Optical properties and scattering distribution of thermographic phosphors

The optical properties and scattering distribution of thermographic phosphors have been demonstrated using a combined experimental and numerical method. ZnO:Zn and BaMgAl₁₀O₁₇:Eu²⁺ (BAM) are two types of widely used phosphors due to their stable physical properties and high-temperature sensitivities. To study their inter-phosphor light transfer, the angular scattering distribution and light propagation of these two phosphor suspensions was measured using a spectro-goniometric system. A collision-based Monte Carlo ray-tracing model was developed to extract their optical properties, including extinction coefficient, scattering albedo, asymmetry factors, and scattering fraction. With the void fraction around 0.98, the extinction coefficient of ZnO:Zn was determined to be 4.719, while that of F grade BAM and N grade BAM were 11.584 and 9.777, respectively. In addition, BAM had a higher scattering fraction (α = 0.99) than ZnO:Zn (α = 0.88). Due to the higher values of extinction coefficient and scattering fraction, BAM demonstrated more significant scattering than ZnO:Zn. Light transmission through phosphor suspensions was predicted along the direction of the light path. For ZnO:Zn, 70% of flux was scattered when the distance increases to 0.5, while for BAM, the distance was 0.15. Furthermore, with the same mass loading, smaller particle sizes can promote scattering and reduce the amount of light transmitted through phosphor suspensions.Wanxia Zhao, Jan Marti, Aldo Steinfeld, Zeyad T. Alwahab

Sensitive elemental detection using microwave-assisted laser-induced breakdown imaging

Abstract not availableAdeel Iqbal, Zhiwei Sun, Matthew Wall, Zeyad T. Alwahab

Improvement of palladium limit of detection by microwave-assisted laser induced breakdown spectroscopy

Detecting elements such as heavy metals is important in many industrial processes. The techniques currently used are time consuming and require excessive sample preparation. In this paper, we demonstrate microwave-assisted laser-induced breakdown spectroscopy (MW-LIBS) to detect palladium (Pd) in solid samples at ambient conditions. Microwave radiation was introduced by a near field applicator to couple the microwave radiation with the plasma. The results were a 92–fold enhancement in palladium signal with 8-fold improvement in the limit of detection at laser energy levels below 5 mJ (1250 J/cm² laser pulse fluence). We also investigate the optimum experimental parameters of palladium detection for both laser-induced breakdown spectroscopy (LIBS) and MW-LIBS. The maximum signal to noise ratio improvement was achieved at microwave power of 750 W and laser pulse fluence of 157 J/cm² for Pd I 340.46 nm. Finally, we examine the location of the near field applicator (NFA) with respect to the sample to show that the MW-LIBS signal strength was significantly affected by the vertical position compared to the horizontal. The detection limits of palladium with LIBS and MW-LIBS were 40 ppm and 5 ppm respectively.Ahlam A. Al Shuaili, Ahlam M. Al Hadhrami, M.A. Wakil, Zeyad T. Alwahab

Design and application of near-field applicators for efficient microwave-assisted laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) can benefit from sustaining laser generated plasma with microwaves to enhance elemental detection sensitivity. To achieve efficient microwave coupling, critical factors, such as the electromagnetic environment and reflection coefficient of the coupling device, need to be considered to quantitatively predict the electric-field strength in the plasma location. 3D full-wave electromagnetic simulations were used to design near-field microwave applicators suitable to maximize microwave coupling into the short-lived laser-induced plasmas. The simulations pointed out to four effective and practical designs containing varieties of isolation techniques. The four developed microwave applicators were then used to improve the detection of copper present in a mineral ore solid sample, using LIBS and imaging techniques simultaneously. It was found that, with 1.2 kW microwave power, an applicator design with a 30 mm diameter ground plane can significantly boost the signal of copper line 324.754 nm with a factor of 849, which is, to the authors' best knowledge, the highest reported value. Furthermore, an outstanding signal to noise ratio of 166 was recorded in a solid sample containing a certified 3.38 μg g⁻¹ copper concentration.Shengjian Jammy Chen, Adeel Iqbal, Matthew Wall, Christophe Fumeaux and Zeyad T. Alwahab

Effects of the bluff-body diameter on the flow-field characteristics of non-premixed turbulent highly-sooting flames

