An agile manufacturing workcell design

This paper introduces a design for agile manufacturing worked Is intended for light mechanical assembly of products made from similar components (i.e., parts families). We define agile manufacturing as the ability to accomplish rapid changeover from the assembly of one product to the assembly of a different product. Rapid hardware changeover is made possible through the use of robots, flexible part feeders, modular grippers, and modular assembly hardware. The division of assembly, feeding, and unloading tasks between multiple robots is examined with prioritization based upon assembly time. Rapid software changeover will be facilitated by the use of a real-time, object-oriented software environment utilizing graphical simulations for off-line software development. An innovative dual VMEbus controller architecture permits an open software environment while accommodating the closed nature of most commercial robot controllers. These agile features permit new products to be introduced with minimal downtime and system reconfiguration.     

QUENCHING MECHANISMS AND KINETICS OF CAROTENOIDS IN RIBOFLAVIN PHOTOSENSITIZED SINGLET OXYGEN OXIDATION OF VITAMIN D2

The oxidation of vitamin D₂ in a solution of 12% water, 88% acetone and 15 ppm ribqflavin under light or dark was studied by measuring the headspace oxygen. Ribofiavin accelerated the oxidation of vitamin D₂ by singlet oxygen under light, but did not affect vitamin D₂ oxidation under dark. Quenching mechanisms and kinetics within the range of 0–20 ppm β‐cawtene or fucoxanthin and with 0–80 ppm retinyl acetate or retinol on 15 ppm riboflavin photosensitized singlet oxygen oxidation of vitamin D₂ were also studied. The rate of singlet oxygen formation by 15 ppm riboflavin was 1.78 umole oxygen/mL headspace‐hour. The reaction rate constant of vitamin D₂ with singlet oxygen was 2.2 times 10⁷ M^?1A s^?1. The carotenoids minimized the oxidation of vitamin D₂ by quenching singlet oxygen. The total quenching rate constants of retinol, retinyl acetate, jucoxanthin and ft‐carotene were in the order of 1.22 times 10⁸, 5.98 times 10⁸, 1.78 times 10⁹ and 5.00 times 10⁹M^?1. s^?1 respectively, which suggests that as the number of double bonds of carotenoids increases, the quenching rate constant ofcarotenoid increases.     

Softening of Canned Apricots: A Chelation Hypothesis

Infiltration of apricot (Prunus armeniaca L.), Patterson cultivar fruits, which are susceptible to rapid softening, with calcium chloride before processing resulted in definite firming of the canned apricots. Non-susceptible fruits treated with citrate buffers (pH 3.7) showed dramatic post-process softening. In individual, untreated, early, green fruit, firmness after processing was directly correlated with the bound calcium:citrate ratio. Based on a chelation hypothesis, it was proposed that softening was accelerated when chelators such as organic acid anions removed structural calcium from the cell wall once cell membranes were lysed by heating.     

Effects of Variety, Maturity and Processing on Pear Juice Quality and Protein Stability

?Anjou, Comice, and Bartlett pears were processed into clarified juices from hard green and soft ripened fruits. Processing trials with and without SO₂ were conducted. Effects of variety, maturity and processing on browning, turbidity, proteins, and stability were investigated. Browning increased with heat treatment, and was reduced by processing with SO₂. Total soluble protein content increased with fruit maturity and processing with SO₂. Protein fractions from a clarifying enzyme preparation (mainly arabinase and amylase) with MW in the range of 64,000–92,000 and containing glycoproteins were not removed by fining/clarification. They contributed to protein instability in the clarified pear juices, but could be removed by heat treatment (pasteurization) prior to final filtration and bottling. Our results indicate some enzymes added for clarification during processing may contribute to post-clarification haze and sediment formation.     

