Performance and wake analysis of rotors in axial flight using computational fluid dynamics

Flow field around rotors in axial flight is known to be complex especially in steep descent where the rotor is operating inside its own wake. It is often reported that, in this flight condition, the rotor is susceptible to severe wake interactions causing unsteady blade load, severe vibration, loss of performance, as well as poor control and handling. So far, there is little data from experimental and numerical analysis available for rotors in axial flight. In this paper, the steady Reynolds-Averaged Navier-Stokes Computational Fluid Dynamics solver Helicopter Multi-Block was used to predict the performance of rotors in axial flight. The main objective of this study was to improve the basic knowledge about the subject and to validate the flow solver used. The results obtained are presented in the form of surface pressure, rotor performance parameters, and vortex wake trajectories. The detailed velocity field of the tip vortex for a rotor in hover was also investigated, and a strong self-similarity of the swirl velocity profile was found. The predicted results obtained when compared with available experimental data showed a reasonably agreement for hover and descent rate, suggesting unsteady solution for rotors in vortex-ring state

The Design And Simulation Of Flow Mode Electrorheological Damper

Electrorheological (ER) Damper Is A Damper That Utilizes Electrorheological Fluid As The Working Fluid. By Changing The Strength Of Applied Electric Field To The Fluid, The Flow Resistance Of The Fluid Changes And Hence The Damping Characteristic Could Be Adjusted. This Paper Provides Theoretical Formulation To Calculate The Damping Constant Of Semi-Active Flow Mode ER Damper. The Formula Is Developed By Analyzing Fluid Velocity Profile That Flows In Electrode Gap. From The Simulation, It Shows That Electric Field Strength Gives Severe Effect To The Damping Level Of The Damper. Without Applying Electric Field, A Reduction On The Gap Of Electrode From 3 To 1 Mm Will Increase The Damping Constant Value By A Factor Of Only 27, While With A 3 Kvmm–1 Electric Field Being Applied, The Increase Is By A Factor Of 595

Earnings management and corporate tax planning and their impacts on firm value / Nik Mohd Norfadzilah Nik Mohd Rashid

The research aimed to study the impacts of Earnings Management (EM) and Corporate Tax Planing (TP) on the changes of the Firm Value (FV) among public listed companies in Malaysia. Financial determinants of EM and Corporate TP which were both creative accounting strategies that formed the predictor variables, had first been identified. These were obtained from secondary data of 357 selected public listed companies from 2001 until 2012 retrieved from Thompson One Datastream database. Diagnostic analyses were performed to test normality and serial correlation of the data and obtain descriptive statistics including the analysis of variance for both EM and TP among the companies in the selected industries. Hence, in this study the measurement used for EM was related to the Accrual Earnings Management (AEM) and Real Earnings Management (REM) while the measurement for TP referred to accrual-based Effective Tax Rates (ETR1) and cash-based Effective Tax Rate (ETR2) level of the companies. Balance panel data of the selected companies within 12-year period produced 4,284 firm-year observation for further analyses determined by specification methods comprising Pooled Ordinary Least Squares, Fixed Effect and Random Effect regression analyses. The investigation were continued for the first phase of the study which related to the investigation of the financial determinants towards EM and Corporate TP among the companies. Results from the first phase initially disclosed that there was a significant relationship that existed between the selected financial transactions towards the EM and TP in the business transaction activities

MKAS : A modular knockout ATM switch

Simple Knockout Switch [11 exhibits excellent traffic performance (cell loss, cell delay and maximum throughput etc.) under uniform as well as non-uniform traffic patterns (2-6). But being a single stage, its hardware complexity is directly proportional to the switch size N. This problem may bind its implementation for largescale requirements because of the technological and physical constraints of packaging (e. g. chip or board size). Here, we are proposing a two-stage Modular Knockout ATM Switch architecture, which is extendable to large-scale switch sizes without sacrificing any significant decrease in switch performance. The concept of Generalised Knockout Principle in conjunction with Simple Knockout Principle has been utilised to filter, route and resolve the output contention problems in distributed fashion. Using distributed address filtration and shared concentration techniques simplifies the switch functions and reduces the switch complexity to large extent in terms of filters, switching elements and input output interconnection wires

