Modeling and simulation of hard-particle interaction in head/disk interfaces

A hard particle interacting with a slider and a disk in the head/disk interface of hard-disk drives can produce a scratch on the disk and result in data loss. Our work emphasizes modeling and simulation of slider, particle, and disk interactions, scratch generating mechanisms, and linking of scratch to interface design parameters. Two models are presented. The Monte Carlo method was used to calculate scratch probabilities and parametric studies were performed to determine the effect on scratch probability of various parameters, such as friction coefficients, particle mean size, slider wall angles, the ion-milling (IM) etch depth from the air-bearing surface (ABS) of the slider, and the efficacy of additional ABS structures acting as particle shields. Simulation results show that the friction coefficient is a dominant parameter. If the disk friction coefficient is smaller than the slider friction coefficient, scratches are not produced. Using shallow IM depths is an effective and practical way to reduce the scratch probability. Experimental results are very close to the simulation predictions.     

Servers in SCADA applications

Data acquisition and supervisory control and data acquisition (SCADA) systems have evolved from mainframe-based systems to multilevel tiered systems to flat client-server architecture. This paper examines the necessity for this evolution and the technology that spurred it on. A rod mill is discussed as a case study     

On the Computational Complexity of Consumer Decision Rules

A consumer entering a new bookstore can face more than 250,000alternatives. The efficiency of compensatory and noncompensatory decisionrulesfor finding a preferred item depends on the efficiency of their associatedinformation operators. At best, item-by-item information operators lead tolinear computational complexity; set information operators, on the other hand,can lead to constant complexity. We perform an experiment demonstrating thatsubjects are approximately rational in selecting between sublinear and linearrules. Many markets are organized by attributes that enable consumers toemploya set-selection-by-aspect rule using set information operations. In cyberspacedecision rules are encoded as decision aids.     

Observability problem for bearings-only tracking

The state-observability problem for bearings-only tracking of a constant velocity target by a moving observer in two spatial dimensions is analysed. Specifically, we establish general necessary and sufficient conditions for observability and characterize the class of observer motions for which the state remains unobservable. In the course of the analysis, previously developed observability criteria are identified as special cases of our results.     

Complex and dynamic population structures: synthesis, open questions, and future directions

The population structure of an evolutionary algorithm influences the dissemination and mixing of advantageous alleles, and therefore affects search performance. Much recent attention has focused on the analysis of complex population structures, characterized by heterogeneous connectivity distributions, non-trivial clustering properties, and degree–degree correlations. Here, we synthesize the results of these recent studies, discuss their limitations, and highlight several open questions regarding (1) unsolved theoretical issues and (2) the practical utility of complex population structures for evolutionary search. In addition, we will discuss an alternative complex population structure that is known to significantly influence dynamical processes, but has yet to be explored for evolutionary optimization. We then shift our attention toward dynamic population structures, which have received markedly less attention than their static counterparts. We will discuss the strengths and limitations of extant techniques and present open theoretical and experimental questions and directions for future research. In particular, we will focus on the prospects of “active linking,” wherein edges are dynamically rewired according to the genotypic or phenotypic properties of individuals, or according to the success of prior inter-individual interactions.     

Highly effective adsorption of heavy metal ions by a thiol-functionalized magnesium phyllosilicate clay

A thiol-functionalized layered magnesium phyllosilicate material (called Mg-MTMS), prepared by a direct and cost-effective co-condensation synthesis, has been investigated as a high-capacity adsorbent for heavy metal ions. Structural characterization by powder X-ray diffraction, infrared spectroscopy, solid-state 13C and 29Si NMR spectroscopies, and elemental analyses confirms the smectite-type structure and the high organic moiety content of this material. Mg-MTMS was found to be highly effective for the adsorption of Hg(II), Pb(II), and Cd(II) ions, exhibiting unprecedented metal ion uptake capacities of 603, 365, and 210 mg of metal/g of adsorbent, respectively. Mg-MTMS shows an equivalent affinity for the three metal ions, removing them from mixed metal solutions with an equal ion uptake capacity (approximately 400 mg of metal/g of adsorbent). Metal-loaded Mg-MTMS can be regenerated by acid treatment without altering the adsorbent properties. The high effectiveness of Mg-MTMS for the capture of metal ions is attributed to both the high concentration of complexing thiol groups (6.4 mmol of SH/g of Mg-MTMS) and the expansion capability of the framework, which facilitates the accessibility of the binding sites.     

Halothane genotype, pre-slaughter handling and stunning method all influence pork quality

Seventy-six Landrace and four Large White × Landrace pigs (n=80) of 90-134 kg liveweight were randomly allocated to a 2×2×2 factorial experiment to determine the effect of halothane genotype [heterozygous for the halothane gene (Nn) and homozygous dominant (NN)], pre-slaughter handling (minimal and negative) and stunning method (CO(2) stunning and electrical) on pork quality. The rate of muscle pH decline post-slaughter of the m. longissimus thoracis et lumborum (LTL) muscle was faster in Nn pigs compared with NN pigs (0.86 and 0.30 pH units/h, respectively). Pork from Nn pigs was also paler in colour, had higher percentage drip loss and purge and lower sarcoplasmic and myofibrillar protein solubility compared with NN pigs. Pork from CO(2) stunned pigs had a lower drip loss compared to pork from electrically stunned pigs (5.80 and 7.28%, respectively?- means of both genotypes combined). Tenderness of pork assessed at 24 h post-slaughter was not influenced by genotype, pre-slaughter handling or stunning method. However, pork from Nn pigs aged for 5 days post-slaughter was less tender than NN pigs (5.84 and 4.84 kg, respectively). Pale, soft and exudative pork was produced in all negatively handled Nn pigs, regardless of stunning method. The average amount of ecchymosis-affected muscle trimmed from carcasses of electrically stunned pigs was higher compared to pigs stunned with CO(2) (65 and 0.7 g, respectively). These data indicate that although halothane status was the most important factor influencing pork quality, pre-slaughter handling and stunning method also influenced meat and carcass quality.     

Cut-off frequency in radially inhomogeneous single-mode fibre

The limit for single-mode operation in a graded-index fibre has been obtained by calculating the normalised cut-off frequency of the TE01 mode, The affect of diffusion at the core-cladding boundary has been estimated.     

Effect of dip in the referctive index on the cut-off frequency of a single-mode fibre

The normalised frequency for single-mode cut-off in an optical fibre has been calculated as a function of the dip in the refractive index at the centre of the core. For a particular class of profiles, dip width up to 40% have a negligible effect on the propagation characteristics.