Passivity-based Nonlinear Control for a Ballbot to Balance and Transfer

International Journal of Control, Automation and Systems - Ballbot is a robot that can transfer to a given position while maintaining a self-balanced upright posture on a spherical ball. This paper...     

Information leakage in bi‐directional IFD communication system with simultaneously transmitted jamming sequence

In this paper, we describe a simultaneously transmitted jamming (ST‐jamming) for bi‐directional in‐band full‐duplex (IFD) system to improve information security at the physical layer. By exploiting ST‐jamming, each legitimate user transmits data samples and jamming samples together in one orthogonal frequency division multiplexing symbol according to given traffic asymmetry. Regardless of the traffic difference in both directions in IFD communication, eavesdropping of confidential information is prevented in both directions simultaneously without the loss of data rate. We first propose an encoding scheme and the corresponding decoding scheme for ST‐jamming to be used by the legitimate users. In addition, we study a transceiver structure of the legitimate users including a baseband modem uniquely designed for the use of ST‐jamming. The leakage of confidential information at an eavesdropper is then quantified by studying the mutual information between the confidential transmit signals and the received signals of the eavesdropper. Simulation results show that the proposed ST‐jamming significantly reduces the leakage of legitimate information at the eavesdropper.     

Bolstering efficient SSGAs based on an ensemble of probabilistic variable-wise crossover strategies

A crossover operator in genetic algorithms (GAs) plays an essential role as the main search operator to breed offspring by exchanging information between individuals. Although different types of crossover operators have been developed for real-coded GAs (RCGAs), there has been very little research on combining different crossover operators to build more effective and efficient RCGAs. In this work, we propose new steady-state generation alternation-based RCGAs (SSGAs) ameliorated with (i) an ensemble of different probabilistic variable-wise crossover strategies, which is realized by the corresponding parallel populations, to utilize synergetic and complementary effect with their efficient operations, and (ii) efficient operation at each evolution step to obtain further performance enhancement. To investigate the performance of this ensemble with respect to search abilities and computation time, we compare the proposed algorithms against various SSGAs when running 27 benchmark functions. Empirical studies showed that the proposed algorithms exhibit better performance than the contestant SSGAs on these functions. Moreover, a comparison with the state-of-the-art evolutionary algorithms on eight difficult benchmark functions clearly demonstrated outperformance of the proposed algorithms.     

Compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni bulk metallic glasses

Starting from the quaternary Cu47Ti34Zr11Ni8 alloy, the compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni alloys was systematically investigated. Quaternary Cu-Ti-Zr-Ni alloys can be cast directly from the melt into copper molds to form fully amorphous strips or rods with the thickness of 3-6 mm. The evidence of the amorphous nature of the cast rods was provided by X-ray spectra. The measured glass transition temperature (Tg) and crystallization temperature (Tx) were obtained for the alloys using differential scanning calorimetry (DSC) at the heating rate of 20 K/s. In the results, the differences between the glass temperature and the crystallization tempera-ture (△Tx=Tx-Tg) are measured with values ranging up to 33-55 K. The reduced glass transition temperature (Trg), which is the ratio of the glass temperature to the liquidus temperature (T1), is often used as an indication of the glass-forming ability of metallic alloys. For the present Cu-Ti-Zr-Ni alloys, this ratio is typically in the range of 0.5838-0.5959, characteristic of metallic alloys with good glass-forming ability. The elastic constants for several selected alloys were measured using ultrasonic methods. The values of the elastic shear modulus, bulk modulus, and Poisson's ratio were also given.     

Performance Analysis of 3D Localization for a Launch Vehicle Using TOA,AOA, and TDOA

Wireless Personal Communications - In general, a ground telemetry station for a launch vehicle (LV) includes a tracking function only; therefore, position measurements for LV depend on received...     

Noise prediction of multi-rotor UAV by RPM fluctuation correction method

Journal of Mechanical Science and Technology - The multi-rotor type unmanned aerial vehicle (UAV) controls the movement through the rotational speed of each rotor. Since the phase of each rotor is...     

Hydrothermal preparation of carbon microspheres from mono-saccharides and phenolic compounds

Isolated carbon microspheres in a diameter range of 1-4 μm were prepared by hydrothermal treatment of mono-saccharides (xylose for pentose and fructose for hexose) with phenolic compounds-phenol, resorcinol, and phloroglucinol. It was found that addition of these compounds, particularly phloroglucinol, into a sugar solution led to a substantial increase (roughly 20-fold) of the carbon yield. Mono-saccharides are dehydrated into furan compounds during hydrothermal carbonization, and these compounds subsequently react with phloroglucinol, as revealed by examination of high-performance liquid chromatograms. Through elemental analysis and spectroscopic studies, it was found that several oxygen functionalities including hydroxyl, carbonyl, carboxyl, ether, quinone, and ester groups were located throughout the carbon spheres derived from sugars and phloroglucinol. On the basis of the carbon formation mechanism, the C-O-C bond formed by linkage of OH groups of phenolic compounds preferentially exists at the core of carbon spheres whereas the outer carbon surface contains reactive oxygen functionalities such as hydroxyl, carbonyl, carboxylic, and ester groups, corresponding with results obtained with sugar-derived carbon materials.