Graft Polymerization of Methyl Methacrylate- Acrylonitrile onto Poly(ethene-co-1-butene) and Its Toughening Effect on SAN Resin

Poly(ethene-co-1-butene)-graft-methyl methacrylate-acrylonitrile (PEB-g-MAN) was prepared by suspension grafting copolymerization of methyl methacrylate (MMA) and acrylonitrile(AN) onto PEB. PEB-g-MAN/SAN resin blends (ABMS) were prepared by blending PEB-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The effects of AN/(MMA+AN) feed ratio (f_AN), PEB/(PEB+MMA+AN) feed ratio (f_PEB) and benzoyl peroxide (BPO) dosage on the monomer conversion ratio (CR), rubber's grafting ratio (GR), grafting efficiency (GE) of the copolymerization and the toughening effect of PEB-g-MAN on the SAN resin were investigated. FTIR quantitative analysis showed that when the weight percent of AN unit in the unextracted product was 21.5 wt% with f_AN of 25 wt%, the toughening effect of unextracted PEB-g-MAN on SAN resin was the highest. Gel permeation chromatography (GPC) analysis showed that when f_AN was 25 wt%, the grafted copolymer had the lowest molecular weight and ABMS had highest toughness. Transmission electron microscopy (TEM) analysis showed that the highest toughness occurred when the phase structure of ABMS was cocontinuous with f_AN of 25 wt%. When f_AN was 25 wt% PEB-g-MAN domains have numerous small SAN domains in them, which was occlusion structure. Scanning electron microscopy (SEM) analysis indicated that the ABMS fracture surfaces had plastic flow visible, which looked like a craze fibers morphology, for the sample with highest impact strength (f_AN = 25 wt%). Dynamic mechanical thermal analysis (DMA) showed that the miscibility of the PEB phase and SAN phase improved after graft copolymerization of MMA and AN onto PEB.     

Preparation and Properties of Polyethylene Terephthalate (PET)/Near Infrared Reflective Pigment (NIR) Composites

A near infrared reflective (NIR, nickel antimony titanium yellow rutile) pigment filler was incorporated into a polyethylene terephthalate (PET) matrix via a melt blending approach to increase the infrared reflection of PET and limit the thermal heat accumulation in light of environmental and energy conservation concerns. Two different types of surface modifiers, polyethylene glycol (PEG) and cetyltrimethylammonium bromide (CTAB), were used to modify the NIR surface, as NIR–PEG and NIR–CTAB fillers, to investigate the surface modification effect. Fourier transform infrared spectroscopy (FTIR), a Zetasizer, and electron spectroscopy for chemical analysis (ESCA) results suggested a successful adsorption of the organic modifiers onto the NIR surface. Thermogravimetric analysis indicated a higher adsorption degree for the CTAB modifier than the PEG modifier due to the electronic interaction between CTAB and NIR. The thermal crystallization temperature (T_c) for neat NIR-filled samples decreased with increasing NIR content within the PET matrix at first, up to 9°C, but then tended to increase again up to a measurable difference of 6°C with respect to pure PEG, indicating the promotion of the crystallization kinetics of the neat NIR within the PET matrix. On the other hand, a decrease in T_c for all NIR-CTAB or NIR-PEG loadings was found, with the depression close to 10°C for all NIR-CTAB samples regardless of the loading. CTAB modified NIR gave the highest improvement in tensile strength and strain at break in comparison with NIR and NIR-PEG filled samples. The near infrared reflection values of modified PET were higher than those of neat PET. The reflection values appeared to be the highest for some concentrations of the NIR-CTAB filled samples, but were of similar orders of magnitude with those for NIR or NIR-PEG filled samples.     

A meshless model for transient heat conduction analyses of 3D axisymmetric functionally graded solids

A meshless numerical model is developed for analyzing transient heat conductions in three-dimensional （3D） axisymmetric continuously nonhomogeneous functionally graded materials （FGMs）. Axial symmetry of geometry and boundary conditions reduces the original 3D initial-boundary value problem into a two-dimensional （2D） problem. Local weak forms are derived for small polygonal sub-domains which surround nodal points distributed over the cross section. In order to simplify the treatment of the essential boundary conditions, spatial variations of the temperature and heat flux at discrete time instants are interpolated by the natural neighbor interpolation. Moreover, the using of three-node triangular finite element method （FEM） shape functions as test functions reduces the orders of integrands involved in domain integrals. The semi-discrete heat conduction equation is solved numerically with the traditional two-point difference technique in the time domain. Two numerical examples are investigated and excellent results are obtained, demonstrating the potential application of the proposed approach.     

