Microstructural and piezoelectric properties of low temperature sintering PMN-PZT ceramics with the amount of Li2CO3 addition

PMN-PZT ceramics doped with Li₂CO₃ and Bi₂O₃ as sintering aids were manufactured in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, and their micro structural, dielectric and piezoelectric properties were investigated. The sintering aids were proved to lower the sintering temperature of doped PMN-PZT ceramics due to the effect of LiBiO₂ liquid phase. Optimal values for multilayer piezoelectric transformer application, such as electromechanical coupling factor (k_p) of 0.50, mechanical quality factor (Q_m) of 2264, and dielectric constant (K) of 1216, and curie temperature (T_c) of 317 °C were found at 0.1 wt.% Li₂CO₃ added ceramics sintered at 940 °C.     

Backward-motion control of a mobile robot with n passive off-hooked trailers

A passive multiple-trailer system provides various practical advantages for multi-functional service robots. However, motion control is difficult because the kinematic model is highly nonlinear. The kinematic design of a trailer system was proposed in prior research of ours. In this paper, it is shown how the backward motion of a robot with n passive trailers can be controlled. Once the desired trajectory of the last trailer is computed, the control input of the pushing robot is obtained through the proposed control scheme. Some experimental issues on reversing the trailer system are addressed. This paper provides an answer to the following question: “Does the system work well even if there are sensing or modeling errors?” Although it is difficult to obtain general analytic solutions for the above research question, a practical answer will be explored though simplified analysis and experiments. Experimental verifications are carried out using a mobile robot with three passive trailers. The experimental results show that backward-motion control can be successfully carried out by applying the proposed control scheme.     

Performance comparison of illumination methods for finger-vein imaging and liveness detection

Microsystem Technologies - Four laser illumination methods based on a diffuser, concave lens, quasi-static microelectromechanical system (MEMS) scanner, and resonant MEMS scanner, were evaluated...     

Synthesis and electroluminescent properties of copolymers based on PPV with fluoro groups in vinylene units

New electroluminescent copolymers with fluoro groups in vinylene unit, poly(2-ethylhexyloxy-5-methoxy-p-phenylenevinylene-co-2-dimethyloctylsilyl-p-phenylenedifluorovinylene) (MEH-PPV-co-DMOS-PPDFV) and poly(2-dimethyloctylsilyl-p-phenylenevinylene-co-2-dimethyloctylsilyl-p-phenylenedifluorovinylene) (DMOS-PPV-co-DMOS-PPDFV), have been synthesized by the Gilch polymerization. The fluoro groups were introduced on vinylene units to increase the electron affinity of the copolymers. In both types of the copolymers, the band gaps were increasing with higher ratio of DMOS-PPDFV. As compared to the PL spectra in solution state, PL spectra in solid state and EL spectra of both types of copolymers showed red shifted and broad peaks caused by the aggregation. The polymer LEDs of MEH-PPV-co-DMOS-PPDFVs emit light with maximum peaks at around 538-577 nm. By adjusting the feed ratios of DMOS-PPDFV in the copolymers, we could tune the emission colors from orange yellow to green. DMOS-PPV-co-DMOS-PPDFVs showed the maximum EL peaks at about 514-543 nm. DMOS-PPV-co-DMOS-PPDFV with 1:9 feed ratio showed the highest luminescence efficiency of 1.31 lm/W.     

A novel method for VR sickness reduction based on dynamic field of view processing

Virtual Reality - In this paper, we proposed a novel method for virtual reality (VR) sickness reduction based on dynamic field of view (FOV) processing. Dynamic FOV processing is performed based on...     

Microstructural and piezoelectric properties of PZN substituted PMN-PZT ceramics for multilayer piezoelectric transformer

In this paper, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformers, Pb[(Mn_1/3,Nb_2/3)_0.07(Zn_1/3Nb_2/3)_a (Zr_0.48Ti_0.52)_1-0.07-aO₃] ceramics were prepared with the variations of PZN from 2 to 14 mol% and their dielectric and piezoelectric properties were investigated. Sintering temperature was varied from 940 to 1000^∘C. At 8 mol% PZN substituted specimen sintered at 970^∘C, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant and peizoelectric constant(d₃₃) showed the optimal values of 0.536, 1803, 1551 and 328[pC/N], respectively, for multilayer piezoelectric transformer application.     

