The Effect of Micro-Alloying of Sn Plating on Mitigation of Sn Whisker Growth

Tin (Sn) is a key industrial material in coatings on various components in the electronics industry. However, Sn is prone to the development of filament-like whiskers, which is the leading cause of many types of damage to electronics reported in the last several decades. Due to its properties, a tin-lead (Sn-Pb) alloy coating can mitigate Sn whisker growth. However, the demand for Pb-free surface finishes has rekindled interest in the Sn whisker phenomenon. In order to achieve properties similar to those naturally developed in a Sn-Pb alloy coating, we carried out a study on deposited films with other Sn alloys, such as tin-bismuth (Sn-Bi), tin-zinc (Sn-Zn), and tin-copper (Sn-Cu), electrodeposited onto a brass substrate by utilizing a pulse plating technique. The results indicated that the Sn alloy films modified the columnar grain structure of pure Sn into an equiaxed grain structure and increased the incubation period of Sn whisker growth. The primary conclusions were based on analysis of the topography and microstructural characteristics in each case, as well as the stress distribution in the plated films computed by x-ray diffraction, and the?amount of Sn whisker growth in each case, over 6 months under various environmental influences.     

Effect of noisy carrier reference signal and interference on performance of MSK receiver

This paper considers the coherent detection of minimum shift keying signal and a degradation in error rate performance from ideal due to an interference and a phase discrepancy between the carrier of the received signal and the carrier of the receiver. The error rate is calculated for the simple receiver model with integrate‐and‐dump circuits. The reference carrier signal unsteadiness is presented by the probability density function of the first order non‐linear PLL phase error, while the uncertainty due to an interference is involved in the system model with a random phase of cosine signal that accompanied the useful signal. Copyright © 2004 John Wiley & Sons, Ltd.     

超宽带多注速调管的模拟研究

本文介绍了多注速调管的发展历史和现状,以及速调管模拟软件的发展情况。用1．5维软件KIystron-MSU和2．5维软件Arsenal-MSU对超宽带多注速调管进行了设计计算,并对计算结果进行分析,得到了比较好的输出特性。计算结果表明可以实现该超宽带多注速调管,其带宽10-14％,增益40～50dB,效率40～50％。     

Bioactive Titanium Surfaces Enriched with Silver Nanoparticles Through an In Situ Reduction: Looking for a Balance Between Cytocompatibility and Antibacterial Activity

This research aims toward an antibacterial and osteoconductive Ti₆Al₄V surface by chemical etching–oxidation treatment and in situ reduction of silver nanoparticles. Starting from a previously developed process, already proved to enhance the osteoinductive ability of titanium, different parameters are changed to tailor the amount of silver and its distribution across the surface oxide layer thickness. The samples are characterized by scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, release of silver, biofilm formation (Staphylococcus aureus), and cytocompatibility toward human osteoblasts progenitor cells. The total amount of silver in the surface oxide layer depends only on the concentration of the silver precursor. The time of the addition of the silver precursor, during the oxidation treatment, affects the oxide layer thickness, dimension, and distribution of the nanoparticles across the surface oxide: they are larger and accumulate on the outermost layer, if the addition occurs early. The maximum ion release occurs after 24 h and lasts up to 14 days; the later addition of silver precursors leads to sustaining the silver release for a longer time. The samples prepared with the higher concentration of the silver precursor are bactericide, but highly cytotoxic, whereas the other ones are bacteriostatic and moderately cytotoxic.     

Magnetocaloric effect in La<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Ca<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>MnO<Subscript>3</Subscript> for <Emphasis Type="Italic">x</Emphasis> = 0.3, 0.35, and 0.4

We present systematic studies of the magnetocaloric properties of the polycrystalline La_1−x Ca _x MnO₃ system for x = 0.3, 0.35, and 0.4 near a second-order phase transition from a ferromagnetic to a paramagnetic state. The crystal structure of the studied manganites was shown to be in good agreement with previous reports. The value of the magnetocaloric effect has been determined from the measurement of magnetization as a function of temperature and external magnetic field. The maximum entropy change detected in La_0.7Ca_0.3MnO₃ at a field of 2 T reaches 8 J/kg K which exceeds that of gadolinium. In all studied samples, the paramagnetic–ferromagnetic transition is very narrow but no hysteresis is observed and the transitions are identified as second-order ones. The phase transition in La_0.7Ca_0.3MnO₃ appears to be almost of first-order.     

