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Full-Text Articles in Engineering
Hybrid Model Predictive Control Of A Residential Hvac System With On-Site Thermal Energy Generation And Storage, Massimo Fiorentini, Josh Wall, Zhenjun Ma, Julio H. Braslavsky, Paul Cooper
Hybrid Model Predictive Control Of A Residential Hvac System With On-Site Thermal Energy Generation And Storage, Massimo Fiorentini, Josh Wall, Zhenjun Ma, Julio H. Braslavsky, Paul Cooper
Faculty of Engineering and Information Sciences - Papers: Part A
This paper describes the development, implementation and experimental investigation of a Hybrid Model Predictive Control (HMPC) strategy to control solar-assisted heating, ventilation and air-conditioning (HVAC) systems with on-site thermal energy generation and storage. A comprehensive approach to the thermal energy management of a residential building is presented to optimise the scheduling of the available thermal energy resources to meet a comfort objective. The system has a hybrid nature with both continuous variables and discrete, logic-driven operating modes. The proposed control strategy is organized in two hierarchical levels. At the high-level, an HMPC controller with a 24-h prediction horizon and a …
Statistical Shape Model Generation Using Diffeomorphic Surface Registration, Jiaqi Wu, Guangxu Li, Huimin Lu, Hyoung Kim, Philip O. Ogunbona
Statistical Shape Model Generation Using Diffeomorphic Surface Registration, Jiaqi Wu, Guangxu Li, Huimin Lu, Hyoung Kim, Philip O. Ogunbona
Faculty of Engineering and Information Sciences - Papers: Part B
Statistical shape modelling is an efficient and robust method for medical image segmentation in computer-aided diagnosis. The key step in building a statistical shape model is to find corresponding landmarks in each instance of a training set. In this paper, a novel landmark correspondence estimation method that uses edge collapse surface simplification and the sphere registration is proposed. All the landmarks are selected and transformed by spherical conformal mapping from the instances of the training set and the associated correspondence are automatically found on the spheres. We applied our method on 21 cases of 3-D right lung shapes. The results …
Mitigating Tap Changer Limit Cycles In Modern Electricity Networks Embedded With Local Generation Units, Dothinka Ranamuka Rallage, Ashish P. Agalgaonkar, Kashem M. Muttaqi, Md Jan E Alam
Mitigating Tap Changer Limit Cycles In Modern Electricity Networks Embedded With Local Generation Units, Dothinka Ranamuka Rallage, Ashish P. Agalgaonkar, Kashem M. Muttaqi, Md Jan E Alam
Faculty of Engineering and Information Sciences - Papers: Part A
Cascaded on-load tap changers (OLTCs) are widely used for coarse control of voltages in largely interconnected elec- tric power systems. There could be interactions between load dynamics and OLTC control under certain system operating conditions which may lead to the OLTC limit cycle phenomena, thereby resulting into long-term voltage oscillations in the system. In recent years, renewable and nonrenewable local generation (LG) units have been getting interconnected in modern power systems. The existence of OLTC limit cycles in the presence of LG has not been addressed in the literature in greater details. In this paper, the OLTC limit cycle phenomenon, …
A Review Of Protection Systems For Distribution Networks Embedded With Renewable Generation, Joel Kennedy, Philip Ciufo, Ashish P. Agalgaonkar
A Review Of Protection Systems For Distribution Networks Embedded With Renewable Generation, Joel Kennedy, Philip Ciufo, Ashish P. Agalgaonkar
Faculty of Engineering and Information Sciences - Papers: Part A
The rapid growth of grid-connected embedded generation is changing the operational characteristics of power distribution networks. Amongst a range of issues being reported in the research, the effect of these changes on so-called 'traditional protection systems' has not gone without attention. Looking to the future, the possibility of microgrid systems and deliberate islanding of sections of the network will require highly flexible distribution management systems and a re-design of protection strategies. This paper explores the envisaged protection issues concerned with large penetrations of embedded generation in distribution networks extending into auto-reclosure and protection device coordination. A critical review of recently …
