玻璃中永久应力的理论分析与数值模拟

为了分析玻璃退火过程中永久应力的形成规律以及应力值的大小,基于玻璃永久应力的成因分析,建立了弹性体数值模型,给出了永久应力的计算方法和步骤。根据所建模型,利用ansys软件模拟了玻璃退火过程中结构应力和残余温差应力的形成过程,发现结构应力产生于膨胀系数开始发生变化的温度567℃,停止于膨胀系数稳定时的温度480℃。并根据模拟结果,计算出了玻璃中永久应力值的大小：边部压应力1.022MPa,中部张应力0.602MPa。模拟过程比较准确地反应了实际玻璃退火过程中应力的形成过程,根据模拟值求出的应力值大小基本符合玻璃实际应力值情况。     

拖拉机保养中的一些误区

误区一：螺栓越紧越好 在用螺栓、螺母联接的紧固件中，为防止松动，应保证螺本、螺母有足够的预紧力，如缸盖螺栓、连杆螺栓、喷油器压板螺栓等，都必须按规定扭矩拧紧，但又不能拧得过紧，否则会造成联接件在外边作用下产生变形、裂纹和凸起，致使结合面不平；同时螺栓还将产生拉伸永久变形，预紧力下降，甚至造成滑扣或折断，引发事故。     

把优质耕地划入基本农田实行永久保护

为提升耕地保护水平，全面加强耕地质量建设与管理，国土资源部日前制定并出台了《关于提升耕地保护水平全面加强耕地质量建设与管理的通知》。《通知》要求，要加快划定永久基本农田，严格管控优质耕地。重点是将优质耕地划人基本农田实行永久保护，严控建设用地占用优质耕地。乡（镇）土地利用总体规划批准后三个月内，要按照《基本农田划定技术规程》和有关要求，完成基本农田划定工作。要综合运用土地变更调查、农用地分等定级成果，将土地利用总体规划确定的基本农田落到实地，划定边界，设立标志，统一编号，落实到户。要确保划定后的基本农田，原有高等级和集中连片的耕地得到有效保留，坡耕地的比重有所降低，平均质量等级和集中连片程度有所提高。基本农田一经划定，实行永久保护，任何单位和个人未经批准不得改变或者占用。     

经济植物茶条槭的开发利用及其展望

茶条槭(AcerginnalaMaxim.)是槭树科的落叶灌木和小乔木。木材可供细木加工;树形优美,叶型清秀,尤其是秋后叶色鲜红艳丽,极具观赏价值,可用于园林绿化;嫩叶制成茶叶,具有生津止渴,退热明目之功效;更主要的是其树叶可提取大量的没食子酸(Gallicacid),即3,4,5-三羟基苯甲酸。每1kg干叶提取量已达120g以上,而没食子酸广泛应用于医药、化工、食品、轻工、印染、军工等方面。目前销售价格在8~10万元·t-1,可见其经济价值极大。1在制药工业上的应用在制药工业上,以没食子酸为原料现已合成以下药品:1.1合成抗感染药品甲氧苄氨嘧啶(TMP)及其衍生…     

城市周边永久基本农田划定次序研究——以潜江市为例

以湖北省潜江市城市周边地区为例,运用LESA评价方法,对研究区城市周边永久基本农田的划定次序进行了实证探索.研究表明,潜江市城市周边耕地自然质量总体较好,永久基本农田综合质量的优劣主要取决于耕地立地条件的差异.其中,综合评价质量条件最优的耕地面积为27.55 km2,占区域总面积的18.24％,可作为永久基本农田的优先划入区;综合评价质量条件较优的耕地面积为100.64 km2,占区域总面积的66.65％,可划为适宜划入区;综合评价质量条件较差的耕地面积为22.80 km2,占区域总面积的15.11％,可划为永久基本农田的后备划入区.在此基础上,对实际工作中永久基本农田的划定提出了建议.     

国土资源部：基本农田一经划定永久保护

国土资源部下发《关于强化管控落实最严格耕地保护制度的通知》（以下简称《通知》）,要求各地将保护耕地作为土地管理的首要任务,全面强化规划统筹、用途管制、用地节约和执法监管,加快建立共同责任、经济激励和社会监督机制,严守18亿亩耕地红线,确保耕地实有面积基本稳定、质量不下降。     

Experiences with Rice Grown on Permanent Raised Beds: Effect of Crop Establishment Techniques on Water Use,Productivity, Profitability and Soil Physical Properties

In recent years, conventional rice production technologies have been leading to deterioration of soil health and declining farm profitability due to high inputs of water and labor. Conservation agriculture(CA) based resource-conserving technologies i.e. zero-tillage(ZT), raised-bed planting and direct-seeded rice(DSR) have shown promise as alternatives to conventional production technologies to overcome these problems. Present study was undertaken during 2009–2012 to establish an understanding of how permanent raised bed cropping system could be practiced to save water at the field application level to improve water productivity and also have the capability to enhance productivity, profitability and soil physical quality. The results showed that among different crop establishment techniques, conventional-tilled puddle transplanted rice(CT-TPR) required 14%-25% more water than other techniques. Compared with the CT-TPR system, zero till direct-seeded rice(ZT-DSR) consumed 6%–10% less water with almost equal system productivity and demonstrated higher water productivity. Wide raised beds saved about 15%–24% water and grain yield decrease of about 8%. Direct-seeded rice after ZT or reduced tillage or on unpuddled soil provided more net income than CT-TPR. The CTTPR system had higher bulk density and penetration resistance due to compaction caused by the repeated wet tillage in rice. The steady-state infiltration rate and soil aggregation( 0.25 mm) were higher under permanent beds and ZT and lower in the CT-TPR system. Under CT-TPR, soil aggregation was static across seasons, whereas it improved under no-till and permanent beds. Similarly, mean weight diameter of aggregates was higher under ZT and permanent beds and increased over time. The study reveals that to sustain the rice productivity, CA-based planting techniques can be more viable options. However, the long-term effects of these alternative technologies need to be studied under varying agro-ecologies in western Uttar Pradesh, India.