用于锁模光纤激光陀螺的相敏检测

通过采用锁相放大器,演示了一种性能明显提高的锁模光纤激光陀螺.结果表明锁相放大器的输出与转动速率之间具有理想的线性关系,并对两脉冲(在时间间隔测量过程中引起相位误差)之间的光强差不敏感.与以往报道的时间间隔测量相比,演示了长期稳定性提高了二个数量级.     

Application of GDQ scheme to simulate natural convection in a square cavity

The global method of generalized differential quadrature (GDQ) was applied to simulate the natural convection in a square cavity. Numerical results demonstrated that accurate solutions can be obtained using just a few grid points and requiring much less computational effort and storage.     

Rubber elasticity of poly(n-butyl acrylate) networks formed with multifunctional crosslinkers

The rubber elasticity characteristics of poly(n-butyl acrylate) networks crosslinked with tetrafunctional (EGDM and TEGDM), hexafunctional (TMPTM), and octafunctional (PETMA) vinyl crosslinkers were investigated. Both gel—sol analyses and crosslinking efficiency theories were used to evaluate the chemical crosslink contribution v_c and the entanglement contribution v_p to the elastically effective network chains v_e, and the effect of the crosslink junction functionality f on the front factor g. The front factors obtained were in the range of 0.50–0.92, depending upon the network system and the counting method for v_c. The relationship of g = [(f ? 2)/f]/〈r²〉/〈r²〉_o seems reasonable in the case of the tetrafunctional and hexafunctional networks, but deviates in the case of the octafunctional network. It is also evident that the functionality scheme for the front factor could only be valid under the postulate of a high v_p, which increases with increasing v_c, especially in the high v_c region near the Gaussian limit. The average energetic contribution to the retractive force of the present systems, expressed as F_e/F, is ?0.30 ± 0.1.     

The adsorption of chlordane by wheat flour from chlordane-treated shelf paper

Packaged wheat flour stored in direct contact with chlordane-treated shelf paper adsorbed with time appreciable amounts of the pesticide from the paper. Direct contact of the package with the paper was more conducive to flour contamination than it was from exposure of the flour to the vaporized pesticide components from the paper. Sorption effects of the pesticide with flour varied with the mode of exposure and the type of bag used, i.e. when the bags were in direct contact with the shelf paper, the flour packaged in polyethylene bags contained the largest amount of chlordane residue (29 ppm), which decreased about 10 per cent when packaged in single-thickness kraft paper bags and about 35 per cent in double-thickness kraft paper bags. When the bags were separated from direct contact with the shelf paper by means of open glass containers, contamination of the flour was tangibly decreased, whereby the amounts of residue found in the kraft single- and double-thickness paper bags were 0·4 and 0·3 ppm, respectively, compared to only 0·06 ppm in the polyethylene bags.     

Hard coatings on polycarbonate plate by sol–gel reactions of melamine derivative,poly(vinyl alcohol), and silicates

Hard coatings were deposited on a polycarbonate plate using a sol–gel process with a melamine derivative, poly(vinyl alcohol) (PVA), and silicates and examined as potential substitutes for glass in cars. PVA was partially functionalized with (3-isocyanatopropyl)triethoxysilane, and the synthesized polymer was used to form a coating solution with methylated poly(melamine-co-formaldehyde), tetraethoxysilane, and methyltriethoxysilane. The coatings that contained both the melamine and silicate structures were deposited using a sol–gel process. The optimum conditions and formulation to obtain excellent physical properties of the coating were determined. Smooth coatings with the hardness of a 3H class pencil, excellent abrasion resistance and transparency were formed.     

Modeling and control of CO2 separation process with hollow fiber membrane modules

A multi-stage model is developed for CO₂ separation by hollow-fiber membrane. The model permits rapid solution of the governing differential mass and pressure distribution in hollow-fiber gas separation modules using a computational scheme that does not rely on commercial software and conventional numerical methods such as shooting techniques. For 1-stage, 2-stage and 3-stage configurations the changes of required separation areas according to stage cuts are computed. A simple model predictive control technique is employed to provide optimal operation conditions based on the proposed model. Values of stage cuts can easily be identified for various desired mole fractions and recovery rates. From the results of numerical simulations, we can see that the proposed model can be effectively used in the control of gas separation process by hollow-fiber membrane modules.     

Evaluation of antioxidant capacity of sesamol and free radical scavengers at different heating temperatures

Sesamol is a natural antioxidant found in sesame oil from roasted sesame seeds. Activation energy and antioxidant capacity of sesamol were determined and compared with other free radical scavengers (FRSs) including tert‐butylated‐hydroxyquinone (TBHQ), butylated‐hydroxyanisol (BHA), or α‐tocopherol in a lard model system treated with different heating temperature. Each FRS was added in lard and heated at 90, 120, 150, and 180°C for 48, 24, 8, or 2 h, respectively and antioxidant capacity was evaluated by conjugated dienoic acid (CDA) value, conjugated diene hydroperoxides, p‐anisidine value (p‐AV), and a modified 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) method. Apparent activation energy of sesamol was determined as 12.98 kcal/mol in a lard model system. Antioxidant capacity of sesamol was as good as that of TBHQ and was higher than those of BHA and α‐tocopherol at 90, 120, and 150°C based on CDA, conjugated diene hydroperoxides, and p‐AV assays. The results of a modified DPPH method showed that each FRS showed different distribution of radical scavenging compounds from oxidized lipids (RSOLs) during oxidation. Sesamol may replace synthetic FRSs like TBHQ and BHA in processed foods treated with high temperature. Practical application: Processed foods are frequently treated with high temperature during oven‐drying, roasting, baking, and deep‐fat frying. This study showed that sesamol, one of natural antioxidants, had stronger antioxidant capacities than other synthetic FRSs at the temperature ranges from 90 to 180°C. The results of this study can be applied in food industries producing deep‐fat fried foods including snacks, chips, and French fries to extend the shelf‐life of final foods with high temperature treatment.     

Sodium azide and metal chelator effects on 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging compounds from methylene blue photosensitized lard

Thermal oxidation of edible oils can generate 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging compounds from oxidized lipids (RSOLs). However, effects of photosensitization on the formation of RSOLs have not been reported yet. Methylene blue (MB) photosensitization and involvement of singlet oxygen and transition metals on the RSOL formations were determined in stripped lard oils. RSOLs were formed in lard containing MB and visible light irradiation only. Addition of sodium azide decreased RSOLs with concentration dependent manner, which implies singlet oxygen was involved on the RSOL formation. Ethylenediammetetraacetic acid (EDTA), a well known metal chelator, accelerated the formation of RSOLs through protecting the decomposition of MB photosensitizer. Results from p‐anisidine values showed that RSOLs from photosensitization may not be formed from the same pathways compared to thermal oxidation. Practical application: Understanding mechanisms of lipid oxidation can help extend the shelf‐life of foods. Photosensitization plays important roles in accelerating the rates of lipid oxidation. The results of this study showed that foods containing photosensitizers can generate radical scavenging compounds from oxidized lipids (RSOLs) under visible light irradiation and singlet oxygen is involved in the formations of these compounds. However, these compounds may not share the same pathways with thermally oxidized lipids. Metal chelating agents accelerated the rates of lipid oxidation and formation of RSOLs which implies that metal chelators can act as prooxidant. Careful considerations are necessary on the addition of metal chelators because non‐polar photosensitizers can act a prooxidant.