Basic study of a ship navigator's mental workload using salivary NO\documentclass{article}\usepackage{amsmath}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{amsfonts}\pagestyle{empty}\begin{document}$_{3}^{-}$ \end{document}

Evaluation of the mental workload during training for ship handling has usually depended on professionals (captain, pilot) who have lots of experience on board. We are attempting to evaluate a ship navigator's mental workload based on a physiological index. The physiological indices, namely heart rate variability (R–R interval), nasal temperature, and salivary amylase, are good indices for reading the mental workload during ship handling. Moreover, we find the possibility of using salivary NO$_{3}^{-}$ as a good index for evaluating the ship navigator's mental workload. Salivary NO$_{3}^{-}$ is expected to have a specific characteristic to represent quick response on the spot and the trend. We confirmed the response of students during simulator training, and then carried out the experiment on professionals on a real ship. We propose that salivary NO$_{3}^{-}$ can show a ship navigator's stress for ship handling in the simulator and on a real ship. This work to evaluate the ship navigator's mental workload using salivary NO$_{3}^{-}$ is the first attempt worldwide. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Relative permittivity and conductivity of water‐treed region in XLPE estimated by an equivalent circuit

By dividing a water‐treed XLPE sheet sample of 1 mm thickness into a nondegraded region and a water‐treed one, relative permittivity and AC conductivity σ_AC2 of the water‐treed region have been estimated using an equivalent circuit. The variation of and σ_AC2 with the length r of the water‐treed region has been discussed based on the Sillars model. It was concluded that the volume fraction of water in the water‐treed layer is in the range from 0.5% to 1.5% for the most‐degraded XLPE sheet, which depends on the ratio of axes of spheroids to which water‐filled voids and channels are compared. It was also concluded that the AC conductivity of water in the water‐treed region ranges from 3 × 10^?3 S/m to 2 × 10^?2 S/m. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(3): 7–14, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10332     

Electrical properties of polylactic acid with nucleating agent added

We examined the electrical properties of polylactic acid (PLA) with a nucleating agent added. The PLA with added nucleating agent was then heat‐treated at 100 °C for 30 seconds. The crystallinity of the PLA with added nucleating agent increased to more than 40%, and its crystallization speed also increased significantly. The temperature dependence of the conductivity (σ) was investigated; at temperatures higher than 60 °C, σ of PLA to which the nucleating agent had been added showed a tendency to become lower than σ of PLA to which no nucleating agent had been added. The temperature dependence of the dielectric breakdown strength ( ) was investigated. of the PLA with added nucleating agent was about 5.0 MV/cm at 25 °C. Of particular note was the fact that the of PLA with added nucleating agent was about 4.7 MV/cm at 100 °C, which is about 3 times the value for PLA with no added nucleating agent. The temperature dependence of the relative dielectric constant (?_r^″) and the relative dielectric loss factor (?_r^″) was investigated. The peak dielectric absorption value of ?_r^″ for the PLA to which nucleating agent had been added showed a tendency to be lower than that of the PLA to which no nucleating agent had been added. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(3): 25–31, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21293     

Controller reduction via frequency weightings considering $H_{\infty}$ property preservation

In this paper, a new controller reduction method is proposed to preserve the property using frequency weightings. It is necessary to consider decreasing degradation of property for controller reduction. It is well known that all controllers are represented by free parameters which are stable and bounded. In the paper, frequency weightings are given to stabilize the free parameters, and low‐order controller is provided by using frequency‐weighted balanced technique. Some numerical examples are given to show the effectiveness of the method. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 63–69, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20683     

Quantitative evaluation of lightning surge range voltage–time characteristics in high‐pressure SF6 gas

Gas‐insulated switchgear (GIS) is subjected to very fast transient overvoltages such as lightning surges or disconnector switching surges. Therefore, the sparkover voltage and time (V?t) characteristics of SF₆ in a very short time range of less than are of great interest from the viewpoint of insulation design and coordination for a GIS. This paper describes the V?t characteristics of SF₆ at a gas pressure of 0.5 MPa using a steep‐front square impulse voltage under a quasi‐uniform field gap and presents a quantitative evaluation of the V?t characteristics for a nonstandard lightning impulse voltage. In the case of a square impulse, the V?t characteristics of positive polarity were observed to be almost flat over a long time range from 80 ns to , and rose steeply over a short time range from 80 ns down to 20 ns. For negative polarity, the V?t characteristics exhibit a gentle rise from 200 ns down to 40 ns. In the estimation of V?t characteristics, the equal‐area criterion parameters were quantitatively estimated using the square impulse. For a nonstandard lighting impulse, we found that application of the equal‐area criterion with these parameters for the nonoscillating impulse and oscillating impulse of up to 5.3 MHz as a model of lightning surge and disconnector switching surge is possible. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 8– 17, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20309     

