An Experimental Investigation of Perturbations on Vortex Breakdown over Delta Wings

An experimental investigation on vortex breakdown on delta wings at high angles of attack is presented. As suggested by previous works, perturbations are used to change the platform of the delta wings to reduce the detrimental effects of vortex breakdown brought about by the Self-Induction Theory. Different patterns of ‘round’ perturbations are tested to obtain the favourable lift and drag characteristics for each wing. With the best pattern identified later, optimization of the shape of perturbation is explored to further improve the results. ‘Teardrop’ and ‘diamond’ perturbations are introduced as basis of comparison. Force measurements were conducted over a range of α = 0 to 40° to justify the concept of surface shaping and evaluate its effectiveness. Dye flow visualization were used to obtain sectional views of the leading-edge vortices as they break down for a series of delta wings having sweep angles of 60°, 65° and 70°. The wings are tested constantly at a low speed of U∞ = 0.05 m/s in a water tunnel facility. A combination of side and plan views provides information on the three-dimensional nature of the vortex structure before, during and after breakdown. Details of the flow at α =15° for every wing are identified in still photographs while the dynamic characteristics of the breakdown process are examined from recorded high-speed movies. The force measurement supported by the flow visualization shows that certain combinations of perturbations indeed provide encouraging results. For wings with perturbations, generally, the vortex structure transforms from a linear structure to a wavy or “kink” structure which effectively delay or even suppress vortex breakdown. Various results have shown an increase of approximately 10% in lift characteristics and delay of stall angle for certain scenarios. The best results have been for the 60° wing where the ‘teardrop’ bulge in a mild perturbation pattern managed to improve lift characteristics by about 15% over the whole range of angle of attack for the tests. Results for the 65° wing and 70° wing are generally positive with the ‘teardrop’ perturbation again providing the best results, however with existence of discrepancies over certain angles of attack

Corporate Waqf University: a sustainability model / Ridzwan Bakar ... [et al.]

Globalization and economic pressure faced by governments including Malaysia, have led universities to be independent and source out their own fund for development, operation and research activity. In Malaysian case, the government has launched National Higher Education Strategic Plan Beyond 2020 to prepare for new challenges. As a result, the plan offers new autonomy for public universities. While government gives special attention to public university, literature provides limited discussion on the funding and sustainability of private universities. As such, this paper aims at exploring waqf as one of the financing instruments for private university’s sustainability. The paper proposes conceptual model to transform conventional method of financing university into corporate waqf university (CoWU), based on Yayasan Universiti Multimedia (YUM) experience. The study expands previous research and highlights the potential of transforming existing conventional endowment to Islamic endowment (waqf). The study adopts qualititative approach where desk research, interview, discussion, benchmarking as well as primary data collection were employed. It opens up possibilities and proposes practical model where corporate sector and university can work together to establish and fund corporate waqf university. The study also examines issues in implementing corporate waqf university, discusses opportunities and challenges in managing waqf for higher learning institutions. Finally, the paper suggests some pertinent points for policy maker and practitioner consideration

Mechanical properties of kenaf fibre thermoplastic polyurethane-natural rubber composites

Thermoplastic polyurethane-natural rubber TPUR-NR composites filled with treated and untreated kenaf fiber as filler were prepared at different TPUR and NR contents. The content of kenaf fiber was maintained at 12.5 wt % and the fiber was treated with 6 % solution of sodium hydroxide (NaOH), then dried for 24 hours in 100 °C, hot blended with polymer components, pulverized and pressed. The mechanical properties of the composites such as tensile, flexural and impact strength were determined, and their dependence on NaOH treatment of kenaf fibers was investigated. The analysis using scanning electron microscope (SEM) was implemented to identify the effect of alkali treatment on the microstructure of kenaf fiber and TPUR-NR composites. An improvement of fiber surface roughness and bonding between the fiber and polymer as well as an increase in impact energy and elongation at break of the composites was observed

The effect of sea water treatment on the impact and flexural strength of sugar palm fibre reinforced epoxy composites

