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Influence of Gamma Radiation on Optical and Dielectric Properties of Dyed Polyvinyl Alcohol Film Dosimeters
Get PDFThe influence of y-rays on the optical absorption and inelastic scattering, dielectric
properties and conductivity of radiation-sensitive dyed polyvinyl alcohol (TBIPVA)
film dosimeters containing chloral hydrate and acid-sensitive Thymol blue dye were
evaluated for possible use as food irradiation indicators. The dyed PVA films of
different concentrations of chloral hydrate were irradiated with the absorbed doses
ranging up to 12 kGy using y-rays from Cobalt-60. The dehydrochlorination of
chloral hydrate and radiolysis of water molecules induced by ionising radiations
accelerated the formation of hydrochloric acid in the polymer matrix, which caused
the change in colour of the dosimeters from yellow to red at the critical doses
depending on the concentration of chloral hydrate. This radiation-induced colour
change was analysed using UV-Vis spectrometer, where the absorption spectra
produced two visible maximal bands, peaking at 445 nm and 554 nm. The dose
response at 445 nm and 554 nm increases and decreases respectively with absorbed
dose. The inelastic Raman scattering spectra of photons corresponding to the Raman
frequency shifts of unirradiated and irradiated films were measured using a
dispersive Raman spectrometer, which provide direct evidence of molecular structure changes induced by ionising radiation and the subsequent chemical effects.
The spectral intensities of Raman shifts at 815, 1984, 2350 and 2560 cm-' bands
correspond to C-CI, C=O, C=C and S-H bonds respectively were studied, which
provide the dose response to the molecular vibration of the dosimeters. From
dielectric and conductivity studies it is found that the dyed polymer dosimeters are
ionic polymer materials. The dielectric constant (E'), dielectric loss (E") and the
electrical conductivity o(o) characteristics of the dosimeters were measured at
different frequencies ranging from 20 Hz to I MHz. The dielectric constant and
dielectric loss increase with absorbed dose at low frequencies and are independent of
dose at higher frequencies for all chloral hydrate concentration. The AC conductivity
(o) increases with absorbed dose and frequency due to the formation of radiationinduced
free radicals, cations and anions in the polymer matrix and due to ejected
electrons in the conduction bands. Thus, the resistance derived from the impedance
measurement, decreases with absorbed dose. Finally, the films were subjected to
stability tests using digital densitometry method at different time intervals during
post-irradiation storage. The results show the change in optical density is minimal
over the period of 70 days for all irradiated samples. This suggests the dosimeters
have optical absorption stability characteristics for use as alternative radiationsensitive
dosimeters in irradiation facilities as long as they are shielded from sunlight
or fluorescent lighting by wrapping with black plastic bag
Properties of poly (vinylidene fluoride)-co-poly (vinylimidazole) solid polymer electrolytes prepared by radiation-induced grafting method for proton exchange membrane fuel cell / Ajis Lepit
Get PDFSolid polymer membranes based on graft copolymerization of 1-Vinylimidazole (VIm) onto polyvinylidene fluoride (PVDF) were synthesized. The graft copolymerization process was carried out under nitrogen atmosphere by a radiationinduced grafting (RiG) in aqueous medium. Ferrous ions were used as a redox initiator system. Radiation effects onto PVDF and VIm were investigated with the aim to develope a highly-stable grafted solid polymer membrane for potential use in proton exchange membrane fuel cells. Polymer membranes consist of PVDF as a polymer host and VIm as a monomer were prepared by solution casting technique. Prior to that, PVDF was exposed to γ-rays ranging from 20 to 100 kGy using RiG method to form free radicals that capable to initiate graft copolymerization of VIm onto PVDF backbone as a side chain.Various grafting conditions such as absorbtion dose, effects of different solvents and addition of Iron (II) sulfate heptahydrate were determined. Results showed that the degree of grafting (DG) was strongly influenced by the type of solvent used to dissolve the VIm. The grafted polyvinylimidazole (PVIm) onto PVDF was estimated using gravimetric analysis. DG of the VIm onto PVDF was also found to be dependent on the absorbtion dose exposed