Viscous warm pressure bulging process of AZ31B magnesium alloy with different ellipticity dies

Based on the bulging principle of different ellipticity dies, the methyl vinyl silicone rubber with excellent thermal stability and heat transfer performance was chosen as the viscous medium. The finite element analysis and experiments of viscous warm pressure bulging （VWPB） of AZ31B magnesium alloy were conducted to analyze the influence of different ellipticity dies on the formability of AZ31B magnesium alloy. At the same time, based on the grid strain rule, the forming limit diagram （FLD） of VWPB of AZ31B magnesium alloy was obtained through measuring the strain of bulging specimens. The results showed that at the temperature range of viscous medium thermal stability, the viscous medium can fit the geometry variation of sheet and generate non-uniform pressure field, and as the die ellipticity increases, the difference value of non-uniform pressure reduces. Meanwhile, according to the FLD, the relationship between part complexity and ultimate deformation was investigated.

从“常常”,“往往”谈对外汉语近义副词辨析

在词汇教学中,副词所占的比例虽然不大,但却不容忽视。很多留学生话语不连贯,主要原因就在于对副词掌握不够。对于近义副词,留学生更是不能准确运用。在教科书和工具书中,对于近义副词往往采用以词解释词的方法,让留学生无从下手。本文基于这样的思考,以＂常常＂、＂往往＂为例,提出了一条实用的辨析近义副词的思路。这条思路不一定把每一个近义副词都区分的明明白白,但是对于留学生来说,确实是＂日常必需品＂。

Analysis of Drought Changes and Drought Mitigation in Xiji County of Ningxia

[Objective] The aim was to study the characteristics of the changes of extreme weather climate incidents such as severe drought in northwest and rainstorm in Xiji County of Ningxia. [Method] Precipitation anomaly percentage was applied to divide drought level and for statistics analysis. Seasonal index, linear tendency, and 5-years gliding average were used to reflect the trend of drought changes. The circulation wave of temporal sequence used polynomial expression to simulate the interannual variation scale. The positive part of the polynomial expression used bar chart to simulate interannual variation scale. [Result] The index of drought season from November to June was large. The general trend of annual drought was increasing. The drought of interannual scale was most serious around 1977, about 15 and 20 years. The drought in recent years went up. The general situation of drought, interannual scale and changes of interannual scales from March to May and from September to October were discussed. Based on the weather at 500 hPa, the first rain in Xiji and the drought-turning-into-rain situation were classified. [Conclusion]These may provide reference value to the prevention and mitigation of drought.

Effects of Inorganic Sodium Salt in Soil on Concentration of Zinc Ion in Different Patterns

[Objective] The aim was to study on effects of inorganic sodium salt in soil on concentration of zinc ion in different patterns. [Method] Tessier sequential extraction was used to study on effects of inorganic sodium salts （in different species and different concentrations） on concentration of zinc ion in different patterns. [Result] Different inorganic sodium salts had different effects on zinc form. Content of ex- changeable Zn would reduce if Na2CO3 or Na2SO4 was added and the content would increase if NaCI was added. Content of carbonate zinc, which was significantly influ- enced by Na2SO4, would increase if NaCI or Na2SO4 was added, and would decrease if Na2CO3 was added. For Zn bound to Fe-Mn oxides and organic matters, and residual Zn, the contents would decrease if NaCI or Na2SO4 was added and the decrease showed much more significantly if high concentration sodium salts were added. In addition, content of Zn bound to Fe-Mn oxides decreased if Na2CO3 was added. If low concentration Na2CO3 was added, Zn bound to organic matters and residual would increase in content but would lower if high concentration one was added. [Conclusion] The research provided references for measurement of heavy metal ion content in soil in different places.