Optimal load shedding for microgrids with unlimited DGs

Recent years, increasing trends on electrical supply demand, make us to search for the new alternative in supplying the electrical power. A study in micro grid system with embedded Distribution Generations (DGs) to the system is rapidly increasing. Micro grid system basically is design either operate in islanding mode or interconnect with the main grid system. In any condition, the system must have reliable power supply and operating at low transmission power loss. During the emergency state such as outages of power due to electrical or mechanical faults in the system, it is important for the system to shed any load in order to maintain the system stability and security. In order to reduce the transmission loss, it is very important to calculate best size of the DGs as well as to find the best positions in locating the DG itself.. Analytical Hierarchy Process (AHP) has been applied to find and calculate the load shedding priorities based on decision alternatives which have been made. The main objective of this project is to optimize the load shedding in the micro grid system with unlimited DG’s by applied optimization technique Gravitational Search Algorithm (GSA). The technique is used to optimize the placement and sizing of DGs, as well as to optimal the load shedding. Several load shedding schemes have been proposed and studied in this project such as load shedding with fixed priority index, without priority index and with dynamic priority index. The proposed technique was tested on the IEEE 69 Test Bus Distribution system

Design, Rapid Prototyping, and Testing of the Darrieus Wind Turbine

This report contains design, rapid prototyping and testing of the Darrieus wind turbine. The Darrieus wind turbine rotates in the same sense regardless of the direction of the air stream. In order to maximize its efficiency, several variations of this turbine design will be required for testing and evaluation. One of the objectives of this project is to test parameters that will affect the performance of the Darrieus wind turbine. Two parameters that will evaluated for evaluation is number of blades of the turbine and diameter of the turbine. Also for each turbine, the minimum wind speed required to start the rotation and the speed it can rotate with varying wind speed will be determined. Three prototypes are created for testing purposes. Results showed that the increase the diameter of the turbine will reduce the rotation of the turbine. In addition higher number of blades will increase the rotation of the wind turbine

The performance of students in university subjects at UTM’s

TITAS has been introduced in the university curriculum as one of the general subjects/courses that all students are required to take. At UTM’s franchised centres, it has been discovered that many students have obtained very poor grades for this subject. The reasons for the poor performance had to be determined and this study attempted to discover the main reasons why students performed badly in the subject. The study found that among others it was a problem of attitudes both on the part of the teacher as well as the student besides communication problems between UTM and its franchised centres that contributed to the problem

Sulphur Dioxide: Comparative Study of Three Analytical Methods and Determination in Malaysian Foods

The study was conducted in four phases. In the first phase, three methods of analysis were studied on eight different types of foods. The methods were (i) the Shipton's modification of the Monier-Williams' method or the Shipton method, (ii) the modified Rankine method, and (iii) the Iodine distillation method. The eight types of foods were meehoon, orange cordial, mashed potato (granule), pickled nutmeg, strawberry jam, mayonnaise, orange juice and wine. Comparative studies showed that the Iodine distillation method gave the highest mean values followed by the Shipton and modified Rankine methods, and this was true for seven out of the eight types of food studied. Recovery studies showed that the Shipton method was reliable for foods with sulphur dioxide content of more than 50 ppm, namely meehoon, cordial, mashed potato (granule) and pickled nutmeg. The second phase focussed on the study of methods for foods with less than 50 ppm, that is strawberry jam, mayonnaise, orange juice and wine. The methods were (i) the Shipton method, and (ii) the Wedzicha method. Comparative studies showed that results obtained by the Shipton method were higher than those obtained by the Wedzicha method, and this was true for all the foods studied. From the recovery studies, it was found that the Wedzicha method was the method of choice for foods with less than 50 ppm of sulphur dioxide although it is also reliable for foods which contain more than 50 ppm sulphur dioxide. The correlation between the Shipton and Wedzicha methods were studied in the third phase ofthe study. It was observed that the methods showed good correlation for foods with sulphur dioxide content of more than 200 ppm, moderate correlation for food with sulphur dioxide content of between 50 - 200 ppm and bad correlation for food with sulphur content of less than 50 ppm. The prevalence of sulphur dioxide in eighty-six types of foods were studied in the last phase. It was found that 30.23% ofthe foods contravene the Food Regulations 1985 in the sulphur dioxide content. The estimate of the Daily Dietary Intake (DDI) was calculated and it was much lower than the Acceptable Daily Intake (ADI) for sulphur dioxide

