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Search Results: 1 - 10 of 1599 matches for " Siti Hajar Othman "
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Effect of Postdeposition Heat Treatment on the Crystallinity, Size, and Photocatalytic Activity of Nanoparticles Produced via Chemical Vapour Deposition
Siti Hajar Othman,Suraya Abdul Rashid,Tinia Idaty Mohd Ghazi,Norhafizah Abdullah
Journal of Nanomaterials , 2010, DOI: 10.1155/2010/512785
Abstract: Titanium dioxide ( ) nanoparticles were produced using chemical vapour deposition (CVD) at different deposition temperatures (300–700°C). All the samples were heat treated at their respective deposition temperatures and at a fixed temperature of 400°C. A scanning electron microscope (SEM), a transmission electron microscope (TEM), and X-ray diffraction (XRD) were used to characterize the nanoparticles in terms of size and crystallinity. The photocatalytic activity was investigated via degradation of methylene blue under UV light. The effects of post deposition heat treatment are discussed in terms of crystallinity, nanoparticle size as well as photocatalytic activity. Crystallinity was found to have a much larger impact on photocatalytic activity compared to nanoparticle size. Samples having a higher degree of crystallinity were more photocatalytically active despite being relatively larger in size. Surprisingly, the photocatalytic activity of the samples reduced when heat treated at temperatures lower than the deposition temperature despite showing an improvement in crystallinity. 1. Introduction The most popular choice of photocatalyst is titanium dioxide (TiO2), and much of the published work on photocatalysis uses this material [1, 2]. TiO2 is a promising photocatalyst due to its easy availability, low cost, photoactivity, high stability, nontoxicity, hydrophilicity, and high refractive index. TiO2 can be used for a variety of purposes including self-cleaning surfaces, antibacterial, air purification, and water treatment applications. Lately there has been an increasing amount of research done to enhance the photocatalytic efficiency of TiO2 for better use of this photocatalyst. One of the ways to improve the photocatalytic efficiency of TiO2 is by heat treatment. Generally, heat treatment is a process to remove a volatile fraction or to cause a phase transition in solid materials. Heat treatment of TiO2 has the advantage of removing organic impurities within the TiO2 and promotes crystallinity for better photocatalytic efficiency [3]. The impurities within TiO2 may arise during the synthesis process. For example, carbon impurities within TiO2 may originate from the organic precursor used during sample preparation. Meanwhile, the crystal structure of TiO2 is known to exist in a stable phase called rutile and two metastable phases called anatase and brookite. Anatase is irreversibly transformed into rutile upon application of heat. Although the rutile phase has a wide variety of applications, primarily in the pigment industry, the anatase phase with
Fe-Doped TiO2 Nanoparticles Produced via MOCVD: Synthesis, Characterization, and Photocatalytic Activity
Siti Hajar Othman,Suraya Abdul Rashid,Tinia Idaty Mohd Ghazi,Norhafizah Abdullah
Journal of Nanomaterials , 2011, DOI: 10.1155/2011/571601
Abstract: Iron (Fe)-doped titanium dioxide (TiO2) nanoparticles were produced via the metallorganic chemical vapour deposition (MOCVD) method at 700∘C. Different amounts of ferrocene as the Fe dopant source (0.001–0.05 g) were introduced inside the reactor together with the titanium precursor in order to synthesize different Fe dopant concentrations of TiO2 nanoparticles. Nitrogen (N2) adsorption results showed that increasing the Fe dopant concentration caused a slight increase in the surface area of the nanoparticles due to the decrease in nanoparticle size. The UV-diffuse reflectance spectra demonstrated an absorption shift in Fe-doped TiO2 nanoparticles to longer wavelengths, thus showing an enhancement of the absorption in the visible spectrum. Bandgap energy values determined from the UV-diffuse reflectance spectra data decreased with an increase in the Fe dopant concentrations. The photocatalytic activity of Fe-doped TiO2 nanoparticles was investigated via degradation of methylene blue under UV and fluorescent light. It was found that Fe doping reduced the photocatalytic activity of the samples. Based on X-ray photoelectron spectroscopy (XPS) results, it is believed that this is due to the unfavourable location of Fe3
Dispersion and Stabilization of Photocatalytic TiO2 Nanoparticles in Aqueous Suspension for Coatings Applications
Siti Hajar Othman,Suraya Abdul Rashid,Tinia Idaty Mohd Ghazi,Norhafizah Abdullah
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/718214
Abstract: To produce titanium dioxide (TiO2) nanoparticle coatings, it is desirable that the nanoparticles are dispersed into a liquid solution and remain stable for a certain period of time. Controlling the dispersion and aggregation of the nanoparticles is crucial to exploit the advantages of the nanometer-sized TiO2 particles. In this work, TiO2 nanoparticles were dispersed and stabilized in aqueous suspensions using two common dispersants which were polyacrylic acid (PAA) and ammonium polymethacrylate (Darvan C). The effect of parameters such as ultrasonication amplitude and type and amount of dispersants on the dispersibility and stability of the TiO2 aqueous suspensions were examined. Rupture followed by erosion was determined to be the main break up mechanisms when ultrasonication was employed. The addition of dispersant was found to produce more dispersed and more stabilized aqueous suspension. 3 wt.% of PAA with average molecular weight () of 2000 g/mol (PAA 2000) was determined to produce the best and most stable dispersion. The suspensions were then coated on quartz glass, whereby the photocatalytic activity of the coatings was studied via the degradation of formaldehyde gas under UV light. The coatings were demonstrated to be photocatalytically active.
