Description:
Opportunistic access of licensed spectrum using a cognitive radio network (CRN) is getting research attraction due to its ability to improve utilisation of this scarce resource without affecting the primary users (PUs). To improve wide acceptability of CRN, it must be equipped with efficient protocols to deal with multiple primary networks to provision QoS guarantee for demand-driven applications by the secondary users (SUs). In this paper, an accurate unsaturated throughput analysis is presented for our novel CSMA/CA-based multi-channel cognitive radio medium access control (MCR-MAC) protocol. Developed by modifying the 4-way handshaking-based IEEE 802.11 DCF, MCR-MAC dynamically assigns contending SUs to free channels using an innovative random arbitration scheme while keeping cognitive interference to the PUs in check by attenuating the packet size. Not only has the analytical model covered the full spectrum, from very light load to saturation, extensive simulation results have validated the accuracy of the analysis.
Description:
This paper presents an investigative study in which data were gathered and used in underground mining to improve the planned maintenance program and reliability of the shearer loader in the underground mining. A cost effective maintenance and operation strategy and practices is mandatory to meet the production demand and the required level of service of this critical asset of the plant. The study conducted and presented in this paper includes a detailed review of failure history data and the use of analytical technique available to understand failure characteristics and its effect on the throughput and the overall performance of the longwall operation. This is to achieve further productivity increases to meet business goals. Analytical tools such as Failure Mode and Effect and Criticality Analysis (FMECA) and Weibull analysis were used in this investigation. The study has highlighted the criticality of some failures and the actions needed in this industrial case to improve the reliability and planned maintenance for a better mining productivity.
Description:
The purpose of this paper is to provide greater insight into environmental accountability and disclosure from a functionalist perspective. Discussion of the utility of information supplied by corporations to discharge accountability is dependent on societal attitudes to the function of the corporation in society, corporate environmental responsibility and the issue of economic growth. Similarly, the usefulness of environmental information is predicated on perceptions of society as to the importance of environmental issues. The polarisation and politicisation of opinion regarding global warming denies scientific evidence and compounds issues of accountability and disclosure. A postal questionnaire was used to determine societal attitudes to key aspects of corporate functionality, accountability and disclosure. Questionnaire participants were drawn from three categories of society; shareholders, environmentalists and shareholder / environmentalists. Results indicate that the majority of respondents believe the function of the corporation in society is economic and social but there is a significant difference between shareholders and the other user groups. The preferred option of respondents regarding environmental accountability is for companies to be in advance of law and opinion. The sustainable development position, described a continuum, is supported by the shareholder and shareholder/environmentalist groups. The survey research method adopted in this paper suffers from the stated perceptions of respondents rather than attempting to reveal attitudes via alternative approaches. This study demonstrates that there is an attitudinal change towards corporate responsibility that will necessitate re-evaluation of corporate disclosure and accountability.
Description:
The purpose of this paper is to provide greater insight into environmental accountability and disclosure from a functionalist perspective. Discussion of the utility of information supplied by corporations to discharge accountability is dependent on societal attitudes to the function of the corporation in society, corporate environmental responsibility and the issue of economic growth. Similarly, the usefulness of environmental information is predicated on perceptions of society as to the importance of environmental issues. The polarisation and politicisation of opinion regarding global warming denies scientific evidence and compounds issues of accountability and disclosure. A postal questionnaire was used to determine societal attitudes to key aspects of corporate functionality, accountability and disclosure. Questionnaire participants were drawn from three categories of society; shareholders, environmentalists and shareholder / environmentalists. Results indicate that the majority of respondents believe the function of the corporation in society is economic and social but there is a significant difference between shareholders and the other user groups. The preferred option of respondents regarding environmental accountability is for companies to be in advance of law and opinion. The sustainable development position, described a continuum, is supported by the shareholder and shareholder/environmentalist groups. The survey research method adopted in this paper suffers from the stated perceptions of respondents rather than attempting to reveal attitudes via alternative approaches. This study demonstrates that there is an attitudinal change towards corporate responsibility that will necessitate re-evaluation of corporate disclosure and accountability.
Description:
Energized parts within power transformer are isolated using paper insulation and are immersed in insulating oil. Hence, transformer oil and paper insulation are essential sources to detect incipient and fast developing power transformer faults. Several chemical diagnoses techniques are developed to examine the condition of paper insulation such as degree of polymerization, carbon oxides, furanic compounds and methanol. The principle and limitation of these diagnoses are discussed and compared in this paper.
