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Poly (Butylene Adipate-Co-Terephthalate) and Poly (Ɛ-Caprolactone) and Their Bionanocomposites with Cellulose Nanocrystals: Thermo-Mechanical Properties and Cell Viability Study
No full textAlthough nanocomposites have recently attracted special interest in the tissue engineering area, due to their potential to reinforce scaffolds for hard tissues applications, a number of variables must be set prior to any clinical application. This manuscript addresses the evaluation of thermo-mechanical properties and of cell proliferation of cellulose nanocrystals (CNC), poly(butylene adipate-co-terephthalate) (PBAT), poly(ε-caprolactone) (PCL) films and their bionanocomposites with 2 wt% of CNC obtained by casting technique. Cellulose nanocrystals extracted from Balsa wood by acid hydrolysis were used as a reinforcing phase in PBAT and PCL matrix films. The films and pure CNC at different concentrations were cultured with osteoblasts MG-63 and the cell proliferation was assessed by AlamarBlue® assay. The thermal-mechanical properties of the films were evaluated by dynamic-mechanical thermal analysis (DMTA). It was found by DMTA that the CNC acted as reinforcing agent. The addition of CNCs in the PBAT and PCL matrices induced higher storage moduli due to the reinforcement effects of CNCs. The cell viability results showed that neat CNC favored osteoblast proliferation and both PBAT and PCL films incorporated with CNC were biocompatible and supported cell proliferation along time. The nature of the polymeric matrix or the presence of CNC practically did not affect the cell proliferation, confirming they have no in vitro toxicity. Such features make cellulose nanocrystals a suitable candidate for the reinforcement of biodegradable scaffolds for tissue engineering and biomedical applications
Chitosan/Nanocrystalline Cellulose Biocomposites Based on Date Palm (Phoenix Dactylifera L.) Sheath Fibers
No full textIn this study, nanocrystalline celluloses were used to enhance physical, mechanical and water vapor barrier properties of chitosan films for potential food packaging applications. Two different mineral acids (sulfuric and phosphoric) were used to extract nanocrystalline cellulose from date palm sheath fibers. The influence of cellulose I and cellulose II on the properties of the isolated nanocrystalline celluloses (e.g., yield, energy and length of intra- and intermolecular hydrogen bonds, and degree of substitution) were studied too. The characteristics of chitosan biocomposite film with phosphorylated nanocrystalline cellulose were compared to those with sulfated nanocrystalline cellulose. Results showed that besides cellulose polymorphism, the ionic ester groups on the surface of nanocrystalline cellulose is one of the factors influencing the physical, chemical, mechanical, and water vapor barrier properties in chitosan/nanocrystalline cellulose biocomposites
Synthesis of a Fully Biobased Polyfunctional Vinyl Oligomer and Their UV Cured Films Prepared via Thiol-ene Coupling
No full textIn this paper, a fully bio-based vinyl oligomer with high functionalities was successfully prepared from rapeseed oil by three modification steps: epoxidation of rapeseed oil, solvent-free and catalyst-free ring opening by 10-undecylenic acid followed by esterification with 10-undecenoyl chloride. Then, the renewable polymers were prepared by photo-polymerization of these modified vegetable oils with typical thiol monomers: pentaerythritol tetrakis (3-mercaptopropionate), pentaerythritol tris (3-mercaptopropionate) and 1,2-ethanedithiol. The synthesis of the vinyl oligomer was monitored by nuclear magnetic resonance and Fourier-transform infrared spectroscopy. The average number of the carbon-carbon double bonds of the resulting vinyl oligomer is high to be 7.2. The kinetic of thiol-ene photo-polymerization of vegetable oil- based vinyl oligomer was studied by FTIR-ATR analyses. In addition, the thermo-physical properties, thermal stability and solvent resistance of these UV cured films were characterized. The polymers from 1,2-ethanedithiol exhibit higher gel content, storage modulus and glass transition temperature than those from other thiol monomers due to the high crosslinking densities of the resulting polymers. All polymers show excellent thermal stability up to 290oC. The resulting polymers exhibit thermo-physical properties, excellent water resistance and thermals stability, which is promising to find application in coatings and adhesives
Effect of Stacking Sequences on the Mechanical and Damping Properties of Flax Glass Fiber Hybrid
