基于机器学习的维吾尔文文本分类研究

随着Internet上维吾尔文信息的迅速发展,维吾尔文文本分类成为处理和组织这些大量文本数据的关键技术。研究维吾尔文文本分类相关技术和方法,针对维吾尔文文本在向量空间模型（VSM）表示下的高维性,采用词干提取和IG相结合的方法对表示空间进行降维。采用基于机器学习的分类算法（kNN和Na?ve Bayes）对维吾尔文文本语料进行了分类实验并分析了实验结果。     

Fly ash concrete subjected to thermal cyclic loads

The present study describes the behaviour of concrete as well as fly ash concrete when subjected to varying number of high temperature heating cycles. A Concrete mix (1:2.37:2.98) with 340 kg/m³ cement and w/cm ratio 0.45 was prepared. Cement was replaced by varying percentages (0%, 20%, 40%, 50% and 60%) of fly ash by weight of cement. The concrete was subjected to a constant temperature of 200°C for 7, 14, 21 and 28 heating cycles. One heating cycle corresponds to 8 h heating and subsequent cooling in 24 h. Subsequently the effect of temperature on the properties of the concrete was investigated and compared with that of the properties of unheated concrete. The compressive strength of plain as well as fly ash concrete increased when it was subjected to thermal cyclic loads. Moreover, the compressive strength increased with an increase in number of heating cycles. Thermal conductivity of concrete was found to decrease with an increase in the fly ash content.     

INFLUENCE OF ANTE-MORTEM GLYCOLYSIS AND DEPHOSPHORYLATlON OF HIGH ENERGY PHOSPHATES ON BEEF AGING AND TENDERNESS

The effects of ante-mortem glycolysis, and rapid post-mortem drop in pH and dephosphorylation of high energy phosphates on beef tenderness were studied using twelve major muscles from carcasses having post-slaughter pH values in the ranges 6.7–7.1 and 5.8–6.2. In muscles which had low post-slaughter pH, dephosphorylation of high energy phosphates and pH changes were complete in about 16 hr postmortem. On the other hand, these changes continued for up to 32 hr post-mortem in muscles which had high post-slaughter pH. Muscles with high post-slaughter pH values required about 7 days of aging to attain maximum tenderness, and were more tender than the corresponding low post-slaughter pH muscles aged for the same length of time or longer. Results suggest that the simple measurement of pH within 1 hr after slaughter may be useful for assessing the required aging time and the ultimate tenderness of beef.     

Influence of Reconstituted Dark and Light Chicken Muscle Myosin Filaments on the Morphology and Strength of Heat-Induced Gels

The morphological characteristics and heat-induced gel properties of filaments reconstituted from dark and light chicken muscle myosin by dialysis (slow filamentogenesis) and dilution (fast filamentogenesis) methods were studied. The solubility/turbidity properties of myosin isolated from dark and light muscles were quite similar at different pH values and temperatures, but the morphological characteristics of reconstituted filaments of dark and light myosin varied markedly, depending upon whether they were formed by dialysis or dilution.     

THE WEDGE FRACTURE TEST A NEW METHOD FOR MEASUREMENT OF FOOD TEXTURE

The fracture properties of foods are relevant to texture but can be difficult to measure because of limitations of size or shape. Many established engineering tests for the measurement of crack growth and unstable propagation of cracks require specific test geometries, sizes and compliances of the specimen. With food materials this is rarely possible. The wedge penetration technique can usefully be adapted to foods to determine fracture parameters of brittle and semi-brittle foods such as moderately hard cheeses and raw and cooked fruits and vegetables.     

Effect of Preparation and Service on the Thiamin Content of Oven-Baked Chicken

Chicken breast halves were oven-baked and evaluated for thiamin content when prepared and served under a cafeteria-style foodservice system. After preparation, they were held on a steam table for 90 min, frozen stored for 4 wk and finally reheated using conventional and microwave ovens. Thiamin determinations were conducted on raw, cooked, hot-held, frozen-cooked and reheated samples. The mean total percent cooking losses for the freshly cooked chicken were 20.4 ± 10.9%. The steam table holding for 90 min resulted in 4.4 ± 0.7% evaporation losses. The mean percent evaporation losses for the microwave reheated chicken were not significantly different from those of the conventionally reheated samples. No significant differences were noted in the moisture and fat content among various treatments. The thiamin content of raw meat when calculated on a dry, fat-free basis was significantly higher than the thiamin content of the cooked meat. There were no significant differences in the thiamin content after various treatments.     

HYDROGEN SULFIDE PRODUCTION BY HEATING DIFFERENT PROTEIN FRACTIONS OF TUNA MEAT

Raw albacore tuna was separated into water-soluble and water-insoluble fractions. The water-soluble fraction was separated into two fractions by trichloroacetic acid (2.5%). The water-insoluble fraction was extracted with NaCl (0.45 M), and then the insoluble fraction was further extracted with urea solution (6 M). H₂S production upon heating of each fraction was determined by the reflux-trap technique. Water-soluble proteins produced 71% of the H₂S, while the corresponding contribution from the insoluble fraction was 29%. Non-protein soluble components and salt-soluble proteins produced insignificant amounts of H₂S. Significant increase in the amount of H₂S was observed when water-insoluble proteins were treated with urea and TCA solutions.     

EFFECT OF TEMPERATURE DURING POST-MORTEM GLYCOLYSIS AND DEPHOSPHORYLATION OF HIGH ENERGY PHOSPHATES ON POULTRY MEAT TENDERNESS

SUMMARY– Tests made on pectoralis major muscles having post-slaughter pH values ranging between 6.1–7.0, indicated that holding poultry meat at 30 and 37°C during the onset of rigor mortis caused toughness. This toughening effect of high temperature appeared to occur when the pH level of the meat dropped from a value of about 6.3 to its ultimate low value and the adenosine triphosphate content dropped below 40% of its initial concentration. Holding temperatures at 10, 15 and 25°C during the onset of rigor mortis, or cooling to 15°C before the pH value dropped to about 6.3 produced more tender meat. After completion of post-mortem glycolysis and dephosphorylation of high energy phosphates, high temperature had no deleterious effect on tenderness. These results indicate that dephosphorylation of adenosine triphosphate at high temperature affects the mode or extent of stiffening of the muscular tissue and prevents tenderization.