青菜中二甲戊灵的残留分析方法

采用乙腈提取,固相基质分散净化,气相色谱电子捕获检测器检测,研究了青菜中二甲戊灵的残留分析方法.结果表明,该方法回收率97.8%～104.2%,变异系数在6.2%～8.8%,青菜中二甲戊灵最低检测浓度为0.037 mg/kg.     

Microstructure and creep properties of high Cr resisting weld metal alloyed with Co

A 9% Cr ferritic steel weld metal containing 1% Co, partially substituted for nickel, was prepared by submerged arc welding (SAW) processing. The microstructure and creep properties of the weld metal were investigated. The microstructure exhibited a fully tempered martensitic structure free of δ-ferrite. The creep properties of the obtained weld metal were inferior to those of the P92 base metal at 600 and 650 °C. The values of A and n for weld metal in the Norton power law constitution at 650 °C are 1.1×10?21 and 8.1, respectively.     

Effect of direct quenching on microstructure and mechanical properties of medium-carbon Nb-bearing steel

The influence of direct quenching （DQ） on microstructure and mechanical properties of 0.19C-1.7Si-1.0 Mn-0.05Nb steel was studied. The microstructure and mechanical properties of reheat quenched and tempered （RQ＆T） steel plate were compared with those of direct quenched and tempered （DQ＆T） steel plates which were hot rolled at different finish rolling tem-peratures （1173 K and 1123 K）, i.e., recrystallization-controlled-rolled direct-quenched （RCR＆DQ） and controlled-rolled direct-quenched （CR＆DQ）, respectively. The strengths generally increased in the following order： RQ＆T〈RCR＆DQ＆T〈 CR＆DQ＆T. Strength differences between the CR＆DQ＆T and RQ＆T conditions as high as 14% were observed at the tempered temperature of 573 K. The optical microscopy of the CR＆DQ＆T steel showed deformed grains elongated along the rolling direction, while complete equiaxed grains were visible in RQ＆T and RCR＆DQ＆T steels. Transmission electron microscopy （TEM） and electron backscattering diffraction （EBSD） of the DQ steels showed smaller block width and higher density of dislocations. Inheritance of austenite deformation substructure by the martensite and differences in martensite block width were ruled out as major causes for the strength differences between DQ and RQ steels.     

Microstructures and mechanical properties of SiBCNAl ceramics produced by mechanical alloying and subsequent hot pressing

Amorphous SiBCNAl powders were prepared via a mechanical alloying (MA) technique using crystalline silicon (Si), hexagonal boron nitride (h-BN), graphite (C), and aluminum (Al) as starting materials. SiBCNAl powders were consolidated by a hot pressing (HP) technique at 1800 °C under a pressure of 30 MPa in argon and nitrogen. The sintering atmosphere had a great influence on the microstructures and mechanical properties of the ceramics. The two ceramics had different phase compositions and fracture surface morphologies. For the ceramics sintered in argon, flexural strength, fracture toughness, elastic modulus and Vickers hardness were 421.90 MPa, 3.40 MPa·m1/2, 174.10 GPa, and 12.74 GPa, respectively. For the ceramics sintered in nitrogen, the mechanical properties increased, except for the Vickers hardness, and the values of the above properties were 526.80 MPa, 5.25 MPa·m1/2, 222.10 GPa, and 11.63 GPa, respectively.     

Effect of agarose content on microstructures and mechanical properties of porous silicon nitride ceramics produced by gelcasting

<正>Porous Si3N4 self-reinforce ceramics were prepared by gelcasting using agarose solutions. By changing the agarose content in the slurries, the porous silicon nitride ceramics with different porosities, α→β-Si3N4 phase transformation, and mechanical properties were obtained. When the agarose content changed from 0.2% to 0.8% (w/w, based on powder), the porosities increased from 10.3% to 21.4%, while the fracture strength decreased from 455 to 316 MPa and the fracture toughness decreased from 6.6 to 5.5 MPa·m1/2. Many fibrous β-Si3N4 grains grown from the internal wall of the round pores is the typical microstructure of the gelcasting porous silicon nitride ceramic. Both elongated β-Si3N4 grains and suitable interfacial bonding strength contributes to high fracture toughness by favoring crack deflection and bridging. The growth mechanisms of fibrous grains resulted from the synergy of solution-diffusion-reprecipitation and vapor-liquid-solid (VLS).     

CeO2掺杂对BaTiO3系统微观结构及介电性能的影响

对稀土氧化物CeO2掺杂的BaTiO3系统微观结构和介电性能进行了研究。结果表明,在BaTiO3陶瓷中掺杂CeO2会产生细晶效应、介电常数增大以及介电损耗减小等现象。由X射线衍射仪（XRD）计算可知,c轴变长,a轴变短,增强,Ti^4＋“自发极化强度,因而介电常数有所提高。由于Ce^4＋离子进行A位取代,Ce^4＋离子半径（0．103nm）小于Ba^2＋离子半径（0．135nm）,导致晶格常数有所减小,居里温度向低温移动。掺杂CeO2的摩尔分数为0．5％的BaTiO3陶瓷在1240℃下烧成的主要性能指标为：室温介电常数ε25℃≈3160,介电损耗-0．9％,-55℃到125℃范围内最大电容量变化率不超过±15％。     

英汉工具主语句的认知研究

文章从语义分析入手,基于体验和认知之上,分析英汉工具主语句的认知理据性。工具主语句是语言使用者采用的非典型主语句,目的是突显以工具为图形的意象,是突显原则和经济原则共同选择的结果,说明了语言使用者不是纯客观地描写现实世界,而是受主体对客观世界认知方式的影响。     

废砖再生集料配制小型混凝土空心砌块研究

对废砖再生集料生产混凝土空心砌块的若干关键技术进行了初步探索。设计了一套废砖的破碎、筛分和分选工艺并测试了废砖再生集料的基本性能。针对废砖再生集料的特点,完善了再生混凝土空心砌块的成型工艺。在试验研究的基础上,考察了废砖再生集料混凝土空心砌块的抗压强度和热工性能。试验结果表明,通过优化废砖再生集料的含量,掺加粉煤灰和聚丙烯纤维,可以获得强度等级为MU5-MU7．5,抗开裂性能和保温性能良好的混凝土空心砌块。     

明清徽州民间的众存祀会

众存祀会系设置众存产业以祀祖的组织,具有自发性、平等性和灵活性,属于宗族之下血缘性的结合,并主要依靠契约关系予以维系,是宗族组织内部祀祖的基本形式之一.由明及清,徽州众存祀会分布广泛,数量可观,长期存在,相沿成俗,它与宗族组织在祭祀功能上是互补共存的.     

分形康托多层结构的光学传输特性

在分形理论的基础上,将分形康托序列引入到一维光子晶体的设计中来,得到了一维准分形康托多层结构,采用传输矩阵法研究了分形康托多层结构的光学传输特性,讨论了该结构的分形维数以及光学传输谱的Scalability和Sequential Splitting特性.这种结构可用于超窄带光子晶体滤波器,在光学精密测量和光通信超密集波分复用等领域中有一定的应用价值.