Heavy Metals in Surface Soils of Kota Bharu Landfill Site and its Relations to The Growth and Macronutrients Uptake of Acacia Mangium

A study of heavy metals distribution in landfill surface soil, surface water and landfill leachate and its relations to Acacia mangium growth and macronutrients uptake was conducted in a landfill in Kota Bharu, Kelantan. Five heavy metals, particularly Fe, Cr, Zn, Cu and Cd was analyzed in this study and results shows elevated heavy metals concentration level compared to the control surface soil. The distribution of the heavy metals in the surface soil from the landfill varies throughout the study site. The concentration decreased prominently in the river sediment adjacent to the landfill. The concentration of Fe was the highest that ranged between 1993.4 – 2404.6μg/g, followed by Zn, 18.08 – 54.10 μg/g; Cr, 2.67 – 62.10 μg/g; Cu, 5.21 – 18.60 μg/g and Cd, 0.70 – 1.52 μg/g of soil dry weight. However, compared to DOE soil threshold concentration, this landfill was only slightly contaminated with Cd that exceeds the threshold with an average of 0.94 μg/g. Heavy metals speciation by sequential extraction of landfill surface ii soil shows that the surface soil was not yet contaminated with heavy metals as the anthropogenic fraction is less than 30% of the total concentration of heavy metals of the surface soil and mainly attached to the organic matter. Concentration of heavy metals in landfill leachate shows higher level than the surface water. However, the levels of heavy metals in both water samples were still considered as low compared to other landfills due to dilution by rain and river nearby. Cu concentrations in water samples were generally higher than other heavy metals that ranged between 0.03 – 6.14 mg/L whereas Cd and Cr were generally very low, below detectable limits. The level of accumulation in A. mangium leaves was highest for Fe that ranged between 139.5 – 537.6 μg/g, followed by Cr 45.54 – 357.3 μg/g, Zn 29.36 - 57.23μg/g, Cu 6.88 - 15.61μg/g and Cd 1.63 - 3.48μg/g. However, Fe shows no significant difference in the level of accumulation between landfill and control plants. Heavy metals accumulation level in A. mangium leaves have very wide range dependent on the leaves sampled. However, from the soil-plant concentration ratio, heavy metals uptakes by A. mangium in landfill site were found higher than control plants especially for Cr and Cd. Generally the concentration of heavy metals was found so much higher in the plants tissues rather than in the landfill surface soil and landfill leachate or surface water. Relation between heavy metals accumulation in A. mangium and growth and macronutrient uptake was not demonstrated this study as the N, P, K level in control and landfill site do not show any significant correlation with heavy metals concentrations. Uptakes of N and P in landfill A. mangium were found higher than control but on the contrary, K was found higher iii in control plants. Growth of A.mangium in landfill was slightly different with control plants as there are tendency of A. mangium in landfill site to produce many branches, leaves and incisive increase of trunk diameter whereas, control plants tends to gained heights very quick. This is due to different soil type and climatic factors influence rather than heavy metals level in the plants’ tissue. This study also proposed A. mangium is tolerant to Cd and Cr however the use of A. mangium as general bioindicator for heavy metals was not probable as only Cd and Cr was highly accumulated. A. mangium can be used for phytoremediation of low contaminated soil as shown in his study. Furthermore, landfill site is this study found it suitable to be used as A. mangium culture site

The relationship between stress, workload, and time management towards students performance

Worklife balance is very important for individuals to ensure a sense of balance of achievement and pleasure in their life. In the context of working while studying, there are certain important aspects that need to be taken seriously so that both can be done well. This study was conducted to determine the relationship of worklife balance (i.e stress, workload, and time management) among part time postgraduate student performance in Universiti Utara Malaysia (UUM). A survey data from 155 postgraduate part time students of Othman Yeop Abdullah (OYA) Graduate School of Business were used in order to achieve the objective of this study. The regression results showed that the stress and time management is significantly and positively related to the student performance. It also showed that workload have negative relationships on student performance. The implications of the theory, practical, academic and regulations of the findings in this study were discussed in detail. Therefore, this study concluded that the worklife balance has become a vital link to the performance of part-time working students