A protein microbolometer for focal plane arrays

 Conventional forward-looking infrared (FLIR) devices made of a cooled platinum silicide, cooled mercury-cadmium-telluride, or indium antimonide are costly, in part, because they require an initial cool-down period and need additional power for a cooling pump. Using proteins and DNAs in an uncooled microbolometer will significantly improve the performance of the current technology. Received: 23 October 1998 / Reviewed and accepted: 7 December 1998     

A hot-pressed PLZT under DC bias for field-stabilized pyroelectric detector applications

 The temperature dependence of the pyroelectric response of a hot-pressed PLZT (lead lanthanide zirconate titanate) (9.5/65/35) under a modest dc electric bias field has been investigated in an assessment of the performance of this material for applications in small-area pyroelectric devices. A strong pyroelectric response has been induced in the material at and above its transition temperature by the application of an electric field. The electrical resistivity, relative dielectic constant, loss tangent, ferroelectic hysteresis, and pyroelectric coefficients are reported. The material shows a very high figure of merit for a dielectric bolometer application that is competitive with existing relaxor ferroelectric materials such as Pb(Mg_1/3Nb_2/3)O₃ (PMN) and Pb(Sc_1/2Ta_1/2)O₃ (PST). Received: 21 March 1997 / Accepted: 6 May 1997     

Piston-driven laminar flow and heat transfer in a plane channel with a sudden expansion

 This paper presents a numerical study of piston-driven heat transfer and fluid flow in a plane channel containing a sudden expansion. The numerical method employed is based on a control-volume-based finite element method for incompressible flow with a staggered and moving grid and SIMPLER algorithm for pressure-velocity coupling. The numerical results show a good agreement with the experimental data reported in the literature. Results concerning time and space evolution of the thermal and flow fields are presented for different values of the expansion ratio, the initial clearance volume, and the piston velocity. Received: 20 April 2002 / Accepted: 23 January 2003     

A complex variable boundary collocation method for plane elastic problems

 Lagrange interpolation is extended to the complex plane in this paper. It turns out to be composed of two parts: polynomial and rational interpolations of an analytical function. Based on Lagrange interpolation in the complex plane, a complex variable boundary collocation approach is constructed. The method is truly meshless and singularity free. It features high accuracy obtained by use of a small number of nodes as well as dimensionality advantage, that is, a two-dimensional problem is reduced to a one-dimensional one. The method is applied to two-dimensional problems in the theory of plane elasticity. Numerical examples are in very good agreement with analytical ones. The method is easy to be implemented and capable to be able to give the stress states at any point within the solution domain. Received: 20 August 2002 / Accepted: 31 January 2003     

Simultaneous optimal design of structural topology, actuator locations and control parameters for a plate structure

 Simultaneous optimization with respect to the structural topology, actuator locations and control parameters of an actively controlled plate structure is investigated in this paper. The system consists of a clamped-free plate, a H ₂ controller and four surface-bonded piezoelectric actuators utilized for suppressing the bending and torsional vibrations induced by external disturbances. The plate is represented by a rectangular design domain which is discretized by a regular finite element mesh and for each element the parameter indicating the presence or absence of material is used as a topology design variable. Due to the unavailability of large-scale 0–1 optimization algorithms, the binary variables of the original topology design problem are relaxed so that they can take all values between 0 and 1. The popular techniques in the topology optimization area including penalization, filtering and perimeter restriction are also used to suppress numerical problems such as intermediate thickness, checkerboards, and mesh dependence. Moreover, since it is not efficient to treat the structural and control design variables equally within the same framework, a nested solving approach is adopted in which the controller syntheses are considered as sub processes included in the main optimization process dealing with the structural topology and actuator locations. The structural and actuator variables are solved in the main optimization by the method of moving asymptotes, while the control parameters are designed in the sub optimization processes by solving the Ricatti equations. Numerical examples show that the approach used in this paper can produce systems with clear structural topology and high control performance. Received 16 November 2001 / Accepted 26 February 2002     

Giga-scale disposal: a real frontier for ceramic research

 Industry is faced with the environmental problem of finding a home for materials that are generated as a result of manufacturing processes, so-called by-products or industrial wastes. As long as cheap ”landfill” costs are available, these materials, which are generated in the giga-tons/yr quantities, will continue to adversely impact our environment. The goal of these activities focuses on applying knowledge, normally concentrated on ”high-tech” materials, to address the utilization of the overwhelming volumes of industrial by-products in the manufacture of ”low-tec” solutions to environmental problems. One such successful application of coal derived fly ash for the manufacture of controlled low-strength structural fills for the reclamation of open pit coal mines is discussed in detail. These projects demonstrate that chemical and physical aspects of materials reacted at the ”nano-scale” enable the developments of successful ”giga-scale” technologies. Received: 18 December 1998 / Reviewed and accepted: 5 Jaunary 1999     

