天然抗菌剂纳米乳液的制备、抑菌机理及在肉类保鲜中的应用研究进展

肉类富含蛋白质、脂肪等营养物质,在加工或贮藏过程中易受到微生物的污染而发生腐败变质。天然抗菌剂作为一种肉类保鲜剂,因具有良好的抑菌活性、安全性及生物可降解性而受到广泛关注。然而,有些天然抗菌剂具有高挥发性、低水溶性、热不稳定等缺陷,导致其在肉类保鲜中的应用受到局限。纳米乳液作为一种包埋系统,能够将天然抗菌剂包埋在其内部,以提高天然抗菌剂的稳定性和抑菌活性,并改善天然抗菌剂的释放性能,从而缓解天然抗菌剂的局限性。本文综述天然抗菌剂纳米乳液的构成和制备方法,并在此基础上进一步论述天然抗菌剂纳米乳液的抑菌机理与优势以及天然抗菌剂纳米乳液在肉类保鲜中的研究进展,以期为天然抗菌剂纳米乳液在肉类保鲜中的应用提供理论基础和实践指导。     

不同前处理方法对花生粕酶解液中黄曲霉毒素含量的影响

研究了弱碱高温处理法、H_2O_2处理法和不同过滤介质去除黄曲霉毒素的效果。结果表明,弱碱高温处理对原料中的黄曲霉毒素有较好的去除效果,花生粕经过121℃,pH10,60min处理,黄曲霉毒素的破坏率高达84.5%,最终酶解上清液中黄曲霉毒素的含量为0.344ng/mL,达到欧盟安全标准;用H_2O_2处理,低浓度H_2O_2对于黄曲霉毒素的破坏很少,当浓度达到1600mg/kg,酶解上清液中的黄曲霉毒素达到0.104ng/mL,相对于不加H_2O_2处理的酶解上清液,其黄曲霉毒素减少率达94.87%,但高浓度的H_2O_2处理不利干酶解的进行;对于不同的过滤介质,以活性碳吸附去毒效果较好,但同时氨态氮的损失率高达7.03%。综合考虑实验的各方面因素,如成本问题以及脱毒后酶解的蛋白回收率和氨态氮含量问题,选择先在121℃,pH10条件下处理60min,酶解48h,然后用普通滤纸过滤进行脱毒处理,此时酶解上清液中的黄曲霉毒素达到0.244ng/mL。     

大豆多肽对大强度训练举重运动员肌肉代谢的影响

观察大豆多肽对力量项目运动员促进肌肉恢复的作用,为大豆多肽应用于运动员训练实践提供依据。以8名举重运动员为对象,进行了大豆多肽应用效果观察。结果显示:补充大豆多肽能减轻举重运动员运动后血清肌酸激酶的升高,提示大豆多肽有促进损伤组织修复,减少细胞内肌酸激酶外漏作用。同时,80%最大负荷深蹲时腿部和腰部肌肉肌电信号的测试表明,补充大豆多肽能使肌肉的工作效率增加,抗疲劳能力提高。     

桌面出版系统的网点扩大补偿措施

重点讨论桌面出版系统在制版阶段利用ＰｏｓｔＳｃｒｉｐｔ语言提供的变换函数功能以补偿网点扩大，并给出了照排机标定的一个实例。最后，还介绍了如何在图像处理软件内去补偿印刷阶段的网点扩大。     

基于NSGA-Ⅱ算法的小型分布式能源系统设计优化

以大连市某小型居民建筑为对象,采用DeST软件,得到该建筑的冷、热、电及生活热水负荷。通过确定建筑在工作日、周末的逐时内、外热扰,计算建筑夏、冬季典型日逐时负荷。以年总费用和年CO₂、NO₂排放量为目标函数,以负荷间的能流平衡、设备的性能为约束,得到系统设备容量配置的Pareto最优解集。通过TOPSIS优选法得到最优容量配置。最后与传统分供系统对比,系统最优方案解集具有运行节能和环保优势。     

The effect of inlet pressure distortion on the performance of an axisymmetric compact tube heat exchanger with radial counter flow type for hypersonic pre-cooled aero-engine

The compact tube heat exchanger located behind the air-intake can achieve quick cooling of high-temperature air to ensure the normal operation of the pre-cooled aeroengine. It has great impact on the engine’s performance. The total pressure distribution at the heat exchanger inlet is inevitably uneven due to the influence of the air-intake. This paper studies the effect of three typical inlet distortions with different amplitudes using porous model and dual cell model. The results indicated that the outlet total pressure distortion is not sensitive to the inlet total pressure distortion. However, it affects the total pressure recovery and the total temperature distortion at the outlet by altering the pressure loss in the heat exchanger upstream and the flux distribution at the heat-transfer-zone entrance, respectively. This leads to a reduction of heat transfer. The effect of inlet distortions varies with distortion type. And it becomes more severe with increasing distortion.

     

Influence of flow coefficient on unsteady impeller loading induced by impeller-diffuser interaction

Unsteady Reynolds-averaged Navier-Stokes (URANS) simulation has been conducted to investigate how the flow coefficient affects unsteady impeller loading. Simulations have been carried out at three flow coefficients — near stall, design, and near choke conditions — for a centrifugal compressor with a radial gap of 1.04. For computational efficiency, the unsteady simulation has been conducted for two impeller and diffuser passages via the Fourier transformation method. Unsteady loading is the largest at the near stall condition; second largest at the near choke condition; and smallest at the design condition. Relative to the design condition, the near stall condition shows lower minimum loading, and the near choke condition shows higher maximum loading. Thus, both off-design conditions result in higher unsteady loading than at the design condition. Such increases at off-design conditions stem from the variations in the pitch-wise static pressure at the diffuser vane inlet caused by the diffuser vane incidence.

     

熔盐单罐双盘管释热换热器布置方式优选

为了获得单罐内盘管换热器最佳的布置方式,利用数值计算的方法研究相同换热器面积不同盘管换热器布置方式对单罐蓄热系统释热性能的影响规律。结果表明,叉排双螺旋盘管换热器的释热性能优于单排盘管换热器,且内盘管高外盘管低（hi=90 mm,ho=174 mm）的布置方式换热器其释热功率、出口温度以及累计释热量最大。     

木质素基超疏水涂层的制备及其应用性能研究

超疏水涂层由于其广泛的应用前景,近年来备受关注.然而,利用天然聚合物制备超疏水材料和超疏水涂层仍然缺乏一种简单、经济的方法.本文通过取代反应制备了超疏水性木质素-PFTEOS粉体.由于该粉体与基体无关的特性和优异的超疏水性,可用于各种基体制备超疏水性涂层.所制备的涂层疏水性极强,水接触角最高可达169°,同时具有良好的...     

Effects of Laser Quenching on Impact Toughness and Fracture Morphologies of 40CrNiMo High Strength Steel

The surface of 40CrNiMo steel was quenched with a CO₂ laser, Charpy impact test was conducted at temperatures of 20, 0, and ?20 °C, and the impact absorption energies were measured. The fracture morphologies were observed with SEM, and the influence of microhardness, residual stress, and retained austenite on mechanical behavior of impact fracture after laser quenching was discussed. The results show that the hardened layer depth is more than 1 mm after laser quenching, and hardness is about 480-500 HV. The fracture morphology of the sample is dimple rupture at a temperature of 20 °C; with the lower temperature the fracture dimples become smaller. At a temperature of ?20 °C, the fracture morphologies change from ductile to brittle, which is mainly cleavage fracture. The increase in surface hardness, production of compressive residual stress, and existence of retained austenite after laser quenching are the main mechanisms of increasing impact toughness.