The influence of proton irradiation on the corrosion of HT-9 during immersion in lead bismuth eutectic

The impedance properties of the oxide on the martensitic-ferritic steel HT-9 were characterized during proton irradiation at the LANSCE WNR facility. Prior to the irradiation experiment, samples were pre-oxidized in moist air resulting in an oxide scale that was on the order of 3 μm thick. Samples were then irradiated during immersion in 473 K lead-bismuth eutectic at a proton current of approximately 63 nA. To assess corrosion rate in real-time, a sinusoidal voltage perturbation was applied across the oxide surface as a function of frequency and the corresponding current response was measured. This method yielded values of oxide impedance which were used in conjunction with Wagner’s oxidation theory to calculate corrosion rate. In general, proton irradiation was associated with an increase in corrosion rate.     

The effect of washing on physicochemical changes in packaged, sliced green peppers

Whole green bell peppers (Capsicum annuum L.) were obtained through a local fresh‐cut company. They were washed in a 100 ppm chlorine solution, dried and then sliced into 0.5‐cm wide strips. A bulk sample of slices was divided into four treatments: (1) no wash, (2) one wash in fresh distilled water, (3) two sequential washes in fresh distilled water, and (4) three sequential washes in fresh distilled water. Retention of firmness of the pepper slices during storage at 7 °C improved with the number of washes after cutting. The modification of package atmosphere was less in all wash treatments than in the ‘no wash’ control. The sliced tissues of ‘no wash’ controls had higher levels of acetaldehyde and ethyl acetate. Analysis of the wash water revealed that sequential washes with water removed incremental amounts of acetaldehyde and soluble phenols from the cut surfaces of the tissue. These results show that washing has a dramatic effect on physicochemical measures of quality in green pepper slices, and it is likely that this effect is mediated by the removal of stress‐related compounds produced during the cutting operation. While acetaldehyde and total phenolics were the two stress‐related compounds measured in the wash water, it may be that other compounds removed in the wash water could have contributed to the beneficial effects on quality reported in this study.     

Behaviour of thujone during distillation and possible concentration ranges in pre‐ban absinthe

A discrepancy in the magnitude of thujone concentrations in distilled pre‐ban absinthe has existed until now. Concentrations of 260 mg L^?1 were derived at by theoretical calculations. Tests of authentic pre‐ban absinthes and studies concerning absinthes produced according to historic recipes found concentrations below 10 mg L^?1. In this study, the behaviour of thujone during distillation was studied and a significant discrimination was determined (80% yield in water‐cum‐steam distillation). The thujone concentrations in distilled pre‐ban absinthe were then calculated with regard to the composition of wormwood derived from a literature review. Due to the large deviations of oil content and thujone concentration of wormwood, a typical Absinthe Suisse de Pontarlier from Duplais' 1855 recipe might have contained between zero and a maximum of 76 mg L^?1 of thujone, the average was calculated as 23 mg L^?1 with a standard deviation of 21 mg L^?1. It was proven that the previous calculations overestimated the thujone content of distilled absinthe and the discrepancy was resolved as our new calculations are in good accord with the experimental findings. Copyright © 2007 Society of Chemical Industry     

H.26L中整数变换的研究及改进

针对DCT变换存在浮点运算、运算量大等问题,H.26L提出了整数变换,它能够很好地消除浮点运算,避免逆变换不匹配,但存在精度不高的问题。在基于提升结构(liftingstructure)的无乘法二进制DCT(binDCT)的基础上,对参数进行选择优化,并将浮点DCT、整数变换和binDCT在结构和性能上进行比较分析,选择一组binDCT参数,使binDCT既能避免浮点运算又能降低运算量,且更有利于压缩。     

H.26L中熵编码原理分析及改进

分析了H.26L中熵编码的原理和特点,比较了两种不同熵编码方法的优缺点、性能差异和发展方向,提出了一种基于量化参数QP的熵编码改进方法。实验证明这种方法能在信道传输率变化到一定程度时,动态调整熵编码的方法,使H.26L熵编码器在复杂度和编码效率两方面作出合理的权衡。     

基于开关信号理论的电流控阈技术及I^2L施密特电路

本文在开关－信号理论的指导下，采用电流信号表示逻辑值，对Ｉ＾２Ｌ电路中如何实现阈值控制进行了研究，在此基础上，提出了实现阈值控制电路的接地开关运算表示式，并用于设计相应的三值Ｉ＾２Ｌ施密持反相器电路，用ＰＳＰＩＣＥ程序模拟证明了所设计的电路具有理想的施密特电路特性。     

Loss of ascorbic acid during storage of Conference pears in relation to the appearance of brown heart

To investigate the causes of brown heart (BH) in Conference pears, the contents of ascorbic acid (AA) and dehydroascorbic acid (DHAA) in fruits were studied during the first period of storage. AA was studied in 1999 and 2000, DHAA in 1999 only. Pears from normal and very late harvest stored immediately or after a delay in a controlled atmosphere with 2% O₂ and low (0.7%) or high (5%) CO₂ were compared. DHAA content did not change during storage in any treatment. AA decreased in storage according to an exponential model. The rate of AA loss was different in the two years and was higher in late‐harvest fruits and in those stored in 5% CO₂. BH appeared in different treatments when AA decreased below a threshold, which was about 2 mg kg^?1 fresh weight, corresponding to 5% of the AA content at harvest. The frequency and severity of symptoms depended linearly on the time spent by fruits in low‐ascorbate conditions. Advanced maturity at harvest and storage in high CO₂ determine the appearance of BH and increase the rate of AA loss, probably through a reduction in the turnover of antioxidants. © 2002 Society of Chemical Industry     

316L不锈钢粉真空松装烧结的研究

研究了316L不锈钢粉注射成形等低压成形工艺的粉末真空松装烧结行为及其影响因素。通过添加石墨实现脱氧控碳,分析比较了气、水雾化粉真空松装还原烧结行为的差异。     

Runge Kutta Type Methods for Isodynamical Matrix Flows: Applications to Balanced Realizations

Recently several numerical methods have been proposed for solving isospectral problems which are matrix differential systems whose solutions preserve the spectrum during the evolution. In this paper we consider matrix differential systems called isodynamical flows in which only a component of the matrix solution preserves the eigenvalues during the evolution and we propose procedures for their numerical solution. Applications of such numerical procedures may be found in systems theory, in particular in balancing realization problems. Several numerical tests will be reported. Received April 27, 2001; revised October 25, 2001 Published online February 18, 2002