Oxygen uptake: A procedure for evaluating oxidative stability and performances of polymers

The oxygen uptake method is presented as a reliable alternative for characterization of the polymer aging. The method is able to provide kinetic information on destructive processes, effectiveness of stabilization, and differences between ostensibly similar compounds. Amounts of oxygen reacted with time can be recorded with simple devices. The application of a derivative method provides the evolution of oxidation rate and the moment when the peroxide intermediates reach steady state. Change in testing temperature allows calculation of process activation energy. In addition, thermodynamic potentials can be assessed starting from the changes in oxygen uptake with time. The method can provide useful information on characteristic durability relationships over large ranges of temperatures or pressures. Advantages of the testing procedure include: requirement of small samples (∼20 mg) in various state (solids, powders, films, thin sheets, liquids, granules; monosystems or blends; virgin or degraded). The results obtained by oxygen uptake measurements are in good agreement with data obtained by other methods. Received: 11 December 2000 / Reviewed and accepted: 13 December 2000     

Dynamics of a gas bubble rising through a thin immersed layer of granular material: an experimental study

 Packings of non-cohesive grains, immersed in a fluid, differ significantly from classical porous media as the grains, subjected to stresses and flows, can move within the sample, changing then the local properties of the material. We study experimentally the conditions for a gas to pass through a layer of immersed granular material. Above a threshold pressure, which depends mainly on the grains size and on the surface free energy of the liquid-gas interface, the gas creates a channel within the whole thickness of the layer. Received: 23 January 2002     

A mixed least squares method for solving problems in linear elasticity: theoretical study

 In a previous paper we proposed a mixed least squares method for solving problems in linear elasticity. The solution to the equations of linear elasticity was obtained via minimization of a least squares functional depending on displacements and stresses. The performance of the method was tested numerically for low order elements for classical examples with well known analytical solutions. In this paper we derive a condition for the existence and uniqueness of the solution of the discrete problem for both compressible and incompressible cases, and verify the uniqueness of the solution analytically for two low order piece-wise polynomial FEM spaces. Received: 20 January 2001 / Accepted: 14 June 2002 The authors gratefully acknowledge the financial support provided by NASA George C. Marshall Space Flight Centre under contract number NAS8-38779.     

Recombinant glycans on an S-layer self-assembly protein: a new dimension for nanopatterned biomaterials

Crucial biological phenomena are mediated through carbohydrates that are displayed in a defined manner and interact with molecular scale precision. We lay the groundwork for the integration of recombinant carbohydrates into a "biomolecular construction kit" for the design of new biomaterials, by utilizing the self-assembly system of the crystalline cell surface (S)-layer protein SgsE of Geobacillus stearothermophilus NRS 2004/3a. SgsE is a naturally O-glycosylated protein, with intrinsic properties that allow it to function as a nanopatterned matrix for the periodic display of glycans. By using a combined carbohydrate/protein engineering approach, two types of S-layer neoglycoproteins are produced in Escherichia coli. Based on the identification of a suitable periplasmic targeting system for the SgsE self-assembly protein as a cellular prerequisite for protein glycosylation, and on engineering of one of the natural protein O-glycosylation sites into a target for N-glycosylation, the heptasaccharide from the AcrA protein of Campylobacter jejuni and the O7 polysaccharide of E. coli are co- or post-translationally transferred to the S-layer protein by the action of the oligosaccharyltransferase PglB. The degree of glycosylation of the S-layer neoglycoproteins after purification from the periplasmic fraction reaches completeness. Electron microscopy reveals that recombinant glycosylation is fully compatible with the S-layer protein self-assembly system. Tailor-made ("functional") nanopatterned, self-assembling neoglycoproteins may open up new strategies for influencing and controlling complex biological systems with potential applications in the areas of biomimetics, drug targeting, vaccine design, or diagnostics.     

Experimental validation of a computationally efficient beam element for combined finite–discrete element modelling of structures in distress

 The combined finite/discrete element method is adopted to model the pre-failure and post failure transient dynamics of reinforced concrete structures. For this purpose a novel beam element is introduced in order to increase CPU and RAM efficiency. In this paper the accuracy and reliability of this element is assessed when used in dynamic loading conditions. Experiments, which have already been undertaken at the Swiss Federal Institute of Technology, are used for comparison and validation. The results indicate that the element introduced is capable of accurately modelling inertia and contact effects in pre and post failure dynamics, up to collapse. Received: 1 August 2002 / Accepted: 9 January 2002 A debt of gratitude is owed to Prof. Bachman and Mrs. N. Ammann for their kind and sincerely appreciated assistance in the provision of the reports from the Swiss Federal Institute of Technology. The assistance provided by Dr. W. Ammann and Dr. S. Heubbe-Walker in the translation of the reports is also gratefully acknowledged.     

