Über die Verzerrungen von Wanderwellen auf kurzen Leitungen

Zusammenfassung Es wurde experimentell bewiesen, daß eine geeignete Leitung (konstanter Wellenwiderstand, keine Glimmentladung), eine einmalig hindurchgehende Wanderwelle nicht merklich verzerrt, auch wenn die Leitungslänge 75 m beträgt.Man konnte also klarstellen, daß die zu Beginn des Durchbruchs auftretende Abrundung der Durchschlagskurve eine physikalische Realität ist.Es hat sich ferner bei Untersuchung der vom statischen Durchschlag herrührenden Wanderwelle gezeigt, daß der Spannungsverlauf an der Funkenstrecke, wenn der Durchschlag durch Lichtanstoßen bei kleinerer als bei statischer Spannung erfolgt, derselbe ist wie bei statischer Spannung.Besonders vorteilhaft erwies sich die benutzte Meßanordnung, wenn man parallel der zu untersuchenden Funkenstrecke sehr kleine oder sehr große Kapazität schaltete. Eine Veränderung der Steilheit ergab sich dabei nicht und dies steht im Einklang mit der Toeplerschen Theorie über die Funkenkonstante. Es wurde wiederum die sehr große Reproduzierbarkeit der Durchschlagskurve (bis zu 50 kV) nachgewiesen.Herrn Prof. Dr.-Ing. E. h. W. Rogowski, der die Arbeit veranlaßte und sie durch seinen Rat förderte, sowie auch Herrn Dr.-Ing. Westermann, der die Durchführung der Versuche unterstützte, sei aufrichtig gedankt.     

LIS–lnterlink—connecting laboratory information systems to remote primary health–care centres via the Internet

A pilot study was performed to evaluate the feasibility of using the Internet to securely deliver patient laboratory results, and the system has subsequently gone into routine use in Poland. The system went from design to pilot and then to live implementation within a four-month period, resulting in the LIS-Interlink software product. Test results are retrieved at regular intervals from the BioLink^TM LIS (Laboratory Information System), encrypted and transferred to a secure area on the Web server. The primary health-care centres dial into the Internet using a local-cell service provided by Polish Telecom (TP), obtain a TCP/IP address using the TP DHCP server, and perform HTTP ‘get’ and ‘post’ operations to obtain the files by secure handshaking. The data are then automatically inserted into a local SQL database (with optional printing of incoming reports)for cumulative reporting and searching functions. The local database is fully multi-user and can be accessed from different clinics within the centres by a variety of networking protocols.     

Analysis of acoustic and optical signals used as a basis for controlling laser‐welding processes

Stud joints of 2017 aluminium alloy were friction welded and its joint strength was examined. A stair zone was formed at the weld interface. Although the hardness of the stair zone was almost the same as base metals, the heat-affected zone of the bar and the plate was softened. The tensile strength of joints tended to increase with a pressure and a friction time, and the highest tensile strength was 275 MPa (63.1% joint efficiency for the bar base metal). In the bending testing, joints were cracked in the weld zone at a bending angle of less than 5°. In the fatigue testing, joints fractured near the weld interface and the fatigue strength of joints increased as the tensile strength of joints was high.     

Das Gleichrichterverfahren zur Hochspannungsmessung mit Glimmlichtgleichrichtern

Electrical Engineering - Man kann beim Gleichrichterverfahren Glimmlichtgleichrichter an Stelle der Elektronenröhren anwenden, wenn man gleichzeitig die zu den Gleichrichtern parallele...     

New threshold voltage definition for undoped symmetrical DG MOSFET

A new threshold definition is proposed for symmetrical undoped double gate MOS (DGMOS). Threshold voltage is calculated using the potential model described in [1] with only two fitting parameters, the values of which do not depend on device geometry. Comparison with the results of numerical simulations and other models of V_T is presented and good accuracy of the new model is demonstrated.     

Buckling of thin-walled girders under compound load

A theoretical study of the local buckling kof thin-walled girders with closed polygonal cross-sections is presented. The load of the girder consists of compression, asymmetrical bending and shear. The parabolic distribution of shear stresses in webs is included in the theoretical considerations. The energy method is employed and sine and polynomial series are applied to describe the deflections of any wall. A sample of the results of numerical calculations is presented for a girder with rectangular cross-section subjected to bending and shear. Some results for a girder under asymmetrical bending are also included.     

