The geodesic dynamic relaxation method for problems of equilibrium with equality constraint conditions

This paper presents an extension to the existing dynamic relaxation method to include equality constraint conditions in the process. The existing dynamic relaxation method is presented as a general, gradient‐based, minimization technique. This representation allows for the introduction of the projected gradient, discrete parallel transportation and pull back operators that enable the formulation of the geodesic dynamic relaxation method, a method that accounts for equality constraint conditions. The characteristics of both the existing and geodesic dynamic relaxation methods are discussed in terms of the system's conservation of energy, damping (viscous, kinetic, and drift), and geometry generation. Particular attention is drawn to the introduction of a novel damping approach named drift damping. This technique is essentially a combination of viscous and kinetic damping. It allows for a smooth and fast convergence rate in both the existing and geodesic dynamic relaxation processes. The case study was performed on the form‐finding of an iconic, ridge‐and‐valley, pre‐stressed membrane system, which is supported by masts. The study shows the potential of the proposed method to account for specified (total) length requirements. The geodesic dynamic relaxation technique is widely applicable to the form‐finding of force‐modeled systems (including mechanically and pressurized pre‐stressed membranes) where equality constraint control is desired. Copyright © 2014 John Wiley & Sons, Ltd.     

Risk hedging against the fuel price fluctuation in energy service business

Energy service business, or energy service company (ESCO), is expanding among industrial users as a means of energy saving. The ESCO business normally tends to become a long-term operation. During the operation, fluctuations of fuel and electricity costs significantly impact on the stability of the profit from ESCO business. Therefore, it is essential to reduce the risk of fuel and electricity cost fluctuations. Generally, a transaction called “financial derivative” is used as a measure of hedging against the fuel price fluctuation. In the case of ESCO business, it is necessary to manage the risk of both electricity and fuel price fluctuations because the variation in electricity price strongly affects the profit from ESCO as that in fuel price does.     

Characterization of electrode/electrolyte interface for lithium batteries using in situ synchrotron X-ray reflectometry—A new experimental technique for LiCoO2 model electrode

A new experimental technique was developed for detecting structure changes at electrode/electrolyte interface of lithium cell using X-ray reflectometry and two-dimensional model electrodes with a restricted lattice-plane. The electrodes were constructed with an epitaxial film of LiCoO₂ synthesized by pulsed laser deposition method. The orientation of the epitaxial film depends on the substrate plane; the 2D layer of LiCoO₂ is parallel to the SrTiO₃ (1 1 1) substrate (_(0 0 3)LiCoO₂//_(1 1 1)SrTiO₃)$({(003)}_{\text{LiCo}{\text{O}}_2}//{(111)}_{\text{SrTi}{\text{O}}_3})$, while the 2D layer is perpendicular to the SrTiO₃ (1 1 0) substrate (_(1 1 0)LiCoO₂//_(1 1 0)SrTiO₃)$({(110)}_{\text{LiCo}{\text{O}}_2}//{(110)}_{\text{SrTi}{\text{O}}_3})$. The anisotropic properties were confirmed by electrochemical measurements. Ex situ X-ray reflectivity measurements indicated that the impurity layer existed on the as-grown LiCoO₂ was dissolved and a new SEI layer with lower density was formed after soaking into the electrolyte. In situ X-ray reflectivity measurements indicated that the surface roughness of the intercalation (1 1 0) plane increased with applying voltages, while no significant changes in surface morphology were observed for the intercalation non-active (0 0 3) plane during the pristine stage of the charge–discharge process.     

Measuring method of three thermophysical parameters of solids by a thermal probe with instantaneous point contact: Discussion about applicability and measuring conditions

An instrument for the measuring method reported in the previous paper is a handy tester for three thermophysical parameters of solids in situ. Discussions about measurement errors caused by not strictly satisfying the measuring conditions, such as size and shape of the testing body, and about optimum initial temperature difference between thermal probe and testing body have been done. As a result of the experiment varying the shape of a probe end, it is shown that the radius of the contacting surface on a testing body has no influence on measuring thermophysical parameters. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(3): 202–211, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10085     

Comparison of the SiH4---C2H4 and SiH2Cl2---C2H4 systems during the synthesis of silicon carbide ultrafine particles by laser-induced gas-phase reaction

The synthesis conditions of SiC ultrafine particles from SiH₄ and C₂H₄ using a CO₂ laser were studied and a comparison was made between SiH₄---C₂H₄ and SiH₂Cl₂---C₂H₄ systems. Ultrafine SiC particles were synthesized by irradiating a SiH₄ and C₂H₄ gas mixture with a CO₂ laser at atmospheric pressure. SiC particles were obtained at a laser power of more than 0·92 kW/cm².

