Vibration fracture behavior of Sn–9Zn–<Emphasis Type="Italic">x</Emphasis>Cu lead-free solders

The effect of Cu content on the microstructure and the vibration deformation mechanisms of a potential lead-free solder, Sn–9Zn–xCu (x = 0.2, 0.5, 0.7, 1.0 wt.%), are examined in this study. Results show that Zn-rich phase and Sn–Zn eutectic decreased, while Cu–Zn intermetallic compound and proeutectic Sn-rich phase increased with increasing the Cu content. For the specimens with high Cu content (0.7Cu and 1.0Cu), hard massive Cu₅Zn₈ existed mostly amongst the proeutectic Sn-rich phase dendrites, and Zn-rich dispersed unevenly, leading to the deterioration in the tensile strength and ductility. Under a constant vibration force and constant initial-deflection testing, the high Cu specimen with a higher damping capacity was able to absorb more vibration energy and thus possessed a greater vibration fracture resistance. In addition, the lamellar-deformed structures (LDS) and Cu₅Zn₈ were able to increase the crack tortuosity, which in turn increased the crack propagation resistance.     

Microstructural characteristics of PTA-overlayed NbC on pure Ti

This study uses the technique of PTA (plasma transferred arc) to overlay NbC reinforcing particles on the surface of commercially pure Ti in order to investigate the microstructural features of the overlayer and the interface between the overlayer and base metal by changing the overlaying current. The results indicate that the matrix phase of the overlayer was -Ti containing about 10 at.% Nb and 1 at.% C. NbC and precipitated TiC produced by dissolved NbC reacted with Ti dispersed in the matrix. The microstructure of the cross-section of the overlayer (from surface to base metal), which was composed of -Ti, can be separated into three layers: an upper overlayer with TiC, a middle overlayer with TiC and NbC, and a lower overlayer (interfacial layer and heat affected zone, HAZ). Due to solidification beginning at the interface and the effect of dilution, the TiC in the interfacial layer was finer. Owing to faster solidification under low-current conditions, the TiC particles were finer than under high-current conditions. Also, dendritic TiC under a low-current in the upper overlayer was also finer than under a high-current. Meanwhile, TiC precipitate that resulted from heterogeneous nucleation and Gibbs' free energy was also found around NbC. This NbC diffusion layer between TiC and NbC may have been βNb₂C phase.     

我厂烧碱成本偏高的原因探讨

我厂是国内大型氯碱骨干企业,设计规模为10万t/a烧碱,采用隔膜电解法制碱工艺,主要产品有质量分数分别为30％液碱、45％液碱和96％片碱。多年来我厂烧碱的各项主要经济技术指标均居全国同行业先进水平,但烧碱生产成本不容乐观,在全国同行业中处于中下游水平,制约了我厂经济效益的提高。为明确差距的根源所在,我们通过查阅中国氯碱工业协会发布的2001年1—10月的全国氯碱行业基本情况统计资料,选取一些地理位置、规模与我厂相似的企业平均相关数据,与我厂同期成本情况做一个比较分析。     

Spinal cord herniation after stabbing injury

The commercially available spray management valve provided consistent flow rates when used with hand-compression sprayer systems. The 15-psi spray management valve maintained a constant flow rate of 180, 150, and 155 ml/min in combination with a fine 45 degrees flat fan nozzle and Hudson. B&G, and Chapin hand-compression sprayers, respectively. The 30-psi spray management valve maintained a constant flow rate and adequate spray-on time when combined with the coarse flat fan nozzle for each of the 3 hand-compression sprayers tested.     

The effects of die shapes and additives on the physical and biodegradable properties of biodegradable cushioning extruded foams

