草莓果实冲击损伤的预测模型

利用自制的冲击试验台,对草莓果实由碰撞引起的机械损伤和耐贮特性的变化规律进行较系统的研究。提出了草莓果实的耐冲击高度范围,并通过回归分析,建立了不同冲击条件下果实冲击损伤的数学预测模型,其理论值与实测值具有很好的一致性,可用于预测相应条件下的草莓果实碰撞损伤规律。     

集体林权改革对乡村治理效用影响的研究

从乡村治理的角度探讨集体林权改革带给林区农村除经济方面以外的其他各方面的效用。论述了林权改革对林区稳定的作用、宣传作用;探讨了林改给林农思想观念与生活方式带来的变化,指出了林改促进了村容村貌以及社保机制的建立;促进了基层组织建设与村民的自治,并且林改催生的林业合作组织同时具有乡村治理的效能。因此得出了结论:集体林权改革对林区农村乡村治理效用存在积极的作用。     

水杉人工林抚育间伐的效果比较

在１５ａ生水杉人工林内设立标准地，定量机械间伐，定期测定生长量，对抚育间伐７ａ后的效果及经济效益进行分析，结果表明：（１）不同初植密度的林分采用较小的强度ｐｎ＝２５％，３３％进行间伐，与对照林分相比，平均每公顷生长量分别提高５．９７，９．２７ｍ３，增加９．５７％，１４．８７％；采用较大强度ｐｎ＝５０％进行间伐，与对照林分相比，平均每公顷生长量下降９．７ｍ３，减少１５．５７％。（２）抚育间伐过的林分（间伐强度ｐｎ＝２５％，３３％，５０％）与对照林分相比，单位面积保留木平均生长率分别提高１．３４％，２．００％，１．９７％。（３）抚育间伐的林分与对照林分相比，平均每公顷总产值和利润分别增加６２７８，５７８４元，增长７．７％，９．５％。     

洞庭湖生态与环境影响因子研究

洞庭湖是我国第二大淡水湖,千百年来洪水为患。1949年以来湖体加速萎缩,水、旱灾频发,生态与环境出现种种新问题。对洞庭湖环境与生态问题进行研究后发现,宏观湖体萎缩、湖区气候持续变暖、新的江湖关系显现的复杂脆弱性、洞庭湖区日益工业化与城镇化以及缺乏权威法规的制约是造成洞庭湖生态与环境恶化的新老因子。     

国内科研评价制度对科技期刊的影响

通过分析在中国现有的科研评价制度下科技期刊发展存在优秀稿件外流、审稿不严、编校水平低、学术诚信不高等问题的基础上,对科技期刊的发展提出了建议。     

矿粒粒径对深海采矿扬矿泵磨损特性的影响

为研究矿粒粒径对深海采矿扬矿泵过流部件磨损特性的影响,采用DPM模型模拟泵内固液两相流动,并以基于流体动力学的Oka磨损模型仿真颗粒对过流部件的磨损,分析扬矿泵在不同矿粒粒径下的磨损规律.研究结果表明:随着矿粒粒径的增大,首级叶轮及次级叶轮的前后盖板磨损量分布逐渐均匀,前盖板磨损量的集中区域从出口压力面向叶轮中部及进口吸力面转移,后盖板磨损量集中分布区域从进口吸力面一侧向出口压力面一侧转移,叶片进口和出口的磨损面积均逐渐增大;首级空间导叶及次级空间导叶的叶片背面进口磨损面积逐渐增大,在轮毂出口处磨损区域向外逐渐偏移,且该位置磨损面积逐渐减小;当矿粒粒径从1.0 mm增大到5.0 mm时,首级叶轮和次级叶轮的前盖板最大磨损量分别上升132.9%和104.2%,首级叶轮和次级叶轮的叶片最大磨损量分别上升172.3%和142.5%,首级叶轮和次级叶轮的后盖板最大磨损量分别上升251.4%和102.3%,首级导叶和次级导叶的最大磨损量分别下降87.08%和74.26%.     

Friction and Wear Characteristics of Plastic Alloy Bearings under Different Lubricating Condition

Ultra High Molecular Weight Polyethylene (UHMW-PE) is a kind of high anti-wear engineering plastic with many excellent physical and mechanical performances. It has been widely applied in the field of mechanism such as bearing and pump. Effect of load, speed, time on friction and wear properties of Ultra High Molecular Weight Polyethylene(UHMW-PE)plastic alloy bearings under different Lubricating Condition are studied by using MPV-200 model friction and wear testing machine. The test results show that water lubrication reduces the friction coefficient of bearings but increases the wear rate as compared with dry friction. At the same time, wear mechanisms are analyzed systemically. It provides a theoretic basic for practical application of plastic alloy bearings     

Experimental analysis of the abrasive belt follow-up grinding of Zirconium-4 alloys tubes and pipes

Abrasive belt grinding experiments of Zr-4 nuclear power tube are carried out by using three different abrasive belts with same size, and the interactive generating mechanism between abrasive and workpiece is analyzed, the main factors of material removal rate and surface roughness of Zr-4 alloys are obtained. With the help of the advanced test facilities, the abrasive grain abrasion and surface topography of the workpiece are observed. The metallographic structure and microhardness of the layer of burnt surface during Zr-4 alloys Grinding are analyzed. Some conclusions are given as follows: the material removal rate and surface roughness are mainly affected by the factors of belt speed, grinding pressure, hardness of the contact wheel and abrasive type, of which, the belt speed is the strongest factor. The adhesion wear of the Zirconium corundum and aluminium oxide abrasive grit is more serious, the most important wear form of silicon carbide is abrasion wear. With the onset of grinding burn, the mechanical properties of Zr-4 alloys are deteriorated obviously. The results provide a theoretical and experimental basis for technical optimization in the grinding of Zr-4 alloys with efficiency and high quality.     

Sliding friction test analysis of TiAlN/TiN coatings on 40Cr steel

TiAlN/TiN duplex coating is made on the surface of 40Cr steel by means of multi-arc ion plating technology. Carrying capacity and tribological properties of TiAlN/TiN duplex coating are investigated with a UMT-2 wear tester without lubrication. The surface morphology of wear specimens are observed by scanning electron microscope(SEM). Elements of wear scar center and their content are analyzed by EDS. Tribological properties of TiAlN/TiN coating are evaluated through comparing with 40Cr in friction coefficient and wear volume. The results show that tribological properties of TiAlN/TiN duplex coating is better than 40Cr. The TiAlN/TiN films is superior in reducing friction and wear resistance, and can successfully resist abrasive wear and adhesive wear.     

Observance–Influence Analysis: A Case Study in a Forest Recreation Area

Importance–performance (I-P) analysis is a common evaluative measure in forest recreation management. However, concerns with I-P analysis have been raised. In this study, the observance–influence (O-I) analysis technique modified from I-P analysis was adapted for analysing the observance of various use and resource impacts by on-site visitors, and the influence that these impact conditions have on forest recreation area visitor experiences. During the summer and autumn of 2000, 476 Worak-san Forest National Park visitors in Korea were surveyed. The O-I grid generated from the survey data indicated that managers are doing a good job. The grid revealed most impacts clustering in the low priority concern and no concern quadrants. Impacts shown to be of most concern related to utility poles and power lines, poor maintenance of buildings, dead and dying trees, and discourteous behaviour. The O-I grid analysis model has considerable utility for park managers in analysing visitors’ perceptions of park impacts.