Analysis Of The Oceanic Wave Dynamics For Generation Of Electrical Energy Using A Linear Generator, Omar Farrok, Md Rabiul Islam, Md Rafiqul Islam Sheikh
Analysis Of The Oceanic Wave Dynamics For Generation Of Electrical Energy Using A Linear Generator, Omar Farrok, Md Rabiul Islam, Md Rafiqul Islam Sheikh
Faculty of Engineering and Information Sciences - Papers: Part B
Electricity generation from oceanic wave depends on the wave dynamics and the behavior of the ocean. In this paper, a permanent magnet linear generator (PMLG) has been designed and analyzed for oceanic wave energy conversion. The proposed PMLG design is suitable for the point absorber type wave energy device. A mathematical model of ocean wave is presented to observe the output characteristics and performance of the PMLG with the variation of ocean waves. The generated voltage, current, power, applied force, magnetic flux linkage, and force components of the proposed PMLG have been presented for different sea wave conditions. The commercially …
Optimizing Distributed Generation Parameters Through Economic Feasibility Assessment, Kashem M. Muttaqi, An D. T Le, Jamshid Aghaei, Esmaeil Mahboubi-Moghaddam, Michael Negnevitsky, Gerard Ledwich
Optimizing Distributed Generation Parameters Through Economic Feasibility Assessment, Kashem M. Muttaqi, An D. T Le, Jamshid Aghaei, Esmaeil Mahboubi-Moghaddam, Michael Negnevitsky, Gerard Ledwich
Faculty of Engineering and Information Sciences - Papers: Part A
To meet the fast growth of electricity demand, the traditional network solution tends to expand existing substations, build more new substations, and build transmission lines. Distributed Generation (DG) is posed as an alternative method for the network providers not only to accommodate the load increase and relieve network overload, but also to offer other additional technical and economic benefits. This paper addresses the issue of DG planning and has proposed a technique for optimizing the DG size and location to minimize the overall investment and operational cost of the system. The proposed optimization methodology assesses the compatibility of different generation …
Over-Voltage Mitigation Within Distribution Networks With A High Renewable Distributed Generation Penetration, Joel Kennedy, Philip Ciufo, Ashish Agalgaonkar
Over-Voltage Mitigation Within Distribution Networks With A High Renewable Distributed Generation Penetration, Joel Kennedy, Philip Ciufo, Ashish Agalgaonkar
Dr Philip Ciufo
The rapid growth of grid-connected distributed generation has increased the likelihood of over-voltage occurrences in distribution networks. In recent times, much research has taken place in order to develop a control strategy to mitigate the voltage rise problem. However, most of the published strategies require re-tuning when additional resources are connected, or have a strong dependence on network parameters, such as fault level. This paper proposes a novel over-voltage mitigation scheme that has many advantages not observed in literature. Firstly, the control scheme can integrate with an existing feeder in a plug-and-play fashion. No prior analysis is necessary to configure …
Dc-Link Fault Current Limiter-Based Fault Ride-Through Scheme For Inverter-Based Distributed Generation, Amin Jalilian, Mehrdad Tarafdar Hagh, Mehdi Abapour, Kashem M. Muttaqi
Dc-Link Fault Current Limiter-Based Fault Ride-Through Scheme For Inverter-Based Distributed Generation, Amin Jalilian, Mehrdad Tarafdar Hagh, Mehdi Abapour, Kashem M. Muttaqi
Faculty of Engineering and Information Sciences - Papers: Part A
Owing to increasing the penetration level of the inverter-based distributed generations (IBDGs) in power systems, their fault ride-through (FRT) capability has become one of the essential issues of new grid codes. This study proposes a novel DC-link fault current limiter (DLFCL)-based FRT scheme to improve the FRT capability in IBDG units. The DLFCL module has almost no effect on normal operation of IBDG. When a short-circuit fault occurs in power system, the DLFCL module effectively limits the inverter output current and protects its switching devices. The employed DLFCL does not need any control, measurement and gate driving system. Also, it …
