Qualitätssicherung von Widerstandspunktschweißverbindungen mit Hilfe der Schallemissionsanalyse (SEA)

Quality Control of Spot Weldings by Acoustic Emission The quality control of spot weldings has to be performed continuously during welding. Acoustic Emission (AE) is a suitable method for online surveillance of the welding process. Several measuring parameters of AE are tested with regard to the characterization of the spot weld quality during the welding process. It is shown that the quality of the spot weld can be evaluated by measuring the energy of the AE signals during the welding process. This parameter can be applied also for controlling the welding time of each spot weld under constant current load. On the other hand, the quality of the spot welds can be estimated by measuring the AE count during cooling after finishing the weld spot. By this method the welding process can be controlled with regard to the tendency in the long run.     

冷轧板孔洞缺陷成因分析

冷轧板孔洞是薄规格冷轧产品中常见的一种缺陷。孔洞大致可分为三大类：正常拉裂类孔洞主要与基体的夹杂有关;疤块孔洞与坑状孔洞主要为钢基掉块或异物压入基体形成,其它类孔洞与轧制工艺过程控制有关;冷轧因素引起的孔洞与轧制力及张力分配不合理、冷轧异物压入及板型不良等因素有关、本文重点对热轧工序原因造成的冷轧孔洞缺陷进行了分析,采用扫描电镜、金相显微镜、热轧在线表面检测仪等设备对比分析了冷轧板出现的孔洞缺陷出现的原因,根据分析结果制定了相关的措施。     

Delayed crystallization of ultrathin Gd2O3 layers on Si(111) observed by in situ X-ray diffraction

ABSTRACT: We studied the early stages of Gd2O3 epitaxy on Si(111) in real time by synchrotron-based, high-resolution X-ray diffraction and by reflection high-energy electron diffraction. A comparison between model calculations and the measured X-ray scattering, and the change of reflection high-energy electron diffraction patterns both indicate that the growth begins without forming a three-dimensional crystalline film. The cubic bixbyite structure of Gd2O3 appears only after a few monolayers of deposition.     

Use of the Medingen automated analyzer with evaluating unit as an automatic digital photometer]

Common errors in managing shock in children are failure to recognize shock, failure to recognize continuing blood loss, and inadequate replacement due to lack of familiarity with the normal blood volume of children. For practical purposes, the normal blood volume of every child is considered to be 40 ml/lb (88 ml/kg). In hypovolemic shock the blood volume is reduced by at least one fourth. For initial management, an intravenous line is established, blood is drawn for cross matching, and 10 ml/lb (22 ml/kg) of Ringer's lactate solution is administered as rapidly as possible. If this bolus, which represents one fourth of the normal blood volume, brings the blood pressure to normal, only maintenance fluid is then administered. If the child remains hypotensive, a second bolus of 10 ml/lb (22 ml/kg) is administered rapidly. Children who require a second bolus of Ringer's lactate solution nearly always need blood transfusion also. Many have occult bleeding, usually in the abdomen. If intra-abdominal bleeding is thought to be possible but not definitely present, paracentesis using an angiocath is performed. If no blood returns, 10 ml/lb (22 ml/kg) of saline is instilled and the return considered significant if more than slightly pink.     

640 Mbit/s waveguide transmitter at 38 GHz

The principle of a digital waveguide transmitter working at 38 GHz is given. A pulse-code-modulation simulator, with a bit rate of 640 Mbit/s, produces the modulation signal and also allows error-rate measurements. Typical switching times of the modulator are less than 500 ps. These results have been obtained by use of a varactor diode installed in a rectangular R band waveguide.     

On the numerical approximation of a degenerated hyperbolic system

The heat exchanger in a heat pump system may be conveniently described by a degenerated hyperbolic system, namely the zero Mach-number limit of the Euler equations. This leads to a mixed hyperbolic/parabolic system with coupled time-dependent boundary conditions. We propose a method-of-lines discretisation by using an upwinding scheme. We derive stability estimates for the linearisation with frozen coefficients. The resulting differential–algebraic equation has a perturbation index of 2 and a weak instability with respect to the space step size. The latter property is validated experimentally even for the nonlinear system. In contrast, the perturbation index did not exceed one in the numerical experiments.