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In the present study, we offer an in-depth analysis over the microstructure, thickness and product composition of the interfacial reaction layer generated upon CBN/Cu-Sn-Ti active filler metal at 1223 K. Current findings demonstrate that adequate wettability and satisfactory bonding have been achieved via chemical reactions between Ti and N, B. More importantly, we report, for the first time, the formation of a three-layer juxtaposition of reaction products, namely, TiN, TiB2 and TiB, along the diffusion path of Ti. Meanwhile, we determine the average layer thickness to be 1.24 μm. Through deep etching, we unambiguously present morphologies of the newly formed TiN and TiB2, which are columnar and bulky, respectively, and constitute the formation of a high strength metallurgical interfacial bonding layer, and is crucial towards gaining enhanced grinding performance. Finally, we propose a possible reaction sequence and mechanism that govern the nucleation and growth of corresponding crystals.

Effects of different holding time on CBN/Cu-Sn-Ti composites have been thoroughly documented. It is revealed that adequate wetting can only take place at 30 minutes and beyond. The thickness of reaction layer is governed by Ti diffusion, and follows a parabolic growth rate until Ti is fully consumed at the compensation of interfacial reactions. Concurrently, more stable Cu3Sn1 has been generated due to the decomposition of unstable Cu41Sn11, which leads to an enhanced wear performance.

Cubic boron nitride (CBN)/Cu-Sn-Ti composites as potential superabrasive products are prepared. It is found that as the temperature increases, porosity keeps decreasing from 1123 K to 1223 K but becomes virtually constant afterward, which is inversely coupled to the reaction layer thickness variation. Weight loss arrives at the minimum value at 1223 K. Deep etching over the interfacial region reveals that TiN and TiB2 compounds have been generated, and their roles in determining wear properties are postulated.

Cubic boron nitride (CBN) grains are brazed by Cu-Sn-Ti filler metal in vacuum at 1223 K. Wetting behaviors, reaction layer features, and elemental distribution characteristics have been systematically investigated through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results show that when the TiH2 content is 5 wt pct, virtually no sharp-edged, partially coated, and uncoated CBN grains can be observed, indicating that adequate wetting could be achieved. Moreover, a continuous reaction layer with uniform thickness (1.30 μm) consisting of TiN, TiB2, and TiB is obtained, which indicates that large numbers of TiN, TiB2, and TiB compounds could have been formed at the interface. However, when the TiH2 content exceeds 5 wt pct, the thickness of the reaction layer is no longer significantly expanding and excessive Ti present in the matrix will lower the volume percentage of Cu3Sn1 phase, which will reduce the bonding strength of the brazing samples. Wear tests indicate that the minimum weight loss also occurs at 5 wt pct TiH2.

Frequent occurrence of severe haze in Beijing indicates the importance of effective decisions and clear goals to reduce the concentration of particulate matter in the atmosphere. To achieve this goal, elucidation of the elements governing fine particulate matter concentrations should be considered as one of the priorities. In this paper, we proposed a statistical model based on physical understanding of the diffusion of air pollutants by wind to investigate the sensitivity of fine particulate matter and its precursor gases concentrations to wind speed and direction. By using our method, it is possible to determine the major wind directions that have large impact on air quality for a particular area. Our results showed that the influence of wind on the concentration of particulate matter and its precursor gases varies spatially over Beijing. Our method suggested that both local emission sources of fine particulate matter and its precursor gas (NO2) and transported SO2 from regional industries should be reduced for the remediation of severe air pollution scenarios, especially in the Beijing urban area. Our approach serves as a good complement for commonly used approaches for source apportionment analysis without exploiting complicated methods. The method shows its feasibility in identifying air pollutant emission sources based on wind patterns and can be used in other regions as an aid in air pollution controlling programs.

In this paper, we discuss the problem of stable matching with hybrid preferences among the three agent sets U, $$V_1$$ and $$V_2$$ . We consider two hybrid preferences. One is that the agents of set U has a strict preference to the agents of set $$V_1 \times V_2$$ , and the agents of set $$V_1$$ and $$V_2$$ have a strict preference to the agents of set U respectively. The other is that the agents of set U has a strict preference to the agents of set $$V_1 \times V_2$$ , and the agents of set $$V_1 \times V_2$$ has a strict preference to the agents of set U.

Ground level monitoring of Particulate Matter (PM) is limited by spatial coverage and resolution, in spite of possessing high temporal resolution and accuracy. Atmospheric Aerosol Optical Depth (AOD), a product of space-borne remote sensing, has shown significant potential for estimating ground level PM concentrations. Several approaches have been used to improve the correlation between AOD-PM by providing corrections for the aerosol vertical profile and ground level humidity. However, the effects of the vertical profile of humidity and aerosol size on the AOD-PM relationship requires further study. In this paper, we propose a method for developing an AOD-PM_(2.5) relationship by retrieving the vertical profile of relative humidity via ground observation data and aerosol size distribution in Beijing. Moreover, a series of Hanel growth coefficients (γ) are applied to determine the specific value, which maximizes the correlation. The results show that applying our proposed method can improve the correlation from R = 0.610 to R = 0.707 for Terra and R = 0.707 to 0.752 for Aqua. The best correlations were obtained for γ = 1.2 and 1.3 for Terra and Aqua, respectively. A good correlation (R = 0.8) between ground based and MODIS based PM_(2.5) measurements, together with employing MODIS to predict true air pollution levels (65% accuracy), suggests that the vertical profile of RH derived via ground level observation and aerosol size should be considered and applied to models in future studies, which utilize satellite data for air pollution monitoring and controlling.

Cu–Ti intermetallic compounds are usually prepared by solid-solid Cu/Ti diffusion couples. However, we offer a rather unique approach to prepare Cu–Ti phases by simply mixing Cu and Ti powders and heating them at 1373 K. Typical CuTi2, CuTi and Cu4Ti3 phases are profusely formed. Intermetallic stoichiometry, morphology and the sequence of nucleation and growth between them are discussed in detail. Meanwhile, pertinent properties, such as hardness and fracture toughness are characterized. It is believed such technique may pave a way for faster production of Cu–Ti alloys with fine-tuned properties.