Power Generation Analysis Of Powerwindow, A Linear Wind Generator, Using Computational Fluid Dynamic Simulations, Seyed A. Jafari, Farzad Safaei, Buyung Kosasih, K C. Kwok
Power Generation Analysis Of Powerwindow, A Linear Wind Generator, Using Computational Fluid Dynamic Simulations, Seyed A. Jafari, Farzad Safaei, Buyung Kosasih, K C. Kwok
Faculty of Engineering and Information Sciences - Papers: Part A
A new linear wind generator (LWG), named PowerWindow, is introduced. The modular and scalable LWG is capable of generating power in low wind velocity condition, and hence can be an effective and safe power generator in built environments. The aerodynamic mechanism of the LWG power generation is elucidated using computational fluid dynamic (CFD) simulations, and the results are validated against the experimental data obtained from the prototype wind tunnel tests. The simulations provide important insights into the flow field in and around LWG particularly over the front and rear blades and how each one contributes to the power generation. This …
Over-Voltage Mitigation Within Distribution Networks With A High Renewable Distributed Generation Penetration, Joel Kennedy, Philip Ciufo, Ashish Agalgaonkar
Over-Voltage Mitigation Within Distribution Networks With A High Renewable Distributed Generation Penetration, Joel Kennedy, Philip Ciufo, Ashish Agalgaonkar
Faculty of Engineering and Information Sciences - Papers: Part A
The rapid growth of grid-connected distributed generation has increased the likelihood of over-voltage occurrences in distribution networks. In recent times, much research has taken place in order to develop a control strategy to mitigate the voltage rise problem. However, most of the published strategies require re-tuning when additional resources are connected, or have a strong dependence on network parameters, such as fault level. This paper proposes a novel over-voltage mitigation scheme that has many advantages not observed in literature. Firstly, the control scheme can integrate with an existing feeder in a plug-and-play fashion. No prior analysis is necessary to configure …
A Tool-Path Generation Strategy For Wire And Arc Additive Manufacturing, Donghong Ding, Zengxi Stephen Pan, Dominic Cuiuri, Huijun Li
A Tool-Path Generation Strategy For Wire And Arc Additive Manufacturing, Donghong Ding, Zengxi Stephen Pan, Dominic Cuiuri, Huijun Li
Faculty of Engineering and Information Sciences - Papers: Part A
This paper presents an algorithm to automatically generate optimal tool-paths for the wire and arc additive manufacturing (WAAM) process for a large class of geometries. The algorithm firstly decomposes 2D geometries into a set of convex polygons based on a divide-and-conquer strategy. Then, for each convex polygon, an optimal scan direction is identified and a continuous tool-path is generated using a combination of zigzag and contour pattern strategies. Finally, all individual sub-paths are connected to form a closed curve. This tool-path generation strategy fulfils the design requirements of WAAM, including simple implementation, a minimized number of starting-stopping points, and high …
Generation Alpha At The Intersection Of Technology, Play And Motivation, Holly Tootell, Mark Freeman, Alison E. Freeman
Generation Alpha At The Intersection Of Technology, Play And Motivation, Holly Tootell, Mark Freeman, Alison E. Freeman
Faculty of Engineering and Information Sciences - Papers: Part A
This paper considers the intersection of technology and play through the novel approach of gamification and its application to early years education. The intrinsic connection between play and technology is becoming increasingly significant in early years education. By creating an awareness of the early years adoption of technology into guiding frameworks, and then exploring the makeup of gaming elements, this paper draws connections for guiding principles in adopting more technology-focused play opportunities for Generation Alpha.
