13474 research outputs found
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Pulse generation in 1.55 μm region using a metal carbide absorber / Muhammad Afiq Ashraf Badsha Sahib
No full textAttributed to their unique properties of compact structure, good flexibility, and low cost, pulsed fiber lasers are excellent light sources for various applications, such as optical communications, biology or medical sciences, micromachining etc. Passive Q-switching and mode-locking techniques are two common methods for generating pulsed lasers, with the key component of a saturable absorber (SA). Titanium silicon carbide (Ti3SiC2) MAX phase and titanium carbide (Ti3C2Tx) MXene are typical transition-metal carbide materials with excellent nonlinear and temperature resilience characteristics, which are emerging as promising saturable absorption materials for pulsed fiber lasers. In this dissertation, Ti3SiC2 and Ti3C2Tx have been used to develop thin film based SAs using a drop casting technique while using a PVA as a host polymer. The fabricated Ti3SiC2 and Ti3C2Tx thin films have a modulation depth of 51 %, 4.8 %, respectively and thus suitable for Q-switching and mode-locking applications. By integrating the prepared Ti3SiC2/PVA thin film into an EDFL cavity, stable Q-switched pulses operating at 1561.8 nm were obtained and the maximum energy of 100.7 nJ was achieved at a repetition rate of 43.5 kHz. The minimum pulse width of the output pulses was 5.6 μs at a pump power of 71.5 mW. The Ti3SiC2 PVA thin film also capable of achieving picosecond pulse when integrated with the extended EDFL ring cavity with a length of 106 m. The proposed mode locked EDFL operated at repetition frequency of 1.88 MHz with a pulse width of 3.03 ps, maximum pulse energy of 6.0 nJ and maximum peak power of 2.0 kW. This study also successfully demonstrated the use of a Ti3C2Tx MXene SA for Q-switching application. The results show that the SA successfully produces Q-switched laser pulses with a pulse width of 3.11 μs and repetition rate of 65.59 kHz at the input pump power of 66.3 mW. At the same pump power, the pulse energy is 125 nJ and the maximum output power is 8.17 mW. It is also found that the Ti3C2Tx PVA SA successfully produces mode-locked pulses within a pump power from 40.2 mW to 87.2 mW. It operates at 1561.2 nm with a repetition rate of 1.89 MHz and pulse width of 154 ns. At 87.2 mW pump power, the average output power, pulse energy and peak power is 11.85 mW, 6.24 nJ, and 40.7 mW, respectively. These results validated the simplicity and feasibility of both SAs for producing a stable Q-switched and mode-locked pulse train
DTPA and EGTA as FE(III) complexing agents for enhancing uv/persulfate advanced oxidation process in aqueous sulfamethazine removal / Ng Kuan Aeng
No full textIn recent years, the pollution of pharmaceuticals in the environment has become a growing concern due to their potentially harmful effects on living organisms. Exposure to these pharmaceutically active contaminants has been linked to diverse health consequences. One of the most important point sources is the wastewater treatment plants which are generally not designed to remove such emerging compounds. In this context, a more promising way to treat pharmaceuticals in wastewater is through advanced oxidation processes (AOPs). Fe(II) is one of the frequently used environmentally friendly catalysts in AOPs. However, Fe(II) can be oxidized easily into inactive Fe(III) hydroxide. Consequently, a strategy to produce water-soluble Fe(III) complexes has been proposed to generate Fe(II) in situ during water treatment. When exposed to UV irradiation, these Fe(III) complexes can release Fe(II), which can catalyze the AOPs. So far, ethylenediamine-N,N-disuccinic acid (EDDS), is one of the well-known ligands used to produce water-soluble Fe(III) complex for AOPs. Incorporating water-soluble Fe(III)-EDDS in UV and sunlight-driven AOPs is an effective method for treating organic pollutants in water. However, EDDS is not cost-efficient for water treatment, and cost may limit its application in large-scale water treatment. Therefore, this study explored the potential of diethylenetriaminepentaacetic acid (DTPA) and ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) as an alternative to EDDS. In this study, Fe(III)-DTPA and Fe(III)-EGTA complexes were prepared and employed as catalysts to enhance the performance of UV-activated