The structure-tunable synthesis and magnetic properties of Fe3O4 nanocrystals

Magnetite nanocrystals with tunable crystalline structures (orthorhombic and cubic) were synthesized via a simple oxidation-coprecipitation approach basing on the reaction of FeSO₄·7H₂O with C₆H₁₂N₄. The average diameter of prepared orthorhombic Fe₃O₄ nanorods were 15 nm while their lengths were approximately 150~200 nm. As-prepared cubic counterparts were composed of 10 nm sized nanoparticles. XRD, FESEM, TEM, SAED and HRTEM were then used to characterize our samples. In addition, magnetic measurements showed the saturation magnetization of orthorhombic magnetite was lower than that of cubic ones. Mössbauer spectroscopy verified the samples possessed the nature of cubic magnetite. Finally, a possible growth mechanism for orthorhombic nanorods and cubic nanoparticles was also discussed.     

监测点波长对高双折射光纤环镜轴向应变灵敏度的影响

研究了高双折射光纤环镜监测点波长对轴向应变灵敏度的影响. 经理论推导得出高双折射光纤环镜轴向应变灵敏度公式. 结果表明: 当高双折射光纤材料选定后, 灵敏度随着监测点波长的增大而增大; 当监测点选定后, 监测点的灵敏度为常数, 波长变化与应变成线性关系. 实验选取不同波长的波峰进行应变灵敏度监测, 对各监测点进行数据拟合, 实验结果与理论分析一致. 研究结果对提高高双折射光纤环镜应变、温度等灵敏度具有指导意义. 关键词： 波长 灵敏度 监测点 高双折射光纤环镜     

Mixed multi-region design of diffractive optical element for projection exposure system

The diffractive optical element (DOE) is widely used to generate various illumination modes in the projection lithography system. The working principle and design methods of the DOE are discussed in detail in this paper. A mixed multi-region design method is proposed to calculate the phase of DOE based on the poor spatial coherence of excimer laser, using the Gerchberg–Saxton (GS) algorithm. The DOEs generating circular, dipole and quadrupole illumination modes are designed and simulated by three different methods: single region design, repeated multi-region design and mixed multi-region design. The performance of these DOEs are compared and analyzed with these three design methods. The mixed multi-region design method is used to design the DOEs generating three illumination modes, the diffraction efficiencies are greater than 85%, and the non-uniformities of illumination are less than 3%. The analysis results indicate that the DOE designed by the mixed multi-region design can achieve higher diffraction efficiency and illumination uniformity of the far-field intensity distribution without modifying the GS algorithm.     

Ranking spreaders by decomposing complex networks

Ranking the nodes? ability of spreading in networks is crucial for designing efficient strategies to hinder spreading in the case of diseases or accelerate spreading in the case of information dissemination. In the well-known k-shell method, nodes are ranked only according to the links between the remaining nodes (residual links) while the links connecting to the removed nodes (exhausted links) are entirely ignored. In this Letter, we propose a mixed degree decomposition (MDD) procedure in which both the residual degree and the exhausted degree are considered. By simulating the epidemic spreading process on real networks, we show that the MDD method can outperform the k-shell and degree methods in ranking spreaders.     

Near-infrared downconversion in Eu2＋ and Pr3＋ co-doped KSrPO4 phosphor

A novel near-infrared (NIR) downconversion (DC) phosphor KSrPO4 :Eu2+ , Pr3+ is synthesized by the conventional high temperature solid-state reaction. The Eu2+ acts as an efficient sensitizer for Pr3+ in the KSrPO4 host. With broad-band near-ultraviolet light excitation induced by the 4f→5d transition of Eu2+ , the characteristic NIR emission of Pr3+ , peaking at 974 nm and 1019 nm due to 3P0 → 1G4 and 1G4 → 3H4 transitions, is generated as a result of the energy transfer from Eu2+ to Pr3+ . The luminescence spectra in both the visible and the NIR regions and the decay lifetime curves of Eu2+ prove the energy transfer from Eu2+ to Pr3+ . This Eu2+ and Pr3+ co-doped KSrPO4 phosphor may be a promising candidate to modify the spectral mismatch behavior of crystalline solar cells and sunlight.     

KTP和7.5mol%Nb:KTP晶体在Nd:YAG激光中的倍频和和频

本文在获得精确的7.5mol%Nb:KTP晶体的Sellmeier主折射率色散方程的基础上,计算7.5mol%Nb:KTP晶体对1.0642μm和1.3188μmNd:YAG激光的倍频和和频的型相位匹配曲线.通过研究KTP和7.5mol%Nb:KTP晶体的主折射率,双折射率和相位匹配,可以看出Nb掺入KTP晶体后产生的折射率和双折射率的色散和各向异型的变化是引起KTP晶体相位变化的根本原因.