Fractional-order filters for active damping in a lithographic tool

In a lithographic tool used in semiconductor manufacturing, vibrations in the projection lens reduce image contrast and can limit the system's resolution. Active damping by direct velocity feedback can reduce this effect, but requires sufficient amplitude roll-off for higher frequencies in the open-loop transfer function. Ongoing mass decoupling, however, tends to increase the transfer function magnitude. Stability is endangered by phase lag induced by control loop components and non-collocation of the actuator or sensor. Conventional lowpass filtering is not possible because of the minimum induced 90° phase shift. This paper introduces the usage of fractional-order filters with an order smaller than one in the feedback controller. The filter's reduced phase lag allows amplitude reduction for higher frequencies without stability risk. Implementation of 1/2-order and 2/3-order filters, and their effect in an active damping system for a lithographic tool's projection lens, are shown.     

Risk-based approach to developing a national residue sampling plan for testing under European Union regulation for veterinary medicinal products and coccidiostat feed additives in domestic animal production

A ranking system for veterinary medicinal products and coccidiostat feed additives has been developed as a tool to be applied in a risk-based approach to the residue testing programme for foods of animal origin in the Irish National Residue Control Plan (NRCP). Three characteristics of substances that may occur as residues in food are included in the developed risk ranking system: Potency, as measured by the acceptable daily intake assigned by the European Medicines Agency Committee for Medicinal Products for Veterinary Use, to each substance; Usage, as measured by the three factors of Number of Doses, use on Individual animals or for Group treatment, and Withdrawal Period; and Residue Occurrence, as measured by the number of Non-Compliant Samples in the NRCP. For both Number of Doses and Non-Compliant Samples, data for the 5-year period 2008–12 have been used. The risk ranking system for substances was developed for beef cattle, sheep and goats, pigs, chickens and dairy cattle using a scoring system applied to the various parameters described above to give an overall score based on the following equation: Potency × Usage (Number of Doses + Individual/Group Use + Withdrawal Period) × Residue Occurrence. Applying this risk ranking system, the following substances are ranked very highly: antimicrobials such as amoxicillin (for all species except pigs), marbofloxacillin (for beef cattle), oxytetracycline (for all species except chickens), sulfadiazine with trimethoprim (for pigs and chickens) and tilmicosin (for chickens); antiparasitic drugs, such as the benzimidazoles triclabendazole (for beef and dairy cattle), fenbendazole/oxfendazole (for sheep/goats and dairy cattle) and albendazole (for dairy cattle), the avermectin ivermectin (for beef cattle), and anti-fluke drugs closantel and rafoxanide (for sheep/goats); the anticoccidials monensin, narasin, nicarbazin and toltrazuril (for chickens). The risk ranking system described is a relatively simple system designed to provide a reliable basis for selecting the veterinary medicinal products and coccidiostat feed additives that might be prioritised for residue testing.     

Inhibition of yeast‐to‐filamentous growth transitions in Candida albicans by a small molecule inducer of mammalian apoptosis

The opportunistic fungal pathogen of humans Candida albicans is able to grow in different morphological forms such as round or oval yeasts and filamentous hyphae and pseudohyphae. Morphogenesis, the ability to switch between the yeast and filamentous growth forms, is important for adapting to new microenvironments in the human host and for pathogenesis. The molecular pathways governing morphogenesis are complex and incompletely understood. Previously, we identified several small organic molecules that specifically inhibit the initiation of hyphal growth in C. albicans without affecting cell viability or budded growth. One molecule from that screen is known to induce apoptosis in mammalian cells. In this study, we have screened additional inducers of mammalian apoptosis and identified BH3I‐1, as well as several structural derivatives of BH3I‐1, that act as specific inhibitors of morphogenesis under a variety of environmental conditions. Chemical epistasis experiments suggest that BH3I‐1 acts downstream of the hypha‐specific gene regulators Rfg1, Nrg1 and Ume6.     

