• Structure and blood compatibility of highly oriented PLA/MWNTs composites produced by solid hot drawing

      Li, Z.; Zhao, X.; Ye, L.; Coates, Philip D.; Caton-Rose, Philip D.; Martyn, Michael T. (2014-02-12)
      Highly oriented poly(lactic acid) (PLA)/multi-walled carbon nanotubes (MWNTs) composites were fabricated through solid hot drawing technology in an effort to improve the mechanical properties and blood biocompatibility of PLA as blood-contacting medical devices. It was found that proper MWNTs content and drawing orientation can improve the tensile strength and modulus of PLA dramatically. With the increase in draw ratio, the cold crystallization peak became smaller, and the glass transition and the melting peak of PLA moved to high temperature, while the crystallinity increased, and the grain size decreased, indicating the stress-induced crystallization of PLA during drawing. MWNTs showed a nucleation effect on PLA, leading to the rise in the melting temperature, increase in crystallinity and reduction of spherulite size for the composites. Moreover, the intensity of (002) diffraction of MWNTs increased with draw ratio, indicating that MWNTs were preferentially aligned and oriented during drawing. Microstructure observation demonstrated that PLA matrix had an ordered fibrillar bundle structure, and MWNTs in the composite tended to align parallel to the drawing direction. In addition, the dispersion of MWNTs in PLA was also improved by orientation. Introduction of MWNTs and drawing orientation could significantly enhance the blood compatibility of PLA by prolonging kinetic clotting time, reducing hemolysis ratio and platelet activation.
    • Structure and blood compatibility of highly oriented poly(l-lactic acid) chain extended by ethylene glycol diglycidyl ether

      Li, Z.; Zhao, X.; Ye, L.; Coates, Philip D.; Caton-Rose, Philip D.; Martyn, Michael T. (2015-01-15)
      Highly-oriented poly(l-lactic acid) (PLLA) with fibrillar structure and micro-grooves was fabricated through solid hot drawing technology for further improving the mechanical properties and blood biocompatibility of PLLA as blood-contacting medical devices. In order to enhance the melt strength and thus obtain high orientation degree, PLLA was first chain extended with ethylene glycol diglycidyl ether (EGDE). The extending degree as high as 25.79 mol% can be obtained at 0.7 wt% EGDE content. The complex viscosity, storage and viscous modulus for chain extended PLLA were improved resulting from the enhancement of molecular entanglement, and consequently higher draw ratio can be achieved during the subsequent hot stretching. The tensile strength and modulus of PLLA were improved dramatically by stretching. The stress-induced crystallization of PLLA occurred during drawing. The interfacial tension (γs·blood) between PLLA surface and blood decreased by chain extension and molecular orientation, indicating the weakened interaction between bioactive substance in the blood and the surface of PLLA. Modification and orientation could significantly enhance the blood compatibility of PLLA by prolonging clotting time and decreasing hemolysis ratio, protein adsorption and platelet activation. The bionic character of oriented PLLA and its anti-coagulation mechanism were tried to be explored.
    • Structure and blood compatibility of highly oriented poly(lactic acid)/thermoplastic polyurethane blends produced by solid hot stretching

      Zhao, X.; Ye, L.; Coates, Philip D.; Caton-Rose, Philip D. (2013-08-27)
      Highly oriented poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends were fabricated through solid hot stretching technology in an effort to improve the mechanical properties and blood biocompatibility of PLA as blood-contacting medical devices. It was found that the tensile strength and modulus of the blends can be improved dramatically by stretching. With the increase of draw ratio, the cold crystallization peak became smaller, and the glass transition and the melting peak moved to high temperature, while the crystallinity increased, and the grain size of PLA decreased, indicating of the stress-induced crystallization during drawing. The oriented blends exhibited structures with longitudinal striations which indicate the presence of micro-fibers. TPU phase was finely and homogeneously dispersed in the PLA, and after drawing, TPU domains were elongated to ellipsoid. The introduction of TPU and orientation could enhance the blood compatibility of PLA by prolonging kinetic clotting time, and decreasing hemolysis ratio and platelet activation.
    • Structure and functions of the ventral tube of the clover springtail Sminthurus viridis (Collembola Sminthuridae)

