Tunable microwave resonators and oscillators using magnetostatic waves

The status of magnetostatic wave (MSW) straight-edge resonators (SERs) and their applications in tunable oscillator circuits are reviewed. The resonators are based on magnetostatic waves propagating in high-Q cavities fabricated in thin ferrimagnetic yttrium iron garnet (YIG) films. The resonance frequency of these resonators can be tuned using a bias magnetic field. The theory of operation and design criteria for the straight-edge resonators are described with emphasis on the effect of the resonator parameters on the tuning range, power handling, and phase noise performance. The use of the SER as the frequency-selective element in oscillator circuits is reported. Examples of tunable oscillators are included.     

A polar-based guided multi-objective evolutionary algorithm to search for optimal solutions interested by decision-makers in a logistics network design problem

In practical multi-objective optimization problems, respective decision-makers might be interested in some optimal solutions that have objective values closer to their specified values. Guided multi-objective evolutionary algorithms (guided MOEAs) have been significantly used to guide their evolutionary search direction toward these optimal solutions using by decision makers. However, most guided MOEAs need to be iteratively and interactively evaluated and then guided by decision-makers through re-formulating or re-weighting objectives, and it might negatively affect the algorithms performance. In this paper, a novel guided MOEA that uses a dynamic polar-based region around a particular point in objective space is proposed. Based on the region, new selection operations are designed such that the algorithm can guide the evolutionary search toward optimal solutions that are close to the particular point in objective space without the iterative and interactive efforts. The proposed guided MOEA is tested on the multi-criteria decision-making problem of flexible logistics network design with different desired points. Experimental results show that the proposed guided MOEA outperforms two most effective guided and non-guided MOEAs, R-NSGA-II and NSGA-II.     

Mechanical,flow, and morphological properties of talc‐ and kaolin‐filled polypropylene hybrid composites

Polypropylene (PP) hybrid composites have been produced by compounding two types of mineral fillers, viz., talc and kaolin with PP copolymer using a twin screw extruder. The PP hybrid composite was injection‐molded into dumbbell specimen for tensile, flexural, and impact properties characterizations. MFI and SEM studies were used to characterize the flow and morphological properties of the PP hybrid composites. The result shows that most of the hybrid composites showed a significant decrease in flow, tensile, flexural, and impact properties compared with the single filler‐filled PP composites. However, a hybridization effect was seen for the PPT20K10 hybrid composites, through the synergistic coalescence of positive characteristics from 20 wt % of talc and 10 wt % of kaolin. This hybrid formulation have given an economically advantageous material with the mechanical properties (tensile, flexural, and impact) comparable to those of the talc‐filled PP composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 434–441, 2007     

Effects of hygrothermally decomposed polyurethane on the curing and mechanical properties of carbon black‐filled epoxidized natural rubber vulcanizates

Hygrothermally decomposed polyurethane (HD‐PUR) was mixed up to 20 phr in epoxidized natural rubber (with 50 mol % epoxidation; ENR50) recipes, and the curing and mechanical behaviors were studied. Mechanical testing of the ENR50/HD‐PUR vulcanizates determined the tensile, tear, compression‐set, hardness, abrasion, hysteresis, and resilience properties. No significant changes were observed in the tensile properties with the incorporation of HD‐PUR. The ENR50 compounds showed an increase in compression set with increasing HD‐PUR content. Rubbers cured by a semi‐efficient vulcanization system gave the best overall performance. A further improvement in curing and mechanical properties was achieved by the carbon black grade N330 being replaced with a more active grade (N375). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2265–2276, 2002     

Modification of oil palm empty fruit bunches with maleic anhydride: The effect on the tensile and dimensional stability properties of empty fruit bunch/polypropylene composites

Oil palm empty fruit bunch (EFB)‐filled polypropylene (PP) composites were produced. The EFB filler was chemically modified with maleic anhydride (MAH). The effects of the filler size and chemical modification of EFBs on the tensile and dimensional stability properties of EFB–PP composites were studied. The composites with MAH‐treated EFBs showed higher tensile strengths than those with untreated EFBs. This was attributed to the enhanced compatibility between the MAH‐treated EFBs and PP matrix, as shown in a scanning electron microscopy study. Fourier transform infrared analysis showed evidence of C?C and C?O bonds from MAH at 1630 and 1730 cm^?1, respectively. The MAH‐treated PP composites showed lower water absorption and thickness swelling than those with untreated EFBs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 827–835, 2003     

Rheological properties of poly(vinyl chloride) / epoxidized natural rubber blends. Part II: The effect of processing variables

The effect of processing variables on the rheological properties of PVC/ENR blends was investigated. The role of crosslinking in determining the flow behavior of blends was also examined by means of dynamically cured blends. It was found that PVC/ENR blends yield melts that are power law fluids. The flow of the melts improves with an increase in temperature and shear rate. However, the introduction of crosslinks reverses this trend, although under more rigorous conditions, the influence of crosslinks is superseded, and subsequently, flow becomes shear rate and temperature dependent. PVC/ENR systems also manifested elastic phenomena. The dependence of the elastic phenomena such as die swell and melt fracture on L/D ratio of the die was demonstrated.     

