钢丝的疲劳强度与疲劳寿命

采用制绳钢丝样品，测定其疲劳寿命和疲劳强度；利用成组试验法和升降法，在用数据统计分析和处理实验结果的基础上，绘制出钢丝的存活率—应力—寿命曲线；讨论钢丝具有较高存活率的疲劳寿命的安全性，进一步探讨钢丝安全疲劳强度在Ｐ—Ｓ—Ｎ曲线上长寿命区的应用，补偿了靠成组试验法很难测定该区疲劳寿命分布的缺点。     

履带车辆履带板销耳孔和履带销的磨损寿命计算及加速寿命试验方法

本文针对履带车辆工作环境和条件以及履带板销耳孔和履带销磨损失效情况，借助定型试验数据，对履带板销耳孔（以下简称销耳孔）和履带销磨损寿命及规律进行了分析，得出了它们的磨损寿命规律可用威布尔分布来描述，并给出了磨损量和磨损寿命计算方法。最后以此为基础，建立起销耳孔和履带销的磨损失效物理模型和加速寿命试验方法。     

电容器高温寿命试验系统的设计

阐述了电容器高温寿命试验系统的工作原理,系统提供了电容器高温寿命试验所需的试验温度和试验电压,采用计算机监控系统实现试验电源的控制和检测,高温箱的控制和检测,以及电容器漏电流的实时采集、显示和录取,提高了高温寿命试验效率和自动化水平。     

毛纺粉冶钢领寿命的可靠性统计

本文运用可靠性理论,对近年来的一些试验钢领作了分析,指出毛纺粉冶钢领的寿命近似地服从威布尔分布,对试验钢领的寿命分布进行了参数估计,在此基础上绘制了试验钢领的寿命分布函数图形和概率密度函数图形.同时研究了钢领的可靠度函数,指出钢领的寿命是由其可靠寿命决定的,并对试验钢领的可靠寿命和平均寿命进行了估算,从而使我们对粉冶钢领寿命的评估有了科学的理论依据.     

自动络筒机可靠性测定试验

通过对青岛自动络筒机进行可靠性测定试验的实践，从试验方案，寿命分布，故障模式及判据的确定，现场试验的实施以及对数据收集分析处理等环节逐一进行分析研究，以求寻到一种合理，简便，实施经济的自动络筒机可靠性试验方法。     

金刚石浓度、粒度和强度对锯片切割性能的影响

文章通过一系列试验数据，总结出锯片效率和寿命与金刚石浓度粒度强度变化规律的关系，为优化锯片性能提供依据。     

提高甘蔗榨辊壳压榨效率及寿命的一种新方法

提出一种提高甘蔗榨辊壳压榨效率及寿命的新方法。经使用试验证明，该方法简单易行，经济效益显著。     

焊接式齿圈的齿面热处理工艺及改进

因为齿圈早期出现轮齿严重磨损的情况，所以需对齿面进行中频感应淬火的热处理，经过多次试验，最终确定了齿面热处理工艺，延长了齿圈的耐磨寿命．     

影响不锈弹簧疲劳性能因素分析

汽车门锁用WPBφ0.80 mm不锈弹簧在做锁体寿命试验时,同批次寿命差异较大。对疲劳寿命为28723次的弹簧断口进行分析,弹簧表面出现纵向裂纹;对原料晶粒度进行测定,疲劳寿命为17万～18万次的原料晶粒度为6.5级,疲劳寿命约23万次的原料晶粒度为9级。通过采用新旧模具生产的弹簧钢丝加工成扭簧后,疲劳寿命分别约24万次和22万次。采用酸浸试验加强对原料的检测,选择细晶粒原料,提高模具质量等措施可有效提高扭簧的疲劳寿命。     

微型Ni—W电沉积金刚石磨具的开发及其在硅切槽中的应用

探讨了直径为100μm的微型Ni—W电沉积金刚石磨具的制作方法及其在硅切槽中的加工特性，以评价该磨具的加工性能和优化制作条件。在制作磨粒直径为2～4μm的磨具时，通过射流搅拌电沉积溶液可获得较为均匀的磨粒分布，从而减小了磨具寿命的差异。关于磨具状态和磨具寿命，试验得出了最佳电流密度。从磨具寿命的角度出发，对磨削速度和进给量进行了优化。     

