Slope stability analysis considering fully saturated poro-elasto-plasticity by an image-based scaled boundary finite element approach
- Wijesinghe, Dakshith, Dyson, Ashley, You, Greg, Khandelwal, Manoj, Natarajan, Sundararajan, Chan, Andrew, Ooi, Ean Tat
- Authors: Wijesinghe, Dakshith , Dyson, Ashley , You, Greg , Khandelwal, Manoj , Natarajan, Sundararajan , Chan, Andrew , Ooi, Ean Tat
- Date: 2024
- Type: Text , Journal article
- Relation: Engineering Analysis with Boundary Elements Vol. 158, no. (2024), p. 160-181
- Full Text:
- Reviewed:
- Description: Open pit mines are large geotechnical structures. Their stability is an important consideration in the mining industry. The deformations of geotechnical structures often involve the coupled interaction between the pore fluid pressure and the nonlinear deformation of soil, characterised by poro-elasto-plastic behaviour. This paper develops the scaled boundary finite element method (SBFEM) to address poro-elasto-plastic in slope stability problems. It builds upon a previously developed elasto-plastic formulation to consider the effect of pore fluid pressure and its interaction with the nonlinear deformation within the soil. The pore pressure field introduces an additional variable in the governing equations that is similarly discretised using SBFEM shape functions. The SBFEM is implemented together with a pixel-based quadtree mesh generation technique, enabling automatic meshing directly from digital images. This leads to efficient automation when modelling problems with iterative changes in the geometry such as in optimisation of construction processes during the rehabilitation of slopes. The formulation is validated first using a standard numerical benchmark. Application of the developed technique in construction applications in slopes where the stability and effect of pore water pressure is considered e.g., tailings dam construction and optimisation of backfilling process is demonstrated in three examples to demonstrate feasibility. © 2023 The Authors
- Authors: Wijesinghe, Dakshith , Dyson, Ashley , You, Greg , Khandelwal, Manoj , Natarajan, Sundararajan , Chan, Andrew , Ooi, Ean Tat
- Date: 2024
- Type: Text , Journal article
- Relation: Engineering Analysis with Boundary Elements Vol. 158, no. (2024), p. 160-181
- Full Text:
- Reviewed:
- Description: Open pit mines are large geotechnical structures. Their stability is an important consideration in the mining industry. The deformations of geotechnical structures often involve the coupled interaction between the pore fluid pressure and the nonlinear deformation of soil, characterised by poro-elasto-plastic behaviour. This paper develops the scaled boundary finite element method (SBFEM) to address poro-elasto-plastic in slope stability problems. It builds upon a previously developed elasto-plastic formulation to consider the effect of pore fluid pressure and its interaction with the nonlinear deformation within the soil. The pore pressure field introduces an additional variable in the governing equations that is similarly discretised using SBFEM shape functions. The SBFEM is implemented together with a pixel-based quadtree mesh generation technique, enabling automatic meshing directly from digital images. This leads to efficient automation when modelling problems with iterative changes in the geometry such as in optimisation of construction processes during the rehabilitation of slopes. The formulation is validated first using a standard numerical benchmark. Application of the developed technique in construction applications in slopes where the stability and effect of pore water pressure is considered e.g., tailings dam construction and optimisation of backfilling process is demonstrated in three examples to demonstrate feasibility. © 2023 The Authors
Extremality and stationarity of collections of sets : metric, slope and normal cone characterisations
- Bui, Hoa
- Authors: Bui, Hoa
- Date: 2019
- Type: Text , Thesis , PhD
- Full Text:
- Description: Variational analysis, a relatively new area of research in mathematics, has become one of the most powerful tools in nonsmooth optimisation and neighbouring areas. The extremal principle, a tool to substitute the conventional separation theorem in the general nonconvex environment, is a fundamental result in variational analysis. There have seen many attempts to generalise the conventional extremal principle in order to tackle certain optimisation models. Models involving collections of sets, initiated by the extremal principle, have proved their usefulness in analysis and optimisation, with non-intersection properties (or their absence) being at the core of many applications: recall the ubiquitous convex separation theorem, extremal principle, Dubovitskii Milyutin formalism and various transversality/regularity properties. We study elementary nonintersection properties of collections of sets, making the core of the conventional definitions of extremality and stationarity. In the setting of general Banach/Asplund spaces, we establish nonlinear primal (slope) and linear/nonlinear dual (generalised separation) characterisations of these non-intersection properties. We establish a series of consequences of our main results covering all known formulations of extremality/ stationarity and generalised separability properties. This research develops a universal theory, unifying all the current extensions of the extremal principle, providing new results and better understanding for the exquisite theory of variational analysis. This new study also results in direct solutions for many open questions and new future research directions in the fields of variational analysis and optimisation. Some new nonlinear characterisations of the conventional extremality/stationarity properties are obtained. For the first time, the intrinsic transversality property is characterised in primal space without involving normal cones. This characterisation brings a new perspective on intrinsic transversality. In the process, we thoroughly expose and classify all quantitative geometric and metric characterisations of transversality properties of collections of sets and regularity properties of set-valued mappings.
