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The effects of Ni content on the microstructure and the wetting behavior of Sn–9Zn– x Ni solders on Al and Cu substrates, as well as the mechanical properties and electrochemical corrosion behavior of Al/Sn–9Zn– x Ni/Cu solder joints, were investigated. The microstructure of Sn–9Zn– x Ni revealed that tiny Zn and coarsened Ni 5 Zn 21 phases dispersed in the β-Sn matrix. The wettability of Sn–9Zn–xNi solders on Al substrate was much better than that on Cu substrate. With increasing Ni content, the wettability on Cu substrate was slightly improved but became worse on Al substrate. In the Al/Sn–9Zn– x Ni/Cu joints, an Al 4.2 Cu 3.2 Zn 0.7 intermetallic compound (IMC) layer formed at the Sn–9Zn– x Ni/Cu interfaces, while an Al-Zn-Sn solid solution layer formed at the Sn–9Zn– x Ni/Al interface. The mixed compounds of Ni 3 Sn 4 and Al 3 Ni dispersed in the solder matrix and coarsened with increasing Ni content, thus leading to a reduction in shear strength of the Al/Sn–9Zn– x Ni/Cu joints. Al particles were segregated at both interfaces in the solder joints. The corrosion potentials of Sn–9Zn–xNi solders continuously increased with increasing Ni content. The Al/Sn–9Zn–0.25Ni/Cu joint was found to have the best electrochemical corrosion resistance in 5% NaCl solution.

The detachment frequency of coalesced bubbles is one of the important parameters in the boiling heat transfer model at high heat flux. Although some researches on detachment frequency of coalesced bubbles have been done for common liquids, the work on cryogenic liquids is relatively insufficient. A visual experimental apparatus was built for observing the boiling in liquid nitrogen. The growth process of coalesced bubbles was recorded by a high-speed camera, emphasizing on the detachment frequency of coalesced bubbles from the circular, horizontal heating surfaces. The effects of the heating surface material, the surface diameter and the heat flux on the detachment frequency were analyzed. The available empirical correlations from common liquids are compared with our experimental data to check their applicability in liquid nitrogen, where the detachment frequency is 13.47 s−1.

Data are presented on the reaction J/psi--> p pbar eta using 7.8 million J/psi triggers collected by the BEjing Spectrometer (BES). A partial wave analysis is performed. A clear enhancement near the p eta(pbar eta) threshold is observed. It is fitted with a JP=1/2- resonance with mass $M= 1530\pm 10$ MeV and width $\Gamma = 95\pm 25$ MeV. In addition, there is a peak around 1650 MeV with JP=1/2- preferred also, fitted with $M =1647\pm 20$ MeV and $\Gamma = 145^{+80}_{-45}$ MeV. These two N* resonances are believed to be the two well established states, S11(1535) and S11(1650), respectively. It is the first partial wave study of the production of these resonances from J/psi decays.

The commercial application of rare earth magnets has been in part held back by their poor corrosion resistance. As part of e!orts to overcome this problem two types of nickel coatings were electroplated on the surface of Nd 2 Fe 14 B substrates, one from an acidic plating solution and the other from an alkaline solution. The corrosion characteristics of both coatings were evaluated both by electrochemical potentiodynamic polarisation and by physical exposure to high-humidity environments. The results showed that both coatings enhanced the corrosion resistance of substrate. However, both the degree of protection a!orded by the coating and the strength of its adhesion to the substrate strongly depended on the chemical composition of the original plating solution. The coating plated from the acidic solution provided a high degree of protection against both aqueous and atmospheric corrosion, whilst that plated from the alkaline solution behaved only marginally better than the bare substrate. It was postulated that the poor performance of the coatings plated from the alkaline bath could have been due to the spontaneous formation of a passive oxide "lm between the Nd 2 Fe 14 B substrate and the nickel coating. ( 2001 Elsevier Science B.V. All rights reserved.

BES data on $J/\psi \to \gamma (K^{\pm} K_S^0 \pi^{\mp})$ are presented. There is a strong peak due to $\eta(1440)/\iota$, which is fitted with a Breit-Wigner amplitude with $s$-dependent widths for decays to $K^*K$, $\kappa K$, $\eta \pi\pi$ and $\rho\rho$; $\kappa$ refers to the $K\pi$ S-wave. At a $K\bar{K}\pi$ mass of $\sim 2040$ MeV, there is a second peak with width $\sim 400$ MeV; $J^P = 0^-$ is preferred over $1^+$ and $2^-$ respectively by 5.2 and 6.8 standard deviations. It is a possible candidate for a $0^-$ $s\bar sg$ hybrid partner of $\pi(1800)$.

A single-phased La2CuO4+δ sample with Tc of 17 K prepared by electrochemical oxidation is reported in this paper. Its structural and physical properties are studied by X-ray diffraction, resistance, magnetic susceptibility and thermopower measurements for the first time. It is found that the hole concentration is around 0.12, and the structure is pseudo-tetragonal. The Tc suppression, compared with other Tc’s in La2CuO4+δ system, is considered to be an indication of the “stripe pinning” in the La2CuO4+δ related to the famous “1/8 problem”.

A partial wave analysis of BES J/psi --> gamma(eta pi(+)pi(-)) data has been performed in the mass region 1.1 to 2.0 GeV. A peak is observed due to eta(1440) in the eta pi(+)pi(-) invariant mass distribution; J(P) = 0(-) is preferred over li. Its mass is M = 1385 +/- 7 MeV and it decays into both eta sigma and a(0)(980)pi, with BR[a(0)(980)pi, a(0) --> eta pi/eta sigma] = 0.70 +/- 0.12(stat) +/- 0.20(syst). Destructive interference between the two decay modes is observed. In addition, in the higher eta pi(+)pi(-) mass region, there is a definite 2(-+) signal, with M = 1840 +/- 15 MeV and Gamma = 170 +/- 40 MeV and an additional 0(-+) signal at 1760 +/- 35 MeV. We also find a possible contribution from a 1(++) signal decaying dominantly through a(0)(980)pi; its mass and width are fitted to be M = 1505 +/- 20 MeV and Gamma = 130(-20)(+50) MeV. (C) 1999 Elsevier Science B.V. All rights reserved.

Theta burst stimulation (TBS) is a variant of repetitive transcranial magnetic stimulation (rTMS) protocols. This technique has advantages over classic regular pulse rTMS including speed of delivery and low intensity of stimulation. This makes TBS an attractive form of stimulation to use in experimental and particularly clinical settings.

A new transient based protection criterion for high voltage transmission line based on the wavelet transform results of voltage transient signals at the two ends of the line is presented. The difference of high frequency voltage transients at the two ends of the transmission line when in-zone faulted and out-zone faulted is analyzed, and the transient voltage content ratio and transient voltage singularity ratio are deduced. Two-end transient voltage protection criterion using the transient voltage singularity ratio is proposed, and the principles of the protection settings are given. The calculation of transient voltage content ratio and transient voltage singularity ratio using wavelet transform is deduced. Simulations of different fault locations and different fault types are carried out for testing and analyzing the protection criterion.