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Saline-alkali soil sustainable use and improved technologies Liu xx Abstract: The development and utilization of saline-alkali soil has a significant contribution to food production. However, the lack of water resources, climate change, development and utilization of saline-alkali soil more challenging. The article summarizes the sustainable use of saline-alkali soil in recent years research has made important progress. Improved governance saline-alkali soil, and promote efficient use of saline agriculture to ensure food security and promote sustainable development of agriculture is one important way. The progress and development of agricultural science and technology, continue to maintain and improve access to saline-alkali soil in agricultural productivity. Of saline soil area of about million hectares, million hectares of arable land salinization,Nearly 1/5 of the arable land salinization, saline-alkali soil improvement technology development is extremely important practical significance for our country especially the inland arid agricultural irrigation area in the rural economy sustained and healthy development, land governance, ecological and environmental protection. From the three aspects of the improvement of saline-alkali soil, water conservancy, agricultural practices, as well as chemical and biotechnology, the saline-alkali soil improvement techniques, and put forward the improved new ideas of the "weaknesses, comprehensive management of saline : saline-alkali soil; sustainable use; improvement; technical measures这是在Google翻译的。

Since ChinaUniversityEnrollment began inthe latenineteen ninties,college students employment difficult problemarose,in recent years,decreasedinitial employmentrate of university graduates,supply and demand ratiois increased,the employment situation is not optimistic,receivedwidespread attention from all sectors of society,college studentsemploymentproblem has become one ofthe most last outbreak of the financialcrisis sweeping the globe,so that morecollege students employmentdifficult,this paper analyzesthe employment situation of university studentsfrom many aspects,in order tolet the studentsunderstand the currentsocial situation,the employment problemand thus a better solution补充：The characteristics ofthe largestemployment of college students isthe totalincrease ingraduates,high,andemployment situation ofwhole andnot improved the status quois contradictory,the difficult employment of college studentshasbecome an indisputable fact,investigate its reason,mainly is thedislocation oftalent supply andmarket demand,and thegraduates'Comprehensive toimprove the quality of personnel training,is the key tosolvethe difficult problem ofemployment of university students.

Hot Deformation Behavior of metal an important aspect of research is to study the metal in the process of hot deformation behavior of the flow stress, as well as changes in the law of the mechanical properties of the macro-response behavior is the flow stress. According to the theory of deformation, the flow stress of metal materials in a one-way refers to the deformation conditions sufficient to achieve plastic deformation of the stress intensity. Metals and alloys in the plastic working process, the flow stress determined the deformation of the size of equipment needed to load and the size of the required energy consumption. Generally speaking, the impact of the metal flow stress factors in general can be divided into internal factors and external factors. The main external factors, including deformation temperature, strain rate and strain (deformation), they are internal factors of the flow stress of metallic materials. Deformation temperature on the impact of flow stress as follows: flow stress with deformation temperature lower, but reduced somewhat different, that is, the higher strain rate, with the increase in deformation temperature, flow stress gradient reduced more Great. Strain rate on the impact of flow stress: the higher the strain rate, the greater the value of flow stress, and increase the flow stress with temperature changes, temperature, the higher the lower the rate of increase. The rate of increase of flow stress is not maintained at a fixed value, but as the strain rate changes. Internal factors include the chemical composition of metals, metal the microstructure changes such as dynamic recovery and dynamic recrystallization, such as work hardening. High-temperature mechanical deformation of metallic materials from high temperature creep behavior of metals on the basis of developed. Metals and alloys the existence of thermal processing thermal activation process, the strain rate thermal activation process control. Deformation under different conditions using different expressions, but also related to thermal activation, the dislocation movement, such as the micro-mechanism. This paper AZ31 magnesium alloy sheet for the study, the RG-based microcomputer-controlled universal testing machine, metallographic microscope and scanning electron microscopy tools, research and analysis of magnesium alloy at different temperatures forming performance, flow stress and microstructure changes in the law. The following conclusions: 1. Extrusion, cross-rolling, cold-rolled, hot-rolled, as well as the level of casting AZ31 magnesium alloy sheet metal microstructure is equiaxed structure, the grain size of 5 ~ 25μm; 2. Extrusion of magnesium alloy sheet metal grain size is about 5 ~ μm, the strain rate is less than , the deformation temperature is higher than 150 ℃, the extension rate of greater than 45%, and with the strain rate lower or raise the temperature of the peak flow stress also be reduced accordingly. When the temperature is 425 ℃, then the peak steady-state flow stress is almost equal to the flow stress at the time that the peak stress does not appear, and its value in between 18 ~ 20MPa, and the extension rate of 132%. 3. Cross-rolled sheet metal so that the peak flow stress decreased significantly increased plasticity. (And can reduce or eliminate the anisotropic material to improve the performance of its punch, so that elongation of the material significantly increased for deep-drawing deformation even provided a good internal organization.) At a temperature of 425 ℃, strain rate is less than , the elongation δ> 225%, alloy shows superplasticity. 4. 250 ~ 425 ℃ temperature range, semi-continuous casting + annealing cold-rolled sheet before and after the stress - strain curve changes little elongation δ are greater than 65%. Cold-rolled sheet can be used directly in temperatures greater than 250 ℃ forming thermal processing. 5. At a high temperature to soften and as a result of the role of dynamic recrystallization results of horizontal continuous casting + anisotropic cold-rolled sheet has been significantly improved. At 250 ℃ when the sheet are an extension of the rate of 118 percent, the smallest anisotropy alloys. 6. At a temperature less than 220 ℃, the fracture morphology of the main axis for large and small dimples, such as composition, surface tear edge clarity, and depth of dimples smaller size; When the temperature is greater than 240 ℃ when the equiaxed the edge of dimples appear fine grains, the occurrence of a fracture. Magnesium alloy at high temperature phase of the basic fracture along fracture, with the strain rate increased, the fracture mode transformed to the ductile fracture trend. AZ31 magnesium alloy in the plastic deformation occurred during the dynamic recrystallization and grain growth.

Liu xx saline-alkali land sustainable utilization and improved technology abstract: saline-alkali land resources development and utilization has an important contribution to food the lack of water resources, climate change, make the development and utilization of saline-alkali work more article system in recent years are summarized the important progress was made in saline-alkali land sustainable utilization land improvement of saline-alkali land management, and promote agricultural efficient use is the guarantee food security, one of the important ways to promote agricultural sustainable agricultural science and technology progress and development of saline-alkali land access to continue to maintain and improve the agricultural saline soil area of about million hectares, million hectares arable land salinization, nearly 1/5 of the cultivated land salinization-alkalization, alkali-saline land use of the development of technology, especially in China, arid agriculture irrigation area of sustained and healthy development of rural economy, land management, ecological environment protection has extremely important practical improvement of saline-alkali water conservancy, agriculture and three aspects of chemical and biological technology, are reviewed in this paper saline-alkali improvement of technology, and put forward "foster strengths and circumvent weaknesses, comprehensive treatment" alkali-saline land.