- Description: Doctor of Philosophy
- Authors: Bui, Hoa
- Date: 2019
- Type: Text , Thesis , PhD
- Full Text:
- Description: Variational analysis, a relatively new area of research in mathematics, has become one of the most powerful tools in nonsmooth optimisation and neighbouring areas. The extremal principle, a tool to substitute the conventional separation theorem in the general nonconvex environment, is a fundamental result in variational analysis. There have seen many attempts to generalise the conventional extremal principle in order to tackle certain optimisation models. Models involving collections of sets, initiated by the extremal principle, have proved their usefulness in analysis and optimisation, with non-intersection properties (or their absence) being at the core of many applications: recall the ubiquitous convex separation theorem, extremal principle, Dubovitskii Milyutin formalism and various transversality/regularity properties. We study elementary nonintersection properties of collections of sets, making the core of the conventional definitions of extremality and stationarity. In the setting of general Banach/Asplund spaces, we establish nonlinear primal (slope) and linear/nonlinear dual (generalised separation) characterisations of these non-intersection properties. We establish a series of consequences of our main results covering all known formulations of extremality/ stationarity and generalised separability properties. This research develops a universal theory, unifying all the current extensions of the extremal principle, providing new results and better understanding for the exquisite theory of variational analysis. This new study also results in direct solutions for many open questions and new future research directions in the fields of variational analysis and optimisation. Some new nonlinear characterisations of the conventional extremality/stationarity properties are obtained. For the first time, the intrinsic transversality property is characterised in primal space without involving normal cones. This characterisation brings a new perspective on intrinsic transversality. In the process, we thoroughly expose and classify all quantitative geometric and metric characterisations of transversality properties of collections of sets and regularity properties of set-valued mappings.
- Description: Doctor of Philosophy
Mine evaluation optimisation
- Authors: Grigoryev, Igor
- Date: 2019
- Type: Text , Thesis , PhD
- Full Text:
- Description: The definition of a mineral resource during exploration is a fundamental part of lease evaluation, which establishes the fair market value of the entire asset being explored in the open market. Since exact prediction of grades between sampled points is not currently possible by conventional methods, an exact agreement between predicted and actual grades will nearly always contain some error. These errors affect the evaluation of resources so impacting on characterisation of risks, financial projections and decisions about whether it is necessary to carry on with the further phases or not. The knowledge about minerals below the surface, even when it is based upon extensive geophysical analysis and drilling, is often too fragmentary to indicate with assurance where to drill, how deep to drill and what can be expected. Thus, the exploration team knows only the density of the rock and the grade along the core. The purpose of this study is to improve the process of resource evaluation in the exploration stage by increasing prediction accuracy and making an alternative assessment about the spatial characteristics of gold mineralisation. There is significant industrial interest in finding alternatives which may speed up the drilling phase, identify anomalies, worthwhile targets and help in establishing fair market value. Recent developments in nonconvex optimisation and high-dimensional statistics have led to the idea that some engineering problems such as predicting gold variability at the exploration stage can be solved with the application of clusterwise linear and penalised maximum likelihood regression techniques. This thesis attempts to solve the distribution of the mineralisation in the underlying geology using clusterwise linear regression and convex Least Absolute Shrinkage and Selection Operator (LASSO) techniques. The two presented optimisation techniques compute predictive solutions within a domain using physical data provided directly from drillholes. The decision-support techniques attempt a useful compromise between the traditional and recently introduced methods in optimisation and regression analysis that are developed to improve exploration targeting and to predict the gold occurrences at previously unsampled locations.
- Description: Doctor of Philosophy
- Authors: Grigoryev, Igor
- Date: 2019
- Type: Text , Thesis , PhD
- Full Text:
- Description: The definition of a mineral resource during exploration is a fundamental part of lease evaluation, which establishes the fair market value of the entire asset being explored in the open market. Since exact prediction of grades between sampled points is not currently possible by conventional methods, an exact agreement between predicted and actual grades will nearly always contain some error. These errors affect the evaluation of resources so impacting on characterisation of risks, financial projections and decisions about whether it is necessary to carry on with the further phases or not. The knowledge about minerals below the surface, even when it is based upon extensive geophysical analysis and drilling, is often too fragmentary to indicate with assurance where to drill, how deep to drill and what can be expected. Thus, the exploration team knows only the density of the rock and the grade along the core. The purpose of this study is to improve the process of resource evaluation in the exploration stage by increasing prediction accuracy and making an alternative assessment about the spatial characteristics of gold mineralisation. There is significant industrial interest in finding alternatives which may speed up the drilling phase, identify anomalies, worthwhile targets and help in establishing fair market value. Recent developments in nonconvex optimisation and high-dimensional statistics have led to the idea that some engineering problems such as predicting gold variability at the exploration stage can be solved with the application of clusterwise linear and penalised maximum likelihood regression techniques. This thesis attempts to solve the distribution of the mineralisation in the underlying geology using clusterwise linear regression and convex Least Absolute Shrinkage and Selection Operator (LASSO) techniques. The two presented optimisation techniques compute predictive solutions within a domain using physical data provided directly from drillholes. The decision-support techniques attempt a useful compromise between the traditional and recently introduced methods in optimisation and regression analysis that are developed to improve exploration targeting and to predict the gold occurrences at previously unsampled locations.
- Description: Doctor of Philosophy
Testing the robustness of optimal operating plans under various future hydro-climatic scenarios
- Godoy, Walter, Barton, Andrew, Wilson, K., Perera, B.
- Authors: Godoy, Walter , Barton, Andrew , Wilson, K. , Perera, B.
