Reconstructing the Local Twist of Coronal Magnetic Fields and the Three-Dimensional Shape of the Field Lines from Coronal Loops in EUV and X-Ray Images

Non-linear force-free fields are the most general case of force-free fields, but the hardest to model as well. There are numerous methods of computing such fields by extrapolating vector magnetograms from the photosphere, but very few attempts have so far made quantitative use of coronal morphology. We present a method to make such quantitative use of X-Ray and EUV images of coronal loops. Each individual loop is fit to a field line of a linear force-free field, allowing the estimation of the field line's twist, three-dimensional geometry and the field strength along it. We assess the validity of such a reconstruction since the actual corona is probably not a linear force-free field and that the superposition of linear force-free fields is generally not itself a force-free field. To do so, we perform a series of tests on non-linear force-free fields, described in Low & Lou (1990). For model loops we project field lines onto the photosphere. We compare several results of the method with the original field, in particular the three-dimensional loop shapes, local twist (coronal alpha), distribution of twist in the model photosphere and strength of the magnetic field. We find that, (i) for these trial fields, the method reconstructs twist with mean absolute deviation of at most 15% of the range of photospheric twist, (ii) that heights of the loops are reconstructed with mean absolute deviation of at most 5% of the range of trial heights and (iii) that the magnitude of non-potential contribution to photospheric field is reconstructed with mean absolute deviation of at most 10% of the maximal value.Comment: submitted to Ap

Influence of blade aerodynamic model on prediction of helicopter rotor aeroacoustic signatures

Brown’s vorticity transport model has been used to investigate how the local blade aerodynamic model influences the quality of the prediction of the high-frequency airloads associated with blade–vortex interactions, and thus the accuracy with which the acoustic signature of a helicopter rotor can be predicted. The vorticity transport model can accurately resolve the structure of the wake of the rotor and allows significant flexibility in the way that the blade loading can be represented. The Second Higher-Harmonic Control Aeroacoustics Rotor Test was initiated to provide experimental insight into the acoustic signature of a rotor in cases of strong blade–vortex interaction. Predictions of two models for the local blade aerodynamics are compared with the test data. A marked improvement in accuracy of the predicted high-frequency airloads and acoustic signature is obtained when a lifting-chord model for the blade aerodynamics is used instead of a lifting-line-type approach. Errors in the amplitude and phase of the acoustic peaks are reduced, and the quality of the prediction is affected to a lesser extent by the computational resolution of the wake, with the lifting-chord model producing the best representation of the distribution of sound pressure below the rotor

Influence of blade aerodynamic model on the prediction of helicopter high-frequency airloads

Brown’s vorticity transport model has been used to investigate the influence of the blade aerodynamic model on the accuracy with which the high-frequency airloads associated with helicopter blade–vortex interactions can be predicted. The model yields an accurate representation of the wake structure yet allows significant flexibility in the way that the blade loading can be represented. A simple lifting-line model and a somewhat more sophisticated liftingchord model, based on unsteady thin aerofoil theory, are compared. A marked improvement in the accuracy of the predicted high-frequency airloads of the higher harmonic control aeroacoustic rotor is obtained when the liftingchord model is used instead of the lifting-line approach, and the quality of the prediction is affected less by the computational resolution of the wake. The lifting-line model overpredicts the amplitude of the lift response to blade–vortex interactions as the computational grid is refined, exposing the fundamental deficiencies in this approach when modeling the aerodynamic response of the blade to interactions with vortices that are much smaller than its chord. The airloads that are predicted using the lifting-chord model are relatively insensitive to the resolution of the computation, and there are fundamental reasons to believe that properly converged numerical solutions may be attainable using this approach

Effects of flame retardance additives on the mechanical and fire performance of natural fibre composites