No full textThe aim of this study is to show the interest of the mechanical and dynamical properties of glass-flax hybrid composites. Therefore, various staking sequences of glass-flax hybrid composites were manufactured and tested in free vibrations. The damping coefficients were identified by fitting the experimental responses of free-free bending vibrations. The obtained results show that the staking sequences and the position of flax fiber layers in the hybrid composites changed the properties, so a classification of different stacking sequences was established. In fact, the hybrid laminate made of two glass external layers placed on both sides of four flax layers is very interesting in term of its mechanical and damping properties. Indeed, it showed better specific bending modulus and loss factor than glass composites with proportions of 31 and 39%, respectively. A study of a structure of this composite has been made to validate the obtained results
Decision Support Strategy in Selecting Natural Fiber Materials for Automotive Side-Door Impact Beam Composites
No full textThe enforcement on sustainable design and environmental-friendly products has attracted the interest of researchers and engineers in the context of replacing metals and synthetic fibers with natural based fibers, especially in the automotive industry. However, studies on sustainable natural fiber material selection in the automotive industry are limited. Evaluation for the side-door impact beam was conducted by gathering product design specification from literature which amounted to seven criteria and it was forwarded to ten decision makers with automotive engineering and product design background for evaluation. The weightage required for decision-making was obtained using the Analytic Hierarchy Process (AHP) method based on six criteria. Following this, the best natural fiber materials to be used as reinforcement in polymer composites were selected using the VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method. The results using both the AHP and VIKOR method showed that kenaf was the best natural fiber for the side-door impact beam composites. The result showed the lowest VIKOR value, QA1 = 0.0000, which was determined to be within the acceptable advantage and acceptable stability conditions. It can be concluded that the application of integrated AHP-VIKOR method resulted in a systematic and justified solution towards the decision-making process
Strain Transfer Mechanism of Grating Ends Fiber Bragg Grating for Structural Health Monitoring
No full textThe grating ends bonding fiber Bragg grating (FBG) sensor has been widely used in sensor packages such as substrate type and clamp type for health monitoring of large structures. However, owing to the shear deformation of the adhesive layer of FBG, the strain measured by FBG is often different from the strain of actual matrix, which causes strain measurement errors. This investigation aims at improving the measurement accuracy of strain for the grating ends surface-bonded FBG. To fulfill this objective, a strain transfer equation of the grating ends bonding FBG is derived, and a theoretical model of the average strain transfer from the matrix to the optical fiber is developed. Moreover, parameters that influence the average strain transfer rate from the matrix to the optical fiber are analyzed. A selection scheme of bonding parameters by numerical simulation is provided, which is significantly advantageous over that of the grating bonding FBG. The theoretical equation is verified by finite element method (FEM). Compared with the existing model, the proposed model has higher measurement accuracy. Experimental tests are performed to validate the effectiveness of the proposed model on the equal-intensity cantilever beam, whose surface is attached to the bare FBG with grating ends bonding and strain gauge by using epoxy glue. The results show that there is a great agreement between the outcome of the bare FBG and that of the strain gauge, and the corrected strain is closer to the true strain. The proposed model provides a theoretical basis for the design of the grating ends surface-bonded FBG strain sensor for health monitoring of large structures
Coverless Information Hiding Based on the Molecular Structure Images of Material