Controlled Low-Temperature Vacuum Dehydration–A New Approach for Low-Temperature and Low-Pressure Food Drying

The processes of freeze-drying, vacuum drying and controlled low-temperature vacuum dehydration (CLTV) were used to dry clam paste and a gelatin-microcrystalline cellulose model food system. CLTV was carried out as cold as possible without freezing the product. Much less drying time was required for CLTV and vacuum drying than for freeze-drying. The mass transfer resistance for both freeze-drying and CLTV was less than that of vacuum drying. Functional properties were closer to those of freeze-drying than to vacuum drying. CLTV versus freeze-drying showed a 30% reduction in enthalpy change and 40% reduction in running cost. Microbiological analysis, used to monitor the safety of processing clam paste, showed that the process was satisfactory relative to common parameters.     

Fire and explosion hazards associated with milk spray drying operations*

Recent reports in the literature indicate that incidents involving fires and explosions in the spray drying of milk products are increasing in number. While milk powder is not highly explosible, the conditions for a dust explosion, apart from the ignition source, are almost always present in certain areas of a spray drying system during its normal operation. Self-ignition of deposits is known to be possible at the high temperatures in a spray drier. At best, this can cause product degradation and discoloration and at worst it can provide the source of ignition for an explosion. This paper is an attempt to draw together recent work on fire and explosion prevention and protection for milk powders.     

Quality and Shelf-life of Fresh Cut Carrot Slices as Affected by Slicing Method

The effects of slicing method on the quality and storage-life of modified atmosphere packaged carrot slices were determined using microscopy, sensory evaluation, microbial counts and a range of physical and chemical tests. Slicing caused physical damage, physiological stress and enhanced microbial growth. The severity of these effects were in the order of blunt machine blade > sharp machine blade > razor blade. These findings provide insights into the magnitude and basis of slicing effects and also confirm the importance of gentle processing and the use of a sharp blade.     

消息推送在移动高级应用中的研究与实现

为了使移动终端用户能够及时查看到电力业务更新消息,提出消息推送技术在移动高级应用中的研究。首先介绍消息推送的实现方式及原理,然后就iOS与Android系统两大主流移动系统平台的消息推送机制进行研究,提出在两大主流移动系统平台上实现消息推送的解决方案,并在企业移动驾驶舱的高级应用中实现消息推送,使终端用户能够实时查看到更新的消息。     

TOMATO PERICARP TISSUE RESONANCE AND ITS USE IN TEXTURE EVALUATION

The use of resonance properties, measured by dynamic oscillation using a constant stress rheometer, as textural parameters for excised pericarp tissue of tomato ( Lycopersicon esculentum Mill cv Trust) fruit during 21 days of ambient temperature ripening was assessed relative to the large-deformation behavior measured by flat-plate compression. The resonance frequency (f_r) of excised tissue discs decreased significantly (P < 0.05) over the first 9–12 days, and then approached a relatively low and constant value with subsequent ripening. A significant (P < 0.05) increase in associated resonance strain amplitude (y_max) became apparent after the first 9–12 days of tomato fruit ripening. Ripening-associated changes in bioyield and failure strengths, toughness, and apparent elastic and failure deformability moduli derived from flat-plate compression tests were similar to those observed for tissue f_r. Results were consistent with a change in the dominant mode of tissue failure from cell relaxation and rupture to debonding after 9–12 days of fruit ripening. A significant (P < 0.05) semilogarithmic relationship was observed between f_r, but not y_max, and compression parameters, allowing for reasonable prediction of large-deformation behavior on the basis of measurement of only f_r. The results demonstrate that resonance frequency may provide a useful parameter in the evaluation of tomato pericarp tissue texture.     

SELECTION OF VARIABLES FOR LINEARIZED TRUSS OPTIMIZATION

Three possible variable selections for linearized truss optimization are compared. The available evidence shows that a variable choice of member stresses and member cross-sectional areas is inferior to either of the other two variable combinations, member stresses and reciprocal areas or member forces and cross-sectional areas. The properties of the member force/area variable choice are determined analytically and it is suggested that this selection may well be at least equally as powerful as the member stress/reciprocal area formulation.