Gift-wrapping based preimage computation algorithm

Based on a classical convex hull algorithm called gift-wrapping, the purpose of the paper is to provide a new algorithm for computing the vertices of a polytope called preimage—roughly the set of naive digital planes containing a finite subset S of Z³. The vertices of the upper hemisphere, the ones of the lower hemisphere and at last the equatorial vertices are computed independently. The principle of the algorithm is based on duality and especially on the fact that the vertices of the preimage correspond to faces of the input set S or of its chords set S?S∪{(0,0,1)}. It allows to go from one vertex to another by gift-wrapping until the whole region of interest has been explored.     

Tailoring Structure-Borne Sound through Bandgap Engineering in Phononic Crystals and Metamaterials: A Comprehensive Review

In solid state physics, a bandgap (BG) refers to a range of energies where no electronic states can exist. This concept was extended to classical waves, spawning the entire fields of photonic and phononic crystals where BGs are frequency (or wavelength) intervals where wave propagation is prohibited. For elastic waves, BGs are found in periodically alternating mechanical properties (i.e., stiffness and density). This gives birth to phononic crystals and later elastic metamaterials that have enabled unprecedented functionalities for a wide range of applications. Planar metamaterials are built for vibration shielding, while a myriad of works focus on integrating phononic crystals in microsystems for filtering, waveguiding, and dynamical strain energy confinement in optomechanical systems. Furthermore, the past decade has witnessed the rise of topological insulators, which leads to the creation of elastodynamic analogs of topological insulators for robust manipulation of mechanical waves. Meanwhile, additive manufacturing has enabled the realization of 3D architected elastic metamaterials, which extends their functionalities. This review aims to comprehensively delineate the rich physical background and the state-of-the art in elastic metamaterials and phononic crystals that possess engineered BGs for different functionalities and applications, and to provide a roadmap for future directions of these manmade materials.     

Electrical Systems for Automatic Handling and Electric Heating of Slabs

The availability of large quantities of electrical power and sophisticated means of control has justified the use of induction methods in heating large steel slabs to rolling mill temperatures. Capable of delivering 210 MW, a unique power system, comprising power transformers, autotransformers, static switches, and capacitor banks, provides eighteen induction heaters with controlled electrical energy. The entire system can deliver 600 ton/h of steel to the rolling mill. The basic overall automatic control scheme involves the operations of slab handling control, heater control, static power switching, and computer control. The control functions, including phase balance and demand limit control, are described and discussed. The features and operation of the static power switch, capable of switching close to 10 000 A, are presented. Used as a protective device, the switch can clear up to 210 000-A faults in less than one cycle.     

Modelling and experimental evaluation of reaction kinetics in reactive extraction for chiral separation of amines, amino acids and amino-alcohols

This paper reports on determination of the intrinsic reaction kinetics in reactive extraction of chiral compounds. It is important to know the mass transfer rates and reaction kinetics separately for a reliable scale-up. A kinetic model is developed to interpret the experimental data from the selected model reactor, the modified Lewis cell. The two-phase homogeneous reaction model was selected over the interfacial reaction model, because physical partitioning is considerable in all systems studied. It was shown by simulations and by theoretical considerations that conventional regime analysis fails for reactive extraction in a number of regimes, because the conditions of an irreversible reaction and a negligible resistance to mass transfer in the non-reactive phase are generally not fulfilled in reactive extraction. Furthermore, it follows from the simulations that enhancement of mass transfer by reaction may be partly invisible. Finally, it becomes clear that only the fraction of the species that is in the right ‘extractable’ form should be used in the calculations. As the conventional regime analysis cannot be applied to determine the reaction kinetics in the chiral systems, first the mass transfer rate was measured during physical extraction to determine the location of the main resistance to mass transfer. Then the enhancement of mass transfer was measured during reactive extraction. By model simulation, it was determined how much enhancement of mass transfer should be observable. In this way, it was concluded that the reaction kinetics of the azophenolic crown ether system are between fast and instantaneous, and the reaction kinetics of the Cu(II)-N-dodecyl-L-hydroxyproline system are between slow and fast. The Lewis cell is not the most suitable model contactor to determine reaction kinetics in reactive extraction systems.     

Transient relaxation of the normal state resistance of tin microstrips in the presence of current bias

The transient relaxation of the normal state resistance in tin microstrips has been measured. The microstrips were current-biased below their dc critical current and excited into the normal state with electro optically produced current pulses, with durations as short as 600 psec, by temporarily exceeding the critical current. The effective relaxation time was measured by directly observing the voltage across the microstrip during the normal-superconducting transient. A region was observed in which the relaxation time decreased with increasing current pulse height. The relaxation time was found to be independent of temperature over the range 0.95T/T _c 0.77.     

