Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

基于整体变分和变换域分析的复合去噪模型

本文在泛函空间理论基础上提出了一种整体变分与小波阈值萎缩复合的图像去噪模型。复合模型在小空间规整化约束下实现整体变分优化去噪,保持图像边缘特征减弱值阶跃现象;复合模型处理图像中不存在Gibbs现象且可应用于大噪声图像恢复缺失信息。DCT变换是一种表征图像纹理特征的变换域处理方式,本文最后将DCT变换引入复合模型,得到保持纹理特征的复合去噪模型。理论和实验证明了本文提出的模型在图像去噪中的有效性。     

一种新的变分去噪模型定参方法

以全变分去噪模型为例,从梯度下降法解相应的欧拉方程着手,提出一种新的定参方法对图像进行去噪,根据新方法选取的参数,同时保证均值和方差估计式。且求解偏微分方程选取的初值不是噪声图像而是对噪声图像进行小波分解后,保留低频系数,只对高频系数设置阈值,再重构后的图像。根据新选取的初值对相应的偏微分方程进行差分迭代求解,数值仿真结果表明,该方法选取的初值具有更好的去噪效果。     

基于激光透射模型的烟雾对可见光遮蔽能力分析

以烟雾遮蔽能力检测系统为平台,测试了常规烟幕黄磷在0.38～0.76μm可见光波段的全遮蔽能力(TOP),并通过粒度分析仪测量了黄磷烟雾随时间变化的粒度改变.在假设磷烟雾粒子为单分散系球形粒子的前提下,基于激光透射模型建立了全遮蔽能力的理论计算模型,并进一步推导了不同粒度情况下具有吸收指数的黄磷烟雾的TOP值,所得到的计算结果与实验值相近.结果表明.中等湿度、室温条件下,黄磷成烟后10～30 s内,粒径分布在0.5～3μm范围,并且随时问增加而减小,TOP值随粒径变小有下降趋势.     

Titanium‐Catalyzed Enantioselective Synthesis of α‐Ambrinol

We describe the first enantioselective synthesis of the odorant compound (−)‐α‐ambrinol (96% ee) from commercial geranylacetone. The key steps are a Jacobsen’s asymmetric epoxidation and a titanium‐catalyzed stereoselective cyclization initiated by radical epoxide opening. The oxirane ring opening proceeds with retention of configuration at the epoxide chiral center, giving a secondary alcohol which can be advantageously exploited to raise the ee provided by the synthetic sequence. We also synthesized (+)‐α‐ambrinol by a closely related procedure, showing the synthetic versatility of combining titanium‐catalyzed cyclization with Jacobsen’s epoxidation reactions.     

西瓜藤中黄酮类化合物提取工艺的优化

采用乙醇溶液提取西瓜藤中总黄酮,通过单因素试验和正交试验研究了固液比、提取时间、提取温度和乙醇浓度对总黄酮提取率的影响。结果表明,最优提取条件为：固液比1∶20、提取时间4h,提取温度80℃、乙醇浓度60%。     

Total phenolic content and antioxidant properties of eclipse black beans (Phaseolus vulgaris L.) as affected by processing methods

ABSTRACT:  The effects of soaking, boiling, and steaming processes on the phenolic components and antioxidant activity of black beans were investigated. All processed beans exhibited significantly ( P < 0.05) lower antioxidant activities than raw beans in total phenolic content (TPC), DPPH free radical scavenging activity (DPPH), and oxygen radical absorbing capacity (ORAC). Steaming processes resulted in a greater retention of TPC and ORAC values than the boiling processes. Pressure boiling shortened processing time compared to regular boiling, resulted in insignificant differences in TPC, but significantly increased in ORAC as compared to the regular boiling method. Pressure steaming resulted in significant decreases in TPC, DPPH, while significantly increased in ORAC compared to regular steaming. Greater TPC, DPPH, and ORAC values were detected in boiling water than in the soaking and steaming water. Mass balance analysis showed that boiling caused more dry solid loss than steaming. All of these results indicated that processing methods significantly changed contents and activities of antioxidant components of black beans. Steam processing exhibited several advantages in appearance and texture of the cooked product, shortening processing time, and in greater retention of TPC and antioxidant activities. Steam processing may be used to develop high-quality health-promoting black bean products.     

