2792 research outputs found
Sort by
Time-resolved radiation dosimetry using a cerium and terbium Co-doped YAG crystal scintillator
No full textTime-resolved radiation dosimetry is an important factor in ensuring dose delivery during radiotherapy is within the prescribed doses for treatment. One method for time-resolved radiation dosimetry is by radioluminescence (RL) measurement technique using doped-silica optical fibre scintillators. The benefits of RL measurement technique include the capability to measure in real-time, high spatial resolution, and greater adaptability. Additionally, time-resolved dosimetry can be achieved by employing suitable scintillators with short rise and decay time. Silica optical fibre scintillators when doped with suitable dopants, provides the temporal resolution required for pulse-by-pulse dosimetry. Yttrium Aluminium Garnet (YAG) crystal optical fiber doped with Cerium and Terbium are discussed as a possible scintillator for time-resolved radiation dosimetry. The Cerium and Terbium co-doped YAG crystal scintillator samples are irradiated under a 6 MV photon beam from a Elekta Synergy® LINAC. The irradiation doses ranged from 100 cGy/min to 600 cGy/min. The measurements were made using an RL system with a gating time of 1μs. Linear RL response to dose of the irradiated scintillator samples was shown with minimal detectable memory, no afterglow or plateau effects. A rise time of 189.3 ns and a decay time of 260 ns were recorded, indicating promising potential for time-resolved radiation dosimetry
Reduction of Radar Cross Section by Adopting Symmetrical Coding Metamaterial Design for Terahertz Frequency Applications
Get PDFThis work focused on the novel and compact 1-bit symmetrical coding-based metamaterial for radar cross section reduction in terahertz frequencies. A couple of coding particles were constructed to impersonate the elements '0' and '1', which have phase differences of 180. All the analytical simulations were performed by adopting Computer Simulation Technology Microwave Studio 2019 software. Moreover, the transmission coefficient of the element '1' was examined as well by adopting similar software and validated by a high-frequency structure simulator. Meanwhile, the frequency range from 0 to 3 THz was set in this work. The phase response properties of each element were examined before constructing various coding metamaterial designs in smaller and bigger lattices. The proposed unit cells exhibit phase responses at 0.84 THz and 1.54 THz, respectively. Meanwhile, the analysis of various coding sequences was carried out and they manifest interesting monostatic and bistatic radar cross section (RCS) reduction performances. The Coding Sequence 2 manifests the best bistatic RCS reduction values in smaller lattices, which reduced from −69.8 dBm2 to −65.5 dBm2 at 1.54 THz. On the other hand, the monostatic RCS values for all lattices have an inclined line until they reach a frequency of 1.0 THz from more than −60 dBm2. However, from the 1.0 THz to 3.0 THz frequency range the RCS values have moderate discrepancies among the horizontal line for each lattice. Furthermore, two parametric studies were performed to examine the RCS reduction behaviour, for instance, multi-layer structures and as well tilt positioning of the proposed coding metamaterial. Overall it indicates that the integration of coding-based metamaterial successfully reduced the RCS values
Absorbed dose calculation for a realistic CT-derived mouse phantom irradiated with a standard Cs-137 cell irradiator using a Monte Carlo method
Get PDFComputed tomography (CT) derived Monte Carlo (MC) phantoms allow dose determination within small animal models that is not feasible with in-vivo dosimetry. The aim of this study was to develop a CT-derived MC phantom generated from a mouse with a xenograft tumour that could then be used to calculate both the dose heterogeneity in the tumour volume and out of field scattered dose for pre-clinical small animal irradiation experiments. A BEAMnrc Monte-Carlo model has been built of our irradiation system that comprises a lead collimator with a 1 cm diameter aperture fitted to a Cs-137 gamma irradiator. The MC model of the irradiation system was validated by comparing the calculated dose results with dosimetric film measurement in a polymethyl methacrylate (PMMA) phantom using a 1D gamma-index analysis. Dose distributions in the MC mouse phantom were calculated and visualized on the CT-image data. Dose volume histograms (DVHs) were generated for the tumour and organs at risk (OARs). The effect of the xenographic tumour volume on the scattered out of field dose was also investigated. The defined gamma index analysis criteria were met, indicating that our MC simulation is a valid model for MC mouse phantom dose calculations. MC dose calculations showed a maximum out of field dose to the mouse of 7% of Dmax. Absorbed dose to the tumour varies in the range 60%-100% of Dmax. DVH analysis demonstrated that tumour received an inhomogeneous dose of 12 Gy-20 Gy (for 20 Gy prescribed dose) while out of field doses to all OARs were minimized (1.29 Gy-1.38 Gy). Variation of the xenographic tumour volume exhibited no significant effect on the out of field scattered
dose to OARs. The CT derived MC mouse model presented here is a useful tool for tumour dose verifications as well as investigating the doses to normal tissue (in out of field) for preclinical radiobiological research
Defect characteristic of oxygen-deficient Ge-doped preform using photoluminescence spectroscopy