A Novel Tuning Method For Advanced Line Drop Compensator And Its Application To Response Coordination Of Distributed Generation With Voltage Regulating Devices, Kashem M. Muttaqi, An D. T Le, Michael Negnevitsky, Gerard Ledwich
A Novel Tuning Method For Advanced Line Drop Compensator And Its Application To Response Coordination Of Distributed Generation With Voltage Regulating Devices, Kashem M. Muttaqi, An D. T Le, Michael Negnevitsky, Gerard Ledwich
Faculty of Engineering and Information Sciences - Papers: Part A
Nowadays, integration of small-scale electricity generators, known as Distributed Generation (DG), into distribution networks has become increasingly popular. This tendency together with the falling price of DG units has a great potential in giving the DG a better chance to participate in voltage regulation process, in parallel with other regulating devices already available in the distribution systems. The voltage control issue turns out to be a very challenging problem for distribution engineers, since existing control coordination schemes need to be reconsidered to take into account the DG operation. In this paper, a control coordination approach is proposed, which is able …
Dispatch Strategy To Minimise Uncertainty In Wind Power Generation In The Australian National Electricity Market, Amila Wickramasinghe, Lasantha G. Meegahapola, Ashish P. Agalgaonkar, Sarath Perera
Dispatch Strategy To Minimise Uncertainty In Wind Power Generation In The Australian National Electricity Market, Amila Wickramasinghe, Lasantha G. Meegahapola, Ashish P. Agalgaonkar, Sarath Perera
Faculty of Engineering and Information Sciences - Papers: Part A
2014 ACPE. With increased penetration of wind power, scheduling generators to meet the forecast demand of a power system is becoming an increasingly challenging task for the system operators. Uncertainty associated with the generation expected from wind plants adds to the load demand uncertainty, making it necessary to retain additional reserves to maintain the balance between demand and supply of power. In the Australian national electricity market (NEM), sophisticated wind forecasting techniques are employed to reduce the uncertainty in wind generation. Despite being able to project the contribution of wind power to a reasonable accuracy, wind power plants are currently …
Optimal Design Of Vertical Ground Heat Exchangers By Using Entropy Generation Minimization Method And Genetic Algorithms, Su Huang, Zhenjun Ma, Paul Cooper
Optimal Design Of Vertical Ground Heat Exchangers By Using Entropy Generation Minimization Method And Genetic Algorithms, Su Huang, Zhenjun Ma, Paul Cooper
Faculty of Engineering and Information Sciences - Papers: Part A
This paper presents the development and validation of an optimal design methodology for vertical U-tube ground heat exchangers (GHEs) used in HVAC systems. The dimensionless entropy generation number obtained by scaling the entropy generation due to heat transfer and pressure drop, on the ratio of the heat transfer rate to the average fluid temperature of vertical GHEs is employed as the objective function. Five design variables are first selected based on the global sensitivity analysis and then optimized by a genetic algorithm optimization technique. The entropy generation process combines the heat transfer and fluid mechanics with thermodynamic analysis. A case …
An Approach For Assessing The Effectiveness Of Multiple-Feature-Based Svm Method For Islanding Detection Of Distributed Generation, Mollah R. Alam, Kashem M. Muttaqi, Abdesselam Bouzerdoum
An Approach For Assessing The Effectiveness Of Multiple-Feature-Based Svm Method For Islanding Detection Of Distributed Generation, Mollah R. Alam, Kashem M. Muttaqi, Abdesselam Bouzerdoum
Faculty of Engineering and Information Sciences - Papers: Part A
Islanding detection is a critical protection issue, as conventional protection schemes such as vector surge (VS) and rate of change of frequency relays do not guarantee islanding detection for all network conditions. Integration of multiple distributed generation (DG) units of different sizes and technologies into distribution grids makes this issue even more critical. This paper presents a comprehensive analysis of the effectiveness of a new method for islanding detection in DG networks. The proposed method, which is based on multiple features and support vector machine (SVM) classification, has the potential to overcome the limitations of conventional protection schemes. The multifeature-based …
Solar Pv Power Generation Forecasting Using Hybrid Intelligent Algorithms And Uncertainty Quantification Based On Bootstrap Confidence Intervals, Donna Alhakeem