- Date: 2018
- Type: Text , Conference paper
- Relation: 2018 Hydrology and Water Resources Symposium: Water and Communities, HWRS 2018 p. 267-283
- Full Text:
- Reviewed:
- Description: A key challenge for water resources planning processes around the world is to develop operating plans that are optimal under a range of hydro-climatic conditions. The consequences of such long term planning decisions can vary in terms of the social, economic, and environmental impacts. Given these potential impacts, it is important that operating plans are tested under a range of hydro-climatic conditions to ensure that they are sufficiently robust to withstand future changes in climate. The aim of this study is to present a procedure for testing the robustness of optimal operating plans for complex water resources systems using a combined multi-objective optimisation and sustainability assessment approach. The approach embeds an optimisation-simulation (O-S) model which is applied to an 18-objective function multi-objective optimisation problem of the Wimmera-Mallee Water Supply System (WMWSS). The WMWSS is a multi-reservoir system located in Western Victoria (Australia) which is operated to meet a range of competing interests for water using complex operating rules. The O-S model is applied to the WMWSS to search for optimal operating plans over a 100-year period into the future assuming two plausible greenhouse gas (GHG) emission levels. The two GHG emission scenarios represent lower and higher ends of the estimated range of projected GHG emissions, providing a wide range of future hydro-climatic conditions. A robustness test is used to evaluate the validity of the most sustainable optimal operating plans under the two GHG emmission scenarios and also those found previously under a historic hydro-climatic sequence. The test results show that the status quo or base case operating plan is optimal but is neither the highest nor the lowest in terms of the level of sustainability that could be achieved in the WMWSS, under historic and the higher GHG emission scenario. Moreover, the results show that the most sustainable optimal operating plans found under the three hydro-climatic scenarios are sufficiently robust to withstand the full range of hydro-climatic conditions considered whereas the base case operating plan is not as robust. The risks involved in the implementation of operating plans which exhibit large deviations from the base case operating plan are discussed. These risks highlight the importance of problem formulation and sensitivity analysis of the optimal operating plans in order to find real world solutions to real world problems. © CURRAN-CONFERENCE. All rights reserved.
- Authors: Godoy, Walter , Barton, Andrew , Wilson, K. , Perera, B.
- Date: 2018
- Type: Text , Conference paper
- Relation: 2018 Hydrology and Water Resources Symposium: Water and Communities, HWRS 2018 p. 267-283
- Full Text:
- Reviewed:
- Description: A key challenge for water resources planning processes around the world is to develop operating plans that are optimal under a range of hydro-climatic conditions. The consequences of such long term planning decisions can vary in terms of the social, economic, and environmental impacts. Given these potential impacts, it is important that operating plans are tested under a range of hydro-climatic conditions to ensure that they are sufficiently robust to withstand future changes in climate. The aim of this study is to present a procedure for testing the robustness of optimal operating plans for complex water resources systems using a combined multi-objective optimisation and sustainability assessment approach. The approach embeds an optimisation-simulation (O-S) model which is applied to an 18-objective function multi-objective optimisation problem of the Wimmera-Mallee Water Supply System (WMWSS). The WMWSS is a multi-reservoir system located in Western Victoria (Australia) which is operated to meet a range of competing interests for water using complex operating rules. The O-S model is applied to the WMWSS to search for optimal operating plans over a 100-year period into the future assuming two plausible greenhouse gas (GHG) emission levels. The two GHG emission scenarios represent lower and higher ends of the estimated range of projected GHG emissions, providing a wide range of future hydro-climatic conditions. A robustness test is used to evaluate the validity of the most sustainable optimal operating plans under the two GHG emmission scenarios and also those found previously under a historic hydro-climatic sequence. The test results show that the status quo or base case operating plan is optimal but is neither the highest nor the lowest in terms of the level of sustainability that could be achieved in the WMWSS, under historic and the higher GHG emission scenario. Moreover, the results show that the most sustainable optimal operating plans found under the three hydro-climatic scenarios are sufficiently robust to withstand the full range of hydro-climatic conditions considered whereas the base case operating plan is not as robust. The risks involved in the implementation of operating plans which exhibit large deviations from the base case operating plan are discussed. These risks highlight the importance of problem formulation and sensitivity analysis of the optimal operating plans in order to find real world solutions to real world problems. © CURRAN-CONFERENCE. All rights reserved.
Lost in optimisation of water distribution systems? A literature review of system operation
- Mala-Jetmarova, Helena, Sultanova, Nargiz, Savic, Dragan
- Authors: Mala-Jetmarova, Helena , Sultanova, Nargiz , Savic, Dragan
- Date: 2017
- Type: Text , Journal article , Review
- Relation: Environmental Modelling and Software Vol. 93, no. (2017), p. 209-254
- Full Text:
- Reviewed:
- Description: Optimisation of the operation of water distribution systems has been an active research field for almost half a century. It has focused mainly on optimal pump operation to minimise pumping costs and optimal water quality management to ensure that standards at customer nodes are met. This paper provides a systematic review by bringing together over two hundred publications from the past three decades, which are relevant to operational optimisation of water distribution systems, particularly optimal pump operation, valve control and system operation for water quality purposes of both urban drinking and regional multiquality water distribution systems. Uniquely, it also contains substantial and thorough information for over one hundred publications in a tabular form, which lists optimisation models inclusive of objectives, constraints, decision variables, solution methodologies used and other details. Research challenges in terms of simulation models, optimisation model formulation, selection of optimisation method and postprocessing needs have also been identified. © 2017
- Authors: Mala-Jetmarova, Helena , Sultanova, Nargiz , Savic, Dragan
- Date: 2017
- Type: Text , Journal article , Review
- Relation: Environmental Modelling and Software Vol. 93, no. (2017), p. 209-254
- Full Text:
- Reviewed:
- Description: Optimisation of the operation of water distribution systems has been an active research field for almost half a century. It has focused mainly on optimal pump operation to minimise pumping costs and optimal water quality management to ensure that standards at customer nodes are met. This paper provides a systematic review by bringing together over two hundred publications from the past three decades, which are relevant to operational optimisation of water distribution systems, particularly optimal pump operation, valve control and system operation for water quality purposes of both urban drinking and regional multiquality water distribution systems. Uniquely, it also contains substantial and thorough information for over one hundred publications in a tabular form, which lists optimisation models inclusive of objectives, constraints, decision variables, solution methodologies used and other details. Research challenges in terms of simulation models, optimisation model formulation, selection of optimisation method and postprocessing needs have also been identified. © 2017
Energy-balanced transmission policies for wireless sensor networks
- Azad, Arman, Kamruzzaman, Joarder
- Authors: Azad, Arman , Kamruzzaman, Joarder
- Date: 2011
- Type: Text , Journal article
- Relation: IEEE Transactions on Mobile Computing Vol. 10, no. 7 (2011), p. 927-940
- Full Text:
- Reviewed:
- Description: Transmission policy, in addition to topology control, routing, and MAC protocols, can play a vital role in extending network lifetime. Existing transmission policies, however, cause an extremely unbalanced energy usage that contributes to early demise of some sensors reducing overall network's lifetime drastically. Considering cocentric rings around the sink, we decompose the transmission distance of traditional multihop scheme into two parts: ring thickness and hop size, analyze the traffic and energy usage distribution among sensors and determine how energy usage varies and critical ring shifts with hop size. Based on above observations, we propose a transmission scheme and determine the optimal ring thickness and hop size by formulating network lifetime as an optimization problem. Numerical results show substantial improvements in terms of network lifetime and energy usage distribution over existing policies. Two other variations of this policy are also presented by redefining the optimization problem considering: 1) concomitant hop size variation by sensors over lifetime along with optimal duty cycles, and 2) a distinct set of hop sizes for sensors in each ring. Both variations bring increasingly uniform energy usage with lower critical energy and further improves lifetime. A heuristic for distributed implementation of each policy is also presented.
