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An electrically conducting `organic–inorganic' crystalline type composite cation-exchange material, the polypyrrole/polyantimonic acid system was prepared by incorporating polypyrrole into an inorganic precipitate of polyantimonic acid. The temperature dependence of the electrical conductivity of this composite system was measured on compressed pellets by using a 4-in-line-probe dc electrical conductivity-measuring instrument. The conductivity values lie in the semiconductor region, i.e., they are of the order of 10−5–10−4 S cm−1 and follow the Arrhenius equation. The energy of activation of electrical conduction was also calculated. This system also possessed an improved ion-exchange capacity, high chemical and thermal stabilities, reproducibility and selectivity for some specific metal ions. Kinetic studies of exchange for some divalent metal ions of alkaline earths and transition metals were carried out under conditions favoring a particle diffusion-controlled ion-exchange phenomenon and some physical parameters such as the self diffusion coefficient D 0, the energy of activation E a and the entropy of activation ΔS * were determined.
The Li4P2O7 and Li2Cu2P6O18 phase formation and its correlation with luminescent properties in Cu+ doped Li3PO4 were studied. The study shows that in air annealed samples minor phase of Li4P2O7 along with Li2Cu2P6O18 is formed. The amount of Li4P2O7 is inversely proportional to the annealing temperature whereas amount of Li2Cu2P6O18 increases with annealing temperature. These phases affect luminescence properties of the material significantly. The Cu+ luminescence decreases with the increase in Li2Cu2P6O18 whereas, the TL–OSL sensitivity is found to be a function of amount of Li4P2O7 phase present in the sample. Of the sample annealed at various temperatures maximum OSL sensitivity is obtained for the 600°C annealed sample for which 20% Li4P2O7 phase is detected which is maximum among all air heated samples. The minimum sensitivity is observed in case of sample melted in air in which 3% of this phase is detected. Vacuum heated sample also shows minimum sensitivity, in which no Li4P2O7 phase is detected.
The possibility to improve the electrochemical behaviour of AB5-alloy commercial electrodes was studied using different carbons as support, such as carbon blacks and a selection of commercial and in-lab synthesised carbon nanotubes. The carbons selected for this work present different morphologies (i.e., spherical and tubular). Furthermore, they also present a variation of the porous structure and subsequent surface area, which are also going to influence their further electrochemical behaviour. Carbon samples were texturally characterised by the adsorption–desorption of N2 and CO2 at 77 and 273K, respectively. The carbon structure was analysed by XRD, Raman, TEM, and the chemistry of the samples was also characterised by elemental analysis. The charge and discharge techniques, cyclic voltammetry, rate capability and linear polarisation were used for the electrochemical characterisation of the electrodes studied. The electrochemical behaviour of all the samples was related to their morphological, textural and chemical properties. The results show that there is a clear influence of the nature of the carbon support on the hydriding/dehydriding reaction of the alloy, and in the case of active carbons the kinetics decreases with the increase of the surface area of the carbon support.
Ragone plot is a conventional tool to compare different energy storage systems in terms of energy and power densities. The selection of the most suitable Li-ion technology for a given application is usually based on the specific energy and power extracted from datasheets at ambient temperatures (25 °C). However, these values are highly temperature-dependent. This study investigates experimentally and via numerical simulations a quantification of the energy and power densities for two different Li-ion chemistry cells in a wide operating temperature range. The experimental results reveal that these values determined from constant current discharge are approximately 15% higher than those determined for a constant power discharge. Therefore, a simple and efficient coupled electrical–thermal model based on an equivalent circuit model (ECM) is proposed, which is able to estimate the voltage, temperature, and available discharged energy of 18,650 Li-ion cells with a good accuracy. Moreover, all parameters in the model can be directly identified with manufacturer’s datasheets at 25 °C. Then, the proposed Ragone plot model can be extended to wider temperature and power ranges. The relative error of the simulated energy density is below 2% for both technologies for all operating conditions from – 20 °C to 55 °C. Thus, a non-isothermal Ragone plot is established by considering the thermal effect for the first time. The proposed method could be employed as a conception aid tool for the selection of Li-ion cells in a system design process.
