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:
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:
Students’ conceptions of learning or preconceived views of what learning means to students have been found to play a significant role in how they choose to approach their learning. This study investigates conceptions of learning held by accounting students in their second- and third-years in university. The study is based on phenomenographic and content-analytic approaches applied to survey responses of 207 accounting students from an Australian university. In the first phase of the analysis we identify 6 learning conceptions. Learning is conceived as: (1) increase of knowledge; (2) understanding; (3) knowledge acquisition for application; (4) a pathway to success; (5) seeing in new ways; and (6) self-development. Compared to similar studies we did not find evidence of the conception ‘learning as memorisation’. In contrast to prior research ‘learning as understanding’ emerged as a lower- order conception of learning in accounting students in this study. In the second phase we find that, after controlling for a range of factors that are likely to affect students’ conceptions of learning third-year students are more likely to adopt a higher-order conception. However, majority of the students, including third year students, continue to adopt low-order conceptions. These findings highlight the need to extend student learning beyond the acquisition of technical skills and knowledge to instil higher-order learning conceptions which underpin the development of generic skills much demanded of professional accountants. As a result, the findings of this study have implications for curriculum and assessment design, and learning and teaching practice in accounting degree programs.
Description:
Participatory Sensing System (PSS) is an emerging technology for collection of useful information as the use of smart-phones has been increasing lately among community people. It has a wide range of applications like environmental monitoring, product price sharing, health monitoring etc. But people have to share their location and other information which is a high privacy risk. Our main contribution of this work is to develop a technique for PSS which can provide privacy protection for the participants in manageable time in real world.
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:
Frequency Response Analysis (FRA) has been growing in popularity in recent times as a tool to detect mechanical deformation within power transformers. To conduct the test, the transformer has to be taken out of service which may cause interruption to the electricity grid. Moreover, because FRA relies on graphical analysis, it calls for an expert person to analyse the results as so far, there is no standard code for FRA interpretation worldwide. In this paper an online technique is introduced to detect the internal faults within a power transformer by constructing the voltage-current (V-I) locus diagram to provide a current state of the transformer health condition. The technique does not call for any special equipment as it uses the existing metering devices attached to any power transformer to monitor the input voltage, output voltage and the input current at the power frequency and hence online monitoring can be realised. Various types of faults have been simulated to assess its impact on the proposed locus. A Matlab code based on digital image processing is developed to calculate any deviation of the V-I locus with respect to the reference one and to identify the type of fault.
Description:
Frequency Response Analysis (FRA) has been growing in popularity in recent times as a tool to detect mechanical deformation within power transformers. To conduct the test, the transformer has to be taken out of service which may cause interruption to the electricity grid. Moreover, because FRA relies on graphical analysis, it calls for an expert person to analyse the results as so far, there is no standard code for FRA interpretation worldwide. In this paper an online technique is introduced to detect the internal faults within a power transformer by constructing the voltage-current (V-I) locus diagram to provide a current state of the transformer health condition. The technique does not call for any special equipment as it uses the existing metering devices attached to any power transformer to monitor the input voltage, output voltage and the input current at the power frequency and hence online monitoring can be realised. Various types of faults have been simulated to assess its impact on the proposed locus. A Matlab code based on digital image processing is developed to calculate any deviation of the V-I locus with respect to the reference one and to identify the type of fault.
Description:
Every day in online games designed to entertain, an unknown percentage of users are experiencing what is known as 'Griefing'. Griefing is used to describe when a player within a multiplayer online environment intentionally disrupts another player's game experience for his/her own personal enjoyment or material gain. Unrestrained, griefing could lead to a downward spiral of the number of people playing Massively Multiplayer Online Role-Playing Games (MMORPG)s, and possibly the death of smaller MMORPGs. Big game publishers may not wish to risk supporting the genre. There have been studies conducted in the past that attempt to define griefing and the different forms it takes in MMORPGs. These were outlined from the perception of the general player, and so did not examine differences in perception of griefing by different types of players. The authors conducted an online survey with the intention to discover the perception of various in-game actions previously identified in research as griefing, among griefers and griefing victims. In general players who identified themselves as griefers were more likely to regard these actions as a part of the game people had to learn to accept and not griefing. However some patterns of commonality were also observed between griefers and subjects of griefing, with some actions previously identified as griefing in the literature less commonly regarded as griefing by both player types in this survey.
