Supercritical fluid technologies for the advanced processing of plant raw materials

Publications dedicated to the application of supercritical fluids in the advanced processing of plant raw materials for the production of a wide range of products such as ethanol, liquid and gaseous fuels, sugars, organic acids, and oils are reviewed and analyzed. The specific features of the supercritical fluid technologies and their advantages over the existing traditional methods for the processing of plant raw materials are demonstrated.     

Rare-earth-doped materials for applications in quantum information storage and signal processing

Realization of practical quantum memory and optical signal processing systems critically depends on suitable materials that offer specific combinations of properties. Solid-state materials such as rare-earth ions doped into dielectric crystals are one of the most promising candidates for several quantum information storage protocols, including quantum storage of single photons. This article provides an overview of rare-earth-doped material properties and summarizes some of the most promising materials studied in our laboratory and by other groups for applications in quantum information storage and for ultra-wide bandwidth signal processing. Understanding and controlling spectral diffusion in these materials, which ultimately limits the achievable performance of any quantum memory system, is also briefly reviewed. Applications in quantum information impose stringent requirements on laser phase and frequency stability, and employing a narrow spectral hole in the inhomogeneous absorption profile in these materials as a frequency reference can dramatically improve laser stability. We review our work on laser frequency and phase stabilization and report our recent results on using a narrow spectral hole as a passive dynamic spectral filter for laser phase noise suppression, which can dramatically narrow the laser linewidth with or without the requirement of active feedback.     

H2 storage efficiency and sorption kinetics in composite materials

We have prepared two different kinds of composite materials for hydrogen storage and studied their H₂ storage capacity and desorption kinetics. The first composite material consists of magnesium-containing transition metal nanoclusters distributed in the Mg matrix (Mg:TM): this composite material shows better H₂ desorption performances than pure Mg. This improvement is attributed to the role of the MgH₂-TM nanocluster interface as preferential site for hexagonal Mg (h-Mg) nucleation and to the rapid formation of interconnected h-Mg domains where H diffusion during desorption occurs. The second composite material consists of LaNi₅ particles (size<30 μm) distributed in a polymeric matrix. The H₂ storage capacity is negligible at low metal content (50 wt%) when the metal particles are completely embedded in the polymeric matrix. The H₂ storage capacity is comparable to that of the pure LaNi₅ powders at high metal content (80 wt%) when a percolative distribution is assumed by the LaNi₅ particles: this evidence points out the role of metal-metal interfaces and of interconnected metallic networks for H transport.     

Enhancement of light-emitting efficiency using combined plasmonic Ag grating and dielectric grating

Based on the analysis of the near-field evanescent wave in total internal reflection, the flip-chip light-emitting diode (LED) structure was proposed by placing a plasmonic Ag grating and a perforated sapphire grating in the substrate. The finite difference time domain (FDTD) method has been applied to study the spectral properties of the hybrid structure and the enhancement factor of light extraction efficiency of the LED model. From the computation examples, the effects of structure parameters on the extraction enhancement have been investigated. The results indicate that the plasmonic grating can enhance the near-field evanescent wave and couple it to propagation wave in the specific wavelength bands, which leads to the photons emitting out of the LED chip with high extraction efficiency. Due to the combined gratings used, the enhancement factor of the light extraction efficiency can reach approximately 4 times at a relatively longer wavelength.     

Enhancement of sensitivity in optical waveguide sensors using left-handed materials

We show analytically that the sensitivity of an optical waveguide sensor can be dramatically enhanced by using a metamaterial with negative permittivity and permeability. The variation of the sensitivity of the proposed waveguide sensor with different parameters of the waveguide is studied. It is found that the sensitivity of the sensor increases with the increasing thickness of the metamaterial due to the surface polariton generation.     

On the acoustic radiation efficiency of local resonance based stop band materials

The application of materials with stop bands is emerging as a novel way of creating meta-materials with good vibrational behaviour. The acoustic radiation efficiency in these stop band zones is often not investigated. This paper formulates an uncoupled vibro-acoustic unit cell model of a plate with local resonant stop band behaviour, based on the addition of a grid of tuned resonators. The results are compared with a vibro-acoustic coupled model for a finite equivalent of the infinite structure. It is shown that the beneficial vibration reduction that is achieved in a stop band can be acoustically reduced or enhanced by the change in radiation efficiency of the structure. When care is taken in the design of the stop band, a stop band material with good vibro-acoustic behaviour can be achieved.     

