Kinetic Parameters Evaluation for Isoprene Mixed with Aluminum Oxide

AbstractWe analyzed the basic hazard characteristics for isoprene in the manufacturing process by evaluating the runaway reaction, kinetic parameters and safety parameters in this study. Experiments were carried out by calculating the thermal decomposition reactions for isoprene and mixed with aluminum oxide in non-isothermal conditions by differential scanning calorimetry (DSC). Afterwards results indicated that isoprene had a conjugated double bond of unstable structure, and therefore it was prone to produce exothermic reaction during the process of polymerization. Aluminum oxide was applied to mix with isoprene, which could increase the heat release rate. Based on the results, safety information should be provided to government and relevant industries for prevention the accident occur in relevant plants

Effect of selective post-aging treatment on subsurface damage of quasicrystal reinforced Al composite manufactured by selective laser melting

In this work, Al-Fe-Cr quasicrystal reinforced Al matrix composite was in-situ prepared by using selective laser melting from powder mixture of Al-Cu-Fe-Cr quasicrystal and pure Al. The effect of selective post-aging treatment on microstructure and mechanical properties were determined with focus on the metastable phases. The microstructural analysis, which was determined by X-ray diffraction and scanning electron microscopy, indicates that the Al-based intermetallic is precipitated from supersaturated α-Al after the aging process. Moreover, the compression tests were performed on the samples in form of dense and lattice structures (50% porosity). The elastic modules of dense and lattice structural samples reduce from 21.3 GPa and 4.4–14.6 GPa and 3.6 GPa by using a low cooling-rated aging process. After aging process, the compressive deformation behavior of dense part changes from elastic-plastic-fracture mode to elastic-plastic-densification mode. On the other hand, the failure mechanism of lattice structural sample changes from rapid-single-stage to slow-double-stage with an improvement of the strain at failure

Theory of Melting and the Optical Properties of Gold/DNA Nanocomposites

We describe a simple model for the melting and optical properties of a DNA/gold nanoparticle aggregate. The optical properties at fixed wavelength change dramatically at the melting transition, which is found to be higher and narrower in temperature for larger particles, and much sharper than that of an isolated DNA link. All these features are in agreement with available experiments. The aggregate is modeled as a cluster of gold nanoparticles on a periodic lattice connected by DNA bonds, and the extinction coefficient is computed using the discrete dipole approximation. Melting takes place as an increasing number of these bonds break with increasing temperature. The melting temperature corresponds approximately to the bond percolation threshold.Comment: 5 pages, 4 figure. To be published in Phys. Rev.

The ecology of sex explains patterns of helping in arthropod societies

Authors thank the Natural Sciences and Engineering Research Council of Canada (NGD), the Clarendon Fund (NGD) and the Natural Environment Research Council (LR, NE/K009516/1; AG, NE/K009524/1) for funding.Across arthropod societies, sib-rearing (e.g. nursing or nest defence) may be provided by females, by males or by both sexes. According to Hamilton's ‘haplodiploidy hypothesis’, this diversity reflects the relatedness consequences of diploid vs. haplodiploid inheritance. However, an alternative ‘preadaptation hypothesis’ instead emphasises an interplay of ecology and the co-option of ancestral, sexually dimorphic traits for sib-rearing. The preadaptation hypothesis has recently received empirical support, but remains to be formalised. Here, we mathematically model the coevolution of sex-specific helping and sex allocation, contrasting these hypotheses. We find that ploidy per se has little effect. Rather, the ecology of sex shapes patterns of helping: sex-specific preadaptation strongly influences who helps; a freely adjustable sex ratio magnifies sex biases and promotes helping; and sib-mating, promiscuity, and reproductive autonomy also modulate the sex and abundance of helpers. An empirical survey reveals that patterns of sex-specific helping in arthropod taxa are consistent with the preadaptation hypothesis.Publisher PDFPeer reviewe