Parameter estimation of horizontal multilayer earth based on complex image method and improved particle swarm optimization

Grounding grids are buried underground to reduce the earth resistance and provide ways for overvoltage protection and current leakage. With regard to the safety evaluation and fault diagnosis of substations, it is vital to know the accurate earth parameters before detecting the fault sites of grounding grid in substations. The estimation of earth parameters is used to solve the inverse problem of calculating apparent resistivity using given earth parameters. First, complex image methods are used to solve the improper integration with the assistance of Prony's expansion which is utilized to calculate the coefficients for the Lipschitz's expansions in this article. Also, by considering the root mean square error and absolute error (AbsE), we focus on different aspects of the effectiveness of the estimation. The root mean square error between the measured and calculated apparent resistivity ($\rho^a_{\mathrm{md}}$ and $\rho^a_{\mathrm{cd}}$, respectively) is set up as the main objective function, and AbsE as a supplemental criterion for measuring the estimation. Afterwards, improved particle swarm optimization is adopted to minimize the objective function with a constraint function. Resulting from the outstanding global searching characteristics, accurate soil parameters are much easier to obtain. A method to artificially regulate the initial values is proposed in this article, and two cases are introduced to validate the effectiveness. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

filtering for switched discrete‐time systems under asynchronous switching: A dwell‐time dependent Lyapunov functional method

In this article, the filtering problem for switched discrete‐time linear systems under asynchronous switching is addressed in the framework of dwell time, where ‘asynchronous switching’ covers more general and practical cases, for example, the switching lags caused by mode identification process are taken into consideration. Firstly, a novel dwell‐time dependent Lyapunov function (DTDLF) is introduced to solve stability and ?₂ gain analysis problems. The main advantage of DTDLF approach is that the derived conditions are all convex in system matrices, so it is convenient to be applied into filter design with performance instead of weighted performance as many other previous results. Thus, on the basis of DTLDF, a dwell‐time dependent filter with time‐varying structure is proposed to achieve the desirable non‐weighted filtering performance. It is notable that the proposed approach can also easily characterize the relationships among filtering performance, dwell time, and asynchronous time. Two examples are provided to validate the theoretical findings in this paper. Copyright © 2014 John Wiley & Sons, Ltd.     

Design of a low‐power high open‐loop gain operational amplifier for capacitively‐coupled instrumentation amplifiers

We present the design of a low‐power high open‐loop gain opamp for use in chopper‐stabilized capacitively coupled instrumentation amplifiers (CCIAs). The opamp utilizes the current‐reuse folded‐cascode topology and a low‐power gain‐boosting technique to maximize its power efficiency and open‐loop gain. The proposed technique is applied to the designs of two CCIAs: the conservative CCIA with a moderate current scaling ratio and the stringent CCIA with a very high current scaling ratio. Utilizing the current scaling ratio of 4:1, the conservative CCIA, designed and fabricated in a 0.18 μ m CMOS process, consumes a total current of 1.69 μ A from a 0.8‐V supply voltage and achieves a thermal noise floor of 56.5 nV/ . Utilizing the current scaling ratio of 38:1, the stringent CCIA, designed and simulated in a 0.13 μ m CMOS process, consumes a total current of 1.4 μ A and achieves a thermal noise floor of 48 nV/ . The proposed design technique should benefit the designs of low‐power instrumentation amplifiers in advanced processes in which channel‐length modulation and the limited current consumption and supply voltage make the designs of high open‐loop gain opamps difficult. Copyright © 2017 John Wiley & Sons, Ltd.     

