Characterization of calcium oxide derived from waste eggshell and its application as CO2 sorbent

The carbonation-calcination looping cycle of calcium-based sorbents is considered as an attractive method for CO₂ capture from combustion gases because it can reduce the cost during the capture steps compared to conventional technologies, e.g., solvent scrubbing. In this study, waste eggshell was used as raw material for calcium oxide-based sorbent production. The commercially available calcium carbonate was employed for comparison purpose. Calcination behavior, crystal type and crystallinity, surface chemistry, qualitative and quantitative elemental information, specific surface area and pore size, morphology of the waste eggshell and the calcined waste eggshell were characterized by thermal gravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF), N₂ sorption analysis and scanning electron microscopy (SEM), respectively. The carbonation-calcination cycles were carried out using a TGA unit with high purity CO₂ (99.999%). It was found that the carbonation conversion of the calcined eggshell was higher than that of the calcined commercially available calcium carbonate after several cycles at the same reaction conditions. This could be due to the fact that the calcined eggshell exhibited smaller particle size and appeared more macropore volume than the calcined commercially available calcium carbonate. As results, the calcined eggshell provided a higher exposed surface for the surface reaction of CO₂.     

Extraction of biologically active compounds from Sideritis ssp. L.

In this study extraction of polyphenols and flavonoids from cultivated hybrid Sideritis scardica × Sideritis syriaca, known for its rich content of phenolics and flavonoids with antioxidant activity, was investigated. Extractions have been done by ethanol and water-ethanol, respectively. High equilibrium values of the extracted species were obtained—17.55 mg/(g solid) total phenolics and 5.7 mg/(g solid) total flavonoids with ethanol as solvent. The influence of the solvent on the total yield and the content of biologically active compounds were studied. Maximum polyphenolics and flavonoids extraction was observed for water-ethanol solvent ratio 20/80. Increase of the content of ethanol in the solvents led to lower total yield of extracts but higher percentage of polyphenolics. The extraction kinetics showed that 90% of the phenolic compounds were extracted during the first 2.5 h. The experimental kinetics was described by a constant effective diffusion coefficient D_e = 1.5 × 10⁻¹² m²/s in the solid, accounting for the actual particle size distribution.     

The gain and noise figure of Yb-Er-codoped fiber amplifiers based on the temperature-dependent model

A novel temperature-dependent model for Yb³⁺-Er³⁺-codoped fiber amplifier (EYDFA) based on the energy transfer from Yb³⁺ to Er³⁺ is established. Using appropriate fiber and energy transfer parameters, the coupled rate equations is numerically solved at 25 and 40 °C. The pumping powers are 100 and 200 mW at a pump wavelength of 1060 nm. The signal gain and noise characteristics of a 0.3 m erbium/ytterbium co-doped fiber (EYDF) in a single-pass configuration are investigated by using 1, 10 and 100 μW signals at 1535 nm. A maximum signal gain of 40.5 dB and a corresponding noise figure of 3.65 dB at the temperature of 25 °C are achieved.     

Performance enhancement of the DSRC system using frequency-domain equalization for 5.9 GHz DSRC applications

This paper proposes the use of equalization concepts in frequency domain that exploit the frequency domain channel matrix to combat inter-carrier interference (ICI) instead of inter-symbol interference (ISI) in 5.9 GHz Dedicated Short Range Communications (DSRC) systems. The physical layer (PHY) of DSRC is currently being developed by work group of IEEE 802.11p. The conventional system currently assumes static channel characteristics. Channel tracking schemes were investigated and the Viterbi-aided channel estimation scheme was proposed for DSRC systems that did not explicitly exploit the ICI components caused by the time-varying channels. The performance of the DSRC system is investigated for a time-varying channel using a conventional DSRC model, a decision-directed (Viterbi-aided) channel estimation model, and the frequency-domain equalization design. It is shown that the DSRC system with the frequency-domain equalization achieves a considerable performance enhancement compared to both the conventional and the Viterbi-aided channel estimation schemes in terms of both packet error rate (PER) and bit error rate (BER) at relatively high and low velocities.     

Design of 3.1–10.6 GHz ultra-wideband CMOS low noise amplifier with current reuse technique

A new low complexity ultra-wideband 3.1–10.6 GHz low noise amplifier (LNA), designed in a chartered 0.18 μm RFCMOS technology, is presented in this paper. The ultra-wideband LNA only consists of two simple amplifiers with an inter-stage inductor connected. The first stage utilizing a resistive current reuse and dual inductive degeneration techniques is used to attain a wideband input matching and low noise figure. A common source amplifier with inductive peaking technique as the second stage achieves high flat gain and wide the −3 dB bandwidth of the overall amplifier simultaneously. The implemented ultra-wideband LNA presents a maximum power gain of 15.6 dB, a high reverse isolation of −45 dB and a good input/output return losses are better than −10 dB in the frequency range of 3.1–10.6 GHz. An excellent noise figure (NF) of 2.8–4.7 dB was obtained in the required band with a power dissipation of 14.1 mW under a supply voltage of 1.5 V. An input-referred third-order intercept point (IIP3) is −7.1 dBm at 6 GHz. The chip area including testing pads is only 0.8 mm × 0.9 mm.     

