5975 research outputs found
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Item Response Theory: An Introduction to Latent Trait Models to Test and Item Development
No full textTesting in educational system perform a number of functions, the results from a test can be used to make a number of decisions in education. It is therefore well accepted in the education literature that, testing is an important element of education. To effectively utilize the tests in educational policies and quality assurance its validity and reliability estimates are necessary. There are two generally acceptable frameworks used in evaluating the quality of test in educational and psychological measurements, these are; Classical Test Theory (CTT) and Item Response Theory (IRT). The estimates of test items validity and reliability depend on a particular measurement model used. It is vital for a test developer to be familiar with the different test development and item analysis methods in order to facilitate the development of a new test. The CTT is a traditional approach which was widely criticise in the measurement community for its shortcomings such as sample dependency of coefficient measures and estimates of measurement error. However, the IRT is a modern approach which provides solutions to most of the CTT’s identified shortcomings. This paper therefore, provides a comprehensive overview of the IRT and its procedures as applied to test item development and analysis. The paper concludes with some suggestions for test developers and test specialists at all levels to adopt IRT for its identified crucial theoretical and empirical gains over CTT. IRT based parameter estimates should be superior and reliable than CTT based parameter estimates. With these features, IRT can help resolve the problems associated with test design based on CTT
Mediation Role of Locus of Control on the Relationship of Learned-helplessness and Academic Procrastination among College Students in Penang, Malaysia.
No full textThis study aims to study the mediation role of locus of control on the impact of learned helplessness on students’ academic procrastination. Studies reported that more than 70% university students procrastinate, and one of the causes is the perception that one is vulnerable or helpless in finishing the procrastinate tasks. It was hypothesized that internal locus of control iLOC can reduce the effect if the learned helplessness (LH) on academic procrastination. Data was collected from 60 university students by utilizing instruments such as Duttweiller’s Internal Control Scale, Pure Procrastination Scale (adapted for academic setting) and Learned Helplessness Scale. Multiple regression with Process add-on showed that full mediation occurred; the prediction of LH on procrastination became insignificant when iLOC is controlled. In other words, when students believe that they are in control of their events, the less likely they will procrastinate doing their tasks due to helpless feeling
Student Engagement and Assessment Modes: A Study
No full textThe aim of this project is to attempt a factorial analysis of the congruence amongst three layers of assessments of Oral Presentation: Expert, Self, and Peer. Participants included graduate and undergraduate students of Asian background studying Research Writing at a technological university. The research instrument consisted of a set of assessment checklists with weighted and specified criteria for Expert, Self and Peer assessment of research presentations. Broader criteria were based on the following four factors: Use of spoken media, Use of visuals, Interrelationships, and Communicative Effect. Participants received training and were involved in a practice session on self and peer assessment before engaging in the assessment tasks. While the pilot study is unable to conclusively establish congruence among the modes of assessment, it is expected that results from a wider database would indicate the nature of well-defined assessment criteria and the ways they can be effectively communicated to assessors. The present study suggests that the differences in ratings given by peers and experts are not due to a lack of capability on the part of students, but due to lack of orientation and training. It is necessary to evolve criteria that are well-documented to enable students to evaluate their own performance as well as the performance of their peers as effectively as done by experts
Performances Concatenated LDPC based STBC-OFDM System and MRC Receivers
No full textThis paper presents the bit error rate performance of the low density parity check (LDPC) with the concatenation of convolutional channel coding based orthogonal frequency-division-multiplexing (OFDM) using space time block coded (STBC). The OFDM wireless communication system incorporates 3/4-rated convolutional encoder under various digital modulations (BPSK, QPSK and QAM) over an additative white gaussian noise (AWGN) and fading (Raleigh and Rician) channels. At the receiving section of the simulated system, Maximum Ratio combining (MRC) channel equalization technique has been implemented to extract transmitted symbols without enhancing noise power
Hysteresis-based Voltage and Current Control Techniques for Grid Connected Solar Photovoltaic Systems: Comparative Study