This paper presents a joint experimental and computational study of the effect of the bluff-body diameter on the flow field and residence time distribution (RTD) in a set of turbulent non-premixed ethylene/nitrogen flames with a high soot load. A novel optical design has been developed to undertake the PIV measurements successfully in highly-sooting turbulent flames, using polarizing filters. The mean velocity components and turbulent intensity are reported for three bluff-body burners with different bluff-body diameters (38, 50, and 64 mm), but which are otherwise identical in all other dimensions. The central jet diameter of 4.6 mm was supplied with a mixture of ethylene and nitrogen (4:1, by volume) to achieve a bulk Reynolds number of 15,000 for the reacting cases. Isothermal cases were also investigated to isolate the effect of heat release on the flow fiel. Pure nitrogen was utilized in the isothermal cases where the Reynolds number was kept the same as the reacting cases. The annular bulk velocity of the co-flowing air was kept constant at 20 m/s for all experiments. Computationally, a 2-D RANS model was developed, validated against the experimental data and was mainly used to investigate the effect of the bluff body diameter on the residence time in the recirculation zone. The flow structure for both isothermal and reacting cases was found to be consistent with the literature, exhibiting similar vortical structures of the recirculating zone and mixture fraction distribution, for similar momentum flux ratios. The flame length and volume were found to decrease by 20% and 9%, respectively, as the bluff diameter was increased from 38mm to 64mm. The length of the recirculation zone for the isothermal cases was found to be ~1.2DBB, while for the reacting cases it was ~1.5–1.75DBB. A stochastic tracking model was employed to estimate the pseudo-particles’ residence time distribution in the recirculation region. The model revealed that an increase in the bluff body diameter from 38mm to 64 mm leads to tripling of the mean residence time within the recirculation zone. Thermal radiation measurements from the recirculation zone show a 35% increase as the bluff body diameter is increased from 38 mm to 64 mm, whilst the total radiation from the whole flame drops by 15%, which is deduced to be due mostly to the decrease in flame volume. The effect of these differences on soot propensity and transport are described briefly and will be the subject of future investigations.A. Rowhani, Z. W. Sun, P. R. Medwell, Z. T. Alwahabi, G. J. Nathan and B. B. Dall

Impact of acoustic forcing on soot evolution and temperature in ethylene-air flames

This combined numerical and experimental study assesses the transient coupling of soot formation, flame chemistry and fluid transport in ethylene-air coflow flames at acoustic forcing frequencies of 20 and 40 Hz. The measurements report soot volume fraction and flow velocity. For the computational analysis, the numerical code’s capability in modeling soot formation is first demonstrated in a steady coflow flame. Soot volume fraction and temperature measurements from different laboratories and optical techniques are used for validation. Then, acoustic forcing is applied to investigate the transient behavior of this multi-dimensional combustion problem. Forcing at different frequencies and amplitudes provokes very distinct transient soot, temperature, and flow conditions. The discussed steady ethylene-air flame is excited with 20 and 40 Hz, corresponding to Strouhal numbers of 0.23 and 0.46. For both frequencies, forcing amplitudes of 20, 50, and 60% are studied numerically and validated against measurements at 50%. With a start-up transient analysis, the computation time to reach a periodic state is evaluated and soot volume fraction predictions are then compared with the measurements. A reduction in maximum soot volume fraction for the increased forcing frequency is observed experimentally and numerically. The decrease in maximum soot volume fraction is explained by a residence time analysis revealing shorter maximum fluid parcel residence times for the 40 Hz than for the 20 Hz case. It is also found that at 40 Hz the transient evolution of maximum soot production and forced fuel velocity is almost synchronized, while for the 20 Hz case, a time lag of 32.5 ms is observed, corresponding to 65% of a full period.Agnes Jocher, Kae Ken Foo, Zhiwei Sun, Bassam Dally, Heinz Pitsch, Zeyad Alwahabi, Graham Natha

Evolution of the accreditation program for healthcare organizations in KSA: From present to future

