The aerospace community has long studied active flutter control. Recently, a novel idea, which is energy harvesting from wing vibration under the assumption that a certain magnitude of vibration is allowed, has been attracting attention. The balancing problem between piezoelectric energy harvesting and active control is an active research topic. In our previous work, we developed a coupled analysis system for active control of piezoelectric–structure–fluid interaction problems. In the present study, we integrate a piezoelectric energy harvester model. With numerical examples, we considered the limit cycle oscillation (LCO) of a cantilevered beam in an axial flow. Then, we showed that LCO suppression was achieved while the energy scavenged by harvesters was at least as much as the energy consumed by the active control.
This paper presents the machine learning-based detection of foreign metal object for the wireless power transfer device including differential coils. To test the proposed method, the differential voltages are computed using finite element method for about 1500 cases with and without an aluminum cylinder at driving frequency of 85 kHz considering misalignment between the primal and secondary coils. It has been shown that gradient boosting decision tree and random forests classifier have the accuracy over 90% when input voltages and differential voltages are inputted together.
This study presents the evaluation results of the validity of the visualization map of the ambient dose rate at 1 m above the ground level using an artificial neural network. The dose rate map created using the artificial neural network-based method is found to reproduce ground-based survey results better than conventional methods. Suggested to improve the validity of the airborne radiation survey visualization, applying the color data obtained using a photogrammetry system is a new experience.
This paper describes a method for measuring the ac resistance of sending and receiving coils during wireless power transfer. This method focuses on the ratio of the input voltage to the coil current. The coil resistances measured by this method were compared with the calculated values obtained by finite element analysis. Further, the validity of the measurement and calculation for the coil constants were examined by solving simultaneous equations for sending and receiving coil current for an equivalent circuit for a wireless power transfer system and obtaining the input and output power and power transfer efficiency.
Photonic crystals are widely employed in industry fields due to their bandgap property, which can confine and propagate electromagnetic waves inside the structure as a photonic waveguide. As this property can be adopted to propagate distinct frequency waves by changing the photonic structure, photonic crystals are also applied in frequency demultiplexer design. The finite-difference time-domain (FDTD) method is commonly applied to simulate electromagnetic wave propagations in photonic crystals, helping determine the desired bandgaps for frequency demultiplexers. Meanwhile, the multivariate empirical mode decomposition (MEMD) nonlinearly decomposes multivariate signals in the instantaneous frequency domain. Therefore, MEMD can verify and visualize the designed frequency demultiplexer made of photonic crystals by considering simulation results as a multi-channel signal. This research aims to propose a method to design and evaluate frequency demultiplexers using FDTD and MEMD. In this paper, photonic crystal bandgaps are adopted to design a frequency demultiplexer to separate two different frequency electromagnetic waves. Then, MEMD is employed to the result of frequency demultiplexer propagation simulated by FDTD. Our results reveal that the frequency demultiplexer made of photonic crystals can be designed using the bandgap properties, and its simulation results by FDTD method can be verified and visualized in the instantaneous frequency domain using MEMD.
A wavelet Galerkin method (WGM) is presented to analyze mechanical behaviors of 3D elastic solids. A set of linear B-spline scaling/wavelet functions is employed as the basis functions. The wavelet bases have a nature of multiresolution analysis (MRA). The MRA property works well in the WGM to control spatial resolution of the model. Steep gradients of physical values in stress concentration region can be refined by superposing the higher resolution wavelet functions onto the low resolution bases. Since the linear B-spline wavelet function do not have so-called Kronecker delta property, a special treatment is required to handle the essential boundary conditions (BCs). In this study, applicability of the penalty method and multiple point constraint technique are studied for the BC enforcements in the 3D solid mechanics problems. Accuracy and effectiveness of the presented approach are examined through several numerical examples.
This paper presents various experimental scalograms of electrocardiograms (ECG) from which the accuracy of discrimination between shockable and non-shockable arrhythmia is improved. To derive the scalograms, for the ECG signals the Gabor wavelet transform, having the various pseudo-differential operator like operators, is applied. Also, for the transformed signals, several nonlinear transforms by means of nonlinear functions are performed. These scalograms are analyzed by the normalized spectrum index (NSI) to find the statistical characteristics, and then the qualitative evaluation is performed to select the best pair of pseudo-differential operator and nonlinear function. Through the best pair selected, a good discrimination performance in the decision algorithm is guaranteed. The histogram is used in the decision stage to distinguish the shockable and non-shockable arrhythmia.
The purpose of this paper is to verify the effectiveness of Model Following Servo Control (MFSC) as a stabilizing control measure for systems with uncontrollable disturbances. Both the gravity compensation control system of the 1-link manipulator and the head-position control system of the two-wheeled robot is designed. In gravitational compensation control, gravitational acceleration is defined as an uncontrollable state. In the head-position control, the frictional force in the axial direction of the skidding wheel is defined as an uncontrollable state. The effectiveness of the MFSC as a stabilizing control system for systems containing uncontrollable states is verified via numerical simulations.