EXTENSION OF THE SHELF-LIFE OF BURFI BY PACKAGING

Burfi, an Indian milk‐based sweet, is susceptible to microbial spoilage that restricts its shelf life to 10 days. Large‐scale marketability of burfi and its export potential requires longer shelf life. Therefore, our aim was maximizing shelf life by packaging means. Studies were carried out on burfi in different packaging materials under different atmospheres – normal packing, vacuum packing and use of a free‐oxygen absorber – at 65% RH/27C. Normal packing even in barrier film did not effectively control microbial spoilage. Vacuum packing, although it retarded microbial growth, adversely affected texture and sensory quality. A free‐oxygen absorber coupled with high‐barrier materials like metallized films/foil laminates offered more than 45 days shelf life. Stored samples could be grouped by principal component analysis. The major sensory attributes contributing to grouping were color, firmness, chewiness, creamy and rancid notes. Sensory firmness and chewiness were found to have good correlation with instrumentally measured texture values.     

SHELF-LIFE SIMULATION OF PACKAGED RICE CRACKERS

ABSTRACT

Two varieties of rice crackers (RC‐1 and RC‐2) were packaged in two types of packaging materials, polyethylene and polypropylene pouches, and stored at 30C/75% RH and 30C/85% RH to simulate actual storage conditions and determine shelf‐life. The main composition differences in the samples were in their fat content (1.87% for RC‐1 and 21.09% for RC‐2) and initial moisture content (4.12% for RC‐1 and 2.28% for RC‐2). The shelf‐life of this product is mainly affected by moisture adsorption as evidenced by sensory evaluation. Guggenheim‐Anderson‐de Boer (GAB) model was used to fit the moisture sorption isotherm. Good precision of fit was found as measured by a determination coefficient (R²) close to 1. The shelf‐life was then predicted based on the relationship between permeability coefficient of the packaging materials and moisture adsorbed by the rice crackers determined by the GAB equation. The validation of the simulations against the experimental shelf‐life gave R² of 0.90 and 0.51, and root mean square error of 2.93 and 5.20 for RC‐1 and RC‐2, respectively. The simulation model was found to be applicable for a rapid and accurate shelf‐life prediction of RC‐1. However, a large difference between experimental and simulated shelf‐life of RC‐2 was probably because the moisture content may not be the only parameter influencing the shelf‐life of the RC‐2 samples. Other factors may also significantly affect the shelf‐life characteristics of the packaged rice crackers.

PRACTICAL APPLICATIONS

For a low‐moisture food product, actual storage testing by a long‐term stability study involves storing a packaged product under typical storage conditions and examining the product at regular time intervals. The testing is costly and time consuming, since most low‐moisture food products have a shelf‐life of several weeks or even months. This paper describes the shelf‐life prediction of two varieties of rice crackers having different compositions using a simulation model based on the relationship between barrier property of the packaging materials and moisture adsorbed by the rice crackers determined by the Guggenheim‐Anderson‐de Boer (GAB) model. The shelf‐life simulation provides a powerful support tool for shelf‐life estimation and packaging development.

     

DETERMINING THE SHELF–LIFE OF FROZEN PIZZA

The shelf–life of a frozen food product depends upon the quality of raw materials, rate of freezing, storage temperature and constant maintenance, and product handling by the retailer and consumer. Microbiological tests are of limited application, but chemical tests can be a direct measure of shelf–life. Sensory quality tests are presently accepted for determining frozen pizza shelf–life. Accelerated shelf–life tests are needed. Although open dating of food products encourages better handling, it contributes little to microbiological quality. The best–if–used–by date is preferred by consumers and is most appropriate for frozen pizza provided accurate determination of shelf–life can be made.     

INFLUENCE OF TEMPERATURE ON SHELF LIFE OF BUTTERHEAD LETTUCE LEAVES UNDER PASSIVE MODIFIED ATMOSPHERE PACKAGING

The aim of the present work was to study the influence of temperature on sensory and microbiological qualities, and on shelf life of butterhead lettuce leaves in passive modified atmosphere packages. Butterhead lettuce was washed and placed under ambient air in 30  ×  40 cm polypropylene bags, and stored at 5, 10 and 15C. A first-order equation was obtained for the development of the evaluated appearance sensory attributes as a function of storage time. For all the evaluated storage temperatures, microbiological shelf lives (14, 17 and 42 days at 5, 10 and 15C) were higher than estimated sensory shelf lives (8, 14 and 26 days at 5, 10 and 15C), showing that shelf life of lettuce in passive modified atmosphere packages was limited by sensory properties and not by microbial growth.

