A profile of the speech therapy and audiology clientele at a tertiary hospital in the Western Cape

It became evident in the light of proposed changes in the healthcare system in South Africa that there was little descriptive client data with regard to Speech Therapy and Audiology Services in South Africa to support proactive service planning. This study therefore aimed to describe trends in the demographic, diagnostic, and attendance variables of first-time clients who had attended the Speech Therapy and Audiology out-patient department (OPD) at a tertiary hospital in the Western Cape over a five-year period (1999-2003). A longitudinal, retrolective, descriptive survey was conducted. Records were reviewed for a sample of the population of all new clients who had attended the Speech Therapy and Audiology OPD in the five-year time frame. Data was collected using a form designed for this purpose. The data was coded and then analysed descriptively. It was found that the highest percentages of subjects attended for a hearing loss or voice disorder. The ENT department at the study hospital made the highest percentage of referrals to the Speech Therapy and Audiology Department. This was followed by referrals from the education sector. The age profile showed the highest percentage of subjects to be in the age category of 7-12 years. Similar percentages of male and female subjects were found. English was the language that a client was most likely to speak. Geographically the highest percentage of subjects attending were from the Klipfontein region, followed by the Central area. Attendance data showed that just over 70 % of subjects attended within a three-month period or attended no more than two appointments. Percentage of appointments attended decreased with increasing numbers of booked appointments. Implications of this research include issues around record keeping and service delivery. The results of this study cannot be generalized to all Speech Therapy and Audiology services in South Africa. However, the data may serve as a guide for planning services. Further research addressing service delivery issues is needed with the field of Speech Therapy and Audiology

