Effects of civil war: scientific cooperation in the republics of the former Yugoslavia and the province of Kosovo

In this study we investigate the scientific output of Yugoslavia and its successor republics viz. Serbia, Croatia, Slovenia, Bosnia & Herzegovina, Macedonia and Montenegro. Additionally, Kosovo was included as a separate entity, since it recently declared its independence. The publications and cooperation between the republics are analyzed for the years from 1970 until 2007. In contrast to similar studies, we examine a larger time window and take into consideration not only the three big republics (Serbia, Croatia, and Slovenia) but also include the smaller ones, namely Bosnia & Herzegovina, Macedonia and Montenegro. For our analysis we introduce two new indicators: the normalized cooperation score (R^(cs)_iR^{rm (cs)}_{i}) and the dominance factor (D^(c)_iD^{rm (c)}_{i}), a measure of dominance within a weighted network. Furthermore, we develop and assess the reliability of various techniques for visualizing our findings. We found that the civil wars had a severe impact on the inner-Yugoslav cooperation network. Additionally it seems, as if with the ending of the conflicts a process of recovery started.     

An assessment of in vivo failures of alumina ceramic total hip joint replacements

Several cases of alumina ceramic hip replacement failures are reviewed fractographically. Three main findings are illustrated. Firstly, there is evidence that surgeons can damage the femoral head bore surface during surgery. Secondly, three of the failures described are of extended neck designs which are weaker than those of normal or short length in axial laboratory testing. Under physiological loading, such geometry can lead to levering forces, inappropriate localized contact with the metallic stem and stress concentrations. Delayed failure can ensue, with a fracture pattern quite different from that seen in conventional uniaxial testing. Thirdly, while some failures show head bore surfaces which are clean apart from metallic witness marking, others show brown stains and white deposits suggesting poor conformal contact. We suspect either stems become damaged during surgery before mounting the head or entrapment of debris, pointing to handling care and cleanliness varying between hospitals.     

Models of SEC elution curves for binary and multi‐component polymers

BACKGROUND: Frequently, the unimodal shape of size‐exclusion chromatography (SEC) elution curves is taken as evidence that the polymer sample being analysed contains no minority components in significant quantities. The legitimacy of this assumption, however, has never been checked systematically. RESULTS: An algorithm for the simulation of SEC elution curves of multi‐component polymer systems has been developed. Using the algorithm, the shapes of the overall SEC curves with a wide range of parameters describing binary systems were generated and scanned. The crucial parameters determining the shape of the elution curves are the ratio of the molecular weights of the components, the breadth of the molecular weight distribution of the components, the mass fractions of the components and the band broadening. CONCLUSION: A detailed inspection of the curves shows that the identification of the presence of minority components in such systems from the shapes of the elution curves is more difficult then generally assumed. The absence of peak irregularities, such as minima or inflection points, widely used as a proof of absence of minority components, is a highly unreliable criterion. Copyright © 2008 Society of Chemical Industry     

Reliability of masonry walls subjected to in‐plane loading: A slip failure along head joints / Zuverlässigkeit von Mauerwerkswänden bei Belastung in der Ebene: Versagen entlang der Stoßfugenflucht

Masonry structures are a sustainable, economical and traditionally widely used type of construction. However, current masonry design codes are rather conservative, so there is a growing need for revision i.e. calibration of safety factors to improve the allocation of material resources. In this paper, we investigate the probability of occurrence of slip failure along head joints (perpends) in masonry subjected to in‐plane loading. An appropriate limit state function is established and the masonry material properties and loads are defined as random variables in order to simulate likelihood of occurrence of a slip failure regime along the head joints. Furthermore, an example of masonry wall with probabilistic analysis outcomes using Monte Carlo simulation is presented and recommendations for further work are provided.     

