New linear piezoelectric actuator based on traveling wave

A novel design of linear type piezoelectric actuator is proposed and analyzed in the paper. Actuator has a beam shape with cut-out hole. Traveling wave is generated on the top area of the actuator applying harmonic oscillations on the ends of the beam. These oscillations are generated by two piezoceramic elements and transferred to the ends of the beam. Electrodes of piezoceramic elements are excited by harmonic voltage with phase difference of ?/2. Numerical modeling based on finite element method was performed to find resonant frequencies and modal shapes of the actuator and to calculate the trajectories of contact point movements under different excitation schemes. A prototype of the piezoelectric actuator was built and measurements of top surface oscillations were performed. Results of numerical and experimental studies are discusse

Factors influencing the recovery of organic nitrogen from fresh human urine dosed with organic/inorganic acids and concentrated by evaporation in ambient conditions

To feed the world without transgressing regional and planetary boundaries for nitrogen and phosphorus, one promising strategy is to return nutrients present in domestic wastewater to farmland. This study tested a novel approach for producing bio-based solid fertilisers by concentrating source-separated human urine through acidification and dehydration. Thermodynamic simulations and laboratory experiments were conducted to evaluate changes in chemistry of real fresh urine dosed and dehydrated using two different organic and inorganic acids. The results showed that an acid dose of 1.36 g H2SO4 L-1, 2.86 g H3PO4 L-1, 2.53 g C2H2O4 center dot 2H(2)O L-1 and 5.9 g C6H8O7 L-1 was sufficient to maintain pH <= 3.0 and prevent enzymatic ureolysis in urine during dehydration. Unlike alkaline dehydration using Ca(OH)(2) where calcite formation limits the nutrient content of fertiliser products (e.g. <15 % nitrogen), there is greater value proposition in acid dehydration of urine, as the products contain 17.9-21.2 % nitrogen, 1.1-3.6 % phosphorus, 4.2-5.6 % potassium and 15.4-19.4 % carbon. While the treatment recovered all phosphorus, recovery of nitrogen in the solid products was 74 % (+/- 4 %). Follow-up experiments revealed that hydrolytic breakdown of urea to ammonia, chemically or enzymatically, was not the reason for the nitrogen losses. Instead, we posit that urea breaks down to ammonium cyanate, which then reacts with amino and sulfhydryl groups of amino acids excreted in urine. Overall, the organic acids evaluated in this study are promising for decentralised urine treatment, as they are naturally present in food and therefore already excreted in human urine

A device to characterize optical fibres

ATLAS is a general purpose experiment approved for the LHC collider at CERN. An important component of the detector is the central hadronic calorimeter; for its construction more than 600,000 Wave Length Shifting (WLS) fibres (corresponding to a total length of 1,120 Km) have been used. We have built and put into operation a dedicated instrument for the measurement of light yield and attenuation length over groups of 20 fibres at a time. The overall accuracy achieved in the measurement of light yield (attenuation length) is 1.5% (3%). We also report the results obtained using this method in the quality control of a large sample of fibres.Comment: 17 pages 20 figeres submitted to NIM journa

Drying fresh human urine in magnesium-doped alkaline substrates: Capture of free ammonia, inhibition of enzymatic urea hydrolysis & minimisation of chemical urea hydrolysis

Recycling urine can reduce the flux of reactive nitrogen in the environment. This paper presents a novel approach to recover all N (Ntot) from urine, including ammonia (TAN; about 5% of Ntot), which is usually volatilised when alkalised urine is dehydrated. As analytical methods for measuring N have a standard deviation of at least 5%, real fresh urine was fortified with ammonia (urineN) or ammonia and phosphate (urineNP) so that TAN comprised 10% of Ntot. The urine was then added to different magnesium-based alkaline substrates (MgO, Mg(OH)2, MgCl2 + Mg(OH)2) and dried at 38 C. Chemical speciation modelling suggested that, irrespective of the substrate, >98% of Ntot in urineNP was recovered and 86% of TAN was precipitated as struvite. Experimental results showed that 10 throughout the treatment, urease enzyme-catalysed degradation of urea to ammonia is prevented, resulting in complete recovery of all nutrients. The end-product is a solid fertiliser containing 10-11% nitrogen, 1-2% phosphorus and 2-3% potassium

Postural balance strategies for experienced rhythmic gymnasts in two-legged stands

Objective: The purpose of this study was to find out the indicators of the distribution of plantar pressure in the two-legged stands with open and closed eyes in experienced rhythmic gymnasts.Materials and methods: 31 highly qualified gymnasts (candidates and masters of sports of Russia), age 18.5 ± 0.5 years, experience in rhythmic gymnastics 13.5 ± 1.5, performed three upright postures on the footscan ® podometric platform of RSscan: the main stand, a modified Romberg test with open and closed eyes. Postural control was assessed by quantifying the plantar pressure (P%) in relation to 4 zones of the right and left foot and the trajectory of the movement of the center of pressure (CP) over time intervals.Results: The results of the study showed the presence of a right-sided distribution of plantar pressure in two-legged stands in experienced gymnasts. The regulation of posture occurs mainly in the anterior-posterior direction, but has different strategies for managing balance. The sagittal-cross pattern determines the interaction of plantar pressure between the right and left feet in the basic pose. The Romberg test with open eyes (EO) and closed eyes (EC) characterizes sagittal-parallel and sagittal-asymmetric balance, respectively. We revealed an increase in the vibrations of the gymnast's body in the absence of visual information for only the first 12 seconds.Conclusions: We have identified a variety of combinations of two types of strategies while maintaining posture in simple poses. This indicates the ability of experienced gymnasts to fine-tune the postural stability, including in the absence of visual information

