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In electromagnetic compatibility (EMC) design, it is important to mitigate the dominant effect among those caused by many unintentional parasitic elements or couplings. However, the dominant effect is usually unclear and hence EMC engineers often resort to trial and error to find an effective counterplan. This paper presents an approach for aiding engineers in finding a better design plan using topology optimization, which is a simulation-based structural optimization method. The proposed approach is applied to the conductor pattern design in simple circuits of electromagnetic interference filters, in which the dominant effect is conduction or induction noise depending on the circuit parameters. It is demonstrated that a structure with a reduced dominant effect is obtained automatically, and the utilization of the optimized result for EMC design is also discussed.

We propose a novel framework based on multi-fidelity design optimization for indirectly solving computationally hard topology optimization problems. The primary concept of the proposed framework is to divide an original topology optimization problem into two subproblems, i.e., low- and high-fidelity design optimization problems. Hence, artificial design parameters, referred to as seeding parameters, are incorporated into the low-fidelity design optimization problem that is formulated on the basis of a pseudo-topology optimization problem. Meanwhile, the role of high-fidelity design optimization is to obtain a promising initial guess from a dataset comprising topology-optimized design candidates, and subsequently solve a surrogate optimization problem under a restricted design solution space. We apply the proposed framework to a topology optimization problem for the design of flow fields in battery systems, and confirm the efficacy through numerical investigations.

Topology optimization, a simulation-based optimization technique to mathematically derive an optimal structure, is applied to the conductor design of an inductance cancellation structure to reduce common-and differential-mode noise. The design of an appropriate conductor pattern for an inductance cancellation structure is difficult due to the unintentional magnetic couplings between the multiple loops mounted to cancel the parasitic inductances of X and Y capacitors. In topology optimization, this design problem is formulated as an optimization problem and an optimal structure is obtained by repeated modification of the conductor pattern using mathematical programming. The performance of circuit boards before and after optimization is evaluated using mixed-mode s-parameters. Both simulation and experimental measurement verify that the effect of inductance cancellation is improved by this optimization.

Environments along the coast of Greenland are rapidly changing under the influence of a warming climate in the Arctic. To better understand the changes in the coastal environments, we performed researches in the Qaanaaq region in northwestern Greenland as a part of the ArCS (Arctic Challenge for Sustainability) Project. Mass loss of ice caps and marine-terminating outlet glaciers were quantified by field and satellite observations. Measurements and sampling in fjords revealed the important role of glacial meltwater discharge in marine ecosystems. Flooding of a glacial stream in Qaanaaq and landslides in a nearby settlement were investigated to identify the drivers of the incidents. Our study observed rapid changes in the coastal environments, and their critical impact on the society in Qaanaaq. We organized workshops with the residents to absorb local and indigenous knowledge, as well as to share the results and data obtained in the project. Continuous effort towards obtaining long-term observations requiring involvement of local communities is crucial to contribute to a sustainable future in Greenland.

In this paper, we propose grayscale-free topology optimization for a reactor design problem where the electromagnetic performance needs to be optimized. A reactor is an electric device to boost electric voltage, and is used as a part of a DC-DC converter in electric and hybrid vehicles. When designing reactors, we need to consider many performance indicators such as inductance and fringing loss. In general, high-performance reactor design that satisfies all requirements is not obvious, and topology optimization is promising for such non-trivial design problems. In this paper, we therefore establish a framework for the electromagnetic design of an in-vehicle reactor on the basis of boundary tracking type level-set topology optimization, which realizes grayscale-free topology optimization. Because of its grayscale-free characteristic, the established framework can completely resolve the numerical problems caused by the so-called grayscale elements. We present several numerical examples to demonstrate the usefulness of the established framework, and we discuss the possibilities for the expansion of the established framework to more difficult and valuable design problems.

