Evolution of Surface Acoustic Waves in an Optical Microfiber

This paper reports stimulated Brillouin scattering characterization in a tapered optical fiber using full-vectorial finite element-based numerical methods. Numerical simulations of both optical and acoustic waves’ propagation through a tapered microfiber have been carried out. Acoustic modes over a range of wavenumber for different fiber core radii are obtained and nature of their both dominant and non-dominant displacement vector profiles are studied and discussed. Acoustic mode profiles show confinement of the acoustic wave predominantly at the core cladding interface. In addition, the acoustooptical overlap factors at different fiber radii are also presented

Measurement of a wide-range of X-ray doses using specialty doped silica fibres

Using six types of tailor-made doped optical fibres, we carry out thermoluminescent (TL) studies of X-rays, investigating the TL yield for doses from 20 mGy through to 50 Gy. Dosimetric parameters were investigated for nominal 8 wt% Ge doped fibres that in two cases were co-doped, using B in one case and Br in the other. A comparative measurement of surface analysis has also been made for non-annealed and annealed capillary fibres, use being made of X-ray Photoelectron Spectroscopy (XPS) analysis. Comparison was made with the conventional TL phosphor LiF in the form of the proprietary product TLD-100, including dose response and glow curves investigated for X-rays generated at 60 kVp over a dose range from 2 cGy to 50 Gy. The energy response of the fibres was also performed for X-rays generated at peak accelerating potentials of 80 kVp, 140 kVp, 250 kVp and 6 MV photons for an absorbed dose of 2 Gy. Present results show the samples to be suitable for use as TL dosimeters, with good linearity of response and a simple glow curve (simple trap) distribution. It has been established that the TL performance of an irradiated fibre is not only influenced by radiation parameters such as energy, dose-rate and total dose but also the type of fibre

Fluorescence dynamics of graphene quantum dots for detecting lard substance

Graphene Quantum Dots (GQD) is used for detecting lard substance. It is discovered that the fluorescence for a GQD with a size approximately 5nm in size will have a peak at 675nm. Introducing lard substance to the GQD will induce a broad fluorescence spectrum at the range of 415 till 715nm. Higher fluorescence is observed from 760nm till 860nm showing the dynamics fluorescence changes when lard is applied. These fluorescence dynamics when lard is introduced is due to the functional groups of Carbon-Carbon interaction between GQD and lard

Dosimetric characteristics of fabricated Ge-doped silica optical fibre for small-field dosimetry

We study 3 mm long germanium-doped (Ge-doped) silica fibres for small-field dosimetry, seeking to overcome spatial resolution and charged-particle disequilibrium issues, also any associated dose deviation from that of computerised treatment plan dose delivery. Investigation has been made of the thermoluminescent (TL) dependency of locally fabricated 6 mol% Ge-doped preforms subsequently made into cylindrical (CF) and flat fibres (FF), also commercial Ge-doped fibres (COMM), the dopant and mechanical strain created in fibres production providing the trapping levels generating the TL yield. A Perspex phantom was designed for study of angular dependency, fibres being positioned at angles ranging from 0° to 90° while a scanning electron microscopy with energy dispersive X-ray (SEM/EDX) analysis study allowed evaluation of relative Ge content of the three TL types. Flat Fibre dose repeatability was found to be similar to that for the commercial fibre (in the range 2%–6%), improving appreciably upon that for the cylindrical fibre (<14%), also exhibiting highly linear response up to 80 Gy (R2 ≥ 99%) and near angular independence (<3%). The notable signal fading of the FF (25%) would need to be carefully accounted for in applications. This work provides support for the viability of 6 mol% Ge-doped preforms subsequently fabricated into Flat Fibres for use in small-field dosimetry, offering a suitably dose-sensitive fibre arrangement

The barriers and causes of building information modelling usage for interior design industry

Building Information Modeling (BIM) has since developed alongside the improvement in the construction industry, purposely to simulate the design, management, construction and documentation. It facilitates and monitors the construction through visualization and emphasizes on various inputs to virtually design and construct a building using specific software. This study aims to identify and elaborate barriers of BIM usage in interior design industry in Malaysia. This study is initiated with a pilot survey utilising sixteen respondents that has been randomly chosen. Respondents are attached with interior design firms that are registered by Lembaga Arkitek Malaysia (LAM). The research findings are expected to provide significant information to encourage BIM adoption among interior design firms

Process intensification of 2-ethylhexyl caprylate/caprate synthesis via a pulsed loop reactor: Multi-objective optimization

This work proposes the optimization of 2-ethylhexyl (2-EH) caprylate/caprate synthesis in a pulsed loop reactor, and the energy efficiency of the reactor was assessed. 2-EH caprylate/caprate can be used as a biodegradable base fluid. Only 0.4 wt% catalyst concentration was used in the reaction. The face-centred central composite design (FCCD) experiment coupled response surface methodology (RSM) has been implemented to screen independent parameters. The optimization process showed that vacuum pressure was the most influential factor followed by oscillation speed, temperature and time. The maximum conversion of 98 % and yield of 89 % were achieved under optimal conditions of 78 °C, 10 mbar, 20 min and 155 rpm. Meanwhile, energy balance calculation indicated that the usage of low vacuum pressure not only significantly reduced the total heat duty from 1381 kJ (1 atm) to 823 kJ (10 mbar) but also alleviated the reaction temperature from 172 °C (1 atm) to 78 °C (10 mbar). The calculation also demonstrated that the reflux-stirred tank reactor produced a lower conversion and yield of ester yet 6 kJ higher total heat duty compared to the pulsed loop reactor, indicating a cost-saving with the pulsed loop reactor. ROBIAH BINTI YUNUS// SITI ZULAIKA BINTI RAZALI, SURAYA BINTI ABDUL RASHID, LIM HONG NGEE

