电子封装、QFP和MCM热变形的实验及数值分析

0Introduction Anelectronicpackageisgenerallyconstructedwithanactivesiliconchip,mountisland,gold wires,leadframesandsoldersasshowninFig.1(a).Toprotectfromtheenvironment,thesilicon chipisusuallyencapsulatedinresin.SincethesematerialshavedifferentCTE(coeffic…     

Two-Dimensional Cellular Automata for Pseudo-Random Pattern Generators and for Highly Secure Stream Ciphers

Pseudo-random properties of a class of two-dimensional (2-D) 5-neighborhood cellular automata (CA), built around nonlinear (OR, AND) and linear (XOR) Boolean functions are studied. The site values at each step of the 2-D CA evolution are taken in parallel and form pseudo-random sequences, which satisfy the criteria established for pseudo random number generator (PRNG): long period, excellent random qualities, single bit error propagation (avalanche criteria), easy and fast generation of the random bits. A block-scheme for secure Stream Cipher based on 2-D CA is proposed. The 2-D CA based PRNG algorithm has simple structure, use space-invariant and local interconnections and can be easily realized in very large scale integration or parallel optoelectronic architectures.     

On the anomalous sound propagation of nematics just above the clearing point

The sound attenuation coefficient due to the critical fluctuations of the order parameter is formulated in the isotropic phase of nematics by taking account of the mode-coupling effects between the order parameter and the hydrodynamic shear mode. The result is compared with the available experimental data.     

Exhaustive search of the configurational space of heat-shock protein 90 with its inhibitor by multicanonical molecular dynamics based dynamic docking

Multicanonical molecular dynamics based dynamic docking was used to exhaustively search the configurational space of an inhibitor binding to the N-terminal domain of heat-shock protein 90 (Hsp90). The obtained structures at 300 K cover a wide structural ensemble, with the top two clusters ranked by their free energy coinciding with the native binding site. The representative structure of the most stable cluster reproduced the experimental binding configuration, but an interesting conformational change in Hsp90 could be observed. The combined effects of solvation and ligand binding shift the equilibrium from a preferred loop-in conformation in the unbound state to an α-helical one in the bound state for the flexible lid region of Hsp90. Thus, our dynamic docking method is effective at predicting the native binding site while exhaustively sampling a wide configurational space, modulating the protein structure upon binding.     

Experimental analysis of thermal displacement and strain distributions in a small outline J-leaded electronic package by using wedged-glass phase-shifting moiré interferometry

To evaluate the influence of a printed wiring board (PWB) with a high coefficients of thermal expansion (CTE) on the thermal deformation of a small outline J-leaded electronic package (SOJ), a newly developed phase-shifting method was applied to moiré interferometry. This phase-shifting moiré interferometry method uses a wedged glass plate as a phase shifter to obtain displacement fields with a sensitivity of 100 nm/line. This technique also enabled the quantitative determination of strain distributions in all observation areas. Thermal loading was applied from room temperature (25 °C) to an elevated temperature (100 °C), and then the thermal strains of SOJ with and without the PWB were compared. The results showed that the concentrations of the longitudinal strains ε_xx and ε_yy became increasingly prominent when mounted on the PWB, and the shear strains γ_xy were concentrated at the corners of the silicon chip. The values of these strains increased by about 50% when the SOJ was mounted on the PWB.     

Semidirect Products of Association Schemes

In his 1996 work developing the theory of association schemes as a generalized group theory, Zieschang introduced the concept of the semidirect product as a possible product operation of certain association schemes. In this paper we extend the semidirect product operation into the entire set of association schemes. We then derive a way to decompose certain association schemes into smaller association schemes. We also investigate to what extent this product helps us to understand and characterize the structure of association schemes. We give some examples to show that the semidirect product produces many schemes that cannot be described as neither the direct product nor the wreath product of smaller schemes.This research was supported by Com²MaC-KOSEF, Korea.     

On Quasi-thin Association Schemes with Odd Number of Points

Let (X, R) be an association scheme in the sense of P.-H. Zieschang (1996, “An Algebraic Approach to Association Schemes,” Lecture Notes in Mathematics, Vol. 1628, Springer, New York/Berlin), where X is a finite set and R is a partition of X × X. We say that (X, R) is quasi-thin if each element of R has a valency of at most two. In this paper we focus on quasi-thin association schemes with an odd number of points and obtain that (X, R) has a regular automorphism group when n_O^θ(R) is square-free.     

Synthesis of cyclo‐olefin copolymer latexes and their carbon nanotube composite nanoparticles

An efficient and environmentally benign synthetic method for the production of the stabilized cyclo‐olefin copolymer latexes and their carbon nanotube composite nanoparticles has been developed using an emulsion ring opening metathesis copolymerization catalyzed by the 2nd generation Grubbs catalyst in aqueous solution. Homopolymerizations of norbornene (NB) and dicyclopentadiene (DCPD) in aqueous solution yield unstable polymer latexes in combination with a large amount of their flocculation fractions. Copolymerizations of NB or DCPD with a selected liquid cyclo‐olefin comonomer dramatically improve not only the colloidal stability of the copolymer latexes but also the thermal stability of the copolymer nanoparticles. The liquid cyclo‐olefin comonomer plays a double role as a liquefied agent for the solid NB and DCPD monomers before the emulsification treatment, and a reactive comonomer itself to control entirely the copolymerization system. The as‐prepared cyclo‐olefin copolymer latexes exhibit an exceptionally high compatibility with a well‐dispersed carbon nanotube (CNT) in aqueous solution due to strong π–π interactions between the graphitic surfaces of the CNT with the C‐C double bonds located on the cyclo‐olefin copolymer main chains. Accordingly, a binary blending of these two well‐dispersed colloidal systems in aqueous solution led to the fabrication, for the first time, of the highly electrical conductive cyclo‐olefin copolymer/CNT composite nanoparticles. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4584–4591