Cooking evaluation of crayfish (Procambarus clarkia) subjected to microwave and conduction heating: A visualized strategy to understand the heat-induced quality changes of food

The evaluation of food cooking process is an important way to understand the heat-induced quality changes and optimize the heating process. To understand the quality changes in crayfish tail heated by microwave (MW) and boiling water (BW), the protein denaturation, cooking uniformity and overheating degree of tails were visually evaluated based on the theories of reaction kinetics and maturity value in this work. Protein denaturation analysis showed that heat-induced protein denaturation in crayfish tails heated by MW and BW followed first-order reaction kinetics and had similar one-dimensional denaturation patterns and temperatures, but their distributions were non-uniform and with reverse trends. Moreover, strong correlations between protein denaturation degree and heat-induced qualities changes were observed in crayfish tail during heating. The cooking uniformity and overheating degree of crayfish tail heated by MW and BW were evaluated by the maturity value (M_v) and overheating value (O_v), respectively. Evaluations showed that the profiles of M_v and O_v in the crayfish tail were non-uniform and with reverse trends, and there was lower ΔM_v and ${\overline{\mathrm{O}}}_{\mathrm{v}}$ for crayfish tail heated by MW than by BW, but higher O_v occurred in the centre, which corresponded to the texture of crayfish tails heated by MW was more susceptible than by BW when proteins had completely denatured.Industrial relevanceThe general patterns of cooking process in crayfish tail during microwave heating and boiling have been visually evaluated and compared based on the theories of reaction kinetics and maturity value, which enriched the knowledge for the application of microwave in the industrial thermal processing of crayfish and reaction kinetics in the analysis of cooking (especially microwave heating). Furthermore, the theory of maturity value was introduced into the evaluation of the cooking uniformity and overcooked degree in crayfish tail during the heating, which provided a new strategy for the cooking evaluation of food.     

一种基于分数阶傅里叶变换的LPI雷达检测方法

为实现检测和精确提取LPI（Low probability of intercepting）雷达中脉冲压缩（PC）雷达信号的参数,文章提出基于数字信道化的接收机,采用频域子带分数阶傅里叶变换聚焦、滤波处理方法,以增强雷达信号检测与去噪能力,实现对雷达弱信号的检测和参数提取。文中给出了数字信道化接收机结构和分数阶傅里叶滤波步骤,仿真及性能分析。     

基于LASAR的数字电路可测试性设计仿真

随着故障诊断技术的发展,利用专业的仿真工具对实际电路进行可测试性分析仿真用的越来越普遍。LASAR(逻辑自动激励与响应)就是一套优秀的用于数字电路测试开发和逻辑分析的仿真软件系统。介绍了利用LASAR故障仿真进行数字电路可测试性分析的方法。通过对一个实际电路进行仿真,具体说明了该方法在实际工程当中的应用。     

基于小波变换的雷达辐射源信号特征提取

在小波多分辨分析的基础上提出一种对雷达辐射源信号进行脉内特征提取方法,该方法能够从信号中有效提取定量信息。将小波变换后低频逼近小波系数的能量分布熵,与经过尺度相关去噪计算后反映信号边缘的高频细节小波系数能量分布熵一起构成雷达辐射源信号的二维特征向量。通过对10种雷达辐射源信号的特征提取和分类仿真实验,结果表明：提取的样本特征在低信噪比下具有很好的抗噪性和可聚类性,证明了本文方法的有效性。     

控制力矩陀螺框架伺服系统期望补偿自适应鲁棒控制

本文针对控制力矩陀螺框架伺服系统中存在的参数不确定性、摩擦非线性及外部干扰问题,提出了一种考虑LuGre摩擦的自适应鲁棒控制方法.针对陀螺框架伺服系统未知惯量和阻尼系数、LuGre摩擦参数不确定性及未知外部干扰上界,设计参数更新律对其进行估计.在此基础上,为提高系统对不确定参数及未知干扰的鲁棒性,设计带有期望补偿的自适应鲁棒控制器,可实现对LuGre摩擦非线性的精确补偿,同时减小测量信号噪声及外部干扰对系统的不利影响.应用Lyapunov稳定性理论分析了闭环系统的稳定性.对挠性航天器姿态机动控制的仿真结果,验证了所提方法的有效性.     

