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Development of Cardanol-Based Polyol via Click Chemistry and Crosslinking with Melamine Formaldehyde Resin for Coating Applications
Get PDFThe research work presented in this article deals with the synthesis of cardanol-based polyol and its curing with hexabutoxymethyl melamine (HBMM) for application in coatings. Cardanol-based polyol was prepared via thiol-ene click reaction using thioglycerol. Unsaturation present in the long chain of cardanol was successfully utilized to synthesize polyol via thiol-ene coupling. The reaction was carried out between cardanol and thioglycerol in the presence of Irgacure 184 (photoinitiator) and 1,8-Diazabicyclo[5.4.0]undec-7-ene (catalyst) under UV light for 12 h at 80 °C. After completion of the reaction, one mole of thioglycerol was successfully added across the double bond of a fatty chain of cardanol and confirmed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy and hydroxyl and iodine values were determined. Furthermore, the polyol thus prepared was cured with commercial HBMM in various proportions, such as 1:0.6, 1:0.8 and 1:1, on an equivalent basis. The coatings were then characterized for mechanical, chemical, optical, thermal and anticorrosive properties. It was observed that coatings exhibited excellent performance properties as compared to that of its acrylic counterpart
Polyisocyanuratoesters: Renewable Linear Polyesters with High Flame Retardancy
No full textBiobased urea nowadays attracts increasing attention as a biomass resource with giant potential, which benefits from the development of biobased ammonia and ecological sanitation system. Urea is an ideal feedstock for chemical industry and developing new urea-based pol ymer materials can take advantage of the urea resource. In this work, a class of renewable linear polyesters, nam ely polyisocyanuratoesters (PICEs) were synthesized from a urea-based monomer bis(2-carbomethoxyethyl) isocyanurate and biobased aliphatic diols. Compared with conventional aliphatic polyesters, PICEs containing isocyanurate rings in the polymer chain backbone exhibit outstanding flame retardancy that both PICE-4 (the number ‘4’ refers to the number of methylene in diols, e.g. 4 for butylene and 6 for hexylene) and PICE-6 have hig h limiting oxygen index values over 30%. In the UL 94 tests, PICE-6 reaches V-1 rating; while V-2 is found for PI CE-10. All PICEs exhibit similar pyrolysis behavior that the temperatures of 5% weight loss are around 320°C. PI CEs are found to have glass transition among 20°C-45°C. No crystallization behavior is observed without annealing except for PICE-10, which can crystallize even at room temperature
The Analysis of Wall Shear Stress Modulated by Acute Exercise in the Human Common Carotid Artery with an Elastic Tube Model
Get PDFAssessment of the magnitude and pattern of wall shear stress (WSS) in vivo is the prerequisite for studying the quantitative relationship between exercise-induced WSS and arterial endothelial function. In the previous studies, the calculation of the WSS modulated by exercise training was primarily based upon the rigid tube model, which did not take non-linear effects of vessel elastic deformation into consideration. In this study, with an elastic tube model, we estimated the effect of a bout of 30-minute acute cycling exercise on the WSS and the flow rate in the common carotid artery according to the measured inner diameter, center-line blood flow velocity, heart rates and the brachial blood pressures before and after exercise training. Furthermore, the roles of exercise-induced arterial diameter and blood flow rate in the change of WSS were also determined. The numerical results demonstrate that acute exercise significantly increases the magnitudes of blood flow rate and WSS. Moreover, the vessel elastic deformation is a non-negligible factor in the calculation of the WSS induced by exercise, which generates greater effects on the minimum WSS than the maximum WSS. Additionally, the contributions of exercise-induced variations in blood flow rate and diameter are almost identical in the change of the mean WSS
Hemodynamics of Enhanced External Counterpulsation with Different Coronary Stenosis