The progress of rural electrification in Indonesia faces specific problems because of the fragmented geography of Indonesia. The major electricity grid and a number of isolated local grids cannot economically reach many rural areas [1]. A photovoltaic system is one suitable solution because of its flexibility, low environmental impact and freedom from fuel requirements. The Agency for Assessment and Application of Technology has been carrying out technology assessments and applications in an effort to introduce photovoltaic applications in Indonesia. Recently the Agency for Assessment and Application of Technology and the Bavarian Ministry for Economic Affairs, Transport and Technology have established a pilot project of photovoltaic systems in the District of Lamongan, East Java Province. This pilot project is an integrated activity, which includes several agriculture activities such as: a fishing pond, chicken farming, a banana plantation which is grown on the little dike of the pond, a chicken incubator and solar boat systems. This paper will explain, elaborate and discuss the technical specification and results of implementation of the systems.
The brain has the ability to flexibly perform many tasks, but the underlying mechanism cannot be elucidated in traditional experimental and modeling studies designed for one task at a time. Here, we trained single network models to perform 20 cognitive tasks that depend on working memory, decision making, categorization, and inhibitory control. We found that after training, recurrent units can develop into clusters that are functionally specialized for different cognitive processes, and we introduce a simple yet effective measure to quantify relationships between single-unit neural representations of tasks. Learning often gives rise to compositionality of task representations, a critical feature for cognitive flexibility, whereby one task can be performed by recombining instructions for other tasks. Finally, networks developed mixed task selectivity similar to recorded prefrontal neurons after learning multiple tasks sequentially with a continual-learning technique. This work provides a computational platform to investigate neural representations of many cognitive tasks.
A summary of studies by photoelectron spectroscopy of the reactions of prototypical ethereal and alkyl carbonate solvents with lithium metal in ultra-high vacuum (UHV) is presented. The Li/solvent interface is formed by condensing solvent vapor onto the surface of freshly vacuum evaporated Li at 130 K. The reaction is observed by obtaining core-level photoelectron spectra as a function of temperature. The interfacial reactions are distinctly different for the ethereal vs. the carbonate solvents. The ethers, both cyclic (THF and 1,3-dioxolane) and linear (glymes), react initially to form an LiOR or radical anion (1,3-dioxolane) precursor, followed by the formation of a polyether layer. In the carbonates, there is a significant difference between linear and cyclical forms. The linear carbonates (DMC and DEC) are more reactive, reacting even below the melting point, and produce both LiOCO2R and LiR (alkyl lithium). There are no unreacted solvent molecules left on the surface at room temperature. Since alkyl lithium is soluble in the bulk solvent, the lithium surface will not passivate in this solvent until considerable dissolution of lithium has occurred. The cyclic carbonate PC forms only insoluble LiOCO2R, but no unreacted PC (or PC-like molecule) remains at room temperature. Thus, the corrosion of lithium in DMC/DEC is predicted to be significantly greater than in PC. Since the ethers incorporate a significant amount of solvent molecule in the passive layer, e.g. by polymerization, the SEI layer formed in the ethers is predicted to be more highly conducting than in the carbonates. This prediction is based on the chemistry of the pure solvent molecules, absent real life impurities, e.g. water, or an anion, which may react preferentially with lithium.
The aim of this paper was to conduct lab-scale investigation of a new roof design concept termed “the thermoelectric roof solar collector (TE-RSC)” for power generation using solar energy. The TE-RSC was composed of a transparent acrylic sheet, air gap, a copper plate, thermoelectric modules and a rectangular fin heat sink. The incident solar radiation heats up the copper plate so that a temperature difference is created between the TE module that generates a direct current. This current generated was used to run a fan for cooling the TE modules. The TE-RSC surface area was 0.0525 m2 and 10 thermoelectric cooling modules (Tianjin Lantian model TEC1-12708) were used. Investigations were done by varying solar radiation, simulated by using a halogen lamp, between 400 and 1000 W/m2. It was found that this new roof design can generate about 1.2 W under solar radiation intensity of about 800 W/m2 at ambient temperature varying between 30 and 35 °C. The corresponding air velocity generated by the ventilation fan was about 1.7 m/s. Therefore, the proposed TE-RSC concept seems to be an interesting new alternative for various purposes such as power generation in remote areas, roof heat gain reduction and indoor ventilation of spaces.