The Implementation of The n-term Formula to Improve Student Ability in Determining the Rules of a Numeric Sequence
Akhsanul In’am,Siti Hajar
International Education Studies , 2013, DOI: 10.5539/ies.v6n4p67
Abstract: A good-quality teacher may determines a good-quality learning, thus good-quality students will be the results. In order to have a good-quality learning, a lot of strategies and methods can be adopted. The objective of this research is to improve students’ ability in determining the rules of a numeric sequence and analysing the effectiveness of the implementation of the n-term to determine the rule of a number. A research classroom method administered at the State Islamic Junior High School Malang-Indonesia is adopted. The results show that the implementation of the n term formula may improve the students’ ability in determining the numeric sequence in the State Islamic Junior High School Malang-Indonesia. Some suggestions are offered: a) observation of learning activities should always be made to obtain inputs on the implementation; b) learning innovations should always be made to base on facts obtained through observation; c) the results of this study may be used for reference for further development in learning numeric sequences that enable students to be more interested in studying mathematics.
International Journal of Engineering Science and Technology , 2012,
Abstract: Due to climate change and global warming, the possibility of floods may increase to occur in Malaysia. Water level forecasting are important for the water catchment management in particular for flood warning systems. The aim of this study is to predict water level with input variables monthly rainfall and rate of evaporation takenfrom the same catchment at Dungun River, Terengganu-Malaysia, using ARIMA and Artificial Neural Network (ANN). The process of pre-processing data has been made to the original rainfall data since they contain imperfect characteristics data. Our experiments show that the ANN with cleansing rainfall data gives better performance than ARIMA and ANN without cleansing data.
The Effect of Job Satisfaction and Family Satisfaction on Work- Family Conflict (W-FC) and Family-Work Conflict (F-WC) among Married Female Nurses in Shiraz-Iran
Hajar Namayandeh,Rumaya Juhari,Siti Nor Yaacob
Asian Social Science , 2011, DOI: 10.5539/ass.v7n2p88
Abstract: The present study highlights the significance of job satisfaction as one of the most important work factors on W-FC and F-WC. This paper also examines the effects of one of the essential family factor which is family satisfaction on W-FC and F-WC. The respondents for this study consist of 198 married female nurses working in public hospitals in Shiraz-Iran. The findings revealed that married female nurses with high level of job satisfaction tend to report low level of W-FC. Unlike previous studies, the finding also indicates that there is no significant relationship between the respondents’ job satisfaction and F-WC, which may be explained by the specific cultural context in Iran. This study also established that high level of family satisfaction is associated with low level of W-FC and F-WC. Implications are discussed and recommendations are made regarding future researches in this area.
The Effect of Gender Role Orientation on Work Interference with Family (WIF) and Family Interference with Work (FIW) among Married Female Nurses in Shiraz-Iran
Hajar Namayandeh,Siti Nor Yaacob,Rumaya Juhari
Asian Culture and History , 2010, DOI: 10.5539/ach.v2n2p165
Abstract: The present study highlights the significance of gender role orientation as one of the most important individual factors on WIF and FIW. Furthermore, this paper also examines the effects of some of the essential personal backgrounds such as age, job experience and duration of marriage on WIF and FIW. This study consists of 198 married female nurses in Shiraz-Iran. The findings revealed that married female nurses who adopt more egalitarian gender role attitude are associated with higher WIF. Unlike previous studies, the finding also indicates that respondents who adopt a more egalitarian gender role attitude experienced higher FIW, which may be explained by the specific cultural context in Iran. This study also established that female nurses with older age, more years of job experience, and longer duration of marriage, perceived lower level of WIF and FIW. Implications are discussed and recommendations are made regarding future researches in this area.
