Search

Jumping Rope (JR) is a consecutive jump exercise and needs upper and lower body movements skills with the rope. JR requires an effective vertical take-off from ground and landing on ground to maintain successive coordination of whole body movements. In this study, we newly developed the index of real-time feedback to improve successive coordination movement using an inertial measurement unit (IMU) during JR movements. 86 elementary-school and junior high-school children participated in this study. They performed basic jump and backward jump for 30 seconds with a IMU on their back. After the measurement, maximum value, root mean square (RMS) value and autocorrelation coefficient from vertical acceleration were calculated to confirm the relationship between vertical acceleration and autocorrelation coefficient during JR. As the results, the maximum value of vertical acceleration had strongly negative correlations with autocorrelation coefficient in basic jump (r > -0.73, p -0.50, p -0.51, p -0.52, p < 0.01).

Multiple-input multiple-output (MIMO) communication systems using multiple low-Earth orbital (LEO) satellites achieve higher capacity than conventional LEO systems. However, in previous research, control signals are allocated to a different frequency band for each satellite signal in order to estimate its Doppler frequency. The increase in the number of satellites reduces unoccupied MIMO signal bandwidth and hence the overall capacity. This study aimed to prevent such capacity reduction by introducing the superimposition of control signals. Such control signals occupy a frequency bandwidth of the equivalent of only one control signal; therefore, they can prevent the reduction of the overall capacity. The main challenge is estimating the satellites' Doppler frequencies from the waveforms of Doppler-affected superimposed control signals. To overcome this challenge, we propose the adoption of a deep learning technique.

In this study, we have developed a new practical system for estimating circadian rhythm by using smart wear that can measure electrocardiogram (ECG) during sleep. This system can estimate the time and heart rate (HR) value to reach the lowest point in circadian rhythm. We show the system in detail. And for further application, we conducted the experiment for showing the effects of jet lag on the circadian rhythm by using the developed system. The results showed that the time of the lowest HR shifted earlier and the lowest HR was higher in case of traveling in a westward direction.

The aim of this study is to develop a wearable EMG measurement system on forearm to discriminate some wrist gestures. We used sport arm sleeve for base of this system and paste conductive elastomer on the base by thermo compression for EMG electrodes. This system has six pair of electrodes on around forearm for detecting EMG signal by bipolar lead. Five healthy students person took part in our experiment (male: 4, female: 1, age: $22\pm 2$ years). At the first, subjects performed four gestures; palmar flexion, dorsal flexion, radial flexion, ulnar flexion. We measured surface EMG of these gestures by our developed system and investigated these data's feasibility of classification. Measured data was calculated for 2 seconds Root Mean Square while keeping each gesture. Secondly, we fit the Support Vector Machine (SVM) for EMG data after RMS processing to classify wrist gestures. There are some channels characteristically show high RMS value in each gesture. As a result of evaluating the performance of the classifier with k-fold cross validation, the mean accuracy of classification was 97.23±0.27%.

This paper presents a capacity study of multi-input and multi-output (MIMO) low earth orbit (LEO) satellite communication systems. Because of their low propagation loss and low latency, LEO satellites are attracting the attention of researchers. MIMO transmission is possible for LEO terminals as they connect to many satellites, which offers higher capacities than current geostationary earth orbit (GEO) systems which offer connections to just single satellites. One difficulty is that LEO satellites experience Doppler frequency shift, which is a significant determiner of MIMO-LEO system performance. We take account of the Doppler frequency shift in deriving the capacity of MIMO-LEO satellite communication systems. Simulations show that the MIMO transmission by three satellites achieves the greatest improvement in system capacity of the conventional system if the bandwidth is limited to 10 MHz; a four-fold increase, on average, is seen for 12 GHz down link channels in the Ku band. Moreover, further capacity improve-ment can be achieved if the system bandwidth is sufficiently larg-er than the Doppler frequency.

An exponentially Increasing number of wireless-LAN (WLAN) devices In a dense environment causes a decrease in throughput owing to collisions among the devices and the lack of contiguous bandwidth. The next-generation standard of 802.11ax improves spectrum efficiency by additionally supporting 1024 (1K) QAM, OFDMA with 80+80MHz; these impose several challenges to silicon design. 1K-QAM demands extreme IQ balance with an IRR better than −50dB over a wide frequency range up to 80MHz to achieve at least −35dB RX EVM or less. Noise characteristics better than −44dBc LO integrated phase noise as well as 50dB isolation between each TRX chain are mandatory. To best make use of the essential features defined in the 11ax standard, a real-time and arbitrary spectrum-resource control capability at each access point (AP) is beneficial both in terms of further improvement in spectrum efficiency as well as communication reliability in ISM coexisting bands and legacy WLAN. Interference identification of the order of 10μe while incorporating everything into a strictly limited silicon area is key to launching the advanced unique functionality. This paper presents a fully integrated 4×4 802.11abgn/ac/ax-compliant AP transceiver SoC. The chip offers frequency-dependent IQ (FD-IQ) mismatch calibration for both amplitude and phase, low-noise TX BB and multimode LO distribution techniques, and real-time interference detection including 2.4GHz inverter-type microwave (MW) ovens.

This paper studies a multi-satellite multi-beam system with single frequency reuse which applies the MIMO (Multi Input Multi Output) technique. To improve the spectral efficiency of satellite systems in support of broadband communications, MIMO is the one of the most important approaches. Since it was difficult to achieve high spectral efficiency by simply combining a multi-beam system with single frequency reuse and a multiple satellite system, this paper newly proposes a pre- coding technique that takes account of the frequency offsets caused by the multiple satellites. We then evaluate our proposal by a cumulative distribution function (CDF) related to channel capacity and show the improvement of the spectral efficiency compared to the conventional satellite systems.

This paper proposes a variable stiffness robot using a shape memory gel (SMG). Variable stiffness robots are useful to handle uneven objects in uneven environments such as home and office. Variable stiffness of rigid-link robots can be realized using motor control. Most of these robots require expensive force sensors. Flexible mechanical parts enable robots to realize low stiffness at the end-effectors without force sensors. However, high stiffness is hard to be realized by the robots with flexible mechanical parts. We propose another method to realize the variable stiffness of the robot without force sensors. We use a cold SMG for a rigid link and a hot SMG for a flexible link. A temperature control system of the SMG is developed, and any SMG link can be used as both a rigid link and a flexible link. Experiments of the application using the system are performed to illustrate the validity of our proposed method.

The objective of this research is to reduce intersymbol interference (ISI) and intercarrier interference (ICI) in a highly mobile environment by optimizing the performance of Biorthogonal Frequency Division Multiplexing (BFDM). In timefrequency dispersive channels, reducing the signal interference depends on the shaping of the signal pulse. BFDM was invented to reduce the interference through a flexible design of the signal pulse shaping. However, the shape of the Gaussian pulses used in BFDM is not always optimized in every situation and as a result the interference is not always minimized. This research seeks to optimize the shape of the Gaussian pulse. In particular, we optimize the Gaussian pulse in BFDM by maximizing the ratio of the ambiguity function of the transmitter (Gaussian) and its receiver pulses. Numerical results obtained show that the proposed method is effective for the optimization of BFDM. Furthermore, we show that the optimized BFDM outperforms the conventional OFDM in time-frequency dispersive channels.