Institute of Electrical and Electronics EngineersActa Medica Okayama2169-3536122024WLAN Channel Status Duration Prediction for Audio and Video Services Using Probabilistic Neural Networks2820128211ENYafeiHouFaculty of Environmental, Life, Natural Science and Technology, Okayama UniversitySatoshiDennoFaculty of Environmental, Life, Natural Science and Technology, Okayama UniversityDue to massive increase in wireless access from smartphones, IoT devices, WLAN is aiming to improve its spectrum efficiency (SE) using many technologies. Some interesting techniques for WLAN systems are flexible allocation of frequency resource and cognitive radio (CR) techniques which expect to find more useful spectrum resource by modeling and then predicting of channel status using the captured statistics information of the used spectrum. This paper investigates the prediction accuracy of busy/idle duration of two major wireless services: audio service and video service using neural network based predictor. We first study the statistics distribution of their time-series busy/idle (B/I) duration, and then analyze the predictability of the busy/idle duration based on the predictability theory. Then, we propose a data categorization (DC) method which categorizes the duration of recent B/I duration according the their ranges to make the duration of next data be distributed into several streams. From the predictability analysis of each stream and the prediction performance using the probabilistic neural network (PNN), it can be confirmed that the proposed DC can improve the prediction accuracy of time-series data in partial streams.No potential conflict of interest relevant to this article was reported.Institute of Electrical and Electronics EngineersActa Medica Okayama2169-3536112023A Proposal of an Axial-Flux Permanent-Magnet Machine Employing SMC Core With Tooth-Tips Constructed by One-Pressing Process: Improving Torque and Manufacturability109435109447ENRenTsunataGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityMasatsuguTakemotoGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityJunImaiGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityTatsuyaSaitoSumitomo Electric Industries Ltd.TomoyukiUenoSumitomo Electric Industries Ltd.This study aims to improve the torque performance and manufacturability of axial-flux permanent magnet (AFPM) machines. Hence, we propose a novel AFPM machine that employs a soft magnetic composite (SMC) core with tooth-tips constructed by a one-pressing process and die. In this paper, the proposed AFPM machine is compared to two conventional AFPM machines using an SMC core. One of them has open-slot structure without tooth-tips. Another model employs an SMC core with tooth-tips pressed by a conventional pressing process that requires multiple operations and dies. As a result of the comparison, the proposed AFPM machine realizes a much higher torque than the two conventional machines. Additionally, the manufacturability of an SMC core with tooth-tips pressed by the proposed method is superior to the conventional one because the proposed structure can be realized by the one-pressing process and die. Furthermore, two prototypes of the proposed AFPM machine and the conventional one with an open-slot structure are fabricated, and then, they are compared by experiments. Consequently, the proposed AFPM machine achieves a 15.7% higher torque than that of the conventional machine using an open-slot structure. Finally, this paper presents an improved design of an AFPM machine with SMC cores using the proposed pressing process. As a result, the proposed AFPM realizes a 20% larger torque than that of a conventional model employing an open-slot structure.No potential conflict of interest relevant to this article was reported.Institute of Electrical and Electronics EngineersActa Medica Okayama2169-3536112023Design and Analysis of Hybrid-Excitation Variable Flux Memory Motor for Traction Applications: Improving Output Power in High-Speed Area During Six-Step Operation Mode8202482036ENRenTsunataGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityKeitoYokomichiGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityMasatsuguTakemotoGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityJunImaiGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityVariable flux motors with adjustable magnetic flux have been gaining attention because of their capability to simultaneously achieve a high torque density and high efficiency. In addition, the output power characteristic, which is related to acceleration performance, in high-speed areas is important in traction applications. However, typical traction motors have lower output power in high-speed areas. In this paper, a Hybrid-Excitation Variable Flux Memory Motor (HE-VFMM) is therefore proposed to enhance output power characteristics under six-step operation mode in high-speed area. The proposed HE-VFMM can perform magnetic flux adjustment with two components: field winding and variable flux permanent magnet (VPM), thus dramatically increasing flux adjustment range. The simulation results show the proposed HE-VFMM achieves 23.7% higher output power at 17,000 rpm than that of an existing traction motor in Prius 4th generation that has the same size while maintaining high efficiency in the frequently used operating area. Additionally, it was found that variable magnetic flux is very effective in enhancing the output power, especially in the high-speed region because the magnetic saturation in the stator core is mitigated by field-weakening control. Consequently, as the rotational speed increases, an increase ratio of the output power caused by the adjustable magnetic flux becomes higher. This paper shows that the proposed HE-VFMM is an effective method for improving the problem of low output power in high-speed regions in traction motors.No potential conflict of interest relevant to this article was reported.Institute of Electrical and Electronics EngineersActa Medica Okayama2169-3536112023Stargazer: Long-Term and Multiregional Measurement of Timing/ Geolocation-Based Cloaking5275052762ENShotaFujiiGraduate School of Natural Science and Technology, Okayama UniversityTakayukiSatoResearch and Development Group, Hitachi Ltd.ShoAokiResearch and Development