Modelling Gas Transmission in Cylindrical Dynamic Accumulation Oxygen Transmission Rate Chambers to Explore Implications of Oxygen Sensor Location Relative to Samples

A model was developed to simulate oxygen accumulation in space and time within cylindrical dynamic accumulation chambers that are used to measure oxygen transmission rate (OTR) of materials. The model is based on Fick's law of diffusion and was validated against actual OTR measurements of polymer film samples. Measured OTR values and thicknesses were inputted into the model and oxygen concentrations outputted by the model. OTRs determined from the output of the model was in close agreement to within 0.3–3% of the measured OTR. Oxygen concentration versus time curves generated from model output oxygen concentrations and experimentally measured oxygen concentrations for three actual films were also in agreement. The model was then used to simulate results from three hypothetical test films at varying chamber lengths in order to evaluate effects of accumulation chamber dimensions relative to films on resulting OTR measurements. A typical design scenario was used, where the oxygen sensor is mounted on the chamber wall opposite the sample film. Results demonstrate that dynamic accumulation OTR instrument designers have considerable flexibility in choosing accumulation chamber dimensions because deviations in OTR are only expected to occur at impractically extreme chamber lengths (>10 m) for the entire envelope of OTRs expected for typical packaging films. Copyright © 2014 John Wiley & Sons, Ltd.     

Public reaction to wind development in California

Substantial controversy has been produced from the location of over 4000 wind turbines in San Gorgonio Pass, California. The principal point of controversy is the conflicting land use which results from developing wind power in a populated area. A public opinion survey was conducted which demonstrated that the vocal opposition to the wind turbines so commonly expressed is not borne out in fact. While there is indeed some opposition to the development of wind power at this site, particularly in terms of aesthetic degradation, the majority of respondents favoured the development. This level of approval will be of interest to those developing large wind projects elsewhere.     

Feasibility of Using Titanium Machine Turnings in Powder Metallurgy Processes

JOM - The use of titanium machine turnings has been identified as a possible ultralow-cost method to produce titanium powder. However, very little data are available on the viability of this...     

Urban flood impact assessment: A state-of-the-art review

Flooding can cause major disruptions in cities, and lead to significant impacts on people, the economy and on the environment. These impacts may be exacerbated by climate and socio-economic changes. Resilience thinking has become an important way for city planners and decision makers to manage flood risks.

Despite different definitions of resilience, a consistent theme is that flood resilient cities are impacted less by extreme flood events. Therefore, flood risk professionals and planners need to understand flood impacts to build flood resilient cities. This paper presents a state-of-the-art literature review on flood impact assessment in urban areas, detailing their application, and their limitations. It describes both techniques for dealing with individual categories of impacts, as well as methodologies for integrating them. The paper will also identify future avenues for progress in improving the techniques.     

Chilled ceilings and displacement ventilation

Displacement ventilation and chilled ceiling systems have been promoted as being ‘greener’ alternatives to other common forms of air conditioning system. They have been viewed by some of the building services industry as a welcome departure from the traditional ‘North American’ systems of air conditioning most frequently adopted to date, and could be viewed as a more suitable alternative for use in the moderate climatic conditions of the UK.This paper reviews some of the authors' recent and current work on the performance of these systems in office environments.     

Modeling of Nd-Oxide Grain Boundary Phases in Nd-Fe-B Sintered Magnets

We use atomistic and micromagnetic simulations combined with atomic-scale, aberration-corrected transmission electron microscopy to study the anisotropy profile of the interface between a Nd₂O₃-hP5 and a Nd₂Fe₁₄B phase. It is shown that a hybrid Morse-Buckingham potential approach can be used to study mixed-metallic and oxide-rich systems and to calculate surface-energy-induced large strains and potentially large relaxation effects on the adjacent grains. These are used to derive a magnetoelastic anisotropy energy from a first-order perturbation of the magnetoelastic Hamiltonian and are used to evaluate its effect on coercivity. It is shown that the change in coercivity originates from these distortions in the Nd₂Fe₁₄B crystal lattice close to the grain boundary, and the coercivity can be evaluated using such a multiscale modeling approach.     

Potential integrals for uniform and linear source distributions on polygonal and polyhedral domains

Formulas for the potentials due to uniform and Linearly varying source distributions defined on simply shaped domains are systematically developed and presented. Domains considered are infinite planar strips, infinite cylinders of polygonal cross sections, planar surfaces with polygonal boundaries, and volumetric regions with polyhedral boundaries. The expressions obtained are compact in form and their application in the numerical solution of electromagnetics problems by the method of moments is illustrated.