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The 2011 Tohoku earthquake caused radionuclide 137Cs be directly released into the ocean from the Fukushima Dai-ichi nuclear power plants. A high-resolution global-coastal nesting ocean model was established to simulate the initial spread of 137Cs as conservative tracer over the shelf of Japan after the accident. The major advantage in the current model system is to use unstructured grids to resolve the power plant and the coastal geometry with a grid resolution much higher than that used in previous modeling experiments. Therefore, it gives us an opportunity to examine the necessity whether the detailed structure of the Power plant should be considered for numerical experiment of 137Cs dispersion or not. This could provide us an alternative insight into the physical processes that lead to its spread of 137Cs over the shelf of Japan. Our results suggested that to resolve the dispersion process from the source point to the south and north discharging canal is critical for an accurate prediction of the spread of 137Cs to the 30 km sites off the coast. Moreover, a 2 km grid resolution along Japan coast is probably not high enough to resolve the plume correctly. Finally, the model- data comparison suggested that the physical process associated with the transfer of dissolved 137Cs into the sediment phase could potentially be important and should be considered in the future tracer modeling. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) has been attracting a lot of attention in recent years for its ability to greatly improve the convenience of our lives. Moreover, WPT for Electric Vehicles (EVs) has become an important key to the spread of EVs. The efficiency of WPT using magnetic field resonant coupling can be evaluated by the kQ product, but the optimal coil design method to maximize the kQ product at a specific frequency has not yet been established. In this paper, taking the Test station GA‐WPT1 and the Test station VA‐WPT1/Z3 of SAE J2954, which is officially defined as the standard for WPT while the electric vehicle is stationary in October 2020, as examples, the coil parameters that maximize the kQ product in the case of the coreless are determined according to the proposed method. An efficiency of 99.13% was obtained with a transmission distance of 200 mm and the number of turns of N1 = 34 and N2 = 30. Also, since all analyses can be derived immediately except for the analysis of the Litz wire to be used, the optimization time could be reduced significantly compared with the electromagnetic field analysis. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Intrinsic localized mode (ILM) can be generated in multiple mass‐spring systems using nonlinear springs, and ILM has attracted a lot of attention due to its special vibration modes that are not found in linear systems. However, the difficulty of creating nonlinearity remains a barrier to ILM research. In this paper, we propose a rotating magnetic spring based on magnetic nonlinearity. The nonlinear restoring properties of the proposed magnetic spring are confirmed by finite element method (FEA). Finally, using the restoring properties obtained from FEA, it is shown that ILM can be excited by MATLAB numerical analysis. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In this paper we define a line-cell conversion problem that has been reported as a new technical innovation in Japanese industry, and we construct a mathematical model to describe it. By numerical analysis of the model based on simulation experiments, we gain insight into line-cell conversion problems, such as (1) how many cells should be formatted, (2) how many workers should be assigned in each cell, and (3) how many workers should be rested on a shortened conveyor line when a conveyor assembly line is converted into cells, in order to optimise system performance, which is defined as the total throughput time and total labour power. Therefore, the model can be used as an evaluation tool in the case where (i) a company wants to change its production system (usually a belt conveyor line) to a new one (including cellular manufacturing), and (ii) a company wants to evaluate the performance of its converted system. [ABSTRACT FROM AUTHOR]

Summary: The damped outrigger system is known to efficiently provide additional damping in buildings with heights of over 250 m. However, particularly for supertall buildings in the center of Tokyo, Japan, the outrigger truss from the center core to the exterior columns need to span distances of more than 20 m. This increases the flexural stiffness demand on the outrigger that leads to larger truss depths making the damped outrigger system inefficient. For such tall buildings with large plans, a new damping modification system, the "damped braced tube system" is proposed, where the exterior surface of the elastic mega braces are partially removed vertically to create a split and are replaced with dissipaters (energy‐dissipation devices). The damped braced tube system enhances the seismic performance as the exterior surfaces of the elastic mega braces work together with the damped slits like in a coupled wall system and increases the overall damping ratio. In this paper, numerical models were constructed based on a real project in Japan consisting of a 397‐m supertall building employing the damped tubular braced system using oil dampers (referred to as viscous dissipaters). A series of generalized response spectrum based numerical analyses and optimizations were performed to minimize the seismic response. The proposed system exhibited improved damping performance with the first to third mode damping ratios reaching to more than 7% while providing a wide range of options for dissipater distribution for design. Finally, the elevation of the slit's base is recommended to be equal to 0.22 of the total building height considering the trade‐off relationship between the first modal damping ratio and the fundamental period. [ABSTRACT FROM AUTHOR]

France (CEA and FRAMATOME) and Japan (JAEA, MFBR, and MHI) teams have carried out collaborative works to have common technical views regarding a sodium-cooled fast reactor (SFR) concept. This paper mainly describes the capabilities of ASTRID 600 to demonstrate SFR technologies of both countries. Japan has studied the feasibility of an enhanced high burnup low-void effect (CFV) core and fuel using oxide dispersion-strengthened steel cladding in ASTRID 600, considering Japan's target for core performance. The neutronics design of the core has satisfied most required design targets and conditions. Regarding passive shutdown capabilities, Japan team has performed a preliminary numerical analysis for ASTRID 600 using a complementary safety device (CSD), called a self-actuated shutdown system (SASS), one of the safest approaches in Japan. Japan's team used the SASS in place of the hydraulically suspended absorber rod, called RBH, one of the safest approaches of France, to investigate the potential of the SASS as a design measure common to the countries. The preliminary analysis has shown that the SASS can satisfy the countries' main requirements. This study has also revealed that the mitigation measures of ASTRID 600 against a severe accident are promising to achieve in-vessel retention for both countries. [ABSTRACT FROM AUTHOR]

