Observation space for lowest PDOP in absolute‐range‐based 2‐D wireless location systems

A closed‐form expression for the position dilution of precision (PDOP) in absolute‐range‐based two‐dimensional (2‐D) wireless location systems is derived. Then, using the closed‐form expression, the observation space (OS) required for achieving the lowest PDOP of $2/\sqrt{N}$ is studied, where N is the number of measuring points. The OS is measured by central angle of a sector which covers all measuring points. The target is located at the vertex of the sector. It is shown that, for achieving the lowest PDOP of $2/\sqrt{N}$, the OS is required to be larger than or equal to π/2 while N is even. When N = 3, the OS is instead required to be larger than or equal to 2π/3. It is also shown that the OS of 2π/3 is sufficient to achieve the lowest PDOP of $2/\sqrt{N}$ while N is odd. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

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     

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     

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.     

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:      

Numerical analysis of transmission coefficient,LDOS, and DOS in superlattice nanostructures of cubic $$\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}$$ resonant tunneling MODFETs

Numerical analysis of the transmission coefficient, local density of states, and density of states in superlattice nanostructures of cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}\) resonant tunneling modulation-doped field-effect transistors (MODFETs) using \(\hbox {next}{} \mathbf{nano}^{3}\) software and the contact block reduction method is presented. This method is a variant of non-equilibrium Green’s function formalism, which has been integrated into the \(\hbox {next}\mathbf{nano}^{3}\) software package. Using this formalism in order to model any quantum devices and estimate their charge profiles by computing transmission coefficient, local density of states (LDOS) and density of states (DOS). This formalism can also be used to describe the quantum transport limit in ballistic devices very efficiently. In particular, we investigated the influences of the aluminum mole fraction and the thickness and width of the cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N}\) on the transmission coefficient. The results of this work show that, for narrow width of 5 nm and low Al mole fraction of \(x = 20\,\%\) of barrier layers, cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}\) superlattice nanostructures with very high density of states of 407 \(\hbox {eV}^{-1}\) at the resonance energy are preferred to achieve the maximum transmission coefficient. We also calculated the local density of states of superlattice nanostructures of cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}\) to resolve the apparent contradiction between the structure and manufacturability of new-generation resonant tunneling MODFET devices for terahertz and high-power applications.     

Atomistic tight-binding simulations of quaternary-alloyed $$\hbox {Zn}_{x}\hbox {Cd}_{1-x}\hbox {S}_{y}\hbox {Se}_{1-y}$$ nanocrystals

Advancement of alloyed nanocrystals with attractive structural and optical properties for use in a wide range of physical, chemical, and biological applications represents a growing research field. Employing atomistic tight-binding theory combined with the virtual crystal approximation, the electronic structure and optical properties of quaternary-alloyed \(\hbox {Zn}_{{x}}\hbox {Cd}_{1-{x}} \hbox {S}_{{y}}\hbox {Se}_{1-{y}}\) nanocrystals with experimentally synthesized compositions (x and y) and sizes were investigated. Analysis of the results shows that the physical properties are mainly sensitive to the concentrations (x and y) and the diameter. With decreasing x and y contents, the optical bandgap is reduced because the contributions of the materials with narrower bulk bandgap (ZnSe and CdSe) is mostly promoted. The optical bandgap is reduced with increasing diameter due to the quantum confinement effect. The optical bandgap calculated based on tight-binding calculations shows discrepancy of less than 0.4 eV from experiment. Most importantly, the optical emission is continuously tunable across the entire visible spectrum. The conduction and valence bands are predominantly contributed by cation and anion atoms, respectively. The optical properties are obviously improved in Cd- and Se-rich quaternary \(\hbox {Zn}_{{x}}\hbox {Cd}_{1-{x}} \hbox {S}_{{y}}\hbox {Se}_{1-{y}}\) nanocrystals with large diameter. The atomistic electron–hole interactions can be hybrid-engineered by tuning either the contents (x and y) or diameter. The Stokes shift becomes more pronounced with decreasing alloy concentrations (x and y) and diameter, as described by the trend of the atomistic electron–hole exchange interaction. The present systematic study provides a new avenue to understand the unique size- and composition-dependent structural and optical properties of quaternary-alloyed \(\hbox {Zn}_{{x}}\hbox {Cd}_{1-{x}} \hbox {S}_{{y}}\hbox {Se}_{1-{y}}\) nanocrystals for broad use in multicolor bioimaging, biosensing, light-emitting diodes, solar cells, and other nanodevice applications.     

