Optimum design of electromagnetic shielding rooms with minimum usage of absorbing materials

In this article, a novel method has been proposed to optimize the electromagnetic shielding rooms. This method is based on using minimum electromagnetic absorbing materials on the inner surface of the rooms. The positions of the absorbing materials are found optimally to produce a “best” performance for the shielding rooms. The ray‐tracing method is used to predict the shielding effectiveness (SE) of the electromagnetic shielding rooms with apertures. The performance of the proposed method is verified by a comprehensive example. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010.     

NOx adsorption behavior of LaFeO3 and LaMnO3+δ and its influence on potentiometric sensor response

NO_x adsorption behavior on LaFeO₃ (LFO) and LaMnO_3+δ (LMO) was characterized using temperature controlled methods and mass spectrometry. Temperature program desorption revealed decomposition of complex surface species formation when NO or NO₂ was adsorbed on LFO and LMO. LFO exhibited higher adsorption capacity for NO_x species than LMO and was shown to be more active for NO_x surface conversion. Both effects were attributed to the different B-site cations, with iron in LFO in the 3+ valence state, and manganese in LMO in the 3+ and 4+ valence states. Results from diffuse reflectance infrared spectroscopy were used to identify specific nitrite and nitrate species that are formed on the surfaces of LFO and LMO at room temperature. Temperature programmed reaction revealed a complex NO₂ decomposition mechanism to NO and O₂ for LFO and LMO in which the formation of nitrite and nitrate species serve as intermediates below ∼600 °C. NO_x sensing mechanisms were considered and predicted based on the types and quantities of surface species formed.     

基于初始磁导率的铁氧体裂纹检测

铁氧体是电子电路中广泛使用的抗干扰元件,生产中应力引发的内部缺陷裂纹严重影响其电气性能。其传统检测方法准确率低、速度慢,难以满足产品的快速检测需求。将基于初始磁导率的缺陷检测方法运用于铁氧体工件的检测,对检测传感器进行优化,使之能够在微小激励下获得准确的输出响应。对改进前后的传感器进行了对比实验,分别就其结构、尺寸、磁导率等参数进行了针对性分析,证明了该检测方法和参数优化的有效性。     

工业赤磷除铁工艺研究

采用双级逆流串联反应流程,对工业赤磷除铁工艺进行研究,讨论了影响除铁效果的主要因素,选最佳除工艺条件为：反应温度８８－９０℃,单级反应时间４．５－５．５ｈ,助剂Ｍ与工业赤磷的比例１：１２０,在此条件下,铁的去除率达到９８％以上,赤磷中含铁量降至０．００８％以下。     

Effect of Nb on the transformation kinetics of low carbon （manganese） steel during deformation of undercooled austenite

The hot compression tests using Gleeble 1500 were performed by varying the true strain up to 1.6 （80% reduction） in Nbfree and Nb-microalloyed steels. The effect of Nb addition on the transformation kinetics during deformation of undercooled austenite was investigated. It was found that as compared with Nb-free steel, the transformation incubation period of Nb-bearing steel was prolonged and the transformation kinetics curves parallelly moved to higher strain because of the solute Nb drag effect. Studies on kinetics also showed that the deformation-enhanced ferrite transformation （DEFT） of the two steels were composed of three stages, which can be expressed by the J-M-A equations individually. However, the parameter n related to the mode of nucleation and growth is somewhat different in the first and second stages of the two steels, and the same in the third stage for both the steels corresponding to the nucleation Of retained austenite.     

超级铁精矿提纯与锶铁氧体预烧料试验研究

对武钢金山店的磁铁精矿进行提纯，得到了超纯磁铁精矿（TFe〉71．5％，SiO2〈0．5％）。以该超纯磁铁精矿与分析纯碳酸锶及添加剂为原料，通过对配比、预烧温度、保温时间等条件进行优化得到了性能较好的锶铁氧体预烧料。     

稀土和Ca、Mg元素对高强度钢焊接热影响区组织和韧性的影响

研究了低合金高强度非调质中厚板钢中添加稀土(REM)和Ca、Mg微量元素对大线高能焊接热影响区(HAZ)显微组织微细化和晶内针状铁素体(IAF)形成的影响.结果表明,添加REM和Ca、Mg元素可在钢的HAZ中形成弥散稳定的氧硫化物(CeCa)2O2S和(CeMg)2O2,热轧奥氏体化(1450℃)和焊接热输入10 kJ/mm时都十分稳定,比传统采用TiN强化的钢具有更优良的低温韧性.有效地控制细小弥散的氧硫化合物,能获得适中的奥氏体有效晶粒尺寸和提供HAZ中形成晶内针状铁素体及稳定活性的形核位置.促进晶内铁素体协同形核生长,有效地使得HAZ组织微细化.     

碳含量对高钒高速钢冲击磨损性能的影响

在含钒量约为10%的条件下,利用自行研制的WM-1型冲击磨损试验机研究碳含量在1.76%～3.65%范围内变化对高钒高速钢冲击磨损性能的影响.结果表明:含碳量低于2.3%,高钒高速钢的基体为铁素体,磨损机理主要是冲刷和塑性变形,耐磨性很差.含碳量达到2.3%后,基体以马氏体为主,耐磨性比低碳的高钒高速钢大幅提高.当碳含量达到3.0%时,耐磨性达到峰值.继续提高碳含量,晶界处以铬钼为主碳化物的量增加,冲击过程中裂纹在该处萌生,产生剥落现象,造成耐磨性下降.     

钒氮钢中晶粒细化研究

 采用Gleeble 3500热模拟试验机，在相同工艺条件下，对比研究了钒氮钢、钒钢以及碳锰钢的晶粒细化效果。结果表明，钒氮钢的晶粒细化效果最显著，铁素体的晶粒尺寸可达61 μm，这主要与在奥氏体区中析出的V(C，N)有关。奥氏体区析出的V(C，N)，不但可抑制奥氏体晶粒长大，同时还可以作为铁素体的形核核心，诱导晶内铁素体形成，大大增加铁素体形核率，从而提高了相变细化的比率。     

化学共沉淀法制备的BaNiZnCexFe16-xO27超微粉末的微波吸收特性

采用化学共沉淀法制备了BaNiZnCexFe16-xO27铁氧体吸波材料,就铈元素的含量对钡镍锌铁氧体吸波性能的影响进行了对比研究.实验发现在涂层厚度为1mm,测试频段为8.2GHz～12.5GHz频率范围内,当x=0.03时,该铁氧体材料的微波吸收特性最佳,在11.6GHz处,最大吸收值达13.6dB,10 dB以上带宽大于1.4GHz,其复介电常数ε″最大值为1.3,复磁导率μ″最大值为0.78,添加铈是提高钡镍锌铁氧体吸波材料性能的一种有效途径.