Solar Pv Power Generation Forecasting Using Hybrid Intelligent Algorithms And Uncertainty Quantification Based On Bootstrap Confidence Intervals, Donna Alhakeem
Open Access Theses & Dissertations
This Thesis focuses on short-term photovoltaic forecasting (STPVF) for the power generation of a solar PV system using probabilistic forecasts and deterministic forecasts. Uncertainty estimation, in the form of a probabilistic forecast, is emphasized in this Thesis to quantify the uncertainties of the deterministic forecasts. Two hybrid intelligent models are proposed in two separate chapters to perform the STPVF. In Chapter 4, the framework of the deterministic proposed hybrid intelligent model is presented, which is a combination of wavelet transform (WT) that is a data filtering technique and a soft computing model (SCM) that is generalized regression neural network (GRNN). …
Impact Of Wind Generation Mix On Transient Stability For An Interconnected Power System, Lasantha Meegahapola, Damian Flynn, Jason Kennedy, Tim Littler
Impact Of Wind Generation Mix On Transient Stability For An Interconnected Power System, Lasantha Meegahapola, Damian Flynn, Jason Kennedy, Tim Littler
Dr Lasantha G Meegahapola
The rapid growth of wind generation in many European countries is pushing power systems into uncharted territory. As additional wind generators are installed, the changing generation mix may impact on power system stability. This paper adopts the New England 39 bus system as a test system for transient stability analysis. Thermal generator models are based on a likely future plant mix for existing systems, while varying capacities of fixed-speed induction generators (FSIG) and doubly-fed induction generators (DFIG) are considered. The main emphasis here has been placed on the impact of wind technology mix on inter-area oscillations following transient grid disturbances. …
Voltage Security Constrained Reactive Power Optimization Incorporating Wind Generation, L G. Meegahapola, E Vittal, A Keane, D Flynn
Voltage Security Constrained Reactive Power Optimization Incorporating Wind Generation, L G. Meegahapola, E Vittal, A Keane, D Flynn
Dr Lasantha G Meegahapola
This paper presents a comparative analysis between conventional optimal power flow (OPF) and voltage constrained OPF strategies with wind generation. The study has been performed using the New England 39 bus system with 12 doublyfed induction generator (DFIG) based wind farms installed across the network. A voltage security assessment is carried out to determine the critical wind farms for voltage stability enhancement. The power losses and individual wind farm reactive power generation have been compared with and without voltage stability constraints imposed on the OPF simulation. It is shown that voltage constrained OPF leads to much greater active power losses …
Flicker Propagation Analysis In Distribution Networks With Embedded Generation, D Perera, L Meegahapola, S Perera, P Ciufo
Flicker Propagation Analysis In Distribution Networks With Embedded Generation, D Perera, L Meegahapola, S Perera, P Ciufo
Dr Lasantha G Meegahapola
Embedded generators such as wind generators can produce observable voltage fluctuations during variable wind conditions hence flicker. The flicker produced by such intermittent and fluctuating generating sources can propagate to other parts of the distribution network while creating power quality issues in distribution feeders. This study presents a flicker emission analysis for a doubly-fed induction generator (DFIG) based wind farm and investigate the pertinent factors which influence flicker propagation and attenuation in distribution feeders. Study has shown that voltage fluctuations are significantly influenced by the attenuation characteristics of various load types (i.e. constant power, impedance and current loads) connected to …
Flicker Propagation Analysis In Distribution Networks With Embedded Generation, D Perera, L Meegahapola, S Perera, P Ciufo
Flicker Propagation Analysis In Distribution Networks With Embedded Generation, D Perera, L Meegahapola, S Perera, P Ciufo
Dr Philip Ciufo
Embedded generators such as wind generators can produce observable voltage fluctuations during variable wind conditions hence flicker. The flicker produced by such intermittent and fluctuating generating sources can propagate to other parts of the distribution network while creating power quality issues in distribution feeders. This study presents a flicker emission analysis for a doubly-fed induction generator (DFIG) based wind farm and investigate the pertinent factors which influence flicker propagation and attenuation in distribution feeders. Study has shown that voltage fluctuations are significantly influenced by the attenuation characteristics of various load types (i.e. constant power, impedance and current loads) connected to …