Description:
Energized parts within power transformer are isolated using paper insulation and are immersed in insulating oil. Hence, transformer oil and paper insulation are essential sources to detect incipient and fast developing power transformer faults. Several chemical diagnoses techniques are developed to examine the condition of paper insulation such as degree of polymerization, carbon oxides, furanic compounds and methanol. The principle and limitation of these diagnoses are discussed and compared in this paper.
Description:
Obstructive Sleep Apnoea (OSA), a sleeping disorder, is a serious health issue with significant public health implications. Due to the interrupted sleep, OSA patients suffer with excessive day-time sleepiness, fatigue and other health complexities that lead to on-road and work-related accidents and incur billions of dollars per year. Traditionally, treatment of OSA begins with nasal continuous positive airway pressure (CPAP). Alternatively, Mandibular Repositioning Appliances or surgical interventions can be used. Although Maxillomandibular Advancement (MMA) surgery is often advised as the last line of treatment due to the expense and significant changes in the facial appearance, it is the only permanent solution to OSA with a definitive outcome especially for the patients with significant facial deformation or anomalies. In this article, three dimensional (3D) image-guided predictive algorithms are proposed to improve the treatment planning and overall outcome of the MMA surgery. 3D analysis of the facial surface data and Computational Biomechanics-based 3D modelling of airway segmented from Cone Beam Computed Tomography (CBCT) data are proposed to predict the required physiological changes to ensure optimal air-flow through the airway. Moreover, 3D Computer Graphics-based techniques are proposed to visualise and demonstrate the expected facial outcomes to inform patients and surgeons prior to this non-reversible surgery.
Description:
In this paper, the height variation in LIDAR (Light Detection And Ranging) point cloud data and point density are analyzed to remove the false building detection in highly vegetation and hilly sites. In general, the LIDAR points in a tree area have higher height variations than those in a building area. Moreover, the density of points having similar height values is lower in a tree area than in a building area. The proposed method uses such information as an improvement to a current state-of-the-art building detection method. The qualitative and object-based quantitative analyzes have been performed to verify the effectiveness of the proposed building detection method as compared with a current method. The analysis shows that proposed building detection method successfully reduces false building detection (i.e. trees in high complex sites of Australia and Germany), and the average correctness and quality have been improved by 6.36% and 6.16% respectively.
Description:
In this paper, the height variation in LIDAR (Light Detection And Ranging) point cloud data and point density are analyzed to remove the false building detection in highly vegetation and hilly sites. In general, the LIDAR points in a tree area have higher height variations than those in a building area. Moreover, the density of points having similar height values is lower in a tree area than in a building area. The proposed method uses such information as an improvement to a current state-of-the-art building detection method. The qualitative and object-based quantitative analyzes have been performed to verify the effectiveness of the proposed building detection method as compared with a current method. The analysis shows that proposed building detection method successfully reduces false building detection (i.e. trees in high complex sites of Australia and Germany), and the average correctness and quality have been improved by 6.36% and 6.16% respectively.
Description:
A reliability optimization model is proposed in this paper for multi-state weighted k-out-of-n systems. In this model, income generated by components through each functioning period is used as a reliability index. Therefore, time value of money is used in the presented optimization model to estimate both system's reliability and cost. The system reliability is evaluated by Universal Generating Function (UGF). The model's objective function is to maximize the net present value (NPV) of the system. Therefore, it would maximize the system reliability and minimize the system cost simultaneously. A numerical example is presented in this paper to illustrate the model by finding the optimal design of the system, and the best time for maintenance plan. Also, a discussion is provided based on the result.
Description:
IEC 61850 Standard was introduced to address the challenge presented by existence of the multiple protocols in substation communications, which include many proprietary protocols; and to address the challenge introduced by legacy complicated substation from both cost and complicity. In this paper, the simulation results of different types of IEC 61850 network system configurations using OPNET Modeler simulation software were presented and the influence on data rate and delay characteristics of these system configurations were evaluated. The simulated results confirm that the ring configured system suitable for higher loading characteristics and higher system reliability.