PRACTICAL APPLICATIONS

Sensory shelf life of lettuce in passive modified atmosphere packages was estimated using consumer data, which are an improvement of a more arbitrary criteria presented in most studies. Moreover, if failure criteria used in other studies were applied, consumer rejection at the end of shelf life would be higher, suggesting that more conservative criteria are necessary to assure the product's quality at the end of its shelf life.     

生活方式对服装流行的影响

主要研究了女大学生的时尚行为对服饰流行的影响。具体从生活理念对流行的影响;生活方式对流行的影响;女大学生受大众传媒的引导等方面来研究。     

IMPROVEMENT OF SHELF LIFE STABILITY OF CAKES

ABSTRACT

The effects of new ingredient strategies to slow down starch retrogradation rate in cakes were investigated. In this study, devil's fudge cakes were formulated using gum, modified starch and enzyme technology. Cake samples that were prepared with combinations of gums, bacterial amylases and pregelatinized starch were found to have slower starch retrogradation rates. An accelerated shelf life protocol was followed to observe the effect of predescribed ingredients on slowing the starch retrogradation rate. The samples were evaluated for moisture content, water activity, texture and thermal properties, as well as morphological characteristics. The staling rate was found to be accelerated by the fluctuations in temperature from high to low temperatures. Modified starches, enzymes and gums were found to decrease the rate of staling and improve product quality. The formulated cakes were found to have 25% lower toughness and hardness values as compared with the control product. It was found that for all the cake formulations, there was a significant decrease in both hardness and toughness values, whereas springiness values did not change much. The basic differences within formulations were created by incorporation of gums, enzymes, soluble fibers, emulsifiers and modified flours in the cake.

PRACTICAL APPLICATIONS

Nutritional balance is quite important for each individual. For certain groups of people, based on their activity levels, high energy supplies are required to help them to achieve their optimal performance. Cakes, waffles and pancakes are in the group of breakfast bakery items that provide high energy for these groups of people. In bakery food products, staling reactions start before microbial deteriorations; as a result, they are the major factor in determining shelf life. Cakes that are acceptable to the consumers should be moist and soft in texture. Starch retrogradation is the primary mechanism determining the shelf life of the product. Although the product is microbiologically safe, the adverse affects of starch crystals on textural properties is the main cause of product rejection by the consumer, which leads to huge economical losses. The current methods of controlling starch retrogradation lean on technologies of the 1980s. Despite several studies on bread staling, there is hardly any study on the staling mechanism of cakes and other bakery food items. This study provides information on how to retard staling in cakes by the use of an in‐house developed accelerated shelf life protocol.     

TEXTURE OF TEMPERATE FRUITS

Temperate fruits may be classed into two groups on the basis of their texture. One group comprises fruits that soften greatly as they ripen. These are characterized by a soft melting texture and usually have a relatively short shelf life. The measurement of the texture of these fruits is relatively straightforward. The second group encompasses fruits that soften moderately as they ripen. These are characterized by a firm, crisp, fracturable texture and have a relatively long storage life. The measurement of their texture poses a number of complex problems. Some factors that affect the firmness of temperate fruits are the kind, size, variety, maturity and temperature of the fruit, and cultural factors.     

EFFECT OF VARIOUS ANTIBIOTIC APPLICATIONS ON SOME CHEMICAL, MICROBIAL AND PHYSICAL PROPERTIES OF LAMB

This study was carried out to investigate the effect of various application methods for a chlortetracycline (CTC) and oxytetracycline (OTC) combination (0.9 mg of each per kg of meat) on the shelf‐life of lamb during storage. Twelve‐fat, tail type Akkaraman male lambs were divided into four groups by a “block assignment method”. The first group was kept as the control (C), while the others were subjected to applications as “injection antemortem (A)”, “immersion (I)” and “spraying (S)”. Meat samples were stored at 4C for 12 days. The specimens from loin and leg were tested for microbial, chemical and physical criteria. The results indicated that a CTC and OTC combination extended the shelf‐life of lamb at 4C in an increasing order from A to S to 1. The last one may be used to extend the shelf‐life of lamb during refrigerated storage.