Theoretical study of elastic properties of SiC nanowires of different shapes

The atomic structure and elastic properties of silicon carbide nanowires of different shapes and effective sizes were studied using density functional theory and classical molecular mechanics. Upon surface relaxation, surface reconstruction led to the splitting of the wire geometry, forming both hexagonal (surface) and cubic phases (bulk). The behavior of the pristine SiC wires under compression and stretching was studied and Young's moduli were obtained. For Y-shaped SiC nanowires the effective Young's moduli and behavior in inelastic regime were elucidated.     

Performance evaluation of the SX‐6 vector architecture for scientific computations

The growing gap between sustained and peak performance for scientific applications is a well‐known problem in high‐performance computing. The recent development of parallel vector systems offers the potential to reduce this gap for many computational science codes and deliver a substantial increase in computing capabilities. This paper examines the intranode performance of the NEC SX‐6 vector processor, and compares it against the cache‐based IBM Power3 and Power4 superscalar architectures, across a number of key scientific computing areas. First, we present the performance of a microbenchmark suite that examines many low‐level machine characteristics. Next, we study the behavior of the NAS Parallel Benchmarks. Finally, we evaluate the performance of several scientific computing codes. Overall results demonstrate that the SX‐6 achieves high performance on a large fraction of our application suite and often significantly outperforms the cache‐based architectures. However, certain classes of applications are not easily amenable to vectorization and would require extensive algorithm and implementation reengineering to utilize the SX‐6 effectively. Copyright © 2005 John Wiley & Sons, Ltd.     

Hypothese von Coulomb und mehrachsige Betonfestigkeit

Coulomb‐hypothesis and multiaxial concrete strength. The article deals with the well‐known Coulomb‐hypothesis, applied to the multiaxial stress‐stage. The friction‐coefficient is defined as a shearing coefficient in main pressure direction and as an inner reciprocal value of the rigidity decrease in transverse direction to the pressure line. The cohesion of concrete texture, firstly assumed isotropic, is described as an inner prestressing compression force. In most cases the multiaxial calculation is experimentally proved. Although the comparison is acceptable, further experiments may be necessary.     

A case study on the object-oriented framework for modeling product families with the dominant variation of the topology in the one-of-a-kind production

Traditional configuration-based product family modeling techniques do not yield favorable solutions for modeling the product families with the dominant product topology variations. This paper presents the case study for the modeling of variations of the product configuration, parameters, and topologies in mass production of custom windows and doors in a one-of-a-kind production (OKP) company. The case study is based on the object-oriented product family modeling framework we developed for OKP which is characterized by the dominant product variation by topology. The problem of variation in topology in our framework is solved by the manual model transformation in the computer-aided design module which creates a new metamodel of products with the desired topology and which is the basis for a further, automatic model transformation. Usage of our framework has a positive effect on the level of the product customizations and shortening of the leading time which helps OKP companies in obtaining a better position at the market. Our software solution for the designing and manufacturing of custom windows and doors based on our framework is implemented in more than 300 mostly small- and medium-sized enterprises. It proves our concept which can be used for the realization of the information systems for computer-aided one-of-a-kind production in the companies with a different production plan.     

Residual service life test for a machine with friction

A test and heat friction based method for evaluation of the technical condition and residual service life of machinery is presented. It is applicable for mechanisms in which friction of the moving parts leads to wear and to increased heat release. The diagnostic parameter adopted is the peak point of the temperature change rate, observed on the machine casing during the starting stage. The method was tested on the SAWA power reduction gears of KOCKS heavy portal transtainer cranes. Copyright © 2006 John Wiley & Sons, Ltd.     

SDS-PAGE under focusing conditions: an electrokinetic transport phenomenon based on charge compensation

A novel method is reported for mass separation of proteins, based on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Unlike conventional SDS-PAGE, in which separation by mass of SDS-laden polypeptide chains is obtained in constant concentration or porosity gradient gels, the present method, called "SDS-PAGE focusing", exploits a "steady-state" process by which the SDS-protein micelles are driven to stationary zones along the migration path against a gradient of positive charges affixed to the neutral polyacrylamide matrix. As the total negative surface charge of such complexes matches the surrounding charge density of the matrix, the SDS-protein complex stops migrating and remains stationary, as typical of steady-state separation techniques. As a result of this mechanism, the proteins are separated in an unorthodox way, with the smaller proteins/peptides staying closer to the application point and larger proteins migrating further down toward the anodic gel end. This results in a positive slope of the Mr vs migration plot, vs a negative slope in conventional SDS-PAGE. Moreover, such a plot is linear (by design), whereas in standard SDS-PAGE it is semi- or even double logarithmic. Particularly advantageous appears the ability of the present method to fine-tune the separation of small-size fragments and tryptic digests, where conventional SDS-PAGE usually fails. Additionally, by exploiting constant plateaus of charges, rather than gradients, it is possible to amplify the separation between species having closely spaced Mr values, down to a limit of approximately 150 Da. This increases the resolution by at least 1 order of magnitude as compared with standard SDS-PAGE, where for a proper separation of two adjacent species, an Mr increment of approximately 3000 Da is needed.     

Computational study of the effect of core–skin structure on the mechanical properties of carbon nanofibers

Journal of Materials Science - The effect of the core–skin structure on the mechanical properties of carbon nanofibers is investigated in large-scale molecular dynamics simulations of tensile...     

Negative refraction in semiconductor metamaterials

An optical metamaterial is a composite in which subwavelength features, rather than the constituent materials, control the macroscopic electromagnetic properties of the material. Recently, properly designed metamaterials have garnered much interest because of their unusual interaction with electromagnetic waves. Whereas nature seems to have limits on the type of materials that exist, newly invented metamaterials are not bound by such constraints. These newly accessible electromagnetic properties make these materials an excellent platform for demonstrating unusual optical phenomena and unique applications such as subwavelength imaging and planar lens design. 'Negative-index materials', as first proposed, required the permittivity, epsilon, and permeability, mu, to be simultaneously less than zero, but such materials face limitations. Here, we demonstrate a comparatively low-loss, three-dimensional, all-semiconductor metamaterial that exhibits negative refraction for all incidence angles in the long-wave infrared region and requires only an anisotropic dielectric function with a single resonance. Using reflection and transmission measurements and a comprehensive model of the material, we demonstrate that our material exhibits negative refraction. This is furthermore confirmed through a straightforward beam optics experiment. This work will influence future metamaterial designs and their incorporation into optical semiconductor devices.