      Chen, C-G.; Chen, T.; Hua, B-Z.; Wan, Tao Ruan (2019-01-29)
      Springtails (Collembola) are unique in Hexapoda for bearing a ventral tube (collophore) on the first abdominal segment. Although numerous studies have been conducted on the functions of the ventral tube, its fine structure has not been thoroughly elucidated to date. In this paper, we observed the jumping behavior of the clover springtail Sminthurus viridis (Linnaeus, 1758) and dissected the ventral tube using light microscopy to elucidate the fine structure and the possible function of the ventral tube. The results show that a pair of eversible vesicles can be extended from the apical opening of the ventral tube. The eversible vesicles are furnished with numerous small papillae, and can be divided into a basal part and a distal part. The eversible vesicles have a central lumen connected to the tiny papillae and leading to the body cavity. The eversible vesicles can reach any part of the body, and may serve as following functions: (a) absorbing moisture; (b) uptaking water; (c) cleaning the body surface; and (d) fastening the body on a smooth surface.
    • Structure and Property of Microinjection Molded Poly(lactic acid) with High Degree of Long Chain Branching

      Zhao, Z.-G.; Yang, Q.; Coates, Philip D.; Whiteside, Benjamin R.; Kelly, Adrian L.; Huang, Y.-J.; Wu, P.-P. (2018-08-22)
      Long chain branches (LCB) are successfully grafted to linear poly(lactic acid) (PLA) using functional group reactions with pentaerythritol triacrylate (PETA) and tetraethylthiuram disulfide (TETDS). Results show a high branching degree of PLA (∼49.5%) can be effectively obtained with adding only 1 wt % PETA, contributing remarkably to enhancing strain hardening. The density of the nuclei formed during nonisothermal crystallization for LCB-PLA samples is markedly increased contrasted with PLA, resulting in significantly enhancing crystallinity from 13.3% to 41%, the onset crystallization temperature (∼20 °C), and the crystallization rate. Interestingly, compared with mini-injection molding, the elevated wall shear rates (and corresponding shear stresses) prove to be beneficial to the creation of special crystalline morphologies (β-crystal form) and oriented structures under microinjection molding conditions, resulting in the improvement of tensile strength by ∼45 MPa.
    • Structure evolution and orientation mechanism of long-chain-branched poly (lactic acid) in the process of solid die drawing

      Li, J.; Li, Z.; Ye, L.; Zhao, X.; Coates, Philip D.; Caton-Rose, Philip D. (2017-05)
      Highly oriented long-chain-branched poly (lactic acid) (LCB-PLA) was prepared and the structure evolution was studied in the process of solid die drawing by compared with poly (lactic acid) (PLA). During drawing, samples underwent not only die drawing process but also free drawing process. Drawing speed presented a prominent effect on the free drawing process, while die thickness showed a more obvious influence on the die drawing process. For PLA, free drawing process mainly contributed to its final orientation degree and crystallinity, and thus the mechanical properties of PLA were greatly influenced by drawing speed. However, for LCB-PLA, die drawing process made a greater contribution to the final orientation degree and crystallinity, and its mechanical properties were mainly affected by die thickness. Under the same drawing condition, the tensile strength and modulus of LCB-PLA were always higher than those of PLA, and reached up to 228 MPa and 7.2 GPa, respectively, which basically met the requirement for born fixation materials. Samples which only underwent die drawing showed obvious “sandwich” structure, and the thickness of the oriented skin layer for LCB-PLA was thicker than that for PLA, suggesting that shear-induced orientation can be easily retained due to the enhanced entanglement between long branched chains. After drawing, LCB-PLA samples showed smaller lamellae size (Llateral) but larger long period (Lac) compared with PLA, suggesting that the low chain mobility restricted the motion of chain slipping of LCB-PLA and thus resulted in the fragmentation of neighboring crystal lamella by chain stretched-out.
    • Strut-and-tie model based on crack band theory for deep beams