This paper proposes a new construction method for 2-D IIR digital filters with all-pass subfilters as components. Recently, numerous studies have been made to construct digital filters by combining all-pass characteristics. This paper is based on the construction by a parallel connection of an all- pass subfilter and delay element, which can realize approximately the linear phase characteristic. First, the basic design for 1-D digital filters as well as its properties are described. Then the theory for the 1-D case is extended to the 2-D case, and a new construction method for 2-D digital filters with low-pass characteristics with circular symmetry is shown. The proposed method features the following. The phase characteristic is approximately linear in the passband. The filter can be realized with a smaller number of multipliers than in the traditional method. The coefficient sensitivity is low. [ABSTRACT FROM AUTHOR]

Early estimation of biological growth of organisms is an indispensable task in ecology and related research areas. The biological growth is always time-continuous, while our observations of the phenomenon are time-discrete in practice. The formalism of the discrete costly observation (DCO) enables us to mathematically bridge the two qualitatively different processes. This formalism is still germinating, and its practical applications have not been carried out. This paper presents a first application of the DCO formalism to a cost-effective early estimation problem of the biological growth, and its mathematical and numerical analysis. Growth dynamics of organisms, which are fishery resources in this paper, is governed by a stochastic differential equation whose solution is observed discretely. The optimality equation to be solved for finding the most cost-effective observation policy is derived as a fixed point problem based on degenerate parabolic partial differential equations. The fixed point problem turns out to be uniquely solvable. A recursive approximation of the fixed point problem is presented and its solvability in a viscosity sense is discussed. A finite different scheme is then employed to fully-discretize the recursive equations. The present model is finally applied to a problem of Japanese smelt Plecoglossus altivelis altivelis (Ayu): an important inland fishery resource in Japan. [ABSTRACT FROM AUTHOR]

In recent years, liquefaction due to major earthquake caused serious damages to many infrastructures and houses around the world. In order to protect people's daily life and infrastructure from the disaster, development of effective and economical countermeasure against liquefaction that can be applied to existing houses is becoming increasingly important. Although many liquefaction countermeasures have been developed by many researchers, most of them require large construction machines and are costly, which limits their application to existing structures. For this reason, a liquefaction countermeasure, called as groundwaterlevel decreasing method, has been proposed in Japan. This method has already been put into practice and the construction of the countermeasure has finished several years ago. The purpose of this method is to change a liquefied layer to a non-liquefied layer by lowering the groundwater level. Yet the performance of this method has not been fully evaluated quantitatively. Therefore, in this paper, numerical analysis using FEM method was carried out to evaluate the liquefaction damage before and after the lowering of groundwater level. The calculation is conducted with 2D soil-water coupling finite element-finite difference (FE-FD) analysis based on a rotating-hardening elastoplastic constitutive model. From the analyses, it is found that the effective stress of the ground below under-groundwater level increases significantly because of the lowering of groundwaterlevel, resulting in an increase in resistance to liquefaction and mitigating the settlement damage of ground. [ABSTRACT FROM AUTHOR]

Vector error-correction models (VECM) are increasingly being used to capture dynamic relationships between financial variables. Estimation and interpretation of such models can be enhanced if zero restrictions are allowed in the coefficient matrices. Conventional use of full-order models may weaken the power of statistical inferences due to over-parameterization. The paper demonstrates the usefulness of this approach for the analysis of exchange rate relationships. Specifically, the paper examines the relationship between the money supply and the Euro and provides a test of purchasing power parity (PPP) in Japan. The latter test results shed light on the adjustment mechanisms through which PPP is achieved. In addition, it is clear that the proposed ZNZ patterned VECM modeling provides better insights from this kind of financial time-series analysis. The paper also shows that causality detection in an I(d) system can be revealed identically from the ZNZ patterned VECMs or the equivalent VAR models. [ABSTRACT FROM AUTHOR]

Although Luneburg lenses are already in practical use, few papers have been published on their wave-optical analysis. This is due to the difficulty in the wave-optical analysis of the electromagnetic field in an inhomogeneous medium with a large radius, in addition to the fact that most researchers have been interested so far in a geometrical-optic analysis. Increased applications of this type of lens to a microwave hand require more precise analysis from the wave-optics viewpoint. This paper deals with the wave-optical analysis of a cylindrical Luneburg lens. Taking several numerical analysis methods, the relationship between the number of terms of a truncated series and the accuracy of the analysis, and the relationship between the computation time and the accuracy of the analysis are examined. A method is proposed which can be applied to a lens having a large radius compared with the wavelength. By using this method, actual numerical analyses are carried out, and the focus characteristics and the distribution of the heat generation (the power dissipation density) in the lens are shown. These are compared with the results of published numerical analyses. Some interesting results, which cannot be obtained from a conventional geometrical-optic analysis, are obtained by the proposed method. [ABSTRACT FROM AUTHOR]

It is important to know the scattering properties of objects buried underground so that the techniques of imaging the buried objects by electromagnetic waves may be established. This paper analyzes numerically the transient scattering characteristics by the finite difference time domain (FDTD) method where an infinitely long perfect conductor of arbitrary cross section is buried in the ground and an infinitely long current source is located above the ground surface parallel to the object. The calculation error resulting from the approximation of the scattering object by square mesh is decreased by introducing the field interpolation which satisfies the boundary conditions of the scattering surface. The spatial distribution of the electromagnetic field at each step of the calculation is shown. Moreover, the propagation characteristics of the wave near the ground surface and the scattering characteristics of various objects are studied and the presence of two types of waves, i.e., direct and lateral, is confirmed between the source and ground and between the object and ground. [ABSTRACT FROM AUTHOR]

In this paper, numerical modeling and analysis of a hybrid-spar floating wind turbine is presented. The hybrid-spar consists of steel at the upper part and precast prestressed concrete at the lower part. Such a configuration is referred to as a hybrid-spar in this paper. The hybrid spar was successfully installed offshore of Kabashima island, Goto city, Nagasaki prefecture, Japan, on Oct. 18, 2013 (see Utsunomiya et al., 2015, "Design and Installation of a Hybrid-Spar Floating Wind Turbine Platform," ASME Paper No. OMAE2015-41544 for details). In this paper, some details on numerical modeling of the hybrid-spar for design load analysis are presented. Then, the validation of the numerical analysis model is presented for a full-scale hybrid-spar model with 2-MW wind turbine. The comparison has been made for the natural periods and the response during rated power production test. Basically, both comparisons have shown good agreement between the measured values and the simulation, showing reliability of the developed code and the numerical model. [ABSTRACT FROM AUTHOR]