Orthotropic elastic moduli of composite structures can be identified by nonlinear least squares fit between measured and computed natural frequencies. However, due to measurement errors contained in the measured natural frequencies and mode shapes, the process of elastic moduli identification is error-prone. This paper proposes an efficient method to estimate the errors in the elastic moduli caused by the measurement errors in the natural frequencies. The method utilizes an efficient semi-analytic expression of the sensitivities of the eigenvalues with respect to the orthotropic elastic moduli. First, the first-order approximation of the analytic sensitivity of orthotropic elastic moduli with respect to the measurement errors is introduced. The approximation is then used to estimate the variability of the identified elastic moduli due to the measurement errors. It is shown that the aspect ratio of the test specimen greatly affects the standard deviation of the identified elastic moduli. Second, using the first-order approximation, the effects of aspect ratio of the test specimen as well as the values of the elastic moduli are further investigated. Based on the results of numerical experiments, guidelines for the dimension of the test specimen for the elastic moduli identification are proposed.

In this paper, a combined numerical–experimental methodology for the identification of elastic moduli of orthotropic media is presented. Special attention is given to the laminated electrical steel sheets, which are modeled as orthotropic media with nine independent engineering elastic moduli. The elastic moduli are determined specifically for use with finite element vibration analyses. We propose a three-step methodology based on a conventional nonlinear least squares fit between measured and computed natural frequencies. The methodology consists of: (1) successive augmentations of the objective function by increasing the number of modes, (2) initial condition updates, and (3) appropriate selection of the natural frequencies based on their sensitivities on the elastic moduli. Using the results of numerical experiments, it is shown that the proposed method achieves more accurate converged solution than a conventional approach. Finally, the proposed method is applied to measured natural frequencies and mode shapes of the laminated electrical steel sheets. It is shown that the method can successfully identify the orthotropic elastic moduli that can reproduce the measured natural frequencies and frequency response functions by using finite element analyses with a reasonable accuracy.

In this paper, we report design and characteristics of a compact and low-loss multicast switch (MCS) based on a high Δ planar lightwave circuit (PLC) which consists of ZrO2 doped silica glass. Chip size of an 8 × 8 MCS consists of an eight-arrayed 1 × 8 splitter and an eight-arrayed 8 × 1 switch is reduced to 30 mm × 9 mm by using the ZrO2-SiO2 PLC with 5.5%-Δ. Eight-input and eight-output ports of the MCS are arrayed at the one side of the chip, and coupled to optical fibers with a 16-fiber V-groove array. A high Δ fiber is used to reduce coupling loss to the ZrO2-SiO2 PLC, and the high Δ fiber is spliced to a single-mode fiber (SMF) by using low-loss splicing technique. Coupling loss between the ZrO2-SiO2 PLC and the SMF is reduced to 0.4 dB/facet. Average insertion loss of the fabricated MCS is 12.8 dB including coupling loss to the SMF. Extinction ratio and polarization dependent loss of the MCS are over 50 dB and less than 0.5 dB in L-band, respectively.

In the High Arctic, recent acceleration of geomorphological processes is having extreme impact on archaeological landscapes. In this paper, we consider implication for circumpolar archaeology, and focus analysis on a study area of critical importance to the local Inughuit community at Siorapaluk – a small settlement in Northwest Greenland. Using a combination of ground survey, historical satellite images, and Geographic Information Systems (GIS), we analyze damage zones to understand the character, timing, and extent of destruction. Three types of geomorphological processes are identified as causing significant damage, including: 1) debris flows, 2) active-layer detachment slides, and 3) alluvial deposition. These processes, we demonstrate, were amplified by extraordinary rainfall events that took place in the summers of 2016 and 2017 against a backdrop of broader climate change induced shifts in arctic precipitation. Further instability in the amount and seasonality of precipitation can be expected, and archaeological consequences will expand to areas that have so far been unaffected. The scale of mass movement that we document may be unprecedented in terms of the landscape’s post-glacial development, and likely represents the onset of a new state in erosional maturity. We use our results to suggest criteria that can help predict and identify areas most at risk, which will be a critical component of prioritizing response measures. The suddenness through which mass movement went from background threat to primary destructive process makes the case of Siorapaluk relevant to archaeologists working in periglacial landscapes worldwide.