      Yang, Keun-Hyeok; Ashour, Ashraf F. (2011-10)
      A simplified strut-and-tie model including size effect based on the crack band theory is proposed to evaluate the shear capacity of deep beams. Concrete struts are idealized as uniformly tapered prismatic members with a stress relief strip whereas horizontal and vertical shear reinforcements are assumed to be an internally statically indeterminate system. The shear transfer mechanism of concrete and shear reinforcement is then driven by using the energy equilibrium in the stress relief strip and crack band zone of concrete struts. The shear capacity predictions of deep beams obtained from the present models are in better agreement with 637 test results than those determined from strut-and-tie models proposed by ACI 318-08, EC-2, and Tan and Cheng. In addition, the trend of the shear capacity of deep beams against different parameters as predicted by the present models has a consistent agreement with that observed from experimental results. In particular, the present model shows that the normalized shear capacity of deep beams is proportional to (h)−0.25, where h = section overall depth.
    • A study into the use of the process failure mode and effects analysis (PFMEA) in the automotive industry in the UK.

      Johnson, K.G.; Khan, M. Khurshid (2003)
      This paper describes a study made into the application of PFMEA in a sample of suppliers to an automotive manufacturing company in the UK. The objectives of the research were to study the concerns and inhibitors that PFMEA users have, establish how the effectiveness could be determined, evaluate PFMEA use as a problem prevention technique and to recommend best practice. The research methodology included the use of interviews, workshops and questionnaires involving 150 quality approved suppliers. Conclusions were drawn to show that the PFMEA technique has its limitations, caused by a number of issues. Recommendations for overcoming these limitations of the PFMEA process are presented.
    • A study of commercial vehicle brake judder transmission using multi-body dynamic analysis

      Hussain, Khalid; Yang, S.H.; Day, Andrew J. (2007)
      Braking-induced forced vibration, known as brake judder in road vehicles, causes dissatisfaction to drivers and passengers and also damage and possible early failure in components and systems. In this paper, the transmission of judder vibration from the point of generation (the brake friction pair) through the vehicle structure to the driver is investigated for the particular case of a heavy commercial vehicle. The investigation uses a computer simulation multi-body dynamic model based on the automatic dynamic analysis of mechanical systems software to identify any characteristics of the vehicle suspension design that might influence the vibration transmission from the wheel to the driver. The model uses a simplified rigid chassis and cab to lump the chassis parameters, so that the investigation can focus on the front axle/suspension design, which is a beam axle leaf spring arrangement, and the rear axle/suspension assembly, which is a tandem axle bogie design. Results from the modelling indicate that brake judder vibration is transmitted to the chassis of the vehicle through a leaf spring `wind-up¿ mode and a `walking¿ mode associated with the rear tandem axle. Of particular interest is the longitudinal vibration transmitted through the chassis, since this creates a direct vibration transmission path to the cab and driver. The simulation results were compared with the previously published experimental work on the same design of commercial vehicle, and agreement between the predicted and the measured vibration characteristics and frequencies was found. It is concluded that the rear suspension design parameters could affect the transmission of brake judder vibration to the cab and driver and that a tandem rear axle offers some design opportunity to control the transmission of brake judder vibrations from the wheel to the cab and driver. Given that brake judder has so far defied all attempts to eliminate completely from vehicle brake systems, this is potentially an important opportunity.
    • Study of industrial naphtha catalytic reforming reactions via modelling and simulation

      Zakari, A.Y.; Aderemi, B.O.; Patel, Rajnikant; Mujtaba, Iqbal M. (2019-04)
      Steady state and dynamic modelling and simulation of catalytic reforming unit of Kaduna Refining & Petrochemical Company, NNPC (Nigeria) was carried to find out the behaviour of the reactions under both steady and unsteady state conditions. The basic model together with kinetic and thermodynamic parameters and properties were taken from the literature but is developed in gPROMS (an equation oriented modelling software) model building platform for the first time rather than in MATLAB or other modelling platform used by other researchers in the past. The simulation was performed using gPROMS and the predictions were validated against those available in the literature. The validated model was then used to monitor the behaviour of the temperature, concentrations of parafins, naphthenes and aromatics with respect to both time and height of the reactor of the industrial refinery of Nigeria. Hydrogen yield, Research octane number (RON) and temperature profiles are also reported. The components behave similarly in terms of reactions in the reactors but the time to attain quasi-steady state is different. The results are in good agreement with the industrial plant data.
    • Study of injection moulded long glass fibre-reinforced polypropylene and the effect on the fibre length and orientation distribution

