Developing new chemical–rheological models and chemical–durability indices of bitumen

Significant correlation among chemical properties, rheological characteristics and durability of bitumen is very important in evaluating and modifying bitumen. However, a number of previous studies found inconsistent correlation. Therefore, a study on developing new chemical-rheological models and chemical-durability indices was carried out. Two bitumen fractionation method, Rostler and Corbett methods were used to extract each chemical fraction of bitumen. A number of experiments were conducted to evaluate the effect of each chemical fraction on bitumen rheology such as the effect of asphaltenes, polar aromatics, naphthene aromatics, nitrogen bases, first acidaffins, second acidaffins and paraffins on elastic modulus (G’), viscous modulus (G”) or fatigue factor (G*sin[δ]), and rutting fator (G*/sin[δ]). Two bitumen from different sources, namely Petronas petroleum bitumen and Buton rock asphalt (BRA) bitumen, were used. New chemical�rheological models were formulated to estimate the bitumen rheology in corporating parameters which are G’, G” or (G*sin[δ]), and (G*/sin[δ]) based on the chemical properties. Furthermore, new chemical durability indices that may indicate the ageing rate of bitumen during short-term and long-term ageing were also formulated. Based on statistical analyses, the models and the indices, which were developed by using chemical properties according to Rostler method were found to be invalid because the real and the predicted rheology were significantly different. While according to Corbett method the models and the indices were valid because the differences is not significant since t-score of the models and the indices were maximum 2.679 and 2.119 or less than t-critical 2.797 and 2.861 respectively). The novelties of this study are the new models and the new indices can be used to predict the bitumen rheology and ageing rate based on the chemical composition. Furthermore, they are very important as guides in modifying a bitumen chemical composition to produce a bitumen mixture with the desired rheology and short-term or long-term ageing rat

Optimizing Service Differentiation Scheme with Sized-based Queue Management in DiffServ Networks

In this paper we introduced Modified Sized-based Queue Management as a dropping scheme that aims to fairly prioritize and allocate more service to VoIP traffic over bulk data like FTP as the former one usually has small packet size with less impact to the network congestion. In the same time, we want to guarantee that this prioritization is fair enough for both traffic types. On the other hand we study the total link delay over the congestive link with the attempt to alleviate this congestion as much as possible at the by function of early congestion notification. Our M-SQM scheme has been evaluated with NS2 experiments to measure the packets received from both and total link-delay for different traffic. The performance evaluation results of M-SQM have been validated and graphically compared with the performance of other three legacy AQMs (RED, RIO, and PI). It is depicted that our M-SQM outperformed these AQMs in providing QoS level of service differentiation.Comment: 10 pages, 9 figures, 1 table, Submitted to Journal of Telecommunication

Job satisfaction of secondary school teachers in Tawau, Sabah

In order for the teachers to function effectively in a school system, it is important that teachers need to seek satisfaction and happiness not only in the intrinsic aspects of teaching job but also in other dimensions related to the teacher work experience in the wider social environment. This paper examines the level and differences in the job satisfaction of 200 Sabah secondary school teachers with respect to the various teachers characteristics identified as gender, service category, job title, tenure and place of origin. Data was collected through survey questionnaire. The finding reveals that secondary school teachers in Tawau, Sabah are generally satisfied with their job. There is significant relationship between job satisfaction and gender, whereby the male teachers are generally more satisfied than female teachers. The graduate teachers are more satisfied than non-graduate teachers. The higher ranking teachers are more satisfied than the ordinary teachers. Also, older teachers are more satisfied than younger teachers. However, there is no significant relationship between places of origin of teachers with job satisfaction. Based on the findings, several recommendations are proposed

Analysis Of Doppler Reactivity Coefficient On The Typical Pwr-1000 Reactor With Mox Fuel

Doppler coefficient is defined as a relation between fuel temperature changes and reactivity changes in the nuclear reactor core. Doppler reactivity coefficient needs to be known because of its relation to the safety of reactor operation. This study is intended to determine the safety level of the  typical PWR-1000 core by calculating the Doppler reactivity coefficient in the core with UO2 and MOX fuels. The  typical PWR-1000 core  is similar to the PWR AP1000 core designed by Westinghouse but without Integrated Fuel Burnable Absorber (IFBA) and Pyrex. Inside the core, there are  UO2 fuel elements with 3.40 % and 4.45 % enrichment, and MOX fuel elements with 0.2 % enrichment. By its own way, the presence of Plutonium in the MOX fuel will contribute to the change in core reactivity. The calculation was conducted using MCNPX code with the ENDF/B- VII nuclear data. The reactivity change was investigated at various temperatures. The calculation results show that the core reactivity coefficient of both UO2 and MOX fuel are negative, so that the reactor is operated safely

Personal characteristics, occupational stress and turnover intentions among school teachers in Negeri Sembilan, Malaysia

Stress is considered as a serious problem in the modern workplace. This paper summarizes occupational stress and turnover intentions experienced by secondary school teachers in the state of Negeri Sembilan, Malaysia. The aim of this study is to investigate the differences across different personal characteristics of the teachers and their level of stress and turnover intention. A total of 150 self-administered questionnaires were collected from secondary schools in the state of Negeri Sembilan. The study reveals that there are significant differences between teachers’ personal characteristics with occupational stress and turnover intention. This study also revealed that there is a positive significant relationship between occupational stress and turnover intention experienced by these teachers. Based on the results, some recommendations are provided