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91.
In view of environmental footprints and growing demand for green energy materials, employing biomass by eliminating lignin and hemicellulose has been topic of recent interests due to their applications in food packaging, textile, automobile, and polymer industries. Herein, we report on optimization of the cellulose extraction (removal of lignin and hemicellulose) from agro-waste (wheat straw) by the response surface methodology (RSM), where, the Box Behnken Design has been implemented to study the effect of sodium hydroxide/sodium hypochlorite amount, temperature, and time on the extraction process. Fourier transform infrared spectroscopy, X-ray diffraction study, and thermal degradation analysis indicate the successful isolation of cellulose with maximum (56%) removal of hemicellulose and lignin under optimal conditions. Furthermore, nano-indenter analysis and tensile strength have been examined for cellulose/poly(lactide) biocomposites at different wt.% of cellulose, which indicated better tensile strength (28.15 MPa), tensile modulus (2430.24 MPa), and elongation at break (1.89%) as compared to intrinsic poly(lactide). Such studies on the cellulose extraction with optimized conditions and their mechanically stable biocomposites will pave the way for their utilization in polymer industrial applications. 相似文献
92.
Chun Fah Mok Yern Chee Ching Noor Azuan Abu Osman Farina Muhamad Mohd Usman Mohd Junaidi Jia H. Choo 《应用聚合物科学杂志》2020,137(35):49044
In the quest on improving composite formulations for environmental sustainability, maleic acid (MA) cross-linked poly(vinyl alcohol) (PVA)-α-chitin composites reinforced by oil palm empty fruit bunch fibers (OPEFB)-derived nanocellulose crystals (NCC) had been successfully prepared. Based on the Fourier transform infrared (FTIR) spectroscopic analysis, it was proven that molecular interactions of the cross-linker to the polymeric networks was through conjugated ester linkage. Differential scanning calorimetry (DSC) showed that the influence of MA was minimal toward crystallization in the PVA/chitin/NCC composite. Maximum tensile strength, elongation at break and Young's modulus of the respective PVA/chitin/NCC composites were achieved at different content of MA, dependent on the PVA/chitin mass ratio. Among all compositions, a maximum Young's modulus was achieved at 30 wt% MA loading in PVA/chitin-30/NCC, amounting to 2,413.81 ± 167.36 MPa. Moreover, the mechanical properties and selected physicochemical properties (swelling, gel content, and contact angle) of the PVA/chitin/NCC composites could be tailored by varying the chitin content (10–30 wt%) and MA content (10–50 wt% based on total mass of composite). In brief, this chemically cross-linked PVA-based biocomposites formulated with sustainable resources exhibited tunable physicochemical and mechanical properties. 相似文献
93.
Ahmet Sarı Mohammed Ouikhalfan Hassan Chehouani Gökhan Hekimoğlu Alper Bicer Amir Al-Ahmed Fahad A. Al-Sulaiman Vineet Veer Tyagi 《Polymer Engineering and Science》2020,60(5):909-916
In this work, polyethylene glycol (PEG) as a phase change material (PCM) was incorporated with palygorskite (Pal) clay to develop a novel form-stable composite PCM (F-SCPCM). The Pal/PEG(40 wt%) composite was defined as F-SCPCM and characterized using SEM/EDS, FT-IR, XRD, DSC, and TGA techniques. The DSC results revealed that the F-SCPCM has a melting temperature of 32.5°C and latent heat capacity of 64.3 J/g for thermal energy storage (TES) applications. Thermal cycling test showed that the F-SCPCM had good cycling thermal/chemical stability after 500 cycles. The TGA data proved that that both cycled and non-cycled F-SCPCMs had considerable high thermal durability. Consequently, the created F-SCPCM could be considered as an additive material for production of green construction components with TES capability. POLYM. ENG. SCI., 60:909–916, 2020. © 2020 Society of Plastics Engineers 相似文献
94.
Naif A. Darwish Fahad M. Al Sadoon Muhammad Qasim 《Chemical Engineering Communications》2018,205(1):12-22
This work addresses the determination of stability limits and consolute critical conditions for multicomponent liquid mixtures. Using the NRTL model, thermodynamic stability and criticality criteria are implemented for ternary liquid mixtures to predict stability limit loci and critical composition at its specified temperature and pressure. The method is general and applicable for the prediction of spinodal curves and critical points for liquid–liquid-phase transitions in multicomponent liquid mixture using liquid–liquid equilibrium data even over a limited range of composition. Stability limits’ loci for 18 aqueous and 3 nonaqueous ternary liquid mixtures were used in validating the method. For ternary systems that were studied over the whole composition range including the critical zone, where experimental compositions at the critical point were available, the predicted results agree with the experimental measurements within 0.7?mol%. 相似文献
95.