      Parveen, Bushra; Caton-Rose, Philip D.; Costa, F.; Jin, X.; Hine, P. (2014)
      Long glass fibre (LGF) composites are extensively used in manufacturing to produce components with enhanced mechanical properties. Long fibres with length 12 to 25mm are added to a thermoplastic matrix. However severe fibre breakage can occur in the injection moulding process resulting in shorter fibre length distribution (FLD). The majority of this breakage occurs due to the melt experiencing extreme shear stress during the preparation and injection stage. Care should be taken to ensure that the longer fibres make it through the injection moulding process without their length being significantly degraded. This study is based on commercial 12 mm long glass-fibre reinforced polypropylene (PP) and short glass fibre Nylon. Due to the semi-flexiable behaviour of long glass fibres, the fibre orientation distribution (FOD) will differ from the orientation distribution of short glass fibre in an injection molded part. In order to investigate the effect the change in fibre length has on the fibre orientation distribution or vice versa, FOD data was measured using the 2D section image analyser. The overall purpose of the research is to show how the orientation distribution chnages in an injection moulded centre gated disc and end gated plaque geometry and to compare this data against fibre orientation predictions obtained from Autodesk Moldflow Simulation Insight.
    • A study of the quadratic molecular stress function constitutive model in simulation

      Olley, Peter (2004)
      Constitutive models that conform to separable KBKZ specification have been shown to fit steady-state strain hardening rheological data in planar and uniaxial elongational flows, but with inaccuracy in the rate of strain hardening. The single parameter Molecular Stress Function model of Wagner [Rheol. Acta, 39 (2000), 97-109] has been shown to accurately fit the rise-rate in experimental data for a number of strain hardening and strain softening materials. We study this models accuracy against the well characterised IUPAC LDPE data, and present a method for full implementation of this model for flow solution which is suitable for incorporating into existing separable KBKZ software. A new method for particle tracking in arbitrarily aligned meshes, which is efficient and robust, is given. The Quadratic Molecular Stress Function (QMSF) model is compared to existing separable KBKZ based models, including one which is capable of giving planar strain hardening; the QMSF is shown to fit experimental rheological and contraction flow data more convincingly. The issue of `negative correction pressures¿ notable in some Doi-Edwards based models is addressed. The cause is identified, and leads to a logical method of calculation which does not give these anomalous results.
    • Study on antenna mutual coupling suppression using integrated metasurface isolator for SAR and MIMO applications

      Alibakhshikenari, M.; Virdee, B.S.; See, C.H.; Abd-Alhameed, Raed A.; Falcone, F.; Andujar, A.; Anguera, J.; Limiti, E. (2018-09-27)
      A metasurface based decoupling structure that is composed of a square-wave slot pattern with exaggerated corners that is implemented on a rectangular microstrip provides high-isolation between adjacent patch antennas for Synthetic Aperture Radar (SAR) and Multi-Input-Multi-Output (MIMO) systems. The proposed 1×2 symmetric array antenna integrated with the proposed decoupling isolation structure is designed to operate at ISM bands of X, Ku, K, and Ka. With the proposed mutual coupling suppression technique (i) the average isolation in the respective ISM bands listed above is 7 dB, 10 dB, 5 dB, and 10 dB; and (ii) edge-to-edge gap between adjacent radiation elements is reduced to 10 mm (0.28λ). The average antenna gain improvement with the metasurface isolator is 2 dBi.
    • Study on isolation improvement between closely-packed patch antenna arrays based on fractal metamaterial electromagnetic bandgap structures

      Alibakhshikenari, M.; Virdee, B.S.; See, C.H.; Abd-Alhameed, Raed A.; Ali, Ammar H.; Falcone, F.; Limiti, E. (2018-11)
      A decoupling metamaterial (MTM) configuration based on fractal electromagnetic-bandgap (EMBG) structure is shown to significantly enhance isolation between transmitting and receiving antenna elements in a closely-packed patch antenna array. The MTM-EMBG structure is cross-shaped assembly with fractal-shaped slots etched in each arm of the cross. The fractals are composed of four interconnected-`Y-shaped' slots that are separated with an inverted-`T-shaped' slot. The MTM-EMBG structure is placed between the individual patch antennas in a 2 × 2 antenna array. Measured results show the average inter-element isolation improvement in the frequency band of interest is 17, 37 and 17 dB between radiation elements #1 & #2, #1 & #3, and #1 & #4, respectively. With the proposed method there is no need for using metallic-via-holes. The proposed array covers the frequency range of 8-9.25 GHz for X-band applications, which corresponds to a fractional-bandwidth of 14.5%. With the proposed method the edge-to-edge gap between adjacent antenna elements can be reduced to 0.5λ 0 with no degradation in the antenna array's radiation gain pattern. Across the array's operating band, the measured gain varies between 4 and 7 dBi, and the radiation efficiency varies from 74.22 and 88.71%. The proposed method is applicable in the implementation of closely-packed patch antenna arrays used in SAR and MIMO systems.
    • Study on specific absorption rate