EMBEDDED 2-SPHERES IN INDEFINITE 4-MANIFOLDS

The main results are as follows.Let be an element of H2, where γ, δ1,…δn. arestandard generators. Suppose2≤n≤9.(1) If for some i and some i, then ζ can be represented by a smoothly embedded 2-sphere.(2) If ζ is a characteristic homology class, then ζ cannot be represented by a smoothlyembedded 2-sphere except for ζ2 = 16l+1 - n, l = 0 and (3) If ζ= dη for some d∈Z, where η is a primitive ordinary homology class with η2 = 0,then ζ is eqivalent to (d; d, 0,..., 0) and can be represented by a smoothly embedded 2-sphere.

BOUNDS ON COINCIDENCE INDICES ON NON-ORIENTABLE SURFACES

This paper presents some results about bounds for coincidence indices of Nielsen coincidence classes for maps between nonorientable surfaces. Denoting by Kn the nonorientable surface constructed by a connected sum of n torus with a Klein bottle, the author proves: (i) for pairs of maps between two Klein bottles or for pairs of maps from a Klein bottle to a surface Kn the coincidence class index is bounded. (ii) for pairs of maps from Kn to the Klein bottle the coincidence class index is unbounded. Other boundedness results are given for more technical conditions, including one for self maps.

Stabilization of 4-manifolds

The complex surface X obtained by 8 points blown up on CP2 and Barlow’s surface Y are homeomorphic,but not diffeomorphic.Using the Gromov-Witten invariant Ruan showed that the stabilized manifolds X×S2and Y×S2are not deformation equivalent.In this note,we show that the stabilized manifolds X×S1and Y×S1are diffeomorphic and non-deformation equivalent in cosymplectic sense.

On a Spectral Sequence for Twisted Cohomologies

Let （Ω＊ （M）, d） be the de Rham cochain complex for a smooth compact closed manifolds M of dimension n. For an odd-degree closed form H, there is a twisted de Rham cochain complex （Ω＊ （M）, d ＋ H∧） and its associated twisted de Rham cohomology H＊ （M, H）. The authors show that there exists a spectral sequence {Ep/r.q, dr } derived from the filtration Fp（Ω＊ （M）） = （¤i〉p Ωi（M） of Ω＊ （M）, which converges to the twisted de Rham cohomology H＊（M, H）. It is also shown that the differentials in the spectral sequence can be given in terms of cup products and specific elements of Massey products as well, which generalizes a result of Atiyah and Segal. Some results about the indeterminacy of differentials are also given in this paper.

Osteoinductivity assay of the variability of repeated extractions of bone morphogenetic proteins from bovine bone at different times

Objective: To observe the activity of repeated extracts of bone matrix and the production of purified bone morphogenetic proteins (BMPs). Methods: BMPs were extracted 1- 4 times from fresh bovine cortical bone by the modified Urist’s method, with each collected precipitate separated and lyophilized as partially purified BMPs. Another fresh bovine bone was extracted three times and the precipitates were mixed and lyophilized. Meanwhile,the alkaline phosphatase (ALP) activity was measured by an in vitro assay employing cultured C2C12 mouse myoblast cells through the osteoinductivity of bovine BMPs extracted four times at days 1, 4, 7, and 14, and the correlation between BMPs quantities and costing during extraction processes was analyzed.Results: The BMPs purified and the cost showed a positive correlation (r=(0.969)). To separate and lyophilize each collected precipitate as partially purified BMPs raised the cost, and mixed precipitates also cost much. ALP activities of the 1st and mixed extractions of BMPs were shown to be highly osteoinductive and keep a significantly high level (P<(0.05)-(0.01)) 4 days after culturing, compared with the 2nd, 3rd and 4th extractions, especially the control group. However, the more times the extraction was done, the less activity of BMPs was shown and more costing was. The x-ray and histological analysis also showed that the 1st extraction of BMPs induced more ossicles and new bone formation.Conclusions: The results indicated that BMPs enhanced the abilities of osteoinductivity in C2C12 culture in vitro. The first extraction of BMPs from bone is fitfull, the second extraction should be enough, while, the 3rd and 4th extractions are unnecessary for they cost more and waste more time, say nothing of mixed extractions.