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.     

N-(1-萘乙酰基)-N'-(4-氨替吡啉基)硫脲(NAT)对小麦生理活性影响的初步研究

以新合成的NAT配制成不同浓度(0.1、1.0、10.50mg·L~(-1))的水溶液,对小麦进行漫种、水培幼苗和大田灌浆期叶面喷洒处理,以与NAT相同浓度的NAA作对比,研究了喷后一定时期小麦叶片生理活性和收割时籽粒千粒重。结果表明,NAT使小麦在不同生长发育时期叶片中的叶绿素含量均增加;幼苗叶片呼吸速率下降;幼苗期低浓度处理NR活性增高,高浓度显著抑制,灌浆期则随处理浓度的升高而显著增加;籽粒千粒重明显高于对照。不论对叶片生理活性还是对籽粒千粒重的影响,NAT的总体效果均明显优于NAA,其中以1 mg·L~(-1)左右浓度的NAT处理效果最佳。     

玉米对低温胁迫的生理响应及不同品种间耐低温能力比较

以中国北方普遍种植的5个玉米品种为供试材料,探索玉米在低温胁迫下的生理响应规律,测试并分析了玉米苗期的光合速率、电导率、脯氨酸浓度的变化,并以此特性参数为依据对作物的抗低温特性进行综合评价。所得到的基本结论如下：光合速率降低幅度较小、电导率增加幅度较低、脯氨酸浓度提高显著的品种,具有较强的抗低温特性;试验中所采用的5个玉米品种,其抗低温冻害能力由强到弱依次为：沈单10号,中单306,农大108,晋单32,陕单902。     

An exergy assessment model of the environmental impacts of building energy use

Buildings, as products of built environment creation made by human kind, consume a substantial amount of energy. Building energy performance attracts much attention from many countries. Two things building energy use affects are fossil energy co     

An EOQ Model Taking Account of the Variable Selling Price Under Stock Dependent Selling Rate

In 1995, Padmanabhan and Vrat presented inventory models for deteriorating items with a constant selling price and stock dependent selling rate . Based on the result, in 2000, Kun-Jen Chung, Peter Chu and Shaw-Ping Lan devoloped the necessary and sufficient conditions of the existence and uniqueness of the optimal solutions of the profit per unit time functions without backlogging and with complete backlogging. Actually, the selling price need not be constant, it may be variable . This paper puts forward an EOQ model when the selling price is variable without backlogging, discusses the existence and uniqueness of optimum solution. The example is provided to illustrate the model. The theoretical evidence is provided for the inventory system to make management decision.     

Performance Analysis of Anti-CW Interference in MC-CDMA Systems

The multicarrier-code division multiple access (MC-CDMA),which is the combination of direct sequence CDMA (DS-CDMA) and orthogonal frequency division multiplexing (OFDM) techniques, offers various advantages over single-carrier CDMA system. Some of the advantages are that MC-CDMA systems possess can remove the intersymbol interference (ISI) and enhance narrow-band interference suppression capabilities. So the MC-CDMA technique becomes a focus in the field of mobile communication. The authors introduce the typical MC-CDMA system model, discuss the decision statisticalvariable in Rayleigh fading channel included the CW interference, and give the expressions of probability of error in uplink. An approach is proposed with Modified Equal Gain Combining (MEGC) to decrease the effect of CW interference. Theoretical analysis and numerical results show that the anti-CW interference performance of MC-CDMA system can be improved used the MEGC approach.     

一个CRISPR/Cas9-VQR基因编辑系统的构建

CRISPR/Cas9系统是一种广泛应用于细菌、酵母、动物和植物中的基因组定点编辑技术,但该编辑系统的使用范围受PAM (proto-spacer-motif)位点NGG的限制。本研究通过突变Streptococcus pyogenes Cas9 (SpCas9)编码氨基酸(1135位的天冬氨酸D突变成缬氨酸V, 1335位的精氨酸R突变为谷胱氨酸Q, 1337位的苏氨酸T突变为精氨酸R,命名该突变子为Cas9-VQR)改造其识别PAM为NGA的位点以扩大其使用范围。并使用玉米Ubi启动子启动Cas9-VQR基因、优化SpCas9的密码子、加入保守的核定位信号序列、增加单子叶植物中保守的3′UTR序列和使用水稻U6启动子启动gRNA来修饰该编辑系统。结果表明Cas9-VQR系统能够识别PAM为NGA的位点,并进行有效的切割。体外酶切活性检测结果表明Cas9-VQR的切割效率为5%～70%。水稻转化检测结果表明Cas9-VQR的切割效率约为27.5%～70.5%,平均切割效率为46.23%。本研究拓宽了CRISPR/Cas9系统在作物中的使用范围,特别是NGA PAM位点较高的作物。     

瑞金市典型村农村居民点内部结构差异分析及整理潜力测算

为了优化农村居民点内部结构和分布,实现土地资源的可持续利用,农村居民点整理正成为实现这一战略的重要手段。笔者以瑞金市为例,以农村居民点内部结构差异分析为基础,采用“三级标准”制,运用户均宅基地标准法计算出农村居民点整理潜力。结果表明,不同农村居民点整理潜力存在差异。因此,对于不同农村居民点,必须采取不同措施进行用地整理,优化农村居民点内部结构。     

木醋液对桃蚜生长繁殖的急慢性效应

为了明确木醋液对桃蚜短、长期影响,以桃蚜为试虫,用100倍稀释木醋液处理小白菜饲养蚜虫,测得桃蚜繁殖发育数据.结果 显示,木醋液处理显著缩短桃蚜繁殖期,而F1代繁殖期比F0代繁殖期延长37％;F0代和F1代产蚜总量与对照组相比分别降低62％和66％;处理组F1代和F2代的存活率比对照组降低23％和24％,但F1代和F2...     

山东禹城地区土壤入渗特性的空间变异研究

在中科院禹城综合试验站102 m×52 m面积内选择样点,采用经典统计学和地质统计学方法,对土壤稳渗率和入渗经验指数的空间变异性进行研究.结果表明,土壤稳渗率和入渗经验指数均服从对数正态分布,表现出空间变异结构,但不是完全的随机变异,在一定范围内存在着空间相关现象.利用克立格最优内插估值法,绘制了土壤稳渗率和入渗经验指数的等值线图,可准确、直观地了解该地区农田土壤垂向透水性的空间分布规律.