On the in‐situ polymerization of cyclic butylene terephthalate oligomers: DSC and rheological studies

The thermal and rheological behaviors of cyclic butylene terephthalate (CBT) were studied with differential scanning calorimetry (DSC) and plate–plate rheometry, respectively. DSC scans were taken at different heating rates. The related first‐heat thermograms indicated crystallization and melting of the resulting poly (butylene terephthalate) (PBT) only at very low heating rate (0.5°C/min). As the crystallization and melting enthalpies were closely matched, one could conclude that the polymerization is essentially athermic. The polymerization was accompanied by a steep increase of the melt viscosity in isothermal rheological tests performed in the temperature range T = 145–210°C. Changes in the viscoelasticity of the polymerizing CBT and crystallizing PBT could be best followed by considering the changes in the phase angle. Viscosity increased with the conversion exponentially in the first approximation. POLYM. ENG. SCI., 46:743–750, 2006. © 2006 Society of Plastics Engineers     

Sustainability-guided life-cycle design and assessment for bio-based composite foams: Integrate flame retardancy/lightweight in usage and energy utilization after service

Sustainable development strategy has aroused a great interest in biomass resources as alternative raw materials. A kind of biomass-derived poly(butylene succinate) (PBS), has been developed as porous foams to reduce resource exhaustion and meet lightweight demands. For fire-safety in-service, graphene oxide (GO) was functionalized by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to combine flame-retardant elements and heat-barrier function. Hence, a very low loading level of P-containing GO as only 5 wt% could reduce peak heat release rate (pHRR) and total heat release (THR) of PBS-based foams by 58.5% and 22.3%, respectively. Meanwhile, N-/P-doped mesoporous char with a specific surface area of 136 m²/g, which derived from combustion of flame-retardant foaming PBS, contributes to a potential of energy storage applications in the capacitor or the anode of Li-ion battery with long-term stability. Overall, the sustainability of bio-based polyester could integrate lightweight of foaming, and be extended to utilization after use via facile combustion inspired by flame-retardancy design.     

An Efficient Schema Transformation Technique for Data Migration from Relational to Column-Oriented Databases

Data transformation is the core process in migrating database from relational database to NoSQL database such as column-oriented database. However, there is no standard guideline for data transformation from relational database to NoSQL database. A number of schema transformation techniques have been proposed to improve data transformation process and resulted better query processing time when compared to the relational database query processing time. However, these approaches produced redundant tables in the resulted schema that in turn consume large unnecessary storage size and produce high query processing time due to the generated schema with redundant column families in the transformed column-oriented database. In this paper, an efficient data transformation technique from relational database to column-oriented database is proposed. The proposed schema transformation technique is based on the combination of denormalization approach, data access pattern and multiple-nested schema. In order to validate the proposed work, the proposed technique is implemented by transforming data from MySQL database to HBase database. A benchmark transformation technique is also performed in which the query processing time and the storage size are compared. Based on the experimental results, the proposed transformation technique showed significant improvement in terms query processing time and storage space usage due to the reduced number of column families in the column-oriented database.     

Effects of peroxide crosslinking on the mechanical and morphological properties of poly(ethylene‐co‐vinyl acetate)/zeolite composites

Uncrosslinked and chemically crosslinked ethylene‐vinyl acetate copolymers (EVAs) with 5–25 volume percentages of zeolite were prepared in a melt‐mixing process and then compression‐molded on a hot‐press machine according to standard test specifications. The mechanical properties measured by tensile test showed a reduction in tensile strength and elongation at break with increasing zeolite content. However, an increasing trend was observed for tensile modulus with addition of zeolite. Experimental results for ultimate stress were compared with those from Pukanszky equation. The experimental data showed a good fit to the Pukanszky model. The improvement in the interfacial interaction for crosslinked composites was also confirmed by this model. Morphological changes of EVA/zeolite composites were analyzed by scanning electron microscopy (SEM). The fractured surface of the composites indicated more complex morphology at higher zeolite loading. The influence of crosslinking induced by 2 wt% of dicumyl peroxide on the properties of EVA/zeolite composites was also investigated. The crosslinked composites showed better tensile properties than the uncrosslinked ones, a result which might be an indication of enhanced interaction between the EVA and zeolite. Density measurements, gel content determinations, and Fourier transform infrared analyses were also performed to evaluate the crosslink content of the composites. The changes in the properties of chemically crosslinked EVA/zeolite composites were observed. Meanwhile, SEM micrographs of the crosslinked EVA/zeolite composites showed better interfacial strength between zeolite and the EVA matrix as compared to that of the uncrosslinked composites. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers