OBJECTIVES Many paediatric antiretroviral therapy (ART) programmes in Southern Africa rely on CD4⁺ to monitor ART. We assessed the benefit of replacing CD4⁺ by viral load monitoring. DESIGN A mathematical modelling study. METHODS A simulation model of HIV progression over 5 years in children on ART, parameterized by data from seven South African cohorts. We simulated treatment programmes wi...

A new static alignment method for trans-tibial prostheses is suggested using the individual load line as a reference. Standing posture and static alignment of 18 experienced trans-tibial prosthetic users with good walking ability were determined and compared with 20 healthy persons. The individual load line was defined by means of the new Otto Bock alignment system "L.A.S.A.R. Posture". The sag...

The principle of load balancing is examined for dynamic resource allocation subject to certain constraints The emphasis is on the performance of simple allocation strategies which can be implemented on line Either nite capacity constraints on resources or migration of load can be incorporated into the setup The load balancing problem is formulated as a stochastic optimal control problem Variant...

This paper describes a methodology for obtaining minimum load-shed at selected buses from voltage stability margin viewpoint. The buses for load-shed have been selected based on line voltage stability index and its sensitivities at operating point. Computational algorithms for minimum load-shed have been developed using conventional particle swarm optimization (PSO) and coordinated aggregation ...

Under unbalanced supply condition low order harmonics will appear at the input and output terminals of the PWM AC to DC converter. Based on the positive and negative sequence components, an unbalanced transfer matrix in terms of the input phase voltages is derived. An on-line method using a neural network (NN) is used to implement this transfer matrix. It is shown that by using an additional lo...

Voltage instability is a major concern in operation of power systems and it is well known that voltage instability and collapse have led to blackout or abnormally low voltages in a significant part of the power system. Consequently, tracking the proximity of the power system to an insecure voltage condition has become an important element of any protection and control scheme. The expected time ...

In a hierarchical server environment jobs are to be assigned in an on-line fashion to a collection of servers which form a hierarchy of capability: each job requests a specific server meeting its needs, but the system is free to assign it either to that server or to any other server higher in the hierarchy. Each job carries a certain load, which it imparts to the server it is assigned to. The g...

In this paper, an optimal power flow based approach has been applied for multi-transactions deregulated environment for ATC determination with SVC and STATCOM. The main contribution of the paper is (i) OPF based approach for evaluation of ATC with multi-transactions, (ii) ATC enhancement with FACTS devices viz. SVC and STATCOM for intact and line contingency cases, (iii) Impact of ZIP load on A...