      Asif, Rameez; Abd-Alhameed, Raed A.; Bin-Melha, Mohammed S.; Qureshi, A.; See, Chan H.; Abdulraheem, Yasir I.; Mapoka, Trust T.; Noras, James M. (2014)
      In the past fifty years it has been clearly identified that the presence of biological tissues effect the performance of the antenna and considerable effort has been made to improve the characteristics of the mobile phone antenna's but very less effort has been put in to evaluate the effects of the radio frequency and energy absorption by the biological organisms and their effect. In this work as part of a bigger work package we have evaluated the effects of the handset orientation on the values of SAR and radiation efficiency as well as the effect of the distance upon these values. The study has produced some very interesting results showing that the most common way of holding the mobile phone i.e. microphone close to the mouth produces the highest SAR values.
    • A study proposing a data model for a dementia care mapping (DCM) data warehouse for potential secondary uses of dementia care data

      Khalid, Shehla; Small, Neil A.; Neagu, Daniel; Surr, C. (2019-01-01)
      Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. There is growing emphasis on sharing and reusing dementia care-related datasets to improve the quality of dementia care. Consequently, there is a need to develop data management solutions for collecting, integrating and storing these data in formats that enhance opportunities for reuse. Dementia Care Mapping (DCM) is an observational tool that is in widespread use internationally. It produces rich, evidence-based data on dementia care quality. Currently, that data is primarily used locally, within dementia care services, to assess and improve quality of care. Information-rich DCM data provides opportunities for secondary use including research into improving the quality of dementia care. But an effective data management solution is required to facilitate this. A rationale for the warehousing of DCM data as a technical data management solution is suggested. The authors also propose a data model for a DCM data warehouse and present user-identified challenges for reusing DCM data within a warehouse.
    • Submerged flexible vegetation impact on open channel flow velocity distribution: An analytical modelling study on drag and friction

      Pu, Jaan H.; Hussain, Awesar; Guo, Yakun; Vardakastanis, Nikolaos; Hanmaiahgari, P.R.; Lam, Dennis (2019-06)
      In this paper, an analytical model that represents the streamwise velocity distribution for open channel flow with submerged flexible vegetation is studied. In the present vegetated flow modelling, the whole flow field has been separated into two layers vertically: a vegetated layer and a non-vegetated free-water layer. Within the vegetated layer, an analysis of the mechanisms affecting water flow through flexible vegetation has been conducted. In the non-vegetated layer, a modified log-law equation that represents the velocity profile varying with vegetation height has been investigated. Based on the studied analytical model, a sensitivity analysis has been conducted to assess the influences of the drag and friction coefficients on the flow velocity. The investigated ranges of drag and friction coefficients have also been compared to published values. The findings suggest that the drag and friction coefficient values are non-constant at different depths and vegetation densities, unlike the constant values commonly suggested in literature. This phenomenon is particularly clear for flows with flexible vegetation, which is characterised by large deflection.
    • Subsystems of a finite quantum system and Bell-like inequalities

      Vourdas, Apostolos (2014)
      The set of subsystems Sigma(m) of a finite quantum system Sigma(n) with variables in Z(n) together with logical connectives, is a Heyting algebra. The probabilities tau(m vertical bar rho(n)) Tr vertical bar B(m)rho(n)] (where B(m) is the projector to Sigma(m)) are compatible with associativity of the join in the Heyting algebra, only if the variables belong to the same chain. Consequently, contextuality in the present formalism, has the chains as contexts. Various Bell-like inequalities are discussed. They are violated, and this proves that quantum mechanics is a contextual theory.