- Authors: Azad, Arman , Kamruzzaman, Joarder
- Date: 2011
- Type: Text , Journal article
- Relation: IEEE Transactions on Mobile Computing Vol. 10, no. 7 (2011), p. 927-940
- Full Text:
- Reviewed:
- Description: Transmission policy, in addition to topology control, routing, and MAC protocols, can play a vital role in extending network lifetime. Existing transmission policies, however, cause an extremely unbalanced energy usage that contributes to early demise of some sensors reducing overall network's lifetime drastically. Considering cocentric rings around the sink, we decompose the transmission distance of traditional multihop scheme into two parts: ring thickness and hop size, analyze the traffic and energy usage distribution among sensors and determine how energy usage varies and critical ring shifts with hop size. Based on above observations, we propose a transmission scheme and determine the optimal ring thickness and hop size by formulating network lifetime as an optimization problem. Numerical results show substantial improvements in terms of network lifetime and energy usage distribution over existing policies. Two other variations of this policy are also presented by redefining the optimization problem considering: 1) concomitant hop size variation by sensors over lifetime along with optimal duty cycles, and 2) a distinct set of hop sizes for sensors in each ring. Both variations bring increasingly uniform energy usage with lower critical energy and further improves lifetime. A heuristic for distributed implementation of each policy is also presented.
Vibration analysis : Optimization of parameters of the two mass model based on Kelvin elements
- Kuznetsov, Alexey, Mammadov, Musa, Sultan, Ibrahim, Hajilarov, Eldar
- Authors: Kuznetsov, Alexey , Mammadov, Musa , Sultan, Ibrahim , Hajilarov, Eldar
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at 8th IEEE International Conference on Control and Automation, ICCA 2010, Asia Gulf Hotel, Xiamen, China : 9th-11th June 2010 p. 1326-1332
- Full Text:
- Description: In this paper we consider the problem of finding optimal parameters of the two mass model that represents vehicle suspension systems. The analysis of the problem is based on finding analytical solution of the system of coupled Ordinary Differential Equations (ODE). Such a technique allows us to generate optimization problem, where an objective function should be minimized, in accordance with ISO 2631 standard formula of admissible acceleration levels. That ensures maximum comfort for a driver and passenger in a moving vehicle on the considered highways.
- Description: 2003008232
- Authors: Kuznetsov, Alexey , Mammadov, Musa , Sultan, Ibrahim , Hajilarov, Eldar
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at 8th IEEE International Conference on Control and Automation, ICCA 2010, Asia Gulf Hotel, Xiamen, China : 9th-11th June 2010 p. 1326-1332
- Full Text:
- Description: In this paper we consider the problem of finding optimal parameters of the two mass model that represents vehicle suspension systems. The analysis of the problem is based on finding analytical solution of the system of coupled Ordinary Differential Equations (ODE). Such a technique allows us to generate optimization problem, where an objective function should be minimized, in accordance with ISO 2631 standard formula of admissible acceleration levels. That ensures maximum comfort for a driver and passenger in a moving vehicle on the considered highways.
- Description: 2003008232
The impact of various drying kinetics models on the prediction of sample temperature-time and moisture content-time profiles during moisture removal from stratum corneum
- Kar, S., Chen, Xiao Dong, Adhikari, Benu, Lin, S. X. Q.
- Authors: Kar, S. , Chen, Xiao Dong , Adhikari, Benu , Lin, S. X. Q.
- Date: 2009
- Type: Text , Journal article
- Relation: Chemical Engineering Research and Design Vol. 87, no. 5 (2009), p. 739-755
- Full Text:
- Reviewed:
- Description: An attempt has been made here to model the moisture transport kinetics across porcine stratum corneum. Samples of porcine skin were dissected in the form of 'thin layers' (i.e. stratum corneum) of dimensions of 11.3 × 11.3 mm (70-200 μm thick). These layers were dried in a laboratory convection air dryer at 37 °C (normal human body temperature). The changes in weights of the samples were noted. The weight loss data was then converted in terms of moisture content (dry basis) and were monitored over time. Thereafter they were fitted against an empirical equation notably the Page model (Model 1) and the solution generated by the Fickian diffusion equation (Model 2). The current paper demonstrates the effectiveness of these two models in prediction of the sample temperature during drying. Furthermore, it also demonstrates the variation in spatial distribution of moisture content within the skin sample when moisture content and temperature dependency are introduced in the diffusivity. Such findings are important especially when developing skin multi-compartment physiologically based pharmacokinetic (PBPK) models to assess transdermal permeation of various hydrophilic penetrants. © 2008 The Institution of Chemical Engineers.
