聚环氧琥珀酸的合成及其阻垢性能

研究了环氧琥珀酸的聚合条件对其黏度和阻垢率的影响。优化的聚合条件为:用NaOH调节pH=11,加入1.85g Ca(OH)2,在95℃反应2h;聚环氧琥珀酸黏度为60mPa.s时,阻垢率最高。随着聚环氧琥珀酸加入量的增加,其阻垢性能随之提高;在高加入量(20mg/L)下,聚环氧琥珀酸的阻垢性能接近其它羧酸类和含磷阻垢剂;用聚环氧琥珀酸逐渐替代羟基乙叉二膦酸,其阻垢率降低,但用聚环氧琥珀酸替代50%的氨基三甲叉膦酸和2-膦酸丁烷-1,2,4-三羧酸,其阻垢性能基本不变。     

Evaluation on Dorsey Method in Surface Tension Measurement of Solder Liquids Containing Surfactants

With the purpose of developing a feasible approach for measuring the surface tension of solders containing surfactants, the surface tension of Sn–3Ag–0.5Cu–xP solder alloys, with various drop sizes as well as different phosphorus (P) content, was evaluated using the Dorsey method based on the sessile drop test. The results show that the accuracy of the surface tension calculations depends on both of sessile drop size and the liquid metal composition. With a proper drop size, in the range of 4.5 mm to 5.3 mm in equivalent spherical diameters, the deviation of the surface tension calculation can be limited to 1.43 mN·m^?1 and 6.30 mN·m^?1 for SnAgCu and SnAgCu–P, respectively. The surface tension of SnAgCu–xP solder alloys decreases quickly to a minimum value when the P content reaches 0.5 wt% and subsequently increases slowly with the P content further increasing. The formation of a P-enriched surface layer and Sn₄P₃ intermetallic phases is regarded to be responsible for the decreasing and subsequent increasing of surface tension, respectively.     

Method for Assessing Grain Boundary Density in High-Strength,High-Toughness Ferritic Weld Metal

Metallurgical and Materials Transactions A - A method for measuring peak values on the maxlength-area fraction curve and the perimeter-area fraction curve with morphological photos using Image Pro...     

A comparative study on text representation schemes in text categorization

It is well known that the classification effectiveness of the text categorization system is not simply a matter of learning algorithms. Text representation factors are also at work. This paper will consider the ways in which the effectiveness of text classifiers is linked to the five text representation factors: “stop words removal”, “word stemming”, “indexing”, “weighting”, and “normalization”. Statistical analyses of experimental results show that performing “normalization” can always promote effectiveness of text classifiers significantly. The effects of the other factors are not as great as expected. Contradictory to common sense, a simple binary indexing method can sometimes be helpful for text categorization.     

电磁铆钉加热器的设计与实现

以TMS320LF2407型DSP为控制核心，设计出了一种基于磁感应加热原理的电磁铆钉加热系统。在介绍其组成的基础上，重点阐述了系统的工作原理、设计思想及软、硬件实现方法；详细介绍了各功能部件的设计依据和实际应用参数。运行结果表明，系统工作可靠、使用方便，且具有效率高、加热速度快等特点。     

Effects of heat input on microstructure and mechanical property of Al/Ti joints by rectangular spot laser welding-brazing method

A rectangular spot laser welding–brazing method was developed to join butted Ti/Al dissimilar alloys. In order to evaluate effects of heat input on mechanical property of the joints, microstructure of the joints were characterized. TiAl₃ intermetallic compounds (IMCs) were found at the joint interface in the case of low-heat input and TiAl₃, TiAl, Ti₅Si₃, and Ti₃Al IMCs were observed at high-heat input. Results of tensile test showed that the joints fracture in the fusion zone under the condition of low-heat input and in the interfacial reaction layer or the fusion zone with a mass of porosities at high-heat input. In addition, tensile strength of specimens broken at the fusion zone is higher obviously than that at the interface or the fusion zone with a mass of porosities, and tensile strength of the joints is up to 290 MPa.     

铁基自熔合金涂层T/M-GSA电弧钎涂研究

利用自制的药芯焊丝,通过T/M-GSA电弧钎涂工艺在Q235钢表面制备了铁基自熔合金涂层,涂层有较好的成形性,表面光亮致密且与基体为冶金结合。采用SEM,EDS,XRD和显微硬度分析,研究了涂层的微观组织、相组成和硬度分布。结果表明:涂层的微观组织主要是固溶了较多Cr,Si的γ-(Fe,Ni)作为涂层的基体相,少量的先析出相(Cr,Fe)_7C_3和大量的(Cr,Fe)_7C_3+γ-(Fe,Ni)共晶作为基体的支撑骨架。涂层平均的显微硬度超过HV_(0.1)500,约是钢基体的3倍。Cr,Si元素固溶在γ-(Fe,Ni)相中的引起的固溶强化以及析出的(Cr,Fe)_7C_3高硬度相是涂层得以强化的主要原因。     

再生骨料混凝土抗拉强度和抗剪强度试验研究

考虑混凝土两个强度等级(C20、C30)和再生骨料取代率,进行再生混凝土劈裂抗拉试验、非标准试件的抗折试验和等高变宽梁的抗剪试验,研究再生混凝土抗拉、抗剪性能和变形,获得了以下成果:1)再生混凝土的劈裂强度稍低于普通混凝土。2)再生混凝土抗折强度离散范围较大,与立方体抗压强度间没有显著的回归关系。3)再生混凝土的抗剪能力随取代率增加没有明显的变化,极限切应力与混凝土的强度回归相关性较差。4)抗剪试验梁的主拉应变曲线在大约70%最大值以下时呈直线,超过此值以后逐渐弯曲。试验实测的名义切应力、剪切弹性模量较低。     

室内燃气泄漏扩散爆炸危险区域分布规律

根据家用厨房的实际情况,建立了可燃气体泄漏扩散的几何模型。运用CFD数值模拟软件Fluent14.0对室内燃气泄漏扩散的浓度场进行了有效的数值模拟,重点考察和分析了室内燃气爆炸危险区域的时空分布规律,从而为室内燃烧爆炸事故的预防和事故危险性评价提供理论依据研究结果表明,在空间上,燃气泄漏初期,爆炸危险区域位于泄漏源的上部,且随着时间的推移,爆炸危险区域不断扩大并整体有往下辽移柏趋势。最终迁移至地面附近:在时间上,随若燃气泄漏扩散的不断发展,危险爆炸区域的范围由小变大,再由大变小且在房间下部持续的时间明显大于中上部。     

强制冷却对大型铸钢件组织与性能的影响

采用模拟装置铸造了φ70×300毫米的砂型试样和强制冷却试样。利用电子计算机进行数值模拟,计算出两类试样在凝固过程中的温度梯度 G、凝固速度 R 以及 G/R 的比值,强制冷却使大型铸钢件的细晶区扩大,柱状晶区向内转动,粗大等轴晶区减少。与传统观念相反,发现适宜的强制冷却可以使魏氏组织具有很高的冲击韧性。