Get PDFEnhanced external counterpulsation (EECP) is able to treat myocardial ischemia, which is usually caused by coronary artery stenosis. However, the underlying mechanisms regarding why this technique is effective in treating myocardial ischemia remains unclear and there is no patient-specific counterpulsation mode for different rates of coronary artery stenosis in clinic. This study sought to investigate the hemodynamic effect of varied coronary artery stenosis rates when using EECP and the necessity of adopting targeted counterpulsation mode to consider different rates of coronary artery stenosis. Three 3-dimensional (3D) coronary models with different stenosis rates, including 55% (Model 1), 65% (Model 2), and 75% (Model 3), were generated, then coupled with a 0-dimensional (0D) lumped parametric model of the blood circulatory system. EECP was applied to the 0D/3D coupled models to study the hemodynamic response of the coronary artery. Under the same counterpulsation mode, the ratio of diastolic blood pressure to systolic blood pressure of 3 models during counterpulsation was 1.4, and the cardiac output and coronary artery flow rate increased significantly. The low wall shear stress (WSS) and high oscillatory shear index (OSI) areas were mainly located at the posterior end of the stenosis and coronary artery bifurcation. Moreover, with an increase in the rate of coronary artery stenosis, the increased percentage of flow rate through the coronary artery stenosis and area-averaged WSS decreased. The geometric multiscale model in this study can be used to effectively simulate the hemodynamic characteristics of cardiovascular system following the application of EECP. Local precise hemodynamic effect of the coronary artery stenosis can be observed. It was found from the hemodynamic factors that the coronary artery with lower stenosis rate more likely led to better vascular endothelial remodeling. Thus, it is necessary to adopt patient-specific counterpulsation mode accounting for different condition of coronary artery stenosis
Influence of Geometric Design Variable and Bone Quality on Stress Distribution for Zirconia Dental Implants-A 3D Finite Element Analysis
Get PDFThis study aims to investigate the effects of variable thread pitch on stress distribution in bones of different bone qualities under two different loading conditions (Vertical, and Horizontal) for a Zirconia dental implant. For this purpose, a three dimensional finite element model of the mandibular premolar section and three single threaded implants of 0.8 mm, 1.6 mm, 2.4 mm pitch was designed. Finite element analysis software was used to develop the model and three different bone qualities (Type II, Type III, and Type IV) were prepared. A vertical load of 200 N, and a horizontal load of 100 N was applied at the abutment surface. The von-Mises stress criterion was used to analyze the results. The crestal bony-region of the mandibular section was subjected to maximum von-Mises stresses for all bone qualities. The outcome of this study indicates that, horizontal loading had more influence on stress distribution than vertical loading, regardless of the bone qualities and pitch values. Varying the dental implant pitch does not cause any decrease in stress distribution in bone, when the bone density decreased. The study concluded that implants with minimum pitch values induced lesser stress values at the implant-bone interface
Modeling and Control Strategy of Built-in Skin Effect Electric Tracing System
Get PDFIn order to ensure the safety of fluid flow in deep-water submarine pipelines, a safe and energy-saving built-in skin effect electric heat tracing technology was adopted as the thermal management strategy. The magnetic field distribution of built-in skin effect heating system is analyzed based on the mechanism of built-in skin effect heating system, so as to obtain the equivalent circuit model of built-in skin effect electric heating system. Meanwhile, heating power is introduced as an intermediate variable to establish the relationship between power supply frequency and built-in skin effect heating temperature. Aiming at the skin effect electric heating system, an Active Disturbance Rejection Control (ADRC) method is proposed macroscopically based on Hammerstein model. Firstly, the parameters of Hammerstein model are identified and optimized using the auxiliary model and standard particle swarm optimization algorithm. Then, the ADRC controller of linear link is designed, and the required heating temperature is used to solve the intermediate variable heating power. Finally, inversion calculation is applied in the nonlinear link to solve the required power frequency, so as to achieve the purpose of efficient heating and verify the feasibility and effectiveness of control strategy through simulation
acSB: Anti-Collision Selective-Based Broadcast Protocol in CR-AdHocs
