Study on the preparation and mechanical properties of injection‐moulded wood‐based plastics

The objectives of this study were to prepare injection‐moulded wood‐based plastics and to characterize their mechanical properties. Injection‐moulded wood‐based plastics with satisfactory flexural (65.7 MPa) and tensile strengths (30.1 MPa) were successfully obtained through a simple reaction of mulberry branch meal with phthalic anhydride (PA) in 1‐methylimidazole under mild condition. The X‐ ray diffraction results indicated complete disruption of the crystallinity of cellulose because the pattern obtained for esterified fiber was almost a straight line without any peaks. The peaks in the Fourier transform infrared spectroscopy spectra (1738 and 748 cm^?1) and NMR spectra (173.3 and 133.5 ppm) indicated the attachment of 0‐carboxybenzoyl groups onto the wood fibers via ester bonds. The differential scanning calorimetry curves showed that the glass transition temperature decreased with increasing weight percentage gain (WPG). The derivative thermogravimetric analysis curves indicated that esterified wood fiber was less thermally stable than the untreated fiber and that the component tends to be homogeneous with increasing WPG. Scanning electron microscope revealed that the fractured surfaces of most samples were smooth and uniform but that high temperature and less PA dosage could lead to the appearance of holes and cracks. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41376.     

Enhanced thermal stability of biomedical thermoplastic polyurethane with the addition of cellulose nanocrystals

Freeze‐dried cellulose nanocrystals (CNCs) were dispersed in the thermoplastic polyurethane [Pellethane 2363‐55D (P55D)] by a solvent casting method to fabricate CNC‐reinforced nanocomposites. This study demonstrated that the addition of small amounts (1–5 wt %) of CNCs to P55D increased the thermal degradation temperature while maintaining a similar stiffness, strength, and elongation of the neat P55D. CNC additions to P55D did not alter the glass‐transition temperature, but the onset decomposition temperature was shifted from 286 to 327°C when 1 wt % CNCs was dispersed in the matrix. The higher onset decomposition temperature was attributed to the formation of hydrogen bonds between the hydroxyl groups on the CNC surface and urethane groups in the hard block of P55D. The ultimate tensile strength and strain to failure (ε_f) of the nanocomposites were minimally affected by additions up to 5 wt % CNCs, whereas the elastic modulus was increased by about 70%. The observation that ε_f was unchanged with the addition of up to 5 wt % CNCs suggested that the flow/sliding of the hard blocks and chains were not hindered by the presence of the CNCs during plastic deformation. The ramifications of this study was that CNC additions resulted in wider processing temperatures of P55D for various biomedical devices while maintaining a similar stiffness, strength, and elongation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41970.     

Wet spun fibers from solutions of cellulose in an ionic liquid with suspended carbon nanoparticles

Wet spun fibers from solutions of dissolving pulp in 1‐ethyl‐3‐methylimidazolium acetate (EmimAc) with up to 50 wt % (based on cellulose) suspended carbon black and graphene nanoplatelets particles were studied. Carbon fillers were dispersed by simple shearing in a Couette type mixer and the resulting spin dope was extruded into a hot water coagulation bath from a single hole spinneret. Microstructure, mechanical properties, and electrical conductivity were assessed as a function of filler loading and discussed in comparison to melt spun fibers with similar fillers. The coagulation process and subsequent drying of wet spun fibers was found to produce a significant microporosity, more so the higher the filler loading. The electrical percolation threshold was quite high in the wet spun fibers and relatively modest values of conductivity were obtained with regard to the high filler loadings. Carbon black was found to be superior to graphene nanoplatelets. This was related to flow‐induced orientation effects. The mechanical properties of the carbon‐filled fibers were found to be similar or lower compared to the pure cellulose fibers because of low interfacial interactions and formation of microporosity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41417.     

Kinetics of isothermal decomposition in polycrystalline β CuAlBe alloys

The kinetics of the microstructural evolution of the metastable β phase during isothermal aging in a Cu–22.60Al–3.26Be (at%) polycrystalline shape memory alloy has been studied by electrical resistivity measurements and microscopical examinations. With an isothermal treatment at around 820 K, the alloy rapidly decomposes into γ₂ phase with dendritic morphology, while between 670 K and 760 K the formation of α′ phase followed by the eutectoid decomposition is observed. A TTT diagram was estimated and the stability boundaries of the β phase in the studied alloy were compared with those of other Cu-based shape memory alloys.     

Production of citreoviridin by Penicillium citreonigrum strains associated with rice consumption and beriberi cases in the Maranhão State,Brazil

The aim of this study was to determine the levels of Penicillium citreonigrum and citreoviridin present in rice samples from Maranhão State, Brazil, where an outbreak of beriberi was reported and 32 deaths occurred (7% of the notified cases died in 2006). The ability of P. citreonigrum to produce citreoviridin was assessed, and a total of 420 samples of 21 different kinds of rice were collected. Mycobiota isolation and identification, the ability of citreoviridin strains to produce toxin, and the natural occurrence of citreoviridin were established. Rice samples were found to have high fungal counts and showed increasing levels from 2004 to 2007 harvest years. The most frequent genus was Aspergillus followed by Penicillium and Cladosporium. Ten out of eleven strains of P. citreonigrum were able to produce citreoviridin. Three rice samples had levels of citreoviridin ranging from 12 to 96.7 ng g^?1, and two bran samples had levels of 128 and 254 ng g^?1. These samples contaminated with P. citreonigrum and citreoviridin were involved in the beriberi cases from Maranhão State. Monitoring rice for mycotoxins in areas where this substrate is the basic food is crucial to prevent outbreaks like the one reported in this study, to improve management practice, and to diminish exposure risk of humans to these harmful toxins.     

安全适用、经济合理的设计、施工、监理建筑幕墙

只有正确区分建筑幕墙和采光顶或金属屋面、建筑门窗及其它建筑外装饰，才能保证安全适用、经济合理的设计、施工、监理建筑幕墙，满足建筑效果的需要。     

关于随机变量和的特征函数

给出一个两两独立但不相互独立的n(n≥3)个随机变量的一般形式上的反例，以此说明不相互独立的随机变量的和的特征函数可以等于各个分量特征函数的乘积．     

Creep characteristics of glass reinforced cement under flexural loading

Tests are reported on the flexural creep behaviour and flexural strength characteristics of mortar specimens reinforced with 5.0% by weight glass fibres. The specimens were cut off from flat sheet materials produced by premixing and spray suction casting processes. It is shown that fibre reinforcement reduced the deflections under sustained flexural load. The results show unmistakably a very significant influence of the fibre reinforcement in reducing creep strains. Fibres were generally more effective in controlling compression creep than tensile creep. Strength reductions were observed with time which were insignificant in specimens produced with the spray suction method.     

试论正反艺术手法

文章就建筑设计中的“正反”艺术手法结合实例进行了分析。“正反”艺术手法是“对立统一”规律在建筑创作中的运用，它当为一种有效的创作手法。