A linear induction motor (LIM) is suitable for use in trains. The motor can be used in both wheel-suspended and contact-less types such as the Linear Metro and HSST trains in Japan. The LIM has end winding as well as asymmetrical winding. The end effect is a major problem in the LIM, and it makes the analysis, design, and control of motors difficult. This paper describes a method that combines numerical analysis and the equivalent circuit for the LIM in order to design a high-performance controller for the LIM that includes the end effect. A sample basic field-oriented control scheme that is based on the plant model is applied to the LIM in order to check the control performance. The theory of rotary induction motors is used for verification. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(2): 44-54, 2012; Published online in Wiley Online Library (). DOI 10.1002/eej.21171 [ABSTRACT FROM AUTHOR]

Recently, the printed dipole antenna has attracted attention as a two-dimensional array element which is electromagnetically coupled to an open-type feed line. This paper analyzes the characteristics of the printed dipole which is excited by an infinitely long microstrip line, by applying the method of moment to Richmond's reaction equation. If we assume that the feed line is sufficiently close to the ground plane, the dipole which is placed perpendicular to the feed line is treated as an equivalent parallel element. If the dipole forms a rotation angle with the feed line at the center of the dipole, it is regarded as an equivalent series element. Through a comparison of theoretical and experimental results for their frequency characteristics of equivalent impedances, the appropriateness of the theory has been confirmed. Basic characteristics were examined by numerical analyses for equivalent impedances of a microstripline-fed printed dipole antenna, the distribution of the electric current on the dipole, and the antenna radiation pattern. [ABSTRACT FROM AUTHOR]

Densely built areas with poor thermal insulation suffer from high thermal environmental risks and generally consume high energy in summer. Determining the relationship between density and energy consumption is necessary, particularly when implementing urban heat island (UHI) countermeasures. This study evaluated the effects of density and UHI countermeasures on the energy consumption and indoor thermal comfort of a detached house in a typical densely built wooden house area in Yokohama City, Japan. Three densities and six countermeasures were considered. Annual hourly simulations based on the SCIENCE-Vent thermal environment simulation model yielded the following results: in densely built wooden house areas, the energy consumption and thermal discomfort increased with density. The green roof yielded the largest energy savings in the cooling and heating seasons, demonstrating the highest annual energy savings with 5.7%. Density had little impact on rooftop countermeasures, but the effect of the high-reflectance walls increased with density, and the reduction in annual energy consumption (air conditioning and lighting) is 2.6%, 3.0%, 3.6% in 37%, 47%, and 59% density cases, respectively. The impact of thermal countermeasures on indoor thermal comfort varied according to the thermal control mechanism. [ABSTRACT FROM AUTHOR]

On March 11, 2011, a large earthquake and subsequent tsunami near the east coast of Japan destroyed the Fukushima Daiichi nuclear power plant (FD-NPP), causing a massive release of nuclear contaminants. In this paper, a Pacific basin-wide physical dispersion model is developed and used to investigate the transport of nuclear contaminants. The Pacific circulation model, based on the Regional Ocean Modeling System (ROMS), is forced with air-sea flux climatology derived from COADS (the Comprehensive Ocean-Atmosphere Data Set). It is shown that ocean current dominates nuclear contaminant transport. Following the Kuroshio Extension and North Pacific Current, nuclear contaminants at the surface will move eastward in the Pacific as far as 140°W, thereafter dividing into two branches. For the south branch, nuclear contaminants will be transported westward by the equatorial current, and can reach the Philippines after 10 years' time. In contrast, the north branch will arrive at the American west coast and then migrate to the Bering Sea. At 200 m water depth, part of the nuclear materials will move southwestward along with deep ocean circulation, which could potentially reach the east coast of Taiwan. The other part will move to the west coast of America and separate into two branches. One will move northward along the west coast of Alaska, while the other will travel southward to the Hawaiian Islands. The transport of radiation contaminants below 500 m is slow, and will primarily remain in the central Pacific. The physical dispersion model results show that high concentrations of the radioactive isotope cesium-137 (Cs) will move eastward and reach the central Pacific and west coast of North America in two and eight years, respectively. The sea areas influenced by the nuclear contaminants continue to expand, while peak concentrations decrease in the North Pacific. [ABSTRACT FROM AUTHOR]

Described is the process of trial, adjustment, and development of the joint complex of models consisting of the WRF-ARW (Weather Research and Forecasting) regional hydrodynamic model (the United States) and radionuclide transport model from the NOSTRADAMUS package. Using these models, the computation is carried out of the fallout and radiation dose rate on the territory of Japan after the Fukushima nuclear power plant accident. To adjust the hydrodynamic model, its results were preliminarily compared with the data of observations at the mast and the assessment of the model complex was based on the data of atmospheric tracer concentration measurements during the in situ experiments carried out in 1983-1985 near Karlsruhe (Germany). Described is the version of hydrodynamic prognostic model and radionuclide transport model prepared for the present paper. Given are the results of the statistical analysis of different numerical experiments of the model complex and the results of the simulation of radiation conditions on the territory of Japan after the Fukushima Dai-ichi nuclear power plant accident. It is demonstrated that the errors in the vertical distribution of the model wind are extremely sensitive to the type of parameterization of surface and boundary layers in the model. The comparison of computed and measured values demonstrated their satisfactory coincidence. [ABSTRACT FROM AUTHOR]

The structure of the array antenna for the reception antenna of the digital terrestrial television broadcasting in Japan is optimized by PSO algorithm. The unbalanced fed ultra low profile inverted L antenna is used as the driven element and two wires are located at the forward and backward directions of the driven element. In the case of antenna size of 170 mm by 325 mm by 29 mm, the return loss bandwidth less than -10 dB is satisfied at the whole broadcasting frequency band (240 MHz) and the directivity of 5.44 dBi to 7.19 dBi is obtained. In the numerical analysis, the electromagnetic simulator WIPL-D based on the method of moment is used. [ABSTRACT FROM AUTHOR]

