可记录媒体的检测策略

可记录媒体或者一次性写入媒体在过去的几年中无疑已经成为各种光盘格式中的新贵。目前CD-R已经达到了发展的颤峰,而DVD-R正在以不容置疑的迅猛发展速度成为新一代记录媒体的先锋。尽管CD-R和DVD-R之间存在着很多的不同,它们都需要完善的品质控制。     

有线和无线宽带接入产品技术

射频存储系统的目标市场有两个，一个是宽带网络，一个是无线局域网：下图介绍的是第一公里的无线宽带接入系统。图的中央有一个中枢（hub)，它的周围是一个分布网络。这是一个包括光和电的、数据和模拟结合的网络，这种系统在中国的大城市都有广泛的部署。圆圈是飞利浦开发的一些结点、中枢和分布网络，包括放大器和光电设备。     

Online Calculation and Prediction of the Strip Temperature in a Hot Strip Finishing Mill

The paper deals with a physical model for the calculation of the strip temperature in a hot rolling mill. Beside the heat transfer from the strip to the environment in the different mill sections a sub‐model for the material properties of steel including phase transitions is introduced. For the application in a process automation system an online adaptation of the model to the current state of the mill is indispensable. The adaptation is explained in detail.     

Thermische Anmerkungen zu Zeitkonstanten von Wänden

Zusammenfassung Man erh?lt kompakte Approximationen von Laplace-übergangsfunktionen, wenn die Koeffizienten des Nenners aus den Zeitkonstanten des Systems abgeleitet werden. (üblicherweise führt dies auf das Problem der Nullstellensuche einer transzendenten Funktion.) Es ist bekannt (Gough [1], Stephenson [2]), da? für die meisten W?nde drei Zeitkonstanten ausreichen, um hinreichend genaue übergansfunktionen zu erhalten. Die Taylor-Entwicklung der Kettenmatrix im Laplaceraum wird für beliebige W?nde mit eindimensionalem W?rmestrom mit der Picard'schen Methode berechnet. Für ebene Mehrschichtw?nde ist dafür eine explizite L?sung angegeben. Die ersten N Zeitkonstanten werden n?herungsweise aus der (N+1). Ordnung der Partial-Summe der Taylor-Entwicklung berechnet. Dies wird mit einer generalisierten Pade-Approximation bewerkstelligt, die eine Totzeit enth?lt und direkt auf ein Nennerpolynom führt (ohne transzendente Wurzeln). Die Wurzeln konvergieren geometrisch zu den Eigenwerten mit wachsendem N (die Eigenwerte stellen die reziproken Zeitkonstanten dar). Die Komplexit?t der gesamten Prozedur liegt kaum über derjenigen für ein System mit konzentrierten Parametern der Ordnung N+1. Es werden Beispiele angegeben, um mit den „exakten” Frequenzg?ngen zu vergleichen.     

Peripheral nerve stimulation by time-varying magnetic fields

PURPOSE: A study was performed to assess the stimulation threshold for healthy adults using sinusoidally oscillating gradients. METHOD: One hundred thirteen healthy adults were examined in the study. ECG and physiological parameters were measured. All measurements were performed of both the head and the abdomen. The subjects were measured in the supine position with the region of interest positioned in the center of the gradient coils. The measurement was performed for three orthogonal, four oblique, and double oblique orientations. RESULTS: No volunteer reported painful, severe stimulation. The mean thresholds for peripheral stimulation in head and body measurement were similar: 85.5% of stimulation during examination of the head and 87.6% during measurements of the abdomen were reported when the y-gradient was used. CONCLUSION: The greatest frequency of reported stimulations occurs when the y-gradient is used. This was confirmed by the results and supports the hypothesis that orthogonal to the y-axis the body has its largest conductive loop, resulting in the strongest peripheral stimulation.     

Initial experiences with the MR "magnitude contrast angiography of the lower extremities

45 patients with occlusive peripheral vascular disease were examined by MR angiography in a retrospective study. A FISP 3D sequence was used by acquiring a rephased and a dephased data set. The individual slices were post-processed by using a maximum-intensity-projection algorithm. The MRA results of the popliteal and tibioperoneal arteries were compared to conventional or digital angiography. In comparing these techniques MR angiography cannot be accepted for pre- and postoperative staging of patients with occlusive peripheral vascular disease. In future new MRA techniques may be useful in postoperative staging of patients with peripheral vascular stenosis.     

Evaluation of NDT methods for detection of prestressing steel damage at post-tensioned concrete structures

For an assessment of the risk potential of existing structures, where in the case of prestressing steel damage the load-bearing capacity could be significantly affected, non-destructive testing techniques which enable reliable evaluation of the condition of the prestressing steels are of utmost importance. During the demolition of a post-tensioned concrete bridge in Berlin where damage of prestressing wires due to hydrogen-induced stress corrosion cracking were found in former investigations, parts of the girders of the bridge superstructure could be taken out. After non-destructive investigations by means of two testing techniques based on magnetic leakage flux measurement and one technique based on electromagnetic resonance measurement, subsequent removal of the concrete cover up to the ducts, opening the ducts and evaluation of the prestressing steels allowed a verification of the results obtained by the NDT methods. From the results it can be concluded that areas with fractures of several wires can be detected by the two techniques based on magnetic leakage flux measurement.