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     

Superhigh frequency magnetic properties and electromagnetic attenuation applications for \mathrm { BaMn_{x}Ti_{x}Fe_{12-2x}O_{19}} composites

Superhigh frequency microwave magnetic properties and attenuation characteristics at K and Ka bands have been studied for M-type barium hexaferrite $\mathrm {BaMn_{x}Ti_{x}Fe_{12-2x}O_{19}}$ ( $x=0.4-1.0$ ) composites with c-axis anisotropy. The complex permeability of the composites has resonancelike dispersion with relatively large imaginary permeability $\mu ''_{\max }$ of 1.1 and high resonance frequency $f_{R}$ of 20–28 GHz. $f_{R}$ is determined by the anisotropy fields $H_{a}$ . The composites show good attenuation properties with percentage bandwidth of 30–40 % and small thickness of 0.08–0.1 cm at K and Ka bands, thus being potential candidates for electromagnetic attenuation applications.     

Structural,electrical and optical properties of $$\hbox {InGaZnO}_{4}$$ and $$\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}$$In29Sn3O48: a first-principles study

First-principles calculations were performed to investigate the electrical and optical properties of \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) with Sn-doped \(\hbox {In}_{2}\hbox {O}_{3}\) and \(\hbox {InGaZnO}_{4}\) (IGZO). The band structure, density of states, optical properties including dielectric function, loss function, reflectivity and absorption coefficient are calculated. The calculated total energy shows that the most stable crystal structures are type III for \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) and type II for \(\hbox {InGaZnO}_{4}\). The band structure indicates the both \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) and \(\hbox {InGaZnO}_{4}\) are direct gap semiconductors. The intrinsic band gap of \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) is much narrower than that of \(\hbox {InGaZnO}_{4}\), and results in a better electrical conductivity for \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\). The density of states shows the main hybridization occurring between In-4d and O-2p states for \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) while between In-4d In-5p, Zn-4s and O-2p states for \(\hbox {InGaZnO}_{4}\) near the valence band maximum. The reflectivity index \(R({\omega })\) shows that the peak value of \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) and \(\hbox {InGaZnO}_{4}\) appears only in the ultraviolet range, indicating that these two materials have all excellent transparency. In addition, the absorption coefficient \({\alpha }({\omega })\) of both \(\hbox {In}_{29}\hbox {Sn}_{3}\hbox {O}_{48}\) and \(\hbox {InGaZnO}_{4}\) is high in the ultraviolet frequency range, and therefore they show, a high UV absorption rate.     

Analog and RF performance of doping-less tunnel FETs with $$\hbox {Si}_{0.55} \hbox {Ge}_{0.45}$$ source

