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The Sn4.7Ag1.7Cu+Ag composite solder/Cu joint was prepared with Sn4.7Ag1.7Cu+Ag composite solder by transient liquid phase (TLP) bonding process.The microstructure of the joints under constant temperature aging was observed by SEM, combined with EDS, the microstructure and properties of the joints under different processes were compared and analyzed. The results show that the service performance of Sn4.7Ag1.7Cu+Ag/Cu joint at high temperature (300℃) is improved with the increase of Ag particle content. When the content of Ag is 25% (mass fraction), the joint does not break after 15 days of service at 83℃ higher than the melting point (217℃) of the base solder, and the tensile strength is 25.74 MPa, which achieves the purpose of low-temperature welding and high-temperature service. Comparing with Sn4.7Ag1.7Cu/Cu joints under reflow welding, with the aging process, the residual Ag particles in Sn4.7Ag1.7Cu+Ag composite solder/Cu joint are dissolved and a large number of Ag3Sn compounds are produced near the interface of the joint. A large number of bulk Ag3Sn compounds can effectively inhibit the diffusion of Sn into the Cu substrate and achieve the purpose of inhibiting the growth of the Cu3Sn layer.Under the condition of service temperature of 200℃, with the aging process, the mechanical properties of the Sn4.7Ag1.7Cu+Ag composite solder/Cu joint first decrease and then increase, then decrease to a stable state, and its mechanical properties are better than that of the Sn4.7Ag1.7Cu/Cu joint.

By adding a longitudinal AC magnetic field and using HS201 pure copper wire as the filler metal, TIG butt joint experiments were conducted on T2 copper and Q235 steel plates, both with the thickness of 2 mm, to study the joint formation, organization and mechanical properties when the magnetic field was added. The results show that the surface of weld zone is formed well after adding magnetic field. The best technological parameter is as follows: when welding current I=95 A, welding speed v=95 mm/min, magnetic field frequency f=25~35 Hz, magnetic field current IE=0.4~0.6 A, the mechanical properties of the joint is good, and the maximum tensile strength is 223.5 MPa, which is 44.5% higher than that without magnetic field. Copper-steel TIG welding joint is mainly divided into steel-HAZ, fusion zone, weld zone and copper-HAZ. After the addition of AC magnetic field, the morphology of ferrite in steel side heat affected zone changes from massive to needle like and lateral strip; the microstructure of weld zone changes from cellular crystal to fine and uniform cellular dendrite; the microstructure of copper-HAZ is obviously refined. After adding magnetic field, the types of phases in the fusion zone and weld zone of the joint have no change, which are composed of (α-Fe)+(ε-Cu); the solute segregation in the fusion zone is improved, and the (α-Fe)+(ε-Cu) particles change from coarse dispersion to fine aggregation; the microstructure of the weld zone is refined and its uniformity is obviously improved, which makes the hardness gradient of fusion zone and weld zone relatively decrease.

The atrophy of the entrance channel in the North Branch of Changjiang Estuary and the sediment supplied by landward tidal flow from the sea to the branch, threaten the sustainable use of the numerous ports and wharves along the riversides. Four different plans of two groups to mitigate the shrinking of the North Branch were proposed and tested. The plans in the first group aimed to expand the entrance channel and the upper section of the North Branch through dredging. The purpose of the plans in the second group was to reduce the landward tidal volume in the lower section of the North Branch to reduce the sediment import from the sea. The effects of these plans were simulated by a 2D computational hydrodynamic model, and the results such as tidal volume at different sections, the portions of tidal volume in different branches, and the high and low tidal levels at the monitoring points, were obtained and compared. After that, one plan from each group was recommended. The measures of the recommended plans have been mostly adopted in the report of Revision of the Comprehensive Regulation and Development Plan of the Changjiang Estuary.

The aim of this study was to explore the characteristics of and preventive management strategies for suicidal inpatients in a general hospital.

Objective To study the anti-caries efficacy of arginine dentifrice on early childhood caries in the rural area of Chengdu city in order to explore better early intervention measures on caries.Methods Two schools in Chengdu rural area were randomly chosen. Subjects were chosen according to the inclusion and exclusion criteria. All subjects were randomly divided into 2 groups, the experimental group used toothpaste containing 1.5% arginine and 1 450 F - ppm, control group used toothpaste containing 1 450 F - ppm, a comprehensive inspection of the dental caries of the 2 groups of subjects were recorded. The results were recorded by EpiData software for data entry, using SPSS 13.0 statistical software analysis data.Results 1 years later, the prevalence, the mean decayed missing filled teeth of deciduous teeth (dmft) of the experimental group was significantly lower than the control group. The number of new dmft score (t = 1.58, P = 0.001), the new decayed missing filled teeth surfaces (dmfs) number (t = 1.16, P = 0.001), The new permanent teeth DMFT number (t = 1.02, P = 0.005), new permanent teeth decay missing filling surface number (t = 1.03, P = 0.002) in the experimental group of deciduous teeth were lower than the control group. And the difference was statistically significant.Conclusion Toothpaste containing 1.5% arginine and 1 450 F - ppm is more significant on children’s dental caries prevention effect compared with the toothpaste containing 1 450 F - ppm only.

