High‐precision positioning with strain feedback using piezoelectric element

This paper presents a novel control methodology for robust high‐precision positioning systems. This methodology is based on strain feedback using a piezoelectric element. The mechanical vibration modes at around the control bandwidth cause deterioration of system stability. This prevents the positioning performance from being robust, particularly against variations in the vibration frequency. In this research, therefore, a robust positioning system was designed by applying an additional compensation loop by strain feedback; here, a piezoelectric element that acts as a strain sensor detects the vibration signal. This makes the performance of the system robust. The proposed compensation approach has been verified by numerical analyses and by experiments using a positioning device for industrial galvano scanners. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(4): 41–50, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21267     

Evaluation of microscopic structural randomness in SiO2 by analysis of photoluminescence decay profiles

Microscopic structural randomness in SiO₂, a typical electrical insulating material, was evaluated by observing the decay profile of the photoluminescence due to oxygen vacancies (≡Si-Si≡). As samples with different degrees of randomness, an ion-implanted thermal SiO₂ film, SiO₂ films formed by plasma-enhanced chemical vapor deposition of tetraethoxysilane with and without doped fluorine, a buried oxide film prepared by SIMOX (separation by ion-implanted oxygen), and a bulk silica glass prepared by the soot-remelting method were tested. By analyzing the decay profile with a stretched exponential function, it was found that the deviation of the decay profile from a single exponential function is larger in the samples whose infrared absorption properties and HF etch rate suggest greater structural randomness. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119 (3): 1–6, 1997     

Fast computation and stable convergence technique for unbalanced load flow calculation in large‐scale systems

This paper presents a new method of unbalanced load flow calculation to improve complexity by the method of advanced symmetrical coordinates. Usually, the electric power system has been calculated only by the positive phase sequence component on the assumption that three‐phase transmission lines and loads are balanced. However, many ultrahigh‐voltage transmission lines are not transposed, and therefore mutual inductances cause negative sequence currents in the trunk transmission system. Negative sequence currents cause heating of generators and transformers, and therefore the three‐phase sequence component should be calculated accurately. We examined the fast computation and good convergence performance of unbalanced load flow calculation by models of three‐phase transmission lines, transformers, and loads. The proposed method is not the phase coordinate system but the method of symmetrical coordinates. This technique decreases numerical complexity by the use of a simplified Jacobian matrix. The convergence performance of this method is inferior to that of the usual Newton–Raphson method. As a consequence, the problem of poor convergence performance is alleviated by a technique for the newly developed deceleration Newton method. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(1): 17–24, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21034     

Development of a reduction-responsive amino acid that induces peptide bond cleavage in hypoxic cells

Hypoxia-responsive amino acids are indispensable in the preparation of hypoxic tumor-specific peptidyl prodrugs. In this paper, the design and synthesis of a reduction-responsive amino acid that induces peptide bond cleavage after reduction of the nitro group are described. Application to hypoxia-responsive peptide bond cleavage system is also reported.     

Synthesis and some properties of silylated chitins as key intermediates for chemical modifications

Triethylsilyl- and triphenylsilyl-chitins were synthesized from β-chitin in addition to trimethylsilyl-chitin, and the resulting three kinds of silylated chitins were evaluated in terms of solubility, stability, and reactivity as precursors for chemical modifications. Triethylsilylation was effected under appropriate conditions though less facilely than trimethylsilylation. Triphenylsilylation was sluggish, and full substitution appeared to be difficult. The silylated products were soluble in organic solvents unlike the starting chitin. Of the three derivatives, trimethylsilyl-chitin was the most soluble and reactive, but the least stable. Triethylsilyl-chitin would be a convenient intermediate for modifications because of the considerable reactivity and stability, and triphenylsilyl-chitin may be a useful protected derivative.     

Role of Alumina in the Preparation of Platelike NaNbO3 Powder by Molten Salt Synthesis and Proposal of New Preparation Method

The preparation of platelike NaNbO₃ grains via single‐step molten salt synthesis using Bi₂O₃, Na₂CO₃, Nb₂O₅, and NaCl as reactants was examined. When a new alumina crucible was used, platelike NaNbO₃ grains were obtained, but a repeatedly used alumina crucible resulted in irregularly shaped NaNbO₃ grains. When a platinum crucible was used, even NaNbO₃ could not be obtained. Addition of alumina substrates and alumina granules to the reaction mixture in the platinum crucible resulted in the formation of platelike NaNbO₃ grains and second‐phase grains. The second‐phase grains, which were composed of Al₂O₃, Bi₂O₃, Na₂O, and Nb₂O₅ and had a pyrochlore structure, could be removed by sieving. The second phase acted as a scavenger for Bi₂O₃ and hence, the possibility of using another scavenger was attempted. The new scavenger was a mixture of Na₂CO₃ and Nb₂O₅, and using them, platelike NaNbO₃ grains were successfully obtained with NaNb₅Bi₂O₁₆ as a byproduct, which could then be removed by sieving.     