Vanadium redox flow battery (VRFB) is a rechargeable battery, which has attracted attention as a next-generation electrochemical energy storage system. It is widely known that achieving high performance in terms of power density is critical for the commercialization of VRFBs. The aim of this paper is to propose a computational design approach for automatically generating an optimized flow field design of a VRFB to achieve high performance without relying on the designer’s intuition. To realize this, we focus on generating a freeform configuration of the flow field in a VRFB via topology optimization, which is known as a powerful design tool that is based on numerical optimization. In this study, to improve the mass transfer effect in a VRFB, we formulate the topology optimization problem as a maximization problem of the electrode surface concentration in the negative electrode during the charging process. We demonstrate through numerical investigation that a topology-optimized flow field can be obtained. As a result, it is revealed that the interdigitated flow field is an optimal flow field of the VRFB under the investigated operating conditions.

We report a low-loss connecting technique between silicon waveguides and standard single-mode fibers using a unique extremely-high-Δ silica-based PLC. 32-port coupling with coupling losses of 1.4∼1.6 dB/facet and pitch conversion has been demonstrated.

This paper presents an optimization method for the design of permanent magnet synchronous motor (PMSM) rotor considering a yoke structure and a permanent magnet (PM) layout. PMSM rotor is composed of the yoke and PMs, whose designs greatly influence the PMSM performance. There was a problem in conventional PMSM optimal design method that an obtained PM shape becomes complex. Therefore, the layout of PM with a specific shape is optimized in this study. The topology optimization is applied to the yoke structural optimization. To incorporate the yoke topology and the PM layout optimization problems into the PMSM rotor design problem, it is necessary to correlate those solutions during the optimization process. However, it is difficult to solve those problems simultaneously or individually because of those problems being connected strongly. In order to address the issue, response surface methodology is employed to combine the yoke topology optimization problem and the PM layout optimization problem by focusing on a hierarchy of problems. The effectiveness of the proposed method is shown by a numerical example.

The aim of this research is to reduce the amount of high frequency noise propagating through space in a low-pass filter. Generally, high frequency noise is generated from power electronics equipment that is responsible for converting direct current and alternating current in hybrid cars. A device consisting of capacitors and inductors called the low-pass filter is used for absorbing the high frequency noise. Ideally, the low-pass filter absorbs more noise as its frequency is higher, but in practice, the noise absorption rate decreases beyond a certain frequency. This is because of the following reasons. The magnetic flux is generated from a current loop in the circuit according to Ampere’s circuital law. Then, this magnetic flux causes high frequency noise at the output terminal according to Faraday’s law of induction. This phenomenon is called magnetic coupling. The amount of noise that appears at the output terminal depends on the layout of the conductor on the circuit board. Conventionally, designers reduced the area of the current loop to avoid the influence of magnetic coupling. However, it was difficult for them to quantitatively predict the influence and design the conductor pattern optimally. In contrast, a topology optimization method is valid for obtaining a mathematically evident optimal structure. Topology optimization method usually allows grayscale area, which holds intermediate density value. For the conductor layout problem, it is difficult to appropriately set the current conductivity to the intermediate material density, and this possibly causes a computational error. For these reasons, we propose a grayscale-free topology optimization method for the conductor layout that minimize the influence of the magnetic coupling. Several numerical examples are provided to confirm that the appropriate optimal structures are obtained.