Effect of surface preparation on the durability of NiCoCrAlY coatings for oxidation protection and bond coats for thermal barrier coatings

A principal concern with alumina‐forming coatings for high‐temperature oxidation protection and bond coats (BCs) for ceramic thermal barrier coatings (TBCs) used in gas turbines is the spalling of the alumina scales during service. This paper describes the effects of BC surface preparation on the durability of NiCoCrAlY coatings exposed under thermal cycling conditions. State‐of‐the‐art TBC systems deposited by electron beam physical vapor deposition (EBPVD) with NiCoCrAlY overlay BCs were found to fail as the result of defects which included transient oxides, defects in the BC surface, defects in the as‐deposited microstructure of the TBC, and excessive oxidation of reactive element additions. In some instances, the TBC life was greatly extended by surface treatments, such as fine polishing. The oxidation behavior of NiCoCrAlY coatings, absent a TBC, was found to be sensitive to Y content and to surface preparation. This paper describes how a variety of surface treatments affected coating lives and failure mechanisms.     

Effects of beta3-integrin blockade (c7E3) on the response to angioplasty and intra-arterial stenting in atherosclerotic nonhuman primates

Because the beta3-antagonist abciximab (c7E3 Fab) has significantly improved late outcomes after coronary angioplasty, the beta3 integrins have been implicated in the arterial response to injury. However, the mechanisms underlying this benefit are unknown. The observation that c7E3 binds beta3 integrins on vascular cells (alphavbeta3) with affinity equal to that for the platelet glycoprotein IIb/IIIa integrin has led to the hypothesis that c7E3 may act directly on the artery wall to prevent restenosis after angioplasty. To test this hypothesis, we studied the effects of c7E3 on structural changes within the artery wall after angioplasty or stent angioplasty in 23 male cynomolgus monkeys with established atherosclerosis. Animals were randomly assigned to receive either a bolus of c7E3 (0.4 mg/kg IV, n=11) followed by a 48-hour infusion (0. 2 microg. kg-1. min-1) or an equal volume of vehicle (n=12). Animals received weight-adjusted aspirin and heparin and then underwent unilateral iliac artery experimental angioplasty and subclavian artery stent angioplasty (Palmaz). Iliac artery lumen diameter (LD) was determined by angiography at baseline (LDPre), after angioplasty (LDPost), and 35 days later (LDDay35). Arteries were then fixed by perfusion and removed for analysis. Lumen, intima, media, and external elastic lamina (EEL) areas were measured in iliac artery cross sections. Values from each injured iliac artery were normalized to the contralateral uninjured iliac artery to control for interanimal variability in baseline artery size and atherosclerosis extent. Intimal area was also measured in subclavian stent cross sections. c7E3 blocked platelet aggregation and prolonged the bleeding time from 2.8+/-1.1 to 19.8+/-2.5 minutes, P<0.001. Experimental angioplasty increased LDPost an average of 28%, and the initial gain was similar in both groups (P=NS). Despite an anti-platelet effect, c7E3 did not inhibit iliac lumen narrowing (LDDay35-LDPost: c7E3, -0.69+/-0.17 versus vehicle, -0.99+/-.17 mm, P=0.35); intimal hyperplasia (neointima area: c7E3, 1.12+/-.28 versus vehicle, 1.22+/-.20 mm2, P=0.77); or decrease in artery wall size (EEL area [percent of uninjured control]: c7E3, 101+/-7% versus vehicle, 121+/-7%). Stent intimal hyperplasia was also unaltered by c7E3 treatment (neointimal area: c7E3, 1.09+/-0.16 versus vehicle, 1. 28+/-0.11 mm2, P=0.36). These results suggest that the benefits of c7E3 treatment in coronary angioplasty were not from inhibition of intimal hyperplasia or improved artery wall remodeling. Alternative mechanisms should be explored to explain improved late outcomes after angioplasty in patients treated with c7E3.