No full textStudy has been made of the Photoluminescence properties of Ge-doped silica preforms fabricated using the MCVD process and subsequently subjected to γ-ray irradiation. The photoluminescence emissions pointed to the presence of defects related to oxygen vacancies. Two types of preform were fabricated, obtained using a different flow rate and deposition temperature for each case. Results from the absorption spectra of the samples named as P1 and P2, show a signature absorption peak at 5.1 eV and 6.8 eV, indicative of oxygen-deficient and oxygen-rich defects respectively. Photoluminescence investigation have been carried out before and after the irradiation process with both samples reveal two main peaks at 1.5 eV. The highest intensity at 1.5 eV is known as an interaction between the Non- Bridging Oxygen Hole Centre (NBHOC) with the presence of impurity in the glass matrix. Upon irradiation, weak peak can be observed at 1.8 eV, sample P1 and P2, the PL intensity increases by a factor of 20 × and 50 × , respectively. This peak is associated with the oxygen deficient state in the sample. The peak referring to defect known as Germanium Lone Pair Centre (GLPC) are observed in both samples, peak shown at 3.1 eV, regardless of the Germanium Oxygen Deficient Centre (GODC) content. In regard to this, it can be concluded that this defect is generated independently in all germanium samples and are not correlated with the GODC band observed in the absorption band
Significant shortcomings in vape product labelling
No full textThe current lack of adequate labelling on vape liquids, also known as e-liquid or e-juice, has contributed to an increase in acute nicotine poisoning among children.
An ongoing study by Look Keyun, Dr Ser Hooi Leng, Dr Amar Daud Iskandar Abdullah, and Prof Long Chiau Ming at the School of Medical and Life Sciences, Sunway University, emphasises the urgent requirement for comprehensive labelling regulations
The impact of working capital management on manufacturing firms' profitability - an emerging market perspective
Get PDFPurpose: This study aims to investigate the effects of working capital management on firm profitability of listed manufacturing companies in Malaysia.
Design/methodology/approach: This study uses account payables, inventory turnover, account receivables, cash conversion cycle, firm size, growth, leverage and current ratio as accounting information variables. Secondary data was collected for all variables over a ten-year period, i.e. 2009 to 2018 and was obtained from the annual report published via Bursa Malaysia (Malaysian Stock Exchange) official website. Data was analyzed by using IBM SPSS Statistics Subscription software. Descriptive statistics, correlation analysis and multiple regression analysis were utilized in this study.
Findings: The results revealed that inventory turnover in days, account receivables and firm size have a positive significant relationship with manufacturing firms’ profitability, while account payables and cash conversion cycle have a positive insignificant relationship.
Research limitations/implications: The sample size is too small for any generalization. A mixed method approach in the future could contribute to a holistic finding.
Practical implications: Since these variables contained significant influence on firm profitability, it is recommended that listed manufacturing companies should prepare a complete and timely manner of accounting information based on the regulation context in Malaysia.
Social implications: It provides an empirical evidence on the importance of working capital management amongst the manufacturing concerns in Malaysia and its impact on its business sustainability.
Originality/value: This study contributes to the limited research on working capital management involving manufacturing companies in Malaysia
Time to lock arms against tyranny
No full textI AM still processing the past week of my tour and conference up north.
Aside from the excitement of touring and the networking between fellow artists and academics at conferences, it also gets me “in the zone”, as it is popularly known to creative types and psychologists.
While being in the zone is often associated with being intensely focused and fulfilled in one activity at a time, I also feel you can so for days or even weeks, if the conditions are right
Malaysian musicians in Memphis
No full textMY band and I, Azmyl & the Truly Asia, touched down in Memphis, Tennessee, on Wednesday afternoon (Memphis time).
It was a total of 36 hours of waiting around, connecting flights, and of course, flying.
I chose a flight – we were given several route options – that included a 12-hour layover in Tokyo since, well, why not get a chance to also hang out in a layover city since it’s an option
Selling the drama
No full textMIDWAY through my Azmyl & the Truly Asia US Tour about two weeks back, I made a cheeky post on my personal Facebook page about how a local mainstream press would prefer to cover a story (most probably syndicated) about a Singaporean band that was robbed while they were just at the start of their own US tour over an actual Malaysian band touring the US at the same time.
I say “cheeky” because I noted that I had sent press releases about my upcoming US tour to the mainstream media (by mainstream I mean those publications that still have a print version) but none had taken the bait, let alone shown any interest
On the road again
No full textAFTER about a month back from my band’s US Tour in May, I’m back on the road again for the next 10 days supporting (and helping with the logistics) for Indonesian singer-songwriter Rull Darwis’s Kembali Malaysia Tour 2023.
While my US jaunt with band Azmyl & the Truly Asia might not have been the most extensive – we only covered three cities, playing two back-to-back slots at the Beale Street Music Festival in Memphis, Tennessee – the emotional experience of being there and performing did eventually wear me out when I returned to Malaysia