Description:
Stickiness of whey protein isolate (WPI) and spray dried lactose droplets was studied at two air temperatures (65±0.5°C, 80±0.5°C), 0.75 m/s air velocity and 2-2.5% relative humidity using an in situ stickiness testing device. A stainless steel probe with 50 mm/min contact/withdrawal speed was used. The moisture and temperature histories were measured through parallel experiments. In each case, the surface of the lactose droplet remained sticky and failed cohesively until the surface was completely surrounded with crystals. The crystal layer remained fragile, fractured upon the probe contact and a thin layer of solution came out to the probe surface even after the moisture (u, dry basis) was lower than 0.2. WPI droplets formed thin and smooth skin immediately after coming in contact with hot air. The tensile strength of this skin increased rapidly and peaked (u = 2.14 at 45°C and u = 1. 47 at 65.7°C) fairly early during drying process. WPI droplet surface became completely non-sticky soon after attaining the peak tensile strength (u =1.32 at 53.4 °C and u= 1.05 at 68.8°C), mainly due to transformation of the outer layer of the skin into glassy material. The skin forming and surface active nature of WPI was exploited to minimize the stickiness of honey during spray drying. Replacement of 5% (w/w) maltodextrin with WPI raised the powder recovery of honey solids from 28% to 80%. Stickiness of the WPI on glass, Teflon and polyurethane surfaces was studied by replacing the contact surface of the probe with these materials. It was found that the stickiness of glass surface was the highest at test temperatures. Teflon surface offered the lowest stickiness at the test temperatures making it suitable materials to minimize solution/particle stickiness through coating.
Description:
This paper investigates the impact of time delay in the control of a grid-connected microgrid with renewable energy resources. The considered microgrid has a critical load that needs to be powered and protected in the event of grid voltage disturbance while the microgrid maintains connection to the grid. Three case studies are performed considering three different time delays to indicate the advantages of fast communication system in the performance of renewable microgrids. Detailed simulation results illustrate that the proposed communication system using IEC 61850 substation automation standard provides better voltage and current quality to the critical local load with larger phase and gain margins while keeping the microgid connected to main grid.
Description:
This paper investigates the impact of time delay in the control of a grid-connected microgrid with renewable energy resources. The considered microgrid has a critical load that needs to be powered and protected in the event of grid voltage disturbance while the microgrid maintains connection to the grid. Three case studies are performed considering three different time delays to indicate the advantages of fast communication system in the performance of renewable microgrids. Detailed simulation results illustrate that the proposed communication system using IEC 61850 substation automation standard provides better voltage and current quality to the critical local load with larger phase and gain margins while keeping the microgid connected to main grid.
Description:
Performance of industrial products is very important for an industry. Conventional methods for performance analysis consider a normality assumption and limited to low dimensional data. Different manufacturing processes very often have products with quality characteristics that do not follow normal distribution. In such cases fitting a known non-normal distribution to these quality characteristics would lead to erroneous results while assessing the performance of products. In this paper, we propose a novel method for non-normal multivariate process performance analysis. We have proposed a Constraint-based Evolutionary Algorithm (EA) approach for optimal estimation of the parameters of non-normal multivariate process. Furthermore, a geometric distance based method has been employed to reduce higher dimensionality of data to lower dimension. The efficacy of the proposed method is assessed by using the proportion of nonconformance (PNC) criterion to summarize the performance of EA approach. The experimental results from constraint-based EA have been compared to those obtained using steepest descent and simulated annealing (SA) approaches.
Description:
Nowadays every business is using different quantitative measures and techniques to assess performance of their products / services. It is well known that different manufacturing processes very often manufacture products with quality characteristics that do not follow normal distribution. In such cases, fitting a known non-normal distribution to these quality characteristics would lead to erroneous results. Furthermore, there is always more than one characteristic Critical to Quality (CTQ) in the process outcomes and very often these quality characteristics are correlated with each other. In this paper, we assess performance of such a bivariate process data which is non-normal as well as correlated. We will use the geometric distance approach to reduce the dimension of the correlated non-normal bivariate data and then fit Burr distribution to the geometric distance variable. The optimal parameters of the fitted Burr distribution are estimated using Evolutionary Algorithm (EA). The results are compared with those using Simulated Annealing (SA) algorithm. The proportion of nonconformance (PNC) for process measurements is then obtained by using the fitted Burr distributions based on the two methods. The results based on both search algorithms are then compared with the exact proportion of nonconformance of the data. Finally, a case study using real data is presented.