In order to miniaturize an antenna mounted on mobile devices, the platform excitation has been studied. In this paper, the novel excitation method for the metal plate with 100 mm × 50 mm is proposed. For the platform excitation, characteristic mode analysis (CMA) is used to clarify the current distribution. The planar folded dipole antenna is employed to excite the current distributions on the metal plate which is obtained by CMA. We verify the validation of the proposed method by simulation and measurement. As a result, the measured results are in good agreement with the simulated results and the maximum actual gain of 4.3 dBi is obtained at 2.45 GHz.
In this paper, the recent progress of computing singular values of a generalized tensor sum is described. To be specific, the already-known algorithms are classified into three groups: to compute the maximum and minimum singular values, the minimum singular values only, and an arbitrary singular value. All the algorithms are constructed over tensor space, leading to largely memory-efficient. Among them, regarding the speed of convergence, the algorithm for maximum and minimum singular values still has room to be improved for non-symmetric generalized tensor sum by some suitable choices of the initial guess. Considering the tensor structure of the initial guess, we experimentally show that some new initial guesses are efficient for computing the maximum and minimum singular values.
Atoms moving in an optical vortex beam are subjected to the azimuthal Doppler effect in addition to the usual longitudinal Doppler effect. This fact extends the capabilities of plasma flow measurement using laser-induced fluorescence to the direction perpendicular to the laser path by employing optical vortex beams. Furthermore, by assuming a uniform flow traversing the beam, the LIF spectrum undergoes deformation due to the spatial dependence of the resonant absorption condition. Preliminary experiments were performed for metastable argon ions in the vicinity of a negatively biased electrode immersed in a plasma. An increase in the standard deviation of the spectrum was observed when a negative voltage was applied to the electrode, which qualitatively agrees with our previous numerical study.
The stability of DNA double-stranded structure is examined by pulling atoms using steered molecular dynamics simulations. We use the base sequence to which DNA helicase binds; it acts to separate a double-stranded chain into single-stranded ones. The force is applied to atoms in the middle of the strand and they are pulled perpendicular to the helical axis of DNA. The force profile basically corresponds to the fraction of Watson-Crick hydrogen bonds which shows jumps and plateaus. The work for double-stranded separation can be interpreted in conjunction with the way to break hydrogen bonds. When some hydrogen bonds are broken at once, the bigger force is needed, and it leads to morework.
This study proposes a computational method for gas-particle flows with large temperature variations. To efficiently accelerate fully explicit computations of low-Mach-number compressible flows, we use the reduced speed of sound technique for the fractional step method. The direct-forcing fictitious domain method is implemented to perform flow calculations on Eulerian grids in Cartesian coordinates. The proposed method is applied to two types of numerical experiments: single particle sedimentation and multiple particle transport in natural convection. The numerical results demonstrate that the proposed method can reasonably calculate mechanical and thermal interactions between particles and gas flows with large temperature variations.
A plasma fluid model based on the anisotropic ion pressure (AIP model) is applied to a GAMMA 10/PDX configuration and the fundamental physics regarding the ion pressure anisotropy is studied by examining various patterns of anisotropic ion heating. It is demonstrated that plasmas accompanied by highly anisotropic ion temperature plus sonic transitions can be successfully solved with AIP model. It is also shown that treating the anisotropic ion pressure can facilitate the understanding of the behavior of high temperature plasmas in inhomogeneous magnetic fields compared to a conventional model dealing with the isotropic ion pressure (the Braginskii's equations).
The goal of this study is to establish a simple experimental system to examine the rate of double strand breaks (DSBs) of genome-sized DNA molecules under irradiation of β-rays from tritium under well-controlled conditions for the validation of computer simulation on interactions of biomolecules and ionizing radiation. Irradiation effects were insignificant at tritium concentration of 1300 Bq/cm3, indicating that the effects of β-rays were far smaller than those of oxidation and/or thermal motion at the low dose rate (4.3 μGy/h). Clear increase in DSB rate was observed at tritium concentrations of 3.0—4.0 MBq/cm3. The temperature dependence of DSB rate was examined by using the high concentration tritiated water.
Herein, a cylindrical cloak based on the arrangement density control of multilayer ceramic capacitors (MLCCs) is proposed. The unit cell structure is designed by locating an MLCC between two dielectric substrates. By adjusting the period length of the unit cell structure, the effective permeability of the unit cell can be controlled, thereby enabling the design of the cylindrical cloak. The cylindrical cloak using MLCCs is fabricated and measured in this study. The validity of the simulation results is confirmed by comparing them with the measured results.