- Description: 2003006794
- Authors: Kar, S. , Chen, Xiao Dong , Adhikari, Benu , Lin, S. X. Q.
- Date: 2009
- Type: Text , Journal article
- Relation: Chemical Engineering Research and Design Vol. 87, no. 5 (2009), p. 739-755
- Full Text:
- Reviewed:
- Description: An attempt has been made here to model the moisture transport kinetics across porcine stratum corneum. Samples of porcine skin were dissected in the form of 'thin layers' (i.e. stratum corneum) of dimensions of 11.3 × 11.3 mm (70-200 μm thick). These layers were dried in a laboratory convection air dryer at 37 °C (normal human body temperature). The changes in weights of the samples were noted. The weight loss data was then converted in terms of moisture content (dry basis) and were monitored over time. Thereafter they were fitted against an empirical equation notably the Page model (Model 1) and the solution generated by the Fickian diffusion equation (Model 2). The current paper demonstrates the effectiveness of these two models in prediction of the sample temperature during drying. Furthermore, it also demonstrates the variation in spatial distribution of moisture content within the skin sample when moisture content and temperature dependency are introduced in the diffusivity. Such findings are important especially when developing skin multi-compartment physiologically based pharmacokinetic (PBPK) models to assess transdermal permeation of various hydrophilic penetrants. © 2008 The Institution of Chemical Engineers.
- Description: 2003006794
An approximate subgradient algorithm for unconstrained nonsmooth, nonconvex optimization
- Bagirov, Adil, Ganjehlou, Asef Nazari
- Authors: Bagirov, Adil , Ganjehlou, Asef Nazari
- Date: 2008
- Type: Text , Journal article
- Relation: Mathematical Methods of Operations Research Vol. 67, no. 2 (2008), p. 187-206
- Relation: http://purl.org/au-research/grants/arc/DP0666061
- Full Text:
- Reviewed:
- Description: In this paper a new algorithm for minimizing locally Lipschitz functions is developed. Descent directions in this algorithm are computed by solving a system of linear inequalities. The convergence of the algorithm is proved for quasidifferentiable semismooth functions. We present the results of numerical experiments with both regular and nonregular objective functions. We also compare the proposed algorithm with two different versions of the subgradient method using the results of numerical experiments. These results demonstrate the superiority of the proposed algorithm over the subgradient method. © 2007 Springer-Verlag.
- Description: C1
- Authors: Bagirov, Adil , Ganjehlou, Asef Nazari
- Date: 2008
- Type: Text , Journal article
- Relation: Mathematical Methods of Operations Research Vol. 67, no. 2 (2008), p. 187-206
- Relation: http://purl.org/au-research/grants/arc/DP0666061
- Full Text:
- Reviewed:
- Description: In this paper a new algorithm for minimizing locally Lipschitz functions is developed. Descent directions in this algorithm are computed by solving a system of linear inequalities. The convergence of the algorithm is proved for quasidifferentiable semismooth functions. We present the results of numerical experiments with both regular and nonregular objective functions. We also compare the proposed algorithm with two different versions of the subgradient method using the results of numerical experiments. These results demonstrate the superiority of the proposed algorithm over the subgradient method. © 2007 Springer-Verlag.
- Description: C1
Challenging issues in dynamic reconfiguration of telecommunication networks
- Dzalilov, Zari, Ouveysi, Iradj
- Authors: Dzalilov, Zari , Ouveysi, Iradj
- Date: 2008
- Type: Text , Conference paper
- Relation: Paper presented at Second International Conference: Problems of Cybernetics and Informatics, PCI 2008, Baku, Azerbaijan : 10th-12th September 2008 p. 48-51
- Full Text:
- Description: For the last quarter of a century understanding of the nature of telecommunication network traffic has been considered as an important research topic. Any well-designed recovery strategy has to take into account the different resilience requirements of the single traffic flows in order to avoid excessive usage of bandwidth for standby links. Here we discuss the issues of a reconfiguration procedure in order to perform network recovery in the case of any failure scenario in the telecommunication networks. We explain the complexities arising in the real life application and propose an optimization technique in order to minimize the size of the optimization problem in the process of reconfiguration. Our suggestion to achieve this is to find the minimal sub-graph surrounding the failure region that contains the required unused capacity to perform network recovery task.
- Description: 2003006857
- Authors: Dzalilov, Zari , Ouveysi, Iradj
- Date: 2008
- Type: Text , Conference paper
- Relation: Paper presented at Second International Conference: Problems of Cybernetics and Informatics, PCI 2008, Baku, Azerbaijan : 10th-12th September 2008 p. 48-51
- Full Text:
- Description: For the last quarter of a century understanding of the nature of telecommunication network traffic has been considered as an important research topic. Any well-designed recovery strategy has to take into account the different resilience requirements of the single traffic flows in order to avoid excessive usage of bandwidth for standby links. Here we discuss the issues of a reconfiguration procedure in order to perform network recovery in the case of any failure scenario in the telecommunication networks. We explain the complexities arising in the real life application and propose an optimization technique in order to minimize the size of the optimization problem in the process of reconfiguration. Our suggestion to achieve this is to find the minimal sub-graph surrounding the failure region that contains the required unused capacity to perform network recovery task.
