磁场处理对面团发酵特性的影响及作用机制

磁场可通过影响水分子的排布改变食品内部水分分布进而改善食品的品质。本研究分别在0、0.5、1.0、1.5、2.0mT的磁场强度条件下发酵面团1h,通过低场核磁、原位拉曼光谱等技术研究了磁场处理对面团发酵特性、水分分布及蛋白分子结构的影响,以期为开发高品质的中式美食提供理论基础。结果显示:随着磁场强度的增大,面团的发酵能力呈先上升后下降的趋势,在磁场强度为1.5 mT时对发酵力的影响最为显著;馒头的比容呈现先上升后下降的趋势,在磁场强度在1.0 mT时,馒头的比容为2.24 mL/g;馒头的硬度、黏性、咀嚼性呈现先下降后上升的趋势,弹性、内聚性、回复性没有明显的变化;强结合水与自由水含量呈先下降后上升趋势,弱结合水含量呈先上升后下降的趋势,在磁场强度为1.0 mT时,对水分分布的影响最为显著;α-螺旋相对含量呈先上升后下降的趋势,无规卷曲呈先下降后上升的趋势,在磁场强度为0.5 mT时α-螺旋相对含量最高,为54%,无规卷曲相对含量最低,为21%。适当的磁场处理可以提高面团的发酵力、馒头的比容和质构特性,加速面团中的水分分布,提高面筋网络的稳定性。综上,磁场处理可以通过改善面团中水分的分布、提高水分均匀度以及改变面筋蛋白的分子结构,提高面团的发酵特性以及馒头的质构特性。

碳达峰条件下的压细水雾灭火技术的前景分析

随着社会经济的快速发展,各类密集型人员居住和工作、交通运输等基础设施也得到了迅速发展,其消防安全就显得尤为重要。本文针对碳达峰条件的要求,分析了各类消防装置的应用现状,提出了当前常用消防系统灭火效能的不足,分析了高压细水雾灭火系统的特点,提出了碳达峰条件下广泛应用密闭空间建筑消防系统的趋势。

Application of Smith Predictor Based on Single Neural Network in Cold Rolling Shape Control

Flatness is one of the most important criterion factors to evaluate the quality of the steel strip. To improve the strip＇ s flatness quality, the most frequently used methodology is to employ the closed-loop automatic shape control system. However, in the shape control system, the shape-meter is always installed at the down way of the exit of the cold rolling mill and can not sense the changes of the strip flatness in the rolling gap directly. This kind of installation results in the delay of the feedback in the control system. Therefore, the stability and response performance of the system are strongly affected by the delay. At present, there is still no mature way to design controllers for systems with time delay. Although the conventional PID controller used in most practical applications has the capability to compensate the delay, the effect of the compensation is limited, especially for the systems with long time delay. Smith predictor, as a compensator for solving this problem, is now widely used in industry systems. However, the request of highly precise model of the system and the poor adaptive performance to the changes of related parameters limit the application of the Smith predictor in practice. In order to overcome the drawbacks of the Smith predictor, a new Smith predictor based on single neural network PID （SNN-PID） is proposed. Because the single neural network is employed into the Smith predictor to improve the controller＇s self-adaptability, the adaptive capability to the varying parameters of the system is improved. Meanwhile, for the purpose of solving the problems such as time-consuming and complicated calculation of the neural networks in real time, the learning coefficient of neural network is divided into several stages as usually done in expert control system. Therefore, the control system can obtain fast response due to the improved calculation speed of the neural networks. In order to validate the performance of the proposed controller, the experiment is conducted on the shape control system in a 300 mm four-high reversing cold rolling mill. The experimental results show that the SNN-PID with Smith predictor controller can effectively compensate the delay effects and achieve better control performance than the conventional PID controller.