Non-relativistic CFT and Semi-classical Strings

We study different features of 3D non-relativistic CFT using gravity description. As the corresponding gravity solution can be embedded into the type IIB string theory, we study semi-classical closed/open strings in this background. In particular we consider folded rotating and circular pulsating closed strings where we find the anomalous dimension of the dual operators as a function of their quantum numbers. We also consider moving open strings in this background which can be used to compute the drag force. In particular we find that for slowly moving particles, the energy is lost exponentially and the characteristic time is given in terms of the temperature, while for fast moving particles the energy loss goes as inverse of the time and the characteristic time is independent of the temperature.Comment: 20 pages, Latex file; V2: typos corrected, ref. adde

Scaling of anisotropy flows in intermediate energy heavy ion collisions

Anisotropic flows ($v_1$, $v_2$ and $v_4$) of light nuclear clusters are studied by a nucleonic transport model in intermediate energy heavy ion collisions. The number-of-nucleon scalings of the directed flow ($v_1$) and elliptic flow ($v_2$) are demonstrated for light nuclear clusters. Moreover, the ratios of $v_4/v_2^2$ of nuclear clusters show a constant value of 1/2 regardless of the transverse momentum. The above phenomena can be understood by the coalescence mechanism in nucleonic level and are worthy to be explored in experiments.Comment: Invited talk at "IX International Conference on Nucleus-Nucleus Collisions", Rio de Janeiro, Aug 28- Sept 1, 2006; to appear on the proceeding issue in Nuclear Physics

In-situ synthesis of aluminum/nano-quasicrystalline Al-Fe-Cr composite by using selective laser melting

In this research, Al-Fe-Cr quasicrystal (QC) reinforced Al-based metal matrix composites were in-situ manufactured by using selective laser melting (SLM) from the powder mixture. The parametrical optimization based on our previous work was performed with focus on laser scanning speed. From the optimized parameters, an almost dense (99.7%) free-crack sample was fabricated with an ultra-fine microstructure. A phase transition from decagonal QC Al65Cu25Fe10Cr5 to icosahedral QC Al91Fe4Cr5 could be observed as laser scanning speed decreases. Differential scanning calorimetry curves show that the QC phase is quiet stable until 500 °C. And then, the effects of annealing temperature on the microstructural and mechanical properties were determined. The results indicate that the recrystallization and growth behavior of α-Al grains could be prevented by QC particle during annealing. Furthermore, the growth of QC particle, which tends to form a porous structure, leads an improvement of Young modulus and decline of ductility

Branes at Quantum Criticality

In this paper we propose new non-relativistic p+1 dimensional theory. This theory is defined in such a way that the potential term obeys the principle of detailed balance where the generating action corresponds to p-brane action. This condition ensures that the norm of the vacuum wave functional of p+1 dimensional theory is equal to the partition function of p-brane theory.Comment: 17 pages, references added, typos fixed,v2. minor change

Scaling of Anisotropic Flow and Momentum-Space Densities for Light Particles in Intermediate Energy Heavy Ion Collisions

Anisotropic flows ($v_2$ and $v_4$) of light nuclear clusters are studied by Isospin-Dependent Quantum Molecular Dynamics model for the system of $^{86}$Kr + $^{124}$Sn at intermediate energy and large impact parameters. Number-of-nucleon scaling of the elliptic flow ($v_2$) are demonstrated for the light fragments up to $A$ = 4, and the ratio of $v_4/v_2^2$ shows a constant value of 1/2. In addition, the momentum-space densities of different clusters are also surveyed as functions of transverse momentum, in-plane transverse momentum and azimuth angle relative to the reaction plane. The results can be essentially described by momentum-space power law. All the above phenomena indicate that there exists a number-of-nucleon scaling for both anisotropic flow and momentum-space densities for light clusters, which can be understood by the coalescence mechanism in nucleonic degree of freedom for the cluster formation.Comment: 8 pages, 3 figures; to be published in Physics Letters