persulfate (UV/PS) in sulfamethazine removal. The synthesized Fe(III)-DTPA and Fe(III)-EGTA catalysts were characterized using UV-Vis and FTIR spectroscopy. The screening experiment showed that both Fe(III)-DTPA and Fe(III)-EGTA could significantly improve the percentage removal of sulfamethazine in UV/PS, and their performance was comparable with Fe(III)-EDDS. Based on the results, Fe(III)-DTPA released the highest concentration of Fe(II), followed by Fe(III)-EDDS and Fe(III)-EGTA. The optimum ratio of persulfate concentration to the concentration of Fe(III)-DTPA and Fe(III)-EGTA were found to be 100:1 and 100:2.5, respectively. Under the optimized condition obtained using respond surface methodology, the predicted percentage of sulfamethazine removal was ~99% for Fe(III)-DTPA and Fe(III)-EGTA which is similar to Fe(III)-EDDS catalysts. In the experiment, the mean percentage removal of sulfamethazine in the selected real water samples ranged from 93.6 to 99.6%, which is in range with the predicted value. These results suggested that both Fe(III)-DTPA and Fe(III)-EGTA are cost-efficient alternatives to the well-known Fe(III)-EDDS
Local government capacity for earthquake disaster risk reduction in Malaysia: Case studies in Bentong and Selayang areas / Mateen Zayani Abu Bakar
No full textThe study investigates the status of earthquake disaster risk reduction (DRR) capacity of local governments (LG) in Malaysia, and the factors that influence LG’s capacity to reduce earthquake risk. Currently there is a lack of understanding and systematic study of the capacity of LGs to address earthquake DRR even though LGs in Malaysia are at the forefront to carry out DRR actions at the local level. The research used a qualitative methodology based on a comparative case study design involving two cases of LGs in Malaysia that has the risk in dealing with earthquakes i.e. Bentong Municipal Council and Selayang Municipal Council. The study employs semi-structured interviews and documentation analysis as its data collection methods. A capacity assessment framework (CAF) has been developed based on key capacity categories that have been identified according to the powers and responsibilities of LG as outlined by UNDRR, and components of UNDP capacity building. The findings of this study suggest that inadequacy of LGs in Malaysia to address earthquake DRR measures are mainly due to several capacity issues: insufficient financial backing, lack of knowledge and required expertise, lack of specific unit to tackle DRR issues, and low utilisation of existing resources such as inter-agency networking and regulations. The findings highlighted the need to empower LGs with improved capacities and governance structure. The paper concludes with several recommendations on how LGs can address key capacity gaps identified in this study
Stance in the news reporting of the Arab-Israeli conflict in al-Jazeera and Washington Post / Abdallah Z.A Warshagha
No full textThis study examines the journalistic discursive strategies of stance taking with references to selected voices in the reporting of the Arab-Israeli conflict in two international newspapers: Washington Post (WP) and Al Jazeera (English) (AJE). The study employs a Discourse Analysis framework by integrating the Faircloughian critical discourse perspective (Fairclough, 2010) and Martin and White's (2005) appraisal framework. This conceptual framework informs the analysis of the evaluative and affective dimensions of language, shedding light on underlying values, standpoints, power dynamics and attitudes. A total of 117 news texts were collected from AJE, and 113 news texts were sourced from WP. The findings unveil variabilities and resemblances in the patterns of how (inter)personal emotions (i.e., affect) and judgements (i.e., social sanction and social esteem) are operated and disseminated by AJE and WP. The findings also disclose that manners of engagement i.e., ‘endorse,’ ‘attest’ and ‘acknowledge’ in both newspapers are primarily included in noteworthy methods through which the writers can construct their evaluative language. The writers have subjectively adopted some external voices to potentially meet their own assessments and narrow down the possibility of (including dialogic voices) dissenting their assumptions or challenging their views. Both medias have alternative or multiple voices acknowledge the epistemic sources in a way