Human safety and health and ‘green’ environmental sustainability are major concerns to the world community. To material scientists and engineers, these concerns meant that they have to device new ways of treating or producing materials. Over the last decade, natural fibres had been treated chemically to enhance fibre-matrix interfacial adhesion and this trend continues until today. The goal of this study is to find a suitable replacement for chemical treatment of natural fibres. The use of biological base treatment agent in the form of sea water to enhance fibre-matrix interfacial adhesion in sugar palm fibre reinforced epoxy composites was studied. Sugar palm fibre was soaked in the sea water for the duration of 30 days. Impact and flexural tests were carried out in order to examine the effectiveness of this treatment in accordance to the ASTM D256 and ASTM D790 respectively. Scanning electron microscope (SEM) was used to analyse the surface fibres and fractured composites. It was experimentally proven that the sea water treated composites of 20% and 30% fibre content had higher impact value at 18.46 MPa and 14.16 MPa with 5.06% and 4.27% of improvements respectively, when compared to untreated composites. Similar result was reported for flexural strength of 30% fibre content which had higher impact value at 53.87 MPa with 7.35% of improvements. For the composite of 20% fibre content, reverse trend result was obtained at 54.22 MPa with decrease 8.12% compared to untreated composites. In conclusion, sea water treatment significantly improved surface characteristics of fibres by removal of the outer layer of hemicellulose and pectin and led to improve fibre-matrix interface. This caused a direct result of higher impact and flexural strength compared to untreated composites

A novel evaluation tool for enhancing the selection of natural fibres for polymeric composites based on fiber moisture content criterion

A systematic evaluation tool for natural fibers’ capabilities based on moisture content criterion (MCC) was developed and introduced as a new evaluation method. This MCC evaluation tool is designed to predict the behavior of the available natural fibers regarding distinctive desirable characteristics under the effect of the moisture absorption phenomenon. Here, the capabilities of different natural fiber types commonly used in industry, in addition to date palm fibers, were systematically investigated based on MCC. The results demonstrated that MCC is capable of predicting the relative reduction of fiber performance regarding a particular beneficial property because of the effect of moisture absorption. The strong agreements between the predicted values of MCC and results reported in the literature verify its usefulness as an evaluation tool and demonstrate its added value steps in predicting the relative behavior of fibers with a minimal range of errors compared with experimental measurements. Therefore, MCC is capable of better evaluating natural fibers regarding distinctive criteria in a systematic manner, leading to more realistic decisions about their capabilities and therefore enhancing the selection process for both better sustainable design possibilities and industrial product development

Mechanical properties of kenaf bast and core fibre reinforced unsaturated polyester composites

Kenaf fibre has high potential to be used for composite reinforcement in biocomposite material. It is made up of an inner woody core and an outer fibrous bark surrounding the core. The aim of this study was to compare the mechanical properties of short kenaf bast and core fibre reinforced unsaturated polyester composites with varying fibre weight fraction i.e. 0%, 5%, 10%, 20%, 30% and 40%. The compression moulding technique was used to prepare the composite specimens for tensile, flexural and impact tests in accordance to the ASTM D5083, ASTM D790 and ASTM D256 respectively. The overall results showed that the composites reinforced with kenaf bast fibre had higher mechanical properties than kenaf core fibre composites. The results also showed that the optimum fibre content for achieving highest tensile strength for both bast and core fibre composites was 20%wt. It was also observed that the elongation at break for both composites decreased as the fibre content increased. For the flexural strength, the optimum fibre content for both composites was 10%wt while for impact strength, it was at 10%wt and 5%wt for bast and core fibre composites respectively

Combined multi-criteria evaluation stage technique as an agro waste evaluation indicator for polymeric composites: date palm fibre as a case study

The final features of natural fiber composites (NFCs) depend on the integrated characteristics of their constituents. In the industry today, natural agro waste fibers are evaluated using a limited number of criteria. In this work, a combined multi-criteria evaluation stage technique (CMCEST) is introduced as a simple efficient systematic indicator to enhance evaluation of the available natural agro wastes for polymeric composites. In this proposed technique, criteria affecting the proper selection of natural agro waste fibers were combined and divided into sequence stages as follows: single-evaluation-criterion (SEC), combined-double-evaluation-criterion (CDEC), combined-triple-evaluation-criterion (CTEC), etc. These stages are based on combined physical, mechanical, and economic evaluation criteria and can be extended to several further stages to include other beneficial characteristics. The effectiveness of this technique was demonstrated by evaluating coir, date palm, jute, hemp, kenaf, and oil palm fibers simultaneously. This combined evaluation criteria can lead to more informative decisions regarding selection of the most suitable fiber type for polymeric composites. The CMCEST enhancements can reveal new potential fiber types through better evaluation schemes, help achieve clearer indications of the capabilities of available agro wastes to enhance composites, and determine proper ecological waste management practices. Utilizing the proposed technique, the date palm fiber type was found to be quite promising due to beneficial characteristics revealed in CTEC, which provides a reasonable, cheap, and eco-friendly alternative material suitable for different applications

