Design of multivariable feedback systems with infinite gain margin and decoupling

This letter discusses the problem of designing a feedback compensator that attains the infinite gain margin under the uncertainties of feedback gains. A sufficient condition is given for the existence of compensators and then it is shown that the condition becomes necessary subject to the requirement that the feedback system is decoupled. The nonlinear case is also discussed.     

Antitumor activity of degraded products of lentinan: its correlation with molecular weight

Twelve of 25 patients with mixed connective tissue disease complained of xerostomia and/or ocular symptoms of keratoconjunctivitis sicca. In addition to the clinical features of mixed connective tissue disease, all 12 patients had high titers of antibody to the ribonuclease-sensitive component of the extractable nuclear antigen. Eight patients had both clinical xerostomia and keratoconjunctivitis sicca, one had keratoconjunctivitis sicca and salivary gland enlargement, while there had xerostomia but no ocular complaints. Sj?rgren's syndrome was confirmed in all 12 patients by means of Schirmer's tests, Rose Bengal staining tests, salivary gland scintiscans, radionuclide excretion studies in saliva, parotid sialographies, and lip biopsies. At least three of these tests were abnormal in all patients.     

Dipolar-decoupled carbon-13 NMR study of highly oriented polyethylene films

Summary High-resolution solid-state ¹³C NMR spectra and ¹³C relaxation times T₁ and T₁ have been measured at 40–100° C for uniaxially oriented polyethylene films with the drawing direction parallel to the magnetic field; this sample has a unique morphological structure that the noncrystalline chains are nearly disordered irrespective of the high degree of drawing. A sharp resonance line(line A) appears at the position corresponding to the principal value ₃₃ of the chemical shift tensor for the CH₂ carbons with the trans-trans conformation. Another sharp linedine B) is observed at almost the same chemical shift as for the CH₂ carbons of polyethylene in solution. Although these observations are similar to those for a cold-drawn polyethylene sample reported previously, line B is much enhanced in intensity and the linewidth is narrower in the present sample, reflecting the disorientation of the noncrystalline component. It is found from T₁ measurements that line A contains two components with different molecular mobility, both being assigned to the crystalline components. On the other hand, the line B is composed of a single component assignable to the noncrystalline component with liquid-like molecular mobility.     

Co-carbonization of solvent fractions of hydrogenated and alkylated SRC pitches in studies of formation of needle-cokes

The optical texture of cokes from two SRC pitches of different coking properties, from co-carbonizations of these materials and of hydrogenated and alkylated products has been studied. The objective, relative to formation of needle-cokes, is to correlate the optical texture of cokes with the chemical structure of the pitch materials using both benzene-soluble (BS) and insoluble (BI) fractions of the pitches. Hydrogenation improved the compatibility of the BS fraction of the inferior SRC pitch (No. 2) with the BI fractions of the two pitches (non-hydrogenated) using a ratio of only 1 to 9. Before hydrogenation, a ratio of BS to BI of 8 to 2 did not give a needle-coke. In contrast, alkylation destroyed the compatibility of the BS fraction of the superior SRC pitch (No. 1) with the BI fraction (non-alkylated) using a ratio of 6 to 4, and which gave a needle-coke before alkylation. Hydrogenation of the alkylated material restored the compatability. The relevance of these studies to industrial carbonization processes is discussed in terms of chemical treatment and the hydrogen economy.     

Injection molding of 316L stainless steel microstructures

Micro powder injection molding (PIM) is a promising process for low cost fabrication of three-dimensional microstructures. The PIM can be used for a wide range of metal and ceramic materials, combined with the potential for mass production. In this paper, initial study on the molding of 316L stainless steel microstructures was investigated. Three different micro-cavity shapes were used. Small powder with mean size of 4 m was used with two multi-component binder systems. Microstructures with dimension as small as 35 m could be injection molded. For successful molding, the binder system must provide high green strength to withstand ejection from the mold and suitable molding parameters used. For example, a high mold temperature is required and ejection speed must be reduced. The cross-sections of the microstructures are precisely replicated. The general shape in the depth direction is replicated although it is not as good as that for the cross-section. More work has to be conducted to realize the full potentials of the process.The authors would like to thank the Nanyang Technological University for awarding a research grant to conduct this research and Adeka Fine Chemicals (Tokyo) for the supply of PAN 250 binder.     