Tailoring radiation pattern through designed structures using near-zero-index materials

Due to the zero phase variation and impedance matching to free space, zero-index material is found to have applications in tailoring the electromagnetic radiation patterns. We design a two-dimensional rectangular or triangular slab made of near-zero-index materials with an arc hole. Such structures can implement the beam transformation from cylindrical wave to parallel wave in the predefined direction. We also combine two concave slabs made of near-zero-index materials to perform the compression or expansion of planar wave beam. All the simulation results show that our designs have perfect performance.     

Quantitative studies of pyrocarbon‐coated materials using synchrotron radiation

Phase‐contrast imaging provides enhanced image contrast and is important for non‐destructive evaluation of structural materials. In this paper, experimental results on in‐line phase‐contrast imaging using a synchrotron source (ELETTRA, Italy) for objects required in material science applications are discussed. Experiments have been carried out on two types of samples, pyrocarbon‐coated zirconia and pyrocarbon‐coated alumina microspheres. These have applications in both reactor and industrial fields. The phase‐contrast imaging technique is found to be very useful in visualizing and determining the coating thickness of pyrocarbon on zirconia and alumina microspheres. The experiments were carried out at X‐ray energies of 16, 18 and 20 keV and different object‐to‐detector distances. The results describe the contrast values and signal‐to‐noise ratio for both samples. A comprehensive study was carried out to determine the thickness of the pyrocarbon coating on zirconia and alumina microspheres of diameter 500 µm. The advantages of phase‐contrast images are discussed in terms of contrast and resolution, and a comparison is made with absorption images. The results show considerable improvement in contrast with phase‐contrast imaging as compared with absorption radiography.     

Detection of delamination defects in CFRP materials using ultrasonic signal processing

In this paper, signal processing techniques are tested for their ability to resolve echoes associated with delaminations in carbon fiber-reinforced polymer multi-layered composite materials (CFRP) detected by ultrasonic methods. These methods include split spectrum processing (SSP) and the expectation-maximization (EM) algorithm. A simulation study on defect detection was performed, and results were validated experimentally on CFRP with and without delamination defects taken from aircraft. Comparison of the methods for their ability to resolve echoes are made.     

Interaction of biological and nonbiological surfaces. New opportunities for research and technologies using synchrotron radiation

The applicability of synchrotron radiation to implementation of medical ideas associated with introduction of nonbiological objects into a human body—implants, drug nanocapsules, and X-ray therapeutic means (metal nanoparticles and nanocrystalline phosphors and scintillators)—is considered. Synchrotron radiation presents new possibilities of analyzing the surface with a resolution comparable to the sizes of biological nanostructures involved in interactions such as chemical and biochemical modification of implant surfaces in vitro; activation of implant surface integration with biological tissue in a tissue culture (in vitro) and in vivo; biochemical modification of therapeutic nanoparticle surface in vitro; immunocamouflage by host proteins; attachment of “molecular targets”, i.e., antibodies, to target tissue to provide targeted delivery vehicles; and local activation of X-ray therapeutic drugs and drug nanocapsules in biological tissues. A functional block diagram of a medical technological station is given.     

Enhancement of parametric efficiency by saturation suppression

The energy conservation equations due to Westervelt are used to show that saturation effects in a finite amplitude wave can in principle be suppressed, if the attenuation coefficient at the second harmonic frequency of the primary wave can be selectively increased. Introduction of microscopic air bubbles which are resonant at the second harmonic frequency is proposed as a scheme for applying this idea to a parametric array operating in water. The parameter of non-linearity also increases when the bubbles are introduced; hence parametric efficiency would be enhanced by both of these effects.     

Enhancement of phosphor efficiency via composition modification

The luminescence efficiency of Mn4+-doped CaAl12O19 (Mn:CAO) is significantly improved by composition modification. The leading mechanism that quenches the Mn4+ photoluminescence is the formation of Mn4+ pairs in the lattice of CaAl12O19 (CAO) with interstitial O2- for charge compensation. Mixing Mg2+ ions into the CAO lattice may form Mn4+-Mg2+ pairs and reduce the number of Mn4+ pairs, thus enhancing the Mn4+ luminescence efficiency by more than three times. It is shown that the presence of Mg2+ leads to formation of additional phases that also affect the optical properties of Mn4+.     

