The fractionation, carbonisation and characterisation of electro-spun lignin fibres

Polyacrylonitrile (PAN) continues to be the primary precursor that is used for the production of carbon fibres. However, PAN is derived from petroleum and it is not a sustainable precursor in the long-term. This current research was focused on identifying bio-based precursors that could be used as an alternative for the production of fibrous preforms that could subsequently be carbonised. In the first instance, lignin was purchased from Domtar PC sales centre (Germany) and it is referred to as softwood Kraft lignin (BioChoice®) in the thesis. Lignin was chosen because of its high aromatic content, availability and it is known to cross-link. The as-received lignin was characterised using a range of analytical techniques. The analyses indicated the presence of impurities such as small concentrations of carbohydrates and inorganics. The carbohydrates and inorganic content in the BioChoice® lignin were found to be 4.4% and 1.3%. Two methods were considered to reduce the carbohydrate and inorganic contents in the as-received and these were acid-washing and solvent fractionation. The acid-washing was carried out using nitric acid. The solvent fractionation of as-received lignin was carried out using acetone; this was extended to include ethanol and propanol. The inorganic content in the BioChoice® lignin was reduced from 1.3% to 0.1% after solvent fractionation in acetone. However, the inorganic content after acid-washing was 0.34%. Solvent fractionation was found to be simpler and time-efficient for removing the inorganic content in lignin when compared with acid-washing and hence, it was adopted as a preferred method to purify the lignin prior to electro-spinning. The majority of the initial electro-spinning experiments were undertaken using acetone-fractionated lignin using a binary solvent of acetone and dimethyl sulfoxide but the reproducibility was not consistent. The majority of the studies in the literature with regard to producing fibres with lignin have involved the use of synthetic polymer blends. For example, polyvinyl alcohol, polyvinyl acetate, polyethylene oxide and PAN. In the current study, a novel approach of electro-spinning with a 100% blend of acetone-soluble and ethanol-soluble lignin was demonstrated for the first time. These fractions were electro-spun using a mixture (2:1) of acetone and dimethyl sulfoxide. The electro-spun fibres inspected in this study were found to be void-free with a relatively uniform and circular cross-section. From the numerous micrographs that were inspected, there was no evidence to suggest the presence of fused fibres. The above-mentioned electro-spun fibres had a random orientation, as is the case with conventional electro-spinning using a ground conductor. In this study, a new ground electrode made from graphite was designed to enable the electro-spinning of aligned fibres. A series of detailed experiments were undertaken to derive the heat-treatment regime for the as-spun fibres. This was necessary to prevent fibre fusion during subsequent oxidative and carbonisation treatments. The optimum heat treatment for the as-spun 100% lignin fibres was found to be drying at 140 °C in a vacuum oven for 6 hours prior to thermo-stabilisation at 250 °C in air and carbonisation in nitrogen. The sp2 graphitic content in the carbonised fibres, as inferred by Raman spectroscopy, was found to be in the order 1000 °C < 1200 °C < 1500 °C. The BioChoice® lignin was obtained from a commercial source and the decision was made to extract lignin from coir. Coir was chosen because it has the highest lignin content of all plant matter. The procedures and protocols for the extraction were developed and the lignin was characterised as mentioned previously. The lignin was electro-spun using a binary solvent of acetone and dimethylsulfoxide. It is proposed that coir with its high lignin content (32%) can be used as a renewable and sustainable precursor for the production of preforms for the production of carbon fibres

Multiscale Representations for Manifold-Valued Data

We describe multiscale representations for data observed on equispaced grids and taking values in manifolds such as the sphere $S^2$, the special orthogonal group $SO(3)$, the positive definite matrices $SPD(n)$, and the Grassmann manifolds $G(n,k)$. The representations are based on the deployment of Deslauriers--Dubuc and average-interpolating pyramids "in the tangent plane" of such manifolds, using the $Exp$ and $Log$ maps of those manifolds. The representations provide "wavelet coefficients" which can be thresholded, quantized, and scaled in much the same way as traditional wavelet coefficients. Tasks such as compression, noise removal, contrast enhancement, and stochastic simulation are facilitated by this representation. The approach applies to general manifolds but is particularly suited to the manifolds we consider, i.e., Riemannian symmetric spaces, such as $S^{n-1}$, $SO(n)$, $G(n,k)$, where the $Exp$ and $Log$ maps are effectively computable. Applications to manifold-valued data sources of a geometric nature (motion, orientation, diffusion) seem particularly immediate. A software toolbox, SymmLab, can reproduce the results discussed in this paper

حذف المضاف وأسراره البلاغية في القرآن الكريم (دراسة بلاغية تحليلية): Hadzf al-Mudaf and its rhetorical secrets in safwat al Tafasir- Surah Al-Baqarah as a model (Rhetorical and analytical study)