In this study, efforts were focused on the effects of the operating parameters, i.e. die shapes (DS), PVA ratio (PR), additives (AT) on the physical and biodegradable properties of the corn/PVA extrudates. We also evaluated the extrudates as cushioning materials. The process variables were the operating, conditions, die shapes (○, ∞, ? and O ), PVA ratio (40%, 50%, 60%) and additives [sodium bicarbonate (NaHCO₃), calcium carbonate (CaCO₃) and calcium hydroxide (Ca(OH)₂)]. The experiment is a 4 × 3 × 3 factorial design. Samples of each treatment were collected and the physical, mechanical and chemical properties were measured and analysed using the PROC ANOVA and PROC CORR of the SAS 6.0 software package. 35 The experimental results indicated that: (a) The change of die shapes (DS) had a significant effect on the longitudinal expansion, bulk density, compressibility and biodegradability properties of the extrudates; (b) the change of PVA ratio (PR) had a significant effect on the longitudinal expansion, bulk density and compressibility, but no effect on the biodegradability properties of the extrudates; and (c) the change of additives (AT) had a significant effect on the longitudinal expansion, bulk density and compressibility, but no effect on the spring index of the extrudates. Copyright © 2003 John Wiley & Sons, Ltd.     

Untersuchungen über das Strangpressen kubisch-flächenzentrierter Metalle. Teil II: Kraftbedarf und Kraftverteilung

Investigation of the extrudability of face-centred cubic metals Part II: During continuous extrusion at certain intervals dry oxides are discharged. This is explained with the aid of rheological investigations. If a shearing device according to DIN standard is used the results may show errors in a range of 70% and more. A new device is described which avoids this source of error. The shear strength of high purity aluminium was determined at various temperatures and rates of deformation. Investigations were conducted under similar conditions on the extrusion of aluminium and a relationship between shear strength and power requirement was established. On this basis the power requirement to extrude new alloys may be predicted by comparing the shear strength of this alloy with the shear strength of an alloy whose extrudability is known. Direct extrusion experiments under isothermal conditions were conducted in the reduction range R = 1.2–300. The linear relationship in double logarithmic scale exists only in the range of R = 4–40. Indirect extrusion experiments also showed a linear relationship below the reduction rate R = 4 in a logarithmic scale. It was found that during indirect extrusion a dead metal zone is also formed and this explains the divergence of the found pressure distribution from the theoretical values. The normal pressure of the container was measured at a number of points at various temperatures and reduction rates. In the range of 150°–170°C peculiar unsteadiness occured. Normal pressure on the change of the velocity of extrusion was investigated with the aid of a stepped-down die and a strong dependence was found. A device was developed to compare the plasticity of cubic face centered metals, and it was found that the maximum plasticity is reached at 90% of the melting point in degrees absolute. Efficiency investigations during extrusion showed that the power consumption required to overcome the radial shear in continuous extrusion is 60% to 77%, whereas the power required to overcome the total shear in extrusion in a piston driven press is 94% to 87%. Extrusions inside a calorimeter showed, on the basis of mechanothermodynamic conversion, that 85% to 94% of the power was used for the deformation of the metal.     

99mTc-MIBI used for diagnosis of portal hypertension: an experimental study

The authors investigated the relationship between portal-systemic shunting and portal pressure in 16 CCl4-induced cirrhotic wistar rats by 99mTc-MIBI photography of heart and liver. Based on radio-counts taken at 30 minutes after 99mTc-MIBI was given per rectum 8 rats or medial clonic vein 8 rats, heart radio-counts/liver radio-counts (H/L) and portal-systemic shunting index (SI) were recorded. It was shown that 1. H/L and SI of the two cirrhotic groups were greater than those of normals (P < 0.001); 2. H/L in cirrhotic rats by rectum 99mTc-MIBI administration was more closely related to free portal pressure (FPP, r = 0.83, P < 0.01) than in those by venous route (r = 0.74, P < 0.05) and its regressive formation FPP (kPa) = 0. 24 + 4.06 (H/L) was deduced and used to calculate portal pressure of cirrhotic rats. The very good relationship between the calculated and measured portal venous pressure was shown in a group of 12 cirrhotic rats (r = 0.85, P < 0.01). These findings suggested that the rectum administration of 99mTc-MIBI may be a useful method in calculating portal pressure and portal-systemic shunting in portal hypertensive patients.     

The software engineering of a microcomputer application system

A system development methodology is outlined before describing its application to the development of a microcomputer system. Structured analysis techniques were used for determining the information flow through the system. The system was then structured into modules using structured design and information hiding techniques. The detailed design of the system was described in pseudocode. The system was coded in assembler supplemented by a set of structured programming macros. A systematic bottom-up testing procedure was adopted for system integration.