In this paper, topology optimization is applied to the design of power semiconductor devices. The doping density distribution of power semiconductor devices is optimized using a density-based topology optimization method. The density method is suitable for the design of power semiconductor devices because doping density can take on continuous values and is intrinsically free from the gray-scale problem. To verify the effectiveness of topology optimization, optimization was conducted for two types of two-dimensional design problems. At first, optimization of a p-n diode was performed to improve the trade-off between the breakdown voltage and on-resistance. This is formulated as a single-objective optimization problem with the Kreisselmeier-Steinhauser (KS) objective function of the electric field, which indicates the breakdown voltage characteristics, under the constraint of the on-resistance. By optimization, a p-i-n diode, which is a well-known diode structure, is obtained and the trade-off is improved. Next, optimization of an edge termination structure was performed to improve the breakdown voltage characteristics with the consideration of ion implantation, which is one of the fabrication processes used for semiconductor devices, under the process variation. The optimized structure obtained is ensured to be manufacturable and more robust with respect to the dose amount variation of ion implantation than the initial structure. These results demonstrate the effectiveness of topology optimization for the design of power semiconductor devices.

We investigated submerged ruins from the 1923 Nebukawa landslide, which was caused by the 1923 Kanto earthquake. The on-land areas affected by the landslide have been restored and evidence of the landslide is mostly gone, but huge structures that appear to be man-made have been observed by divers on the seafloor near the area of the landslide. We used a fish finder designed for leisure use and other low-cost equipment to conduct a marine acoustic survey. Because the affected area off Nebukawa is close to shore and shallow and the tools were sufficiently lightweight, we were able to use an inflatable raft for the survey. We created a bathymetric map and side-scan images showing features of the landslide mass and scattered huge structures exposed on the seafloor. After the acoustic investigations, we conducted a diving investigation and were able to ascertain that the structures were made of concrete and were most likely parts of the old Nebukawa station. The ruins were displaced about 260 to 320 m horizontally from the original station location (to 110–170 m offshore) and were mixed with coarse rock fragments from the landslide mass. The distribution of bottom materials suggests that the landslide struck the seafloor and then traveled as far as 460 m offshore from the coastline. The landslide had an equivalent coefficient of friction (H/L) of about 0.15, indicating high mobility. The landslide probably transformed into a turbulent flow mixed with basal sandy sediments, which propelled the debris farther offshore.

A general topology optimization method, which is capable of simultaneous design of density and orientation of anisotropic material, is proposed by introducing orientation design variables in addition to the density design variable. In this work, the Cartesian components of the orientation vector are utilized as the orientation design variables. The proposed method supports continuous orientation design, which is out of the scope of discrete material optimization approaches, as well as design using discrete angle sets. The advantage of this approach is that vector element representation is less likely to fail into local optima because it depends less on designs of former steps, especially compared with using the angle as a design variable (Continuous Fiber Angle Optimization) by providing a flexible path from one angle to another with relaxation of orientation design space. An additional advantage is that it is compatible with various projection or filtering methods such as sensitivity filters and density filters because it is free from unphysical bound or discontinuity such as the one at theta = 2 pi and theta = 0 seen with direct angle representation. One complication of Cartesian component representation is the point-wise quadratic bound of the design variables; that is, each pair of element values has to reside in a given circular bound. To overcome this issue, we propose an isoparametric projection method, which transforms box bounds into circular bounds by a coordinate transformation with isoparametric shape functions without having the singular point that is seen at the origin with polar coordinate representation. A new topology optimization method is built by taking advantage of the aforementioned features and modern topology optimization techniques. Several numerical examples are provided to demonstrate its capability. Copyright (C) 2014 John Wiley & Sons, Ltd.

In this paper, the effects of compaction method on deformation and strength properties of asandy soil were examined by means of triaxial and unconfined compression tests and bender element test. AX-ray CT scan was also employed for providing us with image of structure of two sandy soils (n.b., sample Aand B). The undrained shear strength and dilatancy characteristics were seemingly affected by thecompaction method employed, and also the aspect depended on the soil type. The Ghh/Gvh -value of sample Awas larger than that of sample B. The result would mean that the Ghh/Gvh -value reflecting soil anisotropy isstrongly related to the shear strength and dilatancy characteristics. In addition, the variation of d and Dc ofthe statically compacted specimens is more significant than that of the dynamically compacted specimens.These variations in terms of d and Dc may also affect the deformation and strength characteristics.