Indium tin oxide nanorod electrodes for polymer photovoltaics

We have deposited indium tin oxide (ITO) nanorods on glass and glass/ITO substrates by DC sputtering and by e-beam deposition. The properties of the nanorods deposited by different methods and on different substrates have been investigated. The ITO nanorods were also used as an electrode in bulk heterojunction polymer solar cells. We found that the nanorod morphology and sheet resistance had a significant effect on the solar cell performance, with significant improvements in the efficiency compared to commercial ITO film substrates in all cases except for e-beam deposited nanorods on glass that had high sheet resistance. The best power conversion efficiency achieved was 3.2 % (for sputtered ITO nanorods on ITO), compared to 2.1 % for commercial ITO substrates.     

Fabrication of nanoplasmonic arrays with square symmetry using spin-coating method

A spin-coating method was applied for the first time to prepare a colloid monolayer on the optical crossed gratings used as a template. Four polystyrene colloids of various nominal sizes and different surface charges were spin-coated on templates with periods matched to the particles size. Three types of coverage were described depending on the spin-coating parameters and particles type. The optimal coverage was obtained for all four particles sizes. A way of finding the right spin-coating parameters was proposed. The analysis of a coverage capability of polystyrene particles showed that neutral particles have the highest ability to order on the templates used. Large monolayered areas of ordered particles were used as a lithographic mask for generating a pattern of gold nanoparticles with a square symmetry. A few hundred square micrometers large, continuous and fully defect-free areas of gold nanoparticles were produced on the nearly entire surface of the templated substrates.     

Why do overqualified incumbents deviate? Examining multiple mediators.

In the modern marketplace, especially when unemployment is high, more and more Americans find themselves overqualified (i.e., possessing more competencies than the job requires). Using and extending person-environment fit theory and the stressor-emotion model of counterproductive work behaviors (CWBs), we examine whether overqualified employees are more likely to display CWBs than employees who feel their positions match their qualification levels. Further, we examine why overqualified employees may behave in counterproductive ways and compare the empirical viability of several theoretically derived competing mediators. Based on data from a sample of full-time employees (n = 215), we found that consistent with the theoretical frameworks, overqualified incumbents display nondesirable counterproductive work behaviors because they become cynical about the meaningfulness of their activities. We further show that although poor person-job fit or inadequate psychological contracts can motivate such misbehavior, cynicism dominates as a reason for why overqualified employees engage in counterproductive work behaviors. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Augmented Lagrangian based reconstruction of non-uniformly sub-Nyquist sampled MRI data

MRI has recently been identified as a promising application for compressed-sensing-like regularization because of its potential to speed up the acquisition while maintaining the image quality. Thereby non-uniform k-space trajectories, such as random or spiral trajectories, are becoming more and more important, because they are well suited to be used within the compressed-sensing (CS) acquisition framework. In this paper, we propose a new reconstruction technique for non-uniformly sub-Nyquist sampled k-space data. Several parts make up this technique, such as the non-uniform Fourier transform (NUFT), the discrete shearlet transform and a augmented Lagrangian based optimization algorithm. Because MRI images are real-valued, we introduce a new imaginary value suppressing prior, which attenuates imaginary components of MRI images during reconstruction, resulting in a better overall image quality. Further, a preconditioning based on the Voronoi cell size of each NUFT data point speeds up the conjugate gradient optimization used as part of the optimization algorithm. The resulting algorithm converges in a relatively small number of iterations and guarantees solutions that fully comply to the imposed constraints. The results show that the algorithm is applicable not only to sub-Nyquist sampled k-space reconstruction, but also to MR image fusion and/or resolution enhancement.     

Transmission electron microscopic observation of dislocations in x-phthalocyanine crystals

Transmission electron microscopy has been utilized to directly reveal the defects that are present in thin single crystals of x-phthalocyanine polymorph. The bright field images are characteristic of dislocation arrays while the associated diffraction patterns indicate that the parent monoclinic structure of x-phthalocyanine may undergo a stress-induced phase transformation into a daughter orthorhombic structure. The transformation is akin to a martensitic process as a result of the operation of an invariant plane strain. The dislocation arrays observed have been interpreted in terms of slip dislocations.