Electrostatic precipitation

Electrostatic precipitators have been used widely in industry, and play an important role in environmental protection. An electrostatic precipitator (ESP) can be operated with a high collection efficiency and a low pressure drop. Recently, an ESP also has been used for cleaning indoor air. In this review, principles of electrostatic precipitation, such as particle charging, migration velocity of charged particles and collection efficiency, are described. The performance of the ESP deteriorates by abnormal phenomena, including back corona for treating high resistivity dust, abnormal re-entrainment for low resistivity dust, and corona quenching for fine dusts. To cope with these phenomena, new technologies have been developed. Pulsed energization is a technique which copes with high resistivity dusts, and this results in lower power consumption. Using pulsed energization, non-thermal plasma can be generated and chemical reactions can be promoted for treating gaseous pollutants such as NO and volatile organic compounds. Wet ESP can also remove dusts and gaseous pollutants simultaneously. These new advancements will widen the field of application of electrostatic precipitation. Some novel applications of ESP, such as removal of dioxin from incinerators, are also included in this review     

Adaptive Modulation/TDMA/TDD with Convolutionally Coded Type-II Hybrid ARQ for Wireless Communication Systems

This paper proposes a time divisionmultiple access/time division duplex (TDMA/TDD)-basedadaptive modulation system (AMS) with aconvolutionally coded Type-II Hybrid automatic repeatrequest (ARQ) protocol to achieve high throughput datatransmission in wireless communication systems. First,this paper discusses the cause of throughputlimitation of the conventional fixed-rate quaternaryphase shift keying (QPSK) with ARQ protocol andsuggests that the effective means to improvethroughput performance are the reduction ofre-transmission probability under bad channelcondition and the increase of transmission bit rate perTDMA/TDD slot under good channel condition. Based onthese strategies, this paper discusses an AMS with aconvolutionally coded type-II hybrid ARQ protocol(type-II hybrid ARQ/AMS) and evaluates itsperformance by computer simulation. The resultsconfirm that the proposed type-II hybrid ARQ/AMS candrastically improve throughput performances comparedto the conventional fixed-rate QPSK with selectiverepeat ARQ protocol (SR-ARQ/QPSK) or a simplecombination of SR-ARQ and AMS (SR-ARQ/AMS) under anychannel conditions, especially under severe channelconditions.     

Effects of local damage on asymptotic stress field of a growing creep crack

A parametric study on the effects of local damage field on the crack-tip stress field of a growing Mode I creep crack is performed in the framework of Continuum Damage Mechanics (CDM). According to the results of creep crack growth analysis based on CDM and Finite Element Method, the damage distribution1-(D/D _cr)=h(θ)r^m represented by a power law function of the radiusr from the crack tip is postulated for the damage variableD. The damage effects are incorporated into the Norton creep law by means of the hypothesis of strain equivalence of CDM. The resulting two-point boundary value problems of differential equations for the growing creep cracks in the states of plane strain and plane stress are solved by means of a shooting method. For a given creep exponentn of the Norton law, the exponentp of the asymptotic stress field σ _ij ∞r ^p is found to be governed by the exponentm of the power law damage distributionr ^m.     

Electrochemical conversion of carbon dioxide to formic acid on Pb in KOH/methanol electrolyte at ambient temperature and pressure

The electrochemical reduction of CO₂ in KOH/methanol-based electrolyte has been investigated on a lead wire electrode at ambient temperature and pressure. The major products of electrochemical reduction of CO₂ were formic acid, CO and methane. The formation of formic acid from CO₂ predominated in the potential range −1.8 to −2.5 V vs Ag/AgCl (saturated KCl). Hydrogen evolution in competition with CO₂ reduction was observed at only 3.5% faradaic efficiency. The partial current density for CO₂ reduction was more than 22 times larger than that for hydrogen evolution. Study of the Tafel plot showed that the reduction of CO₂ to formic acid and CO was not limited by mass transfer in this potential range.     

Synthesis of methacrylic acid-styrene block copolymers by living radical polymerization in the presence of chitosan

The existence of living growing end radicals in the radical polymerization of sodium methacrylate (MAA·Na) in the presence of chitosan acetate salt has been ascertained by preparing block copolymers with styrene as secondary comonomer. When polymerization of MAA·Na eventually reached 93.4% conversion after 144 h at 30°C, secondary comonomer styrene added to the system undergoes further polymerization. Solvent extraction was performed to separate the homopolymers and block copolymers in order to determine the properties of the product. The results of the solubilities, of gel permeation chromatography and of ¹H nuclear magnetic resonance showed the characteristics of the block copolymers.     

