Cold-worked and hydrogen chargedNbHf as studied by TDPAC and positron lifetime measurements

Time differential perturbed angular correlation (TDPAC) and positron life-time measurements on cold-worked and hydrogen chargedNbHf indicate a strong binding of hydrogen decorated vacancy clusters with Hf impurities. Both TDPAC and positron lifetime results are mutually consistent on this aspect. Transformation of H-vacancy clusters into H-bubbles is indicated by the positron lifetime behaviour at annealing temperatures beyond 900 K. Impurity effects like oxygen pickup and coating of voids cannot be ruled out at elevated temperatures.     

Precipitation hardening in 350 grade maraging steel

Evolution of microstructure in a 350 grade commercial maraging steel has been examined. In the earlier stages of aging, the strengthening phases are formed by the heterogeneous precipitation, and these phases have been identified as intermetallic compounds of the Ni₃ (Ti, Mo) and Fe₂Mo types. The kinetics of precipitation are studied in terms of the activation energy by carrying out isothermal hardness measurements of aged material. The mechanical properties in the peak-aged and overaged conditions were evaluated and the flow behavior examined. The overaging behavior of the steel has been studied and the formation of austenite of different morphologies identified. The crystallography of the austenite has been examined in detail. From the microstructural examination of peak-aged and deformed samples, it could be inferred that the dislocation-precipitate interaction is by precipitate shearing. Increased work hardening of the material in the overaged condition was suggestive of looping of precipitates by dislocations.     

Permeability measurements of the flow of interdendritic liquid in equiaxed aluminum-silicon alloys

A method developed recently for measuring instantaneous permeability in the mushy zone of aluminum-copper alloys is used to measure permeability in aluminum-silicon alloys. Permeability was also measured in packed glass beads using water, because measurements could be conducted in the absence of microstructural coarsening. Experimental data are compared with the Kozeny-Carman equation to determine the value of k _C , the Kozeny-Carman constant. The results indicate that when k _C =5.0, all the instantaneous permeability data agree well with the Kozeny-Carman equation. Factors affecting the accuracy of permeability measurements, such as surface oxidation of the sample, flow channeling during the test, microstructural coarsening, and liquid fraction reduction due to back diffusion in the solid are discussed. An experimental technique that minimizes errors due to these factors is outlined.     

Early detection of visual field progression in glaucoma: a comparison of PROGRESSOR and STATPAC 2

AIM: To compare the performance of PROGRESSOR (pointwise linear regression) and STATPAC 2 (comparison with baseline values) in detecting early deterioration in the visual fields of glaucoma patients. METHODS: Visual field series from 19 untreated normal tension glaucoma eyes which were deteriorating on clinical grounds were analysed by PROGRESSOR and STATPAC 2. Progression criteria for PROGRESSOR were (1) inner points: slope < -1 dB/year, p < 0.05 and (2) edge points: slope < -2 dB/year, p < 0.05. Criteria for STATPAC 2 were p < 0.05 change probability for any point on three consecutive fields. Detection time was defined as the time interval between the initial field and the first field in which at least one progressing point was identified. Detection times produced by the two techniques were compared. RESULTS: PROGRESSOR and STATPAC 2 agreed on progression in all 19 eyes. Mean detection time for PROGRESSOR was 1.077 (SD 0.985) years and for STATPAC 2 was 2.161 (1.357) years. PROGRESSOR detected progression sooner than STATPAC 2 in 18 eyes (p < 0.01), Wilcoxon matched pairs signed rank test). PROGRESSOR detected progression earlier by a mean of 1.085 (0.936) years. CONCLUSIONS: PROGRESSOR consistently detected progression earlier than STATPAC 2. The PROGRESSOR software is a useful tool for the early detection of visual field deterioration in glaucoma.     

蓝牙模块的测试方案

测试项目在蓝牙环境中，哪些方面需要测试？蓝牙模块包括连接到主机设备的无线电 (硬件)和堆栈 (软件)。协议是构成堆栈的一套代码，在生产车间中将不会测试协议。修订系统软件可能会改变硬件性能，但必须在设计集成阶段对其进行粼选。需要使用的一些重要参数，如误码率(BER)、功率电平等对功能进行测试。选择测试必需理解由于无线电的设计方式哪些内容可能会改变，并根据测试的项目查看其发挥的作用。它是否提供了独特的功能？没有提供哪些功能？如打印机使用的蓝牙链路。在技术得到验证前，打印机可能仍会通过电缆提供打印功能，因此测…     

Effect of series compensation on the voltage instability of EHV long lines

In this paper, the effects of the operating conditions and dynamic performance on the voltage instability phenomena of EHV lines with series compensation is discussed. Exponential modelling of loads and exact long-line equations are used in the analysis. Graphs showing the variations of the receiving-end voltage and the transformer tap ratio with time for an assumed load variation are given. It is shown that when series compensation is provided, the chances of voltage instability occurring are less. The effect of switched series compensation on the voltage instability is also investigated. The error in using short-line equations for the analysis of voltage instability phenomena is highlighted. The random loading conditions of the system and the random load parameter variations are also considered for the first time in analysing the voltage instability phenomenon.     

Effect of Sb, P, Sn and B on the microstructure and creep properties of normalized and tempered 1.25 Cr-0.5 Mo steels

A program to study the effect of Sb, P, Sn and B on creep properties of four normalized and tempered 1.25 Cr-0.5 Mo steels at 538°C (1000°F) has been completed. Results show that even a combined addition of large amounts of Sb, P and Sn does not affect short time creep strength or ductility of the steel at 538°C (1000°F). Addition of B resulted in an increase or decrease of creep strength depending on the nature of the impurity species present, presumably due to B-impurity interactions. Regardless of the effect on creep strength, B additions caused sharp reductions in rupture ductility in all cases. Comparison of the present results on the four laboratory steels (100 pct bainite) with results of a previous study on a commercial steel (60 pct bainite + 40 pct ferrite) show that the effect of microstructure becomes negligible and rupture strength values of the various steels at 538°C (1000°F) approach each other at rupture times in excess of 10⁴ h.     

Localization of angiotensin AT1 receptors in the rat heart conduction system

We characterized angiotensin II receptor subtypes in the conduction system of the rat heart using quantitative autoradiography. In both the sinoatrial and atrioventricular nodes, binding could be totally displaced by losartan, and was insensitive to PD 123177, indicating that angiotensin II receptors in the conduction system of the rat heart belong to the AT1 subtype. Angiotensin AT1 receptors could play a direct role in the regulation of the heart chronotropic properties.