Group, Hitachi Ltd.YuTsudaNational Institute of Information and Communications TechnologyNobutakaKawaguchiResearch and Development Group, Hitachi Ltd.TomohiroShigemotoResearch and Development Group, Hitachi Ltd.MasatoTeradaResearch and Development Group, Hitachi Ltd.Malicious hosts have come to play a significant and varied role in today's cyber attacks. Some of these hosts are equipped with a technique called cloaking, which discriminates between access from potential victims and others and then returns malicious content only to potential victims. This is a serious threat because it can evade detection by security vendors and researchers and cause serious damage. As such, cloaking is being extensively investigated, especially for phishing sites. We are currently engaged in a long-term cloaking study of a broader range of threats. In the present study, we implemented Stargazer, which actively monitors malicious hosts and detects geographic and temporal cloaking, and collected 30,359,410 observations between November 2019 and February 2022 for 18,397 targets from 13 sites where our sensors are installed. Our analysis confirmed that cloaking techniques are widely abused, i.e., not only in the context of specific threats such as phishing. This includes geographic and time-based cloaking, which is difficult to detect with single-site or one-shot observations. Furthermore, we found that malicious hosts that perform cloaking include those that survive for relatively long periods of time, and those whose contents are not present in VirusTotal. This suggests that it is not easy to observe and analyze the cloaking malicious hosts with existing technologies. The results of this study have deepened our understanding of various types of cloaking, including geographic and temporal ones, and will help in the development of future cloaking detection methods.No potential conflict of interest relevant to this article was reported.Institute of Electrical and Electronics EngineersActa Medica Okayama2169-3536112023Artificial Neural Network Based Audio Reinforcement for Computer Assisted Rote Learning3946639483ENParisaSupitayakulGraduate School of Natural Science and Technology, Okayama UniversityZeynep YücelGraduate School of Natural Science and Technology, Okayama UniversityAkitoMondenGraduate School of Natural Science and Technology, Okayama UniversityThe dual-channel assumption of the cognitive theory of multimedia learning suggests that importing a large amount of information through a single (visual or audio) channel overloads that channel, causing partial loss of information, while importing it simultaneously through multiple channels relieves the burden on them and leads to the registration of a larger amount of information. In light of such knowledge, this study investigates the possibility of reinforcing visual stimuli with audio for supporting e-learners in memorization tasks. Specifically, we consider three kinds of learning material and two kinds of audio stimuli and partially reinforce each kind of material with each kind of stimuli in an arbitrary way. In a series of experiments, we determine the particular type of audio, which offers the highest improvement for each kind of material. Our work stands out as being the first study investigating the differences in memory performance in relation to different combinations of learning content and stimulus. Our key findings from the experiments are: (i) E-learning is more effective in refreshing memory rather than studying from scratch, (ii) Non-informative audio is more suited to verbal content, whereas informative audio is better for numerical content, (iii) Constant audio triggering degrades learning performance and thus audio triggering should be handled with care. Based on these findings, we develop an ANN-based estimator to determine the proper moment for triggering audio (i.e. when memory performance is estimated to be declining) and carry out follow-up experiments for testing the integrated framework. Our contributions involve (i) determination of the most effective audio for each content type, (ii) estimation of memory deterioration based on learners' interaction logs, and (iii) the proposal of improvement of memory registration through auditory reinforcement. We believe that such findings constitute encouraging evidence the memory registration of e-learners can be enhanced with content-aware audio incorporation.No potential conflict of interest relevant to this article was reported.Institute of Electrical and Electronics EngineersActa Medica Okayama2169-353692021Development of an Eye-Gaze Input System With High Speed and Accuracy through Target Prediction Based on Homing Eye Movements2268822697ENAtsuoMurataDepartment of Intelligent Mechanical Systems, Graduate School of Natural Science and Technology, Okayama UniversityToshihisaDoiDepartment of Intelligent Mechanical Systems, Graduate School of Natural Science and Technology, Okayama UniversityKazushiKageyamaDepartment of Intelligent Mechanical Systems, Graduate School of Natural Science and Technology, Okayama UniversityWaldemarKarwowskiEngineering and Management Systems, University of Central FloridaIn this study, a method to predict a target on the basis of the trajectory of eye movements and to increase the pointing speed while maintaining high predictive accuracy is proposed. First, a predictive method based on ballistic (fast) eye movements (Approach 1) was evaluated in terms of pointing speed and predictive accuracy. In Approach 1, the so-called Midas touch problem (pointing to an unintended target) occurred, particularly when a small number of samples was used to predict a target. Therefore, to overcome the poor predictive accuracy of Approach 1, we developed a new predictive method (Approach 2) using homing (slow) eye movements rather than ballistic (fast) eye movements. Approach 2 overcame the disadvantage (inaccurate prediction) of Approach 1 by shortening the pointing time while maintaining high predictive accuracy.No potential conflict of interest relevant to this article was reported.Institute of Electrical and Electronics EngineersActa Medica Okayama2169-353692021Capacity Loss From Localization Error in MIMO Channel Using Leaky Coaxial Cable1592915938ENJunjieZhuGraduate School of