Enhancement of measurement accuracy in fiber Bragg grating sensors by using digital signal processing

Wavelength detection accuracy in fiber Bragg grating (FBG) sensors can be increased by use of digital signal processing after photo-detection. Finite impulse response and infinite impulse response algorithms were implemented and used to improve the wavelength detection accuracy of peak detection and time-zero-crossing techniques. The wavelength detection resolution can be improved by an order of magnitude compared with that obtained directly from an optical spectrum analyzer/tunable laser.     

Enhancement of light extraction efficiency of organic light emitting diodes using nanostructured indium tin oxide

Improved outcoupling efficiency of organic light emitting diodes (OLEDs) is demonstrated by incorporating a nanostructured indium tin oxide (NSITO) film between a conducting anode and a glass substrate. NSITO film was fabricated using rf-sputtering at oblique angle (85°). Significant reduction in refractive index and improved transmission of NSITO film was observed. OLEDs were then fabricated onto NSITO film to extract the ITO-glass waveguided modes. Extraction efficiency was enhanced by 80% without introducing any detrimental effects to operating voltage, current density, and angular invariance of emission spectra of OLEDs.     

Enhancement of efficiency of vibration suppression using piezoelectric elements and LR circuit by amplification of electrical resonance

This paper describes a vibration suppression method based on passive vibration suppression using a piezoelectric element and an LR circuit. The proposed method applies a voltage that is proportional to the displacement or acceleration of the host structure to the LR circuit in series. Because the applied voltage equivalently increases the voltage generated by the piezoelectric effect in the piezoelectric element, the effect of the vibration suppression is increased with an increase in the applied voltage. The proposed method is categorized as a hybrid vibration suppression method that involves only an analog circuit. The governing equations were formulated, and the optimum values of the inductance and resistance were theoretically derived using the two fixed point method as well as the passive method. The characteristic features of the proposed method were theoretically investigated by comparing the added stiffness and damping, amount of the applied voltage, and time-averaged power of the applied voltage with those of the conventional methods. In addition, the stability of the proposed method was theoretically analyzed. The effectiveness of the proposed method and the theoretical analysis were verified through experiments.     

Oxygen electrocatalysis in chemical energy conversion and storage technologies

Oxygen electrocatalysis that we first defined is considered as the most important phenomenon in almost all electrochemical industries because it is the most sluggish reaction that governs the overall reaction rate in electrochemical cells. In this review, we cover two main areas of oxygen–water electrocatalysis, oxygen reduction to water and oxygen evolution from water. In particular, it aims to provide the readers with an understanding of the critical scientific challenges facing the development of oxygen electrocatalysts, various unique attributes of recent novel catalysts, the latest developments in electrode construction and the outlook for future generation of oxygen electrocatalysts. This review will be of value to both electrochemists and other applied scientists interested in this field of electrocatalysis.     

Enhancement of noise reduction efficiency based on compensation in the ANC headset using fixed-point DSP

In this paper, we have proposed a new algorithm considering commutation error and feedback effect to enhance the convergence rate and noise reduction efficiency of ANC controller. In order to improve noise reduction performance of the ANC headset with fixed-point DSP, we have proposed a new FxLMS algorithm, FxLMS CF, which considers the commutation error and feedback. Also, using a non-real-time simulation, we have decided the phase and amplitude compensation factors of anti-noise signal considering round-off and quantization error, nonlinear distortion and delay of analog device. We estimated the phase and amplitude compensation factors by simulation without using any special measuring devices or analysis devices, and reduced the broadband noise by 24 dB.     

高温超导材料技术专利数据统计分析

利用德温特专利数据库和汤姆森数据分析软件(TDA),对1988-2007年20间高温超导材料技术的专利进行统计分析,从专利申请的年度分布、国家/地区分布、机构分布、技术领域特点、专利保护策略等方面探讨了高温超导材料技术的整体发展状况。     

Fine structure of angular selectivity of diffraction efficiency of holograms recorded on materials polymerized by IR radiation

Journal of Experimental and Theoretical Physics - Asymmetry in the angular selectivity of the diffraction efficiency observed in polymer-dispersed liquid-crystal holograms polymerizing under the...