Interfacial microstructure and mechanical properties of tungsten carbide brazed joints using Ag-Cu-Zn + Ni/Mn filler alloy

WC-Co hard metal was furnace brazed by Ag-Cu-Zn+Ni/Mn filler alloy using a tube furnace under high-purity argon at 730 °C. The influence of brazing time and gap size of joints was studied. The results revealed the maximum shear strength of (156±7) MPa for samples with 150 µm gap size at a holding time 15 min. The characterization and microstructure of the brazed joints were characterized by SEM, EDS and XRD. The results showed that increasing the time from 5 to 15 min could provide a better chance for the liquid interlayer to flow towards the base metal. However, the formation of some metallic phases such as Mn₃W₃C at brazing time longer than 15 min resulted in decreased shear strength of the joint.     

Development of hierarchical surface roughness on porous poly (vinylidene fluoride) membrane for membrane distillation process

The surface hydrophobicity of a poly (vinylidene fluoride) membrane was increased through the phase separation of polycarbonate (PC) solution on the membrane surface. A variety of characterization techniques including surface contact angle measurement, scanning electron microscopy, liquid entry pressure measurement, atomic force microscopy, porosity measurement, pore size measurement, and attenuated total reflectance-Fourier transform infrared spectroscopy were performed to investigate the membrane surface modification. According to the results, the formation of PC deposits on the membrane surface provided hierarchical structures consisting of micro and nanoscale roughness which enhanced the surface hydrophobicity. Direct contact membrane distillation (DCMD) experiments, in which an aqueous solution of sodium chloride (3.5 wt%) resembling the seawater was used as feed, were carried out to assess the performance of membranes. This surface modification technique led to the improved pore wetting resistance of the coated membrane in DCMD application. This novel method is believed to have a great potential to apply on a wide variety of membranes for MD application.     

Syntheses and Characterization of Two New M(II)-5,5′-dimethyl-2,2′-bipyridine (M = Cd and Pb) Coordination Polymers and Study of Their Thermal and Electrochemical Properties

Two new cadmium(II) and lead(II)-thiocyanato coordination polymers with 5,5′-dimethyl-2,2′-bipyridine (5,5′-dm-2,2′-bpy) as chelating ligands were synthesized and characterized by elemental analysis, IR and ¹H NMR spectroscopy and by X-ray crystallography. Thermal and electrochemical properties were also studied as well. These complexes have formed formula [Cd(5,5′-dm-2,2′-bpy)(NCS)₂]_n (1) and [Pb(5,5′-dm-2,2′-bpy)(CH₃COO)(NCS)]_n (2). The coordination numbers of Cd^II in 1 and Pb^II in 2 are six (CdN₄S₂) and seven (PbN₃O₃S₂), respectively. In 2, “stereo-chemically active” electron lone pairs and the coordination spheres were hemidirected. Bridging properties of thiocyanato anions in 1 and 2 created one- and two-dimensional coordination polymers, respectively. The supramolecular features in these complexes were guided and controlled by weak directional intermolecular interactions.     

Antibacterial activity of Artemisia persica Boiss essential oil against Escherichia coli O157: H7 and Listeria monocytogenes in probiotic Doogh

This study was conducted to assess the antibacterial efficacy of Artemisia persica Boiss essential oil (APBEO) at a concentration of 75 and 150 ppm with probiotic bacterium Lactobacillus paracasei in preserving the microbial and organoleptic quality of Doogh during storage at 4°C. The results indicated a gradual increase in acidity, whereas a decline in pH was noted in all the samples (p < .05). The addition of APBEO (150 ppm) and probiotics in doogh exhibited a synergistic effect and increased death rate of L. monocytogenes and E. coli O157: H7 in Doogh samples after 15 days. Also, the high score of overall acceptability was associated with the sample with 75 ppm APBEO. The incorporation of APBEO and probiotics in the sample exhibited a synergistic trend to ensure the safety of doogh and keep the quality of products.     

混凝土路面早期裂缝的探析与防治

本文介绍了混凝土路面早期裂缝的特征及形成原因 ,施工时 ,根据不同的成因 ,采取相应的预防措施 ,使早期裂缝出现概率降低到最低限度     

Decisive aspects in the evolution of microprocessors

The incessant market demand for higher and higher processor performance called for a continuous increase of clock frequencies as well as an impressive evolution of the microarchitecture. In this paper, we focus on the latter, highlighting major microarchitectural improvements that were introduced to more effectively utilize instruction level parallelism (ILP) in commercial performance-oriented microprocessors. We will show that designers increased the throughput of the microarchitecture at the ILP level basically by subsequently introducing temporal, issue, and intrainstruction parallelism in such a way that exploiting parallelism along one dimension compelled to introduce parallelism along a new dimension as well to further increase performance. In addition, each basic technique used to implement parallel operation along a certain dimension inevitably caused processing bottlenecks in the microarchitecture, whose elimination gave birth to the introduction of innovative auxiliary techniques. On the other hand, the auxiliary techniques applied allow the basic technique of parallel operation to reach its limits, evoking the debut of a new dimension of parallel operation in the microarchitecture. The sequence of basic and auxiliary techniques coined to increase the efficiency of microarchitectures constitutes a fascinating framework for the evolution of microarchitectures, as presented in our paper.     

用参数不匹配混沌系统的脉冲同步方法抑制铁磁谐振过电压

根据非线性动力学理论和铁磁谐振的特性,提出一种新的抑制铁磁谐振的概念——用同步脉冲控制理论使过电压系统与正常工作的系统同步。通过Matlab软件仿真计算,表明该方法能有效实现谐振系统与正常系统的快速同步,大幅降低控制能量,并突破以往研究仅抑制混沌形态过电压的局限。同时,首次应用ATP-EMTP软件对采用脉冲抑制铁磁谐振的方法进行仿真,仿真结果同样验证了该理论的有效性。