Environmental-adaptive indoor radio path loss model for wireless sensor networks localization

In the received signal strength indicator (RSSI) based indoor wireless sensor networks localization system, RSSI measurements are very susceptible to multipath fading, anisotropy of antenna, low supply voltage of node and so on, which will cause the system failure to achieve a high location accuracy. This paper presents an environmental-adaptive path loss model. In the process of localization, the calibrated coefficient LSV of low supply voltage, which can be determined by monitoring the supply voltage of the sender, is used to calibrate ranging errors caused by its low supply voltage. The blind node utilizes the absolute value of RSSI to generate the phase of the corresponding receiver's location so as to determine the correction coefficient of indoor multipath fading R_i. Furthermore, in order to improve the accuracy of RSSI measurements, we also take full consideration of the effect of antenna to accurately determine the corresponding path loss model of the two communication nodes. The proposed path loss model is suitable for the majority of wireless location systems that are on the basis of RSSI-based ranging techniques. Experiment results show that the estimation accuracy and adaptability of the proposed path loss model are significantly higher than that of the traditional one.     

Using patents and publications to assess R&D efficiency in the states of the USA

Even with the USA spending the largest amounts in R&D, its share in total patent grants worldwide has been declining. This decline is also evident in its share of world scientific publications. These developments have been termed by some as the “American Paradox”. Extant research on R&D efficiency and technological innovation capability has considered the USA as a homogeneous entity and has not focused at the sub-national level. This paper analyses the R&D efficiency of 50 US states and the District of Columbia. R&D efficiency is calculated as the ratio of patents granted and scientific publications to R&D expenditures. Only 14 states out of the 51 regions are found to exhibit positive changes in R&D efficiency between 2004 and 2008. Comparing this performance with that of the BRICS nations over the same period we find that Brazil, India, China and South Korea show significant improvements in R&D efficiency with India taking the lead. This research identifies the states in the US with the highest R&D efficiency and presents benchmarks which can be followed by policy interventions. The paper highlights the importance of conducting analyses of R&D efficiency using patents and publications at the sub-national level for informed policy making.     

Exploratory analytics on patent data sets using the SIMPLE platform

Exploratory Analytics is the process of analyzing data for the purpose of forming hypotheses. Patent data sets, because they are relatively large and diverse and because they consist of a mixture of structured and unstructured information present a formidable challenge and a great opportunity in applying exploratory analytics techniques. In this paper we describe methods we have implemented for effective exploratory analytics on patent data sets using an interactive approach and a web based software tool called SIMPLE. We use real-world case studies to demonstrate the effectiveness of our exploratory analytics approach in the discovery of useful information from the patent corpus.     

Mixed enrichment for the finite element method in heterogeneous media

Problems of multiple scales of interest or of locally nonsmooth solutions may often involve heterogeneous media. These problems are usually very demanding in terms of computations with the conventional finite element method. On the other hand, different enriched finite element methods such as the partition of unity, which proved to be very successful in treating similar problems, are developed and studied for homogeneous media. In this work, we present a new idea to extend the partition of unity finite element method to treat heterogeneous materials. The idea is studied in applications to wave scattering and heat transfer problems where significant advantages are noted over the standard finite element method. Although presented within the partition of unity context, the same enrichment idea can also be extended to other enriched methods to deal with heterogeneous materials. Copyright © 2014 John Wiley & Sons, Ltd.     

A classical molecular dynamics study of the correlation between the Bredig transition and thermal conductivity of stoichiometric uranium dioxide

Thermophysical properties of uranium dioxide are investigated by classical molecular dynamics for temperatures from 300 K to 3000 K. An increase of specific heat in the temperature range from 1300 K to 2500 K is noted. Comparison with a theoretical model shows that the origin of this behavior is only due to anharmonicity. Such characteristic features of the Bredig transition as the peak in specific heat and high ionic conductivity are investigated. We show that one more important feature was left unnoticed: the rise in the lattice contribution to thermal conductivity at high temperatures. An explanation is provided for this effect which is specific to superionic conductors. Reasonable agreement with experimental data up to 3000 K is obtained for thermal conductivity, even in the absence of electronic excitations.