to the samples. The best absorbtion dose where the sufficent grafting occured between polymer based and monomer was at 60 kGy. Concentration of ferrous ions was observed to play a major role to initiate grafted VIm onto PVDF samples namely PVDF-co-PVIm membranes during induction of radiation. Samples were then complexed in acid sulfuric to prepare functional solid polymer electrolyte membranes as well as to enhance their ionic conductivity. The PVDF-co-PVIm solid polymer electrolyte membranes were then characterized by degree of swelling, water uptake, ion exchange capacity and degree of protonation. The PVDF, PVDF-co-PVIm, protonated PVDF-co-PVIm, and silicon dioxide composited PVDF-co-PVIm membranes also were: (a) morphology structurally characterized by Field Emission Scanning Electron Microscopy (FESEM) as well as X-ray Diffraction (XRD) (b) thermally characterized by Differential Scanning Calorimetry (DSC)/Thermogrametric Analysis (TGA) studies for phase transition & thermal stability (c) electrically/electrochemically characterized by Electrochemistry impedance spectrocopy (EIS) and transference number (d) optically characterized by Fourier Transform Infrared spectroscopy (FTIR) studies (e) mechanically characterized by Dynamic Mechanical Analysis (DMA). FTIR analysis demonstrated the occurence of scission in the C-H bond of PVDF main chain when exposed to γ-rays. The C-H bonds were observed to reduce in peak intensities and shift in peak position. FESEM reveals that the surface of the pure PVDF becomes rough containing chain grooves, nanopores and the crystal surface was homogenously covered by PVIm after grafted copolymerization. The storage modulus and loss modulus of PVDF-co-PVIm membrane show high mechanical strength at temperature up to 150 oC. However, the addition of silicon dioxide onto PVDF-co-PVIm reduced the storage modulus and loss modulus of membrane. The protonation of PVDF-coPVIm membrane enhanced ionic conductivity after complexation in sulfuric acid up to 10-4 Scm-1 at room temperature and up to 10-3 Scm-1 at 100oC temperature. The protonated PVDF-co-PVIm could be a good potential candidate as a proton conducting membrane for fuel cells application
Properties of poly (vinylidene fluoride)-co-poly (vinylimidazole) solid polymer electrolytes prepared by radiation-induced grafting method for proton exchange membrane fuel cell / Ajis Lepit
Get PDFSolid polymer membranes based on graft copolymerization of 1-Vinylimidazole (VIm) onto polyvinylidene fluoride (PVDF) were synthesized. The graft copolymerization process was carried out under nitrogen atmosphere by a radiationinduced grafting (RiG) in aqueous medium. Ferrous ions were used as a redox initiator system. Radiation effects onto PVDF and VIm were investigated with the aim to develope a highly-stable grafted solid polymer membrane for potential use in proton exchange membrane fuel cells. Polymer membranes consist of PVDF as a polymer host and VIm as a monomer were prepared by solution casting technique. Prior to that, PVDF was exposed to -rays ranging from 20 to 100 kGy using RiG method to form free radicals that capable to initiate graft copolymerization of VIm onto PVDF backbone as a side chain.Various grafting conditions such as absorbtion dose, effects of different solvents and addition of Iron (II) sulfate heptahydrate were determined. Results showed that the degree of grafting (DG) was strongly influenced by the type of solvent used to dissolve the VIm. The grafted polyvinylimidazole (PVIm) onto PVDF was estimated using gravimetric analysis. DG of the VIm onto PVDF was also found to be dependent on the absorbtion dose exposed to the samples. The best absorbtion dose where the sufficent grafting occured between polymer based and monomer was at 60 kGy. Concentration of ferrous ions was observed to play a major role to initiate grafted VIm onto PVDF samples namely PVDF-co-PVIm membranes during induction of radiation. Samples were then complexed in acid sulfuric to prepare functional solid polymer electrolyte membranes as well as to enhance their ionic conductivity
Senario pilihan raya ke-12 di Sabah: antara calon atau parti / Ansir Salim dan Ajis Lepit
Get PDFKajian ini telah dijalankan semasa pilihan raya ke-12 yang meliputi kawasan Parlimen
P184 - Libaran, P183-Beluran dan lima kawasan Dewan Undangan Negeri (DUN) iaitu
N39 - Sugut, N40 - Labuk, N41 - Gum-Gum, N42 - Sungai Sibuga dan N43 - Sekong di
Sandakan, Sabah yang memfokuskan kawasan yang ditandingi parti atau calon UMNO.
