Novel T-rail electrodes for substrate removed low-voltage high-speed GaAs/AlGaAs electrooptic modulators

A novel traveling-wave electrode utilizing capacitively loaded T-rail elements was developed for low-voltage high-speed substrate-removed GaAs/AlGaAs electrooptic modulators. Electrodes with varying dimensions were fabricated and characterized. Electrode phase velocity, characteristic impedance, loss coefficient, and capacitive loading were extracted from the measured s-parameters up to 40 GHz. Electrode was also simulated using a finite-element solver. The measured and calculated electrode capacitance values were found to be in excellent agreement, showing that the electrode can be precisely designed. Approaches were outlined to provide a group velocity-matched very high-speed modulator electrode suitable for a low drive-voltage substrate-removed GaAs/AlGaAs electro-optic modulator     

Order restricted randomized designs for control versus treatment comparison

We develop a method of randomizing units to treatments that relies on subjective judgement or on possible coarse modeling to produce restrictions on the randomization. The procedure thus fits within the general framework of ranked set sampling. However, instead of selecting a single unit from each set for full measurement, all units within a set are used. The units within a set are assigned to different treatments. Such an assignment translates the positive dependence among units within a set into a reduction in variation of contrasting features of the treatments. A test for treatment versus control comparison, with controlled familywise error rate, is developed along with the associated confidence intervals. The new procedure is shown to be superior to corresponding procedures based on completely randomized or ranked set sample designs. The superiority appears both in asymptotic relative efficiency and in power for finite sample sizes. Importantly, this test does not rely on perfect rankings; rather, the information in the data on the quality of rankings is exploited to maintain the level of the test when rankings are imperfect. The asymptotic relative efficiency of the test is not affected by estimation of the quality of rankings, and the finite sample performance is only mildly affected.     

Synthesis of 5,6-O-Cyclohexylidene-1-amino-3-azahexane and Its Co(II), Ni(II), Cu(II) Complexes

5,6-O-Cyclohexylidene-1-amino-3-azahexane (L) is synthesized from 1-chloro-2,3-O-cyclohexylidenepropane, which is prepared by the reaction between epichlorohydrin and cyclohexanone. In this reaction, BF₃ · OEt₂ is used as a catalyst. Complexes of Co(II), Ni(II) and Cu(II) acetates with this ligand are prepared. The structures of the ligand and its complexes are proposed based on elemental analysis, IR and UV-VIS spectroscopy, magnetic susceptibility, conductometry, and ¹H and ¹³C NMR spectroscopy.     

New 3-hydroxyflavone derivatives for probing hydrophobic sites in microheterogeneous systems

Nine new 3-hydroxyflavone derivatives as fluorescent molecular sensors having two well-separated emission bands were synthesized. These sensors can occupy well-determined locations and orientations in macromolecular ensembles, such as micelles due to their finely-tuned designs. These polarity-sensitive dyes can incorporate into the anhydrous hydrophobic core of aqueous micelles.     

The annealing behavior of implanted nitrogen in fcc stainless steel

Post-implantation annealing of N-implanted 304 stainless steel at 400 °C has been investigated by conversion electron Mössbauer spectroscopy, X-ray diffraction and Auger electron spectroscopy. After a 1 h anneal, the near complete dissolution of the as-implanted Fe₂N-like nitride phase results in a 9 at.% N fcc solid-solution phase. After the final anneal (64 h), N has diffused to a depth of about 2 m and remains in solid solution with an average content of 4 at.%. An average N diffusion coefficient at 400 °C is estimated to be 10^-12-10^-14 cm²/s, depending on anneal time, too small to explain the deep penetration observed in high-flux, high-dose N-implanted stainless steel. The present results provide additional evidence for beam controlled N migration where Cr plays an important role.     

On the design considerations of solid-state power amplifiers for satellite communications: A systems perspective

Conventional solid-state power amplifier (SSPA) design approach isolates radio frequency (RF) design from communication theory. In this paper, a unified SSPA design approach is proposed, which optimizes SSPA parameters (bias voltage and input RF signal power) to minimize total DC power consumption while satisfying received SNR constraint specified by the link budget. The effect of SSPA nonlinearity is quantified by the error vector magnitude measured at its output and the corresponding received SNR degradation is analyzed. Using the quantitative metrics for received SNR, it is possible to evaluate highly nonlinear SSPA classes such as Class-B or deep-Class AB, which are normally not considered in conventional SSPA design approach to be used in satellite communication applications.     

Iron speciation by solid phase extraction and flame atomic absorption spectrometry using N,N′-bis-(2-hydroxy-5-bromobenzyl)-2-hydroxy-1,3-diiminopropane

A new Schiff base, N,N′-bis-(2-hydroxy-5-bromobenzyl)-2-hydroxy-1,3-diiminopropane, has been synthesized for the very sensitive determination of iron(III) and iron(II) in natural water samples. It enabled a very selective and rapid method for iron determination to be developed. The method has also been applied to total iron determination in sediment samples. In the preconcentration system, the Schiff base reagent is mixed with the samples and chelates containing iron(III). The complexes are then adsorbed on silica gel within a column system. Elution of the adsorbed chelate from the silica gel was performed with a small volume of acetone containing 2.5% nitric acid. The iron is measured off-line by flame atomic absorption spectrometry. The method can be applied to the preconcentration, separation and speciation of iron. The effects of parameters such as pH, sample flow rate, eluent flow rate, foreign ions and ligand concentration have been investigated. The effect of humic acid that can produce complexes with metal ions in natural systems has also been investigated. The results obtained indicate that the method is not affected by the presence of up to 10 ppm humic acid, which would be a very high concentration to be present in natural systems. The solid phase extraction method developed has been applied to the determination of iron in both natural water samples and sediment samples. The LOD was found to be 0.17 mg L⁻¹ when no preconcentration was used, although preconcentration factors of 100 could be achieved. The recovery values for spiked samples were between 100 and 104%. The results were compared statistically with those from the standard 1,10 phenanthroline method used for iron speciation in water systems. A Student’s t-test indicated no significant difference between the two methods. In addition, this method was applied to the analysis of a certified sediment sample, LGC 6156. Generally, a 10-fold preconcentration factor was required for the analysis of natural water samples.     

Effective binuclear Pd(II) complexes for Suzuki reactions in water

A series of new ionic binuclear Pd(II) complexes supported by water‐soluble bis(α‐diimine) ligands were prepared and employed as catalysts for the palladium‐catalyzed Suzuki reaction in aqueous media. The binuclear nature of the complexes increased the reaction rate, while electronic and steric modification of the ligand frameworks had a remarkable influence upon the catalytic activity of the palladium complexes. The catalysts were shown to be homogeneous through mercury poisoning experiments and complexes could be recycled more than 10 times without loss of catalytic activity. Copyright © 2013 John Wiley & Sons, Ltd.     

Optimal throughput performance in full-duplex relay assisted cognitive networks

Wireless Networks - In this paper, we study a full-duplex cooperative cognitive radio network with multiple full-duplex secondary users acting as potential relays for transmitting the packets of a...