无铅松香芯焊锡丝中新型助焊剂的研制

通过扩展率实验对松香芯焊锡丝用助焊剂的成分及配比进行选择及优化,然后通过添加一种天然植物油(C油)对该优化过的助焊剂进行进一步改进,依据行业标准对制备的助焊剂进行了测试。结果表明,这款助焊剂不含卤素、无腐蚀性、表面绝缘电阻高(1.68×10~(11)Ω);无铅SnCu焊锡丝在使用这款助焊剂时,焊接效果好,松香飞溅值为0.3%,扩展率为75.9%。     

阵列天线互耦补偿技术研究

分析阵列天线的互耦机理,利用电磁散射理论研究阵列天线的散射特性,得到阵列天线的散射矩阵,并根据散射矩阵中的实际物理意义,将矩阵进行分解,推导出阵列天线的互耦补偿公式,避免了复杂的计算,并在实际测试数据的基础上,利用提出的算法进行互耦补偿,验证了该算法的有效性。     

太湖水体悬浮颗粒物生物光学模型及MERIS数据反演

根据太湖悬浮颗粒物生物光学特性建立的悬浮颗粒物红外单波段生物光学模型具有明确的机理性.利用2006年至2009年野外实测悬浮颗粒物浓度和水体光学数据对该生物光学模型进行检验和分析.结果表明,悬浮颗粒物比后向散射系数的时空差异是影响总悬浮颗粒物生物光学模型精度的主要因素.总悬浮颗粒物在红外波长的吸收系数对总悬浮颗粒物生物光学模型精度也具有显著的影响.根据中分辨率光谱成像仪(MERIS)悬浮颗粒物 反演结果和野外实测风速数据,太湖沉积物再悬浮将显著增加水体中悬浮颗粒物的含量.     

扩散温度和时间对晶体硅太阳电池性能的影响

研究了薄层方块电阻对单晶硅太阳电池的开路电压(Voc)、短路电流(Isc)、填充因子(FF)和转换效率(η)的影响。通过控制扩散温度和时间制备了具有不同薄层方块电阻的单晶硅太阳电池。结果表明:当扩散温度和时间分别为863℃和1 050 s时,电池性能得到了有效的改善,其平均开路电压、短路电流、填充因子和转换效率分别为0.64 V,5.58 A,0.755和17.3%。     

基于Cascode级间匹配的多频段LNA设计

提出了一种Cascode级间匹配电路,能够优化Cascode放大器的噪声系数、增益及高频稳定性。应用该电路,设计了一款多频段射频低噪声放大器(LNA)。采用0.25μm GaAs工艺进行实现,输入、输出阻抗匹配网络采用片外元件。测试结果表明,通过重配置片外元件的参数,该LNA可工作于0.7~1.1 GHz、1.6~2.1 GHz、2.3~2.8 GHz这三个频段,增益分别为25±2 dB、19.5±0.5 dB和18±1 dB,噪声系数分别低于0.6 dB、0.7 dB和0.9 dB,OIP3均大于30 dBm。该LNA对于GSM/WCDMA/LTE通信基站以及L/S频段接收机等设备具有一定的应用价值。     

洁净手术室空调的低频噪声控制

对洁净空调中风机的低频噪声产生和控制作了介绍,重点介绍了微穿孔消声器和阻尼减振技术。并提出医院、生物安全和动物试验用L或C计权计量室内噪声,并考核倍频程的噪声参数。     

Bacterial Growth and Volatile Compounds in Yoghurt-Type Products from Soymilk Containing Bifidobacterium ssp

The growth of bacteria normally used to produce yoghurt was compared in soymilk and cow milk. Whether or not Bifidobacterium ssp. was present, fermented soymilks [soyoghurt (S), soyoghurt + bifi-dobacteria (SB)] were less acidic than fermented cow milks [yoghurt (Y), yoghurt + bifidobacteria (YB)]. When bifidobacteria were present (in SB), streptococci were more numerous than lactobacilli. Bifidobacteria in YB stimulated maximal growth of both yoghurt bacteria. In comparison to nonfermented milks, acetaldehyde and diacetyl increased in all cultures. Ethanol increased only in S/SB and acetone was detected only in Y/YB. Quantities of volatile products in Y/'YB were slightly lower than those in Y/S. In all cultures, n-hexanal was almost totally absent.     

Flavor Constituents of Aqueous Fraction Extracted from Comte Cheese by Liquid Carbon Dioxide

Isolation, purification and identification of some low-molecular-weight compounds from a water-soluble extract of Comté cheese was achieved. We used liquid CO₂ extraction, subsequent fractionation (by gel permeation and reserve-phase HPLC) and mass spectometry. Major constituents were N-acyl amino acids (N-acetyl methionine, N-propionyl methionine, N-propionyl leucine, N-propionyl phenylalanine), dike-topiperazines (cyclo(Pro-Pro), cyclo(Pro-Val), cyclo(Pro-Phe), cy clo(Pro-Leu), cyclo(Pro-Ala)) and non-peptide compounds (theo-bromine, 4-methyl-t-thiazoleethanol, uracil, (5–6)dihydro-uracil, thymine). These compounds were synthesized and tasted. Most were bitter. N-propionyl methionine had a cheese flavor but was not detected when added to a simulated cheese at 180 mg/L.     

Microwave active resonator band-pass filters in various mmic technologies

In this article, two topologies of L-C parallel active resonators are presented. These circuits are realized in MMIC technology, using three transistors which could be MESFET, hemt or HBT. The survey of these resonators shows the possibility, by controling the values of a resistor and/or a capacitor, on the one hand, to tune the resonance frequency of these circuits, and on the other hand, to cancel out their losses so as to obtain negative conductance. Compact, lossless and narrow-band filters are then implemented using previous active resonators. To date, the use of mesfet technology has reduced the synthesis of such active filters in S-band and at X-band low frequencies. Now, however, hemt and HBT technologies allow the extension of their implementation to the whole X-band. This survey is illustrated by the simulated response of a 10 GHz filter with a 500 MHz 3 dB bandwidth. The mmic technology is a 0.2 μm hemt one. The simulated performances of this filter achieve a mean transmission gain of 0. 5 dB, with a reflection loss higher than 10 dB at 10 GHz,     

基于遗传算法的火箭转塔伺服系统最优PID控制研究

文中对某火箭发射装置的模拟位置伺服控制系统进行了研究.针对系统进行了建模和相关参数的计算;最后对系统进行仿真,得到基于遗传算法的最优的控制器参数Kp,Ki,Kd.仿真结果表明,基于遗传算法的PID控制器可以实现工程的性能指标要求,具有很好的效果.