Assessment of the harmonic behaviour of a utility-scale photovoltaic plant

Thesis (MScEng)--Stellenbosch University, 2017.ENGLISH ABSTRACT: The rapidly increasing deployment of utility-scale solar photovoltaic (PV) plants worldwide presents new technical challenges including the risk of unacceptably high harmonic voltage distortion in the utility network. PV plants affect the harmonic voltage distortion at their point of common coupling primarily by two distinct mechanisms: generation of harmonic currents due to switching action of the inverters and introduction of series and parallel resonances caused by connection of the plant to the network. The objective of this study is to investigate the harmonic behaviour of utility-scale PV plants based on the case-study of a 75 MW PV plant in the Northern Cape province of South Africa. In this work, a harmonic simulation model of a PV plant is developed in DIgSILENT PowerFactory which represents the passive network components with sufficient accuracy to study the frequency response over the harmonic frequency band from 50 to 2500 Hz. 10-minute and 3-second aggregated harmonic measurement data and event-triggered waveform data were captured over a 12-day period using an IEC 61000-4-30 Class A power quality meter installed at the plant’s 132 kV point of connection (POC). A quality assessment of harmonic measurement data shows that the accuracy of harmonic voltage and current measurements are likely to be significantly affected by quantisation and transducer error for even and higher-order harmonics. Analysis of the 3-second aggregated harmonic quantities indicates that their fluctuation during each 10-minute period is sufficiently small that the 10-minute average values adequately approximate the short-term and long-term behaviour of the plant. The harmonic behaviour of the plant is investigated by considering the relationship between harmonic voltage and current emissions and active power, reactive power and time of day. Certain harmonic voltages increase with increasing plant active power output whilst others decrease but all harmonic currents remain constant or increase with increasing active power. It was not possible to quantify the relative impact of active and reactive power variation as the plant operates in voltage control mode. Brief periods of high harmonic current distortion were noted during start up and shut down of the plant. High harmonic currents at the 23rd harmonic order correspond with a series resonance identified in the model thus validating the POC frequency sweep simulation. A comparative analysis of different published methods for assessment of the harmonic emissions contribution of the PV plant is performed. All methods show similar trends in identifying dominant harmonics and general harmonic behaviour but the magnitudes of the calculated emissions differ significantly in some instances. Where accurate frequency sweep data of the utility network and phasor measurement data are both available, the plant model enables application of the harmonic vector method to discriminate between utility and plant contributions. Simulated voltage emissions based using the manufacturer’s quoted inverter current emissions do not closely match measured emissions due to the complexity of active source interactions within the real power system. Comparison of the mean, 75th percentile and 90th percentile emissions assessments demonstrate the effectiveness of percentile assessment in eliminating outlying high distortion periods from the assessed results.AFRIKAANSE OPSOMMING: Die vinnige toenemende implementering van grootskaalse sonkragfotovoltaïese (PV) aanlegte wêreldwyd, bied nuwe tegniese uitdagings, insluitende die risiko van onaanvaarbare hoë harmoniese spanningvervorming in die netwerk. PV aanlegte beïnvloed die harmoniese spanningvervorming by hul punt van algemene koppeling, hoofsaaklik deur twee afsonderlike meganismes: die opwekking van harmoniese strome as gevolg van die skakel aksie van die omkeerders en die inleiding van reeks en parallelle resonansies wat veroorsaak word deur die koppel van die kragstasie aan die netwerk. Die doel van hierdie studie is om die harmoniese gedrag van grootskaalse-PV aanlegte te ondersoek, gebaseer op die gevallestudie van 'n 75 MW PV kragstasie in die Noord-Kaaps provinsie van Suid-Afrika. In hierdie werk word 'n harmoniese simulasiemodel van 'n PV-aanleg ontwikkel in DIgSILENT PowerFactory, wat die passiewe netwerk komponente verteenwoordig met voldoende akkuraatheid, om die frekwensieweergawe oor die harmoniese frekwensieband van 50 tot 2500 Hz te bestudeer. 10-minute en 3-sekonde geaggregeerde harmoniese metingsdata en gebeurtenisgeaktiveerde golfvormdata is oor 'n tydperk van 12 dae opgeneem met behulp van 'n IEC 61000-4-30 klas A kragkwaliteitsmeter geïnstalleer by die substasie se 132 kV punt van verbinding (POC). 'n Kwaliteitsbeoordeling van harmoniese metingsdata toon dat die akkuraatheid van harmoniese spanning en stroommetings waarskynlik aansienlik beïnvloed sal word deur kwantiserings en oorvormer foute vir ewe en hoër-orde harmonieke. Analise van die 3-sekonde geaggregeerde harmoniese waardes dui aan dat hul fluktuasie gedurende elke 10 minute tydperk klein genoeg is, sodat die 10-minute gemiddelde waardes die korttermyn- en langtermyngedrag van die aanleg ‘n voldoende benadering is. Die harmoniese gedrag van die aanleg word ondersoek deur die verband tussen harmoniese spanning en stroom emissies en aktiewe krag, reaktiewe krag en tyd van die dag te oorweeg. Sekere harmoniese spannings verhoog met toenemende aktiewe kraguitset, terwyl ander afneem, maar alle harmoniese strome bly konstant of verhoog met toenemende aktiewe kraguitset. Dit was nie moontlik om die relatiewe impak van aktiewe en reaktiewe kragvariasie te kwantifiseer nie aangesien die aanleg in die spanningskontrolemodus funksioneer. Kort tydperke van hoë harmoniese stroomvervorming is tydens die aanvang en afsluiting van die aanleg opgemerk. Hoë harmoniese strome op die 23ste harmoniek stem ooreen met 'n reeks resonansie wat in die model geïdentifiseer is en dus valideer die POC-frekwensie sweep simulasie. 'n Vergelykende analise van verskillende gepubliseerde metodes vir die assessering van die harmoniese emissie bydrae van die PV-aanleg word uitgevoer. Alle metodes toon soortgelyke neigings in die identifisering van dominante harmonieke en algemene harmoniese gedrag, maar die groottes van die berekende emissies verskil in sommige gevalle beduidend. Waar akkurate frekwensie sweep data van die netwerk en fasor meting data albei beskikbaar is, maak die model dit moontlik vir die toepassing van die harmoniese vektor metode om te onderskei tussen netwerk en PV-aanleg bydraes. Gesimuleerde spanningsemissies gebaseer op die vervaardiger se verklaarde omkeerder-emissies, pas nie noukeurig ooreen met gemete emissies nie as gevolg van die kompleksiteit van aktiewe broninteraksies binne die werklike kragstelsel. Vergelyking van die gemiddelde 75ste persentiel- en 90ste persentielemissiesevaluasies toon die effektiwiteit van persentielassessering om die afgeleë hoë vervormingsperiode uit die geassesseerde resultate te elimineer