A comparative analysis of the effect of temperature on band-gap energy of gallium nitride and its stability beyond room temperature using a Bose–Einstein model and Varshni'S model

High temperature stability of the band-gap energy of the active layer material of a semiconductor device is one of the major challenges in the field of semiconductor optoelectronic device design. It is essential to ensure the stability in different band-gap energy-dependent characteristics of the semiconductor material used to fabricate these devices either directly or indirectly. Different models have been widely used to analyze the band-gap energy-dependent characteristics at different temperatures. The most commonly used methods to analyze the temperature dependence of band-gap energy of semiconductor materials are: the Passler model, the Bose–Einstein model, and Varshni’s model. This paper is going to report the limitation of the Bose–Einstein model through a comparative analysis between the Bose–Einstein model and Varshni’s model. The numerical analysis is carried out considering GaN, as it is one of the most widely used semiconductor materials all over the world. From the numerical results it is ascertained that below the temperature of 95 K both the models show almost same characteristics. However, beyond 95 K Varshni’s model shows weaker temperature dependence than that of the Bose–Einstein model. Varshni’s model shows that the band-gap energy of GaN at 300 K is found to be 3.43 eV, which establishes a good agreement with the theoretically calculated band-gap energy of GaN for operation at room temperature. Kestabilan bahan peranti semikonduktor pada suhu tinggi di lapisan aktif jurang tenaga (band-gap) adalah salah satu cabaran penting dalam bidang reka bentuk peranti optoelektronik semikonduktor. Faktor ini bergantung kepada bahan semikonduktor yang digunakan untuk proses fabrikasi peranti elektronik ini samada secara langsung atau tidak langsung, bagi memastikan kestabilan dalam pelbagai jurang lapisan tenaga. Model yang berbeza telah digunakan secara meluas untuk mengkaji kebergantungan ciri jurang lapisan tenaga bahan semikonduktor pada suhu yang berbeza. Kaedah yang paling biasa digunakan untuk menganalisa kebergantungan jurang lapisan tenaga bahan semikonduktor pada suhu adalah: model Passler, model Bose-Einstein dan model Varshni. Sementara itu pada suhu melebihi 95K, model Varshni menunjukkan kebergantungan pada suhu adalah lemah berbanding model Bose-Einstein. Model Varshni menunjukkan bahawa jurang tenaga bagi GaN pada suhu 300 K adalah 3.43 eV, di mana ia adalah tepat dan bersamaan dengan kiraan teori pada jurang lapisan tenaga GaN untuk beroperasi pada suhu bilik

Design of non destructive testing on composite material using parallel plate electrical capacitance tomography: a conceptual framework

In this paper, a conceptual framework for a non destructive testing to check defect on composite material using parallel plate electrical capacitance tomography is being proposed. At the early stage, the possibility of using this method is being simulated using Comsol Multiphysic software. The simulation process has shown promising results to make this concept works. When a dielectric material is placed between the parallel plates, the permittivity distribution can be observed. As the number of electrodes of the sensor are increased from 2 to 8 electrodes, the capacitance value increase from 2.0131e-11-2.3532e-14i F to 5.2474e-11-3.0756e-13i F. Furthermore, there are significant results when the size and the permittivity of the object are varies

Utilization of Renewable Biomass and Waste Materials for Production of Environmentally-Friendly, Bio-based Composites

The introduction of renewable biomass into a polymer matrix is an option competing with other possibilities, such as energy recovery and/or re-use in the carbonized state, or production of chemicals, such as, in the case of ligno-cellulosic waste, concentrates on the production of simple sugars, then possibly leading to the development of biopolymers. These competitive applications have also some interest and market, however with a considerable energy, water and materials consumption, due also to the not always high yielding. Other possibilities for renewable biomass are therefore being used as fillers to increase mechanical performance of polymers or to allow e.g., the absorption of toxic chemicals. This review concentrates on the use of biomass as close as possible to the “as received” state, therefore avoiding whenever suitable any thermal treatment. More specifically, it focuses on its introduction into the three categories of oil-based (or bio-based replacement) of engineered polymers, into industrial biopolymers, such as poly(lactic acid) (PLA) and self-developed biopolymers, such as thermoplastic starch (TPS)

Recent advances in silica glass optical fiber for dosimetry applications

In this paper, we review the highly promising silica glass, fabricated as doped and undoped optical fiber for intended use in radiation dosimetry. The dosimetry techniques reviewed here, underpinned by intrinsic and extrinsic defects in silica glass, focus on Thermoluminescence (TL), Optically Stimulated Luminescence (OSL) and Radioluminescence (RL), with occasional references to the much more established Radiation Induced Attenuation (RIA). The other focus in this review is on the various materials that have been reported earlier as dopants and modifiers used in silica glass optical fiber radiation dosimeters. This article also elaborates on recently reported optical fiber structures, namely, cylindrical fibers, photonic crystal fibers and flat fibers, as well as dimensions and shapes used for optimization of dosimeter performance. The various types of optical fiber radiation dosimeters are subsequently reviewed for various applications ranging from medical dosimetry such as in external beam radiotherapy, brachytherapy and diagnostic imaging, as well as in industrial processing and space dosimetry covering a dynamic dose range from μGy to kGy. Investigated dosimetric characteristics include reproducibility, fading, dose response, reciprocity between luminescence yield to dose-rate and energy dependence. The review is completed by a brief discussion on limitations and future developments in optical fiber radiation dosimetry