that can intersubjectively ensures/foregrounds the writers’ attitude and stance. This indicates that both newspapers construct conflict discourse according to certain dimensions where they can elevate their feelings, commitments, attitudes, and judgements concerning selected themes or events. The journalists emphasize establishing hard news based on emotional dimensions i.e., negativity/positivity (over accuracy and objectivity) that can attract the attention of the audience consciously or subconsciously towards certain awareness, beliefs and reactions. AJE and WP constitute newsworthiness based on undertaken socio-cultural practices, ideologies and political implications that may restrict standards of fairness, objectivity and nuanced reporting in conflict discourse, and thus produce ideologically-driven reporting. This can lead to a polarization of public opinion, escalation of the conflict and creation of further divisions between communities. AJE often takes a critical stance towards bias and double standards of the US administration in their approach to the conflict. So, AJE prioritizes the Arab voices that adopt Muslim perspectives or Arab identity and struggle against the Israeli occupation and US prejudice. WP, on the other hand, tends to frame the conflict in terms of US commitments, policies or/and interests in the region which may express why the WP ignores Arab/Palestinian grievances. In this view, language of conflict reporting plays a multi-function task especially in the key issues of a conflict. Journalists and news institutions should acknowledge that their emotional evaluation can affect their reporting and may indirectly consequent in more hostility and collective violence, and thus hinder the prospects of peaceful resolution
Maritime transportation system, economy distribution and seaport network efficiency using fuzzy data envelopment analysis with clustering approach / Dineswary Nadarajan
No full textThe maritime transportation system is investigated by considering the marine traffic flow passing through Westport, Malaysia along the Strait of Malacca as a local case study. Firstly the Westport’s operational scheduling at the yard and land sides are explained and proposed. Next, dispersing and merging functions based on single junction theory that defined the marine traffic flows through the Westport are proposed so that the final macroscopic model describing that local maritime transportation system can be developed for the first time. This study utilizes multiple methods commonly used in assessing the maritime economy distribution where it is found that the import economy has more equality as compared to the export economy. Distance to Competitive Balance (DCB) has firstly applied in the thesis to determine the market concentration of 15 top leading import and export economies of the world. Tobit regression and data envelopment analysis (DEA) are conducted in seaport network efficiency measurement of 133 countries using LSCI as one of the output variable. In order to overcome the uncertainty in the real data, fuzzy DEA (FDEA) is performed by utilizing triangular fuzzy number (TrFN) and trapezoidal fuzzy number (TpFn) in the DEA calculation where the result comparisons have been done. As part of the present study’s original contribution, fuzzy linear regression modelling is also explored to highlight the interval-based regression technique using Possibilistic Linear Regression Least Squares (PLRLS) method. PLRLS determines the interval of minimum and maximum seaport network efficiency scores which gives better estimation overview of the score bounds than the regular regression model. Moreover, the unsupervised k-means, hierarchical and hierarchical k-means (hkmeans) strategies are imposed on the DEA and FDEA datasets of the seaport network efficiency scores. Clustering results between the three strategies are analysed and compared. Here, 133 global seaport countries are fitted into four efficiency clusters newly introduced in this thesis, namely low connectivity (LC), medium connectivity (MC), high connectivity (HC) and very high connectivity (VHC). Finally the hkmeans strategy is proposed as the best strategy for the seaport network efficiency clustering due to better countries composition in the four clusters and due to hkmeans strategy eliminates the drawback issues in the k-means and hierarchical clustering strategies
