Kumi Nakai 교수

The problem of selecting an optimal set of sensors estimating a high-dimensional data is considered. Objective functions based on D-, A-, and E-optimality criteria of optimal design are adopted to greedy methods, that maximize the determinant, minimize the trace of the inverse, and maximize the minimum eigenvalue of the Fisher information matrix, respectively. First, the Fisher information matrix is derived depending on the numbers of latent state variables and sensors. Then, a unified formulati

In this study, a nondominated-solution-based multi-objective greedy method is proposed and applied to a sensor selection problem based on the multiple indices of the optimal design of experiments. The proposed method simultaneously considers multiple set functions and applies the idea of Pareto ranking for the selection of sets. Specifically, a new index is iteratively added to the nondominated solutions of sets, and the multi-objective functions are evaluated for new sets. The nondominated solu

A discharge plasma simulation based on a three-fluid model is generally utilized to understand the physical mechanism in a dielectric barrier discharge (DBD) plasma actuator. In this study, the influence of chemical reactions considered in a numerical model on the simulation results is investigated from the viewpoint of electrohydrodynamic (EHD) force generation in the DBD plasma actuator. Positive and negative streamers are simulated utilizing three types of models considering different reactio

The validity of numerical modeling of discharge plasma in dielectric barrier discharge plasma actuator is evaluated by comparing the simulation and experimental results under the same conditions. Discharge plasma behavior is numerically simulated based on a three-fluid plasma model. Regarding the induced jet structure, although the simulation tends to underestimate the jet thickness and overestimate the maximum velocity, the discrepancies are small considering the quite simple modeling. In addit

SUMMARY The ‘big’ seismic data not only acquired by seismometers but also acquired by vibrometers installed in buildings and infrastructure and accelerometers installed in smartphones will be certainly utilized for seismic research in the near future. Since it is impractical to utilize all the seismic big data in terms of the computational cost, methods which can select observation sites depending on the purpose are indispensable. We propose an observation site selection method for the accurate

Tri-electrode plasma actuators (TED-PAs) can induce a stronger jet than that of conventional two-electrode plasma actuators (DBDPAs). For practical application of a TED-PA, it is significant to develop a TED-PA engineering model for implementing CFD simulations. In this study, we model the body force distribution generated by a TED-PA utilizing the Suzen model, which is one of engineering models used for DBDPAs. First, we define a function to describe the charge distribution profile on the diele

In this study, a nondominated-solution-based multi-objective greedy method is proposed and applied to a sensor selection problem based on the multiple indices of the optimal design of experiments. The proposed method simultaneously considers multiple set functions and applies the idea of Pareto ranking for the selection of sets. Specifically, a new index is iteratively added to the nondominated solutions of sets, and the multi-objective functions are evaluated for new sets. The nondominated solu

A discharge plasma simulation based on a fluid model is carried out in order to investigate the effect of chemical reactions considered in the model on the reproducibility of electrohydrodynamic (EHD) force generation and gas heating processes in dielectric barrier discharge (DBD) plasma actuator. Single micro-discharges with positive and negative polarities are simulated utilizing two models with different reactions: simple model considering typical 6 reactions and model considering recombinati

The ``big'' seismic data not only acquired by seismometers but also acquired by vibrometers installed in buildings and infrastructure and accelerometers installed in smartphones will be certainly utilized for seismic research in the near future. Since it is impractical to utilize all the seismic big data in terms of the computational cost, methods which can select observation sites depending on the purpose are indispensable. We propose an observation site selection method for the accurate recons

A three-fluid plasma model, in which the electron, one type of positive ion and one type of negative ion are considered as plasma particles is generally utilized to understand the underlying physics in DBD plasma actuator. In this study, a parametric study is conducted to investigate the effect of plasma particles and reactions in numerical modeling on the simulation results from the viewpoint of body force generation. First, detailed model, in which each ion is separately taken into account is

Tri-electrode plasma actuator (TED-PA) can generate stronger jet than that of conventional two-electrode type plasma actuator. The performance improvement of TED-PA is mainly contributed by body force generation around the DC electrode. In this study, in order to obtain knowledge to enhance the body force generation around DC electrode, we numerically analyze following three cases; without opposite electrode (two-electrode configuration), electrically-grounded opposite electrode, AC-powered oppo

A parametric study is conducted to evaluate the validity of numerical modeling of discharge plasma in DBD plasma actuator. Discharge plasma behavior is numerically simulated based on the three-fluid plasma model, in which the electron, one type of positive ion and one type of negative ion are taken into account. Firstly, the thrust force and electric power consumption obtained in the simulations are compared with experimental results reported by previous studies. The simulation qualitatively pro