Natural Science and Technology, Okayama UniversityYafeiHouGraduate School of Natural Science and Technology, Okayama UniversityKentaNagayamaGraduate School of Natural Science and Technology, Okayama UniversitySatoshiDennoGraduate School of Natural Science and Technology, Okayama UniversityLeaky coaxial (LCX) cable has been employed as antennas for wireless traffic over many linear-cell scenarios such as railway station, tunnels and shopping malls. In addition, LCX can be used for user localization and wireless power transfer (WPT). Compared with the equal power allocation method, the power allocation method for LCX system using positional information (PI) can improve its capacity with the same level of computational complexity. In this paper, we will investigate the level of capacity loss on the 2.4 GHz and 5 GHz band for the conventional equal power (EP) allocation method, the water-filling (WF) based power allocation, and our proposed low-complexity power allocation method for LCX system with PI. The results show that LCX system with our proposed method using PI can reduce the capacity loss due to localization error than that of others.No potential conflict of interest relevant to this article was reported.Institute of Electrical and Electronics EngineersActa Medica Okayama15566013152019Near-Optimal Detection for Binary Tardos Code by Estimating Collusion Strategy20692080EN TatsuyaYasuiGraduate School of Science and Technology, Okayama UniversityMinoruKuribayashiGraduate School of Science and Technology, Okayama UniversityNobuoFunabikiGraduate School of Natural Science and Technology, Okayama UniversityIsaoEchizenNational Institute of InformaticsA previously proposed optimal detector for bias-based fingerprinting codes such as Tardos and Nuida requires two kinds of important information: the number of colluders and the collusion strategy used to generate the pirated codeword. An estimator has now been derived for these two parameters. The bias in the pirated codeword is measured by observing the number of zeros and ones and compared with possible bias patterns calculated using information about the collusion strategy and number of colluders. Computer simulation demonstrated that the collusion strategy and number of colluders can be estimated with high probability and that the traceability of a detector using the proposed estimator is extremely close to being optimal.No potential conflict of interest relevant to this article was reported.Institute of Electrical and Electronics EngineersActa Medica Okayama1999Application of pneumatic parallel manipulator as haptic human interface185190ENMasahiroTakaiwaToshiroNoritsuguWhen humans and robots implement a cooperative task, information (intention) transfer between them is an important problem as the task becomes complicated. In the paper, a haptic interface using a pneumatic parallel manipulator is developed to realize ginformation transfer by means of contacth. The contact information given by the human, namely contact force vector and contact point on the manipulator, is detected by the interface itself and such information is transferred to the robot by being connected with some reference signal. The pneumatic parallel manipulator works as a kind of elastic body even when its position is controlled owing to the air compressibility. Focusing on this characteristic and introducing an idea of compliance center with a spherical shell, contact force vector and contact point are detected without a force sensor. The validity of the proposed method is confirmed through some experiments.No potential conflict of interest relevant to this article was reported.Institute of Electrical and Electronics EngineersActa Medica Okayama1999Development of a video-rate range finder using dynamic threshold method for characteristic point detection932937ENYutakaTanakaAkioGofukuNobuoTakedaIsakuNagaiThis study develops a video-rate stereo range finding circuit to obtain the depth of objects in a scene by processing video signals (R, G, B, and brightness signals) from binocular CCD cameras. The electronic circuit implements a dynamic threshold method to decrease the affect of signal noise in characteristic point detection, where a video signal from each CCD camera is compared with multiple thresholds, shifting dynamically by feeding back the previous comparison result. Several object depth measurement experiments for simple indoor scenes show that the dynamic threshold method gives high acquisition and correct rates of depth data compared with those by a fixed threshold method for the video signals and a relative method for R, G, and B signals utilized in the authors' previous range finders.No potential conflict of interest relevant to this article was reported.Institute of Electrical and Electronics EngineersActa Medica Okayama1997Visual tracking of redundant features5151ENKoichiHashimotoAtsuhitoAokiToshiroNoritsuguThis paper presents how the control performance of the feature-based visual servo system is improved by utilizing redundant features. Effectiveness of the redundant features is evaluated by the smallest singular value of the image Jacobian which is closely related to the accuracy in the world coordinate system. An LQ control scheme is used to resolve the controllability problem. Usefulness of the redundant features is verified by the real time experiments on a PUMA 560 manipulator.No potential conflict of interest relevant to this article was reported.Institute of Electrical and Electronics EngineersActa Medica Okayama21996Development of a tactile sensing flexible actuator723728ENYutakaTanakaAkioGofukuYujiFujino<p>The disadvantages of flexible artificial fingers have been improved. The finger is provided with the tactile sense by two types of sensors to detect when the finger tip touches an object and to estimate both the finger force and object size. The rigidity is enhanced by equipping the finger with a reinforcing material similar to that of human bone. A prototype robot hand with four fingers has been manufactured for experiments and mounted on an industrial articulated robot. The effectiveness of the improved robot hand finger was confirmed throughout experimental tests of grasping action</p>No potential conflict of interest relevant to this article was reported.