基于试验二维随机骨料再生混凝土抗压强度研究

制作42个再生混凝土立方体试块并测试其立方体抗压强度,基于二维随机骨料理论推导符合试验用粗骨料级配的二维骨料分布曲线,生成二维随机骨料混凝土有限元模型模拟其抗压强度并与试验结果进行对比.结果表明：再生混凝土抗压强度总体上随再生粗骨料取代率的上升而降低,但再生粗骨料取代率为50%时,试验与有限元模拟结果均存在强度升高的变异现象.随着再生粗骨料取代率的上升,再生混凝土抗压强度峰值应力对应的平均应变有所延后.     

废旧棉纺织品机械拉毛法回收纤维实验研究

废旧纺织品回收再利用是解决全球环境和资源问题的一种方法,机械拉毛法回收再利用废旧纺织品是使回收和再生变为现实的一种简单可行的方法.自制拉毛简易装置,经实验研究发现,在对废旧棉纺织品使用拉毛法回收纤维时,其排列间隔、钉子露出长度和钉子尺寸等对拉毛效果有一定的影响.     

Prices

Assessed or estimated prices and values for the major types of crude oils traded on spot markets. Updated on a monthly basis. Official sales prices (except as otherwise noted) and are generally market-related, subject in some cases to retroactive adjustment. Updated on a monthly basis.     

Antioxidant Activity of Osage Orange Extract in Soybean Oil and Fish Oil during Storage

The food industry is seeking natural antioxidants for edible oils that have comparable activity to synthetic counterparts. In this study, Osage orange extract (OOE) rich in osajin (42.9%) and pomiferin (30.0%) was obtained after hexane extraction of the fruit, and its antioxidant activity was examined in stripped soybean oil (SBO) and fish oil (FO), in which antioxidants and polar compounds were removed. The antioxidant activity of OOE was compared with commercial natural antioxidants (i.e., rosemary extract and mixed tocopherols) and a synthetic antioxidant, butylated hydroxytoluene (BHT), during storage at 25 and 40 °C. The 0.1% OOE had stronger antioxidant activity than 0.1% rosemary extract and 0.1% mixed tocopherols in both oils at 25 and 40 °C. Its activity was similar to 0.02% BHT in SBO and was similar or slightly stronger than 0.02% BHT in FO. When OOE was studied at 0.05, 0.1, and 0.2%, there was a weak dose–response in SBO but a stronger dose–response in FO. Headspace volatile analysis using solid phase micro-extraction (SPME) combined with GC–MS indicated that 0.1% OOE was very effective in preventing the formation of volatile oxidation products in both oils. Although it should be further tested for safety before the actual use, this study shows that OOE can be developed as an antioxidant for edible oils.     

Optimization of the in Situ Transesterification of Grain Sorghum (Milo) DDGS to Fatty Acid Methyl Esters and Fatty Acid Ethyl Esters

Distillers grains and solubles generated from the ethanol fermentation of grains contain acylglycerols (AG) that can be successfully converted to fatty acid methyl esters (FAME) and fatty acid ethyl esters (FAEE), commonly known as biodiesel. However, when grain sorghum (milo) DDGS were used as a feedstock for in situ transesterification (IST) under the previously established optimal conditions for other AG-bearing substrates, the yield plateaued at only 32.2% (corrected in this study to 24.2%). Several IST studies have reported significantly higher conversions of AG-bearing substrates to FAME. Therefore, the goal of this IST study was to improve the conversion of the AG in milo DDGS to FAME and FAEE by varying the temperature of reaction, the concentrations of the base (sodium methylate, NaOMe), volume of methanol and ethanol, and the amount of moisture in DDGS. Methyl tert-butyl ester was also evaluated as a co-solvent intended to improve miscibility and reaction rate. Among these variables, the most effective change was an increase in temperature from 40 to 65 °C. The most successful reaction used a AG:NaOMe:MeOH molar ratio of 1.0:2.6:168.9. Those reaction conditions used 4.8 mmol NaOMe dissolved in 12.6 mL MeOH and resulted in a 79.8% conversion of AG to FAME.     

涂层硬质合金回收料生产硬质合金的工艺探索

利用废旧涂层硬质合金回收料生产硬质合金,通过采用适当的工艺方法,可以生产出质量较好的再生硬质合金产品。     

微型核磁共振传感器实时监测汽轮机油老化状态

汽轮机油被广泛应用于火力发电厂汽轮机的调节系统,随着使用年限的增加,其润滑性能和电气性能会随之下降。针对汽轮机油老化状态缺少简单有效的实时监测手段这一问题,提出用核磁共振技术进行检测,并设计了一种方便实时监测的微型核磁共振传感器。传感器尺寸为30 mm ×30 mm ×36 mm,重107 g,可以浸泡在汽轮机油中对其进行检测。通过对来自两个发电厂的不同使用年限的汽轮机油进行测量实验发现：汽轮机油的核磁共振参数有效横向弛豫时间T2ef与纵向弛豫时间T1随着其使用年限的增加而减小。该传感器制作成本低,尺寸微小,操作方便,使得实时监测汽轮机油的老化状态成为一种可能。     

模拟酸雨环境下再生混凝土的电化学测试与分析

利用硫酸溶液模拟人工酸雨环境,对其对再生混凝土性能的影响进行了测试和总结。试验过程中,电化学工作站测试出自腐蚀电位负值变大,混凝土保护层的电阻值变小,钢筋的腐蚀速率明显增大。试验所得数据及结论为进一步研究酸雨对再生混凝土性能影响问题提供基础和依据,为再生骨料混凝土的扩大应用和耐久性设计提供参考。     

再生混凝土材料声学特性参数分析

为在混凝土无损检测中采集到高信噪比的声发射信号,对再生混凝土材料的声学特性参数进行了试验研究。通过模拟加载确定了声发射检测环境的门槛值,采用断芯试验测试了再生混凝土材料的检测时间参数,包括峰值鉴别时间(PDT)、撞击鉴别时间(HDT)和撞击闭锁时间(HLT);同时确定了信号在再生混凝土材料中的传播波速,为再生混凝土材料声发射检测参数的设置提供了一定的试验依据。该声发射检测参数设置具有操作简单易行、实时动态、对原有建筑物损伤小等特点,在混凝土结构声发射检测中具有较好的适用性。     

绝缘油介质损耗与体积电阻率测试仪空杯电容值的计算

绝缘油介质损耗与体积电阻率测试仪的试验油杯是仪器的重要组成部分,以空气为介质的油杯电容值影响仪器的测量准确度和校准结果。为了得到准确的油杯电容值,依据油杯几何结构,采用圆锥体电容与圆柱体电容并联分布的物理模型,推导获得理论计算公式,并进行建模仿真比较。结果表明,所述理论计算方法有较高准确度,可用于指导测试仪的设计和校准工作。