Estimation Of Capacity Credits For Wind Generation Plants In The South East Australian Power Grid, Md Abu Abdullah, Kashem Muttaqi, Ashish Agalgaonkar, Darmawan Sutanto
Estimation Of Capacity Credits For Wind Generation Plants In The South East Australian Power Grid, Md Abu Abdullah, Kashem Muttaqi, Ashish Agalgaonkar, Darmawan Sutanto
Faculty of Engineering and Information Sciences - Papers: Part A
It is important to estimate the contribution of the wind generation plants in the evaluation of system generation adequacy for power generation planning. Australia has recently proposed to utilize the diversity of the wind energy resources in Southeast Australian power grid through existing inter-State interconnections. This paper aims to present a probabilistic adequacy model for the capacity credit estimation of wind generation plants in interconnected power systems. In particular, the proposed adequacy model will be applied to investigate how sharing of wind energy resource diversity can enhance the capacity credit of the wind generation plants. The impact of the inter-tie …
Mip-Based Stochastic Security-Constrained Daily Hydrothermal Generation Scheduling, J Aghaei, M Karami, K M. Muttaqi, A Ahmadi, H A. Shayanfar
Mip-Based Stochastic Security-Constrained Daily Hydrothermal Generation Scheduling, J Aghaei, M Karami, K M. Muttaqi, A Ahmadi, H A. Shayanfar
Faculty of Engineering and Information Sciences - Papers: Part A
This paper presents the application of a mixedinteger programming (MIP) approach for solving stochastic security-constrained daily hydrothermal generation scheduling (SCDHGS). Power system uncertainties including generating units and branch contingencies and load uncertainty are explicitly considered in the stochastic programming of SCDHGS. The roulette wheel mechanism and lattice Monte Carlo simulation (LMCS) are first employed for random scenario generation wherein the stochastic SCDHGS procedure is converted into its respective deterministic equivalents (scenarios). Then, the generating units are scheduled through MIP over the set of deterministic scenarios for the purpose of minimizing the cost of supplying energy and ancillary services over the …
Capacity Deferral Credit Evaluation Of Renewable Distributed Generation, M A. Abdullah, K M. Muttaqi, A P. Agalgaonkar, D Sutanto
Capacity Deferral Credit Evaluation Of Renewable Distributed Generation, M A. Abdullah, K M. Muttaqi, A P. Agalgaonkar, D Sutanto
Faculty of Engineering and Information Sciences - Papers: Part A
Renewable distributed generation (DG) units can aid in distribution network planning and can be utilized in distribution expansion planning. In order to support the development of distributed renewable resources in the distribution network and to make these resources competitive in the energy market, a well justified credit scheme needs to be devised. In this paper, an analytical method has been developed to estimate the capacity deferral credit of renewable DGs that can be claimed from distribution system operators (DSOs) due to the deferral of conventional distribution network expansion options. The distribution network adequacy has been assessed using the combined multistate …
The Algorithm Of Equal Acceptance Region For Detecting Copy Number Alterations: Applications To Next-Generation Sequencing Data, Yan-Xia Lin
Faculty of Engineering and Information Sciences - Papers: Part A
The information of copy number alterations (gains and losses) in tumour genomes can be used to discovery cancer-causing genes. The estimate of copy number can be obtained from the estimate copy number ratio. The higher the depth of underlying sequencing data, the more accurate the estimate of copy number ratio. At the same time, the higher depth of a sequencing data used in copy number analysis, the more cost of data analysis. To develop a method for identifying a necessary depth of sequencing data for copy number analysis before test data are produced is of interest. In this paper, we …
Voltage Security Constrained Reactive Power Optimization Incorporating Wind Generation, L G. Meegahapola, E Vittal, A Keane, D Flynn
Voltage Security Constrained Reactive Power Optimization Incorporating Wind Generation, L G. Meegahapola, E Vittal, A Keane, D Flynn
Faculty of Engineering and Information Sciences - Papers: Part A