Kajian bertujuan untuk melihat dan menganalisis senario piliharanya di kawasan tumpuan
kajian yang bermula dari penamaan calon hingga ke hari keputusan pilihan raya
diumumkan pada malam 8 Mac 2008. Ini termasuklah melihat dan menganalisis tren
pengundi, kepimpinan dan isu-isu yang dibangkitkan oleh masyarakat kawasan berkenaan.
Kaedah yang dijalankan dalam kajian ini ialah tinjauan langsung di kawasan terlibat,
temuramah dengan rakyat dan bakal calon dan analisis media massa. Hasil kajian
mendapati pengundi Cina mengundi atas noma wakilnya dan bukan parti yang diwakili,
secara umumnya pengundi masyarakat Islam menolak calon pemerintah
walaubagaimanpunfaktorpolitik wang mampu merubah keputusan yang memihak kepada
calon pemerintah. Manakala majoriti kecil pengundi masyarakat bukan Islam tidak
mempengaruhi atau tidak memberi kesan hasil keputusan pilihan raya. Hasil pilihan
rayajelas wujudnya pertentangan undi antara menolak calon atau parti. Calon-calon
yang tidak disenangi oleh pengundi majoriti masyarakat setempat berdasarkan masalahmasalah
calon seperti kelemahan, kredilbiliti dan karisma calon yang bertanding. Majoriti
pengundi masih lagi selesa dan selamat dibawah parti pemerintah yang sedia ada dan
tidak berani untuk menukar kerajaan. Kesimpulannya prestasi parti pemerintah dan politik
wang mampu mengekalkan sokongan kepada rakya
Selection of the best Pre-Diploma science student using a fuzzy approach / Mazalan Sarahintu, Zamali Tarmudi and Ajis Lepit
Get PDFEvaluating students' academic performance using appropriate techniques is crucial to ensure a fair assessment of their qualities. This paper proposes a fuzzy logic method for specifically selecting the best pre-diploma science student in Universiti Teknologi MARA (UiTM) Cawangan Sabah. The method considers not only academic achievement, but also soft skills and other abilities in the evaluation process. A case study, was conducted based on the results of the students of the November 2013 - March 2014 intake. It was found that our proposed approach had the unique advantage of clearly distinguishing every single score obtained by the students. Also. the results showed that the approach is highly beneficial for problem-solving under uncertainty data sets environment
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Evaluation of pre-diploma students using fuzzy approach / Zamali Tarmudi, Mazalan Sarahintu and Ajis Lepit
Get PDFThis paper discusses the comprehensive evaluation of Pre-Diploma (Science) students in recent semesters using fuzzy approach. It focuses on how we can select the best students based on both academic performance and soft skills for university recognition purposes. The approach utilizes membership functions to derive the membership values for the entire course which registered for first semester. Then the approach employs the intersection of fuzzy goals and constraints concept to identify the best students among the best in terms of academic performance, soft skills as well as their attitude. A case study was conducted based on session intake of November 2013 - March 2014. It was found that our proposed approach has unique advantage in the sense that it can distinguish clearly for every single score marks obtained by the students. Also, the results show that the approach is highly beneficial for problem solving under uncertainty data sets environment
Fabrication of MSM UV photodetector based on ZnO films synthesized by RF magnetron sputtering / Halim Ahmad, Mat Johar Abdullah and Ajis Lepit
Get PDFC-axis oriented ZnO films were deposited on SiO2/Si substrates through RF magnetron sputtering, MSM UV photodetector using Ag/ZnO/Ag configuration were fabricated from the as prepared film while the heat treated film was used to fabricate MSM Schottky barrier UV photodetector using Al/ZnO/Ag configuration. The crystalline and optical quality of the film had improved after the heat treatment. It was found that the Schottky barrier heights as prepared and heat treated using Ag/ZnO interface was around 0.74 and 0.76 eV respectively. The leakage current was reduced from 18.6 mA to 0.6 μA at 5V after post deposition annealing when compared with that of as deposited ZnO.The Ag/ZnO/Ag configuration showed a faster decay time of 212 s
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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