Electrodeposition of compact layers of lead dioxide was performed in order to prepare anode materials. Depending on the mode of preparation, the relative amounts of the two crystallographic forms α and β were different. Cyclic voltammetry experiments were performed in concentrated sulphuric acid for the study of the PbO2/PbSO4 transformation. Whatever the composition of the deposit (pure α form, pure β form or α+β mixtures), only one passivation peak may be observed at low potential during the first reduction scan, corresponding to the transformation of bulky PbO2 crystallites into PbSO4. PbO2 is recovered during the reverse re-oxidation scan. In all the following voltammograms, two reduction peaks are observed. They are attributed to the transformation of (i) the remaining bulky PbO2 crystallites (low potential peak) and (ii) the small PbO2 crystallites resulting from the re-oxidation of PbSO4 (high potential peak). The bulky PbO2 crystallites are gradually transformed into smaller particles so that larger and larger amounts of active mass are involved in the reduction process. The results are discussed, taking into account those obtained from X-ray diffractograms. In addition, a method is proposed for the calculation of the current efficiency of the PbO2 electrodeposition. The lead dioxide layer was first completely reduced in hot acid medium, and the amount of resulting soluble Pb(II) was determined by square wave voltammetry, using a mercury electrode. The results obtained with acid or alkaline plating solutions differ considerably and indicate that PbO2 formed in alkaline plating solutions is highly non-stoichiometric.
The HeartWare® Ventricular Assist System is the newest circulatory support device to be commercially launched in Europe. Here we report the most recent international clinical experience with the system. The HeartWare® Ventricular Assist System is a small, full support (10L/min) centrifugal pump with advanced flow characteristics it employs a wearless hydromagnetic impeller system operated by external controller and battery components. Since March 2006, 99 patients at 10 centers received the device. The pump was implanted in the pericardial space in all patients using a midline sternotomy or thoracotomy without requirement for an abdominal pump pocket. There were 86 males and 13 females ranging in age from 16 to 74 years (mean 50.4 ±13.3) of which 32% had ischemic disease. BSA ranged from 1.35 to 2.56 m2 (mean 1.9 ± 0.23).The implant technique varied with 82 patients having a sternotomy and 17 undergoing a thoracotomy. 96/99 implants used CPB. The duration of support was a mean of 251 ± 243 days with 26 patients supported > 1 year and 6 patients supported > 2 years. The most common significant adverse events were all cause bleeding (0.35 events/patient year) and all cause infection (0.33 events/patient year). 22 patients were been transplanted, 4 were weaned after recovery, 61 remain on support and 12 patients have died. Currently, 88% of these 99 patients are alive on the device, have been transplanted, or have survived 60 days after weaning for recovery. Actuarial survival at 2.5 years is 80%. Long term circulatory support with the miniature HeartWare® Ventricular Assist System is feasible. The device performs well for greater than 1 year with low adverse event rates. The data also demonstrate the versatility of the HeartWare® System to support a wide range of patients using minimally invasive implant techniques.