An innovative configuration of pocket-type rock-fall protective cable-net structure, known as Long-span Pocket-type Rock-net (LPR), has been developed in Japan. The global performance of the proposed system was initially checked by the experimental (full-scale) modelling. Given the various limitations of the physical experiments, particularly for the parametric study to have a detailed understanding of the newly developed system, a reliable and simplified method of numerical modelling is felt necessary. Again, given the sophistication involved with the method of numerical simulation, a yet simplified modelling approach may prove more effective. On top of this background, this paper presents a three-tier modelling of a design of LPR. After physical modelling, which has revealed that the displacement response may be taken more vital for LPR performance, Finite Element based numerical modelling is presented. The programme LS-DYNA is used and the models are calibrated and verified with the element- and structure-level experiments. Finally, a simple analytical modelling consisting of the equivalently linear and elastic, lumped-mass, single-degree-of-freedom system, capable of predicting the global displacement response, is proposed based on the basic principles of conservation of linear momentum and energy. The model is back-calculated and modified from the analyses of the verified numerical model. [ABSTRACT FROM AUTHOR]

Background: A quantitative measurement of inequality in geographic accessibility to pediatric care as well as that of mean distance or travel time is very important for priority setting to ensure fair access to pediatric facilities. However, conventional techniques for measuring inequality is inappropriate in geographic settings. Since inequality measures of access distance or travel time is strongly influenced by the background geographic distribution patterns, they cannot be directly used for regional comparisons of geographic accessibility. The objective of this study is to resolve this issue by using a standardization approach. Methods: Travel times to the nearest pediatric care were calculated for all children in Oita Prefecture, Japan. Relative mean differences were considered as the inequality measure for secondary medical service areas, and were standardized with an expected value estimated from a Monte Carlo simulation based on complete spatial randomness. Results: The observed mean travel times in the area considered averaged 4.50 minutes, ranging from 1.83 to 7.02 minutes. The mean of the observed inequality measure was 1.1, ranging from 0.9 to 1.3. The expected values of the inequality measure varied according to the background geographic distribution pattern of children, which ranged from 0.3 to 0.7. After standardizing the observed inequality measure with the expected one, we found that the ranks of the inequality measure were reversed for the observed areas. Conclusions: Using the indicator proposed in this paper, it is possible to compare the inequality in geographic accessibility among regions. Such a comparison may facilitate priority setting in health policy and planning. [ABSTRACT FROM AUTHOR]

To establish the wildfire danger rating system, detailed data of wildfire and some related parameters such as weather, population and tree species are required. In this paper, the raw data of weather parameters in Japan are first expanded into more detailed data. The daily value of each weather parameter in each third-level mesh, which is about 1 km × 1 km in size, from year 1999 to 2000 is calculated by means of inverse distance weighted interpolation. Expansion results for third-level meshes are demonstrated. Fire probability for each parameter is calculated and analyzed. It is found that the dependency relation of fire probability on some parameters have surprisingly regular format. The data calculated and analyzed in the paper and the results may act as a basic database for wildfire researchers, and are expected to promote the study of wildfire danger rating method and the development of such systems. [ABSTRACT FROM AUTHOR]

Wireless power transfer to electric vehicles while driving is a technology that is currently attracting attention as it has the potential to solve the problems faced by EVs that will become popular worldwide in the future. In the case of dynamic wireless power transfer (DWPT) to electric vehicles, it is necessary to transmit the required power with high efficiency and ensure safety. While there are multiple safety requirements, there are also regulatory values for the magnetic field strength emitted from the coil, which must be satisfied before it can be implemented in society. This research aims to speed up the design of coils by using only numerical analysis, in contrast to conventional coil design using electromagnetic field analysis. In the future construction of wireless power transfer systems, it is of great significance to discuss the design using only numerical analysis, as there are many design parameters. Experiments were carried out and compared with the numerical analysis and found to be in agreement. A power transmission of 20 kW converted value was carried out to verify the effect of the size, pitch, and number of turns of the transmission coils on the efficiency and magnetic field strength. The effect of input voltage was also discussed by simulation, and the optimum coil was derived. As a result, when the coil size was 800 × 600 mm, the number of turns was 46, the pitch was 6.1 mm and the input voltage was 1400 V, the analysis showed that a power transmission of 20 kW with an efficiency of 99.3% and a far magnetic field leakage strength of 81.6 dBμA/m could be achieved. Even with a coreless coil, the magnetic field strength could be below the regulation value. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Earthquake is a threat to all kinds of structures including underground structures. Before the 1995 Hyogoken-Nanbu Japan earthquake, however, it was considered that underground structures are at minimum seismic risk in comparison to above-ground structures unless they are crossing the active faults. The collapse of Daikai station in the Kobe subway system during the 1995 Hyogoken-Nanbu earthquake exhibited that underground structures are at high risk of earthquake with shallow overburden. Though researches have been done on this issue, it is still necessary to investigate further the mechanical behavior of underground structure during an earthquake and corresponding efficient seismic enhancement. In this paper, in order to find out an optimum ground-improvement pattern for a rectangular-shaped box culvert constructed in soft ground that does not meet the present seismic requirement, numerical tests with nonlinear 2D/3D dynamic FEM are conducted. Different patterns of the ground improvement for the box curvet constructed with cut-and-cover method are investigated to find out an optimum pattern that can reduce the impact of earthquake in the most effective way. In the 2D/3D dynamic finite element analysis, the ground is Toyoura sand, typical clean sand, and its nonlinear mechanical behavior is described by Cyclic Mobility model. Validity of the proposed numerical method is firstly confirmed with 1 g shaking table test and then numerical tests are conducted to find out the optimum pattern for the ground improvement. Finally, an effective pattern of ground improvement for existing box culvert is proposed by the numerical analysis. [ABSTRACT FROM AUTHOR]