We developed a PBS-integrated coherent mixer using a ZrO2-SiO2 PLC. Small chip size of 2.3mm×7.0mm, low insertion loss of 7.7dB and 10.3dB for signal and LO ports, and high polarization extinction ratio of more than 20dB are achieved.

A circuit clot is one of the most frequent complications during extracorporeal membrane oxygenation (ECMO) support. We identify coagulation/fibrinolysis markers for predicting ECMO circuit exchange because of circuit clots during ECMO support. Ten patients with acute pulmonary failure who underwent veno-venous ECMO were enrolled between January 2014 and December 2016. ECMO support lasted 106 days. The 6 days on which the ECMO circuits were exchanged were considered as circuit clot (+) group, while the remaining 100 days were considered as circuit clot (−) group. The predictors of ECMO circuit exchange because of circuit clots were identified. The mean duration of ECMO support was 10 ± 13 days, and the mean number of ECMO circuit exchange was 0.6 ± 1.1 times per patient. Thrombin-antithrombin complex (TAT) and soluble fibrin (SF) were higher in the circuit clot (+) group than in the circuit clot (−) group (both P

Personal robot is a new technological solution where various IoT machines collaborate and provide new type of services. In this research, we develop a cloud-network based personal robot platform technologies, which offer advanced IoT services through its cost-effective strategy. As for the man-machine interaction, two stage dialog system was implemented, i.e. local side and the cloud server side. Also the cloud server has an ability to download various IoT applications. In this study, we tested the proposed system using smartphone as one of the IoT devices using data retrieval application. Our preliminary usability test showed good overall performance, however, we found that the interaction timing needs to be improved.

We examined whether AN69ST (acrylonitrile and methallyl sulfonate copolymer) membranes adsorb nafamostat mesilate. This study retrospectively analyzed 87 continuous hemodiafiltration sessions in vivo. We divided the continuous hemodiafiltration sessions into AN69ST and non-AN69ST groups using the nafamostat mesilate dose and activated clotting time as indicators of nafamostat mesilate adsorption onto the membrane. Furthermore, we studied the in vitro adsorption of nafamostat mesilate from nafamostat mesilate solutions onto four different hemodialysis membranes. This in vivo study shows that nafamostat mesilate doses were significantly higher, but activated clotting times were shorter (P0.001) in the AN69ST group than in the non-AN69ST group. These results suggest that AN69ST adsorbs nafamostat mesilate. Further, the in vitro experiments show that nafamostat mesilate adsorbs AN69ST on membranes significantly more than the other membranes tested. These in vitro and clinical findings provide evidence that AN69ST may adsorb nafamostat mesilate.

Summary This paper proposes a level-set based topology optimization method incorporating a boundary tracking mesh generating method and nonlinear programming. Because the boundary tracking mesh is always conformed to the structural boundary, good approximation to the boundary is maintained during optimization; therefore, structural design problems are solved completely without grayscale material. Previously, we introduced the boundary tracking mesh generating method into level-set based topology optimization and updated the design variables by solving the level-set equation. In order to adapt our previous method to general structural optimization frameworks, the incorporation of the method with nonlinear programming is investigated in this paper. To successfully incorporate nonlinear programming, the optimization problem is regularized using a double-well potential. Furthermore, the sensitivities with respect to the design variables are strictly derived to maintain consistency in mathematical programming. We expect the investigation to open up a new class of grayscale-free topology optimization. The usefulness of the proposed method is demonstrated using several numerical examples targeting two-dimensional compliant mechanism and metallic waveguide design problems. Copyright © 2014 John Wiley & Sons, Ltd.

