电网设备线夹开裂原因

某电力公司变电站用铝合金设备线夹在运行过程发生批次开裂事故,通过宏观观察、断口分析、化学成分分析、力学性能测试、冷冻模拟试验等方法,对设备线夹的开裂原因和开裂机理进行了分析。结果表明:设备线夹焊缝存在焊接缺陷,导致焊缝强度下降;设备线夹接线管底部存在积水空间,寒冷天气下积水结冰,体积膨胀,使焊缝承受设计工况外的负载而过载开裂,造成了线夹开裂。     

Icy affairs: Understanding recent advancements in the freezing and frozen storage of fish

Freezing methods have evolved over the last 30 years. This review states the effect of various freezing methods on the quality of fish and seafood. Freezing temperatures, freezing, and frozen storage temperatures were also analyzed and reviewed. The changes in the ice crystal, protein, and lipid affect the fish quality and nutritional value during freezing and frozen storage. Freezing methods when combined with various additives or preprocessing approaches help improve the efficacy of freezing and frozen storage. Several experimental or emerging methods also have positive effects on the products' quality. According to the metadata reanalysis of quality markers, freshly frozen fish using different freezing methods may vary much in terms of ice diameter, but not others. High pressure freezing or immersion freezing-derived fish retains the best quality through frozen storage. More data are required on freezing methods (electrical-assisted freezing, microwave-assisted freezing, magnetic-assisted freezing, radiofrequency-assisted freezing, and the commercial's application and investment should be considered in the future. This review sheds light on finding a balanced initial shear force during freezing and the use of certain additives to control freezing-related damages. Focusing on ice diameter alone may be futile (e.g., liquid N₂ freezing). Future optimization of technologies should be in a way that several processes along the farm to fork such as freezing, frozen storage, thawing, thermal processing of fish, and even refabrication of food should mutually complement each other's needs to deliver safe and high-quality fish to the consumer's plate, even after a prolonged shelf-life.     

Effects of four multi-compound freezing medium on the quality of red drum (Sciaenops ocellatus) during frozen storage

Taking air freezing (AF) as the reference, the effects of four types of multi-compound freezing medium for cryogenic liquid quick-freezing (immersion freezing, IF) on the freezing rate, quality and myofibrillar protein (MP) denaturation of red drum (Sciaenops ocellatus) fillets during frozen storage (−18°C) from days 0 to 90 were studied. Samples were gathered on days 0, 15, 30, 45, 60 and 90 for analysis. The results showed that IF groups (IF-1: 20% ethanol, 30% propylene glycol, 10% sodium chloride aqueous solution; IF-2: 20% ethanol, 20% propylene glycol, 10% glycerol, 10% sodium chloride aqueous solution; IF-3: 20% ethanol, 20% propylene glycol, 10% polyethylene glycol, 10% sodium chloride aqueous solution; IF-4: 20% ethanol, 20% propylene glycol, 5% glycerol, 5% polyethylene glycol, 10% sodium chloride aqueous solution) significantly shortened the time to cross the formation zone of maximum ice crystals while the freezing rate was 6.13 times higher than the AF group after adding 30% propylene glycol as the freezing medium. Furthermore, compared with the AF group, the IF groups significantly reduced losses in the water-holding capacity, the myofibrillar fragmentation index, microstructure damage, texture characteristics, drip loss and water migration (P < 0.05). In addition, the MP of IF groups had higher maximum transition temperatures (T_max1 and T_max2), total sulfhydryl content, Ca²⁺-ATPase activity and relative α-helix content compared with the AF group. In conclusion, IF could significantly increase the freezing rate of red drum fillets, and slow down quality deterioration and denaturation of MP during frozen storage for 90 days (−18°C). In particular, IF-2 (20% ethanol, 20% propylene glycol, 10% glycerol, 10% sodium chloride aqueous solution) was found to be more suitable for the immersion freezing of marine fish among the four multi-compound freezing medium.     

低压静电场辅助冷冻对竹笋品质的影响

为研究低压静电场辅助冷冻对竹笋冻结特性的影响，以冻结曲线、硬度、水分损失率、水分迁移、冰晶形态和组织微观结构为指标，探究低压静电场辅助冷冻（－35 ℃）和普通冷冻（－35 ℃）条件下竹笋品质的变化规律。结果表明：低压静电场辅助冷冻提高了冻结效率，改变了冰晶形态及分布，减轻了组织微观结构破损程度，改善了解冻汁液流失情况。与静电板间距10、20、30、40 cm处的冷冻竹笋解冻后水分损失率分别为14.16%、12.58%、9.73%、10.44%，显著低于对照组（21.01%）（P＜0.05），硬度分别为461.19、507.48、496.65 g和455.31 g，显著高于对照组（350.70 g）（P＜0.05）。低场核磁共振分析结果表明，在低压静电场辅助冷冻下竹笋解冻后汁液流失减少，扫描电子显微镜观察结果显示，竹笋纤维排列整齐，组织微观结构保持较好。低压静电场辅助冷冻可有效改善竹笋品质，可为利用低压静电场进行果蔬的冷冻贮藏和冷链运输提供参考。     