An improvement in the calculation of the magnetic field for an arbitrary geometry coil with rectangular cross section Int. J. Numer. Model. 2005; 18(6):493–504

The above article was published in Volume 18, Issue 6, Pages 493–504, (October 2005). A number of imperfections were subsequently identified and have been corrected below. On page 497, the following equation has been corrected to: On page 501, the following equation has been corrected to: On page 502, the following equation has been corrected to:      

2‐matrix‐based finite element linear solver for fast transient thermal analysis of high‐performance ICs

In this article, we propose ²‐based finite element (FE) solver for transient thermal analysis of high‐performance integrated circuits (ICs). ²‐matrix is a special subclass of hierarchical matrix or ‐matrix, which was shown to provide a data‐sparse way to approximate the matrices and their inverses with almost linear space and time complexities. In this work, we show that ²‐based mathematical framework can also be applied to FE‐based transient analysis of thermal parabolic partial differential equations. We show how the thermal matrix can be approximated by ²‐representations with controlled error. Then, we demonstrate that both storage and time complexities of the new solver are bounded by , where N is the matrix size. The method can be applied to any thermal structures for both steady and transient analysis. The numerical results from 3D ICs demonstrate the linear scalability of the proposed method in terms of both memory footprint and CPU time. The comparison with existing product‐quality LU solvers, CSPARSE and UMFPACK, on a number of 3D IC thermal matrices, shows that the new method is much more memory efficient than these methods, which however prevents the demonstration of the potential speedup of the proposed method over those methods. Copyright © 2014 John Wiley & Sons, Ltd.     

Analytical formula of induced electric fields in a spherical conductor by an ELF dipole magnetic field source

An analytical formula of induced electric field E in a spherical conductor by an ELF dipole magnetic field source is mathematically derived in vector form based on the equivalent mutlipole moment method with reexpansion technique (RE‐EMMM), where M _‖ and are parallel and perpendicular components of M , respectively. The validity of the formula is confirmed in the following three ways: (i) the derivation of the formula from the Sarvas equation with the reciprocity theorem derived by Eaton; (ii) the convergence of the formula to that of homogeneous magnetic field when M _‖ is located at the infinite distance; (iii) comparison of the analytical solutions with numerical solutions by RE‐EMMM. Furthermore, a formula for the trajectory, which satisfies E = 0 , is derived for the field by M _‖. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 8– 17, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20739     

Uncertainty evaluation for estimates from recursive projection algorithms

In this paper we consider parameter estimation of linear systems described by y_i = a θ + e_i, where the ith measurement y_i is linearly dependent on the parameter vector θ ε ?^?p through the regressor vector a ε ?^?p and the measurement error e_i is unknown but bounded. Some properties of previously presented algorithms for recursive parameter identification in the unknown but bounded error (UBBE) context are discussed. In particular it is analysed how different levels of information on the error structure can influence the choice of the identification algorithms and the possibility of evaluating the reliability of the estimates. Attention is also focused on the influence that forgetting schemes have on the estimates and on their confidence evaluation.     

Excitation and steam‐valving coordinated robust controller design for multi‐machine power systems based on the multi‐index nonlinear robust control approach

This paper proposes a novel multi‐index nonlinear robust control (MNRC) approach for multi‐machine power systems. The MNRC approach combines multi‐index nonlinear control with the control theory. With the multi‐index nonlinear control, which selects the output functions as arithmetic combination of state variables, multiple performance indices of the controlled system can be achieved simultaneously in the nonlinear control framework. The control is able to ensure that the system possess the desired robust performance during disturbance. Then, excitation and steam‐valving coordinated robust controllers are developed based on the MNRC approach for multi‐machine power systems. The effectiveness of the proposed robust controller is evaluated by a six‐machine power system simulation. Simulation results show that the expected dynamic and steady‐state performances of power system can be achieved with the MNRC approach. Meanwhile, it is able to achieve the prescribed system performance despite the presence of disturbances. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A 0.5‐V 5.9‐fJ/conversion‐step SAR ADC in 0.18‐μm CMOS

In this paper, we present a 434‐nW 8‐bit successive approximation register analog‐to‐digital converter (SAR ADC). We mainly consider the optimization of power consumption. A modified split‐capacitor array involving a novel switching scheme is proposed, which reduces the switching power consumption to just 13.8 for the single‐ended scheme without any losses in performance. Based on the SMIC CMOS 0.1 μm EEPROM 2P4M process, the simulation results show that at 0.5 V supply voltage, 300 kS/s sample frequency, and 4.98 kHz input frequency, the ADC achieves an signal‐to‐noise‐plus‐distortion ratio (SNDR) of 49.58 dB and effective number of bits (ENOB) of 7.94, and consumes 434 nW, resulting in a figure of merit of 5.9 fJ/conversion step. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Operating principles of pin diodes