- Description: 2003006857
A model for adaptive rescheduling of flights in emergencies (MARFE)
- Filar, Jerzy, Manyem, Prabhu, Panton, David, White, Kevin
- Authors: Filar, Jerzy , Manyem, Prabhu , Panton, David , White, Kevin
- Date: 2007
- Type: Text , Journal article
- Relation: Journal of Industrial and Management Optimization Vol. 3, no. 2 (May 2007), p. 335-356
- Full Text:
- Reviewed:
- Description: Disruptions to commercial airline schedules are frequent and can inflict significant costs. In this paper we continue a line of research initiated by Vranas, Bertsimas and Odoni [15, 16], that aims to develop techniques facilitating rapid return to normal operations whenever disruptions occur. Ground Holding is a technique that has been successfully employed to combat disruptions at North American airports. However, this alone is insufficient to cope with the problem. We develop an adaptive optimization model that allows the implementation of other tactics, such as flight cancellations, airborne holding and diversions. While the approach is generic, our model incorporates features of Sydney airport in Australia, such as a night curfew from 11:00pm to 6:00am. For an actual day when there was a significant capacity drop, we demonstrate that our model clearly outperforms the actions that were initiated by the air traffic controllers at Sydney.
- Description: C1
- Description: 2003004883
- Authors: Filar, Jerzy , Manyem, Prabhu , Panton, David , White, Kevin
- Date: 2007
- Type: Text , Journal article
- Relation: Journal of Industrial and Management Optimization Vol. 3, no. 2 (May 2007), p. 335-356
- Full Text:
- Reviewed:
- Description: Disruptions to commercial airline schedules are frequent and can inflict significant costs. In this paper we continue a line of research initiated by Vranas, Bertsimas and Odoni [15, 16], that aims to develop techniques facilitating rapid return to normal operations whenever disruptions occur. Ground Holding is a technique that has been successfully employed to combat disruptions at North American airports. However, this alone is insufficient to cope with the problem. We develop an adaptive optimization model that allows the implementation of other tactics, such as flight cancellations, airborne holding and diversions. While the approach is generic, our model incorporates features of Sydney airport in Australia, such as a night curfew from 11:00pm to 6:00am. For an actual day when there was a significant capacity drop, we demonstrate that our model clearly outperforms the actions that were initiated by the air traffic controllers at Sydney.
- Description: C1
- Description: 2003004883
Coverage in WLAN : Optimization model and algorithm
- Kouhbor, Shahnaz, Ugon, Julien, Mammadov, Musa, Rubinov, Alex, Kruger, Alexander
- Authors: Kouhbor, Shahnaz , Ugon, Julien , Mammadov, Musa , Rubinov, Alex , Kruger, Alexander
- Date: 2006
- Type: Text , Conference paper
- Relation: Paper presented at the First International Conference on Wireless Broadband and Ultra Wideband Communications, AusWireless 2006, Sydney : 13th March, 2006
- Full Text:
- Reviewed:
- Description: When designing wireless communication systems, it is very important to know the optimum numbers of access points (APs) in order to provide a reliable design. In this paper we describe a mathematical model developed for finding the optimal number and location of APs. A new Global Optimization Algorithm (AGOP) is used to solve the problem. Results obtained demonstrate that the model and software are able to solve optimal coverage problems for design areas with different types of obstacles and number of users.
- Description: 2003001757
- Authors: Kouhbor, Shahnaz , Ugon, Julien , Mammadov, Musa , Rubinov, Alex , Kruger, Alexander
- Date: 2006
- Type: Text , Conference paper
- Relation: Paper presented at the First International Conference on Wireless Broadband and Ultra Wideband Communications, AusWireless 2006, Sydney : 13th March, 2006
- Full Text:
- Reviewed:
- Description: When designing wireless communication systems, it is very important to know the optimum numbers of access points (APs) in order to provide a reliable design. In this paper we describe a mathematical model developed for finding the optimal number and location of APs. A new Global Optimization Algorithm (AGOP) is used to solve the problem. Results obtained demonstrate that the model and software are able to solve optimal coverage problems for design areas with different types of obstacles and number of users.
- Description: 2003001757
A new algorithm for the placement of WLAN access point based on nonsmooth optimization technique
- Kouhbor, Shahnaz, Ugon, Julien, Kruger, Alexander, Rubinov, Alex, Branch, Philip
- Authors: Kouhbor, Shahnaz , Ugon, Julien , Kruger, Alexander , Rubinov, Alex , Branch, Philip
- Date: 2005
- Type: Text , Conference paper
- Relation: Paper presented at the 7th International Conference on Advanced Communication Technology, Phoenix Park, Korea : 21st February, 2005
- Full Text:
- Reviewed:
- Description: In wireless local area network (WLAN), signal coverage is obtained by proper placement of access points (APs). The impact of incorrect placement of APs is significant. If they are placed too far apart, they generate a coverage gap but if they are too close to each other, this leads to excessive co-channel interferences. In this paper, we describe a mathematical model we have developed to find the optimal number and location of APs. To solve the problem, we use an optimization algorithm developed at the University of Ballarat called discrete gradient algorithm. Results indicate that our model is able to solve optimal coverage problems for different numbers of users.
