汽液相变及亚稳态理论研究

基于唯象理论,分析了汽泡核化速率和过热度以及相变驱动力和唯象系数的关系。运用经典热力学原理,建立了气泡生成、长大数学模型。利用亚稳态相图,对过热液流体亚稳态性质进行了研究。结果表明,气泡核化速率随过热度增大而增加,并具有极限值;唯象系数在相变过程中存在最大值,具有质量转化率和相变驱动力的增大速率不相同步的特点;随压力降低,气相质量转化率在达到某一值后下降趋势不再明显,相反,随压力升高,相变达到等密度点后,气相完全转变为液态。气泡生成、长大数学模型可用于指导流体微观理论研究。

Growth Performance, Carcass Yield and Meat Quality of Korean Native Duck

This study was carried out to investigate the growth performance, carcass yield and meat quality of large-type Korean native ducks （KND）. A total of 420 day-old ducklings were divided into four treatments （seven replicates/treatment, 15 birds/replicate） by strains （A and B） and gender （male and female） in a 2 × 2 factorial arrangement under complete randomized design. The body weight （BW） of female KND was higher at week 2 and for male it was higher in week 8 （P 〈 0.05）. BW gain, feed intake and feed conversion ratio of male KND were higher than those of female KND （P 〈 0.05） during week 0 to week 8. The carcass yield of both strains increased from 6 weeks to 8 weeks （P 〈 0.05）. The breast meat ratio was the highest at week 8 whereas the leg meat ratio was the highest at 6 weeks of age in both strains （P 〈 0.01）. Lightness （L＊）, yellowness （b＊） and juiciness of meat were the highest at 6 weeks （P 〈 0.05）. Moisture, ash and fat contents of meat were the highest at 7 weeks （P 〈 0.05） and protein content was the highest at 8 weeks （P 〈 0.01）. These results may provide the basic data on growth performance and meat quality of large-type KND, which can be used for genetic improvements and rearing at commercial scale.

Synthesis of Wax Esters by Lipase-catalyzed Esterification with Immobilized Lipase from Candida sp. 99-125

Wax esters were synthesized in a solvent free system catalyzed by immobilized lipase from Candida sp. 99-125, with oleic acid and cetyl alcohol. The effects of substrate molar ratio, lipase dosage and water removal were investigated in a 50 ml flask incubated in a thermostatic cultivation cabinet. The optimized conditions were: temperature 40 ℃, shaking at 170 r·min-1, acid/alcohol molar ratio 1:0.9, lipase dosage in 10% (by mass) of oleic acid, and open reaction for water removal. As a result, the conversion rate reached 98% for reaction of 8 h. The volume of reactor was scaled up to 1 L three-neck flask. The optimized parameters were: 200 r·min-1 agitation speed, 2.5% (by mass) lipase dosage, others were the same as the parameters described above. The conversion rate reached 95% for reaction of 24 h. The lipase retained 46% conversion rate after reuse for 6, 7 batches. The products were purified by removing remained cetyl alcohol and fatty acids with ethanol and saturated sodium carbonate so-lution, respectively. The purity of the wax ester, cetyl oleate, was 96%. The physical and chemical properties of cetyl oleate were tested and compared with those of jojoba oil. The results show that the product cetyl oleate has great potential to use as the substitute of natural jojoba oil.

Physicochemical effects on sulfite transformation in a lipidrich Chlorella sp.strain

SO2 is very rapidly hydrated to sulfurous acid in water solution at pH value above 6.0, whereby sulfite is yielded from the disassociation of protons. We aimed to improve the sulfite transformation efficiency and provide a basis for the direct utilization of SO2 from flue gas by a microalgal suspension. Chlorella sp. XQ-20044 was cultured in a medium with 20 mmol/L sodium sulfite under different physicochemical conditions. Under light conditions, sulfite concentration in the algal suspension reduced linearly over time, and was completely converted into sulfate within 8 h. The highest sulfite transformation rate （3.25 mmol/ （L.h）） was obtained under the following conditions： 35℃, light intensity of 300 μmol/（m^2·s）, NaHCO3 concentration of 6 g/L, initial cell density （OD540） of 0.8 and pH of 9-10. There was a positive correlation between sulfite transformation rate and the growth of Chlorella, with the conditions favorable to algal growth giving better sulfite transformation. Although oxygen in the air plays a role in the transformation of SO3^2- to SO^2-, the transformation is mainly dependent on the metabolic activity of algal cells. Chlorella sp. XQ-20044 is capable of tolerating high sulfite concentration, and can utilize sulfite as the sole sulfur source for maintaining healthy growth. We found that sulfite 〈20 mmol/L had no obvious effect on the total lipid content and fatty acid profiles of the algae, Thus, the results suggest it is feasible to use flue gas for the mass production of feedstock for biodiesel using Chlorella sp. XQ-20044, without preliminary removal of SO2, assuming there is adequate control of the pH.