Biomimetic Lamellar Chitosan Scaffold for Soft Gingival Tissue Regeneration

Mucogingival surgery has become a common procedure for soft gingival tissue reparation in dental clinical practice, which mainly relies on autograft or commercial collagen membranes (CM). However, the autograft faces grand challenges in source availability and long-term post-surgery pain management, and the CM is restricted by its poor mechanical properties in an aqueous environment. Here, it is reported that a bio-inspired lamellar chitosan scaffold (LCS) with long range ordered porous structure, manufactured through a bidirectional freezing method, can serve as a promising gingival tissue engineering material. The LCS not only exhibits excellent mechanical properties in the hydrated state but also accelerates vessel formation and soft tissue regeneration in vivo. Most interestingly, the LCS is found to be capable of inducing macrophage differentiation to M2 macrophages, which is thought to play an important role in tissue regeneration. These advantages combined with its easy and low-cost preparation process make the LCS a promising candidate for dental clinical applications.     

液氮/液氨速冻鮰鱼片理化性质与组织结构变化

研究分析液氮与液氨速冻对斑点叉尾鮰鱼肉品质的影响。新鲜斑点叉尾鮰分割鱼片后分别进行工业隧道式液氮喷淋速冻（－90 ℃、35 min）、隧道式液氨速冻（－35 ℃、90 min），速冻样品置于－18 ℃下贮藏90 d。分析比较新鲜鱼肉以及速冻鱼肉在不同冻藏时间解冻损失率、蒸煮损失率、加压失水率、剪切力、pH值、K值、挥发性盐基氮（total volatile basic nitrogen，TVB-N）含量、三甲胺（trimethylamine，TMA）含量与硫代巴比妥酸反应物（thiobarbituric acid reactive substance，TBARs）值，应用荧光显微镜观察鱼肉组织微观结构变化。结果表明：与新鲜鱼肉相比，速冻鱼肉蒸煮损失率增加，加压失水率、剪切力、pH值降低，K值、TVB-N含量、TMA含量、TBARs值均呈上升趋势；随着冻藏时间延长，速冻鱼肉理化性质发生劣变；鱼肉速冻后肌肉细胞面积减小，细胞间隙增大；相比液氨速冻，液氮速冻更有利于保持鱼肉持水性、新鲜度以及组织结构完整性，可有效抑制鱼肉冻藏期间的品质劣变。综上，液氮速冻可以有效保持冷冻鱼肉品质，冻藏30 d内，液氮速冻鱼肉品质特性更接近于新鲜鱼肉。     

超声波解冻对羊肉品质的影响

以20 ℃静水解冻组为对照，在相同水温条件下，研究不同超声波功率（120、180、240、300 W）对解冻 后羊肉品质的影响。结果表明：与对照组相比，超声波解冻组解冻时间显著缩短，解冻后羊肉红度值（a*）和嫩度 显著提高，180 W超声波解冻处理组羊肉黄度值（b*）最高（P＜0.05）；随着超声波功率的增加，解冻后羊肉的 汁液损失率显著增大（P＜0.05），pH值和亮度值（L*）显著降低（P＜0.05）；随着超声波功率的增加，解冻后羊 肉菌落总数显著降低（P＜0.05），其中180、240 W超声波处理组显著低于120 W处理组（P＜0.05）。综合分析可 知，超声波解冻与静水解冻相比显著提高了羊肉的解冻速率和羊肉新鲜度，且对羊肉的脂肪酸组成和相对含量没有 显著影响，但超声波解冻后羊肉肉色偏暗，解冻汁液流失率偏高。240 W超声波解冻对羊肉品质的负面影响最小， 因此选择240 W作为羊肉最佳解冻功率。     

空气解冻温度对猪里脊肉品质的影响

以冷冻猪里脊肉为研究对象，在4、12、20、30 ℃温度条件下对其进行空气解冻，测定猪里脊肉解冻时 间、汁液流失率、蒸煮损失率、保水性、pH值、色泽、水分分布、质构和微观结构等特性变化。结果表明：猪里 脊肉汁液流失率与解冻时间呈非线性关系；12、20 ℃空气解冻对猪里脊肉的保水性影响较小；不同空气解冻温 度对猪里脊肉pH值、亮度值和红度值无显著影响；30 ℃空气解冻对猪里脊肉中不易流动水影响最小，稳定性 最好，其次为20、4、12 ℃；与对照组鲜肉相比，不同温度空气解冻处理组猪里脊肉蒸煮后硬度存在显著差异 （P＜0.05）；12 ℃空气解冻后猪里脊肉中肌纤维间空隙变大。不同空气解冻温度对猪里脊肉品质的影响存在 差异性。