In equations describing switched-capacitor (SC) circuits, the switching equation of some switching instant is represented by Vc+ = F · Vc- + G · u+. Historically, the transformation matrices F and G have been obtained by the limiting method, in which each switching resistance approaches infinity or zero. This method derives the transformation matrices F and G directly. But it has numerical instability for large-scale SC circuits, because Frame's method is used. In this paper, we propose two methods to obtain the transformation matrix F from a characteristic matrix C. The first method is the Danielevsky's method, and the second is the backward Euler method. We also propose another method to transform F to G by means of characteristic matrices given by circuit topology, by relation of zero input and the zero state responses. The results of the simulation are represented by a simulator. [ABSTRACT FROM AUTHOR]

This paper describes a new method for designing two-dimensional (2-D) digital filters with complex coefficients having circularly symmetric and fan characteristics by applying variable transformation (spectral variable) to one-dimensional (l-D) IIR digital filters with complex coefficients. A 2-D digital filter with complex coefficients has an advantage in that it can increase greatly the degree of freedom for design, since once it satisfies the design specification partly in the frequency plane, its characteristics can be arbitrary in other regions. Here, a design method is proposed which makes positive use of this property of the complex coefficient digital filters. Since we have introduced the complex coefficient filters into spectral transformation functions and 1-D prototype filters, there is no constraint on cutoff frequency (radius) accomplishable in circularly symmetric filters. In fan filters even a characteristic that has been difficult to design unless one uses optimization techniques, has become easy to design by means of variable transformation without using any optimization techniques. Moreover, the stability of the resulting IIR filters is guaranteed in simple conditions. [ABSTRACT FROM AUTHOR]

The development of Floating Offshore Wind Turbines (FOWT) has been progressing steadily. To utilize the moderate water depth of 50–100 m ocean space around Japan, a barge-type FOWT was installed in Kitakyushu as part of a demonstration project conducted by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. The FOWT mounts a 3 MW two-bladed wind turbine with blade diameter of 100 m and hub height of 72 m. The barge-type floating support structure is equipped with a moonpool in the center and a skirt at its bottom and is moored with 9 lines of catenary chains. To investigate the dynamic behavior of the barge-type FOWT in extreme condition and the validity of the numerical simulation in modeling the effect of the complex flow around the floating structure to the FOWT's motion response, the FOWT's motion data during typhoon Tapah on 23 September 2019 were measured and compared with the simulation results. As the results, the simulation results showed a good agreement in general to the measurement data. However, some shifts in the peak frequency of the simulation's motion spectrum and a disagreement in waves with shorter wave periods were also observed. The possible causes of these differences are discussed thoroughly in this paper. [ABSTRACT FROM AUTHOR]

The multi-directional site response of a well-documented downhole array in Japan is numerically investigated with three directional (3-D) dynamic hydro-mechanically (HM) coupled Finite Element (FE) analysis. The paper discusses the challenges that 3-D modelling poses in the calibration of a cyclic nonlinear model, giving particular emphasis on the independent simulation of the shear and volumetric deformation mechanisms. The employed FE model is validated by comparing the predicted site response against the recorded motions obtained from the KiK-net downhole array monitoring system in Japan. The results show that, by employing the appropriate numerical model, a good agreement can be achieved between the numerical results and the monitored acceleration response in all three directions simultaneously. Furthermore, the comparison with the recorded response highlights the significance of the independent modelling of the shear and volumetric deformation mechanisms to the improvement of the numerical predictions of multi-directional site response. [ABSTRACT FROM AUTHOR]

Natural ester is viewed as the most promising future alternative to mineral oil due to its high degradability, but its inferior breakdown characteristics prevent its application of large power equipment. The purpose of this research is to investigate the breakdown characteristics of natural ester. First, the natural ester's ionization potential and molecular number density are calculated. Then, an improved natural ester streamer discharge model is developed using the Poisson's equation and the carrier continuity equation, taking into account the effect of temperature on carrier mobility and incorporating the computed ionization potential and other factors. The results for different lightning impulse voltages were analyzed by COMSOL software. Comparing the mineral oil, the results indicate that the natural ester breakdown voltage is close to and slightly lower than that of the mineral oil but the acceleration voltage is very similar to the breakdown voltage. The lower ability of esters in prevention against the development of fast and energetic streamers is consistent with the description of the experimental results. In addition, the model takes into account the effect of temperature on the carrier mobility. As the applied voltage increases, the change of temperature in the streamer channel accelerates the carrier motion and promotes the propagation of the streamer. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The voltage across a 77‐kV‐class transmission line surge arrester (TLSA) and the heat in the TLSA have been computed using the finite‐difference time‐domain (FDTD) method for a lightning current having a magnitude of 50 kA, a risetime of 1 μs, and a half‐peak width of about 100 μs. The TLSA is represented with series‐connected‐nine ZnO elements, each of which has a length of 36 mm and a diameter of 32 mm. The ZnO element is represented with many 2 × 2 × 2 mm cubic cells, each of which has a nonlinear resistivity in each of the x‐, y‐, and z‐directions dependent on the electric field in each direction and the temperature in each cell. From the spatial and temporal distributions of FDTD‐computed heat in the TLSA, the spatial and temporal distributions of thermal stress in the TLSA have been computed using the finite‐element method. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

We investigate the size of primary balance that can be sustained and the change in public debt and physical capital under transition dynamics in the Japanese economy. For our investigation, we construct a simple overlapping generations model. We find that a large primary surplus, 13.8–18.7% of GDP, is needed to prevent the public debt-to-GDP ratio from diverging infinitely. We also show that even if the large primary surplus can be maintained, the Japanese economy faces a sharp reduction in physical capital from 191 to 70.0% of GDP on the transition path. [ABSTRACT FROM AUTHOR]

