Particle Size of Milk Protein Concentrate Powder Affects the Texture of High‐Protein Nutrition Bars During Storage

Milk protein concentrate powder with 85% protein (MPC85) was jet‐milled to give 2 particle size distributions (that is, JM‐Coarse and JM‐Fine) or freeze‐dried (FD), in order to improve the functional properties of MPC85 for use in high‐protein nutrition (HPN) bars. Volume‐weighted mean diameter decreased from 86 μm to 49, 22, and 8 μm in FD, JM‐Coarse, and JM‐Fine, respectively (P < 0.05). The MPC85 powders modified by jet‐milling and freeze‐drying were significantly denser than the control MPC85 (P < 0.05). Volume of occluded air in the modified powders decreased (P < 0.05) by an order of magnitude, yet only FD possessed a lower volume of interstitial air (P < 0.05). Particle size reduction and freeze‐drying MPC85 decreased its water holding capacity and improved its dispersibility by at least 20%. Contact angle measurements showed that these modifications increased initial hydrophobicity and did not improve wettability. HPN bars made from JM‐Fine or FD were firmer by 40 or 17 N, respectively, than the control on day 0 (P < 0.05). HPN bar maximum compressive force increased by 38%, 33%, and 242% after 42 d at 32 °C when formulated with JM‐Fine, FD, or control MPC85, respectively. HPN bars prepared with JM‐Fine were less crumbly than those formulated with control or FD MPC85. Physically altering the particle structure of MPC85 improved its ability to plasticize within HPN bars and this improved their cohesiveness and textural stability.     

400级热轧带肋钢筋质量判据若干问题探讨

针对GB1499.2-2007第1号修改单XG1-2009对热轧带肋钢筋金相组织提出的要求,对不同生产工艺条件两组外表无差别的400级热轧带肋钢筋按GB1499.2-2007/XG1-2009进行理化检验,发现了两者金相组织不同,从钢筋的化学元素、力学性能及焊接性能对其金相组织判定的可行性进行了分析,对XG1-2009表述的明确性,执行的可操作性进行了探讨。     

输电线路岩石锚筋基础中使用高强度钢材的可行性探讨

山区输电线路的岩石锚筋基础是环保、经济的新型基础型式,普遍采用HRB335、HRB400 钢筋,钢筋屈服强度较低,而且当基础作用力大时,其经济性不明显。通过分析得到,高强度钢筋用于该种基础型式是可行的,而且经济合理、安全可靠、省材环保,并且可以使岩石的抗剪性能、岩石和砂浆的粘结强度、钢筋和砂浆的粘结强度得到充分发挥。     

40Mn2圆钢成品剪切断口裂纹成因分析与对策

40Mn2圆钢作为锰系合金结构钢产品,因其良好的加工性和使用性广泛用于机加工行业,本文介绍了该产品在用户机加工冷剪剪切下料及圆钢轧后冷剪剪切工序中产生端部裂纹的基本形貌,分析了产生此问题的冶炼及轧制工艺原因,并针对此现象采取降低铸坯中心疏松、减少气孔、提高剪切温度等对策,最终解决这一问题。     

Microstructural Changes in High‐Protein Nutrition Bars Formulated with Extruded or Toasted Milk Protein Concentrate

Milk protein concentrates with more than 80% protein (that is, MPC80) are underutilized as the primary protein source in high‐protein nutrition bars as they impart crumbliness and cause hardening during storage. High‐protein nutrition bar texture changes are often associated with internal protein aggregations and macronutrient phase separation. These changes were investigated in model high‐protein nutrition bars formulated with MPC80 and physically modified MPC80s. High‐protein nutrition bars formulated with extruded MPC80s hardened slower than those formulated with toasted or unmodified MPC80. Extruded MPC80 had reduced free sulfhydryl group exposure, whereas measurable increases were seen in the toasted MPC80. High‐protein nutrition bar textural performance may be related to the number of exposed free sulfhydryl groups in MPC80. Protein aggregations resulting from ingredient modification and high‐protein nutrition bar storage were studied with sodium dodecyl sulfate polyacrylamide gel electrophoresis. Disulfide‐based protein aggregations and changes in free sulfhydryl concentration were not consistently relatable to high‐protein nutrition bar texture change. However, the high‐protein nutrition bars formulated with extruded MPC80 were less prone to phase separations, as depicted by confocal laser scanning microscopy, and underwent less texture change during storage than those formulated with toasted or unmodified MPC80.     

纳米氧化铝对混凝土静动态力学性能的影响

制备了掺量为0.2％的纳米氧化铝混凝土(NAC),采用HYY系列液压伺服试验系统和φ100 mm分离式霍普金森压杆分别研究了NAC的准静态及在不同应变率下的动态力学性能.结果表明:准静态荷载下,NAC的强度及变形性能较素混凝土(PC)明显提高,抗压强度提高约44.5％.动荷载作用下,NAC的应变率敏感性显著,随着应变率的增大,峰值应力显著提高,极限应变增幅明显.此外,掺入纳米氧化铝后,NAC的强度和变形性能较之PC亦均提升显著.分析峰值韧度指标可知,随着应变率的提高,NAC的峰值韧度近似线性增大,纳米氧化铝的增韧效果十分显著.通过电镜扫描微观机理分析,纳米氧化铝提高了水泥硬化浆体的密实度,改善了混凝土界面过渡区,进而改善了NAC的强度和韧性.     

新安煤矿下向导硐法揭煤技术分析

为降低下向揭煤工程量、提高揭煤效率及安全效果,新安煤矿针对井下现场情况对常规下向揭煤技术中的导硐施工设计及揭煤安全防护措施进行了优化和改进,其中,揭煤导硐设计中灵活使用各种掘进方法和优化采掘距离,前掘待掘进巷底时沿煤层走向平行掘进,后反向手镐掘进落底;揭煤安全防护中将金属挡栏设计为矩形框架、挡车梯及钢丝网三要素组成,并且钢丝网相互绞合。通过在工作面的现场应用及对比,发现优化后的揭煤技术具有所耗工程量更小、导硐及炮眼布置灵活、安全防护措施使用便捷等优势,能够为煤矿下向导硐揭煤提供借鉴。     

液压马达式汽车主动稳定杆系统建模与控制

以液压马达式主动稳定杆系统为研究对象,推导得到了液压马达式主动稳定杆的非线性动力学模型。利用线性化反馈的滑模控制方法设计了其控制器,并利用Lyapunov理论对控制系统的稳定性进行了证明。通过CarSim和MATLAB/Simulink对主动稳定杆系统进行了联合仿真,得出安装液压马达式主动稳定杆系统的车辆在双移线工况下运行的响应曲线。为了验证设计的控制方法,进行了实车试验。结果表明,与被动稳定杆相比,主动稳定杆系统具有较好的抗侧倾特性以及乘坐舒适性。