Description:
Subwavelength grating (SWG) structures make an excellent alternative antireflective (AR) coating due to its capacity to reduce the reflection losses in GaAs solar cells. The SWG structures allow the gradual change in refractive index that confirms an excellent AR coating and the light trapping properties when compare with planar thin film structures. Finite-difference time domain (FDTD) method is used to simulate the reflection losses of the SWG structure in GaAs solar cells. The FDTD simulation results show that the slightly change of incident angle affect the reflection losses of all nano-grating structure. The simulation results also confirmed that the reflection loss of nano-grating structure maintained optimum within ~±5° of incident angle tolerance for the grating height over 300-nm for minimizing the reflection losses in GaAs solar cells.
Description:
The distributed generation (DG) mixture in an active distribution network can provide different levels of network benefits and benefits external to the network. This paper investigates this problem in detail and proposes an approach to assess the DG mixture for hybrid benefits through the sequential simulation of optimized samples. A case study is performed incorporating Wind and PV generation as intermittent DG, diesels, their life-cycle costs (LCCs), and contribution to greenhouse-gas (GHG) abatement. Results suggest that specific operating conditions in a network can dominate the DG mixture and deliver the combined benefits. Wind and diesel hybrid operation can be the most beneficial DG mixture in an active distribution network compared to any other DG combination with current costing structure.
Description:
From Materials to Structures: Advancement Through Innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012
Description:
From Materials to Structures: Advancement Through Innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012
Description:
The industrial robot is one of the popular devices used in fully automatic production lines as material handling tool. A consequential problem is finding a cyclic robot movement which gives the maximum cell output in mass production environments. The Robotic Cell Scheduling Problem (RCSP) is predominantly separated into two different problems: Single-Function Robotic Cell (SFRC) and Multi-Function Robotic Cell (MFRC) scheduling problem. These problems are layout-oriented and operation-oriented, respectively. Literature concerning with former case considered a robotic system served by a transporting robot performing a single task. This kind of transporting robot is usually called Single-Function Robot (SFR). For the latter case, the robotic system served by a Multi-Function Robot (MFR) which simultaneously perform an arbitrary task in addition to parts transportation task. Giving a real-life example of MFRs, the use of a class of grippers performing in-process control is significantly increased in industry. The grippers, install at the end of MFR arm, can perform quality control tasks (e.g. accurately measure diameters) while part is carried to next machine. Figure 1 shows an example of these grippers used for measuring the diameter of crankshaft [1]. The measuring heads are integrated into the automation by adding gages and crankshaft locating features to MFR using in these lines. Also, there is a special kind of MFR, namely SDA10, which is suitable for assembly and part transfer in production lines especially if fixturing is costly [2]. Thus, it is crucial to undertake a comprehensive research onto effect of MFRs on production rate.
Description:
In tele-operation applications, especially in surgery, haptic devices need to exhibit a high degree of rigidity and accuracy. This paper deals with the development of a spherical parallel manipulator (SPM) that enables the satisfaction of those characteristics. The parallel architecture enables the use of this kind of robot as master in a tele-operation system. Moreover, the SPM has a center of rotation that makes it a natural candidate and more adapted to minimally invasive surgery application. However, the parallel manipulator presents a poor behavior in singular configuration. In this paper we discuss the technique we used to overcome the singularity effects. We also present the methodology of using additional sensor to avoid kinematic structure problem without design changes. The investigation of the developed solution is detailed in this paper. Also, the experimental results of the newly developed haptic device are presented in this paper.
Description:
This paper proposes a hybrid Newton-Raphson and genetic algorithm for the estimation of double cage induction motor parameters from commonly available manufacturer data. The hybrid algorithm was tested on a large data set of 6,380 IEC and NEMA motors and then compared with a baseline Newton-Raphson algorithm. The simulation results show that while the proposed hybrid algorithm is more computationally intensive, it does make significant improvements to convergence and error rates.
Description:
This paper proposes a hybrid Newton-Raphson and genetic algorithm for the estimation of double cage induction motor parameters from commonly available manufacturer data. The hybrid algorithm was tested on a large data set of 6,380 IEC and NEMA motors and then compared with a baseline Newton-Raphson algorithm. The simulation results show that while the proposed hybrid algorithm is more computationally intensive, it does make significant improvements to convergence and error rates.
Description:
From Materials to Structures: Advancement Through Innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012