Red polymer light-emitting devices based on dye-dispersed poly (9,9-dioctylfluorene-alt-benzothiadiazole)

A polymer-organic host-guest emitter (POHGE) system for obtaining polymer light-emitting diodes (PLEDs) with pure red emission and high luminance is proposed. The POHGE system was prepared by the fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetra-methyljulolidy-9-enyl)-4H-pyran (DCJTB) doped in green-emitting polymer poly (9,9-dioctylfluorene-alt-benzothiadiazole) (BTF8). A photoluminescence (PL) quenching phenomenon was observed owing to the higher doping amount of DCJTB dopant. In this study, the red DCJTB dopant emits with high luminance and without concentration quenching when the host BTF8 emitting layer is doped with a small amount of the red guest DCJTB dopant. An optimal amount of DCCJTB dopant was obtained at 2 mg. Devices with a configuration of indium tin oxide (ITO)/poly (ethylenedioxythiophene) doped with poly (styrenesulfonate) (PEDOT:PSS)/BTF8:DCJTB/Ca/Al were fabricated. This device achieved an electroluminescence (EL) efficiency of 1.33 cd/A at 6 V. The emission area is 1.5 × 0.5 cm². The devices show the red light emission with a peak at about 630 nm. The color coordinate in Commission Internationale d’Eclairage (CIE) chromaticity is at x = 0.64 and y = 0.36.     

InGaP/InGaAs Pseudomorphic Heterodoped-Channel FETs With a Field Plate and a Reduced Gate Length by Splitting Gate Metal

Depositing gate metal across a step undercut between the Schottky barrier layer and the insulator-like layer is employed to obtain a reduced gate length of 0.4 mum with an additional 0.6-mum field plate from a 1-mum gate window. Most dc and ac characteristics including current density (I_DSS=451mA/mm), transconductance (g_m,max=225mS/mm), breakdown voltages (V_BD(DS)/V _BD(GD)=22/-25.5V), gate-voltage swing (GVS=2.24V), cutoff, and maximum oscillation frequencies (f_t/f_max=17.2/32GHz) are improved as compared to those of a 1-mum gate device without field plate. At a V_DS of 4.0 V, a maximum power added efficiency of 36% with an output power of 13.9 dBm and a power gain of 8.7 dB are obtained at a frequency of 1.8 GHz. The saturated output power and the linear power gain are 316 mW/mm and 13 dB, respectively     

A Low-Power Fullband 802.11a/b/g WLAN Transceiver With On-Chip PA

A low-power fullband 802.11a/b/g WLAN transceiver in 0.15-mum CMOS technology is described. The zero-IF transceiver achieves a receiver noise figure of 4.4/4 dB for the 2.4-GHz/5-GHz bands, respectively. The corresponding sensitivity at 54-Mb/s operation is -72 dBm for 802.11g and -74 dBm for 802.11a using actual PER measurement. An on-chip PA delivers 20 dBm output P1-dB. A new I/Q compensation scheme is implemented in local oscillator (LO) and an image rejection of better than 52 dB is observed. The transmitter delivers 10/1.5 dBm (2.4-/5-GHz) EVM-compliant output power for a 64-QAM OFDM signal at 54-Mb/s. The power consumption is 117/135 mW (1.8-V) in the receive mode and 570/233.1 mW in the transmit mode for 2.4/5 GHz, respectively. The low power consumption, high integration and robustness (-40 to 140degC) make this transceiver suitable for portable applications     

Electrokinetic micromixing of charged and non-charged samples near nano–microchannel junction

A nano–microchannel flow mixer comprising a polydimethylsiloxane (PDMS) microchannel and a Nafion nanoporous membrane is fabricated. It is shown that when an electric field is applied across the device, an ion enrichment/ion depletion effect occurs near the nano–microchannel junction. The mixing performance of the proposed device is examined for three different samples, namely fluorescein (negatively charged), Rhodamine 6G (positively charged), and Rhodamine B (electroneutral). It is shown that a mixing effect is obtained only for the Rhodamine B solution. Thus, it is inferred that nano–microchannel devices such as that presented in this study and those presented in the literature are unsuitable for biomolecule detection applications since such molecules are generally charged.     