Improved Relief Grinding Method of Gear Hob with Equal Relief Angle

The regrinding error is the main factor affecting the eligible length of hob tooth,how to decrease the regrinding error is a hot issue in the research area of hob grinding.At present,researches focus on changing the trajectory of relief moving,because of no unified relief grinding path planning method,the research result is restricted in the practical application.For solving the problem,the calculation model of the hob relief angle is established with the Archimedes relieving motion to analyze the interaction between the increasing relief angle of the hob and the accelerating tooth profile errors.Based on it,the improved relief grinding method of gear hob is proposed with equal relief angle（ERA）.Furthermore,the relief grinding method with ERA is developed with the following two steps.Firstly,the convergence numerical solution algorithm of the tooth top curve is designed to form the wheel motion path which is compared with that of traditional grinding.The second step is to establish the solution model of ERA grinding wheel.In order to verify the effect of the method,hob grinding simulation system of 3D solid was built under the AutoCAD environment.The regrinding errors is analyzed by intercepting the hob axial profiles of the various regrinding angles with Boolean operations and further converting it to basic rack tooth,then the simulation example of zero rake straight flute hob is used to compare the regrinding errors between ERA grinding and traditional grinding.Finally,the experiments were implemented on the five-axis CNC relief grinder with the relief motion of ERA grinding driven by cam.The results of experiments show that the method can effectively reduce the regrinding errors of hob and grind expediently gear hob of AA rank and over.This research provide an effective model of relief moving path plan reducing regrinding error,and have practicable value in CNC relief grinder.

Pressure control strategy for pump motor energy transfer unit

Multi-level pressure source system is a novel hydraulic system with distinct advantage of energy saving. In order to balance each pressure level of the multi-level pressure source system, a pump motor energy transfer unit is usually equipped. However, the pump motor energy transfer has the characteristics of poor starting and low response, which cause long time of pressure adjustment and large pressure jitter when the transformer is switched to system suddenly and the motor-side pressure has pressure impact when rail of the pump-side is switched. To address these problems, this paper proposes a compound control strategy of feedforward compensation control with Fuzzy-PID to improve the controllability of the multi-level pressure source system. A test rig of the pump motor energy transfer unit is built and the controllability of compound controller and PID controller are compared. The experiment results show that, compared with the traditional PID, the adjustment time and the pressure impact are reduced by 20% and 25% with the proposed compound control strategy. Therefore, the presented compound control strategy can be used to improve starting performance and robustness of the pump motor energy transfer unit control system.

等离子体预处理对花生粕蛋白酶解特性的影响

本研究以花生粕为实验原料,通过高效液相色谱仪、扫描电子显微镜等手段,研究不同等离子体预处理对花生粕蛋白的分子量大小、氨基酸组成以及微观结构的影响规律。与对照相比,经过等离子体预处理的花生粕蛋白的水解度提高了10.69%;高效液相色谱仪和氨基酸分析仪结果表明,经过等离子体预处理后的花生粕蛋白的分子量主要集中在200~1000 u,其中Glu、Arg、Asp、Leu和Phe 5种氨基酸在花生粕蛋白的水解过程中起到了重要作用;通过对处理120 s的花生粕蛋白进行酶解动力学参数测定,与对照相比,等离子体预处理组的KA保持基本不变,而K_(M)下降了14.67%;在1000倍的扫描电镜下发现处理后的花生粕蛋白结构受到破坏。本文系统揭示了等离子体调控过程中底物蛋白关键结构域变化与其酶解特性之间的内在关联机制,为制备高效酶解和结构紧凑的花生粕蛋白提供了理论基础。

贻贝蒸煮液添加对酱油品质的影响

为提高贻贝蒸煮液的经济价值和贻贝的综合利用率,减少环境污染,同时开发新型酱油品种,将贻贝蒸煮液添加至低盐稀态发酵酱油曲料中进行发酵,制备贻贝酱油,试验设置3组测试组(贻贝蒸煮液添加量分别为5%,10%和15%)和对照组(不添加)。结果表明,贻贝酱油(10%添加量)的可溶性无盐固形物含量16.83 g/100 m L,全氮含量1.55 g/100 m L,均达到国标特级酱油标准,氨基酸态氮含量0.75 g/100 m L,达到国标一级酱油标准;贻贝酱油中鲜味氨基酸占比较高,同时必需氨基酸含量以及醇类、酯类、酚类等风味物质的含量高于某特级酱油。试验制备的贻贝酱油风味独特营养价值高,有望为贻贝蒸煮液的综合利用提供新途径,提高经济效益同时降低污染。