Home energy management (HEM) is one of the crucial requirements for future smart grid environment. Usually, utility companies motivate residential consumers to participate in household demand side management (DSM) techniques. The residential consumers’ main intention is to reduce their electricity bills whereas utilities’ primary goal is to reduce their system peak load demand. The benefits of DSM can be enhanced with smart energy storage systems. In this paper, an intelligent multi-objective household DSM with battery storage systems is proposed to minimize both the objectives simultaneously. Generally, the residential DSM deals with various controllable appliances that normally have different operating time priorities according to the consumers’ preferences. Because of this, the DSM problem is modelled as a mixed integer optimization problem. In this paper, the multi-objective mixed integer linear programming technique (MOMILP) is used to solve the proposed residential DSM problem. The proposed model is tested on a system having four different residential consumers. The benefits of the battery energy storage systems are analysed by taking six different scenarios. An economic analysis of each residential consumer's battery storage system with load uncertainty modelling is also done in this paper. Simulation results of various scenarios with different objectives demonstrate the effectiveness of the proposed model.
In an attempt to provide a favorable active material of Li+ supercapacitor for HEV use, we modified the surface of an activated carbon fiber felt by coating with some transition metal oxides after mild-oxidation treatment. Major source of enhancing capacitance is attributed to be due to the nano-ionics mechanism proposed by Maier and coworkers. Cyclic voltammetry and constant current charge–discharge performance were examined for the surface modified samples in view of power capability. The oxides of Ag, Cu, Pd, and Sn were found effective to enhance the capacitance and high rate charge/discharge performance. The cycleability test was performed as well.
Mobile counter anion exchange of electropolymerized polyaniline (PANI) films with the anions in acid solutions has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy, Raman, UV–vis, and fluorescence spectra. The studied acids include camphorsulfonic acid, p-toluene sulfonic acid, HCl, HClO4, H2SO4 and H3PO4. In two cases of small and large counter ions of PANI films, CV tests have been performed alternately three times in each of two electrolytes containing organic or inorganic acid. The investigation of electrochemical and spectrophotometric measurements reveals that large counter anions can be easily replaced by the small anions; and the reverse exchange also occurs, but shows very low efficiency. This indicates that the achieved anion exchange in both cases leads to the remarkable alteration in electrochemical behavior and electrical conductance of PANI films. This implies counter anions, whatever the original or redoping ones, play an important role in the electrical, electrochemical, even optical properties of PANI. However, the polymer morphology does not be changed after exchange tests. This allows us to point out a ‘morphology-memory’ effect which is very significant for the development and application of PANI films with the same morphology and different properties.
The effect of conductive carbon additives (acetylene black with various specific surface areas and ketjen black) on the electrochemical performance of LiCoPO4 is investigated to develop 5 V-class lithium-ion batteries with good cyclability. The irreversible reactions between electrolyte and LiCoPO4 electrode can be kept small in addition to realizing reversible and a small amount of intercalation/deintercalation of PF6 − into/from the graphite structure of carbon when using acetylene black with a low surface area as a conductive additive. However, the low surface area reduces the utilization of LiCoPO4, and degrades its cycle performance owing to the decrease of contact area between LiCoPO4 and carbon during charge and discharge cycles. On the other hand, ketjen black with a high surface area enhances the capacity of LiCoPO4, while it induces a large amount of irreversible reactions and the anion intercalation, leading to the rapid capacity fading. By using acetylene black with a moderate surface area as a conductive additive for LiCoPO4 electrode, the superior cycle performance can be achieved, which is attributed to the formation of good conductive network among LiCoPO4 particles by the carbon additive with an appropriate surface area to minimize the irreversible decompose reactions of electrolyte and the anion intercalation.
Purpose This study aimed (1) to compare the skeletal maturity and activity participation pattern between children with and without developmental coordination disorder (DCD); and (2) to determine whether activity participation pattern was associated with the skeletal development among children with DCD. Materials and methods Thirty-three children with DCD (mean age: 7.76 years) and 30 typically developing children (mean age: 7.60 years) were recruited. Skeletal maturity was assessed with the Sunlight BonAge system. Motor ability was evaluated by the Movement assessment battery for Children-2 (MABC-2). Participation patterns were evaluated using the Children Assessment of Participation and Enjoyment assessment. Analysis of variance was used to compare the outcome variables between the two groups. Multiple regression analysis was performed to examine the relationship between skeletal development, motor performance and activity participation intensity in children with DCD. Results The DCD group had significantly delayed skeletal development, lower MABC-2 derived scores, and participated less intensely in various types of physical activities than their typically developing peers. After accounting for the effects of age and sex, activity participation intensity score remained significantly associated with delay in skeletal development, explaining 28.0% of the variance (F change1, 29 =11.341, p =0.002). Conclusion Skeletal development is delayed in pre-pubertal children with DCD. Limited activity participation intensity appears to be one of the contributing factors.
