Applications of neural networks in high-speed communicationnetworks

Modern communication networks are expected to have hundreds or thousands of network nodes to which thousands of users are connected. Neural networks can contribute to this emerging new telecommunication infrastructure by providing fast, flexible, adaptive, and intelligent control. This article discusses the neural networks used for solving various control problems in high-speed communication networks     

Performance of a New Ion Source for KSTAR Tokamak Plasma Heating

In the experimental campaign of 2010 and 2011 on KSTAR, the NBI-1 system was equipped with one prototype ion source and operated successfully, providing a neutral beam power of 0.7-1.6 MW to the tokamak plasma. The new ion source planned for the 2012 KSTAR campaign had a much more advanced performance compared with the previous one. The target performance of the new ion source was to provide a neutral deuterium beam of 2 MW to the tokamak plasma. The ion source was newly designed, fabricated, and assembled in 2011. The new ion source was then conditioned up to 64 A/100 keV over a 2-hour beam extraction and performance tested at the NB test stand （NBTS） at the Korea Atomic Energy Research Institute （KAERI） in 2012. The measured optimum perveance at which the beam divergence is a minimum was about 2.5μP, and the minimum beam divergent angle was under 1.0° at 60 keV. These results indicate that the 2.0 MW neutral beam power at 100 keV required for the heating of plasma in KSTAR can be delivered by the installation of the new ion source in the KSTAR NBI-1 system.     

PIEZOELECTRIC PROPERTIES OF ((Na0.5K0.5)1−xLix)(Nb0.8Ta0.2)O3 CERAMICS

ABSTRACT

In the ((Na_0.5K_0.5)_1?x)Li_x)(Nb_0.8Ta_0.2)O₃ (NKLNT) system, dense ceramics were developed by conventional sintering process. The electrical properties of NKLNT ceramics were investigated as a function of Li substitution. When the sample sintered at 1100°C for 4 h with the substitution of 2 mol% Li at the morphotropic phase boundary, electro-mechanical coupling factor (k_P) and piezoelectric coefficient (d₃₃) were found to reach the highest values of 0.42 and 210 pC/N, respectively. These excellent piezoelectric and electromechanical properties indicate that this system is potentially good candidate for lead-free material for a wide range of electro-mechanical transducer applications.     

Dielectrophoretic assembly of semiconducting single-walled carbon nanotube transistor

A novel burning technique for making a semiconducting single-walled carbon nanotubes (SWNTs) transistor assembled by the dielectrophoretic force was suggested. The fabrication process consisted of two steps. First, to align and attach a bundle of SWNTs between the source and drain, the alternating (AC) voltage was applied to the electrodes. When a bundle of SWNTs was connected between two electrodes, some of metallic nanotubes and semi-conducing nanotubes existed together. The second step is to burn the metallic SWNTS by applying the voltage between two electrodes. With increasing the voltage, more current flowed through the metallic SWNTs, thus, the metallic SWNTs burnt earlier than the semiconducting one. This technique enables to obtain only semi-conducting SWNTs connection in the transistor. Through the I—V characteristic graph, the moment of metallic SWNTs burning and the characteristic of semi-conducing nanotubes were verified.     

27Al MAS-NMR study of inorganic polymer formation at ambient temperature

Inorganic polymers are a novel class of materials formed by the polymerization of silicon, aluminium and oxygen species to form an amorphous three-dimensional framework structure. The basis of this process is the alkaline solutions to induce a certain amount of Si and Al atoms to dissolve from a feedstock such as aluminosilicate. A study of ²⁷Al MAS-NMR was carried out in an attempt to understand the reaction mechanism of the inorganic polymerization at ambient temperature. Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) were also employed to establish the composition and microstructure of the inorganic polymerization. Specimens were prepared with different Al/Si mole ratios from the starting materials. The higher the Al content, the more sufficient the Al atoms that can combine with SiO₄, and the longer the reaction time, the more the bonded Si-O-Al-O polymer structure, and then the higher the Al content, the fewer the octahedral Al with a uniform Si-O-Al-O structure in four directions, because four Al atoms are combined with SiO₄, resulting in a uniform Si-O-Al-O structure in four directions. The results show that they have an amorphous microstructure.     

Hybrid functional IrO2-TiO2 thin film resistor prepared by atomic layer deposition for thermal inkjet printheads

IrO₂-TiO₂ thin films were prepared by atomic layer deposition using Ir(EtCp)(COD) and titanium isopropoxide (TTIP). The resistivity of IrO₂-TiO₂ thin films can be easily controlled from 1 500 to 356.7 μωcm by the IrO₂ intermixing ratio from 0.55 to 0.78 in the IrO₂-TiO₂ thin films. The low temperature coefficient of resistance(TCR) values can be obtained by adopting IrO₂-TiO₂ composite thin films. Moreover, the change in the resistivity of IrO₂-TiO₂ thin films was below 10% even after O₂ annealing process at 600 °C. The step stress test results show that IrO₂-TiO₂ films have better characteristics than conventional TaN_0.8 heater resistor. Therefore, IrO₂-TiO₂ composite thin films can be used as a heater resistor material in thermal inkjet printhead.     

Tool path generation and tolerance analysis for free-form surfaces

This paper focuses on developing algorithms that generate tool paths for free-form surfaces based on the accuracy of a desired manufactured part. A manufacturing part is represented by mathematical curves and surfaces. Using the mathematical representation of the manufacturing part, we generate reliable and near-optimal tool paths as well as cutter location data file for post-processing. This algorithm includes two components. First is the forward-step function that determines the maximum distance, called forward step, between two cutter contact (CC) points with a given tolerance. This function is independent of the surface type and is applicable to all continuous parametric surfaces that are twice differentiable. The second component is the side step function which determines the maximum distance, called side step, between two adjacent tool paths with a given scallop height. This algorithm reduces manufacturing and computing time as well as the CC points while keeping the given tolerance and scallop height in the tool paths. Several parts, for which the CC points are generated using the proposed algorithm, are machined using a three-axes milling machine. As part of the validation process, the tool paths generated during machining are analyzed to compare the machined part and the desired part.     

Note: real time control of a tunable vibration absorber based on magnetorheological elastomer for suppressing tonal vibrations

An adaptive tunable vibration absober based on magnetorheological elastomer (MRE) is designed as an intelligent device for auto-tuning itself to the time-varying harmonic disturbance force to reduce the unwanted vibration of the primary system in the steady state. The objectives of this note are to develop and implement a continuous control method for a MRE tunable vibration absorber (TVA) and to evaluate its performance in suppressing time-varying tonal vibrations. In the proposed control, the stiffness of MREs is continuously varied based on a nonlinear tuning function that relates the response of the system to the input magnetic field density. Through experiments, it will be shown that the proposed MRE TVA reduces in real time the transmission of a time-varying excited vibration of 48-55 Hz, which shows the potential applicability of the MRE in reducing unwanted vibration to precision devices.     

Genetic algorithm tuned PI controller on PMSM simplified vector control

A simple control structure in servo system is occasionally needed for simple industrial application which precise and high control performance is not exessively important so that the cost production can be reduced efficiently. Simplified vector control, which has simple control structure, is utilized as the permanent magnet synchronous motor control algorithm and genetic algorithm is used to tune three PI controllers used in simplified vector control. The control performance is obtained from simulation and investigated to verify the feasibility of the algorithm to be applied in the real application. Simulation results show that the speed and torque responses of the system in both continuous time and discrete time can achieve good performances. Furthermore, simplified vector control combined with genetic algorithm has a similar perfofmance with conventional field oriented control algorithm and possible to be realized into the real simple application in the future.