近红外光谱吸收技术的无线电子鼻设计

基于近红外光谱吸收技术,设计并开发出了一套能够高效、准确地对目标气体进行检测的电子鼻系统。电子鼻系统主要包括近红外激光发射单元、气室单元、系统控制单元、人机界面单元。主成分分析(PCA)算法和反向传播(BP)神经网络通过LabVIEW所提供的MATLAB Script节点,集成到上位机软件中,并用来对采集到的数据进行分析。结果表明,该电子鼻在网络训练次数达到1 000次以上时达到稳定,且精度达到0.000 1。对白醋、米醋和苹果醋进行食品分辨,识别准确率达到100%,实现了高精度、高稳定度和高分辨率的设计目标,具有较好的应用前景。     

Transglutaminase cross-linking of milk proteins and impact on yoghurt gel properties

A novel yoghurt process was investigated in which milk proteins were covalently cross-linked by a microbial transglutaminase (TG) preparation containing glutathione (TG+GSH). As unheated milk is normally less reactive towards TG, TG+GSH was applied to enable non-inhibited cross-linking without requiring a pre-heat treatment beyond pasteurisation conditions. After the TG+GSH incubation phase, the enzyme was inactivated by heat treatment of the yoghurt milk prior to fermentation. During yoghurt fermentation, no negative effect of TG+GSH on fermentation time was found. Protein cross-linking by TG+GSH was enhanced, resulting in higher apparent viscosity and a higher degree of protein polymerisation than that given by TG without GSH. Furthermore, different ratios of casein to whey proteins (CWP ratios) were used to investigate the effect of both protein fractions on covalently cross-linked yoghurt gel structures. The results showed a relationship between extent of cross-linking, apparent viscosity and CWP ratio of the yoghurt gels. During storage for up to 6 weeks at 4 °C, no changes in rheological properties and degree of protein polymerisation were measurable for stirred yoghurt gels prepared from cross-linked milk proteins.     

掺Tm光纤MOPA准相位匹配单程倍频的单频激光器

为获得0.9 μm近红外波段连续波单频激光输出,用50 mm长的PPLN晶体对掺Tm光纤激光MOPA的连续波1 925.08 nm单频激光输出进行单程倍频,通过聚焦参数和准相位匹配温度优化,在43.4 W基频光功率实现了最高9.07 W的962.5 nm二次谐波输出,转换效率达到20.9%。二次谐波为单纵模运转,水平和竖直方向光束质量因子分别为1.36和1.52。实验中研究了聚焦因子和相位匹配温度对倍频转换效率的影响,并讨论了聚焦条件和准相位匹配温度带宽之间的相互关系。实验结果表明:Tm光纤激光准相位匹配单程倍频是获得0.9 μm波段连续波单频激光输出的有效方法。     

基于分层节点识别策略的中低压配电网同期线损优化系统的研究

作为电力工业的综合性经济指标之一,线损率可直接反映电网结构及其运行方式的合理性,同时也严重影响着电力企业的经济效益。随着智能电网的快速发展,对配电网的同期线损有了更高的要求。设计了10 kV中低压配电网同期线损优化系统,由数据采集单元、传输单元及分析单元三部分构成。其中,GPRS公网和230 M无线专网作为信息传输的通道;数据分析单元由数据读取、拓扑分析及线损计算构成。针对目前电量采集过程中数据缺失严重、同期线损取数及计算过程中误差较大、可靠性低等问题,在线损计算过程中,引入了分层式节点识别策略,提出了基于支持向量机的负荷节点智能识别方法,可有效、快速求取各种负荷节点的注入电流,从而降低了非同期数据所带来的线损误差。利用实际案例验证了配电网同期线损优化系统在线损计算中的可行性和有效性,该系统可为智能配网的规划设计、生产运行和运营管理等方面提供可靠的依据。     

绿光泵浦的黄光波段可调谐窄线宽光学参量振荡器

为实现波长可调谐的窄线宽黄光波段激光输出,设计搭建了以倍频声光调Q Nd:YAG激光器的532 nm脉冲绿光输出为泵浦源、以II类相位匹配磷酸钛氧钾（KTP）晶体为非线性介质的折叠腔光学参量振荡器（OPO）。首先产生腔内振荡的近红外可调谐闲频光,在此基础上基于LBO晶体I类非临界相位匹配方式对OPO的闲频光进行内腔倍频,得到波长调谐范围587.2~595.2 nm的黄光波段输出。为改善OPO光谱特性,在OPO闲频光谐振腔内插入熔融石英标准具,有效压缩了OPO输出黄光的光谱线宽。绿光泵浦源脉冲重复频率10 kHz、平均功率24.0 W下在波长591.2 nm处获得了最高黄光输出功率2.89 W,光束质量因子M2=3.4,从532 nm泵浦光到黄光输出的转换效率为12.0%,脉冲宽度37 ns,对应峰值功率7.8 kW。此时黄光光谱半高全宽为0.15 nm,相比未在OPO腔内插入标准具自由运转状态下的光谱得到明显改善。     