Crystallization behavior of polybutene-1 in the anisotropic system blended with polypropylene

Development of supermolecular structure in drawn polypropylene (PP)/polybutene-1 (PB-1) blends was studied. PP (matrix)/PB-1 (70/30) blend films were drawn and heat-treated at fixed length or free ends at temperatures above the melting point of PB-1. It was found that a long axis of the PB-1 lamella is aligned perpendicular to the draw direction, and the c-axis of the PB-1 crystal is oriented perpendicular both to the draw direction and the plane of the surface of the blend film. Drawn, then heat-treated PP/PB-1 blend films gave a SAX pattern having a cross type scattering maximum on the meridian. It was confirmed that vertical scattering originates from the PB-1 crystal developed during melt recrystallization. It was proposed that the structural development of PB-1 in drawn PP/PB-1 film can be explained on the basis of transcrystallization of PB-1 in the confined 2-dimensional space in the PP matrix. The kinetics of isothermal crystallization of PB-1 was examined by use of a DSC technique. The result supports the conclusion that the heterogeneous nucleation of PB-1 followed by 2-dimensional crystal growth prevailed in oriented PP/PB-1 blend film.     

Characteristics of electrical power generation from lead zirconate titanatepiezoelectric ceramics under cyclic loading

The influence of oscillation condition on the electrical power generation properties of lead zirconate titanate (PZT) piezoelectric ceramics is investigated. It is found that the power generation increases with an increase of both applied load and load frequency. At lower loading frequencies, e.g., 0.1 and 0.5 Hz, the voltage rises instantly to the maximum level under square-wave mode, although the voltage increases gradually under triangular-wave mode. After this initial increase, there is a rapid fall to zero, followed by generation of increasingly negative voltage as the applied load is removed for both wave modes. Variation of the voltage is reflected by the cyclic loading at higher loading frequencies, 15 and 30 Hz. On the basis of the obtained experimental results for the two wave modes, the electrical power generation characteristics of PZT ceramics are proposed, and the voltages generated during loading and unloading are accurately estimated by numerical analysis.     

Photochemical and photophysical reactions of poly(propylene imine) dendrimers tethering cinnamamide groups

Here we report on photochemical and photophysical properties of poly(propylene imine) dendrimers tethering cinnamamide groups at the peripheral positions. Photoexcitation of the dendrimer solutions with 313 nm brought about monotonous decrease of absorption band of trans-cinnamamide around 270 nm as a result of trans-to-cis photoisomerization and [2+2] photocycloaddition. The first-generation dendrimer showed preferential formation of cis-isomer, whereas photocycloaddition was more favorable for the third- and fifth-generation dendrimers. Interestingly, the third- and fifth-generation dendrimers could encapsulate phosphorescent donors into the dendrimer nanocavities. When the dendrimers capturing the donors were excited at 365 nm, photocycloaddition proceeded efficiently through triplet-triplet energy transfer. By analyzing phosphorescence spectra with theoretical Perrin’s formula, we found that this triplet-triplet energy transfer is quenched within a radius of ∼0.5 nm. Such triplet-triplet energy transfer within dendrimer nanocavities would provide promising strategy to design and fabricate novel molecular devices by utilizing the dendrimers.     

Ammoxidation of propylene by pulse reaction technique

The ammoxidation of propylene on Fe-Bi-P mixed oxide catalyst was studied at 500 °C by the pulse reaction technique, to examine the effects of P(P = 0–4) and P (P/P = 0–3) on the catalyst activity. Since the ammoxidation of propylene proceeds through consumption of oxygen from the catalyst even in the absence of oxygen, the reduction of catalyst progresses with the number of O₂-free pulse, losing its activity. In the presence of oxygen, however, the conversion of propylene and the selectivities of acrylonitrile, acetonitrile, CO₂, and CO vary with the pulse number, but settle to some steady values corresponding to P/P. It is also found that the conversion and the selectivities depend on the oxidation state of the catalyst, the latter also depending on P/P in the reactants, and that the catalyst working in the flow system may be being reduced to some extent.     

Selective reduction of nitric oxide with propene over platinum-group based catalysts: Studies of surface species and catalytic activity

The reduction of nitric oxide by propene in the presence of oxygen over platinum-group metals supported on TiO₂, ZnO, ZrO₂, and Al₂O₃ has been investigated by combined diffuse reflectance FT-IR spectroscopy and catalytic activity studies under flow reaction conditions at 523–673 K and atmospheric pressure. The catalytic activity for the selective reduction of nitric oxide and the intensity of the IR bands due to reaction species depended strongly on the nature of the support, type of supported metal, reaction time and temperature. The main surface species detectable by IR were adsorbed hydrocarbons (2900–3080 cm⁻¹), isocyanate (2180, and 2232–2254 cm⁻¹), cyanide (2125 cm⁻¹), nitrosonium (1901 cm⁻¹), CO₂ (2343–2357 cm⁻¹), CO (2058 cm⁻¹) and carbonate (1300–1650 cm⁻¹) species. In the case of rhodium containing catalysts, when supported on Al₂O₃, they exhibited both the highest concentration of surface species and the highest activity for nitric oxide reduction and selectivity to nitrogen. The catalytic activity and the IR intensities of the nitrosonium and isocyanate bands increased with reaction temperature, reached their maximum between 570 and 620 K, and then decreased at higher temperatures. The IR band intensities due to nitrogen containing surface species were found to be strongly correlated to the activity for nitric oxide conversion and only slightly related to the selectivity to dinitrogen.