The coupled vibration in a rotating multi-disk rotor system

The influence on coupling vibrations among shaft-torsion and blade-bending coupling vibrations of a multi-disk rotor system was investigated analytically. The natural frequencies and the mode shapes of the system were solved for one- to three-disk cases as examples. First, numerical results showed how the natural frequencies varied with blades in a disk unit. The diagrams of the coupling mode shapes were drawn. From the results, it was found that the inter-blade (BB) modes were of repeated frequencies of (N_b-1) multiplicity for number blades. At multi-disk unit, the shaft-blade (SB) modes added to N_d modes for number disks. The BB modes were of repeated frequencies of [N_d×(N_b-1)] multiplicity for number disks. Numerical calculations also revealed that the natural frequencies were affected by disk distance. In the rotation effect, the times of instability will due to the number of disk. And, the more disk rotor causes instability earlier than the less disk case.     

Effects of high-order surface stress on buckling and resonance behavior of nanowires

A theoretical framework, accounting for high-order surface stress, is implemented in a continuum mechanics model based on the Euler-Bernoulli theory of beams and columns to simulate the buckling and resonance behavior of nanowires (NWs). Closed-form expressions for the critical buckling load of uniaxial compression of NWs are derived for different types of end conditions. Size-dependent overall Young’s modulus is characterized versus the diameter of the NWs and is compared with the experimental data. The resonance frequency of NWs is also studied and compared with the simulation results based on nonlinear, finite deformation kinematics. We demonstrate that the present prediction considering both surface moment and surface stress agrees well with the experimental data, while the pure surface stress model may not be able to capture the general trend when the NW’s diameter is less than a certain size. We conclude that the present continuum mechanics approach, considering both high-order surface effects, could be served as one of the feasible tools to analyze the mechanical behavior of nanostructures.     

A novel energy‐retaining inverter for AC arc welding machines

A novel energy‐retaining power supply for AC arc welding machines is proposed in this paper. In this kind of power supply, current‐steering diodes connected across the output chokes keep the inductor current continuous and retain the energy during the commutation period, hence reducing the commutation time to ensure a better welding performance. In addition, the stored energy can be released in the next energy transfer cycle to raise the conversion efficiency. The circuit operations and design procedures are likewise examined thoroughly. Experimental results on a prototype inverter for driving a 100‐A AC arc welding machine are recorded to validate the effectiveness of the presented scheme. Copyright © 2010 John Wiley & Sons, Ltd.     

Influence of mechanical properties in carbon black (CB) filled isotactic polypropylene (iPP) and propylene-ethylene block copolymer

The mechanical properties of isotactic polypropylene (iPP) and propylene-ethylene block copolymer (Co-PP) with carbon black (CB) were added as a filler. By mixing appropriate amounts of the two components through melt-blending in a twin-screw extruder, the blended pellets were prepared to a series of test specimens by injection molding. A scanning electron microscopic study was performed of the morphologies of the impact fractured surfaces. The blending of CB in Co-PP not only improves the impact strength, but also improves the flexural modulus and tensile strength; however, the heat distortion temperature (HDT) of the Co-PP/CB blends decreased with greater filler content. Furthermore, the filler of CB improves the tensile yield strength only at low filler content in iPP/CB blends, and the heat distortion temperature (HDT) and flexural modulus of the iPP/CB blends increased with greater filler content. The impact behavior is not good for the iPP/CB blends. Overall, Co-PP/CB has better interaction of molecules than iPP/CB. © 1996 John Wiley & Sons, Inc.     

Soapless emulsion polymerization of methyl methacrylate. II. Simulation of polymer particle formation

In this work, a generalized mathematical model was developed to estimate the variation of particle concentration during the entire course of soapless emulsion polymerization of methylmethacrylate (MMA). All of the factors, such as oligomeric radical absorption or desorption by polymer particles, coagulation between polymer particles, and the termination effect on the formation mechanism of polymer particles, were considered and included in this model. When appropriate parameters were selected, this model could be successfully used to interpret the experimental behavior of particle concentration during the entire reaction. Under different conditions, the rate of polymerization, the number of radicals in each particle, the instantaneous average molecular weight of polymers, and the rate constant of termination were also calculated. All of them coincided with the experimental results quite well. © 1996 John Wiley & Sons, Inc.