Kelas pengajian al-Quran secara dalam talian dan bersemuka: Kajian keberkesanan di pusat bimbingan al-Quran dan hafazan al-Baghdadi, Batu Belah Klang / Suhaila Zakaria
No full textSituasi pandemik COVID-19 menjadikan perkembangan dunia pendidikan al-Quran seiring dengan kepelbagaian medium teknologi zaman kini. Sebelum arahan Perintah Kawalan Pergerakan (PKP) dikeluarkan, kebanyakan pusat pengajian al-Quran dilaksanakan secara bersemuka namun pandemik COVID-19 telah menjejaskan kaedah pengajaran dan pembelajaran (PdP) secara bersemuka kepada dalam talian. Oleh itu, kajian ini dilaksanakan bagi mengkaji keberkesanan kelas pengajian al-Quran secara dalam talian dan bersemuka khususnya di Pusat Bimbingan Al-Quran Dan Hafazan Al-Baghdadi, Batu Belah Klang. Seterusnya, metode penyelidikan yang digunakan bagi proses pengumpulan data adalah metode soal selidik dengan mengedarkan borang soal selidik dan ujian bacaan al-Quran serta menyediakan platform Google Form kepada 140 orang responden dalam kalangan pelajar kelas pengajian al-Quran secara dalam talian dan bersemuka di ABB. Kemudian, data-data soal selidik yang diperolehi dikumpulkan dan dianalisis melalui Statistical Package for The Social Sciences (SPSS) versi 26.0 menerusi metode statistik deskriptif yang merangkumi kekerapan, peratusan, min, sisihan piawai dan ujian-t. Dapatan kajian menunjukkan bahawa tidak terdapat perbezaan yang signifikan responden terhadap kaedah PdP dan pelaksanaan kelas pengajian al-Quran secara dalam talian dan bersemuka walaupun terdapat perbezaan yang signifikan responen terhadap kebolehan diri menguasai bacaan al-Quran secara dalam talian dan bersemuka. Hasil kajian ini dapat membantu memberikan gambaran keseluruhan tentang keberkesanan kelas pengajian al-Quran secara dalam talian dan bersemuka yang dilaksanakan di ABB. Akhirnya kajian ini, mengemukakan rumusan dan beberapa cadangan kepada pihak berkaitan supaya kelas pengajian al-Quran dapat dilaksanakan dengan baik, lebih menarik minat pelajar dan mampu melahirkan insan yang memartabatkan pendidikan al-Quran selari dengan panduan al-Quran dan al-Hadith
Complete decompositions of groups and related problems / Wang Kah Lun
No full textAbstract not availabl
Synthesis and biological evaluation of natural quinone chalcones and unnatural analogues / Shelly Gapil Tiamas @ Edwin
No full textApoptosis is a type of programmed cell death that multicellular organisms to regulate tissue homeostasis through the elimination of useless or potentially harmful cells. The key players of apoptosis are caspases, a family of protease whose activation is induced by two major signalling pathways, extrinsic and intrinsic pathways. One of these main apoptotic pathways is regulated by proteins from Bcl-2 family (the intrinsic pathway). Numerous studies in recent years have shown that anti-apoptotic Bcl-2, Bcl-xL and Mcl-1 protein overexpression is involved in the developments of anticancer therapies, leading to the development of new anticancer drugs. The feasibility of disrupting protein-protein interactions between anti- and pro-apoptotic members of the Bcl-2 family proteins, using a small molecule inhibitor has been demonstrated. As a result, Venetoclax was the first to be approved by the FDA in 2016 as an inhibitor of antiapoptotic proteins. In the past decades, tremendous efforts have been made to isolate novel natural products, from microbes, plants, and other living organisms, to assess their anticancer properties and to explore the mechanism of action. It is estimated that between 1981 and 2019, approximately 25% of all newly approved anti-cancer drugs were related to natural products. Screening of plants extract, marine organism or microorganism can provide highly original and functional bioactive molecules that are unlikely obtained by screening synthetic libraries. Thus, our objective is to develop new compounds, derived from plants, that restore apoptosis by targeting proteins of Bcl-2 family. The phytochemical study of Fissistigma latifolium, a Malaysian Annonaceae, led to the isolation of new prenylated chalcones with good affinity for anti-apoptotic proteins. Based on these promising results, a bioinspired total synthesis of the natural compounds isolated in our laboratory was developed in a diastereoselective fashion. Indeed, the cyclohexene core was built by a key Diels-Alder cycloaddition inspired by the biosynthesis of these prenylated chalcones. Then, the two enantiomers of fislatifolic acid and fislatifolione were prepared with a good overall yield and a complete diastereoselective. The evaluation on anti-apoptotic proteins revealed that one enantiomer of (+)-acid fislatifolic is a good inhibitor of Bcl-xL and Bcl-2 proteins on a micromolar range. Surprisingly, the (+)-Weinreb amide intermediate had a promising activity on Mcl-1 and Bcl-2. This led us to elaborate more than 20 amide analogues and evaluation on the anti-apoptotic proteins
