Electromagnetic radio frequency heating in the pulsed electric current sintering (PECS) process

Pulsed electric current sintering offers rapid sintering of many materials compared with hot press sintering. Earlier studies had demonstrated that neither sparks nor plasma formation occur in a typical apparatus such as Dr. Sinter™. Hitchcock et al. showed that electromagnetic radio frequency (rf) emission occurred during the pulsing current and suggested this emission was a relevant augmentation to the hot press sintering in addition to the current flow in the specimen. In this report the importance of rf emission in the sintering process is demonstrated and opportunities to further exploit this approach to improve the sintering process are suggested

Comparative characterization of P91 and 10CrMo9-10 creep resistant steel welds

Abstract:Abstract: P91 and 10CrMo9-10 creep resistant steels are critical to the performance of boiler tubes and power generating plants in general. Components made from these materials are mainly joined by welding. This paper reports on the comparative study of the effect of TIG and SMAW welding on the mechanical performance of P91 and 10CrMo9-10. TIG was used for root welding while SMAW was used for weld filling of V-butt joints. Specimens of the two alloys prepared using recommended welding procedures are evaluated using optical microscopy and Vickers micro hardness assessment. Some specimens were post weld heat treated while others were not. Post weld heat treated (PWHT) specimens exhibited similar properties as the corresponding base materials for both steels. TIG welding resulted in significant grain size reduction in both steels. PWHT produced more consistent grain structure, which is favorable

Performance Evaluation of Wireless Communication in a Modular Heliostat Field.

Thesis (MEng)--Stellenbosch University, 2021.ENGLISH ABSTRACT: Concentrating Solar Thermal (CST) is differentiated from other renewable energy technologies by the ability to store large amounts of thermal energy cost-effectively. CST, and especially Central Receiver Systems (CRS), still require further develop- ment to drive down the Levelised Cost of Electricity (LCOE) to remain economi- cally competitive in the renewable energy market. Heliostats are used in CRS to reflect sunlight onto a central receiver. Data trans- mission is required between a central server and Local Control Units (LCUs) to enable high precision tracking, over-the-air calibration updates, and swift emer- gency reaction. Wireless communication technologies have shown both capital cost and construction time saving potential for CST plants, but practical performance knowledge of operation in heliostat fields is limited. The purpose of this study is to evaluate the feasibility of wireless communica- tion within a CST field b y m eans o f p ractical t ests a imed t o d etermine t he influ- ence of interference, dense networks, and transmission range on the network per- formance. The project forms part of the H2020 PREMA project, which aims to advance novel energy systems in the drying and pre-heating of furnace manganese ore. A communication network consisting of 50 LCUs, capable of controlling 300 heliostats, was designed and implemented to simulate data transmission in a CST network. Performance experiments were conducted at the Helio100 site to de- termine the effect of various performance limiting factors. Experimental results showed a high performing, robust wireless communication system with a worst- case polling rate of 0.79 s, which satisfies a m ajor r equirement o f t he communi- cation network. The thesis concludes that wireless communication is feasible in a CST field, which could lead to the reduction of capital costs and construction time, reducing the LCOE of CST plants.AFRIKAANSE OPSOMMING: Gekonsentreerde Sonkrag (GSK) word onderskei van ander hernubare energie tegnologieë deur die vermoë om groot hoeveelhede termiese energie koste effektief te stoor. Gekonsentreerde sonkrag, en veral sentrale ontvangersisteme, benodig nog verdere ontwikkeling om die gelykte koste van elektrisiteit te verlaag om ekonomies kompeterend te bly in die hernubare energie mark. Heliostate word in sentrale ontvangersisteme gebruik om sonlig op ’n sentrale ontvanger te weerkaats. Data-oordrag is nodig tussen ’n sentrale bediener en plaas- like beheer eenhede om hoë akkuraatheid volgingsbeweging, oor die lug kalibrasie- opdaterings en vinnige noodreaksie moontlik te maak. Draadlose kommunikasie- tegnologie het die potensiaal vir kapitaal kostebesparings en konstruksie tydbespa- rings vir GSK-aanlegte getoon, maar praktiese kennis oor die netwerk gedrag in heliostaat velde is beperk. Die doel van hierdie studie is om die uitvoerbaarheid van draadlose kommunika- sie binne ’n sentrale ontvangersisteem te evalueer aan die hand van praktiese toetse om die invloed van interferensie, digte netwerke en die transmissie afstand, op die netwerk werking te bepaal. Die projek vorm deel van die H2020 PREMA-projek, wat streef om nuwe energie stelsels te bevorder vir die droog en voorverhitting pro- ses van mangaanerts. ’n Kommunikasienetwerk bestaande uit 50 plaaslike beheer eenhede, wat 300 heliostate kan beheer, is ontwerp en geïmplementeer om data-oordrag in ’n gekon- sentreerde sonkrag netwerk te simuleer. ’n Eksperimentele ondersoek is op die Helio100-terrein gedoen om die effek van verskillende netwerk beperkende faktore te bepaal. Eksperimentele resultate toon ’n hoë prestasie, robuuste draadlose kommuni- kasiestelsel wat, in die slegste geval, die hele netwerk binne 0.79 s kan bedien en so ’n hoofvereiste van die kommunikasie netwerk bevredig. Die tesis het tot die gevolgtrekking gekom dat draadlose kommunikasie binne ’n GSK heliostaat veld uitvoerbaar is en dat dit moontlik tot ’n verlaging in kapitaal koste en konstruksie tyd in sentrale ontvangersisteme kan lei en die gelykte koste van elektrisiteit van gekonsentreerde sonkrag aanlegte kan verminder.Master