Description:
Nowadays every business is using different quantitative measures and techniques to assess performance of their products / services. It is well known that different manufacturing processes very often manufacture products with quality characteristics that do not follow normal distribution. In such cases, fitting a known non-normal distribution to these quality characteristics would lead to erroneous results. Furthermore, there is always more than one characteristic Critical to Quality (CTQ) in the process outcomes and very often these quality characteristics are correlated with each other. In this paper, we assess performance of such a bivariate process data which is non-normal as well as correlated. We will use the geometric distance approach to reduce the dimension of the correlated non-normal bivariate data and then fit Burr distribution to the geometric distance variable. The optimal parameters of the fitted Burr distribution are estimated using Evolutionary Algorithm (EA). The results are compared with those using Simulated Annealing (SA) algorithm. The proportion of nonconformance (PNC) for process measurements is then obtained by using the fitted Burr distributions based on the two methods. The results based on both search algorithms are then compared with the exact proportion of nonconformance of the data. Finally, a case study using real data is presented.
Description:
In this paper, we propose a mobility model and present its simulation tool to generate realistic mobility traces for mobile ad hoc network. The mobility model is capable of creating realistic node movement pattern in the presence of geographic constraints by exploiting the concepts of anchors. The model dynamically places anchors depending upon the context of the environment through which nodes are guided to move towards the destination, and obstacles of arbitrary shapes with or without doorways and any existing pathways, in full or part of the terrain can be incorporated which makes the simulation environment more realistic. The characteristics of the proposed mobility model tested on a real world university campus map at various movement patterns are presented that illustrate the impact of the mobility model on the performance of a routing protocol and usefulness of the proposed scenario generation tool.
Description:
Measurement of apoptotic markers in tumors can be directly correlated with the cell cycle phase using flow cytometry (FCM). The conventional DNA content analysis requires cell permeabilization to stain nuclei with fluorescent probes such as propidium iodide or use of a costly UV-excitation line for Hoechst 33342 probe. The access to FCM is also still limited to centralized core facilities due to its inherent high costs and complex operation. This work describes development and proof-of-concept validation of a portable and user-friendly microfluidic flow cytometer (μFCM) that can perform multivariate real time analysis on live cells using sampling volumes as small as 10 microliters. The μFCM system employs disposable microfluidic cartridges fabricated using injection molding in poly(methylmethacrylate) transparent thermoplastic. Furthermore, the dedicated and miniaturized electronic hardware interface enables up to six parameter detection using a combination of spatially separated solid-state 473 (10 mW) and 640 nm (20 mW) lasers and x-y stage for rapid laser alignment adjustment. We provide new evidence that a simple 2D flow focusing on a chip is sufficient to measure cellular DNA content in live tumor cells using a far-red DNA probe DRAQ5. The feasibility of using the μFCM system for a dose-response profiling of investigational anti-cancer agents on human hematopoietic cancer cells is also demonstrated. The data show that μFCM can provide a viable novel alternative to conventional FCM for multiparameter detection of caspase activation and dissipation of mitochondrial inner membrane potential (ΔΨm) in relation to DNA content (cell cycle phase) in live tumor cells.
Description:
Measurement of apoptotic markers in tumors can be directly correlated with the cell cycle phase using flow cytometry (FCM). The conventional DNA content analysis requires cell permeabilization to stain nuclei with fluorescent probes such as propidium iodide or use of a costly UV-excitation line for Hoechst 33342 probe. The access to FCM is also still limited to centralized core facilities due to its inherent high costs and complex operation. This work describes development and proof-of-concept validation of a portable and user-friendly microfluidic flow cytometer (
Description:
We investigate the comparative performance of state-owned commercial banks (SOCBs) and private commercial banks (PCBs) of Bangladesh with respect to efficiency and profitability in financing international trade. Taking a ten-year panel data over 2003-2012 of all four SOCBs and four categorised PCBs, we apply the non-parametric approach data envelopment analysis (DEA) to measure and compare efficiency of the banks using output-oriented Malmquist Productivity Indices (MPI). Furthermore, we develop some specialised profitability ratios on trade financing business of the banks to measure profitability. Our results suggest that PCBs are more efficient and profitable compared to SOCBs' although PCBs provide less trade financing than SOCBs'. The study recommends SOCBs to progress technologically for sustaining themselves in the competitive banking sector of Bangladesh. Moreover, we identify the sources of profitability that would explain the banks' strategic position in trade financing business which would motivate more banks to support international traders through trade financing.