Mansur Usman Dawaki Abdulrahman Lado Maharaz Alhaji Yusuf Bassam A. Lawan Umar F. Galadanci 《Food and Energy Security》2019,8(1)
This article presents a review on the opportunities available in the drier savannahs of Northern Nigeria for the production of soil organic amendments to improve soil productivity and enhance carbon sequestration through a synergistic system. The use of soil organic amendments in the farming systems of the drier savannas of Nigeria is below optimal principally because of the low level of awareness among small‐holder farmers in the region and production cost/benefit disadvantage. Given the large quantities of organic wastes generated in expanding cities in the region and non‐feed agricultural waste resources from rural and peri‐urban areas, there is potential to approach waste management from the perspective of waste conversion in a synergistic approach to minimize production cost especially in the form of energy savings. This will enhance the availability of materials such as biochar and compost which have been advocated as two principal materials with properties that can improve poor soils, such as those in the region under consideration. When coupled with risk management and extension strategies targeting farmer education, the products may be adoptable across the vast arable fields in the region thereby maximizing use advantage. 相似文献
96.
Due to their good mechanical properties, high molecular weight polyesters (PEs) are highly desirable for a wide range of applications especially in the packaging industry. However, the synthesis of high molecular weight polymers by energy efficient methods is difficult. In this study, a series of semi-aromatic PEs were synthesized via the alternating ring-opening copolymerization (ROCOP) of phthalic anhydride (PA) and cyclohexene oxide (CHO) using a salen chromium(III) complex as a catalyst and 4-(dimethylamino)pyridine as a cocatalyst. By varying the molar ratios between CHO and PA, PEs of different molecular weights were obtained. Hexamethylene diisocyanate was used as a chain extender that further increased the molecular weights of these PEs. These chain extended aromatic polyesters (PE-Xs) showed significant improvement in the glass transition temperature (Tg) values. Thus, integration of ROCOP with the chain extension method can be used as an effective strategy to prepare high molecular weight PEs with improved thermal stabilities and enhanced mechanical properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47200. 相似文献
97.
Azeem Irshad Shehzad Ashraf Chaudhry Muhammad Shafiq Muhammad Usman Muhammad Asif Anwar Ghani 《International Journal of Communication Systems》2019,32(14)
The mobile cloud computing (MCC) has enriched the quality of services that the clients access from remote cloud‐based servers. The growth in the number of wireless users for MCC has further augmented the requirement for a robust and efficient authenticated key agreement mechanism. Formerly, the users would access cloud services from various cloud‐based service providers and authenticate one another only after communicating with the trusted third party (TTP). This requirement for the clients to access the TTP during each mutual authentication session, in earlier schemes, contributes to the redundant latency overheads for the protocol. Recently, Tsai et al have presented a bilinear pairing based multi‐server authentication (MSA) protocol, to bypass the TTP, at least during mutual authentication. The scheme construction works fine, as far as the elimination of TTP involvement for authentication has been concerned. However, Tsai et al scheme has been found vulnerable to server spoofing attack and desynchronization attack, and lacks smart card‐based user verification, which renders the protocol inapt for practical implementation in different access networks. Hence, we have proposed an improved model designed with bilinear pairing operations, countering the identified threats as posed to Tsai scheme. Additionally, the proposed scheme is backed up by performance evaluation and formal security analysis. 相似文献
98.
Asma Al Kindi Dawood Al Abri Ahmed Al Maashri Fahad Bait‐Shiginah 《International Journal of Communication Systems》2019,32(15)
Social Internet of Things (SIoT) is an evolution of the Internet of Things, where objects interact socially with each other in the sense that they can independently establish new relationships, offer, or discover services, in order to accomplish their tasks with minimum involvement of the user. This additional convenience comes at the expense of higher risk of speeding up malware propagation through the dynamically created relationships. Because of the undesirable effects of malware (eg, disruption of device operation), it is essential to understand their spreading behavior in order to minimize their negative impacts. In this paper, we analyze malware propagation behavior in SIoT and investigate different parameters that influence spreading of malware. Toward that end, a simulator has been developed to simulate the spreading process of malware in SIoT. Many propagation scenarios were analyzed using the proposed simulator. Simulation results show that adding more relationships in the SIoT or increasing the number of owned objects per user has increased malware spreading rate. For example, the time to infect all objects is faster by 45% when objects communicate through four relationships compared with the case when objects communicate through only two relationships in SIoT. We also investigated ways to restrict the malware spreading. Results show that preventing objects from establishing dynamic social relationship slows down the infection by 40% compared with the next best scenario (ie, blocking co‐location relationships), which means more time for vendors to patch up their products. 相似文献
99.
100.
Configuration management (CM) is not a new set of ideas, what it does represent is an effective way for project managers to use a formalized methodology in order that they can manage status and changes to it throughout the lifecycle. This research sets out to identify and prioritize the obstacles in the effective implementation of the CM practices, categorize these obstacles into more manageable groups of factors, and analyse the effects of multiple factors on the identification and rating of these barriers. Nineteen barriers are finalized and prioritized on the basis of their criticality and as a result three groups (managerial and organizational barriers, implementation barriers, and planning and process barriers) are extracted with the help of factor analysis. This study will help both configuration management and project management professionals to plan better and avoid the impacts of these key obstacles from much earlier in the definition phase. 相似文献