Aqueous Pesticide Degradation by Ozonation and Ozone-Based Advanced Oxidation Processes: A Review (Part I)

Pesticide pollution of surface water and groundwater has been recognized as a major problem in many countries because of their persistence in aquatic environment and potential adverse health effects. Among various water and wastewater treatment options, ozonation and ozone-based advanced oxidation processes, such as ozone/hydrogen peroxide, ozone/ultraviolet irradiation, and ozone/hydrogen peroxide/ultraviolet irradiation, are likely key technologies for degrading and detoxifying these pollutants in water and wastewater. In this paper, ozone-based treatment of four major groups of pesticides, namely carbamates, chlorophenoxy compounds, organochlorines, and organophosphates, are reviewed. Degree of pesticide degradation, reaction kinetics, identity and characteristics of degradation by-products and intermediates, and possible degradation pathways are covered and discussed.     

Aqueous Pesticide Degradation by Ozonation and Ozone-Based Advanced Oxidation Processes: A Review (Part II)

Pesticides are known to be persistent in surface water and groundwater supplies and as a result, their existence in these water sources has been recognized as a major problem in many countries. The occurrence of these persistent pesticides in water bodies can also cause potential adverse public and environmental health effects. Among many water and wastewater treatment options, ozonation and ozone-based advanced oxidation processes, such as ozone/hydrogen peroxide, ozone/ultraviolet irradiation, and ozone/hydrogen peroxide/ultraviolet irradiation, possess a high potential for degrading and detoxifying these pollutants in water and wastewater. In this paper, ozone based treatment of four major groups of pesticides, namely aniline-based compounds, pyridines and pyrimidines, triazines, and substituted ureas, as well as that of several miscellaneous pesticides are reviewed. Degree of pesticide degradation, reaction kinetics, identity and characteristics of degradation by-products, and possible degradation pathways are covered and discussed.     

Structure Change of Ca2SiO4 Solid Solutions with Ba Concentration

A series of Ba-bearing Ca₂SiO₄ solid solutions (C₂S( ss )), (Ba _x Ca_{1− x} )₂SiO₄ with 0.075 x 0.30, were prepared and examined by X-ray and electron beam diffraction. They are all made up of orthorhombic domains 120° different in orientation around the common c axis of the former α phase. The C₂S solid solution with x = 0.075 shows a superstructure incommensurate along the a axis with λ (modulation wavelength) = 3.5 and commensurate along the c axis with Δ= 3. With x = 0.15, modulation is observed only along the a axis and Δ= 3.4. No evidence of superstructure is found with x = 0.24; the space group and cell dimensions are comparable with those of pure α '_H-C₂S. The C₂S( ss ) with x = 0.30 gives a superlattice with the cell-edge length of 3 b . All the C₂S( ss ), when reheated at 1000°C for 24 h, produced lamellae of the trigonal phase T nearly in parallel with (001) of the host α '_L phase. The crystallographic orientation between the two phases is

This indicates that the above Ba-bearing C₂S( ss ) phases occur as precursors to the thermodynamically more stable two-phase mixtures.     

Microwave Characteristics of A(B3+1/2B5+1/2)O3 Ceramics (A = Ba, Ca, Sr; B3+= La, Nd, Sm, Yb; B5+= Nb, Ta)

Dielectric properties of A(B³⁺_1/2B⁵⁺_1/2)O₃ (A = Ba, Ca, Sr; B³⁺= La, Nd, Sm, Yb; B⁵⁺= Nb, Ta) ceramics have been investigated at microwave frequencies. Sr(B³⁺_1/2B⁵⁺_1/2)O₃ and Ca(B³⁺_1/2B⁵⁺_1/2)O₃ ceramics have relative dielectric constants (ε _r ) above 20 and negative temperature coefficients of resonant frequency (T _f ). In the group of Ba(B³⁺_1/2B⁵⁺_1/2)O₃ ceramics, T _f changes from + 118 ppm/° to nearly zero according to the kinds of B-site ions. Among the ceramics investigated, Sr(Sm_1/2Ta_1/2)O₃ ceramics have the highest Q values at microwave frequencies. For Sr(Sm_1/2Ta_1/2)O₃ ceramics Q = 7000, ε _r = 27.7, and T _f =−62.5 ppm/° at 8.5 GHz. The microstructure of Sr(Sm_1/2Ta_1/2)O₃ ceramics is composed of a matrix of the ternary compound (Sr-Sm-Ta-O system) and secondary phase grains of the binary compound (Sm-Ta-O system).