熔模铸造的工艺过程及防止缺陷产生的方法

熔模铸造又称“失蜡铸造”,在我国具有悠久的历史。它是一种无分型面的特种铸造方法,是利用易熔材料制成模样,然后涂挂耐火材料,硬化后再将模样熔化排出型外,从而获得无分型面铸型的铸造方法。由于获得的铸件具有较高的尺寸精度和表面光洁度,故又称“熔模精密铸造”。为此,就熔模铸造的工艺过程进行了详述,并对铸件缺陷产生的原因和防止方法进行了分析,以利于生产者进行工艺控制和质量控制。     

Effect of dietary supplementation of medium-chain fatty acids on growth performance and prevalence of carcass defects in broiler chickens raised in different stocking densities

A 3 × 3 factorial experiment was conducted to examine the effect of medium-chain fatty acids (MCFA) on performance and occurrence of carcass defects in broiler chickens raised in stocking densities of 14, 16, and 18 birds/m². A total number of 720 Ross 308 broiler chicks that were 1 d old were reared up to 49 d of age. Corn- and soybean meal (SBM)–based starter and grower diets were supplemented with 0, 1.5, and 2 g/kg Aromabiotic and provided to the birds ad libitum. Inclusion of 2 g/kg Aromabiotic in the diet significantly improved weight gain of the birds during 1 to 21 d of age compared with control birds (P< 0.001). A significant reduction in mortality (P= 0.004) and a significant increase in European performance efficiency index (EPEI;P= 0.036) were noted in the birds that received diets containing 2 g/kg Aromabiotic compared with control birds at 49 d of age. The birds grown in a placement density of 18 birds/m²had significantly improved FCR along with reduced feed intake (FI) during 1 to 49 d of age compared with those reared in a density of 14 birds/m². The mean EPEI was significantly greater in the birds raised in a density of 16 birds/m²(P< 0.001). At 48 d of age, litter caking was significantly increased in the birds raised in a density of 18 birds/m²and decreased in the birds that received dietary supplementation of Aromabiotic (P< 0.05). The influence of dietary Aromabiotic was significant related to reduced incidence and severity of footpad lesions and hock burns (P< 0.01). Frequency of lesions with a score of 2 to 5 on footpad and hock significantly increased for the birds raised in densities higher than 14 birds/m². It was concluded that dietary supplementation of 2 g/kg Aromabiotic improved early productive performance of broiler chickens and enhanced the PEI mainly due to decreased mortality. Dietary Aromabiotic improved broiler welfare as indicated by reduced foot defects in the birds raised in placement densities of 16 and 18 birds/m².     

Measurement and analysis of SF6 decomposition products under two types of partial discharges

In order to recognize partial discharge by analysis of SF6 decomposition products, the decomposition characteristic of SF6 under different partial discharges should be investigated, and also the feature parameters of decomposition products should be found. The decomposition of SF6 is simulated under partial discharge generated by needle defect and contamination defect respectively on the SF6 decomposition equipment made especially for the experiment. Three kinds of byproducts namely CF4, SO2F2 and SOF2 are detected, and their concentration changes with time are also studied. After that, the characteristics of three kinds of concentration ratios namely SOF2/SO2F2, SO2F2/CF4 and SOF2/CF4 under two defects are analyzed. The results show that SOF2, SO2F2 and CF4 exist in the byproducts under both the two defects. Moreover, the increase rules of the three kinds of byproducts under two defects are obviously different. Meanwhile the results illustrate that the three contamination ratios under the two defects have a notable disparity. Therefore the concentration ratios of the decomposition products can be used as feature parameters for partial discharge recognition.     

应用红外热像技术检测木材孔洞缺陷

为了提高木材空洞缺陷的红外检测精度,采用空洞模拟手段,以6个含有不同径级的人工孔洞缺陷的色木试样为研究对象,应用人工红外灯和烘干箱法,研究孔径缺陷识别的最佳加热时间和最佳加热温度,探讨热源选择对不同孔径大小的试材检测效果的影响。研究结果表明:随着试样缺陷孔径的不断减小,最佳加热时间和最佳加热温度都逐渐减少;在一定孔径范围内热像图能较为准确的反映木材缺陷的位置及大小情况;随着试样缺陷孔径的不断减小,检测效果越来越不明显。     

超声波检测对管道焊接缺陷类别的判断与分析

长输管道焊缝的焊接缺陷是影响管道安全性的主要因素之一,其危害的大小不仅与缺陷的大小和位置有关,还取决于缺陷的类别。因此,在管道焊缝缺陷检测中对缺陷类别进行判定,是提升检测结果准确率的有效途径。利用超声波技术对试样管道焊接部位缺陷扫查,根据静态和动态反射回波图对比出各类焊接缺陷基本特征图,对于管道监测、有效维护和维修具有重要的意义。     

Experimental Analysis of Infrared Thermography for Detecting Internal Defects of Decorative Layer on Exterior Wall

Internal defects of decorative layer on exterior wall, including mortar and ceramic tile decorative layers, were detected using thermal infrared imager. Variable characteristics of surface temperature for decorative layer heated by external heating source were studied. The distribution and variation law of surface temperature on decorative layer with time and space were obtained,and the influences of thickness,area and embedded depth of internal defect on image quality were analyzed. It is revealed that the thicker, bigger and shallower internal defect are more easily detected. The surface temperature of internal defect is maximum temperature point of approximate symmetry along with width direction. Based on the test results, the prediction model of dimensions for internal defect was established through statistical analysis technique, which can provide a reference for the related follow-up study and practical project application.     

原油管道螺旋焊缝开裂原因分析

某原油管道在运行期间发生了螺旋焊缝开裂事故,通过对管道开裂处进行宏观检查、断口微观形貌分析、能谱分析、显微组织分析、硬度测试和材料性能拉伸试验,结果表明,螺旋焊缝中存在焊接缺陷,使得管道的承载能力降低,在积水的作用下发生了螺旋焊缝开裂。     

基于空频变换的木材缺陷图像分割

针对木材缺陷这一自然纹理型事物,为了提取出其缺陷目标部分,进行下一步的分析和识别,采用一种空频变换方法对缺陷图像进行分割。选取虫眼、死节、活节3类木材缺陷图像样本各50个,构造一组多通道的Gabor滤波器对缺陷图像进行滤波,并提取出图像的多方向Gabor能量特征。最后结合模糊聚类算法和数学形态学后处理操作对缺陷图像进行了成功的分割。实验结果表明,此方法对3种木材缺陷图像的平均分割正确率分别达到了95.81%、94.58%、96.52%,证明了该方法的有效性。     

论货币犯罪的立法缺陷及其完善

我国惩治货币犯罪的立法存在缺陷,如没有将“变造货币”作为出售、购买或运输假币等罪的犯罪对象,持有、使用假币等罪的立案标准过低,没有把制造、提供制假设备的行为规定为犯罪,没有根据使用假币的不同情形规定不同的刑事责任,没有将单位作为伪造货币等犯罪的主体,缺乏对货币犯罪被害人利益的保护等。建议修改法律降低立案标准,将变造货币作为犯罪对象,增设非法运输、携带假币印版、印模罪等相关罪名,根据使用假币的不同情形细化刑事责任,扩大单位犯罪主体范围,加强对货币犯罪被害人利益的保护等。