Effects of genotype and treatment on the antioxidant activity of sweet potato in Taiwan

Six genotypes of sweet potato commercially available in Taiwan, including TNG57, TNG66, TNG68, TYY1, RP and WP, were used as samples in this study of the effects of steaming and kneading with pre-steaming treatments on the antioxidant components and antioxidant properties of methanolic extracts. Steam treatment increased the total phenols contents of all genotypes (2–13 times), flavonoids content of RP (1.3 times) and anthocyanins contents of RP and WP (5–6 times). Steam treatment also increased the reducing power and scavenging DPPH radical effect of sweet potato flours. For the methanolic extracts of steamed and kneaded flours, reducing powers were 0.02–1.70 at 5.0 mg ml⁻¹ and the scavenging effects on DPPH radicals were 19–92% at 2.5 mg ml⁻¹. Both showed the order of RP > WP > TYY1 and TNG66 > TNG57 and TNG68. However, the chelating effect of the six genotypes at 1.0 mg ml⁻¹ ranged from 50% to 73%. Contents of total phenols, flavonoids, and anthocyanins of sweet potato flours were significantly positively correlated with the reducing power and scavenging DPPH radical effects. After steaming and kneading treatments, RP showed the highest increase in the contents of total phenols, flavonoids and anthocyanins among the six genotypes studied.     

离心铸造汽缸套白斑产生机理

针对离心铸造汽缸套的白斑特征，以模拟试验手段探寻原因。用金属凝固理论解释白斑形成机理。经过装车试用，验证了白斑对摩擦性能的影响。     

新型固定式电站锅炉空气预热器热点检测系统

针对移动式空气预热器热点检测系统机构易“卡死”、热点检测严重滞后等问题,利用红外阵列传感器具有较宽测量范围的特点,设计了一种固定式热点检测方案.基于红外阵列传感器,设计了基于Dempster-Shfer(DS)证据理论的热点判断方法.     

固定化酵母薯干原料酒精发酵中试研究

本文论述了固定化酵母薯干原料带渣酒精发酵的中试结果。中试生物反应器容积为１０００Ｌ，采用改性海藻酸钙凝胶为固定化酵母细胞的载体。中试研究中设计了较合理的中试工艺流程，优选出较佳的发酵条件，并考察了生物反应器的性能。试验获得了如下结果：中试装置已运转１９２天，固定化酵母仍保持高活力，并可继续运转；发酵成熟醪酒精含量达６．５～８．０％（ｖ），它比同期传统式酒精发酵高出０．３～０．４％；淀粉利用率达９１～９２％；固定化酵母生物反应器的乙醇生产能力为９．５ＫｇＥｔＯＨ／Ｍ￣３·ｈ，它可比传统式发酵罐的生产能力提高１０～１２倍。     

一种基于等效间距法的低散射阵列设计

针对阵列天线在某些角域出现强散射的现象,提出了一种等效间距法并分析了强散射点的产生机理,给出了抑制散射峰值同时满足辐射要求的最佳折中阵列间距确定准则。运用该方法对8单元贴片阵列进行了实例验证,结果表明:设计的贴片阵列可以在满足辐射性能的基础上,带内和带外单站雷达散射截面的强散射点得到了有效抑制,使其在绝大多数入射角处于低散射状态,从而证明了该方法可以快速、有效地指导兼顾辐射性能的低散射阵列设计。     

无线传感器网络自适应区域路由算法

2009年8月,随着‘感知中国’的提出,国内众多学者对无线传感器网络开展了日益深入的研究,而节省网络能耗则是研究的首要问题。主要针对延长传感器网络生存时间、增强网络的可靠性的目标,提出一种自适应区域路由算法（ARRA）,它包括对WSN进行区域规划、区域自治以及区域负载均衡三个方面。分析和仿真同时表明,ARRA实现了传感器网络的能量均衡,降低了网络能耗,并能提升某些热点区域的生存周期和可靠性。     

陶瓷管壳金属化黑斑的成因探讨

对陶瓷管壳在金属化过程中产生的黑斑进行观察和检测分析 ,对其产生原因进行了探讨并提出一些改进措施。     

Changes in cuticle compositions and crystal structure of ‘Bingtang’ sweet orange fruits (Citrus sinensis) during storage

Changes in composition and structure of orange cuticle during storage at 4°C or 25°C for 40 days were investigated. The total epicuticular wax content of fruits increased during storage at 4°C for 30 days and then decreased as storage time prolonged to 40 days, while it increased continuously at 25°C for 40 days. The total intracuticular wax content of fruits increased to 9.70 μg cm^?2 stored at 4°C for 10 days and then decreased to 6.74 μg cm^?2 for 40 days. The total intracuticular wax content of fruits was decreased to 5.17 μg cm^?2 stored at 25°C for 10 days and then increased to 10.06 μg cm^?2 for 30 days. Fatty acids were the most abundant component of the epicuticular wax and terpenoids were restricted to the intracuticular wax. Terpenoids were restricted to the intracuticular wax, and their amounts in the fruit stored at 4°C increased continuously during the first 20 days of storage at 4°C and then decreased as storage time increased up to 40 days. Although significant changes were found in the contents of the cutin monomer, their proportions did not change significantly during storage at 4°C or 25°C. Size of wax platelets crystals wax increased during storage of fruits at 4°C up to 30 days; however, the crystals were degraded and decreased as storage prolonged to 40 days. Furthermore, the shape of the fruit cuticle surface wax crystals changed from flattened platelets to small granulelike after storage at 25°C for 20–40 days. The obtained results provide detailed information about the changes in orange cuticle occur during storage at varying temperatures, which may help in preserving the quality of citrus fruits during storage.     

Optimisation of processing variables in the preparation of sweet potato chips using response surface methodology

Models capable of predicting the product quality of sweet potato chips have been developed using response surface methodology and used to determine the optimum processing conditions. Moisture loss, oil uptake, crispness (measured using a bending-snapping test in the TA.XT2 Texture Analyser), and sensory attributes such as colour, flavour, and texture were used to assess the product quality in the preparation of sweet potato chips. The optimum conditions which were attained for maximum moisture loss (11.65% on wet basis), minimum oil uptake (2.57%), crispness (794.37 g), colour score (7), flavour score (7) and texture score (7) were: frying temperature, 174.7 °C; salt concentration, 0.45%; citric acid concentration, 0.37%; potassium metabisulphite concentration, 0.65%; and frying time, 26 s.     

Steady and dynamic shear rheology of sweet potato starch–xanthan gum mixtures

The effect of xanthan gum at different concentrations (0.2–0.6% w/w) on the rheological properties of sweet potato starch (SPS) pastes was evaluated under steady and dynamic shear conditions. The presence of xanthan resulted in an increase in the consistency index and vane yield stress of SPS. The effect of temperature on the apparent viscosity of SPS–xanthan mixtures is well described by the Arrhenius equation. Dynamic moduli (G′, G″, and η^*) values of the mixtures increased with an increase in xanthan concentration while the tan δ values decreased. The addition of xanthan appeared to contribute to the elastic properties of the weak network of the SPS pastes. The structure development rate constant (k) of gelation during ageing was strongly influenced by the presence of xanthan. This suggests that the phase separation process caused by the incompatibility phenomena between the amylose component in starch and xanthan can increase the elastic characteristics of the SPS–xanthan mixtures.