Heavy metal elementals can be enriched in soil at mineral products yard, which become a problem of environmental pollution caused by elemental migration, transformation and circulation in underground water. In this experimentation the modified BCR sequential extraction method was applied to the chemical species analysis of Cd, As and Pb. Based on the properties of these three elementals, the chemical species of Cd, As and Pb were divided into four fractions: exchangeable, reducible, oxidizable and residual, and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) were used to measure the content of Cd, As and Pb. Morphological analysis standard reference material GBW 07436 was conducted to verify the accuracy of the three step extraction state. Contents of chemical species of Cd, As and Pb in soil from six mineral products yard were analyzed, including contents of three step extraction state plus the residual and the total contents of the desired metals elements. The recoveries were from 84.54% to 102.88%. The analysis results for actual samples demonstrated the contents of Cd, As and Pb in non-residual fraction were in order as Cd (79.40%-94.94%)>Pb(24.27%-37.73%)>As (22.89%-31.51%), which indicated Cd is easy to enter the biosphere. This method has resolved the problem to extract the chemical species of heavy metal elements in soil from port mineral products yard, and has profound significance to the treatment of contaminated soil.

High carbon-chrome iron samples can be decomposed using strong oxidizing acid, mixed acid or by the alkali fusion method under high temperature. These chemical procedures are complex, especially the alkali fusion method, which introduces a large amount of interfering ions such as Na+. Microwave digestion technology is widely used in the pretreatment process of insoluble samples. This pretreatment method combined with Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) has been reported to determine Fe in high carbon-chrome iron. Based on previous studies, a method for the simultaneous determination of silicon, manganese and phosphorus has been established in this study. HNO3 is conducted to digest easy decomposition components in high carbon-chrome iron. HClO4 and HF are then loaded to digest carbides and silicides. Since there is a reduction in the volume of HClO4, the process is stable and safe. Using high carbon-chrome iron standard materials to set up the calibration curve, and Y, In and Bi as internal standard elements, the detection limits of silicon manganese and phosphorus were 0.0017%, 0.0025% and 0.0033%, respectively. Precision and accuracy of this method were verified by using high carbon-chrome iron standard materials of GSB 03-1562—2003, GSB 03-1058—1999 and GSB 03-1059—1999. The results were consistent with the certified values. The relative standard deviations (RSD) are in the range 0.8%-6.0% (n=11), and the relative deviations (RE) are from 0.044% to 0.227%. This method has the advantage of digesting the sample completely, is safe and has a simple operation process and a high degree of accuracy, which can also be used for the determination of several elements in high carbon-chrome iron.

Determination of trace elements in minerals usually requires pre-concentration and separation with many spectral line interferences during measurement. The concentrate ores were calcined at high temperature to remove the C and S. The calcinates were then digested by using the HCl-auqa regia-HF acids system. The D290 anion exchange resin and activated charcoal procedures were conducted to enrich Pt and Pd. The contents of Pt and pd were obtained by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) with internal standard elements of Y, In and Bi and measured isotopes of 105Pd and 195Pt. The absorption property and separation conditions of D290 anion exchange resin to trace Pt and Pd in copper concentrate ores were studied. The enrichment effects of Pt and Pd were above 90%, the recoveries were 92.0% and 96.0%, and the relative standard deviations (RSD, n=6) were smaller than 4%. The detection limits of the method were 0.126 ng/g and 0.105 ng/g for Pt and Pd. The presented method mostly reduced the inferences from other ions to the target elements of Pt and Pd. Moreover, the collision reaction between the internal standard elements and high purity Ar effectively reduced the matrix effect and isobaric interference. Five random geological samples were analyzed by this method in comparison with the method of NiS fire assay ICP-MS and the established method had the advantages of simple pretreatment and high enrichment of Pt and Pd with lower detection limits.

Oviposition site selection is an important aspect of the behavioural ecology of insects. A comparison of the habitats used by a species enhances our understanding of their adaptation to altered environments. We collected data on the oviposition behaviours of Gasterophilus pecorum (Diptera: Gasterophilidae) in its habitat in Kalamaili Nature Reserve (KNR), Xinjiang, China between March and October 2014. We found 91 quadrats were used by G. pecorum for oviposition. Examining 13 ecological factors using the t-test, chi-square test, and principal component analysis showed that G. pecorum’s oviposition habitat was preferentially on slopes with inclinations of 10–30° that were semi-sunny, semi-cloudy slopes, in positions high or low on the slopes, with preferences for total plants lower than 10% and Stipa capillata coverage lower than 10% on the low slopes, but Ceratoides latens coverage on the high and intermediate slopes, when the numbers of plant species and families were lower than five. G. pecorum often selected sites at a distance