The rheological characterization of fluorinated thermoplastics using squeezing flow viscometry

A squeezing flow viscometer was developed to characterize the rheological properties of luorinated thermoplastics. The viscosities of CTFE (polychlorotrifluorethylene) and FEP (a copolymer of tetrafluoroethylene and hexafluoropropylene) were determined using the viscometer by assuming that the shear-rate dependent viscosity can be described by a power-law, a truncated power-law, or an Ellis model. The results were in agreement with the viscosities measured with steady shear cone-and-plate viscometry and oscillatory cone-and-plate rheometry. Although the squeezing flow behavior of the polymers can be well explained by the purely viscous models, the power-law model is valid only for a limited range of shear-rates whereas the other two models are useful over a relatively wide range.     

Improving light fastness of natural dyes on cotton yarn

The objectives of this study were to evaluate the light fastness of selected natural dyes (madder, weld and woad) and the effect of some commonly used antioxidants and UV absorbers on the light fastness of these dyes.

The photofading rate curves of madder and weld fixed on cotton correspond to type II fading rate curves described by Giles. These results are in concordance with those of Cox-Crews. The woad presents a type III fading rate curve, similar to the indigo fading rate curve presented by Cox-Crews.

A poor light fastness of the three natural dyes in comparison with synthetic ones is established beyond question. Nevertheless, the use of some additives can improve this default of natural dyes. In all the cases, the use of UV absorbers or antioxidants improved the light fastness of dyed fabrics. The most effectives were the vitamin C and the gallic acid.     

Transitioning laser technology to support air force depot transformation needs

The U.S. Air Force and the Environmental Security Technology Certification Program (ESTCP) funded a multi-year collaborative project to test the ability of portable hand-held laser coating removal systems (PLCRS) to remove organic coatings from metallic and non-metallic substrates in an effort to reduce the use of hazardous chemicals and/or solid waste generated from more conventional removal methods. A 250 W carbon dioxide, 40 W neodymium: yttrium, aluminum, garnet (Nd:YAG), and 120 W Nd:YAG laser systems were evaluated for removing a variety of primer and topcoat combinations on 2024 T-3 and 7075 T-6 (bare and aluminum clad with chromate conversion coatings or chromic acid anodize), 4130 steel, honeycomb materials, Kevlar, graphite epoxy, and fiberglass epoxy substrates. Engineering tests were conducted to assess coating removal rate, physical substrate damage, modification of substrate properties, and impact on subsequent paint adhesion. The results of engineering tests were compared to baseline data (i.e., virgin material) and test data available in the literature for conventional coating removal techniques.     

DHAPM: A New Host Auto-configuration Protocol for Highly Dynamic MANETs

MANETs are self-organizing infrastructure-less networks formed on the fly by a group of wireless nodes. The lack of central administration in these networks necessitates host auto-configuration. The proposed auto-configuration protocols to date are either not robust enough to respond efficiently to the dynamic nature of the MANETs or they are resource greedy. Also, there has been no detailed attempt made to compare the effectiveness of these protocols which is essential to judge relative merits and demerits. This paper presents a new stateful robust host auto-configuration protocol which is based on dynamically selected Address Agents (AAs) that maintain a distributed address table. The performance of the proposed protocol is comprehensively compared with a representative protocol that employs a different address table management technique.

Combined Ligand‐ and Receptor‐Based Virtual Screening Methodology to Identify Structurally Diverse Protein Tyrosine Phosphatase 1B Inhibitors

Protein tyrosine phosphatase 1B (PTP1B) is a potential drug target for diabetes and obesity. However, the design of PTP1B inhibitors that combine potency and bioavailability is a great challenge, and new leads are needed to circumvent this problem. Virtual screening (VS) workflows can be used to find new PTP1B inhibitors with little chemical similarity to existing inhibitors. Unfortunately, previous VS workflows for the identification of PTP1B inhibitors have several limitations, such as a small number of experimentally tested compounds and the low bioactivity of those compounds. We developed a VS workflow capable of identifying 15 structurally diverse PTP1B inhibitors from 20 compounds, the bioactivity of which was tested in vitro. Moreover, we identified two PTP1B inhibitors with the highest bioactivity reported by any VS campaign (i.e., IC₅₀ values of 1.4 and 2.1 μm ), which could be used as new lead compounds.