Modelling for flexible manufacturing systems and structural properties of optimal work routing policy

We consider flexible manufacturing systems (FMSs) which are composed of a set of workstations linked together with a material handling system (MHS). Each workstation consists of an input buffer, a single machine and an output buffer. The MHS consisting of a single cart routes work among the workstations according to the process paths required by the work. We deal with an optimal control problem in this FMS. We model the FMS as a closed queueing network. In the model, the cart routes the work to the workstations in accordance with a Markov routing with exponentially distributed routing time, and the machines process work with exponentially distributed processing time. An objective is to find a work routing policy that maximizes the total expected reward earned by operating machines. This optimal control problem is formulated as an undiscounted semi-Markov decision process. Structural properties of an optimal policy are analysed. Moreover, a sufficient condition is derived for the optimal policy to be of control limit type. An example is given to illustrate the result.     

Fading and broadening of electron diffraction spot from beam-damaged multiple monolayer films

In contrast to the increase in the extinction dose for thick specimens, observed broadening rates of diffraction spots from behenic acid multiple monolayers were independent of specimen thickness. This result leads to the conclusion that specimens are always decaying at the same rate although the periodicity of crystals still remains in thick specimens. The conclusion is interpreted as being the result of the radiation damage mechanism based on longitudinal motions of long chain molecules. For the evaluation of beam damage effect the broadening rate and the extinction dose should be used as indicator for the radiation sensitivity of crystals and for the possibility of observing diffraction patterns, respectively.     

Adsorption of Methyl Orange on Starches

Adsorption characteristics of methyl orange were investigated on kudzu, sweet potato, corn, rice, wheat, potato and snake gourd starches. No adsorption of methyl orange, an anionic dye, was observed on potato starch and snake gourd starch because of the presence of phosphate esters. Adsorption isotherms were found to fit both the Langmuir equation and Freundlich equation in all others. The degree of adsorption by kudzu, sweet potato, corn and wheat starches was related to the number of hydroxyl groups. We suggested methyl orange was confined to a monolayer on surface hydroxyl groups of the starches.     

Determination of Sweet Potato Starch Mixed in Kudzu Starch by Moisture Sorption Method

Moisture sorption isotherms of kudzu starch, sweet potato starch, and their mixtures were measured at 20°C by a gravimetric method with a vacuum apparatus. Correlation was found between the mixture ratio of sweet potato starch to kudzu starch and moisture content of the mixed starches at a water activity of 0.750; the correlation coefficient was 0.9955. The moisture sorption method could be used to determine the amount of sweet potato starch mixed in commercial kudzu starch.     

Equilibrium Isotherm Equations to Represent Moisture Sorption on Starch

Langmuir, Freundlich, BET, Harkins and Jura, Halsey, Smith, Henderson, and Chung and Pfost equations were used to fit experimental moisture sorption data at 20°C for kudzu, sweet potato, corn, potato, rice, wheat, and snake gourd starches. Goodness of fit (from calculated average residue), standard deviation, and standard error and range of water activity indicated Henderson and Chung and Pfost equations fitted the data well over a wide a_w range to 0.85. The large value of constants in Henderson and Chung and Pfost equations indicated stability of the microporous structure to moisture sorption. For larger constants, the microporous structures were more stable.     

凝胶色谱法(GPC)测定硫酸香菇多糖的含量及分子量

本文以GPC法,测定了硫酸香菇多糖的含量,线性范围0.05～0.5mg(y=-8176x+374628r=0.9999)。平均回收率为101.2％。RSD为0.46％。(n=6)并对其分子量进行了测定。比较了不同柱子上硫酸香菇多糖的色谱行为。