- Description: E1
- Description: 2003001376
- Authors: Kouhbor, Shahnaz , Ugon, Julien , Kruger, Alexander , Rubinov, Alex , Branch, Philip
- Date: 2005
- Type: Text , Conference paper
- Relation: Paper presented at the 7th International Conference on Advanced Communication Technology, Phoenix Park, Korea : 21st February, 2005
- Full Text:
- Reviewed:
- Description: In wireless local area network (WLAN), signal coverage is obtained by proper placement of access points (APs). The impact of incorrect placement of APs is significant. If they are placed too far apart, they generate a coverage gap but if they are too close to each other, this leads to excessive co-channel interferences. In this paper, we describe a mathematical model we have developed to find the optimal number and location of APs. To solve the problem, we use an optimization algorithm developed at the University of Ballarat called discrete gradient algorithm. Results indicate that our model is able to solve optimal coverage problems for different numbers of users.
- Description: E1
- Description: 2003001376
An algorithm for minimizing clustering functions
- Authors: Bagirov, Adil , Ugon, Julien
- Date: 2005
- Type: Text , Journal article
- Relation: Optimization Vol. 54, no. 4-5 (Aug-Oct 2005), p. 351-368
- Full Text:
- Reviewed:
- Description: The problem of cluster analysis is formulated as a problem of nonsmooth, nonconvex optimization. An algorithm for solving the latter optimization problem is developed which allows one to significantly reduce the computational efforts. This algorithm is based on the so-called discrete gradient method. Results of numerical experiments are presented which demonstrate the effectiveness of the proposed algorithm.
- Description: C1
- Description: 2003001266
- Authors: Bagirov, Adil , Ugon, Julien
- Date: 2005
- Type: Text , Journal article
- Relation: Optimization Vol. 54, no. 4-5 (Aug-Oct 2005), p. 351-368
- Full Text:
- Reviewed:
- Description: The problem of cluster analysis is formulated as a problem of nonsmooth, nonconvex optimization. An algorithm for solving the latter optimization problem is developed which allows one to significantly reduce the computational efforts. This algorithm is based on the so-called discrete gradient method. Results of numerical experiments are presented which demonstrate the effectiveness of the proposed algorithm.
- Description: C1
- Description: 2003001266
Data mining with combined use of optimization techniques and self-organizing maps for improving risk grouping rules : Application to prostate cancer patients
- Churilov, Leonid, Bagirov, Adil, Schwartz, Daniel, Smith, Kate, Dally, Michael
- Authors: Churilov, Leonid , Bagirov, Adil , Schwartz, Daniel , Smith, Kate , Dally, Michael
- Date: 2005
- Type: Text , Journal article
- Relation: Journal of Management Information Systems Vol. 21, no. 4 (2005), p. 85-100
- Full Text:
- Reviewed:
- Description: Data mining techniques provide a popular and powerful tool set to generate various data-driven classification systems. In this paper, we investigate the combined use of self-organizing maps (SOM) and nonsmooth nonconvex optimization techniques in order to produce a working case of a data-driven risk classification system. The optimization approach strengthens the validity of SOM results, and the improved classification system increases both the quality of prediction and the homogeneity within the risk groups. Accurate classification of prostate cancer patients into risk groups is important to assist in the identification of appropriate treatment paths. We start with the existing rules and aim to improve classification accuracy by identifying inconsistencies utilizing self-organizing maps as a data visualization tool. Then, we progress to the study of assigning prostate cancer patients into homogenous groups with the aim to support future clinical treatment decisions. Using the case of prostate cancer patients grouping, we demonstrate strong potential of data-driven risk classification schemes for addressing the risk grouping issues in more general organizational settings. © 2005 M.E. Sharpe, Inc.
- Description: C1
- Description: 2003001265
- Authors: Churilov, Leonid , Bagirov, Adil , Schwartz, Daniel , Smith, Kate , Dally, Michael
- Date: 2005
- Type: Text , Journal article
- Relation: Journal of Management Information Systems Vol. 21, no. 4 (2005), p. 85-100
- Full Text:
- Reviewed:
- Description: Data mining techniques provide a popular and powerful tool set to generate various data-driven classification systems. In this paper, we investigate the combined use of self-organizing maps (SOM) and nonsmooth nonconvex optimization techniques in order to produce a working case of a data-driven risk classification system. The optimization approach strengthens the validity of SOM results, and the improved classification system increases both the quality of prediction and the homogeneity within the risk groups. Accurate classification of prostate cancer patients into risk groups is important to assist in the identification of appropriate treatment paths. We start with the existing rules and aim to improve classification accuracy by identifying inconsistencies utilizing self-organizing maps as a data visualization tool. Then, we progress to the study of assigning prostate cancer patients into homogenous groups with the aim to support future clinical treatment decisions. Using the case of prostate cancer patients grouping, we demonstrate strong potential of data-driven risk classification schemes for addressing the risk grouping issues in more general organizational settings. © 2005 M.E. Sharpe, Inc.
- Description: C1
- Description: 2003001265
Increasing cut surface quality with various cutting nozzle head oscillations for abrasive aquajet machining
- Patel, Keyurkumar, Chen, Frank
- Authors: Patel, Keyurkumar , Chen, Frank
- Date: 2003
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture Vol. 217, no. 7 (2003), p. 1037-1041
- Full Text:
- Reviewed:
- Description: The short paper introduces different nozzle oscillation cutting methods, which are developed using theoretical formulae as well as experimental resources. A comparison study was conducted using different surface texture parameters between a straight cut and different oscillation cutting methods with the same cutting parameters. An optimum oscillation cutting method is suggested. A significant amount of increase in surface quality was obtained.
- Description: C1
- Description: 2003000346
- Authors: Patel, Keyurkumar , Chen, Frank
- Date: 2003
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture Vol. 217, no. 7 (2003), p. 1037-1041
- Full Text:
- Reviewed:
- Description: The short paper introduces different nozzle oscillation cutting methods, which are developed using theoretical formulae as well as experimental resources. A comparison study was conducted using different surface texture parameters between a straight cut and different oscillation cutting methods with the same cutting parameters. An optimum oscillation cutting method is suggested. A significant amount of increase in surface quality was obtained.