Get PDFThe traditional information hiding methods embed the secret information by modifying the carrier, which will inevitably leave traces of modification on the carrier. In this way, it is hard to resist the detection of steganalysis algorithm. To address this problem, the concept of coverless information hiding was proposed. Coverless information hiding can effectively resist steganalysis algorithm, since it uses unmodified natural stego-carriers to represent and convey confidential information. However, the state-of-the-arts method has a low hidden capacity, which makes it less appealing. Because the pixel values of different regions of the molecular structure images of material (MSIM) are usually different, this paper proposes a novel coverless information hiding method based on MSIM, which utilizes the average value of sub-image’s pixels to represent the secret information, according to the mapping between pixel value intervals and secret information. In addition, we employ a pseudo-random label sequence that is used to determine the position of sub-images to improve the security of the method. And the histogram of the Bag of words model (BOW) is used to determine the number of sub-images in the image that convey secret information. Moreover, to improve the retrieval efficiency, we built a multi-level inverted index structure. Furthermore, the proposed method can also be used for other natural images. Compared with the state-of-the-arts, experimental results and analysis manifest that our method has better performance in anti-steganalysis, security and capacity
Effect of Different Shapes of Conformal Cooling Channel on the Parameters of Injection Molding
Get PDFCooling system improvement is important in injection molding to get better quality and productivity. The aim of this paper was to compare the different shapes of the conformal cooling channels (CCC) with constant surface area and CCC with constant volume in injection molding using Mold-flow Insight 2016 software. Also the CCC results were compared with conventional cooling channels. Four different shapes of the CCC such as circular, elliptical, rectangular and semi-circular were proposed. The locations of the cooling channels were also kept constant. The results in terms of cooling time, cycle time reduction and improvement in quality of the product shows that no significant effect of CCC’s shapes when surface area of CCC kept constant. On the other hand the rectangular CCC shows better result as compared to other shapes of CCC when volume of CCC were kept constant
Securing Display Path for Security-Sensitive Applications on Mobile Devices
Get PDFWhile smart devices based on ARM processor bring us a lot of convenience, they also become an attractive target of cyber-attacks. The threat is exaggerated as commodity OSes usually have a large code base and suffer from various software vulnerabilities. Nowadays, adversaries prefer to steal sensitive data by leaking the content of display output by a security-sensitive application. A promising solution is to exploit the hardware visualization extensions provided by modern ARM processors to construct a secure display path between the applications and the display device. In this work, we present a scheme named SecDisplay for trusted display service, it protects sensitive data displayed from being stolen or tampered surreptitiously by a compromised OS. The TCB of SecDisplay mainly consists of a tiny hypervisor and a super light-weight rendering painter, and has only ~1400 lines of code. We implemented a prototype of SecDisplay and evaluated its performance overhead. The results show that SecDisplay only incurs an average drop of 3.4%
Localization Algorithm of Indoor Wi-Fi Access Points Based on Signal Strength Relative Relationship and Region Division
Get PDFPrecise localization techniques for indoor Wi-Fi access points (APs) have important application in the security inspection. However, due to the interference of environment factors such as multipath propagation and NLOS (Non-Line-of-Sight), the existing methods for localization indoor Wi-Fi access points based on RSS ranging tend to have lower accuracy as the RSS (Received Signal Strength) is difficult to accurately measure. Therefore, the localization algorithm of indoor Wi-Fi access points based on the signal strength relative relationship and region division is proposed in this paper. The algorithm hierarchically divide the room where the target Wi-Fi AP is located, on the region division line, a modified signal collection device is used to measure RSS in two directions of each reference point. All RSS values are compared and the region where the RSS value has the relative largest signal strength is located as next candidate region. The location coordinate of the target Wi-Fi AP is obtained when the localization region of the target Wi-Fi AP is successively approximated until the candidate region is smaller than the accuracy threshold. There are 360 experiments carried out in this paper with 8 types of Wi-Fi APs including fixed APs and portable APs. The experimental results show that the average localization error of the proposed localization algorithm is 0.30 meters, and the minimum localization error is 0.16 meters, which is significantly higher than the localization accuracy of the existing typical indoor Wi-Fi access point localization methods