新鲜瘦肉的换气包装技术

采用换气包装技术包装新鲜瘦肉可以有效地延长新鲜瘦肉的货架寿命。换气包装技术主要包含真空包装和充气包装二个工艺过程。文中给出了充填气体和包装材料的选用方法。     

Microbiological, physicochemical and organoleptic changes in dry-salted olives of Thassos variety stored under different modified atmospheres at 4 and 20 °C

Microbiological, physico-chemical and organoleptic changes were studied in dry-salted olives, cv. Thassos, stored under different atmospheres (100% carbon dioxide and nitrogen, 40% CO₂/30%O₂/30%N₂ and air) at 4 and 20 °C for 180 days. The initial microbial flora comprised of yeasts, no lactic acid bacteria, enterobacteria, pseudomonads or Staphylococcus aureus were detected, as the low water activity/high salt content does not favour their growth. At 4 °C, the population of yeasts declined steadily throughout storage but to a different extent depending on the gaseous atmospheres. At 20 °C, there was an initial decline in yeast counts in all samples followed by a steady increase until the end of the storage period. The CO₂ atmosphere was most effective at keeping the number of yeasts low at both storage temperatures. All gas atmospheres prevented fungal growth at both temperatures apart from the samples stored in air. The pH, a_w and salt content of the olives did not change significantly throughout the storage period. The prevailing yeast species was the salt tolerant Candida famata . The organoleptic characteristics did not differ significantly among differently treated olives. However, increased rancidity and reduced fruit colour was observed in the samples stored at 20 °C.     

改性粉体压制成型近似模型

表面改性后的无硬团聚超细粉具有良好的压制成型性能。表面酯膜的减摩润滑作用，使粉体在一定应力下流动性和分散性显著提高，压制过程的中后期应力传递准符合帕斯卡模型及均匀递减模型。     

Performance of 60 GHz Virtual Cellular Networks Using Multiple Receiving Antennas

During the past years, research covering propagation, channelcharacterization and wireless systems performance have yield asubstantial knowledge of the 60 GHz channel. The unlicensed 60 GHzfrequency band presents many attractive properties for wirelesscommunications. The environments in which the 60 GHzinfrastructure are to be designed are typically propagation- andcoverage-limited. This paper describes the important factors thatmust be taken into account when designing a wireless local areanetwork (WLAN) architecture operating in this frequency band.Therefore, we motivate the reasons of using distributedtransmitting antennas and multiple receiving antennas (MRA) inorder to mitigate the poor Direction of Arrival (DoA) diversityand to exploit the spatial diversity at the receiver. Such asystem can be considered as a multiple input multiple output(MIMO) system. We investigate the advantages of combining aVirtual Cellular Network (VCN) (using single frequency network anddistributed antennas) and MRA for the downlink. Several ways tocombine the signals with different levels of complexity arepresented. In the most complex case using Singular ValueDecomposition (SVD), it is possible to add coherently thecontribution of each antenna in a virtual cell while retaining thepath diversity inherent to the VCN infrastructure. The schemesyield several advantages: symbol diversity is improved, pathdiversity is still present, antenna gain using multiplebeamformers is increased and the multipath can be reduced. Theconcept is applicable to most types of single frequency networksbut it is especially well appropriate for the 60 GHz VCN/WLANusing orthogonal frequency division multiplexing (OFDM).Simulations give a realistic performance for QPSK, 8-PSK, and16-QAM baseband modulations with a 256-subcarrier OFDM using arate 1/2–convolutional code for a 2 ×2 VCN system.Results show a E_b/N₀ improvement of up to 6.2 dB usingthesingular value decomposition method with 16-QAM compared to thesingle input single output (SISO) coded reference.     