Continuous Flow Microwave‐Assisted Processing and Aseptic Packaging of Purple‐Fleshed Sweetpotato Purees

ABSTRACT: Pumpable purees from purple‐flesh sweetpotatoes (PFSP) were subjected to microwave heating using a 60 kW, 915 MHz continuous flow system, followed by aseptic packaging in flexible containers to obtain a shelf‐stable product. Initial test runs were conducted using a 5 kW 915 MHz microwave system to measure dielectric in‐line properties and examine the puree temperature profiles. The results demonstrated uniformity in heating of the puree at sterilization temperatures (>121 °C), and the dielectric constants and loss factors were within the range of published values for orange‐fleshed sweetpotato purees. The pilot‐scale test runs in a 60 kW microwave unit produced shelf‐stable puree packages stable at room temperature. Polyphenolic content of the PFSP purees were evaluated and the results showed that while total phenolics increased (5.9%) and total monomeric anthocyanins slightly decreased (14.5%) with microwave application, antioxidant activity determined by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging activity and oxygen radical absorbance capacity (ORAC) assays did not significantly change as a result of microwave processing. Color values showed that microwave‐processed samples differed from fresh puree in saturation and hue angle, but not in overall color change. PFSP purees increased in gel strength when microwave processed, packaged, and stored, but the gel could be easily disrupted into flowable purees. Overall, high‐quality retention can be obtained by microwave processing and aseptic packaging of PFSP purees so that they can be used as functional food ingredients.     

Resistance to aerobic deterioration of total mixed ration silage: effect of ration formulation,air infiltration and storage period on fermentation characteristics and aerobic stability

BACKGROUND: High aerobic stability can be expected when wet brewers' grains are stored as a total mixed ration (TMR) silage. To understand the factors affecting the stability, the effects of ration formulation, air infiltration and storage period were studied. RESULTS: A TMR containing wet brewers' grains, hay, maize, wheat bran, beet pulp and molasses was ensiled in laboratory silos for 14 and 56 days. The effects of hay species (lucerne or sudangrass) and air infiltration (Exp. 1) and of excluding one, two or three items from the six ingredients (Exp. 2) were examined. Ethanol was the main fermentation product in all TMR silages in this study. Aerobic deterioration occurred in 14 day silages prepared with sudangrass hay along with air infiltration (Exp. 1), and with the simplest recipe where three items (hay, maize and wheat bran) were excluded (Exp. 2). No deterioration occurred in 56 day silages regardless of ration formulation and air infiltration. Yeasts receded in 56 day silages, except with the simplest recipe, to the 10² cfu g^?1 level and remained undetectable in the presence of air (Exp. 2). CONCLUSION: TMR silage can resist aerobic deterioration provided that a sufficient ensiling period has elapsed. Silages stored for only a few weeks may be susceptible to deterioration when air is infiltrated or where fewer ingredients are used in the TMR mixture. Copyright © 2007 Society of Chemical Industry     

大孔吸附树脂纯化山茱萸总皂苷的动态洗脱条件研究

运用单因素试验和正交试验研究了山茱萸总皂苷在HPD-300大孔吸附树脂上的动态洗脱工艺,经极差分析和方差分析确定了其最佳操作条件。结果表明,最佳蒸馏水洗脱条件为：水洗流速1.0BV/h,用水量2.2BV,水洗时间2.2h;最佳洗脱剂洗脱条件为乙醇浓度50%,洗脱流速2.0BV/h,洗脱剂用量4.5BV。