A simple formula for calculation of power loss in digitaltransmission lines

Presented is a two-parameter model of line loss in which the frequency dependence of loss is determined by way of the loss at the selected frequency and the conductor diameter. The model quite faithfully represents the actual loss of the line, and is much better than the often used √f model     

Functionalization of sodium titanate nanoribbons with silanes and their use in the reinforcement of epoxy nanocomposites

This paper reports on the surface functionalization of sodium titanate nanoribbons (NaTiNRs) with four different silane coupling agents: 3‐(aminopropyl)tri‐ethoxysilane, triethoxyoctylsilane, 3‐glycidyloxypropyltrimethoxysilane, and 3‐aminopropylmethyl diethoxysilane. The functionalized NaTiNRs were used to prepare epoxy‐based nanocomposites with three different wt% of nanofillers (1, 2 and 3 wt% per epoxy). The properties of the prepared nanocomposites were then compared with the pure epoxy resin. The functionalized NaTiNRs, as well as the epoxy and prepared nanocomposites, were characterized using Fourier‐transform infrared spectroscopy, simultaneous differential scanning calorimetry‐thermogravimetric analysis (DSC‐TGA), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and dynamic mechanical analysis. The SEM results showed that the 2‐ and 3‐functional silanes are not the best choice for the modification as they glue the NaTiNRs together into clusters. As a consequence, the glass‐transition temperatures and the mechanical properties are not strongly influenced by the addition of functionalized NaTiNRs. Nevertheless, the influence of the type of silane can be observed. Furthermore, the thermal stability of the prepared nanocomposites increases with the increased loading of the functionalized NaTiNRs. POLYM. COMPOS. 34:1382–1388, 2013. © 2013 Society of Plastics Engineers     

Structural and mechanical properties of polystyrene nanocomposites with 1D titanate nanostructures prepared by an extrusion process

Polystyrene (PS) nanocomposites with titanate nanotubes and titanate nanoribbons were prepared by an extrusion process at 180°C. Nanocomposites with 1 wt% of nanofillers and pure PS that had also been exposed to the extrusion process were comparatively examined with scanning electron microscopy (SEM), electron dispersive X‐ray spectrometry (EDS) mapping, solid state proton nuclear magnetic resonance measurements (¹H NMR), tensile tests, and shear creep measurements. SEM images and EDS mapping analysis show that titanate nanoribbons homogeneously distribute at a micrometer length‐scale in the PS matrix during the extrusion process. This is not the case for titanate nanotubes, which show a stronger tendency to form clusters. Solid state ¹H NMR studies, however, proved that the nanocomposites are inhomogeneous at a nanometric scale where structural components with highly mobile PS molecules coexist with domains of rigid PS molecules. Differences in the ¹H spin‐lattice relaxation at and above the glass transition temperature T_g = 373 K suggest that nanofillers affect the thermodynamic properties of nanocomposite domains. Only a slight increase in mechanical tensile properties was observed in the case of the nanocomposite containing 1 wt% of titanate nanoribbons (TiNRs) probably reflecting a weak interaction between the polymer matrix and the nanofiller. Nevertheless, our results prove that the use of functionalized TiNRs may, in combination with the extrusion process, represent a very promising starting point for the preparation of TiNR nanocomposites at the industrial level. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Smart sport equipment: SmartSki prototype for biofeedback applications in skiing

Miniature sensors are already integrated into various sport equipment. A combination of body-attached sensor devices and sensors integrated into the sport equipment, together with an adequate sensor fusion algorithms, can help with developing better sport’s gear, speed up the learning process, and improve the skill level and performance. The paper presents our SmartSki system including SmartSki prototype, measuring equipment, and several SmartSki applications. The SmartSki system was functionally tested and verified by a group of alpine skiing experts through several snow tests during the period of 1 year. The snow test results were used to improve the prototype and extract several important skiing parameters that are used in various feedback applications, for example, in a trainer feedback system or in a real-time biofeedback system for the skier. We are confident that the SmartSki can offer many benefits to recreational skiers, ski equipment manufacturers, ski schools, coaches, and even professional skiers.     

Validation of smartphone gyroscopes for mobile biofeedback applications

Smartphones are currently the most pervasive wearable devices. One particular use of smartphone inertial sensors is motion tracking in various mobile systems and applications. The objective of this study is to validate smartphone gyroscopes for angular tracking in mobile biofeedback applications. The validation method includes measurements of angular motion performed concurrently by a smartphone gyroscope and a professional optical tracking system serving as the reference. The comparison of the measurement results shows that the inaccuracies of a calibrated smartphone gyroscope for various movements are between 0.42° and 1.15°. Based on the measurement results and the general requirements of biofeedback applications, smartphone gyroscopes are sufficiently accurate for angular motion tracking in mobile biofeedback applications.     

Selective etching of metallic single-wall carbon nanotubes with hydrogen plasma

We present Raman scattering and scanning tunnelling microscopy (STM) measurements on hydrogen plasma etched single-wall carbon nanotubes (SWNTs). Interestingly, both the STM and Raman spectroscopy show that the metallic SWNTs are dramatically altered and highly defected by the plasma treatment. In addition, structural characterizations show that metal catalysts are detached from the ends of the SWNT bundles. For semiconducting SWNTs we observe no feature of defects or etching along the nanotubes. Raman spectra in the radial breathing mode region of plasma-treated SWNT material show that most of the tubes are semiconducting. These results show that hydrogen plasma treatment favours etching of metallic nanotubes over semiconducting ones and therefore could be used to tailor the electronic properties of SWNT raw materials.     

Sensitive and rapid hydrogen sensors based on Pd–WO3 thick films with different morphologies

WO₃ loaded with noble metals is well-known to be sensitive to reducing gases and can be used as hydrogen sensor. This paper presents a simple and attractive method concerning the preparation of hydrogen sensors based on Pd-loaded WO₃ nanocomposites with different morphologies. The influences of the morphology of WO₃ and the palladium growth on its surface on the hydrogen sensing performances are studied. WO₃ nanospheres, nanowires and nanolamellae were synthesized by different methods starting from the same precursor (H₂WO₄·nH₂O) which has been obtained by acidification of sodium tungstate (Na₂WO₄). The prepared WO₃ nanostructures were modified with the Pd by dispersing them in a PdCl₂ containing solvent using sonication (giving Pd-WO₃ inks). The sensors were prepared by screen-printing thick films (∼10 μm) of these inks on alumina substrates fitted with gold electrodes. The response of Pd-loaded WO₃ sensors to hydrogen was checked for the different morphologies at working temperatures ranging from 180 to 240 °C. The sensors prepared from nanolamellae showed the highest response while the nanowires presented the shortest response time to hydrogen.