Volatilization and recovery of mercury from mercury wastewater produced in the course of laboratory work using Acidithiobacillus ferrooxidans SUG 2-2 cells

The iron-oxidizing bacterium Acidithiobacillus ferrooxidans SUG 2-2 is markedly resistant to mercuric chloride and can volatilize mercury (Hg0) from mercuric ion (Hg2+) under acidic conditions. To develop a microbial technique to volatilize and recover mercury from acidic and organic compound-containing mercury wastewater, which is usually produced in the course of everyday laboratory work in Okayama University, the effects of organic and inorganic chemicals on the mercury volatilization activity of A. ferrooxidans cells were studied. Among 55 chemicals tested, the mercury volatilization from a reaction mixture (pH 2.5) containing resting cells of SUG 2-2 (1 mg of protein) and mercury chloride (14 nmol) was strongly inhibited by AgNO3 (0.05 mM), K2CrO7 (1.0 mM), cysteine (1.0 mM), trichloroethylene (1 microM), and commercially produced detergents (0.05%). However, the strong inhibition by trichloroethylene and detergents was not observed when these organic compounds were chemically decomposed using Fenton's method before the treatment of the wastewater with SUG 2-2 cells. When 20 ml of water acidified with sulfuric acid (pH 2.5) containing ferrous sulfate (3%), diluted mercury wastewater (17.5 nmol of Hg2+) and SUG 2-2 cells (0.05 mg of protein) were incubated for 10 d at 30 degrees C, 47% of the total mercury in the wastewater was volatilized and recovered into a trapping reagent for metal mercury. However, when the organic compounds in the mercury wastewater were decomposed using Fenton's method and then treated with A. ferrooxidans cells, approximately 100% of the total mercury in the wastewater was volatilized and recovered.     

Novel gene assay by probe-regulated simultaneous separation using capillary electrophoresis (CE-PRESS)

A novel methodology, a probe-regulated simultaneous separation using capillary electrophoresis (CE-PRESS), was developed for simultaneous assay of multiple genes. The single-stranded (ss) DNA-polymer conjugate-probes were placed in a capillary, and then a mixture of target ssDNAs was injected. These ssDNAs were hybridized with corresponding complementary ssDNA-polymer conjugate-probes after charging the capillary. Two resulting double-stranded (ds) complexes of ssDNAs and ssDNA-polymer conjugate-probes were detected at different migration times. We found that the electrophoretic mobilities of two ssDNA-poly(acrylamide) conjugate-probes [-(5'-GCCACCAGC-3')m-AAm(n)- and -(5'-ACCTTCACT-3')p-AAm(q)-; AAm, acrylamide] obtained by copolymerizing 5'-methacryloyl-modified ssDNA and AAm were different, depending on their molar fraction of ssDNA, although the ssDNAs chain lengths were the same. Two ssDNAs (5'-GCTGGTGGC-3' and 5'-AGTGAAGGT-3') having the same chain length were successfully separated with our novel system, although the separation of these ssDNAs is impossible in conventional capillary electrophoresis systems.     

Effect of Impurities on the Electronic Structure of Vortex Core Investigated by Microwave Surface Impedance Measurement

We investigated the microwave surface impedance in Zn doped YBa₂Cu₃O _y . For low Zn concentrations, crossover frequency _p and viscosity of vortex do not change significantly (at maximum, factor of 2). This is in sharp contrast to the dramatic change in the zero-field quasiparticle scattering time. The robust nature of viscosity on the impurity doping suggests that the quasiparticle scattering time in the vortex core is determined by a different mechanism from that outside the core.     

Second-Order Approximation for DOA Estimation of Near-Field Sources

The direction-of-arrival estimation of near-field sources can be formulated as a multidimensional nonlinear optimization problem, where a performance index is minimized with respect to azimuth, range, and source power. For the single source case, under the assumption that the range is relatively larger than the interelement distance, we use the second-order approximation to derive a simpler performance index parameterized by azimuth only. The minimization of the new index is easier than that of the original one parameterized by azimuth, range, and source power. Moreover, the proposed method considers the degradation of signal powers, giving more accurate estimation results. Also for the multiple source case, an efficient computation method is developed by using the second-order approximation.