Studies on Dielectric and UV Shielding Properties of Epoxy Functionalized Alumina/Silane-Modified Amine Epoxy Nanocomposites

In the present work, 3-glycidyloxypropyltrimethoxysilane functionalized alumina (F-Al₂O₃) was prepared and the formation of chemical bonding was confirmed with FTIR spectroscopy. Varying weight percentages of (5, 10, 15 and 20 wt%) glycidyl F-Al₂O₃ were reinforced with blend of diaminophenoxydimethylsilane and epoxy resin and then cured with diamonodiphenylmethane. The surface morphology of samples was analyzed before and after UV exposure for 168 h using SEM. The 20 wt% F-Al₂O₃ reinforced epoxy nanocomposite sample possesses higher thermal stability, higher dielectric constant and better UV radiation resistant properties than that of other weight percentages of F-Al₂O₃ reinforced epoxy nanocomposites.     

Soluble conducting poly(dipropargyl ether) formation studied using ultraviolet-visible spectroscopy

Cyclopolymerization of dipropargyl ether was carried out in nitrogen atmosphere with different initiators (KSCN/KCl/KBr/KI) in dimethyl formamide. The rate of polymerization was determined for different conditions and used for comparing the efficiency of the initiators. KSCN and KI were found to be effective initiators for cyclopolymerization. The resulting polymer exhibits good solubility in common organic solvents and exhibited solvatochromic behaviour. The results from ¹H NMR, FT-IR and UV-Visible spectra of poly(dipropargyl ether), PDPE supported the idea that the resulting polymer possesses polyene structure having cyclic recurring units in the polymer backbone. Conductivity, thermogravimetric analysis and electroactivity of the polymer were also studied. The results from UV-Visible, FTIR spectroscopy and conductivity measurements clearly revealed the doped nature of PDPE.     

A Routing Algorithm Framework for Survivable Optical Networks Based on Resource Consumption Minimization

In this paper, we consider the problem of determining primary and backup paths for survivable optical wavelength-division multiplexed mesh networks. We propose a distributed routing mechanism, which is called Least Resource Consumption Routing, that tries to minimize the combined cost of the primary and the backup paths. The proposed cost model includes the effect of various factors such as mean load, variance of the load on the route, number of converters required by the route, and the length of the route. Further, we model the route cost in such a way that it is extensible to include any new parameters and vary their relative importance. The performance studies conducted for the 14-node National Science Foundation Network and a 30-node topology show that the proposed scheme leads to significant improvements in blocking probability at low and moderate loads. Further, the proposed cost model also reduces the number of converters required to obtain a target blocking performance as compared to some other techniques proposed in the literature.     

An integrated approach for water minimisation in a PVC manufacturing process

This paper presents a water minimisation study carried out for a polyvinyl chloride (PVC) resins manufacturing plant. Due to the complexity of the mixed batch and continuous polymerisation process, an integrated process integration approach, which consists of process synthesis, analysis and optimisation was used for this work. A simulation model was first developed in a batch process simulation software, SuperPro Designer V6.0, based on the operating condition of a PVC manufacturing process. The batch simulation model captured the essential information needed for a water minimisation study, e.g. process duration, water mass flow, etc. Data extracted from the simulation model was later used in the water minimisation study, utilising the widely established process synthesis technique of water pinch analysis. Two water saving scenarios were presented. Scenario 1 reports a fresh water and wastewater reduction of 28.5 and 90.1% respectively, for the maximum water recovery scheme without water storage system. In Scenario 2, higher fresh water and wastewater reduction are reported at 31.7 and 100% respectively, when water storage tank is installed in the water network.     

Hydrogenation of Benzaldehyde over Palladium Intercalated Bentonite Catalysts: Kinetic Studies

Bentonite, a 2:1 type swellable phyllosilicate clay mineral having exchangeable inorganic cations in the interlamellar space to nullify their charge deficiency was used to generate palladium nanoparticles. It was found that 1% w/w palladium nanoparticles were generated in the interlamellar space using adsorption excess technique. The synthesized catalysts were characterized by using XRD, TEM, BET surface area analysis, and AAS. The modified clay catalysts were tested for their catalytic activity towards the hydrogenation of benzaldehyde to benzyl alcohol in liquid phase using a high-pressure reactor at various temperatures and pressures. High selectivity (100%) towards the desired product of benzyl alcohol was achieved with conversion over 80% in all cases. These results showed different hydrogen dependency for the reaction at various temperatures. The kinetics of the reaction was studied using Langmuir Hinshelwood single site model. The rate constant was determined using pseudo first-order kinetics and activation energy for benzaldehyde hydrogenation was calculated at various temperatures using Arrhenius equation and was found to decrease with increase in temperature.     

Dielectric properties study of surface engineered nano$$\hbox {TiO}_{2}$$/epoxy composites

Nanodielectrics are promising materials that can efficiently store a large amount of electrical energy that are desirable for many electronic and power devices. Control of polymer–particle interface in nanodielectrics is very critical in not only obtaining the improved quality of dispersion but also in altering the dielectric properties. Various surface modifying agents with linear (alkyl), aromatic (phenyl) and extended aromatic (naphthyl) chemical nature were employed at the epoxy–nano\(\hbox {TiO}_{2}\) interface. All the surface-modifying agents were successful in passivating the nanoparticles surface and in obtaining the improved quality of polymer–particle dispersion and improved glass transition temperature comparatively. However, all the surface modifiers were not successful in obtaining the improved dielectric properties of the nanodielectrics, especially dielectric breakdown resistance. Only the extended aromatic group at the polymer–particle interface, which is more electron withdrawing in electronic nature than phenyl and alkyl structures, was successful in improving the dielectric breakdown resistance. Thus, the choice of surface-modifying agent based on its chemical and electronic nature is very important in optimizing the dielectric properties of nanodielectrics. Naphthyl phosphate-modified nano\(\hbox {TiO}_{2}\)–epoxy composite films of \(\sim \)90–100 \(\upmu \)m thick at 5 vol% particle concentration yielded higher dielectric breakdown resistance than pure epoxy polymer and thereby resulted in about 90% higher electrical energy storage density than the pure epoxy film.     