New linear piezoelectric actuator based on traveling wave

A novel design of linear type piezoelectric actuator is proposed and analyzed in the paper. Actuator has a beam shape with cut-out hole. Traveling wave is generated on the top area of the actuator applying harmonic oscillations on the ends of the beam. These oscillations are generated by two piezoceramic elements and transferred to the ends of the beam. Electrodes of piezoceramic elements are excited by harmonic voltage with phase difference of ?/2. Numerical modeling based on finite element method was performed to find resonant frequencies and modal shapes of the actuator and to calculate the trajectories of contact point movements under different excitation schemes. A prototype of the piezoelectric actuator was built and measurements of top surface oscillations were performed. Results of numerical and experimental studies are discusse

РАЗДЕЛЬНОЕ ОПРЕДЕЛЕНИЕ ФОТОЭЛЕКТРИЧЕСКИХ ПАРАМЕТРОВ БАЗОВОЙ ОБЛАСТИ КРЕМНИЕВЫХ СТРУКТУР P+—N(P)—N+–ТИПА БЕСКОНТАКТНЫМ МЕТОДОМ ПО ОТНОШЕНИЯМ КОЭФФИЦИЕНТОВ СОБИРАНИЯ ПРИ ДВУХ ДЛИНАХ ВОЛН

A noncontact method for the determination of recombination parameters of p(n) layer local ranges of silicon n+−p(n)−p+ structures is considered. The method is based on local illumination of the investigated structure by two different absorbed light beams. Initially both beams illuminate simultaneously one side of the local range of this structure and then another side. The intensities оf the light beams are modulated at one frequency so the alternative photo−voltage becomes equal to zero. In this case the short current regime is established for its alternating component. As a consequence the nonilluminated parts of the structure do not shunt its illuminated part. The ratios of the light beam intensities are measured under these conditions. In this work we calculated nomograms for separate determination of the nonequilibrium charge carrier lifetime of the illuminated p(n) local space and its surface recombination velocity using the measured intensity ratios. The calculations were performed at low injection level for one dimensional case. The nomograms were calculated at wave lengths of 1064 and 808 nm for various thicknesses of the n+−p(n)−p+ structures and various modulation frequencies. It was found that the nomograms almost do not depend on the modulation frequency if the live time of the nonequilibrium charge carriers is less than the modulation period. Furthermore, we observed that the nomograms shift substantially and change their shape for thin structures if the diffusion time of nonquilibrium charge carriers from the rear side of the structure to its face side becomes less than their lifetime. In this case the nomograms may be only used for the determination of the surface recombination velocity of the nonquilibrium charge carriers at the rear side of the structure.Рассмотрен бесконтактный метод определения рекомбинационных параметров локальных участков p(n)−слоя кремниевых структур n+—p(n)—p+−типа. Метод основан на локальном освещении исследуемой структуры двумя различно поглощаемыми лучами света. Оба луча освещают одновременно сначала одну сторону локальной области этой структуры, а затем противоположную. Интенсивности лучей света модулируются так, что суммарная переменная фотоЭДС обращается в 0. В этом случае осуществляется режим тока короткого замыкания для его переменной составляющей. В результате неосвещаемые участки структуры не шунтируют освещаемый участок. При этих условиях измеряют отношения интенсивностей лучей света. Вычислены номограммы для раздельного определения времени жизни неравновесных носителей заряда в освещаемой части p(n)−области и скорости их поверхностной рекомбинации на основании измеряемых отношений интенсивностей. Расчеты проведены для случая низкого уровня инжекции в одномерном приближении Номограммы вычислены для длин волн 1064 и 808 нм при различных толщинах n+—p(n)—p+−структур и частотах модуляции. Было обнаружено, что номограммы практически не зависят от частоты модуляции, еcли время жизни неравновесных носителей заряда меньше периода модуляции. Установлено, что номограммы существенно смещаются и изменяются по форме для тонких структур, если время диффузии неравновесных носителей заряда от тыльной стороны структуры до ее лицевой стороны становится меньше их времени жизни. В этом случае номограммы могут быть использованы лишь для определения скорости поверхностной рекомбинации на тыльной стороне структуры

On the generalized concentration and molecular mass dependencies of macromolecular self-diffusion in polymer solutions

Self-diffusion experimental data obtained with the n.m.r. pulsed gradient spin-echo method in polyethylene oxide (PEO), polystyrene (PS), dextran, gelatine, cellulose triacetate (CT), poly(dimethyl siloxane) (PDMS) solutions and melts in a wide range of solvents, with molecular mass (M) and concentration (ø), were analysed to show the existence of common dependencies for Ds(M) and Ds(ø). The general law for Ds(ø) is expressed as f( ø \ ̂o) = Ds(ø) L(ø)Ds(0) and is correct for the solvent quality ranging from θ to 'good'. The existence of the generalized f( ø \ ̂o) was examined for the 17 different polymer-solvent systems. With the use of the generalized function, where Ds(O)=lim Ds \ ̂o,Ds(O)≈M-β, \ ̂≈M- 2-β 3 nearly 100 Ds(ø) dependencies were described. The renormalization function L(ø) accounts for the local dynamic properties of the concentration dependence. © 1988