Papers by Keyword: POD

Abstract: The Port of Durban (PoD) is currently upgrading its existing power supply to a supply voltage of 132 kV. The existing 33 kV supply cables are old and have exceeded their designed life resulting in unplanned power outages. The existing 33 kV switchgear is old and obsolete as a result it is difficult to maintain. The existing maximum demand capacity will not be able to cater for the additional loads required for the planned expansion developments.The electrical load flow is a very important and fundamental tool for the analysis of any power systems and in the operations as well as planning stages. The electrical load flow study was conducted using PowaMaster software to analyse the behaviour of PoD’s electrical network post implementation of the new substation onto the currently existing network. In performing the electrical load flow study, load diversification is one of the critical input parameters that was considered because it is a true representation of the network behavior. The load forecasting was based on the planned developments commissioned between 2017 and 2027. The electrical load flow study was also to validate if all the new selected reticulation cables and transformers as part of the design have been correctly sized and will be able to operate reliably without compromising security of firm supply with the implementation of all the planned future loads. This report entails the results of the electrical load flow study that was conducted to analyse the voltage stability and system reliability of the PoD’s electrical network in conjunction with new 132/33 kV Langeberg Substation.

Abstract: Structural Health Monitoring (SHM) techniques have gained an increased interest to be utilised alongside NDI techniques for aircraft maintenance. However, to take the SHM methodologies from the laboratory conditions to actual structures under real load conditions requires them to be assessed in terms of reliability and robustness. In this work, a statistical analysis is carried out for an SHM system for damage detection and characterisation in composite structures. The sensitivity of the platform to parameters such as noise, sensor failure, placement tolerances and bonding has been investigated and reported.

Abstract: Structural Health Monitoring (SHM) techniques have gained an increased interest to be utilised alongside NDI techniques for aircraft maintenance. However, to take the SHM methodologies from the laboratory conditions to actual structures under real load conditions requires them to be assessed in terms of reliability and robustness. In this work, a statistical analysis is carried out for a passive SHM system capable of impact detection and identification. The sensitivity of the platform to parameters such as noise, sensor failure and in-service load conditions has been investigated and reported.

Abstract: Modular structured multilevel inverter is very useful for electrical application especially in high power and high voltage applications. The main function of this multilevel inverter is to produce multilevel AC output voltage from several separate DC sources. This project is to derive a new mathematical formulation of multilevel voltage source inverter switching instants. The proposed method for this project is based on the sinusoidal natural sampling PWM (SPWM) by comparing several modified modulation signal with a triangular carrier signal. This resulting intersection points between this modulation and carrier signal become the switching instants of the PWM pulses. Derivation also based on Phase opposition disposition (POD). A cascaded multilevel inverter is selected as a topology for this project due to major advantages compare with other topology. The derived formula is analyzed by using MATLAB simulation software. It is found that the results that use the derived formula are almost identical to simulation result.

Abstract: To study aerodynamic interference of twin-deck sections under vortex-induced vibration (VIV), a series of wind tunnel tests are implemented. Horizontal interval ratio (D/B) is taken into consideration a factor influencing VIV behavior, and the results are compared with single section. Surface pressure distribution of the twin sections are acquired by synchronous pressure measurements when the sections are under vertical and torsional VIV. Proper orthogonal decomposition (POD) is employed to reconstruct the randomly fluctuating wind pressure field. It identifies the vertical and torsional vibration frequency of model and energy proportion of eigenmodes. VIV behavior of twin-deck sections is different from single section, and it changes with different D/B. In general, the position, where D/B=1, is unfavorable to VIV behavior of twin-deck sections. The aerodynamic interference does not always amplify or restrain the amplitude of VIV. Several lower modes can reconstruct fluctuating pressure field to the accuracy meeting the requirement of engineering.

Abstract: When the pod works in the air, pod can produce the overshoot and stability. To solve this problem, the study demonstrates that the fuzzy-PID was used to control the pod. Simulink simulation module of Matlab was using to establish a control system model pod exterior orientation framework to verify the simulation, anti-jamming performance and tracking performance of the system. The results show that fuzzy PID control method can make the system have good stability, noise immunity and tracking capability.

Abstract: In this paper a parametric design procedure of electrical machines used in naval propulsion systems is developed. The algorithm uses a series of design characteristics i.e. the type of the machine, the winding configuration and key geometrical properties, as parameters and is implemented on MATLAB® script allowing for a straightforward incorporation with other development tools. Using the proposed algorithm, two of the most common machine configurations involved in marine electrical propulsion systems i.e. the Induction Motor and the Synchronous Permanent Magnet Motor, are designed and 2D finite element modeling and analysis is performed. MATLAB® is used to interact with the FEMM software package through ActiveX framework, allowing for a detailed calculation of the electromagnetic properties of the machines examined.

Abstract: In the present paper, a combined method of large eddy simulations for non-premixed combustion in a turbulent flow coupled with proper orthogonal decomposition of instantaneous velocity, pressure and temperature fields is developed in order to identify the effect of coherent structure and to obtain a reduced order model for control model. First we investigate the reacting flow using Large Eddy Simulations technique. This physical model is pertinent to internal flows inside the hybrid rocket motors. The turbulence-combustion interaction is based on a combination of finite rate/eddy dissipation model applied to a reduced chemical mechanism with four reactions. Next, the paper refers to the derivation of a Reduced Order Model (ROM) for the same problem, based on the Proper Orthogonal Decomposition (POD) technique. ROMs are used to obtain fast and accurate results, needed in the areas of flow control. The flow and thermal fields obtained with ROMs are compared with the ones obtained from the full simulation and an analysis on the number of modes required to achieve the desired accuracy is presented. Finally, a static control technique is proposed.

Abstract: Gamma irradiation has been widely applied in biology and medicine in terms of biological effects from low doses stimulation to high-doses inhibition. This study investigates the physiological responses for plantlets of Pepper, Eggplant, and Chinese Cabbage by low-doses of ¹³⁷Cs-γ irradiation. The results show that the POD activity and the content of MDA and soluble protein increased after gamma irradiation except for Chinese Cabbage. A significant positive correlation was observed between POD and MDA. Soluble Protein and the others had a negative correlation for Chinese Cabbage. Mechanisms of plants under irradiation should have a more profound study in order to determine the correlation.

Abstract: This paper is concerned with the prediction of part distortion induced by residual stress relief during machining. Aeronautical manufacturing requires nowadays the production of large monolithic parts from workpieces obtained by forging or rolling operations. Residual stresses induced during these forming steps are often consequent and represent a significant obstacle for manufacturers. Re-equilibration of initial residual stresses induced by material removal causes the part to deform.The method presented in this paper provides a tool for predicting changes in the geometry of the part occurring during machining and after unclamping. This prediction is based on an on-line data acquisition. From the predicted shape, the manufacturer is able to anticipate extra conforming steps eventually required afterwards and an updated toolpath accounting for geometrical changes happening during the on-going operation can be derived.The impact of the unknown initial residual stresses on the part deformation during machining is predicted on-line by comparing measured deformations to a reduced basis of mechanically admissible evolutions for the part geometry induced by material removal. This reduced basis is extracted from a larger database constructed off-line thanks to machining simulations and observations of previously machined similar parts.An auxiliary database for post-machining distortion is constructed similarly and makes possible a quick and reliable on-line prediction of the final shape of the part (i.e. after unclamping).