This paper reports studies of a doping-less tunnel field-effect transistor (TFET) with a \(\hbox {Si}_{0.55} \hbox {Ge}_{0.45}\) source structure aimed at improving the performance of charge-plasma-based doping-less TFETs. The proposed device achieves an improved ON-state current (\(I_{{\mathrm{ON}}} \sim {4.88} \times {10}^{-5}\,{\mathrm{A}}/\upmu {\mathrm{m}}\)), an \(I_\mathrm{ON}/I_\mathrm{OFF}\) ratio of \({6.91} \times {10}^{12}\), an average subthreshold slope (\(\hbox {AV-SS}\)) of \(\sim \) \({64.79}\,{\mathrm{mV/dec}}\), and a point subthreshold slope (SS) of 14.95 mV/dec. This paper compares the analog and radio of frequency (RF) parameters of this device with those of a conventional doping-less TFET (DLTFET), including the transconductance (\(g_{{\mathrm{m}}}\)), transconductance-to-drain-current ratio \((g_\mathrm{m}/I_\mathrm{D})\), output conductance \((g_\mathrm{d})\), intrinsic gain (\(A_{{\mathrm{V}}}\)), early voltage (\(V_{{\mathrm{EA}}}\)), total gate capacitance (\( C_{{\mathrm{gg}}}\)), and unity-gain frequency (\(f_{{\mathrm{T}}}\)). Based on the simulated results, the \(\hbox {Si}_{0.55}\hbox {Ge}_{0.45}\)-source DLTFET is found to offer superior analog as well as RF performance.     

First-principle calculations of electronic and ferromagnetic properties of $$\hbox {Al}_{1-x}\hbox {V}_{x}\hbox {Sb}$$

We have used the first-principle calculations of density functional theory within full-potential linearized augmented plane-wave method to investigate the electronic and ferromagnetic properties of \(\hbox {Al}_{1-x}\hbox {V}_{x}\hbox {Sb}\) alloys. The electronic structures of \(\hbox {Al}_{0.25}\hbox {V}_{0.75}\hbox {Sb}, \hbox {Al}_{0.5}\hbox {V}_{0.5}\hbox {Sb}\) and \(\hbox {Al}_{0.75}\hbox {V}_{0.25}\hbox {Sb}\) exhibit a half-metallic ferromagnetic character with spin polarization of 100 %. The total magnetic moment per V atom for each compound is integral Bohr magneton of 2 \(\mu _{\mathrm{B}}\), confirming the half-metallic feature of \(\hbox {Al}_{1-x}\hbox {V}_{x}\hbox {Sb}\). Therefore, these materials are half-metallic ferromagnets useful for possible spintronics applications.     

Nonstoichiometry and Electrical Conductivity of Nanocrystalline CeO{2 - x}

We synthesized dense CeO polycrystals of 10 nm grain size and characterized their electrical conductivity, in order to determine whether the defect properties of nanocrystalline solids fundamentally differ from those of conventional materials. The nanocrystals exhibit enhanced electronic conductivity, greatly reduced grain boundary impedance, and a heat of reduction more than 2.4 eV lower per oxygen vacancy compared to their coarse-grained counterparts. We propose that defect formation at low energy grain boundary sites is responsible for these properties, and that nanocrystalline oxides represent bulk materials possessing the defect thermodynamics of interfaces.     

Effects of the gas flow rate on the ionic conductivity of {\text{CaZr}}_{0.95} {\text{In}}_{0.05} {\text{O}}_{3 - \delta } ceramics

With coarse CaCO₃, nano ZrO₂ and In₂O₃ as raw materials, fine ${\text{CaZr}}_{0.95} {\text{In}}_{0.05} {\text{O}}_{3 - \delta } $ powders were synthesized at 1000°C by an optimized solid-state method. With the powders, ceramics with relative density as high as 98% were successfully fabricated at the temperature as low as 1400°C. The effects of gas flow rate on the conductivity of the ${\text{CaZr}}_{0.95} {\text{In}}_{0.05} {\text{O}}_{3 - \delta } $ ceramics under wet air conditions were first studied. The results showed that with the increase of temperature, the effects became more and more significant. In order to gain insight into the ion transfer mechanism of the electrolyte, the absorption and diffusion processes were analyzed. It was suggested that at lower temperature, the diffusion step was the rate-determining step. However, with the increase of the temperature, the adsorption process became the rate-determining step at lower flow rates.     