伺服系统的电磁兼容设计

针对现代电子装置装备伺服系统后所产生的复杂电磁环境,本文介绍了有关电磁兼容设计的理论依据、所采取的有效措施以及取得的显著效果,并结合工程实际,系统地阐述了伺服系统中行之有效的电磁兼容设计方法。     

Realizing excellent energy storage properties in Na0.5Bi0.5TiO3-based lead-free relaxor ferroelectrics

Development of lead-free dielectric capacitors with high recoverable energy storage density (W_rec), large energy storage efficiency (η), and wide usage temperature range are in high demanded for pulse power systems. Herein, we realized the enhancement of energy storage properties [high W_rec = 3.76 J/cm³, large η = 78.80 %, and broad operating temperature range (20?180 °C)] in lead-free Na_0.5Bi_0.5TiO₃ (BNT)-based relaxor ferroelectrics via component regulation. Excellent energy storage properties mainly originate from suppressing early polarization saturation and improving dielectric breakdown strength (E_b). Domain evolution on the nanoscale offers robust support to suppression of early polarization saturation. The enhancement of E_b can be derived from the contribution of the Mg-rich phase, which is also corroborative via first-principles calculation on basis of density functional theory (DFT). We believe that these findings in this work may provide a practicable guideline to build new lead-free ceramics for electrical energy storage applications.     

A detecting method for spherical fuel elements in pebble-bed HTGR using eddy current detection

In pebble-bed high temperature gas-cooled reactors (HTGRs), spherical fuel elements move inside pipelines of a handling system, which should be controlled precisely. A detecting method for these elements is proposed in this paper, which is achieved by a detecting system with self-diagnosis function. Detecting signals are obtained by sensors installed outside pipes. A signal identification algorithm was designed for graphite ball detection. Electromagnetic simulations and detecting experiments were performed for system optimization and development of the method. The results show that the proposed method is capable for spherical fuel elements detection, and can be successfully used in practical application.     

一种四信道比幅测向校正方法

四信道比幅测向是一种在雷达告警系统中广泛采用的测向方法,通过测向天线对4个不同到达方向电磁波的幅度比较来测量辐射源方向。针对传统比幅测向校正算法的局限,介绍了比幅测向系统的模型及原理,通过公式推导对影响测向精度的因素进行了分析,并结合典型的雷达告警系统组成框图,提出了一种新的四信道比幅测向校正方法。通过实际测试表明,该方法提高了系统测向精度并使得系统的可生产性、可维护性有了提高。     

Expanding gaudefroyite family to Sr2MBi(REEO)3(BO3)4 (M = Ca,Sr, Ba; REE = Y,Eu) borates with large second harmonic generation responses

The synthesis, crystal structure, and characterization of a few new noncentrosymmetric rare-earth borates of gaudefroyite family Sr₂MBi(REEO)₃(BO₃)₄ (M = Ca, Sr, Ba; REE = Y, Eu) are represented. Samples of Sr₂MBi(YO)₃(BO₃)₄ (M = Ca, Sr, Ba) borates were synthesized by multi-step solid state reactions. The crystal structures of Sr₃Bi(YO)₃(BO₃)₄, Sr₂CaBi(YO)₃(BO₃)₄ and Sr₂BaBi(YO)₃(BO₃)₄ were refined in P6₃ space group to R₁ 0.059, 0.058 and 0.018, respectively. Second-harmonic generation measured with Kurtz-Perry powder technique shows an increase in the nonlinear optical activity of materials by almost two times upon partial substitutions of Sr for Ca and Ba in the Sr₃Bi(REEO)₃(BO₃)₄ and its decrease if Y atoms are replaced by Eu. Thermal expansion coefficients for Sr₂MBi(YO)₃(BO₃)₄ (M = Ca, Sr, Ba) borates and Ca₄(MnO)₃(BO₃)₃(CO₃) gaudefroyite are calculated for the first time. Thermal expansion of these compounds is almost isotropic due to the arrangement of BO₃ units which are located in the ab and ac planes.