Factors that Affect Pellet Quality： A Review

Pelleting is the most popular thermal processing technique in poultry industry. Birds fed pelleted diets have greater feed intake and weight gain, and better feed conversion ratio. However, this better performance can only be achieved, if the pellets remain intact until they are ingested by the birds. Many factors may affect pellet physical quality, such as feed nutritional composition, ingredient particle size, conditioning temperature and time, feed moisture, etc.. Despite their importance, sometimes these factors are not managed properly, therefore, pelleted feed may not contain a high amount of intact pellets. In addition, the possible interactions among these variables may yield different responses in comparison with those expected when individual factors are considered. Very few experiments have been conducted to evaluate the impact of combined factors on pellet quality. This may be explained by the presence of many qualitative and quantitative factors in the manufacturing process. Research indicates that heat processing and feed formulation, especially fat inclusion level, are the factors which have the biggest influence on pellet quality. Strategies, such as the expansion process and fat inclusion restriction or post pellet liquid fat application could be implemented to produce high physical quality pellets. More research is needed to identify which factors have a positive or negative effect on pelleting process and to find new strategies to improve pellet physical quality.

Use of Silage Acid Devil Fish （pterygoplichthys spp.） as Protein Supplement in Finishing Beef Cattle

Animal nutrition is one of the most important limiting factors in animal production, especially in ruminants, providing proteins being the main constraint, due to the limited availability and high cost of protein sources （oilseed meals）. Currently in the dam ＂El lnfiernillo＂ in Michoacan Mexico, has a large population of devil fish （Pterygoplichthys spp.）, which is an economic and ecological problem, because it is not consumed by humans and causes pollution to be discarded directly into the environment. For that reason the objective of this study was to evaluate the use of silage acid devil fish （SADF） in fattening beef cattle as a protein supplement. SADF is defined as a product semi-liquid or pasty mixed with formic acid, which leads to a decrease in pH to near 4.0. Used 18 young bulls （Bos taurus × Bos indicus） for 60 days with a starting weight of 278.9 ± 51.2 kg, housed in individual pens with food and water ad libitum were randomly assigned to three treatments with different levels of inclusion SADF （0%, 12% and 18%）. They were weighed to the beginning of the experiment and later every 30 days, previous fasting of 24 hours. To determine the food consumption, weigh every day the offered food and the surplus. There were no significant differences （P 〈 0.05） among treatments with different levels of inclusion of SADF with respect to daily weight gain, with values of 952 ± 324, 927 ±322 and 854 ± 307 g/day, respectively. The dry matter intake （DMI） was 8.9, 9.3 and 7.7 kg/day to 0%, 12% and 18% of SADF, respectively. In the same values for feed conversion were 9.34, 10.03 and 9.01 kg DMI/kg of weigh live, and carcass yield of 60.6%, 60.3% and 58.5%, respectively. It is concluded that fish silage acid devil is an excellent alternative in feeding beef cattle as a protein supplement.

铁矿石烧结过程中不同类型准颗粒的燃烧特性

采用竖直管式炉研究了焦炭粒径、黏附层、黏附比、焦粉比例对不同类型准颗粒质量转化率和燃料氮转化率的影响.结果表明,对于S和S'型准颗粒,质量转化率均随焦炭粒径的增大而降低;对于S'型准颗粒,燃料氮转化率随着焦炭粒径的增大而减小,而对于存在黏附层的S型准颗粒,内核焦炭粒径越大,燃料氮转化率越大;通过对比S和S'型准颗粒的燃烧情况,发现黏附层的存在有利于提高准颗粒的质量转化率和燃料氮转化率;对于C型准颗粒,黏附比越大,质量转化率和燃料氮转化率均越小; P型准颗粒的质量转化率随着焦粉比例的增加而减小,燃料氮转化率在焦粉比例为50%时达到最低值.

考虑汽化的喷嘴高温气流注水两相流动规律

针对某火箭发动机考虑汽化的注水气液两相流问题,研究了液态水的汽化机理。根据不同环境压力下水的饱和温度建立了汽化模型,编制适合于液态水的专用汽化相变求解程序,并通过添加汽化组分源项及热源项的方法将汽化相变计算嵌入到多相流场控制方程中,实现了考虑液态水汽化相变的三维多相流场求解。结合经典算例进行了对比,特征点的两相流场温度计算值和试验的误差控制在8.5%以内,验证了程序三维计算的可靠性。距火箭喷嘴不同距离横截面的两相质量转化率曲线显示,质量转化率从最低值上升到最高值,然后降低到最低值,揭示了考虑相变的气液两相相间反应转化机理。该方法可为运载火箭发射平台发射起始阶段水室的汽化降温提供参考。

Catalytic effect of carbon-based electrode materials in energy storage devices

The catalytic effect of electrode materials is one of the most crucial factors for achieving efficient electrochemical energy conversion and storage.Carbon-based metal composites were widely synthesized and employed as electrode materials because of their inherited outstanding properties.Usually,electrode materials can provide a higher capacity than the anticipated values,even beyond the theoretical limit.The origin of the extra capacity has not yet been explained accurately,and its formation mechanism is still ambiguous.Herein,we first summarized the current research progress and drawbacks in energy storage devices(ESDs),and elaborated the role of catalytic effect in enhancing the performance of ESDs as follows:promoting the evolution of the solid electrolyte interphase(SEI),accelerating the reversible conversion of discharge/charge products,and improving the conversion speed of the intermediate and the utilization rate of the active materials,thereby avoiding the shuttling effect.Additionally,a particular focus was placed on the interaction between the catalytic effect and energy storage performance in order to highlight the efficacy and role of the catalytic effect.We hope that this review could provide innovative ideas for designing the electrode materials with an efficient catalytic effect for ESDs to promote the development of this research field.