Design and characteristics of a new type laminar plasma torch for materials processing

Laminar plasma jet(LPJ) generated by laminar plasma torch(LPT) has a favorable temperature and velocity distribution. Thus, it is superior to the turbulent plasma jet in material processing.However, most of the reported LPTs usually operate at a relatively low output power with a relatively low arc voltage and thermal efficiency, which limits its capabilities. In this context, this paper attempts to design a new type of high-power LPT with a relatively low arc current and a high thermal efficiency. In the first section, the design principle of the main components is studied and discussed in detail, and a new high-power LPT is proposed. Then, the experimental characteristics of the proposed high-power LPT are examined. Experimental results reveal the following characteristics of the proposed LPT.(1) The max jet length of the proposed LPT reaches at 540 mm.(2) Its mean arc voltage is higher than 290 V when the LPT works with arc currents lower than 200 A, leading to an output power greater than 50 kW.(3) The mean thermal efficiency is higher than 50%. Lastly, the proposed LPT has been applied to spheroidize the aluminum oxide powers. The experiment results for the production of spherical powders show that the proposed LPT has a good characteristic for material processing.     

Modeling and design of 3-D MPPT for ultra low power RF energy harvesters

Radio-Frequency (RF) energy harvesting must cope with the limited availability and high variability of the energy source. In this paper, the modeling of an RF harvester for ultra low power environments is presented. A mathematical model based on theoretical analysis is developed. The model demonstrates that the maximum transferred power point is located in a three-dimensional space defined by the input capacitance, the output voltage, and the load resistance of the rectifier circuit. Moreover, the mathematical model returns results in substantial agreement with the SPICE simulation results, while guaranteeing a remarkable reduction of the required computation time. Furthermore, the paper reports the implementation of a mixed signal system for the 3-D MPPT, to be embedded in an RF harvester, in a 65 nm CMOS technology. The circuit exhibits a simulated power consumption lower than 100 nW, making this solution suitable for ultra low power harvesting.     

机械合金化FeS/Cu复合材料的摩擦磨损性能

以FeS和CuSn8Ni1粉末为原料，利用机械合金化技术和粉末冶金技术制备了FeS/Cu复合材料，探讨了不同载荷情况下所制备的FeS/Cu复合材料的摩擦学性能及润滑膜与转移膜特征。结果表明：机械合金化提高了FeS与铜合金基体界面结合性能，进而提高了材料减摩耐磨性能；当载荷较小时，摩擦副表面接触不稳定，复合转移膜不连续，摩擦因数波动大；载荷较大时，复合转移膜易破损，材料的减摩耐磨性能变差；当载荷为150 N时，载荷适宜，材料表面软化，复合转移膜更加完整，摩擦因数较小。     

异螺距万分尺设计

介绍了一种螺旋万分尺的结构设计。该万分尺的微分筒采用双螺纹,两螺纹的螺旋方向相同,螺距不同。采用V型槽和V型块精确定位来增加量程。测量最小刻度可达0.001 mm,读数精度达0.0001 mm。万分尺采用纯机械结构,结构原理简单,制造安装方便。     

Suppression of forced vibration due to chip segmentation in ultrasonic elliptical vibration cutting of titanium alloy Ti–6Al–4V

Ultrasonic elliptical vibration cutting of titanium alloy Ti–6Al–4V is investigated in this research. Because products made of Ti–6Al–4V alloy are usually designed for possessing low-rigidity structures or good-quality cut surfaces, machining requirements such as low cutting forces and slow rate of tool wear need to be fulfilled for realization of their precision machining. Therefore, the ultrasonic elliptical vibration cutting is applied as a novel machining method for those products. Machinability of Ti–6Al–4V alloy by the ultrasonic elliptical vibration cutting with cemented carbide tools is examined to figure out suitable cutting conditions for precision machining of Ti–6Al–4V alloy. As experimental results, generated chips, cutting forces, and profiles of cut surfaces are indicated. A forced vibration problem occurred due to the segmented chip formation, which is also well-known in the ordinary non-vibration cutting. Therefore, characteristics of the forced vibration due to the chip segmentation are investigated in this research. Through the experiments, it is found that the frequency and magnitude of the forced vibration have relation with the average uncut chip thickness and cutting width. Especially, it is found that the averaging effect can suppress the forced vibration, i.e. the chip segmentation tends to occur randomly over the large cutting width, and hence the force fluctuations with random phases tend to cancel each other as the cutting width increases relatively against the average uncut chip thickness. Based on the investigations, a new practical strategy to suppress the forced vibration due to chip segmentation is proposed and verified. Using the proposed method significantly decreased cutting forces and good quality of surfaces are obtained when the forced vibration is suppressed compared to the ordinary non-vibration cutting results. Therefore, the results suggest that the precision machining can be realized without sacrificing the machining efficiency by increasing the width of cut and decreasing the average uncut chip thickness.     

