Some commentary on the choice of rotor bar material for inductionmotors

Almost any metal can be used in the design of the squirrel cage of an induction machine. Obviously lead is not used because of its low melting point and magnesium because of its low flash point. Others are rejected because of the cost, lack of strength, resistance, thermal conductivity, or manufacturability including ease of joining. Basically, the choice fails to two materials, aluminum and copper and their alloys. For lowest cost of manufacture, especially for mass production, aluminum surpasses copper. In order to determine which of the two materials is the best takes the combined skills of an electrical, a mechanical and a metallurgical engineer. This paper discusses some of the considerations in the choice of rotor bar material     

Similarity study of ROSA-III and fist large break cuonterpart tests to BWR large break LOCA

A large break test in a recirculation pump suction line with the assumption of LPCI-diesel generator failure was conducted at the ROSA-III test facility of Japan Atomic Energy Research Institute. A counterpart test was also performed at the FIST test facility of General Electric Company. The objective of the tests was to develop common understanding and interpretation of the controlling thermal-hydraulic phenomena during a large break LOCA of a BWR. The fundamental thermal-hydraulic phenomena in the ROSA-III and FIST tests such as the system pressure, mixture level and fuel rod surface temperatures agreed well. The FIST test had more bundle uncovery than that in ROSA-III since lower plenum steam in the FIST test flowed out of the jet pumps when they uncovered allowing more liquid to drain from the bundle. The ROSA-III and FIST tests and a BWR counterpart were analyzed with the RELAP5/MODI (cycle 018) code. The similarity of the ROSA-III and FIST large break tests to a BWR large break LOCA has been confirmed through comparison of calculated results though they are slightly different in details. It is perhaps desirable to reexamine the DNB and interphase drag correlations and the jet pump models usedin the code.     

On the elastic flexibility of axially loaded omega and toroidal bellows

The present paper draws together previous theoretical solutions on bellows and derives new results where necessary, to summarise the various theories in a unified picture. In so doing, a number of features can be highlighted which might otherwise escape attention. The strong similarities of solutions based on different equations or different methods of evaluation, emergy automatically for both omega and toroidal bellows under axial loading.Although most previous theoretical investigations on omega and toroidal bellows have involved the application of energy methods, a number of interesting aspects of these solutions have not been highlighted. In particular the solutions lead to bounds on flexibility characteristics on the basis of small displacement linear elastic theory. A companion paper extends the analyses to cater for creep behaviour.     

Three-dimensional ADF imaging of individual atoms by through-focal series scanning transmission electron microscopy

Aberration correction in scanning transmission electron microscopy has more than doubled the lateral resolution, greatly improving the visibility of individual impurity or dopant atoms. Depth resolution is increased five-fold, to the nanometer level. We show how a through-focal series of images enables single Hf atoms to be located inside an advanced gate dielectric device structure to a precision of better than 0.1 x 0.1 x 0.5 nm. This depth sectioning method for three-dimensional characterization has potential applications to many other fields, including polycrystalline materials, catalysts and biological structures.     

Guidelines for the use of carotid endarterectomy: current recommendations from the Canadian Neurosurgical Society

OBJECTIVE: To assess preoperative diagnosis of intra-abdominal acute diseases manifesting as a RAAA and determine treatment options. DESIGN: Retrospective review, with a mean follow-up period of 4 years. SETTING: Vascular Department, Medical School, University "Federico II" of Naples, Italy. METHODS: In 12 patients (8.7%) with clinical suggestion of RAAA were found other intra-abdominal acute lesions, associated with asymptomatic aortic aneurysm in 10 of them and absence in one; the remainder had an intact common iliac artery aneurysm. Sonography was performed in the operating room in 5 patients (41.6%) in shock, 4 hemodynamically stable patients (33.3%) had CT scanning or MRI investigations, while 3 (25%) underwent surgery directly. INTERVENTIONS: Three patients were not operated; one half of patients were submitted to emergency laparotomy and in the remaining 3 patients a preoperative preparation was made. Simultaneous aneurysm repair and nonvascular procedures were performed in 4 patients; nonvascular operations alone were carried out in 5 patients. 4 patients underwent a successful later treatment of their aneurysms: two aneurysmectomy and two endoluminal stenting were done within 4 months. RESULTS: Weight loss and fever were found at 58.3% and 50% of patients with concomitant intra-abdominal acute diseases; both were present in 41.6%. Noninvasive imaging techniques detected associate lesions in 6 of 8 patients (75%) and absence of aneurysm in one having a bleeding adrenal mass. There were three in-hospital deaths: one patient died of metastatic disease without operation and two after surgery (22.2%). Two late deaths from cancer cachexia occurred at 11 months and 3.6 years. CONCLUSIONS: Atypical findings, such as weight loss and fever may be suggestive of coincident lesions in patients with suspected RAAA. Noninvasive assessment may identify associated diseases simulating aneurysmal rupture, without a delay in the treatment. A selective policy of medical or operative therapy may be effective to minimize risk of complications and mortality rate.