乳制品中沙门氏菌分子检测方法的验证研究

目的验证沙门氏菌、非沙门菌及阳性核酸模板对MICROFAST?沙门氏菌核酸检测试剂盒(PCR-探针法)的特异性和稳定性,同时比对试剂盒法与GB 4789.4—2016培养法定性检测结果的一致性。方法用实验室保存的30株沙门氏菌和15株非沙门氏菌菌株验证MICROFAST?沙门氏菌核酸检测试剂盒(PCR-探针法)的特异性。通过人工添加不同浓度沙门氏菌对30个乳制品样本,采用国家标准法和试剂盒法同时检验,探究方法的一致性。选择制备好的5份阳性核酸模板,每个模板分别使用3个批次的试剂盒进行检测,对实验结果进行重复性和显著性分析,确定不同试剂盒批次间是否存在显著性差异。结果 30株沙门氏菌菌株和15株非沙门氏菌菌株的特异性检测结果表明,MICROFAST?沙门氏菌核酸检测试剂盒(PCR-探针法)对沙门氏菌的特异性符合预期。人工添加的阳性样本检测结果表明,在乳制品样本范围内,试剂盒的假阳性率与假阴性率为0。3个批次的试剂盒对5份阳性模板检测结果之间没有显著性差异,变异系数CV均小于1%。结论该试剂盒方法与国家标准法相比,具有操作简单、快速等优势,适合乳制品加工过程微生物快速检测。     

Modification of the nitrogen solubility properties of soy protein isolate following proteolysis and transglutaminase cross-linking

The effect of (a) limited hydrolysis [0.5–2.0% degree of hydrolysis (DH)] with Alcalase™, (b) cross-linking with transglutaminase (TGase) and (c) combinations of these modifications on the nitrogen solubility (pH 3–8) of soy protein isolate (SPI) was investigated. Between pH 3.0 and 5.0, SPI hydrolysates, hydrolysates of cross-linked SPI and the cross-linked products of SPI hydrolysates displayed significant (P<0.05) increases in solubility compared to unmodified SPI. Cross-linking pre- or post hydrolysis did not alter the overall trend of increased (P<0.05) solubility relative to the unmodified control at low pH. At 2% DH, cross-linking pre- or post-hydrolysis resulted in greater solubility (P<0.05) than that observed in hydrolysates per se at low pH. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS–PAGE) indicated that the 22 kDa 11S basic polypeptide was relatively resistant to Alcalase hydrolysis and that the 18 and 22 kDa 11S basic polypeptides were not susceptible to TGase cross-linking. The results demonstrate that a combination of enzymatic treatments and the order in which they are applied may have potential for creating novel food ingredients with improved functional properties, especially those properties that are dependant on high solubility at low pH.     

Functionality of milk protein concentrate 80 with emulsifying salts and its applications in analogue cheeses

Milk protein concentrate 80 (MPC80) was prepared with different emulsifying salts (ES). The effects on particle size (D50), solubility, and surface hydrophobicity (H₀) of MPC80 were then observed after production. The molecular weight and secondary structure of MPC80 protein were also investigated through sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier Transform Infrared (FTIR) spectrometry. Particle size (D50) was reduced from 31.37 to 20.67 μm following the addition of sodium phosphate (SPS). The solubility of MPC80 fortified with sodium citrate salt (SCS), SPS, and sodium pyrophosphate (SPP) was improved by 80.32, 78.23, and 55.80%, respectively. The SDS-PAGE pattern showed no significant difference between the control and single-ES-fortified samples, but major protein bands (α_s-CN, β-CN, κ-CN, BSA, and β-LG) had a stronger intensity than binary-ES-fortified MPC80. The FTIR results showed that the β-sheet content of ES-fortified MPC80 was relatively higher than that in the control. Compared with analogue cheeses made by MPC80 with and without ES, SCS–SPP (92:8)-modified MPC80 presented a better fluid mass and homogeneous colour.     

离轴三反光学系统中反射膜的研制

离轴三反光学系统由于具有工作波段宽,像质优良且杂散光易于控制等优势,因而被广泛用作光谱成像系统的设计方案。文中采用Code V软件,对光学系统进行了设计,基于光的偏振理论,推导出薄膜样品和系统的偏振保真度与相位差之间的换算关系,选择铝材料作为基底材料,银(Ag)、三氧化二铝(Al₂O₃)和二氧化钛(TiO₂)为镀膜材料。根据光学薄膜基础理论,设计出光线38.5°入射,在1 545~1 555 nm处R_S>99.96%,R_P>99.8%,P光和S光相位延迟小于1°的反射膜。结合膜系设计软件进行膜系设计和模拟分析,在德国莱宝光学公司设计生产的高性能光学镀膜机上完成了离轴三反光学系统中铝合金表面反射膜的制备。采用Lamda1050光谱仪对镀膜样品的S光、P光反射光谱和相位进行测试,测试结果满足设计要求。该研究具有重要的实际意义和工程价值。     

星敏感器光学系统设计及杂散光抑制技术研究

在星敏感器实际应用中,光学系统杂散光的存在会引起星点模糊或者被遮挡。文中根据星敏感器对口径、视场、光谱范围和探测能力的要求,采用Code V软件完成了星敏感器光学系统的设计,最终设计参数为口径15 mm、视场18°、光谱范围400~750 nm、探测能力5等星,并利用CAD画图软件设计了锥形结构遮光罩,遮光罩叶片视场边界为19°,共9片挡光环,最前端面距离窗口玻璃190.76 mm,最前端面口径108.76 mm,太阳规避角25°,同时利用ASAP软件分析了光学系统对杂散光的抑制能力,根据杂散光评价指标点源透射比(PST),在25°太阳规避角时,系统满足5等星探测能力需求,验证了杂散光分析方法、分析模型的正确性。