No full textSolar PV system development and integration with existing grid is very fast in recent years all over the world, as they require limited maintenance, pollution free and simple structure. When observing the factors affecting the performance of the grid connected solar photovoltaic system, the inverter output voltage with harmonics add with the harmonics generated due to the non-linear loads, retain a bigger challenge to maintain power quality in the grid. To maintain grid power quality, better inverter control technique should be developed. This paper presents the two control techniques for grid-tied inverters. This study developed the hysteresis controller for the inverter. Hysteresis controller used in this work two way (i) Voltage control mode (ii) Current control mode. Matlab/Simulink model is developed for the proposed system. Further the study presents the comparative evaluation of the performance of both control techniques based on the percentage of total harmonic distortion (THD) with the limits specified by the standards such as IEEE 1547 and IEC 61727 and IEEE Std 519-2014
CSPCR: Cloud Security, Privacy and Compliance Readiness - A Trustworthy Framework
No full textThe privacy, handling, management and security of information in a cloud environment are complex and tedious tasks to achieve. With minimum investment and reduced cost of operations an organization can avail and apply the benefits of cloud computing into its business. This computing paradigm is based upon a pay as per your usage model. Moreover, security, privacy, compliance, risk management and service level agreement are critical issues in cloud computing environment. In fact, there is dire need of a model which can tackle and handle all the security and privacy issues. Therefore, we suggest a CSPCR model for evaluating the preparation of an organization to handle or to counter the threats, hazards in cloud computing environment. CSPCR discusses rules and regulations which are considered as pre-requisites in migrating or shifting to cloud computing services
Maximum Power Point Tracking of Wind Turbine Conversion Chain Variable Speed Based on DFIG
No full textWind energy has many advantages, it does not pollute and it is an inexhaustible source. However, the cost of this energy is still too high to compete with traditional fossil sources. The yield of a wind turbine depends on three parameters: the power of the wind, the turbine power curve and the ability of the generator to respond to fluctuations in the wind. This article presented the MPPT of a wind turbine system equipped with an asynchronous generator has dual power under MatlabSimulink program, in the first time we simulated all the conversion chain with complete model of DFIG and vector control in second stepthen applied the extracted maximum power MPPT strategists, this command is effective and has several advantages it offered to kept the maximum power delivered to network despite all the parameter is change
Implementation of NN controlled DVR for Enhancing The Power Quality By Mitigating Harmonics
No full textNow a days there is a widespread use of semiconductor devices, which are mostly implemented as the power switches for converters and inverters. These converters and inverters play a vital role in power systems both in transmission and distribution systems. This provides a way for the introduction of harmonics in the power system which leads to poor power quality. To overcome this many solutions have been suggested by the research community but each solution holds its own merits and demerits. Of all these suggested solutions, the Dynamic Voltage Restorer is one of the most cost effective systems for various power quality issues. In this paper the DVR is considered for enhancing the power quality by reducing the harmonics generated because of sensitive loads. Here the power quality is enhanced by controlling the DVR using Neural Network Controller which is trained by Levenberg Marquardt algorithm. In this paper the THD analysis of the voltage quantity is analysed by introducing an unbalanced three phase fault in the system. The simulation is done by using MATLAB/Simulink. From the results, it is verified that the harmonics are reduced by the NN controlled DVR unit. Also the simulation results are verified with the hardware results.
Multi-Objective Evolutionary Programming for Static VAR Compensator (SVC) in Power System Considering Contingencies (N-m)
No full textStatic VAR Compensators (SVCs) is a Flexible Alternating Current Transmission System (FACTS) device that can control the power flow in transmission lines by injecting capacitive or inductive current components at the midpoint of interconnection line or in load areas. This device is capable of minimizing the overall system losses and concurrently improves the voltage stability. A line index, namely SVSI becomes indicator for the placement of SVC and the parameters of SVCs are tuned by using the multi-objective evolutionary programming technique, effectively able to control the power. The algorithm was tested on IEEE-30 Bus Reliability Test System (RTS). Comparative studies were conducted based on the performance of SVC in terms of their location and sizing for installations in power system
Simulation Models of Energy Cables in SPICE
No full textAccurate modeling of cables is important to study the behavior of high frequency disturbances in power converter systems. This paper reviews and compares two popular methodologies to model energy cables – an improved per unit length parameters based model and a Laplace SPICE element based model. The two models presented take into account the frequency dependence of the parameters of the cable. A ladder network is used for this purpose in the per unit length based model. The Laplace SPICE element model is generated from from a rational function approximation for the admittance parameters that are frequency dependant. The rational function approximation is obtained using a well known vector fitting algorithm. The time and frequency domain solutions of a two wire energy cable, obtained from the two models, agree well