Identification of Microorganism from Ragi for Bioethanol Production by API Kit
Noorhisham Tan Kofli,Siti Hajar Mohd Dayaon
Journal of Applied Sciences , 2010,
Abstract: Ragi is one of the fermentation starters in food fermentation. Domestic ragi from Sarawak (for tapé and tuak) and Pahang (tapé), which are made from mixtures of rice floor, spices and water or sugarcane juice, naturally contains filamentous fungi, bacteria and yeasts. This research is aim to identify the microorganisms in the domestic ragi by using API kit after screening and isolating the microbes by selected media (YPD and Sabaroud). From the results, Cryptococcus humicola and Candida glabrata are identified in the Sarawak (tapé) sample, while Cryptococcus humicola, Saccharomyces cerevisiae, Candida glabrata and Rhodotorula glutinis were identified in the Sarawak (tuak) sample and for Pahang (tapé) sample, Cryptococcus humicola, Saccharomyces cerevisiae and Candida guilliermondii was identified by using both API kit (20C AUX and ID 32C).
An Online Malicious Spam Email Detection System Using Resource Allocating Network with Locality Sensitive Hashing  [PDF]
Siti-Hajar-Aminah Ali, Seiichi Ozawa, Junji Nakazato, Tao Ban, Jumpei Shimamura
Journal of Intelligent Learning Systems and Applications (JILSA) , 2015, DOI: 10.4236/jilsa.2015.72005
Abstract: In this paper, we propose a new online system that can quickly detect malicious spam emails and adapt to the changes in the email contents and the Uniform Resource Locator (URL) links leading to malicious websites by updating the system daily. We introduce an autonomous function for a server to generate training examples, in which double-bounce emails are automatically collected and their class labels are given by a crawler-type software to analyze the website maliciousness called SPIKE. In general, since spammers use botnets to spread numerous malicious emails within a short time, such distributed spam emails often have the same or similar contents. Therefore, it is not necessary for all spam emails to be learned. To adapt to new malicious campaigns quickly, only new types of spam emails should be selected for learning and this can be realized by introducing an active learning scheme into a classifier model. For this purpose, we adopt Resource Allocating Network with Locality Sensitive Hashing (RAN-LSH) as a classifier model with a data selection function. In RAN-LSH, the same or similar spam emails that have already been learned are quickly searched for a hash table in Locally Sensitive Hashing (LSH), in which the matched similar emails located in “well-learned” are discarded without being used as training data. To analyze email contents, we adopt the Bag of Words (BoW) approach and generate feature vectors whose attributes are transformed based on the normalized term frequency-inverse document frequency (TF-IDF). We use a data set of double-bounce spam emails collected at National Institute of Information and Communications Technology (NICT) in Japan from March 1st, 2013 until May 10th, 2013 to evaluate the performance of the proposed system. The results confirm that the proposed spam email detection system has capability of detecting with high detection rate.
Sketching Engineering Design in STEM Classroom: A Systematic Review  [PDF]
Siti Hajar Aisyah Zainuddin, Zanaton H. Iksan
Creative Education (CE) , 2019, DOI: 10.4236/ce.2019.1012204
Abstract: Numerous studies in the last two decades have attempted to explain the significant relationship between effects of freehand sketching especially in the initial phase of idea generation in engineering design process approach. However, freehand sketches are not favoured by novice designer while generating design task. This paper aim to map how sketching skills benefit STEM-enriched learning environment and enabling visually communicated ideas to craft novelty solutions. This systematic review analysed nine papers that use sketch as design tool in STEM enriched engineering design activities. The literature is retrieved from established online database such as SCOPUS and EBSCOHOST. Sketch significantly proves as powerful tool in prompting visual ideas, reflect prior knowledge, aid communication and collaborative practise and engage active learning. The infancy of research using matured student sample, different ethnic and social economic background will create interesting research opportunities in multiracial nation.>
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