Determination of Thermal Conductivity of Silicate Matrix for Applications in Effective Media Theory

Silicate materials have an irreplaceable role in the construction industry. They are mainly represented by cement-based- or lime-based materials, such as concrete, cement mortar, or lime plaster, and consist of three phases: the solid matrix and air and water present in the pores. Therefore, their effective thermal conductivity depends on thermal conductivities of the involved phases. Due to the time-consuming experimental determination of the effective thermal conductivity, its calculation by means of homogenization techniques presents a reasonable alternative. In the homogenization theory, both volumetric content and particular property of each phase need to be identified. For porous materials the most problematic part is to accurately identify thermal conductivity of the solid matrix. Due to the complex composition of silicate materials, the thermal conductivity of the matrix can be determined only approximately, based on the knowledge of thermal conductivities of its major compounds. In this paper, the thermal conductivity of silicate matrix is determined using the measurement of a sufficiently large set of experimental data. Cement pastes with different open porosities are prepared, dried, and their effective thermal conductivity is determined using a transient heat-pulse method. The thermal conductivity of the matrix is calculated by means of extrapolation of the effective thermal conductivity versus porosity functions to zero porosity. Its practical applicability is demonstrated by calculating the effective thermal conductivity of a three-phase silicate material and comparing it with experimental data.     

Robust Single-Walled Carbon Nanotube-Infiltrated Carbon Fiber Electrodes for Structural Supercapacitors: from Reductive Dissolution to High Performance Devices

Multifunctional electrodes for structural supercapacitors are prepared by vacuum infiltration of single-walled carbon nanotubes (SWCNTs) into woven carbon fibers (CFs); the use of reductive charging chemistry to form nanotubide solutions ensured a high degree of individualization. The route is highly versatile, as shown by comparing four different commercial nanotube feedstocks. In film form, the pure nanotubide networks (“buckypapers”) are highly conductive (up to 2000 S cm⁻¹) with high surface area (>1000 m² g⁻¹) and great electrochemical performance (capacitance of 101 F g⁻¹, energy density of 27.5 Wh kg⁻¹ and power density of 135 kW kg⁻¹). Uniformly integrating these SWCNT networks throughout the CF fabrics significantly increased electrical conductivity (up to 318 S cm⁻¹), surface area (up to 196 m² g⁻¹), and in-plane shear properties, all simultaneously. The CNT-infiltrated CFs electrodes exhibited intrinsically high specific energy (2.6–4.2 Wh kg⁻¹) and power (6.0–8.7 kW kg⁻¹) densities in pure 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) electrolyte. Multifunctional structural supercapacitors based on CNT-coated CFs offer a substantial increase in capacitive performance while maintaining the tensile mechanical properties of the as-received CF-based composite. This non-damaging approach to modify CFs with highly graphitic, high surface area nanocarbons provides a new route to structural energy storage systems.     

Model-based Crowd Behaviours in Human-solution Space

Realistic crowd simulation has been pursued for decades, but it still necessitates tedious human labour and a lot of trial and error. The majority of currently used crowd modelling is either empirical (model-based) or data-driven (model-free). Model-based methods cannot fit observed data precisely, whereas model-free methods are limited by the availability/quality of data and are uninterpretable. In this paper, we aim at taking advantage of both model-based and data-driven approaches. In order to accomplish this, we propose a new simulation framework built on a physics-based model that is designed to be data-friendly. Both the general prior knowledge about crowds encoded by the physics-based model and the specific real-world crowd data at hand jointly influence the system dynamics. With a multi-granularity physics-based model, the framework combines microscopic and macroscopic motion control. Each simulation step is formulated as an energy optimization problem, where the minimizer is the desired crowd behaviour. In contrast to traditional optimization-based methods which seek the theoretical minimizer, we designed an acceleration-aware data-driven scheme to compute the minimizer from real-world data in order to achieve higher realism by parameterizing both velocity and acceleration. Experiments demonstrate that our method can produce crowd animations that are more realistically behaved in a variety of scales and scenarios when compared to the earlier methods.     

Vortex-Antivortex Lattices in Superconducting Films with Magnetic Pinning Arrays

No Heading We found a rich variety of vortex structures when a thin superconducting film (SC) is covered with a lattice of out-of-plane magnetized magnetic dots (MDs). The vortices are confined to the MD regions, and antivortices nucleate into regular lattices which relax through several second order transitions towards single-dot vortex-antivortex configurations with increasing period of the magnetic array. Creation of vortex-antivortex pairs with increasing MD-magnetization is controlled by a single quantity - the superfluid velocity. We demonstrate that due to the vortex-antivortex pairs and the supercurrents induced by the MDs, the critical current in the sample actually increases if exposed to a homogeneous external magnetic field, contrary to conventional SC behavior. We explain further experimental implications, such as the magnetic field-induced-superconductivity.PACS numbers: 74.78.–w, 74.25.Op, 74.25.Qt, 74.25.Dw.