الملخص: ممارسة الطب المبني على الأدلة والبراهين العلمية المثبتة حجر أساس لتقديم رعاية طبية ذات جودة عالية وبالتالي الوصول إلى نتائج صحية مرضية، ولهذا تفرض العديد من الدول برامج إعتماد في القطاع الصحي. إحدى هذه البرامج هو سباهي في المملكة العربية السعودية، والعديد من الدراسات ربطت حصول المنشأة الصحية على اعتماد سباهي مع تحقيقها لنتائج إيجابية في الرعاية الطبية، وبالرغم من ذلك هناك تحديات في مجال اعتماد المنشآت الصحية داخل المملكة العربية السعودية ، منها التباين و التنوع في مواقع و جودة الرعاية الصحية المراد تقييمها وأيضا طبيعة و سرعة تطورقطاع الرعاية الصحية مما يؤدي إلى ظهورتحديات مختلفة. و محاولة سباهي في التغلب على هذه التحديات تظهر من خلال تطوير معايير التقييم، والحصول على الاعتماد الدولي، وتدريب المقيمين لتقييم المنشآت الصحية في جميع أنحاء المملكة العربية السعودية، نجاح هذه الجهود سيساعد في تعزيز مصداقية نظام الرعاية الطبية في السعودية على تقديم رعاية ذات جودة عالية وبالتالي تصبح مقصداً علاجياً عالمياً. Abstract: Delivering high-quality care is a cornerstone of achieving satisfying health outcomes, and evidence-based medicine is the basis for doing so. For that, some governments mandate accreditation programs for the healthcare sector. One of these programs is CBAHI in KSA (SA), and many studies have shown positive healthcare outcomes associated with CBAHI accreditation in SA. While these achievements indicate progress, challenges remain. Variability in the quality of healthcare services across different regions of SA is a concern. Furthermore, the fact that healthcare is a complex industry that is rapidly evolving poses many challenges. CBAHI tries to overcome these challenges by continuously developing standards, obtaining international accreditation, and training surveyors to assess healthcare facilities across SA. The success of these efforts will help enhance the SA healthcare system's credibility and attract international patients who are seeking high-quality care

Engineering of Solid-State Random Lasing in Nanoporous Anodic Alumina Photonic Crystals

Random lasing provides new opportunities to engineer cost-competitive, highly controllable, and integrable light sources for a broad range of photonic technologies such as sensing, hyperspectral imaging, high-resolution spectroscopic analysis, and photonic circuits. In this study, we engineer the self-organized structure of nanoporous anodic alumina (NAA) through the electrochemical oxidation of aluminum to generate a palette of model nanoporous platforms with tailored, hexagonally distributed, straight cylindrical nanopores. The inner surface of these platforms is functionalized with a model organic fluorophore via micellar solubilization of a surfactant. The resultant organic− inorganic composite structures provide model platforms to develop optically pumped solid-state random lasers with well-resolved, intense lasing bands. The effect of NAA’s geometric features on the random lasing characteristics of these model platforms is elucidated by precisely engineering its nanopore diameter, nanopore length, interpore distance, and ordering. Structural engineering of NAA makes it possible to tune and maximize random-lasing emissions, resulting in strong, polarized lasing at ∼628 nm characterized by a remarkably high-quality-gain product of ∼1433, a polarization quality of ∼0.9, and a lasing threshold of ∼0.87 mJ pulse−1.Satyathiran Gunenthiran, Juan Wang, Huong Nguyen Que Tran, Khoa Nhu Tran, Siew Yee Lim, Cheryl Suwen Law, Andrew D. Abell, Zeyad T. Alwahabi, and Abel Santo

Lasing from Narrow Bandwidth Light-Emitting One-Dimensional Nanoporous Photonic Crystals

Nanoporous anodic alumina (NAA) is an emerging platform material for photonics and light-based applications. However, demonstrations of narrow bandwidth lasing emissions from this optical material remain limited. Here, we demonstrate that narrow bandwidth NAA-based gradient-index filters (NAAGIFs) can be optically engineered to achieve high-quality visible lasing. NAA-GIFs fabricated by a modified sinusoidal pulse anodization approach feature a well-resolved, intense, high-quality photonic stopband (PSB). The inner surface of NAA-GIFs is functionalized with rhodamine B (RhoB) fluorophore molecules through micellar solubilization of sodium dodecyl sulfate (SDS) surfactant. Systematic variation of the ratio of SDS and RhoB enables the precise engineering of the light-emitting functional layer to maximize light-driven lasing associated with the slow photon effect at the red edge of NAA-GIFs’ PSB. It is found that the optimal surfactant-to-fluorophore ratio, namely, 20 mM SDS to 0.81 mM RhoB, results in a strong, polarized lasing at ∼612 nm. This lasing was characterized by a remarkably high-quality−gain product of ∼536, a Purcell factor of 2.2, a lasing threshold of ∼0.15 mJ per pulse, and a high-quality polarization ratio of ∼0.7. Our results benefit the advancement of the NAA-based lasing technology for a variety of photonic disciplines such as sensing, tweezing, light harvesting, and photodetection.Satyathiran Gunenthiran, Juan Wang, Wanxia Zhao, Cheryl Suwen Law, Siew Yee Lim, Jamie A. McInnes, Heike Ebendorff-Heidepriem, Andrew D. Abell, Zeyad T. Alwahabi, and Abel Santo