Cost of breast preservation surgery for cancer

CITATION: Smit, B. J., Liebenberg, T. J. & Du Toit, D. F. 1992. Cost of breast preservation surgery for cancer. South African Medical Journal, 82:481.The original publication is available at http://www.samj.org.za[No abstract available]Publisher’s versio

Cortical lens opacities in the young patient- an indication for a lipogram?

Aim. To determine the characteristics and prevalence of lenticular opacification in patients with underlying dyslipidaemia.Methods. Eighty patients of both genders and all ages (18- 90 years) were enrolled in the trial if they met the inclusion criteria for dyslipidaernia: Patients were included if their fasting serum cholesterol and triglyceride concentrations were > 5.2 mmol/l and > 2.3 mmol/l, respectively, when measured on three separate occasions over a 1-month period. Patients were excluded if they suffered from any condition known to cause or predispose them to elevated lipid levels or lenticular opacification. Lenticular changes were assessed by means of a slit-lamp through the fully dilated pupil and other physical signs were documented subsequent to thorough physical evaluation.Results. In addition to the classic clinic signs of dyslipidaemia, 31% of patients had cortical lens opacities. Cortical opacities were twice as prevalent as Achilles tendon thickening (16.3%) in our study, the second most prevalent sign of elevated lipid levels. In the subgroup of patients aged under 50 years, 55% had lenticular opacities, predominantly cortical (80%).Conclusions. Cortical lens opacification was the most prevalent sign of dyslipidaemia and it occurred at a relatively young age in our trial population in those patients who were affected. Cortical lenticular opacification should be regarded as an indication for blood lipid profile evaluation

PROBLEMS IN THE OPERATION OF LARGE CRYOGENIC SYSTEMS

Two liquid-hydrogen test facilities were operated for fourteen months. These cells have the capability for transfer of liquid hydrogen at flow rates up to 100 lbs/sec and have a total storage capacity for liquid hydrogen of 156,000 gallons. A number of design and operational problems were met, for example, stresses in 8-in. diameter transfer lines, times and quantities of liquid hydrogen required for cooldown of transfer lines, dewar instrumentation, gas requirements for pressurization of liquid hydrogen filled dewars, and techniques for warmup of large cryogenic dewars. Solutions to many of these problems are described and outstanding problems discussed on the basis of current observations. In addition, some techniques are described that are employed for safe operation of the liquid hydrogen facility, including helium block systems for leaky valves, room inerting to prevent fire or explosion in the event of a hydrogen leak, and the purity control of dewar pressurizing gases and the purity control of purges of gas and liquld hydrogen transfer lines. A summary is included of major modifications that are planned or underway for these test facilities. (auth

Ulnar impaction syndrome : a case series and imaging approach

Ulnar-sided wrist pain can be attributed to many pathological processes. This can include traumatic, inflammatory or degenerative conditions. Ulnar impaction syndrome is a group of syndromes that are degenerative conditions of the wrist caused by an abnormal joint configuration or due to abnormal use. This leads to an increase in axial loading across the ulnar side of the wrist with resultant joint degeneration. The structures in the wrist concerned in this syndrome are the triangular fibrocartilage complex, the distal radio-ulnar joint and the lunate triquetral bones at their ulnar articulations. Even though a number of modalities exist to image the wrist, the options for accurately assessing ulnar impaction syndrome are limited and may be challenging. Accurate assessment of the triangular fibro-cartilage complex is essential, as it lies central in the classification of the disease.http://www.scielo.org.za/scielo.php?script=sci_serial&pid=1681-150X&lng=pt&nrm=isoam2017Radiolog

The open abdomen : Part 2 : Management of the open abdomen using temporary abdominal closure

Management of the open abdomen is a complex undertaking, as it not only involves difficult wound healing but also the prevention of many serious local and systemic complications. In this article the different types of temporary wound closure methods and their pros and cons are discussed. It appears from our experience that specific negative-pressure dressings produce the best outcomes with regard to morbidity and mortality, as they are adapted to address the particular needs of different grades of open abdomen.http://www.woundhealingsa.co.za/index.php/WHS