretory vesicles.     

Preparation and characterization of r.f.-sputtered multilayered TiN---Au films

TiN---Au films with multiple intermediate layers deposited by r.f. sputtering are suggested as a solution to the problem of adhesion of gold films to TiN coatings. Their optical and mechanical properties are investigated and compared with those of conventional electroplated gold films. Various analysis techniques have been used: Auger electron spectroscopy to determine the composition profiles, the direct tensile test for adhesion characteristics, optical rub test for scratch characteristics, salt spray test for corrosion characteristics and the selected ordinate method to identify the color of resultant films. It is shown that poor adhesion of gold films of TiN coatings can be overcome. Resultant multilayered TiN---Au films show the same color as that of commercially available electroplated gold films and their reflectivity reaches 98% of that of gold films over the wavelength range studied. For further applications, electrical properties of multilayered TiN---Au have also been studied. The sheet resistance of these TiN---Au films on n-Si and p-Si is in the range 0.54ω/□–6.12ω/□. Thus these multilayered structures may be used as durable contacts for microelectronic applications.     

Soft handoff algorithms for CDMA cellular networks

This paper discusses the design of soft handoff algorithms for cellular communication systems. The handoff process is modeled as a hybrid system and handoff design is cast as an optimization problem based on such a model. Performance is evaluated in terms of call quality, average number of active base stations, average number of active set updates, and average amount of interference. A soft handoff algorithm, which achieves a tradeoff between these performance criteria, is obtained using principles of dynamic programming. One key feature of the algorithm is that it incorporates the effects of mobility and shadow fading in the handoff decision. Different diversity combining schemes are considered including selective combining, equal gain combining (EGC), and various optimized combining (OC) methods in the soft handoff mode. For EGC and OC, Wilkinson's and Schwartz and Yeh's methods are used to compute the statistics for the power sum of the signals. Simulation results indicate that the performance of the handoff algorithm is a function of the different combining schemes and of the different methods used to compute the statistics of the power sum. Moreover, it is observed that interference cancellation is important in order for the algorithm to be viable for cellular systems which experience interference due to using nonorthogonal multiple access.     

A meta-analytic review of the relationship between absence and turnover.

A meta-analysis that combined 33 correlations from 17 studies found a corrected average correlation of .330 between absence and turnover. The type of absence measure did not moderate the covariation between absence and turnover, but industry type and study duration did act as moderators. The results are discussed in the context of the "withdrawal" approach to understanding employee behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of a Sensor Fusion Strategy for Robotic Application Based on Geometric Optimization

Fusion of multi-sensor information is an important technology, which is growing exponentially due to its tremendous application potential in many areas. Effective fusion of data from sensors is very critical in increasing an intelligent system's capability to accomplish complex tasks. Appropriate fusion technologies are needed to be developed specially when a system requires redundant sensors to be used. More the redundancy in sensors, more is the computational complexity for controlling the system and more is its intelligence level. This research presents a strategy developed for multiple sensor fusion, based on geometric optimization. Each sensor's uncertainty has been modeled using classical Lagrangian optimization techniques. However, the uniqueness and effectiveness of the present technique lies on the fact that starting from the optimized value as initial estimate the accuracy of the sensory information has further been improved up to any pre defined bounded range, by developing two architectures – FFA (fission–fusion architecture) and FDD (fusion in differential domain). Sufficient evidences and analyses have been provided in the paper to show its effectiveness in various applications.     

Nonminimum phase channel equalization using noncausal filters

The Viterbi algorithm is the optimum method for detection of a data sequence in the presence of intersymbol interference and additive white Gaussian noise. Since its computational complexity is very large, several simplifications and alternative methods have been proposed, most of which are more effective when dealing with minimum phase channels. We present a novel technique for the equalization of nonminimum phase channels that employs noncausal all-pass filters operating in reversed time. The impulse response of the equalized channel approximates a minimum phase sequence with higher energy concentration at its left-hand end than at the right-hand end. The method can be modified to obtain a desired impulse response with few nonzero samples with only minor variations in noise level, providing significant complexity reduction in the Viterbi algorithm for detection. In addition, a twopass decoding strategy is developed, leading to significant improvement in performance with little increase in computational cost. Simulation results are included to verify the advantages of the proposed techniques