Heuristic algorithms for scheduling heat-treatment furnaces of steel casting industries

This paper addresses a research problem of scheduling parallel, non-identical batch processors in the presence of dynamic job arrivals, incompatible job-families and non-identical job sizes. We were led to this problem through a real-world application involving the scheduling of heat-treatment operations of steel casting. The scheduling of furnaces for heat-treatment of castings is of considerable interest as a large proportion of the total production time is the processing times of these operations. In view of the computational intractability of this type of problem, a few heuristic algorithms have been designed for maximizing the utilization of heat-treatment furnaces of steel casting manufacturing. Extensive computational experiments were carried out to compare the performance of the heuristics with the estimated optimal value (using the Weibull technique) and for relative effectiveness among the heuristics. Further, the computational experiments show that the heuristic algorithms proposed in this paper are capable of obtaining near (statistically estimated) optimal utilization of heat-treatment furnaces and are also capable of solving any large size real-life problems with a relatively low computational effort.     

Effect of divalent cation substitution in the magnetoplumbite structured BaFe12O19 system

Synthesis of magnetically ordered barium hexaferrite powders and the adjustment of magnetic properties for perpendicular magnetic recording media are realized through substitution of divalent cation (Ca) in the BaFe₁₂O₁₉ system. The Ca²⁺ substituted Ba_1?xCa_xFe₁₂O₁₉ (where x = 0.05, 0.1, 0.15 and 0.2) compounds have been prepared through solid state reaction technique. The powder X-ray diffraction analysis reveals that all the prepared compounds crystallized in magnetoplumbite hexagonal structure and the flat hexagonal platelet morphology of the crystallites was identified through scanning electron microscopy. The formation of magnetoplumbite structured Ba_1?xCa_xFe₁₂O₁₉ system due to mechanical activation was supported by micro-Raman measurements. Both pure and Ca substituted BaFe₁₂O₁₉ compounds exhibit sharp intense peaks which reveals defect free environment in the crystal lattice. From the room temperature magnetization studies, it was observed that the saturation magnetization (M_S) and remanent magnetization (M_R) values drastically decreases for the Ba_0.95Ca_0.05Fe₁₂O₁₉ compound which may be due to the existence of spin canting effect and leads to the reduction of super exchange fields. The increase in M_S and M_R values for the Ba_0.9Ca_0.1Fe₁₂O₁₉ and Ba_0.85Ca_0.15Fe₁₂O₁₉ compounds could be attributed to the enhanced hyperfine fields at 12k and 2b sites due to the strengthening of Fe³⁺–O–Fe³⁺ super exchange interactions. A large reduction in the coercivity value from 3,090 to 1,548 Gauss may be attributed to the fall in magneto crystalline anisotropy. The high temperature magnetization studies infer that while increasing substitution level of Ca in the BaFe₁₂O₁₉ system results in decreasing trend in Curie temperature. The room temperature dielectric measurement shows that the incorporation of Ca²⁺ in the BaFe₁₂O₁₉ system results with increase in the dielectric constant and this case substantiates the space charge polarization. The magnetically ordered BaFe particulate having higher saturation and low coercivity values with superior magnetic and dielectric behaviour exhibiting the possibility for future high-recording-density storage products.     

Streamlined life cycle assessment of residue utilization options in <Emphasis Type="Italic">Tongkat Ali </Emphasis>(<Emphasis Type="Italic">Eurycoma longifolia</Emphasis>) water extract manufacturing process

Life cycle assessment (LCA) is often used to compare alternative process options in terms of their overall impact on the environment to easily identify the most environmentally friendly alternative. In this work, a streamlined LCA study was conducted to assess three different residue utilization schemes for Tongkat Ali (Eurycoma longifolia) extract production. The case study was firstly simulated using a batch process simulation software. The results of mass and energy balances obtained from the simulation software were then subjected to life cycle analysis. By evaluating the different schemes for using the fibrous residue from the extraction process, the potential for environmental process improvement was identified. Overall, use of the residue as process fuel was found to be the most environmentally friendly option. It produces the least emissions and reduces resource usage per unit of product than the other options evaluated.     

On using peer-to-peer communication in cellular wireless data networks

A recent class of approaches for enhancing the performance of cellular wireless data networks has focused on improving the underlying network model. It has been shown that using the peer-to-peer network model, a mode of communication typically seen in ad hoc wireless networks, can result in performance improvements such as increased data rate, reduced transmission power, better load balancing, and enhanced network coverage. However, the true impact of adopting the peer-to-peer network model in such an environment is yet to be fully understood. In this paper, we investigate the performance benefits and drawbacks of using the peer-to-peer network model for Internet access in cellular wireless data networks. We find that, although the peer-to-peer network model has significantly better spatial reuse characteristics, the improved spatial reuse does not translate into better throughput performance. Instead, we observe that using the peer-to-peer network model as-is might actually degrade the throughput performance of the network. We identify and discuss the reasons behind these observations. Using the insights gained through the performance evaluations, we then propose two categories of approaches to improve the performance of the peer-to-peer network model: approaches that leverage assistance from the base station and approaches that leverage the relaying capability of multihomed hosts. Through simulation results, we show that using the peer-to-peer network model in cellular wireless data networks is a promising approach when the network model is complemented with appropriate mechanisms.