Electrostatic actuators, actuators actuated by electrostatic forces, are now widely used as sensors and switches, especially in Micro-Electro-Mechanical Systems (MEMS). Among different kinds of electrostatic actuators, the comb drive type is one of the most popular because it has a relatively large range of displacement. In design problems for electrostatic actuators, the driving force profile is of primary engineering importance. In this paper, we develop a structural optimization method for comb drive electrostatic actuators that achieves prescribed driving force profiles, based on a level set-based shape optimization method that provides optimal configurations with clear boundaries, solutions that are valid in an engineering sense. Accurate calculation of the electrostatic forces that occur on the structural boundaries during optimization is important for developing actuators that operate with prescribed driving forces. In the conventional level set-based shape optimization methods, inaccuracies in the calculation of these electrostatic forces occur because the structural boundaries are seldom aligned with the finite element method (FEM) nodes. To precisely calculate the electrostatic forces, we developed a mesh adaptation scheme by which the finite element nodes are brought into alignment with the structural boundaries at every iteration of the optimization procedure. In the following, we explain the details of the proposed level set-based shape optimization method, in which a multi-objective optimization problem is formulated to achieve a prescribed driving force profile. The sensitivity is derived using the adjoint variable method. Four numerical examples are provided, to examine the suitability of the proposed optimization method.

This paper deals with structural optimization for designing periodic structures in a hole array wavelength filter. The hole array wavelength filter that consists of metallic thin film and dielectric enables to transmit narrow bandwidth light. It is known that transmission spectrum can be changed not only by the periodicity of hole array but also by the shape of holes. For optimizing the hole shape, the level set method is used in this study. In the ordinary level set method, the boundaries are implicitly expressed by the zero level set of a scalar function, called the level set function, within a fixed mesh. Therefore, the material interpolation becomes numerically awkward within the elements across the implicit zero level set because those elements inevitably take on intermediate material properties even if the boundary of zero level set are mathematically clear. As the result, the optimization is likely to yield wrong solution. Here, a new level set optimization method incorporating Arbitrary Lagrangian Eulerian method is proposed to eliminate intermediate values on the interfaces perfectly. As a result, the proposed method can successfully perform the structural optimization of hole shape without intermediate values.

This paper presents a novel winglet design of a fin-and-tube heat exchanger, and its performance regarding heat transfer enhancement is numerically investigated. In this study, the fin pattern is designed considering the shape, arrangement, and number of the winglets, because a higher degree of freedom for the structural design results in further improvement of the performance. To obtain promising features for the winglet design, topology optimization is applied in a simplified model that incorporates key factors of the physical phenomena. The optimization problem is formulated as a maximization problem of the heat extraction by the winglets in a two-dimensional simplified model under lowered Reynolds number flows. The optimized configurations are evaluated via three-dimensional high-fidelity analyses to obtain a promising design candidate. A manufacturable fin pattern is then designed from the promising candidate. The results indicate that the gradually curved winglets along the flow can enhance the heat transfer at a moderate pressure loss. The proposed fin demonstrates up to 16.0% improvement in the quality factor j / f compared with a fin with rectangular winglet pairs.

We analyzed high-quality drill cores with 100% recovery drilled into a gravitationally deformed dip-slope of a shale-dominated sequence of sediments in Japan. The slope had undulating surfaces but no well-defined landslide scarps, suggesting that parts of the slope had undergone gravitational deformation but had not completely separated from the surrounding bedrock. The gravitational deformation of shale and sandstone is characterized by disintegration and brecciation of sediments and the formation of pulverized zones with poorly developed planar structures, jigsaw-like structures, and fracture openings. Shear zones are distributed intermittently within the slope but have not merged discernably into a through-going master sliding surface. Incipient landslide shear zones form openings within coherent rock by shearing along bedding, with these shear zones potentially developing downward in a stepwise manner, which may be related to stress redistribution induced by river incision.