Analytical models of the pin diode in a small‐current operation are not known yet. This article presents a simple analytical model of the pin diode operation with its confirmation by a numerical simulation. At the onset, carrier recombinations are not included for the sake of simplicity. The exact J_F?V_F characteristic could have been induced only by accounting for the Boltzmann distribution of each carrier across the junctions and the diffusion current of each minority carrier in a p‐anode or n‐cathode. Based on this new model, the modifications of hole–electron densities product (n_en_h) across junctions, a rough estimation of the large operational current, its carrier distributions, and the effect of carrier recombination on the carrier distribution are plainly estimated and are also compared with the simulation results. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(4): 47–56, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20844     

Universal iterative learning control using adaptive high-gain feedback

Convergence theorems for adaptive (universal) iterative learning control systems provide a well-defined convergence criterion parametrized by a single adaptive gain parameter. The convergence is in the weak topology of L(0,T) with T finite and applies to both finite-dimensional systems and a class of infinite-dimensional systems.     

Development of NbTi superconducting strands and cables for the field winding of a 200‐MW‐class high‐energy‐density superconducting generator

The NbTi superconducting strands and cables for the field winding of the 200‐MW‐class high‐energy‐density‐type superconducting generator are developed. They are composed of Cu/Cu‐10wt%Ni/Nb‐46.5wt%Ti superconducting strands and the 10‐kA (at 5 T)‐class 9‐strand compacted cables. The diameter of strands is 1.33 mm, and the 9‐strand compacted cables are 2.4 mm thick and 6.0 mm wide. In order to produce high‐current‐density NbTi strands, we made strands under controlled aging heat treatments, the total and final strains, and the strains between heat treatments, by using large‐scale extruder. Moreover, in order to produce high‐stability and low‐AC‐loss NbTi strands and cables, the matrix ratio of strands and the cross sections of strands are optimized. The current density of NbTi filaments for the four‐time‐aging manufactured 1.33‐mm‐diameter strands was J_C=3150 A/mm² at 5 T, 1150 A/mm² at 8 T. The critical current of the 9‐strand compacted cable is 10.7 kA at 5 T. The AC losses of the final compacted cables are less than 100 kW/m³ at 5 T, 5 T/s, that is, decreased to less than half of the target of the AC loss value (< at 5 T, 5 T/s). Compared with the strand (Cu ratio 1.77), the minimum quench energy (MQE) of the strand (Cu ratio>2) increased about 40% at the operation mode current of the superconducting generator. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(3): 24– 31, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20266     

Dynamic model of one‐cycle control for converters operating in continuous and discontinuous conduction modes

In this paper a new dynamic model of one‐cycle‐controlled converters operating either in continuous or in discontinuous conduction mode (DCM) is introduced. The static and dynamic behaviour is analysed by using sampled‐data modelling combined with the small‐signal linearization of the average model of the converter's power stage. The proposed model is valid for frequencies up to half the switching frequency and, while the other dynamic models presented in the literature cover continuous conduction mode only, it also gives an accurate prediction of the system's dynamic behaviour in the DCM. The model allows to determine the closed‐form expression of the reference‐to‐output transfer function G of the system, which is a fundamental prerequisite for the design of a conventional output feedback control circuit aimed at improving the dynamic behaviour of the system in response to load variations. In this paper it is also shown that one‐cycle control does not work properly in switching converters operating in deep DCM if some specific design constraints are not fulfilled. The theoretical predictions are confirmed by the results of suitable numerical simulations and laboratory experiments on a one‐cycle‐controlled buck‐switching converter. Copyright © 2008 John Wiley & Sons, Ltd.     

Temporary overvoltage duty of surge arresters in noneffectively grounded systems

Important characteristics of metal oxide surge arresters depend on the specified temporary overvoltage duty requirement due to the volt–ampere characteristics. However, there are few reports on the duty of surge arresters in noneffectively grounded systems. The temporary overvoltages of 1.43 pu proposed in effectively grounded systems is too low compared with nearly pu in a line‐to‐ground fault. The overvoltages due to a combination of a line‐to‐ground and load rejection, where not only the main power circuits but also control systems such as AVRs participate, is rare but probably the severest case. Here the overvoltage duty of surger arresters is clarified for various residual voltage levels and system conditions. The severest condition is that in a system including a cable line because of operation of the UEL of the AVR. © 1999 Scripta Technica, Electr Eng Jpn, 128(4): 38–46, 1999