Li5La3Ta2O12 (LLTa) is a promising solid electrolyte for all-solid-state batteries due to its high stability in contact with Li metal, however, low Li ion conductivity of LLTa has restricted its application. In this study, improvement of the Li ion conductivity of LLTa solid electrolyte by substitution of Ge4+ for Ta5+ is studied because the improvement is thought to be achieved by increase of charge carrier concentration caused by the substitution of low valence Ge4+ for high valence Ta5+. The Ge substitution shrinks a lattice of cubic LLTa due to small ion radius of Ge4+ (0.530 Å) compared with Ta5+ (0.640 Å). The Li ion conductivity of LLTa is improved by the Ge substitution. The highest bulk and total Li ion conductivities are obtained in Li5.25La3Ta1.75Ge0.25O12 prepared by spark plasma sintering at 1100 °C and the values are 1.3 × 10−4 and 8.4 × 10−5 S cm−1 at 28 °C, respectively. The lithium transference number of the Ge-substituted LLTa determined by Hebb-Wagner (HW) polarization method is ≈ 1. Also, it is verified that the new solid electrolyte is stable in a potential range of 0–10 V vs. Li/Li+, indicating that the Ge-substituted LLTa is a promising solid electrolyte for all-solid-state battery application.
Mobile devices can perceive greater details of user states with the increasing integration of mobile sensors into a pervasive computing framework, yet they consume large amounts of batteries and computational resources. This paper proposes a semantic management method which efficiently integrates multiple contexts into the mobile system by analyzing the semantic hierarchy and temporal relations. The proposed method semantically decides the recognition order of the contexts and identifies each context using a corresponding dynamic Bayesian network (DBN). To sort out the contexts, we designed a semantic network using a knowledge-driven approach, whereas DBNs are constructed with a data-driven approach. The proposed method was validated on a pervasive computing framework, which included multiple mobile sensors (such as motion sensors, data-gloves, and bio-signal sensors). Experimental results showed that the semantic management of multiple contexts dramatically reduced the recognition cost.
With this paper, we share some of the results of a post-doctoral research project investigating the epistemic beliefs of Romanian medical students and how these operate within the context of learning English for medical purposes. A battery of questionnaires (EBS, BALLI, SILL) were used in a survey on 160 1st year medical students at the end of the academic year 2011-2012. Data analysis included descriptive statistics, appropriate correlations and factor analyses, corroborated with observed classroom behaviour and performance over one academic year. The results invite discussion at several levels, e.g. methodological, cultural, curricular.
A carbon nanotubes (CNTs)-nickel–cobalt hydroxide nanoflake core–shell structure is designed and fabricated by a facile one-step chemical bath deposition method. Structure analysis confirms that the as-synthesized hydroxides are conformally coated on the surface of CNTs with a hydrotalcite structure. The incorporation of Co into nickel hydroxides can improve the electrical conductivity together with intercalated sulphate ions into the interlayer spacing to enlarge the lattice space, which further improves the rate capabilities and cycling stability. Electrochemical data demonstrates that the hybrid hydroxide with Ni–Co molar ratio of 1:2 exhibits a high specific capacitance of 1151 F g−1 at 1 A g−1 and an excellent high rate capability, with 61% retention after a 70-fold increase in current densities. Its specific capacitance can maintain 77% of the initial value after 10,000 cycles. The nickel–cobalt hydroxide nanoflakes-CNTs hybrid shows a great potential of being an electrode material for supercapacitors with its high specific capacitance, good rate capability and long-term cycling life.