The behavior of the reaction flame temperature and the extent of the laser light absorption by SiH₄---C₂H₄ was different from that of SiH₂Cl₂---C₂H₄, although an abrupt temperature increase was observed in both cases. In the case of SiH₄---C₂H₄ an abrupt increase in the laser light absorption was not observed, whilst it was observed in the case of SiH₂Cl₂---C₂H₄. This difference resulted from the difference in liability to form solid carbon particles.     

Preparation, Structure, and Properties of Thermally and Mechanically Improved Aluminum Titanate Ceramics Doped with Alkali Feldspar

Aluminum titanate (AT) ceramic materials doped with alkali feldspar ((Na_0.6K_0.4)AlSi₃O₈) have been prepared. These ceramics exhibited high sinterability, large resistance to thermal decomposition, and large flexure strength. The existence of liquid-phase feldspar at sintering temperatures promoted the formation of AT ceramics as the sintering agent. It was considered that silicon ions substituting for aluminum ions at the surface of AT crystal grains lowered the surface energy and hindered the diffusion of Ti⁴⁺ and Al³⁺, giving rise to the large resistance to thermal decomposition. As a result, doping with alkali feldspar was found to effectively improve the mechanical and thermal properties of AT ceramics.     

A modified power control scheme for remedying the effects of traffic nonuniformity in LEO satellite communications systems

It has been shown in our previous studies that the geographical traffic nonuniformity considerably affects the performance of the low earth orbit satellite communications systems. In this paper, a new scheme for improving the throughput characteristics of these systems at nonuniform traffic distribution is proposed. In this method, some parts of the users under the satellite which is flying over the area with high traffic load are assigned to its neighbor satellites with lower transmitting power levels. It is shown that the method equalizes the traffic loads of the satellites to some degree and, hence, can improve the throughput characteristics of the system.     

Effect of water‐miscible solvents on the organic solvent‐resistant tyrosinase from Streptomyces sp. REN‐21

The effect of various water‐miscible organic solvents (ethanol, methanol, acetone, acetonitrile, N,N‐dimethylformamide (DMF) and dimethylsulfoxide (DMSO)) on the kinetics of 4‐tert‐butylcatechol (tBC) oxidation in the presence of different samples of organic solvent‐resistant tyrosinase (OSRT) has been studied. In contrast to mushroom tyrosinase the enzyme shows a high relative stability in solutions of organic solvents and increased activity toward the bulky and hydrophobic substrate, tBC, in respect to catechol. Rates of the studied OSRT‐catalyzed reactions are however reduced by the presence of organic solvents and for all studied samples of OSRT decrease exponentially with the content of an organic solvent. The effect has been satisfactorily described by the effect of organic solvents on the thermodynamic activity of tBC. The correlation of the inhibition parameters with the hydrophobicity of a particular solvent (log P), its intrinsic molar volume, V_i, and the Dimroth–Reichardt parameter, E_T(30), are shown. The results allow also the prediction of OSRT activity in aqueous solutions of water‐miscible organic solvents. Copyright © 2003 Society of Chemical Industry     

Novel three‐phase current‐regulated digital PWM and its behavioral analysis

There have been various studies of PWM algorithms for a three‐phase voltage‐source AC/DC power converter since the analog modulation scheme based on a triangular carrier wave was proposed in the 1960s. The PWM algorithm can be considered the heart of electronic power conversion. With progress in digital technology, there is an increasing need for gate signals to be generated directly by digital ICs, such as MPU, DSP, or FPGA/CPLD. This paper analyzes quantitatively the precision of current control of digital PWM taking account of both the sampling period and the delay time (the latter is inevitably accompanied by a digital procedure). The delay time is shown to have a double effect on the current error. In addition, the paper theoretically derives the conditions for digital PWM to meet the PPCR (Pulse Polarity Consistency Rule, that is, the next gate command moves only to the adjacent ones or commands). So far as the authors know, no paper has presented the mathematical requirements for PPCR taking account of the effect of the delay time of digital PWM. The derived theoretical results are summarized as digital PWM design criteria for a three‐phase PWM converter in order to facilitate practical implementation of the theory, guaranteeing PPCR behavior as well as quantitative accuracy of current regulation. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 62–77, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10330