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     

Filament-to-dielectric band alignments in $$\hbox {TiO}_{2}$$ and $$\hbox {HfO}_{2}$$HfO2 resistive RAMs

The next-generation nonvolatile memory storage may well be based on resistive random access memories (RRAMs). \(\hbox {TiO}_{2}\) and \(\hbox {HfO}_{2}\) have been widely used as the resistive switching layer for RRAM devices. However, the electronic properties of the filament-to-dielectric interfaces are still not well understood yet, compared to those of the electrodes and the dielectric. In this work, we study the electronic structures of three typical filament and dielectric structures, \(\hbox {Ti}_{4}\hbox {O}_{7}/\hbox {TiO}_{2}\), \(\hbox {Hf}_{2}\hbox {O}_{3}/\hbox {HfO}_{2}\) and \(\hbox {Hf}/\hbox {HfO}_{2}\), using ab initio calculations. We implement the GGA-1/2 method, which rectifies the band gaps of GGA through self-energy correction. Our calculation predicts an ohmic contact for the \(\hbox {Ti}_{4}\hbox {O}_{7}/\hbox {TiO}_{2}\) interface, where the defective \(\hbox {Ti}_{4}\hbox {O}_{7}\) phase was experimentally identified as the filament composition in \(\hbox {TiO}_{2}\). However, there is a finite Schottky barrier existing in either \(\hbox {Hf}_{2}\hbox {O}_{3}/\hbox {HfO}_{2}\) interface (1.96 eV) or \(\hbox {Hf}/\hbox {HfO}_{2}\) interface (0.61 eV), the two probable filament–dielectric configurations in hafnia-based RRAM. Our results suggest that the distinct filament-to-dielectric band alignments in \(\hbox {TiO}_{x}\) and \(\hbox {HfO}_{x}\) systems account for the much larger resistance window for the latter.     

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     

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.     

Oxygen permeability, stability and electrochemical behavior of \Pr _{2} {\text{NiO}}_{{4 + \delta }} -based materials

The high-temperature electronic and ionic transport properties, thermal expansion and stability of dense $ \Pr _{2} {\text{NiO}}_{{4 + \delta }} ,\Pr _{2} {\text{Ni}}_{{0.9}} {\text{Fe}}_{{0.1}} {\text{O}}_{{4 + \delta }} $ and $ \Pr _{2} {\text{Ni}}_{{0.8}} {\text{Cu}}_{{0.2}} {\text{O}}_{{4 + \delta }} $ ceramics have been appraised in comparison with K₂NiF₄-type lanthanum nickelate. Under oxidizing conditions, the extensive oxygen uptake at temperatures below 1073–1223 K leads to reversible decomposition of Pr₂NiO₄-based solid solutions into Ruddlesden–Popper type Pr₄Ni₃O₁₀ and praseodymium oxide phases. The substitution of nickel with copper decreases the oxygen content and phase transition temperature, whilst the incorporation of iron cations has opposite effects. Both types of doping tend to decrease stability in reducing atmospheres as estimated from the oxygen partial pressure dependencies of total conductivity and Seebeck coefficient. The steady-state oxygen permeability of $ \Pr _{2} {\text{NiO}}_{{4 + \delta }} $ ceramics at 1173–1223 K, limited by both surface-exchange kinetics and bulk ionic conduction, is similar to that of $ {\text{La}}_{2} {\text{NiO}}_{{4 + \delta }} $ . The phase transformation on cooling results in considerably higher electronic conductivity and oxygen permeation, but is associated also with significant volume changes revealed by dilatometry. At 973–1073 K, porous $ \Pr _{2} {\text{Ni}}_{{0.8}} {\text{Cu}}_{{0.2}} {\text{O}}_{{4 + \delta }} $ electrodes deposited onto lanthanum gallate-based solid electrolyte exhibit lower anodic overpotentials compared to $ {\text{La}}_{2} {\text{Ni}}_{{0.8}} {\text{Cu}}_{{0.2}} {\text{O}}_{{4 + \delta }} $ , whilst cathodic reduction decreases their performance.