This paper presents a comparative analysis between conventional optimal power flow (OPF) and voltage constrained OPF strategies with wind generation. The study has been performed using the New England 39 bus system with 12 doublyfed induction generator (DFIG) based wind farms installed across the network. A voltage security assessment is carried out to determine the critical wind farms for voltage stability enhancement. The power losses and individual wind farm reactive power generation have been compared with and without voltage stability constraints imposed on the OPF simulation. It is shown that voltage constrained OPF leads to much greater active power losses …
Flicker Propagation Analysis In Distribution Networks With Embedded Generation, D Perera, L Meegahapola, S Perera, P Ciufo
Flicker Propagation Analysis In Distribution Networks With Embedded Generation, D Perera, L Meegahapola, S Perera, P Ciufo
Faculty of Engineering and Information Sciences - Papers: Part A
Embedded generators such as wind generators can produce observable voltage fluctuations during variable wind conditions hence flicker. The flicker produced by such intermittent and fluctuating generating sources can propagate to other parts of the distribution network while creating power quality issues in distribution feeders. This study presents a flicker emission analysis for a doubly-fed induction generator (DFIG) based wind farm and investigate the pertinent factors which influence flicker propagation and attenuation in distribution feeders. Study has shown that voltage fluctuations are significantly influenced by the attenuation characteristics of various load types (i.e. constant power, impedance and current loads) connected to …
Cavity Enhanced Stimulated Brillouin Scattering In An Optical Ship For Multiorder Stokes Generation, Ravi Pant, Enbang Li, Duk-Yong Choi, Christopher Poulton, Stephen J. Madden, Barry Luther-Davies, Benjamin J. Eggleton
Cavity Enhanced Stimulated Brillouin Scattering In An Optical Ship For Multiorder Stokes Generation, Ravi Pant, Enbang Li, Duk-Yong Choi, Christopher Poulton, Stephen J. Madden, Barry Luther-Davies, Benjamin J. Eggleton
Faculty of Engineering and Information Sciences - Papers: Part A
We report the first demonstration of on-chip cascaded stimulated Brillouin scattering (SBS). Cascaded SBS is characterized in a 4 cm long chalcogenide ( As2S3 ) rib waveguide where the end facet reflections provide a monolithic Fabry–Perot (FP) resonator. The presence of the FP cavity reduces the Brillouin gain threshold, which enables observation of cascaded SBS at reduced pump powers. We observe up to three orders of Stokes waves in the backscattered signal at a coupled peak power of 1.34 W . Anti-Stokes waves due to four-wave mixing between the pump and the Stokes wave were observed in the forward spectrum.
Femtosecond Second-Harmonic Generation In Periodically Poled Lithium Niobate Waveguides Written By Femtosecond Laser Pulses, Zhangchao Huang, Chenghou Tu, Shuanggen Zhang, Yongnan Li, Fuyun Lu, Yaxian Fan, Enbang Li
Femtosecond Second-Harmonic Generation In Periodically Poled Lithium Niobate Waveguides Written By Femtosecond Laser Pulses, Zhangchao Huang, Chenghou Tu, Shuanggen Zhang, Yongnan Li, Fuyun Lu, Yaxian Fan, Enbang Li
Faculty of Engineering and Information Sciences - Papers: Part A
We present in this Letter the second-harmonic generation of femtosecond pulses in double-line-written waveguides fabricated in periodically poled lithium niobate (PPLN) with femtosecond laser pulses. In a 10-mm-long sample, a normalized conversion efficiency of 12.6% W−1 cm−2 has been achieved for 40 fs pump pulses with the wavelengths centered at 1550 nm. Simulation results show that in PPLN waveguides the FWHM of wavelength tuning curve for 40 fs pump pulses is 42 nm, which is 15 times of that for 40 ps pump pulses.
Psdboost: Matrix-Generation Linear Programming For Positive Semidefinite Matrices Learning, Chunhua Shen, Alan Welsh, Lei Wang
Psdboost: Matrix-Generation Linear Programming For Positive Semidefinite Matrices Learning, Chunhua Shen, Alan Welsh, Lei Wang
Faculty of Engineering and Information Sciences - Papers: Part A
In this work, we consider the problem of learning a positive semidefinite matrix. The critical issue is how to preserve positive semidefiniteness during the course of learning. Our algorithm is mainly inspired by LPBoost [1] and the general greedy convex optimization framework of Zhang [2]. We demonstrate the essence of the algorithm, termed PSDBoost (positive semidefinite Boosting), by focusing on a few different applications in machine learning. The proposed PSDBoost algorithm extends traditional Boosting algorithms in that its parameter is a positive semidefinite matrix with trace being one instead of a classifier. PSDBoost is based on the observation that any …