Inspection of pipeline girth welds with ultrasonic phased array technique

A novel automatic ultrasonic system used for the inspection of pipeline girth welds is developed, in which a linear phased array transducer using electronic scan is adopted. Optimal array parameters are determined based on a mathematical model of acoustic field for linear phased army derived from Huygens＇ principle. The testing method and the system structure are introduced. The experimental results show that the phased array transducer system has the same detectability as that of conventional ultrasonic transducer system, but the system architecture can be simplified greatly, and the testing flexibility and the testing speed can be improved greatly.     

汽车软件中实时任务调度机制研究

介绍了实时操作系统任务调度机制和传统查找最高优先级任务优先级的算法,并对该算法存在的问题进行分析.然后针对汽车电子应用特点对传统的优先级循环查找法存在的缺点进行分析,提出用查表法改进查找算法,这样改进了系统的运行时间确定性和稳定性,提高了软件的快速执行能力,实现对汽车电子工作现场的精确控制.     

大数据时代零售业客户管理的变革研究——以吉林省长春市为例

大数据在零售业中的战略意义不仅仅在于掌握庞大的数据信息,更在于如何专业化处理此类数据,特别是将精确数据引入客户关系管理方面。从原有客户关系理论中提出"精确数据"的新理念,通过对精确客户数据保证客户关系管理的认知理解和吉林省长春市零售业竞争环境分析,探讨了CRM在长春市内零售业中的应用现状,建立了一套适合零售业的CRM系统架构,并提出了实施策略。     

Electro-optically Q-switched 946 nm laser of a composite Nd:YAG crystal

A depolarization phenomenon in an electro-optical crystal in a quasi-three-level 946 nm Nd:YAG laser is observed. A compensation of the thermal effects in electro-optical crystals is achieved by employing a quarter-wave plate, with one optical axis parallel to the laser polarization. This technique allows for the production of an electro-optically Q-switched 946 nm Nd:YAG laser at 1 k Hz. A maximum output power of 350 m W at 1 k Hz repetition frequency and 11 ns pulse duration are achieved with an output coupler of 10% transmission under the incident pump power of 11.1 W, corresponding to a peak power of ～32 k W.     

双花千里光中一个新的呋喃骈雅槛蓝烷型倍半萜

从藏药双花千里光中分离得到2个倍半萜类化合物,经过HR-ESIMS,1D和2D NMR等光谱技术,将上述化合物鉴定为6-oxo-9α-angloyloxy-10βH-furanoeremophilane(1)和spiroeuryolide(2).化合物1为新的呋喃骈雅槛蓝烷倍半萜.同时,对文献报告中化合物2的13C NMR数据进行了纠正.     

电化学处理对硝基苯酚模拟废水的研究

以钛钌电极为阳极、钢板为阴极,对含对硝基苯酚（PNP）的模拟废水进行了电化学处理．试验研究了外加电压、极板间距、电解质质量分数、溶液pH值、电解时间等因素对PNP处理效果的影响,结果表明：外加电压7V,pH=10～11,极板间距2cm。支持电解质Na2S04质量分数0．5％的条件下,电解5h,PNP的去除率可达89．3％．     

Single-frequency, single-polarization ytterbium-doped fiber laser by self-injection locking

We demonstrated a stable single-frequency, single-polarization operation of ytterbium-doped fiber laser. As a novel practical method to realize single-polarization operation of fiber distributed Bragg reflector (DBR)laser, we proposed self-injection locking (SIL) with an active fiber ring feedback cavity. The laser has high output power exceeding 15 mW, wavelength of 1053.20 nm, and side-mode suppression ratio greater than 60 dB. The SIL fiber laser shows the improvements in output power and side-mode suppression compared with the fiber DBR laser. No mode-hopping is observed within 2 hours.     

陈题新解 温故知新——记一次新课程理念指导下的竞赛辅导活动成果

[一道陈题]在水平面放一个半径为R的环,另一个同样大小的环以速度ν从它旁边运动过去,如图1所示.找出两个环的交叉点A的速度νA与它们的圆心之间的距离d的关系式.     

关于提高水利维修养护质量的几点建议

水利维修养护工程中质量控制的优劣直接关系着整个工程的成败，它关系到人民的生命财产安全和国家的荣誉及民族的形象。     

藏红花愈伤组织诱导和褐化抑制

对藏红花的球茎、无菌芽和幼叶的愈伤组织诱导条件进行研究,同时探讨愈伤组织诱导过程中的褐化和污染问题.结果表明:与球茎相比,以无菌芽和幼叶为外植体,愈伤组织诱导率较高,诱导时间较短,但形成的愈伤组织易褐化.较大球茎(≥20 g)也是藏红花愈伤组织诱导较好的外植体,愈伤组织诱导速度随球茎储藏时间的增加而升高.含有2.0 mg/L 2,4二氯苯氧乙酸(2,4D)和0.5 mg/L 6苄氨基嘌呤(6BA)的MS(Murashige and Skoog)培养基有利于球茎愈伤组织的诱导,30 d愈伤组织诱导率可达70%以上.在愈伤组织诱导过程中,连续转接外植体至新鲜培养基可以有效降低褐化率,而在培养基中添加活性炭(AC)和聚乙烯吡咯烷酮(PVP)不能有效抑制褐化.表面灭菌前采用流水冲洗过夜可有效减少球茎表面附生菌,明显降低污染率.