This study addresses the phenomenon of Hadzf al-Mudaf (deletion) in the Holy Qur’an through an analytical and Rhetorical study. It is a pure grammatical study which concluded that the Hadzf al-Mudaf (deletion) is a prominent linguistic phenomenon especially in the Arabic language and the Holy Qur’an. This research aims to investigate the verses in that contain on hadzf mudaf and its secrets, and purposes of its use in the  holy Qur´an, and describe the content of educational values that can be utilized and applied in daily life. The conclusion of this study is that Faith and aqidah education is a basic education in  the holy Quran. Delivered through several stories of the Messengers of Allah, including the prophet, Ibrahim, Ismail, Ishaq, Musa And more other conveyed the message of tawheed to their people with patience. the Qur´an has a hadzf ijaz which is beneficial for various purposes including ikhtishar and ihtiraz, tafhim and i’zham. Key words: Hadzf Mudaf, holy Quran, secrets, rhetoric

Multi-Layered Hierarchical Bounding Box based interaction in virtual environments

International audienceInteraction techniques play a vital role in the success and effectiveness of a virtual environment. Therefore, researchers have put much effort on the design and development of easy, realistic and intuitive interaction techniques. In this paper we present a new interaction technique specifically designed for educational environments. The technique uses a step by step and hierarchical approach to have information rich, selection/ manipulation and exploration of an object and its constituent parts (objects). The technique is implemented and evaluated in a virtual environment having a human skeleton designed in 3DS max. Subjective evaluation reveals that the technique is very useful and suitable for educational virtual environments

Association of risk factors with early knee osteoarthritis in patients presented to tertiary care hospital: A cross-sectional study

Aim: To determine the risk factors associated with early knee osteoarthritis in patients presented to tertiary care hospital. Methods: This cross sectional study was conducted on 120 patients presenting with early knee osteoarthritis at Sialkot Medical College Sialkot Pakistan from November, 2022 to April, 2023. We assessed the risk factors associated with early knee osteoarthritis. Results: Mean age recorded was 50.80±8.94 years. Majority of the patients were females. About 30% of the patients were house wives while 53.3% were office employees and 16.7% were laborers. About 20% patients had normal BMI while 35% overweight and 45% obese. About 60% patients were diabetic and 69.2% patients had vitamin D deficiency. Conclusion: Profession, obesity, diabetes and vitamin D deficiency are leading risk factors with early knee osteoarthritis in patients

Multiscale Representations For Manifold-Valued Data

We describe multiscale representations for data observed on equispaced grids and taking values in manifolds such as: the sphere S², the special orthogonal group SO(3), the positive definite matrices SPD(n), and the Grassmann manifolds G(n, k). The representations are based on the deployment of Deslauriers-Dubuc and Average-Interpolating pyramids `in the tangent plane&apos; of such manifolds, using the Exp and Log maps of those manifolds. The representations provide `wavelet coefficients&apos; which can be thresholded, quantized, and scaled much as traditional wavelet coefficients. Tasks such as compression, noise removal, contrast enhancement, and stochastic simulation are facilitated by this representation. The approach applies to general manifolds, but is particularly suited to the manifolds we consider, i.e. Riemannian symmetric spaces, such as S , SO(n), G(n, k), where the Exp and Log maps are effectively computable. Applications to manifold-valued data sources of a geometric nature (motion, orientation, diffusion) seem particularly immediate. A software toolbox, SymmLab, can reproduce the results discussed in this paper

A Wideband High-Isolation Microstrip MIMO Circularly-Polarized Antenna Based on Parasitic Elements

This work presents a wideband, all-side square-cut square patch multiple-input, multiple-output circularly-polarized (MIMO-CP) high-isolation antenna. The MIMO-CP antenna contains a two-port square cut on all corners of the square patch, and parasitic elements of 9 × 5 periodic square metallic plates are designed and operated. The outer dimensions of the antenna are 40 × 70 mm2, and the FR4 substrate height is 1.6 mm. The proposed antenna with the parasitic elements improves impedance matching and enhances S-parameters and axial ratio (AR). In the suggested MIMO-CP antenna, a parasitic element is designed and placed around the antenna periodically to reduce mutual coupling (MC) and improve CP. Simulated results show that the suggested antenna has a wide bandwidth (BW) from 4.89 to 6.85 GHz for S11 and was < −10 dB with AR ≤ 3 dB from 5.42 to 6.58 GHz, with a peak gain of 6.6 dB. The suggested antennas have more than 30 dB isolation and a low profile, are affordable, easily made, and are CP. To make a comparison with the measured and simulated results, a MIMO-CP antenna structure was fabricated and tested. The suggested antenna is better in terms of efficiency, envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and total active reflection coefficient (TARC). The proposed antenna is adequate for WLAN applications