Advanced buck converter power supply ABCPS for APT

The United States Department of Energy (DOE) is planning to fabricate an Accelerator for the Production of Tritium (APT) at their Savannah River Site, to provide Tritium for national defense. The 1700 million electron volt (MeV) proton beam accelerator will be powered by radio frequency (RF) klystrons. A direct current (DC) power supply is required for each of the approximately two hundred and fifty 1-megawatt (MW) continuous wave klystrons in the RF power system. The requirements are that the power supply meet output performance specifications, provide fault protection for the klystron, have high efficiency, high reliability, good maintainability, and be readily manufacturable. As the power supplies are one of the largest cost elements in the accelerator, a technology review was made to determine the most economical approach to satisfy the requirements. A switch-mode power supply employing a buck-regulator was identified as being potentially the lowest cost approach. As the switch represents a certain development risk, a small-scale prototype has been constructed for evaluation, and has resulted in the decision to fabricate a full-scale prototype power supply. A description of the hardware will be presented

Bis[μ-N,N′-bis(2,6-diisopropylphenyl)ethene-1,2-diamido]-1,4(η2);1:2κ4 N:N;3:4κ4 N:N-bis(diethyl ether)-1κO,4κO-di-μ-hydrido-2:3κ4 H:H-2,3-dichromium(II)-1,4-dilithium(I) pentane hemisolvate

The title compound, [Cr2Li2(C26H36N2)2(μ-H)2(C4H10O)2]·0.5C5H12, is a binuclear chromium complex bridged by two hydrogen atoms. Each chromium atom is coordinated in a distorted square-planar geometry by one chelating bis­(2,6-diisopropyl­phen­yl)ethene-1,2-diamido ligand via its two N atoms. Additionally, two diametrically opposed lithium ether adducts coordinate in an η4 mode on the backbone of the ligands. There is a crystallographic inversion center in the middle of the Cr2H2 ring. One of the isopropyl groups is disordered over two positions in a 0.567 (7):0.433 (7) ratio. Disorder is also observed in the pentane hemisolvate molecule

Robot-assisted laparoscopic transperitoneal pelvic lymphadenectomy and metastasectomy for melanoma: initial report of two cases

Robotic pelvic lymphadenectomy is a well established procedure in the urologic and gynecologic literature. To our knowledge robotic pelvic lymphadectomy for metastatic melanoma has yet to be described. Herein we present the first report of robot-assisted pelvic lymphadenectomy in malignant melanoma. After placement of six laparoscopic ports (12 mm camera, three 8-mm robotic ports, 12-mm and 5-mm assistant ports) the DaVinci S robot (Intuitive Surgical, CA, USA) was docked in standard fashion with the patient in low lithotomy. In both cases the patients had enlarged pelvic lymph nodes on computed tomography and complete excision of these masses was accomplished along with complete lymphadenectomy extending from Cooper’s ligament to just below the hypogastric artery in case 1 and to level of the bifurcation of aorta in case 2. A PK Maryland Dissector and monopolar scissors were used for dissection. Both patients were discharged on postoperative day #1. Robotic pelvic lymphadenectomy can be safely used for management of patients with metastatic melanoma involving the pelvic lymph nodes. Compared with the standard open procedure, pelvic lymphadenectomy with robotic assistance is associated with excellent vision and minimum morbidity