With the increasing of extreme rainfall frequency, landslides accompanied by mudslides often lead to serious casualties and property damage. On 3rd July 2021, a debris flow occurred in Izu Mountain area, Shizuoka County, Japan, and then resulted in 26 deaths and 131 houses destroyed, where houses were mainly built along the banks of the creek. In order to analyse the landslide state and distribution, a two-dimensional debris flow dynamic model (Massflow) was selected to simulate the process of the landslide-generated debris flow. When the model results are considered together with remote sensing images, the volume distribution of the unstable landslide is also able to be determined. The results show that (1) the affected areas are mainly concentrated at the outfall of the gully and on both sides of the streets. (2) The pore pressure ratio is an important factor affecting the damage range of this debris flow. (3) The increase of the pore pressure ratio in the landslide make the movement distance of debris flow increase significantly. [ABSTRACT FROM AUTHOR]

Around the world, and especially in Japan, the tearing down of social infrastructure, including civil engineering structures, has been increasing due to the aging of these constructions, which were built during a period of high economic growth, and a decrease in their utilization caused by a recent drop in the population. The number of existing pile foundations being pulled out has gradually risen to a higher number than that of pile foundations being newly installed. However, after the pulling-out of a pile foundation, the mechanical characteristics of the surrounding ground are of great concern due to the existence of the holes that form when the existing piles are removed (extraction holes). In this study, a three-dimensional elasto-plastic consolidation analysis was performed to examine the effect of the extraction holes of removed piles on the static properties of the surrounding ground. As examples of the results of the analysis, if an extraction hole of a removed pile is left as it is, large ground subsidence will occur near the extraction hole of removed pile, especially at the lower part of the clay layer near the hole. The greater the number of extraction holes of removed piles, the greater the compressive stress acting on the extraction holes after the pile removal. Therefore, the filler should exhibit strength early as the number of extraction holes of removed piles increases. [ABSTRACT FROM AUTHOR]

Abstract: As temporary structures, steel-sheet-pile-quay (SSPQ) retaining walls have been widely used to counteract excavation problems in Japan not only in urban areas, but also in mountainous areas. The most important features of retaining walls are that they are easy to install in any narrow space, they can be reused many times in different types of soil and, above all, they are strong enough to resist any kind of earth pressure. The shortcoming of retaining walls, however, is that the deformation of the structures may sometimes be rather large, which might become an obstacle for geotechnical engineers wanting to use them as permanent structures. In this paper, centrifuge model tests [1] on the seismic performance of SSPQ retaining walls are simulated systematically with a two-dimensional (2D) dynamic analysis using the finite element method (FEM). In the centrifuge model tests, an SSPQ retaining wall subjected to five consecutive seismic waves is considered. To analyze the influence of the soil density on the performance of the retaining wall and the ground, a middle dense Toyoura sand ground (D r =60%) and a dense Toyoura sand ground (D r =75%) are used. In the analysis, the seismic behavior of the SSPQ retaining wall and the surrounding ground are described separately by beam elements and a cyclic mobility model in which the stress-induced anisotropy, the density and the structure of the ground can be described in a unified way. In order to clarify the influence of the fixed boundary adopted in the centrifuge model vibration tests, an analysis in prototype scale, that completely corresponds to the conditions of the centrifuge model tests, and an analysis in full scale, that corresponds to the real ground conditions, are carried out. By comparing the calculated results with the results of the centrifuge model vibration tests, the anti-seismic capacity of the SSPQ retaining wall and the dynamic performance of the ground during earthquakes are discussed in detail. The accuracy of the evaluation method using FEM is also verified. The purpose of this study is to establish an evaluation approach for the seismic behavior of SSPQ retaining walls as permanent earth-balanced structures. [Copyright &y& Elsevier]

Abstract: Protracted recession in Japan for the last twenty years is characterized by persistent deflation and negative output gap. Recently, Inoue et al. presented the concept of “trap of credit creation” which represents mechanism of the persistent deflation based on zero-interest-rate economy. Three new Keynesian DGE models by Inoue et al. explain this type of deflation as a steady state of a system. The DGE models, which are based on optimization for utility function, derive simultaneous nonlinear differential equations. In the present paper, we study dynamical features on the steady states of the three DGE models (i.e. Model I, II, and III), using numerical calculation: i.e. we analyze stability of steady states, using Jacobian matrices. Model I and II correspond to models for positive-interest-rate economy, and Model III suggests mechanism of the recession characterized as trap of credit creation under zero-interest-rate economy. We show each of the models have a stable steady state. This result supports adequacy of the present models, which can shed light on mechanism of the protracted recession. [Copyright &y& Elsevier]

In recent years, various networks have come to exist in our surroundings. This not only includes examples such as the internet and airline routes that can be thought of as networks; protein interactions are also networks. A network is defined as an arrangement of nodes (points) and links (lines). An "economic network design problem" can be discussed by assuming that a vertex is an economic player and that a link represents some connection between economic players. An economic player can mean an individual, an association, a city, a nation and so forth. A connection between economic players signifies items such as a transport link, a telecommunication net or an economic regional alliance. In this paper, an "economic network design problem" is modeled based on Jackson and Wolinsky's connections model, and the utility function of the network is defined. In the field of economics, generally, the game theory approach is adopted for analysis of network formation. However, we encounter difficulties when a network has many heterogeneous nodes. Therefore, we suggest that the optimization of an "economic network design problem" can be solved using evolutionary computation. As an example of an "economic network design problem," we consider an optimization problem of a network between regions in West Japan. In addition, the priority of the network maintenance is clarified via the optimum network obtained in the simulation. [ABSTRACT FROM AUTHOR]

Abstract: In 1972 mural paintings of Takamatsuzuka tumulus were discovered and have been conserved on site for 35 years, but fungi growth on the mural paintings was not suppressed. In 2007 the stone chamber was dismantled and removed to the facility for conservation and restoration. The purposes of our study are to clarify the main cause of the deterioration and to propose a suitable method to prevent the deterioration for preserving them on site. In this paper, we developed the two-dimensional analysis model by considering the actual change of the surrounding mound because of the excavation in 1972, and perform the analysis of heat behavior of Takamatsuzuka tumulus before and after excavation and compare effects of different sun-shading methods on heat behavior of the stone chamber. The main results are as follows: (1) after the excavation, the inside surface temperature distribution of the stone chamber and the amplitude of indoor temperature become larger. (2) Using the sun-shading panel in the area of excavation is an effective method to reduce the average indoor temperature; however, it has no influence on reducing the temperature distribution of the stone chamber and the temperature difference between the inside wall and indoor. [Copyright &y& Elsevier]

Abstract: In the current Japanese bridge design code, the seismic load of only one direction (1-dimension, 1-d) is considered. However, in fact, an actual seismic load has three components for N–S (north–south), E–W (east–west) and U–D (up–down) directions. The current paper presents a series of numerical results of steel box columns, which are used as piers of viaduct, under 3-d seismic load with 3 components. Two types of ground motion patterns of the main shock and the maximum aftershock measured in the Chuetsu Earthquake in 2004 are used as the seismic load. The results indicate that the severer deformation arises in the columns under 2-d (N–S and E–W components) or 3-d seismic load than the 1-d load by the main shock. However, under the aftershock, which contains ground motion of higher frequency, 1-d load gives larger displacement. [Copyright &y& Elsevier]

Most of the exterior walls of wooden houses in Japan have a vented air layer between the exterior cladding and the insulation. This vented air layer is designed to dehumidify the exterior walls by discharging humidity to the outside and allowing outdoor air to enter, thereby decreasing the risk of condensation on the exterior wall during winter. It is assumed that the source of this moisture is the indoor air, and that the outdoor air is drier. However, the outdoor air is often highly humid during the rainy season and may become a source of moisture. The vented air layer also allows rain water to drain away. Any rain water penetrating through the exterior cladding is drained away through the vented air layer. However, rain can also enter the vented air space through the air inlets. Since it takes a certain amount of time for all the rain water to drain away, water may accumulate in the vented air layer and produce high humidity in the exterior wall. In order to evaluate the effectiveness of an exterior wall with a vented air layer, its hygrothermal characteristics should be investigated, taking the effect of rain water into consideration. This paper describes a case of moisture damage where stain appeared on the outer surface of the plywood wall in a wooden residential building. Experiments were carried out in climate chambers to clarify the conditions that are causing stain. Hygrothermal conditions in the vented air layer were simulated using heat, air, and moisture model, and the causes of staining were investigated. [ABSTRACT FROM AUTHOR]

Abstract: A numerical method, which combines the boundary element method (BEM) and the volume of the fluid method (VOF method), has been presented to solve wave–structure interactions; the intense wave motion at the proximity of the structure is modeled by the VOF method and the rest of the fluid region is modeled by the BEM. The combined method can considerably reduce the time-consuming VOF domain, and thus practically makes it possible to apply the VOF method for random wave calculations, in which long time computations are usually required to obtain statistically meaningful results, and therefore the use of the single-VOF model often becomes prohibitive in terms of computational time and storage memories. A VOF model CADMAS-SURF, which is based on SMAC scheme and had been constructed by a number of VOF researchers in coastal engineering in Japan, is used in the combined BEM–VOF model. The two-way coupling treatment, which enables us to deal with bidirectional wave propagations, which was originally given for the SOLA-VOF model by Yan et al. (2003a) and later improved by Kim et al. (2007), was modified for the SMAC scheme. The coupling treatments are described in detail in the paper. The validity of the combined BEM–VOF model was investigated by comparing the numerical results with the theoretical results for the propagations of Stokes 5th order waves and random waves. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an integrated multicriteria analysis method for the quantitative evaluation of a state’s nuclear nonproliferation credibility level. Underscoring the implications of policy on the sources of political demand for nuclear weapons rather than focusing on efforts to restrict the supply of specific weapons technology from the “haves” to the “have-nots”, the proposed methodology considers the political, social, and cultural dimensions of nuclear proliferation. This methodology comprises three steps: (1) identifying the factors that influence credibility formation and employing them to construct a criteria tree that will illustrate the relationships among these factors; (2) defining the weight coefficients of each criterion through pairwise comparisons of the Analytical Hierarchy Process (AHP); and (3) assigning numerical scores to a state under each criterion and combining them with the weight coefficients in order to provide an overall assessment of the state. The functionality of this methodology is examined by assessing the current level of nuclear nonproliferation credibility of four countries: Japan, North Korea, South Korea, and Switzerland. [Copyright &y& Elsevier]

Abstract: A detection of a defect of a helical heating tube installed in the fast breeder reactor “Monju” in Japan is done by a feeding of an eddy current testing (ECT) probe with magnetic sensor into the tube. An undesirable vibration of the ECT probe always happens under a certain condition and makes the inspection difficult. Several characteristics of the vibration have been made clear by some experiments using a mock-up, but the essential factor of the vibration is still unclear. In this paper, a numerical simulation of the vibration is implemented on the assumption that the vibration is caused by Coulomb friction. An analytical model, which is obtained as a lumped mass model, is a large-scale non-linear vibration system and many computational costs are ordinarily required to carry out the simulations. The Transfer Influence Coefficient Method is applied so that the simulation is efficiently carried out. The results of simulation qualitatively agree well with the experimental results. It confirms the validity of the assumption that the vibration is caused by Coulomb friction. [Copyright &y& Elsevier]

The Tunnel Sealing Experiment (TSX) was an international project developed by Canada, Japan, France, and the United States. The TSX consisted of a clay bulkhead and a concrete bulkhead. The two bulkheads were at opposite ends of a 12-m-long sand-filled chamber. The heating phase involved the circulation of heated water through the TSX chamber to raise the temperature of the sealing system. This was done to evaluate the influence of elevated temperature on the performance of the bulkheads. Numerical analyses to simulate the thermohydromechanical evolution of the clay bulkhead and the surrounding rock of the TSX were performed using MOTIF finite-element program and compared with measured data. This paper focuses on a preliminary interpretation of the results from the fully coupled thermohydromechanical modeling of the clay bulkhead and the adjacent rock during heating. Discussion of the issues that will affect the ability to model a field application is provided in the course of comparing simulated and measured results. [ABSTRACT FROM AUTHOR]

Magnetic stimulation is widely used as a medical treatment for neurological diseases. A reduction in the size of magnetic stimulation devices is desirable, however, because the coils are relatively large compared with electrode stimulation devices. Furthermore, in transcranial magnetic stimulation, the exact magnetically evoked areas in the brain and the mechanisms of neural activation are largely unknown. This study aimed to develop a new implantable microcoil device that stimulates the brain locally, on the order of several tens of micrometers, as well as to understand the mechanisms of micromagnetic stimulation‐induced neural activity. First, to investigate the effects of microcoil shape on neural activation, the induced electric fields of semicircular microcoils with different diameters were calculated numerically in a microcoil model using the standard finite element method. Next, on the basis of the obtained numerical results from the microcoil model with different diameters, we compared the spatial properties of the possible activated areas in neural tissue and examined the most effective microcoil shape for neural activation. Finally, we measured microcoil‐evoked responses using autofluorescent flavoprotein imaging of the mouse brain in vivo, evaluated the validity of our proposed microcoil devices, and discussed possible future improvements for a chronic implant. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Welcome to the first issue of the modified Fluid Dynamics Research (FDR) journal, which is now being published by IOP Publishing on behalf of the Japan Society of Fluid Mechanics. Since its launch in 1986, FDR has become a well-established international journal that publishes theoretical, numerical and experimental studies contributing to the fundamental understanding and application of fluid phenomena. It has also been an invaluable resource for physicists and researchers in engineering interested in problems relevant to the motion of fluids. From 2009, FDR will be edited by a new international Editorial Board, with the strong intention of establishing the journal further and bringing it to a wider audience. In this new-look FDR, which will be published six times per year, readers will find several special sections containing high quality invited reviews and papers written by leading researchers who have been selected by the international Editorial Board. This is in addition to the regular papers on a variety of topical subjects by active researchers in the field. As before, there are no publication charges for standard articles, and now article numbering has been adopted, enabling accepted papers to be published online more quickly, ahead of print publication. In order to maintain a balanced and up-to-date perspective, we welcome feedback from our readers regarding the content of the journal, as well as suggestions for topics to cover and areas to highlight. Finally, I would like to thank our authors, members of the international Editorial Board, and the staff at IOP Publishing for producing this first issue. We hope you will enjoy reading this renewed and exciting journal for the international fluid dynamics community. [ABSTRACT FROM AUTHOR]

The purpose of our study is to (i) investigate the effects of the number of products, product attributes, and prices on consumer confusion, (ii) conduct a numerical analysis to check the robustness of the results, and (iii) present an example of the cell phone market in Japan. Following an ideal point model and embedding the number of products and product attributes, we clarify how these factors affect consumer confusion and purchase probability. We show that as the number of product attributes increases, the choice probability of each product becomes equal, implying that consumer confusion occurs. This result is robust to the introduction of prices as strategic variables. [ABSTRACT FROM AUTHOR]

We performed kinetic studies of the growth of sulfate-reducing bacteria (SRB) indigenous to the water in an oilfield in Japan. The SRB growth was most active in injection water supplemented with ethanol; therefore, the SRB inhabiting the injection water of the reservoir were assumed to grow predominantly by assimilating sulfate and ethanol and generating H2S. Based on this mechanism and the results of incubation experiments in the injection water, we derived numerical models that calculate the growth rate and H2S generation of the SRB under three variables (temperature, sulfate concentration, and ethanol concentration). [ABSTRACT FROM AUTHOR]

Throughout history, large tsunamis have frequently affected the Sanriku area of the Pacific coast of the Tohoku region, Japan, which faces the Japan Trench. Although a few studies have examined paleo-tsunami deposits along the Sanriku coast, additional studies of paleo-earthquakes and tsunamis are needed to improve our knowledge of the timing, recurrence interval, and size of historical and pre-historic tsunamis. At Noda Village, in Iwate Prefecture on the northern Sanriku coast, we found at least four distinct gravelly sand layers based on correlation and chronological data. Sedimentary features such as grain size and thickness suggest that extreme waves from the sea formed these layers. Numerical modeling of storm waves further confirmed that even extremely large storm waves cannot account for the distribution of the gravelly sand layers, suggesting that these deposits are highly likely to have formed by tsunami waves. The numerical method of storm waves can be useful to identify sand layers as tsunami deposits if the deposits are observed far inland or at high elevations. The depositional age of the youngest tsunami deposit is consistent with the AD 869 Jogan earthquake tsunami, a possible predecessor of the AD 2011 Tohoku-oki tsunami. If this is the case, then the study site currently defines the possible northern extent of the AD 869 Jogan tsunami deposit, which is an important step in improving the tsunami source model of the AD 869 Jogan tsunami. Our results suggest that four large tsunamis struck the Noda site between 1100 and 2700 cal BP. The local tsunami sizes are comparable to the AD 2011 and AD 1896 Meiji Sanriku tsunamis, considering the landward extent of each tsunami deposit. [ABSTRACT FROM AUTHOR]

In light of the disastrous the 2011 Tohoku Pacific Earthquake, the government of Japan has conducted studies to revise the seismic design code, and elevated peak ground accelerations have been adopted. Consequently, revisions on existing design to comply with the updated code are required for public projects that are still undergoing. The design safety needs to be reassessed, and implementation of strengthening measures is required if deemed necessary. For liquefaction countermeasures, ground treatment techniques that could increase the density of soils are often the preferable alternatives. The treatment usually increases the in situ SPT-N or CPT-q values, which in turn would increase the resistance of soil against liquefaction. For many public infrastructures in Japan supported by bored piles embedded partly or entirely in sandy soils, reevaluation of design safety against soil liquefaction would be required. In an assessment of possible retrofitting countermeasures for an infrastructure foundation, ground treatment has been considered. In this case study, effect of ground treatment on response of piles in liquefiable soils was investigated with numerical analyses using FLAC. Results provide insights into this ground treatment effect and useful information for consideration in future design or decision making. [ABSTRACT FROM AUTHOR]