Effects of storage under a modified atmosphere on the microbiological and organoleptic qualities of ground beef prepared from pasteurized manufacturing beef

A 40‐kg lot of manufacturing beef, i.e. meat used for the production of ground beef products, was collected at a beef packing plant. The lot was divided into two batches. One batch was pasteurized by immersion in water at 85 °C for 60 s, the other batch was not pasteurized. Both batches were then ground. The ground meat was packed in overwrapped trays, which were master packaged under a modified atmosphere of 70% O₂ : 30% CO₂. The master packs were stored at 2 °C for up to 12 days. At the time of pack preparation and at 2‐day intervals, a master pack containing pasteurized and another pack containing unpasteurized meat, were opened and retail packs from each master pack were displayed at 4 °C for 3 days. Samples for microbiological analysis were obtained at the times of opening master packs and at the end of display. Displayed meat was assessed daily for colour, discoloration and retail appearance, and for odour intensity and acceptability at the end of display. After either a period of storage or a period of storage and display, the numbers of bacteria recovered from pasteurized meat were less than the numbers recovered from unpasteurized meat. The colour of pasteurized meat was perceived as being paler than that of unpasteurized meat, but discoloration was similar or less, and retail appearance was similar or better for pasteurized than unpasteurized meat at all times. The odours of displayed, pasteurized meat were generally somewhat less intense and more acceptable than those of unpasteurized meat. The findings indicate that pasteurization of manufacturing beef to improve the microbiological safety of ground beef provides a product of acceptable appearance and enhanced stability during storage under a modified atmosphere and subsequent display in air.     

Comparison of Three Quantum Correction Models for the Charge Density in MOS Inversion Layers

In order to obtain high density integration for MOS devices, it is necessary to reduce the gate oxide thickness and increase the substrate doping concentration. This results in a narrow and deep potential well in which electrons are confined at the semiconductor-insulator interface and it becomes necessary to take quantum mechanical (QM) effects into consideration. In this study, we compare three well established quantum correction models, i.e., the Hänsch model (Hänsch W. et al. 1989. Solid State Electronics 32(10): 839–849), the modified local density approximation (MLDA) model (Paasch G. and Ubensee H. 1982. Phys. Stat. Sol. (b) 113: 165–178), and the density-gradient (D-G) model (Ancona M.G. and Tiersten H.F. 1987. Physical Review B 35(15): 7959–7965; Ancona M.G. 1997. JTCAD 97–100) in terms of accuracy for predicting the inversion layer charge distribution.     

Control charts for processes subject to random shocks

In this paper, a charting technique for controlling processes subject to random shocks is presented. This type of process is common in a high-yield production environment and the conventional Shewhart control charts are not efficient for its monitoring and control. This technique is able to detect process improvement, easy for decision making, and more concise and informative than other methods used for this type of process. In addition, it could provide diagnostic information which is highly useful in practice.     

故障检测与诊断的SPRT方法及其修正

本文简单介绍了基于对新息序列处理而进行故障检测与诊断的 SPRT 法,然后针对这种方法有检测迟延的不足,给出了均值和方差都发生变化的修正的 SPRT 检测与诊断方法,并做了一些分析.     

铝支撑酸化蒙脱土的表征及催化性能

通过ＸＲＤ、脱吸附分析、ＦＴＩＲ、骨架振动红外光谱等手段表征了铝支撑酸化蒙脱土。结果表明：经酸化后的蒙脱土再进行铝交联，具有较强的固体酸性，对柴油转化为汽油和联二苯丙烯烷基化反应都有较高的催化活性。本文也讨论了固体酸对催化活性的影响。     

Sensory quality and internal atmosphere of fresh-cut Golden Delicious apples

The sensory shelf‐life of Golden Delicious fresh‐cut apples, dipped in 10 g L^?1 ascorbic acid and 5 g L^?1 calcium chloride and packaged under different modified atmosphere conditions, was assessed throughout refrigerated storage. An initial atmosphere of 0 kPa O₂ and plastic packages of an O₂ permeability of 15 cm³ m^?2 bar^?1 day^?1 were very effective in preserving the initial colour and firmness of apple cubes during at least 3 weeks of storage. These conditions resulted in increased respiration coefficients, which curbed the product consumer acceptance beyond the second week of storage. However, reduced ethylene and CO₂ production limited the appearance of fermentative metabolites during this period.