- Description: C1
- Description: 2003000346
New algorithm to find a shape of a finite set of points
- Sukhorukova, Nadezda, Ugon, Julien
- Authors: Sukhorukova, Nadezda , Ugon, Julien
- Date: 2003
- Type: Text , Conference paper
- Relation: Paper presented at the Symposium on Industrial Optimisation and the 9th Australian Optimisation Day, Perth : 30th September, 2002
- Full Text:
- Reviewed:
- Description: Very often in data classification problems we have to determine a shape of a finite set of points within datasets. One of the most common approaches to represent such sets is to determine them as collections of several groups of points. The goal of this project is to develop some algorithms to find a shape for each group. Numerical experiments using the Discrete Gradient method have been done. The results are presented.
- Description: E1
- Description: 2003000351
- Authors: Sukhorukova, Nadezda , Ugon, Julien
- Date: 2003
- Type: Text , Conference paper
- Relation: Paper presented at the Symposium on Industrial Optimisation and the 9th Australian Optimisation Day, Perth : 30th September, 2002
- Full Text:
- Reviewed:
- Description: Very often in data classification problems we have to determine a shape of a finite set of points within datasets. One of the most common approaches to represent such sets is to determine them as collections of several groups of points. The goal of this project is to develop some algorithms to find a shape for each group. Numerical experiments using the Discrete Gradient method have been done. The results are presented.
- Description: E1
- Description: 2003000351
The discrete gradient evolutionary strategy method for global optimization
- Abbas, Hussein, Bagirov, Adil, Zhang, Jiapu
- Authors: Abbas, Hussein , Bagirov, Adil , Zhang, Jiapu
- Date: 2003
- Type: Text , Conference paper
- Relation: Paper presented at the Congress on Evolutionary Computation CEC 2003, Canberra : 8th December, 2003
- Full Text:
- Reviewed:
- Description: Global optimization problems continue to be a challenge in computational mathematics. The field is progressing in two streams: deterministic and heuristic approaches. In this paper, we present a hybrid method that uses the discrete gradient method, which is a derivative free local search method, and evolutionary strategies. We show that the hybridization of the two methods is better than each of them in isolation.
- Description: E1
- Description: 2003000440
- Authors: Abbas, Hussein , Bagirov, Adil , Zhang, Jiapu
- Date: 2003
- Type: Text , Conference paper
- Relation: Paper presented at the Congress on Evolutionary Computation CEC 2003, Canberra : 8th December, 2003
- Full Text:
- Reviewed:
- Description: Global optimization problems continue to be a challenge in computational mathematics. The field is progressing in two streams: deterministic and heuristic approaches. In this paper, we present a hybrid method that uses the discrete gradient method, which is a derivative free local search method, and evolutionary strategies. We show that the hybridization of the two methods is better than each of them in isolation.
- Description: E1
- Description: 2003000440
Unsupervised and supervised data classification via nonsmooth and global optimisation
- Bagirov, Adil, Rubinov, Alex, Sukhorukova, Nadezda, Yearwood, John
- Authors: Bagirov, Adil , Rubinov, Alex , Sukhorukova, Nadezda , Yearwood, John
- Date: 2003
- Type: Text , Journal article
- Relation: Top Vol. 11, no. 1 (2003), p. 1-92
- Full Text:
- Reviewed:
- Description: We examine various methods for data clustering and data classification that are based on the minimization of the so-called cluster function and its modications. These functions are nonsmooth and nonconvex. We use Discrete Gradient methods for their local minimization. We consider also a combination of this method with the cutting angle method for global minimization. We present and discuss results of numerical experiments.
- Description: C1
- Description: 2003000421
- Authors: Bagirov, Adil , Rubinov, Alex , Sukhorukova, Nadezda , Yearwood, John
- Date: 2003
- Type: Text , Journal article
- Relation: Top Vol. 11, no. 1 (2003), p. 1-92
- Full Text:
- Reviewed:
- Description: We examine various methods for data clustering and data classification that are based on the minimization of the so-called cluster function and its modications. These functions are nonsmooth and nonconvex. We use Discrete Gradient methods for their local minimization. We consider also a combination of this method with the cutting angle method for global minimization. We present and discuss results of numerical experiments.
- Description: C1
- Description: 2003000421
Abstract convexity of positive homogenous functions
- Rubinov, Alex, Dzalilov, Zari
- Authors: Rubinov, Alex , Dzalilov, Zari
- Date: 2002
- Type: Text , Journal article
- Relation: Journal of Statistics and Management Systems Vol. 5, no. 1 (2002), p. 1-19
- Full Text:
- Reviewed:
- Description: This paper is a survey of recent results to abstract convexity of positively homogeneous functions, that is, to a representation of such functions as the upper (lower) envelope of sets of fairly simple functions. In particular, we study sup-min and max-min representations of positively homogeneous of degree one functions through linear functions and various kinds of the so-called exhausters.
- Description: C1
- Description: 2003003353
- Authors: Rubinov, Alex , Dzalilov, Zari
- Date: 2002
- Type: Text , Journal article
- Relation: Journal of Statistics and Management Systems Vol. 5, no. 1 (2002), p. 1-19
- Full Text:
- Reviewed:
- Description: This paper is a survey of recent results to abstract convexity of positively homogeneous functions, that is, to a representation of such functions as the upper (lower) envelope of sets of fairly simple functions. In particular, we study sup-min and max-min representations of positively homogeneous of degree one functions through linear functions and various kinds of the so-called exhausters.
- Description: C1
- Description: 2003003353
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