高强不锈钢绞线网与ECC黏结-滑移关系模型

高强不锈钢绞线网与ECC的黏结是二者协同工作的基础，且黏结 滑移关系模型是其黏结性能的综合反映，故通过对17组51个高强不锈钢绞网增强ECC薄板试件进行单边拉拔试验，研究横向钢绞线间距、纵向钢绞线直径和相对锚固长度等因素对钢绞线网在ECC中黏结性能的影响规律。试验结果表明，横向钢绞线的设置可使黏结破坏由脆性破坏转变为延性破坏；高强不锈钢绞线网与ECC的黏结滑移曲线可分为5个阶段，分别为上升段、微降段、延性强化段、下降段和残余段。基于试验结果，对钢绞线网在ECC中的黏结破坏特征和黏结 滑移机理进行分析，在相关黏结-滑移关系模型的基础上，提出钢绞线网与ECC的黏结 滑移关系模型，并进行模型参数分析。所提模型及模型参数计算公式与试验结果吻合良好，能较好地反映钢绞线网与ECC的界面黏结滑移特征。     

Simulation and energy optimization of the stabilizer tower of a pyrolysis gasoline hydrogenation unit

Energy optimization of second distillation tower of a pyrolysis gasoline hydrogenation unit has been studied by the thermal cycle of vapor recompression method. The mentioned cycle is connected to the second distillation tower of the stabilizer of pyrolysis gasoline, and the results are found promising. The composite pinch curve for both the current and the optimized methods are shown. Moreover, an increase in the heat transfer rate in heat exchanger E-1014 causes energy recovery in reboiler. According to simulation results, by vapor recompression to 1970 kPa and using this heat source for thermal integration, condenser and reboiler’s energies are decreased by 56.93 and 30.4 percentage, respectively.     

Data quality and uncertainty assessment methodology for pavement LCA

In performing pavement life cycle assessment (LCA), users are facing various reports of energy intensity coefficient (EIC) of pavement materials which differ considerably among data sources and therefore alter the LCA results significantly. Instead of selecting a certain EIC without or of little explanation for the current pavement LCA practices, this study proposed a methodology to build probability density function (PDF) for EIC based on available data-set and their qualities. Each data was first evaluated about the data quality indicator (DQI) through data quality pedigree matrix and converted to PDF in modified Beta distribution form. Three weighting methods, the DQI one, coefficient of variation (COV) one and analytical hierarchy process (AHP) one, were developed to assign weightings for different data. Monte Carlo simulation was run with the weighted PDF of each data as input to obtain the ultimate PDF for EIC. A case study to estimate the bitumen’s EIC with eight data samples were performed using the proposed methodology. It is found (1): the estimates by the proposed methodology is of higher reliability (lower COV) compared to any single data due to utilisation of information of the overall data samples; (2) the AHP weighting method is most favoured despite the results of the three weighting methods are close; (3) the central estimates of bitumen’s EIC are between5.4~5.8 MJ/kg. The proposed methodology is helpful in aiding calculating EICs for pavement materials and capturing uncertainties in LCA results in a statistical sense.     

单一低渗透突出煤层水力冲孔工艺优化应用分析

为了有效提高单一低渗透突出煤层的瓦斯抽采效率，以高压水射流冲击理论为指导，针对平煤股份八矿己组突出煤层特征建立数值模型，模拟分析水力冲孔应力分布规律，通过现场实测分析冲孔有效影响范围，进一步优化设计冲孔参数、指导现场施工。现场应用表明，水力冲孔是一种行之有效的方法，对单一低渗透突出煤层实施水力冲孔卸压增透、提高瓦斯抽采效果具有重要意义。     

臭氧氧化-循环喷淋法处理钨钼选矿废水

采用臭氧氧化-循环喷淋法去除钨钼选矿废水中COD,研究了pH值、臭氧流量、循环频率对COD去除效果的影响。结果表明: 废水COD去除率随pH值、臭氧流量、循环频率增大而增加,在pH值为10、臭氧流量3.0 L/min、循环频率4.0次/min条件下,氧化120 min后废水COD含量由131 mg/L降至11.5 mg/L,COD去除率达91.2%,满足《污水综合排放标准》(GB 8978-1996)一级标准。与O₂、NaClO处理废水COD的对比试验结果表明,循环喷淋法结合O₃表现出较好的COD去除效果。