Logistics Orchestration Modeling and Evaluation for Humanitarian Relief

10.1109/SOLI.2012.6273499Proceedings of 2012 IEEE International Conference on Service Operations and Logistics, and Informatics, SOLI 201225-3

Mechanism of enhancement of intumescent fire retardancy by metal acetates in polypropylene

The effects of cobalt acetate (CoAc), manganese acetate (MnAc), nickel acetate (NiAc) and zincacetate (ZnAc) as fire retardant additive in intumescent polypropylene (PP) formulations containing PP/ammonium polyphosphate (APP)/pentaerythritol (PER) are reported. The limiting oxygen index (LOI) and vertical burning (UL94) tests and cone calorimetry were used to quantify the enhancement. Environmental chamber rheometry, thermal gravimetric analysis and the morphology of the residual char were used to investigate the mechanism of enhancement. The incorporation of small quantities of metal acetates had a significant influence on the fire behaviour. As an example, 0.7 wt% MnAc improved the UL 94 rating of PP/APP+PER (mass ratio 100/25, with APP/PER=3/1) sample from V-2 to V-0, while 1 wt% MnAc reduced the peak heat release rate and the total heat release by 18% and 12% in the cone calorimeter. Rheological data, cone calorimetry, and photographs of the residual char showed how the fire retardancy of the systems were affected by the melt viscosity, which depended on the loading of metal acetate. During thermal decomposition, the metal acetates promote the crosslinking of the polymer and the fire retardant, reinforcing the protective intumescent layer. While, the effect is most potent at the optimal metal loadings. At higher MnAc loadings, the benefit of a stronger char is overwhelmed by the adverse effect of crosslinking on the transition char layer. Thus, this paper offers a new insight into the mechanism of the intumescent fire retarded PP system

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

An Efficient and Provably-Secure Identity-based Signcryption Scheme for Multiple PKGs

In this paper, based on the scheme proposed by Barreto et al in ASIACRYPT 2005, an identity-based signcryption scheme in multiple Private Key Generator (PKG) environment is proposed, which mitigates the problems referred to users\u27 private keys escrow and distribution in single PKG system. For security of the scheme, it is proved to satisfy the properties of message confidentiality and existential signature-unforgeability, assuming the intractability of the q-Strong Diffie-Hellman problem and the q-Bilinear Diffie-Hellman Inversion problem. For efficiency, compared with the state-of-the-art signcryption schemes of the same kind, our proposal needs less pairing computations and is shown to be the most efficient identity-based signcryption schemes for multiple PKGs up to date

Influence of secondary thermal cycle on softening behavior and mechanism of heat affected zone in TIG-welded spray formed 7055 aluminum alloy

In this study, fine position samples of heat affected zone under single and secondary thermal cycles were simulated by heat treatment method. The influence of secondary thermal cycle on softening behavior and mechanism of heat affected zone in TIG-welded spray formed 7055 aluminum alloy were studied. The results showed that the mechanical properties of the solid solution zone decreased after the second thermal cycle. The hardness of the solid solution zone decreased from 180HV to 103HV and the tensile strength decreased from 570 MPa to 346 MPa after the second thermal cycle. The main reasons for the reduction of mechanical properties in the solid solution zone after the second thermal cycle were the weakening of the solid solution strengthening effect and the occurrence of over-aging. After the second thermal cycle in the over-aging zone, the mechanical properties decreased and then increased with the increase of the thermal cycle temperature. The lowest hardness value in the over-aging zone after the second thermal cycle decreased from 124HV to 103HV, and the tensile strength decreased from 410 MPa to 284 MPa. The main reason for the decrease of mechanical properties in the overaging zone after the secondary thermal cycle was the intensification of overaging caused by the coarsening of η phase. Overall, the width of the heat affected zone increased after the secondary thermal cycle, and the most seriously softened area extended toward the fusion line

Green and Scalable Fabrication of Core–Shell Biobased Flame Retardants for Reducing Flammability of Polylactic Acid

The design of flame-retardant biocomposites based on biobased flame retardants (FRs) represents a promising direction for creating a sustainable world. To date, it remains a major challenge to explore a green and scalable strategy for the design of highly effective, biobased FRs for bioplastics, such as polylactic acid (PLA). Herein, we have demonstrated a green, facile fabrication approach for a core–shell-structured biobased flame retardant (APP@CS@PA-Na) via layer-by-layer assembly using water as the assembly media. With electrostatic interactions, APP@CS@PA-Na was prepared by sequential assembly of ammonium polyphosphate (APP) with positively charged chitosan (CS) and then negatively charged phytic acid salt (PA-Na). The addition of APP@CS@PA-Na can enhance both the flame retardancy and the toughness of PLA. With the addition of 10 wt % APP@CS@PA-Na, the resultant PLA composite can pass an UL-94 V-0 rating and meanwhile shows an increased elongation at break by 28.4%, compared with that of neat PLA (8.1%). Through the analysis of the volatile gases and the residues, the flame retardant mechanism of APP@CS@PA-Na in PLA plays the key role in the condensed-phase. This work will broaden the practical application field of PLA, such as in electric and electronic and fibers fields

Fabrication of fullerene (C60) decorated carbon nanotubes and their application in flame-retarding polypropylene

Multi-walled carbon nanotubes were decorated with fullerene (C 60) via a three-step chemical functionalization, with the goal of combining their unique physical and chemical characteristics and simultaneously improving the solubility of CNTs in organic solvents. C60 molecules, about 0.67% by molecule, were homogeneously bonded onto the surface of the CNTs. Electron microscopy clearly shows that C60 molecules are introduced onto the surface of the CNTs, and this is also evidenced by their UV-VIS absorption spectra. Cone calorimetry measurements showed that compared with pristine CNTs, fullerene-decorated CNTs further reduced the flammability of polypropylene, which may be due to the free-radical-trapping effect of C 60 and the barrier effect of the CNT network

Effects of reactive compatibilization on the morphological, thermal, mechanical and rheological properties of intumescent flame retarded polypropylene

Flame-retardant polypropylene (PP) samples were in situ compatibilized with maleic anhydride grafted PP. Compatibilization reaction was verified by an IR spectrum and gel content measurements. Electron microscopy images showed that compatibilization could considerably reduce the size of the flame-retardant domains, control the phase morphology, and improve the interfacial adhesion between PP and intumescent flame retardant (IFR) with different IFR loading levels. The limiting oxygen index (LOI) of flame-retardant PP increased to different extents after compatibilization, indicating an improvement in the flame retardancy. Compatibilization enhanced the thermal stability to some extent and remarkably delayed thermal oxidative degradation of flame-retardant PP. For PP containing 20 wt % flame retardant, the temperature at which the maximum weight loss rate occurred was enhanced by about 99 °C after compatibilization. The storage modulus and glass transition temperatures were elevated to different extents. Tensile strengths of samples reduced in the presence of flame retardant alone but in the additional presence of compatibilizer were restored to levels similar to those of pure PP. Elongation-at-break values, however, showed IFR concentration-dependent reductions that were less for compatibilized samples. Furthermore, the complex viscosity of a compatibilized PP melt turned slightly smaller, which is favorable to melt processing