Earthquakes in mountainous areas may produce many landslides that involve abundant snow, but few observations have been made of these hazardous phenomena. The 12 March 2011 north Nagano Prefecture earthquake (MJMA 6.7) occurred in a mountainous part of Japan that typically has an annual snow cover of more than 2 m, and it induced many snowy landslides. Some of these traveled relatively long distances. We examined the snowy Tatsunokuchi landslide to reconstruct the landsliding processes over deep snow. We infer that the Tatsunokuchi landslide occurred by collapse of a rock debris mass of 5 × 104 m3 that plunged into the abundant snow, forming a mixture of snow and rock debris, which then traveled on top of the snow. Later, the displaced mass included a large amount of snow which was pushed forward at the front and to the sides. The velocity of the landslide was estimated to be approximately 14 m/s. It appears that the displaced mass, having only a small proportion of rock debris, had a low enough density to travel easily on top of the snow. Our observations suggest that there was much liquid water at the base of the displaced mass shortly after the event. Our results suggest that landslides may damage wider areas than expected if they travel over deep snow.

Deep-seated landslides in pelitic schists are common in many countries, but are poorly investigated and understood. In this study we present the first detailed examination and modelling of landslide mechanisms in these materials. We found that pelitic schist commonly contains black, graphite-rich layers on a scale of millimeter to centimeter thickness that are typically weaker than neighboring layers. By examining microscopic textures in borehole samples obtained from landslide masses of pelitic schist, we find that ductile gravitational shearing commonly occurs within these weaker layers, accompanied by brittle fracture in the surrounding layers. To investigate these mechanisms, we have performed high-precision direct shear tests, using a novel back-pressured shearbox, on artificial rock samples both with and without graphite layers placed between pre-cut shear surfaces. The tests used normal stresses up to 800 kPa (equivalent to 32 m depth of burial). We found that the coefficients of friction for samples with graphite layers embedded in the artificial rock samples (0.30, representing an angle of internal friction of 16.7°) were much lower than those without graphite layers on the pre-cut surface (0.85). The shear strength of the artificial rocks with embedded layers of graphite decreased abruptly with increasing areal extent of the graphite layer along the shear surface, from which it can be inferred that the continuity of a graphite layer in natural pelitic schist has a considerable effect on shear resistance. These results suggest that even comparatively low dip angles of schistosity in pelitic schist could initiate microscopic slip along the graphite-rich layers.

SUMMARY In this paper, we propose a new BEM for level-set based topology optimization. In the proposed BEM, the nodal coordinates of the boundary element are replaced with the nodal level-set function and the nodal coordinates of the Eulerian mesh that maintains the level-set function. Because this replacement causes the nodal coordinates of the boundary element to disappear, the boundary element mesh appears to be immersed in the Eulerian mesh. Therefore, we call the proposed BEM an immersed BEM. The relationship between the nodal coordinates of the boundary element and the nodal level-set function of the Eulerian mesh is clearly represented, and therefore, the sensitivities with respect to the nodal level-set function are strictly derived in the immersed BEM. Furthermore, the immersed BEM completely eliminates grayscale elements that are known to cause numerical difficulties in topology optimization. By using the immersed BEM, we construct a concrete topology optimization method for solving the minimum compliance problem. We provide some numerical examples and discuss the usefulness of the constructed optimization method on the basis of the obtained results. Copyright © 2012 John Wiley & Sons, Ltd.

SUMMARY Most topology optimization problems are formulated as constrained optimization problems; thus, mathematical programming has been the mainstream. On the other hand, solving topology optimization problems using time evolution equations, seen in the level set-based and the phase field-based methods, is yet another approach. One issue is the treatment of multiple constraints, which is difficult to incorporate within time evolution equations. Another issue is the extra re-initialization steps that interrupt the time integration from time to time. This paper proposes a way to describe, using a Heaviside projection-based representation, a time-dependent diffusion equation that addresses these two issues. The constraints are treated using a modified augmented Lagrangian approach in which the Lagrange multipliers are updated by simple ordinary differential equations. The proposed method is easy to implement using a high-level finite element code. Also, it is very practical in the sense that one can fully utilize the existing framework of the code: GUI, parallelized solvers, animations, data imports/exports, and so on. The effectiveness of the proposed method is demonstrated through numerical examples in both the planar and spatial cases. Copyright © 2012 John Wiley & Sons, Ltd.