Performance evaluation of an in-pipe hydropower system with vertical axis parallel turbine / Aima Mariaty Ahmad
No full textThe performance evaluation of an in-pipe hydropower system with vertical axis parallel turbines prototype in a pipeline has been investigated in order to generate renewable energy. This is because the excess pressure, kinetic energy, and potential energy in flowing water can be used to generate electricity when water is used rather than wasted.
Therefore, this study led to the development of a new design of an in-pipe hydropower prototype called prototype 40 (P40). This prototype is designed by dividing the water flow into two parts, namely the main water channel and the power generation (PG) channel. The PG channel contains a turbine on the side of the pipe. The flow of water in the PG channel is controlled by valves located in the inlet and outlet channels. If service and maintenance work needs to be done, the valves on the PG line can be closed to stop the water flow. This will not affect the water flow on the main channel as the water flow works normally. With the division of this water flow, it will not interfere with the water supply to consumers, which has become the main concern for water suppliers.
An experiment was conducted on a laboratory scale to determine the increased power and efficiency of the prototype. The proposed method includes theoretical design, building a prototype, testing its performance, and analysing the data that was collected.
Based on the findings, the prototype has worked according to the intended design. It allows most of the water to flow while using some of the water pressure for power generation. Therefore, the prototypes should be recommended for real-world implementation towards Technology Readiness Level (TRLs) 6 or higher
Forecasting of PM2.5 in Malaysia using hybrid artificial neural network / Pavithra Chinatamby
No full textParticulate matter with aerodynamic diameter of less than 2.5 microns (PM2.5) is becoming a prominent air pollutant in our atmosphere currently and it causes serious effects to human health upon prolonged exposure. Forecasting the level of PM2.5 earlier can help us to take necessary actions to avoid the exposures but identifying the best prediction model that can handle the big air quality data is a huge challenge. This research is aimed to identify the most reliable prediction model to predict the level of PM2.5 pollutant. The air quality and meteorological data measured at industrial areas from the year 2017 to 2019 were collected from Department of Environment (DOE), Malaysia. The prediction model was build using multi-layered feedforward artificial neural network (FANN) which is a type of artificial neural network (ANN) method. FANN model with six different training algorithms with thirteen different training functions were analysed, compared and top five different training functions were selected. Then, hybrid models were created where FANN model was infused with dimensionally reduced data using Principal Component Analysis (PCA) and Partial Least-Squares (PLS) techniques respectively. The performance of hybrid models such as PCA-FANN and PLS-FANN were compared with the FANN model and other regression models. The regression models analysed in this research are multiple linear regression (MLR), principal component regression (PCR) and partial least squares regression (PLSR). All these models were evaluated based on the highest R2 value and lowest RMSE, MAE and MAPE values obtained. The ascending order according to the modelling performance are PCR< MLR< PLSR< PCA-FANN< PLS-FANN. The PLS-FANN hybrid model with Levenberg Marquardt (trainlm) as training function has topped the ranking by obtaining the highest R2 value of 0.9999 with the lowest RMSE and MAE values for the testing datasets which are 0.001 and 0.0005 respectively. It is the best performed and the most reliable model compared to the other models