A review on pineapple leaves fibre and its composites

Natural fibre based composites are under intensive study due to their ecofriendly nature and peculiar properties. The advantage of natural fibres is their continuous supply, easy and safe handling, and biodegradable nature. Although natural fibres exhibit admirable physical and mechanical properties, it varies with the plant source, species, geography, and so forth. Pineapple leave fibre (PALF) is one of the abundantly available wastes materials of Malaysia and has not been studied yet as it is required. A detailed study of chemical, physical, and mechanical properties will bring out logical and reasonable utilization of PALF for various applications. From the socioeconomic prospective, PALF can be a new source of raw material to the industries and can be potential replacement of the expensive and nonrenewable synthetic fibre. However, few studies on PALF have been done describing the interfacial adhesion between fibres and reinforcement compatibility of fibre but a detailed study on PALF properties is not available. In this review, author covered the basic information of PALF and compared the chemical, physical, and mechanical properties with other natural fibres. Furthermore, it summarizes the recent work reported on physical, mechanical, and thermal properties of PALF reinforced polymer composites with its potential applications

Natural fibre-reinforced Thermoplastic starch composites

Increasing awareness among the world population of the need to protect the environment has motivated research on agricultural residues. This is due to the abundant sources of agricultural crop wastes that cause handling problems. Agricultural crop residues such as oil palm, pineapple leaf, banana and sugar palm are produced on the scale of billions of tons around the world. They are available in abundance, at low cost, and they are also renewable sources of biomass. Hence natural fibres are potential sources in the design of new green materials associated with polymer matrices. Recently, sugar palm fibre has become the most popular reinforcement material for researchers owing to its high durability. It is important to note that biopolymers that act as a matrix can be produced from the sugar palm tree itself. This chapter reports the preparation of an environmentally friendly composite where the matrix (sugar palm starch) and fibre (sugar palm fibre) are derived from one source, the sugar palm tree. The resulting materials are termed "biocomposites" or " green" composites, and are considered to be totally biodegradable

Antioxidant and antiproliferative activities of Malaysian sea cucumber, (Holothuria edulis Lesson), extracts

Sea cucumber is a marine invertebrate of the phylum Echinodermata and the class Holothuroidea that found on the sea floor worldwide. In Asia, many of sea cucumber species are considered as traditional food items and have been used in featment of numerous diseases such as eczema, arthritis and hypertension. Previous scientific studies have shown multiple biological activities of sea cucumber species as antinociceptive, antimicrobial and antifungal properties. This study was conducted to investigate the antioxidant and antiproliferative activities of aqueous and organic extracts from sea cucumber, Holothuria edulis. Two different free radical systems were used to evaluate antioxidant activity of H. edulis, stable radical l,l-diphenyl-2- picrylhydrazyl (DPPH.) and linoleic acid free radical mediated p-carotene bleaching. In addition, Folin-Ciocalteau reagent was used to determine the total phenolic content of the exfacts. The inhibitory effect of the exfacts on proliferation of MCF-7 (human breast adenocarcinoma) and TEI (Human esophageal squamous cell carcinoma) human cancer cell lines were demonstrated by 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Our data showed that the gallic acid equivalent (GAE) of the total phenolic content in aqueous extract (GAE : 7.33 mglg) is higher than an organic extact (GAE = 2.17 mglg). An aqueous extract also exhibited higher.antioxidant capacity by using DPPH assay (ICso = 2.04 mg/ml vs. 8.73 mlmL in organic extract), as well as by using p-carotene bleaching assay (Antioxidant Activity : 42.69 %o vs. 28.52 % in organic extract). On the other hand, an organic extact showed higher antiproliferative effect against MCF-7 and TEI cancer cells, giving ICso : 28.0 and 17.5 pdmL, respectively than aqueous extract, that gave ICso : 133.0 pilmL against MCF- '7 and76.0 pgmL against TEl. In conclusion, frndings of this study revealed that H. edulis as a promising source ofnatural antioxidants and anticancer products