Get PDFAs a fundamental operation in ad hoc networks, broadcast could achieve efficient message propagations. Particularl y in the cognitive radio ad hoc network where unlicensed users have different sets of available channels, broadcasts are carried out on multiple channels. Accordingly, channel selection and collision avoidance are challenging issues to balance the efficiency against the reliability of broadcasting. In this paper, an anti-collision selective broadcast protocol, called acSB, is proposed. A channel selection algorithm based on limited neighbor information is considered to maximize success rates of transmissions once the sender and receiver have the same channel. Moreover, an anti-collision scheme is adopted to avoid simultaneous rebroadcasts. Consequently, the proposed broadcast acSB outperforms other approaches in terms of smaller transmission delay, higher message reach rate and fewer broadcast collisions evaluated by simulations under different scenarios
Chemical Modification of Cassava Starch by Transesterification Using Vegetable Oil/Aluminum Chloride
No full textChemical modification of cassava starch by transesterification of a vegetable oil (palm kernel oil) using aluminum chloride as a Lewis acid catalyst was achieved under relatively mild conditions (temperature 60–110 °C; atmospheric pressure). The reaction was carried out without any additional solvent. The modified starch was characterized by degree of substitution (DS), FTIR, X-ray diffraction and thermal analysis. DS of 0.09 to 0.53 were obtained. The cassava starch presented an X-ray diffraction pattern of a type A starch. X-ray analyses showed that the reaction did not significantly affect the crystallinity of starch. The modified starch films (MStF) adsorbed less water than the reference native starch film (NStF) at all the relative humidities investigated. The MStF were also less soluble in water. The tensile tests showed an increase of the strength and a decrease of the flexibility of MStF compared to the reference NStF. The results showed that this chemical route could be used to increase the water resistance of starch-based materials
Exact Solutions of the Cubic Duffing Equation by Leaf Functions under Free Vibration
No full textExact solutions of the cubic Duffing equation with the initial conditions are presented. These exact solutions are expressed in terms of leaf functions and trigonometric functions. The leaf function r=sleafn(t) or r=cleafn(t) satisfies the ordinary differential equation dx2/dt2=-nr2n-1. The second-order differential of the leaf function is equal to -n times the function raised to the (2n-1) power of the leaf function. By using the leaf functions, the exact solutions of the cubic Duffing equation can be derived under several conditions. These solutions are constructed using the integral functions of leaf functions sleaf2(t) and cleaf2(t) for the phase of a trigonometric function. Since the leaf function and the trigonometric function are used in combination, a highly accurate solution of the Duffing equation can be easily obtained based on the data of leaf functions. In this study, seven types of the exact solutions are derived from leaf functions; the derivation of the seven exact solutions is detailed in the paper. Finally, waves obtained by the exact solutions are graphically visualized with the numerical results
Numerical Study of Natural Convection in a Right Triangular Enclosure with Sinusoidal Hot Wall and Different Configurations of Cold Walls
Get PDFThe numerical investigation of present work examines the free convection cooling of the base hot wall of a right-angled triangular cavity filled with water. The outline of the base wall is changed from smooth to sinusoidal shapes with different heights. The width (w) of the wave is fixed at 0.2 L and the height (h) of the sinusoidal shape wall is varied from 0.01 H to 0.03 H. The hot wall is cooled from the partially active side and inclined walls which are detached from the middle and structured in four different configurations namely AB, BC, AD, and CD. The problem has been solved to explore the effect of constrained parameters such as a sinusoidal hot wall, partially active cold walls’ configurations and Rayleigh number (105-107) on fluid flow and heat transfer. The study reveals that the flow pattern of the fluid is affected due to the configurations of cold walls and with the increase of Rayleigh number. The enhancement in heat transfer rate, in fact, is found to be more pronounced for the amalgamation of the sinusoidal hot wall and the cold walls configuration AB for all Rayleigh number. However, the blends of these are appealing eloquently at low Rayleigh number