Novel efficient blue materials with 4H-cyclopenta[def]phenanthrene for OLEDs

Novel blue emitters, 2-[10-(4,4-dioctyl-4H-cyclopenta[def]phenanthrene-2-yl)-9-anthryl]-4,4-dioctyl-4H-cyclopenta[def]phenanthrene (OCPA) and 4,4,4′,4′,4″,4″-hexaoctyl-2,6′:2′,6″-tercyclopenta[def]phenanthrene (TerCPP) have been synthesized and characterized. The introduction of cyclopenta[def]phenanthrene units into the structure of OCPA and TerCPP leads LEDs with high efficiency and pure blue emission. Thermal analysis of OCPA and TerCPP reveals their high thermal stability. Their decomposition temperatures are around 410 °C for OCPA and 425 °C for TerCPP. The high-quality amorphous films of OCPA and TerCPP were prepared by vapor deposition. UV–visible absorption spectra of the thin films of these compounds appear at about 303–400 nm, and their maximum PL emission appeared at about 434 and 401 nm, respectively. The multi-layered OLEDs with the configuration of ITO/with or without PEDOT:PSS/NPD/OCPA or TerCPP/BAlq or BCP/Alq₃/LiF/Al were fabricated to investigate the electroluminescent properties and the current–voltage–luminescence characteristics of the compounds. Multi-layer organic EL devices with OCPA and TerCPP as an emitting layer produced bright blue (434 nm) and sky blue emissions (440 nm), respectively. The device of OCPA with the configuration of ITO/NPD/OCPA/BAlq/Alq₃/LiF/Al showed the turn-on voltage of about 5.6 V, the maximum brightness of 2500 cd/m² (at 11 V), the maximum luminescence efficiency of 1.2 cd/A, and CIE coordinates of 0.16 and 0.12 which are quite close to that of the National Television System Committee (NTSC) standard blue (0.14, 0.08).     

The maximal downstroke of epicardial potentials as an index of electrical activity in mouse hearts

The maximal upstroke of transmembrane voltage (dV(m)/dt(max)) has been used as an indirect measure of sodium current I(Na) upon activation in cardiac myocytes. However, sodium influx generates not only the upstroke of V(m), but also the downstroke of the extracellular potentials V(e) including epicardial surface potentials V(es). The purpose of this study was to evaluate the magnitude of the maximal downstroke of V(es) (|dV(es)/dt (min)|) as a global index of electrical activation, based on the relationship of dV(m)/dt(max) to I(Na). To fulfill this purpose, we examined |dV(es)/dt(min)| experimentally using isolated perfused mouse hearts and computationally using a 3-D cardiac tissue bidomain model. In experimental studies, a custom-made cylindrical "cage" array with 64 electrodes was slipped over mouse hearts to measure V(es) during hyperkalemia, ischemia, and hypoxia, which are conditions that decrease I(Na). Values of |dV(es)/dt(min)| from each electrode were normalized (|dV(es)/dt (min)|(n)) and averaged (|dV(es)/dt(min)|(na)). Results showed that |dV(es)/dt(min)|(na) decreased during hyperkalemia by 28, 59, and 79% at 8, 10, and 12?mM [K(+)](o), respectively. |dV(es)/dt(min)| also decreased by 54 and 84% 20 min after the onset of ischemia and hypoxia, respectively. In computational studies, |dV(es)/dt(min)| was compared to dV(m)/dt(max) at different levels of the maximum sodium conductance G(Na), extracellular potassium ion concentration [K(+)](o), and intracellular sodium ion concentration [Na(+)](i), which all influence levels of I(Na). Changes in |dV(es)/dt(min)|(n) were similar to dV(m)/dt (max) during alterations of G(Na), [K(+)](o), and [Na(+)](i). Our results demonstrate that |dV(es)/dt(min)|(na) is a robust global index of electrical activation for use in mouse hearts and, similar to dV(m)/dt(max), can be used to probe electrophysiological alterations reliably. The index can be readily measured and evaluated, which makes it attractive for characterization of, for instance, genetically modified mouse hearts and drug effects on cardiac tissue.     

BIDES: A BIST design expert system

BIDES is an expert system for incorporating BIST into a hardware design that is described in VHDL. Based on the BILBO technique, the BIDES system allocates pseudorandom pattern generators and signature analysis registers to each combinational logic module in a design in such a way that given constraints on testing time and hardware overhead are satisfied. This assignment is performed using the iterative process of regeneration and evaluation of various BIST implementations. In order to effectively perform regeneration, an abstraction hierarchy for a BIST design is introduced and a hierarchical planning technique is employed using this structure. This formulation also leads to an easily modifiable system. Prolog is used for implementing the system.Now with Samsung Electronics, Chase Plaza Bldg. SF, 34–35 Jeong-Dong, Choong-Ku, Seoul, Korea.