This paper deals with continuum-based compliant mechanism design. In topology optimization, filtering techniques are used for the regularization of the design space. In the density design representation, convolution-type filters inherently produce gray transition regions between solids and voids. In order to reduce the gray transition regions, projection schemes have recently been proposed. Binarization, however, still leads to one-node connected hinges in compliant mechanism design. In this paper, we propose a method that incorporates the level set and arbitrary Lagrangian Eulerian methods so that the gray transition regions are completely excluded and one-node connected hinges are not formed.

Little is known about bacterial dynamics in the oligotrophic ocean, particularly about cultivable bacteria. We examined the abundance of total and cultivable bacteria in relation to changes in biogeochemical conditions in the eastern Atlantic Ocean with special regard to Vibrio spp., a group of bacteria that can cause diseases in human and aquatic organisms. Surface, deep water and plankton (55 µm) samples were collected between 50◦ N and 24◦ S. Chlorophyll-a was very low (99 %) were found in the nanoplankton fraction (

SUMMARY In the last decade, metamaterials have been gaining attention and have been investigated because of their unique characteristics, which conventional materials do not have, such as negative refraction indexes. However, it is sometimes difficult to design metamaterials on the basis of experience and theoretical considerations because the relationship between their electromagnetic characteristics and structure is often vague. A mathematical structural design methodology targeting metamaterials may therefore be useful for expanding the engineering applications of metamaterials in industry. In this paper, a new level set-based topology optimization method is proposed for designing composite right- and left-handed transmission lines, each of which consists of a waveguide and periodically located dielectric resonators. Such transmission lines function as a fundamental metamaterial. In the proposed method, the shape and topology of the dielectric resonators are represented by the level set function, and topology optimization problems are formulated on the basis of the level set-based representation. Copyright © 2011 John Wiley & Sons, Ltd.

In this paper, we propose a level set-based topology optimization method targeting metallic waveguide design problems, where the skin effect must be taken into account since the metallic waveguides are generally used in the high-frequency range where this effect critically affects performance. One of the most reasonable approaches to represent the skin effect is to impose an electric field constraint condition on the surface of the metal. To implement this approach, we develop a boundary-tracking scheme for the arbitrary Lagrangian Eulerian (ALE) mesh pertaining to the zero iso-contour of the level set function that is given in an Eulerian mesh, and impose Dirichlet boundary conditions at the nodes on the zero iso-contour in the ALE mesh to compute the electric field. Since the ALE mesh accurately tracks the zero iso-contour at every optimization iteration, the electric field is always appropriately computed during optimization. For the sensitivity analysis, we compute the nodal coordinate sensitivities in the ALE mesh and smooth them by solving a Helmholtz-type partial differential equation. The obtained smoothed sensitivities are used to compute the normal velocity in the level set equation that is solved using the Eulerian mesh, and the level set function is updated based on the computed normal velocity. Finally, the utility of the proposed method is discussed through several numerical examples. Copyright © 2011 John Wiley & Sons, Ltd.

We present a design optimization method of H-plane waveguide components, based on the level set method with the finite element method. In this paper, we propose a new formulation for the improvement of a level set function, which describes shape, location, and connectivity of dielectric in a design region. Employing the optimization procedure, we demonstrate that optimized structures of an H-plane waveguide filter and T-junction are obtained from an initial structure composed of several circular blocks of dielectric. We present a design optimization method of H-plane waveguide components, based on the level set method with the finite element method. In this paper, we propose a new formulation for the improvement of a level set function, which describes shape, location, and connectivity of dielectric in a design region. Employing the optimization procedure, we demonstrate that optimized structures of an H-plane waveguide filter and T-junction are obtained from an initial structure composed of several circular blocks of dielectric.