Metal foaming by a powder metallurgy method: Production, properties and applications

 A method for fabricating metal foams based on the powder metallurgy process is presented. This foaming process allows for the production of complex-shaped foam parts, metal foam sandwich panels and foam filled hollow profiles. A range of alloys can be foamed using this method including aluminum, zinc, tin, lead and steel. The as-produced part has a closed-cell microstructure and a high fraction of porosity (typical range from 40–90% porosity). Selected mechanical properties of metal foams are evaluated, including the loading of foam samples with and without face skins and the axial crushing of tubular structures with foam reinforcement. Potential applications are discussed such as light-weight construction and energy absorption for both military and civilian uses. Received: 22 July 1998 / Accepted: 4 September 1998     

The phenomenon of anisotropy of the resistance to microcleavage for a carbon steel prestrained in compression

The effect of compressive plastic prestrain on the resistance of carbon steels to microcleavage is investigated using grade 30 steel as an example. Precompression is found to result in the occurrence of anisotropy of the “brittle” strength R_mc of the steel, the essence of which is in its decrease for specimens cut out in the longitudinal direction and increase in the microcleavage resistance for specimens cut out in the transverse one. It is shown that the main cause of this effect are oriented residual stresses. The value of the oriented residual stresses for specimens cut out in the longitudinal and transverse direction is estimated. A strong embrittlement of the steel is observed in the longitudinal direction after compression. The shift in the ductile-brittle transition temperature reaches the maximum value of 168°C. __________ Translated from Problemy Prochnosti, No. 6, pp. 91–102, November–December, 2007.     

Standard free energy change of formation per unit volume: a new parameter for evaluating nucleation and growth of oxides, sulphides, carbides and nitrides

 The present paper introduces a thermodynamic parameter, the standard free energy changes of formation of oxide, sulphide, carbide and nitride per unit volume, as a criterion for comparing the formation tendency of these compounds. The diagrams for the standard free energy change of formation of common oxides, sulphides, carbides and nitrides per unit volume vs temperature have been calculated and established based on the available thermodynamic data. It is believed that these diagrams can provide better explanations to some oxidation phenomena including the effects of reactive elements on the selective oxidation of Cr₂O₃ and Al₂O₃. Received: 12 September 1997 / Accepted: 16 September 1997     

Poly(acrylic acid) + zinc diacetate composites: High temperature service and electric conductivity

Poly(acrylic acid) + zinc diacetate hybrid composites have been prepared by precipitation from aqueous solutions and drying. The lowest glass transition temperature T_g determined by differential scanning calorimetry (DSC) is 392°C, providing a service temperature range unusually large for polymer-based materials (PBMs). Thermogravimetric analysis (TGA) shows that thermal decomposition begins some 10–20 K above each T_g. The alternating current impedance was determined in the nitrogen atmosphere from 370°C to 530°C. Dynamic dielectric measurements were performed between 20°C and 350°C, also under nitrogen. In contrast to typical PBMs, there is evidence of ionic conduction in some of the composites. The dynamic dielectric properties depend on the composition. The materials obtained are usable in medical applications and as high durability low friction coatings. Received: 19 February 1999 / Reviewed and accepted: 13 March 1999     

Biomaterials innovation: it’s a long road to the operating room

 An innovative process for forming a wide variety of porous biomaterials was conceived of and developed over several years at a University and later by a company that licensed the early patents. The family of patents formed the basis for several promising innovative biomaterials devices. However, only one commercial product has been realized. That product is the very successfull coralline hydroxyapatite (HA) now widely used in orthopaedic surgery, oral and maxillofacial bone repair and plastic surgery. This paper challenges the equation of discovery with a genuine innovation which reaches the marketplace. The paper reviews several aspects of the innovation and development history with an emphasis on the challenges of bringing any new biomaterial through all the conceptual, developmental, business and regulatory hurdles. New class three medical devices require huge investments of time and money typically requiring a minimum of eight years and 15–20 million dollars per new device to take it from concept to an approved product. These hurdles are so high that most research innovations in biomaterials never get put into the developmental pipeline. This paper is presented from an anecdotal perspective of an innovator who has had a continuous research and development involvement in the technology but has no significant management involvement beyond the early startup activities. It differs from predecessors is that it deals not only with the initial step of discovery but in the very difficult steps that follow on the road to a real innovation. Several strategies that may help other R&D groups outside the biomedical industry shorten the development cycle and increase the probability that a given biomaterials innovation can be seen through to approved product are discussed. Guidelines are suggested for culling out ideas that are technically sound but that likely won’t lead to successful products. Received: 2 January 1997 / Accepted: 27 March 1997