The incorporation of sustainability is becoming increasingly important in manufacturing practices worldwide. This includes the development of natural fibre composites with mechanical and flammability characteristics suitable for structural interiors. Composites manufactured from kenaf fibres and polypropylene (PP) were investigated as to their suitability as materials for the interiors of buildings, aircraft and such-like. Natural fibres like kenaf act as fuel sources during combustion, and hence, flame retardants are added to the mix. In the present study, the ammonium polyphosphate (APP)-based flame retardant Budit® 3167 was used to address this issue. Limited studies exist on how the inclusion of APP influences the composites’ mechanical properties. Hence the main objective of this research project was to evaluate the effect of adding Budit 3167 on both mechanical and flammability properties of kenaf-PP composites. Kenaf-PP composites were manufactured with various fibre weight percentages, with and without Budit 3167. The composites were subjected to different experiments to assess their mechanical and flammability behaviour. It was found that Budit 3167 not only improved the flammability properties of the composites, but also the tensile and flexural moduli due to the flame retardant behaving like a particle reinforcement. However, weak interfacial bonds arising from the addition of Budit 3167 led to a decrease in mechanical strength, providing a basis for further investigation. It was concluded that kenafPP composites with Budit 3167 show good potential as a sustainable alternative for structural interiors

VALIDATION OF ANTIBODY RAPID TEST FOR SEVERE ACUTE RESPIRATORY SYNDROME CORONAVIRUS-2 INFECTION IN BETHESDA HOSPITAL YOGYAKARTA

Since March 2020, Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection has been around in Indonesia with a case fatality rate was 4.7% on August, 1th 2020. So far, the Real-Time Polymerase Chain Reaction (RT-PCR) method is the gold standard for the SARS-CoV-2 infection diagnosis. This method, however, has some limitations where it has a longturnaround time, complicated operations, and high prices. Hence, the rapid test kits are now readily available to identify the SARS-CoV-2 patients. The purpose of this study is to measure the diagnostic performance, including sensitivity, specificity, positive and negative predictive value, likelihood ratio or LR of antibody rapid test if compared with RT-PCR for the SARS-CoV-2 suspected patients in Bethesda Hospital Yogyakarta. This research was analytical observational research with a cross-sectional design approach, in which data were collected retrospectively. The instruments used in this study included e-medical record (ERM), Laboratory Information System (LIS) data from patients with suspected SARS-CoV-2 infection in Bethesda Hospital Yogyakarta. We collected demographic data of patients, RT-PCR results, antibody rapid test results using Standard Q COVID-19 IgM/IgG Combo. The data were obtained from 50 patients. The results showed that the Rapid test kit has a 100% sensitivity value, 74.4% specificity value, 38.9% positive and 100% negative predictive value, 3906 positive likelihood ratio compared with the RT-PCR results

A cross-cultural comparison of sleep patterns between typically developing children and children with ASD living in Saudi Arabia and the United Kingdom

Background: Sleep is crucial for child development, especially for children with ASD. While it is known that children with ASD experience more severe sleep problems and that these problems tend to persist compared to their typically developing counterparts, these findings tend to come from only Western countries. A cross-cultural study is important to understand if the prevailing understanding of sleep in children with ASD can be extended to different cultural backgrounds. Aim: A cross-cultural study is conducted, involving typically developing children and children with ASD aged 5–12 across two countries: Saudi Arabia and the United Kingdom. Methods and procedures: Using a combination of questionnaires measuring ASD severity (CARS-2), sleep quality (CSHQ), sociodemographic and lifestyle variables and sleep diaries, 244 children were sampled using a mixture of snowball and convenience sampling methods. Outcomes and results: Children with ASD experience more sleep problems compared to typically developing children in Saudi Arabia, and these problems similarly persist across time. Specifically, it was found that children with ASD in Saudi Arabia experience greater sleep onset latency and a greater number of night awakenings. Additionally, across the ASD groups, it was found that children from Saudi Arabia generally experienced poorer sleep than children in the United Kingdom in terms of shorter sleep duration, although children in the United Kingdom tended to report more instances of sleep anxiety and parasomnias. Conclusions and implications: Several reasons such as parental education about sleep hygiene, cultural influences and social hours were put forward as potential explanations for cross-cultural differences. Findings served to emphasise the importance of culturally-appropriate interventions and public education regarding child sleep